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castor framework castor data binding framework java features like java java-to-xml binding java-to-sql persistence paths java objects xml documents relational tables etc castor one oldest data binding projects basic process flows include class generation marshalling unmarshalling etc marshalling framework includes set classdescriptors fielddescription describe objects class generation similar jaxb zeus castor supports xml schema instead dtds dtds supported castor unmarshalling marshalling dealt marshall unmarshall methods respectively marshalling conversion process java xml carried unmarshalling conversion process xml java carried mapping files equivalent binding schema allows transforms names xml java vice versa castor offers additional features present jaxb additional features include code marshalling may look like follows code unmarshalling may look like follows sample mapping file may look like follows
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Databases
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control-flow graph computer science control-flow graph cfg representation using graph notation paths might traversed program execution control-flow graph due frances e. allen notes reese t. prosser used boolean connectivity matrices flow analysis cfg essential many compiler optimizations static-analysis tools control-flow graph node graph represents basic block i.e straight-line piece code without jumps jump targets jump targets start block jumps end block directed edges used represent jumps control flow presentations two specially designated blocks entry block control enters flow graph exit block control flow leaves construction procedure cfg every edge a→b property cfg thus obtained least conceptually starting program full flow graph—i.e graph every node represents individual instruction—and performing edge contraction every edge falsifies predicate i.e contracting every edge whose source single exit whose destination single entry contraction-based algorithm practical importance except visualization aid understanding cfg construction cfg efficiently constructed directly program scanning basic blocks consider following fragment code 4 basic blocks 0 1 b 2 3 c 4 5 particular case entry block exit block lines 4 5 jump targets graph fragment edges b c b c d. reachability graph property useful optimization subgraph connected subgraph containing entry block subgraph unreachable execution unreachable code normal conditions safely removed exit block unreachable entry block infinite loop may exist infinite loops detectable see halting problem halting order may also exist unreachable code infinite loops possible even programmer explicitly code optimizations like constant propagation constant folding followed jump threading collapse multiple basic blocks one cause edges removed cfg etc. thus possibly disconnecting parts graph block dominates block n every path entry reaches block n pass block m. entry block dominates blocks reverse direction block postdominates block n every path n exit pass block m. exit block postdominates blocks said block immediately dominates block n dominates n intervening block p dominates p p dominates n. words last dominator paths entry n. block unique immediate dominator similarly notion immediate postdominator analogous immediate dominator dominator tree ancillary data structure depicting dominator relationships arc block block n immediate dominator n. graph tree since block unique immediate dominator tree rooted entry block dominator tree calculated efficiently using lengauer–tarjan algorithm postdominator tree analogous dominator tree tree rooted exit block back edge edge points block already met depth-first dfs traversal graph back edges typical loops critical edge edge neither edge leaving source block edge entering destination block edges must split new block must created middle edge order insert computations edge without affecting edges abnormal edge edge whose destination unknown exception handling constructs produce edges tend inhibit optimization impossible edge also known fake edge edge added graph solely preserve property exit block postdominates blocks ever traversed loop header sometimes called entry point loop dominator target loop-forming back edge loop header dominates blocks loop body block may loop header one loop loop may multiple entry points case loop header suppose block dominator several incoming edges back edges loop header advantageous several optimization passes break two blocks m. contents back edges moved rest edges moved point new edge inserted immediate dominator beginning would empty passes like loop-invariant code motion could populate called loop pre-header would loop header reducible cfg one edges partitioned two disjoint sets forward edges back edges structured programming languages often designed cfgs produce reducible common structured programming statements break continue produce reducible graphs produce irreducible graphs statements goto needed irreducible graphs may also produced compiler optimizations loop connectedness cfg defined respect given depth-first search tree dfst cfg dfst rooted start node cover every node cfg edges cfg run node one dfst ancestors including called back edges loop connectedness largest number back edges found cycle-free path cfg reducible cfg loop connectedness independent dfst chosen loop connectedness used reason time complexity data-flow analysis
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Programming language topics
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black bass 1986 video game objective player catch many black bass possible sunrise sunset player may select beginner game ranking game ranking game requires password player may select location lake start begin fishing simply tossing lure desired power start process fish lured moving lure around bites player try reeling much constant reeling leads line breaking loss fish lure casting rounds player make certain selections among selections available option change type color lure used
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Computer architecture
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cmd.exe cmd cmd command name cmd.exe executable file name also known command prompt default window title command-line interpreter os/2 ecomstation windows nt windows ce reactos operating systems counterpart command.com dos windows 9x systems analogous unix shells used unix-like systems initial version cmd.exe windows nt developed therese stowell cmd.exe interacts user command-line interface windows interface implemented win32 console cmd.exe may take advantage features available native programs platform example os/2 use real pipes command pipelines allowing sides pipeline run concurrently result possible redirect standard error stream command.com uses temporary files runs two sides serially one windows cmd.exe mostly compatible command.com provides following extensions internal commands also improved
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Operating systems
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comparison microsoft windows versions microsoft windows name several families computer software operating systems created microsoft microsoft first introduced operating environment named windows november 1985 add-on ms-dos response growing interest graphical user interfaces guis versions microsoft windows commercial proprietary software basic general information windows windows embedded compact windows ce variation microsoft windows operating system minimalistic computers embedded systems windows ce distinctly different kernel rather trimmed-down version desktop windows supported intel x86 compatibles mips arm hitachi superh processors windows mobile microsoft discontinued line operating systems smartphones windows phone microsoft discontinued line operating systems smartphones possible install ms-dos variants 7.0 7.1 without graphics user interface windows independent installation dos windows desired dos ought installed prior windows start small partition system must transferred dangerous system dos-command files constituting dos simply copied files located dos-root entire command directory stand-alone installation ms-dos 8 possible designed work real mode windows nothing else windows nt kernel powers recent windows operating systems runs ia-32 x64 itanium processors various versions windows support various file systems including fat12 fat16 fat32 hpfs ntfs along network file systems shared computers iso 9660 udf file systems used cds dvds optical discs blu-ray file system usually limited application certain media example cds must use iso 9660 udf windows vista ntfs file system operating system installed windows embedded ce 6.0 windows vista service pack 1 windows server 2008 onwards support exfat file system suitable usb flash drives installing windows requires internal external optical drive keyboard mouse recommended input devices though versions support touchscreen operating systems prior vista drive must capable reading cd media windows vista onwards drive must dvd-compatible drive may detached installing windows maximum limits physical memory ram windows address vary depending windows version ia-32 x64 versions
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Operating systems
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personal data personal data also known personal information personally identifying information pii sensitive personal information spi information relating identifying person abbreviation pii widely accepted united states phrase abbreviates four common variants based personal personally identifiable identifying equivalent legal purposes effective definitions vary depending jurisdiction purposes term used european data protection regimes centre primarily around general data protection regulation term personal data significantly broader determines scope regulatory regime national institute standards technology special publication 800-122 defines personally identifying information information individual maintained agency including 1 information used distinguish trace individual identity name social security number date place birth mother maiden name biometric records 2 information linked linkable individual medical educational financial employment information example user ip address classed pii classified linked pii however european union ip address internet subscriber may classed personal data concept pii become prevalent information technology internet made easier collect pii leading profitable market collecting reselling pii pii also exploited criminals stalk steal identity person aid planning criminal acts response threats many website privacy policies specifically address gathering pii lawmakers european parliament enacted series legislation general data protection regulation gdpr limit distribution accessibility pii personally identifying information legal concept technical concept utilised jurisdictions versatility power modern re-identification algorithms absence pii data mean remaining data identify individuals attributes may uniquely identifying attribute potentially identifying combination others attributes referred quasi-identifiers pseudo-identifiers data may constitute pii united states highly likely remain personal data european data protection law u.s. government used term personally identifiable 2007 memorandum executive office president office management budget omb usage appears us standards nist guide protecting confidentiality personally identifiable information sp 800-122 omb memorandum defines pii follows term similar pii personal data defined eu directive 95/46/ec purposes directive however eu rules clearer notion data subject potentially identified additional processing attributes—quasi- pseudo-identifiers gdpr personal data defined information relating identified identifiable natural person 'data subject identifiable natural person one identified directly indirectly particular reference identifier name identification number location data online identifier one factors specific physical physiological genetic mental economic cultural social identity natural person another term similar pii personal information defined section california data breach notification law sb1386 concept information combination given sb1386 definition key correctly distinguishing pii defined omb personal information defined sb1386 information name lacks context said sb1386 personal information must said pii defined omb example name john smith meaning current context therefore sb1386 personal information pii social security number ssn without name associated identity context information sb1386 personal information pii example ssn 078-05-1120 pii sb1386 personal information however combination valid name correct ssn sb1386 personal information combination name context may also considered pii example person name list patients hiv clinic however necessary name combined context order pii reason distinction bits information names although may sufficient make identification may later combined information identify persons expose harm according omb always case pii sensitive context may taken account deciding whether certain pii sensitive australia privacy act 1988 deals protection individual privacy using oecd privacy principles 1980s set broad principles-based regulatory model unlike us coverage generally based broad principles specific technologies business practices data items section 6 relevant definition critical detail definition 'personal information also applies individual indirectly identified raises question reasonableness assume theoretically possible identify person information include name address contain clues could pursued find relates much extra effort take make unreasonable information could identified instance information involves ip address relevant isp stores logs could easily inspected sufficient legal justification re-link ip address account holder identity reasonably ascertained linking used expensive slow difficult becomes easier change answer point appears definition significantly broader californian example given thus australian privacy law respects weakly enforced may cover broader category data information us law particular online behavioral advertising businesses based us surreptitiously collecting information people countries form cookies bugs trackers like may find preference avoid implications wanting build psychographic profile particular person using rubric 'we n't collect personal information may find make sense broader definition like australian privacy act european data protection law utilize concept personally identifiable information scope instead determined non-synonymous wider concept personal data examples found eu privacy website twelve information privacy principles privacy act 1993 apply federal act data protection 19 june 1992 force since 1993 set strict protection privacy prohibiting virtually processing personal data expressly authorized data subjects protection subject authority federal data protection information commissioner additionally person may ask writing company managing data files correction deletion personal data company must respond within thirty days privacy act 1974 pub.l 93–579 88 stat 1896 enacted december 31 1974 5 u.s.c § 552a united states federal law establishes code fair information practice governs collection maintenance use dissemination personally identifiable information individuals maintained systems records federal agencies one primary focuses health insurance portability accountability act hipaa protect patient protected health information phi similar pii u.s. senate proposed privacy act 2005 attempted strictly limit display purchase sale pii without person consent similarly proposed anti-phishing act 2005 attempted prevent acquiring pii phishing u.s. lawmakers paid special attention social security number easily used commit identity theft proposed social security number protection act 2005 proposed identity theft prevention act 2005 sought limit distribution individual social security number national institute standards technology physical sciences laboratory non-regulatory agency united states department commerce mission promote innovation industrial competitiveness following data often used express purpose distinguishing individual identity clearly classify personally identifiable information definition used national institute standards technology described detail following less often used distinguish individual identity traits shared many people however potentially pii may combined personal information identify individual person wishes remain anonymous descriptions often employ several 34-year-old white male works target note information still private sense person may wish become publicly known without personally identifiable moreover sometimes multiple pieces information none sufficient uniquely identify individual may uniquely identify person combined one reason multiple pieces evidence usually presented criminal trials shown 1990 87 population united states could uniquely identified gender zip code full date birth hacker internet slang practice finding releasing information called doxing sometimes used deter collaboration law enforcement occasion doxing trigger arrest particularly law enforcement agencies suspect doxed individual may panic disappear forensics particularly identification prosecution criminals personally identifiable information critical establishing evidence criminal procedure criminals may go great trouble avoid leaving pii personal data key component online identity exploited individuals instance data altered used create fake documents hijack mail boxes phone calls harass people like data breach ee limited company another key case referred financial identity theft usually bank account credit card information stolen used sold personal data also used create fake online identity including fake accounts profiles referred identity cloning identity fraud celebrities gather data users easily even individuals concerned especially personal purpose widely known sockpuppet critical information password date birth id documents social insurance number used log different websites see password reuse account verification gather information access content also several agencies ask discretion subject related work safety employees reason united states department defense dod strict policies controlling release personally identifiable information dod personnel many intelligence agencies similar policies sometimes point employees disclose friends work agency similar identity protection concerns exist witness protection programs women shelters victims domestic violence threats second half 20th century digital revolution introduced privacy economics trade personal data value data change time different contexts disclosing data reverse information asymmetry though costs unclear relation companies consumers often imperfect information regarding data collected purposes consequences writing 2015 alessandro acquisti curtis taylor liad wagman identified three waves trade personal data
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Computer security
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gparted gparted acronym gnome partition editor gtk front-end gnu parted official gnome partition-editing application alongside disks gparted used creating deleting resizing moving checking copying disk partitions file systems useful creating space new operating systems reorganizing disk usage copying data residing hard disks mirroring one partition another disk imaging gparted uses libparted detect manipulate devices partition tables several optional file system tools provide support file systems included libparted optional packages detected runtime require rebuild gparted gparted written c++ uses gtkmm interface gtk general approach keep gui simple possible conformity gnome human interface guidelines gparted project provides live operating system including gparted written live cd live usb media operating system based debian gnu/linux gparted also available gnu/linux live cds including recent versions puppy knoppix systemrescuecd parted magic gparted preinstalled booting try ubuntu mode ubuntu installation media alternative software disks gnome disks gparted supports following operations file systems provided features enabled compile-time required tools present system 'copy field indicates whether gparted capable cloning mentioned filesystem gparted capable cloning using mouse gesture copy paste gparted capable cloning entire disk one partition time file system cloned mounted gparted clones partitions filesystem-level result capable cloning different target-size partitions source long size source filesystem exceed size target partition
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Operating systems
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advanced scsi programming interface computing aspi advanced scsi programming interface adaptec-developed programming interface standardizes communication computer bus scsi driver module one hand scsi atapi peripherals aspi manager software provides interface aspi modules device drivers applications direct scsi support scsi host adapter scsi devices connected host adapter aspi manager specific host adapter operating system primary role abstract host adapter specifics provide generic software interface scsi devices windows 9x windows nt aspi manager generic relies services scsi miniport drivers systems aspi interface designed applications require scsi pass-through functionality cd-rom burning software primary operations supported aspi discovery host adapters attached devices submitting scsi commands devices via srbs scsi request blocks aspi supports concurrent execution scsi commands originally inspired driver architecture developed douglas w. goodall ampro computers 1983 aspi developed adaptec around 1990 initially designed support dos os/2 windows 3.x novell netware originally written support scsi devices support atapi devices added later scsi host adapter vendors example buslogic dpt ami future domain dtc shipped aspi managers hardware adaptec also developed generic scsi disk cd-rom drivers dos aspicd.sys aspidisk.sys microsoft licensed interface use windows 9x series time microsoft developed scsi pass interface spti in-house substitute worked nt platform microsoft include aspi windows 2000/xp favor spti users may still download aspi adaptec number cd/dvd applications also continue offer implementations aspi layer support usb drives dos panasonic developed universal aspi driver usbaspi.sys bypasses lack native usb support dos aspi provided following drivers
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Operating systems
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infosec institute infosec institute technology training company provides certification-based training courses security professionals enterprise-grade security awareness phishing training businesses agencies technology professionals company training library provides multi-course tracks job function certification-specific training short-form continuing education training course library includes 95 courses covering topics like ethical hacking network security mobile forensics infosec institute securityiq integrates security awareness training phishing simulations personalized learning scales employees ’ security aptitudes roles learning styles infosec institute founded 1998 team information security instructors
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Computer security
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jamf pro jamf pro formerly casper suite apple device management solution used system administrators configure automate administration tasks mac os x ios tvos devices product includes server client agent software runs ios mac os x tvos jamf offers on-premises cloud-based mobile device management well agent managing mac os x. jamf pro flagship product company centralizes device management allows policy creation restricts device features software equipped features management tools remote setup remote lock wipe minneapolis-based jamf software started eau claire wisconsin zach halmstad chip pearson 2002 releasing casper suite casper suite rebranded jamf pro 2017.. vista equity partners acquired majority shares jamf december 2017 ibm selected jamf pro manage macs 2015 ibm chief technology officer fletcher previn announced surpassed 277,000 devices 2017 making largest mac deployment world ibm claimed mac cheaper manage windows counterparts jamf partnership microsoft allows jamf pro communicate intune
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Computer security
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directory-based coherence directory-based coherence mechanism handle cache coherence problem distributed shared memory dsm a.k.a non-uniform memory access numa another popular way use special type computer bus nodes shared bus a.k.a system bus directory-based coherence uses special directory serve instead shared bus bus-based coherence protocols designs use corresponding medium i.e directory bus tool facilitate communication different nodes guarantee coherence protocol working properly along communicating nodes directory based cache coherence done using directory keep track status cache blocks status block includes cache coherence state block nodes sharing block time used eliminate need broadcast signals nodes send nodes interested single block following advantages disadvantages directory based cache coherence protocol according discussion clear using bus based systems seems attractive relatively small systems however directory based systems become crucial system scale number nodes grows kind trade-off simplicity scalability comparing bus-based directory-based cache coherence designs idea directory-based cache coherence systems began long ago idea dash directory architecture shared-memory first proposed c.k tang mid 1970s however applying cache coherence proposed years later specifically 1978 researchers stanford university proposed first version coherence systems called stanford dash paper described system difficulties improvements associated designs beside approach several attempts done provide scalable systems instance bbn butterfly introduced 1985 ibm pr3 introduced 1987 examples scalable multiprocessor systems however systems drawback example bbn butterfly caches similarly ibm pr3 provide hardware cache coherence limits performance designs especially employing high performance processors limitations competitors made easier dash based systems get chosen designing cache coherence systems systems needing scalability cache-based nodes 1985 james archibald jean-loup baer university washington published paper proposes economical expandable modular variation global directory approach term hardware use design 1992 daniel lenoski stanford university published paper proposing advances cache coherence protocols directory-based systems 1996 paper introduced design sgi origin 2000 family server computers employing directory based cache coherence subsequent origin 3000 introduced july 2000 unlike snoopy coherence protocols directory based coherence approach information caches copy block maintained structure called directory directory based scheme participating caches broadcast requests sharing caches block order locate cached copies instead queries directory retrieve information block cached copies sends particular processors hence traffic saving compared snoopy protocol large well optimized applications data sharing data read little sharing data frequently read written directory approach result substantial traffic saving compared broadcast/snoopy approach applications shown data flow diagram actors involved distributed shared memory system implementing directory based coherence protocol requestor owner nodes maintain state transition similar snoopy coherence protocols like mesi protocol however unlike bus based implementation nodes communicate using common bus directory based implementation uses message passing model exchange information required maintaining cache coherence directory node acts serializing point communications directed node maintain correctness directory node keeps track overall state cache block entire cache system processors three states explanation directory state transition finite state machine refer image 1 captured table addition cache state directory must track processors data shared state required sending invalidation intervention requests individual processor caches cache block shared state popular implementation approaches please note protocol described basic implementation race conditions occur due fact directory sync caches also messages processors overlapping complex implementations available like scalable coherent interface multiple states dash cache coherence protocol another protocol uses directory-based coherence scheme dash protocol uses clustered approach processors inside cluster kept coherent using bus based snooping scheme clusters connected directory approach even though various protocols use different implementations tracking cache blocks however concept directory remains
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Computer architecture
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filter driver filter driver microsoft windows driver extends modifies function peripheral devices supports specialized device personal computer driver program module inserted existing driver stack perform specific function filter driver affect normal working existing driver stack major way written either microsoft vendor hardware number filter drivers added windows upper level filter drivers sit primary driver device function driver lower level filter drivers sit function driver bus driver filters may work certain brand device mouse keyboard may perform operation class devices mouse keyboard windows dev center hardware pages explain upper lower filter drivers detail example generic usb camera uvc driver usbvideo.sys function driver bus driver handles usb data host controller devices lower level filter modifies behavior camera hardware e.g watching interrupt packets camera switch fits function bus drivers upper level filter typically provide added-value features camera additional processing video stream e.g colour changes identification objects applying overlays fit function driver user application connected camera another type filter driver bus e.g usb pci pcie filter driver may added top bus driver example acpi bus filter added support power management device
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Operating systems
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privatos privatos operating system used blackphone june 1 2014 june 30 2016 targeted users sought improved privacy security provided encryption phone calls emails texts internet browsing privatos modified version android forked android 4.4.2 came bundle security-minded tools however contrast android privatos open source company shipped privatos sgp technologies joint venture makers geeksphone silent circle concept encrypted phone long interest silent circle founder pgp creator phil zimmerman video blackphone website zimmerman said company stated operating system able “ close backdoors ” usually found major mobile operating systems major features privatos anonymous search privacy-enabled bundled apps smart disabling wi-fi except trusted hotspots control app permissions private communication calling texting video chat browsing file sharing conference calls geeksphone also claimed phone would receive frequent secure updates blackphone directly ars technica praised blackphone security center privatos gave control app permissions liked privatos came bundled silent phone silent text disconnect vpn disconnect search services ars like phone ’ performance mediocre using custom os meant google play benefits google ecosystem spotty support sideloaded apps reliance amazon third-party app stores month using device joshua drake accuvant concluded blackphone security claims overstated criticizing closed-source nature os lack os kernel hardening features praising fast patching added features
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Operating systems
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spin-up spin-up refers process hard disk drive optical disc drive accelerating platters inserted optical disc stopped state operational speed period time taken drive perform process referred spin-up time average reported hard disks s.m.a.r.t attribute required operational speed depends design disk drive typical speeds hard disks 2400 3600 4200 5400 7200 10000 15000 revolutions per minute rpm achieving speeds require significant portion available power budget computer system application power disks must carefully controlled operational speed optical disc drives may vary depending type disc mode operation see constant linear velocity spin-up hard disks generally occurs beginning computer boot process however modern computers ability stop drive machine already running means energy conservation noise reduction machine running requires access stopped drive delay incurred drive spun also depends type mechanism used within drive process spun needs energy input drive already spinning operation speeds since effort required electric motor accelerate platters opposed maintaining speed computers multiple hard drives method called staggered spin-up employed prevent excessive power-consumption spin-up may result power shortage power consumption spin-up often highest power draw different operating states hard disk drive staggered spin-up typically starts one drive time either waiting drive signal ready allowing predefined period time pass starting next drive power supply able supply sufficient current start multiple drives time common staggered spin-up ssu power-up standby puis different features help control spin-up multiple drives within computer system disk subsystem defined ata specifications standards see serial ata information one feature called power-up standby puis also called pm2 used serial ata sata parallel ata sometimes called pata ide hard disk drives puis requires bios and/or driver support use power applied hard disk drive drive spin-up puis spin-up command issued computer system bios raid controller must issue command tell drive spin-up accessed puis enabled tools hdparm drives support feature another feature called staggered spin-up ssu used serial ata sata hard disk drives common power-up standby puis require special commands get drive spin-up drive electronics waits sata data phy physical i/f activate spin-up drive computer system bios and/or raid controller raid driver set delay control different drives spin-up western digital hard disk drives pin 11 sata power interface controls whether staggered spin-up ssu enabled pin 11 also used activity led connection drive initially powered drive senses whether pin 11 left floating high 1 logic state grounded low 0 logic state ssu disabled pin 11 grounded disabled drive spin-up soon power applied ssu enabled pin 11 left floating driven high high 1 logic state drive spin-up sata phy interface becomes active connection sata controller sata raid controller sata sata raid controller control many drives spun-up ssu puis features configured software firmware manufacturer information fujitsu serial ata interface mobile hard disk drives whitepaper note staggered spin-up disks feature many multi-drive systems using sata raid typically used mobile platforms
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Operating systems
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timeline computer viruses worms timeline computer viruses worms presents chronological timeline noteworthy computer viruses computer worms trojan horses similar malware related research events
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Computer security
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rvu protocol rvu protocol rvu pseudo-acronym pronounced r-view application layer protocol combines pre-existing digital living network alliance dlna standards new remote user interface rui protocol works similar remote desktop protocol rdp rvu rui protocol intended allow rvu-enabled client tv receive pixel-accurate display user interface available rvu server rvu combined dlna ability transmit media video photos music across home network allows entire user experience media server transmitted rvu client makes user interface available via rui protocol processing done server software plug-ins happen host computer user interface streamed client devices protocol primarily intended operate home network rvu protocol developed focus passing broadcast video coming multichannel video programming distributor residential gateway dedicated media server consumer electronic devices home however protocol much broader applications rvu protocol defined solve problem provide consistent television user interface throughout home without requiring use dedicated set-top box television rvu protocol communications protocol runs media server device multiple client devices rvu uses open standards including dlna upnp already use consumer electronics field clients consist various manufacturer-branded tvs blu-ray players client devices server generates user guide data sends client display way clients low complexity thin client devices still providing full user interface experience user rvu compliant device connected rvu server tv viewer watch different content room home viewers access prerecorded live content server via client device set-top box present user guide experience rvu supports networking existing home infrastructure agnostic transport mechanism work wireless technologies 802.11 wired technologies ethernet moca rvu supports remote user interface rui allows user interactions trick play e.g. pause rewind running interactive applications device render interface even though media center specific software plug-ins might installed however media files streamed different protocol render media extender needs implementation codec used package media locally installed client works extender codec host computer enough alternatively media trans-coded fly host computer codec supported client rvu protocol specification v1.0 released 3 december 2009 rvu protocol specification v1.0 currently ratified board available members implementation rvu protocol specification v2.0 became available january 7 2013 specification large part dependent dlna specification specification uses dtcp/ip link protection copyright-protected commercial content one device another rvu certification devices subject certification rvu alliance certification procedures development rvu alliance
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Internet protocols
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hy hy alternately hylang programming language dialect language lisp designed interact language python translating expressions python abstract syntax tree ast hy introduced python conference pycon 2013 paul tagliamonte similar kawa clojure mapping s-expressions onto java virtual machine jvm hy meant operate transparent lisp front end python abstract syntax lisp allows operating code data metaprogramming thus hy used write domain-specific languages hy also allows python libraries including standard library imported accessed alongside hy code compiling step converting data structure python ast language documentation
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Programming language topics
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dropsuite dropsuite limited formerly branded dropmysite global cloud software platform founded 2011 provides cloud backup archiving recovery solutions based singapore public company listed australian securities exchange asx dse originally dropsuite provided website backup services expanded services include cloud backup office 365 cloud backup g suite gmail email archiving additional solutions include gdpr responder ediscovery insights bi ransomware protection dropsuite began development name dropmysite september 2011 john fearon ’ business website needed backup solution ’ find service met needs fearon raised 300,000 first round funding singaporean television show called angel ’ gate 2012 created email backup service called dropmyemail october 31 2013 charif elansari took ceo 2014 smartphone backup service called dropmymobile launched dropmysite local offices us singapore japan india entered partnership xpress hosting web-hosting company mexico getting access 100,000 customers 500,000 domains dropmysite also announced partnerships gmo cloud paperboy japan october 3 2015 godaddy launched cloud backup service websites powered dropmysite 2016 company rebranded name dropsuite dec 29 2016 company went public australia securities exchange via backdoor listing 2017 dropsuite entered distribution agreement ingram micro october 22 2018 dropsuite entered cloud distribution partnership pax8 2019 dsd europe announced partnership dropsuite adding dropsuite ’ microsoft office 365 cloud backup email backup cloud backup services management team consists people different continents including asia africa north america australia dropsuite limited dse asx publicly listed company australian securities exchange originally dropmysite privately held technology startup received seed funding crystal horse investments stanley street labs angel investors backend dropmysite originally based amazon aws infrastructure dropsuite provides data backup support many country-locations americas europe asia africa utilizes amazon web services data center support ensure data remains within country borders needed user data stored online user agents download install dropsuite ’ cloud services protect user ’ information military grade 256-bit advanced encryption allow legal grade email archiving compatible microsoft office 365 g suite gmail hosted exchange open-xchange imap/pop email servers
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Computer security
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manual memory management computer science manual memory management refers usage manual instructions programmer identify deallocate unused objects garbage mid-1990s majority programming languages used industry supported manual memory management though garbage collection existed since 1959 introduced lisp today however languages garbage collection java increasingly popular languages objective-c swift provide similar functionality automatic reference counting main manually managed languages still widespread use today c c++ – see c dynamic memory allocation programming languages use manual techniques determine allocate new object free store c uses codice_1 function c++ java use codice_2 operator many languages python allocate objects free store determination object ought created object creation generally trivial unproblematic though techniques object pools mean object may created immediate use fundamental issue object destruction – determination object longer needed i.e garbage arranging underlying storage returned free store re-use manual memory allocation also specified manually programmer via functions codice_3 c codice_4 operator c++ – contrasts automatic destruction objects held automatic variables notably non-static local variables functions destroyed end scope c c++ manual memory management known enable several major classes bugs program used incorrectly notably violations memory safety memory leaks significant source security bugs languages exclusively use garbage collection known avoid last two classes defects memory leaks still occur bounded leaks frequently occur generational conservative garbage collection generally less severe memory leaks manual systems manual memory management one correctness advantage allows automatic resource management via resource acquisition initialization raii paradigm arises objects scarce system resources like graphics resources file handles database connections must relinquished object destroyed – lifetime resource ownership tied lifetime object languages manual management arrange acquiring resource object initialization constructor releasing object destruction destructor occurs precise time known resource acquisition initialization also used deterministic reference counting c++ ability put use automate memory deallocation within otherwise-manual framework use codice_5 template language standard library perform memory management common paradigm codice_5 suitable object usage patterns however approach usable garbage collected languages – notably tracing garbage collectors advanced reference counting – due finalization non-deterministic sometimes occurring difficult define determine finalizer method might called commonly known finalizer problem java gc 'd languages frequently use manual management scarce system resources besides memory via dispose pattern object manages resources expected implement codice_7 method releases resources marks object inactive programmers expected invoke codice_7 manually appropriate prevent leaking scarce graphics resources depending codice_9 method java implements finalizers release graphics resources widely viewed poor programming practice among java programmers similarly analogous codice_10 method python relied releasing resources stack resources resources acquired released within single block code automated various language constructs python codice_11 c codice_12 java codice_13-with-resources many advocates manual memory management argue affords superior performance compared automatic techniques garbage collection traditionally latency biggest advantage longer case manual allocation frequently superior locality reference manual allocation also known appropriate systems memory scarce resource due faster reclamation memory systems frequently thrash size program working set approaches size available memory unused objects garbage-collected system remain unreclaimed state longer manually managed systems immediately reclaimed increasing effective working set size manual management number documented performance disadvantages latency debated point changed time early garbage collectors simple implementations performing poorly compared manual memory management sophisticated modern garbage collectors often performing well better manual memory management manual allocation suffer long pause times occur simple stop-the-world garbage collection although modern garbage collectors collection cycles often noticeable manual memory management garbage collection suffer potentially unbounded deallocation times – manual memory management deallocating single object may require deallocating members recursively members members etc. garbage collection may long collection cycles especially issue real time systems unbounded collection cycles generally unacceptable real-time garbage collection possible pausing garbage collector real-time manual memory management requires avoiding large deallocations manually pausing deallocation
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Operating systems
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christmas tree packet information technology christmas tree packet packet every single option set whatever protocol use term derives fanciful image little option bit header represented different-colored light bulb turned packet lit like christmas tree also known kamikaze packet nastygram lamp test segment christmas tree packets used method tcp/ip stack fingerprinting exposing underlying nature tcp/ip stack sending packets awaiting analyzing responses used part scanning system tcp header christmas tree packet flags fin urg psh set many operating systems implement compliance internet protocol standard rfc 791 varying incomplete ways observing host responds odd packet christmas tree packet inferences made regarding host operating system versions microsoft windows bsd/os hp-ux cisco ios mvs irix display behaviors differ rfc standard queried said packets large number christmas tree packets also used conduct dos attack exploiting fact christmas tree packets require much processing routers end-hosts usual packets christmas tree packets easily detected intrusion-detection systems advanced firewalls network security point view christmas tree packets always suspicious indicate high probability network reconnaissance activities
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Computer security
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wheel computing computing term wheel refers user account wheel bit system setting provides additional special system privileges empower user execute restricted commands ordinary user accounts access term wheel first applied computer user privilege levels introduction tenex operating system later distributed name tops-20 1960s early 1970s term derived slang phrase big wheel referring person great power influence 1980s term imported unix culture due migration operating system developers users tenex/tops-20 unix modern unix systems generally use user groups security protocol control access privileges wheel group special user group used unix systems mostly bsd systems control access su sudo command allows user masquerade another user usually super user .. ubuntu creates group called codice_1 similar purpose wheel group phrase wheel war originated stanford university first documented 1983 version jargon file 'wheel war characterized part immature 'larval phase wherein students administrative privileges would attempt lock university multi-user see also multiseat computer system sometimes causing unintentional harm users
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Operating systems
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chinese speech synthesis chinese speech synthesis application speech synthesis chinese language usually standard chinese poses additional difficulties due chinese characters frequently different pronunciations different contexts complex prosody essential convey meaning words sometimes difficulty obtaining agreement among native speakers concerning correct pronunciation certain phonemes recordings concatenated desired combination joins sound forced usual simple concatenation-based speech synthesis severely affect prosody synthesizers also inflexible terms speed expression however synthesizers rely corpus noticeable degradation performance given unusual awkward phrases ekho open source tts simply concatenates sampled syllables currently supports cantonese mandarin experimentally korean mandarin syllables pitched-normalised praat modified version used gradint synthesis partials cjkware.com used ship product called keytip putonghua reader worked similarly contained 120 megabytes sound recordings gsm-compressed 40 megabytes evaluation version comprising 10,000 multi-syllable dictionary words plus single-syllable recordings 6 different prosodies 4 tones neutral tone extra third-tone recording use end phrase lightweight open-source speech project espeak approach synthesis experimented mandarin cantonese espeak used google translate may 2010 december 2010 commercial product yuet also lightweight intended suitable resource-constrained environments like embedded systems written scratch ansi c starting 2013 yuet claims built-in nlp model require separate dictionary speech synthesised engine claims clear word boundaries emphasis appropriate words communication author required obtain copy espeak yuet synthesis speech cantonese mandarin input text output corresponding romanisation cantonese yuet uses yale espeak uses jyutping use pinyin mandarin espeak concern word boundaries n't change question syllable spoken corpus-based approach sound natural cases err dealing unusual phrases ca n't matched corpus synthesiser engine typically large hundreds even thousands megabytes due size corpus anhui ustc iflytek co. ltd iflytek published w3c paper adapted speech synthesis markup language produce mark-up language called chinese speech synthesis markup language cssml include additional markup clarify pronunciation characters add prosody information amount data involved disclosed iflytek seen commercial products iflytek licensed technology example bider speechplus 1.3 gigabyte download 1.2 gigabytes used highly compressed data single chinese voice iflytek synthesiser also synthesise mixed chinese english text voice e.g chinese sentences containing english words claim english synthesis average iflytek corpus appears heavily dependent chinese characters possible synthesize pinyin alone sometimes possible means cssml add pinyin characters disambiguate multiple possible pronunciations always work online interactive demonstration neospeech speech synthesis accepts chinese characters also pinyin enclosed proprietary vtml markup mac os chinese speech synthesizers available version 9 removed 10.0 reinstated 10.7 lion corpus-based approach taken tsinghua university sinosonic harbin dialect voice data taking 800 megabytes planned offered download link never activated nowadays references found internet archive bell labs approach demonstrated online 1997 subsequently removed described monograph multilingual text-to-speech synthesis bell labs approach springer october 31 1997 former employee responsible project chilin shih subsequently worked university illinois put notes methods website
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Computational linguistics
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msnbot msnbot web-crawling robot type internet bot deployed microsoft collect documents web build searchable index msn search engine went beta 2004 full public release 2005 month october 2010 saw official retirement msnbot active web crawling duties replacement bingbot september 2015 msnbot still active microsoft bing webmaster help howto documentation still indicated msnbot active would retire soon verification tool bingbot previously recognise msnbot ip addresses test executed 2016-02-22 resulted yes verdict ip address 157.55.39.150 yes ip address verified bingbot ip address name msnbot-157-55-39-150.search.msn.com
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Web technology
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haskell programming language haskell statically typed purely functional programming language type inference lazy evaluation type classes enable type-safe operator overloading originated haskell main implementation glasgow haskell compiler named logician haskell curry haskell based semantics syntax miranda programming language served focus efforts initial haskell working group haskell used widely academia industry latest standard haskell haskell 2010. haskell committee working next standard haskell 2020 following release miranda research software ltd. 1985 interest lazy functional languages grew 1987 dozen non-strict purely functional programming languages existed miranda widely used proprietary software conference functional programming languages computer architecture fpca '87 portland oregon strong consensus committee formed define open standard languages committee purpose consolidate existing functional languages common one serve basis future research functional-language design first version haskell haskell 1.0 defined 1990 committee efforts resulted series language definitions 1.0 1.1 1.2 1.3 1.4 late 1997 series culminated haskell 98 intended specify stable minimal portable version language accompanying standard library teaching base future extensions committee expressly welcomed creating extensions variants haskell 98 via adding incorporating experimental features february 1999 haskell 98 language standard originally published haskell 98 report january 2003 revised version published haskell 98 language libraries revised report language continues evolve rapidly glasgow haskell compiler ghc implementation representing current de facto standard early 2006 process defining successor haskell 98 standard informally named haskell prime began intended ongoing incremental process revise language definition producing new revision per year first revision named haskell 2010 announced november 2009 published july 2010 haskell 2010 incremental update language mostly incorporating several well-used uncontroversial features previously enabled via compiler-specific flags haskell features lazy evaluation lambda expressions pattern matching list comprehension type classes type polymorphism purely functional language means functions generally side effects distinct construct exists represent side effects orthogonal type functions pure function return side effect subsequently executed modeling impure functions languages haskell strong static type system based hindley–milner type inference principal innovation area type classes originally conceived principled way add overloading language since finding many uses construct represents side effects example monad monads general framework model different kinds computation including error handling nondeterminism parsing software transactional memory monads defined ordinary datatypes haskell provides syntactic sugar use haskell open published specification multiple implementations exist main implementation glasgow haskell compiler ghc interpreter native-code compiler runs platforms ghc noted rich type system incorporating recent innovations generalized algebraic data types type families computer language benchmarks game also highlights high-performance implementation concurrency parallelism active growing community exists around language 5,400 third-party open-source libraries tools available online package repository hackage hello world program haskell last line strictly necessary factorial function haskell defined different ways integer type arbitrary-precision code compute values codice_10 456,574-digit number loss precision implementation algorithm similar quick sort lists first element taken pivot haskell logo top page generated haskell code listed implementations distributed open source licenses implementations fully nearly comply haskell 98 standard include implementations longer actively maintained include implementations fully haskell 98 compliant using variant haskell language include several web frameworks written haskell including jan-willem maessen 2002 simon peyton jones 2003 discussed problems associated lazy evaluation also acknowledging theoretical motives addition purely practical considerations improved performance note addition adding performance overhead lazy evaluation makes difficult programmers reason performance code particularly space use bastiaan heeren daan leijen arjan van ijzendoorn 2003 also observed stumbling blocks haskell learners subtle syntax sophisticated type system haskell double edged sword – highly appreciated experienced programmers also source frustration among beginners since generality haskell often leads cryptic error messages address researchers utrecht university developed advanced interpreter called helium improved user-friendliness error messages limiting generality haskell features particular removing support type classes ben lippmeier designed disciple strict-by-default lazy explicit annotation dialect haskell type-and-effect system address haskell difficulties reasoning lazy evaluation using traditional data structures mutable arrays argues p. 20 destructive update furnishes programmer two important powerful tools ... set efficient array-like data structures managing collections objects ... ability broadcast new value parts program minimal burden programmer robert harper one authors standard ml given reasons using haskell teach introductory programming among difficulty reasoning resource use non-strict evaluation lazy evaluation complicates definition data types inductive reasoning inferiority haskell old class system compared ml module system haskell build tool cabal historically criticised poorly handling multiple versions library problem know cabal hell stackage server stack build tool made response criticisms.. clean close slightly older relative haskell biggest deviation haskell use uniqueness types instead monads i/o side-effects series languages inspired haskell different type systems developed including java virtual machine jvm based related languages include haskell served testbed many new ideas language design many haskell variants produced exploring new language ideas including haskell community meets regularly research development activities main events since 2006 series organized hackathons occurred hac series aimed improving programming language tools libraries
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Programming language topics
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apache oozie apache oozie server-based workflow scheduling system manage hadoop jobs workflows oozie defined collection control flow action nodes directed acyclic graph control flow nodes define beginning end workflow start end failure nodes well mechanism control workflow execution path decision fork join nodes action nodes mechanism workflow triggers execution computation/processing task oozie provides support different types actions including hadoop mapreduce hadoop distributed file system operations pig ssh email oozie also extended support additional types actions oozie workflows parameterised using variables codice_1 within workflow definition submitting workflow job values parameters must provided properly parameterized using different output directories several identical workflow jobs run concurrently oozie implemented java web application runs java servlet container distributed apache license 2.0
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Distributed computing architecture
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remote component environment remote component environment rce integration environment scientists engineers analyze design simulate complex systems e.g. aircraft satellites space vehicle focusses collaboration multidisciplinary teams treating complex systems requires many experts several analysis design simulation tools rce tools integrated coupled workflows rce executes workflows fetches results involved tool servers rce extensible supports different scientific applications slightly different requirements rce built upon eclipse rich client platform rcp open source published eclipse public license epl development rce platform took place sesis project previously platform known reconfigurable computing environment since open sourced name changed remote component environment
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Distributed computing architecture
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back mac back mac feature introduced mac os x leopard 10.5 uses wide-area bonjour securely discover services across internet automatically configure ad hoc on-demand point-to-point encrypted connections computers using ipsec current version feature requires users icloud set well apple id due generality back mac work many bonjour-enabled services screen sharing similar apple remote desktop file sharing users must router supports either universal plug play upnp nat port mapping protocol nat-pmp either features enabled connected router uses udp port 4500 point-to-point ipsec connections may mapped different udp ports public side nat router october 12 2011 apple included back mac icloud service rather previously used mobileme thus making free use august 9 2018 apple updated support document note back mac would part macos mojave 10.14 release.the support document updated may 31 2019 indicate back mac services would discontinued versions macos july 1 2019 back mac used edit transfer files one mac another one instance apple store employee used technology capture image person stole macbook using built isight webcam
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Internet protocols
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data security data security means protecting digital data database destructive forces unwanted actions unauthorized users cyberattack data breach disk encryption refers encryption technology encrypts data hard disk drive disk encryption typically takes form either software see disk encryption software hardware see disk encryption hardware disk encryption often referred on-the-fly encryption otfe transparent encryption software-based security solutions encrypt data protect theft however malicious program hacker could corrupt data order make unrecoverable making system unusable hardware-based security solutions prevent read write access data hence offer strong protection tampering unauthorized access hardware based security assisted computer security offers alternative software-only computer security security tokens using pkcs 11 may secure due physical access required order compromised access enabled token connected correct pin entered see two-factor authentication however dongles used anyone gain physical access newer technologies hardware-based security solves problem offering full proof security data working hardware-based security hardware device allows user log log set different privilege levels manual actions device uses biometric technology prevent malicious users logging logging changing privilege levels current state user device read controllers peripheral devices hard disks illegal access malicious user malicious program interrupted based current state user hard disk dvd controllers making illegal access data impossible hardware-based access control secure protection provided operating systems operating systems vulnerable malicious attacks viruses hackers data hard disks corrupted malicious access obtained hardware-based protection software manipulate user privilege levels impossible hacker malicious program gain access secure data protected hardware perform unauthorized privileged operations assumption broken hardware malicious contains backdoor hardware protects operating system image file system privileges tampered therefore completely secure system created using combination hardware-based security secure system administration policies backups used ensure data lost recovered another source considered essential keep backup data industries process recommended files importance user data masking structured data process obscuring masking specific data within database table cell ensure data security maintained sensitive information exposed unauthorized personnel may include masking data users example banking customer representatives see last 4 digits customers national identity number developers need real production data test new software releases able see sensitive financial data outsourcing vendors etc data erasure method software based overwriting completely destroys electronic data residing hard drive digital media ensure sensitive data lost asset retired reused uk data protection act used ensure personal data accessible concerns provides redress individuals inaccuracies particularly important ensure individuals treated fairly example credit checking purposes data protection act states individuals companies legitimate lawful reasons process personal information shared data privacy day international holiday started council europe occurs every january 28 since general data protection regulation gdpr european union eu became law may 25 2018 organizations may face significant penalties €20million 4 annual revenue comply regulation intended gdpr force organizations understand data privacy risks take appropriate measures reduce risk unauthorized disclosure consumers ’ private information international standards iso/iec 27001:2013 iso/iec 27002:2013 covers data security topic information security one cardinal principles stored information i.e data owned clear whose responsibility protect control access data following examples organizations help strengthen standardize computing security trusted computing group organization helps standardize computing security technologies payment card industry data security standard proprietary international information security standard organizations handle cardholder information major debit credit prepaid e-purse atm pos point sale cards general data protection regulation gdpr proposed european commission strengthen unify data protection individuals within european union eu whilst addressing export personal data outside eu
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Computer security
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universal windows platform universal windows platform uwp api created microsoft first introduced windows 10 purpose platform help develop universal apps run windows 10 windows 10 mobile xbox one hololens without need re-written supported windows app development using c++ c vb.net xaml api implemented c++ supported c++ vb.net c f javascript designed extension windows runtime platform first introduced windows server 2012 windows 8 uwp allowed developers create apps would potentially run multiple types devices uwp part windows 10 windows 10 mobile uwp apps run earlier windows versions apps capable implementing platform natively developed using visual studio 2015 visual studio 2017 older metro-style apps windows 8.1 windows phone 8.1 universal 8.1 needed modifications migrate uwp 2015 build keynote microsoft announced collection uwp bridges allow android ios apps ported windows 10 mobile windows bridge android codenamed astoria runtime environment would allow android apps written java c++ run windows 10 mobile published windows store kevin gallo technical lead windows developer platform explained layer contained limitations google mobile services certain core apis available apps deep integration background tasks messaging software would run well environment windows bridge ios codenamed islandwood open-source middleware toolkit allows ios apps developed objective-c ported windows 10 mobile using visual studio 2015 convert xcode project visual studio project early build windows bridge ios released open-source software mit license august 6 2015 android version closed beta february 2016 microsoft announced ceased development windows bridge android citing redundancies due ios already primary platform multi-platform development windows bridge ios produced native code require os-level emulator instead microsoft encouraged use c multi-platform app development using tools xamarin acquired prior announcement windows platform features later versions exclusive uwp software specifically packaged usable architectures existing win32 platform xaml windows forms however 2019 microsoft taken steps reduce parity application platforms make uwp features usable inside non-uwp software microsoft introduced xaml islands method embedding uwp controls widgets non-uwp software part windows 10 may 2019 update stated would also allow uwp functions windows runtime components invoked within non-packaged software uwp extension windows runtime universal windows apps created using uwp longer indicate written specific os manifest build instead target one device families pc smartphone tablet xbox one using universal windows platform bridges extensions allow app automatically utilize capabilities available particular device currently running universal app may run either mobile phone tablet provide suitable experiences universal app running smartphone may start behaving way would running pc phone connected desktop computer suitable docking station games developed uwp subject technical restrictions including incompatibility multi-video card setups difficulties modding game using game programs fraps overlays gaming-oriented chat clients key binding managers uwp support directx 11.1 later games built older directx versions work build 2016 microsoft xbox division head phil spencer announced company attempting address issues would improve viability uwp pc games stating microsoft committed ensuring meet exceed performance expectations full-screen games well additional features including support overlays modding support amd freesync nvidia g-sync technologies disabling v-sync later added uwp epic games founder tim sweeney criticized uwp walled garden since default uwp software may published installed via windows store default requiring changes system settings enable installation external software similarly android additionally certain operating system features exclusive uwp used non-uwp software video games sweeney characterized moves aggressive move microsoft ever made attempting transform pcs closed platform felt moves meant put third-party gaming storefronts steam disadvantage microsoft curtailing users freedom install full-featured pc software subverting rights developers publishers maintain direct relationship customers sweeney argued end-users able download uwp software install manner non-uwp software windows vp kevin gallo addressed sweeney concerns stating windows 10 november update enabled people easily side-load apps default ux required want make windows best development platform regardless technologies used offer tools help developers existing code bases html/javascript .net win32 c++ objective-c bring code windows integrate uwp capabilities xamarin uwp developers reach windows 10 devices use large percentage c code deliver fully native mobile app experiences ios android live interview giant bomb e3 2016 coverage spencer defended mixed reception uwp-exclusive releases stating n't gone swimmingly gone well still definitely concern uwp store somehow linked way nefarious also discussed microsoft relationships third-party developers distributors steam considering service critical part gaming success windows stating microsoft planned continue releasing games platform well going areas cooperate going areas compete end result better gamers spencer also stated friend sweeney frequent contact may 30 2019 microsoft announced would support distribution win32 games microsoft store spencer since promoted head gaming operations microsoft reporting directly ceo satya nadella explained developers preferred architecture allow customization control developers players come expect open windows gaming ecosystem also announced future xbox game studios releases windows would made available third-party storefronts steam rather exclusive microsoft store verge considered developments consistent executives larger strategies surrounding interoperability collaboration competitors admissions microsoft uwp ecosystem failure also citing microsoft efforts decouple uwp-exclusive features platform allow distribution win32 software microsoft store unsuccessful windows 10 mobile
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Operating systems
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cpu power dissipation central processing unit power dissipation cpu power dissipation process central processing units cpus consume electrical energy dissipate energy form heat due resistance electronic circuits designing cpus perform tasks efficiently without overheating major consideration nearly cpu manufacturers date cpu implementations use little power example cpus mobile phones often use watts electricity microcontrollers used embedded systems may consume milliwatts even little microwatts comparison cpus general-purpose personal computers desktops laptops dissipate significantly power higher complexity speed microelectronic cpus may consume power order watts hundreds watts historically early cpus implemented vacuum tubes consumed power order many kilowatts cpus desktop computers typically use significant portion power consumed computer major uses include fast video cards contain graphics processing units power supplies laptops lcd backlight also uses significant portion overall power energy-saving features instituted personal computers idle overall consumption today high-performance cpus considerable strong contrast much lower energy consumption cpus designed low-power devices one cpu intel xscale run 600 mhz consuming 1 w power whereas intel x86 pc processors performance bracket consume times energy engineering reasons pattern processor manufacturers usually release two power consumption numbers cpu example pentium 4 2.8 ghz 68.4 w typical thermal power 85 w maximum thermal power cpu idle draw far less typical thermal power datasheets normally contain thermal design power tdp maximum amount heat generated cpu cooling system computer required dissipate intel advanced micro devices amd defined tdp maximum heat generation thermally significant periods running worst-case non-synthetic workloads thus tdp reflecting actual maximum power processor ensures computer able handle essentially applications without exceeding thermal envelope requiring cooling system maximum theoretical power would cost favor extra headroom processing power many applications cpu components idle much time idle power contributes significantly overall system power usage cpu uses power management features reduce energy use components motherboard chipset take larger proportion computer energy applications computer often heavily loaded scientific computing performance per watt much computing cpu per unit energy becomes significant several factors contributing cpu power consumption include dynamic power consumption short-circuit power consumption power loss due transistor leakage currents formula_1 dynamic power consumption originates activity logic gates inside cpu logic gates toggle energy flowing capacitors inside charged discharged dynamic power consumed cpu approximately proportional cpu frequency square cpu voltage capacitance frequency voltage logic gates toggle transistors inside may change states takes finite amount time may happen brief amount time transistors conducting simultaneously direct path source ground results short-circuit power loss magnitude power dependent logic gate rather complex model macro level power consumption due leakage power emanates micro-level transistors small amounts currents always flowing differently doped parts transistor magnitude currents depend state transistor dimensions physical properties sometimes temperature total amount leakage currents tends inflate increasing temperature decreasing transistor sizes dynamic short-circuit power consumption dependent clock frequency leakage current dependent cpu supply voltage shown energy consumption program shows convex energy behavior meaning exists optimal cpu frequency energy consumption minimal power consumption reduced several ways including following historically processor manufacturers consistently delivered increases clock rates instruction-level parallelism single-threaded code executed faster newer processors modification recently order manage cpu power dissipation processor makers favor multi-core chip designs thus software needs written multi-threaded multi-process manner take full advantage hardware many multi-threaded development paradigms introduce overhead see linear increase speed compared number processors particularly true accessing shared dependent resources due lock contention effect becomes noticeable number processors increases recently ibm exploring ways distribute computing power efficiently mimicking distributional properties human brain
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Computer architecture
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via technologies via technologies inc. taiwanese manufacturer integrated circuits mainly motherboard chipsets cpus memory world largest independent manufacturer motherboard chipsets fabless semiconductor company via conducts research development chipsets in-house subcontracts actual silicon manufacturing third-party merchant foundries tsmc company founded 1987 fremont california usa cher wang 1992 decided move headquarters taipei taiwan order establish closer partnerships substantial growing manufacturing base taiwan neighbouring china 1999 via acquired cyrix division national semiconductor year via acquired centaur technology integrated device technology marking entry x86 microprocessor market via maker via c3 via c7 via nano processors epia platform cyrix mediagx platform remained national semiconductor 2001 via established s3 graphics joint venture january 2005 via began via pc-1 initiative develop information communication technology systems benefit access computers internet february 2005 via celebrated production 100 millionth via amd chipset 29 august 2008 via announced would release official 2d accelerated linux drivers chipsets would also release 3d accelerated drivers 2013 via entered agreement shanghai municipal government create fabless semiconductor company called zhaoxin joint venture producing x86 compatible cpus chinese market via business focuses integrated chipsets pc market among pc users via best known motherboard core-logic chipsets however via products include audio controllers network/connectivity controllers low-power cpus even cd/dvd-writer chipsets pc peripheral vendors asus buy chipsets inclusion product brands late 1990s via began diversifying core-logic business company since made business acquisitions form cpu division graphics division sound division advances silicon manufacturing continue increase level integration functionality chipsets via need divisions remain competitive core-logic market via produced multiple x86 compatible cpus acquisitions cyrix centaur technology via still produces cpus zhaoxin joint venture via x86 processors also contain undocumented alternate instruction set via established important supplier pc components chipsets socket 7 platform apollo vp3 chipset via pioneered agp support socket 7 processors via present market position derives success pentium iii chipsets intel discontinued development sdram chipsets stated policy rdram memory would supported going forward since rdram expensive offered obvious performance advantages manufacturers found could ship performance-equivalent pcs lower cost using via chipsets response increasing market competition via decided buy ailing s3 graphics business savage chipset fast enough survive discrete solution low manufacturing cost made ideal integrated solution part via northbridge via s3 brand generally held onto 10 share pc graphics market behind intel amd nvidia via also includes via envy soundcard motherboards offers 24-bit sound pentium 4 chipset designs struggled win market share face legal threats intel k8t800 chipset athlon 64 popular via also continued development via c3 via c7 processors targeting small light low power applications market space via successful january 2008 via unveiled via nano 11 mm × 11 mm footprint vm-enabled x86-64 processor debuted may 2008 ultra-mobile pcs basis idt centaur acquisition via appears come possession least three patents cover key aspects processor technology used intel basis negotiating leverage patents offered 2003 via arrived agreement intel allowed ten-year patent cross license enabling via continue design manufacture x86 compatible cpus via also granted three-year grace period could continue use intel socket infrastructure
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Computer architecture
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usenet death penalty usenet usenet death penalty udp final penalty may issued internet service providers single users produce much spam fail adhere usenet standards messages fall jurisdiction usenet death penalty cancelled cancelled messages deleted usenet servers allowed propagate causes users affected isp unable post usenet puts pressure isp change policies notable cases include actions taken uunet compuserve excite home three types usenet death penalty effective udp must supported large number servers majority major transit servers otherwise articles propagate throughout smaller slower peerings udps casual acts announced beforehand owner offending server contacted given several chances correct perceived problem since effects users server udp significant users want post impact udp induce operators offending server address problems quickly udps issued america online bbn planet compuserve erols internet netcom tiac uunet first udp software written karl kleinpaste 1990 though disagreement term coined net abuse faq claims 1993 message posted 18 august year claims coined years earlier eliot lear udp implemented uunet 1 august 1997 became host many spammers unresponsive abuse complaints forced provider implement antispam policies tools close open relays executives called udp digital terrorism threatened legal action asserted planning move spammers anyway volume spam uunet decreased organizers called penalty august 6 though announcement stifled cancel messages udp opponents active udp implemented compuserve 18 november 1997 lifted following day company implemented anti-spamming measures instituted new acceptable use policy addressing spamming udp scheduled begin excite home 19 january 2000 lifted day scheduled begin isp began scanning misconfigured proxy servers home users computers blamed spam originating network
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Computer security
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comparison firewalls following comparison notable firewalls starting simple home firewalls sophisticated enterprise-level firewalls firewall solutions provided software solutions run general purpose operating systems following table lists different firewall software installed configured different general purpose operating systems general computer appliance computing device specific function limited configuration ability software appliance set computer programs might combined enough operating system jeos run optimally industry standard computer hardware virtual machine firewall appliance combination firewall software operating system purposely built run firewall system dedicated hardware virtual machine include following table lists different firewall appliances features strictly firewall features sometimes bundled firewall software exist platform note features marked yes even implemented separate module comes platform firewall sits ids real-time firewall logs/sniffs/blocks suspicious connections part rule-set vpn virtual private network types pptp l2tp mpls ipsec ssl/ssh profile selection user switch sets firewall settings e.g use work home public connections
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Computer security
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field-programmable gate array field-programmable gate array fpga integrated circuit designed configured customer designer manufacturinghence term field-programmable fpga configuration generally specified using hardware description language hdl similar used application-specific integrated circuit asic circuit diagrams previously used specify configuration increasingly rare due advent electronic design automation tools fpgas contain array programmable logic blocks hierarchy reconfigurable interconnects allow blocks wired together like many logic gates inter-wired different configurations logic blocks configured perform complex combinational functions merely simple logic gates like xor fpgas logic blocks also include memory elements may simple flip-flops complete blocks memory many fpgas reprogrammed implement different logic functions allowing flexible reconfigurable computing performed computer software contemporary field-programmable gate arrays fpgas large resources logic gates ram blocks implement complex digital computations fpga designs employ fast i/o rates bidirectional data buses becomes challenge verify correct timing valid data within setup time hold time floor planning enables resource allocation within fpgas meet time constraints fpgas used implement logical function asic perform ability update functionality shipping partial re-configuration portion design low non-recurring engineering costs relative asic design notwithstanding generally higher unit cost offer advantages many applications fpgas analog features addition digital functions common analog feature programmable slew rate output pin allowing engineer set low rates lightly loaded pins would otherwise ring couple unacceptably set higher rates heavily loaded pins high-speed channels would otherwise run slowly also common quartz-crystal oscillators on-chip resistance-capacitance oscillators phase-locked loops embedded voltage-controlled oscillators used clock generation management high-speed serializer-deserializer serdes transmit clocks receiver clock recovery fairly common differential comparators input pins designed connected differential signaling channels mixed signal fpgas integrated peripheral analog-to-digital converters adcs digital-to-analog converters dacs analog signal conditioning blocks allowing operate system-on-a-chip soc devices blur line fpga carries digital ones zeros internal programmable interconnect fabric field-programmable analog array fpaa carries analog values internal programmable interconnect fabric fpga industry sprouted programmable read-only memory prom programmable logic devices plds proms plds option programmed batches factory field field-programmable however programmable logic hard-wired logic gates altera founded 1983 delivered industry first reprogrammable logic device 1984 – ep300 – featured quartz window package allowed users shine ultra-violet lamp die erase eprom cells held device configuration december 2015 intel acquired altera xilinx co-founders ross freeman bernard vonderschmitt invented first commercially viable field-programmable gate array 1985 – xc2064 xc2064 programmable gates programmable interconnects gates beginnings new technology market xc2064 64 configurable logic blocks clbs two three-input lookup tables luts 20 years later freeman entered national inventors hall fame invention 1987 naval surface warfare center funded experiment proposed steve casselman develop computer would implement 600,000 reprogrammable gates casselman successful patent related system issued 1992 altera xilinx continued unchallenged quickly grew 1985 mid-1990s competitors sprouted eroding significant market share 1993 actel microsemi serving 18 percent market 2013 altera 31 percent actel 10 percent xilinx 36 percent together represented approximately 77 percent fpga market 1990s period rapid growth fpgas circuit sophistication volume production early 1990s fpgas primarily used telecommunications networking end decade fpgas found way consumer automotive industrial applications companies like microsoft started use fpgas accelerate high-performance computationally intensive systems like data centers operate bing search engine due performance per watt advantage fpgas deliver microsoft began using fpgas accelerate bing 2014 2018 began deploying fpgas across data center workloads azure cloud computing platform 2012 coarse-grained architectural approach taken step combining logic blocks interconnects traditional fpgas embedded microprocessors related peripherals form complete system programmable chip work mirrors architecture created ron perlof hana potash burroughs advanced systems group 1982 combined reconfigurable cpu architecture single chip called sb24 examples hybrid technologies found xilinx zynq-7000 programmable soc includes 1.0 ghz dual-core arm cortex-a9 mpcore processor embedded within fpga logic fabric altera arria v fpga includes 800 mhz dual-core arm cortex-a9 mpcore atmel fpslic another device uses avr processor combination atmel programmable logic architecture microsemi smartfusion devices incorporate arm cortex-m3 hard processor core 512 kb flash 64 kb ram analog peripherals multi-channel analog-to-digital converters digital-to-analog converters flash memory-based fpga fabric alternate approach using hard-macro processors make use soft processor ip cores implemented within fpga logic nios ii microblaze mico32 examples popular softcore processors many modern fpgas programmed run time led idea reconfigurable computing reconfigurable systems – cpus reconfigure suit task hand additionally new non-fpga architectures beginning emerge software-configurable microprocessors stretch s5000 adopt hybrid approach providing array processor cores fpga-like programmable cores chip design start new custom design implementation fpga historically fpgas slower less energy efficient generally achieved less functionality fixed asic counterparts older study showed designs implemented fpgas need average 40 times much area draw 12 times much dynamic power run one third speed corresponding asic implementations recently fpgas xilinx virtex-7 altera stratix 5 come rival corresponding asic assp application-specific standard part standalone usb interface chip solutions providing significantly reduced power usage increased speed lower materials cost minimal implementation real-estate increased possibilities re-configuration 'on-the-fly design included 6 10 asics achieved using one fpga advantages fpgas include ability re-program already deployed i.e field fix bugs often include shorter time market lower non-recurring engineering costs vendors also take middle road via fpga prototyping developing prototype hardware fpgas manufacture final version asic longer modified design committed xilinx claimed several market technology dynamics changing asic/fpga paradigm february 2009 trends make fpgas better alternative asics larger number higher-volume applications historically used company attributes growing number fpga design starts see fpgas capability partial re-configuration lets one portion device re-programmed portions continue running primary differences complex programmable logic devices cplds fpgas architectural cpld comparatively restrictive structure consisting one programmable sum-of-products logic arrays feeding relatively small number clocked registers result cplds less flexible advantage predictable timing delays fpga architectures hand dominated interconnect makes far flexible terms range designs practical implementation also far complex design least requiring complex electronic design automation eda software practice distinction fpgas cplds often one size fpgas usually much larger terms resources cplds typically fpgas contain complex embedded functions adders multipliers memory serializer/deserializers another common distinction cplds contain embedded flash memory store configuration fpgas usually require external non-volatile memory always design requires simple instant-on logic already configured power-up cplds generally preferred applications fpgas generally preferred sometimes cplds fpgas used single system design designs cplds generally perform glue logic functions responsible “ booting ” fpga well controlling reset boot sequence complete circuit board therefore depending application may judicious use fpgas cplds single design fpgas advantages disadvantages compared asics secure microprocessors concerning hardware security fpgas flexibility makes malicious modifications fabrication lower risk previously many fpgas design bitstream exposed fpga loads external memory typically every power-on major fpga vendors offer spectrum security solutions designers bitstream encryption authentication example altera xilinx offer aes encryption 256-bit bitstreams stored external flash memory fpgas store configuration internally nonvolatile flash memory microsemi proasic 3 lattice xp2 programmable devices expose bitstream need encryption addition flash memory lookup table provides single event upset protection space applications customers wanting higher guarantee tamper resistance use write-once antifuse fpgas vendors microsemi stratix 10 fpgas socs altera introduced secure device manager physically uncloneable functions provide high levels protection physical attacks 2012 researchers sergei skorobogatov christopher woods demonstrated fpgas vulnerable hostile intent discovered critical backdoor vulnerability manufactured silicon part actel/microsemi proasic 3 making vulnerable many levels reprogramming crypto access keys accessing unencrypted bitstream modifying low-level silicon features extracting configuration data fpga used solve problem computable trivially proven fact fpgas used implement soft microprocessor xilinx microblaze altera nios ii advantage lies significantly faster applications parallel nature optimality terms number gates used certain processes fpgas originally began competitors cplds implement glue logic printed circuit boards size capabilities speed increased fpgas took additional functions point marketed full systems chips socs particularly introduction dedicated multipliers fpga architectures late 1990s applications traditionally sole reserve digital signal processor hardware dsps began incorporate fpgas instead another trend use fpgas hardware acceleration one use fpga accelerate certain parts algorithm share part computation fpga generic processor search engine bing noted adopting fpga acceleration search algorithm 2014. fpgas seeing increased use ai accelerators including microsoft so-termed project catapult accelerating artificial neural networks machine learning applications traditionally fpgas reserved specific vertical applications volume production small low-volume applications premium companies pay hardware cost per unit programmable chip affordable development resources spent creating asic new cost performance dynamics broadened range viable applications common fpga architecture consists array logic blocks i/o pads routing channels generally routing channels width number wires multiple i/o pads may fit height one row width one column array application circuit must mapped fpga adequate resources number clbs/labs i/os required easily determined design number routing tracks needed may vary considerably even among designs amount logic example crossbar switch requires much routing systolic array gate count since unused routing tracks increase cost decrease performance part without providing benefit fpga manufacturers try provide enough tracks designs fit terms lookup tables luts i/os routed determined estimates derived rent rule experiments existing designs network-on-chip architectures routing interconnection developed general logic block consists logical cells called alm le slice etc. typical cell consists 4-input lut full adder fa d-type flip-flop shown luts figure split two 3-input luts normal mode combined 4-input lut left multiplexer mux arithmetic mode outputs fed adder selection mode programmed middle mux output either synchronous asynchronous depending programming mux right figure example practice entire parts adder stored functions luts order save space modern fpga families expand upon capabilities include higher level functionality fixed silicon common functions embedded circuit reduces area required gives functions increased speed compared building logical primitives examples include multipliers generic dsp blocks embedded processors high speed i/o logic embedded memories higher-end fpgas contain high speed multi-gigabit transceivers hard ip cores processor cores ethernet medium access control units pci/pci express controllers external memory controllers cores exist alongside programmable fabric built transistors instead luts asic-level performance power consumption without consuming significant amount fabric resources leaving fabric free application-specific logic multi-gigabit transceivers also contain high performance analog input output circuitry along high-speed serializers deserializers components built luts higher-level physical layer phy functionality line coding may may implemented alongside serializers deserializers hard logic depending fpga circuitry built inside fpga synchronous circuitry requires clock signal fpgas contain dedicated global regional routing networks clock reset delivered minimal skew also fpgas generally contain analog phase-locked loop and/or delay-locked loop components synthesize new clock frequencies well attenuate jitter complex designs use multiple clocks different frequency phase relationships forming separate clock domains clock signals generated locally oscillator recovered high speed serial data stream care must taken building clock domain crossing circuitry avoid metastability fpgas generally contain block rams capable working dual port rams different clocks aiding construction building fifos dual port buffers connect differing clock domains shrink size power consumption fpgas vendors tabula xilinx introduced 3d stacked architectures following introduction 28 nm 7-series fpgas xilinx said several highest-density parts fpga product lines constructed using multiple dies one package employing technology developed 3d construction stacked-die assemblies xilinx approach stacks several three four active fpga dies side-by-side silicon interposer – single piece silicon carries passive interconnect multi-die construction also allows different parts fpga created different process technologies process requirements different fpga fabric high speed 28 gbit/s serial transceivers fpga built way called heterogeneous fpga altera heterogeneous approach involves using single monolithic fpga die connecting die/technologies fpga using intel embedded multi-die interconnect bridge emib technology labview define behavior fpga user provides design hardware description language hdl schematic design hdl form suited work large structures possible specify high-level functional behavior rather drawing every piece hand however schematic entry allow easier visualization design component modules using electronic design automation tool technology-mapped netlist generated netlist fit actual fpga architecture using process called place-and-route usually performed fpga company proprietary place-and-route software user validate map place route results via timing analysis simulation verification validation methodologies design validation process complete binary file generated typically using fpga vendor proprietary software used re- configure fpga file transferred fpga/cpld via serial interface jtag external memory device like eeprom common hdls vhdl verilog well extensions systemverilog however attempt reduce complexity designing hdls compared equivalent assembly languages moves raise abstraction level introduction alternative languages national instruments labview graphical programming language sometimes referred g fpga add-in module available target program fpga hardware simplify design complex systems fpgas exist libraries predefined complex functions circuits tested optimized speed design process predefined circuits commonly called intellectual property ip cores available fpga vendors third-party ip suppliers rarely free typically released proprietary licenses predefined circuits available developer communities opencores typically released free open source licenses gpl bsd similar license sources designs known open-source hardware typical design flow fpga application developer simulate design multiple stages throughout design process initially rtl description vhdl verilog simulated creating test benches simulate system observe results synthesis engine mapped design netlist netlist translated gate-level description simulation repeated confirm synthesis proceeded without errors finally design laid fpga point propagation delays added simulation run values back-annotated onto netlist recently opencl open computing language used programmers take advantage performance power efficiencies fpgas provide opencl allows programmers develop code c programming language target fpga functions opencl kernels using opencl constructs information see high-level synthesis c hdl 2016 long-time industry rivals xilinx altera intel subsidiary fpga market leaders time controlled nearly 90 percent market xilinx altera provide proprietary electronic design automation software windows linux ise/vivado quartus enables engineers design analyze simulate synthesize compile designs manufacturers include march 2010 tabula announced fpga technology uses time-multiplexed logic interconnect claims potential cost savings high-density applications march 24 2015 tabula officially shut june 1 2015 intel announced would acquire altera approximately 16.7 billion completed acquisition december 30 2015
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Computer architecture
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security testing security testing process intended reveal flaws security mechanisms information system protect data maintain functionality intended due logical limitations security testing passing security testing indication flaws exist system adequately satisfies security requirements typical security requirements may include specific elements confidentiality integrity authentication availability authorization non-repudiation actual security requirements tested depend security requirements implemented system security testing term number different meanings completed number different ways security taxonomy helps us understand different approaches meanings providing base level work integrity information refers protecting information modified unauthorized parties might involve confirming identity person tracing origins artifact ensuring product packaging labeling claims assuring computer program trusted one common terms used delivery security testing
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Computer security
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database directive directive 96/9/ec european parliament council 11 march 1996 legal protection databases directive european union field copyright law made internal market provisions treaty rome harmonises treatment databases copyright law sui generis right creators databases qualify copyright article 1 2 defines database collection independent works data materials arranged systematic methodical way individually accessible electronic means non-electronic databases also covered para 14 preamble computer program used create database included para 23 preamble copyright protection software governed directive 91/250/eec article 3 databases reason selection arrangement contents constitute author intellectual creation protected copyright collections criterion may used member states may relaxation criterion protection collections berne convention protection literary artistic works covers collections literary artistic works requires creativity selection arrangement contents practice difference likely slight copyright database separate without prejudice copyright entries acts restricted copyright similar types work art 5 shall prevent lawful use database lawful user art 6 1 member states may provide following limitations art 6 2 well applying traditional limitations copyright copyright protection usually lasts seventy years death last publicly identified author anonymous pseudonymous works gain protection later 70 years work lawfully made available public 70 years creation national legislation makes particular provision collective works legal person i.e body corporate rights holder term protection calculated way anonymous pseudonymous works exception natural persons created work given credit versions made available public term protection calculated according lives authors art 1 directive 93/98/eec copyright protection available databases aim complete entries selected objective criteria covered sui generis database rights copyright protects creativity author database rights specifically protect qualitatively and/or quantitatively substantial investment either obtaining verification presentation contents substantial investment need financial database protected art 7 1 database rights held first instance person corporation made substantial investment long article 11 3 provides negotiation treaties ensure reciprocal treatment outside eu 2006 treaty exists holder database rights may prohibit extraction and/or re-utilization whole substantial part contents substantial part evaluated qualitatively and/or quantitatively reutilisation subject exhaustion rights public lending act extraction re-utilization lawful user database available public may freely extract and/or re-use insubstantial parts database art 8 holder database rights may place restrictions purpose insubstantial parts used however users may perform acts conflict normal exploitation database unreasonably prejudice legitimate interests maker database prejudice copyright entries limitations may provided database rights copyright databases art 9 database rights last fifteen years end year database made available public end year completion private databases art 10 substantial change could considered substantial new investment lead new term database rights could principle perpetual database rights independent copyright database two could principle held different people especially jurisdictions prohibit corporate ownership copyright database rights compared rights phonogram film producers
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Databases
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sparse image sparse image type disk image file used macos grows size user adds data image taking much disk space stored encrypted sparse image files used secure user home directory filevault feature mac os x snow leopard earlier sparse images created using disk utility unlike full image file .dmg takes much actual space real disk represents regardless amount unused space sparse image file .sparseimage takes much actual disk space data contained within maximum capacity assigned creation two limitations therefore worth noting regarding use image file format mac os x leopard introduced concept sparse bundle instead single big file sparse bundle bundle directory containing number files called bands order 8 mb size means even though end user sparse bundle appears single file composed smaller files mac os x 10.8 bands 8 mib content image changes one band files changed created deleted allows backup software time machine operate efficiently sparse bundle advantages time machine
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Operating systems
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nsakey computer security cryptography _nsakey variable name discovered windows nt 4 service pack 5 released unstripped symbolic debugging data august 1999 andrew d. fernandes cryptonym corporation variable contained 1024-bit public key microsoft operating systems require cryptography suites work operating systems digital signature since microsoft-approved cryptography suites installed used component windows possible keep export copies operating system products windows installed compliance export administration regulations ear enforced us department commerce bureau industry security bis already known microsoft used two keys primary spare either create valid signatures microsoft failed remove debugging symbols advapi32.dll security encryption driver released service pack 5 windows nt 4.0 andrew fernandes chief scientist cryptonym found primary key stored variable _key second key labeled _nsakey fernandes published discovery touching flurry speculation conspiracy theories including possibility second key owned united states national security agency nsa allowed intelligence agency subvert windows user security presentation computers freedom privacy 2000 cfp2000 conference duncan campbell senior research fellow electronic privacy information center epic mentioned _nsakey controversy example outstanding issue related security surveillance addition dr. nicko van someren found third key windows 2000 doubted legitimate purpose declared looks fishy microsoft denied speculations _nsakey report inaccurate unfounded key question microsoft key maintained safeguarded microsoft shared key nsa party microsoft said key symbol _nsakey nsa technical review authority u.s. export controls key ensures compliance u.s. export laws richard purcell microsoft director corporate privacy approached campbell presentation expressed wish clear confusion doubts _nsakey immediately conference scott culp microsoft security response center contacted campbell offered answer questions correspondence began cordially soon became strained campbell apparently felt culp evasive culp apparently felt campbell hostilely repeating questions already answered 28 april 2000 culp stated definitely reached end discussion ... rapidly spiraling realm conspiracy theory campbell inquiries went unanswered microsoft claimed third key beta builds windows 2000 purpose signing cryptographic service providers http //web.archive.org/web/19990422142445/http //www.mozilla.org:80/crypto-faq.html says fact possible certain circumstances obtain export license software invoking cryptographic functions api example microsoft implementation microsoft cryptographic api cryptoapi specification approved export us even though implements api third parties including third parties outside us add separate modules cryptographic service providers csps implementing cryptographic functionality export approval presumably made possible cryptoapi implementation requires third party csps digitally signed microsoft rejects attempts call csps signed b signing process microsoft ensure compliance relevant us export control regulations e.g. presumably would sign csp developed outside us implements strong cryptography c microsoft cryptoapi implementation available executable form thus presumed reasonably resistant user tampering disable csp digital signature check software industry question whether bxa ear specific requirements backup keys however none claim legal technical expertise necessary authoritatively discuss document following theories presented microsoft stated second key present backup guard possibility losing primary secret key fernandes doubts explanation pointing generally accepted way guard loss secret key secret splitting would divide key several different parts would distributed throughout senior management stated would far robust using two keys second key also lost microsoft would need patch upgrade every copy windows world well every cryptographic module ever signed hand microsoft failed think consequences key loss created first key without using secret splitting secure hardware n't allow protection weakened key generation nsa pointed problem part review process might explain microsoft weakened scheme second key new one called _nsakey second key might backed using secret splitting losing keys need n't problem another possibility microsoft included second key able sign cryptographic modules outside united states still complying bxa ear cryptographic modules signed multiple locations using multiple keys reasonable approach however cryptographic module ever found signed _nsakey microsoft denies certification authority exists microsoft denied nsa access _nsakey secret key possible remove second _nsakey using following note windows software 1999 good news among bad however turns flaw way crypto_verify function implemented way crypto verification occurs users easily eliminate replace nsa key operating system without modifying microsoft original components since nsa key easily replaced means non-us companies free install strong crypto services windows without microsoft nsa approval thus nsa effectively removed export control strong crypto windows demonstration program replaces nsa key found cryptonym website september 1999 anonymous researcher reverse-engineered primary key _nsakey pgp-compatible format published key servers
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Operating systems
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manning law manning law describes combination principles need balanced design growth universal linguistic dependencies dependencies used describe model syntactic relations languages supports natural language processing major topic event thousands linguistics ai researchers working widely-adopted law put forward christopher manning manning law described consisting six directives may necessarily apply simultaneously often conflict degree
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Computational linguistics
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socket socket also known socket 462 cpu socket used amd processors ranging athlon thunderbird athlon xp/mp 3200+ amd budget processors including duron sempron socket also supports amd geode nx embedded processors derived mobile athlon xp socket zero insertion force pin grid array type 462 pins nine pins blocked socket prevent accidental insertion socket 370 cpus hence number 462 front side bus frequencies supported amd athlon xp sempron 133 mhz 166 mhz 200 mhz socket supports 32-bit cpus socket replaced socket 754 socket 939 2003 2004 respectively except use geode nx processors initially launched 100 mhz fsb support earliest chipsets evolved stepwise faster 200 mhz fsb maintaining pin compatibility throughout lifetime however clock timing bios voltage differences restrict compatibility older chipsets later processors socket dimensions 5.59 cm 5.24 cm without lever x 6.55 cm 2.2 2.06 without lever x 2.58 amd recommends mass socket cpu cooler exceed 300 grams 10.6 ounces heavier coolers may result damage die system properly handled socket processors athlon sempron duron geode nx following mechanical maximum load limits exceeded heatsink assembly shipping conditions standard use load limits may crack processor die make unusable load limits quite small compared load limits socket 478 processors indeed small many users ended cracked processors trying remove attach heatsinks fragile processor core made installing non-standard non-certified heatsink solutions risky business
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Computer architecture
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julie beth lovins julie beth lovins computational linguist first published stemming algorithm word matching 1968 lovins stemmer single pass context sensitive stemmer removes endings based longest-match principle stemmer first published extremely well developed considering date release main influence large amount future work area -adam g. et al lovins born october 19th 1945 washington d.c. grew amherst massachusetts father gerald h. lovins worked engineer mother miriam lovins worked social services administrator lovins brother amory lovins environmental scientist co-founder chief scientist rocky mountain institute undergraduate degree lovins attended pembroke college women college brown university later combined brown university 1971 penbroke college lovins studied mathematics linguistics graduated honors thesis named study idioms received inaugural bloch fellowship 1970 linguistic society america attend graduate school lovins obtained 1970 phd 1973 university chicago studying linguistics university chicago dissertation titled loan phonology -- subject matter revision thesis loanwords phonological structure japanese published 1975 indiana university linguistics club following lovins phd spent year working linguist-at-large university tokyo language research institute english conversation teacher joined faculty tsuda college professor english linguistics taught seven years time faculty member tsuda college lovins also served guest researcher university tokyo research institute logopedics phoniatrics research center speech science teaching japanese phonology prestigious japanese universities abroad lovins moved back u.s. work computing industry worked early speech synthesis bell labs murray hill new jersey bell labs lovins worked osamu fujimura renown japanese linguist credited pioneer speech sciences lovins also worked software engineer various companies silicon valley served consultant computational linguistics throughout 1990s consultant called business language doctor lovins published article work developing stemming algorithm research laboratory electronics mit 1968 lovins stemming algorithm frequently referred lovins stemmer stemming algorithm process taking word suffixes reducing root base word stemming algorithms used improve accuracy information retrieval domain analysis algorithms help find variants terms looked stemming algorithms helpful likely users look particular word might interested related words stemming algorithms prevalent search engines google implement word stemming 2003 means 2003 google search word warm would returned related words like warmth warming first published stemming algorithm lovins work set precedent influenced future work stemming algorithms porter stemmer published martin porter 1980 recognized widely common stemming algorithm stemming english additionally dawson stemmer developed john dawson extension lovins stemmer lovins stemmer follows rule-based affix elimination approach removes longest suffix word word recoded convert stem valid words process split two phases first phase word compared pre-determined list endings word found contain one endings ending removed leaving stem word second phase standardizes spelling exceptions come first phase ensure words slightly different stems properly matched together example word dried phase one results dri match word dry second phase takes care exceptions compared stemmers lovins algorithm fast equipped handle irregular plural words like person people disadvantages many suffixes available table endings sometimes highly unreliable frequently fails form words stems match stems like-meaning words reason technical vocabulary used author lovins moved mountain view california 1979 later old mountain view 1981 partner later husband dr. greg fowler software engineer advocate environmental issues blind free time husband enjoyed taking walks volunteering local community lovins actively volunteered organizations like old mountain view neighborhood association mountain view friends library league women voters mountain view cool cities team mountain view sustainability task force 2016 lovins husband died unexpectedly following heart attack eighteen days husband died lovins diagnosed brain cancer passed away january 26th 2018 hospice surrounded friends caregivers
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Computational linguistics
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microsoft biztalk server microsoft biztalk server simply biztalk inter-organizational middleware system ioms biztalk server previously positioned application server microsoft changed strategy released appfabric server became official application server research firm gartner consider microsoft offering one 'leaders application integration suites discussion product direction biztalk especially cloud software becoming common microsoft continues support update product offer coverage popular conferences worldwide partner conference azure ipaas integration platform service equivalents biztalk api management logic apps service bus event grid 2013-11-21 2018-05-31 included azure biztalk services successor biztalk 2016 product roadmap slated completion approximately 9 months following general availability windows server 2019 common scenario biztalk enables companies integrate manage automated business processes exchanging business documents purchase orders invoices disparate applications within across organizational boundaries development biztalk server done microsoft visual studio developer create transformation maps transforming one message type another example xml file transformed sap idocs messages inside biztalk implemented xml documents defined xml schemas xsd standard maps implemented xslt standard orchestrations implemented ws-bpel compatible process language xlang schemas maps pipelines orchestrations created visually using graphical tools within microsoft visual studio additional functionality delivered .net assemblies called existing modules—including instance orchestrations maps pipelines business rules starting 2000 following versions released following incomplete list technical features biztalk server human-centric processes implemented directly biztalk server need additional applications like microsoft sharepoint server biztalk server runtime built publish/subscribe architecture sometimes called content-based publish/subscribe messages published biztalk transformed desired format routed one subscribers biztalk makes processing safe serialization called dehydration biztalk terminology placing messages database waiting external events thus preventing data loss architecture binds biztalk microsoft sql server processing flow tracked administrators using administration console biztalk supports transaction flow whole line one customer another biztalk orchestrations also implement long-running transactions biztalk uses adapters communications different protocols message formats specific software products adapters edi file http sftp ftp smtp pop3 soap sql msmq mllp azure logic app azure api management microsoft sharepoint server ibm mainframe zseries cics ims midrange iseries as/400 server ibm db2 ibm websphere mq adapters wcf adapter set added 2006 r2 includes wcf-wshttp wcf-basichttp wcf-nettcp wcf-netmsmq wcf-netnamedpipe wcf-custom wcf-customisolated adapters microsoft also ships biztalk adapter pack includes wcf-based adapters lob systems currently includes adapters sap oracle database oracle e-business suite microsoft sql server mysql peoplesoft enterprise siebel systems additional adapters active directory example available third party microsoft biztalk core partners
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Distributed computing architecture
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contentbox modular cms contentbox modular cms open-source content management system cfml created ortus solutions corp. contentbox designed modular hmvc software based hibernate orm coldbox platform contentbox modular cms dual-licensed apache v2 commercial license contentbox modular cms cfml-powered web application runs modern cfml engine including adobe coldfusion 9 lucee 4.5 railo 2 contentbox modular cms also delivered war file standard java servlet container apache tomcat
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Programming language topics
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john threat john lee a.k.a john threat used name corrupt member masters deception mod new york based hacker group early '90s result participation great hacker war mod rival hacker group legion doom indicted federal wiretapping charges 1992 pled guilty sentenced one year federal detention center participation great hacker war landed cover wired magazine 1994 lee born july 6 1973 brooklyn new york grew brownsville member decepticons brooklyn-based street gang formed early '80s named villains saturday morning cartoon transformers lee attended stuyvesant high school went new york university freshman year nyu lee sentenced prison role great hacker war lee also editing producing directing credits film television 2004 founded mediathreat llc film production company 2005 directed original documentary dead prez bigger hip hop 2011 co-directed music video make single ca n't friends everyone diane martel lee also gained notoriety 2001 revealed anonymous editor urbanexpose.com controversial entertainment gossip website
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Computer security
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cyber resilience review cyber resilience review crr assessment method developed united states department homeland security dhs voluntary examination operational resilience cyber security practices offered cost dhs operators critical infrastructure state local tribal territorial governments crr service-oriented approach meaning one foundational principles crr organization deploys assets people information technology facilities support specific operational missions services crr offered facilitated workshop format self-assessment package workshop version crr led dhs facilitator critical infrastructure facility workshop typically takes 6–8 hours complete draws cross section personnel critical infrastructure organization information collected facilitated crr protected disclosure protected critical infrastructure information act 2002 information disclosed freedom information act request used civil litigation used regulatory purposes crr self-assessment package allows organization conduct assessment without need direct dhs assistance available download dhs critical infrastructure cyber community voluntary program website package includes automated data answer capture report generation tool facilitation guide comprehensive explanation question crosswalk crr practices criteria national institute standards technology nist cybersecurity framework questions asked crr resulting report versions assessment dhs partnered cert division software engineering institute carnegie mellon university design deploy crr goals practices found assessment derived cert resilience management model cert-rmm version 1.0 crr introduced 2009 received significant revision 2014 crr comprises 42 goals 141 specific practices extracted cert-rmm organized 10 domains domain composed purpose statement set specific goals associated practice questions unique domain standard set maturity indicator level mil questions mil questions examine institutionalization practices within organization.the performance organization scored mil scale scale depicts capability divided five levels mil1-incomplete mil2-performed mil3-managed mil4-measured mil5-defined institutionalization means cybersecurity practices become deeper lasting part organization managed supported meaningful ways cybersecurity practices become institutionalized—or “ embedded ” —managers confidence practices ’ predictability reliability practices also become likely sustained times disruption stress organization maturity also lead tighter alignment cybersecurity activities organization ’ business drivers example mature organizations managers provide oversight particular domain evaluate effectiveness security activities domain comprises number goals practice questions varies domain set mil questions concepts encompass domains crr questions three possible responses “ yes ” “ ” “ incomplete crr measures performance organization practice goal domain mil levels scores calculated individual model elements aggregated totals scoring rubric establishes following conditions met organization said achieving domain performed state practices define domain observable determination made degree practices conditions tested applying common set 13 mil questions domain mil1 achieved consistent architecture mil scale mils cumulative achieve mil specific domain organization must perform practices level preceding mils example organization must perform domain practices mil1 mil2 achieve mil2 domain crr participants receive comprehensive report containing results question domains report also provides graphical summaries organization ’ performance goal domain levels depicted heat-map matrix detailed representation allows organizations target improvement fine-grained level organizations participating facilitated crrs receives additional set graphs depicting performance organization compared prior participants crr report includes potential path toward improving performance practice options consideration primarily sourced cert-rmm nist special publications organizations also use crr results measure perform relation criteria nist cybersecurity framework correlation feature introduced february 2014
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Computer security
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dce distributed file system dce distributed file system dce/dfs remote file access protocol used distributed computing environment variant andrew file system afs based afs version 3.0 protocol developed commercially transarc corporation afs version 3.0 turn based afs version 2.0 protocol also used coda disconnected file system originally developed carnegie mellon university dce/dfs consisted multiple cooperative components provided network file system strong file system semantics attempting mimic behavior posix local file systems taking advantage performance optimizations possible dce/dfs client system utilized locally managed cache would contain copies regions original file client system would coordinate server system original copy file stored ensure multiple clients accessing file would re-fetch cached copy file data original file changed advantage approach provided good performance even slow network connections file access actually done local cached regions file server failed client could continue making changes file locally storing back server became available dce/dfs also divorced concept logical units management filesets underlying volume fileset stored allowed administrative control location fileset manner transparent end user support advanced dce/dfs features local journaling file system dce/lfs also known episode developed provide full range support options ibm maintained since 2005 http //www-306.ibm.com/software/stormgmt/dfs/ ibm working replacement dce/dfs called adfs advanced distributed file system one major goal project decouple dfs complexities dce cell directory services cds security services secd another key feature would elimination enctype limitations associated dce/rpc public mention effort made since 2005 leading many believe project killed dce distributed file system dfs adopted open software foundation 1989 part distributed computing environment
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Computer file systems
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isomorphic javascript isomorphic javascript also known universal javascript describes javascript applications run client server isomorphic javascript works context single-page application spa typical spa application logic including routing encapsulated bundled javascript file sent client whilst frees server handle many requests also makes initial load slow client entire application needs sent client isomorphic javascript client web page first requested server view page generated server similar server-side dynamic web pages sent client client render view immediately initial view rendered complete spa downloaded background subsequent actions handled client-side naming term 'isomorphic javascript matter controversy term 'isomorphic first coined charlie robbins nodejitsu one company blog posts spike brehm software engineer airbnb wrote another blog post using term however others proposed use term universal javascript instead several isomorphic javascript frameworks libraries created notably meteor framework react library others includes next.js nuxt rendr derby miso ezel catberry
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Programming language topics
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oxygenos oxygenos customized version android mobile operating system developed chinese smartphone manufacturer oneplus exclusively smartphones oxygenos developed overseas market also another version os designed specifically chinese home market called hydrogenos interview published 3 september 2016 xda developers revealed oneplus actively merging platforms oxygenos hydrogenos single cohesive operating system notable features version 2.0 2.1.1 include app permissions waves maxxaudio swiftkey keyboard off-screen gestures custom icons dark mode manual camera mode raw support 3rd party apps like camera fv-5 2.75 14 june 2016 oneplus released oxygenos 3.0 version android modifications internal tuning like gestures shelf dark mode oneplus 31 december 2016 oneplus released oxygenos 4.0.0 based android nougat includes features several modifications public via ota download 31 january 2018 oneplus released oxygenos 5.0.3 based android oreo public via ota download may 2018 oneplus launched oneplus 6 oxygenos based android oreo 8.1 29 october 2018 oneplus launched oneplus 6t oxygenos 9.0 based android pie 25 december 2018 oneplus released oxygenos 9.0.0 based android pie oneplus 5/5t public via ota download 10 october 2017 security researcher discovered oxygenos system service named devicemanagerservice collects sensitive data sends back oneplus servers service collects many data points including device serial number phone number imei network connections timestamped records user activity within every app users uninstall system service via adb later oneplus released statement data collection analytics claiming data used system improvement optimization shared third parties disabled users system settings oneplus also says revising data analysis mechanism longer collect certain data 2014 oneplus promised close stock bloat-free highly customizable experience soon held name rom contest search name 30 january 2015 oneplus officially announced names oxygenos hydrogenos winner contest midifire belgium flown headquarters shenzhen got meet team along ceo pete lau
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Operating systems
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apple media tool apple media tool multimedia authoring tool associated programming environment sold apple late 1990s primarily aimed producing multimedia presentations distribution cd-rom aimed graphic designers programming experience featured advanced user interface object-oriented user model made production rich complex presentations easy amt system developed patrick soquet developer belgium working arborescence french company later acquired havas 1993 onwards marketed apple development done independent team led soquet 1996 development tool taken apple 2.1 version program developed house team engineers california led dan crow 1997 apple decided concentrate multimedia offerings quicktime hypercard rights amt returned havas patrick soquet acquired rights co-founded tribeworks developed new tool based aml called ishell major features apple media tool graphical authoring tool amt associated programming environment apple media tool programming environment amtpe compiler debugger underlying apple media language aml also known key language amt notable one first authoring systems support embedding apple pioneering qtvr movie format aml object-oriented programming language based eiffel specialized multimedia programming although amt require programming experience use produced complete aml programs compiled byte code interpreted runtime interpreter ampte could used enhance aml code create complex programs example accessing database retrieve media aml conceptually similar java write run anywhere approach cross-platform development runtime interpreters classic mac os windows platforms
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Programming language topics
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noisy channel model noisy channel model framework used spell checkers question answering speech recognition machine translation model goal find intended word given word letters scrambled manner given alphabet formula_1 let formula_2 set finite strings formula_1 let dictionary formula_4 valid words subset formula_2 i.e. formula_6 noisy channel matrix formula_8 intended word formula_9 scrambled word actually received consider english alphabet formula_10 subset formula_6 makes dictionary valid english words several mistakes may occur typing including construct noisy channel matrix formula_12 must consider probability mistake given intended word formula_13 formula_8 formula_9 probabilities may gathered example considering levenshtein distance formula_16 formula_17 comparing draft essay one manually edited spelling goal noisy channel model find intended word given scrambled word received decision function formula_18 function given scrambled word returns intended word methods constructing decision function include maximum likelihood rule maximum posteriori rule minimum distance rule cases may better accept scrambled word intended word rather attempt find intended word dictionary example word schönfinkeling may dictionary might fact intended word
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Computational linguistics
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linpus linux linpus linux fedora-based operating system created taiwanese firm linpus technologies inc. linpus designed specifically fully support asian market full unicode support chinese japanese languages special version linpus lite written run devices lower-cost hardware netbooks icon tab-based simple mode designed new users conventional style pc mode wanting microsoft windows-like interface targeted handheld devices smaller screens supports resolutions low vga 640×480 acer aspire one norhtec gecko netbooks come linpus lite linux pre-installed also version acer revo 3610 3700 linpus linux pre-installed version normal desktop computers servers also available well multimedia version called linpus media center media center version offers upgrade pack purchase patent licenses mpeg-la dvd mp3 wmv codecs linpus system contains free open source operating system also acer-specific shareware users classify nagware asks register acer website purchase full version fact acer distribution contains software prevents system considered fully free/open operating system
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Operating systems
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forth programming language forth imperative stack-based computer programming language environment originally designed charles chuck moore language features include structured programming reflection ability examine modify program structure execution concatenative programming functions composed juxtaposition extensibility programmer create new commands although acronym language name sometimes spelled capital letters forth following customary usage earlier years procedural programming language without type checking forth features interactive execution commands making suitable shell systems lack formal operating system ability compile sequences commands later execution much forth existence standard technique compile threaded code modern implementations generate optimized machine code like language compilers forth used open firmware boot loader space applications philae spacecraft embedded systems involve interaction hardware bestselling 1986 computer game starflight electronic arts written custom forth free software gforth implementation actively maintained several commercially supported systems forth simple yet extensible language modularity extensibility permit writing significant programs forth environment combines compiler interactive shell user defines runs subroutines called words words tested redefined debugged source entered without recompiling restarting whole program syntactic elements including variables basic operators defined words forth environments vary resulting program stored ideally running program effect manually re-entering source programming environments recursive subroutines use stack control flow structure typically also stores local variables including subroutine parameters call value system c forth often local variables however call-by-value instead intermediate values kept another stack different one uses return addresses loop counters etc words operate directly topmost values first two stacks may therefore called parameter data stack often simply stack second function-call stack called linkage return stack abbreviated rstack special rstack manipulation functions provided kernel allow used temporary storage within word often used counted loops otherwise used pass parameters manipulate data words specified terms effect stack typically parameters placed top stack word executes execution parameters erased replaced return values arithmetic operators follows rule reverse polish notation see examples illustrating stack usage forth used successfully large complex projects applications developed competent disciplined professionals proven easily maintained evolving hardware platforms decades use forth niche astronomical space applications forth still used today many embedded systems small computerized devices portability efficient memory use short development time fast execution speed implemented efficiently modern risc processors processors use forth machine language produced uses forth include open firmware boot roms used apple ibm sun olpc xo-1 forth evolved charles h. moore personal programming system continuous development since 1968 forth first exposed programmers early 1970s starting elizabeth rather us national radio astronomy observatory work nrao charles moore elizabeth rather formed forth inc. 1973 refining porting forth systems dozens platforms next decade forth named 1968 file holding interpreter labeled fourth 4th next generation software—but ibm 1130 operating system restricted file names 5 characters moore saw forth successor compile-link-go third-generation programming languages software fourth generation hardware fourth-generation programming language term come used charles moore frequently moved job job career early pressure developing language ease porting different computer architectures forth system often used bring new hardware example forth first resident software new intel 8086 chip 1978 macforth first resident development system 128k macintosh 1984 forth inc. microforth developed intel 8080 motorola 6800 zilog z80 microprocessors starting 1976 microforth later used hobbyists generate forth systems architectures 6502 1978 wide dissemination finally led standardization language common practice codified de facto standards forth-79 forth-83 years 1979 1983 respectively standards unified ansi 1994 commonly referred ans forth forth became popular 1980s well suited small microcomputers time compact portable least one home computer british jupiter ace forth rom-resident operating system canon cat also used forth system programming rockwell produced single-chip microcomputers resident forth kernels r65f11 r65f12 complete family tree tu-wien insoft graforth version forth graphics extensions apple ii asyst forth expansion measuring controlling pcs 2018 source original 1130 version forth recovered updated run restored emulated 1130 system forth relies heavily explicit use data stack reverse polish notation rpn postfix notation commonly used calculators hewlett-packard rpn operator placed operands opposed common infix notation operator placed operands postfix notation makes language easier parse extend forth flexibility makes static bnf grammar inappropriate monolithic compiler extending compiler requires writing new word instead modifying grammar changing underlying implementation using rpn one could get result mathematical expression codice_1 way command line first puts numbers 25 10 implied stack br word codice_2 multiplies two numbers top stack replaces product number 50 placed stack br word codice_3 adds previous product codice_4 moves output new line formatting purposes could omitted but—in implementations—without output would occur line input would less readable example finally codice_5 command prints result user terminal everything completed successfully point text interpreter outputs prompt codice_6 moves new line get input without needing anything explicit even forth structural features stack-based example code defines new word word term used subroutine called codice_7 using following commands codice_8 duplicates number stack codice_9 places 6 top stack codice_10 compares top two numbers stack 6 codice_8ed input replaces true-or-false value codice_12 takes true-or-false value chooses execute commands immediately skip codice_13 codice_14 discards value stack codice_15 ends conditional text parentheses comment advising word expects number stack return possibly changed number codice_7 word equivalent function written c programming language using function written succinctly could run word follows first interpreter pushes number 1 8 onto stack calls codice_7 pops number pushes result codice_4 moves output new line readability finally call codice_5 pops result prints user terminal forth explicit grammar interpreter reads line input user input device parsed word using spaces delimiter systems recognise additional whitespace characters interpreter finds word looks word dictionary word found interpreter executes code associated word returns parse rest input stream word n't found word assumed number attempt made convert number push stack successful interpreter continues parsing input stream otherwise lookup number conversion fail interpreter prints word followed error message indicating word recognised flushes input stream waits new user input definition new word started word codice_20 colon ends word codice_21 semi-colon example compile word codice_22 makes name findable dictionary executed typing codice_23 console print codice_24 forth systems include assembler allows one specify words using processor facilities lowest level mostly assembler tucked away separate namespace wordlist relatively users want use forth assemblers may use reverse-polish syntax parameters instruction precede instruction designs vary widely specific forth implementation typical reverse-polish assembler prepares operands stack mnemonic copy whole instruction memory last step forth assembler nature macro assembler easy define alias registers according role forth system e.g datastackpointer register used stack pointer forth systems run host operating system microsoft windows linux version unix use host operating system file system source data files ansi forth standard describes words used i/o modern forth systems use normal text files source even embedded embedded system resident compiler gets source via serial line classic forth systems traditionally use neither operating system file system instead storing code files source code stored disk blocks written physical disk addresses word codice_25 employed translate number 1k-sized block disk space address buffer containing data managed automatically forth system block use become rare since mid-1990s hosted system blocks allocated normal file case multitasking commonly cooperative round-robin scheduling normally available although multitasking words support covered ansi forth standard word codice_26 used save current task execution context locate next task restore execution context task stacks private copies control variables scratch area swapping tasks simple efficient result forth multitaskers available even simple microcontrollers intel 8051 atmel avr ti msp430 non-standard facilities include mechanism issuing calls host os windowing systems many provide extensions employ scheduling provided operating system typically larger different set words stand-alone forth codice_26 word task creation suspension destruction modification priority full-featured forth system source code compile technique commonly called meta-compilation self-hosting forth programmers although term n't exactly match meta-compilation normally defined usual method redefine handful words place compiled bits memory compiler words use specially named versions fetch store redirected buffer area memory buffer area simulates accesses memory area beginning different address code buffer compilers define words access target computer memory host compiling computer memory fetch store operations redefined code space compiler assembler etc recompiled using new definitions fetch store effectively reuses code compiler interpreter forth system code compiled version stored buffer buffer memory written disk ways provided load temporarily memory testing new version appears work written previous version numerous variations compilers exist different environments embedded systems code may instead written another computer technique known cross compilation serial port even single ttl bit keeping word names non-executing parts dictionary original compiling computer minimum definitions forth compiler words fetch store byte word commands forth word executed often time-consuming part writing remote port constructing initial program implement fetch store execute many modern microprocessors integrated debugging features motorola cpu32 eliminate task basic data structure forth dictionary maps words executable code named data structures dictionary laid memory tree linked lists links proceeding latest recently defined word oldest sentinel value usually null pointer found context switch causes list search start different leaf linked list search continues branch merges main trunk leading eventually back sentinel root several dictionaries rare cases meta-compilation dictionary might isolated stand-alone effect resembles nesting namespaces overload keywords depending context defined word generally consists head body head consisting name field nf link field lf body consisting code field cf parameter field pf head body dictionary entry treated separately may contiguous example forth program recompiled new platform head may remain compiling computer body goes new platform environments embedded systems heads occupy memory unnecessarily however cross-compilers may put heads target target expected support interactive forth exact format dictionary entry prescribed implementations vary however certain components almost always present though exact size order may vary described structure dictionary entry might look way name field starts prefix giving length word name typically 32 bytes several bits flags character representation word name follows prefix depending particular implementation forth may one nul '\0 bytes alignment link field contains pointer previously defined word pointer may relative displacement absolute address points next oldest sibling code field pointer either address word execute code data parameter field beginning machine code processor execute directly colon defined words code field pointer points word save current forth instruction pointer ip return stack load ip new address continue execution words processor call/return instructions compiler monolithic program consists forth words visible system usable programmer allows programmer change compiler words special purposes compile time flag name field set words compile time behavior simple words execute code whether typed command line embedded code compiling compiler simply places code threaded pointer word classic examples compile-time words control structures codice_12 codice_29 almost forth control structures almost compiler implemented compile-time words apart rarely used control flow words found implementations conditional return forth control flow words executed compilation compile various combinations primitive words along branch addresses instance codice_12 codice_29 words match set codice_32 unconditional branch codice_33 pop value stack branch false counted loop control flow words work similarly set combinations primitive words work counter compilation data stack used support control structure balancing nesting back-patching branch addresses snippet would compiled following sequence inside definition numbers codice_32 represent relative jump addresses codice_35 primitive word pushing literal number onto data stack word codice_20 colon parses name parameter creates dictionary entry colon definition enters compilation state interpreter continues read space-delimited words user input device word found interpreter executes compilation semantics associated word instead interpretation semantics default compilation semantics word append interpretation semantics current definition word codice_21 semi-colon finishes current definition returns interpretation state example word whose compilation semantics differ default interpretation semantics codice_21 semi-colon control flow words several words undefined ans forth meaning must used inside definitions interactive command line interpreter state changed manually words codice_39 left-bracket codice_40 right-bracket enter interpretation state compilation state respectively words used word codice_41 calculate value compilation insert calculated value current colon definition codice_41 compilation semantics take object data stack append semantics current colon definition place object data stack ans forth current state interpreter read flag codice_43 contains value true compilation state false otherwise allows implementation so-called state-smart words behavior changes according current state interpreter word codice_44 marks recent colon definition immediate word effectively replacing compilation semantics interpretation semantics immediate words normally executed compilation compiled overridden programmer either state codice_21 example immediate word ans forth word codice_46 takes name parameter appends compilation semantics named word current definition even word marked immediate forth-83 defined separate words codice_47 codice_48 force compilation non-immediate immediate words respectively ans forth unnamed words defined word codice_49 compiles following words next codice_21 semi-colon leaves execution token data stack execution token provides opaque handle compiled semantics similar function pointers c programming language execution tokens stored variables word codice_51 takes execution token data stack performs associated semantics word codice_52 compile-comma takes execution token data stack appends associated semantics current definition word codice_53 tick takes name word parameter returns execution token associated word data stack interpretation state codice_54 equivalent codice_55 words codice_20 colon codice_46 codice_53 tick examples parsing words take arguments user input device instead data stack another example word codice_59 paren reads ignores following words including next right parenthesis used place comments colon definition similarly word codice_60 backslash used comments continue end current line parsed correctly codice_59 paren codice_60 backslash must separated whitespace following comment text forth systems body code definition consists either machine language form threaded code original forth follows informal fig standard forth interest group til threaded interpretive language also called indirect-threaded code direct-threaded subroutine threaded forths also become popular modern times fastest modern forths use subroutine threading insert simple words macros perform peephole optimization optimizing strategies make code smaller faster word variable data object cf points runtime code associated defining word created defining word characteristic defining behavior creating dictionary entry plus possibly allocating initializing data space also specifies behavior instance class words constructed defining word examples include forth also provides facility programmer define new application-specific defining words specifying custom defining behavior instance behavior examples include circular buffers named bits i/o port automatically indexed arrays data objects defined similar words global scope function provided local variables languages provided data stack forth although forth also real local variables forth programming style uses named data objects compared languages typically data objects used contain data used number words tasks multitasked implementation forth enforce consistency data type usage programmer responsibility use appropriate operators fetch store values perform operations data words written forth compiled executable form classical indirect threaded implementations compile lists addresses words executed turn many modern systems generate actual machine code including calls external words code others expanded place systems optimizing compilers generally speaking forth program saved memory image compiled program single command e.g. run executed compiled version loaded development programmer uses interpreter repl mode execute test little piece developed forth programmers therefore advocate loose top-down design bottom-up development continuous testing integration top-down design usually separation program vocabularies used high-level sets tools write final program well-designed forth program reads like natural language implements single solution also sets tools attack related problems one possible implementation word codice_4 carriage return causes following output displayed new line parsing word codice_69 dot-quote reads double-quote delimited string appends code current definition parsed string displayed execution space character separating word codice_69 string codice_71 included part string needed parser recognizes codice_69 forth word standard forth system also interpreter output obtained typing following code fragment forth console codice_73 dot-paren immediate word parses parenthesis-delimited string displays word codice_69 space character separating codice_73 codice_71 part string word codice_4 comes text print convention forth interpreter start output new line also convention interpreter waits input end previous line codice_78 prompt implied flush-buffer action forth codice_4 sometimes programming languages definition word codice_80 executed emits single character codice_81 definition written use ascii value codice_81 character 81 directly text parentheses comment ignored compiler word codice_83 takes value data stack displays corresponding character following redefinition codice_80 uses words codice_39 left-bracket codice_40 right-bracket codice_87 codice_41 temporarily switch interpreter state calculate ascii value codice_81 character return compilation state append calculated value current colon definition parsing word codice_87 takes space-delimited word parameter places value first character data stack word codice_91 immediate version codice_87 using codice_91 example definition codice_80 could rewritten like definition used codice_60 backslash describing comment codice_87 codice_91 predefined ans forth using codice_44 codice_46 codice_91 could defined like 1987 ron rivest developed rc4 cipher-system rsa data security inc code extremely simple written programmers description array 256 bytes different every time array used changes swapping two bytes swaps controlled counters j initially 0 get new add 1 get new j add array byte new exchange array bytes j code array byte sum array bytes j xored byte plaintext encrypt ciphertext decrypt array initialized first setting 0 255 step using j getting new j adding array byte key byte swapping array bytes j finally j set 0 additions modulo 256 following standard forth version uses core core extension words one many ways test code forth virtual machine simple implement standard reference implementation numerous implementations language addition supporting standard varieties desktop computer systems posix microsoft windows mac os x many forth systems also target variety embedded systems listed prominent systems conform 1994 ans forth standard
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Programming language topics
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postrank postrank social media analytics service used proprietary ranking algorithm measure social engagement published content based blog comments links internet bookmarks clicks page views activities social network services twitter digg facebook myspace june 2011 postrank acquired google company formerly called aiderss inc october 2008 aiderss re-launched website postrank.com focus company work core postrank technology july 2009 company officially changed name postrank inc company developed offered multiple services acquisition postrank functionality integrated google analytics
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Web technology
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elasticity data store elasticity data store relates flexibility data model clustering capabilities greater number data model changes tolerated easily clustering managed elastic data store considered clustering elasticity ease adding removing nodes distributed data store usually difficult delicate task done expert relational database system nosql data stores like apache cassandra easy solution node added/removed changes properties adding specifying least one seed relational databases often inelastic predefined data model adapted redesign nosql data stores however fixed schema row different number even different type columns concerning data store modifications schema problem makes kind data stores elastic concerning data model drawback programmer take account data model may change time
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Databases
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sensor observation service sensor observation service sos web service query real-time sensor data sensor data time series part sensor web offered sensor data comprises descriptions sensors encoded sensor model language sensorml measured values observations measurements encoding format web service well file formats open standards specifications name defined open geospatial consortium ogc sos supports transactional profile sos-t new sensors registered service interface measuring values inserted sos implementation used data in-situ well remote sensing sensors furthermore sensors either mobile stationary since 2007 sos official ogc standard advantage sos sensor data kind available standardized format using standardized operations thus web-based access sensor data simplified also allows easy integration existing spatial data infrastructures geographic information systems 2016 ogc approved sensorthings api standard specification new restful json-based standard provide functions similar sos sensorthings api sos based ogc/iso 19156:2011 two specifications demonstrated ogc iot pilot interoperate sos three so-called core operations must provided implementation getcapabilities operation allows query service description service interface available sensor data using sos getobservation function probably important utilized retrieve data specific sensors describesensor function returns detailed information sensor sensor system producing processes ogc sos well-defined terminology better understanding important terms sos standard ogc ultimately defines service interface implementation currently several open source implementations service also proprietary implementations exist
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Web technology
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popfile popfile free open-source cross-platform mail filter originally written perl john graham-cumming maintained team volunteers uses naive bayes classifier filter mail allows filter learn classify mail according user preferences typically used filter spam mail also used sort mail user defined buckets categories example user may define bucket work email sorted program works several different modes popular mode sets proxy email client pop3 server mail downloaded via pop3 filter identifies classifies mail makes user defined modification subject line appending name appropriate bucket user sets rules mail client sort mail based subject line modification html based interface used instruct popfile allowing users correct errors classifications thus train system sensitive user specific requirements alternative subject-line modification supplement system also configured use custom mail headers instead another possible mode popfile work imap client monitors imap server incoming mail also messages moved user incoming emails categorized immediately moved folder corresponding categorization train popfile mode user needs move message correct folder i.e folder popfile moved message
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Computer security
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comparison distributed file systems computing distributed file system dfs network file system file system allows access files multiple hosts sharing via computer network makes possible multiple users multiple machines share files storage resources distributed file systems differ performance mutability content handling concurrent writes handling permanent temporary loss nodes storage policy storing content researchers made functional experimental analysis several distributed file systems including hdfs ceph gluster lustre old 1.6.x version moosefs although document 4 years old lot information may outdated e.g moosefs time writing stable 2.0 beta 3.0 version ha metadata server since 2.0 mentioned document cloud based remote distributed storage major vendors different apis different consistency models
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Computer file systems
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lucid programming language lucid dataflow programming language designed experiment non-von neumann programming models designed bill wadge ed ashcroft described 1985 book lucid dataflow programming language plucid first interpreter lucid lucid uses demand-driven model data computation statement understood equation defining network processors communication lines data flows variable infinite stream values every function filter transformer iteration simulated 'current values 'fby read 'followed operator allowing composition streams lucid based algebra histories history infinite sequence data items operationally history thought record changing values variable history operations first next understood ways suggested names lucid originally conceived kind disciplined mathematically pure single-assignment language verification would much simplified however dataflow interpretation important influence direction lucid evolved lucid dataflow languages expression contains variable yet bound waits variable bound proceeding expression like codice_1 wait x bound returning output expression important consequence explicit logic updating related values avoided results substantial code reduction compared mainstream languages variable lucid stream values expression codice_2 defines stream using operator 'fby mnemonic followed fby defines comes previous expression instance stream produces 1,2,3 ... values stream addressed operators assuming x variable used codice_3 fetches first value stream x codice_4 current value stream codice_5 fetches next value stream codice_6 operator thing 'as soon condition given becomes true codice_7 upon operator repeats old value stream x updates new values stream p makes codice_8 value available serves slow stream x i.e codice_9 stream x new values appearing upon truth p. computation carried defining filters transformation functions act time-varying streams data fac fib total running_avg prime qsort eof first else follow qsort b0 qsort b1 fi -- -- -- -- whenever -- -- qsort -- -- -- -- sqroot avg square h
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Programming language topics
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list linux-supported computer architectures basic components linux family operating systems based linux kernel gnu c library busybox forks thereof like μclinux uclibc programmed certain level abstraction mind also distinct code paths assembly language c source code support certain hardware therefore source code successfully compiled onor cross-compiled fora great number computer architectures furthermore required free open-source software also developed interface linux hardware linux executed example compilers available e.g gnu compiler collection gcc llvm/clang cross-compilation number complete toolchains available like gnu toolchain openwrt buildroot openembedded yocto project targeted embedded use cases portability section linux kernel article contains information references technical details note components like display server programs like blender present absent fundamentally software ported i.e specifically adapted kind hardware supposed executed level abstraction kept mind programming software first place dictates necessary effort relevant term porting target computer architecture comprises instruction set microarchitecture processor least cpu target also comprises system design entire system supercomputer desktop computer soc e.g case unique bus used former times memory controller part chipset motherboard cpu-die although support specific instruction set task compiler software must written certain level abstraction mind make portability possible code written assembly language specific instruction set support specific microarchitecture includes optimizations cpu cache hierarchy tlb etc additional processors particularly freescale 68000 coldfire supported mmu-less μclinux variant
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Computer architecture
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usage data usage data effective way evaluating true relevancy value website example users arrive web site go back immediately high bounce rate chances ’ relevant query first place however user repeatedly visits web site spends long time site high likelihood extremely relevant comes search engines relevant valuable sites get promoted irrelevant sites get demoted search engines want results highly relevant web users make sure web users keep returning search engine future searches best way establish relevance users know use web sites cookies used search engines maintain history user ’ search activity
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Web technology
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tape management system tape management system tms computer software manages usage retention computer backup tapes may done stand-alone function part broader backup software package modern tape management system tms usually used conjunction backup applications generally used manage magnetic tape media contains backup information electronically stored information tape management systems used organizations locate track rotate media according organizations internal policies well government regulations stand-alone tape management systems predominant mainframe platforms tape used backup base load storage medium mainframe systems ibm z/os provide basic support tape inventory control via os catalog cataloging files optional usually required additional software package following operations usually achieved using operating system hooks intercept file open close operations
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Computer security
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time-of-check time-of-use software development time-of-check time-of-use toctou tocttou toc/tou class software bugs caused race condition involving checking state part system security credential use results check simple example follows consider web application allows user edit pages also allows administrators lock pages prevent editing user requests edit page getting form used alter content user submits form administrator locks page prevent editing however since editing already begun user submits form edits already made accepted user began editing appropriate authorization checked user indeed allowed edit however authorization used later time edits longer allowed toctou race conditions common unix operations file system occur contexts including local sockets improper use database transactions early 1990s mail utility bsd 4.3 unix exploitable race condition temporary files used codice_1 function early versions openssh exploitable race condition unix domain sockets remain problem modern systems 2019 toctou race condition docker allows root access filesystem host platform unix following c code used codice_2 program toctou bug access intended check whether real user executed codice_2 program would normally allowed write file i.e. codice_4 checks real userid rather effective userid race condition vulnerable attack example attacker exploit race condition codice_5 codice_6 trick codice_2 victim overwriting entry system password database toctou races used privilege escalation get administrative access machine although sequence events requires precise timing possible attacker arrange conditions without much difficulty implication applications assume state managed operating system case file system namespace change system calls exploiting toctou race condition requires precise timing ensure attacker operations interleave properly victim example attacker must execute codice_8 system call precisely codice_5 codice_6 general attack attacker must scheduled execution operation victim also known single-stepping victim case bsd 4.3 mail utility mktemp attacker simply keep launching mail utility one process keep guessing temporary file names keep making symlinks another process attack usually succeed less one minute techniques single-stepping victim program include file system mazes algorithmic complexity attacks cases attacker manipulates os state control scheduling victim file system mazes force victim read directory entry os cache os puts victim sleep reading directory disk algorithmic complexity attacks force victim spend entire scheduling quantum inside single system call traversing kernel hash table cached file names attacker creates large number files names hash value file victim look despite conceptual simplicity toctou race conditions difficult avoid eliminate one general technique use exception handling instead checking philosophy eafp – easier ask forgiveness permission rather lbyl – look leap – case check failure assumptions hold detected use time exception context file system toctou race conditions fundamental challenge ensuring file system changed two system calls 2004 impossibility result published showing portable deterministic technique avoiding toctou race conditions since impossibility result libraries tracking file descriptors ensuring correctness proposed researchers alternative solution proposed research community unix systems adopt transactions file system os kernel transactions provide concurrency control abstraction os used prevent toctou races production unix kernel yet adopted transactions proof-of-concept research prototypes developed linux including valor file system txos kernel microsoft windows added transactions ntfs file system microsoft discourages use indicated may removed future version windows file locking common technique preventing race conditions single file extend file system namespace metadata locking work well networked filesystems prevent toctou race conditions setuid binaries possible solution use codice_11 system call change effective user perform codice_12 differences codice_13 operating systems problematic
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Computer security
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game ii game ii known phantis spain action game developed published dinamic software 1987 amstrad cpc atari st commodore 64 ms-dos msx zx spectrum game ii mix scrolling shoot 'em game similar r-type platform game similar turrican four phases six levels versions game split two parts due size restrictions story begins arkon hero rebellion managed defeat evil empress gremla free galaxy oppressive rule original spanish version phantis player controls major locke tries rescue boyfriend arkon captured forces loyal vengeful unnamed heir gremla featured cover art imprisoned planet phantis english-language version titled game ii arkon job rescue commander serena game versions although originally conceived independent game title phantis became sequel game atari st version never published spain exists game ii title game promotion included appearance model dressed queen gremla trade convention pc show '88 game given generally mediocre reviews received scores 69 amstrad action 55 commodore user 60-63 games machine 62 sinclair user amstrad computer user gave 17/20
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Computer architecture
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spooling computing spooling specialized form multi-programming purpose copying data different devices contemporary systems usually used mediating computer application slow peripheral printer spooling allows programs hand work done peripheral proceed tasks begin input transcribed dedicated program spooler maintains orderly sequence jobs peripheral feeds data rate conversely slow input peripherals card reader spooler maintain sequence computational jobs waiting data starting job relevant input available see batch processing spool refers sequence jobs storage area held many cases spooler able drive devices full rated speed minimal impact processing spooling combination buffering queueing nowadays common use spooling printing documents formatted printing stored queue speed computer retrieved printed speed printer multiple processes write documents spool without waiting perform tasks spooler process operates printer example large organization prepares payroll cheques computation takes minutes even seconds printing process might take hours payroll program printed cheques directly would unable proceed computations cheques printed similarly spooling added pc operating systems word processors unable anything else including interact user printing spooler print management software often includes variety related features allowing priorities assigned print jobs notifying users documents printed distributing print jobs among several printers selecting appropriate paper document etc print server applies spooling techniques allow many computers share printer group printers print spoolers configured add banner page also called burst page job sheet printer separator front document separate documents identify document e.g title often also state printed e.g username job name banner pages valuable office environments many people share small number printers depending configuration banner pages might generated client computer centralized print server printer printers using fanfold continuous forms leading banner page would often printed twice one copy would always face-up jobs separated page might include lines printed fold would visible along edge stack printed output allowing operator easily separate jobs systems would also print banner page end job assuring users collected printout spooling also used mediate access punched card readers punches magnetic tape drives slow sequential i/o devices allows application run speed cpu operating peripheral devices full rates speed batch processing system uses spooling maintain queue ready-to-run tasks started soon system resources process store forward messaging systems uucp used spool refer inbound outbound message queues terminology still found documentation email usenet software even though messages often delivered immediately nowadays peripheral devices always much slower core processing units especially severe problem early mainframes example job read punched cards generated printed output directly forced run speed slow mechanical devices first spooling programs ibm spool system 7070-io-076 copied data punched cards magnetic tape tape back punched cards printers hard disks even faster support random access started replace use magnetic tape middle 1960s 1970s eliminated use tape unit record equipment ibm mainframes early 1960s slow common use small offline machine 1401 instead spooling term spool probably originates simultaneous peripheral operations on-line spool software derivation uncertain simultaneous peripheral operations on-line may backronym another explanation refers spools reels magnetic tape
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Operating systems
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samantha fox strip poker samantha fox strip poker 1986 erotic video game developed software communications published martech games published commodore 64 amstrad cpc bbc micro msx zx spectrum game one first erotic video games include real human part theme erotic games players complete difficult tasks rewarded nudity video game programmed wolfgang smith graphics edited malcolm smith author music rob hubbard credited name john york music includes cover entertainer scott joplin stripper david rose players plays 5-card 7-card stud poker british model singer samantha fox beating results taking clothes topless zzap felt music well-suited style game commodore format magazine thought idea anybody using game way experience titillating content depressing due require effort player uvejuegos thought game prime example strange 1980s spiegel placed game within sub-genre early pixelated digi-ladies dubious beauty along artworx strip poker 1984
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Computer architecture
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setuptools setuptools package development process library designed facilitate packaging python projects enhancing python standard library distutils distribution utilities includes 2013 distribute fork setuptools merged back setuptools 0.7 python wheels replaced eggs python eggs way bundling additional information python project allows project dependencies checked satisfied runtime well allowing projects provide plugins projects python pip replaced easyinstall easyinstall package manager python provides standard format distributing python programs libraries based python eggs format easyinstall module bundled setuptools analogous rubygems ruby easyinstall fully fledged package manager list local packages update pip python package manager pypm python applications designed fulfill similar role easyinstall distribute fork created specifically due lack progress easyinstall development default easyinstall looks python package index pypi desired packages uses metadata download install package dependencies
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Operating systems
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ultrasparc ii ultrasparc ii code-named blackbird microprocessor implementation sparc v9 instruction set architecture isa developed sun microsystems marc tremblay chief architect introduced 1997 development ultrasparc operating higher clock frequencies 250 mhz eventually reaching 650 mhz die contained 5.4 million transistors area 149 mm² fabricated texas instruments 0.35 µm process dissipated 25 w 205 mhz used 2.5 v power supply l2 cache capacity 1 4 mb 1999 ultrasparc ii ported 0.25 µm process version code-named sapphire-black operated 360 480 mhz possessed die area 126 mm² dissipated 21 w 400 mhz power supply voltage reduced 1.9 v. supported l2 cache capacity increased 1 8 mb ultrasparc ii basis four derivatives ultrasparc iie hummingbird embedded version introduced 2000 operated 400 500 mhz fabricated 0.18 µm process aluminium interconnects dissipated maximum 13 w 500 mhz used 1.5 1.7 v power supply 256 kb l2 cache ultrasparc iii sabre featuring on-chip pci controller low-cost version introduced 1997 operated 270 360 mhz fabricated 0.35 µm process possessed die size 156 mm² dissipated 21 w used 1.9 v power supply 256 kb 2 mb l2 cache 1998 version code-named sapphire-red fabricated 0.25 µm process enabling microprocessor operate 333 480 mhz dissipated 21 w 440 mhz used 1.9 v power supply ultrasparc iie+ iii introduced 2002 code-named phantom operated 550 650 mhz fabricated 0.18 µm process copper interconnect dissipated 17.6 w used 1.7 v power supply 512 kb l2 cache gemini first attempt sun produce multithreaded microprocessor taped cancelled introduced announcement ultrasparc t1 niagara microprocessor early 2004 consisted two ultrasparc ii cores on-die l2 cache single chip dac 2004 abstracts described dual-core ultrasparc ii processor session 40 dual-core ultrasparc 2003 based upon ultrasparc ii microarchitecture featured ddr-1 memory controller jbus interface parity protected l1 cache ecc protected dual 512kb on-chip level 2 cache 1.2 ghz clock frequency 80 million transistors 206mm^2 die size dissipated 23 watts power
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Computer architecture
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java servlet java servlet java software component extends capabilities server although servlets respond many types requests commonly implement web containers hosting web applications web servers thus qualify server-side servlet web api web servlets java counterpart dynamic web content technologies php asp.net java servlet processes stores java class java ee conforms java servlet api standard implementing java classes respond requests servlets could principle communicate client–server protocol often used http thus servlet often used shorthand http servlet thus software developer may use servlet add dynamic content web server using java platform generated content commonly html may data xml commonly json servlets maintain state session variables across many server transactions using http cookies url mapping java servlet api extent superseded two standard java technologies web services deploy run servlet web container must used web container also known servlet container essentially component web server interacts servlets web container responsible managing lifecycle servlets mapping url particular servlet ensuring url requester correct access rights servlet api contained java package hierarchy defines expected interactions web container servlet object receives request generates response based request basic servlet package defines java objects represent servlet requests responses well objects reflect servlet configuration parameters execution environment package defines http-specific subclasses generic servlet elements including session management objects track multiple requests responses web server client servlets may packaged war file web application servlets generated automatically javaserver pages jsp javaserver pages compiler difference servlets jsp servlets typically embed html inside java code jsps embed java code html direct usage servlets generate html shown example become rare higher level mvc web framework java ee jsf still explicitly uses servlet technology low level request/response handling via somewhat older usage use servlets conjunction jsps pattern called model 2 flavor model–view–controller current version servlet 4.0 java servlets api first publicly announced inaugural javaone conference may 1996 two months announcements conference first public implementation made available javasoft website first alpha java web server jws known codename jeeves would eventually shipped product june 5 1997 blog java.net sun veteran glassfish lead jim driscoll details history servlet technology james gosling first thought servlets early days java concept become product december 1996 sun shipped jws java platform enterprise edition made specification servlet1 specification created pavni diwanji worked sun microsystems version 1.0 finalized june 1997 starting version 2.2 specification developed java community process three methods central life cycle servlet codice_1 codice_2 codice_3 implemented every servlet invoked specific times server following typical user scenario methods following example servlet prints many times codice_2 method called note codice_16 subclass codice_17 implementation codice_18 interface codice_2 method codice_16 class dispatches requests methods codice_21 codice_22 codice_23 codice_24 according http request example codice_2 overridden distinguish http request method serves import java.io.ioexception import javax.servlet.servletconfig import javax.servlet.servletexception import javax.servlet.http.httpservlet import javax.servlet.http.httpservletrequest import javax.servlet.http.httpservletresponse public class servletlifecycleexample extends httpservlet specification servlet technology implemented many products see list implementations web container page
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Programming language topics
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media type media type formerly known mime type two-part identifier file formats format contents transmitted internet internet assigned numbers authority iana official authority standardization publication classifications media types originally defined request comments 2045 november 1996 part mime multipurpose internet mail extensions specification denoting type email message content attachments hence original name mime type media types also used internet protocols http document file formats html similar purpose media type consists type subtype structured tree media type optionally define suffix parameters currently registered types codice_2 codice_3 codice_4 codice_5 codice_6 codice_7 codice_8 codice_9 codice_10 codice_11 unofficial top-level name common use called chemical example html file might designated codice_12 example codice_10 type codice_14 subtype codice_15 optional parameter indicating character encoding subtype typically consists media format may must also contain content tree prefix producer product suffix according different rules registration trees types subtypes parameter names case-insensitive parameter values usually case-sensitive may interpreted case-insensitive fashion depending intended use media types registered using iana registration procedures efficiency flexibility media type registration process different structures subtypes registered registration trees distinguished use tree prefixes currently following trees created standard prefix vendor codice_44 prefix personal vanity codice_45 prefix unregistered codice_46 prefix registration trees first defined november 1996 obsoleted rfc 2048 currently rfc 6838 new registration trees may created ietf standards action external registration management well-known permanent organizations e.g scientific societies standards tree use tree prefix examples codice_16 codice_40 registrations standards tree must either associated ietf specifications approved directly iesg registered iana recognized standards-related organization vendor tree includes media types associated publicly available products uses codice_44 tree prefix examples codice_27 codice_31 terms vendor producer considered equivalent context industry consortia well non-commercial entities register media types vendor tree registration vendor tree may created anyone needs interchange files associated software product set products however registration belongs vendor organization producing software employs type registered vendor organization time elect assert ownership registration done third party personal vanity tree includes media types associated non publicly available products experimental media types uses codice_45 tree prefix examples codice_56 codice_57 unregistered tree includes media types intended exclusively use private environments active agreement parties exchanging uses codice_46 tree prefix examples codice_60 codice_61 media types tree registered according rfc 6838 published january 2013 use types unregistered tree strongly discouraged addition subtypes prefixed codice_62 codice_63 longer considered members tree according obsoleted rfc 2048 published november 1996 —it rarely ever necessary use unregistered types use codice_46 codice_62 codice_63 prefixes discouraged obsoleted rfc 1590 published september 1993 stated use codice_62 codice_63 prefix may used unregistered subtypes media types widely deployed subtype prefixed codice_62 codice_63 without registered possible re-registered proper prefixed subtype possible media type approval media types reviewer iesg registered standards tree unprefixed subtype suffix augmentation media type definition additionally specify underlying structure media type media types make use named structured syntax use appropriate iana registered codice_71 structured syntax registered unregistered suffixes used since january 2013 structured syntax suffix registration procedures defined rfc 6838 examples currently registered suffixes codice_72 codice_73 codice_74 codice_75 codice_76 codice_77 codice_78 codice_79 rfc 7049 codice_80 codice_72 suffix defined since january 2001 rfc 3023 formal registration codice_72 suffix suffixes defined since january 2013 rfc 6839 mailcap derived phrase mail capability type meta file used configure mime-aware applications mail clients web browsers render files different mime-types mailcap format defined rfc 1524 user agent configuration mechanism multimedia mail format information defined internet standard supported unix systems lines comments starting character mime-type followed handle mime type first part called content-type second part called view-command example codice_83 says file encoded mime type codice_84 run xmpeg program file name parameter associated file mime.types file associates filename extensions mime type mime type properly set unnecessary mime types may incorrectly set set generic type codice_85 codice_86 allows one fall back extension cases similarly since many file systems store mime type information instead rely filename extension mime.types file frequently used web servers determine mime type viewing file two work together follows codice_86 associates extension mime type codice_88 associates mime type program unix-type systems mime.types file usually located codice_89 and/or codice_90 format simply line space-delimited list mime type followed zero extensions example html type associated extensions codice_91 codice_92 following line mime.types file dates netscape used different format used key-value pairs comma-separated list extensions together standard header consisting specific comment identifies file mime.types file follows
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Operating systems
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windows desktop gadgets windows desktop gadgets called windows sidebar windows vista discontinued widget engine microsoft gadgets introduced windows vista features sidebar anchored side desktop widgets perform various tasks displaying time date windows vista widgets restricted sidebar windows 7 freely moved anywhere desktop windows desktop gadgets discontinued windows 8 windows 8 live tiles perform similar function visible start menu visible run restrictive environment making less risky also less useful purposes like system monitoring windows sidebar originated microsoft research project called sideshow confused windows sideshow developed summer 2000 used internally microsoft included clock traffic reports im integration windows sidebar appeared build 3683 windows vista circa september 2002 originally intended replace notification area quick launch toolbar windows plans scrapped development reset mid-2004 windows sidebar rebuilt began appear windows vista builds second half 2005 reviewers macintosh enthusiasts pointed sidebar similarities form function konfabulator yahoo widget engine appeared several years previously dashboard widget engine first included apple inc. mac os x v10.4 released months earlier windows 7 windows sidebar renamed windows desktop gadgets sidebar included windows 7 windows desktop gadgets included beta releases windows 8 make final release instead 10 july 2012 intervening time last beta windows 8 final release microsoft issued security advisory disable sidebar desktop gadgets windows vista 7 security vulnerability could allow remote code execution windows desktop gadgets feature windows vista windows 7 excluding windows server family operating system hosts mini-applications gadgets combination scripts html code use cases include displaying system time downloading displaying rss feeds controlling software windows media player windows vista gadgets run docked sidebar windows 7 float anywhere desktop also possible run multiple instances gadget simultaneously windows vista 7 sidebar also works windows xp windows vista ships eleven gadgets calendar clock contacts cpu meter currency conversion feed headlines notes picture puzzle slide show stocks weather several gadgets available vista beta app launcher feed viewer number puzzle recycle bin egg timer never made final release windows vista windows 7 adds media center gadget removes contacts notes stocks gadgets originally microsoft provided link web site called windows live gallery additional sidebar gadgets created third-party developers could downloaded site officially retired october 1 2011
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Operating systems
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forward compatibility forward compatibility upward compatibility design characteristic allows system accept input intended later version concept applied entire systems electrical interfaces telecommunication signals data communication protocols file formats computer programming languages standard supports forward compatibility product complies earlier versions gracefully process input designed later versions standard ignoring new parts understand objective forward compatible technology old devices recognise data generated new devices forward compatibility older system usually means backward compatibility new system i.e ability process data old system new system usually full compatibility older one able process generate data format older system forward compatibility extensibility forward compatible design process least data future version extensible design makes upgrading easy example design ideas found web browsers point time current browser forward compatible gracefully accepts newer version html whereas easily browser code upgraded process newer html determines extensible introduction fm stereo transmission color television allowed forward compatibility since monophonic fm radio receivers black-and-white tv sets still could receive signal new transmitter also allowed backward compatibility since new receivers could receive monophonic black-and-white signals generated old transmitters html designed treat tags way inert unstyled inline elements unless appearance behavior overridden either browser default settings scripts styles included page makes new features degrade gracefully older browsers one case work intended script style blocks whose content meant interpreted browser instead part page cases dealt enclosing content within comment blocks products designed forward compatible referred nuc upwardly compatible cases might intentional designers form vendor lock-in software regression example cubicle producer considers changing cubicle design one designer promotes changing footprint 4 foot square 1.2 meter square immediately sales manager calls nuc problem understood footprint changes existing customers considering buying producer fit different sized unit office designed 4 foot square cubicle planned obsolescence type upward compatibility rather adopting policy backwards compatibility companies adopt commercial policy backwards incompatibility newer apps require newer devices
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Computer architecture
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covert channel computer security covert channel type attack creates capability transfer information objects processes supposed allowed communicate computer security policy term originated 1973 lampson defined channels intended information transfer service program effect system load distinguish legitimate channels subjected access controls compusec covert channel called hidden access control mechanisms secure operating systems since use legitimate data transfer mechanisms computer system typically read write therefore detected controlled security mechanisms underlie secure operating systems covert channels exceedingly hard install real systems often detected monitoring system performance addition suffer low signal-to-noise ratio low data rates typically order bits per second also removed manually high degree assurance secure systems well established covert channel analysis strategies covert channels distinct often confused legitimate channel exploitations attack low-assurance pseudo-secure systems using schemes steganography even less sophisticated schemes disguise prohibited objects inside legitimate information objects legitimate channel misuse steganography specifically form covert channel covert channels tunnel secure operating systems require special measures control covert channel analysis proven way control covert channels contrast secure operating systems easily prevent misuse legitimate channels distinguishing important analysis legitimate channels hidden objects often misrepresented successful countermeasure legitimate channel misuse amounts analysis large amounts software shown early 1972 impractical without informed misled believe analysis manage risk legitimate channels trusted computer security evaluation criteria tcsec set criteria deprecated established national computer security center agency managed united states national security agency lampson definition covert channel paraphrased tcsec specifically refer ways transferring information higher classification compartment lower classification shared processing environment difficult completely insulate one process effects another process operating environment covert channel created sender process modulates condition free space availability service wait time execute detected receiving process tcsec defines two kinds covert channels tcsec also known orange book requires analysis covert storage channels classified b2 system analysis covert timing channels requirement class b3 use delays packets transmitted computer networks first explored girling covert communication work motivated many works establish detect covert communication analyze fundamental limitations scenarios ordinary things existence file time used computation medium covert channel communicates covert channels easy find media numerous frequently used two relatively old techniques remain standards locating potential covert channels one works analyzing resources system works source-code level possibility covert channels completely eliminated although significantly reduced careful design analysis detection covert channel made difficult using characteristics communications medium legitimate channel never controlled examined legitimate users example file opened closed program specific timed pattern detected another program pattern interpreted string bits forming covert channel since unlikely legitimate users check patterns file opening closing operations type covert channel remain undetected long periods similar case port knocking usual communications timing requests irrelevant unwatched port knocking makes significant handel sandford presented research study covert channels within general design network communication protocols employ osi model basis development characterize system elements potential used data hiding adopted approach advantages standards opposed specific network environments architectures considered study aim present foolproof steganographic schemes rather establish basic principles data hiding seven osi layers besides suggesting use reserved fields protocols headers easily detectable higher network layers also propose possibility timing channels involving csma/cd manipulation physical layer work identifies covert channel merit covert channel analysis consider issues interoperability data hiding techniques network nodes covert channel capacity estimation effect data hiding network terms complexity compatibility moreover generality techniques fully justified practice since osi model exist per se functional systems girling first analyzes covert channels network environment work focuses local area networks lans three obvious covert channels two storage channel one timing channel identified demonstrates real examples bandwidth possibilities simple covert channels lans specific lan environment author introduced notion wiretapper monitors activities specific transmitter lan covertly communicating parties transmitter wiretapper covert information according girling communicated following obvious ways scenario transmits covert information when-is-sent ” strategy therefore termed timing covert channel time transmit block data calculated function software processing time network speed network block sizes protocol overhead assuming block various sizes transmitted lan software overhead computed average novel time evaluation used estimate bandwidth capacity covert channels also presented work paves way future research focusing ip tcp headers tcp/ip protocol suite article published craig rowland devises proper encoding decoding techniques utilizing ip identification field tcp initial sequence number acknowledge sequence number fields techniques implemented simple utility written linux systems running version 2.0 kernels rowland provides proof concept well practical encoding decoding techniques exploitation covert channels using tcp/ip protocol suite techniques analyzed considering security mechanisms like firewall network address translation however non-detectability covert communication techniques questionable instance case sequence number field tcp header manipulated encoding scheme adopted every time alphabet covertly communicated encoded sequence number moreover usages sequence number field well acknowledgment field made specific ascii coding english language alphabet proposed since fields take account receipt data bytes pertaining specific network packet rowland several authors academia published work covert channels tcp/ip protocol suite including plethora countermeasures ranging statistical approaches machine learning research network covert channels overlaps domain network steganography emerged later
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Computer security
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unified communications service unified communications service ucaas category service cloud delivery mechanisms enterprise communications similar platform service paas data center capacity made available enterprise consumption model service provider ucaas unified communications services made available cloud businesses smb enterprise ucaas part global industry trend towards cloud services also known digital transformation ucaas first came prominence 2014 heels cloud movement traditionally enterprises acquired deployed communications infrastructure far economical approach enterprises could deploy pbx switches avoid cost individual phone lines employee advent ip virtualization data center economics shifted back favour service provider model service provider invests virtualized data centre negating need enterprise offers flexible consumption model prior cloud service providers offered ip centrex hosted communications services almost identical ucaas capability except fact “ virtualization ” meant economics ucaas much compelling examples prominent ucaas providers include telserv twilio voxbone telnyx 8x8 zoom video communications primary rationale ucaas fact allows company shift capital investment capex operating cost model opex addition provides companies ability rapidly increase consumption i.e consume licenses decrease consumption without need capital traditional communications model companies must acquire capacity ahead demand rarely get totally correct means over-capacity secondly growing sophistication enterprise unified communications meant companies must invest capital must invest staff order able support growing sophistication adding new features upgrades non-trivial communications critical success business productivity staff maintenance infrastructure requires high level expertise continues grow companies able off-load complexity service providers ucaas model well ensuring always latest versions features historically enterprise government organizations needed keep carriage provider i.e access pstn highly competitive position allowed service provider lock centrex solution may able achieve best carriage rates carriage becoming commodity uc license becoming premium much less risk moving sp ucaas solution features benefits ucaas platform gartner considers uc encompassing six functions significant level internal competition within organizations whether retain existing enterprise communications platform move cloud-based ucaas model number arguments moving ucaas security one common reasons given – companies cautious putting data cloud show sps better placed combat security breach much likely discipline around redundancy data perhaps valid reason concern level customization achieved generally understood on-premises communications platform staff achieve much higher levels customization enterprise course totally dependent capabilities company ’ staff without highly experienced staff organizations easily fall behind sophistication features productivity communications tools jury still total cost ownership tco on-premises ucaas many studies topic difficult compare two solutions given many enterprise companies rarely appreciate true tco on-premises
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Distributed computing architecture
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alf proof assistant alf another logical framework structure editor monomorphic martin-löf type theory developed chalmers university predecessor alfa agda cayenne coq proof assistants dependently typed programming languages first language support inductive families dependent pattern matching
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Programming language topics
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high-availability cluster high-availability clusters also known ha clusters fail-over clusters groups computers support server applications reliably utilized minimum amount down-time operate using high availability software harness redundant computers groups clusters provide continued service system components fail without clustering server running particular application crashes application unavailable crashed server fixed ha clustering remedies situation detecting hardware/software faults immediately restarting application another system without requiring administrative intervention process known failover part process clustering software may configure node starting application example appropriate file systems may need imported mounted network hardware may configured supporting applications may need running well ha clusters often used critical databases file sharing network business applications customer services electronic commerce websites ha cluster implementations attempt build redundancy cluster eliminate single points failure including multiple network connections data storage redundantly connected via storage area networks ha clusters usually use heartbeat private network connection used monitor health status node cluster one subtle serious condition clustering software must able handle split-brain occurs private links go simultaneously cluster nodes still running happens node cluster may mistakenly decide every node gone attempt start services nodes still running duplicate instances services may cause data corruption shared storage ha clusters often also use quorum witness storage local cloud avoid scenario witness device shared two halves split cluster event cluster members communicate e.g. failed heartbeat member access witness become active every application run high-availability cluster environment necessary design decisions need made early software design phase order run high-availability cluster environment application must satisfy least following technical requirements last two critical reliable function cluster difficult satisfy fully common size ha cluster two-node cluster since minimum required provide redundancy many clusters consist many sometimes dozens nodes attached diagram good overview classic ha cluster caveat make mention quorum/witness functionality see configurations sometimes categorized one following models terms logical host cluster logical host used describe network address used access services provided cluster logical host identity tied single cluster node actually network address/hostname linked service provided cluster cluster node running database goes database restarted another cluster node ha clusters usually use available techniques make individual systems shared infrastructure reliable possible include features help minimize chances clustering failover systems required failover service provided unavailable least little measures avoid failover preferred systems handle failures distributed computing different strategies cure failure instance apache cassandra api hector defines three ways configure failover several free commercial solutions available
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Computer architecture
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wizzy active lifestyle telephone wizzy active lifestyle telephone w.a.l.t prototype phone companion created apple computer collaboration bellsouth w.a.l.t featured touchscreen fax functionality on-display caller id built-in address book customizable ringtones online banking access system based powerbook 100 included touchscreen stylus handwriting recognition operating system based system 6 hypercard gui announced 1993 system mass-produced prototype machine sold ebay 2012 2019 video demonstration prototype machine uploaded internet
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Computer architecture
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logic computable functions logic computable functions lcf deductive system computable functions proposed dana scott 1969 memorandum unpublished 1993 inspired
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Programming language topics
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guard information security information security guard device system allowing computers otherwise separate networks communicate subject configured constraints many respects guard like firewall guards may similar functionality gateway whereas firewall designed limit traffic certain services guard aims control information exchange network communication supporting business level unlike firewall guard provides assurance effective providing control even attack failure conditions guard typically sit protected network external network ensure protected network safe threats posed external network leaks sensitive information external network guard usually dual-homed though guards connect two networks acts full application layer proxy engaging separate communications interface guard pass business information carried protocols one network another information passes configured checks provide required protection development guards began late 1970s creation several secure communications processors guard applications secure communications processors high assurance operating systems security kernels developed support controlled plain-text bypasses packet network encryption devices guard applications designed sanitise data exported classified system remove sensitive information honeywell secure communications processor scomp early guard platform evaluated dod computer security center orange book evaluation criteria level a1 rsre secure user environment sue ran pdp-11/34 simple separation kernel designed constructed t4 division royal signals radar establishment rsre malvern england advanced command control architectural testbed accat guard developed export email classified system human review stage later developments guards addressed problem automatic downgrading information exported classified system secure network server sns mail guard smg enforced source/destination address whitelists security label checks attachment type filtering digital signatures ensure sensitive information released firewalls later development arriving around 1987 time functionality firewalls increased provide similar capabilities guards main difference remaining guards built way provide assurance effective protecting network swipsy firewall toolkit developed defence evaluation research agency act general guard platform swipsy layered top trusted solaris 8 guards initially designed control release information classified systems protecting confidentiality sensitive information handled protected system since scope extended cover controls import data order protect integrity information availability services protected network guards generally provide following functionality guards functionally equivalent bastion host acting application proxy placed within dmz network proxy imposes necessary controls data exchanged provide protection external threats internal leaks distinguished way constructed dmz network relies outer packet filtering firewalls route traffic bastion host firewalls function incorrectly may pass traffic dmz without passing bastion host checks imposed proxies bypassed also networking stack bastion host behaves incorrectly may route traffic dmz without passing proxies guard constructed software needs function correctly minimised work needed demonstrate third party also minimised guards engineered provide assurance apply appropriate checks guards use trusted operating system separate security critical checker components less critical protocol handling components way failure protocol handling components cause data bypass checker example security-enhanced linux used nexor guards solaris 10 trusted extensions used radiant mercury isse guard deep-secure type enforcement controls developed lock operating system used sidewinder guards also use physically separate computers ensure critical components bypassed government-off-the-shelf products commercial-off-the-shelf products
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Computer security
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rozofs rozofs free software distributed file system comes free software licensed gnu gpl v2 rozofs uses erasure coding redundancy rozo provides open source posix filesystem built top distributed file system architecture similar google file system lustre ceph rozo specificity lies way data stored data stored translated several chunks using mojette transform distributed across storage devices way retrieved even several pieces unavailable hand chunks meaningless alone redundancy schemes based coding techniques like one used rozofs allow achieve significant storage savings compared simple replication file system comprises three components rozo systems invited snia data storage innovation conference june 2016
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Computer file systems
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motorola 68012 motorola mc68012 processor 16/32-bit microprocessor early 1980s 84-pin pga version motorola mc68010 memory space extended 2 gb read-modify-write cycle rmc pin indicating indivisible read-modify-write cycle progress added order help design multiprocessor systems virtual memory processors hold memory accesses cycle complete features mc68010 preserved expansion memory space caused issue programs used high byte address store data programming trick successful processors 24-bit address bus 68000 68010 similar problem affected 68020
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Computer architecture
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cybergeddon cybergeddon tech cyber- lit computer hebrew megiddo extracted har megiddo mountain final battle refers cataclysm resulting large-scale sabotage computerized networks systems activities combines cyberterrorism cyberwarfare cybercrime hacktivism scenarios wide-scale internet disruption economic collapse economic industrial infrastructure could targeted banks industrial control systems since 2012 amount internet-based attacks complexity increased cybergeddon possibility fireeye ceo ashar aziz explained interview bloomberg attacks critical infrastructures power grid financial institutions could wreak havoc united states economy fact world economy
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Computer security
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skyline operator skyline operator subject optimization problem used query filter results database keep objects worse operator extension sql proposed börzsönyi et al classic example application skyline operator involves selecting hotel holiday user wants hotel cheap close beach however hotels close beach may also expensive case skyline operator would present hotels worse hotel price distance beach give example sql börzsönyi et al proposed following syntax skyline operator ... denote dimensions skyline min max diff specify whether value dimension minimised maximised simply different skyline operator implemented directly sql using current sql constructs however shown slow algorithms proposed make use divide conquer indices mapreduce general-purpose computing graphics cards skyline queries data streams i.e continuous skyline queries studied context parallel query processing multicores owing wide diffusion real-time decision making problems data streaming analytics
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Databases
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microsoft forefront microsoft forefront discontinued family line-of-business security software microsoft corporation microsoft forefront products designed help protect computer networks network servers microsoft exchange server microsoft sharepoint server individual devices 2015 actively developed forefront product forefront identity manager forefront includes following products predecessor forefront server protection products antigen line antivirus products created sybari software sybari acquired microsoft 2005 first microsoft-branded version product called microsoft forefront security sharepoint fssp version 10 fssp version 10 supports microsoft office sharepoint server 2007 microsoft windows sharepoint services version 3 whereas fpsp last version product supports microsoft office sharepoint server 2010 microsoft sharepoint foundation 2010 microsoft office sharepoint server 2007 sp1 windows sharepoint services version 3 sp1
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Computer security
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motorola 68008 motorola 68008 8/16/32-bit microprocessor made motorola version motorola 68000 8-bit external data bus well smaller address bus original 68000 introduced 1979 24-bit address bus 16-bit data bus relatively large buses made hard design low-cost system based 68000 difficult lay circuit board needed lot supporting circuitry 16-bit data bus also required twice many memory chips 8-bit one 68008 introduced 1982 designed work low-cost 8-bit memory systems smaller data bus half fast 68000 clock speed however still faster competing 8-bit microprocessors 68008 internally based 32-bit data registers 16-bit data bus except smaller data address buses 68008 behaved identically 68000 internal organization microarchitecture 68008 hmos chip came speed grade two distinct versions chip original version came 48-pin dual in-line package 20-bit address bus allowing use 1 megabyte memory later version came 52-pin plastic leaded chip carrier version provided 22-bit address bus could support ram computer systems used 68008 main processor sinclair ql personal computer best known however 68008 popular embedded systems motorola ended production 68008 1996
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Computer architecture
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crack password software crack unix password cracking program designed allow system administrators locate users may weak passwords vulnerable dictionary attack crack first standalone password cracker unix systems later first introduce programmable dictionary generation crack began 1990 alec muffett unix system administrator university wales aberystwyth trying improve dan farmer 'pwc cracker cops found re-engineering memory management got noticeable performance increase led total rewrite became crack v2.0 development improve usability first public release crack version 2.7a posted usenet newsgroups alt.sources alt.security 15 july 1991 crack v3.2a+fcrypt posted comp.sources.misc 23 august 1991 introduced optimised version unix crypt function still really faster version already available packages release crack v4.0a 3 november 1991 however introduced several new features made formidable tool system administrators arsenal crack v5.0a released 2000 introduce new features instead concentrated improving code introducing flexibility ability integrate crypt variants needed attack md5 password hashes used modern unix linux windows nt systems also bundled crack v6 minimalist password cracker crack v7 brute force password cracker randal l. schwartz notable perl programming expert 1995 prosecuted using crack password file system intel case verdict eventually expunged crack also used kevin mitnick hacking sun microsystems 1993 traditional password cracking tools simply fed pre-existing dictionary words crypt function crack v4.0a introduced ability apply rules word list generate modified versions word lists could range simple change extremely complex documentation gives example rules could also process gecos field password file allowing program use stored names users addition existing word lists crack dictionary generation rule syntax subsequently borrowed extended solar designer john ripper dictionary generation software crack subsequently reused muffett create cracklib proactive password checking library bundled debian red hat enterprise linux-derived linux distributions password cracking inherently embarrassingly parallel crack v4.0a introduced ability use network heterogeneous workstations connected shared filesystem parts distributed password cracking effort required provide crack configuration file containing machine names processing power rates flags required build crack machines call -network option
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Computer security
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project trillian project trillian effort industry consortium port linux kernel itanium processor project started may 1999 goal releasing distribution time initial release itanium scheduled early 2000 end 1999 project included caldera systems cern cygnus solutions hewlett-packard ibm intel red hat sgi suse turbolinux va linux systems project released resulting code february 2000 code became part linux baseline kernel year release first itanium processor trillian project able two reasons successful completion project trillian resulting linux kernel used manufacturers itanium systems hp ibm dell sgi fujitsu unisys hitachi groupe bull notable exception hp linux either primary os os manufacturer supports itanium ongoing free open source software support linux itanium subsequently coalesced gelato
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Operating systems
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freeciv freeciv single- multiplayer turn-based strategy game workstations personal computers inspired proprietary sid meier civilization series available desktop computer operating systems available online browser based version released gnu general public license freeciv free open source software game default settings closest civilization ii gameplay graphics including units isometric grid players take role tribal leaders 4000 b.c must guide peoples centuries time new technologies discovered allow construction new city buildings deployment new units players wage war one another form diplomatic relationships game ends one civilization eradicated others accomplished goal space colonization given deadline one civilization remains deadline player highest score wins points awarded size civilization wealth cultural scientific advances computer science department aarhus university three students avid players xpilot sid meier civilization stand-alone pc game ms-dos decided find whether two could fused x-based multiplayer civilization-like strategy game students—peter unold claus leth gregersen allan ove kjeldbjerg—started development november 1995 first playable version released january 1996 bugfixing small enhancements april rules game close civilization client/server architecture basically xpilot developers freeciv 1.0 successful proof concept rather boring game went back xpilot players developers took made game available many operating systems including linux solaris ultrix amiga os microsoft windows linux distributions started include freeciv main development goal remained make civilization-like game playable internet participants different continents even connected 14400 bit/s modems freeciv achieved using asynchronous client-server protocol turn human users play concurrently actions sent server processing without awaiting results kept game playable network latency hundreds milliseconds 1998 computer players added could soon beat newcomers game ease using minor forms cheating computer players implemented directly server play concurrently human players separately turns game grew popularity public server installed games could played around clock retained games published post-game analysis webpage per-player statistics animated map replay subsequent 1.x releases improved gui improved gameplay added many small features time winning strategy proved city smallpox sprawling map many small cities fast possible whoever could develop fastest would win game growing developing individual cities n't worthwhile practice around 2002 experienced players would form teams start game fork freeciv included specific features team play version 2.0 released 2005 introduced several important changes became beneficial develop large cities full trade routes advanced technologies re-balancing various costs benefits introduction team playing features advanced diplomacy made coop gaming attractive developing one empire necessitated careful plan city development including phases rapture city populations grow quickly relatively peaceful conditions hence games almost always played teams typically took longer finish compared 1.x games 2006 tcp udp port number 5556 assigned freeciv iana 2017 hosted gna 15 years freeciv moved source repository github freeciv configurable specific rules played freeciv default mode civilization mode civilization ii mode custom mode one several players act game administrators configure game rules typically modified rules order play game freeciv user must start freeciv client connect freeciv server initially server pre-game phase phase clients connect game configuration parameters changed point server may ordered start game response creates game players nations game map assigns every player either freeciv client computer player specified configuration point game run ends terminated server never get back pre-game state user also start game directly client automatically starts freeciv server connects starts game freeciv graphics system configurable originally map display always overhead mode like civ isometric mode like civ ii iii optionally hexagonal tiling like civ v vi added later modes look customized switching alternative set graphics called tileset sounds replaced well freeciv supports human-to-human multiplayer gameplay artificial intelligence ai computer players game turn based human players move simultaneously ai players move separately partly start turn partly end releases 2.0 ai players could engage diplomatic relationships human players current releases ai players engage predictable rules-based diplomacy version 2.2.0 included map editor termed civworld create new scenarios well edit map currently played basic scripting available freeciv available civworld version 2.3 increased limit players 30 126 different clients available sdl gtk+ version3 xaw3d qt client added version 2.5 freeciv interface available 30 different languages addition gaelic covered bbc tv originally developed irix freeciv ported many different operating systems distributed many linux distributions offers installers microsoft windows known run mac os x morphos solaris ultrix qnx os/2 cygwin amigaos aros risc os maemo zeta skyos various bsds smartphones tablets running android version 2.4 mac os x version 2.3 windows versions older windows xp sp3 longer supported freeciv available portableapps format freeciv-web version freeciv playable online modern web browser supports 2d isometric graphics 3d graphics using webgl 3d version referred freeciv webgl 3d game fork freeciv project goal redesigning desktop game version played online freeciv-web introduced several new features play-by-email support freely available anyone online support playing game real-world map location choosing map using mapbox available commercial games genre game default settings closest civilization ii gameplay graphics including units isometric grid proposal create web-version freeciv made 6 april 2007 freeciv mailing lists documented freeciv.org wiki freeciv-web originally created andreas røsdal maintained several freeciv developers github freeciv-web free open source software freeciv c server released gnu general public license freeciv-web client released gnu affero general public license freeciv-web supports human-to-human multiplayer gameplay artificial intelligence ai computer players features similar freeciv c client although user-interface ported c client yet freeciv-web played online number servers two frequented http //www.freecivweb.org/ http //freeciv.xyz/ features required play full game freeciv place including rendering isometric map technology research many dialogs managing cities units players game also supports scenario-games includes maps world north america france italy japan iberian peninsula servers offer multiple varieties game single-player multiplayer free-for-all play-by-email longturn freeciv-web formerly playable play.freeciv.org march 3 2018 play.freeciv.org shut project revived april 8 group volunteers freecivweb.org freeciv longturn specialized large-group-multiplayer-online-strategy lagmos variant freeciv featuring daylong game turns large amounts human opponents per map allowing optimal timing build strategic plans readapt circumstances turn matches last anytime weeks months commonly involve 20 30 players one longturn first game called lt0 started around 2004 polish civilization fanpage civ.org.pl conducted longturn.net decided game bit slow paced new 3x movement ruleset devised – basically units movement points vision radius tripled july 2019 latest game lt47 changes settings rulesets discussed longturn forum greatturn similar concept another server since 2017 freeciv-web offers similar one turn per day variant gacivs mmo-rts variant freeciv ruleset devised support time-based instead turn-based strategy 2000 cnn placed freeciv among top 10 linux games holidays 2005 o'reilly article open source mac gaming freeciv recommended 2008 apcmag.com named freeciv among top 5 best free open source games linux format selected hotpick april 2010 october 2014 freeciv described example art unix programming eric s. raymond studies courses used freeciv platform experimenting design programming intelligent agents 2016 freeciv used challenge chess go commercial ai
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Operating systems
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omnirom omnirom open-source operating system smartphones tablet computers based android mobile platform involves number prominent developers projects omnirom founded reaction commercialisation rom project cyanogenmod launch project provided custom firmware based android jelly bean moved android kitkat shortly release kitkat firmware included support galaxy note ii galaxy note galaxy s3 galaxy s4 nexus 4 nexus 5 nexus 7 2012 lg optimus g galaxy s2 htc one 2013 oppo find 5 sony xperia acer iconia a500 htc explorer lenovo a6000 june 2015 project started release nightly builds based android lollipop asus transformer pad asus transformer pad infinity nexus 4 nexus 5 nexus 6 nexus 7 nexus 10 oppo find 7/7a oneplus one sony xperia z sony xperia zl project working new version firmware based android pie
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Operating systems
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internet security internet security branch computer security specifically related internet often involving browser security world wide web also network security applies applications operating systems whole objective establish rules measures use attacks internet internet represents insecure channel exchanging information leads high risk intrusion fraud phishing online viruses trojans worms many methods used protect transfer data including encryption from-the-ground-up engineering current focus prevention much real time protection well known new threats internet user tricked forced downloading software malicious intent onto computer software comes many forms viruses trojan horses spyware worms denial-of-service attack dos attack distributed denial-of-service attack ddos attack attempt make computer resource unavailable intended users another way understanding ddos seeing attacks cloud computing environment growing due essential characteristics cloud computing although means carry motives targets dos attack may vary generally consists concerted efforts prevent internet site service functioning efficiently temporarily indefinitely according businesses participated international business security survey 25 respondents experienced dos attack 2007 16.8 experienced one 2010 dos attacks often use bots botnet carry attack phishing attack targets online users extraction sensitive information username password credit card information phishing occurs attacker pretends trustworthy entity either via email web page victims directed fake web pages dressed look legitimate via spoof emails instant messenger/social media avenues often tactics email spoofing used make emails appear legitimate senders long complex subdomains hide real website host insurance group rsa said phishing accounted worldwide losses 10.8 billion 2016 applications used access internet resources may contain security vulnerabilities memory safety bugs flawed authentication checks severe bugs give network attackers full control computer security applications suites incapable adequate defense kinds attacks common widespread web-browser application vulnerability so-called cross-origin resource sharing vulnerability- maximum security privacy make sure adopt adequate countermeasures example patches provided webkit-based browsers tcp/ip protocols may secured cryptographic methods security protocols protocols include secure sockets layer ssl succeeded transport layer security tls web traffic pretty good privacy pgp email ipsec network layer security ipsec designed protect tcp/ip communication secure manner set security extensions developed internet task force ietf provides security authentication ip layer transforming data using encryption two main types transformation form basis ipsec authentication header ah esp two protocols provide data integrity data origin authentication anti-replay service protocols used alone combination provide desired set security services internet protocol ip layer basic components ipsec security architecture described terms following functionalities set security services provided ip layer includes access control data origin integrity protection replays confidentiality algorithm allows sets work independently without affecting parts implementation ipsec implementation operated host security gateway environment giving protection ip traffic multi-factor authentication mfa method computer access control user granted access successfully presenting several separate pieces evidence authentication mechanism – typically least two following categories knowledge something know possession something inherence something internet resources websites email may secured using multi-factor authentication online sites offer customers ability use six-digit code randomly changes every 30–60 seconds security token keys security token built mathematical computations manipulate numbers based current time built device means every thirty seconds certain array numbers possible would correct validate access online account website user logging would made aware device serial number would know computation correct time built device verify number given indeed one handful six-digit numbers works given 30-60 second cycle 30–60 seconds device present new random six-digit number log website email messages composed delivered stored multiple step process starts message composition user finishes composing message sends message transformed standard format rfc 2822 formatted message afterwards message transmitted using network connection mail client referred mail user agent mua connects mail transfer agent mta operating mail server mail client provides sender ’ identity server next using mail server commands client sends recipient list mail server client supplies message mail server receives processes message several events occur recipient server identification connection establishment message transmission using domain name system dns services sender ’ mail server determines mail server recipient server opens connection recipient mail server sends message employing process similar used originating client delivering message recipient pretty good privacy provides confidentiality encrypting messages transmitted data files stored using encryption algorithm triple des cast-128 email messages protected using cryptography various ways following first two methods message signing message body encryption often used together however encrypting transmissions mail servers typically used two organizations want protect emails regularly sent example organizations could establish virtual private network vpn encrypt communications mail servers internet unlike methods encrypt message body vpn encrypt entire messages including email header information senders recipients subjects cases organizations may need protect header information however vpn solution alone provide message signing mechanism provide protection email messages along entire route sender recipient mime transforms non-ascii data sender site network virtual terminal nvt ascii data delivers client simple mail transfer protocol smtp sent internet server smtp receiver side receives nvt ascii data delivers mime transformed back original non-ascii data message authentication code mac cryptography method uses secret key encrypt message method outputs mac value decrypted receiver using secret key used sender message authentication code protects message data integrity well authenticity computer firewall controls access networks generally consists gateways filters vary one firewall another firewalls also screen network traffic able block traffic dangerous firewalls act intermediate server smtp hypertext transfer protocol http connections firewalls impose restrictions incoming outgoing network packets private networks incoming outgoing traffic must pass firewall authorized traffic allowed pass firewalls create checkpoints internal private network public internet also known choke points borrowed identical military term combat limiting geographical feature firewalls create choke points based ip source tcp port number also serve platform ipsec using tunnel mode capability firewall used implement vpns firewalls also limit network exposure hiding internal network system information public internet packet filter first generation firewall processes network traffic packet-by-packet basis main job filter traffic remote ip host router needed connect internal network internet router known screening router screens packets leaving entering network stateful firewall circuit-level gateway proxy server operates network level open systems interconnection osi model statically defines traffic allowed circuit proxies forward network packets formatted unit data containing given port number port permitted algorithm main advantage proxy server ability provide network address translation nat hide user ip address internet effectively protecting internal information internet application-level firewall third generation firewall proxy server operates top osi model ip suite application level network packet forwarded connection established using known protocol application-level gateways notable analyzing entire messages rather individual packets data data sent received web browser statistics tend affect amount web browser exploited example internet explorer 6 used majority web browser market share considered extremely insecure vulnerabilities exploited due former popularity since browser choice evenly distributed internet explorer 28.5 firefox 18.4 google chrome 40.8 vulnerabilities exploited many different browsers antivirus software internet security programs protect programmable device attack detecting eliminating malware antivirus software mainly shareware early years internet several free security applications internet choose platforms password manager software application helps user store organize passwords password managers usually store passwords encrypted requiring user create master password single ideally strong password grants user access entire password database top bottom called security suites first offered sale 2003 mcafee contain suite firewalls anti-virus anti-spyware also offer theft protection portable storage device safety check private internet browsing cloud anti-spam file shredder make security-related decisions answering popup windows several free charge
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Computer security
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shorewall shorewall open source firewall tool linux builds upon netfilter iptables/ipchains system built linux kernel making easier manage complex configuration schemes providing higher level abstraction describing rules using text files daemon since run continuously rather configures rules kernel allow disallow traffic system shorewall configured group plain-text configuration files graphical user interface though webmin module available separately monitoring utility packaged shorewall used watch status system operates assist testing shorewall mainly used network installations opposed personal computer firewall since strength lies ability work zones dmz 'net zone zone would different rules making easy example relaxed rules company intranet yet clamp traffic coming internet plain-text configuration files usually well-commented easy use though shorewall may difficult new users handle firewall systems graphical front-ends recent stable version 5.2.3 18 february 2019 primary developer tom eastep announced retiring project 5.2.3 would final release starting version 4 shorewall began using perl-based compiler frontend previously used shell-based compiler frontend support ipv6 firewalling included since version 4.2.4
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Computer security
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compaq portable iii compaq portable iii pc/at-compatible computer released compaq computer corporation 1987 advertised much smaller lighter previous portable x86-pcs however still quite large today standards three models announced release model 1 list price equipped intel 80286 ram floppy colored gas-plasma display options included model 20 added model 40 upgraded also optional isa expansion chassis allowed 2 full length 16-bit isa add-in cards power supplied using mains electricity outlet battery exists
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Computer architecture
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zero-day computing zero-day also known 0-day vulnerability computer-software vulnerability unknown unaddressed interested mitigating vulnerability including vendor target software vulnerability mitigated hackers exploit adversely affect computer programs data additional computers network exploit directed zero-day called zero-day exploit zero-day attack jargon computer security day zero day interested party presumably vendor targeted system learns vulnerability leading vulnerability called zero-day vendor learns vulnerability vendor usually create patches advise workarounds mitigate fewer days since day zero higher chance fix mitigation developed even fix developed fewer days since day zero higher probability attack afflicted software successful every user software applied fix zero-day exploits unless vulnerability inadvertently fixed e.g unrelated update happens also obviate need fix specific vulnerability probability user applied vendor-supplied patch fixes problem zero exploit would remain available zero-day attacks severe threat malware writers exploit zero-day vulnerabilities several different attack vectors sometimes users visit rogue websites malicious code site exploit vulnerabilities web browsers web browsers particular target criminals widespread distribution usage cybercriminals well international vendors spyware israel ’ nso group also send malicious e-mail attachments via smtp exploit vulnerabilities application opening attachment exploits take advantage common file types numerous frequent evidenced increasing appearances databases like us-cert criminals engineer malware take advantage file type exploits compromise attacked systems steal confidential data time software exploit first becomes active time number vulnerable systems shrinks insignificance known window vulnerability wov time-line software vulnerability defined following main events thus formula length window vulnerability – formulation always true ≤ ≤ t. note day zero example hacker first discover vulnerability vendor might learn much later day zero normal vulnerabilities – 0 implies software vendor aware vulnerability time publish security patch hacker could craft workable exploit zero-day exploits – ≤ 0 exploit became active patch made available disclosing known vulnerabilities software vendor hopes reach reached thus avoiding exploits however vendor guarantees hackers find vulnerabilities furthermore hackers analyze security patches thereby discover underlying vulnerabilities automatically generate working exploits exploits used effectively time t. practice size wov varies systems vendors individual vulnerabilities often measured days one report 2006 estimating average 28 days zero-day protection ability provide protection zero-day exploits since zero-day attacks generally unknown public often difficult defend zero-day attacks often effective secure networks remain undetected even launched thus users so-called secure systems must also exercise common sense practice safe computing habits many techniques exist limit effectiveness zero-day memory corruption vulnerabilities buffer overflows protection mechanisms exist contemporary operating systems macos windows vista beyond see also security safety features new windows vista solaris linux unix unix-like environments windows xp service pack 2 includes limited protection generic memory corruption vulnerabilities previous versions include even less desktop server protection software also exists mitigate zero-day buffer overflow vulnerabilities typically technologies involve heuristic termination analysis—stopping cause harm suggested solution kind may reach algorithmically impossible general case analyze arbitrary code determine malicious analysis reduces halting problem linear bounded automaton unsolvable however unnecessary address general case sort programs categories malicious non-malicious circumstances order eliminate wide range malicious behaviors suffices recognize safety limited set programs e.g. access modify given subset machine resources rejecting safe unsafe programs require integrity safe programs maintained may prove difficult face kernel level exploit zeroday emergency response team zert group software engineers worked release non-vendor patches zero-day exploits march 9 2017 press release vault 7 documents released wikileaks 2 days previously julian assange states much leak remainder included unpatched vulnerabilities working companies microsoft google get vulnerabilities patched would release information would put public risk fixes released manufacturers would release details vulnerabilities zero-day worms take advantage surprise attack still unknown computer security professionals recent history shows increasing rate worm propagation well designed worms spread fast devastating consequences internet systems differing ideologies exist relative collection use zero-day vulnerability information many computer security vendors perform research zero-day vulnerabilities order better understand nature vulnerabilities exploitation individuals computer worms viruses alternatively vendors purchase vulnerabilities augment research capacity example program tippingpoint zero day initiative selling buying vulnerabilities technically illegal parts world lot controversy method disclosure 2006 german decision include article 6 convention cybercrime eu framework decision attacks information systems may make selling even manufacturing vulnerabilities illegal formal programs follow form rain forest puppy disclosure guidelines recent ois guidelines security vulnerability reporting response general rules forbid public disclosure vulnerabilities without notification vendor adequate time produce patch zero-day virus also known zero-day malware next-generation malware previously unknown computer virus malware specific antivirus software signatures yet available traditionally antivirus software relies upon signatures identify malware effective defend malware unless samples already obtained signatures generated updates distributed users signature-based approaches effective zero-day viruses modern antivirus software still uses signatures also carries types analysis code analysis machine code file analysed see anything looks suspicious typically malware characteristic behaviour code analysis attempts detect present code although useful code analysis significant limitations always easy determine section code intended particularly complex deliberately written intention defeating analysis another limitation code analysis time resources available competitive world antivirus software always balance effectiveness analysis time delay involved one approach overcome limitations code analysis antivirus software run suspect sections code safe sandbox observe behavior orders magnitude faster analyzing code must resist detect attempts code detect sandbox generic signatures signatures specific certain behaviour rather specific item malware new malware totally novel variation earlier malware contains code one earlier examples malware thus results previous analysis used new malware generally accepted antivirus industry vendors signature-based protection identically effective signature available item malware every product unless dysfunctional detect however vendors significantly faster others becoming aware new viruses and/or updating customers signature databases detect wide range effectiveness terms zero-day virus protection german computer magazine c't found detection rates zero-day viruses varied 20 68 primarily area zero-day virus performance manufacturers compete mid-april 2017 hackers known shadow brokers tsb —allegedly linked russian government—released files nsa initially regarded alleged nsa later confirmed internal details snowden include series 'zero-day exploits targeting microsoft windows software tool penetrate society worldwide interbank financial telecommunication swift service provider ars technica reported shadow brokers hacking claims mid-january 2017 april shadow brokers posted exploits proof vulnerabilities equities process first revealed publicly 2016 process used u.s. federal government determine case-by-case basis treat zero-day computer security vulnerabilities whether disclose public help improve general computer security keep secret offensive use government adversaries process criticized number deficiencies including restriction non-disclosure agreements lack risk ratings special treatment nsa less whole-hearted commitment disclosure default option virus signature unique pattern code used detect identify specific viruses antivirus scans file signatures compares database known malicious codes match file flagged treated threat major limitation signature-based detection capable flagging already known malware making completely useless zero-day attacks chronological order
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Computer security
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dec multia multia later re-branded universal desktop box line desktop computers introduced digital equipment corporation 7 november 1994 line notable units offered either alpha axp intel pentium processor cpu hardware backplane cpu interchangeable alpha intel versions intended run windows nt multia compact case left little room expansion cards restricted air flow cause premature hardware failure due overheating properly cared enthusiasts remedy placing multia vertically instead horizontally allowing heated air escape via vents top although still requires preventing multia overheating due factors e.g environmental alpha multias included either alpha 21066 alpha 21066a microprocessor running 166 mhz 233 mhz respectively came 16 24 mb ram standard expandable 128 mb officially practice 256 mb 21066 budget version alpha 21064 processor narrower 64-bit versus 128-bit slower bus thus performance roughly equivalent pentium running 100 mhz integer operations superior floating-point furthermore standard ram capacity severe restriction performance workstations alpha-based multias came tga dec 21030 graphics adapter standard peripherals alpha intel models included scsi host adapter dec 21040 ethernet controller two pcmcia slots two rs-232 ports bi-directional parallel port 2.5 3.5 scsi ata hard disk 340 mb 1.6 gb ps/2 keyboard mouse ports pci slot models 2.5-inch hard disks multia models comprised 1996 digital began offering alpha multia without windows nt renamed line universal desktop box nicknamed udb prices quite low first time many enthusiasts hobbyists could afford alpha axp-based computer multia udb run windows nt alpha windows nt 4.0 service pack 6 although windows 2000 never officially released alpha platform windows 2000 beta released fact runs multia linux netbsd available multia additionally digital unix openvms configured run multia certain limitations although initially operating systems disabled running budget multia line alpha-based multia came configured arc firmware console running windows nt although srm also available intel-based multia used bios
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Computer architecture
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audio-visual speech recognition audio visual speech recognition avsr technique uses image processing capabilities lip reading aid speech recognition systems recognizing undeterministic phones giving preponderance among near probability decisions system lip reading speech recognition works separately results mixed stage feature fusion name suggests two parts first one audio part second one visual part audio part use features like log mel spectogram mfcc etc raw audio samples build model get feature vector visual part generally use variant convolutional neural network compress image feature vector concatenate two vectors audio visual try predict target object
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Computational linguistics
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synchronous context-free grammar synchronous context-free grammars syncfg scfg confused stochastic cfgs type formal grammar designed use transfer-based machine translation rules grammars apply two languages time capturing grammatical structures translations theory syncfgs borrows syntax-directed transduction syntax-based machine translation modeling reordering clauses occurs translating sentence correspondences phrase-structure rules source target languages performance scfg-based mt systems found comparable even better state-of-the-art phrase-based machine translation systems several algorithms exist perform translation using syncfgs rules syncfg superficially similar cfg rules except specify structure two phrases time one source language language translated one target language numeric indices indicate correspondences non-terminals constituent trees chiang gives chinese/english example rule indicates phrase formed chinese structure yu variables standing subphrases corresponding structure english independently translated english
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Computational linguistics
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ios 4 ios 4 fourth major release ios mobile operating system developed apple inc. successor iphone os 3 announced company worldwide developers conference june 7 2010 released june 21 2010. ios 4 first ios version issued ios rebranding dropping iphone os naming convention previous versions succeeded ios 5 october 12 2011. ios 4 introduced folders home screen significantly increasing number apps displayed support custom wallpapers also added although limited newer devices due animation performance requirements operating system also added multitasking feature letting apps dealing internet calling location audio playback function background whereas similar restricted fast app switching technology enabled app left inactive background users switch apps ios 4 also added system-wide spell checking feature enabled ibooks iphone unified mail inbox combine content different email providers introduced game center social gaming facetime video calling ios 4 update introduced performance battery problems iphone 3g devices apple investigating matter promising then-upcoming updates however company became subject lawsuit unsatisfied customer issues around time release iphone 4 subsequent antenna problems made apple focus unsuccessfully attempting patch issues software updates ios 4 introduced apple worldwide developers conference keynote address june 7 2010 notably first ios release named simply ios ditched iphone os naming pattern previous versions ios 4 officially released june 21 2010. ios 4.0.1 released july 15 2010 first update ios 4 update changed method calculating carrier signal strength improved accuracy ios 4.0.2 released august 11 2010 fix exploit taking advantage pdf file format vulnerabilities ios 4.1 released september 8 2010 update included high dynamic range hdr technology improved quality photos captured iphone 4 added game center social gaming network ability upload high definition videos captured iphone 4 youtube mobileme also featured bug fixes performance improvements ios 4.2.1 released november 22 2010 first version bring major ios 4 features introduced iphone ipad although ios 4.2 released developers testing purposes bugs discovered replaced 4.2.1 consumer release also last version ios run iphone 3g ipod touch 2nd generation due hardware limitations performance issues ios 4.2.5 announced january 11 2011 adding exclusive wi-fi hotspot support cdma version iphone 4. ios 4.3 released march 4 2011 adding support personal wi-fi hotspots itunes home sharing improvements airplay minor improvements ipad 1 run ios 4.3 due hardware restrictions ios 4.3.1 released march 25 2011 fix ipod touch screen glitches along stability improvements cellular connectivity iphone models ios 4.3.2 released april 14 2011 fixes frozen calls facetime connectivity issues cellular models ipad ios 4.3.3 released may 4 2011 fix location bugs ios 4.3.4 released july 15 2011 fixing security vulnerabilities ios 4.3.5 released july 25 2011 security update fix certificate validation ios 4 raised maximum number home screen apps 180 2,160 due addition folders folders would automatically named based containing apps respective app store category ability add custom wallpapers home screen also added though feature notably absent iphone 3g second-generation ipod touch due poor performance icon animations ios 4 introduced multitasking feature allowed users switch apps instantly double-clicking home button implemented way cause excessive battery drain multitasking limited apps dealing internet calling location audio playback similar fast app switching technology meant users could leave app enter another original app remaining background user returns feature notably absent iphone 3g second-generation ipod touch due performance issues ios 4 introduced spell checking feature underlined misspelled words red tapping word would provide pop-up recommended replacement camera app could take pictures 5 times digital zoom ios 4 introduced iphone ipod touch support ibooks already included ipad though default app available app store mail app featured unified inbox ios 4 allowing users see messages email accounts displayed together single inbox also gained support mobileme e-mail aliases multiple exchange accounts business users ios 4.1 added new app called game center online multiplayer social gaming network allows users invite friends play games compare scores leaderboard available iphone 3g ios 4 introduced facetime videotelephony app uses device camera allow user make video calls facetime users feature absent iphone 3gs third-generation ipod touch lower due lack required features front-facing camera safari mobile web browser ios 4 added bing search option addition google yahoo ios 4.2 specific words phrases page searched iphone 3g users reported performance battery issues upgrading ios 4 apple started investigation matter july 2010 november apple sued issues unsatisfied customer alleging violating consumer legal remedies act unfair business practices false deceptive advertising allegations apple knew software would cause problems older models apple n't responded allegations wrote reply another unsatisfied customer august updates coming soon versions ios 4 alarm clock clock app problem dst would go hour early late upon release iphone 4 users reported technical problems phone antennas apple attempted fix issue ios 4.0.1 failed first-generation iphone first-generation ipod touch run ios 4 due hardware limitations marked first time apple dropped support older devices
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Operating systems
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blackberry enterprise server blackberry enterprise server designates middleware software package part blackberry wireless platform supplied blackberry limited software service connects messaging collaboration software mdaemon messaging server microsoft exchange lotus domino novell groupwise enterprise networks redirects emails synchronizes contacts calendaring information servers desktop workstations mobile devices third-party connectors exist including scalix zarafa zimbra google apps bes connector although supported blackberry limited june 2018 blackberry enterprise server renamed blackberry unified endpoint manager uem prior version 4.0 bes largely two separate codebases 2.2 version domino 3.6 version exchange version 4.0 beyond much code integrated separate distributions still remain supported mail platform beginning version 4.1.2 company introduced new option blackberry enterprise server applications provides secure wireless gateway blackberry devices without requiring device owner possess email account latest major revision version 5.0 released 2009 exchange domino support groupwise added 2010 support growing number multiple devices ownership models operating environments blackberry reinvented enterprise mobility management emm bringing together mobile device management security unified communications applications launching blackberry enterprise service 10 bes 10 represents unification simplification products deliver integrated end-to-end solution mobile device management enables enterprises manage entire device fleet ever types devices brands ownership operating system blackberry 10 ios android type usage security enables enterprises secured end-to-end mobility unified communication enables enterprises integrate voice messaging pim apps social experiences applications enables enterprises manage business productivity personal apps bes 5 consists set windows services carry basic operations system windows services include additional services may installed depending configuration bes also produces set log files operation called bes event log log files include bes v4.0 4.1 system connecting microsoft exchange bes typically deployed managed within enterprise messaging administrators example individuals already responsible managing microsoft exchange lotus domino novell groupwise sometimes dedicated person usually called blackberry bes administrator 2010 rim offering blackberry enterprise server express edition user limitations free minor feature limitations requires data plan bes plan enables near-instant seamless mail calendar integration existing exchange server incoming emails often appear blackberry handset appear outlook owa clients advantage existing outlook web access model blackberry internet service offers.the free download requires license code may delayed due demand january 2007 rim offering free version bes called blackberry professional software free download blackberry website includes 1 user license bpse provides ... wireless communications collaboration solution designed specifically small medium-sized businesses comes one cal client access license meaning one blackberry handheld activated server add 29 additional cals total 30 upgrade blackberry enterprise server time.it available notes exchange environments bps based 4.1 code simplified management tool limited amount patches released bps stuck v 4.1.4 full bes 4.1.6 plus maintenance releases bps missing functions full bes get sp6 onwards rich content email free/busy search remote search blackberry professional software originally called blackberry enterprise server express first appeared version 4 bes full bes express full cost limited maximum number clients 1 cal included free renamed bes express bps still thing later introduced bes express 5 rather different previous bes express bps primarily allows non-bes devices/subscribers full-fat blackberry experience finally cost/feature competitive exchange activesync devices i.e provides full synchronisation read/unread status deletions mail subfolders including sent items contacts calendar without license costs without requirement expensive sometimes extremely difficult acquire bes tariff example orange uk may make difficult supply bes package/provisioning less 10 handsets time operators often extreme difficulty applying bes package handsets/subscribers originally bis supplied groupwise rim offered blackberry enterprise server version 5.0 available blackberry enterprise server resource kit brk collection useful tools resources released expand manageability blackberry enterprise server tools available free download brk release developed certified compatible particular bes service pack version brk includes tools also special support tools available contact support group bes 10 helps enterprises manage different devices unified interface components deliver experience
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Operating systems
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gpd win gpd win windows-based handheld computer equipped keyboard gaming controls x86-based device runs full version windows 10 home device envisioned primarily video game console emulation pc gaming mind capable running x86 windows-based application run within confines device technical specifications first announced october 2015 crowd funded via indiegogo two crowdfunding sites japan china released october 2016 gamepad digital gpd technology company based shenzhen china among products created several handheld video game consoles run android arm architecture instance gpd xd gpd win meant way play pc games pc-based video game console emulators hypervisors vmware virtualbox clients handheld device appeal win intended x86 windows handheld pc console offers far pc emulator gaming support architectures operating systems widely used mobile devices linux android arm hardware proprietary systems gpd widely touts ability device indiegogo page video demonstrations gamepad digital first pitched idea gpd win community october 2015 concept market research planning november december physical design hardware specifications determined march 2016 initial prototypes finished debugged shipped select sources gpd started accepting pre-orders june 2016 several online retailers including indiegogo page pre-order backers offered device discounted price 330 estimated final retail price 499 settling price 330 release initial stated goal 100,000 april 2016 project well exceeded said goal 535 616,000 raised july 2016 august 2016 small batch shipment industry personnel shipped september pre-order promotional pricing ceased gpd started shipping final product october 2016 pre-order backers receiving devices first gpd win runs windows 10 home gpd stated per april 2014 microsoft decision windows free devices screens smaller 9 inches however devices shipped backers windows 10 product key input initial boot setup device unlike windows smartphones win able run x86 windows application also run pc laptops desktops april 2017 several patches available linux kernel allow mostly complete functionality win full desktop gnu/linux like ubuntu.. also ways get android work gpd win guide install make dual-boot https //www.black-seraph.com gpd win full qwerty keyboard includes 67 standard keys 10 expanded function keys gaming controller stylized similar openpandora dragonbox pyra style keyboard controller layout one d-pad two analog sticks four face buttons four shoulder buttons two shoulder gpd win initially intended use intel atom x5-z8500 cherry trail cpu however gpd eventually upgraded intended cpu likely due availability concerns instead win came intel atom x7-z8750 64-bit quad-core cpu base clock speed around 1.60 ghz turbo boost 2.56 ghz graphics processor intel hd graphics integrated gpu base clock speed 200 mhz turbo boost 600 mhz gpd win uses 4gb lpddr3-1600 ram 64gb rom emmc 4.51 single microsd slot officially support maximum 128gb storage however unofficially support microsd card 256gb gpd win 15.5×9.7cm size 5.5-inch 1280×720 720p h-ips multi-directional touch screen 16:9 ratio reinforced gorilla glass 3 audio system consists built-in speaker using realtek alc5645 driver microphone jack supports popular audio video image formats including mp3 mp4 3gp wmv/wma flac avi mov jpg png bmp gpd win 6700mah polymer lithium-ion battery usb c charging interface 5 v/2.5 stated ability play 80 continuous hours music 6–8 hours online video online gaming bluetooth 4.0 802.11 b/g/n/ac 5 ghz 2.4 ghz wifi capable gamepad digital continued support gpd win past release taking user feedback account driver hardware updates january 10 2017 gpd revised gpd win hardware providing fix intel graphics driver stability issues fixing ac charging/boot bug described reviews section improved cooling well improving tactile feedback d-pad buttons keyboard includes software update improves buttons responsiveness makes changes built-in mouse functionality gamepad digital began shipping gpd win backers october 2016 jc torres slashgear gave win 7/10 stating solid technical specs per expected needs ambitious windows 10-based handheld console industry dominated linux-based handhelds well rounded features however also noted inconsistent build quality among models mediocre sound quality loud low ultimately calls exceptional device brad linder liliputing gave quick review noting unit sent review overheating issues benchmarking speaker placement typically caused user cover fingers however noted solid device price niche capable playing surprising amount pc games video game console emulators windows store steam given tablet-pc specs however meant high-end gaming strongly resource-intensive emulation linus sebastian made video review gpd win linustechtips youtube page complimented gaming multitasking capabilities impressed hardware specs hardware design features overall include i/o ports features instance common macbook lament system flaws among shoulder buttons felt cheaply assembled 5.5 720p screen friendly scaling device bug must plugged ac adapter pressing power button order boot otherwise simply loads charging screen must plugged back system boot starts issue since fixed subsequent releases official verdict deciding whether worth price user win made excited prospect umpcs capable near future hardware progresses compared apple first iphone stating revolutionary great concept flaws execution ambitious practical set much better future gamepad digital announced gpd win 2 early 2017 win 2 significant upgrade able run aaa spec games well better video game console emulation intel core m3 cpu intel hd 615 graphics 8gb lpddr3 ram 128gb m.2 solid-state drive well i/o ports gpd win external hardware changes including moving analog knobs outward d-input dropped additional shoulder button shoulder six total price crowdfunding backers 649 tentative retail price 899 indiegogo campaign launched january 15 2018 final release date may 2018 indiegogo campaign saw rapid success far surpassing stated goal within days
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Operating systems
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toad data modeler toad data modeler database design tool allowing users visually create maintain document new existing database systems deploy changes data structures across different platforms used construct logical physical data models compare synchronize models generate complex sql/ddl create modify scripts reverse forward engineer databases data warehouse systems toad data modelling software used database design maintenance documentation toad data modeler previously called case studio 2 acquired charonware quest software 2006 quest software acquired dell september 28 2012 october 31 2016 dell finalized sale dell software francisco partners elliott management relaunched november 1 2016 quest software toad products typically 2 releases per year
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Databases
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rsdl restful service description language rsdl machine- human-readable xml description http-based web applications typically rest web services language defined michael pasternak work ovirt restful api allows documenting model resource provided service relationships operations parameters must supplied operations specifies parameters mandated describes possible overloads parameters sets rsdl intended simplify reuse web services based http architecture web platform- language-independent aims promote reuse applications beyond basic use web browser humans machines unlike wadl concentrates describing uris stand-alone entry points application invoked different ways require traversing uri components figure uri structure supports uri/headers/body parameters overloads makes human-readable easily consumed humans machines rsdl represents different uris stand-alone entry points application following resource uris one figure methods available given resources resources consumed uri rsdl contains necessary information generate http request easily consumed accessing uri internals uri rsdl contains rel description attributes describing meaning given operation uri humans easily fetch available operations given collection/resource simply locating different descriptors within uri
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Web technology
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