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fork system call computing particularly context unix operating system workalikes fork operation whereby process creates copy usually system call implemented kernel fork primary historically method process creation unix-like operating systems multitasking operating systems processes running programs need way create new processes e.g run programs fork variants typically way unix-like systems process start execution different program first forks create copy copy called child process calls exec system call overlay program ceases execution former program favor fork operation creates separate address space child child process exact copy memory segments parent process modern unix variants follow virtual memory model sunos-4.0 copy-on-write semantics implemented physical memory need actually copied instead virtual memory pages processes may refer pages physical memory one writes page copied optimization important common case fork used conjunction exec execute new program typically child process performs small set actions ceases execution program favour program started requires parent data structures process calls fork deemed parent process newly created process child fork processes run program resume execution though called system call inspect call return value determine status child parent act accordingly one earliest references fork concept appeared multiprocessor system design melvin conway published 1962 conway paper motivated implementation l. peter deutsch fork genie time-sharing system concept borrowed ken thompson earliest appearance research unix fork later became standard interface posix child process starts copy parent file descriptors interprocess communication parent process often create pipe several pipes forking processes close ends pipes n't need vfork variant fork calling convention much semantics used restricted situations originated 3bsd version unix first unix support virtual memory standardized posix permitted vfork exactly behavior fork marked obsolescent 2004 edition replaced posix_spawn typically implemented via vfork subsequent editions vfork system call issued parent process suspended child process either completed execution replaced new executable image via one exec family system calls child borrows mmu setup parent memory pages shared among parent child process copying done particular copy-on-write semantics hence child process makes modification shared pages new page created modified pages visible parent process since absolutely page copying involved consuming additional memory technique optimization plain fork full-copy environments used exec posix using vfork purpose except prelude immediate call function exec family select operations gives rise undefined behavior vfork child borrows data structures rather copying vfork still faster fork uses copy write semantics system v support function call system vr4 introduced memory sharing causes error-prone similarly linux man page vfork strongly discourages use problems include deadlocks might occur multi-threaded programs due interactions dynamic linking replacement interface posix introduced family functions combine actions fork exec functions may implemented library routines terms done linux terms better performance done solaris posix specification notes designed kernel operations especially operating systems running constrained hardware real-time systems 4.4bsd implementation got rid vfork implementation causing vfork behavior fork later reinstated netbsd operating system performance reasons embedded operating systems uclinux omit fork implement vfork need operate devices copy-on-write impossible implement due lack mmu plan 9 operating system created designers unix includes fork also variant called rfork permits fine-grained sharing resources parent child processes including address space except stack segment unique process environment variables filesystem namespace makes unified interface creation processes threads within freebsd irix adopted rfork system call plan 9 latter renaming sproc clone system call linux kernel creates child process may share parts execution context parent like freebsd rfork irix sproc linux clone inspired plan 9 rfork used implement threads though application programmers typically use higher-level interface pthreads implemented top clone separate stacks feature plan 9 irix omitted according linus torvalds causes much overhead original design vms operating system 1977 copy operation subsequent mutation content specific addresses new process forking considered risky errors current process state may copied child process metaphor process spawning used component memory layout new process newly constructed scratch spawn metaphor later adopted microsoft operating systems 1993 posix-compatibility component vm/cms openextensions provides limited implementation fork parent suspended child executes child parent share address space essentially vfork labelled fork note applies cms guest operating system vm guest operating systems linux provide standard fork functionality following variant hello world program demonstrates mechanics system call c programming language program forks two processes deciding functionality perform based return value fork system call boilerplate code header inclusions omitted follows dissection program first statement calls system call split execution two processes return value recorded variable type posix type process identifiers pids minus one indicates error new process created error message printed successful two processes executing function point returned make processes perform different tasks program must branch return value determine whether executing child process parent process child process return value appears zero invalid process identifier child process prints desired greeting message exits technical reasons posix function must used instead c standard function process parent receives process identifier child always positive number parent process passes identifier system call suspend execution child exited happened parent resumes execution exits means statement
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Computer architecture
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moab cluster suite moab cluster suite cluster workload management package available adaptive computing inc. integrates scheduling managing monitoring reporting cluster workloads moab cluster suite simplifies unifies management across one multiple hardware operating system storage network license resource manager environments moab development based open source maui cluster scheduler job scheduling package maui associated maui scheduler molokini edition developed project sourceforge site independent original maui scheduler moab feature set expanded greatly since divergence maui many new capabilities comparison list available adaptive computing enterprises inc. site
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Distributed computing architecture
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kernel marker kernel markers static kernel instrumentation support mechanism linux kernel source code allowing special tools lttng systemtap trace information exposed probe points kernel markers declared kernel code one-liners form name marker unique name format_string describes remaining arguments types marker depending whether probe connected code wants hook trace point first calls register probe callback marker point pdata private data value code wants pass probe later probe turned using using markers negligible overhead thanks part immediate values another support mechanism embeds switches code dynamically turned without using memory reference thus saving cache lines initial motivation create static instrumentation infrastructure large performance overhead induced predating dynamic instrumentation mechanism kprobe mechanism depends breakpoints static instrumentation also easily survive source code changes markers source code kernel markers consisted essentially c preprocessing macro added instrumented function branch function call neither stack setup function call executed instrumentation enabled identifying branch executing stack setup function call unlikely using gcc built-in expect hint given compiler position tracing instructions away cache lines involved standard kernel execution two kernel markers drawbacks identified led replacement tracepoints patch-set implementing merged version 2.6.24 released january 24 2008 address issues regarding kernel markers mathieu desnoyers original author implemented simpler type-safe version static probe points named tracepoints patch-set implementing tracepoints merged version 2.6.28 released december 25 2008 starting kernel markers slowly removed kernel sources eventually fully removed linux kernel 2.6.32 released december 3 2009
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Operating systems
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lr-attributed grammar lr-attributed grammars special type attribute grammars allow attributes evaluated lr parsing result attribute evaluation lr-attributed grammars incorporated conveniently bottom-up parsing zyacc based lr-attributed grammars subset l-attributed grammars attributes evaluated one left-to-right traversal abstract syntax tree superset s-attributed grammars allow synthesized attributes yacc common hack use global variables simulate kind inherited attributes thus lr-attribution
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Programming language topics
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spy sweeper spy sweeper software product detects removes spyware viruses optional anti-virus component installed personal computers microsoft windows webroot software webroot discontinued support spy sweeper 12/31/2012 spy sweeper examines files computer hard disk drive well objects memory windows registry cookies quarantines suspicious objects finds normally purchased yearly subscription broadband services msn premium also offer rebranded versions spy sweeper part subscription webroot offers two versions spy sweeper zero-cost 'spy scan offering real-time protection spyware full version allows removal spyware licenses full version cost around us 30 used one year one computer 40 two years webroot also sells multiple-license subscriptions allowing users install product multiple computers using single subscription purchasing either single-user three-machine enterprise licenses kevin thomas identical twin brother steven thomas founder webroot software invented idea spy sweeper behind scenes kevin thomas richard koontz webroots ace programmer worked hard developing spy sweeper despite odds ceo time david moll richard working home hours finished spy sweeper initial version finally released september 2004 time neither kevin thomas richard koontz ever received credit invention spy sweeper october 2006 webroot released spy sweeper antivirus includes removal protection computer viruses anti-virus component based anti-virus product made software vendor sophos june 2007 version 5.5 released included ability scan email attachments improved user interface windows 2000 users upgrade v5.5 october 2008 version 6.0 released product many awards press first anti-spyware product receive checkmark certification testing company west coast labs also received editor choice award pc magazine best buy award pc world spy sweeper known webroot secure anywhere
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Computer security
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hp touchpad hp touchpad tablet computer developed designed hewlett-packard hp touchpad launched july 1 2011 united states july 15 canada united kingdom france germany august 15 australia august 18 2011 49 days touchpad launched united states hp announced would discontinue current devices running webos remaining touchpad stock received substantial price reductions quickly sold hp touchpad announced february 9 2011 webos think beyond event held fort mason center san francisco alongside hp veer hp pre 3 initial sales device sold 25,000 270,000 units meet hp expectations rapidly becoming overshadowed launch ipad 2 march august 16 2011 reported best buy refused pay hp touchpad stock europe touchpad estimated sold 12,000 first month release australia harvey norman exclusive retailer sold 1,200 units four days sale industry commentators suggested lack apps platform lackluster advertising hindering sales august 18 hp announced would discontinue webos devices hp cto shane robison noted touchpad half generation generation behind ipad n't going drive volume years later member development team described device made cast-off reject ipad parts august 19 2011 hp announced substantial price drop touchpad canada usa price 99 16gb model 149 32gb model quickly sold large numbers buyers acquired touchpad firesale prices brick-and-mortar retailers reportedly sold entire inventories within hours morning august 20 online retailers including barnes noble amazon.com best buy took orders august 22 rapidly exceeded inventory forced cancel many orders similar sale held australian harvey norman stores several stores selling inventory within hour similar sales took place uk several stores reducing prices £89 16gb £115 32gb hp touchpad became tablet highest approval rating hp touchpad stock immediately sold domestically overseas consumers rushing take advantage price promotion following successful sale clear component suppliers inventories touch panels batteries chassis hp announced august 30 would make another production run touchpad units used fulfill existing orders businesses like tiger direct best buy bundles set price 249.99 299.99 following meg whitman appointment ceo hp conjunction announcement company plans continue developing webos open-source operating system said company would continue using os devices specifically resuming use tablets said would happen 2012 would probably take place 2013 february 2013 hp sold source code transferred remaining webos team lg effectively ending webos deployment tablets consumer products hp touchpad touchscreen tablet runs hp webos several notable features touchpad uses card multitasking found palm pre phones integrated webcam front hp touchpad enables video conferencing backlit home button bottom hp touchpad also allows haptic feedback vibration function hardware includes arm-based qualcomm snapdragon processor 1gb ram touch share allows pre 3 mobile share information websites touching sensors touchpad sensors touchpad receive calls text messages forwarded phone using palm profile well make receive calls via skype application independent site estimated 16gb 32gb hp touchpad contained 296.15 318.15 materials respectively cost assemble 10 hp touchpad 9.7 inch 1024×768 pixel gorilla glass multitouch capacitive touch screen interaction finger capacitive stylus available separate purchase touchpad virtual keyboard configured one four preset sizes number row top common qwerty layout touchpad also features invensense 3-axis gyroscope touchpad three separate physical buttons sleep/wake button top right home button bottom front launches card view app launcher set volume rockers right device holding power button home button together creates screen snapshot touchpad stereo speakers feature beats audio atheros ar6003 chipset supports dual band 2.4 ghz 5 ghz wi-fi 802.11a/b/g/n bluetooth 2.1 edr a2dp stereo bluetooth tablet share urls phone calls text messages webos phones via bluetooth pairing pairing non-webos smartphones enabled software update 3.0.4 touchpad uses rechargeable 6000 6300 mah lithium-ion polymer battery rated 3,7 v total 22,2 wh charged via microusb connector optional wireless charging touchstone charger using touchstone touchpad enters mode called exhibition mode displays simple information clock schedule media battery life estimated nine hours hp review engadget battery lasted eight half hours july 2011 hp announced webos hardware roadmap included hp touchpad 4g faster 1.5 ghz processor 32 gb flash memory integrated a-gps 3.5g hspa+ wireless mobile broadband capabilities demo models displayed press show released sale except hp employees later appeared ebay craigslist august white model 64 gb flash memory 1.5 ghz processor wi-fi – without 3.5g – built small quantities shipped small number touchpad go models codenamed opal 7-inch display 32 gb flash memory 1.5-ghz processor cellular capabilities made sent technology review websites smaller touchpads however mass-produced overall inspiration later carried hp slate 7 touchpad sold webos operating system offers video chat wireless printing hp printers email integration ebooks web browsing document editing access hp catalog additional apps downloaded webos card-based multitasking environment open applications arranged stacks webos unobtrusively notifies users messages emails calendar agenda items appearing top right screen rapidly reviewed swipe gesture webos 3.0 integrates adobe flash last updated version 3.0.5 january 12 2012 hp supports funding new open source project webos scalability easy app development base attracts developers open source webos provides standardized java development tools build port apps webos rapidly open webos released hp directly work touchpad due proprietary code hp however released open source webos community edition use touchpad october 6 2011 reported customers received new touchpads android installed instead webos hp investigating unofficial release commented october 22 2011 android 2.3 gingerbread alpha version became available touchpad port based cyanogenmod enhanced distribution android allows touchpad run android apps natively android port touchpad replace webos provides multi-boot touchpad owners start tablets android webos oss android 3.0 'honeycomb ported touchpad source code publicly available january 17 2012 port android 4.0 ice cream sandwich based cyanogenmod 9 became available preliminary alpha build alpha 0 features including hardware-accelerated video playback microphone camera functional time updated alpha 0.5 around january 24 2012 alpha 0.6 around january 30 2012 bringing fixes stability improvements february 2 2012 hp released source code android 2.3 hp touchpad cyanogenmod team received source code hp started working touchpad tablet port phonenews.com reported android kernel based qualcomm ’ reference android source code used hp internally accelerate release touchpad never intended public use rather ensure touchpad ’ hardware would ready release consumers alongside webos 3 webos 3 lagging behind hardware development android also used manufacturing lines test touchpads ultimately flashed webos cyanogenmod 9 cm9 based android 4.0.4 official stable builds features working also unofficial cm10 cm10.1 cm10.2 cm11 based builds features working cm11 builds stability daily use dependent kernel used development kernels based linux 3.0 3.4 proceeding rom based 3.4 kernel unstable may features missing rom based 3.0 kernel generally stable android 5.0 works touchpad although sluggish android 7.0 nougat made available september 2016 via evervolv android open source project aosp rom authored flintman nearly feature complete usable runs better 5.1 android 7.1.1 nougat made available around december 2016 via evervolv authored flintman well second option lineageos authored invisiblek android 9.0 pie made available april 2019 via evervolv android open source project aosp rom linux distributions compiled arm architecture successfully run via chroot also x11 windowing system common many linux systems ported run within webos allows graphical applications made linux run webos port ubuntu run natively touchpad development january 2012 boots via moboot multiboot bootloader using method android port port early alpha stage functional development ended 2012 addition ubuntu alpha port arch linux arm january 2012 provides full touchscreen support gnome 3 lxde wi-fi access bluetooth camera sound installed using previously mentioned moboot method luneos linux-based operating system designed specifically native execution touch devices touchstone wireless charging dock charging touchstone touchpad set exhibition mode allowing user choose display photos digital photo frame upcoming appointments clock items using third party extensions touchstone also enables wireless communication hp pre3 touchpad tapping specific region transfer web links pre technology known “ touch share ” touchstone usb power cable attached usb standard-a plug end must plugged high-power usb power adapter hp touchpad power adapter newer high-current usb adapter hp shows warning user manual plug laptop north america touchstone ships ac power adapter included touchpad bluetooth wireless keyboard typical qwerty layout plus additional keys special touchpad capabilities power slide switch bottom two aa batteries required special touchpad keys power card view cursor left/up/right/down volume +/- mute brightness +/- fast forward play-pause rewind show virtual keyboard show type show notifications keyboard pair bluetooth devices key functions may missing keyboard layout outside alpha numeric keys specific touchpad power adapter converts wall ac usb dc accessory contains following items touchpad adapter cable touchstone adapter-only ships accessory protective case doubles stand watching videos typing holes edges case access microusb connector 3.5 mm jack connector internal microphone folded open opening speaker along binding edge case raised surface power volume buttons easily found touchpad charge case using either microusb cable touchstone dock early reviews hp touchpad mixed david pogue new york times wrote works beautifully conveys far information ipad 2 tablet offers real multitasking open apps always running jason chen gizmodo wrote actually holding touchpad say deceptively heavy around weight ipad 'd think would lighter back made plastic said overly heavy heavier 'd think looking matt buchanan also writing gizmodo praised os interface concept 'good conceptually described performance slow motion ... give thing six months could amazing well guess says everything needs said verge also noted poor performance describing interface 'intuitive natural 'sluggish unfinished ... bit hard sell right due firesale touchpad hp led non-apple tablets sold us 2011 december 2011 hp touchpad second desired tablet 5 percent share tablet sales estimated 903,354 devices sold hp touchpad firesale effect future android tablet sales low pricing scheme compared ipad used kindle fire nexus 7 commercially successful android tablets originally priced 199
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Operating systems
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mobile operating system mobile operating system mobile os operating system phones tablets smartwatches mobile devices computers typical laptops 'mobile operating systems usually used considered mobile ones originally designed desktop computers historically need specific mobile features distinction becoming blurred newer operating systems hybrids made uses mobile operating systems combine features personal computer operating system features useful mobile handheld use usually including following considered essential modern mobile systems wireless inbuilt modem sim tray telephony data connection touchscreen cellular bluetooth wi-fi protected access wi-fi global positioning system gps mobile navigation video- single-frame picture cameras speech recognition voice recorder music player near field communication infrared blaster q1 2018 383 million smartphones sold 86.2 percent running android 12.9 percent running ios android alone popular popular desktop operating system windows general smartphone use even without tablets outnumber desktop use mobile devices mobile communications abilities e.g. smartphones contain two mobile operating systemsthe main user-facing software platform supplemented second low-level proprietary real-time operating system operates radio hardware research shown low-level systems may contain range security vulnerabilities permitting malicious base stations gain high levels control mobile device mobile operating systems majority use since 2017 measured web use even smartphones running excluding tablets used kind device thus traditional desktop os minority used kind os see usage share operating systems however variations occur popularity regions desktop-minority also applies days regions united states united kingdom mobile operating system milestones mirror development mobile phones smartphones operating systems often run atop baseband real time operating systems handle hardware aspects phone android based modified linux kernel mobile operating system developed google inc besides largest installed base worldwide smartphones also popular operating system general purpose computers category includes desktop computers mobile devices even though android popular operating system regular desktop personal computers pcs although android operating system free open-source software devices sold much software bundled including google apps vendor-installed software proprietary software closed source android releases 2.0 1.0 1.5 1.6 used exclusively mobile phones android 2.x releases mostly used mobile phones also tablets android 3.0 tablet-oriented release officially run mobile phones phone tablet compatibility merged android 4.0 current android version 9.0 pie android releases named sweets dessert items except first second releases android one software experience runs unmodified android operating system closely resembles running pixel devices previously google nexus program unlike stock androids running market android one ui closely resembles pixel ui due android one software experience developed google distributed partners signup program nokia xiaomi thus overall ui intended clean possible oem partners may tweak add additional apps cameras firmware otherwise apps handled google proprietary apps update handled google internally tested oem distributed via ota update end users designed alibaba based android amazfit os mobile operating system based android develop xiaomi backed huami higher-end amazfit series smartwatch amazfit pace verge stratos due android based operating system therefore side loaded android apk file run smartwatch similar miui although amazfit os based open source aosp consists closed source proprietary software blackberry secure operating system developed blackberry based android open source project aosp officially announced name android based front-end touch interface august 2017 announcement blackberry secure running blackberry brand devices blackberry priv dtek 50/60 blackberry keyone currently blackberry plan license blackberry secure oem coloros custom front-end touch interface based android open source project aosp developed oppo electronics corp. oppo officially releases coloros every oppo device released official rom oneplus one emotion user interface emui front-end touch interface developed huawei technologies co. ltd. based google android open source project aosp emui preinstalled huawei honor devices based open source android operating system consists closed source proprietary software /e/ operating system forked source code lineageos based android supports currently 76 devices april 2019 /e/ targets android smart phone devices uses microg replacement google play services flyme os operating system developed meizu technology co. ltd. open source os based google android open source project aosp flyme os mainly installed meizu smartphones mx series however also official rom support android devices funtouch os fork android developed vivo funtouch os difference traditional android ui funtouch os includes features unavailable former customizable gestures communication drawer bottom top swipe security centre lock screen resize options long screen shot eye protection changing warmer color temperature others funtouch os respects looks similar ios made apple grapheneos formerly named android hardening variant android runs pixel 2 pixel 3 hardware mainly developed daniel micay aims focus security privacy htc sense software suite developed htc used primarily company android-based devices serving successor htc touchflo 3d software windows mobile sense modifies many aspects android user experience incorporating added features altered home screen keyboard widgets htc-developed applications redesigned applications first device sense htc hero released 2009 indus os custom mobile operating system based android open source project aosp developed indus os team based india longer valid 2018indus os available micromax intex karbonn indian smartphone brands lg ux formerly named optimus ui front-end touch interface developed lg electronics partners featuring full touch user interface sometimes incorrectly identified operating system lg ux used internally lg sophisticated feature phones tablet computers available licensing external parties optimus ui 2 based android 4.1.2 released optimus k ii optimus neo 3 features refined user interface compared prior version based android 4.1.1 would include together new functionality voice shutter quick memo lineage android distribution custom mobile operating system based android open source project aosp serves successor highly popular custom rom cyanogenmod forked december 2016 cyanogen inc. announced discontinuing development shut infrastructure behind project since cyanogen inc. retained rights cyanogen name project rebranded fork lineageos similar cyanogenmod include proprietary apps unless user installs allows android users longer obtain update support manufacturer continue updating os version latest one based official release google aosp heavy theme customization mifavor custom android ui developed zte smartphone running android platform similar android ui mifavor replace stock apps zte owns apps however ux still closely similar stock android mi user interface miui developed chinese electronic company xiaomi inc. mobile operating system based android open source project aosp miui mostly found xiaomi smartphones mi redmi series however also official rom support android devices although miui based aosp open source consists closed source proprietary software miui poco custom mobile operating system based miui based android open source project aosp like predecessor also develop xiaomi inc unlike original miui miui poco specifically customized poco series smartphone including difference ui frequent update compare original miui like miui based open source aosp miui poco also consists closed source proprietary software oxygenos based open source android open source project aosp developed oneplus replace cyanogen os oneplus devices oneplus one preinstalled oneplus 2 oneplus x oneplus 3 oneplus 3t oneplus 5 oneplus 5t oneplus 6 stated oneplus oxygenos focused stabilizing maintaining stock like found nexus devices consists mainly google apps minor ui customization maintain sleekness pure android pixel ui developed google based open source android unlike nexus phones google shipped stock android ui came first generation pixel phones slightly modified compared stock android part google pixel software pixel ui home launcher closed source proprietary thus available pixel family devices however third party mods allow non pixel smartphones install pixel launcher google feed integration replicant custom mobile operating system based android proprietary drivers bloat closed source software removed samsung experience formerly called touchwiz front-end touch interface developed samsung electronics partners featuring full touch user interface sometimes incorrectly identified independent operating system samsung experience used internally samsung smartphones feature phones tablet computers available licensing external parties closed source proprietary android version samsung experience also comes samsung-made apps preloaded except starting galaxy s6 removed samsung pre-loaded apps installed leaving one galaxy apps save storage space initially due removal microsd release samsung galaxy s8 s8+ samsung experience 8.1 preinstall introducing new function known samsung dex similar concept microsoft continuum samsung dex allowed high end galaxy devices s8/s8+ note 8 connect docking station extends functionality allow desktop-like functionality connecting keyboard mouse monitor samsung also announced linux galaxy allows use standard linux distribution dex platform sony xperia ui formerly known timescape ui front-end ui developed sony mobile formerly sony ericsson sony xperia series running android platform sony xperia ui mostly consists sony application sony music formerly known walkman music player albums video player time timescape ui ui different standard android ui instead traditional apps dock bottom part located four corner home screen middle screen consist widget however recent development ui closely resemble stock android zenui front-end touch interface developed asus partners featuring full touch user interface zenui used asus android phones tablet computers available licensing external parties zenui also comes preloaded asus-made apps like zenlink pc link share link party link remote link non-android operating systems listed following sections chrome os operating system designed google based linux kernel uses google chrome web browser principal user interface result chrome os primarily supports web applications google announced project july 2009 conceiving operating system applications user data reside cloud hence chrome os primarily runs web applications due increase popularity 2 1 pcs recent chromebooks introduced touch screen capability android applications starting become available operating system 2014 2016 access android apps entire google play store introduced supported chrome os devices support android applications chromebook devices positioned tablet based instead notebooks chrome os available pre-installed hardware google manufacturing partners open source equivalent chromium os compiled downloaded source code early google provided design goals chrome os otherwise released technical description fuchsia capability-based real-time operating system rtos currently developed google first discovered mysterious code post github august 2016 without official announcement contrast prior google-developed operating systems chrome os android based linux kernels fuchsia based new microkernel called zircon derived little kernel small operating system intended embedded systems upon inspection media outlets noted code post github suggested fuchsia capability run universal devices embedded systems smartphones tablets personal computers may 2017 fuchsia updated user interface along developer writing project experimental prompting media speculation google intentions operating system including possibility replacing android liteos lightweight open source real-time operating system part huawei 1+2+1 internet things solution similar google android things samsung tizen huawei liteos features lightweight low-power fast-response multi-sensor collaboration multi-protocol interconnect connectivity enabling iot terminals quickly access network huawei liteos make intelligent hardware development easier thereby accelerating realization interconnection things currently liteos introduce consumer market huawei watch gt series smartbands current liteos version list pureos debian gnu/linux derivative using free software developed purism already used purism laptops planned use librem 5 smartphone purism partnership gnome kde aims separate cpu baseband processor include hardware kill switches phone wi-fi bluetooth camera microphone baseband processor provide gnome kde plasma mobile options desktop environment sailfish os jolla open source gnu general public license gpl middleware stack core comes mer sailfish due jolla business model due alliances various partners due intentional design os internals capable adopt several layers third party software including jolla software e.g jolla ui proprietary software closed source components proprietary many different kinds licences however user replace open source components like e.g nemo ui instead jolla ui nokia abandoned 2011 meego project meego team left nokia established jolla company use meego mer business opportunities mer standard allows launched hardware kernel compatible mer 2012 linux sailfish os based meego using middleware mer core stack distribution launched public use first device jolla smartphone unveiled may 20 2013 2015 jolla tablet launched brics countries declared officially supported os jolla started licensing sailfish os 2.0 third parties devices sold updateable sailfish 2.0 limits sailfish os version release named finnish lake tizen based linux kernel mobile operating system hosted linux foundation together support tizen association guided technical steering group composed intel samsung tizen operating system devices including smartphones tablets in-vehicle infotainment ivi devices smart tvs open source system however sdk closed source proprietary aims offer consistent user experience across devices tizen main components linux kernel webkit runtime according intel tizen combines best limo meego html5 apps emphasized meego encouraging members transition tizen stating future belongs html5-based applications outside relatively small percentage apps firmly convinced investment needs shift toward html5 tizen targeted variety platforms handsets touch pc smart tvs in-vehicle entertainment may 17 2013 tizen released version 2.1 code-named nectarine tizen open source ux ui layer developed samsung mainly closed source proprietary touchwiz ui samsung z series smartphone current tizen version list ubuntu touch canonical ltd.. open source uses gpl license ubuntu touch os built using android linux kernel using android drivers services via lxc container use java-like code android desktop environment ubuntu touch planned available one default desktop options librem 5 running pureos operating system though canonical formally announced discontinuing ubuntu mobile os integral component unity8 independent german non-profit ubports community/ foundation paperwork pending local berlin-government decided take project canonical started ubuntu touch based ubuntu 15.04 vivid vervet ubports upgraded base nearest current long-term support version ubuntu 16.04 lts xenial xerus original canonical ubuntu touch version list ubports ubuntu touch version list plasma mobile kde desktop environment mobile phones intended compatible several different mobile phone operating systems including pureos running librem 5 open source mobile operating systems active development include luneos based webos postmarketos based alpine linux gnu/linux distribution maemo leste meizu pro 5 ubuntu edition meizu mx4 ubuntu edition running ubuntu touch necuno using gnu/linux distribution plasma mobile desktop kde proprietary version amazfit os develop xiaomi backed huami amazfit bip smartwatch however instead based android based proprietary operating system thus able install third party apps apks ios formerly named iphone os created apple inc second largest installed base worldwide smartphones largest profits due aggressive price competition android-based manufacturers closed source proprietary built open source darwin operating system iphone ipod touch ipad second third-generation apple tv use ios derived macos native third party applications officially supported release iphone os 2.0 july 11 2008 jailbreaking allowed third party applications installed recent years jailbreaking scene changed drastically due apple continued efforts secure operating system prevent unauthorized modifications currently jailbreaks recent iterations ios semi-untethered requires device re-jailbroken every boot exploits jailbreaks becoming increasingly hard find use currently ios devices developed apple manufactured foxconn another apple partners watchos operating system apple watch developed apple inc based ios operating system many similar features released april 24 2015 along apple watch device runs watchos currently widely used wearable operating system features focus convenience able place phone calls send texts health fitness heart rate tracking current version watchos operating system watchos 5 windows 10 personal computer operating system developed released microsoft part windows nt family operating systems released july 29 2015 like predecessors designed run across multiple microsoft product pcs tablets windows user interface revised handle transitions mouse-oriented interface touchscreen-optimized interface based available input devices—particularly 2-in-1 pcs windows 10 also introduces universal apps expanding metro-style apps apps designed run across multiple microsoft product families nearly identical code—including pcs tablets smartphones embedded systems xbox one surface hub mixed reality current windows 10 version list kaios kai based firefox os unlike mobile operating systems focus smartphones kaios developed mainly feature phones giving access advanced technologies usually found smartphones app stores wi-fi/4g capabilities blackberry 10 based qnx os blackberry smartphone os closed source proprietary runs phones tablets manufactured blackberry one dominant platforms world late 2000s global market share reduced significantly mid-2010s late 2016 blackberry announced continue support os promise release 10.3.3 therefore blackberry 10 would receive major updates blackberry partners would focus android base development current blackberry 10 version list windows 10 mobile formerly called windows phone microsoft closed source proprietary unveiled february 15 2010 windows phone includes user interface inspired microsoft metro design language integrated microsoft services onedrive office xbox music xbox video xbox live games bing also integrates many non-microsoft services facebook google accounts windows phone devices made primarily microsoft mobile/nokia also htc samsung january 21 2015 microsoft announced windows phone brand phased replaced windows 10 mobile bringing tighter integration unification pc counterpart windows 10 provide platform smartphones tablets screen sizes 8 inches october 2017 microsoft officially announced would longer push major updates windows 10 mobile instead would put maintenance mode microsoft would push bug fixes general improvements therefore windows 10 mobile would receive new feature updates current windows 10 mobile version list cyanogenmod custom mobile operating system based android open source project aosp custom rom co-developed cyanogenmod community os include proprietary apps unless user installed due open source nature cyanogenmod allowed android users could longer obtain update support manufacturer continue updating os version latest one based official releases google aosp heavy theme customization last version os cyanogenmod 13 based android asus december 24 2016 cyanogenmod announced blog would longer releasing cyanogenmod updates development moved lineageos cyanogen os based cyanogenmod maintained cyanogen inc however included proprietary apps available commercial uses firefox os project name boot gecko also known b2g mozilla open source mobile operating system released mozilla public license built android linux kernel used android drivers use java-like code android according ars technica mozilla says b2g motivated desire demonstrate standards-based open web potential competitive alternative existing single-vendor application development stacks offered dominant mobile operating systems september 2016 mozilla announced work firefox os ceased b2g-related code would removed mozilla-central meego non-profit organization linux foundation open source gpl 2010 mobile world congress barcelona nokia intel unveiled meego mobile operating system combined moblin maemo create open-sourced experience users across devices 2011 nokia announced would longer pursue meego favor windows phone nokia announced nokia n9 june 21 2011 nokia connection event singapore lg announced support platform maemo platform developed nokia smartphones internet tablets open source gpl based debian gnu/linux draws much graphical user interface gui frameworks libraries gnome project uses matchbox window manager gtk-based hildon gui application framework webos developed palm webos open source mobile operating system running linux kernel initially developed palm launched palm pre acquired hp two phones veer pre 3 tablet touchpad running webos introduced 2011 august 18 2011 hp announced webos hardware would discontinued would continue support update webos software develop webos ecosystem hp released webos open source name open webos plans update additional features february 25 2013 hp announced sale webos lg electronics used operating system smart internet-connected tvs however hp retained patents underlying webos cloud-based services app catalog 1999 research motion released first blackberry devices providing secure real-time push-email communications wireless devices services blackberry messenger provide integration communications single inbox september 2012 rim announced 200 millionth blackberry smartphone shipped september 2014 around 46 million active blackberry service subscribers early 2010s rim undergone platform transition changing company name blackberry limited making new devices new platform named blackberry 10 windows mobile discontinued operating system microsoft replaced windows phone closed source proprietary windows ce operating system windows mobile middleware widely spread asia mostly uses android two improved variants operating system windows mobile 6 professional touch screen devices windows mobile 6 standard unveiled february 2007 criticized user interface optimized touch input fingers instead usable stylus like ios mobile os supports touch screen physical bluetooth keyboard configurations microsoft phased windows mobile os focus windows phone windows phone family mobile operating systems developed microsoft smartphones replacement successor windows mobile zune windows phone features new user interface derived metro design language windows phone replaced windows 10 mobile 2015 symbian platform developed nokia models smartphones proprietary software however used ericsson sonyericsson sending benq operating system discontinued 2012 although slimmed-down version basic phones still developed july 2014 microsoft officially shelved platform favor windows phone acquisition nokia bada platform stylized bada korean 바다 operating system mobile devices smartphones tablet computers developed samsung electronics name derived 바다 bada meaning ocean sea korean ranges mid- high-end smartphones foster adoption bada os since 2011 samsung reportedly considered releasing source code open-source license expanding device support include smart tvs samsung announced june 2012 intentions merge bada tizen project would meanwhile use bada operating system parallel google android os microsoft windows phone smartphones bada-powered devices branded wave name samsung android-powered devices branded name galaxy february 25 2013 samsung announced stop developing bada moving development tizen instead bug reporting finally terminated april 2014 palm os/garnet os access co closed source proprietary webos introduced palm january 2009 successor palm os web 2.0 technologies open architecture multitasking abilities 2006 android ios exist 64 million smartphones sold 2018 q1 383.5 million smartphones sold global market share 85.9 android 14.1 ios according statcounter web use statistics proxy use smartphones alone without tablets majority use globally desktop computers used much less android particular popular windows use varies however continent smartphones way popular biggest continents i.e asia desktop still popular though north america desktop still popular many countries overall 44.9 first quarter 2017 smartphones popular even many developed countries countries continent desktop-minority european countries south america e.g haiti north america asia africa smartphone-majority poland turkey highest 57.68 62.33 respectively ireland smartphone use 45.55 outnumbers desktop use mobile whole gains majority including tablet share 9.12 spain also slightly desktop-minority range measured mobile web use varies lot country statcounter press release recognizes india amongst world leaders use mobile surf internet big countries share around 80 desktop 19.56 russia trailing 17.8 mobile use desktop rest smartphones alone without tablets first gained majority december 2016 desktop-majority lost month n't christmas-time fluke close majority smartphone majority happened march 2017 week november 7–13 2016 smartphones alone without tablets overtook desktop first time short period non-full-month mobile-majority applies countries paraguay south america poland europe turkey asia africa world still desktop-majority e.g united states 54.89 days however territories united states puerto rico desktop way majority windows 30 overtaken android october 22 2016 subsequent weekends mobile showed majority since october 27 desktop n't shown majority even weekdays smartphones alone showed majority since december 23 end year share topping 58.22 christmas day mobile -majority share smartphones tablets could added giving 63.22 majority unusually high top similarly high also happened monday april 17 2017 smartphones share slightly lower tablet share slightly higher combined 62.88 formerly according statcounter press release world turned desktop-minority 49 desktop use month mobile n't ranked higher tablet share added exceed desktop share note
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Operating systems
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crossbeam systems crossbeam systems headquartered boxborough massachusetts offices europe latin america asia pacific crossbeam systems acquired blue coat systems december 2012 crossbeam brand fully absorbed blue coat crossbeam systems acquired blue coat systems december 2012 crossbeam brand fully absorbed blue coat crossbeam systems inc. incorporated november 23 1999 stephen justus mike akerman throop wilder joining founding team member 2000 since beginning crossbeam focused designing manufacturing range network security products peter george led company 2001 june 2007 ceo president pete fiore took company 2007 led company growth profitability death december 2009 march 2010 continues today ceo president november 9 2012 crossbeam systems inc. acquired private equity firm thoma bravo company publicly disclose acquisition price terms deal december 17 2012 blue coat systems announced acquiring crossbeam systems deal expected close december 31 2012 company ’ main product x-series network security product family introduced september 2001 way telecommunications operators consolidate security server appliance infrastructure one chassis acts virtual security architecture ‘ network box. ’ x-series architecture consists five major components including chassis operating system three types hardware blades modules past 11-plus years x-series product family including modules operating systems gone six major generational upgrades october 2010 5th generation upgrade x-series family network security platforms include x20 x30 x60 x80-s october 2011 crossbeam completed portfolio added 6th generation network processor module npm-9610 npm-9650 7 7 independent validation 6th generation x-series platform performance crossbeam together spirent european advanced network test centre eantc heavy reading set create new real-world methodology testing network security gprs 4g-lte mobile operator network methodology independently tested eantc crossbeam x80-s platform
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Computer security
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mark abene mark t. abene born february 23 1972 american infosec expert entrepreneur originally new york city better known pseudonym phiber optik member hacker groups legion doom masters deception phiber optik high-profile hacker 1980s early 1990s appearing new york times harper esquire debates television important figure 1995 non-fiction book masters deception — gang ruled cyberspace abene first contact computers around 9 years age local department store would often pass time parents shopped first computer trs-80 mc-10 4 kilobytes ram 32-column screen lower case cassette tape recorder load save programs customary time computer connected television set use monitor receiving gifts ram upgrade 20k 300 baud modem parents used computer access compuserve shortly discovered world dialup bbses via people met compuserve cb simulator first nationwide online chat bbses abene discovered dialups guest accounts dec minicomputers running rsts/e tops-10 operating systems part boces educational program long island new york accessing dec minicomputers realized programming environment much powerful home computer began taking books library order learn programming languages available ability remotely save load back programs would still next time logged profound effect abene came view rather simple computer window much larger world learned programming fundamental security concepts early years abene honed skill understanding intricacies nationwide telephone network mid-1980s first introduced members legion doom lod loosely knit group highly respected teenage hackers shared abene uncompromising desire understand technology main focus explore telecommunications systems minicomputer mainframe operating systems large-scale packet data networks eventual decline lod toward late 1980s largely due fragmentation dissention within group coupled legal prosecution handful members caused abene increasingly align local group up-and-coming hackers came known masters deception mod january 24 1990 abene mod members homes searched property seized u.s. secret service largely based government suspicions caused corporation network crash week earlier january 15 abene personally accused secret service done much search seizure weeks later admitted crash result flawed software update switching systems long distance network thus human error part february 1991 abene arrested charged computer tampering computer trespass first degree new york state offenses laws time considered “ gray area ” concerning information security abene minor time pleaded guilty first two offenses ultimately accepted plea agreement lesser misdemeanor charge sentenced 35 hours community service abene four members masters deception also arrested december 1991 indicted manhattan federal grand jury july 8 1992 11-count charge indictment relied heavily evidence collected court-approved wire tapping telephone conversations mod members according u.s. attorney otto obermaier first investigative use court-authorized wiretaps obtain conversations data transmissions computer hackers united states according july 9 1992 newsletter electronic frontier foundation defendants faced maximum term 50 years prison fines 2.5 million found guilty counts despite fact abene minor time crimes allegedly committed involved small fraction sub-charges often passive way plea arrangement resulted far harshest sentence 12 months imprisonment three years probation 600 hours community service serving one-year sentence federal prison camp schuylkill pennsylvania abene released november 1994 january 1995 huge celebration called phiberphest '95 held honor manhattan irving plaza ballroom/nightclub time joshua quittner called first underground hero information age robin hood cyberspace upon leaving jail phiber optik made cafe hang spot many people inside outside hacker world felt abene made example judged according earlier court standards abene built significant reputation hacker sub-culture example regularly appearing radio show hook hosted eric corley a.k.a emmanuel goldstein debating defending morals motivations hackers public forums interviews lecturing history telecommunications technology night courses several new york city universities time indictment working mindvox early bbs/isp founded two new york lod members subsequently echonyc multi-user bbs early isp echo users echo management hackers around nation expected abene get probation months jail time co-defendants previous offenders charged hacking offenses received rather lenient punishments given new-found enthusiasm using knowledge constructive ends general feeling optimistic prior sentencing statement made u.s. attorney otto obermeier conjunction indication message ought delivered indictment conduct tolerated irrespective age particular accused ostensible purpose interpreted abene supporters mean mod made example show authorities could handle perceived hacker threat sentencing judge stanton said defendant stands symbol today hacking crimes constitute real threat expanding information highway reinforcing view relatively harmless teacher judged symbol hackers abene spoken subject security many publications new york times washington post wall street journal time appeared speaker hacker security industry conferences worldwide frequently visits universities speak students information security years security consultant joined forces former legion doom member dave buchwald third colleague andrew brown create security consulting firm crossbar security crossbar provided consulting services third party companies principals conducted business u.s. japan brazil sweden result dot com bust crossbar ultimately went defunct 2001 largely due cuts corporate security spending abene made acting début inside man fiction film urchin completed 2006 released us february 2007 hacker notables dave buchwald emmanuel goldstein also seen 2009 founded tracevector intrusion detection firm makes use supercomputing data analytics currently resides silicon valley
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Computer security
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fuzzing fuzzing fuzz testing automated software testing technique involves providing invalid unexpected random data inputs computer program program monitored exceptions crashes failing built-in code assertions potential memory leaks typically fuzzers used test programs take structured inputs structure specified e.g. file format protocol distinguishes valid invalid input effective fuzzer generates semi-valid inputs valid enough directly rejected parser create unexpected behaviors deeper program invalid enough expose corner cases properly dealt purpose security input crosses trust boundary often interesting example important fuzz code handles upload file user fuzz code parses configuration file accessible privileged user testing programs random inputs dates back 1950s data still stored punched cards programmers would use punched cards pulled trash card decks random numbers input computer programs execution revealed undesired behavior bug detected fixed execution random inputs also called random testing monkey testing 1981 duran ntafos formally investigated effectiveness testing program random inputs random testing widely perceived worst means testing program authors could show cost-effective alternative systematic testing techniques 1983 steve capps developed monkey tool would generate random inputs classic mac os applications macpaint figurative monkey refers infinite monkey theorem states monkey hitting keys random typewriter keyboard infinite amount time eventually type entire works shakespeare case testing monkey would write particular sequence inputs trigger crash term fuzzing originates 1988 class project taught barton miller university wisconsin fuzz test unix utility meant automatically generate random files command-line parameters utility project designed test reliability unix programs executing large number random inputs quick succession crashed also provided early debugging tools determine cause category detected failure allow researchers conduct similar experiments software source code tools test procedures raw result data made publicly available later term fuzzing limited command-line utilities 1991 crashme tool released intended test robustness unix unix-like operating systems executing random machine instructions 1995 fuzzer used test gui-based tools x window system network protocols system library apis april 2012 google announced clusterfuzz cloud-based fuzzing infrastructure security-critical components chromium web browser security researchers upload fuzzers collect bug bounties clusterfuzz finds crash uploaded fuzzer september 2014 shellshock disclosed family security bugs widely used unix bash shell vulnerabilities shellshock found using fuzzer afl many internet-facing services web server deployments use bash process certain requests allowing attacker cause vulnerable versions bash execute arbitrary commands allow attacker gain unauthorized access computer system april 2015 hanno böck showed fuzzer afl could found 2014 heartbleed vulnerability heartbleed vulnerability disclosed april 2014 serious vulnerability allows adversaries decipher otherwise encrypted communication vulnerability accidentally introduced openssl implements tls used majority servers internet shodan reported 238,000 machines still vulnerable april 2016 200,000 january 2017 august 2016 defense advanced research projects agency darpa held finals first cyber grand challenge fully automated capture-the-flag competition lasted 11 hours objective develop automatic defense systems discover exploit correct software flaws real-time fuzzing used effective offense strategy discover flaws software opponents showed tremendous potential automation vulnerability detection winner system called mayhem developed team forallsecure led david brumley september 2016 microsoft announced project springfield cloud-based fuzz testing service finding security critical bugs software december 2016 google announced oss-fuzz allows continuous fuzzing several security-critical open-source projects black hat 2018 christopher domas demonstrated use fuzzing expose existence hidden risc core processor core able bypass existing security checks execute ring 0 commands ring 3 fuzzer categorized follows mutation-based fuzzer leverages existing corpus seed inputs fuzzing generates inputs modifying rather mutating provided seeds example fuzzing image library libpng user would provide set valid png image files seeds mutation-based fuzzer would modify seeds produce semi-valid variants seed corpus seed files may contain thousands potentially similar inputs automated seed selection test suite reduction allows users pick best seeds order maximize total number bugs found fuzz campaign generation-based fuzzer generates inputs scratch instance smart generation-based fuzzer takes input model provided user generate new inputs unlike mutation-based fuzzers generation-based fuzzer depend existence quality corpus seed inputs fuzzers capability generate inputs scratch generate inputs mutation existing seeds typically fuzzers used generate inputs programs take structured inputs file sequence keyboard mouse events sequence messages structure distinguishes valid input accepted processed program invalid input quickly rejected program constitutes valid input may explicitly specified input model examples input models formal grammars file formats gui-models network protocols even items normally considered input fuzzed contents databases shared memory environment variables precise interleaving threads effective fuzzer generates semi-valid inputs valid enough directly rejected parser invalid enough might stress corner cases exercise interesting program behaviours smart model-based grammar-based protocol-based fuzzer leverages input model generate greater proportion valid inputs instance input modelled abstract syntax tree smart mutation-based fuzzer would employ random transformations move complete subtrees one node another input modelled formal grammar smart generation-based fuzzer would instantiate production rules generate inputs valid respect grammar however generally input model must explicitly provided difficult model proprietary unknown complex large corpus valid invalid inputs available grammar induction technique angluin l* algorithm would able generate input model dumb fuzzer require input model thus employed fuzz wider variety programs instance afl dumb mutation-based fuzzer modifies seed file flipping random bits substituting random bytes interesting values moving deleting blocks data however dumb fuzzer might generate lower proportion valid inputs stress parser code rather main components program disadvantage dumb fuzzers illustrated means construction valid checksum cyclic redundancy check crc crc error-detecting code ensures integrity data contained input file preserved transmission checksum computed input data recorded file program processes received file recorded checksum match re-computed checksum file rejected invalid fuzzer unaware crc unlikely generate correct checksum however attempts identify re-compute potential checksum mutated input dumb mutation-based fuzzer modified protected data typically fuzzer considered effective achieves higher degree code coverage rationale fuzzer exercise certain structural elements program also able reveal bugs hiding elements program elements considered critical others instance division operator might cause division zero error system call may crash program black-box fuzzer treats program black box unaware internal program structure instance random testing tool generates inputs random considered blackbox fuzzer hence blackbox fuzzer execute several hundred inputs per second easily parallelized scale programs arbitrary size however blackbox fuzzers may scratch surface expose shallow bugs hence attempts develop blackbox fuzzers incrementally learn internal structure behavior program fuzzing observing program output given input instance learnlib employs active learning generate automaton represents behavior web application white-box fuzzer leverages program analysis systematically increase code coverage reach certain critical program locations instance sage leverages symbolic execution systematically explore different paths program program specification available whitebox fuzzer might leverage techniques model-based testing generate inputs check program outputs program specification whitebox fuzzer effective exposing bugs hide deep program however time used analysis program specification become prohibitive whitebox fuzzer takes relatively long generate input blackbox fuzzer efficient hence attempts combine efficiency blackbox fuzzers effectiveness whitebox fuzzers gray-box fuzzer leverages instrumentation rather program analysis glean information program instance afl libfuzzer utilize lightweight instrumentation trace basic block transitions exercised input leads reasonable performance overhead informs fuzzer increase code coverage fuzzing makes gray-box fuzzers extremely efficient vulnerability detection tools fuzzing used mostly automated technique expose vulnerabilities security-critical programs might exploited malicious intent generally fuzzing used demonstrate presence bugs rather absence running fuzzing campaign several weeks without finding bug prove program correct program may still fail input executed yet executing program inputs prohibitively expensive objective prove program correct inputs formal specification must exist techniques formal methods must used order expose bugs fuzzer must able distinguish expected normal unexpected buggy program behavior however machine always distinguish bug feature automated software testing also called test oracle problem typically fuzzer distinguishes crashing non-crashing inputs absence specifications use simple objective measure crashes easily identified might indicate potential vulnerabilities e.g. denial service arbitrary code execution however absence crash indicate absence vulnerability instance program written c may may crash input causes buffer overflow rather program behavior undefined make fuzzer sensitive failures crashes sanitizers used inject assertions crash program failure detected different sanitizers different kinds bugs fuzzing also used detect differential bugs reference implementation available automated regression testing generated inputs executed two versions program automated differential testing generated inputs executed two implementations program e.g. lighttpd httpd implementations web server two variants produce different output input one may buggy examined closely static program analysis analyzes program without actually executing might lead false positives tool reports problems program actually exist fuzzing combination dynamic program analysis used try generate input actually witnesses reported problem modern web browsers undergo extensive fuzzing chromium code google chrome continuously fuzzed chrome security team 15,000 cores microsoft edge internet explorer microsoft performed fuzzed testing 670 machine-years product development generating 400 billion dom manipulations 1 billion html files fuzzer produces large number inputs relatively short time instance 2016 google oss-fuzz project produced around 4 trillion inputs week hence many fuzzers provide toolchain automates otherwise manual tedious tasks follow automated generation failure-inducing inputs automated bug triage used group large number failure-inducing inputs root cause prioritize individual bug severity fuzzer produces large number inputs many failure-inducing ones may effectively expose software bug bugs security-critical patched higher priority instance cert coordination center provides linux triage tools group crashing inputs produced stack trace lists group according probability exploitable microsoft security research centre msec developed exploitable tool first creates hash crashing input determine uniqueness assigns exploitability rating previously unreported triaged bugs might automatically reported bug tracking system instance oss-fuzz runs large-scale long-running fuzzing campaigns several security-critical software projects previously unreported distinct bug reported directly bug tracker oss-fuzz bug tracker automatically informs maintainer vulnerable software checks regular intervals whether bug fixed recent revision using uploaded minimized failure-inducing input automated input minimization test case reduction automated debugging technique isolate part failure-inducing input actually inducing failure failure-inducing input large mostly malformed might difficult developer understand exactly causing bug given failure-inducing input automated minimization tool would remove many input bytes possible still reproducing original bug instance delta debugging automated input minimization technique employs extended binary search algorithm find minimal input
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Computer security
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voice computing voice computing discipline develops hardware software process voice inputs spans many fields including human-computer interaction conversational computing linguistics natural language processing automatic speech recognition speech synthesis audio engineering digital signal processing cloud computing data science ethics law information security voice computing become increasingly significant modern times especially advent smart speakers like amazon echo google assistant shift towards serverless computing improved accuracy speech recognition text-to-speech models voice computing rich history first scientists like wolfgang kempelen started build speech machines produce earliest synthetic speech sounds led work thomas edison record audio dictation machines play back corporate settings 1950s-1960s primitive attempts build automated speech recognition systems bell labs ibm others however 1980s hidden markov models used recognize 1,000 words speech recognition systems became relevant around 2011 siri emerged apple iphones first voice assistant accessible consumers innovation led dramatic shift building voice-first computing architectures ps4 released sony north america 2013 70+ million devices amazon released amazon echo 2014 30+ million devices microsoft released cortana 2015 400 million windows 10 users google released google assistant 2016 2 billion active monthly users android phones apple released homepod 2018 500,000 devices sold 1 billion devices active ios/siri shifts along advancements cloud infrastructure e.g amazon web services codecs solidified voice computing field made widely relevant public large voice computer assembled hardware software process voice inputs note voice computers necessarily need screen traditional amazon echo embodiments traditional laptop computers mobile phones could used voice computers moreover become increasingly interfaces voice computers advent iot-enabled devices within cars televisions september 2018 currently 20,000 types devices compatible amazon alexa voice computing software read/write record clean encrypt/decrypt playback transcode transcribe compress publish featurize model visualize voice files popular software packages related voice computing voice computing applications span many industries including voice assistants healthcare e-commerce finance supply chain agriculture text-to-speech security marketing customer support recruiting cloud computing microphones speakers podcasting voice technology projected grow cagr 19-25 2025 making attractive industry startups investors alike united states states varying telephone call recording laws states legal record conversation consent one party others consent parties required moreover coppa significant law protect minors using internet increasing number minors interacting voice computing devices e.g amazon alexa federal trade commission recently relaxed copaa rule children issue voice searches commands lastly gdpr new european law governs right forgotten many clauses eu citizens gdpr also clear companies need outline clear measures obtain consent audio recordings made define purpose scope recordings used e.g. training purposes bar valid consent raised gdpr consents must freely given specific informed unambiguous tacit consent longer sufficient many research conferences relate voice computing include google assistant roughly 2,000 actions january 2018 50,000 alexa skills worldwide september 2018 june 2017 google released audioset large-scale collection human-labeled 10-second sound clips drawn youtube videos contains 1,010,480 videos human speech files 2,793.5 hours total released part ieee icassp 2017 conference november 2017 mozilla foundation released common voice project collection speech files help contribute larger open source machine learning community voicebank currently 12gb size 500 hours english-language voice data collected 112 countries since project inception june 2017 dataset already resulted creative projects like deepspeech model open source transcription model
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Computational linguistics
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distributed shared memory computer science distributed shared memory dsm form memory architecture physically separated memories addressed one logically shared address space term shared mean single centralized memory address space shared physical address two processors refers location memory distributed global address space dgas similar term wide class software hardware implementations node cluster access shared memory addition node non-shared private memory distributed-memory system often called multicomputer consists multiple independent processing nodes local memory modules connected general interconnection network software dsm systems implemented operating system programming library thought extensions underlying virtual memory architecture implemented operating system systems transparent developer means underlying distributed memory completely hidden users contrast software dsm systems implemented library language level transparent developers usually program differently however systems offer portable approach dsm system implementations distributed shared memory system implements shared-memory model physically distributed memory system usually two methods achieving distributed shared memory three ways implementing software distributed shared memory software dsm systems also flexibility organize shared memory region different ways page based approach organizes shared memory pages fixed size contrast object based approach organizes shared memory region abstract space storing shareable objects variable sizes another commonly seen implementation uses tuple space unit sharing tuple shared memory architecture may involve separating memory shared parts distributed amongst nodes main memory distributing memory nodes coherence protocol chosen accordance consistency model maintains memory coherence memory coherence necessary system organizes dsm able track maintain state data blocks nodes across memories comprising system basic dsm track least three states among nodes given block directory state dictate block uncached u state dictate block exclusively owned modified owned em state dictate block shared blocks come directory organization transition u em ownership state initial node state transition nodes begin reading block two primary methods allowing system track blocks cached condition across node home-centric request-response uses home service requests drive states whereas requester-centric allows node drive manage requests home home-centric system dsm avoid handle request-response races nodes allowing one transaction occur time home node decided transaction finished—usually home received responding processor response request example intel qpi home-source mode requester-centric system dsm allow nodes talk home means multiple nodes attempt start transaction requires additional considerations ensure coherence example one node processing block receives request block another node send nack negative acknowledgement tell initiator processing node ca n't fulfill request right away example intel qpi snoop-source mode dsm must follow certain rules maintain consistency read write order viewed among nodes called system consistency model suppose n processes mi memory operations process operations executed sequentially conclude m1 m2 … mn m1 m2 … mn possible interleaves operations issue conclusion determining correctness interleaved operations memory coherence dsm defines interleaves permitted two type replication algorithm read replication write replication read replication multiple nodes read time one node write write application multiple nodes read write time.the write requests handled sequencer replication shared data general tends however preserving coherence consistency may become challenging
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Distributed computing architecture
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rotational cryptanalysis cryptography rotational cryptanalysis generic cryptanalytic attack algorithms rely three operations modular addition rotation xor — arx short algorithms relying operations popular relatively cheap hardware software run constant time making safe timing attacks common implementations basic idea rotational cryptanalysis bit rotation xor operations preserve correlations bit-rotated pairs inputs addition bit-rotated inputs also partially preserves bit rotation correlations rotational pairs inputs thus used see cipher cascaded arx operations greater degree might expected ability see correlations rounds processing exploited break cipher way similar differential cryptanalysis term rotational cryptanalysis coined dmitry khovratovich ivica nikolić 2010 paper rotational cryptanalysis arx presented best cryptanalytic attacks time reduced-round threefish cipher — part skein hash function sha-3 competition candidate follow-up attack authors christian rechberger breaks collision resistance 53 72 rounds skein-256 57 72 rounds skein-512 also affects threefish cipher
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Computer security
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newwave newwave discontinued object-oriented graphical desktop environment office productivity tool pcs running early versions microsoft windows beginning 2.0 developed hewlett-packard introduced commercially 1988 used hp vectras ibm compatible pcs running ms windows user perspective newwave ran top ms windows completely replaced standard windows desktop program manager user interface object-oriented desktop interface hp promoted newwave release windows 95 time development product ceased due incompatibility new operating system newwave gui together contemporaneous nextstep gui introduced shaded 3-d look feel later widely adopted hp encouraged independent software vendors produce versions applications took advantage newwave functionality allowing data handled objects instead files one early example samna corporation later acquired lotus produced edition microsoft windows word processor ami pro entitled ‘ ’ ami pro newwave ’ ’ june 20 1988 microsoft corporation hewlett-packard issued press release announcing inclusion newwave support up-coming release microsoft excel newwave featured icons scheduled scripts form agents hot connects hp incorporated newwave multi-platform office automation offerings running proprietary mpe hp-ux unix minicomputer operating systems developed newwave versions key email database document management personal productivity communications network management tools branded related solutions “ hp newwave office ” banner prior integration hp newwave solution set known “ business system plus ” “ newwave office ” term used previously describe main newwave user desktop original november 1987 press release hewlett-packard described newwave “ application environment designed provide personal computer users single method access data files multiple sources company ’ network ” developed hp ’ personal software division psd santa clara california united states part distributed computing environment strategy three years work 100 employees original version newwave ran ibm compatible pcs required ms-dos 3.2 later ms-windows 2.0 later key features newwave included hp described omf means binding applications data together form “ objects ” compound documents addition ms-windows-style indexed help articles newwave introduced context-sensitive help facility allowed user click ‘ help ’ menu option added query symbol mouse arrow switched ‘ help mode ’ user could click part newwave environment menu command help item displayed pop-up window working conjunction newwave agent computer-based training functionality newwave allowed developers build interactive lessons desktop environment applications allowed users learn actual live applications non-destructive way feature dropped later versions newwave due increased disk requirements imposed limited hard disk space available pcs time newwave agent task-recording execution facility could work across multiple applications users could record sequence tasks performed within newwave environment recorded tasks generated basic-like source-code could repeated unmodified edited expanded create sophisticated automated interactive activities newwave included built-in applications fully integrated object management facility newwave agent online help computer based training features non-native newwave applications could integrated environment using “ advanced bridges ” allowing live data embedded compound documents standard end-user version hp newwave included bridges hp ’ pc applications hp graphics gallery ms windows tools calculator calendar notepad etc many common third-party applications users could also create bridges applications using included bridge builder tool bridges could exported use newwave-enabled systems often shared amongst newwave user community hp described newwave write basic-to-intermediate level “ see get ” wysiwig word processor support compound documents newwave mail available separate native newwave product could act client hp ’ proprietary deskmanager openmail email server solutions hp succeeded establishing third-party developer program following release newwave software developer ’ kit sdk february 1988 newwave enabled third-party applications included third-party application bridges shipped end-user release hp newwave included eight-year life hp newwave underwent several functional cosmetic changes including revision desktop interface dropping built-in computer based training facility alleged similarities macintosh gui newwave subject unsuccessful look feel lawsuit apple see apple v. microsoft praising hp serious sincere effort give windows complete object-oriented gui stewart alsop ii 1988 doubted software developers would create software newwave hp considered standard setter ibm microsoft desktop-metaphor plans existing applications needed substantial redesign rewrite effectively use hp newwave never adopted mainstream end-user environment although adopted number corporate clients basis office productivity projects including hp success licensing newwave hardware manufacturers january 1990 hp stated intention provide newwave capabilities unix motif os/2 presentation manager although versions never released hp contribute newwave technology projects run open software foundation hp member articles august 1989 issue hewlett-packard journal volume 40 number 4
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Operating systems
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cloudme cloudme file storage service operated cloudme ab offers cloud storage file synchronization client software features blue folder appears devices content files synchronized devices cloudme service offered freemium business model provides encrypted ssl connection ssl extended validation certificate cloudme provides client software microsoft windows macos linux android ios google tv samsung smart tv wd tv windows storage server nas web browsers cloud sync storage provider cloudme strong focus european market differentiates storage providers mobility media features like samsung smarttv support recently novell announced support cloudme service dynamic file services suite novosoft handy backup version 7.3 also announced support cloudme winzip also integrated cloudme many third party mobile apps software available cloudme many using webdav support cloudme cloudme founded daniel arthursson 2012 mainly owned xcerion company runs servers operates sweden european union 2012 cloudme received red herring top 100 global company alwayson global 250 award white bull 2012 yearling award white bull 2014 longhorn award previously cloudme.com called icloud.com service changed name apple acquired domain trademark rumoured 4.5 million dollars visitors icloud.com directed cloudme.com name change former icloud.com service split two companies services cloudme file sync storage cloudtop virtual cloud desktop previously main attraction icloud.com service included file storage xcerion major owner cloudme cloudtop initially gained investment 12 million build icloud service using saas model cloudme service provided free version 3 gb storage 19 gb referral program model often called freemium premium versions either 10 25 100 200 500 gb storage consumers 2 tb 5 tb business closest competitor cloudme dropbox cloudme features cloud storage sync solution allows users store access share content people outside service sharing done email text messaging facebook google files stored blue folder synchronized connected computers devices web desktop cloud os service called cloudtop.com available uses cloudme internet file system cloudme ab located drottninggatan 23 linköping sweden
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Distributed computing architecture
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procurify procurify cloud-based procurement software company located vancouver british columbia canada founded 2013 ceo aman mann cto eugene dong coo kenneth loi procurify main product offering cloud-based procurement solution used manage company spending companies offer procurement solutions typically focus automation company spending real-time current procurify platform considered horizontal rather industry specific procurify cloud based procurement software solution used companies manage organizational purchasing procurement like e-procurement solutions available procurify focuses providing users features including digital purchase order submission accounts payable automation procurify hosted amazon web services built using django solution available saas procurify offered browser-based mobile procurement software company founders bcit school business alumni graduated together operations management 2011 idea procurify came bcit class project founders randomly placed together consult vancouver-based business internal processes november 2012 joined growlab accelerator program february 2013 procurify graduated vancouver-based incubator program growlab april 2014 procurify raised total 1.2 million seed round venture capitalists nexus ventures bdc mark cuban july 2015 procurify raised another seed round totaling 4 million point nine capital nexus venture partners business development bank canada bdc hootsuite ceo ryan holmes chief revenue officer steve johnson also participated round
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Distributed computing architecture
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sparc t5 sparc t5 fifth generation multicore microprocessor oracle sparc t-series family first presented hot chips 24 august 2012 officially introduced oracle sparc t5 servers march 2013 processor designed offer high multithreaded performance 16 cores per chip 8 threads per core well high single threaded performance chip processor uses sparc s3 core design predecessor sparc t4 processor implemented 28 nm process runs 3.6 ghz s3 core dual-issue core uses dynamic threading out-of-order execution incorporates one floating point unit one dedicated cryptographic unit per core 64-bit sparc version 9 based processor 16 cores supporting 128 threads per processor scales 1,024 threads 8 socket system changes include support pcie version 3.0 new cache coherence protocol chart shows differences t5 t4 processor chips sparc t5 also introduces new power management feature consists hardware support processor software allows system administrator use feature users select policy system responds over-temperature over-current events dynamic voltage frequency scaling aka dvfs policy set maintain peak frequency trade performance power consumption sparc t5 processor used oracle entry mid-size sparc t5-2 t5-4 t5-8 servers servers use processor frequency number cores per chip cache configuration t5 processor includes crossbar network connects 16 cores l2 caches shared l3 cache multiprocessor cache coherence maintained using directory-based protocol design scales eight sockets without additional silicon glueless snoopy based protocol used sparc t4 systems replaced order reduce memory latency reduce coherency bandwidth consumption
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Computer architecture
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eurocat medicine eurocat european organization describes network population-based registries epidemiological surveillance congenital anomalies covering 1.5 million births 20 countries europe founded 1979 goal improving collection data congenital disorders standardization data published extensions helps provide unique codes individual conditions approximately quarter new births european union reported eurocat
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Databases
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terminology model terminology model refinement concept system within terminology model concepts object types specific problem subject area defined subject matter experts terms concept object type definitions definitions subordinated concepts characteristics properties besides object types terminology model allows defining hierarchical classifications definitions object type property behavior definition casual relations terminology model means subject matter experts express knowledge subject subject specific terms since terminology model structured rather similar object-oriented database schema transformed without loss information object-oriented database schema thus terminology model method problem analysis one side mean defining database schema side several terminology models developed published field statistics
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Databases
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ralph griswold ralph e. griswold may 19 1934 modesto ca – october 4 2006 tucson az computer scientist known research high-level programming languages symbolic computation language credits include string processing language snobol sl5 icon attended stanford university receiving bachelor degree physics m.s ph.d. electrical engineering griswold went bell labs 1962 studied ideas non-numerical computation snobol outcome radically different language time still became head labs programming research development department 1967 1971 hired university arizona first professor computer science subsequently organized department head 1981 arizona griswold developed icon earlier ratfor implementation icon discarded language rewritten scratch c unix 1990 griswold appointed regents professor retired 1995 one founders bell labs software culture spawned unix c many essential contributions modern software ralph griswold brought academic research brilliance also experience value system demanded research ideas tested fire proven useful usable real users good-looking diagrams academic papers retirement interests turned mathematical aspects weaving griswold died october 4 2006 cancer griswold son bill griswold also computer scientist
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Programming language topics
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moore law moore law observation number transistors dense integrated circuit doubles every two years observation named gordon moore co-founder fairchild semiconductor ceo intel whose 1965 paper described doubling every year number components per integrated circuit projected rate growth would continue least another decade 1975 looking forward next decade revised forecast doubling every two years compound annual growth rate cagr 41.4 period often quoted 18 months prediction intel executive david house combination effect transistors transistors faster moore prediction proved accurate several decades used semiconductor industry guide long-term planning set targets research development r advancements digital electronics strongly linked moore law rapid scaling mosfet metal-oxide-semiconductor field-effect transistor devices quality-adjusted microprocessor prices memory capacity ram flash sensors even number size pixels digital cameras digital electronics contributed world economic growth late twentieth early twenty-first centuries moore law describes driving force technological social change productivity economic growth moore law observation projection historical trend physical natural law although rate held steady 1975 around 2012 rate faster first decade general logically sound extrapolate historical growth rate indefinite future example 2010 update international technology roadmap semiconductors predicted growth would slow around 2013 2015 gordon moore foresaw rate progress would reach saturation see moore law dying next decade intel stated 2015 pace advancement slowed starting 22 nm feature width around 2012 continuing 14 nm brian krzanich former ceo intel announced cadence today closer two half years two intel also stated 2017 hyperscaling would able continue trend moore law offset increased cadence aggressively scaling beyond typical doubling transistors krzanich cited moore 1975 revision precedent current deceleration results technical challenges natural part history moore law late 2010s two semiconductor manufacturers able produce semiconductor nodes keep pace moore law tsmc samsung electronics 10 nm 7 nm 5 nm nodes production plans 3 nm nodes whereas pace slowed intel semiconductor manufacturers 1959 douglas engelbart discussed projected downscaling integrated circuit size article microelectronics art similitude engelbart presented ideas 1960 international solid-state circuits conference moore present audience thirty-fifth anniversary issue electronics magazine published april 19 1965 gordon e. moore working director research development fairchild semiconductor time asked predict going happen semiconductor components industry next ten years response brief article entitled cramming components onto integrated circuits within editorial speculated 1975 would possible contain many 65,000 components single quarter-inch semiconductor complexity minimum component costs increased rate roughly factor two per year certainly short term rate expected continue increase longer term rate increase bit uncertain although reason believe remain nearly constant least 10 years reasoning log-linear relationship device complexity higher circuit density reduced cost time 1975 ieee international electron devices meeting moore revised forecast rate semiconductor complexity would continue double annually 1980 would decrease rate doubling approximately every two years outlined several contributing factors exponential behavior shortly 1975 caltech professor carver mead popularized term moore law despite popular misconception moore adamant predict doubling every 18 months rather david house intel colleague factored increasing performance transistors conclude integrated circuits would double performance every 18 months moore law came widely accepted goal industry cited competitive semiconductor manufacturers strove increase processing power moore viewed eponymous law surprising optimistic moore law violation murphy law everything gets better better observation even seen self-fulfilling prophecy however rate improvement physical dimensions known dennard scaling mosfet scaling slowed semiconductor manufacturers recent years much industry shifting circa 2016 using semiconductor scaling driver focus meeting needs major computing applications april 2005 intel offered us 10,000 purchase copy original electronics issue moore article appeared engineer living united kingdom first find copy offer intel late 2010s two semiconductor manufacturers able produce semiconductor nodes keep pace moore law tsmc samsung electronics 10 nm 7 nm 5 nm nodes production plans 3 nm nodes whereas pace slowed intel semiconductor manufacturers cost computer power consumer falls cost producers fulfill moore law follows opposite trend r manufacturing test costs increased steadily new generation chips rising manufacturing costs important consideration sustaining moore law led formulation moore second law also called rock law capital cost semiconductor fab also increases exponentially time numerous innovations scientists engineers sustained moore law since beginning integrated circuit ic era key innovations listed examples breakthroughs advanced integrated circuit semiconductor device fabrication technology allowing transistor counts grow seven orders magnitude less five decades computer industry technology road maps predicted 2001 moore law would continue several generations semiconductor chips depending doubling time used calculations could mean hundredfold increase transistor count per chip within decade semiconductor industry technology roadmap used three-year doubling time microprocessors leading tenfold increase decade intel reported 2005 stating downsizing silicon chips good economics could continue following decade 2008 predicting trend 2029 one key challenges engineering future nanoscale transistors design gates device dimension shrinks controlling current flow thin channel becomes difficult compared finfets gate dielectric three sides channel gate-all-around mosfet gaafet structure even better gate control new technology advances may help sustain moore law improved performance without reduced feature size physical limits transistor scaling source-to-drain leakage limited gate metals limited options channel material reached new avenues continued scaling open promising approaches rely using spin state electron spintronics tunnel junctions advanced confinement channel materials via nano-wire geometry comprehensive list available device choices shows wide range device options open continuing moore law next decades spin-based logic memory options developed actively industrial labs well academic labs vast majority current transistors ics composed principally doped silicon alloys silicon fabricated single nanometer transistors short-channel effects adversely change desired material properties silicon functional transistor several non-silicon substitutes fabrication small nanometer transistors one proposed material indium gallium arsenide ingaas compared silicon germanium counterparts ingaas transistors promising future high-speed low-power logic applications intrinsic characteristics iii-v compound semiconductors quantum well tunnel effect transistors based ingaas proposed alternatives traditional mosfet designs research also showing biological micro-cells capable impressive computational power energy efficient various forms graphene studied graphene electronics eg graphene nanoribbon transistors shown great promise since appearance publications 2008 bulk graphene band gap zero thus used transistors constant conductivity inability turn zigzag edges nanoribbons introduce localized energy states conduction valence bands thus bandgap enables switching fabricated transistor example typical gnr width 10 nm desirable bandgap energy 0.4ev research need performed however sub 50 nm graphene layers resistivity value increases thus electron mobility decreases semiconductor industry forecasters including gordon moore expect moore law end around 2025 april 2005 gordon moore stated interview projection sustained indefinitely ca n't continue forever nature exponentials push eventually disaster happens also noted transistors eventually would reach limits miniaturization atomic levels 2016 international technology roadmap semiconductors using moore law drive industry since 1998 produced final roadmap longer centered research development plan moore law instead outlined might called moore strategy needs applications drive chip development rather focus semiconductor scaling application drivers range smartphones ai data centers new initiative generalized roadmapping started ieee initiative rebooting computing named international roadmap devices systems irds technological change combination better technology 2011 study journal science showed peak rate change world capacity compute information 1998 world technological capacity compute information general-purpose computers grew 88 per year since technological change clearly slowed recent times every new year allowed humans carry roughly 60 computation possibly could executed existing general-purpose computers year still exponential shows rate technological change varies time primary driving force economic growth growth productivity moore law factors productivity moore 1995 expected rate technological progress going controlled financial realities reverse could occur around late-1990s however economists reporting productivity growth key economic indicator innovation acceleration rate semiconductor progress contributed surge u.s. productivity growth reached 3.4 per year 1997–2004 outpacing 1.6 per year 1972–1996 2005–2013 economist richard g. anderson notes numerous studies traced cause productivity acceleration technological innovations production semiconductors sharply reduced prices components products contain well expanding capabilities products alternative source improved performance microarchitecture techniques exploiting growth available transistor count out-of-order execution on-chip caching prefetching reduce memory latency bottleneck expense using transistors increasing processor complexity increases described empirically pollack rule states performance increases due microarchitecture techniques approximate square root complexity number transistors area processor years processor makers delivered increases clock rates instruction-level parallelism single-threaded code executed faster newer processors modification manage cpu power dissipation processor makers favor multi-core chip designs software written multi-threaded manner take full advantage hardware many multi-threaded development paradigms introduce overhead see linear increase speed vs number processors particularly true accessing shared dependent resources due lock contention effect becomes noticeable number processors increases cases roughly 45 increase processor transistors translated roughly 10–20 increase processing power hand processor manufacturers taking advantage 'extra space transistor shrinkage provides add specialized processing units deal features graphics video cryptography one example intel parallel javascript extension adds support multiple cores also non-general processing features chips part migration client side scripting toward html5 negative implication moore law obsolescence technologies continue rapidly improve improvements may significant enough render predecessor technologies obsolete rapidly situations security survivability hardware data paramount resources limited rapid obsolescence may pose obstacles smooth continued operations toxic materials used production modern computers obsolescence properly managed may lead harmful environmental impacts hand obsolescence may sometimes desirable company profit immensely regular purchase often expensive new equipment instead retaining one device longer period time industry well aware may utilize planned obsolescence method increasing profits moore law affected performance technologies significantly michael s. malone wrote moore war following apparent success shock awe early days iraq war progress development guided weapons depends electronic technology improvements circuit density low-power operation associated moore law also contributed development technologies including mobile telephones 3-d printing several measures digital technology improving exponential rates related moore law including size cost density speed components moore wrote density components component transistor resistor diode capacitor minimum cost transistors per integrated circuit – popular formulation doubling number transistors integrated circuits every two years end 1970s moore law became known limit number transistors complex chips graph top shows trend holds true today density minimum cost per transistor – formulation given moore 1965 paper density transistors achieved density transistors cost per transistor lowest transistors put chip cost make transistor decreases chance chip work due defect increases 1965 moore examined density transistors cost minimized observed transistors made smaller advances photolithography number would increase rate roughly factor two per year dennard scaling – suggests power requirements proportional area voltage current proportional length transistors combined moore law performance per watt would grow roughly rate transistor density doubling every 1–2 years according dennard scaling transistor dimensions scaled 30 0.7x every technology generation thus reducing area 50 reduces delay 30 0.7x therefore increases operating frequency 40 1.4x finally keep electric field constant voltage reduced 30 reducing energy 65 power 1.4x frequency 50 therefore every technology generation transistor density doubles circuit becomes 40 faster power consumption twice number transistors stays exponential processor transistor growth predicted moore always translate exponentially greater practical cpu performance since around 2005–2007 dennard scaling appears broken even though moore law continued several years yielded dividends improved performance primary reason cited breakdown small sizes current leakage poses greater challenges also causes chip heat creates threat thermal runaway therefore increases energy costs breakdown dennard scaling prompted switch among chip manufacturers greater focus multicore processors gains offered switching cores lower gains would achieved dennard scaling continued another departure dennard scaling intel microprocessors adopted non-planar tri-gate finfet 22 nm 2012 faster consumes less power conventional planar transistor quality adjusted price equipment – price information technology computers peripheral equipment adjusted quality inflation declined 16 per year average five decades 1959 2009 rate quality-adjusted microprocessor price improvement likewise varies linear log scale microprocessor price improvement accelerated late 1990s reaching 60 per year halving every nine months versus typical 30 improvement rate halving every two years years earlier later laptop microprocessors particular improved 25–35 per year 2004–2010 slowed 15–25 per year 2010–2013 number transistors per chip explain quality-adjusted microprocessor prices fully moore 1995 paper limit moore law strict linearity transistor count definition 'moore law come refer almost anything related semiconductor industry plotted semi-log paper approximates straight line hesitate review origins restrict definition hard disk drive areal density – similar observation sometimes called kryder law made 2005 hard disk drive areal density several decades rapid progress areal density advancement slowed significantly around 2010 noise related smaller grain size disk media thermal stability writability using available magnetic fields fiber-optic capacity – number bits per second sent optical fiber increases exponentially faster moore law keck law honor donald keck network capacity – according gerry/gerald butters former head lucent optical networking group bell labs another version called butters law photonics formulation deliberately parallels moore law butters law says amount data coming optical fiber doubling every nine months thus cost transmitting bit optical network decreases half every nine months availability wavelength-division multiplexing sometimes called wdm increased capacity could placed single fiber much factor 100 optical networking dense wavelength-division multiplexing dwdm rapidly bringing cost networking progress seems assured result wholesale price data traffic collapsed dot-com bubble nielsen law says bandwidth available users increases 50 annually pixels per dollar – similarly barry hendy kodak australia plotted pixels per dollar basic measure value digital camera demonstrating historical linearity log scale market opportunity predict future trend digital camera price lcd led screens resolution great moore law compensator tgmlc also known wirth law – generally referred software bloat principle successive generations computer software increase size complexity thereby offsetting performance gains predicted moore law 2008 article infoworld randall c. kennedy formerly intel introduces term using successive versions microsoft office year 2000 2007 premise despite gains computational performance time period according moore law office 2007 performed task half speed prototypical year 2007 computer compared office 2000 year 2000 computer library expansion – calculated 1945 fremont rider double capacity every 16 years sufficient space made available advocated replacing bulky decaying printed works miniaturized microform analog photographs could duplicated on-demand library patrons institutions foresee digital technology would follow decades later replace analog microform digital imaging storage transmission media automated potentially lossless digital technologies allowed vast increases rapidity information growth era sometimes called information age carlson curve – term coined economist describe biotechnological equivalent moore law named author rob carlson carlson accurately predicted doubling time dna sequencing technologies measured cost performance would least fast moore law carlson curves illustrate rapid cases hyperexponential decreases cost increases performance variety technologies including dna sequencing dna synthesis range physical computational tools used protein expression determining protein structures eroom law – pharmaceutical drug development observation deliberately written moore law spelled backwards order contrast exponential advancements forms technology transistors time states cost developing new drug roughly doubles every nine years experience curve effects says doubling cumulative production virtually product service accompanied approximate constant percentage reduction unit cost acknowledged first documented qualitative description dates 1885 power curve used describe phenomenon 1936 discussion cost airplanes
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Computer architecture
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cram-md5 cryptography cram-md5 challenge-response authentication mechanism cram based hmac-md5 algorithm one mechanisms supported simple authentication security layer sasl often used email software part smtp authentication authentication pop imap users well applications implementing ldap xmpp beep protocols software requires authentication unencrypted connections cram-md5 preferred mechanisms transmit passwords clear codice_1 codice_2 however ca n't prevent derivation password brute-force attack less effective alternative mechanisms avoid passwords use connections encrypted transport layer security tls cram-md5 protocol involves single challenge response cycle initiated server one-way hash fresh random challenge provide three types security cram-md5 defined ietf standards-track document rfc 2195 supersedes rfc 2095 earlier 1997 de facto standards define cram-md5 authentication method email mailbox-management protocols pop imap cram-md5 one authentication methods supported simple authentication security layer sasl defined 2006 rfc 4422 supersedes 1997 standard rfc 2222 internet assigned numbers authority iana maintains registry sasl mechanisms including cram-md5 limited use cram-md5 required on-demand mail relay odmr defined rfc 2645
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Computer security
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black hat briefings black hat briefings commonly referred black hat computer security conference provides security consulting training briefings hackers corporations government agencies around world black hat brings together variety people interested information security ranging non-technical individuals executives hackers industry leading security professionals conference takes place regularly las vegas barcelona london abu dhabi conference also hosted amsterdam tokyo washington d.c. past black hat founded 1997 jeff moss also founded def con today moss conference chair black hat review board considered premier information security conferences world black hat started single annual conference las vegas nevada held multiple locations around world black hat acquired cmp media subsidiary u.k.-based united business media ubm 2005 black hat typically scheduled prior def con many attendees going conferences black hat perceived security industry corporate security conference whereas def con informal conference composed three major sections black hat briefings black hat trainings black hat arsenal briefings composed tracks covering various topics including reverse engineering identity privacy hacking briefings also contain keynote speeches leading voices information security field including robert lentz chief security officer united states department defense michael lynn amit yoran former director national cyber security division department homeland security general keith b. alexander former director national security agency former commander united states cyber command training offered various computer security vendors individual security professionals conference hosted national security agency information assurance manager course various courses cisco systems offensive security others arsenal portion conference dedicated giving researchers open source community place showcase latest open-source information security tools arsenal primarily consists live tool demonstrations setting attendees able ask questions tools sometimes use arsenal added 2010 toolswatch maintains archive black hat briefings arsenals black hat known antics hacker contingent disclosures brought talks conference attendees known hijack wireless connections hotels hack hotel television billing systems even hack automated teller machine hotel lobby 2009 web sites belonging handful security researchers groups hacked passwords private e-mails im chats sensitive documents exposed vandalized site dan kaminsky days conference black hat usa 2009 usb thumb drive passed around among attendees found infected conficker virus 2008 three men expelled packet sniffing press room local area network past companies attempted ban researchers disclosing vital information products black hat usa 2005 cisco systems tried stop michael lynn speaking vulnerability said could let hackers virtually shut internet however recent years researchers worked vendors resolve issues vendors challenged hackers attack products
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Computer security
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incident response team incident response team emergency response team ert group people prepare respond emergency incident natural disaster interruption business operations incident response teams common public service organizations well organizations team generally composed specific members designated incident occurs although certain circumstances team may ad hoc group willing volunteers incident response team members ideally trained prepared fulfill roles required specific situation example serve incident commander event large-scale public emergency size incident grows resources drawn event command situation may shift several phases small-scale event usually volunteer ad hoc team may respond events large small specific member ad hoc teams may work jointly unified command system individual team members trained various aspects response either medical assistance/first aid hazardous material spills hostage situations information systems attacks disaster relief ideally team already defined protocol set actions perform mitigate negative effects incident incident response teams address two different types incidents first types public covers larger incidents affect community whole natural disasters hurricane tornado earthquake etc terrorism large-scale chemical spills epidemics type organizational would incident happens somewhat smaller scale affects mostly single company organization examples organizational incidents include bomb threats computer incidents theft accidental exposure sensitive data exposure intellectual property trade secrets product contamination predefined roles typically filled individuals formally trained standby times scheduled hours teams organized ranks clearly defined chain command examples include teams formed response ad hoc volunteer groups many groups created notion true first respondents civilians incident due teams generally made individuals jobs unrelated situation respond due proximity personal attachment sight incident examples include
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Computer security
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pascal microarchitecture pascal codename gpu microarchitecture developed nvidia successor maxwell architecture architecture first introduced april 2016 release tesla p100 gp100 april 5 2016 primarily used geforce 10 series starting geforce gtx 1080 gtx 1070 using gp104 gpu released may 17 2016 june 10 2016 respectively pascal manufactured using tsmc 16nm finfet process later samsung 14nm finfet process architecture named 17th century french mathematician physicist blaise pascal march 18 2019 nvidia announced driver due april 2019 would enable directx raytracing pascal-based cards starting gtx 1060 6 gb 16 series cards feature reserved turing-based rtx series point march 2014 nvidia announced successor maxwell would pascal microarchitecture announced may 6 2016 released may 27 year tesla p100 gp100 chip different version pascal architecture compared gtx gpus gp104 chip shader units gp104 maxwell-like design architectural improvements gp100 architecture include following architectural improvements gp104 architecture include following chip partitioned graphics processor clusters gpcs gp104 chips gpc encompasses 5 sms streaming multiprocessor corresponds amd compute unit smp encompasses 128 single-precision alus cuda cores gp104 chips 64 single-precision alus gp100 chips amd calls cu compute unit compared nvidia calls sm streaming multiprocessor cu versions consist 64 shader processors i.e 4 simd vector units 16-lane wide 64 nvidia regularly calling shader processors cuda cores experimented different numbers polymorph engine version 4.0 unit responsible tessellation corresponds functionally amd geometric processor moved shader module tpc allow one polymorph engine feed multiple sms within tpc gp104 chip sm consists 128 single-precision alus cuda cores gp100 64 single-precision alus due different organization chips like number double precision alus theoretical double precision performance gp100 half theoretical one single precision ratio 1/32 gp104 chip theoretical single-precision processing power pascal gpu gflops computed 2 x operations per fma instruction per cuda core per cycle × number cuda cores × core clock speed ghz theoretical double-precision processing power pascal gpu 1/2 single precision performance nvidia gp100 1/32 nvidia gp102 gp104 gp106 gp107 gp108 theoretical half-precision processing power pascal gpu 2× single precision performance gp100 1/64 gp102 gp104 gp106 gp107 gp108 pascal next architecture preliminarily codenamed volta nvidia announced volta gpu would feature high bandwidth memory unified memory complete fp16 support two times fp32 nvlink still known volta part consumer lineup may replaced ampere turing microarchitectures
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Computer architecture
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slub software slub unqueued slab allocator memory management mechanism intended efficient memory allocation kernel objects displays desirable property eliminating fragmentation caused allocations deallocations technique used retain allocated memory contains data object certain type reuse upon subsequent allocations objects type used linux became default allocator since 2.6.23
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Computer architecture
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windows ink windows ink software suite windows 10 contains applications features oriented towards pen computing introduced windows 10 anniversary update suite includes sticky notes sketchpad screen sketch applications tablet pc supports pen input windows ink workspace icon taskbar enabled default otherwise enabled manually user windows ink workspace menu contains links top bottom described simple blank canvas quickly easily draw idea doodle create solve problems place user sketch whatever comes mind without launching full blown drawing program sketchbook clip studio paint includes small subset features full-blown drawing programs digital ruler pen options first run loads image unfinished landscape sketches saved images however possible open re-load previously saved sketch user opens windows ink workspace menu screenshot taken screen shown preview snip sketch item menu user taps draw screenshot using controls aforementioned sketchpad feature similar screen write feature samsung galaxy note devices
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Operating systems
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dmailer dmailer specialized portable backup synchronization software range mobile devices including usb flash drives memory cards external hard disk drives mp3 players embedded phone memories sim cards flash-based memory cards mobile phones serving consumers original equipment manufacturers oems dmailer designed developed manufactured marketed portable backup synchronization software dmailer software products bundled sandisk western digital verbatim corporation imation lacie lexar manufacturers ’ portable storage products worldwide dmailer licensed patent-pending synchronization engine technology number companies company flagship product dmailer sync available 19 languages sold 130 countries worldwide 50 million copies shipped date dmailer ’ data backup software supports local online backup march 23 2010 dmailer launched free version backup software dmailer backup v3 software application allows users perform live backup online backup storage device well back pc mac platforms locally via usb drive cd mobile device external hard drive software installation needed restore data included 2 gb free storage online dmailer online online storage service backed secure copies remote server access computer dmailer backup v3 restores data original location elsewhere also performs customized backup product customer support dmailer sync product dmailer online service discontinued dmailer technical assets bought gemalto included yuuwaa service established 2001 dmailer ’ head office located marseille france regional american office chicago illinois local presence australia company founded december 2001 brigitte léonardi winner national contest assistance creation innovative technology companies awarded french ministry research anvar dmailer ’ executives represented nine nationalities ten spoken languages international business experience spanning america north south europe asia pacific dmailer privately held software company received venture capital funding two sources december 2007 bnp paribas private equity alto invest 3.7 million funding provided supports company ’ ongoing r program geared towards delivering efficient productive software solutions customers skype corel microsoft apple developer connection paca mobile center usb simposium dmailer offers branded backup synchronization multimedia software see software listings patent-pending synchronization engine found solutions sold global manufacturers usb flash drives memory cards external hard disk drives dmailer first launched email management application 2001 french “ demêler ” means “ sort organize ” precisely goal first software company help people manage emails 2004 company developed synchronization software called “ dmailer sync ” let users synchronize pcs portable usb drive year dmailer made first oem deal sandisk developed product called “ cruzer sync ” basically dmailer sync branded sandisk cruzer drives 2006 dmailer started shipping dmailer sync along western digital hard drives branded wd sync 2007 2008 dmailer sync shipped along lacie lexar drives “ lacie sync ” “ lexar sync ” respectively 2009 dmailer came backup software called “ dmailer backup ” shipped maxell edgetech verbatim lexar portable drives dmailer backup also available free standalone product customers dmailer sync dmailer backup coupled “ dmailer online ” online storage service lets users backup files online secure servers anytime anywhere access 2009 dmailer also launched product called “ mediamove ” media management software lets user preview media files move phone camera mp3 pc mac share friends upload online media-sharing services dmailer ’ products powered “ dmailer engine ” dmailer engines developed result eight years research development three engines available today serving consumers original equipment manufacturers oems dmailer designs develops manufactures markets portable backup synchronization software solutions dmailer products bundled sandisk western digital verbatim corporation imation lacie lexar manufacturers portable storage products worldwide dmailer licenses patent-pending synchronization engine technology number companies dmailer backup dmailer sync dmailer received deloitte ’ technology fast50 france technology fast500 emea awards 2008 2009 respectively
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Computer security
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cpan comprehensive perl archive network cpan repository 250,000 software modules accompanying documentation 39,000 distributions written perl programming language 12,000 contributors cpan denote either archive network perl program acts interface network automated software installer somewhat like package manager software cpan free open source software cpan conceived 1993 active online since october 1995 based ctan model began place unify structure scattered perl archives like many programming languages perl mechanisms use external libraries code making one file contain common routines used several programs perl calls modules perl modules typically installed one several directories whose paths placed perl interpreter first compiled unix-like operating systems common paths include /usr/lib/perl5 /usr/local/lib/perl5 several subdirectories perl comes small set core modules perform bootstrapping tasks codice_1 used building installing extension modules others like cgi.pm merely commonly used cpan main purpose help programmers locate modules programs included perl standard distribution structure decentralized authors maintain improve modules forking creating competing modules task purpose common formal bug tracking system third-party bug tracking system cpan designated suggested official method reporting issues modules continuous development modules rare many abandoned authors go years new versions released sometimes maintainer appointed abandoned module release new versions module accept patches community module time permits cpan revision control system although source modules often stored github also complete history cpan modules available gitpan project allowing easily see complete history modules easy maintenance forks cpan also used distribute new versions perl well related projects parrot perl 6 files cpan referred distributions distribution may consist one modules documentation files programs packaged common archiving format gzipped tar archive zip file distributions often contain installation scripts usually called makefile.pl build.pl test scripts run verify contents distribution functioning properly new distributions uploaded perl authors upload server pause see section uploading distributions pause 2003 distributions started include metadata files called meta.yml indicating distribution name version dependencies useful information however distributions contain metadata metadata present distribution pause software usually try analyze code distribution look information necessarily reliable thousands distributions cpan needs structured useful distributions cpan divided 24 broad chapters based purpose internationalization locale archiving compression conversion mail usenet news distributions also browsed author finally natural hierarchy perl module names codice_2 codice_3 sometimes used browse modules cpan cpan module distributions usually names form cgi-application-3.1 used module name replaced dash version number appended name convention many prominent distributions break convention especially contain multiple modules security restrictions prevent distribution ever replaced virtually distribution names include version number distribution infrastructure cpan consists worldwide network 250 mirrors 60 countries full mirror hosts around 20 gigabytes data mirrors update hourly daily bidaily cpan master site sites major ftp servers mirror lots software others simply servers owned companies use perl heavily least two mirrors every continent except antarctica several search engines written help perl programmers sort cpan official includes textual search browsable index modules extracted copies distributions currently cpan may 16 2018 perl foundation announced search.cpan.org would shut june 29 2018 19 years operation due aging codebase maintenance burden users transitioned redirected third-party alternative metacpan cpan testers group volunteers download test distributions uploaded cpan enables authors modules tested many platforms environments would otherwise access thus helping promote portability well degree quality smoke testers send reports collated used variety presentation websites including main reports site statistics dependencies also perl core module named cpan usually differentiated repository using name cpan.pm cpan.pm mainly interactive shell used search download install distributions interactive shell called cpan also provided perl core usual way running cpan.pm short configuration process mirror selection uses tools available user computer automatically download unpack compile test install modules also capable updating recently effort replace cpan.pm something cleaner modern resulted cpanplus cpan++ set modules cpanplus separates back-end work downloading compiling installing modules interactive shell used issue commands also supports several advanced features cryptographic signature checking test result reporting finally cpanplus uninstall distribution cpanplus added perl core version 5.10.0 modules check distribution dependencies set recursively install prerequisites either automatically individual user approval support ftp http work firewalls proxies authors upload new distributions cpan perl authors upload server pause must request pause account registered may use web interface pause.perl.org ftp interface upload files directory delete pause warn administrator user uploads module already exists unless listed co-maintainer specified pause web interface experienced perl programmers often comment half perl power cpan called perl killer app roughly equivalent pecl pear php pypi python package index repository python rubygems ruby cran r npm node.js luarocks lua hackage haskell cpan use arbitrated name spaces testing regime well defined documentation style makes generally superior archive languages major languages java c++ nothing similar cpan though java central maven given importance perl developer community cpan shapes shaped perl culture self-appointed master librarian jarkko hietaniemi often takes part april fools day jokes 1 april 2002 site temporarily named cjan j stood java 2003 codice_4 domain name redirected matt script archive site infamous perl community badly written code distributions cpan distributed jokes codice_5 hierarchy reserved joke modules instance codice_6 adds codice_7 function n't run code given complement codice_8 built-in even outside codice_5 hierarchy modules still written largely amusement one example codice_10 used write perl programs subset latin 2005 group perl developers also interest javascript got together create jsan javascript archive network jsan near-direct port cpan infrastructure use javascript language lifespan cohesive community 2008 chance meeting cpan admin adam kennedy open source developers conference linux kernel developer rusty russell created ccan comprehensive c archive network ccan direct port cpan architecture use c language
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Operating systems
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steve jobs steven paul jobs february 24 1955 – october 5 2011 american business magnate entrepreneur investor chairman chief executive officer ceo co-founder apple inc. chairman majority shareholder pixar member walt disney company board directors following acquisition pixar founder chairman ceo next jobs widely recognized pioneer microcomputer revolution 1970s 1980s along apple co-founder steve wozniak jobs born san francisco california put adoption raised san francisco bay area attended reed college 1972 dropping year traveled india 1974 seeking enlightenment studying zen buddhism declassified fbi report states used marijuana lsd college told reporter taking lsd one two three important things done life jobs wozniak co-founded apple 1976 sell wozniak apple personal computer together duo gained fame wealth year later apple ii one first highly successful mass-produced personal computers jobs saw commercial potential xerox alto 1979 mouse-driven graphical user interface gui led development unsuccessful apple lisa 1983 followed breakthrough macintosh 1984 first mass-produced computer gui macintosh introduced desktop publishing industry 1985 addition apple laserwriter first laser printer feature vector graphics jobs forced apple 1985 long power struggle company board then-ceo john sculley year jobs took apple members found next computer platform development company specialized computers higher-education business markets addition helped develop visual effects industry funded computer graphics division george lucas lucasfilm 1986 new company pixar produced first 3d computer animated film toy story 1995 apple merged next 1997 jobs became ceo former company within months largely responsible helping revive apple verge bankruptcy worked closely designer jony ive develop line products larger cultural ramifications beginning 1997 think different advertising campaign leading imac itunes itunes store apple store ipod iphone app store ipad 2001 original mac os replaced completely new mac os x based next nextstep platform giving os modern unix-based foundation first time jobs diagnosed pancreatic neuroendocrine tumor 2003 died respiratory arrest related tumor age 56 october 5 2011 steven paul jobs born february 24 1955 abdulfattah jandali joanne schieble adopted paul clara jobs nee hagopian biological father abdulfattah john al- jandali arabic عبد الفتاح الجندلي b 1931 grew homs syria born arab muslim household undergraduate american university beirut lebanon student activist spent time jail political activities pursued phd university wisconsin met joanne carole schieble catholic swiss german descent doctoral candidate jandali teaching assistant course schieble taking although age mona simpson jobs biological sister notes maternal grandparents happy daughter dating muslim walter isaacson steve jobs official biographer additionally states schieble father threatened cut joanne completely continued relationship jobs adoptive father paul reinhold jobs coast guard mechanic leaving coast guard paul jobs married clara hagopian 1946 clara daughter armenian immigrants grew san francisco paul jobs repo man repaired cars attempts start family halted clara ectopic pregnancy leading consider adoption 1955 schieble became pregnant jobs 1954 jandali spent summer family homs syria jandali stated much love joanne ... sadly father tyrant forbade marry syria told wanted give baby adoption according jandali schieble deliberately involve process without telling joanne upped left move san francisco baby without anyone knowing including ... want bring shame onto family thought best everyone schieble gave birth jobs february 24 1955 san francisco chose adoptive couple catholic well-educated wealthy couple changed mind however decided adopt girl instead baby boy placed paul clara jobs neither college education schieble refused sign adoption papers took matter court attempt baby placed different family consented releasing baby paul clara promised would attend college steve jobs high school mother clara admitted girlfriend 17-year-old chrisann brennan frightened love steve first six months life ... scared going take away even case steve difficult child time two felt made mistake wanted return chrisann shared mother comment steve stated already aware would later say deeply loved indulged paul clara many years later steve jobs wife laurene also noted felt really blessed two parents jobs would become upset paul clara referred adoptive parents regarded parents 1,000 regard biological parents jobs referred sperm egg bank harsh way sperm bank thing nothing paul clara adopted jobs sister patricia 1957 family moved mountain view california 1961 time paul built workbench garage son order pass along love mechanics jobs meanwhile admired father craftsmanship knew build anything needed cabinet would build built fence gave hammer could work ... n't fixing cars ... eager hang dad time ten jobs deeply involved electronics befriended many engineers lived neighborhood difficulty making friends children age however seen classmates loner jobs difficulty functioning traditional classroom tended resist authority figures frequently misbehaved suspended times clara taught read toddler jobs stated pretty bored school turned little terror ... seen us third grade basically destroyed teacher frequently played pranks others monta loma elementary school mountain view father paul abused child never reprimanded however instead blamed school placing enough challenge brilliant son jobs would later credit fourth grade teacher imogene teddy hill turning around taught advanced fourth grade class took month get hip situation bribed learning would say really want finish workbook 'll give five bucks finish really kindled passion learning things learned year think learned year school wanted skip next two years grade school go straight junior high learn foreign language parents wisely would n't let happen jobs skipped fifth grade transferred sixth grade crittenden middle school mountain view became socially awkward loner jobs often bullied gave parents ultimatum either take crittenden would drop school though jobs family well used savings 1967 buy new home would allow jobs change schools new house three-bedroom home crist drive los altos california better cupertino school district cupertino california embedded environment even heavily populated engineering families mountain view home house declared historic site 2013 first site apple computer owned patty occupied jobs step-mother marilyn 13 1968 jobs given summer job bill hewlett hewlett-packard jobs cold-called ask parts electronics project n't know ended giving parts got job summer working hewlett-packard line assembling frequency counters ... well assembling may strong putting screws n't matter heaven bill fernandez fellow electronics hobbyist jobs grade cupertino junior high first friend 1967 move fernandez later commented reason kids eighth grade n't like jobs thought odd one friends fernandez eventually introduced jobs 18-year-old electronics whiz homestead high alum steve wozniak lived across street fernandez location los altos home meant jobs would able attend nearby homestead high school strong ties silicon valley began first year late 1968 along fernandez neither jobs fernandez whose father lawyer came engineering households thus decided enroll john mccollum electronics 1 mccollum rebellious jobs grown hair long become involved growing counterculture would eventually clash jobs began lose interest class also interest sports would later say n't took jock always loner underwent change mid-1970 got stoned first time discovered shakespeare dylan thomas classic stuff read moby dick went back junior taking creative writing classes jobs also later noted official biographer started listen music whole lot started read outside science technology—shakespeare plato loved king lear ... senior phenomenal ap english class teacher guy looked like ernest hemingway took bunch us snowshoeing yosemite point jobs developed two different circles friends involved electronics engineering interested art literature dual interests particularly reflected jobs senior year best friends wozniak first girlfriend artistic homestead junior chrisann brennan 1971 wozniak began attending university california berkeley jobs would visit times week experience led study nearby stanford university student union jobs also decided rather join electronics club would put light shows friend homestead avant-garde jazz program described homestead classmate kind brain kind hippie ... never fit either group smart enough nerd n't nerdy intellectual hippies wanted get wasted time kind outsider high school everything revolved around group n't carefully defined group n't anybody individual world individuality suspect senior year late 1971 taking freshman english class stanford working homestead underground film project chrisann brennan mid-1972 graduation leaving reed college jobs brennan rented house roommate al summer brennan jobs steve wozniak found advertisement posted de anza college bulletin board job required people dress characters alice wonderland brennan portrayed alice wozniak jobs al portrayed white rabbit mad hatter later year jobs enrolled reed college portland oregon reed expensive school paul clara could ill afford spending much life savings son higher education brennan remained involved jobs reed also met friend reed daniel kottke first time jobs also became friends reed student body president robert friedland brennan senior homestead plans attend college supportive jobs told planned drop reed want spend parents money neither father jobs adoptive parents gone college jobs continued attend auditing classes included course calligraphy taught robert palladino jobs longer official student brennan stopped visiting jobs later asked come live house rented near reed campus refused started seeing women interested someone met art class brennan speculated house jobs attempt make relationship monogamous 2005 commencement speech stanford university jobs stated period slept floor friends dorm rooms returned coke bottles food money got weekly free meals local hare krishna temple speech jobs said never dropped single calligraphy course college mac would never multiple typefaces proportionally spaced fonts mid-1973 jobs moved back san francisco bay area renting apartment brennan states point relationship complicated could n't break connection could n't commit steve could n't either jobs hitchhiked worked around west coast brennan would occasionally join time brennan notes little little steve separated never able fully let go never talked breaking going separate ways n't conversation one person says continued grow apart jobs would still seek visit working health food store live-in babysitter remained involved continuing see people 1973 steve wozniak designed version classic video game pong finishing wozniak gave board jobs took game atari inc. los gatos california atari thought jobs built gave job technician atari cofounder nolan bushnell later described difficult valuable pointing often smartest guy room would let people know early 1974 jobs living brennan describes simple life los gatos cabin working atari saving money impending trip india brennan visited twice cabin states memoir memories cabin consist jobs reading giving copy listening south indian music using japanese meditation pillow brennan believed distant negative toward brennan states memoir met jobs right left india tried give 100 bill earned atari initially refused accept eventually accepted money jobs traveled india mid-1974 visit neem karoli baba kainchi ashram reed friend eventual apple employee daniel kottke search spiritual enlightenment got neem karoli ashram almost deserted neem karoli baba died september 1973 made long trek dry riverbed ashram haidakhan babaji india spent lot time bus rides delhi uttar pradesh himachal pradesh staying seven months jobs left india returned us ahead daniel kottke jobs changed appearance head shaved wore traditional indian clothing time jobs experimented psychedelics later calling lsd experiences one two three important things done life spent period one farm commune oregon owned robert friedland brennan joined period time period jobs brennan became practitioners zen buddhism zen master kōbun chino otogawa jobs living parents backyard toolshed converted bedroom sleeping bag mat books candle meditation pillow jobs engaged lengthy meditation retreats tassajara zen mountain center oldest sōtō zen monastery us considered taking monastic residence eihei-ji japan maintained lifelong appreciation zen jobs would later say people around share countercultural roots could fully relate thinking jobs returned atari assigned create circuit board arcade video game breakout according bushnell atari offered ttl chip eliminated machine jobs little specialized knowledge circuit board design made deal wozniak split fee evenly wozniak could minimize number chips much amazement atari engineers wozniak reduced ttl count 46 design tight impossible reproduce assembly line according wozniak jobs told atari gave 700 instead 5,000 paid wozniak share thus 350 wozniak learn actual bonus ten years later said jobs told explained needed money wozniak would given wozniak designed low-cost digital blue box generate necessary tones manipulate telephone network allowing free long-distance calls jobs decided could make money selling clandestine sales illegal blue boxes went well perhaps planted seed jobs mind electronics could fun profitable jobs 1994 interview recalled took six months wozniak figure build blue boxes jobs said blue boxes would apple states showed could take large companies beat jobs wozniak attended meetings homebrew computer club 1975 stepping stone development marketing first apple computer 1976 wozniak designed developed apple computer showed jobs suggested sell jobs wozniak ronald wayne founded apple computer called apple inc. garage jobs los altos home crist drive wayne stayed short time leaving jobs wozniak active primary cofounders company two decided name apple jobs returned one farm commune oregon told wozniak time spent farm apple orchard neighbor crist drive recalled jobs odd individual would greet clients underwear hanging barefoot hippie-like another neighbor larry waterland earned phd chemical engineering stanford recalled dismissing jobs budding business 'you punched cards put big deck said mainframe machines time 'steve took garage circuit board chip dumont tv set panasonic cassette tape deck keyboard said 'this apple computer said 'you 've got joking dismissed whole idea jobs friend reed college india daniel kottke recalled early apple employee person worked garage ... woz would show week latest code steve jobs n't get hands dirty sense kottke also stated much early work took place jobs kitchen spent hours phone trying find investors company received funding then-semi-retired intel product marketing manager engineer mike markkula scott mcnealy one cofounders sun microsystems said jobs broke glass age ceiling silicon valley 'd created successful company young age markkula brought apple attention arthur rock looking crowded apple booth home brew computer show started 60,000 investment went apple board returned journey india brennan visited jobs parents home still living period jobs brennan fell love brennan noted changes attributes kobun also still following also time jobs displayed prototype apple computer brennan parents living room brennan notes shift time period two main influences jobs apple kobun early 1977 jobs would spend time together home duveneck ranch los altos served hostel environmental education center brennan also worked teacher inner city children came learn farm 1977 jobs wozniak introduced apple ii west coast computer faire first consumer product sold apple computer one first highly successful mass-produced microcomputer products world designed primarily steve wozniak jobs oversaw development apple ii unusual case rod holt developed unique power supply jobs usually went work wearing black long-sleeved mock turtleneck made issey miyake sometimes reported st. croix brand levi 501 blue jeans new balance 991 sneakers said choice inspired stuart geman noted applied mathematics professor brown university jobs told biographer walter isaacson ... came like idea uniform daily convenience rationale claimed ability convey signature style jobs became successful new company relationship brennan grew complex 1977 success apple part relationship brennan daniel kottke jobs moved house near apple office cupertino brennan eventually took position shipping department apple brennan relationship jobs deteriorating position apple grew began consider ending relationship small changes october 1977 brennan approached rod holt asked take paid apprenticeship designing blueprints apples holt jobs believed would good position given artistic abilities holt particularly eager take position puzzled ambivalence toward brennan decision however overshadowed fact realized pregnant jobs father took days tell jobs whose face according brennan turned ugly news time according brennan beginning third trimester jobs said never wanted ask get abortion n't want also refused discuss pregnancy brennan confused estranged mother afraid discuss matter father also feel comfortable idea abortion chose instead discuss matter kobun encouraged keep baby pledged support meanwhile holt waiting decision internship brennan stated jobs continued encourage take internship stating could pregnant work apple take job n't get problem brennan however notes felt ashamed thought growing belly professional environment apple child unpredictable turn punishing sentimentally ridiculous could endured brennan turned internship decided leave apple stated jobs told give baby adoption sorry never going help alone brennan welfare cleaning houses earn money would sometimes ask jobs money always refused brennan hid pregnancy long could living variety homes continuing work zen meditation time according brennan jobs started seed people notion slept around infertile meant could child weeks due give birth brennan invited deliver baby one farm accepted offer jobs 23 age biological parents brennan gave birth baby lisa brennan may 17 1978 jobs went birth contacted robert friedland mutual friend farm owner distant jobs worked name baby discussed sitting fields blanket brennan suggested name lisa jobs also liked notes jobs attached name lisa also publicly denying paternity would discover later time jobs preparing unveil new kind computer wanted give female name first choice claire st. clare also stated never gave permission use baby name computer hid plans jobs also worked team come phrase local integrated software architecture alternative explanation apple lisa decades later however jobs admitted biographer walter isaacson obviously named daughter brennan would come intense criticism jobs claimed n't want money wants according brennan apple mike scott wanted jobs give money apple executives advised ignore fight tried go paternity settlement jobs denied paternity dna test established lisa father required give brennan 385 month addition returning welfare money received jobs gave 500 month time apple went public jobs became millionaire brennan worked waitress palo alto later brennan agreed give interview michael moritz time magazine time person year special released january 3 1983 discussed relationship jobs rather name jobs person year magazine named computer machine year issue jobs questioned reliability paternity test stated probability paternity jobs steven ... 94.1 jobs responded arguing 28 male population united states could father time also noted baby girl machine apple placed much hope future share name lisa jobs worth 1 million 1978 23 years old grew 250 million time 25 according estimates also one youngest people ever make forbes list nation richest people—and one handful done without inherited wealth 1978 apple recruited mike scott national semiconductor serve ceo turned several turbulent years 1983 jobs lured john sculley away pepsi-cola serve apple ceo asking want spend rest life selling sugared water want chance change world 1982 jobs bought apartment two top floors san remo manhattan building politically progressive reputation although never lived spent years renovating help i. m. pei 2003 sold u2 singer bono 1984 jobs bought jackling house estate resided decade leased several years 2000 stopped maintaining house allowing exposure weather degrade 2004 jobs received permission town woodside demolish house order build smaller contemporary styled one years court house finally demolished 2011 months died early 1984 apple introduced macintosh based lisa xerox parc mouse-driven graphical user interface conceived early apple employee jef raskin following year apple aired super bowl television commercial titled 1984 apple annual shareholders meeting january 24 1984 emotional jobs introduced macintosh wildly enthusiastic audience andy hertzfeld described scene pandemonium though marketed received fanfare expensive macintosh hard sell shortly release 1985 bill gates then-developing company microsoft threatened stop developing mac applications unless granted license mac operating system software microsoft developing graphical user interface ... dos calling windows n't want apple sue similarities windows gui mac interface sculley granted microsoft license later led problems apple addition cheap ibm pc clones ran microsoft software graphical user interface began appear although macintosh preceded clones far expensive late 1980s windows user interface getting better better thus taking increasingly share apple windows-based ibm-pc clones also led development additional guis ibm topview digital research gem thus graphical user interface beginning taken granted undermining apparent advantage mac ... seemed clear 1980s wound apple could n't go alone indefinitely whole ibm-clone market sculley jobs respective visions company greatly differed former favored open architecture computers like apple ii sold education small business home markets less vulnerable ibm jobs wanted company focus closed architecture macintosh business alternative ibm pc president ceo sculley little control chairman board jobs macintosh division apple ii division operated like separate companies duplicating services although products provided 85 percent apple sales early 1985 company january 1985 annual meeting mention apple ii division employees many left including wozniak stated company going wrong direction last five years sold stock macintosh failure defeat pc strengthened sculley position company may 1985 sculley—encouraged arthur rock—decided reorganize apple proposed plan board would remove jobs macintosh group put charge new product development move would effectively render jobs powerless within apple response jobs developed plan get rid sculley take apple however jobs confronted plan leaked said would leave apple board declined resignation asked reconsider sculley also told jobs votes needed go ahead reorganization months later september 17 1985 jobs submitted letter resignation apple board five additional senior apple employees also resigned joined jobs new venture next following resignation apple 1985 jobs founded next inc. 7 million year later running money sought venture capital product horizon eventually jobs attracted attention billionaire ross perot invested heavily company next computer shown world considered jobs comeback event lavish invitation gala launch event described multimedia extravaganza celebration held louise m. davies symphony hall san francisco california wednesday october 12 1988 steve wozniak said 2013 interview jobs next really getting head together next workstations first released 1990 priced like apple lisa next workstation technologically advanced designed education sector largely dismissed cost-prohibitive educational institutions next workstation known technical strengths chief among object-oriented software development system jobs marketed next products financial scientific academic community highlighting innovative experimental new technologies mach kernel digital signal processor chip built-in ethernet port making use next computer english computer scientist tim berners-lee invented world wide web 1990 cern switzerland revised second generation nextcube released 1990 jobs touted first interpersonal computer would replace personal computer innovative nextmail multimedia email system nextcube could share voice image graphics video email first time interpersonal computing going revolutionize human communications groupwork jobs told reporters jobs ran next obsession aesthetic perfection evidenced development attention nextcube magnesium case put considerable strain next hardware division 1993 sold 50,000 machines next transitioned fully software development release nextstep/intel company reported first profit 1.03 million 1994 1996 next software inc. released webobjects framework web application development next acquired apple inc. 1997 webobjects used build run apple store mobileme services itunes store 1986 jobs funded spinout graphics group later renamed pixar lucasfilm computer graphics division price 10 million 5 million given company capital 5 million paid lucasfilm technology rights first film produced pixar disney partnership toy story 1995 jobs credited executive producer brought fame critical acclaim studio released next 15 years pixar creative chief john lasseter company produced box-office hits bug life 1998 toy story 2 1999 monsters inc. 2001 finding nemo 2003 incredibles 2004 cars 2006 ratatouille 2007 wall-e 2008 2009 toy story 3 2010 finding nemo incredibles ratatouille wall-e toy story 3 received academy award best animated feature award introduced 2001 2003 2004 pixar contract disney running jobs disney chief executive michael eisner tried failed negotiate new partnership early 2004 jobs announced pixar would seek new partner distribute films contract disney expired october 2005 bob iger replaced eisner disney iger quickly worked mend relations jobs pixar january 24 2006 jobs iger announced disney agreed purchase pixar all-stock transaction worth 7.4 billion deal closed jobs became walt disney company largest single shareholder approximately seven percent company stock jobs holdings disney far exceeded eisner holds 1.7 disney family member roy e. disney 2009 death held 1 company stock whose criticisms eisner—especially soured disney relationship pixar—accelerated eisner ousting upon completion merger jobs received 7 disney shares joined board directors largest individual shareholder upon jobs death shares disney transferred steven p. jobs trust led laurene jobs floyd norman pixar described jobs mature mellow individual never interfered creative process filmmakers early june 2014 pixar cofounder walt disney animation studios president ed catmull revealed jobs advised explain understand disagreements catmull released book creativity inc. 2014 recounts numerous experiences working jobs regarding manner dealing jobs catmull writes chrisann brennan notes jobs forced apple apologized many times behavior towards lisa also states jobs said never took responsibility sorry time jobs developed strong relationship lisa nine jobs name birth certificate changed lisa brennan lisa brennan-jobs addition jobs brennan developed working relationship co-parent lisa change brennan credits influence newly found biological sister mona simpson worked repair relationship lisa jobs jobs found mona first finding birth mother joanne schieble simpson shortly left apple jobs contact birth family adoptive mother clara lifetime however would later tell official biographer walter isaacson never wanted paul clara feel like n't consider parents totally parents ... loved much never wanted know search even reporters keep quiet found however 1986 31 clara diagnosed lung cancer began spend great deal time learned details background adoption information motivated find biological mother jobs found birth certificate name san francisco doctor schieble turned pregnant although doctor help jobs alive left letter jobs opened upon death died soon afterwards jobs given letter stated mother unmarried graduate student wisconsin named joanne schieble jobs contacted schieble clara died received permission father paul addition respect paul asked media report search jobs stated motivated find birth mother curiosity need see okay thank 'm glad n't end abortion twenty-three went lot schieble emotional first meeting though n't familiar history apple jobs role told pressured signing adoption papers said regretted giving repeatedly apologized jobs schieble would develop friendly relationship throughout rest life would spend christmas together first visit schieble told jobs sister mona aware brother schieble arranged meet new york mona worked first impression jobs totally straightforward lovely normal sweet guy simpson jobs went long walk get know jobs later told biographer mona completely thrilled first life mother emotionally affectionate toward got know became really good friends family n't know 'd without ca n't imagine better sister adopted sister patty never close jobs learned family history six months given adoption schieble father died wed jandali daughter mona jandali states finishing phd returned syria work period schieble left divorced 1962 also states divorce lost contact mona period time also bear responsibility away daughter four years old mother divorced went syria got back touch 10 years lost touch mother moved n't know since 10 years ago 've constant contact see three times year organized trip last year visit syria lebanon went relative florida years later schieble married ice skating teacher george simpson mona jandali took stepfather last name thus became mona simpson 1970 divorced schieble took mona los angeles raised jobs told official biographer meeting simpson wanted become involved ongoing search father found working sacramento decided simpson would meet jandali simpson spoke several hours point told left teaching restaurant business also said schieble given another child away adoption 'll never see baby baby gone simpson mention met jobs jandali told simpson managed mediterranean restaurant near san jose successful technology people used come even steve jobs ... oh yeah used come sweet guy big tipper hearing visit jobs recalled amazing ... restaurant times remember meeting owner syrian balding shook hands however jobs want meet jandali wealthy man n't trust try blackmail go press ... asked mona tell jandali later discovered relationship jobs online blog contacted simpson asked thing steve jobs simpson told true later commented father thoughtful beautiful storyteller passive ... never contacted steve simpson researched syrian roots began meet members family assumed jobs would eventually want meet father never jobs also never showed interest syrian heritage middle east simpson fictionalized search father 1992 novel lost father malek jandali cousin 1989 jobs first met future wife laurene powell gave lecture stanford graduate school business student soon event stated laurene right front row lecture hall could n't take eyes ... kept losing train thought started feeling little giddy lecture jobs met parking lot invited dinner point forward together minor exceptions rest life powell father died young mother raised middle class new jersey home similar one jobs grew received ba university pennsylvania spent short period high finance found n't interest decided pursue mba stanford instead addition unlike jobs athletic followed professional sports also brought much self-sufficiency relationship private public person jobs proposed new year day 1990 fistful freshly picked wildflowers married march 18 1991 buddhist ceremony ahwahnee hotel yosemite national park fifty people including father paul sister mona attended ceremony conducted jobs guru kobun chino otogawa vegan wedding cake shape yosemite half dome wedding ended hike laurene brothers snowball fight jobs reported said mona see mona ... laurene descended joe namath 're descended john muir jobs powell first child reed born september 1991 jobs father paul died year half later march 5 1993 jobs powell two children erin born august 1995 eve born 1998 family lived palo alto california journalist grew locally remembered owning house scariest halloween decorations palo alto ... n't remember seeing busy terrified 1996 apple announced would buy next 427 million deal finalized february 1997 bringing jobs back company cofounded jobs became de facto chief then-ceo gil amelio ousted july 1997 formally named interim chief executive september march 1998 concentrate apple efforts returning profitability jobs terminated number projects newton cyberdog opendoc coming months many employees developed fear encountering jobs riding elevator afraid might job doors opened reality jobs summary executions rare handful victims enough terrorize whole company jobs changed licensing program macintosh clones making costly manufacturers continue making machines purchase next much company technology found way apple products notably nextstep evolved mac os x jobs guidance company increased sales significantly introduction imac new products since appealing designs powerful branding worked well apple 2000 macworld expo jobs officially dropped interim modifier title apple became permanent ceo jobs quipped time would using title iceo company subsequently branched introducing improving upon digital appliances introduction ipod portable music player itunes digital music software itunes store company made forays consumer electronics music distribution june 29 2007 apple entered cellular phone business introduction iphone multi-touch display cell phone also included features ipod mobile browser revolutionized mobile browsing scene nurturing open-ended innovation jobs also reminded employees real artists ship jobs public war words dell computer ceo michael dell starting 1987 jobs first criticized dell making un-innovative beige boxes october 6 1997 gartner symposium dell asked would ran then-troubled apple computer company said 'd shut give money back shareholders 2006 jobs sent email employees apple market capitalization rose dell jobs admired criticized consummate skill persuasion salesmanship dubbed reality distortion field particularly evident keynote speeches colloquially known stevenotes macworld expos apple worldwide developers conferences jobs board member gap inc. 1999 2002 2001 jobs granted stock options amount 7.5 million shares apple exercise price 18.30 alleged options backdated exercise price 21.10 alleged jobs thereby incurred taxable income 20,000,000 report apple overstated earnings amount result jobs potentially faced number criminal charges civil penalties case subject active criminal civil government investigations though independent internal apple investigation completed december 29 2006 found jobs unaware issues options granted returned without exercised 2003 2005 jobs responded criticism apple poor recycling programs e-waste us lashing environmental advocates apple annual meeting cupertino april weeks later apple announced would take back ipods free retail stores computer takeback campaign responded flying banner plane stanford university graduation jobs commencement speaker banner read steve n't mini-player—recycle e-waste 2006 expanded apple recycling programs us customer buys new mac program includes shipping environmentally friendly disposal old systems success apple unique products services provided several years stable financial returns propelling apple become world valuable publicly traded company 2011 jobs perceived demanding perfectionist always aspired position businesses products forefront information technology industry foreseeing setting innovation style trends summed self-concept end keynote speech macworld conference expo january 2007 quoting ice hockey player wayne gretzky july 1 2008 billion class action suit filed several members apple board directors revenue lost alleged securities fraud 2011 interview biographer walter isaacson jobs revealed met us president barack obama complained nation shortage software engineers told obama headed one-term presidency jobs proposed foreign student got engineering degree us university automatically offered green card meeting jobs commented president smart kept explaining us reasons things ca n't get done infuriates october 2003 jobs diagnosed cancer mid-2004 announced employees cancerous tumor pancreas prognosis pancreatic cancer usually poor jobs stated rare much less aggressive type known islet cell neuroendocrine tumor despite diagnosis jobs resisted doctors recommendations medical intervention nine months instead relying alternative medicine thwart disease according harvard researcher ramzi amri choice alternative treatment led unnecessarily early death doctors agree jobs diet insufficient address disease however cancer researcher alternative medicine critic david gorski wrote impossible know whether much might decreased chances surviving cancer flirtation woo best guess jobs probably modestly decreased chances survival barrie r. cassileth chief memorial sloan kettering cancer center integrative medicine department said jobs faith alternative medicine likely cost life ... kind pancreatic cancer treatable curable ... essentially committed suicide according jobs biographer walter isaacson nine months refused undergo surgery pancreatic cancer – decision later regretted health declined instead tried vegan diet acupuncture herbal remedies treatments found online even consulted psychic also influenced doctor ran clinic advised juice fasts bowel cleansings unproven approaches finally surgery july 2004 eventually underwent pancreaticoduodenectomy whipple procedure july 2004 appeared remove tumor successfully jobs receive chemotherapy radiation therapy jobs absence tim cook head worldwide sales operations apple ran company early august 2006 jobs delivered keynote apple annual worldwide developers conference thin almost gaunt appearance unusually listless delivery together choice delegate significant portions keynote presenters inspired flurry media internet speculation state health contrast according ars technica journal report worldwide developers conference wwdc attendees saw jobs person said looked fine following keynote apple spokesperson said steve health robust two years later similar concerns followed jobs 2008 wwdc keynote address apple officials stated jobs victim common bug taking antibiotics others surmised cachectic appearance due whipple procedure july conference call discussing apple earnings participants responded repeated questions jobs health insisting private matter others said shareholders right know given jobs hands-on approach running company based off-the-record phone conversation jobs new york times reported health problems amounted good deal common bug n't life-threatening n't recurrence cancer august 28 2008 bloomberg mistakenly published 2500-word obituary jobs corporate news service containing blank spaces age cause death news carriers customarily stockpile up-to-date obituaries facilitate news delivery event well-known figure death although error promptly rectified many news carriers blogs reported intensifying rumors concerning jobs health jobs responded apple september 2008 let rock keynote paraphrasing mark twain reports death greatly exaggerated subsequent media event jobs concluded presentation slide reading 110/70 referring blood pressure stating would address questions health december 16 2008 apple announced marketing vice-president phil schiller would deliver company final keynote address macworld conference expo 2009 reviving questions jobs health statement given january 5 2009 apple.com jobs said suffering hormone imbalance several months january 14 2009 jobs wrote internal apple memo previous week learned health-related issues complex originally thought announced six-month leave absence end june 2009 allow better focus health tim cook previously acted ceo jobs 2004 absence became acting ceo apple jobs still involved major strategic decisions 2009 tim cook offered portion liver jobs since share rare blood type donor liver regenerate tissue operation jobs yelled 'll never let 'll never april 2009 jobs underwent liver transplant methodist university hospital transplant institute memphis tennessee jobs prognosis described excellent january 17 2011 year half jobs returned work following liver transplant apple announced granted medical leave absence jobs announced leave letter employees stating decision made could focus health time 2009 medical leave apple announced tim cook would run day-to-day operations jobs would continue involved major strategic decisions company leave jobs appeared ipad 2 launch event march 2 wwdc keynote introducing icloud june 6 cupertino city council june 7 august 24 2011 jobs announced resignation apple ceo writing board always said ever came day could longer meet duties expectations apple ceo would first let know unfortunately day come jobs became chairman board named tim cook successor ceo jobs continued work apple day death six weeks later jobs died palo alto california home around 3 p.m. pdt october 5 2011 due complications relapse previously treated islet-cell pancreatic neuroendocrine tumor resulted respiratory arrest lost consciousness day died wife children sisters side sister mona simpson described death thus steve final words hours earlier monosyllables repeated three times embarking 'd looked sister patty long time children life partner laurene shoulders past steve final words 'oh wow oh wow oh wow lost consciousness died several hours later small private funeral held october 7 2011 details respect jobs family made public apple pixar issued announcements death apple announced day plans public service encouraging well-wishers send remembrance messages email address created receive messages apple microsoft flew flags half-staff throughout respective headquarters campuses bob iger ordered disney properties including walt disney world disneyland fly flags half-staff october 6 12 2011 two weeks following death apple displayed corporate web site simple page showed jobs name lifespan next grayscale portrait october 19 2011 apple employees held private memorial service jobs apple campus cupertino jobs widow laurene attendance well cook bill campbell norah jones al gore coldplay apple retail stores closed briefly employees could attend memorial video service uploaded apple website california governor jerry brown declared sunday october 16 2011 steve jobs day day invitation-only memorial held stanford university attendance included apple tech company executives members media celebrities close friends jobs politicians along jobs family bono yo yo joan baez performed service lasted longer hour service highly secured guards university gates helicopter flying overhead area news station attendee given small brown box farewell gift jobs box contained copy autobiography yogi paramahansa yogananda apple co-founder steve wozniak former owner would become pixar george lucas ref name= http //postcards.blogs.fortune.cnn.com/2011/10/06/george-lucas-steve-jobs/ /ref former rival microsoft co-founder bill gates president barack obama offered statements response death jobs buried unmarked grave alta mesa memorial park nonsectarian cemetery palo alto steve jobs subject number books films lisa brennan-jobs jobs eldest daughter described jobs memoir sexually inappropriate described patterns cruel behavior adolescent years jobs design aesthetic influenced philosophies zen buddhism india experienced buddhism seven-month spiritual journey sense intuition influenced spiritual people studied also learned many references sources modernist architectural style joseph eichler industrial designs richard sapper dieter rams according apple cofounder steve wozniak steve n't ever code n't engineer n't original design ... daniel kottke one apple earliest employees college friend jobs stated woz jobs woz innovator inventor steve jobs marketing person listed either primary inventor co-inventor 346 united states patents patent applications related range technologies actual computer portable devices user interfaces including touch-based speakers keyboards power adapters staircases clasps sleeves lanyards packages jobs contributions patents look feel product industrial design chief jonathan ive name along 200 patents design patents specific product designs example jobs listed primary inventor patents original lamp-style imacs well powerbook g4 titanium opposed utility patents inventions 43 issued us patents inventions patent mac os x dock user interface magnification feature issued day died although jobs little involvement engineering technical side original apple computers jobs later used ceo position directly involve product design involved many projects throughout career long-time marketing executive confidant joanna hoffman known one employees apple next could successfully stand jobs also engaging even terminally ill hospital jobs sketched new devices would hold ipad hospital bed also despised oxygen monitor finger suggested ways revise design simplicity since death former apple ceo 141 patents inventors win lifetimes currently jobs holds 450 patents apple ii 8-bit home computer one world first highly successful mass-produced microcomputer products designed primarily steve wozniak jobs oversaw development apple ii unusual case rod holt developed unique power supply introduced 1977 west coast computer faire jobs wozniak first consumer product sold apple computer lisa personal computer designed apple early 1980s first personal computer offer graphical user interface machine aimed individual business users development lisa began 1978 lisa sold poorly 100,000 units sold 1982 jobs forced lisa project joined macintosh project macintosh direct descendant lisa although obvious similarities systems final revision lisa 2/10 modified sold macintosh xl joined original macintosh team jobs took project wozniak experienced traumatic airplane accident temporarily left company jobs introduced macintosh computer january 24 1984 first mass-market personal computer featuring integral graphical user interface mouse first model later renamed macintosh 128k uniqueness amongst populous family subsequently updated models also based apple proprietary architecture since 1998 apple largely phased macintosh name favor mac though product family nicknamed mac mac since development first model macintosh introduced us 1.5 million ridley scott television commercial 1984 notably aired third quarter super bowl xviii january 22 1984 people consider ad watershed event masterpiece regis mckenna called ad successful mac 1984 uses unnamed heroine represent coming macintosh indicated picasso-style picture computer white tank top means saving humanity conformity ibm attempts dominate computer industry ad alludes george orwell novel nineteen eighty-four describes dystopian future ruled televised big brother macintosh however expensive hindered ability competitive market already dominated commodore 64 consumers well ibm personal computer accompanying clone market businesses macintosh systems still found success education desktop publishing kept apple second-largest pc manufacturer next decade jobs forced apple 1985 started company built workstation computers next computer introduced 1988 lavish launch event tim berners-lee created world first web browser worldwideweb using next computer next computer operating system named nextstep basis darwin kernel operating system apple products namely macos ios watchos audioos apple imac introduced 1998 innovative design directly result jobs return apple apple boasted back computer looks better front anyone else described cartoonlike first imac clad bondi blue plastic unlike personal computer came 1999 apple introduced graphite gray apple imac since varied shape colour size considerably maintaining all-in-one design design ideas intended create connection user handle breathing light effect computer went sleep apple imac sold 1,299 time imac also featured forward-thinking changes eschewing floppy disk drive moving exclusively usb connecting peripherals latter change resulted imac success interface popularised among third-party peripheral makers—as evidenced fact many early usb peripherals made translucent plastic match imac design itunes media player media library online radio broadcaster mobile device management application developed apple used play download organize digital audio video well types media available itunes store personal computers running macos microsoft windows operating systems itunes store also available ipod touch iphone ipad itunes store users purchase download music music videos television shows audiobooks podcasts movies movie rentals countries ringtones available iphone ipod touch fourth generation onward application software iphone ipad ipod touch downloaded app store first generation ipod released october 23 2001 major innovation ipod small size achieved using 1.8 hard drive compared 2.5 drives common players time capacity first generation ipod ranged 5 gb 10 gb ipod sold us 399 100,000 ipods sold end 2001 introduction ipod resulted apple becoming major player music industry also ipod success prepared way itunes music store iphone 1st generation ipod apple released hard drive-based ipod classic touchscreen ipod touch video-capable ipod nano screenless ipod shuffle following years apple began work first iphone 2005 first iphone released june 29 2007 iphone created sensation survey indicated six ten americans aware release time declared invention year 2007 completed iphone multimedia capabilities functioned quad-band touch screen smartphone year later iphone 3g released july 2008 three key features support gps 3g data tri-band umts/hsdpa june 2009 iphone 3gs whose improvements included voice control better camera faster processor introduced phil schiller iphone 4 thinner previous models five megapixel camera capable recording video 720p hd adds secondary front-facing camera video calls major feature iphone 4s introduced october 2011 siri virtual assistant capable voice recognition ipad ios-based line tablet computers designed marketed apple first ipad released april 3 2010 recent ipad models ipad 2017 ipad pro ipad mini 4 released september 9 2015 march 24 2017 user interface built around device multi-touch screen including virtual keyboard ipad includes built-in wi-fi cellular connectivity select models 250 million ipads sold
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Operating systems
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tony hoare sir charles antony richard hoare born 11 january 1934 british computer scientist developed sorting algorithm quicksort 1959/1960 also developed hoare logic verifying program correctness formal language communicating sequential processes csp specify interactions concurrent processes including dining philosophers problem inspiration occam programming language born colombo ceylon sri lanka british parents tony hoare father colonial civil servant mother daughter tea planter hoare educated england dragon school oxford king school canterbury studied classics philosophy greats merton college oxford graduating 1956 18 months national service royal navy learned russian returned university oxford 1958 study postgraduate certificate statistics began computer programming taught autocode ferranti mercury leslie fox went moscow state university british council exchange student studied machine translation andrey kolmogorov 1960 hoare left soviet union began working elliott brothers ltd small computer manufacturing firm located london implemented algol 60 began developing major algorithms became professor computing science queen university belfast 1968 1977 returned oxford professor computing lead programming research group oxford university computing laboratory department computer science university oxford following death christopher strachey emeritus professor also principal researcher microsoft research cambridge england hoare significant work following areas sorting selection algorithm quicksort quickselect hoare logic formal language communicating sequential processes csp used specify interactions concurrent processes structuring computer operating systems using monitor concept axiomatic specification programming languages speaking software conference called qcon london 2009 apologised inventing null reference many years leadership oxford department worked formal specification languages csp z achieve expected take-up industry 1995 hoare led reflect upon original assumptions 1962 hoare married jill pym member research team
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Programming language topics
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yottabyte llc yottabyte llc software-defined data center sddc company founded 2010 headquartered bloomfield township oakland county michigan yottabyte also operates three physical data centers throughout united states yottabyte software enables companies build virtual data centers industry standard server storage networking gear software yottabyte founded 2010 founders include greg campbell vice president technology paul e. hodges iii president ceo duane tursi yottabyte concept originated campbell hodges sitting conference room tossing around ideas campbell cto developed yottabyte software architecture yottabyte llc named cool vendor compute platform gartner 2016 runner virtualization trailblazers 2015 tech trailblazers september 2016 yottabyte partnered university michigan accelerate data-intensive research project known yottabyte research cloud gives scientists access high-performance secure flexible computing environments enables analysis sensitive data sets restricted federal privacy laws proprietary access agreements confidentiality requirements may 2017 yottabyte brought michael j. aloe board senior vice president sales operations aloe announced chief operations officer coo may 2018
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Distributed computing architecture
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palm pre palm pre styled palm prē multitasking smartphone designed marketed palm multi-touch screen sliding keyboard smartphone first use palm linux based mobile operating system webos pre functions camera phone portable media player location navigation capabilities pre also serves personal information manager number communication collaboration applications bluetooth wi-fi connectivity built-in pre launched united states america june 6 2009 sprint later canada bell mobility gsm version original pre launched later 2009 number networks europe mexico revised model palm pre plus doubled available memory internal storage launched january 25 2010 verizon wireless later released mobility may 16 2010 third generation palm pre palm pre 2 uses hp webos 2.0 announced october 2010 palm pre became fastest selling phone sprint history widely praised device palm debuted pre 2009 consumer electronics show first mobile phone use texas instruments omap 3430 processor well initial us exclusive carrier agreement sprint operates cdma network prior device launch known internally codename castle white castle 'slider hamburgers since palm first slider phone apple accused pre copying elements user interface apple coo tim cook stating stand people ripping ip palm responding tools necessary defend hinting palm large portfolio patents may 19 2009 sprint palm announced pre would available beginning june 6 2009 united states may 28 2009 verizon wireless announced would also carry palm pre six months later comment sprint spokesperson indicated launch carrier would us exclusivity rights pre 2009 sprint ceo dan hesse commented company palm agreed discuss length exclusivity deal remarked six months july 7 2009 telefónica announced would exclusively carry palm pre uk spain ireland germany o2 movistar networks availability winter holidays palm pre available longer available uk july 27 2009 company second quarter conference call verizon chief operating officer denny strigl announced verizon wireless would begin selling palm pre early 2010 news coverage launch noted sales quantity record sprint phone launch estimated sales approximately 50,000 units day 100,000 week however reports stated sales pre july beginning august much lower expected august 27 2009 bell canada made palm pre available bell supporting data services evdo network november 11 2009 palm announced pre would available mexico naming telcel exclusive carrier pre nation sales mexico began november 27 new version smartphone palm pre plus announced ces 2010 differences included removal center button 16 gb storage memory 8 gb original pre doubling ram 256 mb 512 mb back cover already touchstone compatible keyboard slider mechanism also refined us initially sold exclusively along pixi plus verizon wireless march 22 2010 palm announced would releasing pre plus pixi plus network coming months o2 launched palm pre plus may 16 2010 us 149.99 free touchstone charger new customers october 19 2010 hp announced third generation palm pre palm pre 2 used hp webos 2.0 device 1 ghz processor 512 mb ram 5-megapixel camera adobe flash player 10.1 beta durable hardware including gorilla glass screen phone released consumers france 2010 october sfr canada 2010 december rogers u.s. 2011 february verizon also available unlocked hp hp stated verizon wireless customers would able use skype mobile skype-to-skype calls messaging webos 2.0 released consumer use december 2011 hp provided firmware update 2.2.4 original palm pre cpu 600 mhz texas instruments omap 3430 arm cortex a8 powervr sgx underclocked 500 mhz uses marvell sd8686 chip wireless lan sdio adapter wifi stmicroelectronics vx6852 3.15-megapixel resolution sensor 2048 x 1536 camera pre phones feature 3.1-inch capacitive touchscreen 24-bit color 320×480 resolution hvga liquid-crystal display touchscreen allows manipulation ui fingers instead stylus commonly used older palm phones pdas display gesture area touch-sensitive area led underlighting permits additional touch commands pre full qwerty keyboard pre keyboard slides curved ergonomics addition keyboard device features single button center gesture area absent pre plus volume rocker switch side ringer switch top pre features three input sensors allow respond surroundings accelerometer automatically changes orientation display landscape portrait device rotated user hands ambient light sensor allows pre automatically adjust brightness display proximity sensor allows pre disregard touch inputs phone held close user face call original pre 3 megapixel digital camera led flash pre available high-speed connectivity either evdo rev umts hsdpa depending location pre also includes 802.11b/g wifi bluetooth 2.1+edr support a2dp stereo headsets a-gps support turn-by-turn navigation also included though access agps features remains locked verizon wireless users charging data-transfer pre uses microusb connector usb 2.0 support audio output supported standard 3.5 mm headphone jack phone reports support bluetooth dun protocol sprint permitted use pre tethered phone modem mode verizon support tethering via mobile hot spot support homebrew community many patches apps allow change settings pre one includes free hotspot app sprint users pre 8 gb internal flash storage approximately 7.4 gb user accessible pre flash memory card slot pre plus 16 gb internal flash storage pre charged either using supplied microusb cable using optional accessory wireless charging using electromagnetic induction charging dock dubbed touchstone charger touchstone charger requires compatible back cover also sold separately pre pre plus comes touchstone-compatible back cover included possible access developer mode writing konami code entered upupdowndownleftrightleftrightbastart home screen also possible write webos20090606 pre first palm device use webos linux-based platform replaced palm previous palm os webos interface based system cards used manage multitasking webos also supports multi-touch gestures enabling navigational input made using touchscreen pre include virtual keyboard portrait-oriented slide-out keyboard onscreen virtual keyboard embedded code made available third party patch hundreds third party patches allow users customize usability interface pre webos includes feature called synergy integrates information many sources webos allows user sign accounts gmail yahoo facebook linkedin microsoft outlook via exchange activesync contacts sources integrated single list synergy highly innovative regarded many highlight new operating system received criticism undiscerning included contacts application example engadget commented contacts simply birthdays extracted facebook device makes use cloud based services model uses desktop sync client style palm hotsync synchronization method however palm referenced number solutions users need sync desktop software like palm desktop microsoft outlook ibm lotus notes additionally mark/space inc. announced macintosh desktop sync software chapura software windows palm offered online guide help customers official homebrew third-party packages webos reviewed main article according former debian developer joey hess palm pre periodically sends users information palm palm gathers users gps information along data every application used long used information uploaded palm daily basis opt-out user first uses gps system common mobile carriers google maps also opt-out gps data sent google showcased 2009 january five months prelaunch pre received positive reviews winning cnet best show best category cell phones smartphones people voice ces 2009 palm pre suffered numerous quality issues slider mechanism felt loose could cause wiggle issue became known oreo twist users palm aimed address issue pre plus making slider mechanism stronger curved plastic screen seemed delicate sometimes cracking pocket reports faulty headphone jacks palm pre plus characters sometimes appeared twice typing although user hit key many reviews noted poor build quality phones engadget second open letter palm cited hardware issues plagued pre outward acknowledgment rush correct added 've seen countless reports read many blog posts recall heard sorts horror stories broken sliders power buttons stop functioning oreo cookie effect hell even first review unit broke overall sales modest outset users expressed intense concern slow pace webos upgrade releases absence substantially improved hardware comments critical lengthy delay releasing promised flash application dysfunctional document handling pdf files speculation could underlying technological business reasons slow release webos 2 upgrade existing phones concern eventually released webos 2 upgrade would incompatible palm os emulation media opinion 2010 december enthusiastic fastest-selling cell phone sprint history pre described palm swan song since sales enough keep company afloat leading acquisition hp nonetheless pre still regarded innovative even ten years launch
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Operating systems
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qualified website authentication certificate qualified website authentication certificate qwac certificate qualified digital certificate trust services defined eidas regulation enisa report proposed six strategies twelve recommended actions escalated approach targets important aspects detected critical improving website authentication market europe successfully introducing qualified website authentication certificates means increase transparency market different types website authentication certificates domain validated dv organization validated ov extended validation ev another distinction made among types website authentication certificates relates number domains secured certificate single domain wildcard multi domain extended validation certificates offer highest quality terms assurance identity certificate owner among existing types certificate market typically use ev certificate indicated green color – varies browser eidas regulation taken account established market industrial standardization efforts objective create disruption existing initiatives optimize effort qualified providers align eu regulations existing market standards eidas regulation trust services defined electronic services normally provided trust service providers tsps consist electronic signatures electronic seals electronic time stamps electronic registered delivery services website authentication essence eidas regulation provides framework promote website authentication certificates one five trust service defined eidas regulation article 45 sets requirement trust service providers issuing qualified website authentication certificates qualified implies requirements qualified trust service providers qtsps described previous section applicable annex iv defines content qualified certificates website authentication
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Computer security
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thttpd thttpd tiny/turbo/throttling http server open source software web server acme laboratories designed simplicity small execution footprint speed thttpd single-threaded portable compiles cleanly unix-like operating systems including freebsd sunos 4 solaris 2 bsd/os linux osf/1 executable memory size 50 kb used simplified replacement feature-rich servers uniquely suited service high volume requests static data—for example image hosting server first thttpd stands variously tiny turbo throttling thttpd bandwidth throttling feature enables server administrator limit maximum bit rate certain types files may transferred example administrator may choose restrict transfer jpeg image files 20 kilobytes per second prevents connection becoming saturated server still responsive heavy load tradeoff file transfer speed reduced thttpd support x-forwarded-for header least 2 public forks thttpd
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Web technology
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universal access apple universal access component mac os x operating system provides computing abilities people visual impairment hearing impairment physical disability universal access preference pane system preferences application includes four sub-components providing different options settings
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Operating systems
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hostages video game hostages tactical shooter video game developed published infogrames released acorn electron archimedes atari st amiga apple iigs amstrad cpc bbc micro commodore 64 ms-dos msx nes zx spectrum platforms 1988 game released hostage rescue mission united states operation jupiter france nes port titled rescue embassy mission hostages terrorist group overrun embassy paris player takes control six-man gign team mission free hostages game split two three depending platform distinct sections hostages well received critics game received 5 5 stars dragon computer gaming world gave pc version positive review noting poor joystick keyboard response significant problem otherwise great game compute called hostages one better amiga combat games noting involve aliens swords sequel hostages titled alcatraz released infogrames amiga atari st dos platforms 1992
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Computer architecture
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atari tos tos operating system also tramiel operating system jack tramiel owner atari corp. time operating system atari st range computers range includes 520st 1040st stf/m/fm ste variants mega st/ste later 32-bit machines tt falcon030 developed using new version tos called multitos allowed multitasking recently users developed tos freemint atari tos operating system debuted atari 520st 1985 tos combines digital research gem gui running top dos-like gemdos features include flat memory model ms-dos-compatible disk format starting tos 1.04 support midi variant scsi called acsi later versions atari tos usually run rom chips contained computer thus local hard drives available home computers almost instant-running os tos booted floppy disks first sts half year st introduced st models started shipping latest version tos rom tos consisted following following extensions tos loaded separately true multitasking directly supported tos allowed six desk accessories loaded system similar tsrs terminate stay resident pcs multitos developed allow tos preemptively multitask tos desktop uses icons represent files devices windows dialog boxes display info desktop file desktop.inf read determine window settings icon placements drive icons otherwise standard default desktop two floppy icons trash icon used later versions use newdesk.inf saving reading desktop configuration executable files identified extensions tos programs gem programs auto boot placing folder named auto tos 1.4 allows gem programs set load automatically install application dialog programs *.ttp extensions environments used auto boot desktop accessories placed root directory default drive loaded automatically atari tos based gemdos uses modified fat12 hard disks fat16 file system major differences fact boot sector need contain ibm compatible jump sequence beginning typically 0xe9 0x 0x 0xeb 0x 0x90 lack tos 1.04 oem identifier compatible pc-based systems fact checksum used mark boot sector executable pc format uses signature word 0x55 0xaa instead executable boot sectors atari platform typically start mc68k jump opcode e.g 0x603c last two byte word must sum rest boot sector big-endian word form 0x1234 order bootable unlike ms-dos gemdos would typically allow disks unusual sector track counts disks 10 even 11 sectors per track 80 formatted tracks uncommon atari community typically safe combination 10 sectors per track 80 tracks used yielding unformatted capacity 800kb many users pushed capacity double density disks 900kb using custom formats gemdos disc file systems read using dos windows 9x tos 4.92 version multitos multitasking version tos format .img designed written rom chip tos 4 rom contains five user-selectable language versions
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Operating systems
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netware file system computing netware file system nwfs file system based heavily modified version fat used novell netware operating system default file system volumes versions 2.x 4.x default file system sys volume continuing version 5.x novell developed two varieties nwfs novell storage services nss released 1998 superseded nwfs format nwfs on-disk format never publicly documented novell published specifications 32-bit nwfs larger files file system utilized performance feature named turbo fat transparent file compression also supported although significant impact performance file serving every name space requires separate directory entry file maximum number directory entries 16,000,000 two resident name spaces would reduce usable maximum number directory entries 8,000,000 three 5,333,333 16-bit nwfs could handle volumes 256 mib however name-space support dedicated api handle macintosh clients
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Computer file systems
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tcpdump tcpdump common packet analyzer runs command line allows user display tcp/ip packets transmitted received network computer attached distributed bsd license tcpdump free software tcpdump works unix-like operating systems linux solaris freebsd dragonfly bsd netbsd openbsd openwrt macos hp-ux 11i aix systems tcpdump uses libpcap library capture packets port tcpdump windows called windump uses winpcap windows port libpcap tcpdump originally written 1988 van jacobson sally floyd vern paxson steven mccanne time working lawrence berkeley laboratory network research group late 1990s numerous versions tcpdump distributed part various operating systems numerous patches well coordinated michael richardson mcr bill fenner created www.tcpdump.org 1999. tcpdump prints contents network packets read packets network interface card previously created saved packet file tcpdump write packets standard output file also possible use tcpdump specific purpose intercepting displaying communications another user computer user necessary privileges system acting router gateway unencrypted traffic telnet http passes use tcpdump view login ids passwords urls content websites viewed unencrypted information user may optionally apply bpf-based filter limit number packets seen tcpdump renders output usable networks high volume traffic example available capture interfaces linux system unix-like operating systems user must superuser privileges use tcpdump packet capturing mechanisms systems require elevated privileges however -z option may used drop privileges specific unprivileged user capturing set unix-like operating systems packet capturing mechanism configured allow non-privileged users use done superuser privileges required
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Computer security
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phyreengine phyreengine free use game engine sony interactive entertainment despite origins sony compatible playstation platforms support playstation 4 playstation 3 playstation vr playstation vita playstation portable microsoft windows opengl directx 11 google android apple ios phyreengine adopted several game studios used 200 published titles phyreengine distributed installable package includes full source code microsoft windows tools provided flexible use license allows playstation 3 game developer publisher tools middleware company create software based partly fully phyreengine platform engine uses sophisticated parallel processing techniques optimized synergistic processor unit spu cell broadband engine ps3 easily ported multi-core architectures phyreengine supports opengl direct3d addition low level ps3 libgcm library provides fully functional “ game templates ” source code including support havok complete xs nvidia physx bullet physics development phyreengine started 2003 create graphics engine playstation 3 first public demonstration occurred 2006 phyreengine launched gdc 2008 phyreengine finalist european develop industry excellence awards 2008 technical innovation category 2009 game engine category new features including deferred rendering showcased gdc 2009 version 2.40 released march 2009 included new “ foliage rendering ” system provides tools technology render ultra-realistic trees plants easily integrated games psp version engine announced sony gdc 2010 version 3.0 released 2011 new powerful asset pipeline combining enhanced versions already robust exporters powerful processing tool generate optimized assets platform also new rewritten level editor permits far data-driven approach authoring games using phyreengine version 3.0 phyreengine adds support playstation vita
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Computer architecture
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network scheduler network scheduler also called packet scheduler queueing discipline qdisc queueing algorithm arbiter node packet switching communication network manages sequence network packets transmit receive queues network interface controller several network schedulers available different operating systems implement many existing network scheduling algorithms network scheduler logic decides network packet forward next network scheduler associated queuing system storing network packets temporarily transmitted systems may single multiple queues case may hold packets one flow classification priority cases may possible schedule transmissions within constraints system cases network scheduler responsible deciding traffic forward gets dropped course time many network queueing disciplines developed provides specific reordering dropping network packets inside various transmit receive buffers queuing disciplines commonly used attempts compensate various networking conditions like reducing latency certain classes network packets generally used part quality service qos measures examples algorithms suitable managing network traffic include several implemented linux kernel modules freely available bufferbloat phenomenon packet-switched networks excess buffering packets causes high latency packet delay variation bufferbloat addressed network scheduler strategically discards packets avoid unnecessarily high buffering backlog examples include codel random early detection network scheduler may responsibility implementation specific network traffic control initiatives network traffic control umbrella term measures aimed reducing congest latency packet loss specifically active queue management aqm selective dropping queued network packets achieve larger goal preventing excessive network congestion scheduler must choose packets drop traffic shaping smooths bandwidth requirements traffic flows delaying transmission packets queued bursts scheduler decides timing transmitted packets quality service prioritization traffic based service class differentiated services reserved connection integrated services linux kernel packet scheduler integral part linux kernel network stack manages transmit receive ring buffers nics working layer 2 osi model handling ethernet frames example packet scheduler configured using utility called codice_1 short traffic control default queuing discipline packet scheduler uses fifo implementation called pfifo_fast although systemd since version 217 changes default queuing discipline fq_codel codice_2 codice_3 utilities enable system administrators configure buffer sizes codice_4 codice_5 device separately terms number ethernet frames regardless size linux kernel network stack contains several buffers managed network scheduler berkeley packet filter filters attached packet scheduler classifiers ebpf functionality brought version 4.1 linux kernel 2015 extends classic bpf programmable classifiers ebpf compiled using llvm ebpf backend loaded running kernel using codice_1 utility altq implementation network scheduler bsds openbsd version 5.5 altq replaced hfsc scheduler
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Operating systems
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standard database management analysis standard database management analysis
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Databases
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xproc xproc w3c recommendation define xml transformation language define xml pipelines example abbreviated xproc file pipeline consists two atomic steps xinclude validate pipeline three inputs “ source ” source document “ schemas ” list w3c xml schemas “ parameters ” passing parameters xinclude step reads pipeline input “ source ” produces result document validate step reads pipeline input “ schemas ” output xinclude step produces result document result validation “ result ” result pipeline equivalent less abbreviated xproc pipeline
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Programming language topics
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jlab jlab numerical computational environment implemented java main scripting engine jlab groovysci extension groovy additionally interpreted j-scripts similar matlab dynamic linking java class code supported jlab environment aims provide matlab/scilab like scientific computing platform supported scripting engines implemented java language current implementation jlab coexist two scripting engines
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Programming language topics
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web annotation web annotation online annotation associated web resource typically web page web annotation system user add modify remove information web resource without modifying resource annotations thought layer top existing resource annotation layer usually visible users share annotation system cases web annotation tool type social software tool web-based text annotation systems see text annotation web annotation used following purposes annotations considered additional layer respect comments comments published publisher hosts original document annotations added top may eventually become comments turn may integrated version document web annotations first standardised february 23 2017 release three official recommendations w3c web annotation working group w3c also previous web annotation standardisation effort annotea see conceived part semantic web many systems require software installed enable features fact noted footnotes software required additional software provided third party
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Web technology
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syn flood syn flood form denial-of-service attack attacker sends succession codice_1 requests target system attempt consume enough server resources make system unresponsive legitimate traffic normally client attempts start tcp connection server client server exchange series messages normally runs like called tcp three-way handshake foundation every connection established using tcp protocol syn flood attack works responding server expected codice_4 code malicious client either simply send expected codice_4 spoofing source ip address codice_1 causing server send codice_3 falsified ip address – send codice_4 knows never sent codice_1 server wait acknowledgement time simple network congestion could also cause missing codice_4 however attack half-open connections created malicious client bind resources server may eventually exceed resources available server point server connect clients whether legitimate otherwise effectively denies service legitimate clients systems may also malfunction crash operating system functions starved resources way number well-known countermeasures listed rfc 4987 including
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Computer security
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lucideus lucideus enterprise cyber security platforms company incubated iit bombay backed cisco former chairman ceo john chambers protects multiple fortune 500 companies governments around world name lucideus derived lucifer satan deus god business hacking good company offers safe security assessment framework enterprise artificial intelligence machine learning platform used cyber-security risk analysis mitigation lucideus worked university delhi year-long postgraduate diploma course cyber security also signed r partnership agreements ground research cyber security technion university mit 2012 saket modi computer science engineer founded lucideus along co-founders vidit baxi rahul tyagi gathered together team security professionals started company objective providing cyber security training beginning 2013 lucideus launched range enterprise cyber security services company today works actively areas 2017 lucideus launched cyber risk assessment platform safe safe security assessment framework enterprises integrates existing technology stack enterprise provide real-time cyber risk assessment score number 0-5 macro level across organisation broken micro-level scoring safe score individually asset safe security assessment framework enterprise de-jargonizes cyber security understanding providing ‘ one ’ number standard 0 5 estimates overall cyber health organisation takes account controls across people process technology lucideus aims make cyber risk informed business decision allow security team communicate non tech specialists cxos business unit leaders board cyber security posture enterprise lucideus pure-play cyber security services platforms provider builds delivers information security services generic customised pro actively secure continuously monitor re-actively respond cyber threats technology stack one companies 100 oscp offensive security certified professional certified delivery team enterprise cyber security services follows proactive continuous reactive approach security lucideus responsible security assessment applications built national payments corporation india bharat interface money bhim payment app november 2018 lucideus announced series funding 5m led john chambers
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Computer security
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cosix cosix chinese unix operating system developed since 1989 china national computer software technology service corporation cs jointly developed 64-bit version compaq released 1999 early version cosix kernel developed based unix system v 64-bit version based tru64 unix linux distribution named cosix linux developed cs released 1999 technical relationship cosix
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Operating systems
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branch queue computer architecture branch predictions branch queue takes place branch predictor predicts branch taken branch queue stores predictions used later branch queue consists 2 values taken taken branch queue helps algorithms increase parallelism optimization software implemented hardware one falls hardware software co-design
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Computer architecture
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eos operating system eos discontinued operating system developed eta systems spin-off division control data corporation use eta10 line supercomputers 1980s eos preceded binary executable compatible cdc vsos operating system cyber 205 like vsos eos demand paged virtual memory vs part 2 pages sizes improved virtual memory performance eta faster hardware pipelines though roots interactive livermore time sharing system ltss vsos focused batch-oriented operating system vsos run many institutions application-oriented performance historic focus supercomputing set features behind times limited user base address feature deficiency make operating system normal use vsos characteristics married unix characteristics hybrid os os intended effective batch work drove hardware maximum interactive use development unix workstation eos written mainly cybil pascal-like programming language created control data later cyber operating systems new effort vsos implemented impl fortran-like language created ltss implementation command line appearance systems similar lineage going back univac exec*8 eos released early hardware deliveries typical problems early os releases customers delayed payment supercomputer installations eta later released port unix eta-10 line quickly accepted customer base however port started single-processor kernel transparently exploit hardware architecture 8 large application cpus applications
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Operating systems
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garbage collection computer science computer science garbage collection gc form automatic memory management garbage collector collector attempts reclaim garbage memory occupied objects longer use program garbage collection invented john mccarthy around 1959 simplify manual memory management lisp garbage collection essentially opposite manual memory management requires programmer specify objects deallocate return memory system however many systems use combination approaches including techniques stack allocation region inference like memory management techniques garbage collection may take significant proportion total processing time program result significant influence performance good implementations enough memory depending application garbage collection faster manual memory management opposite also true often case past sub-optimal gc algorithms resources memory network sockets database handles user interaction windows file device descriptors typically handled garbage collection methods used manage resources particularly destructors may suffice manage memory well leaving need gc gc systems allow resources associated region memory collected causes resource reclaimed called finalization finalization may introduce complications limiting usability intolerable latency disuse reclaim especially limited resources lack control thread performs work reclaiming basic principles garbage collection find data objects program accessed future reclaim resources used objects many programming languages require garbage collection either part language specification example java c go scripting languages effectively practical implementation example formal languages like lambda calculus said garbage collected languages languages designed use manual memory management garbage-collected implementations available example c c++ languages like ada modula-3 c++/cli allow garbage collection manual memory management co-exist application using separate heaps collected manually managed objects others like garbage-collected allow user manually delete objects also entirely disable garbage collection speed required integrating garbage collection language compiler runtime system enables much wider choice methods post-hoc gc systems exist automatic reference counting arc including require recompilation post-hoc gc sometimes distinguished litter collection garbage collector almost always closely integrated memory allocator garbage collection frees programmer manually dealing memory deallocation result certain categories bugs eliminated substantially reduced bugs addressed garbage collection security implications typically garbage collection certain disadvantages including consuming additional resources performance impacts possible stalls program execution incompatibility manual resource management garbage collection consumes computing resources deciding memory free even though programmer may already known information penalty convenience annotating object lifetime manually source code overhead lead decreased uneven performance peer-reviewed paper came conclusion gc needs five times memory compensate overhead perform fast explicit memory management interaction memory hierarchy effects make overhead intolerable circumstances hard predict detect routine testing impact performance also given apple reason adopting garbage collection ios despite desired feature moment garbage actually collected unpredictable resulting stalls pauses shift/free memory scattered throughout session unpredictable stalls unacceptable real-time environments transaction processing interactive programs incremental concurrent real-time garbage collectors address problems varying trade-offs modern gc implementations try minimize blocking stop-the-world stalls much work possible background i.e separate thread example marking unreachable garbage instances application process continues run spite advancements example .net clr paradigm still difficult maintain large heaps millions objects resident objects get promoted older generations without incurring noticeable delays sometimes seconds need explicit manual resource management release/close non-gced resources object oriented language becomes transitive composition non-deterministic gc system resource resource-like object requires manual resource management release/close object used part another object composed object also become resource-like object requires manual resource management release/close tracing garbage collection common type garbage collection much garbage collection often refers tracing garbage collection rather methods reference counting overall strategy consists determining objects garbage collected tracing objects reachable chain references certain root objects considering rest garbage collecting however large number algorithms used implementation widely varying complexity performance characteristics reference counting garbage collection object count number references garbage identified reference count zero object reference count incremented reference created decremented reference destroyed count reaches zero object memory reclaimed manual memory management unlike tracing garbage collection reference counting guarantees objects destroyed soon last reference destroyed usually accesses memory either cpu caches objects freed directly pointed thus tends significant negative side effects cpu cache virtual memory operation number disadvantages reference counting generally solved mitigated sophisticated algorithms escape analysis compile-time technique convert heap allocations stack allocations thereby reducing amount garbage collection done analysis determines whether object allocated inside function accessible outside function-local allocation found accessible another function thread allocation said “ escape ” done stack otherwise object may allocated directly stack released function returns bypassing heap associated memory management costs generally speaking higher-level programming languages likely garbage collection standard feature languages built garbage collection added library boehm garbage collector c c++ functional programming languages ml haskell apl garbage collection built lisp especially notable first functional programming language first language introduce garbage collection dynamic languages ruby julia perl 5 php version 5.3 use reference counting javascript ecmascript also tend use gc object-oriented programming languages smalltalk java usually provide integrated garbage collection notable exceptions c++ delphi destructors historically languages intended beginners basic logo often used garbage collection heap-allocated variable-length data types strings lists burden programmers manual memory management early microcomputers limited memory slow processors basic garbage collection could often cause apparently random inexplicable pauses midst program operation basic interpreters applesoft basic apple ii family repeatedly scanned string descriptors string highest address order compact toward high memory resulting n performance could introduce minutes-long pauses execution string-intensive programs replacement garbage collector applesoft basic published call-a.p.p.l.e january 1981 pages 40–45 randy wigginton identified group strings every pass heap cut collection time dramatically basic.system released prodos 1983 provided windowing garbage collector basic reduced collections fraction second objective-c traditionally garbage collection release os x 10.5 2007 apple introduced garbage collection objective-c 2.0 using in-house developed runtime collector however 2012 release os x 10.8 garbage collection deprecated favor llvm automatic reference counter arc introduced os x 10.7 furthermore since may 2015 apple even forbids usage garbage collection new os x applications app store ios garbage collection never introduced due problems application responsivity performance instead ios uses arc garbage collection rarely used embedded real-time systems perceived need tight control use limited resources however garbage collectors compatible limited environments developed microsoft .net micro framework .net nanoframework java platform micro edition embedded software platforms like larger cousins include garbage collection among popular garbage collectors jdk could named commonly people compare garbage collectors terms ram consumption optimization receive different results compile-time garbage collection form static analysis allowing memory reused reclaimed based invariants known compilation form garbage collection studied mercury programming language saw greater usage introduction llvm automatic reference counter arc apple ecosystem ios os x 2011 incremental concurrent real-time garbage collectors developed baker algorithm lieberman algorithm baker algorithm allocation done either half single region memory becomes half full garbage collection performed moves live objects half remaining objects implicitly deallocated running program 'mutator check object references correct half move across background task finding objects generational garbage collection schemes based empirical observation objects die young generational garbage collection two allocation regions generations kept kept separate based object age new objects created young generation regularly collected generation full objects still referenced older regions copied next oldest generation occasionally full scan performed high-level language computer architectures include hardware support real-time garbage collection implementations real-time garbage collectors use tracing real-time garbage collectors meet hard real-time constraints used real-time operating system
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Operating systems
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honeytoken field computer security honeytokens honeypots computer systems value lies use abuse generalization ideas honeypot canary values often used stack protection schemes honeytokens necessarily prevent tampering data instead give administrator measure confidence data integrity honeytokens fictitious words records added legitimate databases allow administrators track data situations would n't normally able track cloud based networks data stolen honey tokens allow administrators identify stolen leaked three locations medical records different honey tokens form fake medical records could added location different honeytoken would set records chosen unique unlikely ever appear legitimate traffic also detected network intrusion-detection system ids alerting system administrator things would otherwise go unnoticed one case go beyond merely ensuring integrity reactive security mechanisms may actually prevent malicious activity e.g dropping packets containing honeytoken router however mechanisms pitfalls might cause serious problems honeytoken poorly chosen appeared otherwise legitimate network traffic dropped term first coined augusto paes de barros 2003 honeytokens exist many forms dead fake account database entry would selected malicious queries making concept ideally suited ensuring data integrity particular example honeytoken fake email address used track mailing list stolen
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Computer security
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ax.25 ax.25 amateur x.25 data link layer protocol originally derived layer 2 x.25 protocol suite designed use amateur radio operators used extensively amateur packet radio networks ax.25 v2.0 later occupies data link layer second layer osi model responsible establishing link-layer connections transferring data encapsulated frames nodes detecting errors introduced communications channel ax.25 pre-osi-model protocol original specification written cleanly separate osi layers rectified version 2.0 1984 assumes compliance osi level 2 ax.25 commonly used data link layer network layer ipv4 tcp used top ax.25 supports limited form source routing although possible build ax.25 switches similar way ethernet switches work yet accomplished ax.25 define physical layer implementation practice 1200 baud bell 202 tones 9600 baud g3ruh dfsk almost exclusively used vhf uhf hf standard transmission mode 300 baud bell 103 tones although little use ax.25 hf exists today physical layer ax.25 defines physical layer state machine timers related transmitter receiver switching delays link layer ax.25 uses hdlc frame syntax procedures iso 3309 frames transmitted nrzi encoding hdlc specifies syntax semantics variable-length address field frame ax.25 specifies field subdivided multiple addresses source address zero repeater addresses destination address embedded control fields use repeaters simplify compliance amateur radio rules addresses derive station call signs source destination repeater stations media access control follows carrier sense multiple access approach collision recovery csma/cr ax.25 supports virtual-circuit connected datagram-style connectionless modes operation latter used great effect automatic packet reporting system aprs simple source routing mechanism using digipeaters available datalink level digipeaters act simplex repeaters receiving decoding retransmitting packets local stations allow multi-hop connections established two stations unable communicate directly digipeaters use modify information frame address field perform function ax.25 specification defines complete albeit point point network layer protocol seen little use outside keyboard-to-keyboard keyboard-to-bbs connections net/rom rose texnet exist provide routing nodes principle variety layer 3 protocols used ax.25 including ubiquitous internet protocol approach used amprnet amateur radio tcp/ip network using ax.25 ui-frames datalink layer traditionally amateur radio operators connected ax.25 networks use terminal node controller contains microprocessor implementation protocol firmware devices allow network resources accessed using dumb terminal transceiver ax.25 also implemented personal computers example linux kernel includes native support ax.25 computer connects tranceiver via audio interface via simple modem computers also interconnect computers bridged routed tncs tranceivers located elsewhere using bpq ethernet framing also natively supported linux kernel facilitate modern setups actual tranceivers directly placed antenna mast creating 'low loss shorter rf wiring need replacing expensive long thick coax cables amplifiers cheap fiber rfi ways /emp/lightning resistant copper ethernet wiring bpq ethernet framing allows connect entire stacks tnc+tranceiver pairs existing network computers access radio links offered simulaniously transparently bridged communicate internally ax.25 filtered routing select specific tncs/radio frequencies note linux kernel ax.25 implementation contain bugs mainly disconnecting sessions bug appears slipped time due maintenance people using exclusively aprs virtual channel connected mode example tap interfaces supporting full 7 bytes call sign string length interface drivers expect 6 byte hw address mac up-to-7 byte one like ax.25 use requires ax.25 often used tnc implements kiss framing low-cost alternative using expensive uncommon hdlc controller cards kiss framing part ax.25 protocol sent air merely serves encapsulate protocol frames way successfully pass serial link tnc kiss framing derived slip makes many assumptions two endpoints involved conversation slip two slip-connected hosts kiss assumed kiss framing link serial host computer pc involved among things makes awkward address multiple tncs without multiple serial data channels alternatives kiss exist address limitations 6pack ax.25 frequently used establish direct point-to-point links packet radio stations without additional network layers sufficient keyboard-to-keyboard contacts stations accessing local bulletin board systems dx clusters recent years aprs become popular application tunneling ax.25 packets ip axip axudp used encapsulate ax.25 ip udp packets speeds commonly used transmit packet radio data rarely higher 9,600 bit/s typically 1,200 bit/s use additional network layers ax.25 impractical due data overhead involved limitation ax.25 per se places constraints sophistication applications designed use hdlc protocols identify frame address ax.25 implementation hdlc includes sender destination station call-sign plus ssid value range 0 15 frame address itu warc2003 radio amateur station callsign specification amended earlier maximum length six characters raised seven characters however ax.25 built-in hard limit six characters means seven-character callsign used ax.25 network ax.25 lacks explicit port sap ssid often assumes role thus one service per ax.25 station ssid address often kludged around varying degrees success amateurs notably phil karn ka9q argued ax.25 well-suited operation noisy limited-bandwidth radio links citing lack forward error correction fec automatic data compression however viable widely adopted successor ax.25 yet emerge likely reasons may include despite limitations extension ax.25 protocol supporting forward error correction created tapr extension called fx.25 small gadget transmitters need know transmitted need monitor channel occupation radio receiver rssi received signal strength indication know send transmitting interleaved reed-solomon fec signal smart modulation needs lot fewer resources reception signal thus sufficient microprocessor might cost usd 5 instead usd 30 system cost might stay us 50 transmitter included however recent years ability receive well send using cheap microcontrollers atmel avr motorola 68hc08 families demonstrated seems however new system compatible current bell 202 modulation unlikely widely adopted current modulation seems fulfill sufficient need little motivation exists move superior design especially new design requires significant hardware purchases
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Internet protocols
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eclr-attributed grammar eclr-attributed grammars special type attribute grammars variant lr-attributed grammars equivalence relation inherited attributes used optimize attribute evaluation ec stands equivalence class rie based eclr-attributed grammars superset lr-attributed grammars
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Programming language topics
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hp veer veer smartphone announced hp february 9 2011 device uses hp webos powered qualcomm snapdragon processor 2.6-inch screen smartphone notable credit card-sized dimensions depth comparable size deck cards device seen successor palm line-up pixi earlier centro models hp veer announced february 9 2011 along hp pre 3 hp touchpad veer released us may 15 2011 network marketed hp veer 4g device slated support touch-to-share proximity-based sharing feature later update official update supporting touch-to-share released although several users purchased devices ebay fully implemented touch-to-share sms sharing support following hp announcement august 18 would cease development webos hardware veer discontinued similar touchpad price lowered significantly firesale hp veer powered qualcomm snapdragon msm7230 system-on-a-chip made qualcomm based 45 nanometer cmos process veer snapdragon composed principally scorpion cpu running 800mhz adreno 205 gpu digital signal processor cellular transmission/reception/processing gsm umts gpsone gps module audio subsystem scorpion core implements armv7 architecture similar arm cortex-a8 supports arm neon instruction set extensions vfpv3 floating-point extensions referred “ venum ” media processing engine scorpion accelerate example image processing camera main purpose venum engine boost performance scorpion cpu multimedia processing resulting power saving task completed faster less power consumed processor venum media processing engine one without adreno 205 gpu supports opengl es 2.0 opengl es 1.1 openvg 1.1 egl 1.3 direct3d mobile svgt 1.2 directdraw hp veer 66 mm 2.6 inch capacitive touchscreen resolution 320 x 400 pixel touchscreen designed bare finger multiple fingers multi-touch sensing accelerometer allows orientation screen change portrait landscape mode proximity sensor deactivates display touchscreen device brought near face call slide-out 4-row qwerty keyboard microphone located slide-out keyboard left side device volume button upper right side power button top side ringer switch vibration mode usb 3.5 mm connectivities provided proprietary magnetic connector battery rated 910 mah non-removable hp states provides 5.0 hours talk time 300 hours standby time 8 gb board 6.5 gb available user microsd card socket veer shipped either webos 2.1.1 2.1.2 depending region seen official update since following pre-installed applications
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Operating systems
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rootkitrevealer rootkitrevealer proprietary freeware tool rootkit detection microsoft windows bryce cogswell mark russinovich runs windows xp windows server 2003 32-bit-versions output lists windows registry file system api discrepancies may indicate presence rootkit tool triggered sony bmg copy protection rootkit scandal rootkitrevealer longer developed
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Computer security
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rpmdrake rpmdrake graphical interface urpmi permits installation software packages provided part mandriva linux mageia rosa package installation application written gtk2-perl allows rpmdrake free software available gnu general public license version 2. urpmi developed guillaume cottenceau rafael garcia-suarez thierry vignaud first mandriva mageia see
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Operating systems
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watercraft watercraft also known marine vessels waterborne vessels vehicles used water including ships boats hovercraft submarines watercraft usually propulsive capability whether sail oar paddle engine hence distinct simple device merely floats log raft watercraft would described either ship boat however numerous craft many people would consider neither ship boat surfboards used paddle board underwater robots seaplanes torpedoes although ships typically larger boats distinction two categories one size per se term watercraft unlike terms aircraft spacecraft rarely used describe individual object rather term serves unify category ranges jet skis aircraft carriers vessel may used saltwater freshwater pleasure recreation physical exercise commerce transport military missions usually purposes behind watercraft designs skills seafaring education leisure activities fishing resource extraction transportation cargo passengers conducting combat salvage operations general purpose water vehicle identifies utility maritime industry sub-sector design water vehicle created usually seeks achieve balance internal capacity tonnage speed seaworthiness tonnage predominantly consideration transport operations speed important warships safety primary consideration less experienced often smaller less stable training leisure vehicles due great level regulatory compliance required larger watercraft ensures infrequent instances foundering sea application extensive computer modeling ship model basin testing shipyard construction begins historically water vehicles propelled people poles paddles oars manipulation sails propel wind pressure and/or lift variety engineered machinery create subsurface thrust process internal combustion electricity technological history watercraft european history divided reference marine propulsion simple paddle craft oared galleys 8th century bce 15th century lateen sail age discovery early 15th century early 17th century full rigged ships age sail 16th mid 19th century age steam reciprocating marine steam engine roughly 1770 1914 steam turbine later gas turbine internal combustion engines using diesel fuel petrol lng fuels turn 20th century supplemented degree nuclear marine propulsion since 1950s naval watercraft current technological development seeks identify cheaper renewable less polluting sources propulsion watercraft shapes sizes secondary applications technology watercraft used structural materials navigation aids case warships weapon systems purpose usage physical environment define materials used construction historically included grasses leather timbers metals combined timber without silicate plastic derivatives others watercraft registration registration watercraft government authority united states consists alphanumeric string called vessel registration number issued state department motor vehicles navigation aids varied time astronomical observation mechanical mechanisms recently analogue digital computer devices rely gps systems naval weapon systems closely followed development land weapons developing development steam propulsion coupled rapid-firing breech-loading guns naval combat often concluded boarding combat opposing crews since early 20th century substantial development technologies allow force projection naval task force land objective using marine infantry
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Databases
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security log security log used track security-related information computer system examples include according stefan axelsson unix installations run form security logging software mainly security logging facilities expensive terms disk storage processing time cost associated analyzing audit trail either manually special software
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Computer security
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strsafe.h strsafe.h non-standard c header file provided windows sdk starting windows xp service pack 2 provides safer buffer handling provided standard c string functions widely known security issues involving buffer overruns used correctly functions included strsafe.h replace standard c string handling i/o functions including codice_1 codice_2 codice_3 codice_4 strsafe functions require length string either characters bytes parameter operation would exceed length destination buffer operation fails string still terminated null final valid index using library functions result undefined behavior independent security researchers noted security issues still possible functions strsafe.h passed correct buffer length use library recommended united states department homeland security
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Operating systems
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clustered file system clustered file system file system shared simultaneously mounted multiple servers several approaches clustering employ clustered file system direct attached storage node clustered file systems provide features like location-independent addressing redundancy improve reliability reduce complexity parts cluster parallel file systems type clustered file system spread data across multiple storage nodes usually redundancy performance shared-disk file system uses storage area network san allow multiple computers gain direct disk access block level access control translation file-level operations applications use block-level operations used san must take place client node common type clustered file system shared-disk file system —by adding mechanisms concurrency control—provides consistent serializable view file system avoiding corruption unintended data loss even multiple clients try access files time shared-disk file-systems commonly employ sort fencing mechanism prevent data corruption case node failures unfenced device cause data corruption loses communication sister nodes tries access information nodes accessing underlying storage area network may use number block-level protocols including scsi iscsi hyperscsi ata ethernet aoe fibre channel network block device infiniband different architectural approaches shared-disk filesystem distribute file information across servers cluster fully distributed others utilize centralized metadata server achieve result enabling servers access data shared storage device distributed file systems share block level access storage use network protocol commonly known network file systems even though file systems use network send data distributed file systems restrict access file system depending access lists capabilities servers clients depending protocol designed difference distributed file system distributed data store distributed file system allows files accessed using interfaces semantics local files example mounting/unmounting listing directories read/write byte boundaries system native permission model distributed data stores contrast require using different api library different semantics often database distributed file system may also created software implementing ibm distributed data management architecture ddm programs running one computer use local interfaces semantics create manage access files located networked computers client requests trapped converted equivalent messages defined ddm using protocols also defined ddm messages transmitted specified remote computer ddm server program interprets messages uses file system interfaces computer locate interact specified file distributed file systems may aim transparency number aspects aim invisible client programs see system similar local file system behind scenes distributed file system handles locating files transporting data potentially providing features listed incompatible timesharing system used virtual devices transparent inter-machine file system access 1960s file servers developed 1970s 1976 digital equipment corporation created file access listener fal implementation data access protocol part decnet phase ii became first widely used network file system 1985 sun microsystems created file system called network file system nfs became first widely used internet protocol based network file system notable network file systems andrew file system afs apple filing protocol afp netware core protocol ncp server message block smb also known common internet file system cifs 1986 ibm announced client server support distributed data management architecture ddm system/36 system/38 ibm mainframe computers running cics followed support ibm personal computer as/400 ibm mainframe computers mvs vse operating systems flexos ddm also became foundation distributed relational database architecture also known drda many peer-to-peer network protocols open-source distributed file systems cloud closed-source clustered file systems e. g. 9p afs coda cifs/smb dce/dfs lustre panfs google file system mnet chord project network-attached storage nas provides storage file system like shared disk file system top storage area network san nas typically uses file-based protocols opposed block-based protocols san would use nfs popular unix systems smb/cifs server message block/common internet file system used ms windows systems afp used apple macintosh computers ncp used oes novell netware failure disk hardware given storage node cluster create single point failure result data loss unavailability fault tolerance high availability provided data replication one sort another data remains intact available despite failure single piece equipment examples see lists distributed fault-tolerant file systems distributed parallel fault-tolerant file systems common performance measurement clustered file system amount time needed satisfy service requests conventional systems time consists disk-access time small amount cpu-processing time clustered file system remote access additional overhead due distributed structure includes time deliver request server time deliver response client direction cpu overhead running communication protocol software concurrency control becomes issue one person client accessing file block want update hence updates file one client interfere access updates clients problem complex file systems due concurrent overlapping writes different writers write overlapping regions file concurrently problem usually handled concurrency control locking may either built file system provided add-on protocol ibm mainframes 1970s could share physical disks file systems machine channel connection drives control units 1980s digital equipment corporation tops-20 openvms clusters vax/alpha/ia64 included shared disk file systems
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Computer file systems
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keycloak keycloak open source software product allow single sign-on identity management access management aimed modern applications services jboss community project stewardship red hat use upstream project rh-sso product conceptual perspective tool intent make easy secure applications services little coding first production release keycloak september 2014 development started year earlier 2016 red hat switched rh sso product based picketlink framework based keycloak upstream project followed merging picketlink codebase keycloak extent keycloak also considered replacement red hat jboss sso open source product previously superseded picketlink jboss.org redirecting old jbosssso subsite keycloak website jboss name registered trade mark red hat moved upstream open source projects names avoid using jboss jboss wildfly commonly recognized example among many features keycloak include 2 main components keycloak
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Computer security
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context-free grammar formal language theory context-free grammar cfg certain type formal grammar set production rules describe possible strings given formal language production rules simple replacements example rule formula_1 replaces formula_2 formula_3 multiple replacement rules given value example formula_1 formula_5 means formula_2 replaced either formula_3 formula_8 context-free grammars rules one-to-one one-to-many one-to-none rules applied regardless context left-hand side production rule always nonterminal symbol means symbol appear resulting formal language case language contains letters formula_3 formula_8 formula_11 rules also applied reverse check whether string grammatically correct according grammar example context-free grammar describes two-letter strings containing letters formula_3 formula_8 formula_14 formula_1 formula_5 start nonterminal symbol formula_17 use rule formula_14 turn formula_17 formula_20 apply one two later rules example apply formula_5 first formula_2 get formula_23 apply formula_1 second formula_2 get formula_26 since formula_3 formula_8 terminal symbols context-free grammars terminal symbols never appear left hand side production rule rules applied process used applying last two rules different orders order get possible strings within simple context-free grammar languages generated context-free grammars known context-free languages cfl different context-free grammars generate context-free language important distinguish properties language intrinsic properties properties particular grammar extrinsic properties language equality question two given context-free grammars generate language undecidable context-free grammars arise linguistics used describe structure sentences words natural language fact invented linguist noam chomsky purpose really lived original expectation contrast computer science use recursively-defined concepts increased used early application grammars used describe structure programming languages newer application used essential part extensible markup language xml called document type definition linguistics authors use term phrase structure grammar refer context-free grammars whereby phrase-structure grammars distinct dependency grammars computer science popular notation context-free grammars backus–naur form bnf since time pāṇini least linguists described grammars languages terms block structure described sentences recursively built smaller phrases eventually individual words word elements essential property block structures logical units never overlap example sentence logically parenthesized logical metasymbols follows context-free grammar provides simple mathematically precise mechanism describing methods phrases natural language built smaller blocks capturing block structure sentences natural way simplicity makes formalism amenable rigorous mathematical study important features natural language syntax agreement reference part context-free grammar basic recursive structure sentences way clauses nest inside clauses way lists adjectives adverbs swallowed nouns verbs described exactly context-free grammars special form semi-thue systems general form date back work axel thue formalism context-free grammars developed mid-1950s noam chomsky also classification special type formal grammar called phrase-structure grammars chomsky called phrase structure grammar also known constituency grammar whereby constituency grammars stand contrast dependency grammars chomsky generative grammar framework syntax natural language described context-free rules combined transformation rules block structure introduced computer programming languages algol project 1957–1960 consequence also featured context-free grammar describe resulting algol syntax became standard feature computer languages notation grammars used concrete descriptions computer languages came known backus–naur form two members algol language design committee block structure aspect context-free grammars capture fundamental grammar terms syntax grammar often identified context-free grammar rules especially computer science formal constraints captured grammar considered part semantics language context-free grammars simple enough allow construction efficient parsing algorithms given string determine whether generated grammar earley parser example algorithm widely used lr parsers simpler algorithms deal restrictive subsets context-free grammars context-free grammar defined 4-tuple formula_29 production rule formalized mathematically pair formula_32 formula_33 nonterminal formula_34 string variables and/or terminals rather using ordered pair notation production rules usually written using arrow operator left hand side right hand side formula_35 allowed empty string case customary denote ε form formula_36 called -production common list right-hand sides left-hand side line using pipe symbol separate rules formula_37 formula_38 hence written formula_39 case formula_40 formula_41 called first second alternative respectively strings formula_42 say directly yields written formula_43 formula_44 formula_33 formula_46 formula_47 formula_48 thus result applying rule formula_49 strings formula_50 say yields written formula_51 formula_52 textbooks formula_53 formula_54 case formula_55 i.e. formula_56 relation formula_57 holds words formula_58 formula_59 reflexive transitive closure allowing word yield transitive closure requiring least one step formula_60 respectively language grammar formula_29 set language said context-free language cfl exists cfg formula_63 non-deterministic pushdown automata recognize exactly context-free languages context-free grammar said proper every context-free grammar effectively transformed weakly equivalent one without unreachable symbols weakly equivalent one without unproductive symbols weakly equivalent one without cycles every context-free grammar producing ε effectively transformed weakly equivalent one without ε-productions altogether every grammar effectively transformed weakly equivalent proper cfg grammar formula_68 productions context-free proper since includes ε-production typical derivation grammar makes clear formula_69 language context-free however proved regular productions added context-free grammar set palindromes alphabet obtained canonical example context-free grammar parenthesis matching representative general case two terminal symbols one nonterminal symbol s. production rules first rule allows symbol multiply second rule allows symbol become enclosed matching parentheses third rule terminates recursion second canonical example two different kinds matching nested parentheses described productions terminal symbols nonterminal s. following sequence derived grammar context-free grammar pair characters way brackets simplest example grammar generates language formula_70 regular according pumping lemma regular languages special character ε stands empty string changing grammar obtain grammar generating language formula_71 instead differs contains empty string original grammar context-free grammar language consisting strings b containing unequal number b nonterminal generate strings number b nonterminal u generates strings b nonterminal v generates strings fewer b omitting third alternative rule u v n't restrict grammar language another example non-regular language formula_72 context-free generated following context-free grammar formation rules terms formulas formal logic fit definition context-free grammar except set symbols may infinite may one start symbol contrast well-formed nested parentheses square brackets previous section context-free grammar generating sequences two different types parentheses separately balanced disregarding two types need nest inside one another example fact language context free proven using pumping lemma context-free languages proof contradiction observing words form formula_73 belong language language belongs instead general class described conjunctive grammar turn also includes non-context-free languages language words form formula_74 every regular grammar context-free context-free grammars regular following context-free grammar however also regular terminals b nonterminal s. language described nonempty strings formula_75s formula_76s end formula_75 grammar regular rule one nonterminal right-hand side nonterminals end right-hand side every regular grammar corresponds directly nondeterministic finite automaton know regular language using pipe symbols grammar described tersely follows derivation string grammar sequence grammar rule applications transform start symbol string derivation proves string belongs grammar language derivation fully determined giving step clarity intermediate string usually given well instance grammar string derived derivation often strategy followed deterministically determines next nonterminal rewrite given strategy derivation completely determined sequence rules applied instance leftmost derivation summarized distinction leftmost derivation rightmost derivation important parsers transformation input defined giving piece code every grammar rule executed whenever rule applied therefore important know whether parser determines leftmost rightmost derivation determines order pieces code executed see example parsers lr parsers derivation also imposes sense hierarchical structure string derived example string 1 1 derived according leftmost derivation structure string would ... indicates substring recognized belonging s. hierarchy also seen tree tree called parse tree concrete syntax tree string contrast abstract syntax tree case presented leftmost rightmost derivations define parse tree however another rightmost derivation string defines following parse tree note however parse trees obtained leftmost rightmost derivations example last tree obtained leftmost derivation follows string language grammar one parsing tree grammar said ambiguous grammar grammars usually hard parse parser always decide grammar rule apply usually ambiguity feature grammar language unambiguous grammar found generates context-free language however certain languages generated ambiguous grammars languages called inherently ambiguous languages context-free grammar syntactically correct infix algebraic expressions variables x z grammar example generate string follows note many choices made underway rewrite going performed next choices look quite arbitrary matter fact sense string finally generated always example second third rewrites could done opposite order also many choices made rule apply selected codice_1 changing choices made order made usually affects terminal string comes end let look detail consider parse tree derivation starting top step step tree expanded unexpanded codice_1es nonterminals remain picking different order expansion produce different derivation parse tree parse tree change pick different rule apply position tree different parse tree still produce terminal string codice_3 case yes particular grammar possible grammars property called ambiguous example codice_4 produced two different parse trees however language described grammar inherently ambiguous alternative unambiguous grammar given language example picking codice_1 start symbol alternative grammar produce codice_4 parse tree similar left one i.e implicitly assuming association codice_7 according standard operator precedence elaborate unambiguous context-free grammars constructed produce parse trees obey desired operator precedence associativity rules every context-free grammar generate empty string transformed one ε-production rule empty string product grammar generate empty string necessary include rule formula_78 need ε-rule every context-free grammar ε-production equivalent grammar chomsky normal form grammar greibach normal form equivalent means two grammars generate language especially simple form production rules chomsky normal form grammars theoretical practical implications instance given context-free grammar one use chomsky normal form construct polynomial-time algorithm decides whether given string language represented grammar cyk algorithm context-free languages closed various operations languages k l context-free result following operations closed general intersection hence neither complementation set difference following decidable problems context-free grammars parsing problem checking whether given word belongs language given context-free grammar decidable using one general-purpose parsing algorithms context-free parsing chomsky normal form grammars shown leslie g. valiant reducible boolean matrix multiplication thus inheriting complexity upper bound n conversely lillian lee shown n boolean matrix multiplication reducible n cfg parsing thus establishing kind lower bound latter decidable whether given non-terminal context-free grammar reachable whether productive whether nullable derive empty string decidable whether given grammar regular grammar well whether k grammar given k ≥0 k given latter problem undecidable given context-free language neither decidable whether regular whether k language given k algorithms decide whether language given context-free language empty well whether finite questions undecidable wider classes grammars become decidable context-free grammars e.g emptiness problem whether grammar generates terminal strings undecidable context-sensitive grammars decidable context-free grammars however many problems undecidable even context-free grammars examples given cfg generate language strings alphabet terminal symbols used rules reduction demonstrated problem well-known undecidable problem determining whether turing machine accepts particular input halting problem reduction uses concept computation history string describing entire computation turing machine cfg constructed generates strings accepting computation histories particular turing machine particular input thus accept strings machine n't accept input given two cfgs generate language undecidability problem direct consequence previous impossible even decide whether cfg equivalent trivial cfg defining language strings given two cfgs first one generate strings second one generate problem decidable language equality could decided two cfgs g1 g2 generate language l g1 subset l g2 l g2 subset l g1 using greibach theorem shown two following problems undecidable given cfg ambiguous undecidability problem follows fact algorithm determine ambiguity existed post correspondence problem could decided known undecidable given two cfgs string derivable grammars problem decidable undecidable post correspondence problem could decided given strings formula_79 alphabet formula_80 let grammar consist rule formula_82 denotes reversed string formula_83 formula_76 n't occur among formula_85 let grammar consist rule post problem given formula_79 solution share derivable string obvious way extend context-free grammar formalism allow nonterminals arguments values passed along within rules allows natural language features agreement reference programming language analogs correct use definition identifiers expressed natural way e.g easily express english sentences subject verb must agree number computer science examples approach include affix grammars attribute grammars indexed grammars van wijngaarden two-level grammars similar extensions exist linguistics extended context-free grammar regular right part grammar one right-hand side production rules allowed regular expression grammar terminals nonterminals extended context-free grammars describe exactly context-free languages another extension allow additional terminal symbols appear left-hand side rules constraining application produces formalism context-sensitive grammars number important subclasses context-free grammars lr parsing extends parsing support larger range grammars turn generalized lr parsing extends lr parsing support arbitrary context-free grammars grammars lr grammars essentially performs parsing lr parsing respectively nondeterministic grammars efficient expected although glr parsing developed 1980s many new language definitions parser generators continue based lalr lr parsing present day chomsky initially hoped overcome limitations context-free grammars adding transformation rules rules another standard device traditional linguistics e.g passivization english much generative grammar devoted finding ways refining descriptive mechanisms phrase-structure grammar transformation rules exactly kinds things expressed natural language actually allows allowing arbitrary transformations meet goal much powerful turing complete unless significant restrictions added e.g transformations introduce rewrite symbols context-free fashion chomsky general position regarding non-context-freeness natural language held since although specific examples regarding inadequacy context-free grammars terms weak generative capacity later disproved gerald gazdar geoffrey pullum argued despite non-context-free constructions natural language cross-serial dependencies swiss german reduplication bambara vast majority forms natural language indeed context-free
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Programming language topics
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stata stata general-purpose statistical software package created 1985 statacorp users work research especially fields economics sociology political science biomedicine epidemiology stata capabilities include data management statistical analysis graphics simulations regression custom programming also system disseminate user-written programs lets grow continuously name stata syllabic abbreviation words statistics data faq official forum stata insists correct english pronunciation stata must remain mystery stay-ta sta-ta stah-ta considered acceptable four major builds version stata small stata smaller student version educational purchase longer available stata always emphasized command-line interface facilitates replicable analyses starting version 8.0 however stata included graphical user interface based qt framework uses menus dialog boxes give access nearly built-in commands generates code always displayed easing transition command line interface flexible scripting language dataset viewed edited spreadsheet format version 11 commands executed data browser editor opened stata open single dataset one time stata holds entire dataset random-access virtual memory limits use extremely large datasets mitigated extent efficient internal storage integer storage types occupy one two bytes rather four single-precision 4 bytes rather double-precision 8 bytes default floating-point numbers dataset always rectangular format variables hold number observations mathematical terms vectors length although entries may missing values stata import data variety formats includes ascii data formats csv databank formats spreadsheet formats including various excel formats stata proprietary file formats changed time although every stata release includes new dataset format every version stata read older dataset formats write current recent previous dataset format using saveold command thus current stata release always open datasets created older versions older versions read newer format datasets stata read write sas xport format datasets natively using fdause fdasave commands econometric applications including gretl directly import stata file formats stata allows user-written commands distributed so-called ado-files straightforwardly downloaded internet indistinguishable user built-in commands respect stata combines extensibility often associated open-source packages features usually associated commercial packages software verification technical support professional documentation user-written commands later adopted statacorp become part subsequent official release appropriate checking certification documentation stata active email list august 1994 statalist 1000 messages per month turned web forum march 2014 still called statalist statacorp employees regularly contribute statalist maintained marcello pagano harvard school public health statacorp articles use stata new user-written commands published quarterly peer-reviewed stata journal stata journal quarterly publication containing articles statistics data analysis teaching methods effective use stata language user group meetings held annually united states stata conference uk germany italy less frequently several countries annual stata conference held united states hosted statacorp lp local stata distributors host user group meetings countries however stata developers frequently travel present meetings established societies act 10 may 2008 singapore stata users group world first government-approved users group registration 2048/2008 unique entity t08ss0091a slogan shaping data meaningfully non-profit organisation stataugs organise regular meetings provides programming statistical advice users singapore informal means active members stataugs mostly engaged biomedical research perform linear ols regression x optional part allows restrict sample used command subset example command applied females sample one could specify female == 1. br perform logistic regression x display scatter plot x restricted values x 10 perform ols regression x white heteroscedasticity-consistent standard errors calculate akaike information criterion aic bayesian information criterion bic regression code fizzbuzz since 2000 statacorp released new major release stata incrementing integer part version number roughly every two years users must pay fee wish upgrade latest major release minor releases incrementing decimal part version number sometimes made available major releases available free downloadable updates licence previous major release dates releases available stata website stata 16 released june 26 2019 stata versioning system designed give high degree backward compatibility ensuring code written previous releases continues work however users careful save open data among different versions
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Programming language topics
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focused crawler focused crawler web crawler collects web pages satisfy specific property carefully prioritizing crawl frontier managing hyperlink exploration process predicates may based simple deterministic surface properties example crawler mission may crawl pages .jp domain predicates may softer comparative e.g. crawl pages baseball crawl pages large pagerank important page property pertains topics leading topical crawlers example topical crawler may deployed collect pages solar power swine flu even abstract concepts like controversy minimizing resources spent fetching pages topics crawl frontier management may device used focused crawlers may use web directory web text index backlinks web artifact focused crawler must predict probability unvisited page relevant actually downloading page possible predictor anchor text links approach taken pinkerton crawler developed early days web topical crawling first introduced filippo menczer chakrabarti et al coined term focused crawler used text classifier prioritize crawl frontier andrew mccallum co-authors also used reinforcement learning focus crawlers diligenti et al traced context graph leading relevant pages text content train classifiers form online reinforcement learning used along features extracted dom tree text linking pages continually train classifiers guide crawl review topical crawling algorithms menczer et al show simple strategies effective short crawls sophisticated techniques reinforcement learning evolutionary adaptation give best performance longer crawls shown spatial information important classify web documents another type focused crawlers semantic focused crawler makes use domain ontologies represent topical maps link web pages relevant ontological concepts selection categorization purposes addition ontologies automatically updated crawling process dong et al introduced ontology-learning-based crawler using support vector machine update content ontological concepts crawling web pages crawlers also focused page properties topics cho et al study variety crawl prioritization policies effects link popularity fetched pages najork weiner show breadth-first crawling starting popular seed pages leads collecting large-pagerank pages early crawl refinements involving detection stale poorly maintained pages reported eiron et al. kind semantic focused crawler making use idea reinforcement learning introduced meusel et al using online-based classification algorithms combination bandit-based selection strategy efficiently crawl pages markup languages like rdfa microformats microdata performance focused crawler depends richness links specific topic searched focused crawling usually relies general web search engine providing starting points davison presented studies web links text explain focused crawling succeeds broad topics similar studies presented chakrabarti et al. seed selection important focused crawlers significantly influence crawling efficiency whitelist strategy start focus crawl list high quality seed urls limit crawling scope domains urls high quality seeds selected based list url candidates accumulated sufficient long period general web crawling whitelist updated periodically created
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Web technology
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textedit api textedit name collection application programming interfaces apis classic mac os performing text editing apis originally designed provide common text handling system support text entry fields dialog boxes simple text editing within macintosh gui time extended provide advanced text editing features limited original scope led fundamental limitations apple repeatedly stated textedit word processor therefore providing rich text editing always left third-party developers basic limitations textedit include first incarnation textedit provided support single style text applied text block adequate intended use supporting text entry fields later support added styled text textedit could used complex text editing tasks text editing areas web browsers etc textedit remains part carbon api macos superseded numerous solutions including atsui carbon third party waste text engine well nstext related classes within cocoa
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Operating systems
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relational data stream management system relational data stream management system rdsms distributed in-memory data stream management system dsms designed use standards-compliant sql queries process unstructured structured data streams real-time unlike sql queries executed traditional rdbms return result exit sql queries executed rdsms exit generating results continuously new data become available continuous sql queries rdsms use sql window function analyze join aggregate data streams fixed sliding windows windows specified time-based row-based continuous sql queries rdsms conform ansi sql standards common rdsms sql query performed declarative codice_1 statement continuous sql codice_1 operates data across one data streams optional keywords clauses include codice_3 optional codice_4 subclause specify rules joining multiple data streams codice_5 clause comparison predicate restrict records returned query codice_6 project streams common values smaller set codice_7 filter records resulting codice_6 codice_9 sort results following example continuous data stream aggregation using codice_1 query aggregates sensor stream weather monitoring station codice_1query aggregates minimum maximum average temperature values one-second time period returning continuous stream aggregated results one second intervals rdsms sql queries also operate data streams time row-based windows following example shows second continuous sql query using codice_12 clause one-second duration codice_12 clause changes behavior query output result new record arrives hence output stream incrementally updated results zero result latency
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Databases
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deli linux desktop light linux deli linux short desktop linux distribution old pcs version 0.6.1 deli linux based slackware 7 using linux 2.2 deli linux version 0.7 development scratch linux 2.4.33.3 longer based slackware os still used slackware package management additionally new port system based crux deli linux based uclibc instead gnu c library port openbsd korn shell used default shell version 0.8 introduced pacman package manager 0.8 series focus internationalisation version 0.8.0 also switched web browser netsurf skipstone previously konqueror embedded dillo deli linux pre-packaged abiword siag office office suites web browser netsurf skipstone included email clients mutt sylpheed window managers icewm fluxbox included editing deli linux offers e3 elvis beaver since deli linux ships lightweight software many popular open source packages included gnome kde emacs mozilla thunderbird deli linux needs 386 32 mb ram minimum however linux swap partition needs selected setup run deli less 48 mb ram work smoothly 486 full installation packages requires nearly 750 mb hard disk space august 2010 developers announced deli linux discontinued instead two successor projects connochaetos deli cate connochaetos created 2010 arch linux derivative targeting i586 pentium 1 later processors time arch required least i686 trying follow gnu free system distribution guidelines fsdg discontinued july 2013 due maintainer lack time project financial situation project failure get endorsement free software foundation fsdg-compliant however june 2015 development connochaetos resumed longer derivative arch linux derivative slackware salix os another project deli cate runs 386 486 pentium-class machines
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Operating systems
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file locking file locking mechanism restricts access computer file allowing one user process access specific time systems implement locking prevent classic interceding update scenario typical example race condition enforcing serialization update processes given file following example illustrates interceding update problem operating systems support concept record locking means individual records within given file may locked thereby increasing number concurrent update processes database maintenance uses file locking whereby serialize access entire physical file underlying database although prevent process accessing file efficient individually locking large number regions file removing overhead acquiring releasing lock poor use file locks like computer lock result poor performance deadlocks file locking may also refer additional security applied computer user either using windows security ntfs permissions installing third party file locking software ibm pioneered file locking 1963 use mainframe computers using os/360 termed exclusive control microsoft windows uses three distinct mechanisms manage access shared files windows inherits semantics share-access controls ms-dos system sharing introduced ms-dos 3.3 thus application must explicitly allow sharing opens file otherwise exclusive read write delete access file closed types access retrieve attributes file allowed file opened shared access applications may use byte-range locking control access specific regions file byte-range locks specify region file offset length type lock shared exclusive note region file locked required data within file applications sometimes exploit ability implement functionality applications use file read/write apis windows byte-range locks enforced also referred mandatory locks file systems execute within windows applications use file mapping apis windows byte-range locks enforced also referred advisory locks byte-range locking may also side-effects windows system example windows file-sharing mechanism typically disable client side caching file clients byte-range locks used client control file access client observe slower access read write operations must sent server file stored improper error-handling application program lead scenario file locked either using share access byte-range file locking accessed applications user may able restore file access manually terminating malfunctioning program typically done task manager utility sharing mode dwsharemode parameter createfile function used open files determines file-sharing sharing mode specified allow sharing file read write delete access combination subsequent attempts open file must compatible previously granted sharing-access file file closed sharing-access restrictions adjusted remove restrictions imposed specific file open byte-range locking type determined dwflags parameter lockfileex function used lock region file windows api function lockfile also used acquires exclusive lock region file file containing executable program file currently running computer system program e.g exe com dll cpl binary program file format normally locked operating system preventing application modifying deleting attempt denied sharing violation error despite fact program file opened application however access still allowed example running application file renamed copied read even executing files accessed applications windows using file handles file handles explored process explorer utility utility also used force-close handles without needing terminate application holding cause undefined behavior since program receive unexpected error using force-closed handle may even operate unexpected file since handle number may recycled microsoft windows xp server 2003 editions introduced volume snapshot vss capability ntfs allowing open files accessed backup software despite exclusive locks however unless software rewritten specifically support feature snapshot crash consistent properly supported applications assist operating system creating transactionally consistent snapshots commercial software accessing locked files windows include file access manager open file manager work installing drivers access files kernel mode unix-like operating systems including linux apple macos normally automatically lock open files several kinds file-locking mechanisms available different flavors unix many operating systems support one kind compatibility common mechanism two mechanisms may separate may implemented atop although types locks configured mandatory file locks unix default advisory means cooperating processes may use locks coordinate access file among uncooperative processes also free ignore locks access file way choose words file locks lock file lockers i/o two kinds locks offered shared locks exclusive locks case codice_1 different kinds locks may applied different sections byte ranges file else whole file shared locks held multiple processes time exclusive lock held one process coexist shared lock acquire shared lock process must wait processes hold exclusive locks acquire exclusive lock process must wait processes hold either kind lock unlike locks created codice_1 created codice_3 preserved across codice_4s making useful forking servers therefore possible one process hold exclusive lock file provided processes share filial relationship exclusive lock initially created single process duplicated across codice_4 shared locks sometimes called read locks exclusive locks sometimes called write locks however locks unix advisory n't enforced thus possible database concept shared writes vs. exclusive writes example changing field place may permitted shared access whereas garbage-collecting rewriting database may require exclusive access file locks apply actual file rather file name important since unix allows multiple names refer file together non-mandatory locking leads great flexibility accessing files multiple processes hand cooperative locking approach lead problems process writes file without obeying file locks set processes reason unix-like operating systems also offer limited support mandatory locking systems file whose setgid bit whose group execution bit file opened subject automatic mandatory locking underlying filesystem supports however non-local nfs partitions tend disregard bit file subject mandatory locking attempts read region locked exclusive lock write region locked shared exclusive lock block lock released strategy first originated system v seen today solaris hp-ux linux operating systems part posix however bsd-derived operating systems freebsd openbsd netbsd apple macos support linux also supports mandatory locking special -o mand parameter filesystem mounting rarely used unix-like operating systems prevent attempts open executable file running program writing third form locking separate provided codice_1 codice_3 one process hold exclusive codice_3 given file exclusive lock duplicated across later codice_4 simplifies coding network servers helps prevent race conditions confusing unaware mandatory locks effect codice_10 system call consequently certain programs may effectively circumvent mandatory locking authors advanced programming unix environment second edition observed codice_11 editor indeed page 456 whether codice_3 locks work network filesystems nfs implementation dependent bsd systems codice_3 calls file descriptor open file nfs-mounted partition successful no-ops linux prior 2.6.12 codice_3 calls nfs files would act locally kernel 2.6.12 implement codice_3 calls nfs files using posix byte-range locks locks visible nfs clients implement codice_1-style posix locks invisible lock upgrades downgrades release old lock applying new lock application downgrades exclusive lock shared lock another application blocked waiting exclusive lock latter application may get exclusive lock lock first application means lock downgrades block may counterintuitive codice_1 locks associated file given process removed file descriptor file closed process even lock never requested file descriptor also codice_1 locks inherited child process codice_1 close semantics particularly troublesome applications call subroutine libraries may access files neither bugs occurs using real codice_3-style locks preservation lock status open file descriptors passed another process using unix domain socket implementation dependent one source lock failure occurs buffered i/o buffers assigned user local workspace rather operating system buffer pool fread fwrite commonly used buffered i/o section file read another attempt read section likely obtain data local buffer problem another user attached file local buffers thing happening fwrite data obtained buffer fread obtaining data file user could changed could use flock exclusive access prevents simultaneous writes since reads reading buffer file data changed user 1 lost user 2 overwritten best solution problem use unbuffered i/o read write flock also means using lseek instead fseek ftell course 'll make adjustments function parameters results returned generally speaking buffered i/o unsafe used shared files amiga os lock file directory acquired using codice_21 function codice_22 lock shared processes read file/directory ca n't modify delete exclusive process successfully acquires lock access modify object lock whole object part lock must released codice_23 function unlike unix operating system implicitly unlock object process terminates shell scripts programs often use strategy similar use file locking creation lock files files whose contents irrelevant although often one find process identifier holder lock file whose sole purpose signal presence resource locked lock file often best approach resource controlled regular file using methods locking files apply example lock file might govern access set related resources several different files directories group disk partitions selected access higher level protocols like servers database connections using lock files care must taken ensure operations atomic obtain lock process must verify lock file exist create whilst preventing another process creating meantime various methods include lock files often named tilde codice_27 prefixed name file locking locking resource file may named arbitrarily certain mozilla products firefox thunderbird sunbird use type file resource lock mechanism using temporary file named parent.lock unlocker utility used determine process locking file displays list processes well choices process kill task unlock etc along list file options delete rename unix-like systems utilities used inspect state file locks process filename windows systems file locked possible schedule moving deletion performed next reboot approach typically used installers replace locked system files version control systems file locking used prevent two users changing file version parallel saving second user overwrite first user changed implemented marking locked files read-only file system user wanting change file performs unlock also called checkout operation check-in store operation done lock reverted nobody else allowed unlock file
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Computer file systems
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intent android intent android operating system software mechanism allows users coordinate functions different activities achieve task intent messaging object provides facility performing late runtime binding code different applications android development environment significant use launching activities thought glue activities intents provide inter-application messaging system encourages collaboration component reuse intent basically passive data structure holding abstract description action performed dummies likens intent flicking switch intent turn light perform action flipping switch position concept created way allow developers easily remix different apps allow type task called activity handled application best suited even provided third party although concept new android architecture n't require elevated privileges access components makes open platform activities android defined classes control life cycle task user interface activities supported application declared manifest applications read activities supported intents one application start particular activities different application latter supports message type intent analysis 2011 researchers university california berkeley found intents pose security risk allowing attackers read content messages insert malicious messages applications
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Operating systems
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deception technology deception technology emerging category cyber security defense deception technology products detect analyze defend zero-day advanced attacks often real time automated accurate provide insight malicious activity within internal networks may unseen types cyber defense deception technology enables proactive security posture seeking deceive attackers detect defeat allowing enterprise return normal operations existing defense-in-depth cyber technologies struggled increasing wave sophisticated persistent human attackers technologies seek primarily defend perimeter firewalls end-point security defend perimeter 100 certainty cyber-attackers penetrate networks move unimpeded months stealing data intellectual property heuristics may find attacker within network often generate many alerts critical alerts missed since 2014 attacks accelerated evidence cyber-attackers penetrating traditional defenses rapidly increasing rate deception technology considers human attacker point view method exploiting navigating networks identify exfiltrate data integrates existing technologies provide new visibility internal networks share high probability alerts threat intelligence existing infrastructure deception technology automates creation traps decoys and/or lures mixed among within existing resources provide layer protection stop attackers penetrated network traps decoys assets either use real licensed operating system software emulations devices traps decoys use emulations also imitate medical devices automated teller machines atms retail point sale systems switches routers much lures generally real information technology resources files varying kinds placed actual assets upon penetrating network attackers seek establish backdoor use identify exfiltrate data intellectual property begin moving laterally internal vlans almost immediately look one traps decoys interacting one decoys trigger alert alerts high probability almost always coincide ongoing attack deception designed lure attacker – attacker may consider worthy asset continue injecting malware deception technology generally allows automated static dynamic analysis injected malware provides reports automation security operations personnel deception technology may also identify indicators compromise ioc suspect end-points part compromise cycle automation also allows automated memory analysis suspect end-point automatically isolating suspect end-point many partner integrations allow variety implementation paths existing enterprise government customers internet things iot devices usually scanned legacy defense depth cyber defense remain prime targets attackers within network deception technology identify attackers moving laterally network within devices integrated turnkey devices utilize embedded operating systems allow operating systems scanned closely protected embedded end-point intrusion detection software also well protected deception technology deployment network examples include process control systems scada used many manufacturing applications global basis deception technology associated discovery zombie zero attack vector wherein deception technology identified attacker utilizing malware embedded barcode readers manufactured overseas medical devices particular vulnerable cyber attacks within healthcare networks fda-certified devices closed systems accessible standard cyber defense software deception technology surround protect devices identify attackers using backdoor placement data exfiltration recent documented cyber attacks medical devices include x-ray machines ct scanners mri scanners blood gas analyzers pacs systems many networks utilizing devices protected deception technology attack vector called medical device hijack medjack estimated penetrated many hospitals worldwide specialized deception technology products capable addressing rise ransomware select products deceive ransomware engaging attack decoy resource isolating infection points alerting cyber defense software team honeypots perhaps first simple form deception honeypot appeared simply unprotected information technology resource presented attractive way prospective attacker already within network notion honeypots deceiving attackers perhaps delaying identifying ultimately supporting efforts shut attack good one potential benefits aside early honeypots exhibit challenges functionality integrity overall efficacy meeting goals key lack automation enabled broad scale deployment deployment strategy would seek cover enterprise tens thousands vlans must protected wo n't economically efficient using manual processes manual configuration gap legacy honeypots modern deception technology diminished time continue modern honeypots constitute low end deception technology space today traditional cyber defense technologies firewalls end-point security generate many alerts large enterprise alert volume may reach cases millions alerts per day security operations personnel process activity easily yet takes one successful penetration compromise entire network deception technology produces alerts end product binary process probability essentially reduced two values 0 100 party seeks identify ping enter view trap decoy utilizes lure immediately identified behavior anyone touching traps lures advantage heuristics probability-based approaches many thousands extraneous alerts techniques generate best practice shows deception technology stand-alone strategy deception technology additional compatible layer existing defense-in-depth cyber defense partner integrations make useful goal add protection advanced sophisticated human attackers successfully penetrate perimeter technical innovation deception technology received market industry analyst identified ten top technologies information security 2016 one deception technology industry analyst predicted august 2016 deception technology market currently 2016 approximately 50 100 million globally predicted 100 million 200 million revenue 2018 analyst earlier noted 2018 ... 10 percent enterprises use deception tools tactics actively participate deception operations attackers gartner also noted deception technology far underutilized technology provide serious advantages attackers cyber attackers two important analysts recently predicted market size exceeding 1 billion 2020 adoption fueled part continued highly visible targeted attacks large enterprise government institutions globally market research media estimates cumulative deception technology market value 12 billion 2017–2022 growing 19 cagr
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Computer security
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mega-d botnet mega-d also known alias ozdok botnet peak responsible sending 32 spam worldwide october 14 2008 u.s federal trade commission cooperation marshal software tracked owners botnet froze assets november 6 2009 security company fireeye inc. disabled mega-d botnet disabling command control structure akin srizbi botnet takedown late 2008 mega-d/ozdok takedown involved coordination dozens internet service providers domain name registrars non-profit organizations like shadowserver m86 security researchers estimated take immediate effect spam botnet november 9 2009 spam stopped altogether although small trickle weekend directed couple small uk-based domains monitored since botnet bounced back exceeding pre-takedown levels nov. 22 constituting 17 worldwide spam dec. 13 july 2010 researchers university california berkeley published model mega-d protocol state-machine revealing internals proprietary protocol first time protocol obtained automatic reverse engineering technique developed berkeley researchers among contributions research paper reveals flaw mega-d protocol allowing template milking i.e. unauthorized spam template downloading flaw could used acquire spam templates train spam filters spam hits network november 2010 oleg nikolaenko arrested las vegas nevada federal bureau investigation charged violations can-spam act 2003 nikolaenko suspected operating mega-d botnet create zombie network many 500,000 infected computers
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Computer security
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eva hajičová eva hajičová born 23 august 1935 czech linguist specializing topic–focus articulation corpus linguistics 2006 awarded association computational linguistics acl lifetime achievement award named fellow acl 2011
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Computational linguistics
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basic09 basic09 structured basic programming language dialect developed microware behalf motorola then-new motorola 6809 cpu released february 1980 primarily used os-9 operating system released 1979 microware also released version os-9/68k 68000 microware basic contrast typical basics era basic09 includes multi-pass compiler produces compact bytecode known i-code i-code replaces number data structures found basics direct pointers code values speeding performance users compile code using codice_1 command point called directly os-9 operated native code case packed code cut-down version basic09 runtime system used runb improving memory footprint load time language includes number structured programming additions including local variables ability ignore line numbers favor named routines user-defined structures several distinct base data types including 16-bit 8-bit byte integers addition floating point strings key difference basic09 conventional basics era like canonical microsoft basic addition codice_2/codice_3 structure created separately executable blocks code code codice_2 common complete programs basics including variables local code executed stand-alone fashion codice_2s called using codice_6 command could include variables function-call semantics instance codice_7 calls procedure named codice_8 takes two parameters parameters imported procedure using codice_9 keyword example codice_10 side-effect use named procedures resulting memory workspace effect namespace respect basic09 system appears user directory callable programs contrasts typical basics one program available given time construction larger programs calling library-like code generally requires source code copy pasted separate programs basic09 user codice_11 procedures name workspace call code construct larger programs separately stored procedures addition code workspace program called codice_6 procedure name could found would look disk file name run worked basic09 code also executable program including machine language files meant basic09 could easily call system routines addition codice_6 common basic commands likewise used names instance codice_14 would print source code list procedure named bob codice_15 prints procedures currently memory adding codice_16 codice_17 added pretty printing indented loops branches improve readability one could also codice_18 codice_11 procedures storage addition organizational properties codice_2 basic09 also included number extensions flow control statements found basic provide structure instance codice_21 statement could used traditional codice_21 ... codice_23 format single line could used structured multi-line format codice_24 loops naturally structured format codice_25 placed line basic09 also added codice_26 codice_27 additional clarity working non-indexed loops also included center-exit codice_28 used codice_29 statement testing anywhere loop body basic09 included several built-in data types addition traditional string string 40-bit floating point real types found basics era also included 16-bit signed integer 8-bit unsigned byte logical boolean type boolean types packed bytes single boolean used entire 8-bit byte store single value language provided separate bytewise boolean operators bitwise operations bytes integers contrast basics also operated different base types basic09 decorate variable name indicate type instead used codice_30 definitions instance codice_31 declare two boolean variables codice_32 array five integers additionally basic09 included codice_33 keyword allowed compound types defined element listed single line separated semicolons instance defines employee record type named codice_34 three elements codice_35 codice_36 codice_37 employee_record type used definition like type instance codice_38 defines array 100 employee_record elements accessed code using dot notation instance codice_39 line numbers used basic dialects primarily way support editor users would edit particular lines code typing number text following either adding replacing lines already memory every line code number also made suitable indicating target codice_40 codice_41 compared languages like fortran separate line label used purpose basic09 normally use line numbers editor modified allow user edit lines without referring number however basic09 assume sort full-screen capability using cursor keys option instead system separate editor prompt allowed user move using keys moving forward backward one line time insert new line code without line number user left blank start statement note language case sensitive user-provided values like procedure variable names keywords keywords typed editor lower case shown upper case program codice_17ed basic09 allowed multiple statements single line code used separator instead used dialects used colon codice_43 assignment operator addition normal codice_44 codice_43 identical effect codice_44 made difference assignments comparisons obvious internal multipass compiler converts basic09 source code tokenized optimized bytecode called i-code i-code differs traditional tokenizing approach found basics number items placed directly memory instead using references looked instance ms-based interpreters variable reference code left string format variable codice_47 would represented memory three letters val execution variable encountered code interpreter look string table variables find associated storage address memory finally read value stored location table usually constructed value follows name save time final lookup contrast i-code address variable determined advance reference code replaced address avoids runtime search variable table optimizations include separate codice_24 routine used index variable integer separate integer real math libraries added performance basic09 also included codice_1 command took procedure name returned optimized version optimizations included removing non-coding instructions like code comments replacement constant expressions single value instance codice_1 would recognize codice_51 contains constants right replaces code codice_52 requires single operation runtime addition removing division square root codice_1 reduced memory footprint procedure improved performance 10 30 although common run programs within basic09 enviornment basics basic09 also shipped separate run-only version code known runb runb removed editing debugging features system half size full basic09 result purpose runb primarily run packed modules called programs meant user typed name basic09 module os/9 command line module marked packed opened run runb instead basic09 reduces memory footprint improves load time
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Programming language topics
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zoho corporation zoho corporation indian software development company focus zoho corporation lies web-based business tools information technology including office tools suite internet things management platform suite management software company founded 1996 sridhar vembu tony thomas pleasanton california offices seven countries global headquarters chennai 1996 2009 company known adventnet inc. adventnet expanded operations japan june 2001 zoho crm released 2005 followed releases projects creator sheet 2006 zoho expanded collaboration space release zoho docs zoho meeting 2007 2008 company added invoicing mail applications claims reached 10 lakh 1 million users august year 2009 company renamed zoho corporation online office suite name company launched grew without outside funding privately owned interview 2016 founder ceo sridhar vembu said one reasons zoho shunning outside funding financialisation associated investments would often put immense pressure funded company focus excessively return investments company would lose sight human objectives whereas beyond money also mission purpose life first zoho user conference zoholics launched 2012 year since 2005 zoho released additional applications 2017 released zoho one comprehensive suite zoho applications zoho headquartered chennai tamil nadu 2019 12 offices around world us headquarters currently pleasanton california plans move austin texas 2021 research development campus estancia park chennai zoho office tenkasi tirunelveli district tamil nadu product zoho desk built launched company operates china also offices singapore japan bulk support operations carried office chennai.zoho also office renigunta andhra pradesh operating office since 2018
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Distributed computing architecture
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radio link control radio link control rlc layer 2 radio link protocol used umts lte air interface protocol specified 3gpp ts 25.322 umts ts 36.322 lte ts 38.322 5g new radio nr rlc located top 3gpp mac-layer pdcp-layer main tasks rlc protocol rlc features specific lte 1 re-segmentation 2 rlc sdu discard notified upper layer
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Internet protocols
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fully undetectable fully undetectable usually shortened fud stand data encrypted making appear random noise also stand software detected anti-viruses scan performed term used hacker circles refer something appears clean many anti-viruses even though hacking tool
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Computer security
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biocompute object biocompute object bco project community-driven initiative build framework standardizing sharing computations analyses generated high-throughput sequencing hts also referred next-generation sequencing ngs massively parallel sequencing mps originally started collaborative contract george washington university food drug administration project grown include 20 universities biotechnology companies public-private partnerships pharmaceutical companies including seven bridges harvard medical school bco aims ease exchange hts workflows various organizations fda pharmaceutical companies contract research organizations bioinformatic platform providers academic researchers one biggest challenges bioinformatics documenting sharing scientific workflows way computation results peer-reviewed reliably reproduced bioinformatic pipelines typically use multiple pieces software typically multiple versions available multiple input parameters multiple outputs possibly platform-specific configurations experimental parameters laboratory protocol small changes computational parameters may large impact scientific validity results biocompute framework provides object oriented design bco contains details pipeline used constructed digitally signed shared biocompute concept originally developed satisfy fda regulatory research review needs evaluation validation verification genomics data however biocompute framework follows fair data principles used broadly provide communication interoperability different platforms industries scientists regulators standardization genomic data biocompute objects mostly useful three groups users 1 academic researchers carrying new genetic experiments 2 pharma/biotech companies wish submit work fda regulatory review 3 clinical settings hospitals labs offer genetic tests personalized medicine utility academic researchers ability reproduce experimental data accurately less uncertainty utility entities wishing submit work fda streamlined approach less uncertainty ability accurately reproduce work clinical settings critical hts data clinical metadata transmitted accurate way ideally standardized way readable stakeholder including regulatory partners biocompute object json format minimum contains software versions parameters necessary evaluate verify computational pipeline may also contain input data files links reference genomes executable docker components biocompute object integrated hl7 fhir provenance resource common workflow language research object biocompute object working group facilitates means different stakeholders provide input current practices bco working group formed preparation 2017 hts computational standards regulatory sciences workshop initially made workshop participants continual growth bco working group direct result interaction variety stakeholders interested communities standardization computational hts data processing public-private partnerships formed universities private genomic data companies software platforms government regulatory institutions easy point entry new individuals institutions bco project participate discussion best practices objects
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Computer architecture
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geoffrey knauth geoffrey s. knauth board directors free software foundation teaches computer science lycoming college contributed gnu objective-c collection library degree economics harvard university
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Operating systems
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dares wins ii dares wins ii run gun game developed published alligata software released 1985 commodore 64 well amstrad cpc atari 8-bit family bbc micro commodore 16 plus/4 msx zx spectrum game remake earlier dares wins given injunction accused similar commando main character lone soldier sent enemy territory wielding gun five grenades player must capture eight enemy outposts massive opposition player blow vehicles rescue prisoners level player takes long prisoners executed firing squad zzap 64 rated game 90/100 calling game fantastic landscapes incredible revisited game 7 years later gave revised rating 78/100 saying n't weathered years well still playable dion guy nintendo life called game something wished nintendo virtual console lot fun despite extremely difficult
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Computer architecture
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popek goldberg virtualization requirements popek goldberg virtualization requirements set conditions sufficient computer architecture support system virtualization efficiently introduced gerald j. popek robert p. goldberg 1974 article formal requirements virtualizable third generation architectures even though requirements derived simplifying assumptions still represent convenient way determining whether computer architecture supports efficient virtualization provide guidelines design virtualized computer architectures system virtual machines capable virtualizing full set hardware resources including processor processors memory storage resources peripheral devices virtual machine monitor vmm also called hypervisor piece software provides abstraction virtual machine three properties interest analyzing environment created vmm terminology popek goldberg vmm must present three properties terminology used reference book smith nair 2005 vmms typically assumed satisfy equivalence resource control properties additionally meeting performance property called efficient vmms popek goldberg describe characteristics instruction set architecture isa physical machine must possess order run vmms possess properties analysis derives characteristics using model third generation architectures e.g. ibm 360 honeywell 6000 dec pdp-10 nevertheless general enough extended modern machines model includes processor operates either system user mode access linear uniformly addressable memory assumed subset instruction set available system mode memory addressed relative relocation register i/o interrupts modelled derive virtualization theorems give sufficient necessary conditions virtualization popek goldberg introduce classification instructions isa 3 different groups main result popek goldberg analysis expressed follows theorem 1 conventional third-generation computer effective vmm may constructed set sensitive instructions computer subset set privileged instructions intuitively theorem states build vmm sufficient instructions could affect correct functioning vmm sensitive instructions always trap pass control vmm guarantees resource control property non-privileged instructions must instead executed natively i.e. efficiently holding equivalence property also follows theorem also provides simple technique implementing vmm called trap-and-emulate virtualization recently called classic virtualization sensitive instructions behave nicely vmm trap emulate every one related problem deriving sufficient conditions recursive virtualization conditions vmm run copy built popek goldberg present following sufficient conditions theorem 2 conventional third-generation computer recursively virtualizable architectures like non-hardware-assisted x86 meet conditions virtualized classic way architectures still fully virtualized x86 case meaning cpu mmu level using different techniques like binary translation replaces sensitive instructions generate traps sometimes called critical instructions additional processing however makes vmm less efficient theory hardware traps non-negligible performance cost well well-tuned caching binary translation system may achieve comparable performance case x86 binary translation relative first generation x86 hardware assist merely made sensitive instructions trappable effectively gives theorem different sufficiency conditions theorem 3 hybrid vmm may constructed third generation machine set user sensitive instructions subset set privileged instructions conditions isa virtualization expressed theorem 1 may relaxed expense efficiency property vmms non-virtualizable isas popek goldberg sense routinely built virtualization architectures requires correct handling critical instructions i.e. sensitive unprivileged instructions one approach known patching adopts techniques commonly used dynamic recompilation critical instructions discovered run-time replaced trap vmm various mechanisms caching emulation code hardware assists proposed make patching process efficient different approach paravirtualization requires guest operating systems modified ported running virtual environment section presents relevant architectures relate virtualization requirements pdp-10 architecture instructions sensitive alter query processor mode privileged instructions save restore condition codes containing user iot bits sensitive instructions system/370 privileged satisfies virtualization requirements motorola mc68000 single unprivileged sensitive instruction instruction sensitive allows access entire status register includes condition codes also user/supervisor bit interrupt level trace control later family members starting mc68010 move sr instruction made privileged new move ccr instruction provided allow access condition code register ia-32 instruction set pentium processor contains 18 sensitive unprivileged instructions categorized two groups introduction amd-v intel vt-x instruction sets 2005 allows x86 processors meet popek goldberg virtualization requirements effort needed support virtualization ia-64 architecture described 2000 article magenheimer christian hyperprivileged mode ultrasparc architecture specified ultrasparc architecture 2005 defines sun4v platform super-set sun4u platform still compliant sparc v9 level-1 specification sensitive instructions powerpc instruction set privileged efficiency requirement popek goldberg definition vmm concerns execution non-privileged instructions must execute natively distinguishes vmm general class hardware emulation software unfortunately even architecture meets popek goldberg requirements performance virtual machine differ significantly actual hardware early experiments performed system/370 meets formal requirements theorem 1 showed performance virtual machine could low 21 native machine benchmarks cost trapping emulating privileged instructions vmm significant led ibm engineers introduce number hardware assists roughly doubled performance system/370 virtual machines assists added several stages end 100 assists late models system/370 one main driving factors development hardware assists system/370 virtual memory guest operating system implemented virtual memory even non-privileged instructions could experience longer execution times penalty imposed requirement access translation tables used native execution see shadow page tables
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Computer architecture
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siod scheme one defun humorously scheme one day siod programming language dialect language lisp small-size implementation dialect scheme written c designed embedded inside c programs notable perhaps smallest practical implementation lisp-like language written george j. carrette originally free open-source software released gnu lesser general public license lgpl siod features include
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Programming language topics
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victor yngve victor h. yngve july 5 1920 – january 15 2012 professor emeritus linguistics university chicago one earliest researchers computational linguistics natural language processing use computers analyze process languages created first program produce random well-formed output sentences given text children book called engineer small little train importantly showed computer processing terms human brain process sentences certain kind complexity ones exceed depth limit nothing length kind established independently george miller depth limit seven plus minus two sentence constituents memory given time yngve also author comit first string processing language compare snobol trac perl developed ibm 700/7000 series computers yngve collaborators mit 1957-1965 yngve created language supporting computerized research field linguistics specifically area machine translation natural language processing 1970 paper getting word edgewise yngve coined term 'back channel behavior describe conversational phenomenon day known linguistic literature back-channeling according duncan yngve paper also suggested term turn-taking independently erving goffman duncan 1972 283
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Computational linguistics
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wide-issue wide-issue architecture computer processor issues one instruction per clock cycle considered three broad types
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Computer architecture
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perforce perforce legally perforce software inc. minneapolis minnesota-based developer software used application development including version control software web-based repository management developer collaboration application lifecycle management agile planning software software sold helix hansoft brand names company equally owned private equity firms clearlake capital francisco partners perforce software founded 1995 alameda california christopher seiwald software developer computer science graduate uc berkeley first product also called perforce version control system allowing companies collaborate large software projects keeping track changes source code binary files june 2013 company released helix swarm tool developers working different geographical areas collaborate code review june 2014 company released version perforce versioning engine known p4d supported concurrency ability program run multiple parts concurrently march 2015 company renamed product perforce helix supported distributed development support included security features allowing suspicious usage tracking helix security capabilities included ip threat detection capabilities co-developed analytics vendor interset october company collaborated gitlab release gitswarm software tool combined github distributed workflow developers perforce single code repository february 2016 seiwald sold company investment group summit partners janet dryer named new ceo company headquarters relocated minneapolis november perforce announced acquisition seapine software provider application lifecycle management alm tools seapine testtrack alm software rebranded helix alm september 2017 company acquired uppsala sweden-based hansoft developer agile planning software also september perforce announced acquired finnish repository management services company deveo deveo products merged perforce helix teamhub first solo venture git-based development teams january 2018 summit partners sold perforce private equity firm clearlake capital may perforce acquired uk-based programming research prqa static code analysis firm june company announced ceo janet dryer moving role chair board coo/cfo mark ties taking role ceo october company acquired mobile web automation testing company perfecto january 2019 perforce announced acquisition rogue wave software software company focus development tools high-performance computing april 2019 private equity firm francisco partners acquired 50 perforce becoming equal partner clearlake capital perforce develops software used software developers manage code development process product line includes following helix core formerly perforce helix company versioning control engine large scale development environments helix version control system manages central database master repository file versions helix core clients fall roughly five categories git command gui web plugin perforce system make part content available git repositories users git clients work file content history git commits visible users clients perforce changelists vice versa users submit changed files together changelists applied atomic commits server client software released pre-built executables microsoft windows macos linux solaris freebsd operating systems helix alm formerly testtrack suite tools used application lifecycle management alm allowing developers manage product system development phases one product software originally developed seapine software acquired perforce rebranded helix alm provides centralized suite capabilities managing requirements defects issues testing throughout software development cycle three components suite company develops helix qac static code analysis software tool c c++ programming languages perforce customers software developers wide variety companies including netflix sap disney intuit nyse company considered leader gaming space 18 top 20 games developers including ubisoft electronic arts using perforce version control company headquartered minneapolis minnesota november 2017 listed additional offices alameda california mason ohio hallbergmoos germany helsinki finland sydney australia uppsala sweden wokingham england
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Distributed computing architecture
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cache computing computing cache aue hardware software component stores data future requests data served faster data stored cache might result earlier computation copy data stored elsewhere cache hit occurs requested data found cache cache miss occurs cache hits served reading data cache faster recomputing result reading slower data store thus requests served cache faster system performs cost-effective enable efficient use data caches must relatively small nevertheless caches proven many areas computing typical computer applications access data high degree locality reference access patterns exhibit temporal locality data requested recently requested already spatial locality data requested stored physically close data already requested inherent trade-off size speed given larger resource implies greater physical distances also tradeoff expensive premium technologies sram vs cheaper easily mass-produced commodities dram hard disks buffering provided cache benefits bandwidth latency larger resource incurs significant latency access e.g take hundreds clock cycles modern 4 ghz processor reach dram mitigated reading large chunks hope subsequent reads nearby locations prediction explicit prefetching might also guess future reads come make requests ahead time done correctly latency bypassed altogether use cache also allows higher throughput underlying resource assembling multiple fine grain transfers larger efficient requests case dram circuits might served wider data bus example consider program accessing bytes 32-bit address space served 128-bit off-chip data bus individual uncached byte accesses would allow 1/16th total bandwidth used 80 data movement would memory addresses instead data reading larger chunks reduces fraction bandwidth required transmitting address information hardware implements cache block memory temporary storage data likely used central processing units cpus hard disk drives hdds frequently use cache web browsers web servers cache made pool entries entry associated data copy data backing store entry also tag specifies identity data backing store entry copy cache client cpu web browser operating system needs access data presumed exist backing store first checks cache entry found tag matching desired data data entry used instead situation known cache hit example web browser program might check local cache disk see local copy contents web page particular url example url tag content web page data percentage accesses result cache hits known hit rate hit ratio cache alternative situation cache checked found contain entry desired tag known cache miss requires expensive access data backing store requested data retrieved typically copied cache ready next access cache miss previously existing cache entry removed order make room newly retrieved data heuristic used select entry replace known replacement policy one popular replacement policy least recently used lru replaces oldest entry entry accessed less recently entry see cache algorithm efficient caching algorithms compute use-hit frequency size stored contents well latencies throughputs cache backing store works well larger amounts data longer latencies slower throughputs experienced hard drives networks efficient use within cpu cache system writes data cache must point write data backing store well timing write controlled known write policy two basic writing approaches write-back cache complex implement since needs track locations written mark dirty later writing backing store data locations written back backing store evicted cache effect referred lazy write reason read miss write-back cache requires block replaced another often require two memory accesses service one write replaced data cache back store one retrieve needed data policies may also trigger data write-back client may make many changes data cache explicitly notify cache write back data since data returned requester write operations decision needs made write misses whether data would loaded cache defined two approaches write-through write-back policies use either write-miss policies usually paired way entities cache may change data backing store case copy cache may become out-of-date stale alternatively client updates data cache copies data caches become stale communication protocols cache managers keep data consistent known coherency protocols small memories close cpu operate faster much larger main memory cpus since 1980s used one caches sometimes cascaded levels modern high-end embedded desktop server microprocessors may many six types cache levels functions examples caches specific function d-cache i-cache translation lookaside buffer mmu earlier graphics processing units gpus often limited read-only texture caches introduced morton order swizzled textures improve 2d cache coherency cache misses would drastically affect performance e.g mipmapping used caching important leverage 32-bit wider transfers texture data often little 4 bits per pixel indexed complex patterns arbitrary uv coordinates perspective transformations inverse texture mapping gpus advanced especially gpgpu compute shaders developed progressively larger increasingly general caches including instruction caches shaders exhibiting increasingly common functionality cpu caches example gt200 architecture gpus feature l2 cache fermi gpu 768 kb last-level cache kepler gpu 1536 kb last-level cache maxwell gpu 2048 kb last-level cache caches grown handle synchronisation primitives threads atomic operations interface cpu-style mmu digital signal processors similarly generalised years earlier designs used scratchpad memory fed dma modern dsps qualcomm hexagon often include similar set caches cpu e.g modified harvard architecture shared l2 split l1 i-cache d-cache memory management unit mmu fetches page table entries main memory specialized cache used recording results virtual address physical address translations specialized cache called translation lookaside buffer tlb cpu caches generally managed entirely hardware variety software manages caches page cache main memory example disk cache managed operating system kernel disk buffer integrated part hard disk drive sometimes misleadingly referred disk cache main functions write sequencing read prefetching repeated cache hits relatively rare due small size buffer comparison drive capacity however high-end disk controllers often on-board cache hard disk drive data blocks finally fast local hard disk drive also cache information held even slower data storage devices remote servers web cache local tape drives optical jukeboxes scheme main concept hierarchical storage management also fast flash-based solid-state drives ssds used caches slower rotational-media hard disk drives working together hybrid drives solid-state hybrid drives sshds web browsers web proxy servers employ web caches store previous responses web servers web pages images web caches reduce amount information needs transmitted across network information previously stored cache often re-used reduces bandwidth processing requirements web server helps improve responsiveness users web web browsers employ built-in web cache internet service providers isps organizations also use caching proxy server web cache shared among users network another form cache p2p caching files sought peer-to-peer applications stored isp cache accelerate p2p transfers similarly decentralised equivalents exist allow communities perform task p2p traffic example corelli cache store data computed demand rather retrieved backing store memoization optimization technique stores results resource-consuming function calls within lookup table allowing subsequent calls reuse stored results avoid repeated computation related dynamic programming algorithm design methodology also thought means caching bind dns daemon caches mapping domain names ip addresses resolver library write-through operation common operating unreliable networks like ethernet lan enormous complexity coherency protocol required multiple write-back caches communication unreliable instance web page caches client-side network file system caches like nfs smb typically read-only write-through specifically keep network protocol simple reliable search engines also frequently make web pages indexed available cache example google provides cached link next search result prove useful web pages web server temporarily permanently inaccessible another type caching storing computed results likely needed memoization example ccache program caches output compilation order speed later compilation runs database caching substantially improve throughput database applications example processing indexes data dictionaries frequently used subsets data distributed cache uses networked hosts provide scalability reliability performance application hosts co-located spread different geographical regions semantics buffer cache totally different even fundamental differences intent process caching process buffering fundamentally caching realizes performance increase transfers data repeatedly transferred caching system may realize performance increase upon initial typically write transfer data item performance increase due buffering occurring within caching system read caches data item must fetched residing location least order subsequent reads data item realize performance increase virtue able fetched cache faster intermediate storage rather data residing location write caches performance increase writing data item may realized upon first write data item virtue data item immediately stored cache intermediate storage deferring transfer data item residing storage later stage else occurring background process contrary strict buffering caching process must adhere potentially distributed cache coherency protocol order maintain consistency cache intermediate storage location data resides buffering hand typical caching implementations data item read written first time effectively buffered case write mostly realizing performance increase application write originated additionally portion caching protocol individual writes deferred batch writes form buffering portion caching protocol individual reads deferred batch reads also form buffering although form may negatively impact performance least initial reads even though may positively impact performance sum individual reads practice caching almost always involves form buffering strict buffering involve caching buffer temporary memory location traditionally used cpu instructions directly address data stored peripheral devices thus addressable memory used intermediate stage additionally buffer may feasible large block data assembled disassembled required storage device data may delivered different order produced also whole buffer data usually transferred sequentially example hard disk buffering sometimes increases transfer performance reduces variation jitter transfer latency opposed caching intent reduce latency benefits present even buffered data written buffer read buffer cache also increases transfer performance part increase similarly comes possibility multiple small transfers combine one large block main performance-gain occurs good chance data read cache multiple times written data soon read cache sole purpose reduce accesses underlying slower storage cache also usually abstraction layer designed invisible perspective neighboring layers
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Computer architecture
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hitdynamics hitdynamics provider web analytics software allowing website owners track traffic sites ascertain traffic sources deliver conversions sales company founded internet entrepreneur max polyakov january 2005 acquired 6 march 2006 hitwise company technology exists web analytics arm hitwise suite cupid plc also founded max polyakov
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Web technology
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zygalski sheets method zygalski sheets cryptologic technique used polish cipher bureau world war ii war also british cryptologists bletchley park decrypt messages enciphered german enigma machines zygalski-sheet apparatus takes name polish cipher bureau mathematician–cryptologist henryk zygalski invented october 1938 zygalski device comprised set 26 perforated sheets initially six possible sequences inserting three rotors enigma machine scrambler sheet related starting position left slowest-moving rotor 26 × 26 matrix represented 676 possible starting positions middle right rotors duplicated horizontally vertically a–z a–y sheets punched holes positions would allow female occur polish mathematician–cryptologist marian rejewski writes perforated-sheets device operated like rejewski card-catalog method developed using cyclometer zygalski-sheet procedure independent number plugboard plug connections enigma machine cipher bureau manual manufacture sheets security reasons done mathematician-cryptologists using razor blades time-consuming 15 december 1938 third job finished date germans introduced rotors iv v thus increasing labor making sheets tenfold since ten times many sheets needed 60 possible combinations sequences enigma machine 3 rotors selected among 5 25 july 1939 five weeks outbreak world war ii polish general staff cipher bureau disclosed french british allies warsaw cryptologic achievements breaking enigma ciphers part disclosures involved zygalski perforated-sheet method british bletchley park near london england undertook production two complete sets perforated sheets work done aid perforators section headed john r.f jeffreys sheets known bletchley netz netzverfahren net method though later remembered gordon welchman jeffreys sheets latter term however referred another catalog produced jeffreys section first set completed late december 1939 28 december part second set delivered polish cryptologists escaped german-overrun poland pc bruno outside paris france remaining sheets completed 7 january 1940 couriered alan turing france shortly thereafter help writes rejewski continued solving enigma daily keys sheets used poles make first wartime decryption enigma message 17 january 1940 may 1940 germans completely changed procedure enciphering message keys exception norwegian network result zygalski sheets use though herivel tip could still used
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Computer security
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abracadabra video game abracadabra text adventure game developed odisea software published proein soft line spanish amstrad cpc msx zx spectrum 1988 year 1209 knight named clus d'eledorf bewitched jealous queen saligia enamored become ghost haunting castle burgenfels would confess love game divided two parts part one clus find way rid witch break curse escape prison second part clus needs seek rescue beloved princess violeta greenwald forest game well received spanish video game press microhobby called excellent game high level graphic quality importantly stunning setting realization fantasy adventure game provides elements necessary satisfy even demanding fans genre micromania gave score 8/10 caad opined among adventures existing spanish market one definitely best
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Computer architecture
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us cyber challenge us cyber challenge private-public partnership program dedicated finding high level cybersecurity talent endeavor significantly reduce shortage today cyber workforce program identifies attracts recruits trains next generation cybersecurity professionals us cyber challenge currently program council cybersecurity center internet security us cyber challenge founded 2010 karen s. evans former administrator office electronic government information technology office management budget mission us cyber challenge fill workforce gap cybersecurity professionals process assessment training employment networking summer 2015 us cyber challenge hosted four camps across country two camps statewide camps located delaware illinois two camps regional camps located virginia eastern regional utah western regional camp schedule order qualify invitation one four cyber camps individuals must compete online qualifying competition cyber quests 2015 cyber quests schedule
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Computer security
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query plan query plan query execution plan ordered set steps used access data sql relational database management system specific case relational model concept access plans since sql declarative typically large number alternative ways execute given query widely varying performance query submitted database query optimizer evaluates different correct possible plans executing query returns considers best option query optimizers imperfect database users administrators sometimes need manually examine tune plans produced optimizer get better performance given database management system may offer one mechanisms returning plan given query packages feature tools generate graphical representation query plan tools allow special mode set connection cause dbms return textual description query plan another mechanism retrieving query plan involves querying virtual database table executing query examined oracle instance achieved using explain plan statement textual plan given query screenshot shown indicates query engine scan primary key index employee table matching seek primary key index contactid column contact table find matching rows resulting rows side shown nested loops join operator sorted returned result set connection order tune query user must understand different operators database may use ones might efficient others still providing semantically correct query results reviewing query plan present opportunities new indexes changes existing indexes also show database properly taking advantage existing indexes see query optimizer query optimizer always choose efficient query plan given query databases query plan reviewed problems found query optimizer gives hints improve databases alternatives express query queries return results tried query tools generate embedded hints query use optimizer databases like oracle provide plan table query tuning plan table return cost time executing query oracle offers two optimization approaches rbo slowly deprecated cbo used tables referenced query must analyzed analyze table dba launch code dbms_stats package tools query optimization include
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Databases
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computer multitasking computing multitasking concurrent execution multiple tasks also known processes certain period time new tasks interrupt already started ones finish instead waiting end result computer executes segments multiple tasks interleaved manner tasks share common processing resources central processing units cpus main memory multitasking automatically interrupts running program saving state partial results memory contents computer register contents loading saved state another program transferring control context switch may initiated fixed time intervals pre-emptive multitasking running program may coded signal supervisory software interrupted cooperative multitasking multitasking require parallel execution multiple tasks exactly time instead allows one task advance given period time even multiprocessor computers multitasking allows many tasks run cpus multitasking common feature computer operating systems allows efficient use computer hardware program waiting external event user input input/output transfer peripheral complete central processor still used another program time-sharing system multiple human operators use processor dedicated use behind scenes computer serving many users multitasking individual programs multiprogramming systems task runs must wait external event operating system scheduler forcibly swaps running task cpu real-time systems designed control industrial robots require timely processing single processor might shared calculations machine movement communications user interface often multitasking operating systems include measures change priority individual tasks important jobs receive processor time considered less significant depending operating system task might large entire application program might made smaller threads carry portions overall program processor intended use multitasking operating systems may include special hardware securely support multiple tasks memory protection protection rings ensure supervisory software damaged subverted user-mode program errors term multitasking become international term word used many languages german italian dutch danish norwegian early days computing cpu time expensive peripherals slow computer ran program needed access peripheral central processing unit cpu would stop executing program instructions peripheral processed data usually inefficient first computer using multiprogramming system british leo iii owned j. lyons co. batch processing several different programs loaded computer memory first one began run first program reached instruction waiting peripheral context program stored away second program memory given chance run process continued programs finished running use multiprogramming enhanced arrival virtual memory virtual machine technology enabled individual programs make use memory operating system resources concurrently running programs practical purposes non-existent invisible multiprogramming n't give guarantee program run timely manner indeed first program may well run hours without needing access peripheral users waiting interactive terminal problem users handed deck punched cards operator came back hours later printed results multiprogramming greatly reduced wait times multiple batches processed early multitasking systems used applications voluntarily ceded time one another approach eventually supported many computer operating systems known today cooperative multitasking although rarely used larger systems except specific applications cics jes2 subsystem cooperative multitasking scheduling scheme employed microsoft windows classic mac os enable multiple applications run simultaneously cooperative multitasking still used today risc os systems cooperatively multitasked system relies process regularly giving time processes system one poorly designed program consume cpu time either performing extensive calculations busy waiting would cause whole system hang server environment hazard makes entire environment unacceptably fragile preemptive multitasking allows computer system reliably guarantee process regular slice operating time also allows system deal rapidly important external events like incoming data might require immediate attention one another process operating systems developed take advantage hardware capabilities run multiple processes preemptively preemptive multitasking implemented pdp-6 monitor multics 1964 os/360 mft 1967 unix 1969 available operating systems computers small dec pdp-8 core feature unix-like operating systems linux solaris bsd derivatives well modern versions windows specific time processes grouped two categories waiting input output called i/o bound fully utilizing cpu cpu bound primitive systems software would often poll busywait waiting requested input disk keyboard network input time system performing useful work advent interrupts preemptive multitasking i/o bound processes could blocked put hold pending arrival necessary data allowing processes utilize cpu arrival requested data would generate interrupt blocked processes could guaranteed timely return execution earliest preemptive multitasking os available home users sinclair qdos sinclair ql released 1984 people bought machine commodore amiga released following year first commercially successful home computer use technology multimedia abilities make clear ancestor contemporary multitasking personal computers microsoft made preemptive multitasking core feature flagship operating system early 1990s developing windows nt 3.1 windows 95 later adopted apple macintosh mac os x unix-like operating system uses preemptive multitasking native applications similar model used windows 9x windows nt family native 32-bit applications multitasked preemptively 64-bit editions windows x86-64 itanium architectures longer support legacy 16-bit applications thus provide preemptive multitasking supported applications another reason multitasking design real-time computing systems number possibly unrelated external activities needed controlled single processor system systems hierarchical interrupt system coupled process prioritization ensure key activities given greater share available process time multitasking greatly improved throughput computers programmers started implement applications sets cooperating processes e. g. one process gathering input data one process processing input data one process writing results disk however required tools allow processes efficiently exchange data threads born idea efficient way cooperating processes exchange data would share entire memory space thus threads effectively processes run memory context share resources parent processes open files threads described lightweight processes switching threads involve changing memory context threads scheduled preemptively operating systems provide variant threads named fibers scheduled cooperatively operating systems provide fibers application may implement fibers using repeated calls worker functions fibers even lightweight threads somewhat easier program although tend lose benefits threads machines multiple processors systems directly support multithreading hardware essential multitasking system safely effectively share access system resources access memory must strictly managed ensure process inadvertently deliberately read write memory locations outside process address space done purpose general system stability data integrity well data security general memory access management responsibility operating system kernel combination hardware mechanisms provide supporting functionalities memory management unit mmu process attempts access memory location outside memory space mmu denies request signals kernel take appropriate actions usually results forcibly terminating offending process depending software kernel design specific error question user may receive access violation error message segmentation fault well designed correctly implemented multitasking system given process never directly access memory belongs another process exception rule case shared memory example system v inter-process communication mechanism kernel allocates memory mutually shared multiple processes features often used database management software postgresql inadequate memory protection mechanisms either due flaws design poor implementations allow security vulnerabilities may potentially exploited malicious software use swap file swap partition way operating system provide memory physically available keeping portions primary memory secondary storage multitasking memory swapping two completely unrelated techniques often used together swapping memory allows tasks loaded time typically multitasking system allows another process run running process hits point wait portion memory reloaded secondary storage processes entirely independent much trouble program multitasking environment complexity multitasking systems comes need share computer resources tasks synchronize operation co-operating tasks various concurrent computing techniques used avoid potential problems caused multiple tasks attempting access resource bigger systems sometimes built central processor number i/o processors kind asymmetric multiprocessing years multitasking systems refined modern operating systems generally include detailed mechanisms prioritizing processes symmetric multiprocessing introduced new complexities capabilities
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Operating systems
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run-time infrastructure simulation simulation run-time infrastructure rti middleware required implementing high level architecture hla rti fundamental component hla provides set software services necessary support federates coordinate operations data exchange runtime execution sense implementation hla interface specification part specification modern rti implementations conform ieee 1516 and/or hla 1.3 api specifications specifications include network protocol rti implementors rti create specification due interoperability rti products often rti versions assumed unless vendor specifies interoperability products versions
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Distributed computing architecture
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golvellius sega licensed franchise 1988 released remake game master system mark iii japan featuring enhanced graphics entirely different overworld dungeon layouts version released worldwide name golvellius valley doom later year 1988 compile released yet another remake msx2 system titled game featured mostly graphics ones sega master system version overworld dungeon layouts entirely different 2009 announced dotemu/d4 entreprise golvellius re-released iphone os platform scenario three different versions golvellius ending promised sequel never developed/released however spin-off game titled super cooks came included 1989 release disc station special shoka gou
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Computer architecture
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propel php propel free open-source mit object-relational mapping toolkit written php also integral part php framework symfony default orm including version 1.2 propel project started august 2003 availability beta versions php version 5 version 5 php finally able provide level support object-oriented programming made projects like propel possible also created demand hitherto-missing components large-scale object-oriented architectures propel originally based apache torque project java language orm project propel primary function provide mapping php classes database tables accomplish propel includes generator component uses source code generation build php classes based datamodel definition written xml propel also includes runtime component manages connections transactions idiosyncratic rules describe workings rdbms used propel
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Databases
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imagination creator creator family single-board computers developed imagination technologies promote educational research software development based mips architecture first board platform creator ci20 released august 2014 second development kit called creator ci40 introduced kickstarter campaign november 2015 creator ci20 board based ingenic jz4780 mobile-class application processor contains dual-core 1.2 ghz mips32 cpu 32k l1 cache 512k l2 cache ieee754 floating point unit coupled powervr sgx540 gpu processor supports mxu 32-bit simd extension addition board provides creator ci40 board based cxt200 chip optimized specifically iot applications contains dual-core dual-threaded 550 mhz mips interaptiv cpu 32k l1 cache 512k l2 cache ieee754 floating point unit coupled ensigma c4500 wi-fi radio processor addition board provides creator boards support creator iot framework open source software package based lwm2m protocol developed open mobile alliance
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Computer architecture
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lga 1356 lga 1356 land grid array 1356 pins also called socket b2 intel microprocessor socket released q1 2012 two processor 2p i.e dual socket segment server market supports 3 64-bit wide ddr3 channels whereas socket lga 2011 supports 4 channels socket lga 1155 supports 2 channels lga 1356 one two sockets designed replacement lga 1366 cpu socket lga 2011 known socket r lga 1356 1356 protruding pins make contact pads processor processors lga 1356 lga 1366 sockets compatible since different socket notches supports intel sandy bridge-en microprocessors code-named romley-en marketed xeon e5-2400 series main difference lga 2011 lga 1356 2 intel quickpath interconnect qpi connections lga 2011 1 qpi connection lga 1356 noticeable differences include 24 lanes pci express pci-e version 3.0 connections compared 40 lanes lga 2011 three channels ddr3 support compared four lga 2011 ddr3 channel support one dimm applicable ddr3 ddr3-l plans leaked early 2011 estimated releases first quarter 2012 september 2011 releases estimated end first quarter 2012 socket b2 processors following mechanical maximum load limits exceeded heatsink assembly shipping conditions standard use load limits crack processor die make unusable processors using socket static load limit previous models using lga 1366 socket b
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Computer architecture
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pnuts pnuts dynamic scripting language java platform designed used dual language system java programming language goals pnuts project provide small fast scripting language tight integration java language pnuts uses syntax simple friendly java developers also expressive java pnuts share type system java code easily invoke define pnuts functions likewise pnuts code easily manipulate java objects pnuts code even define java classes pnuts compiles java byte codes classes used java like class class written pnuts even later replaced class written java code changes pnuts syntax look similar java following code sample written java also valid pnuts script alternatively expressiveness pnuts could utilized pnuts originally developed 1997 toyokazu tomatsu testing tool java classes pnuts since extended mainly focusing essential functionality required java-based scripting engine module system bytecode compiler commercial usage pnuts includes rockwell automation factorytalk development system looks like project longer development
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Programming language topics
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m-expression computer programming m-expressions meta-expressions early proposed syntax lisp programming language inspired contemporary languages fortran algol john mccarthy published first paper lisp 1960 research fellow massachusetts institute technology described language symbolic expressions s-expressions could represent complex structures lists defined set primitive operations s-expressions language meta-expressions m-expressions could used define complex operations finally showed meta-language could represented s-expressions resulting system potentially self-hosting mccarthy planned develop automatic lisp compiler using m-expressions language syntax s-expressions describe compiler internal processes stephen b. russell read paper suggested s-expressions convenient syntax although mccarthy disapproved idea russell colleague daniel j. edwards hand-coded interpreter program could execute s-expressions program adopted mccarthy research group establishing s-expressions dominant form lisp mccarthy reflected fate m-expressions 1979 recent circa 2003 variant i-expressions use indentation indicate parentheses implicitly thus ways intermediate s-expressions m-expressions i-expressions introduced scheme request implementation 49 auxiliary syntax scheme widely adopted
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Programming language topics
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