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baseline protection catalogs baseline protection catalogs it-grundschutz-kataloge baseline protection manual 2005 collection documents german federal office security information technology bsi provide useful information detecting weaknesses combating attacks information technology environment cluster collection encompasses 3000 pages including introduction catalogs serves basis baseline protection certification enterprise baseline protection protection encompasses standard security measures typical systems normal protection needs detection assessment weak points systems often occurs way risk assessment wherein threat potential assessed costs damage system group similar systems investigated individually approach time-intensive expensive protection may rather proceed typical threat applies 80 cases recommend adequate countermeasures way security level achieved viewed adequate cases consequently replace expensive risk assessment cases security needs greater protection used basis action familiarize user manual contains introduction explanations approach baseline protection series concept role definitions glossary component catalogs threat catalogs measures catalogs follow introductory sections forms cross-reference tables supplement collection available federal office security information technology bsi internet platform also find baseline protection guide containing support functions implementing baseline protection procedural detail catalog element identified individual mnemonic laid according following scheme catalog groups named first c stands component measure threat followed layer number affected element finally serial number within layer identifies element component catalog central element contains following five layers overall aspects infrastructure systems networks applications partitioning layers clearly isolates personnel groups impacted given layer layer question first layer addressed management including personnel outsourcing second addressed in-house technicians regarding structural aspects infrastructure layer system administrators cover third layer looking characteristics systems including clients servers private branch exchanges fax machines fourth layer falls within network administrators task area fifth within applications administrator user concerning software like database management systems e-mail web servers individual component follows layout component number composed layer number component located unique number within layer given threat situation depicted short description component examining facts itemization individual threat sources ultimately follows present supplementary information necessary work establish baseline protection necessary measures presented text short illustrations text follows facts life cycle question includes planning design acquisition necessary realization operation selection necessary preventive measures complete depiction individual measures collected list arranged according measures catalog structure rather life cycle process classification measures categories b c z undertaken category measures entry point subject b measures expand category c ultimately necessary baseline protection certification category z measures additional measures proven practice keep component compact possible global aspects collected one component specific information collected second example apache web server general b 5.4 web server component measures threats web server depicted would apply well b5.11 component deals specifically apache web server components must successfully implemented guarantee system security respective measures threats introduced component also relevant components way network individual components arises baseline protection catalogs threat catalogs connection component catalogs offer detail potential threats systems threat catalogs follow general layout layers force majeure organizational deficiencies spurious human action technical failure premeditated acts distinguished according bsi knowledge collected catalogs necessary establish baseline protection baseline protection however demand understanding measures well vigilance management individual threat sources described briefly finally examples damages triggered threat sources given measures catalogs summarize actions necessary achieve baseline protection measures appropriate several system components described centrally process layers used structuring individual measures groups following layers formed infrastructure organization personnel hardware software communication preventive measures managers initially named initiate realize measures respective measures description detailed description measures follows finally control questions regarding correct realization given realization measures personnel verify whether adaptation operation question necessary deviations initial measures documented future reference besides information summarized baseline protection manual federal office data security provides material internet forms provided serve remedy protection needs certain system components table summarizes measures applied individual components regard measure named degree realization determined degrees realization considerable yes partial distinguished finally realization terminated manager named measures realization possible reasons entered adjacent field later traceability conclusion consists cost assessment besides forms cross-reference tables another useful supplement summarize measures important threats individual components measures well threats cited mnemonics measures cited priority classification table contains correlations measures threats address however cross-reference tables cite important threats measure cited given threat applicable individual system superfluous baseline protection ensured measures realized
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Computer security
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threaded code computer science term threaded code refers programming technique code form essentially consists entirely calls subroutines often found compiler implementations generate code form and/or implemented form code may processed interpreter may simply sequence machine code call instructions threaded code better code density code generated alternative code generation techniques alternative calling conventions sometimes expense slightly slower execution speed however program small enough fit fully computer processor cache may run faster larger program suffers many cache misses small programs may also run faster programs fill cache switching threads threaded code best known implementation technique commonly used programming languages forth many implementations basic implementations cobol early versions b languages small minicomputers amateur radio satellites common way make computer programs 'translate computer program written symbolic language machine code using compiler code typically fast nonportable since binary code designed specific computer hardware platform different approach uses virtual machine instruction set particular target hardware interpreter executes new target hardware early computers relatively little memory example data general nova ibm 1130 many first apple ii computers 4 kb ram installed consequently lot time spent trying find ways reduce size programs would fit memory available time computers relatively slow simple interpretation noticeably slower executing machine code instead writing every step operation every part program needed programmers saved memory writing step operations see n't repeat placing subroutine processcode refactoringis used today although different reasons top-level application programs may consist nothing subroutine calls many subroutines turn also consist nothing lower level subroutine calls mainframes early microprocessors rca 1802 required several instructions call subroutine top-level application many subroutines sequence constantly repeated subroutine address changing one call next using memory store instructions repeatedly wasteful save space programmers squeezed series subroutine calls list containing contiguous addresses sub-routines used tiny interpreter call subroutine turn identical way programmers squeezed series jumps branch table dispatch table virtual method table list containing destination addresses used small selector branch selected destination threaded code techniques program becomes list entry points actual code executed years programmers created many variations interpreter small selector particular address list addresses may extracted using index general purpose register pointer addresses may direct indirect contiguous non-contiguous linked pointers relative absolute resolved compile time dynamically built one variation best situations save space programmers squeezed lists subroutine calls simple lists subroutine addresses used small loop call subroutine turn example following pseudocode uses technique add two numbers b example list labeled thread variable ip instruction pointer tracks place within list another variable sp stack pointer contains address elsewhere memory available hold value temporarily calling loop codice_1 simple repeated inline end subroutine control jumps end subroutine start another instead jumping twice via codice_1 example called direct threaded code dtc although technique older first widely circulated use term threaded code probably bell article threaded code 1973 charles h. moore invented compact notation 1970 forth virtual machine indirect threaded code itc originally moore invented easy fast nova minicomputers indirection bit every address said published remarks byte magazine forth issue found convenient propagated later forth designs forth compilers compile forth programs direct-threaded code others make indirect-threaded code programs act either way practically executable threaded code uses one another methods invoking subroutines method called threading model addresses thread addresses machine language form simple may overheads thread consists machine addresses parameters must loaded indirectly memory forth systems produce direct-threaded code many machines direct-threading faster subroutine threading see reference example stack machine might execute sequence push push b add might translated following thread routines codice_3 initialized address labeled codice_4 i.e. address codice_5 stored alternatively operands may included thread remove indirection needed makes thread larger indirect threading uses pointers locations turn point machine code indirect pointer may followed operands stored indirect block rather storing repeatedly thread thus indirect code often compact direct-threaded code indirection also typically makes slower though still usually faster bytecode interpreters handler operands include values types space savings direct-threaded code may significant older forth systems typically produce indirect-threaded code example goal execute push push b add following might used codice_3 initialized address codice_7 code fragment codice_8 codice_9 found double-indirecting codice_3 indirect block operands fragment found indirect block following fragment address requires keeping current subroutine codice_3 unlike previous examples contained next subroutine called so-called subroutine-threaded code also call-threaded code consists series machine-language call instructions addresses functions call opposed direct threading use jump early compilers algol fortran cobol forth systems often produced subroutine-threaded code code many systems operated last-in-first-out lifo stack operands well-developed compiler theory modern processors special hardware support subroutine call return instructions overhead one extra machine instruction per dispatch somewhat diminished anton ertl stated contrast popular myths subroutine threading usually slower direct threading however ertl recent tests show subroutine threading faster direct threading 15 25 test cases ertl recent tests show direct threading fastest threading model xeon opteron athlon processors indirect threading fastest threading model pentium processors subroutine threading fastest threading model pentium 4 pentium iii ppc processors example call threading push push b add token threaded code uses lists 8 12-bit indexes table pointers token threaded code notably compact without much special effort programmer usually half three-fourths size threaded-codes quarter eighth size compiled code table pointers either indirect direct forth compilers produce token threaded code programmers consider p-code generated pascal compilers well bytecodes used .net java basic c compilers token-threading common approach historically bytecode uses 8-bit opcodes often stack-based virtual machine typical interpreter known decode dispatch interpreter follows form virtual machine uses byte-size instructions codice_12 simply fetch codice_13 often commonly used 1-byte instructions plus less-common multibyte instructions case codice_12 complex decoding single byte opcodes simply efficiently handled branch table using opcode directly index instructions individual operations simple push add overhead involved deciding execute larger cost actually executing interpreters often much slower machine code however complex compound instructions overhead percentage proportionally less significant huffman threaded code consists lists tokens stored huffman codes huffman code variable length bit string used identify unique token huffman-threaded interpreter locates subroutines using index table tree pointers navigated huffman code huffman threaded code one compact representations known computer program basically index codes organized measuring frequency subroutine occurs code frequent calls given shortest codes operations approximately equal frequencies given codes nearly equal bit-lengths huffman-threaded systems implemented direct-threaded forth systems used pack large amounts slow-running code small cheap microcontrollers published uses smart cards toys calculators watches bit-oriented tokenized code used pbasic seen kind huffman threaded code example string threading operations identified strings usually looked-up hash table used charles h. moore earliest forth implementations university illinois experimental hardware-interpreted computer language also used bashforth examples show branches interpreters branch changes thread pointer codice_3 example conditional branch top-of-stack value zero might encoded follows note codice_16 location jump address handler must skipped codice_17 whether branch taken separating data return stacks machine eliminates great deal stack management code substantially reducing size threaded code dual-stack principle originated three times independently burroughs large systems forth postscript used java virtual machines three registers often present threaded virtual machine another one exists passing data subroutines 'words often threaded virtual machines implementations forth simple virtual machine heart consisting three primitives indirect-threaded virtual machine one given operations perhaps simplest fastest interpreter virtual machine
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Programming language topics
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c hdl c hdl tools convert c language c-like computer code hardware description language hdl vhdl verilog converted code synthesized translated hardware device field-programmable gate array compared software equivalent designs hardware consume less power yielding higher performance per watt execute faster lower latency parallelism higher throughput however system design functional verification hardware description language tedious time-consuming systems engineers often write critical modules hdl modules high-level language synthesize hdl c hdl high-level synthesis tools c another name methodology rtl refers register transfer level representation program necessary implement logic early development c hdl done ian page charles sweeney colleagues oxford university 1990s developed handel-c language commercialized research forming embedded solutions limited esl 1999 renamed celoxica september 2000 2008 embedded systems departments celoxica sold catalytic 3 million later merged become agility computing january 2009 mentor graphics acquired agility c synthesis assets celoxica continues trade concentrating hardware acceleration financial industries c hdl techniques commonly applied applications unacceptably high execution times existing general-purpose supercomputer architectures examples include bioinformatics computational fluid dynamics cfd financial processing oil gas survey data analysis embedded applications requiring high performance real-time data processing also area use system-on-chip soc design may also take advantage c hdl techniques c-to-vhdl compilers useful large designs implementing code might change future designing large application entirely hdl may difficult time-consuming abstraction high level language large application often reduce total development time furthermore application coded hdl almost certainly difficult modify one coded higher level language designer needs add new functionality application adding lines c code almost always easier remodeling equivalent hdl code flow hdl tools similar aim flow rather c-based design
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Programming language topics
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x86-64 x86-64 also known x64 x86_64 amd64 intel 64 64-bit version x86 instruction set introduces two new modes operation 64-bit mode compatibility mode along new 4-level paging mode 64-bit mode new paging mode supports vastly larger amounts virtual memory physical memory possible 32-bit predecessors allowing programs store larger amounts data memory x86-64 also expands general-purpose registers 64-bit well extends number 8 limited fixed functionality e.g stack management 16 fully general provides numerous enhancements floating point operations supported via mandatory sse2-like instructions x87/mmx style registers generally used still available even 64-bit mode instead set 32 vector registers 128 bits used store one two double-precision numbers one four single precision numbers various integer formats 64-bit mode instructions modified support 64-bit operands 64-bit addressing mode compatibility mode allows 16- 32-bit user applications run unmodified coexisting 64-bit applications 64-bit operating system supports full x86 16-bit 32-bit instruction sets remain implemented hardware without intervening emulation older executables run little performance penalty newer modified applications take advantage new features processor design achieve performance improvements also processor supporting x86-64 still powers real mode full backward compatibility x86 processors done since 80286 original specification created amd released 2000 implemented amd intel via amd k8 microarchitecture opteron athlon64 processors first implement first significant addition x86 architecture designed company intel intel forced follow suit introduced modified netburst family software-compatible amd specification via technologies introduced x86-64 via isaiah architecture via nano x86-64 architecture distinct intel itanium architecture formerly ia-64 compatible native instruction set level x86 architecture operating systems applications written one run amd64 created alternative radically different ia-64 architecture designed intel hewlett packard originally announced 1999 full specification became available august 2000 amd64 architecture positioned amd beginning evolutionary way add 64-bit computing capabilities existing x86 architecture opposed intel approach creating entirely new 64-bit architecture ia-64 first amd64-based processor opteron released april 2003 amd processors implementing amd64 architecture include opteron athlon 64 athlon 64 x2 athlon 64 fx athlon ii followed x2 x3 x4 indicate number cores xlt models turion 64 turion 64 x2 sempron palermo e6 stepping manila models phenom followed x3 x4 indicate number cores phenom ii followed x2 x3 x4 x6 indicate number cores fx fusion/apu ryzen/epyc primary defining characteristic amd64 availability 64-bit general-purpose processor registers example rax rbx 64-bit integer arithmetic logical operations 64-bit virtual addresses designers took opportunity make improvements well significant changes described although virtual addresses 64 bits wide 64-bit mode current implementations chips known planning stages allow entire virtual address space 2 bytes 16 eb used would approximately four billion times size virtual address space 32-bit machines operating systems applications need large address space foreseeable future implementing wide virtual addresses would simply increase complexity cost address translation real benefit amd therefore decided first implementations architecture least significant 48 bits virtual address would actually used address translation page table lookup addition amd specification requires significant 16 bits virtual address bits 48 63 must copies bit 47 manner akin sign extension requirement met processor raise exception addresses complying rule referred canonical form canonical form addresses run 0 00007fff'ffffffff ffff8000'00000000 ffffffff'ffffffff total 256 tb usable virtual address space still 65,536 times larger virtual 4 gb address space 32-bit machines feature eases later scalability true 64-bit addressing many operating systems including limited windows nt family take higher-addressed half address space named kernel space leave lower-addressed half user space application code user mode stacks heaps data regions canonical address design ensures every amd64 compliant implementation effect two memory halves lower half starts 00000000'00000000 grows upwards virtual address bits become available higher half docked top address space grows downwards also enforcing canonical form addresses checking unused address bits prevents use operating system tagged pointers flags privilege markers etc. use could become problematic architecture extended implement virtual address bits first versions windows x64 even use full 256 tb restricted 8 tb user space 8 tb kernel space windows support entire 48-bit address space windows 8.1 released october 2013 64-bit addressing mode long mode superset physical address extensions pae page sizes may 4 kb 2 bytes 2 mb 2 bytes long mode also supports page sizes 1 gb 2 bytes rather three-level page table system used systems pae mode systems running long mode use four levels page table pae page-directory pointer table extended four entries 512 additional page-map level 4 pml4 table added containing 512 entries 48-bit implementations full mapping hierarchy 4 kb pages whole 48-bit space would take bit 512 gb memory 0.195 256 tb virtual space intel proposed scheme five-level page table implemented would allow intel 64 processors support 57-bit virtual address space operating system also limit virtual address space details applicable given operating system compatibility characteristics section current amd64 processors support physical address space 2 bytes ram 256 tb however known x86-64 motherboards support 256 tb ram operating system may place additional limits amount ram usable supported details point given operating system compatibility characteristics section article architecture two primary modes operation long mode legacy mode long mode architecture intended primary mode operation combination processor native 64-bit mode combined 32-bit 16-bit compatibility mode used 64-bit operating systems 64-bit operating system 64-bit programs run 64-bit mode 32-bit 16-bit protected mode applications need use either real mode virtual 8086 mode order execute time run compatibility mode real-mode programs programs use virtual 8086 mode time run long mode unless modes emulated software however programs may started operating system running long mode processors supporting vt-x amd-v creating virtual processor running desired mode since basic instruction set almost performance penalty executing protected mode x86 code unlike intel ia-64 differences underlying instruction set mean running 32-bit code must done either emulation x86 making process slower dedicated x86 coprocessor however x86-64 platform many x86 applications could benefit 64-bit recompile due additional registers 64-bit code guaranteed sse2-based fpu support compiler use optimization however applications regularly handle integers wider 32 bits cryptographic algorithms need rewrite code handling huge integers order take advantage 64-bit registers legacy mode mode used 32-bit 16-bit protected mode operating systems mode processor acts like older x86 processor 16-bit 32-bit code executed legacy mode allows maximum 32 bit virtual addressing limits virtual address space 4 gb 64-bit programs run legacy mode intel 64 intel implementation x86-64 used implemented various processors made intel historically amd developed produced processors instruction sets patterned intel original designs x86-64 roles reversed intel found position adopting isa amd created extension intel x86 processor line intel project originally codenamed yamhill yamhill river oregon willamette valley several years denying existence intel announced february 2004 idf project indeed underway intel chairman time craig barrett admitted one worst-kept secrets intel name instruction set changed several times name used idf ct presumably clackamas technology another codename oregon river within weeks began referring ia-32e ia-32 extensions march 2004 unveiled official name em64t extended memory 64 technology late 2006 intel began instead using name intel 64 implementation paralleling amd use name amd64 first processor implement intel 64 multi-socket processor xeon code-named nocona june 2004 contrast initial prescott chips february 2004 enable feature intel subsequently began selling intel 64-enabled pentium 4s using e0 revision prescott core sold oem market pentium 4 model f. e0 revision also adds execute disable xd intel name nx bit intel 64 included current xeon code-named irwindale intel official launch intel 64 name em64t time mainstream desktop processors n0 stepping prescott-2m first intel mobile processor implementing intel 64 merom version core 2 processor released july 27 2006 none intel earlier notebook cpus core duo pentium celeron mobile pentium 4 implement intel 64 intel processors implementing intel64 architecture include pentium 4 f-series/5x1 series 506 516 celeron models 3x1 3x6 355 347 352 360 365 later celerons models xeon since nocona models pentium dual-core processors since merom-2m atom 230 330 d410 d425 d510 d525 n450 n455 n470 n475 n550 n570 n2600 n2800 versions pentium pentium extreme edition core 2 core i9 core i7 core i5 core i3 processors xeon phi 7200 series processors via technologies introduced first implementation x86-64 architecture 2008 five years development cpu division centaur technology codenamed isaiah 64-bit architecture unveiled january 24 2008 launched may 29 via nano brand name processor supports number via-specific x86 extensions designed boost efficiency low-power appliances expected isaiah architecture twice fast integer performance four times fast floating-point performance previous-generation via esther equivalent clock speed power consumption also expected par previous-generation via cpus thermal design power ranging 5 w 25 w. completely new design isaiah architecture built support features like x86-64 instruction set x86 virtualization unavailable predecessors via c7 line retaining encryption extensions although nearly identical differences two instruction sets semantics seldom used machine instructions situations mainly used system programming compilers generally produce executables i.e machine code avoid differences least ordinary application programs therefore interest mainly developers compilers operating systems similar must deal individual special system instructions supercomputers tracked top500 appearance 64-bit extensions x86 architecture enabled 64-bit x86 processors amd intel light olive circles red circles diagram provided section respectively replace risc processor architectures previously used systems including pa-risc sparc alpha others well 32-bit x86 green dots purple dots diagram even though intel initially tried unsuccessfully replace x86 new incompatible 64-bit architecture itanium processor main non-x86 cpu architecture still used supercomputing power isa used ibm power microprocessors blue diamond pattern diagram sparc far behind numbers top500 2011 fujitsu sparc64 viiifx based supercomputer without co-processors reached number one since dropped top-10 first arm-based supercomputer appeared list 2018 recent years non-cpu architecture co-processors gpgpu also played big role performance intel xeon phi knights corner coprocessors implement subset x86-64 vector extensions also used along x86-64 processors tianhe-2 supercomputer following operating systems releases support x86-64 architecture long mode preliminary infrastructure work started february 2004 x86-64 port development later stalled development started july 2007 continued google summer code 2008 soc 2009 first official release contain x86-64 support version 2.4 freebsd first added x86-64 support name amd64 experimental architecture 5.1-release june 2003 included standard distribution architecture 5.2-release january 2004 since freebsd designated tier 1 platform 6.0-release version cleaned quirks running x86 executables amd64 drivers work x86 architecture work currently done integrate fully x86 application binary interface abi manner linux 32-bit abi compatibility currently works x86-64 architecture support first committed netbsd source tree june 19 2001 netbsd 2.0 released december 9 2004 netbsd/amd64 fully integrated supported port 32-bit code still supported 64-bit mode netbsd-32 kernel compatibility layer 32-bit syscalls nx bit used provide non-executable stack heap per-page granularity segment granularity used 32-bit x86 openbsd supported amd64 since openbsd 3.5 released may 1 2004 complete in-tree implementation amd64 support achieved prior hardware initial release amd loaned several machines project hackathon year openbsd developers taken platform support nx bit allowed easy implementation w^x feature code amd64 port openbsd also runs intel 64 processors contains cloned use amd64 extensions since intel left page table nx bit early intel 64 processors w^x capability intel cpus later intel 64 processors added nx bit name xd bit symmetric multiprocessing smp works openbsd amd64 port starting release 3.6 november 1 2004 possible enter long mode dos without dos extender user must return real mode order call bios dos interrupts may also possible enter long mode dos extender similar dos/4gw complex since x86-64 lacks virtual 8086 mode dos aware benefits expected unless running dos emulation adequate virtualization driver backend example mass storage interface linux first operating system kernel run x86-64 architecture long mode starting 2.4 version 2001 preceding hardware availability linux also provides backward compatibility running 32-bit executables permits programs recompiled long mode retaining use 32-bit programs several linux distributions currently ship x86-64-native kernels userlands arch linux suse mandriva debian allow users install set 32-bit components libraries installing 64-bit dvd thus allowing existing 32-bit applications run alongside 64-bit os distributions fedora slackware ubuntu available one version compiled 32-bit architecture another compiled 64-bit architecture fedora red hat enterprise linux allow concurrent installation userland components 32 64-bit versions 64-bit system x32 abi application binary interface introduced linux 3.4 allows programs compiled x32 abi run 64-bit mode x86-64 using 32-bit pointers data fields though limits program virtual address space 4 gb also decreases memory footprint program cases allow run faster 64-bit linux allows 128 tb virtual address space individual processes address approximately 64 tb physical memory subject processor system limitations mac os x 10.4.7 higher versions mac os x 10.4 run 64-bit command-line tools using posix math libraries 64-bit intel-based machines versions mac os x 10.4 10.5 run 64-bit powerpc machines libraries frameworks work 64-bit applications mac os x 10.4 kernel kernel extensions 32-bit mac os x 10.5 supports 64-bit gui applications using cocoa quartz opengl x11 64-bit intel-based machines well 64-bit powerpc machines non-gui libraries frameworks also support 64-bit applications platforms kernel kernel extensions 32-bit mac os x 10.6 first version macos supports 64-bit kernel however 64-bit computers run 64-bit kernel 64-bit computers run 64-bit kernel default 64-bit kernel like 32-bit kernel supports 32-bit applications kernels also support 64-bit applications 32-bit applications virtual address space limit 4 gb either kernel os x 10.8 includes 64-bit kernel continues support 32-bit applications 64-bit kernel support 32-bit kernel extensions 32-bit kernel support 64-bit kernel extensions macos uses universal binary format package 32- 64-bit versions application library code single file appropriate version automatically selected load time mac os x 10.6 universal binary format also used kernel kernel extensions support 32-bit 64-bit kernels solaris 10 later releases support x86-64 architecture solaris 10 sparc architecture one operating system image contains 32-bit kernel 64-bit kernel labeled x64/x86 dvd-rom image default behavior boot 64-bit kernel allowing 64-bit existing new 32-bit executables run 32-bit kernel also manually selected case 32-bit executables run codice_24 command used determine system running 64-bit kernel solaris 11 64-bit kernel provided however 64-bit kernel supports 32- 64-bit executables libraries system calls x64 editions microsoft windows client server—windows xp professional x64 edition windows server 2003 x64 edition—were released march 2005 internally actually build 5.2.3790.1830 sp1 share source base operating system binaries even system updates released unified packages much manner windows 2000 professional server editions x86 windows vista also many different editions released january 2007 windows 7 released july 2009 windows server 2008 r2 sold x64 itanium editions later versions windows server offer x64 edition versions windows x64 prior windows 8.1 windows server 2012 r2 offer following windows 8.1 windows server 2012 r2 user mode kernel mode virtual address spaces extended 128 tb versions windows install processors lack codice_17 instruction following additional characteristics apply x64 versions windows playstation 4 xbox one successors incorporate amd x86-64 processors based jaguar microarchitecture firmware games written x86-64 code legacy x86 code involved since amd64 intel 64 substantially similar many software hardware products use one vendor-neutral term indicate compatibility implementations amd original designation processor architecture x86-64 still sometimes used purpose variant x86_64 companies microsoft sun microsystems/oracle corporation use contraction x64 marketing material term ia-64 refers itanium processor confused x86-64 completely different instruction set many operating systems products especially introduced x86-64 support prior intel entry market use term amd64 amd64 refer amd64 intel 64. x86-64/amd64 solely developed amd amd holds patents techniques used amd64 patents must licensed amd order implement amd64 intel entered cross-licensing agreement amd licensing amd patents existing x86 techniques licensing amd patents techniques used x86-64 2009 amd intel settled several lawsuits cross-licensing disagreements extending cross-licensing agreements
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Computer architecture
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filter software filter computer program subroutine process stream producing another stream single filter used individually frequently strung together form pipeline operating systems unix rich filter programs windows 7 later also rich filters include windows powershell comparison however filters built cmd.exe original command-line interface windows significant enhancements relative similar filter commands available ms-dos os x includes filters underlying unix base also automator allows filters known actions strung together form pipeline unix unix-like operating systems filter program gets data standard input main input stream writes main results standard output main output stream auxiliary input may come command line flags configuration files auxiliary output may go standard error command syntax getting data device file standard input input operator codice_1 similarly send data device file standard output output operator codice_2 append data lines existing output file one use append operator codice_3 filters may strung together pipeline pipe operator codice_4 operator signifies main output command left passed main input command right unix philosophy encourages combining small discrete tools accomplish larger tasks classic filter unix ken thompson doug mcilroy cites ingrained tools outlook irrevocably operating system later tools imitating simplest prints lines containing character string output following example finds registered users foo part username using cut command take first field username line unix system password file passing input grep searches input lines containing character string foo prints output common unix filter programs cat cut grep head sort uniq tail programs like awk sed used build quite complex filters fully programmable unix filters also used data scientists get quick overview file based dataset two standard filters early days dos-based computers find sort examples filters may used batch files *.bat *.cmd etc. use command shell environment many filters available built windows freeware shareware commercial programs number mimic function features filters unix filtering programs graphical user interface gui enable users design customized filter suit special data processing and/or data mining requirements windows command prompt inherited ms-dos commands improved added example windows server 2003 features six command-line filters modifying active directory chained piping dsadd dsget dsmod dsmove dsrm dsquery windows powershell adds entire host filters known cmdlets chained together pipe except simple ones e.g codice_5 following example gets list files codice_6 folder gets size sorts size ascending order shows three filters codice_7 codice_8 codice_9 chained pipes
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Operating systems
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instruction set architecture instruction set architecture isa abstract model computer also referred architecture computer architecture realization isa called implementation isa permits multiple implementations may vary performance physical size monetary cost among things isa serves interface software hardware software written isa run different implementations isa enabled binary compatibility different generations computers easily achieved development computer families developments helped lower cost computers increase applicability reasons isa one important abstractions computing today isa defines everything machine language programmer needs know order program computer isa defines differs isas general isas define supported data types state main memory registers semantics memory consistency addressing modes instruction set set machine instructions comprises computer machine language input/output model instruction set architecture distinguished microarchitecture set processor design techniques used particular processor implement instruction set processors different microarchitectures share common instruction set example intel pentium advanced micro devices athlon implement nearly identical versions x86 instruction set radically different internal designs concept architecture distinct design specific machine developed fred brooks ibm design phase system/360 virtual machines support bytecode isa smalltalk java virtual machine microsoft common language runtime implement translating bytecode commonly used code paths native machine code addition virtual machines execute less frequently used code paths interpretation see just-in-time compilation transmeta implemented x86 instruction set atop vliw processors fashion isa may classified number different ways common classification architectural complexity complex instruction set computer cisc many specialized instructions may rarely used practical programs reduced instruction set computer risc simplifies processor efficiently implementing instructions frequently used programs less common operations implemented subroutines resulting additional processor execution time offset infrequent use types include long instruction word vliw architectures closely related long instruction word liw explicitly parallel instruction computing epic architectures architectures seek exploit instruction-level parallelism less hardware risc cisc making compiler responsible instruction issue scheduling architectures even less complexity studied minimal instruction set computer misc one instruction set computer oisc theoretically important types commercialized machine language built discrete statements instructions processing architecture given instruction may specify complex operations built combining simple instructions executed sequentially otherwise directed control flow instructions examples operations common many instruction sets include processors may include complex instructions instruction set single complex instruction something may take many instructions computers instructions typified instructions take multiple steps control multiple functional units otherwise appear larger scale bulk simple instructions implemented given processor examples complex instructions include complex instructions common cisc instruction sets risc instruction sets risc instruction sets may include well risc instruction sets generally include alu operations memory operands instructions move large blocks memory risc instruction sets include simd vector instructions perform arithmetic operation multiple pieces data time simd instructions ability manipulating large vectors matrices minimal time simd instructions allow easy parallelization algorithms commonly involved sound image video processing various simd implementations brought market trade names mmx 3dnow altivec traditional architectures instruction includes opcode specifies operation perform add contents memory register —and zero operand specifiers may specify registers memory locations literal data operand specifiers may addressing modes determining meaning may fixed fields long instruction word vliw architectures include many microcode architectures multiple simultaneous opcodes operands specified single instruction exotic instruction sets opcode field transport triggered architectures tta operand forth virtual machine 0-operand instruction sets lack operand specifier fields stack machines including nosc conditional instructions often predicate field—a bits encode specific condition cause operation performed rather performed example conditional branch instruction executed branch taken condition true execution proceeds different part program executed branch taken condition false execution continues sequentially instruction sets also conditional moves move executed data stored target location condition true executed target location modified condition false similarly ibm z/architecture conditional store instruction instruction sets include predicate field every instruction called branch predication instruction sets may categorized maximum number operands explicitly specified instructions due large number bits needed encode three registers 3-operand instruction risc architectures 16-bit instructions invariably 2-operand designs atmel avr ti msp430 versions arm thumb risc architectures 32-bit instructions usually 3-operand designs arm avr32 mips power isa sparc architectures instruction specifies number operands registers memory locations immediate values explicitly instructions give one operands implicitly stored top stack implicit register operands given implicitly fewer operands need specified instruction destination operand explicitly specifies destination additional operand must supplied consequently number operands encoded instruction may differ mathematically necessary number arguments logical arithmetic operation arity operands either encoded opcode representation instruction else given values addresses following instruction register pressure measures availability free registers point time program execution register pressure high large number available registers use thus higher register pressure often register contents must spilled memory increasing number registers architecture decreases register pressure increases cost embedded instruction sets thumb suffer extremely high register pressure small register sets general-purpose risc isas like mips alpha enjoy low register pressure cisc isas like x86-64 offer low register pressure despite smaller register sets due many addressing modes optimizations sub-register addressing memory operands alu instructions absolute addressing pc-relative addressing register-to-register spills cisc isas offer size length instruction varies widely little four bits microcontrollers many hundreds bits vliw systems processors used personal computers mainframes supercomputers instruction sizes 8 64 bits longest possible instruction x86 15 bytes 120 bits within instruction set different instructions may different lengths architectures notably reduced instruction set computers risc typically corresponding architecture word size architectures instructions variable length typically integral multiples byte halfword arm thumb-extension mixed variable encoding two fixed usually 32-bit 16-bit encodings instructions mixed freely must switched branch exception boundary armv8 risc instruction set normally fixed instruction length often 4 bytes 32 bits whereas typical cisc instruction set may instructions widely varying length 1 15 bytes x86 fixed-length instructions less complicated handle variable-length instructions several reasons check whether instruction straddles cache line virtual memory page boundary instance therefore somewhat easier optimize speed early computers memory expensive minimizing size program make sure would fit limited memory often central thus combined size instructions needed perform particular task code density important characteristic instruction set computers high code density often complex instructions procedure entry parameterized returns loops etc therefore retroactively named complex instruction set computers cisc however typical frequent cisc instructions merely combine basic alu operation add access one operands memory using addressing modes direct indirect indexed etc. certain architectures may allow two three operands including result directly memory may able perform functions automatic pointer increment etc software-implemented instruction sets may even complex powerful instructions reduced instruction-set computers risc first widely implemented period rapidly growing memory subsystems sacrifice code density simplify implementation circuitry try increase performance via higher clock frequencies registers single risc instruction typically performs single operation add registers load memory location register risc instruction set normally fixed instruction length whereas typical cisc instruction set instructions widely varying length however risc computers normally require often longer instructions implement given task inherently make less optimal use bus bandwidth cache memories certain embedded risc isas like thumb avr32 typically exhibit high density owing technique called code compression technique packs two 16-bit instructions one 32-bit instruction unpacked decode stage executed two instructions minimal instruction set computers misc form stack machine separate instructions 16-64 multiple instructions fit single machine word types cores often take little silicon implement easily realized fpga multi-core form code density misc similar code density risc increased instruction density offset requiring primitive instructions task research executable compression mechanism improving code density mathematics kolmogorov complexity describes challenges limits instructions constituting program rarely specified using internal numeric form machine code may specified programmers using assembly language commonly may generated programming languages compilers design instruction sets complex issue two stages history microprocessor first cisc complex instruction set computer many different instructions 1970s however places like ibm research found many instructions set could eliminated result risc reduced instruction set computer architecture uses smaller set instructions simpler instruction set may offer potential higher speeds reduced processor size reduced power consumption however complex set may optimize common operations improve memory cache efficiency simplify programming instruction set designers reserve one opcodes kind system call software interrupt example mos technology 6502 uses 00 zilog z80 uses eight codes c7 cf d7 df e7 ef f7 ff motorola 68000 use codes range a000..afff fast virtual machines much easier implement instruction set meets popek goldberg virtualization requirements nop slide used immunity-aware programming much easier implement unprogrammed state memory interpreted nop systems multiple processors non-blocking synchronization algorithms much easier implement instruction set includes support something fetch-and-add load-link/store-conditional ll/sc atomic compare-and-swap given instruction set implemented variety ways ways implementing particular instruction set provide programming model implementations instruction set able run executables various ways implementing instruction set give different tradeoffs cost performance power consumption size etc designing microarchitecture processor engineers use blocks hard-wired electronic circuitry often designed separately adders multiplexers counters registers alus etc kind register transfer language often used describe decoding sequencing instruction isa using physical microarchitecture two basic ways build control unit implement description although many designs use middle ways compromises designs use combination hardwired design microcode control unit cpu designs use writable control store—they compile instruction set writable ram flash inside cpu rekursiv processor imsys cjip fpga reconfigurable computing isa also emulated software interpreter naturally due interpretation overhead slower directly running programs emulated hardware unless hardware running emulator order magnitude faster today common practice vendors new isas microarchitectures make software emulators available software developers hardware implementation ready often details implementation strong influence particular instructions selected instruction set example many implementations instruction pipeline allow single memory load memory store per instruction leading load-store architecture risc another example early ways implementing instruction pipeline led delay slot demands high-speed digital signal processing pushed opposite direction—forcing instructions implemented particular way example perform digital filters fast enough mac instruction typical digital signal processor dsp must use kind harvard architecture fetch instruction two data words simultaneously requires single-cycle multiply–accumulate multiplier
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Computer architecture
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list disk operating systems list disk operating systems acronym dos used form names many simply referred dos within respective communities
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Operating systems
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lisp machine lisp lisp machine lisp programming language dialect language lisp direct descendant maclisp initially developed mid late 1970s system programming language massachusetts institute technology mit lisp machines lisp machine lisp also lisp dialect influence design common lisp lisp machine lisp branched three dialects symbolics named variant zetalisp lisp machines inc. later texas instruments ti explorer would share common code base dialect lisp machine lisp would differ version maintained mit ai lab richard stallman others lisp machine manual describes lisp machine lisp language detail manual popularly termed chine nual full title printed across front back covers letters appeared front name sometimes abbreviated blending two words chinual lisp machine lisp features
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Programming language topics
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maclisp maclisp maclisp sometimes styled maclisp maclisp programming language dialect language lisp originated massachusetts institute technology mit project mac derived prefix late 1960s based lisp 1.5 richard greenblatt main developer original codebase pdp-6 jon l. white responsible later maintenance development name maclisp began used early 1970s distinguish forks pdp-6 lisp notably bbn lisp maclisp descendant lisp 1.5 maclisp departs lisp 1.5 using value cell access store dynamic values variables lisp 1.5 used linear search association list determine variable value maclisp variable evaluation faster different variable semantics maclisp also employed reader macros make readable input output termed input/output i/o instead entering codice_1 one could enter codice_2 get s-expression although implementations put functions property list maclisp uses different syntax define functions maclisp also load-on-demand feature maclisp began digital equipment corporation pdp-6 pdp-10 computers running incompatible timesharing system later ported pdp-10 operating systems example timesharing total operating system tops-10 tops-20 original implementation assembly language later implementation multics used pl/i maclisp developed considerably lifetime major features added language systems would typically correspond major release numbers maclisp used implement macsyma computer algebra system cas symbolic algebra program macsyma development also drove several features maclisp shrdlu blocks-world program written maclisp language widespread use artificial intelligence ai research community early 1980s also used implement programming languages planner scheme multics maclisp used implement first lisp-based emacs maclisp influential lisp implementation longer maintained actively runs pdp-10 emulators used experimenting early ai programs maclisp began small fixed number data types cons cell atom later termed symbol integer floating-point number later additions included arrays never first-class data types arbitrary-precision integers bignums strings tuples objects except inums implemented pointers data type determined block memory pointed special case small numbers inums programs could interpreted compiled compiled behavior interpreted except local variables lexical default compiled code unless declared special error checking done inline operations car cdr ncomplr compiler mid-1970s introduced fast numeric support lisp languages generating machine code instructions arithmetic rather calling interpretive routines dispatched data type made lisp arithmetic comparable speed fortran scalar operations though fortran array loop implementation remained much faster original version limited 18-bit word memory address pdp-10 considerable effort expended keeping implementation lean simple multics maclisp far larger address space costly use memory processing power pdp-10 exceeded lisp machine invented lisp machine lisp direct descendant maclisp several lisp dialects also use need unify community resulted modern common lisp language maclisp named project mac unrelated apple macintosh mac computer predates decades various lisp systems macintosh particular similarity maclisp
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Programming language topics
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eloquens software eloquens™ text-to-speech software whose first version released 1993 cselt first commercial speech synthesis software able speak italian first commercial product research center cselt field voice technology built diphone-technology aimed reach high computational efficiency result produced voice still robotic natural previous generation voice implemented musa cselt past eloquens applied automatically read timetables italian train stations telephone services provided telecom italia e.g automated address book service nowadays released freeware nowadays typically used spoken comments many youtube videos
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Computational linguistics
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kernel operating system kernel computer program core computer operating system complete control everything system systems one first programs loaded start-up bootloader handles rest start-up well input/output requests software translating data-processing instructions central processing unit handles memory peripherals like keyboards monitors printers speakers critical code kernel usually loaded separate area memory protected access application programs less critical parts operating system kernel performs tasks running processes managing hardware devices hard disk handling interrupts protected kernel space contrast application programs like browsers word processors audio video players use separate area memory user space separation prevents user data kernel data interfering causing instability slowness well preventing malfunctioning application programs crashing entire operating system kernel interface low-level abstraction layer process makes requests kernel called system call kernel designs differ manage system calls resources monolithic kernel runs operating system instructions address space speed microkernel runs processes user space modularity kernel primary function mediate access computer resources including key aspects necessary resource management definition execution domain address space protection mechanism used mediate access resources within domain kernels also provide methods synchronization inter-process communication ipc implementations may within kernel kernel also rely processes running although kernel must provide inter-process communication order provide access facilities provided kernels must also provide running programs method make requests access facilities kernel full access system memory must allow processes safely access memory require often first step virtual addressing usually achieved paging and/or segmentation virtual addressing allows kernel make given physical address appear another address virtual address virtual address spaces may different different processes memory one process accesses particular virtual address may different memory another process accesses address allows every program behave one apart kernel running thus prevents applications crashing many systems program virtual address may refer data currently memory layer indirection provided virtual addressing allows operating system use data stores like hard drive store would otherwise remain main memory ram result operating systems allow programs use memory system physically available program needs data currently ram cpu signals kernel happened kernel responds writing contents inactive memory block disk necessary replacing data requested program program resumed point stopped scheme generally known demand paging virtual addressing also allows creation virtual partitions memory two disjointed areas one reserved kernel kernel space applications user space applications permitted processor address kernel memory thus preventing application damaging running kernel fundamental partition memory space contributed much current designs actual general-purpose kernels almost universal systems although research kernels e.g singularity take approaches perform useful functions processes need access peripherals connected computer controlled kernel device drivers device driver computer program enables operating system interact hardware device provides operating system information control communicate certain piece hardware driver important vital piece program application design goal driver abstraction function driver translate os-mandated abstract function calls programming calls device-specific calls theory device work correctly suitable driver device drivers used things video cards sound cards printers scanners modems lan cards common levels abstraction device drivers 1 hardware side 2 software side example show user something screen application would make request kernel would forward request display driver responsible actually plotting character/pixel kernel must maintain list available devices list may known advance e.g embedded system kernel rewritten available hardware changes configured user typical older pcs systems designed personal use detected operating system run time normally called plug play plug play system device manager first performs scan different hardware buses peripheral component interconnect pci universal serial bus usb detect installed devices searches appropriate drivers device management os-specific topic drivers handled differently kind kernel design every case kernel provide i/o allow drivers physically access devices port memory location important decisions made designing device management system designs accesses may involve context switches making operation cpu-intensive easily causing significant performance overhead computing system call process requests service operating system kernel normally permission run system calls provide interface process operating system operations interacting system require permissions available user level process e.g i/o performed device present system form communication processes requires use system calls system call mechanism used application program request service operating system use machine-code instruction causes processor change mode example would supervisor mode protected mode operating system performs actions like accessing hardware devices memory management unit generally operating system provides library sits operating system normal programs usually c library glibc windows api library handles low-level details passing information kernel switching supervisor mode system calls include close open read wait write actually perform useful work process must able access services provided kernel implemented differently kernel provide c library api turn invokes related kernel functions method invoking kernel function varies kernel kernel memory isolation use impossible user process call kernel directly would violation processor access control rules possibilities important consideration design kernel support provides protection faults fault tolerance malicious behaviours security two aspects usually clearly distinguished adoption distinction kernel design leads rejection hierarchical structure protection mechanisms policies provided kernel classified according several criteria including static enforced compile time dynamic enforced run time pre-emptive post-detection according protection principles satisfy e.g denning whether hardware supported language based whether open mechanism binding policy many support hierarchical protection domains typically implemented using cpu modes many kernels provide implementation capabilities i.e objects provided user code allow limited access underlying object managed kernel common example occurs file handling file representation information stored permanent storage device kernel may able perform many different operations e.g read write delete execute file contents user level application may permitted perform operations e.g may allowed read file common implementation kernel provide object application typically called file handle application may invoke operations validity kernel checks time operation requested system may extended cover objects kernel manages indeed objects provided user applications efficient simple way provide hardware support capabilities delegate mmu responsibility checking access-rights every memory access mechanism called capability-based addressing commercial computer architectures lack mmu support capabilities alternative approach simulate capabilities using commonly supported hierarchical domains approach protected object must reside address space application access kernel also maintains list capabilities memory application needs access object protected capability performs system call kernel checks whether application capability grants permission perform requested action permitted performs access either directly delegating request another user-level process performance cost address space switching limits practicality approach systems complex interactions objects used current operating systems objects accessed frequently expected perform quickly approaches protection mechanism firmware supported instead simulated higher levels e.g simulating capabilities manipulating page tables hardware direct support possible performance implications lack hardware support may issue however systems choose use language-based protection important kernel design decision choice abstraction levels security mechanisms policies implemented kernel security mechanisms play critical role supporting security higher levels one approach use firmware kernel support fault tolerance see build security policy malicious behavior top adding features cryptography mechanisms necessary delegating responsibility compiler approaches delegate enforcement security policy compiler and/or application level often called language-based security lack many critical security mechanisms current mainstream operating systems impedes implementation adequate security policies application abstraction level fact common misconception computer security security policy implemented application regardless kernel support typical computer systems today use hardware-enforced rules programs allowed access data processor monitors execution stops program violates rule e.g. user process read write kernel memory systems lack support capabilities processes isolated using separate address spaces calls user processes kernel regulated requiring use one above-described system call methods alternative approach use language-based protection language-based protection system kernel allow code execute produced trusted language compiler language may designed impossible programmer instruct something violate security requirement advantages approach include disadvantages include examples systems language-based protection include jx microsoft singularity edsger dijkstra proved logical point view atomic lock unlock operations operating binary semaphores sufficient primitives express functionality process cooperation however approach generally held lacking terms safety efficiency whereas message passing approach flexible number approaches either lower- higher-level available well many modern kernels providing support systems shared memory remote procedure calls idea kernel i/o devices handled uniformly processes parallel co-operating processes first proposed implemented brinch hansen although similar ideas suggested 1967 hansen description common processes called internal processes i/o devices called external processes similar physical memory allowing applications direct access controller ports registers cause controller malfunction system crash depending complexity device devices get surprisingly complex program use several different controllers providing abstract interface manage device important interface normally done device driver hardware abstraction layer frequently applications require access devices kernel must maintain list devices querying system way done bios one various system buses pci/pcie usb application requests operation device displaying character kernel needs send request current active video driver video driver turn needs carry request example inter process communication ipc naturally listed tasks features provided many ways differ design implementation principle separation mechanism policy substantial difference philosophy micro monolithic kernels mechanism support allows implementation many different policies policy particular mode operation instance mechanism may provide user log-in attempts call authorization server determine whether access granted policy may authorization server request password check encrypted password stored database mechanism generic policy could easily changed e.g requiring use security token mechanism policy integrated module minimal microkernel basic policies included mechanisms allows running top kernel remaining part operating system applications decide policies adopt memory management high level process scheduling file system management etc. monolithic kernel instead tends include many policies therefore restricting rest system rely per brinch hansen presented arguments favour separation mechanism policy failure properly fulfill separation one major causes lack substantial innovation existing operating systems problem common computer architecture monolithic design induced kernel mode user mode architectural approach protection technically called hierarchical protection domains common conventional commercial systems fact every module needing protection therefore preferably included kernel link monolithic design privileged mode reconducted key issue mechanism-policy separation fact privileged mode architectural approach melds together protection mechanism security policies major alternative architectural approach capability-based addressing clearly distinguishes two leading naturally microkernel design see separation protection security monolithic kernels execute code address space kernel space microkernels try run services user space aiming improve maintainability modularity codebase kernels fit exactly one categories rather found two designs called hybrid kernels exotic designs nanokernels exokernels available seldom used production systems xen hypervisor example exokernel monolithic kernel os services run along main kernel thread thus also residing memory area approach provides rich powerful hardware access developers unix developer ken thompson maintain easier implement monolithic kernel microkernels main disadvantages monolithic kernels dependencies system components bug device driver might crash entire system fact large kernels become difficult maintain monolithic kernels traditionally used unix-like operating systems contain operating system core functions device drivers traditional design unix systems monolithic kernel one single program contains code necessary perform every kernel-related task every part accessed programs put library kernel space device drivers scheduler memory handling file systems network stacks many system calls provided applications allow access services monolithic kernel initially loaded subsystems may needed tuned point fast faster one specifically designed hardware although relevant general sense modern monolithic kernels linux freebsd fall category unix-like operating systems feature ability load modules runtime thereby allowing easy extension kernel capabilities required helping minimize amount code running kernel space monolithic kernel advantages hinge points work monolithic kernel done via system calls interfaces usually kept tabular structure access subsystem within kernel disk operations essentially calls made within programs checked copy request passed system call hence far travel monolithic linux kernel made extremely small ability dynamically load modules also ease customization fact versions small enough fit together large number utilities programs single floppy disk still provide fully functional operating system one popular mulinux ability miniaturize kernel also led rapid growth use linux embedded systems types kernels consist core functions operating system device drivers ability load modules runtime provide rich powerful abstractions underlying hardware provide small set simple hardware abstractions use applications called servers provide functionality particular approach defines high-level virtual interface hardware set system calls implement operating system services process management concurrency memory management several modules run supervisor mode design several flaws limitations microkernel also abbreviated μk uk term describing approach operating system design functionality system moved traditional kernel set servers communicate minimal kernel leaving little possible system space much possible user space microkernel designed specific platform device ever going needs operate microkernel approach consists defining simple abstraction hardware set primitives system calls implement minimal os services memory management multitasking inter-process communication services including normally provided kernel networking implemented user-space programs referred servers microkernels easier maintain monolithic kernels large number system calls context switches might slow system typically generate overhead plain function calls parts really require privileged mode kernel space ipc inter-process communication basic scheduler scheduling primitives basic memory handling basic i/o primitives many critical parts running user space complete scheduler memory handling file systems network stacks micro kernels invented reaction traditional monolithic kernel design whereby system functionality put one static program running special system mode processor microkernel fundamental tasks performed able access necessarily hardware manage memory coordinate message passing processes systems use micro kernels qnx hurd case qnx hurd user sessions entire snapshots system views referred essence microkernel architecture illustrates advantages micro kernels use message passing system sort handle requests one server another message passing system generally operates port basis microkernel example request memory sent port opened microkernel request sent within microkernel steps similar system calls rationale would bring modularity system architecture would entail cleaner system easier debug dynamically modify customizable users needs performing part operating systems like gnu hurd minix mklinux qnx redox os although micro kernels small combination required auxiliary code fact often larger monolithic kernels advocates monolithic kernels also point two-tiered structure microkernel systems operating system interact directly hardware creates not-insignificant cost terms system efficiency types kernels normally provide minimal services defining memory address spaces inter-process communication ipc process management functions running hardware processes handled directly micro kernels proponents micro kernels point monolithic kernels disadvantage error kernel cause entire system crash however microkernel kernel process crashes still possible prevent crash system whole merely restarting service caused error services provided kernel networking implemented user-space programs referred servers servers allow operating system modified simply starting stopping programs machine without networking support instance networking server started task moving kernel move data various applications servers creates overhead detrimental efficiency micro kernels comparison monolithic kernels disadvantages microkernel exist however disadvantages micro kernels extremely context based example work well small single purpose critical systems many processes need run complications process management effectively mitigated microkernel allows implementation remaining part operating system normal application program written high-level language use different operating systems top unchanged kernel also possible dynamically switch among operating systems one active simultaneously computer kernel grows grows size vulnerability trusted computing base besides reducing security problem enlarging memory footprint mitigated degree perfecting virtual memory system computer architectures virtual memory support reduce kernel footprint extensive editing performed carefully remove unneeded code difficult non-obvious interdependencies parts kernel millions lines code early 1990s due various shortcomings monolithic kernels versus microkernels monolithic kernels considered obsolete virtually operating system researchers result design linux monolithic kernel rather microkernel topic famous debate linus torvalds andrew tanenbaum merit sides argument presented tanenbaum–torvalds debate monolithic kernels designed code address space kernel space developers argue necessary increase performance system developers also maintain monolithic systems extremely efficient well written monolithic model tends efficient use shared kernel memory rather slower ipc system microkernel designs typically based message passing performance microkernels poor 1980s early 1990s however studies empirically measured performance microkernels analyze reasons inefficiency explanations data left folklore assumption due increased frequency switches kernel-mode user-mode increased frequency inter-process communication increased frequency context switches fact guessed 1995 reasons poor performance microkernels might well 1 actual inefficiency whole microkernel approach 2 particular concepts implemented microkernels 3 particular implementation concepts therefore remained studied solution build efficient microkernel unlike previous attempts apply correct construction techniques end hierarchical protection domains architecture leads design monolithic kernel significant performance drawback time interaction different levels protection i.e process manipulate data structure 'user mode 'supervisor mode since requires message copying value mid-1990s researchers abandoned belief careful tuning could reduce overhead dramatically recently newer microkernels optimized performance l4 k42 addressed problems hybrid kernels used commercial operating systems microsoft windows nt 3.1 nt 3.5 nt 3.51 nt 4.0 2000 xp vista 7 8 8.1 10 apple inc macos uses hybrid kernel called xnu based upon code osf/1 mach kernel osfmk 7.3 freebsd monolithic kernel similar micro kernels except include additional code kernel-space increase performance kernels represent compromise implemented developers demonstrated pure micro kernels provide high performance types kernels extensions micro kernels properties monolithic kernels unlike monolithic kernels types kernels unable load modules runtime hybrid kernels micro kernels non-essential code kernel-space order code run quickly would user-space hybrid kernels compromise monolithic microkernel designs implies running services network stack filesystem kernel space reduce performance overhead traditional microkernel still running kernel code device drivers servers user space many traditionally monolithic kernels least adding actively exploiting module capability well known kernels linux kernel modular kernel essentially parts built core kernel binary binaries load memory demand important note code tainted module potential destabilize running kernel many people become confused point discussing micro kernels possible write driver microkernel completely separate memory space test going live kernel module loaded accesses monolithic portion memory space adding needs therefore opening doorway possible pollution advantages modular hybrid kernel modules generally communicate kernel using module interface sort interface generalized although particular given operating system always possible use modules often device drivers may need flexibility module interface affords essentially two system calls often safety checks done monolithic kernel may done twice disadvantages modular approach nanokernel delegates virtually services including even basic ones like interrupt controllers timer device drivers make kernel memory requirement even smaller traditional microkernel exokernels still-experimental approach operating system design differ types kernels functionality limited protection multiplexing raw hardware providing hardware abstractions top develop applications separation hardware protection hardware management enables application developers determine make efficient use available hardware specific program exokernels extremely small however accompanied library operating systems see also unikernel providing application developers functionalities conventional operating system major advantage exokernel-based systems incorporate multiple library operating systems exporting different api example one high level ui development one real-time control strictly speaking operating system thus kernel required run computer programs directly loaded executed bare metal machine provided authors programs willing work without hardware abstraction operating system support early computers operated way 1950s early 1960s reset reloaded execution different programs eventually small ancillary programs program loaders debuggers left memory runs loaded rom developed formed basis became early operating system kernels bare metal approach still used today video game consoles embedded systems general newer computers use modern operating systems kernels 1969 rc 4000 multiprogramming system introduced system design philosophy small nucleus upon operating systems different purposes could built orderly manner would called microkernel approach decade preceding unix computers grown enormously power point computer operators looking new ways get people use spare time machines one major developments era time-sharing whereby number users would get small slices computer time rate appeared connected slower machine development time-sharing systems led number problems one users particularly universities systems developed seemed want hack system get cpu time reason security access control became major focus multics project 1965 another ongoing issue properly handling computing resources users spent time staring terminal thinking input instead actually using resources computer time-sharing system give cpu time active user periods finally systems typically offered memory hierarchy several layers deep partitioning expensive resource led major developments virtual memory systems commodore amiga released 1985 among first certainly successful home computers feature advanced kernel architecture amigaos kernel executive component exec.library uses microkernel message-passing design kernel components like graphics.library direct access hardware memory protection kernel almost always running user mode special actions executed kernel mode user-mode applications ask operating system execute code kernel mode design phase unix programmers decided model every high-level device file believed purpose computation data transformation instance printers represented file known location data copied file printed systems provide similar functionality tended virtualize devices lower level devices files would instances lower level concept virtualizing system file level allowed users manipulate entire system using existing file management utilities concepts dramatically simplifying operation extension paradigm unix allows programmers manipulate files using series small programs using concept pipes allowed users complete operations stages feeding file chain single-purpose tools although end result using smaller programs way dramatically increased flexibility well ease development use allowing user modify workflow adding removing program chain unix model operating system consists two parts first huge collection utility programs drive operations second kernel runs programs unix programming standpoint distinction two fairly thin kernel program running supervisor mode acts program loader supervisor small utility programs making rest system provide locking i/o services programs beyond kernel n't intervene user space years computing model changed unix treatment everything file byte stream longer universally applicable although terminal could treated file byte stream printed read seem true graphical user interface networking posed another problem even network communication compared file access low-level packet-oriented architecture dealt discrete chunks data whole files capability computers grew unix became increasingly cluttered code also modularity unix kernel extensively scalable kernels might 100,000 lines code seventies eighties kernels modern unix successors like linux 13 million lines modern unix-derivatives generally based module-loading monolithic kernels examples linux kernel many distributions well berkeley software distribution variant kernels freebsd dragonflybsd openbsd netbsd macos apart alternatives amateur developers maintain active operating system development community populated self-written hobby kernels mostly end sharing many features linux freebsd dragonflybsd openbsd netbsd kernels and/or compatible apple first launched classic mac os 1984 bundled macintosh personal computer apple moved nanokernel design mac os 8.6 modern macos originally named mac os x based darwin uses hybrid kernel called xnu created combining 4.3bsd kernel mach kernel microsoft windows first released 1985 add-on ms-dos dependence another operating system initial releases windows prior windows 95 considered operating environment confused operating system product line continued evolve 1980s 1990s windows 9x series adding 32-bit addressing pre-emptive multitasking ended release windows 2000 microsoft also developed windows nt operating system similar interface intended high-end business users line started release windows nt 3.1 1993 introduced general users release windows xp october 2001—replacing windows 9x completely different much sophisticated operating system line continues windows 10 architecture windows nt kernel considered hybrid kernel kernel contains tasks window manager ipc managers client/server layered subsystem model supervisory program supervisor computer program usually part operating system controls execution routines regulates work scheduling input/output operations error actions similar functions regulates flow work data processing system historically term essentially associated ibm line mainframe operating systems starting os/360 operating systems supervisor generally called kernel 1970s ibm abstracted supervisor state hardware resulting hypervisor enabled full virtualization i.e capacity run multiple operating systems machine totally independently hence first system called virtual machine vm although mach developed carnegie mellon university 1985 1994 best-known general-purpose microkernel microkernels developed specific aims l4 microkernel family mainly l3 l4 kernel created demonstrate microkernels necessarily slow newer implementations fiasco pistachio able run linux next l4 processes separate address spaces additionally qnx microkernel principally used embedded systems open-source software minix originally created educational purposes focussed highly reliable self-healing microkernel os
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Computer architecture
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nuodb nuodb database company based cambridge massachusetts founded 2008 nuodb recognized gartner magic quadrant technology used dassault systèmes kodiak uae exchange alfa systems firm founded 2008 nimbusdb changed name nuodb 2011 company co-founders barry s. morris became company ceo jim starkey nuodb based cambridge massachusetts nuodb patented elastically scalable database patent filed march 8 2011 approved july 17 2012 u.s. patent 8,224,860 states inventor jim starkey 2012 firm received 12 million total venture capital 2013 gartner listed nuodb niche player magic quadrant operational database management systems boston business journal mass high tech named nuodb one 2014 innovation stars february 2014 nuodb announced extension series b funding round led dassault systèmes round added 14.2 million company funding morgenthaler ventures hummer winblad venture partners longworth venture partners participated round 2015 gartner listed nuodb time visionary magic quadrant operational database management systems morris company founding ceo became executive chairman july 2015 bob walmsley previously executive vice president sales services promoted ceo nuodb raised 17 million financing round 2016 existing investors including dassault systèmes hummer winblad venture partners longworth venture partners morgenthaler ventures time company raised total 59.7 million funding causesquare announced partnership nuodb 2017 nuodb became official database social engagement platform connects causes organizations donors volunteers nuodb elastic sql database cloud applications nuodb database sql compliant called newsql distributed object architecture works cloud means new server added order scale-out database database runs faster database scales without sharding database distributes tasks amongst several processors avoid bottlenecks data uses peer-to-peer messaging route tasks nodes acid compliant database uses tiered approach — comprising multiple redundant tiers transaction engines te storage managers sm approach helps scale data predictably cloud nuodb domains consist several redundant tes sms run platform adding database capacity done adding tes sms nuodb 2.6 release added support active-active database deployments across multiple amazon web services aws availability zones unlike database systems nuodb makes possible expand databases adding servers rather simply replacing hardware system designed align – expand upon – ibm computer scientist edgar f. codd ’ 12 rules relational databases adds ability run anywhere elastic scalability nonstop availability single logical database distributed security system process 1 million transactions per second available free developer version community edition professional paid version enterprise version community edition expanded january 31 2017 enable scale-out across multiple hosts
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Databases
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ats programming language ats applied type system programming language designed unify programming formal specification ats support combining theorem proving practical programming use advanced type systems past version computer language benchmarks game demonstrated performance ats comparable c c++ programming languages using theorem proving strict type checking compiler detect prove implemented functions susceptible bugs division zero memory leaks buffer overflow forms memory corruption verifying pointer arithmetic reference counting program compiles additionally using integrated theorem-proving system ats ats/lf programmer may make use static constructs intertwined operative code prove function attains specification ats derived mostly ml ocaml programming languages earlier language dependent ml author incorporated language latest version ats1 anairiats released v0.2.12 2015-01-20 first version ats2 postiats released september 2013 primary focus ats support theorem proving combination practical programming theorem proving one prove instance implemented function produce memory leaks also prevents bugs might otherwise found testing incorporates system similar proof assistants usually aim verify mathematical proofs—except ats uses ability prove implementations functions operate correctly produce expected output simple example function using division programmer may prove divisor never equal zero preventing division zero error let say divisor x computed 5 times length list one prove case non-empty list x non-zero since x product two non-zero numbers 5 length practical example would proving reference counting retain count allocated block memory counted correctly pointer one know quite literally prove object deallocated prematurely memory leaks occur benefit ats system since theorem proving occurs strictly within compiler effect speed executable program ats code often harder compile standard c code compiles programmer certain running correctly degree specified proofs assuming compiler runtime system correct ats proofs separate implementation possible implement function without proving programmer desires according author hongwei xi ats efficiency largely due way data represented language tail-call optimizations generally important efficiency functional programming languages data stored flat unboxed representation rather boxed representation codice_1 expresses predicates algebraic types predicates pseudo‑code somewhat similar ats source see valid ats source ats code fact int int proof type non tail-recursive factorial proposition theorem proving construction dataprop evaluation fact1 n-1 returns pair proof_n_minus_1 result_of_n_minus_1 used calculation fact1 n proofs express predicates proposition fact n r implies fact n r remember dataprop fact int int note int x also int x monovalued type int x value fun fact n nat n n int n r int fact n r int r implement main0 argc argv added single file compiled follows compilation work various back end c compilers e.g gcc garbage collection used unless explicitly stated -d_ats_gcats compiles gives expected result val x int char 15 c // x.0 15 x.1 c' '| separator functions return wrapped result value evaluation predicates ... universal quantification sortdef nat int 0 // prelude ∀ ∈ int ... // .. ∀ b ∈ type ... fun ype ptr_get0 l addr pf l p ptr l l case+ val+ type+ viewtype+ ... dataviews often declared encode recursively defined relations linear resources nowiki dataview array_v viewt ype+ int addr /nowiki datatypes lists dataviewtype similar datatype linear dataviewtype programmer allowed explicitly free deallocate safe manner memory used storing constructors associated dataviewtype local variables stack array allocation see val var declarations
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Programming language topics
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cyber security agency singapore cyber security agency singapore csa singaporean government agency prime minister office administratively managed ministry communications information provides centralised oversight national cyber security functions works public private sector leads protect singapore ’ critical services energy banking sectors formed 1 april 2015 agency also engages various industries stakeholders heighten cyber security awareness well ensure development singapore ’ cyber security headed ministry defence deputy secretary technology david koh minister-in-charge s. iswaran ministry communications information cyber security agency took functions previously carried singapore infocomm technology security authority sitsa ministry home affairs sitsa set 2009 national specialist authority overseeing operational security csa also took roles undertaken then-infocomm development authority ida singapore computer emergency response team facilitates detection resolution prevention security-related incidents internet agency builds upon government ’ cyber security capabilities include strategy policy development cyber security operations industry development outreach well public communications engagement organised events singapore international cyber week sicw 2016 5,000 attendees close 50 countries sicw also saw launch singapore ’ cybersecurity strategy second edition sicw held 18 21 september 2017 singapore also host 2nd asean ministerial conference cybersecurity year october 2016 prime minister launched singapore ’ cybersecurity strategy aim create resilient trusted cyber environment singapore four pillars underpin strategy part singapore cybersecurity strategy internet access civil servants work station cut-off david koh chief executive newly formed cyber security agency said officials realised much data secure way secure attack surface like building zillion windows doors fire escapes security experts commented move may raise defense cyber attack slightly risk damaging productivity civil servants working four dozen statutory boards cutting people serve
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Computer security
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hierarchical cluster engine project hierarchical cluster engine hce foss complex solution construct custom network mesh distributed network cluster structure several relations types nodes formalize data flow processing goes upper node level central source point nodes backward formalize management requests handling multiple source points support native reducing multiple nodes results aggregation duplicates elimination sorting internally support powerful full-text search engine data storage provide transactions-less transactional requests processing support flexible run-time changes cluster infrastructure many languages bindings client-side integration apis one product build c++ language project became successor associative search machine asm full-text web search engine project developed 2006 2012 ioix ukraine set applications used construct different distributed solutions like remote processes execution management data processing including text mining nlp web sites crawling including incremental periodic flexible adaptive scheduling rss feeds custom structured web sites data scraping include pre-defined custom scrapers xpath templates sequential optimized scraping algorithms web-search engine complete cycle including crawling scraping distributed search index based sphinx indexing engine corporate integrated full-text search based distributed sphinx engine index many another applied solutions similar business logic heart main component hce project hce-node application application integrates complete set base functionality support network infrastructure hierarchical cluster construction full-text search system integration hce application area hierarchical cluster engine hce-node roles cluster structure internally hce-node application contains seven basic handler threads handler acts special black-box messages processor/dispatcher used combination work one five different roles node dtm dc applications provided set functional tests demo operations automation scripts based linux shell bundle distribution provided zip archive needs environmental support get functionality ready linux os daemon application implements business-logic functionality distributed web crawler document data processor based dtm application main functionality hce-node drce functional object functionality uses web crawling processing another related tasks isolated session executable modules common business logic encapsulation also crawler contains raw contents storage subsystem based file system customized support key-value storage sql application uses several drce clusters construct network infrastructure mysql sqlite back-end indexed data sites urls contents configuration properties well key-value data storage processed contents pages documents additionally administrative user interface web-application available manage easy flexible way also ui implements several automation data collect process algorithms using schedules aggregation scraped data several projects creation data archives exporting data external sql database custom schema many statistical reports periodic data crawling scraping activity many linux os multi-thread daemon application implements business-logic functionality tasks management uses drce cluster execution environment manage tasks remote processes implements general management operations distributed tasks scheduling execution state check os resources monitoring application used parallel tasks execution state monitoring hierarchical network cluster infrastructure custom nodes connection schema multipurpose application aimed cover needs projects big data computations distributed data processing multi-host data processing os system resources balancing limitations supports several balancing modes including multicast random round-robin system resource usage algorithms also provides high level state check statistics diagnostic automation based natural hierarchy relations nodes supports messages routing tasks data balancing method tasks management set different role functionality separated console applications united chains get sequential data processing server-side functionality used self-sufficient tools utilities designed get common functional units typical web projects need get huge data web another sources pars convert process supports unified input-output interface json format messages interaction first implementation utilities application highlighter utility get fast parallel multi-algorithmic textual patterns highlighting provides cli ui works filter console tool uses json format protocol messages input output interaction highlight algorithm text processing gets search query string textual context input returns textual content marks entrances patterns search query additional stat information patterns usually lexical words depend stemming tokenizing processes complex constructions several pre-configured vm images vmware virtualbox uploaded get start process faster user name “ root ” password target user dts archive “ hce ” password vm files zipped gnu general public license version 2
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Web technology
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industry standard architecture industry standard architecture isa 16-bit internal bus ibm pc/at similar computers based intel 80286 immediate successors 1980s bus largely backward compatible 8-bit bus 8088-based ibm pc including ibm pc/xt well ibm pc compatibles originally referred pc/at-bus also termed i/o channel ibm isa term coined retronym competing pc-clone manufacturers late 1980s early 1990s reaction ibm attempts replace at-bus new incompatible micro channel architecture 16-bit isa bus also used 32-bit processors several years attempt extend 32 bits called extended industry standard architecture eisa successful however later buses vesa local bus pci used instead often along isa slots mainboard derivatives bus structure still used ata/ide pcmcia standard compact flash pc/104 bus internally within super i/o chips isa bus developed team led mark dean ibm part ibm pc project 1981 compaq created term industry standard architecture isa replace pc compatible isa originated 8-bit system 16-bit version ibm bus introduced release ibm pc/at 1984 1988 32-bit extended industry standard architecture eisa standard proposed gang nine group pc-compatible manufacturers included compaq process retroactively renamed bus isa avoid infringing ibm trademark pc/at computer ibm designed 8-bit version buffered interface motherboard buses intel 8088 16/8 bit cpu ibm pc pc/xt 16-bit version upgrade motherboard buses intel 80286 cpu used ibm isa bus therefore synchronous cpu clock sophisticated buffering methods implemented chipsets interface isa much faster cpus isa designed connect peripheral cards motherboard allows bus mastering first 16 mb main memory addressable original 8-bit bus ran 4.77 mhz clock 8088 cpu ibm pc pc/xt original 16-bit bus ran cpu clock 80286 ibm pc/at computers 6 mhz first models 8 mhz later models ibm rt pc also used 16-bit bus isa also used non-ibm compatible machines motorola 68k-based apollo 68020 amiga 3000 68030 workstations short-lived hobbit later powerpc-based bebox companies like dell improved bus performance 1987 ibm replaced bus proprietary micro channel architecture mca mca overcame many limitations apparent isa also effort ibm regain control pc architecture pc market mca far advanced isa many features would later appear pci however mca also closed standard whereas ibm released full specifications circuit schematics isa computer manufacturers responded mca developing extended industry standard architecture eisa later vesa local bus vlb vlb used electronic parts originally intended mca component manufacturers already equipped manufacture eisa vlb backwards-compatible expansions isa bus users isa-based machines know special information hardware adding system handful devices essentially plug-n-play rare users frequently configure parameters adding new device irq line i/o address dma channel mca done away complication pci actually incorporated many ideas first explored mca though directly descended eisa trouble configuration eventually led creation isa pnp plug-n-play system used combination modifications hardware system bios operating system software automatically manage resource allocations reality isa pnp could troublesome become well-supported architecture final days pci slots first physically-incompatible expansion ports directly squeeze isa motherboard first motherboards largely isa including pci slots mid-1990s two slot types roughly balanced isa slots soon minority consumer systems microsoft pc 99 specification recommended isa slots removed entirely though system architecture still required isa present vestigial way internally handle floppy drive serial ports etc. software compatible lpc bus created isa slots remained years towards turn century common see systems accelerated graphics port agp sitting near central processing unit array pci slots one two isa slots near end late 2008 even floppy disk drives serial ports disappearing extinction vestigial isa lpc bus chipsets horizon pci slots rotated compared isa counterparts—pci cards essentially inserted upside-down allowing isa pci connectors squeeze together motherboard one two connectors used slot time allowed greater flexibility attachment ata hard disk interface directly descended 16-bit isa pc/at ata origins hardcards integrated hard disk drive hdd hard disk controller hdc onto one card best awkward worst damaging motherboard isa slots designed support heavy devices hdds next generation integrated drive electronics drives moved drive controller drive bay used ribbon cable simple interface board connect isa slot ata basically standardization arrangement plus uniform command structure software interface hdc within drive ata since separated isa bus connected directly local bus usually integration chipset much higher clock rates data throughput isa could support ata clear characteristics 16-bit isa 16-bit transfer size signal timing pio modes interrupt dma mechanisms pc/xt-bus eight-bit isa bus used intel 8086 intel 8088 systems ibm pc ibm pc xt 1980s among 62 pins demultiplexed electrically buffered versions 8 data 20 address lines 8088 processor along power lines clocks read/write strobes interrupt lines etc power lines included −5 v ±12 v order directly support pmos enhancement mode nmos circuits dynamic rams among things xt bus architecture uses single intel 8259 pic giving eight vectorized prioritized interrupt lines four dma channels originally provided intel 8237 3 dma channels brought xt bus expansion slots 2 normally already allocated machine functions diskette drive hard disk controller pc/at-bus 16-bit 80286- version pc/xt bus introduced ibm pc/at bus officially termed i/o channel ibm extends xt-bus adding second shorter edge connector in-line eight-bit xt-bus connector unchanged retaining compatibility 8-bit cards second connector adds four additional address lines total 24 8 additional data lines total 16 also adds new interrupt lines connected second 8259 pic connected one lines first 4 × 16-bit dma channels well control lines select 8- 16-bit transfers 16-bit bus slot originally used two standard edge connector sockets early ibm pc/at machines however popularity at-architecture 16-bit isa bus manufacturers introduced specialized 98-pin connectors integrated two sockets one unit found almost every at-class pc manufactured mid-1980s isa slot connector typically black distinguishing brown eisa connectors white pci connectors motherboard devices dedicated irqs present slots 16-bit devices use either pc-bus pc/at-bus irqs therefore possible connect 6 devices use one 8-bit irq 5 devices use one 16-bit irq time 4 devices may use one 8-bit dma channel 3 devices use one 16-bit dma channel originally bus clock synchronous cpu clock resulting varying bus clock frequencies among many different ibm clones market sometimes high 16 20 mhz leading software electrical timing problems certain isa cards bus speeds designed later motherboards integrated chipsets used separate clock generator clock divider either fixed isa bus frequency 4 6 8 mhz allowed user adjust frequency via bios setup used higher bus frequency isa cards certain hercules-compatible video cards instance could show significant performance improvements memory address decoding selection 8 16-bit transfer mode limited 128 kib sections leading problems mixing 8- 16-bit cards could co-exist 128 kib area memcs16 line required set based value la17-23 isa still used today specialized industrial purposes 2008 iei technologies released modern motherboard intel core 2 duo processors addition special i/o features equipped two isa slots marketed industrial military users invested expensive specialized isa bus adaptors available pci bus versions similarly adek industrial computers releasing motherboard early 2013 intel core i3/i5/i7 processors contains one non-dma isa slot pc/104 bus used industrial embedded applications derivative isa bus utilizing signal lines different connectors lpc bus replaced isa bus connection legacy i/o devices recent motherboards physically quite different lpc looks like isa software peculiarities isa 16 mib dma limit corresponds full address space intel 80286 cpu used original ibm likely stick around explained history section isa basis development ata interface used ata a.k.a ide recently serial ata sata hard disks physically ata essentially simple subset isa 16 data bits support exactly one irq one dma channel 3 address bits isa subset ata adds two ide address select chip select lines unique signal lines specific ata/ide hard disks cable select/spindle sync line addition physical interface channel ata goes beyond far outside scope isa also specifying set physical device registers implemented every ata ide drive full set protocols device commands controlling fixed disk drives using registers ata device registers accessed using address bits address select signals ata physical interface channel operations ata hard disks performed using ata-specified protocols ata command set earliest versions ata standard featured simple protocols basic command set comparable command sets mfm rll controllers preceded ata controllers latest ata standards much complex protocols instruction sets include optional commands protocols providing advanced optional-use features sizable hidden system storage areas password security locking programmable geometry translation deviation isa ata isa bus remained locked single standard clock rate backward hardware compatibility ata interface offered many different speed modes could select among match maximum speed supported attached drives kept adding faster speeds later versions ata standard 133 mb/s ata-6 latest forms ata ran much faster isa provided connected directly local bus faster isa bus 16-bit ata/ide interface 8-bit xt-ide also known xta interface hard disks nearly popular ata become xt-ide hardware fairly hard find xt-ide adapters available 8-bit isa cards xta sockets also present motherboards amstrad later xt clones well short-lived line philips units xta pinout similar ata eight data lines two address lines used physical device registers completely different meanings hard drives seagate st351a/x could support either type interface selected jumper many later successor motherboards integrated hard drive interface relied separate hard drive interface plugged isa/eisa/vlb slot even 80486 based units shipped mfm/rll interfaces drives instead increasingly common at-ide commodore built xt-ide based peripheral hard drive memory expansion unit a590 amiga 500 500+ computers also supported scsi drive at-ide type interfaces entered keyboard-cased amiga line upon introduction a600 a1200 integrated interface 44 pin connector many owners removed 2,5 inch bracket installed 3,5 inch drive adapter cable pcmcia specification seen superset ata standard pcmcia hard disk interfaces included pcmcia flash drives allows mutual configuration port drive ata mode de facto extension pcmcia flash drives additionally allow simple ata mode enabled pulling single pin low pcmcia hardware firmware unnecessary use ata drive connected ata port pcmcia flash drive ata adapters thus simple inexpensive guaranteed work every standard pcmcia flash drive adapters used generic pcmcia ports pcmcia interface much complex ata although modern computers physical isa buses ibm compatible computers — x86 x86-64 non-mainframe non-embedded — isa buses allocated physical address space embedded controller chips southbridge cpus provide services temperature monitoring voltage readings buses isa devices ieee started standardization isa bus 1985 called p996 specification however despite even books published p996 specification never officially progressed past draft status still existing user base old computers isa cards still manufactured e.g usb ports complete single board computers based modern processors usb 3.0 sata
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Computer architecture
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ubuntu mobile ubuntu mobile internet device edition discontinued ubuntu distribution planned run intel mobile internet device platform x86 mobile computers based intel atom processor planned use gnome framework hildon basis gui equipment producers would able customize distributions including options flash java custom interfaces ubuntu mobile stopped development 2009 successor ubuntu phones announced january 2 2013 according canonical ubuntu mobile would provide uncompromised web 2.0 experience include features web browsing email media camera voip instant messaging gps blogging digital tv games contacts calendars regular software updates designed fully operable using simple touchscreen interface june 2008 ubuntu mobile 8.04 released ubuntu mobile ended active development 2009 9.10 alpha 6 mark shuttleworth announced ubuntu 14.04 ubuntu support smartphones tablets smart tvs smart screens car head units smartwatches resulted successor ubuntu touch project announced january 2 2013
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Operating systems
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boot image control boot image control strategy common way reduce total cost ownership organizations large numbers similar computers used users common needs e.g large corporation government agency considered part enterprise application integration larger shops use term since applications part boot image modify boot image desktop os windows vista includes tools boot image control displacing third party tools mac os always flexible handling boot drives simplifying control reducing need move boot images around drives increasingly boot image control network operating system function often large computer vendor required explain bid response rfp intend simplify purchaser boot image control problems attendant service costs total cost ownership correlates strongly total number different images total number computers major cost concern three basic strategies commonly advised organizations closely track control set common standards acquisition new computer hardware typically practice thin client strategy strategy reduce total cost operations depends several factors departmental boot image strategy seems flexible complexity creating managing several large boot images determining department needs upgrade applications easily outweigh especially users object try subvert discipline waiting regular boot turn upgrade machines user allowed discipline soon degrades effectively bunch home computer whose issues really diagnosable comparable situation thin clients may become practical answer many organizations use thin clients applications require high security involve unreliable users repurpose older machines continued use much simplifies boot image control facilitating centralized management computers many advantages control images simpler disadvantages thin clients many organizations try gain advantages thin clients without disadvantages treating many standard machines terminals much greater capabilities buy new computers put demanding applications administrators perform regular often bi-annual boot turn re-images many older off-spec machines new hardware deployed higher-end use procedure called cascading oldest hardware repurposed simpler software let continue use less demanding access-controlled applications subjects much rigorous control minimize number images total cost operations correlates strongly total number different images total number computers minimize number images requires additional discipline desktop computing increasingly relying web services making thin client approach viable departmental boot images may remain simply instantiate part semantic service-oriented architecture especially larger organizations service component architecture would simplify implementation control mechanisms especially single application language like java used custom applications enterprise importantly shift software service large vendors means applications tied machines number variant boot images required applications installed reduced open configuration technologies bitfrost openid even xmpp would also simplify configuration boot images authentication would longer dealt desktop/laptop device large system vendors increasingly provide dvds boot image standard machine shipped customer usually includes tools diagnose changes machine download drivers
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Operating systems
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citrix systems citrix systems inc. american multinational software company provides server application desktop virtualization networking software service saas cloud computing technologies citrix solutions claimed use 400,000 clients worldwide including 99 fortune 100 98 fortune 500 company founded richardson texas 1989 ed iacobucci served chairman departure 2000 began developing remote access products microsoft operating systems licensing source code microsoft partnership company throughout history 1990s citrix came prominence industry leader thin client technology enabling purpose-built devices access remote servers resources company launched first initial public offering 1995 competitors experienced large revenue increases 1995 1999 citrix acquired sequoia software corp. 2001 expertcity provider remote desktop products 2003 followed dozen acquisitions 2005 2012 allowed citrix expand server desktop virtualization cloud computing infrastructure service software service offerings 2014 citrix acquired framehawk used technology improve delivery virtual desktops applications wireless networks 2016 part us 1.8 billion product deal logmein citrix spun goto product line new business entity entitled getgo 2017 citrix completed merger getgo logmein products citrix corporate headquarters fort lauderdale florida santa clara california subsidiary operations california massachusetts additional development centers australia canada denmark germany india united kingdom citrix january 2018 reported revenue continuing operations 2.82 billion fiscal year 2017 compared 2.74 billion fiscal year 2016 3 increase april 2017 company employed approximately 8,100 employees worldwide citrix founded richardson texas 1989 former ibm developer ed iacobucci 3 million funding following initial setup development iacobucci moved company former home coral springs florida company first employees five engineers ibm iacobucci convinced join team iacobucci served chairman company roger roberts became ceo citrix 1990 citrix originally named citrus changed name existing company claimed trademark rights citrix name portmanteau citrus unix company first product citrix multiuser extension os/2 developed two years citrix licensed os/2 source code microsoft developed independent computing architecture ica protocol citrix multiuser multiuser allowed multiple users working separate computers remote access software server even computers built run os/2 three days product launched 1991 microsoft announced would switching os/2 windows switch made multiuser nearly unusable without significant changes make compatible windows dos company discussed closing 1991 investments intel microsoft kleiner perkins caufield byers among others allowed company work new version multiuser multi-win version 2.0 released 1992 compatible dos applications allowed five users 1993 citrix released new remote applications server winview ability run dos windows applications 1994 company yearly revenue equaled us 10 million company launched winframe multi-user operating system based microsoft windows nt 1995 new product allowed 15 users first thin client windows citrix initial public offering december 1995 company share price doubled 15 30 mid-1990s citrix became leader growing industry competitors company revenues doubled year year 1995 1999 following weeks discussions iacobucci able persuade microsoft agree license citrix technology windows nt server 4.0 resulted windows terminal server edition 1998 agreement allowed citrix keep position marketplace nt 4.0 compatible citrix also earned 75 million agreement along royalty arrangement valued approximately 100 million citrix released metaframe 1.0 conjunction terminal server edition due weaknesses microsoft remote desktop protocol rdp terminal server edition worked best using ica protocol developed citrix found metaframe meant citrix technology purchased installed machines running terminal server edition 1997 company opened new headquarters fort lauderdale florida also opened offices sydney london paris year 1998 mark templeton became ceo citrix serving vice president marketing also 1998 licensed ica protocol ibm key tronics citrix licensed ica protocol motorola use digital wireless handsets 1999 1999 thin-client model citrix used became software trend company customers increased 15 million major clients included sears chevron sudden drop stocks 2000 led iacobucci leaving company ceo mark templeton demoted president senior executive officer templeton later reinstated 2001 2001 citrix acquired sequoia software corp. 185 million year released metaframe xp new platform using metaframe technology later rebranded citrix presentation server 2005 july 9 2002 citrix announced 10 job cut time company employed 1,900 workers announcement stock hit five-year low citrix acquired expertcity provider remote desktop products december 2003 225 million cash stock acquisition largest company date acquisition citrix gained expertcity existing products gotomypc gotoassist expertcity became citrix online division company 2004 company introduced citrix gotomeeting 2005 2012 company acquired dozen companies allowed expand new markets citrix acquired acceleration hardware maker netscaler 2005 allowed company offer optimized application delivery company entered server desktop virtualization market purchase xensource august 2007 citrix expanded cloud infrastructure service iaas offerings august 2010 acquisition vmlogix february 2011 citrix entered european software service saas market acquisition netviewer 2007 company opened headquarters silicon valley 2008 company changed name presentation server product line xenapp also 2008 citrix announced expanded alliance microsoft desktop virtualization solutions january 29 2009 citrix announced 460 employee positions would cut comprising 10 workforce august 2010 citrix announced partnership google bring company products chrome os devices july 14 2015 citrix added full support windows 10 desktop virtualization products company became leader iaas acquisition cloud.com provider cloud infrastructure companies july 2011 citrix began offering vdi-in-a-box small medium businesses acquisition kaviza may 2011 company acquired technology cloud-based file sharing storage purchase sharefile october 2011 may 2012 citrix acquired virtual computer maker intelligent desktop virtualization technology used company xenclient enterprise edition citrix entered mobile video telecom markets june 2012 company acquired bytemobile also 2012 company acquired zenprise zenprise mobile application management mam technology released xenmobile february 2013 citrix acquired framehawk january 2014 order use company technology improve delivery virtual desktops applications wireless networks including cellular speed quality may poor may 2014 citrix acquired scalextreme bolster cloud capabilities core business unit xendesktop xenapp auto scaling patching automation complex deployments cloud january 29 2015 citrix announced 700 full-time 200 contractor positions would eliminated constituted 10 workforce cuts expected save 90 100 million year two hundred layoffs occurred fort lauderdale florida company headquartered company 10,081 employees february 2015 december 2015 citrix employed approximately 9,500 people noted november restructure due eliminate nearly 700 full-time jobs december 31 2018 citrix approximately 8,200 employees citrix reported net income 251.7 million 2014 339.5 million 2013 july 2015 company announced several changes board directors including robert calderoni becoming executive chairman adding jesse cohn senior partner activist hedge fund elliott management month company announced president ceo mark templeton would retire replacement found october 21 company named executive chairman robert calderoni interim president ceo january 2016 kirill tatarinov former microsoft executive named president ceo citrix joined company board calderoni remained executive chairman board july 2016 part deal boston-based saas company logmein citrix announced spun goto product line included gotomeeting gotowebinar gotowebcast gototraining gotoassist gotomypc wholly owned subsidiary called getgo february 2017 citrix completed merger getgo became subsidiary logmein transaction valued approximately 1.8 billion david henshall became company ceo july 2017 also 2017 citrix expanded partnership google may google announced would add support run citrix xenapp chrome web browser including graphics processing unit acceleration july companies announced working allow citrix cloud deploy virtualized apps desktops google cloud october 2017 citrix told regulators plans lay staff across functions consolidate offices fall 2017 2018 company carried layoffs raleigh north carolina office closures santa barbara california tempe arizona citrix unveiled citrix analytics security software 2017 citrix synergy conference orlando florida may 2017 software detects responds security threats relying artificial intelligence 2018 citrix changed names products represent shift cloud operating model company stated made name changes present unified product line end users create manage deploy workspaces apps data single console company dropped xen netscaler brand names xenapp xendesktop became citrix virtual apps desktops xenmobile became citrix endpoint management sharefile integration became citrix content collaboration xenserver became citrix hypervisor cedexis became citrix intelligent traffic management netscaler products kept identities yet netscaler brand name replaced citrix citrix governed ten member board directors citrix headquarters fort lauderdale florida santa clara california united states offices california north carolina citrix research development centers located u.s. australia india japan greece united kingdom citrix organized three units workspace services delivery network mobility apps citrix licenses services products directly clients including professionals smes companies called value-added resellers resell products services adding additional features citrix publicly traded ticker symbol ctxs 2014 company ranked 741 fortune 1000 1,793 forbes global 2000 citrix revenue 2015 equaled us 3.28 billion increase 3.14 billion 2014 2.91 billion 2013 citrix expanded added new technologies services number mergers acquisitions first acquisition datapac 1997 citrix purchased order utilize datapac technology position asia-pacific region major acquisitions include expertcity 2004 netscaler 2005 xensource 2007 sharefile 2011 2015 citrix acquired nearly 50 companies november 2018 citrix paid 200m acquire sapho software startup develops micro apps workers citrix creates software allows individuals enterprise work collaborate remotely regardless device network main areas company works desktop apps desktop service daas networking cloud software service saas citrix offers number products related desktop application virtualization tools allow access windows desktops applications independently machine actually device operating system citrix xenapp provides application virtualization integrated part xendesktop citrix xendesktop citrix vdi-in-a-box xenclient provide desktop virtualization desktopplayer mac allows online offline access windows virtual desktops macs citrix workspace cloud platform building delivering desktops applications cloud sharefile allows companies organizations sync share files xenmobile offers mobile app device management citrix receiver client software allows universal access virtual applications desktops appdna software provides application migration management citrix technology enables service providers provide desktop service daas offerings customers including business apps desktops products include worx mobile apps secure email browser document sharing citrix workspace suite mobile workspaces citrix products related cloud computing networking include citrix xenserver server virtualization netscaler brand network appliances including wan optimization devices software-defined wan delivery equipment application delivery controllers adc gateways appfirewall web application firewall managed cloud management software citrix cloud company also bytemobile adaptive traffic management aims optimize mobile video services traffic management policy control caching bytemobile insight provides mobile data subscriber analytics citrix software service saas products focused collaboration communications offerings include podio cloud-based collaboration service openvoice provides audio conferencing company philanthropic activities include corporate giving—such corporate donations in-kind gifts—and employee match programs addition citrix employees allowed take two paid volunteer days year participate company annual global day impact —an event encourages citrix employees volunteer local communities near fort lauderdale headquarters citrix provided business training non-profit teams particular company helped local non-profit organization launch computer wheels offer training low-income neighborhoods 2007 company connected broward county florida neighborhood agogo ghana donated technology training furthermore company raleigh office began program called project code 2014 leads youth local boys girls clubs coding exercises teaches computer science addition philanthropic activities citrix donated open-source technology non-profit software organizations continue development gain contributors citrix gave cloudstack apache foundation 2012 xen hypervisor linux foundation 2013
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Distributed computing architecture
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xkms xml key management specification xkms uses web services framework make easier developers secure inter-application communication using public key infrastructure pki xml key management specification protocol developed w3c describes distribution registration public keys services access xkms compliant server order receive updated key information encryption authentication xkms consists two parts x-krss defines protocols needed register public key information x-krss generate key material making key recovery easier created manually x-kiss outlines syntax applications use delegate tasks needed process key information element xml signature trust service cases goal xkms allow complexity traditional pki implementations offloaded client external service approach originally suggested diffie hellman new directions paper generally considered impractical time leading commercial development focusing certificate based approach proposed loren kohnfelder team developed original xkms proposal submitted w3c included warwick ford phillip hallam-baker editor brian lamacchia architectural approach closely related mit pgp key server originally created maintained brian lamacchia realization xml closely related saml first edition also edited hallam-baker time xkms proposed security infrastructure defined entirely new soap protocol web services result large part xkms specification concerned definition security 'bindings specific web services protocols
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Computer security
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information security information security sometimes shortened infosec practice protecting information mitigating information risks part information risk management typically involves preventing least reducing probability unauthorized/inappropriate access use disclosure disruption deletion/destruction corruption modification inspection recording devaluation although may also involve reducing adverse impacts incidents information may take form e.g electronic physical. tangible e.g paperwork intangible e.g knowledge information security primary focus balanced protection confidentiality integrity availability data also known cia triad maintaining focus efficient policy implementation without hampering organization productivity largely achieved structured risk management process involves standardize discipline academics professionals collaborate offer guidance policies industry standards password antivirus software firewall encryption software legal liability security awareness training forth standardization may driven wide variety laws regulations affect data accessed processed stored transferred destroyed however implementation standards guidance within entity may limited effect culture continual improvement n't adopted core information security information assurance act maintaining confidentiality integrity availability cia information ensuring information compromised way critical issues arise issues include limited natural disasters computer/server malfunction physical theft paper-based business operations still prevalent requiring set information secuy practices enterprise digital initiatives increasingly emphasized information assurance typically dealt information technology security specialists specialists apply information security technology often form computer system worthwhile note computer necessarily mean home desktop computer device processor memory devices range non-networked standalone devices simple calculators networked mobile computing devices smartphones tablet computers security specialists almost always found major enterprise/establishment due nature value data within larger businesses responsible keeping technology within company secure malicious cyber attacks often attempt acquire critical private information gain control internal systems field information security grown evolved significantly recent years offers many areas specialization including securing networks allied infrastructure securing applications databases security testing information systems auditing business continuity planning electronic record discovery digital forensics information security professionals stable employment 80 percent professionals change employer employment period year number professionals projected continuously grow 11 percent annually 2014 2019 information security threats come many different forms common threats today software attacks theft intellectual property identity theft theft equipment information sabotage information extortion people experienced software attacks sort viruses worms phishing attacks trojan horses common examples software attacks theft intellectual property also extensive issue many businesses information technology field identity theft attempt act someone else usually obtain person personal information take advantage access vital information social engineering theft equipment information becoming prevalent today due fact devices today mobile prone theft also become far desirable amount data capacity increases sabotage usually consists destruction organization website attempt cause loss confidence part customers information extortion consists theft company property information attempt receive payment exchange returning information property back owner ransomware many ways help protect attacks one functional precautions conduct periodical user awareness number one threat organisation users internal employees also called insider threats governments military corporations financial institutions hospitals non-profit organisations private businesses amass great deal confidential information employees customers products research financial status confidential information business customers finances new product line fall hands competitor black hat hacker business customers could suffer widespread irreparable financial loss well damage company reputation business perspective information security must balanced cost gordon-loeb model provides mathematical economic approach addressing concern individual information security significant effect privacy viewed differently various cultures possible responses security threat risk since early days communication diplomats military commanders understood necessary provide mechanism protect confidentiality correspondence means detecting tampering julius caesar credited invention caesar cipher c. 50 b.c. created order prevent secret messages read message fall wrong hands however part protection achieved application procedural handling controls sensitive information marked indicate protected transported trusted persons guarded stored secure environment strong box postal services expanded governments created official organizations intercept decipher read reseal letters e.g. u.k. secret office founded 1653 mid-nineteenth century complex classification systems developed allow governments manage information according degree sensitivity example british government codified extent publication official secrets act 1889 time first world war multi-tier classification systems used communicate information various fronts encouraged greater use code making breaking sections diplomatic military headquarters encoding became sophisticated wars machines employed scramble unscramble information volume information shared allied countries second world war necessitated formal alignment classification systems procedural controls arcane range markings evolved indicate could handle documents usually officers rather enlisted troops stored increasingly complex safes storage facilities developed enigma machine employed germans encrypt data warfare successfully decrypted alan turing regarded striking example creating using secured information procedures evolved ensure documents destroyed properly failure follow procedures led greatest intelligence coups war e.g. capture u-570 end twentieth century early years twenty-first century saw rapid advancements telecommunications computing hardware software data encryption availability smaller powerful less expensive computing equipment made electronic data processing within reach small business home user computers quickly became interconnected internet rapid growth widespread use electronic data processing electronic business conducted internet along numerous occurrences international terrorism fueled need better methods protecting computers information store process transmit academic disciplines computer security information assurance emerged along numerous professional organizations sharing common goals ensuring security reliability information systems various definitions information security suggested summarized different sources cia triad confidentiality integrity availability heart information security members classic infosec triad—confidentiality integrity availability—are interchangeably referred literature security attributes properties security goals fundamental aspects information criteria critical information characteristics basic building blocks however debate continues whether cia triad sufficient address rapidly changing technology business requirements recommendations consider expanding intersections availability confidentiality well relationship security privacy principles accountability sometimes proposed pointed issues non-repudiation fit well within three core concepts 1992 revised 2002 oecd guidelines security information systems networks proposed nine generally accepted principles awareness responsibility response ethics democracy risk assessment security design implementation security management reassessment building upon 2004 nist engineering principles information technology security proposed 33 principles derived guidelines practices 1998 donn parker proposed alternative model classic cia triad called six atomic elements information elements confidentiality possession integrity authenticity availability utility merits parkerian hexad subject debate amongst security professionals 2011 open group published information security management standard o-ism3 standard proposed operational definition key concepts security elements called security objectives related access control 9 availability 3 data quality 1 compliance technical 4 2009 dod software protection initiative released three tenets cybersecurity system susceptibility access flaw capability exploit flaw neither models widely adopted information security confidentiality property information made available disclosed unauthorized individuals entities processes similar privacy two words n't interchangeable rather confidentiality component privacy implements protect data unauthorized viewers examples confidentiality electronic data compromised include laptop theft password theft sensitive emails sent incorrect individuals information security data integrity means maintaining assuring accuracy completeness data entire lifecycle means data modified unauthorized undetected manner thing referential integrity databases although viewed special case consistency understood classic acid model transaction processing information security systems typically provide message integrity alongside confidentiality information system serve purpose information must available needed means computing systems used store process information security controls used protect communication channels used access must functioning correctly high availability systems aim remain available times preventing service disruptions due power outages hardware failures system upgrades ensuring availability also involves preventing denial-of-service attacks flood incoming messages target system essentially forcing shut realm information security availability often viewed one important parts successful information security program ultimately end-users need able perform job functions ensuring availability organization able perform standards organization stakeholders expect involve topics proxy configurations outside web access ability access shared drives ability send emails executives oftentimes understand technical side information security look availability easy fix often requires collaboration many different organizational teams network operations development operations incident response policy/change management successful information security team involves many different key roles mesh align cia triad provided effectively law non-repudiation implies one intention fulfill obligations contract also implies one party transaction deny received transaction party deny sent transaction important note technology cryptographic systems assist non-repudiation efforts concept core legal concept transcending realm technology instance sufficient show message matches digital signature signed sender private key thus sender could sent message nobody else could altered transit data integrity alleged sender could return demonstrate digital signature algorithm vulnerable flawed allege prove signing key compromised fault violations may may lie sender assertions may may relieve sender liability assertion would invalidate claim signature necessarily proves authenticity integrity sender may repudiate message authenticity integrity pre-requisites non-repudiation certified information systems auditor cisa review manual 2006 provides following definition risk management risk management process identifying vulnerabilities threats information resources used organization achieving business objectives deciding countermeasures take reducing risk acceptable level based value information resource organization two things definition may need clarification first process risk management ongoing iterative process must repeated indefinitely business environment constantly changing new threats vulnerabilities emerge every day second choice countermeasures controls used manage risks must strike balance productivity cost effectiveness countermeasure value informational asset protected risk analysis risk evaluation processes limitations since security incidents occur emerge context rarity uniqueness give rise unpredictable threats analysis phenomena characterized breakdowns surprises side-effects requires theoretical approach able examine interpret subjectively detail incident risk likelihood something bad happen causes harm informational asset loss asset vulnerability weakness could used endanger cause harm informational asset threat anything man-made act nature potential cause harm likelihood threat use vulnerability cause harm creates risk threat use vulnerability inflict harm impact context information security impact loss availability integrity confidentiality possibly losses lost income loss life loss real property pointed possible identify risks possible eliminate risk remaining risk called residual risk risk assessment carried team people knowledge specific areas business membership team may vary time different parts business assessed assessment may use subjective qualitative analysis based informed opinion reliable dollar figures historical information available analysis may use quantitative analysis research shown vulnerable point information systems human user operator designer human iso/iec 27002:2005 code practice information security management recommends following examined risk assessment broad terms risk management process consists given risk management choose accept risk based upon relative low value asset relative low frequency occurrence relative low impact business leadership may choose mitigate risk selecting implementing appropriate control measures reduce risk cases risk transferred another business buying insurance outsourcing another business reality risks may disputed cases leadership may choose deny risk selecting implementing proper security controls initially help organization bring risk acceptable levels control selection follow based risk assessment controls vary nature fundamentally ways protecting confidentiality integrity availability information iso/iec 27001 defined controls different areas organizations implement additional controls according requirement organization iso/iec 27002 offers guideline organizational information security standards administrative controls consist approved written policies procedures standards guidelines administrative controls form framework running business managing people inform people business run day-to-day operations conducted laws regulations created government bodies also type administrative control inform business industry sectors policies procedures standards guidelines must followed – payment card industry data security standard pci dss required visa mastercard example examples administrative controls include corporate security policy password policy hiring policies disciplinary policies administrative controls form basis selection implementation logical physical controls logical physical controls manifestations administrative controls paramount importance logical controls also called technical controls use software data monitor control access information computing systems passwords network host-based firewalls network intrusion detection systems access control lists data encryption examples logical controls important logical control frequently overlooked principle least privilege requires individual program system process granted access privileges necessary perform task blatant example failure adhere principle least privilege logging windows user administrator read email surf web violations principle also occur individual collects additional access privileges time happens employees job duties change employees promoted new position employees transferred another department access privileges required new duties frequently added onto already existing access privileges may longer necessary appropriate physical controls monitor control environment work place computing facilities also monitor control access facilities include doors locks heating air conditioning smoke fire alarms fire suppression systems cameras barricades fencing security guards cable locks etc separating network workplace functional areas also physical controls important physical control frequently overlooked separation duties ensures individual complete critical task example employee submits request reimbursement also able authorize payment print check applications programmer also server administrator database administrator roles responsibilities must separated one another information security must protect information throughout lifespan initial creation information final disposal information information must protected motion rest lifetime information may pass many different information processing systems many different parts information processing systems many different ways information information systems threatened fully protect information lifetime component information processing system must protection mechanisms building layering overlapping security measures called defense depth contrast metal chain famously strong weakest link defense depth strategy aims structure one defensive measure fail measures continue provide protection recall earlier discussion administrative controls logical controls physical controls three types controls used form basis upon build defense depth strategy approach defense depth conceptualized three distinct layers planes laid one top additional insight defense depth gained thinking forming layers onion data core onion people next outer layer onion network security host-based security application security forming outermost layers onion perspectives equally valid provides valuable insight implementation good defense depth strategy important aspect information security risk management recognizing value information defining appropriate procedures protection requirements information information equal information requires degree protection requires information assigned security classification first step information classification identify member senior management owner particular information classified next develop classification policy policy describe different classification labels define criteria information assigned particular label list required security controls classification factors influence classification information assigned include much value information organization old information whether information become obsolete laws regulatory requirements also important considerations classifying information information systems audit control association isaca business model information security also serves tool security professionals examine security systems perspective creating environment security managed holistically allowing actual risks addressed type information security classification labels selected used depend nature organization examples employees organization well business partners must trained classification schema understand required security controls handling procedures classification classification particular information asset assigned reviewed periodically ensure classification still appropriate information ensure security controls required classification place followed right procedures access protected information must restricted people authorized access information computer programs many cases computers process information must also authorized requires mechanisms place control access protected information sophistication access control mechanisms parity value information protected sensitive valuable information stronger control mechanisms need foundation access control mechanisms built start identification authentication access control generally considered three steps identification authentication authorization identification assertion someone something person makes statement hello name john doe making claim however claim may may true john doe granted access protected information necessary verify person claiming john doe really john doe typically claim form username entering username claiming person username belongs authentication act verifying claim identity john doe goes bank make withdrawal tells bank teller john doe claim identity bank teller asks see photo id hands teller driver license bank teller checks license make sure john doe printed compares photograph license person claiming john doe photo name match person teller authenticated john doe claimed similarly entering correct password user providing evidence he/she person username belongs three different types information used authentication strong authentication requires providing one type authentication information two-factor authentication username common form identification computer systems today password common form authentication usernames passwords served purpose increasingly inadequate usernames passwords slowly replaced supplemented sophisticated authentication mechanisms time-based one-time password algorithms person program computer successfully identified authenticated must determined informational resources permitted access actions allowed perform run view create delete change called authorization authorization access information computing services begins administrative policies procedures policies prescribe information computing services accessed conditions access control mechanisms configured enforce policies different computing systems equipped different kinds access control mechanisms may even offer choice different access control mechanisms access control mechanism system offers based upon one three approaches access control may derived combination three approaches non-discretionary approach consolidates access control centralized administration access information resources usually based individuals function role organization tasks individual must perform discretionary approach gives creator owner information resource ability control access resources mandatory access control approach access granted denied basing upon security classification assigned information resource examples common access control mechanisms use today include role-based access control available many advanced database management systems simple file permissions provided unix windows operating systems group policy objects provided windows network systems kerberos radius tacacs simple access lists used many firewalls routers effective policies security controls must enforceable upheld effective policies ensure people held accountable actions u.s. treasury guidelines systems processing sensitive proprietary information example states failed successful authentication access attempts must logged access information must leave type audit trail also need-to-know principle needs effect talking access control principle gives access rights person perform job functions principle used government dealing difference clearances even though two employees different departments top-secret clearance must need-to-know order information exchanged within need-to-know principle network administrators grant employee least amount privileges prevent employees accessing supposed need-to-know helps enforce confidentiality-integrity-availability triad need-to-know directly impacts confidential area triad information security uses cryptography transform usable information form renders unusable anyone authorized user process called encryption information encrypted rendered unusable transformed back original usable form authorized user possesses cryptographic key process decryption cryptography used information security protect information unauthorized accidental disclosure information transit either electronically physically information storage cryptography provides information security useful applications well including improved authentication methods message digests digital signatures non-repudiation encrypted network communications older less secure applications telnet file transfer protocol ftp slowly replaced secure applications secure shell ssh use encrypted network communications wireless communications encrypted using protocols wpa/wpa2 older less secure wep wired communications itu‑t g.hn secured using aes encryption x.1035 authentication key exchange software applications gnupg pgp used encrypt data files email cryptography introduce security problems implemented correctly cryptographic solutions need implemented using industry-accepted solutions undergone rigorous peer review independent experts cryptography length strength encryption key also important consideration key weak short produce weak encryption keys used encryption decryption must protected degree rigor confidential information must protected unauthorized disclosure destruction must available needed public key infrastructure pki solutions address many problems surround key management terms reasonable prudent person due care due diligence used fields finance securities law many years recent years terms found way fields computing information security u.s. federal sentencing guidelines make possible hold corporate officers liable failing exercise due care due diligence management information systems business world stockholders customers business partners governments expectation corporate officers run business accordance accepted business practices compliance laws regulatory requirements often described reasonable prudent person rule prudent person takes due care ensure everything necessary done operate business sound business principles legal ethical manner prudent person also diligent mindful attentive ongoing due care business field information security harris offers following definitions due care due diligence due care steps taken show company taken responsibility activities take place within corporation taken necessary steps help protect company resources employees nowiki due diligence /nowiki continual activities make sure protection mechanisms continually maintained operational attention made two important points definitions first due care steps taken show means steps verified measured even produce tangible artifacts second due diligence continual activities means people actually things monitor maintain protection mechanisms activities ongoing organizations responsibility practicing duty care applying information security duty care risk analysis standard docra provides principles practices evaluating risk considers parties could affected risks docra helps evaluate safeguards appropriate protecting others harm presenting reasonable burden increased data breach litigation companies must balance security controls compliance mission software engineering institute carnegie mellon university publication titled governing enterprise security ges implementation guide defines characteristics effective security governance include incident response plan group policies dictate organizations reaction cyber attack security breach identified plan initiated important note legal implications data breach knowing local federal laws critical every plan unique needs organization involve skill set part team example lawyer may included response plan help navigate legal implications data breach mentioned every plan unique plans include following good preparation includes development incident response team skills need used team would penetration testing computer forensics network security etc team also keep track trends cybersecurity modern attack strategies training program end users important well modern attack strategies target users network part incident response plan identifies security event end user reports information admin notices irregularities investigation launched incident log crucial part step members team updating log ensure information flows fast possible identified security breach occurred next step activated phase irt works isolate areas breach took place limit scope security event phase important preserve information forensically analyzed later process containment could simple physically containing server room complex segmenting network allow spread virus threat identified removed affected systems could include using deleting malicious files terminating compromised accounts deleting components events require step however important fully understand event moving step help ensure threat completely removed stage systems restored back original operation stage could include recovery data changing user access information updating firewall rules policies prevent breach future executing step system could still vulnerable future security threats step information gathered process used make future decisions security step crucial ensure future events prevented using information train admins critical process step also used process information distributed entities experienced security event change management formal process directing controlling alterations information processing environment includes alterations desktop computers network servers software objectives change management reduce risks posed changes information processing environment improve stability reliability processing environment changes made objective change management prevent hinder necessary changes implemented change information processing environment introduces element risk even apparently simple changes unexpected effects one management many responsibilities management risk change management tool managing risks introduced changes information processing environment part change management process ensures changes implemented inopportune times may disrupt critical business processes interfere changes implemented every change needs managed kinds changes part everyday routine information processing adhere predefined procedure reduces overall level risk processing environment creating new user account deploying new desktop computer examples changes generally require change management however relocating user file shares upgrading email server pose much higher level risk processing environment normal everyday activity critical first steps change management defining change communicating definition b defining scope change system change management usually overseen change review board composed representatives key business areas security networking systems administrators database administration application developers desktop support help desk tasks change review board facilitated use automated work flow application responsibility change review board ensure organization documented change management procedures followed change management process follows change management procedures simple follow easy use greatly reduce overall risks created changes made information processing environment good change management procedures improve overall quality success changes implemented accomplished planning peer review documentation communication iso/iec 20000 visible ops handbook implementing itil 4 practical auditable steps full book summary information technology infrastructure library provide valuable guidance implementing efficient effective change management program information security business continuity management bcm concerns arrangements aiming protect organization critical business functions interruption due incidents least minimize effects bcm essential organization keep technology business line current threats continuation business usual bcm included organizations risk analysis plan ensure necessary business functions need keep going event type threat business function encompasses whereas bcm takes broad approach minimizing disaster-related risks reducing probability severity incidents disaster recovery plan drp focuses specifically resuming business operations quickly possible disaster disaster recovery plan invoked soon disaster occurs lays steps necessary recover critical information communications technology ict infrastructure disaster recovery planning includes establishing planning group performing risk assessment establishing priorities developing recovery strategies preparing inventories documentation plan developing verification criteria procedure lastly implementing plan partial listing governmental laws regulations various parts world significant effect data processing information security important industry sector regulations also included significant impact information security describing simply security aware employees information security culture ideas customs social behaviors organization impact information security positive negative ways cultural concepts help different segments organization work effectively work effectiveness towards information security within organization way employees think feel security actions take big impact information security organizations roer petric 2017 identify seven core dimensions information security culture organizations andersson reimers 2014 found employees often see part organization information security effort often take actions ignore organizational information security best interests research shows information security culture needs improved continuously information security culture analysis change authors commented never ending process cycle evaluation change maintenance manage information security culture five steps taken pre-evaluation strategic planning operative planning implementation post-evaluation international organization standardization iso consortium national standards institutes 157 countries coordinated secretariat geneva switzerland iso world largest developer standards iso 15443 information technology – security techniques – framework security assurance iso/iec 27002 information technology – security techniques – code practice information security management iso-20000 information technology – service management iso/iec 27001 information technology – security techniques – information security management systems – requirements particular interest information security professionals us national institute standards technology nist non-regulatory federal agency within u.s. department commerce nist computer security division develops standards metrics tests validation programs well publishes standards guidelines increase secure planning implementation management operation nist also custodian u.s. federal information processing standard publications fips internet society professional membership society 100 organizations 20,000 individual members 180 countries provides leadership addressing issues confront future internet organizational home groups responsible internet infrastructure standards including internet engineering task force ietf internet architecture board iab isoc hosts requests comments rfcs includes official internet protocol standards rfc-2196 site security handbook information security forum isf global nonprofit organization several hundred leading organizations financial services manufacturing telecommunications consumer goods government areas undertakes research information security practices offers advice biannual standard good practice detailed advisories members institute information security professionals iisp independent non-profit body governed members principal objective advancing professionalism information security practitioners thereby professionalism industry whole institute developed iisp skills framework framework describes range competencies expected information security information assurance professionals effective performance roles developed collaboration private public sector organizations world-renowned academics security leaders german federal office information security german bundesamt für sicherheit der informationstechnik bsi bsi-standards 100-1 100-4 set recommendations including methods processes procedures approaches measures relating information security bsi-standard 100-2 it-grundschutz methodology describes information security management implemented operated standard includes specific guide baseline protection catalogs also known it-grundschutz catalogs 2005 catalogs formerly known baseline protection manual catalogs collection documents useful detecting combating security-relevant weak points environment cluster collection encompasses september 2013 4,400 pages introduction catalogs it-grundschutz approach aligned iso/iec 2700x family european telecommunications standards institute standardized catalog information security indicators headed industrial specification group isg isi
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Computer security
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clip compiler clip compiler compiler clipper programming language additional features libraries gtk fivewin netto mysql odbc cti tcp gzip interbase oracle postgres quite fast support hyper-six foxpro rdd compile existing clipper source code minor changes support features original compiler access multiple types databases oracle informix interbase mysql postgres xbase dialects tables foxpro visual foxpro comix indexes ndx ntx cdx supports object-oriented programming preprocessor dynamic static libraries several functions math string management arrays vectors clip licensed gpl type license uses gnu cc compiler
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Programming language topics
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network computer network computer nc diskless desktop computer device made oracle corporation 1996 2000 devices designed manufactured alliance included sun microsystems ibm others devices designed minimum specifications based network computer reference profile brand also employed marketing term try popularize design computer within enterprise among consumers nc brand mainly intended inspire range desktop computers various suppliers virtue diskless design use inexpensive components software cheaper easier manage standard fat client desktops however due commoditization standard desktop components due increasing availability popularity various software options using full desktops diskless nodes thin clients hybrid clients network computer brand never achieved popularity hoped oracle eventually mothballed term network computer used diskless desktop computer thin client failure nc impact scale predicted larry ellison may caused number factors firstly prices pcs quickly fell 1000 making competition hard secondly software available ncs neither mature open thirdly idea could simply ahead time nc launch 1996 typical home internet connection 28.8 kbit/s modem dialup simply insufficient delivery executable content world wide web considered mainstream breakout year 1998 prior internet service providers advertised mainstream press least outside us knowledge internet limited could held back uptake would seen niche device obvious appeal ncs ended used 'dumb terminals intended replace proprietary backend infrastructure readily available 1990s era ncs often network-booted minimal unix x serve x terminals nc purists may consider suboptimal use nc hardware ncs work well terminals considerably cheaper purpose-built terminal hardware initial network computing standard network computer reference profile ncref required 'nc appliances supported html java http jpeg key standards many ncs use intel cpus microsoft software microsoft intel developed competing standard called netpc alternatives ncref webref motorola hds network systems odin national semiconductor hds workstation stated ship end june 1996 acorn network computer oracle initial reference implementation nc development subcontracted british company acorn computers adapted create ncos acorn made use local partner companies ant icon technology design edge fulfil contract 1997 apple announced mac nc attempt develop pippin network computer platform end 1997 steve jobs discontinued macintosh clone efforts effectively killing pippin although key components mac nc technology inherited original imac first generation netstation design netstation trademark licensed nchannel provided consumer equipment internet service associated infrastructure uk market months nchannel split two entities netchannel provided internet service netproducts provided consumer hardware netproducts started working acorn develop next-generation product netstation ii started developing email-only set-top-box tvemail netproducts went voluntary liquidation 1998 either project completed sun microsystems developed javastation javaos-based nc based sparc hardware initially similar sun range unix workstations ibm launched network station september 1996 later reference design network station used netbsd-based ncos booted lan as/400 ibm pc server network station supported local execution basic applications web browser console addition x capability also implemented allow locally remotely run applications used machine practice lack real applications meant little hardware x terminal ibm network station originally based powerpc architecture final models used intel pentium processors see idea behind nc existing contemporary times system cloud computing particular google chrome os wired magazine daniel roth claims failure network computer eventually led development cloud computing large contribution transition attributed eric schmidt cto sun microsystems proponent network computer eventually became ceo google google large purveyor cloud technology notably google docs spreadsheets
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Computer architecture
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privacystar privacystar service identifies calling provides call complaint filing reports federal trade commission privacystar service available web mobile applications android ios several applications powered privacystar call text blocking available applications along privacystar ’ iphone lookup+ application enable users file potential debt collector telemarketer violations directly ftc application captures detailed information possible fair debt collection practices act violations including date time number identity allows users easily provide information regulatory agencies may take action privacystar 1.2 million users blocked 120 million calls filed 300,000 complaints directly federal trade commission september 2012 fact privacystar leading source call complaint data reported ftc 2015 users filed 31 call complaints february 13 2013 privacystar launched free sms spam complaint filing feature android smartphones application allows users file text message spam complaints addition existing ability file call complaints directly federal trade commission android phones founded 2008 jeff stalnaker josh smith privacystar based little rock arkansas jeff stalnaker president ceo company prior privacystar stalnaker held position division president financial services division acxiom marketing company josh smith coo privacystar charles morgan executive chairman board first orion corp. private company developed markets privacystar
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Computer security
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multimedia pc multimedia pc mpc recommended configuration personal computer pc cd-rom drive standard set named multimedia pc marketing council working group software publishers association spa software information industry association mpmc comprised companies including microsoft creative labs dell gateway fujitsu pc required standards could called mpc licensing use logo spa cd-rom drives coming market 1990 difficult concisely communicate consumer hardware requirements using multimedia software mostly meant displaying video synced audio pc via cd-rom drive mpc standard supposed communicate concisely consumer buying hardware software could simply look mpc logo assured compatibility mpc program mixed results primarily vast number pcs sold different brands windows became ubiquitous pcs specifying minimum recommended windows versions features often clearer consumers mpc nomenclature standardized term failed catch software publishers association turned away consumer software late 1990s interest mpc standard vanished problem software labeling continues especially field computer games multitude 3d video cards manufactured extremely wide range capabilities common industry labeling standard let consumers know whether card powerful enough let play particular game first mpc minimum standard set 1991 1993 mpc level 2 minimum standard announced 1996 mpc level 3 announced
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Computer architecture
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system virtual machine computing system virtual machine virtual machine provides complete system platform supports execution complete operating system os usually emulate existing architecture built purpose either providing platform run programs real hardware available use example executing otherwise obsolete platforms multiple instances virtual machines leading efficient use computing resources terms energy consumption cost effectiveness known hardware virtualization key cloud computing environment vm originally defined popek goldberg efficient isolated duplicate real machine system virtual machine advantages main disadvantages vms multiple vms running guest operating system frequently engaged server consolidation order avoid interference separate vms actual machine platform desire run multiple operating systems initial motivation virtual machines allow time-sharing among several single-tasking operating systems respects system virtual machine considered generalization concept virtual memory historically preceded ibm cp/cms first systems allow full virtualization implemented time sharing providing user single-user operating system cms unlike virtual memory system virtual machine entitled user write privileged instructions code approach certain advantages adding input/output devices allowed standard system technology evolves virtual memory purposes virtualization new systems memory overcommitment may applied manage memory sharing among multiple virtual machines one actual computer operating system may possible share memory pages identical contents among multiple virtual machines run physical machine may result mapping physical page technique known kernel samepage merging particularly useful read-only pages contain code segments particular would case multiple virtual machines running similar software software libraries web servers middleware components etc guest operating systems need compliant host hardware thereby making possible run different operating systems computer e.g. microsoft windows linux previous versions operating system support future software use virtual machines support separate guest operating systems popular regard embedded systems typical use would run real-time operating system simultaneously preferred complex operating system linux windows another use would novel unproven software still developmental stage runs inside sandbox virtual machines advantages operating system development may include improved debugging access faster reboots different virtualization techniques used based desired usage native execution based direct virtualization underlying raw hardware thus provides multiple instances architecture real machine based capable running complete operating systems virtual machines also emulate different architectures allow execution software applications operating systems written another cpu architecture operating-system-level virtualization allows resources computer partitioned via kernel support multiple isolated user space instances usually called containers may look feel like real machines end users computer architectures capable hardware-assisted virtualization enables efficient full virtualization using virtualization-specific hardware capabilities primarily host cpus approach described full virtualization hardware implemented using type 1 type 2 hypervisor type 1 hypervisor runs directly hardware type 2 hypervisor runs another operating system linux windows virtual machine run operating system supported underlying hardware users thus run two different guest operating systems simultaneously separate private virtual computers pioneer system using concept ibm cp-40 first 1967 version ibm cp/cms 1967–1972 precursor ibm vm family 1972–present vm architecture users run relatively simple interactive computing single-user operating system cms guest top vm control program vm-cp approach kept cms design simple running alone control program quietly provides multitasking resource management services behind scenes addition cms communication system tasks performed multitasking vms rscs gcs tcp/ip unix users run ibm operating systems mvs even new cp z/os even simple cms could run threaded environment listserv trickle z/vm current version vm used support hundreds thousands virtual machines given mainframe installations use linux z systems run web servers linux runs operating system within many virtual machines full virtualization particularly helpful operating system development experimental new code run time older stable versions separate virtual machine process even recursive ibm debugged new versions virtual machine operating system vm virtual machine running older version vm even used technique simulate new hardware standard x86 instruction set architecture used modern pcs actually meet popek goldberg virtualization requirements notably execution mode sensitive machine instructions always trap would allow per-instruction virtualization despite limitations several software packages managed provide virtualization x86 architecture even though dynamic recompilation privileged code first implemented vmware incurs performance overhead compared vm running natively virtualizable architecture ibm system/370 motorola mc68020 several software packages virtual pc virtualbox parallels workstation virtual iron manage implement virtualization x86 hardware intel amd introduced features x86 processors enable virtualization hardware well virtualization resources single machine multiple independent nodes cluster combined accessed single virtual numa machine virtual machines also perform role emulator allowing software applications operating systems written another computer processor architecture run operating-system-level virtualization server virtualization technology virtualizes servers operating system kernel layer thought partitioning single physical server sliced multiple small partitions otherwise called virtual environments virtual private servers vps guests zones etc partition looks feels like real server point view users example solaris zones supports multiple guest operating systems running operating system solaris 10 guest operating systems use kernel level operating system version separate copy operating system different kernel version using solaris kernel zones solaris native zones also requires host operating system version solaris operating systems manufacturers supported however solaris branded zones would need used operating systems zones another example system workload partitions wpars introduced version 6.1 ibm aix operating system system wpars software partitions running one instance global aix os environment operating system level architecture low overhead helps maximize efficient use server resources virtualization introduces negligible overhead allows running hundreds virtual private servers single physical server contrast approaches full virtualization like vmware paravirtualization like xen uml achieve level density due overhead running multiple kernels side operating system-level virtualization allow running different operating systems i.e. different kernels although different libraries distributions etc possible.different virtualization techniques used based desired usage native execution based direct virtualization underlying raw hardware thus provides multiple instances architecture real machine based capable running complete operating systems virtual machines also emulate different architectures allow execution software applications operating systems written another cpu architecture operating-system-level virtualization allows resources computer partitioned via kernel support multiple isolated user space instances usually called containers may look feel like real machines end users computer architectures capable hardware-assisted virtualization enables efficient full virtualization using virtualization-specific hardware capabilities primarily host cpus examples virtualization-enabled hardware include following
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Operating systems
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datavail datavail remote database administration provider based broomfield colorado company provides services db2 oracle sql mysql databases according inc. company largest provider remote database administration services north america mark perlstein serves company president ceo datavail founded result spin-off stratavia 2008 november datavail moved headquarters downtown denver colorado broomfield colorado company managed 7000 databases 47 corporate clients year november 2010 datavail appointed mark perlstein ceo company acquired blue gecko seattle-based managed service provider july 2012 blue gecko began operating subsidiary datavail acquisition company 283 percent three-year growth rate 900 employees 3 branches india
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Databases
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ia-32 ia-32 short intel architecture 32-bit sometimes also called i386 32-bit version x86 instruction set architecture designed intel first implemented 80386 microprocessor 1985 ia-32 first incarnation x86 supports 32-bit computing result ia-32 term may used metonym refer x86 versions support 32-bit computing within various programming language directives ia-32 still sometimes referred i386 architecture contexts certain iterations ia-32 isa sometimes labelled i486 i586 i686 referring instruction supersets offered 80486 p5 p6 microarchitectures respectively updates offered numerous additions alongside base ia-32 set i.e floating-point capabilities mmx extensions intel historically largest manufacturer ia-32 processors second biggest supplier amd 1990s via transmeta chip manufacturers also produced ia-32 compatible processors e.g winchip modern era intel still produces ia-32 processors intel quark microcontroller platform however since 2000s majority manufacturers intel included moved almost exclusively implementing cpus based 64-bit variant x86 x86-64 x86-64 specification offers legacy operating modes operate ia-32 isa backwards compatibility even given contemporary prevalence x86-64 2018 ia-32 protected mode versions many modern operating systems still maintained e.g microsoft windows ubuntu linux distribution spite ia-32 name causing potential confusion 64-bit evolution x86 originated amd would known ia-64 name instead belonging intel itanium architecture primary defining characteristic ia-32 availability 32-bit general-purpose processor registers example eax ebx 32-bit integer arithmetic logical operations 32-bit offsets within segment protected mode translation segmented addresses 32-bit linear addresses designers took opportunity make improvements well significant changes described
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Computer architecture
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armulator arm instruction set simulator armulator one software development tools provided development systems business unit arm limited users arm-based chips owes heritage early development instruction set sophie wilson part heritage still visible provision tube bbc micro model armulator armulator written c provides instruction set simulator provides virtual platform system emulation comes ready emulate arm processor certain arm coprocessors processor part embedded system licensees may extend armulator add implementations additional hardware armulator model armulator provides number services help time-based behaviour event scheduling ships examples memory mapped co-processor expansions way use armulator emulate entire embedded system key limitation armulator simulate single arm cpu one time although almost arm cores arm11 available performance armulator good technology employed 1000 host pc instructions per arm instruction means emulated speeds 1 mhz normal pcs mid late 90s accuracy good although classed cycle count accurate rather cycle accurate arm pipeline n't fully modeled although register interlocks resolution instruction consequence single stepping register interlocks ignored different cycle counts returned program simply run unavoidable testing armulator always time consuming challenge full arm architecture validation suites employed 1 million lines c code fairly hefty product armulator allows runtime debugging using either armsd arm symbolic debugger either graphical debuggers shipped sdt later ads products armulator suffered invisible tool text file configuration armul.conf many found complex configure armulator ii formed basis high accuracy cycle callable co-verification models arm processors covs models see cycle accurate simulator basis many coverification systems arm processors armulator available broad range platforms life including mac risc os platforms dec alpha hp-ux solaris sunos windows linux mid-90s reluctance support windows platforms pre-windows 95 relatively challenging platform late 90 early 00 support removed solaris windows linux although undoubtedly code base remains littered pragmas ifdef riscos armulator ii shipped early arm toolkits well later sdt 2.5 sdt 2.5.1 ads 1.0 ads 1.1 ads 1.2 rcvt 1.0 also separately rviss special models produced development cpus notably arm9e arm10 arm11 models helped architectural decisions thumb-2 trustzone armulator gradually phased replaced just-in-time compilation-based high performance cpu system models see fastsim link armulator made open source basis gnu version armulator key differences memory interface services also instruction decode done differently gnu armulator available part gdb debugger arm gnu tools armulator ii formed basis high accuracy cycle callable co-verification models arm processors covs models see cycle accurate simulator basis many coverification systems arm processors mentor graphic seamless market leading covs system supports many arm cores many cpus armulator ii shipped early arm toolkits well later sdt 2.5 sdt 2.5.1 ads 1.0 ads 1.1 ads 1.2 rvct 1.0 also separately rviss key contributors armulator ii mike williams louise jameson charles lavender donald sinclair chris lamb rebecca bryan worked armulator engineer later product manager significant input also made allan skillman working arm coverification models time key contributor armulator dave jaggar special models produced development cpus notably arm9e arm10 arm11 models helped architectural decisions thumb-2 trustzone
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Computer architecture
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firechat firechat proprietary mobile app developed open garden uses wireless mesh networking enable smartphones connect via bluetooth wi-fi apple ’ multipeer connectivity framework without internet connection connecting peer-to-peer though designed purpose mind firechat used communication tool civil protests app first introduced march 2014 iphones followed april 3 version android devices july 2015 firechat introduced private messaging possible post messages public chatrooms may 2016 firechat introduced firechat alerts allow users send push alerts specific time place feature aimed aid workers disaster relief developed partnership marikina city philippines firechat first became popular 2014 iraq following government restrictions internet use thereafter hong kong protests 2015 firechat also promoted protesters 2015 ecuadorian protests september 11 2015 pro-independence demonstration called free way catalan republic firechat used 131,000 times january 2016 students protested university hyderabad india following suicide phd student named rohith vemula students reported used firechat university shut wi-fi current version oct 2018 seems fork riot.im june 2014 firechat developers told wired p eople need understand tool communicate anything would put harmful situation discovered somebody hostile ... meant secure private communications july 2015 firechat claims use end-to-end encryption protect one-to-one private messages
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Distributed computing architecture
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leaning toothpick syndrome computer programming leaning toothpick syndrome lts situation quoted expression becomes unreadable contains large number escape characters usually backslashes avoid delimiter collision official perl documentation introduced term wider usage phrase used describe regular expressions match unix-style paths elements separated slashes codice_1 slash also used default regular expression delimiter must escaped back slash codice_2 leading frequent escaped slashes represented codice_3 doubled urls yields codice_4 escaped codice_5 similar phenomenon occurs dos/windows paths backslash used path separator requiring doubled backslash codice_6 – -escaped regular expression inside escaped string requiring codice_7 match single backslash extreme cases regular expression escaped string matching uniform naming convention path begins codice_6 requires 8 backslashes codice_9 due 2 backslashes double-escaped lts appears many programming languages many situations including patterns match uniform resource identifiers uris programs output quoted text many quines fall latter category consider following perl regular expression intended match uris identify files codice_10 directory ftp site perl like sed solves problem allowing many characters delimiters regular expression example following three examples equivalent expression given -- use wikipedia syntax highlighter handle perl color misleadingly -- pre /pre common translation convert backslashes forward slashes pre /pre may easier understand written like pre /pre perl program print html link tag url link text stored variables codice_11 codice_12 respectively might look like notice use backslashes escape quoted double-quote characters syntaxhighlight lang= html using single quotes delimit string feasible perl expand variables inside single-quoted strings code example would work intended using codice_13 function viable solution many languages perl c php codice_14 operator perl allows delimiter documents especially well suited multi-line strings however documents n't allowed proper indentation 5.26 example shows perl syntax print « here_it_ends href= url text /a here_it_ends c programming language handles lts use codice_15 symbol start string literals initial quotation marks e.g rather otherwise requiring c++11 standard adds raw strings string contains characters codice_16 optional delimiter used codice_17 following example go indicates string raw using backtick delimiter c \foo\bar.txt raw strings may contain character except backticks escape code backtick raw string raw strings may also span multiple lines example strings codice_18 codice_19 equivalent string spans multiple lines. string that\nspans multiple\nlines python similar construct using codice_20 one also use together triple quotes ruby uses single quote indicate raw string filepath c \foo\bar.txt' also allows change delimiter like perl r ftp // ^/ */pub/ r ftp // ^/ */pub/ scala allows usage triple quotes order prevent escaping confusion triple quotes also allow multiline strings shown sed regular expressions particularly using operator much similar perl sed predecessor perl default delimiter delimiter used default s/regexp/replacement/ regexp replacement also valid form example match pub directory perl example replace foo default escaping slashes using exclamation point delimiter instead yields
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Programming language topics
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hewlett-packard hewlett-packard company commonly referred hp stylized hp hewlett-packard american multinational information technology company headquartered palo alto california developed provided wide variety hardware components well software related services consumers small- medium-sized businesses smbs large enterprises including customers government health education sectors company founded one-car garage palo alto bill hewlett david packard initially produced line electronic test equipment hp world leading pc manufacturer 2007 q2 2013 time lenovo ranked ahead hp hp specialized developing manufacturing computing data storage networking hardware designing software delivering services major product lines included personal computing devices enterprise industry standard servers related storage devices networking products software diverse range printers imaging products hp directly marketed products households small- medium-sized businesses enterprises well via online distribution consumer-electronics office-supply retailers software partners major technology vendors hp also services consulting business around products partner products hewlett-packard company events included spin-off electronic bio-analytical measurement instruments part business agilent technologies 1999 merger compaq 2002 acquisition eds 2008 led combined revenues 118.4 billion 2008 fortune 500 ranking 9 2009 november 2009 hp announced acquisition 3com deal closing april 12 2010 april 28 2010 hp announced buyout palm inc. 1.2 billion september 2 2010 hp bidding war 3par 33 share offer 2.07 billion dell declined match hewlett-packard spun enterprise products services business hewlett packard enterprise november 1 2015 hewlett-packard held onto pc printer businesses renamed hp inc. bill hewlett david packard graduated degrees electrical engineering stanford university 1935 company originated garage nearby palo alto fellowship past professor frederick terman stanford great depression considered terman mentor forming hewlett-packard 1938 packard hewlett began part-time work rented garage initial capital investment us 538 1939 hewlett packard decided formalize partnership tossed coin decide whether company founded would called hewlett-packard hp packard-hewlett hp incorporated august 18 1947 went public november 6 1957 many projects worked first financially successful product precision audio oscillator model hp200a innovation use small incandescent light bulb known pilot light temperature dependent resistor critical portion circuit negative feedback loop stabilized amplitude output sinusoidal waveform allowed sell model 200a 89.40 competitors selling less stable oscillators 200 model 200 series generators continued production least 1972 200ab still tube-based improved design years one company earliest customers walt disney productions bought eight model 200b oscillators 71.50 use certifying fantasound surround sound systems installed theaters movie fantasia worked counter-radar technology artillery shell fuses world war ii allowed packard hewlett exempt draft hp recognized symbolic founder silicon valley although actively investigate semiconductor devices years traitorous eight abandoned william shockley create fairchild semiconductor 1957 hewlett-packard hp associates division established around 1960 developed semiconductor devices primarily internal use hp associates co-founded another former bell labs researcher mosfet mos transistor inventor mohamed atalla served director semiconductor research instruments calculators products using semiconductor devices hp associates 1960s hp partnered sony yokogawa electric companies japan develop several high-quality products products huge success high costs building hp-looking products japan hp yokogawa formed joint venture yokogawa-hewlett-packard 1963 market hp products japan hp bought yokogawa electric share hewlett-packard japan 1999 hp spun small company dynac specialize digital equipment name picked hp logo hp could turned upside reverse reflect image logo dy new company eventually dynac changed dymec folded back hp 1959 hp experimented using digital equipment corporation dec minicomputers instruments deciding would easier build another small design team deal dec hp entered computer market 1966 hp 2100 hp 1000 series minicomputers simple accumulator-based design two accumulator registers hp 1000 models two index registers series produced 20 years spite several attempts replace forerunner hp 9800 hp 250 series desktop business computers hp 3000 advanced stack-based design business computing server later redesigned risc technology hp 2640 series smart intelligent terminals introduced forms-based interfaces ascii terminals also introduced screen labeled function keys commonly used gas pumps bank atms hp 2640 series included one first bit mapped graphics displays combined hp 2100 21mx f-series microcoded scientific instruction set enabled first commercial wysiwyg presentation program bruno later became program hp-draw hp 3000 although scoffed formative days computing hp would eventually surpass even ibm world largest technology vendor terms sales although programma 101 first commercial desktop computer hp identified wired magazine producer world first device called personal computer hewlett-packard 9100a introduced 1968 programma 101 called computer personale italian fiera di milano 1966 hp called desktop calculator bill hewlett said called computer would rejected customers computer gurus n't look like ibm therefore decided call calculator nonsense disappeared engineering triumph time logic circuit produced without integrated circuits assembly cpu entirely executed discrete components crt display magnetic-card storage printer price around 5,000 machine keyboard cross scientific calculator adding machine alphabetic keyboard steve wozniak co-founder apple originally designed apple computer working hp offered right first refusal work take company wanted stay scientific business industrial markets wozniak said hp turned 5 times loyalty hp made hesitant start apple steve jobs company earned global respect variety products introduced world first handheld scientific electronic calculator 1972 hp-35 first handheld programmable 1974 hp-65 first alphanumeric programmable expandable 1979 hp-41c first symbolic graphing calculator hp-28c like scientific business calculators oscilloscopes logic analyzers measurement instruments reputation sturdiness usability latter products part spin-off agilent product line later spun agilent keysight technologies company design philosophy period summarized design guy next bench 98x5 series technical desktop computers started 1975 9815 cheaper 80 series technical computers started 1979 85 machines used version basic programming language available immediately switched used proprietary magnetic tape storage hp computers similar capabilities much later ibm personal computer although limitations available technology forced prices high 1984 hp introduced inkjet laser printers desktop along scanner product line later developed successful multifunction products significant single-unit printer/scanner/copier/fax machines print mechanisms hp tremendously popular laserjet line laser printers depend almost entirely canon inc. components print engines turn use technology developed xerox hp develops hardware firmware software convert data dots printing march 3 1986 hp registered hp.com domain name making ninth internet .com domain ever registered 1987 palo alto garage hewlett packard started business designated california state historical landmark 1990s hp expanded computer product line initially targeted university research business users reach consumers hp also grew acquisitions bought apollo computer 1989 convex computer 1995 later decade hp opened hpshopping.com independent subsidiary sell online direct consumers 2005 store renamed hp home home office store 1995 1998 hewlett-packard sponsors english football team tottenham hotspur 1999 businesses related computers storage imaging spun hp form agilent technologies agilent spin-off largest initial public offering history silicon valley spin-off created 8 billion company 30,000 employees manufacturing scientific instruments semiconductors optical networking devices electronic test equipment telecom wireless r production july 1999 hp appointed carly fiorina formerly lucent first female ceo fortune-20 company dow jones industrial average fiorina received larger signing offer predecessors fiorina served ceo technology downturn early 2000s led merger compaq disastrous according cnn led firing 30,000 u.s. employees leadership company doubled size tenure ceo beset damaging leaks hp board directors asked fiorina step 2005 following boardroom disagreement resigned february 9 2005 1997 hp sold 120 million worth printers computer products iran european subsidiary dubai-based east distributor despite u.s. export sanctions prohibiting deals imposed bill clinton executive orders issued 1995 story initially reported boston globe triggered inquiry sec hp responded products worth 120 million sold fiscal year 2008 distribution way redington gulf company based netherlands sales took place foreign subsidiary hp violated sanctions hp named redington gulf wholesaler year 2003 turn published press release stating seeds redington-hewlett-packard relationship sowed six years ago one market — iran time redington gulf three employees whose sole purpose sell hp products iran market according former officials worked sanctions hp using loophole routing sales foreign subsidiary hp ended relationship redington gulf sec inquiry september 3 2001 hp announced agreement reached compaq merge two companies may 2002 passing shareholder vote hp officially merged compaq prior plans place consolidate companies product teams product lines compaq already taken digital equipment corporation 1998 hp therefore still offers support former digital equipment products pdp-11 vax alphaserver merger occurred proxy fight bill hewlett son walter objected merger compaq bought tandem computers 1997 started ex-hp employees digital equipment corporation 1998 following strategy hp became major player desktops laptops servers many different markets merger compaq new ticker symbol became hpq combination two previous symbols hwp cpq show significance alliance also key letters two companies hewlett-packard compaq latter company famous q logo products 2004 hp released dv 1000 series including hp pavilion dv 1658 1040 two years later may 2006 hp began campaign computer personal campaign designed bring back fact pc personal product campaign utilized viral marketing sophisticated visuals website www.hp.com/personal ads featured pharrell petra nemcova mark burnett mark cuban alicia keys jay-z gwen stefani shaun white january 2005 following years performance included hp compaq merger fell short disappointing earning reports board asked fiorina resign chair chief executive officer company following news fiorina departure hp stock jumped 6.9 percent robert wayman chief financial officer hp served interim ceo board undertook formal search replacement mark hurd ncr corporation hired take ceo president effective 1 april 2005 hurd board top choice given revival ncr took place leadership 2006 hp unveiled several new products including desktops enhanced notebooks workstation software manage openview client configuration manager 2.0 year hp share price skyrocketed due consistent results last couple quarters year hurd plan cutback hp workforce lower costs july 2007 hp signed definitive agreement acquire opsware cash tender deal values company 14.25 per share combined opsware software oracle enterprise management software first years hurd new role hp stock price doubled end fiscal 2007 hp hit 100 billion mark first time company annual revenue reached 104 billion allowing hp overtake competitor ibm may 13 2008 hp electronic data systems eds announced signed definitive agreement hp would purchase eds june 30 hp announced waiting period hart-scott-rodino antitrust improvements act 1976 expired transaction still requires eds stockholder approval regulatory clearance european commission non-u.s. jurisdictions subject satisfaction waiver closing conditions specified merger agreement agreement finalized august 26 2008 13 billion publicly announced eds would re-branded eds hp company first targeted layoff 24,600 former eds workers announced september 15 2008 company 2008 annual report gave number 24,700 completed end 2009 round factored purchase price 19.5 billion liability goodwill september 23 2009 eds known hp enterprise services november 11 2009 3com hewlett-packard announced hewlett-packard would acquiring 3com 2.7 billion cash acquisition one biggest size among series takeovers acquisitions technology giants push way become one-stop shops since beginning financial crisis 2007 tech giants constantly felt pressure expand beyond current market niches dell purchased perot systems recently invade technology consulting business area previously dominated ibm hewlett-packard latest move marked incursion enterprise networking gear market dominated cisco april 28 2010 palm inc. hewlett-packard announced hp would buy palm 1.2 billion cash debt announcement rumored either htc dell research motion hp would buy palm adding palm handsets hp product line created overlap ipaq series mobile devices thought significantly improve hp mobile presence ipaqdevices selling well buying palm gave hp library valuable patents well mobile operating platform known webos july 1 2010 acquisition palm final purchase palm webos began big gamble – build hp ecosystem july 1 2011 hp launched first tablet named hp touchpad bringing webos tablet devices september 2 2010 hp bidding war 3par 33 share offer 2.07 billion dell declined match hp acquisition palm phased compaq brand august 6 2010 ceo mark hurd resigned amid controversy cfo cathie lesjak assumed role interim ceo hurd turned hp around widely regarded one silicon valley star ceos leadership hp became largest computer company world measured total revenue accused sexual harassment colleague allegations deemed baseless investigation led questions concerning 1000 20000 private expenses lack disclosure related friendship observers argued hurd innocent board asked resignation avoid negative pr public analysis divided saw commendable tough action hp handling expenses irregularities saw ill-advised hasty expensive reaction ousting remarkably capable leader turned business around hp hurd oversaw series acquisitions worth 20 billion allowed company expand services networking equipment smartphones shares hp dropped 8.4 after-hours trading hitting 52-week low 9 billion market capitalization shaved larry ellison publicly attacked hp board ousting stating hp board made worst personnel decision since idiots apple board fired steve jobs many years ago september 30 2010 léo apotheker named hp new ceo president apotheker appointment sparked strong reaction oracle chief executive larry ellison complained apotheker charge sap one subsidiaries systematically stealing software oracle sap accepted subsidiary closed illegally accessed oracle intellectual property following hurd departure hp seen market problematic margins falling failed redirect establish major new markets cloud mobile services apotheker strategy broadly aim disposing hardware moving profitable software services sector august 18 2011 hp announced would strategically exit smartphone tablet computer business focusing higher-margin strategic priorities cloud solutions software emphasis enterprise commercial government markets also contemplated selling personal computer division spinning separate company quitting 'pc business continuing sell servers equipment business customers strategy already undertaken ibm 2005 hp stock continued drop 40 including 25 one day august 19 2011 company abruptly announced number decisions discontinue webos device business mobile phones tablet computers intent sell personal computer division time hp largest personal computer manufacturer world acquire british big data software firm autonomy 79 premium seen externally absurdly high price business known concerns accounts media analysts described hp actions botched strategy shift chaotic attempt rapidly reposition hp enhance earnings ultimately cost apotheker job autonomy acquisition objected even hp cfo september 22 2011 hp board directors fired apotheker chief executive effective immediately replaced fellow board member former ebay chief meg whitman raymond j lane executive chairman though apotheker served barely ten months received 13 million compensation hp lost 30 billion market capitalization tenure weeks later hp announced review concluded pc division integrated critical business operations company reaffirmed commitment personal systems group year later november 2012 wrote-down almost 9 billion related autonomy acquisition see takeover autonomy became subject intense litigation hp accused autonomy previous management fraudulently exaggerating autonomy financial position called law enforcement regulators countries autonomy previous management accused hp textbook obfuscation finger pointing protect hp executives criticism conceal hp culpability prior knowledge autonomy financial position gross mismanagement autonomy acquisition march 21 2012 hp said printing pc divisions would become one unit headed todd bradley pc division printing chief vyomesh joshi leaving company may 23 2012 hp announced plans lay approximately 27,000 employees posting profit decline 31 second quarter 2012 profit decline account growing popularity smart phones tablets mobile devices slowed sale personal computers may 30 2012 hp unveiled first net zero energy data center hp data center plans use solar energy renewable sources instead traditional power grids july 10 2012 hp server monitoring software discovered previously unknown security vulnerability security warning given customers two vulnerabilities patch released one month later hp official site training center hacked defaced pakistani hacker known 'hitcher demonstrate web vulnerability september 10 2012 hp revised restructuring figures cutting 29,000 jobs hp already cut 3,800 jobs – around 7 percent revised 29,000 figure – july 2012 december 31 2013 hp revised number jobs cut 29,000 34,000 october 2014 current number jobs cut end 2013 24,600 end 2013 company 317,500 employees may 22 2014 hp announced would cut 11,000 16,000 jobs addition 34,000 announced 2013 gradually shaping hp nimble lower-cost customer partner-centric company successfully compete across rapidly changing landscape ceo meg whitman said time june 2014 hp discover customer event las vegas meg whitman martin fink announced project radically new computer architecture called machine based memristors silicon photonics machine supposed come commercialization end decade meanwhile representing 75 research activity hp labs october 6 2014 hewlett-packard announced planning split two separate companies separating personal computer printer businesses technology services split first reported wall street journal confirmed media would result two publicly traded companies hewlett packard enterprise hp inc. meg whitman would serve chairman hp inc. ceo hewlett packard enterprise patricia russo would chairman enterprise business dion weisler would ceo hp inc. october 29 2014 hewlett-packard announced new sprout personal computer may 2015 company announced would selling controlling 51 percent stake chinese data-networking business tsinghua unigroup fee least 2.4 billion november 1 2015 previously announced hewlett-packard changed name hp inc. spun hewlett packard enterprise new publicly traded company hp inc. retains hewlett-packard stock price history stock ticker symbol hewlett packard enterprise trades symbol hp global operations directed headquarters palo alto california usa u.s. operations directed facility unincorporated harris county texas near houston latin america offices unincorporated miami-dade county florida u.s. near miami europe offices meyrin switzerland near geneva also research center paris-saclay cluster 20 km south paris france asia-pacific offices singapore also large operations leixlip ireland austin texas boise idaho corvallis oregon fort collins colorado roseville california saint petersburg florida san diego california tulsa oklahoma vancouver washington conway arkansas plano texas former headquarters eds hp acquired uk hp based large site bracknell berkshire offices various uk locations including landmark office tower london 88 wood street recent acquisition 3com expand employee base marlborough massachusetts company also large workforce numerous offices bucharest romania bangalore india address back end operations mphasis headquartered bangalore also enabled hp increase footprint city subsidiary eds company acquired hp produces lines printers scanners digital cameras calculators pdas servers workstation computers computers home small-business use many computers came 2002 merger compaq hp promotes supplying hardware software also full range services design implement support infrastructure hp imaging printing group ipg described company 2005 leading imaging printing systems provider world printer hardware printing supplies scanning devices providing solutions across customer segments individual consumers small medium businesses large enterprises products technology associated ipg include december 23 2008 hp released iprint photo iphone free downloadable software application allows printing 4 x 6 photos hp personal systems group psg claims one leading vendors personal computers pcs world based unit volume shipped annual revenue psg deals hp resold apple ipod november 2005 hp enterprise business eb incorporates hp technology services enterprise services amalgamation former eds known hp services hp enterprise security services oversees professional services network security information security information assurance/ compliancy hp software division enterprise servers storage networking group essn enterprise servers storage networking group essn oversees back end products like storage servers hp networking former procurve responsible nw family products business unit essn hp software division company enterprise software unit years hp produced marketed brand enterprise-management software hp openview september 2005 hp purchased several software companies part publicized deliberate strategy augment software offerings large business customers hp software sells several categories software including hp software also provides software service saas cloud computing solutions software services including consulting education professional services support hp office strategy technology four main functions office strategy technology comes hp labs research arm hp founded 1966 hp labs aims deliver new technologies create business opportunities go beyond hp current strategies examples recent hp labs technology includes memory spot chip 2006 hp idealab provides web forum early-state innovations encourage open feedback consumers development community hp also offers managed services provide complete it-support solutions companies organizations examples include founders developed management style came known hp way hewlett words hp way core ideology ... includes deep respect individual dedication affordable quality reliability commitment community responsibility view company exists make technical contributions advancement welfare humanity following tenets hp way july 2007 company announced met target set 2004 recycle one billion pounds electronics toner ink cartridges set new goal recycling two billion pounds hardware end 2010 2006 company recovered 187 million pounds electronics 73 percent closest competitor 2008 hp released supply chain emissions data — industry first september 2009 newsweek ranked hp 1 2009 green rankings america 500 largest corporations according environmentalleader.com hewlett-packard earned number one position due greenhouse gas ghg emission reduction programs first major company report ghg emissions associated supply chain according ranking addition hp made effort remove toxic substances products though greenpeace targeted company better hp took top spot corporate responsibility magazine 100 best corporate citizens list 2010 list cited pr week one america important business rankings hp beat russell 1000 index companies leadership seven categories including environment climate changes corporate philanthropy 2009 hp ranked fifth fortune magazine named hp one world admired companies 2010 placing 2 computer industry 32 overall list top 50 year computer industry hp ranked 1 social responsibility long-term investment global competitiveness use corporate assets may 2011 hp released global responsibility report covering accomplishments 2010 report company tenth provides comprehensive view hp global citizenship programs performance goals describes hp uses technology influence expertise make positive impact world company 2009 report best corporate responsibility report year 2009 reports claims hp decreased total energy use 9 percent compared 2008 hp recovered total 118,000 tonnes electronic products supplies recycling 2009 including 61 million print cartridges april 2010 san francisco chronicle article hp one 12 companies commended designing products safe start following principles green chemistry commendations came environment california environmental advocacy group praised select companies golden state bay area efforts keep planet clean green may 2010 hp named one world ethical companies ethisphere institute second year row hp made list ethisphere reviewed researched analyzed thousands nominations 100 countries 35 industries create 2010 list hp one 100 companies earn distinction top winner computer hardware vendor recognized ethisphere honors firms promote ethical business standards practices going beyond legal minimums introducing innovative ideas benefit public hp listed greenpeace guide greener electronics ranks electronics manufacturers according policies sustainability energy climate green products november 2011 hp secured 1st place 15 ranking climbing 3 places increased score 5.9 5.5 scored points new sustainable operations criteria best program measuring reducing emissions greenhouse gases suppliers scoring maximum points thorough paper procurement policy november 2012 report hp ranked second score 5.7 hp especially well disclosure externally verified greenhouse gas emissions setting targets reducing however greenpeace reports hp risks penalty point future editions due fact member trade associations commented energy efficiency standards hp earned recognition work area data privacy security 2010 company ranked 4 ponemon institute annual study trusted companies privacy since 2006 hp worked directly u.s. congress federal trade commission ftc department commerce establish new strategy federal legislation hp played key role work toward december 2010 ftc report protecting consumer privacy era rapid change winning nine straight annual respected company china awards economic observer peking university hp china added 10 year contribution award list accolades award aims identify companies business china outstanding sustained performance business operations development corporate social responsibility 2012 rankings consumer electronics companies progress relating conflict minerals enough project rated hp second 24 companies calling pioneer progress according businessweek study hp world 11th valuable brand 2009 hp many sponsorships one well known sponsorship epcot walt disney world resort 1995 1999 2013 hp shirt sponsor premier league club tottenham hotspur f.c 1997 1999 sponsors australian football league club north melbourne football club also sponsored bmw williams formula 1 team 2005 sponsorship formerly held compaq 2010 sponsor renault f1 hewlett-packard also naming rights arrangement hp pavilion san jose home san jose sharks nhl hockey team 2013 arena naming rights acquired sap ag renaming arena sap center san jose company also maintains number corporate sponsorships business sector including sponsorships trade organisations including fespa print trade exhibitions o'reilly media velocity web development conference acquisition compaq 2002 hp maintained compaq presario brand low-end home desktops laptops hp compaq brand business desktops laptops hp proliant brand intel-architecture servers hp pavilion brand used home entertainment laptops home desktops tandem nonstop servers branded hp integrity nonstop march 2003 hp restated first-quarter cash flow operations reducing 18 percent accounting error actual cash flow operations 647 million 791 million reported earlier hp shifted 144 million net cash used investing activities september 5 2006 shawn cabalfin david o'neil newsweek wrote hp general counsel behest chairwoman patricia dunn contracted team independent security experts investigate board members several journalists order identify source information leak turn security experts recruited private investigators used spying technique known pretexting pretexting involved investigators impersonating hp board members nine journalists including reporters cnet new york times wall street journal order obtain phone records information leaked related hp long-term strategy published part cnet article january 2006 hp employees accused criminal acts since acquitted november 2007 hewlett-packard released bios update covering wide range laptops intent speed computer fan well run constantly whether computer reason prevent overheating defective nvidia graphics processing units gpus shipped many original equipment manufacturers including hewlett-packard dell apple defect concerned new packaging material used nvidia 2007 onwards joining graphics chip onto motherboard perform well thermal cycling prone develop stress cracks – effectively severing connection gpu motherboard leading blank screen july 2008 hp issued extension initial one-year warranty replace motherboards selected models however option extended models defective nvidia chipsets despite research showing computers also affected fault furthermore replacement motherboard temporary fix since fault inherent units affected models point manufacture including replacement motherboards offered hp free 'repair since point several websites documenting issue notably www.hplies.com forum dedicated refer hewlett-packard multi-million dollar cover issue www.nvidiadefect.com details specifics fault offers advice owners affected computers several small-claims lawsuits filed several states well suits filed countries hewlett-packard also faced class-action lawsuit 2009 i7 processor computers complainants stated systems locked within 30 minutes powering consistently even replaced newer i7 systems lockups continued june 15 2011 hp filed lawsuit california superior court santa clara claiming oracle corporation breached agreement support itanium microprocessor used hp high-end enterprise servers june 15 2011 hp sent formal legal demand letter oracle attempt force world 3 software maker reverse decision discontinue software development intel itanium microprocessor build servers hp lawsuit 2012 requiring oracle continue produce software compatible itanium processor hp awarded 3 billion damages oracle june 30 2016 hp argued oracle canceling support damaged hp itanium server brand oracle announced appeal decision damages november 2012 hp recorded writedown around 8.8 billion related acquisition year earlier uk based autonomy corporation plc hp accused autonomy deliberately inflating value company prior takeover former management team autonomy flatly rejected charge autonomy specialized analysis large scale unstructured big data 2010 uk largest successful software business maintained aggressively entrepreneurial marketing approach controls described rod iron said include zero tolerance firing weakest 5 sales force quarter compensating best sales staff like rock stars time hp fired previous ceo expenses irregularities year appointed léo apotheker ceo president hp seen problematic market margins falling failed redirect establish major new markets cloud mobile services apotheker strategy aim disposing hardware moving profitable software services sector part strategy autonomy acquired hp october 2011 hp paid 10.3 billion 87.3 shares valuing autonomy around 11.7 billion £7.4 billion overall premium around 79 market price deal widely criticized absurdly high botched strategy shift chaotic attempt rapidly reposition hp enhance earnings objected even hp cfo within year apotheker fired major culture clashes became apparent hp written 8.8 billion autonomy value hp claim resulted accounting improprieties misrepresentations disclosure failures previous management turn accuse hp textbook example defensive stalling conceal evidence prior knowledge gross mismanagement undermining company noting public awareness since 2009 financial reporting issues even hp cfo disagreed price paid external observers generally state small part write-off appears due accounting mis-statements hp overpaid businesses previously serious fraud office united kingdom u.s. securities exchange commission joined fbi investigating potential anomalies hp incurred much damage stock falling decades low three lawsuits brought shareholders hp fall value hp shares august 2014 united states district court judge threw proposed settlement autonomy previous management argued would collusive intended divert scrutiny hp responsibility knowledge essentially engaging plaintiff attorneys existing cases redirecting previous autonomy vendors management fee 48 million plaintiffs agreeing end claims hp management similarly redirect claims previous autonomy vendors management january 2015 sfo closed investigation likelihood successful prosecution low dispute still litigated us investigated uk ireland financial reporting council june 9 2015 hp agreed pay 100 million investors bought hp shares august 19 2011 november 20 2012 settle suite autonomy purchase october 25 2012 richard falk human rights council special rapporteur situation human rights palestinian territories occupied since 1967 called boycotting hp together businesses profiting israeli settlements occupied palestinian lands brought operations line international human rights humanitarian law 2014 presbyterian church voted move forward divestment hp protest israeli policies toward palestinians 2015 city portland human rights commission requested place caterpillar g4s hewlett-packard motorola solutions city buy list april 9 2014 administrative proceeding securities exchange commission settled hp consenting order acknowledging hp violated foreign corrupt practices act fcpa hp subsidiaries russia poland mexico made improper payments government officials obtain retain lucrative public contracts sec order finds hp subsidiary russia paid 2 million agents various shell companies russian government official retain multimillion-dollar contract federal prosecutor office poland hp subsidiary provided gifts cash bribes worth 600,000 polish government official obtain contracts national police agency part bid win software sale mexico state-owned petroleum company hp subsidiary mexico paid 1 million inflated commissions consultant close ties company officials money funneled one officials hp agreed pay 108 million settle sec charges parallel criminal case
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Distributed computing architecture
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lauri love lauri love born 14 december 1984 united kingdom british activist charged stealing data united states government computers including united states army missile defense agency nasa via computer intrusion love stradishall suffolk parents alexander love prison chaplain hm prison highpoint north sirkka-liisa love finnish citizen also works prison live stradishall dual citizenship united kingdom finland dropping sixth form college working turkey plant love applied finnish passport served finnish army six months became conscientious objector finished another six months obligation alternative civilian service applied university nottingham england dropped second term physical mental collapse university glasgow scotland dropped second year health reasons part 2011 hetherington house occupation student protest glasgow university love indictment united states 2013 district new jersey 2014 southern district new york eastern district virginia allegedly breaching thousands computer systems united states elsewhere – including computer networks federal agencies – steal massive quantities confidential data united states attempted extradite face charges love american attorney tor ekeland love two day extradition hearing 28 29 june 2016 westminster magistrates court london father testified lauri love asperger syndrome extradited also hearing simon baron-cohen psychologist testified love extradited diagnosed disorders also include eczema psychosis depression love lives home parents baron-cohen stated love told would commit suicide extradited love father testified son diagnosed autism adult serving finnish army baron-cohen diagnosed love asperger syndrome 2012 love end 20s love testified extradition hearing 29 june 2016 suggested court love family crafted media strategy garner public support extradition love supported courage foundation love barrister extradition hearing ben cooper doughty street chambers case adjourned 16 september 2016 westminster magistrates court judge ruled love could extradited united states love solicitor karen todner said would appeal 5 february 2018 lord chief justice lord burnett mr justice ouseley high court upheld appeal extradition ruling would oppressive prosecute mr love england offences national crime agency nca arrested love 2013 february 2015 bbc news revealed love taking legal action return computers seized nca arrested may 2016 judge nina tempia westminster magistrates court ruled love tell nca passwords encryption keys january 2018 announced novelist frederick forsyth would publish novel inspired lauri love gary mckinnon stories
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Computer security
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intel gma intel graphics media accelerator gma series integrated graphics processors introduced 2004 intel replacing earlier intel extreme graphics series succeeded intel hd iris graphics series series targets market low-cost graphics solutions products series integrated onto motherboard limited graphics processing power use computer main memory storage instead dedicated video memory commonly found netbooks low-priced laptops desktop computers well business computers need high levels graphics capability early 2007 90 pc motherboards sold integrated gpu gma line gpus replaces earlier intel extreme graphics intel740 line latter discrete unit form agp pci cards technology evolved companies real3d lockheed martin later intel integrated i740 core intel 810 chipset original architecture gma systems supported functions hardware relied host cpu handle least graphics pipeline decreasing performance however introduction intel 4th generation gma architecture gma x3000 2006 many functions built hardware providing increase performance 4th generation gma combines fixed function capabilities threaded array programmable executions units providing advantages graphics video performance many advantages new gma architecture come ability flexibly switch needed executing graphics-related tasks video-related tasks gma performance widely criticized past slow computer games sometimes nicknamed intel gmd graphics media decelerator essentially referred world first graphics decelerator since s3 virge latest gma generation ease many concerns casual gamer despite similarities intel main series gma integrated graphics processors igps based powervr technology intel licensed imagination technologies intel used low-power powervr mbx designs chipsets supporting xscale platform since sale xscale 2006 licensed powervr sgx used gma 500 igp use atom platform introduction platform controller hub graphics media accelerator series ceased cpu-based intel hd iris graphics series created gma 900 first graphics core produced intel graphics media accelerator product name incorporated intel 910g 915g 915gx chipsets 3d architecture gma 900 significant upgrade previous extreme 3d graphics processors 4 pixel per clock cycle design supporting directx 9 pixel shader model 2.0 operates clock rate ranging 160 333 mhz depending particular chipset 333 mhz peak pixel fill-rate 1332 megapixels per second however architecture still lacks support hardware transform lighting similar vertex shader technologies like previous intel integrated graphics parts gma 900 hardware support mpeg-2 motion compensation color-space conversion directdraw overlay processor uses different separate clock generators display render cores display unit includes 400 mhz ramdac two 25–200 mpixel/s serial dvo ports two display controllers mobile chipsets two 18-bit 25–112 mhz lvds transmitters included gma 950 second graphics core produced intel graphics media accelerator product name incorporated intel 945g chipsets processor includes 400 mhz 256-bit core supporting 10.6 gb/s memory bandwidth ddr2-667 system ram 224 mb max video memory dvmt scheme 1.6 gpixels/s 1.6 gtexels/s fill rate max resolution 2048x1536 analog digital displays 2 sdvo ports flat-panels and/or tv-out via add2 cards media expansion cards 3d-wise gma 950 supports four pixels per clock rendering microsoft directx 9.0 hardware acceleration vertex shader 3.0 opengl 1.4 arb extensions windows integrated graphics found q33 q35 g31 g33 chipsets supports pixel shader 2.0 opengl 1.4 hardware vertex shader n't supported found intel atom d4xx d5xx n4xx n5xx codenamed pineview processors like gma 3100 gma 3000 close relative gma900/950 completely different gma x3000 series supports 384 mb video memory windows xp driver directx 9.0c shader model 2.0 opengl 1.4 microsoft windows opengl 2.1 linux 946gz q963 q965 chipsets use gma 3000 graphics core gma 3000 3d core different x3000 despite similar names based directly previous generation gma 900 gma 950 graphics belonging i915 family pixel vertex shaders support shader model 2.0b features vertex shaders still software-emulated addition hardware video acceleration hardware-based idct computation procamp video stream independent color correction vc-1 decoding implemented hardware gma 3000-equipped chipsets q965 retains dual independent display support core speed rated 400 mhz 1.6 gpixel/s fill rate datasheets listed 667 mhz core white paper memory controller address maximum 256 mb system memory integrated serial dvo ports increased top speed 270 mpixel/s gma x3000 desktop substantially redesigned compared previous gma iterations used intel g965 north bridge controller gma x3000 launched july 2006 gma x3000 underlying 3d rendering hardware organized unified shader processor consisting 8 scalar execution units pipeline process video vertex texture operations central scheduler dynamically dispatches threads pipeline resources maximize rendering throughput decrease impact individual pipeline stalls however due scalar nature execution units process data single pixel component time gma x3000 supports directx 9.0 vertex pixel shader model 3.0 features processor consists different clock domains meaning entire chip operate clock speed causes difficulty measuring peak throughput various functions adding confusion listed 667 mhz intel g965 white paper listed 400 mhz intel g965 datasheet various rules define igp processing capabilities memory controller address maximum 384 mb memory according white paper 256 mb datasheet gma x3500 upgrade gma x3000 used desktop g35 shaders support shader model 4.0 features architecturally gma x3500 similar gma x3000 graphics cores running 667 mhz major difference gma x3500 supports shader model 4.0 directx 10 whereas earlier x3000 supports shader model 3.0 directx 9 x3500 also adds hardware-assistance playback vc-1 video gma x3100 mobile version gma x3500 used intel gl960/gm965 chipsets also gs965 chipset x3100 supports hardware transform lighting eight programmable shader units 384 mb video memory display cores run 333 mhz gm965 320 mhz gl960 render cores run 500 mhz gm965 400 mhz gl960 x3100 display unit includes 300 mhz ramdac two 25–112 mhz lvds transmitters 2 dvo encoders tv encoder windows driver supports directx 10.0 shader model 4.0 opengl 1.5 linux opengl 2.1 supported integrated graphics found b43 q43 q45 chipsets gma x4500 gma x4500hd desktop platforms launched june 2008 gma x4500 used g43 chipset gma x4500hd used g45 chipset gma x4500 also used g41 chipset released september 2008 difference gma x4500 gma x4500hd gma x4500hd capable full 1080p high-definition video playback including blu-ray disc movies like x3500 x4500 supports directx 10 shader model 4.0 features intel designed gma x4500 200 faster gma 3100 g33 chipset 3dmark06 performance 70 faster gma x3500 g35 chipset gma 4500mhd laptops launched july 16 2008 featurewise 4500mhd identical desktop cousin x4500hd gma 4500mhd used gl40 gs40 gm45 gs45 chipsets gma x4700mhd laptops launched october 2008 last product intel gma way belongs 4500mhd series used gm47 chipsets montevina features 80 shading units 10 texture mapping units 1 rops compared 4500mhd frequency increased 640 mhz intel developed new set low power graphics architecture based powervr available linux drivers support much intel sch system controller hub codenamed poulsbo atom processor z5xx series features gma 500 graphic system rather developed in-house core powervr sgx 535 core licensed imagination technologies intel describes flexible programmable architecture supports shader-based technology 2d 3d advanced 3d graphics high-definition video decode image processing features include screen tiling internal true color processing zero overhead anti-aliasing programmable shader 3d accelerator 32-bit floating-point operations revised version previous intel sch system controller hub atom z6xx series cpu codenamed lincroft essentially graphic system gma 500 clocked double speed 200 mhz 400 mhz integrated graphics system released intel atom cedar trail 32 nm based powervr sgx545 unlike original powervr solution model clocked 400 mhz instead 200 mhz specifically found intel atom n2600 processor atom d2500 models supports directx version 9.0c similar gma 3600 version clocked 640 mhz found atom n2800 atom d2550 atom d2500 atom d2600 atom d2700 models supports directx version 9.0c protected audio video path pavp restricts data path within computer video playback e.g. blu-ray discs supported newer chipsets e.g intel g45 operating systems since windows vista pavp configured bios different modes supported default setting bios pavp lite within intel hd graphics successor intel gma similar technology called intel insider exists mac os x 10.4 supports gma 950 since used previous revisions macbook macmini 17-inch imacs used intel-based mac minis mac mini released march 3 2009 mac os x 10.5 leopard contains drivers gma x3100 used recent revision macbook range late-release versions mac os x 10.4 also support gma 900 due use apple developer transition kit used powerpc-to-intel transition however special modifications kext file must made enable core image quartz extreme although new macbook line longer uses x3100 mac os x 10.5 leopard ships drivers supporting require modifications kext file mac os x 10.6 snow leopard includes new 64-bit kernel addition 32-bit one include 64-bit x3100 drivers means although macbooks x3100 64-bit capable processors efi mac os x must load 32-bit kernel support 32-bit x3100 drivers november 9 10.6.2 update ships 64-bit x3100 drivers apple removed 64-bit gma x3100 drivers later thus affected macs forced back 32-bit kernel despite 64-bit clean terms hardware firmware 64-bit drivers offered os x lion subsequently os x mountain lion dropped 32-bit kernel booting combination two changes graphics driver code resulted many mac revisions unable upgrade mountain lion gpus replaced macbook macbook pro notebooks instead shipped far powerful nvidia geforce 9400m 15 17 macbook pro notebooks shipped additional geforce 9600gt supporting hybrid power switch gpus nvidia geforce 9400m chipset implemented apple macbooks support composite s-video output freebsd 8.0 supports following intel graphic chipsets i810 i810-dc100 i810e i815 i830m 845g 852gm 855gm 865g 915g 915gm 945g 945gm 965g 965q 946gz 965gm,945gme g33 q33 q35 g35 gm45 g45 q45 g43 g41 chipsets practice chipsets 4500mhd supported drm 3d using freebsd 9 work integrate gem kms currently adding support i-series integrated graphics improving support earlier chipsets august 2006 intel added support open-source x.org/xfree86 drivers latest 965 series include gma x 3000 core drivers developed intel tungsten graphics may 2007 version 2.0 driver xorg-video-intel released added support 965gm chipset addition 2.0 driver added native video mode programming support chipsets i830 forward version added support automatic video mode detection selection monitor hot plug dynamic extended merged desktops per-monitor screen rotation features built x.org 7.3 x server release eventually supported across open source x.org video drivers version 2.1 released july 2007 added support g33 q33 q35 chipsets g35 also supported linux driver common x.org drivers linux license combination gpl linux kernel parts mit parts drivers mainly developed intel tungsten graphics contract since chipsets documentation publicly available long time january 2008 intel released complete developer documentation time latest chipsets 965 g35 chipset allowing external developers involvement april 2009 intel released documentation newer g45 graphics including x4500 chipsets may 2009 intel employee eric anholt stated intel still working getting docs 8xx chipsets linux support hardware accelerated h.264 playback available working x4500hd x4500mhd using vaapi g45-h264 branch gma 500 gma 600 gma 3600 gma 3650 powervr based chips incompatible intel genx gpu architecture family intel supported foss drivers current available foss drivers included linux 3.3 onwards support 2d acceleration 3d acceleration ubuntu supports gma500 poulsbo ubuntu-mobile gma500 repositories launchpad support present experimental way 11.10 12.04 installation procedure simple drivers lead many bugs ubuntu 12.10 2d support included joli os linux-based os optimized netbooks driver gma500 built pixielive gnu/linux live distribution optimized gma500 netbooks boot usb pendrive sd card harddisk intel releases official linux drivers iegd intel embedded graphic driver supporting linux distributions dedicated embedded market november 2009 linux foundation released details new rewritten linux driver would support chipset intel upcoming chipsets direct rendering manager x.org parts would free software 3d component using gallium3d still proprietary oracle solaris 11 provides 64-bit video driver support following intel graphic chipsets i810 i810-dc100 i810e i815 i830m 845g 852gm/855gm 865g 915g e7221 i915 915gm 945g 945gm 945gme pineview gm pineview g 965g g35 965q 946gz 965gm 965gme/gle g33 q35 q33 gm45 4 series g45/g43 q45/q43 g41 b43 clarkdale arrandale sandybridge desktop gt1 sandybridge desktop gt2 sandybridge desktop gt2+ sandybridge mobile gt1 sandybridge mobile gt2 sandybridge mobile gt2+ ivybridge mobile gt1 ivybridge mobile gt2 ivybridge desktop gt1 ivybridge desktop gt2 ivybridge server gt1 ivybridge server gt2 solaris open-source community developers provide additional driver support intel hd graphics 4000/2500 graphic-based chipsets aka ivy bridge opengl 3.0/glsl 1.30 new libva/va-api library enabling hardware accelerated video decode prevailing coding standards today mpeg-2 mpeg-4 asp/h.263 mpeg-4 avc/h.264 vc-1/wmv3 gma 900 theoretically capable running windows vista aero interface certified directx 9 compliant however whql certified wddm driver made available presumably due lack hardware scheduler gpu intel gma 900 also first intel integrated gpu support drivers windows 9x operating systems including 98 many owners gma900 hardware believed would able run aero systems early release candidates vista permitted xddm drivers run aero intel however contends microsoft final specs aero/wddm certification permit releasing wddm driver gma900 due issues hardware scheduler mentioned final version vista released wddm driver released last minute pulling opengl capabilities gma drivers windows vista left large number gma based workstations unable perform basic 3d hardware acceleration opengl unable run many vista premium applications windows dvd maker windows 7 aero effects enabled vga compatibility driver via software rendering native gma900 drivers available windows 8 since xddm support removed operating system gma900 based laptops windows 7 users may experience serious bug related chipset native backlight control method failing change brightness resulting brightness becoming stuck particular value driver installation bug occur windows 7 initially released public commonly observed running windows update bug also occurs gma3150 based laptops igp capable displaying aero interface windows vista drivers shipped windows vista since beta versions became available mid-2006 also run windows 7 aero interface since intel released drivers windows 7 mid-june 2009 gma 950 integrated many netbooks built intel 945gse express chipset able display resolution 2048×1536 75 hz utilizing 224 mb shared memory reviews igp negative since many games need pixel shader 2.0 higher supported hardware vertex shader 2.0 software-emulated games crysis start frame rates acceptable l vertex shaders 3.0 supported intel newest 15.6 drivers windows vista september 2 2007 xp support vs3 l introduced august 10 2007 intel announced march 2007 beta drivers would available june 2007 june 1 2007 pre-beta early beta drivers released windows xp vista beta drivers vista xp released june 19 since hardware l vertex shading enabled drivers individual applications forced fall back software rendering raises performance compatibility certain cases selection based testing intel preselected driver .inf file intel released production version drivers 32-bit 64-bit windows vista enable aero graphics intel introduced directx 10 x3100 x3500 gpus vista 15.9 drivers 2008 though release dx10 drivers x3000 uncertain wddm 1.1 supported x3100 dxva-hd opengl 2.0 support available since vista 15.11 drivers xp 14.36 drivers windows 8 ships driver x3100 september 2010 latest available driver revisions intel website windows xp vista 7 performance functionality gma processors limited attaining performance low-cost discrete gpus best old directx 6 gpus riva tnt2 worst thus 're sometimes even dubbed graphics media decelerators though actual performance depended cpu well ram amount speed example atom n450 cpu gma 3150 perform comparably riva tnt2 pc tualatin pentium 3 even worse gpu sometimes even underclocked hindering already poor performance even features games 3d applications may unsupported gmas particularly older ones gma x3x00 unified shader design allows complete hardware functionality line still issues games significantly limited performance intel put page 'known issues solutions version intel graphics media accelerator software development concerns integrated graphics software development forum review conducted april 2007 tech report determined gma x3000 performance comparable nvidia geforce 6150 review gma x3000 unable run pc games battlefield 2 however extremetech review found games n't graphically demanding sims 2 civilization iv look good gma x3000 used run reviews performed tech report extremetech anandtech concluded amd radeon x1250 integrated graphics solutions based amd 690g chipset better choice gma x3000 based g965 chipset especially considering 3d gaming performance price review performed register hardware december 2007 author leo waldock argued gma x3500 capable running pc game requires directx 10 addition directx 10 support gma x3500 irrelevant review gma x3500 used run crysis f.e.a.r extraction point able render 4 14 frames per second respectively game end review concluded overall x3500 made minimal advances gma x3000 review published may 2008 gma x4500 showed superior game performance lowest-end 1-year-older geforce 8400m graphics card cpu-bound tests losing still low-end geforce 8400m gs slower cpu
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Computer architecture
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mac filtering computer networking mac filtering refers security access control method whereby mac address assigned network card used determine access network mac addresses uniquely assigned card using mac filtering network permits denies network access specific devices use blacklists whitelists restriction network access use lists straightforward individual person identified mac address rather device authorized person need whitelist entry device would use access network giving network additional protection mac filtering circumvented using packet analyzer find valid mac using mac spoofing access network using address mac address filtering considered security obscurity effectiveness based secrecy implementation components many devices support mac filtering device basis whitelisted mac addresses allowed port device blacklisted mac addresses blocked ports devices cisco catalyst switches support mac filtering port-by-port basis referred port security port security may configured statically list dynamically based first given number addresses detected combination two methods port security configured default settings allow one mac address per port shut port allowed number addresses exceeded mac filtering also used enterprise wireless networks multiple access points prevent clients communicating access point configured allows clients talk default gateway wireless clients
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Internet protocols
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sims freeplay sims freeplay strategic life simulation game developed ea mobile later firemonkeys studios free version sims mobile devices released ios december 15 2011 released android february 15 2012 released blackberry 10 july 31 2013 released windows phone 8 september 12 2013 game released fire os october 2012 sims freeplay players build design houses customize create maximum 100 virtual people called sims players control sims satisfy wishes let complete different kinds actions gain simoleons lifestyle points social points three currencies game game runs real-time takes real time complete actions actions must instructed players unlike windows version sims degree autonomy players progress 55 levels unlock content furniture sims ’ houses purchased virtual currencies previously mentioned families sims children provided one one adult limit amount allowable couples due limit people player town however player buys items online store become vip allow increase number sims town game quests players required complete well optional quests discovery quests may choose pursue sims must bake cake age completion certain quota discovery quests make cake takes 24 hours costs 5 lifestyle points three styles currency simoleons gained completing actions baking/cooking gardening sending sims work lifestyle ponts gained completing hobby collections tasks social points gained completing social tasks rewarded 1-2 social points game detail sims 4 sims mobile choices sim customization limited unless bought real currency time complete actions takes realistic times complete actions take 3 days game regularly updated new content many events competitions announced freeplay official facebook page updates commonly include elements various expansion packs stuff packs main series april 2017 windows phones longer receive updates game june 2018 pregnancy baby showers added game said fans requested feature added game ever since freeplay launched update sims marry option given add baby family october 15 2018 augmented reality multiplayer added july 2019 autosave function available
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Operating systems
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hardware security hardware security discipline originated cryptographic engineering involves hardware design access control secure multi-party computation secure key storage ensuring code authenticity measures ensure supply chain built product secure among things hardware security module hsm physical computing device safeguards manages digital keys strong authentication provides cryptoprocessing modules traditionally come form plug-in card external device attaches directly computer network server hardware backdoors backdoors hardware conceptionally related hardware trojan ht malicious modification electronic system particularly context integrated circuit physical unclonable function puf physical entity embodied physical structure easy evaluate hard predict individual puf device must easy make practically impossible duplicate even given exact manufacturing process produced respect hardware analog one-way function name physical unclonable function might little misleading pufs clonable pufs noisy therefore achieve requirements function today pufs usually implemented integrated circuits typically used applications high security requirements many attacks sensitive data resources reported organizations occur within organization
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Computer security
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slob slob simple list blocks allocator one three available memory allocators linux kernel two slab slub slob allocator designed require little memory implementation housekeeping use small systems embedded systems unfortunately major limitation slob allocator suffers greatly internal fragmentation slob currently uses first-fit algorithm uses first available space memory 2008 reply linus torvalds linux mailing list made suggested use best-fit algorithm tries find memory block suits needs best best fit finds smallest space fits required amount available avoiding loss performance fragmentation consolidation memory default linux kernel used slab allocation system version 2.6.23 slub allocation became default config_slab flag disabled kernel falls back using slob allocator slob allocator used dslinux nintendo ds handheld console
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Computer architecture
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bestcrypt bestcrypt commercial disk encryption app windows linux os x developed jetico inc oy bestcrypt comes two editions volume encryption edition encrypts entire disk volumes container encryption edition encrypts virtual disks stored computer files also provides complimentary data erasure utility bcwipe bestcrypt supports wide variety block cipher algorithms including aes serpent blowfish twofish des triple des gost 28147-89 ciphers support cbc lrw modes operation aes twofish serpent also support xts mode
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Computer file systems
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sean hastings sean hastings born 1969 entrepreneur cypherpunk author security expert best known founding ceo havenco world first formal data 1997 hastings worked cryptographic protocols tools free u.s. cryptographic export restrictions vincent cate started international conference financial cryptography anguilla year hastings founded havenco 2000 originally incorporating country residence anguilla second incorporation channel islands hastings ceo co-founders included ryan lackey sameer parekh immediately following public launch havenco subject great deal press coverage including hastings appearance along several cofounders royal family sealand cover wired july 2000 issue company entirely nationalised government sealand 2002 commercial failure mounting tensions 2002 hastings began work seasteading patri friedman project aimed building floating communities free restrictions current governments collaboration continued 2009 including talk hastings seasteading institute annual conference hastings cofounder eric s. raymond green-span open source infrastructure trust reputation management begun march 2009 hastings also author paul rosenberg book god wants dead vera verba 2007 takes look lighter side atheism anarchy
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Computer security
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live partition mobility live partition mobility chargeable live migration feature ibm power6 power7 power8 power9 servers available since 2007 allows running lpar relocated one system another concept similar vmware vmotion live partition mobility component powervm enterprise edition hardware feature provides ability move aix ibm linux logical partitions one system another mobility process transfers system environment includes processor state memory attached virtual devices connected users source target systems must access network sans need type requirement use power6 power7 power8 processors partitions relocated must fully virtualized i.e dedicated i/o adapters although possible use multi-pathing software fail virtual adapters duration move sized partition moved essentially memory copied asynchronously one system another create clone running partition dirty pages re-copied necessary threshold reached i.e high percentage pages successfully copied across partition transitioned target machine remaining pages copied across synchronously agents carry memory copying nominated virtual i/o servers machine standard ethernet network used data transmission live partition mobility used avoid outages planned server maintenance load balancing across multiple servers energy conservation
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Computer architecture
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polestar xeus polestar xeus cloud computing software manufactured nkia corporation south korea used manage iaas solutions provides various functions required management cloud systems reporting sla usage amount particular users times management construction performance events statistics virtual machines storage networks resource use policy management features gui-based drag-and-drop workflow api connection cloud systems polestar xeus compatible iaas solutions including vmware vsphere microsoft hyper-v citrix xen red hat enterprise virtualization nkia provides polestar xeus south korea
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Distributed computing architecture
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interpreted language interpreted language type programming language implementations execute instructions directly freely without previously compiling program machine-language instructions interpreter executes program directly translating statement sequence one subroutines another language often machine code terms interpreted language compiled language well defined theory programming language either interpreted compiled modern programming language implementation increasingly popular platform provide options interpreted languages also contrasted machine languages functionally execution interpretation mean thing — fetching next instruction/statement program executing although interpreted byte code additionally identical machine code form assembler representation term interpreted sometimes reserved software processed languages virtual machine emulator top native i.e hardware processor principle programs many languages may compiled interpreted emulated executed natively designation applied solely based common implementation practice rather representing essential property language many languages implemented using compilers interpreters including basic c lisp pascal java c compiled bytecode virtual-machine-friendly interpreted language lisp implementations freely mix interpreted compiled code distinction compiler interpreter always well defined many language processors combination early days computing language design heavily influenced decision use compiling interpreting mode execution example smalltalk 1980 designed interpreted run-time allows generic objects dynamically interact initially interpreted languages compiled line-by-line line compiled executed loop subroutine caused certain lines executed multiple times would recompiled every time become much less common so-called interpreted languages use intermediate representation combines compiling interpreting examples include intermediate representation compiled java time execution ruby time change source detected execution python interpreting language gives implementations additional flexibility compiled implementations features often easier implement interpreters compilers include furthermore source code read copied giving users freedom disadvantages interpreted languages several criteria used determine whether particular language likely called compiled interpreted users definitive compiled languages interpreter-like properties vice versa many languages first compiled bytecode ѕometimes bytecode also compiled native binary using aot compiler executed natively hardware processor
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Programming language topics
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multicoreware multicoreware inc software development company offering products services related hevc video compression ii machine learning specifically convolutional neural networks iii compilers heterogeneous computing iv software performance optimization multicoreware customers include amazon amd arm microsoft google telestream bbright technologies multicoreware founded 2009 today offices 3 countries – usa china india multicoreware placed 110 inc. 5000 list fastest growing private companies america year 2014 st. louis missouri based technology start-up accelerator iten listed company list top ten tech startups st. louis area three consecutive years 2012–2014 multicoreware ranked 22nd fastest growing private company silicon valley silicon valley business journal october 2014 july 2014 multicoreware named ee times silicon 60 list hot startups watch multicoreware inc. tie50 awards finalist tiecon2014 multicoreware leads development x265 hevc encoder x265 based x264 h.264/mpeg-4 avc encoder similar command-line syntax feature set x265 offered either gnu general public license gpl 2 license commercial license february 2014 telestream vantage transcode multiscreen became first commercial product introduce x265 encoding technology october 2015 video group moscow state university identified x265 highest overall efficiency i.e lowest bit rate target quality level first comparison hevc encoders lipsync tool automatically detects audio-video synchronization errors video using machine learning deep learning technologies errors detected without digital fingerprinting watermarking multicoreware offers uhdcode hevc video decoder api available x86 arm xbox 360 ps3 opencl accelerated supports hevc main/ main10 profiles march 2015 multicoreware launched x265 hevc upgrade includes x265 encoder application uhdcode directshow filter allowing hevc video playback 64-bit windows media player multicore cross platform architecture mxpa heterogeneous computing stack based llvm framework capable supporting opencl renderscript cuda c++ amp hcc open source parallel c++ compiler hsa opencl 1.2 hcc provides compiler frontends c++amp c++ source parallel stl openmp multicoreware one world ’ largest heterogeneous computing teams across globe offers accelerated software development services multicoreware contributor member khronos group active several standards full range services include
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Web technology
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unix-like unix-like sometimes referred un*x *nix operating system one behaves manner similar unix system necessarily conforming certified version single unix specification unix-like application one behaves like corresponding unix command shell standard defining term difference opinion possible degree given operating system application unix-like term include free open-source operating systems inspired bell labs unix designed emulate features commercial proprietary work-alikes even versions based licensed unix source code may sufficiently unix-like pass certification bear unix trademark open group owns unix trademark administers single unix specification unix name used certification mark approve construction unix-like consider misuse trademark guidelines require unix presented uppercase otherwise distinguished surrounding text strongly encourage using branding adjective generic word system discourage use hyphenated phrases parties frequently treat unix genericized trademark add wildcard character name make abbreviation like un*x *nix since unix-like systems often unix-like names aix a/ux hp-ux irix linux minix ultrix xenix xinu xnu patterns literally match many system names still generally recognized refer unix descendant work-alike system even completely dissimilar names darwin/macos illumos/solaris freebsd 2007 wayne r. gray sued dispute status unix trademark lost case lost appeal court upholding trademark ownership unix-like systems started appear late 1970s early 1980s many proprietary versions idris 1978 unos 1982 coherent 1983 uniflex 1985 aimed provide businesses functionality available academic users unix allowed relatively inexpensive commercial binary sub-licensing unix 1979 variety proprietary systems developed based including aix hp-ux irix sunos tru64 ultrix xenix largely displaced proprietary clones growing incompatibility among systems led creation interoperability standards including posix single unix specification various free low-cost unrestricted substitutes unix emerged 1980s 1990s including 4.4bsd linux minix turn basis commercial unix-like systems bsd/os macos several versions mac os x/macos running intel-based mac computers certified single unix specification bsd variants descendants unix developed university california berkeley unix source code bell labs however bsd code base evolved since replacing code since bsd variants certified compliant single unix specification referred unix-like rather unix dennis ritchie one original creators unix expressed opinion unix-like systems linux de facto unix systems eric s. raymond rob landley suggested three kinds unix-like systems systems historical connection codebase commercial unix systems fall category bsd systems descendants work done university california berkeley late 1970s early 1980s systems original code still trace ancestry designs systemslargely commercial naturehave determined open group meet single unix specification allowed carry unix name systems commercial derivatives system v code base one form another although apple macos 10.5 later bsd variant certified systems ibm z/os earned trademark posix compatibility layer otherwise inherently unix systems many ancient unix systems longer meet definition broadly unix-like system behaves manner roughly consistent unix specification including program manages login command line sessions specifically refer systems linux minix behave similarly unix system genetic trademark connection code base free/open-source implementations unix design whether genetic unix fall restricted definition third category due expense obtaining open group certification costs thousands dollars commercial closed source systems around 2001 linux given opportunity get certification including free help posix chair andrew josey symbolic price one dollar activities make linux posix-compliant josey prepared list differences posix standard linux standard base specification august 2005 project shut missing interest lsb work group non-unix-like operating systems provide unix-like compatibility layer variable degrees unix-like functionality means windows-unix interoperability include
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Operating systems
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salesforce tower salesforce tower formerly known transbay tower office skyscraper south market district downtown san francisco located 415 mission street first fremont streets next transbay transit center site salesforce tower centerpiece san francisco transbay redevelopment plan plan contains mix office transportation retail residential uses upon completion 2018 became tallest skyscraper san francisco skyline top roof height overall height surpassing transamerica pyramid also second-tallest building west mississippi river wilshire grand center los angeles though salesforce tower taller wilshire grand center decorative spire excluded shorter roofline los angeles u.s. bank tower developer hines interests limited partnership proposal architect césar pelli pelli clarke pelli architects selected winner global competition 2007 entitle purchase site seven-member jury development experts assembled transbay joint powers authority tjpa selected hines proposals forest city enterprises architect richard rogers rockefeller development group corp. skidmore owings merrill 2012 boston properties acquired 50 stake project 2013 acquired hines remaining interest become 95 owners project site tower dilapidated area formerly used ground-level entrance san francisco transbay terminal demolished 2011 tjpa sold parcel boston properties hines us 192 million ceremonial groundbreaking new tower occurred march 27 2013 below-grade construction work starting late 2013 project joint venture general contractors clark construction hathaway dinwiddie construction footprint salesforce tower rests land fill near san francisco original waterfront area prone soil liquefaction earthquakes account seismic risk tower uses design modeled withstand strongest earthquakes expected region foundation includes 42 piles driven nearly bedrock thick foundation mat development originally contracted spec hines major tenant lease secured beforehand april 11 2014 salesforce.com announced signed lease become building anchor tenant previously known transbay tower building renamed salesforce tower lease valued us 560 million 15 half years starting 2017 tower opened 2018 61 floors decorative crown reaching original proposal called tower height later reduced building first tenants began moving january 8 2018 upon opening building 97 leased tenants including salesforce covington burling wework bain company accenture mcdermott emery hellman friedman 61st floor known ohana floor serves observation deck lounge salesforce employees guests made available use nonprofits evenings weekends transbay transit center located foot building february 5 2019 company announced opened advanced registration public tours ohana floor every month starting february 23 10 april 2019 council tall buildings urban habitat ctbuh named salesforce tower “ best tall building worldwide 2019 17th annual ctbuh international best tall building awards symposium ceremony dinner celebrated grand hyatt shenzhen shenzhen china
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Distributed computing architecture
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parsing parsing syntax analysis syntactic analysis process analysing string symbols either natural language computer languages data structures conforming rules formal grammar term parsing comes latin pars orationis meaning part speech term slightly different meanings different branches linguistics computer science traditional sentence parsing often performed method understanding exact meaning sentence word sometimes aid devices sentence diagrams usually emphasizes importance grammatical divisions subject predicate within computational linguistics term used refer formal analysis computer sentence string words constituents resulting parse tree showing syntactic relation may also contain semantic information term also used psycholinguistics describing language comprehension context parsing refers way human beings analyze sentence phrase spoken language text terms grammatical constituents identifying parts speech syntactic relations etc term especially common discussing linguistic cues help speakers interpret garden-path sentences within computer science term used analysis computer languages referring syntactic analysis input code component parts order facilitate writing compilers interpreters term may also used describe split separation traditional grammatical exercise parsing sometimes known clause analysis involves breaking text component parts speech explanation form function syntactic relationship part determined large part study language conjugations declensions quite intricate heavily inflected languages parse phrase 'man bites dog involves noting singular noun 'man subject sentence verb 'bites third person singular present tense verb 'to bite singular noun 'dog object sentence techniques sentence diagrams sometimes used indicate relation elements sentence parsing formerly central teaching grammar throughout english-speaking world widely regarded basic use understanding written language however general teaching techniques longer current machine translation natural language processing systems written texts human languages parsed computer programs human sentences easily parsed programs substantial ambiguity structure human language whose usage convey meaning semantics amongst potentially unlimited range possibilities germane particular case utterance man bites dog versus dog bites man definite one detail another language might appear man dog bites reliance larger context distinguish two possibilities indeed difference concern difficult prepare formal rules describe informal behaviour even though clear rules followed order parse natural language data researchers must first agree grammar used choice syntax affected linguistic computational concerns instance parsing systems use lexical functional grammar general parsing grammars type known np-complete head-driven phrase structure grammar another linguistic formalism popular parsing community research efforts focused less complex formalisms one used penn treebank shallow parsing aims find boundaries major constituents noun phrases another popular strategy avoiding linguistic controversy dependency grammar parsing modern parsers least partly statistical rely corpus training data already annotated parsed hand approach allows system gather information frequency various constructions occur specific contexts see machine learning approaches used include straightforward pcfgs probabilistic context-free grammars maximum entropy neural nets successful systems use lexical statistics consider identities words involved well part speech however systems vulnerable overfitting require kind smoothing effective parsing algorithms natural language rely grammar 'nice properties manually designed grammars programming languages mentioned earlier grammar formalisms difficult parse computationally general even desired structure context-free kind context-free approximation grammar used perform first pass algorithms use context-free grammars often rely variant cyk algorithm usually heuristic prune away unlikely analyses save time see chart parsing however systems trade speed accuracy using e.g. linear-time versions shift-reduce algorithm somewhat recent development parse reranking parser proposes large number analyses complex system selects best option semantic parsers convert texts representations meanings psycholinguistics parsing involves assignment words categories formation ontological insights evaluation meaning sentence according rules syntax drawn inferences made word sentence known connotation normally occurs words heard read consequently psycholinguistic models parsing necessity incremental meaning build interpretation sentence processed normally expressed terms partial syntactic structure creation initially wrong structures occurs interpreting garden path sentences discourse analysis examines ways analyze language use semiotic events persuasive language may called rhetoric parser software component takes input data frequently text builds data structure – often kind parse tree abstract syntax tree hierarchical structure giving structural representation input checking correct syntax parsing may preceded followed steps may combined single step parser often preceded separate lexical analyser creates tokens sequence input characters alternatively combined scannerless parsing parsers may programmed hand may automatically semi-automatically generated parser generator parsing complementary templating produces formatted output may applied different domains often appear together scanf/printf pair input front end parsing output back end code generation stages compiler input parser often text computer language may also text natural language less structured textual data case generally certain parts text extracted rather parse tree constructed parsers range simple functions scanf complex programs frontend c++ compiler html parser web browser important class simple parsing done using regular expressions group regular expressions defines regular language regular expression engine automatically generating parser language allowing pattern matching extraction text contexts regular expressions instead used prior parsing lexing step whose output used parser use parsers varies input case data languages parser often found file reading facility program reading html xml text examples markup languages case programming languages parser component compiler interpreter parses source code computer programming language create form internal representation parser key step compiler frontend programming languages tend specified terms deterministic context-free grammar fast efficient parsers written compilers parsing done one pass multiple passes – see one-pass compiler multi-pass compiler implied disadvantages one-pass compiler largely overcome adding fix-ups provision made code relocation forward pass fix-ups applied backwards current program segment recognized completed example fix-up mechanism would useful would forward goto statement target goto unknown program segment completed case application fix-up would delayed target goto recognized conversely backward goto require fix-up location already known context-free grammars limited extent express requirements language informally reason memory language limited grammar remember presence construct arbitrarily long input necessary language example name must declared may referenced powerful grammars express constraint however parsed efficiently thus common strategy create relaxed parser context-free grammar accepts superset desired language constructs accepts invalid constructs later unwanted constructs filtered semantic analysis contextual analysis step example python following syntactically valid code following code however syntactically valid terms context-free grammar yielding syntax tree structure previous syntactically invalid terms context-sensitive grammar requires variables initialized use rather analyzed parsing stage caught checking values syntax tree hence part semantic analysis context-sensitive syntax practice often easily analyzed semantics following example demonstrates common case parsing computer language two levels grammar lexical syntactic first stage token generation lexical analysis input character stream split meaningful symbols defined grammar regular expressions example calculator program would look input codice_1 split tokens codice_2 codice_3 codice_4 codice_5 codice_6 codice_7 codice_8 codice_9 codice_10 meaningful symbol context arithmetic expression lexer would contain rules tell characters codice_3 codice_6 codice_9 codice_4 codice_8 mark start new token meaningless tokens like codice_16 codice_17 generated next stage parsing syntactic analysis checking tokens form allowable expression usually done reference context-free grammar recursively defines components make expression order must appear however rules defining programming languages expressed context-free grammars alone example type validity proper declaration identifiers rules formally expressed attribute grammars final phase semantic parsing analysis working implications expression validated taking appropriate action case calculator interpreter action evaluate expression program compiler hand would generate kind code attribute grammars also used define actions task parser essentially determine input derived start symbol grammar done essentially two ways parsers recursive-descent parser examples top-down parsers accommodate left recursive production rules although believed simple implementations top-down parsing accommodate direct indirect left-recursion may require exponential time space complexity parsing ambiguous context-free grammars sophisticated algorithms top-down parsing created frost hafiz callaghan accommodate ambiguity left recursion polynomial time generate polynomial-size representations potentially exponential number parse trees algorithm able produce left-most right-most derivations input regard given context-free grammar important distinction regard parsers whether parser generates leftmost derivation rightmost derivation see context-free grammar parsers generate leftmost derivation lr parsers generate rightmost derivation although usually reverse algorithms designed visual programming languages parsers visual languages sometimes based graph grammars adaptive parsing algorithms used construct self-extending natural language user interfaces well known parser development tools include following also see comparison parser generators lookahead establishes maximum incoming tokens parser use decide rule use lookahead especially relevant lr lalr parsers often explicitly indicated affixing lookahead algorithm name parentheses lalr 1 programming languages primary target parsers carefully defined way parser limited lookahead typically one parse parsers limited lookahead often efficient one important change trend came 1990 terence parr created antlr ph.d. thesis parser generator efficient k parsers k fixed value lr parsers typically actions seeing token shift add token stack later reduction reduce pop tokens stack form syntactic construct end error known rule applies conflict know whether shift reduce lookahead two advantages example parsing expression programming languages except apl smalltalk algebraic formulas give higher precedence multiplication addition case correct interpretation example note rule4 semantic rule possible rewrite grammar incorporate syntax however rules translated syntax initially input 1 2 3 parse tree resulting code correct according language semantics correctly parse without lookahead three solutions parse tree generated correct simply non-lookahead parsers strategy followed lalr parsers
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Programming language topics
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robocop 1988 video game robocop beat 'em up/run gun arcade game developed published data east 1988 based 1987 film name sub-licensed data east ocean software obtained rights orion pictures script stage robocop hybrid game featuring elements beat 'em well run gun titles despite arcade game numerous versions appeared home computers video game consoles first group released 1988 apple ii pc compatibles amiga atari st apple pc ports developed quicksilver software amiga st versions developed directly ocean data east published game north america nes port followed 1989 developed sakata sas co version trs-80 coco 3 ocean developed published version game boy 1990 1989 ocean released different robocop game bore loose resemblance arcade version produced commodore 64 msx zx spectrum tandy color computer 3 amstrad cpc well pc compatibles meaning pcs ended two entirely different robocop games north american european audiences many ocean c64 titles cassette disk versions released north american release also published data east based disk version c64 robocop versions notorious high numbers bugs 2015 cracker group nostalgia released completely bug-fixed robocop compatible pal ntsc machines port game atari jaguar planned never released zx spectrum version robocop achieved particular critical success receiving crash smash award crash 94 sinclair user sinclair gave 8.8 10 also placing number 94 sinclair official top 100 overall opinion game better original arcade game capture original material smooth scrolling animation sampled speech sound effects highlighted addition zx spectrum robocop one biggest selling games time platform number one sales charts year half entered charts april 1989 still top five february 1991 readers ys voted 9th best game time title theme ocean software versions composed jonathan dunn become well known serene calm tune heavily contrasted tone actual game source material version theme heard game boy port later licensed european kitchen appliance company ariston use series tv adverts song also used theme song charlie brooker documentary videogames changed world well music internet short dilbert 3 song sampled lil b song bad mixtape white flame
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Computer architecture
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microsoft jet database engine microsoft jet database engine also microsoft jet engine simply jet database engine several microsoft products built first version jet developed 1992 consisting three modules could used manipulate database jet stands joint engine technology microsoft access visual basic use used jet underlying database engine however superseded general use first microsoft desktop engine msde later sql server express larger database needs jet databases upgraded microsoft parlance up-sized microsoft flagship sql server database product however mean ms jet red database match ms sql server storage capacity 5 billion record ms jet red database compression encryption turned requires 1 terabyte disk storage space comprising hundreds *.mdb files acting partial table database jet part relational database management system rdbms allows manipulation relational databases offers single interface software use access microsoft databases provides support security referential integrity transaction processing indexing record page locking data replication later versions engine extended run sql queries store character data unicode format create database views allow bi-directional replication microsoft sql server three modules jet one native jet isam driver dynamic link library dll directly manipulate microsoft access database files mdb using indexed sequential access method isam another one modules contains isam drivers dlls allow access variety isam databases among xbase paradox btrieve foxpro depending version jet final module data access objects dao dll dao provides api allows programmers access jet databases using programming language jet allows multiple users access database concurrently prevent data corrupted invalidated multiple users try edit record page database jet employs locking policy single user modify database records items database user applied lock gives exclusive access record lock released jet versions version 4 page locking model used jet 4 record locking model employed microsoft databases organized data pages fixed-length 2 kb jet 4 4 kb jet 4 data structures data stored records variable length may take less one page page locking model works locking pages instead individual records though less resource-intensive also means user locks one record records page collaterally locked result user access collaterally locked records even though user accessing need locked jet 4 record locking model eliminates collateral locks every record use available two mechanisms microsoft uses locking pessimistic locking optimistic locking pessimistic locking record page locked immediately lock requested optimistic locking locking delayed edited record saved conflicts less likely occur optimistic locking since record locked short period time however optimistic locking one certain update succeed another user could lock record first pessimistic locking update guaranteed succeed lock obtained users must wait lock released order make changes lock conflicts either require user wait cause request fail usually timeout common pessimistic locking jet supports transaction processing database systems capability odbc systems one-level transaction processing several isam systems like paradox support transaction processing transaction series operations performed database must done together — known atomicity one acid atomicity consistency isolation durability concepts considered key transaction processing features database management system transaction processing work jet 3.0 programmer needed begin transaction manually perform operations needed performed transaction commit save transaction transaction committed changes made memory actually written disk transactions number advantages independent database updates one main advantages transactions abandoned problem occurs transaction called rolling back transaction rollback restores state database records precisely state transaction began transactions also permit state database remain consistent system failure occurs middle sequence updates required atomic chance updates end written database either succeed changes discarded database system restarts odbc in-memory policy transactions also allow many updates record occur entirely within memory one expensive disk write end implicit transactions supported jet 3.0 transactions started automatically last transaction committed database implicit transactions jet occurred sql dml statement issued however found negative performance impact 32-bit windows windows 95 windows 98 jet 3.5 microsoft removed implicit transactions sql dml statements made jet enforces entity integrity referential integrity jet default prevent change record breaks referential integrity jet databases instead use propagation constraints cascading updates cascading deletes maintain referential integrity jet also supports business rules also known constraints rules apply column enforce data might placed table column example rule might applied allow date entered date_logged column earlier current date time rule might applied forces people enter positive value numeric field access jet databases done per user-level user information kept separate system database access controlled object system instance table query jet 4 microsoft implemented functionality allows database administrators set security via sql commands create add alter drop user drop group commands subset ansi sql 92 standard also apply grant/revoke commands jet 2 released security could also set programmatically dao queries mechanisms jet uses retrieve data database defined microsoft qbe query example microsoft access sql window access basic data access objects dao language converted sql select statement query compiled — involves parsing query involves syntax checking determining columns query database table converted internal jet query object format tokenized organised tree like structure jet 3.0 onwards optimised using microsoft rushmore query optimisation technology query executed results passed back application user requested data jet passes data retrieved query dynaset set data dynamically linked back database instead query result stored temporary table data updated directly user dynaset allows user view update data contained dynaset thus university lecturer queries students received distinction assignment finds error student record would need update data dynaset would automatically update student database record without need send specific update query storing query results temporary table jet originally started 1992 underlying data access technology came microsoft internal database product development project code named cirrus cirrus developed pre-release version visual basic code used database engine microsoft access tony goodhew worked microsoft time says would reasonably accurate say stage jet name team assigned work db engine modules access rather component team vb visual basic 3.0 basically tear access graft onto vb 've jet/odbc problems vb 3.0 jet became componentised access 2.0 released access odbc developers used parts jet code produce odbc driver retrofit provided allowed visual basic 3.0 users use updated jet issued access 2.0 jet 2.0 released several dynamic linked libraries dlls utilised application software microsoft access database dlls windows libraries common code used one application—by keeping code one application uses common library applications use independently code maintenance reduced functionality applications increases less development effort jet 2.0 comprised three dlls jet dll data access objects dao dll several external isam dlls jet dll determined sort database accessing perform requested data source mdb file microsoft access format would directly read write data file data source external would call correct odbc driver perform request dao dll component programmers could use interface jet engine mainly used visual basic access basic programmers isam dlls set modules allowed jet access three isam based databases xbase paradox btrieve jet 2.0 replaced jet 2.1 used database structure different locking strategies making incompatible jet 2.0 jet 3.0 included many enhancements including new index structure reduced storage size time taken create indices highly duplicated removal read locks index pages new mechanism page reuse new compacting method compacting database resulted indices stored clustered-index format new page allocation mechanism improve jet read-ahead capabilities improved delete operations speeded processing multithreading three threads used perform read ahead write behind cache maintenance implicit transactions users instruct engine start manually commit transactions database new sort engine long values memos binary data types stored separate tables dynamic buffering whereby jet cache dynamically allocated start limit changed first first fifo buffer replacement policy least recently used lru buffer replacement policy jet 3.0 also allowed database replication jet 3.0 replaced jet 3.5 uses database structure different locking strategies making incompatible jet 3.0 jet 4.0 gained numerous additional features enhancements microsoft access versions access 2000 access 2010 included upsizing wizard could upsize upgrade jet database equivalent database sql server table structure data many attributes original database reports queries macros security handled tool meaning manual modifications might needed application heavily reliant jet features standalone version jet 4 database engine component microsoft data access components mdac included every version windows windows 2000 jet database engine 32-bit run natively 64-bit versions windows meant native 64-bit applications 64-bit versions sql server could access data stored mdb files odbc ole db means except intermediate 32-bit software running wow64 acted proxy 64-bit client version 2007 onwards access includes office-specific version jet initially called office access connectivity engine ace called access database engine however ms-access consultants vba developers specialize ms-access likely refer ace database engine engine backward-compatible previous versions jet engine could read write .mdb files earlier access versions introduced new default file format .accdb brought several improvements access including complex data types multivalue fields attachment data type history tracking memo fields also brought security changes encryption improvements enabled integration microsoft windows sharepoint services 3.0 microsoft office outlook 2007 engine microsoft access 2010 discontinued support access 1.0 access 2.0 lotus 1-2-3 paradox files 64-bit version access 2010 ace driver/provider introduced essence provides 64-bit version jet driver part windows operating system available redistributable engine microsoft access 2013 discontinued support access 95 access 97 xbase files also discontinued support replication version 1608 microsoft access 2016 restored support xbase files version 1703 introduced large number data type data access technology standpoint jet considered deprecated technology microsoft microsoft continues support ace part microsoft access microsoft provides jet drivers microsoft windows therefore third party software support jet databases almost exclusively found windows open source project attempts enable working jet databases platforms mdb tools much extended java port named jackcess
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Databases
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internet control message protocol internet control message protocol icmp supporting protocol internet protocol suite used network devices including routers send error messages operational information indicating example requested service available host router could reached icmp differs transport protocols tcp udp typically used exchange data systems regularly employed end-user network applications exception diagnostic tools like ping traceroute icmp ipv4 defined rfc 792 icmp part internet protocol suite defined rfc 792 icmp messages typically used diagnostic control purposes generated response errors ip operations specified rfc 1122 icmp errors directed source ip address originating packet example every device intermediate router forwarding ip datagram first decrements time live ttl field ip header one resulting ttl 0 packet discarded icmp time exceeded transit message sent datagram source address many commonly used network utilities based icmp messages traceroute command implemented transmitting ip datagrams specially set ip ttl header fields looking icmp time exceeded transit destination unreachable messages generated response related ping utility implemented using icmp echo request echo reply messages icmp uses basic support ip higher level protocol however icmp actually integral part ip although icmp messages contained within standard ip packets icmp messages usually processed special case distinguished normal ip processing many cases necessary inspect contents icmp message deliver appropriate error message application responsible transmission ip packet prompted sending icmp message icmp network layer protocol tcp udp port number associated icmp packets numbers associated transport layer icmp packet encapsulated ipv4 packet packet consists header data sections icmp header starts ipv4 header identified ip protocol number 1 icmp packets 8-byte header variable-sized data section first 4 bytes header fixed format last 4 bytes depend type/code icmp packet icmp error messages contain data section includes copy entire ipv4 header plus least first eight bytes data ipv4 packet caused error message maximum length icmp error messages 576 bytes data used host match message appropriate process higher level protocol uses port numbers assumed first eight bytes original datagram data variable size icmp packet data section exploited ping death large fragmented ping packets used denial-of-service attacks icmp data also used create covert channels communication channels known icmp tunnels control messages identified value type field code field gives additional context information message control messages deprecated since protocol first introduced source quench requests sender decrease rate messages sent router host message may generated router host sufficient buffer space process request may occur router host buffer approaching limit data sent high speed host several hosts time particular router network although router buffering capabilities buffering limited within specified range router queue data capacity limited buffering space thus queue gets filled incoming data discarded queue longer full acknowledgement mechanism present network layer client know whether data reached destination successfully hence remedial measures taken network layer avoid kind situations measures referred source quench source quench mechanism router sees incoming data rate much faster outgoing data rate sends icmp message clients informing slow data transfer speeds wait certain amount time attempting send data client receives message automatically slow outgoing data rate wait sufficient amount time enables router empty queue thus source quench icmp message acts flow control network layer since research suggested icmp source quench ineffective unfair antidote congestion routers creation source quench messages deprecated 1995 rfc 1812 furthermore forwarding kind reaction flow control actions source quench messages deprecated 2012 rfc 6633 redirect requests data packets sent alternative route icmp redirect mechanism routers convey routing information hosts message informs host update routing information send packets alternative route host tries send data router r1 r1 sends data another router r2 direct path host r2 available host r2 ethernet segment r1 send redirect message inform host best route destination via r2 host send packets destination directly r2 router still send original datagram intended destination however datagram contains routing information message sent even better route available rfc 1122 states redirects sent gateways sent internet hosts time exceeded generated gateway inform source discarded datagram due time live field reaching zero time exceeded message may also sent host fails reassemble fragmented datagram within time limit time exceeded messages used traceroute utility identify gateways path two hosts timestamp used time synchronization originating timestamp set time milliseconds since midnight sender last touched packet receive transmit timestamps used timestamp reply replies timestamp message consists originating timestamp sent sender timestamp well receive timestamp indicating timestamp received transmit timestamp indicating timestamp reply sent address mask request normally sent host router order obtain appropriate subnet mask recipients reply message address mask reply message icmp address mask request may used part reconnaissance attack gather information target network therefore icmp address mask reply disabled default cisco ios address mask reply used reply address mask request message appropriate subnet mask destination unreachable generated host inbound gateway inform client destination unreachable reason reasons message may include physical connection host exist distance infinite indicated protocol port active data must fragmented 'do n't fragment flag unreachable tcp ports notably respond tcp rst rather destination unreachable type 3 might expected destination unreachable never reported ip multicast transmissions
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Internet protocols
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stored procedure stored procedure also termed proc storp sproc stopro storedproc storeproc sp sp subroutine available applications access relational database management system rdbms procedures stored database data dictionary uses stored procedures include data-validation integrated database access-control mechanisms furthermore stored procedures consolidate centralize logic originally implemented applications save time memory extensive complex processing requires execution several sql statements saved stored procedures applications call procedures one use nested stored procedures executing one stored procedure within another stored procedures may return result sets i.e. results codice_1 statement result sets processed using cursors stored procedures associating result-set locator applications stored procedures may also contain declared variables processing data cursors allow loop multiple rows table stored-procedure flow-control statements typically include codice_2 codice_3 codice_4 codice_5 codice_6 statements stored procedures receive variables return results modify variables return depending variable declared stored procedures similar user-defined functions udfs major difference udfs used like expression within sql statements whereas stored procedures must invoked using codice_7 statement exact correct implementation stored procedures varies one database system major database vendors support form depending database system stored procedures implemented variety programming languages example sql java c c++ stored procedures written non-sql languages may may execute sql statements increasing adoption stored procedures led introduction procedural elements sql language standards part sql/psm made sql imperative programming language database systems offer proprietary vendor-specific extensions exceeding sql/psm standard specification java stored procedures exists well sql/jrt systems stored procedures used control transaction management others stored procedures run inside transaction transactions effectively transparent stored procedures also invoked database trigger condition handler example stored procedure may triggered insert specific table update specific field table code inside stored procedure would executed writing stored procedures condition handlers also allows database administrators track errors system greater detail using stored procedures catch errors record audit information database external resource like file prepared statements take ordinary statement query parameterize different literal values used later time like stored procedures stored server efficiency provide protection sql injection attacks although simpler declarative prepared statements ordinarily written use procedural logic operate variables simple interface client-side implementations prepared statements widely reusable dbms
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Databases
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application security application security encompasses measures taken improve security application often finding fixing preventing security vulnerabilities different techniques used surface security vulnerabilities different stages applications lifecycle design development deployment upgrade maintenance always evolving largely consistent set common security flaws seen across different applications see common flaws different techniques find different subsets security vulnerabilities lurking application effective different times software lifecycle represent different tradeoffs time effort cost vulnerabilities found utilizing techniques appropriately throughout software development life cycle sdlc maximize security role application security team according patterns practices improving web application security book following classes common application security threats attacks owasp community publishes list top 10 vulnerabilities web applications outlines best security practices organizations aiming create open standards industry 2017 organization lists top application security threats proportion mobile devices providing open platform functionality expected continue increase future openness platforms offers significant opportunities parts mobile eco-system delivering ability flexible program service delivery= options may installed removed refreshed multiple times line user ’ needs requirements however openness comes responsibility unrestricted access mobile resources apis applications unknown untrusted origin could result damage user device network managed suitable security architectures network precautions application security provided form open os mobile devices symbian os microsoft brew etc. 2017 google expanded vulnerability reward program cover vulnerabilities found applications developed third parties made available google play store industry groups also created recommendations including gsm association open mobile terminal platform omtp several strategies enhance mobile application security including security testing techniques scour vulnerabilities security holes applications vulnerabilities leave applications open exploitation ideally security testing implemented throughout entire software development life cycle sdlc vulnerabilities may addressed timely thorough manner unfortunately testing often conducted afterthought end development cycle growth continuous delivery devops popular software development deployment models continuous security models becoming popular vulnerability scanners specifically web application scanners otherwise known penetration testing tools i.e ethical hacking tools historically used security organizations within corporations security consultants automate security testing http request/responses however substitute need actual source code review physical code reviews application source code accomplished manually automated fashion given common size individual programs often 500,000 lines code human brain execute comprehensive data flow analysis needed order completely check circuitous paths application program find vulnerability points human brain suited filtering interrupting reporting outputs automated source code analysis tools available commercially versus trying trace every possible path compiled code base find root cause level vulnerabilities many kinds automated tools identifying vulnerabilities applications require great deal security expertise use others designed fully automated use results dependent types information source binary http traffic configuration libraries connections provided tool quality analysis scope vulnerabilities covered common technologies used identifying application vulnerabilities include static application security testing sast technology frequently used source code analysis tool method analyzes source code security vulnerabilities prior launch application used strengthen code method produces fewer false positives implementations requires access application source code requires expert configuration lots processing power dynamic application security testing dast technology able find visible vulnerabilities feeding url automated scanner method highly scalable easily integrated quick dast drawbacks lie need expert configuration high possibility false positives negatives interactive application security testing iast solution assesses applications within using software instrumentation technique allows iast combine strengths sast dast methods well providing access code http traffic library information backend connections configuration information iast products require application attacked others used normal quality assurance testing advances professional malware targeted internet customers online organizations seen change web application design requirements since 2007 generally assumed sizable percentage internet users compromised malware data coming infected host may tainted therefore application security begun manifest advanced anti-fraud heuristic detection systems back-office rather within client-side web server code 2016 runtime application self-protection rasp technologies developed rasp technology deployed within alongside application runtime environment instruments application enables detection prevention attacks cert coordination center describes coordinated vulnerability disclosure cvd “ process reducing adversary advantage information security vulnerability mitigated. ” cvd iterative multi-phase process involves multiple stakeholders users vendors security researchers may different priorities must work together resolve vulnerability cvd processes involve multiple stakeholders managing communication vulnerability resolution critical success operational perspective many tools processes aid cvd include email web forms bug tracking systems coordinated vulnerability platforms
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Computer security
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socks socks internet protocol exchanges network packets client server proxy server socks5 additionally provides authentication authorized users may access server practically socks server proxies tcp connections arbitrary ip address provides means udp packets forwarded socks performs layer 5 osi model session layer intermediate layer presentation layer transport layer socks server accepts incoming client connection tcp port 1080 protocol originally developed/designed david koblas system administrator mips computer systems mips taken silicon graphics 1992 koblas presented paper socks year usenix security symposium making socks publicly available protocol extended version 4 ying-da lee nec socks reference architecture client owned permeo technologies spin-off nec blue coat systems bought permeo technologies socks5 protocol originally security protocol made firewalls security products easier administer approved ietf 1996 protocol developed collaboration aventail corporation markets technology outside asia socks de facto standard circuit-level gateways another use socks circumvention tool allowing traffic bypass internet filtering access content otherwise blocked e.g. governments workplaces schools country-specific web services ssh suites openssh support dynamic port forwarding allows user create local socks proxy free user limitations connecting predefined remote port server tor onion proxy software presents socks interface clients hacked computers may configured socks proxy software obscuring control botnet optimise credit card fraud socks operates lower level http proxying socks uses handshake protocol inform proxy software connection client trying make acts transparently possible whereas regular proxy may interpret rewrite headers say employ another underlying protocol ftp however http proxy simply forwards http request desired http server though http proxying different usage model mind connect method allows forwarding tcp connections however socks proxies also forward udp traffic work reverse http proxies http proxies traditionally aware http protocol performing higher-level filtering though usually applies get post methods connect method bill wishes communicate jane internet firewall exists network bill authorized communicate jane directly bill connects socks proxy network informing connection wishes make jane socks proxy opens connection firewall facilitates communication bill jane information technical specifics socks protocol see sections bill wishes download web page jane runs web server bill directly connect jane server firewall put place network order communicate server bill connects network http proxy web browser communicates proxy exactly way would directly jane server possible sends standard http request header http proxy connects jane server transmits back bill data jane server returns typical socks4 connection request looks like socks client socks server socks server socks client example socks4 request connect fred 66.102.7.99:80 server replies ok point onwards data sent socks client socks server relayed 66.102.7.99 vice versa command field may 0x01 connect 0x02 bind bind command allows incoming connections protocols active ftp socks4a extends socks4 protocol allow client specify destination domain name rather ip address useful client resolve destination host domain name ip address client set first three bytes dstip null last byte non-zero value corresponds ip address 0.0.0.x x nonzero inadmissible destination address thus never occur client resolve domain name following null byte terminating userid client must send destination domain name terminate another null byte used connect bind requests client socks server server socks client server using protocol socks4a must check dstip request packet represents address 0.0.0.x nonzero x server must read domain name client sends packet server resolve domain name make connection destination host socks5 protocol defined rfc 1928 extension socks4 protocol offers choices authentication adds support ipv6 udp latter used dns lookups initial handshake consists following authentication methods supported numbered follows initial greeting client server choice communicated subsequent authentication method-dependent username password authentication method 0x02 described rfc 1929 username/password authentication client authentication request server response username/password authentication client connection request server response client software must native socks support order connect socks programs allow users circumvent limitations
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Internet protocols
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nokia x platform nokia x platform linux-based mobile operating system software platform originally developed nokia subsequently microsoft mobile introduced 24 february 2014 forked android used devices nokia x family also next nokia linux project ill-fated meego 17 july 2014 acquisition nokia devices unit microsoft announced nokia x smartphones introduced marking end nokia x platform within months introduction phones succeeded low-cost lumia devices microsoft mobile brand name nokia x software platform based android open source project aosp linux kernel nokia combined android apps nokia experiences maps nokia xpress mixradio microsoft services skype outlook nokia officially described software bringing best worlds also encompasses features asha platform fastlane notification centre user interface mimics windows phone os heavily compared amazon.com fire os also based aosp google applications replaced nokia microsoft first released google play store included nokia offering apps nokia store however since v2.1 update september 2014 users allowed install google play various google services third party tools users attempt install google services nokia x devices would usually get bricked would require nokia software recovery tool restore data february 2014 75 android apps compatible platform nokia also noted developers port remaining missing apps matter hours attempt encourage developers contribute platform previously added compatible android apps without developer approval sdk available platform includes emulator based android emulator nokia discouraging developers using windows phone design patterns encouraging android design guidelines nokia x. nokia vp developer relations commented nokia imaging sdk likely ported platform windows phone
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Operating systems
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blacklist computing computing blacklist blocklist basic access control mechanism allows elements email addresses users passwords urls ip addresses domain names file hashes etc except explicitly mentioned items list denied access opposite whitelist means items list let whatever gate used greylist contains items temporarily blocked temporarily allowed additional step performed blacklists applied various points security architecture host web proxy dns servers email server firewall directory servers application authentication gateways type element blocked influenced access control location dns servers may well-suited block domain names example urls firewall well-suited blocking ip addresses less blocking malicious files passwords example uses include company might prevent list software running network school might prevent access list web sites computers business wants ensure computer users choosing easily guessed poor passwords blacklists used protect variety systems computing content blacklist likely needs targeted type system defended information system includes end-point hosts like user machines servers blacklist location may include certain types software allowed run company environment example company might blacklist peer peer file sharing systems addition software people devices web sites also blacklisted email providers anti-spam feature essentially blacklists certain email addresses deemed unwanted example user wearies unstoppable emails particular address may blacklist address email client automatically route messages address junk-mail folder delete without notifying user e-mail spam filter may keep blacklist email addresses mail would prevented reaching intended destination may also use sending domain names sending ip addresses implement general block addition private email blacklists lists kept public use including goal blacklist web browser prevent user visiting malicious deceitful web page via filtering locally common web browsing blacklist google safe browsing installed default firefox safari chrome blacklisting also apply user credentials common systems websites blacklist certain reserved usernames allowed chosen system website user populations reserved usernames commonly associated built-in system administration functions password blacklists similar username blacklists typically contain significantly entries username blacklists password blacklists applied prevent users choosing passwords easily guessed well known could lead unauthorized access malicious parties password blacklists deployed additional layer security usually addition password policy sets requirements password length and/or character complexity significant number password combinations fulfill many password policies still easily guessed i.e. password123 qwerty123 blacklists distributed variety ways use simple mailing lists dnsbl common distribution method leverages dns lists make use rsync high-volume exchanges data web-server functions may used either simple get requests may used complicated interfaces restful api expressed recent conference paper focusing blacklists domain names ip addresses used internet security lists generally intersect therefore appears lists converge one set malicious indicators concern combined economic model means blacklists essential part network defense need used concert whitelists greylists example would adblock plus blocklist includes number features including whitelists within blacklist adding prefix two symbols two pipe symbols e.g ||www.blocksite.com
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Computer security
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mass assignment vulnerability mass assignment computer vulnerability active record pattern web application abused modify data items user normally allowed access password granted permissions administrator status many web application frameworks offer active record object-relational mapping features external data serialization formats automatically converted input internal objects turn database record fields framework interface conversion permissive application designer n't mark specific fields immutable possible overwrite fields never intended modified outside e.g admin permissions flag vulnerabilities found applications written ruby rails asp.net mvc java play framework 2012 mass assignment ruby rails allowed bypassing mapping restrictions resulted proof concept injection unauthorized ssh public keys user accounts github vulnerabilities ruby rails allowed creation internal objects specially crafted json structure asp.net core mapping restriction declared using codice_1 attribute
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Computer security
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f-script programming language f-script object-oriented scripting programming language apple macos operating system developed philippe mougin f-script interactive language based smalltalk using macos native cocoa api f-script based pure object paradigm every entity manipulated within language object base syntax concepts identical language smalltalk canonical example object-oriented language specific extensions support array programming language apl f-script provides interpreted interactive environment support workspaces provide rich set functions including object persistence distributed objects graphical user interface gui framework database access among things like smalltalk f-script syntax simple without requiring specific notation control structures provided unified manner codice_1 operation unlike smalltalk f-script provides specific notational extensions support codice_2 class using curly brackets describe literal arrays may contain f-script expressions example codice_3 valid array literal empty array denoted codice_4 arrays arrays supported transparently since array another object message expressions f-script similar smalltalk specify object receiver message operation called message argument objects needed operation f-script supports unary binary keyword messages f-script message semantics extended support array programming recognizing array operation adding numerical vectors must viewed generating number messages relating elements vectors involved thus codice_5 codice_6 f-script allows codice_7 f-script chiefly used lightweight scripting layer top macos cocoa application programming interface api embedded applications using f-script framework interface builder palettes also used interactively f-script interpreter prototype applications finally used explore applications object hierarchies using injector f-script anywhere
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Programming language topics
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mark shuttleworth mark richard shuttleworth born 18 september 1973 south african british entrepreneur founder ceo canonical ltd. company behind development linux-based ubuntu operating system 2002 became first south african travel space space tourist lives isle man holds dual citizenship south africa united kingdom born welkom south africa orange free state surgeon nursery-school teacher shuttleworth attended school western province preparatory school eventually became head boy 1986 followed one term rondebosch boys high school bishops/diocesan college head boy 1991 shuttleworth obtained bachelor business science degree finance information systems university cape town lived smuts hall student became involved installation first residential internet connections university 1995 shuttleworth founded still-extant thawte consulting company specialized digital certificates internet security december 1999 thawte acquired verisign earning shuttleworth r3.5 billion million equivalent million september 2000 shuttleworth formed hbd venture capital dragons business incubator venture capital provider march 2004 formed canonical ltd. promotion commercial support free software projects especially ubuntu operating system december 2009 shuttleworth stepped ceo canonical ltd jane silber took canonical ceo position shuttleworth resumed position ceo canonical july 2017 end silber tenure 1990s shuttleworth participated one developers debian operating system 2001 formed shuttleworth foundation nonprofit organisation dedicated social innovation also funds educational free open source software projects south africa freedom toaster 2004 returned free software world funding development ubuntu linux distribution based debian company canonical ltd 2005 founded ubuntu foundation made initial investment 10 million dollars ubuntu project shuttleworth often referred tongue-in-cheek title self-appointed benevolent dictator life sabdfl come list names people hire project shuttleworth took six months debian mailing list archives travelling antarctica aboard icebreaker kapitan khlebnikov early 2004 september 2005 purchased 65 stake impi linux 15 october 2006 announced mark shuttleworth became first patron kde highest level sponsorship available relationship ended 2012 together financial support kubuntu ubuntu variant kde main desktop 17 december 2009 mark announced effective march 2010 would step ceo canonical focus energy product design partnership customers jane silber coo canonical since 2004 took job ceo canonical september 2010 received honorary degree open university work 9 november 2012 shuttleworth kenneth rogoff took part debate opposite garry kasparov peter thiel oxford union entitled innovation enigma 25 october 2013 shuttleworth ubuntu awarded austrian anti-privacy big brother award sending local ubuntu unity dash searches canonical servers default year earlier 2012 shuttleworth defended anonymisation method used shuttleworth gained worldwide fame 25 april 2002 second self-funded space tourist first-ever south african space flying space adventures launched aboard russian soyuz tm-34 mission spaceflight participant paying approximately voyage two days later soyuz spacecraft arrived international space station spent eight days participating experiments related aids genome research 5 may 2002 returned earth soyuz tm-33 order participate flight shuttleworth undergo one year training preparation including seven months spent star city russia space radio conversation nelson mandela 14-year-old south african girl michelle foster asked marry politely dodged question stating honoured question changing subject terminally ill foster provided opportunity conversation mark shuttleworth nelson mandela reach dream foundation private jet bombardier global express often referred canonical one fact owned hbd venture capital company dragon depicted side plane norman hbd venture capital mascot upon moving r2.5 billion capital south africa isle man south african reserve bank imposed r250 million levy order release assets shuttleworth appealed lengthy legal battle reserve bank ordered repay r250 million plus interest shuttleworth announced would donating entire amount trust established help others take cases constitutional court 18 june 2015 constitutional court south africa reversed set aside findings lower courts ruling dominant purpose exit charge regulate conduct rather raise revenue
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Operating systems
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shade sandbox shade sandbox sandbox-based isolation program developed eugene balabanov shade distributed consumers shareware solution creates isolated virtual environment within computer rather running software browsing internet directly instead perform actions fenced-off safe area mechanism creates highly controlled environment running untested untrustworthy apps without threatening host operating system shade sandbox basically plugin security toolkit engine platform enables developers build security-related solutions file monitors api spy utilities course virtual environments platform available corporate customers vendor site suggests capabilities platform provides plugins findmysoft rated shade sandbox 5 5 stars naming essential softpedia describes shade simple yet reliable anti-virus protection
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Computer security
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sweet16 sweet16 interpreted byte-code language invented steve wozniak implemented part integer basic rom apple ii series computers created wozniak needed manipulate 16-bit pointer data implementation basic apple ii 8-bit computer sweet16 code executed running 16-bit processor sixteen internal 16-bit little-endian registers named registers well-defined functions 16 virtual registers 32 bytes total located zero page apple ii real physical memory map – values stored low byte followed high byte sweet16 interpreter located integer basic rom according wozniak sweet16 implementation model frugal coding taking 300 bytes memory sweet16 runs one-tenth speed equivalent native 6502 code
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Programming language topics
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iso 9660 iso 9660 file system optical disc media published international organization standardization iso file system considered international technical standard since specification available anybody purchase implementations written many operating systems iso 9660 traces roots high sierra format file system high sierra arranged file information dense sequential layout minimize nonsequential access using hierarchical eight levels directories deep tree file system arrangement similar unix fat facilitate cross platform compatibility defined minimal set common file attributes directory ordinary file time recording name attributes name extension version used separate system use area future optional extensions file may specified high sierra adopted december 1986 changes international standard ecma international ecma-119 submitted fast tracking iso eventually accepted iso 9660:1988 2013 iso published amendment 1 iso 9660 standard introducing new data structures relaxed file name rules intended bring harmonization iso 9660 widely used 'joliet specification december 2017 3rd edition ecma-119 published technically identical iso 9660 amendment 1 following rough overall structure iso 9660 file system system area first 32,768 data bytes disc 16 sectors 2,048 bytes unused iso 9660 therefore available uses example cd-rom may contain alternative file system descriptor area often used hybrid cds offer classic mac os-specific macos-specific content multi-byte values stored twice little-endian big-endian format either one-after-another specification calls both-byte orders duplicated data structures path table structures designed unaligned members endian encoding however help implementors data structures need read byte-wise convert properly aligned data data area begins set one volume descriptors terminated volume descriptor set terminator collectively volume descriptor set acts header data area describing content similar bios parameter block used fat hpfs ntfs formatted disks volume descriptor set terminator simply particular type volume descriptor purpose marking end set structures volume descriptor 2048 bytes size fitting perfectly single mode 1 mode 2 form 1 sector following structure data field volume descriptor may subdivided several fields exact content depending type standard volume descriptor types following iso 9660 compliant disc contains least one primary volume descriptor describing file system volume descriptor set terminator indicating end descriptor sequence primary volume descriptor provides information volume characteristics metadata including root directory record indicates sector root directory located fields contain description name volume information created application size logical blocks file system uses segment volume also stored field inside primary volume descriptor well amount space occupied volume measured number logical blocks addition primary volume descriptor supplementary volume descriptors enhanced volume descriptors may present supplementary volume descriptors describe volume primary volume descriptor normally used providing additional code page support standard code tables insufficient standard specifies iso 2022 used managing code sets wider 8 bytes iso 2375 escape sequences used identify particular code page used consequently iso 9660 supports international single-byte multi-byte character sets provided fit framework referenced standards however iso 9660 specify code pages guaranteed supported use code tables defined standard subject agreement originator recipient volume enhanced volume descriptors introduced iso 9660 amendment 1 relax requirements volume descriptors directory records referenced example directory depth exceed eight file identifiers need contain file version number length file directory identifier maximized 207 redundant copies volume descriptor also included case first copy descriptor becomes corrupt directory entries stored following location root directory entry evaluation filenames begun directories files stored extents sequential series sectors files directories differentiated file attribute indicates nature similar unix attributes file stored directory entry describes file optionally extended attribute record locate file directory names file path checked sequentially going location directory obtain location subsequent subdirectory however file also located path table provided file system path table stores information directory parent location disc since path table stored contiguous region searched much faster jumping particular locations directory file path thus reducing seek time standard specifies three nested levels interchange paraphrased section 10 additional restrictions body standard depth directory hierarchy must exceed 8 root directory level 1 path length file must exceed 255 section 6.8.2.1 standard also specifies following name restrictions sections 7.5 7.6 path tables summarize directory structure relevant directory hierarchy providing directory identifier location extent directory recorded length extended attributes associated directory index parent directory path table entry restrictions filename length 8 characters plus 3 character extension interchange level 1 directory depth 8 levels including root directory serious limitation iso 9660 file system rock ridge extension works around eight-directory depth limit folding paths practice however drivers oses care directory depth rule often ignored addition restrictions mentioned cd-rom producer may choose one lower levels interchange specified chapter 10 standard restrict file name length 30 characters 8+3 file identifiers 8 directory identifiers order promote interchangeability implementations implement full standard sometimes mistakenly interpreted restriction iso 9660 standard numbers iso 9660 file systems except single byte value used gmt offset unsigned numbers length file extent disc stored 32 bit value allows maximum length 4.2 gb precisely one byte less 4 gib note older operating systems may handle values incorrectly i.e signed instead unsigned would make impossible access files larger 2 gb size latter holds true also operating systems without large file support based often assumed file iso 9660 formatted disc larger 2-1 size file size stored unsigned 32 bit value 2-1 maximum however possible circumvent limitation using multi-extent fragmentation feature iso 9660 level 3 create iso 9660 file systems single files 8 tib files larger 4 gib split multiple extents sequential series sectors exceeding 4 gib limit example free software infrarecorder imgburn mkisofs well roxio toast able create iso 9660 file systems use multi-extent files store files larger 4 gib appropriate media recordable dvds empirical tests 4.2 gb fragmented file dvd media shown microsoft windows xp supports mac os x 10.4.8 handle case properly case mac os x driver appears support file fragmentation i.e supports iso 9660 level 2 level 3 linux supports multiple extents another limitation number directories iso image structure called path table directory image path table provides number parent directory entry problem parent directory number 16-bit number limiting range 1 65,535 content directory written also different place making path table redundant suitable fast searching operating systems e.g windows use path table others e.g linux iso image disc consists 65,535 directories readable linux early windows versions files additional directories visible show empty zero length software tools problems managing path table directory limit exceeded popular application using iso format mkisofs aborts path table overflow nero burning rom windows pinnacle instant cd/dvd check whether problem occurs produce invalid iso file disc without warning several extensions iso 9660 relax limitations operating systems support extensions name translation file trans.tbl must used located every directory including root directory obsolete since operating systems use today iso 13490 standard extension iso 9660 format adds support multiple sessions disc since iso 9660 design read-only pre-mastered file system data written one go session medium written provision altering stored content iso 13490 created allow adding files writeable disc cd-r multiple sessions iso 13346/ecma-167 standard designed conjunction iso 13490 standard address shortcomings iso 9660 subset evolved udf format adopted dvds jis x 0606:1998 also known iso 9660:1999 japanese industrial standard draft created japanese national body jtc1 n4222 order make improvements remove limitations original iso 9660 standard draft submitted 1998 ratified iso standard yet changes includes removal restrictions imposed original standard extending maximum file name length 207 characters removing eight-level maximum directory nesting limit removing special meaning dot character filenames operating systems allow relaxations well reading optical discs several disc authoring tools nero burning rom mkisofs imgburn support so-called iso 9660:1999 mode sometimes called iso 9660 v2 iso 9660 level 4 mode removes restrictions following guidelines iso 9660:1999 draft iso 9660 file system images iso images common way electronically transfer contents cd-roms often filename extension codice_1 codice_2 less common also use commonly referred isos operating systems support reading iso 9660 formatted discs new versions support extensions rock ridge joliet operating systems support extensions usually show basic non-extended features plain iso 9660 disc operating systems support iso 9660 extensions include following
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Computer file systems
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unicore unicore uniform interface computing resources grid computing technology resources supercomputers cluster systems information stored databases unicore developed two projects funded german ministry education research bmbf european-funded projects unicore evolved middleware system used several supercomputer centers unicore served basis research projects unicore technology open source bsd licence available sourceforge concept grid computing first introduced book grid blueprint new computing infrastructure end 1998 1997 development unicore initiated german supercomputer centers alternative globus toolkit first prototype developed german unicore project foundations production version laid follow-up project unicore plus ended 2002 follow-up european projects extended functionality worked towards providing implementations open grid forum standards resulted release unicore 6 28 august 2007 unicore consists three layers user server target system tier user tier represented various clients primary clients unicore rich client graphical user interface based eclipse framework unicore commandline client ucc clients use soap web services communicate server tier xml documents used transmit platform site independent descriptions computational data related tasks resource information workflow specifications client server servers accessible via secure socket layer protocol single secure entry point unicore site gateway accepts authenticates requests forwards target service server unicore/x used access particular set grid resources site unicore supports many different system architectures ensures organization full control resources unicore/x servers may used access supercomputer linux cluster single pc unicore/x server creates concrete target system specific actions xml job description abstract job objects ajo received client available unicore services include job submission job management file access file transfer client-server server-server storage operations mkdir ls etc workflow submission management target system tier consists target system interface tsi directly interfaces underlying local operating system resource management system security within unicore relies usage permanent x.509 certificates issued trusted certification authority ca certificates used provide single sign-on unicore client i.e password requests handed user addition certificates used authentication authorization including mapping unicore user certificates local accounts e.g unix uid/gid signing xml requests sent ssl based communication channels across 'insecure internet links using x.509 certificates one example consideration well-known standards e.g released global grid forum ggf within unicore architecture trust delegation unicore uses signed saml assertions local authorisation controlled xacml policies components unicore technology open source software bsd license downloaded sourceforge repository many european international research projects base grid software implementations unicore e.g eurogrid grip openmolgrid viola japanese naregi project projects extended extending set core unicore functions including new features specific research project focus goals projects limited computer science community scientific domains bioengineering computational chemistry also using unicore basis work research like openmolgrid chemomentum projects within european deisa project leading hpc centers europe joined deploy operate pervasive distributed heterogeneous multi-tera-scale supercomputing platform unicore used grid middleware access deisa resources unicore deployed distributed computing infrastructures europe prace european grid infrastructure egi foreseen deployed upcoming extreme science engineering discovery environment xsede infrastructure united states unicore successfully used production environments e.g within john von neumann-institute computing nic access 294912 core jugene ibm bluegene/p supercomputer 26304 core juropa cluster users resources come broad field scientific domains including e.g astrophysics quantum physics medicine biology computational chemistry climatology
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Distributed computing architecture
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language primitive computing language primitives simplest elements available programming language primitive smallest 'unit processing available programmer given machine atomic element expression language primitives units meaning i.e. semantic value language thus different tokens parser minimal elements syntax machine instruction usually generated assembler program often considered smallest unit processing although always case typically performs perceived one operation copying byte string bytes one computer memory location another adding one processor register another many today computers however actually embody even lower unit processing known microcode interprets machine code microcode instructions would genuine primitives instructions would typically available modification hardware vendor programmers high-level programming language hll program composed discrete statements primitive data types may also perceived perform single operation represent single data item higher semantic level provided machine copying data item one location another may actually involve many machine instructions instance finally hll statements particularly involving loops generate thousands even millions primitives low-level programming language lll comprise genuine instruction path length processor execute lowest level perception referred abstraction penalty interpreted language statement similarities hll primitives added layer statement executed manner similar hll statement must first processed interpreter process may involve many primitives target machine language fourth-generation programming languages 4gl fifth-generation programming languages 5gl simple one-to-many correspondence high-to-low level primitives elements interpreted language primitives embodied 4gl 5gl specifications approach original problem less procedural language construct oriented toward problem solving systems engineering
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Programming language topics
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sproxil sproxil american venture capital-backed for-profit company based cambridge massachusetts provides consumer product verification service called mobile authentication service mas help consumers avoid purchasing counterfeit products service first mobile authentication service mas launch nigeria iso 27001 iso 9001 certified company also offers supply chain protection solutions including track trace mobile-based loyalty marketing programs advisory services sproxil operations nigeria mali ghana serving west africa tanzania kenya serving east africa india pakistan asia sproxil ’ service places security label scratch-off panel protected products consumers scratch panel point purchase reveal unique one-time use code form mass serialization code sent via sms mobile app country-specific short code consumer receives reply almost instantly indicating product genuine suspicious company also 24/7 call center provide support verification process take anonymous reports suspicious counterfeiting activity sproxil ’ services currently used several pharmaceutical companies fight counterfeit drugs fake drug market according world customs organization estimated 200 billion year industry problem counterfeit drugs particularly acute emerging markets world health organization estimates 30 drugs markets fake may harmful consumers date sproxil protects products across multiple industries including pharmaceuticals agribusiness automotive parts beauty personal care etc 2010 nafdac nigerian government agency overseeing food drugs endorsed sproxil platform service widely deployed throughout nigeria april 2011 cnn published video discussing role sproxil played fight counterfeit drugs nigeria sproxil along pfizer vodafone waterhealth international committed business call action bcta global leadership initiative made companies apply core business expertise achievement eight internationally agreed millennium development goals mdgs sproxil ceo ashifi gogo praised former united states president bill clinton described gogo ’ work “ genuinely remarkable achievement. ” february 2011 sproxil announced received 1.8 million funding acumen fund funding used help company expand india johnson johnson gsk glaxosmithkline using sproxil services africa nigerian distributor merck kgaa named biofem june 2011 sproxil launched operations india july 2011 kenya pharmacy poisons board ppb also adopted similar text message-based anti-counterfeiting systems early 2012 sproxil announced one million people africa checked medicines using text-message based verification service developed sproxil august 2012 sproxil bharti airtel global telecommunications company announced partnership combat counterfeit drug market africa using mpa airtel offer service absolutely free users charge sms based verification february 2013 sproxil signed east african cables protect electric cables zinduka initiative initiative utilizes mpa solution help consumers verify electrical cables genuine purchase partnership marked sproxil expansion non-pharmaceutical markets industries uses sproxil solution textile clothing underwear also around time prashant yadav senior research fellow director healthcare research initiative joined sproxil board advisors yadav expert pharmaceutical healthcare supply chain management emerging markets formerly professor supply chain management mit-zaragoza international logistics program currently serves advisor multiple organizations area pharmaceutical supply chains ceo ashifi gogo recently named white house immigrant innovator champion change schwab foundation social entrepreneur year 2014 work sproxil 2014 company expanded mobile authentication services originally available consumers sms call center adding mobile apps web app solution suite year sproxil became iso-27001 information security controls iso-9001 quality management systems certified comprehensive review internal processes soon kenya-based agribusiness company juanco sps officially launched consumer-facing project protects pesticide bestox 100ec mpa technology date company processed 75 million verifications consumers highest recorded number verifications kind 2017 unilever global development award 2016 innovative healthcare service provider year 2015 interface health excellence ihx challenge 2015 frost sullivan enabling technology leadership award 2014 schwab foundation social entrepreneur year award 2013 uspto patents humanity award 2013 1 health care 7 overall fast company magazine world 50 innovative companies 2012 ismp cheers award george didomizio industry award 2012 icc world business development award 2010 honorable mention global finals ibm entrepreneur smartcamp competition 2010 masschallenge finalist 2010 mobile infrastructure award mitx 2010 people ’ choice award accelerate michigan 2010 prize winner african diaspora marketplace 2010 audience choice award life sciences xconomy xsite 2009 outstanding commitment award global health clinton global initiative university
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Computer security
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arm cortex-a12 arm cortex-a12 32-bit processor core licensed arm holdings implementing armv7-a architecture provides 4 cache-coherent cores cortex-a12 successor cortex-a9 arm renamed a12 variant cortex-a17 since second revision core early 2014 indistinguishable performance arm claims cortex-a12 core 40 percent powerful cortex-a9 core new features found cortex-a9 include hardware virtualization 40-bit large physical address extensions lpae addressing announced supporting big.little however shortly afterwards arm cortex-a17 announced upgraded version capability key features cortex-a12 core
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Computer architecture
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principles compiler design principles compiler design alfred aho jeffrey ullman classic textbook compilers computer programming languages often called dragon book cover depicts knight dragon battle dragon green labeled complexity compiler construction knight wields lance shield labeled lalr parser generator syntax directed translation respectively rides horse labeled data flow analysis book may called green dragon book distinguish successor aho sethi ullman red dragon book second edition compilers principles techniques tools added fourth author monica s. lam dragon became purple hence becoming purple dragon book book also contains entire code making compiler back cover offers original inspiration cover design dragon replaced windmills knight quixote book published addison-wesley acknowledgments mention book entirely typeset bell labs using troff unix operating system little time seen outside laboratories
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Programming language topics
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ship registration hong kong hong kong shipping register set 1990 hong kong merchant shipping registration ordinance administered marine department hong kong since transfer sovereignty united kingdom 1997 hong kong authorised basic law government people ’ republic china using name “ hong kong china ” maintain separate ship registration system april 1999 hong kong government launched new measures improve ship registration system hong kong cooperation government shipping industry total tonnage ship registry hong kong reached 100 millions gross tonnes 2,440 vessels registered january 2016 hong kong ship register world ’ fourth largest ship register world ’ largest national flag register first time registration fee ship determined according gross tonnage gt annual tonnage charge ship determined referring net tonnage nt minimum annual tonnage charge hk 1,500 every tonne 1000 nt costing extra hk 3.5 15,000 nt whereby rate lowers hk 3 per tonne thereafter charge would exceed hk 77,500 annual tonnage charge atc reduction scheme since february 2006 annual tonnage charge atc reduction scheme enacted reduce long term cost ship owners whereby every two years qualifying period satisfying registered ship owner would right enjoy six months atc reduction following year general ship eligible registration ship 3 types registration full registration provisional registration bare boat charter registration registration procedures requires submission ship hong kong shipping register full provisional registration mortgages ship registered agents hk flag registration include hong kong registered ships enjoy 30 preferential port dues mainland china ports since january 2000 order reduce port light dues hong kong registered ships hksar expects sign agreements countries two-tier charging system income derived international trade hong kong registered ships exempted profits tax hksar also entered bilateral double taxation relief agreements 40 countries include agreement avoidance double taxation dta denmark germany netherlands norway singapore sri lanka united kingdom united states reciprocal tax exemption rte chile korea new zealand comprehensive dta cdta austria belgium brunei canada czech france guernsey hungary indonesia ireland italy japan jersey korea kuwait liechtenstein luxembourg mainland china malaysia malta mexico netherlands new zealand portugal qatar romania south africa spain switzerland thailand united arab emirates united kingdom vietnam flag state quality control fsqc system based information system monitor quality hong kong registered ships analyzing collecting information unqualified conditions ship identified flag state inspection pre-registration quality control prqc system involves marine department inspect ship ’ condition registered hong kong ship meet safety pollution prevention standards announced international maritime organization
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Databases
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gregor kiczales gregor kiczales american computer scientist currently full time professor computer science university british columbia vancouver british columbia canada best known developing concept aspect-oriented programming aspectj extension java programming language designed working xerox parc also one co-authors specification common lisp object system author book art metaobject protocol along jim des rivières daniel g. bobrow kiczales work throughout years focused allowing software engineers create programs look much possible like design reduce complexity make code maintenance easier ultimately improving software quality pursuing undergraduate studies mit kiczales started research career 1980 mit lab computer science stayed 1983 1984 joined xerox palo alto research center software research lab member research staff becoming principal scientist 1996 throughout time parc kiczales developed important research works including aspect-oriented programming aspectj left parc 1999 focus computer science education 2000 moved canada joined department computer science university british columbia tenured professor ubc kiczales started software practices lab designed number courses related software engineering programming languages importantly designed cpsc 110 introductory programming course ubc curriculum students take first year undergraduate studies course focuses systematic program design means design recipes 2002 co-founded intentional software charles simonyi left company 2003 order return ubc 2012 senior aito dahl-nygaard prize work common lisp object system named acm fellow contributions aspect-oriented programming july 2017 appointed executive director ubc extended learning
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Programming language topics
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author domain signing practices computing author domain signing practices adsp optional extension dkim e-mail authentication scheme whereby domain publish signing practices adopts relaying mail behalf associated authors adsp adopted standards track rfc 5617 august 2009 declared historic november 2013 ... almost deployment use 4 years since ... author address one specified header field defined rfc 5322 unusual cases one address defined field rfc 5322 provides sender field used instead domains 5322- addresses necessarily elaborated purported responsible address covered sender id specified rfc 4407 domain 5322- address also necessarily envelope sender address defined rfc 5321 also known smtp mail envelope- 5321- return-path optionally protected spf specified rfc 7208 author domain signature valid dkim signature domain name dkim signing entity i.e. tag dkim-signature header field domain name author address binding recognizes higher value author domain signatures valid signatures may happen found message fact proves entity controls dns zone author — hence also destination replies message author — relayed author message likely author submitted message proper message submission agent message qualification verified independently published domain signing practice practices published dns record author domain author address john.doe example.com may set three possible signing practices provided adsp specification explicitly discourages publishing record different unknown domains independent users usage policy explicitly restrict sending mail designated mail servers since mail sent independently organization signed however explicitly caveat worded straightforward understand purpose limitations adsp one adsp authors holds better publish private lists discardable domains maintained competent people rather letting domain state policy recognizing spec shipped untested prototype author popular adsp implementation proposed downgrade adsp experimental status later actually downgraded historical consideration dmarc covers less use case influential tied time adsp known asp author signing practices original ssp sender signing practices protocol naming poll domainkeys dkim predecessor outbound signing policy consisting single character domain signs email otherwise dkim intentionally avoided signers policies considerations dkim validate message field directly policy-neutral authentication protocol association signer right use field visible end users deferred separate specification eric allman author sendmail editor adsp specification ietf dkim working group draft adsp specification started june 2007 went 11 revisions lengthy discussion published rfc august 2009 declared historic four years later november 2013 ... almost deployment use 4 years since ...
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Computer security
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king knight game became square first north american release redmond subsidiary squaresoft first release independent company 1986 release title screen credits workss programming king knight saw second release 1987 nec pc-8801mkii sr sharp x1 versions game retitled king knight special released exclusively japan first game designed hironobu sakaguchi famicom nobuo uematsu provided musical score king knight uematsu third work video game music composition king knight follows basic storyline many nes-era role-playing video games displayed princess claire olthea kidnapped kingdom izander player must choose one four heroes knight/warrior ray jack wizard kaliva monster/gigant barusa kid thief toby train set forth attack gargatua castle defeat evil dragon tolfida rescue princess king knight vertically scrolling shooter main objective dodge destroy onscreen enemies obstacles various items however add depth game character player collect various power-ups increase character level maximum twenty levels per character many seven jump increases seven speed increases three weapon increases three shield increases also life ups collected increase character life meter also life downs avoided onscreen icons affect stage hidden cave entrances/exits secret revealer reveals hidden stones block progress finally four types elements collected level vital completion last stage elements simply elements b c d. stage various power-ups element type cave caves given level always house least one element type mention various powerups vital player finds caves always hidden generally found middle stage caves also statues shoot fireballs end cave dragon fight dragon defeated player exit cave continue level differences present famicom msx versions king knight japanese north american versions well japanese famicom version american nes version king knight differed little title screen disparity title screen reflected copyright publisher msx version king knight differed famicom version variety ways opening modified prior intro screen players could specify type controller would like use either keyboard joystick in-game dynamics similar although differences exist msx version flanks screen closed stage maps moved slightly items appear original locations finally msx version may seem easier characters sustain damage attacks developers also took advantage technological capabilities available msx upgrade msx port featured sound channels famicom many music tracks sound effects altered improved msx version also boasts wider range colors updated graphics new monster boss designs dragons end caves example replaced lizard-like monsters new sidebar displayed player life meter allocated power-ups allocated elements msx could smoothly render vertical scrolling – unlike famicom – movement graphics choppy comparison changes similar changes took place square final fantasy ported msx2 september 18 2016 square enix announced remake titled king knight wrath dark dragon ios android produced daisuke motohashi developed flame hearts developed mobile spin-off associated final fantasy xv game borrows original version scrolling action role-playing game style adds new camera perspective orchestral version former chiptune soundtrack game free-to-play four-player multiplayer mode square enix announced game september 2016 tokyo game show promotional material placed game final fantasy xv universe alongside justice monsters five another mobile companion game series square enix announced earlier 2016 king knight wrath dark dragon planned release android ios platforms japan 2016 announcement north american release game release postponed 2017 released worldwide september 13 2017 end service subsequently announced game take place june 26 2018 less year worldwide release king knight one video games adapted manga titled published gamest comics collection april 1999 drawn kouta hirano king knight given 3/10 ign 3/10 well nintendo life
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Computer architecture
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cesg listed adviser scheme cesg listed adviser scheme programme run cesg provide pool information assurance consultants government departments public-sector bodies uk clas consultants advised systems handle protectively marked information including secret instance may advised gsi accreditation clas consultants held security clearance least sc clas consultants developed risk assessments line is1 risk management accreditation document sets rmads line is2 2011 entry clas closed replacement system designed 2013 'new clas implemented open membership 'new clas required members cesg certified professionals clas closed january 2016 cesg certified professional ccp scheme recognises expertise working information assurance cyber security arenas government industry sets standard ia professionals working sector provides rigorous independent assessment competence ia professionals ccp status endorsement ia expertise confirms information risk support business managed balanced pragmatic way clas closed ccp cesg-approved credential applies individual professionals rather companies
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Computer security
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mollom mollom web service analyzed quality content posted websites included comments contact-form messages blogs forum posts mollom screened contributions posted participating websites mollom originally developed dries buytaert also founder lead developer drupal cms used three specific technologies detect spam malicious content machine learning text analytics captcha according acquia mollom launch march 2008 acquisition acquia august 2012 mollom blocked one billion spam messages customers including sony music stanford university twitter mollom acquired acquia august 2012 april 27 2017 company announced would stop sale mollom service may 1 2017 service shut completely april 2 2018 blocked 13.5 billion spam comments since inception
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Computer security
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ibmdos.com ibmdos.com filename dos kernel loaded initially invoked dos bios ibmbio.com boot process contains hardware-independent parts operating system including embedded fat12 fat16 newer versions fat32 file system code well code provide dos api applications file exists pc dos 1.0 7.10 dr dos 5.0 higher except dr-dos 7.06 ms-dos using msdos.sys version 1.10 6.22 purpose dr dos 3.31 3.41 used equivalent drbdos.sys file instead compatibility purposes dos applications ibmdos.com file name briefly also used ibm version os/2 1.0 resembled os2dos.com os/2 kernel file used microsoft default file located root directory bootable drive/partition normally c hidden read-only system file attributes set ibmdos.com binary image containing executable code rather true com-style program hidden attribute set keep file accidentally invoked command prompt would lead crash necessary dr-dos 7.02 higher systems file fat binary also containing tiny com-style stub displaying version info exiting gracefully loaded inappropriately digital research terminology kernel component operating system called bdos basic disk operating system term originally coined gary kildall 1975 cp/m continued used dri operating systems except concurrent dos 286 flexos microsoft used name well referring kernel msx-dos operating system fat file system specific code called fdos dri terminology
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Operating systems
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karen todner karen elizabeth todner born april 1962 nuneaton england british solicitor clients include hacker ryan cleary linked lulzsec gary mckinnon known pentagon hacker lauri love todner qualified solicitor 1987 20s became founding member kaim todner llp law firm london kaim todner solicitors formed 1990 specialising criminal law particular expertise extradition beginning march 2016 todner practise acquired one legal alternative business structure originally set 2013 came shortly todner announced intention close practice due legal aid cuts since acquisition one legal todner firm kaim todner continued operating name part one legal alternative business structure todner commented delighted secured way firm continue working present format umbrella one legal karen left kaim todner one legal september 2017 found www.karentodner.com todner appeared number extradition cases early case successful defence gary mckinnon set new legal precedent british law mckinnon legal team applied judicial review home secretary rejection medical evidence stated could easily tried uk unnecessary cruel inhumane inflict stress removing homeland family medical support network starting winter 2013 todner started representing lauri love british student arrested suspicion hacking us military computers love accused committing cyber attacks part hacktivist campaign 2012 2013 protest death aaron swartz computer programmer committed suicide facing 35 years us prison charges computer misuse september 2016 decision made extradite love us todner said confident appeal 100 mps showed support love campaign extradition order overturned health grounds october 2016 announced mp barry sheerman chair parliamentary commission autism write president obama asking throw extradition request leaves office january 2017 wednesday 12 october 2016 house commons prime ministers questions david burrowes mp raised case lauri love issues difficulties faced various forms autism come contact justice system others including national autistic society liberty courage foundation showed support love appeal 24 october 105 cross-party backbenchers signed letter president obama raising deep concern safety lauri love pointing long history serious mental health issues depression episodes psychosis november 2016 home secretary amber rudd backed decision extradite love america todner stated fears driven suicide extradited lodging appeal home office decision letter home office opposing love extradition risk suicide wrote we.. urge recognise seriousness mr love mental illness withdraw request extradition permit prosecution proceed england mr love would able stand trial bail support close family medical support network love said home secretary refused send us trial called home secretary decision extradite ‘ aberration justice ’ legal team kaim todner solicitors pointed uk citizen accused hacking extradited us todner also stated home secretary refused extradite love uk–us extradition treaty 2003 unfair repealed 25 april 2017 high court accepted love appeal extradition lodged todner behalf hearing date yet set however todner commented reason permission granted high court acknowledge grounds raised issues great importance delighted news lauri continue everything ensure prevention extradition united states america starting 2012 todner represented david mcintyre queen lancashire regiment soldier war veteran served afghanistan bosnia northern ireland iraq mclntyre accused overcharging us peace group security contract running firm employed team 20 provide security american clients including iraqi ambassador us overcharging us government security services baghdad iraq mcintyre left army 2002 set security company called quantum risk eight counts fraud mcintyre charged relate claims overcharged us peace group security contract running quantum risk december 2008 july 2009 mcintyre business closed 2009 followed enrolment royal military police served afghanistan july 2012 mcintyre arrested uniform operational setting afghanistan flown country 45 minutes later appeared westminster magistrates court london 36 hours later mcintyre faced eight counts fraud concerning contract united states institute peace usip alleged overcharged organisation 100,000 us dollars £65,000 us extradition request approved home secretary theresa may mcintyre appealed submitting report british army consultant psychiatrist confirming suffered ptsd todner commented firm consider detail secretary state conclusion see whether seek judicial review decision
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Computer security
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ekoparty ekoparty annual computer security conference brings together variety people interested information security briefings take place regularly buenos aires argentina ekoparty founded 2001 juan pablo daniel borgna leonardo pigner federico kirschbaum jerónimo basaldúa francisco amato addition talks ekoparty different activities like workshops wargames wardriving lockpicking challenges forensics challenges
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Computer security
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tacpol programming language tacpol tactical procedure oriented language block structured programming language developed united states army tacfire tactical fire direction command control application tacpol similar pl/i unlike pl/i tacpol keywords—called particles —are reserved words used identifiers roughly 100 reserved words tacpol identifiers length longer eight characters first five concatenated last three characters actually used tacpol supports fixed-point binary numeric data fixed-length character strings 512 bytes fixed-length bit strings 32 bits support floating point numeric data pointers arrays may three dimensions dynamic bounds permitted additional types records called groups limited single level nesting tables arrays groups unions called cells control structures include if-then-else iteration case statements procedures may value parameters quantity parameters – reference without type-checking parameterless procedure label parameters tacpol compiler ran generated code an/gyk-12 militarized version litton industries l-3050 32-bit minicomputer
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Programming language topics
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pvts pilo visual tools scheme pvts basic interpreter implementation visualization tools scheme programming language developed rollins college written java pvts contains interpreter also known read-eval-print loop well three visualization modules global environment viewer function call viewer data structure viewer pvts free software licensed gnu general public license gpl available online pvts limited interpreter capabilities cover r5rs standard scheme language standard purpose software display graphically scheme code aid students learning language
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Programming language topics
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linux assigned names numbers authority linux assigned names numbers authority lanana central registry names numbers used within linux created 2000 h. peter anvin 2013 along filesystem hierarchy standard matters moved linux standard base operates linux foundation auspices per russ herrold linux device list created 1992 rick miller maintained 1993 1995 adopted h. peter anvin 2000 created lanana maintain list similar lists future name registry playful reference iana central registry names numbers used internet 2002 lanana became official workgroup free standards group
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Operating systems
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android automotive android automotive variation google android operating system tailored use vehicle dashboards introduced march 2017 platform developed google intel together car manufacturers volvo audi project aims provide operating system codebase vehicle manufacturers develop version operating system besides infotainment tasks messaging navigation music playback operating system aims handle vehicle-specific functions controlling air conditioning contrarily android auto android automotive full operating system running vehicle device relying external device operate operating system first announced google march 2017 february 2018 polestar volvo ’ brand electric performance cars announced polestar 2 first car built-in android automotive expected release 2020 april 2019 google opened apis developers start developing applications android automotive
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Operating systems
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vdso vdso virtual dynamic shared object kernel mechanism exporting carefully selected set kernel space routines user space applications applications call kernel space routines in-process without incurring performance penalty context switch inherent calling kernel space routines means system call interface vdso developed offer vsyscall features overcoming limitations small amount statically allocated memory allows 4 system calls addresses abi process compromises security security issue mitigated emulating virtual system call emulation introduces additional latency vdso uses standard mechanisms linking loading i.e standard executable linkable format elf format vdso memory area allocated user space exposes kernel functionalities vdso dynamically allocated offers improved safety memory space randomization supports 4 system calls vdso links provided via glibc library kernel vdso support traditional syscall made vdso helps reduce calling overhead simple kernel routines also work way select best system-call method computer architectures ia-32 advantage methods exported routines provide proper dwarf debug attributed record format debugging information implementation generally implies hooks dynamic linker find vdsos
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Operating systems
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authentication authentication authentikos real genuine αὐθέντης authentes author act proving assertion identity computer system user contrast identification act indicating person thing identity authentication process verifying identity might involve validating personal identity documents verifying authenticity website digital certificate determining age artifact carbon dating ensuring product document counterfeit authentication relevant multiple fields art antiques anthropology common problem verifying given artifact produced certain person certain place period history computer science verifying user identity often required allow access confidential data systems authentication considered three types first type authentication accepting proof identity given credible person first-hand evidence identity genuine authentication required art physical objects proof could friend family member colleague attesting item provenance perhaps witnessed item creator possession autographed sports memorabilia could involve someone attesting witnessed object signed vendor selling branded items implies authenticity may evidence every step supply chain authenticated centralized authority-based trust relationships back secure internet communication known public certificate authorities decentralized peer-based trust also known web trust used personal services email files pretty good privacy gnu privacy guard trust established known individuals signing cryptographic key key signing parties instance second type authentication comparing attributes object known objects origin example art expert might look similarities style painting check location form signature compare object old photograph archaeologist hand might use carbon dating verify age artifact chemical spectroscopic analysis materials used compare style construction decoration artifacts similar origin physics sound light comparison known physical environment used examine authenticity audio recordings photographs videos documents verified created ink paper readily available time item implied creation attribute comparison may vulnerable forgery general relies facts creating forgery indistinguishable genuine artifact requires expert knowledge mistakes easily made amount effort required considerably greater amount profit gained forgery art antiques certificates great importance authenticating object interest value certificates however also forged authentication poses problem instance son han van meegeren well-known art-forger forged work father provided certificate provenance well see article jacques van meegeren criminal civil penalties fraud forgery counterfeiting reduce incentive falsification depending risk getting caught currency financial instruments commonly use second type authentication method bills coins cheques incorporate hard-to-duplicate physical features fine printing engraving distinctive feel watermarks holographic imagery easy trained receivers verify third type authentication relies documentation external affirmations criminal courts rules evidence often require establishing chain custody evidence presented accomplished written evidence log testimony police detectives forensics staff handled antiques accompanied certificates attesting authenticity signed sports memorabilia usually accompanied certificate authenticity external records problems forgery perjury also vulnerable separated artifact lost computer science user given access secure systems based user credentials imply authenticity network administrator give user password provide user key card access device allow system access case authenticity implied guaranteed consumer goods pharmaceuticals perfume fashion clothing use three forms authentication prevent counterfeit goods taking advantage popular brand reputation damaging brand owner sales reputation mentioned item sale reputable store implicitly attests genuine first type authentication second type authentication might involve comparing quality craftsmanship item expensive handbag genuine articles third type authentication could presence trademark item legally protected marking identifying feature aids consumers identification genuine brand-name goods software companies taken great steps protect counterfeiters including adding holograms security rings security threads color shifting ink ways someone may authenticated fall three categories based known factors authentication something user knows something user something user authentication factor covers range elements used authenticate verify person identity prior granted access approving transaction request signing document work product granting authority others establishing chain authority security research determined positive authentication elements least two preferably three factors verified three factors classes elements factor weakest level authentication single component one three categories factors used authenticate individual ’ identity use one factor offer much protection misuse malicious intrusion type authentication recommended financial personally relevant transactions warrant higher level security multi-factor authentication involves two authentication factors something know something something two-factor authentication special case multi-factor authentication involving exactly two factors example using bankcard something user along pin something user knows provides two-factor authentication business networks may require users provide password knowledge factor pseudorandom number security token ownership factor access very-high-security system might require mantrap screening height weight facial fingerprint checks several inherence factor elements plus pin day code knowledge factor elements still two-factor authentication frequent types authentication available use authenticating online users differ level security provided combining factors one three categories factors authentication u.s. government national information assurance glossary defines strong authentication layered authentication approach relying two authenticators establish identity originator receiver information european central bank ecb defined strong authentication procedure based two three authentication factors factors used must mutually independent least one factor must non-reusable non-replicable except case inherence factor must also incapable stolen internet european well us-american understanding strong authentication similar multi-factor authentication 2fa exceeding rigorous requirements fast identity online fido alliance striving establish technical specifications strong authentication conventional computer systems authenticate users initial log-in session cause critical security flaw resolve problem systems need continuous user authentication methods continuously monitor authenticate users based biometric trait study used behavioural biometrics based writing styles continuous authentication method recent research shown possibility using smartphones ’ sensors accessories extract behavioral attributes touch dynamics keystroke dynamics gait recognition attributes known behavioral biometrics could used verify identify users implicitly continuously smartphones authentication systems built based behavioral biometric traits known active continuous authentication systems term digital authentication also known electronic authentication refers group processes confidence user identities established presented via electronic methods information system also referred e-authentication digital authentication process creates technical challenges need authenticate individuals entities remotely network american national institute standards technology nist created generic model digital authentication describes processes used accomplish secure authentication authentication information pose special problems electronic communication vulnerability man-in-the-middle attacks whereby third party taps communication stream poses two communicating parties order intercept information extra identity factors required authenticate party identity counterfeit products often offered consumers authentic counterfeit consumer goods electronics music apparel counterfeit medications sold legitimate efforts control supply chain educate consumers help ensure authentic products sold used even security printing packages labels nameplates however subject counterfeiting secure key storage device used authentication consumer electronics network authentication license management supply chain management etc generally device authenticated needs sort wireless wired digital connection either host system network nonetheless component authenticated need electronic nature authentication chip mechanically attached read connector host e.g authenticated ink tank use printer products services secure coprocessors applied offer solution much difficult counterfeit options time easily verified packaging labeling engineered help reduce risks counterfeit consumer goods theft resale products package constructions difficult copy pilfer-indicating seals counterfeit goods unauthorized sales diversion material substitution tampering reduced anti-counterfeiting technologies packages may include authentication seals use security printing help indicate package contents counterfeit subject counterfeiting packages also include anti-theft devices dye-packs rfid tags electronic article surveillance tags activated detected devices exit points require specialized tools deactivate anti-counterfeiting technologies used packaging include literary forgery involve imitating style famous author original manuscript typewritten text recording available medium packaging – anything box e-mail headers help prove disprove authenticity document however text audio video copied new media possibly leaving informational content use authentication various systems invented allow authors provide means readers reliably authenticate given message originated relayed involve authentication factors like opposite problem detection plagiarism information different author passed person work common technique proving plagiarism discovery another copy similar text different attribution cases excessively high quality style mismatch may raise suspicion plagiarism literacy authentication readers ’ process questioning veracity aspect literature verifying questions via research fundamental question authentication literature – one believe related authentication project therefore reading writing activity students documents relevant research process builds students critical literacy documentation materials literature go beyond narrative texts likely include informational texts primary sources multimedia process typically involves internet hands-on library research authenticating historical fiction particular readers consider extent major historical events well culture portrayed e.g. language clothing food gender roles believable period historically fingerprints used authoritative method authentication court cases us elsewhere raised fundamental doubts fingerprint reliability outside legal system well fingerprints shown easily spoofable british telecom top computer-security official noting fingerprint readers already tricked one spoof another hybrid two-tiered authentication methods offer compelling solution private keys encrypted fingerprint inside usb device computer data context cryptographic methods developed see digital signature challenge-response authentication currently spoofable originator key compromised originator anyone attacker knows n't know compromise irrelevant known whether cryptographically based authentication methods provably secure since unanticipated mathematical developments may make vulnerable attack future occur may call question much authentication past particular digitally signed contract may questioned new attack cryptography underlying signature discovered process authorization distinct authentication whereas authentication process verifying say authorization process verifying permitted trying mean authorization presupposes authentication anonymous agent could authorized limited action set one familiar use authentication authorization access control computer system supposed used authorized must attempt detect exclude unauthorized access therefore usually controlled insisting authentication procedure establish degree confidence identity user granting privileges established identity
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Computer security
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cdp spoofing computer networking cdp spoofing technique employed compromise operation network devices use cisco discovery protocol cdp discovering neighboring devices cdp spoofing network security threat mitigated taking precautionary measures order prevent cisco discovery protocol cdp created computer networking company cisco originally developed 1994 original intent make easier find devices network cdp may used cisco routers switches network equipment advertise software version capabilities ip address two versions cdp cdpv1 cdpv2 cdpv1 original version involved finding basic information networking devices devices able receive information networking device directly connected cdpv2 predecessor first version extensive previous version includes utilities checking errors made configuring two devices e.g configuring mismatched native vlans cdp enabled globally default cisco routers switches servers protocol disabled globally however disabled interface encapsulation changed re-enabled interface protocol often used aid network administrators finding discovering devices easier devices discovered easier help certain network problems device arrangement network management networking tasks although beneficial features attackers accumulate information devices leaves device type ip address ios version exposed vulnerable attackers use information mimic devices steal information create various network problems recommended disable cdp entire device rather interfaces fully mitigate threat cdp spoofing attacks cdp suggest disabling cdp used device necessity device although cdp enabled default disabled re-enabled globally interfaces command syntaxhighlight config cdp run /syntaxhighlight disable globally syntaxhighlight config cdp run /syntaxhighlight enable certain interface syntaxhighlight config-if cdp enable /syntaxhighlight disable certain interface syntaxhighlight config-if cdp enable /syntaxhighlight table display whether device established connection another device devices syntaxhighlight device name show cdp neighbors /syntaxhighlight note command show names devices ports connecting devices model name/number features device show traffic passed cdp devices syntaxhighlight device name show cdp traffic /syntaxhighlight commands help mitigate detect cdp attacks cdp spoofing also help discover flaws within system e.g mismatched native vlans could inhibiting connection devices router running cdp receives cdp packet begins build table shows neighboring devices discovered devices discovered intermittently send packet updated information packet contains various information interface ’ device ’ types names packets sent cdp encrypted creating messages devices easily read plain-text cdp spoofing creation forged packets impersonate devices either real arbitrary attack type denial-of-service dos attack used flood connected devices using cdp attacker exploit functionality sending thousands spoofed cdp packets 01:00:0c cc cc cc fill neighbor tables devices network running cdp happens traffic network may dropped device resources necessary route device command line interface may also become unresponsive making difficult disable cdp ongoing attack administrators may disable cdp result make network secure cost able benefit cdp
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Computer security
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login computer security logging logging signing signing process individual gains access computer system identifying authenticating user credentials typically form username matching password credentials sometimes referred login logon sign-in sign-on practice modern secure systems also often require second factor extra security access longer needed user log log sign sign logging usually used enter specific page trespassers see user logged login token may used track actions user taken connected site logging may performed explicitly user taking actions entering appropriate command clicking website link labeled also done implicitly user powering workstation closing web browser window leaving website refreshing webpage within defined period case websites use cookies track sessions user logs session-only cookies site usually deleted user computer addition server invalidates associations session making session-handle user cookie store useless feature comes handy user using public computer computer using public wireless connection security precaution one rely implicit means logging system especially public computer instead one explicitly log wait confirmation request taken place logging computer leaving common security practice preventing unauthorized users tampering also people choose password-protected screensaver set activate period inactivity requiring user re-enter login credentials unlock screensaver gain access system different methods logging may via image fingerprints eye scan password oral textual input etc terms became common time sharing systems 1960s bulletin board systems bbs 1970s early home computers personal computers generally require windows nt os/2 linux 1990s noun login comes verb log analogy verb clock computer systems keep log users access system term log comes chip log historically used record distance travelled sea recorded ship log log book sign connotes idea based analogy manually signing log visitors book agreed difference meaning three terms login logon sign different technical communities tend prefer one another – unix novell linux apple typically using login apple style guide saying users log file server log ... contrast microsoft style guides traditionally suggested opposite prescribed log logon past microsoft reserved sign accessing internet windows 8 onwards moved sign terminology local authentication
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Computer security
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final fantasy video game final fantasy fantasy role-playing video game developed published square 1987 first game square final fantasy series created hironobu sakaguchi originally released nes final fantasy remade several video game consoles frequently packaged final fantasy ii video game collections story follows four youths called light warriors carry one world four elemental orbs darkened four elemental fiends together quest defeat evil forces restore light orbs save world final fantasy originally conceived working title fighting fantasy trademark issues dire circumstances surrounding square well sakaguchi prompted name changed game great commercial success received generally positive reviews spawned many successful sequels supplementary titles form final fantasy series original regarded one influential successful role-playing games nintendo entertainment system playing major role popularizing genre critical praise focused game graphics criticism targeted time spent wandering search random battle encounters raise player experience level march 2003 versions final fantasy sold combined total two million copies worldwide final fantasy four basic game modes overworld map town dungeon maps battle screen menu screen overworld map scaled-down version game fictional world player uses direct characters various locations primary means travel across overworld foot ship canoe airship become available player progresses exception battles preset locations bosses enemies randomly encountered field maps overworld map traveling foot canoe ship must either fought fled game plot develops player progresses towns dungeons town citizens offer helpful information others shops sell items equipment dungeons appear areas include forests caves mountains swamps underwater caverns buildings dungeons often treasure chests containing rare items available stores game menu screen allows player keep track experience points levels choose equipment characters wield use items magic character basic attribute level range one fifty determined character amount experience gaining level increases character attributes maximum hit points hp represents character remaining health character dies reach zero hp characters gain experience points winning battles combat final fantasy menu-based player selects action list options attack magic item battles turn-based continue either side flees defeated player party wins character gain experience gil flees returned map screen every character party dies game unsaved progress lost final fantasy first game show player characters right side screen enemies left side screen opposed first-person view player begins game choosing four characters form party locked choice duration game character occupation character class different attributes abilities either innate acquired six classes fighter thief black belt red mage white mage black mage later game player option character undergo class upgrade whereby sprite portraits mature classes gain ability use weapons magic previously could use game contains variety weapons armor items bought found make characters powerful combat character eight inventory slots four hold weapons four hold armor character class restrictions weapons armor may use weapons armor magical used combat cast spells magical artifacts provide protection certain spells shops characters buy items help recover traveling items available include potions heal characters remove ailments like poison petrification tents cabins used world map heal player optionally save game houses also recovers party magic saving special items may gained quests magic common ability game several character classes use spells divided two groups white defensive healing black debilitating destructive magic bought white black magic shops assigned characters whose occupation allows use spells classified level one eight four white four black spells per level character may learn three spells per level white black mages potentially learn respective spells red mages ninja knight use high-level magic final fantasy takes place fantasy world three large continents elemental powers world determined state four crystals governing one four classical elements earth fire water wind world final fantasy inhabited numerous races including humans elves dwarves mermaids dragons robots non-human races one town game although individuals sometimes found human towns areas well four hundred years prior start game lefeinish people used power wind craft airships giant space station called floating castle game watched country decline wind crystal went dark two hundred years later violent storms sank massive shrine served center ocean-based civilization water crystal went dark earth crystal fire crystal followed plaguing earth raging wildfires devastating agricultural town melmond plains vegetation decayed time later sage lukahn tells prophecy four light warriors come save world time darkness game begins appearance four youthful light warriors heroes story carry one darkened orbs initially light warriors access kingdom coneria ruined temple fiends warriors rescue princess sara evil knight garland king coneria builds bridge enables light warriors passage east town pravoka light warriors liberate town bikke band pirates acquire pirates ship use warriors embark chain delivery quests shores aldi sea first retrieve stolen crown marsh cave king ruined castle turns dark elf astos defeating gains crystal eye return blind witch matoya exchange herb needed awaken elf prince cursed astos elf prince gives light warriors mystic key capable unlocking door key unlocks storage room coneria castle holds tnt nerrick one dwarves cave dwarf/dwarf village destroys small isthmus using tnt connecting aldi sea outside world visiting near-ruined town melmond light warriors go earth cave defeat vampire retrieve star ruby gains passage sage sadda cave sadda rod warriors venture deeper earth cave destroy earth fiend lich light warriors obtain canoe enter gurgu volcano defeat fire fiend kary levistone nearby ice cave allows raise airship reach northern continents prove courage retrieving rat tail castle ordeal king dragons bahamut promotes light warrior kind gesture repaid fairy receiving special liquid produces oxygen warriors use help defeat water fiend kraken sunken shrine also recover slab allows linguist named dr. unne teach lefeinish language lefeinish give light warriors access floating castle tiamat wind fiend taken four fiends defeated orbs restored portal opens temple fiends takes 2000 years past warriors discover four fiends sent garland archdemon chaos back time sent fiends future creating time loop could live forever light warriors defeat chaos thus ending paradox return home ending paradox however light warriors changed future one heroic deeds remain unknown outside legend hironobu sakaguchi intended make role-playing game rpg long time employer square refused give permission expected low sales product however rpg dragon quest released proved hit japan company reconsidered stance genre approved sakaguchi vision rpg inspired three colleagues volunteered join project headed thought rough boss spite unsuccessful creations eventually final fantasy developed team seven core staff members within square referred a-team sakaguchi convinced fellow game designers koichi ishii akitoshi kawazu join project kawazu mainly responsible battle system sequences based heavily tabletop game dungeons dragons rpg wizardry example enemies weaknesses elements fire ice included japanese rpgs point kawazu grown fond aspects western rpgs decided incorporate final fantasy also advocated player option freely choose party member classes beginning game feels fun rpg begins create character scenario written freelance writer kenji terada based story sakaguchi ishii heavily influenced game setting idea crystals also suggested illustrator yoshitaka amano character designer sakaguchi declined first never heard artist name sakaguchi showed ishii drawings magazine clippings told art style looking ishii revealed actually created amano hence leading involvement game music final fantasy composed nobuo uematsu marked 16th video game music composition iranian-american programmer nasir gebelli hired code game initially tried understand aspects gameplay soon advised sakaguchi program design concepts explain everything gebelli detail gebelli also responsible creating considered first rpg minigame sliding puzzle added game despite part original game design among developers graphic designer kazuko shibuya programmers kiyoshi yoshii ken narita well debugger hiroyuki ito project started show promise designer hiromichi tanaka b-team joined aid development lack faith sakaguchi team well unpopularity within company motivated staff members give best sakaguchi took in-development rom game japanese magazine famicom tsushin would review however famitsu gave game extensive coverage initially 200,000 copies shipped sakaguchi pleaded company make 400,000 help spawn sequel management agreed original nes version successfully shipped 520,000 copies japan following successful north american localization dragon quest nintendo america translated final fantasy english published north america 1990 north american version final fantasy met modest success partly due nintendo then-aggressive marketing tactics version game marketed pal region final fantasy origins 2003 years several theories emerged game called final fantasy 2015 sakaguchi stated beginning team wished name could shortened way game title could abbreviated latin script pronounced four syllables japanese language original working title sakaguchi rpg concept fighting fantasy changed avoid issues tabletop game name already released reason choosing word final form eventual title final fantasy explained twofold uematsu one thing stemmed sakaguchi personal situation would quit game industry gone back university game sold well another square threat bankruptcy time meant game could company last although sakaguchi confirmed theories later downplayed rationale choosing word final saying definitely back-to-the-wall type situation back word starts f would fine final fantasy remade several times different platforms frequently packaged final fantasy ii various collections remakes retain basic story battle mechanics various changes made different areas including graphics sound specific game elements final fantasy first re-released msx2 system published microcabin japan june 1989 access almost three times much storage space famicom version suffered problems present nintendo cartridge media including noticeable loading times also minor graphical upgrades much-improved music tracks sound effects 1994 final fantasy i・ii compilation final fantasy final fantasy ii launched famicom version released japan graphical updates wonderswan color remake released japan december 9 2000 featured many new graphical changes 8-bit graphics original famicom game updated battle scenes incorporated full background images character enemy sprites redrawn look like ones super famicom final fantasy games japan final fantasy final fantasy ii re-released separately combined game playstation collection released japan 2002 final fantasy ii premium package europe north america 2003 final fantasy origins version similar wonderswan color remake featured several changes detailed graphics remixed soundtrack added full motion video sequences art galleries yoshitaka amano illustrations memo save function december 18 2012 port re-released part final fantasy 25th anniversary ultimate box release final fantasy ii dawn souls like final fantasy origins port first two games series released game boy advance 2004 dawn souls version incorporates various new elements including four additional dungeons updated bestiary minor changes square enix released version final fantasy two japanese mobile phone networks 2004 version ntt docomo foma 900i series launched march title final fantasy subsequent release cdma 1x win-compatible phones launched august another titular version released softbank yahoo keitai phones july 3 2006 games refined graphics compared original 8-bit game advanced many later console handheld ports square enix planned release version north american mobile phones 2006 delayed 2010 released collaboration namco retains game difficulty mp system original famicom version elements updated graphics spell names monster names bosses items areas borrowed game boy advance wonderswan color versions including additional areas monsters present gba version game data saved original famicom version using tent sleeping bag cottage going inn however three save game slots temporary save option available game 20th anniversary final fantasy square enix remade final fantasy final fantasy ii playstation portable games released japan north america 2007 european territories 2008 psp version features higher-resolution 2d graphics full motion video sequences remixed soundtrack new dungeon well bonus dungeons dawn souls script dawn souls version aside new dungeon square enix released original nes version game wii virtual console service japan may 26 2009 north america october 5 2009 pal region import may 7 2010 february 25 2010 square enix released ios version final fantasy based psp port touch controls worldwide june 13 2012 square enix released windows phone version based ios version july 27 2012 square enix released android port largely based ios version though lacking new dungeons 20th-anniversary edition november 11 2016 game alongside 29 games included nes classic edition nintendo classic mini nintendo entertainment system released nintendo final fantasy well received critics commercially successful original nes version shipped 520,000 copies japan according square publicity department japanese famicom msx releases sold combined 600,000 copies north american nes release sold 700,000 copies march 31 2003 game including re-releases remakes time shipped 1.99 million copies worldwide 1.21 million copies shipped japan 780,000 abroad november 19 2007 another playstation portable version shipped 140,000 copies editors ign ranked final fantasy 11th best game nes calling game class system diverse praising convenient use vehicles means traveling across world map gamesradar ranked eighth best nes game ever made staff felt dragon warrior introduced gamers genre final fantasy popularized 2004 readers retro gamer voted final fantasy 93rd top retro game staff noting despite poor visuals relatively simple quest many still consider original best exception ffvii 2006 final fantasy appeared japanese magazine famitsu top 100 games list readers voted 63rd best game time gamefaqs users made similar list 2005 ranked final fantasy 76th rated 49th best game made nintendo system nintendo power top 200 games list 2008 nintendo power ranked 19th best nintendo entertainment system video game praising setting basics console role-playing games along dragon warrior citing examples epic stories leveling random battles character classes final fantasy one influential early console role-playing games played major role legitimizing popularizing genre according ign matt casamassina final fantasy storyline deeper engaging story original dragon quest known dragon warrior north america modern critics pointed game poorly paced contemporary standards involves much time wandering search random battle encounters raise experience levels money exploring solving puzzles reviewers find level-building exploration portions game amusing ones 1987 famitsu initially described original final fantasy one many imitated dragon quest formula game considered weakest difficult installment series subsequent versions final fantasy garnered mostly favorable reviews media peer schneider ign enjoyed wonderswan color version praising graphical improvements especially environments characters monsters famitsu scored version 30 40 final fantasy origins generally well-received gamepro said music fantastic graphics suitably retro cuteness reviews generally positive jeremy dunham ign giving particular praise improved english translation saying better previous version game playstation portable version critically successful previous releases gamespot kevin vanord cited visuals strongest enhancement stated additional random enemy encounters updated graphics add much value dawn souls package rated 76th nintendo power top 200 games list soundtrack album released together score final fantasy ii 1989 game tracks became mainstays final fantasy series prelude arpeggio played title screen opening theme played party crosses bridge early game later referred final fantasy theme victory fanfare played every victorious battle opening motif battle theme also reused number times series theme song plays player characters first cross bridge coneria become recurring theme music series featured numbered final fantasy titles final fantasy also basis series finale video game-themed cartoon series entitled fractured fantasy captain n 8-bit theater sprite-based webcomic created brian clevinger parodies game become popular gaming community since started march 2001 elements video game also appeared series fighting games dissidia final fantasy dissidia 012 final fantasy dissidia final fantasy nt warrior light based yoshitaka amano design lead character garland respective hero villain representing final fantasy warrior light voiced toshihiko seki japanese version grant george english version garland voiced kenji utsumi dissidia final fantasy 012 dissidia final fantasy kōji ishii dissidia final fantasy nt japanese versions christopher sabat english versions games add background information world final fantasy instance dissidia 012 final fantasy names world final fantasy world order distinguish world b world dissidia characters music final fantasy also appeared theatrhythm final fantasy series
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Computer architecture
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address resolution protocol address resolution protocol arp communication protocol used discovering link layer address mac address associated given internet layer address typically ipv4 address mapping critical function internet protocol suite arp defined 1982 internet standard std 37 arp implemented many combinations network data link layer technologies ipv4 chaosnet decnet xerox parc universal packet pup using ieee 802 standards fddi x.25 frame relay asynchronous transfer mode atm ipv4 ieee 802.3 ieee 802.11 common usage internet protocol version 6 ipv6 networks functionality arp provided neighbor discovery protocol ndp address resolution protocol request-response protocol whose messages encapsulated link layer protocol communicated within boundaries single network never routed across internetworking nodes property places arp link layer internet protocol suite address resolution protocol uses simple message format containing one address resolution request response size arp message depends link layer network layer address sizes message header specifies types network use layer well size addresses message header completed operation code request 1 reply 2 payload packet consists four addresses hardware protocol address sender receiver hosts principal packet structure arp packets shown following table illustrates case ipv4 networks running ethernet scenario packet 48-bit fields sender hardware address sha target hardware address tha 32-bit fields corresponding sender target protocol addresses spa tpa arp packet size case 28 bytes arp protocol parameter values standardized maintained internet assigned numbers authority iana ethertype arp 0x0806 appears ethernet frame header payload arp packet confused ptype appears within encapsulated arp packet two computers office computer 1 computer 2 connected local area network ethernet cables network switches intervening gateways routers computer 1 packet send computer 2 dns determines computer 2 ip address 192.168.0.55 send message also requires computer 2 mac address first computer 1 uses cached arp table look 192.168.0.55 existing records computer 2 mac address 00 eb:24 b2:05 ac mac address found sends ethernet frame destination address 00 eb:24 b2:05 ac containing ip packet onto link cache produce result 192.168.0.55 computer 1 send broadcast arp request message destination ff ff ff ff ff ff mac address accepted computers local network requesting answer 192.168.0.55 computer 2 responds arp response message containing mac ip addresses part fielding request computer 2 may insert entry computer 1 arp table future use computer 1 receives caches response information arp table send packet arp probe arp request constructed all-zero sender ip address spa term used ipv4 address conflict detection specification beginning use ipv4 address whether received manual configuration dhcp means host implementing specification must test see address already use broadcasting arp probe packets arp may also used simple announcement protocol useful updating hosts mappings hardware address sender ip address mac address changed announcement also called gratuitous arp message usually broadcast arp request containing sender protocol address spa target field tpa=spa target hardware address tha set zero alternative way broadcast arp reply sender hardware protocol addresses sha spa duplicated target fields tpa=spa tha=sha gratuitous arp request message gratuitous arp reply messages standards-based methods arp request preferred devices may configured use either two types garp arp announcement intended solicit reply instead updates cached entries arp tables hosts receive packet operation code may indicate request reply arp standard specifies opcode processed arp table updated address fields many operating systems perform gratuitous arp startup helps resolve problems would otherwise occur example network card recently changed changing ip-address-to-mac-address mapping hosts still old mapping arp caches gratuitous arp also used interface drivers provide load balancing incoming traffic team network cards used announce different mac address within team receive incoming packets arp announcements used defend link-local ip addresses zeroconf protocol ip address takeover within high-availability clusters arp mediation refers process resolving layer 2 addresses virtual private wire service vpws different resolution protocols used connected circuits e.g. ethernet one end frame relay ipv4 provider edge pe device discovers ip address locally attached customer edge ce device distributes ip address corresponding remote pe device pe device responds local arp requests using ip address remote ce device hardware address local pe device ipv6 pe device discovers ip address local remote ce devices intercepts local neighbor discovery nd inverse neighbor discovery ind packets forwards remote pe device inverse address resolution protocol inverse arp inarp used obtain network layer addresses example ip addresses nodes data link layer layer 2 addresses primarily used frame relay dlci atm networks layer 2 addresses virtual circuits sometimes obtained layer 2 signaling corresponding layer 3 addresses must available virtual circuits used since arp translates layer 3 addresses layer 2 addresses inarp may described inverse addition inarp implemented protocol extension arp uses packet format arp different operation codes reverse address resolution protocol reverse arp rarp like inarp translates layer 2 addresses layer 3 addresses however inarp requesting station queries layer 3 address another node whereas rarp used obtain layer 3 address requesting station address configuration purposes rarp obsolete replaced bootp later superseded dynamic host configuration protocol dhcp arp provide methods authenticating arp replies network arp replies come systems one required layer 2 address arp proxy system answers arp request behalf another system forward traffic normally part network design dialup internet service contrast arp spoofing answering system spoofer replies request another system address aim intercepting data bound system malicious user may use arp spoofing perform man-in-the-middle denial-of-service attack users network various software exists detect perform arp spoofing attacks though arp provide methods protection attacks ipv6 uses neighbor discovery protocol extensions secure neighbor discovery rather arp computers also maintain lists known addresses rather using active protocol model computer maintains database mapping layer 3 addresses e.g. ip addresses layer 2 addresses e.g. ethernet mac addresses data maintained primarily interpreting arp packets local network link thus often called arp cache traditionally methods also used maintain mapping addresses static configuration files centrally maintained lists since least 1980s networked computers utility called 'arp interrogating manipulating table embedded systems networked cameras networked power distribution devices lack user interface use so-called arp stuffing make initial network connection although misnomer arp involved solution issue network management consumer devices specifically allocation ip addresses ethernet devices solution adopted follows devices typically method disable process device operating normally vulnerable attack
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Internet protocols
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bootstrapping node bootstrapping node also known rendezvous host node overlay network provides initial configuration information newly joining nodes may successfully join overlay network bootstrapping nodes predominantly found decentralized peer-to-peer p2p networks dynamically changing identities configurations member nodes networks attempting join p2p network specific discovery membership protocols configuration information may required newly joining node unaware protocols newly established joining node able communicate nodes ultimately join network furthermore protocols configuration requirements may dynamically change infrastructure membership p2p network evolves therefore need able dynamically inform newly joining node required protocols configurations several methods may used joining node identify bootstrapping nodes objective bootstrapping node provide newly joining nodes sufficient configuration information new node may successfully join network access resources shared content discovery protocol information instruct new node discover peers network membership protocol information instruct new node request-to-join subsequently join peer groups network configuration information overlay network dependent instructions may provided example overlay dependent instructions instructing new node obtain zone configuration information may designed p2p network admission control used joining network supports trust management include things encryption/signature protocols admission policies
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Distributed computing architecture
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ieee 802.2 ieee 802.2 original name iso/iec 8802-2 standard defines logical link control llc upper portion data link layer osi model original standard developed institute electrical electronics engineers ieee collaboration american national standards institute ansi adopted international organization standardization iso 1998 still remains integral part family ieee 802 standards local metropolitan networks llc software component provides uniform interface user data link service usually network layer llc may offer three types services conversely llc uses services media access control mac dependent specific transmission medium ethernet token ring fddi 802.11 etc. using llc compulsory ieee 802 networks exception ethernet also used fiber distributed data interface fddi part ieee 802 family ieee 802.2 sublayer adds control information message created upper layer passed llc transmission another node data link resulting packet generally referred llc protocol data unit pdu additional information added llc sublayer llc header llc header consist dsap destination service access point ssap source service access point control field two 8-bit fields dsap ssap allow multiplex various upper layer protocols llc however many protocols use subnetwork access protocol snap extension allows using ethertype values specify protocol transported atop ieee 802.2 also allows vendors define protocol value spaces 8 16 bit hdlc-style control field serves distinguish communication mode specify specific operation facilitate connection control flow control connection mode acknowledgements acknowledged connectionless mode ieee 802.2 provides two connectionless one connection-oriented operational modes use multicasts broadcasts reduce network traffic information needs propagated stations network however type 1 service provides guarantees regarding order received frames compared order sent sender even get acknowledgment frames received device conforming ieee 802.2 standard must support service type 1 network node assigned llc class according service types supports 802.2 llc pdu following format subnetwork access protocol snap extension used located start information field 802.2 header includes two eight-bit address fields called service access points sap collectively lsap osi terminology although lsap fields 8 bits long low-order bit reserved special purposes leaving 128 values available purposes low-order bit dsap indicates whether contains individual group address low-order bit ssap indicates whether packet command response packet remaining 7 bits ssap specify lsap always individual address packet transmitted lsap numbers globally assigned ieee uniquely identify well established international standards protocols families protocols assigned one saps may operate directly top 802.2 llc protocols may use subnetwork access protocol snap ieee 802.2 indicated hexadecimal value 0xaa 0xab source response ssap dsap snap extension allows using ethertype values private protocol id spaces ieee 802 networks used datagram connection-oriented network services ethernet ieee 802.3 networks exception ieee 802.3x-1997 standard explicitly allowed using ethernet ii framing 16-bit field mac addresses carry length frame followed ieee 802.2 llc header ethertype value followed upper layer data framing datagram services supported data link layer although ipv4 assigned lsap value 6 0x6 arp assigned lsap value 152 0x98 ipv4 almost never directly encapsulated 802.2 llc frames without snap headers instead internet standard rfc 1042 usually used encapsulating ipv4 traffic 802.2 llc frames snap headers fddi ieee 802 networks ethernet ethernet networks typically use ethernet ii framing ethertype 0x800 ip 0x806 arp ipx protocol used novell netware networks supports additional ethernet frame type 802.3 raw ultimately supporting four frame types ethernet 802.3 raw 802.2 llc 802.2 snap ethernet ii two frame types fddi non-ethernet ieee 802 networks 802.2 llc 802.2 snap possible use diverse framings single network possible even upper layer protocol case nodes using unlike framings directly communicate following destination source sap fields control field ieee 802.2 conceptually derived hdlc three types pdus carry data most-often used unacknowledged connectionless mode u-format used identified value '11 lower two bits single-byte control field
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Internet protocols
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interworking labs interworking labs privately owned company scotts valley california business optimizing application performance applications embedded systems founded 1993 chris wellens marshall rose first company formed specifically test network protocol compliance products tests allow computer devices many different companies communicate networks interworking labs products diagnose replicate re-mediate application performance problems company first product silvercreek tests simple network management protocol snmp agent implementation switch server phone hundreds thousands individual tests including conformance stress robustness negative testing tests detect diagnose implementation errors private standard mibs well snmpv1 v2c v3 stacks implementations maxwell family products emulate real world networks problems delays rerouting corruption impaired packets protocols domain name system delays limited bandwidth new impairments added maxwell using c c++ python extensions controlled via graphical command line script interfaces supports set protocol impairments tcp/ip dhcp icmp tls sip testing maxwell products named maxwell demon thought experiment 19th century physicist james clerk maxwell maxwell ’ demon demonstrated second law thermodynamics—which says entropy increases—is true average thought experiment maxwell imagined double chamber uniform mixture hot cold gas molecules demon intelligent sits two chambers operating trap door every time cold low-energy molecule comes demon opens door lets molecule side eventually cold gas molecules one side chamber hot ones although molecules continue move randomly introduction intelligence system reduces entropy instead increasing maxwell product sits middle network conversation opens closes figurative door basis specific criteria maxwell intelligently modifies packet based pre-selected criteria sends packet way interworking labs advised internet engineering task force ietf maxwell network emulations reproduce real conditions lab products deployed interworking labs co-founded 1993 chris wellens marshall rose two met 1992 interop company mountain view california wellens director technology rose interop program committee also working group chair ietf simple network management protocol snmp wellens—who overseeing trade fair 5000-node interopnet well array interoperability demonstrations network protocols— noticed engineers different companies often interpreted network protocols differently ended struggling make products send receive data one another—sometimes minutes showcase demonstrations engineers asked interop create interoperability lab network communication issues could worked private less stressful environment interop founder ceo dan lynch concluded industry needed interoperability testing lab lynch asked wellens write business plan permanent interoperability lab rose proposed lab first task create try set tests snmp protocol since snmp area familiar one engineers particular problems interop wellens volunteered organize group developers interoperability test summit rose would create set tests assist developing initial plan time however ziff-davis acquired interop chose proceed interoperability lab wellens lynch agreed pursue idea 1993 wellens established interworking labs january 1994 organized first snmp interoperability test summit using 50 snmp tests written rose first test summit large number implementations failed rose tests.. results persuaded several major corporations interoperability testing would critical component functioning networks participants second 1994 snmp test summit included cabletron systems cisco systems eicon technology empirical tools technologies epilogue technology corp. fujitisu ossi ibm ibm research network general corp. peer networks snmp research synoptics communications tgv inc. wellfleet communications 2000 wellens asked karl auerbach join interworking labs board directors 2002 wellens hired auerbach part cisco advanced internet architecture group serve chief technology officer interworking labs advisory board consisted several members ietf expertise networking protocols andy bierman jeff case dave perkins randy presuhn steve waldbusser wireless networks used hospitals police military turned computer networks essential lifeline utilities computer networks keep economies transportation energy food supplies flowing commonly belong critical infrastructure region performance networks adverse conditions significant concern militaries industry local regional governments according wellens ucita significantly protected software publishers liability failure products software publishers may become increasingly liable consequences network failures—especially comprehensive networking testing existed used online retailers example demonstrate multimillion-dollar losses due network problems security flaws network collapse denial service attack video links
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Computer security
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two-phase locking databases transaction processing two-phase locking 2pl concurrency control method guarantees serializability also name resulting set database transaction schedules histories protocol utilizes locks applied transaction data may block interpreted signals stop transactions accessing data transaction life 2pl protocol locks applied removed two phases two types locks utilized basic protocol shared exclusive locks refinements basic protocol may utilize lock types using locks block processes 2pl may subject deadlocks result mutual blocking two transactions lock system object associated shared resource data item elementary type row database page memory database lock database object data-access lock may need acquired transaction accessing object correct use locks prevents undesired incorrect inconsistent operations shared resources concurrent transactions database object existing lock acquired one transaction needs accessed another transaction existing lock object type intended access checked system existing lock type allow specific attempted concurrent access type transaction attempting access blocked according predefined agreement/scheme practice lock object directly block transaction operation upon object rather blocks transaction acquiring another lock object needed held/owned transaction performing operation thus locking mechanism needed operation blocking controlled proper lock blocking scheme indicates lock type blocks lock type two major types locks utilized common interactions lock types defined blocking behavior follows several variations refinements major lock types exist respective variations blocking behavior first lock blocks another lock two locks called incompatible otherwise locks compatible often lock types blocking interactions presented technical literature lock compatibility table following example common major lock types according two-phase locking protocol transaction handles locks two distinct consecutive phases transaction execution two phase locking rule summarized never acquire lock lock released serializability property guaranteed schedule transactions obey rule typically without explicit knowledge transaction end phase 1 safely determined transaction completed processing requested commit case locks released phase 2 difference 2pl c2pl c2pl transactions obtain locks need transactions begin ensure transaction already holds locks block waiting locks conservative 2pl prevents deadlocks comply s2pl protocol transaction needs comply 2pl release write exclusive locks ended i.e. either committed aborted hand read shared locks released regularly phase 2 protocol appropriate b-trees causes bottleneck b-trees always starts searching parent root rigorousness rigorous scheduling rigorous two-phase locking comply strong strict two-phase locking ss2pl locking protocol releases write exclusive read shared locks applied transaction transaction ended i.e. completing executing ready becoming either committed aborted protocol also complies s2pl rules transaction obeying ss2pl viewed phase 1 lasts transaction entire execution duration phase 2 degenerate phase 2 thus one phase actually left two-phase name seems still utilized due historical development concept 2pl 2pl super-class ss2pl property schedule also called rigorousness also name class schedules property ss2pl schedule also called rigorous schedule term rigorousness free unnecessary legacy two-phase well independent locking mechanism principle blocking mechanisms utilized property respective locking mechanism sometimes referred rigorous 2pl ss2pl special case s2pl i.e. ss2pl class schedules proper subclass s2pl every ss2pl schedule also s2pl schedule s2pl schedules exist ss2pl ss2pl concurrency control protocol choice database systems utilized since early days 1970s proven effective mechanism many situations provides besides serializability also strictness special case cascadeless recoverability instrumental efficient database recovery also commitment ordering co participating distributed environments co based distributed serializability global serializability solutions employed subset co efficient implementation distributed ss2pl exists without distributed lock manager dlm distributed deadlocks see resolved automatically fact ss2pl employed multi database systems ensures global serializability known years discovery co co came understanding role atomic commitment protocol maintaining global serializability well observation automatic distributed deadlock resolution see detailed example distributed ss2pl matter fact ss2pl inheriting properties recoverability co significant subset 2pl general form besides comprising simple serializability mechanism however serializability also implied co known provide ss2pl significant qualities 2pl general form well combined strictness i.e. strict 2pl s2pl known utilized practice popular ss2pl require marking end phase 1 2pl s2pl thus simpler implement also unlike general 2pl ss2pl provides mentioned useful strictness commitment ordering properties many variants ss2pl exist utilize various lock types various semantics different situations including cases lock-type change transaction notable variants use multiple granularity locking comments two schedule classes define schedules respective properties common schedules either one contains strictly contains equal incomparable containment relationships among 2pl classes major schedule classes summarized following diagram 2pl subclasses inherently blocking means optimistic implementations exist whenever optimistic 2pl mentioned refers different mechanism class includes also schedules 2pl class locks block data-access operations mutual blocking transactions results deadlock execution transactions stalled completion reached thus deadlocks need resolved complete transactions executions release related computing resources deadlock reflection potential cycle precedence graph would occur without blocking deadlock resolved aborting transaction involved potential cycle breaking cycle often detected using wait-for graph graph conflicts blocked locks materialized conflicts materialized database due blocked operations reflected precedence graph affect serializability indicates transaction waiting lock release transaction cycle means deadlock aborting one transaction per cycle sufficient break cycle transaction aborted due deadlock resolution application decide next usually application restart transaction beginning may delay action give transactions sufficient time finish order avoid causing another deadlock distributed environment atomic commitment protocol typically two-phase commit 2pc protocol utilized atomicity recoverable data data transaction control partitioned among 2pc participants i.e. data object controlled single 2pc participant distributed global deadlocks deadlocks involving two participants 2pc resolved automatically follows ss2pl effectively utilized distributed environment global deadlocks due locking generate voting-deadlocks 2pc resolved automatically 2pc see commitment ordering co exact characterization voting-deadlocks global cycles reference except co articles known notice general case 2pl global deadlocks similarly resolved automatically synchronization point protocol phase-1 end distributed transaction synchronization point achieved voting notifying local phase-1 end propagated participants distributed transaction way decision point atomic commitment analogy decision point co conflicting operation 2pl happen phase-1 end synchronization point resulting voting-deadlock case global data-access deadlock voting-deadlock also locking based global deadlock automatically resolved protocol aborting transaction involved missing vote typically using timeout comment
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Databases
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hit internet hit request web server file web page image javascript cascading style sheet may many hits per page view since html page contain multiple files images
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Web technology
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m2mi corporation machine-to-machine intelligence m2mi corp founded nasa research park moffett federal airfield provides authentic platform m2m internet things economy m2mi founded 2006 geoffrey barnard m2mi founding member oasis mqtt standards group geoffrey barnard served chair security sub-committee m2mi m2m intelligence® application provides m2m iot application globally connect manage secure perform in-stream analysis quickly monetize organization connected assets strong focus cybersecurity privacy m2mi also provides iot security suite professional edition™ designed securing industrial applications enforcing specific industry compliance allows organizations quickly generate deploy iot device code comply industry ’ regulations professional edition includes means device owners monitor devices health using intuitive dashboards alerts group commands insight analytics includes set optimized ciphers resource limited devices iot security suite professional edition™ designed handle security across devices iot gateways network infrastructures
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Distributed computing architecture
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silvermont silvermont microarchitecture low-power atom celeron pentium branded processors used systems chip socs made intel silvermont forms basis total four soc families silvermont announced news media may 6 2013 intel headquarters santa clara california intel repeatedly said first bay trail devices would available holiday 2013 timeframe leaked slides showed release window bay trail-t august 28 – september 13 2013 avoton rangeley announced available second half 2013 first merrifield devices announced 1h14 airmont 14 nm die shrink silvermont launched early 2015 first seen atom x7-z8700 used microsoft surface 3 airmont microarchitecture includes following soc families silvermont based cores also used modified knight landing iteration intel xeon phi hpc chips silvermont first atom processor feature out-of-order architecture intel revealed q4 2016 quarterly report quality issues c2000 product family effect financial performance company data center group quarter erratum named avr54 published intel state defect chip lpc clock affected systems may experience inability boot may cease operation workaround available requiring platform hardware changes soc failures thought led failures cisco synology products though discussion c2000 root cause failure reported non-disclosure agreement many vendors intel released new c0 stepping c2000 series april 2017 corrected bug july 2017 intel published similar quality issue affects also atom e3800 series embedded processors erratum named vli89 published intel state similar issue atom c2000 defect chip lpc clock affected systems may experience inability boot may cease operation issues extend also usb bus sd card circuitry happen certain conditions activity high several years april 2018 intel announced releasing new d1 stepping fix issue lpc usb sd card buses circuitry degradation issues also apply bay trail processors intel celeron j1900 n2800/n2900 series also pentium n3500 j2850 j2900 series celeron j1800 j1750 series based affected silicon cisco stated failures atom c2000 processors occur early 18 months use higher failure rates occurring 36 months mitigations found limit impact systems firmware update lpc bus called lpc_clkrun reduces utilization lpc interface turn decreases eliminates lpc bus degradation systems however compatible new firmware usb maximum 10 active time 50tb transmit traffic life expectancy lifetime port recommended use sd card boot device remove card system use 14nm airmont architecture processors also affected design flaws noted braswell specification update chp49 errata addition lpc sd card circuitry degradation issues 14nm designs also issues real time clock rtc circuitry degradation usb buses however affected unspecified firmware changes required mitigate rtc circuitry degradation intel plan release new stepping braswell intel admitted issue stating impact consumers depends use condition list desktop processors follows found bug blueprint c2000 cpus family may cause failure embedded ethernet ports list server processors follows list upcoming communications processors follows list embedded processors follows list mobile processors follows list tablet hybrid processors follows list smartphone processors follows list smartphone processors follows list desktop processors follows list mobile processors follows list smartphone tablet processors follows silvermont based processor cores used knights landing versions intel xeon phi multiprocessor hpc chips changes hpc including avx-512 vector units
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Computer architecture
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multilingual multiscript plant name database multilingual multiscript plant name database mmpnd multilingual database names taxa plants located university melbourne managed maintained michel h. porcher database includes names taxa 900 genera higher plants counting mushrooms addition scientific name synonyms contains names taxa 82 major languages website says includes 70 languages 40 languages dialects included mmpnd mentioned many taxa grin-global germplasm resources information network references porcher m. h. et al searchable world wide web multilingual multiscript plant name database mmpnd on-line resource pl names international plant names index ipni mentions multilingual multiscript plant name database searchable language script holds lot information including index medicinal plants regarding aims mmpnd following said ... intention cover many useful plants possible useful one part world however weed even noxious weed another political stand whether selection species declared useful people provided get minimum information handle data basically foresee 8 categories plants order decreasing importance consider vegetables cereals fruits mushrooms fungi herbs pasture fodder crops medicinal plants may termed utilitarian crops fibre oil crops stimulants etc feel last fifty years first 3 categories attracting far little attention taxonomists especially species level three groups edible plants include world staple foods related cultivars selections bred improved centuries basic ingredients world ethnic cuisines ... first objective focus useful plants cultivated ones database currently contains names plants economic importance well names savage plants genus last updating indicated multilingual names presented genera follows indexes plant names various languages en abutilon allium chinense amaranthus tricolor banana beetroot orange beta vulgaris black-eyed pea blood banana ... 95 citations ca 11 citations de ... 34 citations es ... 27 citations fr ... 28 citations
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Databases
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illinois security lab illinois security lab research laboratory university illinois urbana–champaign established 2004 support research education computer network security lab part computer science department information trust institute current research projects concern health information technology critical infrastructure protection past projects addressed messaging networking privacy lab performing work strategic healthcare advanced research projects security sharps project developing security privacy technologies help remove key barriers prevent use health information systems implementing electronic health records health information exchanges telemedicine networked control systems electric power grid use computers tasks like protecting substations overloads digital protective relays metering facilities advanced meters lab developed attested meter provide security privacy advanced meters worked security building automation systems substation automation advances networking distributed computing medical devices combining changes way health care financed growing number elderly people produce strong prospects widespread use assisted living health care approach benefit transferring medical information collected homes dedicated facilities clinicians data networks lab explored security engineering systems prototypes field trials formal methods based architecture uses partially trusted assisted living service provider alsp third party intermediary assisted persons clinicians scalable distributed systems demand ability express adapt diverse policies numerous distinct administrative domains lab introduced technologies messaging systems adaptive security policies based wsemail internet messaging implemented web service attribute-based messaging abm addressing based attributes recipients although significant progress formal analysis security integrity confidentiality relatively less progress treating denial-of-service attacks lab explored techniques based shared channel model envisions bandwidth limiting factor attacks focuses host-based counter-measures selective verification exploits adversary bandwidth limitations favor valid parties also developing new formal methods reasoning dynamic configuration vpns many new information technologies profound impact privacy threats provoked legislation calls deeper regulation lab developed ways treat privacy rules formally including better ways reason using formal methods conformance implications regulations quantify classify privacy attitudes control risks new technologies lab showed formally encode hipaa consent regulations using privacy apis analyzed model checking
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Computer security
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craig chambers craig chambers computer scientist google since 2007 prior professor department computer science engineering university washington received b.s degree computer science mit 1986 ph.d. computer science stanford 1992 best known influential research language self introduced prototypes alternative classes code-splitting compilation technique generates separate code paths fast general cases speed execution dynamically-typed programs
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Programming language topics
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motorola g5 project motorola g5 project unsuccessful attempt around 2000-2001 create 64-bit powerpc processor successor motorola powerpc 7400 series roadmaps era designated powerpc 7500 suggested motorola working g5 chip said chip failed early stages mass production thus could widely made usable chip apple began producing 64-bit systems g5 brand used ibm powerpc 970 also known powerpc g5
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Computer architecture
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semantic web service semantic web service like conventional web services server end client–server system machine-to-machine interaction via world wide web semantic services component semantic web use markup makes data machine-readable detailed sophisticated way compared human-readable html usually easily understood computer programs mainstream xml standards interoperation web services specify syntactic interoperability semantic meaning messages example web services description language wsdl specify operations available web service structure data sent received specify semantic meaning data semantic constraints data requires programmers reach specific agreements interaction web services makes automatic web service composition difficult semantic web services built around universal standards interchange semantic data makes easy programmers combine data different sources services without losing meaning web services activated behind scenes web browser makes request web server uses various web services construct sophisticated reply would able semantic web services also used automatic programs run without connection web browser semantic-web-services platform uses owl web ontology language allow data service providers semantically describe resources using third-party ontologies sswap simple semantic web architecture protocol sswap establishes lightweight protocol owl classes predicates see sswap protocol concept canonical graph enable providers logically describe service service essentially transformation possibly null input subject possibly null output object services semantically discoverable based subsumption hierarchies well input output data types sadi semantic automated discovery integration semantic-web-service initiative consists set design-practices semantic-web-service publishing minimizes use non-standard protocols message structures sadi services natively consume data rdf resource description framework format input output data must instances owl individuals input output classes defined owl-dl unlike canonical web services sadi services use soap messaging protocol unlike sswap sadi services project-specific messaging scaffold services invoked passing rdf instance data service endpoint http post multiplexing achieved sending one owl individual http post invocation sadi imposes single constraint behavior service uri output individual must uri corresponding input individual practice results services create semantic linkages input output service thus chaining sadi services together workflow results uninterrupted linked data graph choreography concerned describing external visible behavior services set message exchanges optionally following message exchange pattern mep functionality consumer point view orchestration deals describing number services two cooperate communicate aim achieving common goal
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Web technology
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spss spss statistics software package used interactive batched statistical analysis long produced spss inc. acquired ibm 2009 current versions 2015 named ibm spss statistics software name originally stood statistical package social sciences spss reflecting original market although software popular fields well including health sciences marketing research hub published full-length freely accessible spss video tutorial playlist spss widely used program statistical analysis social science also used market researchers health researchers survey companies government education researchers marketing organizations data miners others original spss manual nie bent hull 1970 described one sociology influential books allowing ordinary researchers statistical analysis addition statistical analysis data management case selection file reshaping creating derived data data documentation metadata dictionary stored datafile features base software statistics included base software many features spss statistics accessible via pull-down menus programmed proprietary 4gl command syntax language command syntax programming benefits reproducible output simplifying repetitive tasks handling complex data manipulations analyses additionally complex applications programmed syntax accessible menu structure pull-down menu interface also generates command syntax displayed output although default settings changed make syntax visible user also pasted syntax file using paste button present menu programs run interactively unattended using supplied production job facility additionally macro language used write command language subroutines python programmability extension access information data dictionary data dynamically build command syntax programs python programmability extension introduced spss 14 replaced less functional sax basic scripts purposes although saxbasic remains available addition python extension allows spss run statistics free software package r. version 14 onwards spss driven externally python vb.net program using supplied plug-ins version 20 onwards two scripting facilities well many scripts included installation media normally installed default spss statistics places constraints internal file structure data types data processing matching files together considerably simplify programming spss datasets two-dimensional table structure rows typically represent cases individuals households columns represent measurements age sex household income two data types defined numeric text string data processing occurs sequentially case-by-case file dataset files matched one-to-one one-to-many many-to-many addition cases-by-variables structure processing separate matrix session one process data matrices using matrix linear algebra operations graphical user interface two views toggled clicking one two tabs bottom left spss statistics window 'data view shows spreadsheet view cases rows variables columns unlike spreadsheets data cells contain numbers text formulas stored cells 'variable view displays metadata dictionary row represents variable shows variable name variable label value label print width measurement type variety characteristics cells views manually edited defining file structure allowing data entry without using command syntax may sufficient small datasets larger datasets statistical surveys often created data entry software entered computer-assisted personal interviewing scanning using optical character recognition optical mark recognition software direct capture online questionnaires datasets read spss spss statistics read write data ascii text files including hierarchical files statistics packages spreadsheets databases spss statistics read write external relational database tables via odbc sql statistical output proprietary file format *.spv file supporting pivot tables addition in-package viewer stand-alone reader downloaded proprietary output exported text microsoft word pdf excel formats alternatively output captured data using oms command text tab-delimited text pdf xls html xml spss dataset variety graphic image formats jpeg png bmp emf several variants spss statistics exist spss statistics gradpacks highly discounted versions sold students spss statistics server version spss statistics client/server architecture add-on packages enhance base software additional features examples include complex samples adjust clustered stratified samples custom tables create publication-ready tables spss statistics available either annual monthly subscription license spss statistics launched version 25 aug 08 2017 spss v25 adds new advanced statistics random effects solution results genlinmixed robust standard errors glm/unianova profile plots error bars within advanced statistics custom tables add-on v25 also includes new bayesian statistics capabilities method statistical inference publication ready charts powerful new charting capabilities including new default templates ability share microsoft office applications software released first version 1968 statistical package social sciences spss developed norman h. nie dale h. bent c. hadlai hull principals incorporated spss inc. 1975 early versions spss statistics written fortran designed batch processing mainframes including example ibm icl versions originally using punched cards data program input processing run read command file spss commands either raw input file fixed format data single record type 'getfile data saved previous run save precious computer time 'edit run could done check command syntax without analysing data version 10 spss-x 1983 data files could contain multiple record types prior spss 16.0 different versions spss available windows mac os x unix spss statistics version 13.0 mac os x compatible intel-based macintosh computers due rosetta emulation software causing errors calculations spss statistics 15.0 windows needed downloadable hotfix installed order compatible windows vista version 16.0 version runs windows mac linux graphical user interface written java mac os version provided universal binary making fully compatible powerpc intel-based mac hardware spss inc announced july 28 2009 acquired ibm us 1.2 billion dispute ownership name spss 2009 2010 product referred pasw predictive analytics software january 2010 became spss ibm company complete transfer business ibm done october 1 2010 date spss ibm company ceased exist ibm spss fully integrated ibm corporation one brands ibm software group business analytics portfolio together ibm algorithmics ibm cognos ibm openpages companion software ibm spss family used data mining text analytics ibm spss modeler realtime credit scoring services ibm spss collaboration deployment services spss data collection spss dimensions sold 2015 unicom systems inc. division unicom global merged integrated software suite unicom intelligence survey design survey deployment data collection data management reporting ida interactive data analysis software package originated formerly national opinion research center norc university chicago initially offered hp-2000 somewhat later ownership spss also available dec decsystem-20 scss software product intended online use ibm mainframes although c conversational also represented distinction regarding data stored used column-oriented rather row-oriented internal database gave good interactive response time spss conversational statistical system scss whose strong point spss cross-tabulation
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Programming language topics
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warmux warmux free open-source video game turn-based artillery game genre started wormux 2002 game renamed warmux november 2010 avoid potential trademark conflicts game multiplatform many desktop computer mobile platforms available several players play together typically one using team game played online every player uses version game 2 modes private mode one must provide opponents one address port public mode index server publish game online games available since 0.8beta1 supertuxkart teams styled mascots various free software projects gnu linux freebsd kde gimp openoffice.org firefox thunderbird suse workrave nufw spip bugzilla 0.9.0 cpu player selected single player gameplay allowing compete computer-driven teams feature first appeared 0.7.9 hidden due limited abilities project started december 2002 lawrence azzoug moy wormux game developed source code data free software distributed terms gnu general public license originally developed based clanlib library project later switched sdl due cross-platform sdl middle-layer game ported many oses platforms windows unix-like systems including linux freebsd android amigaos 4 aros maemo symbian^3 mac os x november 2010 old name nowiki /nowiki wormux nowiki /nowiki dropped favor nowiki /nowiki warmux nowiki /nowiki name nowiki /nowiki wormux nowiki /nowiki originally homage old classic worms games among popular artillery game genre developers decided renaming project order avoid possible confusion latest version 11.04.1 released 30th april 2011 community fell apart game development abandoned around 2012 domain name lost acquired cyber squatters project transferred gna.org repository could restart development warmux project went gna shutdown may 2017 critiques game generally positive raiden realm praised game similarity original worms games saying anyone ever loved played famous worms pc game series wormux game well noting even n't much fan ... 'll find wormux none less captivating enjoyable fosswire declared wormux makes formidable clone original series absolutely love wormux right minifrag.com said wormux loaded turn-based cartoon combat goodness netbook gamer wormux everything going also included linuxlinks listing 42 best free linux games well holding four five star rating linux game tome wormux selected september 2008 hotpick linux format game became quite popular packaged several linux distributions different versions game downloaded via gna 2009 march 2016 least 123,000 times
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Operating systems
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distributed operating system distributed operating system software collection independent networked communicating physically separate computational nodes handle jobs serviced multiple cpus individual node holds specific software subset global aggregate operating system subset composite two distinct service provisioners first ubiquitous minimal kernel microkernel directly controls node hardware second higher-level collection system management components coordinate node individual collaborative activities components abstract microkernel functions support user applications microkernel management components collection work together support system goal integrating multiple resources processing functionality efficient stable system seamless integration individual nodes global system referred transparency single system image describing illusion provided users global system appearance single computational entity distributed os provides essential services functionality required os adds attributes particular configurations allow support additional requirements increased scale availability user distributed os works manner similar single-node monolithic operating system although consists multiple nodes appears users applications single-node separating minimal system-level functionality additional user-level modular services provides separation mechanism policy mechanism policy simply interpreted something done versus something done respectively separation increases flexibility scalability locale typically node kernel provides minimally complete set node-level utilities necessary operating node underlying hardware resources mechanisms include allocation management disposition node resources processes communication input/output management support functions within kernel communications sub-system foremost importance distributed os distributed os kernel often supports minimal set functions including low-level address space management thread management inter-process communication ipc kernel design referred microkernel modular nature enhances reliability security essential features distributed os common kernel identically replicated nodes system therefore nodes system use similar hardware combination minimal design ubiquitous node coverage enhances global system extensibility ability dynamically introduce new nodes services system management components software processes define node policies components part os outside kernel components provide higher-level communication process resource management reliability performance security components match functions single-entity system adding transparency required distributed environment distributed nature os requires additional services support node responsibilities global system addition system management components accept defensive responsibilities reliability availability persistence responsibilities conflict consistent approach balanced perspective deep understanding overall system assist identifying diminishing returns separation policy mechanism mitigates conflicts architecture design distributed operating system must realize individual node global system goals architecture design must approached manner consistent separating policy mechanism distributed operating system attempts provide efficient reliable distributed computing framework allowing absolute minimal user awareness underlying command control efforts multi-level collaboration kernel system management components turn distinct nodes distributed operating system functional challenge distributed operating system point system must maintain perfect harmony purpose simultaneously maintain complete disconnect intent implementation challenge distributed operating system opportunity produce foundation framework reliable efficient available robust extensible scalable system however opportunity comes high cost complexity distributed operating system exceptional degree inherent complexity could easily render entire system anathema user logical price realizing distributed operation system must calculated terms overcoming vast amounts complexity many areas many levels calculation includes depth breadth range design investment architectural planning required achieving even modest implementation design development considerations critical unforgiving instance deep understanding distributed operating system overall architectural design detail required exceptionally early point exhausting array design considerations inherent development distributed operating system design considerations potentially affect many others significant degree leads massive effort balanced approach terms individual design considerations many permutations aid effort rely documented experience research distributed computing power research experimentation efforts began earnest 1970s continued 1990s focused interest peaking late 1980s number distributed operating systems introduced period however implementations achieved even modest commercial success fundamental pioneering implementations primitive distributed operating system component concepts date early 1950s individual steps focused directly distributed computing time many may realized important impact pioneering efforts laid important groundwork inspired continued research areas related distributed computing mid-1970s research produced important advances distributed computing breakthroughs provided solid stable foundation efforts continued 1990s accelerating proliferation multi-processor multi-core processor systems research led resurgence distributed os concept one first efforts dyseac general-purpose synchronous computer one earliest publications association computing machinery april 1954 researcher national bureau standards national institute standards technology nist presented detailed specification dyseac introduction focused upon requirements intended applications including flexible communications also mentioned computers specification discussed architecture multi-computer systems preferring peer-to-peer rather master-slave one earliest examples computer distributed control dept army reports certified reliable passed acceptance tests april 1954 completed delivered time may 1954 portable computer housed tractor-trailer 2 attendant vehicles 6 tons refrigeration capacity described experimental input-output system lincoln tx-2 emphasized flexible simultaneously operational input-output devices i.e. multiprogramming design tx-2 modular supporting high degree modification expansion system employed multiple-sequence program technique technique allowed multiple program counters associate one 32 possible sequences program code explicitly prioritized sequences could interleaved executed concurrently affecting computation process also control flow sequences switching devices well much discussion related device sequencing similar dyseac tx-2 separately programmed devices operate simultaneously increasing throughput full power central unit available device tx-2 another example system exhibiting distributed control central unit dedicated control one early effort abstracting memory access intercommunicating cells cell composed collection memory elements memory element basically binary electronic flip-flop relay within cell two types elements symbol cell cell structure stores data string symbols consisting name set parameters information linked cell associations theory contended addressing wasteful non-valuable level indirection information accessed two ways direct cross-retrieval direct retrieval accepts name returns parameter set cross-retrieval projects parameter sets returns set names containing given subset parameters similar modified hash table data structure allowed multiple values parameters key name configuration ideal distributed systems constant-time projection memory storing retrieval inherently atomic exclusive cellular memory intrinsic distributed characteristics would invaluable impact user hardware/device application programming interfaces indirect authors considering distributed systems stating algorithms scalable synchronization shared-memory multiprocessors measurements distributed file system memory coherence shared virtual memory systems transactions transactional memory composable memory transactions transactional memory architectural support lock-free data structures software transactional memory dynamic-sized data structures software transactional memory oceanstore architecture global-scale persistent storage weighted voting replicated data sanity checks byzantine generals problem fail-stop processors approach designing fault-tolerant computing systems recoverability distributed snapshots determining global states distributed systems optimistic recovery distributed systems better illustrate point examine three system architectures centralized decentralized distributed examination consider three structural aspects organization connection control organization describes system physical arrangement characteristics connection covers communication pathways among nodes control manages operation earlier two considerations centralized system one level structure constituent elements directly depend upon single control element decentralized system hierarchical bottom level unites subsets system entities entity subsets turn combine higher levels ultimately culminating central master element distributed system collection autonomous elements concept levels centralized systems connect constituents directly central master entity hub spoke fashion decentralized system aka network system incorporates direct indirect paths constituent elements central entity typically configured hierarchy one shortest path two elements finally distributed operating system requires pattern direct indirect connections possible two elements consider 1970s phenomena “ string art ” spirograph drawing fully connected system spider web interstate highway system u.s. cities examples partially connected system centralized decentralized systems directed flows connection central entity distributed systems communicate along arbitrary paths pivotal notion third consideration control involves allocating tasks data system elements balancing efficiency responsiveness complexity centralized decentralized systems offer control potentially easing administration limiting options distributed systems difficult explicitly control scale better horizontally offer fewer points system-wide failure associations conform needs imposed design organizational chaos transparency single-system image refers ability application treat system operates without regard whether distributed without regard hardware implementation details many areas system benefit transparency including access location performance naming migration consideration transparency directly affects decision making every aspect design distributed operating system transparency impose certain requirements and/or restrictions design considerations systems optionally violate transparency varying degrees meet specific application requirements example distributed operating system may present hard drive one computer c drive another computer g user require knowledge device drivers drive location devices work way application perspective less transparent interface might require application know computer hosts drive transparency domains inter-process communication ipc implementation general communication process interaction dataflow threads and/or processes within node nodes distributed os intra-node inter-node communication requirements drive low-level ipc design typical approach implementing communication functions support transparency sense interprocess communication greatest underlying concept low-level design considerations distributed operating system process management provides policies mechanisms effective efficient sharing resources distributed processes policies mechanisms support operations involving allocation de-allocation processes ports processors well mechanisms run suspend migrate halt resume process execution resources operations either local remote respect distributed os maintains state synchronization processes system example load balancing common process management function load balancing monitors node performance responsible shifting activity across nodes system balance one load balancing function picking process move kernel may employ several selection mechanisms including priority-based choice mechanism chooses process based policy 'newest request system implements policy systems resources memory files devices etc distributed throughout system given moment nodes may light idle workloads load sharing load balancing require many policy-oriented decisions ranging finding idle cpus move move many algorithms exist aid decisions however calls second level decision making policy choosing algorithm best suited scenario conditions surrounding scenario distributed os provide necessary resources services achieve high levels reliability ability prevent and/or recover errors faults physical logical defects cause errors system system reliable must somehow overcome adverse effects faults primary methods dealing faults include fault avoidance fault tolerance fault detection recovery fault avoidance covers proactive measures taken minimize occurrence faults proactive measures form transactions replication backups fault tolerance ability system continue operation presence fault event system detect recover full functionality event actions taken make every effort preserve single system image availability fraction time system respond requests many benchmark metrics quantify performance throughput response time job completions per unit time system utilization etc respect distributed os performance often distills balance process parallelism ipc managing task granularity parallelism sensible relation messages required support extremely effective also identifying beneficial migrate process data rather copy data effective well cooperating concurrent processes inherent need synchronization ensures changes happen correct predictable fashion three basic situations define scope need improper synchronization lead multiple failure modes including loss atomicity consistency isolation durability deadlock livelock loss serializability flexibility distributed operating system enhanced modular characteristics distributed os providing richer set higher-level services completeness quality kernel/microkernel simplifies implementation services potentially enables service providers greater choice providers services architectural design e1 distributed operating system cronus distributed operating system design development minix distributed operating system
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Operating systems
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