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pdp-11 architecture pdp-11 architecture instruction set architecture isa developed digital equipment corporation dec implemented central processing units cpus microprocessors used pdp-11 minicomputers wide use 1970s eventually overshadowed powerful vax-11 architecture 1980s sixteen-bit words stored little-endian least significant bytes first thirty-two-bit data—supported extensions basic architecture e.g. floating point fpu instruction set double-words extended instruction set long data commercial instruction set —are stored one format including unusual middle-endian format sometimes referred pdp-endian pdp-11 16-bit addresses address 64 kb time pdp-11 yielded vax 8-bit bytes hexadecimal notation becoming standard industry however numeric values pdp-11 always use octal notation amount memory attached pdp-11 always stated number words basic logical address space 32k words high 4k physical address space addresses 160000 177777 absence memory management populated input/output registers bus respond addresses range originally fully loaded pdp-11 28k words processor reserves low memory addresses two-word vectors give program counter processor status word begin service routine i/o device interrupts program places address vector bus indicate service routine take control lowest vectors service routines handle various types trap traps occur program errors attempt execute undefined instruction also program executes instruction bpt emt iot trap request service operating system article pdp-11 describes 16-bit logical address space became insurmountable limitation life pdp-11 following techniques used work around limitation cpu contains eight general-purpose 16-bit registers r0 r7 register r7 program counter pc although register used stack pointer r6 stack pointer sp used hardware interrupts traps r5 often used point current procedure call frame speed context switching pdp-11 models provide dual r1-r5 register sets kernel supervisor present user modes separate memory maps also separate stack pointers user program cause system malfunction storing invalid value stack pointer register instructions allocate six bits specify operand three bits select one eight addressing modes three bits select one eight general registers use three-bit groups makes octal notation natural following sections item includes example operand would written assembly language prototypical single-operand instruction symbol opr rn means one registers written r0 r7 rn signifies contents register following eight modes applied general register effects applied r6 stack pointer sp r7 program counter pc set separately following sections index index deferred modes x 16-bit value taken second word instruction double-operand instructions operands use modes instructions three words long autoincrementation autodecrementation register 1 byte instructions 2 word instructions 2 whenever deferred mode used since quantity register addresses word pointer r7 program counter specified four addressing modes naturally yield useful effects common use absolute mode—whose syntax combines immediate deferred mode—is specify input/output registers registers device specific memory addresses relative mode simpler syntax typical referring program variables jump destinations program uses relative mode relative deferred mode exclusively internal references position-independent contains assumptions location loaded arbitrary memory location even moved need addresses adjusted reflect location relocated computing addresses relative current location processor performed relocation fly immediate absolute modes merely autoincrement autoincrement deferred mode respectively applied pc auxiliary word instruction table says pc next instruction automatically incremented past auxiliary word pc always points words autoincrementation always 2 r6 also written sp used hardware stack traps interrupts convention enforced set modes pdp-11 provides stack grows downward—toward lower addresses—as items pushed onto mode applied sp register programmer elects use software stack addressing modes following effects although software stacks contain bytes sp always stack words autoincrementation autodecrementation sp always 2 pdp-11 operates bytes words bytes specified register number—identifying register low-order byte—or memory location words specified register number memory location low-order byte must even number instructions take operands bit 15 set specify byte addressing clear specify word addressing lists following two sections assembly-language programmer appended b instruction symbol specify byte operation example mov became movb instructions example mark sob implemented pdp-11 models high-order four bits specify operation performed bit 15 generally selecting word versus byte addressing two groups six bits specify mode register defined two operands add sub instructions use word addressing byte-oriented variations additional two-operand instructions require register source operand register pair used written r r+1 first register contains low-order bits must even second register contains high-order bits remainder exception multiply instruction r may odd high 16 bits result stored high-order nine bits specify operation performed bit 15 generally selecting word versus byte addressing many operations seems combinations high-order four bits taken double-operand instructions single group six bits specifies mode register defined single operand branch instructions take conditional effect based state condition codes psw branch instruction typically preceded two-operand cmp compare bit bit test one-operand tst test instruction arithmetic logic instructions also set condition codes contrast intel processors x86 architecture mov instructions set branch instruction could used branch depending whether value moved zero negative high-order byte specifies operation bits 8 9 10 op-code bit 15 reversing branch sense low-order byte offset relative current location program counter offset number words multiplied 2 combined program counter signed number enabling branches forward backward code limited range branch instructions meant code grew target addresses branches would become unreachable programmer would change one-word br two-word jmp instruction next group jmp conditional forms programmer would change beq bne branched around jmp sob subtract one branch listed two-operand instructions another conditional branch instruction jsr instruction could save register stack programs need feature specified pc register jsr pc address routine returned using rts pc routine called instance jsr r4 address old value r4 would top stack return address jsr would r4 let routine gain access values coded in-line specifying r4 in-line pointers specifying r4 autoincrementation moved past data point caller code resumed routine would specify rts r4 return caller four condition codes processor status word psw instructions group digital called micro-programmed single bit instruction word referenced single condition code assembler define syntax specify every combination symbols scc ccc assembled instruction set cleared respectively four condition codes eis option 11/35/40 11/03 standard newer processors fis instruction set option pdp-11/35/40 11/03 optional floating point processor option 11/45 subsequent models cis implemented optional microcode 11/23/24 add-in module 11/44 one version 11/74 provided string decimal instructions used cobol dibol psw mapped memory address 177 776 instructions found earliest pdp-11s gave programs direct access register pdp-11s provided multiple instruction spaces data spaces set non-orthogonal move instructions gave access spaces example routines operating system handled run-time service calls would use instructions exchange information caller life pdp-11 subtle differences arose implementation instructions combinations addressing modes though implementation regarded correct inconsistencies affect ordinary use pdp-11 pdp-11 processor speed varied model memory configuration op code addressing modes instruction timing three components execute/fetch instruction access time source destination last two components depended addressing mode example pdp-11/70 circa 1975 instruction form add x r r n fetch/execute time 1.35 microseconds plus source destination times 0.6 microseconds total instruction time 2.55 microseconds case addressed memory cache added 1.02 microseconds register-to-register add r r n could execute cache 0.3 microseconds floating point even complex since overlap cpu floating-point processor general floating point significantly slower single-precision floating add instruction could range 2.4 5.5 microseconds plus time fetch operands pdp-11 operated priority level 0 7 declared three bits processor status word psw high-end models could operate choice modes kernel privileged user application sometimes supervisor according two bits psw request interrupt bus device would assert one four common bus lines br4 br7 processor responded higher numbers indicated greater urgency perhaps data might lost desired sector might rotate contact read/write heads unless processor responded quickly printer readiness another character lowest priority br4 would remain ready indefinitely processor operating level 5 br6 br7 would order processor operating 3 lower would grant interrupt 7 would grant none bus requests granted lost merely deferred device needing service would continue assert bus request whenever interrupt exceeded processor priority level processor asserted corresponding bus grant bg4 bg7 bus-grant lines common lines daisy chain input gate output previous gate chain gate bus device device physically closer processor earlier daisy chain device made request sensing bus-grant input could conclude control bus pass grant signal next device bus device made request propagated bus-grant input bus-grant output giving next closest device chance reply devices occupy adjacent slots processor board grant continuity cards inserted empty slots propagated bus-grant line control bus device dropped bus request placed bus memory address two-word vector processor saved program counter pc psw entered kernel mode loaded new values specified vector device br6 new psw vector would typically specify 6 new processor priority processor would honor urgent requests br7 service routine defer requests lower priority new pc processor jumped service routine interrupting device routine operated device least removing condition caused interrupt routine ended rti return interrupt instruction restored pc psw processor granted interrupt bus request made error device responded bus grant processor timed performed trap would suggest bad hardware macro-11 assembly language pdp-11 successor pal-11 program assembler loader earlier version pdp-11 assembly language without macro facilities macro-11 supported dec pdp-11 operating systems pdp-11 unix systems also include assembler called structurally similar macro-11 different syntax fewer features folk myth instruction set architecture pdp-11 influenced idiomatic use b programming language pdp-11 increment decrement addressing modes correspond codice_1 codice_2 constructs c. codice_3 codice_4 register variables expression codice_5 could compiled single machine instruction dennis ritchie says folk myth historically impossible however c programming language take advantage several low-level programming features pdp-11 resulting inclusion new processors
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Computer architecture
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site security handbook site security handbook rfc 2196 guide setting computer security policies procedures sites systems internet however information provided also useful sites yet connected internet guide lists issues factors site must consider setting policies makes number recommendations provides discussions relevant areas guide framework setting security policies procedures order effective set policies procedures site make many decisions gain agreement communicate implement policies guide product ietf ssh working group published 1997 obsoleting earlier rfc 1244 1991
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Computer security
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alphonse f. la porta alphonse f. la porta born january 15 1939 career member senior foreign service served u.s ambassador mongolia december 1997 november 2000 subsequently served political advisor u.s. commander-in-chief regional headquarters allied forces southern europe january 2001 november 2003 alphonse la porta born january 15 1939 brooklyn new york family moved south shore long island – first oceanside lynbrook.when young parents first generation immigrants worked hair dressers father came sicily mother ukraine child attended davison avenue elementary school malverne junior high school finally graduating malverne high school 1956 enrolled georgetown university school foreign service graduating 1960 took foreign service exam passing written portion failing score passing grade oral exams decided pursue master degree new york university 1960 1962 entered u.s. army worked army intelligence finished enlistment 1963 began pursue ph.d. georgetown university recruited work national security agency retook foreign service exam 1963–64 time passed exams entered foreign service 1965 first assignment office planning management 1967 1970 political officer chief consular section u.s. embassy jakarta indonesia position attested passport application stanley ann dunham soetoro mother president barack h. obama thus become part barack obama citizenship conspiracy theories principal officer u.s. consulate medan 1978–1981 1985 1987 la porta served state department office management operations moved deputy chief mission u.s. embassy wellington new zealand 1987 1991 amb la porta washington-based assignments included working bureau east asian pacific affairs director office cambodian genocide investigation executive assistant president special representative philippine economic reform deputy director office indonesia malaysia brunei singapore affairs becoming u.s ambassador mongolia 1997 served president vice president american foreign service association 1995 1997 ambassador la porta retired u.s. foreign service september 2003 38 years service president united states-indonesia society usindo 2004 2007 currently managing partner trans pacific partners llc tpp provides professional support military exercises pacific europe latin america serves consultant civil preparedness disaster management amb la porta graduate national war college georgetown university school foreign service 1960 new york university served commissioned officer united states army 1961 1963 speaks indonesian turkish
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Computer security
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zmw attack zmw attack hypothetical denial-of-service attack internet routing infrastructure named ying zhang z. morley mao jia wang researchers published original paper considered possibility relies using targeted denial-of-service attacks links carrying bgp connections autonomous systems attempt overwhelm routers default-free zone routing updates leading disruption forcing perform continuous route recalculations 2010 security researcher max schuchard published paper considering possibility using botnet perform zmw attack internet entire core infrastructure hypothetically allowing botnet 250,000 computers crash entire internet
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Computer security
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conceptual interoperability conceptual interoperability concept simulation theory however broadly applicable model-based information technology domains early ideas harkrider lunceford simulation composability studied detail petty weisel formulated current working definition composability capability select assemble simulation components various combinations simulation systems satisfy specific user requirements defining characteristic composability ability combine recombine components different simulation systems different purposes recent rand study provided coherent overview state composability military simulation systems within u.s. department defense many findings much broader applicability resulting challenges produced layered views petty weisel distinguish idea interoperability coping technical challenges composability dealing modeling issues research virginia modeling analysis simulation center vmasc refined layers define levels conceptual interoperability model lcim definition undergone gradual improvement since first discussion current version lcim first documented turnitsa different levels characterized follows lcim shows layered approach support composable services necessary ws standards described earlier able manage levels particular specific upper layers worth mentioning however lcim focuses technical support information systems command control information systems military context alberts hayes point organizational social aspects often even important tolk proposes layered framework measures merits dealing questions like tactical strategic alignment objectives even political coalition partners within contribution however focus information system aspects page et al suggest defining composability realm model interoperability realm software implementation model addition research introduces integratability coping hardware-side configuration side connectivity author supports categorization recommends following distinction dealing issues simulation system interoperability include meaningful simulation-to-simulation system interoperation ideas complement lcim lcim successfully applied domain modeling simulation generally model-based interoperability challenges pointed lcim used descriptive prescriptive mode recently recommended extend lcim interoperability maturity matrix acm sigsim scs sponsored expert discussion scs spring simulation multiconference san diego ca april 11 2013 professor tolk addressed composability grand challenge modeling simulation thinking cloud-based simulation proposed following two definitions referred latest work research team utilizes model theory lcim form slight variations thereof applied simulation many domains well examples given 500 journal articles book chapters conference papers referencing lcim ideas health human sciences http //aspe.hhs.gov/sp/reports/2010/erpreqlim/report.shtml medical simulation weininger s. jaffe m.b. robkin m. rausch t. arney d. goldman j.m. 2016 importance state context safe interoperable medical systems ieee journal translational engineering health medicine 4 pp.1-10 internet things kolbe niklas jérémy robert sylvain kubler yves le traon proficient productivity tool semantic interoperability open iot ecosystem proceedings 14th eai international conference mobile ubiquitous systems computing networking services 2017 department energy smartgrid http //www.gridwiseac.org/pdfs/interopframework_v1_1.pdf enterprise interoperability geographic information systems digital library ecosystem adaptive instructional systems workshop proceedings 2nd ais standards workshop opening address understanding ais problem space dr. robert sottilare original information based tolk 2006 comes semantic web pads implications dynamic web pads pp 55–62 20th workshop principles advanced distributed simulation pads'06 http //doi.ieeecomputersociety.org/10.1109/pads.2006.39 tolk diallo sy turnitsa cd winters ls 2006 composable web services net-centric applications journal defense modeling simulation jdms volume 3 number 1 pp 27-44 january 2006 enhanced several user contributions additions since
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Computer architecture
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slowdroid slowdroid denial-of-service attack allows single mobile device take network server requiring minimal bandwidth attack created research purposes maurizio aiello developed enrico cambiaso ieiit institute national research council italy released android application slowdroid behavior similar slow dos attacks slowloris since creates many connections victim order saturate resources listening daemon application one difference sent payload case slowdroid compliant specific protocol instead sending forged http request endless sequence spaces sent instead characteristic makes slowdroid able target different protocols payload another difference sending data sending phase instead sending sequence characters slowloris slowdroid sends single character hence reducing bandwidth amounts finally main difference implementation slowdroid implemented executed android mobile operating system platform slowdroid initially published google play store due developers terms service application removed store currently available researchers website
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Computer security
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invicta networks invicta networks computer security company founded victor sheymov former kgb officer exfiltrated moscow brought united states 1980 company products use technology shifts ip addresses company claims makes impossible hack company technology mentioned film breach film
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Computer security
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first department first department charge secrecy political security workplace every enterprise institution soviet union dealt kind technical scientific information plants r institutions etc printing capabilities e.g. publishing houses every branch central statistical administration successor state statistics committee goskomstat also first department control access distribution publication official economic population social statistics copies especially sensitive documents numbered labeled stamped secret official use cases official use version documents mimicked public use versions format provided much detailed information first departments part kgb subordinated management enterprise institution among functions control access information considered state secret foreign travel publications first department also kept account usage copying devices xerographers printing presses typewriters etc prevent unsanctioned copying including samizdat
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Computer security
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gzip gzip file format software application used file compression decompression program created jean-loup gailly mark adler free software replacement compress program used early unix systems intended use gnu g gnu version 0.1 first publicly released 31 october 1992 version 1.0 followed february 1993. gzip based deflate algorithm combination lz77 huffman coding deflate intended replacement lzw patent-encumbered data compression algorithms time limited usability compress popular archivers gzip often also used refer gzip file format although file format also allows multiple streams concatenated gzipped files simply decompressed concatenated originally one file gzip normally used compress single files compressed archives typically created assembling collections files single tar archive also called tarball compressing archive gzip final compressed file usually extension gzip confused zip archive format also uses deflate zip format hold collections files without external archiver less compact compressed tarballs holding data compresses files individually take advantage redundancy files solid compression various implementations program written commonly known gnu project implementation using lempel-ziv coding lz77 openbsd version gzip actually compress program support gzip format added openbsd 3.4 g specific version stands gratis freebsd dragonfly bsd netbsd use bsd-licensed implementation instead gnu version actually command-line interface zlib intended compatible gnu implementation options implementations originally come netbsd support decompression bzip2 unix pack format alternative compression program achieving 3-8 better compression zopfli achieves gzip-compatible compression using exhaustive algorithms expense compression time required affect decompression time codice_3 written mark adler compatible gzip speeds compression using available cpu cores threads tar utility included linux distributions extract .tar.gz files passing option e.g. zlib abstraction deflate algorithm library form includes support gzip file format lightweight stream format api zlib stream format deflate gzip file format standardized respectively rfc 1950 rfc 1951 rfc 1952 gzip format used http compression technique used speed sending html content world wide web one three standard formats http compression specified rfc 2616 rfc also specifies zlib format called deflate equal gzip format except gzip adds eleven bytes overhead form headers trailers still gzip format sometimes recommended zlib internet explorer implement standard correctly handle zlib format specified rfc 1950. zlib deflate used internally portable network graphics png format since late 1990s bzip2 file compression utility based block-sorting algorithm gained popularity gzip replacement produces considerably smaller files especially source code structured text cost memory processing time factor 4 advancecomp 7-zip produce gzip-compatible files using internal deflate implementation better compression ratios gzip itself—at cost processor time compared reference implementation
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Computer file systems
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stack buffer overflow software stack buffer overflow stack buffer overrun occurs program writes memory address program call stack outside intended data structure usually fixed-length buffer stack buffer overflow bugs caused program writes data buffer located stack actually allocated buffer almost always results corruption adjacent data stack cases overflow triggered mistake often cause program crash operate incorrectly stack buffer overflow type general programming malfunction known buffer overflow buffer overrun overfilling buffer stack likely derail program execution overfilling buffer heap stack contains return addresses active function calls stack buffer overflow caused deliberately part attack known stack smashing affected program running special privileges accepts data untrusted network hosts e.g webserver bug potential security vulnerability stack buffer filled data supplied untrusted user user corrupt stack way inject executable code running program take control process one oldest reliable methods attackers gain unauthorized access computer canonical method exploiting stack-based buffer overflow overwrite function return address pointer attacker-controlled data usually stack illustrated codice_1 following example code takes argument command line copies local stack variable codice_2 works fine command-line arguments smaller 12 characters see figure b arguments larger 11 characters long result corruption stack maximum number characters safe one less size buffer c programming language strings terminated null byte character twelve-character input thus requires thirteen bytes store input followed sentinel zero byte zero byte ends overwriting memory location one byte beyond end buffer program stack codice_3 various inputs notice figure c argument larger 11 bytes supplied command line codice_3 overwrites local stack data saved frame pointer importantly return address codice_3 returns pops return address stack jumps address i.e starts executing instructions address thus attacker overwritten return address pointer stack buffer codice_6 contains attacker-supplied data actual stack buffer overflow exploit string would instead shellcode suitable platform desired function program special privileges e.g suid bit set run superuser attacker could use vulnerability gain superuser privileges affected machine attacker also modify internal variable values exploit bugs example number platforms subtle differences implementation call stack affect way stack buffer overflow exploit work machine architectures store top-level return address call stack register means overwritten return address used later unwinding call stack another example machine-specific detail affect choice exploitation techniques fact risc-style machine architectures allow unaligned access memory combined fixed length machine opcodes machine limitation make jump esp technique almost impossible implement one exception program actually contains unlikely code explicitly jump stack register within topic stack buffer overflows often-discussed-but-rarely-seen architecture one stack grows opposite direction change architecture frequently suggested solution stack buffer overflow problem overflow stack buffer occurs within stack frame overwrite return pointer investigation claimed protection finds naïve solution best overflow occurs buffer previous stack frame still overwrite return pointer allow malicious exploitation bug instance example return pointer codice_7 overwritten overflow actually occurs within stack frame codice_8 however buffer overflows call codice_8 resides previous stack frame return pointer codice_8 numerically higher memory address buffer means instead return pointer codice_7 overwritten return pointer codice_8 overwritten means growing stack opposite direction change details stack buffer overflows exploitable reduce significantly number exploitable bugs years number control-flow integrity schemes developed inhibit malicious stack buffer overflow exploitation may usually classified three categories stack canaries named analogy canary coal mine used detect stack buffer overflow execution malicious code occur method works placing small integer value randomly chosen program start memory stack return pointer buffer overflows overwrite memory lower higher memory addresses order overwrite return pointer thus take control process canary value must also overwritten value checked make sure changed routine uses return pointer stack technique greatly increase difficulty exploiting stack buffer overflow forces attacker gain control instruction pointer non-traditional means corrupting important variables stack another approach preventing stack buffer overflow exploitation enforce memory policy stack memory region disallows execution stack w^x write xor execute means order execute shellcode stack attacker must either find way disable execution protection memory find way put her/his shellcode payload non-protected region memory method becoming popular hardware support no-execute flag available desktop processors method definitely makes canonical approach stack buffer overflow exploitation fail without problems first common find ways store shellcode unprotected memory regions like heap little need change way exploitation even ways damning so-called return libc method shellcode creation attack malicious payload load stack shellcode proper call stack execution vectored chain standard library calls usually effect disabling memory execute protections allowing shellcode run normal works execution never actually vectors stack variant return-to-libc return-oriented programming rop sets series return addresses executes small sequence cherry-picked machine instructions within existing program code system libraries sequence ends return so-called gadgets accomplish simple register manipulation similar execution returning stringing together achieves attacker ends even possible use returnless return-oriented programming exploiting instructions groups instructions behave much like return instruction instead separating code data another mitigation technique introduce randomization memory space executing program since attacker needs determine executable code used resides either executable payload provided executable stack one constructed using code reuse ret2libc return-oriented programming rop randomizing memory layout concept prevent attacker knowing code however implementations typically randomize everything usually executable loaded fixed address hence even aslr address space layout randomization combined nonexecutable stack attacker use fixed region memory therefore programs compiled pie position-independent executables even region memory randomized entropy randomization different implementation implementation low enough entropy problem terms brute forcing memory space randomized
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Computer security
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cylinder-head-sector cylinder-head-sector chs early method giving addresses physical block data hard disk drive 3d-coordinate system made vertical coordinate head horizontal radial coordinate cylinder angular coordinate sector head selects circular surface platter disk one two sides cylinder cylindrical intersection stack platters disk centered around disk spindle combined together cylinder head intersect circular line precisely circular strip physical data blocks called track sector finally selects data block track addressed viewed sort angular component chs addresses exposed instead simple linear addresses going 0 total block count disk 1 early hard drives n't come embedded disk controller would hide physical layout separate generic controller card used operating system know exact physical geometry specific drive attached controller correctly address data blocks geometry became complicated example introduction zone bit recording drive sizes grew time chs addressing method became restrictive since late 1980s hard drives begun shipping embedded disk controller good knowledge physical geometry would however report false geometry computer e.g. larger number heads actually present gain addressable space logical chs values would translated controller thus chs addressing longer corresponded physical attributes drive soon hard drive interfaces replaced chs scheme logical block addressing many tools manipulating master boot record mbr partition table still aligned partitions cylinder boundaries thus artifacts chs addressing still seen partitioning programs 2010s early 2010s disk size limitations imposed mbr became problematic guid partition table gpt designed replacement modern computers without mbr longer use notions chs addressing chs addressing process identifying individual sectors aka physical block data disk position track track determined head cylinder numbers terms explained bottom disk addressing sector smallest unit disk controllers introduce address translations map logical physical positions e.g. zone bit recording stores fewer sectors shorter inner tracks physical disk formats necessarily cylindrical sector numbers track skewed floppy disks controllers use physical sector sizes 128 256 512 1024 bytes e.g. pc/ax whereby formats 512 bytes per physical sector became dominant 1980s common physical sector size harddisks today 512 bytes hard disks 520 bytes per sector well non-ibm compatible machines 2005 seagate custom hard disks used sector sizes 1024 bytes per sector advanced format hard disks use 4096 bytes per physical sector 4kn since 2010 also able emulate 512 byte sectors 512e transitional period magneto-optical drives use sector sizes 512 1024 bytes 5.25-inch drives 512 2048 bytes 3.5-inch drives chs addressing sector numbers always start 1 sector 0 lead confusion since logical sector addressing schemes e.g. logical block addressing lba relative sector addressing dos typically start counting 0 physical disk geometries maximal sector number determined low level format disk however disk access bios ibm-pc compatible machines sector number encoded six bits resulting maximal number 111111 63 sectors per track maximum still use virtual chs geometries tracks thin concentric circular strips sectors least one head required read single track respect disk geometries terms track cylinder closely related single double sided floppy disk track common term two heads cylinder common term strictly speaking track given codice_1 combination consisting codice_2 sectors cylinder consists codice_3 sectors cylinder division data disk drive used chs addressing mode fixed block architecture disk cylinder–head–record cchhr addressing mode ckd disk concept concentric hollow cylindrical slices physical disks platters collecting respective circular tracks aligned stack platters number cylinders disk drive exactly equals number tracks single surface drive comprises track number platter spanning tracks across platter surface able store data without regard whether track bad cylinders vertically formed tracks words track 12 platter 0 plus track 12 platter 1 etc cylinder 12 forms direct access storage device dasd drum memory devices ibm 2321 data cell might give blocks addresses include cylinder address although cylinder address n't select geometric cylindrical slice device device called head reads writes data hard drive manipulating magnetic medium composes surface associated disk platter naturally platter 2 sides thus 2 surfaces data manipulated usually 2 heads per platter one per side sometimes term side substituted head since platters might separated head assemblies removable media floppy drive codice_4 addressing supported ibm-pc compatible bioses code used eight bits theoretically 256 heads counted head 0 255 codice_5 however bug versions microsoft dos/ibm pc dos including 7.10 cause operating systems crash boot encountering volumes 256 heads therefore compatible bioses use mappings 255 heads codice_6 including virtual codice_7 geometries historical oddity affect maximum disk size old bios int 13h code well old pc dos similar operating systems codice_8 mb actually codice_9 mb yields known 8 gb limit context relevant definition 8 gb 8192 mb another incorrect limit would require chs codice_10 64 sectors per track tracks cylinders counted 0 i.e. track 0 first outer-most track floppy cylindrical disks old bios code supported ten bits chs addressing 1024 cylinders codice_11 adding six bits sectors eight bits heads results 24 bits supported bios interrupt 13h subtracting disallowed sector number 0 codice_12 tracks corresponds 128 mb sector size 512 bytes codice_13 codice_14 confirms roughly 8 gb limit chs addressing starts codice_15 maximal value codice_16 codice_17 bits codice_18 24 bits limited 255 heads chs values used specify geometry disk count cylinder 0 head 0 resulting maximum codice_19 codice_20 24 bits 256 255 heads chs tuples specifying geometry actually means sectors per track virtual geometry still matches capacity disk contains codice_21 sectors larger hard disks come use cylinder become also logical disk structure standardised 16 065 sectors codice_22 chs addressing 28 bits eide ata-2 permits eight bits sectors still starting 1 i.e. sectors 1…255 four bits heads 0…15 sixteen bits cylinders 0…65535 results roughly 128 gb limit actually codice_23 sectors corresponding 130560 mb sector size 512 bytes codice_24 bits ata-2 specification also covered ralf brown interrupt list old working draft expired standard published old bios limit 1024 cylinders ata limit 16 heads combined effect codice_25 sectors i.e. 504 mb limit sector size 512 bios translation schemes known echs revised echs mitigated limitation using 128 240 instead 16 heads simultaneously reducing numbers cylinders sectors fit codice_26 echs limit 4032 mb codice_27 revised echs limit 7560 mb given total number sectors disk unix communities employ term block refer sector group sectors example linux fdisk utility version 2.25 displayed partition sizes using 1024-byte blocks clusters allocation units data various file systems fat ntfs etc data mainly consists files clusters directly affected physical virtual geometry disk i.e. cluster begin sector near end given codice_1 track end sector physically logically next codice_1 track 2002 ata-6 specification introduced optional 48 bits logical block addressing declared chs addressing obsolete still allowed implement ata-5 translations unsurprisingly chs lba translation formula given also matches last ata-5 chs translation ata-5 specification chs support mandatory 16 514 064 sectors optional larger disks ata-5 limit corresponds chs codice_30 equivalent disk capacities 16514064 16383×16×63 1032×254×63 requires 24 14+4+6 bits 16383 1 2 chs tuples mapped onto lba addresses using following formula lba address n number heads disk n maximum number sectors per track c h chs address logical sector number formula ecma-107 iso/iec 9293:1994 superseding iso 9293:1987 standards fat file systems matches exactly lba formula given logical block address logical sector number lsn synonyms formula use number cylinders requires number heads number sectors per track disk geometry chs tuple addresses different logical sector numbers depending geometry examples help visualize sequencing sectors linear lba model note cylinder head record format used count key data ckd hard disks ibm mainframes since least 1960s largely comparable cylinder head sector format used pcs save sector size fixed could vary track track based needs application contemporary use disk geometry presented mainframe emulated storage firmware longer relation physical disk geometry earlier hard drives used pc mfm rll drives divided cylinder equal number sectors chs values matched physical properties drive drive chs tuple codice_43 would 500 tracks per side platter two platters 4 heads 32 sectors per track total 32 768 000 bytes 31.25 mb ata/ide drives much efficient storing data replaced archaic mfm rll drives use zone bit recording zbr number sectors dividing track varies location groups tracks surface platter tracks nearer edge platter contain blocks data tracks close spindle physical space within given track near edge platter thus chs addressing scheme correspond directly physical geometry drives due varying number sectors per track different regions platter many drives still surplus sectors less 1 cylinder size end drive since total number sectors rarely ever ends cylinder boundary ata/ide drive set system bios configuration cylinders heads sectors exceed capacity drive bios since drive convert given chs value actual address specific hardware configuration however cause compatibility problems operating systems microsoft dos older version windows partition must start end cylinder boundary modern operating systems windows xp included may disregard rule still cause compatibility issues especially user wants perform dual booting drive microsoft follow rule internal disk partition tools since windows vista
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Computer file systems
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amigaguide amigaguide hypertext document file format designed amiga files stored ascii possible read edit file without need special software since workbench 2.1 amiga guide system o.s inline help files reading manuals hypertext formatting elements launched amigaos based viewer called simply amigaguide included standard feature amiga system users earlier versions workbench could view files downloading program library amigaguide 34 distributed public domain collections floppy disks example fred fish collection could downloaded directly aminet software repository starting amigaos 3.0 amigaguide tool replaced complete flexible multiview amigaguide default tool viewing amigaguide files used amigaos 2.1 also basic text viewer ascii documents handle multiple files thanks cross-linking tables called xref multiview basically void container natural gui various datatypes open multiview default tool media file including amigaguide files invoked mouse clicking recognized existing correspondent datatype although amigaguide format almost solely used documenting amiga programs viewers available several platforms amigaguide document simple ascii-formatted document edited normal text editor viewed text reader software amigaguide commands begin pronounced 'at symbol recognized amigaguide document first line include text codice_1 three categories commands global node attributes global commands usually specified beginning document nodes defined apply nodes document technically anywhere many commands used globally nodes node commands usable inside node node endnode affect node used attributes may specified anywhere normal line addition symbol attributes always use pair braces enclose attribute name possibly additional arguments commands index help next prev toc all-purpose hypertext link specify nodes jump support naming nodes within current document also support path along name lets node located amigaguide document shown simply embossed text squared buttons page multiview access node another document simply required put amigados file path node name point view amigaguide simple hypertext language since amigaos 3.0 user jump file supported amiga datatypes – pictures animation anything uses multiview program handle internal support datatype amiga standard user must still give node name even though file amigaguide file nodes – syntax codice_2
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Operating systems
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pc-based ibm-compatible mainframes since rise personal computer 1980s ibm vendors created pc-based ibm-compatible mainframes compatible larger ibm mainframe computers period time pc-based mainframe-compatible systems lower price require much electricity floor space however sacrificed performance dependable mainframe-class hardware products popular mainframe developers education training settings small companies non-critical processing certain disaster relief roles field insurance adjustment systems hurricane relief mid-1990s mainframes large machines often occupied entire rooms rooms often air conditioned special power arrangements accommodate three-phase electric power required machines modern mainframes physically comparatively small require little special building arrangements ibm demonstrated use mainframe instruction set first desktop computer—the ibm 5100 released 1975 product used microcode execute many system/370 processor instructions could run slightly modified version ibm apl mainframe program interpreter 1980 rumors spread new ibm personal computer perhaps miniaturized version ibm system/370 1981 ibm personal computer appeared based system 370 architecture however ibm use new pc platform create exotic combinations additional hardware could execute s/370 instructions locally october 1983 ibm announced ibm personal computer xt/370 essentially three-in-one product could run pc dos locally could also act 3270 terminal finally—its important distinguishing feature relative ibm 3270 pc—was could execute s/370 instructions locally xt/370 ibm personal computer xt system unit 5160 three custom 8-bit cards processor card 370pc-p contained two modified motorola 68000 chips could emulate s/370 fixed-point instructions non-floating-point instructions intel 8087 coprocessor modified emulate s/370 floating point instructions second card 370pc-m connected first unique card back connector contained 512 kib memory third card pc3277-em 3270 terminal emulator required download system software host mainframe xt/370 computer booted dos ran vm/pc control program card memory space added additional system memory first 256 kib motherboard memory could used move data 512 kib expansion card expansion memory dual ported provided additional 384 kib xt machine bringing total ram xt side 640 kib memory arbitrator could bank switch second 128 kib bank card banks allowing xt intel 8088 processor address ram 370pc-m card besides 416 kb usable ram s/370 applications xt/370 also supported 4 mb virtual memory using hard drive paging device ibm claimed xt/370 reached 0.1 mips data fit ram 1984 list price xt/370 typical configuration approximately 12,000 compared favorably ibm mainframes /mips basis example ibm 4341 delivered 1.2 mips 500,000 theoretically reduced demand customers mainframes offloading load onto smaller computer customers purchased xt/370s likely increased overall load mainframes increasing ibm mainframe sales similarly mainframe version vm/cms vm/pc also created illusion virtual disks pc version maintained pc-dos files either floppy hard disk example cms virtual disk belonging user fred device address 101 stored dos file fred.101 cms import export commands allowed extraction files virtual drives well ascii/ebcdic conversion xt/370 came xt-style 83-key keyboard 10 function keys newer revisions xt/370 dropped pc3277-em favor ibm 3278/79 boards xt/370 among xt systems could use second hard drive mounted 5161 expansion chassis byte 1984 called xt/370 qualified success magazine praised ibm fitting 370 features xt hoped technical improvements might result even better computer 1984 ibm introduced ibm personal computer at/370 similar cards xt/370 updated software supporting larger hard disks dma transfers 3277 card at/370 processor card system almost 60 faster xt/370 at/370 used different 16-bit interface co-processing cards xt called pc/370-p2 pc/370-m2 latter card still 512 kb memory 480 kb usable programs s/370 mode 32 kb reserved microcode storage terminal emulation function at/370 came 3278/79 emulation adapter late-series xt/370 at/370 motherboard equipped 512 kb ram at/370 also ran vm/pc pc dos 3.0 instead 2.10 xt version used vm/pc version 2 launched november 1985 improved performance 50 allowed add-on memory addition disk used page cache vm november 1985 computerworld article noted machine slow selling april 1988 ibm introduced system/370 workstation shipping customers since august 1987 officially called ibm 7437 vm/sp technical workstation later also known personal system/370 freestanding tower connected mca card installed ps/2 model 60 70 80 7437 tower contained processor 16main memory ps/2 provided i/o disk storage 7437 ran ibm vm/sp operating system one ibm representative described 7437 like 9370 single terminal intended existing s/370 users november 1988 list price 18,100 minimum 25-unit order one intended roles provide single-user s/370-compatible computer could run computer-aided design engineering applications originated ibm mainframes cadam catia graphics support provided ibm 5080 graphics system floor-standing tower 5080 connected 7437 ps/2 via cable mca adapter later ibm introduced personal/370 aka p/370 single slot 32-bit mca card added ps/2 rs/6000 computer run system/370 oss like music/sp vm vse parallel os/2 ps/2 aix rs/6000 supporting multiple concurrent users complete implementation s/370 processor including fpu co-processor 16 mb memory management standard i/o channels provided via host os/hardware additional 370 channel card added provide mainframe-specific i/o 3270 local control units 3400/3480 tape drives 7171 protocol converters although single-card product p/370 ran three times faster 7437 attaining 3.5 mips par low-end ibm 4381 subsequent book author claims 4.1 mips p/370 personal/370 available early november 1989 although special bid basis 1995 ibm introduced card enhanced s/390 microprocessor complex supported ibm esa/390 architecture pc-based system ibm pc-related products evolved support well employing card ibm part number 8640-pb0 ibm pc server 330 1998 ibm pc server 500 models important goal design s/390 processor card complete compatibility existing mainframe operating systems software processor implements esa/390 xa instructions prevents need instruction translation three generations card r/390 designation used expansion card used ibm rs/6000 server original r/390 featured 67 77 mhz power2 processor 32 512 mb ram depending configuration mca p/390 expansion card installed mca rs/6000 system pci p/390 card installed number early pci rs/6000s configurations referred r/390 r/390 servers need run aix version 4 host operating system p/390 designation used expansion card used ibm pc server less expensive r/390 original p/390 server housed ibm pc server 500 featured 90 mhz intel pentium processor running os/2 model revised mid-1996 rebranded pc server 520 featured 133 mhz intel pentium processor models came standard 32 mb ram expandable 256 mb pc server 500 featured eight mca expansion slots pc server 520 added two pci expansion slots removed two mca slots s/390 integrated server aka s/390 mainframe housed comparably small case hxwxd 82 x 52 x 111 cm became available november 1998 intended customers require i/o bandwidth performance s/390 multiprise 3000 size 256 mb ecc memory single cmos main processor performance 8 mips used s/390 cpu used integrated server fact p/390 e-card pentium ii used iosp i/o service processor supports four escon four parallel channels standard pci isa slots present maximum 255 gb internal harddisks supported 16x 18gb hds 2x hds redundancy supported oss os/390 mvs/esa vm/esa vse/esa fujitsu offers two pc-compatible systems make lower end fujitsu s/390-based bs2000 mainframe product line sq100 slower configuration using dual-core 2.93ghz intel xeon e7220 processors capable 200rpf performance sq200 introduced recently uses six-core 2.66ghz xeon x7542 processors performance 700rpf intel 64-based bs2000 mainframes run linux windows separate partitions fujitsu also continues make custom s/390-native processors mainframe hardware high end bs2000 line since late 1990s pc processors become fast enough perform mainframe emulation without need coprocessor card currently several personal computer emulators available support system/390 z/architecture
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Computer architecture
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john c. inglis john chris inglis also known chris inglis former deputy director national security agency retired deputy director january 10 2014 inglis born baltimore maryland 29 october 1954 graduated andover high school linthicum 1972 inglis distinguished eagle scout high school inglis attended united states air force academy graduating 1976 distinguished graduate bachelor science degree engineering mechanics inglis training includes undergraduate instructor pilot training also attended air war college designated outstanding graduate
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Computer security
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display data channel display data channel ddc collection protocols digital communication computer display graphics adapter enable display communicate supported display modes adapter enable computer host adjust monitor parameters brightness contrast standard created video electronics standards association vesa ddc suite standards aims provide plug play experience computer displays ddc1 ddc2b/ab/b+/bi protocols physical link monitor video card originally carried either two three pins 15-pin analog vga connector extended display identification data edid companion standard defines compact binary file format describing monitor capabilities supported graphics modes stored read-only memory eeprom chip programmed manufacturer monitor format uses description block containing 128 bytes data optional extension blocks provide additional information current version enhanced edid e-edid release v2.0 first version ddc standard adopted august 1994 included edid 1.0 format specified ddc1 ddc2b ddc2ab physical links ddc version 2 introduced april 1996 split edid separate standard introduced ddc2b+ protocol ddc version 3 december 1997 introduced ddc2bi protocol support vesa plug display flat panel display interface separate device addresses requiring comply edid 2.0 ddc standard superseded e-ddc 1999 prior ddc vga standard reserved four pins analog vga connector known id0 id1 id2 id3 pins 11 12 4 15 identification monitor type id pins attached resistors pull one ground gnd allowed definition monitor type open n/c connected meaning monitor commonly documented scheme id3 pin unused 3 remaining pins defined id0 pulled gnd color monitors monochrome monitors pulled id1 gnd finally id2 pulled gnd signaled monitor capable 1024×768 resolution ibm 8514 scheme input states id pins would encode monitor type follows elaborate schemes also existed used 4 id pins manipulating hsync vsync signals order extract 16 bits 4 id pin values 4 combinations hsync vsync states monitor identification ddc changed purpose id pins incorporate serial link interface however transition change backwards-compatible video cards using old scheme could problems ddc-capable monitor connected ddc signal send video graphics array vga monitor ic protocol using master serial clock serial data pins ddc1 simple low-speed unidirectional serial link protocol pin 12 id1 functions data line continuously transmits 128-byte edid block data clock synchronised vertical sync providing typical clock rates 60 100 hz display devices implemented protocol common version called ddc2b based i²c serial bus pin 12 id1 vga connector used data pin i²c bus formerly-unused pin 15 became i²c clock pin 9 previously used mechanical key supplied +5v dc power 50ma drive eeprom allows host read edid even monitor powered though i²c fully bidirectional supports multiple bus-masters ddc2b unidirectional allows one bus master graphics adapter monitor acts slave device 7-bit i²c address 50h provides 128-256 bytes read-only edid access always read first i²c octet always a1h ddc2ab implementation i²c-based 100 kbit/s access.bus interface allowed monitor manufacturers support external access.bus peripherals mouse keyboard little additional effort devices monitors briefly available mid 1990s disappeared introduction usb ddc2b+ ddc2bi scaled-down versions ddc2ab support monitor graphics card devices still allow bidirectional communication ddc2 exclusive vga connector dvi hdmi connectors feature dedicated ddc2b wires ddc/ci command interface standard introduced august 1998 specifies means computer send commands monitor well receive sensor data monitor bidirectional link specific commands control monitors defined separate monitor control command set mccs standard version 1.0 released september 1998 ddc/ci monitors sometimes supplied external color sensor allow automatic calibration monitor color balance tilting ddc/ci monitors support auto-pivot function rotation sensor monitor enables operating system keep display upright monitor moved portrait landscape positions ddc/ci monitors support small subset mccs commands undocumented commands many manufacturers pay attention ddc/ci past almost monitors support general mccs commands brightness contrast management ddc/ci standard describes full suite bidirectional control protocols ddc2ab ddc2bi ddc2b+ single standard provides means packaging monitor control command set commands ddc/ci version 1.1 adopted october 2004 monitor control command set version 2.0 adopted october 2003 new mccs v3 introduced july 2006 though n't gain enough industry attention yet latest release v2 standard version 2.2 adopted february 2009 enhanced display data channel e-ddc recent revision ddc standard version 1 introduced september 1999 featured addition segment pointer allowed 32 kbytes display information storage use enhanced edid e-edid standard earlier ddc implementations used simple 8-bit data offset communicating edid memory monitor limiting storage size 2 bytes 256 bytes allowing use cheap 2-kbit eeproms e-ddc special i²c addressing scheme introduced multiple 256-byte segments could selected single 8-bit segment index passed display via i²c address 30h access always write first i²c octet always 60h data selected segment immediately read via regular ddc2 address using repeated i²c 'start signal however vesa specification defines segment index value range 00h 7fh allows addressing 128 segments × 256 bytes segment index register volatile defaulting zero automatically resetting zero nack stop therefore must set every time access data first 256-byte segment performed auto-reset mechanism provide backward compatibility example ddc2b hosts otherwise may stuck segment 00h rare cases important changes removal ddc1 ddc2ab protocols deprecation separate vesa p fpdi device addresses clarifications ddc power requirements e-ddc version 1.1 approved march 2004 featured support hdmi consumer electronics e-ddc version 1.2 approved december 2007 introduced support displayport dedicated ddc2b links uses bidirectional auxiliary channel edid mccs communication displayid standards e-ddc version 1.3 september 2017 contains corrections errata minor clarifications kvm switches keyboard-video-mouse video extenders handle ddc traffic incorrectly making necessary disable monitor plug play features operating system maybe even physically remove pin 12 serial data pin analog vga cables connect device multiple pcs microsoft windows features standard plug play monitor driver uses display edid information construct list supported monitor modes display resolution control panel applet allows user disable driver plug play features manually select resolution refresh rate supported video card many video card manufacturers third parties provide control applications allow user select custom display mode conform edid information monitor .inf file
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Computer architecture
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zonealarm z100g zonealarm secure wireless router z100g discontinued unified threat management security router home soho market z100g developed sofaware technologies check point company hardware similar sofaware safe office vpn-1 edge lines software differs features license allows user access degree zonealarm z100g provides networking security related features including
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Computer security
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arm9 arm9 group older 32-bit risc arm processor cores licensed arm holdings microcontroller use arm9 core family consists arm9tdmi arm940t arm9e-s arm966e-s arm920t arm922t arm946e-s arm9ej-s arm926ej-s arm968e-s arm996hs since arm9 cores released 1998 2006 longer recommended new ic designs instead arm cortex-a arm cortex-m arm cortex-r cores preferred design generation arm moved von neumann architecture princeton architecture modified meaning split cache harvard architecture separate instruction data buses caches significantly increasing potential speed silicon chips integrating cores package modified harvard architecture chips combining two address buses side separated cpu caches tightly coupled memories two subfamilies implementing different arm architecture versions key improvements arm7 cores enabled spending transistors include additionally arm9 cores incorporate enhanced dsp instructions multiply-accumulate support efficient implementations digital signal processing algorithms switching von neumann architecture entailed non-unified cache instruction fetches evict data vice versa arm9 cores separate data address bus signals chip designers use various ways cases connect least part address space von neumann style used instructions data usually ahb interconnect connecting dram interface external bus interface usable flash memory hybrids longer pure harvard architecture processors arm holdings neither manufactures sells cpu devices based designs rather licenses processor architecture interested parties arm offers variety licensing terms varying cost deliverables licensees arm provides integratable hardware description arm core well complete software development toolset right sell manufactured silicon containing arm cpu integrated device manufacturers idm receive arm processor ip synthesizable rtl written verilog form ability perform architectural level optimizations extensions allows manufacturer achieve custom design goals higher clock speed low power consumption instruction set extensions optimizations size debug support etc determine components included particular arm cpu chip consult manufacturer datasheet related documentation arm mpcore family multicore processors support software written using either asymmetric amp symmetric smp multiprocessor programming paradigms amp development central processing unit within mpcore may viewed independent processor follow traditional single processor development strategies arm9tdmi successor popular arm7tdmi core also based armv4t architecture cores based support 32-bit arm 16-bit thumb instruction sets include arm9e arm9ej sibling implement basic arm9tdmi pipeline add support armv5te architecture includes dsp-esque instruction set extensions addition multiplier unit width doubled halving time required multiplication operations support 32-bit 16-bit sometimes 8-bit instruction sets amount documentation arm chips daunting especially newcomers documentation microcontrollers past decades would easily inclusive single document chips evolved documentation grown total documentation especially hard grasp arm chips since consists documents ic manufacturer documents cpu core vendor arm holdings typical top-down documentation tree high-level marketing slides datasheet exact physical chip detailed reference manual describes common peripherals aspects physical chips within series reference manual exact arm core processor within chip reference manual arm architecture core includes detailed description instruction sets ic manufacturer additional documents including evaluation board user manuals application notes getting started development software software library documents errata
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Computer architecture
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spanish network excellence cybersecurity research spanish network excellence cybersecurity research renic research initiative promote cybersecurity interests spain
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Computer security
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property list macos ios nextstep gnustep programming frameworks property list files files store serialized objects property list files use filename extension .plist thus often referred p-list files property list files often used store user settings also used store information bundles applications task served resource fork old mac os since data represented property lists somewhat abstract underlying file format implemented many ways namely nextstep used one format represent property list subsequent gnustep macos frameworks introduced differing formats nextstep property lists designed human-readable edited hand serialized ascii syntax somewhat like programming language strings represented binary data represented arrays represented dictionaries represented one limitation original next property list format could represent nsvalue number boolean etc object gnustep adopts nextstep format additions first supports nsvalue objects represented plain ascii second supports nsdate objects serialized *dyyyy-mm-dd hh mm ss timezone gnustep also read write property lists formats used macos macos also read nextstep format apple sets aside favor two new formats mac os x 10.0 nextstep format deprecated new xml format introduced public dtd defined apple xml format supports non-ascii characters storing nsvalue objects unlike gnustep ascii property list format apple ascii property list format support since xml files however space-efficient means storage mac os x 10.2 introduced new format property list files stored binary files starting mac os x 10.4 default format preference files mac os x 10.7 support reading writing files json format introduced json property lists fully compatible though example property lists native date data types json format support conversely json permits null values property lists support explicit nulls plutil utility introduced mac os x 10.2 used check syntax property lists convert property list file one format another also defaults utility introduced nextstep used manipulate plist files used storage preferences also known os x defaults hence name command line via preferences domain utility used edit arbitrary plist files another tool plistbuddy command line utility resides /usr/libexec/plistbuddy useful merging plist files altering entries related software development xml json property lists hand-editable text editor additionally apple provides support xcode editing property lists hierarchical viewer/editor handle plists formatted binary xml json mac os x 10.4 apple provides applescript interface reading property list files system events application mac os x 10.5 apple provides applescript interface editing creating writing property list files well xml format tags related foundation classes corefoundation types data storage formats follows binary file format documented comment block c code source file apple open sourced implementation binary plists foundation library apple describes implementation opaque plist manual page documentation means reliance format discouraged binary file format magic number first bytes file indicate valid plist file text bplist binary file store information captured xml json file formats array set dictionary binary types made pointers objref keyref entries index object table file means binary plists capture fact example separate array dictionary serialized file data element stored captured xml file converting binary file result copy data element placed xml file additionally binary file uid type used identify data items serialized practice uid type simply expanded 64 bit integer complete list data stored taken c code source file follows although best known apple darwin systems including ios macos plist files also present windows computers apple software itunes safari installed windows files typically binary files although applications may generate plist files formats windows plist files stored user ’ home directory following path plist files windows typically store preferences information rather using windows registry options editing plist files windows extensive macos file xml json format care text editor notepad++ used apple ships utility named plutil.exe apple application support package part itunes convert binary plist files xml edited text xml editor plisteditorpro afterwards convert back binary using plutil.exe provides zero cost solution plist editing windows commercial tool plistinator plist editor handles xml binary plist files windows introduced 2006 first released netbsd 4.0 2007 proplib library used serialising data kernel userland one sample users proplib second revision sysmon envsys framework system monitoring netbsd proplib library also ported dragonfly 2010 available since dragonfly bsd 2.8
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Operating systems
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type safety computer science type safety extent programming language discourages prevents type errors type error erroneous undesirable program behaviour caused discrepancy differing data types program constants variables methods functions e.g. treating integer int floating-point number float type safety sometimes alternatively considered property computer program rather language program written languages type-safe facilities circumvented programmers adopt practices exhibit poor type safety formal type-theoretic definition type safety considerably stronger understood programmers type enforcement static catching potential errors compile time dynamic associating type information values run-time consulting needed detect imminent errors combination behaviors classified type errors given programming language usually result attempts perform operations values appropriate data type classification partly based opinion may imply operation leading program crashes security flaws obvious failures legitimate need considered error may imply contravention programmer explicit intent communicated via typing annotations erroneous type-safe context static compile-time type systems type safety usually involves among things guarantee eventual value expression legitimate member expression static type precise requirement subtle — see example subtype polymorphism complications type safety closely linked memory safety restriction ability copy arbitrary bit patterns one memory location another instance implementation language type formula_1 sequence bits appropriate length represent legitimate member formula_1 language allows data copied variable type formula_1 type-safe operation might assign non-formula_1 value variable conversely language type-unsafe extent allowing arbitrary integer used pointer memory-safe statically typed languages provide degree type safety strictly stronger memory safety type systems enforce proper use abstract data types defined programmers even strictly necessary memory safety prevention kind catastrophic failure type-safe code accesses memory locations authorized access discussion type safety specifically refers memory type safety confused type safety broader respect example type-safe code read values another object private fields robin milner provided following slogan describe type safety appropriate formalization slogan depends style formal semantics used particular language context denotational semantics type safety means value expression well-typed say type τ bona fide member set corresponding τ 1994 andrew wright matthias felleisen formulated standard definition proof technique type safety languages defined operational semantics approach type safety determined two properties semantics programming language properties exist vacuum linked semantics programming language describe large space varied languages fit criteria since notion well typed program part static semantics programming language notion getting stuck going wrong property dynamic semantics vijay saraswat provides following definition type safety ultimately aimed excluding problems e.g type safety usually requirement toy language proposed academic programming language research many languages hand big human-generated type safety proofs often require checking thousands cases nevertheless languages standard ml rigorously defined semantics proved meet one definition type safety languages haskell believed meet definition type safety provided certain escape features used example haskell unsafeperformio used escape usual restricted environment i/o possible circumvents type system used break type safety type punning another example escape feature regardless properties language definition certain errors may occur run-time due bugs implementation linked libraries written languages errors could render given implementation type unsafe certain circumstances early version sun java virtual machine vulnerable sort problem programming languages often colloquially classified strongly typed weakly typed also loosely typed refer certain aspects type safety 1974 liskov zilles defined strongly-typed language one whenever object passed calling function called function type must compatible type declared called function 1977 jackson wrote strongly typed language data area distinct type process state communication requirements terms types contrast weakly typed language may produce unpredictable results may perform implicit type conversion object oriented languages type safety usually intrinsic fact type system place expressed terms class definitions class essentially defines structure objects derived api contract handling objects time new object created comply contract function exchanges objects derived specific class implementing specific interface adhere contract hence function operations permitted object defined methods class object implements guarantee object integrity preserved exceptions object oriented languages allow dynamic modification object structure use reflection modify content object overcome constraints imposed class methods definitions ada designed suitable embedded systems device drivers forms system programming also encourage type-safe programming resolve conflicting goals ada confines type-unsafety certain set special constructs whose names usually begin string unchecked_ unchecked_deallocation effectively banned unit ada text applying pragma pure unit expected programmers use unchecked_ constructs carefully necessary programs use type-safe spark programming language subset ada eliminating potential ambiguities insecurities time adding statically checked contracts language features available spark avoids issues dangling pointers disallowing allocation run time entirely ada2012 adds statically checked contracts language form pre- post-conditions well type invariants c programming language type-safe limited contexts example compile-time error generated attempt made convert pointer one type structure pointer another type structure unless explicit cast used however number common operations non-type-safe example usual way print integer something like codice_2 codice_3 tells codice_4 run-time expect integer argument something like codice_5 tells function expect pointer character-string yet supplies integer argument may accepted compilers produce undefined results partially mitigated compilers gcc checking type correspondences printf arguments format strings addition c like ada provides unspecified undefined explicit conversions unlike ada idioms use conversions common helped give c type-unsafe reputation example standard way allocate memory heap invoke memory allocation function codice_6 argument indicating many bytes required function returns untyped pointer type codice_7 calling code must explicitly implicitly cast appropriate pointer type pre-standardized implementations c required explicit cast therefore code codice_8 became accepted practice features c++ promote type-safe code c type-safe statically type-safe support untyped pointers must accessed using unsafe keyword prohibited compiler level inherent support run-time cast validation casts validated using keyword return null reference cast invalid using c-style cast throw exception cast invalid see c sharp conversion operators undue reliance object type types derived runs risk defeating purpose c type system usually better practice abandon object references favour generics similar templates c++ generics java java language designed enforce type safety anything java happens inside object object instance class implement type safety enforcement object usage needs allocated java allows usage primitive types inside properly allocated objects sometimes part type safety implemented indirectly e.g class bigdecimal represents floating point number arbitrary precision handles numbers expressed finite representation operation bigdecimal.divide calculates new object division two numbers expressed bigdecimal case division finite representation one computes e.g 1/3=0.33333 ... divide method raise exception rounding mode defined operation hence library rather language guarantees object respects contract implicit class definition sml rigorously defined semantics known type-safe however implementations sml including standard ml new jersey sml/nj syntactic variant mythryl mlton provide libraries offer certain unsafe operations facilities often used conjunction implementations foreign function interfaces interact non-ml code c libraries may require data laid specific ways another example sml/nj interactive toplevel must use unsafe operations execute ml code entered user modula-2 strongly typed language design philosophy require unsafe facilities explicitly marked unsafe achieved moving facilities built-in pseudo-library called system must imported used import thus makes visible facilities used unfortunately consequently implemented original language report implementation still remained unsafe facilities type cast syntax variant records inherited pascal could used without prior import difficulty moving facilities system pseudo-module lack identifier facility could imported since identifiers imported syntax iso modula-2 standard corrected type cast facility changing type cast syntax function called cast imported pseudo-module system however unsafe facilities variant records remained available without import pseudo-module system recent revision language applied original design philosophy rigorously first pseudo-module system renamed unsafe make unsafe nature facilities imported explicit remaining unsafe facilities either removed altogether example variant records moved pseudo-module unsafe facilities identifier could imported enabling identifiers introduced order enable facility corresponding enabling identifier must imported pseudo-module unsafe unsafe facilities remain language require import unsafe pascal number type safety requirements kept compilers pascal compiler dictates strict typing two variables assigned unless either compatible conversion integer real assigned identical subtype example following code fragment strict typing variable defined twotypes compatible dualtypes identical even though components user defined type identical assignment t1 d2 illegal assignment t1 t2 would legal subtypes defined identical however assignment t1.q d1.q would legal general common lisp type-safe language common lisp compiler responsible inserting dynamic checks operations whose type safety proven statically however programmer may indicate program compiled lower level dynamic type-checking program compiled mode considered type-safe following examples illustrates c++ cast operators break type safety used incorrectly first example shows basic data types incorrectly casted example codice_9 explicitly prevents compiler performing safe conversion integer floating-point value program runs output garbage floating-point value problem could avoided instead writing codice_10 next example shows object references incorrectly downcasted two child classes members different types downcasting parent class pointer child class pointer resulting pointer may point valid object correct type example leads garbage value printed problem could avoided replacing codice_11 codice_12 throws exception invalid casts
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Programming language topics
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signed encrypted email internet signed encrypted email internet seeoti initiative approach providing small medium enterprises ability communicate securely one another government defence ministries major aerospace defence contractors allowing play full part defence supply chain seeoti implements secure email specifications defined transglobal secure collaboration program tscp support interoperable signing encryption email messages federated environment addition security labelling email messages supported network border guard able check labels even though messages encrypted meets goal protecting intellectual property global business environment particular importance uk cyber security strategy intellectual property seen key growth economy deep-secure organised trial seeoti uk mod uk council electronic business integrated commercial shelf cots products titus boldon james deep-secure provide system email security functionality deep-secure selected overall winner ukceb excellence awards 2011 work seeoti february 2012 deep-secure partners adept4 intercede trustis providing seeoti solution service nexor provide compatible products
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Computer security
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goodsync goodsync backup file synchronization program used synchronizing files two directories either one computer computer another storage device e.g another computer removable disc flash drive smartphone computer remote computer server goodsync allows version files maintained multiple computing devices words two devices synchronized user sure current version file available devices regardless last modified several versions
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Computer security
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initiative open authentication initiative open authentication oath industry-wide collaboration develop open reference architecture using open standards promote adoption strong authentication close thirty coordinating contributing members proposing standards variety authentication technologies aim lowering costs simplifying use name oath acronym phrase open authentication pronounced english word oath oath related oauth open standard authorization
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Computer security
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open programming language open programming language opl embedded programming language portable devices run symbian operating system found nokia 9200 9300 9500 communicator series mobile telephone/personal digital assistant pda sony ericsson p800 p900 p910 series classic psion pdas series 3 5/5mx series 7 netbook/netpad well mc218 opl part standard application suite opl also included psion teklogix industrial handhelds workabout mx opl interpreted language similar basic fully visual basic-compatible language oval also developed language originally called organiser programming language developed psion ltd psion organiser designed colly myers first iteration implemented richard harrison martin stamp first implementation without graphics original psion organiser referred psion organiser 1984 came bundled science finance math data packs became truly accessible built-in software psion organiser ii 1986 language went used psion series 3 later psion retired portable digital assistant market project delayed 2003 fledgling symbian developer program released open source language developed sourceforge opl-dev project language available symbian os v8 later mainly due lack interest support major symbian licencees nokia sony ericsson hence opl likely never made available newer generation symbian os phones sony ericsson p990 m600 w950 p1i nokia e61i e90 2010 nokia device developers encouraged use python s60 instead see python s60 console version hello world program gui version nokia series 80 user interface opl structured programming language opl programs contain procedures much like functions programming languages example cruel interrogative program yes button assigned shortcut ctrl+y ctrl+n represented n respectively user input dialog tested statement printing appropriate responses screen note 'get keyword gets user input without using dialog box used simply wait keypress terminating program otherwise would end immediately without giving time user read text output dialog also stored variable variables specific procedure must declared local keyword global variables defined global keyword table uses example variable called 'var opl interfaced advanced psion series 3 features means operating system calls later psion series 5mx changed so-called 'opx library stored system rom z drive 'opx libraries also made available nokia 9210 nokia 9300 nokia 9500 communicators adding opxs routines handling sms managing bluetooth communication opl features include letter g beginning graphical functions letter 'm menus letter 'd dialogs
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Operating systems
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sequenced packet exchange sequenced packet exchange spx osi-model transport layer protocol ipx/spx protocol stack reliable connection-oriented protocol similar tcp protocol tcp/ip datagram rather stream protocol spx packet begins header following structure connection control fields contains 4 single-bit flags datastream type serves close spx connection purpose two values used
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Internet protocols
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martin odersky martin odersky born 5 september 1958 german computer scientist professor programming methods école polytechnique fédérale de lausanne epfl switzerland specializes code analysis programming languages designed scala programming language generic java pizza others implemented gj compiler implementation became basis javac java compiler 2007 inducted fellow association computing machinery 1989 received ph.d. eth zurich supervision niklaus wirth best known designer several programming languages including pascal postdoctoral work ibm yale university 12 may 2011 odersky collaborators launched typesafe inc. renamed lightbend inc. company provide commercial support training services scala currently serves chairman chief architect teaches two courses coursera online learning platform functional programming principles scala functional program design scala
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Programming language topics
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hacker video game hacker 1985 computer game activision designed steve cartwright released amiga amstrad cpc apple ii atari 8-bit family atari st commodore 64 macintosh ms-dos msx zx spectrum activision executive jim levy introduced hacker reporters pretending something gone wrong attempt connect line company headquarters demonstrate new game several attempts logged mysterious non-activision computer explaining ladies gentlemen game player assumes role hacker person experienced breaking secure computer systems accidentally acquires access non-public system game shipped information play thus building concept player hack system player must attempt hack magma ltd. computer system beginning game guessing logon password password becomes obvious gaining access another means entry later stage game typing help h initial command line gives clue since initial attempts consist guessing likely failing access eventually granted due supposed malfunction security system player player asked identify various parts robot unit pointing cursor relevant parts pressing joystick button parts exotic technical names asynchronous data compactor phlamson joint —this allows room error initially trying guess part name belongs failure identify part correctly forces player take retest 100 percent identification made point player allowed continue player gains control robot travel around globe via secret tunnels deep within earth game text states robot powered manner magma evident player logged magma company network acting remote user global subterranean transport network various strange messages broadcast hinting dangerous experiments company getting far player informed shredded portions secret document containing magma ltd. plans world domination stolen player instructed retrieve document bargaining spies stole located various locations throughout globe player warned must retrieved order prevent u.s. government thwarting plans point player objective clear retrieve strips stolen document deliver washington d.c robot tunnel system extensive unmarked getting around initially exercise trial error throughout globe several cities robot surface interact people primarily spies want bargain piece evidence various surfacing cities player must try convince agents turn piece evidence initially player 5,000 bargain arsenal items grows time bargaining real challenge game determining spy wants get eventually spies whims satisfied pieces secret document note different copies game even computer platform differences items spies want n't enough however magma ltd. discovers player break-in shortly penetration launches security satellite intersects player position demands information supposedly legitimate user would know information queried given player previously game questions answered player taken careful notes information asked rather obscure put pressure player satellites allow player pass checks 4 times another catch cause player get disconnected due suspicious activity addition player time limit tracked movements sru makes player take long system automatically disconnect anyway regardless satellites sensors network also start fail limiting player ability see turns tunnels ahead eventually sru located forcing player rely maps tunnel network make player goes near australia network automatic game issued however knowledge may help future play evading check since game lacks save game feature player fails must start beginning try solve game puzzles late 1987 50,000 copies hacker sold activision third best-selling commodore game info rated hacker four stars five describing interesting concept fair good graphics sound compute praised game initial realism concluded worthy addition software collection especially enjoy adventure games require bit thought investment time ahoy wrote puzzle nature certain enthrall repel others ... repeated play integral part reaching solution enjoy protracted battle wits find hacker lively test abilities game followed 1986 much difficult sequel player actually recruited based upon assumed success activities original game tasked controlling robot time infiltrate secure facility order retrieve documents known doomsday papers well-guarded vault ensure security united states
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Computer architecture
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aircrack-ng aircrack-ng network software suite consisting detector packet sniffer wep wpa/wpa2-psk cracker analysis tool 802.11 wireless lans works wireless network interface controller whose driver supports raw monitoring mode sniff 802.11a 802.11b 802.11g traffic program runs linux freebsd macos openbsd windows linux version packaged openwrt also ported android zaurus pda maemo platforms proof concept port made iphone april 2007 team darmstadt university technology germany developed new attack method based paper released rc4 cipher adi shamir new attack named 'ptw decreases number initialization vectors ivs needed decrypt wep key included aircrack-ng suite since 0.9 release aircrack-ng fork original aircrack project found preinstalled tool many linux distributions kali linux parrot share common attributes developed project debian aircrack-ng software suite includes
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Computer security
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open firmware open firmware openboot sun microsystems parlance standard defining interfaces computer firmware system formerly endorsed institute electrical electronics engineers ieee originated sun used sun apple ibm arm non-x86 pci chipset vendors open firmware allows system load platform-independent drivers directly pci card improving compatibility open firmware may accessed forth language shell interface achieves essentially functionality later efi standard initiated intel lower overhead open firmware described ieee standard ieee 1275-1994 reaffirmed open firmware working group ofwg since 1998 therefore officially withdrawn ieee several commercial implementations open firmware released open source community 2006 including sun openboot firmworks openfirmware codegen smartfirmware source code available openbios project sun implementation available bsd license open firmware forth code may compiled fcode bytecode independent computer architecture details instruction set memory hierarchy pci card may include program compiled fcode runs open firmware system way provide platform-independent boot-time diagnostics configuration code device drivers fcode also compact disk driver may require one two kilobytes therefore many i/o cards used sun systems macintoshes used open firmware fcode implements ans forth subset open firmware library open firmware furthermore defines standard way describe hardware system helps operating system better understand host computer relying less user configuration hardware polling example open firmware essential reliably identifying slave i²c devices like temperature sensors hardware monitoring whereas alternative solution performing blind probe i²c bus done software like lm_sensors generic hardware known result serious hardware issues certain circumstances based upon interactive programming language open firmware used efficiently test bring new hardware allows drivers written tested interactively operational video mouse drivers prerequisite graphical interface suitable end-user diagnostics apple shipped diagnostic operating system many power macintoshes sun also shipped fcode-based diagnostic tool suite called openboot diagnostics obdiag used customer service support hardware manufacturing teams sun sparc systems open firmware interface displayed console terminal bootstrapping system software keyboard connected main video display used console terminal open firmware re-entered time pressing keyboard keyboard connected first serial line system usually used console open firmware re-entered sending break serial line system software running various open firmware settings read written using codice_1 command powerpc-based macintosh open firmware interface accessed pressing keys startup using standard pc usb keyboard intel-based macintoshes use open firmware use extensible firmware interface following apple transition intel processors also early versions powerbook 3400 connect open firmware input output modem port default functionality generally used developers troubleshooting i.t personnel common users mac os x operating system provides high level graphical user interface change commonly used open firmware settings instance possible specify boot disk partition without directly using open firmware interface limitations e.g possible select boot usb mass-storage devices open firmware allows imac boot using codice_2 command open firmware settings changed using codice_3 command system software running pegasos interface accessed pressing startup ibm power systems open firmware ok prompt accessed sms boot menu sms boot menu accessed pressing boot sequence hardware checking os boot olpc xo-1 laptop open firmware access requires developer key obtained registration olpc installing key upon power-on boot countdown interrupted upper left key get forth prompt
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Operating systems
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shadow stack computer security shadow stack mechanism protecting procedure stored return address stack buffer overflow shadow stack second separate stack shadows program call stack function prologue function stores return address call stack shadow stack function epilogue function loads return address call stack shadow stack compares two records return address differ attack detected typical course action simply terminate program alert system administrators possible intrusion attempt shadow stack similar stack canaries mechanisms aim maintain control-flow integrity protected program detecting attacks tamper stored return address attacker exploitation attempt shadow stacks implemented recompiling programs modified prologues epilogues dynamic binary rewriting techniques achieve effect hardware support unlike call stack also stores local program variables passed arguments spilled registers data shadow stack typically stores second copy function return address shadow stacks provide protection return addresses stack canaries rely secrecy canary value vulnerable non-contiguous write attacks shadow stacks protected guard pages information hiding attacker would also need locate shadow stack overwrite return address stored like stack canaries shadow stacks protect stack data return addresses offer incomplete protection security vulnerabilities result memory safety errors 2016 intel announced upcoming hardware support shadow stacks control-flow enforcement technology shadow stacks face compatibility problems program throws exception longjmp occurs return address top shadow stack match return address popped call stack typical solution problem pop entries shadow stack matching return address found terminate program match found shadow stack multithreaded program would call stack executing thread would also shadow stack shadowing call stacks
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Computer security
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access control matrix computer science access control matrix access matrix abstract formal security model protection state computer systems characterizes rights subject respect every object system first introduced butler w. lampson 1971 access matrix envisioned rectangular array cells one row per subject one column per object entry cell – entry particular subject-object pair – indicates access mode subject permitted exercise object column equivalent access control list object row equivalent access profile subject according model protection state computer system abstracted set objects formula_1 set entities needs protected e.g processes files memory pages set subjects formula_2 consists active entities e.g users processes exists set rights formula_3 form formula_4 formula_5 formula_6 formula_7 right thereby specifies kind access subject allowed process object matrix example exists two processes file device first process ability execute second read file write information device second process read information first define granularity protection mechanisms access control matrix used model static access permissions type access control system model rules permissions change particular system therefore gives incomplete description system access control security policy access control matrix thought abstract model permissions given point time literal implementation two-dimensional array would excessive memory requirements capability-based security access control lists categories concrete access control mechanisms whose static permissions modeled using access control matrices although two mechanisms sometimes presented example butler lampson protection paper simply row-based column-based implementations access control matrix view criticized drawing misleading equivalence systems take account dynamic behaviour
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Computer security
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chameleon botnet chameleon botnet botnet discovered february 28 2013 security research firm spider.io involved infection 120,000 computers generated average 6 million us dollars per month advertising traffic traffic generated infected systems looked advertising parties regular end users browsed web seen legitimate web traffic affected computers windows pcs majority private pcs residential systems make actions software look like legitimate human behavior made mouse infected systems move around pages browsers rebooted system sessions crashed also sophisticated adobe flash javascript scripts executed infected systems least 202 websites targeted botnet 9 billion advertisements served side effect web traffic generated botnet infected systems likely suffered general operating lag slow network connectivity well symptoms indicators pc possibly infected malware removal software like clamwin exterminate infection could removed infected system also possible deactivate malware changing registry infected windows pc manually
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Computer security
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shadowserver shadowserver foundation nonprofit security organization gathers analyzes data malicious internet activity including malware botnets computer fraud sends daily network reports subscribers works law enforcement organizations around world cybercrime investigations established 2004 volunteer watchdog group liaises national governments csirts network providers academic institutions financial institutions fortune 500 companies end users improve internet security enhance product capability advance research dismantle criminal infrastructure shadowserver scans ipv4 internet 30 times per day harvests data malware spam bots botnets using large-scale sensor networks honeypots honeyclients placed throughout world uses sinkholes collect data bots ddos attacks also receives additional malware sinkhole data governments industry partners law enforcement agencies established reciprocal data-sharing agreements shadowserver shadowserver stores raw malware data permanently repository new data collected shadowserver analyzes using thousands virtual sandboxes hundreds iron sandboxes regularly re-analyzes raw data previously collected results analyses stored organization analysis cluster shadowserver sends daily custom reports users subscribed reports contain data shadowserver collected analyzed suspicious activity able detect within specific networks regions subscriber responsible example national government might receive data aggregated geo-spatial coordinates defined latitude longitude international network provider might receive data filtered asn shadowserver liaises security organizations national governments csirts dismantle global cybercrime networks example worked fbi europol interpol take avalanche network 2016 also helps law enforcement partners develop strategies cyber security threats mitigate threats emerge focusing cases involve criminal abuse internet ’ infrastructure
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Computer security
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virtual telecommunications access method virtual telecommunications access method vtam ibm subsystem implements systems network architecture sna mainframe environments vtam provides application programming interface api communication applications controls communication equipment adapters controllers modern terminology vtam provides communication stack device drivers vtam introduced 1974 series delays major component sna along 370x network control program ncp synchronous data link control sdlc ibm terminology vtam access method software allowing application programs read write data external devices called 'virtual introduced time ibm introducing virtual memory upgrading operating systems system/360 series virtual storage versions vtam supposed successor older telecommunications access methods basic telecommunications access method btam telecommunications access method tcam maintained compatibility reasons vtam comparable virtual storage access method vsam time new supposedly converged access method disk storage originally vtam provided free charge like systems software time however vtam 2 last version freely available acf/vtam advanced communication function/virtual telecommunications access method introduced 1976 provided licence fee major new feature acf/vtam multisystem networking facility introduced implementation intersystem communication among multiple s/370s. limited version acf/vtam known acf/vtame advanced communications function virtual telecommunications access method entry made available dos/vse systems running ibm 4300 vtam renamed sna services feature communications server os/390 software package also provides tcp/ip functions vtam supports several network protocols including sdlc token ring start-stop bisync local channel attached 3270 devices later tcp/ip vtam network communication took place integrated communication adapter mainframe separate programmable front-end processor ibm 3745/3746 communications processor operating system network control program ncp machines longer actively marketed ibm still supported ibm provides hardware maintenance microcode updates estimated 20,000 installed 3745/3746 controllers robust third party industry smaller 3745/3746 specialty companies provide controllers upgrades features related support services vtam sna still use many enterprises initially vtam allowed communication mainframes peripheral equipment terminals distributed processors minicomputers later 'cross-domain services introduced confused tcp/ip domains allowing sna networks one mainframe subsequent development sna network interconnect allowing networks different organizational entities firms interconnected high degree independence finally advanced peer peer networking functions appn added vtam appn mainframe longer heart network nodes network considered peers one reasons appn introduced act decnet-killer time appn actually shipped popularity decnet already declined appn considered overly complex 2012 largely superseded tcp/ip
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Operating systems
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gameframe gameframe hybrid computer system first used online video games industry amalgamation different technologies architectures supercomputers mainframes namely high computing power high throughput 2007 hoplon ibm jointly started gameframe project used ibm system z mainframe computer attached cell/b.e blades eight-core parallel-processing chips power sony playstation 3 host online game taikodom project carried co-operation ibm university california san diego 2009 although cell blades account required computing power high data throughput mainframe particular interest system z provides high level security massive workload handling assuring execution administrative tasks guaranteeing enduring connectivity huge number clients cell/b.e takes resource demanding calculations thus enabling system z fulfill job combination effective financially attractive game server system computation-intensive tasks offloaded expensive cpu cycles system z carried much economical cell blades without offloading server system required would end costing much would financially feasible unlike typical game clusters gameframe handle required transactions e.g keeping track user spaceships weapons virtual money even players simulation trajectory objects checking collisions unified consistent fashion thus host thousand users time slow experienced users added games numerous players like world warcraft tackled problem splitting work among multiple clusters creating duplicate worlds n't communicate cell-augmented mainframe runs hoplon virtual-world middleware called bitverse uses ibm websphere xd db2 software around gameframe ibm virtual universe community evolved
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Computer architecture
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colony video game colony action-adventure game released 1987 amstrad cpc atari 8-bit family commodore 64 msx zx spectrum mastertronic bulldog label owing overpopulation humanity found necessary grow food colonies planets unfortunately mushroom-growing planet player responsible also inhabited hostile native aliens resemble giant insects player must use droid control maintain harvest mushrooms well look protect colony gameplay takes place flip-screen environment consisting colony made-up storehouses specialist buildings mushroom fields areas solar panels surrounding desert alien planet filled various giant insects colony quite complicated game numerous things player must look-after purpose colony grow mushrooms shipment back earth mushrooms grow green i.e lush areas begin seeds quickly grow eventually reaching stage maturity point collected order deposited money later pick-up spacecraft unfortunately mushrooms one many things insects like eat player pick mature mushrooms partially eaten aliens deposited award payment unfit human consumption colony surrounded security fence keeps giant insects colony causing mischief therein unfortunately fence constantly attack insects chew way player droid must maintain fence destroying marauding insects replacing damaged destroyed pieces fence damaged fence sections deposited fence storehouse repair three different types security-fencing used barbed wire weakest wooden-fencing default fencing-type already use around colony game starts steel fencing strongest fencing type colony powered free-standing solar panels located within colony provide power order recharge droid shields weapons well landing beacon required spaceship land unfortunately insects chew pieces well devastate colony power supply checked fencing droid repair damaged panels correct storehouse well find replacements destroyed panels plenty mushrooms grown safely packed-away pick-up player send message earth spaceship sent en route colony pick player also order supplies extra seeds fencing panels useful items ship deliver game provides eta ship player must keep eye ship requires colony landing beacon arrives beacon ship land landing-bay player must screen time droid crushed drop crates supplies pay mushrooms money used next ordering supplies beacon ship dump supplies random surrounding desert many lost aliens beacon drains colony power-supply quickly important leave long necessary also ensure colony power-storage suitably high activating player droid also set traps almost anywhere colony desert order destroy giant insects traps work addition also permanent traps covering areas colony completely open desert e.g main entrance fencing traps always destroy insects wander without disappearing however reliant colony power supply player allows power drop low traps disappear
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Computer architecture
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network socket network socket internal endpoint sending receiving data within node computer network concretely representation endpoint networking software protocol stack entry table listing communication protocol destination status etc form system resource term socket analogous physical female connectors communication two nodes channel visualized cable two male connectors plugging sockets node similarly term port another term female connector used external endpoints node term socket also used internal endpoint local inter-process communication ipc network however analogy strained network communication need one-to-one dedicated communication channel process refer socket using socket descriptor type handle process first requests protocol stack create socket stack returns descriptor process identify socket process passes descriptor back protocol stack wishes send receive data using socket unlike ports sockets specific one node local resources referred directly nodes sockets necessarily associated persistent connection channel communication two nodes necessarily single endpoint example datagram socket used connectionless communication multicast socket used send multiple nodes however practice internet communication sockets generally used connect specific endpoint often persistent connection practice socket usually refers socket internet protocol ip network socket may called internet socket particular transmission control protocol tcp protocol one-to-one connections context sockets assumed associated specific socket address namely ip address port number local node corresponding socket address foreign node node associated socket used foreign process associating socket socket address called binding note local process communicate foreign process sending receiving data foreign socket address access foreign socket use foreign socket descriptor internal foreign node example connection 10.20.30.40:4444 50.60.70.80:8888 local ip address local port foreign ip address foreign port also associated socket end corresponding internal representation connection protocol stack node referred locally numerical socket descriptors say 317 one side 922 process node 10.20.30.40 request communicate node 50.60.70.80 port 8888 request protocol stack create socket communicate destination created socket received socket descriptor 317 communicate via socket using descriptor 317 protocol stack forward data node 50.60.70.80 port 8888 however process node 10.20.30.40 request communicate based foreign socket descriptor e.g socket 922 socket 922 node 50.60.70.80 internal foreign node usable protocol stack node 10.20.30.40 protocol stack today usually provided operating system rather separate library instance set services allow processes communicate network using protocols stack implements operating system forwards payload incoming ip packets corresponding application extracting socket address information ip transport protocol headers stripping headers application data application programming interface api programs use communicate protocol stack using network sockets called socket api development application programs utilize api called socket programming network programming internet socket apis usually based berkeley sockets standard berkeley sockets standard sockets form file descriptor due unix philosophy everything file analogies sockets files functions read write open close practice differences strain analogy different interfaces send receive used socket inter-process communication end generally socket standard internet protocols tcp udp socket address combination ip address port number much like one end telephone connection combination phone number particular extension sockets need source address example sending data program binds socket source address socket used receive data sent address based address internet sockets deliver incoming data packets appropriate application process socket often refers specifically internet socket tcp socket internet socket minimally characterized following distinctions socket internal representation socket descriptor abstract identifier socket address public address subtle always distinguished everyday usage specific definitions socket differ authors ietf request comments internet standards many textbooks well article term socket refers entity uniquely identified socket number textbooks term socket refers local socket address i.e combination ip address port number original definition socket given rfc 147 related arpa network 1971 socket specified 32 bit number even sockets identifying receiving sockets odd sockets identifying sending sockets today however socket communications bidirectional within operating system application created socket socket referred unique integer value called socket descriptor unix-like operating systems microsoft windows command-line tools netstat ss used list established sockets related information example modeled according berkeley socket interface sends string hello world via tcp port 80 host address 1.2.3.4 illustrates creation socket getsocket connecting remote host sending string finally closing socket several types internet socket available datagram socket type network socket provides connectionless point sending receiving data packets packet sent received datagram socket individually addressed routed order reliability guaranteed datagram sockets multiple packets sent one machine process another may arrive order might arrive sending udp broadcasts network always enabled datagram socket order receive broadcast packets datagram socket bound wildcard address broadcast packets may also received datagram socket bound specific address stream socket type network socket provides connection-oriented sequenced unique flow data without record boundaries well-defined mechanisms creating destroying connections detecting errors stream socket transmits data reliably order out-of-band capabilities internet stream sockets typically implemented top tcp applications run across networks using tcp/ip protocol sctp may also used stream sockets raw socket network socket allows direct sending receiving ip packets without protocol-specific transport layer formatting types sockets payload automatically encapsulated according chosen transport layer protocol e.g tcp udp socket user unaware existence protocol headers broadcast payload reading raw socket headers usually included transmitting packets raw socket automatic addition header optional raw sockets used security related applications like nmap one possible use case raw sockets implementation new transport-layer protocols user space raw sockets typically available network equipment used routing protocols internet group management protocol igmpv4 open shortest path first ospf internet control message protocol icmp used among things ping utility socket application programming interfaces apis example based berkeley sockets support raw sockets windows xp released 2001 raw socket support implemented winsock interface three years later microsoft limited winsock raw socket support security concerns socket types implemented transport protocols systems network architecture sna see also unix domain sockets uds internal inter-process communication computer processes provide application services referred servers create sockets start listening state sockets waiting initiatives client programs tcp server may serve several clients concurrently creating child process client establishing tcp connection child process client unique dedicated sockets created connection established state socket-to-socket virtual connection virtual circuit vc also known tcp session established remote socket providing duplex byte stream server may create several concurrently established tcp sockets local port number local ip address mapped server-child process serving client process treated different sockets operating system since remote socket address client ip address and/or port number different i.e since different socket pair tuples udp socket established state since udp connectionless therefore netstat show state udp socket udp server create new child processes every concurrently served client process handles incoming data packets remote clients sequentially socket implies udp sockets identified remote address local address although message associated remote address communicating local remote sockets called socket pairs socket pair described unique 4-tuple consisting source destination ip addresses port numbers i.e local remote socket addresses seen discussion tcp case unique socket pair 4-tuple assigned socket number udp case unique local socket address assigned socket number term socket dates rfc 147 1971 used arpanet today implementations sockets based berkeley sockets 1983 internet winsock 1991 api implementations exist streams-based transport layer interface tli 1983 berkeley sockets also known bsd socket api originated 4.2bsd unix operating system released 1983 api 1989 however could uc berkeley release versions operating system networking library free licensing constraints copyright-protected unix 1987 tli networking application programming interface provided unix system v release 3 svr3 continued release 4 svr4 early implementations written tops-20 mvs vm ibm-dos pcip socket primarily concept used transport layer internet model networking equipment routers switches require implementations transport layer operate link layer level switches internet layer routers however stateful network firewalls network address translators proxy servers keep track active socket pairs also fair queuing layer 3 switching quality service qos support routers packet flows may identified extracting information socket pairs raw sockets typically available network equipment used routing protocols igrp ospf internet control message protocol icmp
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Internet protocols
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telephony application programming interface telephony application programming interface tapi microsoft windows api provides computer telephony integration enables pcs running microsoft windows use telephone services different versions tapi available different versions windows tapi allows applications control telephony functions computer telephone network data fax voice calls includes basic functions dialing answering hanging call also supports supplementary functions hold transfer conference call park found pbx isdn telephone systems tapi used primarily control either modems recently control business telephone system pbx handsets controlling pbx handset driver provided manufacturer telephone system manufacturers provide drivers allow control multiple handsets traditionally called third-party control manufacturers provide drivers allow control single handset called first-party control third-party drivers designed allow applications see and/or control multiple extensions time telephone systems permit one third-party connection time first-party drivers designed allow applications monitor and/or control one extension time telephone systems naturally permit many connections simultaneously modem connections nature first-party tapi also used control voice-enabled telephony devices including voice modems dedicated hardware dialogic cards tapi introduced 1993 result joint development microsoft intel first publicly available version tapi version 1.3 released patch top microsoft windows 3.1 version 1.3 drivers 16-bit version 1.3 longer supported although msdn development library cds still contain files patches microsoft windows 95 tapi integrated operating system first version windows 95 tapi 1.4 tapi 1.4 support 32-bit applications tapi standard supports connections individual computers lan connections serving number computers tapi 2.0 introduced windows nt 4.0 version 2.0 first version windows nt platform made significant step forward supporting acd pbx-specific functionality 1997 microsoft released tapi version 2.1 version tapi available downloadable update first version supported microsoft windows 95 windows nt/2000 platforms tapi 3.0 released 1999 together windows 2000 version enables ip telephony voip providing simple generic methods making connections two using h.323 using ip multicast computers also offers ability access media stream msp driver involved connection windows xp included tapi 3.1 tapi 2.2 tapi 3.1 supports microsoft component object model provides set com objects application programmers version uses file terminals allow applications record streaming data file play recorded data back stream usb phone tsp telephony service provider also included allows application control usb phone use streaming endpoint tapi 3.0 tapi 3.1 available operating systems earlier windows 2000 windows xp respectively telephony server application programming interface tsapi similar standard developed novell netware servers tapi uses microsoft canonical address format telephone numbers make phone calls derivative e.123 international notation canonical address text string following format codice_1 area code subaddress name optional latter carry extension number direct inward dialing calling party name used isdn/e1/t1 telecommunication protocols dialing rules used transform canonical phone number dialable calling sequence modem depending user location dialing rules include variable-length dialing area code trunk access international access prefixes well central office access calling card/credit card numbers calling sequence contain dialable numbers digits codice_2 dtmf tones codice_3 formatting characters codice_4 control characters codice_5 correspond dial command hayes command set following control characters defined common misconception tapi 3.0 tapi 3.1 replaces tapi 2.x tapi 2.x earlier versions written c api uses pointers structures consequently tapi 2.x easy access c c++ applications awkward use many programming languages tapi 3.x designed component object model com interface done intent making accessible higher level applications developed vb environments provide easy access com n't deal c-style pointers tapi 3.x slightly different set functionality tapi 2.x addition integrated media control significant addition tapi 3.x n't include functionality tapi 2.x like support phone class one notable issue tapi 3.x lack support managed code .net environment documented microsoft kb article 841712 microsoft currently plans support tapi 3.x directly .net programming languages however mark smith provided managed c++ library called itapi3 2.x wrapper .net developers provide libraries work indirectly tapi enabled pbxs one often overlooked reason application developer might choose tapi 2.x tapi 3.x hardware vendors recommendation even though tapi provides abstract model phone lines telephony applications still heavily impacted specific behavior underlying hardware troubleshooting behavior issues usually requires software hardware vendors collaborate almost 1:1 relationship tapi service provider tsp interface tapi 2.x interface collaboration often easier application designed using tapi 2.x experience tapi 3.x varies significantly hardware vendors windows tapi support almost universal telephony hardware voice modems internal external computer expansion boards dialogic telephony cards notable exception never natively supported tapi avaya communication manager relied solely tsapi interface connectivity many pbx systems provide tapi-compliant modem interfaces tapi compatible pbx solutions include aastra 400/800 aastra mx-one alcatel oxo/oxe avaya bcm ip office cisco call manager ericsson-lg emg80 ipecs ipldk nec-philips is3000 ipc100/500 nec sl1000 sv8100/9100 nitsuko dxe600/328 panasonic kx-tda/tde/ncp kx-ns1000 samsung officeserv unify 3000/4000 openscape office shoretel wildix zyxel x6004/x2002 third party drivers often available telephone systems n't drivers made manufacturers
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Operating systems
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architecture interoperable information systems architecture interoperable information systems aios reference architecture development interoperable enterprise information systems enterprises public administrations want engage automated business processes organizations systems must able work together i.e need interoperable aios represents generic building plan organizations develop interoperable information systems systematically adjusting extending internal information systems aios described doctoral thesis based results various research projects interoperability independent specific products vendors describes generically different layers views relationships technical means needed efficiently establish interoperable information systems aim combines concepts service-oriented architecture collaborative business business process modelling seen complementary aris well-known architecture internal information systems business processes similar automation processes inside organizations automation cross-organizational business processes important trend endeavor collaborating organizations rather strive loose coupling information systems instead tight integration collaborating information systems able work together retain much independency possible characteristic also called interoperability context collaborating organizations business interoperability i.e capability autonomous organizations execute collaborative business process among information systems systems process information i.e capture transport transform store offer information following conception prevailing information systems research information system comprises hardware software enterprise also related human actors business functions processes well organization structures broad understanding example also embodied zachman framework architecture defined “ fundamental organization system embodied components relationships environment principles governing design evolution ” sinz defines information system architecture building plan information system sense specification documentation components relationships covering relevant viewpoints well constructions rules creation building plan accordingly architecture interoperable information systems defined building plan cross-organizational information system enables organizations execute collaborative business process among following work interoperable information systems conducted european research projects 2010 architecture interoperable information systems aios published reference construction loosely coupled interoperating information systems systematic model-based enactment collaborative business processes aios aims primarily large organizations want interoperate aim describes internal information system elements systematically connected information systems collaboration partners main elements aios one element comprised third category bii-repository organization publishes content business interoperability interface bii collaboration partners since comprises external views information system elements provides publishing discovery functionalities needed service-oriented architecture bii externally relevant processes services organization structures etc described various levels technical granularity enabling organizations search also business-level elements technical artifacts different traditional soa approach instead one central service directory various partner-specific repositories implemented static part architecture builds three orthogonal axes enterprise dimensions levels technical granularity colloborative views similar private public global views known business process workflow modeling aios corresponding private public global views information system elements provided describe business processes comprehensively axis provides distinct views processes functions data organizational elements thus combination axis collaborative views private public global views processes functions data organizational roles provided description system elements different levels technical granularity supports systematic development collaborative information systems starting business requirements definition going way code level apart construction aspect thereby also multi-dimensional interoperability description provided facilitating synchronization collaborating systems level similar example aris omg mda three levels used
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Computer architecture
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thread safety thread safety computer programming concept applicable multi-threaded code thread-safe code manipulates shared data structures manner ensures threads behave properly fulfill design specifications without unintended interaction various strategies making thread-safe data structures program may execute code several threads simultaneously shared address space threads access virtually memory every thread thread safety property allows code run multithreaded environments re-establishing correspondences actual flow control text program means synchronization software libraries provide certain thread-safety guarantees example concurrent reads might guaranteed thread-safe concurrent writes might whether program using library thread-safe depends whether uses library manner consistent guarantees different vendors use slightly different terminology thread-safety thread safety guarantees usually also include design steps prevent limit risk different forms deadlocks well optimizations maximize concurrent performance however deadlock-free guarantees always given since deadlocks caused callbacks violation architectural layering independent library discuss two approaches avoiding race conditions achieve thread safety first class approaches focuses avoiding shared state includes second class approaches synchronization-related used situations shared state avoided following piece java code method thread-safe class counter c programming language thread stack however static variable kept stack threads share simultaneous access multiple threads overlap running function possible static variable might changed one thread another midway checking difficult-to-diagnose logic error may compile run properly time called race condition one common way avoid use another shared variable lock mutex mutual exclusion following piece c code function thread-safe reentrant int increment_counter codice_1 called different threads without problem since mutex used synchronize access shared codice_2 variable function used reentrant interrupt handler second interrupt arises mutex locked second routine hang forever interrupt servicing disable interrupts whole system could suffer function implemented thread-safe reentrant using lock-free atomics c++11 int increment_counter
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Programming language topics
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celtix celtix java enterprise service bus esb runtime set apis make easy add transports message formats security features goal simplify construction integration flexible reuse technical business components using standards-based service-oriented architecture celtix code base merged codehaus xfire form apache cxf project
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Web technology
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pair gain telephony pair gain transmitting multiple pots signals twisted pairs traditionally used single traditional subscriber line telephone systems pair gain effect creating additional subscriber lines typically used expedient way solve subscriber line shortage problems using existing wiring instead installing new wires central office customer premises term invented middle 20th century analogy earlier use gain extend telephone local loops far telephone exchange pair gain system consists concentrators multiplexers combine separate signals single signal transmitted existing copper cable pair signals separated individual subscriber lines customer premises pair gain unit performs multiplexing simply provide second telephone connection single subscriber line called analog multi-line carrier aml circumstances customer wants add new phone line fax machine dial-up internet connection larger analog pair gain system made anaconda 1960s provided seven lines pair gain units expand number subscriber lines available single copper pair many sixty large pair gain units stored serving area interfaces metal cabinets typically resembling small apartment-sized refrigerators alongside near roadways overlie communications rights-of-way dacs digital access carrier system form pair gain used united kingdom uses form time division multiple access called isdn analog pair gain came disfavor 21st century detrimental high speed dial-up modem connections support 56k incompatible digital subscriber line dsl systems 20th century subscriber loop carrier systems similar problems recent digital pair gain systems however restore 56k dsl capabilities performing functions dslam pair gain device recently term pair gain used refer multiplex/demultiplex unit used central office end users equipment used copper twisted pair digital loop carrier called remote integrated multiplexer australia installed broadband internet subscribers may disappointed informed although initial line checks successful high speed connections adsl unavailable due infrastructure issues problem pair gain lines carry high speed data
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Internet protocols
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government communications headquarters government communications headquarters gchq intelligence security organisation responsible providing signals intelligence sigint information assurance government armed forces united kingdom based doughnut suburbs cheltenham gchq responsibility country secretary state foreign commonwealth affairs part foreign office director ranks permanent secretary gchq originally established first world war government code cypher school gc cs known name 1946 second world war located bletchley park responsible breaking german enigma codes two main components gchq composite signals organisation cso responsible gathering information national cyber security centre ncsc responsible securing uk communications joint technical language service jtls small department cross-government resource responsible mainly technical language support translation interpreting services across government departments co-located gchq administrative purposes 2013 gchq received considerable media attention former national security agency contractor edward snowden revealed agency process collecting online telephone data uk via tempora programme snowden revelations began spate ongoing disclosures global surveillance guardian newspaper forced destroy incriminating files given snowden threats lawsuits uk government gchq led director gchq jeremy fleming corporate board made executive non-executive directors reporting corporate board first world war british army royal navy separate signals intelligence agencies mi1b nid25 initially known room 40 respectively 1919 cabinet secret service committee chaired lord curzon recommended peacetime codebreaking agency created task given director naval intelligence hugh sinclair sinclair merged staff nid25 mi1b new organisation initially consisted around 25–30 officers similar number clerical staff titled government code cypher school cover-name chosen victor forbes foreign office alastair denniston member nid25 appointed operational head initially control admiralty located watergate house adelphi london public function advise security codes cyphers used government departments assist provision also secret directive study methods cypher communications used foreign powers gc cs officially formed 1 november 1919 produced first decrypt prior date 19 october second world war gc cs relatively small department 1922 main focus gc cs diplomatic traffic service traffic ever worth circulating initiative lord curzon transferred admiralty foreign office gc cs came supervision hugh sinclair 1923 chief sis director gc cs 1925 organisations co-located different floors broadway buildings opposite st. james park messages decrypted gc cs distributed blue-jacketed files became known bjs 1920s gc cs successfully reading soviet union diplomatic ciphers however may 1927 row clandestine soviet support general strike distribution subversive propaganda prime minister stanley baldwin made details decrypts public second world war gc cs based largely bletchley park present-day milton keynes working understanding german enigma machine lorenz ciphers 1940 gc cs working diplomatic codes ciphers 26 countries tackling 150 diplomatic cryptosystems senior staff included alastair denniston oliver strachey dilly knox john tiltman edward travis ernst fetterlein josh cooper donald michie alan turing gordon welchman joan clarke max newman william tutte i. j jack good peter calvocoressi hugh foss outstation far east far east combined bureau set hong kong 1935 moved singapore 1939 subsequently japanese advance malay peninsula army raf codebreakers went wireless experimental centre delhi india navy codebreakers fecb went colombo ceylon kilindini near mombasa kenya gc cs renamed government communications headquarters june 1946 gchq first based eastcote 1951 moved outskirts cheltenham setting two sites – oakley benhall duncan campbell mark hosenball revealed existence gchq 1976 article time result hosenball deported uk gchq low profile media 1983 trial geoffrey prime kgb mole within gchq created considerable media interest since days second world war us british intelligence shared information gchq means shares information gets information national security agency nsa united states 1984 gchq centre political row conservative government margaret thatcher prohibited employees belonging trade union claimed joining union would conflict national security number mass national one-day strikes held protest decision seen first step wider bans trade unions appeals british courts european commission human rights unsuccessful government offered sum money employee agreed give union membership appeal ilo resulted decision government actions violation freedom association protection right organise convention ban eventually lifted incoming labour government 1997 government communications group public commercial services union pcs formed represent interested employees grades 2000 group 14 former gchq employees dismissed refusing give union membership offered re-employment three accepted intelligence services act 1994 placed activities intelligence agencies legal footing first time defining purpose british parliament intelligence security committee given remit examine expenditure administration policy three intelligence agencies objectives gchq defined working interests national security particular reference defence foreign policies majesty government interests economic wellbeing united kingdom support prevention detection serious crime introduction intelligence agency act late 1993 former prime minister jim callaghan described gchq full blown bureaucracy adding future bodies created provide oversight intelligence agencies investigate whether functions gchq carries today still necessary 1993 wake squidgygate affair gchq denied intercepting recording disclosing telephone calls british royal family late 1993 civil servant michael quinlan advised deep review work gchq following conclusion review intelligence requirements resources imposed 3 cut agency chief secretary treasury jonathan aitken subsequently held face face discussions intelligence agency directors assess savings wake quinlan review aldrich 2010 suggests sir john adye director gchq performed badly meetings aitken leading aitken conclude gchq suffering out-of-date methods management out-of-date methods assessing priorities gchq budget £850 million 1993 £ compared £125 million security service sis mi5 mi6 december 1994 businessman roger hurn commissioned begin review gchq concluded march 1995 hurn report recommended cut £100 million gchq budget large reduction suffered british intelligence agency since end world war ii j division gchq collected sigint russia disappeared result cuts cuts mostly reversed 2000 wake threats violent non-state actors risks increased terrorism organised crime illegal access nuclear chemical biological weapons david omand became director gchq 1996 greatly restructured agency face new changing targets rapid technological change omand introduced concept sinews sigint new systems allowed flexible working methods avoiding overlaps work creating fourteen domains well-defined working scope tenure omand also saw planning creation doughnut gchq modern headquarters located 176-acre site benhall near cheltenham doughnut would largest building constructed secret intelligence operations outside united states operations gchq chum hom kwok listening station hong kong ended 1994 gchq hong kong operations extremely important relationship nsa contributed investment equipment station anticipation transfer hong kong chinese government 1997 hong kong stations operations moved geraldton australia operations used gchq intelligence-gathering capabilities 1990s included monitoring communications iraqi soldiers gulf war dissident republican terrorists real ira various factions involved yugoslav wars criminal kenneth noye mid 1990s gchq began assist investigation cybercrime end 2003 gchq moved new circular hq popularly known doughnut time second-largest public-sector building project europe estimated cost £337 million new building designed gensler constructed carillion became base gchq cheltenham operations public spotlight fell gchq late 2003 early 2004 following sacking katharine gun leaked observer confidential email agents united states national security agency addressed gchq agents wiretapping un delegates run-up 2003 iraq war gchq gains intelligence monitoring wide variety communications electronic signals number stations established uk overseas listening stations cheltenham bude scarborough ascension island united states menwith hill ayios nikolaos station cyprus run british army gchq march 2010 gchq criticised intelligence security committee problems security practices failing meet targets work targeted cyber attacks revealed edward snowden guardian gchq spied foreign politicians visiting 2009 g-20 london summit eavesdropping phonecalls emails monitoring computers cases even ongoing summit via keyloggers installed summit according edward snowden gchq two principal umbrella programs collecting communications gchq also access us internet monitoring programme prism since least june 2010 prism said give national security agency fbi easy access systems nine world top internet companies including google facebook microsoft apple yahoo skype february 2014 guardian based documents provided snowden revealed gchq indiscriminately collected 1.8 million private yahoo webcam images users across world month nbc intercept based documents released snowden revealed joint threat research intelligence group cne units within gchq mission cyber operations based dirty tricks shut enemy communications discredit plant misinformation enemies operations 5 gchq operations according conference slideshow presented gchq soon becoming director gchq 2014 robert hannigan wrote article financial times topic internet surveillance stating however much large us technology companies may dislike become command control networks choice terrorists criminals gchq sister agencies tackle challenges scale without greater support private sector arguing internet users would comfortable better sustainable relationship intelligence agencies tech companies since 2013 global surveillance disclosures large us technology companies improved security become less co-operative foreign intelligence agencies including uk generally requiring us court order disclosing data however head uk technology industry group techuk rejected claims stating understood issues disclosure obligations must based upon clear transparent legal framework effective oversight rather suggested deal industry government 2015 documents obtained intercept us national security agency whistleblower edward snowden revealed gchq carried mass-surveillance operation codenamed karma police since 2008 karma police operation swept ip address internet users visiting websites program established public scrutiny oversight karma police powerful spying tool conjunction gchq programs ip addresses could cross-referenced data goal program according documents either web browsing profile every visible user internet b user profile every visible website internet 2015 gchq admitted first time court conducts computer hacking 2017 us press secretary sean spicer alleged gchq conducted surveillance us president donald trump basing allegation statements made media commentator fox news segment us government formally apologised allegations promised would repeated however surveillance russian agents pick contacts made trump campaign team run election passed us agencies 31 october 2018 gchq joined instagram well mission gather intelligence gchq long-time corresponding mission assist protection british government communications government code cypher school gc cs created 1919 overt task providing security advice gc cs security section located mansfield college oxford second world war april 1946 gc cs became gchq gchq security section moved oxford join rest organisation eastcote later year 1952 1954 intelligence mission gchq relocated cheltenham security section remained eastcote march 1954 became separate independent organisation london communications security agency lcsa 1958 renamed london communications-electronic security agency lcesa april 1965 gpo mod units merged lcesa become communications-electronic security department cesd october 1969 cesd merged gchq becoming communications-electronic security group cesg 1977 cesg relocated eastcote cheltenham cesg continued uk national technical authority information assurance including cryptography cesg manufacture security equipment worked industry ensure availability suitable products services gchq funded research areas example centre quantum computing oxford university heilbronn institute university bristol 21st century cesg ran number assurance schemes check clas commercial product assurance cpa cesg assisted products service caps late 1969 concept public key encryption developed proven james h. ellis worked cesg cesd since 1965 ellis lacked necessary number theory expertise necessary build workable system subsequently feasible implementation scheme via asymmetric key algorithm invented another staff member clifford cocks mathematics graduate fact kept secret 1997 2016 national cyber security centre established gchq located london uk authority cyber security absorbed replaced cesg well activities previously existed outside gchq centre cyber assessment cca computer emergency response team uk cert uk cyber-related responsibilities centre protection national infrastructure cpni joint technical language service jtls established 1955 drawing members small ministry defence technical language team others initially provide standard english translations organisational expressions foreign language discover correct english equivalents technical terms foreign languages discover correct expansions abbreviations language remit jtls expanded ensuing years cover technical language support interpreting translation services across uk government local public sector services gloucestershire surrounding counties jtls also produces publishes foreign language working aids crown copyright conducts research machine translation on-line dictionaries glossaries jtls co-located gchq administrative purposes gchq operates partnership equivalent agencies worldwide number bi-lateral multi-lateral relationships principal united states national security agency canada communications security establishment australia australian signals directorate new zealand government communications security bureau mechanism uk-us security agreement broad intelligence-sharing agreement encompassing range intelligence collection methods relationships alleged include shared collection methods system described popular media echelon well analysed product gchq legal basis enshrined intelligence services act 1994 section 3 follows activities involve interception communications permitted regulation investigatory powers act 2000 kind interception carried warrant issued secretary state human rights act 1998 requires intelligence agencies including gchq respect citizens rights described european convention human rights prime minister nominates cross-party members parliament intelligence security committee remit committee includes oversight intelligence security activities reports made directly parliament functions increased justice security act 2013 provide access investigatory powers judicial oversight gchq conduct exercised investigatory powers tribunal uk also independent intelligence services commissioner interception communications commissioner former senior judges investigatory powers tribunal ruled december 2014 gchq breach european convention human rights activities compliant articles 8 right privacy 10 freedom expression european convention human rights however tribunal stated february 2015 one particular aspect data-sharing arrangement allowed uk intelligence services request data us surveillance programmes prism upstream contravention human rights law prior two paragraphs additional information providing details procedures safeguards disclosed public december 2014 furthermore ipt ruled legislative framework united kingdom permit mass surveillance gchq collects analyses data bulk practice mass surveillance complements independent reports interception communications commissioner special report made intelligence security committee parliament although several shortcomings potential improvements oversight legislative framework highlighted despite inherent secrecy around much gchq work investigations carried uk government snowden disclosures admitted various abuses security services report intelligence security committee isc 2015 revealed small number staff uk intelligence agencies found misuse surveillance powers one case leading dismissal member staff gchq although laws place time make abuses criminal offence later year ruling investigatory powers tribunal found gchq acted unlawfully conducting surveillance two human rights organisations closed hearing found government breach internal surveillance policies accessing retaining communications egyptian initiative personal rights legal resources centre south africa second time ipt history made positive determination favour applicants closed session another ipt case 2015 gchq conceded january 2010 regime interception/obtaining analysis use disclosure destruction legally privileged material accordance law purposes article 8 2 european convention human rights accordingly unlawful admission made connection case brought abdel hakim belhaj libyan opponent former gaddafi regime wife fatima bouchar couple accused british ministers officials participating unlawful abduction kidnapping removal libya march 2004 gaddafi still power 2015 complaint green party mp caroline lucas british intelligence services including gchq spying mps allegedly defiance laws prohibiting gchq introduced policy march 2015 require approval prime minister minister deliberately targeting communications parliamentarian then-home secretary theresa may told parliament 2014 investigatory powers tribunal investigated complaint ruled contrary allegation law gave communications parliament special protection wilson doctrine merely acts political convention controversial gchq case determined scope judicial review prerogative powers crown residual powers common law council civil service unions v minister civil service 1985 ac 374 often known simply gchq case case prerogative order council used prime minister minister civil service ban trade union activities civil servants working gchq order issued without consultation house lords decide whether reviewable judicial review held executive action immune judicial review simply uses powers derived common law rather statute thus prerogative reviewable following list heads operational heads gchq gc cs following stations former stations operated since cold war stations former stations gchq certified training gct scheme established certify two main levels cyber security training also degree masters level courses gct scheme designed help organisations find right training also met gchq exacting standards designed assure high quality cyber security training courses training provider also undergone rigorous quality checks gct process carried apmg independent certification body scheme part national cyber security programme established government develop knowledge skills capability aspects cyber security based iisp skills framework historical drama film imitation game 2014 featured benedict cumberbatch portraying alan turing efforts break enigma code employed government code cypher school gchq set number cryptic online challenges public used attract interest recruitment starting late 1999 response 2004 challenge described excellent challenge set 2015 600,000 attempts also published gchq puzzle book 2016 sold 300,000 copies proceeds going charity second book published october 2018 gchq units gchq specifics uk agencies elsewhere
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Computer security
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transport triggered architecture computer architecture transport triggered architecture tta kind processor design programs directly control internal transport buses processor computation happens side effect data transports writing data triggering port functional unit triggers functional unit start computation similar happens systolic array due modular structure tta ideal processor template application-specific instruction-set processors asip customized datapath without inflexibility design cost fixed function hardware accelerators typically transport triggered processor multiple transport buses multiple functional units connected buses provides opportunities instruction level parallelism parallelism statically defined programmer respect obviously due large instruction word width tta architecture resembles long instruction word vliw architecture tta instruction word composed multiple slots one slot per bus slot determines data transport takes place corresponding bus fine-grained control allows optimizations possible conventional processor example software transfer data directly functional units without using registers transport triggering exposes microarchitectural details normally hidden programmers greatly simplifies control logic processor many decisions normally done run time fixed compile time however also means binary compiled one tta processor run another one without recompilation even small difference architecture two binary incompatibility problem addition complexity implementing full context switch makes ttas suitable embedded systems general purpose computing one instruction set computer architectures tta architecture one processors based built one processors based sold commercially ttas seen exposed datapath vliw architectures vliw programmed using operations tta splits operation execution multiple move operations low level programming model enables several benefits comparison standard vliw example tta architecture provide parallelism simpler register files vliw programmer control timing operand result data transports complexity number input output ports register file rf need scaled according worst case issue/completion scenario multiple parallel instructions important unique software optimization enabled transport programming called software bypassing case software bypassing programmer bypasses register file write back moving data directly next functional unit operand ports optimization applied aggressively original move transports result register file eliminated completely thus reducing register file port pressure freeing general purpose register temporary variables reduced register pressure addition simplifying required complexity rf hardware lead significant cpu energy savings important benefit especially mobile embedded systems tta processors built independent function units register files connected transport buses sockets function unit implements one operations implement functionality ranging simple addition integers complex arbitrary user-defined application-specific computation operands operations transferred function unit ports function unit may independent pipeline case function unit fully pipelined new operation takes multiple clock cycles finish started every clock cycle hand pipeline always accept new operation start requests old one still executing data memory access communication outside processor handled using special function units function units implement memory accessing operations connect memory module often called load/store units control unit special case function units controls execution programs control unit access instruction memory order fetch instructions executed order allow executed programs transfer execution jump arbitrary position executed program control unit provides control flow operations control unit usually instruction pipeline consists stages fetching decoding executing program instructions register files contain general purpose registers used store variables programs like function units also register files input output ports number read write ports capability able read write multiple registers clock cycle vary register file interconnect architecture consists transport buses connected function unit ports means sockets due expense connectivity usual reduce number connections units function units register files tta said fully connected case path unit output port every unit input ports sockets provide means programming tta processors allowing select bus-to-port connections socket enabled time instant thus data transports taking place clock cycle programmed defining source destination socket/port connection enabled bus tta implementations support conditional execution conditional execution implemented aid guards data transport conditionalized guard connected register often 1-bit conditional register bus case value guarded register evaluates false zero data transport programmed bus guard connected squashed written destination unconditional data transports connected guard always executed processors including tta processors include control flow instructions alter program counter used implement subroutines if-then-else for-loop etc assembly language tta processors typically includes control flow instructions unconditional branches jump conditional relative branches bnz subroutine call call conditional return retnz etc look corresponding assembly language instructions processors like operations tta machine instructions implemented move instructions special function unit tta implementations support conditional execution sttack first move prototype implement control flow instructions conditional move program counter tta implementations support unconditional data transports maxq typically special function unit tightly connected program counter responds variety destination addresses address used destination move different effect program counter—each relative branch condition instruction different destination address condition destination addresses used call retnz etc traditional processor architectures processor usually programmed defining executed operations operands example addition instruction risc architecture could look like following example operation adds values general-purpose registers r1 r2 stores result register r3 coarsely execution instruction processor probably results translating instruction control signals control interconnection network connections function units interconnection network used transfer current values registers r1 r2 function unit capable executing add operation often called alu arithmetic-logic unit finally control signal selects triggers addition operation alu result transferred back register r3 tta programs define operations data transports needed write read operand values operation triggered writing data triggering operand operation thus operation executed side effect triggering data transport therefore executing addition operation tta requires three data transport definitions also called moves move defines endpoints data transport taking place transport bus instance move state data transport function unit f port 1 register file r register index 2 take place bus b1 case multiple buses target processor bus utilized parallel clock cycle thus possible exploit data transport level parallelism scheduling several data transports instruction addition operation executed tta processor follows second move write second operand function unit called alu triggers addition operation makes result addition available output port 'result execution latency 'add ports associated alu may act accumulator allowing creation macro instructions abstract away underlying tta leading philosophy ttas move complexity hardware software due several additional hazards introduced programmer one delay slots programmer visible operation latency function units timing completely responsibility programmer programmer schedule instructions result neither read early late hardware detection lock processor case result read early consider example architecture operation add latency 1 operation mul latency 3 triggering add operation possible read result next instruction next clock cycle case mul one wait two instructions result read result ready 3rd instruction triggering instruction reading result early results reading result previously triggered operation case operation triggered previously function unit read value undefined hand result must read early enough make sure next operation result overwrite yet unread result output port due abundance programmer-visible processor context practically includes addition register file contents also function unit pipeline register contents and/or function unit input output ports context saves required external interrupt support become complex expensive implement tta processor therefore interrupts usually supported tta processors task delegated external hardware e.g. i/o processor need avoided using alternative synchronization/communication mechanism polling
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Computer architecture
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heat lanrev heat lanrev formerly absolute manage systems lifecycle management software used system administrators automate administration tasks product includes server client agent software runs windows mac os x. vancouver-based absolute acquired lanrev pole position software december 2009 us 12.1 million cash 500,000 shares absolute common stock lanrev rebranded absolute manage february 2010 july 2015 absolute announced intention divest absolute manage sale absolute manage heat software completed october 5 2015 us 11.0 million product renamed heat lanrev 2010 robbins v. lower merion school district case plaintiffs charged two suburban philadelphia high schools secretly spied students surreptitiously remotely activating webcams embedded school-issued laptops students using home therefore infringed privacy rights schools admitted secretly snapping 66,000 webshots screenshots including webcam shots students bedrooms lanrev software used lower merion school district student laptop program overseen network technician michael perbix february 2010 perbix administrators district accused using software take undisclosed unauthorized photographs students webcams macintosh laptops lawsuit brought parents 15-year-old sophomore blake robbins allegedly accused illicit behavior seen computer webcam bedroom photographs taken laptop reported stolen allegedly used evidence disciplinary action fbi investigated incident philadelphia federal judge intervened sort issues relating lawsuit perbix previously praised theft track name feature lets administrators remotely photograph potential thieves computer reported stolen noting youtube video produced ’ excellent feature yes used yes gleaned results us fantastic feature trying to—especially ’ school environment lot laptops ’ worried know laptops getting missing ’ actually laptops thought stolen actually still classroom misplaced time found back turn tracking know good twenty snapshots teacher students using machines classroom lanrev new owner absolute software denounced use software illegal purpose emphasizing theft recovery left law enforcement professionals denied knowledge complicity either perbix school district actions absolute stated next update lanrev would permanently disable theft track
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Computer security
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database engine database engine storage engine underlying software component database management system dbms uses create read update delete crud data database database management systems include application programming interface api allows user interact underlying engine without going user interface dbms term database engine frequently used interchangeably database server database management system 'database instance refers processes memory structures running database engine many modern dbms support multiple storage engines within database example mysql supports innodb well myisam storage engines transactional additional engine types include database bits laid storage data structures groupings take advantage known effective algorithms retrieve manipulate properties typically storage designed meet requirements various areas extensively utilize storage including databases dbms operation always simultaneously utilizes several storage types e.g. memory external storage respective layout methods principle database storage viewed linear address space every bit data unique address address space practice small percentage addresses kept initial reference points also requires storage data accessed indirection using displacement calculations distance bits reference points data structures define access paths using pointers needed data effective manner optimized needed data access operations database operation resides simultaneously several types storage forming storage hierarchy nature contemporary computers database part inside computer hosts dbms resides partially replicated volatile storage data pieces database processed/manipulated reside inside processor possibly processor caches data read from/written memory typically computer bus far typically volatile storage components computer memory communicating data transferred to/from external storage typically standard storage interfaces networks e.g. fibre channel iscsi storage array common external storage unit typically storage hierarchy fast cache typically consisting volatile fast dram connected via standard interfaces drives possibly different speeds like flash drives magnetic disk drives non-volatile drives may connected magnetic tapes typically least active parts large database may reside database backup generations typically correlation exists currently storage speed price faster storage typically volatile data structure abstract construct embeds data well defined manner efficient data structure allows manipulation data efficient ways data manipulation may include data insertion deletion updating retrieval various modes certain data structure type may effective certain operations ineffective others data structure type selected upon dbms development best meet operations needed types data contains type data structure selected certain task typically also takes consideration type storage resides e.g. speed access minimal size storage chunk accessed etc. dbmss database administrators flexibility select among options data structures contain user data performance reasons sometimes data structures selectable parameters tune database performance databases may store data many data structure types common examples following contrast conventional row-orientation relational databases also column-oriented correlational way store data particular structure general substantial performance improvement gained different types database objects usually utilized together laid storage proximity clustered usually allows retrieve needed related objects storage minimum number input operations sometimes substantially time consuming even in-memory databases clustering provides performance advantage due common utilization large caches input-output operations memory similar resulting behavior example may beneficial cluster record item stock respective order records decision whether cluster certain objects depends objects utilization statistics object sizes caches sizes storage types etc indexing technique storage engines use improving database performance many types indexes share common property reduce need examine every entry running query large databases reduce query time/cost orders magnitude simplest form index sorted list values searched using binary search adjacent reference location entry analogous index back book data multiple indexes employee database could indexed last name hire date indexes affect performance results database designers add remove indexes without changing application logic reducing maintenance costs database grows database usage evolves indexes speed data access consume space database must updated time data altered indexes therefore speed data access slow data maintenance two properties determine whether given index worth cost
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Databases
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bitsight bitsight cybersecurity ratings company analyzes companies government agencies educational institutions based back bay boston security ratings delivered bitsight used banks insurance companies among organizations company rated 100,000 businesses respect cybersecurity bitsight founded 2011 currently united states-based international employees 2016 bitsight raised us 40 million funding month september 2014 bitsight acquired anubisnetworks portugal-based cybersecurity firm tracks real-time data threats september 2016 bitsight raised 40 million series c round led ggv capital participation flybridge capital partners globespan capital partners menlo ventures shaun mcconnon vc divisions comcast ventures liberty global ventures singtel innov8 shaun mcconnon stepped ceo bitsight july 2017 remains executive chairman board ceo position filled tom turner june 2018 bitsight closed 60 million series funding bringing company total funding 155 million bitsight series financing led warburg pincus participation existing investors menlo ventures ggv capital singtel innov8 2018 company located cambridge purchased property order shift back bay bitsight currently located forbes estimated bitsight revenue us 100 million 2018 organizations purchase bitsight services order understand security risks associated sharing sensitive data business partners 2018 bitsight serves clients including lowe aig safeway produced 100,000 ratings respect cybersecurity companies bitsight assembles models produce company ratings based scale enables insurers rule ability businesses receive coverage respect services amy feldman forbes writes customers pay subscription basis annual fees ranging thousand dollars analyze single company 1 million review thousands suppliers similar credit score bitsight ratings range 250 900 bitsight released report examining ransomware infection across six industry sectors compiled 18,996 companies security ratings included examination ransomware infection across sectors education energy/utilities finance government healthcare retail companies security rating services spaces include riskrecon securityscorecard upguard others
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Computer security
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joint cybernetic operations command italy joint cybernetic operations command cioc italian cyberwarfare military unit project italian cyber command modelled united states cyber command envisaged 2015 defence white paper joint cybernetic operations command established 30 september 2017 intended achieve initial operational capability end 2018 full operational capability 2019 joint cybernetic operations command tasks areas information security computer network operations cyber warfare cyber security designed force provider according cioc commander air brigade general francesco vestito command two operational focus cyber-defence cyber network-defence cyber defence related static defence protection network carried cooperation rest italian military order ensure integrity network availability data flows cyber network-defence related ability carry vulnerability assessment penetration test order provide quick intervention joint cybernetic operations command supports protects military operations conducts offensive operations functions coordinating body italian armed forces italian cyber security institutions according defence undersecretary gioacchino alfano command intended operate mainly joint inter-agency nato contexts well coordination university economic worlds regard domestic cyber security organization department information security leadership via deputy director responsible cyber security operational arms joint cybernetic operations command state police cnaipic centro anticrimine informatico per la protezione delle infrastrutture critiche critical facilities anti-informatic crime protection centre well national cert ministries linked national cert cyber infrastructures command directly dependent chief defence staff defence staff italian armed forces particular depends deputy commander operations joint cybernetic operations command consists command staff element personnel section operational unit training unit cyber branch tlc school chiavari experimental unit tasked study malaware countermeasures command recruit also personnel part military operational unit handles cyber operational cells actual operational pawns cells tasked operate field field commander may employ order achieve operational goals command located near military intelligence service centro intelligence interforze castel malnome near rome far leonardo da vinci–fiumicino airport
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Computer security
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tagsistant tagsistant semantic file system linux kernel written c based fuse unlike traditional file systems use hierarchies directories locate objects tagsistant introduces concept tags computing file system type data store could used store retrieve update files file uniquely located path user must know path advance access file path necessarily include information content file tagsistant uses complementary approach based tags user create set tags apply tags files directories objects devices pipes ... user search objects match subset tags called query kind approach well suited managing user contents like pictures audio recordings movies text documents incompatible system files like libraries commands configurations univocity path security requirement prevent access wrong content tagsistant file system features four main directories tags created sub directories codice_1 directory used queries complying syntax subquery arbitrarily long list tags concatenated directories portion path delimited codice_1 codice_5 actual query codice_6 operator joins results different sub-queries one single list codice_5 operator ends query returned result following query object must tagged codice_9 codice_10 codice_9 codice_12 object tagged codice_10 codice_12 codice_9 retrieved query syntax deliberately violates posix file system semantics allowing path token descendant like codice_16 codice_9 appears twice consequence recursive scan tagsistant file system exit error endlessly loop done unix codice_18 ~/tagsistant_mountpoint find tags/ tags/ tags/document tags/document/+ tags/document/+/document tags/document/+/document/+ tags/document/+/document/+/document tags/document/+/document/+/document/+ drawback balanced possibility list tags inside query order query codice_19 completely equivalent codice_20 codice_21 equivalent codice_22 codice_5 element precise purpose restoring posix semantics path codice_24 refers traditional directory recursive scan path properly perform tagsistant features simple reasoner expands results query including objects tagged related tags relation two tags established inside codice_25 directory following three level pattern codice_27 element includes is_equivalent include rock tag music tag unix command codice_28 used reasoner recursively resolve relations allowing creation complex structures web relations created inside codice_25 directory constitutes basic form ontology tagsistant features autotagging plugin stack gets called file symlink written plugin called declared mime type matches list working plugins released tagsistant 0.6 limited tagsistant file system corresponding repository containing codice_38 directory objects actually saved codice_39 file holding tagging information sqlite database mysql database engine specified codice_40 argument codice_39 file empty another file named codice_42 glib ini store repository configuration tagsistant 0.6 compatible mysql sqlite dialects sql tag reasoning tagging resolution porting logic sql dialects possible differences basic constructs especially intersect sql keyword must considered codice_38 directory introduced provide quick way access objects without using tags objects listed inode number prefixed codice_44 directory features read-only files containing usage statistics file codice_45 holds compile time information current repository configuration highlighted relying external database store tags tagging information could cause complete loss metadata database gets corrupted highlighted using flat namespace tends overcrowd codice_1 directory could mitigated introducing triple tags
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Computer file systems
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url template url template way specify url includes parameters must substituted url resolved standardized rfc 6570 march 2012 syntax usually enclose parameter braces example convention parameter percent encoded unless follows question mark building urls björk firstname =björk lastname =guðmundsdóttir would
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Web technology
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ssse3 supplemental streaming simd extensions 3 ssse3 sse3s simd instruction set created intel fourth iteration sse technology ssse3 first introduced intel processors based core microarchitecture june 26 2006 woodcrest xeons ssse3 referred codenames tejas new instructions tni merom new instructions mni first processor designs intended support ssse3 contains 16 new discrete instructions instruction act 64-bit mmx 128-bit xmm registers therefore intel materials refer 32 new instructions according intel ssse3 provide 32 instructions represented 14 mnemonics accelerate computations packed integers include table satsw x read 'saturate signed word takes signed integer x converts −32768 less −32768 +32767 greater 32767 leaves unchanged otherwise normal intel architecture bytes 8 bits words 16 bits dwords 32 bits 'register refers mmx xmm vector register nawaf 9
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Computer architecture
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sap hana sap hana in-memory column-oriented relational database management system developed marketed sap se primary function database server store retrieve data requested applications addition performs advanced analytics predictive analytics spatial data processing text analytics text search streaming analytics graph data processing includes extract transform load etl capabilities well application server early development sap hana number technologies developed acquired sap se included trex search engine in-memory column-oriented search engine p*time in-memory online transaction processing oltp platform acquired sap 2005 maxdb in-memory livecache engine first major demonstration platform 2008 teams sap se hasso plattner institute stanford university demonstrated application architecture real-time analytics aggregation former sap se executive vishal sikka mentioned architecture hasso new architecture name hana stabilized people referred product new database software previously called sap high-performance analytic appliance first product shipped late november 2010 mid-2011 technology attracted interest experienced business customers considered early days hana support sap netweaver business warehouse announced september 2011 availability november 2012 sap promoted aspects cloud computing october 2012 sap announced platform service offering called sap hana cloud platform variant called sap hana one used smaller amount memory may 2013 managed private cloud offering called hana enterprise cloud service announced may 2013 business suite hana became available enabling customers run sap enterprise resource planning functions hana platform s/4hana released 2015 written specifically hana platform combines functionality erp crm srm others single hana system s/4hana intended simplified business suite replacing earlier generation erp systems likely sap focus innovations s/4hana customers using non-hana systems raised concerns locked sap products since s/4hana requires sap hana system run customers running sap business suite applications hardware certified sap would need migrate sap-certified hana database choose features offered s/4hana rather versioning software utilizes service packs referred support package stacks sps updates support package stacks released every 6 months november 2016 sap announced sap hana 2 offers enhancements multiple areas database management application management includes two new cloud services text analysis earth observation analysis hana customers upgrade hana 2 sps10 customers running sps9 must first upgrade sps12 upgrading hana 2 sps01 key distinctions hana previous generation sap systems column-oriented in-memory database combines olap oltp operations single system thus general sap hana oltap system storing data main memory rather disk provides faster data access extension faster querying processing storing data in-memory confers performance advantages costly form data storage observing data access patterns 85 data enterprise system may infrequently accessed therefore cost-effective store frequently accessed hot data in-memory less frequently accessed warm data stored disk approach sap termed dynamic tiering column-oriented systems store data single column location rather storing data single row location row-oriented systems enable performance improvements olap queries large datasets allows greater vertical compression similar types data single column read times column-stored data fast enough consolidated views data performed fly removing need maintaining aggregate views associated data redundancy although row-oriented systems traditionally favored oltp in-memory storage opens techniques develop hybrid systems suitable olap oltp capabilities removing need maintain separate systems oltp olap operations sap hana information modeling also known sap hana data modeling part hana application development modeling methodology expose operational data end user reusable virtual objects named calculation views used modelling process sap hana manages concurrency use multiversion concurrency control mvcc gives every transaction snapshot database point time mvcc database needs update item data overwrite old data new data instead mark old data obsolete add newer version scale-out environment hana keep volumes petabyte data in-memory returning query results second however ram still much expensive disk-space scale-out feasible certain time critical use-cases sap hana includes number analytic engines various kinds data processing business function library includes number algorithms made available address common business data processing algorithms asset depreciation rolling forecast moving average predictive analytics library includes native algorithms calculating common statistical measures areas clustering classification time series analysis hana incorporates open source statistical programming language r supported language within stored procedures column-store database offers graph database capabilities graph engine processes cypher query language also visual graph manipulation via tool called graph viewer graph data structures stored directly relational tables hana column store pre-built algorithms graph engine include pattern matching neighborhood search single shortest path strongly connected components typical usage situations graph engine include examples like supply chain traceability fraud detection logistics route planning hana also includes spatial database engine implements spatial data types sql extensions crud operations spatial data hana certified open geospatial consortium integrates esri arcgis geographic information system addition numerical statistical algorithms hana perform text analytics enterprise text search hana search capability based “ fuzzy ” fault-tolerant search much like modern web-based search engines results include statistical measure relevant search results search criteria include threshold accuracy results analyses available include identifying entities people dates places organizations requests problems entity extraction catered specific use cases voice customer customer preferences expectations enterprise i.e mergers acquisitions products organizations public sector public persons events organizations custom extraction dictionaries also implemented besides database data analytics capabilities sap hana web-based application server hosting user-facing applications tightly integrated database analytics engines hana xs advanced engine xsa natively works node.js javaee languages runtimes xsa based cloud foundry architecture thus supports notion “ bring language ” allowing developers develop deploy applications written languages runtimes xsa implements natively well deploying applications microservices xsa also allows server-side javascript xsjs supporting application server suite application lifecycle management tools allowing development deployment monitoring user-facing applications hana deployed on-premises cloud number cloud service providers hana deployed on-premises new appliance certified hardware vendor alternatively existing hardware components storage network used part implementation approach sap calls tailored data center integration tdi hana certified run multiple operating systems including suse linux enterprise server red hat enterprise linux supported hardware platforms on-premise deployment include intel 64 power systems system designed support horizontal vertical scaling multiple cloud providers offer sap hana infrastructure service basis including sap also offer cloud services form sap hana licensing primarily divided two categories runtime license used run sap applications sap business warehouse powered sap hana sap s/4hana full use license used run sap non-sap applications licensing used create custom applications part full use license features grouped editions targeting various use cases addition capabilities streaming etl licensed additional options march 9 2017 sap hana available express edition streamlined version run laptops resource-limited environments license sap hana express edition free charge even productive use 32 gb ram additional capacity increases purchased
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Databases
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download valley download valley cluster software companies israel producing delivering adware installed alongside downloads software primary purpose monetize shareware downloads software items commonly browser toolbars adware browser hijackers spyware malware another group products download managers possibly designed induce trick user install adware downloading piece desired software mobile app certain source term refer actual geographical region valley pun based silicon valley common practice using downloads deliver bundled software users many companies located tel aviv surrounding region used israeli media well reports related business download managers download valley companies used major download portals software hosts including download.com cnet softonic.com sourceforge smaller adware companies sweetpacks smilebox purchased larger company perion networks 41 million 32 million ibario claimed worth 100 million early 2014 conduit valued 1.4 billion jp morgan 2012 revenues frequently near 100 million several 100 million large companies perion 87 million 2013 conduit claimed 500 million 2012 much lower operating net income perion 3.88 million operating 310.000 net income 2013 numbers highly volatile since technical legal preconditions quickly change profit opportunities 2013 2014 changes web browsers prevent unwanted toolbar installs new policy microsoft towards advertising lead expectation main profit methods companies would soon work longer perion stock lost roughly two thirds value 2014 13.25 january 4.53 december 29 many products may designed way install solicited user downloads desired product create revenue software usually distributed free may use invasive harmful techniques achieve installs installers may installed adware frequently attempts hide identity prevent disabling removal restoring previous settings spy user system browsing habits download install unwanted software open backdoors possibly malicious attacks many security software vendors list products category potentially unwanted programs pup also pus pua grayware offer detection removal category distinct genuine malware used software companies opposed criminal underground programmers threaten practice litigation 2013 download valley company ibario accused security software vendor trend micro distributing sefnit/mevade malware installer related ukrainian company considered immediately responsible malware unnamed download valley executive admitted wall street journal companies employ teams 15 developers break security suites try block software
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Computer security
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clx common lisp clx standard x window system client library common lisp equivalent xlib library c programming language clx written solely common lisp use xlib clx contains data types functions macros interact x server sending requests receiving events replies
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Programming language topics
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mobilenotifier mobilenotifier free open-source alert messaging system written peter hajas jailbroken ios devices including iphone ipod touch ipad ios 4.0 mobile notifier written reproduction android notifications currently released bsd license lead developer peter hajas left work apple project continued developers software hooks operating system replace built-in modal notification user interface maintains queue unread messages user late may 2011 mobilenotifier 230,000 downloads mobilenotifier developed conjunction rensselaer center open source software rensselaer polytechnic institute mobilenotifier beta released 29 may 2011 included following new features solved following issues released 4 may 2011 included following new features solved following issues released 27 february 2011 included following new features solved following issues released 18 february 2011 included following new features solved following issues mobilenotifier beta1 officially released solved following issues
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Computer security
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alcor alcor early computer language definition created alcor group consortium universities research institutions manufacturers europe united states founded 1959 60 members 1966 group aim common compiler specification subset algol 60 algol meeting copenhagen 1958 alcor acronym algol converter addition naming alcor astronomical reference algol named addition programming application star algol way alcor also named astronomical reference star alcor europe high level machine architecture algol 60 devised emulated various real computers among siemens 2002 ibm 7090 algol manual published provided detailed introduction features language many program snippets four appendixes
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Programming language topics
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general packet radio service general packet radio service gprs packet oriented mobile data standard 2g 3g cellular communication network global system mobile communications gsm gprs established european telecommunications standards institute etsi response earlier cdpd i-mode packet-switched cellular technologies maintained 3rd generation partnership project 3gpp gprs typically sold according total volume data transferred billing cycle contrast circuit switched data usually billed per minute connection time sometimes one-third minute increments usage gprs bundled data cap may charged per mb data speed limited disallowed gprs best-effort service implying variable throughput latency depend number users sharing service concurrently opposed circuit switching certain quality service qos guaranteed connection 2g systems gprs provides data rates 56–114 kbit/sec 2g cellular technology combined gprs sometimes described 2.5g technology second 2g third 3g generations mobile telephony provides moderate-speed data transfer using unused time division multiple access tdma channels example gsm system gprs integrated gsm release 97 newer releases gprs core network allows 2g 3g wcdma mobile networks transmit ip packets external networks internet gprs system integrated part gsm network switching subsystem gprs extends gsm packet circuit switched data capabilities makes following services possible sms gprs used sms transmission speed 30 sms messages per minute may achieved much faster using ordinary sms gsm whose sms transmission speed 6 10 sms messages per minute gprs supports following protocols tcp/ip used phone one ip addresses allocated gprs store forward ip packets phone even handover tcp restores packets lost e.g due radio noise induced pause devices supporting gprs grouped three classes class device must service gprs gsm networks together effectively needs two radios avoid hardware requirement gprs mobile device may implement dual transfer mode dtm feature dtm-capable mobile handle gsm packets gprs packets network coordination ensure types transmitted time devices considered pseudo-class sometimes referred simple class networks supported dtm since 2007 usb 3g/gprs modems terminal-like interface usb v.42bis rfc 1144 data formats models include external antenna connector modem cards laptop pcs external usb modems available similar shape size computer mouse pendrive gprs connection established reference access point name apn apn defines services wireless application protocol wap access short message service sms multimedia messaging service mms internet communication services email world wide web access order set gprs connection wireless modem user must specify apn optionally user name password rarely ip address provided network operator gsm module gprs modules similar modems ’ one difference modem external piece equipment whereas gsm module gprs module integrated within electrical electronic equipment embedded piece hardware gsm mobile hand complete embedded system comes embedded processors dedicated provide functional interface user mobile network upload download speeds achieved gprs depend number factors multiple access methods used gsm gprs based frequency division duplex fdd tdma session user assigned one pair up-link down-link frequency channels combined time domain statistical multiplexing makes possible several users share frequency channel packets constant length corresponding gsm time slot down-link uses first-come first-served packet scheduling up-link uses scheme similar reservation aloha r-aloha means slotted aloha s-aloha used reservation inquiries contention phase actual data transferred using dynamic tdma first-come first-served channel encoding process gprs consists two steps first cyclic code used add parity bits also referred block check sequence followed coding possibly punctured convolutional code coding schemes cs-1 cs-4 specify number parity bits generated cyclic code puncturing rate convolutional code coding schemes cs-1 cs-3 convolutional code rate 1/2 i.e input bit converted two coded bits coding schemes cs-2 cs-3 output convolutional code punctured achieve desired code rate coding scheme cs-4 convolutional coding applied following table summarises options least robust fastest coding scheme cs-4 available near base transceiver station bts robust coding scheme cs-1 used mobile station ms away bts using cs-4 possible achieve user speed 20.0 kbit/s per time slot however using scheme cell coverage 25 normal cs-1 achieve user speed 8.0 kbit/s per time slot 98 normal coverage newer network equipment adapt transfer speed automatically depending mobile location addition gprs two gsm technologies deliver data services circuit-switched data csd high-speed circuit-switched data hscsd contrast shared nature gprs instead establish dedicated circuit usually billed per minute applications video calling may prefer hscsd especially continuous flow data endpoints following table summarises possible configurations gprs circuit switched data services multislot class determines speed data transfer available uplink downlink directions value 1 45 network uses allocate radio channels uplink downlink direction multislot class values greater 31 referred high multislot classes multislot allocation represented example 5+2 first number number downlink timeslots second number uplink timeslots allocated use mobile station commonly used value class 10 many gprs/egprs mobiles uses maximum 4 timeslots downlink direction 2 timeslots uplink direction however simultaneously maximum number 5 simultaneous timeslots used uplink downlink network automatically configure either 3+2 4+1 operation depending nature data transfer high end mobiles usually also supporting umts also support gprs/edge multislot class 32 according 3gpp ts 45.002 release 12 table b.1 mobile stations class support 5 timeslots downlink 3 timeslots uplink maximum number 6 simultaneously used timeslots data traffic concentrated downlink direction network configure connection 5+1 operation data transferred uplink network time change constellation 4+2 3+3 best reception conditions i.e best edge modulation coding scheme used 5 timeslots carry bandwidth 5*59.2 kbit/s 296 kbit/s uplink direction 3 timeslots carry bandwidth 3*59.2 kbit/s 177.6 kbit/s multislot class identifies following different multislot class specification detailed annex b 3gpp technical specification 45.002 multiplexing multiple access radio path maximum speed gprs connection offered 2003 similar modem connection analog wire telephone network 32–40 kbit/s depending phone used latency high round-trip time rtt typically 600–700 ms often reaches 1s gprs typically prioritized lower speech thus quality connection varies greatly devices latency/rtt improvements via example extended ul tbf mode feature generally available also network upgrades features available certain operators enhancements active round-trip time reduced resulting significant increase application-level throughput speeds gprs opened 2000 packet-switched data service embedded channel-switched cellular radio network gsm gprs extends reach fixed internet connecting mobile terminals worldwide cellpac protocol developed 1991-1993 trigger point starting 1993 specification standard gprs etsi smg especially cellpac voice data functions introduced 1993 etsi workshop contribution anticipate later known roots gprs workshop contribution referenced 22 gprs related us-patents successor systems gsm/gprs like w-cdma umts lte rely key gprs functions mobile internet access introduced cellpac according study history gprs development bernhard walke student peter decker inventors gprs – first system providing worldwide mobile internet access
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Internet protocols
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imprivata imprivata security company based lexington massachusetts founded 2002 imprivata develops sells onesign platform securing employee access desktops networks applications using single sign-on 2017 imprivata 1,700 clients several offices across america europe australia imprivata customers primarily healthcare industries imprivata became public company june 25 2014 listed new york stock exchange acquired private equity investment firm thoma bravo llc 2016 imprivata founded phil scarfo david ting developed identity management technology working polaroid corporation ’ small business incubator company shipped first product onesign enterprise single sign-on appliance 2004 2005 imprivata expanded europe africa middle east 2006 imprivata founder david ting selected infoworld one top 25 chief technology officers year 2009 imprivata acquired assets identiphi manufacturer reseller biometric technology including safsolution product line 2011 acquired assets validus medical systems santa cruz california incorporated imprivata cortext technology july 2016 imprivata announced agreed acquired thoma bravo private equity firm based san francisco 19.25 per share estimated total 544 million omar hussain chief executive time imprivata onesign helps companies manage user access authentication product reviews suggest onesign allows companies enable enterprise applications single sign without requiring custom scripting modifications existing directories onesign also strengthen user authentication desktops networks replacing passwords range authentication options include finger biometrics proximity cards smart cards many national government id cards one-time-password tokens employee ’ physical location product reviews also comment onesign ability simplify compliance reporting consolidating employee strong authentication application access events single database
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Computer security
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linux router project linux router project lrp defunct networking-centric micro linux distribution released versions lrp small enough fit single 1.44mb floppy disk made building maintaining routers access servers thin servers thin clients network appliances typically embedded systems next trivial lrp conceived primarily developed dave cinege 1997 2002 began originally 'router floppy evolved streamlined general purpose network operating system lrp oldest embedded linux distribution formed whole part basis many embedded system distributions commercial products followed several parts developed specifically enhanced lrp still found common usage today posixness busybox dave cinege worked version 4.0 rewrite lrp late 2000 january 2001 began testing ideas proof concept code claimed radical departure status quo surprise new direction seemed ideal prompting abandon work done lrp 4.0 begin scratch new os named lrp 5.0 lrp 5.0 development headed towards complete rewrite reimplementation linux userland new standard design outside posix specification stated purpose provide modern standard base operating system suitable application including embedded systems appliances servers desktop computers cinege however stopped work several months later due financial reasons refused release work even name os due animosity towards computer industry perceived plundering open source authors work large corporations may 6 2003 cinege updated lrp website reflect project abandoned
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Operating systems
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qed manifesto qed manifesto proposal computer-based database mathematical knowledge strictly formalized proofs checked automatically q.e.d means latin meaning demonstrated idea project arose 1993 mainly impetus robert boyer goals project tentatively named qed project project qed outlined qed manifesto document first published 1994 input several researchers explicit authorship deliberately avoided dedicated mailing list created two scientific conferences qed took place first one 1994 argonne national laboratories second 1995 warsaw organized mizar group project seems died 1996 never produced discussions plans 2007 paper freek wiedijk identifies two reasons failure project order importance nonetheless qed-style projects regularly proposed mizar library successfully formalized large portion undergraduate mathematics largest library another project metamath proof database 2014 twenty years qed manifesto workshop organized part vienna summer logic
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Programming language topics
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retain retain mainframe based database system accessed via ibm 3270 terminals likely emulators used internally within ibm providing service support ibm field personnel customers acronym retain stands remote technical assistance information network historically two different similar systems called retain first dating mid-1960s system provided technical information people ibm field engineering division form short bulletins tips organized according machine type number software according software component id number information accessible using simple query commands ibm service branch office terminals terminals supported early retain system typewriter-type terminals ibm 2740 terminals also used access ibm field instruction system fis provided education form programmed instruction courseware retain system built software framework fis fact early support retain actually written language course system primarily used provide field support system/360 family mainframe systems although used also disseminate technical information older systems 1970 concurrent announcement system/370 next generation mainframes system/360 new system announced called retain/370 system designed use special technical support centers located regional centers rather branch office new system designed support display terminals rather old typewriter-based ones special version 2915 display originally designed airline reservations systems sabre used 2915 small keyboard-display driven large electronic controller data interchange unit ibm 2948 2948 supported 31 display terminals located within hundred feet cost display system large controller prevented 2915 terminals utilized branch offices thus use regional support centers system older retain system continued used several years afterwards running parallel retain/370 still providing direct support branch-office terminals sometimes called retain/360 system although designation never formalized time retain/370 became available via 3270 terminals branch offices old retain system phased retain/370 renamed simply retain retain/370 ran special applications designed technical support center use powerful feature full-text search engine enabling text documents system retrieved using boolean search requests similar concept full-text search engines use today internet google altavista although limited searching individual words combinations words without reference word-adjacency retain/370 first ibm system deployed large scale capability search engine component retain called iris interpretive retrieval information system confused non-ibm software systems name ... ibm never sold search engine product trademark issue mid-1970s retain expanded permit multiple copies database hosted geographically distributed systems retain custom-built data bank manager served foundation retain applications iris search engine modified support mirroring file updates take place automatically across network manner nearly invisible application programs providing high level data integrity change retain hosts created two us locations two europe two south america two japan applications developed ibm programmers raleigh nc moved boulder colorado 1976 work done north harbour uk registered users system numbered thousands 60 countries time system/370 announced along corresponding retain/370 system ibm announced new family computers would equipped permit remote diagnosis hardware problems system/370 installation model 145 telecommunications adapter included capable used remote support hardware diagnostic programs written allow control via remote connection applications retain system could controlled ibm specialists located ibm support center chicago managed paul rushton also including original plant manufacture cpu form support dubbed data link hardware connection made communications device called ibm 2955 adapter stripped-down variant 2701 communications controller could connect 600 bit/s retain system run diagnostics mainly run mostly diagnostics could run locally ibm ce time specialized applications developed programs analyze logouts generated hardware malfunctions i.e machine check interruptions time concept remote support extended software well 1973 1974 special application mvs system could connected via retain ibm support center memory dumps system data could examined remotely application also permitted download software fixes ibm program temporary fixes although 2955 supported 6-bit character code similar 2740 terminal binary transfer memory dump software updates accomplished protocol similar base-64 encoding scheme used today internet email attachments years several projects aimed supplant retain functionality shown lasting presence despite
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Databases
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dbase dbase also stylized dbase one first database management systems microcomputers successful day dbase system includes core database engine query system forms engine programming language ties components together dbase underlying file format file widely used applications needing simple format store structured data dbase originally published ashton-tate microcomputer operating system cp/m 1980 later ported apple ii ibm pc computers running dos pc platform particular dbase became one best-selling software titles number years major upgrade released dbase iii ported wider variety platforms adding unix vms mid-1980s ashton-tate one big three software publishers early business software market others lotus development wordperfect starting mid-1980s several companies produced variations dbase product especially dbase programming language included foxbase+ later renamed foxpro clipper so-called xbase products many technically stronger dbase could push aside market changed disastrous introduction dbase iv whose design stability poor many users switched products time growing use ibm-invented sql structured query language database products another factor user adoption microsoft windows desktop computers shift toward sql windows put pressure makers xbase products invest major redesign provide new capabilities early 1990s xbase products constituted leading database platform implementing business applications size impact xbase market go unnoticed within one year three top xbase firms acquired larger software companies following decade original xbase products faded prominence several disappeared products known dbase still exist owned dbase llc late 1960s fred thompson jet propulsion laboratory jpl using tymshare product named retrieve manage database electronic calculators time expensive products 1971 thompson collaborated jack hatfield programmer jpl write enhanced version retrieve became jpldis project jpldis written fortran univac 1108 mainframe presented publicly 1973 hatfield left jpl 1974 jeb long took role working jpl contractor c. wayne ratliff entered office football pool interest game felt could win pool processing post-game statistics found newspapers order turned attention database system chance came across documentation jpldis used basis port ptdos kit-built imsai 8080 microcomputer called resulting system vulcan mr. spock star trek george tate hal lashlee built two successful start-up companies discount software one first sell pc software programs mail consumers software distributors one first wholesale distributors pc software world entered agreement ratliff market vulcan formed ashton-tate name ashton chosen purely marketing reasons ratliff ported vulcan ptdos cp/m hal pawluk handled marketing nascent company decided change name business-like dbase pawluk devised use lower case all-caps base create distinctive name pawluk suggested calling new product version two ii suggest less buggy initial release dbase ii result became standard cp/m application along wordstar supercalc 1981 ibm commissioned port dbase then-in-development pc resultant program one initial pieces software available ibm pc went sale fall 1981. dbase one professional programs platform time became huge success customer base included end-users increasing number value added resellers vars purchased dbase wrote applications sold completed systems customers may 1983 release dbase ii runtime entrenched dbase var market allowing vars deploy products using lower-cost runtime system although critics stated dbase difficult learn success created many opportunities third parties 1984 1,000 companies offered dbase-related application development libraries code add functionality applications using dbase ii runtime consulting training how-to books company san diego today known advisor media premiered magazine devoted professional use dbase data based advisor circulation exceeded 35,000 eight months activities fueled rapid rise dbase leading product type adam b green helped popularize dbase ii via legal difficulties ashton-tate publisher dbase ii software platforms operating systems proliferated early 1980s company found difficult port assembly language-based dbase target systems led re-write platform c programming language using automated code conversion tools resulting code worked essentially undocumented inhuman syntax problem would prove serious future resulting dbase iii released may 1984 although reviewers widely panned lowered performance product otherwise well reviewed rapid upgrades system stabilized best-seller throughout 1980s formed famous application trio pc compatibles dbase lotus 123 wordperfect fall 1984 company 500 employees taking 40 million year sales vast majority dbase products introduced 1988 delays dbase iv 300 new improved features foxpro made inroads even dbase iv support query example sql enough five years later top 3 implementations dbase language bought microsoft borland computer associates version called dbase plus 8 released used build ... web ... server-based applications along way borland bought ashton tate brought revised dbase iv 1992 focus described designed programmers rather ordinary users handling data dbase provided detailed procedural commands functions dbase application development language integrated navigational database management system ashton-tate labeled relational meet criteria defined dr. edgar f. codd relational model used runtime interpreter architecture allowed user execute commands typing command line dot prompt similarly program scripts text files prg extensions ran interpreter command dbase programs easy write test business person programming experience could develop applications time ashton-tate competitors introduced so-called clone products compilers robust programming features user-defined functions udfs arrays complex data handling ashton-tate competitors also began incorporate sql ansi/iso standard language creating modifying retrieving data stored relational database management systems eventually became clear dbase world expanded far beyond ashton-tate third-party community formed consisting fox software nantucket alpha software data based advisor magazine sbt application development firms major developer groups paperback software launched flexible fast vp-info unique built-in compiler community dbase variants sought create dbase language standard supported ieee committee x3j19 initiative ieee 1192 said xbase distinguish ashton-tate product a-t saw rise xbase illegal threat proprietary technology 1988 filed suit fox software santa cruz operation sco copying dbase structure sequence foxbase+ sco marketed xenix unix versions fox products december 1990 u.s. district judge terry hatter jr. dismissed ashton-tate lawsuit invalidated ashton-tate copyrights disclosing dbase based part public domain jpldis october 1991 case still appeal borland international acquired ashton-tate one merger provisions u.s. justice department required borland end lawsuit fox allow companies use dbase/xbase language without threat legal action end 1992 major software companies raised stakes acquiring leading xbase products borland acquired ashton-tate dbase products later wordtech xbase products microsoft acquired fox software foxbase+ foxpro products computer associates acquired nantucket clipper products advisor media built data based advisor magazine launching foxpro advisor clipper advisor developer magazines journals live conferences developers however planned dbase advisor magazine aborted due market failure dbase iv year 2000 xbase market faded developers shifted new database systems programming languages computer associates later known ca eventually dropped clipper borland restructured sold dbase major acquirers microsoft stuck xbase longest evolving foxpro visual foxpro product longer offered 2006 advisor media stopped last-surviving xbase magazine foxpro advisor era xbase dominance ended still xbase products dbase product line owned dbase llc currently sells dbase™ plus 12.3 dos-based dbase classic™ dbdos™ run 64-bit windows open source implementations available harbour xharbour also clip 2015 new member xbase family born xsharp x language open source project compiler ide well microsoft visual studio integration xsharp produces .net assemblies uses familiar xbase language xsharp product created group four enthusiasts worked vulcan.net project past compiler created top roslyn compiler code code behind c vb compilers microsoft today implementations dbase language expanded include many features targeted business applications including object-oriented programming manipulation remote distributed data via sql internet functionality interaction modern devices following example opens employee table empl gives every manager supervises 1 employees 10-percent raise prints names salaries note one keep mentioning table name assumed current table stays told otherwise origins interpreted interactive language dbase used variety contextual techniques reduce amount typing needed facilitated incremental interactive development also made larger-scale modular programming difficult tenet modular programming correct execution program module must affected external factors state memory variables tables manipulated program modules dbase designed mind developers careful porting borrowing programming code assumed certain context would make writing larger-scale modular code difficult work-area-specific references still possible using arrow notation b- customer multiple tables could manipulated time addition developer foresight name tables appropriately could clearly refer large number tables open time notation employee- salary vacation- start_date alternatively alias command could appended initial opening table statement made referencing table field unambiguous simple example one open table assign alias fashion use emp alias employee henceforth refer table variables employee- name another notable feature re-use clauses different commands example clause limits scope given command somewhat comparable sql clause different commands list delete replace browse etc could accept clause limit filter scope activity simplifies learning language dbase also one first business-oriented languages implement string evaluation tells interpreter evaluate string stored mymacro programming code example feature made dbase programming flexible dynamic sometimes called meta ability profession could allow programming expressions placed inside tables somewhat reminiscent formulas spreadsheet software however could also problematic pre-compiling making programming code secure hacking dbase tended used custom internal applications small medium companies lack protection copying compared compiled software often less issue addition dot-prompt dbase iii iii+ dbase iv came packaged assist application manipulate data queries well appsgen application allowed user generate applications without resorting code writing like 4gl dbase iv appsgen tool based largely portions early cp/m product named personal pearl although language fallen favor primary business language find dbase excellent interactive ad-hoc data manipulation tool whereas sql retrieves data sets relational database rdbms dbase one easily manipulate format analyze perform calculations individual records strings numbers step-by-step imperative procedural way instead trying figure use sql declarative operations granularity operations generally smaller sql making easier split querying table processing easy-to-understand easy-to-test parts example one could insert browse operation filtering aggregation step study intermediate table view applied filter aggregation step applied application development platform dbase fills gap lower-level languages c c++ java high-level proprietary 4gls fourth generation languages purely visual tools providing relative ease-of-use business people less formal programming skill high productivity professional developers willing trade low-level control dbase remained popular teaching tool even sales slowed text-oriented commands easier present printed training material mouse-oriented competitors mouse-oriented commands added product time command language remained popular de facto standard mousing commands tended vendor-specific major legacy dbase file format adopted number applications example shapefile format developed esri spatial data pc arcinfo geographic information system uses .dbf files store feature attribute data microsoft recommends saving microsoft works database file dbase file format read microsoft excel package available emacs read xbase files libreoffice openoffice calc read write generic dbf files dbase database system one first provide header section describing structure data file meant program longer required advance knowledge data structure rather could ask data file structured several variations .dbf file structure dbase-related products .dbf file structures compatible vp-info unique read variants dbf file structure second filetype file format memo fields character fields limited 254 characters memo field 10-byte pointer file include much larger text field dbase limited ability process memo fields xbase languages clipper treated memo fields strings like character fields purposes except permanent storage dbase uses files single indexes multiple-index files holding 1 48 indexes xbase languages vp-info include compatibility files others use different file formats used clipper used foxpro flagship later iterations clipper included drivers indexes jerry pournelle july 1980 called vulcan infuriatingly excellent software powerful documentation poor praised speed sophisticated queries said lot pounding table screaming rage documentation movie office space character peter gibbons programmer played ron livingston working make company systems y2k compliant bookshelf book understanding dbase iii plus alan simpson clearly seen
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Databases
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diskimagemounter diskimagemounter utility handles mounting disk volume images mac os x starting version 10.3 diskimagemounter works either launching daemon handle disk image contacting running dæmon mount disk like bomarchivehelper diskimagemounter gui double-clicked nothing gui program ever displays window progress bar mount options cancel skip verification error report could mount image found /system/library/coreservices/diskimagemounter.app starting version 10.7 apple removed double-click support images using legacy metadata diskimagemounter able open .img ndif .smi self mounting .dc42 disk copy 4.2 .dart dart disk image formats previously supported version 10.6 earlier diskimagemounter supports variety disk image file types
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Operating systems
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linux virtual server linux virtual server lvs load balancing software linux kernel–based operating systems lvs free open-source project started wensong zhang may 1998 subject requirements gnu general public license gpl version 2 mission project build high-performance highly available server linux using clustering technology provides good scalability reliability serviceability major work lvs project develop advanced ip load balancing software ipvs application-level load balancing software ktcpvs cluster management components lvs used building highly scalable highly available network services web email media voip services integrating scalable network services large-scale reliable e-commerce e-government applications lvs-based solutions already deployed many real applications throughout world including wikipedia lvs components depend upon linux netfilter framework source code available codice_1 subdirectory within linux kernel source lvs able handle udp tcp layer-4 protocols well ftp passive connection inspecting layer-7 packets provides hierarchy counters codice_2 directory userland utility program used configure lvs called ipvsadm requires superuser privileges run lvs implements several balancing schedulers listed relevant source files commonly used terms include following setting virtual http server two real servers ipvsadm -a -t 192.168.0.1:80 -s rr ipvsadm -a -t 192.168.0.1:80 -r 172.16.0.1:80 -m ipvsadm -a -t 192.168.0.1:80 -r 172.16.0.2:80 -m first command assigns tcp port 80 ip address 192.168.0.1 virtual server chosen scheduling algorithm load balancing round-robin codice_13 second third commands adding ip addresses real servers lvs setup forwarded network packets shall masked codice_14 querying status configured lvs setup ip virtual server version 1.0.8 size=65536 prot localaddress port scheduler flags tcp 192.168.0.1:80 rr
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Computer architecture
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digital watermarking digital watermark kind marker covertly embedded noise-tolerant signal audio video image data typically used identify ownership copyright signal watermarking process hiding digital information carrier signal hidden information need contain relation carrier signal digital watermarks may used verify authenticity integrity carrier signal show identity owners prominently used tracing copyright infringements banknote authentication like traditional physical watermarks digital watermarks often perceptible certain conditions i.e using algorithm digital watermark distorts carrier signal way becomes easily perceivable may considered less effective depending purpose traditional watermarks may applied visible media like images video whereas digital watermarking signal may audio pictures video texts 3d models signal may carry several different watermarks time unlike metadata added carrier signal digital watermark change size carrier signal needed properties digital watermark depend use case applied marking media files copyright information digital watermark rather robust modifications applied carrier signal instead integrity ensured fragile watermark would applied steganography digital watermarking employ steganographic techniques embed data covertly noisy signals steganography aims imperceptibility human senses digital watermarking tries control robustness top priority since digital copy data original digital watermarking passive protection tool marks data degrade control access data one application digital watermarking source tracking watermark embedded digital signal point distribution copy work found later watermark may retrieved copy source distribution known technique reportedly used detect source illegally copied movies term digital watermark coined andrew tirkel charles osborne december 1992 first successful embedding extraction steganographic spread spectrum watermark demonstrated 1993 andrew tirkel charles osborne gerard rankin watermarks identification marks produced paper making process first watermarks appeared italy 13th century use rapidly spread across europe used means identify paper maker trade guild manufactured paper marks often created wire sewn onto paper mold watermarks continue used today manufacturer marks prevent forgery digital watermarking may used wide range applications information embedded signal called digital watermark although contexts phrase digital watermark means difference watermarked signal cover signal signal watermark embedded called host signal watermarking system usually divided three distinct steps embedding attack detection embedding algorithm accepts host data embedded produces watermarked signal watermarked digital signal transmitted stored usually transmitted another person person makes modification called attack modification may malicious term attack arises copyright protection application third parties may attempt remove digital watermark modification many possible modifications example lossy compression data resolution diminished cropping image video intentionally adding noise detection often called extraction algorithm applied attacked signal attempt extract watermark signal unmodified transmission watermark still present may extracted robust digital watermarking applications extraction algorithm able produce watermark correctly even modifications strong fragile digital watermarking extraction algorithm fail change made signal digital watermark called robust respect transformations embedded information may detected reliably marked signal even degraded number transformations typical image degradations jpeg compression rotation cropping additive noise quantization video content temporal modifications mpeg compression often added list digital watermark called imperceptible watermarked content perceptually equivalent original unwatermarked content general easy create either robust watermarks—or—imperceptible watermarks creation robust—and—imperceptible watermarks proven quite challenging robust imperceptible watermarks proposed tool protection digital content example embedded no-copy-allowed flag professional video content digital watermarking techniques may classified several ways digital watermark called fragile fails detectable slightest modification fragile watermarks commonly used tamper detection integrity proof modifications original work clearly noticeable commonly referred watermarks generalized barcodes digital watermark called semi-fragile resists benign transformations fails detection malignant transformations semi-fragile watermarks commonly used detect malignant transformations digital watermark called robust resists designated class transformations robust watermarks may used copy protection applications carry copy access control information digital watermark called imperceptible original cover signal marked signal perceptually indistinguishable digital watermark called perceptible presence marked signal noticeable e.g digital on-screen graphics like network logo content bug codes opaque images videos images made transparent/translucent convenience consumers due fact block portion view therefore degrading confused perceptual watermarking uses limitations human perception imperceptible length embedded message determines two different main classes digital watermarking schemes digital watermarking method referred spread-spectrum marked signal obtained additive modification spread-spectrum watermarks known modestly robust also low information capacity due host interference digital watermarking method said quantization type marked signal obtained quantization quantization watermarks suffer low robustness high information capacity due rejection host interference digital watermarking method referred amplitude modulation marked signal embedded additive modification similar spread spectrum method particularly embedded spatial domain evaluation digital watermarking schemes may provide detailed information watermark designer end-users therefore different evaluation strategies exist often used watermark designer evaluation single properties show example improvement mostly end-users interested detailed information want know given digital watermarking algorithm may used application scenario parameter sets seems best epson kodak produced cameras security features epson photopc 3000z kodak dc-290 cameras added irremovable features pictures distorted original image making unacceptable applications forensic evidence court according blythe fridrich n either camera provide undisputable proof image origin author secure digital camera sdc proposed saraju mohanty et al 2003 published january 2004 first time proposed blythe fridrich also worked sdc 2004 digital camera would use lossless watermarking embed biometric identifier together cryptographic hash reversible data hiding technique enables images authenticated restored original form removing digital watermark replacing image data overwritten would make images acceptable legal purposes us army also interested technique authentication reconnaissance images digital watermarking relational databases emerged candidate solution provide copyright protection tamper detection traitor tracing maintaining integrity relational data many watermarking techniques proposed literature address purposes survey current state-of-the-art classification different techniques according intent way express watermark cover type granularity level verifiability published 2010 halder et al journal universal computer science..
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Computer security
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douglas parkhill douglas f. parkhill canadian technologist former research minister best known pioneering work called cloud computing work canada telidon videotex project started working canadian ministry communications part department trade industry 1969 previously worked mitre corporation responsible many activities communications satellites computer communications command control systems telecommunications winner treasury board canada secretariat outstanding achievement award 1982 conestoga shield services government industry computer communications research development touche ross award telidon development author several publications including 1966 book challenge computer utility book parkhill thoroughly explored many modern-day characteristics cloud computing elastic provisioning utility service well comparison electricity industry use public private government community forms book mckinsey foundation award distinguished contributions management literature worked dave godfrey canadian writer novelist later book gutenberg two social political meaning computer technology charge research federal department communications time department funding development telidon videotext system heavily involved promoting system overall control program radio broadcast 1980 outlined potential system financial information theatre reservations ability pay print tickets system later documented history telidon project history videotex general
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Distributed computing architecture
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john wainwright computer scientist john wainwright computer scientist born australia pioneered development pure object-based computer languages principal architect two computer languages scriptx 1992–1996 maxscript 1996 1992 wainwright sold apple computer structural framework object based language virtual machine operating system called objects c. became lead architect scriptx language media player developed kaleida labs kaleida labs closed doors 1996 wainwright went serve principal architect maxscript scripting language autodesk 3ds max language used game development part maxis sims animation processing pipeline compared scriptx maxscript explicit syntax support 3d animation wainwright chief technology officer crowd science online advertising technology company co-founded 2007 nephew john martin paul neto crowd science funded granite ventures wainwright also first non-employee amazon.com customer ordering book fluid concepts creative analogies amazon building named
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Programming language topics
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snarfing snarf term used computer programmers meaning grab large document file content data use without author owner permission unix community term means acquisition file set files across network also refers using command line tools transfer files http gopher finger ftp protocols without user interaction method achieving cache coherence multiprocessing computer architecture observation writes cached data example snarf evil twin attack using simple shell script running software like airsnarf create wireless hotspot complete captive portal wireless clients associate snarf access point receive ip dns gateway appear completely normal users dns queries resolve attacker ip number regardless dns settings website attempt visit bring snarf splash page requesting username password username password entered unsuspecting users mailed root localhost reason works
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Computer security
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appirio appirio wipro company information technology consulting company headquartered indianapolis indiana united states offers technology professional services companies wishing adopt public cloud applications includes software-as-a-service platform-as-a-service technologies like salesforce.com google apps appirio founded chris barbin former borland software cio narinder singh glenn weinstein mike ’ brien 2006 2007 appirio established headquarters salesforce.com ’ startup incubator san mateo california 2012 appirio moved headquarters san francisco california august 2015 appirio announced indianapolis office would named company headquarters early 2008 appirio secured series investment 1.1 million salesforce.com angel investors firm next secured 5.6 million series b funding sequoia capital july 2008 series c round came february 2009 10 million funding sequoia capital ggv capital series funding round 60 million followed march 2012 led private equity firm general atlantic october 2009 appirio chief architect jason ouellette released book titled development force.com platform building business applications cloud released addison-wesley professional april 2010 appirio named ondemand company year alwayson selected best place work bay area san francisco business times listed gartner cloud computing/saas integration july 2010 appirio featured new polymath profiles compound-technology innovations technology novel written vinnie mirchandani march 2011 appirio acquired infowelders salesforce consultancy based louisville ky december 2011 appirio acquired saaspoint provider cloud consulting services europe november 2012 went acquire knowledge infusion human resources talent management advisory consulting services firm september 2013 appirio acquired topcoder community 500,000 developers engineers designers find collaborate software development assignments ranging applications websites back-end corporate systems cloudspokes appirio competing platform 75,000 users merged topcoder january 2014 appirio currently headquartered indianapolis satellite offices san francisco california minato tokyo japan london uk dublin ireland sydney australia espoo finland stockholm sweden porto portugal pune bangalore greater noida hyderabad jaipur india appirio runs serverless company utilizing public cloud solutions in-house datacenter 20 october 2016 appirio announced acquired wipro indian information technology services corporation based bangalore india 500 million appirio ranks among firms like acumen solutions bluewolf acquired ibm cloud sherpas acquired accenture market cloud computing solutions increasingly appirio found primary competitor global system integrators accenture deloitte
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Distributed computing architecture
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single-chip cloud computer single-chip cloud computer scc computer processor cpu created intel corporation 2009 48 distinct physical cores communicate architecture similar cloud computer data center cores part processor carry instructions code allow computer run scc product project started intel research multi-core processors parallel processing multiple calculations additionally intel wanted experiment incorporating designs architecture huge cloud computer data centers cloud computing single processing chip took aspect cloud computing many remote servers communicate applied microprocessor new concept intel wanted experiment name single-chip cloud computer originated concept scc currently still used research purposes currently run simple linux operating system chip boot windows applications scc web servers data informatics bioinformatics financial analytics intel developed new chip architecture based huge cloud data centers cores separated across chip able directly communicate chip contains 48 p54c pentium cores connected 4×6 2d-mesh mesh group 24 tiles set four rows six columns tile contained two cores 16 kb 8 per core message passing buffer mpb shared two cores essentially router router allows core communicate previously cores send information back main memory would re-routed cores scc contains 1.3 billion 45 nanometers nm long transistors amplify signals act switch turn core pairs transistors use anywhere 25 125 watts power depending processing demand comparison intel i7 processor uses 156 watts power four ddr3 memory controllers chip connected 2d-mesh well controllers capable addressing 64 gb random-access memory ddr3 memory used help tile communicate others without chip would functional controllers also work transistors control certain tiles turned save power use proper coding implemented pieces put together get functional processor fast powerful energy efficient framework resembling network cloud computers scc comes rcce simple message passing interface provided intel supports basic message buffering operations scc two modes operate processor mode mesh mode processor mode cores executing code system memory programmed i/o inputs outputs system connected system board fpga loading memory configuring processor bootstrapping sustaining initial load currently done software running scc management console embedded chip cores turned routers transistors ram controllers sending receiving large packets data additionally memory map intel plans share technology companies hp yahoo microsoft multiple companies researching scc efficiently quickly advance technology hope make scc scalable 100+ cores one way hope achieve chip able communicate another chip could put two chips together get double cores hope improve parallel programming productivity power management take advantage chip architecture large number cores additionally plan experiment architecture similar chip architectures develop many-core scalable processors maximizes processing power cores power efficient
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Distributed computing architecture
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dropbox service dropbox file hosting service operated american company dropbox inc. headquartered san francisco california offers cloud storage file synchronization personal cloud client software dropbox founded 2007 mit students drew houston arash ferdowsi startup company initial funding seed accelerator combinator dropbox praised receiving crunchie award 2010 best internet application macworld 2009 editor choice award software ranked one valuable startups us world valuation us 10 billion described one combinator successful investments date however dropbox also experienced criticism generated controversy issues including security breaches privacy concerns dropbox blocked china since 2014 five star privacy rating electronic frontier foundation dropbox brings files together one central place creating special folder user computer contents folders synchronized dropbox servers computers devices user installed dropbox keeping files up-to-date devices dropbox uses freemium business model users offered free account set storage size paid subscriptions available offer capacity additional features dropbox basic users given two gigabytes free storage space dropbox plus users given two terabytes storage space well additional features including advanced sharing controls remote wipe optional extended version history add-on dropbox offers computer apps microsoft windows apple macos linux computers mobile apps ios android windows phone smartphones tablets march 2013 company acquired mailbox popular email app april 2014 company introduced dropbox carousel photo video gallery app mailbox carousel shut december 2015 key features apps implemented regular dropbox service october 2015 officially announced dropbox paper collaborative document editor reported effort expand operations towards businesses march 2016 dropbox 500 million users dropbox founder drew houston conceived dropbox concept repeatedly forgetting usb flash drive student mit 2009 meet team post dropbox blog wrote existing services time suffered problems internet latency large files bugs made think much began making something personal use realized could benefit others problems houston founded evenflow inc. may 2007 company behind dropbox shortly thereafter secured seed funding combinator dropbox officially launched 2008 techcrunch disrupt annual technology conference owing trademark disputes proxy inc. evenflow dropbox official domain name get dropbox.com october 2009 acquired current domain dropbox.com october 2009 evenflow inc. renamed dropbox inc interview techcrunch founder stories october 2011 houston explained demo video released dropbox early days one viewer arash ferdowsi ferdowsi impressed formed partnership regards competition houston stated easy explain idea actually really hard dropbox seen steady user growth since inception surpassed 1 million registered users milestone april 2009 followed 2 million september 3 million november passed 50 million users october 2011 100 million november 2012 200 million november 2013 400 million june 2015 500 million march 2016 july 2012 dropbox acquired tapengage startup enables advertisers publishers collaborate tablet-optimized advertising following december dropbox acquired two companies audiogalaxy startup allowing users store music files playlists cloud stream device snapjoy company allowed users aggregate archive view digital photos cameras phones popular apps like flickr instagram picasa view online via ios app july 2013 dropbox acquired endorse mobile coupon startup may 2014 dropbox acquired bubbli startup built innovative ways incorporating 3d technology 2d views packaging mobile app january 2015 dropbox acquired cloudon company provided mobile applications document editing creation time dropbox told techcrunch cloudon base herzliya would become first dropbox office israel july dropbox acquired clementine enterprise communication service april 2014 dropbox acquired photo-sharing company loom would shut integrated then-recently announced carousel document-sharing startup hackpad dropbox later announced april 2017 hackpad would shut july 19 notes migrated dropbox paper dropbox computer apps microsoft windows apple macos linux computers mobile apps ios android windows phone smartphones tablets also offers website interface part partnership microsoft dropbox announced universal windows 10 app january 2016 dropbox apps offer automatic photo uploading feature allowing users automatically upload photos videos cameras tablets sd cards smartphones dedicated camera uploads folder dropbox users given 500 megabytes extra space uploading first photo given 3 gigabytes extra space users continue using method photos july 2014 dropbox introduced streaming sync computer apps streaming sync described new supercharged synchronization speed large files improves upload download time 2 times august 2015 dropbox announced availability universal 2nd factor usb security keys providing two-factor authentication logging services dropbox received initial funding seed accelerator combinator dropbox also raised us 1.2 million series funding sequoia capital 2007 along interest amount converted equity part series investment included fresh slug us 6 million bringing total amount us 7.25 million round closed 2008 documents filed 2009 may 2010 report wall street journal said since founder drew houston started reading eric ries lean startup blog year ago company started trickling new features ready instead waiting launch fully featured product helps test customer appetite says dubbing practice minimum viable product techcrunch reported july 2011 dropbox looking raise us 200 us 300 million valuation end 5 billion 10 billion range ... quite step previous funding rounds totalled tiny 7.2 million noted forbes article dropbox revenue track hit 240 million 2011 april 2012 dropbox announced bono edge two members irish rock band u2 individual investors company march 2017 bloomberg reported dropbox secured us 600 million credit line company expected file initial public offering ipo soon year february 2018 dropbox filed ipo listed nasdaq company initial intent raise 500 million dropbox stock rose 42 percent 29.89 first day trading march 23 2018 may 2018 dropbox never profitable reports positive cash flow dropbox uses freemium business model users offered free account set storage size paid subscriptions available offer capacity additional features dropbox basic users given two gigabytes free storage space expanded referrals users recommend service people people start using service user awarded additional 500 megabytes storage space dropbox basic users earn 16 gigabytes referral program dropbox plus subscription named dropbox pro prior march 2017 gives users 2 terabytes storage space well additional features including november 2013 dropbox announced changes dropbox business would enable users connect personal dropbox business dropbox device folders properly labeled personal work come password contacts settings files furthermore dropbox announced shared audit logs remote wipe business administrators account transfers new features business offering january 2017 dropbox introduced smart sync business enterprise customers feature lets windows macos users see files dropbox folder download specific files on-demand similarly dropbox basic dropbox plus users also earn extra space referrals plus users earn 1 gigabyte per referral 32 gigabytes dropbox business dropbox solution corporations adding business-centered functionality teams including collaboration tools advanced security control unlimited file recovery user management granular permissions options unlimited storage large organizations dropbox offers dropbox enterprise highest tier product offerings adding domain management tools assigned dropbox customer support member help expert advisors deployment user training july 2016 dropbox announced new adminx administrator dashboard business customers offering improved control company files users june 2017 adminx dashboard given redesign additional administrator functions log-in durations custom password strength parameters granular subdomain verifications specified teams september 2012 facebook dropbox integrated allow users facebook groups share files using dropbox 2013 samsung pre-loaded dropbox mobile application android devices dropbox provided extra space users owning samsung devices november 2014 dropbox announced partnership microsoft integrate dropbox microsoft office applications ios android office 365 applications web july 10 2018 dropbox announced partnership salesforce aiming improve brand engagement team productivity dropbox software enables users drop file designated folder file automatically uploaded dropbox cloud-based service made available user computers devices also dropbox software installed keeping file up-to-date systems file user dropbox folder changed dropbox uploads pieces file changed whenever possible file folder deleted users recover within 30 days dropbox plus users recovery time extended one year purchasing extended version history add-on dropbox accounts accessed emails replied year automatically deleted dropbox also offers lan sync feature instead receiving information data dropbox servers computers local network exchange files directly potentially significantly improving synchronization speeds originally dropbox servers computer apps written python july 2014 dropbox began migrating performance-critical backend infrastructure go september 2012 dropbox website code base rewritten javascript coffeescript dropbox originally used amazon s3 storage system store user files 2014 2016 gradually moved away amazon use hardware referred magic pocket due dropbox description place keep stuff ’ get lost always access june 2017 company announced major global network expansion aiming increase synchronization speeds cutting costs expansion starting 14 cities across 7 countries 3 continents adds hundreds gigabits internet connectivity transit providers regional global isps hundreds new peering partners exchange traffic directly rather isp dropbox uses ssl transfers synchronization stores data via advanced encryption standard aes -256 encryption functionality dropbox integrated third-party applications application programming interface api dropbox prevents sharing copyrighted data checking hash files shared public folders users blacklist copyrighted material applies files folders shared users publicly files kept individual dropbox folder shared march 2013 dropbox acquired mailbox popular email app mailbox ceo gentry underwood saying rather grow mailbox 've decided join forces dropbox build together deal developers mailbox joined dropbox kept mailbox running stand-alone app mailbox ceo stated still struggling keep demand want use dropbox ceo drew houston said felt could help mailbox reach much different audience much faster acquisition reported cost 100 million december 2015 dropbox announced shut-down mailbox blog post drew houston arash ferdowsi explained 'll ... using 've learned mailbox build new ways communicate collaborate dropbox april 2014 dropbox introduced carousel photo video gallery combines photos dropbox photos phone automatically backs new ones take carousel sorted photos event date december 2015 dropbox announced shut-down carousel blog post drew houston arash ferdowsi explained 'll taking key features carousel back place photos live dropbox app april 2015 dropbox launched dropbox notes collaborative note-taking service beta testing phase prompting speculation dropbox planning bring product compete google docs techcrunch noted dropbox notes appeared new version project composer previous iteration service roots acquisition hackpad april 2014 october 2015 dropbox announced upcoming launch dropbox paper collaborative document editor noted media result development dropbox notes service earlier 2015 dropbox paper entered open beta august 2016 allowing anyone join test product mobile apps android ios also released january 2017 dropbox paper officially launched aimed businesses dropbox paper described one part online document one part collaboration one part task management tool one part content hub rob baesman dropbox head product allows importing editing collaboration number file types google microsoft others users devised number uses mashups technology expand dropbox functionality include sending files dropbox via gmail using dropbox sync instant messaging chat logs bittorrent management password management remote application launching system monitoring free web hosting service dropbox received several awards including crunchie award 2010 best internet application macworld 2009 editor choice award software nominated 2010 webby award 2010 mac design awards ars technica 2011 business insider named dropbox world sixth valuable startup 2017 publication ranked dropbox eighth valuable us startup valuation 10 billion described one combinator successful investments date apple launched cloud storage service later 2011 icloud n't hold back dropbox growth dropbox mobile iphone app release 2010 among top 10 best apps selected alex ahlund former ceo two websites focused mobile apps company android app also selected one top five best apps list compiled 2010 jason hiner zdnet founders drew houston arash ferdowsi named among top 30 30 entrepreneurs inc. 2011 january 2012 dropbox named startup year techcrunch 2016 company ranked 2 forbes cloud 100 list dropbox subject criticism controversy related multiple incidents including june 2011 authentication problem let accounts accessed several hours without passwords july 2011 privacy policy update language suggesting dropbox ownership users data concerns dropbox employee access users information july 2012 email spam recurrence february 2013 leaked government documents june 2013 information dropbox considered inclusion national security agency prism surveillance program july 2014 comment nsa whistleblower edward snowden criticizing dropbox encryption leak 68 million account passwords internet august 2016 january 2017 accidental data restoration incident years-old supposedly deleted files reappeared users accounts dropbox headquarters located san francisco originally market street expansion china basin landing building july 2011 allowing significant space increase number employees grew company needed expansion february 2014 signed lease two buildings brannan street needing substantial amounts space company started shopping remaining available space companies sublease november 2015 dropbox expanded second u.s. office austin texas february 2014 state texas city austin provided 1.7 million performance-based incentives package dropbox exchange locating office austin december 2012 dropbox set office dublin ireland first office outside united states
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Distributed computing architecture
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cortana cortana virtual assistant created microsoft windows 10 windows 10 mobile windows phone 8.1 invoke smart speaker microsoft band surface headphones xbox one ios android windows mixed reality amazon alexa cortana set reminders recognize natural voice without requirement keyboard input answer questions using information bing search engine cortana currently available english portuguese french german italian spanish chinese japanese language editions depending software platform region used cortana demonstrated first time microsoft build developer conference april 2–4 2014 san francisco launched key ingredient microsoft planned makeover future operating systems windows phone windows named cortana synthetic intelligence character microsoft halo video game franchise originating bungie folklore jen taylor character voice actress returning voice personal assistant us-specific version development cortana started 2009 microsoft speech products team general manager zig serafin chief scientist larry heck heck serafin established vision mission long-range plan microsoft digital-personal-assistant built team expertise create initial prototypes cortana key researchers early efforts included microsoft research researchers dilek hakkani-tür gokhan tur andreas stolcke malcolm slaney research software developer madhu chinthakunta user-experience designer lisa stifelman develop cortana digital assistant team interviewed human personal assistants interviews inspired number unique features cortana including assistant notebook feature originally cortana meant codename petition windows phone uservoice site proved popular made codename official january 2015 microsoft announced availability cortana windows 10 desktops mobile devices part merging windows phone operating system large may 26 2015 microsoft announced cortana would also available mobile platforms android release set july 2015 android apk file containing cortana leaked ahead release officially released along ios version december 2015 e3 2015 microsoft announced cortana would come xbox one part universally designed windows 10 update console number people access cortana 800 million 2019 number questions asked 18 billion since launch microsoft integrated cortana numerous products microsoft edge browser bundled windows 10 microsoft cortana assistant deeply integrated edge browser cortana find opening-hours restaurant sites show retail coupons websites show weather information address bar worldwide partners conference 2015 microsoft demonstrated cortana integration upcoming products gigjam conversely microsoft announced late april 2016 would block anything bing edge used complete cortana searches raising questions anticompetitive behavior company microsoft windows car concept includes cortana concept makes possible drivers make restaurant reservations see places go microsoft build 2016 microsoft announced plans integrate cortana skype microsoft instant messaging service bot allow users order food book trips transcribe video messages make calendar appointments cortana addition bots cortana underline certain words phrases skype conversations relate contacts corporations writer engadget criticised cortana integration skype responding specific keywords feeling chatting search engine due impersonal way bots replied certain words hello bing music bot brought adele song name microsoft also announced microsoft build 2016 cortana would able cloud-synchronise notifications windows 10 mobile windows 10 action center well notifications android devices december 2016 microsoft announced preview calendar.help service enabled people delegate scheduling meetings cortana users interact cortana including email conversations cortana would check people availability outlook calendar google calendar work others cc 'd email schedule meeting service relied automation human-based computation may 2017 microsoft collaboration harman kardon announced invoke voice-activated speaker featuring cortana premium speaker cylindrical design offers 360 degree sound ability make receive calls skype features currently available cortana cortana set reminders recognize natural voice without requirement keyboard input answer questions using information bing search engine e.g. current weather traffic conditions sports scores biographies searches using windows 10 made microsoft bing search engine links open microsoft edge except screen reader narrator used links open internet explorer windows phone 8.1 universal bing smartsearch features incorporated cortana replaces previous bing search app activated user presses search button device cortana includes music recognition service cortana simulate rolling dice flipping coin 'cortana concert watch monitors bing searches determine bands musicians user interested integrates microsoft band watch band windows phone devices connected via bluetooth make reminders phone notifications since lumia denim mobile phone series launched october 2014 active listening added cortana enabling invoked phrase hey cortana controlled usual devices united kingdom o2 received lumia denim update without feature later clarified bug microsoft since fixed cortana integrates services foursquare provide restaurant local attraction recommendations lifx control smart light bulbs cortana stores personal information interests location data reminders contacts notebook draw upon add data learn user specific patterns behaviors users view specify information collected allow control privacy said level control goes beyond comparable assistants users delete information notebook cortana built system reminders example associated specific contact remind user communication contact possibly specific time phone specific location originally reminders specific device cortana installed since windows 10 microsoft synchronizes reminders across devices versions cortana take form two nested animated circles animated indicate activities searching talking main color scheme includes black white background shades blue respective circles cortana windows mobile android capable capturing device notifications sending windows 10 device allows computer user view notifications phone windows 10 action center feature announced early 2016 released later year cortana do-not-disturb mode users specify quiet hours available windows phone 8.1 users users change settings cortana calls users names nicknames also library easter eggs pre-determined remarks asked prediction cortana correctly predicted winners first 14 matches football 2014 fifa world cup knockout stage including semi-finals incorrectly picked brazil netherlands third place play-off match streak topped paul octopus correctly predicted 7 germany 2010 fifa world cup matches well final cortana forecast results various sports nba nfl super bowl icc cricket world cup various european football leagues cortana solve mathematical equations convert units measurement determine exchange rates currencies including bitcoin cortana integrate third-party apps windows 10 directly service starting late 2016 cortana integrated microsoft wunderlist service allowing cortana add act reminders microsoft build 2017 conference microsoft announced cortana would get consumer third-party skills capability similar amazon alexa feb 16 2018 microsoft announced connected home skills added ecobee honeywell lyric honeywell total connect comfort lifx tp-link kasa geeni well support ifttt also added august 15 2018 cortana-alexa integration went public preview microsoft ignite 2018 conference microsoft announced technology adopters program enterprises could build skills could developed deployed azure tenants accessible organizational units security groups presently third-party skills available us us english cortana indexes stores user information disabled cause windows search search web well local computer turned turning cortana delete user data stored microsoft servers deleted user action microsoft criticized requests bing website file called threshold.appcache contains cortana information searches made start menu even cortana disabled windows 10. cortana disabled users aged 13 years uk version cortana speaks british accent uses british idioms chinese version known xiao na speaks mandarin chinese icon featuring face two eyes used regions united kingdom english localised version cortana voiced ginnie watson anglo-french actress singer/songwriter voice-over artist united states english localised version cortana voiced jen taylor voice actress voices cortana namesake virtual assistant halo video game series table identifies localized version cortana currently available except indicated applies windows mobile windows 10 versions assistant natural language processing capabilities cortana derived tellme networks bought microsoft 2007 coupled semantic search database called satori cortana updates delivered independently main windows phone os allowing microsoft provide new features faster pace cortana-related features updated manner features hey cortana require windows phone update service qualcomm snapdragon sensorcore technology
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Operating systems
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fbi criminal cyber response services branch criminal cyber response services branch ccrsb service within federal bureau investigation fbi created 2002 part u.s. government post-9/11 response ccrsb responsible investigating financial crime white-collar crime violent crime organized crime public corruption violations individual civil rights drug-related crime addition branch also oversees computer-based crime related counterterrorism counterintelligence criminal threats united states ccrsb deploys fbi agents analysts computer scientists uses traditional investigative techniques sources wiretaps surveillance forensics ccrsb works conjunction federal state regional agencies 56 field offices national cyber investigative joint task force ncijtf ccrsb operates 24-hour cyber command center cywatch combine resources fbi ncijtf event significant cyber intrusion provide connectivity federal cyber centers government agencies fbi field offices legal attachés private sector also exchange information cyber threats private sector partnerships domestic security alliance council infragard national cyber forensics training alliance ncfta ccrsb maintains overseas legal attaché offices coordinate cyber investigations address jurisdictional hurdles differences law countries collaborating cyber crime centers interpol europol unit also maintains website called cyber shield alliance www.leo.gov provides access cyber training information public means report cyber incidents fbi fbi reports since 2002 seen 80 percent increase number computer intrusion investigations headed fbi executive assistant director ccrsb responsible fbi director deputy director current ccrsb executive assistant director amy hess ccrsb formed unification fbi various traditional crime fighting units speculated establishment national security branch traditional criminal investigations branch within fbi lead formation career paths fbi special agents meaning new agent completed special agent training fbi academy quantico virginia completed mandatory probationary period choose go national security branch go criminal part bureau focus crimes organized crime narcotics civil rights violations fraud violent crime advocates new program say re-organization help fight terrorism making less bureaucratic
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Computer security
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federal service technical export control federal service technical export control fstec fstek military agency russian federation russian ministry defence licenses export weapons dual-use technology items also responsible russian military information security fstec maintains data security threats database russia national vulnerability database requires western technology companies submit source code trade secrets allowing products imported russia fstec also liaises fsb controls cryptography russia 2019 fstec granted astra linux special status regarding use processing russian classified information
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Computer security
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visual dialogscript visual dialogscript vds interpreted programming language microsoft windows used create small fast programs vds large number dialog graphical elements available create professional looking programs vds programs access windows api therefore possible write applications perform advanced tasks programming languages visual basic c++ delphi unlike programming languages syntax vds simple command occupies one line plain english name clearly describes purpose variables typeless hold many kinds information example numbers text functions clearly distinguishable names start like spreadsheet dialogscript language simple syntax unlike ms-dos batch language designed ease use efficiency interpreted run-time engine 10 system variables 0 9 initially script file name 0 command line parameters 1 9 batch file also 26 user variables z contents variables including system ones changed script running also 4032 global variables variables begin letter alphanumerics plus underscores e.g my_variable_1 limit length user-defined variable names comments simple information message box simple warning message box create custom dialog box write windows registry display input prompt dialog box storing result variable visual dialogscript created julian moss jm-tech 1998 version 3.0 emmanuel daunizeau s.a.d.e sarl took ownership development vds modifying improving syntax recently vds marketed british company commercial research ltd. still property emmanuel daunizeau continues develop several versions vds released time several versions available download
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Programming language topics
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distributed r distributed r open source high-performance platform r language splits tasks multiple processing nodes reduce execution time analyze large data sets distributed r enhances r adding distributed data structures parallelism primitives run functions distributed data task scheduler multiple data loaders mostly used implement distributed versions machine learning tasks distributed r written c++ r retains familiar look feel r. hewlett-packard hp provides enterprise support distributed r proprietary additions fast data loader vertica database distributed r begun 2011 indrajit roy shivaram venkataraman alvin auyoung robert s. schreiber research project hp labs open sourced 2014 gplv2 license available github february 2015 distributed r reached first stable version 1.0 along enterprise support hp distributed r platform implement execute distributed applications r. goal extend r distributed computing retaining simplicity look-and-feel r. distributed r consists following components hp vertica provides tight integration database open source distributed r platform hp vertica 7.1 includes features enable fast parallel loading vertica database distribute r. parallel vertica loader five times 5x faster using traditional odbc based connectors vertica database also supports deployment machine learning models database distributed r users call distributed algorithms create machine learning models deploy vertica database use model in-database scoring predictions architectural details vertica database distributed r integration described sigmod 2015 paper
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Distributed computing architecture
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standardization lab automation sila consortium not-for-profit membership organization formed software suppliers system integrators pharma/biotech companies consortium standardization lab automation sila develops introduces new device data interface standards allowing rapid integration lab automation hardware data management systems highly skilled experts member companies contribute sila technical work groups membership open institutions corporations individuals active life science lab automation industry sila consortium provides professional training support certification services suppliers system integrators implementing sila compliant interfaces sila global initiative standardize software interfaces field life science research instrumentation laboratory automation instigated pharmaceutical industry need flexible laboratory automation initiative supported major device software suppliers worldwide understanding mechanisms life requires extensive often repetitive experimentation laboratory automation therefore become instrumental progress life sciences industry provides commercial laboratory devices perform increasingly sophisticated tasks however combining equipment different providers work concert often proves impossible exporting captured data proprietary software analysis frustrating impossible situation leads waste resources available equipment needs replaced compatibility reasons software drivers purchased developed data conversion time consuming technical obstacles impede development higher level autonomous experimentation systems sila enables researchers focus scientific questions reducing equipment connectivity effort minimum achieved using proven tested maintained documentation code advancements seen home consumer electronics marked like usb upnp triggered idea applying similar approach laboratory automation environment possible easily upload pictures digital camera computer time even thinkable replace lab device e.g shaker one brand shaker different brand analyzing situation led conclusion incompatibility result missing interface definitions idea standardized interface based common command set ccs concept born however sila 1.x limitations based xml/soap considered outdated getting started sila 1.x easy process led proposition spin-off group sila consortium develop new standard sila 2 learning sila 1.x taking many concepts sila 2 vision accessible possible major goal create community working development new features sila formed not-for-profit membership organisation sila requires members pay annual membership dues details membership classes related fees found sila not-for-profit membership corporation global footprint membership open institutions corporations individuals active life science lab automation industry sila consortium provides professional training support certification services suppliers system integrators implementing sila compliant interfaces sila foundation standards addresses control data interfaces devices process management lims enterprise systems sila developed released several standards sila considers every entity modern laboratory service focusing behaviour service oriented design structures lead feature definition language fdl concept feature service sila server offers serves common communication base subject matter experts sme experts end users sila built connect systems laboratory laboratory information management systems electronic lab notebooks chromatography software laboratory devices balances pipettors various analytical instruments based http/2 sila uses protocol buffers serialize payload data furthermore sila 2 uses wire format provided grpc sila 2 based microservice architecture basic structure highly comparable web server ≙sila server web client ≙sila client sila device interface standard covers iso/osi levels device control interface physical application layer interface standard based web service/soap communication devices commands generally executed asynchronous manner immediate response delayed event completion command processing error error recovery procedures also supported general behavior devices managed state machine state machine enables also complex behaviors like parallel processing commands command queuing supporting three different integration levels sila provides unique standardized interface lab automation devices process management systems also legacy devices integrated sila compliant systems sila compliance achieved providing native directly embedded sila device interfaces software sila drivers and/or interface converters sila device control data interface standard eases accelerates integration adaptation systems generic device class interfaces providing common command sets grouping devices functionality device classes created sila common command sets define commands device classes sila defines command names number parameters names well return data since commands parameters described wsdl documentation tag commands web service process management software pms automatically generate list available commands device sila defined 30 device classes command library 100 commands commands range mandatory commands needed make transitions state machine required commands specific device class optional commands every device device class might provide functionality addition guidelines implementation supplier-specific device commands parameters provided commands applicable almost every device class example commands setparameter getparameter executemethod widely used also prepareforoutput prepareforinput common enable transport mechanisms transfer labware items device device mandatory commands include operations like reset initialize abort pause addition also locking device exclusive use provided
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Distributed computing architecture
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db2 formerly db2 luw db2 database formerly known db2 linux unix windows database server product developed ibm also known db2 luw brevity part db2 family database products db2 luw common server product member db2 family designed run popular operating systems contrast db2 products specific single platform june 27 2019 ibm released db2 v11.5 artificial intelligence ai database version 11.5 ibm db2® extending legacy dependability adding ai functionality designed help optimize performance support data scientists ’ mission find deeper insights powered built ai db2 11.5 built ai enhancements support popular languages frameworks used ai developers db2 11.5 native language support python ruby go java php node.js sequelize supports popular frameworks visual studio code jupyter notebooks db2 11.5 powered ai since includes features machine learning-based ml optimizer augmented data explorer ade ml optimizer supplement existing cost-based optimizer ade uses natural language querying faceted search natural language generation capabilities make easy users easily explore data stored db2 db2 adds ai functionality top capabilities enterprises relied decades mission-critical transactional analytics workloads supported hardware acceleration in-memory technology db2 columnar data store functionality blu acceleration® feature uses advanced compression techniques deliver reliably faster response times without limitations in- memory-only systems db2 11.5 ’ ai enhancements designed help companies achieve deeper insights quickly support ai applications greater ease combined existing db2 performance-boosting technology new capabilities make db2 perfect solution help business climb ladder robust ai practice db2 part hybrid data management platform offering hybrid data management enables enterprises drive innovation seamlessly accessing sharing analyzing data higher level data management enables structured semistructured unstructured data easily accessed analyzed whether stored premises public cloud private cloud open source combination deployments first release advanced db2 luw db2 universal database version 5 available unix windows os/2 platforms new product stemmed two earlier products db2 common server version 2 db2 parallel edition db2 universal database version 5 continued ibm new direction using common code base support db2 different platforms incorporating shared nothing features db2 parallel edition support large data warehousing databases db2 luw initially called db2 universal database udb time ibm marketing started use term database products notably mainframe z-series db2 thus db2 linux unix windows moniker became necessary distinguish common server db2 luw product single-platform db2 products current db2 luw product runs multiple linux unix distributions red hat enterprise linux suse linux ibm aix hp-ux solaris windows systems earlier versions also ran os/2 multiple editions marketed different sizes organisation uses code base also marketed without db2 name ibm infosphere warehouse edition 2017 db2 udb name became db2 addition standard acid-compliant row-organized relational database functionality key features ibm offers three editions db2 community edition standard server edition advanced server edition ibm db2 community edition free download use redistribute edition ibm db2 data server xml database relational database management system features limited four cpu cores 16 gb ram database size 100 gb enterprise support fix packs db2 community edition limit number users june 27 2019 ibm released db2 v11.5 db2 update designed deliver enhancements help automate data management eliminate etl support artificial intelligence data workloads along update ibm unveiled streamlined offerings free version db2 community edition version db2 contains features include expiration caps version db2 four cpu cores 16 gb ram ibm db2 community edition replaces db2 express edition june 27 2019 ibm announced special free version db2 database called db2 community edition db2 community edition created 11.5 release ibm db2 db2 community edition replaced previously free version ibm db2 known db2 express-c. january 30 2006 ibm announced special free version db2 express edition called db2 express-c db2 express-c edition created 8.2 release ibm db2 db2 express-c created new db2 versions 9.1 codenamed viper 9.5 codename viper 2 9.7 codename cobra 10.01 codename galileo 10.5 codename kepler 11.1 ibm db2 purexml implementation xml database features introduced beta db2 9 community edition download available following platforms ibm® db2 11.5 edition aix® ibm® db2 11.5 edition windows® amd64 intel® em64t systems x64 ibm® db2 11.5 linux® amd64 intel® em64t systems x64 ibm® db2 11.5 linux® power little endian systems also docker image download available community edition ibm db2 community edition limited use 16 gb ram four cpu cores database engine limit number concurrent user connections prior version ibm db2 express-c limited use 16 gb ram increase 4 gb v10.5 two cpu cores db2 community edition feature set similar db2 standard advanced editions main difference community edition lower cpu memory limits supported unsupported following extra features enabled db2 community edition unsupported regular db2 fix packs applied ibm release fixes publish updated installation images remove old ones unix versions need reinstalled possible perform in-place updates windows versions running installation program newer version need access regular db2 fix packs released several times per year need buy db2 standard advanced editions installation images traditionally refreshed every major db2 release sync code second fix pack db2 community editions annual subscriptions instead free trial available indefinitely users want scale beyond four cores 16 gb ram need migrate workload upgraded environment instead users apply license key existing implementation access additional capacity
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Databases
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rise-pak relief information systems earthquakes pakistan abbreviated rise-pak information-sharing web portal created pakistani-american economist asim ijaz khwaja along experts world bank pomona college national database registration authority world online pakistan largest internet service provider hosted website lahore school management sciences created 2005 earthquake kashmir claimed 80,000 lives around 70,000 injured pakistan india afghanistan website displayed maps 4000 villages affected quake database demographic information disaster information assistance received access routes villages area also provided pre-earthquake information showing village-level demographic infrastructure data major road networks distance every village epicentre earthquake
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Databases
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sakhr software company sakhr software company arabic language technology company based kuwait deals products middle east e-governance education wireless security sakhr founded 1982 mohammed alsharekh branching computer hardware company alamiah electronics producing arabic versions msx computers nearly three decades industry us 100 million investments leads field arabic language machine translation ocr speech recognition speech synthesis search localisation company currently 200 employees worldwide research engineering activities silicon valley egypt sales offices u.s. washington dc california kuwait uae dubai abu dhabi oman egypt saudi arabia 2009 sakhr acquired dial directions inc. u.s. silicon valley software company providing language applications mobile cloud-computing environments including wireless carriers telematics “ smartphones ” apple iphone enhance market position emerging mobile application cloud computing market sakhr software following international awards
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Computer architecture
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cynthia solomon cynthia solomon american computer scientist known work artificial intelligence ai popularizing computer science students pioneer fields artificial intelligence computer science educational computing working researcher massachusetts institute technology mit dr. solomon took upon understand program programming language lisp began learning language realized need programming language accessible understandable children throughout research studies education dr. solomon worked full-time computer teacher elementary secondary schools work mainly focused research human-computer interaction children designers working bolt beranek newman worked wally feurzeig seymour papert create first programming language children named logo language created teach concepts programming related lisp dr. solomon attained many accomplishments life vice president r logo computer systems inc. apple logo developed director atari cambridge research laboratory dr. solomon worked program committee constructing modern knowledge marvin minsky institute artificial intelligence 2016 published many writings based research field child education technology classroom dr. solomon conducted workshops elementary schools high schools colleges regarding academic research writing continues contribute field speaking conferences working one laptop per child foundation cynthia admitted struggling classes middle high school mentioned became motivated continue education passion computer science kind music teachers dr. solomon received bachelor arts b.a history radcliffe college early 1960s subsequently studied boston university received master science m.s computer science 1976 received doctor philosophy ph.d. education harvard university 1985 intermittently completing schooling solomon worked several years researcher marvin minsky seymour papert mit later bolt beranek newman receiving b.a radcliffe college dr. solomon taught milton academy milton massachusetts seven years also became technology integration coordinator monsignor haddad middle school needham massachusetts 1980s massachusetts institute technology hired dr. solomon lead atari cambridge research laboratory due success developing logo solomon maintained long relationship working mit media lab one laptop per child foundation dr. solomon still leading worker foundation directed creation educational materials continued teaching consulting scholarship working several esteemed research labs foundations together seymour papert wally feurzeig cynthia designed logo computer programming language 1967 language children experiment words solve math problems make-up stories create games logo widely known use turtle graphics commands movement drawing produced line graphics either screen small robot called turtle 1970s new development logo introduced allowing program viewed multiple colors language created teach concepts programming related lisp functional programming language later logo also enabled papert called body-syntonic reasoning students could understand predict reason turtle motion imagining would turtle substantial differences among many dialects logo situation confused regular appearance turtle graphics programs call logo dr. solomon began develop logo coming realization children needed programming language solomon directed creation educational materials one laptop per child foundation doctoral research harvard led publication critical book computer environments children reflection theories learning education book explores opportunities challenges presented regarding computers learning environments focused specifically elementary school mathematics solomon discusses role computers innovative learning theories solomon also co-author designing multimedia environments children allison druin along many research projects writings contributing knowledge children learning environments conjunction technology 2016 solomon national center women information technology ncwit pioneer award solomon received lifetime achievement award constructionism 2016 introduced seymour papert memorial lecture crossroads 2018 facilitated conversation new uses program education new demographic users
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Programming language topics
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memory technology device memory technology device mtd type device file linux interacting flash memory mtd subsystem created provide abstraction layer hardware-specific device drivers higher-level applications although character block device files already existed semantics n't map well way flash memory devices operate usb sticks mmcs sds compactflashes popular removable devices confused mtds although contain flash memory hidden behind block device interface using flash translation layer using mtd use mtd aware file system jffs2 yaffs recommended mtd subsystem exports block devices well allows use common filesystem like ext4 however using mtd way recommended since neither detection bad blocks kind wear leveling
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Operating systems
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phrasal template phrasal template phrase-long collocation contains one several empty slots may filled words produce individual phrases often restrictions grammatic category words allowed fill particular slots example phrase common stocks rose number number e.g. common stocks rose 1.72 340.36 phrasal templates akin forms blanks filled data word game mad libs makes use phrasal templates notion used natural language processing systems language generators application-oriented report generators neologism snowclone introduced refer special case phrasal templates clone popular clichés example misquotation diana vreeland pink navy blue india may gaven rise template x new black turn evolved x new term phrasal template first appeared linguistic study prosody 1983 n't appear come common use late 1990s
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Computational linguistics
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freebsd foundation freebsd foundation united states-based 501 c 3 registered non-profit organization dedicated supporting freebsd project development community funding comes individual corporate donations used sponsor developers specific activities purchase hardware network infrastructure provide travel grants developer summits freebsd foundation able provide legal representation sign contracts agreements behalf freebsd project also holds freebsd trademark related domain names freebsd foundation received initial 501 c 3 charity status december 7 2000 foundation formally announced world june 27 2001 current board directors follows
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Operating systems
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live usb live usb usb flash drive external hard disk drive containing full operating system booted evolutionary next step live cds added benefit writable storage live usb allowing customizations booted operating system live usbs used embedded systems system administration data recovery test driving persistently save settings install software packages usb device many operating systems including windows xp embedded large portion linux bsd distributions run usb flash drive windows 8 enterprise feature titled windows go similar purpose repair computer booting issues technicians often use lightweight operating systems bootable media command line interface development first live cds graphical user interface made feasible non-technicians repair malfunctioning computers live cds linux based addition repairing computers would occasionally used right operating systems personal computers introduced usb booting early 2000s macintosh computers introducing functionality 1999 beginning power mac g4 agp graphics slot-loading imac g3 models intel-based macs carried functionality booting macos usb specialized usb-based booting proposed ibm 2004 reincarnating pcs portable soulpads boot gnu/linux firewire device live usbs share many benefits limitations live cds also incorporate various applications exist create live usbs examples include rufus fedora live usb creator unetbootin wintousb win32diskimager yumi works variety distributions linux distributions live cds ready-made scripts perform steps automatically addition knoppix ubuntu extra applications installed persistent file system used store changes base install ranges little 16 mib tiny core linux large dvd-sized install 4 gigabytes set live usb system commodity pc hardware following steps must taken knoppix live cds utility boot allows users declare intent write operating system file structures either temporarily ram disk permanently disk flash media preserve added configurations security updates easier recreating usb system may moot since many live usb tools simple use alternative live solution traditional operating system installation elimination swap partitions installation advantage efficient software live installation would still contain software removed persistent file due operating systems installer still included media however full installation without disadvantages due additional write cycles occur full installation life flash drive may slightly reduced mitigate live systems designed store changes ram user powers system writes changes another factor speed storage device destitute performance comparable legacy computers even machines modern parts flash drive transfers speeds one way solve use usb hard drive generally give better performance flash drives regardless connector although many live usbs rely booting open-source operating system linux possible create live usbs windows using diskpart wintousb syslinux common program make bootable usb storage device
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Operating systems
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ipfc ipfc stands internet protocol fibre channel governs set standards created january 2006 address resolution arp transmitting ipv4 ipv6 network packets fibre channel fc network ipfc makes part fc-4 protocol-mapping layer fibre channel system ipfc ip datagram packet wrapped fc frame header transmitted sequence one frames receiver end received frames strips fc headers reassembles ip packet ip datagrams 65,280 bytes size may accommodated arp packet transmission works fashion ip datagram exchange unidirectional although ip tcp allow bidirectional communication within protocols ipfc application protocol typically implemented device driver operating system ip fc plays less important role storage area networking scsi fibre channel ip ethernet ipfc used example provide clock synchronization via network time protocol ntp
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Internet protocols
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rcca security replayable cca security rcca security security notion cryptography relaxes older notion security chosen-ciphertext attack cca precisely adaptive security notion cca2 cca-secure systems rcca secure converse true claim lot use cases cca strong rcca suffices nowadays certain amount cryptographic scheme proved rcca-secure instead cca secure introduced 2003 research publication ran canetti hugo krawczyk jesper b. nielsen
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Computer security
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web log analysis software web log analysis software also called web log analyzer kind web analytics software parses server log file web server based values contained log file derives indicators web server visited reports usually generated immediately data extracted log files alternatively stored database allowing various reports generated demand features supported log analysis packages may include hit filters use pattern matching examine selected log data
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Web technology
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ibm mwave mwave technology developed ibm allowing combination telephony sound card features single adapter card technology centers around mwave digital signal processor dsp technology used time provide combination modem sound card ibm aptiva line thinkpad laptops addition uses specialized mwave cards handled voice recognition isdn networking connectivity similar adapter cards third-party vendors using mwave technology also sold however plagued consumer complaints buggy mwave software hardware ibm eventually turned audio telephony solutions consumer products malcolm ware former developer mwave dates technology back development ibm research lab zurich switzerland 1979 first prototype tested ibm pc 1981 utilized adapter cards mwave given official name used ibm windsurfer isa/mca card ibm manufactured mwave hardware microsoft windows os/2 another revision technology used ibm newly renamed aptiva line one revisions mwave card mwave dolphin card isa legacy card support plug play natively supported windows software featured 28.8k/second fax/modem sound blaster-compatible audio solution one card publicized features software upgradeability version mwave software upgraded modem function 33.6k addition card key support aptiva rapid resume features including wake-up ring various consumer complaints users reporting problems involving either sound modem features separately using time consumers offered check purchase hardware replace mwave card others offered replacement modem sound card one point class action lawsuit filed finally settled 2001 mwave dolphin drivers version 20d stingray version mwave adapter addressed shortcomings dolphin stingray added plug play support ibm eventually stopped using mwave adapter card aptiva computers resorted conventional sound card modem options mwave form another produced mca isa pcmcia busses select thinkpad 600 770 models pci version integrated mwave chip integrated select thinkpad 755 760 765 models isa-based certain sun sparcstation workstations incorporated mwave dsp chip sound card functionality although mwave adapter cards discontinued linux driver pci-based mwave thinkpad 600 770 models developed released ibm
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Computer architecture
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leading edge model leading edge model ibm clone computer first released leading edge hardware july 1985 initially priced 1,495 configured dual 5.25 floppy drives 256 kb ram monochrome monitor manufactured south korean conglomerate daewoo distributed canton massachusetts-based leading edge engineer stephen kahng spent four months designing model cost 200,000 kahng later became ceo macintosh clone maker power computing august 1986 leading edge cut price base model 200 1,295 increased base memory machine 512 kb model immediate success selling 100,000 units first year production continued sell well several years dispute dealers forced leading edge bankruptcy 1989 model initially featured intel 8088 microprocessor 4.77 mhz although later models switch back run 4.77 mhz normal 7.16 mhz high earlier models turbo switch ran 4.77 mhz later ones seemingly rare 7.16 mhz four models known dc-2010 dc-2011 dc-2010e dc-2011e e seems correlate capability running 7.16 mhz unlike ibm pc ibm pc/xt model integrated video disk controller battery backed clock serial parallel ports directly onto motherboard rather putting plug-in cards allowed model half size ibm models four full-length isa expansion slots available motherboard came eight different revisions revision 1 5 7 8 cc1 cc2 wc1 wc2 list motherboard part numbers revision numbers found revisions 1 7 usually found models dc-2010 dc-2011 revisions 8 wc2 either 2010e 2011e wc1 presumably also wc2 7.16 mhz due tight integration model motherboard nonstandard form factor replacing motherboard off-the-shelf upgrade possible model came preinstalled 256 512 640 kb ram lower-capacity machines user upgradeable 640 kb motherboard revisions 7 8 wc1 wc2 came 768 kb ram installed 640 kb available user models featured monochrome/cga selection switch single port used modes models monochrome cga port also switch change modes ports model computers supported special extended graphics mode 640x200 buyer choice floppy disk model fixed disk hard disk model floppy disk model one two 360 kb drives user could run ms-dos programs primary drive work files secondary drive equipped fixed disk model one 360 kib floppy drive either 10 mb 20 mb 30 mb hard disk model 20 mb fixed disk initially released february 1986 cost 1,895 leading edge dealers difficulty keeping 20mb model stock time tandy 1200 equipped 10mb drive sold 1999 buyer also choice amber green monochrome crt monitor unit came ms-dos 2.11 later special edition gw-basic support extended graphics mode also came diagnostics disk disk contained diagnostics program park.com utility used park hard drive heads computer moved models also came word processing program developed leading edge titled leading edge word processor commonly referred acronym 'lewp computer supports microsoft windows operating system version 3.0 last version windows support real mode dataquest estimated model 1 american home-computer market 1986 first year availability 1,495 list price lowest seven compatibles comparable configurations september 1985 infoworld chart half price 2,820 ibm pc along tandy 1000 epson equity series model one first ibm pc compatible computers become popular home use due low price good reviews previously ms-dos ibm compatibles almost exclusively used businesses home computer market dominated commodore apple atari years afterward many home-oriented software packages pc specifically cited model along tandy epson models compatible hardware leading edge phoenix technologies first customer ibm-compatible bios model one first pcs market use phoenix bios although advertised 100 ibm compatible numerous letters published january 13 1986 issue infoworld identified compatibility issues several popular software packages aftermarket hard drives syndicated newspaper columnists t.r reid michael schrage writing april 1986 predicted popularity model would lead hardware software vendors specifically testing compatibility spite early reports model continued sell well early 1987 daewoo producing 13,000 units per month failing keep demand result buyers waited 2–8 weeks taking delivery model also distinction first korean-made pc sold united states time introduction undercut price similar ibm pc compatibles 500 pc magazine october 1985 called model clear winner among six inexpensive pc compatibles tested review noted computer many included hardware features concluded may represent next generation personal computing compact full ibm hardware compatibility allows full featured quite well made alluringly priced model received 4 5 stars infoworld praised computer value high level compatibility december 1985 concluded recommend highly especially budget-conscious beginner positive october 1986 review popular mechanics cited low price quality keyboard received good reviews computer magazines consumer reports magazine
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Computer architecture
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bbn time-sharing system bbn time-sharing system early time-sharing system created bolt beranek newman bbn pdp-1 computer began operation september 1962 digital equipment corporation prototype pdp-1 ready november 1959 machine featured november/december issue datamation magazine bbner ed fredkin saw prototype system eastern joint computer conference boston december 1959 extremely interested given bbn interest dec founder president ken olsen visited explained dec completed construction prototype pdp-1 needed test site month bbn agreed test site regular hourly rates early 1960 obtained prototype pdp-1 first production pdp-1 arrived november 1960 formally accepted april 1961 pdp-1 installed bbn 1960 j.c.r licklider took mit john mccarthy marvin minsky consultants mccarthy advocating concept time-sharing computers found slow progress mit bbn licklider fredkin keenly interested particular fredkin insisted timesharing could done small computer namely pdp-1 fredkin recounts mccarthy recalled 1989 accordingly bbn team largely led sheldon boilen built custom hardware add-ons company second pdp-1 provide external interrupt system magnetic drum swapping storage end bbn acquired first univac fastrand rotating drum 45-mbyte storage capacity access time 0.1 second fall 1962 bbn conducted public demonstration bbn time-sharing system one operator washington d.c. two cambridge.. described mccarthy et al. computer hardware follows pdp-1 single address binary computer 18 bit word five microsecond memory cycle instructions require ten microseconds execute basic memory size 4096 words 65,536 words may addressed indirectly machine used 8192 words 4096 reserved time-sharing system user sees 4096 word memory ... attached computer high speed magnetic drum memory divided 22 fields 4096 words basic operation drum system memory-swap accomplished 33 milliseconds operation 4096 words transferred core memory drum field simultaneously core memory loaded different drum field ... 4096 word drum field allocated saving core image user program running user program run status run 140 milliseconds another user also run status state core memory stored first user core image drum simultaneously second user core image loaded core second user program started appropriate place
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Operating systems
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roca vulnerability roca vulnerability cryptographic weakness allows private key key pair recovered public key keys generated devices vulnerability roca acronym return coppersmith attack vulnerability given identifier cve-2017-15361 vulnerability arises problem approach rsa key generation used software library rsalib provided infineon technologies incorporated many smart cards trusted platform module tpm implementations vulnerability appears recent yubikey 4 tokens often used generate pgp keys keys lengths 512 1024 2048 bits generated using infineon library vulnerable practical roca attack research team discovered attack masaryk university led matúš nemec marek sýs estimate affects around one-quarter current tpm devices globally millions smart cards believed affected team informed infineon rsalib problem february 2017 withheld public notice mid-october citing responsible disclosure time announced attack provided tool test public keys vulnerability published details attack november generating rsa key involves selecting two large randomly-generated prime numbers process time-consuming particularly small devices smart cards addition primes numbers certain properties best security vulnerable rsalib selection process quickly creates primes desired type testing primality numbers form formula_2 product first n successive primes 2 3 5 7 11 13 ... n constant depends desired key size security based secret constants formula_3 formula_4 roca attack exploits particular format primes using variation coppersmith method addition public keys generated way distinctive fingerprint quickly recognized attempting compute discrete logarithm public key mod formula_2 base 65537 computing discrete logarithms large group usually extremely difficult case done efficiently using pohlig–hellman algorithm formula_2 smooth number test site available internet roca authors consider public keys length 512 1024 2048-bits generated rsalib vulnerable details key generation differ different key lengths shorter keys necessarily vulnerable longer keys example 1952-bit rsalib key stronger 2048-bit key 4096-bit key weaker 3072-bit key best mitigation according authors generate rsa keys using stronger method openssl possible roca authors suggest using key lengths less susceptible roca 3936-bit 3072-bit 1952-bits 2048-bit key size maximum
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Computer security
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data control block ibm mainframe operating systems os/360 mvs z/os data control block dcb description dataset program dcb coded assembler programs using dcb macro instruction expands large number define constant instructions high level language programmers use library routines containing dcbs dcb one many control blocks used operating systems control block data area predefined structure similar c codice_1 typically related system functions dcb may compared file structure c much complex offering many options various access methods control block acted application programming interface logical iocs application program usually defined within resided within application program addresses i/o subroutines would resolved linkedit phase compilation else dynamically inserted open time equivalent control block ibm dos/360 dos/vse z/vse operating systems dtf define file many constants variables contained within dcb may left blank i.e. default zero open process results merge constants variables specified dd jcl statement dataset label existing magnetic tape direct-access datasets dcb replacing zero values actual non-zero values control block called jfcb job file control block initially holds information extracted dd statement dataset results merge stored jfcb may also written dscb close process thereby making dataset definition permanent example blksize= variable may usually specified dcb zero dd statement blksize specified non-zero value results program-specified lrecl logical record length jcl-specified blksize physical block size merge two becoming permanent definition dataset
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Operating systems
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crash-only software crash-only software refers computer programs handle failures simply restarting without attempting sophisticated recovery correctly written components crash-only software microreboot known-good state without help user since failure-handling normal startup use methods increase chance bugs failure-handling code noticed except leftover artifacts data corruption severe failure n't occur normal startup crash-only software also benefits end-users often applications save data settings running end use example word processors usually save settings closed crash-only application designed save changed user settings soon changed persistent state matches running machine matter application terminates clean close sudden failure laptop battery state persist erlang computer language originally built ericsson fault-tolerant telephone switches programs structured modules replaced hot swapped without restart entire program module crashes needs updated restarted replaced without affecting part program within open telecom platform often used together erlang exist frameworks simplify automate task
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Operating systems
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jet data access objects jet data access objects general programming interface database access microsoft windows systems primarily jet ace databases dao originally called vt objects dao 1.0 came november 1992 part access 1.0 version 3.5 able bypass jet engine altogether directly access odbc data sources including microsoft sql server enterprise database systems dao 3.6 shipped jet 4.0 access 2007 later uses ace acedao new features supported ace added acedao longer supports odbcdirect dao works creating workspace object database operations performed workspace object exists session object exists within larger database engine object two types database engines jet database engine object odbcdirect database engine jet database engine access 2007 later ace object consists several objects first version dao used snapshot/dynaset/table objects etc dao 2.0 recordset etc objects introduced dao 3.0/3.5 supported old objects using special compatibility tlb removed completely dao 3.6 odbcdirect database engine consists workspace object errors object main differences database engine jet database engine odbc connection objects consist querydef objects recordset objects
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Operating systems
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cutwail botnet cutwail botnet founded around 2007 botnet mostly involved sending spam e-mails bot typically installed infected machines trojan component called pushdo affects computers running microsoft windows june 2009 estimated cutwail botnet largest botnet terms amount infected hosts security provider messagelabs estimated total size botnet around 1.5 2 million individual computers capable sending 74 billion spam messages day 51 million every minute equal 46.5 worldwide spam volume february 2010 botnet activities slightly altered started ddos attack 300 major sites including cia fbi twitter paypal reasons attack n't fully understood experts described accident mainly due lack damage disruption along infrequency attacks august 2010 researchers university california santa barbara ruhr university bochum attempted take botnet managed take offline 20 30 command control servers botnet using cutwail fairly simple botnet bots connect directly command control server receive instructions emails send done task bots report back spammer exact statistics number emails delivered many errors reported cutwail botnet known 0bulk psyche evolution underground market spammers rent instance botnet fee use send spam campaigns services offered botnet advertised russian underground forum spamdot.biz taken 2010 june 2010 least 8 different spam groups using botnet deliver junk mail
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Computer security
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ikee ikee worm spread secure shell connections jailbroken iphones stole apple ids passwords discovered 2009 changed wallpapers photo rick astley iphone owners australia reported smart phones infected worm changed iphone wallpaper rick astley 1980s pop singer affected smartphones owner change default password installation ssh ikee worm infected would find iphones mobile network vulnerable infect well worm would n't affect users n't jailbroken installed ssh iphone worm nothing changing infected user lock screen wallpaper source code ikee worm says written ikex
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Computer security
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mac service data unit mac service data unit media access control service data unit msdu service data unit received logical link control llc sub-layer lies media access control mac sub-layer protocol stack llc mac sub-layers collectively referred data link layer dll
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Internet protocols
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ideas bank ideas bank widely available shared resource usually website people post exchange discuss polish new ideas ideas banks used develop new inventions technologies many corporations installed internal ideas banks gather input employees improve ideation process ideas banks employ voting system estimate idea value cases ideas banks humor-oriented serious counterparts many ideas banks provided free charge set around certain companies general work new inventions although ideas provided community people problems arise people take ideas site begin developing possible way prove idea ideas bank original taken something else front end innovation quite distinct remainder innovation process best ideas discovered managed stage gate oriented project management system work flow defined front end innovation commonly referred fuzzy functions best collaborative system nurtures chaos disruption serendipitous discovery ideas ideas submitted via electronic suggestion box limited incremental innovation things way always better nothing wrong incremental innovation fact ideas leading projects resulting incremental innovation typically yield rapid revenue gains cost savings organizations using collaborative idea management systems get breakthrough radical innovation ideas thought box thinking fuzzy front end innovation benefits collaborative tool serving backbone nurture organization culture innovation everyone log system post objects interest users search information comment information discover experts organization needed result everyone well informed sense collaborative tool serves knowledge management system facebook-like except everyone talking work course collaborative tool also accepts submission ideas idea management software solution manages ideas allowing others comment shaping idea clustering similar ideas utilizing idea management software similarity search capabilities accepting sort voting scheme order score idea worth better idea management software systems use algorithm measure wisdom crowd gauging social media type activity instance means best ideas automatically promoted get combination votes comments votes comments views follows alerts bookmarks similar ideas posted ... combined mathematical formula determine idea best measured group collaborators working ideas unsolicited ideas typically lead incremental innovation get radical breakthrough innovation idea management system needs indulge strategic guidance issuing challenges campaigns seeding essence bottom grown organizational engagement collaborative idea management system managed little bit top strategic guidance company saying 're glad 're talking together us favor talk ... ask ideas address big issues company instance make company 'green next new product us collaborating companies assemble smart people company exchange ideas enhance ideas best ideas automatically promoted need automated promotion mechanism software problem n't wo n't get enough ideas problem 'll get many n't want someone manually filter
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Databases
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audio mining audio mining technique content audio signal automatically analysed searched commonly used field automatic speech recognition analysis tries identify speech within audio audio typically processed speech recognition system order identify word phoneme units likely occur spoken content information may either used immediately pre-defined searches keywords phrases real-time word spotting system output speech recogniser may stored index file one audio mining index files loaded later date order run searches keywords phrases results search normally terms hits regions within files good matches chosen keywords user may able listen audio corresponding hits order verify correct match found audio mining systems used field speech recognition often divided two groups use large vocabulary continuous speech recognisers lvcsr use phonetic recognition musical audio mining also known music information retrieval relates identification perceptually important characteristics piece music melodic harmonic rhythmic structure searches carried find pieces music similar terms melodic harmonic and/or rhythmic characteristics
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Computational linguistics
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