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cruise ship id card cruise ship id card plastic card size credit card serves several functions passengers cruise ship cruise ship id cards scanned entrances ship various points throughout ship either via magnetic strip rfid readers bar code order identify passenger allow entry exit ship allow entry certain areas ship including passenger cabin bill purchases passenger various functions information printed ship card may include rare picture passenger displayed card frequently scanned presence computer display picture passenger screen functions ship card may include
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Computer security
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media transfer protocol media transfer protocol mtp extension picture transfer protocol ptp communications protocol allows media files transferred atomically portable devices whereas ptp designed downloading photographs digital cameras media transfer protocol allows transfer music files digital audio players media files portable media players well personal information personal digital assistants mtp key part wmdrm10-pd digital rights management drm service windows media platform mtp part windows media framework thus closely related windows media player versions microsoft windows operating system windows xp sp2 support mtp windows xp requires windows media player 10 higher later windows versions built-in support microsoft also made available mtp porting kit older versions windows back windows 98 usb implementers forum device working group standardised mtp full-fledged universal serial bus usb device class may 2008 since mtp official extension ptp shares class code main purpose protocol allow transfer media files associated metadata portable devices one transfer function time support operations open edit modify workaround copy hosting system operations copy back protocol originally implemented use across usb extended use across tcp/ip bluetooth windows vista supports mtp tcp/ip windows 7 windows vista platform update windows vista also support mtp bluetooth host connecting mtp device called mtp initiator whereas device mtp responder main reason using mtp rather example usb mass-storage device class msc latter operates granularity mass storage device block usually practice fat block rather logical file level words usb mass storage class designed give host computer undifferentiated access bulk mass storage compact flash rather file system might safely shared target device except specific files host might modifying/accessing practice therefore usb host computer mounted msc partition assumes absolute control storage may safely modified device without risk data corruption host computer severed connection furthermore host computer full control connected storage device risk host computer may corrupt file system reformat file system supported usb device otherwise modify way usb device completely understand mtp ptp specifically overcome issue making unit managed storage local file rather entire possibly large unit mass storage block level way mtp works like transactional file system either entire file written/read nothing storage media affected failed transfers device maintains database/index content disk mtp saves cost re-scanning entire disk every time content modified additionally mtp allows mtp initiators identify specific capabilities device respect file formats functionality particular mtp initiators may provide passwords information unlock files otherwise enable digital rights management nothing specific nature core standard features available via vendor extensions mtpz zune extension mtp specifically denies access files authentication processed possible using windows media player 10 higher mtp advantages marked “ ” disadvantages marked “ ” exposing filesystem metadata index integrity full control device unless operating system exposes mtp devices virtual file systems occur natively windows thus mtp devices assigned drive letters mtp-unaware software able make use devices limiting user mtp-specific programs one specific concern antivirus software host computer may aware mtp devices making potentially less secure mass storage devices although files mtp devices copied moved host use mtp-unaware antivirus software chance scan antivirus scanning might also impractical due blocking regular use device despite identifiability ptp/mtp usb device class libmtp documentation indicates vendor product id combination plays functional role identifying mtp device also windows drivers libmtp includes vast listings vendor product id numbers devices supports along workarounds bugs non-generic methodology hinders mtp drivers forward compatibility new devices mtp specification includes enumeration file formats called object format use enumeration communicating supported file formats formats transferred files apart uncategorized formats beginning list formats grouped categories image audio video document formats category one undefined format followed specific formats also super-generic undefined object format jolla cited lack webm support mtp one reason support video format mobile operating system sailfish os unclear limitation tools spec webm defined mtp 1.1 spec features used efficient alternatives whole-file transfers re-uploads mtp 1.1 spec according go-mtpfs mtp supported windows xp windows media player 10 later versions installed windows vista later mtp support built older versions windows specifically windows 2000 windows 98 windows microsoft released mtp porting kit contains mtp device driver manufacturers creative technology also provide legacy mtp drivers players usually consist mtp porting kit files customized inf file describing specific players mtp-compatible devices assigned drive letters instead appear devices applications windows explorer compared devices implement usb mass storage devices accessed programmatically scripts normal windows programs depend drive letters instead files must manipulated using windows explorer applications specially written mtp support windows mtp-compatible devices support feature called auto sync lets users configure windows media player automatically transfer copied newly acquired content devices whenever connected provided content compatible windows media player auto sync customizable player transfer content meets certain criteria songs rated four stars higher instance changes made file properties user rating file playback counts device propagated back computer device reconnected copies files accessed mtp may remain host computer even reboot accessible user account accessed well user accounts able read user account files including administrative users windows 7 sensor platform supports sensors built mtp-compatible devices free open-source implementation media transfer protocol available libmtp library incorporates product device ids many sources commonly used software mtp support gnome applications like gnome files formerly called nautilus archive manager formerly called file-roller use gio-based gvfs access files mtp devices proper mtp support added gvfs version 1.15.2 2013-01-15 philip langdale early patches gvfs enable google direct i/o extensions available kde project develops mtp kio slave similar level integration gvfs related gnome kde *nix graphical mtp-capable media player gmtp several tools provide fuse based file system mounting mtp devices within unix filesystem hierarchy making accessible program operates files directories examples include mtpfs jmtpfs go-mtpfs simple-mtpfs macos built-in support mtp application digital images third-party drivers mount mtp devices drives also several third-party file transfer applications available mac os x v10.5 later later versions several operating systems including amigaos android aros morphos symbian os support mtp sometimes additional drivers software disadvantage mtp devices android compared usb mass storage although file timestamps preserved copying files android device one computer copying direction file modification timestamps replaced time copy done companies including creative technology intel iriver samsung electronics manufacture devices based microsoft portable media center specification widely adopted mtp supporting devices introduced 2004 consumer electronics show initial period uncertain reactions several large media player producers creative technology iriver adopted mtp protocol place protocols many devices audio software applications support mtp
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Operating systems
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one per desk one per desk opd innovative hybrid personal computer/telecommunications terminal based hardware sinclair ql one per desk built international computers limited icl launched uk 1984 result collaborative project icl sinclair research british telecom begun 1981 originally intended incorporate sinclair flat-screen crt technology rebadged versions opd sold united kingdom merlin tonto australia telecom australia computerphone ql opd borrowed 68008 cpu zx8301/8302 ulas 128 kb ram dual microdrives re-engineered icl greater reliability 8049 intelligent peripheral controller unique opd telephony module incorporating intel 8051 microcontroller also controlled keyboard two pstn lines v.21/v.23 modem plus built-in telephone handset ti tms5220 speech synthesiser automatic answering incoming calls opd supplied either 9-inch monochrome white monitor 14-inch colour monitor monitors also housed power supply opd later 3.5 floppy disk drives also available third-party vendors icl preferred supplier uk local government opds found way onto desks council officers due cost tended issued senior often elderly interest computers secretaries handle administrative work many devices simply used telephones system firmware bfs basic functional software unrelated ql qdos operating system although subset superbasic provided microdrive cartridge bfs provided application-switching voice/data call management call answering phone number directories viewdata terminal emulation simple calculator psion applications suite bundled ql also ported opd xchange available optional rom pack optional application software available rom included various terminal emulators satellite computing icl7561 emulator plus action diary presentation software address book inter-opd communications utilities icl supplied application used synchronise national bingo game across hundreds bingo halls uk integral v.23 dialup modem used provide remote communications central server several uk icl mainframe series 39 customers local government ministry defence sectors used statistics applications opd systems view graphical representations mainframe reports integral v.23 modem used download mainframe british telecom business systems sold opd merlin m1800 tonto bt intended tonto centralised desktop information system able access online services mainframes similar systems bt telephone network tonto retailed £1,500 launch opd peripherals software rom cartridges also badged merlin brand bt withdrew support tonto february 1993 name tonto derived outstanding new telecoms opportunity enhanced version opd produced small numbers united states market 68008fn cpu 256 kb ram standard rs-232 port enhanced firmware telephone answering function female voice slight new jersey accent
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Computer architecture
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christopher strachey christopher s. strachey 16 november 1916 – 18 may 1975 british computer scientist one founders denotational semantics pioneer programming language design member strachey family prominent government arts administration academia christopher strachey born 16 november 1916 oliver strachey rachel ray costelloe hampstead england oliver strachey son richard strachey great grandson sir henry strachey 1st baronet elder sister writer barbara strachey 1919 family moved 51 gordon square stracheys belonged bloomsbury group whose members included virginia woolf john maynard keynes christopher uncle lytton strachey 13 christopher went gresham school holt showed signs brilliance general performed poorly admitted king college cambridge college alan turing 1935 continued neglect studies strachey studied mathematics transferred physics end third year cambridge strachey suffered nervous breakdown possibly related coming terms homosexuality returned cambridge managed lower second natural sciences tripos unable continue education christopher joined standard telephones cables stc research physicist first job providing mathematical analysis design electron tubes used radar complexity calculations required use differential analyser initial experience computing machine sparked strachey interest began research topic application research degree university cambridge rejected strachey continued work stc throughout second world war war fulfilled long-standing ambition becoming schoolmaster st edmund school canterbury teaching mathematics physics three years later able move prestigious harrow school 1949 stayed three years january 1951 friend introduced mike woodger national physical laboratory npl lab successfully built reduced version alan turing automatic computing engine ace concept dated 1945 pilot ace spare time strachey developed program game draughts also known checkers finished preliminary version may 1951 game completely exhausted pilot ace memory draughts program tried run first time 30 july 1951 npl unsuccessful due program errors strachey heard manchester mark 1 much bigger memory asked former fellow-student alan turing manual transcribed program operation codes machine around october 1951 summer 1952 program could play complete game draughts reasonable speed strachey programmed first ever music performed computer rendition british national anthem mark ii manchester electronic computer manchester 1951 later year short extracts three pieces recorded bbc outside broadcasting unit national anthem ba ba black sheep mood researchers university canterbury christchurch restored acetate master disc 2016 results may heard soundcloud may 1952 strachey gave two-part talk study control animals machines cybernetics bbc home service science survey programme strachey worked national research development corporation nrdc 1952 1959 working st. lawrence seaway project able visit several computer centres united states catalogue instruction sets later worked programming elliott 401 computer ferranti pegasus computer together donald b. gillies filed 3 patents computing design including design base registers program relocation also worked analysis vibration aircraft working briefly roger penrose developed concept time-sharing 1959 strachey left nrdc become computer consultant working nrdc emi ferranti organisations number wide-ranging projects work included logical design computers providing autocode later design high-level programming languages contract produce autocode ferranti orion computer strachey hired peter landin became one assistant duration strachey consulting period 1962 remaining consultant accepted position cambridge university 1965 strachey accepted position oxford university first director programming research group later university first professor computer science fellow wolfson college oxford collaborated dana scott strachey elected distinguished fellow british computer society 1971 pioneering work computer science 1973 strachey along robert milne began write essay submitted adams prize competition continued work revising book form strachey seen heard recorded lighthill debate ai see lighthill report strachey contracted illness diagnosed jaundice period seeming recovery returned died infectious hepatitis 18 may 1975 developed combined programming language cpl influential set lecture notes fundamental concepts programming languages formalised distinction l- r- values seen c programming language strachey also coined term currying although invent underlying concept instrumental design ferranti pegasus computer macro language m4 derives much strachey gpm general purpose macrogenerator one earliest macro expansion languages department computer science university oxford christopher strachey professorship computing currently held samson abramsky frs november 2016 strachey 100 event held oxford university celebrate centenary strachey birth including viewing weston library oxford christopher strachey archive held bodleian library collection
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Programming language topics
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interrupt system programming interrupt signal processor emitted hardware software indicating event needs immediate attention interrupt alerts processor high-priority condition requiring interruption current code processor executing processor responds suspending current activities saving state executing function called interrupt handler interrupt service routine isr deal event interruption temporary interrupt handler finishes unless handling interrupt emitted fatal error processor resumes normal activities two types interrupts hardware interrupts software interrupts softirqs hardware interrupts used devices communicate require attention operating system. bare-metal program running cpu oses internally hardware interrupts implemented using electronic alerting signals sent processor external device either part computer disk controller external peripheral example pressing key keyboard moving mouse triggers hardware interrupts cause processor read keystroke mouse position unlike software type described hardware interrupts asynchronous occur middle instruction execution requiring additional care programming act initiating hardware interrupt referred interrupt request irq different devices usually associated different interrupts using unique value associated interrupt makes possible know hardware device caused interrupts interrupt values often called irq lines interrupt lines software interrupts also called exceptions unlike interrupts exceptions occur synchronously respect processor clock sometimes referred synchronous interrupts software interrupt caused either exceptional condition processor special instruction instruction set causes interrupt executed former often called trap exception used errors events occurring program execution exceptional enough handled within program example divide-by-zero exception thrown processor arithmetic logic unit commanded divide number zero instruction error impossible operating system catch exception decide usually aborting process displaying error message software interrupt instructions function similarly subroutine calls used variety purposes request services device drivers like interrupts sent disk controller request reading writing data disk interrupt interrupt handler number hardware interrupts limited number interrupt request irq lines processor may hundreds different software interrupts interrupts commonly used technique computer multitasking especially real-time computing system said interrupt-driven interrupts similar signals difference signals used inter-process communication ipc mediated kernel possibly via system calls handled processes interrupts mediated processor handled kernel kernel may pass interrupt signal process caused typical examples sigsegv sigbus sigill sigfpe hardware interrupts introduced optimization eliminating unproductive waiting time polling loops waiting external events first system use approach dyseac completed 1954 although earlier systems provided error trap functions interrupts may implemented hardware distinct component control lines may integrated memory subsystem implemented hardware distinct component interrupt controller circuit ibm pc programmable interrupt controller pic may connected interrupting device processor interrupt pin multiplex several sources interrupt onto one two cpu lines typically available implemented part memory controller interrupts mapped system memory address space interrupts categorized different types processors typically internal interrupt mask allows software ignore external hardware interrupts set setting clearing mask may faster accessing interrupt mask register imr pic disabling interrupts device cases x86 architecture disabling enabling interrupts processor act memory barrier however may actually slower interrupt leaves machine well-defined state called precise interrupt interrupt four properties interrupt meet requirements called imprecise interrupt phenomenon overall system performance severely hindered excessive amounts processing time spent handling interrupts called interrupt storm univac 1103 computer generally credited earliest use interrupts 1953 earlier univac 1951 arithmetic overflow either triggered execution two-instruction fix-up routine address 0 programmer option caused computer stop ibm 650 1954 incorporated first occurrence interrupt masking national bureau standards dyseac 1954 first use interrupts i/o ibm 704 first use interrupts debugging transfer trap could invoke special routine branch instruction encountered.the mit lincoln laboratory tx-2 system 1957 first provide multiple levels priority interrupts level-triggered interrupt interrupt signaled maintaining interrupt line high low logic level device wishing signal level-triggered interrupt drives interrupt request line active level high low holds level serviced ceases asserting line cpu commands otherwise handles condition caused signal interrupt typically processor samples interrupt input predefined times bus cycle state t2 z80 microprocessor interrupt n't active processor samples cpu n't see one possible use type interrupt minimize spurious signals noisy interrupt line spurious pulse often short noticed multiple devices may share level-triggered interrupt line designed interrupt line must pull-down pull-up resistor actively driven settles inactive state devices actively assert line indicate outstanding interrupt let line float actively drive signaling interrupt line asserted state one one sharing devices signaling outstanding interrupt level-triggered interrupts favored easy share interrupt request line without losing interrupts multiple shared devices interrupt time upon detecting assertion interrupt line cpu must search devices sharing interrupt request line one triggered interrupt detected servicing device cpu may recheck interrupt line status determine whether devices also need service line de-asserted cpu avoids checking remaining devices line since devices interrupt frequently others device interrupts particularly expensive careful ordering device checks employed increase efficiency original pci standard mandated level-triggered interrupts advantage sharing interrupts also serious problems sharing level-triggered interrupts long device line outstanding request service line remains asserted possible detect change status device deferring servicing low-priority device option would prevent detection service requests higher-priority devices device line cpu know service interrupt device permanently blocks interrupts devices edge-triggered interrupt interrupt signaled level transition interrupt line either falling edge high low rising edge low high device wishing signal interrupt drives pulse onto line releases line inactive state pulse short detected polled i/o special hardware may required detect multiple devices may share edge-triggered interrupt line designed interrupt line must pull-down pull-up resistor actively driven settles inactive state default sate devices signal interrupt briefly driving line non-default state let line float actively drive signaling interrupt type connection also referred open collector line carries pulses generated devices analogous pull cord buses trolleys passenger pull signal driver requesting stop however interrupt pulses different devices may merge occur close time avoid losing interrupts cpu must trigger trailing edge pulse e.g rising edge line pulled driven low detecting interrupt cpu must check devices service requirements edge-triggered interrupts suffer problems level-triggered interrupts sharing service low-priority device postponed arbitrarily interrupts high-priority devices continue received get serviced device cpu know service may raise spurious interrupts wo n't interfere interrupt signaling devices however easy edge-triggered interrupt missed example interrupts masked period unless type hardware latch records event impossible recover problem caused many lockups early computer hardware processor know expected something modern hardware often one interrupt status registers latch interrupts requests well-written edge-driven interrupt handling code check registers ensure events missed elderly industry standard architecture isa bus uses edge-triggered interrupts without mandating devices able share irq lines mainstream isa motherboards include pull-up resistors irq lines well-behaved isa devices sharing irq lines work fine parallel port also uses edge-triggered interrupts many older devices assume exclusive use irq lines making electrically unsafe share 3 ways multiple devices sharing line raised first exclusive conduction switching exclusive connection pins next bus connected line listening cards bus must know talk talk ie isa bus talking triggered two ways accumulation latch logic gates logic gates expect continual data flow monitored key signals accumulators trigger remote side excites gate beyond threshold thus negotiated speed required speed versus distance advantages trigger generally method excitation detected rising edge falling edge threshold oscilloscope trigger wide variety shapes conditions triggering software interrupts must built software os app c app trigger table table functions header app os know use appropriately related hardware however confuse hardware interrupts signal cpu cpu enacts software table functions similarly software interrupts systems use hybrid level-triggered edge-triggered signaling hardware looks edge also verifies interrupt signal stays active certain period time common use hybrid interrupt nmi non-maskable interrupt input nmis generally signal major – even catastrophic – system events good implementation signal tries ensure interrupt valid verifying remains active period time 2-step approach helps eliminate false interrupts affecting system message-signaled interrupt use physical interrupt line instead device signals request service sending short message communications medium typically computer bus message might type reserved interrupts might pre-existing type memory write message-signalled interrupts behave much like edge-triggered interrupts interrupt momentary signal rather continuous condition interrupt-handling software treats two much manner typically multiple pending message-signaled interrupts message virtual interrupt line allowed merge closely spaced edge-triggered interrupts merge message-signalled interrupt vectors shared extent underlying communication medium shared additional effort required identity interrupt indicated pattern data bits requiring separate physical conductor many distinct interrupts efficiently handled reduces need sharing interrupt messages also passed serial bus requiring additional lines pci express serial computer bus uses message-signaled interrupts exclusively push button analogy applied computer systems term doorbell doorbell interrupt often used describe mechanism whereby software system signal notify computer hardware device work done typically software system place data well-known mutually agreed upon memory location ring doorbell writing different memory location different memory location often called doorbell region may even multiple doorbells serving different purposes region act writing doorbell region memory rings bell notifies hardware device data ready waiting hardware device would know data valid acted upon would typically write data hard disk drive send network encrypt etc term doorbell interrupt usually misnomer similar interrupt causes work done device however doorbell region sometimes implemented polled region sometimes doorbell region writes physical device registers sometimes doorbell region hardwired directly physical device registers either writing directly physical device registers may cause real interrupt occur device central processor unit cpu one doorbell interrupts compared message signaled interrupts similarities multiple devices sharing interrupt line triggering style act spurious interrupt sources respect many devices one line workload servicing interrupts grows proportion square number devices therefore preferred spread devices evenly across available interrupt lines shortage interrupt lines problem older system designs interrupt lines distinct physical conductors message-signaled interrupts interrupt line virtual favored new system architectures pci express relieve problem considerable extent devices poorly designed programming interface provide way determine whether requested service may lock otherwise misbehave serviced want devices tolerate spurious interrupts also tolerate sharing interrupt line isa cards due often cheap design construction notorious problem devices becoming much rarer hardware logic becomes cheaper new system architectures mandate shareable interrupts interrupts provide low overhead good latency low load degrade significantly high interrupt rate unless care taken prevent several pathologies various forms livelocks system spends time processing interrupts exclusion required tasks extreme conditions large number interrupts like high network traffic may completely stall system avoid problems operating system must schedule network interrupt handling carefully schedules process execution multi-core processors additional performance improvements interrupt handling achieved receive-side scaling rss multiqueue nics used nics provide multiple receive queues associated separate interrupts routing interrupts different cores processing interrupt requests triggered network traffic received single nic distributed among multiple cores distribution interrupts among cores performed automatically operating system routing interrupts usually referred irq affinity manually configured purely software-based implementation receiving traffic distribution known receive packet steering rps distributes received traffic among cores later data path part interrupt handler functionality advantages rps rss include requirements specific hardware advanced traffic distribution filters reduced rate interrupts produced nic downside rps increases rate inter-processor interrupts ipis receive flow steering rfs takes software-based approach accounting application locality performance improvements achieved processing interrupt requests cores particular network packets consumed targeted application typical uses interrupts include following system timers disk i/o power-off signals traps interrupts exist transfer data bytes using uarts ethernet sense key-presses control motors anything else equipment must another typical use generate periodic interrupts dividing output crystal oscillator interrupt handler count interrupts order processor keep time periodic interrupts often used os task scheduler reschedule priorities running processes older computers generated periodic interrupts power line frequency controlled utilities eliminate long-term drift electric clocks example disk interrupt signals completion data transfer disk peripheral process waiting read write file starts another example power-off interrupt predicts requests loss power allowing computer equipment perform orderly shut-down also interrupts used typeahead features buffering events like keystrokes interrupts used allow emulation instructions unimplemented certain models computer line example floating point instructions may implemented hardware systems emulated lower-cost systems execution unimplemented instruction cause interrupt operating system interrupt handler recognize occurrence unimplemented instruction interpret instruction software routine return interrupting program instruction executed provides application software portability across entire line
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Computer architecture
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world cup soccer italia '90 world cup soccer italia '90 football video game released various home computers 1990 virgin mastertronic officially licensed game tournament known simply italia '90 tronix budget reissues different games also released virgin mastertronic sega consoles world cup italia '90 second licensed game based fifa world cup featuring official logo mascot first ill-fated world cup carnival 1986 fifa world cup game based 1989 game world trophy soccer originally arcade game mastertronic amiga-based arcadia machines virgin games bought mastertronic 1988 game released amiga atari st commodore 64 published virgin mastertronic virgin mastertronic obtained official licence world cup sponsor olivetti adapted world trophy soccer game renaming world cup soccer italia '90 also porting amstrad cpc dos zx spectrum attempts made change set tournament teams available match actual 1990 world cup game presented bird's-eye view player gets near goal switches 3d view penalty area player must try score defender arrives screen player choose play england belgium italy spain teams correct coloured strips tournament actual world cup game received mixed reviews amiga action gave overall score 62 reviewers split reviewer alex said graphics well implemented impressed use first-person perspective shooting saving goal reviewer doug concluded 've played fair share soccer games world cup tie-in certainly best game quite hard get hang even get used controls game still n't play well zzap gave scores 44 amiga version 42 commodore 64 praise given graphics review overwhelmingly negative complaints focusing 3d goalmouth section said n't really work unfair anyway mostly despite officially licensed game accurately reflect tournament someone tell world cup may official licence lacks official fixtures teams game became best seller number one selling spectrum game august september 1990 also unofficial italia '90 games including italy 1990 published u.s. gold released official games 1986 1994 tournaments italy '90 soccer released italy 1988 italia 1990 budget publisher codemasters
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Computer architecture
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john romkey john romkey donald w. gillies developed first industry tcp/ip stack ibm pc 1983 founding ftp software commercial tcp/ip stack provider 1986 romkey authored first network analyzer netwatch predating network general sniffer served iab simon hackett connected first appliance toaster internet romkey currently owner blue forest research consulting company mit john romkey authored first tcp/ip stack ms-dos founder ftp software company provided commercial package ms-dos ms windows advent microsoft tcp/ip stacks starting windows 95 ftp software well commercial tcp/ip stacks providers driven business
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Internet protocols
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service data objects service data objects technology allows heterogeneous data accessed uniform way sdo specification originally developed 2004 joint collaboration oracle bea ibm approved java community process jsr 235 version 2.0 specification introduced november 2005 key part service component architecture originally technology known web data objects wdo shipped ibm websphere application server 5.1 ibm websphere studio application developer 5.1.2 similar technologies jdo emf jaxb ado.net service data objects denote use language-agnostic data structures facilitate communication structural tiers various service-providing entities require use tree structure root node provide traversal mechanisms breadth/depth-first allow client programs navigate elements objects static fixed number fields dynamic map-like structure allowing unlimited fields specification defines meta-data fields object graph also provided change summaries allow receiving programs act efficiently specification developed ibm rogue wave oracle sap siebel sybase xcalia software ag within oasis member section open csa since april 2007 collaborative work materials remain collaboration platform open soa informal group actors industry following sdo products available open source implementations sdo specification versions history found
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Programming language topics
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klout klout website mobile app used social media analytics rate users according online social influence via klout score numerical value 1 100 determining user score klout measured size user social media network correlated content created measure users interact content klout launched 2008 lithium technologies acquired site march 2014 closed service may 25 2018 klout used bing facebook foursquare google+ instagram linkedin twitter youtube wikipedia data create klout user profiles assigned unique klout score klout scores ranged 1 100 higher scores corresponding higher ranking breadth strength one online social influence twitter users assigned score users registered klout could link multiple social networks network data aggregated influence user klout score klout measured influence using data points twitter following count follower count retweets list memberships many spam/dead accounts following influential people retweet unique mentions information combined data number social network followings interactions come klout score social networks influenced user klout score twitter facebook google+ linkedin individuals pages corporate/business youtube instagram klout well wikipedia accounts flickr blogger tumblr last.fm wordpress bing also linked users however weigh klout score microsoft announced strategic investment klout september 2012 whereby bing would access klout influence technology klout would access bing search data scoring algorithm klout scores supplemented three nominally specific measures klout calls true reach amplification network impact true reach based size user engaged audience actively engage user messages amplification score relates likelihood one messages generate actions retweets mentions likes comments network impact reflects computed influence value person engaged audience primary business model klout involved companies paying klout perks campaigns company offers free services products klout users match pre-defined set criteria including scores topics geographic locations klout users receive perks obligation write hope effectively advertise products social media klout offered perks program since 2010 according klout ceo joe fernandez 50 partnerships established november 2011 may 2013 klout announced users claimed 1 million perks across 400 campaigns march 2013 klout announced intention begin displaying business analytics aimed helping business brand users learn online audiences september 2012 klout announced information-sharing partnership bing search engine showing klout scores bing searches allowing klout users post items selected bing social media several objections klout methodology raised regarding process scores generated overall societal effect critics pointed klout scores representative influence person really highlighted barack obama president united states lower influence score number bloggers social critics argued klout score devalued authentic online communication promoted social ranking stratification trying quantify human interaction klout attempted address criticisms updated algorithms barack obama importance better reflected site criticized violating privacy minors exploiting users profit john scalzi described principle behind klout operation socially evil exploitation users status anxiety charles stross described service internet equivalent herpes blogging analysis klout terms conditions revealed company business model illegal united kingdom conflicted data protection act 1998 stross advised readers delete klout accounts opt klout services ben rothke concluded klout work cut seems like need beta longer klout applauded trying measure monstrosity called social influence results influence truth carry little influence klout criticised opacity methodology claimed advanced machine learning techniques used leveraging network theory sean golliher analysed klout scores twitter users found simple logarithm number followers sufficient explain 95 variance november 2015 klout released academic paper discussing methodology ieee bigdata 2015 conference spite controversy employers made hiring decisions based klout scores reported article wired man recruited vp position fifteen years experience consulting companies including america online ford kraft eliminated candidate specifically klout score time 34 favour candidate score 67
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Web technology
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death star ilm death star name render farm owned industrial light magic ilm cluster computer originally built sgi since converted linux system built racksaver verari systems amd processors system originally 1,500 processors 750 nodes figure doubled ilm tends quiet supercomputer current configuration known
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Distributed computing architecture
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xedit xedit visual editor vm/cms using block mode ibm 3270 terminals line-mode terminals also supported xedit much line-oriented modern pc unix editors example xedit supports automatic line numbers many commands operate blocks lines pair features allows selective line column editing command example hides lines matching described pattern col column command allows hiding columns specified hence changing example word appears columns 24 thru 28 yes lines word flexible doable another feature command line allows user type arbitrary editor commands ibm 3270 terminals transmit data computer certain special keys pressed program function key pfk program access key pak xedit less interactive many pc unix editors example continuous spell-checking user types problematic notable features screen layout xedit macros scripts written rexx exec 2 exec xedit exposes majority internal state macro environment allowing macros easily read set internal variables control operation kedit 5 dos os/2 supports external rexx interpreter native os/2 rexx quercus rexx dos quercus rexx replacing older mansfield rexx rather limited kexx subset keditw 1.6.1 windows supports internal kexx 5.62 version rexx language macros arranged codice_1 file format xedit written ibm employee xavier de lamberterie first released 1980 predecessor edit sp sp initialism system product used ibm key influences edit older editor cms edgar ibm program product editor cms xedit supported many edgar commands sos screen output simulation major one xedit also supported exec 2 predecessor rexx pcs unix computers began supplant ibm 3270 terminals users wanted text editors resembled xedit accustomed fill need several developers provided similar programs kedit mansfield software group inc. first xedit clone although originally released 1983 first major release version 3.53 dos released 1985 1990 kedit 4.0 version supporting os/2 included command last version dos os/2 kedit 5.0p4 keditw windows version 1.6.1 dated december 2012 earlier windows versions kedit 1.6 supports syntax highlighting various languages including c cobol fortran html java pascal xbase defined codice_2 file format kedit supports built-in rexx-subset called kexx mansfield software created first non-ibm implementation rexx personal rexx 1985 december 2012 mansfield software released 1.6.1 provide compatibility windows 8 extended support least june 32bit versions work also 64bit versions windows 7 vista directly support unicode may 2018 kedit supports windows 10 mansfield promised website support least end 2018 email support least june 2019 sedit first released 1989 another implementation windows unix supports variant rexx language called s/rexx announced 1994 hessling editor written compatibility kedit xedit mind uses regina open source version rexx begun 1990 first released august 1992 also built several implementations rexx including uni-rexx
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Operating systems
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monica s. lam monica sin-ling lam professor computer science department stanford founder moka5 omlet monica lam received b.sc university british columbia 1980 ph.d. computer science carnegie mellon university 1987 lam joined faculty computer science stanford university 1988 contributed research wide range computer systems topics including compilers program analysis operating systems security computer architecture high-performance computing currently directs mobisocial laboratory stanford lam cofounder ceo omlet first mobisocial product launched 2014 omlet open decentralized social networking tool based extensible chat platform collective project research group developed concept livepc subscribers livepc automatically run latest published pc virtual images reboot approach allows computers managed scalably securely 2005 group started company called mokafive transfer technology industry another research project program analysis group developed collection tools improving software security reliability developed first scalable context-sensitive inclusion-based pointer analysis freely available tool called bddbddb allows programmers express context-sensitive analyses simply writing datalog queries tools developed include griffin static dynamic analysis finding security vulnerabilities web applications sql injection static dynamic program query language called pql static memory leak detector called clouseau dynamic buffer overrun detector called cred dynamic error diagnosis tool called diduce previously lam led suif stanford university intermediate format compiler project produced widely used compiler infrastructure known locality optimizations interprocedural parallelization many compiler techniques developed adopted industry research projects included architecture compiler cmu warp machine systolic array vliw processors stanford dash distributed shared memory machine 1998 took sabbatical leave stanford help start tensilica inc. company specializes configurable processor cores lam chaired acm sigplan programming languages design implementation conference 2000 served editorial board acm transactions computer systems numerous program committees conferences languages compilers pldi popl operating systems sosp computer architecture asplos isca lam received following awards honors
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Programming language topics
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user interface privilege isolation user interface privilege isolation uipi technology introduced windows vista windows server 2008 combat shatter attack exploits making use mandatory integrity control prevents processes lower integrity level il sending messages higher il processes except specific set ui messages window messages designed communicate user action processes however used run arbitrary code receiving process context used malicious low il process run arbitrary code context higher il process constitutes unauthorized privilege escalation restricting access vectors code execution data injection uipi mitigate kinds attacks uipi mandatory integrity control generally security feature security boundary ui accessibility applications allowed bypass uipi setting uiaccess value true part manifest file however flag honored windows uipi application must installed program files windows directory application must signed valid code signing authority install application either locations requires least user local administrator privilege running elevated process high integrity level thus malware trying move position bypass uipi must microsoft office 2010 uses uipi protected view sandbox prohibit potentially unsafe documents modifying components files resources system
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Operating systems
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manifest expression manifest expression programming language construct compiler analyse deduce values take without execute program information enable compiler optimizations particular loop nest optimization parallelization data dependency analysis expression called manifest computed outer loop counters constants formal definition given control flow loop condition regulated manifest expressions called manifest loop resp condition practical applications manifest expressions also require expression integral affine stepwise affine variables manifest expression compile time computable function depends manifest variable reference defined variable reference single unambiguous definition particularly relevant procedural languages pointer analysis and/or data flow analysis required find expression defines variable value several defining expressions possible e.g variable assigned condition variable reference manifest
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Programming language topics
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huawei emui huawei emui formerly known emotion ui custom mobile operating system based android huawei uses huawei honor-branded smartphone devices 30 december 2012 huawei introduced emotion ui 1.0 based android 4.0 features voice assistant app chinese customizable homescreens theme-switching company rolled installation files ascend p1 website company claims “ probably world ’ emotional system ” 4 september 2014 company announced emui 3.0 along ascend mate 7 pre-ifa event berlin user interface ever since called emui instead emotion ui features new app store china markets late 2015 huawei launched emui 4.0 redesigned interface based android 6.0 along huawei mate 8 2016 emui 5.0 introduced huawei mate 9 2017 rom images removed official website huawei says provide convenient satisfactory update service since users must rely over-the-air ota updates late 2017 emui 8.0 launched skipping emui 6.0 7.0 combine android versions along huawei mate 10 release emphasises different ai-capabilities huawei unveiled emui 9.0 german consumer electronics exhibition ifa 2018 version emui based android pie new features improvements include new gesture navigation system moving many features bottom screen easier one-handed use reorganized settings page digital balance dashboard gpu turbo 2.0 performance improvements etc update version named emui 9.1 released june 2019 new features improvements include gpu turbo 3.0 new file system called extendable read-only file system erofs file sharing feature onehop huawei vlog improvements new ar features etc emui 10 based android q announced 9 august 2019 huawei developer conference 2019 beta version emui 10 set released 8 september 2019 first coming huawei p30 p30 pro flagship smartphones new features improvements include system-wide dark mode redesigned camera app new emui logo new system font permission control changes introduced android q tweaks animations etc
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Operating systems
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ucspi-tcp ucspi-tcp public domain unix tcp command-line tool building tcp client-server applications consists super-server tcpserver tcpclient application life qmail dave sill 2 january 2006 appendix b.3 ucspi-tcp acronym unix client-server program interface tcp pronounced ooks-pie tee see pee tcpserver features built-in tcp wrapper-like access control
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Internet protocols
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ipv4 internet protocol version 4 ipv4 fourth version internet protocol ip one core protocols standards-based internetworking methods internet packet-switched networks ipv4 first version deployed production arpanet 1983 still routes internet traffic today despite ongoing deployment successor protocol ipv6 ipv4 described ietf publication rfc 791 september 1981 replacing earlier definition rfc 760 january 1980 ipv4 uses 32-bit address space limits number unique hosts 4,294,967,296 2 large blocks reserved special networking methods internet protocol protocol defines enables internetworking internet layer internet protocol suite essence forms internet uses logical addressing system performs routing forwarding packets source host next router one hop closer intended destination host another network ipv4 connectionless protocol operates best effort delivery model guarantee delivery assure proper sequencing avoidance duplicate delivery aspects including data integrity addressed upper layer transport protocol transmission control protocol tcp ipv4 uses 32-bit addresses limits address space 2 addresses ipv4 reserves special address blocks private networks ~18 million addresses multicast addresses ~270 million addresses ipv4 addresses may represented notation expressing 32-bit integer value often written dot-decimal notation consists four octets address expressed individually decimal numbers separated periods example quad-dotted ip address 192.0.2.235 represents 32-bit decimal number 3221226219 hexadecimal format 0xc00002eb may also expressed dotted hex format 0xc0.0x00.0x02.0xeb octal byte values 0300.0000.0002.0353 cidr notation combines address routing prefix compact format address followed slash character count consecutive 1 bits routing prefix subnet mask address format common use classful networking practiced example loopback address host 127.0.0.1 commonly written 127.1 given belonged class-a network eight bits network mask 24 bits host number original design ipv4 ip address divided two parts network identifier significant octet address host identifier rest address latter also called rest field structure permitted maximum 256 network identifiers quickly found inadequate overcome limit most-significant address octet redefined 1981 create network classes system later became known classful networking revised system defined five classes classes b c different bit lengths network identification rest address used previously identify host within network different sizes fields different classes network class different capacity addressing hosts addition three classes addressing hosts class defined multicast addressing class e reserved future applications dividing existing classful networks subnets began 1985 publication division made flexible introduction variable-length subnet masks vlsm 1987 1993 based work introduced classless inter-domain routing cidr expressed number bits significant instance /24 class-based scheme dubbed classful contrast cidr designed permit repartitioning address space smaller larger blocks addresses could allocated users hierarchical structure created cidr managed internet assigned numbers authority iana regional internet registries rirs rir maintains publicly searchable whois database provides information ip address assignments internet engineering task force ietf internet assigned numbers authority iana restricted general use various reserved ip addresses special purposes notably addresses used multicast traffic provide addressing space unrestricted uses private networks section begin=ipv4-special-address-blocks/ approximately four billion addresses defined ipv4 18 million addresses three ranges reserved use private networks packets addresses ranges routable public internet ignored public routers therefore private hosts directly communicate public networks require network address translation routing gateway purpose section begin=ipv4-private-networks/ since two private networks e.g. two branch offices directly interoperate via public internet two networks must bridged across internet via virtual private network vpn ip tunnel encapsulates packets including headers containing private addresses protocol layer transmission across public network additionally encapsulated packets may encrypted transmission across public networks secure data rfc 3927 defines special address block 169.254.0.0/16 link-local addressing addresses valid link local network segment point-to-point connection directly connected host uses addresses routable like private addresses addresses source destination packets traversing internet addresses primarily used address autoconfiguration zeroconf host obtain ip address dhcp server internal configuration methods address block reserved standards existed address autoconfiguration microsoft created implementation called automatic private ip addressing apipa deployed millions machines became de facto standard many years later may 2005 ietf defined formal standard rfc 3927 entitled dynamic configuration ipv4 link-local addresses class network 127.0.0.0 classless network 127.0.0.0/8 reserved loopback ip packets whose source addresses belong network never appear outside host modus operandi network expands upon loopback interface networks subnet masks least 24 bits i.e class c networks classful networking networks cidr suffixes /24 /30 255.255.255.0–255.255.255.252 may address ending 0 255 classful addressing prescribed three possible subnet masks class 255.0.0.0 /8 class b 255.255.0.0 /16 class c 255.255.255.0 /24 example subnet 192.168.5.0/255.255.255.0 192.168.5.0/24 identifier 192.168.5.0 commonly used refer entire subnet avoid ambiguity representation address ending octet 0 reserved broadcast address address allows information sent interfaces given subnet rather specific machine generally broadcast address found obtaining bit complement subnet mask performing bitwise operation network identifier words broadcast address last address address range subnet example broadcast address network 192.168.5.0 192.168.5.255 networks size /24 larger broadcast address always ends 255 however mean every address ending 0 255 used host address example /16 subnet 192.168.0.0/255.255.0.0 equivalent address range 192.168.0.0–192.168.255.255 broadcast address 192.168.255.255 one use following addresses hosts even though end 255 192.168.1.255 192.168.2.255 etc also 192.168.0.0 network identifier must assigned interface addresses 192.168.1.0 192.168.2.0 etc. may assigned despite ending 0 past conflict network addresses broadcast addresses arose software used non-standard broadcast addresses zeros instead ones networks smaller /24 broadcast addresses necessarily end 255 example cidr subnet 203.0.113.16/28 broadcast address 203.0.113.31 hosts internet usually known names e.g. www.example.com primarily ip address used routing network interface identification use domain names requires translating called resolving addresses vice versa analogous looking phone number phone book using recipient name translation addresses domain names performed domain name system dns hierarchical distributed naming system allows subdelegation name spaces dns servers since 1980s apparent pool available ipv4 addresses depleted rate initially anticipated original design network address system main market forces accelerated ipv4 address depletion included threat exhaustion motivated introduction number remedial technologies classful networks classless inter-domain routing cidr methods network address translation nat strict usage-based allocation policies provide long-term solution pending address exhaustion ipv6 created 1990s made many addresses available increasing address size 128 bits ipv6 commercial deployment since 2006 primary address pool internet maintained iana exhausted 3 february 2011 last 5 blocks allocated 5 rirs apnic first rir exhaust regional pool 15 april 2011 except small amount address space reserved transition ipv6 allocated much restricted policy accepted standard long term solution use ipv6 increased address size 128 bits providing vastly increased address space also allows improved route aggregation across internet offers large subnetwork allocations minimum 2 host addresses end-users however ipv4-only hosts directly communicate ipv6-only hosts ipv6 alone provide immediate solution ipv4 exhaustion problem migration ipv6 progress completion expected take considerable time ip packet consists header section data section ip packet data checksum footer data section typically link layer encapsulates ip packets frames crc footer detects errors typically end-to-end tcp layer checksum detects errors ipv4 packet header consists 14 fields 13 required 14th field optional aptly named options fields header packed significant byte first big endian diagram discussion significant bits considered come first msb 0 bit numbering significant bit numbered 0 version field actually found four significant bits first byte example internet header length ihl field 4 bits number 32-bit words since ipv4 header may contain variable number options field specifies size header also coincides offset data minimum value field 5 indicates length 5 × 32 bits 160 bits 20 bytes 4-bit field maximum value 15 words 15 × 32 bits 480 bits 60 bytes fragment offset field measured units eight-byte blocks 13 bits long specifies offset particular fragment relative beginning original unfragmented ip datagram first fragment offset zero allows maximum offset 2 – 1 × 8 65,528 bytes would exceed maximum ip packet length 65,535 bytes header length included 65,528 20 65,548 bytes options field often used note value ihl field must include enough extra 32-bit words hold options plus padding needed ensure header contains integer number 32-bit words list options may terminated eol end options list 0x00 option necessary end options would otherwise coincide end header possible options put header follows packets containing options may considered dangerous routers blocked packet payload included checksum contents interpreted based value protocol header field common payload protocols see list ip protocol numbers complete list internet protocol enables traffic networks design accommodates networks diverse physical nature independent underlying transmission technology used link layer networks different hardware usually vary transmission speed also maximum transmission unit mtu one network wants transmit datagrams network smaller mtu may fragment datagrams ipv4 function placed internet layer performed ipv4 routers thus require implementation higher layers function routing ip packets contrast ipv6 next generation internet protocol allow routers perform fragmentation hosts must determine path mtu sending datagrams router receives packet examines destination address determines outgoing interface use interface mtu packet size bigger mtu fragment df bit packet header set 0 router may fragment packet router divides packet fragments max size fragment mtu minus ip header size 20 bytes minimum 60 bytes maximum router puts fragment packet fragment packet following changes example mtu 1,500 bytes header size 20 bytes fragment offsets would multiples formula_1 multiples 0 185 370 555 740 ... possible packet fragmented one router fragments fragmented another router example packet 4,520 bytes including 20 bytes ip header without options fragmented two packets link mtu 2,500 bytes total data size preserved 2480 bytes 2020 bytes 4500 bytes offsets formula_2 formula_3 link mtu 1,500 bytes fragment results two fragments data size preserved 1480 1000 2480 1480 540 2020 also case fragments bit remains 1 fragments came 1 last fragment arrives works usual mf bit set 0 last one course identification field continues value re-fragmented fragments way even fragments re-fragmented receiver knows initially started packet last offset last data size used calculate total data size formula_4 receiver knows packet fragment least one following conditions true receiver identifies matching fragments using foreign local address protocol id identification field receiver reassembles data fragments id using fragment offset fragments flag receiver receives last fragment fragments flag set 0 calculate size original data payload multiplying last fragment offset eight adding last fragment data size given example calculation 495*8 540 4500 bytes receiver fragments reassembled correct sequence according offsets form original datagram ip addresses tied permanent manner hardware identifications indeed network interface multiple ip addresses modern operating systems hosts routers need additional mechanisms identify relationship device interfaces ip addresses order properly deliver ip packet destination host link address resolution protocol arp performs ip-address-to-hardware-address translation ipv4 hardware address also called mac address addition reverse correlation often necessary example ip host booted connected network needs determine ip address unless address preconfigured administrator protocols inverse correlations exist internet protocol suite currently used methods dynamic host configuration protocol dhcp bootstrap protocol bootp infrequently reverse arp
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Internet protocols
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ipv6 internet protocol version 6 ipv6 recent version internet protocol ip communications protocol provides identification location system computers networks routes traffic across internet ipv6 developed internet engineering task force ietf deal long-anticipated problem ipv4 address exhaustion ipv6 intended replace ipv4 december 1998 ipv6 became draft standard ietf subsequently ratified internet standard 14 july 2017 devices internet assigned unique ip address identification location definition rapid growth internet commercialization 1990s became evident far addresses would needed connect devices ipv4 address space available 1998 internet engineering task force ietf formalized successor protocol ipv6 uses 128-bit address theoretically allowing 2 approximately addresses actual number slightly smaller multiple ranges reserved special use completely excluded use total number possible ipv6 addresses times many ipv4 uses 32-bit addresses provides approximately 4.3 billion addresses two protocols designed interoperable complicating transition ipv6 however several ipv6 transition mechanisms devised permit communication ipv4 ipv6 hosts ipv6 provides technical benefits addition larger addressing space particular permits hierarchical address allocation methods facilitate route aggregation across internet thus limit expansion routing tables use multicast addressing expanded simplified provides additional optimization delivery services device mobility security configuration aspects considered design protocol ipv6 addresses represented eight groups separated colons four hexadecimal digits full representation may simplified several methods notation example 2001:0db8:0000:0000:0000:8a2e:0370:7334 becomes 2001 db8 :8a2e:370:7334 ipv6 internet layer protocol packet-switched internetworking provides end-to-end datagram transmission across multiple ip networks closely adhering design principles developed previous version protocol internet protocol version 4 ipv4 addition offering addresses ipv6 also implements features present ipv4 simplifies aspects address configuration network renumbering router announcements changing network connectivity providers simplifies processing packets routers placing responsibility packet fragmentation end points ipv6 subnet size standardized fixing size host identifier portion address 64 bits network security design requirement ipv6 architecture included original specification ipsec addressing architecture ipv6 defined allows three different types transmission unicast anycast multicast internet protocol version 4 ipv4 first publicly used version internet protocol ipv4 developed research project defense advanced research projects agency darpa united states department defense agency becoming foundation internet world wide web ipv4 includes addressing system uses numerical identifiers consisting 32 bits addresses typically displayed quad-dotted notation decimal values four octets range 0 255 8 bits per number thus ipv4 provides addressing capability 2 approximately 4.3 billion addresses address exhaustion initially concern ipv4 version originally presumed test darpa networking concepts first decade operation internet became apparent methods developed conserve address space early 1990s even redesign addressing system using classless network model became clear would suffice prevent ipv4 address exhaustion changes internet infrastructure needed last unassigned top-level address blocks 16 million ipv4 addresses allocated february 2011 internet assigned numbers authority iana five regional internet registries rirs however rir still available address pools expected continue standard address allocation policies one /8 classless inter-domain routing cidr block remains blocks 1024 addresses /22 provided rirs local internet registry lir september 2015 asia-pacific network information centre apnic réseaux ip européens network coordination centre ripe_ncc latin america caribbean network information centre lacnic american registry internet numbers arin reached stage leaves african network information center afrinic sole regional internet registry still using normal protocol distributing ipv4 addresses november 2018 afrinic minimum allocation /22 1024 ipv4 addresses lir may receive additional allocation 80 address space utilized widely expected internet use ipv4 alongside ipv6 foreseeable future direct communication ipv4 ipv6 network protocols possible internet data transmitted form network packets ipv6 specifies new packet format designed minimize packet header processing routers headers ipv4 packets ipv6 packets significantly different two protocols interoperable however transport application-layer protocols need little change operate ipv6 exceptions application protocols embed internet-layer addresses file transfer protocol ftp network time protocol ntp new address format may cause conflicts existing protocol syntax main advantage ipv6 ipv4 larger address space length ipv6 address 128 bits compared 32 bits ipv4 address space therefore 2 approximately addresses 340,282,366,920,938,463,463,374,607,431,768,211,456 approximately 340 undecillion 340 billion billion billion billion addresses ipv4 addresses reserved special uses addition ipv4 address space poorly allocated 2011 approximately 14 available addresses utilized numbers large intent designers ipv6 address space assure geographical saturation usable addresses rather longer addresses simplify allocation addresses enable efficient route aggregation allow implementation special addressing features ipv4 complex classless inter-domain routing cidr methods developed make best use small address space standard size subnet ipv6 2 addresses square size entire ipv4 address space thus actual address space utilization rates small ipv6 network management routing efficiency improved large subnet space hierarchical route aggregation multicasting transmission packet multiple destinations single send operation part base specification ipv6 ipv4 optional although commonly implemented feature ipv6 multicast addressing features protocols common ipv4 multicast also provides changes improvements eliminating need certain protocols ipv6 implement traditional ip broadcast i.e transmission packet hosts attached link using special broadcast address therefore define broadcast addresses ipv6 result achieved sending packet link-local nodes multicast group address ff02 :1 analogous ipv4 multicasting address 224.0.0.1 ipv6 also provides new multicast implementations including embedding rendezvous point addresses ipv6 multicast group address simplifies deployment inter-domain solutions ipv4 difficult organization get even one globally routable multicast group assignment implementation inter-domain solutions arcane unicast address assignments local internet registry ipv6 least 64-bit routing prefix yielding smallest subnet size available ipv6 also 64 bits assignment possible embed unicast address prefix ipv6 multicast address format still providing 32-bit block least significant bits address approximately 4.2 billion multicast group identifiers thus user ipv6 subnet automatically available set globally routable source-specific multicast groups multicast applications ipv6 hosts configure automatically connected ipv6 network using neighbor discovery protocol via internet control message protocol version 6 icmpv6 router discovery messages first connected network host sends link-local router solicitation multicast request configuration parameters routers respond request router advertisement packet contains internet layer configuration parameters routers present special case requirements address configuration often sources autoconfiguration information router prefix advertisements stateless configuration routers achieved special router renumbering protocol renumbering existing network new connectivity provider different routing prefixes major effort ipv4 ipv6 however changing prefix announced routers principle renumber entire network since host identifiers least-significant 64 bits address independently self-configured host ipv6 stateless address auto-configuration unsuitable ipv6 like ipv4 allows stateful configuration dynamic host configuration protocol version 6 dhcpv6 manual static configuration hosts like ipv4 ipv6 supports globally unique ip addresses design ipv6 intended re-emphasize end-to-end principle network design originally conceived establishment early internet approach device network unique address globally reachable directly location internet unique ip address potentially used track network activity device moreover using ipv6 address auto-configuration interface identifier mac address network card used make public ipv6 interface identifier unique exposing type hardware used providing unique handle user online activity autoconfiguration basis network card mac address therefore particular privacy concern mobile devices laptops access internet different local area networks mac based interface identifier would always stay thus mac address based interface identifier used track movement usage particular mobile device ipv6 developed mid-90s internet accessed large number mobile devices privacy priority become today address privacy concerns slaac protocol updated mechanisms termed “ privacy extensions stateless address autoconfiguration ipv6 ” codified rfc 4941 rfc 7217 rfc 8064 prevents ipv6 address leaking mac address device first method generate interface identifier randomly interface identifier generated two devices local area network duplicate address detection dad function ipv6 neighbor discovery protocol ndp resolve situation slaac privacy extension also implements time configurable ipv6 interface addresses discarded new interface identifier generated typically time configured 24 hours ipv6 autoconfiguration generate set new ipv6 host address every day stable address needed another method generate interface identifier secret key network prefix since 2017 method codified rfc 7217 preferred stable private address according ietf late 2014 slaac privacy extensions functionality implemented following operating systems microsoft windows windows xp versions mac os x 10.7 onward versions ios since 4.3 versions android since 4.0 ice cream sandwich privacy extension enabled default windows since xp sp1 os x since 10.7 ios since version 4.3 linux distributions enabled privacy extensions well internet protocol security ipsec originally developed ipv6 found widespread deployment first ipv4 re-engineered ipsec mandatory part ipv6 protocol implementations internet key exchange ike recommended rfc 6434 inclusion ipsec ipv6 implementations downgraded recommendation considered impractical require full ipsec implementation types devices may use ipv6 however rfc 4301 ipv6 protocol implementations implement ipsec need implement ikev2 need support minimum set cryptographic algorithms requirement help make ipsec implementations interoperable devices different vendors ipsec authentication header ah encapsulating security payload header esp implemented ipv6 extension headers packet header ipv6 simpler ipv4 header many rarely used fields moved optional header extensions simplified ipv6 packet header process packet forwarding routers simplified although ipv6 packet headers least twice size ipv4 packet headers packet processing routers generally efficient less processing required routers due headers aligned match common word sizes moreover ipv6 header include checksum ipv4 header checksum calculated ipv4 header recalculated routers every time time live called hop limit ipv6 protocol reduced one absence checksum ipv6 header furthers end-to-end principle internet design envisioned processing network occurs leaf nodes integrity protection data encapsulated ipv6 packet assumed assured link layer error detection higher-layer protocols namely transmission control protocol tcp user datagram protocol udp transport layer thus ipv4 allowed udp datagram headers checksum indicated 0 header field ipv6 requires checksum udp headers ipv6 routers perform ip fragmentation ipv6 hosts required either perform path mtu discovery perform end-to-end fragmentation send packets larger default maximum transmission unit mtu 1280 octets unlike mobile ipv4 mobile ipv6 avoids triangular routing therefore efficient native ipv6 ipv6 routers may also allow entire subnets move new router connection point without renumbering ipv6 packet header minimum size 40 octets 320 bits options implemented extensions provides opportunity extend protocol future without affecting core packet structure however study 2015 indicated network operators dropped ipv6 packets extension headers traversed transit autonomous systems ipv4 limits packets 65,535 2−1 octets payload ipv6 node optionally handle packets limit referred jumbograms large 4,294,967,295 2−1 octets use jumbograms may improve performance high-mtu links use jumbograms indicated jumbo payload option extension header ipv6 packet two parts header payload header consists fixed portion minimal functionality required packets may followed optional extensions implement special features fixed header occupies first 40 octets 320 bits ipv6 packet contains source destination addresses traffic classification options hop counter type optional extension payload follows header next header field tells receiver interpret data follows header packet contains options field contains option type next option next header field last option points upper-layer protocol carried packet payload extension headers carry options used special treatment packet network e.g. routing fragmentation security using ipsec framework without special options payload must less jumbo payload option hop-by-hop options extension header payload must less 4 gb unlike ipv4 routers never fragment packet hosts expected use path mtu discovery make packets small enough reach destination without needing fragmented see ipv6 packet fragmentation ipv6 addresses 128 bits design ipv6 address space implements different design philosophy ipv4 subnetting used improve efficiency utilization small address space ipv6 address space deemed large enough foreseeable future local area subnet always uses 64 bits host portion address designated interface identifier most-significant 64 bits used routing prefix identifier unique within subnet host connected ipv6 mechanism automatic address detection address autoconfiguration always produces unique assignments 128 bits ipv6 address represented 8 groups 16 bits group written four hexadecimal digits sometimes called hextets formally hexadectets informally quibble quad-nibble groups separated colons example representation convenience ipv6 address may abbreviated shorter notations application following rules example application rules loopback address defined may abbreviated using rules ipv6 address may one representation ietf issued proposed standard representing text interfaces ipv6 hosts require link-local address ipv6 link-local address derived mac address interface prefix process involves filling address space prefix bits left-justified most-significant bit filling mac address eui-64 format least-significant bits bits remain filled two parts set zero ipv6 implement broadcast functionality address resolution protocol arp based neighbor discovery protocol ndp nd used link layer map layer 3 ipv6 addresses layer 2 addresses mac address ethernet network cards ndp relies icmpv6 multicast transmission ipv6 hosts verify uniqueness ipv6 addresses local area network lan sending neighbor solicitation message asking link layer address ipv6 address host lan using address responds lan mac addresses designed unique network card minimizes chances duplication generated link-local address ipv6 host determines lan connected router network card ipv6 implementation sending icmpv6 router solicitation message all-routers multicast group link-local address source answer predetermined number attempts host concludes routers connected get response router network information inside needed create globally unique address also two flag bits tell host whether use dhcp get information addresses assignment procedure global addresses similar local address construction prefix supplied router advertisements network multiple prefix announcements cause multiple addresses configured stateless address autoconfiguration slaac requires address block defined local internet registries assigned least blocks divide among subordinate networks initial recommendation stated assignment subnet end-consumer sites replaced recommends giving home sites significantly single recommend every home site given either specifically considered remains seen isps honor recommendation example initial trials comcast customers given single network domain name system dns hostnames mapped ipv6 addresses aaaa quad-a resource records reverse resolution ietf reserved domain ip6.arpa name space hierarchically divided 1-digit hexadecimal representation nibble units 4 bits ipv6 address scheme defined dual-stack host queries dns server resolve fully qualified domain name fqdn dns client host sends two dns requests one querying records querying aaaa records host operating system may configured preference address selection rules alternate record type used early dns implementations ipv6 designed facilitate network renumbering a6 records forward lookup number innovations bit-string labels dname records defined references discussion pros cons schemes deprecated experimental status ipv6 foreseen supplant ipv4 instantaneously protocols continue operate simultaneously time therefore ipv6 transition mechanisms needed enable ipv6 hosts reach ipv4 services allow isolated ipv6 hosts networks reach ipv4 infrastructure according silvia hagen dual-stack implementation ipv4 ipv6 devices easiest way migrate ipv6 many transition mechanisms use tunneling encapsulate ipv6 traffic within ipv4 networks vice versa imperfect solution reduces maximum transmission unit mtu link therefore complicates path mtu discovery may increase latency dual-stack ip implementations provide complete ipv4 ipv6 protocol stacks operating system computer network device top common physical layer implementation ethernet permits dual-stack hosts participate ipv6 ipv4 networks simultaneously method defined device dual-stack implementation operating system ipv4 ipv6 address communicate nodes lan internet using either ipv4 ipv6 domain name system dns protocol used ip protocols resolve fully qualified domain names fqdn ip addresses dual stack requires resolving dns server resolve types addresses dual stack dns server would hold ipv4 addresses records ipv6 addresses aaaa records depending destination resolved dns name server may return ipv4 ipv6 ip address default address selection mechanism preferred protocol needs configured either hosts dns server ietf published happy eyeballs assist dual stack applications connect using ipv4 ipv6 prefer ipv6 connection available however dual-stack also needs implemented routers host service dns server returned ipv6 address dual-stack clients configured prefer ipv6 network able forward ipv6 packets using ipv6 versions routing protocols dual stack networks protocols place application layer migrated ipv6 dual-stack supported major operating system network device vendors legacy networking hardware servers n't support ipv6 internet service providers isps increasingly providing business private customers public-facing ipv6 global unicast addresses however local area network lan ipv4 still used isp provide public facing ipv6 ipv4 lan addresses translated public facing ipv6 address using nat64 network address translation nat mechanism isps provide customers public-facing ipv4 ipv6 addresses thus supporting dual stack networking isps exhausted globally routable ipv4 address pool meanwhile isp customers still trying reach ipv4 web servers destinations significant percentage isps regional internet registry rir zones obtained ipv6 address space includes many world ’ major isps mobile network operators verizon wireless starhub cable chubu telecommunications kabel deutschland swisscom t-mobile internode telefonica isps still allocate customers ipv4 addresses many isps allocate customers ipv6 dual stack ipv4 ipv6 isps report share ipv6 traffic customers network anything 20 40 mid-2017 ipv6 traffic still accounted fraction total traffic several large internet exchange points ixps ams-ix reported 2 seattleix reported 7 2017 survey found many dsl customers served dual stack isp request dns servers resolve fully qualified domain names ipv6 addresses survey also found majority traffic ipv6-ready webserver resources still requested served ipv4 mostly due isp customers use dual stack facility provided isp lesser extent due customers ipv4-only isps technical basis tunneling encapsulating ipv6 packets ipv4 packets outlined rfc 4213 internet backbone ipv4-only one frequently used tunneling protocols 6to4 teredo tunneling also frequently used integrating ipv6 lans ipv4 internet backbone teredo outlined rfc 4380 allows ipv6 local area networks tunnel ipv4 networks encapsulating ipv6 packets within udp teredo relay ipv6 router mediates teredo server native ipv6 network expected 6to4 teredo would widely deployed isp networks would switch native ipv6 2014 google statistics showed use mechanisms dropped almost 0 hybrid dual-stack ipv6/ipv4 implementations recognize special class addresses ipv4-mapped ipv6 addresses addresses typically written 96-bit prefix standard ipv6 format remaining 32 bits written customary dot-decimal notation ipv4 addresses group consist 80-bit prefix zeros next 16 bits ones remaining least-significant 32 bits contain ipv4 address example :ffff:192.0.2.128 represents ipv4 address 192.0.2.128 another deprecated format ipv4-compatible ipv6 addresses :192.0.2.128 significant internal differences ipv4 ipv6 protocol stacks lower-level functionality available programmers ipv6 stack work used ipv4-mapped addresses common ipv6 stacks implement ipv4-mapped address feature either ipv6 ipv4 stacks separate implementations e.g. microsoft windows 2000 xp server 2003 security concerns openbsd operating systems program must open separate socket ip protocol uses systems e.g. linux kernel netbsd freebsd feature controlled socket option ipv6_v6only specified compatibility ipv6 networking mainly software firmware issue however much older hardware could principle upgraded likely replaced instead 2010 american registry internet numbers arin suggested internet servers prepared serve ipv6-only clients january 2012 host software may ipv4 ipv6 networking software may support dual-stack hybrid dual-stack operation many popular applications networking capabilities compliant software transitioning mechanisms outlined ipv6 implemented major operating systems use commercial business home consumer environments personal computers smartphones running recent major operating system versions support ipv6 cablelabs consortium published 160 mbit/s docsis 3.0 ipv6-ready specification cable modems august 2006 docsis 2.0 updated docsis 2.0 ipv6 provide ipv6 support may available firmware upgrade addition nodes ipv6 enabled default software manufacturer may result inadvertent creation shadow networks causing ipv6 traffic flowing networks ipv4 security management place may also occur operating system upgrades newer operating system enables ipv6 default older one failing update security infrastructure accommodate ipv6 lead ipv6 traffic bypassing shadow networks occurred business networks enterprises replacing windows xp systems ipv6 stack enabled default windows 7 systems ipv6 stack implementors therefore recommended disabling ipv4 mapped addresses instead using dual-stack network supporting ipv4 ipv6 necessary research shown use fragmentation leveraged evade network security controls similar ipv4 result requires first fragment ipv6 packet contains entire ipv6 header chain pathological fragmentation cases forbidden additionally result research evasion ra-guard deprecated use fragmentation neighbor discovery discouraged use fragmentation secure neighbor discovery send due anticipated global growth internet internet engineering task force ietf early 1990s started effort develop next generation ip protocol beginning 1992 several proposals appeared expanded internet addressing system end 1992 ietf announced call white papers september 1993 ietf created temporary ad-hoc ip next generation ipng area deal specifically issues new area led allison mankin scott bradner directorate 15 engineers diverse backgrounds direction-setting preliminary document review working-group members j. allard microsoft steve bellovin jim bound digital equipment corporation ross callon wellfleet brian carpenter cern dave clark mit john curran nearnet steve deering xerox dino farinacci cisco paul francis ntt eric fleischmann boeing mark knopper ameritech greg minshall novell rob ullmann lotus lixia zhang xerox internet engineering task force adopted ipng model 25 july 1994 formation several ipng working groups 1996 series rfcs released defining internet protocol version 6 ipv6 starting version 5 used experimental internet stream protocol first rfc standardize ipv6 1995 became obsoleted 1998 july 2017 rfc replaced 1993 introduction classless inter-domain routing cidr routing ip address allocation internet extensive use network address translation nat delayed ipv4 address exhaustion final phase exhaustion started 3 february 2011 universities among early adopters ipv6 virginia tech deployed ipv6 trial location 2004 since expanded ipv6 deployment across campus network 2016 82 traffic network used ipv6 imperial college london experimenting ipv6 deployment since 2003 2016 ipv6 traffic networks averaged 20 40 significant portion ipv6 traffic generated high energy physics collaboration cern depends entirely ipv6 since 2008 domain name system dns supports ipv6 year ipv6 first used major world event 2008 summer olympic games beijing 4 domain names 16.2 networks internet ipv6 protocol support 2014 ipv4 still carried 99 worldwide internet traffic deployment ipv6 internet backbone progress 2018 25.3 54,000 autonomous systems advertised ipv4 ipv6 prefixes global border gateway protocol bgp routing database 243 networks advertised ipv6 prefix internet backbone transit networks offering ipv6 support exist every country globally except parts africa middle east china mid-2018 major european broadband isps deployed ipv6 majority customers british sky broadcasting provided 86 customers ipv6 deutsche telekom 56 deployment ipv6 xs4all netherlands 73 deployment belgium broadband isps voo telenet 73 63 ipv6 deployment respectively united states broadband isp comcast ipv6 deployment 66 2018 comcast reported estimated 36.1 million ipv6 users reported 22.3 million ipv6 users internet exchanges amsterdam seattle large exchanges publicly show ipv6 traffic statistics october 2018 tracking 2.9 7.7 growing 1.9 -2.6 per year respectively percentage users reaching google services ipv6 29 26 alexa top 1000 web servers support ipv6 according internet society report state ipv6 deployment 2018 major mobile network providers drove ipv6 adoption japan mobile network providers nippon telegraph telephone ntt kddi softbank pushed forward ipv6 deployment india ipv6 adoption advanced jio lte network covers india ’ 29 states reaches 80 country ’ population 2018 jio estimated 237.6 million ipv6 users united states ipv6 adoption pioneered verizon wireless 2009 verizon mandated ipv6 operation reduced ipv4 optional capability lte cellular hardware verizon productively deployed ipv6 across existing ipv4 network avoid network complexity arose networks using private network ipv4 address space 2018 80 traffic verizon wireless major content providers using ipv6 united states data centers transitioned ipv6 networking since 2018 facebook eliminating ipv4 data centers network-facing load balancers accept ipv4 ipv6 traffic linkedin microsoft stated intentions move networks ipv6 google linkedin akamai 2018 deploying ipv6 data center networks connecting natively ipv6 end users governments including united states china issued guidelines requirements ipv6 capability
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Internet protocols
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open network computing remote procedure call open network computing onc remote procedure call rpc remote procedure call system onc originally developed sun microsystems 1980s part network file system project sometimes referred sun rpc onc based calling conventions used unix c programming language serializes data using external data representation xdr also found use encode decode data files accessed one platform onc delivers xdr payload using either udp tcp access rpc services machine provided via port mapper listens queries well-known port number 111 udp tcp onc rpc described rfc 1831 published 1995 rfc 5531 published 2009 current version authentication mechanisms used onc rpc described rfc 2695 rfc 2203 rfc 2623 implementations onc rpc exist unix-like systems microsoft supplies implementation windows microsoft windows services unix product addition number third-party implementation onc rpc windows exist including versions c/c++ java .net see external links 2009 sun relicensed onc rpc code standard 3-clause bsd license reconfirmed oracle corporation 2010 following confusion scope relicensing onc considered lean mean limited appeal generalized rpc system wans heterogeneous environments systems dce corba soap generally used wider role
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Internet protocols
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internet protocol internet protocol ip principal communications protocol internet protocol suite relaying datagrams across network boundaries routing function enables internetworking essentially establishes internet ip task delivering packets source host destination host solely based ip addresses packet headers purpose ip defines packet structures encapsulate data delivered also defines addressing methods used label datagram source destination information historically ip connectionless datagram service original transmission control program introduced vint cerf bob kahn 1974 complemented connection-oriented service became basis transmission control protocol tcp internet protocol suite therefore often referred tcp/ip first major version ip internet protocol version 4 ipv4 dominant protocol internet successor internet protocol version 6 ipv6 growing adoption reaching almost 25 internet traffic october 2018 internet protocol responsible addressing host interfaces encapsulating data datagrams including fragmentation reassembly routing datagrams source host interface destination host interface across one ip networks purposes internet protocol defines format packets provides addressing system datagram two components header payload ip header includes source ip address destination ip address metadata needed route deliver datagram payload data transported method nesting data payload packet header called encapsulation ip addressing entails assignment ip addresses associated parameters host interfaces address space divided subnetworks involving designation network prefixes ip routing performed hosts well routers whose main function transport packets across network boundaries routers communicate one another via specially designed routing protocols either interior gateway protocols exterior gateway protocols needed topology network may 1974 institute electrical electronics engineers ieee published paper entitled protocol packet network intercommunication paper authors vint cerf bob kahn described internetworking protocol sharing resources using packet switching among network nodes central control component model transmission control program incorporated connection-oriented links datagram services hosts monolithic transmission control program later divided modular architecture consisting transmission control protocol user datagram protocol transport layer internet protocol internet layer model became known department defense dod internet model internet protocol suite informally tcp/ip ip versions 0 3 experimental versions used 1977 1979 following internet experiment note ien documents describe versions internet protocol prior modern version ipv4 dominant internetworking protocol internet layer use today ipv4 number 4 protocol version number carried every ip datagram ipv4 described 1981 version number 5 used internet stream protocol experimental streaming protocol successor ipv4 ipv6 ipv6 result several years experimentation dialog various protocol models proposed tp/ix pip tuba tcp udp bigger addresses prominent difference version 4 size addresses ipv4 uses 32 bits addressing yielding c. 4.3 billion addresses ipv6 uses 128-bit addresses providing ca 340 undecillion addresses although adoption ipv6 slow united states government systems demonstrated basic infrastructure support ipv6 assignment new protocol ipv6 uncertain due diligence revealed ipv6 yet used previously internet protocols assigned numbers according iana ipv7 ipv8 ipv9 ipv9 aka tcp udp big addresses resurfaced mid-2004 purportedly researched adopted china china disowns april 1 1994 ietf published april fools day joke ipv9 design internet protocol suite adheres end-to-end principle concept adapted cyclades project end-to-end principle network infrastructure considered inherently unreliable single network element transmission medium dynamic terms availability links nodes central monitoring performance measurement facility exists tracks maintains state network benefit reducing network complexity intelligence network purposely located end nodes consequence design internet protocol provides best-effort delivery service characterized unreliable network architectural language connectionless protocol contrast connection-oriented communication various error conditions may occur data corruption packet loss duplication routing dynamic meaning every packet treated independently network maintains state based path prior packets different packets may routed destination via different paths resulting out-of-order delivery receiver error conditions network must detected compensated participating end nodes upper layer protocols internet protocol suite responsible resolving reliability issues example host may buffer network data ensure correct ordering data delivered application ipv4 provides safeguards ensure header ip packet error-free routing node discards packets fail header checksum test although internet control message protocol icmp provides notification errors routing node required notify either end node errors ipv6 contrast operates without header checksums since current link layer technology assumed provide sufficient error detection dynamic nature internet diversity components provide guarantee particular path actually capable suitable performing data transmission requested one technical constraints size data packets allowed given link facilities exist examine maximum transmission unit mtu size local link path mtu discovery used entire intended path destination ipv4 internetworking layer ability automatically fragment original datagram smaller units transmission case ip provides re-ordering fragments delivered order ipv6 network perform fragmentation reassembly per end-to-end principle requires end stations higher-layer protocols avoid exceeding network mtu transmission control protocol tcp example protocol adjusts segment size smaller mtu user datagram protocol udp icmp disregard mtu size thereby forcing ip fragment oversized datagrams design phase arpanet early internet security aspects needs public international network could adequately anticipated consequently many internet protocols exhibited vulnerabilities highlighted network attacks later security assessments 2008 thorough security assessment proposed mitigation problems published ietf pursuing studies
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Internet protocols
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jim christy jim christy born 1951 retired government 2013 director futures exploration fx department defense cyber crime center dc3 fx charge establishing strategic relationships us government private agencies academia christy director defense cyber crime institute 2003–2006 director operations defense computer forensics laboratory 2001-2003 christy chief air force office special investigations afosi computer crime investigations unit 1989-1996 founder world largest digital forensics shop notable involvement high priority government computer security christy joined air force 19 later became computer operator pentagon got job computer crime investigator afosi 1986 1986 christy investigated notorious hanover hackers band west german digital delinquents stole information united states defense department computers sold soviet kgb first hacker case afosi agent 1991 christy founded pentagon first digital forensics lab air force 1998 air force lab became department defense computer forensics laboratory supporting investigative agencies department defense 2016 jim christy asked tom colbert join db cooper cold case team christy put together team go undercover online help colbert team prove real identity db cooper identified history channel documentary aired july 2016
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Computer security
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intermezzo file system intermezzo distributed file system written linux kernel distributed gnu general public license included standard linux kernel version 2.4.15 dropped version 2.6 intermezzo designed work top existing journaling file system ext3 jfs reiserfs xfs developed around 1999 intermezzo system consists server holds master copy file system one clients cache file system works either replication mode client maintains duplicate entire file system on-demand mode client requests files needs capturing writes server file system journal streaming client systems replayed intermezzo described high availability file system since client continue operate even connection server lost period disconnection updates logged propagated connection restored conflicts detected handled according conflict resolution policy although best policy likely avoid conflicts typical applications replication mode typical applications on-demand mode distributed file serving file transfer protocol ftp www desktop workstations intermezzo started part coda file system project carnegie mellon university took many design decisions coda share code coda turn branch openafs project designed enhanced scalability performance modularity easy integration existing file systems paper presented open source convention august 1999 peter j. braam michael callahan phil schwan company called stelias computing created web site late 1999 announced beta test version january 2000 although supported standard linux kernel version 2.4 intermezzo removed 2.6 series developers moved new project named lustre company called cluster file systems around 2001 development continued 2003 web site maintained 2008
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Computer file systems
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mobile device forensics mobile device forensics branch digital forensics relating recovery digital evidence data mobile device forensically sound conditions phrase mobile device usually refers mobile phones however also relate digital device internal memory communication ability including pda devices gps devices tablet computers use mobile phones/devices crime widely recognised years forensic study mobile devices relatively new field dating early 2000s late 1990s proliferation phones particularly smartphones digital devices consumer market caused demand forensic examination devices could met existing computer forensics techniques mobile devices used save several types personal information contacts photos calendars notes sms mms messages smartphones may additionally contain video email web browsing information location information social networking messages contacts growing need mobile forensics due several reasons prominent reasons mobile device forensics particularly challenging number levels evidential technical challenges exist example cell site analysis following use mobile phone usage coverage exact science consequently whilst possible determine roughly cell site zone call made received yet possible say degree certainty mobile phone call emanated specific location e.g residential address result challenges wide variety tools exist extract evidence mobile devices one tool method acquire evidence devices therefore recommended forensic examiners especially wishing qualify expert witnesses court undergo extensive training order understand tool method acquires evidence maintains standards forensic soundness meets legal requirements daubert standard frye standard field study forensic examination mobile devices dates late 1990s early 2000s role mobile phones crime long recognized law enforcement increased availability devices consumer market wider array communication platforms support e.g email web browsing demand forensic examination grew early efforts examine mobile devices used similar techniques first computer forensics investigations analysing phone contents directly via screen photographing important content however proved time-consuming process number mobile devices began increase investigators called efficient means extracting data enterprising mobile forensic examiners sometimes used cell phone pda synchronization software back device data forensic computer imaging sometimes simply performed computer forensics hard drive suspect computer data synchronized however type software could write phone well reading could retrieve deleted data forensic examiners found could retrieve even deleted data using flasher twister boxes tools developed oems flash phone memory debugging updating however flasher boxes invasive change data complicated use developed forensic tools perform neither hash verifications cases audit trails physical forensic examinations therefore better alternatives remained necessary meet demands commercial tools appeared allowed examiners recover phone memory minimal disruption analyse separately time commercial techniques developed recovery deleted data proprietary mobile devices become possible specialist tools moreover commercial tools even automated much extraction process rendering possible even minimally trained first responders—who currently much likely encounter suspects mobile devices possession compared computers—to perform basic extractions triage data preview purposes mobile device forensics best known application law enforcement investigations also useful military intelligence corporate investigations private investigations criminal civil defense electronic discovery mobile device technology advances amount types data found mobile device constantly increasing evidence potentially recovered mobile phone may come several different sources including handset memory sim card attached memory cards sd cards traditionally mobile phone forensics associated recovering sms mms messaging well call logs contact lists phone imei/esn information however newer generations smartphones also include wider varieties information web browsing wireless network settings geolocation information including geotags contained within image metadata e-mail forms rich internet media including important data—such social networking service posts contacts—now retained smartphone 'apps nowadays mostly flash memory consisting nand types used mobile devices external memory devices sim cards sd cards commonly found within gps devices well mobile phones mmc cards cf cards memory stick although technically part mobile device forensics call detail records occasionally text messages wireless carriers often serve back evidence obtained mobile phone seized useful call history and/or text messages deleted phone location-based services turned call detail records cell site tower dumps show phone owner location whether stationary moving i.e. whether phone signal bounced side single tower different sides multiple towers along particular path travel carrier data device data together used corroborate information sources instance video surveillance footage eyewitness accounts determine general location non-geotagged image video taken european union requires member countries retain certain telecommunications data use investigations includes data calls made retrieved location mobile phone determined geographical data must also retained united states however requirement exists standards govern long carriers retain data even must retain example text messages may retained week two call logs may retained anywhere weeks several months reduce risk evidence lost law enforcement agents must submit preservation letter carrier must back search warrant forensics process mobile devices broadly matches branches digital forensics however particular concerns apply generally process broken three main categories seizure acquisition examination/analysis aspects computer forensic process intake validation documentation/reporting archiving still apply seizing mobile devices covered legal considerations digital media mobiles often recovered switched aim seizure preserve evidence device often transported state avoid shutdown would change files addition investigator first responder would risk user lock activation however leaving phone carries another risk device still make network/cellular connection may bring new data overwriting evidence prevent connection mobile devices often transported examined within faraday cage bag even two disadvantages method first renders device unusable touch screen keypad used second device search network connection drain battery quickly devices batteries often recharged investigator risks phone user lock activated therefore network isolation advisable either placing device airplane mode cloning sim card technique also useful device missing sim card entirely second step forensic process acquisition case usually referring retrieval material device compared bit-copy imaging used computer forensics due proprietary nature mobiles often possible acquire data powered mobile device acquisition performed live advanced smartphones using advanced memory management connecting recharger putting faraday cage may good practice mobile device would recognize network disconnection therefore would change status information trigger memory manager write data acquisition tools mobile devices commercial nature consist hardware software component often automated increasing number mobile devices use high-level file systems similar file systems computers methods tools taken hard disk forensics need slight changes fat file system generally used nand memory difference block size used larger 512 bytes hard disks depends used memory type e.g. type 64 128 256 nand memory 16 128 256 512 kilobyte different software tools extract data memory image one could use specialized automated forensic software products generic file viewers hex editor search characteristics file headers advantage hex editor deeper insight memory management working hex editor means lot handwork file system well file header knowledge contrast specialized forensic software simplifies search extracts data may find everything accessdata sleuthkit encase mention forensic software products analyze memory images since tool extracts possible information advisable use two tools examination currently february 2010 software solution get evidences flash memories mobile device data extraction classified according continuum along methods become technical “ forensically sound ” tools become expensive analysis takes longer examiners need training methods even become invasive examiner utilizes user interface investigate content phone memory therefore device used normal examiner taking pictures screen contents method advantage operating system makes unnecessary use specialized tools equipment transform raw data human interpretable information practice method applied cell phones pdas navigation systems disadvantages data visible operating system recovered data available form pictures process time-consuming logical acquisition implies bit-by-bit copy logical storage objects e.g. directories files reside logical storage e.g. file system partition logical acquisition advantage system data structures easier tool extract organize logical extraction acquires information device using original equipment manufacturer application programming interface synchronizing phone contents personal computer logical extraction generally easier work produce large binary blob however skilled forensic examiner able extract far information physical extraction logical extraction usually produce deleted information due normally removed phone file system however cases—particularly platforms built sqlite ios android—the phone may keep database file information overwrite information simply marks deleted available later overwriting cases device allows file system access synchronization interface possible recover deleted information file system extraction useful understanding file structure web browsing history app usage well providing examiner ability perform analysis traditional computer forensic tools physical acquisition implies bit-for-bit copy entire physical store e.g flash memory therefore method similar examination personal computer physical acquisition advantage allowing deleted files data remnants examined physical extraction acquires information device direct access flash memories generally harder achieve device original equipment manufacturer needs secure arbitrary reading memory therefore device may locked certain operator get around security mobile forensics tool vendors often develop boot loaders enabling forensic tool access memory often also bypass user passcodes pattern locks generally physical extraction split two steps dumping phase decoding phase brute force acquisition performed 3rd party passcode brute force tools send series passcodes passwords mobile device time consuming method effective nonetheless technique uses trial error attempt create correct combination password pin authenticate access mobile device despite process taking extensive amount time still one best methods employ forensic professional unable obtain passcode current available software hardware become quite easy break encryption mobile devices password file obtain passcode two manufacturers become public since release iphone5 cellebrite grayshift manufacturers intended law enforcement agencies police departments cellbrite ufed ultimate unit costs 40,000 us dollars grashifts system costs 15,000 brute forcing tools connected device physically send codes ios devices starting 0000 9999 sequence correct code successfully entered code entry successful full access device given data extraction commence early investigations consisted live manual analysis mobile devices examiners photographing writing useful material use evidence without forensic photography equipment fernico zrt edec eclipse project-a-phone disadvantage risking modification device content well leaving many parts proprietary operating system inaccessible recent years number hardware/software tools emerged recover logical physical evidence mobile devices tools consist hardware software portions hardware includes number cables connect mobile device acquisition machine software exists extract evidence occasionally even analyse recently mobile device forensic tools developed field response military units demand fast accurate anti-terrorism intelligence law enforcement demand forensic previewing capabilities crime scene search warrant execution exigent circumstances mobile forensic tools often ruggedized harsh environments e.g battlefield rough treatment e.g dropped submerged water generally impossible one tool capture evidence mobile devices mobile forensic professionals recommend examiners establish entire toolkits consisting mix commercial open source broad support narrow support forensic tools together accessories battery chargers faraday bags signal disruption equipment forth current tools include cellebrite ufed oxygen forensic detective susteen secure view micro systemation xry tools additionally developed address increasing criminal usage phones manufactured chinese chipsets include mediatek mtk spreadtrum mstar tools include cellebrite chinex xry pinpoint open source mobile forensics tools platform-specific geared toward smartphone analysis though originally designed forensics tool bitpim widely used cdma phones well lg vx4400/vx6000 many sanyo sprint cell phones commonly referred chip-off technique within industry last intrusive method get memory image desolder non-volatile memory chip connect memory chip reader method contains potential danger total data destruction possible destroy chip content heat required desoldering invention bga technology possible attach probes pins memory chip recover memory probes bga technique bonds chips directly onto pcb molten solder balls longer possible attach probes desoldering chips done carefully slowly heat destroy chip data chip desoldered pcb baked oven eliminate remaining water prevents so-called popcorn effect remaining water would blow chip package desoldering mainly three methods melt solder hot air infrared light steam-phasing infrared light technology works focused infrared light beam onto specific integrated circuit used small chips hot air steam methods focus much infrared technique desoldering chip re-balling process cleans chip adds new tin balls chip re-balling done two different ways third method makes entire re-balling process unnecessary chip connected adapter y-shaped springs spring-loaded pogo pins y-shaped springs need ball onto pin establish electric connection pogo pins used directly pads chip without balls advantage forensic desoldering device need functional copy without changes original data made disadvantage re-balling devices expensive process costly risks total data loss hence forensic desoldering done experienced laboratories existing standardized interfaces reading data built several mobile devices e.g. get position data gps equipment nmea get deceleration information airbag units mobile devices provide standardized interface exist standard interface mobile devices manufacturers one problem common miniaturizing device parts opens question automatically test functionality quality soldered integrated components problem industry group joint test action group jtag developed test technology called boundary scan despite standardization four tasks jtag device interface used recover memory find correct bits boundary scan register one must know processor memory circuits used connected system bus accessible outside one must find test points jtag interface printed circuit board determine test point used signal jtag port always soldered connectors sometimes necessary open device re-solder access port protocol reading memory must known finally correct voltage must determined prevent damage circuit boundary scan produces complete forensic image volatile non-volatile memory risk data change minimized memory chip n't desoldered generating image slow mobile devices jtag enabled also difficult find test access port mobile devices provide possibility run boot cd connecting network share another device clean tools therefore system commands could way save volatile memory mobile device risk modified system commands must estimated volatile memory really important similar problem arises network connection available secondary memory connected mobile device volatile memory image must saved internal non-volatile memory user data stored likely deleted important data lost system commands cheapest method imply risks data loss every command usage options output must documented commands old modem commands e.g. hayes command set motorola phone commands therefore used device modem support using commands one obtain information operating system deleted data extracted external memory usb flash drive appropriate software e.g. unix command dd needed make bit-level copy furthermore usb flash drives memory protection need special hardware connected computer many usb drives memory cards write-lock switch used prevent data changes making copy usb drive protection switch blocker used mount drive read-only mode exceptional case memory chip desoldered sim memory cards need card reader make copy sim card soundly analyzed possible recover deleted data like contacts text messages android operating system includes dd command blog post android forensic techniques method live image android device using dd command demonstrated flasher tool programming hardware and/or software used program flash device memory e.g. eeprom flash memory tools mainly originate manufacturer service centers debugging repair upgrade services overwrite non-volatile memory depending manufacturer device also read memory make copy originally intended backup memory protected reading e.g. software command destruction fuses read circuit note would prevent writing using memory internally cpu flasher tools easy connect use change data dangerous options make complete copy general exists standard constitutes supported device specific product led situation different vendors define supported device differently situation makes much harder compare products based vendor provided lists supported devices instance device logical extraction using one product produces list calls made device may listed supported vendor another vendor produce much information furthermore different products extract different amounts information different devices leads complex landscape trying overview products general leads situation testing product extensively purchase strongly recommended quite common use least two products complement mobile phone technology evolving rapid pace digital forensics relating mobile devices seems stand still evolving slowly mobile phone forensics catch release cycles mobile phones comprehensive depth framework evaluating mobile forensic toolkits developed data appropriate tools techniques type phone made available timely manner anti-computer forensics difficult small size devices user restricted data accessibility nevertheless developments secure memory hardware security circuits cpu memory chip memory chip read even desoldering
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Computer security
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federated content federated content digital media content designed self-managing support reporting rights management peer-to-peer p2p network ex audio stored digital rights management drm file format
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Distributed computing architecture
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robot battle robot battle programming game microsoft windows players design code adaptable battling robots robot battle takes strategy rather reflexes accuracy timing succeed differentiates one robot next programming player responsible game inspired similar game robotwar robot battle created brad schick 1994 released public free year reached version 1.2 went many versions seeming peak 1.3 1995 1997 david finch released 1.33 community time held together robot battle mailing list rbml closed february 2004 robot battle registry internet forum opened tournaments held new players could helped complicated coding questions could posed answered early 2001 brad began work robot battle 1.4 promised massive upgrade rbml alive ideas suggestions offers help resulted robot battle new players know including new features mid-2001 small company called garagegames showed interest robot battle brad agreed sell game soon first official 1.4 release december 2002 work began robot battle registry forum way storing robots people download well way organise advertise tournaments registry opened may 2003 robot battle steadily growing user base communications registry forums irc first registry available people purchased game since opened anybody robot battle distributed mpl open-source license allowing anybody read code help design robots programs interact game somehow robot battle full version published free november 23 2004 robots robot battle three separate parts body contains tracks square size 33x33 rotates speed 5 degrees per turn gun ability shoot energy missiles damage robots destroy missiles mines cookies collision rotate 10 degrees per turn radar ability scan cookies mines robots walls rotate 15 degrees per turn robots programmed robot scripting language rsl created text editors notepad robots usually worked distributed .prg format coders choose scramble robots distribute .dst files scrambling software created brad robot battle 1.3 later edited joseph fowler aka sorcerer mark duller give two separate programs compatible robot battle 1.4 rsl said resemble many programming languages including basic c javascript robot one many sections separated section names curly brackets init required section sections defined event priority core section need priority contains details robot n't anything else ascan used usually lowest priority least important takes place whenever robot moving events take place object detected radar collided body parts robot controlled commands easiest way make robot look ones come free game combo smart corner events fire rammer shell side liner target walls ii zag robots demonstrate uses simple commands well advanced tactics use radio differences creating robot turned
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Programming language topics
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eckhard bick eckhard bick born 16 july 1958 german-born esperantist studied medicine bonn works researcher computational linguistics active esperanto youth group bonn germana esperanto-junularo nationwide esperanto youth federation since marriage danish woman family live denmark bick obtained degrees english 1983 medicine 1984 pedagogics 1985 bonn university m.a north germanic languages portuguese institute linguistics aarhus university 1994-99 bick dissertation project lexicography described palavras so-called progressive level parser dependency grammar portuguese language based constraint grammar paradigm supported corpus-based research thesis analyzes portuguese lexical morphology morphosyntactics syntax semantics semantic parsing well computer-mediated learning translation book illustrator uta hasekamp co-author tesi la testudo german-language esperanto primer translated books songs plays esperanto published various esperanto games also author extensive esperanto-danish dictionary 35,000 headwords 1990 342 pp. extent comparable classic store esperanto-dansk ordbog great esperanto-danish dictionary lorenz friis peter frey three editions published 1938 1953 1969 31,000 headwords bick dictionary up-to-date today leading dictionary type since 1996 bick led visual interactive syntax learning project institute language communication university southern denmark engaged design programming grammatical tools internet also builds constraint grammars phrase structure grammars visl languages lexical resources annotated corpora known treebanks corpora include grammatical analysis word visl team generated manually revised language data 27 languages cooperation grammarsoft commercializing technology developed rule-based taggers parsers nine languages including english portuguese esperanto scandinavian languages linguist bick researches natural language parsing corpus linguistics though specializes portuguese danish also developed constraint grammars english spanish french language esperanto
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Computational linguistics
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xetron xetron corporation northrop grumman corporation subsidiary government contractor developing software communications systems xetron used produce popular xetron spl-60 low noise audio amplifier tunable comb notch filter 9 july 1992 first iboc transmission sent xetron offices cincinnati since company contracted usadr work project 2000 company awarded 2.1 million contract viasat develop mids-lvt radio system 2011 revealed company worked hbgary palantir attribution deanonymizing internet activists anonymous according documents leaked edward snowden sharing hacking techniques intelligence agencies since least 2010 year developed malicious windows software named orca preventing malware detection antivirus software wikileaks vault 7 disclosures 2017 revealed xetron developed tools allowing unauthorized access cisco routers cia well cinnamon − implant cisco devices according documents also developed software control compromised computers via command servers agency march 2017 company name shows nearly 400 leak documents intercept revealed 2017 employees xetron suddenly subjected polygraph unclear whether due active investigation source leaks simply stepped-up security requirement
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Computer security
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communications controller linux communications controller linux communications controller linux system z ccl ibm software product announced 2005 runs linux system z emulates ibm 37xx communications controller ccl runs unmodified ibm network control program ncp allow consolidation sna network infrastructure ip according ibm sna traffic enters leaves ccl sna network flows osa adapter however wide area network infrastructure need sna consolidate sna traffic use tunneling data link switching dlsw encapsulate sna communication ip network ccl supports ethernet token ring local area network lan connectivity directly connectivity dlsw router x.25 requires ibm npsi software plus third party package ccl support bisync start-stop according ibm figures ccl offers performance average 3745
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Operating systems
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thinkpad ultrabay ultrabay originally ibm name swappable drive bay thinkpad range laptop computers thinkpad product line sold lenovo concept name stayed furthermore used lenovo ideapad series laptops introduced thinkpad 750 series 1995 technology gone redesigns almost every new generation thinkpad may lead confusion following table gives overview different ultrabay types models occurred drives available note optical drive bay g series r40e series thinkpads ultrabay drives fixed removable however mechanically ultrabay 2000-device without surrounding caddy media side different ultrabays relate form factor drives accept machines accept ultrabay devices 12.5 mm thick whereas others limited devices 9.5 mm thick ideapad y400 y500 laptops ultrabay slot swapped another hard drive another fan another nvidia gt650m gt750m gpu work sli system primary video card increased graphics performance existing orders ultrabay y500 dvd burner built optical drive cancelled early june 2013 starting 2014 lenovo changed design thinkpad bay adapter dropped ultrabay terminology use remained thinkpad w540 product option removable serial ata sata caddy accessory screw driver allowed optical drive replaced second 2.5 inch sata storage device battery expansion caddy bay longer offered earlier hot-swap functionality essentially rendered difficult impossible
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Computer architecture
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rsync rsync utility efficiently transferring synchronizing files computer external hard drive across networked computers comparing modification times sizes files commonly found unix-like operating systems rsync algorithm type delta encoding used minimizing network usage zlib may used additional data compression ssh stunnel used security rsync typically used synchronizing files directories two different systems example command codice_1 run rsync use ssh connect codice_2 codice_3 connected invoke remote host rsync two programs determine parts local file need transferred remote file matches local one rsync also operate daemon mode serving receiving files native rsync protocol using rsync // syntax licensed gnu general public license andrew tridgell paul mackerras wrote original rsync first announced 19 june 1996 tridgell discusses design implementation performance rsync chapters 3 5 ph.d. thesis 1999 currently maintained wayne davison flexibility speed scriptability codice_4 become standard linux utility included popular linux distributions ported windows via cygwin grsync sfu freebsd netbsd openbsd macos similar codice_5 codice_6 codice_7 codice_4 requires specification source destination local either may remote generic syntax src file directory list multiple files directories copy dest file directory copy square brackets indicate optional parameters codice_4 synchronize unix clients central unix server using codice_4/codice_11 standard unix accounts used desktop environments example efficiently synchronize files backup copy external hard drive scheduling utility codice_12 carry tasks automated encrypted codice_4-based mirroring multiple hosts central server command line mirror freebsd might look like apache http server supports rsync updating mirrors preferred simplest way mirror putty website current directory use rsync way mimic capabilities time machine macos see also tym make full backup system root directory rsync process operates communicating another rsync process sender receiver startup rsync client connects peer process transfer local file systems mounted host peer created fork setting suitable pipes connection remote host involved rsync starts process handle connection typically secure shell upon connection command issued start rsync process remote host uses connection thus established alternative remote host runs rsync daemon rsync clients connect opening socket tcp port 873 possibly using proxy rsync numerous command line options configuration files specify alternative shells options commands possibly full path port numbers besides using remote shells tunnelling used remote ports appear local server rsync daemon runs possibilities allow adjusting security levels state art naive rsync daemon enough local network default rsync determines files differ sending receiving systems checking modification time size file time size different systems transfers file sending receiving system requires reading file directory information quick miss unusual modifications change neither rsync performs slower comprehensive check invoked codice_14 forces full checksum comparison every file present systems barring rare checksum collisions avoids risk missing changed files cost reading every file present systems rsync utility uses algorithm invented australian computer programmer andrew tridgell efficiently transmitting structure file across communications link receiving computer already similar identical version structure recipient splits copy file chunks computes two checksums chunk md5 hash weaker easier compute 'rolling checksum sends checksums sender sender quickly computes rolling checksum chunk version file differ must sent 're sender uses computationally expensive md5 hash verify chunks sender sends recipient parts file match along information merge blocks recipient version makes copies identical small probability differences chunks sender recipient detected thus remain uncorrected 128 bits md5 plus 32 bits rolling checksum probability order rolling checksum used rsync based mark adler adler-32 checksum used zlib based fletcher checksum sender recipient versions file many sections common utility needs transfer relatively little data synchronize files typical data compression algorithms used files similar uncompressed may different compressed thus entire file need transferred compression programs gzip provide special rsyncable mode allows files efficiently rsynced ensuring local changes uncompressed file yield local changes compressed file rsync supports key features aid significantly data transfers backup include compression decompression data block block using zlib support protocols ssh stunnel utility uses rsync algorithm generate delta files difference file file b like utility diff different delta format delta file applied file turning file b similar patch utility rdiff works well binary files rdiff-backup maintained since 2009 maintains backup mirror file directory either locally remotely network another server rdiff-backup stores incremental rdiff deltas backup possible recreate backup point librsync library used rdiff independent implementation rsync algorithm use rsync network protocol share code rsync application used dropbox rdiff-backup duplicity utilities acrosync library independent cross-platform implementation rsync network protocol unlike librsync wire-compatible rsync protocol version 29 30 released reciprocal public license used commercial rsync software acrosync duplicity variation rdiff-backup allows backups without cooperation storage server simple storage services like amazon s3 works generating hashes block advance encrypting storing server retrieves incremental backup rest data also stored encrypted security purposes macos 10.5 later special codice_15 codice_16 switch allows retaining much hfs file metadata syncing two machines supporting feature achieved transmitting resource fork along data fork zsync rsync-like tool optimized many downloads per file version zsync used linux distributions ubuntu distributing fast changing beta iso image files zsync uses http protocol .zsync files pre-calculated rolling hash minimize server load yet permit diff transfer network optimization rclone open-source tool inspired rsync focuses exclusively cloud storage system providers supports 10 different providers provides rsync-like interface backup local data providers
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Computer security
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caja project caja pronounced google project javascript implementation virtual iframes based principles object-capabilities caja takes javascript technically ecmascript 5 strict mode code html css input rewrites safe subset html css plus single javascript function free variables means way function modify object given reference object host page instead giving direct references dom objects host page typically gives references wrappers sanitize html proxy urls prevent redirecting page allows caja prevent certain phishing attacks prevent cross-site scripting attacks prevent downloading malware also since rewritten programs run frame host page allow one program export object reference another program inter-frame communication simply method invocation word caja spanish box safe bank idea caja safely contain javascript programs well capabilities-based javascript caja currently used google google sites google apps script products 2008 myspace yahoo allianz deployed early version caja later abandoned
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Computer architecture
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multiple console time sharing system multiple console time sharing system mcts operating system developed general motors research laboratories 1970s control data corporation star-100 supercomputer mcts built support gm computer-aided design cad applications mcts based multics
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Operating systems
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mapping airline traffic internet protocol matip stands mapping airline traffic means airline reservation ticketing messaging traffic tcp/ip defined rfc 2351 makes use well-known ports 350 351 matip preferred classic airline traffic lines
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Internet protocols
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proxy arp proxy arp technique proxy device given network answers arp queries ip address network proxy aware location traffic destination offers mac address ostensibly final destination traffic directed proxy address typically routed proxy intended destination via another interface via tunnel process results node responding mac address arp request different ip address proxying purposes sometimes referred publishing typical uses proxy arp arp manipulation techniques basis protocols providing redundancy broadcast networks e.g. ethernet notably common address redundancy protocol virtual router redundancy protocol disadvantage proxy arp include scalability arp resolution proxy required every device routed manner reliability fallback mechanism present masquerading confusing environments proxy arp create dos attacks networks misconfigured example misconfigured router proxy arp ability receive packets destined hosts gives mac address response arp requests hosts/routers may ability correctly forward packets final destination thus blackholing traffic proxy arp hide device misconfigurations missing incorrect default gateway openbsd implements proxy arp
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Internet protocols
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kasiski examination cryptanalysis kasiski examination also referred kasiski test kasiski method method attacking polyalphabetic substitution ciphers vigenère cipher first published friedrich kasiski 1863 seems independently discovered charles babbage early 1846 polyalphabetic substitution ciphers substitution alphabets chosen use keyword kasiski examination allows cryptanalyst deduce length keyword length keyword discovered cryptanalyst lines ciphertext n columns n length keyword column treated ciphertext monoalphabetic substitution cipher column attacked frequency analysis similarly rotor stream cipher machine used method may allow deduction length individual rotors kasiski examination involves looking strings characters repeated ciphertext strings three characters long examination successful distances consecutive occurrences strings likely multiples length keyword thus finding repeated strings narrows possible lengths keyword since take greatest common divisor distances reason test works repeated string occurs plaintext distance corresponding characters multiple keyword length keyword letters line way occurrences string example consider plaintext crypto repeated string distance occurrences 20 characters line plaintext 6-character keyword abcdef 6 divide 20 first instance crypto lines abcdef second instance lines cdefab two instances encrypt different ciphertexts kasiski examination reveal nothing however 5-character keyword abcde 5 divides 20 occurrences crypto line abcdea two instances encrypt ciphertext kasiski examination effective difficulty using kasiski examination lies finding repeated strings hard task perform manually computers make much easier however care still required since repeated strings may coincidence repeat distances misleading cryptanalyst rule coincidences find correct length course monoalphabetic ciphertexts result must cryptanalyzed kasiski actually used superimposition solve vigenère cipher started finding key length took multiple copies message laid one-above-another one shifted left length key kasiski observed column made letters encrypted single alphabet method equivalent one described perhaps easier picture modern attacks polyalphabetic ciphers essentially identical described one improvement coincidence counting instead looking repeating groups modern analyst would take two copies message lay one another modern analysts use computers description illustrates principle computer algorithms implement generalized method br br
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Computer security
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cozi cozi website mobile app intended help families stay organized features include allowing multiple family members manage schedules one account well organize update shopping to-do lists website founded robbie cape jan miksovsky two left microsoft company first product cozi central released september 25 2006 included family calendar shopping lists family messaging photo collage screensaver company based seattle washington cozi freemium version paid version called cozi gold cozi gold additional features include cozi contacts birthday tracker reminders mobile month view change notifications cozi acquired time inc. 2014 meredith corporation acquired time 2018 cozi moved parents network division june 5 2011 cozi set guinness world record longest line ducks row line stretched one mile made 17,782 rubber ducks
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Web technology
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simplenote simplenote note-taking application markdown support addition cross-platform apps accessed via web browsers simplenote externally accessible api allowing clients written macos dashboard widget dashnote nvpy cross-platform simplenote client amongst others addition macos program notational velocity windows utility resophnotes also sync simplenote simplenote originally developed simperium 2008 simplenote premium introduced november 23 2009 removed ads added extra features syncing simplenote dropbox automattic acquired simperium simplenote january 24 2013 september automattic released android version later relaunched simplenote suspending premium service removing ads users may 2016 official client linux simplenote released automattic open sourced code ios android macos simplenote apps august 2016 making client apps open source application reviewed mac life reviewed book lifehacker guide working smarter faster better covered book business iphone ipad app development
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Operating systems
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network access control network access control nac approach computer security attempts unify endpoint security technology antivirus host intrusion prevention vulnerability assessment user system authentication t. network access control nac computer computer network|networking solution uses set protocol computing |protocols define implement policy describes secure access network node networking |nodes devices initially attempt access network nac might integrate automatic remediation process fixing non-compliant nodes allowing access network systems allowing network infrastructure routers switches firewalls work together back office servers end user computing equipment ensure information system operating securely interoperability allowed basic form nac 802.1x standard network access control aims exactly name implies—control access computer networking|network policies including pre-admission endpoint security policy checks post-admission controls users devices go network computer connects computer network permitted access anything unless complies business defined policy including anti-virus protection level system update level configuration computer checked pre-installed software agent access resources remediate resolve update issues policy met computer able access network resources internet within policies defined nac system nac mainly used endpoint health checks often tied role-based access access network given according profile person results posture/health check example enterprise hr department could access hr department files role endpoint meets anti-virus minimums nac represents emerging category security products definition evolving controversial overarching goals concept distilled two prevailing designs nac based whether policies enforced end-stations gain access network former case called pre-admission nac end-stations inspected prior allowed network typical use case pre-admission nac would prevent clients out-of-date antivirus signatures talking sensitive servers alternatively post-admission nac makes enforcement decisions based user actions users provided access network fundamental idea behind nac allow network make access control decisions based intelligence end-systems manner network informed end-systems key design decision key difference among nac systems whether require software agent distributed agents|agent software report end-system characteristics whether use scanning network inventory techniques discern characteristics remotely nac matured software developers microsoft adopted approach providing network access protection|network access protection nap agent part windows 7 vista xp releases also nap compatible agents linux mac os x provide equal intelligence operating systems out-of-band systems agents distributed end-stations report information central console turn control switches enforce policy contrast inline solutions single-box solutions act internal firewalls hierarchical internetworking model|access-layer networks enforce policy out-of-band solutions advantage reusing existing infrastructure inline products easier deploy new networks may provide advanced network enforcement capabilities directly control individual packets wire however products agentless inherent advantages easier less risky out-of-band deployment use techniques provide inline effectiveness non-compliant devices enforcement required network operators deploy nac products expectation legitimate clients denied access network users never out-of-date patch levels nac would unnecessary nac solutions require mechanism remediate end-user problems deny access two common strategies remediation quarantine networks captive portal using nac mobile device|mobile deployment workers connect various wireless network throughout workday involves challenges present wired local area network|lan environment user denied access computer security|security concern productive use device lost impact ability complete job serve customer addition automated remediation takes seconds wired connection may take minutes slower wireless data connection bogging device mobile nac solution gives system administrators greater control whether remediate security concern lower-grade concern out-of-date antivirus software|antivirus signatures may result simple warning user serious issues may result quarantining device policies may set automated remediation pushing applying security patch computing |patches updates withheld device connected wi-fi faster connection working hours allows administrators appropriately balance need security goal keeping workers productive category computer network security
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Computer security
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barracuda networks barracuda networks inc. company providing security networking storage products based network appliances cloud services company security products include products protection email web surfing web hackers instant messaging threats spam spyware trojans viruses company networking storage products include web filtering load balancing application delivery controllers message archiving ng firewalls backup services data protection barracuda networks founded 2003 dean drako founding ceo michael perone zach levow company introduced barracuda spam virus firewall year 2007 company moved headquarters campbell california opened office ann arbor michigan january 2006 closed first outside investment 40 million sequoia capital francisco partners january 29 2008 barracuda networks sued trend micro use open source anti-virus software clam antivirus trend micro claimed violation patent 'anti-virus detection smtp ftp gateway addition providing samples prior art effort render trend micro patent invalid july 2008 barracuda launched countersuit trend micro claiming trend micro violated several antivirus patents barracuda networks acquired ibm december 2008 company launched brbl barracuda reputation block list proprietary dynamic list known spam servers free public use blocking spam gateway soon opening brbl many ip addresses got blacklisted without apparent reason without technical explanation october 2009 barracuda 85,000 customers november 2011 barracuda 130,000 customers january 2014 barracuda 150,000 customers worldwide 2012 company became co-sponsor garmin-barracuda uci protour cycling team entitlement sponsor 2011 indianapolis 500 champion bryan herta autosport indycar series 98 lotus driven alex tagliani defend team championship barracuda networks expanded research development facility ann arbor 12,500 square foot office building depot street 2008 2012 michigan-based research division grown 180 employees outgrowing space june 2012 barracuda signed lease occupy 45,000 square foot office complex previously used borders headquarters maynard st downtown ann arbor july 2012 dean drako barracuda networks co-founder president ceo since founded 2003 resigned operating position remaining company board directors time drako departure company stated achieved profitability nearly ongoing 30 annual percent growth rate since inception 150,000 customers worldwide nearly 1,000 employees 10 offices business 80 countries company created office ceo started ceo search november 2012 long-time emc executive william bj jenkins joined company president ceo jenkins worked emc since 1998 recently served president emc backup recovery systems brs division november 2013 barracuda networks went public new york stock exchange ticker symbol cuda march 2015 barracuda networks expanded business north asia distributed tritech distribution limited hong kong november 2015 barracuda added new next generation firewall firewall family barracuda announced future discontinuation copy cudadrive services may 2016 november 2017 thoma bravo llc private equity firm announced taking barracuda networks private 1.6 billion buyout expected go feb 2018 february 2018 thoma bravo announced completed acquisition may 23 2019 barracuda forays next generation security tackle latest cyber security threats introducing advanced bot protection capabilities september 2007 barracuda networks acquired netcontinuum company providing application controllers secure manage enterprise web applications november 2008 barracuda networks expanded cloud-based backup services acquiring bitleap november 2008 barracuda networks acquired 3sp allowing company introduce secure sockets layer ssl virtual private network vpn products allow secure remote access network file shares internal web sites remote control capabilities desktops servers january 2009 barracuda networks acquired yosemite technologies add software agents incremental backups applications microsoft exchange server sql server windows system states september 2009 barracuda networks acquired controlling interest phion ag austria-based public company delivering enterprise-class firewalls october 2009 barracuda networks acquired purewire inc software service saas company offering cloud based web filtering security april 2013 barracuda networks acquired signnow 2014 barracuda networks purchased c2c systems uk october 2015 barracuda networks acquired intronis november 2017 barracuda purchased sonian november 2017 barracuda announced acquired private equity investment firm thoma bravo llc january 2018 barracuda acquired phishline january 2013 backdoor discovered variety firewall vpn spam filtering gear sold barracuda networks contains undocumented backdoor accounts allow people remotely log access sensitive information researchers austrian security firm warned backdoor secured shortly announcement
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Computer security
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unix unix trademarked unix family multitasking multiuser computer operating systems derive original unix development starting 1970s bell labs research center ken thompson dennis ritchie others initially intended use inside bell system licensed unix outside parties late 1970s leading variety academic commercial unix variants vendors including university california berkeley bsd microsoft xenix ibm aix sun microsystems solaris early 1990s sold rights unix novell sold unix business santa cruz operation sco 1995 unix trademark passed open group neutral industry consortium allows use mark certified operating systems comply single unix specification sus 2014 unix version largest installed base apple macos unix systems characterized modular design sometimes called unix philosophy concept entails operating system provides set simple tools performs limited well-defined function unified filesystem unix filesystem main means communication shell scripting command language unix shell combine tools perform complex workflows unix distinguishes predecessors first portable operating system almost entire operating system written c programming language thus allowing unix reach numerous platforms unix originally meant convenient platform programmers developing software run systems rather non-programmers system grew larger operating system started spreading academic circles users added tools system shared colleagues first unix designed portable multi-tasking later unix gradually gained portability multi-tasking multi-user capabilities time-sharing configuration unix systems characterized various concepts use plain text storing data hierarchical file system treating devices certain types inter-process communication ipc files use large number software tools small programs strung together command-line interpreter using pipes opposed using single monolithic program includes functionality concepts collectively known unix philosophy brian kernighan rob pike summarize unix programming environment idea power system comes relationships among programs programs era standard computer consisted hard disk storage data terminal input output i/o unix file model worked quite well i/o generally linear 1980s non-blocking i/o set inter-process communication mechanisms augmented unix domain sockets shared memory message queues semaphores well network sockets support communication hosts graphical user interfaces developed file model proved inadequate task handling asynchronous events generated mouse early 1980s users began seeing unix potential universal operating system suitable computers sizes unix environment client–server program model essential elements development internet reshaping computing centered networks rather individual computers unix c programming language developed distributed government academic institutions led ported wider variety machine families operating system unix operating system consists many libraries utilities along master control program kernel kernel provides services start stop programs handles file system common low-level tasks programs share schedules access avoid conflicts programs try access resource device simultaneously mediate access kernel special rights reflected division user space kernel space — although microkernel implementations like minix redox functions network protocols may also run user space origins unix date back mid-1960s massachusetts institute technology bell labs general electric developing multics time-sharing operating system ge-645 mainframe computer multics featured several innovations also presented severe problems frustrated size complexity multics goals individual researchers bell labs started withdrawing project last leave ken thompson dennis ritchie douglas mcilroy joe ossanna decided reimplement experiences new project smaller scale new operating system initially without organizational backing also without name new operating system single-tasking system 1970 group coined name unics uniplexed information computing service pronounced eunuchs pun multics stood multiplexed information computer services brian kernighan takes credit idea adds one remember origin final spelling unix dennis ritchie doug mcilroy peter g. neumann also credit kernighan operating system originally written assembly language 1973 version 4 unix rewritten c. version 4 unix however still many pdp-11 dependent codes suitable porting first port platform made five years later 1978 interdata 8/32 bell labs produced several versions unix collectively referred research unix 1975 first source license unix sold donald b. gillies university illinois department computer science uiuc graduate student greg chesson worked unix kernel bell labs instrumental negotiating terms license late 1970s early 1980s influence unix academic circles led large-scale adoption unix bsd system v commercial startups including sequent hp-ux solaris aix xenix late 1980s unix system laboratories sun microsystems developed system v release 4 svr4 subsequently adopted many commercial unix vendors 1990s unix unix-like systems grew popularity bsd linux distributions developed collaboration worldwide network programmers 2000 apple released darwin also unix system became core mac os x operating system later renamed macos unix operating systems widely used modern servers workstations mobile devices late 1980s open operating system standardization effort known posix provided common baseline operating systems ieee based posix around common structure major competing variants unix system publishing first posix standard 1988 early 1990s separate similar effort started industry consortium common open software environment cose initiative eventually became single unix specification sus administered open group starting 1998 open group ieee started austin group provide common definition posix single unix specification 2008 become open group base specification 1999 effort towards compatibility several unix system vendors agreed svr4 executable linkable format elf standard binary object code files common format allows substantial binary compatibility among different unix systems operating cpu architecture filesystem hierarchy standard created provide reference directory layout unix-like operating systems mainly used linux unix system composed several components originally packaged together including development environment libraries documents portable modifiable source code components addition kernel operating system unix self-contained software system one key reasons emerged important teaching learning tool broad influence inclusion components make system large original v7 unix distribution consisting copies compiled binaries plus source code documentation occupied less 10 mb arrived single nine-track magnetic tape printed documentation typeset online sources contained two volumes names filesystem locations unix components changed substantially across history system nonetheless v7 implementation considered many canonical early structure unix system significant impact operating systems achieved reputation interactivity providing software nominal fee educational use running inexpensive hardware easy adapt move different machines unix originally written assembly language soon rewritten c high-level programming language although followed lead multics burroughs unix popularized idea unix drastically simplified file model compared many contemporary operating systems treating kinds files simple byte arrays file system hierarchy contained machine services devices printers terminals disk drives providing uniform interface expense occasionally requiring additional mechanisms ioctl mode flags access features hardware fit simple stream bytes model plan 9 operating system pushed model even eliminated need additional mechanisms unix also popularized hierarchical file system arbitrarily nested subdirectories originally introduced multics common operating systems era ways divide storage device multiple directories sections fixed number levels often one level several major proprietary operating systems eventually added recursive subdirectory capabilities also patterned multics dec rsx-11m group user hierarchy evolved vms directories cp/m volumes evolved ms-dos 2.0+ subdirectories hp mpe group.account hierarchy ibm ssp os/400 library systems folded broader posix file systems making command interpreter ordinary user-level program additional commands provided separate programs another multics innovation popularized unix unix shell used language interactive commands scripting shell scripts – separate job control language like ibm jcl since shell os commands another program user could choose even write shell new commands could added without changing shell unix innovative command-line syntax creating modular chains producer-consumer processes pipelines made powerful programming paradigm coroutines widely available many later command-line interpreters inspired unix shell fundamental simplifying assumption unix focus newline-delimited text nearly file formats binary editors original version unix – entire system configured using textual shell command scripts common denominator i/o system byte – unlike record-based file systems focus text representing nearly everything made unix pipes especially useful encouraged development simple general tools could easily combined perform complicated ad hoc tasks focus text bytes made system far scalable portable systems time text-based applications also proven popular application areas printing languages postscript odf application layer internet protocols e.g. ftp smtp http soap sip unix popularized syntax regular expressions found widespread use unix programming interface became basis widely implemented operating system interface standard posix see c programming language soon spread beyond unix ubiquitous systems applications programming early unix developers important bringing concepts modularity reusability software engineering practice spawning software tools movement time leading developers unix programs ran established set cultural norms developing software norms became important influential technology unix termed unix philosophy tcp/ip networking protocols quickly implemented unix versions widely used relatively inexpensive computers contributed internet explosion worldwide real-time connectivity formed basis implementations many platforms unix policy extensive on-line documentation many years ready access system source code raised programmer expectations contributed launch free software movement 1983 1983 richard stallman announced gnu short gnu unix project ambitious effort create free software unix-like system free sense everyone received copy would free use study modify redistribute gnu project kernel development project gnu hurd yet produced working kernel 1991 linus torvalds released linux kernel free software gnu general public license addition use linux operating system many gnu packages – gnu compiler collection rest gnu toolchain gnu c library gnu core utilities – gone play central roles free unix systems well linux distributions consisting linux kernel large collections compatible software become popular individual users business popular distributions include red hat enterprise linux fedora suse linux enterprise opensuse debian gnu/linux ubuntu linux mint mandriva linux slackware linux arch linux gentoo free derivative bsd unix 386bsd released 1992 led netbsd freebsd projects 1994 settlement lawsuit brought university california berkeley software design inc. usl v. bsdi unix systems laboratories clarified berkeley right distribute bsd unix free desired since bsd unix developed several different product branches including openbsd dragonfly bsd linux bsd increasingly filling market needs traditionally served proprietary unix operating systems well expanding new markets consumer desktop mobile embedded devices modular design unix model sharing components relatively common consequently unix unix-like systems include least bsd code systems also include gnu utilities distributions 1999 interview dennis ritchie voiced opinion linux bsd operating systems continuation basis unix design derivatives unix interview states views unix linux continuation ideas started ken many others many years ago opensolaris open-source counterpart solaris developed sun microsystems included cddl-licensed kernel primarily gnu userland however oracle discontinued project upon acquisition sun prompted group former sun employees members opensolaris community fork opensolaris illumos kernel 2014 illumos remains active open-source system v derivative may 1975 rfc 681 described development network unix center advanced computation university illinois system said present several interesting capabilities arpanet mini-host time unix required license bell laboratories 20,000 us expensive non-university users educational license cost 150 noted bell open suggestions arpanet-wide license specific features found beneficial local processing facilities compilers editors document preparation system efficient file system access control mountable unmountable volumes unified treatment peripherals special files integration network control program ncp within unix file system treatment network connections special files accessed standard unix i/o calls closing files program exit decision desirable minimize amount code added basic unix kernel october 1993 novell company owned rights unix system v source time transferred trademarks unix x/open company open group 1995 sold related business operations santa cruz operation sco whether novell also sold copyrights actual software subject federal lawsuit 2006 sco v. novell novell case appealed august 30 2011 united states court appeals tenth circuit affirmed trial decisions closing case unix vendor sco group inc. accused novell slander title present owner trademark unix open group industry standards consortium systems fully compliant certified single unix specification qualify unix others called unix-like decree open group term unix refers class operating systems specific implementation operating system operating systems meet open group single unix specification able bear unix 98 unix 03 trademarks today operating system vendor pays substantial certification fee annual trademark royalties open group systems licensed use unix trademark include aix hp-ux inspur k-ux irix solaris tru64 unix formerly digital unix osf/1 macos part z/os notably inspur k-ux linux distribution certified unix 03 compliant sometimes representation like un*x *nix *n x used indicate operating systems similar unix comes use asterisk question mark characters wildcard indicators many utilities notation also used describe unix-like systems met requirements unix branding open group open group requests unix always used adjective followed generic term system help avoid creation genericized trademark unix original formatting usage unix remains widespread typeset small caps unix according dennis ritchie presenting original unix paper third operating systems symposium american association computing machinery acm new typesetter troff invented intoxicated able produce small caps many operating system predecessors contemporaries used all-uppercase lettering many people wrote name upper case due force habit acronym trademark names registered different entities different countries trademark laws countries allow trademark name controlled two different entities entity uses trademark easily distinguishable categories result unix used brand name various products including book shelves ink pens bottled glue diapers hair driers food containers several plural forms unix used casually refer multiple brands unix unix-like systems common conventional unixes unices treating unix latin noun third declension also popular pseudo-anglo-saxon plural form unixen common although occasionally seen sun microsystems developer solaris variant asserted term unix plural referencing many implementations
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Operating systems
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ibm 4768 ibm 4768 pcie cryptographic coprocessor hardware security module hsm includes secure cryptoprocessor implemented high-security tamper resistant programmable pcie board specialized cryptographic electronics microprocessor memory random number generator housed within tamper-responding environment provide highly secure subsystem data processing cryptography performed sensitive key material never exposed outside physical secure boundary clear format ibm 4768 designed meet fips pub 140-2 level 4 highest level certification achievable commercial cryptographic devices achieved pci-hsm certification ibm 4768 data sheet describes coprocessor detail ibm supplies two cryptographic-system implementations applications may include financial pin transactions bank-to-clearing-house transactions emv transactions integrated circuit chip based credit cards general-purpose cryptographic applications using symmetric key algorithms hashing algorithms public key algorithms operational keys symmetric rsa private generated coprocessor saved either keystore file application memory encrypted master key coprocessor coprocessor identical master key use keys performance benefits include incorporation elliptic curve cryptography ecc format preserving encryption fpe hardware ibm supports 4768 certain ibm z mainframes crypto express6s cex6s feature code 0893 4768 cex6s part ibm support pervasive encryption drive encrypt data links point various relevant cryptographic standards iso 13491 secure cryptographic devices https //www.iso.org/standard/61137.html iso 9564 pin security https //www.iso.org/standard/68669.html ansi x9.24 part 1 key management using symmetric techniques https //webstore.ansi.org/recorddetail.aspx sku=ansi+x9.24-1-2017 ansi x9.24 part 2 key management using asymmetric techniques https //webstore.ansi.org/recorddetail.aspx sku=ansi+x9.24-2-2016 fips 140-2 https //nvlpubs.nist.gov/nistpubs/fips/nist.fips.140-2.pdf payment card industry pci pin transaction security pts hardware security module hsm modular security requirements search site https //www.pcisecuritystandards.org/document_library
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Computer security
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obj programming language obj programming language family introduced joseph goguen 1976 family declarative ultra high-level languages features abstract types generic modules subsorts subtypes multiple inheritance pattern-matching modulo equations e-strategies user control laziness module expressions combining modules theories views describing module interfaces massively parallel rrm rewrite rule machine members obj family languages include cafeobj eqlog foops kumo maude obj3 obj3 version obj based order-sorted rewriting obj3 agent-oriented runs kyoto common lisp akcl
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Programming language topics
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open threat exchange open threat exchange otx world largest crowd-sourced computer-security platform 80,000 participants 140 countries share 19 million potential threats daily free use founded 2012 otx created run alienvault cybersecurity developer commercial open source solutions manage cyber attacks collaborative threat exchange created partly counterweight criminal hackers successfully working together sharing information viruses malware cyber attacks otx cloud-hosted information sharing covers wide range issues related security including viruses malware intrusion detection firewalls automated tools cleanse aggregate validate publish data shared participants data validated otx platform stripped information identifying participating contributor 2015 otx 2.0 added social network enables members share discuss research security threats including via real-time threat feed users share ip addresses websites attacks originated look specific threats see anyone already left information users subscribe “ pulse ” analysis specific threat including data ioc impact targeted software pulses exported stix json openloc maec csv used automatically update local security products users up-vote comment specific pulses assist others identifying important threats otx combines social contributions automated machine-to-machine tools integrates major security products firewalls perimeter security hardware platform read security report .pdf .csv .json open formats relevant information extracted automatically assisting professionals readily analyze data specific otx components include dashboard details top malicious ips around world check status specific ips notifications organization ip domain found hacker forum blacklist listed otx feature review log files determine communication known malicious ips 2016 alienvault released new version otx allowing participants create private communities discussions groups share information threats within group feature intended facilitate in-depth discussions specific threats particular industries different regions world threat data groups also distributed subscribers managed service providers using otx otx big data platform integrates natural language processing machine learning facilitate collection correlation data many sources including third-party threat feeds websites external api local agents 2015 alienvault partnered intel coordinate real-time threat information otx similar deal hewlett packard announced year facebook ibm threat exchange platforms facebook threatexchange beta requires application invitation join ibm launched ibm-force exchange april 2015
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Computer security
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friedrich l. bauer friedrich ludwig fritz bauer 10 june 1924 – 26 march 2015 german computer scientist professor technical university munich bauer earned abitur 1942 served wehrmacht world war ii 1943 1945 1946 1950 studied mathematics theoretical physics ludwig-maximilians-universität munich bauer received doctorate supervision fritz bopp thesis gruppentheoretische untersuchungen zur theorie der spinwellengleichungen group-theoretic investigations theory spin wave equations 1952 completed habilitation über quadratisch konvergente iterationsverfahren zur lösung von algebraischen gleichungen und eigenwertproblemen quadratically convergent iteration methods solving algebraic equations eigenvalue problems 1954 technical university munich teaching privatdozent ludwig-maximilians-universität 1954 1958 became extraordinary professor applied mathematics university mainz since 1963 worked professor mathematics since 1972 computer science technical university munich retired 1989 bauer early work involved construction computing machinery e.g logical relay computer stanislaus 1951-1955 context first propose widely used stack method expression evaluation bauer also worked committees developed imperative computer programming languages algol 58 successor algol 60 important predecessors modern imperative programming languages 1968 bauer coined term software engineering widespread use since bauer influential figure establishing computer science independent subject german universities scientific contributions spread numerical analysis bauer–fike theorem fundamentals interpretation translation programming languages later works systematics program development especially program transformation methods systems cip-s associated wide-spectrum language system cip-l also wrote well-respected book cryptology decrypted secrets fourth edition doctoral advisor 39 students including manfred broy david gries manfred paul gerhard seegmüller josef stoer peter wynn christoph zenger friedrich bauer married hildegard bauer-vogg father three sons two daughters bauer colleague german representative nato science committee 1967 nato discussing 'the software crisis bauer suggested term 'software engineering way conceive problem solution 1972 bauer published following definition software engineering br establishment use sound engineering principles economically obtain software reliable works real machines efficiently 2014 tu munich renamed largest lecture hall department informatics computer science friedrich bauer
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Programming language topics
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guard interval telecommunications guard intervals used ensure distinct transmissions interfere one another otherwise cause overlapping transmissions transmissions may belong different users tdma user ofdm purpose guard interval introduce immunity propagation delays echoes reflections digital data normally sensitive ofdm beginning symbol preceded guard interval long echoes fall within interval affect receiver ability safely decode actual data data interpreted outside guard interval tdma user timeslot ends guard period avoid data loss reduce interference following user caused propagation delay thus user timeslot protected interference preceding user guard interval guard period end preceding user timeslot common misconception tdma timeslot begins guard interval however itu technical specifications gsm 05.05 clearly define guard period end timeslot thus providing protection data loss within timeslot protection interference following timeslot longer guard periods allow distant echoes tolerated however longer guard intervals reduce channel efficiency example dvb-t four guard intervals available given fractions symbol period hence 1/32 gives lowest protection highest data rate 1/4 results best protection lowest data rate radio waves propagate speed light per 1000 meter 5 μs/mile ideally guard interval longer delay spread channel standard symbol guard interval used 802.11 ofdm increase data rate 802.11n added optional support guard interval provides 11 increase data rate shorter guard interval results higher packet error rate delay spread channel exceed guard interval and/or timing synchronization transmitter receiver precise scheme could developed work whether short guard interval would benefit particular link reduce complexity manufacturers typically implement short guard interval final rate adaptation step device running highest data rate
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Internet protocols
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sparcstation 2 sparcstation 2 ss2 code named calvin sun 4/75 sparc workstation computer sold sun microsystems based sun4c architecture implemented pizza box form factor 40mhz cypress cy7c601 cpu 28.5 mips ti tms390c601a fpu 4.2 mflops known cpu upgrade option weitek 80mhz sparc power µp power-up sparcstation 2 configured 128 mb memory total 64 mb motherboard additional 64 mb using special 32 mb sbus memory card another 32 mb piggy-backed daughterboard 16 ram slots motherboard populated either 1 mb simms total 16 mb 4 mb simms total 64 mb standard 30 pin simms used long use parity error detection rated 80 ns faster sparcstation 2 uses standard 50 pin scsi interface house two 3 1/2 full height disk drives ss2 also comes special auto-ejecting 1.44 mb floppy disk drive modern 80-pin single connector attachment sca scsi drives used internally adapter plastic drive sled used 50-pin drives must cut allow clearance adapter board sca drives may run hotter original scsi drives cause heating issues especially two drives installed ethernet aui port board supplemented add-on sbus cards onboard ethernet provided amd lance am7990 ethernet controller external aui transceivers required connection 10base5 10base2 10baset ethernet physical layer media openboot rom able boot network using rarp tftp sparcstation 2 uses m48t02 battery-backed rtc ram chip handles real time clock boot parameter storage problem chip battery internal means entire chip must replaced battery runs sun4c machines older battery life chip substantial number systems refuse boot additionally sun4c design used reserved bits m48t02 nvram non-standard way since later revisions m48t02 chip exert stricter control bits current m48t02 store nvram data rtc function correctly system may fail auto-boot due incompatibilities modern m48t02s common modify failed nvrams cutting encapsulation patching new battery also possible replace entire encapsulation also contains 32.768 khz clock crystal following operating systems run sparcstation 2
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Computer architecture
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softlayer softlayer technologies inc. dedicated server managed hosting cloud computing provider founded 2005 acquired ibm 2013 softlayer established 2005 lance crosby several ex-coworkers gi partners acquired majority equity stake softlayer august 2010 november year merged company planet internet services softlayers ’ biggest competitor consolidated customer base softlayer brand q1 2011 company reported hosting 81,000 servers 26,000 customers locations throughout united states july 2011 company announced plans international expansion amsterdam singapore add existing network us-based data centers dallas texas san jose california seattle washington santiago de querétaro mexico houston texas washington d.c.. data centers leased via digital realty trust may 2015 company 23 data centers 11 different countries june 4 2013 ibm announced acquisition softlayer disclosed financial terms according reuters deal could fetch 2 billion form ibm cloud services division time acquisition softlayer described biggest privately held cloud infrastructure provider iaas world 2018 softlayer renamed ibm cloud
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Distributed computing architecture
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safe mode safe mode diagnostic mode computer operating system os also refer mode operation application software windows safe mode allows essential system programs services start boot safe mode intended help fix problems within operating system also widely used removing rogue security software microsoft windows macos android linux distributions ubuntu linux mint examples contemporary operating systems implement safe mode called safe boot macos well complex electronic devices safe mode operating system reduced functionality task isolating problems easier since many non-core components disabled sound installation boot safe mode typically major problem disk corruption installation poorly-configured software prevents operating system successfully booting normal operating mode though varies operating system safe mode typically loads essential executable modules disables devices except necessary display information accept input also take form parallel miniature operating system configuration information shared normal operating system example microsoft windows user also choose boot recovery console small text-based troubleshooting mode kept separate main operating system also accessed booting install cd various safe mode options run dysfunctional os features video drivers audio networking disabled safe mode typically provides access utility diagnostic programs user troubleshoot preventing operating system working normally safe mode intended maintenance functionality provides minimal access features microsoft windows safe mode 7/vista /xp /2000/me/98/95 accessed pressing f8 key operating system boots also multi-boot environment multiple versions windows installed side side f8 key pressed os selector prompt get safe mode however windows 8 released 2012 traditional press-f8-for-safe-mode-options ui convention longer works either shift-f8 special gui-based workaround necessary equivalently minimal setting unix-like operating systems single-user mode daemons x window system started root user log emergency repairs maintenance including resetting users passwords machine without need know old one macos holding shift key powering activates safe boot background maintenance features besides mode selection runs file system repair mac os 10.4 disables fonts /system/library/fonts moves trash font caches normally stored /library/caches/com.apple.ats/ uid uid user id number 501 disables startup items login items reset administrative account password unlike windows safe mode networking disabled default requires using safe mode networking enabled macos safe boot always includes networking classic mac os versions 6 7 8 9 similar mode unix root achieved holding shift key booting starts system without extensions application software sometimes offers safe mode well php interpreter prior version 5.4 safe mode offers stricter security measures glasgow haskell compiler version 7.2 offers safe haskell mode restricting usage functions unsafeperformio mozilla firefox safe mode allows user remove extensions may preventing browser loading internet explorer run add-ons mode protected mode cydia mobilesubstrate also safe mode allows user uninstall tweaks extensions may crash springboard
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Operating systems
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tagged architecture computer science tagged architecture particular type computer architecture every word memory constitutes tagged union divided number bits data tag section describes type data interpreted reference type object points notable examples american tagged architectures lisp machines tagged pointer support hardware opcode level burroughs large systems data-driven tagged descriptor-based architecture non-commercial rice computer burroughs lisp machine examples high-level language computer architectures tagging used support types high-level language hardware level addition original xerox smalltalk implementation used least-significant bit 16-bit word tag bit clear hardware would accept aligned memory address set treated shifted 15-bit integer current intel documentation mentions lower bits memory address might similarly used interpreter-based systems soviet union elbrus series supercomputers pioneered use tagged architectures 1973
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Computer architecture
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hb-f9p hb-f9p sony msx2-computer launched 1985 abbreviation hb stands hit bit hb-f9p unusual sense come built floppy disk drive instead built software suite memovision would run automatically unless program cartridge inserted cartridge slot graph key pressed booting memovision could store data special hbi-55 battery backed ram data cartridge sony originally developed hb-55 hb-75 msx1 computers systems contained simple built program called personal databank memovision continuation idea much extended contained stuff like birthday calendar alarm system family databank combination text editor database built calculator timer time calculator rendered pseudo 3d style hb-f9 many different localized variants produced
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Computer architecture
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intel iapx 432 iapx 432 intel advanced performance architecture computer architecture introduced 1981 intel first 32-bit processor design main processor architecture general data processor implemented set two separate integrated circuits due technical limitations time project started 1975 8800 8008 8080 intended intel major design 1980s unlike 8086 designed following year successor 8080 iapx 432 radical departure intel previous designs meant different market niche completely unrelated 8080 x86 product lines iapx 432 project considered commercial failure intel discontinued 1986 iapx 432 referred micromainframe designed programmed entirely high-level languages instruction set architecture also entirely new significant departure intel previous 8008 8080 processors iapx 432 programming model stack machine visible general-purpose registers supported object-oriented programming garbage collection multitasking well conventional memory management directly hardware microcode direct support various data structures also intended allow modern operating systems implemented using far less program code ordinary processors intel imax 432 operating system 432 written entirely ada ada also intended primary language application programming aspects may seen high-level language computer architecture properties features resulted hardware microcode design complex processors era especially microprocessors however internal external buses mostly wider 16-bit like 32-bit microprocessors era 68000 32016 32-bit arithmetical instructions implemented 16-bit alu via random logic microcode kinds sequential logic iapx 432 enlarged address space 8080 also limited fact linear addressing data could still use 16-bit offsets somewhat akin intel first 8086-based designs including contemporary 80286 new 32-bit segment offsets 80386 architecture described publicly detail 1984 using semiconductor technology day intel engineers n't able translate design efficient first implementation along lack optimization premature ada compiler contributed rather slow expensive computer systems performing typical benchmarks roughly 1/4 speed new 80286 chip clock frequency early 1982 initial performance gap rather low-profile low-priced 8086 line probably main reason intel plan replace latter later known x86 iapx 432 failed although engineers saw ways improve next generation design iapx 432 capability architecture started regarded implementation overhead rather simplifying support intended originally designed clock frequencies 10 mhz actual devices sold specified maximum clock speeds 4 mhz 5 mhz 7 mhz 8 mhz peak performance 2 million instructions per second 8 mhz intel 432 project started 1975 year 8-bit intel 8080 completed year 16-bit 8086 project began 432 project initially named 8800 next step beyond existing intel 8008 8080 microprocessors became big step instruction sets 8-bit processors well fitted typical algol-like compiled languages however major problem small native addressing ranges 16k 8008 64k 8080 far small many complex software systems without using kind bank switching memory segmentation similar mechanism built 8086 years later intel aimed build sophisticated complete system lsi chips functionally equal better best 32-bit minicomputers mainframes requiring entire cabinets older chips system would support multiprocessors modular expansion fault tolerance advanced operating systems advanced programming languages large applications ultra reliability ultra security architecture would address needs intel customers decade iapx 432 development team managed bill lattin justin rattner lead engineer rattner would later become cto intel initially team worked santa clara march 1977 lattin team 17 engineers moved intel new site portland lead engineer iapx 432 fred pollack specialized superscalarity later became lead architect i686 chip intel pentium pro soon became clear would take several years many engineers design would similarly take several years progress moore law improved chip manufacturing could fit dense chips meanwhile intel urgently needed simpler interim product meet immediate competition motorola zilog national semiconductor intel began rushed project design 8086 low-risk incremental evolution 8080 using separate design team mass-market 8086 shipped 1978 8086 designed backward-compatible 8080 sense 8080 assembly language could mapped 8086 architecture using special assembler existing 8080 assembly source code albeit executable code thereby made upward compatible new 8086 degree contrast 432 software compatibility migration requirements architects total freedom novel design scratch using whatever techniques guessed would best large-scale systems software applied fashionable computer science concepts universities particularly capability machines object-oriented programming high-level cisc machines ada densely encoded instructions ambitious mix novel features made chip larger complex chip complexity limited clock speed lengthened design schedule core design — main processor — termed general data processor gdp built two integrated circuits one 43201 fetch decode instructions 43202 execute systems would also include 43203 interface processor ip operated channel controller i/o attached processor ap conventional intel 8086 provided processing power i/o subsystem largest designs era two-chip gdp combined count approximately 97,000 transistors single chip ip approximately 49,000 comparison motorola 68000 introduced 1979 approximately 40,000 transistors 1983 intel released two additional integrated circuits iapx 432 interconnect architecture 43204 bus interface unit biu 43205 memory control unit mcu chips allowed nearly glueless multiprocessor systems 63 nodes innovative features iapx 432 detrimental good performance many cases iapx 432 significantly slower instruction throughput conventional microprocessors era national semiconductor 32016 motorola 68010 intel 80286 one problem two-chip implementation gdp limited speed motherboard electrical wiring larger issue capability architecture needed large associative caches run efficiently chips room left instruction set also used bit-aligned variable-length instructions instead usual semi-fixed byte word-aligned formats used majority computer designs instruction decoding therefore complex designs although hamper performance used additional transistors mainly large barrel shifter design already lacking space transistors caches wider buses performance oriented features addition biu designed support fault-tolerant systems 40 bus time held wait states another major problem immature untuned ada compiler used high-cost object-oriented instructions every case instead faster scalar instructions would made sense instance iapx 432 included expensive inter-module procedure call instruction compiler used calls despite existence much faster branch link instructions another slow call enter_environment set memory protection compiler ran every single variable system even variables used inside existing environment checked make matters worse data passed procedures always passed value-return rather reference running dhrystone benchmark parameter passing took ten times longer computations combined according new york times i432 ran 5 10 times slowly competitor motorola 68000 iapx 432 one first systems implement new ieee-754 standard floating-point arithmetic outcome failure 432 microprocessor designers concluded object support chip leads complex design invariably run slowly 432 often cited counter-example proponents risc designs however hold oo support primary problem 432 implementation shortcomings especially compiler mentioned would made cpu design slow since iapx 432 one attempt similar design rekursiv processor although inmos transputer process support similar — fast intel spent considerable time money mindshare 432 skilled team devoted unwilling abandon entirely failure marketplace new architect—glenford myers—was brought produce entirely new architecture implementation core processor would built joint intel/siemens project later biin resulting i960-series processors i960 risc subset became popular time embedded processor market high-end 960mc tagged-memory 960mx marketed military applications according new york times intel collaboration hp merced processor later known itanium company comeback attempt high-end market iapx 432 instruction variable length peculiarly bit rather byte aligned instruction taking 6 321 bits iapx 432 hardware microcode support object-oriented programming capability-based addressing system uses segmented memory 2 segments 64 kb providing total virtual address space 2 bytes physical address space 2 bytes 16 mb programs able reference data instructions address instead must specify segment offset within segment segments referenced access descriptors ads provide index system object table set rights capabilities governing accesses segment segments may access segments contain access descriptors data segments contain ads hardware microcode rigidly enforce distinction data access segments allow software treat data access descriptors vice versa system-defined objects consist either single access segment access segment data segment system-defined segments contain data access descriptors system-defined data designated offsets though operating system user software may extend additional data system object type field checked microcode port object used carrier object needed user program define new object types get full benefit hardware type checking use type control objects tco release 1 iapx 432 architecture system-defined object typically consisted access segment optionally depending object type data segment specified access descriptor fixed offset within access segment release 3 architecture order improve performance access segments data segments combined single segments 128 kb split access part data part 0–64 kb reduced number object table lookups dramatically doubled maximum virtual address space iapx432 recognizes fourteen types predefined system objects software running 432 need explicitly deallocate objects longer needed instead microcode implements part marking portion edsger dijkstra on-the-fly parallel garbage collection algorithm mark-and-sweep style collector entries system object table contain bits used mark object white black grey needed collector imax 432 operating system includes software portion garbage collector executable instructions contained within system instruction object since instructions bit-aligned 16-bit bit displacement instruction object allows object contain 8192 bytes instructions 65,536 bits instructions consist operator consisting class opcode zero three operand references fields organized present information processor sequence required decoding frequently used operators encoded using fewer bits instruction begins 4 6 bit class field indicates number operands called order instruction length operand optionally followed 0 4 bit format field describes operands operands format present come zero three operands described format instruction terminated 0 5 bit opcode classes contain one instruction therefore opcode format field permits gdp appear programmer zero- one- two- three-address architecture format field indicates operand data reference top next-to-top element operand stack
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Computer architecture
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cloudberry lab cloudberry lab software company develops online backup file management solutions integrated 20 cloud storage providers cloudberry backup cloudberry explorer offered personal use “ freemium ” model products including advanced cloudberry backup solutions sold per license free trials available cloudberry managed backup backup-as-a-service solution managed service providers businesses provides centralized management monitoring backup restore desktops servers cloudberry managed backup cloudberry backup support windows windows server macos linux operating systems work microsoft sql server exchange applications vmware microsoft hyper-v virtualization solutions cloudberry lab incorporated 2011 initially releasing cloudberry explorer amazon s3 followed versions microsoft azure google cloud openstack swift 2011 company released cloudberry backup followed releases support windows server imaging microsoft sql server exchange applications bare metal restore windows server desktop operating systems cloudberry backup added support linux mac operating systems 2015 followed editions synology qnap 2012 company introduced cloudberry managed backup saas backup disaster recovery solution managed service providers businesses require centralized administration management larger environments 2018 company introduced cloudberry remote assistant free remote control desktop sharing solution designed secure access control remote desktops servers internet cloudberry lab develops software help managed service providers businesses consumers manage backup disaster recovery perform cloud file management synchronization company main products include cloudberry managed backup cloudberry backup cloudberry explorer cloudberry drive cloudberry backup managed backup solutions automate backup recovery files folders system images cloudberry backup standalone solution managed backup subscription saas offering managed service providers businesses adds centralized administration management reporting products designed backup cloud support backups local disk network shares latest product versions back data 20 different cloud storage providers including amazon s3 amazon glacier azure blob storage google cloud storage backblaze b2 wasabi openstack s3 compatible others cloudberry backup managed backup employ storage-agnostic model customers license software cloudberry contract directly cloud providers choice backup storage customers get choose cloud storage provider offers features pricing best suits needs customers change storage vendors time without change backup vendors way cloudberry lab support customers varying size need products provide end-to-end encryption data cloudberry explorer windows solution free paid licensing options managing files local storage remote online storage versions available amazon s3 microsoft azure google cloud openstack cloudberry drive solution mounts cloud storage windows desktop server product allows customers work cloud storage though local storage cloudberry remote assistant solution remote control desktop sharing software currently beta available microsoft windows free remote assistant encrypts connections includes text voice chat cloudberry lab amazon advanced technology partner company also established partnerships microsoft azure google cloud platform backblaze b2 wasabi autotask connectwise others
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Computer security
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ds4/na digital signal 4/na ds4/na 139.264-mbit/s aggregate-multiplexed signal equivalent 3 digital signal 3s 2,016 digital signal 0s link commonly used long distance fiber carriage broadcast radio television platform 270mb/sec mpeg-2/asi transport stream circuits common use daily digital transmission broadcast television radio interconnecting sport arenas convention centers television stations broadcasters connections become part long-haul serial data transmission fiber sent purely serial data packetizing bandwidth sharing takes place tcp/ip carriers usually supplying circuits specialized often supplied us vyvx switch remote broadcast sports event example typically carried ds4 venue television network full unshared serial data circuit 270 megabits per second historically used appropriate gear circuit used emulate analog standard definition circuit using sampling rate 12-15 mhz carrying samples pcm format replaced dedicated coaxial cable circuits managed digital circuits use became rare early 21st century
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Internet protocols
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bsd/os bsd/os originally called bsd/386 sometimes known bsdi discontinued proprietary version bsd operating system developed berkeley software design inc. bsdi bsd/os reputation reliability server roles renowned unix programmer author w. richard stevens used personal web server reason bsdi formed 1991 members computer systems research group csrg uc berkeley develop sell proprietary version bsd unix pc compatible systems intel 386 later processors made use work previously done bill jolitz port bsd pc platform bsd/386 1.0 released march 1993 company sold licenses support taking advantage terms bsd license permitted use bsd software proprietary systems long credit given author company turn contributed code resources development non-proprietary bsd operating systems meantime jolitz left bsdi independently released open source bsd pcs called 386bsd one advantages bsdi system complete thorough manpage documentation entire system including complete syntax argument explanations examples file usage authors cross-references commands manpage documentation far poorer modern linux systems bsd/386 licenses including source code priced 995 much less unix system v source licenses fact highlighted advertisements part settlement usl v. bsdi bsdi substituted code written university 4.4 bsd-lite release disputed code os effective release 2.0 time release 386 designation become dated bsd/386 renamed bsd/os later releases bsd/os also supported sun sparc-based systems marketing bsd/os became increasingly focused internet server applications however increasingly tight market unix-compatible software late 1990s early 2000s hurt sales bsd/os one end market lacked certification open group bear unix trademark sales force hardware support larger unix vendors simultaneously lacked negligible acquisition cost open source bsds linux bsd/os acquired wind river systems april 2001 wind river discontinued sales bsd/os end 2003 support terminated end 2004
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Operating systems
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national location code national location code nlc four-digit number allocated every railway station ticket issuing point great britain use ticketing system british railway network used issue tickets accounting purposes subset nlcs created british rail based four main digits plus two supplementary digits nlcs introduced method accounting attributing costs revenue railway assets quotation taken 14th edition january 1987 national location code listing book published british railways board widespread use computers within british railways advent national computer systems dealing payroll compilation stores recording accounting wagon control traffic data revenue expenditure accounting market traffic surveys etc. need standard location code became increasingly important order meet need asked november 1966 revise update publication known terminals mileage gazetteer code time opportunity taken include sidings yards depots offices administrative centres etc. 'railway activity ... file developed based six-digit code known british railways national location code first published 1 january 1968 six-digit code split two parts first four digits identify location asset cost centre final two give information specific asset base location including stations ticket-issuing locations 00 first four digits two-digit combinations signify types asset first four digits indicating base location relate ticket issuing first four digits used examples 1960s 1970s various ticket issuing systems use quite localised simple numerical code structures covering limited number stations relevant area universal coding system identify stations nlc introduced nlcs began appear certain types ticket southern region mainstay ncr21 almost immediately introduction fully computerised intis intermediate ticket issuing system early 1980s four-digit version nlc became fully established intis tickets partly pre-printed station name printed ticket nlc next machine printed codes origin destination stations top line ticket intis superseded aptis 1986 latter became universal ticket office system next 15–20 years last aptis machines removed march 2007 aptis tickets nlc station issue printed second line irrespective whether journey started example ticket issued brighton nlc 5268 journey gatwick airport london victoria 5268 nlc covered station associated accounting activities everything tickets issued self-service ticket machines ticket office staff wage slips stations site needed treated separate entities allocated different codes london waterloo east serving south eastern division destinations began late 1980s considered separate station main london waterloo nlc 5598 self-service machines got code 5158 revenue could apportioned correctly relevant division privatisation correct train operating company toc railway network privatised mid-1990s need additional nlcs created 1998 brighton supplied two wall-mounted touch-screen machines cubic transportation systems inc. issuing limited range tickets credit card code 8882 given subsequently erstwhile quickfare machines replaced six fastticket touch-screen machines manufactured shere ltd. bore nlc 8882 well whereas ticket office machines smart terminal supplied shere used station original code 5268 location railway revenue expenditure attributed coded 1960s later came existence subsequently codes allocated location fixed mobile issue tickets location ticket issued journey national rail station examples british railways created 1948 split six operating regions became five 1960s eastern london midland western southern scottish distribution nlcs broadly followed pattern southern region divided three divisions south eastern central south western based three pre-grouping companies nlcs allocated approximately following boundaries follows since privatisation need new codes grown much largely stopped allocated geographical basis especially additional codes given station new station given geographically correct code usually station planned time gap left appropriate section codes example lea green nlc 2339 proposed many years name marshalls cross opened 2000 sometimes chandler ford station reopened original code closed coleshill parkway birmingham nuneaton opened 2007 allocated 9882 relates geographically scotland quirks always existed however
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Databases
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realization linguistics linguistics realization process kind surface representation derived underlying representation way abstract object linguistic analysis comes produced actual language phonemes often said realized speech sounds different sounds realize particular phoneme called allophones realization also subtask natural language generation involves creating actual text human language english french etc syntactic representation number software packages available realization developed academic research groups nlg remainder article concerns realization kind example following java code causes simplenlg system print text women smoke example computer program specified linguistic constituents sentence verb subject also linguistic features plural subject negated information realiser constructed actual sentence realisation involves three kinds processing syntactic realisation using grammatical knowledge choose inflections add function words also decide order components example english subject usually precedes verb negated form smoke smoke morphological realisation computing inflected forms example plural form woman women womans orthographic realisation dealing casing punctuation formatting example capitalising first word sentence examples basic realisers capable considerably complex processing number realisers developed past 20 years systems differ terms complexity sophistication processing robustness dealing unusual cases whether accessed programmatically via api whether take textual representation syntactic structure input also major differences pragmatic factors documentation support licensing terms speed memory usage etc possible describe realisers emerging areas
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Computational linguistics
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object data management group object data management group odmg conceived summer 1991 breakfast object database vendors organized rick cattell sun microsystems 1998 odmg changed name object database management group reflect expansion efforts include specifications object database object-relational mapping products primary goal odmg put forward set specifications allowed developer write portable applications object database object-relational mapping products order data schema programming language bindings data manipulation query languages needed portable 1993 2001 odmg published five revisions specification last revision odmg version 3.0 group disbanded odmg 3.0 published book form 2000 2001 major object database object-relational mapping vendors claimed conformance odmg java language binding compliance components specification mixed 2001 odmg java language binding submitted java community process basis java data objects specification odmg member companies decided concentrate efforts java data objects specification result odmg disbanded 2001 2004 object management group omg granted right revise odmg 3.0 specification omg specification copyright holder morgan kaufmann publishers february 2006 omg announced formation object database technology working group odbt wg plans work 4th generation object database standard
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Databases
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general-purpose macro processor general-purpose macro processor general purpose preprocessor macro processor tied integrated particular language piece software macro processor program copies stream text one place another making systematic set replacements macro processors often embedded programs assemblers compilers sometimes standalone programs used process kind text macro processors used language expansion defining new language constructs expressed terms existing language components systematic text replacements require decision making text reformatting e.g conditional extraction material html file
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Programming language topics
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benoît minisini benoît minisini french programmer best known programming gambas graphical development environment starting programming twelve became interested writing languages compilers assemblers interpreters interest respect basic programming language caused create gambas inspired visual basic benoît said intended gambas best features visual basic without numerous bugs flaws sees program language benoît part-time software job studied école pour l'informatique et les techniques avancées currently lives paris france
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Programming language topics
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stake atstake inc. computer security professional services company cambridge massachusetts united states founded 1999 battery ventures tom crotty sunil dhaliwal scott tobin ted julian initial core team technologists included dan geer chief technical officer east coast security team cambridge technology partners including dave goldsmith january 2000 stake acquired l0pht heavy industries known many hacker employees bringing mudge vice president research development domain name atstake.com july 2000 stake acquired cerberus information security limited london england david mark litchfield robert stein-rostaing launchpad europe middle east africa stake subsequently acquired symantec 2004 addition dan geer mudge stake employed many famous security experts including dildog window snyder dave aitel katie moussouris david litchfield mark kriegsman mike schiffman chris wysopal cris thomas joe grand september 2000 stake recruiter contacted mark abene recruit security consultant position recruiter apparently unaware past felony conviction since stake policy hiring convicted hackers mark informed company representative stake could hire saying ran background check caused debate regarding role convicted hackers working security business stake primarily consulting company also offered information security training stake academy created number software security tools symantec later stopped selling lc5 new customers citing us government export regulations discontinued support december 2006 january 2009 l0phtcrack acquired original authors symantec l0phtcrack 6 announced source boston conference march 11 2009 technology underlying smartrisk analyzer extended eventually brought market symantec spinoff veracode symantec announced acquisition stake september 16 2004 completed transaction october 9 2004 several members stake left form computer security company isec partners 2004 former stake academy instructors rob cheyne paul hinkle later formed information security training company safelight security advisors 2007 remaining portion stake consulting group continues operate security advisory services team within symantec security business practice
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Computer security
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jicwebs jicwebs joint industry committee web standards created uk ireland media industry ensure independence comparability measurement web effect jicwebs works partnership abce jicwebs deciding whether metrics desirable abce deciding whether practical web metrics intended measure activity web sites site centric fashion include measurements audience reach frequency activity levels including use effectiveness advertising web electronic media
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Web technology
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close system call close system call system call used close file descriptor kernel file systems program terminates access file filesystem using close system call flushes file buffers updates file metadata may include end-of-file indicator data de-allocates resources associated file including file descriptor updates system wide table files use programming languages maintain data structure files opened runtime library may close program terminates practice known resource acquisition initialization raii operating systems invoke codice_1 files held program terminates operating systems invoke codice_1 syscall part operating system recovery result system failure close call standardized posix specification function returns zero indicate file closed successfully error occurs value -1 returned errno appropriately set errors occur include
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Computer architecture
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html scripting w3c html standard includes support client-side scripting defines locally executable scripts may used web page particular client-side application web browser may support several script languages script code may executed document loads later time script code written directly html document inside events occur different elements web-page script code may associated event element writing code html attribute name attribute must supported intrinsic event element example onload script executed whenever event occurs element scripts mostly javascript html intrinsic event model consist following events browsers support additional event attributes outside standard netscape navigator supported feature called javascript entities script macros script code could included html attribute values using syntax similar character entity references example code codice_1 calls javascript prompt function ask user wide image html 4.01 specification reserves syntax future support script macros html attributes incorporated later standards supported current browser polyfill entities.js created order allow script macros browsers natively support feature
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Programming language topics
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distributed firewall firewall system group systems router proxy gateway implements set security rules enforce access control two networks protect inside network outside network may hardware device software program running secure host computer either case must least two network interfaces one network intended protect one network exposed firewall sits junction point gateway two networks usually private network public network internet conventional firewalls rely notions restricted topology control entry points function precisely rely assumption everyone one side entry point—the firewall—is trusted anyone side least potentially enemy distributed firewalls host-resident security software applications protect enterprise network servers end-user machines unwanted intrusion offer advantage filtering traffic internet internal network enables prevent hacking attacks originate internet internal network important costly destructive attacks still originate within organization like personal firewalls except offer several important advantages like central management logging cases access-control granularity features necessary implement corporate security policies larger enterprises policies defined pushed enterprise-wide basis feature distributed firewalls centralized management ability populate servers end-users machines configure push consistent security policies helps maximize limited resources ability gather reports maintain updates centrally makes distributed security practical distributed firewalls help two ways remote end-user machines secured secondly secure critical servers network preventing intrusion malicious code jailing code letting protected server used launch pad expanded attacks usually deployed behind traditional firewall provide second layer defense work enabling essential traffic machine protect prohibiting types traffic prevent unwanted intrusions whereas perimeter firewall must take generalist common denominator approach protecting servers network distributed firewalls act specialists problems conventional firewalls lead distributed firewalls follows due increasing line speeds computation intensive protocols firewall must support firewalls tend become congestion points gap processing networking speeds likely increase least foreseeable future computers hence firewalls getting faster combination complex protocols tremendous increase amount data must passed firewall likely continue pace moore law exist protocols new protocols designed difficult process firewall latter lacks certain knowledge readily available endpoints ftp realaudio two protocols although exist application-level proxies handle protocols solutions viewed architecturally “ unclean ” cases invasive likewise dependence network topology pf enforce policy traffic traverses thus traffic exchanged among nodes protected network controlled gives attacker already insider somehow bypass firewall complete freedom act worse yet become trivial anyone establish new unauthorized entry point network without administrator knowledge consent various forms tunnels wireless dial-up access methods allow individuals establish backdoor access bypasses security mechanisms provided traditional firewalls firewalls general intended guard misbehavior insiders tension internal needs connectivity difficulty satisfying needs centralized firewall ipsec protocol suite recently standardized ietf provides network-layer security services packet confidentiality authentication data integrity replay protection automated key management artifact firewall deployment internal traffic seen firewall filtered result internal users mount attacks users networks without firewall able intervene large networks today tend large number entry points performance failover reasons furthermore many sites employ internal firewalls provide form compartmentalization makes administration particularly difficult practical point view regard policy consistency since unified comprehensive management mechanism exists end-to-end encryption also threat firewalls prevents looking packet fields necessary filtering allowing end-to-end encryption firewall implies considerable trust users behalf administrators finally increasing need finer-grained access control standard firewalls readily accommodate without greatly increasing complexity processing requirements distributed firewalls host-resident security software applications protect enterprise network critical endpoints unwanted intrusion servers end-user machines concept security policy defined centrally enforcement policy takes place endpoint hosts routers etc. usually deployed behind traditional firewall provide second layer protection since hosts inside trusted equally machines subverted used launch attacks hosts especially trusted hosts protocols like rlogin thus faithful effort industry security organizations move towards system aspects desktop firewall centralized management like distributed firewalls distributed host-resident firewalls prevent hacking pc use entry point enterprise network compromised pc make whole network vulnerable attacks hacker penetrate enterprise network uncontested steal corrupt corporate assets distributed firewalls often kernel-mode applications sit bottom osi stack operating system filter traffic regardless origin—the internet internal network treat internet internal network unfriendly guard individual machine way perimeter firewall guards overall network distributed firewalls rest three notions basic idea simple compiler translates policy language internal format system management software distributes policy file hosts protected firewall incoming packets accepted rejected inside host according policy cryptographically-verified identity sender one often used term case network security particular distributed firewall policy essential know policies “ security policy ” defines security rules system without defined security policy way know access allowed disallowed simple example firewall distribution policy different varies implementation either directly pushed end systems pulled necessary hosts booting pings central management server check whether central management server active registers central management server requests policies implement central management server provides host security policies example license server security clearance server asked certain communication permitted conventional firewall could lacks important knowledge context request end systems may know things like files involved security levels might information could carried network protocol adding complexity push technique employed policies updated central management side network administrator hosts updated immediately push technology ensures hosts always updated policies time policy language defines inbound outbound connections component network policy domain allowed affect policy decisions layer network rejecting passing certain packets enforcing policies application layer central management component distributed firewalls makes practical secure enterprise-wide servers desktops laptops workstations central management provides greater control efficiency decreases maintenance costs managing global security installations feature addresses need maximize network security resources enabling policies centrally configured deployed monitored updated single workstation distributed firewalls scanned understand current operating policy determine updating required policy distribution scheme guarantee integrity policy transfer distribution policy different varies implementation either directly pushed end systems pulled necessary security policies transmitted central management server implemented host host end part distributed firewall provide administrative control network administrator control implementation policies host allows traffic based security rules implemented distributed firewalls strengths weaknesses compared conventional firewalls far biggest difference course reliance topology network topology permit reliance traditional firewall techniques little choice interesting question two types compare closed single-entry network either work reason choose one types firewalls excellent rejecting connection requests inappropriate services conventional firewalls drop requests border distributed firewalls host interesting question noticed host attempting connect today packets typically discarded notification distributed firewall may choose discard packet assumption legal peers know use ipsec alternatively may instead send back response requesting connection authenticated turn gives notice existence host firewalls built pure packet filters reject stealth scans well one technique example uses fragmented packets pass unexamined port numbers n't present first fragment distributed firewall reassemble packet reject balance sort threat two firewall types least comparable network addresses favored concept using cryptographic mechanisms likely prevents attacks based forged source addresses assumption trusted repository containing necessary credentials subject compromise problems solved conventional firewalls corresponding rules discarding packets network perimeter prevent attacks originating inside network policy domain spread use distributed object-oriented systems like corba client-side use java weaknesses mail readers like wide variety threats residing application intermediate level communication traffic firewall mechanisms perimeter come useful inspecting incoming e-mails known malicious code fingerprints confronted complex thus resource-consuming situations making decisions code like java using framework distributed firewall especially considering policy language allows policy decision application level circumvent problems condition contents communication packets interpreted semantically policy verifying mechanisms stateful inspection packets shows easily adapted requirements allows finer granularity decision making furthermore malicious code contents may completely disguised screening unit network perimeter given use virtual private networks enciphered communication traffic general completely disable policy enforcement conventional firewalls many firewalls detect attempted intrusions functionality provided distributed firewall individual host notice probes forward central location processing correlation former problem hard many hosts already log attempts one make good case detection done event collection problematic especially times poor connectivity central site also risk coordinated attacks effect causing denial-of-service attack central machine given natural view conventional firewall network topology consisting inside outside problems arise one members policy network domain compromised perimeter firewalls enforce policies distinct networks show option circumvent problems arise situation discussed given distributed firewalls independence topological constraints supports enforcement policies whether hosts members outsiders overall policy domain base decisions authenticating mechanisms inherent characteristics networks layout moreover compromise endpoint either legitimate user intruder weaken overall network way leads directly compromise machines given fact deployment virtual private networks prevents sniffing communication traffic attacked machine involved side end-point nearly problems arise conventional firewalls assuming machine taken adversary must lead conclusion policy enforcement mechanisms self may broken installation backdoors machine done quite easily security mechanisms flawed lack perimeter firewall trusted entity anymore might prevent arbitrary traffic entering leaving compromised host additionally use tools like ssh like allow tunneling applications communication prevented without proper knowledge decrypting credentials moreover given fact case attack shown successfully verifying mechanisms self may trusted anymore first glance biggest weakness distributed firewalls greater susceptibility lack cooperation users happens someone changes policy files distributed firewalls reduce threat actual attacks insiders simply making easier set smaller groups users thus one restrict access file server users need rather letting anyone inside company pound also worth expending effort prevent casual subversion policies policies stored simple ascii file user wishing example play game could easily turn protection requiring would-be uncooperative user go trouble probably worthwhile even mechanism theoretically insufficient example policies could digitally signed verified frequently-changing key awkward-to-replace location stringent protections policy enforcement incorporated tamper-resistant network card
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Computer security
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paramount defenses paramount defenses privately held american cyber security company develops cyber security solutions help organizations secure foundational microsoft active directory deployments company founded 2006 sanjay tandon former microsoft program manager active directory security company headquartered newport beach california led founder operates guidance advisory board amongst others includes karen worstell former microsoft chief information security officer ciso donald codling former unit chief liaison federal bureau investigation fbi cyber division department homeland security national cyber security division company also known paramount brief executive summary declassified 2016 describes serious cyber security risk potentially impacts foundational cyber security 85 organizations worldwide paramount defenses founded 2006 2013 united states patent office awarded founder cyber security patent governing accurate determination effective access information systems
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Computer security
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fabric computing fabric computing unified computing involves constructing computing fabric consisting interconnected nodes look like weave fabric viewed/envisaged collectively distance usually phrase refers consolidated high-performance computing system consisting loosely coupled storage networking parallel processing functions linked high bandwidth interconnects 10 gigabit ethernet infiniband term also used describe platforms azure services platform grid computing general common theme interconnected nodes appear single logical unit fundamental components fabrics nodes processor memory and/or peripherals links functional connections nodes term fabric also used association storage area networks switched fabric networking introduction compute resources provides complete unified computing system terms used describe fabrics include unified fabric data center fabric unified data center fabric ian foster director computation institute argonne national laboratory university chicago suggested 2007 grid computing 'fabrics poised become underpinning next-generation enterprise architectures used much greater part many organizations term use since mid late 1990s growth cloud computing cisco evangelism unified data center fabrics followed unified computing evolutionary data center architecture whereby blade servers integrated unified supporting network storage infrastructure starting march 2009 renewed interest technology companies offering unified fabric computing systems include liquid computing corporation egenera mixed reactions cisco architecture particularly rivals claim proprietary systems lock vendors analysts claim ambitious new direction big risk companies ibm hp previously partnered cisco data center projects accounting 2–3bn cisco annual revenue competing 2007 wombat financial software launched wombat data fabric first commercial off-the-shelf software platform providing high performance low-latency rdma-based messaging across infiniband switch main advantages fabrics massive concurrent processing combined huge tightly coupled address space makes possible solve huge computing problems presented delivery cloud computing services scalable able dynamically reconfigured challenges include non-linearly degrading performance curve whereby adding resources linearly increase performance common problem parallel computing maintaining security
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Distributed computing architecture
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object lisp object lisp computer programming language dialect lisp language object-oriented extension lisp dialect lisp machine lisp designed lisp machines inc object lisp also early example prototype-based programming seen competitor object-oriented extensions lisp around time flavors use symbolics common objects developed hewlett-packard commonloops use xerox object lisp also used early versions macintosh common lisp user interface toolkit written using object lisp 14 december 1985 net.lang.lisp usenet post common lisp meeting boston 9-11 december 1985 discusses object lisp objectlisp user manual g. drescher lmi 1985
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Programming language topics
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macintosh startup classic macintosh startup sequence included startup chime happy mac sad mac chimes death done away time release 2016 macbook pro eliminated final remaining startup feature startup chime favor discrete sequence black background audible indicators despite use security feature provided user-friendly audible verification computer nvram configuration authentic apple added startup chime back release 2017 macbook air macintosh startup chime played power-up trying boot operating system sound indicates diagnostic tests run immediately startup found hardware fundamental software problems specific sound differs depending rom greatly varies depending macintosh model first sound version first three macintosh models simple square-wave beep subsequent sounds various chords mark lentczner created code arpeggiated chord used macintosh ii variations sound used jim reekes created startup chime used quadra 700 quadra 800 reekes said startup sound done home studio korg wavestation ex c major chord played hands stretched wide possible 3rd top recall created sound annoyed tri-tone startup chimes felt associated death chimes computer crashes recalls apple give permission change sound secretly snuck sound computers help engineers charge rom chips apple found refused change using various claims order keep new sound intact also creator iconic earconic calls bong startup chime used macintoshes since quadra 840av slightly lower-pitched version chime used pci-based power macs imac g3 macintosh lc lc ii macintosh classic ii use reekes chime instead using f major chord produces ding sound first generation power macintosh computers also use reekes chime instead using chord strummed yamaha 12-string acoustic guitar jazz guitarist stanley jordan power macintosh 5200–6300 computers excluding 5400 5500 bong chime like one used pci-based power macs use unique chime also used television commercials power macintosh powerbook series 1995 1998 20th anniversary macintosh uses another unique sound models built prior introduction power macintosh 1994 sad mac icon error code distinctive sounds displayed failure initial self-diagnostic tests phenomenon referred chimes death chime mac computers 1998-2016 chime used first imac g3 chord f-sharp major chord produced pitch-shifting 840av sound mac startup chime registered trademark united states featured 2008 film wall-e titular robot character fully recharged solar panels well 2007 brad paisley song online apple removed startup chime starting late 2016 macbook pro apple since updated support documentation reflect change removing references startup chime nvram reset instructions model happy mac normal bootup startup icon apple macintosh computer running older versions mac operating system designed susan kare 1980s drawing inspiration design compact macintosh series batman character two-face icon remained unchanged introduction new world rom macs updated 8-bit color happy mac indicates booting successfully begun whereas sad mac along chimes death melody one beeps indicates hardware problem macintosh boots mac os 9 lower system play startup chime screen turn gray happy mac icon appear followed mac os splash screen small welcome macintosh screen system 7.5 earlier underwent several stylistic changes mac os versions 8.6 later also includes version number splash screen example welcome mac os 8.6 early macs internal hard drive computer boots point needs load operating system floppy disk user inserts correct disk mac displays floppy icon blinking question mark later macs folder icon question mark repeatedly changes finder icon shown system folder boot loader file found startup disk introduction mac os x addition blinking system folder icon prohibition icon added show incorrect os version found bomb screen replaced kernel panic originally colored white changed black version 10.3 mac os x 10.1 new happy mac included also last version happy mac icon version 10.2 happy mac symbol replaced apple logo face id logo iphone x based happy mac sad mac symbol used older-generation apple macintosh computers hardware using old world rom open firmware predating onboard usb starting original 128k macintosh ending last nubus-based power macintosh models including first-generation 6100 7100 8100 well powerbook 5300 1400 indicate severe hardware software problem prevented startup occurring successfully sad mac icon displayed along set hexadecimal codes indicate type problem startup different codes different errors used place normal happy mac icon indicates startup-time hardware tests successful 68k models made macintosh ii chimes death played models prior macintosh ii crash silently display sad mac without playing tone powerpc macs play sound effect car crash computers equipped powerpc upgrade card use three note brass fanfare death chime e-natural e-flat followed sound drum macintosh performa 6200 macintosh performa 6300 sad mac may deliberately generated startup pressing interrupt switch macintosh computers one installed pressing command power keys shortly startup chime macintoshes powerbook 540c user presses command power keys boot screen displays play chimes death chimes fraction normal speed sad mac displayed old world rom power macintosh powerbook models based pci architecture use sad mac icon instead play error/car-crash sound hardware failure missing bad memory unusable cpu similar mac os x 10.2 later use universal symbol denote hardware software error renders computer non-bootable ipod damage error occurs hardware firmware example files deleted sad ipod appears similar sad mac instead macintosh ipod chimes death icon also lacks nose frown flipped horizontally also show hexadecimal codes indicating problem occurred ipod error screen show problem occurs newer ipods chimes death macintosh equivalent beep code ibm pc compatibles macintosh models predating adoption pci open firmware chimes death often accompanied sad mac icon middle screen different macintosh series used different death chimes macintosh ii first use death chimes loud eerie upward major arpeggio different chimes many models macintosh quadra centris performa lc macintosh classic played generally softer lower pitched version upward major arpeggio followed three four notes slight variation depending model macintosh powerbook 5300 190 1400 used second half 8-note arpeggio found quadra centris models entire death chime error occurred screen lights macintosh quadra av660 centris av660 used sound single pass roland d-50 digital native dance sample loop nubus based power macintosh models including 6100 7100 8100 series used car crash sound power macintosh performa 6200 6300 series along power macintosh upgrade card used eerily dramatic 3-note brass fanfare rhythm drums cymbals pre-g3 pci power macs beige g3 power macs g3 all-in-one powerbook 2400 3400 g3 used sound glass shattering models display sad mac icon since introduction imac 1998 chimes death longer used replaced series tones indicate hardware errors
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Operating systems
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comparison programming languages associative array comparison programming languages associative arrays compares features associative array data structures array-lookup processing 39 various computer programming languages following comparison associative arrays also mapping hash dictionary various programming languages awk built-in language-level support associative arrays example also loop associated array follows also check element associative array delete elements associative array multi-dimensional associative arrays simulated standard awk using concatenation e.g subsep standard implementation associative array c 3rd party library bsd license available archived source code available posix 1003.1-2001 describes functions codice_1 codice_2 codice_3 another 3rd party library uthash also creates associative arrays c structures structure represents value one structure fields acts key finally glib library also supports associative arrays along many advanced data types recommended implementation gnu project similar glib apple cross-platform core foundation framework provides several basic data types particular reference counted cfdictionary cfmutabledictionary dictionary also initialized entries construction called object initialization foreach loop enumerate entire collection guarantee order order matters programmer could choose use sorteddictionary use .sort linq extension method c++ also form associative array called codice_4 see standard template library containers one could create map information using c++ following code less efficiently creates temporary codice_5 values extension initialization lists c++11 entries added map construction shown iterate list following code c++03 task new c++11 using structured binding available c++17 c++ codice_4 class templated allows data types keys values different different codice_7 instances given instance codice_7 class keys must base type must true values although codice_4 typically implemented using self-balancing binary search tree c++11 defines second map called codice_10 algorithmic characteristics hash table common vendor extension stl well usually called codice_11 available implementations sgi stlport structure cfml equivalent associative array initializing empty dictionary adding items alternatively dictionary initialized items construction dictionary enumerated for-loop guaranteed order offers direct support associative arrays core language – implemented chaining hash table binary trees equivalent example would keys values types keys associative array must type values also loop properties associated values i.e follows property removed follows delphi supports several standard generic containers including tdictionary versions delphi prior 2009 offer direct support associative arrays however simulate associative arrays using tstrings class example erlang offers many approaches represent mappings two common standard library keylists dictionaries keylists lists tuples first element tuple key second value functions operating keylists provided codice_12 module accessing element keylist done codice_13 function dictionaries implemented codice_14 standard library new dictionary created using codice_15 function new key/value pairs stored using codice_16 function serial initialization would idiomatically represented erlang appropriate function dictionary accessed using codice_17 function cases erlang term used key variations include codice_18 module implementing ordered dictionaries codice_19 implementing general balanced trees f constructs maps lists sequences arrays tuples using functions provided map module f represents tuple two elements separated comma list sequence elements enclosed square brackets separated semi-colons values looked via one codice_20 functions codice_21 returns option type value codice_22 successful lookup codice_23 unsuccessful one pattern matching used extract raw value default result example codice_24 value contain string codice_25 f .net language also access features .net framework including codice_26 objects codice_27 objects used purpose c visual basic objects may preferred writing code intended linked languages .net framework visual foxpro implements mapping collection class getkey returns 0 key found see collection foxpro help details go built-in language-level support associative arrays called maps map key type may boolean numeric string array struct pointer interface channel type map type written like map keytype valuetype adding elements one time map literal iterating map haskell programming language report provides one kind associative container list pairs output note lookup function returns maybe value nothing found result found ghc commonly used implementation haskell provides two types associative containers implementations might also provide one polymorphic functional maps represented immutable balanced binary trees output specialized version integer keys also exists data.intmap finally polymorphic hash table output lists pairs functional maps provide purely functional interface idiomatic haskell contrast hash tables provide imperative interface io monad java associative arrays implemented maps part java collections framework since j2se 5.0 introduction generics java collections type specified example associative array mapping strings strings might specified follows method used access key example value expression codice_28 codice_25 code uses hash map store associative array calling constructor class however since code uses methods common interface one could also use self-balancing binary tree calling constructor class implements subinterface without changing definition codice_30 variable rest code use number underlying data structures implement codice_31 interface hash function java used hashmap hashset provided method since every class java inherits every object hash function class override default implementation codice_32 provide custom hash function based properties object codice_33 class also contains method tests object equality another object hashed data structures java rely objects maintaining following contract codice_32 codice_35 methods two objects b order maintain contract class overrides codice_35 must also override codice_32 maybe vice versa codice_32 based properties subset properties codice_35 contract hashed data structures object results codice_32 codice_35 methods change object inserted map reason generally good practice base hash function immutable properties object analogously treemap sorted data structures requires ordering defined data type either data type must already defined ordering implementing interface custom must provided time map constructed hashmap relative ordering keys treemap change inserted map javascript standardized version ecmascript prototype-based object-oriented language javascript object mapping property names values—that associative array one caveat since property names strings string coerced integer keys allowed difference objects also include one feature unrelated associative arrays prototype link object inherit lookup property forward lookup prototype object define property object literal written codice_42 example property name valid identifier quotes omitted e.g lookup written using property access notation either square brackets always works dot notation works identifier keys also loop enumerable properties associated values follows property removed follows mentioned properties strings however since every native object primitive implicitly converted string object including built-in objects array dynamically extended new properties example modern javascript considered bad form use array type associative array consensus object type best purpose reasoning behind array extended via prototype object kept pristine 'for loops work expected associative 'arrays issue drawn focus popularity javascript frameworks make heavy sometimes indiscriminate use prototype extend javascript inbuilt types see javascript array object prototype awareness day information issue declare dictionary access element add element delete element get keys values iterables definition dereference lisp originally conceived list processing language one important data types linked list treated association list alist syntax codice_43 used indicate codice_44ed pair keys values need type within alist lisp scheme provide operators codice_45 manipulate alists ways similar associative arrays linear nature alists used relatively small sets data common lisp also supports hash table data type scheme implemented srfi 69 hash tables greater overhead alists provide much faster access many elements easy construct composite abstract data types lisp using structures and/or object-oriented programming features conjunction lists arrays hash tables lpc implements associative arrays fundamental type known either map mapping depending driver keys values type mapping literal written codice_46 procedural use looks like mappings accessed reading using indexing operator way writing shown phone_book sally smart would return string 555-9999 phone_book john smith would return 0 testing presence done using function member e.g codice_47 deletion accomplished using function called either m_delete map_delete depending driver used like codice_48 lpc drivers amylaar family implement multivalued mappings using secondary numeric index drivers mudos family support multivalued mappings example syntax lpc drivers modern enough support foreach construct allow iteration mapping types using lua table fundamental type used either array numerical index fast associative array keys values type except nil following focuses non-numerical indexes table literal written codice_49 example key valid identifier keyword quotes omitted case sensitive lookup written using either square brackets always works dot notation works identifier keys also loop keys associated values iterators loops entry removed setting nil likewise overwrite values add mathematica uses association expression represent associative arrays access keys strings key keyword necessary list keys values mumps every array associative array built-in language-level direct support associative arrays applies private process-specific arrays stored memory called locals well permanent shared arrays stored disk available concurrently multiple jobs name globals preceded circumflex distinguish local variable names access value element simply requires using name subscript also loop associated array follows cocoa api gnustep handle associative arrays using codice_50 mutable version codice_51 class cluster class allows assignments two objects made copy key object made inserted codice_50 therefore keys must conform codice_53 protocol inserted dictionary value object receives retain message increase reference count value object receive release message deleted dictionary explicitly adding dictionary different object key keys added creation lookup written using codice_54 notation using codice_55 action also loop keys values codice_56 key removed using codice_57 rexx associative arrays called stem variables compound variables stem variables numeric keys typically start 1 go 0 key stem variable used convention count items whole stem rexx easy way automatically accessing keys stem variable typically keys stored separate associative array numeric keys ruby hash used follows ruby supports hash looping iteration following syntax ruby also supports many useful operations hashes merging hashes selecting rejecting elements meet criteria inverting swapping keys values flattening hash array s-lang associative array type example also loop associated array number ways one print sorted-list better take advantage s-lang strong support standard arrays scala provides immutable map class part scala.collection framework scala type inference work codice_58 access array returns option type scala equivalent maybe monad haskell smalltalk dictionary used access entry message codice_59 sent dictionary object gives dictionary hashes/compares based equality holds strong references key value variants exist hash/compare identity identitydictionary keep weak references weakkeydictionary weakvaluedictionary every object implements hash object used key course also value snobol one first first programming languages use associative arrays associative arrays snobol called tables sml'97 standard standard ml programming language provide associative containers however various implementations standard ml provide associative containers library popular standard ml new jersey implementation provides signature somewhat like interface codice_60 defines common interface ordered functional immutable associative arrays several general functors codice_61 codice_62 codice_63 codice_64 allow create corresponding type ordered map types self-balancing binary search tree sorted association list red-black tree splay tree respectively using user-provided structure describe key type comparator functor returns structure follows codice_60 interface addition two pre-defined modules associative arrays integer keys codice_66 codice_67 sml/nj also provides polymorphic hash table monomorphic hash tables also supported using codice_68 functor another standard ml implementation moscow ml also provides associative containers first provides polymorphic hash tables codice_69 structure also functional maps sml/nj library available codice_70 codice_71 codice_72 structures two tcl facilities support associative array semantics array collection variables dict full implementation associative arrays dict look item iterate dict array literal space character variable name must grouped using either curly brackets substitution performed double quotes substitution performed alternatively several array elements set single command providing mappings list words containing whitespace braced access one array entry put standard output result retrieve entire array dictionary result order keys unspecified dictionary unordered array standard implementation common dialects visual basic use dictionary class microsoft scripting runtime shipped visual basic 6 visual basic .net relies collection classes provided .net framework unlike many command line interpreters powershell built-in language-level support defining associative arrays example like javascript property name valid identifier quotes omitted e.g entries separated either semicolon newline e.g keys values .net object type e.g also possible create empty associative array add single entries even associative arrays later new entries also added using array index operator property operator codice_73 method underlying .net object dereference assigned objects array index operator property operator parameterized property codice_74 .net object used loop associative array follows entry removed using codice_75 method underlying .net object hash tables added e.g many data serialization formats also support associative arrays see table json associative arrays also referred objects keys strings yaml associative arrays also called map elements key-value pairs yaml places restrictions type keys particular restricted scalar string values
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Programming language topics
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android froyo android froyo sixth version android codename android mobile operating system developed google spanning versions 2.2 2.2.3 versions longer supported unveiled may 20 2010 google i/o 2010 conference one prominent changes froyo release usb tethering wi-fi hotspot functionality changes include support android cloud device messaging c2dm service enabling push notifications additional application speed improvements implemented jit compilation displayed within applications top-of-the-screen banners new features introduced froyo include following
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Operating systems
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itanium itanium family 64-bit intel microprocessors implement intel itanium architecture formerly called ia-64 intel markets processors enterprise servers high-performance computing systems itanium architecture originated hewlett-packard hp later jointly developed hp intel itanium-based systems produced hp hp integrity servers line several manufacturers 2008 itanium fourth-most deployed microprocessor architecture enterprise-class systems behind x86-64 power isa sparc february 2017 intel released current generation test customers may began shipping volume last processor itanium family intel officially announced end life product discontinuance itanium cpu family january 30th 2019 1989 hp determined reduced instruction set computing risc architectures approaching processing limit one instruction per cycle hp researchers investigated new architecture later named explicitly parallel instruction computing epic allows processor execute multiple instructions clock cycle epic implements form long instruction word vliw architecture single instruction word contains multiple instructions epic compiler determines advance instructions executed time microprocessor simply executes instructions need elaborate mechanisms determine instructions execute parallel goal approach twofold enable deeper inspection code compile time identify additional opportunities parallel execution simplify processor design reduce energy consumption eliminating need runtime scheduling circuitry hp believed longer cost-effective individual enterprise systems companies develop proprietary microprocessors partnered intel 1994 develop ia-64 architecture derived epic intel willing undertake large development effort ia-64 expectation resulting microprocessor would used majority enterprise systems manufacturers hp intel initiated large joint development effort goal delivering first product merced 1998 development intel hp industry analysts predicted ia-64 would dominate servers workstations high-end desktops eventually supplant risc complex instruction set computing cisc architectures general-purpose applications compaq silicon graphics decided abandon development alpha mips architectures respectively favor migrating ia-64 several groups ported operating systems architecture including microsoft windows openvms linux hp-ux solaris tru64 unix monterey/64 latter three canceled reaching market 1997 apparent ia-64 architecture compiler much difficult implement originally thought delivery timeframe merced began slipping intel announced official name processor itanium october 4 1999 within hours name itanic coined usenet newsgroup reference rms titanic unsinkable ocean liner sank maiden voyage 1912 itanic since often used register others imply multibillion-dollar investment itanium—and early hype associated it—would followed relatively quick demise time itanium released june 2001 performance superior competing risc cisc processors itanium competed low-end primarily four-cpu smaller systems servers based x86 processors high-end ibm power sun microsystems sparc processors intel repositioned itanium focus high-end business hpc computing attempting duplicate x86 successful horizontal market i.e. single architecture multiple systems vendors success initial processor version limited replacing pa-risc hp systems alpha compaq systems mips sgi systems though ibm also delivered supercomputer based processor power sparc remained strong 32-bit x86 architecture continued grow enterprise space building economies scale fueled enormous installed base thousand systems using original merced itanium processor sold due relatively poor performance high cost limited software availability recognizing lack software could serious problem future intel made thousands early systems available independent software vendors isvs stimulate development hp intel brought next-generation itanium 2 processor market year later itanium 2 processor released 2002 marketed enterprise servers rather whole gamut high-end computing first itanium 2 code-named mckinley jointly developed hp intel relieved many performance problems original itanium processor mostly caused inefficient memory subsystem mckinley contains 221 million transistors 25 million logic measured 19.5 mm 21.6 mm 421 mm fabricated 180 nm bulk cmos process six layers aluminium metallization 2003 amd released opteron cpu implements 64-bit architecture called amd64 opteron gained rapid acceptance enterprise server space provided easy upgrade x86 influence microsoft intel responded implementing amd x86-64 instruction set architecture instead ia-64 xeon microprocessors 2004 resulting new industry-wide de facto standard intel released new itanium 2 family member codenamed madison 2003 madison used 130 nm process basis new itanium processors montecito released june 2006 march 2005 intel announced working new itanium processor codenamed tukwila released 2007 tukwila would four processor cores would replace itanium bus new common system interface would also used new xeon processor later year intel revised tukwila delivery date late 2008 november 2005 major itanium server manufacturers joined intel number software vendors form itanium solutions alliance promote architecture accelerate software porting alliance announced members would invest 10 billion itanium solutions end decade 2006 intel delivered montecito marketed itanium 2 9000 series dual-core processor roughly doubled performance decreased energy consumption 20 percent intel released itanium 2 9100 series codenamed montvale november 2007 may 2009 schedule tukwila follow-on revised release oems planned first quarter 2010 itanium 9300 series processor codenamed tukwila released february 8 2010 greater performance memory capacity device uses 65 nm process includes two four cores 24 mb on-die caches hyper-threading technology integrated memory controllers implements double-device data correction helps fix memory errors tukwila also implements intel quickpath interconnect qpi replace itanium bus-based architecture peak interprocessor bandwidth 96 gb/s peak memory bandwidth 34 gb/s quickpath processor integrated memory controllers interfaces memory directly using qpi interfaces directly connect processors i/o hubs quickpath also used intel processors using nehalem microarchitecture possibly enabled tukwila nehalem use chipsets tukwila incorporates four memory controllers supports multiple ddr3 dimms via separate memory controller much like nehalem-based xeon processor code-named beckton itanium 9500 series processor codenamed poulson follow-on processor tukwila released november 8 2012 according intel skips 45 nm process technology uses 32 nm process technology features eight cores 12-wide issue architecture multithreading enhancements new instructions take advantage parallelism especially virtualization poulson l3 cache size 32 mb l2 cache size 6 mb 512 kb 256 kb per core die size 544 mm² less predecessor tukwila 698.75 mm² isscc 2011 intel presented paper called 32nm 3.1 billion transistor 12-wide-issue itanium processor mission critical servers given intel history disclosing details itanium microprocessors isscc paper likely referred poulson analyst david kanter speculated poulson would use new microarchitecture advanced form multithreading uses two threads improve performance single threaded multithreaded workloads information also released hot chips conference information presented improvements multithreading resiliency improvements intel instruction replay ras new instructions thread priority integer instruction cache prefetching data access hints intel product change notification pcn 111456-01 lists four models itanium 9500 series cpu later removed revised document parts later listed intel material declaration data sheets mdds database intel later posted itanium 9500 reference manual models following 2012 hewlett-packard co. v. oracle corp. support lawsuit court documents unsealed santa clara county court judge revealed 2008 hewlett-packard paid intel around 440 million keep producing updating itanium microprocessors 2009 2014 2010 two companies signed another 250 million deal obliged intel continue making itanium cpus hp machines 2017 terms agreements hp pay chips gets intel intel launches tukwila poulson kittson kittson+ chips bid gradually boost performance platform rumors successor poulson code named kittson began circulate 2012–2013 first associated forthcoming 22 nm process shrink later revised face declining itanium sales less-ambitious 32 nm node april 2015 intel although yet confirmed formal specifications confirm continued work project meanwhile aggressively multicore xeon e7 platform displaced itanium-based solutions intel roadmap july 2016 hp spin-off hewlett packard enterprise hpe announced computer world kittson would released mid-2017 february 2017 intel reported shipping kittson test customers plans ship volume later year intel officially launched itanium 9700 series processor family may 11 2017 notably kittson microarchitecture improvements poulson higher clock speeds intel announced 9700 series last itanium chips produced models comparison xeon family server processors itanium never high-volume product intel intel release production numbers one industry analyst estimated production rate 200,000 processors per year 2007 according gartner inc. total number itanium servers processors sold vendors 2007 55,000 unclear whether clustered servers counted single server compares 417,000 risc servers spread across risc vendors 8.4 million x86 servers idc reports total 184,000 itanium-based systems sold 2001 2007 combined power/sparc/itanium systems market idc reports power captured 42 revenue sparc captured 32 itanium-based system revenue reached 26 second quarter 2008 according idc analyst 2007 hp accounted perhaps 80 itanium systems revenue according gartner 2008 hp accounted 95 itanium sales hp itanium system sales annual rate 4.4bn end 2008 declined 3.5bn end 2009 compared 35 decline unix system revenue sun 11 drop ibm x86-64 server revenue increase 14 period december 2012 idc released research report stating itanium server shipments would remain flat 2016 annual shipment 26,000 systems decline 50 compared shipments 2008 2006 hp manufactured least 80 itanium systems sold 7,200 first quarter 2006 bulk systems sold enterprise servers machines large-scale technical computing average selling price per system excess us 200,000 typical system uses eight itanium processors 2012 manufacturers offered itanium systems including hp bull nec inspur huawei addition intel offered chassis could used system integrators build itanium systems 2015 hp supplied itanium-based systems hp split late 2015 itanium systems branded integrity handled hewlett-packard enterprise hpe recent major update 2017 integrity i6 hp-ux 11i v3 update 16 hpe also supports operating systems including windows server 2008 r2 linux openvms nonstop itanium affected spectre meltdown itanium bus interfaces rest system via chipset enterprise server manufacturers differentiate systems designing developing chipsets interface processor memory interconnections peripheral controllers chipset heart system-level architecture system design development chipset costs tens millions dollars represents major commitment use itanium ibm created chipset 2003 intel 2002 neither developed chipsets support newer technologies ddr2 pci express tukwila moved away fsb chipsets supporting technologies manufactured itanium server vendors hp fujitsu sgi nec hitachi tukwila itanium processor model designed share common chipset intel xeon processor ex intel xeon processor designed four processor larger servers goal streamline system development reduce costs server oems many develop itanium- xeon-based servers however 2013 goal pushed back evaluated future implementation opportunities itanium supported i.e windows version longer bought following operating systems microsoft announced windows server 2008 r2 would last version windows server support itanium support started xp would also discontinue development itanium versions visual studio sql server likewise red hat enterprise linux 5 first released march 2007 last itanium edition red hat enterprise linux debian longer supports itanium officially last release official support debian 7 wheezy covered long term support lts unofficial support newer debian still available limited form via debian ports last available kernel wheezy-backports linux 3.14.0 released march 30 2014 possible manually update latest 3.14.x version recent kernel versions like 4.17.17 september 2018 addition canonical ltd. chose support itanium ubuntu 10.04 lts released april 2010 discontinued hp supporting certifying linux itanium 9300 tukwila servers late september 2012 nec announced return ia-64 previous noah line proprietary mainframe processors produced quad-core variant 40 nm called noah-6 hp sells virtualization technology itanium called integrity virtual machines allow software run itanium intel supported development compilers optimized platform especially suite compilers starting november 2010 introduction new product suites intel itanium compilers longer bundled intel x86 compilers single product intel offers itanium tools intel x86 tools including compilers independently different product bundles gcc open64 microsoft visual studio 2005 later also able produce machine code itanium according itanium solutions alliance 13,000 applications available itanium-based systems early 2008 though sun contested itanium application counts past isa also supported gelato itanium hpc user group developer community ported supported open-source software itanium emulation technique allows computer execute binary code compiled different type computer ibm acquisition quicktransit 2009 application binary software irix/mips solaris/sparc could run via type emulation called dynamic binary translation linux/itanium similarly hp implemented method execute pa-risc/hp-ux itanium/hp-ux via emulation simplify migration pa-risc customers radically different itanium instruction set itanium processors also run mainframe environment gcos groupe bull several x86 operating systems via instruction set simulators itanium aimed enterprise server high-performance computing hpc markets enterprise- hpc-focused processor lines include oracle fujitsu sparc processors ibm power microprocessors measured quantity sold itanium serious competition comes x86-64 processors including intel xeon line amd opteron line since 2009 servers shipped x86-64 processors 2005 itanium systems accounted 14 hpc systems revenue percentage declined industry shifted x86-64 clusters application october 2008 gartner report tukwila processor stated ... future roadmap itanium looks strong risc peer like power sparc itanium-based computer first appeared list top500 supercomputers november 2001 best position ever achieved itanium 2 based system list 2 achieved june 2004 thunder lawrence livermore national laboratory entered list rmax 19.94 teraflops november 2004 columbia entered list 2 51.8 teraflops least one itanium-based computer top 10 june 2007 peak number itanium-based machines list occurred november 2004 list 84 systems 16.8 june 2012 dropped one system 0.2 itanium system remained list november 2012 itanium processors show progression capability merced proof concept mckinley dramatically improved memory hierarchy allowed itanium become reasonably competitive madison shift 130 nm process allowed enough cache space overcome major performance bottlenecks montecito 90 nm process allowed dual-core implementation major improvement performance per watt montvale added three new features core-level lockstep demand-based switching front-side bus frequency 667 mhz first released 2001 itanium performance disappointing compared better-established risc cisc processors emulation run existing x86 applications operating systems particularly poor one benchmark 2001 reporting equivalent best 100 mhz pentium mode 1.1 ghz pentiums market time itanium failed make significant inroads ia-32 risc suffered following arrival x86-64 systems offered greater compatibility older x86 applications 2009 article history processor — itanium killed computer industry — journalist john c. dvorak reported continues one great fiascos last 50 years tech columnist ashlee vance commented delays underperformance turned product joke chip industry interview donald knuth said itanium approach ... supposed terrific—until turned wished-for compilers basically impossible write red hat microsoft announced plans drop itanium support operating systems due lack market interest however linux distributions gentoo debian remain available itanium march 22 2011 oracle corporation announced would longer develop new products hp-ux itanium although would continue provide support existing products following announcement hp sued oracle breach contract arguing oracle violated conditions imposed settlement oracle hiring former hp ceo mark hurd co-ceo requiring vendor support itanium software time hp discontinues sales itanium-based servers breach harmed business 2012 court ruled favor hp ordered oracle resume support itanium june 2016 hewlett-packard enterprise corporate successor hp server business awarded 3 billion damages lawsuit former intel official reported itanium business become profitable intel late 2009 2009 chip almost entirely deployed servers made hp 95 itanium server market share making main operating system itanium hp-ux march 22 2011 intel reaffirmed commitment itanium multiple generations chips development schedule although itanium attain limited success niche market high-end computing intel originally hoped would find broader acceptance replacement original x86 architecture amd chose different direction designing less radical x86-64 64-bit extension existing x86 architecture microsoft supported forcing intel introduce extensions x86-based processors designs run existing 32-bit applications native hardware speed offering support 64-bit memory addressing enhancements new applications architecture become predominant 64-bit architecture desktop portable market although itanium-based workstations initially introduced companies sgi longer available 1989 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2009 2010 2011 2012 2013 2014 2017 2019
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Computer architecture
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google analytics google analytics web analytics service offered google tracks reports website traffic currently platform inside google marketing platform brand google launched service november 2005 acquiring developer urchin google analytics widely used web analytics service web google analytics provides sdk allows gathering usage data ios android app known google analytics mobile apps google analytics used track website activity users session duration pages per session bounce rate etc along information source traffic integrated google ads users review online campaigns tracking landing page quality conversions goals goals might include sales lead generation viewing specific page downloading particular file google analytics approach show high-level dashboard-type data casual user in-depth data report set google analytics analysis identify poorly performing pages techniques funnel visualization visitors came referrers long stayed website geographical position also provides advanced features including custom visitor segmentation google analytics e-commerce reporting track sales activity performance e-commerce reports shows site transactions revenue many commerce-related metrics september 29 2011 google analytics launched real time analytics enabling user insight visitors currently site user 100 site profiles profile generally corresponds one website limited sites traffic fewer 5 million pageviews per month roughly 2 pageviews per second unless site linked google ads campaign google analytics includes google website optimizer rebranded google analytics content experiments google analytics cohort analysis helps understanding behaviour component groups users apart user population beneficial marketers analysts successful implementation marketing strategy google acquired urchin software corp. april 2005 google service developed urchin demand system also brings ideas adaptive path whose product measure map acquired used redesign google analytics 2006 google continued sell standalone installable urchin webanalytics software network value-added resellers discontinuation march 28 2012 google-branded version rolled november 2005 anyone wished sign however due extremely high demand service new sign-ups suspended week later capacity added system google began using lottery-type invitation-code model august 2006 google sending batches invitation codes server availability permitted since mid-august 2006 service fully available users – whether use google advertising newer version google analytics tracking code known asynchronous tracking code google claims significantly sensitive accurate able track even short activities website previous version delayed page loading performance reasons generally placed codice_1 body close html tag new code placed codice_2 html head tags triggered runs parallel page loading april 2011 google announced availability new version google analytics featuring multiple dashboards custom report options new interface design version later updated features real-time analytics goal flow charts october 2012 another new version google analytics announced called 'universal analytics key differences previous versions cross-platform tracking flexible tracking code collect data device introduction custom dimensions custom metrics march 2016 google released google analytics 360 software suite provides analytics return investment marketing indicators google analytics 360 includes five main products analytics tag manager optimize data studio surveys attribution audience center october 2017 new version google analytics announced called global site tag stated purpose unify tagging system simplify implementation june 2018 google introduced google marketing platform online advertisement analytics brand consists two former brands google doubleclick digital marketing google analytics 360 google analytics implemented page tags case called google analytics tracking code snippet javascript code website owner adds every page website tracking code runs client browser client browses page javascript enabled browser collects visitor data sends google data collection server part request web beacon tracking code loads larger javascript file google web server sets variables user account number larger file currently known ga.js typically 18 kb date file size unknown however recent size 40kbytes may 2018 c dir ga.js /s command pc shows following file sizes 2009 2018 2009/10/07 23,536 ga.js 2014/05/27 40,155 ga.js 2014/10/10 40,924 ga.js 2015/09/13 41,100 ga.js 2017/08/06 43,082 ga.js 2018/04/08 46,275 ga.js file usually loaded however due browser caching assuming caching enabled browser downloads ga.js start visit furthermore websites implement google analytics ga.js code use master file google browser previously visited website running google analytics already file cached machine addition transmitting information google server tracking code sets first party cookie cookies enabled browser visitor computer cookie stores anonymous information called clientid launch universal analytics several cookies storing information whether visitor site new returning visitor timestamp current visit referrer site campaign directed visitor page e.g. search engine keywords banner email visitor arrived site clicking link tagged utm parameters urchin traffic monitor tag values passed database addition google analytics mobile package allows google analytics applied mobile websites mobile package contains server-side tracking codes use php javaserver pages asp.net perl server-side language however many ad filtering programs extensions firefox adblock noscript mobile phone app disconnect mobile block google analytics tracking code prevents traffic users tracked leads holes collected data also privacy networks like tor mask user actual location present inaccurate geographical data small fraction users javascript-enabled/capable browsers turn feature limitations mainly ad filtering program allow significant amount visitor avoid tracker sometimes majority one potential impact data accuracy comes users deleting blocking google analytics cookies without cookies set google analytics collect data individual web user block delete cookies resulting data loss visits google analytics users website owners encourage users disable cookies example making visitors comfortable using site posting privacy policy limitations affect majority web analytics tools use page tags usually javascript programs embedded web pages collect visitor data store cookies visitor computer transmit remote database pretending load tiny graphic beacon another limitation google analytics large websites use sampling generation many reports reduce load servers provide users relatively quick response query google analytics limits reports 500,000 randomly sampled sessions profile level calculations margins error indicated visits metric margins error provided metrics google analytics reports small segments data margin error large several online discussions impact google analytics site performance however google introduced asynchronous javascript code december 2009 reduce risk slowing loading pages tagged ga.js script due ubiquity google analytics raises privacy concerns whenever someone visits website uses google analytics google tracks visit via users ip address order determine user approximate geographic location meet german legal requirements google analytics anonymize ip address google also released browser plugin turns data page visit sent google however browser extension available mobile browsers since plug-in produced distributed google met much discussion criticism furthermore realisation google scripts tracking user behaviours spawned production multiple often open-source browser plug-ins reject tracking cookies plug-ins allow users block google analytics similar sites tracking activities however partially new european privacy laws modern browsers allow users reject tracking cookies though flash cookies separate problem anecdotally reported errors occur behind proxy servers multiple firewalls changing timestamps registering invalid searches webmasters seek mitigate google analytics specific privacy issues employ number alternatives backends hosted machines discontinuation example product urchin webanalytics software google january 20 2015 associated press reported healthcare.gov providing access enrollees personal data private companies specialized advertising mentioning google analytics specifically google offers free google analytics iq lessons google analytics certification test free help center faq google groups forum official google analytics product support new product features announced google analytics blog enterprise support provided google analytics certified partners google academy ads google analytics api used third parties build custom applications reporting tools many applications exist one built run ios apple devices featured apple app store third party products also provide google analytics-based tracking management api core reporting api mcf reporting api real time reporting api subject limits quotas google analytics widely used website statistics service may 2008 pingdom released survey stating 161 500 32 biggest sites globally according alexa rank using google analytics later piece market share analysis claimed google analytics used around 49.95 top 1,000,000 websites ranked 2010 alexa 2012 use around 55 10,000 popular websites august 2013 google analytics used 66.2 10,000 popular websites ordered popularity reported builtwith
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Web technology
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business intelligence 2.0 business intelligence 2.0 bi 2.0 future development existing business intelligence model began mid-2000s data obtained many sources process allows querying real-time corporate data employees approaches data web browser based solution contrast previous proprietary querying tools characterizes previous bi software growth service-oriented architectures soa one main factors happening bi 2.0 intended flexible adaptive normal business intelligence data exchange processes also differ xbrl extensible business reporting language web services various semantic web ontologies enable using data external organization benchmarking type information business intelligence 2.0 believed named web 2.0 although takes elements web 2.0 focus user empowerment community collaboration technologies like rss concept mashups semantic web sometimes called web 3.0 semantic integration shared ontologies enable easier exchange data according analytics expert neil raden bi 2.0 also implies move away standard data warehouse business intelligence tools used give way context contingency need relate information quickly many sources
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Distributed computing architecture
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os-tan os- tan internet meme originated within japanese futaba channel os- tan moe anthropomorphism/personification several operating systems various amateur japanese artists os- tan typically depicted women os- tan representative microsoft windows operating systems usually depicted sisters varying ages -tan element term hypocoristic suffix japanese though initially appearing fan work os- tan proved popular enough microsoft branches singapore taiwan used os- tan concept basis ad campaigns internet explorer microsoft silverlight respectively concept os- tan reported begun personification common perception windows released 2000 microsoft 9x counterpart windows 2000 unstable prone frequent crashes discussions futaba channel likened stereotype fickle troublesome girl personification expanded me- tan created followed characters one early works predominantly feature os- tan interactive flash animation showing possible intro imaginary anime show known trouble windows fansub eventually created partly responsible spread os- tan english language imageboards os- tan original concept pre-dated toy imac girl featured series desktops released august 1998 march 1999 ohzora publishing produced one book based os- tan characters titled includes illustrations 25 contributors also includes 95- tan me- tan xp- tan figures titled os girl 95 os girl os girl xp respectively include molded space 2k- tan named os girl 2k me- tan 2k- tan xp- tan designed guhico stranger workshop 95- tan designed fujisaki shiro h.b.company parthenon production limited company commercialized pink company os- tan products malino deja vu artworks produced document shared folder trilogy sold digital format japanese version windows 7 ultimate dsp edition includes unofficial nanami madobe mascot inspired microsoft taiwan launch official mascot microsoft silverlight hikaru followed giving hikaru sisters lei aoi yu special package japanese windows 7 ultimate dsp edition called touch mouse artist edition touch mouse limited edition artist series came animated tutorial windows theme custom sounds three desktop backgrounds featuring madobe nanami 2009 ubuntu-based comic titled ubunchu serialized kantan ubuntu spinoff weekly ascii magazine authored hiroshi seo english version translated fumihito yoshida hajime mizuno martin owens arturo silva anton ekblad japanese suffix mispronunciation informal intimate diminutive honorific suffix person used friends family pets case mispronunciation used intentionally achieve contrived cute charming effect commonly associated use young children also sometimes added names non-mascot characters personifications whole commonly simply called mascots mascot characters -tan suffix means nothing outside role honorific implications cuteness normal suffixes including -san -chan -kun also used name os- tan depending character speaker preference suffix may omitted entirely name windows 10 mascot officially introduced tōko touko madobe 31 july 2015 confirmed character official facebook page name homonym one readings japanese word 'ten name chosen fans online poll according fictional profile origins madobe family set 100 years future likes online gaming supporting others personal traits excellent student expanding knowledge technology manager often worries since ’ bit spontaneous also enjoys cheering people working hard best part-time job akibano custom computer company rookie level back story rather unusual os- tan japanese windows 8.1 pro dsp edition madobe family version windows navi+ techno-alliance corp. limited 1000 units version windows 8.1 pro 32/64-bit edition three types madobe family picture password wallpapers madobe character voices nanami yū ai claudia madobe family complete edition windows theme pack previously unpublished madobe family designs final pasocom data hikkoshi 9+ licence key skype three-month free trial historical windows logo stickers xp vista 7 8 editions include memorial pack version without voice theme pack stickers 6191 units 64-bit windows memorial pack version sculpt mobile mouse nanami decor 810 units editions available preorder 2013-10-04 release date 2013-10-18 part market launch facebook draw 8 followers took place follower count reaches 80001 total twitter follower count yū ai reach 8001 winners receive yū- ai-themed prizes additional types windows 8.1 pro dsp edition madobe family theme packs also sold ark towerhill zoa corporation tsukumo project white dospara buy unit.com big camera sofmap pc one versions include two types wallpapers christmas new year theme pack system voices japanese windows 8 pro dsp editions released madobe yū yuu madobe ai editions windows navi+ techno-alliance corp. versions 4,000 units per character thus 8,000 total include microsoft wedge touch mouse windows 8 logo character-specific windows theme three theme pack wallpapers event sounds respective character voice picture password images addition limited akihabara editions 444 units per character 888 total sold tokyo akihabara shopping district include madobe ai/yū edition microsoft wedge touch mouse alternate character-specific event sound samples theme pack alternate wallpaper respective character nipponbashi versions 500 units per character sold nipponbashi osaka include microsoft wedge touch mouse ai yū decal three theme pack wall papers two common one character-specific yū ai event sounds nipponbashi packages include different art 32/64-bit version availability depends retailer asuka nishi voices short-haired yū nao tamura voices long-haired ai windows 8 edition unitcom available first 2,888 copies included notepad t-shirt two-way mouse pad pocket media case smart phone stand cleaning two-way pc cleaner yū ai badges freeze blanket extended fictional madobe family tree detailed yū older sister parents eiichi netsu 根津 family shii madobe family yū ai said birthdate 18 november 1996 windows ce release date age 15 height 152 cm conflicts back-story materials suggesting ai younger sister masatakap electrocutica produced windows 8 music video titled window featuring madobe characters nanami yū silhouette claudia video presented opening microsoft keynote second day windows developer days japan 2012 2013 windows navi+ techno-alliance corp. also created separate twitter accounts ai yū respectively two theme songs yū ai – mir8cle days donna mirai demo unveiled 15 june 2013 sold cd bundled windows 8 pro dsp edition sold twinbox akihabara akiba pc reported first 7777 copies japanese windows 7 ultimate dsp editions include special wallpaper sound sets character called voiced nana mizuki character designed wakaba premium set includes windows 7 theme featuring 3 nanami wallpapers 19 event sound sets cd 5 extra nanami sounds regular dsp edition includes digest windows 7 theme including nanami wallpaper event sound set preorder users also download extra nanami wallpaper 6 event sound sets makes first os- tan marketed company producing operating system addition character also got twitter account initial sales event windows 7 dsp edition official profile character also revealed shows madobe nanami born 1992-04-06 release date windows 3.1 17 years age time release lives chiyoda tokyo nanami among extended family 16 members elder brother named goichi 吾一 elder sister named mutsumi むつみ mother named mikaho 美佳穗 madobe 窓辺 family father named kyuuachi 究八 shirato 白戸 family nanami cousin claudia madobe クロード 蔵人 later appeared microsoft cloud girl comic strip windows vista distinguishing characteristic usually horn-shaped pigtails variants four pigtails heterochromatic eyes silver white hair appears frequent although light blue black also seen common costume design white red sailor fuku stockings since release details vista interface look changed slightly black maid outfit emerging popularity matches new default vista color scheme well circular windows logo hair clip identical new start menu button vista also seems finalized version hair colour similar vista wallpapers range light blue yellow green also wears type long coat covers left right sides transparent imitate aero glass effect xp- tan dark-haired girl ribbons hair xp hair ornament typically worn left side windows xp criticized bloating system pretty without useful xp- tan commonly depicted wearing tight clothing big breasts additionally reference memory usage windows xp often seen eating holding empty rice bowl labeled memory variants include version xp home known homeko green hair wears short ponytail two large xp-shaped hairclips cover ears well less common variation representing windows xp media center edition outfits worn two main variants based loading lines windows splash screen startup although variants exist common operating system represented windows 2000 professional typically drawn intelligent professional reserved looking woman short blue hair glasses hair clips resemble cat ears flanking small white bonnet ruffle similar maid bonnet shows windows logo outfit resembles swimsuit suggesting windows logo colors worn long blue coat alluding popular opinion windows 2000 stable dependable windows operating systems due greater stability win2k compared winme released near 2000 2k- tan often described guardian me- tan particular shade blue used drawings similar default windows 2000 desktop color design me- tan personification windows much line japanese concept kawaii cuteness design changed little artist original designs depicted green hair long pigtails wearing maid outfit badge front reminiscent windows active desktop recovery screen often shown rebooting system crash considered hard worker webcomics often depict failing anything tries often literally crashing irritating sisters frozen control tends things showing lack common sense knowledge putting soda microwave oven defending swinging welsh onion many variations exist common depiction windows 98 operating systems pair young girls os- tan representative original release windows 98 shown white blue uniform includes windows logo part neck tie navy blue hair 98 hair clip windows 98 second edition os- tan similar appearance wears green sailor school uniform letters se front two early representations also seen pair stick-limbed pocky boxes face version number drawn crayon reference vulcan 300 character zatch bell anime series early representations still used mecha piloted girls dolls carried girls sometimes even hiding places windows 95 considered oldest modern 32-bit windows operating systems usually represented traditional lady early modern era japan typically depicted gentle-looking brown haired woman kimono hair ribbon showing four windows colors outfit traditional kimono hakama japan wears thick sandals geta feet woman college student typical clothes seen earliest period course modernization japan meiji period taishō period reference modernization windows comparison modernization japan additionally pattern kimono based file hana256.bmp used desktop wallpaper pattern japanese version windows typically depicted engaged drinking tea serving meals housework one recurring theme stories unfamiliarity newer post win-95 technologies usb devices even though osr 2.x supported broadband internet connections also occasionally depicted wielding katana aggressive manner symbolizing generation operating systems microsoft finally achieved full dominance personal computer market windows 3.1 short girl long silver hair long light purple dress large purple bow head often seen carrying small black cat head well acts servant maid sort serves tends dos- tan reference fact windows 3.1 full operating system rather gui ms-dos mac os x girl often portrayed catgirl following apple wild cat naming tradition every mac os x release os x mavericks codename like jaguar panther tiger snow leopard etc. otherwise shown older variation mac os 9 girl wearing white coat wearing airport wireless hub fashioned hat occasionally shown holding publication sort macs often used desktop publishing originally seen bearded penguin reference tux penguin mascot linux kernel image girl helmet flippers chosen human alternative helmet likely metaphor linux kernel oft-claimed excellent security usually horns likely reference gnu software comprises common system programs present nearly linux distributions gear teeth helmet reference kde common desktop environment used gnu/linux shirt reference gnome another common desktop environment often seen spear flags attached representing grub lilo gcc tools linux artist drew konqi tyson tan submitted mascot libreoffice contest run document foundation late 2017 mascot officially accepted foundation developed fandom 8chan reddit msx-dos girl often portrayed young grey-haired girl carrying large cartridge-shaped bag msx-dos logo even short game featuring os- tan player character bag os- tan often shown holding cartridge-shaped likely msxdos2 required cartridge extra 64 kb rom order work americanized versions windows related os- tan named xp-usa me-usa 2k-usa published ohzora fanbook comic strip named trouble windows usa saint muscle heavy associations operating systems supporting programs anti-virus clients web browsers many supporting characters created personify applications examples wired news rated os- tan among lamest technology mascots ever yet strangely compelling
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Operating systems
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cryptol cryptol domain specific programming language cryptography developed portland oregon based software development firm galois inc.. language originally developed use united states national security agency language also used private firms provide information technology systems american company rockwell collins provides aerospace defense contractors united states programming language used aspects developing using cryptography design implementation new ciphers verification existing cryptographic algorithms cryptol designed allow cryptographer watch stream processing functions program manipulate ciphers encryption algorithms
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Programming language topics
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monjin monjin digital interviewing assessment platform powered artificial intelligence described portmanteau skype linkedin monjin founded 2014 industry veterans abhijit kashyape ashutosh kulkarni aniruddha fansalkar prafulla paraskar company led abhijit 100 employees across globe 2016 monjin set operations uk usa sweden 2017 monjin partnered microsoft create first azure-based aggregator platform using interviewers create global assessment standard
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Distributed computing architecture
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interrupt latency computing interrupt latency time elapses interrupt generated source interrupt serviced many operating systems devices serviced soon device interrupt handler executed interrupt latency may affected microprocessor design interrupt controllers interrupt masking operating system os interrupt handling methods usually trade-off interrupt latency throughput processor utilization many techniques cpu os design improve interrupt latency decrease throughput increase processor utilization techniques increase throughput may increase interrupt latency increase processor utilization lastly trying reduce processor utilization may increase interrupt latency decrease throughput minimum interrupt latency largely determined interrupt controller circuit configuration also affect jitter interrupt latency drastically affect real-time schedulability system intel apic architecture well known producing huge amount interrupt latency jitter maximum interrupt latency largely determined methods os uses interrupt handling example processors allow programs disable interrupts putting execution interrupt handlers order protect critical sections code execution critical section interrupt handlers execute safely within critical section blocked save minimum amount information required restart interrupt handler critical sections exited interrupt latency blocked interrupt extended end critical section plus interrupts equal higher priority arrived block place many computer systems require low interrupt latencies especially embedded systems need control machinery real-time sometimes systems use real-time operating system rtos rtos makes promise specified maximum amount time pass executions subroutines order rtos must also guarantee interrupt latency never exceed predefined maximum advanced interrupt controllers implement multitude hardware features order minimize overhead context switches effective interrupt latency include features like also many methods hardware may use help lower requirements shorter interrupt latency order make given interrupt latency tolerable sitation include buffers flow control example network cards implement transmit receive ring buffers interrupt rate limiting hardware flow control buffers allow data stored transferred flow control allows network card pause communications without discard data buffer full modern hardware also implements interrupt rate limiting helps prevent interrupt storms live-lock hardware wait programmable minimum amount time interrupt generates interrupt rate limiting reduces amount time spent servicing interrupts allowing processor spend time useful work exceeding time results soft recoverable hard non-recoverable error
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Computer architecture
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quantum statistical programming language quantum software package programming language statistical survey data validation manipulation tabulation originally developed quantime run unix systems incorporated spss inc. spss mr product line acquisition quantime september 1997
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Programming language topics
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internet protocol suite internet protocol suite conceptual model set communications protocols used internet similar computer networks commonly known tcp/ip foundational protocols suite transmission control protocol tcp internet protocol ip occasionally known department defense dod model development networking method funded united states department defense darpa internet protocol suite provides end-to-end data communication specifying data packetized addressed transmitted routed received functionality organized four abstraction layers classify related protocols according scope networking involved lowest highest layers link layer containing communication methods data remains within single network segment link internet layer providing internetworking independent networks transport layer handling host-to-host communication application layer providing process-to-process data exchange applications technical standards underlying internet protocol suite constituent protocols maintained internet engineering task force ietf internet protocol suite predates osi model comprehensive reference framework general networking systems internet protocol suite resulted research development conducted defense advanced research projects agency darpa late 1960s initiating pioneering arpanet 1969 darpa started work number data transmission technologies 1972 robert e. kahn joined darpa information processing technology office worked satellite packet networks ground-based radio packet networks recognized value able communicate across spring 1973 vinton cerf helped develop existing arpanet network control program ncp protocol joined kahn work open-architecture interconnection models goal designing next protocol generation arpanet summer 1973 kahn cerf worked fundamental reformulation differences local network protocols hidden using common internetwork protocol instead network responsible reliability arpanet function delegated hosts cerf credits hubert zimmermann louis pouzin designer cyclades network important influences design protocol implemented transmission control program first published 1974 initially tcp managed datagram transmissions routing protocol grew researchers recommended division functionality protocol layers advocates included jonathan postel university southern california information sciences institute edited request comments rfcs technical strategic document series documented catalyzed internet development postel stated screwing design internet protocols violating principle layering encapsulation different mechanisms intended create environment upper layers could access needed lower layers monolithic design would inflexible lead scalability issues transmission control program split two distinct protocols transmission control protocol internet protocol design network included recognition provide functions efficiently transmitting routing traffic end nodes intelligence located edge network end nodes design known end-to-end principle using design became possible connect almost network arpanet irrespective local characteristics thereby solving kahn initial internetworking problem one popular expression tcp/ip eventual product cerf kahn work run two tin cans string years later joke ip avian carriers formal protocol specification created successfully tested computer called router provided interface network forwards network packets back forth originally router called gateway term changed avoid confusion types gateways 1973 1974 cerf networking research group stanford worked details idea resulting first tcp specification significant technical influence early networking work xerox parc produced parc universal packet protocol suite much existed around time darpa contracted bbn technologies stanford university university college london develop operational versions protocol different hardware platforms four versions developed tcp v1 tcp v2 tcp v3 ip v3 tcp/ip v4 last protocol still use today 1975 two-network tcp/ip communications test performed stanford university college london november 1977 three-network tcp/ip test conducted sites us uk norway several tcp/ip prototypes developed multiple research centers 1978 1983 march 1982 us department defense declared tcp/ip standard military computer networking year peter t. kirstein research group university college london adopted protocol migration arpanet tcp/ip officially completed flag day january 1 1983 new protocols permanently activated 1985 internet advisory board later internet architecture board held three-day tcp/ip workshop computer industry attended 250 vendor representatives promoting protocol leading increasing commercial use 1985 first interop conference focused network interoperability broader adoption tcp/ip conference founded dan lynch early internet activist beginning large corporations ibm dec attended meeting ibm dec first major corporations adopt tcp/ip despite competing proprietary protocols ibm 1984 barry appelman group tcp/ip development navigated corporate politics get stream tcp/ip products various ibm systems including mvs vm os/2 time several smaller companies ftp software wollongong group began offering tcp/ip stacks dos microsoft windows first vm/cms tcp/ip stack came university wisconsin early tcp/ip stacks written single-handedly programmers jay elinsky ibm research wrote tcp/ip stacks vm/cms os/2 respectively 1984 donald gillies mit wrote ntcp multi-connection tcp ran atop ip/packetdriver layer maintained john romkey mit 1983-4 romkey leveraged tcp 1986 ftp software founded starting 1985 phil karn created multi-connection tcp application ham radio systems ka9q tcp spread tcp/ip fueled june 1989 university california berkeley agreed place tcp/ip code developed bsd unix public domain various corporate vendors including ibm included code commercial tcp/ip software releases microsoft released native tcp/ip stack windows 95 event helped cement tcp/ip dominance protocols microsoft-based networks included ibm systems network architecture sna platforms digital equipment corporation decnet open systems interconnection osi xerox network systems xns british academic network janet converted tcp/ip 1991 end-to-end principle evolved time original expression put maintenance state overall intelligence edges assumed internet connected edges retained state concentrated speed simplicity real-world needs firewalls network address translators web content caches like forced changes principle robustness principle states general implementation must conservative sending behavior liberal receiving behavior must careful send well-formed datagrams must accept datagram interpret e.g. object technical errors meaning still clear second part principle almost important software hosts may contain deficiencies make unwise exploit legal obscure protocol features encapsulation used provide abstraction protocols services encapsulation usually aligned division protocol suite layers general functionality general application highest level model uses set protocols send data layers data encapsulated level early architectural document emphasizes architectural principles layering rfc 1122 titled host requirements structured paragraphs referring layers document refers many architectural principles emphasize layering loosely defines four-layer model layers names numbers follows link layer networking scope local network connection host attached regime called link tcp/ip literature lowest component layer internet protocols tcp/ip designed hardware independent result tcp/ip may implemented top virtually hardware networking technology link layer used move packets internet layer interfaces two different hosts link processes transmitting receiving packets given link controlled software device driver network card well firmware specialized chipsets perform data link functions adding packet header prepare transmission actually transmit frame physical medium tcp/ip model includes specifications translating network addressing methods used internet protocol link layer addresses media access control mac addresses aspects level however implicitly assumed exist link layer explicitly defined tcp/ip model link layer also layer packets may selected sent virtual private network networking tunnels scenario link layer data may considered application data traverses another instantiation ip stack transmission reception another ip connection connection virtual link may established transport protocol even application scope protocol serves tunnel link layer protocol stack thus tcp/ip model dictate strict hierarchical encapsulation sequence link layer tcp/ip model corresponding functions layer 2 open systems interconnection osi model internet layer responsibility sending packets across potentially multiple networks internetworking requires sending data source network destination network process called routing internet protocol performs two basic functions internet layer agnostic data structures transport layer also distinguish operation various transport layer protocols ip carries data variety different upper layer protocols protocols identified unique protocol number example internet control message protocol icmp internet group management protocol igmp protocols 1 2 respectively protocols carried ip icmp used transmit diagnostic information igmp used manage ip multicast data layered top ip perform internetworking functions illustrates differences architecture tcp/ip stack internet osi model tcp/ip model internet layer corresponds layer three open systems interconnection osi model referred network layer internet layer provides unreliable datagram transmission facility hosts located potentially different ip networks forwarding transport layer datagrams appropriate next-hop router relaying destination functionality internet layer makes possible internetworking interworking different ip networks essentially establishes internet internet protocol principal component internet layer defines two addressing systems identify network hosts computers locate network original address system arpanet successor internet internet protocol version 4 ipv4 uses 32-bit ip address therefore capable identifying approximately four billion hosts limitation eliminated 1998 standardization internet protocol version 6 ipv6 uses 128-bit addresses ipv6 production implementations emerged approximately 2006 transport layer establishes basic data channels applications use task-specific data exchange layer establishes host-to-host connectivity meaning provides end-to-end message transfer services independent structure user data logistics exchanging information particular specific purpose independent underlying network protocols layer may provide error control segmentation flow control congestion control application addressing port numbers end-to-end message transmission connecting applications transport layer categorized either connection-oriented implemented tcp connectionless implemented udp purpose providing process-specific transmission channels applications layer establishes concept network port numbered logical construct allocated specifically communication channels application needs many types services port numbers standardized client computers may address specific services server computer without involvement service announcements directory services ip provides best effort delivery transport layer protocols offer reliability however ip run reliable data link protocol high-level data link control hdlc example tcp connection-oriented protocol addresses numerous reliability issues providing reliable byte stream newer stream control transmission protocol sctp also reliable connection-oriented transport mechanism message-stream-oriented—not byte-stream-oriented like tcp—and provides multiple streams multiplexed single connection also provides multi-homing support connection end represented multiple ip addresses representing multiple physical interfaces one fails connection interrupted developed initially telephony applications transport ss7 ip also used applications user datagram protocol connectionless datagram protocol like ip best effort unreliable protocol reliability addressed error detection using weak checksum algorithm udp typically used applications streaming media audio video voice ip etc on-time arrival important reliability simple query/response applications like dns lookups overhead setting reliable connection disproportionately large real-time transport protocol rtp datagram protocol designed real-time data streaming audio video applications given network address distinguished tcp udp port convention certain well known ports associated specific applications tcp/ip model transport host-to-host layer corresponds roughly fourth layer open systems interconnection osi model also called transport layer application layer includes protocols used applications providing user services exchanging application data network connections established lower level protocols may include basic network support services protocols routing host configuration examples application layer protocols include hypertext transfer protocol http file transfer protocol ftp simple mail transfer protocol smtp dynamic host configuration protocol dhcp data coded according application layer protocols encapsulated transport layer protocol units tcp udp messages turn use lower layer protocols effect actual data transfer tcp/ip model consider specifics formatting presenting data define additional layers application transport layers osi model presentation session layers functions realm libraries application programming interfaces application layer protocols generally treat transport layer lower protocols black boxes provide stable network connection across communicate although applications usually aware key qualities transport layer connection end point ip addresses port numbers application layer protocols often associated particular client-server applications common services well-known port numbers reserved internet assigned numbers authority iana example hypertext transfer protocol uses server port 80 telnet uses server port 23 clients connecting service usually use ephemeral ports i.e. port numbers assigned duration transaction random specific range configured application transport layer lower-level layers unconcerned specifics application layer protocols routers switches typically examine encapsulated traffic rather provide conduit however firewall bandwidth throttling applications must interpret application data example resource reservation protocol rsvp also sometimes necessary network address translator nat traversal consider application payload application layer tcp/ip model often compared equivalent combination fifth session sixth presentation seventh application layers open systems interconnection osi model furthermore tcp/ip model distinguishes user protocols support protocols support protocols provide services system network infrastructure user protocols used actual user applications example ftp user protocol dns support protocol following table shows various networking models number layers varies three seven networking models textbooks secondary sources may conflict intent rfc 1122 ietf primary sources three top layers osi model i.e application layer presentation layer session layer distinguished separately tcp/ip model application layer transport layer pure osi protocol applications x.400 also combined requirement tcp/ip protocol stack must impose monolithic architecture transport layer example nfs application protocol runs external data representation xdr presentation protocol turn runs protocol called remote procedure call rpc rpc provides reliable record transmission safely use best-effort udp transport different authors interpreted tcp/ip model differently disagree whether link layer entire tcp/ip model covers osi layer 1 physical layer issues whether hardware layer assumed link layer several authors attempted incorporate osi model layers 1 2 tcp/ip model since commonly referred modern standards example ieee itu often results model five layers link layer network access layer split osi model layers 1 2 ietf protocol development effort concerned strict layering protocols may fit cleanly osi model although rfcs sometimes refer often use old osi layer numbers ietf repeatedly stated internet protocol architecture development intended osi-compliant rfc 3439 addressing internet architecture contains section entitled layering considered harmful example session presentation layers osi suite considered included application layer tcp/ip suite functionality session layer found protocols like http smtp evident protocols like telnet session initiation protocol sip session layer functionality also realized port numbering tcp udp protocols cover transport layer tcp/ip suite functions presentation layer realized tcp/ip applications mime standard data exchange conflicts apparent also original osi model iso 7498 considering annexes model e.g. iso 7498/4 management framework iso 8648 internal organization network layer ionl ionl management framework documents considered icmp igmp defined layer management protocols network layer like manner ionl provides structure subnetwork dependent convergence facilities arp rarp ietf protocols encapsulated recursively demonstrated tunneling protocols generic routing encapsulation gre gre uses mechanism osi uses tunneling network layer internet protocol suite presume specific hardware software environment requires hardware software layer exists capable sending receiving packets computer network result suite implemented essentially every computing platform minimal implementation tcp/ip includes following internet protocol ip address resolution protocol arp internet control message protocol icmp transmission control protocol tcp user datagram protocol udp internet group management protocol igmp addition ip icmp tcp udp internet protocol version 6 requires neighbor discovery protocol ndp icmpv6 igmpv6 often accompanied integrated ipsec security layer application programmers typically concerned interfaces application layer often also transport layer layers services provided tcp/ip stack operating system ip implementations accessible programmers sockets apis unique implementations include lightweight tcp/ip open source stack designed embedded systems ka9q nos stack associated protocols amateur packet radio systems personal computers connected via serial lines microcontroller firmware network adapter typically handles link issues supported driver software operating system non-programmable analog digital electronics normally charge physical components link layer typically using application-specific integrated circuit asic chipset network interface physical standard high-performance routers large extent based fast non-programmable digital electronics carrying link level switching
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Internet protocols
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web sheriff web sheriff anti-piracy company based united kingdom provides intellectual property copyright privacy rights protection services company monitors various websites host links downloads music film web sheriff operation since 2000 two offices uk company founded intellectual property lawyer john giacobbi acts managing director web sheriff sends legal take-down notice bittorrent file sharing sites according los angeles times web sheriff leading advocate soft sell anti-piracy industry web sheriff performs various copy protection services include protection copyright infringement libel cyber-bullying identity theft privacy issues social media policing trading sites recovery fraudulently registered domain names also furnishes online security concert tours web sheriff uses proprietary software web crawler programs search internet using human auditing determine type site posting clients copyrighted material relies heavily phone calls relationship building locating unauthorized links targets persons running sites supposed offending party sent take-down notice action taken torrent sites file sharing sites mediafire rapidshare provide access company remove infringing content los angeles times described company approach representing sharp turn recording industry life-and-death struggle piracy one driven largely performers managers rather record companies contracts protect new music releases company encourages artists represents give fans several tracks ahead release web sheriff founded 2000 former music attorney industry consultant john giacobbi 2005 company responsible removal ken bigley execution footage videos posted terrorist website bigley beheading web sheriff related approached mail sunday authorities refused intervene citing lack power video hosted website entitled headlessamericans.com isp initially refused take saying protected freedom speech complied finally 48 hours argument year work done mail sunday company spokesman writing newspaper disclosed web sheriff also closed extreme pornographic strangulation sites center notorious jane longhurst murder case web sheriff hired prince september 2007 help disappear entirely internet star spokesman related prince believes strongly artist music rights must remain artist thus copyrights protected across board artists ever taken kind action rights web sheriff announced would launch lawsuits youtube ebay pirate bay behalf prince refused compliance removing links unauthorized photos videos music peter sunde co-founder pirate bay dismissed threats stating american law applicable sweden youtube complied removing 2,000 videos site ebay removed 300 auctions november 2007 three fans sites given notice remove images singer lyrics anything linked prince likeness prince fans fought back formed organization called prince fans united hired attorney multiple unauthorized overseas online sites selling merchandise featuring prince shut 2008 company hired bryan adams take fan sites tribute bands well owner domain name pointlookout.com nothing artist company hired axl rose remove unflattering picture claiming copyright belonged axl rose photographer music fans bloggers often initially respond angrily first approached web sheriff clients official unofficial forums according evening standard music blogging sites littered comments sheriff contact details top thanking bloggers obeying rules fans sometimes interpret web sheriff saying 've got eye company reports eventually fans tend respect wishes favored artists cooperating related guardian prodigy fans brainkiller forum engaged web sheriff thread lasted 18 pages fans hostile beginning asked could help band web sheriff method using velvet glove approach appeal fans said randy lewis los angeles times notable successes including lady gaga born way adele 21 journalist also notes despite examples success diplomatic strategy company gentle approach still skeptics critics calling naive brad buckles executive copyright enforcement riaa quoted saying certainly well-intended may work cases problem many many cases 're dealing people respect whatsoever intellectual property record labels artists billboard journalist concludes appeal sites post links unauthorized music engaging fans redirecting authorized content artist strategy future implemented properly
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Computer security
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international medical education directory international medical education directory imed public database worldwide medical schools imed published joint collaboration educational commission foreign medical graduates ecfmg foundation advancement international medical education research faimer information available imed derived data collected educational commission foreign medical graduates ecfmg throughout history evaluating medical education credentials international medical graduates using data starting point foundation advancement international medical education research faimer began developing imed 2001 made publicly available april 2002 april 2014 imed merged avicenna directory create world directory medical schools world directory definitive list medical schools world imed avicenna discontinued 2015
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Databases
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berkeley software design berkeley software design inc. bsdi later bsdi corporation developed sold licenses supported bsd/os originally known bsd/386 commercial partially proprietary variant bsd unix operating system pc compatible later computer systems name chosen similarity berkeley software distribution source primary product specifically 4.3bsd networking release 2 bsdi founded rick adams members computer systems research group csrg university california berkeley including keith bostic kirk mckusick mike karels bill jolitz donn seeley jolitz seeley trent hein working rick adam uunet time became bsdi first employees company began operations 1991 december 1991 usenix secretary former head software convex computer rob kolstad university illinois hired would take company operations two years later bsd/386 released january 1992 full system including source code retailed 995 affordable equivalent source code license rival unix system v cost 20,000 late 1980s rob kolstad direction company decided pursue internet infrastructure primary customer audience mid 1990s top-10 websites world almost using bsd/386 bsd source codebase late 1991 unix system laboratories usl brought lawsuit bsdi alleging bsd/386 contained proprietary trade secrets source code usl acquired novell settlement reached january 1994 bsdi agreed base future releases product called bsd/os csrg 4.4bsd-lite release declared free usl intellectual property rob kolstad university illinois convex computer corporation president bsdi period headed company close decade 1999 bsdi employees sought initial public offering installed new president reach goal soon possible given recent success red hat ipo linux market unfortunately strategy successful soon rob kolstad exited company facing bankruptcy 2000 company merged walnut creek cdrom distributor freeware open source software cd-rom shortly acquired telenet system solutions inc. internet infrastructure server supplier 2001 severe financial pressure excessive leverage bsdi known bsdi time sold software business unit comprising bsd/os former walnut creek freebsd slackware linux open source offerings wind river systems renamed remainder ixsystems renewed focus server hardware wind river dropped sponsorship slackware soon afterwards freebsd unit divested separate entity freebsd mall inc. 2002 faced competition open-source bsd- linux-based operating systems wind river discontinued bsd/os december 2003 many technologies live community-led bsd derivatives like freebsd 2002 offmyserver acquired ixsystems hardware business reverted ixsystems name 2005
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Operating systems
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citrix workspace citrix workspace formerly citrix workspace suite digital workspace software platform developed citrix systems allows multiple users remotely access operate microsoft windows desktops running datacenter public private cloud via devices located elsewhere users able access virtual desktops applications citrix workspace app applications delivered managed via citrix virtual apps virtualization technology led xendesktop first developed 2000 open-source hypervisor research project led ian pratt university cambridge called xen project x86 pratt founded company called xensource 2004 made commercial version xen hypervisor 2007 citrix acquired xensource releasing xendesktop version 2.0 2008 company continues release updated versions xendesktop 7.6 featuring hdx technology enhancements audio video graphics user experience well reduction storage costs associated virtual desktop deployments result improvements citrix provisioning services 2018 software renamed citrix workspace product aim give employees ability work anywhere cutting information technology management costs desktops applications centralized xendesktop also aims provide security data stored devices end users instead saved centralized datacenter cloud infrastructure citrix developed software use medium large enterprise customers citrix workspace able manage deliver applications desktops using connection broker called desktop delivery controller supports multiple hypervisors including citrix hypervisor vmware vsphere microsoft hyper-v nutanix acropolis create virtual machines run applications desktops software allows several types delivery methods compatible multiple architectures including desktops servers datacenters private public hybrid clouds virtualized applications delivered virtual desktops using virtual apps
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Distributed computing architecture
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ad blocking ad blocking ad filtering software capability removing altering online advertising web browser application popular ad blocking tools browser extensions methods also available online advertising exists variety forms including web banners pictures animations embedded audio video text pop-up windows employ audio video autoplay browsers offer ways remove alter advertisements either targeting technologies used deliver ads embedded content delivered browser plug-ins via html5 targeting urls source ads targeting behaviors characteristic ads use html5 autoplay audio video standpoint internet user various fundamental reasons one would want use ad blocking addition manipulated brands publishers representative trade bodies hand argue web ads provide revenue website owners enable website owners create otherwise purchase content website publishers claim prevalent use ad blocking software devices could adversely affect website owner revenue thus turn lower availability free content websites users benefits ad blocking software include quicker loading cleaner looking web pages fewer distractions lower resource waste bandwidth cpu memory etc privacy benefits gained exclusion tracking profiling systems ad delivery platforms blocking ads also save substantial amounts electrical energy lower users power bills additional energy savings also expected grid level fewer data packets need transmitted user machine website server ad blocking software may benefits users quality life decreases internet users exposure advertising marketing industries promote purchase numerous consumer products services potentially harmful unhealthy creating urge buy immediately unwanted advertising also harm advertisers users become annoyed ads irritated users might make conscious effort avoid goods services firms using annoying pop-up ads block web content user trying view users interested making purchases blocking ads also save time ad appears website exerts toll user attention budget since ad enters user field view must either consciously ignored closed dealt way user strongly focused reading solely content seeking likely desire diverted advertisements seek sell unneeded unwanted goods services contrast users actively seeking items purchase might appreciate advertising particular targeted ads another important aspect improving security online advertising subjects users higher risk infecting devices computer viruses surfing pornography websites high-profile case malware distributed advertisements provided youtube malicious customer google doubleclick august 2015 0-day exploit firefox browser discovered advertisement website forbes required users disable ad blocking viewing website users immediately served pop-under malware australian signals directorate recommends individuals organizations block advertisements improve information security posture mitigate potential malvertising attacks machine compromise information security firm webroot also note employing ad blockers provide effective countermeasures malvertising campaigns less technically-sophisticated computer users ad blocking also save money user user personal time worth one dollar per minute unsolicited advertising adds extra minute time user requires reading webpage i.e user must manually identify ads ads click close use techniques either deal tax user intellectual focus way user effectively lost one dollar time order deal ads might generate fractional pennies display-ad revenue website owner problem lost time rapidly spiral control malware accompanies ads ad blocking also reduces page load time saves bandwidth users users pay total transferred bandwidth capped pay-for-usage connections including mobile users worldwide direct financial benefit filtering ad loaded analysis 200 popular news sites ranked alexa 2015 showed mozilla firefox tracking protection lead 39 reduction data usage 44 median reduction page load time according research performed new york times ad blockers reduced data consumption sped load time half 50 news sites including journalists concluded visiting home page boston.com site ad data study every day month would cost equivalent 9.50 data usage ads streaming audio video even presented user interface rapidly consume gigabytes transfer especially faster 4g connection even fixed connections often subject usage limits especially faster connections 100mbit/s quickly saturate network filled streaming media known problem web browsers including firefox restoring sessions often plays multiple embedded ads however annoyance easily averted simply setting web browser clear cookies browsing-history information time browser software closed another preventive option use script blocker enables user disable scripts selectively re-enable certain scripts desired order determine role script user thus quickly learn scripts truly necessary standpoint webpage functionality consequently sources scripts undesirable insight helpful visiting websites general thus precisely controlling scripts run webpage viewed user retains full control happens his/her computer cpu computer screen use mobile desktop ad blocking software designed remove traditional advertising grew 41 worldwide 48 u.s. q2 2014 q2 2015 q2 2015 45 million americans using ad blockers survey research study released q2 2016 metafacts reported 72 million americans 12.8 million adults uk 13.2 million adults france using ad blockers pcs smartphones tablet computers march 2016 internet advertising bureau reported uk adblocking already 22 among people 18 years old one method filtering simply block prevent autoplay flash animation image loading microsoft windows audio video files done browsers easily also improves security privacy crude technological method refined numerous browser extensions every web browser handles task differently general one alters options preferences application extensions filter specific media types additional add-on usually required differentiate ads non-ads using technology wanted unwanted ads behaviors advanced ad blocking filter software allow fine-grained control advertisements features blacklists whitelists regular expression filters certain security features also effect disabling ads antivirus software act ad blocker filtering intermediaries isp providers national governments increasingly common 2015 many web browsers block unsolicited pop-up ads automatically current versions konqueror internet explorer also include content filtering support content filtering added firefox chromium-based browsers opera safari browsers extensions adblock adblock plus ublock origin number sources provide regularly updated filter lists adblock plus provided german software house eyeo gmbh included freeware browser maxthon people republic china default another method filtering advertisements uses cascading style sheets css rules hide specific html xhtml elements beginning 2018 google confirmed built-in ad blocker chrome/chromium browsers would go live 15th february ad blocker blocks certain ads specified better ads standard defined coalition better ads® google board member built-in ad blocking mechanism disputed could unfairly benefit google advertising number external software applications offer ad filtering primary additional feature traditional solution customize http proxy web proxy filter content programs work caching filtering content displayed user browser provides opportunity remove ads also content may offensive inappropriate even malicious drive-by download popular proxy software blocks content effectively include netnanny privoxy squid content-control software main advantage method freedom implementation limitations browser working techniques centralization control proxy used many users proxies good filtering ads several limitations compared browser-based solutions proxies difficult filter transport layer security ssl codice_1 traffic full webpage context available filter well proxies find difficult filter javascript-generated ad content operating systems even aware domain name system dns still offer backward compatibility locally administered list foreign hosts configuration historical reasons stored flat text file default contains hostnames associated ip addresses editing hosts file simple effective dns clients read local hosts file querying remote dns server storing black-hole entries hosts file prevents browser accessing ad server manipulating name resolution ad server local nonexistent ip address codice_2 codice_3 typically used ipv4 addresses simple implement methods circumvented advertisers either hard-coding ip address server hosts ads turn worked around changing local routing table using example iptables blocking firewalls loading advertisements server serves main content blocking name resolution server would also block useful content site using dns sinkhole manipulating hosts file exploits fact operating systems store file ip address domain name pairs consulted browsers using dns server look domain name assigning loopback address known ad server user directs traffic intended reach ad server local machine virtual black hole /dev/null bit bucket advertising blocked using dns server configured block access domains hostnames known serve ads spoofing address users choose use already modified dns server set dedicated device raspberry pi manipulating dns widely employed method manipulate end user sees internet also deployed locally personal purposes china runs root dns eu considered google required google public dns used applications android devices accordingly dns addresses domains used advertising may extremely vulnerable broad form ad substitution whereby domain serves ads entirely swapped one serving local ads subset users especially likely countries notably russia india china advertisers often refuse pay clicks page views dns-level blocking domains non-commercial reasons already common china android apps run local vpn connection host filtering ability dns address without requiring root access approach allows adblocking app download adblocking host files use filter ad networks throughout device blokada dns66 adguard popular apps accomplish adblocking without root permission adblocking active local vpn turned completely stops vpn connection disconnected convenience makes easy access content blocked anti-adblock scripts approach optimizes battery usage reduces internet slowdown caused using external dns vpn adblocking needs overall less configuration devices adtrap use hardware block internet advertising based reviews adtrap device uses linux kernel running version privproxy block ads video streaming music streaming web browser another solution provided network-level ad blocking telcos israeli startup shine internet providers especially mobile operators frequently offer proxies designed reduce network traffic even targeted specifically ad filtering proxy-based arrangements block many types advertisements large bandwidth-consuming otherwise deemed unsuited specific internet connection target device many internet operators block form advertisements time injecting ads promoting services specials content providers argued widespread ad blocking results decreased revenue website sustained advertisements e-commerce-based businesses blocking detected argued since advertisers ultimately paying ads increase revenues eliminating ad blocking would dilute value per impression drive price advertising arguing like click fraud impressions served users use ad blockers little value advertisers consequently argue eliminating ad blocking would increase overall ad revenue content providers long run websites taken countermeasures ad blocking software attempting detect presence ad blockers informing users views outright preventing users accessing content unless disable ad blocking software whitelist website buy ad-removal pass several arguments supporting opposing assertion blocking ads wrong publisher companies taken steps protect rights conduct business according prevailing law suggested european union practice websites scanning ad blocking software may run afoul e-privacy directive claim validated iab europe guidelines released june 2016 stating indeed may legal issue ad blocker detection anti-blocking stakeholders tried refute seems safe assume publishers follow guidelines provided main publisher lobby iab joint effort announced iab sweden prior iab europe guideline matter never materialized would likely found european anti-competition laws august 2017 vendor counter-measures issued demand section 1201 u.s. digital millennium copyright act demand removal domain name associated service ad-blocking filter list vendor argued domain constituted component technological protection measure designed protect copyrighted work thus made violation anti-circumvention law frustrate access 2015 advertisers marketers look involve brands directly entertainment native advertising product placement also known brand integration embedded marketing example product placement would soft drink manufacturer pay reality tv show producer show cast host appear onscreen holding cans soft drink another common product placement automotive manufacturer give free cars producers tv show return show producer depicting characters using vehicles show digital publications turned customers help example guardian asking readers donations help offset falling advertising revenue according newspaper editor-in-chief katharine viner newspaper gets amount money membership paying readers advertising newspaper considered preventing readers accessing content usage ad-blocking software becomes widespread far keeps content accessible readers employ ad-blockers
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Computer security
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method chaining method chaining also known named parameter idiom common syntax invoking multiple method calls object-oriented programming languages method returns object allowing calls chained together single statement without requiring variables store intermediate results local variable declarations syntactic sugar method chaining eliminates extra variable intermediate step developer saved cognitive burden naming variable keeping variable mind method chaining referred producing train wreck due increase number methods come one another line occurs methods chained together similar syntax method cascading method call expression evaluates current object return value method cascading implemented using method chaining method return current object cascading key technique fluent interfaces since chaining widely implemented object-oriented languages cascading n't form cascading-by-chaining returning often referred simply chaining chaining cascading come smalltalk language chaining syntax semantic consequences namely requires methods return object implementing cascading via chaining must current object prevents return value used purpose returning error value common example iostream c++ example codice_1 returns left object allowing chaining compare equivalent another example javascript uses built-in methods array
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Programming language topics
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vampire killer vampire killer platform-adventure video game released konami msx2 computer october 30 1986 parallel version original castlevania debuted month earlier famicom disk system japanese title however msx2 version localized first europe thus published without castlevania branding franchise would start using abroad 1987 nes version released north america neither vampire killer msx2 platform released like castlevania player controls vampire hunter simon belmont ventures dracula castle armed mystical whip inherited father order slay evil count vampire killer shares premise soundtrack characters locations original castlevania structure game play mechanics differ significantly nes counterpart like castlevania vampire killer consists 18 stages boss encounter end every third stage contrast linear level designs castlevania vampire killer features labyrinth-like stages requiring player seek exit next stage also skeleton key required unlock due hardware limitations msx2 vampire killer uses flip screens instead scrolling game played keyboard game controller items weapons obtained breaking candle stands certain walls like nes version also purchasing merchants hidden throughout castle unlocking treasure chests using keys simon default whip also replaced one four weapons chain whip throwing daggers ax cross latter two function like boomerang must retrieved return path player wishes preserve also four items simon carry similar sub-weapons nes version map shows current position location exit used three times pressing f2 holy water used jumping pressing left right mid-air hourglass temporarily paralyzes enemies pressing jumping one two types shields heart points used ammunition holy water hourglass requiring five hearts per use also currency merchants items provide auxiliary effects increasing decreasing prices items sold merchants temporary invulnerability increased walking speed jumping height health recovery defeating boss simon start next stage without previously-accumulated equipment aside number hearts map used already player starts game three lives way gain extra lives continues unless game played game master cartridge second slot playing game master also enable option select stage number lives start well ability skip screens
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Computer architecture
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hi-tech crime enquiry cell hi-tech crime enquiry cell special unit kerala police kerala india began operations 5 may 2006 formed prevent detect defend serious organized high technology crimes unit organized purpose prevent investigate prosecute computer related crimes working government agencies private sector academic institutions foreign counterparts
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Computer security
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hacktool.win32.hackav hacktool.win32.hackav not-a-virus keygen hacktool win32/keygen microsoft malware protection center definition kaspersky labs program designed assist hacking programs often contain signatures potential malware dangerous interfere work pc used hacker get personal information user computer according microsoft malware protection center first known detection goes back july 16 2009 riskware able create license keys illegally downloaded non-registered software kind tool may appear differently depending software tool designed create key following security threats often found pcs related tools
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Computer security
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zen 2 zen 2 codename successor amd zen zen+ microarchitectures due fabricated 7 nanometer node tsmc product sampling planned late 2018 followed commercial release july 2019 powering third generation ryzen processors known ryzen 3000 mainstream desktop chips threadripper 3000 high-end desktop systems computex 2019 amd announced product release date july 7 2019 zen 2 expected bring increase instructions per clock zen nearly large jump excavator zen according userbenchmark.com translates 13 ipc uplift zen+ 2018 consumer electronics show ces amd confirmed zen 2 design complete however release announced 2018 leading analysts predict 2019 release date zen 2 planned include hardware mitigations spectre security vulnerability zen 2-based epyc server cpus codename rome use design multiple cpu dies eight total manufactured 7 nm process chiplets combined 14 nm i/o die mcm package 64 physical cores 128 total compute threads simultaneous multithreading supported per socket 2019 ces amd showed ryzen third-generation engineering sample contains one chiplet eight cores 16 threads lisa su also said expect eight cores final lineup computex 2019 amd revealed zen 2 matisse chips would feature 12 cores weeks later 16 core chip also revealed e3 2019 zen 2 significant departure physical design paradigm amd previous zen architectures zen zen+ zen 2 moves multi-chip module design i/o components cpu laid separate die separation benefits scalability manufacturability physical interfaces n't scale well shrinks process technology separation different die allows components manufactured using larger mature process node cpu dies cpu dies referred amd compact due move i/o components onto another die manufactured using smaller process fewer manufacturing defects larger monolithic die would exhibit addition central i/o die service multiple chiplets making easier construct processors large number cores zen 2 cpu chiplet houses 8 cores arranged two ccx 4 cores chiplets manufactured using tsmc 7 nanometer node 74 80 mm size chiplet 3.9 billion transistors 12 nm iod ~125 mm 2.09 billion transistors amount l3 cache doubled 32 mib core 8-core chiplet access 4 mib l3 compared 2 mib zen zen+ avx2 fully supported increase execution unit width 128-bit 256-bit multiple variants i/o die one manufactured globalfoundries 14 nanometer process another manufactured using company 12 nanometer process 14 nanometer dies features used epyc rome processors whereas 12 nm versions used consumer processors may 26 2019 amd announced six zen 2 based desktop processors included 6-core 8-core variants ryzen 5 ryzen 7 product lines well new ryzen 9 line includes company first 12-core 16-core mainstream desktop processors amd 2nd generation epyc processors known rome features 64 cores launched august 7 2019
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Computer architecture
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xoftspy portable anti-spyware xoftspy portable anti-spyware proprietary application developed paretologic inc. microsoft windows computers anti-spyware program designed run usb drive protect users malicious threats software free download scan user must purchase license clean license valid clean multiple computers u3 usb drive portability useful situations computer heavily infected bogged sluggish accessing computer directly u3 device xoftspy portable removes malware items regardless computer infected unable download anti-spyware programs online xoftspy retired new product name digitalcare
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Computer security
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same-origin policy computing same-origin policy important concept web application security model policy web browser permits scripts contained first web page access data second web page web pages origin origin defined combination uri scheme host name port number policy prevents malicious script one page obtaining access sensitive data another web page page document object model mechanism bears particular significance modern web applications extensively depend http cookies maintain authenticated user sessions servers act based http cookie information reveal sensitive information take state-changing actions strict separation content provided unrelated sites must maintained client-side prevent loss data confidentiality integrity important remember same-origin policy applies scripts means resources images css dynamically-loaded scripts accessed across origins via corresponding html tags fonts notable exception cross site request forgery attacks take advantage fact origin policy apply html tags concept same-origin policy dates back netscape navigator 2 1995 policy originally designed protect access document object model since broadened protect sensitive parts global javascript object modern browsers implement form same-origin policy important security cornerstone policies required match exact specification often extended define roughly compatible security boundaries web technologies microsoft silverlight adobe flash adobe acrobat mechanisms direct dom manipulation xmlhttprequest algorithm used calculate origin uri specified rfc 6454 section 4 absolute uris origin triple protocol host port uri use hierarchical element naming authority see section 3.2 uri absolute uri globally unique identifier used two resources considered origin values exactly illustrate following table gives overview typical outcomes checks url nowiki http //www.example.com/dir/page.html /nowiki unlike browsers internet explorer include port calculation origin using security zone place same-origin policy helps protect sites use authenticated sessions following example illustrates potential security risk could arise without same-origin policy assume user visiting banking website n't log user goes another site malicious javascript code running background requests data banking site user still logged banking site malicious code could anything user could banking site example could get list user last transactions create new transaction etc browser send receive session cookies banking site based domain banking site user visiting malicious site would expect site visiting access banking session cookie true javascript direct access banking session cookie could still send receive requests banking site banking site session cookie script essentially user would even csrf protections banking site would effective circumstances same-origin policy restrictive posing problems large websites use multiple subdomains first number workarounds using fragment identifier codice_1 property used pass data documents residing different domains modern browsers support multiple techniques relaxing same-origin policy controlled manner two windows frames contain scripts set domain value same-origin policy relaxed two windows window interact example cooperating scripts documents loaded orders.example.com catalog.example.com might set document.domain properties “ example.com ” thereby making documents appear origin enabling document read properties setting property implicitly sets port null browsers interpret differently port 80 even unspecified port assure access allowed browser set document.domain property pages technique relaxing same-origin policy standardized name cross-origin resource sharing standard extends http new origin request header new access-control-allow-origin response header allows servers use header explicitly list origins may request file use wildcard allow file requested site browsers firefox 3.5 safari 4 internet explorer 10 use header allow cross-origin http requests xmlhttprequest would otherwise forbidden same-origin policy another technique cross-document messaging allows script one page pass textual messages script another page regardless script origins calling postmessage method window object asynchronously fires onmessage event window triggering user-defined event handlers script one page still directly access methods variables page communicate safely message-passing technique since html script elements allowed retrieve execute content domains page bypass same-origin policy receive json data different domain loading resource returns jsonp payload jsonp payloads consist internal json payload wrapped pre-defined function call script resource loaded browser designated callback function invoked process wrapped json payload modern browsers permit script connect websocket address without applying same-origin policy however recognize websocket uri used insert origin header request indicates origin script requesting connection ensure cross-site security websocket server must compare header data whitelist origins permitted receive reply behavior same-origin checks related mechanisms well-defined number corner cases pseudo-protocols clearly defined host name port associated urls file data etc. historically caused fair number security problems generally undesirable ability locally stored html file access files disk communicate site internet lastly certain types attacks dns rebinding server-side proxies permit host name check partly subverted make possible rogue web pages directly interact sites addresses true canonical origin impact attacks limited specific scenarios since browser still believes interacting attacker site therefore disclose third-party cookies sensitive information attacker even same-origin policy effect without relaxed cross-origin resource sharing certain cross-origin computer attacks performed webrtc used find internal ip address victim attempting connect cross-origin port responses read face same-origin policy javascript still make inferences whether port open closed checking onload/onerror event fires get timeout gives opportunities cross-origin portscanning javascript even fingerprint services cross-origin taking advantage default files example javascript loaded site evil.com attempts open file hxxp //127.0.0.1/images/jenkins.png onload event fires inferred victim runs jenkins computer way attacker find potentially vulnerable services example internal network even face same-origin policy service vulnerable cross-site request forgery even compromised
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Computer security
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trailblazer video game trailblazer video game requires player direct ball along series suspended passages released originally gremlin graphics zx spectrum commodore 64 atari 8-bit family amstrad cpc c16/plus/4 1986 also enhanced version amstrad cpc 3 disc ported amiga atari st 2005 port gizmondo handheld games console released game played either time trial arcade mode music background matches gameplay electronica genre races quite brief usually last 15 45 seconds special fields track let ball jump slow speed warp speed ball invert controls holes game reviewed 1990 dragon 158 hartley patricia kirk lesser role computers column part mastertronic mega pack 10 games previously released europe reviewers gave game 5 5 stars stating favorite disk racing cosmic causeway roads clock robot one really fun zzap 64 reviewers also enjoyed game thought excellent variation race game theme overall rating given 93 steve panak reviewing atari 8-bit version analog computing concluded game original arcade action wristbuster come pike long time one best two-player competition games 've seen
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Computer architecture
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sri lankan cyber security community cyber security information assurance community sri lanka diverse many stakeholders groups contributing support national information cyber security strategy following list stakeholders established information communication technology agency 2006 sri lanka computer emergency response team slcert functions incidentally government private company preview ministry digital infrastructure information technology providing services computer emergency response team finance sector computer security incident response team fincsirt specializes computer security relating banking financial industry sri lanka joint initiative central bank sri lanka slcert sri lankan bankers association national cyber security agency proposed draft cyber security bill techcert formed lk domain registry provides computer security incident response services
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Computer security
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sqlite sqlite relational database management system rdbms contained c library contrast many database management systems sqlite client–server database engine rather embedded end program sqlite acid-compliant implements sql standard generally following postgresql syntax however sqlite uses dynamically weakly typed sql syntax guarantee domain integrity means one example insert string column defined integer sqlite attempt convert data formats appropriate string 123 integer case guarantee conversions store data as-is conversion possible sqlite popular choice embedded database software local/client storage application software web browsers arguably widely deployed database engine used today several widespread browsers operating systems embedded systems mobile phones among others sqlite bindings many programming languages unlike client–server database management systems sqlite engine standalone processes application program communicates instead sqlite library linked thus becomes integral part application program linking may static dynamic application program uses sqlite functionality simple function calls reduce latency database access function calls within single process efficient inter-process communication sqlite stores entire database definitions tables indices data single cross-platform file host machine implements simple design locking entire database file writing sqlite read operations multitasked though writes performed sequentially due server-less design sqlite applications require less configuration client-server databases sqlite called zero-conf require service management startup scripts access control based grant passwords access control handled means file system permissions given database file databases client-server systems use file system permissions give access database files daemon process another implication serverless design several processes may able write database file server-based databases several writers connect daemon able handle locks internally sqlite hand rely file-system locks less knowledge processes accessing database time therefore sqlite preferred choice write-intensive deployments however simple queries little concurrency sqlite performance profits avoiding overhead passing data another process sqlite uses postgresql reference platform would postgresql used make sense sql standard one major deviation exception primary keys sqlite enforce type checking type value dynamic strictly constrained schema although schema trigger conversion storing conversion potentially reversible sqlite strives follow postel rule d. richard hipp designed sqlite spring 2000 working general dynamics contract united states navy hipp designing software used damage-control system aboard guided missile destroyers originally used hp-ux ibm informix database back-end sqlite began tcl extension design goals sqlite allow program operated without installing database management system requiring database administrator hipp based syntax semantics postgresql 6.5 august 2000 version 1.0 sqlite released storage based gdbm gnu database manager sqlite 2.0 replaced gdbm custom b-tree implementation adding transaction capability sqlite 3.0 partially funded america online added internationalization manifest typing major improvements 2011 hipp announced plans add nosql interface managing documents expressed json sqlite databases develop unqlite embeddable document-oriented database sqlite implements sql-92 standard sql lacks features example partially provides triggers write views however provides instead triggers provide functionality provides complex queries still limited alter table function modify delete columns sqlite uses unusual type system sql-compatible dbms instead assigning type column sql database systems types assigned individual values language terms dynamically typed moreover weakly typed ways perl one insert string integer column although sqlite try convert string integer first column preferred type integer adds flexibility columns especially bound dynamically typed scripting language however technique portable sql products common criticism sqlite type system lacks data integrity mechanism provided statically typed columns products sqlite web site describes strict affinity mode feature yet added however implemented constraints like codice_1 tables normally include hidden rowid index column gives faster access database includes integer primary key column sqlite typically optimize treating alias rowid causing contents stored strictly typed 64-bit signed integer changing behavior somewhat like auto-incrementing column future versions sqlite may include command introspect whether column behavior like rowid differentiate columns weakly-typed non-autoincrementing integer primary keys sqlite full unicode function optional several computer processes threads may access database concurrently several read accesses satisfied parallel write access satisfied accesses currently serviced otherwise write access fails error code automatically retried configurable timeout expires concurrent access situation would change dealing temporary tables restriction relaxed version 3.7 write-ahead logging wal turned enabling concurrent reads writes sqlite version 3.7.4 first saw addition fts4 full text search module features enhancements older fts3 module fts4 allows users perform full text searches documents similar search engines search webpages version 3.8.2 added support creating tables without rowid may provide space performance improvements common table expressions support added sqlite version 3.8.3 2015 json1 extension new subtype interfaces sqlite version 3.9 introduced json content managing sqlite code hosted fossil distributed version control system built upon sqlite database standalone command-line program provided sqlite distribution used create database define tables insert change rows run queries manage sqlite database file also serves example writing applications use sqlite library sqlite uses automated regression testing prior release 2 million tests run part release verification starting august 10 2009 release sqlite 3.6.17 sqlite releases 100 branch test coverage one components code coverage tests test harnesses partially public domain partially proprietary sqlite included default large number programming languages provide bindings sqlite including
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Databases
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cloudbleed cloudbleed security bug discovered february 17 2017 affecting cloudflare reverse proxies caused edge servers run past end buffer return memory contained private information http cookies authentication tokens http post bodies sensitive data result data cloudflare customers leaked went cloudflare customers happened server memory particular moment data cached search engines discovery reported google project zero team tavis ormandy posted issue team issue tracker said informed cloudflare problem february 17 proof-of-concept attack got cloudflare server return private messages major dating sites full messages well-known chat service online password manager data frames adult video sites hotel bookings 're talking full https requests client ip addresses full responses cookies passwords keys data everything effects cloudbleed similar 2014 heartbleed bug allowing unauthorized third parties access data memory programs running web servers including data shielded tls extent cloudbleed also could impacted many users heartbleed since affected security content delivery service used close 2 million websites tavis ormandy first discover vulnerability immediately drew comparison heartbleed saying took every ounce strength call issue 'cloudbleed report thursday february 23 2017 cloudflare wrote post noting bug serious leaked memory could contain private information cached search engines also discovered evidence malicious exploits bug reports existence. br greatest period impact february 13 february 18 around 1 every 3,300,000 http requests cloudflare potentially resulting memory leakage ’ 0.00003 requests .cloudflare acknowledged memory could leaked early september 22 2016 company also stated one private keys used machine-to-machine encryption leaked turned underlying bug caused memory leak present ragel-based parser many years memory leaked way internal nginx buffers used introducing cf-html subtly changed buffering enabled leakage even though problems cf-html john graham-cumming cloudflare cto noted cloudflare clients uber okcupid n't directly informed leaks due security risks involved situation “ backdoor communication outside cloudflare — google search engines ” said graham-cumming also said unfortunately ancient piece software contained latent security problem problem showed process migrating away added team already begun testing software possible issues tavis ormandy initially stated really impressed cloudflare quick response dedicated cleaning unfortunate issue however ormandy pressed cloudflare additional information gave several excuses n't make sense sending draft severely downplays risk customers uber stated impact service limited uber spokesperson added handful session tokens involved since changed passwords exposed okcupid ceo elie seidman said cloudflare alerted us last night bug 've looking impact okcupid members initial investigation revealed minimal exposure determine users impacted promptly notify take action protect fitbit representative stated company investigating issue concerned users change passwords immediately many major news outlets advised consumers sites using cloudflare change passwords even accounts protected 2-factor authentication could risk passwords mobile apps could impacted researchers arbor networks alert suggested us truly safe response large-scale information leak update passwords web sites app-related services use every day ... pretty much inc. magazine cybersecurity columnist joseph steinberg however advised people change passwords stating current risk much smaller price paid increased 'cybersecurity fatigue leading much bigger problems future
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Computer security
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valis ii sd style remake released japanese mega drive north american genesis syd valis like titles series valis ii side-scrolling platform game requires player navigate two-dimensional levels battling enemies jumping ledge ledge running player faces boss end level despite details gameplay varying versions versions share several similar features well mobile remake added new stages alternate costumes weapons time passes vecanti set rule next emperor rogles brother voiced hirotaka suzuoki wishes stamp trace former tyrant point murdering supporters rogles might furthermore bloodthirsty tendencies recognize yuko valis sword viable threats claim throne orders minions eliminate first chance thwart megas falls magical blade peace comes dream world yuko returns home resume otherwise ordinary human life telenet japan developed two main versions valis ii around time pc engine cd-rom² released first later published nec north america home computer version believed entered development earlier released pc-88 pc-98 msx sharp x68000 japan featured graphic cutscenes another port game released mega drive japan sd valis telenet genesis north america renovation products syd valis title features gameplay plot original character design changed super deformed sd style north american version game incorrectly identifies yūko syd reuses box art naritore sugoroku '92 front cover project egg released various emulated versions game windows along 2011 compilation complete plus came soundtrack cd figure pc engine also released sunsoft playstation store 2011 1993 cd valis visual collection contains cutscenes pc engine version valis ii valis ii generally positively received critics review scores pc engine turbografx-16 version included 74 games machine 76 italian edition computer video games 70 génération 4 92 joystick 75 tilt three five stars turboplay whose reviewer impressed game visuals music disappointed perceived low difficulty hand sd valis syd valis rated 36 consoles+ 56 joystick 63 joypad sega force bashed dull gameplay despite great levels enemies predicting even platform addicts play james scullion sega pro gave sd valis mediocre score 65 recommending saving money game retrospectively sebastian sponsel sega-16 scored 2 10 stating syd valis disappointment fans non-fans alike ... ’ like game created joke one producers ’ get released anyway
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Computer architecture
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scriptcase scriptcase rad development platform php applications web oriented installed server internet acts like platform developers allows use graphical interface directly web browser automatically generate codes developed netmake year 2000 used mac windows linux operating system using scriptcase php developers generate complete online applications scriptcaseis rapid web development tool aims reduce development time increase productivity developers need xamp like environment web server like apache incl php dabase like mysql browser desktop accessible via network internet develop applications hosting applications server needs webserver incl php database programs finally developed deployed scriptcase longer necessary run application scriptcase used create crud create read update delete applications also enables add custom code manage business rules validation scriptcase lets create forms queries php ranging simple forms forms high level complex elements manipulate data databases mysql postgresql sqlite interbase firebird access oracle ms sqlserver db2 sybase informix odbc connections permits development javascript methods used within ajax events create applications ajax set features services easy fast hand coding navigation pages sections automatic validation fields date currency zip code social security number among others generated reports exported ms word ms excel pdf printed complex sql statements used sub-select joins even stored procedures scriptcase allows users write php handle exceptions create complex validation scriptcase compatible rtl right left writing support right left writing prevalent arabic languages also possible create infrastructure menus login screen security system authentication create tabs group forms queries executed page platform development began 2000 since receiving regular updates addresses web application developers desktops mobiles two ways enables starting developers limited knowledge programming php java basic knowledge databases sql build applications reads updates data web databases also aims experienced developer scriptcase put lot focus business logic rather editing forms build database connections etc pricing model shift buying software till end 2016 lease service 2016 due publication ceo subscribers current users scriptcase nov 14th 2016 prices currently 400- 600 buying software depending many databases supported per developer platform development started 2000 since tool received periodic updates improvements -was sold customers beta mode -big changes interface -native support ajax -internationalization support -graphics flash -new implementations jquery support -focused editing field types creating option edit fields -the biggest change performance 5 times faster -integration paypal -multi-thread processing scriptcase consolidation one strongest tools bi business intelligence migrating features help end user make decisions made major changes grid application option end users create group within application based fields defined developer add totals create graphics addition new graphic application added simplify creation applications implemented new filter functionality dynamic summary grid applications created new graphic application support user-defined combined final graphics new refined filter restricting values according universe exists database group buttons new chart toolbar button editor comes important implementations business intelligence complete redesign charts grids abstracts – pivot tables dashboards significant improvements security pdf report module menu interface redesign development improvement performance php7 among implementations scriptcase still allows advanced settings generated applications meet requirements complex systems also documentation generator integrate whole team
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Programming language topics
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load file load file litigation community commonly referred file used import data coded captured extracted data esi processing database file used link images load files carry commands commanding software carry certain functions data found load files usually ascii text files delimited fields information load files may data documents imported document management software concordance summation may path directory images may reside software link images corresponding records database programs take one load file importing images another importing data others take one load file pieces information ocr search-able text considered data also imported database programs via load files though people prefer load ocr databases running separate command search find desired text commonly used databases corresponding file extensions summation dii csv concordance opt dat sanction sdt ipro lfp ringtail mdb db/textworks txt
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Databases
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sympl sympl obsolete programming language developed control data corporation cdc use cdc 6000 series computer systems 1970s 1980s based subset cdcs version jovial alternative assembly language number important cdc software products implemented sympl including compilers libraries full-screen editor major subsystems sympl compiled imperative procedural language compared fortran day sympl supports simplifications compared jovial include fewer built-in data types recursive calls procedures codice_1 concept
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Programming language topics
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encryption layer storage stack a0kq 9t4x mf5y x32a rhns 0p92 aecx 5ed5 plurality terms used describe implementations disk encryption on-the-fly encryption otfe full disk encryption fde whole disk encryption filesystem-level encryption encrypted filesystem cryptographic filesystem etc refer encryption layer storage stack article describes techniques explains pros cons article reference software hardware implementing techniques see disk encryption software hardware describe cryptographic theory behind see disk encryption theory fully understand techniques listed first need consider stack software hardware computer storage subsystem let us give example stack pc hard disk hardware provides interface read write sectors using logical block addressing lba cylinder-head-sector chs address top software layer interprets partition table stored master boot record mbr represents single hard disk set logical disks top another software layer filesystem represent logical disk collection files organized directories top may software text editor interprets file list text lines layer stack provides interface using interface provided layer example lba-accessible disk logical disk allow read write sectors fixed size given sector number layers called sector-addressable filesystem allows read write data arbitrary length given name file offset inside file text editor allows delete insert characters text file similar communication protocol stack modularity provides great flexibility layer easily replaced another far provides interface example hard disk replaced flash memory rest stack stays unchanged also possible introduce additional layer provides interface layer change data along way example provide on-the-fly encryption decryption encryption layer integrated layer example encryption implemented hardware hard disk single logical disk encrypted file encrypted filesystem even text editor transparently encrypt data storing file terms listed beginning article refer encryption layer different positions unfortunately naming conventions different different speakers general every method data transparently encrypted write decrypted read called on-the-fly encryption otfe although prefer use name encryption sector-addressable layer full disk encryption fde whole disk encryption used refer encryption sector-addressable layer physical disk logical disk whereas others use denote encryption physical disk logical disk filesystem-level encryption cryptographic filesystem used refer filesystem selectively encrypt files stored whereas others distinguish terms use former denote general purpose filesystem supports encryption use latter denote filesystem specifically designed provide encryption uses filesystem store files since many cases people mistakenly assume collocutor assigns meaning terms lot arguments whether particular implementation provides particular feature example one contrasts “ full disk encryption ” “ filesystem-level encryption ” may say software package provides fde whereas opponent contrasts “ fde ” “ logical disk encryption ” “ disk partition encryption ” say package provide fde article explains getting argument important understand meaning speaker assigns terms
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Computer file systems
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