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turing completeness computability theory system data-manipulation rules computer instruction set programming language cellular automaton said turing complete computationally universal used simulate turing machine means system able recognize decide data-manipulation rule sets turing completeness used way express power data-manipulation rule set virtually programming languages today turing complete concept named english mathematician computer scientist alan turing related concept turing equivalence two computers p q called equivalent p simulate q q simulate p. church–turing thesis conjectures function whose values computed algorithm computed turing machine therefore real-world computer simulate turing machine turing equivalent turing machine universal turing machine used simulate turing machine extension computational aspects possible real-world computer show something turing complete enough show used simulate turing complete system example imperative language turing complete conditional branching e.g goto statements branch zero instruction see one instruction set computer ability change arbitrary amount memory e.g ability maintain arbitrary number data items course physical system infinite memory limitation finite memory ignored programming languages otherwise turing complete colloquial usage terms turing complete turing equivalent used mean real-world general-purpose computer computer language approximately simulate computational aspects real-world general-purpose computer computer language real computers constructed far functionally analyzed like single-tape turing machine tape corresponding memory thus associated mathematics apply abstracting operation far enough however real computers limited physical resources linear bounded automaton complete contrast universal computer defined device turing complete instruction set infinite memory infinite available time computability theory several closely related terms used describe computational power computational system abstract machine programming language turing completeness significant every real-world design computing device simulated universal turing machine church–turing thesis states law mathematics universal turing machine principle perform calculation programmable computer says nothing effort needed write program time may take machine perform calculation abilities machine may possess nothing computation charles babbage analytical engine 1830s would first turing-complete machine built time designed babbage appreciated machine capable great feats calculation including primitive logical reasoning appreciate machine could better 1830s 1940s mechanical calculating machines adders multipliers built improved could perform conditional branch therefore turing complete late 19th century leopold kronecker formulated notions computability defining primitive recursive functions functions calculated rote computation enough make universal computer instructions compute allow infinite loop early 20th century david hilbert led program axiomatize mathematics precise axioms precise logical rules deduction could performed machine soon became clear small set deduction rules enough produce consequences set axioms rules proved kurt gödel 1930 enough produce every theorem actual notion computation isolated soon starting gödel incompleteness theorem theorem showed axiom systems limited reasoning computation deduces theorems church turing independently demonstrated hilbert entscheidungsproblem decision problem unsolvable thus identifying computational core incompleteness theorem work along gödel work general recursive functions established sets simple instructions put together able produce computation work gödel showed notion computation essentially unique 1941 konrad zuse completed z3 computer first working turing-complete machine first digital computer modern sense computability theory characterizes problems computational solutions first result computability theory exist problems impossible predict turing-complete system arbitrarily long time classic example halting problem create algorithm takes input program turing-complete language b data fed program determines whether program operating input eventually stop continue forever trivial create algorithm inputs impossible general characteristic program eventual output impossible determine whether characteristic hold impossibility poses problems analyzing real-world computer programs example one write tool entirely protects programmers writing infinite loops protects users supplying input would cause infinite loops one instead limit program executing fixed period time timeout limit power flow control instructions example providing loops iterate items existing array however another theorem shows problems solvable turing-complete languages solved language finite looping abilities i.e. language guarantees every program eventually finish halt language turing complete example language programs guaranteed complete halt compute computable function produced cantor diagonal argument computable functions language computer access infinite tape data may powerful turing machine instance tape might contain solution halting problem turing-undecidable problem infinite tape data called turing oracle even turing oracle random data computable probability 1 since countably many computations uncountably many oracles computer random turing oracle compute things turing machine known laws physics consequences computable series approximations digital computer hypothesis called digital physics states accident universe computable universal turing machine would imply computer powerful universal turing machine built physically computational systems algebras calculi discussed turing complete systems intended studying theoretical computer science intended simple possible would easier understand limits computation programming languages conventional unconventional turing-complete includes rewrite systems turing-complete turing completeness abstract statement ability rather prescription specific language features used implement ability features used achieve turing completeness quite different fortran systems would use loop constructs possibly even goto statements achieve repetition haskell prolog lacking looping almost entirely would use recursion programming languages describing computations von neumann architectures memory ram register control unit two elements make architecture turing-complete even pure functional languages turing-complete turing completeness declarative sql implemented recursive common table expressions unsurprisingly procedural extensions sql plsql etc also turing complete illustrates one reason relatively powerful non-turing-complete languages rare powerful language initially complex tasks applied sooner lack completeness becomes perceived drawback encouraging extension turing complete untyped lambda calculus turing-complete many typed lambda calculi including system f value typed systems based ability represent typical computer programs detecting errors rule 110 conway game life cellular automata turing complete games software turing-complete accident video games card games zero-person games simulations computer hardware many computational languages exist turing complete one example set regular languages generated regular expressions recognized finite automata powerful still turing-complete extension finite automata category pushdown automata context-free grammars commonly used generate parse trees initial stage program compiling examples include early versions pixel shader languages embedded direct3d opengl extensions total functional programming languages charity epigram functions total must terminate charity uses type system control constructs based category theory whereas epigram uses dependent types loop language designed computes functions primitive recursive compute proper subsets total computable functions since full set total computable functions computably enumerable also since functions languages total algorithms recursively enumerable sets written languages contrast turing machines although untyped lambda calculus turing-complete simply typed lambda calculus notion turing-completeness apply languages xml html json yaml s-expressions typically used represent structured data describe computation sometimes referred markup languages properly container languages data description languages
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Programming language topics
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vesa stereo vesa stereo liquid crystal shutter glasses interface standard video electronics standards association vesa stereoscopic 3d displays system drive glasses directly instead providing basic signal power used electronics either inside glasses external unit vesa stereo connector extensively used 3d accelerators well 3d dlp tvs stereo-sync signal changes system changing showing images right eye left eye signal ttl signal high state indicates left eye exposed special software necessarily needed create stereo-sync signal created vertical synchronization signal fed monitor using rgb component video
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Computer architecture
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cloudminds cloudminds operator cloud-based systems intelligent robots founded early 2015 concentrates building safe cloud computing network intelligent robots creating large mixed platform machine learning safe intelligent terminals robot control units rcus founded 2015 cloudminds created cloud-based intelligent robot architecture based cloud brain secure network backed softbank foxconn walden venture investments keytone ventures cloudminds developed in-depth research cloud intelligence integration high-speed security network safe smart devices robot control technology cloudminds built human augmented robotics intelligence hari platform applied significant areas blind guiding operator created world first cloud-based terminal “ data ” series working constructing backbone network worldwide vbn based nuclear technologies cloudminds succeeded realizing mobile intranet cloud services mcs contains function improving information security cloud robot remote controlling technology widely used areas financial medical military public security department large-scale manufacturing industry cloudminds first cloud robot operator builds platform services make robots connect learn possible tendency household robot 2025 company determines develop ground breaking technology ai robotic control network cloud security mobile intranet cloud services mcs platform offers secure device cloud connection high performance low latency private network besides target partner best minds ai smart devices first products include blind guiding robot ai mobile device used control unit generic robots order stimulate end-to-end ecosystem products services used solve complex problems health care manufacturing finance industries data cloud intelligent device serve controller robot cloud brain implemented hardware virtualization qualcomm platform cloudminds also implemented gpu virtualization data data uses self-developed sandwich-like hardware extension architecture based special hardware interface enables support dual lte meta first wearable device based cloud framework cloudminds takes shape helmet visually impaired people support face recognition object recognition path planning obstacle avoidance etc mobile-intranet cloud service mcs made three parts xaas cloud vbn terminal design terminal contains technologies dual chips virtualization applies artificial intelligence activate robot ai mobile xaas cloud based original hari human augmented robotic intelligence architecture realize integration artificial intelligence human intelligence provide image recognition enterprise collaboration different types services xaas cloud currently completed first phase construction providing cloud service platform mcs since august 2015 cloudminds begun construct backbone network worldwide realize network path optimization protocol optimization provide safe high-speed internet service sdn software defined network sdp software defined boundary
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Distributed computing architecture
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mailsite mailsite commercial mail server calendar software contact manager collaborative software developed rockliffe systems mailsite one first mail servers run windows nt using internet standards version 1.2 released 1996 mailsite continual development since 1996 version 10 released 2013 mailsite runs single windows server cluster windows server computers mailsite works natively microsoft outlook versions 2007 2013 mail calendar contacts without requiring outlook plug-ins mailsite includes exchange activesync eas server synchronizing mail calendar contacts mobile devices mailsite also works internet standards-based mail clients mozilla thunderbird mailsite sold three package configurations different markets mailsite se single-server package small medium enterprises mailsite le multi-server package large enterprises mailsite sp provides advanced multi-server clustering service providers hosting companies internet service providers telecommunication companies mailsite provides comprehensive set features groupware mailsite provides native support mail calendar contact sync clients mail
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Internet protocols
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criticism windows 10 windows 10 operating system released microsoft july 2015 criticized reviewers users due issues mostly privacy subject number negative assessments various groups critics noted windows10 heavily emphasizes freemium services contains various advertising facilities outlets considered hidden cost free upgrade offer examples include media storefronts office 365 paid functionality bundled games microsoft solitaire collection default settings display promotions suggested apps start menu tips lock screen may contain advertising ads displayed file explorer office 365 subscriptions redstone 2 builds notifications promoting microsoft edge web browser different browser set default windows 10 home permanently set download updates automatically including cumulative updates security patches drivers users individually select updates install microsoft offers diagnostic tool used hide updates prevent reinstalled already installed uninstalled without rebooting system tom warren verge felt given web browsers google chrome already adopted automatic update system requirement would help keep windows10 devices secure felt 're used family members calling technical support 've failed upgrade latest windows service pack malware disabled windows update days hopefully concerns raised due changes users would unable skip automatic installation updates faulty cause issues certain system configurationsalthough build upgrades also subject public beta testing via windows insider program also concerns forced installation driver updates windows update previously designated optional could cause conflicts drivers installed independently windows update situation occurred prior general release operating system nvidia graphics card driver automatically pushed windows10 users via windows update caused issues prevented use certain functions prevented system booting criticism also directed towards microsoft decision longer provide specific details contents cumulative updates windows 10 february 9 2016 microsoft reversed decision began provide release notes cumulative updates windows website users reported installation november upgrade applications particularly utility programs cpu-z speccy automatically uninstalled upgrade process default programs reset microsoft-specified defaults photos app microsoft edge pdf viewing without warning issues discovered upon launch anniversary update redstone including bug caused devices freeze addressed cumulative update kb3176938 released august 31 2016 fundamental changes windows handles webcams caused many stop working microsoft criticized tactics used promote free upgrade campaign windows 10 including adware-like behaviors using deceptive user interfaces coax users installing operating system downloading installation files without user consent making difficult users suppress advertising notifications wish upgrade 10 upgrade offer marketed initiated using get windows 10 gwx application first downloaded installed via windows update march 2015 registry keys group policy settings could used partially disable gwx mechanism installation patches gwx software via windows update could reset keys back defaults thus reactivate software third-party programs also created assist users applying measures disable gwx september 2015 reported microsoft triggering automatic downloads windows10 installation files compatible windows7 8.1computers configured automatically download install updates regardless whether specifically requested upgrade microsoft officially confirmed change claiming industry practice reduces time installation ensures device readiness move criticized users data caps devices low storage capacity resources consumed automatic downloads 6gb data critics argued microsoft triggered downloading windows10 installation files without user consent october 2015 windows10 began appear optional update windows update interface pre-selected installation systems microsoft spokesperson said mistake download would longer pre-selected default however october 29 2015 microsoft announced planned classify windows10 recommended update windows update interface time 2016 cause automatic download installation files one-time prompt choice install appear december 2015 reported new advertising dialog begun appear containing upgrade upgrade tonight buttons obvious method decline installation besides close button march 2016 users also alleged windows 7 8.1 devices automatically begun upgrading 10 without consent june 2016 gwx dialog behavior changed make closing window imply consent scheduled upgrade despite infoworld editor disputed claims upgrades begun without consent testing showed upgrade windows10 would begin user accepts end-user license agreement eula presented installer would eventually cause windows update time error thus halting installation attempt concluded users may unknowingly clicked accept prompt without full knowledge would begin upgrade december 2016 microsoft chief marketing officer chris capossela admitted company gone far using tactic stating know want people running windows 10 security perspective finding right balance ’ stepping line aggressive something tried lot year think got right january 21 2016 microsoft sued small claims court user whose computer shortly release os attempted upgrade windows10 without consent upgrade failed computer left unstable state thereafter disrupted ability run travel agency court ruled favor user awarded 10,000 damages microsoft appealed however may 2016 microsoft dropped appeal chose pay damages shortly suit reported seattle times microsoft confirmed updating gwx software add explicit options opting free windows 10 upgrade final notification full-screen pop-up window notifying users impending end free upgrade offer contained remind later notify notify three times options concerns shown advocates critics windows10 privacy policies collection use customer data default express settings windows 10 configured send various information microsoft parties including collection user contacts calendar data computer appearance including color chassis associated input data personalize speech typing inking input typing inking data improve recognition allow apps use unique advertising id analytics advertising personalization functionality introduced windows 8.1 allow apps request user location data send data microsoft trusted partners improve location detection windows 8 similar settings except location data collection include trusted partners users opt data collection telemetry data error reporting usage also sent microsoft disabled non-enterprise versions windows 10 use cortana intelligent personal assistant also requires collection data device location data calendar apps use data emails text messages call contacts often interact device ” personalize functionality rock paper shotgun writer alec meer argued microsoft intent data collection lacked transparency stating world 45 pages policy documents opt-out settings split across 13 different settings screens external website constitutes 'real transparency extremetech pointed whilst previously campaigning google similar data collection strategies microsoft hoovers data ways would make google jealous however also pointed requirement vast usage customer data become norm citing increased reliance cloud computing forms external processing well similar data collection requirements services mobile devices google siri august 2015 russian politician nikolai levichev called windows 10 banned use russian government sends user data servers united states federal law requiring online services store data russian users servers within country blocked took effect september 2016 writing zdnet ed bott said lack complaints businesses privacy windows10 indicated utterly normal privacy terms 2015 computerworld editorial preston gralla said kind information windows10 gathers different operating systems gather microsoft held different standard companies microsoft services agreement reads company online services may automatically download software updates configuration changes including prevent accessing services playing counterfeit games using unauthorized hardware peripheral devices critics interpreted statement implying microsoft would scan delete unlicensed software installed devices running windows10 however others pointed agreement specifically microsoft online services microsoft account office 365 skype well xbox live offending passage likely referred digital rights management xbox consoles first-party games plans police pirated video games installed windows10 pcs despite torrent trackers announced plans block windows10 users also arguing operating system could send information anti-piracy groups affiliated microsoft writing allegations ed bott zdnet compared microsoft privacy policy apple google concluded carefully reading microsoft services agreement windows license agreement ... microsoft privacy statement carefully n't see anything looks remotely like big brother columnist kim komando argued microsoft might future run scans disable software hardware sees security threat consistent windows10 update policy following release 10 allegations also surfaced microsoft backported operating system increased data collection windows 7 windows 8 via recommended patches added additional telemetry features updates addition diagnostics tracking service connected specifically microsoft existing customer experience improvement program opt-in program sends additional diagnostic information microsoft addressing issues application insights service third-party software data collection functionality capable transmitting personal information browsing history contents emails chat video calls voice mail photos documents personal files keystrokes microsoft analysis accordance end user license agreement terms services agreement microsoft updated state following october 2017 dutch data protection authority issued complaint asserting windows10 privacy policies comply laws netherlands claims microsoft provide sufficient information information collected full telemetry level processed microsoft disputed claim provide enough disclosure full telemetry level stated working ddpa find appropriate solutions november 2016 kaspersky lab filed antitrust complaint russia regarding bundling windows defender operating system arguing microsoft abusing position favor in-house antivirus software vendors june 2017 kaspersky filed another complaint european commission accusing company frustrating use third-party antivirus software windows 10 defense inferior windows defender including forcibly uninstalling third-party antivirus software upgrades providing enough time antivirus developers certify software new upgrade windows 10 microsoft stated company engages deeply antimalware vendors taken number steps address feedback offered meet kaspersky executives discuss specific concerns june 21 2017 microsoft issued blog post confirming since creators update windows 10 may prompt users temporarily disable virus software upon installation feature update current version deemed compatible operating system would direct users relevant updates software following conclusion update microsoft stated worked vendors perform compatibility testing software update specify versions software compatible direct customers updating microsoft reported result efforts around 95 windows 10 users antivirus application installed already compatible windows 10 creators update microsoft clarified windows defender operates device security software installed security software reports subscription lapsed summer 2018 windows 10 insider update received extreme backlash planned feature would attempted prevent installation web browsers chrome firefox telling users already microsoft edge therefore need change browser
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Operating systems
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execute channel program ibm mainframe operating systems execute channel program excp supervisor call low-level device access programmer responsible providing channel program —a list device-specific commands ccws —to executed i/o channels control units devices excp specifically described os system programmer guide using excp legacy devices legacy datasets may operated relatively high performance excp devices opened made available application specifying macrf= e data control block dcb comprehensive list exits called excp context appendages allows authorized programs override augment many system security data integrity checks appendages really closed subroutines supported compatibility earlier instances os functions several modified extended mvs appendages specified dcb last two characters module name igg019xx xx wa z9 inclusive module names reserved installation-written appendages name form igg019xx reserved use ibm access methods appendages must reside sys1.svclib sys1.lpalib svs later instances os normally device opened excp first extent represented data extent block deb among information deb contains information location size extent data set deb forward- backward-chained dcb system security measure dcb resides unprotected user storage whereas deb resides protected system storage subpool 253 example programmer tries read past end extent exception occurs operation suppressed thereby preventing data integrity exposure deb include additional extents channel program may updated programmer refer next extent excp may reissued end extent exit appendage provided may update channel program next extent operation may re-driven without first going excp processor excp sometimes confused direct access storage device access method direct access storage devices exclusively rather general purpose low-level device access interface supports legacy device type legacy dataset organization accessing device types dataset organizations general start input/output interface startio available mvs/370 subsequent instances os although officially supported interface variation excp execute direct access program xdap used accessing direct access storage provided reading updating existing direct access storage records xdap used add records xdap utilized along bsam bpam effect record additions datasets several os components utilize xdap manner linkage editor iewl particular excp may also used access communications devices attached ibm 2701 2702 2703 communications controllers ibm 370x amdahl 470x front-end processors respective follow-ons operating emulator mode ep partitioned emulator mode pep excp front-end always tcb mode excp type 1 svc mvs/370 subsequent instances os excp processor invokes startio schedule execution channel program although excp processor back-end always srb mode back-end contains emulation code allows appendages developed earlier pre-mvs instances os specifically excp function largely thereby appear tcb mode appendages originally designed distinction complicate conversion certain roll-your-own access methods applications mvs
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Operating systems
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directory traversal attack directory traversal path traversal consists exploiting insufficient security validation sanitization user-supplied input file names characters representing traverse parent directory passed file apis goal attack use affected application gain unauthorized access file system attack exploits lack security software acting exactly supposed opposed exploiting bug code directory traversal also known codice_1 dot dot slash attack directory climbing backtracking forms attack also canonicalization attacks typical example vulnerable application php code attack system could send following http request generating server response repeated codice_1 characters codice_3 caused codice_4 traverse root directory include unix password file codice_5 unix codice_5 common file used demonstrate directory traversal often used crackers try cracking passwords however recent unix systems passwd file contain hashed passwords instead located shadow file read unprivileged users machine however still useful account enumeration machine still displays user accounts system listed known directory traversal attack strings common unix-like directory traversal uses codice_1 characters sudo privilege management program ubiquitous unix vulnerable attack users use glob wildcard e.g chown /opt/myapp/myconfig/* could exploited command sudo chown baduser /opt/myapp/myconfig/../../../etc/passwd microsoft windows dos directory traversal uses codice_8 codice_1 character sequences partition separate root directory labeled codice_10 particular partition c common root directory means directory vulnerabilities windows attack limited single partition kind attack cause numerous microsoft vulnerabilities canonicalization problem web applications scan query string dangerous characters prevent directory traversal however query string usually uri decoded use therefore applications vulnerable percent encoded directory traversal canonicalization problem utf-8 noted source vulnerabilities attack vectors bruce schneier jeffrey streifling microsoft added unicode support web server new way encoding codice_1 introduced code causing attempts directory traversal prevention circumvented multiple percent encodings translated codice_25 codice_26 characters percent encodings decoded corresponding 8-bit characters microsoft webserver historically correct behavior windows dos traditionally used canonical 8-bit characters sets based upon ascii however original utf-8 canonical several strings string encodings translatable string microsoft performed anti-traversal checks without utf-8 canonicalization therefore noticing hex codice_27 hex codice_28 character string comparisons malformed percent encodings codice_29 also utilized use archive formats like zip allows directory traversal attacks files archive written overwrite files filesystem backtracking code uncompresses archive files written check paths files archive engage path traversal possible algorithm preventing directory traversal would user use null character indicating end string order bypass everything _get php-specific
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Computer security
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esc/p esc/p short epson standard code printers sometimes styled escape/p printer control language developed epson control computer printers mainly used dot matrix printers inkjet printers still widely used many receipt printers era dot matrix printers also used manufacturers e.g. nec sometimes modified form time popular mechanism add formatting printed text widely supported software esc/p derives name start escape sequences used start escape character esc ascii code 27 example esc e switch printing bold font esc f switches bold printing esc/p control codes sometimes also referred epson lq codes made popular epson lq series dot matrix printers even though esc/p introduced long lq printers several variants esc/p printers implement commands 2014 modern printers use esc/p instead driven standardized page description language usually pcl postscript use proprietary protocols esc/page current epson impact printers still support esc/p epson stylus inkjets still seem using variant esc/p see gutenprint gimp print project source code examples
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Programming language topics
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freeotp freeotp free open-source software token used two-factor authentication provides implementations hotp totp tokens added scanning qr code manually entering token configuration maintained red hat apache 2.0 license supports android ios
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Computer security
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evaluation assurance level evaluation assurance level eal1 eal7 product system numerical grade assigned following completion common criteria security evaluation international standard effect since 1999 increasing assurance levels reflect added assurance requirements must met achieve common criteria certification intent higher levels provide higher confidence system principal security features reliably implemented eal level measure security system simply states level system tested achieve particular eal computer system must meet specific assurance requirements requirements involve design documentation design analysis functional testing penetration testing higher eals involve detailed documentation analysis testing lower ones achieving higher eal certification generally costs money takes time achieving lower one eal number assigned certified system indicates system completed requirements level although every product system must fulfill assurance requirements achieve particular level fulfill functional requirements functional features certified product established security target document tailored product evaluation therefore product higher eal necessarily secure particular application one lower eal since may different lists functional features security targets product fitness particular security application depends well features listed product security target fulfill application security requirements security targets two products contain necessary security features higher eal indicate trustworthy product application eal1 applicable confidence correct operation required threats security viewed serious value independent assurance required support contention due care exercised respect protection personal similar information eal1 provides evaluation toe target evaluation made available customer including independent testing specification examination guidance documentation provided intended eal1 evaluation could successfully conducted without assistance developer toe minimal cost evaluation level provide evidence toe functions manner consistent documentation provides useful protection identified threats eal2 requires cooperation developer terms delivery design information test results demand effort part developer consistent good commercial practice require substantially increased investment cost time eal2 therefore applicable circumstances developers users require low moderate level independently assured security absence ready availability complete development record situation may arise securing legacy systems eal3 permits conscientious developer gain maximum assurance positive security engineering design stage without substantial alteration existing sound development practices eal3 applicable circumstances developers users require moderate level independently assured security require thorough investigation toe development without substantial re-engineering eal4 permits developer gain maximum assurance positive security engineering based good commercial development practices though rigorous require substantial specialist knowledge skills resources eal4 highest level likely economically feasible retrofit existing product line eal4 therefore applicable circumstances developers users require moderate high level independently assured security conventional commodity toes prepared incur additional security-specific engineering costs commercial operating systems provide conventional user-based security features typically evaluated eal4 examples operating systems aix hp-ux oracle linux netware solaris suse linux enterprise server 9 suse linux enterprise server 10 red hat enterprise linux 5 windows 2000 service pack 3 windows 2003 windows xp windows vista windows 7 windows server 2008 r2 z/os version 2.1 z/vm version 6.3 operating systems provide multilevel security evaluated minimum eal4 examples include trusted solaris solaris 10 release 11/06 trusted extensions early version xts-400 vmware esxi version 3.0.2 3.5 4.0 aix 4.3 aix 5l aix 6 aix7 red hat 6.2 suse linux enterprise server 11 eal 4+ vsphere 5.5 update 2 achieve eal4+ level eal2+ certified june 30 2015 eal5 permits developer gain maximum assurance security engineering based upon rigorous commercial development practices supported moderate application specialist security engineering techniques toe probably designed developed intent achieving eal5 assurance likely additional costs attributable eal5 requirements relative rigorous development without application specialized techniques large eal5 therefore applicable circumstances developers users require high level independently assured security planned development require rigorous development approach without incurring unreasonable costs attributable specialist security engineering techniques numerous smart card devices evaluated eal5 multilevel secure devices tenix interactive link xts-400 stop 6 general-purpose operating system evaluated eal5 augmented lpar ibm system z eal5 certified eal6 permits developers gain high assurance application security engineering techniques rigorous development environment order produce premium toe protecting high-value assets significant risks eal6 therefore applicable development security toes application high risk situations value protected assets justifies additional costs green hills software integrity-178b rtos certified eal6 augmented eal7 applicable development security toes application extremely high risk situations and/or high value assets justifies higher costs practical application eal7 currently limited toes tightly focused security functionality amenable extensive formal analysis tenix interactive link data diode device fox-it fox data diode one-way data communications device claimed evaluated eal7 augmented eal7+ technically speaking higher eal means nothing less evaluation completed stringent set quality assurance requirements often assumed system achieves higher eal provide security features reliably required third-party analysis testing performed security experts reasonable evidence direction little published evidence support assumption 2006 us government accountability office published report common criteria evaluations summarized range costs schedules reported evaluations performed levels eal2 eal4 mid late 1990s vendors reported spending us 1 million even us 2.5 million evaluations comparable eal4 published reports cost various microsoft windows security evaluations cases evaluation may augmented include assurance requirements beyond minimum required particular eal officially indicated following eal number word augmented usually list codes indicate additional requirements shorthand vendors often simply add plus sign eal4+ indicate augmented requirements common criteria standards denote eals shown article prefix eal concatenated digit 1 7 examples eal1 eal3 eal5 practice countries place space prefix digit eal 1 eal 3 eal 5 use plus sign indicate augmentation informal shorthand used product vendors eal4+ eal 4+
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Computer security
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black-bag cryptanalysis cryptography black-bag cryptanalysis euphemism acquisition cryptographic secrets via burglary covert means – rather mathematical technical cryptanalytic attack term refers black bag equipment burglar would carry black bag operation rubber-hose cryptanalysis technically form cryptanalysis term used sardonically however given free availability high strength cryptographic systems type attack much serious threat users mathematical attacks often much easier attempt circumvent cryptographic systems e.g steal password attack directly regardless technique used methods intended capture highly sensitive information e.g cryptographic keys key-rings passwords unencrypted plaintext required information usually copied without removing destroying capture often takes place without victim realising occurred addition burglary covert means might include installation keystroke logging trojan horse software hardware installed near target computers ancillary devices even possible monitor electromagnetic emissions computer displays keyboards distance 20 metres thereby decode typed could done surveillance technicians via form bug concealed somewhere room although sophisticated technology often used black bag cryptanalysis also simple process copying password someone unwisely written piece paper left inside desk drawer case united states v. scarfo highlighted one instance fbi agents using sneak peek warrant placed keystroke logger alleged criminal gang leader
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Computer security
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lego mindstorms nxt lego mindstorms nxt programmable robotics kit released lego late july 2006 replaced first-generation lego mindstorms kit called robotics invention system base kit ships two versions retail version set 8527 education base set set 9797 comes nxt-g programming software optionally labview lego mindstorms variety unofficial languages exist nxc nbc lejos nxj robotc second generation set lego mindstorms nxt 2.0 released august 1 2009 featuring color sensor upgraded capabilities third generation ev3 released september 2013 main component kit brick-shaped computer called nxt intelligent brick take input four sensors control three motors via modified version rj12 cables much similar incompatible rj11 phone cords plastic pin hold cable socket moved slightly right brick 100×60 pixel monochrome lcd four buttons used navigate user interface using hierarchical menus 32-bit arm7tdmi-core atmel at91sam7s256 microcontroller 256 kb flash memory 64 kb ram plus 8-bit atmel avr atmega48 microcontroller bluetooth support also speaker play sound files sampling rates 8 khz power supplied 6 aa 1.5 v batteries consumer version kit li-ion rechargeable battery charger educational version intelligent brick remains unchanged nxt 2.0 black version brick made celebrate 10th anniversary mindstorms system change internals lego released firmware nxt intelligent brick open source along schematics hardware components several developer kits available contain documentation nxt simple programs created using menu nxt intelligent brick complicated programs sound files downloaded using usb port wirelessly using bluetooth files also copied two nxt bricks wirelessly mobile phones used remote control three nxt bricks communicate simultaneously via bluetooth user created programs run retail version kit includes software writing programs run windows mac os personal computers software based national instruments labview provides visual programming language writing simple programs downloading nxt brick means rather requiring users write lines code instead use flowchart like blocks design program nxt-g v2.0 graphical programming environment comes bundled nxt careful construction blocks wires encapsulate complexity nxt-g used real-world programming parallel sequence beams actually parallel threads software quite good running handful parallel sense/respond loops example wait 60 seconds play bonk sound low volume battery low loop blending autonomous control bluetooth remote control language supports virtual instruments lego branded 3rd party sensors/components version 2.0 contains new tutorial challenges remote control custom graphics sound designers new lego color sensor support community support significant example http //www.brickshelf.com/cgi-bin/gallery.cgi f=191310 free tools visual studio express combination robotics developer studio enable programming nxt using c language supported languages include ironpython vb.net bricx command center bricxcc integrated development environment ide used write compile edit nbc nxc programs nxt also bricxcc originally made rcx programs written using nqc via bricxcc different firmware versions flashed nxt using bricxcc bricxcc many utilities nextexplorer upload/download files defragment nxt use file hex viewer nextscreen view nxt lcd capture images video next byte codes nbc simple open source language assembly language syntax used program nxt brick bricxcc also capability decompile standard .rxe nxt executables nbc exactly c nxc high level open-source language similar c built nbc compiler also used program nxt brick nxc basically nqc nxt one widely used third-party programming languages nxt nxc even creating video games nxt possible people even got working grayscale nxt screen robolab 2.9 robolab newer programming environment originally used rcx programmable brick version 2.9 updated used program nxt brick lego announced stop officially supporting robolab robolab 2.9 still available still many user forums sources help available robomind educational software specially developed teach students logic programming robotics strength robomind compactness learning environment allows quickly develop test scripts virtual environment scripts directly transferred lego mindstorms nxt robot see result real life robomind script run standard firmware enchanting brings nxt programming popular scratch ide designed lifelong kindergarten group mit make programming intuitive even young children resulting nxt programs compactness clarity offered programming environment robotc programming-language based c vex vex cortex first tech challenge lego mindstorms robotc runs optimized firmware allows nxt run programs quickly also compresses files large number programs fit nxt like nxt languages robotc requires firmware downloaded robotc interface order run nxtgcc gcc toolchain programming nxt firmware c. lejos nxj high level open source language based java uses custom firmware developed lejos team able write c/c++ nxtosek used requires custom firmware write files nxt icon steve hassenplug ideal resource matlab simulink support lego mindstorms programming freely available information found lego mindstorms support matlab simulink pblua port lua programming language general purpose scripting language lego mindstorms port gnat available nxt relies dedicated run-time kernel based ravenscar profile used goce satellite permits use high-level ada features develop concurrent real-time systems mindstorms nxt urbi yet another language parallel event-driven language interfaces c++/java matlab also component architecture uobject distribution urbi compatible many robots including nao cf robocup bioloid aibo fll nxt navigation open source program help navigation fll competition table uses nxt-g .txt files write programs unknown legally implement fll competitions ruby-nxt library program nxt ruby programming language unlike languages nxt code compiled binary file instead code directly transmitted nxt via bluetooth connection robotics.nxt haskell interface nxt bluetooth supports direct commands messages many sensors also unofficial also support simple message-based control nxt brick via remotely executed program basic nxc code included libnxt utility library talking lego mindstorms nxt intelligent brick relatively low level libnxt targeted mainly platforms official lego mindstorms nxt software overlooks namely linux unices work posix-compliant operating system libusb 0.1 http //libusb.sf.net/ supported windows support also possible win32 port libusb c_nxt library controlling lego nxt licensed gplv2 library allows users control lego nxt via bluetooth controller within c programs library provides low level control high level abstraction library runs gnu+linux pynxc project converts python code exactly c nxc code download lego mindstorms robots nxt-python python module communicates nxt via usb bluetooth supports direct commands several aftermarket sensors software ships newer mindstorms ev3 set used program nxt moment bluetooth supported nxt programs must downloaded via usb cable physical etoys visual programming system different electronic devices supports direct mode compiled mode ch c/c++ interpreter running c/c++ code control lego nxt ev3 firmware upload/download required compilation needed c/c++ code running ch control either lego nxt ev3 multiple nxt/ev3 lego mindstorms nxt 1.0 base kit includes parts included lego mindstorms nxt base kit may bought separately sensors come assembled programmed software see programming people decide information comes sensors programming robot move forward touches something lego also sells adapter vernier sensor product line vernier produces data collection devices related software use education sensors connected nxt brick using 6-position modular connector features analog digital interfaces analog interface backward-compatible using adapter older robotics invention system digital interface capable ic rs-485 communication lego mindstorms nxt 2.0 second set lego lego mindstorms series launched august 5 2009 lego shop u.s set contains 619 pieces including new sensor detect colors priced approximately us 280 c 350 £230 500 lego mindstorms nxt 2.0 successor called lego mindstorms ev3 parts ordered separately original kit sensors included color sensor two touch sensors ultrasonic sensor simple programs created using nxt intelligent brick order create larger complex programs programming software pc required standard programming software nxt-g included package third-party programming software also available listed nxt-g programming software included standard base kit based labview graphical programming features interactive drag-and-drop environment nxt-g powered labview industry standard programming created national instruments labview uses data flow programming create virtual instrument allow advanced programming graphical sense national instruments released toolkit nxt version 1.0 came december 2006 since release several bugs found new sensors created toolkit allow creation new sensors national instruments yet formally release update lego :nxt provides api perl nxt port gnat available nxt requires nxtosek run port includes ada bindings nxt hardware nxtosek next byte codes nbc simple open-source language assembly language syntax used program nxt brick exactly c nxc high level open-source language similar c built top nbc compiler also used program nxt brick nxc basically nqc nxt widely used third-party programming language robotc integrated development environment targeted towards students used program control lego nxt vex rcx arduino robots using programming language based c programming language robomind educational programming environment offers concise scripting language programming simulated robot internationalized scripts however also directly exported lego mindstorms robots require custom firmware order run nxtgcc gcc toolchain programming nxt firmware c. urbi parallel event-driven language interfaces c++/java matlab also component architecture uobject distributed computation urbi compatible many robots including nao cf robocup bioloid aibo lejos nxj high level open source language based java uses custom firmware developed lejos team able write c programming language /c++ nxtosek used requires custom firmware matlab simulink code nxt programming freely available pblua implementation lua programming language general purpose scripting language lego mindstorms fll nxt navigation open source program help navigation fll competition table uses nxt-g .txt files write programs ruby-nxt library program nxt ruby programming language unlike languages nxt code n't compiled binary file instead code directly transmitted nxt via bluetooth connection method execution significantly slower executing compiled code directly robotics.nxt haskell interface nxt bluetooth supports direct commands messages many sensors also unofficial also support simple message-based control nxt brick via remotely executed program basic nxc code included
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Programming language topics
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wavesurfer wavesurfer audio editor widely used studies acoustic phonetics simple fairly powerful program interactive display sound pressure waveforms spectral sections spectrograms pitch tracks transcriptions read write number transcription file formats used industrial speech research including timit wavesurfer free software distributed permissive free software licence wavesurfer provides basic audio editing operations excision copying pasting zero-crossing adjustment effects fading normalization echo inversion reversal replacement silence dc-removal view scientific orientation offer effects interest musicians flange wavesurfer written tcl/tk using snack audio library therefore runs platforms including microsoft windows mac os x linux solaris hp-ux freebsd irix scriptable supports plugins
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Computational linguistics
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dynamic frequency scaling dynamic frequency scaling also known cpu throttling technique computer architecture whereby frequency microprocessor automatically adjusted fly depending actual needs conserve power reduce amount heat generated chip dynamic frequency scaling helps preserve battery mobile devices decrease cooling cost noise quiet computing settings useful security measure overheated systems e.g poor overclocking dynamic frequency scaling used ranges computing systems ranging mobile systems data centers reduce power times low workload dynamic power switching power dissipated per unit time chip c·v·a·f c capacitance switched per clock cycle v voltage activity factor indicating average number switching events undergone transistors chip unit-less quantity f switching frequency voltage therefore main determinant power usage heating voltage required stable operation determined frequency circuit clocked reduced frequency also reduced dynamic power alone account total power chip however also static power primarily various leakage currents due static power consumption asymptotic execution time shown energy consumption piece software shows convex energy behavior i.e. exists optimal cpu frequency energy consumption minimal leakage current become important transistor sizes become smaller threshold voltage levels lower decade ago dynamic power accounted approximately two-thirds total chip power power loss due leakage currents contemporary cpus socs tend dominate total power consumption attempt control leakage power high-k metal-gates power gating common methods dynamic voltage scaling another related power conservation technique often used conjunction frequency scaling frequency chip may run related operating voltage efficiency electrical components voltage regulators decreases increasing temperature power usage may increase temperature since increasing power use may increase temperature increases voltage frequency may increase system power demands even cmos formula indicates vice versa dynamic frequency scaling reduces number instructions processor issue given amount time thus reducing performance hence generally used workload cpu-bound dynamic frequency scaling rarely worthwhile way conserve switching power saving highest possible amount power requires dynamic voltage scaling v component fact modern cpus strongly optimized low power idle states constant-voltage cases efficient run briefly peak speed stay deep idle state longer time called race idle computational sprinting run reduced clock rate long time stay briefly light idle state however reducing voltage along clock rate change trade-offs related-but-opposite technique overclocking whereby processor performance increased ramping processor dynamic frequency beyond manufacturer design specifications one major difference two modern pc systems overclocking mostly done front side bus mainly multiplier normally locked dynamic frequency scaling done multiplier moreover overclocking often static dynamic frequency scaling always dynamic software often incorporate overclocked frequencies frequency scaling algorithm chip degradation risks allowable intel cpu throttling technology speedstep used mobile desktop cpu lines amd employs two different cpu throttling technologies amd cool n'quiet technology used desktop server processor lines aim cool n'quiet save battery life used amd mobile processor line instead purpose producing less heat turn allows system fan spin slower speeds resulting cooler quieter operation hence name technology amd powernow cpu throttling technology used mobile processor line though supporting cpus like amd k6-2+ found desktops well via technologies processors use technology named longhaul powersaver transmeta version called longrun 36-processor asap 1 chip among first multi-core processor chips support completely unconstrained clock operation requiring frequencies maximum allowed including arbitrary changes frequency starts stops 167-processor asap 2 chip first multi-core processor chip enables individual processors make fully unconstrained changes clock frequencies according acpi specs c0 working state modern-day cpu divided so-called p -states performance states allow clock rate reduction -states throttling states throttle cpu actual clock rate inserting stpclk stop clock signals thus omitting duty cycles amd powertune amd zerocore power dynamic frequency scaling technologies gpus power saving technologies performance boosting technologies
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Computer architecture
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util-linux util-linux standard package distributed linux kernel organization use part linux operating system fork util-linux-ng—with ng meaning next generation —was created development stalled renamed back util-linux official version package includes following utilities utilities formerly included removed
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Operating systems
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bell–lapadula model bell–lapadula model blp state machine model used enforcing access control government military applications developed david elliott bell leonard j. lapadula subsequent strong guidance roger r. schell formalize u.s. department defense dod multilevel security mls policy model formal state transition model computer security policy describes set access control rules use security labels objects clearances subjects security labels range sensitive e.g. top secret least sensitive e.g. unclassified public bell–lapadula model example model clear distinction protection security bell–lapadula model focuses data confidentiality controlled access classified information contrast biba integrity model describes rules protection data integrity formal model entities information system divided subjects objects notion secure state defined proven state transition preserves security moving secure state secure state thereby inductively proving system satisfies security objectives model bell–lapadula model built concept state machine set allowable states computer system transition one state another state defined transition functions system state defined secure permitted access modes subjects objects accordance security policy determine whether specific access mode allowed clearance subject compared classification object precisely combination classification set compartments making security level determine subject authorized specific access mode clearance/classification scheme expressed terms lattice model defines one discretionary access control dac rule two mandatory access control mac rules three security properties transfer information high-sensitivity document lower-sensitivity document may happen bell–lapadula model via concept trusted subjects trusted subjects restricted star-property trusted subjects must shown trustworthy regard security policy security model directed toward access control characterized phrase read write compare biba model clark-wilson model chinese wall model bell-lapadula users create content security level i.e secret researchers create secret top-secret files may create public files write-down conversely users view content security level i.e secret researchers view public secret files may view top-secret files read-up bell–lapadula model explicitly defined scope treat following extensively strong star property alternative *-property subjects may write objects matching security level thus write-up operation permitted usual *-property present write-to-same operation strong star property usually discussed context multilevel database management systems motivated integrity concerns strong star property anticipated biba model shown strong integrity combination bell–lapadula model resulted reading writing single level tranquility principle bell–lapadula model states classification subject object change referenced two forms tranquility principle principle strong tranquility states security levels change normal operation system principle weak tranquility states security levels may never change way violate defined security policy weak tranquility desirable allows systems observe principle least privilege processes start low clearance level regardless owners clearance progressively accumulate higher clearance levels actions require
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Computer security
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mos technology 6507 6507 8-bit microprocessor mos technology inc version 6502 packaged 28-pin dip makes cheaper package integrate systems reduction pin count achieved reducing address bus 16 bits 13 limiting memory 64 kb 8 kb removing number pins needed certain applications a15 a13 signals interrupt lines accessible result address 8 kb memory applications time 1975 acceptable overly restrictive entire 65xx cpu family originally conceived line low-cost microprocessors small-scale embedded systems general-purpose computers certainly interactive personal computers generally exist yet 6507 6502 chips use underlying silicon layers differ final metallisation layer ties interrupt lines inactive level vulnerable generating spurious interrupts noise first three digits chip identifier part silicon layers final digit metallisation layer micro-photography 6502 6507 shows difference 6507 widely used two applications best-selling atari 2600 video game console atari 8-bit family peripherals including 850 serial parallel interface floppy disk controllers 810 1050 disk drives 2600 system limited design rom cartridge slot allowed 4 kb external memory addressed 4 kb reserved internal ram i/o chips using minimal-cost partial decoding technique causes ram peripheral device registers mirrored throughout 4 kb machines notably home computers based 650x architecture used either standard 6502 extended rather cut versions order allow memory time 6502 line becoming widely used around 1980 rom ram semiconductor memory prices fallen point 6507 longer worthwhile simplification use new designs ceased point though atari 2600 contained continued sold early 1990s discontinued january 1 1992 however late-model atari 2600 consoles redesigned highly-integrated 2600 jr units necessarily contain separate 6507 chip might integrated cpu custom asic 6507 uses 28-pin configuration 13 address pins 8 data pins seven remaining pins used power cpu timing clock reset cpu request bus wait states rdy pin read/write commands memory mmio devices cpu irq nmi pin processor rdy pin included 28-pin cut-down versions 6502 within atari 2600 rdy used synchronise cpu television video frame function essential 'racing beam method used 6502 atari television interface adaptor chip generate television video signal response specific register access tia assert rdy extend bus cycle end current video scan line
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Computer architecture
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speech manager speech manager classic mac os part operating system used convert text sound data play sound output device speaker speech manager interaction sound manager transparent software application
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Operating systems
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free open-source graphics device driver free open-source graphics device driver software stack controls computer-graphics hardware supports graphics-rendering application programming interfaces apis released free open-source software license graphics device drivers written specific hardware work within specific operating system kernel support range apis used applications access graphics hardware may also control output display display driver part graphics hardware free open-source graphics device drivers developed mesa project driver made compiler rendering api software manages access graphics hardware drivers without freely legally -available source code commonly known binary drivers binary drivers used context operating systems prone ongoing development change linux create problems end users package maintainers problems affect system stability security performance main reason independent development free open-source drivers technical documentation available understanding underlying hardware often gained clean-room reverse engineering based understanding device drivers may written legally published software license rare cases manufacturer driver source code available internet without free license means code studied altered personal use altered usually original source code freely distributed solutions bugs driver easily shared form modified versions driver therefore utility drivers significantly reduced comparison free open-source drivers objections binary-only drivers based copyright security reliability development concerns part wider campaign binary blobs openbsd lead developer theo de raadt said binary driver way fix breaks break product relies binary drivers declared end-of-life manufacturer effectively broken forever project also stated binary drivers hide bugs workarounds bugs observation somewhat vindicated flaws found binary drivers including exploitable bug nvidia 3d drivers discovered october 2006 rapid7 speculated bug existed since 2004 nvidia denied asserting issue communicated july 2006 2004 bug bug x.org nvidia driver binary drivers often work current versions open-source software almost never support development snapshots open-source software usually directly possible developer use nvidia ati proprietary drivers development snapshot x server development snapshot linux kernel features like kernel mode-setting added binary drivers anyone vendors prevents inclusion vendor lacks capacity interest linux kernel development community linus torvalds made strong statements issue binary-only modules refuse even consider tying hands binary-only module ... want people know use binary-only modules problem another kernel developer greg kroah-hartman said binary-only kernel module comply kernel license gnu general public license violates gpl due fun things like derivative works linking stuff writer computer scientist peter gutmann expressed concern digital rights management scheme microsoft windows vista operating system may limit availability documentation required write open drivers since requires operational details device kept confidential case binary drivers objections due free software philosophy software quality security concerns 2006 greg kroah-hartman concluded closed source linux kernel modules illegal simple 've misfortune talking lot different ip lawyers years topic every one 've talked agree way anyone create linux kernel module today closed source violates gpl due fun things like derivative works linking linux kernel never maintained stable in-kernel application binary interface also concerns proprietary drivers may contain backdoors like one found samsung galaxy-series modem drivers applications 3d game engine 3d computer graphics software shunt calculations cpu gpu usually use special-purpose api like opengl direct3d address hardware directly translation api calls gpu opcodes done device driver contains specialized knowledge object optimization due history rigidity proprietary driver development recent surge number community-backed device drivers desktop mobile gpus free open hardware organizations like fossi lowrisc others would also benefit development open graphical hardware standard would provide computer manufacturers hobbyists like complete royalty-free platform develop computing hardware related devices desktop computer market long dominated pc hardware using x86/x86-64 instruction set gpus available pc three major competitors nvidia amd intel main competing factor price hardware raw performance 3d computer games greatly affected efficient translation api calls gpu opcodes display driver video decoder inherent parts graphics card hardware designed assist calculations necessary decoding video streams market pc hardware dwindled seems unlikely new competitors enter market unclear much knowledge one company could gain seeing source code companies drivers mobile sector presents different situation functional blocks application-specific integrated circuit display driver 2- 3d acceleration video decoding encoding separate semiconductor intellectual property sip blocks chip since hardware devices vary substantially portable media players require display driver accelerates video decoding require 3d acceleration development goal raw 3d performance system integration power consumption 2d capabilities also approach abandons traditional method vsync updating display makes better use sample hold technology lower power consumption second quarter 2013 79.3 percent smartphones sold worldwide running version android linux kernel dominates smartphones hardware developers incentive deliver linux drivers hardware due competition incentive make drivers free open-source additional problems android-specific augmentations linux kernel accepted mainline atomic display framework adf adf feature 3.10 aosp kernels provides dma-buf-centric framework android hwcomposer hal kernel driver adf significantly overlaps drm-kms framework adf accepted mainline different set solutions addressing problems known atomic mode setting development projects libhybris harness android device drivers run linux platforms android phoronix compares free drivers source real-world testing uncommon video-game magazines report benchmark testing linux benchmarks phoronix limited scope primarily testing games available linux support automated benchmarking free open-source drivers primarily developed linux linux kernel developers third-party programming enthusiasts employees companies advanced micro devices driver five parts drm kernel-specific vesa driver generally available operating system vesa driver supports graphics cards without acceleration display resolutions limited set programmed video bios manufacturer linux graphics stack evolved detoured x window system core protocol amd proprietary driver amd catalyst radeon available microsoft windows linux formerly fglrx current version downloaded amd site linux distributions contain repositories process replaced amdgpu-pro hybrid driver combining open-source kernel x mesa multimedia drivers closed-source opengl opencl vulkan drivers derived catalyst foss drivers ati-amd gpus developed name radeon xf86-video-ati xserver-xorg-video-radeon still must load proprietary microcode gpu enable hardware acceleration radeon 3d code split six drivers according gpu technology radeon r200 r300 classic drivers r300g r600g radeonsi gallium3d drivers up-to-date feature matrix available support video coding engine unified video decoder free open-source radeon graphics device drivers reverse-engineered based documentation released amd without requirement sign non-disclosure agreement nda documentation began gradually released 2007 contrast amd main competitor graphics field nvidia proprietary driver similar amd catalyst provides support free-graphics initiatives addition providing necessary documentation amd employees contribute code support hardware features 2014 game developers conference company announced exploring strategy change re-base user-space part catalyst free open-source drm kernel module instead proprietary kernel blob components radeon graphics device driver developed core contributors interested parties worldwide 2011 r300g outperformed catalyst cases release amdgpu stack announced dri-devel mailing list april 2015 although amdgpu officially supports gcn 1.2 later graphics cards experimental support gcn 1.0 1.1 graphics cards officially supported radeon driver may enabled via kernel parameter separate libdrm libdrm-amdgpu included since libdrm 2.4.63 nvidia proprietary driver nvidia geforce driver geforce available windows xp x86-x86-64 later linux x86-x86-64-armv7-a os x 10.5 later solaris x86-x86-64 freebsd x86/x86-64 current version downloaded internet linux distributions contain repositories beta nvidia geforce driver 331.13 supports egl interface enabling support wayland conjunction driver nvidia free open-source driver named nv limited supporting 2d acceleration matthew garrett dirk hohndel others called source code confusing nvidia decided deprecate nv adding support fermi later gpus displayport march 2010 december 2009 nvidia announced would support free graphics initiatives company announced would release documentation gpus nouveau based almost entirely information gained reverse engineering project aims produce 3d acceleration x.org/wayland using gallium3d march 26 2012 nouveau drm component marked stable promoted staging area linux kernel nouveau supports tesla- earlier fermi- kepler- maxwell-based gpus nvidia employee alexandre courbot committed extensive patch set adds initial support gk20a tegra k1 nouveau june 2014 codethink reportedly ran wayland-based weston compositor linux kernel 3.15 using egl 100 open-source graphics driver stack tegra k1 feature matrix available july 2014 nouveau unable outperform nvidia geforce driver due missing re-clocking support tegra-re project working reverse-engineer nvidia vliw-based tegra series gpus predate tegra k1 nvidia distributes proprietary device drivers tegra oems part linux tegra formerly l4t development kit nvidia partner avionic design working submitting grate free open-source drivers tegra upstream mainline linux kernel april 2012 company co-founder ceo laid tegra processor roadmap ubuntu unity 2013 gpu technology conference nvidia unified memory driver nvidia-uvm.ko implements memory management pascal volta gpus linux mit licensed source code available nvidia linux driver downloads systems support nvidia-uvm.ko intel history producing commissioning open-source drivers graphics chips exception powervr-based chips 2d x.org driver called xf86-video-intel kernel mode-setting driver linux kernel use video bios switching video modes since bioses limited range modes provides reliable access supported intel video cards company worked optimizing free linux drivers performance approaching windows counterparts especially sandy bridge newer hardware performance optimizations allowed intel driver outperform proprietary windows drivers certain tasks 2011 performance enhancements may also benefit users older hardware support intel llc last level cache l4-cache crystalwell iris pro added linux kernel 3.12 company 20 30 full-time linux graphics developers matrox develops manufactures matrox mystique parhelia g200 g400 g550 although company provides free open-source drivers chipsets older g550 chipsets newer g550 supported closed-source driver s3 graphics develops s3 trio virge savage chrome supported openchrome arm holdings fabless semiconductor company licenses semiconductor intellectual property cores although known licensing arm instruction set cpus based also develop license mali series gpus january 21 2012 phoronix reported luc verhaegen driving reverse-engineering attempt aimed arm holdings mali series gpus specifically mali-200 mali-400 versions reverse-engineering project known lima presented fosdem february 4 2012 february 2 2013 verhaegen demonstrated quake iii arena timedemo mode running top lima driver may 2018 lima developer posted driver inclusion linux kernel arm indicated intention providing support graphics acceleration hardware licensed free open-source license however arm employees sent patches linux kernel support arm hdlcd display controller mali dp500 dp550 dp650 sip blocks december 2015 april 2016 imagination technologies fabless semiconductor company develops licenses semiconductor intellectual property cores among powervr gpus intel manufactured number powervr-based gpus powervr gpus widely used mobile socs company provide foss driver public documentation powervr due wide use embedded devices free software foundation put reverse-engineering powervr driver high-priority project list vivante corporation fabless semiconductor company licenses semiconductor intellectual property cores develops gcxxxx series gpus vivante proprietary closed-source linux driver consists kernel- user-space parts although kernel component open-source gpl user-space components—consisting gles 2 implementations hal library—are contain bulk driver logic wladimir j. van der laan found documented state bits command stream shader isa studying blobs work examining manipulating command-stream dumps etnaviv gallium3d driver written based documentation van der laan work inspired lima driver project produced functional-but-unoptimized gallium3d llvm driver etnaviv driver performed better vivante proprietary code benchmarks supports vivante gc400 gc800 gc1000 gc2000 gc3000 series january 2017 etnaviv added mesa opengl es 2.0 desktop opengl 2.0 support qualcomm develops adreno formerly ati imageon gpu series includes part snapdragon system phoronix slashdot reported 2012 rob clark inspired lima driver working reverse-engineering drivers adreno gpu series referenced blog post clark wrote project spare time qualcomm platform viable target working open 3d graphics employers texas instruments linaro affiliated imagination powervr arm mali cores would primary targets working command streams 2d support 3d commands seemed characteristics driver code published gitorious freedreno moved mesa 2012 working shader assembler completed demonstration versions developed texture mapping phong shading using reverse-engineered shader compiler clark demonstrated freedreno running desktop compositing xbmc media player quake iii arena fosdem february 2 2013 august 2013 kernel component freedreno msm driver accepted mainline available linux kernel 3.12 later ddx driver gained support server-managed file descriptors requiring x.org server version 1.16 july 2014 january 2016 mesa gallium3d-style driver gained support adreno 430 november year driver added support adreno 500 series freedreno used devices 96boards dragonboard 410c nexus 7 2013 traditional linux distributions like debian fedora android broadcom develops designs videocore gpu series part socs since used raspberry pi considerable interest foss driver videocore raspberry pi foundation co-operation broadcom announced october 24 2012 open-sourced arm cpu code drives gpu however announcement misleading according author reverse-engineered lima driver newly open-sourced components allowed message-passing arm cpu videocore offered little insight videocore little additional programability videocore gpu runs rtos handles processing video acceleration done rtos firmware coded proprietary gpu firmware open-sourced date since neither toolchain targeting proprietary gpu documented instruction set advantage could taken firmware source code became available videocoreiv project attempted document videocore gpus february 28 2014 raspberry pi second anniversary broadcom raspberry pi foundation announced release full documentation videocore iv graphics core complete source release graphics stack 3-clause bsd license free-license 3d graphics code committed mesa 29 august 2014 first appeared mesa 10.3 release although silicon integrated systems via technologies expressed limited interest open-source drivers released source code integrated x.org foss developers july 2008 via opened documentation products improve image linux open-source communities company failed work open-source community provide documentation working drm driver leaving expectations linux support unfulfilled january 6 2011 announced via longer interested supporting free graphics initiatives displaylink announced open-source project libdlo goal bringing support usb graphics technology linux platforms code available lgpl license integrated x.org driver displaylink graphics support available kernel udlfb driver fbdev mainline udl/drm driver march 2012 available drm-next tree non-hardware-related vendors may also assist free graphics initiatives red hat two full-time employees david airlie jérôme glisse working radeon software fedora project sponsors fedora graphics test week event launch new linux distribution versions test free graphics drivers companies provided development support include novell vmware project vga aims create low-budget open-source vga-compatible video card open graphics project aims create open-hardware gpu open graphics device v1 dual dvi-i outputs 100-pin idc connector september 2010 first 25 ogd1 boards made available grant application purchase milkymist system chip targeted embedded graphics instead desktop computers supports vga output limited vertex shader 2d texturing unit nyuzi experimental gpgpu processor includes synthesizable hardware design written system verilog instruction set emulator llvm-based c-c++ compiler software libraries tests explores parallel software hardware run terasic de2-115 field-programmable gate array board project uses fpgas generally partially completely closed-source toolchain currently couple open-source toolchains available however lattice-based fpgas notably ice40 ecp5 boards utilize project icestorm trellis respectively also larger ongoing effort create gcc fpgas called symbiflow includes aforementioned fpga toolchains well early-stage open-source toolchain xilinx-based fpgas
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Operating systems
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ibm thinkpad 770 ibm thinkpad 770 laptop designed manufactured ibm targeted business enterprise professional user last lineup thinkpad 700-series succeeding 760 high-end laptop thinkpad lineup line produced october 1997 october 1999 eventually replaced thinkpad models 390x 600x first 770s shipped either windows nt4 95 later shipped 98 pre-installed equipped ibm ultrabay ii allowing option either cd-rom floppy drive one notable feature thinkpad 770 first thinkpad available dvd-rom option addition usb port ac-3 support first 770s featured intel pentium processor running 233 mhz optional 266 mhz upgrade later models introduced intel pentium ii mobile processor 770s use certain processor socket many success installing much powerful processors generating 850 mhz although models run 1024x768 resolution later models capable 1280x1024 resolution use trident cyber 9397 graphics chips 2mb memory 770 4mb memory 770e/770ed
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Computer architecture
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cocoapods cocoapods application level dependency manager objective-c swift languages run objective-c runtime rubymotion provides standard format managing external libraries developed eloy durán fabio pelosin continue manage project help contributions many others began development august 2011 made first public release september 1 2011 cocoapods strongly inspired combination ruby projects rubygems bundler cocoapods focuses source-based distribution third party code automatic integration xcode projects cocoapods runs command line also integrated jetbrains appcode integrated development environment installs dependencies e.g libraries application specification dependencies rather manual copying source files besides installing many different sources “ master ” spec repository—containing metadata many open-source libraries—is maintained git repository hosted github cocoapods dependency resolution system powered molinillo also used large project bundler rubygems berkshelf following podfile example installs afnetworking cocoalumberjack libraries
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Operating systems
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erc32 erc32 radiation-tolerant 32-bit risc processor sparc v7 specification developed space applications developed temic acquired atmel microchip obsolete new designs used dms-r data management system russian computer russian orbital segment handles guidance navigation control onboard systems subsystems control entire iss critical tasks two versions manufactured support chip set version erc32 discontinued
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Computer architecture
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sound manager sound manager part classic apple macintosh operating system classic mac os used control production manipulation sounds macintosh computers sound manager also used parts macintosh system software produce sounds speech manager quicktime replaced core audio mac os x
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Operating systems
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microprinting microprinting production recognizable patterns characters printed medium scale requires magnification read naked eye unaided eye text may appear solid line attempts reproduce methods photocopy image scanning pantograph typically translate dotted solid line unless reproduction method identify recreate patterns scale microprint predominantly used anti-counterfeiting technique due inability easily reproduced digital methods microphotography precedes microprint microprint significantly influenced albert boni 1934 inspired friend writer editor manuel komroff showing experimentations related enlarging photographs occurred boni could reduce rather enlarge photographs technology might enable publication companies libraries access much greater quantities data minimum cost material storage space following decade boni worked develop microprint micro-opaque process pages photographed using 35mm microfilm printed cards using offset lithography process proved produce 6 9 index card stored 100 pages text normal sized publications reproducing boni began readex microprint company produce license technology also published article guide literature photography related subjects 1943 appeared supplemental 18th issue photo-lab index currency commonly exhibits highest quality smallest size microprint demands highest level counterfeiting deterrence example series 2004 united states 20 bill microprint hidden within border lower left corner obverse front side well twenty usa background bank cheques well various items value may also commonly leverage microprinting methods generally extreme size example personal bank cheques commonly place characters mp next signature line check characters represent microprint indicate signature line check features actually microprinted characters microprinted characters used anti-counterfeiting feature due difficulty reproduced prominent mp serves overt deterrent warning item employs microprint microprinting scales may readable human eye without microscopy differentiation microprinting different scales first us postage stamp incorporate microprinting american wildflower series introduced united states postal service 1992 also first commemorative stamp wholly produced offset lithography usps since issued stamps complex microprinting incorporated along dates words abbreviations usps even entire stamp designs composed microprint letters microprint smallest scale producible hand using engraved offset printing plates method intaglio printmaking digital microtext printers utilize specially designed fonts ink purpose ink used commonly micr magnetic ink character recognition toner particles may also polyester based toners styrene acrylate polymer based toners ink limited grayscale may also use color toners even specialized toners containing dyes sensitive ultraviolet infrared radiation producing fluorescence exposed radiations microprint scale capable printing methods produced digital printer regardless resolution device digital fonts designed specifically purpose microprinting pseudo-microprint fonts referred microtext xerox acclaimed developing microtext font claimed could produce characters 1/100th inch tall 1/100th inch equivalent 0.7227 points april 2015 videojet technologies released 1650 high resolution hr 1620 hr continuous inkjet cir printers said capable printing sub-pixel size characters small 0.6mm height equivalent 1.7007 points printers use 40-micron nozzle outputs 100,000 drops per second ink printers make microprinting faster easier produce digitally still reached true sub-pixel size less 1 point smallest scale microtext laser printer produce 0.5pt using gold nanoparticle inks glass substrate scientists concluded possible control production print patterns scale 2 microns printing nano-particle ink suspension heated using gaussian laser heated glass would expand due thermal conductivity gold nano-ink experiments able fuse nano-particles together tighter formation continuous conductive line experiments directly include font characters could translate usage
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Computer security
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casync casync content-addressable synchronisation linux software utility designed distribute frequently-updated file system images internet according creator lennart poettering casync inspired rsync git well tar casync aimed used internet things iot container virtual machine vm portable services operating system os images well backups home directory synchronization casync splits images variable size segments uses sha256 checksums aims work content delivery networks cdns available linux packages available ubuntu fedora arch linux similar software delivers file system images
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Computer security
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cmucam cmucam low cost computer vision device intended robotics research cmucams consist small video camera microcontroller serial interface digital cameras typically use much higher bandwidth connector cmucam lightweight interface allows accessed microcontrollers importantly on-board microprocessor supports simple image processing color blob tracking making rudimentary computer vision capable systems would previously far little power thing used past years high-school first robotics competition way letting participants robots track field elements navigate autonomously cmucam also extremely small form factor reasons relatively popular making small mobile robots original design originally made carnegie mellon university licensed various manufacturers pixy2 latest line cmucam sensors adds line tracking capability onboard light source previous cmucam5 aka original pixy sensors produced collaboration charmed labs austin tx
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Programming language topics
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spotnet spotnet protocol top usenet providing decentralized alternative usenet indexing websites nzb format general spotnet allows users create browse private 'newsservers decentralized repositories files information members share spots file sharing one another similar seeding process torrent sharing spotnet experienced tremendous growth since closure 2011 uses spotnet usenet varied one common creation home media servers several third-party applications allow automatic download categorization spots typically movies tv shows music files assist creation maintenance stored media spotnet articles placed textgroup headered using usenet client order get full experience need client compatible protocol example besides searching clients also functionality commenting spots well adding new ones index clients implement protocol without community-features spotnet xml-based format placed header usenet articles rsa signed xml contains metadata post group articles usually found .nfo file like description/genre/format also references accompanying image zipped nzb file elsewhere usenet message-id article serve link full post similar magnet uri indirectly references required articles links spread media like twitter without need central server hosting full specification protocol see spotnet wiki spotnet uses four usenet groups
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Internet protocols
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indexer programming object-oriented programming indexer allows instances particular class struct indexed like arrays form operator overloading indexers implemented get set accessors similar properties differ static fact indexers accessors take parameters get set accessors called methods using parameter list indexer declaration set accessor still implicit parameter c example usage indexer class
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Programming language topics
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warren teitelman warren teitelman 1941 – august 12 2013 american computer scientist known work programming environments invention first implementation concepts including undo redo spelling correction advising online help dwim mean warren teitelman presented novel scheme real time character recognition master thesis submitted 1966 mit rectangle character drawn divided two parts one shaded unshaded using division computer converts characters ternary vectors list composed 3 values 0 1 − following way pen enters shaded region 1 added vector unshaded region entered 0 appended thesis continued cited several decades submission started arpa principal investigator 1968 1978 responsible design development bbn lisp bolt beranek newman developing idea programming system personal computer used arpanet support users bbn lisp stanford sri usc cmu 1970 named official arpanet pioneer contributions development growth developed programmer assistant part bbn-lisp one first undo function 1971 developed program sds 940 bob kahn allowed experimentation various routing policies order see effect network traffic real time monitoring packets worked senior scientist xerox parc 1972 1984 time designed interlisp bill joy acknowledged many ideas c shell inspired copied interlisp interlisp teitelman invented dwim mean function attempted correct many common typing errors package lisp routines would correct errors automatically minor user intervention —thus making code user meant wrote program developed based upon teitelman writing style idiosyncrasies 1972 used individuals office followed users across industry 1977 bob sproull implemented first client–server window system d-lisp d-lisp used alto display device ran window manager event handler communicating interlisp running maxc pdp-10 clone system pioneered concepts overlapping windows window containing focus top receive events on-line contextual help ability cut copy paste previous commands given shell joined cedar project 1980 research strongly typed languages make sure cedar programming environment benefited lessons interlisp paper “ tour cedar ” widely published quoted even translated several languages eponymous teitelman principle says person requests feature added program add feature find way make easier programmer add feature themself teitelman also early proponent use email multi-tasking feature modern computer joined sun microsystems 1984 became sun ’ first distinguished engineer 1986 also director multi-media sun departure 1992 worked director programming environments rational software also lucid inc. caere corporation one founders startup called baystone software developed crm customer relations management software based action request system remedy corporation invented idea business rules data elements rather code embodied much business process remedy acquired baystone 1998 held position chief scientist crm business unit remedy joined google 2003
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Programming language topics
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sparcstation ipc sparcstation ipc sun 4/40 workstation sold sun microsystems based sun4c architecture enclosed lunchbox chassis sparcstation ipc incorporates fujitsu mb86901a lsi l64801 25 mhz processor sparcstation ipc limited use single-processor machine sparcstation ipc twelve simm memory slots three 4-slot groups group 4 slots filled either four 1mb simms four 4mb simms maximum 48mb sparcstation ipc hold one internal 3.5 50-pin single ended fast-narrow se scsi disk drive 3.5 1.44mb floppy disk drive also supports external scsi devices ide/atapi support modern 80 pin single connector attachment sca drives work adapter fit inside case due size adapter sparcstation ipc following interfaces sparcstation ipc comes on-board amd lance ethernet chipset 15-pin aui connector connect 10base2 10base5 10baset via appropriate transceiver openboot rom able boot network using rarp tftp like sparcstation systems ipc holds system information mac address serial number nvram battery chip dies system able boot without manual intervention keyboard entry boot parameters sparcstation ipc uses m48t02 battery-backed rtc ram chip handles real time clock boot parameter storage issue chip battery internal means entire chip must replaced battery runs sparcstation ipcs made older battery life chip substantial number systems refuse boot additionally sparcstation ipc design used reserved bits m48t02 nvram non-standard way since later revisions m48t02 chip exert stricter control bits current m48t02 store nvram data rtc function correctly system may fail auto-boot due incompatibilities modern m48t02s common modify failed nvrams cutting encapsulation patching new battery also possible replace entire encapsulation also contains 32.768 khz clock crystal following operating systems run sparcstation ipc sparcstation 1+ sun 4/65 architecturally similar housed pizza box form factor sparcstation ipx sun 4/50 later lunchbox form factor system
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Computer architecture
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wide-spectrum language wide-spectrum language wsl programming language designed simultaneously low-level high-level language—possibly non-executable specification language wide-spectrum languages designed support programming methodology based program refinement concept introduced f. l. bauer et al 1978 ... program developed step step applying correctness preserving transformations ... development process thus involves usually multiple reshapings ... since current programming languages contain concepts needed formulation different versions programmer nowadays forced use different languages avoid transition one language another seems appropriate one coherent language frame covering whole spectrum outlined i.e wide spectrum language advantage single language rather separate specification high-level low-level languages program incrementally refined intermediate versions retaining higher-level lower-level constructs bauer group developed cip-l wide-spectrum language cip-s program transformation system
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Programming language topics
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s1 core s1 core codename sirocco open source hardware microprocessor design developed simply risc based sun microsystems ultrasparc t1 s1 core licensed gnu general public license license sun chose opensparc project main goal project keep s1 core simple possible encourage developers major differences t1 s1 include
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Computer architecture
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power isa power isa instruction set architecture isa developed openpower foundation led ibm originally developed defunct power.org industry group power isa evolution powerpc isa created mergers core powerpc isa optional book e embedded applications merger two components 2006 led power.org founders ibm freescale semiconductor isa divided several categories every component defined part category category resides within certain book processors implement set categories different classes processors required implement certain categories example server class processor includes categories base server floating-point 64-bit etc processors implement base category power isa risc load/store architecture multiple sets registers instructions length 32 bits exception vle variable-length encoding subset provides higher code density low-end embedded applications instructions triadic i.e two source operands one destination single double precision ieee-754 compliant floating point operations supported including additional fused multiply–add fma decimal floating-point instructions provisions simd operations integer floating point data 16 elements single instruction support harvard cache i.e split data instruction caches well support unified caches memory operations strictly load/store allow out-of-order execution support big little-endian addressing separate categories moded per-page endianness support 32-bit 64-bit addressing different modes operation include user supervisor hypervisor power isa specification divided five parts called books specification power isa v.2.03 based former powerpc isa v.2.02 power5+ book e extension powerpc specification book included five new chapters regarding auxiliary processing units like dsps altivec extension compliant cores specification power isa v.2.04 finalized june 2007 based power isa v.2.03 includes changes primarily book iii-s part regarding virtualization hypervisor functionality logical partitioning virtual page handling compliant cores specification power isa v.2.05 released december 2007 based power isa v.2.04 includes changes primarily book book iii-s including significant enhancements decimal arithmetic category decimal floating-point book server hypervisor improvements compliant cores specification power isa v.2.06 released february 2009 revised july 2010 based power isa v.2.05 includes extensions power7 processor e500-mc core one significant new feature vector-scalar floating-point instructions vsx book iii-e also includes significant enhancement embedded specification regarding hypervisor virtualisation single multi core implementations spec revised november 2010 power isa v.2.06 revision b spec enhancing virtualization features compliant cores specification power isa v.2.07 released may 2013 based power isa v.2.06 includes major enhancements logical partition functionality transactional memory expanded performance monitoring new storage control features additions vmx vsx vector facilities vsx-2 along aes galois counter mode gcm sha-224 sha-256 sha-384 sha-512 sha-2 cryptographic extensions cyclic redundancy check crc algorithms spec revised april 2015 power isa v.2.07 b spec compliant cores specification power isa v.3.0 released november 2015 first come founding openpower foundation includes enhancements broad spectrum workloads removes server embedded categories retaining backwards compatibility adds support vsx-3 instructions new functions include 128-bit quad-precision floating-point operations random number generator hardware-assisted garbage collection hardware-enforced trusted computing spec revised march 2017 power isa v.3.0 b spec compliant cores
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Computer architecture
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windows phone windows phone previously windows phone live free online companion service windows phone mobile devices microsoft service released conjunction launch windows phone 7 october 21 2010 provides users free mobile phone back-up solution wirelessly synchronizing contacts calendar appointments photos onenote notebooks various tightly-integrated windows live services including people outlook.com calendar microsoft onedrive users access manage information stored windows phone devices via password protected online portal using microsoft account windows phone also includes find phone service facilitates tracking lost stolen phone internet messages similar phone finder services various names available families smartphones similar service windows mobile devices available microsoft phone withdrawn 2011 service updated september 27 2011 conjunction release windows phone 7.5 mango update adding support microsoft scrapbook account management features including viewing app purchase history reinstall apps windows phone store windows phone 8 apollo update windows phone also added family feature allowing parents manage child accounts running windows phone 8 february 2015 microsoft moved find phone feature windows phone site microsoft account website preparation windows 10 windows phone offers following features
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Distributed computing architecture
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pc tools company pc tools founded 2003 formerly known winguides.com software company acquired symantec 2008 new owner eventually discontinued pc tools name company headquarters australia offices luxembourg united states united kingdom ireland ukraine company previously developed distributed security optimization software mac os x microsoft windows platforms 29 november 2006 software owned pc tools downloaded 125 million times pc tools browser defender also called browser defender short browser toolbar internet explorer mozilla firefox browsers windows based computers browser defender allows safe web surfing iantivirus updated 2012 rebranded symantec norton brand pc tools iantivirus free antivirus software intel based apple macintosh computers running mac os 10.5 leopard mac os 10.6 snow leopard initially released june 2008 used detect remove malware spyware malicious exploits using signature-based heuristic detection iantivirus criticized scans macintosh viruses ignoring windows linux viruses praised speed low usage system resources pc tools internet security combination spyware doctor product firewall product anti spam product provided functionality three stand alone products single seamless product symantec longer offering product 18 may 2013 payware designed windows 8 32-/64-bit windows 7 32-/64-bit windows vista 32-/64-bit windows xp 32-bit pc tools registry mechanic first software pc tools released scanned windows registry find errors version 11 released 31 october 2011 last one pc tools spyware doctor anti-malware software spyware doctor detects malware based indicators compromise using spider technology recent version spyware doctor 9 released 31 october 2011 symantec longer offering product 18 may 2013 pc tools spyware doctor antivirus features spyware doctor added anti-virus capabilities symantec sold since 2013 v9 last one available threatexpert web site says advanced automated threat analysis system initialized atas built analyze report actions malware fully automated mode latest version beta version 1.0.1.0 1 march 2008 updates since march 2008 web site seems inactive 18 august 2008 symantec announced signing agreement acquire pc tools pc tools would maintain separate operations financial terms acquisition disclosed symantec acquired pc tools us 262,000,000 6 october 2008 symantec withdrew entire pc tools security portfolio comprising pc tools internet security spyware doctor spyware doctor antivirus 18 may 2013 pc tools sold could renewed 4 december 2013 symantec said would affect pc tools utilities products spyware doctor received pc world best buy award october 2007 issue magazine saying pc tools spyware doctor 5.0 winner outperforming competition detecting removing test set adware spyware samples spyware doctor received several editors choice awards pc magazine including one spyware doctor antivirus 5.5 2008 product also received numerous awards around globe reviews positive early versions spyware doctor 5.0 company rewrote scratch received negative commentary cnet download.com reviews justifies 3-star rating saying trial scans spyware doctor repeatedly flagged several dozen harmless cookies potential threats antispyware product tested also unable learn threat spyware doctor flagged symantec unsuccessfully sued washington resident running fake scans get people pay subscriptions pc tools registry mechanic performance toolkit norton utilities lawsuit claims company intentionally ran fake scans results real new wrinkle adware using stolen certificates disables anti-malware virus protection technical remedies available
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Computer security
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zetagrid zetagrid one time largest distributed computing project designed explore roots riemann zeta function checking one billion roots day roots zeta function particular interest mathematics since presence even single one line rest would disprove riemann hypothesis far-reaching consequences mathematics far every single one failed provide counterexample riemann hypothesis project ended november 2005 due instability hosting provider 10 first zeroes checked results analyzed project administrator stated posted american mathematical society website
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Distributed computing architecture
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list features removed windows 8 windows 8 version windows nt successor windows 7 several features present windows vista windows 7 longer present windows 8
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Operating systems
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shieldsup shieldsup online port scanning service created steve gibson gibson research corporation purpose utility alert users ports opened firewalls nat routers utility scan common file sharing ports well service ports 1-1056 user defined ports sets 64 often recommended checking port vulnerabilities scanning servers static ip addresses 4.79.142.192 4.79.142.207
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Computer security
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typescript typescript open-source programming language developed maintained microsoft strict syntactical superset javascript adds optional static typing language typescript designed development large applications transcompiles javascript typescript superset javascript existing javascript programs also valid typescript programs typescript may used develop javascript applications client-side server-side node.js execution multiple options available transcompilation either default typescript checker used babel compiler invoked convert typescript javascript typescript supports definition files contain type information existing javascript libraries much like c++ header files describe structure existing object files enables programs use values defined files statically typed typescript entities third-party header files popular libraries jquery mongodb d3.js typescript headers node.js basic modules also available allowing development node.js programs within typescript typescript compiler written typescript compiled javascript licensed apache 2.0 license typescript included first-class programming language microsoft visual studio 2013 update 2 later beside c microsoft languages official extension allows visual studio 2012 support typescript well anders hejlsberg lead architect c creator delphi turbo pascal worked development typescript typescript first made public october 2012 version 0.8 two years internal development microsoft soon announcement miguel de icaza praised language criticized lack mature ide support apart microsoft visual studio available linux os x time today support ides particularly eclipse via plug-in contributed palantir technologies various text editors including emacs vim sublime webstorm atom microsoft visual studio code also support typescript typescript 0.9 released 2013 added support generics typescript 1.0 released microsoft build developer conference 2014 visual studio 2013 update 2 provides built-in support typescript july 2014 development team announced new typescript compiler claiming 5× performance gains simultaneously source code initially hosted codeplex moved github 22 september 2016 typescript 2.0 released introduced several features including ability programmers optionally prevent variables assigned values sometimes referred billion-dollar mistake typescript originated shortcomings javascript development large-scale applications microsoft among external customers challenges dealing complex javascript code led demand custom tooling ease developing components language typescript developers sought solution would break compatibility standard cross-platform support knowing current ecmascript standard proposal promised future support class-based programming typescript based proposal led javascript compiler set syntactical language extensions superset based proposal transforms extensions regular javascript sense typescript preview expect ecmascript 2015 unique aspect proposal added typescript optional static typing enables static language analysis facilitates tooling ide support typescript adds support features classes modules arrow function syntax defined ecmascript 2015 standard typescript language extension adds features ecmascript 6 additional features include following features backported ecmascript 2015 syntactically typescript similar jscript .net another microsoft implementation ecma-262 language standard added support static typing classical object-oriented language features classes inheritance interfaces namespaces typescript strict superset ecmascript 2015 superset ecmascript 5 commonly referred javascript javascript program also valid typescript program typescript program seamlessly consume javascript default compiler targets ecmascript 5 current prevailing standard also able generate constructs used ecmascript 3 2015 typescript possible use existing javascript code incorporate popular javascript libraries call typescript-generated code javascript type declarations libraries provided source code typescript provides static typing type annotations enable type checking compile time optional ignored use regular dynamic typing javascript annotations primitive types codice_1 codice_2 codice_3 weakly- dynamically-typed structures type codice_4 type annotations exported separate declarations file make type information available typescript scripts using types already compiled javascript annotations declared existing javascript library done node.js jquery typescript compiler makes use type inference infer types types given example codice_5 method code would inferred returning codice_1 even return type annotation provided based static types codice_7 codice_8 codice_9 compiler knowledge result adding two codice_9 always codice_1 however explicitly declaring return type allows compiler verify correctness type inferred lack declarations defaults dynamic codice_4 type value codice_4 type supports operations value javascript minimal static type checking performed operations codice_4 values typescript script gets compiled option generate declaration file extension codice_15 functions interface components compiled javascript process compiler strips away function method bodies preserves signatures types exported resulting declaration file used describe exported virtual typescript types javascript library module third-party developer consumes typescript concept declaration files analogous concept header file found c/c++ type declaration files written hand existing javascript libraries done jquery node.js large collections declaration files popular javascript libraries hosted github definitelytyped typescript supports ecmascript 2015 classes integrate optional type annotations support typescript supports generic programming typescript distinguishes modules namespaces features typescript support encapsulation classes interfaces functions variables containers namespaces formerly internal modules utilize immediately-invoked function expression javascript encapsulate code whereas modules formerly external modules leverage javascript library patterns amd commonjs typescript compiler named codice_16 written typescript result compiled regular javascript executed javascript engine e.g browser compiler package comes bundled script host execute compiler also available node.js package uses node.js host also alpha version client-side compiler javascript executes typescript code fly upon page load current version compiler supports ecmascript 5 default option allowed target ecmascript 2015 make use language features exclusive version e.g generators classes despite part ecmascript 2015 standard available modes using plug-ins typescript integrated build automation tools including grunt grunt-ts apache maven typescript maven plugin gulp gulp-typescript gradle typescript gradle plugin tslint scans typescript code conformance set standards guidelines eslint standard javascript linter also provided support typescript via community plugins however eslint inability leverage typescript language services precluded certain forms semantic linting program-wide analysis early 2019 tslint team announced linter deprecation favor codice_17 joint effort tslint eslint typescript teams consolidate linting eslint umbrella improved performance community unity developer accessibility
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Programming language topics
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gprp gprp global position routing protocol internet routing protocol like ipv4 ipv6 uses spatial position determined gps host network establish routes host intended supplement ultimately replace traditional internet routing protocols requires cooperation many luminal-speed radio fiber optic hosts route packets efficient way straight line protocol consists mainly concepts ipv4 removing abstraction layer routing table ip address simpler model attempts send packets close straight line possible since change introduces physical constraints geometry network special techniques implemented overcome problems dead zones project began submission 2008 google contest ted coffman goals democratizing internet away need isps vulnerable regulation world governments interest generated idea submitted reddit.com internet community little feedback reddit nothing done concept two years january 2011 coffman decided move forward development due recent surge open platform smart phones wi-fi gps built right coffman sees perfect medium widespread implementation gprp january 2011 gprp c++ class developed tested ted coffman maintain backward-compatibility current internet framework ipv4 gateways discovered using similar techniques dns lookups many traditional ipv4 concepts considered physical forms gprp
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Internet protocols
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windows resource protection windows resource protection feature windows vista replaces windows file protection protects registry keys folders addition critical system files way protects resources differs entirely method used windows file protection windows resource protection works registering notification file changes winlogon changes detected protected system file modified file restored cached copy located compressed folder windir \system32\dllcache windows resource protection works setting discretionary access control lists dacls access control lists acls defined protected resources permission full access modify wrp-protected resources restricted processes using windows modules installer service trustedinstaller.exe administrators longer full rights system files use setupapi take ownership resource add appropriate access control entries aces modify replace trusted installer account used secure core operating system files registry keys windows resource protection protects large number file types wrp also protects several critical folders folder containing wrp-protected files may locked trusted installer able create files subfolders folder folder may partially locked enable administrators create files subfolders folder essential registry keys installed windows vista also protected key protected wrp sub-keys values protected also wrp copies files needed restart windows cache directory located windir \winsxs\backup critical files needed restart windows copied cache directory unlike windows file protection cached entire set protected file types dllcache folder size cache directory list files copied cache modified windows resource protection applies stricter measures protect files result windows file protection available windows vista order replace single protected file windows file protection disabled completely windows resource protection works per-item basis setting acls therefore taking ownership single item particular item replaced items remain protected system file checker also integrated wrp windows vista sfc.exe used check specific folder paths including windows folder boot folder
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Operating systems
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ignitefusion ignitefusion freeware cfml script engine runs cfm script files similar perl php script engines ignitefusion script engine runs executable server cfml engines include adobe coldfusion new atlanta bluedragon railo lucee coral web builder coldfusion
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Programming language topics
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bitchute bitchute video hosting service uses peer-to-peer webtorrent technology founded way avoid content rules enforced platforms like youtube creators banned channels demonetized barred receiving advertising revenue youtube migrated bitchute platform accommodates far-right individuals conspiracy theorists southern poverty law center accuses site hosting hate-fueled material company launched ray vahey january 2017 based peer-to-peer webtorrent system javascript torrenting program run web browser users watch video also seed bitchute rely advertising users send payments video creators directly november 2018 bitchute banned paypal alex jones proud boys tommy robinson several anti-fascists also banned time january 2019 bitchute announced post gab would move domains epik small domain registrar known accepting registration websites host far-right content bitchute accommodated far-right groups individuals criticized southern poverty law center hosting hate-fueled material conflict youtube right-wing video creators inclusion hate speech misinformation videos youtube responded cases banning creators blocking videos channel demonetization vahey described bitchute alternative option avoid bannings demonetization tweaking algorithms send certain content obscurity views increased levels censorship established services like youtube users groups banned youtube migrated bitchute including alex jones far-right conspiracy theory channel infowars prominent far-right alt-right video creators banned youtube cross-post videos bitchute including lauren southern stefan molyneux millennial woes paul joseph watson
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Distributed computing architecture
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invite death invite death type attack voip-system involves sending malformed otherwise malicious sip invite request telephony server resulting crash server telephony usually critical application damage causes significant disruption users poses tremendous acceptance problems voip kinds attacks necessarily affect sip-based systems implementations vulnerabilities voip area affected dos attack also transported messages invite example december 2007 report vulnerability bye message bye bye using obsolete header name also however sending invite packets popular way attacking telephony systems name reference ping death attack caused serious trouble 1995-1997 invite death vulnerability found february 16 2009 vulnerability allows attacker crash server causing remote denial service dos sending single malformed packet impersonator using malformed packet overflow specific string buffers add large number token characters modify fields illegal fashion result server tricked undefined state lead call processing delays unauthorized access complete denial service problem specifically exists opensbc version 1.1.5-25 handling “ via ” field maliciously crafted sip packet invite death packet also used find new vulnerability patched opensbc server network dialog minimization popular open source-based asterisk pbx security advisories cover signaling-related problems also problems protocols resolution problems may malformed sdp attachments codex numbers valid range obsolete headers “ also ” invite death specifically problem operators run servers public internet sip allows usage udp packets easy attacker spoof source address internet send invite death untraceable locations sending kinds requests periodically attackers completely interrupt telephony service choice service provider upgrade systems attack crash system anymore large number voip vulnerabilities exist ip phones dos attacks voip phones less critical attacks central devices like ip-pbx usually endpoint affected
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Computer security
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kiss cryptanalysis cryptanalysis kiss pair identical messages sent using different ciphers one broken term used bletchley park world war ii deciphered message breakable system provided crib piece known plaintext could used read unbroken messages one example messages read german meteorological cipher could used provide cribs reading difficult 4-wheel naval enigma cipher
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Computer security
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data system data system term used refer organized collection symbols processes may used operate symbols organised collection symbols symbol-manipulating operations considered data system hence human-speech analysed level phonemes considered data system incan artefact khipu image stored pixels data system defined terms data model bears resemblance idea physical symbol system symbols within data systems may persistent hence sounds human speech non-persistent symbols decay rapidly air contrast pixels stored peripheral storage device persistent symbols education data system computer system aims provide educators student data help solve educational problems examples data systems include student information systems siss assessment systems instructional management systems imss data-warehousing systems distinctions different types data systems blurring separate systems begin serve functions data systems present data educators over-the-counter data format embed labels supplemental documentation help system make key package/display content decisions improve accuracy data system users ’ data analyses
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Databases
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nobunaga ambition games franchise released nintendo entertainment system game boy mega drive 3do super nes playstation sega saturn playstation 2 playstation 3 xbox 360 wii playstation portable playstation vita playstation 4 nintendo switch title also released macintosh well msx amiga ms-dos march 2018 series shipped 10 million copies worldwide player may choose four campaign scenarios including battle east beginning 1560 daimyo power struggles 1560 ambition untamed 1571 road towards unification 1582 scenario player must allocate resources raise capable military force provide productive economy support military civilian expansion support peasants order sustain respect loyalty gameplay taken turns turn map view corresponding season turn battle corresponding day player may achieve victory numerous means among forcing enemy retreat destroying enemy command unit outlasting invading force prolonging battle opposing force exhausted supplies player make many choices campaign according evan brooks computer gaming world one may transfer soldiers fiefs go war increase taxes causes decrease peasant loyalty may lead rebellion transfer rice gold another fief raise level flood control decreases productivity make non-aggression pact arrange marriage cultivate increases productivity decreases peasant loyalty use merchant buy/sell rice borrow funds purchase weapons recruit military soldiers ninja train army increases fighting efficiency spy rival expand town increases taxes collected decreases peasant loyalty give food/rice peasants/soldiers raise morale steal peasants rival daimyos allocate military strength recuperate even daimyo get sick turn controlled fief computer administration pass turn sony playstation vita released asia traditional chinese versions physically copies versions without power kit top japanese versions released nobunaga ambition series garnered several awards years according koei website various releases series log-in magazine bhs prize minister post telecommunications prize nikkei bp 12th 13th 14th annual best pc software awards cd-rom fan fan year 2001 grand prize north america released five years japanese release critical reception also positive game positively reviewed computer gaming world reviewer evan brooks gave four stars five introduced game detailed economic diplomatic political military simulation unification japan sixteenth century praised graphics among best reviewer ever seen ibm 5x10 hex map battles noted used role-playing game elements including assigning various statistics selected persona time system turn represents year daimyo ages eventually dies old age multiplayer option stated thoroughly enjoyed nobunaga ambition concluded highly recommended rating compute similarly praised ibm pc version calling one best strategic war games ever designed personal computer citing game play user interface documentation console versions lukewarm reception reviewing snes version gamepro praised control interface combat system opined game essentially offers nothing set apart koei previous historical simulators magazine rated genesis version similarly saying like koei games nobunaga easy-to-use detailed menu-driven interface activates load complex commands 1996 next generation listed series collectively number 34 top 100 games time commenting lead designer shou kibasawa tactical genius realizes domestic military strategies interconnected fielding armies accomplished building infrastructure support result nobunaga ambition boasts level strategic complexity series come close matching
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Computer architecture
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netnewswire netnewswire news aggregator macos netnewswire developed brent sheila simmons company ranchero software introduced july 12 2002 netnewswire lite free version missing advanced features commercial version introduced weeks later version 1.0 released february 11 2003 version 2.0 released may 2005 time included custom feed views custom downloading opening podcasts synchronization feeds feed status computers bloglines support built-in tabbed browser october 2005 newsgator bought netnewswire bringing newsgator online rss synchronization service mac brent simmons hired newsgator continue developing software netnewswire 3.0 released june 5 2007 version added spotlight indexing news items integration ical iphoto address book voodoopad growl support new user interface performance enhancements application originally shareware became free release netnewswire 3.1 january 10 2008 netnewswire lite discontinued time netnewswire 3.2 moved advertisement-supported model option purchase application remove ads ios version netnewswire support iphone ipod touch later ipad released first day app store includes syncing unread articles desktop version netnewswire lite 4.0 introduced march 3 2011 mac app store misses several advanced features included netnewswire 3.2 includes completely rewritten code base future used ios versions app netnewswire 4.0 shareware june 3 2011 acquisition netnewswire black pixel announced two years development apparently stalled gap updates 2011 release version 4 open beta june 24 2013 netnewswire 4.0 announced released open beta black pixel announcement also brought news product would commercial product free component though beta would free use final release final release netnewswire 4.0 occurred september 3 2015 august 31 2018 black pixel announced returned netnewswire intellectual property brent simmons september 1 2018 brent simmons released netnewswire 5.0d1 renamed version open source mac rss reader netnewswire well regarded many users reviewers according feedburner netnewswire popular desktop newsreader platforms 2005 software received macworld editor choice award 2003 2005 maintained 4.8 five stars rating among reviewers versiontracker cnet ars technica called netnewswire built-in browser hands-down best mac newsreader walter mossberg technology columnist wall street journal said netnewswire favorite mac
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Internet protocols
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remote shell remote shell rsh command line computer program execute shell commands another user another computer across computer network remote system rsh connects runs rsh daemon rshd daemon typically uses well-known transmission control protocol tcp port number 514 rsh originated part bsd unix operating system along rcp part rlogin package 4.2bsd 1983. rsh since ported operating systems rsh command name another common unix utility restricted shell first appeared pwb/unix system v release 4 restricted shell often located /usr/bin/rsh described rlogin article rsh protocol secure network use sends unencrypted information network among reasons implementations also authenticate sending unencrypted passwords network rsh largely replaced secure shell ssh program even local networks example rsh use following executes command mkdir testdir user remoteuser computer host.example.com running unix-like system command finished rsh terminates command specified rsh log remote system using rlogin network location remote computer looked using domain name system
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Internet protocols
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list internet chess servers list notable internet chess servers
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Internet protocols
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duff device c programming language duff device way manually implementing loop unrolling interleaving two syntactic constructs c loop switch statement discovery credited tom duff november 1983 duff working lucasfilm used speed real-time animation program loop unrolling attempts reduce overhead conditional branching needed check whether loop done executing batch loop bodies per iteration handle cases number iterations divisible unrolled-loop increments common technique among assembly language programmers jump directly middle unrolled loop body handle remainder duff implemented technique c using c case label fall-through feature jump unrolled body duff problem copy 16-bit units shorts c implementations array memory-mapped output register denoted c pointer original code k r c looked follows code assumes initial pointer incremented would required memory-to-memory copy always divisible eight unrolling loop eight-fold would produce following duff realized handle cases divisible eight assembly programmer technique jumping loop body could implemented interlacing structures switch statement loop putting switch labels points loop body correspond remainder duff device similarly applied size unrolled loop eight example based algorithm used widely programmers coding assembly minimizing number tests branches copy duff device appears place implemented c. device valid c virtue two attributes c leads jargon file calls dramatic use yet seen fall c c default fall-through case statements long one controversial features duff said code forms sort argument debate 'm sure whether basic idea loop unrolling number instructions executed loop reduced reducing number loop tests sometimes reducing amount time spent loop example case loop single instruction block code loop test typically performed every iteration loop every time instruction executed instead eight copies instruction placed loop test performed every eight iterations may gain time avoiding seven tests however handles multiple eight iterations requiring something else handle remainder iterations duff device provides solution first performing remainder iterations followed iterating many times necessary multiple eight similar instructions determine number remainder iterations code first calculates total number iterations modulo eight according remainder program execution jump codice_1 statement followed exactly number iterations needed done everything straightforward code continues iterations groups eight instructions become possible since remaining number iterations multiple eight duff device provides compact loop unrolling using case keyword inside outside loop unusual contents case statement traditionally thought block code nested inside case statement reader would typically expect end next case statement according specifications c language necessary indeed case statements appear anywhere inside switch code block depth program execution simply jump next statement wherever may many compilers optimize switch jump table would done assembly implementation primary increase speed versus simple straightforward loop comes loop unwinding reduces number performed branches computationally expensive due need flushand hence stallthe instruction pipeline codice_2 statement used handle remainder data evenly divisible number operations unrolled example eight byte moves unrolled codice_2 handles extra 1–7 bytes automatically automatic handling remainder may best solution systems compilers cases two loops may actually faster one loop unrolled main copy second loop handle remainder problem appears come ability compiler correctly optimize device may also interfere pipelining branch prediction architectures numerous instances duff device removed xfree86 server version 4.0 improvement performance noticeable reduction size executable. ref name= lkml-0008.2/0171 /ref therefore considering code program optimization may worth running benchmarks verify actually fastest code target architecture target optimization level target compiler well weighing risk optimized code later used different platforms fastest code purpose memory-to-memory copies mentioned original use duff device standard c library provides function codice_4 perform worse memory-to-memory copy version code may contain architecture-specific optimizations make significantly faster
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Programming language topics
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dialogos dialogos graphical programming environment design computer system converse voice user dialogs clicked together flowchart dialogos includes bindings control lego mindstorms robots voice bindings sql databases well generic plugin architecture integrate types backends dialogos used computer science courses schools universities teach programming introduce beginners basic principles human/computer interaction dialog design also used research systems dialogos initially developed commercially clt sprachtechnologie gmbh liquidation 2017 rights acquired saarland university software released open-source dialogos control lego mindstorms nxt series uses sensor-nodes obtain values following sensors
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Computational linguistics
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radhia cousot radhia cousot 6 august 1947 – 1 may 2014 french computer scientist known inventing abstract interpretation radhia cousot born 6 august 1947 sakiet sidi youssef tunisia survived went sousse algiers polytechnic school algiers ranked 1st woman specialized mathematical optimization integer linear programming supported unesco fellowship 1972–1975 obtained master degree computer science joseph fourier university grenoble 1972 obtained mathematics nancy 1985 supervision radhia cousot appointed associate research scientist imag laboratory joseph fourier university grenoble 1975–1979 1980 centre national de la recherche scientifique junior research scientist research scientist senior research scientist senior research scientist emerita computer science laboratories henri poincaré university nancy 1980–1983 university paris-sud orsay 1984–1988 école polytechnique 1989–2008 1991 headed research team “ semantics proof abstract interpretation ” école normale supérieure 2006–2014 together husband patrick radhia cousot originator abstract interpretation influential technique formal methods abstract interpretation based three main ideas thesis radhia cousot advanced semantics proof static analysis methods concurrent parallel programs radhia cousot origin contacts airbus january 1999 lead development astrée run-time error analyzer 2001 onwards tool sound static program analysis embedded control/command software developed école normale supérieure distributed absint gmbh german software company specialized static analysis astrée used transportation space medical software industries patrick cousot received acm sigplan programming languages achievement award 2013 ieee computer society ieee computer society harlan d. mills award 2014 “ invention ‘ abstract interpretation ’ development tool support practical application ” since september 2014 radhia cousot best young researcher paper award attributed annually program chair behalf program committee static analysis symposia sas
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Programming language topics
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packet sender typical applications packet sender include packet sender comes built-in tcp udp ssl server multiple ports user specifies remains running listening packets sending packets version v6.2.3 packet sender supports following features packet sender mobile also open source available ios android mit license written xamarin core features desktop packet sender send receive tcp udp cloud
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Computer security
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shablamm nitro-vlb shablamm nitro-vlb computer system used qed r4600 microprocessor implemented vesa local bus peripheral card designed function connected host computer system using intel i486 nitro-vlb conformed arc standard produced marketed shablamm computer upgrade card accelerating windows nt nitro-vlb notable various unique characteristics among personal computer accessories example although system marketed upgrade computers already using 486 processor nitro-vlb fact entirely different architecture specifically mips architecture ia32-based 486 parasitic symbiotic coprocessor nitro-vlb designed co-opt host 486 processor running used four megabytes host 486 motherboard system memory dma buffer although nitro-vlb required separate dram main memory addition memory installed host 486 motherboard type parasite host upgrade card configuration entire motherboard processor implemented expansion card designed connect host motherboard expansion slot configurations rare among computer systems designed run microsoft windows nitro-vlb qed r4600 processor running 100 mhz rated 73.8 specint92 63 specfp92 similar figures first-generation pentium running 66 mhz faster costlier versions designed run 133 mhz 150 mhz initially nitro-vlb system priced 1,095 100 mhz card main memory 1,995 100 mhz card 16 mb main memory copy windows nt 2,595 150 mhz card
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Computer architecture
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compaq portable compaq portable early portable computer one first 100 ibm pc compatible systems compaq computer corporation first product followed others compaq portable series later compaq deskpro series compaq portable announced november 1982 first shipped march 1983 priced us 2,995 single half-height 5¼ 360 kb diskette drive 3,590 dual full-height diskette drives compaq portable folded luggable case size portable sewing machine computer early all-in-one becoming available two years cp/m-based osborne 1 kaypro ii year ms-dos-based entirely ibm pc compatible dynalogic hyperion year commodore sx-64 design influenced xerox notetaker prototype computer developed xerox parc 1976 ibm responded compaq portable ibm portable developed sales force needed comparable computer sell compaq compaq sold 53,000 units first year total 111 million revenue american business record second year revenue hit 329 million setting industry record third year revenue 503.9 million another us business record compaq portable basically hardware ibm pc transplanted luggable case specifically designed fit carry-on luggage airplane compaq bios instead ibm portables shipped 128k ram 1-2 double-sided double-density 360 kb disk drives machine uses unique hybrid ibm mda cga supports latter graphics modes contains cards text fonts rom using internal monochrome monitor 9x14 font used 8x8 one external monitor used user switches internal external monitors pressing user use ibm video standards graphics capabilities high-resolution text larger external monitor graphics hardware also used original compaq deskpro desktop computer despite success compaq portable flaws hardware foam pads keyboards used make contact circuit board pressed would eventually disintegrate time due wear normal use natural wear would render keyboard useless would require full replacement foam pad affected crt display also suffered low refresh rate heavy ghosting compaq efforts possible ibm used mostly off-the-shelf parts pc published full technical documentation microsoft kept right license ms-dos computer manufacturers difficulty bios contained ibm copyrighted code compaq solved problem producing clean room workalike performed documented functions ibm pc bios completely written scratch although numerous companies soon also began selling pc compatibles matched compaq remarkable achievement essentially-complete software compatibility ibm pc typically reaching 95 compatibility best phoenix technologies others began selling similarly reverse-engineered bioss open market first portables used compaq dos 1.13 essentially identical pc dos 1.10 except standalone basic require ibm pc rom cassette basic superseded months dos 2.00 added hard disk support advanced features aside using dos 1.x initial portables similar 16k-64k models ibm pc bios limited 544k ram support expansion roms thus making unable use ega/vga cards hard disks similar hardware dos 2.x ibm xt came compaq upgraded bios although portable offered factory hard disk users commonly installed starting 1984 compaq began offering hard disk-equipped version portable plus 1985 compaq introduced portable 286 replaced compact portable ii redesigned case within months byte wrote testing prototype compaq portable looks like sure winner portability cost high degree compatibility ibm pc reviewer tested ibm pc dos cp/m-86 wordstar supercalc several software packages found worked except one game pc magazine also rated compaq portable highly compatibility reporting tested applications ran praised rugged hardware design sharp display concluded certainly worth consideration anyone seeking run ibm pc software without ibm pc machine first series compaq portable machines
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Computer architecture
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tiobe index tiobe programming community index measure popularity programming languages created maintained tiobe company based eindhoven netherlands tiobe stands importance earnest title comedy play oscar wilde first performed 1895 index calculated number search engine results queries containing name language index covers searches google google blogs msn yahoo baidu wikipedia youtube index updated month current information free long term statistics many years observation sale index authors think may valuable accepting various strategic decisions tiobe focuses turing complete languages provide information popularity instance html according site tiobe index best programming language language lines code written however site claim number web pages may reflect number skilled engineers courses jobs worldwide tiobe index sensitive ranking policy search engines based instance april 2004 google performed cleanup action get rid unfair attempts promote search rank consequence large drop languages java c++ yet languages stayed top table avoid fluctuations tiobe uses multiple search engines august 2016 c reached lowest ratings score since index launched still second popular language java since languages substantially gone still maintaining top two positions tiobe programming language year award goes language biggest annual popularity gain index e.g. go programming language year 2016 pierre carbonnelle challenges tiobe naming objective-c programming language year 2012 arguing may many objective-c pages web rarely read proposes pypl index instead based google trends data shows popularity trends since 2004 worldwide 5 different countries tim bunce author perl dbi critical index methods ranking
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Programming language topics
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modula-2+ modula-2+ programming language descended modula-2 language developed dec systems research center src acorn computers ltd research centre palo alto california modula-2+ modula-2 exceptions threads group developed language led p. rovner 1984 main differences modula-2 modula-2+ used develop topaz operating system dec src firefly multiprocessor topaz applications written modula-2+ programming language grew along development system also build programming environment acorn research center arc language completely disappeared great influence programming languages modula-3 original developers modula-2+ bought acorn olivetti digital equipment corporation compaq compaq bought hewlett-packard olivetti also sold olivetti research center olivetti software technology laboratory bought acorn arc oracle later absorbed dec made src-reports available public
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Programming language topics
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appleshare appleshare product apple computer implemented various network services main purpose act file server using afp protocol network services implemented later versions appleshare included print server using printer access protocol pap web server electronic mail server smb cifs server support file sharing microsoft windows clients earlier versions appleshare supported appletalk network transport protocol later versions sold name appleshare ip allowed use tcp/ip protocol stack used modern networks appleshare provided three different protocols application-layer services appleshare file server appleshare print server appleshare pc appleshare would operate physical network medium early installations used mainly localtalk recently ethernet physical medium could used could directly indirectly connected appleshare server system equivalent third party server products include open-source netatalk suite unix-like systems services macintosh microsoft windows nt 2000 versions mac os system 7 onwards included personal file sharing limited afp implementation obvious difference personal file sharing appleshare former supports small number concurrent remote users versions mac os capable acting client appleshare server via afp later smb appletalk tcp/ip protocols although recent versions macos gradually removed support appletalk favor standard tcp/ip third-party vendors created client software pc maclan discontinued dave implement client functionality windows systems developers offered server software provided similar functionality windows servers grouplogic extremez-ip cyan software macserverip netatalk linux later versions appleshare also implemented smb cifs protocols native file sharing protocols windows machines apple discontinued appleshare product line following release macos server provides equivalent functionality appleshare ip support 3.0.1 macintosh
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Computer file systems
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minix file system minix file system native file system minix operating system minix written scratch andrew s. tanenbaum 1980s unix-like operating system whose source code could used freely education minix file system designed use minix copies basic structure unix file system avoids complex features interest keeping source code clean clear simple meet overall goal minix useful teaching aid linus torvalds first started writing linux operating system kernel 1991 working machine running minix adopted file system layout soon proved problematic since minix restricted filename lengths fourteen characters thirty later versions limited partitions 64 megabytes file system designed teaching purposes performance extended file system ext april 1992 developed replace minix second version ext2 linux obtained commercial-grade file system 1994 minix file system scarcely use among linux users minix file system six components
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Computer file systems
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amiga unix amiga unix informally known amix discontinued full port unix system v release 4 operating system developed commodore-amiga inc. 1990 amiga computer family alternative amigaos shipped default bundled amiga 3000ux commodore unix one first ports svr4 68k architecture amiga a3000ux model even got attention sun microsystems though ultimately nothing came unlike apple a/ux amiga unix contained compatibility layer allow amigaos applications run unix native applications available take advantage amiga significant multimedia capabilities failed find niche quite-competitive unix workstation market early 1990s a3000ux price tag 4,998 also attractive compared unix workstations time nextstation 5,000 base system full api many times number applications available sgi indigo starting 8,000 personal decstation 5000 model 25 starting 5,000 sun hp ibm similarly priced systems a3000ux 68030 noticeably underpowered compared risc-based competitors unlike typical commercial unix distributions time amiga unix included source code vendor-specific enhancements platform-dependent device drivers essentially part n't owned allowing interested users study enhance parts system however source code subject license terms binary part system free software amiga unix also incorporated depended upon many open source components gnu c compiler x window system included source code like many proprietary unix variants small market shares amiga unix vanished mists computer history vendor commodore went business today unix-like operating systems minix netbsd linux available amiga platform
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Operating systems
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zentralblatt math zbmath formerly zentralblatt math major international reviewing service providing reviews abstracts articles pure applied mathematics produced berlin office fiz karlsruhe – leibniz institute information infrastructure gmbh editors european mathematical society ems fiz karlsruhe heidelberg academy sciences zbmath distributed springer science+business media uses mathematics subject classification codes organising reviews topic mathematicians richard courant otto neugebauer harald bohr together publisher ferdinand springer took initiative foundation new mathematical reviewing journal harald bohr brother famous physicist niels bohr worked copenhagen courant neugebauer professors university göttingen time göttingen considered one central places mathematical research appointed mathematicians like david hilbert hermann minkowski carl runge felix klein great organiser mathematics physics göttingen dream building independent mathematical institute spacious rich reference library realised four years death credit achievement particularly due richard courant convinced rockefeller foundation donate large amount money construction service founded 1931 otto neugebauer zentralblatt für mathematik und ihre grenzgebiete contained bibliographical data recently published mathematical articles book together peer reviews done mathematicians world preface first volume intentions zentralblatt formulated follows zentralblatt für mathematik und ihre grenzgebiete aims publish — efficient reliable manner — reviews entire world literature mathematics related areas issues initially appearing monthly name suggests main focus journal mathematics however areas closely related mathematics treated seriously so-called pure mathematics zentralblatt jahrbuch essence agenda zentralblatt published several issues per year issue published soon sufficiently many reviews available frequency three four weeks late 1930s began rejecting jewish reviewers number reviewers england united states resigned protest helped start mathematical reviews competing publication electronic form provided name inka-math acronym information system karlsruhe-database mathematics since least 1980 name later shortened zentralblatt math zentralblatt math abstracting service provides reviews brief accounts contents current articles conference papers books publications mathematics applications related areas reviews predominantly english occasional entries german french reviewers volunteers invited editors based published work recommendation existing reviewer zentralblatt math provided web printed form service reviews 2,300 journals serials worldwide well books conference proceedings zentralblatt math edited european mathematical society fiz karlsruhe heidelberg academy sciences zentralblatt database also incorporates 200,000 entries earlier similar publication jahrbuch über die fortschritte der mathematik jfm 1868 1942 added 2003 access subscription currently first three records search provided free without subscription
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Databases
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rambo iii video game rambo iii series video games based film rambo iii 1988 like film main plots center former vietnam-era green beret john rambo recalled duty one last time rescue former commander colonel sam trautman captured covert operation mission soviet union-controlled afghanistan console versions developed published sega pc dos version developed ocean published taito ocean developed published rest atari st amiga spectrum c64 amstrad taito also released arcade game based film sega master system version released 1988 light gun rail shooter lines operation wolf light phaser supported makes game also unique unlike nes sega master system port ironically port operation wolf long player ammunition game light phaser trigger held supply full automatic shooting ammunition runs though player pull trigger time shooting sega mega drive version released 1989 follows rambo six missions one various objectives besides finding exit level missions prisoners must freed enemy ammunition supplies destroyed rambo controlled overhead perspective several weapons disposal besides machine gun never runs ammo use knife close range kills set timed bombs use famous longbow explosive arrows ammunition bow bombs limited collected dead enemies rambo hand vulnerable killed one hit missions perspective switches view behind rambo additional boss fights take place soviet tanks helicopters must destroyed using crossbow aiming bow rambo move otherwise hide behind rocks obstacles enemy fire reminiscent taito arcade game name also player firing screen helicopters jeeps instead single segment stage whole game played perspective taito released rail shooter based film well features rambo sam trautman playable characters zx spectrum atari st commodore amiga commodore 64 amstrad cpc versions three missions varied console version drastically terms gameplay graphics music
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Computer architecture
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kyvos kyvos big data business intelligence software developed american privately held company named kyvos insights company headquartered los gatos california founded praveen kankariya ceo impetus technologies 2012 software provides olap-based multidimensional analysis big data cloud platforms launched officially june 2015 december year company listed among 10 coolest big data startups 2015 crn magazine software uses olap technology enable business intelligence big data platforms report published forrester research 2016 evaluated several native hadoop business intelligence bi platforms 22 parameters kyvos referred platform gave new life olap bringing hadoop per report kyvos enables analysis hadoop based olap schemas aggregations predefined drill-down paths pre-calculates aggregates multiple levels dimensional hierarchies improve query response times compared sql-on-hadoop platforms users analyze data kyvos visualization tool using bi platforms kyvos originally built hadoop later added support cloud platforms amazon web services aws google cloud microsoft azure initially supported mdx queries integrated data visualization tools excel tableau 2017 kyvos 4.0 added support sql connectivity extending integration bi tools business objects cognos microstrategy power bi qlik late 2018 version 5 software built specifically cloud elastic olap provide cloud native way scale changing data workloads
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Distributed computing architecture
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rocksdb rocksdb high performance embedded database key-value data fork leveldb facebook optimized exploit many central processing unit cpu cores make efficient use fast storage solid-state drives ssd input/output i/o bound workloads based log-structured merge-tree lsm tree data structure written c++ provides official application programming interface api language bindings c++ c java alongside many third-party language bindings rocksdb open-source software originally released bsd 3-clause license however july 2017 project migrated dual license apache 2.0 gplv2 license possibly response apache software foundation blacklist previous bsd+patents license clause rocksdb used production systems various web-scale enterprises including facebook yahoo linkedin rocksdb like leveldb stores keys values arbitrary byte arrays data sorted byte-wise key providing custom comparator rocksdb provides features leveldb plus others list rocksdb features leveldb rocksdb sql database although myrocks combines rocksdb mysql like nosql dbm stores relational data model support sql queries also direct support secondary indexes however user may build internally using column families externally applications use rocksdb library provide server command-line interface rocksdb created facebook dhruba borthakur april 2012 fork leveldb initial stated goal improving performance server workloads embeddable database rocksdb used storage engine within larger database management system dbms example cockroachdb uses rocksdb storage engine mostly transactional workloads rockset uses rocksdb mostly analytical data processing shows rocksdb used storage engine online_transaction_processing online_analytical_processing following projects started replace offer alternative storage engines already-established database systems rocksdb arangodb added rocksdb previous storage engine mmfiles starting arangodb 3.4 rocksdb default storage engine arangodb mongorocks project provides storage module mongodb storage engine rocksdb related program rocks strata tool written go allows managing incremental backups mongodb rocksdb used storage engine myrocks project creates new rocksdb based storage engine mysql in-depth details myrocks presented percona live 2016 mariadb creates myrocks forked rocksdb storage engine since mariadb 10.2.5 cassandra rocksdb improve performance apache cassandra significantly 3-4 times faster general 100 times faster use-cases instagram team facebook developed open-sourced code along benchmarks performance results following database systems applications chosen use rocksdb embedded storage engine ceph bluestore storage layer uses rocksdb metadata management osd devices logdevice logsdb built atop rocksdb facktory background job system uses rocksdb storage ssdb-rocks project uses rocksdb storage engine ssdb nosql database tidb project uses rocksdb storage engine rockset service used operational data analytics uses rocksdb storage engine apache flink uses rocksdb store checkpoints third-party programming language bindings available rocksdb include
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Databases
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absolute openbsd absolute openbsd unix practical paranoid comprehensive guide openbsd operating system michael w. lucas author absolute freebsd cisco routers desperate book assumes basic knowledge design commands user permissions unix-like operating systems book contains troubleshooting tips background information system commands examples assist learning first edition released june 2003 information book became outdated openbsd 3.4 released months later second edition released april 2013 peter n. m. hansteen author book pf technical reviewer
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Operating systems
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virusbuster virusbuster ltd. one hungarian it-security software vendors fully hungarian owned company develops products – brand name virusbuster – hungarian international market protect users computers malware programs various it-security threats august 2012 virusbuster ltd. announced cancellation anti-virus products https //web.archive.org/web/20120810040828/http //www.virusbuster.hu/termekek/termekhirek/virusbuster-termekek-kivezetese-0 1 nowiki /nowiki virusbuster shut entire developing malware analyst team joined sophos legal trade predecessor firm began develop antiviral products end 1980s software named virsec came time well known vendors appeared similar solutions 1992 virsec renamed virusbuster later official formation firm name became name company well 1997 official foundation virusbuster ltd took place next years company produced mainly anti-viral products hungarian market primarily governmental sector 2000 year international opening virusbuster products began participating international test summer year firm began build international partnerships also 2000 2000 2003 virusbuster steadily extended portfolio developments manifested increasing number protected platforms systems also new layered security products target new threats management system firm security products achievements company could offer effective security solutions every organizational customers 2001 first year international foreigner company – australian leprechaun – licensed virusbuster antiviral technology integrate security products 2003 2006 virusbuster strengthened eastern european worldwide market positions antiviral engine company became independent product thus integrated several firms security solutions years virusbuster appeared american market august 2012 agnitum pc security expert manufacturer outpost range security products announced acquisition antivirus technology infrastructure long-term partner virusbuster october 2012 owner virusbuster made decision products services going removed market entire developing malware analyst team joined sophos virusbuster provided customized multi-level virus protection solutions – individual home size organizational – customer groups furthermore virusbuster internet security suite provides full it-protection home users company security products cover important operating systems including workstation server platforms. br according independent it-professionals international test labs products company pretty good solutions aspects speed efficiency security analysts said virusbuster user interface rather traditional according others almost old fashioned gui provides better transparency easier manageability according general opinions products company cover important business platforms protect every it-security threats beside retail solutions different market segments also important company antiviral engine became independent product several international companies licensing virusbuster technology integrated products outpost security suite kaspersky microsoft proteatools beside companies mentioned important strategic partners company different international collaboration projects beginning 2008 virusbuster security researchers found computer malware using name company trick users worm spreading attachment infected e-mails name virusbuster.personal.v3.20.regfile.by.arcade.exe analysis classification virus difficult task since worm variant well known rather old bagle malware family. br first example name misuse virusburst fake antispyware program 2006 name similar virusbusters name – probably accidentally another case similarity perfect br also 2008 29a virus-writing group announced shut one prominent members 29a team also used 'virusbuster alias
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Computer security
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dana scott dana stewart scott born october 11 1932 emeritus hillman university professor computer science philosophy mathematical logic carnegie mellon university retired lives berkeley california research career involved computer science mathematics philosophy work automata theory earned acm turing award 1976 collaborative work christopher strachey 1970s laid foundations modern approaches semantics programming languages worked also modal logic topology category theory received ba mathematics university california berkeley 1954 wrote ph.d. thesis convergent sequences complete theories supervision alonzo church princeton defended thesis 1958 solomon feferman 2005 writes period completing ph.d. studies moved university chicago working instructor 1960 1959 published joint paper michael o. rabin colleague princeton titled finite automata decision problem scott rabin 1959 introduced idea nondeterministic machines automata theory work led joint bestowal turing award two introduction fundamental concept computational complexity theory scott took post assistant professor mathematics back university california berkeley involved classical issues mathematical logic especially set theory tarskian model theory period started supervising ph.d. students james halpern contributions study independence axiom choice edgar lopez-escobar infinitely long formulas countable quantifier degrees scott also began working modal logic period beginning collaboration john lemmon moved claremont california 1963 scott especially interested arthur prior approach tense logic connection treatment time natural-language semantics began collaborating richard montague copeland 2004 known days undergraduate berkeley later scott montague independently discovered important generalisation kripke semantics modal tense logic called scott-montague semantics scott 1970 john lemmon scott began work modal-logic textbook interrupted lemmon death 1966 scott circulated incomplete monograph amongst colleagues introducing number important techniques semantics model theory importantly presenting refinement canonical model became standard introducing technique constructing models filtrations core concepts modern kripke semantics blackburn de rijke venema 2001 scott eventually published work introduction modal logic lemmon scott 1977 following initial observation robert solovay scott formulated concept boolean-valued model solovay petr vopěnka likewise around time 1967 scott published paper proof independence continuum hypothesis used boolean-valued models provide alternate analysis independence continuum hypothesis provided paul cohen work led award leroy p. steele prize 1972 scott took post professor mathematical logic philosophy faculty university oxford 1972 member merton college oxford honorary fellow college period saw scott working christopher strachey two managed despite administrative pressures work providing mathematical foundation semantics programming languages work scott best known together work constitutes scott–strachey approach denotational semantics constitutes one pieces work theoretical computer science perhaps regarded founding one schools computer science one scott contributions formulation domain theory allowing programs involving recursive functions looping-control constructs given denotational semantics additionally provided foundation understanding infinitary continuous information domain theory theory information systems scott work period led bestowal carnegie mellon university scott proposed theory equilogical spaces successor theory domain theory among many advantages category equilogical spaces cartesian closed category whereas category domains 1994 inducted fellow association computing machinery 2012 became fellow american mathematical society
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Programming language topics
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peter tippett peter tippett born 1953 dearborn michigan american physician researcher inventor known contributions information security clinical medicine technology contributions include development anti-virus program corporate vaccine tippett vice president verizon innovations incubator chief medical officer verizon enterprise services 2009 2015 currently founder ceo healthcelerate inc. born 1953 raised dearborn michigan tippett alumnus kalamazoo college holds ph.d. m.d case western reserve university school medicine studied rockefeller university new york nobel prize winner robert bruce merrifield directing doctoral research efforts toward metabolic indicators peptide synthesis completed internship residency internal medicine cleveland metropolitan general hospital spent 1975-1985 engaged biochemical research engaged research case western reserve tippett moonlighted emergency room physician instructor emergency outpatient medicine spent much early clinical career 1989-1995 emergency medicine ohio california received board certification internal medicine 1987 1993 2000 served board computer ethics institute served executive director pacific foundation science medicine 1988 1992 intersection clinical career emerging focus technology particularly arena cybersecurity well use access protocols internet role president chairman certus international publisher developer pc anti-virus security software tippett applied research insights biochemist concept computer viruses develop anti-virus software vaccine later purchased symantec 1992 ceo role cybertrust led merger cybertrust verizon tippett role verizon healthcare security innovations divisions tippett served chairman alliance internet security 2000 represented verizon board directors open identity exchange oix information card foundation addition credited development one first anti-virus programs vaccine tippett pioneered commercialized string now-common technologies including called recovery disk processor image signatures using hash-tables trusted file execution anomaly detection aspects mail merge un-do ran bulletin board system cp/m software first ibm pc created president cleveland osborne group user group computers osborne computer corporation early 1980s chief scientist icsa.net tippett one handful experts identify address iloveyou virus broke may 2000 provided key information department justice david smith writer melissa virus featured cover august 2000 issue time digital magazine tippett work cybersecurity space led roles speaker contributor advisor government private sector organizations 2003-2005 served president information technology committee pitac established congress 1997 high performance computing act 1991 guide administration efforts accelerate development adoption information technologies vital american prosperity 21st century u.s. chamber commerce awarded tippett first leadership health care award chamber ’ first annual health care summit 2012 leadership verizon incubator tippett also chief scientist icsa labs previously served president international computer security association tippett currently adjunct professor division general medical sciences case western reserve university school medicine november 2017 t.e.n. technology information security executive networking relationship-marketing firm announced tippett recipient 2017 ise® luminary leadership award
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Computer security
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transshipment information security information security transshipment technique protecting software services applications ensuring receive data known able handle safely term analogous logistics industry cargo offloaded one means transport another port entry transshipment information extracted data used send encoded data handled safely transshipment messages intercepted business information carry extracted information encoded new message using data format receiving application safely handle example email client may known handle messages simple structure without failure full generality allowed standards transshipment used protect mail client attackers exploit weaknesses ability handle general case transshipment process extracts business information email messages creates new message conveys information using simple structures mail client protected without knowing details weaknesses implementation transshipment function must handle data sent potential attackers useful function must implemented without vulnerable attack achieved using guard technology separates implementation three parts destination proxy interacts message originator extracts business information messages verifier source proxy creates new message carry business information interacts message recipient verifier role ensure source proxy presented business information using simple data format expecting result attack surface limited verifier interface part source proxy interface visible verifier unlike antivirus software use transshipment defends unknown attacks hence zero-day attacks require routine updates signatures heuristics
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Computer security
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troff troff short typesetter roff major component document processing system developed corporation unix operating system troff features commands designate fonts spacing paragraphs margins footnotes unlike many text formatters troff position characters arbitrarily page even overlapping fully programmable input language separate preprocessors used convenient production tables diagrams mathematics inputs troff plain text files created text editor extensive macro packages created various document styles typical distribution troff includes macros formatting research papers man mdoc macros creating unix man pages mv macros creating mountable transparencies ms mm macros letters books technical memoranda reports troff origins traced text-formatting program called runoff written jerome h. saltzer mit ctss operating system mid-1960s name allegedly came phrase 'll run document bob morris ported ge 635 architecture called program roff abbreviation runoff rewritten rf pdp-7 time 1969 doug mcilroy rewrote extended simplified version roff bcpl programming language first version unix developed pdp-7 sitting around bell labs 1971 developers wanted get pdp-11 work operating system order justify cost system proposed would implement document-formatting system patents division first formatting program reimplementation mcillroy roff written joe f. ossanna needed flexible language new version roff called nroff newer roff written provided basis future versions got graphic systems cat phototypesetter ossanna modified nroff support multiple fonts proportional spacing dubbed troff typesetter roff sophisticated output amazed typesetter manufacturer confused peer reviewers thought manuscripts using troff published name troff pronounced rather troff came nroff actually almost program producing output line printers character terminals understood everything troff ignored commands applicable e.g. font changes ossanna troff written pdp-11 assembly language produced output specifically cat phototypesetter rewrote c although 7000 lines uncommented code still dependent cat cat became less common longer supported manufacturer need make support devices became priority ossanna died task completed brian kernighan took task rewriting troff newly rewritten version produced device-independent code easy post-processors read translate appropriate printer codes also new version troff often called ditroff device independent troff several extensions included drawing functions program documentation defines output format ditroff used many modern troff clones like gnu groff troff collection tools including pre- post-processors eventually called documenter workbench dwb continuous development bell labs later spin-off unix system laboratories usl 1994 time softquad took maintenance although brian kernighan continued improve troff thus least following variants original bell labs troff use troff supplanted programs interleaf framemaker latex still used quite extensively remains default formatter unix documentation software reimplemented groff gnu system beginning 1990 addition due open sourcing ancient unix systems well modern successors ditroff based open-sourced versions found opensolaris plan 9 bell labs several versions troff cat ditroff-based available various open-source licenses troff includes sets commands called macros run starting process document macros include setting page headers footers defining new commands generally influencing output formatted command-line argument including macro set -m name led many macro sets known base filename leading m. standard macro sets leading comprehensive list macros available usually listed codice_2 manual page troff evolved since several things done easily troff several preprocessors developed programs transform certain parts document troff input fitting naturally use pipelines unix — sending output one program input another see pipes filters typically preprocessor translates sections input file specially marked passing rest file unchanged embedded preprocessing instructions written simple application-specific programming language provides high degree power flexibility three preprocessors provide troff drawing capabilities defining domain-specific language describing picture yet preprocessors allow drawing complex pictures generating output pic
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Programming language topics
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ibm information management system ibm information management system ims joint hierarchical database information management system extensive transaction processing capabilities ibm designed ims rockwell caterpillar starting 1966 apollo program used inventory large bill materials bom saturn v moon rocket apollo space vehicle first ims ready message appeared ibm 2740 terminal downey california august 14 1968 interim period ims undergone many developments ibm system/360 technology evolved current z/os ibm zenterprise system technologies example ims supports java programming language jdbc xml since late 2005 web services vern watts ims chief architect many years watts joined ibm 1956 worked ibm silicon valley development labs death april 4 2009 continuously worked ims since 1960s ims database component stores data using hierarchical model quite different ibm later released relational database db2 ims hierarchical model implemented using blocks data known segments segment contain several pieces data called fields example customer database may root segment segment top hierarchy fields phone name age child segments may added underneath another segment instance one order segment customer segment representing order customer placed company likewise order segment may many children segments item order unlike databases need define data segment ims segment may defined size 40 bytes define one field six bytes long key field use find segment performing queries ims retrieve save 40 bytes directed program may understand care bytes represent practice often data segment may map cobol copybook besides dl/i query usage field may defined ims data hidden certain applications security reasons database component ims purchased standalone without transaction manager component used systems cics three basic forms ims hierarchical databases dedb performance comes use high performance media manager access method asynchronous write commit optimized code paths logging minimized data updated disk commit undo image logging needed backout function uncommitted changes simply discarded starting ims version 11 dedbs use z/os 64-bit storage database buffers dedbs architecture includes unit work uow concept made effective online reorganization utility simple implement function included base product fast path dedbs built atop vsam dl/i databases built atop either vsam osam restrictions depending database organization although maximum size z/os vsam dataset increased 128 tb years ago ims still limits vsam dataset 4 gb osam 8 gb limitation simply means ims customers use multiple datasets large amounts data vsam osam usually referred access methods ims logical view database referred database organization hdam hidam hisam etc internally data linked using 4-byte pointers addresses database datasets dbdss pointers referred rbas relative byte addresses collectively database-related ims capabilities often called ims db ims db grown evolved nearly four decades support myriad business needs ims assistance z/os hardware coupling facility supports n-way inter-ims sharing databases many large configurations involve multiple ims systems managing common databases technique providing scalable growth system redundancy event hardware software failures ims also robust transaction manager ims tm also known ims dc one big three classic transaction managers along cics bea oracle tuxedo transaction manager interacts end user connected vtam tcp/ip including 3270 web user interfaces another application processes business function banking account withdrawal maintains state throughout process making sure system records business function correctly data store thus ims tm quite like web application operating cgi program example provide interface query update database ims tm typically uses either ims db db2 backend database used alone db2 ims tm component purchased without ims db component ims tm uses messaging queuing paradigm ims control program receives transaction entered terminal web browser application stores transaction message queue memory dataset ims invokes scheduler queued transaction start business application program message processing region message processing region retrieves transaction ims message queue processes reading updating ims and/or db2 databases assuring proper recording transaction required ims enqueues response message back onto ims message queue output message complete available ims control program sends back originating terminal ims tm handle whole process thousands even tens thousands times per second 2013 ibm completed benchmark ims version 13 demonstrating ability process 100,000 transactions per second single ims system prior ims businesses governments write transaction processing environments ims tm provides straightforward easy-to-use reliable standard environment high performance transaction execution fact much world banking industry relies ims including u.s. federal reserve example chances withdrawing money automated teller machine atm trigger ims transaction several chinese banks recently purchased ims support country burgeoning financial industry today ims complements db2 ibm relational database system introduced 1982 general ims performs faster db2 common tasks may require programming effort design maintain non-primary duties relational databases generally proven superior cases requirements especially reporting requirements change frequently require variety viewpoint angles outside primary original function relational data warehouse may used supplement ims database example ims may provide primary atm transactions performs well specific task however nightly copies ims data may copied relational systems variety reports processing tasks may performed data allows kind database focus best relative strength
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Databases
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maxisun maxisun interface system infor sunsystems/sap business one/other erp systems third party business applications original maxisun software developed integrate maximo sunsystems 2001 sapphire systems early versions software “ black box ” systems little could modified client installation taken place history always two main components comprising system data extraction component data conversion component first version system data extraction component sqr script authored originally mro software sapphire data transformation engine originally authored sapphire visual basic since early days maxisun modified make capable configured client sqr extraction tool replaced dedicated program called origin maxisun data conversion engine gained benefit user interface allowed source destination files mapped field line level mapping settings needed dynamic storage facility created using microsoft access database initially later upgraded sql server etl describes methodology behind maxisun middleware interface task broken three distinct parts 1 extract extraction phase records meeting certain pre-defined criteria extracted source system ’ database either series files file system typically xml csv files memory case certain specific interfaces 2 transform transformation phase file data data memory manipulated series rules meet data entry requirements destination system manipulations include limited trimming fields given length creating balanced double entry records performing calculations joining values together etc maxisun supports range standard data manipulation features right box since full user definable .net macro capability literally transformation achieved 3 load load phase transformed data uploaded end point application method appropriate application typically applications receiving data perform level validation data sometimes feedback result sending application examples loading transactions sunsystems via sun systems connect ssc web service loading data maximo interface tables maximo enterprise adapter mea version 7 maximo integration framework mif validates processes data application tables maxisun combines extraction transformation tasks one action – speeds process dramatically means fewer steps interface task check event issue maxisun middleware creates integration hub enabling point point integrations two third party systems uses number methods communicate systems fully configurable perform etl extract transform load tasks meet individual interfacing requirements given third party applications
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Distributed computing architecture
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isabelle proof assistant isabelle automated theorem prover interactive theorem prover higher order logic hol theorem prover lcf-style theorem prover written standard ml based small logical core ease logical correctness isabelle generic provides meta-logic weak type theory used encode object logics like first-order logic fol higher-order logic hol zermelo–fraenkel set theory zfc isabelle main proof method higher-order version resolution based higher-order unification though interactive isabelle also features efficient automatic reasoning tools term rewriting engine tableaux prover well various decision procedures isabelle used formalize numerous theorems mathematics computer science like gödel completeness theorem gödel theorem consistency axiom choice prime number theorem correctness security protocols properties programming language semantics isabelle theorem prover free software released revised bsd license isabelle named lawrence paulson gérard huet daughter isabelle allows proofs written two different styles procedural declarative procedural proofs specify series tactics procedures apply reflecting procedure human mathematician might apply proving result typically hard read describe outcome steps declarative proofs supported isabelle proof language isar hand specify actual mathematical operations performed therefore easily read checked humans procedural style deprecated recent versions isabelle archive formal proofs also recommends declarative style example declarative proof contradiction isar square root two rational written follows isabelle used aid formal methods specification development verification software hardware systems larry paulson keeps list research projects use isabelle following programs provide similar functionality isabelle
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Programming language topics
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quasi-opportunistic supercomputing quasi-opportunistic supercomputing computational paradigm supercomputing large number geographically disperse computers quasi-opportunistic supercomputing aims provide higher quality service opportunistic resource sharing quasi-opportunistic approach coordinates computers often different ownerships achieve reliable fault-tolerant high performance control opportunistic computer grids computational resources used whenever may become available opportunistic match-making approach task scheduling computer grids simpler merely matches tasks whatever resources may available given time demanding supercomputer applications weather simulations computational fluid dynamics remained reach partly due barriers reliable sub-assignment large number tasks well reliable availability resources given time quasi-opportunistic approach enables execution demanding applications within computer grids establishing grid-wise resource allocation agreements fault tolerant message passing abstractly shield failures underlying resources thus maintaining opportunism allowing higher level control general principle grid computing use distributed computing resources diverse administrative domains solve single task using resources become available traditionally grid systems approached task scheduling challenge using opportunistic match-making approach tasks matched whatever resources may available given time boinc developed university california berkeley example volunteer-based opportunistic grid computing system applications based boinc grid reached multi-petaflop levels using close half million computers connected internet whenever volunteer resources become available another system folding home based boinc computes protein folding reached 8.8 petaflops using clients include gpu playstation 3 systems however results applicable top500 ratings run general purpose linpack benchmark key strategy grid computing use middleware partitions pieces program among different computers network although general grid computing success parallel task execution demanding supercomputer applications weather simulations computational fluid dynamics remained reach partly due barriers reliable sub-assignment large number tasks well reliable availability resources given time opportunistic internet primenet server supports gimps one earliest grid computing projects since 1997 researching mersenne prime numbers gimps distributed research currently achieves 60 teraflops volunteer-based computing project use computing resources volunteer grids gimps usually purely opportunistic geographically disperse distributively owned computers contributing whenever become available preset commitments resources available given time hence hypothetically many volunteers unwittingly decide switch computers certain day grid resources become significantly reduced furthermore users find exceedingly costly organize large number opportunistic computing resources manner achieve reasonable high performance computing example structured grid high performance computing deisa supercomputer project organized european community uses computers seven european countries although different parts program executing within deisa may running computers located different countries different ownerships administrations control coordination purely opportunistic approach deisa two level integration scheme inner level consists number strongly connected high performance computer clusters share similar operating systems scheduling mechanisms provide homogeneous computing environment outer level consists heterogeneous systems supercomputing capabilities thus deisa provide somewhat controlled yet dispersed high performance computing services users quasi-opportunistic paradigm aims overcome achieving control assignment tasks distributed resources use pre-negotiated scenarios availability systems within network quasi-opportunistic distributed execution demanding parallel computing software grids focuses implementation grid-wise allocation agreements co-allocation subsystems communication topology-aware allocation mechanisms fault tolerant message passing libraries data pre-conditioning approach fault tolerant message passing essential abstractly shield failures underlying resources quasi-opportunistic approach goes beyond volunteer computing highly distributed systems boinc general grid computing system globus allowing middleware provide almost seamless access many computing clusters existing programs languages fortran c distributed among multiple computing resources key component quasi-opportunistic approach qoscos grid economic-based resource allocation model resources provided based agreements among specific supercomputer administration sites unlike volunteer systems rely altruism specific contractual terms stipulated performance specific types tasks however tit-for-tat paradigms computations paid back via future computations suitable supercomputing applications avoided key component quasi-opportunistic approach reliable message passing system provide distributed checkpoint restart mechanisms computer hardware networks inevitably experience failures way part large computation fails entire run need abandoned restart last saved checkpoint
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Distributed computing architecture
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hol proof assistant hol higher order logic denotes family interactive theorem proving systems using similar higher-order logics implementation strategies systems family follow lcf approach implemented library programming language library implements abstract data type proven theorems new objects type created using functions library correspond inference rules higher-order logic long functions correctly implemented theorems proven system must valid way large system built top small trusted kernel systems hol family use ml programming language successors ml originally developed along lcf serve purpose meta-language theorem proving systems fact name stands meta-language hol systems use variants classical higher-order logic simple axiomatic foundations axioms well-understood semantics logic used hol provers closely related isabelle/hol widely used logic isabelle four hol systems sharing essentially logic still maintained developed although hol predecessor isabelle various hol derivatives hol4 hol light remain active use cakeml project developed formally proven compiler ml previously hol used developed formally proven lisp implementation running arm x86 powerpc hol also used develop formal semantics x86 multiprocessors well semantics machine code power isa arm architectures
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Programming language topics
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bittorrent tracker bittorrent tracker special type server assists communication peers using bittorrent protocol peer-to-peer file sharing software client end-user pc requests file portions requested file residing peer machines sent client reassembled full copy requested file tracker server keeps track file copies reside peer machines ones available time client request helps coordinate efficient transmission reassembly copied file clients already begun downloading file communicate tracker periodically negotiate faster file transfer new peers provide network performance statistics however initial peer-to-peer file download started peer-to-peer communication continue without connection tracker since creation distributed hash table dht method trackerless torrents bittorrent trackers largely become redundant however still often included torrents improve speed peer discovery public open trackers used anyone adding tracker address existing torrent used newly created torrent like openbittorrent pirate bay operated one popular public trackers disabling 2009 amid legal trouble thereafter offered magnet links private tracker bittorrent tracker restricts use requiring users register site method controlling registration used among many private trackers invitation system active contributing members given ability grant new user permission register site new user goes interview process several circumstances legal distribute copyrighted material parts thereof also experiments legally selling content distributed bittorrent using secure tracker system trackers primary reason damaged bittorrent swarm reasons mostly related damaged hacked clients uploading corrupt data reliability trackers improved two main innovations bittorrent protocol multi-tracker torrents contain multiple trackers single torrent file provides redundancy case one tracker fails trackers continue maintain swarm torrent one disadvantage becomes possible multiple unconnected swarms single torrent users connect one specific tracker unable connect another create disjoint set impede efficiency torrent transfer files describes additional extensions peer exchange dht mitigate effect rapidly merging otherwise disjoint graphs peers vuze formerly azureus first bittorrent client implement system distributed hash table dht method alternative incompatible dht system known mainline dht developed simultaneously later adopted bittorrent mainline µtorrent transmission rtorrent ktorrent bitcomet deluge clients current versions official bittorrent client µtorrent bitcomet transmission bitspirit share compatibility mainline dht dht implementations based kademlia version 3.0.5.0 vuze also supports mainline dht addition distributed database use optional application plugin mainlinedht plugin potentially allows vuze client reach bigger swarm bittorrent clients also use peer exchange pex gather peers addition trackers dht peer exchange checks known peers see know peers 3.0.5.0 release vuze major bittorrent clients compatible peer exchange one options http based tracker protocol compact flag flag defined bep 23 specifies tracker compact response encoding ipv4 addresses set 4 bytes 32 bits ipv6 though 128 bits long compact would break ipv6 support handle situation clients trackers must either avoid using compact announces ipv6 implement bep 07 opentracker dirk engling powered one biggest bittorrent trackers pirate bay tracker atrack high performance open source tracker designed run google app engine bitstorm small tracker written php require database server runs php compatible web server bitstorm 2 uses mysql database instead flat file improve scalability bittorious open source commercially supported tracker integrated web-based management portal hefur standalone bittorrent tracker written c++ mit license ocelot bittorrent tracker written c++ gazelle project
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Internet protocols
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microsoft sql server microsoft sql server relational database management system developed microsoft database server software product primary function storing retrieving data requested software applications—which may run either computer another computer across network including internet microsoft markets least dozen different editions microsoft sql server aimed different audiences workloads ranging small single-machine applications large internet-facing applications many concurrent users history microsoft sql server begins first microsoft sql server product—sql server 1.0 16-bit server os/2 operating system 1989—and extends current day following versions supported microsoft sql server 2016 onward product supported x64 processors current version microsoft sql server 2017 released october 2 2017 rtm version 14.1709.3807.1 sql server 2019 released community technology preview slated release manufacturing second half 2019 microsoft makes sql server available multiple editions different feature sets targeting different users editions protocol layer implements external interface sql server operations invoked sql server communicated via microsoft-defined format called tabular data stream tds tds application layer protocol used transfer data database server client initially designed developed sybase inc. sybase sql server relational database engine 1984 later microsoft microsoft sql server tds packets encased physical transport dependent protocols including tcp/ip named pipes shared memory consequently access sql server available protocols addition sql server api also exposed web services data storage database collection tables typed columns sql server supports different data types including primitive types integer float decimal char including character strings varchar variable length character strings binary unstructured blobs data text textual data among others rounding floats integers uses either symmetric arithmetic rounding symmetric round fix depending arguments codice_1 gives 3 microsoft sql server also allows user-defined composite types udts defined used also makes server statistics available virtual tables views called dynamic management views dmvs addition tables database also contain objects including views stored procedures indexes constraints along transaction log sql server database contain maximum 2 objects span multiple os-level files maximum file size 2 bytes 1 exabyte data database stored primary data files extension codice_2 secondary data files identified codice_3 extension used allow data single database spread across one file optionally across one file system log files identified codice_4 extension storage space allocated database divided sequentially numbered pages 8 kb size page basic unit i/o sql server operations page marked 96-byte header stores metadata page including page number page type free space page id object owns page type defines data contained page data stored database index allocation map holds information pages allocated tables indexes change map holds information changes made pages since last backup logging contain large data types image text page basic unit i/o operation space actually managed terms extent consists 8 pages database object either span 8 pages extent uniform extent share extent 7 objects mixed extent row database table span one page limited 8 kb size however data exceeds 8 kb row contains varchar varbinary data data columns moved new page possibly sequence pages called allocation unit replaced pointer data physical storage table rows divided series partitions numbered 1 n partition size user defined default rows single partition table split multiple partitions order spread database computer cluster rows partition stored either b-tree heap structure table associated clustered index allow fast retrieval rows rows stored in-order according index values b-tree providing index data leaf node leaves nodes storing index values leaf data reachable respective nodes index non-clustered rows sorted according index keys indexed view storage structure indexed table table without clustered index stored unordered heap structure however table may non-clustered indices allow fast retrieval rows situations heap structure performance advantages clustered structure heaps b-trees span multiple allocation units sql server buffers pages ram minimize disk i/o 8 kb page buffered in-memory set pages currently buffered called buffer cache amount memory available sql server decides many pages cached memory buffer cache managed buffer manager either reading writing page copies buffer cache subsequent reads writes redirected in-memory copy rather on-disc version page updated disc buffer manager in-memory cache referenced time writing pages back disc asynchronous i/o used whereby i/o operation done background thread operations wait i/o operation complete page written along checksum written reading page back checksum computed matched stored version ensure page damaged tampered meantime sql server allows multiple clients use database concurrently needs control concurrent access shared data ensure data integrity—when multiple clients update data clients attempt read data process changed another client sql server provides two modes concurrency control pessimistic concurrency optimistic concurrency pessimistic concurrency control used sql server controls concurrent access using locks locks either shared exclusive exclusive lock grants user exclusive access data—no user access data long lock held shared locks used data read—multiple users read data locked shared lock acquire exclusive lock latter would wait shared locks released locks applied different levels granularity—on entire tables pages even per-row basis tables indexes either entire index index leaves level granularity used defined per-database basis database administrator fine-grained locking system allows users use table index simultaneously requires resources automatically yield higher performance sql server also includes two lightweight mutual exclusion solutions—latches spinlocks—which less robust locks less resource intensive sql server uses dmvs resources usually busy sql server also monitors worker threads acquire locks ensure end deadlocks—in case sql server takes remedial measures many cases kill one threads entangled deadlock roll back transaction started implement locking sql server contains lock manager lock manager maintains in-memory table manages database objects locks along metadata lock access shared object mediated lock manager either grants access resource blocks sql server also provides optimistic concurrency control mechanism similar multiversion concurrency control used databases mechanism allows new version row created whenever row updated opposed overwriting row i.e. row additionally identified id transaction created version row old well new versions row stored maintained though old versions moved database system database identified codice_5 row process updated requests blocked unlike locking executed older version row request update statement result two different versions rows—both stored database identified respective transaction ids main mode retrieving data sql server database querying query expressed using variant sql called t-sql dialect microsoft sql server shares sybase sql server due legacy query declaratively specifies retrieved processed query processor figures sequence steps necessary retrieve requested data sequence actions necessary execute query called query plan might multiple ways process query example query contains join statement select statement executing join tables executing select results would give result selecting table executing join result different execution plans case sql server chooses plan expected yield results shortest possible time called query optimization performed query processor sql server includes cost-based query optimizer tries optimize cost terms resources take execute query given query query optimizer looks database schema database statistics system load time decides sequence access tables referred query sequence execute operations access method used access tables example table associated index whether index used index column unique columns low selectivity might worthwhile use index access data finally decides whether execute query concurrently concurrent execution costly terms total processor time execution actually split different processors might mean execute faster query plan generated query temporarily cached invocations query cached plan used unused plans discarded time sql server also allows stored procedures defined stored procedures parameterized t-sql queries stored server issued client application case general queries stored procedures accept values sent client input parameters send back results output parameters call defined functions stored procedures including stored procedure set number times selectively provided access unlike queries stored procedures associated name used runtime resolve actual queries also code need sent client every time accessed name reduces network traffic somewhat improves performance execution plans stored procedures also cached necessary t-sql transact-sql microsoft proprietary procedural language extension sql server provides repl read-eval-print-loop instructions extend standard sql instruction set data manipulation dml data definition ddl instructions including sql server-specific settings security database statistics management exposes keywords operations performed sql server including creating altering database schemas entering editing data database well monitoring managing server client applications consume data manage server leverage sql server functionality sending t-sql queries statements processed server results errors returned client application exposes read-only tables server statistics read management functionality exposed via system-defined stored procedures invoked t-sql queries perform management operation also possible create linked servers using t-sql linked servers allow single query process operations performed multiple servers sql server native client native client side data access library microsoft sql server version 2005 onwards natively implements support sql server features including tabular data stream implementation support mirrored sql server databases full support data types supported sql server asynchronous operations query notifications encryption support well receiving multiple result sets single database session sql server native client used hood sql server plug-ins data access technologies including ado ole db sql server native client also directly used bypassing generic data access layers november 28 2011 preview release sql server odbc driver linux released microsoft sql server 2005 includes component named sql clr common language runtime via integrates .net framework unlike applications use .net framework sql server hosts .net framework runtime i.e. memory threading resource management requirements .net framework satisfied sqlos rather underlying windows operating system sqlos provides deadlock detection resolution services .net code well sql clr stored procedures triggers written managed .net language including c vb.net managed code also used define udt user defined types persist database managed code compiled cli assemblies verified type safety registered database invoked like procedure however subset base class library available running code sql clr apis relating user interface functionality available writing code sql clr data stored sql server databases accessed using ado.net apis like managed application accesses sql server data however creates new database session different one code executing avoid sql server provides enhancements ado.net provider allows connection redirected session already hosts running code connections called context connections set setting codice_6 parameter codice_7 connection string sql server also provides several enhancements ado.net api including classes work tabular data single row data well classes work internal metadata data stored database also provides access xml features sql server including xquery support enhancements also available t-sql procedures consequence introduction new xml datatype query value nodes functions sql server also includes assortment add-on services essential operation database system provide value added services top core database management system services either run part sql server component out-of-process windows service presents api control interact sql server machine learning services operates within sql server instance allowing people machine learning data analytics without send data across network limited memory computers services come microsoft r python distributions contain commonly used packages data science along proprietary packages e.g revoscalepy revoscaler microsoftml used create machine models scale analysts either configure client machine connect remote sql server push script executions run r python scripts external script inside t-sql query trained machine learning model stored inside database used scoring used inside instance programming environment cross-instance applications service broker communicates tcp/ip allows different components synchronized via exchange messages service broker runs part database engine provides reliable messaging message queuing platform sql server applications sql server replication services used sql server replicate synchronize database objects either entirety subset objects present across replication agents might database servers across network database caches client side lulla follows publisher/subscriber model i.e. changes sent one database server publisher received others subscribers sql server supports three different types replication sql server analysis services adds olap data mining capabilities sql server databases olap engine supports molap rolap holap storage modes data analysis services supports xml analysis standard underlying communication protocol cube data accessed using mdx linq queries data mining specific functionality exposed via dmx query language analysis services includes various algorithms—decision trees clustering algorithm naive bayes algorithm time series analysis sequence clustering algorithm linear logistic regression analysis neural networks—for use data mining sql server reporting services report generation environment data gathered sql server databases administered via web interface reporting services features web services interface support development custom reporting applications reports created rdl files reports designed using recent versions microsoft visual studio visual studio.net 2003 2005 2008 business intelligence development studio installed included report builder created rdl files rendered variety formats including excel pdf csv xml bmp emf gif jpeg png tiff html web archive originally introduced post-release add-on sql server 2000 notification services bundled part microsoft sql server platform first time sql server 2005 sql server notification services mechanism generating data-driven notifications sent notification services subscribers subscriber registers specific event transaction registered database server trigger event occurs notification services use one three methods send message subscriber informing occurrence event methods include smtp soap writing file filesystem notification services discontinued microsoft release sql server 2008 august 2008 longer officially supported component sql server database platform sql server integration services ssis provides etl capabilities sql server data import data integration data warehousing needs integration services includes gui tools build workflows extracting data various sources querying data transforming data—including aggregation de-duplication de-/normalization merging data—and exporting transformed data destination databases files sql server full text search service specialized indexing querying service unstructured text stored sql server databases full text search index created column character based text data allows words searched text columns performed sql codice_8 operator using sql server full text search service efficient full allows inexact matching source string indicated rank value range 0 1000—a higher rank means accurate match also allows linguistic matching inflectional search i.e. linguistic variants word verb different tense also match given word lower rank exact match proximity searches also supported i.e. words searched occur sequence specified query near also considered match t-sql exposes special operators used access fts capabilities full text search engine divided two processes filter daemon process codice_9 search process codice_10 processes interact sql server search process includes indexer creates full text indexes full text query processor indexer scans text columns database also index binary columns use ifilters extract meaningful text binary blob example microsoft word document stored unstructured binary file database ifilters hosted filter daemon process text extracted filter daemon process breaks sequence words hands indexer indexer filters noise words i.e. words like etc. occur frequently useful search remaining words inverted index created associating word columns found sql server includes gatherer component monitors changes tables invokes indexer case updates full text query received sql server query processor handed fts query processor search process fts query processor breaks query constituent words filters noise words uses inbuilt thesaurus find linguistic variants word words queried inverted index rank accurateness computed results returned client via sql server process sqlcmd command line application comes microsoft sql server exposes management features sql server allows sql queries written executed command prompt also act scripting language create run set sql statements script scripts stored codice_11 file used either management databases create database schema deployment database sqlcmd introduced sql server 2005 continues sql server 2012 2014 2016 predecessor earlier versions osql isql functionally equivalent pertains tsql execution many command line parameters identical although sqlcmd adds extra versatility microsoft visual studio includes native support data programming microsoft sql server used write debug code executed sql clr also includes data designer used graphically create view edit database schemas queries created either visually using code ssms 2008 onwards provides intellisense sql queries well sql server management studio gui tool included sql server 2005 later configuring managing administering components within microsoft sql server tool includes script editors graphical tools work objects features server sql server management studio replaces enterprise manager primary management interface microsoft sql server since sql server 2005 version sql server management studio also available sql server express edition known sql server management studio express ssmse central feature sql server management studio object explorer allows user browse select act upon objects within server used visually observe analyze query plans optimize database performance among others sql server management studio also used create new database alter existing database schema adding modifying tables indexes analyze performance includes query windows provide gui based interface write execute queries sql server operations studio preview cross platform query editor available optional download tool allows users write queries export query results commit sql scripts git repositories perform basic server diagnostics sql server operations studio supports windows mac linux systems business intelligence development studio bids ide microsoft used developing data analysis business intelligence solutions utilizing microsoft sql server analysis services reporting services integration services based microsoft visual studio development environment customized sql server services-specific extensions project types including tools controls projects reports using reporting services cubes data mining structures using analysis services sql server 2012 later ide renamed sql server data tools ssdt
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Databases
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userful userful corporation canadian software company specializes video walls digital signage interactive displays desktop virtualization founded 2003 userful develops software turns standard pc high end video wall controller video wall processor userful head office located calgary alberta privately held for-profit company resellers around world founder chief technology officer timothy griffin founded userful corporation 2003 company commenced work multi-screen desktop computing platform core userful software first userful software release 2002 quickest market uptake low cost approach desktop virtualization schools public libraries locations needed locked virtual desktops military oilfields deployment 2014 userful launched video wall digital signage software built pc network zero client infrastructure desktop virtualization product october 2018 userful named john marshall new chief executive officer february 2009 userful announced claimed world largest desktop virtualization deployment 356,800 virtual desktops brazil may 2012 userful launched version 5 multiseat software added ethernet zero client support april 2012 userful announced partnership viewsonic produce linux-based zero-client product february 2013 userful launched userful multiplatform 6 enables running windows linux browser desktops multiseat environment february 2014 userful launched userful multiplatform 7.0 provides desktop virtualization central management desktops touch screens kiosks october 2014 userful partnered viewsonic create sc-u25 value vdi client userful multiplatform software december 2014 userful launched userful network video wall software turns standard pc video wall controller video wall processor supports ultra-high definition content one core i7 pc multiple video walls 25 standard displays august 2015 version 8.0 userful network video wall released updating core platform userful products improving performance reliability january 2016 version 8.5 userful released updating core platform include core enhancements enhanced support features vdi video walls may 2016 version 8.6 userful released update supports 8k video walls including enhanced features support vdi video walls september 2016 userful released version 8.7 featuring enhancements minor updates december 2016 userful released version 9.0 added many interactive features enhancements video walls digital signage see list userful software products built combination centos linux userful ’ software provisions manages zero clients userful software turns standard pc video wall controller video wall processor delivers content gigabit ethernet network userful software utilizes cpu gpu intel platform process render high resolution real time content release userful network video wall december 2014 world first commercially available video wall solution deliver real-time 4k content standard ethernet network one pc january 2016 userful updated video wall solution world first network video wall capable 6k source content real time ability support 40 screens one standard pc 60 screens high-end pc userful merged virtual desktop platform 8.5 release enabling delivery virtual desktops video wall userful also announced support multi-zone configurations allowing video wall broken sections different real time content played different zones within video wall may 2016 userful released version 8.6 improving display quality use discrete compatible gpus announced support 8k video content playback december 2016 userful launched version 9.0 increased number screens supported 1 pc 100 release also included interactivity tools ability store invoke presets change content zone configurations fly userful multiplatform multiseat desktop virtualization product works oracle virtualbox enable creation management multiple windows linux cloud desktops commercially available hardware userful desktop combines customized configurable gnome desktop managed remotely in-house tools product specifically designed full public computing solution kiosks public access computers desktop settings managed session profiles created stored central web portal pre-book open source pc reservation system originally client software userful/linux windows however opensource windows software since discontinued pre-book feature available people using userful platform public computing wanting advance reservations multi-location time management available cloud subscription feature starting release 8.5 userful ’ desktop virtualization video wall features joined single platform offers virtual desktops video wall digital signage solutions starting release 8.9 public computing features userful desktop pre-book also merged unified platform called userful userful multiseat linux replaced userful multiplatform software turns one linux computer 20 independent computer stations includes educational applications userful multiseat linux software linux-based equivalent windows multipoint server multiseat solutions education sector userful multiseat formerly userful multiplier commercial linux-based multiseat configuration software package allows multiple independent users connect single host pc time monitor keyboard mouse applications
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Operating systems
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logic computable functions logic computable functions lcf interactive automated theorem prover developed universities edinburgh stanford robin milner others 1972 lcf introduced general-purpose programming language ml allow users write theorem-proving tactics theorems system terms special theorem abstract data type ml type system ensures theorems derived using inference rules given operations abstract type successors include hol higher order logic isabelle
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Programming language topics
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disc filing system disc filing system dfs computer file system developed acorn computers initially add-on eurocard-based acorn system 2 1981 education departments western australia south australia announced joint tenders calling supply personal computers schools acorn australian computer distributor barson computers convinced joint managing directors hermann hauser chris curry allow soon released acorn bbc microcomputer offered disk storage part bundle agreed condition barson adapted acorn dfs system 2 without assistance acorn resources available required minor hardware software changes make dfs compatible bbc micro barson tenders states dfs fitted year ahead uk early initiative resulted bbc micro heavily focused education market australia little penetration home computer market arrival acorn electron dfs shipped rom disk controller chip fitted bbc micro motherboard filing system extremely limited functionality storage capability using flat directory structure filename seven letters long plus one letter directory file stored dfs remarkable unlike filing systems single vendor implementation original dfs written acorn continued maintain codebase various disc drive vendors wrote implementations companies wrote dfs implementations included cumana opus watford electronics watford electronics implementation notable supporting 62 files per disc instead usual 31 using non-standard disc format features third-party implementations included able review free space built-in codice_1 codice_2 commands shipped utility disc original acorn dfs acorn followed original dfs series acorn 1770 dfs used disc format earlier version added set extra commands supported improved wd1770 floppy drive controller chip dfs conventionally uses one side double-density 5¼ floppy disc discs formatted either 40 80 track giving capacity 100 200 kb per side ten 256-byte sectors per track fm encoding capacity limited choice intel 8271 controller original bbc micro supports fm encoding mfm encoding already common use time bbc micro launch fm encoding gives half recording capacity mfm given physical disc density fm mfm encoding commonly referred single density double density although discs drives unlike high density uses different drives discs double-density 3½ discs formatted used 1770 dfs intel 8271-based dfs problems many 3½ drives giving single-density capacity fm encoding originally standard practice 3½ discs normally formatted mfm double density using later advanced disc filing system present acorn machines supplied 3½ drives 2009 3½ drives commonly used bbc micros past including use dfs due greater availability easier data interchange recent computers high-density 5¼ 3½ discs supported dfs dfs directly support double-sided discs instead two heads double-sided drive treated two separate logical drives dfs support four volumes numbered 0 3 drive 0 default drive 1 representing second drive attached cable drive 2 referred reverse side drive 0 drive 3 reverse drive 1 support two physical drives due installed base single-sided drives commercial software normally provided single-sided discs flippy discs manually reversed access side discs formatted using 40 80 tracks using codice_3 codice_4 commands drives either 40 80 track common compatibility issue dfs users 40-track discs norm commercial software distribution due installed base 40-track drives 80-track drives became common prices dropped allowing users store data 80-track drive automatically read 40-track discs disc capacity stored sector count catalogue track zero track zero located place 40- 80-track discs allowing disc file system set motor stepping accordingly however intel 8271-based acorn dfs dual-format capability addressed number ways failure use correct setting would result errors dfs codice_5 damage disc drive trying step heads beyond physical end disc surface switching 80 tracks extend catalogue way leaving user prone running filename slots running space disc situation resulted codice_6 error dfs case-preserving case-sensitive prevalence all-capitals filenames likely due bbc micro defaulting caps lock enabled hard soft reset character set quite permissive printable characters 7-bit ascii allowed including spaces excluding sake portability third-party dfs implementations best avoid codice_12 codice_16 leaf names quotation marks allowed although bbc basic requires escaped twice fully qualified filename file specification fsp short contains colon drive number dot directory letter another dot name example file default directory drive 2 called codice_31 would complete specification codice_32 drive directory specifiers optional directories dfs single character prefixes filenames codice_21 codice_34 used group files arrangement flat default directory codice_35 used instead root directory requesting catalogue disc codice_36 codice_37 commands files current directory shown directory prefix one block listed files second block directory prefixes visible example acorn dfs third party dfs implementations may vary slightly top seven files current directory codice_35 drive 0 files directories case codice_39 codice_40 codice_21 codice_42 filename codice_43 shows file locked modification deletion first line contains disc title modification count dfs provides working space divided directory library directory working directory current volume much like working directory command line system library second alternative working directory functions like path benefit able volume requests open files unqualified names first searched working directory failing library directory also searched directory library default directory catalogue file table occupies first two disc sectors one names directories file matching sector holding file locations sizes metadata eight bytes sector used file eight bytes sector reserved 12-byte disc title volume information total number files disc irrespective directory file limited 31 interests saving space significant bit directory letter file used locked read-only flag although physical disks usually formatted either 100 kb 200 kb dfs supports volume sizes 256 kb largest dfs file size allowed volume size minus ½ kb catalogue file sizes stored 18-bit quantity dfs support data fragmentation meaning file data must stored single run consecutive sectors free space prone becoming fragmented random-access file writes fail end file reaches beginning next even though may free sectors elsewhere disc cases dfs aborts codice_44 error codice_45 split file fit available space either failure occurs sector allocation stage error returned codice_46 codice_47 command provided relocate files disc solid block placing free space second block allows next file created fill disc last existing file extended without moved codice_45 virtually deletes existing file copies specified block memory wherever space disc contrast codice_47 command uses program memory buffer relocate files overwriting program data memory like cassette filing system acorn dfs supports bbc micro standard file metadata load address execution address required acorn mos operating system used bbc micro support relocation binary code file loaded address programmer intended contents may refer internal locations absolute addresses execution address also recorded entry point necessarily beginning even within file file attributes limited single bit locked set codice_42 appears right file name catalogue file may altered overwritten deleted dfs discs track dates acorn mos prior version 3 maintain real-time clock instead offer peculiar feature modification count every time catalogue updated count increments count shown parentheses title first line disc catalogue codice_51 catalogue listing shown earlier dfs also supports means start disc software based key sequence shift key held machine soft hard reset dfs checks drive 0 disc containing positive boot flag boot flag either 0 ignore 1 load file 2 run machine code file 3 execute script boot flag positive file called codice_52 looked loaded memory 1 loaded executed machine code 2 fed keyboard buffer 3 option 3 reads exec files text macro files used primitive shell scripts true shell scripts simply series keys typed like recording play back thus loop branch unless input code basic interpreter well used reset executed time operating system codice_53 command exec files file system independent variant dfs called dnfs disc/network filing system contained econet network filing system nfs standard disc filing system tube co-processor support software single rom rom installed two filing systems os initial design dfs based around intel corporation fdc 8271 disc drive controller immediate predecessor 8272 design found ibm personal computer 8271 controller limited functionality obsolete later versions file system various vendors including solidisk acorn watford electronics based later wd1770 wd1772 drive controllers 1770 controller quickly became standard controller acorn range following advent adfs dfs superseded advanced disc filing system adfs fully hierarchical suitable running hard drives bbc micro adfs default filing system bbc master users likely reverted dfs compatibility reasons adfs could read dfs discs adfs also chosen standard filing system risc os
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Computer file systems
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lego proof assistant lego proof assistant developed randy pollack university edinburgh implements several type theories edinburgh logical framework lf calculus constructions coc generalized calculus constructions gcc unified theory dependent types utt
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Programming language topics
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liberian companies companies republic liberia regulated variety laws corporate laws liberia promulgated 50 years ago provide offshore jurisdiction ship owners international financial community liscr liberian international ship corporate registry appointed government liberia agent manage corporate registry act sole registered agent corporations registered liberia place business elsewhere corporate registry managed liscr located dulles virginia us office zurich switzerland two income tax treaties sweden germany force additionally liberia corporate jurisdiction oecd ’ white-list countries substantially implemented tax transparency meet internationally agreed tax standard liberian registry – second largest world – includes 4,300 ships 160 million gross tons accounts 12 percent world ’ oceangoing fleet liberian fleet one youngest nations average vessel age 12 years according u.s. maritime administration liberian-flagged vessels carry one-third oil imported united states liberian registry administered liberian international ship corporate registry liscr llc u.s. owned operated company provides day-to-day management republic liberia rol ship corporate registry addition regional offices many major maritime centers world liberian registry also supported worldwide network 400 nautical inspectors auditors liberian registry open ship owner world order enter liberian registry vessel must less 20 years age must meet high safety standards liberian flagged ships able trade anywhere world crew nationality restrictions taxes liberian vessels conservative rates based net tonnage registration vessels eligible liberian entities registered business entities incorporated jurisdictions registered liberian foreign maritime entity liberian corporations llcs partnerships not-for-profit businesses easily formed special documents required submitted order form confirming details entity requested however accept formation instructions professional user offshore corporations including ship managers manning agents ship owners etc. well trust company managers lawyers accountants investment companies etc accept instructions directly individuals engaged professionally company management acting professional advisor lawyer articles incorporation include minimum name corporation purpose corporation type shares total authorized share capital name incorporator names subscribers shares number initial directors directors shareholders officers need registered liberia thus possible obtain public record form evidence directors shareholders officers particular feature makes administration liberian company particularly simple offshore trust companies unfortunately sometimes create difficulties liberian company enter contract since counter-party must follow paper trail ensure dealing duly elected officials company purpose liberian corporations voluntarily file information needed conduct business liberian companies shall keep correct complete books records account shall keep minutes meetings shareholders actions taken consent shareholders meetings board directors actions taken consent directors meetings executive committee requirement file information public register instead corporation responsible safekeeping records requirement audited accounts liberian corporation decision audit accounts one shareholders take costs 713.50 register company liberia annual registration fee 450.00 requirement company director physically present liberia time capital investment requirements start liberian company maintain non-resident domestic corporation status least 75 previously 50 company shares share subscription rights must owned controlled non-residents liberia liberia special bank secrecy laws like tax havens deterrent liberian offshore corporations actually handle banking transactions within liberia ’ territory borders moreover requirement must bank liberia certified copies filed corporate records available order public
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Databases
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pdf/ua pdf/ua pdf/universal accessibility informal name iso 14289 international standard accessible pdf technology technical specification intended developers implementing pdf writing processing software pdf/ua provides definitive terms requirements accessibility pdf documents applications equipped appropriate software conformance pdf/ua ensures accessibility people disabilities use assistive technology screen readers screen magnifiers joysticks technologies navigate read electronic content february 18 2015 us access board announced proposed rule us federal policy accessibility commonly known section 508 proposed rule identifies pdf/ua equivalent wcag 2.0 appropriate content pdf/ua separate file-format simply way use familiar pdf format invented adobe systems standardized iso 32000 general pdf/ua requires tagged pdf iso 32000-1 14.8 adds variety qualitative requirements especially regarding semantic correctness tags employed pdf/ua complements wcag 2.0 used make pdf files also conform wcag 2.0 2014 update pdf/ua published december 2014 first fully accessible standard iso ever published pdf file distributed iso conforms pdf/ua formal name pdf/ua iso 14289-1 document management applications -- electronic document file format enhancement accessibility -- part 1 use iso 32000-1 pdf/ua-1 pdf/ua specification written software developers pdf/ua support interest persons disabilities require benefit assistive technology reading electronic content pdf/ua conforming files readers assistive technology users guaranteed – far pdf format provide – equal access information benefits pdf/ua extend beyond people disabilities support pdf/ua reader software able reliably reflow text onto small screens provide powerful navigation options transform text appearance improve search engine functionality aid selection copying text pdf/ua project began 2004 aiim standards committee pdf/ua wiki operated aiim contains agendas meeting-minutes public-access documents pertaining development pdf/ua chaired since 2005 duff johnson 2009 aiim pdf/ua committee became u.s. committee iso/awi accepted work item 14289 cherie ekholm microsoft international project leader us committee continued main driver standard development wd cd dis fdis phases iso standards development review comment balloting member bodies iso tc 171 iso 14289-1:2012 pdf/ua published july 2012 minor update iso 14289-1:2014 published december 2014 document available directly iso webstore october 2012 us library congress added pdf/ua list archivable file formats loc guidance states pdf/ua ... preferred format page-oriented content library congress adobe systems largest implementer interactive pdf software announced intention support pdf/ua december 2014 iso published iso 14289-1:2014 minor revision original 2012 document march 2016 aiim ansi published pdf/ua american national standard aiim us committee pdf/ua published following documents support pdf/ua work iso 14289-2 pdf/ua-2 ongoing pdf/ua-2 based pdf 2.0 aiim us committee pdf/ua led development document 2004 2010 draft became iso nwi us iso committees maintain work aiim pdf standards wiki participation subject matter experts software developers interested parties invited encouraged pdf association helps promote pdf/ua variety ways 2011 pdf association created pdf/ua competence center way vendors develop educational resources share experiences regarding implementation pdf/ua matterhorn protocol see product pdf/ua competence center 2012 2013 pdf association helped raise money awareness nv access nvda development world first pdf/ua conforming screen reader august 2013 pdf association pdf/ua competence center published matterhorn protocol set 31 checkpoints 136 failure conditions help software developers make easier document authors create fully accessible pdf files forms june 2014 pdf association pdf/ua competence center published first iteration pdf/ua reference suite set reference-quality documents conforming pdf/ua-1. ref name= pdf/ua reference suite /ref december 2015 pdf association pdf/ua competence center unveiled first public draft tagged pdf best practice guide publication expected summer 2016 pdf association conducted numerous educational seminars pdf/ua throughout europe north america australia 2012 2013 book pdf/ua nutshell produced english german informational brochure also produced languages
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Programming language topics
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dvd player mac os dvd player formerly apple dvd player default dvd player macos supports standard dvd features multiple audio video subtitle tracks well dolby digital 5.1 passthrough dvd access urls closed captions instances users choose vob file open dvd player also fully compatible dvds authored dvd studio pro idvd including hd dvds dvd studio pro macos mojave updated 64-bit sports new icon better touch bar support dvd player complies copyright laws thus enforce restrictive measures dvd technology region-restrictive encodings user-inhibited operations disabled actions even using all-region dvd drive even force apple grab screen-grabbing program cease functioning finder interface dvd player application quit effectively preventing user taking screen captures visual dvd content software contain dts decoder dts tracks played mac built speakers analog output however dts tracks output devices decoder playback supported outputs s/pdif displayport hdmi
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Operating systems
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amazon simple queue service amazon simple queue service amazon sqs distributed message queuing service introduced amazon.com late 2004 supports programmatic sending messages via web service applications way communicate internet sqs intended provide highly scalable hosted message queue resolves issues arising common producer-consumer problem connectivity producer consumer amazon sqs described commoditization messaging service well-known examples messaging service technologies include ibm websphere mq microsoft message queuing unlike technologies users need maintain server amazon sells sqs service per-use rate amazon provides sdks several programming languages including java ruby python .net php javascript java message service jms 1.1 client amazon sqs released december 2014 amazon sqs provides authentication procedures allow secure handling data amazon uses amazon web services aws identification requiring users aws enabled account amazon.com created amazon web services aws cloud computing services aws assigns pair related identifiers aws access keys aws enabled account perform identification first identifier public 20-character access key key included aws service request identify user user using soap protocol ws-security digital signature calculated using secret access key secret access key 40-character private identifier aws uses access key id provided service request look account secret access key amazon.com calculates digital signature key match user considered authentic authentication fails request processed amazon sqs guarantees at-least-once delivery messages stored multiple servers redundancy ensure availability message delivered server available may removed server queue may resent amazon sqs guarantee recipient receive messages order sent sender message ordering important required application place sequencing information within messages allow reordering delivery messages type data contained within restricted message bodies initially limited 8kb size later raised 64kb 2010-07-01 256kb 2013-06-18 larger messages user options get around limitation large message split multiple segments sent separately message data stored using amazon simple storage service amazon s3 amazon dynamodb pointer data transmitted sqs message amazon made extended client library available purpose extension amazon sqs client enables sending receiving messages 2gb via amazon s3 awslabs/amazon-sqs-java-extended-client-lib service supports unlimited queues message traffic sqs automatically delete messages sent message delivered receipt handle generated delivery sent recipient receipts sent message addition sqs requires recipient provide receipt order delete message feature new 2008 message id required message deletion system distributed message may sent case recent receipt handle needed delete message message delivered visibility timeout prevent components consuming clock visibility timeout starts message sent default time 30 seconds queue told delete message time message becomes visible resent queue also consists retention parameter defaulting 4 days message residing queue longer purged automatically retention modified 1 minute 14 days user retention changed messages already queue message queue longer new retention purged dropbox netflix nextdoor examples companies use sqs extensively sqs also widely used within amazon.com first 1 million monthly requests free pricing follows regions date transfer price
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Web technology
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exchange exchange exchange exchange sometimes exchange-to-exchange abbreviated e2e integration certain pairs computer systems qualify e2e paired systems must primary use acting exchange gateway among customers common example connection stock brokerage firms internal systems systems stock market broker trades connections often facilitated middleware services object request brokers e2e partner system primary function clients allowing transfer information conduct transactions form business business b2b commerce model e2e partner b2b gateway clients turn exchanges information least one b2b gateway connection two b2b systems exchanges exchange exchange integration e2e alternative direct application application integration a2a though a2a classified e2e
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Computer architecture
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ws-federation active requestor profile ws-federation active requestor profile web services specification intended work ws-federation specification defines identity authentication authorization mechanisms work across trust realms specification deals specifically applications soap-enabled applications make requests using mechanisms way contrast ws-federation passive requestor profile deals passive requestors web-browsers ws-federation active requestor profile created ibm bea systems microsoft verisign rsa security
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Web technology
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borg cluster manager borg cluster manager used google led widespread use similar approaches docker kubernetes
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Distributed computing architecture
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musa multichannel speaking automaton musa multichannel speaking automaton early prototype speech synthesis machine started 1975 consisted stand-alone computer hardware specialized software implemented diphone-synthesis technology one first real-time tts systems able read italian intellegibile robotic voice also sing managing 8 synthesis channels parallel thanks linear predictive coding technology 1978 released building working prototype 45 rpm audio disk containing trial content synthesis including song fra martino campanaro cappella multiple voices style attached commercial reviews experiment conducted cselt turin italy led giulio modena
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Computational linguistics
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sliding window based part-of-speech tagging sliding window based part-of-speech tagging used part-of-speech tag text high percentage words natural language words context assigned one part speech percentage ambiguous words typically around 30 although depends greatly language solving problem important many areas natural language processing example machine translation changing part-of-speech word dramatically change translation sliding window based part-of-speech taggers programs assign single part-of-speech given lexical form word looking fixed sized window words around word disambiguated two main advantages approach let set grammatical tags application set possible tags may assigned word let vocabulary application let function morphological analysis assigns formula_4 set possible tags formula_5 implemented full-form lexicon morphological analyser let set word classes general partition formula_7 restriction formula_8 words formula_9 receive set tags words word class formula_10 belong ambiguity class normally formula_11 constructed way high frequency words word class contains single word low frequency words word class corresponds single ambiguity class allows good performance high frequency ambiguous words n't require many parameters tagger definitions possible state problem following way given text formula_12 word formula_13 assigned word class formula_14 either using lexicon morphological analyser order get ambiguously tagged text formula_15 job tagger get tagged text formula_16 formula_17 correct possible statistical tagger looks probable tag ambiguously tagged text formula_18 using bayes formula converted formula_21 probability particular tag syntactic probability formula_22 probability tag corresponds text formula_23 lexical probability markov model probabilities approximated products syntactic probabilities modelled first order markov process formula_25 formula_26 delimiter symbols lexical probabilities independent context one form tagging approximate first probability formula formula_29 right context size formula_30 way sliding window algorithm take account context size formula_31 applications formula_32 example tag ambiguous word run sentence runs danger tags words needed taken account
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Computational linguistics
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downgrade attack downgrade attack form cryptographic attack computer system communications protocol makes abandon high-quality mode operation e.g encrypted connection favor older lower-quality mode operation e.g cleartext typically provided backward compatibility older systems example flaw found openssl allowed attacker negotiate use lower version tls client server one common types downgrade attacks another example intercepting web traffic redirecting user secure https version website unencrypted http version downgrade attacks often implemented part man-in-the-middle attack may used way enabling cryptographic attack might possible otherwise downgrade attacks consistent problem ssl/tls family protocols examples attacks include poodle attack downgrade attacks tls protocol take many forms researchers classified downgrade attacks respect four different vectors represents framework reason downgrade attacks follows recent proposals removing backward compatibility often way prevent downgrade attacks however sometimes client server recognize up-to-date manner prevents example web server user agent implement http strict transport security user agent knows server either previously accessed https hsts preload list user agent refuse access site vanilla http even malicious router represents server https-capable
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Computer security
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archone archone arch linux based operating system optimized acer aspire one netbooks usable pcs similar hardware archone preconfigured support hardware acer aspire one drivers network sound graphics special keys webcam active make hardware ready use immediately upon first boot archone uses rolling-release model upgrades archone three versions different desktop manager openbox edition gnome edition kde edition. application software including firefox google chrome skype keepassx hsoconnect gparted gimp openoffice.org vlc mplayer
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Operating systems
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email encryption email encryption encryption email messages protect content read entities intended recipients email encryption may also include authentication email prone disclosure information emails currently transmitted clear encrypted form emails sent using gmail outlook encrypted default possible send unencrypted email using gmail warning icon appear address bar means available tools persons designated recipients read email contents email encryption rely public-key cryptography users publish public key others use encrypt messages keeping secret private key use decrypt messages digitally encrypt sign messages send original design email protocol communication email servers plain text posed huge security risk years various mechanisms proposed encrypt communication email servers encryption may occur transport level aka hop hop end-to-end transport layer encryption often easier set use end-to-end encryption provides stronger defenses difficult set use one commonly used email encryption extensions starttls tls ssl layer plaintext communication allowing email servers upgrade plaintext communication encrypted communication assuming email servers sender recipient side support encrypted communication eavesdropper snooping communication mail servers use sniffer see email contents similar starttls extensions exist communication email client email server see imap4 pop3 stated rfc 2595 starttls may used regardless whether email contents encrypted using another protocol encrypted message revealed altered intermediate email relays words encryption takes place individual smtp relays sender recipient good bad consequences key positive trait transport layer encryption users need change anything encryption automatically occurs send email addition since receiving organizations decrypt email without cooperation end user receiving organizations run virus scanners spam filters delivering email recipient however also means receiving organization anyone breaks organization email system unless steps taken easily read modify email receiving organization considered threat end-to-end encryption necessary electronic frontier foundation encourages use starttls launched 'starttls everywhere initiative make simple easy everyone help ensure communications email ’ vulnerable mass surveillance support starttls become quite common google reports gmail 90 incoming email 90 outgoing email encrypted using starttls 2018-07-24 mandatory certificate verification historically viable internet mail delivery without additional information many certificates verifiable want email delivery fail case result email delivered tls uses opportunistic encryption dane proposed standard makes incremental transition verified encryption internet mail delivery possible starttls everywhere project uses alternative approach support “ preload list ” email servers promised support starttls help detect prevent downgrade attacks end-to-end encryption data encrypted decrypted end points words email sent end-to-end encryption would encrypted source unreadable service providers like gmail transit decrypted endpoint crucially email would decrypted end user computer would remain encrypted unreadable form email service like gmail would n't keys available decrypt email services integrate end-to-end encryption automatically notable protocols end-to-end email encryption include openpgp data encryption standard allows end-users encrypt email contents various software email-client plugins allow users encrypt message using recipient public key sending core openpgp uses public key cryptography scheme email address associated public/private key pair openpgp provides way end users encrypt email without support server sure intended recipient read however usability issues openpgp — requires users set public/private key pairs make public keys available widely also protects content email metadata — untrusted party still observe sent email general downside end end encryption schemes—where server decryption keys—is makes server side search almost impossible thus impacting usability signed encrypted email internet demonstration shown organizations collaborate effectively using secure email previous barriers adoption overcome including use pki bridge provide scalable public key infrastructure pki use network security guards checking encrypted content passing corporate network boundaries avoid encryption used hide malware introduction information leakage transport layer encryption using starttls must set receiving organization typically straightforward valid certificate must obtained starttls must enabled receiving organization email server prevent downgrade attacks organizations send domain 'starttls policy list' full-featured email clients provide native support s/mime secure email digital signing message encryption using certificates encryption options include pgp gnu privacy guard gnupg free commercial software desktop application webmail add-ons available well pgp protect messages also hard use correct way researchers carnegie mellon university published paper 1999 showing people could n't figure sign encrypt messages using current version pgp eight years later another group carnegie mellon researchers published follow-up paper saying although newer version pgp made easy decrypt messages people still struggled encrypting signing messages finding verifying people public encryption keys sharing keys encryption difficult users security compliance managers companies government agencies automate process employees executives using encryption appliances services automate encryption instead relying voluntary co-operation automated encryption based defined policies takes decision process users hands emails routed gateway appliance configured ensure compliance regulatory security policies emails require automatically encrypted sent recipient works organization uses encryption gateway appliance emails automatically decrypted making process transparent user recipients behind encryption gateway need take extra step either procuring public key logging online portal retrieve message
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Computer security
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amd k9 amd k9 represents microarchitecture amd designed replace k8 processors featuring dual-core processing k9 appears originally ambitious 8 issue per clock cycle core redesign k7 k8 processor core one point k9 greyhound project amd worked k7 design team beginning early 2001 tape-out revision a0 scheduled 2003 l1 instruction cache said hold decoded instructions essentially intel trace cache existence massively parallel cpu design concept heavily multi threaded applications also revealed planned successor k8 reportedly canceled conceptualization phase 6 months work one time k9 internal codename dual-core amd64 processors brand athlon 64 x2 however amd distanced old k series naming convention seeks talk portfolio products tailored different markets
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Computer architecture
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chain trust computer security chain trust established validating component hardware software end entity root certificate intended ensure trusted software hardware used still retaining flexibility chain trust designed allow multiple users create use software system would difficult keys stored directly hardware starts hardware boot software digitally signed signing authority sign boot programs enforce security running programs signed allowing signed code access certain features machine process may continue several layers process results chain trust final software trusted certain properties illegally modified signature would invalid previous software would executed previous software trusted turn would loaded signature invalid trustworthiness layer guaranteed one back trust anchor would possible hardware check suitability signature every single piece software however would produce flexibility chain provides chain given link replaced different version provide different properties without go way back trust anchor use multiple layers application general technique improve scalability analogous use multiple certificates certificate chain computer security digital certificates verified using chain trust trust anchor digital certificate root certificate authority ca certificate hierarchy structure certificates allows individuals verify validity certificate issuer certificates issued signed certificates reside higher certificate hierarchy validity trustworthiness given certificate determined corresponding validity certificate signed chain trust certificate chain ordered list certificates containing end-user subscriber certificate intermediate certificates represents intermediate ca enables receiver verify sender intermediate certificates trustworthy process best described page intermediate certificate authority see also x.509 certificate chains description concepts widely used standard digital certificates
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Computer security
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trace-based simulation computer science trace-based simulation refers system simulation performed looking traces program execution system component access purpose performance prediction trace-based simulation may used variety applications analysis solid state disks message passing performance large computer clusters traced-based simulators usually two components one executes actions stores results i.e traces another reads log files traces interpolates new often complex scenarios instance case large computer cluster design execution takes place small number nodes traces left log files simulator reads log files simulates performance much larger number nodes thus providing view performance large applications based execution traces much smaller number nodes
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Distributed computing architecture
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architectural state architectural state part cpu holds state process typically held processor registers includes include actual computation units alu instance
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Computer architecture
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steve gibson computer programmer steven steve tiberius gibson born 26 march 1955 american software engineer security researcher security proponent early 1980s gibson worked light pen technology use apple atari systems 1985 founded gibson research corporation best known spinrite software gibson started working computers teenager got first computing job stanford university artificial intelligence lab 15 years old studied electrical engineering computer science university california berkeley gibson hired programmer california pacific computer company 1980 worked copy protection company products gibson founded gibson laboratories laguna hills california 1981 gibson labs developed light pen apple ii atari platforms went business 1983.. 1985 gibson founded gibson research corporation grc computer software development firm 1986 1993 gibson wrote tech talk column infoworld magazine 1999 gibson created one first adware removal programs called optout 2001 gibson predicted microsoft implementation sock_raw protocol initial release windows xp would lead widespread chaos making easier windows xp users create denial service dos attacks year company website brought dos attack attacks continued two weeks gibson blogged attacks ultimately successful efforts track hacker three years windows xp release microsoft limited raw socket support service pack 2 2005 gibson launched weekly podcast called security leo laporte twit.tv archives hosted grc website 2006 gibson raised possibility windows metafile vulnerability bug actually backdoor intentionally engineered system response microsoft mark russinovich microsoft technet stated bug appeared coding error gibson reasoning based upon microsoft abort procedure documentation misleading 2013 proposed sqrl way simplify process authentication without risk revelation information transaction third party grc created number utilities freeware
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Computer security
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sigspoof sigspoof family security vulnerabilities affected software package gnu privacy guard gnupg since version 0.2.2 released 1998 several software packages make use gnupg also affected pass enigmail un-patched versions affected software sigspoof attacks allow cryptographic signatures convincingly spoofed certain circumstances potentially enables wide range subsidiary attacks succeed according marcus brinkmann discovered sigspoof vulnerabilities june 2018 existence fact present wild long throws question integrity past emails backups software updates ... source code version control systems like git
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Computer security
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