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exist exist-db exist short open source software project nosql databases built xml technology classified nosql document-oriented database system native xml database provides support xml json html binary documents unlike relational database management systems rdbms nosql databases exist-db provides xquery xslt query application programming languages exist-db released version 2.1 gnu lgpl exist-db created 2000 wolfgang meier major versions released 1.0 september 2006 2.0 february 2013 3.0 february 2017 4.0 february 2018 5.0.0-rc1 june 2018. exist-db awarded best xml database year infoworld 2006 company called exist solutions gmbh germany promotes software.. o'reilly book exist-db co-authored adam retter erik siegel exist-db allows software developers persist xml/json/binary documents without writing extensive middleware exist-db follows extends many w3c xml standards xquery exist-db also supports rest interfaces interfacing ajax-type web forms applications xforms may save data using lines code webdav interface exist-db allows users drag drop xml files directly exist-db database exist-db automatically indexes documents using keyword indexing system exist-db support following standards technologies
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Databases
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introhive introhive customer relationship management crm automation relationship intelligence platform designed help companies drive user adoption crm increase sales business development efficiency introhive platform works connect contact account data email systems crm improve team productivity data accuracy completeness information crm introhive established fredericton new brunswick canada offices chicago miami london u.k. chennai india headquartered washington d.c.. introhive founded january 2012 fredericton jody glidden stewart walchli entrepreneurs previously founded content delivery application company chalk media sold research motion 2009 introhive raised substantial venture funding first year canadian us-based investors early 2013 three former executives salesforce.com joined leadership team today introhive numbers 120+ staff across company 6 global offices introhive developed cloud-based software platform utilizes relationships organization ’ employees customers colleagues friends – including social media email electronic calendars contacts introhive platform assesses well person knows someone else assigning relationship score contact designed particularly large organisations hard quantify mine existing connections among employees platform core enterprise relationship management erm solution integrates crm business systems provide sales force automation relationship intelligence crm relationship analytics solutions platform built sales marketing organisations looking increase user adoption crm increase data quality decrease manual data entry crm increase insights business relationships platform provides organizations holistic view knows across company employees customer relationships data gathered crm distributed users platform via pre-meeting digests include company news meeting attendee profiles meeting notes crm information marketing automation information relationship intelligence stock quotes platform designed create enterprise relationship graph enable introhive refers 'warm introductions rather relying sales marketing cold calls
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Distributed computing architecture
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robert watson computer scientist robert nicholas maxwell watson born 3 may 1977 freebsd developer founder trustedbsd project currently employed university lecturer systems security architecture security research group university cambridge computer laboratory watson graduated computer science carnegie mellon university attained phd university cambridge well cambridge worked national institutes health carnegie mellon university trusted information systems network associates mcafee sparta obtained phd computer security university cambridge computer laboratory supervised ross anderson sponsored google watson work supported darpa apple computer navy us government agencies main research interests network security operating system security main open source software contributions include work developing multi-threaded multi-processor freebsd network stack trustedbsd project openbsm writing featured forums acm queue magazine usenix annual technical conference bsdcon slashdot interview also freebsd core team member 2000 2012 watson coauthor standard textbook design implementation freebsd operating system 2nd ed. 2015 marshall kirk mckusick
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Operating systems
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margaret masterman margaret masterman 4 may 1910 – 1 april 1986 british linguist philosopher known pioneering work field computational linguistics especially machine translation founded cambridge language research unit margaret masterman born london 4 may 1910 charles f. g. masterman politician lucy blanche lyttelton politician poet writer 1932 married richard bevan braithwaite philosopher son daughter margaret masterman one six students wittgenstein course 1933–34 whose notes compiled blue book 1955 founded directed cambridge language research unit clru grew informal discussion group major research centre computational linguistics time student newnham college cambridge read modern languages moral sciences philosophy called cambridge language research unit founded small beautiful building called adie museum housed far eastern art small buddhist sculptures built walls carved doors period twenty years starting 1953 source significant research machine translation computational linguistics quantum physics even though outside official university structures cambridge funded grants us agencies afosr onr nsf uk government agencies osti later eu funds luxembourg computing facilities primitive—an ancient icl 1202 computer -- -and serious computation done either cambridge university machine mathematical laboratory—or clru visitors sites us one measure impact staff never exceeded ten people annual lifetime achievement awards association computational linguistics us three awarded clru alumni martin kay karen spärck jones yorick wilks margaret masterman ahead time twenty years many beliefs proposals language processing computer become part common stock ideas artificial intelligence ai machine translation mt fields never able lay adequate claim unacceptable published written later students independently “ discovered ” others trace back especially fields little nothing ten years old ever reread core beliefs language processing must reflect coherence language redundancy signal idea partial inheritance old “ information theoretic ” view language meant processes analysing language must take account repetitive redundant structures writer goes saying thing different ways writer ambiguities removed signal sometimes led overemphasise real explicit redundancy would find rhythmical repetitive verse claim implausibly normal english like could see right led later years key role assigned rhythm stress breathgroupings boundaries impose text processes understanding put crudely claim languages way least part produced creatures breathe fairly regular intervals obvious claims could even entertained chomsky views preeminent language studies however could never give systematic surface criteria breathgroups stress patterns identified surface cues could reduced criteria syntax morphology would become involved actual physics voice patterns views importance semantics language processing continued defend high years chomskyan syntax 1951 1966 much influenced r. h. richens views classification description means language semantic primitives syntax along associated claims semantic pattern matching onto surface text developed actual programs might assumed straightforward believer existence semantic primitives katzian schankian sense nothing could truth far much wittgensteinian sceptic ability limited sublanguage logic take role whole language always argued semantic primitives would make sense empirical criteria discovery theory allowed fact would develop exactly polysemy higher natural language always emphasised functional role primitives example resolving sense ambiguity interlingua mt hoped escape problem origin semantic primitives would lie either empirical classification procedures operating actual texts way speak deriving primitives massive connectionist learning adequate formal theory structure thesauri believed make explicit certain underlying structures semantic relations natural language theory “ primitives ” would emerge naturally organizing classification thesauri years colleagues explored lattice theory underlying formal structure thesauri two concerns went intellectual life owe much period michael halliday university lecturer chinese cambridge colleague c.l.r.u got idea syntactic theory fundamentally semantic pragmatic either categories fundamental definition terms role syntax organizing principle semantic information first ai researcher influenced halliday long terry winograd became preoccupied considerable period nature function chinese ideograms felt clarified empirical way problems wittgenstein wrestled so-called picture-theory-of-truth led exaggerate generality ideogrammatic principles seem hold english really rather like chinese seen correctly meaning atoms highly ambiguous virtually uninflected view found little sympathy dominant linguistic computational currents time main creation 1953 one endured twenty years cambridge language research unit grew informal discussion group heterogeneous membership interested language philosophical computational points view subsequently attempt build language processing programs sound philosophical basis distinctive feature unit work approach language processing specific form took use thesaurus main vehicle semantic operations probably come seen unit major contributions field whole margaret primarily responsible vision language processing possibilities remarkable time computers rudimentary indeed much c.l.r.u work done predecessors computers namely hollerith punched card machines equally margaret determination establishing maintaining unit enormous effort fund raising involved striking fact could continue decades periods public support work hard come tribute margaret persistence charm difficult us days artificial intelligence ordinary market place powerful personal computers realise hard get financial resources needed language-processing research technical resources actual experiments perhaps best comment margaret initiative embarking language processing research specifically machine translation work comes somewhat unexpected source machine translation initial period high hopes large claims cast outer darkness 1966 funding agencies saw little return money reviewing twenty five years artificial intelligence research presidential address american association artificial intelligence 1985 woody bledsoe one long-standing leaders field though areas quite outside language said attempted machine translation fifties sixties may failed right try learned much attempts something difficult c.l.r.u trying far ahead time efforts made tackle fundamental problems computers day capacity modern digital wrist watch despite every kind problem unit produced numerous publications language related subjects including information retrieval automatic classification ten years unit presence strongly felt field always emphasis basic semantic problems language understanding margaret time felt needed syntactic parsing complete parsing necessary anything else semantics language regarded basic part understanding machine ideas c.l.r.u seem curiously modern margaret main contribution life clru continual intellectual stimulus gave research larger natural language processing community wide ranging concerns lateral ideas led example propose thesaurus means carrying many distinct language processing tasks like indexing translation margaret emphasis algorithms testing vital development clru work language processing ideas notable especially worked intellectual qualities sheer joyousness serious research stopped clru 1978 margaret tried restart clru 1980 william williams hope new breed micro-computers could used develop algorithms natural language translation margaret walked 7 miles millington road cambridge orwell purchased two north star horizon computers intelligent artefacts see st robotics installed forth programming language written david sands used various students university cambridge programmed margaret algorithms computers margaret approach natural language translation time split sentence breath group segments since breath group unique meaning could translated target language target sentence reconstructed using translated breath groups contrasted predominant language translation techniques time notably systran used dictionary rule based system still used today margaret died 1986 william williams closed clru unique library early mt documents dumped skip even though two university bodies offered give home one cofounders lucy cavendish college first vice-president 1965–1975 great-niece lucy cavendish college named also founder major inspiration epiphany philosophers group shared membership clru dedicated study relationship science religion forms religious practice 1965 margaret masterman read work nature paradigm fourth international colloquium philosophy science london conducted detailed textual criticism thomas s. kuhn book structure scientific revolutions 1962 characterizing book scientifically perspicuous philosophically obscure masterman praised kuhn one outstanding philosophers science time concept paradigms fundamental idea new one philosophy science criticised thomas kuhn vague inconsistent use concept paradigm noting used least 21 different senses summarized three groups metaparadigms sociological paradigms artefact construct paradigms masterman proposed kuhn critics philosophy science dealt metaparadigms explored insights implications various conceptions criticism accepted thomas kuhn crucial shift concept paradigm incommensurability
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Computational linguistics
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nitol botnet nitol botnet mostly involved spreading malware distributed denial-of-service attacks nitol botnet first discovered around december 2012 analysis botnet indicating botnet mostly prevalent china estimate 85 infections detected china botnet found present systems came brand-new factory indicating trojan installed somewhere assembly manufacturing process according microsoft systems risk also contained counterfeit installation microsoft windows 10 september 2012 microsoft took action nitol botnet obtaining court order subsequently sinkholing 3322.org domain 3322.org domain dynamic dns used botnet creators command control infrastructure controlling botnet microsoft later settled 3322.org operator pen yong allowed latter continue operating domain condition subdomains linked malware remain sinkholed
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Computer security
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cdc scope scope acronym supervisory control program execution name used control data corporation number operating system projects 1960s operating system based original chippewa operating system early 1970s renamed nos/be cdc cyber machines scope operating system file-oriented system using mass storage random access devices designed make use capabilities cdc 6000 computer systems exploits fully multiple-operating modes segments computer main tasks scope controlling job execution storage assignment performing segment overlay loading features include comprehensive input/output functions library maintenance routines dayfile chronologically records jobs run problems encountered aid debugging dumps memory maps available control scope variety assemblers compass compilers algol fortran cobol utility programs sort/merge pert/time export/import respond simscript apt optima etc may operated computer emulation community made repeated attempts recover preserve software running cdc cyber 6000 series emulator screenshot scope 3.1 building scope written programming team sunnyvale california 2,000 miles cdc hardware division considered buggy inefficient piece software though much different many operating systems era cdc arden hills minnesota laboratories referred scope sunnyvale collection programming errors competing operating system mace mansfield cahlander executive greg mansfield dave cahlander authors system started engineering test executive eventually developed complete operating system — modularized rewrite enhancement original chippewa operating system cos never official cdc product copy freely given customer asked one many customers especially advanced ones like university research sites control data decided write next operating system kronos considered current scope system unofficial mace alternative chose abandon scope system base kronos mace software eventually kronos replaced new network operating system nos though many smaller cdc customers continued use scope system rather kronos nos became primary control data operating system customers running mainly batch operations reluctant switch nos system saw benefit shop scope system maintained renamed nos/be batch environment primarily cdc marketing could say mainframe customers using nos operating system
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Operating systems
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database workbench database workbench software application development administration multiple relational databases using sql interoperationality different database systems developed upscene productions databases workbench supports multiple database systems provide software developers interface development environment otherwise different database systems also includes cross database tools database workbench started developer tool specifically interbase interbase workbench initially modeled sql navigator tool oracle database quest software early years interbase became open-source short soon firebird created fork interbase code base main developer database workbench martijn tonies closely involved early development firebird committee member firebird foundation database workbench continued support database systems initially separate firebird workbench release long program became interoperational different database systems initial support multiple database systems led renaming product current title database workbench 2003 also opened path inclusion support database systems support microsoft sql server mysql added 2003 2005 support oracle database nexusdb added sql anywhere support followed 2008 early 2010 full unicode version database workbench released version 5 database workbench released august 2014 free version limited functionality data workbench lite based data workbench 4 also available database workbench supports following relational databases oracle database microsoft sql server sql anywhere firebird nexusdb interbase mysql mariadb postgresql version 5 database workbench runs 32-bit 64 bit windows platforms linux freebsd mac os x database workbench operate using wine database workbench used view create edit tables indexes stored procedures database meta data objects also supports includes several productivity features
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Databases
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nuprl nuprl proof development system providing computer-mediated analysis proofs formal mathematical statements tools software verification optimization originally developed 1980s robert lee constable others system maintained prl project cornell university currently supported version nuprl 5 also known fdl formal digital library nuprl functions automated theorem proving system also used provide proof assistance nuprl uses type system based martin-löf intuitionistic type theory model mathematical statements digital library mathematical theories constructed analyzed variety editors including graphical user interface web-based editor emacs mode variety evaluators inference engines operate statements library translators also allow statements manipulated java ocaml programs overall system controlled variant ml nuprl 5 architecture described distributed open architecture intended primarily used web service rather standalone software interested using web service migrating theories older versions nuprl contact email address given nuprl system web page nuprl first released 1984 first described detail book implementing mathematics nuprl proof development system published 1986 nuprl 2 first unix version nuprl 3 provided machine proof mathematical problems related girard paradox higman lemma nuprl 4 first version developed world wide web used verify cache coherency protocols computer systems current system architecture implemented nuprl 5 first proposed 2000 conference paper reference manual nuprl 5 published 2002 nuprl subject many computer science publications recent 2014 jonprl redprl systems also based computational type theory redprl explicitly inspired nuprl
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Programming language topics
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multicast listener discovery multicast listener discovery mld component internet protocol version 6 ipv6 suite mld used ipv6 routers discovering multicast listeners directly attached link much like internet group management protocol igmp used ipv4 protocol embedded icmpv6 instead using separate protocol mldv1 similar igmpv2 mldv2 similar igmpv3 protocol described rfc 3810 updated rfc 4604 several operating system support mldv2
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Internet protocols
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naemon naemon open-source computer system monitoring network monitoring infrastructure monitoring software application naemon offers monitoring alerting services servers switches applications services alerts users things go wrong alerts second time problem resolved naemon created 2014 fork nagios available red hat centos suse debian ubuntu linux distribution naemon open source software licensed gnu gpl v2 provides
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Computer security
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chez scheme chez scheme programming language dialect implementation language scheme type lisp uses incremental native-code compiler produce native binary files x86 ia-32 x86-64 powerpc sparc processor architectures supported r6rs standard since version 7.9.1 free open-source software released apache license version 2.0 first released 1985 r. kent dybvig originally licensed proprietary software released open-source software github version 9.4 petite chez scheme sibling implementation uses threaded interpreter design instead chez scheme incremental native-code compiler programs written chez scheme run unchanged petite chez scheme long depend using compiler example foreign function interface available compiler petite chez scheme freely distributable may used royalty fees subject license agreement one series benchmarks chez scheme among fastest available scheme implementations sun sparc processor architecture petite chez scheme among slowest implementations common x86 pentium 32-bit processor architecture chez scheme windowing system computer graphics package called scheme widget library supported portable slib library
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Programming language topics
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william john sullivan william john sullivan commonly known john sullivan born december 6 1976 software freedom activist hacker writer john currently executive director free software foundation worked since early 2003 also speaker webmaster gnu project also maintains plannermode delicious-el packages gnu emacs text editor active free software free culture communities sullivan ba philosophy michigan state university mfa writing poetics college sullivan successful policy debater reaching finals ceda nationals semifinals national debate tournament 2007 john main contact behind defective design badvista play ogg campaigns also served chief-webmaster gnu project july 2006 served executive director free software foundation since 2011 john currently delivers speeches following topics english
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Operating systems
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interface description language interface description language interface definition language idl specification language used describe software component application programming interface api idls describe interface language-independent way enabling communication software components share one language example written c++ written java idls commonly used remote procedure call software cases machines either end link may using different operating systems computer languages idls offer bridge two different systems software systems based idls include sun onc rpc open group distributed computing environment ibm system object model object management group corba implements omg idl idl based dce/rpc data distribution service mozilla xpcom microsoft microsoft rpc evolved com dcom facebook thrift wsdl web services
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Programming language topics
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session fixation computer network security session fixation attacks attempt exploit vulnerability system allows one person fixate find set another person session identifier session fixation attacks web based rely session identifiers accepted urls query string post data alice account bank codice_1 mallory intends target alice money bank alice reasonable level trust mallory visit links mallory sends straightforward scenario misconception server accepts server-generated session identifiers safe fixation false scenario like cross-site cookie except rely browser vulnerabilities rather relies fact wildcard cookies set one subdomain affect subdomains scenario attack scenarios result mallory successfully gained access functions data normally reserved alice alternative attack scenario require alice log site rather simply fixing session mallory may able spy alice abuse data enters example mallory may use attacks give alice authenticated session—so alice start using site authentication mallory alice decides purchase something site enters credit card details mallory might able retrieve data confidential data looking historical data stored account type session fixation exploitation differs classic exploitation scenarios since happens unauthenticated part application reverses authentication attacker logging victim session identifiers url query string get variables post variables recommended simplify attack – easy make links forms set get post variables note cookies shared tabs popped browser windows system requires hit domain www.example.com/ code=site1 www.example.com/ code=site2 cookies may conflict one another tabs may required send session identifier url order overcome limitation possible use site1.example.com site2.example.com domain conflicts cookies may incur costs extra ssl certificates behavior seen many sites opening another tab trying side side search results one sessions become unusable attack largely avoided changing session id users log every request specific user requires user authenticated logged site attacker would need know id victim log-in session victim visits link fixed session id however need log account order anything important point session id change attacker able anything important anonymous session id similar technique used solve phishing problem user protects account two passwords solved great extent technique also useful cross-site request forgery attacks session identifier modern systems stored default http cookie moderate level security long session system disregards get/post values however solution vulnerable cross-site request forgery meet statelessness requirement rest enabling https security systems allow applications obtain ssl tls session identifier use ssl/tls session identifier secure many web development languages provide robust built-in functionality ssl/tls session identifiers may suitable critical applications large financial sites due size systems issue however rarely debated even security forums countermeasure session fixation generate new session identifier sid request done even though attacker may trick user accepting known sid sid invalid attacker attempts re-use sid implementation system simple demonstrated following example mallory successfully tricks alice visiting codice_24 http request sent codice_25 codice_25 accepts codice_27 would normally bad however codice_25 secure performs session regeneration codice_25 gets following response alice use codice_30 unknown mallory codice_27 invalid mallory thus unsuccessful session fixation attempt unfortunately session regeneration always possible problems known occur third-party software activex java applets used browser plugins communicate server third-party software could cause logouts session could split two separate sessions implementation sessions includes transmitting sid get post variables might also render back button browsers unusable user would using older invalid session identifier previous request one way improve security accept session identifiers generated server however noted prevent session fixation attacks isset _session 'server_generated_sid session_regenerate_id // generate new session identifier _session 'server_generated_sid true logout function useful allows users indicate session allow requests thus attacks effective session active note following code performs cross-site request forgery checks potentially allowing attacker force users log web application logout defense simple implement advantage providing measure protection unauthorized users accessing authorized user account using machine may left unattended store session variable containing time stamp last access made sid sid used compare current timestamp one stored session difference greater predefined number say 5 minutes destroy session otherwise update session variable current timestamp visiting page browsers set referrer – page contained link followed get page user logged site likely linked outside site e.g. banking websites webmail site kind site users would remain logged great length time referrer site referrer considered suspicious however originating request https page referrer stripped depend security system example codice_8 could employ following security check strpos _server 'http_referer 'http //vulnerable.example.com/ == 0 session_regenerate_id // generate new session identifier one way improve security ensure user appears end user client makes bit harder perform session fixation attacks networks begin conform rfc 3704 anti-spoofing practices ip address becomes reliable source identifier therefore security web site improved verifying source ip address consistent throughout session could performed manner _server 'remote_addr _session 'prev_remoteaddr session_regenerate_id // generate new session identifier _session 'prev_remoteaddr _server 'remote_addr however points consider employing approach sites added security outweighs lack convenience others browsers identify user-agent http headers header normally change use would extremely suspicious happen web application might make use user-agent detection attempt prevent malicious users stealing sessions however trivial bypass attacker easily capture victim user-agent site spoof attack proposed security system relying security obscurity _server 'http_user_agent _session 'prev_useragent session_regenerate_id // generate new session identifier _session 'prev_useragent _server 'http_user_agent however points consider employing approach user agent may change legally cases following examples users defense depth combine several countermeasures idea simple one obstacle trivial overcome several obstacles could hard overcome defense depth strategy could involve http referrers passed ssl/tls https following php script demonstrates several countermeasures combined defense depth manner isset _get 'logout || session_regenerate_id // generate new session identifier _session 'prev_useragent _server 'http_user_agent _session 'prev_remoteaddr _server 'remote_addr note code checks current remote_addr user ip address user-agent remote_addr user-agent previous request might inconvenient sites discussed
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Computer security
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itsec information technology security evaluation criteria itsec structured set criteria evaluating computer security within products systems itsec first published may 1990 france germany netherlands united kingdom based existing work respective countries following extensive international review version 1.2 subsequently published june 1991 commission european communities operational use within evaluation certification schemes since launch itsec 1990 number european countries agreed recognize validity itsec evaluations itsec largely replaced common criteria provides similarly-defined evaluation levels implements target evaluation concept security target document product system evaluated called target evaluation subjected detailed examination security features culminating comprehensive informed functional penetration testing degree examination depends upon level confidence desired target provide different levels confidence itsec defines evaluation levels denoted e0 e6 higher evaluation levels involve extensive examination testing target unlike earlier criteria notably tcsec developed us defense establishment itsec require evaluated targets contain specific technical features order achieve particular assurance level example itsec target might provide authentication integrity features without providing confidentiality availability given target security features documented security target document whose contents evaluated approved target evaluated itsec evaluation based exclusively verifying security features identified security target formal z notation used prove security properties mondex smart card electronic cash system allowing achieve itsec level e6 highest granted security-level classification
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Computer security
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socket 370 socket 370 also known pga370 socket cpu socket first used intel pentium iii celeron processors first complement later replace older slot 1 cpu interface personal computers 370 refers number pin holes socket cpu pins socket 370 replaced socket 423 2000 socket 370 started budget oriented platform 66 mhz fsb ppga mendocino celeron cpus late 1998 move on-die l2 cache removed need pcb design seen slot 1 late 1999 late 2000 intel main desktop socket 100/133 mhz fsb coppermine pentium iiis 2001 tualatin pentium iii processors brought changes infrastructure required dedicated tualatin-compatible motherboards manufacturers would indicate blue instead white socket late sockets typically compatible coppermine processors older mendocino celerons motherboards used socket 370 support intel processors dual cpu configurations others allowed use socket 370 slot 1 cpu although time via-cyrix cyrix iii later renamed via c3 also used socket 370 weight socket 370 cpu cooler exceed 180 grams 6.3 ounces heavier coolers may result damage die system properly handled intel socket 370 processors pentium iii celeron following mechanical maximum load limits exceeded heat sink assembly shipping conditions standard use load limits crack processor die make unusable intel socket 370 processors integrated heat sink pentium iii celeron 1.13–1.4 ghz following mechanical maximum load limits exceeded heatsink assembly shipping conditions standard use load limits crack processor die make unusable
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Computer architecture
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program optimization computer science program optimization software optimization process modifying software system make aspect work efficiently use fewer resources general computer program may optimized executes rapidly make capable operating less memory storage resources draw less power although word optimization shares root optimal rare process optimization produce truly optimal system system generally made optimal absolute terms respect given quality metrics may contrast possible metrics result optimized system typically optimal one application one audience one might reduce amount time program takes perform task price making consume memory application memory space premium one might deliberately choose slower algorithm order use less memory often one size fits design works well cases engineers make trade-offs optimize attributes greatest interest additionally effort required make piece software completely optimal — incapable improvement — almost always reasonable benefits would accrued process optimization may halted completely optimal solution reached fortunately often case greatest improvements come early process optimization occur number levels typically higher levels greater impact harder change later project requiring significant changes complete rewrite need changed thus optimization typically proceed via refinement higher lower initial gains larger achieved less work later gains smaller requiring work however cases overall performance depends performance low-level portions program small changes late stage early consideration low-level details outsized impact typically consideration given efficiency throughout project – though varies significantly – major optimization often considered refinement done late ever longer-running projects typically cycles optimization improving one area reveals limitations another typically curtailed performance acceptable gains become small costly performance part specification program – program unusably slow fit purpose video game 60 hz frames-per-second acceptable 6 frames-per-second unacceptably choppy – performance consideration start ensure system able deliver sufficient performance early prototypes need roughly acceptable performance confidence final system optimization achieve acceptable performance sometimes omitted belief optimization always done later resulting prototype systems far slow – often order magnitude – systems ultimately failures architecturally achieve performance goals intel 432 1981 ones take years work achieve acceptable performance java 1995 achieved acceptable performance hotspot 1999 degree performance changes prototype production system amenable optimization significant source uncertainty risk highest level design may optimized make best use available resources given goals constraints expected use/load architectural design system overwhelmingly affects performance example system network latency-bound network latency main constraint overall performance would optimized minimize network trips ideally making single request requests push protocol rather multiple roundtrips choice design depends goals designing compiler fast compilation key priority one-pass compiler faster multi-pass compiler assuming work speed output code goal slower multi-pass compiler fulfills goal better even though takes longer choice platform programming language occur level changing frequently requires complete rewrite though modular system may allow rewrite component – example python program may rewrite performance-critical sections c. distributed system choice architecture client-server peer-to-peer etc occurs design level may difficult change particularly components replaced sync e.g. old clients given overall design good choice efficient algorithms data structures efficient implementation algorithms data structures comes next design choice algorithms data structures affects efficiency aspect program generally data structures difficult change algorithms data structure assumption performance assumptions used throughout program though minimized use abstract data types function definitions keeping concrete data structure definitions restricted places algorithms primarily consists ensuring algorithms constant 1 logarithmic log n linear n cases log-linear n log n input space time algorithms quadratic complexity n fail scale even linear algorithms cause problems repeatedly called typically replaced constant logarithmic possible beyond asymptotic order growth constant factors matter asymptotically slower algorithm may faster smaller simpler asymptotically faster algorithm faced small input may case occurs reality often hybrid algorithm provide best performance due tradeoff changing size general technique improve performance avoid work good example use fast path common cases improving performance avoiding unnecessary work example using simple text layout algorithm latin text switching complex layout algorithm complex scripts devanagari another important technique caching particularly memoization avoids redundant computations importance caching often many levels caching system cause problems memory use correctness issues stale caches beyond general algorithms implementation abstract machine concrete source code level choices make significant difference example early c compilers codice_1 slower codice_2 unconditional loop codice_1 evaluated 1 conditional jump tested true codice_4 unconditional jump optimizations one nowadays performed optimizing compilers depends source language target machine language compiler difficult understand predict changes time key place understanding compilers machine code improve performance loop-invariant code motion return value optimization examples optimizations reduce need auxiliary variables even result faster performance avoiding round-about optimizations source compile level directives build flags used tune performance options source code compiler respectively using preprocessor defines disable unneeded software features optimizing specific processor models hardware capabilities predicting branching instance source-based software distribution systems bsd ports gentoo portage take advantage form optimization use optimizing compiler tends ensure executable program optimized least much compiler predict lowest level writing code using assembly language designed particular hardware platform produce efficient compact code programmer takes advantage full repertoire machine instructions many operating systems used embedded systems traditionally written assembler code reason programs small programs seldom written start finish assembly due time cost involved compiled high level language assembly hand optimized efficiency size less important large parts may written high-level language modern optimizing compilers greater complexity recent cpus harder write efficient code compiler generates projects need ultimate optimization step much code written today intended run many machines possible consequence programmers compilers n't always take advantage efficient instructions provided newer cpus quirks older models additionally assembly code tuned particular processor without using instructions might still suboptimal different processor expecting different tuning code typically today rather writing assembly language programmers use disassembler analyze output compiler change high-level source code compiled efficiently understand inefficient just-in-time compilers produce customized machine code based run-time data cost compilation overhead technique dates earliest regular expression engines become widespread java hotspot v8 javascript cases adaptive optimization may able perform run time optimization exceeding capability static compilers dynamically adjusting parameters according actual input factors profile-guided optimization ahead-of-time aot compilation optimization technique based run time profiles similar static average case analog dynamic technique adaptive optimization self-modifying code alter response run time conditions order optimize code common assembly language programs cpu designs perform optimizations run time examples include out-of-order execution speculative execution instruction pipelines branch predictors compilers help program take advantage cpu features example instruction scheduling code optimization also broadly categorized platform-dependent platform-independent techniques latter ones effective platforms platform-dependent techniques use specific properties one platform rely parameters depending single platform even single processor writing producing different versions code different processors might therefore needed instance case compile-level optimization platform-independent techniques generic techniques loop unrolling reduction function calls memory efficient routines reduction conditions etc impact cpu architectures similar way great example platform-independent optimization shown inner loop observed loop inner loop performs computations per unit time loop without one inner loop generally serve reduce total instruction path length required complete program and/or reduce total memory usage process hand platform-dependent techniques involve instruction scheduling instruction-level parallelism data-level parallelism cache optimization techniques i.e. parameters differ among various platforms optimal instruction scheduling might different even different processors architecture computational tasks performed several different ways varying efficiency efficient version equivalent functionality known strength reduction example consider following c code snippet whose intention obtain sum integers 1 n code assuming arithmetic overflow rewritten using mathematical formula like optimization sometimes performed automatically optimizing compiler select method algorithm computationally efficient retaining functionality see algorithmic efficiency discussion techniques however significant improvement performance often achieved removing extraneous functionality optimization always obvious intuitive process example optimized version might actually slower original version n sufficiently small particular hardware happens much faster performing addition looping operations multiplication division cases however optimization relies using elaborate algorithms making use special cases special tricks performing complex trade-offs fully optimized program might difficult comprehend hence may contain faults unoptimized versions beyond eliminating obvious antipatterns code level optimizations decrease maintainability optimization generally focus improving one two aspects performance execution time memory usage disk space bandwidth power consumption resource usually require trade-off — one factor optimized expense others example increasing size cache improves run time performance also increases memory consumption common trade-offs include code clarity conciseness instances programmer performing optimization must decide make software better operations cost making operations less efficient trade-offs may sometimes non-technical nature — competitor published benchmark result must beaten order improve commercial success comes perhaps burden making normal usage software less efficient changes sometimes jokingly referred pessimizations optimization may include finding bottleneck system – component limiting factor performance terms code often hot spot – critical part code primary consumer needed resource – though another factor i/o latency network bandwidth computer science resource consumption often follows form power law distribution pareto principle applied resource optimization observing 80 resources typically used 20 operations software engineering often better approximation 90 execution time computer program spent executing 10 code known 90/10 law context complex algorithms data structures perform well many items simple algorithms suitable small amounts data — setup initialization time constant factors complex algorithm outweigh benefit thus hybrid algorithm adaptive algorithm may faster single algorithm performance profiler used narrow decisions functionality fits conditions cases adding memory help make program run faster example filtering program commonly read line filter output line immediately uses enough memory one line performance typically poor due latency disk read caching result similarly effective though also requiring larger memory use optimization reduce readability add code used improve performance may complicate programs systems making harder maintain debug result optimization performance tuning often performed end development stage donald knuth made following two statements optimization forget small efficiencies say 97 time premature optimization root evil yet pass opportunities critical 3 premature optimization phrase used describe situation programmer lets performance considerations affect design piece code result design clean could code incorrect code complicated optimization programmer distracted optimizing deciding whether optimize specific part program amdahl law always considered impact overall program depends much much time actually spent specific part always clear looking code without performance analysis better approach therefore design first code design profile/benchmark resulting code see parts optimized simple elegant design often easier optimize stage profiling may reveal unexpected performance problems would addressed premature optimization practice often necessary keep performance goals mind first designing software programmer balances goals design optimization modern compilers operating systems efficient intended performance increases often fail materialize example caching data application level cached operating system level yield improvements execution even rare case programmer remove failed optimizations production code also true advances hardware often obviate potential improvements yet obscuring code persist future long purpose negated optimization code development using macros takes different forms different languages procedural languages c c++ macros implemented using token substitution nowadays inline functions used type safe alternative many cases cases inlined function body undergo compile-time optimizations compiler including constant folding may move computations compile time many functional programming languages macros implemented using parse-time substitution parse trees/abstract syntax trees claimed makes safer use since many cases interpretation used one way ensure computations performed parse-time sometimes way lisp originated style macro macros often called lisp-like macros similar effect achieved using template metaprogramming c++ cases work moved compile-time difference c macros one side lisp-like macros c++ template metaprogramming side latter tools allow performing arbitrary computations compile-time/parse-time expansion c macros perform computation relies optimizer ability perform additionally c macros directly support recursion iteration turing complete optimization however often difficult predict tools impact project complete see also optimization automated compilers performed programmers gains usually limited local optimization larger global optimizations usually powerful optimization find superior algorithm optimizing whole system usually undertaken programmers complex automated optimizers situation programmers system administrators explicitly change code overall system performs better although produce better efficiency far expensive automated optimizations since many parameters influence program performance program optimization space large meta-heuristics machine learning used address complexity program optimization use profiler performance analyzer find sections program taking resources — bottleneck programmers sometimes believe clear idea bottleneck intuition frequently wrong optimizing unimportant piece code typically little help overall performance bottleneck localized optimization usually starts rethinking algorithm used program often particular algorithm specifically tailored particular problem yielding better performance generic algorithm example task sorting huge list items usually done quicksort routine one efficient generic algorithms characteristic items exploitable example already arranged particular order different method used even custom-made sort routine programmer reasonably sure best algorithm selected code optimization start loops unrolled lower loop overhead although often lead lower speed overloads cpu cache data types small possible used integer arithmetic used instead floating-point see algorithmic efficiency article techniques performance bottlenecks due language limitations rather algorithms data structures used program sometimes critical part program re-written different programming language gives direct access underlying machine example common high-level languages like python modules written c greater speed programs already written c modules written assembly programs written use inline assembler rewriting sections pays circumstances general rule thumb known 90/10 law states 90 time spent 10 code 10 time remaining 90 code putting intellectual effort optimizing small part program huge effect overall speed — correct part located manual optimization sometimes side effect undermining readability thus code optimizations carefully documented preferably using in-line comments effect future development evaluated program performs automated optimization called optimizer optimizers embedded compilers operate compilation optimizers often tailor generated code specific processors today automated optimizations almost exclusively limited compiler optimization however compiler optimizations usually limited fixed set rather general optimizations considerable demand optimizers accept descriptions problem language-specific optimizations allowing engineer specify custom optimizations tools accept descriptions optimizations called program transformation systems beginning applied real software systems c++ high-level languages eiffel esterel optimize programs using intermediate language grid computing distributed computing aims optimize whole system moving tasks computers high usage computers idle time sometimes time taken undertake optimization therein may issue optimizing existing code usually add new features worse might add new bugs previously working code change might manually optimized code might sometimes less readability unoptimized code optimization might impact maintainability well optimization comes price important sure investment worthwhile automatic optimizer optimizing compiler program performs code optimization may optimized either improve efficiency target programs else speed operation compilation performed optimization turned usually takes longer although usually problem programs quite large particular just-in-time compilers performance run time compile component executing together target code key improving overall execution speed
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Programming language topics
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objective-c objective-c general-purpose object-oriented programming language adds smalltalk-style messaging c programming language main programming language supported apple macos ios ipados operating systems respective application programming interfaces apis cocoa cocoa touch introduction swift programming language objective-c originally developed early 1980s selected main language used next nextstep operating system macos ios derived portable objective-c programs use cocoa cocoa touch libraries using parts may ported reimplemented systems also compiled system supported gnu compiler collection gcc clang objective-c source code 'implementation program files usually filename extensions objective-c 'header/interface files extensions c header files objective-c++ files denoted file extension objective-c created primarily brad cox tom love early 1980s company stepstone introduced smalltalk itt corporation programming technology center 1981 earliest work objective-c traces back around time cox intrigued problems true reusability software design programming realized language like smalltalk would invaluable building development environments system developers itt however tom love also recognized backward compatibility c critically important itt telecom engineering milieu cox began writing pre-processor c add abilities smalltalk soon working implementation object-oriented extension c language called oopc object-oriented pre-compiler love hired schlumberger research 1982 opportunity acquire first commercial copy smalltalk-80 influenced development brainchild order demonstrate real progress could made cox showed making interchangeable software components really needed practical changes existing tools specifically needed support objects flexible manner come supplied usable set libraries allow code resources needed code bundled one cross-platform format love cox eventually formed new venture productivity products international ppi commercialize product coupled objective-c compiler class libraries 1986 cox published main description objective-c original form book object-oriented programming evolutionary approach although careful point problem reusability language objective-c often found compared feature feature languages 1988 next licensed objective-c stepstone new name ppi owner objective-c trademark extended gcc compiler support objective-c. next developed appkit foundation kit libraries nextstep user interface interface builder based next workstations failed make great impact marketplace tools widely lauded industry led next drop hardware production focus software tools selling nextstep openstep platform custom programming order circumvent terms gpl next originally intended ship objective-c frontend separately allowing user link gcc produce compiler executable initially accepted richard m. stallman plan rejected stallman consulted gnu lawyers next agreed make objective-c part gcc work extend gcc led steve naroff joined next stepstone compiler changes made available per gpl license terms runtime libraries rendering open source contribution unusable general public led parties developing runtime libraries open source license later steve naroff also principal contributor work apple build objective-c frontend clang gnu project started work free software implementation cocoa named gnustep based openstep standard dennis glatting wrote first gnu objective-c runtime 1992 gnu objective-c runtime use since 1993 one developed kresten krab thorup university student denmark thorup also worked next 1993 1996 acquiring next 1996 apple computer used openstep then-new operating system mac os x included objective-c next objective-c-based developer tool project builder interface design tool interface builder merged one application xcode apple current cocoa api based openstep interface objects significant objective-c environment used active development wwdc 2014 apple introduced new language swift characterized objective-c without c objective-c thin layer atop c strict superset c meaning possible compile c program objective-c compiler freely include c language code within objective-c class objective-c derives object syntax smalltalk syntax non-object-oriented operations including primitive variables pre-processing expressions function declarations function calls identical c syntax object-oriented features implementation smalltalk-style messaging objective-c model object-oriented programming based message passing object instances objective-c one call method one sends message unlike simula-style programming model used c++ difference two concepts code referenced method message name executed simula-style language method name cases bound section code target class compiler smalltalk objective-c target message resolved runtime receiving object interpreting message method identified selector — unique identifier message name often -terminated string representing name — resolved c method pointer implementing consequence message-passing system type checking object message directed — receiver — guaranteed respond message raises exception sending message object pointed pointer would require following code c++ obj- method argument objective-c written follows obj method argument styles programming strengths weaknesses object-oriented programming simula c++ style allows multiple inheritance faster execution using compile-time binding whenever possible support dynamic binding default also forces methods corresponding implementation unless abstract smalltalk-style programming used objective-c allows messages go unimplemented method resolved implementation runtime example message may sent collection objects expected respond without fear producing runtime errors message passing also require object defined compile time implementation still required method called derived object see dynamic typing section advantages dynamic late binding objective-c requires interface implementation class separately declared code blocks convention developers place interface header file implementation code file header files normally suffixed .h similar c header files implementation method files normally suffixed .m similar c code files called class declaration interface class usually defined header file common convention name header file name class e.g would contain interface class interface declaration takes form interface classname superclassname classmethod1 return_type classmethod2 return_type classmethod3 param1_type param1_varname return_type instancemethod1with1parameter param1_type param1_varname return_type instancemethod2with2parameters param1_type param1_varname param2_callname param2_type param2_varname end plus signs denote class methods methods called class instance minus signs denote instance methods called particular instance class class methods also access instance variables code roughly equivalent following c++ interface class classname public superclassname note demonstrates interleaving selector segments argument expressions direct equivalent c/c++ return types standard c type pointer generic objective-c object pointer specific type object nsarray nsimage nsstring pointer class method belongs instancetype default return type generic objective-c type method arguments begin name labeling argument part method name followed colon followed expected argument type parentheses argument name label omitted void setrangestart int start end int end void importdocumentwithname nsstring name withspecifiedpreferences preferences prefs beforepage int insertpage interface declares class interface methods actual code written implementation file implementation method files normally file extension codice_1 originally signified messages implementation classname return_type classmethod return_type instancemethod end methods written using interface declarations comparing objective-c c int method int int function int syntax allows pseudo-naming arguments void changetored float red green float green blue float blue //called like mycolor changecolortored:5.0 green:2.0 blue:6.0 internal representations method vary different implementations objective-c mycolor class instance method might internally labeled refer instance method class method names appended colons changed underscores order parameters part method name changed suit coding style expression true named parameters however internal names function rarely used directly generally messages converted function calls defined objective-c runtime library necessarily known link time method called class receiver object sent message need known runtime objective-c class written instantiated done first allocating uninitialized instance class object initializing object fully functional steps completed steps accomplished one line code never allocated object n't undergone initialization unwise keep intermediate result since codice_2 return different object called instantiation default no-parameter initializer myobject *foo end interface integer display id showstars id showint end implementation integer display id showstars id showint end int main void compilation performed example one experiment leaving lines omitting compilation program still run means possible mix-and-match added categories needed category need ability simply compile objective-c permits class wholly replace another class within program replacing class said pose target class class posing declared deprecated mac os x v10.5 unavailable 64-bit runtime similar functionality achieved using method swizzling categories swaps one method implementation another signature versions still supporting posing messages sent target class instead received posing class several restrictions posing similarly categories allows global augmentation existing classes posing permits two features absent categories example interface customnsapplication nsapplication end implementation customnsapplication void setmainmenu nsmenu* menu end class_poseas customnsapplication class nsapplication class intercepts every invocation setmainmenu nsapplication c language codice_3 pre-compile directive always causes file contents inserted source point objective-c codice_4 directive equivalent except file included per compilation unit obviating need include guards objective-c features often allow flexible often easy solutions programming issues objective-c++ language variant accepted front-end gnu compiler collection clang compile source files use combination c++ objective-c syntax objective-c++ adds c++ extensions objective-c adds c. nothing done unify semantics behind various language features certain restrictions apply 2006 worldwide developers conference apple announced release objective-c 2.0 revision objective-c language include modern garbage collection syntax enhancements runtime performance improvements 64-bit support mac os x v10.5 released october 2007 included objective-c 2.0 compiler gcc 4.6 supports many new objective-c features declared synthesized properties dot syntax fast enumeration optional protocol methods method/protocol/class attributes class extensions new gnu objective-c runtime api objective-c 2.0 provided optional conservative generational garbage collector run backwards-compatible mode runtime turned reference counting operations retain release no-ops objects subject garbage collection garbage collection enabled regular c pointers could qualified __strong also trigger underlying write-barrier compiler intercepts thus participate garbage collection zero-ing weak subsystem also provided pointers marked __weak set zero object simply gc memory collected garbage collector exist ios implementation objective-c 2.0 garbage collection objective-c runs low-priority background thread halt user events intention keeping user experience responsive garbage collection deprecated mac os x v10.8 favor automatic reference counting arc objective-c ios 7 running arm64 uses 19 bits 64-bit word store reference count form tagged pointers objective-c 2.0 introduces new syntax declare instance variables properties optional attributes configure generation accessor methods properties sense public instance variables declaring instance variable property provides external classes access possibly limited e.g read property property may declared readonly may provided storage semantics codice_5 codice_6 codice_7 default properties considered codice_8 results lock preventing multiple threads accessing time property declared codice_9 removes lock interface person nsobject property copy nsstring *name property readonly int age id initwithage int age end properties implemented way codice_10 keyword generates getter setter read-only methods according property declaration alternatively getter setter methods must implemented explicitly codice_11 keyword used indicate accessor methods provided means compiled using clang 3.1 higher properties explicitly declared codice_11 marked codice_13 complete user-implemented getter setter automatically implicitly codice_10 'd implementation person synthesize name id initwithage int initage int age end properties accessed using traditional message passing syntax dot notation key-value coding name via valueforkey setvalue forkey methods person *aperson person alloc initwithage 53 aperson.name steve // note dot notation uses synthesized setter nslog access message dot notation property name direct instance variable access order use dot notation invoke property accessors within instance method self keyword used void introducemyselfwithproperties bool usegetter // note getter vs. ivar access class protocol properties may dynamically type introspection|introspected int int propertycount 0 objc_property_t *propertylist class_copypropertylist aperson class propertycount 0 propertycount i++ objective-c 2.0 provides non-fragile instance variables supported runtime i.e building code 64-bit macos ios modern runtime extra layer indirection added instance variable access allowing dynamic linker adjust instance layout runtime feature allows two important improvements objective-c code instead using nsenumerator object indices iterate collection objective-c 2.0 offers fast enumeration syntax objective-c 2.0 following loops functionally equivalent different performance traits // using nsenumerator nsenumerator *enumerator thepeople objectenumerator person *p p enumerator nextobject nil // using indexes int 0 thepeople count i++ // using fast enumeration person *p thepeople fast enumeration generates efficient code standard enumeration method calls enumerate objects replaced pointer arithmetic using nsfastenumeration protocol class extension syntax category declaration category name methods properties declared added directly main class mostly used alternative category add methods class without advertising public headers advantage class extensions compiler checks privately declared methods actually implemented objective-c applications developed macos make use improvements objective-c 2.0 incompatible operating systems prior 10.5 leopard since fast enumeration generate exactly binaries standard enumeration use cause application crash mac os x version 10.4 earlier blocks nonstandard extension objective-c c programming language |c c++ uses special syntax create closure programming |closures blocks supported mac os x snow leopard|mac os x 10.6 snow leopard later ios 4 later gnustep libobjc2 1.7 compiling clang 3.1 later typedef int ^intblock intblock makecounter int start int increment int main void /* output automatic reference counting arc compile-time feature eliminates need programmers manually manage retain counts using codice_7 codice_16 unlike garbage collection computer science |garbage collection occurs run time arc eliminates overhead separate process managing retain counts arc manual memory management mutually exclusive programmers continue use non-arc code arc-enabled projects disabling arc individual code files xcode also attempt automatically upgrade project arc next apple obj-c runtimes long included short-form way create new strings using literal syntax codice_17 drop corefoundation constants codice_18 codice_19 codice_20 boolean values using format saves programmer use longer codice_21 similar methods certain operations using apple llvm compiler 4.0 later arrays dictionaries numbers codice_22 codice_23 codice_20 classes also created using literal syntax instead methods example without literals nsarray *myarray nsarray arraywithobjects object1 object2 object3 nil nsdictionary *mydictionary1 nsdictionary dictionarywithobject someobject forkey key nsdictionary *mydictionary2 nsdictionary dictionarywithobjectsandkeys object1 key1 object2 key2 nil nsnumber *mynumber nsnumber numberwithint myint nsnumber *mysumnumber= nsnumber numberwithint 2 3 nsnumber *myboolnumber nsnumber numberwithbool yes example literals nsarray *myarray object1 object2 object3 nsdictionary *mydictionary1 key someobject nsdictionary *mydictionary2 key1 object1 key2 object2 nsnumber *mynumber myint nsnumber *mysumnumber 2+3 nsnumber *myboolnumber yes nsnumber *myintegernumber 8 however different string literal compile constants executable literals compile code equivalent method calls particular manually reference-counted memory management objects autoreleased requires added care e.g. used function-static variables kinds globals using apple llvm compiler 4.0 later arrays dictionaries codice_22 codice_23 classes manipulated using subscripting subscripting used retrieve values indexes array keys dictionary mutable objects also used set objects indexes keys code subscripting represented using brackets codice_27 example without subscripting id object1 somearray objectatindex:0 id object2 somedictionary objectforkey key somemutablearray replaceobjectatindex:0 withobject object3 somemutabledictionary setobject object4 forkey key example subscripting id object1 somearray 0 id object2 somedictionary key somemutablearray 0 object3 somemutabledictionary key object4 purchase next apple attempts made make language acceptable programmers familiar java programming language |java smalltalk one attempts introducing dubbed modern syntax objective-c time opposed current classic syntax change behaviour merely alternative syntax instead writing method invocation like instead written similarly declarations went form modern syntax longer supported current dialects objective-c language besides gnu compiler collection|gcc next apple inc.|apple implementation added several extensions original stepstone implementation another free open source software|free open-source objective-c implementation called portable object compiler also exists set extensions implemented portable object compiler differs gcc/next/apple implementation particular includes smalltalk -like blocks objective-c lacks protocols categories two features used extensively openstep derivatives relatives overall poc represents older pre-next stage language evolution roughly conformant brad cox 1991 book also includes runtime library called objectpak based cox original icpak101 library turn derives smalltalk-80 class library quite radically different openstep foundationkit geos 16-bit operating system |pc geos system used programming language known geos objective-c goc despite name similarity two languages similar overall concept use keywords prefixed sign clang compiler suite part llvm project implements objective-c languages winobjc also known bridge open-source objc compiler project started microsoft github way allow reuse ios application code inside windows universal applications windows objective-c development tools provided download gnustep website gnustep development system consists following packages gnustep msys system gnustep core gnustep devel gnustep cairo projectcenter ide like xcode complex gorm interface builder like xcode nib builder objective-c today often used tandem fixed library standard objects often known kit framework cocoa api |cocoa gnustep objfw libraries often come operating system gnustep libraries often come linux -based distributions cocoa comes macos programmer forced inherit functionality existing base class nsobject ofobject objective-c allows declaration new root classes inherit existing functionality originally objective-c-based programming environments typically offered object class base class almost classes inherited introduction openstep next created new base class named nsobject offered additional features object emphasis using object references reference counting instead raw pointers example almost classes cocoa inherit nsobject renaming serve differentiate new default behavior classes within openstep api allowed code used object—the original base class used nextstep less objective-c class libraries —to co-exist runtime code used nsobject limitations introduction two letter prefix also became simplistic form namespaces objective-c lacks using prefix create informal packaging identifier became informal coding standard objective-c community continues day recently package managers started appearing cocoapods aims package manager repository packages lot open-source objective-c code written last years installed using cocoapods objective-c implementations use thin run time system|runtime system written c adds little size application contrast object-oriented systems time created used large virtual machine runtimes programs written objective-c tend much larger size code libraries generally need included software distribution contrast smalltalk systems large amount memory used open window objective-c applications tend larger similar c c++ applications objective-c dynamic typing allow methods stripped inlined since programmer freedom delegate forward calls build selectors fly pass runtime system objective-c compiler assume safe remove unused methods inline calls likewise language implemented atop extant c compilers gnu compiler collection|gcc first preprocessor module rather new compiler allows objective-c leverage huge existing collection c code libraries tools etc existing c libraries wrapped objective-c adapter pattern|wrappers provide oo-style interface aspect similar gobject library vala programming language |vala language widely used development gtk applications practical changes lowered barriers entry|barrier entry likely biggest problem widespread acceptance smalltalk 1980s common criticism objective-c language support namespaces instead programmers forced add prefixes class names traditionally shorter namespace names thus prone collisions 2007 macos classes functions cocoa software |cocoa programming environment prefixed ns e.g nsobject nsbutton identify belonging macos ios core ns derives names classes defined development nextstep since objective-c strict superset c treat c primitive types first-class object s. unlike c++ objective-c support operator overloading also unlike c++ objective-c allows object directly inherit one class forbidding multiple inheritance however cases categories protocols may used alternative ways achieve results objective-c uses dynamic runtime typing method calls function calls cases syscalls many common performance optimizations applied objective-c methods example inlining constant propagation interprocedural optimizations scalar replacement aggregates limits performance objective-c abstractions relative similar abstractions languages c++ optimizations possible first versions objective-c support garbage collection computer science |garbage collection time decision matter debate many people considered long dead times smalltalk performed collection render entire system unusable 3rd party implementations added feature notably gnustep apple implemented mac os x v10.5 however recent versions macos ios garbage collection deprecated favor automatic reference counting arc introduced 2011 arc compiler inserts retain release calls automatically objective-c code based static program analysis|static code analysis automation relieves programmer write memory management code arc also adds weak references objective-c language design implementation c++ objective-c represent fundamentally different approaches extending c. addition c style procedural programming c++ directly supports certain forms object-oriented programming generic programming metaprogramming c++ also comes c++ standard library|a large standard library includes sequence container c++ |several container classes similarly objective-c adds polymorphism object-oriented programming|object-oriented programming dynamic typing reflection computer science |reflection c. objective-c provide standard library per se places objective-c used used openstep -like library openstep cocoa api |cocoa gnustep provides functionality similar c++ standard library one notable difference objective-c provides runtime support reflection computer science |reflective features whereas c++ adds small amount runtime support c. objective-c object queried properties e.g. whether respond certain message c++ possible without use external libraries use reflection part wider distinction dynamic run-time features static compile-time features language although objective-c c++ employ mix features objective-c decidedly geared toward run-time decisions c++ geared toward compile-time decisions tension dynamic static programming involves many classic trade-offs programming dynamic features add flexibility static features add speed type checking generic programming metaprogramming implemented languages using runtime polymorphism c++ takes form virtual function runtime type identification objective-c offers dynamic typing reflection objective-c lacks compile-time polymorphism generic function entirely c++ supports via function overloading template c++ |templates category c programming language family category class-based programming languages category dynamically typed programming languages category gnustep category next category object-oriented programming languages category objective-c category programming languages created 1986
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Operating systems
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database model database model type data model determines logical structure database fundamentally determines manner data stored organized manipulated popular example database model relational model uses table-based format common logical data models databases include object-relational database combines two related structures physical data models include models include given database management system may provide one models optimal structure depends natural organization application data application requirements include transaction rate speed reliability maintainability scalability cost database management systems built around one particular data model although possible products offer support one model various physical data models implement given logical model database software offer user level control tuning physical implementation since choices made significant effect performance model way structuring data also defines set operations performed data relational model example defines operations select project join although operations may explicit particular query language provide foundation query language built flat table model consists single two-dimensional array data elements members given column assumed similar values members row assumed related one another instance columns name password might used part system security database row would specific password associated individual user columns table often type associated defining character data date time information integers floating point numbers tabular format precursor relational model models popular 1960s 1970s nowadays found primarily old legacy systems characterized primarily navigational strong connections logical physical representations deficiencies data independence hierarchical model data organized tree-like structure implying single parent record sort field keeps sibling records particular order hierarchical structures widely used early mainframe database management systems information management system ims ibm describe structure xml documents structure allows one one-to-many relationship two types data structure efficient describe many relationships real world recipes table contents ordering paragraphs/verses nested sorted information hierarchy used physical order records storage record access done navigating downward data structure using pointers combined sequential accessing hierarchical structure inefficient certain database operations full path opposed upward link sort field also included record limitations compensated later ims versions additional logical hierarchies imposed base physical hierarchy network model expands upon hierarchical structure allowing many-to-many relationships tree-like structure allows multiple parents popular replaced relational model defined codasyl specification network model organizes data using two fundamental concepts called records sets records contain fields may organized hierarchically programming language cobol sets confused mathematical sets define one-to-many relationships records one owner many members record may owner number sets member number sets set consists circular linked lists one record type set owner parent appears circle second record type subordinate child may appear multiple times circle way hierarchy may established two record types e.g. type owner b time another set may defined b owner thus sets comprise general directed graph ownership defines direction network construct access records either sequential usually record type navigation circular linked lists network model able represent redundancy data efficiently hierarchical model one path ancestor node descendant operations network model navigational style program maintains current position navigates one record another following relationships record participates records also located supplying key values although essential feature model network databases generally implement set relationships means pointers directly address location record disk gives excellent retrieval performance expense operations database loading reorganization popular dbms products utilized cincom systems total cullinet idms idms gained considerable customer base 1980s adopted relational model sql addition original tools languages object databases invented 1990s use navigational concept provide fast navigation across networks objects generally using object identifiers smart pointers related objects objectivity/db instance implements named one-to-one one-to-many many-to-one many-to-many named relationships cross databases many object databases also support sql combining strengths models inverted file inverted index contents data used keys lookup table values table pointers location instance given content item also logical structure contemporary database indexes might use contents particular columns lookup table inverted file data model put indexes set files next existing flat database files order efficiently directly access needed records files notable using data model adabas dbms software ag introduced 1970 adabas gained considerable customer base exists supported today 1980s adopted relational model sql addition original tools languages document-oriented database clusterpoint uses inverted indexing model provide fast full-text search xml json data objects example relational model introduced e.f. codd 1970 way make database management systems independent particular application mathematical model defined terms predicate logic set theory implementations used mainframe midrange microcomputer systems products generally referred relational databases fact implement model approximation mathematical model defined codd three key terms used extensively relational database models relations attributes domains relation table columns rows named columns relation called attributes domain set values attributes allowed take basic data structure relational model table information particular entity say employee represented rows also called tuples columns thus relation relational database refers various tables database relation set tuples columns enumerate various attributes entity employee name address phone number example row actual instance entity specific employee represented relation result tuple employee table represents various attributes single employee relations thus tables relational database adhere basic rules qualify relations first ordering columns immaterial table second ca n't identical tuples rows table third tuple contain single value attributes relational database contains multiple tables similar one flat database model one strengths relational model principle value occurring two different records belonging table different tables implies relationship among two records yet order enforce explicit integrity constraints relationships records tables also defined explicitly identifying non-identifying parent-child relationships characterized assigning cardinality 1:1 0 1 tables also designated single attribute set attributes act key used uniquely identify tuple table key used uniquely identify row table called primary key keys commonly used join combine data two tables example employee table may contain column named location contains value matches key location table keys also critical creation indexes facilitate fast retrieval data large tables column key multiple columns grouped together compound key necessary define keys advance column used key even originally intended one key external real-world meaning person name book isbn car serial number sometimes called natural key natural key suitable think many people named brown arbitrary surrogate key assigned giving employees id numbers practice databases generated natural keys generated keys used internally create links rows break natural keys used less reliably searches integration databases example records two independently developed databases could matched social security number except social security numbers incorrect missing changed common query language used relational model structured query language sql dimensional model specialized adaptation relational model used represent data data warehouses way data easily summarized using online analytical processing olap queries dimensional model database schema consists single large table facts described using dimensions measures dimension provides context fact participated happened type used queries group related facts together dimensions tend discrete often hierarchical example location might include building state country measure quantity describing fact revenue important measures meaningfully aggregated—for example revenue different locations added together olap query dimensions chosen facts grouped aggregated together create summary dimensional model often implemented top relational model using star schema consisting one highly normalized table containing facts surrounding denormalized tables containing dimension alternative physical implementation called snowflake schema normalizes multi-level hierarchies within dimension multiple tables data warehouse contain multiple dimensional schemas share dimension tables allowing used together coming standard set dimensions important part dimensional modeling high performance made dimensional model popular database structure olap products offering general data model relational model sometimes classified post-relational alternate terms include hybrid database object-enhanced rdbms others data model products incorporates relations constrained e.f. codd information principle requires extensions relational model integrate concepts technologies pre-date relational model example allow representation directed graph trees nodes german company sones implements concept graphdb post-relational products extend relational systems non-relational features others arrived much place adding relational features pre-relational systems paradoxically allows products historically pre-relational pick mumps make plausible claim post-relational resource space model rsm non-relational data model based multi-dimensional classification graph databases allow even general structure network database node may connected node multivalue databases lumpy data store exactly way relational databases also permit level depth relational model approximate using sub-tables nearly identical way xml expresses data given field/attribute multiple right answers time multivalue thought compressed form xml example invoice either multivalue relational data could seen invoice header table one entry per invoice b invoice detail table one entry per line item multivalue model option storing data table embedded table represent detail invoice table one entry per invoice tables needed advantage atomicity invoice conceptual invoice data representation one-to-one also results fewer reads less referential integrity issues dramatic decrease hardware needed support given transaction volume 1990s object-oriented programming paradigm applied database technology creating new database model known object databases aims avoid object-relational impedance mismatch overhead converting information representation database example rows tables representation application program typically objects even type system used particular application defined directly database allowing database enforce data integrity invariants object databases also introduce key ideas object programming encapsulation polymorphism world databases variety ways tried storing objects database products approached problem application programming end making objects manipulated program persistent typically requires addition kind query language since conventional programming languages ability find objects based information content others attacked problem database end defining object-oriented data model database defining database programming language allows full programming capabilities well traditional query facilities object databases suffered lack standardization although standards defined odmg never implemented well enough ensure interoperability products nevertheless object databases used successfully many applications usually specialized applications engineering databases molecular biology databases rather mainstream commercial data processing however object database ideas picked relational vendors influenced extensions made products indeed sql language alternative translating objects relational databases use object-relational mapping orm library
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Databases
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ox programming language ox object-oriented matrix programming language mathematical statistical function library developed jurgen doornik designed econometric programming available windows mac os x linux platforms downloadable console version ox free academic use commercial version available non-academic use according documentation cited whenever results published programming environment econometric modelling oxmetrics based ox
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Programming language topics
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f6 disk f6 disk colloquial name floppy disk containing microsoft windows nt device driver scsi raid system f6 disks used nt-based versions windows including windows 2000 windows server 2003 windows xp starting windows vista floppy f6 disks obsolete setup process supports loading third-party drivers usb drives cd-roms f6 disk named manner used installation process windows setup program must load device drivers disk system windows installed unless disk system established market finalization particular windows release installed drivers included windows installation discs must loaded means f6 disk f6 disk loaded windows setup pressing f6 key immediately windows setup starts message press f6 need install third party scsi raid driver ... briefly flashed screen every time windows setup starts f6 disk contains device drivers root directory prior windows vista f6 disks always floppy disks point f6 prompt shown windows setup loaded drivers media type floppy disks support usb drives cd-roms added windows vista device drivers raid disk controllers often provided cd-roms manufacturers must copied f6 disk used windows setup alternative approach slipstream required sata/scsi/sas/raid/eide drivers windows installation files directory e.g i386 x86 variety means software like nlite create iso image burned cd dvd media
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Operating systems
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dms software reengineering toolkit dms software reengineering toolkit proprietary set program transformation tools available automating custom source program analysis modification translation generation software systems arbitrary mixtures source languages large scale software systems dms used implement wide variety practical tools include domain-specific languages code generation factory control test coverage profiling tools clone detection language migration tools c++ component reengineering. research difficult topics refactoring c++ reliably toolkit provides means defining language grammars produce parsers automatically construct abstract syntax trees asts prettyprinters convert original modified asts back compilable source text parse trees capture prettyprinters regenerate complete detail original source program including source position comments radix format numbers etc. ensure regenerated source text recognizable programmer original text modulo applied transformations many program analysis transformation tools limited ascii western european character sets iso-8859 dms handle well utf-8 utf-16 ebcdic shift-jis variety microsoft character encodings dms uses glr parsing technology enabling handle practical context-free grammars semantic predicates extend capability interesting non-context-free grammars fortran requires matching multiple loops shared continue statements label glr semantic predicates enables dms fortran parser produce asts correctly nested loops parses dms provides attribute grammar evaluators computing custom analyses asts metrics including special support symbol table construction program facts extracted built-in control- data- flow analysis engines local global pointer analysis whole-program call graph extraction symbolic range analysis abstract interpretation changes asts accomplished procedural methods coded parlanse source-to-source tree transformations coded rewrite rules using surface-syntax conditioned extracted program facts using dms rule specification language rsl rewrite rule engine supporting rsl handles associative commutative rules rewrite rule c replace complex condition codice_1 operator written rewrite rules names e.g simplify_conditional_assignment rule match replace pattern pair separated example separate lines readability patterns must correspond language syntax categories case patterns must syntax category statement also separated sympathy patterns target language e.g. c surface syntax coded inside meta-quotes separate rewrite-rule syntax target language backslashes inside meta-quotes represent domain escapes indicate pattern meta variables e.g. \v \e1 \e2 match language construct corresponding metavariable declaration signature line e.g. e1 must syntactic category expression metavariable mentioned multiple times match pattern must match identical subtrees identically shaped v must occur assignments match pattern example metavariables replace pattern replaced corresponding matches left side conditional clause provides additional condition must met rule apply e.g. matched metavariable v arbitrary left-hand side must side effect e.g. form i++ no_side_effects predicate defined analyzer built dms mechanisms achieving complex transformation code accomplished providing number rules cooperate achieve desired effect ruleset focused portions program metaprograms coded parlanse complete example language definition source-to-source transformation rules defined applied shown using high school algebra bit calculus domain-specific language dms variety predefined language front ends covering real dialects c c++ including c++0x c java python php egl fortran cobol visual basic verilog vhdl 20 languages predefined languages enable customizers immediately focus reengineering task rather details languages processed dms additionally unusual implemented parallel programming language parlanse uses symmetric multiprocessors available commodity workstations enables dms provide faster answers large system analyses conversions dms originally motivated theory maintaining designs software called design maintenance systems dms design maintenance system registered trademarks semantic designs
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Programming language topics
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dec batch-11/dos-11 batch-11/dos-11 also known simply dos-11 discontinued operating system digital equipment corporation dec maynard massachusetts first version dos-11 v08-02 released 1970 first operating system run digital pdp-11 minicomputer dos-11 known easy use even day became much less used 1973 release rt-11 operating system dos-11 included dos-11 came xxdp diagnostics monitor program pdp-11 like digital operating systems dos-11 also fortran-iv ansi-66 compiler fortran-iv supported pdp-11 systems less 12k memory dos-11 systems running 8k 12k configurations ran limited version macro-11 assembler pal-11r overlaid form dos-11 operating system kernel one file called monlib.lcl lcl extension acronym linked core image library licil licil could stored type media dos-11 operating system distributed disk dectape punched tape magnetic tape licil file installed hooked onto disk drive contiguous file monitor library name changed monlibcil could booted cil extension acronym core image library core term core memory systems common pdp-11 core image library could created cilus core image library update save program monlibcil typically contained resident monitor rmon keyboard command routine device drivers emt routines clock routines transient monitor dos-11 used compile install early versions rsts-11 rsts/e operating systems however ancestor rsx-11 family operating systems
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Operating systems
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comparison disc image software article comparison notable software applications access manipulate disk image files compares disk image handling features article compares two features supported file formats capabilities software treat image format
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Computer file systems
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metulji botnet metulji botnet discovered june 2011 botnet mainly involved cyberscamming denial service attacks botnet dismantled consisted 12 million individual zombie computers infected butterfly bot making june 2011 largest known botnet known type computers vulnerable tell computer part botnet
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Computer security
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xcode xcode integrated development environment ide macos containing suite software development tools developed apple developing software macos ios ipados watchos tvos first released 2003 latest stable release version 10.3 available via mac app store free charge macos mojave users registered developers download preview releases prior versions suite apple developer website xcode supports source code programming languages c c++ objective-c objective-c++ java applescript python ruby resedit rez swift variety programming models including limited cocoa carbon java third parties added support gnu pascal free pascal ada c perl d. xcode build fat binary files containing code multiple architectures mach-o executable format called universal binary files allow software run powerpc intel-based x86 platforms include 32-bit 64-bit code architectures using ios sdk xcode also used compile debug applications ios run arm architecture processors xcode includes gui tool instruments runs atop dynamic tracing framework dtrace created sun microsystems released part opensolaris main application suite integrated development environment ide also named xcode xcode suite includes apple developer documentation built-in interface builder application used construct graphical user interfaces xcode 4.1 xcode suite included modified version gnu compiler collection xcode 3.1 xcode 4.6.3 included llvm-gcc compiler front ends gnu compiler collection code generator based llvm xcode 3.2 later included clang c/c++/objective-c compiler newly-written front ends code generator based llvm clang static analyzer starting xcode 4.2 clang compiler became default compiler starting xcode 5.0 clang compiler provided xcode 4.6.3 xcode suite used gnu debugger gdb back-end ide debugger starting xcode 4.3 lldb debugger also provided starting xcode 4.5 lldb replaced gdb default back-end ide debugger starting xcode 5.0 gdb longer supplied formerly xcode supported distributing product build process multiple systems one technology involved named shared workgroup build used bonjour protocol automatically discover systems providing compiler services modified version free software product distcc facilitate distribution workloads earlier versions xcode provided system named dedicated network builds features absent supported versions xcode xcode also includes apple webobjects tools frameworks building java web applications web services formerly sold separate product xcode 3.0 apple dropped webobjects development inside xcode wolips used instead xcode 3 still includes webobjects frameworks xcode 1.0 released fall 2003 xcode 1.0 based project builder updated user interface ui zerolink fix continue distributed build support code sense indexing next significant release xcode 1.5 better code completion improved debugger xcode 2.0 released mac os x v10.4 tiger included quartz composer visual programming language better code sense indexing java ant support also included apple reference library tool allows searching reading online documentation apple website documentation installed local computer xcode 2.1 could create universal binary files supported shared precompiled headers unit testing targets conditional breakpoints watchpoints also better dependency analysis final version xcode mac os x v10.4 2.5 xcode 3.0 released mac os x v10.5 leopard notable changes since 2.1 include dtrace debugging tool named instruments refactoring support context-sensitive documentation objective-c 2.0 garbage collection also supports project snapshots provide basic form version control message bubbles show build errors debug values alongside code building four-architecture fat binaries 32 64-bit intel powerpc xcode 3.1 update release developer tools mac os x version included iphone sdk could target non-mac os x platforms including iphone os 2.0 included gcc 4.2 llvm gcc 4.2 compilers another new feature since xcode 3.0 xcode scm support includes subversion 1.5 xcode 3.2 released mac os x v10.6 snow leopard installs earlier version os x supports static program analysis among features also drops official support targeting versions earlier iphone os 3.0 still possible target older versions simulator supports iphone os 2.0 3.1 also java support exiled 3.2 organizer xcode 3.2.6 last version downloaded free users mac os x v10.6 downloading requires free registration apple developer site june 2010 apple worldwide developers conference version 4 xcode announced developer tools state union address version 4 developer tools consolidates xcode editing tools interface builder one application among enhancements apple released final version xcode 4.0 march 9 2011 software made available free registered members 99 per year mac developer program 99 per year ios developer program also sold 4.99 non-members mac app store longer available xcode 4.0 drops support many older systems including powerpc development software development kits sdks mac os x 10.4 10.5 ios sdks older 4.3 deployment target still set produce binaries older platforms mac os platforms one limited creating x86 x86-64 binaries later xcode free general public version 4.1 xcode cost 4.99 xcode 4.1 made available free july 20 2011 day mac os x lion release users mac os x lion mac app store august 29 2011 xcode 4.1 made available mac os x snow leopard members paid mac ios developer programs xcode 4.1 last version include gnu compiler collection gcc instead llvm gcc clang october 12 2011 xcode 4.2 released concurrently release ios 5.0 included many improved features storyboarding automatic reference counting arc xcode 4.2 last version support mac os x 10.6 snow leopard available registered developers paid accounts without paid account 3.2.6 latest download appears snow leopard xcode 4.3 released february 16 2012 distributed one application bundle xcode.app installed mac app store xcode 4.3 reorganizes xcode menu include development tools xcode 4.3.1 released march 7 2012 add support ios 5.1 xcode 4.3.2 released march 22 2012 enhancements ios simulator suggested move lldb debugger versus gdb debugger appear undocumented changes xcode 4.3.3 released may 2012 featured updated sdk mac os x 10.7.4 lion bug fixes xcode 4.4 released july 25 2012 runs mac os x lion 10.7 os x mountain lion 10.8 first version xcode contain os x 10.8 mountain lion sdk xcode 4.4 includes support automatic synthesizing declared properties new objective-c features literal syntax subscripting improved localization august 7 2012 xcode 4.4.1 released bug fixes september 19 2012 ios 6 xcode 4.5 released xcode added support ios 6 4-inch retina display iphone 5 ipod touch 5th generation also brought new objective-c features ios simplified localization added auto-layout support ios october 3 2012 xcode 4.5.1 released bug fixes stability improvements less month later xcode 4.5.2 released support ipad mini ipad retina display bug fixes stability improvements january 28 2013 ios 6.1 xcode 4.6 released june 2013 apple worldwide developers conference version 5 xcode announced september 18 2013 xcode 5.0 released added support ios 7 sdk always support os x 10.8 mountain lion sdk support os x 10.9 mavericks sdk latest included betas version also added version clang generating 64-bit arm code ios 7 apple removed support building garbage collected cocoa binaries xcode 5.1 june 2 2014 worldwide developers conference apple announced version 6 xcode one notable features support swift all-new programming language developed apple xcode 6 also included features like playgrounds live debugging tools september 17 2014 time ios xcode 6 released xcode could downloaded mac app store june 8 2015 apple worldwide developers conference xcode version 7 announced introduced support swift 2 metal os x added support deploying ios devices without apple developer license xcode 7 released september 16 2015 june 13 2016 apple worldwide developers conference xcode version 8 announced introduced support swift 3 xcode 8 released september 13 2016 june 5 2017 apple worldwide developers conference xcode version 9 announced introduced support swift 4 metal 2 also introduced remotely debugging ios tvos devices wirelessly wifi xcode 9 publicly released september 19 2017 june 4 2018 apple worldwide developers conference xcode version 10 announced beta version released day xcode 10 introduced support dark mode announced macos mojave collaboration platforms bitbucket gitlab addition github training machine learning models playgrounds new features swift 4.2 metal 2.1 well improvements editor project build system xcode 10 also dropped support building 32-bit macos apps longer supports subversion integration xcode 10 publicly released september 17 2018 june 3 2019 apple worldwide developers conference xcode version 11 announced beta version released day xcode 11 introduced support new features swift 5.1 well new swiftui framework although interactive ui tools available running macos 10.15 also supports building ipad applications run macos includes integrated support swift package manager contains improvements editor including minimap gives overview source code file quick navigation xcode 11 requires macos 10.14.4 later
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Operating systems
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norton system insight norton system insight part performance monitoring system found norton 2010–2012 lines monitors displays information downloaded files installed applications scans detected security risks also shows number performance alerts addition represents cpu memory usage 30 days graphical way easier understanding provides links norton insight startup manager optimize button defragments system drive system insight launched click performance link
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Computer security
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simple directmedia layer simple directmedia layer sdl cross-platform software development library designed provide hardware abstraction layer computer multimedia hardware components software developers use write high-performance computer games multimedia applications run many operating systems android ios linux macos windows sdl manages video audio input devices cd-rom threads shared object loading networking timers 3d graphics handle opengl vulkan direct3d context common misconception sdl game engine true however library suited building games directly usable indirectly engines built top library internally written c possibly depending target platform c++ objective-c provides application programming interface c bindings languages available free open-source software subject requirements zlib license since version 2.0 prior versions subject gnu lesser general public license zlib license sdl 2.0 freely available static linking closed-source projects unlike sdl 1.2 sdl extensively used industry large small projects 700 games 180 applications 120 demos posted library website sam lantinga created library first releasing early 1998 working loki software got idea porting windows application macintosh used sdl port doom beos see doom source ports several free libraries developed work alongside sdl smpeg openal also founded galaxy gameworks 2008 help commercially support sdl although company plans currently hold due time constraints soon putting galaxy gameworks hold lantinga announced sdl 1.3 would later become sdl 2.0 would licensed zlib license lantinga announced sdl 2.0 14 july 2012 time announcing joining valve corporation first version announced day joined company lantinga announced stable release sdl 2.0.0 13 august 2013 sdl 2.0 major update sdl 1.2 codebase different backwards-compatible api replaces several parts 1.2 api general support multiple input output options feature additions include multiple window support hardware-accelerated 2d graphics better unicode support support mir wayland added sdl 2.0.2 enabled default sdl 2.0.4 version 2.0.4 also provided better support android sdl wrapper around operating-system-specific functions game needs access purpose sdl provide common framework accessing functions multiple operating systems cross-platform sdl provides support 2d pixel operations sound file access event handling timing threading often used complement opengl setting graphical output providing mouse keyboard input since opengl comprises rendering game using simple directmedia layer automatically run every operating system adaptations must applied reduced minimum since sdl also contains abstraction apis frequent functions offered operating system syntax sdl function-based operations done sdl done passing parameters subroutines functions special structures also used store specific information sdl needs handle sdl functions categorized several different subsystems sdl divided several subsystems besides basic low-level support also separate official libraries provide functions comprise standard library provided official website included official documentation non-standard libraries also exist example sdl_collide sourceforge created amir taaki sdl 2.0 library language bindings way sdl designed much source code split separate modules operating system make calls underlying system sdl compiled appropriate modules selected target system following back-ends available sdl 1.2 support risc os dropped 2.0 unofficial sixel back-end available sdl 1.2 rockbox mp3 player firmware also distributes version sdl 1.2 used run games quake years sdl used many commercial non-commercial video game projects instance mobygames listed 120 games using sdl 2013 sdl website listed around 700 games 2012 important commercial examples angry birds unreal tournament ones open-source domain openttd battle wesnoth freeciv cross-platform game releases popular humble indie bundles linux mac android often sdl based sdl also often used later ports new platforms legacy code instance pc game homeworld ported pandora handheld jagged alliance 2 android via sdl also several non video game software uses sdl examples emulators dosbox visualboyadvance several books written development sdl see readings sdl used university courses teaching multimedia computer science instance workshop game programming using libsdl university cadiz 2010 game design discipline utfpr ponta grossa campus 2015
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Operating systems
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mac nc mac nc sometimes referred macintosh nc network thin client expected released apple april 1998 device widely promoted then-apple director larry ellison apparently part oracle network computer initiative mac nc ultimately never released although key components technology inherited original imac released august 1998 may 21 1996 oracle corporation along 30 hardware software vendors announced intent build computers designed around network computer platform idea design technology based profile included diskless computers commonly coded applications using languages java interface internet using common software netscape navigator may 1996 apple became partner network computing effort used apple pippin platform implementation july 9 1997 gil amelio ousted ceo apple board directors steve jobs stepped interim ceo begin critical restructuring company product line would eventually become ceo served position august 2011 oracle corporation ceo apple board member larry ellison announced december 1997 talking harvard computer society apple would release product called macintosh nc april 1998 suggested network computer would near-300 mhz processor 17-inch screen would sell less us 1,000 hard disk drive available extra costing additional 100 steve jobs agree stating unfortunately ellison pretty far base e-mail maybe trying deflect interest really oracle ellison overseen development business alliance produced number network computer-branded devices companies sun ibm apple never manufactured devices oracle alliance endorse network computer reference profile steve jobs already stopped macintosh clone efforts would shut apple pippin concept prospects mac nc ultimately technology shipped netboot release mac os x server 1.0 january 1999
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Computer architecture
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xenomai xenomai real-time development framework cooperating linux kernel provide pervasive interface-agnostic hard real-time support user space applications seamlessly integrated linux environment xenomai project launched august 2001 2003 merged real-time application interface rtai project produce production-grade real-time free software platform linux called rtai/fusion top xenomai abstract real-time operating system rtos core eventually rtai/fusion effort became independent rtai 2005 xenomai project xenomai based abstract rtos core usable building kind real-time interface nucleus exports set generic rtos services number rtos personalities called “ skins ” built nucleus providing specific interface applications using services single generic core implement long list differences xenomai rtai though projects share ideas support rtdm layer major differences derive goals projects aim respective implementation rtai focused lowest technically feasible latencies xenomai also considers clean extensibility rtos skins portability maintainability important goals xenomai path towards ingo molnár preempt_rt support another major difference compared rtai objectives
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Operating systems
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feiteng processor feiteng 飞腾 fēiténg name several computer central processing units designed produced china supercomputing applications microprocessors developed tianjin phytium technology processors also described yinhefeiteng 银河飞騰 yhft family cpu family developed team directed nudt professor xing zuocheng first generation binary compatible intel itanium 2 second generation ft64 system chip cpu 64-bit stream processor ft64 chips used yinhe 银河 supercomputers accelerators feiteng-1000 third generation cpu family manufactured 65 nm technology contains 350 million gates clock frequency 0.8–1 ghz compatible sparcv9 instruction set architecture chip contains 8 cores capable executing 64 threads 3 hypertransport channels coherent links 4 ddr3 memory controllers 8x pcie 2.0 link tianhe-1a supercomputer uses 2,048 feiteng 1000 processors tianhe-1a theoretical peak performance 4.701 petaflops also employing 7,168 nvidia tesla m2050 gpus 14,336 intel xeon x5670 cpus addition ft1000 processors feiteng-1000 eight-core processor based sparc system used operate service nodes tianhe-1 2012 report european high performance computing service stated feiteng used work opensparc project tianhe-2 supercomputer uses 4096 processors galaxy ft-1500 16 cores opensparc architecture based 65 w tdp made 40 nm technology processor cores work 1.8 ghz peak performance ft-1500 115–144 gflops every core may execute 8 interleaving threads supports 256-bit wide simd vector operations including fused mul-add fma cache soc works 2 ghz frequency 16 kb l1i 16 kb l1d 512 kb l2 per core shared 4 mb l3 cache l3 cache 4 segments 1 segment per block 4 cpu cores 1 mb 32-way associative cache uses directory-based cache coherency protocol ft-1500 also ft-1500a arm64 soc designed phytium includes 16 cores armv8 processor 32-lane pcie host 2 gmac on-chip ethernet controller gicv3 interrupt controller support
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Computer architecture
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rdate unix-like operating systems rdate tool querying current time network server optionally setting system time rdate uses time protocol time protocol generally considered obsolete replaced network time protocol ntp used set local system time rdate operates changing system time immediately time date returned server abrupt changes clock settings found cause problems software relying timing led development network time protocol gradually changes system time skip ticks due problems described rdate generally used systems ntp available specialized circumstances required system time set correctly soon possible initial setup services may vulnerable abrupt time-changes started
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Internet protocols
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microsequencer computer architecture engineering sequencer microsequencer generates addresses used step microprogram control store used part control unit cpu stand-alone generator address ranges usually addresses generated combination counter field microinstruction subset instruction register counter used typical case next microinstruction one execute field microinstruction used jumps logic since cpus implement instruction set useful able decode instruction bits directly sequencer select set microinstructions perform cpu instructions modern cisc processors use combination pipelined logic process lower complexity opcodes completed one clock cycle microcode implement ones take multiple clock cycles complete one first integrated microcoded processors ibm palm processor emulated processor instruction microcode used ibm 5100 one first personal computers recent examples similar microsequencer-based processors microcore labs mcl86 mcl51 mcl65 cores emulate intel 8086/8088 8051 mos 6502 instruction sets entirely microcode
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Computer architecture
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soap soap abbreviation simple object access protocol messaging protocol specification exchanging structured information implementation web services computer networks purpose provide extensibility neutrality independence uses xml information set message format relies application layer protocols often hypertext transfer protocol http simple mail transfer protocol smtp message negotiation transmission soap allows processes running disparate operating systems windows linux communicate using extensible markup language xml since web protocols like http installed running operating systems soap allows clients invoke web services receive responses independent language platforms soap provides messaging protocol layer web services protocol stack web services xml-based protocol consisting three parts soap three major characteristics example soap procedures application send soap request server web services enabled—such real-estate price database—with parameters search server returns soap response xml-formatted document resulting data e.g. prices location features since generated data comes standardized machine-parsable format requesting application integrate directly soap architecture consists several layers specifications soap evolved successor xml-rpc though borrows transport interaction neutrality web service addressing envelope/header/body elsewhere probably wddx soap designed object-access protocol 1998 dave winer box bob atkinson mohsen al-ghosein microsoft atkinson al-ghosein working specification made available submitted ietf 13 september 1999 according box due politics within microsoft microsoft hesitation dave winer shipped xml-rpc 1998 submitted internet draft reach rfc status therefore considered standard version 1.1 specification published w3c note 8 may 2000 since version 1.1 reach w3c recommendation status considered standard either version 1.2 specification however became w3c recommendation june 24 2003 soap specification maintained xml protocol working group world wide web consortium group closed 10 july 2009 soap originally stood simple object access protocol version 1.2 standard dropped acronym soap first introduced became underlying layer complex set web services based web services description language wsdl xml schema universal description discovery integration uddi different services especially uddi proved far less interest appreciation gives complete understanding expected role soap compared web services actually evolved soap specification broadly defined consisting following 3 conceptual components protocol concepts encapsulation concepts network concepts soap specification defines messaging framework consists soap message ordinary xml document containing following elements smtp http valid application layer protocols used transport soap http gained wider acceptance works well today internet infrastructure specifically http works well network firewalls soap may also used https protocol http application level uses encrypted transport protocol underneath either simple mutual authentication advocated ws-i method provide web service security stated ws-i basic profile 1.1 major advantage distributed protocols like giop/iiop dcom normally filtered firewalls soap amqp yet another possibility implementations support soap also advantage dcom unaffected security rights configured machines require knowledge transmitting receiving nodes lets soap loosely coupled way possible dcom also soap-over-udp oasis standard xml information set chosen standard message format widespread use major corporations open source development efforts typically xml information set serialized xml wide variety freely available tools significantly eases transition soap-based implementation somewhat lengthy syntax xml benefit drawback promotes readability humans facilitates error detection avoids interoperability problems byte-order endianness slow processing speed cumbersome example corba giop ice dcom use much shorter binary message formats hand hardware appliances available accelerate processing xml messages binary xml also explored means streamlining throughput requirements xml xml messages self-documenting nature usually 'overhead headers footers nested tags delimiters actual data contrast earlier protocols overhead usually relatively small percentage overall message financial messaging soap found result 2–4 times larger message previous protocols fix financial information exchange cdr common data representation xml information set serialized xml instance csv json xml-infoset representations exist also need specify generic transformation framework concept soap bindings allows specific bindings specific application drawback senders receivers support newly defined binding post /instock http/1.1 host www.example.org content-type application/soap+xml charset=utf-8 content-length 299 soapaction http //www.w3.org/2003/05/soap-envelope xml version= 1.0 soap envelope xmlns soap= http //www.w3.org/2003/05/soap-envelope xmlns m= http //www.example.org /soap envelope
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Internet protocols
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messaging architects messaging architects canadian software company specializing e-mail products flagship product netmail integrated email management platform launched march 1995 chronofax company distributor computer-based fax solutions chronofax became tobit software north america result partnership german company called tobit produced fax software novell netware groupwise markets three-and-a-half-year partnership tobit came close company renamed messaging architects messaging architects initially provided add-ons novell groupwise messaging platform company offers integrated email management platform called netmail netmail consolidates company portfolio email software solutions includes netmail secure formerly gwguardian m+guardian netmail archive formerly m+archive netmail search netmail migrate formerly migrator netmail store formerly m+securestore company also provides email platform migration services messaging architects also highly skilled professional services team full novell microsoft exchange certification messaging architects works messaging platform providers provide solutions microsoft exchange novell groupwise lotus notes late 2008 mark crispin inventor imap worked messaging architects senior software engineer developing entirely new imap server based upon distributed mail store extending mix format messaging architects email security email archiving solutions positioned gartner magic quadrant reports 2009 m+archive positioned magic quadrant email active archiving 2009 m+guardian email security solution achieve one gold two vbspam platinum awards virus bulletin anti-spam certification messaging architects also offers range remote on-site services managing email risk co-existence different email platforms including professional services email migration services email consulting email policy training
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Computer security
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rapid rapid high-level programming language used control abb industrial robots rapid introduced along s4 control system 1994 abb superseding arla programming language features language include
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Programming language topics
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richcopy richcopy discontinued file copy utility program developed ken tamaru microsoft corporation multi-threaded may thus circumstances copy files faster utilities available windows operating system additionally similarities like multithreaded copying microsoft utility robocopy provides complete graphical user interface gui whereas robocopy command-line utility although gui interfaces robocopy richcopy copy files opened certain combinations file sharing attributes process may open files exclusive read access withholding file_share_read another company created non-free gs richcopy 360 copy open files developed
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Computer file systems
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shred spam harassment reduction via economic disincentives shred proposed sender-at-risk e-mail stamp mechanism reducing e-mail spamming problem indirectly increasing cost e-mail sending senders unwanted e-mail aims avoid defects earlier sender-at-risk mechanisms main aim shred provide economic incentives legitimate isps clean botnet problem within networks making cheaper continue pay excess postage charges delivered spam messages whilst requiring shred mandated universally adopted effective smtp re-engineered shred differs e-mail postage stamp systems shred stamps represent potential financial liability e-mail sender rather unconditional cost incur replacement cost cancelled e-mail recipient considers e-mail unwanted shred thus effectively electronic reputation system reputation—in form able affix stamps e-mail—is lost complaints bought back money thus imposing financial cost loss reputation presence absence stamp used e-mail receivers together sources information blacklists whitelists content analysis make judgments whether e-mail relayed delivered
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Computer security
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next risc workstation next risc workstation nrw unreleased computer workstation designed next early 1990s successor m68k-based nextcube nextstation initially nrw based motorola 88110 microprocessor due lack confidence motorola commitment 88k architecture later redesigned around dual powerpc 601s pre-production motherboards enclosures produced nrw enter production next exited hardware market 1993
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Operating systems
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web application security web application security branch information security deals specifically security websites web applications web services high level web application security draws principles application security applies specifically internet web systems majority web application attacks occur cross-site scripting xss sql injection attacks typically made possible flawed coding failure sanitize application inputs outputs attacks ranked 2009 cwe/sans top 25 dangerous programming errors according security vendor cenzic top vulnerabilities march 2012 include open web application security project owasp provides free open resources led non-profit called owasp foundation owasp top 10 2017 published result recent research based comprehensive data compiled 40 partner organizations data approximately 2.3 million vulnerabilities discovered across 50,000 applications according owasp top 10 2017 ten critical web application security risks include secure web application development enhanced applying security checkpoints techniques early stages development well throughout software development lifecycle special emphasis applied coding phase development security mechanisms used include threat modeling risk analysis static analysis digital signature among others owasp emerging standards body web application security particular published owasp top 10 describes detail major threats web applications web application security consortium wasc created web hacking incident database whid also produced open source best practice documents web application security whid became owasp project february 2014 security fundamentally based people processes number technical solutions consider designing building testing secure web applications high level solutions include
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Computer security
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tile processor tile processors multicore manycore chips contain one-dimensional commonly two-dimensional arrays identical tiles tile comprises compute unit processing engine cpu caches switch tiles viewed adding switch core core comprises compute unit caches typical tile processor configuration switches tiles connected using one mesh networks tilera tile pro 64 example contains 64 tiles tiles comprises cpu l1 l2 caches switches several mesh networks processors tile configuration include seaforth24 kilocore kc256 xmos xcore microcontrollers massively parallel processor arrays
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Computer architecture
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robotics middleware robotics middleware middleware used complex robot control software systems described software glue make easier robot builders focus specific problem area wide variety projects robotics middleware exist one dominates fact many robotic systems use middleware middleware products rely wide range different standards technologies approaches make use interoperation difficult developers may prefer integrate system player project formerly player/stage project project create free software research robotics sensor systems components include player network server stage robot platform simulators although accurate statistics hard obtain player one popular open-source robot interfaces research post-secondary education major intelligent robotics journals conferences regularly publish papers featuring real simulated robot experiments using player stage rt-middleware common platform standards robots based distributed object technology rt-middleware supports construction various networked robotic systems integration various network-enabled robotic elements called rt-components specification standard rt-components discussed defined object management group omg urbi open source cross-platform software platform c++ used develop applications robotics complex systems based uobject distributed c++ component architecture also includes urbiscript orchestration language parallel event-driven script language uobject components plugged urbiscript appear native objects scripted specify interactions data exchanges uobjects linked urbiscript interpreter executed autonomous processes remote mode either another thread another process machine local network machine distant network miro distributed object oriented framework mobile robot control based corba common object request broker architecture technology miro core components developed aid ace adaptive communications environment object oriented multi-platform framework os-independent interprocess network real time communication use tao ace orb orb object request broker corba implementation designed high performance real time applications currently supported platforms include pioneers b21 robot soccer robots various robotic sensors orca describes goals also state successful think framework objectives must general flexible extensible sufficiently robust high-performance full-featured use commercial applications yet sufficiently simple experimentation university research environments describe approach orca software released lgpl gpl licenses openrdk open-source software framework robotics developing loosely coupled modules provides transparent concurrency management inter-process via sockets intra-process via shared memory blackboard-based communication linking technique allows input/output data ports conceptual system design modules connecting simulators generic robot drivers provided rock robot construction kit software framework development robotic systems underlying component model based orocos rtt real time toolkit rock provides tools required set run high-performance reliable robotic systems wide variety applications research industry contains rich collection ready use drivers modules use system easily extended adding new components isaac nvidia® isaac software development kit sdk developer toolbox accelerating development deployment artificial intelligence-powered robots sdk includes isaac robot engine packages high-performance robotics algorithms perform perception navigation hardware reference applications isaac sim virtual robotics laboratory high-fidelity 3d world simulator accelerates research design development robotics reducing cost risk developers quickly easily train test robots detailed highly realistic scenarios open source community version available github suppported hardware platform includes bom details refer kaya-robot ros robot operating system collection software frameworks robot software development heterogeneous computer cluster ros provides standard operating system services hardware abstraction low-level device control implementation commonly used functionality message-passing processes package management yarp open-source software package written c++ interconnecting sensors processors actuators robots
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Operating systems
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racetrack problem racetrack problem specific instance type race condition racetrack problem flaw system process whereby output and/or result process unexpectedly critically dependent sequence timing events run circular pattern note problem semantically different race condition circular nature problem term originates idea two signals racing circular motion influence output first racetrack problems occur electronics systems especially logic circuits computer software especially multithreaded distributed programs
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Computer security
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webroot window washer webroot window washer tool designed protect user privacy permanently deleting traces web browsing history personal information files computer running microsoft windows currently versions planned program longer updated window washer .95 first launch product originally designed remove unwanted files accumulate computer ’ hard drive surfing internet areas trace file removal include internet history address bar cache cookies recent documents list recycle bin icq history temporary internet files stored computer web search window washer total removal feature completely erases everything found hard drive including operating system beginning 1.0 version launch mid-1998 new process added file deletion process known “ bleaching ” file encryption process seeks files random characters names destroys permanently removes computer ’ hard drive custom cookie selection feature also added allow users select specific cookies excluded deletion process making homepages internet preferences logins passwords stored future visits website software updates also included ability clean chk files created scandisk third party programs files activex java downloaded internet explorer 2.0 version updates launched late 1998 primarily designed able match advancements visual improvements windows 95/98 nt 4.0 window washer adapted user interface allow users use software multiple users programming new window ’ operations systems version window washer also supported netscape 4.5 internet explorer 5.0 well added features came along keyword storing feature search engines personal information stored entered online auto-complete form users also gained ability reassign wash path commonly washed items command-line washes routine cleaning cycles reprogrammed include cleaning information stored windows registry aka “ streams ” deletes tracking paths past actions user additional features 2.0 launch included real-time counter drive space restored items washed added status window custom plug-ins also made available beginning version history pathways left behind popular media programs realplayer adobe acrobat would included wash cycles customizable user interface added feature 3.0 version launch early 2000 additional third party plug-ins made available download well ability wash recent history cache windows media player increased compatibility also added netscape 6 msn explorer 6 aol 6 interface updated include easier custom configuration preferences settings notable upgrade 4.0 version addition automatic check updates feature release also included enhanced password security improvement destroying deleting function bleaching increased efficiency cleaning sweeps overall version 4.0 made window washer compatible aol 7.0 beta netscape 6.1 windows xp internet explorer 6.0 window washer 5.0 eventually included requested feature one-click personal privacy safety option shreds permanently destroys deletes files folders version 5.0 also came built safety feature prompts user confirm requested delete files categories personal files commonly stored operating system files saved files unintentionally deleted 5.0 features included cookie keeper helps maintain internet settings personal favorites option organize frequently visited sites without deleted clean-up cycles 6.0 product launch included completely new user interface well cleaning internet browsers including mozilla firefox version 6.6 latest version product available makes window washer compatible windows 7 windows vista operating system 32 bit 64 bit also includes cleaning functions internet explorer 8
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Computer security
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clearforest clearforest israeli software company developed marketed text analytics text mining solutions founded 1998 clearforest headquarters outside boston development center yehuda company acquired reuters april 2007 markets services names calais opencalais onecalais clearforest previously venture-backed last funding round led greylock ventures closed 2005 investors included db capital partners pitango walden israel booz allen jp morgan partners harbourvest partners february 7 2008 reuters announced launch open calais named-entity recognition semantic analysis service uses clearforest technology april 30 2007 reuters announced would acquire clearforest sources estimate acquisition 25 million clearforest offers several hosted solutions including clearforest also offers text analytics solutions targeted specific business problems including
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Computational linguistics
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uk detector finds database uk detector finds database initiative members metal-detecting community united kingdom promote good practice within hobby online facility detectorists record finds ensure information preserved future generations joining scheme immediate access database uploading details finds instructions provided stage process personal gallery created user entering first record grows may browsed searched way personal database items submitted reviewed scheme team experts full identification details provided confirmed soon possible users also able record detector make model performance different circumstances different types find may assessed
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Databases
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includeos includeos minimal open source unikernel operating system cloud services iot includeos allows users run c++ applications cloud without operating system includeos adds operating system functionality application allowing oneself create 'virtual machine application includeos applications boot tens milliseconds require megabytes disk memory minimalist architecture includeos means virtual memory space turn therefore concept system calls user space
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Operating systems
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palm iiic palm iiic first colour pda made palm inc started sold 1998 ran palm os 3.5 first palm os version native colour support supported paletted 8-bit colour modes machine tft lcd bright indoors palm iiic features classic iii-series connector 8mb ram 20mhz dragonball ezi cpu unit also lithium ion rechargeable battery slightly modified version original palm iii chassis
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Computer architecture
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powerpc 7xx powerpc 7xx family third generation 32-bit powerpc microprocessors designed manufactured ibm motorola freescale semiconductor family called powerpc g3 well-known customer apple inc. introduced november 10 1997 term powerpc g3 often incorrectly imagined microprocessor fact number microprocessors different vendors used designations applied macintosh computers powerbook g3 multicolored imacs ibooks several desktops including beige blue white power macintosh g3s low power requirements small size made processors ideal laptops name lived last days apple ibook 7xx family also widely used embedded devices like printers routers storage devices spacecraft video game consoles 7xx family shortcomings namely lack smp support simd capabilities relatively weak fpu motorola 74xx range processors picked 7xx left powerpc 740 750 codename arthur introduced late 1997 evolutionary replacement powerpc 603e enhancements included faster 60x system bus 66 mhz larger l1 caches 32 kb instruction 32 kb data second integer unit enhanced floating point unit higher core frequency 750 support optional 256 512 1024 kb external unified l2 cache cache controller cache tags on-die cache accessed via dedicated 64-bit bus 740 750 added dynamic branch prediction 64-entry branch target instruction cache btic dynamic branch prediction uses recorded outcome branch stored 512-entry 2-bit branch history table bht predict outcome btic caches first two instructions branch target 740/750 models 6.35 million transistors initially manufactured ibm motorola aluminium based fabrication process die measured 67 mm 0.26 μm reached speeds 366 mhz consuming 7.3 w. 1999 ibm fabricated versions 0.20 μm process copper interconnects increased frequency 500 mhz decreased power consumption 6 w die size 40 mm 740 slightly outperformed pentium ii consuming far less power smaller die off-die l2 cache 750 increased performance approximately 30 situations design successful quickly surpassed powerpc 604e integer performance causing planned 604 successor scrapped powerpc 740 completely pin compatible older 603 allowing upgrades powerbook 1400 2400 even prototype powerbook 500/g3 750 l2 cache bus required pins thus different package 360-pin ball grid array bga powerpc 750 used many computers apple including original imac radiation-hardened processor based powerpc 750 intended use high radiation environments experienced board satellites spacecraft rad750 released purchase 2001 mars science laboratory curiosity mars reconnaissance orbiter spacecraft rad750 board processor 10.4 million transistors manufactured bae systems using either 250 150 nm process die area 130 mm² operates 110 200 mhz cpu withstand 200,000 1,000,000 rads temperature ranges −55 125 °c rad750 packaging logic functions price tag excess us 200,000 high price mainly due radiation hardening revisions powerpc 750 architecture manufacturing stringent quality control requirements extended testing processor chip manufactured motorola revised 740/750 design 1998 shrunk die size 51 mm thanks newer aluminium based fabrication 0.22 μm speeds increased 600 mhz 755 used ibook models model motorola chose keep developing 750 processors favour powerpc 7400 processor cores ibm continued develop powerpc 750 line introduced powerpc 750cx code-named sidewinder 2000 256 kib on-die l2 cache increased performance reducing power consumption complexity 400 mhz drew 4 w. 750cx 20 million transistors including l2 cache die size 43 mm 0.18 μm copper process 750cx used one imac ibook revision 750cxe codename anaconda introduced 2001 minor revision 750cx increased frequency 700 memory bus 100 mhz 133 mhz 750cxe also featured improved floating-point performance 750cx several ibook models last g3-based imac used processor cost reduced version 750cxe called 750cxr available lower frequencies gekko custom central processor nintendo gamecube game console based powerpc 750cxe adds 50 new instructions well modified fpu capable simd functionality 256 kib die l2 cache operates 485 mhz 162 mhz memory bus fabricated ibm 180 nm process die 43 mm large 750fx code-named sahara came 2002 increased frequency 900 mhz bus speed 166 mhz on-die l2 cache 512 kib also featured number improvements memory subsystem enhanced faster 200 mhz 60x bus controller wider l2 cache bus ability lock parts l2 cache manufactured using 0.13 μm copper based fabrication low-k dielectric silicon insulator technology 750fx 39 million transistors die size 35 mm consumes less 4 w 800 mhz typical loads last g3 type processor used apple employed ibook g3 low powered version 750fx available called 750fl 750fx powers nasa orion multi-purpose crew vehicle orion using honeywell international inc. flight computer originally built boeing 787 jet airliner 750gx codenamed gobi revealed 2004 latest powerful 7xx processor ibm on-die 1 mb l2 cache top frequency 1.1 ghz support bus speeds 200 mhz among enhancements compared 750fx manufactured using 0.13 μm process copper interconnects low-k dielectric silicon insulator technology 750gx 44 million transistors die size 52 mm consumes less 9 w 1 ghz typical loads low-power version 750gx available called 750gl 750vx codenamed mojave rumored confirmed canceled version 7xx line would powerful featured version date 4mb die l3 cache 400mhz ddr front side bus implementation altivec used powerpc 970 expected clock high 1.8 ghz starting 1.5 ghz reported additional pipeline stages advanced power management features reported finished ready production december 2003 said timing late get significant orders seeing apple ibook line switched g4s october year thus quickly fell roadmap never released heard since follow chips planned 750vxe would surpassed 2 ghz 750cl evolved 750cxe speeds ranging 400 mhz 1 ghz system bus 240 mhz l2 cache prefetch features graphics related instructions added improve performance added graphics-related functions match closely ones found gekko processor likely 750cl shrink processor general purpose use 750cl manufactured using 90 nm copper based fabrication low-k dielectric silicon insulator technology features 20 million transistors 16 mm die draws 2.7 w 600 mhz 9.8 w 1 ghz cpu wii virtually identical 750cl runs 729 mhz frequency supported stock 750cl measures 4.2 x 4.5 mm 18.9 mm smaller half size gekko microprocessor 43 mm incorporated gamecube first release cpu wii u believed evolution broadway architecture largely unconfirmed characteristics triple core cpu runs 1.24 ghz manufactured 45 nm process ibm ceased publish roadmap 750 family favor marketing custom processor vendor given ibm resources 750 core produced new features long willing buyer particular ibm public plans produce ordinary 750-based microprocessor process smaller 90 nm effectively phasing commodity chip competitive markets networking equipment however ibm make espresso processor nintendo 750 based design improvements multiprocessor support part triple core new 45 nm fabrication process edram instead regular l2 cache unknown changes made design 2015 rochester electronics started providing legacy support devices freescale discontinued 750 designs favor designs based powerpc e500 core powerquicc iii list complete list known 750 based designs pictures illustrations scale
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Computer architecture
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democratic congressional campaign committee cyber attacks friday july 29 2016 democratic congressional campaign committee reported computer systems infiltrated strongly believed us intelligence sources infiltrator groups russian foreign intelligence groups breached democratic national committee computer systems groups known fancy bear cozy bear sofacy crowdstrike assisted efforts deal dccc breach significant concern russians attempting influence 2016 presidential campaign russian cyber intrusions united states government private sector computer systems significantly increased u.s imposed sanctions russia invasion crimea ukraine president obama preference publicize cyber attacks
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Computer security
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areca backup areca backup personal file backup software developed java released gnu general public license gpl 2 areca backup includes backup engine well graphical user interface command-line interface application includes following features areca also provides tools needed handle archives storage modes areca handle multiple storage modes backup types areca handle following types backups areca uses file size last modification time detect modified files one attributes modified whatever value file flagged modified allows fast detection modified files areca downloadable pre-packaged linux windows 2000/windows xp windows vista also runs operating system provided java runtime environment installed version 1.4.2 later translated chinese simplified chinese traditional czech danish dutch english french german hungarian italian japanese russian spanish swedish
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Computer security
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panzura panzura privately held company based us markets computer data storage products panzura founded 2008 randy chou john taylor members founding software team aruba networks company incorporated delaware first headquartered san jose california funded november 2010 12 million company initially funded matrix partners khosla ventures chevron technology ventures arm chevron corporation june 2012 opus capital led round 15 million funding included previous investors round 25 million funding june 2013 included meritech capital partners july 2013 flash memory maker sandisk announced new strategic investor alex lam sandisk joining board observer based campbell california 2013 panzura provides cloud storage data protection specialized cloud storage controllers panzura products accessed using network-attached storage nas protocols allow users secure access latest versions file widely distributed locations industry analysts sometimes call kind product cloud storage gateway available hardware appliance called quicksilver software-only use vmware esx quicksilver best show award may 2012 interop trade show panzura global cloud storage system integrates cloud storage platforms including amazon web services cleversafe emc atmos google hp cloud services nirvanix panzura received three patents technology 2013 panzura offers proprietary software delivered hardware appliances virtual machine licenses installed locally backup actively archive centralize data remote location architectural firm diller scofidio renfro credited panzura technology speeding backup recovery data hurricane sandy california state university northridge also used technology backing data march 2013 panzura announced achieved fips 140-2 security certification national institute standards technology use us government agencies contractors
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Distributed computing architecture
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database tuning database tuning describes group activities used optimize homogenize performance database usually overlaps query tuning refers design database files selection database management system dbms application configuration database environment operating system cpu etc. database tuning aims maximize use system resources perform work efficiently rapidly possible systems designed manage use system resources still much room improve efficiency customizing settings configuration database dbms hardware software configuration disk subsystems examined raid levels configuration block stripe size allocation configuration disks controller cards storage cabinets external storage systems sans transaction logs temporary spaces heavy consumers i/o affect performance users database placing appropriately crucial frequently joined tables indexes placed requested file storage retrieved parallel separate disks simultaneously frequently accessed tables indexes placed separate disks balance i/o prevent read queuing dbms tuning refers tuning dbms configuration memory processing resources computer running dbms typically done configuring dbms resources involved shared host system tuning dbms involve setting recovery interval time needed restore state data particular point time assigning parallelism breaking work single query tasks assigned different processing resources network protocols used communicate database consumers memory allocated data execution plans procedure cache much faster access data memory data storage maintaining sizable cache data makes activities perform faster consideration given work space caching execution plans procedures means reused instead recompiled needed important take much memory possible leaving enough processes os use without excessive paging memory storage processing resources sometimes assigned specific activities improve concurrency server eight processors six could reserved dbms maximize available processing resources database utilizes machine learning learn evaluate performance various workloads database maintenance includes backups column statistics updates defragmentation data inside database files heavily used database transaction log grows rapidly transaction log entries must removed log make room future entries frequent transaction log backups smaller interrupt database activity shorter periods time dbms use statistic histograms find data range table index statistics updates scheduled frequently sample much underlying data possible accurate updated statistics allow query engines make good decisions execution plans well efficiently locate data defragmentation table index data increases efficiency accessing data amount fragmentation depends nature data changed time amount free space database pages accept inserts data without creating additional pages
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Databases
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server-side scripting server-side scripting technique used web development involves employing scripts web server produce response customized user client request website alternative web server deliver static web page scripts written number server-side scripting languages available see server-side scripting distinguished client-side scripting embedded scripts javascript run client-side web browser techniques often used together server-side scripting often used provide customized interface user scripts may assemble client characteristics use customizing response based characteristics user requirements access rights etc server-side scripting also enables website owner hide source code generates interface whereas client-side scripting user access code received client down-side use server-side scripting client needs make requests network server order show new information user via web browser requests slow experience user place load server prevent use application user disconnected server server serves data commonly used manner example according http ftp protocols users may choice number client programs modern web browsers request receive data using protocols case specialized applications programmers may write server client communications protocol used one another programs run user local computer without ever sending receiving data network considered clients operations programs would considered client-side operations netscape introduced implementation javascript server-side scripting netscape enterprise server first released december 1994 soon releasing javascript browsers server-side scripting later used early 1995 fred dufresne developing first web site boston television station wcvb technology described us patent 5835712 patent issued 1998 owned open invention network oin 2010 oin named fred dufresne distinguished inventor work server-side scripting today variety services use server-side scripting deliver results back client paid free service example would wolframalpha computational knowledge engine computes results outside clients environment returns computed result back commonly used service google proprietary search engine searches millions cached results related user specified keyword returns ordered list links back client apple siri application also employs server-side scripting outside web application application takes input computes result returns result back client earlier days web server-side scripting almost exclusively performed using combination c programs perl scripts shell scripts using common gateway interface cgi scripts executed operating system results served back web server many modern web servers directly execute on-line scripting languages asp jsp perl php ruby either web server via extension modules e.g mod_perl mod_php web server example webdna includes embedded database system either form scripting i.e. cgi direct execution used build complex multi-page sites direct execution usually results less overhead lower number calls external interpreters dynamic websites sometimes use custom web application servers glassfish plack python base http server library although may consider server-side scripting using dynamic web-based scripting techniques developers must keen understanding logical temporal physical separation client server user action trigger execution server-side code example developer working classic asp must explicitly cause user browser make request back web server creating interactions easily consume much development time lead unreadable code server-side scripts completely processed servers instead clients clients request page containing server-side scripts applicable server processes scripts returns html page client number server-side scripting languages available including
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Programming language topics
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asynchronous module definition asynchronous module definition amd specification programming language javascript defines application programming interface api defines code module dependencies loads asynchronously desired implementations amd provide following benefits addition loading multiple javascript files runtime amd implementations allow developers encapsulate code smaller logically-organized files way similar programming languages java production deployment developers concatenate minify javascript modules based amd api one file traditional javascript amd specification implemented dojo toolkit requirejs libraries
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Programming language topics
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ibm system/360 ibm system/360 s/360 family mainframe computer systems announced ibm april 7 1964 delivered 1965 1978 first family computers designed cover complete range applications small large commercial scientific design made clear distinction architecture implementation allowing ibm release suite compatible designs different prices partially compatible model 44 expensive systems use microcode implement instruction set features 8-bit byte addressing binary decimal hexadecimal floating-point calculations launch system/360 family introduced ibm solid logic technology slt new technology start powerful smaller computers slowest system/360 model announced 1964 model 30 could perform 34,500 instructions per second memory 8 64 kb high performance models came later 1967 ibm system/360 model 91 could 16.6 million instructions per second larger 360 models could 8 mb main memory though main memory big unusual—a large installation might little 256 kb main storage 512 kb 768 kb 1024 kb common 8 megabytes slower 8 microsecond large capacity storage lcs also available ibm 360 extremely successful market allowing customers purchase smaller system knowledge would always able migrate upward needs grew without reprogramming application software replacing peripheral devices many consider design one successful computers history influencing computer design years come chief architect system/360 gene amdahl project managed fred brooks responsible chairman thomas j. watson jr commercial release piloted another watson lieutenants john r. opel managed launch ibm ’ system 360 mainframe family 1964 application-level compatibility restrictions system/360 software maintained present day system z mainframe servers contrasting at-the-time normal industry practice ibm created entire new series computers small large low- high-performance using instruction set two exceptions specific markets feat allowed customers use cheaper model upgrade larger systems needs increased without time expense rewriting software introduction system/360 business scientific applications used different computers different instruction sets operating systems different-sized computers also instruction sets ibm first manufacturer exploit microcode technology implement compatible range computers widely differing performance although largest fastest models hard-wired logic instead flexibility greatly lowered barriers entry vendors customers choose machines could outgrow machines potentially powerful thus costly meant many companies simply buy computers ibm initially announced series six computers forty common peripherals ibm eventually delivered fourteen models including rare one-off models nasa least expensive model model 20 little 4096 bytes core memory eight 16-bit registers instead sixteen 32-bit registers system/360 models instruction set subset used rest range initial announcement 1964 included models 30 40 50 60 62 70 first three low- middle-range systems aimed ibm 1400 series market three first shipped mid-1965 last three intended replace 7000 series machines never shipped replaced 65 75 first delivered november 1965 january 1966 respectively later additions low-end included models 20 1966 mentioned 22 1971 25 1968 model 20 several sub-models sub-model 5 higher end model model 22 recycled model 30 minor limitations smaller maximum memory configuration slower i/o channels limited slower lower-capacity disk tape devices 30 model 44 1966 specialized model designed scientific computing real-time computing process control featuring additional instructions storage-to-storage instructions five complex instructions eliminated succession high-end machines included model 67 1966 mentioned briefly anticipated 64 66 85 1969 91 1967 anticipated 92 95 1968 195 1971 85 design intermediate system/360 line follow-on system/370 basis 370/165 system/370 version 195 include dynamic address translation implementations differed substantially using different native data path widths presence absence microcode yet extremely compatible except specifically documented models architecturally compatible 91 example designed scientific computing provided out-of-order instruction execution could yield imprecise interrupts program trap occurred several instructions read lacked decimal instruction set used commercial applications new features could added without violating architectural definitions 65 dual-processor version m65mp extensions inter-cpu signalling 85 introduced cache memory models 44 75 91 95 195 implemented hardwired logic rather microcoded models model 67 announced august 1965 first production ibm system offer dynamic address translation virtual memory hardware support time-sharing dat commonly referred mmu experimental one-off unit built based model 40 67 ibm announced models 64 66 dat versions 60 62 almost immediately replaced 67 time 60 62 replaced 65 dat hardware would reappear s/370 series 1972 though initially absent series like close relative 65 67 also offered dual cpus ibm stopped marketing system/360 models end 1977 ibm existing customers large investment software executed second-generation machines several models offered option emulation customer previous computer using combination special hardware special microcode emulation program used emulation instructions simulate target system old programs could run new machine however customers initially halt computer load emulation program ibm later added features modified emulator programs allow emulation 1401 1440 1460 1410 7010 control operating system model 85 later system/370 maintained precedent retaining emulation options allowing emulator programs execute operating system control alongside native programs system/360 excepting model 20 replaced compatible system/370 range 1970 model 20 users targeted move ibm system/3 idea major breakthrough fs technology dropped mid-1970s cost-effectiveness continuity reasons later compatible ibm systems include 4300 family 308x family 3090 es/9000 9672 families system/390 family ibm z series computers mostly identical compatible terms machine code architecture system/360 included amdahl 470 family successors hitachi mainframes univac 9000 series fujitsu facom rca spectra 70 series english electric system 4 system 4 machines built license rca rca sold spectra series univac became univac series 70 univac also developed univac series 90 successors 9000 series series 70 soviet union produced system/360 clone named es evm ibm 5100 portable computer introduced 1975 offered option execute system/360 apl.sv programming language hardware emulator ibm used approach avoid costs delay creating 5100-specific version apl special radiation-hardened otherwise somewhat modified system/360s form system/4 pi avionics computer used several fighter bomber jet aircraft complete 32-bit ap-101 version 4 pi machines used replicated computing nodes fault-tolerant space shuttle computer system five nodes u.s. federal aviation administration operated ibm 9020 special cluster modified system/360s air traffic control 1970 1990s 9020 software apparently still used via emulation newer hardware system/360 introduced number industry standards marketplace system/360 series computer system architecture specification specification makes assumptions implementation rather describes interfaces expected behavior implementation architecture describes mandatory interfaces must available implementations optional interfaces aspects architecture optional features models system/360 except model 20 model 44 implemented specification binary arithmetic logical operations performed register-to-register memory-to-register/register-to-memory standard feature commercial instruction set option installed packed decimal arithmetic could performed memory-to-memory memory-to-register operations scientific instruction set feature installed provided access four floating point registers could programmed either 32-bit 64-bit floating point operations models 85 195 could also operate 128-bit extended-precision floating point numbers stored pairs floating point registers software provided emulation models system/360 used 8-bit byte 32-bit word 64-bit double-word 4-bit nibble machine instructions operators operands could contain register numbers memory addresses complex combination instruction options resulted variety instruction lengths formats memory addressing accomplished using base-plus-displacement scheme registers 1 f 15 displacement encoded 12 bits thus allowing 4096-byte displacement 0-4095 offset address put base register register 0 could used base register index register branch address register 0 reserved indicate address first 4 kb memory register 0 specified described value 0x00000000 implicitly input effective address calculation place whatever value might contained within register 0 specified branch address register branch taken content register 0 ignored side effect instruction performed specific behavior permitted initial execution interrupt routines since base registers would necessarily set 0 first instruction cycles interrupt routine n't needed ipl initial program load boot one always clear register without need save exception model 67 addresses real memory addresses virtual memory available ibm mainframes system/370 series model 67 introduced virtual memory architecture mts cp-67 tss/360 used—but ibm mainline system/360 operating systems system/360 machine-code instructions 2 bytes long memory operands 4 bytes long one operand 6 bytes long two operands instructions always situated 2-byte boundaries operations like mvc move-characters hex d2 move 256 bytes information moving 256 bytes data required multiple mvc operations system/370 series introduced family powerful instructions mvcl move-characters-long instruction supports moving 16 mb single block operand two bytes long typically representing address 4-bit nibble denoting base register 12-bit displacement relative contents register range 000–fff shown hexadecimal numbers address corresponding operand contents specified general-purpose register plus displacement example mvc instruction moves 256 bytes length code 255 hexadecimal ff base register 7 plus displacement 000 base register 8 plus displacement 001 would coded 6-byte instruction d2ff 8001 7000 operator/length/address1/address2 system/360 designed separate system state problem state provided basic level security recoverability programming errors problem user programs could modify data program storage associated system state addressing data operation exception errors made machine enter system state controlled routine operating system could try correct terminate program error similarly could recover certain processor hardware errors machine check routines peripherals interfaced system via channels channel specialized processor instruction set optimized transferring data peripheral main memory modern terms could compared direct memory access dma initially two types channels byte-multiplexer channels known time simply multiplexor channels connecting slow speed devices card readers punches line printers communications controllers selector channels connecting high speed devices disk drives tape drives data cells drums every system/360 except model 20 standard 360 byte-multiplexer channel 1 selector channels smaller models model 50 integrated channels larger models model 65 channels large separate units separate cabinets ibm 2860 2870 60 62 70 allowed 2860 selector channels assumption would smaller 360s attached would slow-speed work byte-multiplexer channel able handle i/o to/from several devices simultaneously device highest rated speeds hence name multiplexed i/o devices onto single data path main memory devices connected byte-multiplexer channel configured operate 1-byte 2-byte 4-byte burst mode larger blocks data used handle progressively faster devices example 2501 card reader operating 600 cards per minute would 1-byte mode 1403-n1 printer would burst mode also byte-multiplexer channels larger models optional selector subchannel section would accommodate tape drives byte-multiplexor channel address typically 0 selector subchannel addresses c0 ff thus tape drives system/360 commonly addressed 0c0-0c7 common byte-multiplexer addresses 00a 2501 card reader 00c/00d 2540 reader/punch 00e/00f 1403-n1 printers 010-013 3211 printers 020-0bf 2701/2703 telecommunications units addresses still commonly used z/vm virtual machines system/360 models 40 50 integrated 1052-7 console usually addressed 01f however connected byte-multiplexer channel rather direct internal connection mainframe model 30 attached different model 1052 1051 control unit models 60 75 also use 1052-7 selector channels enabled i/o high speed devices storage devices attached control unit channel control unit let clusters devices attached channels higher speed models multiple selector channels could operate simultaneously parallel improved overall performance control units connected channels bus tag cable pairs bus cables carried address data information tag cables identified data bus general configuration channel connect devices chain like mainframe—control unit x—control unit y—control unit z control unit assigned capture range addresses services example control unit x might capture addresses 40-4f control unit c0-df control unit z 80-9f capture ranges multiple 8 16 32 64 128 devices aligned appropriate boundaries control unit turn one devices attached example could control unit 6 disks would addressed c0-c5 three general types bus-and-tag cables produced ibm first standard gray bus-and-tag cable followed blue bus-and-tag cable finally tan bus-and-tag cable generally newer cable revisions capable higher speeds longer distances peripherals specified minimum cable revisions upstream downstream cable ordering control units channel also significant control unit strapped high low priority device selection sent mainframe channel selection sent x- y- z- y- x control unit high selection checked outbound direction low inbound direction thus control unit x either 1st 5th either 2nd 4th z 3rd line also possible multiple channels attached control unit multiple mainframes thus providing rich high-performance multiple-access backup capability typically total cable length channel limited 200 feet less preferred control unit accounts 10 feet 200-foot limit ibm introduced new type i/o channel model 85 model 195 2880 block multiplexer channel channel allowed device suspend channel program pending completion i/o operation thus free channel use another device channels support either standard 1.5 mb/second connections 2-byte interface feature 3 mb/second latter use one tag cable two bus cables initial use 2305 fixed-head disk 8 exposures alias addresses rotational position sensing rps standard system/370 thereafter block multiplexer channels operate selector channel allow compatible attachment legacy subsystems uncertain reliability availability new monolithic integrated circuits ibm chose instead design manufacture custom hybrid integrated circuits built 11 mm square ceramic substrates resistors silk screened discrete glass encapsulated transistors diodes added substrate covered metal lid encapsulated plastic create solid logic technology slt module number slt modules flip chip mounted onto small multi-layer printed circuit slt card card one two sockets one edge plugged onto pins one computer slt boards reverse company cards mounted cards pins printed contact areas plugged sockets computer boards twenty slt boards could assembled side-by-side vertically horizontally form logic gate several gates mounted together constituted box-shaped logic frame outer gates generally hinged along one vertical edge could swung open provide access fixed inner gates larger machines could one frame bolted together produce final unit multi-frame central processing unit cpu smaller system/360 models used basic operating system/360 bos/360 tape operating system tos/360 disk operating system/360 dos/360 evolved dos/vs dos/vse vse/af vse/sp vse/esa z/vse larger models used operating system/360 os/360 ibm developed several versions os/360 increasingly powerful features primary control program pcp multiprogramming fixed number tasks mft multiprogramming variable number tasks mvt mvt took long time develop usable system less ambitious mft widely used pcp used intermediate machines final releases os/360 included mft mvt system/370 later machines mft evolved os/vs1 mvt evolved os/vs2 svs single virtual storage various versions mvs multiple virtual storage culminating current z/os announced model 67 august 1965 ibm also announced tss/360 time-sharing system delivery time 67 tss/360 response multics ambitious project included many advanced features performance problems delayed canceled reinstated finally canceled 1971 customers migrated cp-67 mts michigan terminal system tso time sharing option os/360 one several time-sharing systems cp-67 original virtual machine system also known cp/cms cp/67 developed outside ibm mainstream ibm cambridge scientific center cooperation mit researchers cp/cms eventually wide acceptance led development vm/370 virtual machine primary interactive sub operating system known vm/cms conversational monitoring system evolved today z/vm model 20 offered simplified rarely used tape-based system called tps tape processing system dps disk processing system provided support 2311 disk drive tps could run machine 8 kb memory dps required 12 kb pretty hefty model 20 many customers ran quite happily 4 kb cps card processing system tps dps card reader used read job control language cards defined stack jobs run read transaction data customer payments operating system held tape disk results could also stored tapes hard drives stacked job processing became exciting possibility small adventurous computer user little-known little-used suite 80-column punched-card utility programs known basic programming support bps jocularly barely programming support precursor tos available smaller systems ibm created new naming system new components created system/360 although well-known old names like ibm 1403 ibm 1052 retained new naming system components given four-digit numbers starting 2 second digit described type component follows ibm developed new family peripheral equipment system/360 carrying older 1400 series interfaces standardized allowing greater flexibility mix match processors controllers peripherals earlier product lines addition system/360 computers could use certain peripherals originally developed earlier computers earlier peripherals used different numbering system ibm 1403 chain printer 1403 extremely reliable device already earned reputation workhorse sold 1403-n1 adapted system/360 also available optical character recognition ocr readers ibm 1287 ibm 1288 could read alpha numeric a/n numeric hand printed nhp/nhw characters cashier rolls tape full legal size pages time done large optical/logic readers software slow expensive time small systems sold ibm 1052-7 console typewriter tightly integrated cpu — keyboard would physically lock program control certain high-end machines could optionally purchased 2250 graphical display costing upwards us 100,000 360/85 used 5450 display console compatible anything else line later 3066 console 370/165 370/168 used basic display design 360/85 first disk drives system/360 ibm 2302s ibm 2311s 156 kb/second 2302 based earlier 1302 available model 3 two 112.79 mb modules model 4 four modules 2311 removable 1316 disk pack based ibm 1311 theoretical capacity 7.2 mb although actual capacity varied record design used 360/20 1316 pack formatted fixed-length 270 byte sectors giving maximum capacity 5.4mb 1966 first 2314s shipped device eight usable disk drives integral control unit nine drives one reserved spare drive used removable 2316 disk pack capacity nearly 28 mb disk packs 2311 2314 physically large today standards — e.g. 1316 disk pack diameter six platters stacked central spindle top bottom outside platters store data data recorded inner sides top bottom platters sides inner platters providing 10 recording surfaces 10 read/write heads moved together across surfaces platters formatted 203 concentric tracks reduce amount head movement seeking data written virtual cylinder inside top platter inside bottom platter disks usually formatted fixed-sized sectors today hard drives though done cp/cms rather system/360 i/o software could customize length data record variable-length records case magnetic tapes powerful early system/360s used high-speed head-per-track drum storage devices 3,500 rpm 2301 replaced 7320 part original system/360 announcement capacity 4 mb 303.8 kb/second ibm 2303 announced january 31 1966 capacity 3.913 mb drums announced system/360 system/370 niche later filled fixed-head disks 6,000 rpm 2305 appeared 1970 capacities 5 mb 2305-1 11 mb 2305-2 per module although devices large capacity speed transfer rates made attractive high-performance needs typical use overlay linkage e.g os application subroutines program sections written alternate memory regions fixed head disks drums particularly effective paging devices early virtual memory systems 2305 although often called drum actually head-per-track disk device 12 recording surfaces data transfer rate 3 mb per second rarely seen ibm 2321 data cell mechanically complex device contained multiple magnetic strips hold data strips could randomly accessed placed upon cylinder-shaped drum read/write operations returned internal storage cartridge ibm data cell noodle picker among several ibm trademarked speedy mass online direct-access storage peripherals reincarnated recent years virtual tape automated tape librarian peripherals 2321 file capacity 400 mb time 2311 disk drive 7.2 mb ibm data cell proposed fill cost/capacity/speed gap magnetic tapes—which high capacity relatively low cost per stored byte—and disks higher expense per byte installations also found electromechanical operation less dependable opted less mechanical forms direct-access storage model 44 unique offering integrated single-disk drive standard feature drive used 2315 ramkit cartridge provided 1,171,200 bytes storage 2400 tape drives consisted combined drive control unit plus individual 1/2 tape drives attached system/360 ibm switched ibm 7 track 9 track tape format 2400 drives could purchased read wrote 7-track tapes compatibility older ibm 729 tape drives 1967 slower cheaper pair tape drives integrated control unit introduced 2415 1968 ibm 2420 tape system released offering much higher data rates self-threading tape operation 1600bpi packing density remained product line 1979 despite sold leased large numbers mainframe system era system/360 computers remain mainly non-operating property museums collectors examples existing systems include running list remaining system/360s found world inventory remaining system/360 cpus gallery shows operator console register value lamps toggle switches middle pictures emergency pull switch upper right pictures various models us television series mad men 2007–2015 ibm 360 featured plot device company leased system advertising agency prominent background seventh season crowdfunding campaign rescuing restoring ibm 360 system nuremberg received successful funding
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Computer architecture
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openbravo openbravo cloud-based software provider specialized retail solutions head office openbravo s.l located pamplona spain openbravo also offices barcelona paris mexico df kolkata company main product openbravo commerce cloud cloud-based pos retail management solution worldwide distribution implementations software openbravo relies heavily partner network openbravo multiple-time winner infoworld bossie award best open source software application last awarded august 2014 openbravo roots development business administration software first developed two employees university navarra nicolas serrano ismael ciordia involved mid 1990s developing management university used emerging internet technologies work subsequently introduced new approach web applications concept realized new company called tecnicia founded august 2001 serrano ciordia aguinaga 2005 two management consultants manel sarasa josep mitjá asked venture capital company evaluate tecnicia prepare business plan evolution 2006 two consultants joined tecnicia ceo coo respectively around time spanish investment company sodena invested 6.4 million usd development company 2006 company renamed openbravo first product launched openbravo erp code open-sourced april year 2007 company announced acquisition librepos java-based point-of-sale pos application retail hospitality businesses librepos rebranded openbravo pos openbravo java pos may 2008 openbravo attracted three investors amadeus uk gimv belgium adara spain second investment round totalling 12.5 million usd investment launched openbravo one leading open source companies substantial resources develop products services july 2012 openbravo launched openbravo retail vertical solution retail industry including openbravo web pos new pos solution replaced previous openbravo java pos openbravo web pos web mobile responsive pos solution march 2014 openbravo erp renamed openbravo erp platform openbravo retail renamed openbravo commerce platform may 2015 openbravo commerce platform openbravo erp platform renamed openbravo commerce suite openbravo business suite openbravo announces strategic focus retail openbravo also launches openbravo subscription management recurring billing specialized solution recurring transactions based revenue models openbravo present 60 countries global partner network openbravo targets today mid-sized large organizations seeking complete solution manage entire business specific solutions help improve existing legacy systems openbravo focuses strategy retail openbravo commerce suite openbravo erp first product launched openbravo web-based erp business solution small medium-sized companies released openbravo public license based mozilla public license model program originally based compiere erp program also open source released gnu general public license version 2 program among top ten active projects sourceforge january 2008 using openbravo erp organizations automate register common business processes following processes supported sales procurement manufacturing projects finance mrp numerous commercial extensions available openbravo exchange procured users commercial edition openbravo erp paid-for version offers additional functionality compared free community edition integrated administration tools non-technical tool updates upgrades access openbravo exchange service level agreement characteristic openbravo erp application green web interface users maintain company data web-browser openbravo also create export reports data several formats pdf microsoft excel openbravo java-based architecture focuses two development models two models allow integration programs simple interface application open standards openbravo erp integrated open source applications like magento webshop pentaho business intelligence processmaker bpm liferay portal sugarcrm march 2014 openbravo erp renamed openbravo erp platform changed openbravo business suite may 2015 openbravo pos first pos solution offered openbravo java point-of-sale pos application retail hospitality businesses application came existence called tinapos legal reasons application renamed librepos 2007 librepos acquired openbravo known current name program completely integrated openbravo erp integration possible update stock levels financial journals customer data directly central database pos sales executed stores openbravo pos applied using pdas order intake july 2012 openbravo launched new pos solution openbravo web pos included openbravo commerce suite replaced openbravo java pos openbravo business suite launched may 2015 replacing previous openbravo erp platform global management solution built top openbravo technology platform including horizontal erp crm bi functionality across industries see latest confirmed stable cs release business suite release notes openbravo commerce suite openbravo solution retailers multi-channel retail management solution including responsive web mobile pos openbravo web pos backed comprehensive functionality merchandise management supply chain management enterprise management see latest confirmed stable cs release openbravo commerce suite release notes openbravo web pos launched 2012 included openbravo retail solution today openbravo commerce suite responsive web mobile pos solution core component functionality physical stores openbravo technology platform lies heart openbravo solutions modular mobile-enabled cloud-ready platform providing core set technologies allow extending openbravo fit companies needs developing completely new enterprise solutions looking best html5 framework openbravo mobile decided choose enyo openbravo web pos mobile solution openbravo analytics embedded analytics engine provides business intelligence capabilities openbravo solutions provides infrastructure necessary create analytical cubes olap reports combines power high performing open source business intelligence components pentaho use mondrian saiku allied openbravo user interface provide fully integrated analytics solution commercial solution companies recurring billing revenue models including functionality pricing definition automatic revenue recognition accounting openbravo user interface available multiple languages like english spanish french italian brazilian amongst others openbravo solutions distributed subscription-based model customers subscribe number users and/or pos terminals bundled pack services additional options two different commercial editions customers subscribe additional users and/or pos terminals well additional functionality packaged extension modules examples extension modules country localizations connectors like sugarcrm tools developed openbravo partners addition commercial editions community edition exists free limited set capabilities available without professional support available openbravo partners openbravo products distributed following licenses openbravo many partners across world including exceloid soft systems india
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Distributed computing architecture
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scope computer science computer programming scope name binding – association name entity variable – region computer program binding valid name used refer entity region referred parts program name may refer different entity may different binding nothing may unbound scope binding also known visibility entity particularly older technical literature – perspective referenced entity referencing name scope part program scope set bindings – precise definition tricky casual use practice largely corresponds block function file depending language type entity term scope also used refer set entities visible names valid within portion program given point program correctly referred context environment strictly speaking practice programming languages part program refers portion source code area text known lexical scope languages however part program refers portion run time time period execution known dynamic scope terms somewhat misleading – misuse technical terms discussed definition – distinction accurate precise standard respective terms lexical scope main focus article dynamic scope understood contrast lexical scope cases name resolution based lexical scope relatively straightforward use implement use one read backwards source code determine entity name refers implementation one maintain list names contexts compiling interpreting program difficulties arise name masking forward declarations hoisting considerably subtler ones arise non-local variables particularly closures strict definition lexical scope name identifier unambiguous – portion source code binding name entity applies – virtually unchanged 1960 definition specification algol 60 representative language specification follow commonly scope refers given name refer given variable – declaration effect – also apply entities functions types classes labels constants enumerations fundamental distinction scoping part program means languages lexical scope also called static scope name resolution depends location source code lexical context defined named variable function defined contrast languages dynamic scope name resolution depends upon program state name encountered determined execution context calling context practice lexical scope variable definition resolved searching containing block function fails searching outer containing block whereas dynamic scope calling function searched function called calling function progressing call stack course rules first look local definition variable modern languages use lexical scoping variables functions though dynamic scoping used languages notably dialects lisp scripting languages template languages perl 5 offers lexical dynamic scoping even lexically scoped languages scope closures confusing uninitiated depend lexical context closure defined called lexical resolution determined compile time also known early binding dynamic resolution general determined run time thus known late binding object-oriented programming dynamic dispatch selects object method runtime though whether actual name binding done compile time run time depends language de facto dynamic scoping common macro languages directly name resolution instead expand place programming frameworks like angularjs use term scope mean something entirely different used article frameworks scope object programming language use javascript case angularjs used certain ways framework emulate dynamic scope language uses lexical scope variables angularjs scopes scope scope using usual meaning term given part program following usual rules variable scope language like object using inheritance transclusion rules context angularjs sometimes term scope dollar sign used avoid confusion using dollar sign variable names often discouraged style guides scope important component name resolution turn fundamental language semantics name resolution including scope varies programming languages within programming language varies type entity rules scope called scope rules scoping rules together namespaces scoping rules crucial modular programming change one part program break unrelated part discussing scope three basic concepts scope extent context scope context particular frequently confused scope property identifier fixed context property program varies position precisely context property position program either position source code lexical context point run time execution context runtime context calling context execution context consists lexical context current execution point plus additional runtime state call stack thus execution point program variable name scope variable name context meaning context point execution point exits variable name scope returning function variable name goes context narrowly speaking execution program enters exits various scopes point execution identifiers context context hence identifiers come context go context program enters exits scope – however practice usage much looser scope source-code level concept property identifiers particularly variable function names – identifiers source code references entities program – part behavior compiler interpreter language issues scope similar pointers type reference used programs generally using value variable name context variable uninitialized analogous dereferencing accessing value wild pointer undefined however variables destroyed go context analog dangling pointer exist entities variables scope subset lifetime also known extent – name refer variable exists possibly undefined value variables exist necessarily visible variable may exist inaccessible value stored referred within given context accessible via given name case context program scope name cases lifetime irrelevant – label named position source code lifetime identical program statically compiled languages may context given point program likewise static variables – static global variable context entire program static local variable context within function local context lifetime entire run program determining entity identifier refers known name resolution name binding particularly object-oriented programming varies languages given identifier language properly compiler interpreter checks entities context matches case ambiguity two entities name global local variable name name resolution rules used distinguish frequently name resolution relies inner-to-outer rule python legb local enclosing global built-in rule names implicitly resolves narrowest relevant context cases name resolution explicitly specified codice_1 codice_2 keywords python cases default rules overridden two identical identifiers context time referring different entities one says name masking occurring higher-priority name usually innermost masking lower-priority name level variables known variable shadowing due potential logic errors masking languages disallow discourage masking raising error warning compile time run time various programming languages various different scoping rules different kinds declarations identifiers scoping rules large effect language semantics consequently behavior correctness programs languages like c++ accessing unbound variable well-defined semantics may result undefined behavior similar referring dangling pointer declarations identifiers used outside scope generate syntax errors scopes frequently tied language constructs determined implicitly many languages also offer constructs specifically controlling scope scope vary little single expression much entire program many possible gradations simplest scoping rule global scope – entities visible throughout entire program basic modular scoping rule two-level scoping global scope anywhere program local scope within function sophisticated modular programming allows separate module scope names visible within module private module visible outside within function languages c allow block scope restrict scope subset function others notably functional languages allow expression scope restrict scope single expression scopes include file scope notably c functions similarly module scope block scope outside functions notably perl subtle issue exactly scope begins ends languages c scope starts declaration thus different names declared within given block different scopes requires declaring functions use though necessarily defining requires forward declaration cases notably mutual recursion languages javascript python name scope begins start relevant block start function regardless defined names within given block scope javascript known variable hoisting however name bound value varies behavior in-context names undefined value differs python use undefined variables yields runtime error javascript undefined variables usable undefined value function declarations also hoisted top containing function usable throughout function many languages especially functional languages offer feature called let-expressions allow declaration scope single expression convenient example intermediate value needed computation example standard ml codice_3 returns 12 codice_4 expression evaluates 144 using temporary variable named x avoid calling codice_3 twice languages block scope approximate functionality offering syntax block embedded expression example aforementioned standard ml expression could written perl gnu c python auxiliary variables generator expressions list comprehensions python 3 expression scope c variable names function prototype expression scope known context function protocol scope variable names prototype referred may different actual definition – dummies – often omitted though may used generating documentation instance many block-structured programming languages allow scope restricted block known block scope began algol 60 e declaration ... valid block today particularly associated languages pascal c families traditions often block contained within function thus restricting scope part function cases perl block may within function representative example use block scope c code shown two variables scoped loop loop variable n initialized incremented iteration loop auxiliary variable n_squared initialized iteration purpose avoid adding variables function scope relevant particular block – example prevents errors generic loop variable accidentally already set another value example expression codice_6 would generally assigned auxiliary variable body loop would simply written codice_7 complicated examples auxiliary variables useful blocks primarily used control flow loops cases block scope means scope variable depends structure function flow execution however languages block scope typically also allow use naked blocks whose sole purpose allow fine-grained control variable scope example auxiliary variable may defined block used say added variable function scope discarded block ends loop might enclosed block initializes variables used inside loop initialized subtlety several programming languages algol 68 c demonstrated example standardized since c99 block-scope variables declared within body block also within control statement analogous function parameters declared function declaration block function body starts scope whole function body primarily used loops initialization statement separate loop condition unlike loops common idiom block scope used shadowing example inside block auxiliary variable could also called n shadowing parameter name considered poor style due potential errors furthermore descendants c java c despite support block scope local variable made go scope end function allow one local variable hide another languages attempted declaration second n would result syntax error one n variables would renamed block used set value variable block scope requires variable declared outside block complicates use conditional statements single assignment example python use block scope one may initialize variable codice_8 accessible codice_9 statement perl block scope instead requires declaring variable prior block often instead rewritten using multiple assignment initializing variable default value python necessary would perl would case single variable assignment alternative use ternary operator avoid block general possible multiple variable assignments difficult read complex logic significant issue c notably string assignment string initialization automatically allocate memory string assignment already initialized variable requires allocating memory string copy checking successful languages allow concept block scope applied varying extents outside function example perl snippet right counter variable name block scope due use keyword increment_counter function name global scope call increment_counter increase value counter one return new value code outside block call increment_counter otherwise obtain alter value counter idiom allows one define closures perl commonly used programming languages offer way create local variable function subroutine variable whose scope ends goes context function returns cases lifetime variable duration function call – automatic variable created function starts variable declared destroyed function returns – scope variable within function though meaning within depends whether scoping lexical dynamic however languages c also provide static local variables lifetime variable entire lifetime program variable context inside function case static local variables variable created program initializes destroyed program terminates static global variable context within function like automatic local variable importantly lexical scoping variable function scope scope within lexical context function moves context another function called within function moves back context function returns – called functions access local variables calling functions local variables context within body function declared contrast dynamic scoping scope extends runtime context function local variables stay context another function called moving context defining function ends thus local variables context function defined called functions languages lexical scoping nested functions local variables context nested functions since within lexical context functions lexically nested local variable enclosing function known non-local variable nested function function scope also applicable anonymous functions example snippet python code right two functions defined square sum_of_squares square computes square number sum_of_squares computes sum squares number example square 4 4 16 sum_of_squares 4 0 1 2 3 4 30 functions variable named n represents argument function two n variables completely separate unrelated despite name lexically scoped local variables function scope one scope lexically separate function thus n't overlap therefore sum_of_squares call square without n altered similarly sum_of_squares variables named total variables limited scope interfere variables named total might belong function words risk name collision identifiers unrelated identifiers even identical note also name masking occurring one variable named n context given time scopes overlap contrast similar fragment written language dynamic scope n calling function would remain context called function – scopes would overlap – would masked shadowed new n called function function scope significantly complicated functions first-class objects created locally function returned case variables nested function local unbound variables function definition resolve variables enclosing context create closure function also environment variables must returned potentially called different context requires significantly support compiler complicate program analysis scoping rule largely particular c c++ file scope scope variables functions declared top level file within function entire file – rather c declaration end source file precisely translation unit internal linking seen form module scope modules identified files modern languages replaced explicit module scope due presence include statements add variables functions internal context may call include statements difficult determine context body file c code snippet function name sum_of_squares file scope modular programming scope name entire module however may structured across various files paradigm modules basic unit complex program allow information hiding exposing limited interface module scope pioneered modula family languages python influenced modula representative contemporary example object-oriented programming languages lack direct support modules c++ similar structure instead provided class hierarchy classes basic unit program class private methods properly understood context dynamic dispatch rather name resolution scope though often play analogous roles cases facilities available python modules classes code organization module-level function conventionally private method choice programmer declaration global scope effect throughout entire program variable names global scope — called global variables — frequently considered bad practice least languages due possibility name collisions unintentional masking together poor modularity function scope block scope considered preferable however global scope typically used depending language various sorts identifiers names functions names classes data types cases mechanisms namespaces used avoid collisions use local variables — variable names limited scope exist within specific function — helps avoid risk name collision two identically named variables however two different approaches answering question mean within function lexical scoping lexical scope also called static scoping static scope variable name scope certain function scope program text function definition within text variable name exists bound variable value outside text variable name exist contrast dynamic scoping dynamic scope variable name scope certain function scope time-period function executing function running variable name exists bound value function returns variable name exist means function f invokes separately defined function g lexical scoping function g access f local variables assuming text g inside text f dynamic scoping function g access f local variables since g invoked invocation f consider example program right first line creates global variable x initializes 1 second line defines function g prints echoes current value x sets x 2 overwriting previous value third line defines function f creates local variable x hiding identically named global variable initializes 3 calls g. fourth line calls f. fifth line prints current value x exactly program print depends scoping rules language program one uses lexical scoping g prints modifies global variable x g defined outside f program prints 1 2 contrast language uses dynamic scoping g prints modifies f local variable x g called within f program prints 3 1 happens language program bash uses dynamic scoping program prints 3 1 lexical scope name always refers less local lexical environment property program text made independent runtime call stack language implementation matching requires analysis static program text type scoping also called static scoping lexical scoping standard algol-based languages pascal modula-2 ada well modern functional languages ml haskell also used c language syntactic semantic relatives although different kinds limitations static scoping allows programmer reason object references parameters variables constants types functions etc simple name substitutions makes much easier make modular code reason since local naming structure understood isolation contrast dynamic scope forces programmer anticipate possible dynamic contexts module code may invoked example consider pascal program fragment right variable codice_10 visible points never hidden another variable name codice_11 variable codice_12 visible main program hidden codice_13 variable codice_12 visible procedure codice_15 codice_16 variable codice_17 also visible procedure codice_15 codice_16 hide variable variable codice_20 visible procedure codice_16 therefore accessible either procedure codice_15 main program also procedure codice_16 visible procedure codice_15 therefore called main program could another procedure codice_16 declared program outside procedure codice_15 place program codice_16 mentioned determines two procedures named codice_16 represents thus precisely analogous scope variables correct implementation static scope languages first-class nested functions trivial requires function value carry record values variables depends pair function environment called closure depending implementation computer architecture variable lookup may become slightly inefficient deeply lexically nested functions used although well-known techniques mitigate also nested functions refer arguments immediately local variables relative locations known compile time overhead therefore incurred using type nested function applies particular parts program nested functions used naturally programs written language nested functions available c language lexical scoping used algol picked languages since deep binding approximates static lexical scoping introduced lisp 1.5 via funarg device developed steve russell working john mccarthy original lisp interpreter 1960 early lisps used dynamic scoping descendants dynamically scoped languages often adopt static scoping common lisp scheme srfi 15 dynamic static scoping perl another language dynamic scoping added static scoping afterwards languages like pascal c always lexical scoping since influenced ideas went algol 60 although c include lexically nested functions term lexical scope dates least 1967 term lexical scoping dates least 1970 used project mac describe scoping rules lisp dialect mdl known muddle dynamic scope global identifier refers identifier associated recent environment uncommon modern languages technical terms means identifier global stack bindings introducing local variable name codice_29 pushes binding onto global codice_29 stack may empty popped control flow leaves scope evaluating codice_29 context always yields top binding note done compile-time binding stack exists run-time type scoping called dynamic scoping generally certain blocks defined create bindings whose lifetime execution time block adds features static scoping dynamic scoping process however since section code called many different locations situations difficult determine outset bindings apply variable used one exists beneficial application principle least knowledge suggests code avoid depending reasons circumstances variable value simply use value according variable definition narrow interpretation shared data provide flexible system adapting behavior function current state policy system however benefit relies careful documentation variables used way well careful avoidance assumptions variable behavior provide mechanism detect interference different parts program dynamic scoping also voids benefits referential transparency dynamic scoping dangerous modern languages use languages like perl common lisp allow programmer choose static dynamic scoping defining redefining variable examples languages use dynamic scoping include logo emacs lisp latex shell languages bash dash powershell dynamic scoping fairly easy implement find identifier value program could traverse runtime stack checking activation record function stack frame value identifier practice made efficient via use association list stack name/value pairs pairs pushed onto stack whenever declarations made popped whenever variables go scope shallow binding alternative strategy considerably faster making use central reference table associates name stack meanings avoids linear search run-time find particular name care taken properly maintain table note strategies assume last-in-first-out lifo ordering bindings one variable practice bindings ordered even simpler implementation representation dynamic variables simple global variables local binding performed saving original value anonymous location stack invisible program binding scope terminates original value restored location fact dynamic scope originated manner early implementations lisp used obvious strategy implementing local variables practice survives dialects still use gnu emacs lisp lexical scope introduced lisp later equivalent shallow binding scheme except central reference table simply global variable binding environment current meaning variable global value maintaining global variables n't complex instance symbol object dedicated slot global value dynamic scoping provides excellent abstraction thread local storage used way based saving restoring global variable possible implementation strategy variable thread-local key variable accessed thread-local key used access thread-local memory location code generated compiler knows variables dynamic lexical thread-local key exist calling thread global location used variable locally bound prior value stored hidden location stack thread-local storage created variable key new value stored nested overrides variable within thread simply save restore thread-local location initial outer-most override scope terminates thread-local key deleted exposing global version variable thread modern languages macro expansion preprocessor key example de facto dynamic scope macro language transforms source code without resolving names since expansion done place names expanded text resolved notably free variables resolved based expanded loosely called dynamic scoping occurring c preprocessor used macro expansion de facto dynamic scope name resolution example macro expand add codice_8 passed variable identifier later resolved compiler based macro codice_33 called properly expanded dynamic scope independent macro defined properly c preprocessor lexical analysis expanding macro tokenization stage parsing syntax tree name resolution example following code codice_8 macro resolved expansion local variable expansion site seen one key reasons scope helps prevent name collisions allowing identical identifiers refer distinct things restriction identifiers must separate scopes sometimes restriction inconvenient many different things need accessible throughout program generally need identifiers global scope different techniques required avoid name collisions address many languages offer mechanisms organizing global identifiers details mechanisms terms used depend language general idea group identifiers given name — prefix — necessary entity referred qualified identifier consisting identifier plus prefix normally identifiers sense two sets scopes scope usually global scope qualified identifier visible one narrower scopes unqualified identifier without prefix visible well normally groups organized groups nested although many languages support concept details vary greatly languages mechanisms namespaces c++ c serve almost exclusively enable global identifiers organized groups languages mechanisms packages ada structures standard ml combine additional purpose allowing identifiers visible members group object-oriented languages often allow classes singleton objects fulfill purpose whether also mechanism primary purpose furthermore languages often meld approaches example perl packages largely similar c++ namespaces optionally double classes object-oriented programming java organizes variables functions classes organizes classes ada-like packages scoping rules representative languages follow c scope traditionally known linkage visibility particularly variables c lexically scoped language global scope known external linkage form module scope file scope known internal linkage local scope within function within function scopes nested via block scope however standard c support nested functions lifetime visibility variable determined storage class three types lifetimes c static program execution automatic block execution allocated stack manual allocated heap static automatic supported variables handled compiler manually allocated memory must tracked manually across different variables three levels visibility c external linkage global internal linkage roughly file block scope includes functions block scopes nested different levels internal linkage possible use includes internal linkage c visibility translation unit level namely source file processed c preprocessor notably including relevant includes c programs compiled separate object files linked executable library via linker thus name resolution split across compiler resolves names within translation unit loosely compilation unit properly different concept linker resolves names across translation units see linkage discussion c variables block scope enter scope declared top block move scope non-nested function called within block move back scope function returns move scope end block case automatic local variables also allocated declaration deallocated end block static local variables allocated program initialization deallocated program termination following program demonstrates variable block scope coming scope partway block exiting scope fact deallocated block ends program outputs levels scope c. variable names used function prototype function prototype visibility exit scope end function prototype since name used useful compilation may useful documentation label names goto statement function scope case label names switch statements block scope block switch variables intend use program must declared type specifier earlier point code like previous code beginning body function main declared b result type int variable either global local scope global variable variable declared main body source code outside functions local variable one declared within body function block modern versions allow nested lexical scoping go lexically scoped using blocks java lexically scoped java class contain three types variables local variables defined inside method particular block variables local defined lower levels example loop inside method use method local variables way around loop variables local loop destroyed soon loop ends member variables also called fields variables declared within class outside method default variables available methods within class also classes package parameters variables method declarations general set brackets defines particular scope variables top level within class differ behavior depending modifier keywords used definition following table shows access members permitted modifier javascript simple scoping rules variable initialization name resolution rules cause problems widespread use closures callbacks means lexical environment function defined used name resolution different lexical environment called irrelevant name resolution javascript objects name resolution properties separate topic javascript lexical scoping nested function level global scope outermost scope scoping used variables functions meaning function declarations opposed variables function type block scoping codice_35 codice_36 keywords standard since ecmascript 6 block scoping produced wrapping entire block function executing known immediately-invoked function expression iife pattern javascript scoping simple – lexical function-level – associated initialization name resolution rules cause confusion firstly assignment name scope defaults creating new global variable local one secondly create new local variable one must use codice_37 keyword variable created top function value codice_38 variable assigned value assignment expression reached known variable hoisting – declaration initialization hoisted top function thirdly accessing variables initialization yields codice_38 rather syntax error fourthly function declarations declaration initialization hoisted top function unlike variable initialization example following code produces dialog output samp undefined /samp local variable declaration hoisted shadowing global variable initialization variable undefined used functions first-class objects javascript frequently assigned callbacks returned functions function executed name resolution depends originally defined lexical environment definition lexical environment execution environment called nested scopes particular function global local javascript particularly closure used callback sometimes referred scope chain analogy prototype chain object closures produced javascript using nested functions functions first-class objects returning nested function enclosing function includes local variables enclosing function non-local lexical environment returned function yielding closure example closures frequently used javascript due used callbacks indeed hooking function local environment callback returning function creates closure unbound variables function body environment closure based nested scopes current lexical environment scope chain may accidental creating callback based parameters parameters must stored closure otherwise accidentally create closure refers variables enclosing environment may change name resolution properties javascript objects based inheritance prototype tree – path root tree called prototype chain – separate name resolution variables functions lisp dialects various rules scoping original lisp used dynamic scoping scheme inspired algol introduced static lexical scoping lisp family maclisp used dynamic scope default interpreter lexical scope default compiled code though compiled code could access dynamic bindings use codice_40 declarations particular variables however maclisp treated lexical binding optimization one would expect modern languages come closure feature one might expect lexical scoping modern lisps separate operation codice_41 available somewhat clumsily work around issue common lisp adopted lexical scoping scheme clojure islisp lexical scoping ordinary variables also dynamic variables cases explicitly marked must defined codice_42 special form bound codice_43 special form accessed explicit codice_44 special form dialects lisp like emacs lisp still use dynamic scoping default emacs lisp lexical scoping available per-buffer basis variables python function scope module scope global scope names enter scope start context function module globally exit scope non-nested function called context ends name used prior variable initialization raises runtime exception variable simply accessed assigned context name resolution follows legb rule local enclosing global built-in however variable assigned defaults creating local variable scope entire context rules overridden codice_1 codice_2 python 3 declaration prior use allows accessing global variables even intervening nonlocal variable assigning global nonlocal variables simple example function resolves variable global scope note x initialized codice_47 called error raised even though declared codice_47 declared lexically forward reference allowed python assignment creates new local variable change value global variable assignment variable within function causes declared local function hence local variable scope entire function thus using prior assignment raises error differs c local variable scope declaration entire function code raises error default name resolution rules overridden codice_1 codice_2 python 3 keywords code codice_51 declaration codice_52 means x resolves global variable thus accessed already initialized assignment assigns global variable rather declaring new local variable note codice_1 declaration needed codice_47 – since assign variable defaults resolving global variable codice_1 also used nested functions addition allowing assignment global variable unnested function also used access global variable presence nonlocal variable nested functions also codice_2 declaration assigning nonlocal variable similar using codice_1 unnested function r lexically scoped language unlike implementations values free variables determined set global variables r determined environment function created scoping environments may accessed using variety features codice_58 simulate experience dynamic scoping programmer desire block scoping functions access environment scope created variables created modified within function stay variables created modified within function stay unless assignment enclosing environment scope explicitly requested although r lexical scoping default function scopes changed
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Programming language topics
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sap iq sap iq formerly known sap sybase iq sybase iq iq intelligent query column-based petabyte scale relational database software system used business intelligence data warehousing data marts produced sybase inc. sap company primary function analyze large amounts data low-cost highly available environment sap iq often credited pioneering commercialization column-store technology foundation sap iq lies column store technology allows speed compression ad-hoc analysis sap iq open interface approach towards ecosystem sap iq also integrated sap ’ business intelligence portfolio products form end-to-end business analytics software stack integral component sap in-memory data fabric architecture data management platform early 1990s waltham massachusetts-based expressway technologies inc. developed expressway 103 column-based engine optimized analytics would eventually become sybase iq sybase acquired expressway re-introduced product 1995 iq accelerator renamed shortly thereafter sybase iq giving version number 11.0 offering iq product part collection related technologies often found data warehouse including sybase adaptive server enterprise replication server powerdesigner powerdesigner sql anywhere sybase became one first mainstream companies acknowledge need specialized products data warehouse market version 12.0 sybase replaced loosely coupled query interface adaptive server enterprise tight coupling sql anywhere version 16 brings re-engineered column store extreme petabyte scale data volumes extreme data compression 2014 sap hana together partners bmmsoft hp intel netapp red hat announced world ’ largest data warehouse team engineers sap bmmsoft hp intel netapp red hat built data warehouse using sap hana sap iq 16 bmmsoft federated edmt running hp dl580 servers using intel xeon e7-4870 processors red hat enterprise linux 6 netapp fas6290 e5460 storage development testing 12.1pb data warehouse conducted sap/intel petascale lab santa clara calif. audited infosizing independent transaction processing council certified auditor release sp08 version numbers changed align match sap hana ’ version numbers reflect product ’ continuous integration sap hana actual release title sp03 follow-on sp02 covering platforms affected release sap ’ new approach streamlines simplifies data warehousing in-memory data fabric advent big data sap iq coupled sap hana deliver distributed in-memory analytics platform three main applications use cases try capitalize sap iq ’ strengths concerning scalability performance edw big data processor leveraging sap hana ’ in-memory speed operational reporting https //blogs.sap.com/2016/10/12/sap-nls-solution-sap-bw scenario sap enterprise resource planning erp data goes sap hana acts operational data store immediate analysis data analyzed integrated sap iq via near-line storage mechanisms described sap iq acts enterprise data warehouse receives data variety traditional sources oltp databases files systems sap hana operational data store ods https //blogs.sap.com/2019/05/22/q-the-easy-installer-for-sap-iq/ sap iq used edw also augmented hana ’ in-memory technology common uses include planning analysis reports simultaneous oltp processing needed case data flows sap iq sap hana sap businessobjects bi used achieve visibility across platforms user sap iq looks like relational dbms sql-based language layer accessible via odbc/jdbc drivers however inside sybase iq column-oriented dbms stores data tables sections columns data rather rows data like transactional databases column-orientation number advantages search done items matching particular value column data storage objects corresponding data column within table need accessed traditional row-based database would read whole table top bottom another advantage indexed correctly value would stored row data traditional database stored sap iq n-bitindex used access data nbit tiered indexing used allow increased compression fast incremental batch loads additionally column-based storage enables sap iq compress data efficiently fly prior sap iq 16 data page structured array cells fixed size values data type storage approach efficient structured fixed length data hold unstructured variable sized data seen today combat storage inefficiency store variable sized data minimal wasted space page composed cells variable size packed tightly together column store architecture supports variable number cells per page various page formats within column sap iq also applies lempel-ziv-welch lzw compression algorithms data page written disk significantly reduce data volume bitmaps used secondary indexes sap iq massively parallel processing mpp framework based shared-everything environment supports distributed query processing products capable mpp tend based shared-nothing environments benefit shared-everything flexible terms variety queries optimized—especially balancing needs many concurrent users downside extreme cases competition among processors access shared pool storage usually storage-area network lead i/o contention affects query performance 12 however aforementioned storage architecture sap iq allows compute storage layers scale independently also allows resources provisioned on-demand better utilization without restructuring underlying database sap iq uses clustered grid architecture made clusters sap iq servers multiplex clusters used scale performance large numbers concurrent queries queries great complexity built upon shared-everything architecture compute nodes interact shared storage queries ability distribute across compute nodes multiplex coordinator node manages database catalog coordinates transactional writes store nodes reader nodes readers writes like coordinator node storage fabric implemented numerous technologies allow sharing amongst multiplex nodes architecture multiple uses including workload balancing elastic virtual data marts workload balancing achieved sap iq query engine dynamically increasing/decreasing parallelism response changes server activity automatic failover node stops participating query nodes pick work originally assigned failed node query complete client side compatibility external load balances ensures queries initiated physical servers balanced fashion eliminate bottlenecks physical nodes multiplex grouped together “ logical servers ” allow workloads isolated security resource balancing purposes machines added demand changes aim grid architecture enable resiliency even global transactions sap iq loading engine used incremental batch low latency concurrent loading bulk loading client server data files bulk loading process allows multiple load process occur simultaneously loads different tables data loaded databases well files page-level snapshot versioning allows concurrent loads queries locking occurring table level sap replication server enhanced optimize loads sap iq transactions compiled fewest set operations bulk micro-batch loads sap iq performed gives appearance real-time continuous loads bulk loader performs operations parallel make full use server cores remove bottlenecks keep threads productive instead serializing process loading process remains two-phase process first reading raw data creating fp indexes second creating secondary indexes everything executed parallel high group indexes query optimizer relies information columns/rows contain data values structured set tiers increasing move pyramid lastly sap iq introduces write-optimized row level versioned rlv delta store enables high-velocity data loads fast availability data users store minimally indexes compressed row-level locking concurrent write transaction log append acts companion main store data loaded high speed rlv store migrating main store later merging periodically user appear though two separate entities work queries operate transparently across two stores make use users specify particular “ hot ” database tables rlv tables sap iq offers query apis based pure ansi sql standards restrictions include olap full-text search support stored procedures supported ansi sql transact-sql dialects executed scheduled immediate basis well database drivers variety programming languages java c/c++m php perl python ruby ado.net sap iq analytics engine query structured unstructured data join results together sap iq introduced new text index sql “ contains ” clause facilitate searching terms within blob unstructured text sap sybase ’ partnerships vendors allow various binary forms text files ingested sap iq text indexes created text indexes get data ready higher level text analysis applications perform full-text searches within sap iq via select statements select syntax used applications performing tokenization categorization text analysis in-database analytics built upon fundamental concept keeping analytics algorithms close data higher performance extensibility framework called “ in-database analytics ” enables embedding analytic functions inside database engine sap iq moving analytics database instead specialized environment database process error prone slower pre-built functions available natively via partners sap iq providing specialized statistical data mining libraries plug sap iq framework increases sap iq ’ power advance processing analysis data moved database specialized environment analytics data results obtained shared though dbms easily acquired sql interface user defined functions udfs partners extend dbms custom computations providing specialized statistical data mining libraries plug right sap iq enhance performance advanced processing analysis sap iq provides several features included base product licensable separately help protect security user ’ data new feature introduced iq 16 role based access control rbac enables separation duties upholds principle least privilege allowing breakdown privileged operations fine-grained sets individually granted users included part base product users groups permissions database administration authorities user login policies database encryption transport-layer security ipv6 role-based access control database auditing additional features part licensable option called advanced security option fips encryption kerberos authentication ldap authentication database column encryption part ilm sap iq allows users create multiple user dbspaces logical units storage/containers database objects organizing data used separate structured unstructured data group together according age value partition table data dbspaces also marked read-only enable one-time consistency checking back-up another application ilm ability partition tables place moving portions along storage fabric backup capabilities enables storage management process data cycles tiered storage moving faster expensive storage slower cheaper storage ages partitioning data according value multiplex set-up provides scalability high availability compute nodes multiplex coordinator node failover alternate coordinator node sap iq virtual backup also allows users quickly backup data along storage replication technology data continuously copied backups occur quickly “ behind scenes ” virtual backups completed verified test restore enterprise data copied development testing ’ left complete backup transactionally consistent point time sap claims disaster recovery easier shared everything approach mpp sap sybase powerdesigner modelling tool enables users build ilm model deployed sap iq storage types dbspaces lifecycle phases defined ilm model tool used generate reports create partition creation movement scripts sap iq provides federation hadoop distributed file system hdfs popular framework big data enterprise users continue store data hadoop utilize benefits integration achieved four different ways depending user ’ needs client-side federation etl data query federation client-side federation joins data iq hadoop client application level etl federation lets user load hadoop data column store schemas iq hdfs data also joined iq data fly sql queries iq finally results mapreduce jobs combined iq data also fly sap control center replaces sybase central web-based graphical tool administration monitoring sap control center used monitoring sap sybase servers resources node multiplex location well monitoring performance spotting usage trends web application multi-tiered plug-in architecture made server product-based agents bring sap sybase performance back control center server sap iq comes web-enabled application drivers facilitating access sap iq variety web 2.0 programming execution environments python perl php .net ruby query federation databases developers build applications interact multiple data sources time well database platforms vendors federation proxy tables map tables external databases created materialized in-memory tables interacted though resided within sap iq way data sources combined unified view sap iq also supports plugging external algorithms written c++ java sql queries call algorithms allowing execution in-database analytics provides better performance scalability additionally sybase iq also provides drivers access via languages php perl python ruby rails sap iq supports major operating system platforms including sybase claims sybase iq currently installed 2000 customer sites notable customers include comscore inc. corelogic investment technology group itg u.s. internal revenue service irs sybase iq widely used focused data-mart-style deployments also deployed enterprise data warehouse
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Databases
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metal api metal low-level low-overhead hardware-accelerated 3d graphic compute shader application programming interface api developed apple inc. debuted ios 8 metal combines functions similar opengl opencl one api intended bring ios macos tvos apps performance benefits similar apis platforms vulkan debuted mid-february 2016 directx 12 metal object-oriented api invoked using swift objective-c programming languages full-blown control metal framework well related metalkit framework accessible via metal unified graphics compute language according apple promotional materials metal c++ based programming language developers use write code executed gpu graphics general-purpose data-parallel computations since metal based c++ developers find familiar easy use metal graphics compute programs written single unified language allows tighter integration two metal available since june 2 2014 ios devices powered apple a7 later since june 8 2015 macs 2012 models later running os x el capitan june 5 2017 wwdc apple announced second version metal supported macos high sierra ios 11 tvos 11 metal 2 separate api metal supported hardware metal 2 enables efficient profiling debugging xcode accelerated machine learning lower cpu workload support virtual reality macos specificities apple a11 gpu particular ios tvos metal supports apple-designed socs apple a7 newer macos metal supports intel hd iris graphics hd 4000 series newer amd gcn-based gpus nvidia kepler-based gpus newer metal designed around principles modern graphics compute apis vulkan direct3d 12 instructions sent gpu command buffers obtained command queues metal improves capabilities gpgpu programming using compute shaders metal uses specific shading language based c++14 implemented using clang llvm metal better performance opengl several reasons points reduce amount work cpu required successfully execute commands gpu lead overall performance gain cpu used compute tasks according apple 148,000 applications use metal directly 1.7 million use high-level frameworks june 2017 presumably applications games ios notable macos games using metal rendering listed
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Operating systems
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australian plant name index australian plant name index apni online database published names australian vascular plants covers names whether current names synonyms invalid names includes bibliographic typification details information australian plant census including distribution state links resources specimen collection maps plant photographs facility notes comments aspects originally brainchild nancy tyson burbidge began four-volume printed work consisting 3,055 pages containing 60,000 plant names compiled arthur chapman part australian biological resources study abrs 1991 made available online database handed australian national botanic gardens two years later responsibility maintenance given newly formed centre plant biodiversity research recognised australian herbaria authoritative source australian plant nomenclature core component australia virtual herbarium collaborative project 10 million funding aimed providing integrated online access data specimen collections australia major herbaria two query interfaces offered
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Databases
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microsoft visual programming language microsoft visual programming language mvpl visual programming dataflow programming language developed microsoft microsoft robotics studio microsoft visual programming language distinguished microsoft programming languages visual basic c microsoft language true visual programming language microsoft utilized term visual previous programming products reflect large degree development languages performed dragging dropping traditional wysiwyg fashion
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Programming language topics
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audio injection audio injection exploitation digital assistants amazon echo google home apple siri unwanted instructions third party services lack authentication reacting user commands making possible attackers issue activation words commands trigger execution desired actions injection results include fraud burglary data espionage takeover connected systems digital assistants require activation word trigger complete recording audio analysis spoken commands e.g ok google commands spoken natural language processed executed activation word different manufacturer often connected product ’ name possible product owner customize activation word meaning models react word processed language analyzed regards voice recognition authorization individual users result users audible range device authorizations trigger execute actions depending functionality actions range simple actions like music playback controlling lights security critical sensitive actions opening gates executing ordering chargeable transactions reading private information audio injection attacks performed remotely access audible area digital assistant restricted attacked increasing distance transmission either reached overcoming existent acoustic barriers e.g via vending opening momentary opened window via unusual loud playback via amplifiers loudspeakers approach possible control digital assistants rooms floors outside building digital assistants distinguish whether voice commands directly spoken reproduced loudspeaker system means attacks performed via devices support audio playback via loudspeaker radio television used run mass-attacks telephones hands-free systems digital assistants systems text-to-speech-processing misused systems accessed randomly anonymously absence owner well activated remotely critical answering machines automated monitoring function playing message aloud along could used remote precise attacks june 2014 television commercial microsoft depicted actor issuing voice command xbox causing command interpreted xbox systems room television showing commercial december 2016 adam jakowenko showed one virtual assistant could activate another one using tts-processing january 2017 television news coverage child ordering dollhouse amazon alexa interface included news anchor jim patton quoting child quotation triggered orders dollhouses viewers coverage alexa devices running
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Computer security
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mac 68k emulator mac 68k emulator software emulator built versions classic mac os powerpc emulator enabled running applications system code originally written 680x0-based macintosh models exceptions notably connectix ram doubler emulator ran software noticeable impact lower performance relative program compiled powerpc first version written gary davidian originally created use motorola 88000 cpu used apple abortive first attempt risc target platform later version using dynamic recompilation developed eric traut later worked successful emulation projects connectix virtual game station virtual pc prior traut arrival connectix released speed doubler included even faster powerpc 68k emulator versions emulator emulated user subset 68ec040 instruction set 68020/68030 exception stack frame apple developer documents indicate emulator provided operating environment closely resembling macintosh centris 610 system based motorola 68lc040 microprocessor early versions emulated decoding instruction immediately carrying series equivalent powerpc instructions pci powermacs dynamic recompilation emulator used boost performance dynamic recompilation works recompiling common sections code faster powerpc-native sequences locally cached emulator could recognise sequence 680x0 code run previously-cached powerpc code avoid translation emulator theoretically capable emulating 680x0 code faster real 680x0 capable running 68lc040 floating point instructions making feat slightly simpler less impressive one reason emulation successful many apis mac os originally implemented traps 680x0 processor therefore calling api actually recognised 680x0 equivalent error condition would cause handle error one hardware vectors turn vector would look run operating system routine rom ram emulator traps could replaced native powerpc code code emulated application system api called could accelerated native powerpc code also allowed apple time port os powerpc first time-critical aspects rewritten native code leaving much os emulated gradually os rewritten native os got faster time programmer transition powerpc made fairly painless emulator started stopped automatically achieved using new type pointer called universal procedure pointer upp 68k code pointer appeared ordinary pointer code could used however actually led data structure contained special trap instruction flags indicating instruction set architecture isa called code powerpc code upp could passed calluniversalproc function call 68k emulator dealt details presenting passed parameters right order isa question well starting stopping emulator required compilers mac os created upps automatically proper macros used powerpc system libraries contained native stubs transparently call native still-68k functions needed meant dealing dual architecture required little work programmer like os applications could mix match 680x0 powerpc code fairly easily built powerpc versions classic mac os emulator also part classic environment mac os x. powerpc macintosh emulators sheepshaver therefore use emulator well running classic mac os native mac os x outside classic never used emulator
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Computer architecture
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ifttt also known ifttt free web-based service create chains simple conditional statements called applets applet triggered changes occur within web services gmail facebook telegram instagram pinterest example applet may send e-mail message user tweets using hashtag copy photo facebook user archive someone tags user photo addition web-based application service runs ios android february 2015 ifttt renamed original application released new suite apps called lets users create shortcut applications actions 2015 ifttt users created 20 million recipes day functionalities suite apps since integrated redesigned ifttt app december 14 2010 linden tibbets co-founder ifttt posted blog post titled “ ifttt beginning ... ” ifttt website announcing new project first ifttt applications designed developed tibbets co-founder jesse tane september 7 2011 tibbets announced launch official website april 30 2012 users created 1 million tasks june 2012 service entered internet things space integrating belkin wemo devices allowing applets interact physical world july 10 2013 ifttt released iphone app later released version ipad ipod touch april 24 2014 ifttt released version android end 2014 ifttt business valued approximately usd 170 million february 19 2015 ifttt launched three new applications button triggers action press camera automatically uploads image service choice facebook twitter dropbox etc. notes camera except notes instead images november 2016 four apps combined one december 2016 company announced partnership jotform integrate applet create actions applications part revenue ifttt comes ifttt platform partners pay products connected service among ge bmw microsoft google others dropbox new york times twitter slack spotify partners choose various monthly plans lite free use basic 199 enterprise 499 july 2019 ifttt announced tenfold increase monthly charges pricing smaller integration partners ifttt employs following concepts ifttt received positively forbes time wired new york times reader digest microsoft developed comparable product microsoft flow
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Web technology
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database server database server server uses database application provides database services computer programs computers defined client–server model database management systems dbmss frequently provide database-server functionality database management systems mysql rely exclusively client–server model database access others e.g sqlite meant using embedded database users access database server either front end running user computerwhich displays requested dataor back end runs server handles tasks data analysis storage master-slave model database master servers central primary locations data database slave servers synchronized backups master acting proxies database applications respond query language database understands query language converts submitted query server-readable form executes retrieve results examples proprietary database applications include oracle db2 informix microsoft sql server examples free software database applications include postgresql gnu general public licence include ingres mysql every server uses query logic structure sql structured query language query language less relational database applications clarification database server simply server maintains services related clients via database applications db-engines lists 300 dbmss ranking foundations modeling large sets data first introduced charles bachman 1969 bachman introduced data structure diagrams dsds means graphically represent data dsds provided means represent relationships different data entities 1970 codd introduced concept users database ignorant inner workings database codd proposed relational view data later evolved relational model databases use today 1971 database task report group codasyl driving force behind development programming language cobol first proposed data description language describing database data description language describing part data base known program data manipulation language research development databases focused relational model 1970s 1975 bachman demonstrated relational model data structure set similar congruent ways structuring data working honeywell entity-relationship model first proposed current form peter chen 1976 conducting research mit model became frequently used model describe relational databases chen able propose model superior navigational model applicable real world relational model proposed codd
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Databases
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morphological dictionary field computational linguistics morphological dictionary linguistic resource contains correspondences surface form lexical forms words surface forms words found text corresponding lexical form surface form lemma followed grammatical information example part speech gender number english give gives giving gave given surface forms verb give lexical form would give verb two kinds morphological dictionaries aligned non-aligned aligned morphological dictionary correspondence surface form lexical form word aligned character level example θ empty symbol signifies noun signifies plural example left hand side surface form input right hand side lexical form output order used morphological analysis lexical form generated surface form morphological generation order would reversed formally σ alphabet input symbols formula_1 alphabet output symbols aligned morphological dictionary subset formula_2 alphabet possible alignments including empty symbol aligned morphological dictionary set string formula_4 non-aligned morphological dictionary simply set formula_5 pairs input output strings non-aligned morphological dictionary would represent previous example possible convert non-aligned dictionary aligned dictionary besides trivial alignments left right linguistically motivated alignments align characters corresponding morphemes possible frequently exists one lexical form associated surface form word example house may noun singular may verb present tense result necessary function relates input strings corresponding output strings define set formula_6 input words formula_7 correspondence function would formula_8 defined formula_9
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Computational linguistics
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uwsgi uwsgi software application aims developing full stack building hosting services named web server gateway interface wsgi first plugin supported project uwsgi often used serving python web applications conjunction web servers cherokee nginx offer direct support uwsgi native uwsgi protocol
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Web technology
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wireless communications transfer protocol wireless communications transfer protocol wctp method used send messages wireless devices pagers npcs narrowband pcs networks uses http transport layer world wide web development wctp initiated messaging standards committee submitted radio paging community first proposal received sub-committee established improve protocol issue specification sub-committee moved ptc paging technical committee volunteer committee composed industry representatives pcia personal communications industry accepted first full release adopted protocol pcia standard current version wctp 1.3
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Internet protocols
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peer-to-peer web hosting peer-to-peer web hosting using peer-to-peer networking distribute access webpages differentiated client–server model involves distribution web data dedicated web servers user-end client computers p2p web hosting may take form p2p web caches content delivery networks like dijjer coral cache allow users hold copies data single web pages distribute caches users faster access peak traffic
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Distributed computing architecture
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blackspider technologies limited blackspider technologies limited british software company founded 2002 subsequently acquired surfcontrol july 2006 company provided cloud computing services filtering email spam malware blackspider start-up company founded 2002 john cheney reading berkshire uk january 2004 casenove private equity invested £4.6m 6.6m business allowing organisation grow french german markets july 2006 surfcontrol uk listed plc acquired blackspider £19.5m cash point acquisition blackspider £4m historic revenues operating loss £3.1m 1,200 customers october 2007 websense acquired surfcontrol approximately £204m following acquisition surfcontrol websense original blackspider management team including john cheney left found workbooks.com provider web-based crm software small businesses mailcontrol brand name blackspider technologies email filtering services products sold forcepoint brand name hosted email security
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Distributed computing architecture
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software communications architecture software communications architecture sca open architecture framework defines standard way radios instantiate configure manage waveform applications running platform sca separates waveform software underlying hardware platform facilitating waveform software portability re-use avoid costs redeveloping waveforms latest version sca 4.1 sca published joint tactical networking center jtnc architecture developed assist development software defined radio sdr communication systems capturing benefits recent technology advances expected greatly enhance interoperability communication systems reduce development deployment costs architecture also applicable embedded distributed-computing applications communications terminals electronic warfare ew sca structured sca deliberately designed meet commercial application requirements well military applications since sca intended become self-sustaining standard wide cross-section industry invited participate development validation sca sca system specification implementation independent set rules constrain design systems achieve objectives listed core framework cf defines essential core set open software interfaces profiles provide deployment management interconnection intercommunication software application components embedded distributed-computing communication system sense interfaces defined sca part cf standard waveform apis define key software interfaces allow waveform application radio platform interact sca use apis separate waveform software underlying hardware platform facilitating waveform software portability re-use avoid costs redeveloping waveforms
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Internet protocols
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google earth google earth computer program renders 3d representation earth based primarily satellite imagery program maps earth superimposing satellite images aerial photography gis data onto 3d globe allowing users see cities landscapes various angles users explore globe entering addresses coordinates using keyboard mouse program also downloaded smartphone tablet using touch screen stylus navigate users may use program add data using keyhole markup language upload various sources forums blogs google earth able show various kinds images overlaid surface earth also web map service client addition earth navigation google earth provides series tools desktop application additional globes moon mars available well tool viewing night sky flight simulator game also included features allow users view photos various places uploaded panoramio information provided wikipedia locations street view imagery web-based version google earth also includes voyager feature periodically adds in-program tours often presented scientists documentarians google earth viewed threat privacy national security leading program banned multiple countries countries requested certain areas obscured google satellite images usually areas containing military facilities core technology behind google earth originally developed intrinsic graphics late 1990s time company developing 3d gaming software libraries demo 3d software created spinning globe could zoomed similar powers ten film demo popular board intrinsic wanted remain focused gaming 1999 created keyhole inc. headed john hanke keyhole developed way stream large databases mapping data internet client software key part technology acquired patchworks mapping data governments sources product called keyhole earthviewer sold cds use fields real estate urban planning defense intelligence users paid yearly fee service despite making number capital deals nvidia sony small company struggling make payroll employees leaving fortunes company changed early 2003 cnn received discount software exchange placing keyhole logo on-air whenever map used keyhole expect would amount brief 5 10 second prerecorded animation clips used extensively miles o'brien live 2003 invasion iraq allowing cnn millions viewers follow progress war way never seen public interest software exploded keyhole servers able keep demand keyhole soon contacted central intelligence agency venture capital firm in-q-tel national geospatial-intelligence agency use defense mapping databases gave keyhole much-needed cash infusion intrinsic graphics sold 2003 vicarious visions gaming libraries sell well core group engineers management transitioned keyhole hanke remaining head time google finding 25 searches geospatial character including searches maps directions october 2004 google acquired keyhole part strategy better serve users google earth imagery displayed digital globe displays planet surface using single composited image far distance zooming far enough imagery transitions different imagery area finer detail varies date time one area next imagery retrieved satellites aircraft launch nasa usgs landsat 8 satellite google relied partially imagery landsat 7 suffered hardware malfunction left diagonal gaps images 2013 google used datamining remedy issue providing described successor blue marble image earth single large image entire planet achieved combining multiple sets imagery taken landsat 7 eliminate clouds diagonal gaps creating single mosaic image google uses landsat 8 provide imagery higher quality greater frequency imagery hosted google servers contacted application opened requiring internet connection imagery resolution ranges 15 meters resolution 15 centimeters much earth google earth uses digital elevation model data collected nasa shuttle radar topography mission creates impression three-dimensional terrain even imagery two-dimensional every image created google earth using satellite data provided google earth copyrighted map derivative google earth made copyrighted data united states copyright law may used except licenses google provides google allows non-commercial personal use images e.g personal website blog long copyrights attributions preserved contrast images created nasa globe software world wind use blue marble landsat usgs imagery public domain version 5.0 google introduced historical imagery allowing users view earlier imagery clicking clock icon toolbar opens time slider marks time available imagery past feature allows observation area changes time utilizing timelapse feature allows ability view zoomable video far back 32 years google earth shows 3d building models cities including photorealistic 3d imagery first 3d buildings google earth created using 3d modeling applications sketchup beginning 2009 building maker uploaded google earth via 3d warehouse june 2012 google announced would replacing user-generated 3d buildings auto-generated 3d mesh would phased starting select larger cities notable exception cities london toronto required time process detailed imagery vast number buildings reason given greater uniformity 3d buildings compete nokia apple maps already using technology coverage began year 21 cities four countries early 2016 3d imagery expanded hundreds cities 40 countries including every u.s. state encompassing every continent except antarctica 2009 collaboration google museo del prado madrid museum selected 14 paintings photographed displayed resolution 14,000 megapixels inside 3d version prado google earth google maps april 15 2008 version 4.3 google fully integrated street view google earth street view displays 360° panoramic street-level photos select cities surroundings photos taken cameras mounted automobiles viewed different scales many angles navigable arrow icons imposed introduced google earth 5.0 2009 google ocean feature allows users zoom surface ocean view 3d bathymetry supporting 20 content layers contains information leading scientists oceanographers april 14 2009 google added bathymetric data great lakes june 2011 google increased resolution deep ocean floor areas 1-kilometer grids 100 meters high-resolution features developed oceanographers columbia university lamont-doherty earth observatory scientific data collected research cruises sharper focus available 5 percent oceans seen hudson new york city wini seamount near hawaii mendocino ridge u.s pacific coast google programs features including within google earth allowing exploration mars moon view sky earth outer space including surfaces various objects solar system google sky feature introduced google earth 4.2 august 22 2007 browser-based application march 13 2008 android smartphones augmented reality features google sky allows users view stars celestial bodies produced google partnership space telescope science institute stsci baltimore science operations center hubble space telescope dr. alberto conti co-developer dr. carol christian stsci plan add public images 2007 well color images archived data hubble advanced camera surveys newly released hubble pictures added google sky program soon issued new features multi-wavelength data positions major satellites orbits well educational resources provided google earth community also christian conti website sky also visible sky mode constellations stars galaxies animations depicting planets orbits real-time google sky mashup recent astronomical transients using voevent protocol provided voeventnet collaboration programs similar google sky include microsoft worldwide telescope stellarium google mars application within google earth version program imagery planet mars google also operates browser-based version although maps much higher resolution within google earth include 3d terrain well infrared imagery elevation data also extremely-high-resolution images mars reconnaissance orbiter hirise camera similar resolution cities earth finally many high-resolution panoramic images various mars landers mars exploration rovers spirit opportunity viewed similar way google street view mars also small application found near face mars called meliza robot character user speak originally browser application google moon feature allows exploration moon google brought feature google earth 40th anniversary apollo 11 mission july 20 2009 announced demonstrated group invited guests google along buzz aldrin newseum washington d.c. google moon includes several tours including one apollo missions incorporating maps videos street view-style panoramas provided nasa google earth numerous features allow user learn specific places called layers include different forms media including photo video layers include tours guide user specific places set order layers created using keyhole markup language kml users also use create customized layers locations marked placemarks organized folders example user use placemarks list interesting landmarks around globe provide description photos videos viewed clicking placemarks viewing new layer application december 2006 google earth added new integration wikipedia panoramio wikipedia layer entries scraped coordinates via also community-layer project coordinates used different types display different languages supported built-in wikipedia layer panoramio layer features pictures uploaded panoramio users placed google earth based user-provided location data addition flat images google earth also includes layer user-submitted panoramic photos navigable similar way street view google earth includes multiple features allow user monitor current events 2007 google began offering users ability monitor traffic data provided google traffic real time based information crowdsourced gps-identified locations cell phone users google earth 4.2 flight simulator added application originally hidden feature introduced 2007 starting 4.3 given labeled option menu addition keyboard control simulator controlled mouse joystick simulator also runs animation allowing objects planes animate simulator another flight simulator geofs created name gefs-online using google earth plug-in api operate within web browser september 1 2015 program uses open-source program cesiumjs due google earth plug-in discontinued liquid galaxy cluster computers running google earth creating immersive experience september 30 2010 google made configuration schematics rigs public placing code setup guides liquid galaxy wiki liquid galaxy also used panoramic photo viewer using krpano well google street view viewer using peruse-a-rue peruse-a-rue method synchronizing multiple maps api clients google earth released macos linux ios android linux version began version 4 beta google earth native port using qt toolkit free software foundation consider development free compatible client google earth high priority free software project google earth released android february 22 2010 ios october 27 2008 mobile versions google earth make use multi-touch interfaces move globe zoom rotate view allow select current location automotive version google earth made available 2010 audi a8 google earth pro originally business-oriented upgrade google earth features movie maker data importer late january 2015 available 399/year though google decided make free public google earth pro currently standard version google earth desktop application version 7.3 pro version includes add-on software movie making advanced printing precise measurements currently available windows mac os x 10.8 later linux discontinued december 2008 google earth plus paid subscription upgrade google earth provided customers following features become available free google earth one feature gps integration allowed users read tracks waypoints gps device variety third-party applications created provide functionality using basic version google earth generating kml kmz files based user-specified user-recorded waypoints google earth enterprise designed use organizations whose businesses could take advantage program capabilities example globe holds company data available anyone company march 20 2015 google retired google earth enterprise product support ended march 22 2017 google earth enterprise allowed developers create maps 3d globes private use host platform gee fusion gee server gee portable server source code published github apache2 license march 2017 google earth 9 version google earth first released april 18 2017 development two years main feature version launching new web version google earth currently available google chrome version added voyager feature whereby users view portal page containing guided tours led scientists documentarians version also added 'm feeling lucky button represented die takes user random location earth along showing knowledge card containing short excerpt location wikipedia article google earth api free beta service allowing users place version google earth web pages api enabled sophisticated 3d map applications built unveiling google 2008 i/o developer conference company showcased potential applications game player controlled milktruck atop google earth surface google earth api deprecated december 15 2014 remained supported december 15 2015 google chrome ended support netscape plugin api google earth api relies end 2016 november 16 2016 google released virtual reality version google earth valve steam computer gaming platform google earth vr allows users navigate using vr controllers currently compatible oculus rift htc vive virtual reality headsets september 14 2017 part google earth vr 1.4 update google added street view support google earth outreach charity program google promotes donates various non-profit organizations beginning 2007 donations often accompanied layers featured google earth allowing users view non-profit projects goals navigating certain related locations google earth outreach offers online training using google earth google maps public education issues affecting local regions entire globe june 2008 training given 20 indigenous tribes amazon rainforest suruí help preserve culture raise awareness problem deforestation non-profit organizations featured google earth via outreach program include arkive global heritage fund wateraid world wide fund nature google earth engine cloud computing platform processing satellite imagery geospatial observation data provides access large database satellite imagery computational power needed analyze images google earth engine allows observation dynamic changes agriculture natural resources climate using geospatial data landsat satellite program passes places earth every sixteen days google earth engine become platform makes landsat sentinel-2 data easily accessible researchers collaboration google cloud storage google earth engine provides data catalog along computers analysis allows scientists collaborate using data algorithms visualizations platform uses python javascript application programming interfaces making requests servers google earth engine used multiple times tool tracking deforestation initial applications engine included mapping forests mexico identifying water congo basin detecting deforestation amazon rainforest using google earth engine track global forest loss gain university maryland reported overall loss global forest cover carnegie institute science claslite system imazon ’ sisteme de alerta de deforesation sad two institutions partnered google development google earth engine organizations use program build maps forests measure environmental disturbances additionally google earth engine expanded applications range tiger habitat monitoring malaria risk mapping global surface water software criticized number special interest groups including national officials invasion privacy posing threat national security typical argument software provides information military critical installations could used terrorists google earth blocked google iran sudan since 2007 due united states government export restrictions program also blocked morocco since 2006 maroc telecom major service provider country academic realm increasing attention devoted google earth place development digital globes particular international journal digital earth features multiple articles evaluating comparing development google earth differences compared professional scientific governmental platforms google earth role expansion earth observing media examined role shaping shared cultural consciousness regarding climate change humanity capacity treat earth engineerable object
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Internet protocols
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javaserver faces javaserver faces jsf java specification building component-based user interfaces web applications formalized standard java community process part java platform enterprise edition also mvc web framework simplifies construction user interfaces ui server-based applications using reusable ui components page jsf 2 uses facelets default templating system view technologies xul plain java also employed contrast jsf 1.x uses javaserver pages jsp default templating system 2001 original java specification request jsr technology ultimately became javaserver faces proposed developing package name codice_1 june 2001 javaworld would report amy fowler team design javaserver faces api aka moonwalk – application framework creating web-based user interfaces based component-driven ui design-model javaserver faces uses xml files called view templates facelets views codice_2 processes requests loads appropriate view template builds component tree processes events renders response typically html language client state ui components objects scope interest saved end request process called statesaving note transient true restored upon next creation view either client server side save objects states jsf often used together ajax rich internet application development technique ajax combination web development techniques technologies make possible create rich user interfaces user interface components mojarra jsf reference implementation apache myfaces originally developed html ajax added via javascript changed however jsf supports multiple output formats ajax-enabled components easily added enrich jsf-based user interfaces jsf 2.0 specification provides built-in support ajax standardizing ajax request lifecycle providing simple development interfaces ajax events allowing event triggered client go proper validation conversion finally method invocation returning result browser via xml dom update jsf 2 includes support graceful degradation javascript disabled browser following companies projects offer ajax-based jsf frameworks component libraries facelets designed specifically javaserver faces adopted official view technology jsf 2.0 eliminates life-cycle conflicts existed jsp forcing workarounds java developers facelets allows easy component/tag creation using xml markup instead java code chief complaint jsf 1.x new jsf developments also provide wide accessibility java 5 annotations codice_3 codice_4 codice_5 removes need codice_6 cases except framework extension navigation simplified removing need codice_6 navigation cases page transitions invoked simply passing name desired view/facelet addition partial state saving dom updates part built-in standardized ajax support latest jsf release built-in support handling resources like images css javascript allowing artifacts included component libraries separated jar files simply co-located consistent place within web application includes logical naming versioning resources jsf 2.0 also includes number changes like adding support events separate development staging production modes similar codice_8 ruby rails significantly expanding standard set components january 2014 technology radar publication thoughtworks wrote article published november 2014 dzone website titled avoid jsf jens schauder wrote february 2014 çağatay çivici primefaces lead responded thoughtworks criticisms post titled jsf ’ told anymore çivici argues improvements jsf years offer many features embrace modern web development providing option write javascript html css also regarding state çağatay wrote
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Programming language topics
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bradford law bradford law pattern first described samuel c. bradford 1934 estimates exponentially diminishing returns searching references science journals one formulation journals field sorted number articles three groups one-third articles number journals group proportional 1 n n² number related formulations principle many disciplines pattern called pareto distribution practical example suppose researcher five core scientific journals subject suppose month 12 articles interest journals suppose order find another dozen articles interest researcher would go additional 10 journals researcher bradford multiplier b 2 i.e 10/5 new dozen articles researcher need look b times many journals looking 5 10 20 40 etc journals researchers quickly realize little point looking different researchers different numbers core journals different bradford multipliers pattern holds quite well across many subjects may well general pattern human interactions social systems like zipf law related good explanation works knowing useful librarians means specialty sufficient identify core publications field stock rarely researchers need go outside set however impact far greater armed idea inspired vannevar bush famous article may think eugene garfield institute scientific information 1960s developed comprehensive index scientific thinking propagates science citation index sci effect making easy identify exactly scientists science impact journals science appeared also caused discovery expect journals nature science core hard science pattern happen humanities social sciences result pressure scientists publish best journals pressure universities ensure access core set journals hand set core journals may vary less strongly individual researchers even strongly along schools-of-thought divides also danger over-representing majority views journals selected fashion bradford law also known bradford law scattering bradford distribution another general term come use since 2006 information scattering though better categorized secondary information scattering law distribution bibliometrics applied world wide web hjørland nicolaisen 2005 p. 103 identified three kinds scattering found literature bradford law including bradford papers unclear relation kind scattering actually measured interpretation bradford law terms geometric progression suggested v. yatsko introduced additional constant demonstrated bradford distribution applied variety objects distribution articles citations across journals v. yatsko interpretation y-interpretation effectively used compute threshold values case necessary distinguish subsets within set objects successful/unsuccessful applicants developed/underdeveloped regions etc
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Computational linguistics
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bruce perens open source series bruce perens open source series series books edited bruce perens series editor published prentice hall ptr principal topics linux open-source software books intended professional software developers system network administrators power users series published 2002 2006 24 titles series book licensed open publication license made available free download several months publication first book series published open content license
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Operating systems
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two-man rule two-man rule control mechanism designed achieve high level security especially critical material operations rule access actions require presence two authorized people times per us air force instruction afi 91-104 two-person concept designed prevent accidental malicious launch nuclear weapons single individual case minuteman missile launch crews launch order received operators must agree valid comparing authorization code order sealed authenticator special sealed envelope holds code sealed authenticators stored safe two separate locks operator key one lock neither open safe alone also operator one two launch keys order verified must insert keys slots control panel turn simultaneously precaution slots two launch keys positioned far enough apart make impossible one operator reach additional protection missile crew another launch control center must missiles launched total four keys thus required initiate launch submarine commanding officer executive officer must agree order launch valid mutually authorize launch operations personnel instead another party would confirm missile launch case land-based icbms third officer weapons officer must also confirm launch addition set keys distributed among key personnel submarine keys kept safes crew members access keys keys stored special safes board secured combination locks nobody board combination open safes unlock key comes part launch order emergency action message higher authority journalist ron rosenbaum pointed order issued process entirely concerned authenticating identity commanding officers authenticity order safeguards verify order person issuing actually sane notably major harold hering discharged air force asking question know order receive launch missiles came sane president two-man rule applies missile silos submarines check president sole authority order nuclear launch two-person integrity tpi security measure taken prevent single-person access comsec keying material cryptographic manuals tpi accomplished follows time one person possession combinations keys gain lone access security container cryptographic equipment containing comsec material neither one person sole possession comsec material requires tpi security no-lone zone area must staffed two qualified cleared individuals individual must within visual contact visual contact critical component requires no-lone-zone area designation no-lone zone may contain cryptographic component weapon system hardware test nuclear weapon active nuclear weapon controls united states air force usaf policy concerning critical weapons no-lone zone area presence single individual prohibited two-person concept requires presence two individuals knowledgeable task performed capable detecting incorrect unauthorized procedure part regarding task performed two-man rule used safety critical applications presence two people required potentially hazardous operation performed common safety practice example laboratories machine shops context additional security may less important fact one individual injured call help another example firefighters operating hazardous environment i.e interior structure fire hazmat zone also known idlh 'immediately dangerous life health function team least two personnel commonly one team environment team operates unit dual keys require authorization two separate parties particular action taken simplest form dual key security lock requires two keys unlock two keys would possession two separate persons lock could opened parties agreed open time 1963 canada accepted american w-40 nuclear warheads dual key control canadian soil used canadian bomarc missiles similarly many banks implement variant two-man rule secure large sums money valuable items concept unlocking vault requires two individuals different keys vault secured key lock system bank vaults secured combination lock one individual know half combination second person know remaining half point either person know person half lock combination requiring persons physically present order unlock vault extension broader rationale two-man rule regulations companies not-for-profit organizations may require signatures two executives checks rules make harder individual acting alone defraud organization software systems enforce two-man rule whereby certain actions example funds wire transfers take place approved two authorized users helps prevent expensive errors makes difficult commit fraud embezzlement requirements common financial systems also used controls critical infrastructure nuclear reactors electrical power generation dangerous operations biohazard research facilities finally testimony two witnesses valuable various situations deter wrongful act false accusation one prove wrongful act occurred late march 2015 many national aviation authorities and/or airlines made cockpits aircraft flight mandatory two-man no-lone zones result germanwings flight 9525 crash early investigation crash believed cockpit voice recorder audio later supported flight data recorder information co-pilot deliberately crashed aircraft locking cockpit door captain left use toilet
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Computer security
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sme server sme server formerly known e-smith linux distribution based centos offering operating system computers used web file email database servers employs comprehensive ui management-related tasks extensible templates letters sme stand small medium enterprise target market software one notable features distribution template system sme server 9.1 based centos 6.7 based red hat enterprise linux rhel version 32bit pae support 64bit available running apache 2.0 mysql 5.0 php 5 additional addons available current stable version called sme contribs core network environment easy simple access shared files printers sme server software allows easy sharing files printers windows macintosh clients information bay i-bay feature provides easy convenient information storage retrieval multiple groups via web ftp file sharing small business customers looking simple solution works different types connections internet sme server automates process connecting internet connect server supply isp account information server solution acts gateway entire network requires additional client software minimal configuration users immediately start browsing web using email access internet services pervasiveness email small businesses increasingly need support email employees sme server provides secure reliable email server allows easy creation individual group addresses greater versatility works mail client uses industry-standard imap pop3 smtp protocols secure webmail allows users access server web browser anywhere internet send receive e-mail via encrypted 128-bit ssl link top equipped clamav antivirus spamassassin reduce amount unsolicited mail security always priority company starts using internet sme server offers multi-layer architecture protecting external interface packet-filtering service restriction offers selective address port binding application-level access control lists protects internal network intrusion businesses remote branch sites telecommuting employees require remote access email resources local network sme server provides multiple tools webmail access email using browser 128-bit pptp secure client-to-server vpns open secure shell ssh provide encrypted access internal network server resources administrators companies typically require central directory email addresses users access sme server features robust directory service used email clients including outlook outlook express netscape communicator feature implemented using industry-standard ldap protocol small businesses also need secure reliable web presence intranet communicate employees sme server includes apache web server used 60 internet content easily edited updated desktop clients including dynamic content also supports use secure sockets layer ssl connections e-commerce sme server software supports hardware software disk mirroring raid 1 usb disk backup tape backup additional data protection almost packages sme server includes upstream vendors included unmodified purpose take advantage stability comes huge user base uses packages security allow automatic updates soon update available upstream vendor security updates redhat/centos available 2012 centos 4 sme server architecture explicitly supports developers making easy drop software place remove without needing modify existing files extensions easily add new features popular examples asterisk voip pbx hylafax server dansguardian web content filter joomla cms jinzorra jukebox mediawiki thin client server oscommerce online shop
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Operating systems
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online armor personal firewall online armor personal firewall firewall originally developed australian company tall emu program sold emsi software gmbh emsisoft ltd program provides protection microsoft windows operating system inbound outbound attacks three editions product independent proactive security challenge test performed matousec.com online armor premium received score 99 surpassing well-known firewalls zonealarm kaspersky internet security well known vulnerability profiling site company secunia found vulnerabilities march 2008 software though matousec reported weakness 25 march 2008 repaired latest version online armor gained negative positive feedback users reporting serious compatibility problems certain programs f-secure ad muncher noted product website also receiving praise free online support swift response problems 31 march 2015 emsisoft ltd announced discontinued selling new licenses online armor would possible activate new license keys end may 2015 support online armor would officially end 31 march 2016
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Computer security
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syntactic closure computer science syntactic closures implementation strategy hygienic macro system actual arguments macro call enclosed current environment inadvertently reference bindings introduced macro
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Programming language topics
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machine code monitor machine code monitor machine language monitor software allows user enter commands view change memory locations computer options load save memory contents from/to secondary storage full-featured machine code monitors provide detailed control single-stepping execution machine language programs much like debugger include absolute-address code assembly disassembly capabilities machine code monitors became popular home computer era 1970s 1980s sometimes available resident firmware computers e.g. built-in monitor commodore 128 unheard perform one programming monitor lieu full-fledged symbolic assembler even full-featured assemblers became readily available machine code monitor indispensable debugging programs usual technique set break points code undergoing testing e.g. brk instruction 6502 assembly language start program microprocessor encountered break point test program would interrupted control would transferred machine code monitor typically would trigger register dump monitor would await programmer input activities point might include examining memory contents patching code and/or perhaps altering processor registers prior restarting test program general decline scratch-written assembly language software made use machine code monitor somewhat lost art systems higher-level languages employed debuggers used present abstract friendly view happening within program however use machine code monitors persists especially area hobby-built computers
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Operating systems
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xak tower gazzel xak precious package tower gazzel fantasy role-playing video game developed published japanese software developer microcabin game direct sequel technically third installment series tower gazzel sidestory taking place events game released japan latok kart defeated zamu gospel events portrayed xak ii friends intrigued rumours demonic tower man looking like latok roaming neighbourhood appearance false latok kidnapping rune greed family ploys lure two descendants duel tower laid villains al acrila gill berzes demon called zegraya using latok rune plan resurrect ancient demon gazzel demon unimaginable power comparable destroying entire mountain single attack player controls latok looking onto game world bird's-eye view latok swing sword optionally firing magical shots tip expense magic points jump short distances player choose take along one party four characters exploration tower so-called 'support members subtly change latok statistics addition triggering different events within game entirety tower large labyrinth spanning six floors elemental theme darkness basement respectively earth fire water wind heaven first fifth floors game one large puzzle goal reaching bottom floor defeating zegraya gazzel many puzzles revolve around fact floors heavily interconnected floor fire example large wall flames latok pass way water floor large door opened pours large amount water hole floor dousing flames another part puzzles involves choice support member take along support members n't affect latok combat statistics points game passed right support member tagging along even items game latok use right supportmember example latok finds magical scroll lightning spell inscribed n't master enough magic cast certain part first floor seemingly impassable wall rubble fray selected support member snatch lightning scroll latok use blast path rubble game saved fixed point entrance tower prevent player backtrack save game various items found teleport latok support member back entrance fixed point inside tower contrary predecessors tower gazzel use experience point system currency kind appear game latok starts game level 50 end xak ii advance instead occurs xak iii new equipment also unavailable latok sticks sword armor shield xak ii end throughout game eliminates need player spend large amounts time 'leveling collecting enough experience points and/or gold player character grow strong enough buy new equipment respectively way game emphasis puzzle aspect combat kind advancement system retained latok find different pairs gauntlets tower pair enhancing combat statistics game engine almost identical xak ii preserving real-time combat aspect music graphics even recycled previous installment compared xak ii xak gazzel runs much smoother even regular msx2 prompting much less shorter loading times possible supportmembers abilities follows addition single save point game represented healer fell bow except villains game uses little non-player characters emphasising puzzling aspect even
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Computer architecture
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portsnap portsnap system written colin percival secure distribution compressed digitally signed snapshots freebsd ports tree distribution follows client–server model uses transport protocol http pipelined http freebsd 6.0 portsnap part base system including 5.5 previous versions installed ports standalone program run manually cron job one alternatives classic cvsup method advantages include another alternative cvsup cvsync used manage openbsd source tree shares cvsup disadvantages though portsnap package distributed 2-clause bsd license
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Operating systems
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pstoedit pstoedit free computer program converts postscript pdf files vector formats supports many output formats including wmf/emf pdf dxf cgm html means free/shareware plugins svg mif rtf author maintainer wolfgang glunz pstoedit uses ghostscript perform first part conversion process ghostscript converts postscript pdf file basic postscript format translating complex functions basic functions line draw commands second part conversion process consists translating basic functions basic functions output format pstoedit multi platform ms windows setup program available 32bit 64bit complete job including instance making connection ghostscript ms office three interfaces installed command line interface interface means gsview import filter ms office however make actual use ms office interface 50 registration required registration also adds functionality two interfaces licensed gnu general public license pstoedit free software
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Programming language topics
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dalvik software dalvik discontinued process virtual machine vm google android operating system executes applications written android dalvik bytecode format still used distribution format longer runtime newer android versions dalvik integral part android software stack unsupported android versions 4.4 kitkat earlier commonly used mobile devices mobile phones tablet computers devices smart tvs wearables dalvik open-source software originally written dan bornstein named fishing village dalvík eyjafjörður iceland programs android commonly written java compiled bytecode java virtual machine translated dalvik bytecode stored .dex dalvik executable .odex optimized dalvik executable files related terms odex de-odex associated respective bytecode conversions compact dalvik executable format designed systems constrained terms memory processor speed successor dalvik android runtime art uses bytecode .dex files .odex files succession aiming performance improvements transparent end users new runtime environment included first time android 4.4 kitkat technology preview replaced dalvik entirely later versions android 5.0 lollipop first version art included runtime unlike java vms stack machines dalvik vm uses register-based architecture requires fewer typically complex virtual machine instructions dalvik programs written java using android application programming interface api compiled java bytecode converted dalvik instructions necessary tool called dx used convert java .class files .dex format multiple classes included single .dex file duplicate strings constants used multiple class files included .dex output conserve space java bytecode also converted alternative instruction set used dalvik vm uncompressed .dex file typically percent smaller size compressed java archive jar derived .class files dalvik executables may modified installed onto mobile device order gain optimizations byte order may swapped certain data simple data structures function libraries may linked inline empty class objects may short-circuited example optimized low memory requirements dalvik specific characteristics differentiate standard vms according google design dalvik permits device run multiple instances vm efficiently android 2.2 froyo brought trace-based just-in-time jit compilation dalvik optimizing execution applications continually profiling applications time run dynamically compiling frequently executed short segments bytecode native machine code dalvik interprets rest application bytecode native execution short bytecode segments called traces provides significant performance improvements relative merits stack machines versus register-based approaches subject ongoing debate generally stack-based machines must use instructions load data stack manipulate data thus require instructions register machines implement high-level code instructions register machine must encode source destination registers therefore tend larger difference importance vm interpreters opcode dispatch tends expensive along factors similarly relevant just-in-time compilation tests performed armv7 devices 2010 oracle owner java technology standard non-graphical java benchmarks showed hotspot vm java se embedded 2–3 times faster jit-based dalvik vm android 2.2 initial android release included jit compiler 2012 academic benchmarks confirmed factor 3 hotspot dalvik android board also noting dalvik code smaller hotspot furthermore benchmarks performed android device still show factor 100 native applications dalvik application android device upon running benchmarks using early interpreter 2009 java native interface jni native code showed order magnitude speedup dalvik published terms apache license 2.0 say dalvik clean-room implementation rather development top standard java runtime would mean inherit copyright-based license restrictions either standard-edition open-source-edition java runtimes oracle reviewers dispute august 12 2010 oracle acquired sun microsystems april 2009 therefore owns rights java sued google claimed infringement copyrights patents oracle alleged google developing android knowingly directly repeatedly infringed oracle java-related intellectual property may 2012 jury case found google infringe oracle patents trial judge ruled structure java apis used google copyrightable parties agreed zero dollars statutory damages 9 lines copied code
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Operating systems
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virtual enterprise network architecture fabric connect computer networking usage name used extreme networks market extended implementation ieee 802.1aq shortest path bridging mac-in-mac standard fabric connect technology originally developed enterprise solutions r department within nortel networks 2009 avaya inc acquired nortel networks enterprise business solutions transaction included fabric connect intellectual property together ethernet switching platforms supported subsequently fabric connect technology became part extreme networks portfolio virtue 2017 purchase avaya networking business assets avaya era technology promoted lead element virtual enterprise network architecture vena part extreme networks stated acquisition avaya networking assets specifically award-winning fabric technology ... strengthens extreme position leader across education healthcare government markets network virtualization capability based enhanced implementation ieee 802.1aq shortest path bridging spb standard fabric connect offers ability create simplified network dynamically virtualize elements efficiently provision utilize resources thus reducing strain network personnel extreme networks base fabric connect technology spb standard including support nowiki rfc 6329 /nowiki integrated ip routing ip multicast support unified technology allows replacement multiple conventional protocols spanning tree rip and/or ospf ecmp pim simply put fabric connect aim provide network-wide end-to-end multi-layer virtualization adjunct fabric connect technology fabric attach allows network operators extend network virtualization directly conventional wiring closet existing non-fabric ethernet switches automate provisioning devices appropriate virtual network particularly relevant mass unattended network end-point appearing ip phones wireless access points ip cameras fabric attach standardized protocols 802.1ab lldp exchange credentails obtain provisioning information allows client switches automatically re-configured fly parameters let traffic flows map fabric connect edge switches aka backbone edge bridge spb definition functioning fabric attach server switch method described ietf internet draft pending standardization activity fabric attach typically used automate wiring closet connectivity potential extensible use data center virtual machines able dynamically request vlan/vsn virtual service network assignment based upon application requirements range modular chassis-based products featuring carrier-grade linux operation system designed high-performance deployment scenarios need scale multiple terabit switching capacity support 10 40 gigabit ethernet connections designed eventually support 100 gigabit ethernet compact form-factor platform delivering high-density 10/40 gigabit ethernet connectivity targeted mid-market mid-size enterprise core switch applications range high-end 10 gigabit ethernet stackable switches extend fabric-based networking data center top-of-rack support 40 gigabit ethernet via mda slot range high-end gigabit ethernet stackable switches extend fabric-based networking branch metro locations range high-end gigabit ethernet stackable switches provide enterprise-class desktop features including poe offering 10 gbit/s uplink connections switch supports 144 gbit/s virtual backplane capacity delivering 1.152 tbit/s system eight creating virtual backplane stacking configuration mid-range gigabit ethernet stackable switches provide enterprise-class desktop features including poe/poe+ offering 1/10 gbit/s uplink connections switch supports 48gbit/s virtual backplane capacity delivering 384gbit/s system 8 creating virtual backplane stacking configuration entry-level gigabit ethernet stackable switches provide enterprise-class desktop features including poe/poe+ 1 gbit/s uplink connections
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Distributed computing architecture
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cyber threat hunting cyber threat hunting active cyber defence activity process proactively iteratively searching networks detect isolate advanced threats evade existing security solutions contrast traditional threat management measures firewalls intrusion detection systems ids malware sandbox computer security siem systems typically involve investigation evidence-based data warning potential threat threat hunting traditionally manual process security analyst sifts various data information using knowledge familiarity network create hypotheses potential threats limited lateral movement threat actors even effective efficient however threat hunting partially automated machine-assisted well case analyst uses software leverages machine learning user entity behavior analytics ueba inform analyst potential risks analyst investigates potential risks tracking suspicious behavior network thus hunting iterative process meaning must continuously carried loop beginning hypothesis hypothesis focus efforts known exploits potential bad actors assets data value using security data industry reports intelligence hypothesis formed hunt team sets prove disprove validity cyber threat hunts often employ automated manual tools techniques identify compromise detected three types hypotheses analyst researches hypothesis going vast amounts data network results stored used improve automated portion detection system serve foundation future hypotheses detection maturity level dml model expresses threat indicators detected different semantic levels high semantic indicators goal strategy tactics techniques procedure ttp valuable identify low semantic indicators network artifacts atomic indicators ip addresses siem tools typically provide indicators relatively low semantic levels therefore need develop siem tools provide threat indicators higher semantic levels representative notable vendors threat hunting software services include sans institute conducted research surveys effectiveness threat hunting track disrupt cyber adversaries early process possible according survey released 2017 60 hunt threats reported measurable improvements infosec programs based hunting efforts 91 report improvements speed accuracy response two types indicators sans institute identifies threat hunting maturity model follows cyberattackers operate undetected average 99 days obtain administrator credentials less three days according mandiant m-trends report study also showed 53 attacks discovered notification external party average company takes 170 days detect advanced threat 39 days mitigate 43 days recover according ponemon institute
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Computer security
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canigó framework canigó name chosen java ee framework generalitat de catalunya canigó defined common technological framework development execution web applications corporative systems departments generalitat de catalunya covers various functionalities canigó architecture based model–view–controller abstraction process allows division application logics three main components able developed different rols team actually canigó architecture mvc structured framework divided 3 layers 4 cross-cutting modules canigó modular structure gives developers option use needed modules cover project requirements modules defined interfaces isolating chosen implementations canigó based series resources api integration jpa open source packages spring swagger ... also offers extensions packages adding wide catalog reusable components one important architectural basis decoupling frontend backend using rest api architecture allows independent development teams work frontend backend framework consists blocks specified spring open source framework written java platform first version created rod johnson october 2002 last release version 5.0.9 published first week september 2018 canigó designed help configuration web applications also simplify systems construction different pieces easily interchangeable visible service integration security services database connection transactionality etc ... spring provides complete testing system possible develop unitary tests uncoupling objects context making easier execution test cases external data access spring easy task framework manages resources also support apis able bear vast majority java industry data access technologies like jdbc hibernate jpa jdo ibatis main basis canigó architecture completely integrated group also modular best practices java web applications developing technologies actual components constitute system module core framework main features located user authorisation authentication applications access management system since canigo 3.2.0 jsf deprecated presentation layer technology presentation layer responsibility delegated outside framework another teams specialized front-end technologies angular react goal providing simple access different services offered generalitat de catalunya module enables application data persistence retrieval application database management systems module delivers additional features framework module adds feature applications generate execution instrumentation data data ready mined processed monitoring tools
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Programming language topics
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text retrieval conference text retrieval conference trec ongoing series workshops focusing list different information retrieval ir research areas tracks co-sponsored national institute standards technology nist intelligence advanced research projects activity part office director national intelligence began 1992 part tipster text program purpose support encourage research within information retrieval community providing infrastructure necessary large-scale evaluation text retrieval methodologies increase speed lab-to-product transfer technology track challenge wherein nist provides participating groups data sets test problems depending track test problems might questions topics target extractable features uniform scoring performed systems fairly evaluated evaluation results workshop provides place participants collect together thoughts ideas present current future research work new tracks added new research needs identified list current trec 2018 1997 japanese counterpart trec launched first workshop 1999 called ntcir nii test collection ir systems 2000 clef european counterpart specifically vectored towards study cross-language information retrieval launched nist claims within first six years workshops effectiveness retrieval systems approximately doubled conference also first hold large-scale evaluations non-english documents speech video retrieval across languages additionally challenges inspired large body publications technology first developed trec included many world commercial search engines independent report rtii found one-third improvement web search engines 1999 2009 attributable trec enhancements likely saved 3 billion hours time using web search engines ... additionally report showed every 1 nist partners invested trec least 3.35 5.07 benefits accrued u.s. information retrieval researchers private sector academia one study suggests state art ad hoc search advanced substantially past decade referring search topically relevant documents small news web collections gigabytes advances types ad hoc search past decade example test collections created known-item web search found improvements use anchor text title weighting url length useful techniques older ad hoc test collections 2009 new billion-page web collection introduced spam filtering found useful technique ad hoc web search unlike past test collections test collections developed trec useful potentially helping researchers advance state art also allowing developers new commercial retrieval products evaluate effectiveness standard tests past decade trec created new tests enterprise e-mail search genomics search spam filtering e-discovery several retrieval domains trec systems often provide baseline research examples include conference made varied international group researchers developers 2003 93 groups academia industry 22 countries participating
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Computational linguistics
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apptix apptix application service provider asp technology company providing hosted business services software service apptix serves businesses customers highly regulated industries healthcare apptix services include microsoft exchange email voip phone service microsoft sharepoint collaboration services web conferencing/secure im email encryption mobile device management messaging active directory management archiving backup services september 2015 apptix acquired godaddy inc 22.5 million cash deal apptix founded 1997 spun telecomputing asa oslo norway company headquartered herndon virginia usa additional locations florida texas apptix publicly traded oslo stock exchange ose app apptix acquired integrated hosted exchange vendors asp-one mi8 mailstreet 2011 revenues totaled us 40.7 million 5 38.6 millionin 2010 positive net income trends continued first three quarters 2012 apptix microsoft partner offering hosted microsoft exchange microsoft sharepoint services apptix technology partners include parallels well symantec sonian mozy apptix ’ channel partners include insight enterprises megapath cincinnati bell inc. web.com sprint nextel corporation
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Distributed computing architecture
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power6 power6 microprocessor developed ibm implemented power isa v.2.03 became available systems 2007 succeeded power5+ ibm flagship power microprocessor claimed part eclipz project said goal converging ibm server hardware practical hence ipz acronym iseries pseries zseries power6 described international solid-state circuits conference isscc february 2006 additional details added microprocessor forum october 2006 next isscc february 2007 formally announced may 21 2007 released june 8 2007 speeds 3.5 4.2 4.7 ghz company noted prototypes reached 6 ghz power6 reached first silicon middle 2005 bumped 5.0 ghz may 2008 introduction p595 power6 dual-core processor core capable two-way simultaneous multithreading smt power6 approximately 790 million transistors 341 mm large fabricated 65 nm process notable difference power5 power6 executes instructions in-order instead out-of-order change often requires software recompiled optimal performance power6 still achieves significant performance improvements power5+ even unmodified software according lead engineer power6 project power6 also takes advantage viva-2 virtual vector architecture enables combination several power6 nodes act single vector processor core two integer units two binary floating-point units altivec unit novel decimal floating-point unit binary floating-point unit incorporates many microarchitectures logic circuit latch integration techniques achieve 6-cycle 13-fo4 pipeline according company paper unlike servers ibm competitors power6 hardware support ieee 754 decimal arithmetic includes first decimal floating-point unit integrated silicon 50 new floating point instructions handle decimal math conversions binary decimal feature also added z10 microprocessor featured system z10 core 64 kb four-way set-associative instruction cache 64 kb data cache eight-way set-associative design two-stage pipeline supporting two independent 32-bit reads one 64-bit write per cycle core semi-private 4 mib unified l2 cache cache assigned specific core fast access two cores share 32 mib l3 cache die using 80 gb/s bus power6 connect 31 processors using two inter node links 50 gb/s supports 10 logical partitions per core limit 254 per system interface service processor monitors adjusts performance power according set parameters ibm also makes use 5 ghz duty-cycle correction clock distribution network processor network company implements copper distribution wire 3 µm wide 1.2 µm thick power6 design uses dual power supplies logic supply 0.8-to-1.2 volt range sram power supply 150-mv higher thermal characteristics power6 similar power5 dr frank soltis ibm chief scientist said ibm solved power leakage problems associated high frequency using combination 90 nm 65 nm parts power6 design slightly enhanced power6+ introduced april 2009 shipping power 560 570 systems since october 2008 added memory keys secure memory partition feature taken ibm mainframe processors range power6 systems includes express models 520 550 560 enterprise models 570 595 various system models designed serve sized business example 520 express marketed small businesses power 595 marketed large multi-environment data centers main difference express enterprise models latter include capacity upgrade demand cuod capabilities hot-pluggable processor memory books ibm also offers four power6 based blade servers specifications shown table blades support aix linux bladecenter h chassis supported blades running aix linux bladecenter e ht chassis support blades running aix linux supercomputing 2007 sc07 conference reno new water-cooled power 575 revealed 575 composed 2u nodes 32 power6 cores 4.7 ghz 256 gb ram 448 cores installed single frame
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Computer architecture
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bosconian bosconian allows player ship freely roam across open space scrolls directions game also radar tracks position player ship enemy formation attacks space stations objective bosconian score many points possible destroying enemy missiles bases player controls small fighter ship move eight directions fire forward backward round consists number green enemy bases must destroyed advance next round semi-transparent automap helps identify location station consists six cannons arranged hexagon surrounding central core player must either destroy six cannons 200 points shoot core destroy station 1,500 points later rounds core capable defending opening closing launching missiles additionally player must avoid destroy stationary asteroids 10 points mines 20 points variety enemy missiles ships attempt collide ship enemy bases also occasionally launch squadron ships formation attacks — destroying leader causes remaining enemies disperse destroying enemies formation scores extra bonus points spy ship worth random bonus value also appear occasionally must destroyed round go condition red regardless long player taken throughout game digitized voice alerts player various events bosconian definite ending continue player lost lives similar galaga bosconian rolls round 255 round 0 causing game behave abnormally round player successfully complete round 0 game continues round 1 though player started upon scoring 2,000,000 points lives thereafter bosconian 1982 arcade award best science fiction/fantasy coin-op game january 1983 beating atari gravitar sega zaxxon bosconian later appeared several namco museum compilations playstation consoles game also released jakks pacific tv game controllers released part pac-man arcade party arcade machine 2010 home computer sequel bosconian '87 released 1987 amstrad cpc commodore 64 zx spectrum spiritual successor blast released 1989 japan runs namco system 1 hardware bears resemblance namco dragon spirit bosconian related title final blaster released 1990 pc-engine japan featured gameplay akin blast bosconian one first games continuation screen edged fantasy released one month earlier 1981 feature could disabled entirely arcade owners want changing dip switch setting
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Computer architecture
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internet crimes children internet crimes children icac task-force started united states department justice office juvenile justice delinquency prevention ojjdp 1998 primary goals provide state local law enforcement agencies tools prevent internet crimes children encouraging multi-jurisdictional cooperation well educating law enforcement agents parents teachers aims icac task forces catch distributors child pornography internet whether delivered on-line solicited on-line distributed channels catch sexual predators solicit victims internet chat rooms forums methods currently fifty states participate icac
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Computer security
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sentrigo sentrigo privately held software company located santa clara california usa acquisition april 2011 mcafee company founded 2006 nathan shuchami slavik markovich address several key challenges database security specifically inability monitor activity privileged users established credentials nefarious means difficulty maintaining dbms current patch level company products expanded include broader suite database security offerings including database audit vulnerability assessment well investors sentrigo included benchmark capital stata ventures juniper networks hedgehog family products providing vulnerability assessment database activity monitoring purposes reducing risks data breach meeting compliance regulations related sensitive data hedgehog allows customers protect databases oracle microsoft sql server sybase without interfering day-to-day operations company primary product introduced 2007 hedgehog enterprise provides core monitoring capability based sensor server model sensor resides database server os monitors memory/cache suspect database transactions sending alerts real-time management console thus unlike network-based host-based intrusion detection systems ids intrusion prevention systems ips hedgehog fully monitor databases running virtual machines even cloud server java-based application communicates sensors centrally monitor hundreds databases based set policies rules system audit alert suspend sessions violate preset conditions announced september 2010 hedgehog dbscanner enterprise vulnerability assessment solution databases includes capabilities automatically finding databases network subjects 3,000 different security checks reports provide details discovered vulnerabilities current patch level weak passwords shared accounts configuration errors insecure database code dbscanner implemented along hedgehog enterprise case shares common management console run standalone module vpatch solution virtual patching databases overcome problem many customers unable apply security patches databases timely manner may due inability schedule downtime production system time lag testing 3rd party support applications top database numerous reasons sentrigo vpatch includes set rules generate alerts known vulnerabilities exploited used terminate attackers database sessions vpatch rules updated frequent basis new security updates issued dbms vendor new vulnerabilities discovered sentrigo research team partners common practice developing applications web applications particular use fat database accounts common schema pooled connections enhance application performance using approach raises problem full end-to-end user tracking database layer database unable see end-user details like username ip address seeing application server ip common schema account hedgehog identifier solves problem providing application server plug-in captures end-user information transparently propagates database tier using standard database apis application changes required identifier supports custom java .net applications well major business applications technical details available blog entry fuzzor fuzzer oracle open source software tool developed sentrigo fuzzor provides database administrators programmers ability test pl/sql code security vulnerabilities tool discovers vulnerabilities attempting exploit code particularly helpful finding sql injection buffer overflow vulnerabilities sentrigo provides tool free charge
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Computer security
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mdl programming language mdl datatypes lisp mit design language programming language descendant language lisp initial purpose provide high level language support dynamic modeling group massachusetts institute technology mit project mac initially developed 1971 pdp-10 computer time-sharing operating system named incompatible timesharing system later ran tenex tops-20 bsd aegis initial development team consisted gerald sussman carl hewitt artificial intelligence lab chris reeve bruce daniels david cressey dynamic modeling group later stu galley also dynamic modeling group wrote mdl documentation mdl initially called muddle style self-deprecating humor widely understood appreciated outside project mac early citadels information technology name sanitized mdl mdl provides several enhancements classic lisp supports several built-in data types including lists strings arrays user-defined data types offers multithreaded expression evaluation coroutines variables carry local value within scope global value passing data scopes advanced built-in functions supported interactive debugging mdl programs incremental development reconstruction source programs object programs although mdl obsolete features incorporated later versions lisp gerald sussman went develop scheme language collaboration guy steele later wrote specifications common lisp java carl hewitt already published idea language planner mdl project began subsequent thinking planner reflected lessons learned building mdl planner concepts influenced languages prolog smalltalk smalltalk simula turn influenced hewitt future work actor model largest influence mdl software genre interactive fiction game named zork sometimes called dungeon first written mdl later reeve daniels galley members dynamic modeling went start infocom company produced many early commercial works interactive fiction original source code mainframe environment snippet shown downloaded originally russian mirror syntaxhighlight /syntaxhighlight
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Programming language topics
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strongarm strongarm family computer microprocessors developed digital equipment corporation manufactured late 1990s implemented arm v4 instruction set architecture later sold intel 1997 continued manufacture replacing xscale early 2000s strongarm collaborative project dec advanced risc machines create faster arm microprocessor strongarm designed address upper-end low-power embedded market users needed performance arm could deliver able accept external support targets devices newer personal digital assistants set-top boxes traditionally semiconductor division dec located massachusetts order gain access design talent silicon valley dec opened design center palo alto california design center led dan dobberpuhl main design site strongarm project another design site worked project austin texas created ex-dec designers returning apple computer motorola project set 1995 quickly delivered first design sa-110 dec agreed sell strongarm intel part lawsuit settlement 1997 intel used strongarm replace ailing line risc processors i860 i960 semiconductor division dec sold intel many engineers palo alto design group moved sibyte start-up company designing mips system-on-a-chip soc products networking market austin design group spun become alchemy semiconductor another start-up company designing mips socs hand-held market new strongarm core developed intel introduced 2000 xscale sa-110 first microprocessor strongarm family first versions operating 100 160 200 mhz announced 5 february 1996 announced samples versions available volume production slated mid-1996 faster 166 233 mhz versions announced 12 september 1996 samples versions available announcement volume production slated december 1996 throughout 1996 sa-110 highest performing microprocessor portable devices towards end 1996 leading cpu internet/intranet appliances thin client systems sa-110 first design win apple messagepad 2000 also used number products including acorn computers risc pc eidos optima video editing system sa-110 lead designers daniel w. dobberpuhl gregory w. hoeppner liam madden richard t. witek sa-110 simple microarchitecture scalar design executed instructions in-order five-stage classic risc pipeline microprocessor partitioned several blocks ibox ebox immu dmmu biu wb pll ibox contained hardware operated first two stages pipeline program counter fetched decoded issued instructions instruction fetch occurs first stage decode issue second ibox decodes complex instructions arm instruction set translating sequences simpler instructions ibox also handled branch instructions sa-110 branch prediction hardware mechanisms speedy processing execution starts stage three hardware operates stage contained ebox comprises register file arithmetic logic unit alu barrel shifter multiplier condition code logic register file three read ports two write ports alu barrel shifter executed instructions single cycle multiplier pipelined latency multiple cycles immu dmmu memory management units instructions data respectively mmu contained 32-entry fully associative translation lookaside buffer tlb map 4 kb 64 kb 1 mb pages write buffer wb eight 16-byte entries enables pipelining stores bus interface unit biu provided sa-110 external interface pll generates internal clock signal external 3.68 mhz clock signal designed dec contracted centre suisse d'electronique et de microtechnique csem located neuchâtel switzerland instruction cache data cache capacity 16 kb 32-way set-associative virtually addressed sa-110 designed used slow therefore low-cost memory therefore high set associativity allows higher hit rate competing designs use virtual addresses allows memory simultaneously cached uncached caches responsible transistor count take half die area sa-110 contained 2.5 million transistors 7.8 mm 6.4 mm large 49.92 mm fabricated dec proprietary cmos-6 process fab 6 fab hudson massachusetts cmos-6 dec sixth-generation complementary metal–oxide–semiconductor cmos process cmos-6 0.35 µm feature size 0.25 µm effective channel length use sa-110 three levels aluminium interconnect used power supply variable voltage 1.2 2.2 volts v enable designs find balance power consumption performance higher voltages enable higher clock rates sa-110 packaged 144-pin thin quad flat pack tqfp sa-1100 derivative sa-110 developed dec announced 1997 sa-1100 targeted portable applications pdas differs sa-110 providing number features desirable applications accommodate features data cache reduced size 8 kb extra features integrated memory pcmcia color lcd controllers connected on-die system bus five serial i/o channels connected peripheral bus attached system bus memory controller supported fpm edo dram sram flash rom pcmcia controller supports two slots memory address data bus shared pcmcia interface glue logic required serial i/o channels implement slave usb interface sdlc two uarts irda interface mcp synchronous serial port sa-1100 companion chip sa-1101 introduced intel 7 october 1998 sa-1101 provided additional peripherals complement integrated sa-1100 video output port two ps/2 ports usb controller pcmcia controller replaces sa-1100 design device started dec partially complete acquired intel finish design fabricated dec former hudson massachusetts fabrication plant also sold intel sa-1100 contained 2.5 million transistors measured 8.24 mm 9.12 mm 75.15 mm fabricated 0.35 μm cmos process three levels aluminium interconnect packaged 208-pin tqfp one early recipients processor was-ill-fated psion netbook consumer oriented sibling psion series 7 sa-1110 derivative sa-110 developed intel announced 31 march 1999 positioned alternative sa-1100 announcement samples set june 1999 volume later year intel discontinued sa-1110 early 2003 sa-1110 available 133 206 mhz versions differed sa-1100 featuring support 66 mhz 133 mhz version 103 mhz 206 mhz version sdram companion chip provided additional support peripherals sa-1111 sa-1110 packaged 256-pin micro ball grid array used mobile phones personal data assistants pdas compaq later hp ipaq hp jornada sharp sl-5x00 linux based platforms simputer also used run intel web tablet tablet device considered potentially first introduce large screen portable web browsing intel dropped product prior launch 2001 sa-1500 derivative sa-110 developed dec initially targeted set-top boxes designed manufactured low volumes dec never put production intel sa-1500 available 200 300 mhz sa-1500 featured enhanced sa-110 core on-chip coprocessor called attached media processor amp on-chip sdram i/o bus controller sdram controller supported 100 mhz sdram i/o controller implemented 32-bit i/o bus may run frequencies 50 mhz connecting peripherals sa-1501 companion chip amp implemented long instruction word instruction set containing instructions designed multimedia integer floating-point multiply–accumulate simd arithmetic long instruction word 64 bits wide specifies arithmetic operation branch load/store instructions operate operands 64-entry 36-bit register file set control registers amp communicates sa-110 core via on-chip bus shares data cache sa-110 amp contained alu shifter branch unit load/store unit multiply–accumulate unit single-precision floating-point unit amp supported user-defined instructions via 512-entry writable control store sa-1501 companion chip provided additional video audio processing capabilities various i/o functions ps/2 ports parallel port interfaces various peripherals sa-1500 contains 3.3 million transistors measures 60 mm fabricated 0.28 µm cmos process used 1.5 2.0 v internal power supply 3.3 v i/o consuming less 0.5 w 100 mhz 2.5 w 300 mhz packaged 240-pin metal quad flat package 256-ball plastic ball grid array
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Computer architecture
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art loss register art loss register alr world largest database stolen art computerized international database captures information lost stolen art antiques collectables alr london-based independent profit corporate offspring new york-based nonprofit international foundation art research ifar range functions served alr grown number listed items increased database used collectors art trade insurers law enforcement agencies worldwide 1991 ifar helped create art loss register alr commercial enterprise expand market database ifar managed alr u.s. operations 1997 1998 alr assumed full responsibility ifar database although ifar retains ownership 1992 database comprised 20,000 items grew size nearly tenfold first decade first steps towards alr began establishment ifar new york 1969 among explicit goals ifar created compile information stolen art response growth international art thefts ifar began publishing stolen art alert 1976 1990 ifar updating catalogue stolen art 10 times year magnitude problem overwhelmed grown 20,000 manual records ifar successful recording details losses good first step 1991 alr established london commercial company earning fees insurers theft victims founding shareholders included insurance auction houses think conflict interest christie cite note-72 majority shares owned founder julian radcliffe significant capital investment needed ifar could computerised database made available worldwide law enforcement agencies others response growth development ifar museum officials revised policies based assumption discussing theft would scare away potential donors afr initially formed partnership alr later split disagreements strategy issues control change policies secrecy ones emphasize openness gradual mirroring expectation publicizing theft likely promote recovery alr widely criticised methods actions chairman julian radcliffe register consistently lost money personal cash infusions chairman approach adopted alr criticised register contacted owners stolen art saying information revealing fee paid another instance alr lied sotheby ’ saying paintings stolen paintings shipped london seized alr likened approach police misleading suspect investigation
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Databases
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datto company datto inc. american cybersecurity data backup company founded 2007 norwalk connecticut 2017 became subsidiary vista equity partners merged autotask corporation founded 2007 connecticut software programmer austin mcchord mcchord initially built marketed hand-made data backup devices securing first customers 2008 afterwards built system allowed data synchronization two computers building version zenith infotech ran linux end 2009 company 70,000 monthly sales new datto product 2010 caused old systems crash replacement system designed scratch siris released several months later free upgrade 2011 datto credited helping local hospitals impacted tornado joplin missouri retrieve data 2011 sales 9 million following year 25 million established business model sold products primarily managed service providers 2013 company continuing focus small mid-size businesses clients susan g. komen cure several nfl teams september 2013 company raised 25 million first round venture capital financing led general catalyst partners time datto 225 employees posted four consecutive years 300 percent annual growth 2014 datto inc. purchased backupify cloud-to-cloud backup company backupify focused backing data servers complementing datto focus local private clouds november 2015 company garnered 75 million series b funding round mostly led technology crossover ventures 2015 became connecticut first unicorn company early 2017 datto acquired open mesh datto acquired vista equity partners around 1.5 billion late 2017 part deal datto merged vista portfolio company autotask corporation austin mcchord remained ceo combined company mcchord stepped ceo october 2018 remaining board recent years company increased employee number significantly datto 550 employees november 2015 700 employees january 2017 883 workers october 2017 434 norwalk 1,300 employees november 2017 march 2018 number grown 1,400 month datto ranked first among midsize companies democrat chronicle ’ top workplaces list datto builds hardware software data backup recovery purposes 2016 company released siris 3 data protection platform claiming first system market ransomware detection capability
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Computer security
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codd 12 rules codd twelve rules set thirteen rules numbered zero twelve proposed edgar f. codd pioneer relational model databases designed define required database management system order considered relational i.e. relational database management system rdbms sometimes jokingly referred codd twelve commandments codd produced rules part personal campaign prevent vision original relational database diluted database vendors scrambled early 1980s repackage existing products relational veneer rule 12 particularly designed counter positioning rule 0 foundation rule rule 1 information rule rule 2 guaranteed access rule rule 3 systematic treatment null values rule 4 dynamic online catalog based relational model rule 5 comprehensive data sublanguage rule rule 6 view updating rule rule 7 possible high-level insert update delete rule 8 physical data independence rule 9 logical data independence rule 10 integrity independence rule 11 distribution independence rule 12 nonsubversion rule
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Databases
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genghis khan video game genghis khan original full title 1987 turn-based strategy game developed koei originally released nec pc-9801 msx sharp x68000 1988 dos nes 1990 amiga 1990 actually second game series 1985 aoki ōkami shiroki mejika also pc-88 pc-98 msx game takes player inside virtual life either genghis khan one archrivals player must arrange marriages father children appoint family members governmental positions fight order conquer old world armies must drafted soldiers must trained player rule lands england japan game two different ways play first mongol conquest begins year 1175 a.d one player mode players assume control lord temujin must conquer land keeping economy stable army ready fight attacking lands second world conquest goal conquer every opposing country world conquest begins year 1206 a.d started choosing number players difficulty supports 1-4 players players must choose want genghis khan mongols alexios byzantine richard england yoritomo japan player must randomly select stats leader successors player must stop random number choose certain stat done stats chosen certain character redone everyone ready go game begins countries eurasia cycle goes country means used turn comes player country get make three choices choices include training troops buying certain product/quantity merchant drafting soldiers sending treaty going war act takes one choice away three choices used cycle continues every country used turns season changes cycle goes different order seasons determine must pay troops farmers harvest crop food must distributed etc 1989 computer gaming world called genghis khan toughest satisfying richest historical simulation yet 1990 survey pre-20th century wargames magazine gave four five stars 1993 three stars orson scott card viewed unfavorably writing compute compared romance tedium back regarding gameplay another reviewer magazine stated genghis khan excellent prerequisite real leadership experience forces gauge resources making decisions 2008 armağan yavuz co-founder turkish developer taleworlds cited koei genghis khan influence mount blade series
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Computer architecture
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