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symphony os symphony os symphonyone symphony linux live cd linux-based operating system developed ryan p quinn jason spisak alexander drummond distribution dormant 29 june 2011 new build released first symphony os based knoppix since may 2006 release longer based knoppix rather debian unstable features functional hard drive installer symphony os 2007 preview based ubuntu 7.04 symphonyone released april 1 2008 release version 2008.1 based ubuntu 7.10 primary difference symphony os distributions addition mezzo desktop environment environment like aspects symphony designed eye towards extreme simplicity usability example wlan-networks work automatically user action symphony also includes mozilla-driven application environment called orchestra symphony os uses custom packaging system utilizing *.sym package format simple gui user may install application symphony library without dealing dependency hell symphony debian-based also supports debian package format orchestra rapid application development environment written symphony os allows programs composed html cgi-style perl run local gui applications orchestra made two main parts lightweight localhost-only http server written perl slimmed mozilla renderer mozilla used base rendering orchestra applications utilize following technologies mezzo desktop environment created ryan quinn based designs jason spisak added symphony os aims pose new way presenting data user mezzo disposes standard concepts like desktop folder nested menu systems instead presents needed information directly user via main desktop four desk targets tasks files related system programs files trash developers claim makes desktop easier use new desktop environment called conductor development symphony os come dormant stage working new release scheduled time 2013 release built ubuntu 13.04 features redone version mezzo making os comparable design android operating system tablet operating systems creator behind symphony os mentioned distributions website symphonyos.com stated plans creation app-market use advanced packaging tool apt-url option official release date given
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Operating systems
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microsoft customer care framework microsoft customer care framework ccf desktop-based framework used address issues faced service providers caused multiple line business lob systems interacting customers discontinued though many core functions moved add-in microsoft dynamics crm product customer care framework provided core set functions customer support avenues including voice call via call center agents internet portals framework used microsoft server products including biztalk server sharepoint ccf required use microsoft sql server microsoft iis server side uses provide base core set web services ccf targeted medium large enterprises ccf originally developed large call center requirements telecommunication industry ccf different products microsoft 'out box solution requires development configuration build working customer solution framework allows soa methodology development server agent desktop side mandatory non-soa development done normally case primary user interface ccf agent desktop desktop-based user interface ui presents data aggregated various line business lob oss/bss application front ends presents unified view ccf include agent desktop application rather samples including source code provided part framework aif manages loading applications integration event brokering use adapters see hat applications custom integrations account technology hosted application well business processing hat allows separation business rules method used integrate application hat uses microsoft windows workflow foundation wf manage business rules data driven adapters ddas manage application directly bindings written xml connect two ccf 2009 sp1 ships 3 ddas win32 web java jdk 1.6 ddas customized extended additional application types needed version customer care framework ccf 2009 sp1 qfe break upgrading .net framework 3.5 sp1 microsoft composite ui application block used build composite applications within ccf number products similar ccf offered companies well
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Operating systems
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cloud computing manifesto cloud computing manifesto manifesto containing public declaration principles intentions cloud computing providers vendors annotated call action worldwide cloud community dedicated belief cloud open follows earlier development cloud computing bill rights addresses similar issues users point view document developed way open community consensus process response request microsoft 'manifesto created inception open mechanism like wiki public debate comment available creative commons license accordingly hosted mediawiki wiki licensed cc-by-sa 3.0 license original controversial version document called open cloud manifesto sharply criticised microsoft spoke vehemently developed secret shadowy group industry companies raising questions conflicts interest resulting extensive media coverage following days pre-announcement commits official publication document 30 march 2009 spite calls publish earlier time identities signatories several largest technology companies organizations led ibm along omg believed also include cisco hp sun microsystems said revealed amazon google microsoft salesforce.com among known rejected document declining signatories document leaked geva perry blog post 27 march 2009 confirmed authentic shortly afterwards authors public private documents agreed work bring together best points effort open cloud manifesto version developed private secret consortium companies prematurely revealed microsoft senior director developer platform product management steve martin 26 march 2009 claim privately shown copy document warned secret told must signed 'as without modifications additional input point disputed reuven cohen originally believed document author commentators found ironic microsoft speak support open standards others felt criticism justified comparing long ugly war ws-i call open cloud standards later echoed brandon watson microsoft director cloud services ecosystem following principles defined document
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Distributed computing architecture
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zemmix zemmix trade mark brand name south korean electronics company daewoo electronics co. ltd. msx-based video game console brand brand name zemmix longer use name zemmix daewoo released series gaming consoles compatible msx home computer standards consoles production 1985 1995 consoles sold outside south korea consoles designed broadcast standard ntsc low high outputs connecting tv universal adapter connection mains 110/220 volts consoles also letter coming serial number letters indicated color combination console key follows example cpc 51w would white silver zemmix v see zemmix products korean software companies produced software zemmix gaming console zemmix software work msx/msx2/msx2+ computers
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Computer architecture
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tiny banker trojan tiny banker trojan also called tinba malware program targets financial institution websites modified form older form viruses known banker trojans yet much smaller size powerful works establishing man-in-the-browser attacks network sniffing since discovery found infected two dozen major banking institutions united states including td bank chase hsbc wells fargo pnc bank america designed steal users sensitive data account login information banking codes tiny banker first discovered 2012 found infected thousands computers turkey discovered original source code malware leaked online began undergoing individual revisions making process detecting harder institutions highly modified version zeus trojan similar attack method obtain information tinba however found much smaller size smaller size makes malware difficult detect 20kb tinba much smaller known trojan reference average file size web site around 1,000kb difference infected web page clean one difficult anti-malware programs recognize tinba operates using packet sniffing method reading network traffic determine user navigates banking website malware launch one two different actions depending variation popular form tinba form grab webpage causing man-in-the-middle attack trojan uses form grabbing grab keystrokes encrypted https tinba sends keystrokes command control turn causes user information stolen second method tinba used allow user log webpage user malware use page information extract company logo site formatting create pop-up page informing user updates system requesting additional information social security numbers banking institutions inform users never ask information way defend types attacks tinba modified address defense begun asking users type information asked security questions user mother maiden name attempt attacker use information reset password later time tinba also injects system processes attempt convert host machine zombie unwilling member botnet order maintain connection botnet tinba coded four domains one goes loses communication trojan look one others immediately
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Computer security
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kneser–ney smoothing kneser–ney smoothing method primarily used calculate probability distribution n -grams document based histories widely considered effective method smoothing due use absolute discounting subtracting fixed value probability lower order terms omit n -grams lower frequencies approach considered equally effective higher lower order n -grams method proposed 1994 paper reinhard kneser ute essen common example illustrates concept behind method frequency bigram san francisco appears several times training corpus frequency unigram francisco also high relying unigram frequency predict frequencies n -grams leads skewed results however kneser–ney smoothing corrects considering frequency unigram relation possible words preceding let formula_1 number occurrences word formula_2 followed word formula_3 corpus equation bigram probabilities follows formula_4 unigram probability formula_5 depends likely see word formula_6 unfamiliar context estimated number times appears word divided number distinct pairs consecutive words corpus formula_7 please note formula_8 proper distribution values defined way non-negative sum one parameter formula_9 constant denotes discount value subtracted count n-gram usually 0 1 value normalizing constant formula_10 calculated make sum conditional probabilities formula_11 formula_6 equal one observe provided formula_13 formula_6 occurs least context formula_15 corpus discount probability exactly constant amount formula_16 total discount depends linearly number unique words formula_6 occur formula_15 total discount budget spread formula_11 proportionally formula_5 values formula_5 sum one simply define formula_10 equal total discount formula_23 equation extended n-grams let formula_24 formula_25 words formula_6 formula_27 model uses concept absolute-discounting interpolation incorporates information higher lower order language models addition term lower order n-grams adds weight overall probability count higher order n-grams zero similarly weight lower order model decreases count n-gram non zero
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Computational linguistics
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avast avast software s.r.o czech multinational cybersecurity software company headquartered prague czech republic researches develops computer security software machine learning artificial intelligence avast 435 million monthly active users largest market share among anti-malware application vendors worldwide january 2018 company approximately 1,700 employees across 25 offices worldwide avast founded pavel baudiš eduard kučera 1988 cooperative private company since 2010 ipo may 2018 july 2016 avast acquired competitor avg technologies 1.3 billion time avg third-ranked antivirus product dual-listed prague stock exchange london stock exchange constituent ftse 250 index avast founded eduard kučera pavel baudiš 1988 founders met research institute mathematical machines czechoslovakia studied math computer science communist party czechoslovakia would require join communist party study physics institute pavel baudiš discovered vienna virus floppy disk developed first program remove afterwards asked eduard kucera join cofounding avast cooperative cooperative originally called alwil software named avast cooperative changed joint partnership 1991 two years velvet revolution caused regime change czechoslovakia new regime severed ties soviet union reverted country economic system market economy 1995 avast employee ondřej vlček wrote first antivirus program windows 95 operating system 1990s security researchers virus bulletin security testing organization gave avast award every category tested increasing popularity software however late 1990s company struggling financially alwil rebuffed acquisition offers mcafee licensing avast antivirus engine 2001 alwil experiencing financial difficulties converted freemium model offering base avast software product cost result freemium model number users software grew one million 2004 20 million 2006 former symantec executive vince steckler appointed ceo avast 2009 2010 alwil changed name avast adopting name software raised 100 million venture capital investments following december avast filed initial public offering withdrew application following july citing changes market conditions 2012 avast fired outsourced tech support service iyogi discovered iyogi using misleading sales tactics persuade customers buy unnecessary services 2013 avast 200 million users 38 countries translated 43 languages time company 350 employees 2014 cvc capital bought interest avast undisclosed sum purchase valued avast 1 billion later year avast acquired mobile app developer inmite order build avast mobile apps additionally 2014 avast online support forum compromised exposing 400,000 names passwords email addresses 2015 avast largest share market antivirus software july 2016 avast reached agreement buy avg 1.3 billion avg large security company sold software desktops mobile devices july 2017 avast acquired uk-based piriform undisclosed sum piriform developer ccleaner shortly afterwards disclosed someone may created malicious version ccleaner backdoor hackers avast ipo london stock exchange may 2018 valued £2.4bn one uk ’ biggest technology listings ondrej vlcek assumed role ceo co-owner avast plc july 2019 day later changed annual pay 1 pledged board director compensation 100,000 charity avast develops markets business consumer security products servers desktops mobile devices company sells avast product line acquired avg-branded products late 2017 company merged avg avast business product lines working integrate corporate departments companies additionally avast developed utility software products improve battery life mobile devices cleanup unnecessary files hard drive find secure wireless networks create vpn connection internet avast avg consumer security software sold freemium model basic security features free advanced features require purchasing premium version free version also supported ads additionally avast users provide data pc mobile device avast used identify new security threats antivirus scanning browser cleanup secure browser password management network security features provided free firewall anti-spam online banking features purchased according pc pro software nag users upgrading 3 avast users pay premium version 10 us avast business product family includes features endpoint protection wi-fi security antivirus identity protection password management data protection example desktop product look vulnerabilities wi-fi network run applications suspect malicious hardware isolated sandbox avast business managed workplace monitors manages desktops assesses on-site security protocols company also sells management software administrators deploy manage avast installations pc magazine gave avast free antivirus software overall score 8.8 10 gave avg score 8.4 review said avast gets good lab test results overall many features password manager bit limited tests av-test institute avast 2017 received six six points protection usability 3.5 points performance review tom guide said free avast antivirus product good malware protection small footprint system review said avast competitive set features free antivirus product scans slow pushes users install google chrome browser avast antivirus product business users received 4 5 techradar 2017 review said software good features protection configuration excellent interface took much hard drive space n't cover mobile devices according tom guide mobile version inexpensive feature-laden features unreliable work expected pc magazine said mobile version every security feature could want difficult use avg purchased avast 2016 also generally performed well lab tests av-test institute gave avg six six points usability 5.5 points protection 5.5 points performance however avg scored 81.05 virus bulletin lab tests slightly average software good detecting malware disappointing antiphishing screening review tom hardware gave avg software seven ten stars review highlighted software small system footprint good malware protection quick scan option lacks many additional features
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Computer security
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digital multiplex hierarchy telecommunications digital multiplex hierarchy hierarchy consisting ordered repetition tandem digital multiplexers produce signals successively higher data rates level hierarchy digital multiplexing hierarchies may implemented many different configurations depending number channels desired b signaling system used c bit rate allowed communications media currently available digital multiplexers designated dl- ds- m-series operate t-carrier rates design digital multiplex hierarchies care must exercised ensure interoperability multiplexers used hierarchy digroup abbreviation digital group telephony basic group digital multiplex hierarchy north american japanese t-carrier digital hierarchies digroup supports 12 pcm voice channels equivalent services ds1 line rate 2 digroups plus overhead bits 1.544 mbit/s supporting 24 voice channels equivalent services e-carrier european hierarchy digroup supports 15 pcm channels equivalent services ds1 line rate 2 digroups plus overhead bits 2.048 mbit/s supporting 30 voice channels equivalent services
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Internet protocols
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music macro language music macro language mml music description language used sequencing music computer video game systems early automatic music generation functions used arcade games used many computer sounds example early popular arcade game music circus exidy corporation 1977 boom japanese video games heralded 1978 appearance japanese game centers amusement arcades space invaders taito corporation music proprietary closed source 1978 release programmable interval timer intel significant intel 8253 mode 3 square wave generator used music kit computer mz-40k sharp corporation made japan may 1978 another micro computer basic master mb-6880 ja used 5bit d/a converter music automated reference signal also important development method generate using basic software machine assembled hitachi ltd. made japan september 1978 mz-40k featured open architecture program sources therefore kind open source software first commands classical mml appeared internal architecture sp-1002 monitor iocs sp-5001 basic operating systems mz-80k 8-bit computer made sharp corporation 1978 japan incorporated intel 8253 hardware memory mapped i/o sound-related basic statements music tempo beep classical mml used basic described mml commands supplied music statement notes specified three-octave range song sequence mono single tones old code ￣ indicates upper octave old code ＿ indicates lower octave characters cdefgab correspond scale doremi faso lassi semitone indicated following note character note names followed tone length indicated number 0-9 similarly r indicates rest also followed number 0-9 indicating length sound length internal value × tempo values.tone length demisemiquaver 0 sp-1002 internal value 1 whole note 9 sp-1002 internal value 32 music played call 0030 sp-1002 iocs program routine statements tempo n 1-9 slowest 1.tempo 4 similar t=120 popular japanese song tōryanse written using mml mz-731 sharp 1z-007b sp-5001 upper compatible modern mml originally appeared microsoft basic common early 1970s 1980s 8-bit 16-bit era japanese personal computers nec pc-6001 included microsoft basic programmable sound generator 1981 mml especially popular nec personal computers nec pc-8801 2001 release mck music creation kit software compiling mml play music nintendo entertainment system awareness use mml increased mml presently popular among japanese electronic musicians musicians create chiptunes way write music nintendo entertainment system modern mml originated sub-language basic generally included rom micro-computers codice_1 statement uses argument define string tones sound-chip played mml code simple text format whereby letters numbers used describe musical notes played addition various implementations mml add system extensions allowing parameters audio synthesis altered specialized commands simplify entry common musical figures arpeggios though many platforms feature custom extensions letter case requirements minor syntactical features vary slightly implementations fundamental syntax rules commands features define mml present whole part implementations follows addition implementations add keywords symbols system-specific enhancements extensions
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Programming language topics
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mbed mbed platform operating system internet-connected devices based 32-bit arm cortex-m microcontrollers devices also known internet things devices project collaboratively developed arm technology partners applications mbed platform developed using mbed online ide free online code editor compiler web browser needs installed local pc since project compiled cloud i.e remote server using armcc c/c++ compiler mbed ide provides private workspaces ability import export share code distributed mercurial version control used also code documentation generation applications developed also development environments keil µvision iar embedded workbench eclipse gcc arm embedded tools mbed os provides mbed c/c++ software platform tools creating microcontroller firmware runs iot devices consists core libraries provide microcontroller peripheral drivers networking rtos runtime environment build tools test debug scripts connections secured compatible ssl/tls librairies wolfssl supports mbed-rtos components database provides driver libraries components services connected microcontrollers build final product various hardware demo-boards mbed platform first original mbed microcontroller board mbed microcontroller board marketed mbed nxp lpc1768 demo-board based nxp microcontroller arm cortex m3 core running 96 mhz 512 kb flash 64 kb ram well several interfaces including ethernet usb device spi i2c i/o mbed microcontroller received first prize annual edn innovation awards software/embedded tools category 2010 various versions board released nxp lpc2368 arm7tdmi-s nxp lpc1768 cortex-m3 nxp lpc11u24 cortex-m0 microcontrollers mbed hardware development kit hdk designed oems provides information build custom hardware support mbed os consists interface firmware schematics used easily create development boards oem modules re-programmable products suitable production project developed arm conjunction major technology companies mbed developer community development contributions happen different levels
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Computer architecture
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digital transmission group telecommunication digital transmission group group digitized voice data channels bit streams combined single digital bit stream transmission communications media digital transmission groups usually categorized maximum capacity specific number channels however maximum digital transmission group capacity must equal greater sum individual multiplexer input channel capacities
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Internet protocols
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free license free license open license license agreement contains provisions allow individuals reuse another creator work giving four major freedoms without special license uses normally prohibited copyright law commercial license free licenses worldwide royalty-free non-exclusive perpetual see copyright durations free licenses often basis crowdsourcing crowdfunding projects invention term free license focus rights users connected sharing traditions hacker culture 1970s public domain software ecosystem social political free software movement since 1980 open source movement since 1990s rights codified different groups organizations different domains free software definition open source definition debian free software guidelines definition free cultural works open definition definitions transformed licenses using copyright legal mechanism since ideas free/open licenses spread different spheres society open source free culture unified free open-source movement anticopyright wikimedia foundation projects public domain advocacy groups pirate parties connected free open licenses creative commons affiliates 100 jurisdictions world eupl created european union harald welte created gpl-violations.org
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Databases
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emotet emotet banking trojan malware program obtains financial information injecting computer code networking stack infected microsoft windows computer allowing sensitive data stolen via transmission emotet malware also inserts software modules able steal address book data perform denial service attacks systems also functions downloader dropper banking trojans emotet evolved delivery however prominent form inserting malicious documents url links inside body email sometimes disguised invoice pdf attachment first reported germany austria switzerland 2014 united states quickly followed suit encountering emotet malware necessarily fake invoices rather malicious javascript .js files malicious .js files executed emotet malware able infect current host emotet infected host malicious file part malware able intercept log save outgoing network traffic via web browser leading sensitive data compiled access victim bank account emotet member feodo trojan family trojan malware run virtual machine environment emotet changes behavior ways intended mislead malware investigators
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Computer security
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center embedding linguistics center embedding process embedding phrase middle another phrase type often leads difficulty parsing would difficult explain grammatical grounds alone frequently used example involves embedding relative clause inside another one theories natural language parsing difficulty multiple center embedding thought arise limitations human short term memory order process multiple center embeddings store many subjects order connect predicates interesting theoretical point sentences multiple center embedding grammatical unacceptable examples behind noam chomsky comment languages 'designed parsability … may say languages usable chomsky 1991 researchers peter reich came theories though single center embedding acceptable man boy kicked friend mine double center embedding linguist anne de roeck colleagues provided counter-example n't true example-sentences people know produce likely accepted de roeck et al. 1982 linguist fred karlsson provided empirical evidence 2007 maximal degree multiple center-embedding clauses exactly 3 written language provided thirteen genuine examples type various indo-european languages danish english german latin swedish real examples degree 4 recorded spoken language multiple center-embeddings even degree 2 rare practically non-existing karlsson 2007 center embedding focus science fiction novel ian watson embedding plays part ted chiang story life embedding refers types clauses occurring subordinate parts superordinate clause three types sub-clauses complement relative adverbial subordinators relative pronouns indicate sub clause used center embedding abbreviated c c contains words superordinate clause left right sub-clauses multiple center embedding type clause called self-embedding english language create infinite number sentences even though set number words grammatical rules create infinite sentences rules recursion iteration rule recursion come center embedding embedding one sentence within another sentence linguists say center embedding could go forever technically grammatically correct reader would however become confused trying keep track working memory would able store keep track information given enough time piece paper pencil reader could work information sentence made sense embedding used two clauses share common category expand sentence effective optional categories used create extensive embedding sentence brother opened window maid closed -the common category window sentence expanded become brother opened window maid closed brother opened window maid janitor uncle bill hired married closed common category sentence broken multiple sentences make sense reader brother opened window maid closed one married janitor uncle bill hired center embedded sentence difficult comprehend relative clause embedded another relative clause comprehension becomes easier types clause different -- complement clause embedded relative clause relative clause embedded complement clause example- man heard dog killed radio ran away tell sentence center embedded edge embedded depending brackets located sentence 1 joe believes mary thinks john handsome 2 cat dog man hit chased meowed sentence 1 brackets located right sentence right embedded sentence 2 brackets located inside sentence spaced throughout
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Computational linguistics
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battery directive directive 2006/66/ec european parliament council 6 september 2006 batteries accumulators waste batteries accumulators repealing directive 91/157/eec commonly known battery directive regulates manufacture disposal batteries european union aim improving environmental performance batteries accumulators batteries commonly contain hazardous elements mercury cadmium lead incinerated landfilled present risk environment human health directive 91/157/eec adopted 18 march 1991 reduce hazards harmonising eu member states laws disposal recycling batteries containing dangerous substances directive 2006/66/ec repealed directive 91/157/eec directive 2006/66/ec amended directive 2013/56/eu 20 november 2013 regards placing market portable batteries accumulators containing cadmium intended use cordless power tools button cells low mercury content repealing commission decision 2009/603/ec directive like many european compliance directives directly applicable requires legislative action european member states though european directives legislation european union member states must comply avoid legal action european commission bring bear n't however member states retain freedom means implement directive requirements battery directive objective improving environmental performance batteries regulating use certain substances manufacture batteries lead mercury cadmium etc setting standards waste management batteries many european member states passed battery waste management laws among nations belgium sweden germany austria denmark finland united kingdom netherlands france others finland denmark supported total prohibition cadmium batteries belgium sweden battery recycling rates 59 55 respectively finalisation 2006 battery directive european states specific guidelines make rules comport first western european directives dealing waste management council directive 75/442/eec 15 july 1975 waste n't mention batteries chemicals specified regulation particular categories waste later referenced battery directives legislative legal basis first version european council directive batteries accumulators 91/157/eec approved 18 march 1991 covered many battery types including industrial automotive dry-cell lead-acid alkaline nickel-cadmium nickel-metal-hydride lithium lithium-ion mercury etc first program directive set six-year duration starting 1993 1991 battery directive article 3 mi annex stated prohibition exceptions marketing since battery recycling rates 5 directive sought improve rates set recycling goals separate collection recycling provide recycling/collection information consumer responsibility providing separated recycling collection largely given manufacturers recycling requirements found articles 4 6 7 marking provisions including manufacturer responsibility marking battery products contained substances recycling information regulation met heavy resistance disputed deadlines target recycling rates implementation dates weight percentage limits applicable product groups financial responsibility public information campaigns waste management financial impact exclusions financial responsibility given small producer businesses personnel safety decreased reliability greener batteries non-environmental battery marking question automotive battery makers questioned markings batteries relating battery performance arguing quantity car battery electric current output start vehicle extreme weather good indicator battery performance poor implementation first battery directive work began new directive would emphasise battery end-of-life waste management mandated better-structured collection recycling programs also acknowledged research certain substance needed harsher complete arguably unrealistic bans thus onus everyone waste management chain producer consumer rather affecting product design substance bans manufacturers claimed unreasonable consultations revisions first battery directive started 1997 giving interested parties voice legislation policy especially assessing directive economic environmental social impact february 2003 open stakeholders consultation process started published findings online culminated meeting brussels july 2003 waters tested asking extended impact assessments different scenarios proposed ranges regulation example would impact establishing spent battery collection targets 30 80 impact separate spent battery collection 70 100 entities asked goals could met propose collection responsibility models green viewpoint perhaps conciliation committee previous directive limited scope groups side set forth reasons less stringency arguing broadening scope claimed batteries certain metals banned carte blanche waste management effort would hurt confusion perhaps inconvenience public least six drafts 2003 version equivalent second battery directive 2003 revision council directive 2003/0282/cod july 2006 conciliation agreement compromise european council european parliament came three years draft revisions welcomed entities like european portable battery association epba favoured less stringency models european compliance legislation corporation organisations like epba participates working groups members include among players legislators large enterprises—in case battery-makers—trade associations non-governmental organisations directive overall stated objective still protect public interest cleaner environment minimising negative impact environment batteries especially waste cycle depending viewpoint also something compromise 1. manufacturers distributors 3. environmental proponents recent battery directive entered force 26 september 2006 gave european member states 26 september 2008 implement national laws rules batteries art.26 – transposition nations took initiative already started programs passed laws accordance spirit specifications earlier battery directives exception button cells mercury content 2 weight 2006 battery directive restates earlier battery directive prohibition marketing batteries 0.0005 mercury 0.002 cadmium weight however exceptions exist directive also mandates symbols battery labels indicate battery chemical contents lead mercury cadmium used according directive lead content batteries longer restricted initiatives reduce heavy metal batteries promote using less toxic substances batteries dispose batteries properly via regular household waste properly separated research initiatives recycling consumers informed dangers non-compliant disposal old batteries also states must easy consumers remove batteries electronic products disposal automotive industrial batteries leaving landfills incineration prohibited directive preamble point 8 article 7 requires member states maximise separation batteries regular municipal waste requires spent batteries collected separately recycling collection targets called fewer batteries end landfills collection program found annex proposed member states set country standards using battery directive guide minimum levels levels stated terms percents prior annual sales article 3 17 states 'collection rate means given member state given calendar year percentage obtained dividing weight waste portable batteries accumulators collected accordance article 8 1 directive directive 2002/96/ec calendar year average weight portable batteries accumulators producers either sell directly end-users deliver third parties order sell end-users member state calendar year preceding two calendar years member states required provide collection sites accessible free charge public art 8 battery distributors may required provide member states discretion art 8 2 battery manufacturers may refuse take back waste batteries end-consumers irrespective chemical composition origin art 8 3 waste battery collection rate targets specified article 10 minimum targets 25 battery sales 45 battery sales 26 september 2012 2016 respectively art 10 2 collections rates monitored annually outlined annex scheme yearly reporting commission may leeway given form transitional agreements nation special circumstances art 10 4 many exclusions granted manufacturers certain product types cases batteries used safety critical-use applications e.g miners caps exemptions following still place batteries imported third countries non-discriminatory conditions included art 19 member states may use instruments like differential tax rates encourage less toxic batteries recycling art 9 member states required submit implementation reports commission every three years art 22 art 21 marking must indicate separate collections recycling heavy metal content labels state collection information chemical content batteries show symbol crossed-out wheeled recycling bin annex ii indicate battery go bin symbol size specified percent battery area largest side 3 except cylindrical batteries symbol 1.5 total surface area member states set measures effective proportionate dissuasive penalties actions comporting battery directive apprise european commission measures changes art 25 annex battery collection targets mentioned art 10 practice manufacturers batteries need make sure applied legal framework company means need check producer legal terms directive whether fulfilled labelling obligation next step manufacturers distributors define battery strategy register battery compliance schemes control battery compliance monitor recycling recovery results working within framework battery directive manufacturers producers distributors also aware financial aspects registration timelines ensure compliance reduce risks batteries time supported advice suitable qualified persons mercury-containing rechargeable battery management act 1996 similar law united states banning sale mercury-containing batteries except small button cells requiring labelling disposal recycling u.s. state california new york city require recycling rechargeable batteries along state maine require recycling cell phones similar european directives protecting environment health parallel battery directive restriction hazardous substances rohs waste electrical electronic equipment weee registration evaluation authorisation restriction chemicals reach directives
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Computer security
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distributed application specification language dasl programming language distributed application specification language high-level strongly typed programming language originally developed sun microsystems laboratories 1999 2003 part ace project goals project enable rapid development web-based applications based sun j2ee architecture eliminate steep learning curve platform-specific details dasl defines application domain model one logical presentation models logical presentation model consists choreography domain model objects described set forms attached actions dasl generates graphical user interface directly logical presentation dasl unique among modern application programming languages ability generate modern graphic user interface application without requiring programmer define user interface explicitly allowing programmer control look feel generated graphic user interface dasl language partially declarative partially procedural description object/data structures persistence description logical presentation declarative basic object constraints behavior declarative additional object behaviors specified procedurally methods queries defined either declaratively writing methods language development environment practical realization model-driven architecture mda approach programmer uses dasl produce platform-independent model pim language code generators automatically produce deploy platform-specific model psm new psms may introduced writing new code generators key benefit dasl language approach 3rd generation 3gl programming languages enterprise applications specified concise precise way expresses application logic clearly small enterprise application dasl typically implemented 8-10k lines dasl code dasl compiler typically translates 200k lines java xml sql implementation artifacts 200k line figure typical equivalent applications written using 3gls conciseness dasl seen also terms content two representations dasl vs. generated application code java/xml/sql etc. dasl code describes business logic business processes specific application independent deployment middleware frameworks presentation mechanisms core business logic typically represents 2-5 generated application code thus writing understanding maintaining application code much easier dasl level level generated code business logic scattered within various implementation artifacts another advantage using dasl write applications rather conventional 3rd generation languages ides dasl code independent middleware gui presentation frameworks network topology implementation technologies new middleware frameworks developed evolve existing dasl programs migrated without need re-implement example original dasl code generators produced traditional html screens later dasl code generators written use frameworks apache struts technologies javascript browser produce interactive experience today new dasl generators written produce rich internet applications existing dasl applications thus converted rich internet applications recompiling latest code generators dasl combines declarative syntax java-like procedural syntax declarative part language enables defining applications higher level abstraction 3rd generation languages java dasl programmer describe inter-process communication client processes web servers application servers databases details user interface desired application rather programmer describes application set related domain objects including behavior set forms actions annotated basic layout properties contrast highly specialized dsls dasl turing-complete behavior domain objects expressed using combination declarative procedural syntax example constraints objects object attributes expressed declaratively constraint defined either declarative expression procedurally dasl application two primary components business object specification bos describes object domain model consisting persistent transient objects representing domain application application usage specification aus describes actions use cases may performed domain model aus essentially choreography domain objects series forms actions dasl programmer models graphical user interface application annotating logical aus forms actions properties describe basic layout data page rather user interface considerations dominating application specification dasl logical interaction user domain model central user interface derived logical interaction believed dasl unique among languages respect dasl language described published sun labs technical report called dasl language programmer guide reference manual technical report also available part acm digital library http //dl.acm.org/citation.cfm id=1698172 dl=acm coll=dl cfid=800729170 cftoken=37871889 around 1999 two sun researchers bruce daniels bob goldberg started research project sun labs called 'ace project goal simplifying creation java web-based enterprise applications ace language known dasl developed goldberg daniels several colleagues part project ace project language featured article appeared june 2002 sun website well january 2003 edition computing research news entitled sun microsystems laboratories license innovate 'project ace ace dasl development environment demonstrated bruce daniels part james gosling keynote address javaone conference march 2002 business side sun microsystems dasl language used implement public interface sun grid compute utility known gridportal although sun microsystems release commercial implementation dasl language past made technology available selected partners conducted trials using technology dasl referenced association computing machinery portal including paper presented oopsla 2004 conference papers model-driven software development sun/oracle website describing project ace demonstration ace dasl given part james gosling keynote address 2004 java one conference research development dasl language continued rd3 software 2006 2010 rd3 language enhancements code generators dasl made language extensible broadened scope language dynamic http-style web applications rich internet applications addition producing html front ends dasl code generators created produce adobe flex flash front ends modest resources html5 could easily generated well iphone- android-specific implementations language extended define dynamic websites domain-specific web portals include cloud applications example rd3 website implemented dasl program rd3 dasl language supports concept forms nested forms part logical presentation information actions logically grouped user interface controlled using annotations presentation navigation recursive relationships organization charts family trees added language dasl language made extensible third party programmer write code generator plugin java targeted specific dasl object class form allowing object form presented using custom widget customized widgets may computation within user browser application presentation produced dasl turing complete dasl unique among modern application programming languages ability generate modern graphic user interface application without requiring programmer define user interface explicitly using simple annotations programmer modify user interface produced dasl using code generator plugins programmer extend dasl generate specific desired user interface
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Programming language topics
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distributed-queue dual-bus telecommunication distributed-queue dual-bus network dqdb distributed multi-access network supports integrated communications using dual bus distributed queuing b provides access local metropolitan area networks c supports connectionless data transfer connection-oriented data transfer isochronous communications voice communications ieee 802.6 example network providing dqdb access methods dqdb medium access control mac algorithm generally credited robert newman developed algorithm phd thesis 1980s university western australia appreciate innovative value dqdb mac algorithm must seen background lan protocols time based broadcast ethernet ieee 802.3 ring like token ring ieee 802.5 fddi dqdb may thought two token rings one carrying data direction around ring improves reliability important metropolitan area networks man repairs may take longer lan wi-fi damage may inaccessible dqdb standard ieee 802.6 developed atm broadband isdn still early development strong interaction two standards atm cells dqdb frames harmonized settled essentially 48-byte data frame 5-byte header dqdb algorithm distributed queue implemented communicating queue state information via header node dqdb network maintains pair state variables represent position distributed queue size queue headers reverse bus communicated requests inserted distributed queue upstream nodes would know allow dqdb cells pass unused forward bus algorithm remarkable extreme simplicity currently dqdb systems installed many carriers entire cities lengths reach speeds ds3 line 44.736 mbit/s implementations use optical fiber length 100 km speeds around 150 mbit/s
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Internet protocols
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symantec operations readiness tools march 15 2011 symantec released symantec operations readiness tools sort updated version veritas operations services vos sort formerly vos web-based suite services introduced symantec corporation 2008 supports symantec enterprise products veritas storage foundation veritas cluster server vcs netbackup sort collects environmental data aix hp-ux linux solaris windows servers sort identifies risks data centers provides remediation recommendations symantec currently charge customers sort sort uses data collector collect configuration environmental data veritas volume manager vxvm veritas file system vxfs vcs netbackup symantec enterprise products data analyzed potential problems risks summarized reports sort produces three types reports symantec enterprise products sort performs environment-specific checks produce reports risk assessment report example based 155 separate checks product licensing inventory report lists installed software binaries license keys installation upgrade report lists environment-specific prerequisites must met installing upgrading symantec enterprise products example report lists required operating system patches need installed installing symantec enterprise product risk assessment report provides environment-specific configuration assessment recommendations increase performance availability utilization example one checks risk assessment report lists volumes whose mirrors composed logical units disk array logical volumes mirrored higher availability mirrored across separate disk array controllers mirroring logical volumes across separate disk array controllers allows logical volumes continue operate one disk array fail
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Distributed computing architecture
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ultra 5/10 ultra 5 ultra 10 64-bit sun microsystems workstations based ultrasparc microprocessor line available since january 1998 last shipped november 2002 systems notable first sun workstation line introduce various commodity pc compatible hardware components ata hard disks cmd640 pci eide controller ati rage pro video chip ultra 5 came pizzabox style case 270 333 360 400-mhz ultrasparc iii cpu supported maximum 512 mb buffered edo ecc ram four 50ns 168-pin dimm slots included single eide hard disk drive 4 20 gb cd-rom drive three 32-bit 33 mhz pci slots two full-size one short graphics port hd15 parallel printer port db25 two serial ports db25 de9 ethernet port 10base-t/100base-tx headphone line-in line-out microphone 3.5-mm jacks ultra 10 came mid-tower case 300 333 360 440-mhz 64-bit ultrasparc cpu doubled supported ram maximum 1024 mb four dimm slots added room second ata hard disk fourth pci card upa graphics card creator creator3d elite3d
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Computer architecture
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conary package manager conary free software package management system created rpath sas distributed terms apache license version 2.0 relicensed gplv3 2013 focuses installing packages automated dependency resolution distributed online repositories providing concise easy-to-use python-based description language specify build package used foresight linux rpath linux conary updates specific files packages need updated behavior minimizes bandwidth time requirements updating software packages conary also features rollbacks package installation well derived packages conary toolchain includes build server conary packages builds packages inside chroot environments containing package explicitly listed build requirements fundamental packages useful packagers means package builds done inside reproducible environment packagers accidentally introduce dependencies peculiarities machine environment custom configuration files undocumented extra packages
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Operating systems
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drop insert multichannel transmission system drop insert process diverts drop portion multiplexed aggregate signal intermediate point introduces insert different signal subsequent transmission position drop insert practiced example time-division multiplexing tdm time slot frequency band replaced another source diverted signal may demodulated reinserted another transmission system another time slot frequency band time slot frequency band vacated diverted signal need necessarily reoccupied another signal likewise previously unoccupied time slot frequency band may occupied signal inserted drop-and-insert point signals interest drop-and-insert point diverted
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Internet protocols
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dual in-line package microelectronics dual in-line package dip dil dual in-line pin package dipp electronic component package rectangular housing two parallel rows electrical connecting pins package may through-hole mounted printed circuit board pcb inserted socket dual-inline format invented forbes rex rice bryant rogers fairchild r 1964 restricted number leads available circular transistor-style packages became limitation use integrated circuits increasingly complex circuits required signal power supply leads observed rent rule eventually microprocessors similar complex devices required leads could put dip package leading development higher-density chip carriers furthermore square rectangular packages made easier route printed-circuit traces beneath packages dip usually referred dip n n total number pins example microcircuit package two rows seven vertical leads would dip14 photograph upper right shows three dip14 ics common packages three many 64 leads many analog digital integrated circuit types available dip packages arrays transistors switches light emitting diodes resistors dip plugs ribbon cables used standard ic sockets dip packages usually made opaque molded epoxy plastic pressed around tin- silver- gold-plated lead frame supports device die provides connection pins types ic made ceramic dip packages high temperature high reliability required device optical window interior package dip packages secured pcb inserting pins holes board soldering place replacement parts necessary test fixtures programmable devices must removed changes dip socket used sockets include zero insertion force mechanism variations dip package include single row pins e.g resistor array possibly including heat sink tab place second row pins types four rows pins two rows staggered side package dip packages mostly displaced surface-mount package types avoid expense drilling holes pcb allow higher density interconnections dips commonly used integrated circuits ics devices dip packages include resistor networks dip switches led segmented bargraph displays electromechanical relays dip connector plugs ribbon cables common computers electronic equipment dallas semiconductor manufactured integrated dip real-time clock rtc modules contained ic chip non-replaceable 10-year lithium battery dip header blocks discrete components could soldered used groups components needed easily removed configuration changes optional features calibration original dual-in-line package invented bryant buck rogers 1964 working fairchild semiconductor first devices 14 pins looked much like today rectangular shape allowed integrated circuits packaged densely previous round packages package well-suited automated assembly equipment pcb could populated scores hundreds ics components circuit board could soldered one time wave soldering machine passed automated testing machines little human labor required dip packages still large respect integrated circuits within end 20th century surface-mount packages allowed reduction size weight systems dip chips still popular circuit prototyping breadboard easily inserted utilized dips mainstream microelectronics industry 1970s 1980s use declined first decade 21st century due emerging new surface-mount technology smt packages plastic leaded chip carrier plcc small-outline integrated circuit soic though dips continued extensive use 1990s still continue used substantially year 2011 passes modern chips available surface-mount package types number companies sell various prototyping adapters allow smt devices used like dip devices through-hole breadboards soldered prototyping boards stripboard perfboard smt pose quite problem least inconvenience prototyping general characteristics smt advantages mass production difficulties prototyping programmable devices like eproms gals dips remained popular many years due easy handling external programming circuitry i.e. dip devices could simply plugged socket programming device however in-system programming isp technology state art advantage dips rapidly losing importance well 1990s devices fewer 20 leads manufactured dip format addition newer formats since 2000 newer devices often unavailable dip format dips mounted either through-hole soldering sockets sockets allow easy replacement device eliminates risk damage overheating soldering generally sockets used high-value large ics cost much socket devices would frequently inserted removed test equipment eprom programmers zero insertion force socket would used dips also used breadboards temporary mounting arrangement education design development device testing hobbyists one-off construction permanent prototyping use point-to-point wiring dips appearance physically inverted part method inspires informal term dead bug style method body housing dip containing ic chip usually made molded plastic ceramic hermetic nature ceramic housing preferred extremely high reliability devices however vast majority dips manufactured via thermoset molding process epoxy mold compound heated transferred pressure encapsulate device typical cure cycles resins less 2 minutes single cycle may produce hundreds devices leads emerge longer sides package along seam parallel top bottom planes package bent downward approximately 90 degrees slightly less leaving angled slightly outward centerline package body soic smt package resembles typical dip appears essentially notwithstanding size scale except bent leads bent upward equal angle become parallel bottom plane package ceramic cerdip packages epoxy grout used hermetically seal two halves together providing air moisture tight seal protect ic die inside plastic dip pdip packages usually sealed fusing cementing plastic halves around leads high degree hermeticity achieved plastic usually somewhat porous moisture process ensure good microscopic seal leads plastic points around perimeter however contaminants usually still kept well enough device operate reliably decades reasonable care controlled environment inside package lower half leads embedded center package rectangular space chamber void ic die cemented leads package extend diagonally inside package positions emergence along periphery points along rectangular perimeter surrounding die tapering go become fine contacts die ultra-fine bond wires barely visible naked human eye welded die periphery contacts bond pads die connecting one lead bond pad making final connection microcircuits external dip leads bond wires usually taut loop upward slightly allow slack thermal expansion contraction materials single bond wire breaks detaches entire ic may become useless top package covers delicate assemblage without crushing bond wires protecting contamination foreign materials usually company logo alphanumeric codes sometimes words printed top package identify manufacturer type made usually year week number sometimes made proprietary information perhaps revision numbers manufacturing plant codes stepping id codes necessity laying leads basically radial pattern single plane die perimeter two rows periphery package main reason dip packages higher lead counts must wider spacing lead rows effectively limits number leads practical dip package may even small die many bond pads e.g chip 15 inverters requiring 32 leads wider dip would still required accommodate radiating leads internally one reasons four-sided multiple rowed packages pgas introduced around early 1980s large dip package dip64 used motorola 68000 cpu long leads inside package pins die making package unsuitable high speed devices types dip devices built differently molded plastic housings straight leads leads extend directly bottom package led displays particularly housing usually hollow plastic box bottom/back open filled around contained electronic components hard translucent epoxy material leads emerge others dip switches composed two plastic housing parts snapped welded glued together around set contacts tiny mechanical parts leads emerging molded-in holes notches plastic several dip variants ics exist mostly distinguished packaging material eproms sold ceramic dips manufactured circular window clear quartz chip die allow part erased ultraviolet light often chips also sold less expensive windowless pdip cerdip packages one-time programmable otp versions windowed windowless packages also used microcontrollers devices containing eprom memory windowed cerdip-packaged eproms used bios rom many early ibm pc clones adhesive label covering window prevent inadvertent erasure exposure ambient light molded plastic dips much lower cost ceramic packages one 1979 study showed plastic 14 pin dip cost around us 0.63 ceramic package cost us 0.82 single in-line pin package sip sipp one row connecting pins popular dip used packaging ram chips multiple resistors common pin compared dips typical maximum i/o count 64 sips typical maximum i/o count 24 lower package costs one variant single in-line package uses part lead frame heat sink tab multi-leaded power package useful applications audio power amplifiers example rockwell used quad in-line package 42 leads formed staggered rows pps-4 microprocessor family introduced 1973 microprocessors microcontrollers higher lead counts early 1990s qip sometimes called qil package dimensions dil package leads side bent alternating zigzag configuration fit four lines solder pads instead two dil qil design increased spacing solder pads without increasing package size two reasons qil packaged ics added heatsinking tabs ha1306 intel 3m developed ceramic leadless quad in-line package quip introduced 1979 boost microprocessor density economy ceramic leadless quip designed surface-mount use requires socket used intel iapx 432 microprocessor chip set zilog z8-02 external-rom prototyping version z8 microcontroller commonly found dip packages conform jedec standards use inter-lead spacing lead pitch jedec ms-001ba row spacing varies depending lead counts 0.3 7.62 mm jedec ms-001 0.6 inch 15.24 mm jedec ms-011 common less common standardized row spacings include 0.4 inch 10.16 mm jedec ms-010 0.9 inch 22.86 mm well row spacing 0.3 inch 0.6 inch 0.75 inch 0.07 inch 1.778 mm lead pitch former soviet union eastern bloc countries used similar packages metric pin-to-pin spacing 2.5 mm rather number leads always even 0.3 inch spacing typical lead counts 8 14 16 18 28 less common 4 6 20 24 lead counts even number leads dips unused connected nc leads internal chip duplicated e.g two ground pins 0.6 inch spacing typical lead counts 24 28 32 40 less common 36 48 52 64 lead counts microprocessors motorola 68000 zilog z180 used lead counts high 64 typically maximum number leads dip package shown diagram leads numbered consecutively pin 1 identifying notch package top pin 1 top left corner device sometimes pin 1 identified indent paint dot mark example 14-lead dip notch top left leads numbered 1 7 top bottom right row leads numbered 8 14 bottom top dip devices segmented led displays relays replace leads heat sink fin skip leads remaining leads numbered positions leads addition providing human visual identification orientation package notch allows automated chip-insertion machinery confirm correct orientation chip mechanical sensing soic small outline ic surface-mount package currently popular particularly consumer electronics personal computers essentially shrunk version standard ic pdip fundamental difference makes smt device second bend leads flatten parallel bottom plane plastic housing soj small outline j-lead smt packages sop small outline package names considered relatives dip original ancestor soic packages tend half pitch dip sop half fourth dip 0.1 /2.54 mm 0.05 /1.27 mm 0.025 /0.635 mm respectively pin grid array pga packages may considered evolved dip pgas pin centers dips popular microprocessors early mid-1980s 1990s owners personal computers containing intel 80286 p5 pentium processors may familiar pga packages often inserted zif sockets motherboards similarity pga socket may physically compatible dip devices though converse rarely true
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Computer architecture
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android honeycomb android honeycomb codename eighth version android designed devices larger screen sizes particularly tablets longer supported newer versions honeycomb debuted motorola xoom february 2011 besides addition new features honeycomb introduced new so-called holographic user interface theme interaction model built main features android multitasking notifications widgets new features introduced honeycomb include following
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Operating systems
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iris recognition immigration system iris recognition immigration system iris initiative launched 2004 provide automated clearance uk immigration certain frequent travellers functioned one-to-all identification mode searching large database million enrolled frequent travellers see anyone matched presenting iris passenger asked assert identity e.g presenting passport id card would require one-to-one verification test single enrolled identity thus iris exploited great robustness iris recognition making false matches since unlike weak biometrics face recognition could survive vast number opportunities make false matches searching large database instead needing test single asserted identity decommissioned september 2013 favour e-passport entry using biometric data stored e-passport chip requires single asserted identity tested thus could function using weaker biometrics simple one-to-one verification mode iris relied biometric technology authenticate identity part e-borders initiative uk government claimed passengers found system difficult use resulting many false rejections required passengers join normal queue passport presentation main factor behind decision decommission iris cost staffing enrolment offices airport terminals whereas face recognition required submitting passport-type photograph acquired photo-booth without need personal presentation airport enrolment staff system cost £4.9 million develop £4 million operate enrolled passengers could enter uk special automated immigration control barrier incorporating iris recognition camera barriers located certain immigration arrival halls form part immigration passport control enrolment took place airport departure lounge immigration officer assesses eligibility enrols qualifying persons qualified participate scheme eyes photographed order capture iris patterns data stored securely alongside personal details originally iris rolled london heathrow london gatwick birmingham manchester 2004 intended deployment period five years february 2013 iris available heathrow terminals 3 5 barriers decommissioned last operational barriers decommissioned 15 16 september 2013 respectively original deployment plan five years doubled nearly ten years following travellers eligible enrol
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Databases
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dynamic logical partitioning dynamic logical partitioning dlpar capability logical partition lpar reconfigured dynamically without shut operating system runs lpar dlpar enables memory cpu capacity i/o interfaces moved nondisruptively lpars within server dlpar supported operating systems aix i5/os almost power4 follow-on power systems since linux kernel power also supported dlpar dynamic reconfiguration capabilities limited cpu capacity pci devices memory october 2009 seven years aix announcement dlpar memory cpu io slots linux finally added capability dlpar memory power systems fundamentals dlpar described ibm systems journal paper titled dynamic reconfiguration basic building blocks autonomic computing ibm pseries servers later power5 processor added enhanced dlpar capabilities including micro-partitioning 10 lpars configured per processor single multiprocessor server supporting maximum 254 lpars thus 254 independent operating system instances many interesting applications dlpar capabilities primarily used build agile infrastructures automate hardware system resource allocation planning provisioning turn results increased system utilization example memory processor i/o slots added removed moved another lpar without rebooting operating system application running lpar ibm db2 application http //www.ibm.com/developerworks/eserver/articles/db2_dlpar.html aware dlpar events automatically tunes changing lpar resources system z9 zseries mainframes operating systems including linux z systems support even sophisticated forms dynamic lpars relevant lpar-related features mainframe platforms include intelligent resource director sysplex parallel sysplex geographically dispersed parallel sysplex hipersockets system z9 supports 60 lpars single server mainframes also support additional level virtualization using z/vm ability support thousands operating system instances single server
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Operating systems
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uncontrolled format string uncontrolled format string type software vulnerability discovered around 1989 used security exploits originally thought harmless format string exploits used crash program execute harmful code problem stems use unchecked user input format string parameter certain c functions perform formatting codice_1 malicious user may use codice_2 codice_3 format tokens among others print data call stack possibly locations memory one may also write arbitrary data arbitrary locations using codice_4 format token commands codice_1 similar functions write number bytes formatted address stored stack typical exploit uses combination techniques take control instruction pointer ip process example forcing program overwrite address library function return address stack pointer malicious shellcode padding parameters format specifiers used control number bytes output codice_3 token used pop bytes stack beginning format string reached start format string crafted contain address codice_4 format token overwrite address malicious code execute common vulnerability format bugs previously thought harmless resulted vulnerabilities many common tools mitre cve project lists roughly 500 vulnerable programs june 2007 trend analysis ranks 9th most-reported vulnerability type 2001 2006 format string bugs commonly appear programmer wishes output string containing user supplied data either file buffer user programmer may mistakenly write codice_8 instead codice_9 first version interprets codice_10 format string parses formatting instructions may contain second version simply prints string screen programmer intended versions behave identically absence format specifiers string makes easy mistake go unnoticed developer format bugs arise c argument passing conventions type-safe particular codice_11 mechanism allows functions accept number arguments e.g codice_12 popping many arguments call stack wish trusting early arguments indicate many additional arguments popped types format string bugs occur programming languages besides c perl although appear less frequency usually exploited execute code attacker choice format bugs first noted 1989 fuzz testing work done university wisconsin discovered interaction effect c shell csh command history mechanism error routine assumed safe string input use format string bugs attack vector discovered september 1999 tymm twillman security audit proftpd daemon audit uncovered codice_13 directly passed user-generated data without format string extensive tests contrived arguments printf-style functions showed use privilege escalation possible led first posting september 1999 bugtraq mailing list regarding class vulnerabilities including basic exploit still several months however security community became aware full dangers format string vulnerabilities exploits software using method began surface first exploits brought issue common awareness providing remote root access via code execution published simultaneously bugtraq list june 2000 przemysław frasunek person using nickname tf8 seminal paper format string attacks tim newsham published september 2000 detailed technical explanation papers published september 2001 exploiting format string vulnerabilities team teso many compilers statically check format strings produce warnings dangerous suspect formats gnu compiler collection relevant compiler flags codice_14 codice_15 codice_16 codice_17 codice_18 codice_19 useful detecting bad format strings known compile-time format string may come user source external application application must validate format string using care must also taken application generates selects format strings fly gnu c library used codice_20 parameter used detect certain types attacks occurring run-time codice_18 check stringent contrary many security issues root cause format string vulnerabilities relatively easy detect x86-compiled executables codice_12-family functions proper use implies separate argument format string arguments formatted faulty uses functions spotted simply counting number arguments passed function 'argument deficiency strong indicator function misused counting number arguments often made easy x86 due calling convention caller removes arguments pushed onto stack adding stack pointer call simple examination stack correction yields number arguments passed codice_12-family function
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Computer security
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secure network secure network small research consulting company focusing information security based milano italy london united kingdom besides notability italy received international exposure research project bluetooth security co-sponsored f-secure codenamed bluebag also selected black hat briefings conference 2006 las vegas 2009 also organized seacure.it first international technical security conference ever held italy
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Computer security
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list server-side javascript implementations list server-side javascript implementations common server-side programming languages javaserver pages jsp active server pages asp perl php python ruby coldfusion others
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Programming language topics
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krivine machine theoretical computer science krivine machine abstract machine sometimes called virtual machine abstract machine shares features turing machines secd machine krivine machine explains compute recursive function specifically aims define rigorously head normal form reduction lambda term using call-by-name reduction thanks formalism tells details kind reduction works sets theoretical foundation operational semantics functional programming languages hand krivine machine implements call-by-name evaluates body β-redex evaluates parameter words expression λ x u evaluates first λ x evaluating u functional programming would mean order evaluate function applied parameter evaluates first function evaluating parameter krivine machine designed french logician beginning 1980s krivine machine based two concepts related lambda calculus namely head reduction call name redex one says also β-redex term lambda calculus form λ x u term shape λ x u ... u said head redex head normal form term lambda calculus head redex head reduction non empty sequence contractions term contracts head redexes head reduction term supposed head normal form head reduction starts term ends head normal form abstract point view head reduction way program computes evaluates recursive sub-program understand reduction implemented important one aims krivine machine propose process reduct term head normal form describe formally process like turing used abstract machine describe formally notion algorithm used abstract machine describe formally notion head normal form reduction term λ 0 λ 0 λ 0 corresponds one uses explicit variables term λx x λy λz z head normal form λ 0 λ 0 contracts λ 0 yielding head redex λ 0 λ 0 contracts λ 0 therefore head normal form λ 0 λ 0 λ 0 said otherwise head normal form contraction corresponds see krivine machine reduces term λ 0 λ 0 λ 0 implement head reduction term u v application redex one must reduce body u exhibit abstraction therefore create redex v redex appears one reduces reduce always body application first called call name krivine machine implements call name presentation krivine machine given based notations lambda terms use de bruijn indices assumes terms computes head normal forms closed modifies current state anymore case obtains head normal form head normal form represents result computation yields error meaning term started correct however enter infinite sequence transitions means term attempts reducing head normal form corresponds non terminating computation proved krivine machine implements correctly call name head normal form reduction lambda-calculus moreover krivine machine deterministic since pattern state corresponds one machine transition state three components term λ-term de bruijn indices stack environment belong recursive data structure precisely environment stack lists pairs term environment called closures follows insertion head list ℓ stack environment element written ℓ whereas empty list written □ stack location machine stores closures must evaluated furthermore whereas environment association indices closures given time evaluation first element environment closure associated index 0 second element corresponds closure associated index 1 etc machine evaluate index fetches pair term environment closure yields term evaluated environment term must evaluated intuitive explanations allow understanding operating rules machine one writes term p stack e environment states associated three entities written p e. rules explain machine transforms state another state identifying patterns among states initial state aims evaluate term state □ □ term stack environment empty final state absence error form λ □ e words resulting terms abstraction together environment empty stack krivine machine four transitions app abs zero succ transition app removes parameter application put stack evaluation transition abs removes λ term pop closure top stack put top environment closure corresponds de bruijn index 0 new environment transition zero takes first closure environment term closure becomes current term environment closure becomes current environment transition succ removes first closure environment list decreases value index let us evaluate term λ 0 0 λ 0 corresponds term λ x x x λ x x let us start state λ 0 0 λ 0 □ □ conclusion head normal form term λ 0 0 λ 0 λ 0 translates variables head normal form term λ x x x λ x x λ x x let us evaluate term λ 0 λ 0 λ 0 confirms fact normal form term λ 0 λ 0 λ 0 λ 0 content edit translated existing french wikipedia article see history attribution
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Programming language topics
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electromagnetic survivability telecommunication electromagnetic survivability ability system subsystem equipment resume functioning without evidence degradation following temporary exposure adverse electromagnetic environment system subsystem equipment performance may degraded exposure adverse electromagnetic environment system experience permanent damage component burnout prevent proper operation adverse electromagnetic environment removed
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Computer security
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technolangue/easy technolangue/easy first evaluation campaign syntactic parsers french project supported french research ministry ministère de recherche français technolangue/easy included four tasks 2003 2006 13 laboratories companies submitted parser evaluation making total 16 runs 7 research laboratories 3 r institutes 3 private companies said terms existing french parsers competed
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Computational linguistics
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ip address blocking ip address blocking configuration network service requests hosts certain ip addresses rejected unix-like operating systems commonly implement ip address blocking using tcp wrapper configured host access control files /etc/hosts.deny /etc/hosts.allow ip address blocking commonly used protect brute force attacks companies schools offering remote user access use linux programs denyhosts fail2ban protection unauthorized access allowing permitted remote access also useful allowing remote access computers also used internet censorship website ip address block prevent disruptive address access though warning and/or account block may used first dynamic allocation ip addresses isps complicate incoming ip address blocking rendering difficult block specific user without blocking many ip addresses blocks ip address ranges thereby creating collateral damage ip address blocking used restrict access particular geographic area—for example syndication content specific region achieve ip addresses mapped countries assigned used example target nigerian ip addresses due perception business originating country fraudulent thus making extremely difficult legitimate businesses based country interact counterparts rest world make purchases abroad nigerians must rely proxy servers disguise true origin internet request proxy servers methods used bypass blocking traffic ip addresses however anti-proxy strategies available 2013 united states court ruling case craigslist v. 3taps us federal judge charles r. breyer held circumventing address block access website violation computer fraud abuse act cfaa punishable civil damages unauthorized access
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Computer security
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david s. touretzky david s. touretzky research professor computer science department center neural basis cognition carnegie mellon university received ba computer science rutgers university 1978 earned master degree ph.d. 1984 computer science carnegie mellon university touretzky worked internet activist favor freedom speech especially perceives abuse legal system government private authorities notable critic scientology touretzky research interests lie fields artificial intelligence computational neuroscience learning includes machine learning animal learning particular neural representation space rodents e.g. hippocampus robots 2006 recognized distinguished scientist association computing machinery since 1990s touretzky worked expose actions church scientology sees actions organization threat free speech taken prominent part internet-based activism oppose also appearing regularly critic radio print also worked expose sees dangerous potentially life-threatening treatments provided narconon scientology-based drug rehabilitation program maintains web site named stop narconon archives media articles critical program dr. touretzky research narconon primary source information series san francisco chronicle newspaper articles criticizing narconon june 9 june 10 2004 ultimately led organization program rejected california school system early 2005 touretzky undertaken extensive research secret upper levels scientology made information available public ot iii scholarship page concerning xenu nots scholars page concerning higher operating thetan levels pages states academic studies scientology texts proprietary materials therefore legally available due careful application academic fair use provisions copyright law church failed attempts removed repeatedly threatening touretzky lawsuits filing complaints carnegie mellon university carnegie mellon turn issued statements support professor touretzky noting criticism scientology personal affair opinion university touretzky object public attacks church scientology including various dead agent campaigns accused religious bigotry racism misogyny misuse government funds support terrorism collusion pharmaceutical industry among misdeeds david touretzky internet free speech activist supported several movements perceives abuse legal system government private authorities 2000 touretzky testified expert witness defense universal city studios et al v. reimerdes et al. suit brought seven motion picture studios publishers case name refers shawn reimerdes unrelated defendant settled prior trial suit concerned publication dvd decryption software known decss plaintiffs asserted illegal digital millennium copyright act dr. touretzky testified expert computer science expressive nature computer code convinced court code indeed speech touretzky also created online gallery various renditions decss software readers sent renditions decryption algorithm including mathematical description haiku square dance reaction federal prosecution eventual imprisonment 18-year-old political activist sherman austin hosting bomb-making instructions entitled reclaim guide web site dr. touretzky provided mirror carnegie mellon website two years although acknowledged website reposting information violate plain language statute austin convicted may 2004 avoid harassment university controversy media dr. touretzky moved mirror carnegie mellon server private site 2011 touretzky began hosting mirror website george hotz containing executable files instructions facilitating jailbreaking sony playstation 3 sony filed lawsuits hotz hackers aiming utilize takedown provisions dmca remove content internet
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Programming language topics
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pdfvue pdfvue online pdf viewer editor beta release features include viewing commenting annotations page deletion rotation adding fillable form fields pdfs supported browsers include internet explorer firefox safari pdfs uploaded directly imported web address firefox extension redirects pdfs enabling viewing annotation within browser deskpdf pdfvue ramp release also features print pdfvue functionality allowing printable file uploaded pdfvue via print process postscript technology software renamed pdfzen primary features beta release include tools creating filling forms sharing collaborating documents annotating existing pdfs additional functionality includes ability delete rotate pages within pdf pdfvue typewriter tool allows text added pdf allows forms created without fillable fields filled well documents scanned without ocr available annotation tools include addition able fill forms pdfvue features tools creating digital forms current supported fillable form fields include editing pdfs downloaded locally viewed pdf viewer pdfvue also allows pdfs shared via providing hyperlink hosted pdf alternative email attachments annotation tools allows collaboration take place single pdf rather multiple versions shared parties firefox extension renders pdfs using pdfvue servers thus avoiding acrobat plug-in freeze-up well acrobat reader exploits enabled extensions traps url requests low level catching pdfs clicks redirects new tabs address bar providing better level protection unintended pdf launch opened pdfvue.com pdf marked changes saved service available mozilla add ons free charge pdfvue onramp local documents automatically uploaded pdfvue converted text searchable pdf commenting sharing
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Distributed computing architecture
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domain name system domain name system dns hierarchical decentralized naming system computers services resources connected internet private network associates various information domain names assigned participating entities prominently translates readily memorized domain names numerical ip addresses needed locating identifying computer services devices underlying network protocols providing worldwide distributed directory service domain name system essential component functionality internet since 1985 domain name system delegates responsibility assigning domain names mapping names internet resources designating authoritative name servers domain network administrators may delegate authority sub-domains allocated name space name servers mechanism provides distributed fault-tolerant service designed avoid single large central database domain name system also specifies technical functionality database service core defines dns protocol detailed specification data structures data communication exchanges used dns part internet protocol suite internet maintains two principal namespaces domain name hierarchy internet protocol ip address spaces domain name system maintains domain name hierarchy provides translation services address spaces internet name servers communication protocol implement domain name system dns name server server stores dns records domain dns name server responds answers queries database common types records stored dns database start authority soa ip addresses aaaa smtp mail exchangers mx name servers ns pointers reverse dns lookups ptr domain name aliases cname although intended general purpose database dns expanded time store records types data either automatic lookups dnssec records human queries responsible person rp records general purpose database dns also used combating unsolicited email spam storing real-time blackhole list rbl dns database traditionally stored structured text file zone file database systems common often-used analogy explain domain name system serves phone book internet translating human-friendly computer hostnames ip addresses example domain name www.example.com translates addresses ipv4 ipv6 dns quickly transparently updated allowing service location network change without affecting end users continue use hostname users take advantage use meaningful uniform resource locators urls e-mail addresses without know computer actually locates services important ubiquitous function dns central role distributed internet services cloud services content delivery networks user accesses distributed internet service using url domain name url translated ip address server proximal user key functionality dns exploited different users simultaneously receive different translations domain name key point divergence traditional phone-book view dns process using dns assign proximal servers users key providing faster reliable responses internet widely used major internet services dns reflects structure administrative responsibility internet subdomain zone administrative autonomy delegated manager zones operated registry administrative information often complemented registry rdap whois services data used gain insight track responsibility given host internet using simpler memorable name place host numerical address dates back arpanet era stanford research institute sri international maintained text file named hosts.txt mapped host names numerical addresses computers arpanet elizabeth feinler developed maintained first arpanet directory maintenance numerical addresses called assigned numbers list handled jon postel university southern california information sciences institute isi whose team worked closely sri addresses assigned manually computers including hostnames addresses added master file contacting sri network information center nic directed elizabeth feinler telephone business hours later feinler set whois directory server nic retrieval information resources contacts entities team developed concept domains feinler suggested domains based location physical address computer computers educational institutions would domain edu example team managed host naming registry 1972 1989 early 1980s maintaining single centralized host table become slow unwieldy emerging network required automated naming system address technical personnel issues postel directed task forging compromise five competing proposals solutions paul mockapetris mockapetris instead created domain name system internet engineering task force published original specifications rfc 882 rfc 883 november 1983 1984 four uc berkeley students douglas terry mark painter david riggle songnian zhou wrote first unix name server implementation berkeley internet name domain commonly referred bind 1985 kevin dunlap dec substantially revised dns implementation mike karels phil almquist paul vixie maintained bind since early 1990s bind ported windows nt platform widely distributed especially unix systems still widely used dns software internet november 1987 rfc 1034 rfc 1035 superseded 1983 dns specifications several additional request comments proposed extensions core dns protocols domain name space consists tree data structure node leaf tree label zero resource records rr hold information associated domain name domain name consists label possibly concatenated name parent node right separated dot tree sub-divides zones beginning root zone dns zone may consist one domain may consist many domains sub-domains depending administrative choices zone manager dns also partitioned according class separate classes thought array parallel namespace trees administrative responsibility zone may divided creating additional zones authority new zone said delegated designated name server parent zone ceases authoritative new zone definitive descriptions rules forming domain names appear rfc 1035 rfc 1123 rfc 2181 rfc 5892 domain name consists one parts technically called labels conventionally concatenated delimited dots example.com right-most label conveys top-level domain example domain name www.example.com belongs top-level domain com hierarchy domains descends right left label left specifies subdivision subdomain domain right example label example specifies subdomain com domain www subdomain example.com tree subdivisions may 127 levels label may contain zero 63 characters null label length zero reserved root zone full domain name may exceed length 253 characters textual representation internal binary representation dns maximum length requires 255 octets storage also stores length name although technical limitation exists use character domain name labels representable octet hostnames use preferred format character set characters allowed labels subset ascii character set consisting characters z z digits 0 9 hyphen rule known ldh rule letters digits hyphen domain names interpreted case-independent manner labels may start end hyphen additional rule requires top-level domain names all-numeric limited set ascii characters permitted dns prevented representation names words many languages native alphabets scripts make possible icann approved internationalizing domain names applications idna system user applications web browsers map unicode strings valid dns character set using punycode 2009 icann approved installation internationalized domain name country code top-level domains cctld addition many registries existing top-level domain names tld adopted idna system guided rfc 5890 rfc 5891 rfc 5892 rfc 5893 domain name system maintained distributed database system uses client–server model nodes database name servers domain least one authoritative dns server publishes information domain name servers domains subordinate top hierarchy served root name servers servers query looking resolving tld authoritative name server name server gives answers dns queries data configured original source example domain administrator dynamic dns methods contrast answers obtained via query another name server maintains cache data authoritative name server either master server slave server master server server stores original master copies zone records slave server uses special automatic updating mechanism dns protocol communication master maintain identical copy master records every dns zone must assigned set authoritative name servers set servers stored parent domain zone name server ns records authoritative server indicates status supplying definitive answers deemed authoritative setting protocol flag called authoritative answer aa bit responses flag usually reproduced prominently output dns administration query tools dig indicate responding name server authority domain name question domain name resolvers determine domain name servers responsible domain name question sequence queries starting right-most top-level domain label proper operation domain name resolver network host configured initial cache hints known addresses root name servers hints updated periodically administrator retrieving dataset reliable source assuming resolver cached records accelerate process resolution process starts query one root servers typical operation root servers answer directly respond referral authoritative servers e.g. query www.wikipedia.org referred org servers resolver queries servers referred iteratively repeats process receives authoritative answer diagram illustrates process host named fully qualified domain name www.wikipedia.org mechanism would place large traffic burden root servers every resolution internet required starting root practice caching used dns servers off-load root servers result root name servers actually involved relatively small fraction requests theory authoritative name servers sufficient operation internet however authoritative name servers operating every dns query must start recursive queries root zone domain name system user system would implement resolver software capable recursive operation improve efficiency reduce dns traffic across internet increase performance end-user applications domain name system supports dns cache servers store dns query results period time determined configuration time-to-live domain name record question typically caching dns servers also implement recursive algorithm necessary resolve given name starting dns root authoritative name servers queried domain function implemented name server user applications gain efficiency design operation combination dns caching recursive functions name server mandatory functions implemented independently servers special purposes internet service providers typically provide recursive caching name servers customers addition many home networking routers implement dns caches recursors improve efficiency local network client side dns called dns resolver resolver responsible initiating sequencing queries ultimately lead full resolution translation resource sought e.g. translation domain name ip address dns resolvers classified variety query methods recursive non-recursive iterative resolution process may use combination methods non-recursive query dns resolver queries dns server provides record either server authoritative provides partial result without querying servers case caching dns resolver non-recursive query local dns cache delivers result reduces load upstream dns servers caching dns resource records period time initial response upstream dns servers recursive query dns resolver queries single dns server may turn query dns servers behalf requester example simple stub resolver running home router typically makes recursive query dns server run user isp recursive query one dns server answers query completely querying name servers needed typical operation client issues recursive query caching recursive dns server subsequently issues non-recursive queries determine answer send single answer back client resolver another dns server acting recursively behalf resolver negotiates use recursive service using bits query headers dns servers required support recursive queries iterative query procedure process dns resolver queries chain one dns servers server refers client next server chain current server fully resolve request example possible resolution www.example.com would query global root server com server finally example.com server name servers delegations identified name rather ip address means resolving name server must issue another dns request find ip address server referred name given delegation subdomain domain delegation provided circular dependency case name server providing delegation must also provide one ip addresses authoritative name server mentioned delegation information called glue delegating name server provides glue form records additional section dns response provides delegation authority section response glue record combination name server ip address example authoritative name server example.org ns1.example.org computer trying resolve www.example.org first resolves ns1.example.org ns1 contained example.org requires resolving example.org first presents circular dependency break dependency name server top level domain org includes glue along delegation example.org glue records address records provide ip addresses ns1.example.org resolver uses one ip addresses query one domain authoritative servers allows complete dns query standard practice implementing name resolution applications reduce load domain name system servers caching results locally intermediate resolver hosts results obtained dns request always associated time live ttl expiration time results must discarded refreshed ttl set administrator authoritative dns server period validity may vary seconds days even weeks result distributed caching architecture changes dns records propagate throughout network immediately require caches expire refreshed ttl rfc 1912 conveys basic rules determining appropriate ttl values resolvers may override ttl values protocol supports caching sixty-eight years caching negative caching i.e caching fact non-existence record determined name servers authoritative zone must include start authority soa record reporting data requested type exists value minimum field soa record ttl soa used establish ttl negative answer reverse dns lookup query dns domain names ip address known multiple domain names may associated ip address dns stores ip addresses form domain names specially formatted names pointer ptr records within infrastructure top-level domain arpa ipv4 domain in-addr.arpa ipv6 reverse lookup domain ip6.arpa ip address represented name reverse-ordered octet representation ipv4 reverse-ordered nibble representation ipv6 performing reverse lookup dns client converts address formats querying name ptr record following delegation chain dns query example assuming ipv4 address 208.80.152.2 assigned wikimedia represented dns name reverse order 2.152.80.208.in-addr.arpa dns resolver gets pointer ptr request begins querying root servers point servers american registry internet numbers arin 208.in-addr.arpa zone arin servers delegate 152.80.208.in-addr.arpa wikimedia resolver sends another query 2.152.80.208.in-addr.arpa results authoritative response users generally communicate directly dns resolver instead dns resolution takes place transparently applications web browsers e-mail clients internet applications application makes request requires domain name lookup programs send resolution request dns resolver local operating system turn handles communications required dns resolver almost invariably cache see containing recent lookups cache provide answer request resolver return value cache program made request cache contain answer resolver send request one designated dns servers case home users internet service provider machine connects usually supply dns server user either configured server address manually allowed dhcp set however systems administrators configured systems use dns servers dns resolvers point separately maintained name servers organization event name server thus queried follow process outlined either successfully finds result returns results dns resolver assuming found result resolver duly caches result future use hands result back software initiated request large isps configured dns servers violate rules disobeying ttls indicating domain name exist one name servers respond applications web browsers maintain internal dns cache avoid repeated lookups via network practice add extra difficulty debugging dns issues obscures history data caches typically use short caching times – order one minute internet explorer represents notable exception versions ie 3.x cache dns records 24 hours default internet explorer 4.x later versions ie 8 decrease default time value half hour may changed modifying default configuration google chrome triggers specific error message dns issues dns server broken google chrome returns error message domain name system includes several functions features hostnames ip addresses required match one-to-one relationship multiple hostnames may correspond single ip address useful virtual hosting many web sites served single host alternatively single hostname may resolve many ip addresses facilitate fault tolerance load distribution multiple server instances across enterprise global internet dns serves purposes addition translating names ip addresses instance mail transfer agents use dns find best mail server deliver e-mail mx record provides mapping domain mail exchanger provide additional layer fault tolerance load distribution dns used efficient storage distribution ip addresses blacklisted email hosts common method place ip address subject host sub-domain higher level domain name resolve name record indicates positive negative indication example e-mail servers query blacklist.example find specific host connecting blacklist many blacklists either subscription-based free cost available use email administrators anti-spam software provide resilience event computer network failure multiple dns servers usually provided coverage domain top level global dns thirteen groups root name servers exist additional copies distributed worldwide via anycast addressing dynamic dns ddns updates dns server client ip address on-the-fly example moving isps mobile hot spots ip address changes administratively dns protocol uses two types dns messages queries replies format message consists header four sections question answer authority additional space header field flags controls content four sections header section consists following fields identification flags number questions number answers number authority resource records rrs number additional rrs field 16 bit long appears order given identification field used match responses queries flag field consists sub-fields follows flag header ends four 16-bit integers contain number records sections follow order question section simpler format resource record format used sections record usually 1 contains following fields domain name broken discrete labels concatenated label prefixed length label dns primarily uses user datagram protocol udp port number 53 serve requests dns queries consist single udp request client followed single udp reply server length answer exceeds 512 bytes client server support edns larger udp packets used otherwise query sent using transmission control protocol tcp tcp also used tasks zone transfers resolver implementations use tcp queries domain name system specifies database information elements network resources types information elements categorized organized list dns record types resource records rrs record type name number expiration time time live class type-specific data resource records type described resource record set rrset special ordering dns resolvers return entire set upon query servers may implement round-robin ordering achieve load balancing contrast domain name system security extensions dnssec work complete set resource record canonical order sent internet protocol network records use common format specified rfc 1035 name fully qualified domain name node tree wire name may shortened using label compression ends domain names mentioned earlier packet substituted end current domain name free standing used denote current origin type record type indicates format data gives hint intended use example record used translate domain name ipv4 address ns record lists name servers answer lookups dns zone mx record specifies mail server used handle mail domain specified e-mail address rdata data type-specific relevance ip address address records priority hostname mx records well known record types may use label compression rdata field unknown record types must rfc 3597 class record set internet common dns records involving internet hostnames servers ip addresses addition classes chaos ch hesiod hs exist class independent name space potentially different delegations dns zones addition resource records defined zone file domain name system also defines several request types used communication dns nodes wire performing zone transfers axfr/ixfr edns opt domain name system supports wildcard dns records specify names start asterisk label '* e.g. *.example dns records belonging wildcard domain names specify rules generating resource records within single dns zone substituting whole labels matching components query name including specified descendants example following configuration dns zone x.example specifies subdomains including subdomains subdomains x.example use mail exchanger mx a.x.example record a.x.example needed specify mail exchanger ip address result excluding domain name subdomains wildcard matches additional mx record subdomain a.x.example well wildcarded mx record subdomains must also defined dns zone role wildcard records refined rfc 4592 original definition rfc 1034 incomplete resulted misinterpretations implementers original dns protocol limited provisions extension new features 1999 paul vixie published rfc 2671 superseded rfc 6891 extension mechanism called extension mechanisms dns edns introduced optional protocol elements without increasing overhead use accomplished opt pseudo-resource record exists wire transmissions protocol zone files initial extensions also suggested edns0 increasing dns message size udp datagrams dynamic dns updates use update dns opcode add remove resource records dynamically zone database maintained authoritative dns server feature described rfc 2136 facility useful register network clients dns boot become otherwise available network booting client may assigned different ip address time dhcp server possible provide static dns assignments clients originally security concerns major design considerations dns software software deployment early internet network open participation general public however expansion internet commercial sector 1990s changed requirements security measures protect data integrity user authentication several vulnerability issues discovered exploited malicious users one issue dns cache poisoning data distributed caching resolvers pretense authoritative origin server thereby polluting data store potentially false information long expiration times time-to-live subsequently legitimate application requests may redirected network hosts operated malicious intent dns responses traditionally cryptographic signature leading many attack possibilities domain name system security extensions dnssec modify dns add support cryptographically signed responses dnscurve proposed alternative dnssec extensions tsig add support cryptographic authentication trusted peers commonly used authorize zone transfer dynamic update operations domain names may used achieve spoofing effects example paypa1.com different names yet users may unable distinguish graphical user interface depending user chosen typeface many fonts letter l numeral 1 look similar even identical problem acute systems support internationalized domain names many character codes iso 10646 may appear identical typical computer screens vulnerability occasionally exploited phishing techniques forward-confirmed reverse dns also used help validate dns results device looking dns record must communicate dns server considerable attention given adverse privacy implications even dns records easily read modified spoofed due security extensions person access dns server traffic stream wire may little difficulty matching ip address device often identifies user websites email domains visit track often records queried since dns records typically expire must requeried regularly dns also leak otherwise secure private connections attention paid configuration times dns used bypass firewalls malicious persons exfiltrate data since often seen innocuous two main approaches use counter privacy issues dns right use domain name delegated domain name registrars accredited internet corporation assigned names numbers icann organizations opennic charged overseeing name number systems internet addition icann top-level domain tld maintained serviced technically administrative organization operating registry registry responsible operating database names within authoritative zone although term often used tlds registrant person organization asked domain registration registry receives registration information domain name registrar authorized accredited assign names corresponding zone publishes information using whois protocol 2015 usage rdap considered icann publishes complete list tlds tld registries domain name registrars registrant information associated domain names maintained online database accessible whois service 290 country code top-level domains cctlds domain registries maintain whois registrant name servers expiration dates etc information instance denic germany nic holds de domain data 2001 generic top-level domain gtld registries adopted so-called thick registry approach i.e keeping whois data central registries instead registrar databases top-level domains com net thin registry model used domain registry e.g. godaddy bigrock pdr verisign etc. etc holds basic whois data i.e. registrar name servers etc. organizations registrants using org hand public interest registry exclusively domain name registries often called network information centers nic also function registrars end-users addition providing access whois datasets top-level domain registries domains com net org use registry-registrar model consisting many domain name registrars method management registry manages domain name database relationship registrars registrants users domain name customers registrar cases additional subcontracting resellers domain name system defined request comments rfc documents published internet engineering task force internet standards following list rfcs define dns protocol rfcs advisory nature may provide useful information despite defining neither standard bcp rfc 1796 rfcs official status unknown due age clearly labeled
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Internet protocols
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words unix words standard file unix unix-like operating systems simply newline-delimited list dictionary words used instance spell-checking programs words file usually stored debian ubuntu file provided package provider packages etc fedora arch file provided package
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Operating systems
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gatekeeper access control device gatekeeper wireless proximity-based access control authentication device allows user automatically lock computer walking away unlock walking back untethered labs american computer security firm led ceo siddharth potbhare created original gatekeeper 2014 gatekeeper consists key fob device usb dongle transmit wireless signal software manage user credentials device also functions key finder using bluetooth low energy 4.0 locate gatekeeper within proximate adjustable range 30 feet indoors 100 feet outdoors gatekeeper software uses dashboard displays device signal strength allows users select configure lock settings manage user credentials set range computer detects device presence gatekeeper software provides user options enable two-factor authentication 2-fa computer access requiring user enter pin carry gatekeeper login usb dongle lock ever removed computer software immediately locks computer gatekeeper enterprise software integrates gatekeeper hardware allows administrator control deployment management gatekeepers network administrator set security policies gather log data auditing conduct productivity analysis deploy updates client software december 2017 untethered labs announced kickstarter would release halberd key fob new hardware design according company halberd larger design new processor added accelerometer improve device performance battery life halberd subsequently reached funding goal 25,000 raising 50,000 28 days 400 backers expected released january 2018 company also plans release compatible software mac linux systems well single sign-on capabilities 2018
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Computer security
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endurability telecommunication endurability property system subsystem equipment process enables continue function within specified performance limits extended period time usually months despite severe natural man-made disturbance nuclear attack loss external logistic utility support endurability compromised temporary failures local capability exists restore maintain system subsystem equipment process acceptable performance level
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Computer security
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equivalent pulse code modulation noise telecommunication equivalent pulse code modulation pcm noise amount noise power frequency-division multiplexing fdm wire communication channel necessary approximate judgment speech quality created quantizing noise pcm channel
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Internet protocols
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bbm software bbm formerly known full name blackberry messenger proprietary mobile instant messenger videotelephony application included blackberry devices allows messaging voice calls blackberry os blackberry 10 ios android windows mobile users consumer edition ios android bbm consumer developed indonesian company emtek license blackberry limited formerly known research motion consumer edition blackberry os blackberry 10 well paid enterprise edition called bbm enterprise formerly known bbm protected developed fully blackberry limited bbm consumer shut 31 may 2019 however paid enterprise version software bbme still running messages sent via bbm sent internet used blackberry pin system past many service providers allowed sign-in bbm using dedicated blackberry data plan exchanging messages possible single person via dedicated discussion chat groups allowed multiple blackberry devices communicate single session addition offering text-based instant messages bbm also allowed users send pictures voicenotes audio recordings files 16 mb share real time location map stickers wide selection emojis communication possible blackberry devices late 2013 bbm released ios android systems 300 million stickers shared daily approximately 150,000 bbm voice calls placed 190 million bbm users worldwide 2015 blackberry infrastructure handled 30 petabytes data traffic month early 2013 bbm original mobile-first messaging service popular started lose rivals april 2016 indonesia country bbm popular messaging app installed 87.5 android devices country blackberry messenger launched august 1 2005 release blackberry messenger 5.0 blackberry allows users use qr code add respective friends lists rather using numeric pin identification email address associated user blackberry recent blackberry devices also exchange bbm contacts using near field communication technology users also set animated gif pictures display pictures although animated pictures 32kb size limit release blackberry messenger 6.0 introduced additional traits update focused social communication mediums including 'bbm connected apps allow user invite friends share favourite blackberry applications late-december 2011 audience measurement company bbm canada sued rim infringing trademark bbm using initialism blackberry messenger bbm canada used initialism former name bureau broadcast measurement company cited received phone calls users believed connected rim however rim asked case dropped two organizations different industries suit dismissed bbm canada ultimately re-branded numeris release blackberry messenger 7.0 december 2012 voice chat bbm voice call introduced bbm protected secure encrypted enterprise-level messenger launched june 2014 june 27 2016 announced indonesia-based emtek group acquired licensing rights bbm blackberry limited would provide bbm api emtek part six-year 207 million deal 2017 bbm servers moved data center canada google cloud platform-based data center asia april 18 2019 bbm announced discontinue bbm consumer service globally may 31 year users switch paid bbme enterprise version messenger bbm widely reputed uptime reliability however october 10 2011 users service north america europe middle east africa widely affected outage provider rim uk headquarters slough berkshire outage lasted two days blackberry messenger reported unavailable thus seriously affecting company reputation blackberry ceo thorsten heins announced may 14 2013 blackberry messenger available ios android summer 2013 would mark first steps blackberry messenger reaching beyond platform never available competing hardware rumoured blackberry messenger would launch june 27 2013 android ios later denied blackberry actual release date yet announced june 21 2013 blackberry messenger application spotted play store however turned fake worldwide release bbm android slated september 21 2013 officially announced blackberry also announced app would require android versions older 4.x.x ice cream sandwich blackberry confirmed bbm iphone would release september 22 day later official android release would work iphones running ios 6 later however worldwide rollout bbm android iphone september 21 2013 1.1 million android users downloaded leaked blackberry messenger apk caused blackberry cease launching blackberry messenger android ios platforms bbm officially released ios android october 21 2013 5 million downloads recorded first 8 hours release bbm late 2013 no.1 free app app store google play store total app 10 million downloads first day 24 february 2014 blackberry officially confirmed bbm windows phone nokia x would released q2 2014 nokia confirmed bbm would preinstalled nokia x devices june 2016 bbm longer offered windows store april 18 2019 announced bbm consumer service android ios shutting may 31 2019 bbm multi-platform offer personal chats group chat 250 people status updates send receive messages 2000 characters bbm channels bbm voice bbm shop available android ios early january 2014 beta update bbm android released testers update included bbm voice bbm channels february 2014 update 2.0.0.13 officially released android ios users containing awaited features along features including new emoticons changes including new look updates featuring choices show contacts channels filters november 4 2014 bbm scored 1 7 points electronic frontier foundation secure messaging scorecard lost points communications encrypted key provider n't access i.e communications end-to-end encrypted users ca n't verify contacts identities past messages secure encryption keys stolen i.e app provide forward secrecy code open independent review i.e code open-source security design properly documented recent independent code audit enterprise version bbm protected initially scored 3 7 points updated 5 7 points additional information provided blackberry reflected eff changelog dated november 14 2014 lost points past messages secure encryption keys stolen code open independent review may 2011 rim claimed 43 million active blackberry messenger users worldwide 2013 2014 number bbm users increases sharply 100 million 2016 bbm reached 889 million users world ranked 2nd top messaging apps first place belongs telegram january 2018 least 63 million monthly users indonesia
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Operating systems
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mozilla localizations mozilla localizations localized versions mozilla products usually entails product translated certain language language region specific features added localization normally carried teams volunteers mozilla firefox heavily localized cross-platform web browser date first official release november 2004 available 28 different locales including british english/american english european spanish/argentine spanish chinese traditional chinese characters/simplified chinese characters firefox 4 initially shipped 80 locales introduced 10 new locales including 6 african languages following table lists releases firefox precursors microsoft windows operating system listing locales available end version releases mozilla thunderbird email application somewhat fewer localised releases initial release us english since released 45 languages 47 locales though much mozilla web content localized extent localization varies locale locale example mozilla firefox privacy policy currently available english
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Internet protocols
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extended superframe telecommunications extended superframe esf t1 framing standard esf sometimes called d5 framing first used d5 channel bank invented 1980s preferred predecessor superframe includes cyclic redundancy check crc 4000 bit/s channel capacity data link channel used pass out-of-band data equipment requires less frequent synchronization earlier superframe format provides on-line real-time monitoring circuit capability operating condition extended superframe 24 frames long framing bit frame used following manner crc computed using polynomial 24×193 4632 bits framing data previous superframe crc bits forced 1 purpose crc computation purpose small crc take immediate action keep statistics performance link like predecessor superframe every sixth frame least-significant data bit used robbed-bit signaling call supervision state however four bits abcd per channel per extended superframe rather two bits ab provided per superframe unlike superframe possible avoid robbed-bit signalling send call supervision data link instead
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Internet protocols
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sun-4 sun-4 series unix workstations servers produced sun microsystems launched 1987 original sun-4 series vmebus-based systems similar earlier sun-3 series employing microprocessors based sun sparc v7 risc architecture place 68k family processors previous sun models models listed approximately chronological order 1989 sun dropped sun-4 name marketing purposes favor sparcstation sparcserver brands new models although early sparcstation/server models also assigned sun-4-series model numbers example sparcstation 1 also known sun 4/60 practice phased introduction sparcserver 600mp series 1991 term sun-4 continued used engineering context identify basic hardware architecture sparc-based sun systems sun 4/110 4/150 4/260 4/280 systems upgraded sun 4300 cpu board used sparcserver 300 series referred 4/310 4/350 4/360 4/380 respectively sun-4 architecture refers vme-based architecture described used sun 4/100 4/200 sparcserver 300 sparcserver 400 ranges sun-4 support included sunos 3.2 onwards solaris 2.1 2.4 openbsd netbsd also run sun-4 architecture families several variations sun-4 architecture subsequently developed used later computer systems produced sun vendors comprised
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Computer architecture
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system 573 system 573 series arcade system boards konami based original playstation hardware used primarily konami bemani series music video game arcades commonly dance dance revolution series introduced 1998 system 573 available two variants analog digital i/o boards dubbed bemani system 573 analog bemani system 573 digital respectively along third variant called system 573 satellite terminal allows 8 cabinets networked central one
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Computer architecture
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benson k. buffham benson kirk buffham november 26 1919 – april 24 2019 american intelligence official deputy director national security agency 1978 1980 time highest ranking civilian agency born november 26 1919 illinois buffham joined armed forces security agency 1949 went newly formed national security agency 1952 1955 buffham one first nsa employees attend national war college nsa served europe office chief field activities well various positions production organization including deputy assistant director production 1950 took part organizing inspector general office deputy directorship served london senior liaison officer retired 1980 buffham died april 2019 age 99
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Computer security
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treasure island 1984 video game treasure island 1984 computer game based book treasure island robert louis stevenson game player takes role jim hawkins protagonist book battle hordes pirates final showdown long john silver game uses flip-screen style programming done greg duddle music rendered david whittaker version commodore 64 msx released 1984 commodore plus/4 version 1985 start game jim escaped stockade unarmed one possible exit next screen right finds throwing pirate trick throwing cutlass obtain however would foolhardy kill pirate since pirate blocking access anything instead player find pirate blocking access exit perhaps power-up kill thus advancing progress game strategic rationing cutlasses i.e knowing pick use order progress around island major gameplay element none pirates move around throw cutlass jim moved range pirate question lose cutlass always another use pirate rarely throws one cutlass jim hit cutlass thrown touches pirate loses life starts beginning screen however moves way time cutlass lands ground throw pirate kill killed pirate disappears allowing jim pass changed theme pirates asia game re-released willow pattern adventure another adventure game named treasure island published windham classics year 1985
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Computer architecture
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websidestory websidestory inc. later visual sciences founded blaise barrelet 1996 web analytics tool link directory products hitbox hbx company went public september 28 2004 nasdaq wssi 2006 websidestory acquired high-end private data analysis visualization software company visual sciences 57 million year acquisition websidestory rebranded visual sciences inc january 2008 visual sciences inc. acquired omniture nasdaq omtr 394 million websidestory founded headquartered san diego california websidestory originally launched saas business model charging customers monthly fee web analytics finding customers willing pay web analytics proved difficult websidestory pivoted offer limited version analytics product free exchange small advertising banner website users clicked banners directed list top sites owned websidestory creating advertising revenue opportunity unlike many late '90s internet startups websidestory raise angel funding venture capital became profitable customers displaying banners top site list late 1999 websidestory opted target larger brick-and-mortar businesses customers hitbox product customers opted pay in-depth statistics exchange removing traditional hitbox banner websites giving birth hbx product line websidestory financially sound shuttered free version hitbox associated advertising revenues company went public 2004 eventually purchased visual sciences adopting name visual sciences turn acquired omniture 2008 october 2009 omniture acquired adobe systems integrated adobe marketing cloud february 2005 websidestory acquired atomz customizable saas search service
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Web technology
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security level management security level management slm comprises quality assurance system electronic information security aim slm display security status transparently across company time make security measurable quantity transparency measurability form prerequisites making security proactively monitorable improved continuously slm oriented towards phases deming cycle/plan-do-check-act pdca cycle within scope slm abstract security policies compliance guidelines company transposed operative measureable specifications security infrastructure operative aims form security level reached security level checked permanently current performance security systems malware scanner patch systems etc. deviations recognised early adjustments made security system slm falls range duties chief security officer cso chief information officer cio chief information security officer ciso report directly executive board security data availability slm related disciplines security security event management siem analysts gartner summarise magic quadrant security information event management define follows … sim provides reporting analysis data primarily host systems applications secondarily security devices — support security policy compliance management internal threat management regulatory compliance initiatives sim supports monitoring incident management activities security organization … sem improves security incident response capabilities sem processes near-real-time data security devices network devices systems provide real-time event management security operations … sim sem relate infrastructure realising superordinate security aims descriptive strategic management system aims measures revisions actions derived slm unites requisite steps realising measurable functioning security structure management control cycle slm categorised strategic panoply governance via suitable organisation structures processes ensures supports corporate strategy objectives slm allows csos cios cisos prove slm contributing towards protecting electronic data relevant processes adequately therefore makes contribution part governance defining security level plan company specifies security policies executive management defines aims relation integrity confidentiality availability authority classified data order able verify compliance specifications concrete aims individual security systems company need derived abstract security policies security level consists collection measurable limiting threshold values example operative aims like anti-virus systems uk sites need up-to-date longer four hours publication current definition need derived superordinate security policies like employees able work without interrupted limiting threshold values specified separately individually different sites locations countries infrastructure on-site local determining factors need taken consideration example office buildings uk normally equipped high-speed dedicated lines wholly realistic limit deadline supplying computers newest anti-virus definitions hours factory asia slow modem link web realistic limiting value would set somewhat higher control manual control objectives information related technology cobit cobit provides companies instructions transposing subordinate abstract aims measurable aims steps collecting analysing data information current status systems gleaned log file status reports provided individual anti-virus anti-spyware anti-spam consoles monitoring reporting solutions analysing software applications software houses simplify accelerate data collection checking security level check slm prescribes continual reconciliation defined security level current measured values automated real-time reconciliation supplies companies permanent status report security status across locations adjusting security structure act efficient slm allows trend analyses long-term comparative assessments made rolling observation security level weak spots network identified early appropriate adjustments made proactively security systems besides defining specifications engineering introducing operating monitoring maintaining improving documented information security management system iso/iec 27001 also defines specifications implementing suitable security mechanisms infrastructure library itil collection best practices control processes goes far beyond security relation supplies criteria security officers conceive security independent qualitatively measurable service integrate universe business-process-oriented processes itil also works top policies processes procedures job-related instructions assumes superordinate also operative aims need planned implemented controlled evaluated adjusted
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Computer security
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database database organized collection data generally stored accessed electronically computer system databases complex often developed using formal design modeling techniques database management system dbms software interacts end users applications database capture analyze data dbms software additionally encompasses core facilities provided administer database sum total database dbms associated applications referred database system often term database also used loosely refer dbms database system application associated database computer scientists may classify database-management systems according database models support relational databases became dominant 1980s model data rows columns series tables vast majority use sql writing querying data 2000s non-relational databases became popular referred nosql use different query languages formally database refers set related data way organized access data usually provided database management system dbms consisting integrated set computer software allows users interact one databases provides access data contained database although restrictions may exist limit access particular data dbms provides various functions allow entry storage retrieval large quantities information provides ways manage information organized close relationship term database often used casually refer database dbms used manipulate outside world professional information technology term database often used refer collection related data spreadsheet card index size usage requirements typically necessitate use database management system existing dbmss provide various functions allow management database data classified four main functional groups database dbms conform principles particular database model database system refers collectively database model database management system database physically database servers dedicated computers hold actual databases run dbms related software database servers usually multiprocessor computers generous memory raid disk arrays used stable storage raid used recovery data disks fail hardware database accelerators connected one servers via high-speed channel also used large volume transaction processing environments dbmss found heart database applications dbmss may built around custom multitasking kernel built-in networking support modern dbmss typically rely standard operating system provide functions since dbmss comprise significant market computer storage vendors often take account dbms requirements development plans databases dbmss categorized according database model support relational xml type computer run server cluster mobile phone query language used access database sql xquery internal engineering affects performance scalability resilience security sizes capabilities performance databases respective dbmss grown orders magnitude performance increases enabled technology progress areas processors computer memory computer storage computer networks development database technology divided three eras based data model structure navigational sql/relational post-relational two main early navigational data models hierarchical model codasyl model network model relational model first proposed 1970 edgar f. codd departed tradition insisting applications search data content rather following links relational model employs sets ledger-style tables used different type entity mid-1980s computing hardware become powerful enough allow wide deployment relational systems dbmss plus applications early 1990s however relational systems dominated large-scale data processing applications remain dominant ibm db2 oracle mysql microsoft sql server searched dbms dominant database language standardised sql relational model influenced database languages data models object databases developed 1980s overcome inconvenience object-relational impedance mismatch led coining term post-relational also development hybrid object-relational databases next generation post-relational databases late 2000s became known nosql databases introducing fast key-value stores document-oriented databases competing next generation known newsql databases attempted new implementations retained relational/sql model aiming match high performance nosql compared commercially available relational dbmss introduction term database coincided availability direct-access storage disks drums mid-1960s onwards term represented contrast tape-based systems past allowing shared interactive use rather daily batch processing oxford english dictionary cites 1962 report system development corporation california first use term data-base specific technical sense computers grew speed capability number general-purpose database systems emerged mid-1960s number systems come commercial use interest standard began grow charles bachman author one product integrated data store ids founded database task group within codasyl group responsible creation standardization cobol 1971 database task group delivered standard generally became known codasyl approach soon number commercial products based approach entered market codasyl approach relied manual navigation linked data set formed large network applications could find records one three methods later systems added b-trees provide alternate access paths many codasyl databases also added straightforward query language however final tally codasyl complex required significant training effort produce useful applications ibm also dbms 1966 known information management system ims ims development software written apollo program system/360 ims generally similar concept codasyl used strict hierarchy model data navigation instead codasyl network model concepts later became known navigational databases due way data accessed bachman 1973 turing award presentation programmer navigator ims classified ibm hierarchical database idms cincom systems total database classified network databases ims remains use edgar codd worked ibm san jose california one offshoot offices primarily involved development hard disk systems unhappy navigational model codasyl approach notably lack search facility 1970 wrote number papers outlined new approach database construction eventually culminated groundbreaking relational model data large shared data banks paper described new system storing working large databases instead records stored sort linked list free-form records codasyl codd idea use table fixed-length records table used different type entity linked-list system would inefficient storing sparse databases data one record could left empty relational model solved splitting data series normalized tables relations optional elements moved main table would take room needed data may freely inserted deleted edited tables dbms whatever maintenance needed present table view application/user relational model also allowed content database evolve without constant rewriting links pointers relational part comes entities referencing entities known one-to-many relationship like traditional hierarchical model many-to-many relationship like navigational network model thus relational model express hierarchical navigational models well native tabular model allowing pure combined modeling terms three models application requires instance common use database system track information users name login information various addresses phone numbers navigational approach data would placed single record unused items would simply placed database relational approach data would normalized user table address table phone number table instance records would created optional tables address phone numbers actually provided linking information back together key system relational model bit information used key uniquely defining particular record information collected user information stored optional tables would found searching key instance login name user unique addresses phone numbers user would recorded login name key simple re-linking related data back single collection something traditional computer languages designed navigational approach would require programs loop order collect records relational approach would require loops collect information one record codd suggestions set-oriented language would later spawn ubiquitous sql using branch mathematics known tuple calculus demonstrated system could support operations normal databases inserting updating etc well providing simple system finding returning sets data single operation codd paper picked two people berkeley eugene wong michael stonebraker started project known ingres using funding already allocated geographical database project student programmers produce code beginning 1973 ingres delivered first test products generally ready widespread use 1979 ingres similar system r number ways including use language data access known quel time ingres moved emerging sql standard ibm one test implementation relational model prtv production one business system 12 discontinued honeywell wrote mrds multics two new implementations alphora dataphor rel dbms implementations usually called relational actually sql dbmss 1970 university michigan began development micro information management system based d.l childs set-theoretic data model micro used manage large data sets us department labor u.s. environmental protection agency researchers university alberta university michigan wayne state university ran ibm mainframe computers using michigan terminal system system remained production 1998 1970s 1980s attempts made build database systems integrated hardware software underlying philosophy integration would provide higher performance lower cost examples ibm system/38 early offering teradata britton lee inc. database machine another approach hardware support database management icl cafs accelerator hardware disk controller programmable search capabilities long term efforts generally unsuccessful specialized database machines could keep pace rapid development progress general-purpose computers thus database systems nowadays software systems running general-purpose hardware using general-purpose computer data storage however idea still pursued certain applications companies like netezza oracle exadata ibm started working prototype system loosely based codd concepts system r early 1970s first version ready 1974/5 work started multi-table systems data could split data record optional stored single large chunk subsequent multi-user versions tested customers 1978 1979 time standardized query language – sql – added codd ideas establishing workable superior codasyl pushing ibm develop true production version system r known sql/ds later database 2 db2 larry ellison oracle database simply oracle started different chain based ibm papers system r. though oracle v1 implementations completed 1978 n't oracle version 2 ellison beat ibm market 1979 stonebraker went apply lessons ingres develop new database postgres known postgresql postgresql often used global mission critical applications .org .info domain name registries use primary data store many large companies financial institutions sweden codd paper also read mimer sql developed mid-1970s uppsala university 1984 project consolidated independent enterprise another data model entity–relationship model emerged 1976 gained popularity database design emphasized familiar description earlier relational model later entity–relationship constructs retrofitted data modeling construct relational model difference two become irrelevant 1980s ushered age desktop computing new computers empowered users spreadsheets like lotus 1-2-3 database software like dbase dbase product lightweight easy computer user understand box c. wayne ratliff creator dbase stated dbase different programs like basic c fortran cobol lot dirty work already done data manipulation done dbase instead user user concentrate rather mess dirty details opening reading closing files managing space allocation dbase one top selling software titles 1980s early 1990s 1990s along rise object-oriented programming saw growth data various databases handled programmers designers began treat data databases objects say person data database person attributes address phone number age considered belong person instead extraneous data allows relations data relations objects attributes individual fields term object-relational impedance mismatch described inconvenience translating programmed objects database tables object databases object-relational databases attempt solve problem providing object-oriented language sometimes extensions sql programmers use alternative purely relational sql programming side libraries known object-relational mappings orms attempt solve problem xml databases type structured document-oriented database allows querying based xml document attributes xml databases mostly used applications data conveniently viewed collection documents structure vary flexible highly rigid examples include scientific articles patents tax filings personnel records nosql databases often fast require fixed table schemas avoid join operations storing denormalized data designed scale horizontally recent years strong demand massively distributed databases high partition tolerance according cap theorem impossible distributed system simultaneously provide consistency availability partition tolerance guarantees distributed system satisfy two guarantees time three reason many nosql databases using called eventual consistency provide availability partition tolerance guarantees reduced level data consistency newsql class modern relational databases aims provide scalable performance nosql systems online transaction processing read-write workloads still using sql maintaining acid guarantees traditional database system databases used support internal operations organizations underpin online interactions customers suppliers see enterprise software databases used hold administrative information specialized data engineering data economic models examples include computerized library systems flight reservation systems computerized parts inventory systems many content management systems store websites collections webpages database one way classify databases involves type contents example bibliographic document-text statistical multimedia objects another way application area example accounting music compositions movies banking manufacturing insurance third way technical aspect database structure interface type section lists adjectives used characterize different kinds databases connolly begg define database management system dbms software system enables users define create maintain control access database dbms acronym sometime extended indicated underlying database model rdbms relational oodbms ordbms object orientated model ordbms object-relational extensions indicate characteristic ddbms distributed database management systems functionality provided dbms vary enormously core functionality storage retrieval update data codd proposed following functions services fully-fledged general purpose dbms provide also generally expected dbms provide set utilities purposes may necessary administer database effectively including import export monitoring defragmentation analysis utilities core part dbms interacting database application interface sometimes referred database engine often dbmss configuration parameters statically dynamically tuned example maximum amount main memory server database use trend minimise amount manual configuration cases embedded databases need target zero-administration paramount large major enterprise dbmss tended increase size functionality involved thousands human years development effort lifetime early multi-user dbms typically allowed application reside computer access via terminals terminal emulation software client–server architecture development application resided client desktop database server allowing processing distributed evolved multitier architecture incorporating application servers web servers end user interface via web browser database directly connected adjacent tier general-purpose dbms provide public application programming interfaces api optionally processor database languages sql allow applications written interact database special purpose dbms may use private api specifically customised linked single application example email system performing many functions general-purpose dbms message insertion message deletion attachment handling blocklist lookup associating messages email address forth however functions limited required handle email external interaction database via application program interfaces dbms range database tool allows users execute sql queries textually graphically web site happens use database store search information programmer code interactions database sometimes referred datasource via application program interface api via database language particular api language chosen need supported dbms possible indirectly via pre-processor bridging api api aim database independent odbc commonly known example common api include jdbc ado.net database languages special-purpose languages allow one following tasks sometimes distinguished sublanguages database languages specific particular data model notable examples include database language may also incorporate features like database storage container physical materialization database comprises internal physical level database architecture also contains information needed e.g. metadata data data internal data structures reconstruct conceptual level external level internal level needed putting data permanent storage generally responsibility database engine a.k.a storage engine though typically accessed dbms underlying operating system often using operating systems file systems intermediates storage layout storage properties configuration setting extremely important efficient operation dbms thus closely maintained database administrators dbms operation always database residing several types storage e.g. memory external storage database data additional needed information possibly large amounts coded bits data typically reside storage structures look completely different way data look conceptual external levels ways attempt optimize best possible levels reconstruction needed users programs well computing additional types needed information data e.g. querying database dbmss support specifying character encoding used store data multiple encodings used database various low-level database storage structures used storage engine serialize data model written medium choice techniques indexing may used improve performance conventional storage row-oriented also column-oriented correlation databases often storage redundancy employed increase performance common example storing materialized views consist frequently needed external views query results storing views saves expensive computing time needed downsides materialized views overhead incurred updating keep synchronized original updated database data cost storage redundancy occasionally database employs storage redundancy database objects replication one copies increase data availability improve performance simultaneous multiple end-user accesses database object provide resiliency case partial failure distributed database updates replicated object need synchronized across object copies many cases entire database replicated database security deals various aspects protecting database content owners users ranges protection intentional unauthorized database uses unintentional database accesses unauthorized entities e.g. person computer program database access control deals controlling person certain computer program allowed access information database information may comprise specific database objects e.g. record types specific records data structures certain computations certain objects e.g. query types specific queries using specific access paths former e.g. using specific indexes data structures access information database access controls set special authorized database owner personnel uses dedicated protected security dbms interfaces may managed directly individual basis assignment individuals privileges groups elaborate models assignment individuals groups roles granted entitlements data security prevents unauthorized users viewing updating database using passwords users allowed access entire database subsets called subschemas example employee database contain data individual employee one group users may authorized view payroll data others allowed access work history medical data dbms provides way interactively enter update database well interrogate capability allows managing personal databases data security general deals protecting specific chunks data physically i.e. corruption destruction removal e.g. see physical security interpretation parts meaningful information e.g. looking strings bits comprise concluding specific valid credit-card numbers e.g. see data encryption change access logging records accessed attributes changed changed logging services allow forensic database audit later keeping record access occurrences changes sometimes application-level code used record changes rather leaving database monitoring set attempt detect security breaches database transactions used introduce level fault tolerance data integrity recovery crash database transaction unit work typically encapsulating number operations database e.g. reading database object writing acquiring lock etc abstraction supported database also systems transaction well defined boundaries terms program/code executions included transaction determined transaction programmer via special transaction commands acronym acid describes ideal properties database transaction atomicity consistency isolation durability database built one dbms portable another dbms i.e. dbms run however situations desirable migrate database one dbms another reasons primarily economical different dbmss may different total costs ownership tcos functional operational different dbmss may different capabilities migration involves database transformation one dbms type another transformation maintain possible database related application i.e. related application programs intact thus database conceptual external architectural levels maintained transformation may desired also aspects architecture internal level maintained complex large database migration may complicated costly one-time project factored decision migrate spite fact tools may exist help migration specific dbmss typically dbms vendor provides tools help importing databases popular dbmss designing database application next stage building database typically appropriate general-purpose dbms selected used purpose dbms provides needed user interfaces used database administrators define needed application data structures within dbms respective data model user interfaces used select needed dbms parameters like security related storage allocation parameters etc. database ready data structures needed components defined typically populated initial application data database initialization typically distinct project many cases using specialized dbms interfaces support bulk insertion making operational cases database becomes operational empty application data data accumulated operation database created initialised populated needs maintained various database parameters may need changing database may need tuned tuning better performance application data structures may changed added new related application programs may written add application functionality etc sometimes desired bring database back previous state many reasons e.g. cases database found corrupted due software error updated erroneous data achieve backup operation done occasionally continuously desired database state i.e. values data embedding database data structures kept within dedicated backup files many techniques exist effectively decided database administrator bring database back state e.g. specifying state desired point time database state files used restore state static analysis techniques software verification applied also scenario query languages particular *abstract interpretation framework extended field query languages relational databases way support sound approximation techniques semantics query languages tuned according suitable abstractions concrete domain data abstraction relational database system many interesting applications particular security purposes fine grained access control watermarking etc dbms features might include increasingly calls single system incorporates core functionalities build test deployment framework database management source control borrowing developments software industry market offerings devops database first task database designer produce conceptual data model reflects structure information held database common approach develop entity-relationship model often aid drawing tools another popular approach unified modeling language successful data model accurately reflect possible state external world modeled example people one phone number allow information captured designing good conceptual data model requires good understanding application domain typically involves asking deep questions things interest organization like customer also supplier product sold two different forms packaging product different products plane flies new york dubai via frankfurt one flight two maybe even three answers questions establish definitions terminology used entities customers products flights flight segments relationships attributes producing conceptual data model sometimes involves input business processes analysis workflow organization help establish information needed database left example help deciding whether database needs hold historic data well current data produced conceptual data model users happy next stage translate schema implements relevant data structures within database process often called logical database design output logical data model expressed form schema whereas conceptual data model theory least independent choice database technology logical data model expressed terms particular database model supported chosen dbms terms data model database model often used interchangeably article use data model design specific database database model modeling notation used express design popular database model general-purpose databases relational model precisely relational model represented sql language process creating logical database design using model uses methodical approach known normalization goal normalization ensure elementary fact recorded one place insertions updates deletions automatically maintain consistency final stage database design make decisions affect performance scalability recovery security like depend particular dbms often called physical database design output physical data model key goal stage data independence meaning decisions made performance optimization purposes invisible end-users applications two types data independence physical data independence logical data independence physical design driven mainly performance requirements requires good knowledge expected workload access patterns deep understanding features offered chosen dbms another aspect physical database design security involves defining access control database objects well defining security levels methods data database model type data model determines logical structure database fundamentally determines manner data stored organized manipulated popular example database model relational model sql approximation relational uses table-based format common logical data models databases include object-relational database combines two related structures physical data models include models include specialized models optimized particular types data database management system provides three views database data typically one conceptual logical physical internal view data number different external views allows users see database information business-related way rather technical processing viewpoint example financial department company needs payment details employees part company expenses need details employees interest human resources department thus different departments need different views company database three-level database architecture relates concept data independence one major initial driving forces relational model idea changes made certain level affect view higher level example changes internal level affect application programs written using conceptual level interfaces reduces impact making physical changes improve performance conceptual view provides level indirection internal external one hand provides common view database independent different external view structures hand abstracts away details data stored managed internal level principle every level even every external view presented different data model practice usually given dbms uses data model external conceptual levels e.g. relational model internal level hidden inside dbms depends implementation requires different level detail uses types data structure types separating external conceptual internal levels major feature relational database model implementations dominate 21st century databases database technology active research topic since 1960s academia research development groups companies example ibm research research activity includes theory development prototypes notable research topics included models atomic transaction concept related concurrency control techniques query languages query optimization methods raid database research area several dedicated academic journals example acm transactions database systems -tods data knowledge engineering -dke annual conferences e.g. acm sigmod acm pods vldb ieee icde
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Databases
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shopkeep shopkeep cloud-based ipad point sale pos system headquartered new york ny founded 2008 pos system used 23,000 small businesses united states canada retail shops coffee shops restaurants bars system allows merchants ring sales print email receipts pop cash drawer accept credit cards print remotely kitchen right ipad android tablet web-based backoffice allows inventory employee customer management analytics reporting smartphone dashboard app allows merchants view real-time store sales remotely shopkeep co-founded jason richelson co-founder several retail stores brooklyn new york city amy bennett wine store brooklyn fall 2008 point sale software crashed last time david olk former director iac joined third co-founder coo july 2011 help jason amy execute vision raise outside capital eventually closing company first external raise 6 months later december 2011 jason point sale system stores broke decided simpler smarter solution small businesses developed shopkeep pos cloud-based point sale system allow merchants access data even store also developed eyes retailer used expertise create user interface intuitive merchants cashiers stand behind counter jason hired bill walton original system architect engineer build shopkeep platform october 2008 august 2011 first ipad version shopkeep released app store july 2015 shopkeep raised 97 million funding
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Distributed computing architecture
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flagship compiler flagship object oriented procedural programming language based xbase language dialect conventions flagship available cross-compatible different computer platforms linux unix microsoft windows true compiler translates popular database 4gl xbase source code native 32-bit 64-bit executables using source-code databases first flagship version introduced multisoft datentechnik gmbh 1992 port clipper dbase iii+ foxbase foxpro applications different operating systems i.e openserver aix solaris hp-ux sinix many unix systems 1995 also linux ports became available 2002 visual flagship abbreviated vfs announced linux 2004 additionally 32/64-bit based windows operating systems current vfs product line covers common 32-bit 64-bit operating systems windows nt 2000 xp vista 7 server 2008 flagship programming development tool compilers designed mainly professional software developers simple interface also perfectly suitable semi-professionals advanced computer users need create database applications minimal programming effort thanks full clipper compatibility also best suited porting already available dos applications nearly unix linux ms-windows systems learning curve already familiar xbase dialect like dbase foxbase foxpro clipper visual objects etc millions well-trained programmers using easy powerful 4gl syntax years directly switch flagship n't programming experience xbase familiar language c c++ java pascal delphi basic perl etc learning curve short 10 commands able create first application visual flagship makes gui-based application available textual xbase code automatically course object oriented modify behavior using either classes corresponding functions procedural programming source application supports gui textual stream mode e.g web background i/o mode either detected automatically current environment heterogenal application specified compile time run-time using command-line switch example statements stored text file address.prg ... compiled simply ... creates self-containing executable i.e address.exe windows additional examples screenshots available via external links
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Programming language topics
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fiber distributed data interface fiber distributed data interface fddi standard data transmission local area network uses optical fiber standard underlying physical medium although also later specified use copper cable case may called cddi copper distributed data interface standardized tp-pmd twisted-pair physical medium-dependent also referred tp-ddi twisted-pair distributed data interface fddi effectively made obsolete local networks fast ethernet offered 100 mbit/s speeds much lower cost since 1998 gigabit ethernet due speed even lower cost ubiquity fddi provides 100 mbit/s optical standard data transmission local area network extend range although fddi logical topology ring-based token network use ieee 802.5 token ring protocol basis instead protocol derived ieee 802.4 token bus timed token protocol addition covering large geographical areas fddi local area networks support thousands users fddi offers dual-attached station das counter-rotating token ring topology single-attached station sas token bus passing ring topology fddi product american national standards institute x3t9.5 x3t12 conforms open systems interconnection osi model functional layering using protocols standards process started mid 1980s fddi-ii version fddi described 1989 added circuit-switched service capability network could also handle voice video signals work started connect fddi networks synchronous optical networking sonet technology fddi network contains two rings one secondary backup case primary ring fails primary ring offers 100 mbit/s capacity network requirement secondary ring backup also carry data extending capacity 200 mbit/s single ring extend maximum distance dual ring extend fddi larger maximum-frame size 4,352 bytes standard ethernet family supports maximum-frame size 1,500 bytes allowing better effective data rates cases designers normally constructed fddi rings network topology dual ring trees small number devices typically infrastructure devices routers concentrators rather host computers dual-attached rings host computers connect single-attached devices routers concentrators dual ring degenerate form simply collapses single device typically computer-room contained whole dual ring although implementations deployed fddi metropolitan area network fddi requires network topology dual ring actually passes connected device requires device remain continuously operational standard actually allows optical bypasses network engineers consider unreliable error-prone devices workstations minicomputers might come control network managers suitable connection dual ring alternative using dual-attached connection workstation obtain degree resilience dual-homed connection made simultaneously two separate devices fddi ring one connections becomes active one automatically blocked first connection fails backup link takes perceptible delay fddi data frame format pa preamble sd start delimiter fc frame control da destination address sa source address pdu protocol data unit packet data unit fcs frame check sequence checksum ed/fs end delimiter frame status internet engineering task force defined standard transmission internet protocol would protocol data unit case fddi first proposed june 1989 revised 1990 aspects protocol compatible ieee 802.2 standard logical link control example 48-bit mac addresses became popular ethernet family thus protocols address resolution protocol arp could common well fddi considered attractive campus backbone network technology early mid 1990s since existing ethernet networks offered 10 mbit/s data rates token ring networks offered 4 mbit/s 16 mbit/s rates thus relatively high-speed choice era 1994 vendors included cisco systems national semiconductor network peripherals syskonnect acquired marvell technology group 3com fddi installations largely replaced ethernet deployments fddi standards included
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Internet protocols
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iskolinux iskolinux pronounced is-kooh-lee-nux linux distribution packaged maintained manila upm information management system part university philippines thrust migrate linux coined term filipino word iskolar comes phrase iskolar ng bayan loosely referring students national scholars linux operating system iskolinux based beatrix derived knoppix ubuntu turn derived debian operating system lead developers project ariel s. betan eric manuel n. pareja system developers upm distribution live cd installer giving user option boot operating system directly cd without requiring installation local hard drive iskolinux primarily designed desktop operating system include applications commonly used students faculty staff recent version iskolinux v0.12 uses linux kernel version 2.6.7 gnome 2.8 desktop manager future plans include installation commands manual desktop environment filipino
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Operating systems
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place hide greenwald book place hide edward snowden nsa u.s. surveillance state 2014 non-fiction book american investigative journalist glenn greenwald first published may 13 2014 metropolitan books details greenwald role global surveillance disclosures revealed former national security agency contractor edward snowden documents snowden archive cited book freely available online book consists five chapters contact ten days hong kong collect harm surveillance fourth estate plus introduction epilogue introduction greenwald explains background blogger surveillance practices american government attracted edward snowden attention summarizes nature legality evolution practices greenwald concludes discussing global surveillance network created assistance technology companies unique role internet human history facilitator surveillance body book greenwald discusses became involved 2013 global surveillance disclosures began traveling hong kong meet edward snowden contacted greenwald anonymous source purporting evidence government surveillance greenwald continued investigate uncovered information later published much controversy book greenwald also discusses establishment media states traditionally avoid publishing anything would put odds government less helpful comes interests general public review washington post law professor david cole called place hide important illuminating book wrote would important illuminating greenwald able acknowledge choices face regulating surveillance modern age difficult simple answers slate gave mostly positive review stating book ’ offer in-depth portrait leaker serve good primer stake downloaded government ’ precious secrets onto thumb drive book positively reviewed henry porter guardian porter said found reacquainting details surveillance intrusion america nsa britain gchq simply shocking stories rolled last year almost much absorb ... greenwald book tough read find things disturbing porter said reading place hide wondered ... let spies probe lives inadequate controls earth fell propaganda massive apparatus protect control us critically porter felt book lacked ... chart timeline major revelations well proper index feel argument lost momentum middle ... concluding ... whole vigorously executed important book porter reserved criticism felt lack appreciation greenwald importance efforts ewen macaskill fellow guardian writers bringing disclosures publication glenn greenwald received 2014 geschwister-scholl-preis annual german literary award german edition place hide
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Computer security
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intego intego mac security software company company founded 1997 company creates internet security software exclusively mac os x macos including antivirus firewall anti-spam backup software data protection software intego currently offices u.s. seattle washington austin texas also offices paris france nagano japan intego products universal binaries supported several languages english french japanese german spanish italian founded former ceo laurent marteau based paris france intego released first antivirus product 1997 rival antivirus mac os 8 two years later july 1999 intego released netbarrier first personal security software suite mac os 8 october 2000 intego released legacy antivirus software virusbarrier 1.0 mac os 8 mac os 9 intego launched mac security blog mid-2007 blog covers mac security news apple security updates mac malware alerts well news opinion pieces related apple products company launched podcast october 2017 called intego mac podcast intego released current x9 version antivirus security software june 2016
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Computer security
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jack audio connection kit jack audio connection kit jack recursive acronym professional sound server daemon provides real-time low-latency connections audio midi data applications use api jack developed community open-source developers led paul davis open source award 2004 work key piece infrastructure de facto standard professional audio software linux since inception 2002 server free software licensed gnu gpl library licensed permissive gnu lgpl jack use alsa portaudio coreaudio ffado oss hardware back-ends additionally dummy driver useful sound output desired e.g offline rendering audio-over-udp driver exist runs linux macos solaris windows ios freebsd openbsd netbsd jack api standardized consensus two compatible implementations exist jack1 implemented plain c maintenance mode jack2 originally jackdmp re-implementation c++ led stéphane letz aggressive development introduced multi-processor scalability support operating systems linux scheduling requirements jack achieve sufficiently low latencies one driving forces behind real-time optimization effort linux kernel 2.6 series whose initial latency performance disappointing compared older 2.4 series real-time tuning work culminated numerous scheduling improvements mainline kernel creation -rt branch intrusive optimizations release 2.6.24 later config_preempt_rt patch
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Operating systems
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sgi 1600sw 1600sw widescreen flat panel video monitor silicon graphics introduced 1998 many awards release sold 54,000 units notable longevity used models still actively traded ebay decade later despite difficulty adapting monitor run modern video cards due 1600sw openldi video interface formac sold monitor bundled openldi graphics adapter formac pronitron 18/500 radius sold monitor artica differed mainly translucent white case conventional mount sgi sold monitor primarily model am173y01 1600sw revolutionary time featuring 17.3 inch diagonal wide screen panel market dominated crt monitors 1600sw 25:16 aspect ratio referred sgi superwide resolution 1600 x 1024 pixels refresh rate 60 hz 24-bit color 110 dpi makes smaller dot pitch competitive monitors 1600sw shared styling motif sgi visual workstation 320 540 o2 unique troublesome off-center mount display dozen international awards despite age still compares well modern displays produced decade later introduction 1600sw cost neighborhood 2500 4-way monitor switch dr. bott called moniswitch pro ldi allows sharing openldi display among 4 computers must equipped openldi graphics adapter openldi rarely used today popular home office lcd panel monitors use dvi vga standard connector several companies make adapter boxes allow continued use older displays adapters developed 1600sw monitor sgi referred video cards support 1600sw 1600 x 1024 resolution super wide savvy modern cards trouble resolution pc based machines problems screen distortion exist system boot apple macintoshes boot directly proper resolution thus little work 1600sw adapted almost modern computer according original sgi project manager dan evanicky common failure items backlights power supplies point dan expects power supply continuous use failed though monitor likely fine monitors left continuous decade likely faded backlights generic power supplies work unit specifications 3 amps 12 volts 5.5m x 2.5mm center positive coaxial barrel preferably right angle 2005 mr. evanicky purchased entire spares inventory sitting mitsubishi japan order supply enthusiasts repair parts
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Computer architecture
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docker software docker set platform-as-a-service paas products use operating-system-level virtualization deliver software packages called containers containers isolated one another bundle software libraries configuration files communicate well-defined channels containers run single operating-system kernel thus lightweight virtual machines service free premium tiers software hosts containers called docker engine first started 2013 developed docker inc. docker inc. founded solomon hykes sebastien pahl combinator summer 2010 startup incubator group launched 2011 hykes started docker project france internal project within dotcloud platform-as-a-service company initial contributors dotcloud engineers including andrea luzzardi francois-xavier bourlet jeff lindsay also became involved independent collaborator docker debuted public santa clara pycon 2013 released open-source march 2013 time used lxc default execution environment one year later release version 0.9 docker replaced lxc component written go programming language october 15 2014 microsoft announced integration docker engine next windows server release native support docker client role windows june 8 2016 microsoft announced docker could used natively windows 10 hyper-v containers build ship run containers utilizing windows server 2016 technical preview 5 nano server container os image since feature known windows containers made available windows 10 windows server 2016 two types windows containers windows server containers hyper-v isolation former nothing docker falls outside scope article latter however form hardware virtualization opposed os-level virtualization uses docker deliver guest os image guest os image windows nano server image 652 mb size separate end-user license agreement may 6 2019 microsoft announced second version windows subsystem linux wsl version wsl integrates full linux kernel windows 10 docker inc. announced started working version docker windows runs wsl 2 instead full virtual machine according linux.com docker package application dependencies virtual container run linux server helps enable flexibility portability application run whether on-premises public cloud private cloud docker uses resource isolation features linux kernel cgroups kernel namespaces union-capable file system overlayfs allow containers run within single linux instance avoiding overhead starting maintaining virtual machines docker containers lightweight single server virtual machine run several containers simultaneously 2016 analysis found typical docker use case involves running five containers per host many organizations run 10 linux kernel support namespaces mostly isolates application view operating environment including process trees network user ids mounted file systems kernel cgroups provide resource limiting memory cpu since version 0.9 docker includes component called directly use virtualization facilities provided linux kernel addition using abstracted virtualization interfaces via libvirt lxc systemd-nspawn docker implements high-level api provide lightweight containers run processes isolation docker software service offering consists three components
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Operating systems
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contention telecommunications statistical time division multiplexing contention media access method used share broadcast medium contention computer network transmit data time first come-first served system breaks two computers attempt transmit time known collision avoid collisions carrier sensing mechanism used computer listens network attempting transmit network busy waits network quiets carrier detection computers continue listen network transmit computer detects another signal interferes signal sending stops transmitting computers wait random amount time attempt transmit contention methods popular media access control method lans one method handle collisions contention based system optimize collision detection subsequent recovery alternative method handle collisions contention based system attempt avoid systems may utilize strict scheduling guideline identify may use resources systems may senders listen channel immediately prior transmitting determine suitable times transmit collisions condition arises two data stations attempt transmit time shared channel two data stations attempt transmit time half duplex communication link contention based channel access multiple access protocol protocol data packet collisions may occur examples protocols telecommunication term contention also following less usual meanings
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Internet protocols
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frame networking frame digital data transmission unit computer networking telecommunication packet switched systems frame simple container single network packet telecommunications systems frame repeating structure supporting time-division multiplexing frame typically includes frame synchronization features consisting sequence bits symbols indicate receiver beginning end payload data within stream symbols bits receives receiver connected system frame transmission ignores data detects new frame synchronization sequence osi model computer networking frame protocol data unit data link layer frames result final layer encapsulation data transmitted physical layer frame unit transmission link layer protocol consists link layer header followed packet frame separated next interframe gap frame series bits generally composed frame synchronization bits packet payload frame check sequence examples ethernet frames point-to-point protocol ppp frames fibre channel frames v.42 modem frames often frames several different sizes nested inside example using point-to-point protocol ppp asynchronous serial communication eight bits individual byte framed start stop bits payload data bytes network packet framed header footer several packets framed frame boundary octets telecommunications specifically time-division multiplex tdm time-division multiple access tdma variants frame cyclically repeated data block consists fixed number time slots one logical tdm channel tdma transmitter context frame typically entity physical layer tdm application examples sonet/sdh isdn circuit-switched b-channel tdma examples circuit switched data used early cellular voice services frame also entity time-division duplex mobile terminal may transmit time slots receive others
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Internet protocols
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heartbeat computing computer science heartbeat periodic signal generated hardware software indicate normal operation synchronize parts computer system usually heartbeat sent machines regular interval order seconds endpoint receive heartbeat time—usually heartbeat intervals—the machine sent heartbeat assumed failed heartbeat protocol generally used negotiate monitor availability resource floating ip address typically heartbeat starts machine perform election process machines heartbeat network determine machine owns resource heartbeat networks two machines important take account partitioning two halves network could functioning able communicate situation important resource owned one machine one machine partition heartbeat intended used indicate health machine important heartbeat protocol transport runs reliable possible causing failover false alarm may depending resource highly undesirable also important react quickly actual failure important heartbeat reliable reason often desirable heartbeat running one transport instance ethernet segment using udp/ip serial link
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Distributed computing architecture
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porteus operating system porteus formerly slax remix portable operating system based slackware require installation run fixed removable media usb flash drive compact disc porteus available 32-bit 64-bit version porteus project started slax remix beginning 2010 started community project using zen kernel improve update slax os community agreed new name project porteus named 'portability 'proteus 'proteus greek god sea capable changing form according naming announcement porteus forum project leader commented name find name kind synonym 'flexibility portable small flexible modular features included one name porteus porteus 4.0 available seven desktop variants cinnamon kde plasma 5 lxde lxqt mate openbox xfce porteus based substantially modified optimized version linux live scripts run disk usb stick changes saved onto portable device installed hard drive porteus even installed within another system without need create new partition porteus preloaded variety software user selects installing system downloaded selecting various options menu including one four windows management systems browser features porteus uses package manager utilizing slackware porteus kiosk specialized edition porteus operating system minimalist linux distribution web-only terminals firefox google chrome chromium opera set upon installation sole application porteus kiosk provides users locked computing environment designed deployed schools offices public libraries internet cafés business establishment provides internet access clients porteus kiosk installed cd/dvd usb flash drive hard drive bootable storage media compact flash sd/mmc memory cards prior installation system customized kiosk wizard utility allows system browser related tweaks porteus kiosk system open source available free-of-charge although number commercial services custom builds automatic updates software upgrades available version 3.7.0 porteus kiosk able run 32-bit i486 greater 64-bit x86_64 machines google chrome n't support 32-bit machines anymore developers distribution decided follow path hence release 4.0.0 porteus kiosk supports x86_64 architecture system lightweight terms size resources used default image 80 mb size custom kiosk iso depend choice added extra components adobe flash java additional fonts factors reviewing porteus 1.0 june 2011 joe zonker brockmeier wrote users 've missed kde 3.5.x treat porteus portable linux distribution offers 32-bit release trinity fork kde 3.5.x 64-bit release offers kde 4.6.4 distribution appeal everyone might interest enthusiasts live cd distributions old-school kde fans concluded ... porteus looks like nice portable linux distribution aimed expert least experienced linux users something appeal majority linux users particularly users prefer slightly larger depth available packages users nursing older hardware prefer portable distribution porteus interesting project custom live cd iso creation linux magazine wrote issue 160/2014 build portable linux distro porteus building customized linux distribution daunting proposition – unless use porteus wizard clever simple service lets create custom live cd distro fits usb stick loads ram
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Operating systems
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beta basic beta basic basic interpreter sinclair research zx spectrum microcomputer written dr andy wright 1983 sold one-man software house betasoft betasoft also produced regular newsletter/magazine betanews originally started basic toolkit time grew full replacement beta basic completely replaced sinclair basic common time also os providing command line interface cli thus beta basic provided new improved cli editor supported sinclair idiosyncratic single-key entry system basic keywords also allowed keywords spelled letter-for-letter also removed necessity memorising sometimes arcane key combinations necessary enter less-commonly-used basic keywords however single-key entry system also extended mapping spectrum 'graphics characters beta basic new keywords switch keyword entry typed entry merely necessary type single space causing cursor mode change k keyword l lowercase c capital keywords statement could also used alter behaviour example disabling k mode editor listing could optionally automatically prettyprint code possible manually sinclair basic automatic indentation advantage highlighting certain types coding error primarily failing correctly close constructs editing improvements included automatic highlighting current-line indicator small tweak disproportionately helpful ability move cursor well left right huge boon editing long lines combined 64-column display see new functionality section improvements made beta basic much productive environment even coding standard sinclair basic making use betasoft language additions beta basic also basic interpreter right bypassing spectrum rom used library occasionally made calls rom access useful functions worth re-implementing beta basic either rom routines good enough reasons space beta basic run 48 kb memory available spectrum still leave room user code time beta basic sophisticated provided full structured programming named procedures functions complete local variables allowing programming using recursion although supported line numbers necessary offered mode operation completely suppressed display line numbers 128k spectrum machines beta basic provided extended facilities allowing programmers access machine extra memory took form ram disk well allowing programmer save load programs blocks memory screen images ram disc catalogue contents ram disk beta basic also provided commands creation use arrays held ram disk allowing programs running 30 kb free memory spectrum manipulate arrays approaching 80 kb significant extra amount space 1980s standards almost 8-bit basic generally limited 64 kb program data combined beta basic also drove spectrum 256x192 pixel display directly eliminating restrictions rom 32-column text display beta basic offered scalable screen fonts special soft font 4 pixels wide still legible meant beta basic could display 64 columns text across screen making comparable newer 8-bit machines 80-column displays user prepared tolerate characters displayed without gaps 85 column display possible readable allow easy porting basic applications designed 80-column screen text size could controlled programmatically part program display might use 64-column text part 32-column text enlarged reduced intermediate sizes special versions produced users interface 1 zx microdrive subsequently opus discovery disciple plusd disk interfaces well version amstrad spectrum +3 also consideration wright discarded project beta basic suffered limitations 8-bit microprocessors spectrum could address 64 kb contiguous memory due addressing restrictions spectrum zilog z80 cpu 16 kb taken sinclair basic rom leaving 48 kb ram screen took areas used holding interpreter internal data structures beta basic took around 11-12 kb remainder cases leaving 20 kb user programs replacement sinclair editor meant possible use 128k spectrum rom full-screen basic editor compiler available beta basic code existing sinclair basic compilers hisoft basic could handle extended keywords facilities beta basic another remaining sinclair basic limitation single-letter variable names could used strings arrays types 8-bit basic inbuilt support structured programming bbc basic beta basic named procedures need called proc keyword like bbc basic thus became new language keywords allowing language extended however bbc basic considerably quicker fastest basic interpreter time beta basic especially fast though included faster replacements particularly slow rom routines circle arc drawing code development sophisticated new successor spectrum sam coupé alan miles bruce gordon miles gordon technology approached betasoft contracted wright provide basic new machine provided complete basic interpreter drew extensively upon beta basic differently structured language right sinclair rom call upon work around sam basic largely compatible beta basic operated similar manner except areas sam hardware significantly different sam screen extended memory betasoft later released extension sam basic named masterbasic
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Programming language topics
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xconfig xconfig short codice_1 target linux makefile graphical linux compilation utility uses qt xconfig utility invoked running codice_2 base linux source directory qt used since kernel 2.6 kernel 2.4 uses tcl/tk configuration interface gtk+ interface codice_3 also available since kernel 2.6
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Computer architecture
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marie meyer linguist marie anne meyer april 7 1897 – 1969 american linguist spy worked national security agency 1943-60 assigned venona project credited making first recoveries venona codebook studied eight foreign languages first person receive nsa meritorious civilian service award meyer born april 7 1897 raised bloomington illinois attended illinois normal state university normal illinois graduated bachelor degree education 1919 began teaching schools graduation continued education summer sessions university chicago studying french latin august 1930 received master degree latin 1930s 1940s continued study languages taking summer classes sanskrit greek german 1943 meyer hired signal security agency likely german linguist summer 1946 took university chicago course russian assigned venona project national security agency credited making first recoveries venona codebook rest career meyer worked facets russian problem taught russian classes nsa training school 1950 nsa memorandum described meyer highly professional russian linguist holding highest level competency meyer retired 1960 first person receive meritorious civilian service award spent retirement years engaging research catholic university celtic languages died illinois december 1969
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Computer security
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senjyo senjyo センジョー arcade game developed 1983 tehkan known tecmo title game translates japanese 'battlefield simple gameplay involves player controlling fixed turret tank shooting oncoming alien enemies cross-hair target certain number enemies must destroyed progress next stage original arcade cabinet cocktail table game ported published sony corporation 1984 msx computers 2005 senjyo re-released exclusively xbox part tecmo classic arcade collection
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Computer architecture
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windows 10 mobile version history windows 10 mobile mobile operating system developed microsoft released manufacturing november 20 2015 made generally available march 17 2016 october 2017 microsoft announced would pause active development windows 10 mobile last feature update fall creators update future development windows 10 mobile limited maintenance releases security patches windows 10 mobile november update also known version 1511 codenamed threshold 2 first major update windows 10 mobile one series updates threshold codenames carries build number 10.0.10586 released public november 12 2015 update reached end service january 9 2018 windows 10 mobile anniversary update also known version 1607 codenamed redstone 1 second major update windows 10 mobile first series updates redstone codenames carries build number 10.0.14393 first preview released february 19 2016 released public august 16 2016 update reached end service release build 14393.2551 october 9 2018 windows 10 mobile creators update also known version 1703 codenamed redstone 2 third major update windows 10 mobile second series updates redstone codenames carries build number 10.0.15063 first preview released insiders august 17 2016 released public april 25 2017 update reached end service release build 15063.1868 june 11 2019 windows 10 mobile fall creators update also known version 1709 codenamed redstone 3 third major update windows 10 mobile third series updates redstone codenames carries build number 10.0.15254 despite sharing codename version number pc version windows 10 fall creators update redstone 3 update still build part redstone 2 branch first preview released insiders april 14 2017 released public october 24 2017 update set reached end service december 10 2019
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Operating systems
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frequency-shift keying frequency-shift keying fsk frequency modulation scheme digital information transmitted discrete frequency changes carrier signal technology used communication systems telemetry weather balloon radiosondes caller id garage door openers low frequency radio transmission vlf elf bands simplest fsk binary fsk bfsk bfsk uses pair discrete frequencies transmit binary 0s 1s information scheme 1 called mark frequency 0 called space frequency reference implementations fsk modems exist documented detail demodulation binary fsk signal done using goertzel algorithm efficiently even low-power microcontrollers principle fsk implemented using completely independent free-running oscillators switching beginning symbol period general independent oscillators phase therefore amplitude switch-over instant causing sudden discontinuities transmitted signal practice many fsk transmitters use single oscillator process switching different frequency beginning symbol period preserves phase elimination discontinuities phase therefore elimination sudden changes amplitude reduces sideband power reducing interference neighboring channels rather directly modulating frequency digital data symbols instantaneously changing frequency beginning symbol period gaussian frequency-shift keying gfsk filters data pulses gaussian filter make transitions smoother filter advantage reducing sideband power reducing interference neighboring channels cost increasing intersymbol interference used dect bluetooth cypress wirelessusb nordic semiconductor texas instruments lprf z-wave wavenis devices basic data rate bluetooth minimum deviation 115 khz gfsk modulator differs simple frequency-shift keying modulator baseband waveform levels −1 +1 goes fsk modulator passed gaussian filter make transitions smoother limit spectral width gaussian filtering standard way reducing spectral width called pulse shaping application ordinary non-filtered fsk jump −1 +1 +1 −1 modulated waveform changes rapidly introduces large out-of-band spectrum pulse changed going −1 +1 −1 −0.98 −0.93 … +0.93 +0.98 +1 smoother pulse used determine carrier frequency out-of-band spectrum reduced minimum frequency-shift keying minimum-shift keying msk particular spectrally efficient form coherent fsk msk difference higher lower frequency identical half bit rate consequently waveforms represent 0 1 bit differ exactly half carrier period maximum frequency deviation δ 0.25 f f maximum modulating frequency result modulation index 0.5 smallest fsk modulation index chosen waveforms 0 1 orthogonal variant msk called gaussian minimum-shift keying gmsk used gsm mobile phone standard audio frequency-shift keying afsk modulation technique digital data represented changes frequency pitch audio tone yielding encoded signal suitable transmission via radio telephone normally transmitted audio alternates two tones one mark represents binary one space represents binary zero afsk differs regular frequency-shift keying performing modulation baseband frequencies radio applications afsk-modulated signal normally used modulate rf carrier using conventional technique fm transmission afsk always used high-speed data communications since far less efficient power bandwidth modulation modes addition simplicity however afsk advantage encoded signals pass ac-coupled links including equipment originally designed carry music speech afsk used u.s.-based emergency alert system notify stations type emergency locations affected time issue without actually hearing text alert phase 1 radios project 25 system use continuous 4-level fm c4fm modulation 1910 reginald fessenden invented two-tone method transmitting morse code dots dashes replaced different tones equal length intent minimize transmission time early cw transmitters employed arc converter could conveniently keyed instead turning arc key slightly changed transmitter frequency technique known compensation-wave method compensation-wave used receiver spark transmitters used method consumed lot bandwidth caused interference discouraged 1921 early telephone-line modems used audio frequency-shift keying afsk send receive data rates 1200 bits per second bell 103 bell 202 modems used technique even today north american caller id uses 1200 baud afsk form bell 202 standard early microcomputers used specific form afsk modulation kansas city standard store data audio cassettes afsk still widely used amateur radio allows data transmission unmodified voiceband equipment afsk also used united states emergency alert system transmit warning information used higher bitrates weathercopy used weatheradio noaa u.s chu shortwave radio station ottawa ontario canada broadcasts exclusive digital time signal encoded using afsk modulation frequency-shift keying fsk commonly used telephone lines caller id displaying callers numbers remote metering applications several variations technology countries europe european telecommunications standards institute etsi standards 200 778-1 -2 – replacing 300 778-1 -2 – allow 3 physical transport layers telcordia technologies formerly bellcore british telecom bt cable communications association cca combined 2 data formats multiple data message format mdmf single data message format sdmf plus dual-tone multi-frequency dtmf system no-ring mode meter-reading like recognition different types exist attempt define single standard telcordia technologies formerly bellcore standard used united states canada see australia china hong kong singapore sends data first ring tone uses 1200 bits per second bell 202 tone modulation data may sent sdmf – includes date time number – mdmf adds name field british telecom bt united kingdom developed standard wakes display line reversal sends data ccitt v.23 modem tones format similar mdmf used bt wireless networks like late ionica cable companies details found bt supplier information notes sins 227 242 another useful document designing caller identification delivery using xr-2211 bt exar website cable communications association cca united kingdom developed standard sends information short first ring either bell 202 v.23 tones developed new standard rather change street boxes multiplexors could n't cope bt standard uk cable industry use variety switches nortel dms-100 system x system nokia dx220 note use bt standard instead cca one data format similar bt one transport layer like telcordia technologies north american european equipment likely detect
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Computer security
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game sprockets game sprockets collection application programming interfaces apis supporting gaming classic mac os consisted four main parts drawsprocket inputsprocket soundsprocket netsprocket providing library pre-rolled routines common gaming tasks speechsprocket relabelled version speech recognition manager provided speech recognition support quickdraw 3d rave provided 3d hardware acceleration game sprockets first released 1996 saw minor use development cancelled 1997 os x included many features built-in libraries opengl replaced rave 3d acceleration layer netsprocket lives openplay although adoption limited early history macintosh computer strong gaming platform due high-resolution screen digital sound hardware fact every mac came equipped reasonable gaming controller mouse however gaming never supported strong way within apple cases actively discouraged 1990s mac platform greatly increased complexity profusion models different features supporting game across entire lineup required programmer learn intricacies different models time even figuring machine program installed standard solution mid-90s pc gaming evolved powerful market one drivers new computer purchases move ms-dos microsoft windows several microsoft staffers noticed game developers generally ignoring windows due better performance available dos decided windows needed support first-class gaming set ensuring windows would become preferred gaming platform future result introduction directx libraries greatly reduced complexity addressed many performance concerns 3d games became widespread library direct3d became decisive advantage directx grew become almost universal pc gaming mid-90s gaming mac largely dead combination high prices stagnating sales poor performance lack directx-like system resulted game developers leaving mac field droves microsoft several apple staffers took upon redress problem led chris desalvo result two-pronged effort one side game sprockets libraries along rave single target gaming platform pippin game sprockets released 29 march 1996 year wwdc game sprockets one many apple technologies ended development return steve jobs ceo position apple death announced march 1997 press release part wide series layoffs restructuring company moved mac os x based future desalvo wrote fairly lengthy open letter topic noting sprockets might come life future gamesprockets included four main libraries two associated ones discussed turn unlike pre-windows pc system displaying high-resolution color images always easy mac however getting details resolution color depth machine running required number tricks additionally common gaming tasks like switching resolutions fading black intricacies required programmer adjust differences color depth ignored drawsprocket library utilities help programmer address common problems among many separate functions calls allow user select main monitor game multi-screen configurations relatively common cleanly enumerating available resolutions switching various routines fading one image another instead black displaying background images various similar utilities major portion drawsprocket provided abstraction layer page flipping macs included ability page flip hardware others drawsprocket provided single api worked machine using hardware available falling back custom-tuned software blitters related code allowed developers easily create multiple framebuffers draw use page flipping calls quickly display mac always shipped input device suitable gaming mouse even cases devices better suited gaming like joysticks relatively easy make devices emulate mouse keyboard input however model stopped working well joysticks increasing complexity released 1990s new models several axes controlled potentiometers linear input cases mouse emulation simply n't work solution inputsprocket inputsprocket allowed hardware vendor provide driver possible input device driver handled communications input device also presented list capabilities inputsprocket manager inputsprocket displayed installed drivers single universal control panel games linking inputsprocket provided list operations wanted user control control panel user could map operation input apple supplied drivers mice keyboards inputsprocket one widely used game sprockets drivers supplied many devices worked mac greatly expanded mapping inputsprocket onto similar human interface device system part usb standard meant almost usb input device would work least level inputsprocket without effort part developer user macintosh sound manager supported digital sound earliest versions stereo much evolution soundsprocket added support including systems simulate 3d sound programmers could add soundsprocket support programs link in-game objects sounds would appear localized space netsprocket provided abstraction layer made easy developers add networking support games netsprocket supported either appletalk tcp/ip supported naming games player providing passwords used client/server architecture included option allow host run networking code without graphics netsprocket also included functionality assign player id teams player types players observers etc netsprocket also provided code message passing although protocol messages left programmer netsprocket one portion game sprockets lived project whole downsized code released open source apple developed new functionality multiple platform support latest versions support mac os windows linux speechsprocket included game sprockets consisted nothing re-badged version existing speech recognition manager like speechsprocket quickdraw 3d rave considered part overall game sprockets technology although developed supported separately rave thin hardware abstraction layer similar directx direct3d
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Operating systems
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tcp fast open computer networking tcp fast open tfo extension speed opening successive transmission control protocol tcp connections two endpoints works using tfo cookie tcp option cryptographic cookie stored client set upon initial connection server client later reconnects sends initial syn packet along tfo cookie data authenticate successful server may start sending data client even reception final ack packet three-way handshake skipping way round-trip delay lowering latency start data transmission cookie generated applying block cipher keyed key held secret server client ip address generating authentication tag difficult third parties spoof even forge source ip address make two-way connections server ip addresses although uses cryptographic techniques generate cookie tfo intended provide security three-way handshake replaces give form cryptographic protection resulting tcp connection provide identity assurance either endpoint also intended resistant man-in-the-middle attacks resistance required may used combination cryptographic protocol tls ipsec tfo proposal originally presented 2011 published rfc 7413 december 2014 tcp fast open shares goal bypassing three-way handshake tcp earlier proposal 1994 called t/tcp rfc 1644 contrast tcp fast open t/tcp paid attention security opening path vulnerabilities failing gain traction tfo implementations include following
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Internet protocols
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payments service payments service paas marketing phrase used describe software service connect group international payment systems architecture represented layer – overlay – resides top disparate systems provides two-way communications payment system paas communication governed standard apis created paas provider since 1980s credit cards international wire transfer systems like society worldwide interbank financial telecommunication swift primary methods making receiving electronic cross-border payments within individual countries payers payees used various electronic systems make payments united states instance federal reserve bank operates automated clearing house ach system eu countries direct debit preferred method facilitating electronic payments advent world wide web became necessary provide alternative payment systems first consumers hesitant use credit cards web due security concerns entrepreneurs tried market electronic wallet early 1994 cybercash allowed consumers make secure purchases internet cybercash eventually failed march 2000 paypal formed became predominant electronic wallet u.s similar regional services include webmoney yandex.money russia alipay china popular countries significant global reach paypal moneybookers skrill became regional electronic wallets providing greater liquidity still provide free flow funds popular electronic wallet solutions paas designed allow merchants market participants utilize local regional global payments options single interface complexity moving funds providers handled paas layer hidden user generally speaking one interface merchant paas one interface required merchants users required maintain one financial repository
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Distributed computing architecture
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beyondcorp beyondcorp implementation google zero-trust computer security concepts creating zero trust network open source implementation inspired googles research paper access proxy transcend
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Computer security
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epoc operating system epoc mobile operating system developed psion british company founded 1980 began 16-bit operating system psion x86-compatible devices later replaced 32-bit system x86 arm psion licensed 32-bit system hardware manufacturers ericsson distinguish 16-bit system 32-bit operating system sometimes epoc32 technologically major departure 16-bit incarnation came called epoc16 sibo 1998 32-bit version renamed symbian os nokia acquired rights symbian 2010 published symbian source code eclipse public license 2011 nokia rescinded open-source license subsequent releases software name epoc comes word epoch beginning era name shortened four letters accord names software innovations unix mach initially operating system capitalised epoc rather 'epoc since acronym change capital letters made recommendation psion marketing department thereafter rumour circulated technical press epoc acronym electronic piece cheese psion started developing 32-bit operating system 1994 kept epoc brand avoid confusion within company started calling old system epoc16 new one epoc32 became conventional within company refer epoc16 sibo codename psion 16-bit mobile computing initiative change freed use name epoc epoc32 june 1998 psion formed limited company telecommunications corporations nokia ericsson motorola buying symbian ltd.—as new company called—the telecommunications corporations acquired stake psion epoc operating system intellectual property symbian ltd. changed name epoc/epoc32 symbian os debuted november 2000 nokia 9210 communicator smartphone epoc developed psion software mobile-device company founded london 1980 company released first pocket computer 1984 8-bit device called psion organiser 1986 released series improved models organiser ii brand 8-bit era ending psion saw need develop 16-bit operating system drive next generation devices first however needed engineer 16-bit single-board computer—something extremely difficult time codenamed project sibo single-board organiser sixteen-bit organiser develop sibo hardware software needed samples 16-bit microprocessors would programming took year secure chips caused significant delay 1987 development epoc underway single-user preemptive multitasking operating system designed run read-only memory rom operating system programmes written intel 8086 assembly language c. operating system started opened pre-installed programmes advance system could switch quickly enable users write run programmes epoc featured updated version organiser programming language opl first published psion organiser opl simple interpreted language unlike basic 1989 psion released first 16-bit computers equipped new operating system mc200 mc400 mc600 notebooks intel 80c86 processor differed specifications memory capacity among later sibo devices psion 3 1991 3a 1993 3c 1996 workabout series well siena 512k model 1996 final epoc device psion series 3mx 1998 user interface differed device notebook computers wimp interface handheld computers smaller screens pointing device accept input keyboard stylus on-screen programmes represented icons smaller devices user could also access via specialised buttons parallel production 16-bit devices psion developing 32-bit version epoc since late 1994 move 32 bits necessary remain competitive psion wanted mobile operating system could license companies meant system would need portable previous efforts 32-bit operating system engineers wrote new object-oriented codebase c++ transition period old system came called epoc16 new one epoc32 epoc16 designed specifically intel 80186 platform epoc32 built arm computing platform reduced instruction set architecture like epoc16 epoc32 single-user pre-emptive multitasking operating system also featured memory protection essential feature modern operating systems psion licensed epoc32 device manufacturers made possible manufacturers change replace system graphical interface licensing arrangement psion considered spinning-off software division psion software psion pdas graphical user interface called eikon visually eikon refinement design choices psion 8- 16-bit devices early iterations epoc32 codenamed protea first published version called release 1 appeared psion series 5 rom v1.0 june 1997 release 2 never published updated rom version 1.1 series 5 featured release 3 series 5 used psion new user interface eikon one first epoc licensees short-lived company called geofox halted production selling fewer 1,000 units another licensee oregon scientific released budget device called osaris epoc device ship release 4 epoc release 5 premiered march 1999 ran armv4 processors strongarm series addition email messaging data synchronisation features introduced support java development kit made capable running wider variety programmes 2000 epoc gui variations replaced three reference interfaces crystal devices small keyboard quartz communicator devices telecommunication features tended equipped thumb keyboard pearl mobile phones classification supported vga graphics psion deployed release 5 5mx series 1999 revo 1999 netbook 1999 series 7 1999 revo plus 2000 netpad 2001 devices ericsson rebranded psion series 5mx mc218 sonicblue rebranded revo diamond mako like original devices rebranded versions released 1999 ericsson r380 smartphone released november 2000 first device distributed epoc release 5.1 release also known er5u u indicated system supported unicode system text encoding important feature representation diverse languages psion developed er5u-enabled device codenamed conan advance beyond prototype stage device intended bluetooth-enabled successor revo june 1998 psion software became symbian ltd. major joint venture psion phone manufacturers ericsson motorola nokia next release epoc32 release 6 rebranded symbian os decoupled user interface underlying operating system afforded device manufacturers ability burden implementing graphical interface devices final version symbian os released v10.1 final update published 2012
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Operating systems
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securityscorecard securityscorecard information security company rates cybersecurity postures corporate entities scored analysis cyber threat intelligence signals purposes third party management risk management company based new york city new york united states rated cyber security exposures 1,000,000 global companies across 17 categorized industries securityscorecard founded 2013 ceo aleksandr yampolskiy coo sam kassoumeh cro alexander heid joined organization 2014 team guided early stages company 2018 reports indicate company reached size 130 employees january 2017 president donald trump cited securityscorecard report president first public press conference commenting findings annual securityscorecard government cybersecurity report report indicated us government network systems 'the worst level risk compared industries securityscorecard software service platform collects attributes scores overall health enterprise cybersecurity identification exposed vulnerabilities corporate digital assets discovered public internet color-coded letter grades numerical scores calculated based upon identification security vulnerabilities corporate digital assets enterprises scored multiple categories risk web application security network security public availability breached data ip reputation mentions within underground hacker chatter susceptibility social engineering attacks platform used companies satisfy continuous monitoring compliance requirements related digital supply chains well enforcement grc standards securityscorecard used following markets financial services cyber insurance hospitality e-commerce energy public sector retail telecommunications cloud service providers software service providers securityscorecard received financing rounds sequoia capital gv nokia intel moody ngp capital riverwood capital
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Computer security
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operation reduction low power operation reduction low power asic program transformation technique used reduce power consumed specific application program transformation operation changes computational structure nature type computational models interconnections sequencing operations keeping input output behavior intact basically use operation reduction reduce number operations done perform task reduces hardware required turn power consumption example given application specific ic reducing number independent additions required automatically reduces adders required also power consumed operation substitution one operation reduction techniques certain costly operations substituted relatively cheaper operations reduce power consumption typical examples operation substitution techniques given follows popular example operation substitution butterfly example example need compute two values x x x x done sequentially computing terms shown expressions using operation substitution compute using expressions a* x+x x a+a a* x+x x a-a term x+x computed used computations easily workout operations changed number operations changed 4 multiplications 3 2 add/sub 3 critical path first method length 2 latter 3 trade-off delay power based frequency input changing model program less activity switching happens i.e certain inputs less frequently changing made operating single module particular module relatively passive compared others a+b+c+d computed a+b +c+d a+b c+d first one feeds c 2 separate adders relatively slow changing feeding adder profitable synthesis 3 parts allocation number type resources scheduling operation scheduling binding building circuit schedule operations particular order based value program activates many modules always want operations requiring operations completed hand scheduled later consider following code snippet c 0 let us assume profiling shown likely value c 2 therefore c independent mutually exclusive modify code c 2 « 1 else c 0 multiplication replaced shifting operation triggered cases far cheaper multiplication
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Programming language topics
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reflection attack computer security reflection attack method attacking challenge-response authentication system uses protocol directions challenge-response protocol used side authenticate side essential idea attack trick target providing answer challenge general attack outline follows authentication protocol carefully designed target accept response valid thereby leaving attacker one fully authenticated channel connection one simply abandoned common solutions attack described
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Computer security
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xbase++ xbase++ object oriented programming language multiple inheritance polymorphism based xbase language dialect conventions 100 clipper compatible language supporting multiple inheritance polymorphism object oriented programming supports xbase data types including codeblocks xbase++ possible generate applications windows nt 95 98 2000 xp vista windows 7 xbase++ supports old commands say/get define data entry forms well graphic editor create data entry forms similar visual foxpro also visual development environment support oem files dos format ansi windows integrated debugger resource compiler add icons graphics application generate exe dll files xbase++ supports replaceable database drivers rdd provide access multiple database formats clipper databaseengines dbes basic package includes support dbf fox ntx cdx sdf del delimited also supports corba 2.0 visual foxpro 3.0 5.0 database formats access sql servers xbase++ born decision computer associates abandon clipper develop visual objects failure visual objects clipper substitute empowered creation third party libraries creation clipper syntax compilers
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Programming language topics
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startup disk creator startup disk creator usb-creator official tool create live usbs ubuntu live cd iso image tool included default releases ubuntu 8.04 installed ubuntu 8.04 kde frontend released ubuntu 8.10 currently included default kubuntu installations run current version ubuntu distributions enter either usb-creator-gtk usb-creator-kde command line tool available ubuntu gnome 11.04 17.04 also called unity kubuntu kde also windows starting ubuntu 10.10 maverick meerkat accessible inserting live cd cd-rom drive windows running
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Operating systems
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michał zalewski michał zalewski born 19 january 1981 also known user name lcamtuf computer security expert white hat hacker poland former google inc. employee currently vp security engineering snap inc.. prolific vulnerability researcher frequent bugtraq poster since mid-1990s written number programs unix-like operating systems 2005 zalewski wrote silence wire field guide passive reconnaissance indirect attacks computer security book published starch press subsequently translated number languages 2011 zalewski wrote tangled web guide securing modern web applications also published starch press continued research browser security named one 15 influential people security among 100 influential people zalewski one original creators argante virtual open source operating system among projects also created p0f american fuzzy lop
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Computer security
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key management key management refers management cryptographic keys cryptosystem includes dealing generation exchange storage use crypto-shredding destruction replacement keys includes cryptographic protocol design key servers user procedures relevant protocols key management concerns keys user level either users systems contrast key scheduling typically refers internal handling keys within operation cipher successful key management critical security cryptosystem challenging side cryptography sense involves aspects social engineering system policy user training organizational departmental interactions coordination elements contrast pure mathematical practices automated cryptographic systems may use different types keys systems using one may include symmetric keys asymmetric keys symmetric key algorithm keys involved identical encrypting decrypting message keys must chosen carefully distributed stored securely asymmetric keys also known public keys contrast two distinct keys mathematically linked typically used together communicate public key infrastructure pki implementation public key cryptography requires organization establish infrastructure create manage public private key pairs along digital certificates starting point certificate private key management strategy create comprehensive inventory certificates locations responsible parties trivial matter certificates variety sources deployed variety locations different individuals teams simply possible rely list single certificate authority certificates renewed replaced expire cause serious downtime outages considerations keys inventoried key management typically consists three steps exchange storage use prior secured communication users must set details cryptography instances may require exchanging identical keys case symmetric key system others may require possessing party public key public keys openly exchanged corresponding private key kept secret symmetric keys must exchanged secure communication channel formerly exchange key extremely troublesome greatly eased access secure channels diplomatic bag clear text exchange symmetric keys would enable interceptor immediately learn key encrypted data advance public key cryptography 1970s made exchange keys less troublesome since diffie-hellman key exchange protocol published 1975 become possible exchange key insecure communications channel substantially reduced risk key disclosure distribution possible using something akin book code include key indicators clear text attached encrypted message encryption technique used richard sorge code clerk type referring page statistical manual though fact code german army enigma symmetric encryption key mixed type early use key combination secretly distributed key schedules user chosen session key component message modern systems openpgp compatible systems session key symmetric key algorithm distributed encrypted asymmetric key algorithm approach avoids even necessity using key exchange protocol like diffie-hellman key exchange another method key exchange involves encapsulating one key within another typically master key generated exchanged using secure method method usually cumbersome expensive breaking master key multiple parts sending trusted courier example suitable use larger scale master key securely exchanged used securely exchange subsequent keys ease technique usually termed key wrap common technique uses block ciphers cryptographic hash functions related method exchange master key sometimes termed root key derive subsidiary keys needed key data often referred diversification data common use method probably smartcard-based cryptosystems found banking cards bank credit network embeds secret key card secure key storage card production secured production facility point sale card card reader able derive common set session keys based shared secret key card-specific data card serial number method also used keys must related i.e. departmental keys tied divisional keys individual keys tied departmental keys however tying keys way increases damage may result security breach attackers learn something one key reduces entropy regard attacker key involved however distributed keys must stored securely maintain communications security security big concern hence various techniques use likely common encryption application manages keys user depends access password control use key likewise case smartphone keyless access platforms keep identifying door information mobile phones servers encrypt data like low-tech keys users give codes trust major issue length time key used therefore frequency replacement increases attacker required effort keys frequently changed also limits loss information number stored encrypted messages become readable key found decrease frequency key change increases historically symmetric keys used long periods situations key exchange difficult possible intermittently ideally symmetric key change message interaction message become readable key learned e.g stolen cryptanalyzed social engineered several challenges organizations face trying control manage encryption keys key management compliance refers oversight assurance capability able demonstrate keys securely managed includes following individual compliance domains compliance achieved respect national international data protection standards regulations payment card industry data security standard health insurance portability accountability act sarbanes–oxley act general data protection regulation key management system kms also known cryptographic key management system ckms integrated approach generating distributing managing cryptographic keys devices applications may cover aspects security secure generation keys secure exchange keys secure key handling storage client thus kms includes backend functionality key generation distribution replacement well client functionality injecting keys storing managing keys devices many specific applications developed key management systems home grown protocols however systems become interconnected keys need shared different systems facilitate key management standards evolved define protocols used manage exchange cryptographic keys related information kmip extensible key management protocol developed many organizations working within oasis standards body first version released 2010 developed active technical committee protocol allows creation keys distribution among disparate software systems need utilize covers full key life cycle symmetric asymmetric keys variety formats wrapping keys provisioning schemes cryptographic operations well meta data associated keys protocol backed extensive series test cases interoperability testing performed compliant systems year list 80 products conform kmip standard found oasis website security policy key management system provides rules used protect keys metadata key management system supports defined national institute standards technology nist policy shall establish specify rules information protect protection covers complete key life-cycle time key becomes operational elimination bring encryption byoe —also called bring key byok —refers cloud-computing security model allow public-cloud customers use encryption software manage encryption keys security model usually considered marketing stunt critical keys handed third parties cloud providers key owners still left operational burden generating rotating sharing keys public-key infrastructure type key management system uses hierarchical digital certificates provide authentication public keys provide encryption pkis used world wide web traffic commonly form ssl tls group key management means managing keys group communication group communications use multicast communication message sent sender received users main problem multicast group communication security order improve security various keys given users using keys users encrypt messages send secretly ietf.org released rfc 4046 entitled multicast security msec group key management architecture discusses challenges group key management q* ieee security storage working group siswg creating p1619.3 standard key management
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Computer security
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disk operating system disk operating system abbreviated dos computer operating system use disk storage device floppy disk hard disk drive optical disc disk operating system must provide file system organizing reading writing files storage disk strictly speaking definition apply current generations operating systems versions microsoft windows use appropriately used older generations operating systems disk operating systems available mainframes microprocessors home computers usually loaded disks part boot process early days computers disk drives floppy disks modern flash storage devices early storage devices delay lines punched cards paper tape magnetic tape magnetic drums used instead early days microcomputers home computers paper tape audio cassette tape see kansas city standard nothing used instead latter case program data entry done front panel switches directly memory computer terminal keyboard sometimes controlled basic interpreter rom power turned information lost hard disks floppy disk drives require software manage rapid access block storage sequential data microcomputers disk drive kind optional peripheral systems could used tape drive booted without storage device disk operating system component operating system needed disk drive used dos concept began dos/360 1966 ibm system/360 mainframes home personal computers late 1970s 1980s used disk operating system often dos name simply referred dos within respective communities cbm dos commodore 8-bit systems atari dos atari 8-bit family trs-dos trs-80 apple dos apple ii ms-dos ibm pc compatibles usually disk operating system loaded disk among exceptions commodore whose dos resided rom chips disk drives lt. kernal hard disk subsystem commodore 64 commodore 128 models stored dos disk case modern systems loaded dos ram boot time british bbc micro optional disc filing system dfs offered kit disk controller chip rom chip handful logic chips installed inside computer disk operating systems operating system entire computer system
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Operating systems
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h-tcp h-tcp another implementation tcp optimized congestion control algorithm high speed networks high latency lfn long fat networks created researchers hamilton institute ireland h-tcp optional module recent linux 2.6 kernels implemented freebsd 7 h-tcp loss-based algorithm using additive-increase/multiplicative-decrease aimd control tcp congestion window one many tcp congestion avoidance algorithms seeks increase aggressiveness tcp high bandwidth-delay product bdp paths maintaining tcp friendliness small bdp paths h-tcp increases aggressiveness particular rate additive increase time since previous loss increases avoids problem encountered hstcp bic tcp making flows aggressive windows already large thus new flows expected converge fairness faster htcp hstcp bic tcp side effect increasing rate increase time since last packet loss increases flows happen lose packet flows take unfair portion bandwidth techniques overcome currently research phase linux implementation h-tcp also option avoiding rtt unfairness occurs tcp reno particular problem high speed variants tcp although fast tcp algorithm initially introduced h-tcp without mention h stands however often called hamilton tcp hamilton institute created
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Internet protocols
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amd app sdk amd app sdk software development kit amd accelerated parallel processing app amd app sdk also targets heterogeneous system architecture gpu amd app sdk available 32-bit 64-bit versions microsoft windows linux removed amd official website developer stated forum post sdk discontinued required libraries included drivers amd intends developers employ amd app sdk utilize video coding engine hybrid mode create hybrid encoders pair custom motion estimation inverse discrete cosine transform motion compensation hardware entropy encoding achieve faster real-time encoding app sdk 3.0 supports opencl™ 2.0 catalyst omega 15.7 driver amd app sdk v3.0 beta includes samples opencl™ well accelerated libraries bolt open-source c++ template library opencl™ accelerated opencv open computer vision library amd app sdk replaced amd stream sdk formerly named ati stream sdk amd cal compute abstraction layer sdk replaced ati stream sdk available microsoft windows linux 32-bit 64-bit
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Computer architecture
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identifier identifier name identifies labels identity either unique object unique class objects object class may idea physical countable object class thereof physical noncountable substance class thereof abbreviation id often refers identity identification process identifying identifier instance identification identifier may word number letter symbol combination words numbers letters symbols may follow encoding system wherein letters digits words symbols stand represent ideas longer names may simply arbitrary identifier follows encoding system often referred code id code instance iso/iec 11179 metadata registry standard defines code system valid symbols substitute longer values contrast identifiers without symbolic meaning identifiers follow encoding scheme often said arbitrary ids arbitrarily assigned greater meaning sometimes identifiers called codes even actually arbitrary whether speaker believes deeper meaning simply speaking casually imprecisely unique identifier uid identifier refers one instance —only one particular object universe part number identifier unique identifier—for serial number needed identify instance part design thus identifier model identifies class model automobiles ford model comprises whereas unique identifier model serial number 159,862 identifies one specific member class—that one particular model car owned one specific person concepts name identifier denotatively equal terms thus denotatively synonymous always connotatively synonymous code names id numbers often connotatively distinguished names sense traditional natural language naming example jamie zawinski netscape employee number 20 identifiers specific human normal english-language connotation may consider jamie zawinski name identifier whereas considers netscape employee number 20 identifier name emic indistinction rather etic one metadata identifier language-independent label sign token uniquely identifies object within identification scheme suffix identifier also used representation term naming data element id codes may inherently carry metadata along example know food package front identifier 42z-mfr5-p02-243-45 data also metadata tells packaged september 25 2011 3:42pm utc manufactured licensed vendor number 5 peoria il usa plant building 2 243rd package line shift inspected inspector number 45 arbitrary identifiers might lack metadata example food package says 100054678214 id may tell anything except identity—no date manufacturer name production sequence rank inspector number cases arbitrary identifiers sequential serial numbers leak information i.e german tank problem opaque identifiers—identifiers designed avoid leaking even small amount information—include really opaque pointers version 4 uuids computer science identifiers ids lexical tokens name entities identifiers used extensively virtually information processing systems identifying entities makes possible refer essential kind symbolic processing computer languages identifiers tokens also called symbols name language entities kinds entities identifier might denote include variables types labels subroutines packages character sequences constitute identifiers depends lexical grammar language common rule alphanumeric sequences underscore also allowed condition begin digit simplify lexing avoiding confusing integer literals – codice_1 allowed codice_2 – definition used earlier versions c c++ python many languages later versions languages along many modern languages support almost unicode characters identifier however common restriction permit whitespace characters language operators simplifies tokenization making free-form context-free example forbidding codice_3 identifiers due use binary operation means codice_4 codice_5 tokenized allowed codice_4 would identifier addition whitespace identifier particularly problematic spaces allowed identifiers clause codice_7 legal codice_8 identifier tokenizing requires phrasal context condition clause languages allow spaces identifiers however algol 68 algol variants – example following valid statement codice_9 could entered codice_10 keywords represented boldface concretely via stropping algol possible keywords syntactically differentiated risk collision ambiguity spaces eliminated line reconstruction phase source processed via scannerless parsing lexing could context-sensitive languages character sequences lexical form identifier known keywords – example codice_11 frequently keyword clause lexically form codice_12 codice_13 namely sequence letters overlap handled various ways may forbidden identifiers – simplifies tokenization parsing – case reserved words may allowed distinguished ways via stropping keyword sequences may allowed identifiers sense determined context requires context-sensitive lexer non-keywords may also reserved words forbidden identifiers particularly forward compatibility case word may become keyword future languages e.g. pl/1 distinction clear scope accessibility within program identifier either local global global identifier declared outside functions available throughout program local identifier declared within specific function available within function implementations programming languages using compiler identifiers often compile time entities runtime compiled program contains references memory addresses offsets rather textual identifier tokens memory addresses offsets assigned compiler identifier languages support reflection interactive evaluation source code using interpreter incremental compiler identifiers also runtime entities sometimes even first-class objects freely manipulated evaluated lisp called symbols compilers interpreters usually assign semantic meaning identifier based actual character sequence used however exceptions example languages go identifiers uniqueness based spelling visibility html identifier one possible attributes html element unique within document many resources may carry multiple identifiers typical examples inverse also possible multiple resources represented identifier discussed many codes nomenclatural systems originate within small namespace years bleed larger namespaces people interact ways formerly n't e.g. cross-border trade scientific collaboration military alliance general cultural interconnection assimilation dissemination happens limitations original naming convention formerly latent moot become painfully apparent often necessitating retronymy synonymity translation/transcoding limitations generally accompany shift away original context broader one typically system shows implicit context context formerly assumed narrow lack capacity e.g. low number possible ids reflecting outmoded narrow context lack extensibility features defined reserved future needs lack specificity disambiguating capability related context shift longstanding uniqueness encounters novel nonuniqueness within computer science problem called naming collision story origination expansion coden system provides good case example recent-decades technical-nomenclature context capitalization variations seen specific designators reveals instance problem occurring natural languages proper noun/common noun distinction complications must dealt universe every object uid would need namespaces say would constitute one gigantic namespace human minds could never keep track semantically interrelate many uids
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Programming language topics
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fermi microarchitecture fermi codename gpu microarchitecture developed nvidia first released retail april 2010 successor tesla microarchitecture primary microarchitecture used geforce 400 series geforce 500 series followed kepler used alongside kepler geforce 600 series geforce 700 series geforce 800 series latter two mobile gpus workstation market fermi found use quadro x000 series quadro nvs models well nvidia tesla computing modules desktop fermi gpus manufactured 40 nm mobile fermi gpus 40 nm 28 nm fermi oldest microarchitecture nvidia received support microsoft rendering api direct3d 12 feature_level 11 architecture named enrico fermi italian physicist fermi graphic processing units gpus feature 3.0 billion transistors schematic sketched fig 1 sm features 32 single-precision cuda cores 16 load/store units four special function units sfus 64kb block high speed on-chip memory see l1+shared memory subsection interface l2 cache see l2 cache subsection load/store units allow source destination addresses calculated 16 threads per clock load store data from/to cache dram special functions units sfus execute transcendental instructions sin cosine reciprocal square root sfu executes one instruction per thread per clock warp executes eight clocks sfu pipeline decoupled dispatch unit allowing dispatch unit issue execution units sfu occupied integer arithmetic logic unit alu supports full 32-bit precision instructions consistent standard programming language requirements also optimized efficiently support 64-bit extended precision operations floating point unit fpu implements new ieee 754-2008 floating-point standard providing fused multiply-add fma instruction see fused multiply-add subsection single double precision arithmetic 16 double precision fused multiply-add operations performed per sm per clock fused multiply-add fma perform multiplication addition i.e. a*b+c single final rounding step loss precision addition fma accurate performing operations separately fermi architecture uses two-level distributed thread scheduler sm issue instructions consuming two four green execution columns shown schematic fig 1 example sm mix 16 operations 16 first column cores 16 operations 16 second column cores 16 operations load/store units four sfus combinations program specifies note 64-bit floating point operations consumes first two execution columns implies sm issue 32 single-precision 32-bit floating point operations 16 double-precision 64-bit floating point operations time gigathread engine gigathread engine schedules thread blocks various sms dual warp scheduler sm level warp scheduler distributes warps 32 threads execution units threads scheduled groups 32 threads called warps sm features two warp schedulers two instruction dispatch units allowing two warps issued executed concurrently dual warp scheduler selects two warps issues one instruction warp group 16 cores 16 load/store units 4 sfus instructions dual issued two integer instructions two floating instructions mix integer floating point load store sfu instructions issued concurrently double precision instructions support dual dispatch operation theoretical single-precision processing power fermi gpu gflops computed 2 operations per fma instruction per cuda core per cycle × number cuda cores × shader clock speed ghz note previous generation tesla could dual-issue mad+mul cuda cores sfus parallel fermi lost ability issue 32 instructions per cycle per sm keeps 32 cuda cores fully utilized therefore possible leverage sfus reach 2 operations per cuda core per cycle theoretical double-precision processing power fermi gpu 1/2 single precision performance gf100/110 however practice double-precision power available professional quadro tesla cards consumer geforce cards capped 1/8 l1 cache per sm unified l2 cache services operations load store texture registers sm 32k 32-bit registers thread access registers threads maximum number registers used cuda kernel 63 number available registers degrades gracefully 63 21 workload hence resource requirements increases number threads registers high bandwidth 8,000 gb/s l1+shared memory on-chip memory used either cache data individual threads register spilling/l1 cache and/or share data among several threads shared memory 64 kb memory configured either 48 kb shared memory 16 kb l1 cache 16 kb shared memory 48 kb l1 cache shared memory enables threads within thread block cooperate facilitates extensive reuse on-chip data greatly reduces off-chip traffic shared memory accessible threads thread block provides low-latency access 10-20 cycles high bandwidth 1,600 gb/s moderate amounts data intermediate results series calculations one row column data matrix operations line video etc. david patterson says shared memory uses idea local scratchpad local memory local memory meant memory location used hold spilled registers register spilling occurs thread block requires register storage available sm local memory used automatic variables declared device code without nowiki __device__ __shared__ __constant__ /nowiki qualifiers generally automatic variable resides register except following 1 arrays compiler determine indexed constant quantities 2 large structures arrays would consume much register space variable compiler decides spill local memory kernel uses registers available sm l2 cache 768 kb unified l2 cache shared among 16 sms services load store from/to global memory including copies to/from cpu host also texture requests l2 cache subsystem also implements atomic operations used managing access data must shared across thread blocks even kernels global memory accessible threads well host cpu high latency 400-800 cycles see nvidia nvdec formerly called nvcuvid well nvidia purevideo nvidia nvenc
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Computer architecture
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john hughes computer scientist r. john m. hughes born swedish computer scientist professor department computing science chalmers university technology 1984 hughes received phd university oxford thesis design implementation programming languages hughes member functional programming group chalmers much research relates haskell programming language research field programming languages author many influential research papers subject including functional programming matters hughes one developers quickcheck well cofounder ceo quviq provides quickcheck software offers classes use 2016 appeared popular science youtube channel computerphile explaining functional programming quickcheck hughes elected acm fellow 2018 contributions software testing functional programming
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Programming language topics
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on-line encyclopedia integer sequences on-line encyclopedia integer sequences oeis also cited simply sloane online database integer sequences created maintained neil sloane researcher labs foreseeing retirement labs 2012 need independent foundation sloane agreed transfer intellectual property hosting oeis oeis foundation october 2009 sloane president oeis foundation oeis records information integer sequences interest professional amateur mathematicians widely cited contains 320,000 sequences making largest database kind entry contains leading terms sequence keywords mathematical motivations literature links including option generate graph play musical representation sequence database searchable keyword subsequence neil sloane started collecting integer sequences graduate student 1965 support work combinatorics database first stored punched cards published selections database book form twice books well received especially second publication mathematicians supplied sloane steady flow new sequences collection became unmanageable book form database reached 16,000 entries sloane decided go online—first e-mail service august 1994 soon web site 1996 spin-off database work sloane founded journal integer sequences 1998 database continues grow rate 10,000 entries year sloane personally managed 'his sequences almost 40 years starting 2002 board associate editors volunteers helped maintain database 2004 sloane celebrated addition 100,000th sequence database counts marks ishango bone 2006 user interface overhauled advanced search capabilities added 2010 oeis wiki oeis.org created simplify collaboration oeis editors contributors 200,000th sequence added database november 2011 initially entered a200715 moved a200000 week discussion seqfan mailing list following proposal oeis editor-in-chief charles greathouse choose special sequence a200000 besides integer sequences oeis also catalogs sequences fractions digits transcendental numbers complex numbers transforming integer sequences sequences rationals represented two sequences named keyword 'frac sequence numerators sequence denominators example fifth-order farey sequence formula_1 catalogued numerator sequence 1 1 1 2 1 3 2 3 4 denominator sequence 5 4 3 5 2 5 3 4 5 important irrational numbers π 3.1415926535897 ... catalogued representative integer sequences decimal expansions 3 1 4 1 5 9 2 6 5 3 5 8 9 7 9 3 2 3 8 4 6 2 6 4 3 3 8 3 2 7 9 5 0 2 8 8 ... binary expansions 1 1 0 0 1 0 0 1 0 0 0 0 1 1 1 1 1 1 0 1 1 0 1 0 ... continued fraction expansions 3 7 15 1 292 1 1 1 2 1 3 1 14 2 1 1 2 2 2 2 1 84 2 1 1 ... oeis limited plain ascii text 2011 still uses linear form conventional mathematical notation f n functions n running variables etc. greek letters usually represented full names e.g mu μ phi φ every sequence identified letter followed six digits almost always referred leading zeros e.g a000315 rather a315 individual terms sequences separated commas digit groups separated commas periods spaces comments formulas etc. n represents n th term sequence zero often used represent non-existent sequence elements example enumerates smallest prime n ² consecutive primes form n × n magic square least magic constant 0 magic square exists value 1 1×1 magic square 2 3 1480028129 2×2 magic square 2 0 special usage solid mathematical basis certain counting functions example totient valence function n counts solutions φ x 4 solutions 4 solutions 14 hence 14 a014197 0—there solutions occasionally −1 used purpose instead oeis maintains lexicographical order sequences sequence predecessor successor context oeis normalizes sequences lexicographical ordering usually ignoring initial zeros ones also sign element sequences weight distribution codes often omit periodically recurring zeros example consider prime numbers palindromic primes fibonacci sequence lazy caterer sequence coefficients series expansion formula_2 oeis lexicographic order whereas unnormalized lexicographic ordering would order sequences thus 3 5 4 1 2 early history oeis sequences defined terms numbering sequences oeis proposed resisted adding sequences long time partly desire maintain dignity database partly a22 known 11 terms sloane reminisced one earliest self-referential sequences sloane accepted oeis later n n -th term sequence -1 fewer n terms sequence spurred progress finding terms line thought leads question sequence contain number n sequences numbers n oeis sequence contains n n sequence n sequence thus composite number 2808 a053873 sequence composite numbers non-prime 40 a053169 prime numbers n member exactly one two sequences principle determined sequence n belongs two exceptions related two sequences entry chosen contains every field oeis entry 2009 oeis database used philippe guglielmetti measure importance integer number result shown plot right shows clear gap two distinct point clouds uninteresting numbers blue dots interesting numbers occur comparatively often sequences oeis contains essentially prime numbers red numbers form green highly composite numbers yellow phenomenon studied nicolas gauvrit jean-paul delahaye hector zenil explained speed two clouds terms algorithmic complexity gap social factors based artificial preference sequences primes even numbers geometric fibonacci-type sequences sloane gap featured numberphile video 2013
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Databases
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box backup box backup open-source completely automatic online backup system client software sends backup data server data encrypted using secure sockets layer ssl protocol also protected layer on-disk encryption box backup supports linux unix windows mac os x backup clients servers although windows servers recommended authors box backup licensed gnu gpl bsd licenses box backup client-server application client sends data server storage server provides management client via certificates storage quotas data retention together unique robust solution created scales allowing clients low-bandwidth connections effectively perform reliable backups box backup ideal backing laptops computers intermittent low-bandwidth connections capable continuous data protection background starting automatically internet connection present recovering gracefully efficiently connection failures box backup uses modified version rsync algorithm works encrypted blocks allows store data server form server operator read still uploading changed portions data files
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Computer security
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feature connector feature connector internal connector found mostly older isa vesa local bus pci graphics cards also early agp ones intended use devices needed exchange large amounts data graphics card without hogging computer system cpu data bus tv tuner cards video capture cards mpeg video decoders e.g realmagic first generation 3d graphic accelerator cards early examples include ibm ega video adapter several standards existed feature connectors depending bus graphics card type simply 8 16 32-bit wide internal connector transferring data graphics card another device bypassing system cpu memory completely speeds often far exceeded speed normal isa even early pci buses e.g 40 mbyte/s standard isa-based svga 150 mbyte/s vesa-based pci-based one standard 16 bit isa bus ran ~5.3 mbyte/s vesa bus 160 mbyte/s bandwidth feature connector bandwidths far beyond capabilities e.g 386 486 barely handled early pentium depending implementation could uni bi-directional carry analog color information well data unlike analog overlay devices however feature connector carried mainly data essentially allowed expansion card access graphics card video ram directly although directing data stream system cpu ram always possible limiting usefulness mainly display purposes although use rapidly declined introduction faster agp internal bus time feasible way connect certain types graphics-intensive devices average computing system without exceeding available cpu power memory bandwidth without disadvantages limitations purely analog overlay idea accessing video card memory directly resurfaced introduction scalable link interface sli technology although technology aimed connecting two equally powered complete graphic cards produce single increased performance visual output e.g directly interfacing tv tuner cards
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Computer architecture
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dos mz executable dos mz executable format executable file format used .exe files dos file identified ascii string mz hexadecimal 4d 5a beginning file magic number mz initials mark zbikowski one leading developers ms-dos mz dos executable file newer com executable format differs dos executable header contains relocation information allows multiple segments loaded arbitrary memory addresses supports executables larger 64k however format still requires relatively low memory limits limits later bypassed using dos extenders environment exe program run dos found program segment prefix exe files normally separate segments code data stack program execution begins address 0 code segment stack pointer register set whatever value contained header information thus header specifies 512 byte stack stack pointer set 200h possible use separate stack segment simply use code segment stack desired ds data segment register normally contains value cs code segment register loaded actual segment address data segment exe file initialized necessary programmer set generally done via following instructions original dos 1.x api also necessary ds register pointing segment psp program termination done via following instructions program termination would performed retf instruction would retrieve original segment address psp stack jump address 0 contained int 20h instruction dos 2.x api introduced new program termination function int 21h function 4ch require saving psp segment address start program microsoft advised use older dos 1.x method mz dos executables run dos windows 9x-based operating systems 32-bit windows nt-based operating systems execute using built-in virtual dos machine although graphics modes unsupported 64-bit versions windows execute alternative ways run executables include dosbox dosemu wine cygwin mz dos executables created linkers like digital mars optlink ms linker valx open watcom wlink additionally fasm create directly
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Operating systems
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directx microsoft directx collection application programming interfaces apis handling tasks related multimedia especially game programming video microsoft platforms originally names apis began direct direct3d directdraw directmusic directplay directsound forth name directx coined shorthand term apis x standing particular api names soon became name collection microsoft later set develop gaming console x used basis name xbox indicate console based directx technology x initial carried forward naming apis designed xbox xinput cross-platform audio creation tool xact directx pattern continued windows apis direct2d directwrite direct3d 3d graphics api within directx widely used development video games microsoft windows xbox line consoles direct3d also used software applications visualization graphics tasks cad/cam engineering direct3d widely publicized component directx common see names directx direct3d used interchangeably directx software development kit sdk consists runtime libraries redistributable binary form along accompanying documentation headers use coding originally runtimes installed games explicitly user windows 95 launch directx directx included windows 95 oem service release 2 windows 98 windows nt 4.0 shipped directx every version windows released since sdk available free download runtimes proprietary closed-source software source code provided sdk samples starting release windows 8 developer preview directx sdk integrated windows sdk late 1994 microsoft ready release windows 95 next operating system important factor value consumers would place programs would able run three microsoft employees—craig eisler alex st. john eric engstrom—were concerned programmers tended see microsoft previous operating system ms-dos better platform game programming meaning games would developed windows 95 operating system would much success compounded negative reception surrounding windows port video game lion king game used wing crashed compaq presarios came shipped following partnership compaq disney cirrus logic display drivers used presarios thoroughly tested api dos allowed direct access video cards keyboards mice sound devices parts system windows 95—with protected memory model—restricted access working much standardized model microsoft needed quick solution programmers operating system months away released eisler development lead st. john engstrom program manager worked together fix problem solution eventually named directx first version directx released september 1995 windows games sdk win32 replacement dci wing apis windows 3.1 directx allowed versions microsoft windows starting windows 95 incorporate high-performance multimedia eisler wrote frenzy build directx 1 5 blog directx 2.0 became component windows releases windows 95 osr2 windows nt 4.0 mid-1996 since windows 95 still new games released microsoft engaged heavy promotion directx developers generally distrustful microsoft ability build gaming platform windows alex st. john evangelist directx staged elaborate event 1996 computer game developers conference game developer jay barnson described roman theme including real lions togas something resembling indoor carnival event microsoft first introduced direct3d directplay demonstrated multiplayer mechwarrior 2 played internet directx team faced challenging task testing directx release array computer hardware software variety different graphics cards audio cards motherboards cpus input devices games multimedia applications tested beta final release directx team also built distributed tests allowed hardware industry confirm new hardware designs driver releases would compatible directx prior directx microsoft included opengl windows nt platform time opengl required high-end hardware focused engineering cad uses direct3d intended microsoft controlled alternative opengl focused initially game use 3d gaming grew opengl developed include better support programming techniques interactive multimedia applications like games giving developers choice using opengl direct3d 3d graphics api applications point battle began supporters cross-platform opengl windows-only direct3d incidentally opengl supported microsoft directx team developer chose use opengl 3d graphics api apis directx often combined opengl computer games opengl include directx functionality sound joystick support console-specific version directx used basis microsoft xbox xbox 360 xbox one console api api developed jointly microsoft nvidia developed custom graphics hardware used original xbox xbox api similar directx version 8.1 non-updateable like console technologies xbox code named directxbox shortened xbox commercial name 2002 microsoft released directx 9 support use much longer shader programs pixel vertex shader version 2.0 microsoft continued update directx suite since introducing shader model 3.0 directx 9.0c released august 2004 april 2005 directshow removed directx moved microsoft platform sdk instead directx confirmed present microsoft windows phone 8 real-time raytracing announced dxr 2018 original logo resembled deformed radiation warning symbol controversially original name directx project manhattan project reference us nuclear weapons initiative alex st. john head microsoft directx evangelism time claims connotation ultimate outcome manhattan project nuclear bombing japan intentional directx sister project xbox shares similar logo meant displace japanese videogame-makers dominance video-game industry however microsoft publicly denies account instead claiming logo merely artistic design directx composed multiple apis microsoft deprecated still supports directx components directx functionality provided form com-style objects interfaces additionally directx components managed objects built top parts directx managed direct3d xna graphics library top direct3d 9 directx 9 released 2002 windows 98 xp currently supported subsequent versions microsoft continues make changes directx 9c causing support dropped aforementioned operating systems january 2007 windows 2000 xp required also introduced shader model 2.0 containing pixel shader 2.0 vertex shader 2.0 major update directx api directx 10 ships available windows vista later previous versions windows windows xp able run directx 10-exclusive applications rather programs run windows xp system directx 10 hardware simply resort directx 9.0c code path latest available windows xp computers changes directx 10 extensive many former parts directx api deprecated latest directx sdk preserved compatibility directinput deprecated favor xinput directsound deprecated favor cross-platform audio creation tool system xact additionally lost support hardware accelerated audio since vista audio stack renders sound software cpu directplay dplay.dll also removed replaced dplayx.dll games rely dll must duplicate rename dplay.dll order achieve backwards compatibility directx windows vista contains several versions direct3d direct3d 10.1 incremental update direct3d 10.0 shipped required windows vista service pack 1 release mainly sets image quality standards graphics vendors giving developers control image quality also adds support cube map arrays separate blend modes per-mrt coverage mask export pixel shader ability run pixel shader per sample access multi-sampled depth buffers requires video card supports shader model 4.1 higher 32-bit floating-point operations direct3d 10.1 still fully supports direct3d 10 hardware order utilize new features updated hardware required microsoft unveiled directx 11 gamefest 08 event seattle major scheduled features including gpgpu support directcompute direct3d 11 tessellation support improved multi-threading support assist video game developers developing games better utilize multi-core processors direct3d 11 runs windows vista windows 7 windows 8 windows 10 parts new api multi-threaded resource handling supported direct3d 9/10/10.1-class hardware hardware tessellation shader model 5.0 require direct3d 11 supporting hardware microsoft since released direct3d 11 technical preview direct3d 11 strict superset direct3d 10.1 — hardware api features version 10.1 retained new features added necessary exposing new functionality helps keep backwards compatibility previous versions directx microsoft released final platform update windows vista october 27 2009 5 days initial release windows 7 launched direct3d 11 base standard since four updates directx 11 released directx 12 announced microsoft gdc march 20 2014 officially launched alongside windows 10 july 29 2015 primary feature highlight new release directx introduction advanced low-level programming apis direct3d 12 reduce driver overhead developers able implement command lists buffers gpu allowing efficient resource utilization parallel computation lead developer max mcmullen stated main goal direct3d 12 achieve console-level efficiency phone tablet pc release direct3d 12 comes alongside initiatives low-overhead graphics apis including amd mantle amd graphics cards apple metal ios macos khronos group cross-platform vulkan multiadapter support feature directx 12 allowing developers utilize multiple gpus system simultaneously multi-gpu support previously dependent vendor implementations amd crossfirex nvidia sli directx 12 supported fermi later nvidia gpus amd gcn-based chips intel haswell later processors graphics units siggraph 2014 intel released demo showing computer generated asteroid field directx 12 claimed 50–70 efficient directx 11 rendering speed cpu power consumption ashes singularity first publicly available game utilize directx 12 testing ars technica august 2015 revealed slight performance regressions directx 12 directx 11 mode nvidia geforce 980 ti whereas amd radeon r9 290x achieved consistent performance improvements 70 directx 12 scenarios amd outperformed powerful nvidia directx 12 performance discrepancies may due poor nvidia driver optimizations directx 12 even hardware limitations card optimized directx 11 serial execution however exact cause remains unclear directx 12 apis also featured xbox however directx 12 code directly portable pc xbox one due inherent differences two platforms performance improvements directx 12 xbox substantial pc march 2018 directx raytracing dxr announced capable real-time ray-tracing supported hardware dxr api added windows 10 october 2018 update 2019 microsoft announced arrival directx 12 windows 7 version number reported microsoft dxdiag tool version 4.09.0000.0900 higher use x.xx.xxxx.xxxx format version numbers however directx windows xp msdn page claims registry always x.xx.xx.xxxx format put another way table lists version 4.09.00.0904 microsoft dxdiag tool may 4.09.0000.0904 various releases windows included supported various versions directx allowing newer versions operating system continue running applications designed earlier versions directx versions gradually phased favor newer apis drivers hardware apis direct3d directsound need interact hardware device driver hardware manufacturers write drivers particular directx version device driver interface ddi test individual piece hardware make directx compatible hardware devices directx compatible drivers words one must install directx order use hardware early versions directx included up-to-date library directx compatible drivers currently available practice stopped however favor web-based windows update driver-update system allowed users download drivers relevant hardware rather entire library prior directx 10 directx runtime designed backward compatible older drivers meaning newer versions apis designed interoperate older drivers written previous version ddi application programmer query available hardware capabilities using complex system cap bits tied particular hardware feature direct3d 7 earlier would work version ddi direct3d 8 requires minimum ddi level 6 direct3d 9 requires minimum ddi level 7 however direct3d 10 runtime windows vista run older hardware drivers due significantly updated ddi requires unified feature set abandons use cap bits direct3d 10.1 introduces feature levels 10_0 10_1 allow use hardware features defined specified version direct3d api direct3d 11 adds level 11_0 10 level 9 subset direct3d 10 api designed run direct3d 9 hardware three feature levels 9_1 9_2 9_3 grouped common capabilities low med high-end video cards runtime directly uses direct3d 9 ddi provided wddm drivers feature level 11_1 introduced direct3d 11.1 2002 microsoft released version directx compatible microsoft .net framework thus allowing programmers take advantage directx functionality within .net applications using compatible languages managed c++ use c programming language api known managed directx mdx short claimed operate 98 performance underlying native directx apis december 2005 february 2006 april 2006 august 2006 microsoft released successive updates library culminating beta version called managed directx 2.0 managed directx 2.0 consolidated functionality previously scattered multiple assemblies single assembly thus simplifying dependencies software developers development version subsequently discontinued longer supported managed directx 2.0 library expired october 5 2006 gdc 2006 microsoft presented xna framework new managed version directx similar identical managed directx intended assist development games making easier integrate directx high-level shader language hlsl tools one package also supports execution managed code xbox 360 xna game studio express rtm made available december 11 2006 free download windows xp unlike directx runtime managed directx xna framework xbox 360 apis xinput xact etc shipped part windows developers expected redistribute runtime components along games applications microsoft product including latest xna releases provides directx 10 support .net framework approach directx managed languages use third-party libraries like alternatives directx family apis opengl successor vulkan metal mantle features comparable direct3d examples apis include sdl allegro openmax openml openal opencl fmod sfml etc many libraries cross-platform open codebases also alternative implementations aim provide api one wine furthermore developers reactos trying reimplement directx name reactx
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Operating systems
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veeam backup amp replication veeam backup replication proprietary backup app developed veeam virtual environments built vmware vsphere microsoft hyper-v hypervisors software provides backup restore replication functionality virtual machines physical servers workstations well cloud-based workload veeam backup replication operates virtualization layer well manages physical machine backup backs vms image-level using hypervisor ’ snapshots retrieve vm data backups full full copy vm image incremental saving changed blocks data since last backup job run backup increments created using built-in changed block tracking cbt mechanism available backup methods include forward incremental-forever backup forward incremental backup reverse incremental backup additionally ’ option perform active full synthetic full backups. br veeam backup replication provides automated recovery verification backups replicas program starts vm directly backup replica isolated test environment runs tests verification vm image remains read-only state mechanism also used troubleshooting testing patches upgrades veeam backup replication supports software-defined storage technology allows organizing scalable backup repository collection heterogeneous storage devices backups stored on-premises transferred off-site repositories via wan saved tape media long-term retention sent cloud storage cloud storage support available infrastructure-as-a-service iaas model veeam technology cloud connect provides integrated secured backup cloud veeam-powered service providers. br veeam backup replication storage-agnostic also specialized storage integrations storage systems cisco hyperflex emc vnx emc vnxe hp 3par hp storevirtual nimble netapp ibm lenovo storage v series addition separate universal storage api plug-in veeam also provides storage integrations infinidat pure storage uses storage system snapshots source backups recovery vmware vms disks residing storage volumes.. veeam backup replication also build direct nfs agent allows access netapp snapshots directly nas storage bypassing hosts backup restore storage scan operations along backup veeam backup replication perform image-based vm replication creates “ clone ” production vm onsite offsite keeps ready-to-use state vm replica configurable number failover points image-based vm replication also available via veeam cloud connect disaster recovery service draas software provides number data recovery options including br entire vm recovery file-level recovery virtual drive restore application-item recovery veeam backup replication decreases backup files size data traffic built-in data deduplication compression support deduplicating storage systems emc data domain exagrid hp storeonce catalyst netapp cloud backup altavault using deduplicating storage appliances backup repositories allows achieving greater levels deduplication ratios veeam backup replication also provides built-in wan acceleration reduce bandwidth required transferring backups replicas wan built modular scheme veeam backup replication allows setting scalable backup infrastructures software architecture supports onsite offsite cloud-base data protection operations across remote sites geographically dispersed locations installation package veeam backup replication includes set mandatory optional components installed physical virtual machines veeam backup replication positioned part veeam availability suite bundle includes veeam one monitoring reporting capacity planning also installed standalone product available three editions based level provided functionality product licensed number cpu sockets annually upfront-billed subscription licenses per-vm basis veeam backup replication 9.5 update 4 u4 veeam using veeam instance licensing vil lower complexity license key management essentially vil allows single license key instance deployed veeam products backup replication server veeam one windows linux agents number instance keys consumed per machine vary license edition standard enterprise enterprise plus software enabling
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Computer security
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url uniform resource locator url colloquially termed web address reference web resource specifies location computer network mechanism retrieving url specific type uniform resource identifier uri although many people use two terms interchangeably urls occur commonly reference web pages http also used file transfer ftp email mailto database access jdbc many applications web browsers display url web page page address bar typical url could form codice_1 indicates protocol codice_2 hostname codice_3 file name codice_4 uniform resource locators defined 1994 tim berners-lee inventor world wide web uri working group internet engineering task force ietf outcome collaboration started ietf living documents birds feather session 1992 format combines pre-existing system domain names created 1985 file path syntax slashes used separate directory filenames conventions already existed server names could prefixed complete file paths preceded double slash codice_5 berners-lee later expressed regret use dots separate parts domain name within uris wishing used slashes throughout also said given colon following first component uri two slashes domain name unnecessary early 1993 draft html specification referred universal resource locators dropped time june 1994 rfc 1630 october 1994 draft-ietf-uri-url-08.txt every http url conforms syntax generic uri web browser usually dereference url performing http request specified host default port number 80 urls using codice_6 scheme require requests responses made secure connection website internet users distributed throughout world using wide variety languages alphabets expect able create urls local alphabets internationalized resource identifier iri form url includes unicode characters modern browsers support iris parts url requiring special treatment different alphabets domain name path domain name iri known internationalized domain name idn web internet software automatically convert domain name punycode usable domain name system example chinese url codice_7 becomes codice_8 codice_9 indicates character originally ascii url path name also specified user local writing system already encoded converted utf-8 characters part basic url character set escaped hexadecimal using percent-encoding example japanese url codice_10 becomes codice_11 target computer decodes address displays page protocol-relative links prl also known protocol-relative urls prurl urls protocol specified example codice_12 use protocol current page either http https
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Web technology
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cfscript cfscript extension cfml coldfusion platform cfscript resembles javascript coldfusion developers prefer since less visual typographical overhead ordinary cfml considered best practice write coldfusion components business logic cfscript use cfml .cfm files amongst html cfscript code must contained within cfscript tag pair follows unless within pure script-based coldfusion component simple example function simple example component cfscript containing two functions coldfusion 11 railo 4.1+ lucee 4.5+ best fully support cf tags cfscript may direct substitutions tags often still possible achieve results tag script via different syntax example get query variable cfscript without writing udf since coldfusion 8 cfscript supported syntax abbreviations common many programming languages ++ += cfscript two forms comments single line multiline although cfscript javascript similar several key differences following list identifies cfscript features differ javascript
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Programming language topics
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ip address spoofing computer networking ip address spoofing ip spoofing creation internet protocol ip packets false source ip address purpose impersonating another computing system basic protocol sending data internet network many computer networks internet protocol ip protocol specifies ip packet must header contains among things ip address sender packet source ip address normally address packet sent sender address header altered recipient appears packet came another source protocol requires receiving computer send back response source ip address spoofing mainly used sender anticipate network response care response source ip address provides limited information sender may provide general information region city town packet sent provide information identity sender computer used ip address spoofing involving use trusted ip address used network intruders overcome network security measures authentication based ip addresses type attack effective trust relationships exist machines example common corporate networks internal systems trust users log without username password provided connecting another machine internal network must already logged spoofing connection trusted machine attacker network may able access target machine without authentication ip address spoofing frequently used denial-of-service attacks objective flood target overwhelming volume traffic attacker care receiving responses attack packets packets spoofed ip addresses difficult filter since spoofed packet appears come different address hide true source attack denial service attacks use spoofing typically randomly choose addresses entire ip address space though sophisticated spoofing mechanisms might avoid unroutable addresses unused portions ip address space proliferation large botnets makes spoofing less important denial service attacks attackers typically spoofing available tool want use defenses denial-of-service attacks rely validity source ip address attack packets might trouble spoofed packets backscatter technique used observe denial-of-service attack activity internet relies attackers use ip spoofing effectiveness use packets false source ip address always evidence malicious intent example performance testing websites hundreds even thousands vusers virtual users may created executing test script website test order simulate happen system goes live large number users log since user normally ip address commercial testing products hp loadrunner webload others use ip spoofing allowing user return address well configuration services vulnerable ip spoofing packet filtering one defense ip spoofing attacks gateway network usually performs ingress filtering blocking packets outside network source address inside network prevents outside attacker spoofing address internal machine ideally gateway would also perform egress filtering outgoing packets blocking packets inside network source address inside prevents attacker within network performing filtering launching ip spoofing attacks external machines also recommended design network protocols services rely source ip address authentication upper layer protocols provide defense ip spoofing attacks example transmission control protocol tcp uses sequence numbers negotiated remote machine ensure arriving packets part established connection since attacker normally see reply packets sequence number must guessed order hijack connection poor implementation many older operating systems network devices however means tcp sequence numbers predicted term spoofing also sometimes used refer header forgery insertion false misleading information e-mail netnews headers falsified headers used mislead recipient network applications origin message common technique spammers sporgers wish conceal origin messages avoid tracked
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Computer security
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interoperability interoperability characteristic product system whose interfaces completely understood work products systems present future either implementation access without restrictions term initially defined information technology systems engineering services allow information exchange broader definition takes account social political organizational factors impact system system performance task building coherent services users individual components technically different managed different organizations two systems use common data formats communication protocols capable communicating exhibit syntactic interoperability xml sql examples common data formats protocols lower-level data formats also contribute syntactic interoperability ensuring alphabetical characters stored ascii unicode format communicating systems beyond ability two computer systems exchange information semantic interoperability ability automatically interpret information exchanged meaningfully accurately order produce useful results defined end users systems achieve semantic interoperability sides must refer common information exchange reference model content information exchange requests unambiguously defined sent understood possibility promoting result user-driven convergence disparate interpretations information object study research prototypes s3db cross-domain interoperability involves multiple social organizational political legal entities working together common interest and/or information exchange interoperability imply open standards ab-initio i.e definition interoperability imply exchanges range products similar products several different vendors even past future revisions product interoperability may developed post-facto special measure two products excluding rest using open standards vendor forced adapt system dominant system based open standards interoperability compatibility open standards rely broadly consultative inclusive group including representatives vendors academics others holding stake development discusses debates technical economic merits demerits feasibility proposed common protocol doubts reservations members addressed resulting common document endorsed common standard document subsequently released public henceforth becomes open standard usually published available freely nominal cost comers encumbrances various vendors individuals even part original group use standards document make products implement common protocol defined standard thus interoperable design specific liability advantage customer choosing one product another basis standardised features vendors products compete quality implementation user interface ease use performance price host factors keeping customers data intact transferable even chooses switch another competing product business reasons post facto interoperability may result absolute market dominance particular product contravention applicable standards effective standards present time product introduction vendor behind product choose ignore forthcoming standards co-operate standardisation process using near-monopoly insist product sets de facto standard market dominance problem product implementation open minimally encumbered may well closed heavily encumbered e.g patent claims network effect achieving interoperability product critical vendor wishes remain relevant market difficult accomplish lack co-operation equal terms original vendor may well see new vendor potential competitor threat newer implementations often rely clean-room reverse engineering absence technical data achieve interoperability original vendors provide technical data others often name 'encouraging competition data invariably encumbered may limited use availability data equivalent open standard telecommunication term defined two-way radio interoperability composed three dimensions search interoperability refers ability two information collections searched single query specifically related web-based search challenge interoperability stems fact designers web resources typically little need concern exchanging information web resources federated search technology place format requirements data owner emerged one solution search interoperability challenges addition standards oai-pmh rdf sparql emerged recently also help address issue search interoperability related web resources standards also address broader topics interoperability allowing data mining respect software term interoperability used describe capability different programs exchange data via common set exchange formats read write file formats use protocols ability execute binary code different processor platforms 'not contemplated definition interoperability lack interoperability consequence lack attention standardization design program indeed interoperability taken granted non-standards-based portion computing world according iso/iec 2382-01 information technology vocabulary fundamental terms interoperability defined follows capability communicate execute programs transfer data among various functional units manner requires user little knowledge unique characteristics units note definition somewhat ambiguous user program another program latter portion set program required interoperable might well need knowledge characteristics units definition focuses technical side interoperability also pointed interoperability often organizational issue often interoperability significant impact organizations concerned raising issues ownership people want share data dealing information silos labor relations people prepared undergo training usability context apt definition captured term business process interoperability interoperability important economic consequences example research estimated cost inadequate interoperability u.s. capital facilities industry 15.8 billion year competitors products interoperable due causes patents trade secrets coordination failures result may well monopoly market failure reason may prudent user communities governments take steps encourage interoperability various situations least 30 international bodies countries implemented egovernment-based interoperability framework initiatives called e-gif united states niem initiative standards defining organizations sdos provide open public software specifications facilitate interoperability examples include oasis-open organization buildingsmart formerly international alliance interoperability far user communities neutral third party creating standards business process interoperability another example neutral party rfc documents internet engineering task force ietf oslc open service lifecycle collaboration community working finding common standard order software tools share exchange data e.g bugs tasks requirements etc final goal agree open standard interoperability open source alm tools java great example interoperable programming language allows programs written run anywhere java virtual machine one writing program java long use system specific functionality maintain interoperability machines java virtual machine many implementations java virtual machine oracle ibm android etc ... java virtual machine created specification applications maintain compatibility implementation different underlying language interfaces many organizations dedicated interoperability common want push development world wide web towards semantic web concentrate egovernment ebusiness data exchange general internationally network centric operations industry consortium facilitates global interoperability across borders language technical barriers europe instance european commission idabc programme issue european interoperability framework idabc succeeded isa programme also initiated semantic interoperability centre europe semic.eu european land information service eulis established 2006 consortium european national land registers aim service establish single portal customers provided access information individual properties land property registration services associated legal environment united states government core.gov service provides collaboration environment component development sharing registration reuse related national information exchange model niem work component repository national institute standards technology serves agency measurement standards new technology introduced hospitals labs ever-increasing rate need “ plug-and-play ” interoperability – ability take medical device box easily make work one devices – attracted great attention healthcare providers industry increasingly medical devices like incubators imaging mri ct ultrasound others driven sophisticated software must integrate point care electronic systems electronic medical records 2016 regulatory affairs professionals society raps meeting experts field like angela n. johnson ge healthcare representative united states food drug administration provided practical seminars companies developing new medical devices hospitals installing work effectively align interoperable software systems speaking e-government perspective interoperability refers collaboration ability cross-border services citizens businesses public administrations exchanging data challenge due language barriers different specifications formats varieties categorizations many hindrances identified data interpreted differently collaboration limited takes longer efficient instance citizen country wants purchase land country b person asked submit proper address data address data countries include full name details street name number well post code order address details might vary language obstacle order provided address data across language barriers becomes difficult language requires characters almost impossible translation tools available hence egovernment applications need exchange data semantically interoperable manner saves time money reduces sources errors fields practical use found every policy area justice trade participation etc clear concepts interpretation patterns required interoperability important issue law enforcement fire fighting ems public health safety departments first responders need able communicate wide-scale emergencies major area investment research last 12 years traditionally agencies could exchange information operated widely disparate hardware incompatible agencies information systems computer-aided dispatch systems cad records management systems rms functioned largely isolation so-called information islands agencies tried bridge isolation inefficient stop-gap methods large agencies began implementing limited interoperable systems approaches inadequate us lack interoperability public safety realm become evident 9/11 attacks pentagon world trade center structures evidence lack interoperability surfaced agencies tackled aftermath hurricane katrina disaster contrast overall national picture states including utah already made great strides forward utah highway patrol departments utah created statewide data-sharing network using technology company based bountiful utah fatpot technologies commonwealth virginia one leading states united states improving interoperability continually recognized national best practice department homeland security dhs virginia proven practitioner-driven governance structure ensures right players involved decision making training exercises planning efforts interoperability coordinator leverages regional structure better allocate grant funding around commonwealth areas opportunity improve communications interoperability virginia strategic plan communications updated yearly include new initiatives commonwealth – projects efforts tied plan aligned national emergency communications plan authored department homeland security office emergency communications oec state washington seeks enhance interoperability statewide state interoperability executive committee siec established legislature 2003 works assist emergency responder agencies police fire sheriff medical hazmat etc levels government city county state tribal federal define interoperability local region washington recognizes collaborating system design development wireless radio systems enables emergency responder agencies efficiently provide additional services increase interoperability reduce long-term costs work saves lives emergency personnel citizens serve u.s. government making effort overcome nation lack public safety interoperability department homeland security office interoperability compatibility oic pursuing safecom cadip project 25 programs designed help agencies integrate cad systems oic launched cadip august 2007 project partner oic agencies several locations including silicon valley program use case studies identify best practices challenges associated linking cad systems across jurisdictional boundaries lessons create tools resources public safety agencies use build interoperable cad systems communicate across local state federal boundaries force interoperability defined nato ability forces two nations train exercise operate effectively together execution assigned missions tasks additionally nato defines interoperability generally ability act together coherently effectively efficiently achieve allied tactical operational strategic objectives strategic level interoperability enabler coalition building facilitates meaningful contributions coalition partners level interoperability issues center harmonizing world views strategies doctrines force structures interoperability element coalition willingness work together long term achieve maintain shared interests common threats interoperability operational tactical levels strategic/political interoperability technological interoperability come together help allies shape environment manage crises win wars benefits interoperability operational tactical levels generally derive fungibility interchangeability force elements units technological interoperability reflects interfaces organizations systems focuses communications computers also involves technical capabilities systems resulting mission compatibility incompatibility systems data coalition partners technological level benefits interoperability come primarily impacts operational tactical levels terms enhancing fungibility flexibility interoperability used researchers context urban flood risk management cities urban areas worldwide expanding creates complex spaces many interactions environment infrastructure people address complexity manage water urban areas appropriately system systems approach water flood management necessary context interoperability important facilitate system systems thinking flood management defined “ ability water management system redirect water make use system maintain enhance performance function water exceedance events ” assessing complex properties urban infrastructure systems particularly interoperability drainage systems urban systems e.g infrastructure transport could possible expand capacity overall system manage flood water towards achieving improved urban flood resilience software interoperability achieved five interrelated ways important role reducing variability intercommunication software enhancing common understanding end goal achieved desktop interoperability also known interop sub-section software interoperability early days focus ‘ interop ’ integrate web-applications web-applications time open-system ‘ containers ’ developed create virtual desktop environment applications could registered communicate using simple pub/sub patterns rudimentary ui capabilities also supported allowing windows grouped windows today desktop interoperability evolved full-service interop platforms includes container support basic exchange web web also native support application types advanced window management latest interop platforms also include application services universal search notifications user permissions preferences 3rd party application connectors language adapters in-house applications interoperability tends regarded issue experts implications daily living sometimes underrated european union microsoft competition case shows interoperability concerns important questions power relationships 2004 european commission found microsoft abused market power deliberately restricting interoperability windows work group servers non-microsoft work group servers microsoft able protect dominant market position work group server operating systems heart corporate networks microsoft ordered disclose complete accurate interface documentation enable rival vendors compete equal footing “ interoperability remedy ” june 2005 commission market testing new proposal microsoft rejected previous proposals insufficient interoperability also surfaced software patent debate european parliament june–july 2005 critics claim patents techniques required interoperability kept rand reasonable non discriminatory licensing conditions customers pay license fees twice product appropriate case patent protected programme product uses railways greater lesser interoperability depending conforming standards gauge couplings brakes signalling communications loading gauge structure gauge operating rules mention parameters passenger rail service different railway platform height width clearance standards may also cause interoperability problems north american freight intercity passenger railroads highly interoperable systems europe asia africa central south america australia much less parameter difficult overcome reasonable cost incompatibility gauge though variable gauge axle systems increasingly used
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Computer architecture
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gvisor gvisor container sandbox developed google focuses security efficiency ease use.. gvisor implements around 200 linux system calls userspace additional security compared docker containers run directly top linux kernel isolated namespaces contrary linux kernel project written memory-safe programming language prevent common pitfalls frequently occur software written c. gvisor used google production environment like app engine standard environment cloud functions cloud ml engine google cloud run according google brad fitzpatrick recently gvisor integrated google kubernetes engine allows users sandbox kubernetes pods use cases like saas multitenancy
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Operating systems
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elements crm elements crm mac customer relationship management mac crm solution built ntractive apple business using apple devices offered cloud computing subscription-based service elements crm part desktop part cloud main functions include managing leads contact information tracking communication history managing tasks follow-ups tracking email communication creating estimates invoices managing projects architecture overall development elements crm product line initially began 2003 company founder justin bartak first product elements sbm launch october 2007 july 2009 product name changed elements crm ntractive privately held software development company based grand forks north dakota markets business software small medium-sized companies established 2006 company sole product elements crm customer relationship management application aimed small businesses use mac os x computers ipads iphones elements crm cloud based app employs unique site-specific browser merge os x desktop web application functionality product first introduced public keynote address apple 2007 world wide developer conference official launch elements sbm product ’ original name 1.0 took place macworld/iworld 2009 product renamed elements crm 2.0 release awarded honor apple staff pick july 2009 elements crm mac customer relationship management mac crm solution apple business using apple devices offered subscription-based service elements crm part desktop part cloud main functions include managing leads contact information tracking communication history managing tasks follow-ups tracking email communication creating estimates invoices managing projects elements crm ios universal mobile app iphone ipad elements crm ios add-on elements crm desktop app ipad crm version elements crm ios looks works feels like desktop app iphone crm app limited version important functions desktop app mac customer relationship management mac crm approach managing company ’ interaction current future customers apple inc desktop computers ios devices mac crm solutions web-based applications use web browser interaction instead mac crm combination cloud based app built apple programming language objective-c swift programming language mac crms involve using apple devices technology organize automate synchronize sales marketing customer service technical support
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Distributed computing architecture
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plessey system 250 plessey system 250 first operational computer system implement capability-based addressing first sold commercially designed real-time controller computerized telephone switching systems multiprocessing architecture manufactured plessey company plc united kingdom 1970 successfully deployed ministry defence british army ptarmigan project served first gulf war tactical mobile communication network switch
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Computer architecture
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professional association sql server professional association sql server pass global community data professionals use microsoft data platform independent not-for-profit user-run association pass founded 1999 funds microsoft computer associates pass governed board directors elected pass members two-year terms growing membership 100,000 pass currently 250 local pass chapters around world well 20 virtual chapters focused specific topic providing learning opportunities different local languages every fall organization hosts pass summit largest conference world sql server professionals 2013 pass launched pass business analytics conference data business analysts data scientists information architects business analytics ba business intelligence bi pros pass also offers sql server bi ba training international sqlrally conferences free pass sqlsaturday events 24 hours pass virtual events
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Databases
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