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interactive systems corporation interactive systems corporation styled interactive systems corporation abbreviated isc us-based software company first vendor unix operating system outside operating santa monica california founded 1977 peter g. weiner rand corporation researcher previously founded yale university computer science department ph d. advisor brian kernighan one unix developers weiner joined heinz lycklama also veteran previously author version 6 unix port lsi-11 computer isc acquired eastman kodak company 1988 sold isc unix operating system assets sun microsystems september 26 1991 kodak sold remaining parts isc shl systemhouse inc 1993 several former isc staff founded segue software partnered lotus development develop unix version lotus 1-2-3 peter norton computing develop unix version norton utilities isc 1977 offering is/1 version 6 unix variant enhanced office automation running pdp-11 is/3 is/5 enhanced versions unix system iii system v pdp-11 vax isc unix ports ibm pc included variant system iii developed contract ibm known pc/ix personal computer interactive executive also abbreviated pc-ix later versions branded 386/ix finally interactive unix system v/386 based system v release 3.2 isc principal publisher system v.4 intel platform isc also involved development vm/ix unix guest os vm/370 enhancements ix/370 tss/370-based unix system ibm originally developed jointly ca.1980 also developed aix 1.0 advanced interactive executive ibm rt pc contract ibm although ibm awarded development contract aix version 2 aix/386 aix/370 competing locus computing corporation although observers early 1980s expected ibm would choose microsoft xenix version corporation unix microcomputer pc/ix first unix implementation ibm pc xt available directly ibm according bob blake pc/ix product manager ibm primary objective make credible unix system ... try 'ibm-ize product pc-ix system iii unix pc/ix however first unix port xt venix/86 preceded pc/ix year although based older version 7 unix main addition pc/ix ined screen editor isc ined offered multiple windows context-sensitive help paragraph justification margin changes although fully fledged word processor pc/ix omitted system iii fortran compiler tar file archiver add bsd tools like vi c shell one reason porting pc/ix individual applications limited single segment 64 kb ram achieve good filesystem performance pc/ix directly addressed xt hard-drive rather bios gave significant speed advantage compared ms-dos lack true memory protection 8088 chips ibm sold single-user licenses pc/ix pc/ix distribution came 19 floppy disks accompanied 1,800-page manual installed pc/ix took approximately 4.5 mb disk space editorial bill machrone pc magazine time pc/ix launch flagged 900 price show stopper given lack compatibility ms-dos applications pc/ix commercial success although byte august 1984 described complete usable single-user implementation done 8088 noting pc/ix pc outperformed venix pdp-11/23 pc/ix succeeded 386/ix 1985 system vr3 derivative later versions termed interactive unix system v/386 based system v 3.2 though elements bsd added svr3.2 kernel meant diminished compatibility unix ports early nineties interactive unix system praised pc magazine reviewer stability acquisition interactive sun microsystems continued maintain interactive unix system offering low-end alternative system v.4-based solaris even latter ported x86-based desktop machines last version system v/386 release 3.2 version 4.1.1 released july 1998 official support ended july 23 2006 five years sun withdrew product sale version isa 3.0.1 interactive unix system supported 16 mb ram next versions supported 256mb ram pci bus eisa versions always supported 256mb ram
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Operating systems
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python programming language python interpreted high-level general-purpose programming language created guido van rossum first released 1991 python design philosophy emphasizes code readability notable use significant whitespace language constructs object-oriented approach aim help programmers write clear logical code small large-scale projects python dynamically typed garbage-collected supports multiple programming paradigms including procedural object-oriented functional programming python often described batteries included language due comprehensive standard library python conceived late 1980s successor abc language python 2.0 released 2000 introduced features like list comprehensions garbage collection system capable collecting reference cycles python 3.0 released 2008 major revision language completely backward-compatible much python 2 code run unmodified python 3 due concern amount code written python 2 support python 2.7 last release 2.x series extended 2020 language developer guido van rossum shouldered sole responsibility project july 2018 shares leadership member five-person steering council python interpreters available many operating systems global community programmers develops maintains cpython open source reference implementation non-profit organization python software foundation manages directs resources python cpython development python conceived late 1980s guido van rossum centrum wiskunde informatica cwi netherlands successor abc language inspired setl capable exception handling interfacing amoeba operating system implementation began december 1989 van rossum continued python lead developer july 12 2018 announced permanent vacation responsibilities python benevolent dictator life title python community bestowed upon reflect long-term commitment project chief decision-maker january 2019 active python core developers elected brett cannon nick coghlan barry warsaw carol willing van rossum five-member steering council lead project python 2.0 released 16 october 2000 many major new features including cycle-detecting garbage collector support unicode python 3.0 released 3 december 2008 major revision language completely backward-compatible many major features backported python 2.6.x 2.7.x version series releases python 3 include codice_1 utility automates least partially translation python 2 code python 3 python 2.7 end-of-life date initially set 2015 postponed 2020 concern large body existing code could easily forward-ported python 3 january 2017 google announced work python 2.7 go transcompiler improve performance concurrent workloads python multi-paradigm programming language object-oriented programming structured programming fully supported many features support functional programming aspect-oriented programming including metaprogramming metaobjects magic methods many paradigms supported via extensions including design contract logic programming python uses dynamic typing combination reference counting cycle-detecting garbage collector memory management also features dynamic name resolution late binding binds method variable names program execution python design offers support functional programming lisp tradition codice_2 codice_3 codice_4 functions list comprehensions dictionaries sets generator expressions standard library two modules itertools functools implement functional tools borrowed haskell standard ml language core philosophy summarized document zen python pep 20 includes aphorisms rather functionality built core python designed highly extensible compact modularity made particularly popular means adding programmable interfaces existing applications van rossum vision small core language large standard library easily extensible interpreter stemmed frustrations abc espoused opposite approach python strives simpler less-cluttered syntax grammar giving developers choice coding methodology contrast perl one way motto python embraces one—and preferably one—obvious way design philosophy alex martelli fellow python software foundation python book author writes describe something 'clever considered compliment python culture python developers strive avoid premature optimization reject patches non-critical parts cpython reference implementation would offer marginal increases speed cost clarity speed important python programmer move time-critical functions extension modules written languages c use pypy just-in-time compiler cython also available translates python script c makes direct c-level api calls python interpreter important goal python developers keeping fun use reflected language name—a tribute british comedy group monty python—and occasionally playful approaches tutorials reference materials examples refer spam eggs famous monty python sketch instead standard foo bar common neologism python community pythonic wide range meanings related program style say code pythonic say uses python idioms well natural shows fluency language conforms python minimalist philosophy emphasis readability contrast code difficult understand reads like rough transcription another programming language called unpythonic users admirers python especially considered knowledgeable experienced often referred pythonists pythonistas pythoneers python meant easily readable language formatting visually uncluttered often uses english keywords languages use punctuation unlike many languages use curly brackets delimit blocks semicolons statements optional fewer syntactic exceptions special cases c pascal python uses whitespace indentation rather curly brackets keywords delimit blocks increase indentation comes certain statements decrease indentation signifies end current block thus program visual structure accurately represents program semantic structure feature also sometimes termed off-side rule python statements include among others python support tail call optimization first-class continuations according guido van rossum never however better support coroutine-like functionality provided 2.5 extending python generators 2.5 generators lazy iterators information passed unidirectionally generator python 2.5 possible pass information back generator function python 3.3 information passed multiple stack levels python expressions similar languages c java python distinction expressions statements rigidly enforced contrast languages common lisp scheme ruby leads duplicating functionality example statements part expression list comprehensions lambda expressions expressions contain statements particular case assignment statement codice_78 form part conditional expression conditional statement advantage avoiding classic c error mistaking assignment operator codice_79 equality operator codice_36 conditions codice_81 syntactically valid probably unintended c code codice_82 causes syntax error python methods objects functions attached object class syntax codice_83 normal methods functions syntactic sugar codice_84 python methods explicit codice_85 parameter access instance data contrast implicit codice_85 codice_87 object-oriented programming languages e.g. c++ java objective-c ruby python uses duck typing typed objects untyped variable names type constraints checked compile time rather operations object may fail signifying given object suitable type despite dynamically typed python strongly typed forbidding operations well-defined example adding number string rather silently attempting make sense python allows programmers define types using classes often used object-oriented programming new instances classes constructed calling class example codice_88 codice_89 classes instances metaclass codice_90 instance allowing metaprogramming reflection version 3.0 python two kinds classes old-style new-style syntax styles difference whether class codice_91 inherited directly indirectly new-style classes inherit codice_91 instances codice_90 versions python 2 python 2.2 onwards kinds classes used old-style classes eliminated python 3.0 long term plan support gradual typing python 3.5 syntax language allows specifying static types checked default implementation cpython experimental optional static type checker named mypy supports compile-time type checking python usual c language arithmetic operators codice_50 codice_95 codice_96 codice_33 codice_58 also codice_34 exponentiation e.g codice_100 codice_101 new matrix multiply codice_35 operator included version 3.5 additionally unary operator codice_103 essentially inverts bits one argument integers means codice_104 operators include bitwise shift operators codice_105 shifts codice_106 left codice_107 places codice_108 codice_109 shifts codice_106 right codice_107 places codice_112 behavior division changed significantly time division integers produces accurate floating point results rounding towards negative infinity though different languages adds consistency instance means equation codice_126 always true also means equation codice_127 valid positive negative values codice_128 however maintaining validity equation means result codice_129 expected half-open interval 0 b codice_130 positive integer lie interval b 0 codice_130 negative python provides codice_132 function rounding float nearest integer tie-breaking versions 3 use round-away-from-zero codice_133 1.0 codice_134 −1.0 python 3 uses round even codice_135 2 codice_136 2 python allows boolean expressions multiple equality relations manner consistent general use mathematics example expression codice_137 tests whether codice_128 less codice_130 codice_130 less codice_141 c-derived languages interpret expression differently c expression would first evaluate codice_142 resulting 0 1 result would compared codice_141 python extensive built-in support arbitrary precision arithmetic integers transparently switched machine-supported maximum fixed-precision usually 32 64 bits belonging python type codice_144 arbitrary precision belonging python type codice_145 needed latter l suffix textual representation python 3 distinction codice_144 codice_145 types eliminated behavior entirely contained codice_144 class codice_149 type/class module codice_150 since version 2.4 provides decimal floating point numbers arbitrary precision several rounding modes codice_151 type module codice_152 since version 2.6 provides arbitrary precision rational numbers due python extensive mathematics library third-party library numpy extends native capabilities frequently used scientific scripting language aid problems numerical data processing manipulation python large standard library commonly cited one greatest strengths provides tools suited many tasks internet-facing applications many standard formats protocols mime http supported includes modules creating graphical user interfaces connecting relational databases generating pseudorandom numbers arithmetic arbitrary precision decimals manipulating regular expressions unit testing parts standard library covered specifications example web server gateway interface wsgi implementation codice_153 follows pep 333 modules specified code internal documentation test suites supplied however standard library cross-platform python code modules need altering rewriting variant implementations python implementations including cpython include read–eval–print loop repl permitting function command line interpreter user enters statements sequentially receives results immediately shells including idle ipython add abilities auto-completion session state retention syntax highlighting well standard desktop integrated development environments web browser-based ides sagemath intended developing science math-related python programs pythonanywhere browser-based ide hosting environment canopy ide commercial python ide emphasizing scientific computing cpython reference implementation python written c meeting c89 standard several select c99 features compiles python programs intermediate bytecode executed virtual machine cpython distributed large standard library written mixture c native python available many platforms including windows modern unix-like systems platform portability one earliest priorities pypy fast compliant interpreter python 2.7 3.5 just-in-time compiler brings significant speed improvement cpython stackless python significant fork cpython implements microthreads use c memory stack thus allowing massively concurrent programs pypy also stackless version micropython circuitpython python 3 variants optimised microcontrollers includes lego mindstorms ev3 just-in-time python compilers developed unsupported 2005 nokia released python interpreter series 60 mobile phones named pys60 includes many modules cpython implementations additional modules integrate symbian operating system project kept up-to-date run variants s60 platform several third-party modules available nokia n900 also supports python gtk widget libraries enabling programs written run target device several compilers high-level object languages either unrestricted python restricted subset python language similar python source language performance comparison various python implementations non-numerical combinatorial workload presented euroscipy '13 python development conducted largely python enhancement proposal pep process primary mechanism proposing major new features collecting community input issues documenting python design decisions python coding style covered pep 8 outstanding peps reviewed commented python community steering council enhancement language corresponds development cpython reference implementation mailing list python-dev primary forum language development specific issues discussed roundup bug tracker maintained python.org development originally took place self-hosted source-code repository running mercurial python moved github january 2017 cpython public releases come three types distinguished part version number incremented many alpha beta release-candidates also released previews testing final releases although rough schedule release often delayed code ready python development team monitors state code running large unit test suite development using buildbot continuous integration system community python developers also contributed 86,000 software modules python package index pypi official repository third-party python libraries major academic conference python pycon also special python mentoring programmes pyladies python name derived british comedy group monty python python creator guido van rossum enjoyed developing language monty python references appear frequently python code culture example metasyntactic variables often used python literature spam eggs instead traditional foo bar official python documentation also contains various references monty python routines prefix py- used show something related python examples use prefix names python applications libraries include pygame binding sdl python commonly used create games pyqt pygtk bind qt gtk python respectively pypy python implementation originally written python python api documentation generators include since 2003 python consistently ranked top ten popular programming languages tiobe programming community index third popular language behind java c selected programming language year 2007 2010 2018 empirical study found scripting languages python productive conventional languages c java programming problems involving string manipulation search dictionary determined memory consumption often better java much worse c c++ large organizations use python include wikipedia google yahoo cern nasa facebook amazon instagram spotify smaller entities like ilm ita social news networking site reddit written entirely python python serve scripting language web applications e.g. via mod_wsgi apache web server web server gateway interface standard api evolved facilitate applications web frameworks like django pylons pyramid turbogears web2py tornado flask bottle zope support developers design maintenance complex applications pyjs ironpython used develop client-side ajax-based applications sqlalchemy used data mapper relational database twisted framework program communications computers used example dropbox libraries numpy scipy matplotlib allow effective use python scientific computing specialized libraries biopython astropy providing domain-specific functionality sagemath mathematical software notebook interface programmable python library covers many aspects mathematics including algebra combinatorics numerical mathematics number theory calculus python successfully embedded many software products scripting language including finite element method software abaqus 3d parametric modeler like freecad 3d animation packages 3ds max blender cinema 4d lightwave houdini maya modo motionbuilder softimage visual effects compositor nuke 2d imaging programs like gimp inkscape scribus paint shop pro musical notation programs like scorewriter capella gnu debugger uses python pretty printer show complex structures c++ containers esri promotes python best choice writing scripts arcgis also used several video games adopted first three available programming languages google app engine two java go python commonly used artificial intelligence projects help libraries like tensorflow keras scikit-learn scripting language modular architecture simple syntax rich text processing tools python often used natural language processing many operating systems include python standard component ships linux distributions amigaos 4 freebsd package netbsd openbsd package macos used command line terminal many linux distributions use installers written python ubuntu uses ubiquity installer red hat linux fedora use anaconda installer gentoo linux uses python package management system portage python used extensively information security industry including exploit development sugar software one laptop per child xo developed sugar labs written python raspberry pi single-board computer project adopted python main user-programming language libreoffice includes python intends replace java python python scripting provider core feature since version 4.0 7 february 2013 python design philosophy influenced many programming languages python development practices also emulated languages example practice requiring document describing rationale issues surrounding change language python pep also used tcl erlang python received tiobe programming language year awards 2007 2010 2018 award given language greatest growth popularity year measured tiobe index
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Programming language topics
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salesforce tower indianapolis opened 1990 near monument circle indianapolis salesforce tower formerly known bank one tower chase tower originally conceived american fletcher tower tallest building u.s. state indiana 58th tallest building united states surpassed aul tower oneamerica tower indianapolis distinction building twin spires pierce indianapolis skyline 49 floors office retail space 2 building equipment floors peak roof regional headquarters salesforce moved tower late-2010 currently occupies large amount space building tower two spires equal height one functional transmission antenna mast merely architectural decoration building designed klingstubbins built indianapolis-based huber hunt nichols tower step pyramidal cap reflects design indiana war memorial three blocks due north war memorial turn reflects descriptions original mausoleum height building roof specifically designed house communications relay equipment order provide additional revenue building owners past several years two large banners occasionally placed outside north south communication bullpen areas roof support two city professional sports franchises go pacers go colts signs highly visible tallest structure city tower official observation deck views city seen floors 21 27 31 32 33 35 39 40 41 43 44 common areas ohio street side tower side complex additionally views monument circle immediate downtown area seen floors 2 7 10 common areas circle side complex 2017 electronic turnstiles implemented tower security measure turn elevators longer accessible public however visitors passes attained security desk circle tower-side lobbies tower seen various spots around greater indianapolis tower originally conceived late 1970s frank e. mckinney jr. chairman american fletcher corporation holding company american fletcher national bank trust company afnb time indiana largest financial institution allow consolidation expansion company headquarters land slowly assembled building several predecessor structures along ohio street pennsylvania street demolished years early 1980s clear way mckinney hoped would soon indiana tallest office tower construction building began american fletcher became first major indianapolis bank holding company sold out-of-state financial institution agreeing spring 1986 merge ohio rapidly growing banc one corporation upon consummation merger mr. mckinney became chairman bank one indiana operations tower planning picked momentum ground broken construction began 1988 newly designated bank one center tower integrated afnb existing headquarters complex monument circle adjacent market street done mainly secure prestigious monument circle address new tower rises ohio street wabash street east-west alley market ohio thus ohio street entrance tower complex back door concourse-style passageway second level running scioto street north-south alley pennsylvania meridian connect skyscraper attached parking garage along pennsylvania street main entrance original 1960 american national bank building 111 monument circle separate skywalk across scioto connected circle building adjacent fletcher trust building 10 e. market street later removed bank moved operations formerly located structure new tower fletcher trust building subsequently sold since renovated hilton garden inn hotel banc one corporation later renamed bank one corporation went several additional major acquisitions bought j.p. morgan chase early 2000s upon consummation merger indianapolis structure renamed become known chase tower chase allowed attach name logo top building 2013 building changed owners may 6 2016 salesforce announced plans lease hundreds thousands square feet building start moving employees early 2017 building rebranded salesforce tower indianapolis
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Distributed computing architecture
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mapper sperry univac 'mapper 4gl originated 1970s based work 1960s kept current renamed also given extension named ice internet commerce enabler originally available sperry univac 1108 implementations also exist windows nt sun solaris linux gui windows advanced mapper maintain prepare p'roduce executive reports since officially renamed bis business information server called mapper fans began internal product first customer santa fe railway started punched card era input 80 columns data printed reports 120 132 columns attempted go beyond modeling filing cabinet typical era written assember language initially limited string manipulation since corrected macro capability also subsequently added bis product still use still job postings
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Programming language topics
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icab icab web browser mac os alexander clauss derived crystal atari browser cab atari tos compatible computers one browsers still updated classic mac os prior version discontinued version 3.0.5 2008 today classilla browser still maintained os downloadable product fully functional nagware—periodically displaying dialog box asking user register product upgrade pro version icab 2.9.9 supports 68k powerpc macintosh systems running system 7.5 mac os 9.2.2 longer maintained icab 2.9.9 still available download registration icab 2.9.8 runs natively early versions mac os x mac os x compatible versions icab 2.x longer officially available download icab 3.x run powerpc systems running mac os 8.5 mac os 9.2.2 powerpc intel systems running mac os x 10.1 later icab 3 last updated january 2008. icab 4 rewritten use cocoa api webkit rendering engine run powerpc intel systems running mac os 10.3.9 later icab 5 released june 12 2012 runs mac os 10.5 later first versions icab criticized supporting css dom icab 3 introduced improved rendering capabilities including support css2 unicode via atsui toolkit icab 4 switched webkit rendering engine giving rendering abilities apple safari browser 7 june 2009 icab 4.6 using webkit rendering engine became first desktop browser released display score 100/100 pass acid3 test apple safari 4 browser released one day later officially credited first official release browser pass acid3 test score 100/100 icab features filter manager allows users avoid downloading advertisements content currently icab comes two filters advertisements video kinds filters add features youtube video filter adds download link youtube page views icab features website developers including html validity checker automatic page refresh option web inspector dom inspector javascript debugger console icab automatic update option page rendering directly local hard disk automatically reload page changes saved disk html syntax validity checker displays smiley face status bar also optionally toolbar clicking smiley bring list errors page error report tools menu double clicking error display page source offending syntax highlighted html syntax validator first seen author earlier web browser cab icab download manager allows user start stop resume review downloads maintains download history supports downloading individual page whole site crawling many user-selectable crawl-constraint options save portable web archives zip archive containing html images files individual files local hard drive icab also contains following features
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Internet protocols
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erik naggum erik naggum june 13 1965 – june 17 2009 norwegian computer programmer recognized work fields sgml emacs lisp since early 1990s also provocative participant various usenet discussion groups naggum made significant contributions rfc 1123 defines discusses requirements internet host software rfc 2049 defines electronic information transfer various binary formats e-mail 1999 newspaper article dagbladet interviewed aggressive confrontational participation usenet discussion groups erik later stated motto people little herd animals flocking together whenever world becomes uncomfortable … one people motto would probably herd thither hither premature death age 44 june 17 2009 caused massive bleeding ulcer related ulcerative colitis diagnosed 15 years death naggum chairman sgml sighyper sgml special interest group hypertext multimedia see hytime technical commentary iso 8879:1986 archives comp.text.sgml terms high quality sheer mass especially appreciated long painful history time article naggum describes concept universal time time zones handled well lisp code erik contributed enormous number postings usenet 14,300 record many cases erik used x-no-archive header posting parameter requesting services like google groups archive message 1995 erik started journalism watch-group project web campaigning get journalist sacked aftenposten following publication sensationalist story internet relay chat channels used trade child pornography erik naggum contributed free software project emacs text editor almost decade working group member posix.1-2008 ieee std 1003.1-2008 open group technical standard base specifications issue 7 erik listed major contributor rfc 1123 contributed requirement internet mail include four-digit representation years thus avoid y2k issues erik naggum highly controversial passionate something many subjects eagerly often harshly argued point view example rant xml misdesigned especially misused one example would diatribe martin bryan posted 1992 erik naggum hated perl passion considered perl problem problem solver disliked c++ though much hated perl generally thought c++ difficult understand degree 5 people planet truly understood hence little value humanity erik naggum several times stated stupidity rather lacking willingness individuals acquire knowledge subject argument read people arguments open mind less criminal offense known polemic aggression towards considered ignorant individuals much wrote full sarcasm irony could difficult understand truly believed general exaggerations made make point
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Programming language topics
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objectdatabase++ objectdatabase++ odbpp embeddable object-oriented database designed server applications require minimal external maintenance written c++ real-time isam level database ability auto recover system crashes maintaining database integrity unique transaction process allows maintenance indexes tables preventing double allocation index entries could prohibit rollback transactions features odbpp include full multi-process multi-thread transaction control auto real-time database recovery hierarchical object data design native code script access static hash index object ids numerous supported index methods including full-text biometric pattern matching odbpp supports objects hierarchical design similar xml json serialized php hierarchical object separates object databases relational cousins process keeping entire object one record rather spreading multiple tables give object databases distinction relational model traditionally databases designed relational model would separate data several tables use common identifier relate child records back parent model based row within table containing individual pieces data sql databases based design would create joins would reconnect entire relation back together suffering performance limitations object database design instead using multiple tables store data object stored one single record keeps entire object intact reducing need join data back together process storing entire object one table reduces total amount lock reads write operations required also ability store object one record reduce amount file reads writes enables object design maintain efficiency large complex database designs looking images right depicts relational model data spread two tables parent amber children blue object model parent children stored one data record information previously stored within related table stored within sub nested table foo odbpp implements transaction control allows process continue another terminated unique transaction control allows continuing process identify terminated transaction recover database integrity continue mid transaction ability terminate transaction point enables real-time transactions implementation server using method transaction control utilizes four separate file implement entire process flushed change state drive continuing next state creates time consuming process individual write file three separate states entire transaction required pass three separate files initially adds edit deletes written shared memory file enables transaction know resource index value allocated memory file destroy os starts without interfering database integrity used ipc purposes transaction call commit transaction method database bulk work writes entire transaction memory file log file done three stages process first identify changes needed flushed plans rear file written drive header updated indicate presences update secondly file updated finally header modified finalized update state process ensure consistency file always valid process ceases first stage file simply truncated file returned original state transaction ceases second stage next transaction opens file identifies saved plans re-executes saved instructions four files updated manner transaction starts memory file written one update log file transaction protection transaction secured log file odbms able update index table files entire commit process executed concurrently multiple transactions committing simultaneously greatly benefited using solid-state drive although process caching entire transaction memory file committing drive end help reduce entire transaction time comparable non-flushing dbms contrary earlier object database models isam level database odbpp supports large variety indexes initial development object model basic design use schema contained serialized binary object referred id provided index access prevented basic search labels done due fact underlining architecture still based related model since odbpp always designed object model understands hierarchical nature objects capable indexing data contained within objects within database referenced object identifier managed via static hash index static hash index simply array index location containing address object deduced taking id value multiplying 12 adding offset value reveals location physical address object method translating id physical address enables true order one 1 retrieval data regardless many objects stored within database imposing static index table schemata allows real-time compaction file object locks index object allows even locked objects moved within file transactions require space deleting objects file ability move objects within file time also imposes need access via index sql databases may scan records scanning file beginning end real-time compaction prohibits style access b+ tree index primary workhorse databases odbpp exception majority searches carried via seeking index position repetitively call next largest value odbpp supports large number filters b+ tree make results usable example set convert lower case characters upper case set removal white spaces non-alphanumerical characters also provide natural sort order 9 '10 one features odbpp standard dbms data stored within hierarchical object also indexed create situation 0…n index values created one object spatial indexes used allow searching two- three-dimensional coordinates spaces temporal indexes similar idea along one dimensional time odbpp also supports sets spatial data represent key points two three dimension objects finger print human faces sets indexed via spatial index allow group searching search create temporary index many objects least search pattern points within given error odbpp provides full text indexing via token list indexes indexes combination b+ tree bucket overflow text string broken individual tokens indexed b+ tree since multiple object token value id stored bucket overflow similar dynamic hashing design full text searches done scanning tokens b+ tree leaves identifying tokens fit search criteria retrieving matching ids full text search query also provide set logic functions reduce search results number usable allow user search objects contain token token b example odbpp designed function procedural style encapsulated object c++ style although object style still uses procedural method interface database low level example procedural method demonstrated equivalent tscript example reading object database name fooname follows objectdatabase++ also exposed via com wrapper class 'odbpplib.odbpp equivalent c example reading object database name fooname follows
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Databases
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cyber sovereignty cyber sovereignty phrase used field internet governance describe governments desire exercise control internet within borders including political economic cultural technological activities 2015 book data goliath american security expert bruce schneier says cyber sovereignty movement countries russia china france saudi arabia given enormous boost 2013 revelations widespread international nsa surveillance countries pointed justification activities evidence u.s. hypocrisy internet freedom issues
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Computer security
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sound blaster sound blaster family sound cards de facto standard consumer audio ibm pc compatible system platform widespread transition microsoft windows 95 standardized programming interface application level eliminating importance backward compatibility sound blaster evolution pc design led onboard audio electronics commoditized pc audio functionality 1995 sound blaster cards sold 15 million units worldwide accounted seven ten sound card sales creator sound blaster singapore-based firm creative technology limited also known name united states subsidiary creative labs history creative sound cards started release creative music system c/ms ct-1300 board august 1987 contained two philips saa1099 circuits together provided 12 channels square-wave bee-in-a-box stereo sound 4 channels used noise circuits featured earlier various popular electronics magazines around world many years creative tended use off-the-shelf components manufacturers reference designs early products various integrated circuits white black paper stickers fully covering top thus hiding identity c/ms board particular philips chips white pieces paper fantasy cms-301 inscription real creative parts usually consistent ct number references surprisingly board also contained large 40-pin dip integrated circuit bearing ct 1302a ctpl 8708 creative technology programmable logic serigraphed inscription looking exactly like dsp later sound blaster chip allows software automatically detect card certain register reads writes year later 1988 creative marketed c/ms via radio shack name game blaster card identical every way precursor c/ms hardware whereas c/ms package came five floppy disks full utilities song files creative supplied single floppy basic utilities game patches allow sierra online games using sierra creative interpreter engine play music card also included later revision game silpheed added c/ms support 2017 hobbyists developed clone ct1300 pcb sound blaster 1.0 code named killer kard ct1320a released 1989 addition game blaster features 11-voice fm synthesizer using yamaha ym3812 chip also known opl2 provided perfect compatibility market leader adlib sound card gained support pc games preceding year creative used dsp acronym designate digital audio part sound blaster actually stood digital sound processor rather common digital signal processor really simple micro-controller intel mcs-51 family supplied intel matra mhs among others could play back 8-bit monaural sampled sound 23 khz sampling frequency record 8-bit 12 khz sole dsp-like features circuit adpcm decompression primitive non-mpu-401 compatible midi interface adpcm decompression schemes supported 2 1 3 1 4 1 ct1320b variety sound blaster 1.0 typically c/ms chips installed sockets rather soldered pcb though units exist c/ms chips soldered sources note original sound blaster 1.0 produced ct1310 number however topic ongoing debate creative refers ct1310 sound blaster 1.0 website spite limitations less year sound blaster became top-selling expansion card pc achieved providing fully adlib-compatible product additional features often lower price inclusion game port importance early success often forgotten overlooked pcs era include game port game port cards costly around 50 used one expansion slots pcs time given choice adlib card fully compatible sound blaster card came game port saved slot included dsp much price many consumers opted sound blaster in-game support digital portion card happen sound blaster gained dominance microsoft announced multimedia pc mpc november 1990 suggested developers use sound blaster sound card came close complying mpc standard press speculated microsoft based mpc standard sound blaster specifications 1993 computer gaming world wondered would gamer buy competing adlib card sound blaster-compatible creative advertised sound blaster 16 16-bit sound standard slogan get real emphasizing real 100 sound blaster compatibility rhetorically asking manufacturers spend much time comparing sound blaster compute 1989 stated sound blaster ibm-compatible computers taken lead sound music personal computers naming compute choice magazine described quality opening music space quest iii card extraordinary praising quality compared roland mt-32 ad lib versions compute approved card dma creative dissemination technical information concluded more-expensive mt-32 superior sound blaster audio quality better ad lib game blaster released 1990 sound blaster 1.5 ct1320c dropped c/ms chips longer popular game developers instead board two empty sockets could user upgraded purchasing c/ms chips directly creative phillips saa-1099s another source otherwise card functions identically sound blaster 1.0 ct1320u variety layout ct1320c final revision original sound blaster sound blaster 2.0 released october 1991 ct1350 added support auto-init dma assisted producing continuous loop double-buffered sound output similar version 1.0 1.5 used 1-channel 8-bit dac however maximum sampling rate increased 44 khz playback 15 khz record dsp midi uart upgraded full-duplex offered time stamping features yet compatible mpu-401 interface used professional midi equipment sound blaster 2.0 pcb-layout used highly integrated components shrinking board size reducing manufacturing cost owners previous revision sound blaster boards could upgrade board purchasing v2.00 dsp chip creative labs swapping older dsp v1.0x newer replacement upgraded board gained auto-init dma new midi capabilities sound blaster 2.0 expanded sampling rates upgrade necessary full compatibility windows 3.0 multimedia extensions upgrade sound blaster mcv ct5320 version created ibm ps/2 model 50 higher isa-incompatible micro channel architecture bus mcv soundblaster issues outputting audio running ps/2s cpus running faster 16 mhz however joystick interface still inoperable ps/2s designed due slow-speed schottky chips installed none timing issues affect yamaha ym3812 mcv soundblasters released faster schottkys eradicated problems model ct1330 announced may 1991 first significant redesign card core features complied microsoft mpc standard.. sound blaster pro supported faster digital input output sampling rates 22.05 khz stereo 44.1 khz mono added mixer provide crude master volume control independent volume sound sources feeding mixer crude high pass low pass filter sound blaster pro used pair ym3812 chips provide stereo music-synthesis one channel sound blaster pro fully backward compatible original sound blaster line extension adlib sound card sound blaster pro first creative sound card built-in cd-rom interface sound blaster pro cards featured proprietary interface panasonic matsushita mke drive sound blaster pro cards basically 8-bit isa cards use lower 8 data bits isa bus first glance appears 16-bit isa card 'fingers data transfer higher portion bus connector uses 16-bit extension isa bus provide user additional choice irq 10 dma 0 channel found 16-bit portion edge connector short lived joint developed project creative tandy resulted creative/tandy multimedia sound adapter 849-3030 sound blaster pro derived card factory installed tandy multimedia pcs combined ct1330 tandy joystick midi ports mpu-401 compatible revised version sound blaster pro 2 ct1600 replaced ym3812s advanced yamaha ymf262 opl3 otherwise functionally identical original sound blaster pro shortly release sound blaster pro 2 version creative discontinued original sound blaster pro sound blaster pro 2 also sold following on-board cd-rom controllers packaged sound blaster cards initially marketed sold retail-channel creative domination pc audiocard business soon selling sound blaster pro 2 oem ct1680 customers integration pre-assembled pcs creative also sold multimedia upgrade kits containing sound blaster pro kit bundled sound card matsushita cd-rom drive model 531 single-speed 562/3 later double-speed 2x drives several cd-roms multimedia software titles cd-rom technology new kit included cd-rom software representing good value customers one kit named omnicd included 2x matsushita drive along isa controller card software including software toolworks encyclopedia aldus photostyler se compliant mpc level 2 standard sound blaster pro 2 mcv ct5330 version created ibm ps/2 model 50 higher microchannel bus next model sound blaster 16 announced june 1992 introduced sound blaster 16 retained yamaha opl-3 fm synthesis backward compatible programming interface software titles written older sound blasters sound blaster pros would run without modification eventually design proved popular creative made pci version card creative audio revenue grew us 40 million per year nearly us 1 billion following launch sound blaster 16 related products rich sorkin general manager global business time responsible product planning product management marketing oem sales moving card isa bus already approaching obsolescence meant line host-controlled isa dma available pci slot offers line instead card used pci bus mastering transfer data main memory d/a converters since existing dos programs expected able initiate host-controlled isa dma producing sound backward compatibility older sound blaster cards dos programs required software driver work-around since work-around necessarily depended virtual 8086 mode pc cpu order catch reroute accesses isa dma controller card failed number dos games either fully compatible cpu mode needed much free conventional memory could loaded driver occupying part memory microsoft windows problem creative windows driver software could handle isa pci cards correctly sound blaster vibra16 inexpensive single-chip implementation sound blaster 16 oem market creative labs also used chip sound blaster 32 phone blaster phone blaster 28.8 vibra modem ct3120 ct3220 many value-edition cards external yamaha opl3 fm music synthesis retained earlier boards built around vibra16 vibra16s controllers whilst later common vibra16 boards used cqm creative quadratic modulation developed e-mu systems series included vibra16 ct2501 vibra16s ct2502 ct2504 vibra16c ct2505 pnp vibra16xv ct2511 chips primary advantage vibra16 inclusion 14.4 kbit/s telephony modem also functioned telephone released march 1994 sound blaster awe32 advanced waveffects introduced new midi synthesizer section based emu8000 awe32 consisted two distinct audio sections creative digital audio section audio codec optional csp/asp chip socket yamaha opl3 e-mu midi synthesizer section synthesizer section consisted emu8000 sampler effects processor emu8011 1 mb sample rom 512 kb sample ram expandable 28 mb fit new hardware awe32 full-length isa card measuring derivative awe32 design sound blaster 32 sb32 value-oriented offering creative announced june 6 1995 sb32 became new entry-level card awe32 product-line previously held awe32 value sb32 retained awe32 emu8000/emu8011 midi-synthesis engine built-in instrument rom dropped onboard ram wave blaster header csp port sb32 used vibra chip reduce component count meant bass/treble/gain control limited compared awe32 loss onboard ram offset inclusion 30-pin simm ram sockets allow 28 mb ram installed used emu engine awe32 successor sound blaster awe64 november 1996 significantly smaller half-length isa card term misleading — see pictures size comparison offered similar features awe32 also notable improvements including support greater polyphony although product 32 extra software-emulated channels 30-pin simm slots awe32/sb32 replaced proprietary memory format could expensively purchased creative main improvements better compatibility older sb models improved signal-to-noise ratio awe64 came two versions standard version later rebranded value 512kb ram gold version 4 mb ram separate s/pdif output 1998 creative acquired ensoniq corporation manufacturer audiopci card popular oems time full-featured solution wavetable midi sample-based synthesizer 4-speaker directsound3d surround sound a3d emulation dos legacy support via tsr program cheap due lack hardware acceleration full-duplex least ms windows play back several sources creative released many cards using original audiopci chip ensoniq es1370 several boards using revised versions chip es1371 es1373 creative-labeled audiopci chips boards using audiopci tech usually easily identifiable board design chip size look quite similar boards include sound blaster pci64 april 1998 pci128 july 1998 creative ensoniq audiopci vibra pci sound blaster 16 pci es137x chip contains 3 stereo sample rate converters buffers pci busmaster interface analogue interfacing done codec chip runs fixed sampling frequency 44 ensoniq audio pci 48 khz creative versions isa soundcards resampled switched different time bases es137x support soundfonts filter-less midi engine wavetable sample table sets 2 4 8mb size sound blaster live introduced august 1998 use programmable digital signal processor pc-audio unprecedented ibm already done cheap mwave sound- modem-cards turtle beach professional hurricane soundcards live built around creative new emu10k1 chip contained 2.44 million transistors advertised processing flashy 1,000 mips emu10k1 successors use on-card ram/rom storage instrument samples instead used pci busmaster interface access sample-data stored host-pc system memory a/d- d/a- converters well analogue mixing done ac'97 chip running 48 khz sampling rate members sb live family least four-channel analog audio outputs 15-pin midi/joystick multiport game titles eax 1.0 later 2.0 environmental audio extensions briefly competed defunct a3d 2.0 added hardware-accelerated acoustic effects emu10k1 provided high-quality 64-voice sample-based synthesizer a.k.a wavetable self-produced third-party customized patches soundfonts ability resample audio output input apply range real-time dsp effects set audio subchannels present device first model flagship sb/live family sb live gold featuring gold tracings major analog traces external sockets emi-suppressing printed circuit board substrate lacquer gold came standard daughterboard implemented separate 4-channel alternative mini-din digital output creative-branded internal-dac speaker sets s/p-dif digital audio input output separate software mappings fully decoded midi interface separate input output along mini-din converter gold highlighted many features aimed music composition ease-of-use plug-and-play musicians realtime loopback-recording midi-synthesizer full freedom soundfonts environmental effects reverb etc bundled midi-software mainstream model sound blaster live like gold live featured multi-speaker analog output four channels identical music/sound generation capabilities without bundled midi software interfacing-equipment later versions live usually called live 5.1 offered 5.1-channel support adds center channel speaker lfe subwoofer output useful movie watching live 5.1 could also use one 3.5 mm jack ports spdif allowed connection external decoder creative also released soundblaster live player 1024 edition identical regular soundblaster live addition extra software sound blaster pci 512 ct4790 emu10k1-based sound card designed fill lower cost segment live value capable live value features aside limited 512 midi voice polyphony software-based limitation lacking digital i/o removal expansion headers stereo quadraphonic output support card circuit layout somewhat simpler live series sound blaster audigy august 2001 featured audigy processor emu10k2 improved version emu10k1 processor shipped sound blaster live audigy could process four eax environments simultaneously upgraded on-chip dsp native eax 3.0 advanced hd support supported 5.1-channel output audigy controversially advertised 24-bit sound card emu10k2 audio transport dma engine fixed 16-bit sample precision 48 khz like emu10k1 original live audio resampled 48 khz order accepted dsp recording rendering output sound blaster audigy 2 september 2002 featured updated emu10k2 processor sometimes referred emu10k2.5 improved dma engine capable 24-bit precision 192 khz supported stereo playback/record 6.1 capped 96 khz addition audigy 2 supported 6.1 later 7.1 speakers improved signal-to-noise ratio snr audigy 106 vs. 100 decibels also featured built-in dolby digital ex 6.1 7.1 decoding improved dvd play-back audigy 2 line first sound cards receive thx certification sound blaster audigy 2 zs september 2003 essentially audigy 2 updated dac op-amps audigy 2 zs uses cirrus logic cs4382 dac together op-amps produce output snr 108 db slight printed circuit board modifications 7.1 audio support added sound blaster audigy 4 pro november 2004 audigy 2 zs updated dacs adcs new dac cirrus logic cs4398 boosting output snr 113 db breakout box distinguishable difference audigy 2 zs dsp identical audigy 2 zs creative put audigy 4 sticker cover chip making appear new chip audigy 4 pro confused audigy 4 value contains lower quality dacs golden plated jacks audigy 4 value line audigy 2 value series audigy 4 shorter life span predecessors due short window next-generation sound blaster x-fi sound blaster audigy rx september 2013 similar audigy 4 pro dedicated 600-ohm headphone amplifier pcie 1x interface sound blaster audigy fx september 2013 also features 600-ohm amplifier pcie interface lacks emu10k dsp x-fi extreme fidelity released august 2005 came xtremegamer titanium titanium fatal1ty professional titanium fatal1ty champion elite pro configurations 130 nm emu20k1 emu20k2 titanium series models audio chip operates 400 mhz 51 million transistors computational power processor i.e performance estimated 10,000 mips 24 times higher estimated performance predecessor audigy processor beginning 2008 titanium models newer x-fi cards switched pci pci express x1 connectors x-fi active modal architecture ama user choose one three optimization modes gaming entertainment creation enabling combination features chipset x-fi uses eax 5.0 supports 128 3d-positioned voices four effects applied release also included 24-bit crystallizer intended pronounce percussion elements placing emphasis low high pitched parts sound x-fi release offered powerful mixing capabilities available making powerful entry-level card home musicians big improvement x-fi previous audigy designs complete overhaul resampling engine card previous audigy cards dsps locked 48/16 meaning content match resampled card hardware done poorly resulted lot intermodulation distortion many hardcore users worked around means resampling content using high quality software decoders usually form plugin media player creative completely re-wrote resampling method used x-fi dedicated half power dsp process resulting clean resample recon3d series announced september 2011 includes recon3d pcie recon3d fatal1ty professional recon3d fatal1ty champion cards use new integrated sound core3d chip features quartet dsp x-fi series well integrated dac adc i/o interface 56-pin package asia-only recon3d professional audio basically recon3d pcie extra accessories cables recon3d series sound cards support asio recon3d comes bundled software called sbx pro studio sbx pro studio allows users adjust amount virtual surround crystallizer bass smart volume dialog plus recon3d sound cards recon3d also got crystal voice feature reduces pickup background noises like hairdryer vacuum cleaner beamforming microphone used reviews generally positive pricing small model differences raised questions especially low mid priced models recon3d pcie recon3d fatal1ty professional cosmetic differences considerable price difference fatal1ty professional adds beamforming microphone red led lights metal shroud board real hardware improvements sound blaster z-series announced august 2012 includes pci express x1 cards z zx zxr use sound core3d chip previous sound blaster recon3d series z-series improved sound quality recon3d series including dedicated audio hardware op-amps dacs adcs sound blasterx ae-5 announced june 2017 first discrete sound card made creative five years since introduction z-series card first sound blaster series use 32-bit/384 khz sabre 32 ultra dac es9016k2m along custom-designed discrete headphone amplifier 1w output power low output impedance 1 ohm provide high damping factor virtually dynamic headphone card additional rgb lighting courtesy molex power connection accompanying rgb led strip late 2017 white colored model sound card called sound blasterx ae-5 pure edition released 4 rgb led strips instead one standard black model sound blaster ae-7 released july 2019 alongside sound blaster ae-9.it equipped ess sabre 9018 dac features acm audio control module connects sound card via two audio ports available card n't feature rgb lighting contrary ae-5 n't require external power either sound blaster ae-9 announced december 2018 targeting audiophile audience soundcard equipped ess sabre 9038 dac features external audio control module connects sound card mini-hdmi cable containing xlr port microphone toggleable 48 volt phantom power rail sound card features replaceable operational amplifiers sound card external dac consumes 75w thus first sound card creative requires auxiliary power using 6-pin pci-e connector supply power external dac card officially released july 10 2019 celebrate 30 years since introduction original sound blaster sound blasterx series announced gamescom 2015 sound blasterx brand consists usb audio devices gaming headsets gaming mousepads gaming speakers discrete sound card gaming mouse gaming keyboard sound blasterx h3 h5 p5 come blasterx acoustic engine lite software blasterx acoustic engine lite software comes preset audio profiles different game types settings profiles adjustable unlike blasterx acoustic engine pro blasterx acoustic engine lite software available windows pc blasterx acoustic engine pro allows users adjust amount effects save also scout mode voice fx users bind key combinations enable/disable blasterx acoustic engine scout mode voice fx also equalizer tab software users load profiles create profiles equalizer blasterx acoustic engine pro software available windows pc sound blasterx h3 sound blasterx h5 headsets 3.5mm audio jacks sound blasterx p5 earphone inline microphone come audio/mic splitter cable sound blasterx h3 h5 p5 come software called blasterx acoustic engine lite sound blasterx h7 gaming headset usb 3.5mm jack connectivity maximum playback bitrate sample rate 24-bit 96 khz supports 7.1 virtual surround sound blasterx h7 comes blasterx acoustic engine pro software unlike sound blaster e5 built-in microphones rechargeable battery bluetooth connectivity blasterx acoustic engine profiles saved onto device windows used mac computer mac os x software well android ios apps sound blasterx g5 sound blasterx g1 uses blasterx acoustic engine pro software like sound blasterx g5 got 4-pole headphones microphone audio port maximum playback bitrate sample rate 24-bit 96 khz supports 7.1 virtual surround headphones amplifier supports headphones impedances 16 ohms 300 ohms sound blasterx g1 sb-axx1 audio chip able save profiles blasterx acoustic engine device able save profiles x-plus configurator running x-plus mode x-plus configurator software available windows pc profiles x-plus configurator apply equalizer settings tuned certain games sound blasterx g1 support u hear sound blaster cards since 1999 conform microsoft pc 99 standard color-coding external connectors follows awe line 1994 creative cards short text inscriptions backplane card indicating port i.e mic spk aux aux later cards text inscriptions changed icons latest cards creative cards changed use numbers ports flexi-jacks different functions assigned run-time i.e changed speaker output mic color overlay sticker included retail units help consumers identify commonly used functions ports default modes lot audio/data pin connectors jumpers-setting present internal body sound blaster different card card along years productions common pin connector common pin jumper setting especially plug-and-play features drivers audigy 2 zs soft-modded enthusiasts installed creative older cards including sound blaster live audigy audigy 2 claimed offer improved sound quality hardware acceleration higher eax versions games 64-channel mixing audigy 1 overall improvement card performance several forum posts across web reported favorable results technique excepting live users drivers add ability use newer software applications i.e newer mixer applet comments forums developers software mod said live hardware capable eax3 64-channels hardware sound mixing later 2004 creative released updated drivers top-to-bottom audigy audigy 4 line put cards basically feature parity software level 2006 entire audigy lineup uses driver package dsp decoding driver level cards audigy 2 zs 4 still supported official drivers works soft-modded drivers cards hardware dsp like audigy 2 6.1 windows vista released single beta driver creative audigy series usable operating system minimal functionality frequent instability reported users creative forum activist named daniel k. modified drivers x-fi applied audigy live series restoring features came original xp setup cd vista x-fi drivers noticeably better sound quality vista bug fixes newer build last modified version 2.15.0004eq april managed enable x-fi crystallizer work audigy series cards software however patents involved forced remove modified drivers dll patch creative released newer official audigy vista driver 2.18.0000 28 july 2008 due public consumer pressure however form agreement creative daniel k achieved returned creative forums posting updated versions modified drivers released final version modded driver package january 12 2012 recent linux distributions support sound blaster cards via kernel drivers case non-plug-and-play isa cards configuration file /etc/modules must reconfigured writing example sound blaster 16 card installed snd-sb16 isapnp=0 x-fi series cards basic support linux however advanced features like signal routing relay control external i/o consoles supported support newer sound blaster cards z ae series added kernel 4.19-4.20 release timeframe
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Computer architecture
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johanna moore johanna doris moore computational linguist cognitive scientist research publications include contributions natural language generation spoken dialogue systems computational models discourse intelligent tutoring training systems human-computer interaction user modeling knowledge representation received b.s mathematics computer science summa cum laude 1980 m.s computer science 1982 ph.d advisors william swartout gerald estrin 1989 ucla moore held posts ucla 1976–1986 usc information sciences institute 1983–1989 university pittsburgh 1990–1998 since 1998 held chair artificial intelligence within school informatics university edinburgh served director human communication research centre co-director institute language cognition computation 2014-2018 head school informatics succeeded role professor jane hillston moore elected ucla chapter phi beta kappa 1980 held office naval research fellowship 1982 1985 ibm fellow 1985 1987 held national science foundation national young investigator award 1994 1999 chair cognitive science society president association computational linguistics 2004 fellow british computer society 2003 elected fellow royal society edinburgh moore carrying research project june 2015 may 2016 connected digital economy
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Computational linguistics
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japan vulnerability notes japan vulnerability notes jvn japan national vulnerability database maintained japan computer emergency response team coordination center japanese government information-technology promotion agency
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Computer security
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special communications service russia special communications information service federal protective service russian federation spetssvyaz spetssviaz cryptologic intelligence agency federal protective service russia responsible collection analysis foreign communications foreign signals intelligence well protecting russian government communications information systems involves information security cryptanalysis/cryptography service established march 11 2003 successor fapsi created 8th main directorate government communications 16th directorate electronic intelligence kgb september 25 1991 following august coup soviet president mikhail gorbachev dismantled kgb several independent departments one became committee government communications president soviet union december 24 1991 disbanding soviet union organization became federal agency government communications information president russian federation march 11 2003 agency reorganized service special communications information spetssviaz federal security service fsb august 7 2004 spetssviaz incorporated structural sub unit federal protective service fso service created result reform march 11 2003 basis federal agency government communications information fapsi initially special communication service fso according direction regulations service special communications information federal service russian federation service special communication information special communication russia federal special communication information exercising powers within organization provision service security development improving governmental systems kinds special links information gathering federal government agencies public authorities russian federation state bodies august 7 2004 vladimir putin signed decree federal service russian federation according decree service become part fso 16th centre “ military unit 71330 ” inherited fapsi fsb ’ main structural unit signals intelligence consists central unit housed unmarked administrative buildings many different locations across moscow secluded forest enclosures satellite dishes several metres diameter facing different directions located mainly along russia ’ borders signals intelligence facilities also referred information reception centres direct reference main function 16th centre ’ signals intelligence facilities closest estonia krasnoye selo lenin-grad oblast verbnoye kaliningrad oblast neyolovo pskov oblast last one 25 kilometres estonian border 2003 2010 spetssviaz director yuri korneev director special communications service deputy director russian federal protective service
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Computer security
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coh-metrix coh-metrix computational tool produces indices linguistic discourse representations text developed arthur c. graesser danielle mcnamara coh-metrix calculates coherence texts many different measures coh-metrix used many different ways investigate cohesion explicit text coherence mental representation text definition cohesion consists characteristics explicit text play role helping reader mentally connect ideas text graesser mcnamara louwerse 2003 definition coherence subject much debate theoretically coherence text defined interaction linguistic representations knowledge representations coherence defined characteristics text i.e. aspects cohesion likely contribute coherence mental representation coh-metrix measurements provide indices cohesion characteristics according empirical study coh-metrix l2 reading index performs significantly better traditional readability formulas
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Computational linguistics
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smartbear software smartbear software privately-held information technology company delivers tools application performance monitoring apm software development software testing api management company based assembly square somerville greater boston area current smartbear company founded 2009 original smart bear company founded jason cohen 2003 current smartbear software result insight venture partners acquiring three companies smart bear automatedqa pragmatic software 2007 early 2009 companies operated aqa holdings rebranded smartbear software 2010 rebranding company acquired eviware 2011 leading api promoter soapui founder ole lensmar joining company later served chief technology officer cto smartbear year company acquired apm vendor alertsite 2013 smartbear acquired spanish apm vendor lucierna smartbear acquired open source community swagger 2015 founder tony tam joined company head products swagger commercial version swagger swaggerhub 2016 smartbear acquired crossbrowsertesting.com cbt ken hamric founder cbt joined company general manager crossbrowsertesting.com 2017 francisco partners acquired majority stake smartbear software smartbear based greater boston area u.s. offices texas tennessee florida smartbear also offices development centers ireland sweden smartbear current ceo justin teague smartbear software offers 16 commercial products following categories api readiness software testing monitoring code collaboration code optimization two open-source tools soapui swagger api readiness smartbear products include soapui pro api functional testing secure pro api security testing loadui pro api load testing swaggerhub swagger-based api editor smartbear software testing tools include testcomplete automated testing loadcomplete load testing testleft functional testing crossbrowsertesting cloud testing platform monitoring alertsite smartbear application quality performance monitoring tool code collaboration code optimization smartbear offers collaborator code review document review tool aqtime pro performance profiling
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Distributed computing architecture
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global telecoms exploitation global telecoms exploitation reportedly secret british telephonic mass surveillance programme run british signals intelligence computer security agency government communications headquarters gchq existence revealed along sister programme mastering internet june 2013 part global surveillance disclosures former national security agency contractor edward snowden
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Computer security
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cyveillance 2015 cyveillance acquired lookingglass cyber solutions following information date december 2015 cyveillance company involved cyber intelligence industry cyveillance uses proprietary technology platform human analysts identify risks early prevention mitigation cyveillance founded 1997 based reston virginia united states company ’ subscription-based product cyveillance intelligence center hosted solution companies hire cyveillance monitor internet risks information leaks phishing malware attacks online fraud schemes sale stolen credit debit card numbers threats executives events counterfeiting trademark brand abuse united states secret service contracts cyveillance search available information related secret service missions information obtained cyveillance incorporated protective research information management system prism surveillance program existing secret service system cyveillance bought may 2009 uk firm qinetiq initial cash consideration 40 million current management also entitled additional 40 million anniversary closing dependent hitting certain performance numbers cyveillance clients include firms financial services energy technology retail pharmaceutical industries cyveillance provides open source internet intelligence 400 clients including half fortune 100 cyveillance founded 1997 brandy thomas christopher young mark bildner jason thomas originally called online monitoring services renamed 1998 cyveillance 1997 2009 cyveillance privately held qinetiq north america provider information technology engineering solutions u.s. government acquired cyveillance may 2009 2013 qinetiq north america expanded cyveillance management team appointment technical marketing executives qinetiq senior management cyveillance management team numerous websites complained cyveillance traffic following reasons 2 july 2014 cyveillance sent dmca takedown notice github behalf qualcomm caused 116 files repositories blocked github blocked repositories owned cyanogenmod sony mobile even one qualcomms repositories leading speculation notices automatically generated poorly checked 5 july 2014 qualcomm retracted takedown notices apologized reviewing files
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Computer security
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melomics109 melomics109 computer cluster three cabinets customized front panels located universidad de málaga part spanish supercomputing network designed increase computational power provided iamus powered melomics technology composing module melomics109 able create synthesize music variety musical styles music made freely accessible everyone 0music first album composed interpreted melomics109 launched july 21 name melomics aims freely distributing melomics109 production formats album first one released audio mp3 editable format midi cc0 public domain licensing rest melomics109 production browsed listened downloaded free melomics
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Distributed computing architecture
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butasan player controls pig aim game blow pigs throwing bombs bombs randomly spawned across map picked thrown pigs bombs given number 5 30 bomb thrown takes number seconds explode bombs directly hit pigs explode contact various power ups available throughout game gas makes characters fall asleep bonus sub-game involves random pigs popping holes player must knock back hole pig similar mode gameplay whack-a-mole game released various home computer systems zx spectrum commodore 64 msx amstrad cpc u.s. gold psycho pigs u.x.b several criticisms sexism advert game showing semi-naked model holding video game case published specialized magazines
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Computer architecture
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kaavo kaavo cloud computing management company kaavo founded november 2007 u.s. kaavo pioneered top-down application-centric management cloud infrastructure across public private hybrid clouds traditional infrastructure associated management intrinsically ties applications servers servers ip addresses ip addresses switches routers tightly coupled model according experts leaves little room address dynamic nature virtual infrastructure often seen cloud computing models subject matter experts supporting kaavo approach claims cloud applications decoupled servers deployed network infrastructure supports delivers effectively managed unless recognized individual components infrastructure-as-a-service iaas delivers on-demand infrastructure resources however users still need deploy configure applications workloads iaas layer kaavo provides framework automate deployment run-time management production support applications workloads multiple clouds infrastructure-as-a-service layer kaavo claims bottom-up approach traditional data center management tools makes harder manage infrastructure especially dealing scale distributed nature cloud kaavo takes top-down application-centric approach deploying managing applications cloud application-centric cloud management approach systems specific applications managed rather managing servers routers required resources given application managed unified system information deploying managing runtime services levels resources required given application captured top-down single system definition contrast infrastructure-centric bottom-up approach resources servers storage network resources managed individually one key innovations kaavo ability capture deployment run-time management behavior complex application workload single xml document kaavo system definition kaavo published xsd system definition file kaavo imod product uses patented technology based kaavo top-down application-centric management philosophy kaavo uses technology deliver two cloud management products delivered web based product hosted amazon ec2 integrated following public cloud providers amazon ec2 ibm smartcloud logicworks infinicloud rackspace cloud terremark cloud integrated following private cloud platforms cloud.com cloudstack eucalyptus ibm smartcloud openstack vmware vcloud director imod supports multiple cloud providers platforms across application workload service deployments well within single deployment imod also include on-premises physical resources within deployments onsite deployment available enterprise customers within private clouds supports imod saas capabilities api configuring managing applications supported cloud providers platforms kaavo web services use document/literal wrapped style soap compared server-level api provided iaas cloud providers platforms provides higher level abstraction managing systems configuring software web services api allows users deploy applications/workloads across public private hybrid clouds single web services call also provides interface trigger complex workflows response deployment-specific events following registered trademarks kaavo
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Distributed computing architecture
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goback norton goback previously wildfile goback adaptec goback roxio goback disk utility microsoft windows record 8 gb disk changes filesystem idle seconds marks safe points product allows disk drive restored point within available history also allows older versions files restored previous versions whole disk browsed depending disk activity typical history might cover hours days goback replaces master boot record also replaces partition table single partition allows hard drive changed back even event operating system unable boot also protecting filesystem alteration revert information remains correct goback compatible hardware raid drives due changes made partition table cause problems dual booting operating systems hard disk possible retain dual-boot compatibility involve saving partition table enabling goback enabling goback re-writing partition table back disk booting different device live cd may also necessary disable goback prior using certain low level disk utilities formatting software low level utilities first check presence goback combination goback cause data become corrupted another example incompatible program windows version true image windows goback also incompatible products drive vaccine pc restore rollback rx products require access master boot record
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Computer security
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zram zram formerly called compcache linux kernel module creating compressed block device ram i.e ram disk on-the-fly disk compression block device created zram used swap general-purpose ram disk two common uses zram storage temporary files /tmp swap disk initially zram latter function hence original name compcache compressed cache four years linux driver staging area zram introduced mainline linux kernel version 3.14 released march 30 2014 linux kernel version 3.15 onwards released june 8 2014 zram supports multiple compression streams multiple compression algorithms compression algorithms include lz4 lzo default lz4 faster compressing/decompressing compress quite efficiently lzο like system parameters compression algorithm selected via sysfs used compressed swap space zram similar zswap general-purpose ram disk rather in-kernel compressed cache swap pages however unlike zswap zram use hard disk backing store currently possible see patch config_zram_writeback i.e move less-frequently used pages disk hand zswap requires backing store zram used swap zram like zswap also allows linux make efficient use ram since operating system hold pages memory compressed swap amount ram used application memory disk cache particularly effective machines much memory 2012 ubuntu briefly considered enabling zram default computers small amounts installed ram compressed swap space zram/zswap also offers advantages low-end hardware devices embedded devices netbooks devices usually use flash-based storage limited lifespan due write amplification also use provide swap space reduction swap usage result using zram effectively reduces amount wear placed flash-based storage resulting prolonging usable life also using zram results significantly reduced i/o linux systems require swapping google chromeos uses zram default since 2013 android includes zram since version 4.4 lubuntu also started using zram version 13.10
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Operating systems
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air gap networking air gap air wall air gapping network security measure employed one computers ensure secure computer network physically isolated unsecured networks public internet unsecured local area network means computer network network interfaces connected networks physical conceptual air gap analogous air gap used plumbing maintain water quality air-gapped computer network one network interfaces either wired wireless connected outside networks many computers even plugged wired network wireless network interface controller wifi connected nearby wireless networks access internet update software represents security vulnerability air-gapped computers either wireless interface controller permanently disabled physically removed move data outside world air-gapped system necessary write data physical medium thumbdrive physically move computers physical access easier control electronic network interface attacked time exterior insecure system malware infects secure system used export secure data environments networks devices rated handle different levels classified information two disconnected devices networks referred low side high side low unclassified high referring classified classified higher level also occasionally referred red classified black unclassified access policies often based bell–lapadula confidentiality model data moved low-to-high minimal security measures high-to-low requires much stringent procedures ensure protection data higher level classification concept represents nearly maximum protection one network another save turning device way transfer data outside world air-gapped system copy data removable storage medium removable disk usb flash drive physically carry storage system access easily controlled upside network generally regarded closed system terms information signals emissions security unable accessed outside world downside transferring information outside world analyzed computers secure network extraordinarily labor-intensive often involving human security analysis prospective programs data entered onto air-gapped networks possibly even human manual re-entry data following security analysis sophisticated computer viruses use cyberwarfare stuxnet agent.btz designed infect air-gapped systems exploiting security holes related handling removable media possibility using acoustic communication also demonstrated researchers researchers also demonstrated feasibility data exfiltration using fm frequency signals examples types networks systems may air gapped include many systems since added features connect public internet longer effectively air gapped including thermostats internet connections automobiles bluetooth wi-fi cellular phone connectivity limitations imposed devices used environments may include ban wireless connections secure network similar restrictions em leakage secure network use tempest faraday cage scientists 2013 demonstrated viability air gap malware designed defeat air gap isolation using acoustic signaling shortly network security researcher dragos ruiu badbios received press attention 2014 researchers introduced airhopper bifurcated attack pattern showing feasibility data exfiltration isolated computer nearby mobile phone using fm frequency signals 2015 bitwhisper covert signaling channel air-gapped computers using thermal manipulations introduced bitwhisper supports bidirectional communication requires additional dedicated peripheral hardware later 2015 researchers introduced gsmem method exfiltrating data air-gapped computers cellular frequencies transmission generated standard internal bus renders computer small cellular transmitter antenna projectsauron malware discovered 2016 demonstrates infected usb device used remotely leak data air-gapped computer malware remained undetected 5 years relied hidden partitions usb drive visible windows transport channel air-gapped computer computer connected internet presumably way share files two systems nfcdrip name given discovery stealthy data exfiltration nfc near-field communication radio abuse signal detection 2018 although nfc enables devices establish effective communication bringing within centimeters researchers showed abused transmit information much longer range expected 100 meters general malware exploit various hardware combinations leak sensitive information air-gapped systems using air-gap covert channels hardware combinations use number different mediums bridge air-gap including acoustic light seismic magnetic thermal radio-frequency
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Computer security
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tom cross computer security tom cross also known decius american computer security expert hacker cross born 1976 toronto ontario canada grew tennessee father worked telecommunications policy mother registered nurse assistant attended brentwood high school brentwood tennessee attending georgia tech atlanta receiving bachelor degree computer engineering co-founded efga electronic frontiers georgia 1995 1996 co-founded computer sentry software known award-winning cyberangel software laptop anti-theft program 1999-2000 chief engineer dataway computer security firm san francisco 2000-2001 worked iasiaworks director global security engineering 2001 founded industrial memetics developed popular collaborative blogging community memestreams cross speaker several technology conferences including phreaknic summercon first international hackers conference seoul korea is2k internetworld singapore apricot asia-pacific regional internet conference operational technologies also among attendees first ever def con known extensive rant essays speeches technology policy also co-host episodes binary revolution cryptography expert
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Computer security
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windows iot windows iot formerly windows embedded family operating systems microsoft designed use embedded systems microsoft currently three different subfamilies operating systems embedded devices targeting wide market ranging small-footprint real-time devices point sale pos devices like kiosks windows embedded operating systems available original equipment manufacturers oems make available end users preloaded hardware addition volume license customers cases april 2018 microsoft released azure sphere another operating system designed iot applications running linux kernel mid-1998 microsoft worked venturcom company specialized software embedded systems windows nt embedded product windows nt embedded 4.0 got start 1998 small team developers microsoft project known within microsoft impala released 1999 windows nt embedded 4.0—a set tools database approximately 250 components allowed developers put together small windows nt 4.0 run-time images embedded devices tools allowed oems embedded developers create components encapsulating binaries add seamlessly windows nt embedded runtimes containing limited functionality devices minimum run-time images small 9 mb system featuring full win32 api shortly release early 2000 microsoft decided best take architecture make new product leveraging new windows code new windows embedded team formed leadership bruce beachman served product unit manager pum first windows embedded – started recruiting engineers within microsoft team set sights next version decision made stop development windows 2000 embedded start work windows xp embedded product called whistler plans drawn team expanded work started whistler embedded codenamed mantis component count risen 250 10,000—most device-driver components feature set embedded tools enriched include things like basic version control component scripting expandability tools also added make easier start blank slab hardware deploy embedded os quickly easily august 26 2001 beta 2 windows xp embedded released full release planned later year initial team consisted target designer component designer two-parts suite first version windows embedded suite first test team manager bombo sofa lead first xpe test team starting 2000 bruce beachman leadership microsoft shipped first version windows embedded xpe devcon windows hardware conference 2001 2002 bruce beachman left microsoft peter wilson took xpe team pum team merged windows deployment team released xpe sp1 devcon las vegas late 2003 microsoft rebranded windows embedded windows iot starting release embedded versions windows 10 windows 10 iot enterprise based windows 10 enterprise cbb/ltsc/ltsb/sac updated version embedded industry embedded standard plain unlabeled retail/thin client tablet small tablet versions available differing licensing windows 10 iot mobile based windows 10 mobile successor embedded handheld windows 10 iot mobile enterprise adds arm support multiple user profiles advanced lockdown capabilities otherwise identical normal mobile version windows 10 iot core considered successor windows embedded compact although maintains little compatibility optimized smaller lower-cost industry devices also provided free charge use devices like raspberry pi hobbyist use windows 10 iot core pro provides ability defer control updates licensed via distributors otherwise identical normal iot core version windows embedded compact previously known windows embedded ce windows ce version windows embedded small computers embedded systems including consumer electronics devices like set-top boxes video game consoles windows embedded compact modular real-time operating system specialized kernel run 1 mb memory comes platform builder tool used add modules installation image create custom installation depending device used windows embedded compact available arm mips superh x86 processor architectures microsoft made available specialized version windows embedded compact known windows mobile use mobile phones customized image windows embedded compact along specialized modules use mobile phones windows mobile available four variants windows mobile classic pocket pc windows mobile standard smartphones windows mobile professional pda/pocket pc phone edition windows mobile automotive communication/entertainment/information systems used automobiles modified versions windows mobile used portable media centers 2010 windows mobile replaced windows phone 7 also based windows embedded compact compatible previous products windows embedded compact 2013 real-time operating system runs arm x86 sh derivatives architectures included .net framework ui framework various open source drivers services 'modules windows embedded standard brand windows embedded operating systems designed provide enterprises device manufacturers freedom choose capabilities part industry devices intelligent system solutions intended build atms devices healthcare manufacturing industries creating industry-specific devices brand consists windows nt 4.0 embedded windows xp embedded windows embedded standard 2009 wes09 windows embedded standard 7 windows embedded 8 standard provides full win32 api windows embedded standard 2009 includes silverlight .net framework 3.5 internet explorer 7 windows media player 11 rdp 6.1 network access protection microsoft baseline security analyzer support managed windows server update services system center configuration manager windows embedded standard 7 based windows 7 previously codenamed windows embedded 'quebec windows embedded standard 7 includes windows vista windows 7 features aero superfetch readyboost windows firewall windows defender address space layout randomization windows presentation foundation silverlight 2 windows media center among several packages available ia-32 x64 versions released 2010 larger minimum footprint ~300 mb compared 40 mb xpe also requires product activation windows embedded standard 7 released april 27 2010 windows embedded 8 standard released march 20 2013 currently divided two brands fes products binary identical versions oses available retail licensed exclusively use embedded devices available ia-32 well x64 processors windows embedded pro formerly windows embedded enterprise brand consists non server fes products including windows nt workstation windows 2000 professional windows xp professional windows vista business ultimate windows 7 professional ultimate windows 8 pro windows 8.1 pro microsoft renamed windows embedded enterprise windows embedded pro starting windows embedded 8 pro windows embedded server brand consists fes server products including server home server sql server storage server dpm server isa server uag server tmg server unified data storage server etc various years including 2000 2003 2003 r2 2004 2005 2006 2007 2008 2008 r2 2012 2012 r2 etc windows embedded industry brand windows embedded operating systems industry devices point sale systems brand limited windows embedded point service operating system released 2006 based windows xp embedded microsoft also updated version windows embedded point service named windows embedded posready 2009 however windows embedded posready 7 based windows 7 sp1 released 2011 succeeded posready 2009 microsoft since changed name product windows embedded posready windows embedded industry microsoft released windows embedded 8 industry april 2013 followed 8.1 industry october 2013 windows embedded navready also called navigation ready plug-in component windows ce 5.0 useful building portable handheld navigation devices windows embedded automotive formerly microsoft auto windows ce automotive windows automotive windows mobile automotive embedded operating system based windows ce use computer systems automobiles latest release windows embedded automotive 7 announced october 19 2010 january 10 2011 microsoft announced windows embedded handheld 6.5 operating system compatibility windows mobile 6.5 presented enterprise handheld device targeting retailers delivery companies companies rely handheld computing windows embedded handheld retains backward compatibility legacy windows mobile applications windows embedded 8.1 handheld released manufacturing april 23 2014 known simply windows embedded 8 handheld we8h prior release designed next generation windows embedded handheld line-of-business handheld devices built windows phone 8.1 also compatibility five windows embedded 8.1 handheld devices released manufactured bluebird honeywell panasonic listed
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Computer architecture
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nokia n82 nokia n82 high-end smartphone produced nokia announced 14 november 2007 part company nseries line n82 runs symbian os v9.2 s60 3rd edition fp1 n82 inherits much nokia n95 features specifications including gps wi-fi hsdpa major addition xenon flash time n82 called many best camera phone market result sometimes called n95 successor people like n95 nokia n82 critically acclaimed often considered one best symbian devices although sell much available worldwide n82 also perhaps nokia last high-end device candybar form successors opted sliders later touchscreen devices nokia n82 model leaked may 2007 along nokia n81 made official six months later november introduced month nokia n95 8gb latest firmware nokia n82 v35.0.002 released december 2009 n86 8mp 2009 slider considered n82 spiritual successor due high-end camera technology despite lack xenon flash however similar top-of-the-line device candybar form never appeared nokia n82 nokia 6220 classic 2008 second nokia xenon flash n82 includes built-in accelerometer video stabilisation photo orientation keep landscape portrait shots oriented taken automatic 270 degree screen rotation compatible n-gage gaming platform 2.4-inch tft display features 332 mhz processor found n95 n82 almost identical specifications n95 leading called n95 candybar form apart xenon camera flash addition minor technologic differences models 128 mb ram 64 mb n95 8gb variant also 128 mb cif resolution 352x288 front camera qvga 320x240 microusb port rather miniusb removal infrared port first nokia phone xenon flash n82 5-megapixel camera carl zeiss optics considered best camera phone market arrival samsung gt-i8510 discussions head head comparisons two models demonstrate n86 8mp 2009 equipped dual led flash consistently capable outperforming n82 variable lighting primary advantage using led light source video recording whereas xenon flash stronger burst light used recording videos due technical composition mainland china market version n82 different hardware platform wi-fi umts radio removed 3g support different product code rm-314 opposed rm-313 firmware incompatible regular model version readily identified lack wlan scanning display idle screen
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Operating systems
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ibm thinkpad 380 ibm thinkpad 380 notebook computer manufactured 1997 ibm part thinkpad laptop series notable incorporating cd-rom floppy drive considered mid-range laptop ibm time sold well 380 shipped windows 95 capable running windows 3.11 windows nt os/2 warp windows 98 windows red hat linux well various linux distributions originally two models base thinkpad 380 thinkpad 380d equipped cd-rom drive 380 came intel pentium processor running 150 mhz without optional mmx feature 16 mb base ram included base hard drive 1.08 gb size windows 3.11 better operating system choice base model however 32 mb installed could run windows 95 properly models—apart base 380—could run versions windows including windows xp windows xp run smoothly however would need configured least 64 mb ram 2.0 gb hard drive larger
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Computer architecture
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xenon video game xenon 1988 vertical scrolling shooter video game first developed bitmap brothers published melbourne house owned mastertronic featured play-by-phone game saturday-morning kids show get fresh xenon followed 1989 according game instruction manual player assumes role darrian future space pilot federation currently war mysterious violent alien species called xenites lasted decade response mayday transmission captain xod following attack trading fleet darrian forced travel xenite occupied territory order support unlike vertically scrolling shooters player craft two modes flying plane ground tank transition crafts initiated almost time play except mid- end-of-level boss sections well certain levels certain mode forced mode chosen depends nature threat player faces destroying enemies released power-ups player could catch enhance ship originally released atari st xenon quickly ported platforms amiga amstrad cpc commodore 64 dos msx zx spectrum arcade machine version game also released mastertronic arcadia division ran commodore amiga hardware xenon almost universally well received launch reviewers magazines covering range platforms scoring game highly german magazine power play bucked trend awarding score 4.5 10
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Computer architecture
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indicator compromise indicator compromise ioc computer forensics artifact observed network operating system high confidence indicates computer intrusion typical iocs virus signatures ip addresses md5 hashes malware files urls domain names botnet command control servers iocs identified via process incident response computer forensics used early detection future attack attempts using intrusion detection systems antivirus software initiatives standardize format iocs efficient automated processing known indicators usually exchanged within industry traffic light protocol used
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Computer security
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system integration system integration defined engineering process bringing together component sub-systems one system aggregation subsystems cooperating system able deliver overarching functionality ensuring subsystems function together system information technology process linking together different computing systems software applications physically functionally act coordinated whole system integrator integrates discrete systems utilizing variety techniques computer networking enterprise application integration business process management manual programming system integration involves integrating existing often disparate systems way focuses increasing value customer e.g. improved product quality performance time providing value company e.g. reducing operational costs improving response time modern world connected internet role system integration engineers important systems designed connect within system construction systems already deployed vertical integration opposed horizontal integration process integrating subsystems according functionality creating functional entities also referred silos benefit method integration performed quickly involves necessary vendors therefore method cheaper short term hand cost-of-ownership substantially higher seen methods since case new enhanced functionality possible way implement scale system would implementing another silo reusing subsystems create another functionality possible star integration also known spaghetti integration process systems integration system interconnected remaining subsystems observed perspective subsystem integrated connections reminiscent star overall diagram system presented connections look like spaghetti hence name method cost varies interfaces subsystems exporting case subsystems exporting heterogeneous proprietary interfaces integration cost substantially rise time costs needed integrate systems increase exponentially adding additional subsystems feature perspective method often seems preferable due extreme flexibility reuse functionality horizontal integration enterprise service bus esb integration method specialized subsystem dedicated communication subsystems allows cutting number connections interfaces one per subsystem connect directly esb esb capable translating interface another interface allows cutting costs integration provides extreme flexibility systems integrated using method possible completely replace one subsystem another subsystem provides similar functionality exports different interfaces completely transparent rest subsystems action required implement new interface esb new subsystem horizontal scheme misleading however thought cost intermediate data transformation cost shifting responsibility business logic avoided common data format integration method avoid every adapter convert data to/from every applications formats enterprise application integration eai systems usually stipulate application-independent common data format eai system usually provides data transformation service well help convert application-specific common formats done two steps adapter converts information application format bus common format semantic transformations applied converting zip codes city names splitting/merging objects one application objects applications
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Computer architecture
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perl perl family two high-level general-purpose interpreted dynamic programming languages perl usually refers perl 5 may also refer redesigned sister language perl 6 though perl officially acronym various backronyms use including practical extraction reporting language perl originally developed larry wall 1987 general-purpose unix scripting language make report processing easier since undergone many changes revisions perl 6 began redesign perl 5 2000 eventually evolved separate language languages continue developed independently different development teams liberally borrow ideas one another perl languages borrow features programming languages including c shell script sh awk sed wall also alludes basic lisp introduction learning perl schwartz christiansen provide text processing facilities without arbitrary data-length limits many contemporary unix commandline tools facilitating manipulation text files perl 5 gained widespread popularity late 1990s cgi scripting language part due unsurpassed regular expression string parsing abilities addition cgi perl 5 used system administration network programming finance bioinformatics applications guis nicknamed swiss army chainsaw scripting languages flexibility power also ugliness 1998 also referred duct tape holds internet together reference ubiquitous use glue language perceived inelegance larry wall began work perl 1987 working programmer unisys released version 1.0 comp.sources.misc newsgroup december 18 1987 language expanded rapidly next years perl 2 released 1988 featured better regular expression engine perl 3 released 1989 added support binary data streams originally documentation perl single lengthy man page 1991 programming perl known many perl programmers camel book cover published became de facto reference language time perl version number bumped 4 mark major change language identify version well documented book perl 4 went series maintenance releases culminating perl 4.036 1993 whereupon wall abandoned perl 4 begin work perl 5 initial design perl 5 continued 1994 perl5-porters mailing list established may 1994 coordinate work porting perl 5 different platforms remains primary forum development maintenance porting perl 5 perl 5.000 released october 17 1994 nearly complete rewrite interpreter added many new features language including objects references lexical variables modules importantly modules provided mechanism extending language without modifying interpreter allowed core interpreter stabilize even enabled ordinary perl programmers add new language features perl 5 active development since perl 5.001 released march 13 1995 perl 5.002 released february 29 1996 new prototypes feature allowed module authors make subroutines behaved like perl builtins perl 5.003 released june 25 1996 security release one important events perl 5 history took place outside language proper consequence module support october 26 1995 comprehensive perl archive network cpan established repository perl language perl modules may 2017 carries 185,178 modules 35,190 distributions written 13,071 authors mirrored worldwide 245 locations perl 5.004 released may 15 1997 included among things universal package giving perl base object classes automatically derived ability require versions modules another significant development inclusion cgi.pm module contributed perl popularity cgi scripting language perl 5.004 also added support microsoft windows several operating systems perl 5.005 released july 22 1998 release included several enhancements regex engine new hooks backend codice_1 modules codice_2 regex quote operator large selection new core modules added support several operating systems including beos perl 5.6 released march 22 2000 major changes included 64-bit support unicode string representation support files 2 gib keyword developing perl 5.6 decision made switch versioning scheme one similar open source projects 5.005_63 next version became 5.5.640 plans development versions odd numbers stable versions even numbers 2000 wall put forth call suggestions new version perl community process resulted 361 rfc request comments documents used guiding development perl 6 2001 work began apocalypses perl 6 series documents meant summarize change requests present design next generation perl presented digest rfcs rather formal document point perl 6 existed description language perl 5.8 first released july 18 2002 nearly yearly updates since perl 5.8 improved unicode support added new i/o implementation added new thread implementation improved numeric accuracy added several new modules 2013 version still remains popular version perl used red hat 5 suse 10 solaris 10 hp-ux 11.31 aix 5 2004 work began synopses documents originally summarized apocalypses became specification perl 6 language february 2005 audrey tang began work pugs perl 6 interpreter written haskell first concerted effort towards making perl 6 reality effort stalled 2006 december 18 2007 20th anniversary perl 1.0 perl 5.10.0 released perl 5.10.0 included notable new features brought closer perl 6 included switch statement called given regular expressions updates smart match operator ~~ around time development began earnest another implementation perl 6 known rakudo perl developed tandem parrot virtual machine november 2009 rakudo perl regular monthly releases complete implementation perl 6 major change development process perl 5 occurred perl 5.11 development community switched monthly release cycle development releases yearly schedule stable releases plan bugfix point releases follow stable releases every three months april 12 2010 perl 5.12.0 released notable core enhancements include new codice_3 syntax yada yada operator intended mark placeholder code yet implemented implicit strictures full y2038 compliance regex conversion overloading dtrace support unicode 5.2 january 21 2011 perl 5.12.3 released contains updated modules documentation changes version 5.12.4 released june 20 2011 latest version branch 5.12.5 released november 10 2012 may 14 2011 perl 5.14 released json support built-in 5.14.0 latest version branch 5.14.4 released march 10 2013 may 20 2012 perl 5.16 released notable new features include ability specify given version perl one wishes emulate allowing users upgrade version perl still run old scripts would normally incompatible perl 5.16 also updates core support unicode 6.1 may 18 2013 perl 5.18 released notable new features include new dtrace hooks lexical subs core subs overhaul hash security reasons support unicode 6.2 may 27 2014 perl 5.20 released notable new features include subroutine signatures hash slices/new slice syntax postfix dereferencing experimental unicode 6.3 rand using consistent random number generator observers credit release perl 5.10 start modern perl movement particular phrase describes style development embraces use cpan takes advantage recent developments language rigorous creating high quality code book modern perl may visible standard-bearer idea groups enlightened perl organization taken cause late 2012 2013 several projects alternative implementations perl 5 started perl5 perl6 rakudo perl team moe stevan little friends p2 perl11 team reini urban gperl goccy rperl kickstarter project led braswell affiliated perll11 project ponie acronym perl new internal engine ponie project existed 2003 2006 bridge perl 5 perl 6 effort rewrite perl 5 interpreter run parrot perl 6 virtual machine goal ensure future millions lines perl 5 code thousands companies around world ponie project ended 2006 longer actively developed improvements made perl 5 interpreter part ponie folded project perl originally named pearl wall wanted give language short name positive connotations claims considered every three- four-letter word dictionary also considered naming wife gloria wall discovered existing pearl programming language perl official release changed spelling name referring language name normally capitalized perl proper noun referring interpreter program name often uncapitalized perl unix-like file systems case-sensitive release first edition programming perl common refer language perl randal l. schwartz however capitalized language name book make stand better typeset case distinction subsequently documented canonical name occasionally expanded practical extraction report language backronym expansions suggested equally canonical including wall pathologically eclectic rubbish lister manual page perl indeed wall claims name intended inspire many different expansions programming perl published o'reilly media features picture dromedary camel cover commonly called camel book image camel become unofficial symbol perl well general hacker emblem appearing t-shirts clothing items o'reilly owns image trademark licenses non-commercial use requiring acknowledgement link www.perl.com licensing commercial use decided case case basis o'reilly also provides programming republic perl logos non-commercial sites powered perl buttons site uses perl perl foundation owns alternative symbol onion licenses subsidiaries perl mongers perlmonks perl.org others symbol visual pun pearl onion sebastian riedel creator mojolicious created logo depicting raptor dinosaur available cc-sa license version 4.0 logo remixed used different places symbolising perl 5 analogue raptor comes series talks given matt trout beginning 2010 talks aimed perl 5 community-centric period perl 6 hot topic according wall perl two slogans first one way commonly known tmtowtdi second slogan easy things easy hard things possible overall structure perl derives broadly c. perl procedural nature variables expressions assignment statements brace-delimited blocks control structures subroutines perl also takes features shell programming variables marked leading sigils allow variables interpolated directly strings however unlike shell perl uses sigils accesses variables unlike programming languages use sigils sigil n't denote type variable type expression example access list values hash sigil array used sigil hash perl also many built-in functions provide tools often used shell programming although many tools implemented programs external shell sorting calling operating system facilities perl takes lists lisp hashes associative arrays awk regular expressions sed simplify facilitate many parsing text-handling data-management tasks also shared lisp implicit return last value block fact statements value thus also expressions used larger expressions perl 5 added features support complex data structures first-class functions closures values object-oriented programming model include references packages class-based method dispatch lexically scoped variables along compiler directives example codice_4 pragma major additional feature introduced perl 5 ability package code reusable modules wall later stated whole intent perl 5 module system encourage growth perl culture rather perl core versions perl automatic data-typing automatic memory management interpreter knows type storage requirements every data object program allocates frees storage necessary using reference counting deallocate circular data structures without manual intervention legal type conversions — example conversions number string — done automatically run time illegal type conversions fatal errors design perl understood response three broad trends computer industry falling hardware costs rising labor costs improvements compiler technology many earlier computer languages fortran c aimed make efficient use expensive computer hardware contrast perl designed computer programmers could write programs quickly easily perl many features ease task programmer expense greater cpu memory requirements include automatic memory management dynamic typing strings lists hashes regular expressions introspection codice_5 function perl follows theory built-in limits idea similar zero one infinity rule wall trained linguist design perl much informed linguistic principles examples include huffman coding common constructions short good end-weighting important information come first large collection language primitives perl favors language constructs concise natural humans write even complicate perl interpreter perl syntax reflects idea things different look different example scalars arrays hashes different leading sigils array indices hash keys use different kinds braces strings regular expressions different standard delimiters approach contrasted language lisp basic syntax composed simple universal symbolic expressions used purposes perl enforce particular programming paradigm procedural object-oriented functional others even require programmer choose among broad practical bent perl language community culture surround preface programming perl begins perl language getting job done one consequence perl tidy language includes many features tolerates exceptions rules employs heuristics resolve syntactical ambiguities forgiving nature compiler bugs sometimes hard find perl function documentation remarks variant behavior built-in functions list scalar contexts saying general want unless want consistency written specification standard perl language exists perl versions perl 5 plans create one current version perl one implementation interpreter language evolved along interpreter together functional tests stands de facto specification language perl 6 however started specification several projects aim implement specification perl many varied applications compounded availability many standard third-party modules perl chiefly used write cgi scripts large projects written perl include cpanel slash bugzilla rt twiki movable type high-traffic websites use perl extensively include priceline.com craigslist imdb livejournal duckduckgo slashdot ticketmaster also optional component popular lamp technology stack web development lieu php python perl used extensively system programming language debian gnu/linux distribution perl often used glue language tying together systems interfaces specifically designed interoperate data munging converting processing large amounts data tasks creating reports fact strengths intimately linked combination makes perl popular all-purpose language system administrators particularly short programs often called one-liner programs entered run single command line perl code made portable across windows unix code often used suppliers software cots bespoke simplify packaging maintenance software build- deployment-scripts graphical user interfaces guis may developed using perl example perl/tk wxperl commonly used enable user interaction perl scripts interaction may synchronous asynchronous using callbacks update gui perl implemented core interpreter written c together large collection modules written perl c. interpreter 150,000 lines c code compiles 1 mb executable typical machine architectures alternatively interpreter compiled link library embedded programs nearly 500 modules distribution comprising 200,000 lines perl additional 350,000 lines c code much c code modules consists character encoding tables interpreter object-oriented architecture elements perl language—scalars arrays hashes coderefs file handles—are represented interpreter c structs operations structs defined large collection macros typedefs functions constitute perl c api perl api bewildering uninitiated entry points follow consistent naming scheme provides guidance use life perl interpreter divides broadly compile phase run phase perl phases major stages interpreter life-cycle interpreter goes phase phases follow fixed sequence happens perl compile phase compilation happens perl run phase execution significant exceptions perl makes important use capability execute perl code compile phase perl also delay compilation run phase terms indicate kind processing actually occurring moment compile time run time perl compile time points compile phase compile time may also entered run phase compile time code string argument passed codice_6 built-in occurs run phase perl often run time compile phase spends run phase run time code codice_7 blocks executes run time compile phase compile time interpreter parses perl code syntax tree run time executes program walking tree text parsed syntax tree subject optimization executed execution relatively efficient compile-time optimizations syntax tree include constant folding context propagation peephole optimization also performed perl turing-complete grammar parsing affected run-time code executed compile phase therefore perl parsed straight lex/yacc lexer/parser combination instead interpreter implements lexer coordinates modified gnu bison parser resolve ambiguities language often said perl parse perl meaning perl interpreter codice_8 parse perl language perl even general true perl interpreter simulate turing machine compile phase would need decide halting problem order complete parsing every case long-standing result halting problem undecidable therefore even perl always parse perl perl makes unusual choice giving user access full programming power compile phase cost terms theoretical purity high practical inconvenience seems rare programs undertake parse perl source-code analyzers auto-indenters contend ambiguous syntactic constructs also undecidability perl parsing general case adam kennedy ppi project focused parsing perl code document retaining integrity document instead parsing perl executable code even perl always kennedy first conjectured parsing perl suffers 'halting problem later proved perl distributed 250,000 functional tests core perl language 250,000 functional tests core modules run part normal build process extensively exercise interpreter core modules perl developers rely functional tests ensure changes interpreter introduce software bugs additionally perl users see interpreter passes functional tests system high degree confidence working properly perl dual licensed artistic license 1.0 gnu general public license distributions available operating systems particularly prevalent unix unix-like systems ported modern many obsolete platforms six reported exceptions perl compiled source code posix-compliant otherwise-unix-compatible platforms unusual changes required classic mac os environment special port called macperl shipped independently comprehensive perl archive network carries complete list supported platforms links distributions available cpan also source publicly available perl modules part core perl distribution users microsoft windows typically install one native binary distributions perl win32 commonly strawberry perl activeperl compiling perl source code windows possible installations lack requisite c compiler build tools also makes difficult install modules cpan particularly partially written c. activeperl closed source distribution activestate regular releases track core perl releases distribution also includes perl package manager ppm popular tool installing removing upgrading managing use common perl modules included also perlscript windows script host wsh engine implementing perl language visual perl activestate tool adds perl visual studio .net development suite vbscript perl converter well perl compiler windows converters awk sed perl also produced company included activestate cd windows includes distributions plus komodo ide first unix/linux/posix variant thereof 2002 subsequently strawberry perl open source distribution windows regular quarterly releases since january 2008 including new modules feedback requests come strawberry perl aims able install modules like standard perl distributions platforms including compiling xs modules cygwin emulation layer another way running perl windows cygwin provides unix-like environment windows perl cpan available standard pre-compiled packages cygwin setup program since cygwin also includes gcc compiling perl source also possible perl executable included several windows resource kits directory scripting tools implementations perl come mks toolkit interix base earlier implementations windows services unix uwin perl text-handling capabilities used generating sql queries arrays hashes automatic memory management make easy collect process returned data example tim bunce perl dbi application programming interface api arguments api text sql queries thus possible program multiple languages time e.g. generating web page using html javascript sql document use perl variable interpolation programmatically customize sql queries specification perl arrays hashes structures programmatically hold resulting data sets sql query allows high-level mechanism handling large amounts data post-processing perl subprogram early versions perl database interfaces created relinking interpreter client-side database library sufficiently difficult done most-important widely used databases restricted resulting codice_8 executable using one database interface time perl 5 database interfaces implemented perl dbi modules dbi database interface module presents single database-independent interface perl applications dbd database driver modules handle details accessing 50 different databases dbd drivers ansi sql databases dbi provides caching database handles queries greatly improve performance long-lived execution environments mod perl helping high-volume systems avert load spikes slashdot effect modern perl applications especially written using web frameworks catalyst dbi module often used indirectly via object-relational mappers generate sql queries handle data transparently application author computer language benchmarks game compares performance implementations typical programming problems several programming languages submitted perl implementations typically perform toward high end memory-usage spectrum give varied speed results perl performance benchmarks game typical interpreted languages large perl programs start slowly similar programs compiled languages perl compile source every time runs talk yapc :europe 2005 conference subsequent article timely start jean-louis leroy found perl programs took much longer run expected perl interpreter spent significant time finding modules within over-large include path unlike java python ruby perl experimental support pre-compiling therefore perl programs pay overhead penalty every execution run phase typical programs long enough amortized startup time substantial benchmarks measure short execution times likely skewed due overhead number tools introduced improve situation first tool apache mod perl sought address one most-common reasons small perl programs invoked rapidly cgi web development activeperl via microsoft isapi provides similar performance improvements perl code compiled additional overhead execution phase typically n't present programs written compiled languages c c++ examples overhead include bytecode interpretation reference-counting memory management dynamic type-checking perl interpreted language give problems efficiency critical situations critical routines written languages c connected perl via simple inline modules complex flexible xs mechanism perl 5 language usually referred perl continues actively developed perl 5.12.0 released april 2010 new features influenced design perl 6 followed perl 5.14.1 released june 17 2011 perl 5.16.1 released august 9 2012 perl 5.18.0 released may 18 2013 perl 5 development versions released monthly basis major releases coming per year relative proportion internet searches perl programming compared similar searches programming languages steadily declined 10 2005 2 2011 1 2019 2000 perl conference jon orwant made case major new language-initiative led decision begin work redesign language called perl 6 proposals new language features solicited perl community large submitted 300 rfcs wall spent next years digesting rfcs synthesizing coherent framework perl 6 presented design perl 6 series documents called apocalypses numbered correspond chapters programming perl developing specification perl 6 encapsulated design documents called synopsesnumbered correspond apocalypses thesis work bradley m. kuhn overseen wall considered possible use java virtual machine runtime perl kuhn thesis showed approach problematic 2001 decided perl 6 would run cross-language virtual machine called parrot mean languages targeting parrot gain native access cpan allowing level cross-language development 2005 audrey tang created pugs project implementation perl 6 haskell acted continues act test platform perl 6 language separate development actual implementation allowing language designers explore pugs project spawned active perl/haskell cross-language community centered around freenode perl6 irc channel many functional programming influences absorbed perl 6 design team 2012 perl 6 development centered primarily around two compilers 2013 moarvm “ metamodel runtime ” c language-based virtual machine designed primarily rakudo announced rakudo perl implementation moarvm support virtual machines java virtual machine javascript active development perl culture community developed alongside language usenet first public venue perl introduced course evolution perl community shaped growth broadening internet-based services including introduction world wide web community surrounds perl fact topic wall first state onion talk state onion name wall yearly keynote-style summaries progress perl community characterized hallmark humor employing references perl culture wider hacker culture wall linguistic background sometimes family life occasionally even christian background talk first given various perl conferences eventually also published online number irc channels offer support language modules also many examples code written purely entertainment cpan codice_10 example allows writing programs latin upon execution program module translates source code regular perl runs perl community set aside acme namespace modules fun nature scope widened include exploratory experimental code module meant ever used production acme modules deliberately implemented amusing ways includes codice_11 one first modules codice_12 namespace allows program source code whitened i.e. characters replaced whitespace yet still work older versions perl one would write hello world program complex perl program counts seconds given threshold perl interpreter also used one-off scripts command line following example invoked sh-compatible shell bash translates string bob files ending .txt current directory robert perl referred line noise programmers claim syntax makes write-only language earliest mention first edition book learning perl perl 4 tutorial book written randal l. schwartz first chapter states yes sometimes perl looks like line noise uninitiated seasoned perl programmer looks like checksummed line noise mission life also stated accusation perl write-only language could avoided coding proper care perl overview document perlintro states names built-in magic scalar variables look like punctuation line noise however english module provides long short english alternatives perlstyle document states line noise regular expressions could mitigated using codice_13 modifier add whitespace according perl 6 faq perl 6 designed mitigate usual suspects elicit line noise claim perl 5 critics including removal majority punctuation variables sanitization regex syntax perl 6 faq also states sometimes referred perl line noise actual syntax language gerunds prepositions part english language december 2012 blog posting despite claiming rakudo perl 6 failed continue fail unless gets adult supervision chromatic stated design perl 6 well-defined grammar well improved type system unified object system intelligent metamodel metaoperators clearer system context provides niceties pervasive laziness also stated perl 6 coherence consistency perl 5 lacks
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Programming language topics
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bothunter bothunter free utility unix aims detecting botnet activity within network analyzing network traffic comparing patterns characteristic malicious processes version 1.7.2 current earlier version ran microsoft windows xp mentioned web site release 1.7.2 order support application developer sri international collected 10,000 samples malware 2008 bothunter web site states software made possible part research grant u.s. army research office
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Computer security
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opera web browser opera web browser microsoft windows android ios macos linux operating systems developed opera software opera software norwegian software company publicly listed nasdaq stock exchange majority ownership control belonging chinese businessman zhou yahui founder beijing kunlun tech specialises mobile games chinese cybersecurity company qihoo 360 opera chromium-based browser using blink layout engine differentiates distinct user interface features opera conceived telenor research project 1994 bought opera software 1995 commercial software first ten years proprietary presto layout engine presto versions opera received many awards presto development ended milestone transition chromium 2013 also three mobile versions called opera mobile opera touch opera mini gaming browser called opera gx launched 11 june 2019 opera began 1994 research project telenor largest norwegian telecommunications company 1995 branched separate company named opera software opera first publicly released 1996 version 2.10 ran microsoft windows attempt capitalize emerging market internet-connected handheld devices project port opera mobile device platforms started 1998 opera 4.0 released 2000 included new cross-platform core facilitated creation editions opera multiple operating systems platforms point opera trialware purchased trial period ended version 5.0 released 2000 saw end requirement instead opera became ad-sponsored displaying advertisements users paid later versions opera gave user choice seeing banner ads targeted text advertisements google version 8.5 released 2005 advertisements completely removed primary financial support browser came revenue google contract opera default search engine among new features introduced version 9.1 released 2006 fraud protection using technology geotrust digital certificate provider phishtank organization tracks known phishing web sites feature improved expanded version 9.5 geotrust replaced netcraft malware protection haute secure added 2006 opera software asa released well internet channel nintendo ds browser nintendo ds wii gaming systems new javascript engine called carakan javanese alphabet introduced version 10.50 according opera software carakan made opera 10.50 seven times faster sunspider opera 10.10 16th december 2010 opera 11 released featuring extensions tab stacking dragging one tab another allows create group tabs visual mouse gestures changes address bar opera 12 released 14 june 2012 12 february 2013 opera software announced would drop presto layout engine favour webkit implemented google chrome browser using code chromium project opera software planned well contribute code webkit 3 april 2013 google announced would fork components webkit form new layout engine known blink day opera software confirmed would follow google implementing blink layout engine 28 may 2013 beta release opera 15 made available first version based chromium project many distinctive opera features previous versions dropped opera mail separated standalone application derived opera 12 november 2016 original norwegian owner opera sold stake business chinese consortium name golden brick capital private equity fund limited partnership 600 million earlier deal approved regulators january 2017 source code opera 12.15 one last versions still based presto layout engine leaked demonstrate radically different browser could look opera neon dubbed concept browser released january 2017 pc world compared demo models automakers hardware vendors release show visions future instead speed dial also explained following chapter features displays frequently accessed websites resemblance desktop computer icons scattered artistic formation opera originated features later adopted web browsers including speed dial pop-up blocking re-opening recently closed pages private browsing tabbed browsing opera includes bookmarks bar download manager opera also speed dial allows user add unlimited number pages shown thumbnail form page displayed new tab opened speed dial allows user easily navigate selected web pages possible control aspects browser using keyboard shortcuts page zooming allows text images content adobe flash player java platform scalable vector graphics increased decreased size help impaired vision opera software claims opera turbo mode enabled compression servers compress requested web pages except https pages 50 depending upon content sending users process reduces amount data transferred particularly useful crowded slow network connections making web pages load faster costs dependent total amount data usage technique also used opera mini mobile devices smartwatches one security feature option delete private data http cookies browsing history items cache passwords click button lets users erase personal data browsing shared computer visiting site opera displays security badge address bar shows details website including security certificates opera fraud malware protection warns suspicious web pages enabled default checks requested page several databases known phishing malware websites called blacklists january 2007 asa dotzler competing mozilla corporation accused opera software downplaying information security vulnerabilities opera fixed december 2006 dotzler claimed users clearly informed security vulnerabilities present previous version opera thus would realize needed upgrade latest version else risk exploited hackers opera software responded accusations next day 2016 free virtual private network vpn service implemented browser opera said would allow encrypted access websites otherwise blocked provide security public wifi networks either vpn turbo enabled july 2018 opera listed nasdaq stock exchange new york city initial offering 12 per share 2018 built-in cryptocurrency wallet opera web browser released announcing would first browser built-in crypto wallet 13 december 2018 released video showing many decentralized applications like cryptokitties running android version opera web browser opera one first browsers support cascading style sheets css opera software uses release cycle consisting three streams correspond phases development downloaded installed independently developer beta stable new features first introduced developer build depending user feedback may progress beta version eventually released developer stream allows early testing new features mainly targeting developers extension creators early adopters opera developer intended everyday browsing unstable prone failure crashing enables advanced users try new features still development without affecting normal installation browser new versions browser released frequently generally times week beta stream formerly known opera next feature complete package allowing stability quality mature final release new version released every couple weeks streams installed alongside official release without interference different icon help user distinguish variants 2005 adobe systems opted integrate opera rendering engine presto adobe creative suite applications opera technology employed adobe golive adobe photoshop adobe dreamweaver components adobe creative suite opera layout engine also found virtual mechanics sitespinner pro internet channel version opera 9 web browser use nintendo wii created opera software nintendo opera software also implemented nintendo ds browser nintendo handheld systems versions presto layout engine positively reviewed although criticized website compatibility issues issue opera 8.01 higher included workarounds help certain popular problematic web sites display properly versions blink layout engine criticized users missing features ui customization abandoning opera software presto layout engine despite versions blink layout engine praised fast stable handling latest web standards better website compatibility modern-style user interface years opera personal computers received several awards awards include related web browsers web browsers essential features
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Internet protocols
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webscarab webscarab web security application testing tool serves proxy intercepts allows people alter web browser web requests http https web server replies webscarab also may record traffic review webscarab open source tool developed open web application security project owasp implemented java could run across multiple operating systems 2013 official development webscarab slowed appears owasp zed attack proxy zap project another java-based open source proxy tool features active development webscarab official successor although zap forked paros proxy webscarab
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Computer security
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cvar cvar convar abbreviations console variable depending context term found may also stand client variable configuration variable type variable used many computer games computer 3d simulation engines manipulated text based command line interface within game engine often called console commonly hold configuration parameters used anything may potentially accessed and/or modified console common usage cvars server operators customize online game servers
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Programming language topics
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funarg problem computer science funarg problem refers difficulty implementing first-class functions functions first-class objects programming language implementations use stack-based memory allocation functions difficulty arises body nested function refers directly i.e. via argument passing identifiers defined environment function defined environment function call standard resolution either forbid references create closures two subtly different versions funarg problem upwards funarg problem arises returning otherwise transmitting upwards function function call downwards funarg problem arises passing function parameter another function call one function calls another typical program execution local state caller including parameters local variables must preserved order execution proceed callee returns compiled programs local state stored call stack data structure called stack frame activation record stack frame pushed allocated prelude calling another function popped deallocated function returns function call upwards funarg problem arises calling function refers called/exited function state function returned therefore stack frame containing called function state variables must deallocated function returns violating stack-based function call paradigm one solution upwards funarg problem simply allocate activation records heap instead stack rely form garbage collection reference counting deallocate longer needed managing activation records heap historically perceived less efficient stack although partially contradicted perceived impose significant implementation complexity functions typical programs less programs functional programming languages create upwards funargs adding concerns potential overhead associated implementation furthermore approach genuinely difficult languages support garbage collection efficiency-minded compilers employ hybrid approach activation records function allocated stack compiler able deduce static program analysis function creates upwards funargs otherwise activation records allocated heap another solution simply copy value variables closure time closure created cause different behavior case mutable variables state longer shared closures known variables constant approach equivalent ml languages take approach since variables languages bound values—i.e variables changed java also takes approach respect anonymous classes allows one refer variables enclosing scope codice_1 i.e constant languages allow programmer explicitly choose two behaviors php 5.3 anonymous functions require one specify variables include closure using codice_2 clause variable listed reference includes reference original variable otherwise passes value apple blocks anonymous functions captured local variables default captured value one wants share state closures closure outside scope variable must declared codice_3 modifier case variable allocated heap following haskell-inspired pseudocode defines function composition codice_4 operator constructing new function case one argument codice_5 returns result first applying codice_6 codice_5 applying codice_8 λ function carries functions codice_8 codice_6 pointers internal state problem case exists compose function allocates parameter variables codice_8 codice_6 stack codice_13 returns stack frame containing codice_8 codice_6 discarded internal function codice_16 attempts access codice_6 access discarded memory area downwards funarg may also refer function state function actually executing however definition existence downwards funarg contained execution function creates stack frame function usually still stored stack nonetheless existence downwards funargs implies tree structure closures stack frames complicate human machine reasoning program state downwards funarg problem complicates efficient compilation tail recursion code written continuation-passing style special cases intent programmer usually function run limited stack space faster behavior may actually undesirable historically upwards funarg problem proven difficult example pascal programming language allows functions passed arguments returned results thus implementations pascal required address downwards funarg problem upwards one modula-2 oberon programming languages descendants pascal allow functions parameters return values assigned function may nested function c programming language historically avoids main difficulty funarg problem allowing function definitions nested environment every function containing statically-allocated global variables functions pointer function code describes function completely apple proposed implemented closure syntax c solves upwards funarg problem dynamically moving closures stack heap necessary java programming language deals requiring context used nested functions anonymous inner local classes declared final context used lambda expressions effectively final c lambdas closures encapsulate function pointer related variables functional languages functions first-class values passed anywhere thus implementations scheme sml must address upwards downwards funarg problems usually accomplished representing function values heap-allocated closures previously described ocaml compiler employs hybrid technique based program analysis maximize efficiency
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Programming language topics
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imacros imacros browser based application macro recording editing playback web automation testing provided standalone application extensions mozilla firefox google chrome internet explorer web browsers developed iopus/ipswitch adds record replay functionality similar found web testing form filler software macros combined controlled via javascript demo macros javascript code examples included software running strictly javascript based macros removed later versions imacros browser extensions however users use alternative browser like pale moon based older version mozilla firefox use javascript files web based automated testing moon tester tool first created 2001 mathias roth imacros first macro recorder tool specifically designed optimized web browsers form filling april 2012 imacros acquired ipswitch imacros firefox chrome offers feature known social scripting allows users share macros scripts manner similar social bookmarking technically functions distributed web sites embedding imacro controlling javascript inside plain text link along freeware version imacros available proprietary commercial application additional features support web scripting web scraping internet server monitoring web testing addition working html pages commercial editions automate adobe flash adobe flex silverlight java applets using directscreen image recognition technology freeware version imacros contains control flow statements minor exceptions complex conditional code requires scripting available commercial version advanced versions also contain command-line interface application programming interface api automate complicated tasks integrate programs scripts imacros api called scripting interface scripting interface imacros scripting edition designed component object model com object allows user remotely control script imacros browser internet explorer firefox chrome windows programming scripting language
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Programming language topics
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johan helsingius johan julf helsingius born 1961 helsinki finland started ran anon.penet.fi internet remailer anon.penet.fi one popular internet remailers handling 10,000 messages day server first kind use password-protected po box system sending receiving e-mails 1980s system administrator central finnish news node well founding members finnish unix user group 1994 interview wired said created service important able express certain views without everyone knowing 1996 announced remailer would shut due legal pressure church scientology scientology officials upset users helsingius service sending information church obtained court order force reveal identity many site users announcing service closure wrote close remailer time legal issues concerning internet finland yet undefined american electronic frontier foundation eff internet civil rights initiative reported continuously incidents concerning anon.penet.fi collected donations cover legal costs helsingius involved court case settle whether finnish law could force reveal identity anon.penet.fi users closing anon.penet.fi led outbreak outrage solidarity helsingius throughout internet order protect freedom internet helsingius went help found eunet finland part team people established first internet link ussr later eunet acquired qwest communications soon moved kpnqwest qwest joint venture kpn international julf became chief technology officer cto kpnqwest internet entrepreneur serving board various companies e.g basen based finland helsingius lives amsterdam netherlands helsingius studied music traveled widely interests include active sports like mountain climbing aviation
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Computer security
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intel microcode intel microcode microcode runs inside x86 processors made intel since p6 microarchitecture introduced mid-1990s microcode programs patched operating system bios firmware workaround bugs found cpu release intel originally designed microcode updates processor debugging design testing dft initiative following pentium fdiv bug patchable microcode function took wider purpose allow in-field updating without needing product recall p6 later microarchitectures lists x86 instructions internally converted simpler risc-style micro-operations specific particular processor stepping level pentium pro micro-operation 72-bits wide 118-bits wide includes two source fields one destination field ability hold 32-bit immediate value pentium pro able detect parity errors internal microcode report via machine check architecture micro-operations consistent format three source inputs two destination outputs processor performs register renaming map inputs real register file rrf execution out-of-order execution used micro-operations instructions represent may appear order development pentium pro several microcode fixes included a2 b0 steppings pentium ii based p6 pentium pro additional micro-operations added support mmx instruction set several cases microcode assists added handle rare corner-cases reliable way pentium 4 126 micro-operations flight time micro-operations decoded stored execution trace cache 12,000 entries avoid repeated decoding x86 instructions groups six micro-operations packed trace line complex instructions exception handling result jumping microcode rom development pentium 4 microcode accounted 14 processor bugs versus 30 processor bugs development pentium pro intel core microarchitecture introduced 2006 added micro-operations fusion common pairs instructions including comparison followed jump instruction decoders core convert x86 instructions microcode three different ways intel hyper-threading implementation simultaneous multithreading microcode rom trace cache instruction decoders shared micro-operation queue shared mid-1990s facility supplying new microcode initially referred pentium pro stepping data file bios update feature intended user mode applications make bios interrupt call supply new bios update data block bios would partially validate save nonvolatile bios memory could supplied installed processors next boot intel distributed program called codice_1 renamed codice_2 could run dos collections multiple microcode updates concatencated together numerically numbered extension codice_3 codice_4 processor boots using set microcode held inside processor stored internal rom microcode update populates separate sram set match registers act breakpoints within microcode rom allow jumping updated list micro-operations sram match performed microcode instruction pointer uip match registers match resulting jump corresponding destination microcode address original p6 architecture space sram 60 micro-operations multiple match/destination register pairs takes one processor instruction cycle jump rom microcode patched microcode held sram match registers consist microcode match address microcode destination address processor must protection ring zero order initiate microcode update cpu symmetric multiprocessing arrangement needs updated individually update initiated placing address codice_5 register setting codice_6 executing codice_7 write model-specific register intel distributes microcode updates 2,048 2 kilobyte binary blob update contains information processors designed checked result cpuid instruction structure 48-byte header followed 2,000-bytes intended read directly processor updated block encoded differently majority 2,000 bytes used configuration program sram micro-operation contents much smaller final determination validation whether update applied processor performed decryption via processor microcode update specific particular cpu revision designed rejected cpus different stepping level microcode updates encrypted prevent tampering enable validation pentium two layers encryption precise details explicitly documented intel instead known less ten employees microcode updates intel atom nehalem sandy bridge additionally contain extra 520-byte header containing 2048-bit rsa modulus exponent 17 decimal micro architecture example processors supplied length functional length suspected encoding
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Computer architecture
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cloud access security broker cloud access security broker casb sometimes pronounced cas-bee on-premises cloud based software sits cloud service users cloud applications monitors activity enforces security policies casb offer variety services including limited monitoring user activity warning administrators potentially hazardous actions enforcing security policy compliance automatically preventing malware casb may deliver security management broadly speaking security prevention high-risk events whilst management monitoring mitigation high-risk events casbs deliver security must path data access user cloud architecturally might achieved proxy agents end-point device agentless fashion without requiring configuration device agentless casb allow rapid deployment deliver security devices company-managed unmanaged byod agentless casb also respect user privacy inspecting corporate data agent-based casb difficult deploy effective devices managed corporation agent-based casb typically inspect corporate personal data casbs deliver management may use apis inspect data activity cloud alert risky events fact another management capability casb inspect firewall proxy logs usage cloud applications api-only casbs cloudlock offer management using apis provided major saas applications contrast multi-mode casbs e.g netskope ciphercloud offer management security multi-mode casbs may also offer zero-day capabilities protect threats known unknown
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Distributed computing architecture
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scalr scalr hybrid cloud management platform managing private public cloud platforms large enterprises scalr helps enterprises deliver self-service cloud computing maintaining policies around cost automation security compliance scalr founded sebastian stadil 2007 organizational model help standardize processes across teams later became hybrid cloud management platform incorporated 2011 grown rapidly
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Distributed computing architecture
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brutus cluster brutus central high-performance cluster eth zurich introduced public may 2008 new computing cluster called euler announced opened public may 2014 brutus heterogeneous system containing 11 different kinds compute nodes total brutus contains 19,872 cores plus hundreds cluster file servers login nodes management nodes peak performance brutus slightly 200 teraflops 200 × 10 floating-point operations per second thanks heterogeneous nature brutus tackle wide range applications
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Distributed computing architecture
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transterpreter transterpreter computer software interpreter transputer virtual machine programming language occam-π occam-pi portable runtime kroc compiler designed education research concurrency robotics transterpreter developed university kent transterpeter made possible easily run occam-π programs platforms lego mindstorms rcx arduino ia-32 sparc mips cell operating systems linux macos windows dos
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Programming language topics
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great giana sisters great giana sisters 1987 platform game developed german studio time warp productions published rainbow arts known controversial production history similarities nintendo platform game super mario bros. prompted legal pressure producers game scroll screen melody game composed chris hülsbeck popular commodore 64 soundtrack player takes role giana referred gianna scrolling intro also intended name typo made cover art developers went rather cover remade girl suffers nightmare travels 32 stages full monsters collecting ominous diamonds looking sister maria player wins final battle giana awakened sister great giana sisters 2d side-scrolling arcade game player controls either giana sister maria game supports alternating 2 players second player taking control maria level contains number dream crystals gives points collected order make game high score extra life gained collecting 100 dream crystals extra lives also found form hidden lollipop items enemies defeated jumping shooting obtaining relevant powerups enemies include owls rolling eyeballs flesh-eating fish deadly insects fire wheel transforms giana punk ability crush rocks jumping beneath lightning bolt awards giana dream bubbles single projectile shot double lightning gives ability shoot recoiling projectiles strawberries gives ability shoot homing projectiles one defensive item game water-drop protects giana fire number special items also triggered affects entire screen clock freezes enemies on-screen magic bombs kills enemies items found item blocks scattered around stages two types stages game overworld underground stage overworld stages feature green scenery pipe-shaped objects along bottomless pits giana avoid underground stages feature additional hazards water fire well bosses total 32 stages game hidden warp-blocks found jump portions game great giana sisters programmed armin gessert graphics manfred trenz soundtrack composed chris hülsbeck label time warp production inc first original game version released 1987 commodore 64 shortly released amiga amstrad cpc atari st license held black forest games developed sequel according several urban legends nintendo opened lawsuit case time warp productions rainbow arts nintendo saw direct copyright infringement new game super mario bros. fact never lawsuit neither nintendo german programmers claim privy lawsuits myth created shortly game taken stores nintendo later admitted influenced stop sales directly games several factors influenced stop sales game including conspicuous similarities general gameplay first level great giana sisters nearly identical layout first stage found nintendo super mario bros. immediate similarity super mario bros. ensured great giana sisters quickly noticed public video game industry nintendo urged makers great giana sisters withdraw game sale arguing obvious copyright infringement time warp productions rainbow arts immediately stopped production time game began vanishing stores difficulty obtaining copies game led sought collector items game ported numerous systems since release planned port zx spectrum reviewed magazines though eventually cancelled due legal pressures 1993 dutch publisher sunrise released version msx2 programmed jan van valburg unofficially game cloned windows dos linux mac os x amigaos 4 netbsd aros morphos symbian os unofficial clone commodore 64 version also made nintendo ds 2009 mobile version game titled simply giana sisters released android phones appears ouya discover store launch upon release great giana sisters received strong critical praise acclaim gaming magazines across europe zzap 64 described game amazing concluded overall opinion great giana sisters fabulous compelling constantly rewarding arcade adventure powerplay review stated felt game live standards set super mario bros. still achieves entertaining pleasure despite never seeing release zx spectrum version gained favorable reviews spectrum-based magazines crash noted game highly addictive great fun play plenty hidden passages surprise features keep hooked weeks great giana sisters gained strong cult following years citing strong soundtrack unique charm online web resource lemon64 staff member jan egil romestrand remarked game must-have serious c64 games collector 2012 ranks 6th place top 10 games list gamebase 64 chris hülsbeck soundtrack game become one popular video game soundtracks time received 50 remixes popular music arrangement resource remix64 music great giana sisters featured live orchestra concert symphonic shades held cologne germany august 23 2008 arrangement made jonne valtonen performed wdr radio orchestra concert first video game orchestra concert broadcast live radio concert recording received album release 2009 album print still bought digitally amazon since 2009 endorsement manfred trenz fan-made open-source remake c64 version called openggs development hosted sourceforge remake ported mobile devices like pandora 2015 shortly release great giana sisters time warp began developing sequel announced giana 2 arther martha future world new game futuristic setting due trouble caused legal pressure coming nintendo deemed risky small developer produce game associated giana sisters brand time warp renamed game hard n'heavy changed game protagonists robots rather giana sisters hard n'heavy released commodore 64 amiga 1989 april 2009 publisher dtp entertainment developer spellbound interactive owner game intellectual property released new giana sisters game europe graphical update nintendo ds titled giana sisters ds released australia game features all-new levels gameplay elements recreation original game levels unlocked giana sisters ds released north america february 2011 publisher destineer though official website listed available several retailers walmart newegg.com giana sisters 2d hd remake nintendo ds game released october 2015 pc july 2012 black forest games started kickstarter campaign new installment great giana sisters originally titled project giana later retitled describing project grandchild great giana sisters kickstarter funded successfully netting 186,158 goal 150,000 game described direct sequel giana sisters ds features music great giana sisters original composer chris hülsbeck cooperation fabian del priore swedish sid metal band machinae supremacy giana sisters twisted dreams released october 23 2012 pc later releases xbox live arcade playstation network nintendo eshop possibly ouya giana sisters dream runners multiplayer focused platform game released august 2015 pc playstation 4 xbox one received negative reviews
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Computer architecture
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ipswitch inc. ipswitch management software developer small medium sized businesses company founded 1991 headquartered burlington massachusetts operations atlanta alpharetta augusta georgia american fork utah madison wisconsin galway ireland ipswitch sells products directly well distributors resellers oems united states canada latin america europe pacific rim roger greene founded ipswitch 1991 apartment without venture capital funding bank financing company became profitable second year first product ipswitch produced gateway allowed novell inc. ipx networking protocol connect internet protocol 1994 ipswitch launched imail server first product available e-commerce site open market mid-1990s company value-added reseller spyglass mosaic browser 1996 company released beta version whatsup gold commercial version earlier shareware product ws_ping 2008 ipswitch acquired wisconsin-based software producer standard networks inc. product moveit shortly acquisition ipswitch split operations three divisions secure file transfers network management messaging collaboration company acquired salt lake city-based hourglass technologies 2009 following year company acquired compliance system system log analysis software producer dorian software december 2012 ipswitch acquired waldorf germany-based performance testing company iopus known product imacros web-browser extension 2015 ipswitch merged network monitoring file transfer divisions created partnersynergy program ipswitch opened support operations center galway ireland march 2016.. 28 march 2019 ipswitch signed agreement progress software corporation whereby progress acquire ipswitch completion purchase 225 million announced progress may 1st company commits 5 percent profits variety community investment programs designed support interests employees 2010 ipswitch inc. ’ network management division claimed company achieved 5,000 downloads whatsup gold engineer ’ toolkit first month release partnership trees life international planted 5,000 trees one download
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Computer security
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soalib service-oriented architecture library soalib used distribute reusable service-oriented architecture soa software manner similar computing libraries soa consists loosely coupled interoperable services use messaging based simple object access protocol soap representational state transfer rest library computing set compiled modules tested ready reuse similar concept used soa whatever technology used develop service also distributed library form java-based soa library may distributed web archive war enterprise archive ear file formats c c++ .net applications may distributed shared object unix linux dynamic link library windows executable file service-oriented architecture usually tied redesign entire software system determines decompose single software unit loosely coupled components loosely coupled component acts interoperable service task enormous may take significant amount time atomic level atom defined single loosely coupled service self-contained services reusable regardless application example matter built atoms yet material things different atomic level however appear uniform similarly software built loosely coupled services serve atoms redesign process loose coupling difficult determine opposite true means easier build complete software system using available loosely coupled services building service-oriented architecture libraries loosely coupled service complex applications developed making use services new applications depend loosely coupled services long one sticks loose coupling final application also loosely coupled true final application depends many hierarchical loosely coupled systems remains loosely coupled hierarchy based atomic services building soa requires loose coupling services starting point termed atomic services first step determine atomic services build atomic services reuse large number atomic services could created upon composite services built composite service services built upon atomic services consideration cross platform important presently many ways make services host platform platform independent examples building services java jvm available host server run service alternatives building applications full compliance ansi c/c++ none components code reliant upon third party libraries typically means building c/c++ applications using gnu tools gnu c compilers gnu compilers ported operating systems platforms another alternative use c .net language web service common language runtime ported target operating system platform many options available common approaches platform independence already mentioned scope library limited support databases composite integration services built take advantage loosely coupled atomic services operate databases support database access added metadata layer added map various kinds data format database uniform set data types equal meaning databases difficult part time jdbc odbc ado standards database drivers already part task database may store data different formats data may encrypted may stored little endian endianness others big endian therefore data must transformed point services done runtime due changing nature data databases different therefore single api take advantage features databases therefore services use database specific features well multi-vendor databases supported services added database may synchronize database become possible data passed data layer data represented intermediate form intermediate form may native form standards-based usually native form portable means representing xml may best approach data sizes tend large incremental change detection also added libraries must secure libraries soa implementation web services ws-security ws-policy ws-type standards compliance based rest protocols follow respective standards libraries must least support ssl interoperability one important reasons soa important soa library must also include required api could used rapid platform specific development atomic service loosely coupled service independent assumptions absolutely predictable dependencies services atomic services example disk file operation may considered atomic service operations performed service read write delete append file operations information disk file would need full path file possibly access parameters like username password would dependencies composite service designed based atomic services still loosely coupled atomic service integrated service built together make larger soa application building layer layer large soa application may created remain loosely coupled keep integrated services loosely coupled would require services built atomic composite services soon integrated service uses another service somewhat tightly coupled entire service application becomes tightly coupled analogous atomic structures becoming charged one electron missing reason using third party services designer must ensure service remains loosely coupled following hierarchy service-oriented applications designed ideally following soa application design approach cases loose coupling may possible due reliance hardware mechanical systems specialized instruments example service built move robotic arm monitor industrial generators emergency hospital equipment tightly coupled services required tightly coupled services top hierarchy service may reuse tightly coupled services possible derived services based tightly coupled services derived services also become tightly coupled system designed limited scope purpose application
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Web technology
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tea programming language tea high level scripting language java environment combines features scheme tcl java tea proprietary language interpreter subject non-free license project called destea released language :tea cpan provides alternative generating java code based tea code teaclipse open source compiler uses javacc-generated parser parse compile tea source proprietary tea bytecode
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Programming language topics
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bryan cantrill bryan m. cantrill born 1973 american software engineer worked sun microsystems later oracle corporation following acquisition sun left oracle july 25 2010 become vice president engineering joyent. transitioning chief technology officer joyent april 2014 departure july 31 2019 cantrill born vermont later moving colorado attained rank eagle scout studied computer science brown university spending two summers qnx software systems kernel development upon completing b.sc 1996 immediately joined sun microsystems work jeff bonwick solaris performance group 2005 bryan cantrill named one 35 top young innovators technology review mit magazine cantrill included tr35 list development dtrace function os solaris 10 provides non-invasive means real-time tracing diagnosis software sun technologies technologists including dtrace cantrill also received infoworld innovators award year 2006 dtrace trouble-shooting software sun chosen gold winner wall street journal 2006 technology innovation awards contest 2008 cantrill mike shapiro adam leventhal recognized usenix software tools user group stug award provision significant enabling technology together shapiro leventhal cantrill founded fishworks stealth project within sun microsystems produced sun storage 7000 unified storage systems left oracle july 25 2010 become vice president engineering joyent announced transition chief technology officer joyent april 2014 held position announcing departure july 31 2019 member acm queue editorial board online technical discussion solaris linux kernel developer david s. miller 1996 cantrill responded miller lengthy comment one-line reply ever kissed girl 2015 discussion concerning ben noordhuis departure node.js project cantrill said 1996 comment continues cited decades later wrote regrets sending response called stupid cantrill left oracle 2010 used strong analogies multiple times describe point view oracle business behavior cantrill announced fisl 2012 strong preference permissive open source software licenses copyleft licenses calling copyleft gpl license family anti-collaborative viral
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Operating systems
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carrier interferometry carrier interferometry ci spread spectrum scheme designed used orthogonal frequency-division multiplexing ofdm communication system multiplexing multiple access enabling system support multiple users time frequency band like mc-cdma ci-ofdm spreads data symbol frequency domain data symbol carried multiple ofdm subcarriers unlike mc-cdma uses binary-phase hadamard codes code values 0 180 degrees binary pseudonoise ci codes complex-valued orthogonal codes simplest case ci code values coefficients discrete fourier transform dft matrix row column dft matrix provides orthogonal ci spreading code spreads data symbol spreading achieved multiplying vector data symbols dft matrix produce vector coded data symbols coded data symbol mapped ofdm subcarrier via input bin inverse fast fourier transform ifft block contiguous subcarriers may selected achieve better frequency diversity non-contiguous subcarriers distributed wide frequency band used guard interval cyclic prefix cp added baseband ci-ofdm signal signal processed radio front-end convert rf signal transmitted antenna significant advantage ci-ofdm ofdm techniques ci spreading shapes time-domain characteristics transmitted waveform thus ci-ofdm signals much lower peak-to-average-power ratio papr crest factor compared types ofdm greatly improves power efficiency reduces cost power amplifiers used radio transmitter ci-ofdm receiver removes cyclic prefix received ci-ofdm transmission performs ofdm demodulation dft e.g. fft typically used ofdm receivers ci-spread symbol values collected respective subcarriers inverse-mapping process may equalized compensate multipath fading processed spatial demultiplexing ci de-spreader performs inverse-dft spread symbols recover original data symbols since ci coding shape time-domain characteristics transmitted waveform used synthesize various waveforms direct-sequence spread spectrum frequency shift key 4 signals advantage receiver select time-domain frequency-domain equalization based much scattering occurs transmission channel rich scattering environments frequency-domain equalization using ffts requires less computation conventional time-domain equalization performs substantially better ci introduced steve shattil scientist idris communications u.s. pat 5,955,992 filed february 12 1998 first many papers april 1999 concept inspired optical mode-locking frequency-domain synthesis using resonant cavity produces desired time-domain features transmitted optical signal radio systems users share subcarriers use different orthogonal ci codes achieve carrier interference multiple access cima via spectral interferometry mechanisms many applications ci principles published dozens subsequent patent filings conference papers journal articles ci frequency-hopped ofdm described international patent application wo 9941871 ci optical fiber communications mimo described us 7076168 us 6331837 describes spatial demultiplexing using multicarrier signals eliminates need multiple receiver antennas ci coding reference signals disclosed us 7430257 use ci linear network coding onion coding disclosed us 20080095121 random linear codes based natural multipath channel used encode transmitted signals routed nodes multi-hop peer-to-peer network similarity antenna array processing ci processing recognized since earliest work ci ci combined phased arrays continuous phase change subcarriers causes array ’ beam pattern scan space achieves transmit diversity represents early form cyclic delay diversity combinations ci coding mimo precoding studied idea using ci mimo pre-coded distributed antenna systems central coordination first disclosed provisional patent application 2001 ci-based software-defined radio sdr implemented four different protocol stacks developed idris 2000 described us 7418043 spread-ofdm spreading performed across orthogonal subcarriers produce transmit signal expressed x fsb f inverse dft spread-ofdm code matrix b data symbol vector inverse dft typically employs over-sampling factor dimension kxn k n number time-domain samples per ofdm symbol block whereas dimension spread-ofdm code matrix nxn receiver received spread-ofdm signal expressed r hfsb h represents channel matrix since use cyclic prefix ofdm changes toeplitz-like channel matrix circulant matrix received signal represented r fλffsb relationship h fλf definition circulant matrix λ diagonal matrix whose diagonal elements correspond first column circulant channel matrix h. receiver employs dft typical ofdm produce λsb trivial case identity matrix gives regular ofdm without spreading received signal also expressed r fλff λf b λf c circulant matrix defined c fλf λ circulant ’ diagonal matrix thus received signal r written r fλλfb fλλfb signal receiver dft λλfb spreading matrix include pre-equalization diagonal matrix e.g. λ λ case zero-forcing equalization performed receiver dft ofdm demodulator inverse-dft ci de-spreader simplest case ci-ofdm spreading matrix f i.e. λ ci spreading matrix nxn dft matrix since ofdm ’ over-sampled dft kxn k n basic ci spreading matrix performs like sinc pulse-shaping filter maps data symbol cyclically shifted orthogonally positioned pulse formed superposition ofdm subcarriers versions ci produce alternative pulse shapes selecting different diagonal matrices λ
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Internet protocols
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mikie mikie 1984 arcade game produced konami object game guide student named mikie around school classroom locker room collect hearts make letter girlfriend mandy chased various members school staff teachers coaches cafeteria chefs defend game character either head-butt throw basketballs school members briefly stun push students rear end find hearts desks game starts mikie classroom mikie must bump students seats collect hearts 're sitting simultaneously avoiding classroom teacher hearts collected player allowed leave room enter school corridor school corridor mikie chased janitor classroom teacher follows outside way gain access rest school building room representing different challenge level mikie cued proper door enter large flashing opening door result mikie punched coiled boxing glove hairy foot stunning one doors however contains scantily clad girl opening door worth 5,000 points mikie also pick extra points picking lunch boxes opening grate contains burger soda addition head-butting enemies janitor classroom teacher also stunned slamming doors faces second room locker room objective break lockers get hearts pursued janitor cook classroom teacher addition head-butting three bins basketballs located around room mikie pick throw using action button bin holds three basketballs room three cafeteria mikie pursued two cooks classroom teacher one cook stands top room occasionally throws leg meat directly mikie table roasts 3 per table mikie hurl enemies room four sees student dance studio must avoid dancing girls stun well dance instructor yet classroom teacher final stage mikie avoiding football players garden outside school guarding hearts must collect attempting reach girlfriend mandy mikie initially underwent location testing japan international title graphics high school theme would used game overseas releases however konami chose release mike japan due game premise protagonist sneaking school incidents school violence time result alternative version produced japanese arcades titled replaces school setting workplace classroom first level becomes office teacher manager dance studio third level becomes ol office levels hallway gym restaurant outdoor garden mostly unchanged aside graphical modifications football players final level instead security guards game soundtrack features chiptunes rendition beatles songs hard day night twist shout permission granted jasrac japan license displayed instruction card printed circuit board revised version game titled high school graffiti mikie provided less violent action mikie physical attack changed head butt paralyzing shout death animation changed rolling around floor sobbing contrition glass jars mikie head butt three times retrieve heart inside replaced bundles three hearts providing effect without requiring player character head butt glass first level writing blackboard reads failure teaches success instead e=mc2 mikie shout effect classroom teacher completed step loops game version speed enemy characters increases even gaining new abilities mikie ported various home computers ocean software subsidiary imagine software versions released amstrad cpc acorn electron bbc micro commodore 64 zx spectrum sg-1000 version shinnyū shain tōru-kun also released exclusively japan sega
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Computer architecture
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dracut software dracut event-driven initramfs infrastructure dracut tool used create initramfs image copying tools files installed system combining dracut framework usually found /usr/lib/dracut/modules.d unlike existing initramfses dracut framework attempts little hard-coded initramfs possible initramfs basically one purpose—mounting root file system boot process transition real rootfs driven device availability therefore instead hard-coded scripts various things dracut initramfs depends udev create symbolic links device nodes rootfs device node appears mounts switches root helps keep time required initramfs things like 5-second boot made impossible result existence initramfs initramfs generation functionality dracut provided generator modules sourced main dracut tool install specific functionality initramfs live modules subdirectory use functionality provided dracut-functions work currently dracut supports booting btrfs dm raid md raid lvm2 device mapper multipath i/o dm-crypt cifs fcoe iscsi nbd nfs dracut-019 june 2012 introduced ability use systemd process 1 initramfs dracut available official repository distros including dracut default initramfs creation tool opensuse many others
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Computer architecture
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interlock protocol interlock protocol described ron rivest adi shamir designed frustrate eavesdropper attack two parties use anonymous key exchange protocol secure conversation paper proposed using authentication protocol subsequently broken cryptographic protocols rely prior establishment secret public keys passwords however diffie–hellman key exchange protocol introduced concept two parties establishing secure channel least desirable security properties without prior agreement unauthenticated diffie–hellman anonymous key agreement protocol long known subject man middle attack however dream zipless mutually authenticated secure channel remained interlock protocol described method expose middle-man might try compromise two parties use anonymous key agreement secure conversation interlock protocol works roughly follows strength protocol lies fact half encrypted message decrypted thus mallory begins attack intercepts bob alice keys mallory unable decrypt alice half-message encrypted using key re-encrypt using bob key must wait halves message received read succeed duping one parties composes completely new message davies price proposed use interlock protocol authentication book titled security computer networks attack described steven m. bellovin michael merritt subsequent refinement proposed ellison bellovin/merritt attack entails composing fake message send first party passwords may sent using interlock protocol b follows ea b message encrypted key derived diffie–hellman exchange b 1 2 denote first second halves pa/pb passwords b attacker z could send half bogus message—p -- elicit pa point z compromised pa pb attack defeated verifying passwords parts ea z p 1 sent known invalid ea z pa 2 never sent suggested davies however work passwords hashed since half hash useless according bellovin also several methods proposed including using shared secret addition password forced-latency enhancement also prevent certain attacks modified interlock protocol require b server delay responses known duration data encrypted data immediately follows interlock protocol exchange could anything encoded using all-or-nothing transform prevent in-transit modification message 1 could contain encrypted request copy ka 2 could contain decryption key 1 mb 1 could contain encrypted copy kb mb 2 could contain decryption key mb 1 response ok found hash digest data mitm attempted using attack described bellovin paper z man-in-the-middle case receives data approximately 3*t since z perform interlocking exchange b hence attempted mitm attack detected session aborted course z could choose perform interlock protocol b opting instead send mb session would z z b z would n't middle reason interlock protocol effectively used provide authentication although ensure third party modify messages transit without detection
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Computer security
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gmail drive gmail drive free third-party windows shell namespace extension add-on google gmail gmail drive supported google allowed user access virtual drive stored gmail account causing contents gmail account appear new network share user workstation order use add-on user needed gmail e-mail account add-on enabled user use standard windows desktop file copy paste commands transfer files gmail account drive user computer gmail drive based upon gmailfs file system developed richard jones gmail drive published 2004 functional early 2005 predates google later implementation google drive released april 24 2012 2015 official extension page declares project dead order gmail drive operate computer must connected internet user must gmail account broadband connection preferable though necessary operations done gmail consequently internet gmail drive uses inbox gmail account store files creates virtual filesystem top gmail account enabling user save retrieve files stored gmail account directly inside windows explorer gmail drive adds new virtual drive computer computer folder user create new folders copy drag-and-drop files give actual drive letter c preventing use console applications older windows applications user creates new file using gmail drive generates e-mail posts gmail account inbox e-mail appears normal inbox folder using normal gmail interface file attached e-mail attachment gmail drive periodically checks mail account using gmail search function see new files arrived rebuild virtual drive directory structures multiple computers connect one gmail account thus allowing gmail drive act multi-user file server consequently restrictions gmail service also enforced using gmail drive example files larger 25 mb uploaded maximum file size gmail attachments 25 mb past gmail also prevented users transferring certain file types executable zip archives contain executable within users bypassed restriction renaming file extension putting rar 7z archive restriction lifted gnu software package named phpgmaildrive even makes possible link different gmail accounts together manual changes gmail drive built several gmail accounts gmail drive experimental package depends provided google changes google gmail system may render gmail drive temporarily permanently inoperable current gmail drive support accounts hosted google apps gmail program policies explicitly ban gmail drive shell namespace extensions use gmail storage space files e-mail nonetheless immoderate use gmail drive may trigger google temporarily suspend gmail account
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Computer file systems
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commonjs commonjs project goal establish conventions module ecosystem javascript outside web browser primary reason creation major lack commonly accepted form javascript scripts module units could reusable environments different provided conventional web browser e.g web server native desktop applications run javascript scripts project started mozilla engineer kevin dangoor january 2009 initially named serverjs august 2009 project renamed commonjs show broader applicability apis specifications created approved open process specification considered final finished multiple implementations commonjs affiliated ecma international group tc39 working ecmascript members tc39 participate project may 2013 isaac z. schlueter author npm package manager node.js said commonjs made obsolete node.js avoided core node.js developers list specifications includes
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Programming language topics
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honeywell cp-6 cp-6 discontinued computer operating system developed honeywell inc. 1976 backward-compatible work-alike xerox cp-v fully rewritten honeywell level/66 hardware cp-6 command line oriented system terminal emulator allowed use pcs cp-6 terminals 1975 xerox decided sell computer business purchased scientific data systems 1969 deal put together harry sweatt honeywell purchased xerox data systems took xerox sales field computer support staff provide field service support existing customer base xerox made available spare equipment supplies warehouses containing revenues shared 60/40 xerox cp-6 general release 60/40 honeywell three years thereafter following revenue went honeywell early 1960s honeywell built sold large number h200 machines together software 1970 bought computer business general electric cp-6 system including operating system program products developed beginning 1976 honeywell attract xerox cp-v users 750 sigma users buy use honeywell equipment honeywell employed initial team 60 programmers xerox cp-v development team added another 30 programmers plus management staff organized hank hoagland shel klee team housed old xerox marketing office 5250 w. century blvd los angeles became known los angeles development center ladc new operating system called cp-6 ladc reported administratively honeywell computer group phoenix facility honeywell acquired general electric first beta site installed carleton university ottawa canada june 1979 three sites installed end 1979 customers worked ladc directly exchange users group throughout specification development period review approve direction development compromises order feature implementation comshare major xerox customer operating system needed capacity service rapidly expanding timesharing business help ladc hardware engineers using xerox specifications honeywell engineers phoenix built 30 sigma 9 computers 24 comshare 6 customers project initiated 1978 machines sold original retail price delivered beginning third quarter 1979 1981 cp-6 modeled xerox cp-v code completely rewritten new high-level language pl-6 designed built expressly purpose rather assembly language cp-v increasing complexities new virtual addressing hardware honeywell ’ l66 dps 8 line rewrite existing weaknesses addressed many new features added like cp-v cp-6 five access modes operated concurrently batch processing remote batch timesharing transaction processing real-time processing included multiprogramming operated multiple cpus also like cp-v design integrated file management system files equally compatibly available programs executing mode files could sorted indexed keyed relative consecutive order new cp-6 use communications terminal interfaces minicomputer honeywell level 6 -based front-end processors connected locally remotely combination cp-6 included integrated software development system supported included set language processors apl basic cobol fortran rpg idp ids/ii sort/merge pl-6 gmap text formatting program text commonly needed software packages pascal snobol lisp spss bmdp imsl spiceii slam developed carleton university operating system supported inter-system communication job submission file transfer cp-6 systems cp-6 cp-v ibm hasp protocol systems system used communications terminal interfaces honeywell level 6 minicomputer-based front-end processor asynchronous bisynchronous tcp/ip communications protocols supported honeywell hardware system cp-6 consisted mainframe host processor l66 dps8 dps8000 dps90 connected disks tapes printers card equipment connected high-speed channel connected host level 6 mini computer provided processing connection terminals communications lines high-speed channel remote computers including ladc customers on-line support new version download problem fix patches terminal emulator allowed use pcs cp-6 terminals product additions mid eighties included adaptation dps8000 bull mainframe computers cp-6 included on-line problem reporting fix system beginning 1976 system named system technical action request star people oversaw star system starlords programmers direct access customers computers could fix problems directly on-line system used honeywell proprietary network
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Operating systems
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list microsoft windows application programming interfaces frameworks following list microsoft apis frameworks
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Operating systems
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p2psp p2psp peer peer straightforward protocol communication protocol application layer streaming multimedia content internet users play stream sync used build variety live broadcasting services ranging small meetings large systems iptv unlike traditional cs client-server cdn content delivery network based video streaming p2p contributes upstream bandwidth system therefore general p2p systems scalable architectures based model client-server .this protocol helps reducing bandwidth usage source broadcast using upload bandwidth peers connected source p2psp specially defined streaming live footage thus transmitted communications network based packet switching event occurring time way already created recorded events p2psp hybrid structure mesh network every peer connected star network sources every peer connected one server directly pure p2psp overlay lies one extreme one server every peer connected one part media sent peer turn sends part peers connected network extreme large group p2psp teams connected star structure results requirement upload bandwidth source since packet transmitted one time single/multiple source broadcast
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Internet protocols
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just-in-time compilation computing just-in-time jit compilation also dynamic translation run-time compilations way executing computer code involves compilation execution program – run time – rather prior execution often consists source code commonly bytecode translation machine code executed directly system implementing jit compiler typically continuously analyses code executed identifies parts code speedup gained compilation recompilation would outweigh overhead compiling code jit compilation combination two traditional approaches translation machine code – ahead-of-time compilation aot interpretation – combines advantages drawbacks roughly jit compilation combines speed compiled code flexibility interpretation overhead interpreter additional overhead compiling interpreting jit compilation form dynamic compilation allows adaptive optimization dynamic recompilation microarchitecture-specific speedups – thus theory jit compilation yield faster execution static compilation interpretation jit compilation particularly suited dynamic programming languages runtime system handle late-bound data types enforce security guarantees jit compilation applied programs used certain capacities particularly dynamic capacities regular expressions example text editor may compile regular expression provided runtime machine code allow faster matching – done ahead time pattern provided runtime several modern runtime environments rely jit compilation high-speed code execution including implementations java together microsoft .net framework similarly many regular-expression libraries feature jit compilation regular expressions either bytecode machine code jit compilation also used emulators order translate machine code one cpu architecture another common implementation jit compilation first aot compilation bytecode virtual machine code known bytecode compilation jit compilation machine code dynamic compilation rather interpretation bytecode improves runtime performance compared interpretation cost lag due compilation jit compilers translate continuously interpreters caching compiled code minimizes lag future execution code given run since part program compiled significantly less lag entire program compiled prior execution bytecode-compiled system source code translated intermediate representation known bytecode bytecode machine code particular computer may portable among computer architectures bytecode may interpreted run virtual machine jit compiler reads bytecodes many sections full rarely compiles dynamically machine code program run faster done per-file per-function even arbitrary code fragment code compiled executed hence name just-in-time cached reused later without needing recompiled contrast traditional interpreted virtual machine simply interpret bytecode generally much lower performance interpreter even interpret source code without step first compiling bytecode even worse performance statically-compiled code native code compiled prior deployment dynamic compilation environment one compiler used execution common goal using jit techniques reach surpass performance static compilation maintaining advantages bytecode interpretation much heavy lifting parsing original source code performing basic optimization often handled compile time prior deployment compilation bytecode machine code much faster compiling source deployed bytecode portable unlike native code since runtime control compilation like interpreted bytecode run secure sandbox compilers bytecode machine code easier write portable bytecode compiler already done much work jit code generally offers far better performance interpreters addition cases offer better performance static compilation many optimizations feasible run-time jit must render execute native binary image runtime true machine-code jits necessitate platforms allow data executed runtime making using jits harvard architecture-based machine impossible said certain operating systems virtual machines well however special type jit may potentially target physical machine cpu architecture rather optimized vm bytecode limitations raw machine code prevail especially bytecode vm eventually leverages jit native code jit causes slight noticeable delay initial execution application due time taken load compile bytecode sometimes delay called startup time delay warm-up time general optimization jit performs better code generate initial delay also increase jit compiler therefore make trade-off compilation time quality code hopes generate startup time increased io-bound operations addition jit compilation example rt.jar class data file java virtual machine jvm 40 mb jvm must seek lot data contextually huge file one possible optimization used sun hotspot java virtual machine combine interpretation jit compilation application code initially interpreted jvm monitors sequences bytecode frequently executed translates machine code direct execution hardware bytecode executed times saves compilation time reduces initial latency frequently executed bytecode jit compilation used run high speed initial phase slow interpretation additionally since program spends time executing minority code reduced compilation time significant finally initial code interpretation execution statistics collected compilation helps perform better optimization correct tradeoff vary due circumstances example sun java virtual machine two major modes—client server client mode minimal compilation optimization performed reduce startup time server mode extensive compilation optimization performed maximize performance application running sacrificing startup time java just-in-time compilers used runtime measurement number times method executed combined bytecode size method heuristic decide compile still another uses number times executed combined detection loops general much harder accurately predict methods optimize short-running applications long-running ones native image generator ngen microsoft another approach reducing initial delay ngen pre-compiles pre-jits bytecode common intermediate language image machine native code result runtime compilation needed .net framework 2.0 shipped visual studio 2005 runs ngen microsoft library dlls right installation pre-jitting provides way improve startup time however quality code generates might good one jited reasons code compiled statically without profile-guided optimization good jit compiled code extreme case lack profiling data drive instance inline caching also exist java implementations combine aot ahead-of-time compiler either jit compiler excelsior jet interpreter gnu compiler java earliest published jit compiler generally attributed work lisp john mccarthy 1960 seminal paper recursive functions symbolic expressions computation machine part mentions functions translated runtime thereby sparing need save compiler output punch cards although would accurately known compile go system another early example ken thompson 1968 gave one first applications regular expressions pattern matching text editor qed speed thompson implemented regular expression matching jiting ibm 7094 code compatible time-sharing system influential technique deriving compiled code interpretation pioneered mitchell 1970 implemented experimental language lc² smalltalk c. 1983 pioneered new aspects jit compilations example translation machine code done demand result cached later use memory became scarce system would delete code regenerate needed sun self language improved techniques extensively one point fastest smalltalk system world achieving half speed optimized c fully object-oriented language self abandoned sun research went java language term just-in-time compilation borrowed manufacturing term time popularized java james gosling using term 1993 currently jiting used implementations java virtual machine hotspot builds extensively uses research base hp project dynamo experimental jit compiler 'bytecode format machine code format system turned pa-6000 machine code pa-8000 machine code counterintuitively resulted speed ups cases 30 since permitted optimizations machine code level example inlining code better cache usage optimizations calls dynamic libraries many run-time optimizations conventional compilers able attempt 30 march 2019 php announced jit coming php 8 2021 jit compilation fundamentally uses executable data thus poses security challenges possible exploits implementation jit compilation consists compiling source code byte code machine code executing generally done directly memory – jit compiler outputs machine code directly memory immediately executes rather outputting disk invoking code separate program usual ahead time compilation modern architectures runs problem due executable space protection – arbitrary memory executed otherwise potential security hole thus memory must marked executable security reasons done code written memory marked read-only writable/executable memory security hole see w^x instance firefox jit compiler javascript introduced protection release version firefox 46 jit spraying class computer security exploits use jit compilation heap spraying – resulting memory executable allows exploit execution moved heap
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Programming language topics
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fast local internet protocol fast local internet protocol flip suite internet protocols provide security transparency security network management flip designed vrije universiteit amsterdam support remote procedure calling amoeba distributed operating system osi model flip occupies layer 3 thus replacing ip also obviates need transport-level protocol like tcp flip connectionless protocol designed support transparency group communication secure communication easy network management following flip properties helps achieve efficiency requirements
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Internet protocols
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perl data language perl data language abbreviated pdl set free software array programming extensions perl programming language pdl extends data structures built perl include large multidimensional arrays adds functionality manipulate arrays vector objects also provides tools image processing computer modeling physical systems graphical plotting presentation simple operations automatically vectorized across complete arrays higher-dimensional operations matrix multiplication supported pdl vectorized array programming language expression syntax variation standard mathematical vector notation user combine operate large arrays simple expressions respect pdl follows footsteps apl programming language compared commercial languages matlab interactive data language free languages numpy octave unlike matlab idl pdl allows great flexibility indexing vectorization example subroutine normally operates 2-d matrix array passing 3-d data cube generally cause operation happen 2-d layer cube pdl borrows perl least three basic types program structure imperative programming functional programming pipeline programming forms may combined subroutines may loaded either via built-in autoload mechanism via usual perl module mechanism pdl-like functionality included development perl 6 true glue language roots perl pdl borrows several different modules graphics plotting support netpbm provides image file i/o though fits supported natively gnuplot plplot pgplot prima modules supported 2-d graphics plotting applications gnuplot opengl supported 3-d plotting rendering pdl provides facilities read write many open data formats including jpeg png gif ppm mpeg fits netcdf grib raw binary files delimited ascii tables pdl programmers use cpan perl i/o libraries read write data hundreds standard niche file formats installation pdl usually comes interactive shell known perldl used perform simple calculations without requiring user create perl program file typical session perldl would look something like following commands used shell perl statements used program codice_1 module included codice_2 overloaded operator matrix multiplication codice_3 last command shortcut codice_4 core pdl written c. functionality written pp pdl-specific metalanguage handles vectorization simple c snippets interfaces perl host language via perl xs compiler modules written fortran c/pp interface layer many supplied functions written pdl pp available user write c-language extensions pdl also inline module inline :pdlpp allows pp function definitions inserted directly perl script relevant code low-level compiled made available perl subroutine pdl api uses basic perl 5 object-oriented functionality pdl defines new type perl scalar object eponymously called pdl pronounced piddle acts perl scalar contains conventional typed array numeric character values standard perl operators overloaded used pdl objects transparently pdls mixed-and-matched normal perl scalars several hundred object methods operating pdls supplied core modules perl 6 pdl specified trait synopsis 9 january 2013 feature yet implemented rakudo though
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Programming language topics
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zardoz computer security computer security zardoz list formally known security-digest list famous semi-private full disclosure mailing list run neil gorsuch 1989 1991 identified weaknesses systems gave directions find zardoz notable status perennial target computer hackers sought archives list information undisclosed software vulnerabilities access zardoz approved case-by-case basis gorsuch principally reference user account used send subscription requests requests approved root users valid uucp owners system administrators listed nic openness list users unix system administrators regular topic conversation participants expressing concern vulnerabilities exploitation details disclosed list liable spread hackers hand circulation zardoz postings among computer hackers open secret mocked openly famous phrack parody irc channel populated notable security experts majority zardoz participants unix systems administrators c software developers neil gorsuch gene spafford prolific contributors list
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Computer security
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isc ² international information system security certification consortium isc ² non-profit organization specializes training certifications cybersecurity professionals described world largest security organization widely known certification offered isc ² certified information systems security professional cissp certification mid-1980s need arose standardized vendor-neutral certification program provided structure demonstrated competence field security several professional societies recognized certification programs attesting qualifications information security personnel desperately needed june 1988 conference hosted national institutes standards technology nist federal information systems security educators association fissea idaho state university pocatello idaho address need standardized curriculum burgeoning profession organizations attendance included • canadian information processing society cips • computer security institute csi • data processing management association special interest group certified professionals dpma sig-cp • data processing management association special interest group computer security dpma sig-cs • idaho state university isu • information systems security association issa • international federation information processing ifip conference question raised virtually every group represented save nist isu creating professional certification conference participants agreed form consortium would attempt bring together competing agendas various organizations november 1988 special interest group computer security sig-cs member data processing management association dpma brought together several organizations interested isc ² formed mid-1989 non-profit organization goal mind 8 1990 first working committee establish something called common body knowledge cbk formed work done committee resulted first version cbk finalized 1992 cissp credential launched 1994 followed sscp credential 2001 cap credential 2005 csslp credential 2008 ccfp hcispp 2013 ccsp 2015 9 2001 isc ² established europe middle east africa regional office london 2002 isc ² opened asia-pacific regional office hong kong 2015 isc ² introduced north america regional office washington d.c since 2011 isc ² organizes annual isc ² security congress conference 2019 conference first international iteration event held orlando florida isc ² maintains calls common body knowledge information security following certifications certified ansi isc ² meets requirements ansi/iso/iec standard 17024 personnel certification accreditation program accreditation covers cissp sscp cissp-issap cissp-issep cissp-issmp cap csslp certifications isc ² certified professionals required earn continuous professional education cpe credits annual basis order maintain certifications cpe credits obtained attending industry events conferences writing articles/book reviews/books etc certified isc ² professionals required support isc ² code ethics violations code ethics investigated peer review panel within potential revoking certification isc ² along security certification organizations criticized lack education area ethics
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Computer security
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padvish antivirus padvish antivirus commonly known padvish antivirus software package developed iranian company amnpardaz amnpardaz padvish developed distributed home edition business edition server edition endpoint security android also free edition home users word padvish persian پادویش literally means antivirus padvish currently used local industries iei commonly referred saa iran
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Computer security
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comodo group comodo cybersecurity company headquartered clifton new jersey united states company founded 1998 united kingdom melih abdulhayoğlu company relocated united states 2004 products focused computer internet security firm operates certificate authority issues ssl certificates offers information security products enterprises consumers company also helped setting standards contributing ietf internet engineering task force dns certification authority authorization caa resource record comodo member following industry organizations response symantec comment asserting paid antivirus superior free antivirus ceo comodo group challenged symantec 18 september 2010 see whether paid free products better defend consumer malware gcn john breeden understood comodo stance free antivirus software challenging symantec actually pretty smart move based previous reviews av performance 've done gcn lab recent av review year showed functional difference free paid programs terms stopping viruses way many years fact go way back 2006 find av roundup viruses missed companies symantec responded saying comodo interested product included tests independent reviewers comodo volunteered symantec vs. comodo independent review though showdown take place comodo since included multiple independent reviews av-test pc world best antivirus reviews av-comparatives pc mag 23 march 2011 comodo posted report 8 days earlier 15 march 2011 user account affiliate registration authority compromised used create new user account issued nine certificate signing requests nine certificates seven domains issued attack traced ip address 212.95.136.18 originates tehran iran though firm initially reported breach result state-driven attack subsequently stated origin attack may result attacker attempting lay false trail. attack immediately thwarted comodo revoking bogus certificates comodo also stated actively looking ways improve security affiliates update 31 march 2011 comodo stated detected thwarted intrusion reseller user account 26 march 2011 new controls implemented comodo following incident 15 march 2011 removed risk fraudulent issue certificates comodo believed attack perpetrator incident 15 march 2011 regards second incident comodo stated ca infrastructure compromised keys hsms compromised certificates fraudulently issued attempt fraudulently access certificate ordering platform issue certificate failed 26 march 2011 person username comodohacker made several posts pastebin.com claiming iranian responsible attacks issues widely reported led criticism certificates issued revoked 2016 certificates remain revoked microsoft issued security advisory update address issue time event attacks unique comodo – specifics vary ca ca ra ra many entities trusted default holes deemed inevitable february 2015 comodo associated man-in-the-middle enabling tool known privdog claims protect users malicious advertising privdog issued statement 23 february 2015 saying minor intermittent defect detected third party library used privdog standalone application potentially affects small number users potential issue present privdog versions 3.0.96.0 3.0.97.0 potential issue present privdog plug-in distributed comodo browsers comodo distributed version users potentially maximum 6,294 users usa 57,568 users globally could potentially impact third party library used privdog third party library used superfish ... potential issue already corrected update tomorrow automatically update 57,568 users specific privdog versions 2009 microsoft mvp michael burgess accused comodo issuing digital certificates known malware comodo responded notified revoked issued certificates contained rogue malware january 2016 tavis ormandy reported comodo chromodo browser exhibited number vulnerabilities including disabling same-origin policy vulnerability n't browser based open-source code behind google chrome browser rather issue add-on soon comodo became aware issue early february 2016 company released statement fix industry software general always updated patched fixed addressed improved – goes hand hand development cycle ... critical software development companies address issue certain vulnerability found – ensuring never puts customer risk using chromodo immediately received update chromodo browser subsequently discontinued comodo ormandy noted comodo received excellence information security testing award verizon despite vulnerability browser despite vnc delivered default weak authentication despite enabling address space layout randomization aslr despite using access control lists acls throughout product ormandy opinion verizon certification methodology fault october 2015 comodo applied let encrypt comodo let encrypt let encrypt comodo trademarks trademark applications filed almost year internet security research group parent organization let encrypt started using name let encrypt publicly november 2014 despite fact comodo intent use trademark filings acknowledge never used let encrypt brand 24 june 2016 comodo publicly posted forum filed express abandonment trademark applications comodo chief technical officer robin alden said comodo filed express abandonment trademark applications time instead waiting allowing lapse following collaboration let encrypt comodo trademark issue resolved behind us 'd like thank let encrypt team helping bring resolution 25 july 2016 matthew bryant showed comodo website vulnerable dangling markup injection attacks send emails system administrators comodo servers approve wildcard certificate issue request used issue arbitrary wildcard certificates via comodo 30-day positivessl product bryant reached june 2016 25 july 2016 comodo chief technical officer robin alden confirmed fix put place within responsible disclosure date per industry standards
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Computer security
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youos youos web desktop web integrated development environment developed webshaka june 2008 domain acquired german startup company may 2015 project name youos representing mobile platform hyperlocal interaction youos technology used operate german refugee help support system angelaapp 2006 2008 youos replicated desktop environment modern operating system webpage using javascript communicate remote server allows users save current desktop state return later much like hibernation feature many true operating systems multiple users collaborate using single environment youos featured built-in sharing music documents files software alpha stage referred web operating system webshaka application programming interface ide integrated development environment currently development 700 applications created using api 2006 youos listed 7th position pc world list 20 innovative products year youos shut july 30 2008 developers actively developed since november 2006 also could find use since moved projects
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Distributed computing architecture
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intrushield mcafee intrushield network-based intrusion prevention sensor appliance used prevention zero-day dos denial service attacks spyware malware botnets voip threats called mcafee network security platform ^^ broken ^^
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Computer security
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intuition amiga intuition native windowing system user interface ui engine amigaos developed almost entirely rj mical intuition confused workbench amigaos spatial file manager relies intuition handling windows input events intuition internal widget graphics system implemented primarily application-managed graphics library systems following xerox design done rather separate task maintains state standard ui elements independently application makes responsive ui gadgets live even application busy intuition task driven user events mouse keyboard input devices also arbitrates collisions mouse pointer icons control animated icons like guis day amiga intuition followed xerox lead anteceding solutions pragmatically command line interface also included extended functionality platform later releases added improvements like support high-color workbench screens 3d aspect replacement desktop file managers also made available directory opus magellan scalos interface initial releases used blue orange white black palettes intentional – time cheap high-quality video monitors commodore tested output worst televisions could find goal obtaining best possible contrast worst-case conditions due limitations intuition basic widget set developers adopted third-party gui toolkits magic user interface mui reaction object oriented ui engines driven classes graphic objects functions new standard gadgets animated buttons true-color icons etc offered developers standardized attractive interfaces mui similar systems abandoned separation user interface application specified gadgets displayed intuition task actually managed gadgets applications even busy modern day successors workbench environment include ambient morphos scalos workbench amigaos 4 wanderer aros brief article ambient descriptions mui icons menus gadgets aps.fr images zune stay main aros site new object-oriented toolkit amiga-like platforms amigaos morphos aros feelin introduced 2005 makes extensive use xml guidelines uses memory management system memory-pools system shares embedded os semaphores feelin also features non-centralized id allocation system crash-free object invocation mechanism advanced logging system details images feelin found website stewart alsop ii said 1988 intuition among several guis already knocked market apple ibm/microsoft others stating slapped together six months ... lack forethought vision shows criticized intuition drive letters lack network support hundreds small features
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Operating systems
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hekaton database hekaton also known sql server in-memory oltp in-memory database oltp workloads built microsoft sql server hekaton designed collaboration microsoft research released sql server 2014 traditional rdbms systems designed memory resources expensive optimized disk storage hekaton instead optimized working set stored entirely main memory still accessible via t-sql like normal tables fundamentally different dbcc pintable feature earlier sql server versions hekaton announced professional association sql server pass conference 2012
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Databases
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sasa video game sasa arcade video game released msx1 1984 later family computer titled 1985 video game involved obtaining capsules e sometimes suspended balloons main character could use bullets propel bullet count reaches 0 game ends player also lose bullets colliding enemy player player bullets
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Computer architecture
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pulseaudio pulseaudio network-capable sound server program distributed via freedesktop.org project runs mainly linux various bsd distributions freebsd openbsd macos well illumos distributions solaris operating system microsoft windows previously supported via mingw toolchain implementation gnu toolchain includes various tools gcc binutils windows port updated since 2011 however pulseaudio free open-source software licensed terms gnu lesser general public license licensed version 2.1 aforementioned license created 2004 name polypaudio renamed 2006 pulseaudio pulseaudio acts sound server background process accepting sound input one sources processes capture devices etc created background process redirects mentioned sound sources one sinks sound cards remote network pulseaudio servers processes one goals pulseaudio reroute sound streams including processes attempt directly access hardware like legacy oss applications pulseaudio achieves providing adapters applications using audio systems like arts esd typical installation scenario linux user configures alsa use virtual device provided pulseaudio thus applications using alsa output sound pulseaudio uses alsa access real sound card pulseaudio also provides native interface applications want support pulseaudio directly well legacy interface esd applications making suitable drop-in replacement esd oss applications pulseaudio provides codice_1 utility replaces device files codice_2 tricking applications believing exclusive control sound card reality output rerouted pulseaudio libcanberra abstract api desktop event sounds total replacement pulseaudio sample cache api libsydney total replacement pulseaudio streaming api plans made libsydney eventually become audio api used pulseaudio main pulseaudio features include pulseaudio first appeared regular users fedora linux starting version 8 adopted major linux distributions ubuntu debian mageia mandriva linux linux mint opensuse openwrt support pulseaudio gnome project also kde integrated plasma workspaces adding support phonon kde multimedia framework kmix integrated mixer application well speaker setup gui aid configuration multi-channel speakers pulseaudio also available illumos distribution openindiana enabled default mate environment various linux-based mobile devices including nokia n900 nokia n9 palm pre use pulseaudio tizen open-source mobile operating system project linux foundation governed technical steering group tsg composed intel samsung uses pulseaudio jack sound server provides real-time low latency i.e 5 milliseconds less audio performance since jack2 supports efficient load balancing utilizing symmetric multiprocessing load audio clients distributed among several processors jack preferred sound server professional audio applications ardour rezound linuxsampler multiple free audio-production distributions use default audio server possible jack pulseaudio coexist jack running pulseaudio automatically connect jack client allowing pulseaudio clients make record sound time jack clients pipewire audio video server aims support usecases currently handled pulseaudio jack jack pulseaudio sound systems managed multi-purpose integrated audio solutions solutions fully cover mixing sound streaming process still used jack pulseaudio send final audio stream sound card
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Operating systems
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lotus foundations lotus foundations bundled small-business server solutions package ibm package includes lotus domino directory services file management firewall backup web hosting various productivity tools product release direct result ibm acquisition net integration technologies integrated ibm lotus division original pre-acquisition product based net integrator mark 1 server appliance nitix autonomic linux server os lotus foundations introduced market hardware appliance late 2008 software-only appliance also made available 2010 lotus foundations hardware appliance discontinued software-only appliance followed suit february 2011 june 2011 however lotus foundations software appliance reinstated sale ibm sell directly anymore distributing selected business partners instead ibm lotus foundations products withdrawn marketing march 14 2013 longer available purchase support ibm lotus foundations products withdrawn september 30 2014 lotus domino ibm server product provides enterprise-grade e-mail collaboration capabilities custom application platform used application server lotus notes applications and/or web server also built-in database system nsf format lotus foundations firewall gui-based designed ease use features auto-configuration firewall settings firewall allows incoming ftp active passive mode http https smtp allowing outgoing dns ftp http https telnet well imap pop3 smtp mail protocols
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Web technology
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internet internet privately held company provides web analytics services consulting websites intranet mobile sites mobile applications provided services since 1995 company commonly known especially france former name flagship product internet application analytics suite used approximately 20,000 websites mobile applications worldwide company founded 1995 owner alain llorens web agency group focus shifted web analytics 1997 2011 internet recognized strong performer forrester wave™ web analytics q4 2011 report forrester research inc 2014 internet featured latest edition forrester report forrester wave™ web analytics q2 2014 named one 4 top providers web analytics software worldwide 2015 internet launched analytics suite integrated suite applications analytics reporting dashboard creation data visualization data mining app analytics data export 2016 company raised total €4 million funding r recruiting bpifrance cic coface european regional development fund nouvelle-aquitaine region raised €6.5 million 2013 internet provides tools enabling companies organizations measure analyse visitors arrive website mobile site mobile application well subsequent actions behaviors site information visualized dashboards reports shared across organization internet software integrated approximately 30 digital marketing applications company offers specialized consulting services on-site remote france data protection authority cnil recognized internet analytics suite full compliance french cookie regulations audience measurement application granted exemption cnil obtaining cookie consent analytics suite certified independent measurement organizations worldwide including uk abc kia-index tüv saarland ojd espana france acpm according company software complies requirements european commission general data protection regulation data processed europe stored proprietary servers france
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Web technology
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cache control instruction computing cache control instruction hint embedded instruction stream processor intended improve performance hardware caches using foreknowledge memory access pattern supplied programmer compiler may reduce cache pollution reduce bandwidth requirement bypass latencies providing better control working set cache control instructions affect semantics program although several instructions variants supported several processor instruction set architectures arm mips powerpc x86 also termed data cache block touch effect request loading cache line associated given address performed codice_1 instruction x86 instruction set variants bypass higher levels cache hierarchy useful 'streaming context data traversed rather held working set prefetch occur sufficiently far ahead time mitigate latency memory access example loop traversing memory linearly gnu compiler collection intrinsic function codice_2 used invoke programming languages c c++ variant prefetch instruction cache hint used prepare cache lines overwriting contents completely example cpu need n't load anything main memory semantic effect equivalent aligned memset cache-line sized block zero operation effectively free hint used discard cache lines without committing contents main memory care needed since incorrect results possible unlike cache hints semantics program significantly modified used conjunction codice_3 managing temporary data saves unneeded main memory bandwidth cache pollution hint requests immediate eviction cache line making way future allocations used known data longer part working set processors support variant load–store instructions also imply cache hints example codice_4 powerpc instruction set suggests data used i.e. cache line question may pushed head eviction queue whilst keeping use still directly needed recent times cache control instructions become less popular increasingly advanced application processor designs intel arm devote transistors accelerating code written traditional languages e.g. performing automatic prefetch hardware detect linear access patterns fly however techniques may remain valid throughput-oriented processors different throughput vs latency tradeoff may prefer devote area execution units processors support scratchpad memory temporaries may put direct memory access dma transfer data main memory needed approach used cell processor embedded systems allow greater control memory traffic locality working set managed explicit transfers eliminates need expensive cache coherency manycore machine disadvantage requires significantly different programming techniques use hard adapt programs written traditional languages c c++ present programmer uniform view large address space illusion simulated caches traditional microprocessor easily run legacy code may accelerated cache control instructions whilst scratchpad based machine requires dedicated coding ground even function cache control instructions specific certain cache line size practice may vary generations processors architectural family caches may also help coalescing reads writes less predictable access patterns e.g. texture mapping whilst scratchpad dma requires reworking algorithms predictable 'linear traversals scratchpads generally harder use traditional programming models although dataflow models tensorflow might suitable vector processors example modern graphics processing unit gpus xeon phi use massive parallelism achieve high throughput whilst working around memory latency reducing need prefetching many read operations issued parallel subsequent invocations compute kernel calculations may put hold awaiting future data whilst execution units devoted working data past requests data already turned easier programmers leverage conjunction appropriate programming models compute kernels harder apply general purpose programming disadvantage many copies temporary states may held local memory processing element awaiting data flight
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Computer architecture
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conventional pci conventional pci often shortened pci local computer bus attaching hardware devices computer pci abbreviation peripheral component interconnect part pci local bus standard pci bus supports functions found processor bus standardized format independent particular processor native bus devices connected pci bus appear bus master connected directly bus assigned addresses processor address space parallel bus synchronous single bus clock attached devices take either form integrated circuit fitted onto motherboard called planar device pci specification expansion card fits slot pci local bus first implemented ibm pc compatibles displaced combination several slow isa slots one fast vesa local bus slot bus configuration subsequently adopted computer types typical pci cards used pcs include network cards sound cards modems extra ports usb serial tv tuner cards disk controllers pci video cards replaced isa vesa cards growing bandwidth requirements outgrew capabilities pci preferred interface video cards became agp superset pci giving way pci express first version pci found retail desktop computers 32-bit bus using 33 mhz bus clock 5 v signalling although pci 1.0 standard provided 64-bit variant well one locating notch card version 2.0 pci standard introduced 3.3 v slots physically distinguished flipped physical connector prevent accidental insertion 5 v cards universal cards operate either voltage two notches version 2.1 pci standard introduced optional 66 mhz operation server-oriented variant pci called pci-x pci extended operated frequencies 133 mhz pci-x 1.0 533 mhz pci-x 2.0 internal connector laptop cards called mini pci introduced version 2.2 pci specification pci bus also adopted external laptop connector standard cardbus first pci specification developed intel subsequent development standard became responsibility pci special interest group pci-sig conventional pci pci-x sometimes called parallel pci order distinguish technologically recent successor pci express adopted serial lane-based architecture pci heyday desktop computer market approximately 1995–2005 pci pci-x become obsolete purposes however still common modern desktops purposes backwards compatibility low relative cost produce many kinds devices previously available pci expansion cards commonly integrated onto motherboards available usb pci express versions work pci began intel architecture development lab team intel engineers composed primarily adl engineers defined architecture developed proof concept chipset platform saturn partnering teams company desktop pc systems core logic product organizations pci immediately put use servers replacing mca eisa server expansion bus choice mainstream pcs pci slower replace vesa local bus vlb gain significant market penetration late 1994 second-generation pentium pcs 1996 vlb extinct manufacturers adopted pci even 486 computers eisa continued used alongside pci 2000 apple computer adopted pci professional power macintosh computers replacing nubus mid-1995 consumer performa product line replacing lc pds mid-1996 64-bit version plain pci remained rare practice though although used example post-imac g3 g4 power macintosh computers later revisions pci added new features performance improvements including 66 mhz 3.3 v standard 133 mhz pci-x adaptation pci signaling form factors pci-x 1.0b pci-x 2.0 backward compatible pci standards revisions used server hardware consumer pc hardware remained nearly 32 bit 33 mhz 5 volt pci-sig introduced serial pci express time renamed pci conventional pci since motherboard manufacturers included progressively fewer pci slots favor new standard many new motherboards provide pci slots late 2013 pci provides separate memory i/o port address spaces x86 processor family 64 32 bits respectively addresses address spaces assigned software third address space called pci configuration space uses fixed addressing scheme allows software determine amount memory i/o address space needed device device request six areas memory space i/o port space via configuration space registers typical system firmware operating system queries pci buses startup time via pci configuration space find devices present system resources memory space i/o space interrupt lines etc needs allocates resources tells device allocation pci configuration space also contains small amount device type information helps operating system choose device drivers least dialogue user system configuration devices may on-board rom containing executable code x86 pa-risc processors open firmware driver efi driver typically necessary devices used system startup device drivers loaded operating system addition pci latency timers mechanism pci bus-mastering devices share pci bus fairly fair case means devices use large portion available pci bus bandwidth devices able get needed work done note apply pci express devices required follow protocol interrupt lines shared pci bus includes four interrupt lines available device however wired parallel pci bus lines positions interrupt lines rotate slots appears one device inta line intb next intc one single-function devices use inta interrupt signaling device load spread fairly evenly across four available interrupt lines alleviates common problem sharing interrupts mapping pci interrupt lines onto system interrupt lines pci host bridge implementation-dependent platform-specific bios code meant know set interrupt line field device configuration space indicating irq connected pci interrupt lines level-triggered chosen edge-triggering order gain advantage servicing shared interrupt line robustness edge triggered interrupts easy miss later revisions pci specification add support message-signaled interrupts system device signals need service performing memory write rather asserting dedicated line alleviates problem scarcity interrupt lines even interrupt vectors still shared suffer sharing problems level-triggered interrupts also resolves routing problem memory write unpredictably modified device host finally message signaling in-band resolves synchronization problems occur posted writes out-of-band interrupt lines pci express physical interrupt lines uses message-signaled interrupts exclusively specifications represent common version pci used normal pcs pci specification also provides options 3.3 v signaling 64-bit bus width 66 mhz clocking commonly encountered outside pci-x support server motherboards pci bus arbiter performs bus arbitration among multiple masters pci bus number bus masters reside pci bus well requests bus one pair request grant signals dedicated bus master typical pci cards either one two key notches depending signaling voltage cards requiring 3.3 volts notch 56.21 mm card backplate requiring 5 volts notch 104.47 mm backplate allows cards fitted slots voltage support universal cards accepting either voltage key notches pci connector defined 62 contacts side edge connector two four replaced key notches card 60 58 contacts side side refers 'solder side side b refers 'component side card held connector pointing view side backplate right whereas view side b backplate left pinout b sides follows looking motherboard connector pins a1 b1 closest backplate 64-bit pci extends additional 32 contacts side provide ad 63:32 c/be 7:4 par64 parity signal number power ground pins lines connected slot parallel exceptions notes 32-bit pci cards function properly 64-bit pci-x slots bus clock rate limited clock frequency slowest card inherent limitation pci shared bus topology example pci 2.3 66-mhz peripheral installed pci-x bus capable 133 mhz entire bus backplane limited 66 mhz get around limitation many motherboards two pci/pci-x buses one bus intended use high-speed pci-x peripherals bus intended general-purpose peripherals many 64-bit pci-x cards designed work 32-bit mode inserted shorter 32-bit connectors loss performance example adaptec 29160 64-bit scsi interface card however 64-bit pci-x cards work standard 32-bit pci slots installing 64-bit pci-x card 32-bit slot leave 64-bit portion card edge connector connected overhanging requires motherboard components positioned mechanically obstruct overhanging portion card edge connector maximum width pci card 15.24 mm 0.6 inches two bracket heights specified known full-height low-profile bracket backplate part fastens card cage stabilize card also usually contains external connectors attaches window computer case connectors accessible outside backplate typically fixed case either 6-32 m3 screw separate hold-down bracket part case bracket height two different lengths specified total four lengths known full-length half-length full-height cards md1 md2 low-profile cards original full-height cards defined bracket height 120 mm 4.7 inches height full-height cards nominally 107 mm 4.2 inches height includes card edge connector two lengths defined full-height cards known full-length half-length original full-length full-height pci card also known full-size specified length 312 mm 12.283 inches height 107 mm 4.2 inches however modern pci cards half-length smaller see many modern pc cases accommodate length full-size card note length length printed circuit board include angled short leg metal bracket affect e.g packaging dimensions high power pci products active cooling systems extend past nominal dimensions likewise may take one slot space referred double-wide triple-wide cards accordingly half-length full-height card length 175.26 mm 6.9 inches height 107 mm 4.2 inches actual dimensions many cards described half-length full-height lower maximums still fit standard full-height pci slot long use properly located full-height bracket fact practical de facto standard majority modern pci cards fit inside envelope low-profile pci cards also known lppci half-height cards defined bracket reduced height 79.2 mm 3.118 inches low-profile specification assumes 3.3 volt pci slot retention screw also moved 1.35 mm closer fold bracket low profile card maximum height 64.41 mm 2.536 inches including edge connector smaller bracket fit standard desktop tower 3u rack-mount pc case fit many newer small form-factor sff desktop cases 2u rack-mount case cards may known names slim many manufacturers supply types bracket cards bracket typically attached card pair screws allowing installer easily change pci-sig defined two standard lengths low-profile cards known md1 md2 md1 defines shortest 32-bit pci card length 119.91 mm 4.721 inches maximum height 64.41 mm 2.536 inches md2 defines maximum length low profile pci card 167.64 mm 6.600 inches maximum height 64.41 mm 2.536 inches low profile pci card longer md1 length considered md2 card common low-profile card form-factor beside conventional pci many pci express cards also described md2 low-profile form-factor mini pci added pci version 2.2 use laptops uses 32-bit 33 mhz bus powered connections 3.3 v 5 v limited 100 support bus mastering dma standard size mini pci cards approximately quarter full-sized counterparts access card outside case unlike desktop pci cards brackets carrying connectors limits kinds functions mini pci card perform many mini pci devices developed wi-fi fast ethernet bluetooth modems often winmodems sound cards cryptographic accelerators scsi ide–ata sata controllers combination cards mini pci cards used regular pci-equipped hardware using mini pci-to-pci converters mini pci superseded much narrower pci express mini card mini pci cards 2 w maximum power consumption limits functionality implemented form factor also required support clkrun pci signal used start stop pci clock power management purposes three card form factors type type ii type iii cards card connector used type include type ii use 100-pin stacking connector type iii uses 124-pin edge connector i.e connector types ii differs type iii connector edge card like so-dimm additional 24 pins provide extra signals required route i/o back system connector audio ac-link lan phone-line interface type ii cards rj11 rj45 mounted connectors cards must located edge computer docking station rj11 rj45 ports mounted external access mini pci distinct 144-pin micro pci pc/104-plus pci-104 embedded form factors include stacking 120 pin pci connector typically consumer systems specify n × pci slots without specifying actual dimensions space available small-form-factor systems may sufficient allow even half-length pci cards fit despite limitation systems still useful many modern pci cards considerably smaller half-length pci bus traffic consists series pci bus transactions transaction consists address phase followed one data phases direction data phases may initiator target write transaction vice versa read transaction data phases must direction either party may pause halt data phases point one common example low-performance pci device support burst transactions always halts transaction first data phase pci device may initiate transaction first must request permission pci bus arbiter motherboard arbiter grants permission one requesting devices initiator begins address phase broadcasting 32-bit address plus 4-bit command code waits target respond devices examine address one responds cycles later 64-bit addressing done using two-stage address phase initiator broadcasts low 32 address bits accompanied special dual address cycle command code devices support 64-bit addressing simply respond command code next cycle initiator transmits high 32 address bits plus real command code transaction operates identically point ensure compatibility 32-bit pci devices forbidden use dual address cycle necessary i.e high-order address bits zero pci bus transfers 32 bits per data phase initiator transmits 4 active-low byte enable signals indicating 8-bit bytes considered significant particular write must affect enabled bytes target pci device little importance memory reads i/o reads might side effects pci standard explicitly allows data phase bytes enabled must behave no-op pci three address spaces memory i/o address configuration memory addresses 32 bits optionally 64 bits size support caching burst transactions i/o addresses compatibility intel x86 architecture i/o port address space although pci bus specification allows burst transactions address space devices support memory addresses i/o finally pci configuration space provides access 256 bytes special configuration registers per pci device pci slot gets configuration space address range registers used configure devices memory i/o address ranges respond transaction initiators computer first turned pci devices respond configuration space accesses computer bios scans devices assigns memory i/o address ranges address claimed device transaction initiator address phase time causing initiator abort operation case reads customary supply all-ones read data value 0xffffffff case pci devices therefore generally attempt avoid using all-ones value important status registers error easily detected software 16 possible 4-bit command codes 12 assigned exception unique dual address cycle least significant bit command code indicates whether following data phases read data sent target initiator write data sent initiator target pci targets must examine command code well address respond address phases specify unsupported command code commands refer cache lines depend pci configuration space cache line size register set properly may used done soon promulgation pci specification discovered lengthy transactions devices due slow acknowledgments long data bursts combination could cause buffer underrun overrun devices recommendations timing individual phases revision 2.0 made mandatory revision 2.1 additionally revision 2.1 initiators capable bursting two data phases must implement programmable latency timer timer starts counting clock cycles transaction starts initiator asserts frame timer expired arbiter removed gnt initiator must terminate transaction next legal opportunity usually next data phase memory write invalidate transactions must continue end cache line devices unable meet timing restrictions must use combination posted writes memory writes delayed transactions writes reads delayed transaction target records transaction including write data internally aborts asserts stop rather trdy first data phase initiator must retry exactly transaction later interim target internally performs transaction waits retried transaction retried transaction seen buffered result delivered device may target transactions completing one delayed transaction must remember transaction type address byte selects write data value complete correct transaction target limit number delayed transactions record internally simple targets may impose limit 1 force transactions retry without recording dealt current delayed transaction completed two initiators attempt transaction delayed transaction begun one may result delivered harmless target abandons delayed transaction retry succeeds delivering buffered result bus reset 2=32768 clock cycles approximately 1 ms elapse without seeing retry latter never happen normal operation prevents deadlock whole bus one initiator reset malfunctions pci standard permits multiple independent pci buses connected bus bridges forward operations one bus another required although pci tends use many bus bridges pci express systems use many pci express slot appears separate bus connected bridge others generally bus bridge sees transaction one bus must forwarded original transaction must wait forwarded transaction completes result ready one notable exception occurs case memory writes bridge may record write data internally room signal completion write forwarded write completed indeed begun sent yet arrived writes referred posted writes analogy postal mail message although offer great opportunity performance gains rules governing permissible somewhat intricate pci standard permits bus bridges convert multiple bus transactions one larger transaction certain situations improve efficiency pci bus pci bus transactions controlled five main control signals two driven initiator transaction frame irdy three driven target devsel trdy stop two additional arbitration signals req gnt used obtain permission initiate transaction active-low meaning active asserted state low voltage pull-up resistors motherboard ensure remain high inactive deasserted driven device pci bus depend resistors change signal level devices drive signals high one cycle ceasing drive signals pci bus signals sampled rising edge clock signals nominally change falling edge clock giving pci device approximately one half clock cycle decide respond signals observed rising edge one half clock cycle transmit response device pci bus requires every time device driving pci bus signal changes one turnaround cycle must elapse time one device stops driving signal device starts without might period devices driving signal would interfere bus operation combination turnaround cycle requirement drive control line high one cycle ceasing drive means main control lines must high minimum two cycles changing owners pci bus protocol designed rarely limitation special cases notably fast back-to-back transactions necessary insert additional delay meet requirement device pci bus capable acting bus master may initiate transaction device ensure one transaction initiated time master must first wait bus grant signal gnt arbiter located motherboard device separate request line req requests bus arbiter may park bus grant signal device current requests arbiter may remove gnt time device loses gnt may complete current transaction may start one asserting frame unless observes gnt asserted cycle begins arbiter may also provide gnt time including another master transaction transaction either frame irdy asserted deasserted bus idle device may initiate transaction time gnt asserted bus idle pci bus transaction begins address phase initiator seeing gnt bus idle drives target address onto ad 31:0 lines associated command e.g memory read i/o write c/be 3:0 lines pulls frame low device examines address command decides whether respond target asserting devsel device must respond asserting devsel within 3 cycles devices promise respond within 1 2 cycles said fast devsel medium devsel respectively actually time respond 2.5 cycles since pci devices must transmit signals half cycle early received three cycles later note device must latch address first cycle initiator required remove address command bus following cycle even receiving devsel response additional time available interpreting address command captured fifth cycle address phase earlier devices medium devsel faster catch-all subtractive decoding allowed address ranges commonly used isa bus bridge addresses within range 24 bits memory 16 bits i/o sixth cycle response initiator may abort transaction deasserting frame known master abort termination customary pci bus bridges return all-ones data 0xffffffff case pci devices therefore generally designed avoid using all-ones value important status registers error easily detected software rising edge clock 0 initiator observes frame irdy high gnt low drives address command asserts frame time rising edge clock 1 targets latch address begin decoding may respond devsel time clock 2 fast devsel 3 medium 4 slow subtractive decode devices seeing response clock 4 may respond clock 5 master see response clock 5 terminate transaction remove frame clock 6 trdy stop deasserted high address phase initiator may assert irdy soon ready transfer data could theoretically soon clock 2 allow 64-bit addressing master present address two consecutive cycles first sends low-order address bits special dual-cycle address command c/be 3:0 following cycle sends high-order address bits actual command dual-address cycles forbidden high-order address bits zero devices support 64-bit addressing simply respond dual cycle commands addresses pci configuration space access decoded specially low-order address lines specify offset desired pci configuration register high-order address lines ignored instead additional address signal idsel input must high device may assert devsel slot connects different high-order address line idsel pin selected using one-hot encoding upper address lines address phase specifically beginning cycle devsel goes low comes burst one data phases cases initiator drives active-low byte select signals c/be 3:0 lines data ad 31:0 may driven initiator case writes target case reads data phases c/be 3:0 lines interpreted active-low byte enables case write asserted signals indicate four bytes ad bus written addressed location case read indicate bytes initiator interested reads always legal ignore byte enable signals simply return 32 bits cacheable memory resources required always return 32 valid bits byte enables mainly useful i/o space accesses reads side effects data phase four c/be lines deasserted explicitly permitted pci standard must effect target advance address burst access progress data phase continues parties ready complete transfer continue next data phase initiator asserts irdy initiator ready longer needs wait target asserts trdy target ready whichever side providing data must drive ad bus asserting ready signal one participants asserts ready signal may become un-ready otherwise alter control signals end data phase data recipient must latch ad bus cycle sees irdy trdy asserted marks end current data phase indicates just-latched data word transferred maintain full burst speed data sender half clock cycle seeing irdy trdy asserted drive next word onto ad bus continues address cycle illustrated assuming single address cycle medium devsel target responds time clock 3 however time neither side ready transfer data clock 4 initiator ready target clock 5 ready data transfer takes place indicated vertical lines clock 6 target ready transfer initiator clock 7 initiator becomes ready data transferred clocks 8 9 sides remain ready transfer data data transferred maximum possible rate 32 bits per clock cycle case read clock 2 reserved turning around ad bus target permitted drive data bus even capable fast devsel target supports fast devsel could theory begin responding read cycle address presented cycle however reserved ad bus turnaround thus target may drive ad bus thus may assert trdy second cycle transaction note targets fast need special logic enforce condition either side may request burst end current data phase simple pci devices support multi-word bursts always request immediately even devices support bursts limit maximum length support end addressable memory initiator mark data phase final one transaction deasserting frame time asserts irdy cycle target asserts trdy final data transfer complete sides deassert respective rdy signals bus idle master may deassert frame asserting irdy may deassert frame waiting irdy asserted target assert trdy minor exception master abort termination target responds devsel obviously pointless wait trdy case however even case master must assert irdy least one cycle deasserting frame commonly master assert irdy receiving devsel must simply hold irdy asserted one cycle longer ensure bus turnaround timing rules obeyed frame line target requests initiator end burst asserting stop initiator end transaction deasserting frame next legal opportunity wishes transfer data continue separate transaction several ways target always least one cycle target-initiated disconnection allow master deassert frame two sub-cases take amount time one requires additional data phase initiator ends burst time target requests disconnection additional bus cycle memory space accesses words burst may accessed several orders unnecessary low-order address bits ad 1:0 used convey initiator requested order target support particular order must terminate burst first word orders depend cache line size configurable pci devices starting offset within cache line zero modes reduce order cache line toggle cache line wrap modes two forms critical-word-first cache line fetching toggle mode xors supplied address incrementing counter native order intel 486 pentium processors advantage necessary know cache line size implement pci version 2.1 obsoleted toggle mode added cache line wrap mode fetching proceeds linearly wrapping around end cache line one cache line completely fetched fetching jumps starting offset next cache line note pci devices support limited range typical cache line sizes cache line size programmed unexpected value force single-word access pci also supports burst access i/o configuration space linear mode supported rarely used may buggy devices may support properly force single-word access either highest-possible speed four-word write burst terminated master clock edge 1 initiator starts transaction driving address command asserting frame signals idle indicated ^^^ pulled high motherboard pull-up resistors might turnaround cycle cycle 2 target asserts devsel trdy initiator also ready data transfer occurs repeats three cycles last one clock edge 5 master deasserts frame indicating end clock edge 6 ad bus frame undriven turnaround cycle control lines driven high 1 cycle clock edge 7 another initiator start different transaction also turnaround cycle control lines equivalent read burst takes one cycle target must wait 1 cycle ad bus turn around may assert trdy high-speed burst terminated target extra cycle end clock edge 6 target indicates wants stop data initiator already holding irdy low fifth data phase clock edge 7 data transferred pci bus detects parity errors attempt correct retrying operations purely failure indication due need detect parity error happened pci bus actually detects cycles later data phase whichever device driving ad 31:0 lines computes even parity c/be 3:0 lines sends par line one cycle later access rules turnaround cycles ad bus apply par line one cycle later device listening ad bus checks received parity asserts perr parity error line one cycle generally generates processor interrupt processor search pci bus device detected error perr line used data phases target selected parity error detected address phase data phase special cycle devices observe assert serr system error line even bytes masked c/be lines use must still defined value value must used compute parity due need turnaround cycle different devices driving pci bus signals general necessary idle cycle pci bus transactions however circumstances permitted skip idle cycle going directly final cycle one transfer irdy asserted frame deasserted first cycle next frame asserted irdy deasserted initiator may perform back-to-back transactions additional timing constraints may come need turn around target control lines particularly devsel target deasserts devsel driving high cycle following final data phase case back-to-back transactions first cycle address phase second cycle address phase reserved devsel turnaround target different previous one must assert devsel third cycle medium devsel speed one case problem arise initiator knows somehow presumably addresses share sufficient high-order bits second transfer addressed target previous one case may perform back-to-back transactions pci targets must support also possible target keeps track requirements never fast devsel met trivially must wait medium devsel time unless targets capability indicate special bit pci configuration register targets bus initiators may use back-to-back transfers freely subtractive decoding bus bridge must know expect extra delay event back-to-back cycles order advertise back-to-back support starting revision 2.1 pci specification includes optional 64-bit support provided via extended connector provides 64-bit bus extensions ad 63:32 c/be 7:4 par64 number additional power ground pins 64-bit pci connector distinguished 32-bit connector additional 64-bit segment memory transactions 64-bit devices may use 64 bits double data transfer rate non-memory transactions including configuration i/o space accesses may use 64-bit extension 64-bit burst burst addressing works 32-bit transfer address incremented twice per data phase starting address must 64-bit aligned i.e ad2 must 0 data corresponding intervening addresses ad2 1 carried upper half ad bus initiate 64-bit transaction initiator drives starting address ad bus asserts req64 time frame selected target support 64-bit transfer transaction replies asserting ack64 time devsel note target may decide per-transaction basis whether allow 64-bit transfer req64 asserted address phase initiator also drives high 32 bits address copy bus command high half bus address requires 64 bits dual address cycle still required high half bus carries upper half address final command code address phase cycles allows 64-bit target see entire address begin responding earlier initiator sees devsel asserted without ack64 performs 32-bit data phases data would transferred upper half bus first data phase instead transferred second data phase typically initiator drives 64 bits data seeing devsel ack64 missing may cease driving upper half data bus req64 ack64 lines held asserted entire transaction save last data phase deasserted time frame devsel respectively par64 line operates like par line provides even parity ad 63:32 c/be 7:4 valid address phases req64 asserted par64 valid data phases req64 ack64 asserted pci originally included optional support write-back cache coherence required support cacheable memory targets would listen two pins cache bus sdone snoop done sbo snoop backoff rarely implemented practice deleted revision 2.2 pci specification pins re-used smbus access revision 2.3 cache would watch memory accesses without asserting devsel noticed access might cached would drive sdone low snoop done coherence-supporting target would avoid completing data phase asserting trdy observed sdone high case write data clean cache cache would invalidate copy would assert sdone soon established however cache contained dirty data cache would write back access could proceed would assert sbo raising sdone would signal active target assert stop rather trdy causing initiator disconnect retry operation later meantime cache would arbitrate bus write data back memory targets supporting cache coherency also required terminate bursts cross cache lines developing and/or troubleshooting pci bus examination hardware signals important logic analyzers bus analyzers tools collect analyze decode signals users view useful ways
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Computer architecture
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bpel script bpelscript language specify bpel processes provides compact syntax inspired scripting languages javascript ruby full coverage features provided bpel business process execution language bpel xml-based language specify business processes intention act central controller business process provides standardized way programming large service-oriented world soa bpel programming language graphical representation mappings graphical languages business process modeling notation bpmn bpel available programmers familiar syntax like java c ... disregarded therefore especially prototyping teaching would nice programming language omits xml-overhead bpel offers features bpel one option force programmers learn completely new syntax option introduce new syntax bpel therefore bpel simplified syntax called simpel recommended apache ode group referring mix options however simpel equivalent bpel aims specifying business processes order come easy scripting syntax bpelscript introduced referring second option bpelscript forks directly simpel aiming big closeness bpel contrast simpel bpelscript supports bpels constructs including correlation bpelscript provides
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Web technology
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pdf portable document format pdf redundantly pdf format file format developed adobe 1990s present documents including text formatting images manner independent application software hardware operating systems based postscript language pdf file encapsulates complete description fixed-layout flat document including text fonts vector graphics raster images information needed display pdf standardized iso 32000 2008 longer requires royalties implementation today pdf files may contain variety content besides flat text graphics including logical structuring elements interactive elements annotations form-fields layers rich media including video content three dimensional objects using u3d prc various data formats pdf specification also provides encryption digital signatures file attachments metadata enable workflows requiring features adobe systems made pdf specification available free charge 1993 early years pdf popular mainly desktop publishing workflows competed variety formats djvu envoy common ground digital paper farallon replica even adobe postscript format pdf proprietary format controlled adobe released open standard july 1 2008 published international organization standardization iso 32000-1:2008 time control specification passed iso committee volunteer industry experts 2008 adobe published public patent license iso 32000-1 granting royalty-free rights patents owned adobe necessary make use sell distribute pdf compliant implementations pdf 1.7 sixth edition pdf specification became iso 32000-1 includes proprietary technologies defined adobe adobe xml forms architecture xfa javascript extension acrobat referenced iso 32000-1 normative indispensable full implementation iso 32000-1 specification proprietary technologies standardized specification published adobe ’ website many also supported popular third-party implementations pdf july 28 2017 iso 32000-2:2017 pdf 2.0 published iso 32000-2 include proprietary technologies normative references pdf combines three technologies postscript page description language run interpreter generate image process requiring many resources handle graphics standard features programming languages codice_1 codice_2 commands pdf largely based postscript simplified remove flow control features like graphics commands codice_3 remain often postscript-like pdf code generated source postscript file graphics commands output postscript code collected tokenized files graphics fonts document refers also collected everything compressed single file therefore entire postscript world fonts layout measurements remains intact document format pdf several advantages postscript pdf file 7-bit ascii file except certain elements may binary content pdf file starts header containing magic number version format codice_4 format subset cos carousel object structure format cos tree file consists primarily objects eight types furthermore may comments introduced percent sign codice_9 comments may contain 8-bit characters objects may either direct embedded another object indirect indirect objects numbered object number generation number defined codice_10 codice_11 keywords index table also called cross-reference table marked codice_12 keyword follows main body gives byte offset indirect object start file design allows efficient random access objects file also allows small changes made without rewriting entire file incremental update beginning pdf version 1.5 indirect objects may also located special streams known object streams technique reduces size files large numbers small indirect objects especially useful tagged pdf end pdf file trailer introduced codice_13 keyword contains dictionary contains two layouts pdf files non-linear optimized linear optimized non-linear pdf files consume less disk space linear counterparts though slower access portions data required assemble pages document scattered throughout pdf file linear pdf files also called optimized web optimized pdf files constructed manner enables read web browser plugin without waiting entire file download since written disk linear page order fashion pdf files may optimized using adobe acrobat software qpdf basic design graphics represented pdf similar postscript except use transparency added pdf 1.4 pdf graphics use device-independent cartesian coordinate system describe surface page pdf page description use matrix scale rotate skew graphical elements key concept pdf graphics state collection graphical parameters may changed saved restored page description pdf version 1.6 24 graphics state properties important postscript vector graphics pdf constructed paths paths usually composed lines cubic bézier curves also constructed outlines text unlike postscript pdf allow single path mix text outlines lines curves paths stroked filled clipping strokes fills use color set graphics state including patterns pdf supports several types patterns simplest tiling pattern piece artwork specified drawn repeatedly may colored tiling pattern colors specified pattern object uncolored tiling pattern defers color specification time pattern drawn beginning pdf 1.3 also shading pattern draws continuously varying colors seven types shading pattern simplest axial shade type 2 radial shade type 3 raster images pdf called image xobjects represented dictionaries associated stream dictionary describes properties image stream contains image data less commonly raster image may embedded directly page description inline image images typically filtered compression purposes image filters supported pdf include general purpose filters normally image content pdf embedded file pdf allows image data stored external files use external streams alternate images standardized subsets pdf including pdf/a pdf/x prohibit features text pdf represented text elements page content streams text element specifies characters drawn certain positions characters specified using encoding selected font resource font object pdf description digital typeface may either describe characteristics typeface may include embedded font file latter case called embedded font former called unembedded font font files may embedded based widely used standard digital font formats type 1 compressed variant cff truetype beginning pdf 1.6 opentype additionally pdf supports type 3 variant components font described pdf graphic operators fourteen typefaces known standard 14 fonts special significance pdf documents fonts sometimes called base fourteen fonts fonts suitable substitute fonts metrics available pdf readers guaranteed available reader may display correctly system installed fonts may substituted embedded pdf within text strings characters shown using character codes integers map glyphs current font using encoding number predefined encodings including winansi macroman large number encodings east asian languages font built-in encoding although winansi macroman encodings derived historical properties windows macintosh operating systems fonts using encodings work equally well platform pdf specify predefined encoding use font built-in encoding provide lookup table differences predefined built-in encoding recommended truetype fonts encoding mechanisms pdf designed type 1 fonts rules applying truetype fonts complex large fonts fonts non-standard glyphs special encodings identity-h horizontal writing identity-v vertical used fonts necessary provide tounicode table semantic information characters preserved original imaging model pdf like postscript opaque object drawn page completely replaced anything previously marked location pdf 1.4 imaging model extended allow transparency transparency used new objects interact previously marked objects produce blending effects addition transparency pdf done means new extensions designed ignored products written pdf 1.3 earlier specifications result files use small amount transparency might view acceptably older viewers files making extensive use transparency could viewed incorrectly older viewer without warning transparency extensions based key concepts transparency groups blending modes shape alpha model closely aligned features adobe illustrator version 9 blend modes based used adobe photoshop time pdf 1.4 specification published formulas calculating blend modes kept secret adobe since published concept transparency group pdf specification independent existing notions group layer applications adobe illustrator groupings reflect logical relationships among objects meaningful editing objects part imaging model pdf files may contain interactive elements annotations form fields video 3d rich media rich media pdf pdf file including interactive content embedded linked within file interactive forms mechanism add forms pdf file format pdf currently supports two different methods integrating data pdf forms formats today coexist pdf specification acroforms introduced pdf 1.2 format acroforms permit using objects e.g text boxes radio buttons etc code e.g javascript alongside standard pdf action types interactive forms acroforms support submitting resetting importing data submit action transmits names values selected interactive form fields specified uniform resource locator url interactive form field names values may submitted following formats depending settings action ’ exportformat submitpdf xfdf flags acroforms keep form field values external stand-alone files containing key value pairs external files may use forms data format fdf xml forms data format xfdf files usage rights ur signatures define rights import form data files fdf xfdf text csv/tsv formats export form data files fdf xfdf formats forms data format fdf based pdf uses syntax essentially file structure much simpler pdf since body fdf document consists one required object forms data format defined pdf specification since pdf 1.2 forms data format used submitting form data server receiving response incorporating interactive form also used export form data stand-alone files imported back corresponding pdf interactive form xml forms data format xfdf xml version forms data format xfdf implements subset fdf containing forms annotations xfdf equivalents entries fdf dictionary – status encoding javascript pages keys embeddedfdfs differences target addition xfdf allow spawning addition new pages based given data done using fdf file xfdf specification referenced included pdf 1.5 specification later versions described separately xml forms data format specification pdf 1.4 specification allowed form submissions xml format replaced submissions xfdf format pdf 1.5 specification xfdf conforms xml standard december 2016 xfdf 3.0 iso/iec standard formal name iso 19444-1:2016 – document management – xml forms data format – part 1 use iso 32000-2 xfdf 3.0 standard normative reference iso 32000-2 xfdf used way fdf e.g. form data submitted server modifications made sent back new form data imported interactive form also used export form data stand-alone files imported back corresponding pdf interactive form pdf 1.5 adobe systems introduced proprietary format forms adobe xml forms architecture xfa adobe xfa forms compatible iso 32000 acroforms feature pdf processors handle xfa content xfa specification referenced iso 32000-1 pdf 1.7 external proprietary specification entirely deprecated pdf iso 32000-2 pdf 2.0 tagged pdf see clause 14.8 iso 32000 includes document structure semantics information enable reliable text extraction accessibility technically speaking tagged pdf stylized use format builds logical structure framework introduced pdf 1.3 tagged pdf defines set standard structure types attributes allow page content text graphics images extracted reused purposes tagged pdf required situations pdf file intended print since feature optional since rules tagged pdf relatively vague iso 32000-1 support tagged pdf amongst consuming devices including assistive technology uneven time iso 32000-2 however includes improved discussion tagged pdf anticipated facilitate iso-standardized subset pdf specifically targeted accessibility pdf/ua first published 2012 introduction pdf version 1.5 2003 came concept layers layers formally known optional content groups ocgs refer sections content pdf document selectively viewed hidden document authors consumers capability useful cad drawings layered artwork maps multi-language documents etc basically consists optional content properties dictionary added document root dictionary contains array optional content groups ocgs describing set information may individually displayed suppressed plus set optional content configuration dictionaries give status displayed suppressed given ocgs pdf file may encrypted security digitally signed authentication however since sha-1 collision discovered making use pdf format digital signatures using sha-1 shown insecure standard security provided acrobat pdf consists two different methods two different passwords user password encrypts file prevents opening owner password specifies operations restricted even document decrypted include modifying printing copying text graphics document adding modifying text notes acroform fields user password encrypts file owner password instead relying client software respect restrictions owner password easily removed software including free online services thus use restrictions document author places pdf document secure assured file distributed warning displayed applying restrictions using adobe acrobat software create edit pdf files even without removing password freeware open source pdf readers ignore permission protections allow user print make copy excerpts text document limited password protection number commercial solutions offer robust means information rights management restrict document access also reliably enforce permissions ways standard security handler beginning pdf 1.5 usage rights ur signatures used enable additional interactive features available default particular pdf viewer application signature used validate permissions granted bona fide granting authority example used allow user example adobe systems grants permissions enable additional features adobe reader using public-key cryptography adobe reader verifies signature uses certificate adobe-authorized certificate authority pdf application use mechanism purposes pdf files file attachments processors may access open save local filesystem pdf files contain two types metadata first document information dictionary set key/value fields author title subject creation update dates stored optional info trailer file small set fields defined extended additional text values required method deprecated pdf 2.0 pdf 1.4 support added metadata streams using extensible metadata platform xmp add xml standards-based extensible metadata used file formats allows metadata attached stream document information embedded illustrations well whole document attaching document catalog using extensible schema pdfs may encrypted password needed view edit contents pdf 2.0 defines 256-bit aes encryption standard pdf 2.0 files pdf reference also defines ways third parties define encryption systems pdf pdf files may digitally signed complete details implementing digital signatures pdf provided iso 32000-2 pdf files may also contain embedded drm restrictions provide controls limit copying editing printing restrictions depend reader software obey security provide limited pdf documents contain display settings including page display layout zoom level adobe reader uses settings override user default settings opening document free adobe reader remove settings anyone may create applications read write pdf files without pay royalties adobe systems adobe holds patents pdf licenses royalty-free use developing software complying pdf specification pdf files created specifically accessible disabled people pdf file formats use include tags text equivalents captions audio descriptions software automatically produce tagged pdfs feature always enabled default leading screen readers including jaws window-eyes hal kurzweil 1000 3000 read tagged pdf moreover tagged pdfs re-flowed magnified readers visual impairments adding tags older pdfs generated scanned documents present challenges one significant challenges pdf accessibility pdf documents three distinct views depending document creation inconsistent three views physical view ii tags view iii content view physical view displayed printed people consider pdf document tags view screen readers assistive technologies use deliver high-quality navigation reading experience users disabilities content view based physical order objects within pdf content stream may displayed software fully support tags view reflow feature adobe reader pdf/ua international standard accessible pdf based iso 32000-1 first published iso 14289-1 2012 establishes normative language accessible pdf technology pdf attachments carrying viruses first discovered 2001 virus named outlook.pdfworm peachy uses microsoft outlook send attachment adobe pdf file activated adobe acrobat acrobat reader time time new vulnerabilities discovered various versions adobe reader prompting company issue security fixes pdf readers also susceptible one aggravating factor pdf reader configured start automatically web page embedded pdf file providing vector attack malicious web page contains infected pdf file takes advantage vulnerability pdf reader system may compromised even browser secure vulnerabilities result pdf standard allowing pdf documents scripted javascript disabling javascript execution pdf reader help mitigate future exploits although protect exploits parts pdf viewing software security experts say javascript essential pdf reader security benefit comes disabling javascript outweighs compatibility issues caused one way avoiding pdf file exploits local web service convert files another format viewing march 30 2010 security researcher didier stevens reported adobe reader foxit reader exploit runs malicious executable user allows launch asked pdf file often combination vector graphics text bitmap graphics basic types content pdf later pdf revisions pdf document also support links inside document web page forms javascript initially available plugin acrobat 3.0 types embedded contents handled using plug-ins pdf 1.6 supports interactive 3d documents embedded pdf – 3d drawings embedded using u3d prc various data formats two pdf files look similar computer screen may different sizes example high resolution raster image takes space low resolution one typically higher resolution needed printing documents displaying screen things may increase size file embedding full fonts especially asiatic scripts storing text graphics pdf viewers generally provided free charge many versions available variety sources many software options creating pdfs including pdf printing capabilities built macos ios linux distributions libreoffice microsoft office 2007 updated sp2 later wordperfect 9 scribus numerous pdf print drivers microsoft windows pdftex typesetting system docbook pdf tools applications developed around ghostscript adobe acrobat well adobe indesign adobe framemaker adobe illustrator adobe photoshop google online office suite google docs also allows uploading saving pdf raster image processors rips used convert pdf files raster format suitable imaging onto paper media printers digital production presses prepress process known rasterisation rips capable processing pdf directly include adobe pdf print engine adobe systems jaws harlequin rip global graphics documents saved pdf portable document format portable document format archiving forms data format printable document could converted back forth many formats etc companies adobe acrobat provide sdk libraries developers add create pdf features software besides adobe pdf library companies pdftron systems apache pdfbox foxit software provide similar sdks adobe acrobat one example proprietary software allows user annotate highlight add notes already created pdf files one unix application available free software gnu general public license pdfedit freeware foxit reader available microsoft windows macos linux allows annotating documents tracker software pdf-xchange viewer allows annotations markups without restrictions freeware alternative apple macos integrated pdf viewer preview also enable annotations open source software skim latter supporting interaction latex synctex pdfsync integration bibdesk reference management software freeware qiqqa create annotation report summarizes annotations notes one made across library pdfs also web annotation systems support annotation pdf documents formats cases pdfs expected functionality paper documents ink annotation required examples pdf software online services including scribd viewing storing pdfvue online editing thinkfree zamzar conversion 1993 jaws raster image processor global graphics became first shipping prepress rip interpreted pdf natively without conversion another format company released upgrade harlequin rip capability 1997 agfa-gevaert introduced shipped apogee first prepress workflow system based pdf 1997 many commercial offset printers accepted submission press-ready pdf files print source specifically pdf/x-1a subset variations submission press-ready pdf files replacement problematic need receiving collected native working files pdf selected native metafile format mac os x replacing pict format earlier classic mac os imaging model quartz graphics layer based model common display postscript pdf leading nickname display pdf preview application display pdf files version 2.0 later safari web browser system-level support pdf allows mac os x applications create pdf documents automatically provided support os-standard printing architecture files exported pdf 1.3 format according file header taking screenshot mac os x versions 10.0 10.3 image also captured pdf later versions save screen captures png file though behaviour set back pdf desired 2006 pdf widely accepted standard print job format open source development labs printing summit supported print job format common unix printing system desktop application projects gnome kde firefox thunderbird libreoffice openoffice switched emit print jobs pdf desktop printers also support direct pdf printing interpret pdf data without external help currently pdf capable printers also support postscript postscript printers support direct pdf printing free software foundation thought one high priority projects developing free high-quality fully functional set libraries programs implement pdf file format associated technologies iso 32000 standard 2011 however gnu pdf project removed list high priority projects due maturation poppler library enjoyed wider use applications evince gnome desktop environment poppler based xpdf code base also commercial development libraries available listed list pdf software apache pdfbox project apache software foundation open source java library working pdf documents pdfbox licensed apache license
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Programming language topics
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postscript postscript ps page description language electronic publishing desktop publishing business dynamically typed concatenative programming language created adobe systems john warnock charles geschke doug brotz ed taft bill paxton 1982 1984 concepts postscript language seeded 1966 john warnock working evans sutherland computer graphics company time warnock developing interpreter large three-dimensional graphics database new york harbor warnock conceived design system language process graphics concurrently researchers xerox parc developed first laser printer recognized need standard means defining page images 1975-76 bob sproull william newman developed press format eventually used xerox star system drive laser printers press data format rather language lacked flexibility parc mounted interpress effort create successor 1978 warnock left evans sutherland joined xerox parc work martin newell rewrote design system create interpretive language j jam john martin used vlsi design investigation type graphics printing work later evolved expanded interpress language warnock left chuck geschke founded adobe systems december 1982 together doug brotz ed taft bill paxton created simpler language similar interpress called postscript went market 1984 time visited steve jobs urged adapt postscript used language driving laser printers march 1985 apple laserwriter first printer ship postscript sparking desktop publishing dtp revolution mid-1980s combination technical merits widespread availability made postscript language choice graphical output printing applications time interpreter sometimes referred rip raster image processor postscript language common component laser printers 1990s however cost implementation high computers output raw ps code would interpreted printer raster image printer natural resolution required high performance microprocessors ample memory laserwriter used 12 mhz motorola 68000 making faster macintosh computers attached laser printer engines cost thousand dollars added cost ps marginal printer mechanisms fell price cost implementing ps became great fraction overall printer cost addition desktop computers becoming powerful longer made sense offload rasterisation work onto resource-constrained printer 2001 lower-end printer models came support postscript largely due growing competition much cheaper non-postscript ink jet printers new software-based methods render postscript images computer making suitable printer pdf descendant postscript provides one method largely replaced postscript de facto standard electronic document distribution high-end printers postscript processors remain common use dramatically reduce cpu work involved printing documents transferring work rendering postscript images computer printer first version postscript language released market 1984 suffix level 1 added level 2 introduced postscript level 2 introduced 1991 included several improvements improved speed reliability support in-rip separations image decompression example jpeg images could rendered postscript program support composite fonts form mechanism caching reusable content postscript 3 adobe dropped level terminology favor simple versioning came end 1997 along many new dictionary-based versions older operators introduced better color handling new filters allow in-program compression/decompression program chunking advanced error-handling postscript 3 significant terms replacing existing proprietary color electronic prepress systems widely used magazine production introduction smooth shading operations 4096 shades grey rather 256 available postscript level 2 well devicen color space allowed addition additional ink colors called spot colors composite color pages prior introduction postscript printers designed print character output given text—typically ascii—as input number technologies task shared property glyphs physically difficult change stamped onto typewriter keys bands metal optical plates changed degree increasing popularity dot matrix printers characters systems drawn series dots defined font table inside printer grew sophistication dot matrix printers started including several built-in fonts user could select models allowed users upload custom glyphs printer dot matrix printers also introduced ability print raster graphics graphics interpreted computer sent series dots printer using series escape sequences printer control languages varied printer printer requiring program authors create numerous drivers vector graphics printing left special-purpose devices called plotters almost plotters shared common command language hpgl limited use anything printing graphics addition tended expensive slow thus rare laser printers combine best features printers plotters like plotters laser printers offer high quality line art like dot-matrix printers able generate pages text raster graphics unlike either printers plotters laser printer makes possible position high-quality graphics text page postscript made possible exploit fully characteristics offering single control language could used brand printer postscript went beyond typical printer control language complete programming language many applications transform document postscript program execution results original document program sent interpreter printer results printed document one inside another application display document on-screen since document-program regardless destination called device-independent postscript noteworthy implementing 'on-the fly rasterization everything even text specified terms straight lines cubic bézier curves previously found cad applications allows arbitrary scaling rotating transformations postscript program interpreted interpreter converts instructions dots needed form output reason postscript interpreters occasionally called postscript raster image processors rips almost complex postscript handling fonts font system uses ps graphics primitives draw glyphs curves rendered resolution number typographic issues considered approach one issue fonts scale linearly small sizes features glyphs become proportionally large small start look displeasing postscript avoided problem inclusion font hinting additional information provided horizontal vertical bands help identify features letter important rasterizer maintain result significantly better-looking fonts even low resolution formerly believed hand-tuned bitmap fonts required task time technology including hints fonts carefully guarded hinted fonts compressed encrypted adobe called type 1 font also known postscript type 1 font ps1 t1 adobe type 1 type 1 effectively simplification ps system store outline information opposed complete language pdf similar regard adobe would sell licenses type 1 technology wanting add hints fonts license technology left type 3 font also known postscript type 3 font ps3 t3 type 3 fonts allowed sophistication postscript language without standardized approach hinting type 2 font format designed used compact font format cff charstrings implemented reduce overall font file size cff/type2 format later became basis handling postscript outlines opentype fonts cid-keyed font format also designed solve problems ocf/type 0 fonts addressing complex asian-language cjk encoding large character set issues cid-keyed font format used type 1 font format standard cid-keyed fonts type 2 cid-keyed opentype fonts compete adobe system apple designed system truetype around 1991 immediately following announcement truetype adobe published specification type 1 font format retail tools altsys fontographer acquired macromedia january 1995 owned fontlab since may 2005 added ability create type 1 fonts since many free type 1 fonts released instance fonts used tex typesetting system available format early 1990s several systems storing outline-based fonts developed bitstream metafont instance none included general-purpose printing solution therefore widely used late 1990s adobe joined microsoft developing opentype essentially functional superset type 1 truetype formats printed postscript output device unneeded parts opentype font omitted sent device driver would truetype type 1 font depending kind outlines present opentype font 1980s adobe drew revenue licensing fees implementation postscript printers known raster image processor rip number new risc-based platforms became available mid-1980s found adobe support new machines lacking issues cost led third-party implementations postscript becoming common particularly low-cost printers licensing fee sticking point high-end typesetting equipment quest speed demanded support new platforms faster adobe could provide one point microsoft licensed apple postscript-compatible interpreter bought called trueimage apple licensed microsoft new font format truetype apple ended reaching accord adobe licensed genuine postscript printers truetype became standard outline font technology windows macintosh today third-party postscript-compatible interpreters widely used printers multifunction peripherals mfps example csr plc ips ps3 interpreter formerly known phoenixpage standard many printers mfps including developed hewlett-packard sold laserjet color laserjet lines third-party postscript solutions used print mfp manufacturers include jaws harlequin rip global graphics free software version several applications ghostscript several compatible interpreters listed undocumented printing wiki basic inexpensive laser printers support postscript instead coming drivers simply rasterize platform native graphics formats rather converting postscript first postscript support needed printer ghostscript used also number commercial postscript interpreters teletype co. t-script postscript became commercially successful due introduction graphical user interface gui allowing designers directly lay pages eventual output laser printers however gui graphics systems generally much less sophisticated postscript apple quickdraw instance supported basic lines arcs complex b-splines advanced region filling options postscript order take full advantage postscript printing applications computers re-implement features using host platform graphics system led numerous issues on-screen layout would exactly match printed output due differences implementation features computer power grew became possible host ps system computer rather printer led natural evolution ps printing system one could also used host graphics language numerous advantages approach help eliminate possibility different output screen printer also provided powerful graphics system computer allowed printers dumb time cost laser engines falling production setting using postscript display system meant host computer could render low-resolution screen higher resolution printer simply send ps code smart printer offboard printing however postscript written printing mind numerous features made unsuitable direct use interactive display system particular ps based idea collecting ps commands codice_1 command seen point commands read point interpreted output interactive system clearly appropriate ps sort interactivity built example supporting hit detection mouse interactivity obviously apply ps used printer steve jobs left apple started next pitched adobe idea using ps display system new workstation computers result display postscript dps dps added basic functionality improve performance changing many string lookups 32 bit integers adding support direct output every command adding functions allow gui inspect diagram additionally set bindings provided allow ps code called directly c programming language next used bindings nextstep system provide object oriented graphics system although dps written conjunction next adobe sold commercially common feature unix workstations 1990s sun microsystems took another approach creating news instead dps concept allowing ps interact c programs news instead extended ps language suitable running entire gui computer sun added number new commands timers mouse control interrupts systems needed interactivity added data structures language elements allow completely object oriented internally complete gui three fact written news provided time workstations however ongoing efforts standardize x11 system led introduction widespread use sun systems news never became widely used postscript turing-complete programming language belonging concatenative group typically postscript programs produced humans programs however possible write computer programs postscript like programming language postscript interpreted stack-based language similar forth strong dynamic typing data structures inspired found lisp scoped memory since language level 2 garbage collection language syntax uses reverse polish notation makes order operations unambiguous reading program requires practice one keep layout stack mind operators languages term functions take arguments stack place results onto stack literals example numbers effect placing copy stack sophisticated data structures built array dictionary types declared type system sees arrays dictionaries typing discipline applied user-defined types left code implements character used introduce comments postscript programs general convention every postscript program start characters ps interpreter directive devices properly interpret postscript hello world program customary way show small example complete program given language might look like postscript level 2 output device console postscript uses point unit length however unlike versions point postscript uses exactly 72 points inch thus example order draw vertical line 4 cm length sufficient type readably idiomatically one might use following equivalent demonstrates simple procedure definition use mathematical operators codice_2 codice_3 implementations postscript use single-precision reals 24-bit mantissa meaningful use 9 decimal digits specify real number performing calculations may produce unacceptable round-off errors list software used render postscript documents
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Programming language topics
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socket am3 socket am3 cpu socket amd processors am3 launched february 9 2009 successor socket am2+ alongside initial grouping phenom ii processors designed sole principal change am2+ am3 support ddr3 sdram like previous amd socket am3 processor functional data sheet amd document number 40778 made publicly available family 10h amd phenom™ processor product data sheet document 446878 contains brief list features phenom contain substantive technical data regarding socket am3 socket am3 breaks compatibility am2/am2+ processors due subtle change key placement am3 socket 941 pin contacts different layout am2+ processors 940 pins tom hardware removed two obstructing key pins am2+ phenom processor order fit am3 socket processor work am3 socket still worked am2+ socket suggesting compatibility issues run deeper merely key pins likely built-in memory controller am2/am2+ processors supports ddr2 unlike am3 processors support ddr2 ddr3 memory fact motherboards manufactured supported ddr2 ddr3 however one type could used time despite using am3 socket despite using northbridge southbridge found am3 motherboards support am2 am2+ am3 processor am3 processors also support ddr2 backwards-compatible socket am2/am2+ contingent upon bios update motherboard manufacturers including asus gigabyte others labeled existing am2/am2+ boards am3 ready similar indicating bios support provided specified boards allows existing am2/am2+ systems upgrade cpu without upgrade components 4 holes fastening heatsink motherboard placed rectangle lateral lengths 48 mm 96 mm amd sockets socket am2 socket am2+ socket am3 socket am3+ socket fm2 cooling solutions therefore interchangeable am3+ modification am3 socket one additional pin new bulldozer-based am3+ processors backwards-compatible am3 processors broke backwards-compatibility am3+ processors am2 am2+ motherboards processors support ddr2 memory
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Computer architecture
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outline vpn outline vpn free open-source tool deploys shadowsocks servers multiple cloud service providers software suite also includes client software multiple platforms outline developed jigsaw technology incubator created google outline server supports self-hosting well cloud service providers including digitalocean rackspace google cloud platform amazon ec2 installation involves running command command line interface case installing digitalocean graphical user interface outline three main components outline uses shadowsocks protocol communication client server traffic encrypted ietf chacha20 stream cipher 256-bit key authenticated ietf poly1305 authenticator outline free open-source licensed apache license 2.0 audited radically open security claims log users ’ web traffic outline server supports unattended upgrades outline anonymity tool n't provide degree anonymity protections tor routes traffic three hops rather one also protects attacks like browser fingerprinting march 2018 max eddy pcmag stated preview version outline vpn startlingly easy use removes privacy concerns associated vpn companies however eddy criticized software encrypting traffic windows warned users individual use may lack anonymity compared large vpn companies since version 1.2 outline windows client came 'beta effectively beginning encrypt traffic device par outline clients macos chrome os android ios
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Computer security
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unix filesystem unix operating systems inspired file system considered central component operating system also one first parts system designed implemented ken thompson first experimental version unix dated 1969 operating systems filesystem provides information storage retrieval one several forms interprocess communication many small programs traditionally form unix system store information files programs read although pipes complemented role starting third edition also filesystem provides access resources so-called device files entry points terminals printers mice rest article uses unix generic name refer original unix operating system many workalikes filesystem appears one rooted tree directories instead addressing separate volumes disk partitions removable media network shares separate trees done dos windows drive drive letter denotes root file system tree volumes mounted directory causing volume file system tree appear directory larger tree root entire tree denoted codice_1 original bell labs unix two-disk setup customary first disk contained startup programs second contained users files programs second disk mounted empty directory named codice_2 first disk causing two disks appear one filesystem second disks contents viewable codice_3 unix directories contain files instead contain names files paired references so-called inodes turn contain file metadata owner permissions time last access etc. name multiple names file system may refer file feature termed hard link mathematical traits hard links make file system limited type directed acyclic graph although directories still form tree typically may hard-linked originally envisioned 1969 unix file system would fact used general graph hard links directories providing navigation instead path names original unix file system supported three types files ordinary files directories special files also termed device files berkeley software distribution bsd system v added file type used interprocess communication bsd added sockets system v added fifo files bsd also added symbolic links often termed symlinks range file types files refer files complement hard links symlinks modeled similar feature multics differ hard links may span filesystems existence independent target object unix systems may support additional types files certain conventions exist locating kinds files programs system configuration files users home directories first documented codice_4 man page since version 7 unix subsequent versions derivatives clones typically similar man page details directory layout varied time although file system layout part single unix specification several attempts exist standardize parts system v application binary interface intel binary compatibility standard common operating system environment linux foundation filesystem hierarchy standard fhs generalized overview common locations files unix operating system
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Computer file systems
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cuckoo egg cuckoo egg tracking spy maze computer espionage 1989 book written clifford stoll first-person account hunt computer hacker broke computer lawrence berkeley national laboratory lbnl author clifford stoll astronomer training managed computers lawrence berkeley national laboratory lbnl california one day 1986 supervisor dave cleveland asked resolve us 0.75 accounting error computer usage accounts stoll traced error unauthorized user apparently used 9 seconds computer time paid stoll eventually realized unauthorized user hacker acquired superuser access lbnl system exploiting vulnerability movemail function original gnu emacs early course long weekend stoll rounded fifty terminals well teleprinters mostly “ borrowing ” desks co-workers away weekend physically attached fifty incoming phone lines hacker dialed weekend stoll located phone line coming tymnet routing service help tymnet eventually tracked intrusion call center mitre defense contractor mclean virginia next ten months stoll spent enormous amounts time effort tracing hacker origin saw hacker using 1200 baud connection realized intrusion coming telephone modem connection stoll colleagues paul murray lloyd bellknap assisted phone lines returning “ borrowed ” terminals stoll left teleprinter attached intrusion line order see record everything hacker watched hacker sought sometimes gained unauthorized access military bases around united states looking files contained words “ nuclear ” “ sdi ” hacker also copied password files order make dictionary attacks set trojan horses find passwords stoll amazed many high-security sites hacker could easily guess passwords since many system administrators never bothered change passwords factory defaults even military bases hacker sometimes able log “ guest ” password one first — if first — documented cases computer break-in stoll seems first keep daily logbook hacker activities course investigation stoll contacted various agents fbi cia nsa air force osi beginning confusion jurisdiction general reluctance share information fbi particular uninterested large sum money involved studying log book stoll saw hacker familiar vms well unix also noted hacker tended active around middle day pacific time eventually stoll hypothesized since modem bills cheaper night people school day job would lot free time hacking night hacker time zone distance east help tymnet various agents various agencies stoll found intrusion coming west germany via satellite deutsche bundespost german post office also authority german phone system traced calls university bremen order entice hacker reveal stoll set elaborate hoax—known today honeypot—inventing fictitious department lbl supposedly newly formed “ sdi “ contract also fictitious realized hacker particularly interested faux sdi entity filled “ sdinet ” account operated imaginary secretary barbara sherwin large files full impressive-sounding bureaucratese ploy worked deutsche bundespost finally located hacker home hanover hacker name markus hess engaged years selling results hacking soviet kgb ancillary proof hungarian spy contacted fictitious sdinet lbl mail based information could obtained hess apparently kgb method double-checking see hess making information selling stoll later flew germany testify trial hess confederate
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Computer security
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accent kernel accent operating system kernel developed carnegie mellon university cmu accent developed follow-on aleph kernel developed university rochester fixing several problems re-targeting hardware support networks workstation machines specifically three rivers perq instead minicomputers accent part spice project cmu ran 1981 1985 development accent led directly famous mach kernel original aleph project used data copying allow programs communicate applications could open ports would allow receive data sent programs idea write number servers would control resources machine passing data along reached end user respect similar concept unix although implementation much different using messages instead memory turned number problems notably copying memory data general eclipse expensive 1979 one aleph engineers richard rashid left cmu started work new version aleph avoided problems particular accent targeted workstation machines featuring mmu using mmu copy large blocks memory via mapping making memory appear two different places data changed one program another would physically copied using copy-on-write algorithm understand difference consider two interacting programs one feeding file another aleph data provider would copied 2kb time due features eclipse user process accent data simply appeared user process cost instructions sent mmu user process changed data would anything need copied even portions data actually changed another problem aleph ports identified unique id assigned sequentially simple program guess thereby gaining access resources computer granted made aleph system rather insecure address accent made port id internal kernel instances program opening ports handed back different ids stored mapping kernel whenever message sent kernel delivery would first check program access port question comparing mapping table program guessing port numbers longer worked program port ids gave clue real ids kernel attempt talk one explicitly handed kernel error thus accent ports represented capabilities granting rights use resources result handed valid port id kind capability system using subject-specific identifiers capabilities called c-list system years accent project started looking less less interesting early 1980s many felt future gains performance would made adding cpus machines something accent kernel really equipped handle adding problem new generation powerful workstations appearing meaning accent would likely ported anyway likewise unix grown operating system choice experimental work operating system design well development platform user applications order address changes decided end work accent start new system would use accent ports system within unix kernel creating famed mach kernel features accent
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Computer architecture
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esign india aadhaar esign online electronic signature service india facilitate aadhaar holder digitally sign document signature service facilitated authenticating aadhar holder via aadhar-based e-kyc electronic know customer service esign document one aadhaar card mobile number registered aadhaar two things indian citizen sign document remotely without physically present notification issued government india regard stipulates following procedure e-authentication using aadhaar e-kyc services authentication electronic record e-authentication technique shall done organisations individuals seeking obtain esigning service utilize services various service providers empanelled service providers organisations register application service prover submitting requisite documents getting uat access building application around service going audit cert-in empanelled auditor however process registering application service provider cumbersome requires huge investments time money resources complying regulations building suitable application organisations prefer using services plug-n-play gateway providers take responsibility complying regulations hence simplifying process market electonic signatureservice esign service
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Computer security
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clifford stoll clifford paul cliff stoll born june 4 1950 american astronomer author teacher best known investigation 1986 working systems administrator lawrence berkeley national laboratory led capture hacker markus hess stoll subsequent book cuckoo egg details investigation stoll written three books articles non-specialist press e.g. scientific american curta mechanical calculator slide rule frequent contributor mathematics youtube channel numberphile cliff stoll attended hutchinson central technical high school buffalo new york earned b.s astronomy 1973 university buffalo suny studying undergraduate degree suny buffalo stoll worked university electronic music laboratory mentored robert moog received phd university arizona 1980 1960s 1970s stoll assistant chief engineer wbfo public radio station hometown buffalo new york 1986 employed systems administrator lawrence berkeley national laboratory stoll investigated tenacious hacker—later identified kgb recruit markus hess—who stole passwords pirated multiple computer accounts attempted breach us military security identifying intrusion stoll set honeypot hess eventually tracking passing details authorities recognized one first examples digital forensics time gaining cooperation law enforcement challenge due relatively new nature crime described events investigation cuckoo egg tracking spy maze computer espionage paper stalking wily hacker stoll book later chronicled episode wgbh nova titled kgb computer aired pbs stations 1990 1995 book silicon snake oil accompanying article newsweek stoll called prospect e-commerce baloney stoll also raised questions influence internet future society whether would beneficial made various predictions article e.g. e-commerce calling nonviable due lack personal contact secure online funds transfers future printed news publications online database replace daily newspaper article resurfaced boing boing 2010 stoll left self-deprecating comment many mistakes flubs howlers public 1995 howler ... whenever think know happening temper thoughts might wrong cliff ... stoll eighth-grade physics teacher tehiyah day school el cerrito california later taught physics home-schooled teenagers stoll regular contributor msnbc site stoll fcc licensed amateur radio operator call sign k7ta appears frequently brady haran youtube series numberphile stoll sells blown glass klein bottles internet company acme klein bottles stores inventory crawlspace underneath home accesses needed homemade miniature robotic forklift runs company home
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Computer security
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enterprise information technology data repository eitdr enterprise information technology data repository eitdr united states air force official database presented webservice registering information technology systems maintaining portfolio management data database provides portfolio managers senior leaders investment decision support ability track report compliance federal laws regulations eitdr provides automated management processes common access point gather view load update query report store pertinent data disparate systems eitdr serves single point user entry af data electronic interface dod/af systems requiring data united states code title 40 subtitle iii chapter 113 requires air force chief information officer implement portfolio management process maximizing value assessing managing risks associated information technology acquisition use eitdr result law office secretary air force warfighting integration chief information officer saf/xc primary responsibility november 30 2006 eitdr recorded 146 systems operating budgets exceeding 1 million addition fy06 eitdr operations maintenance costs totaled 4.3 million may 1 2017 eitdr replaced itips system record compliance
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Databases
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information technology security audit computer security audit manual systematic measurable technical assessment system application manual assessments include interviewing staff performing security vulnerability scans reviewing application operating system access controls analyzing physical access systems automated assessments caat include system generated audit reports using software monitor report changes files settings system systems include personal computers servers mainframes network routers switches last decades systematic audit record generation also called audit event reporting described ad hoc early days mainframe mini-computing large scale single-vendor custom software systems companies ibm hewlett packard auditing considered mission-critical function last thirty years commercial off-the-shelf cots software applications components micro computers gradually replaced custom software hardware cost-effective business management solutions transition critical nature audit event reporting gradually transformed low priority customer requirements software consumers little else fall back simply accepted lesser standards normal consumer licenses existing cots software disclaim liability security performance data integrity issues using traditional logging methods applications components submit free-form text messages system logging facilities unix syslog process microsoft windows system security application event logs java applications often fall back standard java logging facility log4j text messages usually contain information assumed security-relevant application developer often computer- network-security expert fundamental problem free-form event records application developer individually determines information included audit event record overall format record presented audit log variation format among thousands instrumented applications makes job parsing audit event records analysis tools novell sentinel product example difficult error-prone domain application specific parsing code included analysis tools also difficult maintain changes event formats inevitably work way newer versions applications time contemporary enterprise operating systems including microsoft windows solaris mac os x freebsd via trustedbsd project support audit event logging due requirements common criteria historically orange book freebsd mac os x make use open source openbsm library command suite generate process audit records importance audit event logging increased recent new post-2000 us worldwide legislation mandating corporate enterprise auditing requirements open source projects openxdas bandit project identity component begun used software security reviews openxdas based open group distributed auditing service specification generally computer security audits performed
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Computer security
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computer surveillance workplace computer surveillance workplace use computers monitor activity workplace computer monitoring method collecting performance data employers obtain digitalised employee monitoring computer surveillance may nowadays used alongside traditional security applications closed-circuit television depending upon technology methods used monitoring applications may track activity may target specific activities employees company-owned computer terminal may monitor various devices installed computer e.g. web cameras microphones includes recordings devices also remote broadcasting live feed webcams microphones tools used monitoring employee computer usage incorporate also known employee monitoring industry employee monitoring used multiple reasons including compliance insider threat management employee monitoring software monitor application software including email instant message filesystem print jobs internet surveillance monitoring internet data traffic web access online activity may include monitoring internet traffic including encrypted web browser traffic secure socket layer ssl connections personal web-based email personal banking sites research done american management association nearly 30 percent employers united states monitor employee e-mails labor union contracts forms employment agreements may offer protection monitoring additionally united states public sector employees may protection fourth amendment united states constitution employees california may additional protection specific portions state statute employers may required maintain documentation emails communications regulatory compliance purposes monitoring email instant messaging communications may part requirements software used type surveillance may impose additional restrictions notification requirements based end user license agreement eula example spectorsoft requires employees signed contract stating computer activity may monitored employed additional legal issues may arise information obtained monitoring used illegal malicious purposes organizations without stated computer usage monitoring policy employees typically use company equipment respective discretion cases may visible restrictions monitoring activities performed computer use computer surveillance within employee discipline evaluation process may viewed employees invasion privacy lack trust employers right monitor employees united states course specific rules regulations must follow depending state legislation despite fact almost 80 major companies america actively monitor employees. public opinion still mostly employees ’ side americans still think monitoring workplace entirely acceptable according pew research center 6 respondents care monitored work
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Computer security
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search engine optimization search engine optimization seo process increasing quality quantity website traffic increasing visibility website web page users web search engine seo refers improvement unpaid results known natural organic results excludes direct traffic/visitors purchase paid placement primarily seo pertains search engine seo may target different kinds search including image search video search academic search news search industry-specific vertical search engines optimizing website may involve editing content adding content modifying html associated coding increase relevance specific keywords remove barriers indexing activities search engines promoting site increase number backlinks inbound links another seo tactic may 2015 mobile search surpassed desktop search internet marketing strategy seo considers search engines work computer programmed algorithms dictate search engine behavior people search actual search terms keywords typed search engines search engines preferred targeted audience seo performed website receive visitors search engine higher website ranks search engine results page serp visitors converted customers seo differs local search engine optimization latter focused optimizing business online presence web pages displayed search engines user enters local search products services former instead focused national international searches webmasters content providers began optimizing websites search engines mid-1990s first search engines cataloging early web initially webmasters needed submit address page url various engines would send spider crawl page extract links pages return information found page indexed process involves search engine spider downloading page storing search engine server second program known indexer extracts information page words contains located weight specific words well links page contains information placed scheduler crawling later date website owners recognized value high ranking visibility search engine results creating opportunity white hat black hat seo practitioners according industry analyst danny sullivan phrase search engine optimization probably came use 1997 sullivan credits bruce clay one first people popularize term may 2 2007 jason gambert attempted trademark term seo convincing trademark office arizona seo process involving manipulation keywords marketing service early versions search algorithms relied webmaster-provided information keyword meta tag index files engines like aliweb meta tags provide guide page content using metadata index pages found less reliable however webmaster choice keywords meta tag could potentially inaccurate representation site actual content inaccurate incomplete inconsistent data meta tags could cause pages rank irrelevant searches web content providers also manipulated attributes within html source page attempt rank well search engines 1997 search engine designers recognized webmasters making efforts rank well search engine webmasters even manipulating rankings search results stuffing pages excessive irrelevant keywords early search engines altavista infoseek adjusted algorithms prevent webmasters manipulating rankings relying much factors keyword density exclusively within webmaster control early search engines suffered abuse ranking manipulation provide better results users search engines adapt ensure results pages showed relevant search results rather unrelated pages stuffed numerous keywords unscrupulous webmasters meant moving away heavy reliance term density holistic process scoring semantic signals since success popularity search engine determined ability produce relevant results given search poor quality irrelevant search results could lead users find search sources search engines responded developing complex ranking algorithms taking account additional factors difficult webmasters manipulate 2005 annual conference airweb adversarial information retrieval web created bring together practitioners researchers concerned search engine optimization related topics companies employ overly aggressive techniques get client websites banned search results 2005 wall street journal reported company traffic power allegedly used high-risk techniques failed disclose risks clients wired magazine reported company sued blogger seo aaron wall writing ban google matt cutts later confirmed google fact ban traffic power clients search engines also reached seo industry frequent sponsors guests seo conferences webchats seminars major search engines provide information guidelines help website optimization google sitemaps program help webmasters learn google problems indexing website also provides data google traffic website bing webmaster tools provides way webmasters submit sitemap web feeds allows users determine crawl rate track web pages index status 2015 reported google developing promoting mobile search key feature within future products response many brands began take different approach internet marketing strategies 1998 two graduate students stanford university larry page sergey brin developed backrub search engine relied mathematical algorithm rate prominence web pages number calculated algorithm pagerank function quantity strength inbound links pagerank estimates likelihood given page reached web user randomly surfs web follows links one page another effect means links stronger others higher pagerank page likely reached random web surfer page brin founded google 1998 google attracted loyal following among growing number internet users liked simple design off-page factors pagerank hyperlink analysis considered well on-page factors keyword frequency meta tags headings links site structure enable google avoid kind manipulation seen search engines considered on-page factors rankings although pagerank difficult game webmasters already developed link building tools schemes influence inktomi search engine methods proved similarly applicable gaming pagerank many sites focused exchanging buying selling links often massive scale schemes link farms involved creation thousands sites sole purpose link spamming 2004 search engines incorporated wide range undisclosed factors ranking algorithms reduce impact link manipulation june 2007 new york times saul hansell stated google ranks sites using 200 different signals leading search engines google bing yahoo disclose algorithms use rank pages seo practitioners studied different approaches search engine optimization shared personal opinions patents related search engines provide information better understand search engines 2005 google began personalizing search results user depending history previous searches google crafted results logged users 2007 google announced campaign paid links transfer pagerank june 15 2009 google disclosed taken measures mitigate effects pagerank sculpting use nofollow attribute links matt cutts well-known software engineer google announced google bot would longer treat nofollow links way prevent seo service providers using nofollow pagerank sculpting result change usage nofollow led evaporation pagerank order avoid seo engineers developed alternative techniques replace nofollowed tags obfuscated javascript thus permit pagerank sculpting additionally several solutions suggested include usage iframes flash javascript december 2009 google announced would using web search history users order populate search results june 8 2010 new web indexing system called google caffeine announced designed allow users find news results forum posts content much sooner publishing google caffeine change way google updated index order make things show quicker google according carrie grimes software engineer announced caffeine google caffeine provides 50 percent fresher results web searches last index ... google instant real-time-search introduced late 2010 attempt make search results timely relevant historically site administrators spent months even years optimizing website increase search rankings growth popularity social media sites blogs leading engines made changes algorithms allow fresh content rank quickly within search results february 2011 google announced panda update penalizes websites containing content duplicated websites sources historically websites copied content one another benefited search engine rankings engaging practice however google implemented new system punishes sites whose content unique 2012 google penguin attempted penalize websites used manipulative techniques improve rankings search engine although google penguin presented algorithm aimed fighting web spam really focuses spammy links gauging quality sites links coming 2013 google hummingbird update featured algorithm change designed improve google natural language processing semantic understanding web pages hummingbird language processing system falls newly recognized term 'conversational search system pays attention word query order better match pages meaning query rather words regards changes made search engine optimization content publishers writers hummingbird intended resolve issues getting rid irrelevant content spam allowing google produce high-quality content rely 'trusted authors leading search engines google bing yahoo use crawlers find pages algorithmic search results pages linked search engine indexed pages need submitted found automatically yahoo directory dmoz two major directories closed 2014 2017 respectively required manual submission human editorial review google offers google search console xml sitemap feed created submitted free ensure pages found especially pages discoverable automatically following links addition url submission console yahoo formerly operated paid submission service guaranteed crawling cost per click however practice discontinued 2009 search engine crawlers may look number different factors crawling site every page indexed search engines distance pages root directory site may also factor whether pages get crawled today people searching google using mobile device november 2016 google announced major change way crawling websites started make index mobile-first means mobile version website becomes starting point google includes index avoid undesirable content search indexes webmasters instruct spiders crawl certain files directories standard robots.txt file root directory domain additionally page explicitly excluded search engine database using meta tag specific robots usually meta name= robots content= noindex search engine visits site robots.txt located root directory first file crawled robots.txt file parsed instruct robot pages crawled search engine crawler may keep cached copy file may occasion crawl pages webmaster wish crawled pages typically prevented crawled include login specific pages shopping carts user-specific content search results internal searches march 2007 google warned webmasters prevent indexing internal search results pages considered search spam variety methods increase prominence webpage within search results cross linking pages website provide links important pages may improve visibility writing content includes frequently searched keyword phrase relevant wide variety search queries tend increase traffic updating content keep search engines crawling back frequently give additional weight site adding relevant keywords web page metadata including title tag meta description tend improve relevancy site search listings thus increasing traffic url canonicalization web pages accessible via multiple urls using canonical link element via 301 redirects help make sure links different versions url count towards page link popularity score seo techniques classified two broad categories techniques search engine companies recommend part good design white hat techniques search engines approve black hat search engines attempt minimize effect latter among spamdexing industry commentators classified methods practitioners employ either white hat seo black hat seo white hats tend produce results last long time whereas black hats anticipate sites may eventually banned either temporarily permanently search engines discover seo technique considered white hat conforms search engines guidelines involves deception search engine guidelines written series rules commandments important distinction note white hat seo following guidelines ensuring content search engine indexes subsequently ranks content user see white hat advice generally summed creating content users search engines making content easily accessible online spider algorithms rather attempting trick algorithm intended purpose white hat seo many ways similar web development promotes accessibility although two identical black hat seo attempts improve rankings ways disapproved search engines involve deception one black hat technique uses hidden text either text colored similar background invisible div positioned screen another method gives different page depending whether page requested human visitor search engine technique known cloaking another category sometimes used grey hat seo black hat white hat approaches methods employed avoid site penalized act producing best content users grey hat seo entirely focused improving search engine rankings search engines may penalize sites discover using black hat methods either reducing rankings eliminating listings databases altogether penalties applied either automatically search engines algorithms manual site review one example february 2006 google removal bmw germany ricoh germany use deceptive practices companies however quickly apologized fixed offending pages restored google search engine results page seo appropriate strategy every website internet marketing strategies effective paid advertising pay per click ppc campaigns depending site operator goals search engine marketing sem practice designing running optimizing search engine ad campaigns difference seo simply depicted difference paid unpaid priority ranking search results purpose regards prominence relevance website developers regard sem utmost importance consideration visibility navigate primary listings search successful internet marketing campaign may also depend upon building high quality web pages engage persuade setting analytics programs enable site owners measure results improving site conversion rate november 2015 google released full 160 page version search quality rating guidelines public revealed shift focus towards usefulness mobile search recent years mobile market exploded overtaking use desktops shown statcounter october 2016 analyzed 2.5 million websites found 51.3 pages loaded mobile device google one companies utilizing popularity mobile usage encouraging websites use google search console mobile-friendly test allows companies measure website search engine results user-friendly seo may generate adequate return investment however search engines paid organic search traffic algorithms change guarantees continued referrals due lack guarantees certainty business relies heavily search engine traffic suffer major losses search engines stop sending visitors search engines change algorithms impacting website placement possibly resulting serious loss traffic according google ceo eric schmidt 2010 google made 500 algorithm changes – almost 1.5 per day considered wise business practice website operators liberate dependence search engine traffic addition accessibility terms web crawlers addressed user web accessibility become increasingly important seo optimization techniques highly tuned dominant search engines target market search engines market shares vary market market competition 2003 danny sullivan stated google represented 75 searches markets outside united states google share often larger google remains dominant search engine worldwide 2007 2006 google 85–90 market share germany hundreds seo firms us time five germany june 2008 market share google uk close 90 according hitwise market share achieved number countries 2009 large markets google leading search engine cases google leading given market lagging behind local player notable example markets china japan south korea russia czech republic respectively baidu yahoo japan naver yandex seznam market leaders successful search optimization international markets may require professional translation web pages registration domain name top level domain target market web hosting provides local ip address otherwise fundamental elements search optimization essentially regardless language october 17 2002 searchking filed suit united states district court western district oklahoma search engine google searchking claim google tactics prevent spamdexing constituted tortious interference contractual relations may 27 2003 court granted google motion dismiss complaint searchking failed state claim upon relief may granted march 2006 kinderstart filed lawsuit google search engine rankings kinderstart website removed google index prior lawsuit amount traffic site dropped 70 march 16 2007 united states district court northern district california san jose division dismissed kinderstart complaint without leave amend partially granted google motion rule 11 sanctions kinderstart attorney requiring pay part google legal expenses
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Web technology
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peer-to-peer peer-to-peer p2p computing networking distributed application architecture partitions tasks workloads peers peers equally privileged equipotent participants application said form peer-to-peer network nodes peers make portion resources processing power disk storage network bandwidth directly available network participants without need central coordination servers stable hosts peers suppliers consumers resources contrast traditional client-server model consumption supply resources divided emerging collaborative p2p systems going beyond era peers similar things sharing resources looking diverse peers bring unique resources capabilities virtual community thereby empowering engage greater tasks beyond accomplished individual peers yet beneficial peers p2p systems previously used many application domains architecture popularized file sharing system napster originally released 1999 concept inspired new structures philosophies many areas human interaction social contexts peer-to-peer meme refers egalitarian social networking emerged throughout society enabled internet technologies general p2p systems previously used many application domains concept popularized file sharing systems music-sharing application napster originally released 1999 peer-to-peer movement allowed millions internet users connect directly forming groups collaborating become user-created search engines virtual supercomputers filesystems basic concept peer-to-peer computing envisioned earlier software systems networking discussions reaching back principles stated first request comments rfc 1 tim berners-lee vision world wide web close p2p network assumed user web would active editor contributor creating linking content form interlinked web links early internet open present day two machines connected internet could send packets without firewalls security measures contrasts broadcasting-like structure web developed years precursor internet arpanet successful client-server network every participating node could request serve content however arpanet self-organized lacked ability provide means context content-based routing beyond 'simple address-based routing therefore usenet distributed messaging system often described early peer-to-peer architecture established developed 1979 system enforces decentralized model control basic model client-server model user client perspective offers self-organizing approach newsgroup servers however news servers communicate one another peers propagate usenet news articles entire group network servers consideration applies smtp email sense core email-relaying network mail transfer agents peer-to-peer character periphery e-mail clients direct connections strictly client-server relationship may 1999 millions people internet shawn fanning introduced music file-sharing application called napster napster beginning peer-to-peer networks know today participating users establish virtual network entirely independent physical network without obey administrative authorities restrictions peer-to-peer network designed around notion equal peer nodes simultaneously functioning clients servers nodes network model network arrangement differs client–server model communication usually central server typical example file transfer uses client-server model file transfer protocol ftp service client server programs distinct clients initiate transfer servers satisfy requests peer-to-peer networks generally implement form virtual overlay network top physical network topology nodes overlay form subset nodes physical network data still exchanged directly underlying tcp/ip network application layer peers able communicate directly via logical overlay links corresponds path underlying physical network overlays used indexing peer discovery make p2p system independent physical network topology based nodes linked within overlay network resources indexed located classify networks unstructured structured hybrid two unstructured peer-to-peer networks impose particular structure overlay network design rather formed nodes randomly form connections gnutella gossip kazaa examples unstructured p2p protocols structure globally imposed upon unstructured networks easy build allow localized optimizations different regions overlay also role peers network unstructured networks highly robust face high rates churn —that large numbers peers frequently joining leaving network however primary limitations unstructured networks also arise lack structure particular peer wants find desired piece data network search query must flooded network find many peers possible share data flooding causes high amount signaling traffic network uses cpu/memory requiring every peer process search queries ensure search queries always resolved furthermore since correlation peer content managed guarantee flooding find peer desired data popular content likely available several peers peer searching likely find thing peer looking rare data shared peers highly unlikely search successful structured peer-to-peer networks overlay organized specific topology protocol ensures node efficiently search network file/resource even resource extremely rare common type structured p2p networks implement distributed hash table dht variant consistent hashing used assign ownership file particular peer enables peers search resources network using hash table key value pairs stored dht participating node efficiently retrieve value associated given key however order route traffic efficiently network nodes structured overlay must maintain lists neighbors satisfy specific criteria makes less robust networks high rate churn i.e large numbers nodes frequently joining leaving network recent evaluation p2p resource discovery solutions real workloads pointed several issues dht-based solutions high cost advertising/discovering resources static dynamic load imbalance notable distributed networks use dhts include tixati alternative bittorrent distributed tracker kad network storm botnet yacy coral content distribution network prominent research projects include chord project kademlia past storage utility p-grid self-organized emerging overlay network coopnet content distribution system dht-based networks also widely utilized accomplishing efficient resource discovery grid computing systems aids resource management scheduling applications hybrid models combination peer-to-peer client-server models common hybrid model central server helps peers find spotify example hybrid model 2014 variety hybrid models make trade-offs centralized functionality provided structured server/client network node equality afforded pure peer-to-peer unstructured networks currently hybrid models better performance either pure unstructured networks pure structured networks certain functions searching require centralized functionality benefit decentralized aggregation nodes provided unstructured networks coopnet cooperative networking proposed system off-loading serving peers recently downloaded content proposed computer scientists venkata n. padmanabhan kunwadee sripanidkulchai working microsoft research carnegie mellon university basically server experiences increase load redirects incoming peers peers agreed mirror content thus off-loading balance server information retained server system makes use fact bottle-neck likely outgoing bandwidth cpu hence server-centric design assigns peers peers 'close ip neighbors prefix range attempt use locality multiple peers found file designates node choose fastest neighbors streaming media transmitted clients cache previous stream transmit piece-wise new nodes peer-to-peer systems pose unique challenges computer security perspective like form software p2p applications contain vulnerabilities makes particularly dangerous p2p software however peer-to-peer applications act servers well clients meaning vulnerable remote exploits also since node plays role routing traffic network malicious users perform variety routing attacks denial service attacks examples common routing attacks include incorrect lookup routing whereby malicious nodes deliberately forward requests incorrectly return false results incorrect routing updates malicious nodes corrupt routing tables neighboring nodes sending false information incorrect routing network partition new nodes joining bootstrap via malicious node places new node partition network populated malicious nodes prevalence malware varies different peer-to-peer protocols studies analyzing spread malware p2p networks found example 63 answered download requests gnutella network contained form malware whereas 3 content openft contained malware cases top three common types malware accounted large majority cases 99 gnutella 65 openft another study analyzing traffic kazaa network found 15 500,000 file sample taken infected one 365 different computer viruses tested corrupted data also distributed p2p networks modifying files already shared network example fasttrack network riaa managed introduce faked chunks downloads downloaded files mostly mp3 files files infected riaa virus unusable afterwards contained malicious code riaa also known uploaded fake music movies p2p networks order deter illegal file sharing consequently p2p networks today seen enormous increase security file verification mechanisms modern hashing chunk verification different encryption methods made networks resistant almost type attack even major parts respective network replaced faked nonfunctional hosts decentralized nature p2p networks increases robustness removes single point failure inherent client-server based system nodes arrive demand system increases total capacity system also increases likelihood failure decreases one peer network fails function properly whole network compromised damaged contrast typical client–server architecture clients share demands system resources case clients join system fewer resources available serve client central server fails entire network taken advantages disadvantages p2p networks related topic data backup recovery availability centralized network system administrators forces controlling availability files shared administrators decide longer distribute file simply remove servers longer available users along leaving users powerless deciding distributed throughout community makes entire system vulnerable threats requests government large forces example youtube pressured riaa mpaa entertainment industry filter copyrighted content although server-client networks able monitor manage content availability stability availability content choose host client trouble accessing obscure content shared stable centralized network p2p networks however unreliable sharing unpopular files sharing files p2p network requires least one node network requested data node must able connect node requesting data requirement occasionally hard meet users may delete stop sharing data point sense community users p2p network completely responsible deciding content available unpopular files eventually disappear become unavailable people stop sharing popular files however highly easily distributed popular files p2p network actually stability availability files central networks centralized network simple loss connection server clients enough cause failure p2p networks connections every node must lost order cause data sharing failure centralized system administrators responsible data recovery backups p2p systems node requires backup system lack central authority p2p networks forces recording industry riaa mpaa government unable delete stop sharing content p2p systems p2p networks clients provide use resources means unlike client-server systems content-serving capacity peer-to-peer networks actually increase users begin access content especially protocols bittorrent require users share refer performance measurement study property one major advantages using p2p networks makes setup running costs small original content distributor many file peer-to-peer file sharing networks gnutella g2 edonkey network popularized peer-to-peer technologies peer-to-peer networking involves data transfer one user another without using intermediate server companies developing p2p applications involved numerous legal cases primarily united states conflicts copyright law two major cases grokster vs riaa mgm studios inc. v. grokster ltd. last case court unanimously held defendant peer-to-peer file sharing companies grokster streamcast could sued inducing copyright infringement companies power ledger bovlabs employ peer-to-peer energy trading platforms cooperation among community participants key continued success p2p systems aimed casual human users reach full potential large numbers nodes contribute resources current practice p2p networks often contain large numbers users utilize resources shared nodes share anything often referred freeloader problem freeloading profound impact network cases cause community collapse types networks users natural disincentives cooperate cooperation consumes resources may degrade performance studying social attributes p2p networks challenging due large populations turnover asymmetry interest zero-cost identity variety incentive mechanisms implemented encourage even force nodes contribute resources researchers explored benefits enabling virtual communities self-organize introduce incentives resource sharing cooperation arguing social aspect missing today p2p systems seen goal means self-organized virtual communities built fostered ongoing research efforts designing effective incentive mechanisms p2p systems based principles game theory beginning take psychological information-processing direction peer-to-peer networks e.g freenet place heavy emphasis privacy anonymity—that ensuring contents communications hidden eavesdroppers identities/locations participants concealed public key cryptography used provide encryption data validation authorization authentication data/messages onion routing mix network protocols e.g tarzan used provide anonymity although peer-to-peer networks used legitimate purposes rights holders targeted peer-to-peer involvement sharing copyrighted material peer-to-peer networking involves data transfer one user another without using intermediate server companies developing p2p applications involved numerous legal cases primarily united states primarily issues surrounding copyright law two major cases grokster vs riaa mgm studios inc. v. grokster ltd. cases file sharing technology ruled legal long developers ability prevent sharing copyrighted material establish criminal liability copyright infringement peer-to-peer systems government must prove defendant infringed copyright willingly purpose personal financial gain commercial advantage fair use exceptions allow limited use copyrighted material downloaded without acquiring permission rights holders documents usually news reporting lines research scholarly work controversies developed concern illegitimate use peer-to-peer networks regarding public safety national security file downloaded peer-to-peer network impossible know created file users connected network given time trustworthiness sources potential security threat seen peer-to-peer systems study ordered european union found illegal downloading may lead increase overall video game sales newer games charge extra features levels paper concluded piracy negative financial impact movies music literature study relied self-reported data game purchases use illegal download sites pains taken remove effects false misremembered responses peer-to-peer applications present one core issues network neutrality controversy internet service providers isps known throttle p2p file-sharing traffic due high-bandwidth usage compared web browsing e-mail many uses internet data transferred short intervals relative small quantities p2p file-sharing often consists relatively heavy bandwidth usage due ongoing file transfers swarm/network coordination packets october 2007 comcast one largest broadband internet providers united states started blocking p2p applications bittorrent rationale p2p mostly used share illegal content infrastructure designed continuous high-bandwidth traffic critics point p2p networking legitimate legal uses another way large providers trying control use content internet direct people towards client-server-based application architecture client-server model provides financial barriers-to-entry small publishers individuals less efficient sharing large files reaction bandwidth throttling several p2p applications started implementing protocol obfuscation bittorrent protocol encryption techniques achieving protocol obfuscation involves removing otherwise easily identifiable properties protocols deterministic byte sequences packet sizes making data look random isp solution high bandwidth p2p caching isp stores part files accessed p2p clients order save access internet researchers used computer simulations aid understanding evaluating complex behaviors individuals within network networking research often relies simulation order test evaluate new ideas important requirement process results must reproducible researchers replicate validate extend existing work research reproduced opportunity research hindered even though new simulators continue released research community tends towards handful open-source simulators demand features simulators shown criteria survey high therefore community work together get features open-source software would reduce need custom simulators hence increase repeatability reputability experiments besides stated facts work done ns-2 open source network simulator one research issue related free rider detection punishment explored using ns-2 simulator
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Distributed computing architecture
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pirni pirni pro network security tool designed ios specifically iphone ipod touch devices capable intercepting traffic wireless network segment capturing passwords regular expressions entered user core system pirni written c open-source software licensed gnu general public license pirni pro succeeding version pirni commercial software available cydia store jailbroken apple devices pirni pro supports active dissection non-ciphered protocols given user supplied regular expression dissection application description contains following addition software also offers following features
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Computer security
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smsq/e smsq/e computer operating system originally developed france tony tebby designer original qdos operating system sinclair ql personal computer began life smsq qdos-compatible version sms2 intended miracle systems qxl emulator card pcs later developed extended version smsq/e atari st consists qdos compatible sms kernel rewritten superbasic interpreter called sbasic complete set superbasic procedures functions set extended device drivers originally written ql emulator atari st also integrates many extensions previously available separately ql like toolkit ii quite essential superbasic add-on pointer environment ql mouse windowing system hotkey system 2 smsq/e run unmodified ql runs advanced ql compatible platforms miracle systems super goldcard cpu plug-in cards q60 motherboard late 1995 german author marcel kilgus acquired smsq/e sources adaptation ql emulator qpc emulate specific ql hardware anymore employed specially adapted device drivers achieve tighter integration faster emulation 2000 version 2.94 first ql operating system broke free bounds ql 8 colour screen introducing gd2 graphic device interface version 2 ql compatible 16-bit high colour graphics sub-system version 2.99 system exclusively developed tony tebby marcel kilgus 2002 mr tebby released source code n't include qpc specific parts albeit license open source open source definition step tony tebby finally left ql scene development volunteers continues day early 2013 current source code re-released bsd license currently smsq/e consists approximately 2000 68k assembler source files containing 222,000 lines code
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Operating systems
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ubifs ubifs ubi file system fully unsorted block image file system flash file system unmanaged flash memory devices ubifs works top ubi unsorted block image layer top memory technology device mtd layer file system developed nokia engineers help university szeged hungary development began earnest 2007 first stable release made linux kernel 2.6.27 october 2008 two major differences ubifs jffs2 ubifs supports write caching ubifs errs pessimistic side free space calculation ubifs tends perform better jffs2 large nand flash devices consequence ubifs design goals faster mounting quicker access large files improved write speeds ubifs also preserves improves upon jffs2 on-the-fly compression recoverability power fail tolerance ubifs on-the-fly data compression allows zlib deflate algorithm lzo zstandard ubifs stores indexes flash whereas jffs2 stores filesystem indexes memory directly impacts scalability jffs2 tables must rebuilt every time volume mounted also jffs2 tables may consume enough system ram images may unusable ubi unsorted block images erase block management layer flash memory devices ubi serves two purposes tracking nand flash bad blocks providing wear leveling wear leveling spreads erases writes across entire flash device ubi presents logical erase blocks higher layers maps physical erase blocks ubi written specifically ubifs ubifs deal wear leveling bad blocks however ubi may also useful squashfs nand flash squashfs aware nand flash bad blocks ubi documentation explains complete flash translation layer ftl although ftl also handles bad blocks wear leveling interface ftl provides block device small typically 512 byte sectors written completely independently contrast ubi interface directly exposes erase blocks programmable pages different sizes much larger typical block device sectors filesystems use ubi must aware sizes restrictions blocks must erased written ubi augmented linux 3.7 fastmap support fastmap maintains on-disk version information previously created memory scanning entire flash device code falls back previous mechanism full scan failures older ubi systems simply ignore fastmap information
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Computer file systems
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php php hypertext preprocessor simply php general-purpose programming language originally designed web development originally created rasmus lerdorf 1994 php reference implementation produced php group php originally stood personal home page stands recursive initialism php hypertext preprocessor php code may executed command line interface cli embedded html code used combination various web template systems web content management systems web frameworks php code usually processed php interpreter implemented module web server common gateway interface cgi executable web server outputs results interpreted executed php code may type data generated html code binary image data php used many programming tasks outside web context standalone graphical applications robotic drone control standard php interpreter powered zend engine free software released php license php widely ported deployed web servers almost every operating system platform free charge php language evolved without written formal specification standard 2014 original implementation acting de facto standard implementations aimed follow since 2014 work gone create formal php specification majority sites web using php still version 5.6 older versions prior 7.1 longer officially supported php development team security support provided longer third parties debian php development began 1994 rasmus lerdorf wrote several common gateway interface cgi programs c used maintain personal homepage extended work web forms communicate databases called implementation personal home page/forms interpreter php/fi php/fi could used build simple dynamic web applications accelerate bug reporting improve code lerdorf initially announced release php/fi personal home page tools php tools version 1.0 usenet discussion group comp.infosystems.www.authoring.cgi june 8 1995 release already basic functionality php today included perl-like variables form handling ability embed html syntax resembled perl simpler limited less consistent early php intended new programming language grew organically lerdorf noting retrospect n't know stop never intent write programming language ... absolutely idea write programming language kept adding next logical step way development team began form months work beta testing officially released php/fi 2 november 1997 fact php originally designed instead developed organically led inconsistent naming functions inconsistent ordering parameters cases function names chosen match lower-level libraries php wrapping early versions php length function names used internally hash function names chosen improve distribution hash values zeev suraski andi gutmans rewrote parser 1997 formed base php 3 changing language name recursive acronym php hypertext preprocessor afterwards public testing php 3 began official launch came june 1998 suraski gutmans started new rewrite php core producing zend engine 1999 also founded zend technologies ramat gan israel may 22 2000 php 4 powered zend engine 1.0 released august 2008 branch reached version 4.4.9 php 4 longer development security updates released july 14 2004 php 5 released powered new zend engine ii php 5 included new features improved support object-oriented programming php data objects pdo extension defines lightweight consistent interface accessing databases numerous performance enhancements 2008 php 5 became stable version development late static binding missing php added version 5.3 many high-profile open-source projects ceased support php 4 new code february 5 2008 gophp5 initiative provided consortium php developers promoting transition php 4 php 5 time php interpreters became available existing 32-bit 64-bit operating systems either building php source code using pre-built binaries php versions 5.3 5.4 available microsoft windows binary distributions 32-bit ia-32 builds requiring windows 32-bit compatibility mode using internet information services iis 64-bit windows platform php version 5.5 made 64-bit x86-64 builds available microsoft windows official security support php 5.6 ended 31 december 2018 debian 8.0 jessie extend support june 2020 php received mixed reviews due lacking native unicode support core language level 2005 project headed andrei zmievski initiated bring native unicode support throughout php embedding international components unicode icu library representing text strings utf-16 internally since would cause major changes internals language user code planned release version 6.0 language along major features development however shortage developers understood necessary changes performance problems arising conversion utf-16 rarely used web context led delays project result php 5.3 release created 2009 many non-unicode features back-ported php 6 notably namespaces march 2010 project current form officially abandoned php 5.4 release prepared containing remaining non-unicode features php 6 traits closure re-binding initial hopes new plan would formed unicode integration none adopted 2014 2015 new major php version developed numbered php 7 numbering version involved debate php 6 unicode experiment never released several articles book titles referenced php 6 name might caused confusion new release reuse name vote name php 7 chosen foundation php 7 php branch originally dubbed php next generation phpng authored dmitry stogov xinchen hui nikita popov aimed optimize php performance refactoring zend engine retaining near-complete language compatibility wordpress-based benchmarks served main benchmark suite phpng project showed almost 100 increase performance changes phpng also expected make easier improve performance future compact data structures changes seen better suited successful migration just-in-time jit compiler significant changes reworked zend engine called zend engine 3 succeeding zend engine 2 used php 5 major internal changes phpng must receive new major version number php rather minor php 5 release according php release process major versions php allowed break backward-compatibility code therefore php 7 presented opportunity improvements beyond phpng require backward-compatibility breaks particular involved following changes php 7 also included new language features notably introduces return type declarations functions complement existing parameter type declarations support scalar types integer float string boolean parameter return type declarations beginning june 28 2011 php development team implemented timeline release new versions php system least one release occur every month per year minor release occur may include new features every minor release least supported two years security bug fixes followed least one year security fixes total three-year release process every minor release new features unless small self-contained introduced minor release three-year release process mascot php project elephpant blue elephant php logo side designed vincent pontier 1998 php letters forming shape elephant viewed sideways angle elephpant sometimes differently colored plush toy form many variations mascot made years elephpants based original design vincent pontier considered official community highly collectible extremely rare different variations listed field guide elephpants following hello world program written php code embedded html document doctype html title php hello world program /title php echo p hello world /p however requirement exists php code embedded html simplest version hello world may written like closing tag omitted preferred files containing pure php code well requirement php file contain php code interpreter output data outside php tags unchanged simple text file containing codice_13 give output php interpreter executes php code within delimiters anything outside delimiters processed php although non-php text still subject control structures described php code common delimiters php open close php sections shortened form also exists short delimiter makes script files less portable since support disabled local php configuration therefore discouraged recommendation echo short tag prior php 5.4.0 short syntax echo works codice_14 configuration setting enabled php 5.4.0 later always available purpose delimiters separate php code non-php content javascript code html markup first form delimiters php xhtml xml documents creates correctly formed xml processing instructions means resulting mixture php code markup server-side file well-formed xml variables prefixed dollar symbol type need specified advance php 5 introduced type hinting allows functions force parameters objects specific class arrays interfaces callback functions however php 7.0 type hints could used scalar types integer string unlike function class names variable names case sensitive double-quoted heredoc strings provide ability interpolate variable value string php treats newlines whitespace manner free-form language statements terminated semicolon php three types comment syntax /* */ marks block inline comments // used one-line comments codice_15 statement one several facilities php provides output text terms keywords language syntax php similar c style syntax conditions loops function returns similar syntax languages c c++ c java perl php stores integers platform-dependent range either 64-bit 32-bit 128-bit signed integer equivalent c-language long type unsigned integers converted signed values certain situations behavior different programming languages integer variables assigned using decimal positive negative octal hexadecimal binary notations floating point numbers also stored platform-specific range specified using floating point notation two forms scientific notation php native boolean type similar native boolean types java c++ using boolean type conversion rules non-zero values interpreted true zero false perl c++ null data type represents variable value codice_16 allowed value data type old versions interpreter allowed multiple copies value exist variables resource type represent references resources external sources typically created functions particular extension processed functions extension examples include file image database resources arrays contain elements type php handle including resources objects even arrays order preserved lists values hashes keys values two intermingled php also supports strings used single quotes double quotes nowdoc heredoc syntax standard php library spl attempts solve standard problems implements efficient data access interfaces classes php defines large array functions core language many also available various extensions functions well documented online php documentation however built-in library wide variety naming conventions associated inconsistencies described history custom functions may defined developer function myage int birthyear string echo currently myage 1995 old 2019 output sample program currently 24 years old lieu function pointers functions php referenced string containing name manner normal php functions used example callbacks within function tables user-defined functions may created time without prototyped functions may defined inside code blocks permitting run-time decision whether function defined codice_17 function determines whether function given name already defined function calls must use parentheses exception zero-argument class constructor functions called php operator codice_18 case parentheses optional php 5.3 support anonymous functions closures exist php codice_19 exists since php 4.0.1 merely thin wrapper around codice_20 allows normal php functions created program execution php 5.3 added syntax define anonymous function closure capture variables surrounding scope function getadder x adder getadder 8 echo adder 2 // prints 10 example codice_21 function creates closure using passed argument keyword codice_22 imports variable lexical context takes additional argument returns created closure caller function first-class object meaning stored variable passed parameter functions etc unusually dynamically typed language php supports type declarations function parameters enforced runtime supported classes interfaces since php 5.0 arrays since php 5.1 callables since php 5.4 scalar integer float string boolean types since php 7.0 php 7.0 also type declarations function return types expressed placing type name list parameters preceded colon example codice_23 function earlier example could annotated types like php 7 function getadder int x closure adder getadder 8 echo adder 2 // prints 10 echo adder null // throws exception incorrect type passed adder getadder // would also throw exception default scalar type declarations follow weak typing principles example parameter type codice_24 php would allow integers also convertible numeric strings floats booleans passed function would convert however php 7 strict typing mode used disallows conversions function calls returns within file basic object-oriented programming functionality added php 3 improved php 4 allowed php gain abstraction making creative tasks easier programmers using language object handling completely rewritten php 5 expanding feature set enhancing performance previous versions php objects handled like value types drawback method code make heavy use php reference variables wanted modify object passed rather creating copy new approach objects referenced handle value php 5 introduced private protected member variables methods along abstract classes final classes abstract methods final methods also introduced standard way declaring constructors destructors similar object-oriented languages c++ standard exception handling model furthermore php 5 added interfaces allowed multiple interfaces implemented special interfaces allow objects interact runtime system objects implementing arrayaccess used array syntax objects implementing iterator iteratoraggregate used codice_6 language construct virtual table feature engine static variables bound name instead reference compile time developer creates copy object using reserved word codice_26 zend engine check whether codice_27 method defined call default codice_27 copy object properties codice_27 method defined responsible setting necessary properties created object convenience engine supply function imports properties source object programmer start by-value replica source object override properties need changed following basic example object-oriented programming php php abstract class user class student extends user class teacher extends user students teachers echo students \n foreach students student echo teachers \n foreach teachers teacher // output program // students // hello name alice learn computer science // hello name bob learn computer science // hello name charlie learn business studies // teachers // hello name dan teach computer science information security // hello name erin teach computer science 3d graphics programming // hello name frankie teach online marketing business studies e-commerce visibility php properties methods defined using keywords codice_30 codice_31 codice_32 default public var used codice_33 synonym codice_30 items declared codice_30 accessed everywhere codice_32 limits access inherited classes class defines item codice_31 limits visibility class defines item objects type access private protected members even though instance original complete widely used php implementation powered zend engine known simply php disambiguate implementations sometimes unofficially called zend php zend engine compiles php source code on-the-fly internal format execute thus works interpreter also reference implementation php php formal specification semantics zend php define semantics php due complex nuanced semantics php defined zend works difficult competing implementations offer complete compatibility php single-request-per-script-execution model fact zend engine interpreter leads inefficiency result various products developed help improve php performance order speed execution time compile php source code every time web page accessed php scripts also deployed php engine internal format using opcode cache works caching compiled form php script opcodes shared memory avoid overhead parsing compiling code every time script runs opcode cache zend opcache built php since version 5.5 another example widely used opcode cache alternative php cache apc available pecl extension zend php still popular implementation several implementations developed compilers support jit compilation hence offer performance benefits zend php expense lacking full php compatibility alternative implementations include following php free software released php license stipulates restriction use php makes php license incompatible general public license gpl zend license incompatible due advertising clause similar original bsd license php includes various free open-source libraries source distribution uses resulting php binary builds php fundamentally internet-aware system built-in modules accessing file transfer protocol ftp servers many database servers including postgresql mysql microsoft sql server sqlite embedded database ldap servers others numerous functions familiar c programmers stdio family available standard php builds php allows developers write extensions c add functionality php language php extensions compiled statically php loaded dynamically runtime numerous extensions written add support windows api process management unix-like operating systems multibyte strings unicode curl several popular compression formats php features made available extensions include integration irc dynamic generation images adobe flash content php data objects pdo abstraction layer used accessing databases even speech synthesis language core functions dealing strings arrays also implemented extensions php extension community library pecl project repository extensions php language projects zephir provide ability php extensions created high-level language compiled native php extensions approach instead writing php extensions directly c simplifies development extensions reduces time required programming testing php group consisted ten people thies c. arntzen stig bakken shane caraveo andi gutmans rasmus lerdorf sam ruby sascha schumann zeev suraski jim winstead andrei zmievski zend technologies provides php certification based php 5.5 exam programmers become certified php developers two primary ways adding support php web server – native web server module cgi executable php direct module interface called server application programming interface sapi supported many web servers including apache http server microsoft iis netscape defunct iplanet web servers omnihttpd support internet server application programming interface isapi microsoft web server module interface php module support web server always used common gateway interface cgi fastcgi processor case web server configured use php cgi executable process requests php files php-fpm fastcgi process manager alternative fastcgi implementation php bundled official php distribution since version 5.3.3 compared older fastcgi implementation contains additional features mostly useful heavily loaded web servers using php command-line scripting php command-line interface cli executable needed php supports cli server application programming interface sapi php 4.3.0 main focus sapi developing shell applications using php quite differences cli sapi sapis although share many behaviors php direct module interface called sapi different web servers case php 5 apache 2.0 windows provided form dll file called module among functions provides interface php web server implemented form server understands form known sapi different kinds sapis various web server extensions example addition listed sapis php language include common gateway interface cgi command-line interface cli php also used writing desktop graphical user interface gui applications using php-gtk extension php-gtk included official php distribution extension used php versions 5.1.0 newer common way installing php-gtk compiling source code php installed used cloud environments software development kits sdks provided using cloud-specific features example numerous configuration options supported affecting core php features extensions configuration file codice_40 searched different locations depending way php used configuration file split various sections configuration options also set within web server configuration php general-purpose scripting language especially suited server-side web development case php generally runs web server php code requested file executed php runtime usually create dynamic web page content dynamic images used websites elsewhere also used command-line scripting client-side graphical user interface gui applications php deployed web servers many operating systems platforms used many relational database management systems rdbms web hosting providers support php use clients available free charge php group provides complete source code users build customize extend use originally designed create dynamic web pages php focuses mainly server-side scripting similar server-side scripting languages provide dynamic content web server client microsoft asp.net sun microsystems javaserver pages codice_41 php also attracted development many software frameworks provide building blocks design structure promote rapid application development rad include prado cakephp symfony codeigniter laravel yii framework phalcon zend framework offering features similar web frameworks lamp architecture become popular web industry way deploying web applications php commonly used p bundle alongside linux apache mysql although p may also refer python perl mix three similar packages wamp mamp also available windows macos first letter standing respective operating system although php apache provided part macos base install users packages seek simpler installation mechanism easily kept date 20 million internet domains web services hosted servers php installed codice_42 recorded popular apache http server module php used server-side programming language 79.1 websites 83.5 previously language could determined web content management systems written php include mediawiki joomla ez publish ez platform silverstripe wordpress drupal moodle websites written php back-end and/or user-facing portion include facebook digg tumblr dailymotion slack specific advanced usage scenarios php offers well defined documented way writing custom extensions c c++ besides extending language form additional libraries extensions providing way improving execution speed critical room improvements using true compiled language php also offers well defined ways embedding software projects way php easily used internal scripting language another project also providing tight interfacing project specific internal data structures php received mixed reviews due lacking support multithreading core language level though using threads made possible pthreads pecl extension php used 240 million websites 39 sampled installed 2.1 million web servers command line interface php-cli two activex windows script host scripting engines php produced php 5 used web last updated security updates january 2019 php 5.6.40 2017 3 vulnerabilities listed national vulnerability database linked php historically 30 vulnerabilities listed since 1996 database linked php technical security flaws language core libraries frequent 22 2009 1 total although php applies 20 programs listed recognizing programmers make mistakes languages include taint checking automatically detect lack input validation induces many issues feature developed php inclusion release rejected several times past advanced protection patches suhosin hardening-patch especially designed web hosting environments historically old versions php configuration parameters default values runtime settings made php applications prone security issues among codice_43 codice_44 configuration directives best known latter made url parameters become php variables opening path serious security vulnerabilities allowing attacker set value uninitialized global variable interfere execution php script support magic quotes register globals settings deprecated php 5.3.0 removed php 5.4.0 another example potential runtime-settings vulnerability comes failing disable php execution example using codice_45 configuration directive directory uploaded files stored enabling result execution malicious code embedded within uploaded files best practice either locate image directory outside document root available web server serve via intermediary script disable php execution directory stores uploaded files also enabling dynamic loading php extensions via codice_46 configuration directive shared web hosting environment lead security issues implied type conversions result different values treated equal sometimes programmer intent lead security issues example result comparison codice_47 first compared value treated scientific notation value zero errors like resulted authentication vulnerabilities simple machines forum typo3 phpbb md5 password hashes compared recommended way use hash_equals timing attack safety codice_48 identity operator codice_49 results codice_50 2013 analysis 170,000 website defacements published zone-h frequently 53 used technique exploitation file inclusion vulnerability mostly related insecure usage php functions codice_51 codice_52 codice_53
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Programming language topics
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idex biometrics idex biometrics asa norwegian biometrics company specialising fingerprint imaging fingerprint recognition technology company founded 1996 headquartered oslo 2013 idex opened two u.s.-based offices one silicon valley california another boston massachusetts idex offers fingerprint sensor biometric software identity cards banking cards smart cards access control healthcare iot security solutions fingerprint recognition one form biometric identification examples dna face recognition iris recognition retinal scan well identification based behavioral patterns speaker recognition keystroke dynamics signature recognition idex smartfinger film sensor technology based polymer process technologies offers small ultra-thin flexible swipe fingerprint sensors idex holds early patents low-cost capacitive fingerprint sensors cross-licence apple relating technology idex demonstrated mobile phone-related technology implementations running android platform well technology concept finger print sensors built cover glass mobile phones finger recognition solutions apple iphone ipad using smartfinger launched idex technology also integrated biometric iso-compliant cards 2013 idex added touch sensors planned product portfolio addition swipe sensors november company specified plans deliver product samples touch sensors mid 2014 since idex announcement partnership safran identity security morpho november 2016 commercialize first mass deployable biometric smart cards ot oberthur technologies safran morpho business came together become idemia november 2017 idex announced continued development innovative end-to-end biometric system solutions payment cards idemia. https //globenewswire.com/news-release/2017/11/24/1205671/0/en/idex-expands-partnership-with-idemia-to-advance-biometric-contactless-card-solutions.html idex partnerships global companies including mastercard idemia chutian dragon feitian goldpac hed hengbao excelsecu infineon xh smart tech idex received 2009 frost sullivan global swipe sensor product differentiation innovation year award idex awarded sesame award smartfinger film fingerprint sensor technology 2010 sesames awards ceremony paris france cartes 2012 north america idex displayed latest demonstration products embedding smartfinger technology well smartfinger secure processor software new smartfinger evaluation kit
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Computer security
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silicon dreams silicon dreams trilogy interactive fiction games developed level 9 computing 1980s first game snowball released 1983 followed year later return eden worm paradise 1985 next year vended together first second last silicon dreams early advertisements gave title silicon dream pluralised later level 9 games trilogy used interpreted language termed a-code usable major types home computer time either diskette cassette level 9 self-published game separately compilation published telecomsoft sold united states tradename firebird europe tradename rainbird trilogy set too-distant future humans started colonising space first two instalments player role kim kimberly undercover agent whose goal snowball save colonist spacecraft crashing star return eden stop defence system destination planet eden destroying craft worm paradise player role unnamed citizen eden must travel around city enoch learn secrets earn money save planet games use text parser entering commands prompt parser interpret thousand words control movement actions looks command picking two three words knows ignoring order tries guess meant movement usual commands moving 'north 'south 'east 'west available abbreviated forms n e w well 'up 'down u 'd respectively number directions 'modes movement like 'jump actions understands pick objects opening doors lighting lamps well dropping objects wielding additionally commands invoke 'save 'restore game positions cassette tape floppy disk systems also ram ask 'help turn pictures turn 'words 'pictures respectively 'oops command undo previous commands silicon dreams played three separate games obtain maximum score games must completed order carrying score one adventure next points scored collecting treasures rather specific tasks helping satisfy goal individual game snowball goal get main control room prevent starship snowball 9 crashing star return eden goal get city enoch stop robots destroying snowball 9 worm paradise goal find much information city possible obtain money become member governing party eden saving planet process trilogy set future human race colonizing stars transport network developed entire solar system using accelerator chains big 5 nations earth initiated plan colonise galaxy known terran expansionary phase lasted ninety years 2120 2210 first major activity launch probes outer space probes reported earth-sized planet encountered centuries-long voyage probe followed survey ship ten years later ship mission map planet habitable would signal earth waiting colonists arrive terraform planet second part phase survey ship mined materials asteroids used build robot factory space — process could take decades resulting robots built space factories turn produced better robots also built large satellite dishes collect data sent earth containing latest technological advances terraforming performed robots landed planet built cities also launching probes survey ships space earth received news habitable planet third final part done ten giant passenger discs carrying two hundred thousand colonists stasis towed space next came engine unit linked front discs colony ship completed ready go 2190s fifty colony ships launched eec ceres base among snowball 9 carried first colonists planet eden eridani system next three years accelerator chains beyond pluto fired ten-ton blocks ammonia ice travelling ship snowball 9 caught ice blocks hooks piled around passenger discs forming hollow shell would cover ship would serve shield needed fuel fusion engines later part trip ice shell gave snowball series name receiving last ice block crew put ship autopilot went hibernate passengers leaving ship maintenance robots except brief period activity start deceleration crew slept trip awaking one year reaching eden plan continue deceleration consuming last ice shell put ship orbit around planet delivering passengers gliders would retrieved hooks reused protagonist two first instalments kim kimberley tall athletic intelligent woman brown eyes fair hair born raised hampstead crèche closed thirteen years old due violations android protection acts finished education milton keynes school life malta returned england national service started standard security work occasional surveillance subversive members society ended working counter-espionage agent whilst mid-twenties kim accepted travel undercover snowball 9 last resort worst-case scenario snowball 9 approaches eden something goes wrong crew member murders shipmates destroys communication system sets ship collision course sun robots little automata continue everyday operations oblivious danger ship computer capable thinking awakens kim kimberley deranged crew member destroys exits modified stasis chamber goal finding way reach control room avert disaster snowball originally released 1983 company fourth adventure game using a-code system nick mike pete austin headed development though level 9 previous games featured fantasy theme austin brothers chose science fiction theme original release used version 1 system initially released bbc micro sinclair zx spectrum nascom later followed versions commodore 64 camputers lynx oric-1 atari 8-bit well memotech mtx amstrad cpc enterprise msx noteworthy including seven thousand locations achieve sixty-eight hundred locations passenger disks form colour-coded maze minimal descriptions another peculiar aspect game confusion behind main character gender interview sinclair user chris bourne asked androgynous kim man woman pete austin pointed credit end design 'ms kimberley costume also admitted kim kimberley deliberately unisex name debate came end release return eden made explicit kim man surviving crew members confuse woman tried destroy ship snowball 9 orbiting eden surviving crew members put kim trial evidence mempak control room shows hijacker rather saviour despite fact recording damaged thus unreliable sentence death thrown space kim manages escape aboard stratoglider hour later lands eden point game starts first thing player must find shelter kim moves game snowball 9 crew use ship engine try burn native robots take proof snowball 9 ship expecting hostile alien craft must destroy objective contact robots time ends snowball 9 everyone aboard unlike predecessor return eden two hundred fifty locations level 9 first game feature graphics adventure games included graphics version 2 a-code system allowed level 9 encode location graphics little forty bytes size made possible add graphics every location game formats 32 k ram user could choose display play game text-only mode released platforms predecessor game first cover depicted robot fighting monster plant enoch robot resembled comic book character avoid legal troubles level 9 commissioned godfrey dowson new cover dowson illustration depicted another robot jungle looking towards enoch level 9 satisfied result asked dowson liked third cover much hired dowson artwork re-release old games well future titles pete austin commented game alien theme park gone wild eden universe like larry niven future space ... intended comment superpower intervention third world hundred years arrival colonists aboard snowball 9 planet eden become home half billion people paradise managed robots crime taxes unemployment freedom population lives domed megapolis perhaps due war occurred return eden contact cities surrounding natural world occasional sighting flying saucers keeps population afraid going outside main character nameless citizen enoch starts game beautiful garden everything seems fine picks apple tree worm pops player follows outside garden desert awakens simulation one many forms entertainment available reign third kim garden eden prison allegory sets mood entire game objective explore city player must gather clues unmask government conspiracy behind flying saucers worm paradise third final instalment silicon dreams trilogy departure previous games evolved alongside 12 month enhancement level 9 adventure system standard features include 1,000 word vocabulary highly-advanced english input memory-enhancing text compression familiar much appreciated type-ahead multi-tasking player need never wait picture drawn first game using version 3 a-code system released four fewer platforms excluding lynx memotech mtx nascom oric-1 compared two previous releases another difference player seven days within game clock complete game quests also time-based require player arrive certain locations specific hours achieve desired goal game play remains backdrop longer action adventure political thriller resembles novel nineteen eighty-four similar happened snowball released certain confusion main character identity time story set level 9 fact sheet says ... couple years later kim kimberley become legend eden another article stated worm paradise set 100 years later kim kimberley iii ... furthermore pete austin said worm set eden 50 years future player kim becomes mayor runs place notice sources termed game original name worm paradise silicon dreams second title published telecomsoft first jewels darkness four-game publishing deal signed level 9 april 1986 deal gave level 9 often referred british infocom opportunity revise previous titles add support 16-bit market well possible entry potential lucrative us market subsequently trilogy released total twelve platforms leaving bbc micro enterprise compared worm paradise adding support apple ii amiga amstrad pcw atari st ibm pc dos macintosh games updated version 3 a-code system updated text new graphics inclusion release silicon dreams trilogy 1986 expanded text-only versions releases rainbird release came 215 x 153 x 27 mm cardboard box firebird release came 227 x 163 x 30 mm black plastic box featured 150 x 210 mm 68-page booklet loading instructions guide playing game peter mcbride novella eden song served introduction worm paradise novella also used copy protection device upon restore saved game player enter word page line reference although adventure game released sinclair ql called return eden written oliver neef rich mellor written level 9 game name level 9 never released version trilogy sinclair ql games released individually generally received good initial reviews snowball best text-only adventure prize crash 1984 readers awards return eden received 90 score sinclair programs worm paradise rated sinclair megagame sinclair user classic trilogy released received unanimously good reviews zx spectrum press sinclair user gave sinclair user classic terming ... unqualified success level 9 rainbird sinclair awarded sinclair mega game zx computing monster hit commodore 64 magazine zzap 64 gave 90 score awarded zzap 64 sizzler however reviews found graphics ... truly abysmal blotchy often unrecognisable ... simple design ... others called ... smidgens better added jewel darkness possibly even two smidgens far disappointment zx spectrum version placed fourth september third october 1987 sinclair adventure charts
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Computer architecture
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pantalk pantalk interpreted cross-platform programming language developed early 1980s cojyp hyperpanel lab use canal plus mediahighway interactive tv platform embedded environments pantalk created take much less development time compared java avoiding kid candyshop effect plenty rich language structures may practice serious limitations prevent taken serious computer language outside limited mediahighway digital tv platform outpaced ubiquitous javascript based liberate c based opentv platforms pantalk partially tokenised interpreted language structured code written plain text *.isb files precompiled *.isc files *.isc files compiled bytecode p-code *.isu files features subset simpler control structures operators variable types statements expect compiled interpreted language also features example variables declaration global across whole applications memory allocation management graphics widgets misses basics like data structures subroutines functions outside loading new tokenised file apart system api feels like old style basic variables global pantalk manages single scalar variables multidimensional arrays available types integer real alpha alphanu date time text memory variable written *.clb files precompiled *.cla files *.cla files compiled bytecode p-code *.clu files reads like hybrid 8-bit microcomputer basic pascal working time developers frustrated lack consistency many limitations said 8-bit basic interpreters pantalk script header script name require return end statement end procedure many statements must end semi colon depending certain api areas always two types script panel script also called dependent script independent script panel script panel group graphical objects named widgets graphical object also called widget trigger one several scripts widget invokes script script must panel script panel script invoke types script panel independent script named panel script stored library panel scripts independent script independent script invoked scripts module boot sequence independent script invoke panel script calling script script path must specified path specifies script location module script library pertains
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Programming language topics
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hypertext caching protocol hypertext caching protocol abbreviated htcp used discovering http caches cached data managing sets http caches monitoring cache activity permits full request response headers used cache management expands domain cache management include monitoring remote cache additions deletions requesting immediate deletions sending hints web objects third party locations cacheable objects unavailability web objects multi-octet htcp protocol elements transmitted network byte order reserved fields set binary zero senders left unexamined receivers headers must presented crlf line termination http hostnames specified compatible sender receiver private naming scheme hosts.txt nis use names depending schemes sent htcp neighbors known participate said schemes raw addresses dotted quad ipv4 colon-format ipv6 universal public dns names use private names addresses require special operational care udp must supported htcp agents must isolated network failures delays htcp agent prepared act useful ways response forthcoming responses delayed reordered damaged tcp optional expected used protocol debugging iana assigned port 4827 standard tcp udp port number htcp htcp message following general format
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Internet protocols
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automotive network exchange anxebusiness corp. anx company owns operates automotive network exchange anx large private extranet connects automotive suppliers automotive manufacturers since 2006 anx expanded areas provides managed security compliance connectivity solutions businesses healthcare retail automotive sectors automotive network exchange private extranet initially set maintained automotive industry action group telcordia general motors ford chrysler built private network auto industry 1995 provide consistent reliable speed guaranteed security data transmissions automakers suppliers anx network allows trading partners collaborate electronically product design development solicit process orders facilitate just-in-time manufacturing post shipping schedules 1999 automotive industry action group sold anx network science applications international corporation saic overseer anx network became anx next six years 4,000 companies joined anx network making one largest extranets world 2006 private equity firm one equity partners acquired anxebusiness saic automotive industry heavily dependent collaboration manufacturers suppliers entities act federated virtual companies critical materials parts components services high velocity supply chains imperative success virtual companies must flexible accommodate needs virtual automotive manufacturer enabling formation “ many-to-many ” relationships trading partners simultaneously subscribe multiple model programs opt situation dictates anx network designed built operated deliver highly secure collaboration strategic business partners anx network secure private network uses standard open internet protocols carries traffic private lines leased various carriers ipsec end-to-end encryption anx network provides secure service customers like typical vpn ’ different typical vpn routers make network check every packet make sure comes ip address private network thus nobody customers get network triple des encryption protects customer ’ data potential malicious behavior another customer
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Computer architecture
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ingrid back gnome ranger ii ingrid back text adventure game level 9 released 1988 sequel gnome ranger game standard text adventure limited graphics platforms short novella peter mcbride included 2nd gnettlefield journal explaining background story providing hints play returned holiday wilderness gnome ingrid bottomlow must save home village little moaning destruction greedy property developer jasper quickbuck must get various uncooperative inhabitants village sign petition gameplay similar gnome ranger player must explore ingrid village collecting signatures petition interacting various non-player characters
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Computer architecture
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badblocks badblocks linux utility check bad sectors disk drive creates list sectors used programs like mkfs used future thus cause corruption data part e2fsprogs project port available bsd operating systems run standalone program badblocks gives list blocks problems makes good option checking whether disk drive healthy independent smart data file system checks common use case invocation badblocks part e2fsck passing option codice_1 scan bad blocks prevent data stored blocks done adding list found bad blocks bad block inode prevent affected sectors allocated file directory test done using read-only codice_1 non-destructive read-write codice_3 test method running codice_4 display list bad blocks recorded codice_5 codice_6 badblocks -nvs /dev/sdb would check drive sdb non-destructive read-write mode display progress writing block numbers checked would check sixth partition drive sdb destructive read-write mode -w write-mode writes 4 different patterns whole partition verifies reading back displays progress writing block numbers checked -s show -v verbose data partition overwritten block level entire drive block size 4096 destroys mbrs partitions data alike modern disk drives probably show defective sectors silently remap bad sectors spare tracks running program new drive several days test whole surface reading afterwards s.m.a.r.t data eventually show reallocated sectors using codice_7 option device containing existing file system erases data device
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Computer file systems
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fragmented object fragmented objects truly distributed objects novel design principle extending traditional concept stub based distribution contrast distributed objects physically distributed encapsulate distribution object parts object named fragments may exist different nodes provide object interface client accessing fragmented object unique object identity presumes local fragment fragmented objects may act like rpc-based infrastructure caching smart proxy well therefore clients distinguish access local object local stub local fragment full transparency gained following characteristics fragmented objects arbitrary protocols may chosen internal communication fragments instance allows hide real-time protocols e.g. rtp media streaming behind standard corba interface internal structure fragmented object arranged object developer/deployer may client–server hierarchical peer-to-peer others thus downward compatibility stub based distribution ensured distribution state functionality hidden behind object interface respective distribution fragments also arbitrary addition application using fragmented object also tolerate change distributions achieved exchanging fragment one multiple hosts procedure either triggered user changes object properties fragmented object collectivity fragments e.g. fragment considered failed course exchange request may trigger one internal changes object developer migrate state functionality fragments providing different fragment implementations dynamically change inside fragmented objects flexible internal partitioning achieved providing transparent fault-tolerant replications well
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Distributed computing architecture
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