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sparcstation ipx sparcstation ipx sun 4/50 workstation sold sun microsystems based sun4c architecture enclosed lunchbox chassis sparcstation ipx incorporates fujitsu mb86903 weitek w8701 40 mhz processor weitek sold 80 mhz aftermarket sparc powerup 2000a-080 gcd processor ipx requires rom update v2.9 sparcstation ipx four 72-pin simm slots memory expansion memory uses parity fast page memory fpm simm speeds 50-80ns slots filled individually giving maximum 64mb memory paired memory modules decrease access times via bank interleaving resulting faster memory overall system performance additional 32 64mb sbus board ram expanders fit work ipx using 8-pin j101 header contains additional power clock signals next dma/cache controller sparcstation ipx hold one internal 50 pin idc scsi drive floppy also supports external scsi devices ide/atapi support modern 80 pin single connector attachment sca drives work adapter fit inside case due size adapter sparcstation ipx comes on-board amd lance am7990 ethernet chipset provides aui connection external aui transceivers required connection 10base5 10base2 10baset ethernet physical layer media openboot rom able boot network using rarp tftp like sparcstation systems ipx holds system information mac address serial number nvram battery chip dies system able boot unaided boot parameters entered manually lost power sparcstation ipx includes integrated sun turbo gx cgsix color framebuffer internal sbus frees one sbus slot framebuffer duty makes sparcstation ipx expandable larger form factor sparcstation 2 otherwise shares many architectural similarities sparcstation ipx 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 ipx sparcstation ipc sun 4/40 earlier lunchbox form factor system sparcstation 2 sun 4/75 architecturally similar use cpu sbus ram upgrades
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Computer architecture
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tops file server tops transcendental operating system peer-to-peer lan-based file sharing system best known macintosh implementation also available dos able interoperate unix nfs originally written centram systems west company purchased sun microsystems part sun development nfs ecosystem centram company renamed tops acquisition sun sales tops dried introduction system 7 featured similar file sharing system built-in sun spun nfs developments sitka tops implemented 1980s era computer system featured networking protocol generally unable talk time apple midst macintosh office effort working two external companies develop apple filing protocol afp built top appletalk macintosh office effort ultimately failed one two companies centram decided implement similar system became first version tops tops originally released peer-to-peer file sharing solution mac according pc magazine connecting mac apple laserwriter printer initial intended function appletalk apple file sharing solution appleshare released later unlike tops required dedicated server machine run least mac plus smaller offices tops attractive low-cost solution saw relatively widespread use even introduction appleshare tops managed hold estimated 600,000 client installs tops initially protocol using custom set remote procedure calls able talk tops clients pcs generally lacked networking sort centram addressed problem introducing line localtalk cards pc along tops client files could exchanged two computers filename conversion required centram later introduced flashtalk networking system used external clocking improve localtalk performance zilog scc powering serial ports mac used internal 3.6864 mhz clock could divided provide different standard bit rates fastest rate available internally 230.4 kbit/s used localtalk however system also allowed clock read pin serial port giving rise possibility faster speeds right external equipment flashtalk combined conventional localtalk-like dongle clocking source external power supply using connectors associated software tops could run 770 kbit/s fairly dramatic improvement localtalk also relatively speedy overall era 1 mbit/s networks still common sun purchase tops given problem making client could also access sun file shares using nfs centram solved problem porting file sharing protocol tcp/ip trivial neither mac os windows supported tcp/ip box tops division sun write complete ip stack mac windows centram already written stack tops terminal freeware open source telnet terminal mac additionally majority macintosh systems used localtalk phonenet connectivity could directly connected ethernet-based unix lans worked around problem supporting emerging localtalk-to-ethernet bridging standard known kip short kinetics internet protocol kip encapsulated tcp/ip packets inside appletalk packets allowing sent existing localtalk connections dedicated kip-supporting network bridges available stripped appletalk packaging re-formed ip packets inside sent ethernet one limitation tcp stack support dns requiring users type ip addresses peers wanted communicate network mostly macs windows pcs issue dns widely used systems time kip also reduced need dns allowed mac existing address resolution protocol aarp code within appletalk look appletalk address remote peer communicate tops stack machine find corresponding ip address tops also added new inbox personal connection e-mail system first developed symantec tops attractiveness seriously eroded introduction system 7 1991 tops initially competed dedicated-server appleshare system 7 included file sharing server built-in one proved much faster then-current versions tops tops sales dwindled sun spun division sitka closing entirely 1993
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Computer file systems
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wolfram language wolfram language general multi-paradigm computational language developed wolfram research programming language mathematical symbolic computation program mathematica wolfram programming cloud emphasizes symbolic computation functional programming rule-based programming employ arbitrary structures data includes built-in functions generating running turing machines creating graphics audio analyzing 3d models matrix manipulations solving differential equations extensively documented wolfram language core principles differentiate programming languages includes built-in knowledgebase automation form meta-algorithms superfunctions coherently elegant design structure built-in natural language understanding representation everything symbolic expression wolfram language released raspberry pi 2013 goal making free raspberry pi users included recommended software bundle raspberry pi foundation provides beginners caused controversy due wolfram language proprietary nature plans port wolfram language intel edison announced board introduction ces 2014 2019 link added make wolfram libraries compatible unity game engine giving game developers access language high level functions language officially named june 2013 although programming language mathematica use various forms 30 years since mathematica initial release 2013 internally referred several names wolfram language possible names wolfram research considered include lingua express stephen wolfram son christopher wolfram involved helping create alien language film arrival used wolfram language given portions written language used wolfram language analyze images attempt interpret served model characters approached problem film beginning 2017 wolfram began live stream internal wolfram language development meetings meetings viewers encouraged submit questions comments related development programming language viewers known suggest new functions would like see developed name new functions help solve complex issues faced stephen wolfram research development team live streamed meetings viewed twitch.tv youtube live facebook live following release version 12 wolfram research developers began live streaming presentations highlight new functionalities directly responsible creating unlike development meetings streamed stephen wolfram presentations streamed exclusively twitch.tv
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Programming language topics
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amazon product advertising api amazon product advertising api formerly amazon associates web service a2s known amazon e-commerce service ecs web service application programming interface api gives application programmers access amazon product catalog data accessible via either soap rest protocols enables products listed and/or sold third-party websites applications product amazon services confused amazon web services amazon.com developed product advertising api toward three classifications users api allows clients search browse amazon.com product catalog retrieve detailed product information reviews images interface customer shopping carts purchases amazon third-party website application allows operators site earn 8.5 referral fees motivation behind free product advertising api give partners opportunity earn money promoting amazon products access given developers applications primarily bring least seem potential bring gains amazon
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Web technology
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kung-fu master video game kung-fu master side-scrolling beat 'em game produced irem arcade game 1984 distributed data east north america game initially released japan title tie-in based jackie chan film wheels meals also distributed name spartan x japan however game bearing plot film outside names main protagonist girlfriend allowing irem export game without license simply changing title players control thomas titular kung-fu master fights way five levels devil temple order rescue girlfriend sylvia mysterious crime boss mr. x kung-fu master regarded first beat 'em video game nes port titled kung fu sold 3.5 million cartridges arcade game also inspired 1988 french film name player controls thomas four-way joystick two attack buttons punch kick unlike conventional side-scrolling games joystick used crouch also jump punches kicks performed standing crouching jumping position punches award points kicks damage range shorter underlings encountered player include grippers grab thomas drain energy shaken knife throwers throw two different heights must hit twice tom toms short fighters either grab thomas somersault strike head crouching even-numbered floors player must also deal falling balls pots snakes poisonous moths fire-breathing dragons exploding confetti balls devil temple five floors ending different boss described sons devil start game order complete floor thomas must connect enough strikes completely drain boss energy meter climb stairs next floor thomas fixed time limit complete floor time runs meter completely drained player loses one life must replay entire floor upon completing floor player receives bonus points remaining time energy boss fifth floor mr. x leader gang kidnapped sylvia defeated thomas rescues sylvia game restarts higher difficulty level game produced irem takashi nishiyama also created irem 1982 arcade-hit moon patrol later designed original 1987 street fighter capcom leaving run snk videogame development division creating neo geo arcade system board games like art fighting king fighters '94 samurai shodown well several successors game originally based bruce lee 1972 movie game death five-level devil temple reflecting movie setting five-level pagoda martial arts master level however title changed development make tie-in jackie chan spartan x kung-fu master ported atari 2600 atari 7800 amstrad cpc apple ii commodore 64 nes/famicom msx irem/ascii version seiken achō playchoice-10 arcade nearly nes version zx spectrum nes version converted published nintendo kung fu north america pal region also made 8-bit gameking console name nagual arcade version later included along arcade versions 10-yard fight zippy race iac/irem arcade classics playstation sega saturn released japan 1996 irem i'max arcade version released cell phones amstrad cpc zx spectrum versions game included 1986 compilation sold million 3 along fighter pilot ghostbusters rambo arcade sequel called super kung-fu master reportedly planned never released irem 1988 vigilante intended followup gameplay nearly completely different plot added takes place urban areas new york city nameless titular character must save girlfriend madonna maria sega master system version captured skinheads rogues sega master system version one unique feature ability pick use battering weapon nunchaku either player gets hurt finishes stage begin battling final boss 1990 arcade game received completely different game boy sequel titled kung-fu master spartan x japan similar gameplay arcade game completely different plot setting protagonist along new set enemies different stages new bosses including chainsaw man another strongman napalm bomber ninja shinobi mysterious wealthy kung fu master named zapp morgan leader thomas new abilities back-flip kicks small bombs dropped enemies flat levels modified stages different platforms objects urban city style similar vigilante english version modified japanese version changing look thomas renaming bruce leap add small enemies final stage fighting final boss 1991 japan-exclusive sequel game released famicom titled spartan x 2 like vigilante game boy version kung-fu master spartan x 2 plot also quite different takes place urban area mention sylvia rather johnny spartan member unnamed crime-fighting unit wears red short-sleeved jacket charges foiling 6 drug smugglers including punk named flamey joe magician named chin gen sai boatswain strongman named billy bailey circus trainer named mr. benjamin femme fatale named madda lin crime syndicate leader kung fu master named caeson hawk one unique feature ability crouch second either sending uppercut grab throw enemies behind spartan x 2 receive north american release 2016 included built-in title retro-bit generations retro video game console name kung-fu master 2
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Computer architecture
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blackle blackle website powered google custom search created tony heap heap media aims save energy displaying black background using grayish-white font color search results blackle claims saved 7 mwh electrical energy february 2019 claim public dispute comparison average american household consumes 11 mwh electrical energy per year concept behind blackle computer monitors made use less energy displaying much darker colors blackle based study tested variety crt lcd monitors dispute whether really energy saving effects especially users lcd screens constant backlight concept first brought attention heap media blog post estimated google could save 750 megawatt hours year utilizing crt screens homepage blackle provides count number watt hours claimed saved enabling concept
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Web technology
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microsoft silverlight microsoft silverlight simply silverlight deprecated application framework writing running rich internet applications similar adobe flash plugin silverlight still available browsers early versions silverlight focused streaming media later versions supported multimedia graphics animation game developers support cli languages development tools silverlight also one two application development platforms windows phone web pages use silverlight run windows phone windows mobile versions internet explorer silverlight plugin internet explorer platforms initial launch 2007 reviewers compared product adobe flash according statowl.com microsoft silverlight penetration 64.2 may 2011 usage july 2010 53.6 whereas market leader adobe flash installed 95.3 browsers java supported 76.5 browsers support plugins mutually exclusive one system support three web sites require browser plugin silverlight used provide video streaming nbc coverage 2008 summer olympics beijing 2010 winter olympics vancouver 2008 conventions major united states political parties silverlight also used amazon video netflix instant video streaming services netflix said tech blog 2013 since microsoft announced silverlight end-of-life would moving html5 video industry observers announcing death silverlight early 2011 internally even proponents technology thought extensible application markup language concept bad idea start 2012 microsoft deprecated silverlight html5 windows 8 late beginning 2015 clear microsoft official position future silverlight technology july 2015 microsoft blog post finally clarified matters ... encourage companies using silverlight media begin transition dash/mse/cenc/eme based designs microsoft set overall support end date silverlight 5 october 2021 support ie7-8 removed 2014 2016 depending os support ie9-11 last late 2021 depending os though sic support lifecycle underlying browsers whichever shorter silverlight plugin available microsoft edge supported google chrome since september 2015 firefox since march 2017. fewer 0.1 sites used silverlight 5.3 used adobe flash 2.4 used java silverlight provides retained mode graphics system similar windows presentation foundation wpf integrates multimedia graphics animations interactivity single run-time environment silverlight applications user interfaces declared extensible application markup language xaml programmed using subset .net framework xaml used marking vector graphics animations silverlight also used create windows sidebar gadgets windows vista silverlight supports h.264 video advanced audio coding windows media video wmv windows media audio wma mpeg layer iii mp3 media content across supported browsers without requiring windows media player windows media player activex control windows media browser plug-ins windows media video 9 implementation society motion picture television engineers smpte vc-1 standard silverlight also supports vc-1 video according end user license agreement vc-1 h.264 licensed personal non-commercial use consumer silverlight makes possible dynamically load extensible markup language xml content manipulated document object model dom interface technique consistent conventional ajax techniques silverlight exposes downloader object used download content like scripts media assets data may required application version 2 programming logic written .net language including derivatives common dynamic programming languages like ironruby ironpython free software implementation abandoned named moonlight developed novell cooperation microsoft released bring silverlight versions 1 2 functionality linux freebsd open source platforms although linux distributions include citing redistribution patent concerns however may 2012 moonlight abandoned lack popularity course five years microsoft released five versions varying platform support first version released 2007 fifth final major version may 8 2012 compatible later versions internet explorer web browser microsoft windows except windows rt operating systems safari apple macos mobile devices using windows mobile symbian series 60 platforms cross platform mozilla firefox support silverlight removed firefox 52 released march 2017 mozilla removed support npapi plugins bringing in-line removal npapi plugin support google chrome silverlight requires x86 processor streaming simd extensions sse support supported processors include intel pentium iii amd athlon xp newer amd durons following table presents availability compatibility matrix silverlight versions various operating systems web browsers support opera promised since may 3 2007 david storey chief web opener opera revealed microsoft poster mix conference shown opera integration part silverlight 1.1 however opera never officially supported silverlight linux freebsd functionality available via moonlight pipelight though projects discontinued moonlight available major linux distributions support firefox konqueror opera browsers provided obtained novell miguel de icaza expressed interest working developers operating systems bsd solaris browsers konqueror webkit opera ensure moonlight works fine systems availability moonlight version 1.0 freebsd announced march 2009 since reported actually work current version moonlight 4 preview 1 officially work new versions firefox newer 3.x gnu/linux-based operating systems however installed unofficial way example using add-on compatibility reporter add-on firefox 11 works correctly installed noted moonlight project abandoned may 2012 browser plugin named pipelight used provide silverlight access pipelight requires browser support npapi plugins newer versions firefox chrome opera dropped 2018 pipelight project discontinued silverlight available android ios prevalent operating systems mobile market silverlight primary development environment windows phone based silverlight 4 previous versions windows mobile first community technology preview ctp windows mobile 6 expected second quarter 2008 still officially announced microsoft stopped focusing bringing silverlight windows mobile 6.x nokia announced plans make silverlight mobile available s60 symbian os well series 40 devices nokia internet tablets later sold business microsoft sells android tablets sell alcatel-lucent branded smartphones silverlight mobile supports silverlight 2 content .net languages silverlight windows phone 7.5 based silverlight 4 silverlight applications could written .net programming language development tools used .net languages work silverlight provided target silverlight coreclr hosting application instead .net framework clr microsoft positioned microsoft expression blend companion tool visual studio design silverlight user interface applications visual studio used develop debug silverlight applications create silverlight projects let compiler target coreclr visual studio requires silverlight tools visual studio silverlight control zip format file extension .xap containing list one .net managed assemblies .dll files along appmanifest.xaml file containing list along entry point class assembly hosted html file using object tag example silverlight project contains silverlight.js createsilverlight.js files initializes silverlight plug-in use html pages xaml file ui code-behind files application code silverlight applications debugged manner similar asp.net applications visual studio clr remote cross platform debugging feature used debug silverlight applications running different platform well conjunction release silverlight 2 eclipse added development tool option april 2007 pc world report suggested microsoft intended release certain parts silverlight source code open source software week later sam ramji director platform technology strategy microsoft contradicted rumors confirming company plans open silverlight controls ship silverlight available microsoft public license part separate project known silverlight toolkit silverlight proprietary nature concern competition since may harm open nature world wide web advocates free software also concerned silverlight could another example microsoft embrace extend extinguish strategy microsoft silverlight adobe flash proprietary flash file formats publicly documented standards silverlight silverlight like web technologies uses patent-encumbered audio video codecs mono team abandoned development moonlight free open-source implementation silverlight 1 2 runtimes development discontinued 2012 due poor acceptance silverlight restrictions imposed microsoft project officially supported microsoft agreement novell made not-publicly-available additional specifications access silverlight base class library apis binary codecs test cases available mono team covenant novell granted exclusive access also specified conditions incompatible licensing covers free open source software examples specifically required software must obtained directly novell intermediate recipient must licensed gplv3 similar license free software proponents criticized covenant silverlight criticised living cross-platform operating system compatibility promises especially linux systems compared extensive support apple microsoft desktops internet explorer firefox chrome although microsoft officially collaborating moonlight project bruce chizen ceo adobe systems sells competing proprietary flash platform questioned commitment microsoft keep silverlight platform compatible os besides windows concerns based examples history said microsoft launched products promises ongoing cross-platform compatibility longer apply example internet explorer unix windows media player mac 2007 california several u.s. states asked district judge extend microsoft antitrust case settlement another five years citing number concerns including fear microsoft could use next version windows 'tilt playing field toward silverlight new adobe flash competitor says seattle post-intelligencer article final judgment motion extended settlement two years november 2009 reasons unrelated silverlight
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Operating systems
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distributed coordination function distributed coordination function dcf fundamental medium access control mac technique ieee 802.11-based wlan standard including wi-fi dcf employs carrier-sense multiple access collision avoidance csma/ca binary exponential backoff algorithm dcf requires station wishing transmit listen channel status difs interval channel found busy difs interval station defers transmission network number stations contend wireless medium multiple stations sense channel busy defer access also virtually simultaneously find channel released try seize channel result collisions may occur order avoid collisions dcf also specifies random backoff forces station defer access channel extra period length backoff period determined following equation formula_1 dcf also optional virtual carrier sense mechanism exchanges short request-to-send rts clear-to-send cts frames source destination stations intervals data frame transmissions dcf includes positive acknowledge scheme means frame successfully received destination addressed destination needs send ack frame notify source successful reception dcf solve hidden terminal and/or exposed terminal problem completely alleviates problem use rts cts recommends use larger carrier sensing range dcf defined subclause 9.3 ieee 802.11 standard de facto default setting wi-fi hardware 802.11 dcf consumes significant amount airtime 802.11 control messages usually convey little information example ack message take 60 μs transmit completely includes amount airtime sufficient transmit 3240 bits 54 mbit/s conveys single bit relevant information ieee 802.11 standard also defines optional access method using point coordination function pcf pcf allows access point acting network coordinator manage channel access ieee 802.11e amendment standard enhances dcf pcf new coordination function called hybrid coordination function hcf
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Internet protocols
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comprehensive national cybersecurity initiative comprehensive national cybersecurity initiative cnci established president george w. bush national security presidential directive 54/homeland security presidential directive 23 nspd-54/hspd-23 january 2008 initiative outlines u.s. cybersecurity goals spans multiple agencies including department homeland security office management budget national security agency initial signing initiative hearings initiative 2008 kept classified however march 2010 obama administration declassified limited material regarding project current goals initiative include establishing front line defense network intrusion defending u.s. full spectrum threats counterintelligence strengthening future cybersecurity environment education coordination research main actions cnci january 6 2011 national security agency nsa began building first series data centers pursuant program 1.5 billion community comprehensive national cybersecurity initiative data center also known utah data center located camp williams utah
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Computer security
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viewmax viewmax cua-compliant file manager supplied dr dos versions 5.0 6.0 based cut-down version digital research gem/3 graphical user interface modified run single application viewmax desktop support unneeded functions removed whilst new functions added time nevertheless systems remained close enough viewmax recognize gem desktop accessories .acc executables automatically allow native gem applications .app executables run inside viewmax environment without install launch gem first many display drivers gem 3.xx used viewmax well enabling viewmax used non-standard display adapters higher resolutions possible using default set viewmax drivers also digital research sid86 symbolic instruction debugger shipped dr dos 3.xx provided dedicated functions debug gem applications see gem-specific help sid86 gemsid used viewmax well originally named navigator beta versions viewmax 1.00 distributed dr dos 5.0 1990 provide equivalent dosshell ms-dos/pc dos 4.0 similar appearance digital research previous gem desktops – two fixed-size windows window would either contain icons representing drives directories files representation directory hierarchy supported underlying operating system dr dos file directory passwords access permissions supported network drives including cd-rom drives distinguished icon different local drives 1991 viewmax 2 distributed dr dos 6.0 various graphical improvements made release including controls 3d appearance user-selectable colour schemes directory tree enabled shown beside list icons rather instead various settings could stored configuration files named drdoscfg \viewmax.ini flexible character set support viewmax 2 loaded display fonts standard dos .cpi file depending current code page rather using gem specific character set feature also incorporated freegem since 2005 dos/v-compatible japanese version viewmax distributed dr dos 6.0/v 1992 supported dbcs characters loaded font.sys screenhz.fnt support added dr dos task switcher taskmax present applications would launched separate tasks viewmax could switch taskmgr later operating systems novell dos 7 opendos 7.01 dr-dos 7.02 higher continued emulate task switcher api well viewmax 2 could used switch control multiple concurrently running full-screen dos tasks dr-dos preemptively multitasking kernel emm386 /multi taskmgr well viewmax 3 intended graphical file manager novell next version dr dos viewmax 3 included support colour icons movable resizable windows program groups background images underlying dr-dos optional multi-user security module loaded viewmax would also provide support extended world/group/owner access permission system although viewmax 3 part dr dos panther beta 1 distribution october 1992 never completed apparently abandoned favour apple novell star trek team project 1992/1993 remained unreleased well novell dos 7 dr dos 7.0 called 1994 came without graphical file manager caldera bought remaining digital research assets novell 23 july 1996 initial plans revive gem viewmax technologies low-footprint user interface opendos mobile applications caldera view plans abandoned caldera uk favour dr-webspyder grow closing dr-dos development center caldera uk early 1999 remaining source code viewmax 3 beta version published april 1999 us parent company caldera thin clients gpl following continued community request release sources shortly company changed name lineo switched linux-based technologies three months later various viewmax features previously found gem incorporated freegem since
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Operating systems
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wizard os openbsd 3.7 released may 19 2005 theme song made titled wizard os song chronicled openbsd developers struggle obtain open documentation wireless cards manufacturers taiwan like ralink realtek cooperative companies contacted based work pink floyd notably style 1973 album dark side moon showing similarities great gig sky breathe eclipse parody wizard oz effort theo de raadt project benevolent dictator life received fsf 2004 award advancement free software song co-arranged ty semaka jonathan lewis also recorded mixed mastered song
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Operating systems
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raster interrupt raster interrupt also called horizontal blank interrupt interrupt signal computer system used display timing usually though always generated system graphics chip scan lines frame readied send monitor display interrupt provides mechanism graphics registers changed mid-frame different values interrupt point allows single-color object multiple horizontal color bands example sprite repositioned give illusion sprites system supports limitation changes affect portion display interrupt n't allow colors sprites single scan line several popular home computers video game consoles included graphics chips supporting raster interrupts features could combined work like raster interrupts antic chip used atari 8-bit family includes display list interrupts dlis triggered display drawn antic chip considerably powerful inherently capable many features systems require raster interrupts duplicate antic mix multiple graphics modes screen display horizontal vertical overscan graphics fine scroll selected horizontal regions dlis atari typically used add additional color display reuse player/missile graphics elements c64 vic-ii flexible raster interrupt system raster interrupts cpu intervention necessary reuse sprites screen mix graphics modes selectively scroll screen regions nintendo entertainment system ppu graphics chip support true raster interrupts interrupt set trigger vertical blank interval arbitrary scan line instead required polling hit flag indicated first sprite drawn although early games like super mario bros. castlevania legend zelda managed produce effective split-screen scrolling method cpu-intensive later cartridges incorporated mmc circuitry prominently nintendo mmc3 chip kept track ppu address data lines generated raster interrupts msx2 computers feature dedicated yamaha v9938 video display processor vdp like nes supports 'vertical blank interrupts requires polling 'horizontal blank interrupts commonly used create split screens mix multiple video modes together one screen increase number unique colours screen beyond official spec prominent usage examples aleste series konami space manbow amiga computers include custom coprocessor called copper dedicated servicing raster interrupts copper runs program simple instructions directing wait specific vertical scan line horizontal beam position update contents custom chip hardware register typically used modifying display parameters mixing display modes reusing sprites changing color registers also used trigger cpu interrupt game boy ppu support four raster interrupts set trigger beginning specified scanline end scanlines horizontal blanking beginning scanlines beginning vertical blanking biggest drawback interrupt handler used first three requiring use dispatching code one condition used
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Computer architecture
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miros licence miros licence free content licence software free cultural works graphical literal musical … originated miros project publications isc license used openbsd perceived problems wording america centric strong roots ucb bsd licence historical permission notice disclaimer focus modern explicit legible language usability european except uk specifically german authors hindering adoption authors legislations permissive “ bsd/mit-style ” licence another novelty licence specified kind copyrightable work start meets open source definition debian free software guidelines also open knowledge definition fact approved okfn long osi licence seen formal legal review listed ifross ’ licence centre webpages free software foundation formally added licence either free software licence free documentation license pages software directory category license accepted free content license according free cultural works definition
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Operating systems
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multipurpose transaction protocol multipurpose transaction protocol mtp software proprietary transport protocol developed marketed data expedition inc. dei dei claims mtp offers superior performance reliability compared transmission control protocol tcp transport protocol mtp implemented using user datagram protocol udp packet format uses proprietary flow-control error-correction algorithms achieve reliable delivery data avoid network flooding mtp/ip uses proprietary algorithms compatible software must installed ends communication path use udp packet format permits compatibility standard internet protocol ip network hardware software mtp/ip applications may use available udp port number mtp applications use implemented several operating systems including versions microsoft windows macos linux freebsd solaris hardware platforms include variations x86 power isa arm mtp/ip marketed data expedition inc. trial versions applications use mtp/ip available company website
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Internet protocols
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risk management risk management application risk management methods information technology order manage risk i.e onlyinclude risk management considered component wider enterprise risk management system establishment maintenance continuous update information security management system isms provide strong indication company using systematic approach identification assessment management information security risks different methodologies proposed manage risks divided processes steps /onlyinclude according risk framework encompasses negative impact operations service delivery bring destruction reduction value organization also benefit enabling risk associated missing opportunities use technology enable enhance business project management aspects like overspending late delivery adverse business impact risk strictly tied uncertainty decision theory applied manage risk science i.e rationally making choices uncertainty generally speaking risk product likelihood times impact risk likelihood impact measure risk determined product threat vulnerability asset values current risk management framework risk would tik framework process risk management ongoing iterative process must repeated indefinitely business environment constantly changing new threats vulnerabilities emerge every day choice countermeasures controls used manage risks must strike balance productivity cost effectiveness countermeasure value informational asset protected onlyinclude certified information systems auditor review manual 2006 produced isaca international professional association focused governance provides following definition risk management risk management process identifying vulnerabilities threats information resources used organization achieving business objectives deciding countermeasures take reducing risk acceptable level based value information resource organization /onlyinclude risk management process allows managers balance operational economic costs protective measures achieve gains mission capability protecting systems data support organizations ’ missions process unique environment indeed pervades decision-making areas daily lives head organizational unit must ensure organization capabilities needed accomplish mission mission owners must determine security capabilities systems must provide desired level mission support face real world threats organizations tight budgets security therefore security spending must reviewed thoroughly management decisions well-structured risk management methodology used effectively help management identify appropriate controls providing mission-essential security capabilities risk management world quite complex multi faced activity lot relations complex activities picture right shows relationships different related terms american national information assurance training education center defines risk management field organizations many others comprehensive enterprise risk management erm place four objective categories addressed according committee sponsoring organizations treadway commission coso according risk framework isaca risk transversal four categories risk managed framework enterprise risk management risk appetite risk sensitivity whole enterprise guide risk management process erm provide context business objectives risk management whilst methodology describe specific methods nevertheless specify several processes constitute generic framework need followed processes may broken sub-processes may combined sequence may change risk management exercise must carry processes one form another following table compares processes foreseen three leading standards isaca risk framework recent risk practitioner-guide compares risk iso 27005 term methodology means organized set principles rules drive action particular field knowledge overall comparison illustrated following table due probabilistic nature need cost benefit analysis risks managed following process according nist sp 800-30 divided following steps effective risk management must totally integrated systems development life cycle information risk analysis conducted applications computer installations networks systems development undertaken using structured methodologies step first step iso iso/iec 27005 framework elementary activities foreseen first sub process risk assessment according nist sp 800-30 step implies acquisition relevant information organization determination basic criteria purpose scope boundaries risk management activities organization charge risk management activities purpose usually compliance legal requirements provide evidence due diligence supporting isms certified scope incident reporting plan business continuity plan another area application certification product criteria include risk evaluation risk acceptance impact evaluation criteria conditioned establishing scope boundaries organization studied mission values structure strategy locations cultural environment constraints budgetary cultural political technical organization collected documented guide next steps set organization charge risk management foreseen partially fulfilling requirement provide resources needed establish implement operate monitor review maintain improve isms main roles inside organization risk management recurrent activity deals analysis planning implementation control monitoring implemented measurements enforced security policy contrary risk assessment executed discrete time points e.g year demand etc – performance next assessment provides temporary view assessed risks parameterizing entire risk management process view relationship risk management risk assessment depicted figure adopted octave risk assessment often conducted one iteration first high-level assessment identify high risks iterations detailed analysis major risks risks according national information assurance training education center risk assessment field risk assessment receives input output previous step context establishment output list assessed risks prioritized according risk evaluation criteria process divided following steps following table compares iso 27005 processes risk framework processes iso/iec 27002:2005 code practice information security management recommends following examined risk assessment risk identification states could cause potential loss following identified output sub process made two methods risk assessment information security field quantitative qualitative purely quantitative risk assessment mathematical calculation based security metrics asset system application risk scenario taking consideration different risk factors single loss expectancy sle determined considering probability occurrence given period basis example annual rate occurrence aro annualized loss expectancy determined product aro x sle important point values assets considered involved assets value directly affected resource example consider risk scenario laptop theft threat consider value data related asset contained computer reputation liability company assets deriving lost availability confidentiality data could involved easy understand intangible assets data reputation liability worth much physical resources risk laptop hardware example intangible asset value huge easy evaluate consideration pure quantitative approach qualitative risk assessment three five steps evaluation high low performed organization requires risk assessment performed relatively short time meet small budget significant quantity relevant data available persons performing assessment n't sophisticated mathematical financial risk assessment expertise required qualitative risk assessment performed shorter period time less data qualitative risk assessments typically performed interviews sample personnel relevant groups within organization charged security asset assessed qualitative risk assessments descriptive versus measurable usually qualitative classification done followed quantitative evaluation highest risks compared costs security measures risk estimation input output risk analysis split following steps output list risks value levels assigned documented risk register risks arising security threats adversary attacks may particularly difficult estimate difficulty made worse least system connected internet adversary intent capability may attack physical closeness access necessary initial models proposed problem risk estimation generally three values given asset one loss one cia properties confidentiality integrity availability risk evaluation process receives input output risk analysis process compares risk level risk acceptance criteria prioritise risk list risk treatment indications determine likelihood future adverse event threats system must conjunction potential vulnerabilities controls place system impact refers magnitude harm could caused threat ’ exercise vulnerability level impact governed potential mission impacts produces relative value assets resources affected e.g. criticality sensitivity system components data risk assessment methodology encompasses nine primary steps risk mitigation second process according sp 800-30 third according iso 27005 risk management involves prioritizing evaluating implementing appropriate risk-reducing controls recommended risk assessment process elimination risk usually impractical close impossible responsibility senior management functional business managers use least-cost approach implement appropriate controls decrease mission risk acceptable level minimal adverse impact organization ’ resources mission risk treatment process aim selecting security measures risk produce risk treatment plan output process residual risks subject acceptance management list select appropriate security measures single organization choose appropriate one according business strategy constraints environment circumstances choice rational documented importance accepting risk costly reduce high led fact risk acceptance considered separate process risk transfer apply risk high impact easy reduce significantly likelihood means security controls insurance premium compared mitigation costs eventually evaluating mixed strategy partially treat risk another option outsource risk somebody efficient manage risk risk avoidance describe action ways conducting business changed avoid risk occurrence example choice storing sensitive information customers avoidance risk customer data stolen residual risks i.e risk remaining risk treatment decision taken estimated ensure sufficient protection achieved residual risk unacceptable risk treatment process iterated risk mitigation systematic methodology used senior management reduce mission risk risk mitigation achieved following risk mitigation options address greatest risks strive sufficient risk mitigation lowest cost minimal impact mission capabilities suggestion contained risk communication horizontal process interacts bidirectionally processes risk management purpose establish common understanding aspect risk among organization stakeholder establishing common understanding important since influences decisions taken risk reduction overview method specifically designed process presents comprehensible overview coherence risks measures residual risks achieve common understanding risk management ongoing never ending process within process implemented security measures regularly monitored reviewed ensure work planned changes environment rendered ineffective business requirements vulnerabilities threats change time regular audits scheduled conducted independent party i.e somebody control responsible implementations daily management isms security controls validated technical controls possible complex systems tested verified hardest part validate people knowledge procedural controls effectiveness real application daily business security procedures vulnerability assessment internal external penetration test instruments verifying status security controls information technology security audit organizational procedural control aim evaluating security systems organization evolving quite rapidly risk management cope changes change authorization risk evaluation affected systems processes periodically review risks mitigation actions monitoring system events according security monitoring strategy incident response plan security validation metrics fundamental activities assure optimal level security obtained important monitor new vulnerabilities apply procedural technical security controls like regularly updating software evaluate kinds controls deal zero-day attacks attitude involved people benchmark best practice follow seminars professional associations sector factors assure state art organization risk management practice effective risk management must totally integrated sdlc system ’ sdlc five phases initiation development acquisition implementation operation maintenance disposal risk management methodology regardless sdlc phase assessment conducted risk management iterative process performed major phase sdlc nist sp 800-64 devoted topic early integration security sdlc enables agencies maximize return investment security programs guide focuses information security components sdlc first descriptions key security roles responsibilities needed information system developments provided second sufficient information sdlc provided allow person unfamiliar sdlc process understand relationship information security sdlc document integrates security steps linear sequential a.k.a waterfall sdlc five-step sdlc cited document example one method development intended mandate methodology lastly sp 800-64 provides insight projects initiatives clearly defined sdlc-based developments service-oriented architectures cross-organization projects facility developments security incorporated information systems acquisition development maintenance implementing effective security practices following areas information systems security begins incorporating security requirements process new application system enhancement security designed system beginning security requirements presented vendor requirements phase product purchase formal testing done determine whether product meets required security specifications prior purchasing product correct processing applications essential order prevent errors mitigate loss unauthorized modification misuse information effective coding techniques include validating input output data protecting message integrity using encryption checking processing errors creating activity logs applied properly cryptographic controls provide effective mechanisms protecting confidentiality authenticity integrity information institution develop policies use encryption including proper key management disk encryption one way protect data rest data transit protected alteration unauthorized viewing using ssl certificates issued certificate authority implemented public key infrastructure system files used applications must protected order ensure integrity stability application using source code repositories version control extensive testing production back-off plans appropriate access program code effective measures used protect application files security development support processes essential part comprehensive quality assurance production control process would usually involve training continuous oversight experienced staff applications need monitored patched technical vulnerabilities procedures applying patches include evaluating patches determine appropriateness whether successfully removed case negative impact risk management scientific methodology criticized shallow major risk management programmes large organizations mandated us federal information security management act criticized avoiding complexity accompanies formal probabilistic model risks uncertainty risk management looks like process attempts guess rather formally predict future basis statistical evidence highly subjective assessing value assets likelihood threats occurrence significance impact however better way deal subject emerged quite hard list methods least partially support risk management process efforts direction done enisa report classified different methods regarding completeness free availability tool support result factor analysis information risk fair main document introduction factor analysis information risk fair risk management insight llc november 2006 outline methods lack rigorous definition risk factors fair another methodology deal risk management complements existing methodologies fair good acceptance mainly open group isaca isaca developed methodology called risk address various kind related risks chiefly security related risks integrated cobit general framework manage risk broader concept risk methodologies encompasses negative impact operations service delivery bring destruction reduction value organization also benefit\value enabling risk associated missing opportunities use technology enable enhance business project management aspects like overspending late delivery adverse business impact build security initiative homeland security department united states cites fair initiative build security collaborative effort provides practices tools guidelines rules principles resources software developers architects security practitioners use build security software every phase development chiefly address secure coding 2016 threat sketch launched abbreviated cyber security risk assessment specifically small organizations methodology uses real options forecast prioritize fixed list high-level threats number standards risk risk management description see main article
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Computer security
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mount computing mounting process operating system makes files directories storage device available users access via computer file system general process mounting comprises operating system acquiring access storage medium recognizing reading processing file system structure metadata registering virtual file system vfs component location vfs newly-mounted medium registered called mount point mounting process completed user access files directories medium opposite process mounting called unmounting operating system cuts user access files directories mount point writes remaining queue user data storage device refreshes file system metadata relinquishes access device making storage device safe removal normally computer shutting every mounted storage undergo unmounting process ensure queued data got written preserve integrity file system structure media mount point location partition used root filesystem many different types storage exist including magnetic magneto-optical optical semiconductor solid-state drives magnetic media still common available hard disk drives less frequently floppy disks used storage means information read written must organized knowledge must available operating system organization called filesystem different filesystem provides host operating system metadata knows read write data medium media filesystem volume filesystem raid arrays mounted metadata read operating system use storage unix-like operating systems often include software tools assist mounting process provide new functionality strategies coined auto-mounting reflection purpose many situations file systems root need available soon operating system booted unix-like systems therefore provide facility mounting file systems boot time system administrators define file systems configuration file fstab vfstab solaris also indicates options mount points situations need mount certain file systems boot time although use may desired thereafter utilities unix-like systems allow mounting predefined file systems upon demand removable media become common microcomputer platforms allow programs data transferred machines without physical connection common examples include usb flash drives memory cards cd-roms dvds utilities therefore developed detect presence availability medium mount medium without user intervention unix-like systems also introduced concept called supermounting implemented linux supermount-ng project example floppy disk supermounted physically removed system normal circumstances disk synchronized unmounted removal provided synchronization occurred different disk inserted drive system automatically notices disk changed updates mount point contents reflect new medium similar functionality found windows machines automounter automatically mount file system reference made directory atop mounted usually used file systems network servers rather relying events insertion media would appropriate removable media
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Computer file systems
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logjam computer security logjam security vulnerability diffie–hellman key exchange ranging 512-bit us export-grade 1024-bit keys discovered group computer scientists publicly reported may 20 2015 diffie–hellman key exchange depends security presumed difficulty solving discrete logarithm problem authors took advantage fact number field sieve algorithm generally effective method finding discrete logarithms consists four large computational steps first three depend order group g specific number whose finite log desired results first three steps precomputed saved used solve discrete log problem prime group relatively short time vulnerability known early 1992 turns much internet traffic uses one handful groups order 1024 bits less one approach enabled vulnerability authors demonstrated using man-in-the-middle network attacker downgrade transport layer security tls connection use 512-bit dh export-grade cryptography allowing read exchanged data inject data connection affects https smtps imaps protocols among others authors needed several thousand cpu cores week precompute data single 512-bit prime done however individual logarithms could solved minute using two 18-core intel xeon cpus cve id cve-2015-4000 authors also estimated feasibility attack 1024-bit diffie–hellman primes design many diffie–hellman implementations use pregenerated prime field considered secure since discrete log problem still considered hard big-enough primes even group known reused researchers calculated cost creating logjam precomputation one 1024-bit prime hundreds millions usd noted well within range fy2012 10.5 billion u.s. consolidated cryptologic program includes nsa reuse primes generating precomputation one prime would break two-thirds vpns quarter ssh servers globally researchers noted attack fits claims leaked nsa papers nsa able break much current cryptography recommend using primes 2048 bits defense switching elliptic-curve diffie–hellman ecdh claims pratical implications attack however disputed security researchers eyal ronen adi shamir paper critical review imperfect forward secrecy
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Computer security
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windows driver frameworks windows driver frameworks wdf formerly windows driver foundation set microsoft tools libraries aid creation device drivers windows 2000 later versions windows complements windows driver model abstracting away much boilerplate complexity writing windows drivers wdf consists kernel-mode driver framework kmdf user-mode driver framework umdf individual frameworks provide new object-oriented programming model windows driver development primary goals wdf conceptual scalability reduced duplication enabling developers apply concepts across different driver types reducing code overhead required drivers differs markedly windows driver model wdm requires driver developers fully familiar many complex technical details write basic driver part key achieving conceptual scalability kmdf umdf use opt-in model model allows developer extend override default behavior canonical good driver contrast windows driver model depends driver writer implement aspects driver behavior three types wdf drivers wdf also includes set static verification tools use driver writers tools examine driver code common errors and/or simulate code driver order identify problems difficult detect difficult test bold yes means introduced version windows
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Operating systems
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data transformation services data transformation services dts set objects utilities allow automation extract transform load operations database objects dts packages components utilities called dts tools dts included earlier versions microsoft sql server almost always used sql server databases although could used independently databases dts allows data transformed loaded heterogeneous sources using ole db odbc text-only files supported database dts also allow automation data import transformation scheduled basis perform additional functions ftping files executing external programs addition dts provides alternative method version control backup packages used conjunction version control system microsoft visual sourcesafe sql server versions 6.5 earlier database administrators dbas used sql server transfer manager bulk copy program included sql server transfer data tools significant shortcomings many dbas used third-party tools pervasive data integrator transfer data flexibly easily release sql server 7 1998 data transformation services packaged replace tools sql server 2000 expanded dts functionality several ways introduced new types tasks including ability ftp files move databases database components add messages microsoft message queue dts packages saved visual basic file sql server 2000 expanded save com-compliant language microsoft also integrated packages windows 2000 security made dts tools user-friendly tasks accept input output parameters dts comes editions sql server 7 2000 superseded sql server integration services microsoft sql server 2005 release 2005 dts package fundamental logical component dts every dts object child component package packages used whenever one modifies data using dts metadata data transformation contained within package packages saved directly sql server saved microsoft repository com files sql server 2000 also allows programmer save packages visual basic language file stored vb file package actually scripted—that vb script executed dynamically create package objects component objects package contain number connection objects contain allow package read data ole db-compliant data source expanded handle sorts data functionality package organized tasks steps dts task discrete set functionalities executed single step dts package task defines work item performed part data movement data transformation process job executed data transformation services supplies number tasks part dts object model accessed graphically dts designer accessed programmatically tasks configured individually cover wide variety data copying data transformation notification situations example following types tasks represent actions perform using dts executing single sql statement sending email transferring file ftp step within dts package describes order tasks run precedence constraints describe case damage failure steps executed sequentially parallel packages also contain global variables used throughout package sql server 2000 allows input output parameters tasks greatly expanding usefulness global variables dts packages edited password protected scheduled execution retrieved version dts tools packaged sql server include dts wizards dts designer dts programming interfaces dts wizards used perform simple common dts tasks include import/export wizard copy database wizard provide simplest method copying data ole db data sources great deal functionality available merely using wizard however package created wizard saved later altered one dts tools create publishing wizard also available schedule packages run certain times works sql server agent running otherwise package scheduled executed dts designer graphical tool used build complex dts packages workflows event-driven logic dts designer also used edit customize dts packages created dts wizard connection task dts designer shown specific icon icons joined precedence constraints specify order requirements tasks run one task may run instance another task succeeds fails tasks may run concurrently dts designer criticized unusual quirks limitations inability visually copy paste multiple tasks one time many shortcomings overcome sql server integration services dts successor graphical tool used build queries dts dts packages run command line using dtsrun utility utility invoked using following syntax passing parameters mapped global variables required include typeid rather difficult find microsoft site typeids used passing values
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Databases
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file replication service file replication service frs microsoft windows server service distributing shared files group policy objects replaced windows nt lan manager replication service partially replaced distributed file system replication also known ntfrs name executable file runs service one main uses frs sysvol directory share sysvol directory share particularly important microsoft network used distribute files supporting group policy scripts client computers network since group policies scripts run time user logs system important reliability multiple copies sysvol directory increases resilience spreads workload essential service sysvol directory accessed using network share server copy sysvol directory normally domain controller shown accessing using domain name servers work together provide service called replication partners control file replication windows server 2003 r2 windows server 2008 dfs replication available well file replication service dfs replication state-based replication engine file replication among dfs shares supports replication scheduling bandwidth throttling uses remote differential compression detect replicate change files rather replicating entire files changed windows vista also includes dfs replication service limited peer-to-peer dfs replication service groups frs still used sysvol replication optionally dfs replication may used instead frs replication sysvol shares frs stopped up-level windows server 2008 domain controllers sysvol replication performed using dfs replication default although ntfrs replication also supported windows server 2008/r2 up-level domain controllers sysvol replication performed using dfs replication ntfrs replication disabled altogether
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Computer file systems
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freebsd documentation license freebsd documentation license license covers documentation freebsd operating system license similar 2-clause simplified bsd license used rest freebsd however makes meanings source code compile less ambiguous context documentation also includes mandatory disclaimer ieee open group text manual pages free software foundation classes free documentation license stating permissive non-copyleft free documentation license compatible gnu fdl based freebsd documentation license bsd documentation license created contain terms generic projects well reintroducing 3rd clause restricts use documentation endorsement purposes shown new bsd license
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Operating systems
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polymorphism computer science programming languages type theory polymorphism provision single interface entities different types use single symbol represent multiple different types commonly recognised major classes polymorphism interest polymorphic type systems developed significantly 1960s practical implementations beginning appear end decade ad hoc polymorphism parametric polymorphism originally described christopher strachey fundamental concepts programming languages listed two main classes polymorphism ad hoc polymorphism feature algol 68 parametric polymorphism core feature ml type system 1985 paper peter wegner luca cardelli introduced term inclusion polymorphism model subtypes inheritance citing simula first programming language implement christopher strachey chose term ad hoc polymorphism refer polymorphic functions applied arguments different types behave differently depending type argument applied also known function overloading operator overloading term ad hoc context intended pejorative refers simply fact type polymorphism fundamental feature type system pascal delphi example codice_1 functions seem work generically various types looking invocations considered two entirely distinct functions compiler intents purposes dynamically typed languages situation complex correct function needs invoked might determinable run time implicit type conversion also defined form polymorphism referred coercion polymorphism parametric polymorphism allows function data type written generically handle values uniformly without depending type parametric polymorphism way make language expressive still maintaining full static type-safety concept parametric polymorphism applies data types functions function evaluate applied values different types known polymorphic function data type appear generalized type e.g list elements arbitrary type designated polymorphic data type like generalized type specializations made parametric polymorphism ubiquitous functional programming often simply referred polymorphism following example haskell shows parameterized list data type two parametrically polymorphic functions parametric polymorphism also available several object-oriented languages instance templates c++ name generics c java john c. reynolds later jean-yves girard formally developed notion polymorphism extension lambda calculus called polymorphic lambda calculus system f parametrically polymorphic function necessarily restricted working shape data instead value leading concept parametricity languages employ idea subtyping also called subtype polymorphism inclusion polymorphism restrict range types used particular case polymorphism languages subtyping allows function written take object certain type also work correctly passed object belongs type subtype according liskov substitution principle type relation sometimes written conversely said supertype —written subtype polymorphism usually resolved dynamically see following example make cats dogs subtypes animals procedure codice_2 accepts animal also work correctly subtype passed another example number rational integer types number rational number integer function written take number work equally well passed integer rational passed number actual type object hidden clients black box accessed via object identity fact number type abstract may even possible get hands object whose most-derived type number see abstract data type abstract class particular kind type hierarchy known—especially context scheme programming language—as numerical tower usually contains many types object-oriented programming languages offer subtype polymorphism using subclassing also known inheritance typical implementations class contains called virtual table —a table functions implement polymorphic part class interface—and object contains pointer vtable class consulted whenever polymorphic method called mechanism example goes popular object systems however common lisp object system provide multiple dispatch method calls polymorphic arguments interaction parametric polymorphism subtyping leads concepts variance bounded quantification row polymorphism similar distinct concept subtyping deals structural types allows usage values whose types certain properties without losing remaining type information related concept polytypism data type genericity polytypic function general polymorphic function though one provide fixed ad hoc cases specific data types ad hoc combinator absent polymorphism distinguished implementation selected statically compile time dynamically run time typically via virtual function known respectively static dispatch dynamic dispatch corresponding forms polymorphism accordingly called static polymorphism dynamic polymorphism static polymorphism executes faster dynamic dispatch overhead requires additional compiler support static polymorphism allows greater static analysis compilers notably optimization source code analysis tools human readers programmers dynamic polymorphism flexible slower—for example dynamic polymorphism allows duck typing dynamically linked library may operate objects without knowing full type static polymorphism typically occurs ad hoc polymorphism parametric polymorphism whereas dynamic polymorphism usual subtype polymorphism however possible achieve static polymorphism subtyping sophisticated use template metaprogramming namely curiously recurring template pattern
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Programming language topics
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super hydlide super hydlide action role-playing game sega genesis/mega drive originally released 1987 japan title msx msx2 nec pc-88 ports also released nintendo famicom sharp x68000 game developed hydlide series veterans e soft released worldwide sega genesis mega drive october 6 1989 japan early 1990 united states 1991 europe remake evidences substantial graphical upgrades original hydlide 3 though gameplay remains largely identical release called hollo fighter sega advertising material one first third party published titles released u.s air diver many years events hydlide ii explosion flames appeared near city woods enemies everywhere young man chosen find source evil game incorporates 'good/evil character morality/alignment system like predecessor 1985 player morality meter aligned either justice normal evil game good evil monsters evil monsters attack player character sight good monsters attack player character attacks first killing monster good evil results reward experience points money occasionally piece equipment however player kills good monster points lost statistic called mf moral fiber player mf stat drops zero frequent traps appear across world player manages keep 100 rewards appear form random items found around fairyland unlike hydlide ii however morality meter longer affects way townsfolk react player game also features in-game clock setting day-night cycles character must eat two times day sleep regularly characters stay late fail eat regularly hp attack power gradually drop every item game including money weight total weight items player character carries exceeds load capacity lc move slowly game uses cut scenes opening ending sequences combat system similar ys choice four distinct character classes wide variety equipment spells citing varied experiences offered different playable characters morality system inclusion four save slots gamepro concluded altogether super hydlide lively cart draws epic adventure computer video games scored 81 stating like phantasy star ii huge role-playing game tough game requiring much brain-work criticized graphics sound said job gameplay fairly engrossing concluded arcade fans find lack action rather dull like games steady pace tons puzzles love 2007 alex lucard diehard gamefan listed super hydlide number 27 list top 30 rpgs cited realism instilled gameplay mechanics encumbrance system banks 24-hour clock need eat sleep described game morrowind morrowind production scalebound platinumgames director hideki kamiya said inspired hydlide 3 pc-8801 well sorcerian said hydlide 3 one first games played pc inspirational really hardcore game design one consoles time
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Computer architecture
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stankdawg david blake born 1971 also known stankdawg founder hacking group digital dawgpound ddp long-time member hacking community known regular presenter multiple hacking conferences best known creator binary revolution initiative including founding host producer binary revolution radio long-running weekly internet radio show ran 200 episodes 2003 2007 blake born newport news virginia september 13 1971 received aas associates applied sciences degree university kentucky 1992 bs computer science florida atlantic university well ceh certificate presently lives works computer programmer/analyst orlando florida blake member international high iq society stankdawg staff writer well-known hacker periodical well now-defunct blacklisted 411 magazine also contributing writer several independent zines outbreak frequency radical future frequent co-host default radio regular radio freek america appeared gameradio infonomicon mindwar phreak phactor hpr hacker public radio presented technology conferences def con h.o.p.e. interz0ne outspoken many topics many gotten negative feedback different sources controversial article entitled hacking google adwords defcon13 drew criticism people jason calacanis among others presentation fifth h.o.p.e conference drew surprise as/400 community stankdawg appeared subject television show extreme animal planet demonstrated vulnerabilities wireless internet connections blake chose handle stankdawg college started local hacking group became known digital dawgpound digital dawgpound commonly referred ddp group hackers best known series articles hacker magazines make long-running webcast binary revolution radio active set forums posts high-profile hackers strom carlson decoder phiber optik many stated mission ddp propagate positive image hackers negative mass media stereotype group welcomes new members want learn hacking attempts teach positive aspects steer away negative aspects reinforcing hacker ethic goal show hackers regularly make positive contributions technology society whole ddp founded named stankdawg stated reasons made many friends hacking scene thought would useful everyone begin working together organized fashion motivated fact well-known hacker groups 1980s accomplished great things hacking world lod mod 1988 junior high school stankdawg came name way sweet 16 computer programming competition jokingly referred teammates digital dawgpound stankdawg lurked shadows hacking world many years throughout college many different pseudonyms 1997 popped head public began becoming active irc many smaller hacking forums saw people thought insanely brilliant individuals seemed mindset positive attitude towards hacking decided approach couple see anyone would interested forming group working together always huge emphasis technical competence variety also strength character integrity team mix hackers programmers phone phreakers security professionals artists experience multiple programming languages operating systems ddp members good programmers hackers importantly good people 1999 ddp first official members partnership creativity flowed ddp communicated worked together stankdawg personal site open anyone wanted join fun stankdawg never comfortable fact name domain many people coming site coming articles presentations really appreciating great contributions community members around 2002 watching web site grow quickly decided new community needed created like-minded hackers gathering start biggest ddp project called binary revolution attempt starting true community hackers site grew ddp roster years ddp membership included several staff writers blacklisted 411 magazine including stankdawg bland_inquisitor frequently publish articles provide content appear many media sources across global interweb ddp members also regular speakers hacking conferences def con h.o.p.e. interzone notacon many smaller regional cons ddp members hold memberships mensa international high iq society stankdawg proud diversity team spoken many times binary revolution radio members coasts united states europe even members jamaica brazil many countries ddp maintains blog refer blawg obviously play intentionally misspelled word dawg posts ddp members featured technology-related sites make magazine hackaday hacked gadgets others 2003 stankdawg moved forums personal site new site part project called binary revolution considered movement towards positive hacking community binary revolution best known ddp projects commonly referred simply binrev project created attempt bring hacking community back together working towards common positive goal reclaiming name hackers binary revolution emphasizes positive aspects hacking projects help society variety outlets including monthly meetings weekly radio show binary revolution radio brr video-based series shows called hacktv active message board forums binrev radio show forums although certainly well-known projects actually composed many parts binary revolution radio often shortened brr one part binrev community started hosted blake 2003 featured different co-hosts week covered different aspects hacker culture computer security broadcast via internet stream usually prerecorded florida weekend edited released following tuesday ddp hack radio stream 9:30pm est topics included phreaking identity theft cryptography operating systems programming languages free open source software wi-fi bluetooth social engineering cyberculture information various hacker conventions phreaknic shmoocon h.o.p.e. def con july 2005 blake announced going take break third season show produced black ratchet strom carlson frequent co-hosts blake run time hosted program format rotated standard prerecorded format live format included phone calls listeners blake returned show may 2006 maintained prerecorded format brought community input show bringing members binary revolution community first episode fourth season brr first ever broadcast front live audience hope 6 convention new york city june 2006 final episode 200 took place october 30 2007 marathon episode clocked 7 hours 12 minutes forums grew many posts people looking others area hacker meetings exist approachable reason places meetings sparse information binary revolution meetings started answer problems place forum members get together binrev meetings offer free web hosting meetings help organize meetings keep communications alive help projects grow meetings large cities like chicago orlando others small towns anyone start binrev meeting asking binrev forums brnet official irc network binary revolution active hours day contains general binrev channel also contains many channels specific productive discussion middle 2003 released internet video show entitled hacktv first internet television show hacking grown series several different shows released irregularly since episodes filmed stankdawg south florida lived time wanted show appear professional terms quality made cooperating internet difficult sharing large video files difficult encoded video caused editing problems quality concerns original show released full-length 30 minute episodes also problem since difficult get enough material full-length episodes also content related hacking fringe level stankdawg feel appropriate include show led ideas light difficulties putting together full hacktv original show attempt make show accessible community contributions stankdawg launched new series less focused format video quality focused content ease participation series titled hacktv underground htv u short series allowed anyone contribute content format length video quality allowed people film things basic cameraphone quality video way get content one episode hacktv u used g4techtv show called torrent series hacktv prank style show similar popular punk 'd show mtv time even logo obvious parody punk 'd logo series contains pranks mostly took place conferences also open social engineering light-hearted content docdroppers project community project create centralized place store hacking articles information still maintaining formatting readability old ascii text files existed scattered across internet come go quickly difficult find usually formatted basics sometimes difficult read docdroppers allows users submit articles centralized place searchable easily maintained easy read reference recently project grown include encyclopedia style entries many hacking topics many deleted sites wikipedia caused docdroppers include section hacker history culture among content projects stankdawg directly involved creating/maintaining addition ones mentioned links mentioned referred entry
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Computer security
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palo alto networks palo alto networks inc. nyse panw american multinational cybersecurity company headquarters santa clara california core products platform includes advanced firewalls cloud-based offerings extend firewalls cover aspects security company serves 60,000 organizations 150 countries including 85 fortune 100 home unit 42 threat research team hosts ignite cybersecurity conference company mission statement protect way life digital age preventing successful cyberattacks palo alto networks listed 8th forbes digital 100 june 2018 former google softbank executive nikesh arora joined company chairman ceo palo alto networks founded 2005 israeli-american nir zuk former engineer check point netscreen technologies principal developer first stateful inspection firewall first intrusion prevention system asked started palo alto networks zuk cited objective solving problem enterprises facing existing network security solutions inability safely enable employees use modern applications entailed developing firewall could identify provide fine-grained control applications 2007 company produced shipped first product advanced enterprise firewall branded world first next-generation firewall 2009 gartner released publication defining next-generation firewall contrast traditional firewalls time relied simple rules port numbers protocol block traffic authors stated next-generation firewalls operate inspect layers network stack intelligent enough block threats independently port numbers protocols used particular publication defined next-generation firewall containing addition full capabilities traditional firewalls intrusion prevention systems support in-line deployment without disrupting network operations application awareness full stack visibility allowing fine-grained detection control applications extra-firewall intelligence upgrade paths starting 2011 gartner began listing palo alto networks leader enterprise firewall magic quadrant company debuted nyse july 20 2012 raising 260 million initial public offering 4th-largest tech ipo 2012 2014 palo alto networks founded cyber threat alliance fortinet mcafee symantec not-for-profit organization goal improving cybersecurity greater good encouraging collaboration cybersecurity organizations sharing cyber threat intelligence amongst members 2018 organization 20 members including cisco check point juniper networks sophos company expanded significantly years offering wide selection enterprise cybersecurity services beyond original next-generation firewall offering traps endpoint protection wildfire malware prevention 2017 palo alto networks announced logging service cloud-based service allowing customers amass data machine learning data analytics 2018 company began opening dedicated cybersecurity training facilities around world part global cyber range initiative may 2018 company announced application framework open cloud-delivered ecosystem developers publish security services saas applications instantly delivered company network customers 2018 several leaders high-profile tech companies moved palo alto networks june 2018 former google chief business officer softbank president nikesh arora joined company chairman ceo predecessor mark mclaughlin became vice chairman board directors arora received pay package worth 128 million making one highest paid executives united states september 2018 liane hornsey formerly chief people officer uber joined palo alto networks chief people officer october 2018 amit singh formerly president google cloud succeeded mark anderson president palo alto networks 2019 company announced k2-series 5g-ready next-generation firewall developed service providers 5g iot requirements mind february 2019 company announced cortex ai-based continuous security platform ceo nikesh arora described cortex application framework 2.0 references application framework replaced cortex palo alto networks website palo alto networks offers enterprise cybersecurity platform provides network security cloud security endpoint protection various cloud-delivered security services components security platform listed palo alto networks website include unit 42 palo alto networks threat intelligence team group cybersecurity researchers industry experts use data collected company security platform discover new cyber threats new forms malware malicious actors operating across world group runs popular blog post technical reports analyzing active threats adversaries multiple unit 42 researchers named msrc top 100 microsoft annual ranking top 100 security researchers according fbi palo alto networks unit 42 helped solve multiple cybercrime cases mirai botnet clickfraud botnet cases luminositylink rat case assisted “ operation wire-wire 2018 unit 42 discovered gorgon hacking group believed operating pakistan targeting government organizations united kingdom spain russia united states group detected sending spear-phishing emails attached infected microsoft word documents using exploit commonly used cybercriminals cyber-espionage campaigns september 2018 unit 42 discovered xbash ransomware also performs cryptomining believed tied chinese threat actor iron xbash able propagate like worm deletes databases stored victim hosts october unit 42 warned new cryptomining malware xmrig comes bundled infected adobe flash updates malware uses victim computer resources mine monero cryptocurrency november 2018 palo alto networks announced discovery cannon trojan used target united states european government entities hackers behind malware believed fancy bear russian hacking group believed responsible hacking democratic national committee 2016 malware communicates command control server email uses encryption evade detection
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Computer security
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click analytics click analytics special type web analytics gives special attention clicks point-and-click constitute first stage conversion funnel commonly click analytics focuses on-site analytics editor web site uses click analytics determine performance particular site regards users site clicking also click analytics may happen real-time unreal -time depending type information sought typically frontpage editors high-traffic news media sites want monitor pages real-time optimize content editors designers types stakeholders may analyze clicks wider time frame aid assess performance writers design elements advertisements etc data clicks may gathered least two ways ideally click logged occurs method requires functionality picks relevant information event occurs alternatively one may institute assumption page view result click therefore log simulated click lead page view
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Web technology
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ad hoc configuration protocol ad hoc configuration protocol ahcp autoconfiguration protocol ipv6 dual-stack ipv6/ipv4 networks designed used place router discovery dhcp networks difficult impossible configure server within every link-layer broadcast domain example mobile ad-hoc networks ahcp automatically configure ipv4 ipv6 addresses name servers ntp servers configure default routes since designed run together routing protocol babel olsr external links
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Internet protocols
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mcst-r2000 mcst r2000 64-bit microprocessor developed moscow center sparc technologies mcst fabricated tsmc
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Computer architecture
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retrospect software retrospect family software applications back computers running macos microsoft windows linux 2019 classic mac os operating systems uses client–server backup model means must backup server application running one computer small-footprint client applications running computers backed either single platform mixed platform network destination may tape drive hard disk drive cloud drive company backup server application requires macos windows versions client application run linux or—until 2019—classic mac os product used gui-scripted backup mixed-platform networks primarily small medium-sized businesses software first developed dantz development corporation 1989 initially macintosh platform later windows sales split evenly two variants macintosh variant claiming 90 market dantz development corporation acquired emc corporation 2004 2006 version 7.5 refined first release windows variant emc added performance features needed smes 2009 emc indicated intention add updated user interface separate administration console similar newly released macintosh variant version 8.0 mandatory windows security settings starting windows vista/server 2008 subsequently forbade ui interaction application auto-launched task meanwhile macintosh variant languished emc—with temporary end-of-lifing development revived 2008 emc hired back former engineers —including ex-dantz ones resulted premature release version 8.0 retrospect macintosh temporarily missing key operational features even though added performance features retrospect windows 7.5 may 2010 software sold roxio/sonic solutions 2011 following purchase sonic solutions rovi development software turned privately held company since 2012 retrospect inc. continued sell two variants backup server software nearly identical non-gui code operate differently retrospect windows substitutes view-only dashboard upgraded 2019 web-based management console—with optional deployment shared scripts retrospect macintosh separate administration console basically keeps pre-2009 terminology gui june 2019 holding company storcentric—which also owns drobo—announced acquired retrospect inc. operate independent subsidiary integrating version software drobo hardware retrospect also supports several enterprise client-server backup features include retrospect sold varying backup server capability levels called editions non-expiring license–code prices cover one major version edition dictated number server os computers backed turn specifies maximum number client computers desktop edition used desktop mobile computers linux servers backed non-multithreaded older major versions non-tape devices one non-autoloader tape drive solo edition protects single non-server computer external hard drives add-ons activate additional backup server features via edition-linked license codes may also purchased
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Computer security
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jsr 250 jsr 250 java specification request objective develop annotations information software program part program common semantic concepts java se java ee platforms apply across variety individual technologies envisioned various jsrs would use annotations enable declarative style programming would especially valuable consistency within java ee component jsrs also valuable allow consistency java ee java se jsr 250 java specification request objective define set annotations address common semantic concepts therefore used many java ee java se components avoid redundant annotations across components jsr 250 released 11 may 2006 declarative annotation-driven configuration used java frameworks applications e.g spring makes components framework configurable via annotations importance jsr 250 likely increase future jsr 250 depends jsr 175 therefore also java se 5.0 non-java ee jsr 250 annotations added java se version 6 generated postconstruct predestroy resource resources located package
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Programming language topics
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virut virut cybercrime malware botnet operating least since 2006 one major botnets malware distributors internet january 2013 operations disrupted polish organization naukowa akademicka sieć komputerowa virut malware botnet known used cybercrime activities ddos attacks spam collaboration waledac botnet fraud data theft pay-per-install activities spreads executable file infection infected usb sticks media recently compromised html files thus infecting vulnerable browsers visiting compromised websites infected computers associated least 890,000 ip addresses poland 2012 symantec estimated botnet control 300,000 computers worldwide primarily egypt pakistan southeast asia including india kaspersky report listed virut fifth-most widespread threat third quarter 2012 responsible 5.5 computer infections virut botnet active since least 2006 17 january 2013 polish research development organization data networks operator operator polish .pl top-level domain registry naukowa akademicka sieć komputerowa nask took twenty three domains used virut attempt shut nask spokesperson stated first time nask engaged operation taking domains owing major threat virut botnet posed internet likely virut shut completely control servers located russian .ru top-level domain name registrars outside reach polish nask botnet able look alternate backup hosts enabling criminals operating reestablish control network
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Computer security
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code signing code signing process digitally signing executables scripts confirm software author guarantee code altered corrupted since signed process employs use cryptographic hash validate authenticity integrity code signing provide several valuable features common use code signing provide security deploying programming languages also used help prevent namespace conflicts almost every code signing implementation provide sort digital signature mechanism verify identity author build system checksum verify object modified also used provide versioning information object store meta data object efficacy code signing authentication mechanism software depends security underpinning signing keys public key infrastructure pki technologies integrity system relies publishers securing private keys unauthorized access keys stored software general-purpose computers susceptible compromise therefore secure best practice store keys secure tamper-proof cryptographic hardware devices known hardware security modules hsms many code signing implementations provide way sign code using system involving pair keys one public one private similar process employed tls ssh example case .net developer uses private key sign libraries executables time build key unique developer group sometimes per application object developer either generate key obtain one trusted certificate authority ca code signing particularly valuable distributed environments source given piece code may immediately evident example java applets activex controls active web browser scripting code another important usage safely provide updates patches existing software windows mac os x linux distributions provide updates using code signing ensure possible others maliciously distribute code via patch system allows receiving operating system verify update legitimate even update delivered third parties physical media disks code signing used windows mac os x authenticate software first run ensuring software maliciously tampered third-party distributor download site form code signing used linux platform decentralized nature package manager predominant mode distribution forms software updates patches well open-source model allowing direct inspection source code desired debian-based linux distributions among others validate downloaded packages using public key cryptography public key used authenticate code signature traceable back trusted root authority ca preferably using secure public key infrastructure pki ensure code trusted comes stated source explicitly particular private key ca provides root trust level able assign trust others proxy user trusts ca user presumably trust legitimacy code signed key generated ca one proxies many operating systems frameworks contain built-in trust one existing cas entrust datacard verisign/symantec digicert comodo godaddy globalsign also commonplace large organizations implement private ca internal organization provides features public cas trusted within organization model developers choose provide self-generated key scenario user would normally obtain public key fashion directly developer verify object first time many code signing systems store public key inside signature software frameworks oss check code signature executing allow choose trust developer point first run application developer provide similar system including public keys installer key used ensure subsequent objects need run upgrades plugins another application verified coming developer time-stamping designed circumvent trust warning appear case expired certificate effect time-stamping extends code trust beyond validity period certificate event certificate revoked due compromise specific date time compromising event become part revocation record case time-stamping helps establish whether code signed certificate compromised developers need sign ios tvos apps running real device uploading app store needed prove developer owns valid apple developer id application needs valid profile certificate run devices like security measure code signing defeated users tricked running unsigned code even running code refuses validate system remains secure long private key remains private also important note code signing protect end user malicious activity unintentional software bugs software author — merely ensures software modified anyone author sometimes sandbox systems accept certificates false time-stamp excess usage ram ibm lotus notes pki signing code release 1 client server software execution control lists control levels access data environment file system permitted given users individual design elements including active items scripts actions agents always signed using editor id file includes editor domain public keys core templates mail template signed dedicated id held lotus template development team microsoft implements form code signing based authenticode provided microsoft tested drivers since drivers run kernel destabilize system open system security holes reason microsoft tests drivers submitted whql program driver passed microsoft signs version driver safe 32-bit systems installing drivers validated microsoft possible accepting allow installation prompt warning user code unsigned .net managed code additional mechanism called strong name signing uses public/private keys sha-1 hash opposed certificates however microsoft discourages reliance strong name signing replacement authenticode context consumer devices games consoles unsigned code often used refer application signed cryptographic key normally required software accepted executed console games signed secret key designed console maker game load console several methods get unsigned code execute include software exploits use modchip technique known swap trick running softmod may initially seem obvious simply copying signed application onto another dvd allow boot xbox reason xbox executable file xbe contains media-type flag specifies type media xbe bootable nearly xbox software set executable boot factory produced discs simply copying executable burnable media enough stop execution software however since executable signed simply changing value flag possible alters signature executable causing fail validation checked proliferation connected devices required ability identify authenticate devices ability applies area internet things iot iot requires devices trusted iot code signing software release process ensures integrity iot device software firmware updates defends risks associated tampering device code embedded device credentialing enables control manufacturing process high technology products protects unauthorized production counterfeits together code signing technology ensures physical authenticity authenticity integrity code possess time manufacture use digital birth certificate subsequent upgrades code validation time product lifecycle creating new dimension code signing elevating security awareness need maintain private signing keys secured within dedicated protected environment establish root trust entire system given prevalence malware advanced persistent threats apts many software vendors providers online services enterprise organizations manufacturers high-technology iot devices pressure increase security high technology manufacturing code signing process
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Computer security
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brooks law brooks law observation software project management according adding human resources late software project makes later coined fred brooks 1975 book mythical man-month according brooks incremental person added project makes take less time similar general law diminishing returns economics according brooks law outrageous oversimplification captures general rule brooks points main factors explain works way key points brooks law allow exceptions open door possible solutions first point note brooks law applies projects already late projects brought back kept control people added earlier process also important determine project really late schedule originally overly optimistic scheduling mistakes account large number late projects correcting schedule best way meaningful reliable time frame project completion quantity quality role people added project also must taken consideration one simple way circumvent law overrun project add people needed way extra capacity compensates training communication overhead good programmers specialists added less overhead training people added tasks related project example quality assurance documentation given task clear ramp time minimized modern practices continuous integration test-driven development iterative development significantly reduce inter-developer communication overhead thus allow better scalability new tools software development documentation also help minimize ramp time making simpler new programmers get involved work design patterns simplify distribution work entire team part within framework provided pattern design pattern defines rules programmers follow simplifies communication use standard language provides consistency scalability finally good segmentation helps minimizing communication overhead team members smaller sub-problems solved smaller team top-level team responsible systems integration method work segmentation problem must done correctly first place done incorrectly make problem worse better impeding communication programmers working parts problem actually closely coupled even project plan decreed way finish project invert brooks law bermuda plan 90 developers removed send bermuda remaining 10 complete software
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Computer architecture
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iraqi legal database iraqi legal database ild first comprehensive electronic legal database created arab region project create ild launched 2004 united nations development programme undp programme governance arab region pogar implemented coordination higher judicial council objective behind project make entire corpus iraqi law available judges lawyers academics lawmakers individuals institutions rely legal knowledge single freely accessible source keeping objective ild published online september 2008 makes available users 27,433 legal texts altogether including 7,136 laws 4,265 ministerial instructions 3,268 regulations 5,029 declarations etc. say every single iraqi legal text passed since 1917 ild entirely free-of-charge require users subscribe way iraq country office united nations development programme source funding ild ild available arabic iraqi law translated language systematic manner therefore legal researchers jurists interested iraqi law must carry research arabic non-arabic speaking researchers interested learning ild ’ features may download following powerpoint presentation illustrates translates english ild ’ various functions project originally designed implemented three phases
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Databases
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max operating system max linux distribution sponsored office education autonomous community madrid spain max stands madrid linux used based ubuntu last release max 10 based ubuntu 16.04 lts xenial xerus since 2003 max installed computers schools community madrid max educational linux large set instructive programs addition usual desktop programs max supports common desktop environments max 10 mate installed default main features simplicity stability huge collection software max comes live dvd installable system usb version changelog http //ftp.rediris.es/mirror/max-linux/maxdesktop/max7.5/cambios.txt educamadrid web site
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Operating systems
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open mobile terminal platform open mobile terminal platform omtp forum created mobile network operators discuss standards manufacturers mobile phones mobile devices lifetime omtp included manufacturers huawei lg electronics motorola nokia samsung sony ericsson omtp originally set leading mobile operators time transitioned wholesale applications community end june 2010 nine full members deutsche telekom ag kt orange smart communications telecom italia telefónica telenor vodafone omtp also support two sponsors ericsson nokia omtp recommendations hugely helped standardise mobile operator terminal requirements work gone towards helping defragment deoptionalise operators recommendations omtp ’ focus gathering driving mobile terminal requirements publishing findings recommendations omtp technology neutral recommendations intended deployment across range technology platforms operating systems os middleware layers omtp perhaps best known work field mobile security work encompassed full range mobile device capabilities omtp published recommendations 2007 early 2008 areas positioning enablers advanced device management ims mobile voip later advanced trusted environment omtp tr1 supporting document 'security threats embedded consumer devices released endorsement uk home secretary jacqui smith omtp also published requirements document addressing support advanced sim cards document defines also advanced profiles smart card web server high speed protocol mobile tv contactless omtp also made significant progress getting support use micro-usb standard connector data power full list recommendations found http //www.gsma.com/newsroom/technical-documents/omtp-documents/ 2008 omtp launched new initiative called bondi named australian beach initiative defined new interfaces javascript apis security framework based xacml policy description enable access mobile phone functionalities application invocation application settings camera communications log gallery location messaging persistent data personal information phone status user interaction browser widget engine secure way bondi initiative also open source reference implementation https //web.archive.org/web/20130509121758/https //web.archive.org/web/20130509121758/http //bondi.omtp.org// approved release 1.0 bondi issued june 2009 open source project comprehensive bondi sdk started http //bondisdk.org february 2009 omtp expanded local connectivity specification based micro-usb describe requirements common charger common connector enable sharing battery charger different phones omtp common charging local data connectivity adopted gsm association universal charging system ucs initiative endorsed ctia itu june 2009 european commission reached agreement several major mobile phone providers requirements common external power supply eps compatible new data-enabled phones sold european union eps shares key attributes ucs charger june 2010 omtp transitioned new wholesale applications community omtp activities ceased time either taken within wac organisation standards industry associations turn july 2012 wac closed omtp standards transferred gsma assets personnel transferring apigee
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Computer security
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mutator method computer science mutator method method used control changes variable also widely known setter methods often setter accompanied getter also known accessor returns value private member variable mutator method often used object-oriented programming keeping principle encapsulation according principle member variables class made private hide protect code modified public member function mutator method takes desired new value parameter optionally validates modifies private member variable mutator methods compared assignment operator overloading typically appear different levels object hierarchy mutator methods may also used non-object-oriented environments case reference variable modified passed mutator along new value scenario compiler restrict code bypassing mutator method changing variable directly onus falls developers ensure variable modified mutator method modified directly programming languages support properties offer convenient alternative without giving utility encapsulation examples fully implemented mutator method also validate input data take action triggering event alternative defining mutator accessor methods property blocks give instance variable visibility private access directly outside objects much finer control access rights defined using mutators accessors example parameter may made read-only simply defining accessor mutator visibility two methods may different often useful accessor public mutator remains protected package-private internal block mutator defined provides opportunity validation preprocessing incoming data external access guaranteed come mutator steps bypassed example date represented separate private codice_1 codice_2 codice_3 variables incoming dates split codice_4 mutator consistency private instance variables accessed codice_5 codice_6 cases month values outside 1 12 rejected code accessors conversely allow synthesis useful data representations internal variables keeping structure encapsulated hidden outside modules monetary codice_7 accessor may build string numeric variable number decimal places defined hidden codice_8 parameter modern programming languages often offer ability generate boilerplate mutators accessors single line—as example c codice_9 ruby codice_10 cases code blocks created validation preprocessing synthesis simplified accessors still retain advantage encapsulation simple public instance variables common system designs progress software maintained requirements change demands data become sophisticated many automatic mutators accessors eventually get replaced separate blocks code benefit automatically creating early days implementation public interface class remains identical whether greater sophistication added requiring extensive refactoring manipulation parameters mutators accessors inside class defined often requires additional thought early days implementation little additional code blocks makes difference private instance variable accessed directly validation cross-validation data integrity checks preprocessing sophistication added subtle bugs may appear internal access makes use newer code places bypassed accessor functions less efficient directly fetching storing data fields due extra steps involved however functions often inlined eliminates overhead function call file student.h file student.c file main.c file makefile file student.h file student.cpp example illustrates c idea properties special type class member unlike java explicit methods defined public 'property contains logic handle actions note use built-in undeclared variable codice_11 later c versions .net framework 3.5 example may abbreviated follows without declaring private variable codice_12 using abbreviated syntax means underlying variable longer available inside class result codice_13 portion property must present assignment access restricted codice_13-specific access modifier common lisp object system slot specifications within class definitions may specify codice_15 codice_16 codice_17 options even multiple times define reader methods setter methods accessor methods reader method respective codice_18 method slots always directly accessible names use codice_19 codice_20 slot accessor options define specialized methods use codice_20 clos notion properties although metaobject protocol extension specifies means access slot reader writer function names including ones generated codice_17 option following example shows definition student class using slot options direct slot access defmethod student-age self student defmethod setf student-age new-age self student defmethod set-student-number new-number self student supports getter setter function syntax version 2 language getter setter class/struct methods codice_23 attribute codice_24 instance used like simple class delphi language illustrates concept public property access private field example simple class representing student name stored one see variable name private i.e visible student class setter getter public namely codice_25 codice_26 methods example constructor-function codice_24 used create objects representing student name stored non-standard use prototypes inheritance ecma-6 without using prototypes ecma-6 using defineproperty using traditional objective-c 1.0 syntax manual reference counting one working gnustep ubuntu 12.04 using newer objective-c 2.0 syntax used mac os x 10.6 ios 4 xcode 3.2 generating code described starting os x 10.8 ios 6 using xcode 4.4 syntax even simplified using class :accessor using moose object system example simple class representing student name stored one see variable name private i.e visible student class setter getter public namely codice_25 codice_29 methods example uses python class one variable getter setter racket object system way organize code comes addition modules units rest language object system first-class values lexical scope used control access objects methods struct definitions alternative way define new types values mutators present explicitly required ruby individual accessor mutator methods may defined metaprogramming constructs codice_30 codice_31 may used declare private variable class provide either read-only read-write public access respectively defining individual accessor mutator methods creates space pre-processing validation data read-only simple public access implied codice_32 variable read-write simple public access implied codice_32 variable example illustrates vb.net idea properties used classes similar c explicit use codice_34 codice_35 methods vb.net 2010 auto implemented properties utilized create property without use get set syntax note hidden variable created compiler called codice_36 correspond property codice_12 using another variable within class named codice_36 would result error privileged access underlying variable available within class
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Programming language topics
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google drawings google drawings free web-based diagramming software developed google allows users collaborate work together real time create flowcharts organisational charts website wireframes mind maps concept maps types diagrams google drawings also available chrome app works offline available chrome web store google drawings hosted within google drive files created application default saved google drive originally introduced april 12 2010 google docs drawings tool making drawings google docs google drawings allows multiple users open edit drawings simultaneously real time contains subset features google slides different templates users insert images local hard drive web well shapes arrows scribbles text google drawings set flow-chart symbols shapes dragged dropped place users move resize rotate objects use polylines line connectors also allows editing images including cropping applying masks adding borders features include laying drawings precisely alignment guides snapping grid auto-distribution drawings inserted google documents spreadsheets presentations also published online images downloaded standard formats jpeg svg png pdf
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Distributed computing architecture
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statistical time-division multiplexing statistical multiplexing type communication link sharing similar dynamic bandwidth allocation dba statistical multiplexing communication channel divided arbitrary number variable bitrate digital channels data streams link sharing adapted instantaneous traffic demands data streams transferred channel alternative creating fixed sharing link general time division multiplexing tdm frequency division multiplexing fdm performed correctly statistical multiplexing provide link utilization improvement called statistical multiplexing gain statistical multiplexing facilitated packet mode packet-oriented communication among others utilized packet switched computer networks stream divided packets normally delivered asynchronously first-come first-served fashion alternative fashion packets may delivered according scheduling discipline fair queuing differentiated and/or guaranteed quality service statistical multiplexing analog channel example wireless channel also facilitated following schemes statistical multiplexing normally implies on-demand service rather one preallocates resources data stream statistical multiplexing schemes control user data transmissions time domain statistical multiplexing packet mode communication similar time-division multiplexing tdm except rather assigning data stream recurrent time slot every tdm data stream assigned time slots fixed length data frames variable lengths often appear scheduled randomized order experience varying delay delay fixed tdm statistical multiplexing allows bandwidth divided arbitrarily among variable number channels number channels channel data rate fixed tdm statistical multiplexing ensures slots wasted whereas tdm waste slots transmission capacity link shared users packets static tdm circuit switching carried physical layer osi model tcp/ip model statistical multiplexing carried data link layer statistical multiplexing packet frame contains channel/data stream identification number case datagram communication complete destination address information examples statistical multiplexing digital audio video broadcasting example statistical multiplexer content aggregating device allows broadcasters provide greatest number audio video services given bandwidth sharing pool fixed bandwidth among multiple services streams varying bitrates multiplexer allocates service bandwidth required real-time needs services complex scenes receive bandwidth services less complex ones bandwidth sharing technique produces best video quality lowest possible aggregate bandwidth examples statistical multiplexers include rgb networks bnpxr product line harmonic inc. prostream electra vos product families motorola terayon dm6400 tmir
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Internet protocols
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google education google education service google provides independently customizable versions several google products using domain name provided customer features several web applications similar functionality traditional office suites including gmail hangouts google calendar drive docs sheets slides groups news play sites vault products also tie use chromebooks added g suite domain educational establishment google apps education google apps non-profits accredited 501 c 3 non-profit entities free offer amount storage google apps work accounts addition shared apps calendar docs etc google provides google apps marketplace app store google apps users contains various apps free paid installed customize google education experience user
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Distributed computing architecture
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ibm rsct ibm reliable scalable cluster technology rsct set software components together provide comprehensive clustering environment aix linux solaris windows operating systems rsct infrastructure used variety ibm products provide clusters improved system availability scalability ease use follows list main rsct components management domains peer domains set nodes configured manageability monitoring called management domain cluster set nodes configured high availability called rsct peer domain cluster peer domain set nodes consistent knowledge existence resources shared among node within peer domain rmc depends core set cluster services include topology services group services cluster security services management domain set nodes resources managed monitored one nodes designated management control point mcp nodes considered managed nodes topology services group services used management domain order understand various rsct components used cluster aware nodes cluster configured manageability high availability
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Operating systems
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asset computer security information security computer security network security asset data device component environment supports information-related activities assets generally include hardware e.g servers switches software e.g mission critical applications support systems confidential information assets protected illicit access use disclosure alteration destruction and/or theft resulting loss organization goal information security ensure confidentiality integrity availability assets various threats example hacker might attack system order steal credit card numbers exploiting vulnerability information security experts must assess likely impact attack employ appropriate countermeasures case might put firewall encrypt credit card numbers performing risk analysis important weigh much spend protecting asset cost losing asset also important take account chance loss occurring intangible costs must also factored hacker makes copy company credit card numbers cost anything directly loss fines reputation enormous
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Computer security
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bitcask bitcask erlang application provides api storing retrieving key/value data log-structured hash table design owes lot principles found log-structured file systems draws inspiration number designs involve log file merging bitcask number advantages owing write-once append-only on-disk data-format use in-memory hash-table keys lookups bitcask keeps keys memory times system must enough memory contain entire keyspace addition operational components operating system file-system buffers
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Databases
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ibm system/38 system/38 minicomputer midrange computer server platform manufactured sold ibm corporation system offered number innovative features brainchild frank soltis glenn henry ibm announced system/38 1978 developed code-name pacific made commercially available august 1979 system/38 oriented toward multi-user system environment typical system handled dozen several dozen terminals midrange predecessors system/38 included system/3 system/32 system/34 system/38 offered capacity previous system/34 system/38 chronologically preceded system/36 successor system/34 system/38 nearly called system/380 as/400 nearly called system/40 system/38 superseded as/400 also supported system/36 data programs fairly large extent exceptions as/400 primarily re-marketing system/38 updates operating system including luxurious non-trivial expansion source object names 8 new 10 characters maximum s/38 programs 'observability intact source code embedded within compiled binary executive expense larger compiled object sizes still run as/400 successor systems restore option incorporates recompile back-version source however proprietary vendor application libraries objects compiled without 'observability required original vendor replacement consequent expense upgrading as/400 pricing time tiered exact software priced based upon model speed capacity system installed upon as/400 evolved iseries turn evolved system although 'evolution include significant enhancements hardware operating system capabilities name change usually considered evolution marketing system/38 legacy lives enterprise-class ibm power systems series superseded system 2008 run ibm well aix linux contrast competing proprietary computing architectures early 1980s wang vs hewlett packard hp 3000 long discontinued without compatible upgrade path ibm 5381 system unit contained processor main memory disk storage diskette magazine drive system console keyboard display 5381 available model 100 model 200 ibm 5382 system unit physically identical 5381 powerful processors memory disk storage 5382 available models 300 400 500 600 700 hindsight system/38 architecture probably demanding hardware era first launched struggled overhead software operating system consumed almost 60 mb disk vast sum time leading wags suggest pre-announce code name series pacific actually acronym meaning performance ai n't critical function complete system included central processing unit 512k 768k 1024k 1280k 1536k bytes main storage included memory management unit supporting demand paging used system software implement single-level store architecture system/38 console included keyboard display screen 16 lines 64 characters inconsistent locally attached 5250 terminals either 12x40 24x80 depending model keyboard used system operator entering control language commands diskette magazine drive standard models operating system system/38 called cpf control program facility cpf related ssp operating system ibm system/34 system/36 cpf objects files programs message queues user profiles libraries system/38 also distinction first commercially available ibm midrange computer database management system dbms integrated operating system operational control language system/38 called cl control language cl programs similar concept shell scripts could compiled executed natively system/38 48-bit addressing unique time novel integrated database system system/38 also security built part architecture object library could access controlled user-by-user basis continued expanded throughout as/400 iseries computer lines system/38 descendants commercial computers ever use machine interface architecture isolate application software operating system hardware dependencies including details address size register size compilers system/38 successors generate code high-level instruction set originally called mi machine interface renamed timi technology independent machine interface as/400 mi/timi virtual instruction set instruction set underlying cpu unlike virtual-machine architectures virtual instructions interpreted runtime see p-code machine mi/timi instructions never interpreted constitute intermediate compile time step translated processor instruction set final compilation step mi/timi instructions stored within final program object addition executable machine instructions program moved processor one native instruction set processor another native instruction set mi/timi instructions re-translated native instruction set new machine program executed first time new machine result possible program originally developed system/38 run current ibm hardware without ever recompiled capability allowed as/400 migrate cisc complex instruction set computer risc reduced instruction set computer 1990s mi/timi instructions existed compiled program relatively simple re-translation created new program native new hardware 1986 system/38 announced support distributed data management architecture ddm middleware context distributed system software layer lies operating system applications distributed data management architecture defines environment sharing data enabled system/38 programs create manage access record-oriented files remote system/36 system/38 ibm mainframe systems running cics also allowed programs remote system/36 system/38 computers create manage access files system/38 languages supported system/38 included rpg iii cobol basic pl/i decades later software originally dismissed critics momentary aberration runs better ever many thousands modern iseries ibm/i systems within commercial government enterprises types sizes ibm sold estimated 20,000 system/38s within first five years availability according articles published industry magazines news 34/38 midrange computing although billed minicomputer s/38 much expensive ibm established best-selling system/34 replacement system/36 equal importance difficulty upgrading say system/34 s/38 although machines similarities twinax peripherals rpg programming languages reality different ibm tacitly acknowledged bringing system/36 – upgraded system/34 – launch s/38 marketplace ibm thus found three overlapping incompatible ranges system/34/36 system/38 mainframe /360 architecture system/38 originally designed replace digital equipment corporation time one ibm main competitors able exploit offering wide range products based single architecture ibm counter 9370 'baby mainframe commercial failure
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Computer architecture
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nebula company nebula inc. hardware software company offices mountain view california seattle washington usa nebula developed nebula one cloud computing hardware appliance turned racks standard servers private cloud nebula one private cloud system built openstack open source cloud framework well many open source software projects nebula founded “ fourth paradigm development march 2011 former nasa ames research center chief technology officer chris c. kemp long-time colleague devin carlen entrepreneur steve o'hara software engineer tres henry formerly amazon web services author aws console named head user experience may 2011 nebula closed round series investment led kleiner perkins caufield byers highland capital partners participation google first three investors—andy bechtolsheim ram shriram david cheriton well investors summer 2012 eight members original anso labs acquired rackspace nasa team originally wrote components openstack project joined nebula fall 2012 nebula closed 25 million series b investment led comcast ventures highland capital google executive eric schmidt ’ venture fund innovation endeavors became investor february 2013 silicon india named kemp one ten pioneers cloud computing march 2013 nebula named one cio.com 10 hot cloud companies watch nebula one made generally available april 2 2013 april 1 2015 company announced website confirmed twitter ceasing operations
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Distributed computing architecture
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fastback fastback software application developed late 1980s early 1990s backing ibm pc macintosh computers originally written fifth generation systems inc company located baton rouge louisiana company wanted expand apple market purchased rebranded product touchstone software corporation original fastback unique industry able read computer hard drive write floppy drive simultaneously using full capability dual-channel dma chip found personal computers time combined compression techniques proprietary disk format got data floppy disk made fastback one fastest pc backup programs time 1984 fastback version 5.13 already market 1987 fastback plus 1.0 dos released version subsequent dos versions released unconditional guarantee harm resulting use software terms conditions guarantee contrasted industry norms 1991 fastback plus 3.02 dos released february 1992 company released fastback plus 1.0 windows written pcs running windows 3.0 fastback plus 2.0 included novell dos 7 1994 fastback ii bundled drive 2.4 provide read/write compatibility macintosh 3.5 floppy disk formats new york times wrote standard dos msbackup utility automatically awaken 3 a.m. make full backup onto quarter-inch cassette drive byte 1989 listed fastback plus among distinction winners byte awards stating hard drive recommend package
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Computer security
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tombstone diagram computing tombstone diagrams t-diagrams consist set “ puzzle pieces ” representing compilers related language processing programs used illustrate reason transformations source language left target language right realised implementation language bottom commonly found describing complicated processes bootstrapping porting self-compiling compilers interpreters macro-processors t-diagrams first introduced describing bootstrapping cross-compiling compilers mckeeman et al 1971 melvin conway described broader concept uncol 1958 bratman added 1961 later others including p.d terry gave explanation usage t-diagrams textbooks topic compiler construction t-diagrams also used describe client-server interconnectivity world wide web teaching tool tdiag implemented leipzig university germany
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Programming language topics
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common base event common base event cbe ibm implementation web services distributed management wsdm event format standard ibm also implemented common event infrastructure unified set apis infrastructure creation transmission persistence distribution wide range business system network common base event formatted events
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Web technology
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hobbyist operating system development hobbyist operating system development one involved technical options computer hobbyist definition hobby operating system sometimes vague developer view developers fun learning also seen users view users using toy defined operating system n't big user base development begin existing resources like kernel operating system bootloader also made completely scratch development platform could bare hardware machine nature operating system developed tested virtual machine since hobbyist must claim ownership adapting complex system ever-changing needs technical terrain much enthusiasm common amongst many different groups attracted operating system development elements operating system development include c programming language frequently used hobby operating system programming well assembly language though languages used well use assembly language common small systems especially based eight bit microprocessors mos technology 6502 family zilog z-80 systems lack available resources small output size low-level efficiency hobby operating systems use command-line interface simple text user interface due ease development advanced hobby operating systems may graphical user interface example atheos hobby operating system graphical interface written entirely one programmer section predominantly x86 oriented term bios basic input/output system refers firmware initialises computer hardware provisions load operating system bios also sets standard interface several low-level device drivers boot time bios resources often used hobbyist operating systems especially written 16-bit x86 machines many hobby operating systems developers lack time write complex low level drivers simply want get writing software system soon possible commonly used bios functions videobios disk services used video cards disk drives vary significantly different machines specialised drivers often difficult write use bios uncommon operating systems operate protected mode long mode system must switch back real mode bios drivers run
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Operating systems
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ryan c. gordon ryan c. gordon also known icculus computer programmer former loki software employee responsible icculus.org hosts many loki software projects well several new projects created others gordon site hosts projects duke nukem 3d shadow warrior quake iii arena many free open source projects multiple platforms gordon also created ports proprietary software products linux mac os x platforms include hired port unreal tournament series serious sam series official postal series tripwire interactive coffee stain studios titles prey 2006 also involved porting several non-gaming products second life google earth candy cruncher postal 2 published linux game publishing also described alongside edward rudd instrumental ensuring multi-platform nature humble indie bundle initiatives gordon grew outside philadelphia going college charlotte north carolina currently resides january 3 2010 became engaged girlfriend carrie married later year january 31 2012 wife gave birth first child olive finch gordon also founding member barebones theatre group charlotte summer 1999 loki software ran contest called loki hack atlanta linux showcase goal improving linux port gordon decided give try driving four-hour trip home atlanta loki impressed work decided offer job gordon quickly rose prominence loki working developer game ports quake iii arena eric ultimate solitaire well lead developer descent 3 2000 also wrote several articles online linux news information website linux.com around time founded icculus.org made provide hosting various free open source projects would later used support continue loki free software projects tools loki software gordon picked nickname icculus reference fictional character gamehendge song icculus phish upcoming closure loki forced seek outside employment friend offered job cybercafe forced move parents desperate escape working cash register living found e-mail address artist working developer croteam recently released highly successful serious sam series gordon asked would interested building linux port agreed port first beta released december 5 2002 gained contracts hired port devastation linux america army linux mac os x also contracted epic games port unreal tournament 2003 title linux mac os x port included packaged windows version business relationship continued release unreal tournament 2004 followed original unreal tournament ported linux internally epic published loki upon learning release postal 2 2003 gordon decided contact developer behind wondering would interested making port game linux mac os x. loki previously ported original postal linux interested keeping franchise compatible running scissors agreed finished port shipped february 14 2005 linux game publishing initially handling publishing linux version soon contracted make linux port wolfire games title business relationship would later prove fruitful gordon around time also contracted build linux client online virtual world second life google also utilized services contracted make native linux port google earth application linux functionality finally becoming available starting release version 4 beta june 12 2006 2007 contracted epic games port new unreal tournament 3 title linux mac os x linux game server released december 18 2007 work eventually abandoned linux mac os x clients reasons remain undisclosed october 2008 made surprise announcement working linux client first-person shooter game prey previously porting game linux server 2006 although speculation potential linux release denied developer title past finished port released december 7 2008 october 23 2009 announced plans make universal binary system similar one used mac os x linux systems called project generated considerable controversy several linux kernel developers decrying effort gordon announced project hold early november 2009 later stating would willing work receives help interested party around time also started port game aquaria linux bit blot may 11 2010 wolfire games released source code code branch lugaru gnu general public license also involved source code release aquaria sold part first humble indie bundle also hosted wolfire contracted port mac os x stating could potentially port linux steam ever released linux client gordon also generated controversy summer talk 2010 southeast linuxfest titled anatomy failure criticized aspects kernel development process ported braid linux mac os x allow part humble indie bundle 2 well porting games cogs hammerfight later bundles part ported haaf game engine linux mac os x released port free software license also ported frozen synapse linux included primary part frozen synapse bundle well super meat boy shank humble indie bundle 4 rest 2012 gordon would work several ports humble bundles including space pirates zombies psychonauts would also involved updating old releases well porting several new titles linux included part valve corporation steam linux launch including creating linux ports games red orchestra ostfront 41-45 killing floor tripwire interactive part humble indie bundle 7 promotion gordon ported title dungeon defenders linux making first linux native title utilize unreal engine 3 engine debuted release unreal tournament 3 back 2007 gordon unsuccessfully tried port platform 2013 ported dear esther linux included part humble indie bundle 8 gordon one speakers first ever steam dev days outlined port game linux steamos 2014 ported games goat simulator sanctum 2 linux mac os x coffee stain studios june 19 2014 released new linux port limbo game previously released linux using crossover wrapper part humble indie bundle v something proved controversial time due fully native release order accomplish gordon also port wwise audio middleware previously prevented native port possible icculus.org gordon personal website project incubator similar sourceforge.net ourproject.org gnu savannah gordon often involved projects hosted site universally site hosts port enhancement projects games aliens versus predator jump n bump donkey.bas duke nukem 3d shadow warrior freespace 2 descent 2 black shades ken labyrinth rise triad wolfenstein 3d heretic cooperative rune quake ii build engine unreal unreal tournament mod chzo mythos site also hosts free software projects neverball ioquake3 related projects attempted visual basic re-implementation openal mac os x yahoo messenger client also host freeware project hosted code developers blazing games piga software wolfire games bit blot following list software gordon involved porting except game server ports addition also contracted provide technical assistance gaslamp games developers dungeons dredmor clockwork empires helped develop solely responsible linux os x ports double fine productions costume quest
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Operating systems
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embeddable linux kernel subset embeddable linux kernel subset elks formerly known linux-8086 unix-like operating system kernel subset linux kernel intended 16-bit computers limited processor memory resources machines powered intel 8086 compatible microprocessors supported 32-bit linux elks free software available gnu general public license gpl work early 16-bit x86 8086 80186 80286 computers like ibm pc compatible systems virtual 8086 mode feature 32-bit intel 80386 later cpus found newer machines another useful area single board microcomputers intended educational tools homebrew projects hardware hacking well embedded controller systems e.g automation elks also runs psion 3a 3ar sibo sixteen bit organiser pdas nec v30 cpus providing another possible field operation gadget hardware ported platform effort called elksibo native elks programs may run emulated elksemu allowing 8086 code used linux-i386 effort provide elks eiffel compliant library also exists development linux-8086 started 1995 linux kernel developers alan cox chad page fork standard linux early 1996 project renamed elks embeddable linux kernel subset 1997 first website www.elks.ecs.soton.ac.uk/ offline created elks version 0.0.63 followed august 8 year june 22 1999 elks release 0.0.77 available first version able run graphical user interface nano-x window system july 21 elks booted psion pda sibo architecture elks 0.0.82 came january 10 2000 including sibo port became first official version running computer hardware original 8086 base march 3 year project registered sourceforge new website elks.sourceforge.net january 6 2001 cox declared elks basically dead nonetheless release 0.0.84 came along june 17 2001 charilaos harry kalogirou added tcp/ip networking support seven days later year elks reached 0.0.90 november 17 april 20 2002 kalogirou added virtual memory support disk swapping capability followed nine days later elks release 0.1.0 considered first beta version end year december 18 ede elks distribution edition distribution based elks kernel version 0.0.5 released january 6 2003 brought elks 0.1.2 update 0.1.3 followed may 3 2006 first official release long hiatus development development flightlinux real-time operating system spacecrafts planned project intended uosat-12 eventually settled qcf operating system quadron corporation instead since january 2012 elks development cvs repository migrated git february 2012 numerous patches linux-8086 mailing list committed new repository version 0.1.4 came february 19 2012 released jody bruchon memory riley williams former co-developer included updated floppy disk images fixing compilation bugs previous version removing unused codes may 10 2012 busyelks added repository jody bruchon attempt replace stand-alone binaries take advantage shared code elks support shared libraries busybox-like binaries attempt save space symbolic links eliminating redundant chunks code combining separate programs one bigger binary november 14 2013 project development moved github ethernet fat support added 2017 30 developers contributed project since fork 1995 march 2015 development elks project active reaching milestone 1,000 source code commits march 8 2015 june 2018 many bug fixes improvements performed 583 commits leading 0.2.1 release march 2019 project completed transition obsolete bcc compiler recent gcc-ia16
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Computer architecture
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vax vax discontinued instruction set architecture isa developed digital equipment corporation dec mid-1970s vax-11/780 introduced october 25 1977 first range popular influential computers implementing architecture 32-bit system complex instruction set computer cisc architecture based dec earlier pdp-11 vax virtual address extension designed extend replace dec various programmed data processor pdp isas vax architecture primary features virtual addressing example demand paged virtual memory orthogonal instruction set vax perceived quintessential cisc isa large number assembly-language-programmer-friendly addressing modes machine instructions highly orthogonal architecture instructions complex operations queue insertion deletion polynomial evaluation historically one studied commented-on isa computer history vax succeeded dec alpha instruction set architecture name vax originated acronym virtual address extension vax seen 32-bit extension older 16-bit pdp-11 prime computer early adopter virtual memory manage larger address space early versions vax processor implement compatibility mode emulates many pdp-11 instructions giving 11 vax-11 highlight compatibility later versions offloaded compatibility mode less used cisc instructions emulation operating system software vax instruction set designed powerful orthogonal introduced many programs written assembly language programmer-friendly instruction set important time programs written higher-level language instruction set became less visible ones much concerned compiler writers one unusual aspect vax instruction set presence register masks start subprogram arbitrary bit patterns specify control passed subprogram registers preserved since register masks form data embedded within executable code make linear parsing machine code difficult complicate optimization techniques applied machine code native vax operating system digital vax/vms renamed openvms 1991 early 1992 ported alpha modified comply posix standards branded compliant xpg4 x/open consortium vax architecture openvms operating system engineered concurrently take maximum advantage initial implementation vaxcluster facility vax operating systems included various releases bsd unix 4.3bsd ultrix-32 vaxeln xinu recently netbsd openbsd supported various vax models work done porting linux vax architecture openbsd discontinued support architecture september 2016 first vax model sold vax-11/780 introduced october 25 1977 digital equipment corporation annual meeting shareholders bill strecker c. gordon bell doctoral student carnegie mellon university responsible architecture many different models different prices performance levels capacities subsequently created vax superminicomputers popular early 1980s vax-11/780 used standard cpu benchmarks initially described one-mips machine performance equivalent ibm system/360 ran one mips system/360 implementations previously de facto performance standards actual number instructions executed 1 second 500,000 led complaints marketing exaggeration result definition vax mips speed vax-11/780 computer performing 27 vax mips would run program roughly 27 times faster vax-11/780 within digital community term vup vax unit performance common term mips compare well across different architectures related term cluster vups informally used describe aggregate performance vaxcluster performance vax-11/780 still serves baseline metric brl-cad benchmark performance analysis suite included brl-cad solid modeling software distribution vax-11/780 included subordinate stand-alone lsi-11 computer performed microcode load booting diagnostic functions parent computer dropped subsequent vax models enterprising vax-11/780 users could therefore run three different digital equipment corporation operating systems vms vax processor hard drives either rsx-11s rt-11 lsi-11 single density single drive floppy disk vax went many different implementations original vax 11/780 implemented ttl filled four-by-five-foot cabinet single cpu cpu implementations consisted multiple ecl gate array macrocell array chips included vax 8600 8800 superminis finally vax 9000 mainframe class machines cpu implementations consisted multiple mosfet custom chips included 8100 8200 class machines vax 11-730 725 low-end machines built using bit-slice components microvax represented major transition within vax family time design yet possible implement full vax architecture single vlsi chip even vlsi chips later done v-11 cpu vax 8200/8300 instead microvax first vax implementation move complex vax instructions packed decimal related opcodes emulation software partitioning substantially reduced amount microcode required referred microvax architecture microvax alu registers implemented single gate-array chip rest machine control conventional logic full vlsi microprocessor implementation microvax architecture arrived microvax ii 78032 dc333 cpu 78132 dc335 fpu 78032 first microprocessor on-board memory management unit microvax ii based single quad-sized processor board carried processor chips ran microvms ultrix-32 operating systems machine featured 1 mb on-board memory q22-bus interface dma transfers microvax ii succeeded many microvax models much improved performance memory vlsi vax processors followed form v-11 cvax cvax soc system chip single-chip cvax rigel mariah nvax implementations vax microprocessors extended architecture inexpensive workstations later also supplanted high-end vax models wide range platforms mainframe workstation using one architecture unique computer industry time sundry graphics etched onto cvax microprocessor die phrase cvax ... care enough steal best etched broken russian play hallmark cards slogan intended message soviet engineers known purloining dec computers military applications reverse engineering chip design dec product offerings vax architecture eventually superseded risc technology 1989 dec introduced range workstations servers ran ultrix decstation decsystem respectively based processors implemented mips architecture 1992 dec introduced risc instruction set architecture alpha axp later renamed alpha alpha-based microprocessor decchip 21064 high performance 64-bit design capable running openvms august 2000 compaq announced remaining vax models would discontinued end year 2005 manufacturing vax computers ceased old systems remain widespread use stromasys charon-vax simh software-based vax emulators remain available vax virtual memory divided four sections one gigabyte context addressing 2 bytes size vms p0 used user process space p1 process stack s0 operating system s1 reserved vax four hardware implemented privilege modes vax supports many addressing modes literal register postincrement predecrement register deferred postincrement deferred predecrement deferred displacement byte word long displacement byte word long deferred also indexed may combined many immediate mode synonymous program counter pc postincrement many addressing modes could use program counter also r15 instead registers provided easy generation position-independent code pc-relative addressing vax also load effective address instructions access memory compute address used first vax-based system vax-11/780 member vax-11 family high-end vax 8600 replaced vax-11/780 october 1984 joined entry-level microvax minicomputers vaxstation workstations mid-1980s microvax superseded vax 4000 vax 8000 superseded vax 6000 late 1980s mainframe-class vax 9000 introduced early 1990s fault-tolerant vaxft introduced alpha compatible vax 7000/10000 variant various vax-based systems sold vaxserver cancelled systems include bvax high-end ecl-based vax two ecl-based vax models argonaut raven raven cancelled 1990 vax known gemini also cancelled fall-back case lsi-based scorpio failed never shipped number vax clones authorized unauthorized produced examples include
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Computer architecture
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criticism windows vista windows vista operating system released microsoft consumers january 30 2007 widely criticized reviewers users due issues new security features performance driver support product activation windows vista subject number negative assessments various groups security reasons 64-bit versions windows vista windows 7 well allow signed drivers installed kernel mode code executing kernel mode enjoys wide privileges system signing requirement aims ensure code known origin execute level order driver signed developer/software vendor obtain authenticode certificate sign driver authenticode certificates obtained certificate authorities trusted microsoft microsoft trusts certificate authority verify applicant identity issuing certificate driver signed using valid certificate driver signed using certificate revoked microsoft certificate authority windows refuse load driver following criticisms/claims made regarding requirement microsoft allows developers temporarily locally disable signing requirement systems control hitting f8 boot signing drivers self-issued certificates running kernel debugger one time third-party tool called atsiv existed would allow driver unsigned signed loaded atsiv worked installing signed surrogate driver could directed load driver thus circumventing driver signing requirement since violation driver signing requirement microsoft closed workaround hotfix kb932596 revoking certificate surrogate driver signed security researchers alexander sotirov mark dowd developed technique bypasses many new memory-protection safeguards windows vista address space layout randomization aslr result already existing buffer overflow bugs vista previously exploitable due features may exploitable vulnerability sotirov notes presented weaknesses protection mechanism still requires system attack vulnerability without presence vulnerability techniques ’ really accomplish anything vulnerability sotirov dowd used paper example 2007 animated cursor bug cve-2007-0038 one security researcher dino dai zovi claimed means completely game vista security though sotirov refuted saying articles describe vista security 'broken 'done 'unfixable vulnerabilities completely inaccurate one suggestions saw many discussions people use windows xp fact xp lot protections ’ bypassing aslr ’ even exist another common criticism concerns integration new form digital rights management drm operating system specifically protected video path pvp involves technologies high-bandwidth digital content protection hdcp image constraint token ict features added vista due licensing restrictions hd-dvd consortium blu-ray association concern resolution playback protected content hd dvd blu-ray discs enabled 2012 lack protected channel stop playback audio plays back normal high-definition video downsamples blu-ray hd dvd slightly-better-than-dvd quality video protected video path mandates encryption must used whenever content marked protected travel link might intercepted called user-accessible bus uab additionally devices come contact premium content graphics cards certified microsoft playback starts devices involved checked using hardware functionality scan hfs verify genuine tampered devices required lower resolution 1920×1080 960×540 video signals outputs protected hdcp additionally microsoft maintains global revocation list devices compromised list distributed pcs internet using normal update mechanisms effect revoked driver functionality high-level protected content play functionality including low-definition playback retained peter gutmann computer security expert university auckland new zealand released whitepaper raises following concerns mechanisms free software foundation conducted campaign called badvista vista grounds ed bott author windows vista inside published three-part blog rebuts many gutmann claims bott criticisms summarized follows technology writer george ou states gutmann paper relies unreliable sources gutmann never used windows vista test theories gutmann responded bott ou article states central thesis gutmann article refuted response bott disinformation microsoft published blog entry twenty questions answers windows vista content protection refutes gutmann arguments microsoft mvp paul smith written response gutmann paper counters arguments specifically says microsoft also noted content protection mechanisms existed windows far back windows around time release microsoft stated nearly pcs market today run windows vista pcs sold 2005 capable running vista hardware worked windows xp work works poorly vista vista-compatible drivers available due companies going business lack interest supporting old hardware tom hardware published benchmarks january 2007 showed windows vista executed typical applications slowly windows xp hardware configuration subset benchmarks used provided standard performance evaluation corporation spec later stated results compared generated running windows xp even testing done hardware configuration spec acknowledges apple-to-apples comparison made cases one done tom hardware calling studies invalid comparisons however tom hardware report conceded specviewperf tests suffered heavily lack support opengl graphics library windows vista reason report recommended replacing windows xp vista manufacturers made drivers available report also concluded tests involving real world applications vista performed considerably slower noting disappointed cpu-intensive applications video transcoding xvid dvd xvid mpeg4 mainconcept h.264 encoder performed 18 nearly 24 slower standard benchmark scenarios commonly used applications including photoshop winrar also performed worse vista many low-to-mid-end machines come windows vista pre-installed suffer exceptionally slow performance default vista settings come pre-loaded laptop manufacturers offered downgrade laptops windows xp—for price however price unnecessary microsoft allows users windows vista windows 7 freely downgrade software installing xp phoning microsoft representative new product key first released november 2006 vista performed file operations copying deletion slowly operating systems large copies required migrating one computer another seemed difficult impossible without workarounds using command line inability efficiently perform basic file operations attracted strong criticism six months microsoft confirmed existence problems releasing special performance reliability update later disseminated windows update included service pack 1 nonetheless one benchmark reported show improving performance compared vista original release service pack 1 increase level performance windows xp however benchmark questioned others within zdnet ed bott questions colleagues methods provides benchmarks refute results early vista lifecycle many games showed drop frame rate compared windows xp results largely consequence vista immature drivers graphics cards higher system requirements vista time service pack 1 released mid-2008 gaming benchmarks showed vista par windows xp however games devil may cry 4 crysis left 4 dead stated memory requirements vista 1.5x 2x higher xp concerns expressed windows vista may contain software bloat speaking 2007 university illinois microsoft distinguished engineer eric traut said lot people think windows large bloated operating system maybe fair characterization admit went say core kernel components make core operating system actually pretty streamlined former pc world editor ed bott expressed skepticism claims bloat noting almost every single operating system microsoft ever sold criticized bloated first came even regarded exact opposite ms-dos two consumers sued microsoft united states federal court alleging windows vista capable marketing campaign bait-and-switch tactic computers windows xp pre-installed could run vista basic sometimes even running user-acceptable speed february 2008 seattle judge granted suit class action status permitting purchasers class participate case released documents case well dell presentation march 2007 discussed late changes windows vista permitted hardware certified would require upgrading order use vista lack compatible drivers forced hardware vendors limp issues vista launched one several vista launch appraisals included 158 pages unsealed documents new features vista criticism surfaced concerning use battery power laptops running vista drain battery much rapidly windows xp reducing battery life windows aero visual effects turned battery life equal better windows xp systems release new operating system new features higher requirements higher power consumption normal richard shim analyst idc noted windows xp came true windows 2000 came true according gartner vista dogged fears cases proven many existing applications re-written operate new system cisco reported saying vista solve lot problems every action reaction unforeseen side-effects mutations networks become brittle according pc world software compatibility issues bug worries keep businesses moving microsoft new os citing concerns cost compatibility united states department transportation prohibited workers upgrading vista university pittsburgh medical center said rollout vista significantly behind schedule several key programs still n't compatible including patient scheduling software july 2007 2,000 tested applications compatible vista microsoft published list legacy applications meet works windows vista software standards well list applications meet stringent certified windows vista standards microsoft released application compatibility toolkit 5.0 application migrating vista-incompatible applications virtualization solutions like virtualbox virtual pc 2007 vmware also used last resort continue running vista-incompatible applications legacy versions windows microsoft also provides upgrade advisor tool .net framework must installed internet connection required used existing xp systems flag driver application compatibility issues upgrading vista microsoft also criticized removing heavily discussed features next-generation secure computing base may 2004 winfs august 2004 windows powershell august 2005 though released separately vista prior vista release included vista successor windows 7 securid support may 2006 pc-to-pc synchronization june 2006 initial three pillars vista radically altered reach release date microsoft international pricing vista criticized many expensive differences pricing one country another vary significantly especially considering copies vista ordered shipped worldwide united states could save 42 €26 314 €200 many cases difference price significantly greater case windows xp malaysia pricing vista around rm799 244/€155 current exchange rate united kingdom consumers could paying almost double united states counterparts software since release windows vista january 2007 microsoft reduced retail upgrade price point vista originally vista ultimate full retail priced 399 upgrade 259 prices since reduced 319 219 respectively vista includes enhanced set anti-copying technologies based windows xp windows genuine advantage called software protection platform spp initial release windows vista without service pack 1 spp included reduced-functionality mode system enters detects user failed product activation copy vista identified counterfeit non-genuine microsoft white paper described technology follows analysts questioned behavior especially given imperfect false-positive record behalf spp predecessor given least one temporary validation server outage reportedly flagged many legitimate copies vista xp non-genuine windows update would check fail validation challenge microsoft altered spp significantly windows vista service pack 1 instead reduced-functionality mode installations vista left unactivated 30 days present users nag screen prompts activate operating system log change desktop solid black colour every hour periodically use notification balloons warn users software counterfeiting addition updates classified optional available unactivated copies vista microsoft maintains technical bulletin providing details product activation vista windows vista ultimate users download exclusive windows ultimate extras extras released much slowly expected four available august 2009 almost three years vista released angered users paid extra mainly promised add-ons barry goffe director windows vista ultimate microsoft states unexpectedly delayed releasing several extras microsoft plans ship collection additional windows ultimate extras confident delight passionate windows vista ultimate customers term coined disparaging substitute proper name vista operating system use term popularized use secret diary steve jobs technology pop culture comedic blog author daniel lyons writes persona apple ceo steve jobs use reference failure vista meet sales customer satisfaction expectations lyons published article forbes using term soon picked international media outlets jornal de notícias rádio e televisão de portugal la nación chosun ilbo 163.com
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Operating systems
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tun/tap computer networking tun tap virtual network kernel interfaces network devices supported entirely software differ ordinary network devices backed hardware network adapters universal tun/tap driver originated 2000 merger corresponding drivers solaris linux bsd driver continues maintained part linux freebsd kernels though similar tunneling purposes one time used tun tap apply different layers network stack tun namely network tunnel simulates network layer device operates carrying ip packets tap namely network tap simulates link layer device operates carrying ethernet frames tun used routing tap used creating network bridge packets sent operating system via tun/tap device delivered user-space program attaches device user-space program may also pass packets tun/tap device case tun/tap device delivers injects packets operating-system network stack thus emulating reception external source platforms tun/tap drivers include
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Operating systems
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footprinting footprinting also known reconnaissance technique used gathering information computer systems entities belong get information hacker might use various tools technologies information useful hacker trying crack whole system used computer security lexicon footprinting generally refers one pre-attack phases tasks performed actual attack tools used footprinting sam spade nslookup traceroute nmap neotrace allows hacker gain information target system information used carry attacks system reason may named pre-attack since information reviewed order get complete successful resolution attack crawling process surfing internet get required information target sites surfed include target ’ website blogs social networks information obtained method helpful methods.crawling whois web application used get information target website administrator e-mail address details registration whois large database contains information approximately websites searched domain name search engines google also used gather information target system depends well one knows use search engines collect information used properly attacker gather lots information company career policies etc information also gathered using command tracert traceroute used trace path user target system networks way becomes clear request forwarded devices linux systems tracepath traceroute commands also available traceroute operations negative web search reveal websites performed target website negative websites act resources insight flaws target website attack performed company following information gathered basics footprinting
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Computer security
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dynix dynix dynamic unix unix-like operating system developed sequent computer systems based 4.2bsd modified run intel-based symmetric multiprocessor hardware third major dynix 3.0 version released may 1987 1992 dynix succeeded dynix/ptx based unix system v. ibm obtained rights dynix/ptx 1999 acquired sequent 810 million ibm subsequent project monterey attempt circa 1999 unify aix sequent dynix/ptx operating system unixware 2001 however explosion popularity linux ... prompted ibm quietly ditch version named dynix 4.1.4
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Operating systems
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american innovation competitiveness act american innovation competitiveness act aica united states federal law enacted 2017 act updated instructions national science foundation national institute standards technology nist conduct support research cybersecurity cryptography created director security nist revised program requirements networking information technology research development program coordinates advanced computer research across u.s. government agencies assigned office management budget responsibility create interagency working group reduce administrative burdens federally-funded researchers act authorizes creation interagency advisory panel working groups consider education science technology engineering mathematics stem fields act supports coordination citizen science crowdsourcing federal agencies accomplish missions
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Computer security
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perl 6 perl 6 also known raku member perl family programming languages historically several interpreter compiler implementations written today rakudo perl 6 implementation active development introducing elements many modern historical languages compatibility perl 5 goal though compatibility mode part specification design process perl 6 began 2000 february 2015 post perl foundation blog stated perl6 team attempt get development release version 1.0 available larry birthday september version 1.0 release christmas 25 december 2015 first stable version specification announced development pugs first high-traction implementation began 2005 multiple perl 6 implementation projects rakudo perl 6 based nqp quite perl use moarvm java virtual machine runtime environment releases new version every month including precompiled gnu/linux packages july 2010 project released first rakudo star distribution collection perl 6 implementation related materials larry wall maintains reference grammar known std.pm6 written perl 6 bootstrapped perl 5 perl 6 design process first announced 19 july 2000 fourth day year perl conference larry wall state onion 2000 talk time primary goals remove historical warts language easy things stay easy hard things get easier impossible things get hard general cleanup internal design apis process began series requests comments rfcs process open contributors left aspect language closed change rfc process complete wall reviewed classified request 361 received began process writing several apocalypses term means revealing original goal write one apocalypse chapter programming perl became obvious apocalypse written previous apocalypses invalidated later changes reason set synopses published one relating contents apocalypse subsequent changes reflected updates today perl 6 specification continues almost entirely within synopses also series exegeses written damian conway explain content apocalypse terms practical usage exegesis consists code examples along discussion usage implications examples three primary methods communication used development perl 6 today first irc channel freenode second set mailing lists perl foundation servers perl.org third git source code repository hosted https //github.com/perl6 break compatibility mandated start project immediately allowed changes larry wall suggested initial speech historical warts confusion surrounding sigil usage containers ambiguity codice_1 functions syntactic impact bareword filehandles many problems perl programmers discussed fixing years first issues addressed years perl 6 undergone several alterations direction introduction concepts python ruby early influences pugs interpreter written haskell programming language many functional programming influences absorbed perl 6 design team language mascot camelia perl 6 bug name nod camel mascot associated perl form pun-loving tradition perl community play software bug spiral designs embedded butterfly-like wings resemble characters p6 favored nickname perl 6 off-center eye placement intentional pun wall-eyed one goals behind lively colorful design logo discourage misogyny community opportunity masculine persuasion show sensitive side rakudo perl 6 implementation active development implementation designated official perl 6 implementation rather perl 6 anything passes official test suite rakudo perl 6 targets number virtual machines moarvm java virtual machine javascript moarvm virtual machine built especially rakudo perl 6 nqp compiler toolchain layer perl 6 virtual machines called quite perl 6 nqp implements perl 6 rules parsing perl 6 well abstract syntax tree backend-specific code generation large portions rakudo written perl 6 subset nqp rakudo completely self-hosting implementation concrete plans point make rakudo bootstrapping compiler pugs initial implementation perl 6 written haskell pugs used advanced implementation perl 6 since mid 2007 mostly dormant updates made track current version ghc november 2014 pugs actively maintained 2007 v6-miniperl6 mp6 reimplementation v6-kindaperl6 kp6 written means bootstrap perl-6.0.0 std using perl 5 std full grammar perl 6 written perl 6 theory anything capable parsing std generating executable code suitable bootstrapping system perl 6. kp6 currently compiled mp6 work multiple backends mp6 kp6 full perl 6 implementations designed implement minimum featureset required bootstrap full perl 6 compiler yapsi perl 6 compiler runtime written perl 6 result requires existing perl 6 interpreter one rakudo star releases order run niecza another major perl 6 implementation effort focused optimization efficient implementation research targets common language infrastructure perl 6 specification requests modules identified name version authority possible load specific version module even two modules name differ version authority convenience aliasing short name provided cpan perl 5 module distribution system yet handle perl 6 modules instead prototype module system use perl 5 perl 6 differ fundamentally though general intent keep perl 6 perl perl 6 clearly perl programming language changes intended normalize language make easier novice expert programmers alike understand make easy things easier hard things possible major non-technical difference perl 5 perl 6 perl 6 began specification means perl 6 re-implemented needed also means programmers n't read source code ultimate authority given feature perl 5 documentation regarded excellent even outside perl community even mixed reviews typically note maturity breadth however documentation considered authoritative describes behavior actual perl 5 interpreter informally discrepancies found documentation implementation may lead either changed reflect dynamic drives continuing development refinement perl 5 releases perl 6 dynamic type system perl 5 augmented addition static types example however static typing remains optional programmers things without explicit typing perl 6 offers gradual typing system whereby programmer may choose use static typing use dynamic typing mix two perl 5 defines subroutines without formal parameter lists though simple parameter counting loose type checking done using perl 5 prototypes subroutine arguments passed aliased elements array elements modified changes reflected original data perl 6 introduces true formal parameters language perl 6 subroutine declaration looks like perl 5 formal parameters i.e. variables parameter list aliases actual parameters values passed default aliases constant modified may declared explicitly read-write aliases original value copies using codice_2 codice_3 directives programmer require modified locally perl 6 provides three basic modes parameter passing positional parameters typical ordered list parameters programming languages use parameters may also passed using name unordered way named-only parameter passed specifying name never captures positional argument indicated leading codice_4 character slurpy parameters indicated codice_5 parameter name perl 6 tool creating variadic functions slurpy hash capture remaining passed-by-name parameters whereas slurpy array capture remaining passed-by-position parameters example use three parameter-passing modes positional parameters used always required unless followed codice_6 indicate optional named parameters optional default may marked required adding codice_7 variable name slurpy parameters always optional parameters also passed arbitrary blocks act closures example codice_8 codice_9 loop iterators named following example list traversed 3 elements time passed loop block variables codice_10 generally referred pointy sub pointy block arrow behaves almost exactly like codice_11 keyword introducing anonymous closure anonymous subroutine perl 5 terminology perl 5 sigils – punctuation characters precede variable name – change depending variable used perl 6 sigils invariant means change based whether array array element needed variance perl 5 inspired number agreement english many natural languages however conceptual mapping breaks references come play since may refer data structures even though scalars thus dealing nested data structures may require expression singular plural form single term complexity equivalent either common use natural language programming languages causes high cognitive load writing code manipulate complex data structures compare perl 6 perl 5 supports object-oriented programming via mechanism known blessing reference blessed object particular class blessed object methods invoked using arrow syntax cause perl locate dispatch appropriate subroutine name call blessed variable first argument extremely powerful makes common case object orientation struct-like object associated code unnecessarily difficult addition perl make assumptions object model use method invocation optimized well spirit making easy things easy hard things possible perl 6 retains blessing model supplies robust object model common cases example class encapsulate cartesian point could defined used way dot replaces arrow nod many languages e.g java python etc coalesced around dot syntax method invocation terminology perl 6 codice_12 called attribute languages call fields members method used access attribute called accessor auto-accessors methods created automatically method codice_13 example accessor functions return value attribute class individual attribute declared codice_2 modifier short read/write auto-accessor passed new value set attribute directly assigned lvalue example auto-accessors replaced user-defined methods programmer desire richer interface attribute attributes accessed directly within class definition access must go accessor methods perl 6 object system inspired moose framework introduces many perl 6 oop features perl 5 roles perl 6 take function interfaces java mixins ruby traits smalltalk variant squeak much like classes provide safer composition mechanism used perform composition used classes rather adding inheritance chain roles define nominal types provide semantic names collections behavior state fundamental difference role class classes instantiable roles essentially role bundle possibly abstract methods attributes added class without using inheritance role even added individual object case perl 6 create anonymous subclass add role subclass change object class anonymous subclass example dog mammal dogs inherit certain characteristics mammals mammary glands mammal parent vertebrate backbone dogs may one several distinct types behavior example dog may pet stray guide blind however simply sets additional behaviors added dog cat equally pet stray example hence dog mammal classes pet stray guide roles roles added class object codice_15 keyword opposed inheritance codice_16 keywords reflect differing meanings two features role composition gives class behavior role n't indicate truly thing role although roles distinct classes types role appear variable declaration one would normally put class example blind role human could include attribute type guide attribute could contain guide dog guide horse guide human even guide machine perl regular expression string-processing support always one defining features since perl pattern-matching constructs exceeded capabilities regular language expressions time perl 6 documentation exclusively refer regexen distancing term formal definition perl 6 provides superset perl 5 features respect regexes folding larger framework called rules provide capabilities context-sensitive parsing formalisms syntactic predicates parsing expression grammars antlr well acting closure respect lexical scope rules introduced codice_17 keyword usage quite similar subroutine definition anonymous rules also introduced codice_18 codice_19 keyword simply used inline regexps perl 5 via codice_20 matching codice_21 substitute operators apocalypse 5 larry wall enumerated 20 problems current regex culture among perl regexes compact 'cute much reliance metacharacters little support named captures little support grammars poor integration 'real language perl 5 constructs changed perl 6 optimized different syntactic cues common cases example parentheses round brackets required control flow constructs perl 5 optional also codice_22 comma operator list constructor enclosing parentheses longer required around lists code makes codice_23 array exactly elements 1 2 3 4 perl 6 allows comparisons chain sequence comparisons following allowed treated left-to-right comparison performed result logically combined via codice_24 operation perl 6 uses technique lazy evaluation lists feature functional programming languages haskell code crash attempting assign list infinite size array codice_25 hang indefinitely attempting expand list limited number slots searched simplifies many common tasks perl 6 including input/output operations list transformations parameter passing related lazy evaluation construction lazy lists using codice_26 codice_27 behaving somewhat like generators languages like icon python codice_28 infinite list square numbers lazy evaluation codice_26 ensures elements computed accessed perl 6 introduces concept junctions values composites values simplest form junctions created combining set values junctive operators codice_30 indicates value equal either left right-hand arguments codice_31 indicates value equal left right-hand arguments values used code would use normal value operations performed junction act members junction equally combine according junctive operator codice_32 would yield codice_33 comparisons junctions return single true false result comparison codice_34 junctions return true comparison true one elements junction codice_35 junctions return true comparison true elements junction junctions also used richly augment type system introducing style generic programming constrained junctions types low-level languages concept macros become synonymous textual substitution source-code due widespread use c preprocessor however high-level languages lisp pre-dated c use macros far powerful lisp-like macro concept perl 6 take advantage power sort macro stems fact operates program high-level data structure rather simple text full capabilities programming language disposal perl 6 macro definition look like subroutine method definition operate unparsed strings ast representing pre-parsed code combination two macro definition would look like particular example macro complex c-style textual substitution parsing macro parameter occurs macro operates calling code diagnostic messages would far informative however body macro executed compile time time used many techniques optimization employed even possible entirely eliminate complex computations resulting programs performing work compile-time perl 5 identifier names use ascii alphanumerics underscores also available languages perl 6 alphanumerics include unicode characters addition hyphens apostrophes used certain restrictions followed digit using hyphens instead underscores separate words name leads style coding called kebab-casing highly regarded two-finger typists hello world program common program used introduce language perl 6 hello world — though one way factorial function perl 6 defined different ways quicksort well-known sorting algorithm working implementation using functional programming paradigm succinctly written perl 6 tower hanoi often used introduce recursive programming computer science implementation uses perl 6 multi-dispatch mechanism parametric constraints history perl 6 two waves book writing first wave followed initial announcement perl 6 2000 books reflect state design language time contain mostly outdated material today second wave followed announcement version 1.0 2015 includes several books already published others process writing also book dedicated one first perl 6 virtual machine parrot published 2009 reports different authors new books going published soon based current version 1.0 known version 6.c perl 6
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Programming language topics
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security information event management field computer security security information event management siem software products services combine security information management sim security event management sem provide real-time analysis security alerts generated applications network hardware vendors sell siem software appliances managed services products also used log security data generate reports compliance purposes term initialism siem coined mark nicolett amrit williams gartner 2005 acronyms sem sim siem sometimes used interchangeably generally refer different primary focus products practice many products area mix functions often overlap – many commercial vendors also promote terminology often times commercial vendors provide different combinations functionalities tend improve siem overall log management alone ’ provide real-time insights network security sem wo n't provide complete data deep threat analysis sem log management combined information available siem monitor key focus monitor help manage user service privileges directory services system-configuration changes well providing log auditing review incident response many meanings definitions capabilities evolving requirements continually shape derivatives siem product-categories need voice-centric visibility vsiem voice security information event management provides recent example evolution computer security researcher chris kubecka identified following siem use cases presented hacking conference 28c3 chaos communication congress examples customized rules alert event conditions involve user authentication rules attacks detected infections detected
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Computer security
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consensus computer science fundamental problem distributed computing multi-agent systems achieve overall system reliability presence number faulty processes often requires processes agree data value needed computation examples applications consensus include whether commit transaction database agreeing identity leader state machine replication atomic broadcasts real world applications include clock synchronization pagerank opinion formation smart power grids state estimation control uavs multiple robots/agents general load balancing blockchain others consensus problem requires agreement among number processes agents single data value processes agents may fail unreliable ways consensus protocols must fault tolerant resilient processes must somehow put forth candidate values communicate one another agree single consensus value consensus problem fundamental problem control multi-agent systems one approach generating consensus processes agents agree majority value context majority requires least one half available votes process given vote however one faulty processes may skew resultant outcome consensus may reached reached incorrectly protocols solve consensus problems designed deal limited numbers faulty processes protocols must satisfy number requirements useful instance trivial protocol could processes output binary value 1 useful thus requirement modified output must somehow depend input output value consensus protocol must input value process another requirement process may decide upon output value decision irrevocable process called correct execution experience failure consensus protocol tolerating halting failures must satisfy following properties variations definition integrity may appropriate according application example weaker type integrity would decision value equal value correct process proposed – necessarily integrity condition also known validity literature protocol correctly guarantee consensus amongst n processes fail said t-resilient evaluating performance consensus protocols two factors interest running time message complexity running time given big notation number rounds message exchange function input parameters typically number processes and/or size input domain message complexity refers amount message traffic generated protocol factors may include memory usage size messages varying models computation may define consensus problem models may deal fully connected graphs others may deal rings trees models message authentication allowed whereas others processes completely anonymous shared memory models processes communicate accessing objects shared memory also important area research models communication protocol participants communicate authenticated channels means messages anonymous receivers know source every message receive models assume stronger form authentication message signed sender receiver knows immediate source every message participant initially created message stronger type authentication achieved digital signatures stronger form authentication present protocols tolerate larger number faults two different authentication models often called oral communication written communication models oral communication model immediate source information known whereas stronger written communication models every step along receiver learns immediate source message communication history message special case consensus problem called binary consensus restricts input hence output domain single binary digit 0,1 two types failures process may undergo crash failure byzantine failure crash failure occurs process abruptly stops resume byzantine failure failures absolutely conditions imposed example may occur result malicious actions adversary process experiences byzantine failure may send contradictory conflicting data processes may sleep resume activity lengthy delay two types failures byzantine failures far disruptive thus consensus protocol tolerating byzantine failures must resilient every possible error occur stronger version consensus tolerating byzantine failures given strengthening integrity constraint consensus problem may considered case asynchronous synchronous systems real world communications often inherently asynchronous practical often easier model synchronous systems given asynchronous systems naturally involve issues synchronous ones synchronous systems assumed communications proceed rounds one round process may send messages requires receiving messages processes manner message one round may influence messages sent within round fully asynchronous message-passing distributed system one process may crash failure proved consensus impossible however impossibility result derives worst-case scenario process schedule highly unlikely reality process scheduling degree randomness asynchronous model forms failures handled synchronous consensus protocol instance loss communication link may modelled process suffered byzantine failure three agreement problems interest follows collection formula_5 processes numbered formula_6 formula_7 communicate sending messages one another process formula_6 must transmit value formula_1 processes also known general problem formal requirements consensus protocol may include n processes partially synchronous system system alternates good bad periods synchrony process chooses private value processes communicate rounds determine public value generate consensus vector following requirements shown variations problems equivalent solution problem one type model may solution another problem another type model example solution weak byzantine general problem synchronous authenticated message passing model leads solution weak interactive consistency interactive consistency algorithm solve consensus problem process choose majority value consensus vector consensus value t-resilient anonymous synchronous protocol solves byzantine generals problem formula_14 weak byzantine generals case number failures n number processes systems formula_5 processors formula_16 byzantine shown exists algorithm solves consensus problem formula_17 oral-messages model proof constructed first showing impossibility three-node case formula_18 using result argue partitions processors written-messages model protocols tolerate formula_19 fully asynchronous system consensus solution tolerate one crash failures even requiring non triviality property result sometimes called flp impossibility proof named authors michael j. fischer nancy lynch mike paterson awarded dijkstra prize significant work flp result state consensus never reached merely model assumptions algorithm always reach consensus bounded time practice highly unlikely occur example polynomial time binary consensus protocol tolerates byzantine failures phase king algorithm garay berman algorithm solves consensus synchronous message passing model n processes f failures provided n 4 f phase king algorithm f 1 phases 2 rounds per phase process keeps track preferred output initially equal process input value first round phase process broadcasts preferred value processes receives values processes determines value majority value count second round phase process whose id matches current phase number designated king phase king broadcasts majority value observed first round serves tie breaker process updates preferred value follows count majority value process observed first round greater n /2 f process changes preference majority value otherwise uses phase king value end f 1 phases processes output preferred values google implemented distributed lock service library called chubby chubby maintains lock information small files stored replicated database achieve high availability face failures database implemented top fault-tolerant log layer based paxos consensus algorithm scheme chubby clients communicate paxos master order access/update replicated log i.e. read/write files bitcoin uses proof work maintain consensus peer-to-peer network nodes bitcoin network attempt solve cryptographic proof-of-work problem probability finding solution proportional computational effort hashes per second expended node solves problem version block transactions added peer-to-peer distributed timestamp server accepted nodes node network attempt solve proof-of-work problem sybil attack becomes unfeasible unless attacker 50 computational resources network many peer-to-peer online real-time strategy games use modified lockstep protocol consensus protocol order manage game state players game game action results game state delta broadcast players game along hash total game state player validates change applying delta game state comparing game state hashes hashes agree vote cast players whose game state minority disconnected removed game known desync another well-known approach called msr-type algorithms used widely computer science control theory solve consensus problem shared-memory system concurrent objects must introduced concurrent object shared object data structure helps concurrent processes communicate reach agreement two main methods design concurrent object traditionally designers use critical section solve problem means one process allowed visit concurrent object time others must wait process exits critical section method straightforward easy implement however systems critical sections face risk crashing process dies inside critical section sleeps intolerably long time another implementation concurrent object called wait-free implementation guarantee consensus finite number steps given kind object powerful enough solve consensus problems maurice herlihy gave impossibility universality hierarchy consensus number hierarchy means maximum number processes system reach consensus given object objects higher consensus number implemented objects lower consensus number according hierarchy read/write registers solve consensus even 2-process-system data structure like stack queue solve consensus two processes ca n't objects solve consensus among processes efficient way prove take advantage bivalence assume output binary state bivalent two outputs possible output reachable state 0/1 state called 0-valent/1-valent basic idea make contradiction executing operations get state 0-valent 1-valent however concurrent objects universal means solve consensus among number processes simulate objects way simulate objects universal objects build operations sequence concurrent object
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Computer architecture
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power9 power9 family superscalar multithreading symmetric multiprocessors based power isa announced august 2016 hot chips conference power9-based processors manufactured using 14 nm finfet process 12- 24-core versions scale scale applications possibly variations since power9 architecture open licensing modification openpower foundation members current fastest supercomputer world summit based power9 also using nvidia volta gpus accelerators power9 core comes two variants four-way multithreaded one called smt4 eight-way one called smt8 smt4- smt8-cores similar consist number so-called slices fed common schedulers slice rudimentary 64-bit single-threaded processing core load store unit lsu integer unit alu vector scalar unit vsu simd floating point super-slice combination two slices smt4-core consists 32 kb l1 cache 32 kb l1 data cache instruction fetch unit ifu instruction sequencing unit isu feeds two super-slices smt8-core two sets l1 caches ifus isus feed four super-slices result 12-core 24-core versions power9 consist number slices 96 amount l1 cache power9 core whether smt4 smt8 12-stage pipeline five stages shorter predecessor power8 aims retain clock frequency around 4 ghz first incorporate elements power isa v.3.0 released december 2015 including vsx-3 instructions power9 design made modular used processor variants used licensing different fabrication process ibm chip co-processors compression cryptography well large low-latency edram l3 cache power9 variants ship versions cores disabled due yield reasons raptor computing systems first sold 4-core chips even ibm initially sold ac922 systems 22-core chips even though types chips 24 cores dies lot facilities on-chip helping massive off-chip i/o performance power9 chips made two types cores scale scale configuration power9 cores either smt4 smt8 smt8 cores intended powervm systems smt4 cores intended powernv systems use powervm predominantly run linux power9 chips made scale support directly-attached memory scale chips intended use machines two cpu sockets use buffered memory ibm portal openpower lists three available modules nimbus chip although scale-out smt8 variant powervm also uses lagrange module/socket sforza modules use land grid array 2601-pin socket talos ii – two-socket workstation/server platform using power9 smt4 sforza processors available 2u server 4u server tower eatx mainboard marketed secure owner-controllable free open-source software firmware initially shipping 4-core 8-core 18-core 22-core chip options chips cores available talos ii lite – single-socket version talos ii mainboard made using pcb blackbird – single-socket microatx platform using smt4 sforza processors 4–8 cores 2 ram slots supporting 256gib total barreleye g2 zaius – two-socket server platform using lagrange processors barreleye g2 zaius chassis use zaius power9 motherboard power systems ac922 – 2u 2× power9 smt4 monza 6× nvidia volta gpus 2× capi 2.0 attached accelerators 1 tb ddr4 ram ac abbreviation accelerated computing system also known witherspoon newell power systems l922 – 2u 1–2× power9 smt8 8–12 cores per processor 4 tb ddr4 ram powervm running linux power systems s914 – 4u 1× power9 smt8 4–8 cores 1 tb ddr4 ram powervm running aix/ibm i/linux power systems s922 – 2u 1–2× power9 smt8 4–10 cores per processor 4 tb ddr4 ram powervm running aix/ibm i/linux power systems s924 – 4u 2× power9 smt8 8–12 cores per processor 4 tb ddr4 ram powervm running aix/ibm i/linux power systems h922 – 2u 1–2× power9 smt8 4–10 cores per processor 4 tb ddr4 ram powervm running sap hana linux aix/ibm 25 system power systems h924 – 4u 2× power9 smt8 8–12 cores per processor 4 tb ddr4 ram powervm running sap hana linux aix/ibm 25 system power systems e950 – 4u 2–4× power9 smt8 8–12 cores per processor 16 tb buffered ddr4 ram power systems e980 – 1–4× 4u 4–16× power9 smt8 8–12 cores per processor 64 tb buffered ddr4 ram magna pe2112gtx – 2u two-socket server high performance computing using lagrange processors manufactured wistron summit sierra united states department energy together oak ridge national laboratory lawrence livermore national laboratory contracted ibm nvidia build two supercomputers summit sierra based power9 processors coupled nvidia volta gpus systems slated go online 2017 sierra based ibm power systems ac922 compute node first racks summit delivered oak ridge national laboratory 31 july 2017 marenostrum 4 – one three clusters emerging technologies block fourth marenostrum supercomputer power9 cluster nvidia volta gpus cluster expected provide 1.5 petaflops computing capacity installed emerging technologies block marenostrum 4 exists test new developments might suitable future versions marenostrum predecessor power9 supported freebsd ibm aix ibm linux running without powervm implementation power9 support linux kernel began version 4.6 march 2016 rhel suse debian gnu/linux centos supported
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Computer architecture
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zipeg zipeg open source free software extracts files compressed archives like zip rar 7z others rarely used types zipeg works mac os x windows best known file preview ability incapable compressing files although able extract compressed ones zipeg built top 7-zip backend ui implemented java open source zipeg automatically detects filenames national alphabets code pages correctly translates unicode zipeg reads exif thumbnails jpeg digital photographs uses tool tip style preview item icons
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Computer file systems
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simpy simpy process-based discrete-event simulation framework based standard python event dispatcher based python ’ generators also used asynchronous networking implement multi-agent systems simulated real communication processes simpy simple python generator functions used model active components like customers vehicles agents simpy also provides various types shared resources model limited capacity congestion points like servers checkout counters tunnels version 3.1 also provide monitoring capabilities aid gathering statistics resources processes simulations performed “ fast possible ” real time wall clock time manually stepping events though theoretically possible continuous simulations simpy features carry however simpy overkill simulations fixed step size processes ’ interact shared resources — use simple codice_1 loop case simpy distribution contains tutorials in-depth documentation large number examples simpy released open source software mit license first version released december 2002 one simpy main goals easy use example simple simpy simulation clock process prints current simulation time step
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Programming language topics
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microsoft sync framework microsoft sync framework data synchronization platform microsoft used synchronize data across multiple data stores sync framework includes transport-agnostic architecture data store-specific synchronization providers modelled ado.net data provider api plugged sync framework used offline access data working cached set data submitting changes master database batch well synchronize changes data source across consumers publish/subscribe sync peer-to-peer synchronization multiple data sources sync framework features built-in capabilities conflict detection – whether data changed already updated – flag manual inspection use defined policies try resolve conflict sync services includes embedded sql server compact database store metadata synchronization relationships well sync attempt sync framework api surfaced managed code use .net framework applications well unmanaged code use com applications scheduled ship visual studio 2008 late november 2007 sync framework runtime provides synchronization functionality without tied data store data transport protocols providing data source specific synchronization providers data source supported example using proper synchronization providers files synchronized across computers project updates synchronized across project participants media synchronized across devices sync framework ships three providers microsoft sync services ado.net sync services file systems sync services sse sync services used synchronize devices supplying providers device similarly pim software microsoft office outlook media libraries windows media player also supported providing suitable providers providers used enumerate items data store identified item id addition also maintain synchronization metadata state data store changes enumerated quickly metadata maintained every instance data store replica provider attached metadata maintained includes replica id tick count representing progression time conflict log tombstone log set changes data store seen knowledge replica id tick count pair makes codice_1 encodes state data store time sync framework defines set operation codice_2 object replica codice_3 determines store contains specified change codice_4 merge two knowledge sets codice_5 project knowledge subset items codice_6 create new knowledge set without changes subset items metadata managed metadata storage service uses in-process sql server compact database store metadata per-provider basis sync services api operates creating synchronization session represented codice_7 object synchronization session synchronizes data across two synchronization providers one source data store destination instances providers passed codice_7 object synchronization session destination provider sends knowledge set store source provider compares knowledge destination change set source enumerate changes transfer destination destination provider makes sure changes conflicting merges changes updates knowledge microsoft sync services ado.net synchronization provider synchronizing across databases using ado.net ado.net datasets synchronized source destination persisted database server also support data sources relational database like xml database web service long proxy provided abstract data source data provider available proxy sync services ado.net provider intended use offline applications data central database cached locally application works cached data changes uploaded batch addition provider also used collaborative applications application work local dataset synchronized periodically peer-to-peer manner participants locally datasets stored either using sql server compact database database server supporting ado.net sync services ado.net allows incremental change tracking allows changes replicated rather replicating entire copy sync services file systems provider used synchronize two file system locations either local folders network shares addition mirroring new files changes existing files also synchronized changes files detected using timestamps optionally hashing file contents conflicting changes file detected set automatically resolved conflicting updates file newer edit kept file deleted one replica updated another update take precedence delete two files different content created name across two replicas sync operation one created later persisted rename operation caused files get name retained renaming one deletes configured move file recycle bin recovered necessary sync services file systems provider also provides preview mode enumerates actions taken sync operation without actually performing operations view letting users review changes made synchronization performed peer-to-peer manner neither sync framework sync services file systems provider perform authentication accessing files authentication job application using sync framework api files transferred without encryption use encryption transit custom providers uses encrypted tcp connection needs used sync services file systems provider also supports static filters exclude files based wildcards attributes first release however sync services file systems provider sync either ntfs security descriptors alternate data streams sync services feedsync provider used help synchronize replicas creating feedsync enabled feed either rss atom formats subscribed interested parties provider also used extract items feedsync feed merge changes back data store sync services feedsync uses another provider connect data store sync services feedsync provides services used help synchronize data replica rss atom feeds replica particular repository information synchronized using feedsync producer service synchronization application work synchronization provider create list items replica put rss atom xml stream items published interested subscribers similarly feedsync consumer service helps synchronization application take input rss atom xml stream extract items use synchronization provider apply appropriate changes replica sync framework underlies exchange feed items two feeds cross-subscribed easily synchronized one another peers synchronization community synchronization community set replicas keep data synchronized microsoft sync framework free windows windows mobile devices support platforms available commercial licensing porting kits
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Operating systems
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list cil instructions list instructions instruction set common intermediate language bytecode
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Computer architecture
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message passing computer clusters message passing inherent element computer clusters computer clusters ranging homemade beowulfs fastest supercomputers world rely message passing coordinate activities many nodes encompass message passing computer clusters built commodity servers switches used virtually every internet service recently use computer clusters one thousand nodes spreading number nodes cluster increases rapid growth complexity communication subsystem makes message passing delays interconnect serious performance issue execution parallel programs specific tools may used simulate visualize understand performance message passing computer clusters large computer cluster assembled trace-based simulator use small number nodes help predict performance message passing larger configurations following test runs small number nodes simulator reads execution message transfer log files simulates performance messaging subsystem many messages exchanged much larger number nodes historically two typical approaches communication cluster nodes pvm parallel virtual machine mpi message passing interface however mpi emerged de facto standard message passing computer clusters pvm predates mpi developed oak ridge national laboratory around 1989 provides set software libraries allow computing node act parallel virtual machine provides run-time environment message-passing task resource management fault notification must directly installed every cluster node pvm used user programs written c c++ fortran etc unlike pvm concrete implementation mpi specification rather specific set libraries specification emerged early 1990 discussions 40 organizations initial effort supported arpa national science foundation design mpi drew various features available commercial systems time mpi specifications gave rise specific implementations mpi implementations typically use tcp/ip socket connections mpi widely available communications model enables parallel programs written languages c fortran python etc mpi specification implemented systems mpich open mpi computer clusters use number strategies dealing distribution processing multiple nodes resulting communication overhead computer clusters tianhe-i use different processors message passing used performing computations tiahnhe-i uses two thousand feiteng-1000 processors enhance operation proprietary message passing system computations performed xeon nvidia tesla processors one approach reducing communication overhead use local neighborhoods also called locales specific tasks computational tasks assigned specific neighborhoods cluster increase efficiency using processors closer however given many cases actual topology computer cluster nodes interconnections may known application developers attempting fine tune performance application program level quite difficult given mpi emerged de facto standard computer clusters increase number cluster nodes resulted continued research improve efficiency scalability mpi libraries efforts included research reduce memory footprint mpi libraries earliest days mpi provided facilities performance profiling via pmpi profiling system use pmipi- prefix allows observation entry exit points messages however given high level nature profile type information provides glimpse real behavior communication system need information resulted development mpi-peruse system peruse provides detailed profile enabling applications gain access state-changes within mpi-library achieved registering callbacks peruse invoking triggers message events take place peruse work paraver visualization system paraver two components trace component visual component analyze traces statistics related specific events etc large scale often supercomputer level parallel system developed essential able experiment multiple configurations simulate performance number approaches modeling message passing efficiency scenario ranging analytical models trace-based simulation approaches rely use test environments based artificial communications perform synthetic tests message passing performance systems bigsim provide facilities allowing simulation performance various node topologies message passing scheduling strategies analytical level necessary model communication time term set subcomponents startup latency asymptotic bandwidth number processors well known model hockney model simply relies point point communication using l r message size l startup latency r asymptotic bandwidth mb/s xu hwang generalized hockney model include number processors latency asymptotic bandwidth functions number processors gunawan cai generalized introducing cache size separated messages based sizes obtaining two separate models one messages cache size one specific tools may used simulate understand performance message passing computer clusters instance clustersim uses java-based visual environment discrete-event simulation approach computed nodes network topology visually modeled jobs duration complexity represented specific probability distributions allowing various parallel job scheduling algorithms proposed experimented communication overhead mpi message passing thus simulated better understood context large-scale parallel job execution simulation tools include mpi-sim bigsim mpi-sim execution-driven simulator requires c c++ programs operate clustersim hand uses hybrid higher-level modeling system independent programming language used program execution unlike mpi-sim bigsim trace-driven system simulates based logs executions saved files separate emulator program bigsim includes emulator simulator emulator executes applications small number nodes stores results simulator use simulate activities much larger number nodes emulator stores information sequential execution blocks sebs multiple processors log files seb recording messages sent sources destinations dependencies timings etc simulator reads log files simulates may star additional messages also stored sebs simulator thus provide view performance large applications based execution traces provided emulator much smaller number nodes entire machine available configured
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Distributed computing architecture
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strong customer authentication strong customer authentication sca requirement eu revised directive payment services psd2 payment service providers within european economic area sca requirement comes force 14 september 2019 requirement ensures electronic payments performed multi-factor authentication increase security electronic payments physical card transactions already commonly could termed strong customer authentication eu chip contactless pin generally true internet transactions across eu prior implementation requirement article 97 1 directive requires payment service providers use strong customer authentication payer accesses payment account online br b initiates electronic payment transaction br c carries action remote channel may imply risk payment fraud abuses directive defines strong customer authentication essentially two-factor authentication article 4 30 authentication based use two elements categorised knowledge something user knows possession something user possesses inherence something user independent breach one compromise reliability others designed way protect confidentiality authentication data multiple ways card provider implement sca including 31 january 2013 european central bank ecb issued recommendations internet payment security requiring strong customer authentication ecb requirements technologically neutral order foster innovation competition public submission process ecb identified three solutions strong customer authentication two based reliance authentication new variant 3-d secure incorporates one-time passwords subsequently european commission drafted proposals updated payment services directive including requirement became psd2 psd2 strong customer authentication legal requirement electronic payments credit cards starting september 14 2019 2016 visa criticised proposal making strong customer authentication mandatory grounds could make online payments difficult thus hurt sales online retailers reserve bank india mandates strong authentication online transactions proposal make 3d secure mandatory australia blocked australian competition consumer commission accc numerous objections flaw-related submissions received
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Computer security
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precedence graph precedence graph also named conflict graph serializability graph used context concurrency control databases precedence graph schedule contains precedence graph schedule 3 transactions cycle length 2 two edges committed transactions t1 t2 schedule history conflict serializable notice commit transaction 2 meaning regarding creation precedence graph algorithm test conflict serializability schedule along example schedule formula_10 formula_11 formula_4 formula_5 formula_6 formula_7 formula_8 formula_9
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Databases
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alina malware alina point sale malware pos ram scraper used cybercriminals scrape credit card debit card information point sale system first started scrape information late 2012 resembles jackpos malware executed gets installed user computer checks updates update found removes existing alina code installs latest version new installations adds file path autostart runkey maintain persistence finally adds java.exe appdata directory executes using parameter codice_1 new installations codice_2 upgrades alina inspects user processes help windows api calls alina maintains blacklist processes process information blacklist uses openprocess read process contents memory dump data scraped alina sends c c servers using http post command hardcoded binary
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Computer security
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k7 total security k7 total security developed k7 computing pvt ltd. malware prevention antivirus software provides malware prevention removal subscription period uses signatures heuristics identify viruses features include software firewall e-mail spam filtering phishing protection k7 computing distributes product download box copy oem software k7 computing pvt ltd. software hardware security company founded 1991 jayaraman kesavardhanan chennai india company 90+ employees chennai hq employees around world software research virus detection handled virus lab chennai k7 computing member avar association anti virus asia researchers jayaraman kesavardhanan founder cto k7 computing granted best member award recognition significant contributions avar year 2008 chennai tn 16 december 2008 k7 computing cloud computing division built windows platform k7 cloud solutions formed result k7 computing acquisition binarykarma chennai india based start-up working products area virtualization management j. kesavardhanan serves founder chief technology officer k7 computing developing antivirus software 20 years recognized antivirus software k7 computing k7 total security av-comparatives performance test 2010 version 11 released february 2011 together k7 ultimate security 11 antivirus plus antivirus premium 15 june 2011 k7 released business edition antivirus security k7 enterprise security business orientated antivirus product offering remote management installation home users smartphone users small offices enterprise edition products cloud products see k7 cloud solutions k7 total security released 2002 k7 computing first security suite windows pcs service time offered basic protection internet users anti-virus anti-spyware tools anti-spam basic firewall k7 total security 10 best performing antivirus 2010 av-comparatives well 2011 k7 antivirus plus november 2011 vb-100 award received december 2011 august 2012
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Computer security
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computer fan control fan control management rotational speed electric fan computers various types computer fans used provide adequate cooling different fan control mechanisms balance cooling capacities noise generate commonly accomplished motherboards hardware monitoring circuitry configured end-user bios software perform fan control modern pcs grow powerful requirements electrical power computers convert part electrical power heat generated major components heat production varies system load periods compute-intensive activity generate much heat idle time processors early x86-based computers early 486s need active ventilation power supplies needed forced cooling power supply fans also circulated cooling air rest pc atx standard byproduct increased heat generation fan need move increasing amounts air thus need powerful since must move air area space fans become noisy fans installed pc case produce noise levels 70 db since fan noise increases fifth power fan rotation speed reducing rotations per minute rpm small amount potentially means large reduction fan noise must done cautiously excessive reduction speed may cause components overheat damaged done properly fan noise drastically reduced common cooling fans used computers use standardized connectors two four pins first two pins always used deliver power fan motor rest optional depending fan design type color wires connected pins varies depending number connectors role pin standardized guaranteed system cooling fans equipped either two- three-pin connectors usually designed accept wide range input voltages directly affects rotation speed blades style fan control fan either temperature inside chassis checked outside-of-range temperature detected fans set maximum speed temperature drops threshold fans turned back control method reduces noise issues power requirements periods low usage system operating capacity fan noise become problem standard cooling fan essentially bladed dc motor varying voltage input across acceptable range fan speed fan increase added voltage decrease reduced voltage faster fan means air moved thus higher heat exchange rate ways perform regulation described resistors series fan power pin simplest method reducing fan noise add heat generated inside computer case since voltage drop proportional current fan may start need appropriate power rating variable fan control potentiometers could used along transistor mosfet whose output voltage controlled potentiometer possible use rheostat instead diode series fan reduce voltage output fan silicon diode provides relatively constant voltage drop 0.7 v per diode data sheets specific diode specify voltage drop example 1n4001 silicon diode voltage drop varies approximately 0.7 0.9 v current varies 0.01 1 power rating noted diodes may require cooling operate rated current also noted voltage drop across diode fall temperature causing fan speed like series regulators diode dissipate power equal voltage drop times current passing voltage computer cooling fan receives defined difference voltage wire +12 v ground wire +0 v connecting one wires different voltage voltage fan receives different default 12 v fan designed increasing voltage default 12 v achieved e.g connecting −12 v −5 v power line instead ground wire fan connector connecting 5 v power line +12 v input fan connector procedure 10 17 24 v voltages achieved voltages exceeding 12 v potentially damaging computer fans rated 12 v. however combination modern power supplies longer required provide −5 v power line limited power delivery capability −12 v line usually less 1 power reduces total capacity volt modded fans modern systems safest method volt modding connecting +5 v power line +12 v input fan reduces voltage fan receives +5 v. fans work low voltage fans may run +5 v started rotating reasonable speed another method reducing fan speed moving 5 v wire classical molex power connector place ground wire going fan thereby delivering +7 v 12 v − 5 v 7 v fan however potentially risky method +5 v psu line intended source current sink psu likely get damaged case load 5 v psu line load generated 7 v fans e.g pc enters idle/sleep state also components inside computer using +5 v power might exposed 5 v case short circuit fan common voltage regulator ics like popular lm78xx series sometimes used provide variable constant voltage fans thermally bonded computer chassis one ics provide 1 current voltage 6 8 9 10 v lm7806 lm7808 lm7809 lm7810 respectively adjustable versions like popular lm317 also exist combined potentiometer adjustable regulators allow user vary fan speed several fans currents far excess standard potentiometer could handle higher currents discrete linear regulators relatively simple construct using power transistor mosfet small signal transistor zener diode voltage reference discrete regulators require additional components minimum two transistors three resistors small capacitor allow arbitrarily high currents allowing regulation additional fans accessories linear regulators waste heat produced roughly pulse-width modulation pwm common method controlling computer fans pwm-capable fan usually connected 4-pin connector pinout ground +12 v sense control sense pin used relay rotation speed fan control pin open-drain open-collector output requires pull-up 5 v 3.3 v fan unlike linear voltage regulation fan voltage proportional speed fan driven constant supply voltage speed control performed fan based control signal control signal square wave operating 25 khz duty cycle determining fan speed 25khz used raise sound signal range human hearing use lower frequency could produce audible hum whine typically fan driven 30 100 rated fan speed using signal 100 duty cycle exact speed behavior linear threshold value minimum speed threshold low control levels manufacturer dependent many motherboards feature firmware software regulates fans based processor computer case temperatures another method popular gamers manual fan speed controller mounted expansion slot 5.25 3.5 drive bay come built computer case using switches knobs attached fans speeds adjusted one methods modern motherboards feature hardware monitoring chips capable performing fan control usually pwm method described chips configured bios using specialised software operating system booted processors produce varying levels heat depending system load thus makes sense reduce speed fans idle decrease noise produced fans running full speed load goes point fan speed must adjusted promptly avoid overheating modern hardware monitor chips configured capable independently running monitoring loop without need functioning bios operating system automatic control offered chips may called thermal cruise mode maintaining thermal envelope well fan speed cruise mode maintaining specific fan speed automatically however software capable accessing advanced configuration parameters provided chips common generic software implements basic interfacing chips namely explicit setting duty cycle fan control setting subsequently performing duty cycle adjustments software thus requiring operating system well third-party software continue running main cpu perform monitoring loop may problem system utility crashes point system may overheat due failure fans maintain adequate cooling whilst running reduced voltage speed method software physically controls fan usually pwm see many companies provide software control fan speeds motherboards microsoft windows mac os x/macos also third-party programs work variety motherboards allow wide customization fan behavior depending temperature readings motherboard cpu gpu sensors well allowing manual control two programs speedfan argus monitor
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Computer architecture
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shadow memory shadow memory technique used track store information computer memory used program execution shadow memory consists shadow bytes map individual bits one bytes main memory shadow bytes typically invisible original program used record information original piece data technique utilized memory-error checkers store information parts memory allocated program checked shadow memory used detecting reporting incorrect accesses memory even though program may crashing due segmentation fault similar error checker may also store additional information memory bits defined ones memcheck part valgrind suite uses detect undefined behavior resulting acting printing undefined memory values use shadow memory however limited memory-error checkers information stored shadow bytes fixed instance used threadsanitizer data race detector shadow memory implemented used lot different ways different performance characteristics memcheck instance tracks values bit precision addresssanitizer part clang compiler comparatively fast memcheck like valgrind tools uses binary translation instrumentation run code manipulating shadow memory corresponding program memory use addresssanitizer hand created compile-time inserts error-checking code inline program compilation shadow-memory implementation uses huge reservation virtual memory shadow memory giving different performance characteristics
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Operating systems
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programming language implementation programming language implementation system executing computer programs two general approaches programming language implementation notice compiler directly execute program ultimately order execute program via compilation must translated form serve input interpreter directly hardware piece computer hardware interpret programming language directly language called machine code so-called native code compiler one compiles program machine code actual compilation often separated multiple passes like code generation often assembler language translator generating native code linking loading execution compiler given high level language produces another high level language called translator source source translation often useful add extensions existing languages exploit good portable implementation language example c simplifying development many combinations interpretation compilation possible many modern programming language implementations include elements example smalltalk programming language conventionally implemented compilation bytecode either interpreted compiled virtual machine popular ways use jit aot compiler compilation implementation strategy copied many languages since smalltalk pioneered every programming language requires abstract machines bridge gap high level language low level real machine
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Programming language topics
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sun blade sun blade line blade server computer systems sold sun microsystems 2006 onwards june 2006 sun announced amd opteron-based sun blade 8000 modular blade server system sun blade 8000 chassis hold 10 sun blade x8420 x8440 modules following year sun blade 6000 system launched allowed mixed ultrasparc x64 x86-64 architecture blades sun blade t6300 t6320 modules run solaris use ultrasparc t1 ultrasparc t2 processors respectively sun blade x6220 x6250 modules use amd opteron intel xeon 5000-series processors respectively x-series blades support solaris oracle linux rhel sles windows server vmware
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Computer architecture
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vesa local bus vesa local bus usually abbreviated vl-bus vlb short-lived expansion bus introduced i486 generation x86 ibm compatible personal computers created vesa video electronics standards association vesa local bus worked alongside dominant isa bus provide standardized high-speed conduit intended primarily accelerate video graphics operations vlb provided standardized fast path add-in video card makers could tap greatly accelerated memory-mapped i/o dma still using familiar isa bus handle basic device duties interrupts port-mapped i/o early 1990s i/o bandwidth prevailing isa bus become critical bottleneck pc video graphics performance need faster graphics driven increased adoption graphical user interfaces pc operating systems ibm produce viable successor isa micro channel architecture failed market due ibm requirement license payment licensing fees hardware manufacturers use extension royalty free isa bus form eisa open standard developed counter mca unable offer enough improvement isa meet dramatic increase bandwidth desired graphics thus short time market opening occurred video card manufacturers motherboard chipset makers created proprietary implementations local buses provide graphics cards direct access processor system memory avoided limitations isa bus less costly licensed ibm mca machine important note time migration mca architecture machine isa one insubstantial mca machines generally offer isa slots thus migration mca architecture meant prior investment isa cards made unusable additionally makers mca compatible cards subject ibm licensing fees combined mca greater technical requirements expense implement bad mca required peripheral cards passive members made cards active participants increasing system performance effect making mca version peripheral card significantly expensive isa counterpart ad-hoc manufacturer-specific solutions effective standardized provisions providing interoperability drew attention vesa consortium resulted proposal voluntary royalty free local bus standard 1992 additional benefit standardization beyond primary goal greater graphics card performance devices could also designed utilize performance offered vlb notably mass storage controllers offered vlb providing increased hard disk performance vlb slot simply additional edge connector placed in-line traditional isa eisa connector extended portion often colored distinctive brown result normal isa eisa slot additionally capable accepting vlb-compatible cards traditional isa cards remained compatible would pins past normal isa eisa portion slot reverse also true vlb cards necessity quite long order reach vlb connector reminiscent older full-length expansion cards earlier ibm xt era vlb portion slot looked similar ibm mca slot indeed physical 116-pin connector used mca cards rotated 180 degrees ibm mca standard popular ibm expected ample surplus connector making inexpensive readily available vesa local bus designed stopgap solution problem isa bus limited bandwidth one requirement vlb gain industry adoption minimal burden manufactures implement terms board re-design component costs otherwise manufacturers would convinced change proprietary solutions vlb fundamentally tied card directly 486 processor bus minimal intermediary logic reducing logic design component costs timing arbitration duties strongly dependent cards cpu simplicity vlb unfortunately created several factors served limit useful life substantially despite problems vesa local bus became commonplace later 486 motherboards majority later post-1992 486-based systems featuring vesa local bus video card vlb importantly offered less costly high speed interface consumer systems 1994 pci commonly available outside server market via pentium intel chipsets pci finally displaced vesa local bus also eisa last years 486 market last generation 80486 motherboards featuring pci slots lieu vlb capable isa slots however manufacturers develop offer vip v esa/ sa/ p ci motherboards three slot types
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Computer architecture
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basic-256 basic-256 project learn basics computer programming project started 2007 inspired article “ johnny ca n't code ” david brin main focus provide simple comprehensive environment middle/high school students learn basics computer programming basic-256 simple version basic code editor text output window graphics editor window visible screen however successive versions adding new features namely complete documentation available english russian dutch spanish portuguese
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Programming language topics
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apple a6x apple a6x 32-bit system-on-a-chip soc designed apple inc. introduced launch fourth generation ipad october 23 2012 high-performance variant apple a6 last 32-bit chip released switched 64-bit apple claims a6x twice cpu performance twice graphics performance predecessor apple a5x software updates ipad 4th generation ended 2017 thus ceasing support chip a6x features 1.4 ghz custom apple-designed armv7-a architecture based dual-core cpu called swift introduced apple a6 includes integrated quad-core powervr sgx554mp4 graphics processing unit gpu running 300 mhz quad-channel memory subsystem memory subsystem supports lpddr2-1066 dram increasing theoretical memory bandwidth 17 gb/s unlike a6 similar a5x a6x covered metal heat spreader includes ram package-on-package pop assembly a6x manufactured samsung high-κ metal gate hkmg 32 nm process die area 123 mm 30 larger a6
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Computer architecture
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tesla microarchitecture named pioneering electrical engineer nikola tesla tesla codename gpu microarchitecture developed nvidia released 2006 successor prior microarchitectures nvidia first microarchitecture implement unified shaders used geforce 8 series geforce 9 series geforce 100 series geforce 200 series geforce 300 series gpus collectively manufactured 90 nm 80 nm 65 nm 55 nm 40 nm also geforce 405 quadro fx quadro x000 quadro nvs series nvidia tesla computing modules tesla replaced old fixed-pipeline microarchitectures represented time introduction geforce 7 series competed directly amd first unified shader microarchitecture named terascale development ati work xbox 360 used similar design tesla followed fermi tesla nvidia first microarchitecture implementing unified shader model driver supports direct3d 10 shader model 4.0 opengl 2.1 later drivers opengl 3.3 support architecture design major shift nvidia gpu functionality capability obvious change move separate functional units pixel shaders vertex shaders within previous gpus homogeneous collection universal floating point processors called stream processors perform universal set tasks geforce 8 unified shader architecture consists number stream processors sps unlike vector processing approach taken older shader units sp scalar thus operate one component time makes less complex build still quite flexible universal scalar shader units also advantage efficient number cases compared previous generation vector shader units rely ideal instruction mixture ordering reach peak throughput lower maximum throughput scalar processors compensated efficiency running high clock speed made possible simplicity geforce 8 runs various parts core differing clock speeds clock domains similar operation previous geforce 7 series gpus example stream processors geforce 8800 gtx operate 1.35 ghz clock rate rest chip operating 575 mhz geforce 8 performs significantly better texture filtering predecessors used various optimizations visual tricks speed rendering without impairing filtering quality geforce 8 line correctly renders angle-independent anisotropic filtering algorithm along full trilinear texture filtering g80 though smaller brethren equipped much texture filtering arithmetic ability geforce 7 series allows high-quality filtering much smaller performance hit previously nvidia also introduced new polygon edge anti-aliasing methods including ability gpu rops perform multisample anti-aliasing msaa hdr lighting time correcting various limitations previous generations geforce 8 perform msaa fp16 fp32 texture formats geforce 8 supports 128-bit hdr rendering increase prior cards 64-bit support chip new anti-aliasing technology called coverage sampling aa csaa uses z color coverage information determine final pixel color technique color optimization allows 16x csaa look crisp sharp claimed theoretical single-precision processing power tesla-based cards given flops may hard reach real-world workloads g80/g90/gt200 streaming multiprocessor sm contains 8 shader processors sp unified shader cuda core 2 special function units sfu sp fulfill two single-precision operations per clock 1 multiply 1 add using single mad instruction sfu fulfill four operations per clock four mul multiply instructions one sm whole execute 8 mads 16 operations 8 muls 8 operations per clock 24 operations per clock relatively speaking 3 times number sps therefore calculate theoretical dual-issue mad+mul performance floating point operations per second flops gflops graphics card sp count n shader frequency f ghz formula flops 3 × n × f however leveraging dual-issue performance like mad+mul problematic reasons order estimate performance real-world workloads may helpful ignore sfu assume 1 mad 2 operations per sp per cycle case formula calculate theoretical performance floating point operations per second becomes flops 2 × n × f theoretical double-precision processing power tesla gpu 1/8 single precision performance gt200 double precision support g8x g9x nvenc introduced later chips • 8800 gtx • 8800 ultra
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Computer architecture
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video electronics standards association vesa /ˈviːsə/ formally known video electronics standards association technical standards organization computer display standards organization incorporated california july 1989 office san jose california claims membership 225 companies november 1988 nec home electronics announced creation association develop promote super vga computer display standard successor ibm proprietary video graphics array vga display standard super vga enabled graphics display resolutions 800×600 pixels compared vga maximum resolution 640×480 pixels—a 36 increase organization since issued several additional standards related computer video display following major companies members vesa vesa criticized policy charging non-members published standards people believe practice charging specifications undermined purpose vesa organization according kendall bennett developer vbe/af standard vesa software standards committee closed due lack interest resulting charging high prices specifications time vesa standards available free although vesa hosts free standards documents free collection include newly developed standards even obsolete standards free collection incomplete 2010 current standards documents vesa cost hundreds thousands dollars older standards available free purchase 2017 free downloads require mandatory registration standards bodies provide specifications freely available download many including itu jedec ddwg hdmi hdmi 1.3a time displayport announced vesa criticized developing specification secret track record developing unsuccessful digital interface standards including plug display digital flat panel
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Computer architecture
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shebang unix computing shebang character sequence consisting characters number sign exclamation mark beginning script also called sha-bang hashbang pound-bang hash-pling unix-like operating systems text file shebang used executable program loader mechanism parses rest file initial line interpreter directive loader executes specified interpreter program passing argument path initially used attempting run script program may use file input data example script named path path/to/script starts following line codice_1 program loader instructed run program /bin/sh passing path/to/script first argument linux behavior result kernel user-space code shebang line usually ignored interpreter character comment marker many scripting languages language interpreters use hash mark begin comments still may ignore shebang line recognition purpose form shebang interpreter directive follows interpreter absolute path executable program optional argument string representing single argument white space optional linux file specified interpreter executed execute right contains code kernel execute directly wrapper defined via sysctl executing microsoft .exe binaries using wine contains shebang linux minix interpreter also script chain shebangs wrappers yields directly executable file gets encountered scripts parameters reverse order example file /bin/a executable file elf format file /bin/b contains shebang /bin/a optparam file /bin/c contains shebang /bin/b executing file /bin/c resolves /bin/b /bin/c finally resolves /bin/a optparam /bin/b /bin/c darwin-based operating systems macos solaris file specified interpreter must executable binary script typical shebang lines shebang lines may include specific options passed interpreter however implementations vary parsing behavior options portability one option specified without embedded whitespace portability guidelines found interpreter directives allow scripts data files used commands hiding details implementation users programs removing need prefix scripts interpreter command line bourne shell script identified path some/path/to/foo initial line executed parameters bar baz provides similar result actually executed following command line instead /bin/sh specifies bourne shell end result shell commands file some/path/to/foo executed positional variables 1 2 values bar baz respectively also initial number sign character used introduce comments bourne shell language languages understood many interpreters whole shebang line ignored interpreter however interpreter ignore shebang line thus script consisting following two lines simply echos lines standard output run compared use global association lists file extensions interpreting applications interpreter directive method allows users use interpreters known global system level without administrator rights also allows specific selection interpreter without overloading filename extension namespace one file extension refers one file type allows implementation language script changed without changing invocation syntax programs invokers script need know implementation language script responsible specifying interpreter use shebangs must specify absolute paths paths relative current working directory system executables cause problems systems non-standard file system layout even systems fairly standard paths quite possible variants operating system different locations desired interpreter python example might /usr/bin/python /usr/local/bin/python even something like /home/username/bin/python installed ordinary user sometimes required edit shebang line copying script one computer another path coded script may apply new machine depending consistency past convention placement interpreter reason posix standardize path names posix standardize feature often program /usr/bin/env used circumvent limitation introducing level indirection. followed /usr/bin/env followed desired command without full path example mostly works path /usr/bin/env commonly used env utility invokes first sh found user path typically /bin/sh system setuid script support reintroduce race eliminated /dev/fd workaround described still portability issues openserver 5.0.6 unicos 9.0.2 /bin/env /usr/bin/env another portability problem interpretation command arguments systems including linux split arguments example running script first line like passed one argument /usr/bin/env rather two arguments cygwin also behaves way complex interpreter invocations possible use additional wrapper another problem scripts containing carriage return character immediately shebang perhaps result edited system uses dos line breaks microsoft windows systems interpret carriage return character part interpreter command resulting error message posix requires sh shell capable syntax similar bourne shell although require located /bin/sh example systems solaris posix-compatible shell /usr/xpg4/bin/sh many linux systems recent releases mac os x /bin/sh hard symbolic link /bin/bash bourne shell using syntax specific bash maintaining shebang pointing bourne shell portable shebang actually human-readable instance magic number executable file magic byte string two-character encoding ascii magic number detected exec family functions determine whether file script executable binary presence shebang result execution specified executable usually interpreter script language claimed old versions unix expect normal shebang followed space slash appears untrue rather blanks shebang traditionally allowed sometimes documented space see 1980 email history section shebang characters represented two bytes extended ascii encodings including utf-8 commonly used scripts text files current unix-like systems however utf-8 files may begin optional byte order mark bom exec function specifically detects bytes 0x23 0x21 presence bom shebang prevent script interpreter executed authorities recommend using byte order mark posix unix-like scripts reason wider interoperability philosophical concerns additionally byte order mark necessary utf-8 encoding endianness issues serves identify encoding utf-8 executable file starting interpreter directive simply called script often prefaced name general classification intended interpreter name shebang distinctive two characters may come inexact contraction sharp bang hash bang referring two typical unix names another theory sh shebang default shell sh usually invoked shebang usage current december 1989 probably earlier shebang introduced dennis ritchie edition 7 8 bell laboratories also added bsd releases berkeley computer science research present 2.8bsd activated default 4.2bsd bell laboratories edition 8 unix later editions released public first widely known appearance feature bsd lack interpreter directive support shell scripts apparent documentation version 7 unix 1979 describes instead facility bourne shell files execute permission would handled specially shell would sometimes depending initial characters script spawn subshell would interpret run commands contained file model scripts would behave commands called within bourne shell attempt directly execute file via operating system exec system trap would fail preventing scripts behaving uniformly normal system commands later versions unix-like systems inconsistency removed dennis ritchie introduced kernel support interpreter directives january 1980 version 8 unix following description kernel support interpreter directives spread versions unix one modern implementation seen linux kernel source fs/binfmt_script.c mechanism allows scripts used virtually context normal compiled programs including full system programs even interpreters scripts caveat though early versions kernel support limited length interpreter directive roughly 32 characters 16 first implementation would fail split interpreter name parameters directive quirks additionally modern systems allow entire mechanism constrained disabled security purposes example set-user-id support disabled scripts many systems note even systems full kernel support magic number scripts lacking interpreter directives although usually still requiring execute permission still runnable virtue legacy script handling bourne shell still present many modern descendants scripts interpreted user default shell
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Operating systems
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super flexible super flexible file synchronizer backup file synchronization software allows backing synchronizing files different drives different media cd dvd flash zip remote server
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Computer security
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vesa bios extensions vesa bios extensions vbe vesa standard currently version 3 defines interface used software access compliant video boards high resolutions bit depths opposed traditional int 10h bios calls limited resolutions 640×480 pixels 16 color 4-bit depth less vbe made available video card bios installs boot interrupt vectors point newer cards implement capable vbe 3.0 standard older versions vbe provide real mode interface used without significant performance penalty within protected mode operating systems consequently vbe standard almost never used writing video card drivers vendor thus invent proprietary protocol communicating video card despite common driver thunk real mode interrupt order initialize screen modes gain direct access card linear frame buffer tasks would otherwise require handling many hundreds proprietary variations exist card card standard provides primary functionality vesa bios extensions allows applications determine capabilities graphics card provides ability set display modes found vbe 2.0 adds new features prior vbe 1.2 standard including linear framebuffer access protected mode banking vbe core 2.0 features include superset vbe 2.0 standard standard adds refresh rate control facilities stereo glasses improved multi-buffering functions vbe 2.0 standard vbe/af provides low-level standard interface common acceleration functions available hardware functions defined standard access hardware cursors bit block transfers bit blt screen sprites hardware panning drawing functions supplemental specifications provides device independent interface application software super vga hardware function numbers assigned vesa software standards committee ssc dpms hardware standard allows graphics cards communicate dpms-compliant monitors via special signaling system used existing graphics controllers monitor cables signaling system allows graphics card tell monitor go number different power management power saving states effectively allow monitor turn use allows access special features flat panel controllers provides standard audio services currently version 1.00 vbe/ai specification defines three device classes wave midi volume device types covered provides standard entry vendor specific extensions display data channel ddc digital connection computer display graphics adapter allows display communicate specifications adapter standard created vesa provides hardware independent means operating system application read write data i²c serial control interface although mode number 16-bit value optional vbe mode numbers 14 bits wide bit 15 used vga bios flag clear preserve display memory vbe defined mode numbers follows starting vbe/core 2.0 vesa longer defines new vesa mode numbers longer requires device implement old numbers properly detect information screen mode use function 01h return vbe mode information mode 81ffh special video mode designed preserve current memory contents give access entire video memory beginning vbe 2.0 standard new modes defined vesa old modes longer mandatory use defined modes considered deprecated modern video cards may may use mode numbers even though backward compatibility modern software use correct way software discover available display modes obtain list modes using function 00h return vbe controller information check mode using function 01h return vbe mode information finds mode/s requires modes 264–268 text modes 264 0108h 80 columns × 60 rows 80×60 265 0109h 132×25 266 010ah 132×43 267 010bh 132×50 268 010ch 132×60 table combines modes defined vesa values denoted black along modes commonly used may work graphics cards defined standard linux kernel allows user select vesa mode boot time passing code memory kernel lilo boot loader passes code based vga parameter configuration file takes form 'vga=xxx xxx decimal value 'vga=0xhhh hhh hexadecimal value however 'vga= boot loader parameter directly accept vesa video mode numbers rather linux video mode number vesa number plus 512 case decimal representation plus 0x200 case hexadecimal representation example defined vesa value 257 0x101 representing 640x480 256 colours equivalent linux video mode value 769 0x301 see kernel documentation documentation/svga.txt documentation/fb/vesafb.txt indicated earlier vesa standard defines limited set modes particular none 1,280×1,024 covered instead implementation completely optional graphics adapter manufacturers vendors free utilize whatever additional values please means table modes expressed decimal form may apply graphics adapter vga= also appears select 1,280×800 8-bit various laptops displays br vga= 1,400×1,050 hwinfo hardware detection tool used suse linux gnu/linux distributions use hwinfo get actual mode number need pass parameter kernel command run root pick number corresponding desired resolution modes reported hwinfo hexadecimal use '0x prefix convert decimal vesa bios emulation parallels virtual machine different set non-standard vesa modes build 3214 vbetest reveals modes
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Computer architecture
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ptdos ptdos processor technology disk operating system operating system created late 1970s computers using intel 8080 microprocessor processor technology helios ii disk memory system following list commands supported ptdos 1.4
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Operating systems
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ultrasparc ultrasparc microprocessor developed sun microsystems fabricated texas instruments introduced mid-1995 first microprocessor sun implement 64-bit sparc v9 instruction set architecture isa marc tremblay co-microarchitect ultrasparc four-issue superscalar microprocessor executes instructions in-order nine-stage integer pipeline execution units simplified relative supersparc achieve higher clock frequencies example simplification alus cascaded unlike supersparc avoid restricting clock frequency integer register file 32 64-bit entries sparc isa uses register windows ultrasparc eight actual number registers 144 register file seven read three write ports integer register file provides registers two arithmetic logic units load/store unit two alus execute arithmetic logic shift instructions one execute multiply divide instructions floating-point unit consists five functional units one executes floating point adds subtracts one multiplies one divides square-roots two units executing simd instructions defined visual instruction set vis floating-point register file contains thirty-two 64-bit registers five read ports three write ports ultrasparc two levels cache primary secondary two primary caches one instructions one data capacity 16 kb ultrasparc required mandatory external secondary cache cache unified capacity 512 kb 4 mb direct-mapped return data single cycle external cache implemented synchronous srams clocked frequency microprocessor ratios supported accessed via data bus contained 3.8 million transistors fabricated texas instruments epic-3 process 0.5 µm complementary metal–oxide–semiconductor cmos process four levels metal ultrasparc fabricated bicmos process texas instruments claimed scale well 0.5 µm processes offered little performance improvement process perfected ti mvp digital signal processor dsp features missing three levels metal instead four 0.55 feature size used fabricate ultrasparc avoid repeat fabrication problems encountered supersparc ultrasparc packaged 521-contact plastic ball grid array pbga
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Computer architecture
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rekursiv rekursiv computer processor designed david m. harland mid-1980s linn smart computing glasgow scotland one computer architectures intended implement object-oriented concepts directly hardware form high-level language computer architecture rekursiv operated directly objects rather bits nibbles bytes words virtual memory used persistent object store unusually processor instruction set supported recursion hence name project originated initiative within hi-fi manufacturer linn products improve manufacturing automation systems time ran dec vax minicomputer resulted design lingo object-oriented programming language derived smalltalk algol due poor performance lingo vax subsidiary company linn smart computing ltd. formed develop new processor efficiently run lingo rekursiv processor consisted four gate-array chips named numerik 32-bit alu logik instruction sequencer objekt object-oriented memory management unit klock processor clock support logic small number prototype vmebus boards called hades comprising four chips plus 80 mb ram produced intended installation host system sun-3 workstation although rekursiv never fully developed commercial success several hades boards used academic research projects uk last known copy rekursiv computer ended bottom forth clyde canal glasgow
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Computer architecture
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fossil file system fossil default file system plan 9 bell labs serves network protocol 9p runs user space daemon like plan 9 file servers fossil different file systems due snapshot/archival feature take snapshots entire file system command automatically user-set interval snapshots kept fossil partition long disk space allows partition fills old snapshots removed free disk space snapshot also saved permanently venti fossil venti typically installed together important features include access snapshot one would connect running fossil instance “ mount ” change directory desired snapshot e.g /snapshot/yyyy/mmdd/hhmm yyyy mm dd hh mm meaning year month day hour minute access archive permanent snapshot directory form /archive/yyyy/mmdds yyyy mm dd meaning year month day sequence number would used plan 9 allows modifying namespace advanced ways like redirecting one path another path e.g /bin/ls /archive/2005/1012/bin/ls significantly eases working old versions files fossil available several platforms via plan 9 user space fossil designed implemented sean quinlan jim mckie russ cox bell labs added plan 9 distribution end 2002 became default file system 2003 replacing kfs previous plan 9 archival file system dubbed plan 9 file server fs fs also archival file system originally designed store data worm optical disc system permanent storage fossil provided venti typically stores data hard drives much lower access times optical discs
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Computer file systems
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length extension attack cryptography computer security length extension attack type attack attacker use hash message length message calculate hash message ‖ message attacker-controlled message without needing know content message algorithms like md5 sha-1 sha-2 based merkle–damgård construction susceptible kind attack sha-3 algorithm susceptible merkle–damgård based hash misused message authentication code construction h secret ‖ message message length secret known length extension attack allows anyone include extra information end message produce valid hash without knowing secret note since hmac n't use construction hmac hashes prone length extension attacks vulnerable hashing functions work taking input message using transform internal state input processed hash digest generated outputting internal state function possible reconstruct internal state hash digest used process new data way one may extend message compute hash valid signature new message server delivering waffles specified type specific user location could implemented handle requests given format server would perform request given deliver ten waffles type eggo given location user 1 signature valid user signature used mac signed key known attacker example also vulnerable replay attack sending request signature second time possible attacker modify request example switching requested waffle eggo liege done taking advantage flexibility message format duplicate content query string gives preference latter value flexibility indicate exploit message format message format never designed cryptographically secure first place without signature algorithm help order sign new message typically attacker would need know key message signed generate new signature generating new mac however length extension attack possible feed hash signature given state hashing function continue original request left long know length original request request original key length 14 bytes could determined trying forged requests various assumed lengths checking length results request server accepts valid message fed hashing function often padded many algorithms work input messages whose lengths multiple given size content padding always specified hash function used attacker must include padding bits forged message internal states message original line thus attacker constructs slightly different message using padding rules message includes padding appended original message inside hash function payload case 0x80 followed number 0x00s message length 0x228 552 14+55 *8 length key plus original message appended end attacker knows state behind hashed key/message pair original message identical new message final attacker also knows hash digest point means know internal state hashing function point trivial initialize hashing algorithm point input last characters generate new digest sign new message without original key combining new signature new data new request server see forged request valid request due signature would generated password known
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Computer security
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bigmachines bigmachines software company founded 2000 godard abel christopher shutts headquartered deerfield illinois united states development offices san mateo california hyderabad india bigmachines also european operations offices frankfurt main germany london served bigmachines ag well offices singapore tokyo sydney serving asia-pacific company software designed integrate enterprise resource planning erp customer relationship management crm business systems vista equity partners private equity firm based san francisco acquired majority ownership bigmachines several transactions starting january 2001 vista equity acquired majority ownership company december 2010.shortly vista acquired majority ownership abel left company three years later oracle corporation announced acquiring bigmachines october 24 2013 transaction later completed oracle kept product called cpq cloud company partnered salesforce.com oracle crm on-demand vendavo pros provide software applications crm systems
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Distributed computing architecture
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epigram programming language epigram functional programming language dependent types epigram also refers ide usually packaged language epigram type system strong enough express program specifications goal support smooth transition ordinary programming integrated programs proofs whose correctness checked certified compiler epigram exploits propositions types principle based intuitionistic type theory epigram prototype implemented conor mcbride based joint work james mckinna development continued epigram group nottingham durham st andrews royal holloway uk current experimental implementation epigram system freely available together user manual tutorial background material system used linux windows mac os x currently unmaintained version 2 intended implement observational type theory never officially released however exists github mirror last updated 2012 design epigram epigram 2 inspired development systems agda idris coq epigram uses two-dimensional natural deduction style syntax latex version ascii version examples epigram tutorial following declaration defines natural numbers declaration says codice_1 type kind codice_2 i.e. simple type two constructors codice_3 codice_4 constructor codice_4 takes single codice_1 argument returns codice_1 equivalent haskell declaration codice_8 latex code displayed formula_1 horizontal-line notation read assuming top true infer bottom true example assuming codice_9 type codice_1 codice_11 type codice_1 nothing top bottom statement always true codice_3 type codice_1 cases formula_2 formula_3 formula_4 ... ascii ... ascii epigram essentially typed lambda calculus generalized algebraic data type extensions except two extensions first types first-class entities type formula_5 types arbitrary expressions type formula_5 type equivalence defined terms types normal forms second dependent function type instead formula_7 formula_8 formula_9 bound formula_10 value function argument type formula_11 eventually takes full dependent types implemented epigram powerful abstraction unlike dependent ml value depended upon may valid type sample new formal specification capabilities dependent types bring may found epigram tutorial
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Programming language topics
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erik laykin erik laykin born 1964 los angeles california computer forensics expert cyber-crime investigator erik laykin past president pacific rim director l.a. fbi infragard program well chairman advisory board ec-council electronic commerce council laykin served expert witness court technology investigations co-founder online security inc. charlie balot mid-1990s established initial computer forensic capabilities behalf american investigative agencies kroll inc. investigative group international pinkerton investigations established first commercial computer forensic labs los angeles chicago hong kong catering legal corporate community director navigant consulting inc. nyse nci 2004 2008 established information technology investigations practice worked noted industry leaders jennifer baker james gordon managing director duff phelps llc 2008 co-practice chair global electronic discovery investigations practice led data forensics ediscovery investigative team 2009–2010 behalf court-appointed lehman brothers bankruptcy examiner anton valukis chairman jenner block whose extensive report brought light lehman brothers usage repo 105 laykin appointed california insurance commissioner gubernatorial candidate steve poizner california department insurance anti-fraud task force chaired technology committee laykin featured 2010 history channel e network series partners crime episode control-alt-delete highlighted number high tech investigations asia program syndicated crime investigation network south east asia throughout asia laykin featured 2013 smithsonian channel series forensic firsts catching criminals chronicles variety investigations utilize forensic sciences legal selected laykin one 50 top global digital forensic experts 2014,2015 2016 calling authority e-discovery digital forensics laykin contributing author life death dotcom china published asia law practice 2000 laykin book investigative computer forensics published john wiley sons 2013
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Computer security
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michael tiemann michael tiemann vice president open source affairs red hat inc. former president open source initiative chief technical officer red hat served number boards including embedded linux consortium gnome foundation advisory board board directors activestate tool corp also co-owner amy tiemann manifold recording studios co-founded cygnus solutions 1989 programming contributions free software include authorship gnu c++ compiler work gnu c compiler gnu debugger tiemann featured 2001 documentary revolution os opensource.com profiled 2014 calling one open source great explainers earned bachelor degree moore school electrical engineering 1986 university pennsylvania
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Operating systems
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dynamorio dynamorio bsd licensed dynamic binary instrumentation framework development dynamic program analysis tools dynamorio targets user space applications android linux windows operating systems running aarch32 ia-32 x86-64 instruction set architectures dynamorio originally created dynamic binary optimization system since used security debugging analysis tools dynamorio originated collaboration hewlett-packard dynamo optimization system runtime introspection optimization rio research group mit hence combined name dynamorio first released publicly proprietary binary toolkit june 2002 later open-sourced bsd license january 2009 dynamorio process virtual machine redirects program execution original binary code copy code instrumentation carries actions desired tool added copy changes made original program need specially prepared way dynamorio operates completely run time handles legacy code dynamically loaded libraries dynamically generated code self-modifying code dynamorio monitors control flow capture entire execution target program monitoring adds overhead even tool present dynamorio average overhead 11 percent dynamorio api abstracts away details virtualization process focuses monitoring modifying dynamic code stream program tool insert trampolines program invoke tool actions specific program points tool also insert instrumentation assembly language level provides fine-grained control tool actions tool performance dynamorio supports adaptive optimization adaptive instrumentation allowing tool remove modify instrumentation point throughout execution target program dynamorio invokes tool-registered callbacks number common program event points thread creation library loading system calls signals exceptions api also allows inspecting program libraries address space addition code dynamorio api event callbacks designed cross-platform enabling tool code operate windows linux ia-32 x86-64 dynamorio ensures tool transparency isolating tool resources stack memory file accesses program upon tool operating dynamorio contains libraries extend api provide symbol table access function wrapping replacing memory address tracing utilities first tools built dynamorio focused dynamic optimization number research tools built variety purposes including taint checking profiling applying dynamorio security field resulted technique called program shepherding program shepherding instrumentation monitors origin program instruction control flow instructions order prevent security exploit taking control program 2003 program shepherding commercialized brand-named memory firewall host intrusion prevention software startup company called determina determina acquired vmware august 2007 dr. memory open-source memory debugger built dynamorio released lgpl license dr. memory monitors memory allocations memory accesses using shadow memory detects memory-related programming errors accesses uninitialized memory accesses freed memory heap overflow underflow memory leaks feature set similar valgrind-based memcheck tool though operates windows well linux twice fast memcheck
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Operating systems
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access register ibm terminology access registers hardware registers processor work conjunction general purpose registers giving address space access data spaces address spaces order retrieve data ars introduced mvs/esa
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Operating systems
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workday inc. workday inc. on‑demand cloud-based financial management human capital management software vendor founded david duffield founder former ceo erp company peoplesoft former peoplesoft chief strategist aneel bhusri following oracle hostile takeover peoplesoft 2005 october 2012 launched successful initial public offering valued company 9.5 billion workday founded march 2005 launched november 2006 initially funded duffield venture capital firm greylock partners december 2008 workday moved headquarters walnut creek california pleasanton california peoplesoft founder duffield prior company located february 6 2008 workday announced reached definitive agreement purchase cape clear software may 2008 workday signed large contract flextronics provide human capital management software services large multinational companies publicly disclosed contracts deployments workday include aviva chiquita brands cae inc. fairchild semiconductor rentokil initial thomson reuters time warner april 29 2009 workday announced secured 75 million funding led new enterprise associates existing investors greylock partners workday ceo co‑founder dave duffield also participated round october 24 2011 workday announced 85 million new funding bringing total capital raised 250 million investors latest round included t. rowe price morgan stanley investment management janus bezos expeditions personal investment entity amazon ceo founder jeff bezos spring 2012 workday 310 customers ranging mid-sized businesses fortune 500 companies october 2012 workday launched initial public offering ipo new york stock exchange ticker symbol wday shares priced 28 ended trading friday october 12 48.69 propelled start-up market capitalization nearly 9.5 billion including unexercised stock options sold 22.75 million class shares raising 637 million ipo raised cash launch u.s. technology sector since facebook 16 billion ipo may 2012 shares surged 74 ipo underscoring investor interest cloud computing ceo workday aneel bhusri partner greylock partners handled senior leadership positions earlier career peoplesoft dave duffield serves chairman board workday makes money selling subscriptions services rather selling software outright expenses booked front signs new customer associated revenue recognized life multiyear agreements first quarter 2016 workday announced annual revenue excess 1 billion first time ever fiscal year 2016 duffield holds voting rights workday shares worth 3.4 billion bhusri held rights shares valued 1.3 billion collectively hold 67 company voting shares voting structure makes event hostile takeover much less likely workday released 32 updates product line march 2019 releases major update every 6 months every september march workday adopted ibm cloud primary development testing platform order accelerate worldwide expansion february 2014 workday acquired startup identified artificial intelligence syman create insight apps line products first products running syman announced workday rising 2014 july 2017 workday ceo aneel bhusri announced company decided open platform developers partners third party software result workday enter platform service paas market bhusri said move allow customers build custom extensions applications work workday january 2018 workday announced acquired skipflag makers ai knowledge base builds company internal communications 2013 workday participated round funding big data analytics platform datameer 2014 workday also participated anaplan 100m funding 2017 workday participated duo security 70m funding
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Distributed computing architecture
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bonjour sleep proxy apple bonjour sleep proxy service open source component zero configuration networking designed assist reducing power consumption networked electronic devices device acting sleep proxy server respond multicast dns queries another compatible device gone low power mode low-power-mode device remains asleep sleep proxy server responds multicast dns queries sleep proxy server sees query requires low-power-mode device wake sleep proxy server sends special wake-up-packet magic packet low-power-mode device finally communication parameters updated via multicast dns normal communications proceed apple inc. describes service bonjour sleep proxy support documents service supports wake demand feature first offered mac os x snow leopard sleep proxy service responds address resolution protocol requests behalf low-power-mode device sleep proxy sees ipv4 arp ipv6 nd request one sleeping device addresses answers behalf sleeping device without waking giving mac address current temporary owner address may appear confusing network administrators expecting behaviour changing mac addresses case low-power-mode device communicating via wi-fi wake-up-packet sent via wireless multimedia extensions wmm possible previous implementations wake lan wol wireless hardware must updated enough include wmm support apple provides instructions checking compatibility feature macintosh computers sleep proxy service able advertise bonjour-supported services host computer sleeps examples supported services stuart cheshire page describing steps troubleshooting sleep proxy service implementations local area network seen bonjour browser
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Internet protocols
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demolinux demolinux one first live cd linux distributions created roberto di cosmo vincent balat jean-vincent loddo 1998 demolinux cd created make possible use linux without install hard disk first linux live cd making possible use system graphic mode without stage configuration many live cd linux distributions today one consider demolinux ancestor knoppix demolinux offered users hundreds applications among kde staroffice thanks compressed file system cd could used without modification hard disk user possibility use transparent way space disc store personal data even install new applications using standard tools base distribution version 1 based mandrake linux mandriva linux versions 2 3 used mechanism independent distribution distributed mainly debian basis last versions made possible moreover install linux hard disk thus offering simple installation procedure debian principle used today linux distributions demolinux distributed many computer magazines several countries still downloadable official website evolved since 2002
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Operating systems
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macintosh portable macintosh portable portable computer designed manufactured sold apple computer inc. september 1989 october 1991 first battery-powered macintosh garnered significant excitement critics sales customers quite low featured fast sharp expensive black white active matrix lcd screen hinged design covered keyboard machine use portable one early consumer laptops employ active matrix panel expensive initial powerbook line powerbook 170 used one due high cost cursor pointing function handled built-in trackball could removed located either side keyboard used expensive sram effort maximize battery life provide instant low power sleep mode machine designed deliver high performance cost price weight unlike later portable computers apple manufacturers battery wired series ac power supply possible alternative direct connection ac supply flat battery meant computer could operated original power supply low output several popular unauthorized workarounds devised including use power supply powerbook 100 series provides higher output automotive batteries sealed lead acid cells used portable failed fully discharged batteries longer manufactured rare find original battery hold charge allow computer start possible repack battery new cells use alternative 6 v batteries three lead-acid cells inside battery manufactured gates energy products enersys also used quantum 1 battery packs photographic flash use despite dramatic improvement terms ergonomics offered responsiveness sharpness uniformity active matrix panel one drawbacks portable poor readability low light situations consequently february 1991 apple introduced backlit macintosh portable model m5126 along new screen apple changed sram memory less expensive power-hungry pseudo-sram reduced total ram expansion 8 mb lowered price backlight feature welcomed improvement unfortunately reduced battery life half upgrade kit also offered earlier model well plugged rom expansion slot portable discontinued october 1991 addition 16 pounds 7.2 kilograms 4 inches 10 centimetres thick portable heavy bulky portable computer main contributor weight bulk portable lead-acid batteries three drive configurations available macintosh portable one floppy drive two floppy drives hard drive floppy drive floppy drive macintosh portable 1.44 mb macintosh portable units came hard drive custom-engineered conner cp-3045 known apple hard disk 40sc holds 40 mb data consumes less power compared hard drives time proprietary scsi connector adapters allow standard scsi drives used portable exist expensive macintosh portable powerbook 100 run macintosh system 6.0.4 system 7.5.5 may 2006 pc world rated macintosh portable seventeenth worst tech product time contrast macuser magazine noted machine tended remain relevant therefore tended long usage lifespan bought reducing total cost ownership
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Computer architecture
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extensible user interface protocol extensible user interface protocol xup proposed web standard xup soap-based protocol communicating events user interface user interface described xml document specification limit format xml document event model used communicating xup examples given specification possible user interface languages include xhtml wireless markup language xul xup specification submitted world wide web consortium w3c consortium member martsoft corporation march 2002. w3c note meaning w3c committed developing standard potential recommendation hosted informational purposes
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Web technology
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spatialite spatialite spatial extension sqlite providing vector geodatabase functionality similar postgis oracle spatial sql server spatial extensions although sqlite/spatialite n't based client-server architecture adopt simpler personal architecture i.e whole sql engine directly embedded within application complete database simply ordinary file freely copied even deleted transferred one computer/os different one without special precaution spatialite extends sqlite existing spatial support cover ogc sfs specification n't necessary use spatialite manage spatial data sqlite implementation r-tree indexes geometry types spatialite needed advanced spatial queries support multiple map projections spatialite provided natively linux windows software library well several utilities incorporate spatialite library utilities include command line tools extend sqlite spatial macros graphical gui manipulating spatialite databases data simple desktop gis tool browsing data single binary file spatialite also used gis vector format exchange geospatial data spatialite supports several open standards ogc listed reference implementation proposed geopackage standard
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Databases
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gno/me gno multitasking environment also known gno/me gno short unix-like operating system apple iigs computer developed procyon enterprises sold commercially 1991 august 1996 released freeware development continued devin reade released current version 2.0.6 15 february 1999 source code since released via github. ref name= gno/me source /ref
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Operating systems
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