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mx linux mx linux midweight linux operating system based debian stable using core antix components additional software created packaged mx community developed cooperative venture antix former mepis communities aiming use best tools talents distributions community stated goal combine elegant efficient desktop simple configuration high stability solid performance medium-sized footprint mx linux uses xfce desktop environment kde plasma environments added available spin-off iso images mx linux began discussion future options among members mepis community december 2013 developers antix joined bringing iso build system well live-usb/dvd technology order listed distrowatch mx linux initially presented version antix received distrowatch page separate distribution release first public beta mx-16 november 2 2016 mx-14 series based debian stable wheezy used first xfce 4.10 14.4 release xfce 4.12 mx-14 versions intended fit onto cd constraint limited applications could included series saw gradual evolution mx tools collection handy utilities designed help user variety common tasks often complicated obscure mx-15 moved new debian stable jessie using systemd-shim meaning systemd installed default init sysvinit size limitation lifted enabling developers present user full turnkey product substantial expansion mx tools occurred mx-16 still based debian stable jessie many applications backported added well sources also additions refinements mx tools import advanced antix developments expanded support completely new icon/theme/wallpaper combination mx-16.1 collected bug fixes improvements since mx-16 added new kingfisher theme upgraded streamlined mx tools revised documentation new translations mx-17 changes base debian 9 stretch brings upgraded artwork new mx tools improved live operation via antix many changes detailed mx blog mx-18 continues development mx tools introduces recent kernel enables whole disk encryption adds grub themes splash functionality mx boot options new artwork improved localization included details mx blog mx linux basic tools like installer handles uefi computers gui-based method change linux kernel core antix programs mx stands distros shipping suite user-oriented tools called mx tools many tools developed specifically mx forked existing antix apps existing antix apps couple imported permission outside sources example one interesting mx-snapshot gui tool remaster live installation single .iso file quickly conveniently cloned image bootable disk usb-thumbdrive maintaining settings way installation conveniently migrated distributed new hard-disk usb-thumbdrive requiring next administrative effort since advanced method copying file system developed antix-linux utilizing bind-mounts performs heavy lifting snapshot also serves essentially complete convenient backup installation
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Computer architecture
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bubbler video game bubbler zx spectrum video game developed published ultimate play game 1987 ultimate final title 8-bit home computers evolving rare game isometric platform game style marble madness 1984 crash magazine reviewer ricky disliked impreciseness controls
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Computer architecture
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hsa foundation hsa foundation not-for-profit engineering organization industry academia works development heterogeneous system architecture hsa set royalty-free computer hardware specifications well open source software development tools needed use hsa features application software hsa foundation aims develop define features interfaces various types computer processors including cpus graphics processors dsps well memory systems connect resulting architecture hsa aims make easier program parallel systems built heterogeneous combinations devices hsa foundation founded amd arm holdings imagination technologies mediatek qualcomm samsung texas instruments members include licensors licensees semiconductor intellectual property developers cpus gpus dsps application-specific integrated circuits asics based upon and/or licensed technology academic partners lawrence livermore national laboratory university bologna not-for-profit engineering organization linaro hsa foundation joined linux foundation hsa foundation engineering works upstream projects set requirements determined technical steering committee
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Computer architecture
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honeypot computing computer terminology honeypot computer security mechanism set detect deflect manner counteract attempts unauthorized use information systems generally honeypot consists data example network site appears legitimate part site actually isolated monitored seems contain information resource value attackers blocked similar police sting operations colloquially known baiting suspect honeypots classified based deployment use/action based level involvement based deployment honeypots may classified production honeypots easy use capture limited information used primarily corporations production honeypots placed inside production network production servers organization improve overall state security normally production honeypots low-interaction honeypots easier deploy give less information attacks attackers research honeypots research honeypots run gather information motives tactics black hat community targeting different networks honeypots add direct value specific organization instead used research threats organizations face learn better protect threats research honeypots complex deploy maintain capture extensive information used primarily research military government organizations based design criteria honeypots classified pure honeypots full-fledged production systems activities attacker monitored using bug tap installed honeypot link network software needs installed even though pure honeypot useful stealthiness defense mechanisms ensured controlled mechanism high-interaction honeypots imitate activities production systems host variety services therefore attacker may allowed lot services waste time employing virtual machines multiple honeypots hosted single physical machine therefore even honeypot compromised restored quickly general high-interaction honeypots provide security difficult detect expensive maintain virtual machines available one physical computer must maintained honeypot exorbitantly expensive example honeynet low-interaction honeypots simulate services frequently requested attackers since consume relatively resources multiple virtual machines easily hosted one physical system virtual systems short response time less code required reducing complexity virtual system security example honeyd recently new market segment called deception technology emerged using basic honeypot technology addition advanced automation scale deception technology addresses automated deployment honeypot resources large commercial enterprise government institution malware honeypots used detect malware exploiting known replication attack vectors malware replication vectors usb flash drives easily verified evidence modifications either manual means utilizing special-purpose honeypots emulate drives malware increasingly used search steal cryptocurrencies spammers abuse vulnerable resources open mail relays open proxies servers accept e-mail anyone internet—including spammers—and send destination system administrators created honeypot programs masquerade abusable resources discover spammer activity several capabilities honeypots provide administrators existence fake abusable systems makes abuse difficult risky honeypots powerful countermeasure abuse rely high volume abuse e.g. spammers honeypots reveal abuser ip address provide bulk spam capture enables operators determine spammers urls response mechanisms described m. edwards itpro today apparent source may another abused system spammers abusers may use chain abused systems make detection original starting point abuse traffic difficult indicative power honeypots anti-spam tools early days anti-spam honeypots spammers little concern hiding location felt safe testing vulnerabilities sending spam directly systems honeypots made abuse riskier difficult spam still flows open relays volume much smaller 2001-02 spam originates u.s. spammers hop open relays across political boundaries mask origin honeypot operators may use intercepted relay tests recognize thwart attempts relay spam honeypots thwart may mean accept relay spam decline deliver honeypot operators may discover details concerning spam spammer examining captured spam messages open relay honeypots include jackpot written java jack cleaver smtpot.py written python karl a. krueger spamhole honeypot |spamhole written c. bubblegum proxypot open source honeypot proxypot email address used purpose receive spam also considered spam honeypot compared term spamtrap term honeypot might suitable systems techniques used detect counterattack probes spamtrap spam arrives destination legitimately —exactly non-spam email would arrive amalgam techniques project honey pot distributed open source project uses honeypot pages installed websites around world honeypot pages disseminate uniquely tagged spamtrap email addresses spammers tracked—the corresponding spam mail subsequently sent spamtrap e-mail addresses databases often get attacked intruders using sql injection activities recognized basic firewalls companies often use database firewalls protection available sql database firewalls provide/support honeypot architectures intruder runs trap database web application remains functional honeypots weapons spammers honeypot detection systems spammer-employed counter-weapons detection systems would likely use unique characteristics specific honeypots identify many honeypots in-use utilise set unique characteristics larger daunting seeking detect thereby identify unusual circumstance software situation versionitis large number versions software differing slightly beneficial also advantage easy-to-detect honeypots deployed fred cohen inventor deception toolkit argues every system running honeypot deception port adversaries use detect honeypot cohen believes might deter adversaries two honeypots network form honey net typically honey net used monitoring larger and/or diverse network one honeypot may sufficient honey nets honeypots usually implemented parts larger network intrusion detection systems honey farm centralized collection honeypots analysis tools concept honey net first began 1999 lance spitzner founder honeynet project published paper build honeypot metaphor bear attracted stealing honey common many traditions including germanic celtic slavic common slavic word bear medved honey eater tradition bears stealing honey passed stories folklore especially well known winnie pooh brazilian folk tale boneca de pixe tells stealing monkey trapped puppet made pitch earliest honeypot techniques described clifford stoll 1989 book cuckoo egg 2017 dutch police used honeypot techniques track users darknet market hansa
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Computer security
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samizdat issues regarding 'source open source code samizdat issues regarding 'source open source code 2004 report kenneth brown report suggests linux kernel may created distributed illegally open-source software may generally subject abuses report states linux kernel written using copied source code minix resources acquired improperly possibly illegally linus torvalds also suggests one never certain origins open source code similar misuse copyrighted code may exist open-source projects finally asserts gnu general public license bad economy book greeted widespread rejection technical world repudiated many claimed sources prerelease long delisted distributor site book never given proper release although prerelease pdf available online title reference samizdat form private circulation suppressed literature within soviet-bloc countries extension slang papers contain programming techniques code sometimes sources authorized publication often passed programmer programmer samizdat claims linus torvalds used source code taken minix small unix-like operating system used teaching computer science create linux 0.01 theory mere student could write entire unix-like kernel single-handedly book also recommends government-funded programming never licensed gpl bsd license similar simple permissive licenses states us government book claims methodology references seriously questioned including many quotes support thesis andrew s. tanenbaum author minix dennis ritchie one creators unix richard stallman leader gnu project others said quotes attributed interview adti fact prerelease journal papers ilkka tuomi messageboard posts charles mills henry jones alexey toptygin said commissioned brown find similarities minix linux 0.01 source code found support theory minix source code used create linux study mentioned book toptygin quoted saying asked friend ... wanted code analysis consultancy basis boss kenneth brown ended 10 hours work comparing early versions linux minix looking copied code summarize analysis found evidence whatsoever code copied called ask questions analysis methods results ask would like repeated source comparison tools bit shock apparently ken expecting find gobs copied source code spent conversation trying convince must made mistake since clearly impossible one person write os 'code theft occurred although linux 0.01 written using minix example starting point — minix created tanenbaum example study — code minix actually used tanenbaum agrees point stated much interview ken brown latter researching samizdat furthermore linux 0.01 barely functional first draft far sophisticated industry-grade linux-based operating systems would later grow samizdat detractors also point fact adti funded directly since 1999 microsoft company publishes competing proprietary operating system microsoft windows considers linux one important competitors see halloween documents documents ii month widespread rejection book technical press microsoft also repudiated mid-june spokesman calling “ unhelpful distraction matters most—providing best technology customers. ” notably absent brown research samizdat direct communication torvalds
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Operating systems
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hp universal print driver hp universal print driver upd intelligent print driver supports broad range hp laserjet printers mfps developed hewlett-packard combines general purpose driver unidrv pscript hp proprietary extensions hp upd simplifies driver deployment management advanced print driver ability discover hp printing devices automatically configure device capabilities e.g. duplex color finishing etc. hp universal print driver microsoft windows solution provides two modes operation traditional dynamic traditional mode hp upd behaves similarly traditional print drivers dynamic mode provides discovery auto configuration management features particularly well suited mobile computer users hp ’ universal print driver based microsoft ’ universal core drivers unidrv pscript core drivers usable device specific information used inform core driver actual device settings capabilities accomplish task universal printing dialog box inserted standard print setup dialog box universal printing dialog box allows users choose recently used device enter device ip address search local print devices choose device predefined list regardless device discovery method used microsoft core driver updated accordingly new device information reflected normal print driver user interface hp provides three different universal print drivers pcl5 pcl6 emulation postscript custom default values assigned hp driver configuration utility hp upd available microsoft windows 32-bit 64-bit driver automatically configures one 35 currently supported languages based upon language host system dynamic mode searching devices accomplished using mdns discovery protocol aka bonjour mdns protocol performs satisfactorily devices residing subnet users need enter ip addresses remote devices unless previously discovered available managed printers list whether discovered entered chosen hp universal printing dialog box submits snmp requests target device ’ ip address using enterprise auto configuration eac bidirectional communications port snmp requests ascertain device ’ configurations capabilities results used hp upd update print driver table windows registry accurately reflect target device ’ capabilities results also cached creg recently discovered device list updated provide easy method future selection dynamic mode hp upd considered virtual device therefore new device instances appear printers folder traditional mode hp upd bound print queue behaves like normal printer driver addition bi-directional communications device queries real time print job status mode chosen driver installation dynamic mode universal printing dialog box traditional mode bypasses universal printing dialog box goes directly typical print setup dialog box automatic configuration occur traditional mode users select manual updates ensure device ’ capabilities properly represented hp upd installed either dynamic mode traditional mode depending user requirements hp upd includes driver management features allowing administrators pre-configure deploy manage hp driver software management tools within hp upd include install.exe command line options hp mpa tool active directory templates driver configuration utility driver deployment utility hp web jetadmin install.exe hp upd installer allows driver default settings modified via command line options switches change system-wide behavior hp upd changes specific single print queue hp mpa utility hp mpa utility pre-configures driver default settings managed hp upd environment settings made within hp mpa utility control hp upd user level resulting policies maintained every printer attached hp upd global user policies affect hp upd users hp upd active directory templates hp upd administrative template active directory template added create group policy object manage user upd capabilities settings apply queue uses hp upd care taken locking configuration settings user unable change locked setting hp driver configuration utility hp driver configuration utility dcu windows application used edit configuration file associated particular driver configuration file controls print driver settings takes effect driver installed hp driver deployment utility ddu used pre-configure print driver deployment package run client computer new configuration file configures printer driver installed interfere whql certification ddu contains standalone dcu utility inside package launched pre-configure driver selected ddu tool beyond driver configuration hp upd also employs managed printer lists mpls managed print policies mpp control access devices capabilities technologies used hp upd dynamic mode mpls used searching devices unnecessary users presented predefined list devices choose mpls xml files created manually hp mpa utility exported hp web jetadmin hp upd activated begins searching network mpl file shown figure 6 mpps used control users access device features like color duplex etc default hp upd assumes hp mpa installed server named managed-print result hp upd searches network server find hp managed print policies hp managed printer lists driver also includes status notification pop-ups print submission inform user device status print job status consumable levels graphical popup window displays dashboard toner supply levels links reordering consumables instant support landing page particular hp device model hp upd selected printing attempt communicate directly printer gather status job information printing querying printer snmp get commands network traffic kept minimum present printing desired snps disabled
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Operating systems
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netscout systems netscout systems inc. provider application network performance management products headquartered westford massachusetts netscout serves enterprises community government agencies telecommunications service providers july 2015 netscout acquired communications business danaher corporation including arbor networks fluke networks tektronix communications vss monitoring netscout subsidiaries cayman islands tax netscout systems acquired network general 2007 network general developed original network packet sniffer 1986 merged mcafee associates 1997 form network associates mid-2004 network associates sold sniffer technologies business silver lake partners texas pacific group 275 million cash form network general early 2006 network general acquired fidelia technology adding netvigil business service monitoring technology network application performance analysis tools september 2007 network general agreed acquired netscout systems 205 million netscout systems founded anil singhal narendra popat frontier software 1984 netscout created first rmon based ethernet probe 1992 november 2007 netscout acquired sniffer infinistream network intelligence product lines network general netscout merged product lines allow performance manager product use probes infinistream technologies april 2011 netscout acquired voice video management company psytechnics ipswich u.k acquired fox replay privately held dutch company 2011 later year many years partnering complementing solutions network switch port aggregation netscout moved directly competition partners acquiring privately held simena networks october 2014 netscout systems announced entered definitive agreement acquire communications business science technology company danaher corporation 2.6 billion upon completion merger danaher shareholders would nearly 59.5 percent combined company netscout shareholders would remaining stake analyst firm 451 research technology-industry syndicated research data firm predicted may 2015 acquisition netscout largest company network visibility management space 3,000 employees well 1bn year revenue july 2015 netscout finalized acquisition communications business danaher corporation including arbor networks security systems fluke networks rf wi-fi network troubleshooting analytics tektronix communications traffic inspection customer experience management analytics vss monitoring network packet brokers prepared statement company noted acquisition accelerates netscout ’ strategic progress enabling company offer ... innovative service assurance cyber security solutions adds new employees netscout
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Computer security
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national privacy commission philippines national privacy commission npc independent body created republic act 10173 data privacy act 2012 mandated administer implement provisions act monitor ensure compliance country international standards set data protection attached philippines department information communications technology dict purposes policy coordination remains independent performance functions commission safeguards fundamental human right every individual privacy particularly information privacy ensuring free flow information innovation growth national development order fulfill mandate commission vested broad range powers receiving complaints instituting investigations matters affecting personal data protection compelling entities abide orders matters affecting data privacy also represents philippine government internationally data protection related issues commission formulates implements policies relating protection personal data including relevant circulars advisory guidelines assist organisations understanding complying data privacy act commission also reviews organizational actions relation data protection rules issue decisions directions compliance necessary mandated work relevant sector regulators exercising functions beyond regulating data protection issues npc also undertakes public sector-specific educational outreach activities help organizations adopt good data protection practices help individuals better understand may protect personal data misuse data privacy act 2012 first law philippines acknowledges rights individuals personal data enforcing responsibilities entities process initial definition offered first republic act 8792 section 32 better known ecommerce act philippines formally introduced department trade industry dti department administrative order 08 defining guidelines protection personal data information private sector along anti-cybercrime bill ra 10175 first draft law started 2001 legal regulatory committee former information technology ecommerce council itecc forerunner commission information communication technology cict headed former secretary virgilio ver peña committee chaired atty claro parlade initiative information security privacy sub-committee chaired albert dela cruz president phcert together anti-computer crime fraud division chief atty elfren meneses nbi administrative operational functions provided presidential management staff pms acting cict secretariat rising concerns information technology business process association philippines ibpap absence data privacy law philippine congress passed senate bill 2965 house bill 4115 june 6 2012 president benigno s. aquino iii signed republic act 10173 data privacy act 2012 august 15 2012 law influenced data protection directive apec privacy framework president aquino appointed march 7 2016 raymund liboro inaugural head commission damian domingo o. mapa ivy d. patdu inaugural deputy privacy commissioners fixed terms office continued roles administration president rodrigo duterte consultation various private organizations civil societies series public hearings manila cebu davao implementing rules regulations data privacy act signed august 24 2016 took effect september 9 2016 may 2016 commission formally investigated commission elections commission elections data breach one largest security breach government held personal data february 21 2017 npc announced commission elections investigated another security breach due alleged theft computer containing personal data voters npc also began coordinating different sectors privacy data protection 2016 national privacy commission accepted member international conference data protection privacy commissioners asia pacific privacy authorities
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Computer security
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ultimate software ultimate software american technology company develops sells ultipro cloud-based human capital management hcm software system businesses headquartered weston florida company founded 1990 current president ceo scott scherr released first version software 1993 fourth quarter 2017 ultimate software reported total revenues 940.7 million 2017 company employs 4,200 people services 4,100 customers 160 countries ultimate offices around usa canada uk singapore february 4 2019 hellman friedman capital partners announced would purchase ultimate software group 11 billion purchase closed may 3 2019 ultimate software founded scott scherr company ’ current ceo president 1990 1993 tech company released ultipro hrms/ payroll sold on-premises software servicing core hr payroll company went public nasdaq ulti june 1998 2002 ultipro reintroduced cloud-based software-as-a-service saas provide unified management tool human resources model allowed company hold 33 million client records cloud service 3,400 customers according career builder company announced expanding outside united states opened office london england later year ultimate announced additional expansions singapore company ultipro cloud-based platform delivers human capital management organizations across industries ultipro provides one system record hr payroll talent management according trustradius ultipro includes time attendance employee onboarding performance management compensation management succession management recruiting features like predictive analytics ultipro sold via saas model per-employee-per-month subscription according center generational kinetics center partnered company 2014 conduct research multiple generations workforce research looked work expectations across different generations focus millennials study explored millennials differ prior generations way feel applying job interviewing receiving feedback leaving job 2016 center generational kinetics continued partnership examine drivers motivators behind people workforce study focused organizations understand improve employee experience 2017 fortune magazine ranked ultimate software 7 best place work well 1 best workplace technology prior years fortune ranked ultimate software 6th best workplace millennials 23rd great workplace women 21st best company work additionally forbes ranked company 7th innovative growth company analyst firm nucleus research deemed tech company leader hcm technology past ultimate earned 2011 forrester groundswell award achieving business organizational goals innovation social technology applications 2013 brandon hall gold award best new product feature year
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Distributed computing architecture
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n-gage service n-gage service also referred n-gage 2.0 mobile gaming platform nokia available several nokia smartphones running s60 symbian n-gage provided numerous games 3d graphics application featuring online via n-gage arena social features takes name original 2003 n-gage gaming device succeeded n-gage platform compatible nokia n78 n79 n81 n81 8gb n82 n85 n86 n86 8mp n95 n95 8gb n96 n97 nokia 5320 xpressmusic 5630 xpressmusic 5730 xpressmusic nokia 6210 navigator 6710 navigator 6720 classic e52 e55 e75 due memory issues hinted interview february 2008 support nokia n73 n93 n93i cancelled less two years 30 october 2009 nokia announced new n-gage games would produced reasons cited failure bad development model marketing success apple app store nokia n-gage gaming smartphone 2003 perform well expected upgraded qd version n't improve either instead developing new gaming device change concept nokia explained world e3 2005 planning put n-gage platform several smartphone devices rather releasing specific device although n81 5730 xpressmusic models two dedicated gaming-buttons next screen marketed phone built gaming often nicknamed n-gage next generation public working behind closed doors took little year e3 2006 finally announcing n-gage mobile gaming service set 2007 release also started showing next-gen titles hooked creatures deep fighting game one perhaps visually impressive—even making use motion capture february 2007 nokia announced pilot service finland promote upcoming service nokia showed previews service 2007 game developers conference san francisco california 27 august 2007 nokia confirmed previously leaked n-gage logo official logo upcoming service n-gage gaming service final form finally announced nokia 29 august 2007 nokia used tagline get play promote platform supposed released december 2007 delayed nokia team making sure service ran 'smoothly public beta test n-gage application took place 4 february 2008 27 march 2008 though limited n81 period time referred first access public test client could downloaded free n-gage website final version user access features new application offer along three games try hooked creatures deep space impact kappa base later february nokia also released tetris block breaker deluxe world series poker pro challenge users try none games entirely free offer limited trial testing purposes order experience full game either purchased rented shortly released public hackers managed unpack n-gage installation file components installed separately thus removing n81-only limitation n-gage subsequently reported working nokia nseries devices n73 n95 response nokia released advisory asking users install unsupported version could cause errors issues 20 march official n-gage blog reported first access would come end 27 march though downloaded games time would still playable application updated version released—which occurred 3 april numerous delays many vague release dates n-gage platform finally also quite suddenly released public 3 april 2008 n-gage official website though five phone models compatible begin probably older models less powerful pointed interview earlier year whereas n-gage representative mentioned memory issues n73 launch titles also changed six five brain challenge first two titles n't even included original list included block breaker deluxe tetris instead sixth postponed game space impact kappa base hours launch ikona man behind official n-gage blog say delay currently ensuring block breaker deluxe space impact kappa base tetris running smoothly new application available showroom next week two four days later 7 april nokia posted official press release commenting release new mobile service point fifa 08 also became available purchase release official website also saw small change appearance price tags added games available download event calendar tab support application n-gage compatible devices much players logged website could also see reputation level n-gage level gathered n-gage points also release party held n-gage chat room shortly release several members n-gage team attending answer questions asked t-shirts randomly handed three-hour-long event everyone also promised n-gage points coming party expected launch problem-free numerous people reported trouble downloading purchasing activating games installing application logging n-gage arena n-gage software based solution first generation mmc games compatible new platform though games made comeback form sequel e.g remake/port e.g mile high pinball similarly games developed next-gen n-gage platform work original n-gage n-gage qd adding fact newer s60 software including n-gage client games n't binary-compatible older s60 devices vice versa user interface resembles microsoft ’ xbox live service top n-gage launcher five icons navigated pressing left right phone ’ thumb pad represent user games library profile friends list showroom launcher welcomes user home screen last game played shown along quick links friends progress score table featured game nokia wants highlight week inbox messaging within launcher screen shows games currently installed phone—be trial version full game purchased rented ones trial versions pink stripe says trial far right game icon overlapping looks somewhat like battery meter pay game illustrates progress game bottom list installed games quick link get games takes showroom games paid show pop-up every time play it—asking whether ’ like try free trial either purchase enter unlock code purchased given promotions rent game screen user may also rate games downloaded 1 5 stars well write small verdict next tab profile shows many n-gage points ’ scored far playing reputation level ranging 1-5 stars number friends enlisted chosen avatar/picture represent display white silhouette person orange background per default current status offline online away—the last two assigned personal message n-gage point level list games played gaming history selecting one display many points ’ gathered within chosen game—but also show well friends game users also able look achievements unlocked—or point pickups ’ called go add friend friends list well check highlighted may choose view recent conversations player send message view profile rate player messages sent regardless whether player currently online friends list sorted name availability/status n-gage points gathered showroom displays games available download well game extras expanding game extra content downloading new episodes/adventures adventure game dirk dagger games may browsed genre latest arrivals alphabetical order payment made either using credit card paying phone bill network operator apart actually purchasing game ’ also option renting games downloaded directly phone air gprs wifi user may choose download computer install phone using usb-cable nokia pc suite lot hands-on articles first access client generally reflect positive negative feedback official first access forum n81 users shared thoughts good could 've made better—regarding launcher games currently available biggest issues point players able activate purchased game still trial version play lot players also reporting connection issues head new experience nokia play jaakko kaidesoja say pocket gamer interview 21 february 2008 asked early feedback received feedback positive well received within company critical comments well received well know perfect yet features people want things want check get roadmap several n-gage 2.0 games nominated international mobile gaming awards 2007 two three n-gage 2.0 titles received award 8 may 2008 hooked creatures deep games award 2008 meffy awards cannes prior closure n-gage service nokia released updates n-gage application regular basis first update made available 2 october 2008 dubbed v1.010_131 update included following major changes version 1.20 1459 released 13 may 2009 n't much eliminate bugs 18 august 2009 version 1.40 1557 introduced new start-up icon welcoming screen way breaking installed games speed application slightly improved well updating application may done app itself—by using check updates function device downloaded get n-gage section n-gage.com order n-gage platform games run smoothly n-gage compatible mobile devices share common set specifications screen landscape portrait 320 x 240 pixels except n97 640 x 360 pixels screen graphics stretched displayed letterbox format keep aspect ratio os symbian s60 3rd edition s60 5th edition n97 interface 5 way left right center directional pad dedicated action buttons circle square mapped onto keypad 5 0 portrait mode 2 contextual buttons touch screen interactions supported n97 emulated actions buttons on-screen buttons connectivity 3g wifi required connecting n-gage platform downloading games online functions rankings multiplayer cpu arm11 speed ranges 369 mhz n81 600 mhz e52 gpu 3d graphics hardware accelerator supported games running devices hw-accelerated n95 enhanced performance audio stereo channel n-gage games packaged differently normal symbian applications extension .n-gage run via n-gage application game resources protected drm use native symbian apis instead use proprietary api n-gage sdk n-gage api fact extension rga api available open c++ plug-in select companies allowed access n-gage sdk gain access first must approved nokia sign nda 23 october 2009 49 games released officially n-gage many games cancelled shutting n-gage service see games sequels remakes ports first generation n-gage mmc games games reportedly development cancelled include 30 october 2009 nokia announced new n-gage games would produced effectively shutting n-gage platform n-gage services includes purchasing games various online features reportedly ceased operation end 2010 31 march 2011 nokia closed drm activation service leaving customers unable reactivate purchases case device format software update transition purchases made ovi store compensation given according support staff software purchases supported one year gaming websites e.g pocket gamer link n-gage failure overwhelming competition faces apple iphone ovi gaming cited poor implementation support parent company nokia
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Operating systems
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ado.net ado.net data access technology microsoft .net framework provides communication relational non-relational systems common set components ado.net set computer software components programmers use access data data services database part base class library included microsoft .net framework commonly used programmers access modify data stored relational database systems though also access data non-relational data sources ado.net sometimes considered evolution activex data objects ado technology changed extensively considered entirely new product ado.net conceptually divided consumers data providers consumers applications need access data providers software components implement interface thereby provide data consumer functionality exists visual studio ide create specialized subclasses dataset classes particular database schema allowing convenient access field schema strongly typed properties helps catch programming errors compile-time enhances ide intellisense feature entity framework ef open source object-relational mapping orm framework ado.net part .net framework set technologies ado.net supports development data-oriented software applications architects developers data-oriented applications typically struggled need achieve two different objectives entity framework enables developers work data form domain-specific objects properties customers customer addresses without concern underlying database tables columns data stored entity framework developers work higher level abstraction deal data create maintain data-oriented applications less code traditional applications linq sql formerly called dlinq allows linq used query microsoft sql server databases including sql server compact databases since sql server data may reside remote server sql server query engine use query engine linq instead converts linq query sql query sent sql server processing however since sql server stores data relational data linq works data encapsulated objects two representations must mapped one another reason linq sql also defines mapping framework mapping done defining classes correspond tables database containing certain subset columns table data members
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Operating systems
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jean ichbiah jean david ichbiah 25 march 1940 – 26 january 2007 french computer scientist initial chief designer 1977–1983 ada general-purpose strongly typed programming language certified validated compilers ichbiah descendant greek turkish jews thessaloniki emigrated france 1972 1974 worked designing experimental system implementation language called lis based pascal simula chairman simula user group also one founding members ifip wg 2.4 systems implementation languages joined cii honeywell bull cii-hb louveciennes france becoming member programming research division ichbiah team submitted language design labelled green competition choose united states department defense embedded programming language green selected 1978 continued chief designer language named ada 1980 ichbiah left cii-hb founded alsys corporation la celle-saint-cloud continued language definition standardize ada 83 later went ada compiler business also supplying special validated compiler systems nasa us army others later moved waltham massachusetts subsidiary alsys 1990s ichbiah designed keyboard layout fitaly specifically optimized stylus touch-based input subsequently started textware solutions company sells text entry software pdas tablet pcs well text-entry software medical transcription pcs 1979 jean ichbiah designated chevalier knight french legion honour correspondent french academy sciences received certificate distinguished service united states department defense work ada jean ichbiah died complications brain tumor january 26 2007
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Programming language topics
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maximum segment lifetime maximum segment lifetime time tcp segment exist internetwork system arbitrarily defined long maximum segment lifetime value used determine time_wait interval 2*msl command used many unix systems determine time_wait interval 60000 60 seconds common value freebsd systems description value checked command sysctl gets result linux systems value checked either commands
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Internet protocols
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linux-powered device linux-based devices linux devices computer appliances powered linux kernel possibly parts gnu operating system device manufacturers reasons use linux may various low cost security stability scalability customizability many original equipment manufacturers use free open source software brand products community maintained linux devices also available devices intended run linux time production community effort made possible either full partial linux support open source philosophy free open source software brings software world many people ported linux kernel run devices typical desktop laptop server computer ports performed committed individuals groups provide alternative software favorite hardware original hardware vendors cases supportive efforts linksys wrt54g least tolerate use software end users see tivo hacking others go great lengths try stop alternative implementations android linux-based operating system optimised mobile touchscreen environments—smartphones tablets e-books like developed published maintained google android open source project consultation open handset alliance android relieves smartphone manufacturers costs developing- licensing proprietary handset operating systems first unveiled 2007 android became world widely deployed smartphone platform q4 2010 september 2012 500 million android devices activated 1.3 million devices activated per day google nexus developer phones flagship brand android handsets features capabilities represent state art time launch typically every eleven months cases oems open use software fulfil requirements free software licenses gnu general public license gpl small number cases use masked either deliberately professed ignorance misunderstanding violators usually found public records may forced declare implementations advertising example embedded software engineers mandatory linux experience required careers pages yet site product documentation offers source download offer supply software source required license gpl organizations gpl-violations.org free software foundation fsf software freedom law center sflc organized pursuing violators obtaining compliance usually seek voluntary compliance first step enter legal proceedings blocked notified violations confirm asking supplier examining available product samples even going far make blind purchases product front companies
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Operating systems
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icade icade accessory apple ipad line devices functions miniaturised portable arcade cabinet including physical joystick buttons ipad inserted icade connects device using bluetooth allowing used arcade-style controller compatible games icade input devices include 8-way ball-top joystick eight digital buttons placed inside icade ipad positioned vertically groove behind inputs accommodates landscape-mode play front device coin slot lights show icade powered flashes batteries running low power sourced either two aa batteries ac adapter also possible run ipad docking cable underside icade order charge ipad play internally icade essentially bluetooth keyboard—the joystick buttons simply mapped 24 different standard keys since ipad natively supports bluetooth keyboards able receive inputs icade without requirement special software beyond games designed respond inputs icade sends system also allows bluetooth input devices icontrolpad use protocol order control applications designed icade icade originally announced thinkgeek april 1 2010 april fools day prank however widely covered electronics media potential product thinkgeek responded speculation saying real icade possibility april fools icade stated connect via standard apple dock connector noted potential blocker release due licensing fees restrictions placed dock connections apple shortly revelation icade gag product thinkgeek contacted privately ion audio proposal develop concept thinkgeek ion staff worked tandem project able secure support atari rightsholders large catalogue arcade games thus working icade produced ion audio demonstrated running 1979 arcade title asteroids consumer electronics show january 2011 projected release late spring version replaced dock connection wireless bluetooth one sidestepping potential issues completed device released thinkgeek june 27 2011 ion audio provides document covers information necessary add icade support applications document also includes guidelines acceptance apple avoiding references icade name addition ios app developer stuart carnie manomio freely released unofficial sdk application authors use speed implementation icade controls outside ios development library made available adding icade support adobe flash games icade presents standard bluetooth hid keyboard numeric passcode must entered via buttons control stick pairing mapping used code entry quite straightforward readily apparent icade thus included reference put icade pairing mode hold bottom 4 buttons top white button 6 8 0 enter buttons simultaneously 4 seconds release official icade list http //www.ionaudio.com/products/icade-games reception icade mostly positive ars technica called attractive capable piece hardware exactly want ign referred icade surprisingly functional saying certain please target market toucharcade felt absolute must-have ipad accessory serious retro gamer engadget coverage accessory described well constructed awesome addition gaming collection feelings icade controls mixed positive ign described joystick buttons responsive however noted input configuration little cramped unbearably ars technica reviewer ben kuchera felt joystick little looser would prefer buttons require heavy finger push said controls held heavy hand toucharcade praised buttons finding exactly like 'd find old defender cabinet widest criticism device small library compatible software many early reviews drawing attention fact one icade-compatible title atari greatest hits available launch speaking positively hardware crunchreview felt limited software availability made device one trick pony ign opined 'd pretty passionate lunar lander centipede missile command fan feel disappointed n't play new 99 icade following icade atari taito released respective versions atari arcade invadercade atari arcade connects standard dock connector instead bluetooth atari arcade works atari ’ greatest hits app offers 99 games 10 although criticized flimsy controls taito space invader themed invadercade functions charger ipad plugged additionally invadercade built speakers dedicated volume knob function general media center itunes internet radio functionality compatible ipad ipad 2 invadercade similarly requires taito space invaders hd app run icade jr smaller version icade apps currently somewhat fully supported yet see ion compatibility list runs 50 via thinkgeek uses either iphone ipod touch
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Operating systems
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forté software forté proprietary application server developed forté software used developing scalable highly available enterprise applications forté created integrated solution developing managing client/server applications forté 4gl consists application server tools deploying monitoring application object oriented proprietary programming language tool transactional object oriented language given tool runs forté application server many users simply refer tool applications forté applications product 3.5 million lines c/c++ software ported approximately twelve different operating system environments spanning range ibm mainframes microsoft windows pc first release forté 4gl published august 1994 releasing initial product forté inc. proceeded build several extensions including 1999 forté software came version forte based java instead tool named synerj also referred forté java original tool-based products consisted development ide code repository runtime environment new java product interest sun microsystems bought company tool-based listed bundled together re-branded unified development server uds integration server iplanet division server modules later bundled together enterprise application integration eai sun declared product end-of-life indicating future plans continue development product sun official support forte ceased end april 2009 enterprise application development system forté supported close linkage number different relational database systems including oracle sybase microsoft sql server informix db2 linkages could via sql embedded within tool code via sql constructed fly also support distributed applications developer would create instance specific class would placed user-specified server calls methods instance would sent across network transparently developer would need know underlying details call would transmitted tool object-oriented language following features among others tool code case-insensitive statement always terminated semicolon compound statements enclosed keywords codice_2 codice_3 comments indicated // -- remainder line becomes comment /* ... */ data types simple data types corresponding object data types examples arrays indicated keywords codice_4 first element array indexed 1 variable declaration conditional statements if-statement case-statement iteration loops events event posted e.g following statement statement posts event named codice_5 event one argument named id events handled event handlers example exception handling multithreading new thread launched statement like codice_6
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Programming language topics
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discovery configuration protocol discovery basic configuration protocol dcp protocol definition within profinet context link layer based protocol configure station names ip addresses restricted one subnet mainly used small medium applications without installed dhcp server
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Internet protocols
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radiovis radiovis protocol sideband signalling images text messages broadcast audio service provide richer visual experience application sub-project radiodns allows radio consumption devices look ip-based service based parameters currently tuned broadcast station january 2015 functionality radiovis integrated visual slideshow etsi ts 101 499 v3.1.1 original rvis01 document deprecated protocol enables either streaming text oriented messaging protocol stomp comet deliver text image urls client images acquired http connection technology currently implemented number broadcasters across world including global radio bauer radio uk rté republic ireland südwestrundfunk germany number australian media groups amongst others number software clients exist show protocol well hardware devices pure sensia pure digital colourstream roberts radio
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Internet protocols
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marc stevens cryptology dr. ir marc stevens cryptology researcher known work cryptographic hash collisions creation chosen-prefix hash collision tool hashclash part master degree thesis first gained international notoriety work alexander sotirov jacob appelbaum arjen lenstra david molnar dag arne osvik benne de weger creating rogue ssl certificate presented 2008 25th annual chaos communication congress warning dangers using md5 hash function issuing ssl certificates several years later 2012 according microsoft authors flame malware used similar methodology researchers warned initiating md5 collision forge windows code-signing certificate marc recently awarded google security privacy anti-abuse applied award google selected stevens award recognition work cryptanalysis particular related sha-1 hash function february 2017 first known successful sha-1 collision attack practice termed shattered recognized marc stevens first-credited subsequent paper along cwi amsterdam colleague pierre karpman researchers elie bursztein ange albertini yarik markov alex petit bianco clement baisse google marc currently employed cryptology researcher centrum wiskunde informatica
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Computer security
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write compile anywhere write compile anywhere woca philosophy taken compiler associated software libraries software library/software framework refers capability writing computer program compiled platforms without need modify source code opposed sun write run anywhere slogan cross-platform compatibility implemented source code level rather also compiled binary code level many languages follow woca philosophy c++ pascal see free pascal ada c condition n't use functions beyond provided standard library languages like go go even far system specific things used work system-specific elements system platform-specific files used computer program may also use cross-platform libraries provide abstraction layer hiding differences various platforms things like sockets gui ensuring portability written source code example supported qt lazarus ide via lcl corresponding widgetsets
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Programming language topics
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offsystem owner-free file system system short peer-to-peer distributed file system shared files represented randomized multi-used data blocks instead anonymizing network data blocks anonymized therefore data garbage ever exchanged stored forwarding via intermediate nodes required claims created expressed intention cut gangrene-infested bits copyright industry development started within hacktivism group big hack 2003 hackers cheater512 captainmorgan aqlo whiteraven 2004 rudimentary version finished written php distributed two demo cds following spectralmorning re-implemented functionality 2004 c++ led current mainline client august 14 2006 captainmorgan posted letter closing addressed copyright industry associations america riaa mpaa stating created purpose ending problems consumer copyright infringement 2008 network consisted around 50 nodes april 11 2008 beta test held network size 100 nodes since spectralmorning stopped work late 2008 minor bug fix releases made mainline starting 2007 alternative compatible client developed called blocksnet written ruby well-maintained saw major improvements recent time development 2011 client offload fork mainline seemingly adds features reasons fork unclear another distantly related program monolith uses similar principle created features multi-use blocks networking system kind anonymous fully decentralized p2p file sharing program network contrast anonymous file sharing networks derive anonymity forwarding data blocks via intermediate network nodes derives anonymity anonymizing data files thus system refers brightnet contrast method operation private file sharing systems known darknets traditional forwarding anonymous p2p programs order store file local storage resp block cache choose tuple size formula_1 default 3 split source file formula_2 blocks formula_3 size 128 kib pad random data fit following finally store descriptor list block blocks list larger 128 kib insert blocks formula_11 block cache generate url referencing source file output user local url database retrieve obtain descriptor block blocks contained set size formula_1 following derives anonymity following anonymizes data blocks exchanged instead network forwarding via intermediate nodes required therefore method higher degree efficiency traditional forwarding-based anonymous p2p systems forwarding method requires data block uploaded downloaded several times reaches destination happens 5 15 times. according resulting formula formula_17 equivalent overhead 900 2900 overhead without optimizations 200 formula_2 source file size formula_19 inbound tunnel length formula_20 outbound tunnel length plus 1 hop outbound endpoint inbound gateway efficiency increased implementations
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Computer file systems
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emios emios acronym environmental memory interoperable open service mdd mde platform aims provide range services storing sharing information environmental research activities emios initiated c. faucher june 2006 based environmental memory concepts developed motive cnrs committee specifically franck guarnieri 2003 emios set eclipse plugins based emf distributed terms epl license current version 0.0.1 mainly contains geographic information standards manager gism gism first part emios implements iso 19100 series international standards iso tc211 faucher c. gourmelon f. lafaye j.y. rouan m. mise en place ’ une mémoire environnementale adaptée aux besoins ’ un observatoire du domaine cotier menir revue internationale de géomatique hermès/lavoisier vol 19/1 pp 7-26 2009 http //geo.e-revues.com/ faucher c. lafaye j.y. 2007 model-driven engineering implementing iso 19100 series international standards coastgis 07 8th international symposium gis computer mapping coastal zone management vol 2 p. 424-433 7-10 october santander spain emios web site
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Programming language topics
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acid3 acid3 test web test page web standards project checks web browser compliance elements various web standards particularly document object model dom javascript test successful results acid3 test display gradually increasing fraction counter series colored rectangles number subtests passed indicate percentage displayed screen percentage represent actual percentage conformance test really keep track subtests actually started 100 assumed moreover browser also render page exactly reference page rendered browser like text acid2 test text acid3 reference rendering bitmap order allow certain differences font rendering acid3 development april 2007 released 3 march 2008 main developer ian hickson google employee also wrote acid2 test acid2 focused primarily cascading style sheets css third acid test also focuses technologies used highly interactive websites characteristic web 2.0 ecmascript dom level 2 subtests also concern scalable vector graphics svg extensible markup language xml data uris includes several elements css2 recommendation later removed css2.1 reintroduced world wide web consortium w3c css3 working drafts made candidate recommendations yet april 2017 updated specifications diverged test latest versions google chrome mozilla firefox longer pass test written hickson acknowledges aspects test controversial written test longer reflects consensus web standards purports test especially comes issues affecting mobile browsers main part acid3 written ecmascript javascript consists 100 subtests six groups called buckets including four special subtests 0 97 98 99 compliance criteria require test run browser default settings final rendering must 100/100 score must pixel-identical reference rendering browsers designed personal computers animation smooth taking 33 ms subtest reference hardware equivalent top-of-the-line apple laptop well though slower performance slow device imply non-conformance pass test browser must also display generic favicon browser toolbar favicon image acid3 web server acid3 server asked codice_1 gives 404 response code image data body tests web browser correctly handles 404 error code fetching favicon treating failure displaying generic icon instead test running rectangles added rendered image number subtests passed bucket determine color rectangles note acid3 display exactly many subtests passed bucket example 3 subtests passing 4 subtests passing bucket 2 would render black rectangle acid3 test page completely rendered word acid3 clicked see alert shift-click new window explaining exactly subtests failed error message case one 100 tests passed took much time report includes timing results single test alert reports total time whole acid3 test order render test correctly user agents need implement css 3 text shadows css 2.x downloadable fonts specifications currently consideration w3c standardized required test uses custom truetype font called acidahemtest cover 20x20 red square supporting truetype fonts however required css specification browser supporting opentype fonts cff outlines embedded opentype fonts could support css standard fail test acid3 test glyph rendered downloaded font square made white css thus invisible addition test also uses base64 encoded images advanced selectors css 3 color values hsla well bogus selectors values ignored google employee ian hickson started working test april 2007 development progressed slowly december 2007 work restarted project received public attention january 10 2008 mentioned blogs anne van kesteren time project resided url clearly showing experimental nature nowiki http //www.hixie.ch/tests/evil/acid/003/not_ready_please_do_not_use.html /nowiki despite notice url test received widespread attention web-development community time 84 subtests done january 14 ian hickson announced competition fill missing 16 following developers contributed final test competition even official release acid3 impact browser development dramatic particular webkit score rose 60 87 less month test officially released march 3 2008 guide commentary expected follow within months march 2011 commentary released announcement test complete means considered stable enough actual use problems bugs found test modified fix march 26 2008—the day opera webkit teams announced 100/100 score—developers webkit contacted hickson critical bug acid3 presumably allowed violation svg 1.1 standard pass hickson fixed bug help cameron mccormack member w3c svg working group 2008 development versions presto webkit layout engines used opera safari respectively scored 100/100 test rendered test page correctly time browser using presto webkit layout engines passed performance aspect test google chrome opera mobiledisplayed score 100/100 security concerns downloadable fonts delayed chrome passing version 68 later chrome gets score 97/100 time acid3 release mozilla firefox developers preparing imminent release firefox 3 focusing stability acid3 success consequently firefox 3 score 71 firefox 3.5 scored 93/100 firefox 3.6 scored 94/100 initially firefox 4 scored 97/100 support svg fonts later firefox 4 scored 100/100 svg font tests removed acid3 according mozilla employee robert o'callahan firefox support svg fonts mozilla considered woff superior alternative svg fonts another mozilla engineer boris zbarsky claimed subset specification implemented webkit opera gives benefits web authors users woff asserted implementing svg fonts fully web browser hard designed integration html mind april 2 2010 ian hickson made minor changes test mozilla due privacy concerns altered way gecko handles codice_2 pseudo-class firefox 51.0a1 made regression 100 99 september 14 2016 firefox 55.0a1 regressed 97 may 1 2017 firefox quantum versions 63.0 received 97/100 64.0 got 96/100 microsoft said acid3 agree goal internet explorer 8 ie8 would improve standards tested acid3 ie8 scored 20/100 much worse relevant competitors time acid3 release problems rendering acid3 test page 18 november 2009 internet explorer team posted blog entry early development internet explorer 9 pdc presentation showing internal build browser could score 32/100 throughout 2010 several public developer previews improved internet explorer 9 test scores 55/100 16 march 95/100 4 august dean hachamovich general manager ie team argued striving 100/100 acid3 test neither necessary desirable claimed two acid3 failures related features svg fonts smil animation transition internet explorer 11 edge display score 100/100 early iterations test criticized cherry-picked collection features rarely used well still w3c working draft eric a. meyer notable web standards advocate wrote real point acid3 test n't broad-spectrum standards-support test showpiece something potemkin village shame really needed right exhaustive test suites specifications—xhtml css dom svg implementing enough standard pass test disingenuous nothing standards compliance argued mozilla ux lead alex limi article mythbusting firefox 4 wo n't score 100 acid3 limi argued tests particularly svg fonts relation real usage implementations browsers created solely point raising scores september 17 2011 ian hickson announced update acid3 hickson words håkon wium lie opera software commented parts test might get changed specs hoped change would allow specs change whatever way best web rather constraining changes things happened fit acid3 tested result firefox 4 internet explorer 9 achieved score 100/100 acid3 internet explorer n't render test properly support text-shadow internet explorer 10 parts following standards tested acid3 passing score considered valid browser default settings used following browser settings user actions may invalidate test
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Web technology
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linux schools project linux schools project formerly karoshi translated literally death overwork japanese operating system designed schools linux distribution based ubuntu operating system project maintains two custom distributions one designed use servers use server version client machines server distribution official karoshi client known karoshi client tlsp uses prepackaged gui scripts order simplify install configuration process inexperienced users tlsp originally developed using red hat early 2000s aim making linux adoption easier schools uk linux time considered difficult use educational environments computing expertise mainly came teachers dedicated staff version 5.1.x tlsp moved pclinuxos platform since adopted ubuntu place current production version tlsp 11.1 tlsp downloadable homepage installation steps require initial install ubuntu live cd prompts initiate following machine reboot installation ubuntu install tlsp system initiated automatically tlsp primarily aimed educational environments also suitable use small medium enterprise sme business environment included systems suitable use file print email web e-learning servers leveraging technologies possible administer complete network using integrated web tools using form remote desktop technology tlsp system scalable single multi server system comprising many features chief among ability act primary domain controller windows network tlsp uses built samba ldap servers store user group computer information emulates microsoft windows nt 4.0 server system using technologies providing computer user authentication along file print services local network tlsp creates standard windows domain local network names linuxgrid tlsp uses kixtart scripts set windows xp clients domain providing mandatory profiles users system roaming profiles used recommended due heavy network overhead involved using mandatory profiles folder redirection mapped file shares server allows every user store files documents folder tlsp includes moodle e-learning package several website content management systems including joomla website baker egroupware squirrelmail built system allowing full calendar email facilities installed standalone machine dmz section thus providing increased security systems directly exposed internet particularly interesting inclusion wpkg enables remote installation software windows clients using machine profile stored server possible install software packages hotfixes security updates background also helpful terms creating machine profiles allowing 'blank windows xp machine updated automatically particular wpkg profile machine added domain type technology compared group policy mechanism windows server 2003 particularly machine administration perspective means replacement group policy step right direction first version karoshi client based pclinuxos upgrades system whole led client using modified version ubuntu 10.04 lts gui similar microsoft windows interface interface designed fast run well older hardware june 2012 work started karoshi client version 2 would interface closer gnome 2 windows development client release given robin mccorkell student dover grammar school boys 21 july 2012 karoshi client 2 uploaded sourceforge.net karoshi client contains many applications deemed necessary school work media production software including music production image manipulation video editing software included along programming tools visualization software many ides installed default mainly set use java also supporting c/c++ programming languages c++ compiler standard libraries installed default along boost libraries ncurses mesa libraries opengl programming java development kit installed integrated installed ides xfce used desktop manager customized theme panel layout developer ported clearlooks gtk2 theme gtk3 gnome 3 applications like gedit would display correctly panel layout similar gnome 2 environment compositing effects enabled default environment interface settings locked xfce configuration files due need suitability school environment children may try play settings kde greeter lightdm used log screen due problems kdm ubiquity version karoshi client integrated server distribution previous client releases custom configuration files pulled primary domain controller boot server patch added correct files client released 23 july 2012 difficult integrate tlsp existing windows network without changing address space standard one used tlsp system limitation early versions longer applies kerberos support planned karoshi server client system providing single sign services provided karoshi distribution unfeasible samba 4 released due complexities surrounding integration user resolution file access across multiple operating systems support active directory protocols integration occurred already working client system authenticates using kerberos authenticates successfully moodle samba squid using kerberos credentials
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Operating systems
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panasas panasas data storage company creates network-attached storage technical computing environments founded 1999 garth gibson william courtright panasas computer data storage product company headquartered sunnyvale california panasas received seed funding mohr davidow ventures mdv others first panasas products shipped 2004 year victor m. perez became ceo faye pairman became ceo 2011 panasas developed extension managing parallel file access network file system later integrated parallel nfs pnfs part nfs version 4.1 specification published internet engineering task force rfc 5661 january 2010. pnfs described way nfs protocol process file requests multiple servers storage devices instead handling requests serially panasas supports directflow nfs parallel nfs server message block also known cifs data access protocols integrate existing local area networks panasas blade servers manage metadata serving data directflow nfs cifs clients using 10 gigabit ethernet panasas systems provide data storage management high-performance applications biosciences energy media entertainment manufacturing government research sectors activestor product line scale-out nas appliance integrates hybrid storage hardware hard drives solid state drives panfs parallel file system proprietary directflow data access protocol industry standard nfs cifs network protocols activestor ultra introduced november 2018 newest generation panasas activestor storage system features re-engineered portable file system delivers performance reliability suitably qualified industry standard storage hardware platforms activestor ultra four storage nodes node six hdd drive slots two ssd drive slots node supports six eight hdds zero two ssds activestor ultra deliver 6-7.5 gb/s per 4u enclosure depending configuration minimum configuration three activestor ultra enclosures total bandwidth performance expected 18-22 gb/s activestor ultra designed extreme performance extreme scalability configurations supports flexible networking options activestor ultra/panfs 8 solution aimed hpc shops well enterprises need kind performance parallel file systems afford enterprise customers especially approach intended give kind simplicity low tco demand activestor 20 activestor classic announced august 2016 increased capacity using larger faster disks november 2017 panasas released activestor director 100 activestor hybrid 100 activestor prime disaggregated director blade controller node panasas storage system storage nodes november 2018 panasas introduced activestor ultra featured completely re-engineered portable file system panfs® 8 running industry standard hardware panasas created panfs clustered file system single pool storage global filename space support multiple applications workflows single storage system panfs supports directflow pnfs nfs cifs data access protocols simultaneously panfs 7.0 added freebsd operating foundation gui supports asynchronous push notification system changes without user interaction november 2018 panasas introduced panfs 8 intelligent posix compliant parallel file system incorporates latest software innovations runs linux enable easy portability new industry standard hardware panfs 8 includes newly re-engineered storage node software stack use new activestor ultra family storage nodes panfs theoretically portable across much wider array hardware opening possibility hosting file system third-party storage platforms file system ’ portability also offers panasas flexibility use different hardware suppliers future versions activestor hardware – director storage modules advantage keeping costs potentially offering even options customers panfs 8 optimized match object access update patterns common mixed workloads directflow parallel data access protocol designed panasas activestor directflow avoids protocol i/o bottlenecks accessing panasas storage directly parallel directflow originally supported linux expanded april 2016 support apple macos
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Computer file systems
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proofpoint systems inc. proofpoint systems inc. provider software systems programs support individual organizational performance based silicon valley los altos california founded 2003 jim hill proofpoint systems developed first browser-based performance analysis software systems proofpoint systems research development facilities denver colorado well sales offices phoenix arizona washington d.c. proofpoint systems founded 2003 jim hill retired united states marine corps officer former sun microsystems executive year proofpoint secured contracts united states navy resulting international society performance improvement award 2005 patent proofpoint systems performance analysis support system pass filed april 5 2006 published october 25 2007 pass operates guiding user detailed consistent analysis process ... helping organizational leaders accurately diagnose critical performance productivity issues proofpoint first product comprehensive performance analysis support system compass later developed web-based organizational analysis system management consulting engagements 2006 compass finalist stevie awards category best new product service year proofpoint systems awarded united states navy contracts support strategic planning manpower training education proofpoint offers products services including strategic planning goal development web based diagnostics assessment
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Distributed computing architecture
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amazingports amazingports linux-based software product customized use firewall captive portal billing system hotspots project started 2001 amazingports mainly deployed access control system private public networks deployed single hotspot controller airports hotels private locations hospitals used internet cafes europe 2002 together intel used city-wide wi-fi project 2004 internet roaming 2002 amazingports created 2001 initial vision building free networks later company refocused provided technology network builders company implemented service-oriented provisioning 2002 first implement 802.11a public hotspots europe 2009 2010 administrative system updated features include
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Computer security
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orbexpress ois orbexpress commercial object request broker orb product objective interface systems ada c++ c java programming languages orbexpress features tools developing debugging distributed real-time applications
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Distributed computing architecture
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network security services computing network security services nss comprises set libraries designed support cross-platform development security-enabled client server applications optional support hardware tls/ssl acceleration server side hardware smart cards client side nss provides complete open-source implementation cryptographic libraries supporting transport layer security tls secure sockets layer ssl s/mime previously tri-licensed mozilla public license 1.1 gnu general public license gnu lesser general public license nss upgraded gpl-compatible mpl 2.0 release 3.14 nss originated libraries developed netscape invented ssl security protocol nss software crypto module validated five times 1997 1999 2002 2007 2010 conformance fips 140 security levels 1 2 nss first open source cryptographic library receive fips 140 validation nss libraries passed niscc tls/ssl s/mime test suites 1.6 million test cases invalid input data aol red hat sun microsystems/oracle corporation google companies individual contributors co-developed nss mozilla provides source code repository bug tracking system infrastructure mailing lists discussion groups others named use nss variety products including following nss includes framework developers oems contribute patches assembly code optimize performance platforms mozilla certified nss 3.x 18 platforms nss makes use netscape portable runtime nspr platform-neutral open-source api system functions designed facilitate cross-platform development like nss nspr used heavily multiple products addition libraries apis nss provides security tools required debugging diagnostics certificate key management cryptography-module management development tasks nss comes extensive growing set documentation including introductory material api references codice_1 pages command-line tools sample code programmers utilize nss source shared dynamic libraries every nss release backward-compatible previous releases allowing nss users upgrade new nss shared libraries without recompiling relinking applications nss supports range security standards including following nss supports pkcs 11 interface access cryptographic hardware like tls/ssl accelerators hsm-s smart cards since hardware vendors safenet inc. aep thales also support interface nss-enabled applications work high-speed crypto hardware use private keys residing various smart cards vendors provide necessary middleware nss version 3.13 support advanced encryption standard new instructions aes-ni network security services java jss consists java interface nss supports security standards encryption technologies supported nss jss also provides pure java interface asn.1 types ber/der encoding mozilla cvs tree makes source code java interface nss available
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Internet protocols
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zemra zemra ddos bot first discovered underground forums may 2012 zemra capable http syn flood flooding also simple command control panel protected 256-bit des encryption communicating command control c c server zemra also sends information computer name language settings windows version send data remote location specific date time also opens backdoor tcp port 7710 receive commands remote command-and-control server able monitor devices collect system information execute files even update uninstall necessary
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Computer security
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risks digest risks digest forum risks public computers related systems online periodical published since 1985 committee computers public policy association computing machinery editor peter g. neumann moderated forum concerned security safety computers software technological systems security risk taken broadly risks concerned merely so-called security holes software unintended consequences hazards stemming design lack thereof automated systems recurring subjects include cryptography effects technically ill-considered public policies risks also publishes announcements calls papers various technical conferences technical book reviews usually rob slade though occasionally others although risks forum computer science association contributions readable informative anyone interest subject heavily read system administrators computer security managers well computer scientists engineers risks digest published frequent irregular schedule moderated usenet newsgroup comp.risks exists solely carry digest summaries forum appear columns edited neumann acm sigsoft software engineering notes sen communications acm cacm
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Computer security
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multi-frequency time-division multiple access mf-tdma multi-frequency time-division multiple access technology dynamically sharing bandwidth resources over-the-air two-way communications network
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Internet protocols
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single point failure single point failure spof part system fails stop entire system working spofs undesirable system goal high availability reliability business practice software application industrial system systems made robust adding redundancy potential spofs instance owner small tree care company may one woodchipper chipper breaks may unable complete current job may cancel future jobs obtain replacement redundancy achieved various levels instance owner tree care company may spare parts ready repair wood chipper case fails higher level may second wood chipper bring job site finally highest level may enough equipment available completely replace everything work site case multiple failures assessment potential spof involves identifying critical components complex system would provoke total systems failure case malfunction highly reliable systems rely individual component computing redundancy achieved internal component level system level multiple machines site level replication one would normally deploy load balancer ensure high availability server cluster system level high-availability server cluster individual server may attain internal component redundancy multiple power supplies hard drives components system level redundancy could obtained spare servers waiting take work another server fails since data center often support center operations business logic represents potential spof thus site level entire cluster may replicated another location accessed case primary location becomes unavailable typically addressed part disaster recovery resiliency program paul baran donald davies developed packet switching key part survivable communications networks networks including arpanet internet designed single point failure multiple paths two points network allow points continue communicating packets routing around damage even single failure one particular path one intermediate node network protocols used prevent spof software engineering bottleneck occurs capacity application computer system severely limited single component bottleneck lowest throughput parts transaction path tracking bottlenecks sometimes known hot spots sections code execute frequently i.e highest execution count called performance analysis reduction usually achieved help specialized tools known performance analyzers profilers objective make particular sections code perform fast possible improve overall algorithmic efficiency mistake one component compromise entire system concept single point failure also applied fields outside engineering computers networking corporate supply chain management transportation management design structures create single points failure include bottlenecks series circuits contrast parallel circuits transportation noted recent examples concept recent application included nipigon river bridge canada partial bridge failure january 2016 entirely severed road traffic eastern canada western canada several days located along portion trans-canada highway alternate detour route vehicles take norwalk river railroad bridge norwalk connecticut aging swing bridge sometimes gets stuck opening closing disrupting rail traffic northeast corridor line concept single point failure also applied fields intelligence edward snowden talked dangers described single point failure – sole repository information
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Computer architecture
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relational database relational database digital database based relational model data proposed e. f. codd 1970 software system used maintain relational databases relational database management system rdbms many relational database systems option using standard sql structured query language querying maintaining database term relational database invented e. f. codd ibm 1970 codd introduced term research paper relational model data large shared data banks paper later papers defined meant relational one well-known definition constitutes relational database system composed codd 12 rules however commercial implementations relational model conform codd rules term gradually come describe broader class database systems minimum 1974 ibm began developing system r research project develop prototype rdbms however first commercially available rdbms oracle released 1979 relational software oracle corporation examples rdbms include db2 sap sybase ase informix 1984 first rdbms macintosh began developed code-named silver surfer later released 1987 4th dimension known today 4d first systems relatively faithful implementations relational model first system sold rdbms multics relational data store 1978 ingres ibm bs12 followed common definition rdbms product presents view data collection rows columns even based strictly upon relational theory definition rdbms products typically implement codd 12 rules second school thought argues database implement codd rules current understanding relational model expressed christopher j date hugh darwen others relational view shared many theorists strict adherents codd principles would disqualify dbmss relational clarification often refer rdbmss truly-relational database management systems trdbms naming others pseudo-relational database management systems prdbms 2009 commercial relational dbmss employ sql query language alternative query languages proposed implemented notably pre-1996 implementation ingres quel model organizes data one tables relations columns rows unique key identifying row rows also called records tuples columns also called attributes generally table/relation represents one entity type customer product rows represent instances type entity lee chair columns representing values attributed instance address price row table unique key rows table linked rows tables adding column unique key linked row columns known foreign keys codd showed data relationships arbitrary complexity represented simple set concepts part processing involves consistently able select modify one one row table therefore physical implementations unique primary key pk row table new row written table new unique value primary key generated key system uses primarily accessing table system performance optimized pks natural keys may also identified defined alternate keys ak often several columns needed form ak one reason single integer column usually made pk pks aks ability uniquely identify row within table additional technology may applied ensure unique id across world globally unique identifier broader system requirements primary keys within database used define relationships among tables pk migrates another table becomes foreign key table cell contain one value pk migrates regular entity table design pattern represent either one-to-one one-to-many relationship relational database designs resolve many-to-many relationships creating additional table contains pks entity tables—the relationship becomes entity resolution table named appropriately two fks combined form pk migration pks tables second major reason system-assigned integers used normally pks usually neither efficiency clarity migrating bunch types columns relationships logical connection different tables established basis interaction among tables order database management system dbms operate efficiently accurately must use acid transactions programming within rdbms accomplished using stored procedures sps often procedures used greatly reduce amount information transferred within outside system increased security system design may grant access stored procedures directly tables fundamental stored procedures contain logic needed insert new update existing data complex procedures may written implement additional rules logic related processing selecting data relational database first defined june 1970 edgar codd ibm san jose research laboratory codd view qualifies rdbms summarized codd 12 rules relational database become predominant type database models besides relational model include hierarchical database model network model table summarizes important relational database terms corresponding sql term relation defined set tuples attributes tuple usually represents object information object objects typically physical objects concepts relation usually described table organized rows columns data referenced attribute domain conform constraints relational model specifies tuples relation specific order tuples turn impose order attributes applications access data specifying queries use operations select identify tuples project identify attributes join combine relations relations modified using insert delete update operators new tuples supply explicit values derived query similarly queries identify tuples updating deleting tuples definition unique tuple contains candidate primary key obviously unique however primary key need defined row record tuple definition tuple requires unique require primary key defined tuple unique attributes definition constitute superkey relational database data stored accessed via relations relations store data called base relations implementations called tables relations store data computed applying relational operations relations relations sometimes called derived relations implementations called views queries derived relations convenient act single relation even though may grab information several relations also derived relations used abstraction layer domain describes set possible values given attribute considered constraint value attribute mathematically attaching domain attribute means value attribute must element specified set character string abc instance integer domain integer value 123 another example domain describes possible values field coinface heads tails field coinface accept input values like 0,1 h constraints make possible restrict domain attribute instance constraint restrict given integer attribute values 1 10 constraints provide one method implementing business rules database support subsequent data use within application layer sql implements constraint functionality form check constraints constraints restrict data stored relations usually defined using expressions result boolean value indicating whether data satisfies constraint constraints apply single attributes tuple restricting combinations attributes entire relation since every attribute associated domain constraints domain constraints two principal rules relational model known entity integrity referential integrity primary key uniquely specifies tuple within table order attribute good primary key must repeat natural attributes attributes used describe data entered sometimes good primary keys surrogate keys often used instead surrogate key artificial attribute assigned object uniquely identifies instance table information students school might assigned student id order differentiate surrogate key intrinsic inherent meaning rather useful ability uniquely identify tuple another common occurrence especially regard n cardinality composite key composite key key made two attributes within table together uniquely identify record example database relating students teachers classes classes could uniquely identified composite key room number time slot since class could exactly combination attributes fact use composite key form data verification albeit weak one foreign key field relational table matches primary key column another table relates two keys foreign keys need unique values referencing relation foreign key used cross-reference tables effectively uses values attributes referenced relation restrict domain one attributes referencing relation concept described formally tuples referencing relation projected referencing attributes must exist tuple referenced relation projected attributes values referencing attributes match corresponding values referenced attributes stored procedure executable code associated generally stored database stored procedures usually collect customize common operations like inserting tuple relation gathering statistical information usage patterns encapsulating complex business logic calculations frequently used application programming interface api security simplicity implementations stored procedures sql rdbms often allow developers take advantage procedural extensions often vendor-specific standard declarative sql syntax stored procedures part relational database model commercial implementations include index one way providing quicker access data indexes created combination attributes relation queries filter using attributes find matching tuples randomly using index without check tuple turn analogous using index book go directly page information looking found read entire book find looking relational databases typically supply multiple indexing techniques optimal combination data distribution relation size typical access pattern indices usually implemented via b+ trees r-trees bitmaps indices usually considered part database considered implementation detail though indices usually maintained group maintains parts database use efficient indexes primary foreign keys dramatically improve query performance b-tree indexes result query times proportional log n n number rows table hash indexes result constant time queries size dependency long relevant part index fits memory queries made relational database derived relvars database expressed relational calculus relational algebra original relational algebra codd introduced eight relational operators two groups four operators first four operators based traditional mathematical set operations remaining operators proposed codd involve special operations specific relational databases operators introduced proposed since codd introduction original eight including relational comparison operators extensions offer support nesting hierarchical data among others normalization first proposed codd integral part relational model encompasses set procedures designed eliminate non-simple domains non-atomic values redundancy duplication data turn prevents data manipulation anomalies loss data integrity common forms normalization applied databases called normal forms connolly begg define database management system dbms software system enables users define create maintain control access database rdbms extension acronym sometimes used underlying database relational alternative definition relational database management system database management system dbms based relational model databases widespread use today based model rdbmss common option storage information databases used financial records manufacturing logistical information personnel data applications since 1980s relational databases often replaced legacy hierarchical databases network databases rdbms easier implement administer nonetheless relational databases received continued unsuccessful challenges object database management systems 1980s 1990s introduced attempt address so-called object-relational impedance mismatch relational databases object-oriented application programs well xml database management systems 1990s however due expanse technologies horizontal scaling computer clusters nosql databases recently become popular alternative rdbms databases distributed relational database architecture drda designed workgroup within ibm period 1988 1994 drda enables network connected relational databases cooperate fulfill sql requests messages protocols structural components drda defined distributed data management architecture according db-engines july 2019 widely used systems oracle mysql free software microsoft sql server postgresql free software ibm db2 microsoft access sqlite free software mariadb free software according research company gartner 2011 five leading proprietary software relational database vendors revenue oracle 48.8 ibm 20.2 microsoft 17.0 sap including sybase 4.6 teradata 3.7
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Databases
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list rogue security software following partial list rogue security software grouped families functionally identical versions program repackaged successive new products vendor
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Computer security
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eugene charniak eugene charniak computer science cognitive science professor brown university a.b physics university chicago ph.d. m.i.t computer science research always area language understanding technologies relate knowledge representation reasoning uncertainty learning since early 1990s interested statistical techniques language understanding research area included work subareas part-of-speech tagging probabilistic context-free grammar induction recently syntactic disambiguation word statistics efficient syntactic parsing lexical resource acquisition statistical means fellow american association artificial intelligence previously councilor organization also honored 2011 association computational linguistics lifetime achievement award awarded 2011 calvin rose g hoffman prize 2011 named fellow association computational linguistics 2015 association advancement artificial intelligence aaai classic paper award paper “ statistical parsing context-free grammar word statistics ” presented fourteenth national conference artificial intelligence 1997 published five books
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Computational linguistics
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steganalysis steganalysis study detecting messages hidden using steganography analogous cryptanalysis applied cryptography goal steganalysis identify suspected packages determine whether payload encoded possible recover payload unlike cryptanalysis intercepted data contains message though message encrypted steganalysis generally starts pile suspect data files little information files contain payload steganalyst usually something forensic statistician must start reducing set data files often quite large many cases may entire set files computer subset likely altered problem generally handled statistical analysis set unmodified files type ideally source example model digital camera possible digital camera digital audio cd mp3 files ripped etc set inspected analyzed various statistics simple spectrum analysis since image audio files days compressed lossy compression algorithms jpeg mp3 also attempt look inconsistencies way data compressed example common artifact jpeg compression edge ringing high-frequency components high-contrast edges black text white background distort neighboring pixels distortion predictable simple steganographic encoding algorithms produce artifacts detectably unlikely one case detection suspect files straightforward original unmodified carrier available comparison comparing package original file yield differences caused encoding payload—and thus payload extracted cases single image available complicated analysis techniques may required general steganography attempts make distortion carrier indistinguishable carrier noise floor practice however often improperly simplified deciding make modifications carrier resemble white noise closely possible rather analyzing modeling consistently emulating actual noise characteristics carrier particular many simple steganographic systems simply modify least-significant bit lsb sample causes modified samples different noise profiles unmodified samples also lsbs different noise profiles could expected analysis higher-order bits still show amount noise lsb-only modification detected appropriate algorithms cases detecting encoding densities low 1 reasonable reliability detecting probable steganographic payload often part problem payload may encrypted first encrypting payload always done solely make recovery payload difficult strong ciphers desirable property making payload appear indistinguishable uniformly-distributed noise make detection efforts difficult save steganographic encoding technique trouble distribute signal energy evenly see concerning errors emulating native noise carrier inspection storage device considered likely steganographer may attempt barrage potential analyst effectively misinformation may large set files encoded anything random data white noise meaningless drivel deliberately misleading information encoding density files may slightly higher real ones likewise possible use multiple algorithms varying detectability considered steganalyst may forced checking decoys first potentially wasting significant time computing resources downside technique makes much obvious steganographic software available used obtaining warrant taking action based solely steganalytic evidence dicey proposition unless payload completely recovered decrypted otherwise analyst statistic indicating file may modified modification may result steganographic encoding likely frequently case steganalytic suspicions often backed investigative techniques
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Computer security
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sql syntax syntax sql programming language defined maintained iso/iec sc 32 part iso/iec 9075 standard freely available despite existence standard sql code completely portable among different database systems without adjustments /math sql language subdivided several language elements including operators times suggested implemented skyline operator finding records 'worse others sql codice_1 expression introduced sql-92 general form called searched case sql standard sql tests codice_2 conditions order appear source source specify codice_3 expression sql defaults codice_4 abbreviated syntax—called simple case sql standard—mirrors switch statements syntax uses implicit equality comparisons usual caveats comparing null two short forms special codice_5 expressions codice_6 codice_7 codice_6 expression returns value first non-null operand found working left right null operands equal null equivalent codice_7 expression two operands returns null operands value otherwise value first operand equivalent standard sql allows two formats comments codice_10 ended first newline codice_11 span multiple lines common operation sql query makes use declarative codice_12 statement codice_12 retrieves data one tables expressions standard codice_12 statements persistent effects database non-standard implementations codice_12 persistent effects codice_16 syntax provided databases queries allow user describe desired data leaving database management system dbms carry planning optimizing performing physical operations necessary produce result chooses query includes list columns include final result normally immediately following codice_12 keyword asterisk codice_18 used specify query return columns queried tables codice_12 complex statement sql optional keywords clauses include clauses query particular order execution denoted number right hand side follows following example codice_12 query returns list expensive books query retrieves rows book table price column contains value greater 100.00 result sorted ascending order title asterisk select list indicates columns book table included result set example demonstrates query multiple tables grouping aggregation returning list books number authors associated book example output might resemble following precondition isbn common column name two tables column named title exists book table one could re-write query following form however many vendors either support approach require certain column-naming conventions natural joins work effectively sql includes operators functions calculating values stored values sql allows use expressions select list project data following example returns list books cost 100.00 additional sales_tax column containing sales tax figure calculated 6 price queries nested results one query used another query via relational operator aggregation function nested query also known subquery joins table operations provide computationally superior i.e faster alternatives many cases use subqueries introduces hierarchy execution useful necessary following example aggregation function codice_38 receives input result subquery subquery use values outer query case known correlated subquery since 1999 sql standard allows codice_39 clauses subqueries i.e named subqueries usually called common table expressions also called subquery factoring ctes also recursive referring resulting mechanism allows tree graph traversals represented relations generally fixpoint computations derived table use referencing sql subquery clause essentially derived table subquery selected joined derived table functionality allows user reference subquery table inline view also referred inline view subselect following example sql statement involves join initial book table derived table sales derived table captures associated book sales information using isbn join book table result derived table provides result set additional columns number items sold company sold books concept null allows sql deal missing information relational model word codice_40 reserved keyword sql used identify null special marker comparisons null instance equality clauses results unknown truth value select statements sql returns results clause returns value true i.e. excludes results values false also excludes whose value unknown along true false unknown resulting direct comparisons null thus brings fragment three-valued logic sql truth tables sql uses correspond common fragment kleene lukasiewicz three-valued logic differ definition implication however sql defines operation however disputes semantic interpretation nulls sql treatment outside direct comparisons seen table direct equality comparisons two nulls sql e.g codice_41 return truth value unknown line interpretation null value member data domain rather placeholder mark missing information however principle two nulls n't equal effectively violated sql specification codice_42 codice_43 operators identify nulls consequently set operations sql may produce results representing sure information unlike operations involving explicit comparisons null e.g codice_23 clause discussed codd 1979 proposal basically adopted sql92 semantic inconsistency rationalized arguing removal duplicates set operations happens lower level detail equality testing evaluation retrieval operations however computer-science professor ron van der meyden concluded inconsistencies sql standard mean possible ascribe intuitive logical semantics treatment nulls sql additionally sql operators return unknown comparing anything null directly sql provides two null-specific comparison predicates codice_45 codice_46 test whether data null sql explicitly support universal quantification must work negated existential quantification also row value expression distinct row value expression infixed comparison operator returns true unless operands equal null likewise distinct defined row value expression distinct row value expression also introduced codice_47 type variables according standard also hold unknown values nullable practice number systems e.g postgresql implement boolean unknown boolean null standard says null boolean unknown may used interchangeably mean exactly thing /ref data manipulation language dml subset sql used add update delete data transactions available wrap dml operations codice_59 codice_60 terminate current transaction release data locks absence codice_54 similar statement semantics sql implementation-dependent following example shows classic transfer funds transaction money removed one account added another either removal addition fails entire transaction rolled back data definition language ddl manages table index structure basic items ddl codice_67 codice_68 codice_69 codice_70 codice_71 statements column sql table declares type column may contain ansi sql includes following data types. ref name= iso/iec /ref codice_89 codice_90 data types multipliers codice_91 1 024 codice_92 1 048 576 codice_93 1 073 741 824 codice_94 1 099 511 627 776 optionally used specifying length codice_100 data type multipliers codice_91 1 024 codice_92 1 048 576 codice_93 1 073 741 824 codice_94 1 099 511 627 776 optionally used specifying length codice_47 data type store values codice_107 codice_108 example number 123.45 precision 5 scale 2 precision positive integer determines number significant digits particular radix binary decimal scale non-negative integer scale 0 indicates number integer decimal number scale exact numeric value integer value significant digits divided 10 sql provides functions codice_119 codice_120 round numerical values popular vendor specific functions codice_121 informix db2 postgresql oracle mysql codice_122 informix sqlite sybase oracle postgresql microsoft sql server mimer sql sql function codice_135 used extracting single field seconds instance datetime interval value current system date time database server called using functions like codice_136 codice_137 codice_138 codice_139 popular vendor specific functions codice_140 codice_141 codice_142 codice_143 codice_144 codice_145 codice_146 codice_147 codice_148 codice_149 codice_150 codice_151 data control language dcl authorizes users access manipulate data two main statements example
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Databases
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literal pool computer science specifically compiler assembler design literal pool lookup table used hold literals assembly execution multiple local literal pools typically used computer architectures lack branch instructions long jumps set instructions optimized shorter jumps examples architectures include arm architecture ibm system/360 later architectures number instructions took 12-bit address offsets case compiler would create literal table every 4k page branches whose target less 4k bytes away could taken immediately longer branches required address lookup via literal table entries literal pool placed object relocation table assembly resolved link edit time certain ways literal pool resembles toc global offset table got except implementation considerably simpler may multiple literal tables per object perhaps common type literal pool literal pools used codice_1 pseudo-instruction arm assembly language similar instructions ibm system/360 assembly language compiled load pc-relative addressing mode constant stored literal pool often particular constant value used multiple times program many linkers default store unique constant single combined literal pool improves code size java virtual machine string literal pool class constant pool
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Programming language topics
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nokia e61 nokia e61 smartphone eseries range s60 3rd edition device targeting business users european market announced part new eseries business line 12 october 2005 along nokia e60 e70 q4 2006 cingular rogers wireless deployed similar yet restricted version designated nokia e62 north american brazilian markets e62 substantially similar without 802.11 wifi chipset w-cdma umts 3g support e61 supports 900/1800/1900 bands e62 operate 850/900/1800/1900 order support american networks 12 february 2007 nokia announced e61i follow product nokia e61i smartphone eseries range s60v3 device targeting business users european market update nokia e61 released 2006 product announced 12 february 2007 3gsm world congress main differences e61 include
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Operating systems
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owasp open web application security project owasp online community produces freely-available articles methodologies documentation tools technologies field web application security mark curphey started owasp september 9 2001 jeff williams served volunteer chair owasp late 2003 september 2011. matt konda chaired board owasp foundation 501 c 3 non-profit organization usa established 2004 supports owasp infrastructure projects since 2011 owasp also registered non-profit organization belgium name owasp europe vzw owasp organization received 2014 sc magazine editor choice award
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Computer security
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adriaan van wijngaarden adriaan aad van wijngaarden 2 november 1916 – 7 february 1987 dutch mathematician computer scientist considered many founding father informatica computer science netherlands even though trained engineer van wijngaarden would emphasize promote mathematical aspects computing first numerical analysis programming languages finally design principles programming languages education mechanical engineering received degree delft university technology 1939 studied doctorate hydrodynamics abandoned area joined nationaal luchtvaartlaboratorium 1945 went group england following year learn new technologies developed world war ii van wijngaarden intrigued new idea automatic computing 1 january 1947 became head computing department brand-new mathematisch centrum mc amsterdam made visits england united states gathering ideas construction first dutch computer arra electromechanical construction first demonstrated 1952 year van wijngaarden hired edsger dijkstra worked software arra visiting edinburgh 1958 van wijngaarden seriously injured automobile accident wife killed recovered focused programming language research one designers original algol later algol 68 developed two-level type grammar became known van wijngaarden grammars became director mc 1961 remained post next twenty years 1959 became member royal netherlands academy arts sciences awarded every 5 years 60th anniversary centrum wiskunde informatica 2006 consists bronze sculpture
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Programming language topics
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brad cox brad cox computer scientist known mostly creating objective-c programming language business partner tom love work software engineering specifically software reuse software componentry cox received bachelor science degree organic chemistry mathematics furman university ph.d. department mathematical biology university chicago among first known software projects wrote pdp-8 program simulating clusters neurons worked national institutes health woods hole oceanographic institute moving software profession although cox invented programming language objective-c used early career stated interview masterminds programming book n't interested programming languages rather software components regards languages mere tools building combining parts software cox also entrepreneur founded stepstone company together tom love releasing first objective-c implementation later next acquired objective-c stepstone objective-c continued primary programming language writing software apple os x ios
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Programming language topics
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acoustic telegraphy acoustic telegraphy also known harmonic telegraphy name various methods multiplexing transmitting one telegraph messages simultaneously single telegraph wire using different audio frequencies channels message telegrapher used conventional morse key tap message morse code key pulses transmitted pulses specific audio frequency receiving end device tuned frequency resonated pulses others wire inventors worked acoustic telegraph included charles bourseul thomas edison elisha gray alexander graham bell efforts develop acoustic telegraphy order reduce cost telegraph service led invention telephone thomas edison devices used multiple synchronized tuning forks tuned selected audio frequencies opened closed electrical circuits selected audio frequencies acoustic telegraphy similar concept present-day fdma frequency division multiple access used radio frequencies word acoustic comes greek akoustikos meaning hearing hearing sound waves air acoustic telegraphy devices electromechanical made musical buzzing humming sound waves air feet primary function devices generate sound waves rather generate alternating electrical currents selected audio frequencies wires transmitted telegraphic messages electrically long distances five edison patents assigned western union telegraph company new york
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Internet protocols
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cloudbees cloudbees provider continuous delivery software services initially cloudbees provided platform service paas build run manage web applications cloudbees supported entire application life-cycle development deployment sacha labourey founded company early 2010 investors include matrix partners lightspeed venture partners verizon ventures cloudbees headquartered san jose ca additional offices lewes de richmond va brussels belgium seville spain neuchâtel switzerland sacha labourey founder ceo cloudbees labourey created company provide developers cloud platform made development java applications faster easier starting cloudbees labourey led jboss europe ultimately becoming chief technology officer remaining role red hat acquisition jboss june 2006 left red hat 2009 founded cloudbees one year later several management core developers coming jboss cloudbees expertise middleware proponent open source september 2014 cloudbees stopped offering runtime paas services order focus solely jenkins tool continuous delivery on-premises cloud kohsuke kawaguchi lead developer founder jenkins project well company cto several jenkins core committers also employed cloudbees 2016 company expanded services releasing private software service saas version continuous delivery platform 2016 cloudbees formed alliance github ca technologies others software development delivery february 2018 cloudbees acquired codeship provider continuous integration continuous delivery ci/cd cloud-based service move company said gives broader portfolio ci/cd solutions organizations sizes support several ci/cd philosophies approaches since 2010 cloudbees raised total 100 million venture financing cloudbees funding cloudbees products enable organizations build test deploy applications production utilizing continuous delivery practices continuous delivery important companies transitioning devops environment cloudbees product family includes enterprise version jenkins cloudbees provides commercial support additional plugins open source jenkins cloudbees jenkins platform includes cloudbees jenkins operations center provides central way manage jenkins across organization masters plugin versions easily maintained resources shared jenkins teams teams use cloudbees jenkins platform version jenkins development deploy popular runtime paas offerings pivotal cf google app engine amazon elastic beanstalk release cloudbees jenkins platform — private saas edition provides enterprises self-service access teams across entire organization software gives enterprises ability access cloudbees jenkins platform private cloud dedicated amazon web services cloudbees clients include range enterprises fortune 500 companies
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Distributed computing architecture
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douglas mcilroy malcolm douglas mcilroy born 1932 mathematician engineer programmer 2007 adjunct professor computer science dartmouth college mcilroy best known originally developed unix pipelines software componentry several unix tools spell diff sort join graph speak tr seminal work software componentization makes pioneer component-based software engineering software product line engineering mcilroy earned bachelor degree engineering physics cornell university 1954 ph.d. applied mathematics mit 1959 thesis solution differential equations conical shells taught mit 1954 1958 mcilroy joined bell laboratories 1958 1965 1986 head computing techniques research department birthplace unix operating system thereafter distinguished member technical staff 1967 1968 mcilroy also served visiting lecturer oxford university 1990s mcilroy worked improving sorting techniques particularly co-authored optimized quicksort algorithm jon bentley 1997 mcilroy retired bell labs took position adjunct professor dartmouth college computer science department mcilroy member national academy engineering usenix lifetime achievement award flame software tools award previously served association computing machinery national lecturer turing award chairman member publications planning committee associate editor communications acm journal acm acm transactions programming languages systems also served executive committee csnet mcilroy attributed quote real hero programming one writes negative code meaning negative code taken similar famous apple developer team anecdote i.e. change program source makes number lines code decrease 'negative code overall quality readability speed improves
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Operating systems
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x3j13 x3j13 name technical committee part international committee information technology standards incits named x3 x3j13 committee formed 1986 draw american national standards institute ansi common lisp standard based first edition book common lisp language also termed cltl cltl1 guy l. steele jr. formerly de facto standard language primary output x3j13 american national standard programming language common lisp x3.226/1994 approved december 8 1994 x3j13 later worked international organization standardization iso working group sc22/wg16 internationally standardised dialect lisp named islisp original chair committee doctor robert mathis ohio state university mary van deusen secretary guy l. steele jr. originally vice-chair later years mathis stepped chair steele assumed role efforts committee guided charter successful creation credited coordinating efforts susan p. ennis representative amoco production company charter lays committee goals priorities broadly defined list topics addressed committee formed several subcommittees help members better concentrate efforts cleanup subcommittee chaired larry masinter established standardised format submission proposals voting issue writeups part standard deemed sufficiently useful common lisp hyperspec include cross-reference benefit readers providing information original intent committee decisions writeups also serve historical record alternate solutions problems ultimately adopted chaired sandra loosemore subcommittee created proposals issues relating lisp compiling guy steele acknowledged second edition common lisp language large contribution compiler subcommittee toward clarifying compiling process described first edition parts steele describes vague jon l. white chair iteration subcommittee among issues dealt group generalized codice_1 macro – domain-specific language second edition cltl devotes full chapter algol-like syntax macro differing lisp usual s-expression syntax remains somewhat controversial character subcommittee chaired thom linden task defining standard would deal issues surrounding different character sets resolution matters particularly ability use character name symbol intended make common lisp simpler international users chaired kent pitman error handling subcommittee plugged described biggest outstanding hole common lisp condition system general mechanism handling errors warnings exceptional situations committee referred resulting specification condition system rather error system accommodate one system handling exceptional situations various kinds whether fatal non-fatal whether continuable whether result program error simple resource limit stack overflow conditions signaled one point code may handled another point use term signal different typical operating system notion signals except lisp machines variant use term evolved operating system notion signaling scope committee consequently addressed ansi common lisp standard asynchronous interrupts ieee floating point trapping also scope committee work addressed standard kathy chapman chair drafting subcommittee responsible drafting actual standard document subcommittee oversaw efforts keep terminology consistent accurate throughout committee activities final standard produced x3j13 committee published american national standard x3.226 also hypertext form common lisp hyperspec book common lisp language although authored mostly guy l. steele jr. product ad hoc committee formed around 1980 worked collaboratively produce original de facto standard common lisp formation x3j13 x3j13 began work common lisp language base document proceeded design would become ansi common lisp steele served committee gave permission use parts first edition efforts documents published x3j13 later used together quotations certain committee members production common lisp language second edition released 1990 giving common lisp community way preview many features expected appear committee final standard document edition bears similarity standard content though form however substantive changes made form additions deletions publication book final draft ansi standard sum original edition common lisp language document x3j13 originally based work second edition contrast steele work committee product official status within x3j13 ansi acknowledged second edition preface authorized x3j13 choice content snapshot work progress formally synchronized x3j13 final version reviewed approved x3j13
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Programming language topics
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working set working set concept computer science defines amount memory process requires given time interval peter denning 1968 defines “ working set information formula_1 process time formula_2 collection information referenced process process time interval formula_3 ” typically units information question considered memory pages suggested approximation set pages process access future say next formula_4 time units specifically suggested indication pages ought kept main memory allow progress made execution process effect choice pages kept main memory distinct paged auxiliary storage important many pages process kept main memory fewer processes ready one time pages process kept main memory page fault frequency greatly increased number active non-suspended processes currently executing system approaches zero working set model states process ram pages currently using often approximated recently used pages ram model nothing model meaning pages needs use increases room ram process swapped memory free memory processes use often heavily loaded computer many processes queued processes allowed run one scheduling time slice would refer pages ram causing computer thrash swapping processes memory result processes—even processes temporarily removed memory—finish much sooner would computer attempted run processes also finish much sooner would computer ran one process time completion since allows processes run make progress times one process waiting hard drive global resource words working set strategy prevents thrashing keeping degree multiprogramming high possible thus optimizes cpu utilization throughput main hurdle implementing working set model keeping track working set working set window moving window memory reference new reference appears one end oldest reference drops end page working set referenced working set window avoid overhead keeping list last k referenced pages working set often implemented keeping track time last reference considering working set pages referenced within certain period time working set n't page replacement algorithm page-replacement algorithms designed remove pages n't working set particular process one example modified version clock algorithm called wsclock working set divided code working set data working set distinction important code data separate relevant level memory hierarchy either working set fit level hierarchy thrashing occur addition code data systems virtual memory memory map virtual memory physical memory entries pages working set must cached translation lookaside buffer tlb process progress efficiently distinction exists code data cached small blocks cache lines entire pages address lookup done page level thus even code data working sets fit cache working sets split across many pages virtual address working set may fit tlb causing tlb thrashing analogs working set exist limited resources significantly processes set processes requires frequent interaction multiple processes must coscheduled order progress processes scheduled simultaneously – example two processes one core execute – processes advance rate one interaction per time slice resources include file handles network sockets – example copying one file another simply done two file handles one input one output thus file handle working set size two one file handle available copying still done requires acquiring file handle input reading say buffer releasing acquiring file handle output writing releasing acquiring input file handle repeating similarly server may require many sockets limited would need repeatedly release re-acquire sockets rather thrashing resources typically required program acquire enough resources simply fails
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Operating systems
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gridrpc gridrpc remote procedure call grid paradigm proposed gridrpc working group open grid forum ogf api defined order clients access remote servers simply function call used among numerous grid middleware simplicity implementation standardized ogf 2007 interoperability reasons different existing middleware api followed document describing good use behavior different gridrpc api implementations works conducted gridrpc data management standardized 2011 scope standard offer recommendations implementation middleware deals following topics among existing middleware application programming approaches one simple powerful flexible approach consists using servers available different administrative domains classical client-server remote procedure call rpc paradigm network enabled servers nes implement model also called gridrpc clients submit computation requests resource broker whose goal find server available grid scheduling frequently applied balance work among servers list available servers sent back client client able send data request one suggested servers solve problem thanks growth network bandwidth reduction network latency small computation requests sent servers available grid make effective use today scalable resource platforms important ensure scalability middleware layers well service-oriented approach new several research projects targeted paradigm past main middleware implementing api diet netsolve/gridsolve ninf environments use like saga interface ogf without standardized api calls like ommirpc xtremweb rpc model internet also used several applications transparently internet large optimization problems solved using different approaches simply filling web page remote image processing computations use mathematical libraries studies heuristics resolution methods sparse linear algebra like gridtlse approach providing computation services internet also highly close service oriented computing soa paradigm core cloud computing one simple yet effective mean execute jobs computing grid use gridrpc middleware relies gridrpc paradigm request gridrpc middleware manages management submission input output data execution job remote resource etc make available service programmer must implement two codes client data defined run user requesting service server contains implementation service executed remote resource one step ease development codes conducted define gridrpc api proposed draft november 2002 open grid forum ogf standard since september 2007 thus gridrpc source code involve specific middleware data compiled executed gridrpc compliant middleware due difference choice implementation gridrpc api document describing interoperability gridrpc middleware also written main goals describe difference behaviour gridrpc middleware propose common test gridrpc middleware must pass discussions undertaken data management within gridrpc middleware draft api proposed ogf'21 october 2007 motivation document provide explicit functions manipulate data exchange gridrpc platform client since 1 size data used grid applications may large useless data transfers must avoided 2 data always stored client side may made available either storage resource within gridrpc platform hence side effect fully gridrpc-compliant code written compiled gridrpc middleware implementing gridrpc data management api gridrpc model pictured following figure communications handled 1 servers register services registry 2 client needs execution service contacts registry 3 registry returns handle client 4 client uses handle invoke service server 5 eventually receives back results mechanisms involved api must provide means make synchronous and/or asynchronous calls service latter clients must also able wait blocking non-blocking manner completion given service naturally involves data structures conducts rigorous definition functions api gridrpc data types three main data types needed implement api 1 grpc_function_handle_t type variables representing remote function bound given server allocated client variable used launch service many times desired explicitly invalidated user needed anymore 2 grpc_session_t type variables used identify specific non-blocking gridrpc call variable mandatory obtain information status job order client wait cancel know error status call 3 grpc_error_t groups kind errors returns status codes involved gridrpc api gridrpc functions grpc_initialize grpc_finalize functions similar mpi initialize finalize calls mandatory gridrpc call performed two calls read configuration files make gridrpc environment ready finish order initialize destruct function handle grpc_function_handle_init grpc_function_handle_destruct functions called function handle dynamically associated server resource discovery mechanisms example call grpc_function_handle_default let postpone server selection actual call made handle grpc_get_handle let client retrieve function handle corresponding session id e.g. non-blocking call previously performed depending type call blocking non-blocking client use grpc_call grpc_call_async function latter client possesses call session id used respectively probe wait completion cancel call check error status non-blocking call issuing unique numerous non-blocking calls client use grpc_probe know execution service completed grpc_probe_or know one previous non-blocking calls completed grpc_cancel cancel call grpc_wait block completion requested service grpc_wait_and block services corresponding session ids used parameters finished grpc_wait_or block service corresponding session ids used parameters finished grpc_wait_all block non-blocking calls completed grpc_wait_any wait previously issued non-blocking request completed talk lib +link code must compile give basic example
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Distributed computing architecture
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power5 power5 microprocessor developed fabricated ibm improved version power4 principal improvements support simultaneous multithreading smt on-die memory controller power5 dual-core microprocessor core supporting one physical thread two logical threads total two physical threads four logical threads technical details microprocessor first presented 2003 hot chips conference complete description given microprocessor forum 2003 14 october 2003 power5 sold openly used exclusively ibm partners systems using microprocessor introduced 2004 power5 competed high-end enterprise server market mostly intel itanium 2 lesser extent sun microsystems ultrasparc iv fujitsu sparc64 v. superseded 2005 improved iteration power5+ power5 development power4 addition two-way multithreading required duplication return stack program counter instruction buffer group completion unit store queue thread may resources register files execution units shared although thread sees set registers power5 implements simultaneous multithreading smt two threads executed simultaneously power5 disable smt optimize current workload many resources register files shared two threads increased capacity many cases compensate loss performance number integer floating-point registers increased 120 80 integer 72 floating-point registers power4 floating-point instruction cache also increased capacity 24 entries 20 capacity l2 unified cache increased 1.875 mb set-associativity 10-way unified l3 cache brought on-package instead located externally separate chips capacity increased 36 mb like power4 cache shared two cores cache accessed via two unidirectional 128-bit buses operating half core frequency on-die memory controller supports 64 gb ddr ddr2 memory uses high-frequency serial buses communicate external buffers interface dual inline memory modules dimms microprocessor power5 contains 276 million transistors area 389 mm fabricated ibm 0.13 µm silicon insulator soi complementary metal–oxide–semiconductor cmos process eight layers copper interconnect power5 die packaged either dual chip module dcm multi-chip module mcm dcm contains one power5 die associated l3 cache die mcm contains four power5 dies four l3 cache dies one power5 die measures 95 mm 95 mm several power5 processors high-end systems coupled together act single vector processor technology called viva virtual vector architecture power5+ improved iteration power5 introduced 4 october 2005 improvements initially lower power consumption due newer process fabricated power5+ chip uses 90 nm fabrication process resulted die size decrease 389 mm 243 mm clock frequency increased launch remained 1.5 1.9 ghz 14 february 2006 new versions raised clock frequency 2.2 ghz 2.3 ghz 25 july 2006 power5+ packaged packages previous power5 microprocessors also available quad-chip module qcm containing two power5+ dies two l3 cache dies one power5+ die qcm chips ran clock frequency 1.5 1.8 ghz ibm uses dcm mcm power5 microprocessors system p system server families ds8000 storage server embedded microprocessors high-end infoprint printers dcm power5 microprocessors used ibm high-end intellistation power 285 workstation third-party users power5 microprocessors groupe bull escala servers hitachi sr11000 computers 128 power5+ microprocessors several installations featured 2007 top500 list supercomputers ibm uses power5+ system p5 510q 520q 550q 560q servers
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Computer architecture
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r-type r-type first game run irem 16-bit m72 arcade system initially joke among staff force based dung beetles development team drew inspiration gradius aliens works h.r giger music composed masato ishizaki character design done akio game title stems word ray ray light reference player ray-like weapons used throughout game r-type celebrated critics graphics addictive gameplay although would receive criticism high difficulty level commonly cited one best shoot-em-up video games well one greatest video games time success would prompt creation several sequel spin-off games alongside home ports releases digital distribution services remake game released r-type dx game boy color 2000 3d remake r-type dimensions released xbox 360 2009 later nintendo switch 2018 game composed several sequential levels boss enemy end player controls small spacecraft must navigate terrain fight enemies using various ship weapons player spacecraft default weak rapid-firing main gun powerful gun called wave cannon requires player hold fire build power cannon game player obtain auxiliary device called force resembles glowing orange ball force attached front back player spacecraft detached fly freely attached force provides one three different powerful weapons addition main gun wave cannon detached weapons used force instead resort secondary set guns fired player even force distance spacecraft force secondary use shield completely indestructible block things fired well damage destroy enemies contact inspiration force came partly joke akibo designer envisioning behavior dung beetle r- series title stands ray ray light reference many different types ray-like weapons players use series another theory suggests r-type refers bydo r-strategists r/k selection theory original r-type well received gaming critics however also infamous relentless difficulty zx spectrum version r-type awarded 9/10 january 1989 issue sinclair placed number 6 sinclair official top 100 games machine praised incredible use colour blows away almost every shoot'em spectrum crash congratulated electric dreams retaining frenetic arcade feel producing brilliant game sinclair user praised weapons system difficulty curve c+vg concluded review saying excellent shoot'em challenging addictive absolute must spectrum blasting fanatics r-type placed number 1 rgtv youtube video top 5 shoot 'em ups zx spectrum successful 1988 port master system immediately recognized one best games available sega library mean machines magazine review praised particular graphics high quality challenge offered game awarding overall rating 92 1995 article next generation stated pc engine conversion irem arcade smash r-type still regarded system definitive contribution shoot 'em genre following year listed arcade original ports game number 98 top 100 games time praising art direction graphics design innovations huge bosses retrospective review allgame editor shawn sackenheim described turbografx-16 version r-type accurate home conversion arcade version game furthermore stating shooter started still thrill ride beginning end game runner-up category best coin-op conversion year golden joystick awards behind operation wolf hudson soft developed fairly accurate port r-type released pc engine turbografx 16 consoles although versions suffered slightly lower resolution reduced colour palette sprite flickering slowdown due slightly reduced resolution playfield also scrolls slightly vertical axis whenever player ship approaches top bottom screen japanese release pc engine split across two game cards hucards titled later north american release turbografx-16 contained entire game single card pc engine version r-type notable boss end stage 6 rather prolonged wave enemies versions xbox live arcade game r-type dimensions released february 4 2009 tozai games port original r-type sequel r-type ii played either original 2d graphics new 3d graphics added co-op gameplay functionality analogous version ps3 released may 2014 name r-type dimensions pc engine version r-type one first games confirmed nintendo virtual console north american european versions include eight levels released turbografx-16 japanese release wii split two downloads mirroring original format game pc engine however japanese releases nintendo 3ds wii u use turbografx-16 version instead pc engine one master system version became available well virtual console japan may 19 2009 north america november 2 2009 europe september 25 2009 however due licensing issues version delisted september 30 2011 north america europe october 18 2011 japan 2010 dotemu developed ios port r-type published electronic arts released also android september 2011 tozai games returned 2018 re-issued updated digital-only release r-type dimensions carrying title r-type dimensions ex landing steam playstation 4 nintendo switch.. strictly limited games released physical copies playstation 4 nintendo switch versions february 2019 limited 2,000 3,000 copies respectively collector edition variants also issued contained hardcover artbook dog tags stickers cards limited 1,000 playstation 4 2,000 nintendo switch irem developed number sequels related games including r-type ii armed police unit gallop xmultiply although part series similar themes gameplay released around time r-type ii however games katakis 1988 clone produced factor 5 commodore 64 amiga 1991 konami released xexex game heavily influenced r-type xmultiply game used similar weapons concepts flint combination r-type force x multiply tentacle equipment games similar r-type rezon released allumer 1991 aicom pulstar blazing star later published yumekobo neo geo technosoft 1992 title thunder force iv sega mega drive
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Computer architecture
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programming languages application interpretation programming languages application interpretation plai free programming language textbook shriram krishnamurthi use 30 universities several high-schools book differs programming language texts attempt wed two different styles programming language education one based language surveys another based interpreters former style easy ignore difficult technical points sometimes best understood trying reproduce via implementation latter easy miss high-level picture forest details plai therefore interleaves two using survey approach motivate ideas interpreters understand book accompanied supporting software runs racket programming language since plai constantly development newer material especially assignments found course pages brown university plai also experiment publishing methods essay books software discusses book self-published addition book currently december 2014 available for-pay print also free for-pay electronic editions
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Programming language topics
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qualtrics qualtrics experience management company co-headquarters provo utah seattle washington united states company founded 2002 scott m. smith ryan smith jared smith stuart orgill qualtrics offers subscription software platform world ’ iconic companies use close experience gaps deliver breakthrough results xm platform makes simple organization collect understand take action experience data x-data —the beliefs emotions sentiments customers employees november 11 2018 announced qualtrics would acquired sap acquisition completed january 23rd 2019 2012 company received 70 million series investment sequoia capital accel generally considered two top venture capital firms country largest joint investment date two firms september 2014 sequoia capital accel returned series b funding led insight partners worth 150 million record utah-based company valuing company 1 billion april 2017 qualtrics received series c investment round 180 million returning investors accel sequoia capital insight venture partners series c raised 2.5 billion pre-money valuation lifetime qualtrics raised total 400 million accel insight partners sequoia capital october 19 2018 qualtrics filed s-1 registration statement intention raising gross proceeds 200 million initial public offering ipo class b shares time company listed 9,000 global customers company meant listed nasdaq exchange ticker xm reference flagship experience management product qualtrics xm platform plans ipo scrapped announced november 2018 qualtrics would acquired sap nyse sap 2016 qualtrics ranked 12 forbes cloud 100 list moving 6 2017 qualtrics reported revenue 190.6 million 2016 289.9 million 2017 representing year year growth 52 2016 qualtrics reported overall net loss 12 million free cash flow 3.4 million 2017 qualtrics reported 2.6 million net profit free cash flow 21.3 million may 2016 qualtrics acquired statistical analysis startup statwing undisclosed sum statwing san francisco-based company created point-and-click software advanced statistical analysis april 2018 qualtrics acquired delighted undisclosed sum delighted 1,500 customers time acquisition november 2018 sap announced intent acquire qualtrics sap acquired outstanding shares qualtrics 8 billion usd cash deal sap secured €7 billion financing time announced qualtrics acquisition sap second-biggest purchase ever behind 8.3 billion acquisition travel expense management firm concur 2014 acquisition formally closed january 23 2019 quantitative statistical analysis performed qualtrics cited number professional academic journals qualtrics became first employee management platform measuring employee experiences key metrics powered predictive intelligence researchers often use qualtrics survey tool combine spss analyze survey data employee experiences many types survey data
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Distributed computing architecture
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poul-henning kamp poul-henning kamp born 1966 danish computer software developer known work various projects currently resides slagelse denmark poul-henning kamp committing freebsd project duration responsible widely used md5crypt implementation md5 password hash algorithm vast quantity systems code including freebsd geom storage layer gbde cryptographic storage transform part ufs2 file system implementation freebsd jails malloc library ntp timecounters code lead architect developer open source varnish cache project http accelerator 2006 kamp dispute electronics manufacturer d-link claimed committing ntp vandalism embedding ip address ntp servers routers dispute resolved 27 april 2006 post poul-henning freebsd mailing lists responsible popularization term bike shed discussion derived term bikeshedding describe parkinson law triviality open source projects amount discussion subject receives inversely proportional importance poul-henning kamp known preference beerware license gnu general public license gpl poul-henning kamp made various anti-semitic comments blaming world jews collectively responsible actions israel may 8 2019 tweeted thought anti-semitism *unfounded* hatred jews hate something awful like implement apartheid anti-semitism perfectly justified critique people particular know better clarifying blog post later wrote readily admit probably skilled use twitter stand point kamp went say detests cowardice appaled sic arms atrocities uns human rights done name religion poul-henning kamp published substantial number articles years publications like communications acm acm queue mostly topics computing time keeping selection publications
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Operating systems
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pico-itxe pico-itxe pc pico-itx motherboard specification created via technologies sff-sig announced via technologies october 29 2008 released december 2008 pico-itxe specifications call board half area nano-itx 12 layers deep processor via c7 uses via nanobga2 technology uses ddr2 667/533 so-dimm memory support 2gb video supplied via chrome9 hc3 gpu built-in mpeg-2 4 wmv9 vc1 decoding acceleration bios 4 8 mbit award bios first motherboard produced specification called epia-p710 released december 2008 12 layers deep operating temperature range 0°c 50°c operating humidity level relative non-condensing 0 95 uses 1 ghz via c7-m processor via vx800 chip set rohs compliant onboard vga video-out gigabit ethernet supplied via vt6122 requires connector board hd 5.1 channel audio provided via vt1708b chip following standard i/o connections four i/o expansion boards stacked upon using sumit interface
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Computer architecture
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apple sos sophisticated operating system sos primary operating system developed apple iii computer sos developed apple computer inc. released october 1980 sos single-tasking single-user operating system makes resources apple iii available form menu-driven utility program well programming application programming interface api single program loaded boot time called interpreter loaded interpreter use sos api make requests system sos api divided four main areas apple iii system utilities program shipped apple iii computer provides user interface operating system system configuration file management system utilities program menu-driven performs tasks three categories sos two types devices communicates via device drivers character devices block devices examples sos character devices keyboards serial ports disk drives typical block devices block devices read write one 512-byte blocks time character devices read write single characters time powered apple iii runs system diagnostics reads block number zero built-in diskette drive memory executes sos-formatted diskettes place loader program block zero loader program searches loads executes file named sos.kernel kernel api operating system kernel turn searches loads file named sos.interp interpreter program run sos.driver set device drivers use files loaded control passed sos.interp program apple prodos uses file system sos disk formatted prodos prodos loader sos loader written blocks zero one respectively prodos loader includes code execute apple iii chainload sos loader block one sos prodos co-exist volume software adtpro makes use store apple ii apple iii versions program disk bootable systems 1985 steve wozniak critical apple iii hardware flaws called sos finest operating system microcomputer ever regardless sos advantages system backward-compatible dos 3.2 dos 3.3 apple ii software used time though apple iii designed mostly backward-compatible apple ii plus hardware users must boot apple dos separate disk utilize apple ii series software thus losing advantages sos many average computer users also ready 1980 operating system capabilities flexible configuration options sos offers especially combined apple iii bad reputation due poor engineering high retail price nearly
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Operating systems
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elbrus 2000 elbrus 2000 e2k russian 512-bit wide vliw microprocessor developed moscow center sparc technologies mcst fabricated tsmc supports two instruction set architecture isa thanks unique architecture elbrus 2000 execute 20 instructions per clock even modest clock speed compete much faster clocked superscalar microprocessors running native vliw mode security reasons elbrus 2000 architecture implements dynamic data type-checking execution order prevent unauthorized access pointer additional type information verified associated data accessed
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Computer architecture
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auf wiedersehen monty auf wiedersehen monty german goodbye monty computer game zx spectrum commodore 64 amstrad cpc msx commodore 16 released 1987 fourth monty series following monty innocent monty run successful original written peter harrap shaun hollingworth music rob hubbard ben daglish player controls monty travels around europe collecting money order buy greek island montos safely retire gameplay style flick-screen platform game similar many games 1980s technician ted jet set willy screens representing eiffel tower pyrenees bear relation real-life counterparts typical platform game screens auf wiedersehen monty contains many interesting features peculiarities player discover examples include suddenly attacked bull head spain collecting red cape presumably reference bullfighting car dropped one two places entering screen representing düsseldorf west germany chef hat found sweden reference swedish chef muppets fame also two rooms representing sweden subtitled bjorn borg record luxembourg collected makes monty breakdance game title music may reference radio luxembourg possible get areas game quickly flying airport using air tickets collected throughout game parts game reached manner well money miscellaneous objects collect game points important need certain number points get montos often particular country monty visiting berets france bottles wine glass beer west germany cause monty briefly become drunk control become slightly erratic leading reversal controls repeated jumping monty climbing ladders drainpipes encounters moley christmas released later year monty mole game called impossamole released 1990 took different form previous games console-style arcade game
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Computer architecture
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wholesale applications community wholesale applications community wac organisation set create unified open platform allow mobile software developers easily write applications usable variety devices operating systems networks least 48 companies members organization wac organisation came end gsma announcing july 17 2012 reached agreement integrate wac major programs initiatives gsma additionally apigee acquired technology assets wac wac preceded omtp completed acquisition joint innovation lab 1 october 2010 accelerating commercial launch wac-enabled application stores put position fully operational commercially running end 2010 wholesale application community application development platform based standard technologies html javascript cascading style sheets css specifically platform builds work former open mobile terminal platform ltd. bondi project joint innovation lab jil device apis gsm association oneapi program utilizing web-based technologies rather relying developers write native applications specific devices wac alliance believes spur development applications across much wider range devices group also aims make certain telecoms apis available developers operator billing wac standards development organisation sdo used w3c standard technologies platform particular used w3c widget packaging format specification web apps also furthered use javascript device apis originated omtp bondi project bondi developed defunct open mobile terminals platform omtp jil joint venture china mobile softbank verizon wireless vodafone focused promoting use web based technologies mobile application development jil compliant handsets include sgh-i8320 samsung vodafone 360 h1 27 july 2010 wac announced would join forces jil completed acquisition 1 october 2010 meant developers currently creating jil applications continue working existing jil specification tools software libraries applications deployed jil based devices immediately publication wac specification developers also clear path deploy applications wider range devices supporting wac specification 2011 one question whether large group operators able respond changing market conditions particularly wake influence exerted apple google however vidhya gholkar wac developer relations lead commented mobile 2.0 september 20 2010 wac competing apple similar companies focus making apps available much greater audience requires adherence core set web technologies ability distribute base larger served single device os
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Web technology
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macintosh lc 500 series macintosh lc 500 series series personal computers part apple computer macintosh lc family macintosh computers apple mid-1990s mainstream education-market macintosh featuring all-in-one desktop design built-in 14 crt display cd-rom drive stereo speakers designed successor compact macintosh family computers case similar recently introduced macintosh color classic considerably larger heavier due larger screen bulging midsection house larger electronics 500 series included four main models 520 550 575 580 520 550 using different speeds motorola 68030 575 580 sharing 33mhz motorola 68lc040 processor differing rest hardware computers also sold consumer market department stores macintosh performa brand similar model numbers lc models particular became popular schools small footprint lack cable clutter durability macintosh tv branded lc uses lc 520 case black instead platinum logic board similar lc 550 compact color classic series shares many components able swap logic boards early 500 series machines macintosh lc 520 introduced june 1993 case design larger compact macintosh models precede due large part significantly larger screen lc 520 got start design project codenamed mongo following success color classic apple industrial design group idg began exploring adaptation color classic design language dubbed espresso larger display version would also include cd-rom drive however idg hated design much permanently shelved final concept 1992 apple ceo john sculley demanded large screen all-in-one design fill market strategy less 6 months idg objections apple engineering team retrieved shelved design promptly put production idg universally detested design immediately began re-design project would become power macintosh 5200 lc series less two years later logic board 520 broadly macintosh lc iii motorola 68030 cpu optional motorola 68882 fpu new york times review lc 520 generally positive columnist peter lewis noting 1,599 price point perhaps best value entire macintosh product line ... would difficult put together windows-based pc features price windows computers usually much less expensive macs lewis also noted unit 40-pound weight would make difficult carry home night -- attribute apple previously marketed feature compact macintosh models 1980s macweek wrote timing lc 520 release coincided purchasing timelines schools decision market computer exclusively education market part strategic shift move lc brand away retail market 520 discontinued february 1994 replaced faster otherwise essentially unchanged macintosh lc 550 new 68lc040-equipped macintosh lc 575 apple sold upgrade kits lc 520 brought specifications lc 550 575 initially sold japan canada u.s. educational institutions computer discontinued february 1994 featured caddy-loaded cd-rom drive introduced june 28 1993 macintosh lc 550 replaced lc 520 february 1994 performa variants introduced earlier 550 october 1993 560 january 1994 remained available year longer april 1996 main difference 550 520 faster 68030 cpu clocked 33 mhz instead 25 mhz bus speed also increasing 25 33 mhz like 520 optical drive use loading tray instead utilized caddy disk first inserted caddy loaded drive logic board 550 essentially one used macintosh color classic ii upgrade original color classic available united states apple also offered upgrade package 520 lc 575 logic board two performa variants introduced varying software bundle included 550 included consumer applications performa 560 called money edition owing partnership apple money magazine addition consumer education software also included dozen business software applications lc 575 discontinued favor either lc 580 lower end powerpc-based power macintosh 5200 lc models higher end introduced october 18 1993 introduced january 15 1994 introduced february 2 1994 macintosh lc 575 available 1994 1996 retains all-in-one case lc 520/550 uses lc 475 motherboard motorola 68lc040 cpu speed 33 mhz instead 25 mhz tray-loading optical drive also included high density floppy disk drive cpu clock sometimes given 66 mhz since clock signal frequency however processor runs 33 mhz lc 575 also introduced comm slot included later lc models well may 1994 set performa variants introduced performa 575 577 578 machines identical except amount ram hdd size software packages included performa variants include clarisworks 2.0 quicken 4.0 grolier encyclopedia 1993 time magazine almanac ease educational titles david pogue described machine enthusiastically received mac fans appreciated crisp color screens speedy performance rich sound upgradability power macs line lc variant succeeded macintosh lc 580 performa variants sold 580 discontinued lc 580 performa variants available outside united states model favorite motherboard donor wishing upgrade color classic faster class processor apple also offered upgrade path form powerpc macintosh processor upgrade introduced february 1994 introduced may 1994 macintosh lc 580 sold april 1995 may 1996 like lc 575 built around motorola 68lc040 processor running 33 mhz however instead using sized scsi-only logic boards based lc 475/quadra 605 like lc 575 580 uses larger logic board performa 630 meant changes leading lower prices also lower performance notably hard drives 580 ide drives instead scsi drives also video ram longer mounted simm used 1 mb 4 mb main ram soldered motherboard lastly trinitron display 575 replaced cheaper shadow mask screen causing slight change plastic case surrounding crt one benefit change ability accommodate video capture tv tuner cards designed performa 630 allowed lc 580 users watch record video essentially performing function television well computer lc 580 lc 630 dos compatible introduced time last macintosh desktop systems built around motorola 68000-series processor replacement power macintosh 5200 lc features powerpc processor apple also offered upgrade path 580 form powerpc macintosh processor upgrade 580 also upgraded following logic boards 5200 lc 6200 5260 5300 6300 5400 6400 5500 6500 introduced april 3 1995 introduced april 13 1995 introduced may 1 1995 central processing unit motorola 68lc040 33 mhz 8 kb l1 cache memory 8 mb expandable 52 mb 2 72-pin simms 1 mb 4 mb ram soldered mainboard used video ram storage hard drive 250 mb 500 mb ide floppy drive 1.44 mb superdrive read 400 kb 800 kb diskettes well cd-rom 4x applecd unit expansion 1 lc pds 1 comm slot display 14″ color crt supports 32,768 colors
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Computer architecture
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usability web authentication systems usability web authentication systems refers efficiency user acceptance online authentication systems examples web authentication systems passwords federated identity systems e.g google oauth 2.0 facebook connect mozilla persona email-based single sign-on sso systems e.g saw hatchet qr code-based systems e.g snap2pass webticket system used authenticate user identity web even though usability web authentication systems key consideration selecting system web authentication systems passwords subjected formal usability studies analysis web authentication system needs usable possible whilst compromising security needs ensure system needs restrict access malicious users whilst allowing access authorised users authentication system sufficient security malicious users could easily gain access system hand authentication system complicated restrictive authorised user would able want use strong security achievable system even secure authentication system undermined users system often referred weak links computer security users tend inadvertently increase decrease security system system usable security could suffer users try minimize effort required provide input authentication writing passwords paper usable system could prevent happening users likely oblige authentication requests systems important e.g online banking opposed less important systems e.g forum user visits infrequently mechanisms might ignored users accept security measures certain point becoming annoyed complicated authentication mechanisms important factor usability web authentication system thus convenience factor user around preferred web authentication system web applications password despite poor usability several security concerns widely used system usually contains mechanisms intended increase security e.g requiring users high entropy passwords lead password systems less usable inadvertently less secure users find high entropy passwords harder remember application creators need make paradigm shift develop usable authentication systems take user ’ needs account replacing ubiquitous password based systems usable possibly secure systems could lead major benefits owners application users measure usability web authentication system one use usability–deployability–security uds framework standard metric system usability scale uds framework looks three broad categories namely usability deployability security web authentication system rates tested system either offering offering specific benefit linked one categories authentication system classified either offering offering specific benefit within categories usability deployability security measuring usability web authentication systems allow formal evaluation web authentication system determine ranking system relative others lot research regarding web authentication system currently done tends focus security usability future research evaluated formally usability using comparable metric technique enable comparison various authentication systems well determining whether authentication system meets minimum usability benchmark found security experts tend focus security less usability aspects web authentication systems problematic needs balance security system ease-of-use study conducted 2015 found users tend prefer single sign-on like provided google facebook based systems users preferred systems found fast convenient use single sign-on based systems resulted substantial improvements usability security sso reduces need users remember many usernames passwords well time needed authenticate thereby improving usability system usability become important applications move online require robust reliable authentication systems usable secure use brainwaves authentication systems proposed possible way achieve however research usability studies required
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Computer security
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dew computing dew computing information technology paradigm combines core concept cloud computing capabilities end devices personal computers mobile phones etc. used enhance experience end user comparison using cloud computing dew computing attempts solve major problems related cloud computing technology reliance internet access dropbox example dew computing paradigm provides access files folders cloud addition keeping copies local devices allows user access files times without internet connection connection established files folders synchronized back cloud server term dew computing used information technology first appeared 2015 literature since become field cloud-dew architecture proposed possible solution offline data accessibility problem first scope included web applications broader applications later proposed dew computing model derived original concept cloud computing models also emerged cloud computing including fog computing edge computing dew computing others proponents claim novel models dew computing provide better experiences users cloud computing provides universal access scalability however resources far user control occasionally causes problems classic cloud computing paradigm internet connection servers lost user unable access data dew computing aims solve problem information technology paradigm dew computing seeks use capabilities personal computers along cloud services reliable manner key features dew computing independence collaboration independence means local device must able provide service without continuous connection internet collaboration means application must able connect cloud service synchronize data appropriate use word dew reflects natural phenomena clouds far ground fog closer ground dew ground analogically cloud computing remote service fog computing beside user dew computing user end establish cloud-dew architecture pc dew virtual machine dvm needed dvm isolated environment executing dew server local pc consists least three components dew server ds data analytics server das artificial intelligence dew aid dew computing categories classified based application field dew computing faces number technical challenges including issues related power management processor utility data storage factors impacting use dew computing viability operation system network model communication model programming principles dew recommended engine local dew network personal high productivity database security behaviors browser
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Distributed computing architecture
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peter naur peter naur 25 october 1928 – 3 january 2016 danish computer science pioneer turing award winner last name n bnf notation backus–naur form used description syntax programming languages contributed creation algol 60 programming language naur began career astronomer received phd degree 1957 encounter computers led change profession 1959 1969 employed regnecentralen danish computing company time giving lectures niels bohr institute technical university denmark 1969 1998 naur professor computer science university copenhagen main areas inquiry design structure performance computer programs algorithms areas software engineering software architecture also pioneered naur book computing human activity 1992 collection contributions computer science rejected formalist school programming views programming branch mathematics like associated backus–naur form attributed donald knuth said would prefer called backus normal form naur married computer scientist christiane floyd naur disliked term computer science suggested called datalogy data science former term adopted denmark sweden datalogi latter term used data analysis including statistics databases since middle 1960s computer science practiced denmark peter naur term datalogy science data processes starting regnecentralen university copenhagen copenhagen tradition computer science developed special characteristics means close connection applications fields knowledge tradition least visible area education comprehensive project activity integral part curriculum thus presenting theory aspect realistic solutions known primarily actual experience peter naur early recognized particular educational challenges presented computer science innovations shown quality vitality also universities close connection computer science training formed copenhagen university view computer science characterized peter naur research later years quite outspoken pursuit science whole naur possibly identified empiricist school tells one shall seek deeper connections things manifest world keep observable facts attacked certain strands philosophy psychology viewpoint also developing theory human thinking called synapse-state theory mental life naur 2005 acm a.m. turing award work defining algol 60 programming language particular role editor influential report algorithmic language algol 60 pioneering use bnf recognized naur dane turing award naur died 3 january 2016 short illness numbers refer published bibliography naur published large number articles chapters astronomy computer science issues society classical music psychology education
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Programming language topics
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data pack data pack fact pack pre-made database fed software software agents internet bots chatterbots teach information facts later look words data pack used feed minor updates system common data packs may include abbreviations acronyms dictionaries lexicons technical data country codes rfcs filename extensions tcp udp port numbers country calling codes data packs may come formats csv sql easily parsed imported database management system database may consist key-value pair like association list data packs commonly used within gaming industry provide minor updates within games user downloads update game downloading loads data packs contain updates game minor bug fixes additional content example data pack used update game found references data pack datapack definition similar data packet contains loads information data stores within pack data compressed reduce file size certain programs read data pack therefore data packed vital know whether receiving program able unpack data example data packs able effective deliver information found reference page refer word data pack come many forms mobile data pack mobile data pack refers add-on enable boost amount data use mobile phone rate use data also monitored know much data left mobile data service provides similar service wi-fi allows connect internet purpose data pack increase amount data mobile access example mobile data pack found references
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Databases
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elias levy elias levy also known aleph one computer scientist moderator bugtraq full disclosure vulnerability mailing list may 14 1996 october 15 2001 cto co-founder computer security company securityfocus acquired symantec august 6 2002 also known author article smashing stack fun profit published 1996 phrack magazine issue 49 first high-quality public step-by-step introduction stack buffer overflow vulnerabilities exploitation sale securityfocus symantec august 2002 levy accused many selling compromising high principles bugtraq list full-disclosure mailing list founded part protest sale
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Computer security
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softether vpn softether vpn free open-source cross-platform multi-protocol vpn client vpn server software developed part daiyuu nobori master thesis research university tsukuba vpn protocols ssl vpn l2tp/ipsec openvpn microsoft secure socket tunneling protocol provided single vpn server released using gplv2 license january 4 2014 license switched apache license 2.0 january 21 2019 softether vpn supports nat traversal making useful run vpn servers computers behind residential gateways facility routers firewalls firewalls performing deep packet inspection unable detect softether vpn transport packets vpn tunnel https used camouflage connection softether vpn optimizes performance using full ethernet frame utilization reducing memory copy operations parallel transmission clustering together reduce latency normally associated vpn connections increasing throughput softether vpn server vpn bridge run windows linux os x os x 10.8 freebsd solaris operating systems softether vpn client runs windows linux macos softether vpn server serves softether vpn protocol also serves openvpn microsoft secure socket tunneling protocol sstp ssl vpn etherip l2tpv3 ipsec serves mobile devices running ios android windows phone via l2tp/ipsec vpn clients endpoints supporting vpn protocols may also used includes many routers cisco juniper linksys dd-wrt asus others softether vpn server implements vpn server function listens accepts connections vpn client vpn bridge several vpn protocols vpn server several virtual hubs virtual layer-3 switches virtual hub full layer-2 ethernet packet-switching functions like physical ethernet switch additionally virtual hub configured define ip packet filter entries filter packets virtual hub virtual layer-3 switch layer-3 ip static routing functions like physical router vpn server local bridges local bridge layer-2 packet-switching fabric physical ethernet network-adapter virtual hub administrator defines local bridge virtual hub existing corporate network build remote-access vpn server site-to-site vpn server softether vpn client vpn client program virtualized function ethernet network adapter computer installed softether vpn client establish vpn connection vpn server since vpn server support multiple vpn protocols l2tp/ipsec ms-sstp vpn vpn users required install softether vpn client client computers user uses l2tp/ipsec ms-sstp vpn connect vpn server built-in vpn client programs operating system used establish vpn vpn server however softether vpn client advanced functions e.g detailed vpn communication settings os built-in vpn clients exploit full performance softether vpn server recommended install softether vpn client client computer softether vpn bridge vpn program building site-to-site vpn build site-to-site vpn network system administrator install softether vpn server central site install softether vpn bridge one remote sites vpn bridge connects central vpn server cascade connection cascade connection similar virtualization uplink connection cross-cable connection two physical ethernet switches gui tool administrative tool softether vpn server softether vpn bridge program runs windows linux wine system administrator installs gui tool laptop pc makes connect remote vpn server vpn bridge administration connection made ssl session management commands transported rpc ssl vpncmd cui administrative tool softether vpn server client bridge program runs consoles every supported operating systems user unable use windows linux wine user alternatively use vpncmd manage vpn programs vpncmd also useful execute batch operation creating many users virtual hub creating many virtual hubs vpn server parts architecture softether vpn different typical traditional ipsec-based vpn systems virtual hub software-emulated virtual ethernet switch learns maintains forwarding-database table inside traditional physical ethernet switches implement function hardware softether vpn implements function software vpn server several virtual hubs virtual hub isolated virtual hub performs packet-switching concurrently connected vpn sessions realize communication vpn clients vpn bridges several virtual hubs single instance vpn server virtual hubs isolated security different administrator delegated privilege correspondent virtual hub administrator virtual hub define user-objects acls limited delegated virtual hub virtual network adapter software-emulated virtual ethernet adapter vpn client create several virtual network adapters client computer vpn user establish vpn session virtual network adapter destination virtual hub remote vpn server vpn session established vpn user communicate remote vpn network virtual network adapter since virtual network adapter works physical one applications operating system components used without modification virtual layer-3 switch software-emulated virtual ip router several virtual layer-3 switches created single vpn server instance virtual layer-3 switch virtual ip interfaces connected virtual hubs also several static routing table entries virtual layer-3 switch useful make large-scale site-to-site vpn network although easy way make site-to-site vpn network build layer-2 bridging based vpn number computers huge number broadcasting packets increase load inter-site links prevent scaling problem vpn administrator isolates ip networks virtual layer-3 switch administrator define cascade connection local remote virtual hubs cascade connection established originally-isolated two ethernet segments combined single ethernet segment therefore cascade connection function used build site-to-site layer-2 ethernet bridging since virtual hubs virtual network adapters software-emulated virtual ethernet devices ethernet packets virtual devices communicate physical ethernet devices therefore bridge virtual physical necessary build remote-access vpn site-to-site vpn make bridge local bridge function exchanges ethernet packets virtual hub physical ethernet network adapter combine isolated ethernet segments single ethernet segment defining local bridge softether vpn server vpn client connect vpn server communicate existing ethernet devices e.g servers network equipment local bridge called remote-access vpn network administrator sets remote-site vpn bridge defines two local bridges vpn server vpn bridge defines cascade connection vpn server vpn bridge remote two ethernet segments connected directly layer-2 ethernet level called site-to-site vpn one key features softether vpn transparency firewalls proxy servers nats network address translators softether vpn supports ssl-vpn nat traversal softether vpn uses https protocol order establish vpn tunnel https http ssl protocol uses tcp/ip port 443 may vary destination user chooses ssl-vpn protocol vpn client vpn server softether vpn server vpn client use parallel transmission mechanism improve throughput ssl-vpn tunnel user set number concurrent parallel transmission channels 1 32 environment slow delaying network performance tuning result faster throughput function enabled logical vpn session consist several tcp https connections packets added one appropriate tcp connections calculations optimizing modules packet losses detected tcp connection logical vpn session new packet use another healthy vpn connection fast-switching optimization determine processing tcp connection enables high throughput traditional vpn systems require user ask firewall administrator company open endpoint tcp udp port firewall nat border company internet order reduce necessity open endpoint firewall softether vpn server nat traversal function nat traversal enabled default long enabled softether vpn client computers connect vpn server behind firewall nat special settings firewall nat necessary very-restricted networks permit pass icmp dns packets network tcp udp filtered icmp dns permitted order make possible establish softether vpn client-server session via very-restricted network softether vpn vpn icmp vpn dns function function powerful penetrate restricted firewall vpn packets encapsulated icmp dns packets transmit firewall receiver-side endpoint extracts inner packet capsuled packet useful exploiting public wi-fi public wi-fi pass icmp dns packets filter tcp udp packets vpn server installed home office advance going outdoors enjoy protocol-free network communication using restricted network vpn gate plugin softether vpn allows users connect free vpn servers run volunteers use softether host vpn servers volunteers use personal computers servers vpn gate sponsored university tsukuba
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Computer security
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computer forensics computer forensics also known computer forensic science branch digital forensic science pertaining evidence found computers digital storage media goal computer forensics examine digital media forensically sound manner aim identifying preserving recovering analyzing presenting facts opinions digital information although often associated investigation wide variety computer crime computer forensics may also used civil proceedings discipline involves similar techniques principles data recovery additional guidelines practices designed create legal audit trail evidence computer forensics investigations usually subjected guidelines practices digital evidence used number high-profile cases becoming widely accepted reliable within u.s. european court systems early 1980s personal computers became accessible consumers leading increased use criminal activity example help commit fraud time several new computer crimes recognized cracking discipline computer forensics emerged time method recover investigate digital evidence use court since computer crime computer related crime grown jumped 67 2002 2003 today used investigate wide variety crime including child pornography fraud espionage cyberstalking murder rape discipline also features civil proceedings form information gathering example electronic discovery forensic techniques expert knowledge used explain current state digital artifact computer system storage medium e.g hard disk cd-rom electronic document e.g email message jpeg image scope forensic analysis vary simple information retrieval reconstructing series events 2002 book computer forensics authors kruse heiser define computer forensics involving preservation identification extraction documentation interpretation computer data go describe discipline art science indicating forensic methodology backed flexibility extensive domain knowledge however several methods used extract evidence given computer strategies used law enforcement fairly rigid lack flexibility found civilian world court computer forensic evidence subject usual requirements digital evidence requires information authentic reliably obtained admissible different countries specific guidelines practices evidence recovery united kingdom examiners often follow association chief police officers guidelines help ensure authenticity integrity evidence voluntary guidelines widely accepted british courts computer forensics used evidence criminal law since mid-1980s notable examples include computer forensic investigations usually follow standard digital forensic process phases acquisition examination analysis reporting investigations performed static data i.e acquired images rather live systems change early forensic practices lack specialist tools led investigators commonly working live data number techniques used computer forensics investigations much written many techniques used law enforcement particular seizing evidence machine still active information stored solely ram recovered powering may lost one application live analysis recover ram data example using microsoft cofee tool windd windowsscope prior removing exhibit captureguard gateway bypasses windows login locked computers allowing analysis acquisition physical memory locked computer ram analyzed prior content power loss electrical charge stored memory cells takes time dissipate effect exploited cold boot attack length time data recoverable increased low temperatures higher cell voltages holding unpowered ram −60 °c helps preserve residual data order magnitude improving chances successful recovery however impractical field examination tools needed extract volatile data however require computer forensic lab maintain legitimate chain evidence facilitate work machine necessary law enforcement applies techniques move live running desktop computer include mouse jiggler moves mouse rapidly small movements prevents computer going sleep accidentally usually uninterruptible power supply ups provides power transit however one easiest ways capture data actually saving ram data disk various file systems journaling features ntfs reiserfs keep large portion ram data main storage media operation page files reassembled reconstruct ram time number open source commercial tools exist computer forensics investigation typical forensic analysis includes manual review material media reviewing windows registry suspect information discovering cracking passwords keyword searches topics related crime extracting e-mail pictures review several computer forensics certifications available isfce certified computer examiner digital forensics investigation professional dfip iacrb certified computer forensics examiner top vendor independent certification especially within eu considered ccfp certified cyber forensics professional others worth mention usa apac iacis international association computer investigative specialists offers certified computer forensic examiner cfce program isfcs international society forensic computer examiners® offers certified computer examiner cce program asian school cyber laws offers international level certifications digital evidence analysis digital forensic investigation courses available online class room mode many commercial based forensic software companies also offering proprietary certifications products example guidance software offering ence certification tool encase accessdata offering ace certification tool ftk passmark software offering oce certification tool osforensics x-ways software technology offering x-pert certification software x-ways forensics
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Computer security
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bsd licenses bsd licenses family permissive free software licenses imposing minimal restrictions use distribution covered software contrast copyleft licenses share-alike requirements original bsd license used namesake berkeley software distribution bsd unix-like operating system original version since revised descendants referred modified bsd licenses bsd license class license generally referred bsd-like modified bsd license wide use today similar license originally used bsd version unix bsd license simple license merely requires code retain bsd license notice redistributed source code format reproduce notice redistributed binary format bsd license unlike licenses require source code distributed addition original 4-clause license used bsd several derivative licenses emerged also commonly referred bsd license today typical bsd license 3-clause version revised original 4-clause version bsd licenses following codice_1 organization codice_2 codice_2 codice_4 year copyright published bsd codice_2 regents university california codice_1 university california berkeley releases bsd prior adoption 4-clause bsd license used license clearly ancestral 4-clause bsd license releases include 4.3bsd-tahoe 1988 net/1 1989 although largely replaced 4-clause license license found 4.3bsd-reno net/2 4.4bsd-alpha original bsd license contained clause found later licenses known advertising clause clause eventually became controversial required authors works deriving bsd-licensed work include acknowledgment original source advertising material clause number 3 original license text clause objected grounds people changed license reflect name organization led escalating advertising requirements programs combined together software distribution every occurrence license different name required separate acknowledgment arguing richard stallman stated counted 75 acknowledgments 1997 version netbsd addition clause presented legal problem wishing publish bsd-licensed software relies upon separate programs using gnu gpl advertising clause incompatible gpl allow addition restrictions beyond already imposes gpl publisher free software foundation recommends developers use license though states reason use software already using today original license sometimes called bsd-old 4-clause bsd advertising clause removed license text official bsd william hoskins director office technology licensing uc berkeley bsd distributions removed clause many similar clauses remain bsd-derived code sources unrelated code using derived license original license sometimes referred bsd-old resulting 3-clause version sometimes referred bsd-new names include new bsd revised bsd bsd-3 3-clause bsd version vetted open source license osi bsd license free software foundation refers license modified bsd license states compatible gnu gpl fsf encourages users specific referring license name i.e simply referring bsd license bsd-style avoid confusion original bsd license version allows unlimited redistribution purpose long copyright notices license disclaimers warranty maintained license also contains clause restricting use names contributors endorsement derived work without specific permission even simplified version come use primarily known usage freebsd use early april 29 1999 likely well primary difference new bsd 3-clause license omits non-endorsement clause also adds disclaimer views opinions expressed software free software foundation refers license freebsd license states compatible gnu gpl addition fsf encourages users specific referring license name i.e simply referring bsd license bsd-style modified/new bsd license avoid confusion original bsd license projects netbsd use similar 2-clause license without additional disclaimer version vetted open source license osi simplified bsd license isc license functionally equivalent endorsed openbsd project license template new contributions formerly known free public license 1.0.0 bsd 0-clause license spdx 0bsd goes 2-clause license dropping requirements include copyright notice license text disclaimer either source binary forms freebsd project argues advantages bsd-style licenses companies commercial use-cases due license compatibility proprietary licenses general flexibility stating bsd-style licenses place minimal restrictions future behavior n't legal time-bombs unlike copyleft licenses bsd license allows proprietary use allows software released license incorporated proprietary products works based material may released proprietary license closed source software allowing usual commercial usages 3-clause bsd license like permissive licenses compatible almost foss licenses well proprietary licenses two variants license new bsd license/modified bsd license 3-clause simplified bsd license/freebsd license 2-clause verified gpl-compatible free software licenses free software foundation vetted open source licenses open source initiative original 4-clause bsd license accepted open source license although original considered free software license fsf fsf consider compatible gpl due advertising clause bsd license family one oldest broadly used license family foss ecosystem also many new licenses derived inspired bsd licenses many foss software projects use bsd license instance bsd os family freebsd etc google bionic toybox bsd 3-clause license ranked popularity number five according black duck software sixth according github data
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Operating systems
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displayid displayid vesa standard metadata describing display device capabilities video source designed replace e-edid standard edid structure v1.4 displayid standard initially released december 2007 version 1.1 released march 2009 followed version 1.2 released august 2011 version 1.3 released june 2013 current version 2.0 released september 2017 displayid uses variable-length structures 256 bytes encompass existing edid extensions well new extensions 3d displays embedded displays wide color gamut hdr eotf displayid format includes several blocks describe logical parts display video interfaces display device technology timing details manufacturer information data blocks identified unique tag length block variable fixed specific number bytes base data block mandatory extension blocks optional variable structure based cea edid extension block version 3 first defined cea-861-b displayid standard freely available royalty-free implement version 2.0 introduces new generalized information blocks primarily intended ultrahd high dynamic range hdr displays lcd computer monitors lcd/oled televisions native support bt.2020 color space pq/hlg transfer functions also makes optional predefined crt/lcd timings dmt cea-861 standards switching formula-based structures follow vesa cvt-rb gtf base displayid 2.0 variable-length structure data blocks data block starts mandatory block tag revision number 0-7 payload length 0-248 bytes variable length 251 bytes following blocks currently defined codice_1 product identification block contains standard vendor product ids serial number date manufacture product name comparing legacy block codice_2 microsoft isa plug play identifier replaced ieee oui first used network mac address codice_3 display parameters block contains basic parameters viewable area size pixel count supported color depth factory calibrated rgb color space white point luminance gamma transfer function comparing legacy block codice_4 color calibration values moved block codice_5 max/min luminance values added display size specified 1 mm increments addition default 0.1 mm codice_6 detailed timing block type vii defines cta-861 compatible timings based pixel rate block based type vi block codice_7 codice_8 type viii enumerated timing code block based type iv dmt id block codice_9 provides one-byte two-byte video mode codes defined vesa display monitor timings standard video information codes defined cta-861 hdmi codice_10 type ix formula-based timings block based type v short timings block codice_11 codice_12 dynamic video timing range block based block codice_13 video timing range limits new version allows precise definition pixel rate 1 khz steps adds indication variable refresh rates codice_14 display interface features block describes color depth dynamic range transfer function supported display controller based blocks codice_15 display interface features codice_5 color characteristics codice_17 stereo display interface block based block codice_18and describes stereoscopic 3d/vr modes i.e timings codes stereo frame formats supported display codice_19 tiled display topology block describes displays consist multiple physical display panels driven separate video interface based block codice_20 codice_21 container id block defines unique identifier used associate additional devices may present multifunctional display codice_22 vendor-specific data includes proprietary parameters supported displayid 2.0 structures codice_23 cta displayid block provides information cta-861 edid timings version 1.3 information blocks 0x10-0x1f borrow heavily edid 1.4 standard designed previous generation crt/lcd/dlp/pdp displays following block types defined note indicated difference similar/superseding structures version 2.0 shown sections codice_2 product identification superseded codice_1 difference codice_4 display parameters superseded codice_3 differences codice_5 color characteristics superseded codice_3 display parameters codice_30 type detailed timings superseded codice_6 type vii detailed timings differences codice_32 type ii detailed timings block provides compressed structure less precise pixel coordinates reduced blank intervals comparing type codice_33 type iii short timings block provides short compressed structure uses formula-based cvt timings codice_9 type iv short timing dmt id code block uses video mode codes defined vesa display monitor timings standard well video information codes defined cta-861 hdmi superseded codice_8 enumerated timing codice_11 type v short timings block based type iii short timings block 0x05 provides greater pixel precision supports cvt-rb superseded codice_10 type ix formula-based timings codice_7 type vi detailed timing block supports higher precision pixel clock high-resolution timings block based type block 0x03 allows greater timings precision using 1 khz steps instead 10 khz superseded codice_6 type vii detailed timings codice_40 video timing range limits block describes displays capable variable timings superseded codice_12 dynamic video timings range codice_42 display device data block provides information display panel characteristics embedded applications display technology panel type pixel response times display interface features block superseded codice_14 display interface features data blocks described codice_44 serial number data block provides product serial number ascii string codice_45 general purpose ascii string block provides general purpose text strings may required specific applications codice_46 interface power sequencing block defines display interface signal timings required entering exiting sleep mode codice_47 transfer characteristics block defines detailed gamma curves according vesa display transfer characteristic data block dtcdb standard may required byte 1 codice_5 color characteristics block codice_18 stereo display interface block describes stereoscopic 3d/vr modes superseded codice_17 stereo display interface codice_20 tiled display topology data block defines multi-panel displays superseded codice_19 tiled display topology codice_53 vendor specific block defines proprietary vendor data
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Computer architecture
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manic miner manic miner platform video game originally written zx spectrum matthew smith released bug-byte 1983 later re-released software projects first game miner willy series among early titles platform game genre game inspired atari 8-bit family game miner 2049er since ported numerous home computers video game consoles mobile phones time stand-out features included in-game music sound effects high replay value colourful graphics well designed graphical limitations zx spectrum spectrum video display allowed background foreground colours exchanged automatically without software attention animated load screen appears swap words manic miner manipulation feature spectrum first game in-game music playing required constant cpu attention thought impossible achieved constantly alternating cpu time music game results music stuttery rhythm in-game music hall mountain king edvard grieg music henrik ibsen play peer gynt music plays title screen arrangement blue danube twenty caverns one screen size several flashing objects player must collect willy oxygen supply runs player collected objects one cavern must go now-flashing portal take next cavern player must avoid enemies listed cassette inlay ... poisonous pansies spiders slime worst manic mining robots ... move along predefined paths constant speeds willy also killed falling far players must time precision jumps movements prevent falls collisions enemies extra lives gained every 10,000 points game ends player either lives left completes twenty caverns escapes open air final portal garden right house white picket fence red car parked front left slope leading backyard pond tree white animal resembling cat mouse watches sun set behind pond upon gaining freedom miner willy simply walks right screen never looking back differences bug-byte software projects versions scroll-text attract mode different reflect new copyright also several cosmetic changes although gameplay remains manic miner placed number 25 sinclair official top 100 spectrum games time voted number 6 readers top 100 games time issue winner golden joystick award best arcade style game computer video games magazine march 1983 edition placed third game year 1983 competition game included 97 polygon 500 best games time list official ports exist commodore 64 commodore 16 amstrad cpc bbc micro dragon 32/64 commodore amiga oric 1 game boy advance msx sam coupé mobile phones unofficial ports exist ibm pc compatibles windows dos linux apple macintosh atari st zx81 trs-80 color computer sony playstation nintendo 64 neo geo pocket color acorn archimedes orao z88 pmd 85 hp48 microsoft zune acorn atom commodore 128 sam coupé version programmed matthew holt like zx original requires pixel-perfect timing graphics audio latter františek fuka greatly updated addition original twenty caverns forty additional caverns included release levels designed david ledbury winners competition run sam computers ltd although sam coupé broadly spectrum clone avoided spectrum original limitations colour graphics spectrum pixels could many colours 8 horizontally adjacent pixels within span character block one two colours manic miner port made use removal restriction detailed use colour visibly character sprites version scored 84 sinclair 88 crash game ported czechoslovak computers pmd 85 1985 authors pmd 85 version vít libovický daniel jenne made accurate could bbc micro version solar power generator instead containing completely different room called meteor shower reflecting machines solar power generator beam light instead meteors descend top screen disintegrate hit platforms like skylabs skylab landing bay also forcefields turn layout completely different also last screen still called final barrier complex difficult unlike spectrum version considered fairly easy completely different layout also features blinking forcefields amstrad version effectively spectrum version software projects except eugene lair renamed eugene layout final barrier completely different similar spectrum version bbc version dragon 32 version programmed roy coates two extra rooms i.e 22 altogether cheat mode accessed typing p p penguin retain resolution original dragon version used pmode 4 black/white mode z88 port functionality cheats bug-byte software projects versions levels even background music hp 48 series version somewhat limited low resolution screen size scrolling area rather displaying level whole makes difficult port previously mastered another version otherwise fairly loyal zx spectrum version sound somewhat different sounding colour omitted obvious hardware reasons game play remains similar despite awkward platform commodore 16 version limited number respects mainly due initial lack developer material c16 machine two-week deadline produce test game generate master tape duplication house issues related lack fast loader system c16 cassette deck result took seven minutes game load bug resulted game entering first screen soon tape finished loading instead waiting user start game issues related lack music game sound way video memory mapped c16 resulted number screens removed load time video mapping could correctly handled version game released xbox 360 xbox live indie game name manic miner 360 21st june 2012 sequel manic miner jet set willy followed jet set willy ii software projects also released game style manic miner commodore vic-20 called perils willy addition quite unofficial sequels remakes homages updates released even day including zx81 version homage loading screen appeared one episode 2005 british sitcom nathan barley
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Computer architecture
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steptalk steptalk official gnustep scripting language framework represents separate scriptable servers applications single object environment meant independent programming language used default language smalltalk running objective-c runtime steptalk ported mac os x goal steptalk provide environment gluing applications together provide framework communication users objects applications major goals default scripting language steptalk smalltalk smalltalk simple language easy learn basic principles user must know able use language similar natural language smalltalk uses similar approach objective-c language used gnustep steptalk works platform gnustep works ports native macos cocoa framework developed various contributors
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Programming language topics
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aptitude software aptitude front-end apt debian package manager displays list software packages allows user interactively pick packages install remove especially powerful search system utilizing flexible search patterns initially created debian appeared rpm package manager rpm based distributions well conectiva aptitude based ncurses computer terminal library provides interface incorporates elements commonly seen graphical user interfaces guis pull-down menus addition ncurses interface aptitude provides extensive command-line interface cli even though aptitude one executable file provides command-line functions similar apt- family tools apt-get apt-cache apt-listchanges etc. aptitude also emulates apt-get command-line arguments allowing act full replacement apt-get past recommended aptitude apt-get used interchangeably longer true programs correctly track share common list packages automatically installed satisfy dependencies aptitude created 1999 time two terminal-based apt-like front-ends available dselect program used manage packages debian since apt created console-apt program project considered heir apparent dselect aptitude created experiment object-oriented programming design used console-apt hope would result flexible program broader set features first public release aptitude version 0.0.1 november 18 1999 limited ability view list available packages could actually download install packages version 0.0.4a ability added many improvements version included debian 2.2 code name potato late 2000 whole user interface module rewritten new architecture created based libsigc++ callback library concepts modern widget toolkits gtk+ qt enabled interface become much similar guis previously features pull-down menus pop-up dialogs one aptitude unusual features tiny implementation minesweeper added time first official aptitude release following rewrite 0.2.0. aptitude 0.2.11.1 released debian 3.0 woody time console-apt project renamed deity effectively abandoned maintainers removed woody aptitude also ported jailbroken ios part cydia package manager aptitude states unlike advanced packaging tool super cow powers apt-get super cow powers found issuing command apt-get moo however aptitude issuing moo give user prompt saying easter eggs however issuing aptitude -v moo aptitude -vv moo user see series statements denying super cow powers telling go away ending picture reference antoine de saint-exupéry little prince unlike original apt-get easter egg different versions program different sequences addition package description states aptitude also y2k-compliant non-fattening naturally cleansing housebroken
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Operating systems
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slashdot effect slashdot effect also known slashdotting occurs popular website links smaller website causing massive increase traffic overloads smaller site causing slow even temporarily become unavailable name stems huge influx web traffic would result technology news site slashdot linking websites original circumstances changed flash crowds slashdot reported 2005 diminishing due competition similar sites general adoption elastically scalable cloud hosting platforms effect associated websites metablogs fark digg drudge report imgur reddit twitter leading terms farked drudged reddit effect —or receiving hug death site question google doodles link search results doodle topic also result high increases traffic search results page typically less robust sites unable cope huge increase traffic become unavailable – common causes lack sufficient data bandwidth servers fail cope high number requests traffic quotas sites maintained shared hosting services often fail confronted slashdot effect flash crowd generic term without using specific name describes network phenomenon network host suddenly receives lot traffic sometimes due appearance website blog news column according jargon file term slashdot effect refers phenomenon website becoming virtually unreachable many people hitting site mentioned interesting article popular slashdot news service later extended describe similar effect listed popular site similar generic term flash crowd appropriate term term flash crowd coined 1973 larry niven science fiction short story flash crowd predicted consequence inexpensive teleportation would huge crowds materializing almost instantly sites interesting news stories twenty years later term became commonly used internet describe exponential spikes website server usage passes certain threshold popular interest effect anticipated years earlier 1956 alfred bester novel stars destination reddit effect also used describe viral crowd fundraising efforts addition surge web traffic sites slashdot digg reddit stumbleupon fark consist brief submitted stories self-moderated discussion story typical submission introduces news item website interest linking response large masses readers tend simultaneously rush view referenced sites ensuing flood page requests readers exceed site available bandwidth ability servers respond render site temporarily unreachable major news sites corporate websites typically engineered serve large numbers requests therefore normally exhibit effect websites fall victim may hosted home servers offer large images movie files inefficiently generated dynamic content e.g many database hits every web hit even web hits requesting page websites often became unavailable within minutes story appearance even comments posted occasionally paying slashdot subscribers access stories non-paying users rendered site unavailable even story posted general readership definitive numbers exist regarding precise magnitude slashdot effect estimates put peak mass influx page requests anywhere several hundred several thousand hits per minute flood usually peaked article top site front page gradually subsided story superseded newer items traffic usually remained elevated levels article pushed front page could take 12 18 hours initial posting however articles significantly longer lifetimes due popularity newsworthiness interest linked article 2005 reporters commenting slashdot effect diminishing however effect seen involving twitter popular users mention website targeted website community-based structure term also refer secondary effect large group new users suddenly set accounts start participate community cases considered good thing others viewed disdain prior members quite often sheer number new people brings many unwanted aspects slashdot along trolling vandalism newbie-like behavior bears similarity 1990s usenet concept eternal september many solutions proposed sites deal slashdot effect several systems automatically mirror slashdot-linked pages ensure content remains available even original site becomes unresponsive sites process slashdotted may able mitigate effect temporarily redirecting requests targeted pages one mirrors slashdot mirror sites links servers endorse third party solution mirroring content may constitute breach copyright many cases cause ad revenue lost targeted site
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Computer security
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penelope endersby penelope penny endersby british researcher academic specialising armour explosives appointed chief executive met office december 2018 prior led cyber information systems defence science technology laboratory endersby grew north london educated haberdashers aske school girls elstree studied natural sciences university cambridge member newnham college remains associate newnham became interested materials science metallurgy sponsored british gas researching fuel cells graduating joined royal armament research development establishment 1993 endersby researcher specialising armour explosives served royal armament research development establishment becoming uk expert electric intelligent armours appointed department manager defence science technology laboratory 2009 began focus c4isr cyber security holds royal academy engineering visiting professorship university southampton endersby made division head cyber information systems division defence science technology laboratory 2015 involved international women day celebrations joined council institute physics 2017 endersby appointed chief executive met office december 2018 first woman fill role serves board ploughshare innovations ministry defence united kingdom technology transfer office endersby expert choir singer two children interested wildlife records uk phenology trustee wiltshire wildlife trust
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Computer security
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aikuma aikuma android app collecting speech recordings time-aligned translations app includes text-free interface consecutive interpretation designed users literate aikuma grand prize open source software world challenge 2013 aikuma means meeting place usarufa papuan language software first used 2012 aikuma developed sponsorship national science foundation including 101,501 us project use mobile telephones collect larger amounts data undocumented endangered languages would never possible usual fieldwork aikuma modified version lig-aikuma used collecting substantial quantities audio remote indigenous villages modified version app called lig-aikuma developed université grenoble alpes lig laboratory implements new features elicitation speech text images videos
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Computational linguistics
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smart tag microsoft smart tags early selection-based search feature found later versions microsoft word beta versions internet explorer 6 web browser application recognizes certain words types data converts hyperlink also included microsoft office programs well visual web developer selection-based search allows user invoke online service page using mouse microsoft initially intended technology built windows xp operating system changed plans due public criticism smart tags integrated instances user might benefit added formatting assistance part microsoft control technology presented special shortcut menu listing options paste autocorrect date person name addresses among others flag entered information accordingly smart tags work actions recognizers latter checks whether information entered user included list smart tag terms action associated executed accessed dedicated smart tag button smart tags enabled microsoft word attempts recognize certain types data document example dates names automatically makes text smart tag visually indicated purple dotted underline clicking smart tag selection-based search command bring list possible actions data type example microsoft word words john smith would recognized personal name smart tagged list actions available clicked might open contact schedule meeting add contacts insert address word version 2010 smart tag auto-recognition person name smart tag features longer available within web browser smart tag technology passes way web page underlines words pre-programmed react inserts hyperlinks selecting smart tag like many selection-based search commands involved hover followed mouse click keyboard commands required invoke search click takes destination specified smart tag developer without knowledge permission web site proprietor early tests almost links offered sites products microsoft affiliates smart tags also generated third parties example company might contract technology firm develop set smart tags actions specific products services product names automatically recognized linked actions check quantity stock check price security vendors feared smart tags could used propagating viruses user tracking data collection purposes might violate user privacy another concern could used negative harmful ways linking political candidate name website negative advertising sites response criticism microsoft removed technology windows xp operating system made feature could turned ie office xp however microsoft revisited concept smart tags later versions internet explorer 8 implemented selection-based search feature called internet explorer 8 accelerators unlike smarttags feature automatically parsed page looking text interest accelerators relied upon user select text accelerator applied accelerators interface open developers accelerators included default use microsoft affiliates products could replaced within category another provider desired smart tags also included email sms text messages windows phone example dates email messages automatically recognized tapped opens window allows appointment created date field already filled
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Operating systems
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tom rolander thomas alan rolander american entrepreneur engineer developer multitasking multiuser operating system mp/m created microcomputers 1979 working first employee digital research gary kildall father cp/m cp/m mp/m laid groundwork later digital research operating system families concurrent cp/m concurrent dos multiuser dos also developed cp/net 2013 granted 2013 diamond award entrepreneurial excellence university washington uw
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Operating systems
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high-level programming language computer science high-level programming language programming language strong abstraction details computer contrast low-level programming languages may use natural language elements easier use may automate even hide entirely significant areas computing systems e.g memory management making process developing program simpler understandable using lower-level language amount abstraction provided defines high-level programming language 1960s high-level programming languages using compiler commonly called autocodes examples autocodes cobol fortran first high-level programming language designed computers plankalkül created konrad zuse however implemented time original contributions largely isolated developments due world war ii aside language influence superplan language heinz rutishauser also degree algol first significantly widespread high-level language fortran machine-independent development ibm earlier autocode systems algol defined 1958 1960 committees european american computer scientists introduced recursion well nested functions lexical scope also first language clear distinction value name-parameters corresponding semantics algol also introduced several structured programming concepts while-do if-then-else constructs syntax first described formal notation – backus–naur form bnf roughly period cobol introduced records also called structs lisp introduced fully general lambda abstraction programming language first time high-level language refers higher level abstraction machine language rather dealing registers memory addresses call stacks high-level languages deal variables arrays objects complex arithmetic boolean expressions subroutines functions loops threads locks abstract computer science concepts focus usability optimal program efficiency unlike low-level assembly languages high-level languages language elements translate directly machine native opcodes features string handling routines object-oriented language features file input/output may also present one thing note high-level programming languages languages allow programmer detached separated machine unlike low-level languages like assembly machine language high-level programming amplify programmer instructions trigger lot data movements background without knowledge responsibility power executing instructions handed machine programmer high-level languages intend provide features standardize common tasks permit rich debugging maintain architectural agnosticism low-level languages often produce efficient code optimization specific system architecture abstraction penalty cost high-level programming techniques pay unable optimize performance use certain hardware n't take advantage certain low-level architectural resources high-level programming exhibits features like generic data structures operations run-time interpretation intermediate code files often result execution far operations necessary higher memory consumption larger binary program size reason code needs run particularly quickly efficiently may require use lower-level language even higher-level language would make coding easier many cases critical portions program mostly high-level language hand-coded assembly language leading much faster efficient simply reliably functioning optimised program however growing complexity modern microprocessor architectures well-designed compilers high-level languages frequently produce code comparable efficiency low-level programmers produce hand higher abstraction may allow powerful techniques providing better overall results low-level counterparts particular settings high-level languages designed independent specific computing system architecture facilitates executing program written language computing system compatible support interpreted jit program high-level languages improved designers develop improvements cases new high-level languages evolve one others goal aggregating popular constructs new improved features example scala maintains backward compatibility java means programs libraries written java continue usable even programming shop switches scala makes transition easier lifespan high-level coding indefinite contrast low-level programs rarely survive beyond system architecture written without major revision engineering 'trade-off 'abstraction penalty examples high-level programming languages active use today include python visual basic delphi perl php ecmascript ruby c java many others terms high-level low-level inherently relative decades ago c language similar languages often considered high-level supported concepts expression evaluation parameterised recursive functions data types structures assembly language considered low-level today many programmers might refer c low-level lacks large runtime-system garbage collection etc basically supports scalar operations provides direct memory addressing therefore readily blends assembly language machine level cpus microcontrollers assembly language may regarded higher level often still one-to-one used without macros representation machine code supports concepts constants limited expressions sometimes even variables procedures data structures machine code turn inherently slightly higher level microcode micro-operations used internally many processors three general modes execution modern high-level languages note languages strictly interpreted languages compiled languages rather implementations language behavior use interpreting compiling example algol 60 fortran interpreted even though typically compiled similarly java shows difficulty trying apply labels languages rather implementations java compiled bytecode executed either interpreting java virtual machine jvm compiling typically just-in-time compiler hotspot jvm moreover compiling transcompiling interpreting strictly limited description compiler artifact binary executable il assembly alternatively possible high-level language directly implemented computer – computer directly executes hll code known high-level language computer architecture – computer architecture designed targeted specific high-level language burroughs large systems target machines algol 60 example
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Programming language topics
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low-level programming language low-level programming language programming language provides little abstraction computer instruction set architecture—commands functions language map closely processor instructions generally refers either machine code assembly language word low refers small nonexistent amount abstraction language machine language low-level languages sometimes described close hardware programs written low-level languages tend relatively non-portable low-level languages convert machine code without compiler interpreter – second-generation programming languages use simpler processor called assembler – resulting code runs directly processor program written low-level language made run quickly small memory footprint equivalent program high-level language less efficient use memory low-level languages simple considered difficult use due numerous technical details programmer must remember comparison high-level programming language isolates execution semantics computer architecture specification program simplifies development low-level programming languages sometimes divided two categories first generation second generation machine code language computer process directly without previous transformation currently programmers almost never write programs directly machine code requires attention numerous details high-level language handles automatically furthermore requires memorizing looking numerical codes every instruction extremely difficult modify true machine code stream raw usually binary data programmer coding machine code normally codes instructions data readable form decimal octal hexadecimal translated internal format program called loader toggled computer memory front panel although programs written machine language programmers often become adept reading working core dumps debugging front panel example function hexadecimal representation 32-bit x86 machine code calculate n th fibonacci number second-generation languages provide one abstraction level top machine code early days coding computers like tx-0 pdp-1 first thing mit hackers write assemblers assembly language little semantics formal specification mapping human-readable symbols including symbolic addresses opcodes addresses numeric constants strings typically one machine instruction represented one line assembly code assemblers produce object files link object files loaded assemblers provide macros generate common sequences instructions example fibonacci number calculator x86 assembly language using masm syntax code example hardware features x86 processor registers named manipulated directly function loads input precise location stack 8 bytes higher location stored esp stack pointer performs calculation manipulating values eax ebx ecx edx registers finished returns note assembly language concept returning value result stored eax register ret command simply moves code processing code location stored stack usually instruction immediately one called function author calling code know function stores result eax retrieve x86 assembly language imposes standard returning values function fact concept function calling code examine state procedure returns needs extract value compare function c code similar structure assembly language example significant differences terms abstraction abstractions make c code compilable without modification architecture c compiler written x86 assembly language code specific x86 architecture late 1960s high-level languages pl/s bliss bcpl extended algol burroughs large systems c included degree access low-level programming functions one method inline assembly assembly code embedded high-level language supports feature languages also allow architecture-dependent compiler optimization directives adjust way compiler uses target processor architecture
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Programming language topics
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ifolder ifolder open-source application developed novell inc. intended allow cross-platform file sharing across computer networks ifolder operates concept shared folders folder marked shared contents folder synchronized computers network either directly computers peer-to-peer fashion server intended allow single user synchronize files different computers example work computer home computer share files users example group people collaborating project core ifolder actually project called simias simias actually monitors files changes synchronizes changes controls access permissions folders actual ifolder clients including graphical desktop client web client developed separate programs communicate simias back-end originally conceived developed pgsoft company taken novell 2000 ifolder announced novell march 19 2001 released june 29 2001 software package windows nt/2000 novell netware 5.1 included forthcoming novell netware 6.0 also included ability access shared files web browser ifolder professional edition 2 announced march 13 2002 released month later added support linux solaris web access support windows ce palm os edition also designed share files millions users large companies increased reporting features administrators 2003 ifolder codie award march 22 2004 purchase linux software companies ximian suse novell announced releasing ifolder open source project gpl license also announced open source version ifolder would use mono framework effort ease development ifolder 3.0 released june 22 2005 march 31 2006 novell announced ifolder enterprise server open source april 2 2009 novell released ifolder 3.7.2 included mac client 10.4 10.5 well windows vista client addition improved client lineup version supports ssl ldapgroup support auto-account creation ifolder merge enhanced web access administration ifolder.com website completely redesigned references earlier versions nov 25 2009 novell released ifolder 3.8
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Computer security
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qfs qfs quick file system filesystem oracle tightly integrated sam storage archive manager hence often referred sam-qfs sam provides functionality hierarchical storage manager qfs supports volume management capabilities allowing many disks grouped together file system file system metadata kept separate set disks useful streaming applications long disk seeks tolerated sam extends qfs file system transparently archival storage sam-qfs file system may relatively small gigabytes terabytes disk cache backed petabytes tape bulk storage files copied archival storage background transparently retrieved disk accessed sam-qfs supports four archival copies disk tape optical media may stored remote site also running sam-qfs shared qfs adds multi-writer global filesystem allowing multiple machines read write disks concurrently use multi-ported disks storage area network qfs also single-writer/multi-reader mode used share disks hosts without need network connection sam-qfs originally developed lsc inc purchased sun 2001 sun released sam-qfs source code opensolaris project march 2008 sun acquisition oracle continues develop sam-qfs product later oracle renamed sam-qfs oracle hsm oracle hierarchical storage manager
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Computer file systems
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seal east asia seal east southeast asian context general name printing stamps impressions thereof used lieu signatures personal documents office paperwork contracts art item requiring acknowledgement authorship process started china soon spread across east asia china japan korea currently use mixture seals hand signatures increasingly electronic signatures chinese seals typically made stone sometimes metals wood bamboo plastic ivory typically used red ink cinnabar paste word 印 yìn mandarin japanese korean pronounced specifically refers imprint created seal well appearing combination ideographs words related printing word 印刷 printing pronounced yìnshuā mandarin insatsu japanese colloquial name chop referring kinds seals adapted hindi word chapa malay word cap meaning stamp rubber stamps japan seals hanko historically used identify individuals involved government trading ancient times japanese emperors shōguns samurai personal seal pressed onto edicts public documents show authenticity authority even today japanese citizens companies regularly use name seals signing contract important paperwork chinese emperors families officials used large seals known xǐ later renamed bǎo corresponds great seals western countries usually made jade although hard wood precious metal could also used originally square shape changed rectangular form song dynasty reverted square qing dynasty important seals heirloom seal realm created first emperor china qin shi huang seen legitimising device embodying symbolising mandate heaven heirloom seal passed several dynasties lost beginning ming dynasty partly explains qing emperors obsession creating numerous imperial seals emperors official use alone forbidden city beijing collection 25 seals order reduce significance heirloom seal seals typically bore titles offices rather names owners different seals could used different purposes example qianlong emperor number informal appreciation seals used select paintings collection popular style script government seals imperial eras china song dynasty qing dynasty nine-fold script highly stylised script unreadable untrained government republic china taiwan continued use traditional square seals 13 centimetres side known variety names depending user hierarchy part inaugural ceremony president republic china includes bestowing seal republic china seal honor people republic china seal central people government 1949 1954 square bronze seal side lengths 9 centimetres inscription reads seal central people government people republic china notably seal uses relatively modern song typeface rather ancient seal scripts seal called yìn xǐ nod modernity government seals people republic china today usually circular shape five-pointed star centre circle name governmental institution arranged around star semicircle many classes personal seals denotes person name equivalent today email signature contain person personal philosophy literary inclination shape ranging ovals dragon-shaped carry name person private studio 書齋 literati ancient china although probably lesser forms less rectangular shape two types seal paste depending base material made standard colour vermilion red lighter darker shades red colours used black navy etc specific purposes plant-based paste tends dry quickly silk-based pastes plant extract hold onto oil tightly silk depending paper used plant pastes dry 10 15 minutes absorbent paper faster dries paper absorbs oil also plant pastes tend smudge easily silk pastes due loose binding agent paste kept covered used original container plastic ceramic kept environment away direct sunlight away intense heat prevent drying paste silk based pastes need stirred spatula every month avoid oil sinking drying paste well prepare use good paste would produce clear impression one go impression clear requiring impressions indicates paste either dry cinnabar depleted seal pressed onto printing surface procedure differs according plant silk based paste silk based paste user applies pressure often specially made soft flat surface beneath paper plant based paste user simply applies light pressure lifting seal vertically away imprint may rip damage paper seal usually lifted one side time bent page image may blotted piece paper make dry faster although may smudge usually needs pile soft felt paper paper imprinted clear seal impression many people china possess personal name seal artists scholars collectors intellectuals may possess full set name seals leisure seals studio seals well-made seal made semi-precious stones cost 400 4000 yuan seals still used official purposes number contexts collecting parcels registered post name seal serves identification akin signature banks traditionally method identification also seal seals remain customary form identification cheques mainland china taiwan hong kong signatures required today personal identification often hand signature accompanied seal imprint seals serve identification signatures difficult forge compared forging signature owner access seal seals also often used chinese calligraphy works chinese paintings usually imprinted works order top bottom name seal leisure seal studio seal owners collectors paintings books often add studio seals pieces collected practice act appreciation towards work artworks seals inscriptions owner example qianlong emperor many 20 different seals use inscriptions paintings collected provided tastefully done example obscuring body painting appropriate inscription fine calligraphy etc practice devalue painting could possibly enhance giving provenance especially seal famous celebrated individual possessed work point seals usually carved specialist seal carvers users specialist carvers carve user name stone one standard scripts styles described usually fee hand people take carving seals using soapstone fine knives widely available cheaper paying professional expertise craft material results vary possible individuals carve perfectly legitimate seals novelty souvenir seal carvers also ply tourist business chinatowns tourist destinations china often carve on-the-spot translations foreign names inexpensive soapstone sometimes featuring roman characters though seals functional typically nothing curios may inappropriate serious use could actually devalue deface serious works art determining side seal face may done number ways carving top front face user inscription side face left user dot side face away user seals used much paste possible wiped printing surface edges suitable material seals kept constant environment especially seals made sandalwood black ox horn tall thin seals best kept sides case wobble fall important seals authority society seals encased wrapped golden silk cloth add protection japan seals general referred inkan comprehensive term hanko tends refer seals used less important documents first evidence writing japan hanko dating ad 57 made solid gold given ruler nakoku emperor guangwu han called king na gold seal first emperor trusted vassals held hanko symbol emperor authority noble people began using personal hanko 750 samurai began using sometime feudal period samurai permitted exclusive use red ink modernization began 1870 hanko came general use throughout japanese society government offices corporations usually inkan specific bureau company follow general rules outlined jitsuin following exceptions size comparatively large measuring across handles often extremely ornately carved friezes mythical beasts hand-carved hakubun inscriptions might quotes literature names dates original poetry privy seal japan example weighing 3.55 kg measuring 9.09 cm size used official purposes emperor seals carved square tunnels handle underside specific person slide inkan hollow thus signing document name business bureau name seals usually stored jitsuin -style boxes high security except official ceremonies displayed extremely ornate stands boxes personal use least four kinds seals order formal/official least jitsuin ginkō-in mitome-in gagō-in officially registered seal registered seal needed conduct business important legally binding events jitsuin used purchasing vehicle marrying purchasing land size shape material decoration lettering style jitsuin closely regulated law example hiroshima jitsuin expected roughly usually square rarely rectangular never round irregular oval must contain individual full family given name without abbreviation lettering must red white background shubun roughly equal width lines used throughout name font must one several based ancient historical lettering styles found metal woodcarving ancient forms ideographs commonplace red perimeter must entirely surround name decoration underside working surface seal top sides handle seal may decorated fashion completely undecorated historical animal motifs dates names inscriptions throughout japan rules governing jitsuin design stringent design unique vast majority people entrust creation jitsuin professional paying upward us 20 often closer us 100 using decades people desirous opening new chapter lives—say following divorce death spouse long streak bad luck change career—will often new jitsuin made material usually high quality hard stone far less frequently deerhorn soapstone jade sometimes carved machine carved hand intō seal-engraving blade mirror small specialized wooden vice used intō flat-bladed pencil-sized chisel usually round octagonal cross-section sometimes wrapped string give handle non-slip surface intō held vertically one hand point projecting one fist side opposite one thumb new modern intō range price less us 1 us 100 jitsuin kept secure place bank vault hidden carefully one home 're usually stored thumb-sized rectangular boxes made cardboard covered heavily embroidered green fabric outside red silk red velvet inside held closed white plastic deerhorn splinter tied lid passed fabric loop attached lower half box superficial resemblance coffins 're often called coffins japanese enthusiasts hanko boutiques paste usually stored separately used specifically banking ginkō means bank person savings account passbook contains original impression ginkō-in alongside bank employee seal rules size design vary somewhat bank bank generally contain japanese person full name westerner may permitted use full family name without abbreviated given name smith bill smith w smith wm smith place william smith lettering red white font artistic decoration people custom-made professionals make hand since mass-produced ginkō-in offer security wood stone carried variety thumb-shape -size cases resembling cloth purses plastic pencil cases usually hidden carefully owner home banks always provide stamp pads ink paste addition dry cleaning tissues banks also provide small plastic scrubbing surfaces similar small patches red artificial grass attached counters used scrub accumulated ink paste working surface customers seals moderately formal seal typically used signing postal deliveries signing utility bill payments signing internal company memos confirming receipt internal company mail low-security everyday functions mitome-in commonly stored low-security high-utility places office desk drawers anteroom genkan residence mitome-in form governed far fewer customs jitsuin ginkō-in however mitome-in adhere handful strongly observed customs size attribute strongly governed social custom usually size american penny smaller male usually slightly larger female junior employee always smaller bosses senior co-workers keeping office social hierarchy mitome-in always person family name usually person given name shita namae often round oval square ones uncommon rectangular ones unheard-of always geometric figures red lettering blank field shubun opposite hakubun borderlines around edges optional plastic mitome-in popular japanese names obtained stationery stores less us 1 though ones made inexpensive stone also popular inexpensive prefabricated seals called prefabricated rubber stamps unacceptable business purposes mitome-in lesser seals usually stored inexpensive plastic cases sometimes small supplies red paste stamp pad included japanese also far less formal seal used sign personal letters initial changes documents referred broadly generic term hanko often display single hiragana kanji ideograph katakana character carved often round oval square vary size women tend small traditionally inkan hanko engraved end finger-length stick stone wood bone ivory diameter carving form calligraphic art foreign names may carved rōmaji katakana hiragana kanji inkan standard japanese names may purchased prefabricated almost every stationery store discount store large book store department store carries small do-it-yourself kits making hanko include instructions hiragana fonts written forward mirror-writing 'd appear working surface seal slim tou chisel two three grades sandpaper slim marker pen draw design stone one three mottled inexpensive soft square green finger-size stones modern japan people several inkan certificate authenticity required hanko used significant business transaction registration certification inkan may obtained local municipal office e.g. city hall person receives certificate seal impression known increasing ease modern technology allows hanko fraud beginning cause concern present system able survive signatures used transactions cases signing cell phone contract may used sometimes addition stamp mitome-in transactions jitsuin official mitome-in alone insufficient thus signatures used chinese style seals also utilized ryūkyū kingdom seal first introduced korea approximately 2nd century bc remaining oldest record usage korea kings buyeo used royal seal oksae 옥새 玉璽 bore inscription seal king ye 濊王之印 예왕지인 use seals became popular three kingdoms korea period case state seals monarchic korea two types use gugin 국인 國印 conferred emperor china korean kings intent keeping relations two countries brothers sadae used communications china coronation kings others generally called eobo 어보 御寶 eosae 어새 御璽 used foreign communications countries china domestic uses declaration establishment republic korea 1948 government created new state seal guksae 국새 國璽 used promulgation constitution designation cabinet members ambassadors conference national orders important diplomatic documents seals also used government officials documents types seals called gwanin 관인 官印 supervised specialist officials modern korea use seals still common koreans personal seals every government agency commercial corporation seals use public documents signing also accepted many koreans think formal use seals public documents 2008 constitutional court south-korea upheld supreme court judgement signed handwritten lacked registered seal invalid personal seals korea classified legal status ingam 인감 印鑑 sirin 실인 實印 meaning registered seal seal registered local office registering seal person issue certificate seal registration required document significant business transactions civil services legal system registered seals introduced japanese colonial government 1914 scheduled completely replaced electronic certification system 2013 order counter fraud ingam still remains official means verification binding legal agreement identification government pass 'act confirmation etc personal signature 본인서명사실 확인 등에 관한 법률 2012 allows pre-registered handwritten signatures legal effect ingam ingam used important business dojangs used everyday purpose less-significant official transactions thus koreans two seals traditional arts like china japan artist chinese calligraphy paintings would use seals generally leisure seals studio seals identify his/her work types seals called nakkwan 낙관 落款 seal-carving considered form art many artists carved seals seals joseon-period calligraphist natural historian kim jung-hee aka wandang chusa considered antiquity korean seals made wood jade sometimes ivory value state seals generally made gold high-quality jade rare cases bronze steel seals exist philippines also sealing culture prior spanish colonization however spaniards succeeded colonizing islands abolished practice burned documents captured natives forcefully establishing roman catholic-based rule records philippine seals forgotten 1970 actual ancient seals made ivory found archaeological site butuan seal known butuan ivory seal declared national cultural treasure seal inscribed word butwan native suyat script discovery seal proved theory pre-colonial filipinos least coastal areas used seals paper discovery seal thought ancient filipinos used bamboo metal bark leaves writing presence paper documents classical era philippines also backed research dr. h. otley beyer father philippine anthropology stating spanish friars 'boasted burning ancient philippine documents suyat inscriptions one reasons ancient documents philippines almost non-existent present time ivory seal housed national museum philippines nowadays younger generations trying revive usage seals notably signing pieces art drawings paintings calligraphy literary works seal used lesser extent vietnam authorised organisations businesses also traditional vietnamese artists common vietnam prior french rule thereafter practice signature became commonality although western-like signatures usually seen less authority corporate situation chinese style seals typically used china japan korea occasionally used outside east asia example rulers ilkhanate mongol khanate established hulagu khan persia used seals containing chinese characters diplomatic letters letter arghun french king philip iv letter ghazan pope boniface viii seals sent emperors yuan dynasty ruling dynasty china mongolia especially kublai khan successor emperor chengzong
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Computer security
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journaling file system journaling file system file system keeps track changes yet committed file system main part recording intentions changes data structure known journal usually circular log event system crash power failure file systems brought back online quickly lower likelihood becoming corrupted depending actual implementation journaling file system may keep track stored metadata resulting improved performance expense increased possibility data corruption alternatively journaling file system may track stored data related metadata implementations allow selectable behavior regard 1990 ibm jfs introduced aix 3.1 one first unix commercial filesystems implemented journaling later 1993 microsoft ntfs filesystem 2001 ext3 implemented journaling updating file systems reflect changes files directories usually requires many separate write operations makes possible interruption like power failure system crash writes leave data structures invalid intermediate state example deleting file unix file system involves three steps crash occurs step 1 step 2 orphaned inode hence storage leak crash occurs steps 2 3 blocks previously used file used new files effectively decreasing storage capacity file system re-arranging steps help either step 3 preceded step 1 crash could allow file blocks reused new file meaning partially deleted file would contain part contents another file modifications either file would show hand step 2 preceded step 1 crash would cause file inaccessible despite appearing exist detecting recovering inconsistencies normally requires complete walk data structures example tool fsck file system checker must typically done file system next mounted read-write access file system large relatively little i/o bandwidth take long time result longer downtimes blocks rest system coming back online prevent journaled file system allocates special area—the journal—in records changes make ahead time crash recovery simply involves reading journal file system replaying changes journal file system consistent changes thus said atomic divisible either succeed succeeded originally replayed completely recovery replayed skipped yet completely written journal crash occurred file systems allow journal grow shrink re-allocated regular file others put journal contiguous area hidden file guaranteed move change size file system mounted file systems may also allow external journals separate device solid-state drive battery-backed non-volatile ram changes journal may journaled additional redundancy journal may distributed across multiple physical volumes protect device failure internal format journal must guard crashes journal written many journal implementations jbd2 layer ext4 bracket every change logged checksum understanding crash would leave partially written change missing mismatched checksum simply ignored replaying journal next remount physical journal logs advance copy every block later written main file system crash main file system written write simply replayed completion file system next mounted crash write logged journal partial write missing mismatched checksum ignored next mount physical journals impose significant performance penalty every changed block must committed twice storage may acceptable absolute fault protection required logical journal stores changes file metadata journal trades fault tolerance substantially better write performance file system logical journal still recovers quickly crash may allow unjournaled file data journaled metadata fall sync causing data corruption example appending file may involve three separate writes metadata-only journal step 3 would logged step 3 done steps 1 2 replayed recovery file appended garbage write cache operating systems sorts writes using elevator algorithm similar scheme maximize throughput avoid out-of-order write hazard metadata-only journal writes file data must sorted committed storage associated metadata tricky implement requires coordination within operating system kernel file system driver write cache out-of-order write hazard also occur device write blocks immediately underlying storage flush write-cache disk due deferred write enabled complicate matters many mass storage devices write caches may aggressively reorder writes better performance particularly common magnetic hard drives large seek latencies minimized elevator sorting journaling file systems conservatively assume write-reordering always takes place sacrifice performance correctness forcing device flush cache certain points journal called barriers ext3 ext4 ufs implementations avoid journaling instead implement soft updates order writes way on-disk file system never inconsistent inconsistency created event crash storage leak recover leaks free space map reconciled full walk file system next mount garbage collection usually done background log-structured file systems write-twice penalty apply journal file system occupies entire storage device structured traversed would normal file system full copy-on-write file systems zfs btrfs avoid in-place changes file data writing data newly allocated blocks followed updated metadata would point new data disown old followed metadata pointing superblock root file system hierarchy correctness-preserving properties journal without write-twice overhead
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Computer file systems
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authentication server authentication server provides network service applications use authenticate credentials usually account names passwords users client submits valid set credentials receives cryptographic ticket subsequently use access various services authentication used basis authorization determination whether privilege may granted particular user process privacy keeps information becoming known non-participants non-repudiation inability deny done something authorized done based authentication major authentication algorithms include passwords kerberos public key encryption
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Computer security
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hackintosh hackintosh portmanteau hack macintosh computer runs macos device authorized apple one longer receives official software updates hackintoshing began result apple 2005 transition intel processors away powerpc since 2005 mac computers use x86-64 computer architecture computer manufacturers maintaining binary-code compatibility hackintosh laptops sometimes referred hackbooks .. apple software license macos permits software use computers apple-branded however modern macintosh computers use intel-based hardware limitations keeping software running types intel-based pcs notably companies psystar attempted release products using macos non-apple machines though many hackintosh systems designed solely macos enthusiasts various hacking forums communities methods apple uses prevent macos installed non-apple hardware protected commercial circumvention united states digital millennium copyright act dmca specific changes law regarding concept jailbreaking placed circumvention methods like legal grey area june 6 2005 apple announced plans switch intel processors worldwide developers conference released developer transition kit selected developers cost 999 efforts immediately began attempt run mac os x non-apple hardware developers quickly found error message saying pc hardware configurations supported january 10 2006 apple released 10.4.4 first generation intel-based macs imac macbook pro machines used extensible firmware interface efi platform firmware instead older style bios found x86 motherboards time february 14 2006 initial hack v10.4.4 released internet programmer pseudonym crg92 within hours apple released 10.4.5 update patched author within two weeks april 3 2006 apple released 10.4.6 update patches released within two weeks allowed users install update non-apple computers although include updated kernel 10.4.6 june hackers released 10.4.7 update non-apple computers using 10.4.4 kernel release 10.4.8 update osx86 patches used 10.4.4 kernel rest operating system version 10.4.8 however newer frameworks relied newer kernels led users 10.4.8 encountering many problems apple also started making use sse3 instructions hardware making even difficult users cpus supporting sse2 older pentium 4s get fully compatible system running solve problem hackers community released kernels instructions emulated sse2 equivalents although produced performance penalty throughout years many distros released download internet distros copies mac os x installer disc modified include additional components necessary make os run non-apple hardware prominent member community jas released many distros mac os x tiger containing patched kernels popular distros iatkos kalyway ipc ideneb niresh distros fallen favour osx86 community grew new bootloaders developed made possible use actual copies os x installer early v10.5 build 9a466 community maintained version leopard run non-apple hardware hacker handle brazilmac created one earliest patching processes made convenient users install onto 3rd party hardware using legally obtained retail version apple simplification made brazilmac patch later revisions quickly popular choice many distros five popular builds go name jas kalyway iatkos ipc ideneb although recently builds way boot-132 method described gains popularity however compilations rely work kernel hackers made lorem build 9a466 synthetix builds 9a499 9a527 9a559 toh builds 9a581 9b13 9b18 recently group calling stagexnu called voodoo darwin 9.4.0 contributions trickled various mac osx86 installers readily available internet continue refined updated builds released maintain compatibility apple releases ever-increasing number third-party components osx86 community quick make necessary modifications enable apple latest releases run non-apple hardware within hours leopard release amd/intel sse2/3 kernel patcher created removed hpet requirement original untouched mach_kernel file core component mac os snow leopard released russian hacker netkas created version chameleon boot mac os x v10.6 main problem many people forced modify dsdt use kexts due specific issues soon possible modbin dmitrik released test versions kernel allow boot snow leopard amd machines stable xnu kernels v10.6 released qoopz pcj popular builds based retail name universal intel hazard iatkos since v10.6.2 nawcom qoopz andy vandijck working legacy kernel unsupported cpus apple released developer preview 1 russian hackintosh developer usr-sse2 first created method install lion method consists deploying mac os x v10.7 image flash drive booting via xpc uefi bootloader see duet changes made chameleon source code became possible boot lion updated version chameleon dmitrik also known bronzovka luck creating kernel supported amd systems months 10.7.3 v2 amd support iatkos l2 10.7.2 intel released shortly release developer preview 1 unknown developers managed install version os x pc using modified version chameleon bootloader version released via main project starting version r1997 general public due problems sourced lion era ways installing required patches never made public leaves scene unknown state towards mountain lion since retail release mountain lion several users reported successful setups using installers purchased mac app store along updated versions chameleon tools including distros niresh distro 10.8 intel first released updated 10.8.2 amd intel 10.8.5 uefi support amd intel support versions iatkos ml2 released niresh release multiple new kernels hackintosh 10.9 works although still minor issues kernels aim allow users run mavericks amd older intel cpus lack certain instruction sets latest intel cpus significant efforts made emulate instruction sets like ssse3 present amd k10-based cpus older intel cpus like intel core duo amd latest cpus 'bulldozer architecture onwards contain almost latest instruction sets hence kernels full sse4 support also released two months niresh distro released mavericks supports amd cpus latest intel cpus also custom kernel allows intel atom processors boot mavericks niresh free distro released mavericks since iatkos team decided release mavericks distro specific hardware donation basis initial release os x yosemite 10.10 beta various developers took role updating bootloaders system members osx86 forum insanelymac set update efi bootloader chameleon new os release time later niresh independent osx86 developer released standalone tool known yosemite zone would automatically install new os various features non-apple device minimal input method consisted torrenting os x 10.10 dmg onto usb flash drive macpwn vanilla installation unibeast updated support yosemite distribution yosemite zone released amd processor support vanilla installation yosemite possible via insanelymac pandora box beta 2.0 unibeast type installation uses kexts drivers possible addition using unaltered version os x installation app preferred distributions clover chameleon updated compatible el capitan unibeast macpwn updated support el capitan well since el capitan unibeast multibeast use clover bootloader instead chimera chameleon-based bootloader clover chameleon updated compatible sierra unibeast pandora box macpwn updated support distribution sierra zone 10.12.3 released amd processor support clover macpwn unibeast updated support distro high sierra zone hackintosh zone 10.13 released amd processor support including ryzen cpus clover updated support mojave revision 4514 unibeast also received mojave support intel-based machines apple authorize use mac os x x86 pc ones developed company used technical means although trusted platform module tpm widely mis-reported tie mac os systems distributed developers announcing switch intel chips macos eula forbids installations macos non-apple-branded computer july 3 2008 apple filed lawsuit psystar corporation violating restriction among claims apple claimed psystar violated digital millennium copyright act dmca dodging copy-protection technologies apple uses protect apple employs technological protection measures effectively control access apple copyrighted works specifically apple charged psystar acquiring creating code avoids bypasses removes descrambles decrypts deactivates impairs technological protection measure without apple authority purpose gaining unauthorized access apple copyrighted works brief revealed apple considers methods uses prevent macos installed non-apple hardware protected digital millennium copyright act dmca november 13 2009 court granted apple motion summary judgment found apple copyrights violated well dmca psystar installed apple operating system non-apple computers hearing remedies set december 14 january 14 2009 gadget lab site wired magazine posted video tutorial installing msi wind netbook removed following complaint apple textual instructions remain include eula violation disclaimer may 15 2012 case apple vs. psystar corporation finally ended court ruled psystar violated apple exclusive reproduction right distribution right right create derivative works putting end case copies mac os x tiger started running non-apple hardware found processors unable run os rosetta binary translator made possible run powerpc programs intel processors later kernel required support sse3 instruction set circumvent programmers community released patched kernels included support emulating sse3 instructions using sse2 equivalents october 2005 apple released update 10.4.3 developers required nx bit microprocessor support however patches released circumvent well patched kernels also later released supported amd processors mac os x leopard released october 26 2007 patches created remove hpet requirement kernel efforts also made emulate ssse3 instruction set processors support kernel used os x mavericks made use ssse3 instructions requiring patches extensible firmware interface efi specification defines software interface operating system platform firmware since method generally require copying modification macos considered legal way installing macos non-apple computers despite untested courts early november 2007 group hackers fronted russian hacker known netkas using already modified boot-132 source root david elliot also known dfe developed method emulating efi environment using specially modified darwin bootloader practical terms meant regular pcs meeting minimum set hardware requirements could seen real macintosh computers os allowing use unmodified stock apple kernels long cpu supports thus giving transparent reliable operation several methods real world deployment innovative solution arisen around internet explanation achievement along usage guide provided website digitmemo.com true efi emulation highly sought asset osx86 community previous efforts based upon apple open source darwin project hackintosh gurus allowed users use macos normal pcs patched kernels/kernel modules simply bypassed efi using efi patch hackintosh could boot vanilla unmodified macos kernels use vanilla kernel extensions allowed system compatible future system updates also offered increased stability method also circumvents one aspect apple end user license agreement states modification non-open source components os forbidden mid-2008 new commercial product efi-x released claims allow full simple booting official leopard install disks subsequent install without patching required possibly repackaging boot-132 technology usb-attached device rebel efi another commercial product also seems use open source software thought windows 7 support efi would result pc motherboards replacing bios efi msi announced efinity mainboard early 2008 2011 efi-based computers entered market however none natively boot mac os x due lack hfs+ driver efi implementation boot-132 bootloader provided apple loading xnu kernel mid-2008 new modified boot-132 came scene method allows users conduct leopard-based osx86 installation using stock retail-purchased copy leopard eradicates necessity hacked installation like jas kalyway mentioned previously boot-132 bootloader essentially preloads environment system leopard boot operate bootloader stores necessary files kext files .img collection simply folder luxury new installation method includes ability boot install retail leopard dvd update straight apple without breaking dmca possible problem breaks macos eula bootloader behaves like linux kernel one use mboot-compatible patched syslinux used hack bootloader tells boot-dfe .img file ramdisk initrd known linux users boot-dfe use kexts mkext new boot-dfe tested retail leopard dvd boot install run leopard without build modified dvd since early developer builds mac os x v10.6 members osx86 community booting new operating system using yet another bootloader called pc efi provided russian hacker netkas bootloader voodoo team chameleon chameleon based david elliot boot-132 bootloader supports acpi smbios graphics ethernet injections allows boot macos non-macintosh hardware chameleon supports lot amd well nvidia graphics cards lot branches different developers chameleon currently 2.1 development state fakeefi invented david elliot many years ago operates assumption efi already work leaves activity traces boot-args tables tree efiruntime routines simple form memory starts kernel mach_kernel realefi theoretically flashed instead bios alternatively loadable efi used bios motherboard system invented intel currently active open source development tianocore bootloader named duet capable loading efi designed load mac os x one step needed adapt duet requirements mac os x also newer motherboards already contain efi suitable running macintosh beginning march 2011 slice discussed idea community members resulting development bootloader emulate efi firmware one choice use real uefi firmware boot mac os x march 2007 osx86 community made significant progress development live dvd live dvd allows booting working system mac os x v10.4.8 january 2 2009 insanelymac live dvd team published new method mac os x v10.5.x live dvd could produced allowing users boot fully working macos desktop dvd usb flash drive method reliable previous methods manipulated apple existing netboot imageboot functionalities behaved system running network disk easier produce requiring single script added existing installation distributions live dvd made since inception since notable method shown work normal apple mac hardware also possible run macos virtual machine inside operating systems installed standard pc hardware using virtualization software oracle virtualbox though officially supported oracle likewise also possible install macos vmware software though company states officially supported vmware running apple-labeled computers according apple licensing policies
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Operating systems
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static core static core generally refers microprocessor mpu entirely implemented static logic static core mpu may halted stopping system clock oscillator driving maintaining state resume processing point stopped clock signal restarted long power continues applied static core mpus fabricated cmos process hence consume little power clock stopped making useful designs mpu remains standby mode needed minimal loading power source often battery desirable standby comparison typical microprocessor designs without static core refresh present valid outputs pins specific periods clock cycle clock slowed stopped charge pin leaks capacitors time quickly moving default state longer valid designs run within set range clock frequencies avoid problem static core microprocessors include rca 1802 intel 80386ex wdc w65c02s wdc w65c816s freescale 683xx family many low-power electronics systems designed fully static systems—such example psion organiser trs-80 model 100 galileo spacecraft fully static system processor static core data stored static ram rather dynamic ram design features allow entire system paused indefinitely low power state instantly resumed needed
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Computer architecture
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generalized ttl security mechanism generalized ttl security mechanism gtsm proposed internet data transfer security method relying packet time live ipv4 hop limit ipv6 thus protect protocol stack spoofing denial service attacks desired purpose proposal verify whether packet originated adjacent node protect router infrastructure overload-based attacks protocols gtsm enabled following procedure performed many people given credit creating idea among paul traina jon stewart similar method also proposed ryan mcdowell
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Computer security
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vxd vxd device driver model used microsoft windows/386 386 enhanced mode windows 3.x windows 9x extent also novell dos 7 opendos 7.01 dr-dos 7.02 higher multitasker codice_1 vxds access memory kernel running processes well raw access hardware name vxd abbreviation virtual xxx driver xxx class hardware device derives fact drivers filenames form codice_2 windows 3.x examples vjoyd.386 joystick vmm.386 memory manager vxds usually filename extension codice_3 windows 3.x codice_4 windows 9x vxds written windows 3.x used windows 9x vice versa prior advent windows dos applications would either communicate directly various pieces hardware responding interrupts reading writing device memory etc go dos device driver dos multitasking application would exclusive complete control hardware running though windows applications n't often communicate directly hardware way windows drivers still real standard modes windows 3.x windows/386 onward allowed multiple dos applications execute concurrently executing within virtual machine share physical resources among virtual machines microsoft introduced virtual device drivers drivers solved issues relating conflicting usage physical resources intercepting calls hardware instead machine port representing actual device would represent virtual device could managed operating system although windows 98 introduced windows driver model wdm vxd device drivers used windows 98 windows vxds usable windows nt descendants starting windows 2000 windows nt-based operating systems also use windows driver model windows nt 4 earlier versions must use drivers written specifically using vxd drivers instead wdm drivers windows 9x resulted advanced acpi states like hibernation unavailable vxds confused similarly named ntvdm-specific 'vdds virtual device drivers provide method emulating direct i/o windows nt dos box ntvdm vdds run regular 32-bit user-mode dlls must rely win32 api another wdm driver emulate desired i/o behalf 16-bit program
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Operating systems
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cylance cylance inc. software firm develops antivirus programs kinds computer software prevent rather reactively detect viruses malware company based irvine california cylance described “ first company apply artificial intelligence algorithms machine learning cyber security. ” february 2019 company acquired blackberry limited company mission block computer viruses malware effect user computer cylance founded stuart mcclure ryan permeh mcclure previously co-founder foundstone security consultancy sold mcafee 2004 becoming firm chief tech officer mcclure also author hacking exposed reportedly best-selling security book date cylance founding came result mcclure speeches previously given cybersecurity often asked protected computer noted lacked trust security technology since reactive nature meaning cleaned attack consequently mcclure began developing technology based proactive protection initial funding 15 million reported february 2013 another 20 million february 2014 july 2015 report indicated cylance raised additional 42 million investors including draper fisher jurvetson kohlberg kravis roberts dell capitalone teneleven ventures received 100 million june 2016 lead investors blackstone tactical opportunities part blackstone group insight venture partners mcclure stated cylance antivirus product use typical security features unique signatures heuristics behavioral analysis sandboxing virtualization blacklisting rather product uses artificial intelligence identify stop attackers mcclure stated cylance security features similar human brain way identifying threats wherein teaches computers identify indicators attack operation cleaver covert cyberwarfare operation carried iranian government targets around world specifically critical infrastructure entities cylance uncovered operation described report released late 2014 iranian officials rejected cylance conclusions fbi tacitly confirmed may 2016 cylance announced new collaboration motex osaka-based firm integrate motex lanscope endpoint security management cylanceprotect cylance leading product proactively detects prevents malware end product called cylanceprotect cat collaboration brings cylance activities japanese market february 2019 company acquired blackberry limited 1.4 billion march 2018 cylance 2018 mspworld cup award november 2017 linkedin recognized cylance one top companies startups year 2017 october 2017 cylance certified great place work greatplacetowork.com october 2017 cylance recognized cyber security leader 2017 cyber defense magazine september 2017 cylance announced winner gartner peer insights customer choice award endpoint protection platforms gartner inc august 2017 cylance made inc. magazine inc. 5000 list second year row june 2017 cylance special jury award best show security product interop tokyo 2017 june 2017 cylance top product cylanceprotect named best enterprise security solution 2017 sc media awards europe event may 2017 cylance made cnbc disruptor 50 list second year row april 2017 cylance given 5-star rating crn 2017 partner program guide march 2017 cylanceprotect named best endpoint protection product 2016 sans community july 2016 mcclure named orange county entrepreneur year category technology 2016 cylance ranked 23 forbes cloud 100 list
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Computer security
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gentoo/alt gentoo/alt gentoo linux project created manage porting portage framework features operating systems mac os x free bsds gentoo/alt set pieter van den abeele daniel robbins pieter van den abeele founded gentoo mac os x. gentoo mac os x first non-linux project gentoo focused making gentoo experience available apple operating system introducing portage system separate entity roughly similar fink macports used portage instead debian-like ports-like system later gentoo mac os x made subproject gentoo/alt currently project longer active prime assumption using modifying host os appeared realistic eventually broke packages made hardly maintainable gentoo mac os x superseded gentoo prefix currently gentoo offers mac os x users gentoo/*bsd subproject covers ports bsd-derived operating systems currently consists three sections gentoo/freebsd gentoo/netbsd gentoo/openbsd gentoo/*bsd project umbrella better classify three subprojects often lot similar issues practice decision-making development handled gentoo/alt project subprojects gentoo/freebsd unix-like operating system developed gentoo linux developers order bring gentoo linux design structure tools portage gentoo linux base layout freebsd operating system gentoo gnu toolchain used instead original freebsd one although project longer maintained active gentoo developers instructions allow installation full gentoo/freebsd system freebsd system ebuilds integrated main portage tree port far complete due amount packages needing ported lack proper live cd right freesbie live cd freebsd setup cd used installation current semi official logo gentoo/freebsd daemonized g derived original gentoo linux logo inspired bsd daemon designed marius morawski responding unofficial contest launched diego elio pettenò blog gentoo/netbsd project provide gnu userland managed portage netbsd kernel project started damian florczyk currently x86 architecture targeted system whole incomplete state gentoo/openbsd gentoo/*bsd subproject port gentoo features portage openbsd operating system originally started grant goodyear currently development hiatus iso image based openbsd 3.8 currently maintained karol pasternak downloaded project web site gentoo/dragonflybsd currently unofficial port dragonflybsd kernel project developed robert sebastian gerus unofficial port gnu hurd also developed abandoned late 2006 youngest member gentoo/alt gentoo prefix project emerged gentoo mac os x project suffered multiple practical problems initially allows installation mac os x solaris freebsd linux distributions core principle gentoo prefix installation packages portage done offset thereby leaving host os unmodified side effect administrative privileges required led benda xu gentoo rap android devices installs variant gentoo called gentoo rap directory prefix alongside android linux kernel used android gentoo rap gentoo/interix eprefix port gentoo runs atop interix subsystem windows also known microsoft windows services unix sfu subsystem unix-based applications sua result gentoo/interix project ability install use portage system emerge native windows applications requires visual studio 2008 express edition however feature support wide variety packages supported platforms including interix prefix project mac os x tested supported mac os x tiger leopard snow leopard powerpc ia-32 x86-64 architectures unofficial port solaris operating system portaris announced around 2006 never got public state superseded gentoo prefix project started 2011 google summer code project plan 9 gentoo takes gentoo base overlays userspace inspired plan 9 stated objectives project better hardware support better software support create culture shock people previously used linux systems project presently maintained robert seaton
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Operating systems
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zfs zfs combined file system logical volume manager designed sun microsystems zfs scalable includes extensive protection data corruption support high storage capacities efficient data compression integration concepts filesystem volume management snapshots copy-on-write clones continuous integrity checking automatic repair raid-z native nfsv4 acls precisely configured two main implementations oracle openzfs project extremely similar making zfs widely available within unix-like systems zfs name stands nothing—briefly assigned backronym zettabyte file system longer considered initialism originally zfs proprietary closed-source software developed internally sun part solaris team led cto sun storage business unit sun fellow jeff bonwick 2005 bulk solaris including zfs licensed open-source software common development distribution license cddl opensolaris project zfs became standard feature solaris 10 june 2006 2010 sun microsystems acquired oracle zfs became registered trademark belonging oracle oracle stopped releasing updated source code new opensolaris zfs development effectively reverting oracle zfs closed source response illumos project founded maintain enhance existing open source solaris 2013 openzfs founded coordinate development open source zfs openzfs maintains manages core zfs code organizations using zfs maintain specific code validation processes required zfs integrate within systems openzfs widely used unix-like systems 2017 one analyst described openzfs proven open source data-validating enterprise file system management stored data generally involves two aspects physical volume management one block storage devices hard drives sd cards organization logical block devices seen operating system often involving volume manager raid controller array manager suitable device driver management data files stored logical block devices file system data storage zfs unusual unlike storage systems unifies roles acts volume manager file system therefore complete knowledge physical disks volumes including condition status logical arrangement volumes also files stored zfs designed ensure subject suitable hardware data stored disks lost due physical errors misprocessing hardware operating system bit rot events data corruption may happen time complete control storage system used ensure every step whether related file management disk management verified confirmed corrected needed optimized way storage controller cards separate volume file managers achieve zfs also includes mechanism dataset pool level snapshots replication including snapshot cloning described freebsd documentation one powerful features features even file systems snapshot functionality lack large numbers snapshots taken without degrading performance allowing snapshots used prior risky system operations software changes entire production live file system fully snapshotted several times hour order mitigate data loss due user error malicious activity snapshots rolled back live previous file system states viewed even large file systems leading savings comparison formal backup restore processes snapshots also cloned form new independent file systems pool level snapshot known checkpoint available allows rollback operations may affect entire pool structure add remove entire datasets examples features specific zfs include unlike many file systems zfs intended work towards specific aims primary targets enterprise standard data management commercial environments hardware capable supporting zfs capabilities data resilience resources needed serve data efficiently system configuration poorly matched zfs zfs may underperform significantly 2017 zfs benchmarks zfs developers calomel stated common system design failures include zfs acts volume manager file system terminology layout zfs storage covers two aspects many terms particular zfs list covers zfs commands allow examination physical storage terms devices vdevs organized data pools stored across vdevs various ways various commands expose in-depth statistics zfs internal status internal performance/statistics data allow settings optimized physical devices used zfs hard drives hdds ssds organized groups known vdevs virtual devices used store data vdevs fundamental part zfs conceived groups disks provide redundancy failure physical devices vdev must able maintain integrity data holds must contain enough disks risk data loss within acceptably tiny vdev become unreadable due disk errors otherwise entire pool part also fail see data recovery vdev one vdev acts independent unit redundant storage devices might vdev unused spare disks disks formatted non-zfs filing systems offline disks cache devices physical structure pool defined configuring many vdevs type adding pool zfs exposes manages individual disks within system well vdevs pools datasets volumes organized within pool data automatically distributed zfs across vdevs making pool zfs stripes data pool across vdevs pool speed efficiency vdev user defines completely independent every vdev different types vdev mixed arbitrarily single zfs system data redundancy required data protected physical device failure ensured user organize devices vdevs either using mirrored vdev raidz vdev data single device vdev may lost device develops fault data mirrored raidz vdev lost enough disks fail time system resilvered replacements due recent disk failures zfs vdev continue function service capable providing least one copy data stored although may become slower due error fixing resilvering part self-repair data integrity processes however zfs designed become unreasonably slow due self-repair unless directed administrator since one goals capable uninterrupted continual use even self checking self repair since zfs device redundancy vdev level also means pool stored across several vdevs one vdevs completely fails entire pool content lost similar raid redundancy systems require data stored capable reconstruction enough devices ensure data unlikely lost due physical devices failing therefore intended vdevs made either mirrored devices raidz array devices sufficient redundancy important data zfs automatically limit possible avoid data loss device fails backups replication also expected part data protection vdevs manipulated active use single disk additional devices added create mirrored vdev mirrored vdev physical devices added removed leave larger smaller number mirrored devices single device raidz vdev converted mirror although additional vdevs always added expand storage capacity kind including raidz device vdev marked removal zfs de-allocate data allow removed replaced note devices vdev size zfs may use full capacity disks vdev larger others applies devices within single vdev vdevs independent zfs care different vdevs different sizes built different devices also vdev shrunk size common set aside small amount unused space example 1-2gb multi-tb disk disk needs replacing possible allow slight manufacturing variances replace another disk nominal capacity slightly smaller actual capacity addition devices used main data storage zfs also allows manages devices used caching purposes single devices multiple mirrored devices fully dedicated type cache designated cache usage detailed settings fully deleted created modified without limit live use list zfs cache types given zfs handle devices formatted partitions certain purposes common use generally caches data pools given complete devices multiple complete devices top level data management zfs pool zpool zfs system multiple pools defined vdevs used pool specified pool created others added later zfs use specified vdevs maximize performance storing data – form striping across vdevs therefore important ensure vdev sufficiently redundant loss vdev pool would cause loss pool striping zfs pool expanded time adding new vdevs including system 'live storage space vdevs already allocated pool shrunk data stored across vdevs pool even yet full however explained individual vdevs modified time within stated limits new vdevs added time since addition removal mirrors marking redundant disk offline affect ability vdev store data within pools zfs recognizes two types data store since volumes presented block devices also formatted file system add zfs features file system although usual practice example zfs volume created block device presents partitioned formatted file system ext4 ntfs done either locally network using iscsi similar resulting file system accessible normal also gain zfs benefits data resilience data integrity/scrubbing snapshots additional option data compression snapshots integral feature zfs provide immutable read copies file system single point time even large file systems snapshotted many times every hour sustain tens thousands snapshots snapshot versions individual files entire dataset pool easily accessed searched restored entire snapshot cloned create new copy copied separate server replicated backup pool dataset quickly rolled back specific snapshot snapshots also compared current data check modified data.snapshots take much disk space data deleted space marked free data longer referenced current system snapshot snapshots also easy way avoid impact ransomware generally zfs expect reduce size pool tools reduce set vdevs pool stored tools remove vdevs rolled oracle zfs also exist derivatives openzfs yet generally released openzfs platforms generally therefore 2018 remove entire vdev active use reduce size pool data stored must moved another pool temporary copy made easier deleted later restored backups/copies devices making vdev freed use pool deleted recreated using fewer vdevs smaller size additional capacity added pool time simply adding devices needed defining unused devices vdevs adding new vdevs pool capacity individual vdev generally fixed defined one exception rule single drive mirrored vdevs expanded larger smaller capacities without affecting vdev operation adding larger disks replacing/removing smaller disks shown example pool expanded unused space datasets volumes within pool likewise expanded use unused pool space datasets need fixed size dynamically grow data stored volumes block devices need size defined user must manually resized required done 'live resizing example one major feature distinguishes zfs file systems designed focus data integrity protecting user data disk silent data corruption caused data degradation current spikes bugs disk firmware phantom writes previous write make disk misdirected reads/writes disk accesses wrong block dma parity errors array server memory driver since checksum validates data inside array driver errors data winds wrong buffer inside kernel accidental overwrites swapping live file system etc 1999 study showed neither then-major widespread filesystems ufs ext xfs jfs ntfs hardware raid issues data integrity provided sufficient protection data corruption problems initial research indicates zfs protects data better earlier efforts also faster ufs seen replacement within zfs data integrity achieved using fletcher-based checksum sha-256 hash throughout file system tree block data checksummed checksum value saved pointer block—rather actual block next block pointer checksummed value saved pointer checksumming continues way file system data hierarchy root node also checksummed thus creating merkle tree in-flight data corruption phantom reads/writes data written/read checksums correctly actually wrong undetectable filesystems store checksum data zfs stores checksum block parent block pointer entire pool self-validates block accessed regardless whether data meta-data checksum calculated compared stored checksum value checksums match data passed programming stack process asked values match zfs heal data storage pool provides data redundancy internal mirroring assuming copy data undamaged matching checksums optionally possible provide additional in-pool redundancy specifying means data stored twice three times disk effectively halving reducing one third storage capacity disk additionally kinds data used zfs manage pool stored multiple times default safety even default copies=1 setting copies damaged data exist reconstructed checksums parity data zfs use copy data recreate via raid recovery mechanism recalculate checksum—ideally resulting reproduction originally expected value data passes integrity check system update faulty copies known-good data redundancy restored consistency data held memory cached data arc checked default zfs expected run enterprise quality hardware error correcting ram capability check in-memory data exists enabled using debug flags zfs able guarantee data integrity needs multiple copies data usually spread across multiple disks typically achieved using either raid controller so-called soft raid built file system zfs work hardware raid devices zfs usually work efficiently greater protection data raw access storage devices disks connected system using hardware firmware soft raid controller modifies usual zfs-to-disk i/o path zfs relies disk honest view determine moment data confirmed safely written numerous algorithms designed optimize use caching cache flushing disk handling third-party device performs caching presents drives zfs single system without low level view zfs relies upon much greater chance system perform less optimally failure preventable zfs quickly fully recovered zfs example hardware raid card used zfs may able determine condition disks whether raid array degraded rebuilding may know data corruption place data optimally across disks make selective repairs control repairs balanced ongoing use may able make repairs even could usually hardware raid card interfere raid controllers also usually add controller-dependent data drives prevents software raid accessing user data possible read data compatible hardware raid controller n't always possible controller card develops fault replacement may available cards may understand manufacturer custom data needed manage restore array new card therefore unlike systems raid cards similar used offload resources processing enhance performance reliability zfs strongly recommended methods used typically reduce system performance reliability disks must connected raid controller recommended use plain hba host adapter fanout card configure card jbod mode i.e turn raid caching functions allow devices attached zfs-to-disk i/o pathway unchanged raid card jbod mode may still interfere cache depending upon design may detach drives respond time seen many energy-efficient consumer-grade hard drives may require time-limited error recovery tler /cctl/erc-enabled drives prevent drive dropouts cards suitable even raid functions disabled instead hardware raid zfs employs soft raid offering raid-z parity based like raid 5 similar disk mirroring similar raid 1 schemes highly flexible raid-z data/parity distribution scheme like raid-5 uses dynamic stripe width every block raid stripe regardless blocksize resulting every raid-z write full-stripe write combined copy-on-write transactional semantics zfs eliminates write hole error raid-z also faster traditional raid 5 need perform usual read-modify-write sequence stripes different sizes raid-z reconstruction traverse filesystem metadata determine actual raid-z geometry would impossible filesystem raid array separate products whereas becomes feasible integrated view logical physical structure data going metadata means zfs validate every block 256-bit checksum goes whereas traditional raid products usually addition handling whole-disk failures raid-z also detect correct silent data corruption offering self-healing data reading raid-z block zfs compares checksum data disks return right answer zfs reads parity figures disk returned bad data repairs damaged data returns good data requestor raid-z mirroring require special hardware need nvram reliability need write buffering good performance data protection raid-z zfs provides fast reliable storage using cheap commodity disks five different raid-z modes raid-z0 similar raid 0 offers redundancy raid-z1 similar raid 5 allows one disk fail raid-z2 similar raid 6 allows two disks fail raid-z3 raid 7 configuration allows three disks fail mirroring similar raid 1 allows one disk fail need raid-z3 arose early 2000 muti-terabyte capacity drives became common increase capacity without corresponding increase throughput speeds meant rebuilding array due failed drive could take weeks even months complete time older disks array stressed additional workload could result data corruption drive failure increasing parity raid-z3 reduces chance data loss simply increasing redundancy zfs tool equivalent fsck standard unix linux data checking repair tool file systems instead zfs built-in scrub function regularly examines data repairs silent corruption problems differences official recommendation sun/oracle scrub enterprise-level disks month cheaper commodity disks week zfs 128-bit file system address 1.84 × 10 times data 64-bit systems btrfs maximum limits zfs designed large never encountered practice instance fully populating single zpool 2 bits data would require 3×10 tb hard disk drives theoretical limits zfs oracle solaris encryption capability zfs embedded i/o pipeline writes block may compressed encrypted checksummed deduplicated order policy encryption set dataset level datasets file systems zvols created wrapping keys provided user/administrator changed time without taking file system offline default behaviour wrapping key inherited child data sets data encryption keys randomly generated dataset creation time descendant datasets snapshots clones share data encryption keys command switch new data encryption key clone time provided—this re-encrypt already existing data instead utilising encrypted master-key mechanism zfs automatically allocate data storage across vdevs pool devices vdev way generally maximises performance pool zfs also update write strategy take account new disks added pool added general rule zfs allocates writes across vdevs based free space vdev ensures vdevs proportionately less data already given writes new data stored helps ensure pool becomes used situation develop vdevs become full forcing writes occur limited number devices also means data read reads much frequent writes uses different parts data read many disks possible time giving much higher read performance therefore general rule pools vdevs managed new storage added situation arise vdevs pool almost full others almost empty make pool less efficient pools hot spares compensate failing disks mirroring block devices grouped according physical chassis filesystem continue case failure entire chassis storage pool composition limited similar devices consist ad-hoc heterogeneous collections devices zfs seamlessly pools together subsequently doling space needed arbitrary storage device types added existing pools expand size storage capacity vdevs available file system instances zpool quota set limit amount space file system instance occupy reservation set guarantee space available file system instance zfs uses different layers disk cache speed read write operations ideally data stored ram usually expensive therefore data automatically cached hierarchy optimize performance versus cost often called hybrid storage pools frequently accessed data stored ram less frequently accessed data stored slower media solid state drives ssds data often accessed cached left slow hard drives old data suddenly read lot zfs automatically move ssds ram zfs caching mechanisms include one reads writes case two levels caching exist one computer memory ram one fast storage usually solid state drives ssds total four caches number caches cache divisions queues also exist within zfs example vdev data cache arc cache divided data stored user metadata used zfs control balance zfs uses copy-on-write transactional object model block pointers within filesystem contain 256-bit checksum 256-bit hash currently choice fletcher-2 fletcher-4 sha-256 target block verified block read blocks containing active data never overwritten place instead new block allocated modified data written metadata blocks referencing similarly read reallocated written reduce overhead process multiple updates grouped transaction groups zil intent log write cache used synchronous write semantics required blocks arranged tree checksums see merkle signature scheme advantage copy-on-write zfs writes new data blocks containing old data retained allowing snapshot version file system maintained zfs snapshots consistent reflect entire data existed single point time created extremely quickly since data composing snapshot already stored entire storage pool often snapshotted several times per hour also space efficient since unchanged data shared among file system snapshots snapshots inherently read-only ensuring modified creation although relied sole means backup entire snapshots restored also files directories within snapshots writeable snapshots clones also created resulting two independent file systems share set blocks changes made clone file systems new data blocks created reflect changes unchanged blocks continue shared matter many clones exist implementation copy-on-write principle zfs file systems moved pools also remote hosts network send command creates stream representation file system state stream either describe complete contents file system given snapshot delta snapshots computing delta stream efficient size depends number blocks changed snapshots provides efficient strategy e.g. synchronizing offsite backups high availability mirrors pool dynamic striping across devices maximize throughput means additional devices added zpool stripe width automatically expands include thus disks pool used balances write load across zfs uses variable-sized blocks 128 kb default size available features allow administrator tune maximum block size used certain workloads perform well large blocks data compression enabled variable block sizes used block compressed fit smaller block size smaller size used disk use less storage improve io throughput though cost increased cpu use compression decompression operations zfs filesystem manipulation within storage pool easier volume manipulation within traditional filesystem time effort required create expand zfs filesystem closer making new directory volume manipulation systems pools associated zfs file systems moved different platform architectures including systems implementing different byte orders zfs block pointer format stores filesystem metadata endian-adaptive way individual metadata blocks written native byte order system writing block reading stored endianness match endianness system metadata byte-swapped memory affect stored data usual posix systems files appear applications simple arrays bytes applications creating reading data remain responsible way independent underlying system endianness data deduplication capabilities added zfs source repository end october 2009 relevant opensolaris zfs development packages available since december 3 2009 build 128 effective use deduplication may require large ram capacity recommendations range 1 5 gb ram every tb storage accurate assessment memory required deduplication made referring number unique blocks pool number bytes disk ram core required store record figures reported inbuilt commands zpool zdb insufficient physical memory lack zfs cache result virtual memory thrashing using deduplication cause performance plummet result complete memory starvation deduplication occurs write-time also cpu-intensive also significantly slow system storage vendors use modified versions zfs achieve high data compression ratios two examples 2012 greenbytes tegile may 2014 oracle bought greenbytes zfs deduplication replication technology described deduplication usually recommended due heavy resource requirements especially ram impact performance especially writing specific circumstances system data well-suited space-saving technique authors 2010 study examined ability file systems detect prevent data corruption particular focus zfs observed zfs effective detecting correcting data errors storage devices assumes data ram safe prone error study comments single bit flip memory causes small non-negligible percentage runs experience failure probability committing bad data disk varying 0 3.6 according workload zfs caches pages stores copies metadata ram holds data dirty cache writing disk test made whether checksums still match data point use much risk mitigated one two ways zfs protect data disk failure needs configured redundant storage either raid-z mirrored data copied least two disks single disk used redundant copies data enabled duplicates data logical drive far less safe since vulnerable failure single disk using zfs copies good feature use notebooks desktop computers since disks large least provides limited redundancy single drive historically zfs shipped tools fsck repair damaged file systems file system designed self-repair long built sufficient attention design storage redundancy data pool compromised poor hardware inadequate design redundancy unfortunate mishap point zfs unable mount pool traditionally tools allowed end-user attempt partial salvage stored data led threads online forums zfs developers sometimes tried provide ad-hoc help home small scale users facing loss data due inadequate design poor system management modern zfs improved considerably situation time continues zfs part sun solaris operating system thus available sparc x86-based systems oracle solaris 11 express release os/net consolidation main os code made proprietary closed-source zfs upgrades implementations inside solaris encryption compatible non-proprietary implementations use previous versions zfs creating new zfs pool retain ability use access pool non-proprietary solaris-based distributions recommended upgrade solaris 11 express opensolaris snv_134b thereby stay zfs version 28 opensolaris 2008.05 2008.11 2009.06 use zfs default filesystem dozen 3rd-party distributions nearly dozen mentioned openindiana illumos two new distributions included opensolaris distribution reference page openindiana uses openzfs feature flags implemented illumos zfs version 28 used version 151a3 upgrading opensolaris snv_134 openindiana solaris 11 express one also ability upgrade separately boot solaris 11 express zfs pool one install solaris 11 express first zfs incompatibilities introduced oracle past zfs version 28 openzfs osx abbreviated o3x implementation zfs macos o3x active development close relation zfs linux illumos zfs implementation maintaining feature flag compatibility zfs linux o3x implements zpool version 5000 includes solaris porting layer spl originally written maczfs enhanced include memory management layer based illumos kmem vmem allocators o3x fully featured supporting lz4 compression deduplication arc l2arc slog maczfs free software providing support zfs macos stable legacy branch provides zfs pool version 8 zfs filesystem version 2 development branch based zfs linux openzfs provides updated zfs functionality zfs zpool version 5000 feature flags proprietary implementation zfs zevo available cost greenbytes inc. implementing zfs file system version 5 zfs pool version 28 zevo offered limited zfs feature set pending commercial development sold oracle 2014 unknown future plans edward o'callaghan started initial port zfs dragonflybsd netbsd zfs port started part 2007 google summer code august 2009 code merged netbsd source tree paweł jakub dawidek ported zfs freebsd part freebsd since version 7.0 includes zfsboot allows booting freebsd directly zfs volume freebsd zfs implementation fully functional missing features kernel cifs server iscsi latter added using externally available packages samba used provide userspace cifs server freebsd 7-stable updates series versions 7.x committed uses zpool version 6 freebsd 8 includes much-updated implementation zfs zpool version 13 supported zpool version 14 support added 8-stable branch january 11 2010 included freebsd release 8.1. zpool version 15 supported release 8.2 8-stable branch gained support zpool version v28 zfs version 5 early june 2011 changes released mid-april 2012 freebsd 8.3 freebsd 9.0-release uses zfs pool version 28 freebsd 9.2-release first freebsd version use new feature flags based implementation thus pool version 5000 midnightbsd desktop operating system derived freebsd supports zfs storage pool version 6 0.3-release derived code included freebsd 7.0-release update storage pool 28 progress 0.4-current based 9-stable sources around freebsd 9.1-release code trueos formerly known pc-bsd desktop-oriented distribution freebsd inherits zfs support freenas embedded open source network-attached storage nas distribution based freebsd zfs support freebsd pc-bsd zfs guru embedded open source network-attached storage nas distribution based freebsd pfsense open source bsd based router supports zfs including installation booting zfs pools version 2.4 nas4free embedded open source network-attached storage nas distribution based freebsd zfs support freebsd zfs storage pool version 5000 project continuation freenas 7 series project based freebsd kernel debian gnu/kfreebsd zfs support kernel however additional userland tools required possible zfs root /boot file system case required grub configuration performed debian installer since wheezy release 31 january 2013 zpool version available 14 squeeze release 28 wheezy-9 release although zfs filesystem supports linux-based operating systems difficulties arise linux distribution maintainers wishing provide native support zfs products due potential legal incompatibilities cddl license used zfs code gpl license used linux kernel enable zfs support within linux loadable kernel module containing cddl-licensed zfs code must compiled loaded kernel according free software foundation wording gpl license legally prohibits redistribution resulting product derivative work though viewpoint caused controversy one potential workaround licensing incompatibility trialed 2006 experimental port zfs code linux fuse system filesystem ran entirely userspace instead integrated linux kernel therefore considered derivative work kernel approach functional suffered significant performance penalties compared integrating filesystem native kernel module running kernel space 2016 zfs fuse project appears defunct native port zfs linux produced lawrence livermore national laboratory llnl released march 2013 following key events zfs linux uses openzfs pool version number 5000 indicates features supports defined via feature flags pool version unchanging number expected never conflict version numbers given oracle another native port linux developed kq infotech 2010 port used zvol implementation lawrence livermore national laboratory starting point release supporting zpool v28 announced january 2011 april 2011 kq infotech acquired stec inc. work zfs ceased source code port found github work kq infotech ultimately integrated llnl native port zfs linux license incompatibility may arise distribution compiled binaries containing zfs code generally agreed distribution source code affected gentoo configuring zfs root filesystem well documented required packages installed package repository slackware also provides documentation supporting zfs kernel module built kernel question cddl license compatibility gpl license resurfaced 2015 linux distribution ubuntu announced intended make precompiled openzfs binary kernel modules available end-users directly distribution official package repositories 2016 ubuntu announced legal review resulted conclusion providing support zfs via binary kernel module violation provisions gpl license others software freedom law center followed ubuntu conclusion fsf sfc reiterated opposing view ubuntu 16.04 lts xenial xerus released april 21 2016 allows user install openzfs binary packages directly ubuntu software repositories legal challenge brought canonical regarding distribution packages 2019 ubuntu support install zfs root filesystem maas allows zfs installed root filesystem port open source zfs attempted 2010 hiatus one year development ceased 2012 october 2017 new port openzfs announced jörgen lundman openzfs developer summit list operating systems distributions add-ons support zfs zpool version supports solaris build based zfs designed implemented team sun led jeff bonwick bill moore matthew ahrens announced september 14 2004 development started 2001 source code zfs integrated main trunk solaris development october 31 2005 released part build 27 opensolaris november 16 2005 sun announced zfs included 6/06 update solaris 10 june 2006 one year opening opensolaris community name one point said stand zettabyte file system 2006 longer considered abbreviation zfs file system store 256 quadrillion zettabytes zb september 2007 netapp sued sun claiming zfs infringed netapp patents write anywhere file layout sun counter-sued october year claiming opposite lawsuits ended 2010 undisclosed settlement following list events development open-source zfs implementations first indication apple inc. interest zfs april 2006 post opensolaris.org zfs-discuss mailing list apple employee mentioned interested porting zfs mac os x operating system release version mac os x 10.5 zfs available read-only mode command line lacks possibility create zpools write 10.5 release apple released zfs beta seed v1.1 allowed read-write access creation zpools however installer zfs beta seed v1.1 reported work version 10.5.0 updated version 10.5.1 august 2007 apple opened zfs project mac os forge web site site apple provided source code binaries port zfs includes read-write access installer available third-party developer created one october 2009 apple announced shutdown zfs project mac os forge say hosting involvement zfs summarily discontinued explanation given following statement zfs project discontinued mailing list repository also removed shortly apple would eventually release legally required cddl-derived portion source code final public beta zfs code named 10a286 complete zfs support advertised feature snow leopard server mac os x server 10.6 however time operating system released references feature silently removed features page apple commented regarding omission apple 10a286 source code release versions previously released source binaries preserved new development adopted group enthusiasts maczfs project acted quickly mirror public archives apple project materials would disappeared internet resume development elsewhere maczfs community curated matured project supporting zfs mac os releases since 10.5 project active mailing list july 2012 maczfs implements zpool version 8 zfs version 2 october 2008 release solaris additional historical information commentary found maczfs web site faq 17th september 2013 launch openzfs included zfs-osx become new version maczfs distribution darwin zfs oracle solaris new features introduced version numbers pool file system incremented designate format features available features available specific file system versions require specific pool version distributed development openzfs involves feature flags pool version 5000 unchanging number expected never conflict version numbers given oracle legacy version numbers still exist pool versions 1–28 implied version 5000 illumos uses pool version 5000 purpose future on-disk format changes enabled disabled independently via feature flags note solaris version development sun since release solaris 10 2005 codenamed 'nevada derived opensolaris codebase 'solaris nevada codename next-generation solaris os eventually succeed solaris 10 new code pulled successively new opensolaris 'nevada snapshot builds opensolaris discontinued openindiana forked final build b134 opensolaris published oracle 2010-nov-12 upgrade path solaris 11 express
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Computer file systems
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cloudera cloudera inc. us-based software company provides software platform data engineering data warehousing machine learning analytics runs cloud premises cloudera started hybrid open-source apache hadoop distribution cdh cloudera distribution including apache hadoop targeted enterprise-class deployments technology cloudera states 50 engineering output donated upstream various apache-licensed open source projects apache spark apache hive apache avro apache hbase combine form apache hadoop platform cloudera also sponsor apache software foundation cloudera founded 2008 three engineers google yahoo facebook christophe bisciglia amr awadallah jeff hammerbacher respectively joined former oracle executive mike olson form cloudera 2008 olson ceo sleepycat software creator open-source embedded database engine berkeley db acquired oracle 2006 awadallah yahoo ran one first business units using apache hadoop data analysis facebook hammerbacher used hadoop building analytic applications involving massive volumes user data architect doug cutting also former chairman apache software foundation authored open-source lucene nutch search technologies mike cafarella wrote initial hadoop software 2004 designed managed hadoop storage analysis cluster yahoo joining cloudera 2009 chief operating officer kirk dunn 2015 march 2009 cloudera announced availability cloudera distribution including apache hadoop conjunction 5 million investment led accel partners 2011 company raised 40 million ignition partners accel partners greylock partners meritech capital partners in-q-tel venture capital firm open connections cia june 2013 tom reilly became chief executive although olson remained chairman board chief strategist reilly chief executive arcsight acquired hewlett-packard 2010 march 2014 cloudera announced 900 million funding round led intel capital 740 million intel received 18 share cloudera intel dropped hadoop distribution dedicated 70 intel engineers work exclusively cloudera projects additional funds came rowe price google ventures affiliate msd capital l.p. private investment firm michael s. dell others january 2012 oracle corporation announced partnership cloudera oracle big data appliance january 2013 dell announced partnership cloudera march 2013 intel invested 740 million cloudera 18 investment may 2013 sas institute announced partnership june 2014 accenture announced service offering based cloudera june 2014 cloudera acquired gazzang developed encryption key management software october 2014 cloudera announced first payment card industry data security standard pci mastercard february 2015 deloitte announced alliance cloudera may 2015 capgemini announced marketing program sap hana cloudera july 9 2015 cloudera announced partnership teradata september 2015 cloudera announced kudu storage manager september 2015 microsoft azure announced full support cloudera enterprise january 2016 tata consultancy services announced internet things framework based cloudera sensor data analytics february 2016 emc announces evolution advanced storage dssd support cloudera 2016 cloudera ranked 5 forbes cloud 100 list cloudera filed initial public offering march 2017 april 28 2017 shares listed new york stock exchange symbol cldr september 2017 cloudera acquired fast forward labs ffl leading machine learning applied artificial intelligence research development company effort deepen cloudera ’ expertise application machine learning practical business problems new division headed ffl co-founder ceo hilary mason october 2018 cloudera hortonworks announced would merging all-stock merger equals.. merger completed january 2019 cloudera offers software services support five bundles available on-premise across multiple cloud providers cloudera also offers managed-service offering cloud cloudera also offers following free software versions additional technologies addition open-source distribution
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Distributed computing architecture
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programming paradigm programming paradigms way classify programming languages based features languages classified multiple paradigms paradigms concerned mainly implications execution model language allowing side effects whether sequence operations defined execution model paradigms concerned mainly way code organized grouping code units along state modified code yet others concerned mainly style syntax grammar common programming paradigms include symbolic techniques reflection allow program refer might also considered programming paradigm however compatible major paradigms thus real paradigm right example languages fall imperative paradigm two main features state order operations occur constructs explicitly control order allow side effects state modified one point time within one unit code later read different point time inside different unit code communication units code explicit meanwhile object-oriented programming code organized objects contain state modified code part object object-oriented languages also imperative languages contrast languages fit declarative paradigm state order execute operations instead supply number operations available system along conditions allowed execute implementation language execution model tracks operations free execute chooses order comparison multi-paradigm programming languages software engineering process defined differing methodologies programming languages models computation defined differing paradigms languages designed support one paradigm smalltalk supports object-oriented programming haskell supports functional programming programming languages support multiple paradigms object pascal c++ java c scala visual basic common lisp scheme perl php python ruby wolfram language oz f example programs written c++ object pascal php purely procedural purely object-oriented contain elements paradigms software designers programmers decide use paradigm elements object-oriented programming programs treated set interacting objects functional programming programs treated sequence stateless function evaluations programming computers systems many processors process-oriented programming programs treated sets concurrent processes act logical shared data structures many programming paradigms well known techniques forbid enable instance pure functional programming disallows use side-effects structured programming disallows use goto statement partly reason new paradigms often regarded doctrinaire overly rigid accustomed earlier styles yet avoiding certain techniques make easier understand program behavior prove theorems program correctness programming paradigms also compared programming models allow invoking execution model using api programming models also classified paradigms based features execution model parallel computing using programming model instead language common reason details parallel hardware leak abstractions used program hardware causes programmer map patterns algorithm onto patterns execution model inserted due leakage hardware abstraction consequence one parallel programming language maps well computation problems thus convenient use base sequential language insert api calls parallel execution models via programming model parallel programming models classified according abstractions reflect hardware shared memory distributed memory message passing notions place visible code forth considered flavors programming paradigm apply parallel languages programming models programming language researchers criticise notion paradigms classification programming languages e.g harper krishnamurthi argue many programming languages strictly classified one paradigm rather include features several paradigms see comparison multi-paradigm programming languages different approaches programming developed time identified either time retrospectively early approach consciously identified structured programming advocated since mid 1960s concept programming paradigm dates least 1978 turing award lecture robert w. floyd entitled paradigms programming cites notion paradigm used thomas kuhn structure scientific revolutions 1962 lowest-level programming paradigms machine code directly represents instructions contents program memory sequence numbers assembly language machine instructions represented mnemonics memory addresses given symbolic labels sometimes called first- second-generation languages 1960s assembly languages developed support library copy quite sophisticated conditional macro generation preprocessing abilities call subroutines external variables common sections globals enabling significant code re-use isolation hardware specifics via use logical operators read/write/get/put assembly still used time critical systems often embedded systems gives direct control machine next advance development procedural languages third-generation languages first described high-level languages use vocabulary related problem solved example languages follow procedural paradigm describe step step exactly procedure according particular programmer least followed solve specific problem efficacy efficiency solution therefore entirely subjective highly dependent programmer experience inventiveness ability following widespread use procedural languages object-oriented programming oop languages created simula smalltalk c++ c eiffel php java languages data methods manipulate kept one unit called object perfect encapsulation one distinguishing features oop way another object user would able access data via object methods thus inner workings object may changed without affecting code uses object still controversy raised alexander stepanov richard stallman programmers concerning efficacy oop paradigm versus procedural paradigm need every object associative methods leads skeptics associate oop software bloat attempt resolve dilemma came polymorphism object-oriented programming considered paradigm language possible create even object-oriented assembler language high level assembly hla example fully supports advanced data types object-oriented assembly language programming despite early origins thus differing programming paradigms seen rather like motivational memes advocates rather necessarily representing progress one level next precise comparisons efficacy competing paradigms frequently made difficult new differing terminology applied similar entities processes together numerous implementation distinctions across languages literate programming form imperative programming structures programs human-centered web hypertext essay documentation integral program program structured following logic prose exposition rather compiler convenience independent imperative branch declarative programming paradigms developed languages computer told problem solve problem program structured set properties find expected result procedure follow given database set rules computer tries find solution matching desired properties archetype declarative language fourth generation language sql family functional languages logic programming functional programming subset declarative programming programs written using paradigm use functions blocks code intended behave like mathematical functions functional languages discourage changes value variables assignment making great deal use recursion instead logic programming paradigm views computation automated reasoning body knowledge facts problem domain expressed logic formulas programs executed applying inference rules answer problem found set formulas proved inconsistent symbolic programming paradigm describes programs able manipulate formulas program components data programs thus effectively modify appear learn making suited applications artificial intelligence expert systems natural-language processing computer games languages support paradigm include lisp prolog differentiable programming structures programs differentiated throughout usually via automatic differentiation programming languages support one programming paradigm allow programmers use suitable programming style associated language constructs given job
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Programming language topics
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agent.btz agent.btz also named autorun computer worm infects usb flash drives spyware variant sillyfdc worm used massive 2008 cyberattack us military agent.btz worm dll file written assembler x86-32 bit spreads creating autorun.inf file root drive dll file ability scan computers data open backdoors send backdoors remote command control server 2008 us military base middle east usb flash drive infected agent.btz inserted laptop attached united states central command spread undetected systems classified unclassified order try stop spread worm pentagon banned usb drives removable media device also disabled windows autorun feature computers pentagon spent nearly 14 months cleaning worm military networks russian hackers thought behind attack used code made agent.btz previous attacks according article economist clear agent.btz designed specifically target military networks indeed comes either russia china article los angeles times reported us defense officials described malicious software apparently designed specifically target military networks thought inside russia although clear whether destructive program created individual hacker whether russian government may involvement 2010 american journalist noah shachtman wrote article investigate theory worm written single hacker later analyses kaspersky lab found relations spyware including red october turla flame december 2016 united states fbi dhs issued joint analysis report included attribution agent.btz one russian civilian military intelligence services ris
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Computer security
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online office suite online office suite online productivity suite cloud office suite office suite offered form web application accessed online using web browser allows people work together worldwide time thereby leading web-based collaboration virtual teamwork online office suites installed on-premises offered software service latter basic versions offered free advanced versions often made available subscription fee latest offerings created run pure html5 web pages known progressive web apps longer requiring cloud online connection function online office suites exist proprietary open-source software online office suite may include broad set applications following document creation editing applications publishing applications collaborative applications management applications
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Distributed computing architecture
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ado.net data provider ado.net data provider software component interacts data source ado.net data providers analogous odbc drivers jdbc drivers ole db providers ado.net providers created access simple data stores text file spreadsheet complex databases oracle database microsoft sql server mysql postgresql sqlite ibm db2 sybase ase many others also provide access hierarchical data stores email systems however different data store technologies different capabilities every ado.net provider implement every possible interface available ado.net standard microsoft describes availability interface provider-specific may applicable depending data store technology involved note also providers may augment capabilities data store capabilities known services microsoft parlance components data provider include
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Operating systems
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sanguino3 g-code sanguino3 g-code protocol 3rd-generation reprap project electronics communicate host machine well protocol reprap host communicates subsystems also written binary format storage later replay usually file .s3g extension protocol intended simplification g-code ease processing somewhat limited cpu sanguino arduino-based controller
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Programming language topics
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advanced multimedia supplements computing advanced multimedia supplements also jsr-234 amms api specification java platform practically speaking extension jsr 135 mobile media api providing new features positional 3d audio processing audio video effects processing better controls digital camera better support analog radio tuner including radio data system amms developed java community process jsr 234 jsr-234 defines six feature sets namely media capabilities define minimum implementation requirements order try avoid fragmentation define common minimal base line implementations every jsr-234 implementation must support least one media capability six media capabilities described table addition media capabilities device free support optional features including also implementations targeted mainly mobile device manufacturers
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Programming language topics
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ibm power software power ibm operating system enhancement package provided spooling facilities ibm system/360 running dos/360 retrofitted modified dos/360 upgrades power/vs power/vse available ibm system/370 running dos/vs dos/vse respectively power acronym priority output writers execution processors input readers power operating system enhancement available dos/360 dos/vs dos/vse came packaged third party dos-based operating systems international business machines released power 1969 following public introduction ibm wall street data center 'spooled queued printer card data freeing programs dependent upon speed printers punched card equipment power competed non-ibm products namely datacorp spooler sdi grasp unlike products power required dedicated partition allowed single printer 1403/2311 punch 2520 2540 reader 2540 2501 shared two processing partitions input data asynchronously loaded directed proper partition job class output directed disk stored directed printer punch writer type prt pun job class priority form code provided prt pun control cards input stream operator put proper form printer/punch told power start g pun g prt console device would continue output type available new form encountered would alert operator change forms wait next go command product ran ibm systems s/360 model 30 larger machines generally smaller machines less 128k core memory would called ram today actually magnetic cores strung wire matrices ability run power power/vs ran well later s/370 series usually models 135 145 later 4331 4341 product ran several dos-related platforms hardware platforms included clones included
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Operating systems
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directory access protocol directory access protocol dap computer networking standard promulgated itu-t iso 1988 accessing x.500 directory service dap intended used client computer systems popular implementations full osi protocol stack desktop computers available run hardware operating systems typical time basic operations dap bind read list search compare modify add delete modifyrdn adapted novell directory services nds internet lightweight directory access protocol ldap dap specified x.511
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Internet protocols
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