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zend engine zend engine open source scripting engine interprets php programming language originally developed andi gutmans zeev suraski students technion – israel institute technology later founded company called zend technologies ramat gan israel name zend combination forenames zeev andi first version zend engine appeared 1999 php version 4 written c highly optimized modular back-end first time could used applications outside php zend engine provides memory resource management standard services php language performance reliability extensibility played significant role php increasing popularity followed zend engine ii heart php 5 newest version zend engine iii originally codenamed phpng developed php 7 significantly improves performance source code zend engine freely available zend engine license although parts php license since 2001 part official releases php.net well official git repository github mirror various volunteers contribute php/zend engine codebase zend engine used internally php compiler runtime engine php scripts loaded memory compiled zend opcodes opcodes executed html generated sent client implement web script interpreter need three parts zend takes part 1 completely bit part 2 php takes parts 2 3 zend really forms language core implementing php basics predefined functions
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Programming language topics
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abstract syntax computer science abstract syntax data structure described data type possibly necessarily abstract data type independent particular representation encoding particularly used representation text computer languages generally stored tree structure abstract syntax tree abstract syntax consists structure data contrasted concrete syntax also includes information representation example concrete syntax includes features like parentheses grouping commas lists included abstract syntax implicit structure abstract syntaxes classified first-order abstract syntax foas structure abstract names identifiers still concrete thus requires name resolution higher-order abstract syntax names abstract implemented either computation communications mapping abstract syntax specific machine representations encodings must defined may called concrete syntax language implementation transfer syntax communications compiler internal representation program typically specified abstract syntax terms categories statement expression identifier independent source syntax concrete syntax language compiled though often similar parse tree similar abstract syntax tree typically also contain features parentheses syntactically significant implicit structure abstract syntax tree algebraic data types particularly well-suited implementation abstract syntax
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Programming language topics
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drive-by download drive-by download means two things concerning unintended download computer software internet drive-by downloads may happen visiting website opening e-mail attachment clicking link clicking deceptive pop-up window clicking window mistaken belief example error report computer operating system acknowledged seemingly innocuous advertisement pop-up dismissed cases supplier may claim user consented download although user fact unaware started unwanted malicious software download similarly person visiting site malicious content person may become victim drive-by download attack malicious content may able exploit vulnerabilities browser plugins run malicious code without user ’ knowledge drive-by install installation similar event refers installation rather download though sometimes two terms used interchangeably creating drive-by download attacker must first create malicious content perform attack rise exploit packs contain vulnerabilities needed carry drive-by download attacks skill level needed perform attack reduced next step host malicious content attacker wishes distribute one option attacker host malicious content server however difficulty directing users new page may also hosted compromised legitimate website legitimate website unknowingly distributing attackers content third party service e.g advertisement content loaded client attacker analyze fingerprint client order tailor code exploit vulnerabilities specific client finally attacker exploits necessary vulnerabilities launch drive-by download attack drive-by downloads usually use one two strategies first strategy exploiting api calls various plugins example downloadandinstall api sina activex component properly check parameters allowed downloading execution arbitrary files internet second strategy involves writing shellcode memory exploiting vulnerabilities web browser plugin divert control flow program shell code shellcode executed attacker perform malicious activities often involves downloading installing malware anything including stealing information send back attacker attacker may also take measures prevent detection throughout attack one method rely obfuscation malicious code done use iframes another method encrypt malicious code prevent detection generally attacker encrypts malicious code ciphertext includes decryption method ciphertext detection drive-by download attacks active area research methods detection involve anomaly detection tracks state changes user ’ computer system user visits webpage involves monitoring user ’ computer system anomalous changes web page rendered methods detection include detecting malicious code shellcode written memory attacker ’ exploit another detection method make run-time environments allow javascript code run track behavior runs detection methods include examining contents html pages identify features used identify malicious web pages using characteristics web servers determine page malicious antivirus tools use static signatures match patterns malicious scripts although effective obfuscation techniques detection also possible using low-interaction high-interaction honeyclients drive-by downloads also prevented occurring using script-blockers noscript easily added browsers firefox using script-blocker user disable scripts given webpage selectively re-enable individual scripts one-by-one basis order determine ones truly necessary webpage functionality way whitelist acceptable scripts quickly developed turn facilitates convenient safe efficient browsing websites script-blocking also saves time bandwidth hence money user scripts load advertising especially targeted ads invade user privacy via tracking profiling longer constitute personal drain user his/her resources
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Computer security
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query example query example qbe database query language relational databases devised moshé m. zloof ibm research mid-1970s parallel development sql first graphical query language using visual tables user would enter commands example elements conditions many graphical front-ends databases use ideas qbe today originally limited purpose retrieving data qbe later extended allow operations inserts deletes updates well creation temporary tables motivation behind qbe parser convert user actions statements expressed database manipulation language sql behind scenes statement actually executed suitably comprehensive front-end minimize burden user remember finer details sql easier productive end-users even programmers select tables columns selecting rather typing names context information retrieval qbe somewhat different meaning user submit document several documents ask similar documents retrieved document database see search multiple examples similarity search based comparing document vectors see vector space model qbe seminal work end-user development frequently cited research papers early example topic currently qbe supported several relational database front ends notably microsoft access implements visual query example well microsoft sql server enterprise manager also implemented several object-oriented databases e.g db4o qbe based logical formalism called tableau query although qbe adds extensions much like sql based relational algebra example using suppliers parts database given illustrate qbe works term also refers general technique influenced zloof work whereby items search values used filter results provides way software user perform queries without know query language sql software automatically generate queries user usually behind scenes examples example form b resulting sql note blank items generate sql terms since address blank clause generated example form c resulting sql advanced versions qbe comparison operator options often via pull-down menu contains contains starts greater-than forth another approach text comparisons allow one wildcard character characters example asterisk designated wild wildcard character particular system searching last names using rob* would return match last names rob robert robertson roberto etc
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Databases
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mai basic four mai basic four sometimes written basic/four corporation basic 4 refers variety business basic computers ran company sold name various times given mai basic four inc. mai basic four information systems mai systems corporation mai systems corporation became wholly owned subsidiary softbrands inc. 2006 basic/four corporation created subsidiary management assistance inc. irvine california basic/four sold small business minicomputers assembled microdata corporation cpus mai basic four business basic one first commercially available business basic interpreters mai basic four company originally sold minicomputers later offered superminicomputers microcomputers computers ran operating system basic interpreter integrated 1985 wall street financier bennett s. lebow purchased company experienced significant operating financial losses 1988 lebow used company platform unsuccessful attempted hostile takeover much larger prime computer company released accounting software third-party microcomputers mid 1980 1988 released 80286-based workstation basic4 system utilized many small banks credit unions 1990 company changed name mai systems corp. changed business system integrator instead combined hardware software manufacturer reselling third-party computers installing customer-specific software system
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Programming language topics
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java message service java message service jms api java message-oriented middleware api sending messages two clients implementation handle producer–consumer problem jms part java platform enterprise edition java ee defined specification developed sun microsystems since guided java community process messaging standard allows application components based java ee create send receive read messages allows communication different components distributed application loosely coupled reliable asynchronous messaging form loosely coupled distributed communication context term 'communication understood exchange messages software components message-oriented technologies attempt relax tightly coupled communication tcp network sockets corba rmi introduction intermediary component approach allows software components communicate indirectly benefits include message senders needing precise knowledge receivers advantages messaging include ability integrate heterogeneous platforms reduce system bottlenecks increase scalability respond quickly change jms 2.0 currently maintained java community process jsr 343 following jms elements jms api supports two distinct models point-to-point messaging system messages routed individual consumers maintain queues incoming messages messaging type built concept message queues senders receivers message addressed specific queue receiving clients extract messages queues established hold messages number producers send messages queue message guaranteed delivered consumed one consumer queues retain messages sent messages consumed messages expire consumers registered consume messages queue holds consumer registers consume publish-and-subscribe model supports publishing messages particular message topic subscribers may register interest receiving messages published particular message topic model neither publisher subscriber knows good analogy anonymous bulletin board jms provides way separating application transport layer providing data java classes used communicate different jms providers using java naming directory interface jndi information desired provider classes first use connection factory connect queue topic use populate send publish messages receiving side clients receive subscribe messages rfc 6167 defines codice_1 uri scheme java message service use jms one must jms provider manage sessions queues topics starting java ee version 1.4 jms provider contained java ee application servers implemented using message inflow management java ee connector architecture first made available version following list common jms providers
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Programming language topics
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diane beckman brigadier general m. diane beckman usaf fictional character nbc television series chuck beckman senior official national security agency working within office director national intelligence holds rank brigadier general united states air force revealed spent significant amount time resources hunting orion intersect chief designer re-appeared made deal government little information personal life past service revealed first entered military prior august 14 1974 fought two battles gulf war non-exclusive romantic relationship roan montgomery 20 years see personality beckman also maintains close friendship dr. condoleezza rice general beckman first appeared chuck versus helicopter replacing national intelligence director wendy makkena overseer operation bartowski initially casey sarah protect chuck replacement intersect back online sarah chuck believed occurred chuck would free go back normal life however beckman secretly issued orders casey chuck killed prevent government secrets retained falling wrong hands however destruction second intersect order rescinded additionally operation bartowski effective weapon cia splinter group fulcrum beckman decided chuck far important valuable resource released therefore blocked attempts contact orion intersect removed beckman also made clear chuck ever identified taken protective custody beckman primary role series provide team bartowski intelligence updates chuck flashes assign mission objectives time missions result something chuck flashes course normal day however several occasions beckman issued assignment devising based events elsewhere chuck abilities intersect particularly well-suited beckman seldom personally involved assignments allows team proceed however chuck versus crown vic benched team flash chuck went bad ordered casey locked personal vendetta former mentor botched mission beckman personally involved chuck contacted orion rogue search flew burbank debrief team first time since pilot episode one team supervisors met in-person also first time directly involved episode mission general beckman typically declines interfere directly team dynamics however sarah confrontational attitude towards treatment chuck chuck versus predator led concern sarah emotionally close asset casey attempted cover requested provide unedited report chuck sarah relationship led reassigning cia agent alexandra forrest chuck cia handler directive 49-b forrest subsequently failed protect chuck lacked sarah close personal connection understanding beckman forced acknowledge sarah feelings asset made best choice protect chuck failed operation locate father allowed jill escape beckman decided pull plug operation bartowski ordered casey sarah take chuck permanent custody reversed decision intersect removed chuck head chuck versus colonel chuck versus ring offered chuck analyst position intersect project freed casey return old unit reassigned sarah intersect project bryce larkin rounding beckman interference team ordered sarah apprehend casey upon learning stolen valuable item cia facility casey broken came castle ordered sarah chuck capture dead alive despite three agents eventually working together taking ring cell coerced stealing cia first place beckman could brook casey treason dismissed spot beckman also wished discuss sarah transferring burbank chuck needed less less beckman look lightly three years untold millions dollars spent helping chuck reach potential become understanding chuck hand-wringing second-guessing part process beckman insists seeing video recovered ring knowledge sarah killed shaw wife season 3 finale beckman higher ups cia concerned state operation bartowski chuck particular gets swept away setup staged much alive shaw purpose discredit could take place spies convention five elders ring going take nsa cia team bartowski arrests elders along daniel shaw justin sullivan leading disintegration ring chuck later reveals ellie beckman reinstated allowed resign spy world season 4 premier federal government rebuilt burbank buy secret joint nsa/cia station staffed undercover spies beckman initially installs on-site guise buy manager using big mike old office displaying real forename middle name diane name tag although incongruously prefers personnel continue address general even undercover store withdrawn approval chuck resignation systematically eliminates private sector job opportunities order force return cia buy new improvements buy include trap door drops reluctant chuck bespin-esque tube slide castle rehiring morgan grimes green shirter salesman upstairs operative downstairs beckman reluctantly concedes observation buy undercover staff far efficient pleasant rendering cover virtually transparent accordingly authorizes morgan rehire store former staff appoints store manager stead general beckman series regular character based san fernando valley usually seen video conferences office still on-site management buy reconstruction time shown away fort meade desk field two consecutive episodes supervising arrest alexei volkoff bartowski family forest cabin subsequently participating capture fatima tazi rescue roan montgomery marrakesh morocco latter case called air strike tazi counterfeiting presses personally employed rocket-propelled grenade disable tazi prevent montgomery execution noticeably general dresses usual service uniform even field subordinate military personnel fatigue uniform also occasionally visits team bartowski burbank particularly season 4 although position prevents openly beckman ultimately proves loyalty team chuck versus cliffhanger chuck casey burned clyde decker attempt free alexei volkoff save sarah life beckman provides information volkoff taken identity card enter castle also supposedly left chuck pair sunglasses intent restoring intersect suppressed decker however accidentally put morgan first however noticeably absent chuck sarah wedding end season 4 government concluded operation bartowski stripped castle equipment sold buy more/castle complex concurrently beckman terminated civil service employment chuck sarah morgan although three employed cia nsa arranged either retirement second dismissal casey marine corps beckman involvement chuck intersect project appeared concluded intersect-embedded sunglasses meant chuck addressed gift beckman chuck versus frosted tips beckman came chuck hire carmichael industries help capture man named zorn prevent selling cia secrets later sarah calls beckman regarding intersect glasses learn never sent glasses implied clyde decker responsible end episode beckman clandestinely meets chuck warning since morgan outed intersect decker put kill order subsequently morgan hidden castle beckman arrived remove intersect going call kill order unfortunately one assassins called decker announced viper team bartowski catches viper beckman decker tell hit chuck versus curse beckman calls team officially condemn treason death decker stealing omen virus tapping morse code team flee later rendezvoused casey abandoned bar well sending agent escort woodcombs unfortunately woodcombs assumed beckman agent hostile fled captured rogue agent robyn cunnings chuck brashly gives virus save family casey sarah able arrest cunnings afterwards casey beckman interrogated cunnings threatening use torture device confirming conspiracy cia team bartowski cleared charge treason well casey criminal record however cunnings already released omen virus turn released shaw mastermind behind decker team rogue actions shaw holding sarah hostage beckman forced help chuck infiltrate cia retrieve macau device decker office mission forced kiss chuck dressed santa throw suspicions soon shaw defeated suppressed ring intersect beckman agrees use government funds help team enjoy christmas team bartowski ultimately one last enemy named nicholas quinn ex-cia agent supposed receive original intersect kidnapped sarah uploaded infected intersect morgan brainwashed bidding beckman tried best help team quinn escaped intersect glasses however could use intersect without damaging brain sought pieces key device could alter intersect beckman unaware held piece unexpectedly taken hostage attending concert chinese counterpart quinn placed bomb beneath seat set go music ended luckily jeff lester able delay explosion chuck forced upload perfected intersect save beckman beckman commended former team work offered employ wish beckman portrayed stern woman little tolerance confrontation subordinates abrupt point shows little interest chuck life beyond service intersect beckman frequently overrules chuck sarah objections placing situations put danger compromise personal life ethics firmly believes war fulcrum must use whatever weapons arsenal defeat operation bartowski successful asset fight refuses allow chuck intersect removed demands become spy beckman wryness led actress bonita friedericy name chuckles beckman frequently lies withholds information members team bartowski mostly chuck interest national security beta intersect completed graham released chuck obligations cia nsa immediately ordered casey eliminate order hinted several times first season beckman lied often subject orion solely purpose keeping intersect chuck head forcing become spy later ordered sarah betray chuck chuck could taken underground rescinded chuck resignation end season 3 despite chuck saving life career operation bartowski declared unmitigated success beckman sabotages attempts chuck made gain employment outside cia declaring chuck says later insists chuck sister ellie woodcomb involuntarily used provide government intel intersect orion laptop seems configured allow access program objections team little shown general personal life known friends dr. condoleezza rice beckman one two concurrent nbc fictional characters jack donaghy 30 rock friends former secretary state first episode explore beckman past relationships detail season four episode chuck versus seduction impossible episode confirmed roan montgomery john laroquette maintained ongoing romantic relationship sorts twenty years enjoying periodic rendezvous fall berlin wall pair engaged tryst promised retire 2009 survived subsequently angered montgomery went rogue operation rather meet promised although ongoing committed relationship per se although montgomery professional expertise seduction honey traps beckman entirely conceal jealousy resentment diane admitted intended cancel plans retire recognizing involved work comfortable settling normal life beckman montgomery tracked n't run general montgomery ncs director jane bentley mary bartowski among characters diane comfortable addressing forename beckman puts strongly professional attitude dealing team rarely shows signs emotion caught off-guard chuck announcement orion identified contacted also humorous effect flustered montgomery charms aided team recovering cipher asked chuck life outside nsa reassured casey objected question n't bothered admitted n't uniform chuck versus angel de la muerte first time shown uniform interrupted cocktail party beckman also highly driven tenacious tracked orion years shows wounded pride shock chuck succeeded finding weeks deeply angered chuck insistence freed intersect taken fight fulcrum personally due increasing number men women sent deaths trying defeat sees chuck team group found chink armor outcome going rest squarely chuck shoulders although generally unflappable beckman openly upset pleaded daniel shaw allowed disclose full details team recently completed mission carina chuck versus three words despite professionalism front subordinates also times displayed genuine sympathy concern well-being team visibly concerned realization shaw knowledge sarah killing wife placed sarah danger beckman known reader ayn rand strict professional beckman officially approve chuck sarah beginning romantic relationship however record even acknowledged damn time beckman openly admitted caring chuck chuck versus tooth became apparent intersect taking devastating effect chuck mental state like col. casey bg beckman begrudgingly grown appreciate morgan grimes unusual talents importance keeping intersect i.e. chuck mind functioning properly although initially hired duress condition casey delivery ring director demanded involuntary reinstatement resignation months later almost immediately appointed manager buy recognition knowledge understanding keep cover store appearance genuine morgan regular character shown address forename diane captain although corrected time response displeasure close-ups ms. friedericy costume available infobox several ribbons sequence shown order worn character example kuwait liberation medals saudi arabia kuwait foreign awards follow united states awards precede gwotem gwotsm two stars southwest asia service medal show served two five distinct campaigns gulf war general beckman three awards national defense service medal evidence first entered military prior august 14 1974 three recent periods service medal issued vietnam war january 1 1961 august 14 1974 gulf war august 2 1990 november 30 1995 war terrorism september 11 2001 chuck versus intersect actress wendy makkena appeared role credited national intelligence director casting lists character identified general mary beckman episode intelligence director briefed casey alongside director graham intersect theft dispatching burbank track bryce larkin contact makkena continue appearing role however forced drop unspecified reasons pilot filmed bonita friedericy also auditioned role took makkena left although intelligence director name never used pilot schwartz fedak officially confirmed friedericy suggested two characters general beckman id card reads gen. m. beckman shown chuck chart first seen second-season episode chuck versus lethal weapon matches unofficial name makkena character pilot compounded original pilot script general mary beckman seen speaking director graham video conference screen shown immediately conferences beckman displays large seal essentially u.s coat arms crest replaced globe ringed satellites around words office director national intelligence united states america also suggesting characters
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Computer security
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java platform enterprise edition java enterprise edition java ee formerly java 2 platform enterprise edition j2ee currently jakarta ee set specifications extending java se 8 specifications enterprise features distributed computing web services java ee applications run reference runtimes microservices application servers handle transactions security scalability concurrency management components deploying java ee defined specification specification defines apis application programming interface interactions java community process specifications providers must meet certain conformance requirements order declare products java ee compliant examples contexts java ee referencing runtimes used e-commerce accounting banking information systems platform known java 2 platform enterprise edition j2ee version 1.2 name changed java platform enterprise edition java ee version 1.5 current version called java ee 8 java ee maintained oracle java community process september 12 2017 oracle corporation announced would submit java ee eclipse foundation eclipse top-level project named eclipse enterprise java ee4j eclipse foundation forced change name java ee oracle owns trademark name java february 26 2018 announced new name java ee jakarta ee java ee includes several specifications serve different purposes like generating web pages reading writing database transactional way managing distributed queues java ee apis include several technologies extend functionality base java se apis enterprise javabeans connectors servlets javaserver pages several web service technologies attempt limit footprint web containers physical conceptual terms web profile created subset java ee specifications java ee web profile comprises following although definition java ee implementations provide base level technologies namely java ee spec associated apis differ considerably respect extra features like connectors clustering fault tolerance high availability security etc installed size memory footprint startup time etc code sample shown demonstrates various technologies java ee 7 used together build web form editing user java ee web ui built using servlet javaserver pages jsp javaserver faces jsf facelets example uses jsf facelets explicitly shown input components use java ee bean validation api covers validate constraints assist view java ee uses concept called backing bean example uses contexts dependency injection cdi enterprise javabean ejb implement business logic enterprise javabean ejb dedicated technology java ee actual persistence jdbc java persistence api jpa used example uses ejb jpa explicitly shown jta used covers ejb control transactional behavior defining entity/model classes java ee provides java persistence api jpa expressing constraints entities provides bean validation api example uses technologies
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Programming language topics
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java platform micro edition java platform micro edition java computing platform development deployment portable code embedded mobile devices micro-controllers sensors gateways mobile phones personal digital assistants tv set-top boxes printers java formerly known java 2 platform micro edition j2me platform uses object-oriented java programming language part java software-platform family java designed sun microsystems acquired oracle corporation 2010 platform replaced similar technology personaljava originally developed java community process jsr 68 different flavors java evolved separate jsrs oracle provides reference implementation specification tended provide free binary implementations java runtime environment mobile devices rather relying third parties provide 22 december 2006 java source code licensed gnu general public license released project name phoneme 2008 java platforms currently restricted jre 1.3 features use version class file format internally known version 47.0 oracle ever declare new round java configuration versions support later class file formats language features corresponding jre 1.5 1.6 notably generics entail extra work part platform vendors update jres java devices implement profile common mobile information device profile aimed mobile devices cell phones personal profile aimed consumer products embedded devices like set-top boxes pdas profiles subsets configurations currently two connected limited device configuration cldc connected device configuration cdc 2.1 billion java enabled mobile phones pdas popular sub- 200 devices nokia series 40 also used bada operating system symbian os along native software users windows ce windows mobile maemo meego android download java respective environments proof-of-concept android connected limited device configuration cldc contains strict subset java-class libraries minimum amount needed java virtual machine operate cldc basically used classifying myriad devices fixed configuration configuration provides basic set libraries virtual-machine features must present implementation j2me environment coupled one profiles connected limited device configuration gives developers solid java platform creating applications consumer embedded devices configuration designed devices 160kb 512kb total memory minimum 160kb rom 32kb ram available java platform designed mobile phones mobile information device profile includes gui data storage api midp 2.0 includes basic 2d gaming api applications written profile called midlets almost new cell phones come midp implementation de facto standard downloadable cell phone games however many cellphones run midlets approved carrier especially north america jsr 271 mobile information device profile 3 final release 09 dec 2009 specified 3rd generation mobile information device profile midp3 expanding upon functionality areas well improving interoperability across devices key design goal midp3 backward compatibility midp2 content information module profile imp profile embedded headless devices vending machines industrial embedded applications security systems similar devices either simple display limited network connectivity originally introduced siemens mobile nokia jsr-195 imp 1.0 strict subset midp 1.0 except n't include user interface apis — words n't include support java package codice_1 jsr-228 also known imp-ng imp next generation based midp 2.0 leveraging midp 2.0 new security networking types apis apis codice_2 codice_3 n't include ui apis game api connected device configuration subset java se containing almost libraries gui related richer cldc foundation profile java connected device configuration cdc profile profile intended used devices requiring complete implementation java virtual machine including entire java platform standard edition api typical implementations use subset api set depending additional profiles supported specification developed java community process personal basis profile extends foundation profile include lightweight gui support form awt subset platform bd-j built upon sun provides reference implementation configurations profiles midp cdc starting javame 3.0 sdk netbeans-based ide support single ide contrast numerous binary implementations java platform built sun servers workstations sun provide binaries platforms java targets exception midp 1.0 jre jvm palm os sun provides j2me jre microsoft windows mobile pocket pc based devices despite open-letter campaign sun release rumored internal implementation personaljava known code name captain america third party implementations widely used windows mobile vendors operating systems targeting java implemented docomo form doja savaje savaje os latter company purchased sun april 2007 forms basis sun javafx mobile open-source mika vm aims implement javame cdc/fp certified certified implementations required charge royalties impractical open-source project consequently devices use implementation allowed claim javame cdc compatibility linux-based android operating system uses proprietary version java similar identical java esr consortium devoted standards embedded java especially cost effective standards typical applications domains industrial control machine-to-machine medical e-metering home automation consumer human-to-machine-interface ...
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Programming language topics
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java platform standard edition java platform standard edition java se computing platform development deployment portable code desktop server environments java se formerly known java 2 platform standard edition j2se platform uses java programming language part java software-platform family java se defines range general-purpose apis—such java apis java class library—and also includes java language specification java virtual machine specification one well-known implementations java se oracle corporation java development kit jdk platform known java 2 platform standard edition j2se version 1.2 name changed java platform standard edition java se version 1.5 se used distinguish base platform enterprise edition java ee micro edition java platforms 2 originally intended emphasize major changes introduced version 1.2 removed version 1.6 naming convention changed several times java version history starting j2se 1.4 merlin java se developed java community process produces descriptions proposed final specifications java platform called java specification requests jsr jsr 59 umbrella specification j2se 1.4 jsr 176 specified j2se 5.0 tiger java se 6 mustang released jsr 270 java platform enterprise edition java ee related specification includes classes java se plus number useful programs run servers opposed workstations java platform micro edition java related specification intended provide certified collection java apis development software small resource-constrained devices cell phones pdas set-top boxes java runtime environment jre java development kit jdk actual files downloaded installed computer run develop java programs respectively java package contains fundamental classes interfaces closely tied language runtime system includes root classes form class hierarchy types tied language definition basic exceptions math functions threading security functions well information underlying native system package contains 22 32 codice_1 classes provided jdk 6 main classes interfaces codice_2 classes codice_2 automatically imported every source file package provides flexible types references otherwise available permitting limited interaction application java virtual machine jvm garbage collector important package central enough language language designers give name starts java.lang somewhat special-purpose used lot developers package added j2se 1.2 java expressive system references allows special behavior garbage collection normal reference java known strong reference codice_7 package defines three types references—soft weak phantom references type reference designed specific use reference types extends class provides method return strong reference referent object codice_8 reference cleared reference type phantom method clear reference codice_7 also defines class used applications discussed keep track objects changed reference type codice_10 created optionally registered reference queue application polls reference queue get references changed reachability state reflection constituent java api lets java code examine reflect java components runtime use reflected members classes package along codice_11 accommodate applications debuggers interpreters object inspectors class browsers services object serialization javabeans need access either public members target object based runtime class members declared given class package added jdk 1.1 reflection used instantiate classes invoke methods using names concept allows dynamic programming classes interfaces methods fields constructors discovered used runtime reflection supported metadata jvm program basic techniques involved reflection discovery typically starts object calling method get object codice_12 codice_12 object several methods discovering contents class example codice_12 object obtained either discovery using class literal e.g codice_19 using name class e.g codice_12 object member codice_21 codice_22 codice_23 objects obtained using symbolic name member example codice_21 codice_22 codice_23 objects used dynamically access represented member class example codice_46 package also provides class contains static methods creating manipulating array objects since j2se 1.3 class supports dynamic creation proxy classes implement specified interfaces implementation codice_47 class provided supplied object implements interface codice_48 method called method invoked proxy object—the first parameter proxy object second parameter codice_21 object representing method interface implemented proxy third parameter array parameters passed interface method codice_39 method returns codice_32 result contains result returned code called proxy interface method package contains classes support input output classes package primarily stream-oriented however class random access files also provided central classes package abstract base classes reading writing byte streams respectively related classes abstract base classes reading writing character streams respectively package also miscellaneous classes support interactions host file system stream classes follow decorator pattern extending base subclass add features stream classes subclasses base stream classes typically named one following attributes stream subclasses named using naming pattern codice_52 codice_53 name describing feature codice_54 one codice_55 codice_56 codice_57 codice_58 following table shows sources/destinations supported directly codice_59 package standard library packages provide stream implementations destinations codice_55 returned method java ee class data type handling processing filtering stream data accomplished stream filters filter classes accept another compatible stream object parameter constructor decorate enclosed stream additional features filters created extending one base filter classes codice_57 codice_58 classes really byte streams additional processing performed data stream convert bytes characters use default character encoding platform j2se 5.0 represented returned static method class converts codice_55 codice_57 class converts codice_56 codice_58 classes constructors support specifying character encoding use encoding specified program uses default encoding platform following table shows processes filters codice_59 package directly supports classes extend corresponding codice_68 class class supports random access reading writing files class uses file pointer represents byte-offset within file next read write operation file pointer moved implicitly reading writing explicitly calling methods current position file pointer returned method class represents file directory path file system codice_69 objects support creation deletion renaming files directories manipulation file attributes read-only last modified timestamp codice_69 objects represent directories used get list contained files directories class file descriptor represents source sink destination bytes typically file also console network socket codice_71 objects used create codice_69 streams obtained codice_69 streams codice_74 sockets datagram sockets j2se 1.4 package nio non-blocking i/o added support memory-mapped i/o facilitating i/o operations closer underlying hardware sometimes dramatically better performance codice_75 package provides support number buffer types subpackage provides support different character encodings character data subpackage provides support channels represent connections entities capable performing i/o operations files sockets codice_76 package also provides support fine-grained locking files package supports multiprecision arithmetic including modular arithmetic operations provides multiprecision prime number generators used cryptographic key generation main classes package package provides special io routines networks allowing http requests well common transactions package implements parsing routines strings supports various human-readable languages locale-specific parsing data structures aggregate objects focus package included package collections api organized data structure hierarchy influenced heavily design patterns considerations created support java applet creation package lets applications downloaded network run within guarded sandbox security restrictions easily imposed sandbox developer example may apply digital signature applet thereby labeling safe allows user grant applet permission perform restricted operations accessing local hard drive removes sandbox restrictions digital certificates issued certificate authorities included package various classes developing manipulating beans reusable components defined javabeans architecture architecture provides mechanisms manipulating properties components firing events properties change apis codice_80 intended use bean editing tool beans combined customized manipulated one type bean editor gui designer integrated development environment abstract window toolkit provides access basic set gui widgets based underlying native platform widget set core gui event subsystem interface native windowing system java application also provides several basic layout managers datatransfer package use clipboard drag drop interface input devices mice keyboards well access system tray supporting systems package along codice_81 contains largest number enums 7 jdk 6 package provides java remote method invocation support remote procedure calls two java applications running different jvms support security including message digest algorithm included package implementation jdbc api used access sql databases grouped package package provides support remote communication applications using rmi iiop protocol protocol combines rmi corba features java se core technologies corba rmi-iiop swing collection routines build codice_82 provide platform independent widget toolkit uses 2d drawing routines render user interface components instead relying underlying native operating system gui support package contains largest number classes 133 jdk 6 package along codice_82 also contains largest number enums 7 jdk 6 supports pluggable looks feels plafs widgets gui imitate underlying native system design patterns permeate system especially modification model-view-controller pattern loosens coupling function appearance one inconsistency j2se 1.3 fonts drawn underlying native system java limiting text portability workarounds using bitmap fonts exist general layouts used keep elements within aesthetically consistent gui across platforms package provides error tolerant html parser used writing various web browsers web bots package contains largest number annotation types 30 jdk 6 defines annotations customizing java program elements xml schema mapping package provides support remote communication applications using general inter-orb protocol supports features common object request broker architecture rmi rmi-iiop package calling remote methods objects virtual machines usually via network package contains largest number codice_84 classes 45 jdk 6 communication possibilities corba portable various languages however comes complexity package contains largest number interfaces 39 jdk 6 provides mechanism register orb hooks orb services intercept normal flow execution orb several critical security vulnerabilities reported recent january 2013 security alerts oracle announce critical security-related patches java se
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Programming language topics
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next character set next character set often aliased nextstep encoding vector we8nextstep next-multinational used nextstep openstep operating systems next workstations beginning 1988 based adobe systems postscript ps character set aka adobe standard encoding unused code points filled characters iso 8859-1 latin 1 although differing code points following table shows next character set character shown potential unicode equivalent code points differing adobe standard encoding shown boxed codepoints 00 0 7f 127 nearly identical ascii
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Operating systems
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reliable data protocol reliable data protocol rdp network transport protocol defined rfc 908 updated rfc 1151 meant provide facilities remote loading debugging bulk transfer images data reliable data protocol located transport layer osi model next protocols like tcp udp number 27 list ip protocol numbers similar tcp reliable data protocol connection oriented contrary tcp require sequenced delivery segments reliable data protocol gained popularity though experimental implementations bsd exist
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Internet protocols
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iozone iozone file system benchmark utility originally made william norcott enhanced capps others.. source code available iozone.org mmap file i/o uses posix threads 2007 infoworld bossie awards best file i/o tool windows version iozone uses cygwin builds available aix bsdi hp-ux irix freebsd linux openbsd netbsd osfv3 osfv4 osfv5 sco openserver solaris mac os x windows 95/98/me/nt/2k/xp available test profile phoronix test suite
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Computer file systems
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passports efta member states passports issued european free trade association efta member states iceland liechtenstein norway switzerland used citizens exercise right free movement within efta european economic area eea consists iceland liechtenstein norway addition member states european union instead part eea switzerland series bilateral agreements eu european single market consequently extended exceptions efta member states efta member states also signatories schengen agreement part schengen area citizens efta member states generally rights eu citizens eea countries treated eu citizens purposes travel entry eea countries going border controls enter efta eea member state efta eu citizens possessing valid biometric passports sometimes able use automated gates instead immigration counters whilst citizens using national identity card non-biometric passport non-eea citizens must use immigration counter anyone travelling children must also use immigration counter note efta organisation issue rules passport design validity four countries european union schengen regulations besides global icao regulations efta article used common name countries international civil aviation organization icao issues passport standards treated recommendations national governments size passport booklets normally complies iso/iec 7810 id-3 standard specifies size size b7 format passport cards issued id-1 credit card sized standard efta member states except liechtenstein icao members liechtenstein delegated switzerland implement treaty make applicable territory liechtenstein according council regulation ec 2252/2004 passports travel documents issued schengen member states shall comply minimum security standards passports must incorporate storage medium chip contains holder facial image fingerprints obligation apply identity cards temporary passports travel documents validity one year less regulation limited harmonization security features addition harmonization security features biometrics member states european union started harmonise aspects designs ordinary passports types passports diplomatic service emergency passports passports issued eu member states common recommended lay burgundy colour words “ european union ” followed name country efta member states norway passport burgundy color however coat arms placed name issuing state norway instead name state word passport eu passports iceland liechtenstein hand follows order eu passports issues blue ordinary passports burgundy passports travel document shall contain machine-readable biographical data page shall comply part 1 machine-readable passports icao document 9303 way issued shall comply specifications machine-readable passports set therein newer efta passports contain machine-readable zone contains name nationality information identification page designed way computers fairly easily read information although still human readable since contains letters a–z digits space character bar graph similar apostrophes similar omitted hyphens spaces replaced angle bracket diacritical marks permitted mrz even though may useful distinguish names use diacritical marks mrz could confuse machine-reading equipment names containing non-english letters usually spelled correct way visual non-machine-readable zone passport mapped a-z according standards international civil aviation organization icao machine-readable zone following mapping specified languages efta countries å → aa æ → ae ä → ae ð → ø → oe ö → oe ß → ss þ → th ü → ue letters accents otherwise replaced simple letters françois becomes francois etc. example german names müller becomes mueller groß becomes gross gößmann becomes goessmann icao mapping mostly used computer-generated internationally used documents air tickets sometimes like us visas also simple letters used muller gossmann three possible spelling variants name e.g müller mueller muller different documents sometimes lead confusion use two different spellings within document like passports german-speaking countries may give people unfamiliar foreign orthography impression document forgery recommended use spelling used machine-readable passport zone visas airline tickets etc. refer zone questioned thing applies name long fit airline ticket system otherwise problems arise machine-readable room 39 letters name visual zone contain many fit icelandic passports blue icelandic coat arms emblazoned centre front cover words ísland icelandic iceland english islande french inscribed coat arms words vegabréf icelandic passport english passeport french inscribed coat arms icelandic passports standard biometric symbol bottom vegabréf literally means road letter word used scandinavia historic centuries meaning internal passport icelandic passport includes following data information page ends machine readable zone liechtenstein passports blue coat arms liechtenstein emblazoned centre words fürstentum liechtenstein inscribed coat arms reisepass international biometric passport symbol information page ends machine readable zone regular norwegian passports burgundy colour norway coat arms emblazoned top front cover words norge noreg norway norway bokmål norwegian one two forms norwegian nynorsk norwegian form norwegian english respectively inscribed coat arms word pass passport emblazoned name country new biometric passport standard biometric symbol bottom norwegian passport includes following data information page ends machine-readable zone starting p x x indicates type passport example ordinary passports contain pvnor v presumably means vanlig ordinary norwegian swiss passports red colour words schweizer pass german passeport suisse french passaporto svizzero italian passaport svizzer romansh swiss passport english top right corner swiss equilateral white cross standard biometric symbol placed bottom right hand side swiss passport includes following data full plastic information page information page ends machine readable zone visa requirements administrative entry restrictions authorities states placed citizens european free trade association efta member states efta member states citizens enjoy freedom movement territories accordance efta convention efta nationals also enjoy freedom movement european union eu efta nationals eu citizens visa-exempt legally entitled enter reside countries citizens ’ rights directive also sometimes called free movement directive defines right free movement citizens european economic area eea includes three efta members iceland norway liechtenstein member states eu switzerland member efta eea bound directive rather separate bilateral agreement free movement eu result de facto citizen efta country live work efta countries eu countries citizen eu country live work efta countries voting working sensitive fields government police military citizenship often required non-citizens may rights welfare unemployment benefits citizens efta member states part schengen area area comprising 26 european states officially abolished passport types border control mutual borders area mostly functions single country international travel purposes common visa policy area named schengen agreement since implementation schengen rules border posts closed often entirely removed participating countries pro forma borders subject photo-journalistic art project schengen borders code requires participating states remove obstacles free traffic flow internal borders thus road rail air passengers longer identity checked border guards travelling schengen countries although security controls carriers still permissible travellers still bring passport national identity card one may required alternative holding passport valid national identity card also used exercise right free movement within eea switzerland strictly speaking necessary eea swiss citizen possess valid passport national identity card enter eea switzerland theory eea swiss citizen outside eea switzerland prove his/her nationality means e.g presenting expired passport national identity card citizenship certificate he/she must permitted enter eea switzerland eea swiss citizen unable demonstrate his/her nationality satisfactorily must nonetheless given 'every reasonable opportunity obtain necessary documents delivered within reasonable period time states schengen area strengthened border controls non-schengen countries participating countries required apply strict checks travellers entering exiting schengen area checks co-ordinated european union frontex agency subject common rules details border controls surveillance conditions permission enter schengen area may granted exhaustively detailed schengen borders code. ref name= reg2016/399 regulation eu 2016/399 european parliament council 9 march 2016 union code rules governing movement persons across borders schengen borders code oj l 77 23 march 2016 p. 1 /ref part schengen area reciprocity required comes visa free access since 2001 european union issued two lists regarding visas schengen area white list countries whose nationals require visas annex ii black list countries whose nationals require visas annex per regulation 539/2001 amended regulation 1289/2013 reciprocity required annex ii countries territories means countries must offer visa-free access 90 days citizens 26 schengen member states passport rankings number countries territories holders could visit without visa obtaining visa arrival 2018 follows sourced henley partners passport index 2018 norway allows citizens one passport circumvent certain travel restrictions useful wanting travel passport remains consulate visa application processed wanting apply visas already foreign country also needed circumvent fact visitors whose passports show evidence visit israel allowed enter iran iraq lebanon libya saudi arabia sudan syria yemen however possible get israeli entry exit stamp separate piece paper since efta member state make citizenship laws dual citizenship always possible efta countries iceland allows dual multiple citizenship without restrictions switzerland regulate/restrict conditions naturalization immigrants vary regionally norway allow exceptional cases liechtenstein citizens descent foreigners wanting naturalize citizen efta member state live work efta- eu member states necessarily vote work sensitive fields government police military citizenship often required non-citizens may rights welfare unemployment benefits citizens
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Computer security
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wolfram systemmodeler wolfram systemmodeler developed wolfram mathcore platform engineering well life-science modeling simulation based modelica language provides interactive graphical modeling simulation environment customizable set component libraries features wolfram systemmodeler include wolfram systemmodeler primary interface model center interactive graphical environment including customizable set component libraries models developed model center simulated simulation center software also provides tight integration mathematica environment users develop simulate document analyze wolfram systemmodeler models within mathematica notebooks software used engineering field well life sciences originally developed mathcore engineering mathmodelica acquired wolfram research march 30 2011 re-released wolfram systemmodeler may 23 2012 improved integration wolfram mathematica wolfram systemmodeler uses free object-oriented modeling language modelica language designed modeling physical systems designed support library development model exchange modern language built acausal modeling mathematical equations object-oriented constructs facilitate reuse modeling knowledge since version 11.3 wolfram language supports direct access modelica libraries system simulation analysis notebook interface
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Programming language topics
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beqom beqom global provider compensation management software delivered using cloud computing platform beqom global headquarters nyon switzerland offices throughout north america emea components software include functionality manage sales incentives bonuses equity merit pay long term incentives channel partner incentives beqom founded excentive international 2009 software executives coming hyperion outlooksoft sap company gained notability 2009 one hr software vendors offering comprehensive compensation application year company began worldwide expansion opening north american headquarters september 1 2013 company changed name beqom july 2014 swisscom ventures investing arm swisscom ag renaissance pme swiss pension investing fund managed swiss technology investor vinci capital announced completed financing round beqom help fund international expansion efforts
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Distributed computing architecture
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cs-script cs-script free open-source scripting platform enables creating scripts ecma-compliant c syntax scripts access .net framework mono apis cs-script offers standalone script execution well hosting script engine clr apps newer edition product called cs-script.core works .net core existing .net development tools e.g visual studio sharp develop used allowing editing debugging scripts within traditional .net-aware development environments additionally cs-script support added notepad++ visual studio code via plugins flashdevelop uses cs-script internal scripting engine bring script engine file 100 kb size system .net runtime installed script run scripts run system clr installed including mono cs-script truly object-oriented language supports vb.net c++/cli j .net functionality available including fcl com interop remoting wpf wcf easily available debugger rich ide visual studio third-party ides execution model within script .net application static void main interpretation statement script done even statement frequently used throughout code strong typing luxury available scripting languages software development tasks done language gui development script application becomes easy scripting system extended using new assemblies written .net languages com components script easily converted application vice versa functionality clr application extended scripting run within wsh mixed one wsf file external links
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Programming language topics
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dynaset 1 dynaset short dynamic set set data dynamically linked back database instead query result stored temporary table data updated directly user dynaset allows user view update data contained dynaset thus university lecturer queried students received distinction assignment found error student record would need update data dynaset would automatically update student database record without need send specific update query storing query results temporary table concept initially put forth dr. e.f. codd inventor relational database management system rdbms concept 2 dynaset temporary set data taken one tables underlying file dynaset may query defined access database single table subset table result joining multiple tables dynaset updated file locked opened readonly data dynaset live i.e. changes made data project visual basic executing appear corresponding recordset note dynasets created joining tables typically non-updateable word dynaset coined david risher design meeting microsoft access 1.0
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Databases
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path computing path general form name file directory specifies unique location file system path points file system location following directory tree hierarchy expressed string characters path components separated delimiting character represent directory delimiting character commonly slash backslash character colon though operating systems may use different delimiter paths used extensively computer science represent directory/file relationships common modern operating systems essential construction uniform resource locators urls resources represented either absolute relative paths multics first introduced hierarchical file system directories separated mid-1960s around 1970 unix introduced slash character directory separator 1981 first version microsoft dos released ms-dos 1.0 support file directories also major portion utility commands packaged ms-dos 1.0 came ibm command line syntax used slash character 'switch prefix example codice_1 runs codice_2 command wide list format option use slash still found command interface microsoft windows contrast unix uses dash character command line switch prefix directory support added ms-dos version 2.0 kept switch prefix character backwards compatibility microsoft chose backslash character directory separator looks similar slash character absolute full path points location file system regardless current working directory must include root directory contrast relative path starts given working directory avoiding need provide full absolute path filename considered relative path based current working directory working directory file parent directory file found error result file addressed name japanese korean versions windows may often display '¥ character '₩ character instead directory separator cases code backslash drawn characters early versions ms-dos replaced backslash glyphs display make possible display programs understood 7-bit ascii characters square brackets replaced well see iso 646 windows codepage 932 japanese shift jis codepage 949 korean although even first version windows supported 8-bit iso-8859-1 character set yen sign u+00a5 modern versions windows supports unicode sign u+20a9 much software continue display backslashes found ascii files way preserve backwards compatibility mac os x derivative unix uses unix paths internally however preserve compatibility software familiarity users many portions gui switch typed user internally switch back displaying filenames entered user also changed inverse translation happen programming languages also use paths e.g file opened programming languages use path representation underlying operating system direct access operating system paths hinder portability programs support portable programs java uses file.separator distinguish separated paths seed7 different approach path representation seed7 paths use unix path convention independent operating system windows mapping takes place e.g path /c/users mapped c \users microsoft windows unc short universal naming convention uniform naming convention specifies common syntax describe location network resource shared file directory printer unc syntax windows systems generic form microsoft often refers network path microsoft windows interfaces also allow require unc syntax webdav share access rather url unc syntax extended optional components denote use ssl tcp/ip port number webdav url codice_5 becomes viewed remotely sharedfolder may name different program server sees opening \sharedfolder instead sharedfolder name consists arbitrary name assigned folder defining sharing microsoft windows interfaces also accept long unc microsoft windows uses following types paths versions windows prior windows xp apis accept long device paths could accept 260 characters shell windows xp windows vista explorer.exe allows path names 248 characters long since uncs start two backslashes backslash also used string escaping regular expressions result extreme cases leaning toothpick syndrome escaped string regular expression matching unc begins 8 backslashes – codice_11 – string regular expression require escaping simplified using raw strings c codice_12 python codice_13 regular expression literals perl codice_14 unix-like systems use similar syntax posix allows treating path beginning two slashes implementation-defined manner though cases systems must treat multiple slashes single slashes many applications unix-like systems example scp rcp rsync use resource definitions like urls service name 'smb following worked example discusses behavior unix-style file system would appear terminal terminal application command-line window attached current working directory cwd one wants change current working directory moment relative path desired directory represented short absolute path directory given bobapples relative path directory wanted following may typed command prompt change current working directory bobapples two dots point upwards hierarchy indicate parent directory one dot represents current directory components complex relative path e.g. alone first component relative path represents working directory using refer file current working directory sometimes usefully distinguish resource found default directory means example view specific version manual page instead one installed system contrary popular belief windows system api accepts slash thus unix examples work many applications windows interpret slash purposes treat invalid character thus require enter backslash — notably cmd.exe shell often called terminal typically runs terminal window note many shells available windows tcsh windows powershell allow slash addition indicate single root instead root current disk indicating file disk current one requires prefixing drive letter colon ambiguity ensues colon valid character ms-dos filename thus one file called current directory unc names path starting support slashes following examples show ms-dos/windows-style paths backslashes used match common syntax path points file name located directory turn located root directory drive path refers file called located parent directory current directory drive path denotes file called located directory turn located directory located current directory current drive since example gives drive-specification rather simple path points file named codice_15 located current directory since path lacks directory-specification current drive since drive specification present path refers first serial port com1 example uses path containing slashes directory separator command redirects content file codice_16 command path containing forward slashes often needs surrounded double quotes disambiguate command line switches cd drive letter /program files work root drive letter directory appears treat forward slashes .\ example works also root folder would treated relative path directory name specified forward slashes get following error setting environment variables sometimes necessary provide path contain spaces instance defined c \program files\java ... cause scripts halt encounter space path name get eight-character name windows assigns directory substitution environment variables use directory listing command /x option one level target directory instance following get eight character name directories directly root correct way represent path directory trailing slash period posix windows might think paths end trailing slash directories actuality path ending trailing slash represents files within directory simply path file may may directory path directory even may eventually resolve directory
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Computer file systems
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disk encryption software disk encryption software computer security software protects confidentiality data stored computer media e.g. hard disk floppy disk usb device using disk encryption compared access controls commonly enforced operating system os encryption passively protects data confidentiality even os active example data read directly hardware different os addition crypto-shredding suppresses need erase data end disk lifecycle disk encryption generally refers wholesale encryption operates entire volume mostly transparently user system applications generally distinguished file-level encryption operates user invocation single file group files requires user decide specific files encrypted disk encryption usually includes aspects disk including directories adversary determine content name size file well suited portable devices laptop computers thumb drives particularly susceptible lost stolen used properly someone finding lost device penetrate actual data even know files might present disk data protected using symmetric cryptography key randomly generated disk encryption first established key encrypted way using password pass-phrase known ideally user thereafter order access disk data user must supply password make key available software must done sometime operating system start-up encrypted data used done software disk encryption typically operates level applications system programs low-level device drivers transparently user point view encrypting data produced program physically written disk conversely decrypts data immediately read presented program properly done programs unaware cryptographic operations disk encryption software e.g. truecrypt bestcrypt provide features generally accomplished disk hardware encryption ability mount container files encrypted logical disks file system encrypted logical inner volumes secretly hidden within free space obvious outer volumes strategies provide plausible deniability well-known examples disk encryption software include bitlocker windows filevault apple os/x truecrypt non-commercial freeware application windows os/x linux disk encryption systems veracrypt ciphershed active open source forks discontinued truecrypt project bestcrypt proprietary trialware offers levels plausible deniability might useful user compelled reveal password encrypted volume hidden volumes steganographic feature allows second hidden volume reside within apparent free space visible container volume sometimes known outer volume hidden volume separate file system password encryption key distinct container volume content hidden volume encrypted resides free space file system outer volume—space would otherwise filled random values hidden volume exist outer container brought online thorough disk encryption software whether inner outer volume mounted depends password provided normal password/key outer volume proves valid outer volume mounted password/key hidden volume proves valid existence hidden volume even detected mounted otherwise password/key successfully decrypt either inner outer volume descriptors neither mounted hidden volume created inside visible container volume user store important-looking information user actually mind revealing outer volume whereas sensitive information stored within hidden volume user forced reveal password user reveal password outer volume without disclosing existence hidden volume hidden volume compromised user takes certain precautions overwriting free areas host disk volumes stored file device/partition may intentionally contain discernible signatures unencrypted headers cipher algorithms designed indistinguishable pseudorandom permutation without knowing key presence data encrypted volume also undetectable unless known weaknesses cipher means impossible prove file partition encrypted volume rather random data without password mount characteristic also makes impossible determine volume contains another hidden volume file hosted volume opposed partitions may look place cases since entirely random data placed file intentionally however partition device hosted volume look different partition device wiped common disk wiping tool darik boot nuke one plausibly claim device partition wiped clear personal data portable traveller mode means encryption software run without installation system hard drive mode software typically installs temporary driver portable media since installing driver albeit temporarily administrative privileges still required disk encryption software allows encrypted volumes resized many systems implement fully resort using sparse files achieve encrypted volumes contain header cdb data may backed overwriting data destroy volume ability back useful restoring backup copy data may reset volume password backup taken
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Computer file systems
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.net framework .net framework pronounced dot net software framework developed microsoft runs primarily microsoft windows includes large class library named framework class library fcl provides language interoperability language use code written languages across several programming languages programs written .net framework execute software environment contrast hardware environment named common language runtime clr clr application virtual machine provides services security memory management exception handling computer code written using .net framework called managed code fcl clr together constitute .net framework fcl provides user interface data access database connectivity cryptography web application development numeric algorithms network communications programmers produce software combining source code .net framework libraries framework intended used new applications created windows platform microsoft also produces integrated development environment largely .net software called visual studio .net framework began proprietary software although firm worked standardize software stack almost immediately even first release despite standardization efforts developers mainly free open-source software communities expressed unease selected terms prospects free open-source implementation especially regarding software patents since microsoft changed .net development closely follow contemporary model community-developed software project including issuing update patent promising address concerns .net framework led family .net platforms targeting mobile computing embedded devices alternative operating systems web browser plug-ins reduced version framework .net compact framework available windows ce platforms including windows mobile devices smartphones .net micro framework targeted resource-constrained embedded devices silverlight available web browser plugin mono available many operating systems customized popular smartphone operating systems android ios game engines .net core targets universal windows platform uwp cross-platform cloud computing workloads microsoft began developing .net framework late 1990s originally name next generation windows services ngws part .net strategy late 2000 first beta versions .net 1.0 released august 2000 microsoft intel worked standardize common language infrastructure cli c december 2001 ratified ecma international ecma standards international organisation standardisation iso followed april 2003 current version iso standards iso/iec 23271:2012 iso/iec 23270:2006 microsoft partners hold patents cli c ecma iso require patents essential implementation made available reasonable non-discriminatory terms firms agreed meet terms make patents available royalty-free however apply part .net framework covered ecma-iso standards included windows forms ado.net asp.net patents microsoft holds areas may deterred non-microsoft implementations full framework october 3 2007 microsoft announced source code .net framework 3.5 libraries become available microsoft reference source license ms-rsl source code repository became available online january 16 2008 included bcl asp.net ado.net windows forms wpf xml scott guthrie microsoft promised linq wcf wf libraries added november 12 2014 microsoft announced .net core effort include cross-platform support .net source release microsoft coreclr implementation source entire … library stack .net core adoption conventional bazaar -like open-source development model consolation stewardship .net foundation miguel de icaza describes .net core redesigned version .net based simplified version class libraries microsoft immo landwerth explained .net core would foundation future .net platforms time announcement initial release .net core project seeded subset libraries source code coincided relicensing microsoft existing .net reference source away restrictions ms-rsl landwerth acknowledged disadvantages formerly selected shared license explaining made codename rotor non-starter community-developed open source project meet criteria open source initiative osi approved license november 2014 microsoft also produced update patent grants extends scope beyond prior pledges prior projects like mono existed legal grey area microsoft earlier grants applied technology covered specifications including strictly 4th editions ecma-334 ecma-335 new patent promise however places ceiling specification version even extends .net runtime technologies documented msdn formally specified ecma group project chooses implement allows mono projects maintain feature parity modern .net features introduced since 4th edition published without risk patent litigation implementation features new grant maintain restriction implementation must maintain minimum compliance mandatory parts cli specification march 31 2016 microsoft announced microsoft build completely relicense mono mit license even scenarios formerly commercial license needed microsoft also supplemented prior patent promise mono stating assert applicable patents parties using selling offering sale importing distributing mono announced mono project contributed .net foundation developments followed acquisition xamarin began february 2016 finished march 18 2016 microsoft press release highlights cross-platform commitment allows fully open-source modern server-side .net stack microsoft released source code wpf windows forms winui december 4 2018 may 8th 2019 microsoft announced .net 5.0 released november 2020 based .net core common language infrastructure cli provides language-neutral platform application development execution implementing core aspects .net framework within scope cli functions tied one language available across many languages supported framework .net framework includes common language runtime clr serves execution engine .net framework offers many services memory management type safety exception handling garbage collection security thread management programs written .net framework executed clr programs written .net framework compiled common intermediate language code cil opposed directly compiled machine code execution architecture-specific just-in-time compiler jit turns cil code machine code microsoft move .net core cli virtual execution system ves implementation known coreclr instead clr compiled cil code stored cli assemblies mandated specification assemblies stored portable executable pe file format common windows platform dynamic-link library dll executable exe files assembly consists one files one must contain manifest bearing metadata assembly complete name assembly confused file name disk contains simple text name version number culture public key token assemblies considered equivalent share complete name private key also used creator assembly strong naming public key token identifies private key assembly signed creator key pair typically person signing assembly sign assemblies strong name prior version assembly since creator possesses private key strong naming required add assemblies global assembly cache starting visual studio 2015 .net native compilation technology allows compilation .net code universal windows platform apps directly machine code rather cil code app must written either c visual basic.net .net framework includes implementation cli foundational standard libraries .net framework class library fcl organized hierarchy namespaces built-in application programming interfaces apis part either codice_1 codice_2 namespaces class libraries implement many common functions file reading writing graphic rendering database interaction xml document manipulation class libraries available cli compliant languages fcl implements cli base class library bcl class libraries—some specified cli microsoft specific bcl includes small subset entire class library core set classes serve basic api clr .net framework classes considered part bcl reside codice_3 codice_4 codice_5 bcl classes available .net framework well alternative implementations including .net compact framework microsoft silverlight .net core mono fcl refers entire class library ships .net framework includes expanded set libraries including bcl windows forms asp.net windows presentation foundation wpf also extensions base class libraries ado.net language integrated query linq windows communication foundation wcf workflow foundation wf fcl much larger scope standard libraries languages like c++ comparable scope standard libraries java introduction alternative implementations e.g. silverlight microsoft introduced concept portable class libraries pcl allowing consuming library run one platform proliferation .net platforms pcl approach failed scale pcls defined intersections api surface two platforms next evolutionary step pcl .net standard library created retroactively based codice_6 based apis found uwp silverlight new .net platforms encouraged implement version standard library allowing re-use extant third-party libraries run without new versions .net standard library allows independent evolution library app model layers within .net architecture nuget package manager .net platforms used retrieve third-party libraries .net project global library feed nuget.org private feeds maintained separately e.g. build server file system directory microsoft move .net core cli foundational class libraries implementation known corefx instead fcl atop class libraries multiple app models used create apps .net framework supports console windows forms windows presentation foundation asp.net asp.net core apps default app models offered alternative implementations .net framework console uwp asp.net core available .net core mono used power xamarin app models android ios macos retroactive architectural definition app models showed early 2015 also applied prior technologies like windows forms wpf microsoft introduced c++/cli visual studio 2005 language means compiling visual c++ programs run within .net framework parts c++ program still run within unmanaged visual c++ runtime specially modified parts translated cil code run .net framework clr assemblies compiled using c++/cli compiler termed mixed-mode assemblies since contain native managed code dll assemblies complex reverse engineer since .net decompilers .net reflector reveal managed code computer systems commonly require interaction newer older applications .net framework provides means access functions implemented newer older programs execute outside .net environment access component object model com components provided codice_7 codice_8 namespaces framework access functions via platform invocation services p/invoke access .net functions native applications via reverse p/invoke function .net framework introduces common type system cts defines possible data types programming constructs supported clr may may interact conforming cli specification feature .net framework supports exchange types object instances libraries applications written using conforming .net language cts clr used .net framework also enforce type safety prevents ill-defined casts wrong method invocations memory size issues accessing object also makes cli languages statically typed without type inference however starting .net framework 4.0 dynamic language runtime extended clr allowing dynamically typed languages implemented atop cli microsoft never implemented full framework system except microsoft windows engineered framework cross-platform implementations available operating systems see silverlight § alternative implementations microsoft submitted specifications cli includes core class libraries cts cil c c++/cli ecma international ecma international organization standardization iso making available official standards makes possible third parties create compatible implementations framework languages platforms .net framework security mechanism two general features code access security cas validation verification cas based evidence associated specific assembly typically evidence source assembly whether installed local machine downloaded internet cas uses evidence determine permissions granted code code demand calling code granted specified permission demand causes clr perform call stack walk every assembly method call stack checked required permission assembly granted permission security exception thrown managed cil bytecode easier reverse-engineer native code unless obfuscated decompiler programs enable developers reverse-engineering skills view source code behind unobfuscated .net assemblies contrast apps compiled native machine code much harder reverse-engineer source code almost never produced successfully mainly compiler optimizations lack reflection creates concerns business community possible loss trade secrets bypassing license control mechanisms mitigate microsoft included dotfuscator community edition visual studio .net since 2002 third-party obfuscation tools also available vendors vmware v.i labs turbo red gate software method-level encryption tools .net code available vendors safenet clr frees developer burden managing memory allocating freeing done handles memory management detecting memory safely freed instantiations .net types objects allocated managed heap pool memory managed clr long reference object exists may either direct via graph objects object considered use reference object exists reached used becomes garbage eligible collection .net framework includes garbage collector gc runs periodically separate thread application thread enumerates unusable objects reclaims memory allocated non-deterministic compacting mark-and-sweep garbage collector gc runs set amount memory used enough pressure memory system since guaranteed conditions reclaim memory reached gc runs non-deterministic .net application set roots pointers objects managed heap managed objects include references static objects objects defined local variables method parameters currently scope objects referred cpu registers gc runs pauses application object referred root recursively enumerates objects reachable root objects marks reachable uses cli metadata reflection discover objects encapsulated object recursively walk enumerates objects heap initially allocated contiguously using reflection objects marked reachable garbage mark phase since memory held garbage consequence considered free space however leaves chunks free space objects initially contiguous objects compacted together make free space managed heap contiguous reference object invalidated moving object updated gc reflect new location application resumed garbage collection ends latest version .net framework uses concurrent garbage collection along user code making pauses unnoticeable done background garbage collector used .net framework also generational objects assigned generation newly created objects tagged generation 0 objects survive one garbage collection tagged generation 1 generation 1 objects survive another collection generation 2 framework uses generation 2 objects higher generation objects garbage collected less often lower generation objects raises efficiency garbage collection older objects tend longer lifetimes newer objects ignoring older objects collection runs fewer checks compaction operations needed total application first launched .net framework compiles cil code executable code using just-in-time compiler caches executable program .net native image cache due caching application launches faster subsequent launches although first launch usually slower speed first launch developers may use native image generator utility manually ahead-of-time compile cache .net application garbage collector integrated environment introduce unanticipated delays execution developer little direct control large applications number objects garbage collector needs work become large means take long time visit rearrange .net framework provides support calling streaming simd extensions sse via managed code april 2014 visual studio 2013 update 2 however mono provided support simd extensions version 2.2 within namespace 2009 mono lead developer miguel de icaza expressed hope simd support adopted clr ecma standard streaming simd extensions available x86 cpus since introduction pentium iii architectures arm mips also simd extensions case cpu lacks support extensions instructions simulated software .net framework predominant implementation .net technologies implementations parts framework exist although runtime engine described ecma-iso specification implementations may encumbered patent issues iso standards may include disclaimer attention drawn possibility elements document may subject patent rights iso shall held responsible identifying patent rights harder develop alternatives fcl described open standard may subject copyright restrictions also parts fcl windows-specific functions behavior implementation non-windows platforms problematic alternative implementations parts framework listed microsoft managed code frameworks components licensed follows
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Operating systems
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visma solutions visma solutions finnish joint stock company offers saas business software companies company provides professional services automation software visma severa valueframe e-accounting software visma netvisor budgeting forecasting software visma navita e-invoicing service maventa online signature service visma sign visma solutions part visma group visma solutions founded end year 2012 former joint stock company called netvisor named visma solutions netvisor founded markku nylund studied lappeenranta university technology 2000 netvisor merged bittivisio first version software launched 2002 since netvisor operating joint owned company responsible marketing r activities software 2011 netvisor part visma group end 2012 company ’ name changed visma solutions visma severa founded 2004 ari-pekka salovaara jari kärkkäinen studying lappeenranta university technology time 2010 company acquired visma 2013 part visma solutions company granted various accolades visma severa psa software optimized organizations pr advertising design engineering law architecture accounting firms visma severa used 700 professional companies worldwide main markets finland sweden norway visma netvisor e-accounting software used 20 000 companies software developed 10 years one pioneers field e-accounting saas software netvisor rewarded multiple times example 2005 netvisor ’ eaccounting service nominated world ’ best online service banks 2010 netvisor among ten fastest growing technology companies finland visma navita cloud-based service budgeting forecasting reporting business management data used navita based real-time figures updated directly accounting management systems maventa popular e-invoicing service nordics 150 000 users maventa connected existing erp-system used separate internet based software valueframe psa software suited architects advertising communication agencies consultants visma sign legally binding online signature service visma sign integrated online forms immediate signing used send signing invitations via email text messages
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Distributed computing architecture
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arm cortex-a73 arm cortex-a73 microarchitecture implementing armv8-a 64-bit instruction set designed arm holdings sophia design centre cortex-a73 2-wide decode out-of-order superscalar pipeline cortex-a73 serves successor cortex-a72 designed offer 30 greater performance 30 increased power efficiency design cortex-a73 based 32-bit armv7-a cortex-a17 emphasizing power efficiency sustained peak performance cortex-a73 primarily targeted mobile computing reviews cortex-a73 showed improved integer instructions per clock ipc though lower floating point ipc relative cortex-a72 cortex-a73 available sip core licensees design makes suitable integration sip cores e.g gpu display controller dsp image processor etc one die constituting system chip soc cortex-a73 also first arm core modified arm semi-custom 'built arm license kryo 280 first released semi-custom product though modifications made relative stock cortex-a73 announced hisilicon kirin 960 released 2016 utilizes 4 cortex-a73 cores clocked 2.36 ghz 'big cores big.little arrangement 4 'little arm cortex-a53 cores mediatek helio x30 utilizes 2 cortex-a73 cores 2.56 ghz 'big cores deca-core big.little arrangement 4 cortex-a53 4 cortex-a35 'little cores kryo 280 released march 2017 qualcomm snapdragon 835 uses modified cortex-a73 core soc utilizes 8 kryo 280 cores big.little arrangement two 4-core blocks clocked 2.456 ghz 1.906 ghz modifications made qualcomm relative stock cortex-a73 core unknown resulting kryo 280 core demonstrated increased integer ipc kryo 260 also used cortex-a73 cores though lower clock speeds kryo 280 combination cortex-a53 cores
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Computer architecture
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msstyles msstyles microsoft file format contains bitmaps metadata windows xp skinning engine first introduced windows whistler build 2250 engine unmodified state fully applies .msstyles files digitally signed microsoft luna zune theme default windows xp style known luna additional custom-made styles available internethowever digitally signed four signed styles include royale media center edition energy blue royale noir windows embedded standard ctp refresh zune style custom-made styles used using different methods means manual replacement automation executable files many popular freely distributed theme-patching executable files found online windows vista windows 7 also use .msstyles files skinning like aero.msstyles file however format files completely different .msstyles files transferable windows vista windows xp version .msstyles file contains png images metadata manual way replace three dll files uxtheme.dll shsvcs.dll themeui.dll use unsigned custom visual styles windows vista
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Operating systems
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comparison java c++ comparison java c++ two prominent object-oriented programming languages differences programming languages c++ java traced heritage different design goals c++ designed systems applications programming i.e infrastructure programming extending procedural programming language c designed efficient execution c c++ added support object-oriented programming exception handling lifetime-based resource management raii generic programming template metaprogramming c++ standard library includes generic containers algorithms standard template library stl many general purpose facilities java general-purpose concurrent class-based object-oriented programming language designed minimize implementation dependencies relies java virtual machine secure highly portable bundled extensive library designed provide full abstraction underlying platform java statically typed object-oriented language uses syntax similar incompatible c++ includes documentation system called javadoc different goals development c++ java resulted different principles design trade-offs languages differences follows c++ java provide facilities generic programming templates generics respectively although created solve similar kinds problems similar syntax quite different example comparing exists wikibooks addition running compiled java program computers running java applications generally must also run java virtual machine jvm compiled c++ programs run without external applications early versions java significantly outperformed statically compiled languages c++ program statements two closely related languages may compile machine instructions c++ compiling several byte codes involving several machine instructions interpreted jvm example since performance optimizing complex issue difficult quantify performance difference c++ java general terms benchmarks unreliable biased given different natures languages definitive qualitative differences also difficult draw nutshell inherent inefficiencies hard limits optimizing java given heavily relies flexible high-level abstractions however use powerful jit compiler modern jvm implementations mitigate issues case inefficiencies java great compiled c c++ code called java via jni inefficiencies inherent java language include mainly however number benefits java design realized theorized also performance problems occur c++ c++ language defined iso/iec 14882 iso standard published iso/iec jtc1/sc22/wg21 committee latest post-standardization draft c++11 available well c++ language evolves via open steering committee called c++ standards committee committee composed creator c++ bjarne stroustrup convener herb sutter prominent figures including many representatives industries user-groups i.e. stake-holders open committee anyone free join participate contribute proposals upcoming releases standard technical specifications committee aims release new standard every years although past strict review processes discussions meant longer delays publication new standards 1998 2003 2011 java language defined java language specification book published oracle java language continuously evolves via process called java community process world programming community represented group people organizations java community members—which actively engaged enhancement language sending public requests java specification requests must pass formal public reviews get integrated language lack firm standard java somewhat volatile nature specifications constant source criticism stake-holders wanting stability conservatism addition new language library features contrast c++ committee also receives constant criticism opposite reason i.e. strict conservative taking long release new versions c++ trademark company organization owned individual java trademark oracle corporation
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Programming language topics
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pine email client pine freeware text-based email client developed university washington first version written 1989 announced public march 1992 source code available unix version license written university washington pine longer development replaced alpine client available apache license unix windows linux versions pine unix/linux version text user interface based—its message editor inspired text editor pico windows formerly dos version called pc-pine webpine available individuals associated university washington students faculty etc —a version pine implemented web application moved alpine however still many users software many people believe pine stands pine elm one original authors laurence lundblade insists never case started simply word acronym first choice backronym pine would pine nearly elm time changed university mean program internet news e-mail original announcement said pine originally based elm evolved much since 'pine no-longer elm version 3.91 pine license similar bsd stated university registered trademark pine name respect computer programs used communication electronic mail applications march 1995 version 3.92 holder copyright university washington changed license even source code still available allow modifications changes pine distributed anyone also claimed even old license never allowed distribution modified versions trademark pine name part position matter reaction developers forked version 3.91 name mana mail news agent avoid trademark issue gnu project adopted gnu mana richard stallman claims university washington threatened sue free software foundation distributing modified pine program resulting development mana ceasing versions released pico clone gnu nano also written due change licensing terms pine pico explained nano author blog post criticizing license 2001 university washington later modified license somewhat allow unmodified distribution pine alongside collections free software license still conform open source free software guidelines semi-free software effectively proprietary software 2006 university washington announced stopped development pine pine 4.64 although pine continues supported place new family email tools based upon pine called alpine licensed apache license version 2 november 29 2006 saw first public alpha release forms new approach since alpha test pine always non-public alpine 1.0 publicly released december 20 2007 recent version 2.21.9 released september 19 2017
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Internet protocols
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personal printer data stream personal printer data stream general name family page description language used ibm printers includes proprinter quietwriter quickwriter laserprinter 4019 laserprinter 4029 commands ppds introduced control printers 1981 launch ibm graphics printer 5152 originally called ibm ascii proprinter quickwriter quietwriter data stream name changed ppds ibm laserprinter introduced 1989 ppds different levels functions upward compatible although many laser inkjet printers support ppds support binary printer languages still use esc syntax include printer command language versions 1 5 epson esc/p command set level 1 basic level ppds providing basic services needed printer level represented 9- 24-pin proprinter family printers within level typical differences among printers follows level 2 incorporates enhancements font selection print quality selection paper handling level represented quietwriter quickwriter family products following commands enable use enhancements level 3 provides enhancements previous ppds levels page type printers ibm laserprinter 4019 enhancements level 4 adds new features ibm laserprinter 4029 previous ppds levels features include compression scalable fonts enhanced orientations languages define different printable areas given physical medium pcl ppds use different characteristics orders searching substitute font pcl uses ascii-encoded numerical values command parameters ppds uses binary encoded parameters several modern lexmark printers example lexmark ms510/610 series mfp mx511/611 series support ppds level 4 order provide high level support legacy applications written specifically ibm 4019 4029 laser printers
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Programming language topics
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unistim unistim unified networks ip stimulus deprecated telecommunications protocol developed nortel acquired avaya ip phone terminals soft phones ip pbx communications manufacturers ip pbx equipment aastra alcatel avaya ... followed path developing proprietary protocols protocols gradually replaced complemented standardized protocols including h.323 especially sip protocols works master slave mode operations simply reflect basic actions user perform terminal press button commands sent display network terminal turn light display message stimulus implement easily new facility telephone without modify software embedded terminals simplifies procedures maintenance upgrade installed base sense stimulus protocols differ functional protocols sip h.323 impose one hand service defined standard terminal loads specific logic corresponding service question approach allows manufacturers quickly deliver wide range services without wait services standardized nortel active standardization effort protocols within ietf drawing work pre-standard unistim already developed work nortel ip pbx systems ip centrex platforms 1996 contributions common nortel cisco systems example culminated publication ietf rfc 3054 media gateway ip phone application profile outlining options protocol megaco/h.248 ip command posts unistim protocol implemented avaya ip pbx systems licensed third-party suppliers → history see example release company spectralink details implementation protocol unistim available document telephony data network services telephone filed united states patent 7068641 may 7 1999 secure unistim protocol implemented as5300 cs2100 enables encryption unistim protocol use smc 2450
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Internet protocols
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bashlite bashlite also known gafgyt lizkebab qbot torlus lizardstresser malware infects linux systems order launch distributed denial-of-service attacks ddos originally also known name bashdoor term refers exploit method used malware used launch attacks 400 gbps original version 2014 exploited flaw bash shell shellshock software bug exploit devices running busybox months later variant detected could also infect vulnerable devices local network 2015 source code leaked causing proliferation different variants 2016 reported one million devices infected identifiable devices participating botnets august 2016 almost 96 percent iot devices 95 percent cameras dvrs roughly 4 percent home routers less 1 percent compromised linux servers bashlite written c designed easily cross-compile various computer architectures exact capabilities differ variants common features generate several different types ddos attacks hold open tcp connections send random string junk characters tcp udp port repeatedly send tcp packets specified flags may also mechanism run arbitrary shell commands infected machine facilities reflected amplification attacks bashlite uses client–server model command control protocol used communication essentially lightweight version internet relay chat irc even though supports multiple command control servers variants single command control ip-address hardcoded propagates via brute forcing using built-in dictionary common usernames passwords malware connects random ip addresses attempts login successful logins reported back command control server
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Computer security
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ceph software computing ceph pronounced free-software storage platform implements object storage single distributed computer cluster provides interfaces object- block- file-level storage ceph aims primarily completely distributed operation without single point failure scalable exabyte level freely available ceph replicates data makes fault-tolerant using commodity hardware requiring specific hardware support result design system self-healing self-managing aiming minimize administration time costs ceph employs five distinct kinds daemons fully distributed may run set servers clients different use cases directly interact different subsets ceph striping individual files across multiple nodes achieve higher throughput similar raid0 stripes partitions across multiple hard drives adaptive load balancing supported whereby frequently accessed objects replicated nodes bluestore default recommended storage type production environments ceph storage implementation providing better latency configurability filestore backend avoiding shortcomings filesystem based storage involving additional processing caching layers filestore backend still considered useful stable xfs recommended underlying filesystem type production environments btrfs recommended non-production environments ext4 filesystems recommended resulting limitations maximum rados objects length ceph implements distributed object storage ceph software libraries provide client applications direct access reliable autonomic distributed object store rados object-based storage system also provide foundation ceph features including rados block device rbd rados gateway ceph file system librados software libraries provide access c c++ java php python rados gateway also exposes object store restful interface present native amazon s3 openstack swift apis ceph object storage system allows users mount ceph thin-provisioned block device application writes data ceph using block device ceph automatically stripes replicates data across cluster ceph rados block device rbd also integrates kernel-based virtual machines kvms ceph rbd interfaces ceph object storage system provides librados interface cephfs file system stores block device images objects since rbd built librados rbd inherits librados abilities including read-only snapshots revert snapshot striping images across cluster ceph improves read access performance large block device images block device virtualized providing block storage virtual machines virtualization platforms apache cloudstack openstack opennebula ganeti proxmox virtual environment ceph file system cephfs runs top object storage system provides object storage block device interfaces ceph metadata server cluster provides service maps directories file names file system objects stored within rados clusters metadata server cluster expand contract rebalance file system dynamically distribute data evenly among cluster hosts ensures high performance prevents heavy loads specific hosts within cluster clients mount posix-compatible file system using linux kernel client older fuse-based client also available servers run regular unix daemons ceph initially created sage weil doctoral dissertation advised professor scott a. brandt jack baskin school engineering university california santa cruz ucsc sponsored advanced simulation computing program asc including los alamos national laboratory lanl sandia national laboratories snl lawrence livermore national laboratory llnl first line code ended part ceph written sage weil 2004 summer internship llnl working scalable filesystem metadata management known today ceph mds 2005 part summer project initiated scott a. brandt led carlos maltzahn sage weil created fully functional file system prototype adopted name ceph ceph made debut sage weil giving two presentations november 2006 one usenix osdi 2006 another sc'06 graduation fall 2007 weil continued work ceph full-time core development team expanded include yehuda sadeh weinraub gregory farnum march 19 2010 linus torvalds merged ceph client linux kernel version 2.6.34 released may 16 2010 2012 weil created inktank storage professional services support ceph april 2014 red hat purchased inktank bringing majority ceph development in-house october 2015 ceph community advisory board formed assist community driving direction open source software-defined storage technology charter advisory board includes ceph community members global organizations committed ceph project including individuals canonical cern cisco fujitsu intel red hat sandisk suse name ceph abbreviation cephalopod class molluscs includes octopus name emphasized logo suggests highly parallel behavior octopus chosen associate file system sammy banana slug mascot ucsc cephalopods banana slugs molluscs
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Computer file systems
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jtest jtest automated java software testing static analysis product made parasoft product includes technology data-flow analysis unit test-case generation execution static analysis regression testing code coverage runtime error detection jtest used companies cisco systems transcore aig united guaranty wipro technologies also known used lockheed martin f-35 joint strike fighter program jsf jtest 19th dr.dobb jolt product excellence productivity awards security tool category part parasoft application security solution previously jtest granted codie award software information industry association siia best software testing solution 2007 2005 also technology year award best application test tool infoworld two years row 2006 2007 jtest first received jolt award excellence 2000
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Computer security
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connection broker software engineering connection broker resource manager manages pool connections connection-based resources databases remote desktops enabling rapid reuse connections short-lived processes without overhead setting new connection time connection brokers often used systems using n-tier architectures remote desktop connection brokers perform variety tasks including
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Distributed computing architecture
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nvidia jetson nvidia jetson series embedded computing boards nvidia jetson tk1 tx1 tx2 models carry tegra processor soc nvidia integrates arm architecture central processing unit cpu jetson low-power system designed accelerating machine learning applications jetson family includes following boards published performance modes nvidia jetson tx2 published operation modes nvidia jetson nano various operating systems software might able run jetson board series jetpack software development kit sdk nvidia jetson board series official nvidia download page bears entry jetpack 3.2 uploaded 2018-03-08 states even qnx widely announced jetson platform still success reports installing running specific qnx packages certain nvidia jetson board variants namely package qnx-v3q-23.16.01 seemingly parts based nvidia vibrante linux distribution reported run jetson tk1 pro board
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Computer architecture
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amd accelerated processing unit amd accelerated processing unit apu formerly known fusion marketing term series 64-bit microprocessors advanced micro devices amd designed act central processing unit cpu graphics processing unit gpu single die amd announced first generation apus llano high-performance brazos low-power devices january 2011 second generation trinity high-performance brazos-2 low-power devices announced june 2012 third generation kaveri high performance devices launched january 2014 kabini temash low-power devices announced summer 2013 sony playstation 4 microsoft xbox one eighth generation video game consoles use semi-custom third generation low-power apus intel cpus integrated hd graphics also cpu gpu single die offer hsa features see amd fusion project started 2006 aim developing system chip combined cpu gpu single die amd took key step toward realising vision acquired graphics chipset manufacturer ati 2006 project reportedly required three internal iterations fusion concept create product deemed worthy release reasons contributing delay project include technical difficulties combining cpu gpu die 45 nm process conflicting views role cpu gpu within project first generation desktop laptop apu codenamed llano announced january 4 2011 2011 ces show las vegas released shortly thereafter featured k10 cpu cores radeon hd 6000-series gpu die fm1 socket apu low-power devices announced brazos platform based bobcat microarchitecture radeon hd 6000-series gpu die conference january 2012 corporate fellow phil rogers announced amd would re-brand fusion platform heterogeneous system architecture hsa stating fitting name evolving architecture platform representative entire technical community leading way important area technology programming development however later revealed amd subject trademark infringement lawsuit swiss company arctic used name fusion line power supply products second generation desktop laptop apu codenamed trinity announced amd 2010 financial analyst day released october 2012 featured piledriver cpu cores radeon hd 7000 series gpu cores fm2 socket amd released new apu based piledriver microarchitecture march 12 2013 laptops/mobile june 4 2013 desktops codename richland second generation apu low-power devices brazos 2.0 used exactly apu chip ran higher clock speed rebranded gpu radeon hd7000 series used new io controller chip semi-custom chips introduced microsoft xbox one sony playstation 4 video game consoles third generation technology released 14 january 2014 featuring greater integration cpu gpu desktop laptop variant codenamed kaveri based steamroller architecture low-power variants codenamed kabini temash based jaguar architecture november 2017 hp released envy x360 featuring ryzen 5 2500u apu first 4th generation apu based zen cpu architecture vega graphics architecture amd founding member heterogeneous system architecture hsa foundation consequently actively working developing hsa cooperation members following hardware software implementations available amd apu-branded products amd apus unique architecture amd cpu modules cache discrete-class graphics processor die using bus architecture allows use graphics accelerators opencl integrated graphics processor goal create fully integrated apu according amd eventually feature 'heterogeneous cores capable processing cpu gpu work automatically depending workload requirement first generation apu released june 2011 used desktops laptops based k10 architecture built 32 nm process featuring two four cpu cores thermal design power tdp 65-100 w integrated graphics based radeon hd6000 series support directx 11 opengl 4.2 opencl 1.2 performance comparisons similarly priced intel core i3-2105 llano apu criticised poor cpu performance praised better gpu performance amd later criticised abandoning socket fm1 one generation amd brazos platform introduced january 4 2011 targeting subnotebook netbook low power small form factor markets features 9-watt amd c-series apu codename ontario netbooks low power devices well 18-watt amd e-series apu codename zacate mainstream value notebooks all-in-ones small form factor desktops apus feature one two bobcat x86 cores radeon evergreen series gpu full directx11 directcompute opencl support including uvd3 video acceleration hd video including 1080p amd expanded brazos platform june 5 2011 announcement 5.9-watt amd z-series apu codename desna designed tablet market desna apu based 9-watt ontario apu energy savings achieved lowering cpu gpu northbridge voltages reducing idle clocks cpu gpu well introducing hardware thermal control mode bidirectional turbo core mode also introduced amd announced brazos-t platform october 9 2012 comprised 4.5-watt amd z-series apu codenamed hondo a55t fusion controller hub fch designed tablet computer market hondo apu redesign desna apu amd lowered energy use optimizing apu fch tablet computers deccan platform including krishna wichita apus cancelled 2011 amd originally planned release second half 2012 first iteration second generation platform released october 2012 brought improvements cpu gpu performance desktops laptops platform features 2 4 piledriver cpu cores built 32 nm process tdp 65 w 100 w gpu based radeon hd7000 series support directx 11 opengl 4.2 opencl 1.2 trinity apu praised improvements cpu performance compared llano apu release second iteration generation 12 march 2013 mobile parts 5 june 2013 desktop parts january 2013 jaguar-based kabini temash apus unveiled successors bobcat-based ontario zacate hondo apus kabini apu aimed low-power subnotebook netbook ultra-thin small form factor markets temash apu aimed tablet ultra-low power small form factor markets two four jaguar cores kabini temash apus feature numerous architectural improvements regarding power requirement performance support newer x86-instructions higher ipc count cc6 power state mode clock gating kabini temash amd first also first ever quad-core x86 based socs integrated fusion controller hubs fch kabini temash codenamed yangtze salton respectively yangtze fch features support two usb 3.0 ports two sata 6 gbit/s ports well xhci 1.0 sd/sdio 3.0 protocols sd-card support chips feature directx 11.1-compliant gcn-based graphics well numerous hsa improvements fabricated 28 nm process ft3 ball grid array package taiwan semiconductor manufacturing company tsmc released may 23 2013 playstation 4 xbox one revealed powered 8-core semi-custom jaguar-derived apus third generation platform codenamed kaveri partly released january 14 2014 kaveri contains four steamroller cpu cores clocked 3.9 ghz turbo mode 4.1 ghz 512-core graphics core next gpu two decode units per module instead one allows core decode four instructions per cycle instead two amd trueaudio mantle api on-chip arm cortex-a5 mpcore release new socket fm2+ ian cutress rahul garg anandtech asserted kaveri represented unified system-on-a-chip realisation amd acquisition ati performance 45 w a8-7600 kaveri apu found similar 100 w richland part leading claim amd made significant improvements on-die graphics performance per watt however cpu performance found lag behind similarly-specified intel processors lag unlikely resolved bulldozer family apus a8-7600 component delayed q1 launch h1 launch steamroller architecture components allegedly scale well higher clock speeds amd announced release kaveri apu mobile market june 4 2014 computex 2014 shortly accidental announcement amd website may 26 2014 announcement included components targeted standard voltage low-voltage ultra-low voltage segments market early-access performance testing kaveri prototype laptop anandtech found 35 w fx-7600p competitive similarly-priced 17 w intel i7-4500u synthetic cpu-focused benchmarks significantly better previous integrated gpu systems gpu-focused benchmarks tom hardware reported performance kaveri fx-7600p 35 w intel i7-4702mq finding i7-4702mq significantly better fx-7600p synthetic cpu-focused benchmarks whereas fx-7600p significantly better i7-4702mq intel hd 4600 igpu four games could tested time available team
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Computer architecture
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language-based system language-based system type operating system uses language features provide security instead addition hardware mechanisms systems code referred trusted base responsible approving programs execution assuring perform operations detrimental system stability without first detected dealt common strategy guaranteeing operations impossible base system around high-level language java whose design precludes dangerous constructs many entirely written language minimum amount low-level code used since language-based systems assure ahead time things damage system corrupting memory dereferencing dangling pointers possible avoid expensive address space switches needed traditional oses microkernels popular traditional systems extreme form high-level language computer architecture trusted base pushed hardware entire system written high-level language
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Computer architecture
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super socket 7 super socket 7 also referred super 7 hardware-level extension socket 7 zif socket specification x86 processors compatible motherboards chipsets utilize standard socket 7 connection cpu adding certain features including maximum 100 mhz front-side bus support agp graphics cards super socket 7 used amd k6-2 k6-iii processors final cyrix m-ii processors final idt winchip 2 processors rise mp6 processors backward compatible socket 7 cpu meaning socket 7 cpu used super socket 7 motherboard super socket 7 cpu operate full speed socket 7 motherboard socket 5 cpus pin-compatible super socket 7 motherboards designed super socket 7 supported voltages needed socket 5 cpus amd previously always used intel sockets processors socket 7 last one amd retained legal rights intel hoped discontinuing socket 7 development moving slot 1 amd would left outdated platform making processors non-competitive extending fsb 66 100 mhz super socket 7 gave amd stopgap solution needed developing independent motherboard infrastructure slot architecture cheap served intended purpose many third party chipsets provided via sis others low quality especially regard agp implementations reputation amd gained buggy incompatible motherboards lingered though internal program via raise standards chipsets begun show results k6-iii pentium iii era amd put place quality assurance program athlon processor
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Computer architecture
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clinical practice research datalink clinical practice research datalink cprd observational interventional research service operates part uk department health jointly funded national institute health research nihr medicines healthcare products regulatory agency mhra cprd working closely extensive primary care topic specific comprehensive nihr research networks nhs digital programme would develop current organisation initially developed essex general practitioner dr alan dean facilitate day-to-day management general practice collaboration staff bata shoe factory east tilbury near practice early programmers included czech programmer jan boda 1987 venture capital company set named value added information medical products ltd vamp recruit practices form information base early development team three marcella devenish formerly midwife philip lee-warren formerly senior medical laboratory scientific officer leadership kieran o'mally developed computerised system using bos microcobol development environment period number uk practices using software product igp integrated general practice expanded hundred two half thousand return anonymous healthcare data vamp ltd offered gps cash equivalent gbp 500 month order build vamp research databank research purposes 1988 vamp research databank comprised 57 practices 543,100 patients figure doubled 1.2 million 1990 one year later 970 practices allowed vamp access data 1000 practices straightforward maintenance agreement vamp november 1993 parent company acquired reuters health information donated database department health 1994 time became general practice research database gprd contained data 650 practices 4.4 million active patients time two licensees data dr alan dean professor hershel jick database operated office national statistics 1999 point medicines control agency mca took agency became medicines healthcare products regulatory agency mhra 1 april 2003 following merger medical devices agency mda since use database expanded within uk overseas gprd run sub-division mhra direction dr john parkinson research utility gprd dramatically enhanced linkage datasets individual patient level external datasets included hospital episode statistics death certificates national cancer registry minap cardiovascular disease registry additionally dataset became choice fda major pharma companies following announcement chancellor plan growth commissioned study entitled research capability programme initiated aim assessing available research capabilities uk future potential growth areas sector opportunity identified collaboration department health mhra creating joint research service based upon consolidating expanding existing independent services new service known cprd developed meet expectations criteria outlined plan growth 29 march 2012 medicines healthcare products regulatory agency department health national institute health research nihr launched clinical practice research datalink cprd launch cprd sir kent woods chief executive mhra said clinical practice research datalink provide new data research services improve health patients also make uk world leader life sciences research david willetts minister universities science said uk world leader life sciences research base industry tell us could make better use data order drive medical breakthroughs clinical practice research datalink provide researchers access safeguarded data respects patient confidentiality give valuable insights serious health conditions ultimately help reduce time takes develop new treatments gprd became part data services provision cprd launch april 2012 cprd established new england-wide nhs observational interventional research service built research developments gprd also health research support service hrss previously managed nihr research capability program cprd remains housed within medicines healthcare products regulatory agency one three 'centres within agency cprd builds predecessors capabilities aims provide range services products areas medical research public health care fundamental work cprd collection linkage anonymised data sets provision research services cprd utilises maximum benefit linked data sets uk ’ health system provide researchers access high quality anonymous primary secondary health care data data collected allows researchers access wealth information including nhs provides free point delivery healthcare population 52 million england access data sets nhs england wales scotland northern ireland cprd provide population potentially 64 million patients uk access partnerships established include data sets european countries linking anonomysed primary care data large data registries related data sets means cprd offer huge array data information inclusion medical research studies include areas prescription drugs uses effect long term patient treatment strategy long term health benefit studies epidemic pandemic studies demographic health welfare studies example analysis 100 million gp consultations using cprd data 2016 provided first substantial evidence increase gp clinical workload england cprd range research experience expertise including cprd provides consulting services range research activities provided experienced internal team research service offers advice research methodology research governance well host services drawing expertise predecessors experience cprd research team built reputation conducting high-end research projects protocol development gaining approvals research data analysis report publication writing research capacity cprd resource expertise undertake research projects behalf customers independently variety undertakings commercial regulatory charitable academic sectors huge range studies cprd predecessors published list published papers found cprd research cprd offers range interventional research services facilitate running clinical trials primary health care data collected cprd taken participating gp surgeries united kingdom personal identifiers collected protecting privacy individuals data comes data collected includes
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Databases
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nitrokey nitrokey open source usb key enable secure encryption signing data secret keys always stored inside nitrokey protects malware computer viruses attackers user-chosen pin tamper-proof smart card protect nitrokey case loss theft hardware software nitrokey available open source free software open hardware enables independent parties verify security device nitrokey supported microsoft windows linux macos 2008 jan suhr rudolf böddeker another friend travelling found looking use encrypted emails internet cafés meant secret keys remain secure computer viruses proprietary usb dongles existed time lacked certain ways consequentially established open source project crypto stick august 2008 grew become nitrokey spare-time project founders develop hardware solution enable secure usage email encryption first version crypto stick released 27 december 2009 late 2014 founders decided professionalize project renamed nitrokey nitrokey firmware audited german cybersecurity firm cure53 may 2015 hardware audited company august 2015 first four nitrokey models became available 18 september 2015 several nitrokey models exist nitrokey pro flagship model contains following features upcoming nitrokey storage provides features nitrokey pro additionally contains encrypted mass storage nitrokey developers believes proprietary systems ca n't provide strong security security systems need open source instance cases nsa intercepts security devices shipped implanted backdoors 2011 rsa hacked secret keys securid tokens stolen allowed hackers circumvent authentication revealed 2010 many fips 140-2 level 2 certified usb storage devices various manufacturers could easily cracked using default password nitrokey open source transparency wants provide high secure system avoid security issues proprietary rivals facing nitrokey mission provide best open source security key protect digital lives users
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Computer security
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propagation constraint database systems propagation constraint details happen related table update row rows target table paul beynon-davies 2004 p.108 tables linked using primary key foreign key relationships possible users update one table relationship way relationship longer consistent known breaking referential integrity example breaking referential integrity table employees includes department number 'housewares foreign key table departments user deletes department department table housewares employees records would refer non-existent department number propagation constraints methods used relational database management systems rdbms solve problem ensuring relationships tables preserved without error database textbook beynon-davies explains three ways rdbms handle deletions target related tuples
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Databases
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evil bit evil bit fictional ipv4 packet header field proposed rfc 3514 humorous april fools day rfc 2003 authored steve bellovin rfc recommended last remaining unused bit reserved bit ipv4 packet header used indicate whether packet sent malicious intent thus making computer security engineering easy problem simply ignore messages evil bit set trust rest evil bit become synonym attempts seek simple technical solutions difficult human social problems require willing participation malicious actors particular efforts implement internet censorship using simple technical solutions joke freebsd implemented day removed changes following day linux patch implementing iptables module ipt_evil posted next year furthermore patch freebsd 7 available kept up-to-date extension xmpp protocol xep-0076 malicious stanzas inspired evil bit rfc also quoted otherwise completely serious rfc 3675 .sex considered dangerous may caused proponents .xxx wonder whether internet engineering task force ietf commenting application top-level domain tld document related application april fool 2010 google added codice_1 parameter requests ajax apis
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Computer security
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wevideo wevideo u.s.-headquartered software service company provides collaborative web-based video editing platform works browser company formed 2011 based menlo park california wevideo inc. founded april 2011 initially creaza inc. creaza inc. owns related company norway called creaza education provides suite digital tools k-12 market including comic tools audio editing mind-mapping video editing applications wevideo publicly launched services september 2011 changing name creaza inc. allay confusion creaza education reflect social collaborative nature platform shortly 2011 launch wevideo invited youtube become youtube create partner embedded wevideo editor one number solutions offered youtube help users create better video compositions april 2012 wevideo announced launch partner google drive google ’ cloud-based collaboration storage service michael j. miller ziff brothers investments cited wevideo one favorites 2011 demo fall conference stating presents strong cloud-based consumer video editing solution network world also named wevideo one highlights conference labeling something keep eyes seattle times praised wevideo ability allow multiple editors work video noted videos five editors would require paid membership tech evangelist robert scoble noted wevideo ’ unique collaboration features stated “ wevideo yet another demonstration everything changing due cloud even video editing ” since inception wevideo received number awards including following
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Distributed computing architecture
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icl vme vme virtual machine environment mainframe operating system developed uk company international computers limited icl part fujitsu group originally developed 1970s vme/b later vme 2900 drive icl new 2900 series mainframes operating system known openvme incorporating unix subsystem runs icl series 39 trimetra mainframe computers well industry-standard x64 servers development program new range system started merger international computers tabulators ict english electric computers 1968 one fundamental decisions would feature new operating system number different feasibility design studies carried within icl three notable chief architect vme/b brian warboys subsequently became professor software engineering university manchester number influences seen design example multics icl earlier george 3 operating system however essentially designed scratch vme viewed primarily competing system/360 ibm mainframe commercial operating system adopted ebcdic character encoding creation mid-1970s constraints compatible earlier operating systems vme many ways modern architecture today unix derivatives unix designed 1960s microsoft windows started operating system single-user computers still betrays origins new range first launched october 1974 operating system referred system b time first delivered become vme/b vme/k developed independently according campbell-kelly whim ed mack delivered later smaller mainframes 2960 following financial crisis 1980 new management brought icl christopher laidlaw chairman robb wilmot managing director early decision new management drop vme/k thus july 1981 vme2900 launched although presented customer base merger vme/b vme/k reality vme/b base selected features vme/k grafted provided opportunity drop obsolescent features remained available customers needed form bonvme option 2900 suffix dropped system version 213 sv213 icl launched series 39 1985 successor original 2900 series open prefix added sv294 vme became capable hosting applications written originally unix unix system v release 3 based subsystem called vme/x adapted run vme using ascii character encoding 2007 fujitsu announced vme version run hosted subsystem called supernova within microsoft windows suse red hat enterprise linux x86-64 hardware 2012 vme user group axis announced almost 40 years would disbanding reduced user base vme structured set layers layer access resources different levels abstraction virtual resources provided one layer constructed virtual resources offered layer access resources layer controlled set access levels order process use resource particular access level must access key offering access level concept similar rings protection multics architecture allows 16 access levels outer 6 reserved user-level code orthogonally access levels operating system makes resources available applications form virtual machine virtual machine run multiple processes practice vme virtual machine closer concept process operating systems vme process like thread allocation resources virtual machine uses stack model stack popped resources allocated stack level released calls application operating system therefore made call retains process stack change protection level resulting efficiency system calls one features makes architecture competitive communication virtual machines achieved means events named communication channels shared memory areas hardware architecture also provides semaphore instructions inct increment-and-test tdec test-and-decrement files persistent objects recorded repository called catalogue unlike operating systems file naming hierarchy independent location file particular tape disk volume days need offline storage made easy keep track files regardless location move files locations without renaming well files catalogue keeps track users user groups volumes devices network connections many resources metadata files held object called file description catalogue probably first example would later called entity-relationship database interrupts handled creating new stack frame stack relevant process handling interrupt using new environment popping stack return interrupted process run-time exceptions referred contingencies captured object program error handler opeh produce report equivalent stack trace either interactively written journal compiled object code maintained format called omf object module format unlike many operating systems also format used loader various compilers available well utilities notably collector links code several omf modules single module efficient loading run-time module amender allows patching instructions omf module fix bugs using assembly language syntax command language vme known scl system control language much recognizably typed high-level programming language job control shell languages found operating systems likened scripting languages javascript though surface syntax derived algol 68 scl designed allow line-at-a-time interactive use console command file creation executable scripts programs language compiled object module format way vme programming language declaration procedure within scl also acts definition simple form template allowing procedure invoked interactive terminal fields validated according data types underlying procedure parameters using default procedure parameter values built-in command vocabulary uses consistent naming convention imperative verb followed noun example delete_file display_library_details command written full abbreviated form combines standard abbreviations verb noun example xf x delete f file dlbd display lb library details scl block-structured begin/end blocks serving dual complementary roles defining lexical scope variable declarations defining points resources acquired operating system released variables language accessible applications form environment variables number simple types strings superstrings sequences strings booleans integers also used contain references system resources files network connections possible disassemble scl program omf back scl source code using read_scl rscl command however output always perfect often include errors would stop re-compilation without user intervention simple code example seen 99 bottles beer website realistic example scl used compile program written s3 shown example taken columbia university archive implementations kermit commands illustrated fragment include whenever declares error handling policy assign_library binds local name file directory delete_file makes permanent file temporary deleted end block s3_compile compiles program written s3 command breaks usual verb-noun convention new_message_text_module creates module containing parameterized error messages suitable localization compile_scl compiles scl program object code collect command combines different object code modules single module driven local command file incorporated inline scl delimiters -- -- ++++ sub-commands input newmodule identify names input output modules suppress retain determine external visibility named procedures within collected module listmodule requests report describing output module note used separate parts hierarchic file name leading asterisk denotes local name library bound using assign_library command number parentheses file name version number operating system associates version number every file requests file get latest version unless specified otherwise creating new file default create next version leave previous version intact program however deliberately choosing create version 101 identify public release result icl heavy involvement delivery computer services uk public sector particular special security requirements opcon ccis early entrant market secure systems vme formed core icl activities secure systems arena advantage last large-scale operating system ever designed one built scratch underlying architecture encompassed many primitives needed develop secure system particular hardware assisted access control registers acr limit privileges could taken process including users led uk government central computing telecommunications agency ccta funding project spaceman mid 1980s icl defence technology centre dtc develop enhanced security variant vme icl launched pair complementary products commercial release called high security option hso public sector release including government furnished encryption gfe technologies called government security option gso hso gso formally tested cesg uk security evaluation scheme one predecessors itsec common criteria became first mainstream operating system formally certified series 39 range introduced nodal architecture novel implementation distributed shared memory seen hybrid multiprocessor system cluster design machine consists number nodes node contains order-code processor cpu main memory virtual machines typically located one time one node capability run node relocated one node another discs peripherals shared nodes nodes connected using high-speed optical bus used provide applications virtual shared memory memory segments marked shared public global segments replicated node updates broadcast inter-node network processes use unshared memory segments nodal local run complete isolation nodes processes vme originally written almost entirely s3 specially-designed system programming language based algol 68r however vme/k written primarily sfl assembly language although high-level language used operating system designed independent underlying hardware architecture contrary software hardware architecture closely integrated early 1990s onwards entirely new vme subsystems written partly wholly c programming language earliest days vme developed aid software engineering repository known cades built purpose using underlying idms database cades merely version control system code modules manages aspects software lifecycle requirements capture field maintenance cades used vme module development hold separate definitions data structures modes constants literals procedural interfaces core algorithms multiple versions 'lives components could exist algorithms written system development language sdl converted s3 source pre-processor multiple versions modules could generated application development tools offered vme fall two categories toolset vme unusually homogeneous customers using core set languages tools result tools also well integrated third-party tools made relatively little impression many years large majority vme users wrote applications cobol usually making use idms database tpms transaction processing monitor programming languages included fortran pascal algol 68rs coral 66 rpg2 served minority interests later mid 1980s compilers c became available within outside unix subsystem largely enable porting software relational database systems interesting pl/i subset compiler written eec assist porting programs ibm icl hardware compilers developed within icl share common architecture cases share components code-generators many compilers used module named alice assembly language internal common environment produced early form precompiled code p-code termed rose making compiled object module format omf libraries loadable machine range primary language used developing vme operating system system software compilers transaction processing monitors s3 high level language based many ways algol 68 data types low-level functions operators aligned closely architecture 2900 series assembly language sfl system function language also available used development vme/k whose designers confident high-level language could give adequate performance also idms database system account origins third-party product sfl originally called macro assembler programming language maple 2900 architecture positioned consisting high level language machines name changed request icl marketing developed part toolkit system subsequently cancelled related families assemblers architectures calm-xx running vme palm-xx developed pascal running various hosts developed internal use neither s3 sfl ever promoted commercial development tool end-user applications neither normally delivered standard part operating system explicitly marketed products right sfl s3 however available options user organisations third parties specific need quickbuild application development environment vme highly successful despite fact applications largely locked vme environment environment centred data dictionary system dds also called opendds early successful attempt build comprehensive repository supporting tools full support development lifecycle well database schemas file record descriptions dictionary keeps track objects reports queries screen designs 4gl code also supports variety models requirements capture level entity-relationship models process models quickbuild 4gl packaged two forms high-level declarative languages using jackson structured programming design paradigm applicationmaster unusual approach application design focuses user session running single conversational process completely hiding complexity maintaining state across user interactions 4gl tools screen designer work dds dictionary also holds database schemas considerable reuse metadata rarely achieved 4gls
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Operating systems
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spyhunter software spyhunter anti-spyware computer program microsoft windows windows xp later operating system designed remove malware trojan horses computer worms rootkits malicious software spyhunter currently version 4 receives daily definition updates spyhunter free version allows user scan computer purchase required remove found malware paid version user able receive support built-in helpdesk february 2016 enigma software filed lawsuit bleeping computer computer support website alleged latter engaged smear campaign purpose driving potential customers away spyhunter affiliate competing products turn bleeping computer filed lawsuit enigma software also alleged smear campaign march 2017 enigma software announced press release settlement reached lawsuit bleeping computer cases would dismissed october 2016 enigma software filed lawsuit popular security software vendor malwarebytes lawsuit arose malwarebytes software began targeting spyhunter potentially unwanted program november 7 2017 enigma case dismissed us district court
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Computer security
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dennard scaling dennard scaling also known mosfet scaling scaling law based 1974 paper co-authored robert h. dennard named originally formulated mosfets states roughly transistors get smaller power density stays constant power use stays proportion area voltage current scale downward length dennard observes transistor dimensions scaled 30 0.7x every technology generation thus reducing area 50 reduces delay 30 0.7x therefore increases operating frequency 40 1.4x finally keep electric field constant voltage reduced 30 reducing energy 65 power 1.4x frequency 50 therefore every technology generation transistor density doubles circuit becomes 40 faster power consumption twice number transistors stays moore law says number transistors doubles every two years combined dennard scaling means performance per watt grows rate doubling every two years trend referred koomey law rate doubling originally suggested koomey 1.57 years somewhat faster doubling period moore law recent estimates suggest slowing dynamic switching power consumption cmos circuits proportional frequency historically transistor power reduction afforded dennard scaling allowed manufacturers drastically raise clock frequencies one generation next without significantly increasing overall circuit power consumption since around 2005–2007 dennard scaling appears broken 2016 transistor counts integrated circuits still growing resulting improvements performance gradual speed-ups resulting significant frequency increases primary reason cited breakdown small sizes current leakage poses greater challenges also causes chip heat creates threat thermal runaway therefore increases energy costs breakdown dennard scaling resulting inability increase clock frequencies significantly caused cpu manufacturers focus multicore processors alternative way improve performance increased core count benefits many though means workloads increase active switching elements multiple cores still results increased overall power consumption thus worsens cpu power dissipation issues end result fraction integrated circuit actually active given point time without violating power constraints remaining inactive area referred dark silicon
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Computer architecture
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whitechapel computer works whitechapel computer works ltd. wcw computer workstation company formed east end london united kingdom april 1983 investment greater london enterprise board department trade industry first workstation model mg-1 named milliard gargantubrain hitchhiker guide galaxy mg-1 based national semiconductor ns32016 microprocessor 1024 × 800 pixel monochrome display 40 mb rodime st-506 hard disk optional ethernet interface initially natsemi genix operating system port 4.1bsd unix provided later replaced port 4.2bsd called 42nix mg-1 also partially kernel-based graphical user interface called oriel mg-1 first shipped customers 1984 base price around although oriel released following year distributor united states mg-1 sold north america cybertool systems ltd. 1984 1986 colour version cg-1 also announced 1986 followed mg-200 ns32332 processor 1987 wcw went receivership 1986 soon revived whitechapel workstations ltd. go liquidation april 1988 new company launched hitech-10 hitech-20 workstations r2000 r3000 mips architecture processors respectively ran umips variant unix either x11 news-based guis aimed computer animation applications ex-whitechapel engineers went form algorithmics ltd. specialising mips-based embedded systems algorithmics later acquired mips technologies 2002 rights hitech workstations acquired mistral computer systems ltd. june 1988
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Computer architecture
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macintosh file system macintosh file system mfs volume format disk file system created apple computer storing files 400k floppy disks mfs introduced original apple macintosh computer january 1984 mfs notable introducing resource forks allow storage structured data storing metadata needed support graphical user interface mac os mfs allows file names 255 characters length although finder allow users create names longer 63 characters 31 characters later versions mfs called flat file system support hierarchy directories folders exist concept original mfs-based macintosh work completely differently way modern systems visible finder windows open save dialog boxes always one empty folder volume altered way adding renaming files new empty folder appears thus providing way create new folders mfs stores file directory listing information single file finder creates illusion folders storing files pairs directory handles file handles display contents particular folder mfs scans directory files handle need find separate file containing directory listing macintosh file system support volumes 20 mb size 1,400 files small today standards time seemed expansive compared macintosh 400 kb floppy drive apple introduced hierarchical file system replacement mfs september 1985 mac os 7.6.1 apple removed support writing mfs volumes mac os 8.0 support mfs volumes removed altogether although macos built-in support mfs example vfs plug-in apple called mfslives provides read-only access mfs volumes
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Computer file systems
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data protection act 2012 data protection act 2012 act legislation enacted parliament republic ghana protect privacy personal data individuals regulates process personal information acquired kept used disclosed data controllers data processors requiring compliance certain data protection principles non compliance provisions act may attract either civil liability criminal sanctions depending nature infraction act also establishes data protection commission mandated ensure compliance provisions well maintain data protection register act first introduced ghana parliament 2010 subsequently withdrawn minister communications haruna iddrisu revised parliament passed bill 2012 received presidential assent may 10 2012 notice act gazetted 18 may 2012 accordance section 99 act came effect 16 october 2012 act made 99 sections arranged various headings follows key terms act defined interpretation section section 96 unless context otherwise requires section 96 provides following definitions notable terms “ data controller ” means person either alone jointly persons common persons statutory duty determines purposes manner personal data processed processed “ data processor ” relation personal data means person employee data controller processes data behalf data controller “ data subject ” means individual subject personal data “ foreign data subject ” means data subject information regulated laws foreign jurisdiction sent ghana foreign jurisdiction wholly processing “ personal data ” means data individual identified data b data information possession likely come possession data controller “ processing ” means operation activity set operations automatic means concerns data personal data collection organisation adaptation alteration information data b retrieval consultation use information data c disclosure information data transmission dissemination means available alignment combination blocking erasure destruction information data “ recipient ” means person data disclosed including employee agent data controller data processor data disclosed course processing data data controller include person disclosure made respect particular inquiry pursuant enactment “ special purposes ” means one following purpose journalism b purpose public interest c artistic purposes literary purposes act applicable data originates externally merely transits ghana however protected act section 45 4 act applies ghanaian government purpose government department treated data controller section 91 act provides 8 principles data processors take account processing data order protect privacy individuals principles similar oecd guidelines data protection directive european union data protection principles enumerated section 17 follows accountability principle data protection seen generally fundamental principle compliance requires data controller accountable compliance measures give effect data protection principles act requires person processes personal data ensure data processed without infringing rights data subject processed lawful reasonable manner section 18 1 data processed involves foreign data subject data controller processor must ensure personal data processed according data protection laws originating jurisdiction section 18 2 data processing lawful conditions justify processing present act minimality provision requires personal data processed purpose processed necessary relevant excessive section 19 prior consent data subject also required personal data processed section 20 requirement however subject exceptions instance purpose personal data processed necessary purpose contract data subject party authorised required law protect legitimate interest data subject necessary proper performance statutory duty necessary pursue legitimate interest data controller third party data supplied section 20 1 consent also required processing special personal data section 37 2 b data subject also object processing personal data section 20 2 data processor required stop processing data upon objection section 20 3 terms retention records act prohibits retention personal data period longer necessary achieve purpose collection unless retention required law reasonably necessary lawful purpose related function activity required contractual purposes data subject consented retention section 24 1 retention requirement however applicable personal data kept historical statistical research purposes section 24 2 except records must adequately protected access used unauthorized purposes section 24 3 person uses record personal data make decision data subject data must retained period required law code conduct law code conduct exists period afford data subject opportunity request access record upon expiration retention period personal data must however deleted destroyed manner prevents reconstruction intelligible form record personal data must de-identified sections 24 4 5 6 data subject may also request record personal data data subject held data controller destroyed deleted data controller longer authorisation retain data section 33 1 b act requires data controller collects personal data specific purpose explicitly defined lawful related functions activity person section 22 data controller collects data also required take necessary steps ensure data subject aware purpose data collected section 23 act requires data controller holds personal data collected connection specific purpose processing data must compatible purpose personal data initially obtained section 25 1 circumstances processing meets compatibility requirement include data subjects consents processing information data public domain processing necessary purposes fighting crime legislation concerns protection tax revenue collection conduct court proceedings protection national security public health life health data subject another person section 25 3 section 26 act data controller processes personal data must ensure data complete accurate date misleading regard purpose data collected processed openness principle ensures individuals know participate enforcing rights data protection regime section 27 1 makes mandatory data controller intends process personal data register data protection commission data controller intends collect data must also ensure data subject aware nature data collected persons responsible collection purpose collection well whether supply data mandatory discretionary among things section 27 2 data collected third party act requires data subject informed data collected soon practicable afterwards section 27 3 act provides circumstances notification requirement exempt include necessary avoid compromising law enforcement protect national security relates preparation conduct legal proceedings.section 27 4 also although mandatory data controller appoint data protection supervisor would responsible monitoring compliance act section 58 1 2 data protection supervisor may employee section 58 1 must meet qualification criteria set data protection commission section 58 7 act data controller duty prevent loss damage unauthorized destruction personal data well unlawful access unauthorized processing personal data data controller must therefore adopt appropriate reasonable technical organizational means take necessary steps ensure security personal data possession control section 28 1 data controller also required take reasonable measures identify forestall reasonably foreseeable risks ensure safeguards put place effectively implemented updated continually section 28 2 data controller must also observe generally accepted industry specific best practices securing data section 28 3 well ensure data processors comply security measures section 30 data processor domiciled ghana data controller must ensure data processor complies relevant laws country section 30 4 act also requires data controller soon reasonably practicable notify data protection commission data subject security breaches system take steps ensure integrity system restored section 31 data subject subject proving data subject ’ identity request data controller confirm data controller holds data subject ’ personal data describe nature personal data held identity third party previously access data section 32 1 request must however made reasonable manner within reasonable time paying prescribed fees form generally understandable section 32 2 data subject also request data controller correct delete personal data data subject held data controller inaccurate irrelevant excessive date incomplete misleading section 33 1 upon receipt request data controller must either comply request provide data subject credible evidence support data section 33 2 section 96 special personal data means personal data consists information relates race colour ethnic tribal origin data subject b political opinion data subject c religious beliefs beliefs similar nature data subject physical medical mental health mental condition dna data subject e sexual orientation data subject f commission alleged commission offence individual g proceedings offence committed alleged committed individual disposal proceedings sentence court proceedings act prohibits processing data relates children parental control religious philosophical beliefs ethnic origin race trade union membership political opinions health sexual life criminal behaviour individual section 37 1 special personal data may however processed necessary data subject given consent processing section 37 2 processing personal data necessary exercise right fulfil obligation conferred imposed law employer section 37 3 special personal data relating data subjects may also processed necessary protection vital interest data subject impossible data subject give consent data controller reasonably expected obtain consent consent data subject unreasonably withheld section 37 4 processing special personal data presumed necessary required purpose legal proceedings legal advice medical purposes undertaken health professional subject duty confidentiality patient health professional section 37 6 prohibition processing special personal data relating religious philosophical beliefs apply processing carried religious organisation data subject member institution founded upon religious philosophical principles respect persons associated institution necessary achieve aims institution section 38 1 act data subject right personal data corrected section 33 access personal data section 35 prevent processing personal data causes likely cause unwarranted damage distress section 39 prevent processing personal data purposes direct marketing section 40 require data controller take decision would significantly affect solely processing automatic means section 41 exempt manual data section 42 compensated data controller ’ failure comply provisions act upon proof damages section 43 inaccurate data rectified section 44 act establishes data protection commission two main objects functions dpc section 3 dpc governed 11-member board appointed president ghana act provides certain specific institutional representation section 4 board members allowed hold office period exceeding three years appointed two terms section 5 1 allowances board members approved minister responsible communications consultation minister responsible finance section 9 board officially sworn 1 november 2012 currently chaired prof. justice samuel kofi date-bah retired justice supreme court ghana dpc officially launched 18 november 2014 act also mandates president appoint executive director section 11 shall responsible day-to-day administration dpc well implementation decisions board section 12 mrs. teki akuetteh falconer current executive-director act sources dpc funds include money approved parliament donations grants money accrues dpc performance functions money minister responsible finance approves section 14 dpc also granted power serve enforcement notices data controllers requiring refrain contravening data protection principles section 75 enforcement notice may cancelled varied either dpc motion upon application recipient notice section 76 act provides establishment data protection register maintained dpc data controllers must compulsorily register section 46 applications registration data controller made writing act provides certain particulars business name address applicant description personal data collected description purpose processing personal data section 47 1 knowingly supplying false information amounts offence punishable fine imprisonment section 47 2 also separate entry register must made separate purpose data controller wishes process data section 47 3 dpc right refuse grant application particulars provided inclusion entry register insufficient data controller able provide appropriate safeguards protection privacy data subject opinion dpc applicant merit grant registration section 47 1 upon refusing registration application dpc required inform applicant reasons refusal event applicant may apply high court judicial review decision section 47 2 registration data controller subject renewal every two years section 50 dpc also power cancel registration good cause section 52 offence process personal data without registering section 56 act also provides access public register upon payment prescribed fee section 54 act provides several exemptions different purposes follows processing personal data exempt provisions act relates national security section 60 relation crime taxation section 61 disclosure personal data relating health education social work section 61 prohibited unless required law provisions act also applicable protection members public specified loss malpractice provisions section 63 processing personal data prohibited unless processing undertaken purpose literary artistic material data controller reasonably believes publication would public interest compliance provision incompatible special purposes section 64 provisions non-disclosure apply disclosure required law court section 66 act apply data processed purpose managing individual ’ domestic affairs section 67 data protection principles apply personal data consists references given confidence purposes education appointment office provision service data subject section 68 subject information provisions act apply personal data likely prejudice combat effectiveness armed forces section 69 processed assess suitability person judicial appointment confer national honour section 70 consists information respect claim professional privilege confidentiality section 74 personal data exempt provisions act relates examinations marks processed data controller relation individual ’ results section 72 consists information recorded candidate academic purposes section 73 act prohibits purchase personal data knowing reckless disclosure personal data contravention provision amounts offence section 88 act also makes sale offering sell advertising sale personal data offence section 89 minister responsible communications may consultation dpc make regulations effective implementation act
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Computer security
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glass os glass os google xe version google android operating system designed google glass glass-omap tag used referring modified android code found inside kernel repository following list shows main changes happened update release detailed release notes visit support website initial release xe5 updates included xe6 updates include glass updates automatically air glass check google servers periodically updates update available glass download device install update happens condition active battery charging reliable wi-fi connection root access easily obtained using following script using rooted bootloader adb reboot bootloader enter fastboot mode takes 10-15 seconds fastboot devices verify device fastboot see serial fastboot oem unlock unlocking erases data prompted run command twice sure fastboot flash boot boot.img gain root shell access rooted bootloader fastboot reboot reboot device adb root start adb root adb shell access shell root extract desired factory system image package flash glass back factory specifications run following script boot system images found google glass developer website adb reboot bootloader enter fastboot mode fastboot devices verify device fastboot see serial fastboot flash boot boot.img flash partitions factory images fastboot flash system system.img fastboot flash recovery recovery.img fastboot erase cache optional erase cache userdata partitition fastboot erase userdata fastboot oem lock optional want re-lock bootloader kernel source code easily attainable google repository using following script mkdir path-for-kernel-source cd path-for-kernel-source git clone https //android.googlesource.com/kernel/omap.git build kernel source code first download gcc toolchain repository git clone https //android.googlesource.com/platform/prebuilt export path= path-for-kernel-source /prebuilt/linux-x86/toolchain/arm-eabi-4.4.3/bin path build kernel using commands export arch=arm export subarch=arm export cross_compile=arm-eabi- cd path-for-kernel-source /omap git checkout glass-omap-xrr02 choose suitable release make notle_defconfig make
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Operating systems
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qualification principle programming language theory qualification principle states semantically meaningful syntactic class may admit local definitions words possible include block syntactic class provided phrases class specify kind computation common examples principle includes
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Programming language topics
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pp jailbreak pp jailbreak also commonly known pp pp25 app pp25 jailbreak term describing free chinese app containing tools capable jailbreaking ios 8 devices except apple tv eligible products include ipod touch iphone ipad app developed chinese ios hacking community known pp assistant first released january 19 2015 tools pp jailbreak application help users bypass device restrictions order obtain root access operating system users able install applications customizations typically available app store ios pp jailbreak available chinese notable application able jailbreak ios 8.4 mac ios 8.4 windows pp jailbreak gives users access software unavailable ios app store using cydia ios application digital distribution platform although pp jailbreak initially incompatible cydia includes recommended resources cydia software tools openssh ios user removes pp jailbreak device update device latest ios version due firmware updates apple furthermore device loaded latest ios version go back previous ios version initial release pp jailbreak tool included support ios 9.3 team suspected imminent firmware update apple would fix vulnerabilities used tool pp assistant also known m949mm term ios community developed jailbreaking tools pp jailbreak said fake taig ios jailbreak 25pp pc pp helper freeware software created manage android ios devices including ios 12 using app easily install games create backups view files device automatically clean temp files created software etc also option install apps without using appstore user interface pp helper app chinese language difficult user interface quite easy navigate
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Computer security
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w^x w^x write xor execute spoken w xor x security feature operating systems virtual machines memory protection policy whereby every page process kernel address space may either writable executable without protection program write data cpu instructions area memory intended data arrange run executable instructions dangerous writer memory malicious w^x relatively simple processors support fine-grained page permissions sun sparc sparc64 amd amd64 hewlett-packard pa-risc hp originally digital equipment corporation alpha arm early intel 64 processors lacked nx bit required w^x appeared later chips processors limited features intel i386 w^x requires using cs code segment limit line sand point address space execution permitted data located allowed executable pages placed linker changes generally required separate code trampolines code needed linker library runtime functions data w^x first implemented openbsd 3.3 released may 2003 2004 microsoft introduced similar feature called dep data execution prevention windows xp similar features available operating systems including pax exec shield patches linux netbsd implementation pax although w^x dep protected userland programs existence 2012 microsoft extended windows kernel x86 arm architectures late 2014 early 2015 w^x added openbsd kernel amd64 architecture early 2016 w^x fully implemented netbsd amd64 kernel partially i386 kernel since 2016 firefox 46 virtual machine javascript also implements w^x policy
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Operating systems
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owasp zap owasp zap short zed attack proxy open-source web application security scanner intended used new application security well professional penetration testers one active open web application security project owasp projects given flagship status used proxy server allows user manipulate traffic passes including traffic using https also run daemon mode controlled via rest api zap added thoughtworks technology radar may 2015 trial ring built features include intercepting proxy server traditional ajax web crawlers automated scanner passive scanner forced browsing fuzzer websocket support scripting languages plug-n-hack support plugin-based architecture online ‘ marketplace ’ allows new updated features added gui control panel easy use
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Computer security
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surface 2 surface 2 surface-series windows rt hybrid tablet computer created microsoft unveiled september 23 2013 released october 22 2013 successor original surface january 2015 microsoft longer manufactures surface 2 provide security updates device 2023 pre-orders surface 2 opened september 24 2013 device released october 22 2013 value-added services surface 2 includes 200 gb additional onedrive storage 2 years 1 year free skype calls landlines access skype wifi hotspots january 2015 stock sold microsoft store online microsoft confirmed discontinued production surface 2 surface 2 nokia lumia 2520 remaining windows rt device market discontinued well week later made magnesium alloy toughened glass outer shell surface 2 maintains similar design predecessor bare metal silver color scheme black bezel surface 2 also slightly thinner lighter previous model surface 2 uses 1.7 ghz quad-core nvidia tegra 4 chipset 2 gb ram microsoft claimed new chipset improvements internal hardware made surface 2 three four times faster original surface 10 hours battery life playing videos unlike original surface used 1366 x 768 display surface 2 uses 1080p display surface pro 2 display claimed almost 50 better color previous version well lowest reflectivity among competing tablets device also includes full-size usb 3.0 port 32 64 gb internal storage microsd slot surface 2 ships windows rt 8.1 4g lte model surface 2 launched march 18 2014 comes 64 gb model microsoft cellular partner surface 2 4g lte comes access app pre-installed device actually ships unlocked 4g models also come gps assisted gps glonass surface 2 includes microsoft calls silver-magnesium color scratch resistant compared original surface surface 2 ships windows rt 8.1 office 2013 rt unlike original surface launched office 2013 rt beta later received final release version bundled apps include mail calendar people contacts bing apps including food drink health fitness weather travel stocks sports apps later renamed msn apps like predecessor desktop apps already bundled os forbidden run surface 2 device unlike successor surface 3 classified 2-in-1 pc notable change surface surface 2 hiding desktop tile start screen updated versions surface cover accessories available surface 2 touch cover 2 type cover 2 slightly thinner previous versions include dynamic backlight system touch cover 2 1,092 sensors compared 80 original touch cover keyswitch length type cover 2 reduced 2.5 mm 1.5 mm new power cover accessory also available add 30 wh additional battery capacity device accompanying touch cover 2 type cover 2 wireless adapter allows connected 30 feet away via bluetooth updated kickstand tilted 55-degree angle alongside original 22-degree angle unveiling microsoft also showcased music cover variation touch cover serves dj mixer playback controls 16-button sampler three sliders mainstream public release announced distributed musicians surface remix project campaign initial reviews surface 2 mixed reviewers generally positive device hardware improvements compared original surface however surface 2 often criticized lack support traditional windows desktop programs low number high quality apps available windows store financial report microsoft second quarter 2014 revenue doubled 400 million first quarter 893 million however microsoft still lost 39 million since development costs equaled around 932 million skeptics acknowledged growth despite still losing money surface brand surface 2 reported overheating issues microsoft delivered update try fix issue
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Operating systems
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palm m500 series palm m500 series handheld personal digital assistants consisted three devices palm m500 palm m505 palm m515 series follow-up popular palm v series similar though slightly shorter footprint form factor like palm v series metal cases although m500 plastic back plate 160x160 resolution screen distinguishing features common series sd/mmc expansion slot faster processor new faster usb sync interface new software functionality new vibrating alarms new indicator light mechanical fastener vs. hot-glue case construction later models introduced improved version color display memory palm m500 series palm pilot pdas released march 6 2001 based poll conducted palm computing formerly division 3com determined palm v definitive look ideal pda palm m500 models based palm v form factor slim case slight curvature left right edges power button lit green docking cradle important message available input included four programmable buttons two scrolling buttons touch-sensitive 2-1/4 x 3 screen including 2-1/4 x 3/4 input area palm devices data input stylus pen using graffiti method m500 series models featured secure digital sd multi media card mmc expansion slot sd/mmc slot allowed additional memory upgrades devices well expandable platform add-on devices m500 series also first palm devices incorporate new universal connector universal palm t3 abandoned allowed additional add-on devices common hotsync cradles m500 entry-level model m500 series 8 mb on-board memory featured monochrome screen features common m500 series devices released march 6 2001 part original rollout series operating system palm os version 4.0 upgrade 4.1 processor 33 mhz motorola dragonball vz memory 8 mb display 160x160 pixel b w display 4-bit 16 shades gray size 4.49 x 3.02 x .46 11.41 x 7.67 x 1.17 cm weight 4.162 oz 118 g battery internal lithium polymer rechargeable 2hr recharge time empty ac adapter input 120 v 60 hz 10 w output 5.0 vdc 1.0 irda port expansion slot compatible sd mmc cards m505 time series rollout top-of-the-line model palm devices also 8 mb on-board memory addition standard m500 series features also featured 16-bit color frontlit screen released march 6 2001 part original rollout series operating system palm os version 4.0 upgrade 4.1 processor 33 mhz motorola dragonball vz memory 8 mb 4mb flash 8mb ram display 160x160 pixel color display 65,000+ colors size 4.48 x 3.03 x 0.50 11.38 x 7.70 x 1.27 cm weight 4.8 oz 136g battery internal lithium polymer rechargeable 2hr recharge time empty ac adapter input 120vac 60 hz 11w output 5.0vdc 1.0a irda port expansion slot compatible sd mmc cards march 4 2002 palm released m515 based consumer reviews surveys conducted company m515 developed improved version replacement m505 notable enhancements include 16 mb on-board memory enhanced backlighting system much criticism m505 even backlight dim difficult read environments m515 added additional setting allowing backlight put high considerably brighter predecessor operating system palm os version 4.1 processor 33 mhz motorola dragonball vz memory 16 mb ram 4 mb flash display 160x160 pixel color display 65,000+ colors size 4.48 x 3.03 x 0.50 11.38 x 7.70 x 1.27 cm weight 4.8 oz 139g battery internal lithium polymer rechargeable ac adapter input 120vac 60 hz 11w output 5.0vdc 1.0a irda port expansion slot compatible sd mmc cards
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Computer architecture
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advanced dungeons amp dragons heroes lance advanced dungeons dragons heroes lance video game released january 1988 various home computer systems consoles game based first dragonlance campaign module dungeons dragons fantasy role-playing game dragons despair first dragonlance novel dragons autumn twilight heroes lance focuses journey eight heroes ruined city xak tsaroth must face ancient dragon khisanth retrieve relic disks mishakal heroes lance side-scrolling action game game uses actual dungeons dragons statistics statistics characters exactly rule books eight heroes dragonlance novels series must assembled quest one visible screen time one on-screen hero dies next line appears heroes lance faithful representation books based departure usual role-playing video game style dungeons dragons games gameplay interface consists using one character time horizontally scrolling fighting character different types attacks spells making suited fighting different enemies merely act lives player traditional fighting games removing one main strategies role-playing games game eight heroes make party heroes lance based dragonlance novels margaret weis tracy hickman heroes lance part gold box series nickname titles silver box games nes version developed natsume heroes lance successful ssi 88,808 copies sold computers north america reviewing pre-production copy dos version heroes lance magazine g.m praised graphics excellent audio said would undoubtedly go straight top computer games charts stay several months good computer gaming world gave dos version game similarly positive review electronic gaming monthly columnist seanbaby listed nes version 2nd worst nes game 11th worst video game levi buchanan classic dungeons dragons videogame retrospective ign wrote n't plan well lose lot heroes short period time offered slight strategy angle fans largely preferred pool radiance straight rpg approach pool radiance sales triple heroes lance according gamespy game actually fairly decent side-scroller time frustrating level difficulty along fact could n't save game meant gamers gave game miss storyline game continued two subsequent video games dragons flame shadow sorcerer
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Computer architecture
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data-oriented parsing data-oriented parsing dop also data-oriented processing probabilistic model computational linguistics dop conceived remko scha 1990 aim developing performance-oriented grammar framework unlike probabilistic models dop takes account subtrees contained treebank rather restricted example 2-level subtrees like pcfgs several variants dop developed initial version developed rens bod based tree-substitution grammar recently dop combined lexical-functional grammar lfg resulting dop-lfg finds application machine translation work learning parameter estimation dop also found way machine translation
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Computational linguistics
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acarm-ng acarm-ng alert correlation assessment reaction module next generation open source ids/ips system acarm-ng alert correlation software significantly facilitate analyses traffic computer networks responsible collection correlation alerts sent network host sensors also referred nids hids respectively correlation process aims reduce total number messages need viewed system administrator possible merging similar events groups representing logical pieces malicious activity initial version acarm developed frame positif european research project 2004 2007 written java practical proof concept presented article despite poor scalability efficiency issues software proved highly useful end 2009 became obvious current design serious shortcomings poor performance first place result project discontinued later year new project nicknamed acarm-ng launched aiming replace original acarm acarm-ng bring alert correlation new dimension thank scalability plug-in-based architecture actively developed since 2009 wroclaw centre networking supercomputing part pl-grid project acarm-ng main features include acarm-ng consists 3 main elements correlation daemon wui optional database engine acarm-ng daemon designed scratch framework solution provides core system functionalities like logging alerts correlated meta-alerts passing system parts error recovery multi-threading etc.. rest package plug-ins separated following classes built-in software watchdog provides up-to-date information system status wui makes browsing correlated data easy via graphical tabular representation gathered correlated events system administrator easily see going every moment system lifetime wui daemon interoperate database daemon stores gathered data along correlation results runtime configuration wui entitled read display data notice even though data base engine required running daemon strongly recommended save data persistently rejecting use database makes impossible obtain system information via wui leads loss historical data system restarted events longer processed daemon discarded well often required limit amount incoming data example remove alerts raised periodically cron scripts order allow users adapt system input needs special preprocessor component provided allows define chain accept-if-match reject-if-match rules accept reject incoming alerts enter correlation engine acarm-ng daemon allows addition removal new plug-ins without need recompile core package makes system development testing much easier plug-in used configured main configuration file first persistency provides abstraction storage level generic interface used implement data-saving back-end long transaction mechanism provided recent stable release acarm-ng provides following persistency implementations input provides abstraction data gathering mechanism requirement implementation output alerts acarm-ng-compatible form recent stable release acarm-ng provides following input implementations filter provides abstraction correlation data update mechanism restrictions filter meta-alert though common use correlate similar alerts specially tuned api provided special case recent stable release acarm-ng provides following filter implementations trigger provides abstraction reporting reaction mechanism triggers design allowed change content data initiate response alerts typical use real-time reporting suspicious events administrators example via e-mail automatic reaction detected thread example blocking malicious host firewall recent stable release acarm-ng provides following trigger implementations trigger set independently react specific threshold correlated alerts count rule defined way daemon main preprocessor approach gives fully configurable solution allowing define arbitrary complex rules minimize false-positives especially system configured perform autonomous reaction suspicious events
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Computer security
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microsoft messenger service messenger formerly msn messenger service .net messenger service windows live messenger service instant messaging presence system developed microsoft 1999 use msn messenger software used instant messaging clients including windows 8 windows live messenger microsoft messenger mac outlook.com xbox live third-party clients also connected service communicated using microsoft notification protocol proprietary instant messaging protocol service allowed anyone microsoft account sign communicate real time people signed well april 2013 microsoft merged service skype network existing users able sign skype existing accounts access contact list part merger skype instant messaging functionality running backbone former messenger service despite multiple name changes service client software years messenger service often referred colloquially msn due history msn messenger service known msn messenger service 1999 2001 time microsoft changed name .net messenger service began offering clients longer carried msn name windows messenger client included windows xp originally intended streamlined version msn messenger free advertisements integrated windows nevertheless company continued offer upgrades msn messenger end 2005 previous versions msn messenger windows messenger superseded new program windows live messenger part microsoft launch windows live online services several years official name service remained .net messenger service indicated official network status web page though microsoft rarely used name promote service main client used access service became known windows live messenger microsoft started referring entire service windows live messenger service support documentation mid-2000s service integrate windows operating system automatically simultaneously signing network user logs windows account organizations also integrate microsoft office communications server active directory service december 2011 microsoft released xmpp interface messenger service part larger effort rebrand many windows live services microsoft began referring service simply messenger 2012 microsoft offered following instant messaging clients connected messenger service additionally third-party clients others able access messenger service microsoft messenger criticized use microsoft notification protocol provide encryption makes wiretapping personal conversations messenger possible someone intercepts communication easy unencrypted public wi-fi networks
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Internet protocols
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wbfs wbfs wii backup file system file system developed wii homebrew coder waninkoko uses waninkoko cios works creating wbfs partition sd usb device wii homebrew application may run dump wii game partition titles may launched using wii usb loader uses cios usb 2.0 load games external device although way natively load wbfs partition pc environment run wii emulator dolphin also several applications wbfs managers mac os x linux windows allow transfer iso image files wbfs formatted drive main advantage reduction file size wbfs format allows wii discs filled padding data must present iso wbfs file system strip away
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Computer file systems
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biometric database law biometric database law israeli law knesset passed december 2009 determining fingerprints facial contours would collected israeli residents collected data would integrated onto israeli digital identity cards digital passports biometric government database israeli citizens residents would created would used biometric identification would allow management access control identification individuals assist locating individuals suspected criminal activity law enforcement officials law passed december 2009 determined law gradually applied first phase inclusion one biometric data central database would voluntary laws targets presented first section law addresses serious issues identifying fake id cards passports producing double records person identity theft caused using documentation person identity stolen examples allow misuse identification documents illegal immigration criminal economic offenses activities harm israel national security nowadays identification documents easily forged criminals often try get assistance state workers 2005 2007 interior ministry reported loss theft destruction 150,000 id cards per year submitted requests handed new identity cards many cases question loss theft destruction id cards occurred several times resident three years data israeli police indicates 52 percent individuals submitted requests new identity cards lost stolen and/or destroyed years 1995 2006 criminal record 10 percent criminal record distribution counterfeit documents employees interior ministry would authorized collect biometric identification data israeli population transfer data database would managed biometric database management authority הרשות לניהול המאגר הביומטרי data would used issue resident identification documents verification individual identity means rechecking individual biometric identification data authorized officials police officer employee shin bet employee mossad etc. biometric database would stored separately government older existing identity database although selected government officials would capable linking two databases retrieve additional data opponents law including prominent israeli scientists security experts warned existence database could damage civil liberties state security leaks could used criminals hostile individuals israeli residents
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Databases
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compiled language compiled language programming language whose implementations typically compilers translators generate machine code source code interpreters step-by-step executors source code pre-runtime translation takes place term somewhat vague principle language implemented compiler interpreter combination solutions also common compiler translate source code intermediate form often called p-code bytecode passed interpreter executes programs compiled native code compile time tend faster translated run time due overhead translation process newer technologies just-in-time compilation general improvements translation process starting narrow gap though mixed solutions using bytecode tend toward intermediate efficiency low-level programming languages typically compiled especially efficiency main concern rather cross-platform support languages one-to-one correspondences programmed code hardware operations performed machine code making easier programmers control use central processing unit cpu memory fine detail effort always possible write compilers even traditionally interpreted languages example common lisp compiled java bytecode interpreted java virtual machine c code compiled native machine code directly native code programming languages support multiple compiling targets give control developers choose either execution speed cross-platform compatibility languages commonly considered compiled
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Programming language topics
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solarwinds solarwinds inc. american company develops software businesses help manage networks systems information technology infrastructure solarwinds headquartered austin texas sales product development offices number locations united states several countries around world company publicly traded may 2009 end 2015 october 2018 also acquired number companies still operates original brand names including pingdom papertrail loggly solarwinds officially founded 1999 tulsa oklahoma 2009 maintained profitability since founding company co-founded donald yonce former executive walmart brother david yonce solarwinds released first products trace route ping sweep earlier march 1998 released first web-based network performance monitoring application november 2001 according michael bennett became chief executive officer 2006 solarwinds name chosen early employee company nothing solar wind power 2006 company moved headquarters austin texas 300 company total 450 employees based 2011 2007 solarwinds raised funding austin ventures bain capital insight venture partners solarwinds completed initial public offering 112.5 million may 2009 closing higher prices initial day trading ipo solarwinds followed another opentable online restaurant-reservation service perceived break dry spell caused great recession companies went public bain capital insight venture partners backed ipo used opportunity sell shares offering analysts company executives forecasted continued expansion post-ipo including several acquisitions 2010 bennett retired position ceo replaced company former chief financial officer kevin thompson may 2013 solarwinds announced plans invest operations hub salt lake city utah named forbes best small company america citing high-functioning products low costs impressive company growth 2013 solarwinds employing 900 people october 2015 company disclosed talks then-unnamed party interested acquiring company making solarwinds privately held company acquisition private equity technology investment firms silver lake partners thoma bravo llc announced late 2015 january 2016 solarwinds taken private ownership 4.5 billion deal sale company employed 1,770 people worldwide 510 based austin reported revenues half billion dollars year november 2017 solarwinds released appoptics integrates much solarwind acquired software portfolio including librato traceview single software-as-a-service package appoptics included compatibility amazon web services microsoft azure september 2018 solarwinds filed ipo three years owned private equity firms solarwinds completed ipo october 19 2018 solarwinds reportedly updated network performance monitor product december 2018 enhancements cisco application centric infrastructure aci according wall street journal solarwinds offers freely downloadable software potential clients markets advanced software offering trial versions following funding 2007 solarwinds acquired several companies including neon software ipmonitor corp. opened european sales office ireland ipo 2009 solarwinds acquired number companies products including acquisition new zealand-based software maker kiwi enterprises announced january 2009 solarwinds acquired several companies 2011 ranked 10 forbes magazine list fastest-growing tech companies january 2011 acquired hyper9 inc austin-based virtualization management company undisclosed terms july solarwinds completed acquisition idaho-based network security company trigeo 35 million trigeo offices post falls added list solarwinds location already included satellite offices dallas salt lake city tulsa well operations australia czech republic india ireland singapore early 2012 month acquiring dameware solarwinds acquired patch management software provider eminentware december solarwinds acquired rhinosoft adding company product ftp voyager solarwinds suite tools services may 2013 solarwinds acquired n-able technologies 2013 cloud-based information technology services provider deal reportedly valued 120 million cash october acquired boulder colorado-based database performance management company confio software 103 million agreement solarwinds gained sales office london confio main product ignite 2014 2015 company acquired swedish web-monitoring company pingdom san francisco-based metrics monitoring company librato 40 million log management service papertrail 41 million 2015 solarwinds announced acquisition librato monitoring company capzure technology msp manager software n-able solarwinds previously acquired june 2016 solarwinds acquired logicnow rival remote monitoring software company new subsidiary solarwinds msp formed merging logicnow n-able technologies company announced subsidiary led logicnow former ceo walter scott new title executive vice president 2017 2019 solarwinds acquired spamexperts email security company loggly log management analytics company trusted metrics provider threat monitoring management software samanage service desk asset management provider
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Computer security
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page fault page fault sometimes called pf pf hard fault type exception raised computer hardware running program accesses memory page currently mapped memory management unit mmu virtual address space process logically page may accessible process requires mapping added process page tables may additionally require actual page contents loaded backing store disk processor mmu detects page fault exception handling software handles page faults generally part operating system kernel handling page fault operating system generally tries make required page accessible location physical memory terminates program case illegal memory access contrary fault might suggest valid page faults errors common necessary increase amount memory available programs operating system utilizes virtual memory including openvms microsoft windows unix-like systems including macos linux *bsd solaris aix hp-ux z/os page loaded memory time fault generated marked memory management unit loaded memory called minor soft page fault page fault handler operating system merely needs make entry page memory management unit point page memory indicate page loaded memory need read page memory could happen memory shared different programs page already brought memory programs page could also removed working set process yet written disk erased operating systems use secondary page caching example hp openvms may remove page need written disk remained unchanged since last read disk example place free page list working set deemed large however page contents overwritten page assigned elsewhere meaning still available referenced original process allocated since faults involve disk latency faster less expensive major page faults mechanism used operating system increase amount program memory available demand operating system delays loading parts program disk program attempts use page fault generated page loaded memory time fault called major hard page fault page fault handler os needs find free location either free page memory non-free page memory latter might used another process case os needs write data page written since last modified mark page loaded memory process page table space made available os read data new page memory add entry location memory management unit indicate page loaded thus major faults expensive minor faults add storage access latency interrupted program execution page fault occurs reference address part virtual address space meaning page memory corresponding called invalid page fault page fault handler operating system generally pass segmentation fault offending process indicating access invalid usually results abnormal termination code made invalid reference null pointer usually represented pointer address 0 address space many operating systems set memory management unit indicate page contains address memory include page virtual address space attempts read write memory referenced null pointer get invalid page fault illegal accesses invalid page faults invalid conditions result segmentation fault bus error resulting programming termination crash core dump depending operating system environment often problems caused software bugs hardware memory errors caused overclocking may corrupt pointers make correct software fail also crash operating system operating systems windows unix unix-like systems provide differing mechanisms reporting errors caused page faults windows uses structured exception handling report page fault-based invalid accesses access violation exceptions unix unix-like systems typically use signals sigsegv report error conditions programs program receiving error handle operating system performs default action typically involving termination running process caused error condition notifying user program malfunctioned recent versions windows often report problems simply stating something like program must close experienced user programmer access debugger still retrieve detailed information recent windows versions also write minidump similar principle core dump describing state crashed process unix unix-like operating systems report conditions user error messages segmentation violation bus error may also produce core dump page faults nature degrade performance program operating system degenerate case cause thrashing optimization programs operating system reduce number page faults improve performance program even entire system two primary focuses optimization effort reducing overall memory usage improving memory locality reduce page faults system programmers must make use appropriate page replacement algorithm suits current requirements maximizes page hits many proposed implementing heuristic algorithms reduce incidence page faults generally making physical memory available also reduces page faults major page faults conventional computers use hard disk drives storage significant impact performance average hard disk drive average rotational latency 3 ms seek time 5 ms transfer time 0.05 ms/page therefore total time paging near 8 ms 8,000 μs memory access time 0.2 μs page fault would make operation 40,000 times slower
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Operating systems
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computer security model computer security model scheme specifying enforcing security policies security model may founded upon formal model access rights model computation model distributed computing particular theoretical grounding computer security model implemented computer security policy complete list available articles specific security models see
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Computer security
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semantic role labeling natural language processing semantic role labeling also called shallow semantic parsing process assigns labels words phrases sentence indicate semantic role sentence agent goal result consists detection semantic arguments associated predicate verb sentence classification specific roles example given sentence like mary sold book john task would recognize verb sell representing predicate mary representing seller agent book representing goods theme john representing recipient important step towards making sense meaning sentence semantic analysis sort lower-level abstraction syntax tree i.e categories thus groups fewer clauses category instance book belongs would need two labels possessed possessor whereas book sold john would need two labels goal theme receiver recipient even though two clauses would similar far subject object functions concerned framenet project produced first major computational lexicon systematically described many predicates corresponding roles daniel gildea university california berkeley international computer science institute daniel jurafsky currently teaching stanford university previously working university colorado uc berkeley developed first automatic semantic role labeling system based framenet propbank corpus added manually created semantic role annotations penn treebank corpus wall street journal texts many automatic semantic role labeling systems used propbank training dataset learn annotate new sentences automatically
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Computational linguistics
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gnu/linux naming controversy gnu/linux naming controversy dispute members free software community open-source software community whether refer computer operating systems use combination gnu software linux kernel gnu/linux linux proponents term linux argue far commonly used public media serves generic term systems combine kernel software multiple sources proponents term gnu/linux note gnu alone would good name gnu variants combine gnu operating system software software sources gnu/linux term promoted free software foundation fsf founder richard stallman proponents call correction extended term grounds n't give credit major contributor associated free software philosophy gnu longstanding project begun 1984 develop free operating system argued linux kernel independently created 1991 merely provided substantial missing piece several distributions employ fsf-endorsed name debian trisquel parabola gnu/linux-libre 1983 richard stallman founder free software foundation set forth plans complete unix-like operating system called gnu composed entirely free software september year stallman published manifesto dr. dobb journal detailing new project publicly outlining vision free software software development work began january 1984 1991 gnu mid-level portions operating system almost complete upper level could supplied x window system lower level kernel device drivers system-level utilities daemons still mostly lacking gnu kernel called gnu hurd hurd followed ambitious design proved unexpectedly difficult implement marginally usable independently 1991 linus torvalds released first version linux kernel early linux developers ported gnu code including gnu c compiler run linux free software community adopted use linux kernel missing kernel gnu operating system work filled remaining gaps providing completely free operating system next years several suggestions arose naming operating systems using linux kernel gnu components 1992 yggdrasil linux distribution adopted name linux/gnu/x usenet mailing-list discussions one find usages gnu/linux early 1992 gnu+linux early 1993 debian project one time sponsored free software foundation switched calling product debian gnu/linux early 1994 change followed request richard stallman initially proposed lignux suggested gnu/linux instead hearing complaints awkwardness former term gnu june 1994 bulletin describes linux free unix system 386 machines many utilities libraries gnu january 1995 bulletin switched term gnu/linux instead stallman fsf efforts include gnu name started around 1994 reportedly mostly via private communications above-mentioned request debian 1996 may 1996 stallman released emacs 19.31 autoconf system target linux changed lignux shortly thereafter changed linux-gnu emacs 19.32 included essay linux gnu system suggesting people use terms linux-based gnu system gnu/linux system lignux short later used gnu/linux exclusively essay superseded stallman 1997 essay linux gnu project modern free software open-source software systems composed software many different authors including linux kernel developers gnu project vendors behind x window system desktop- server-based distributions use gnu components gnu c library glibc gnu core utilities coreutils bash 2002 analysis source code red hat linux 7.1 typical linux distribution total size packages gnu project found much larger linux kernel later 2011 analysis ubuntu natty release popular linux distribution main repository found 8 13 consisted gnu components range depending whether gnome considered part gnu 6 taken linux kernel 9 including direct dependencies determining exactly constitutes operating system per se matter continuing debate hand embedded systems handheld devices smartphones like google android residential gateways routers voice ip devices engineered space efficiency mind use linux kernel components gnu system running μclinux likely substitute uclibc glibc busybox coreutils google linux-based android operating system use gnu components libraries replacing glibc google bsd-based bionic c library fsf agrees gnu/linux appropriate name systems also systems use gnu userspace and/or c library top non-linux kernel example debian gnu/hurd gnu userland gnu kernel debian gnu/kfreebsd uses gnu coreutils c library kernel freebsd fsf justifies name gnu/linux primarily grounds gnu project specifically developing complete system argue linux kernel filled one final gaps large number gnu components gnu source code used systems secondary argument addition fsf also argues gnu/linux recognizes role idealism played building community helps public recognize practical importance ideals contrast focus technical advantage rather freedom linux kernel developers case linux kernel notable recurring examples focus technical advantage freedom come long-time inclusion linux kernel many non-free firmware files files non-free license terms ordinary understanding operating system includes kernel—the specific subsystem directly interfaces hardware—and userland software employed user application software control computer moreover name gnu name linux intentionally related name unix unix always conceptually included c library userland tools well kernel 1991 release notes versions 0.01 0.11 linux kernel released gnu general public license version 0.12 torvalds wrote torvalds also wrote 1992 tanenbaum-torvalds debate tanenbaum criticized torvalds developing linux monolithic kernel considered obsolete inferior microkernels mach believed linux would rejected favor gnu hurd microkernel stalled development years use word linux refer kernel operating system entire distributions often leads confusion distinctions among three many gnu packages key part almost every linux distribution particularly gnu toolchain present distros unless android included media sources sometimes make erroneous statements well claiming entire operating system rather simply kernel written torvalds confusion legal threats public relations campaigns apparently directed kernel launched sco group alexis de tocqueville institution adti misinterpreted many commentators assume whole operating system targeted sco adti even accused deliberately exploiting confusion regarding suggestions renaming efforts stem egotism personal pique stallman responded interest giving credit gnu project people think want ego fed course 'm asking call 'stallmanix stallman admitted irritation although believes justified response seeing idealistic project stymied made ineffective people n't usually give credit done concluding 're idealist like ruin whole decade response another common argument see fsf acknowledges many people contributed system short name credit argues justify calling system linux continuing speak subject 2010 stallman stated naming simply matter giving equal mention gnu project system widely referred linux people tend think linux started mr. torvalds 1991 think comes vision life really bad problem linux far widespread name eric s. raymond writes linux entry jargon file linus torvalds asked documentary revolution os whether name gnu/linux justified replied earlier comment torvalds naming controversy name gnu/linux particularly using stallman preferred pronunciation see criticized perceived clumsiness verbosity factor torvalds cited downfall operating systems 386bsd linux journal speculated stallman advocacy combined name stems frustration linus got glory stallman wanted others suggested regardless merits stallman persistence sometimes seems lost cause makes gnu look bad example larry mcvoy author bitkeeper used manage linux kernel development opined claiming credit makes one look foolish greedy many users vendors prefer name linux jim gettys one original developers x window system point inclusion non-gnu non-kernel tools kde libreoffice firefox end-user operating systems based linux kernel although gnu/linux often pronounced without slash stallman recommends explicitly saying word slash plus i.e gnu+linux order avoid mistaken suggestion linux kernel gnu package case gnu linux-libre
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Operating systems
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responsible disclosure computer security elsewhere responsible disclosure vulnerability disclosure model vulnerability issue disclosed period time allows vulnerability issue patched mended period distinguishes model full disclosure developers hardware software often require time resources repair mistakes hackers computer security scientists opinion social responsibility make public aware vulnerabilities high impact hiding problems could cause feeling false security avoid involved parties join forces agree period time repairing vulnerability preventing future damage depending potential impact vulnerability expected time needed emergency fix workaround developed applied factors period may vary days several months easier patch software using internet distribution channel responsible disclosure fails satisfy security researchers expect financially compensated reporting vulnerabilities vendor expectation compensation might viewed extortion market vulnerabilities developed vulnerability commercialization remains hotly debated topic tied concept vulnerability disclosure today two primary players commercial vulnerability market idefense started vulnerability contributor program vcp 2003 tippingpoint zero-day initiative zdi started 2005 organisations follow responsible disclosure process material bought march 2003 december 2007 average 7.5 vulnerabilities affecting microsoft apple processed either vcp zdi independent firms financially supporting responsible disclosure paying bug bounties include facebook google mozilla barracuda networks vendor-sec responsible disclosure mailing list many cert groups coordinate responsible disclosures google project zero 90-day disclosure deadline starts notifying vendors vulnerability details shared public defensive community 90 days sooner vendor releases fix zdi 120-day disclosure deadline starts receiving response vendor selected security vulnerabilities resolved applying responsible disclosure
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Computer security
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mebroot mebroot master boot record based rootkit used botnets including torpig sophisticated trojan horse uses stealth strategies hide user trojan opens back door victim computer allows attacker complete control computer trojan infects mbr allow start even operating system starts allows bypass safeguards embed deep within operating system known trojan intercept read/write operations embed deep within network drivers allows ability bypass firewalls communicate securely using custom encrypted tunnel command control server allows attacker install malware viruses applications trojan commonly steals information victim computer attempt small financial gain mebroot linked anserin another trojan logs keystrokes steals banking information gives evidence showing financial motive likely behind mebroot trojan tries avoid detection hooking atapi.sys also embeds ntoskrnl.exe mebroot executable files registry keys driver modules makes harder detect without antivirus software addition running antivirus software one also remove trojan wiping repairing master boot record hard drive operating system three variants mebroot discovered estimated first version compiled november 2007 december mebroot started drive-by downloads early 2008 second wave attacks arrived february 2008 second variant discovered accompanied modified installer march 2008 third variant discovered attacks became widespread since third variant trojan upgraded try outwit antivirus software unknown mebroot still wild mebroot currently known distributed visiting malicious websites way application exploit estimated 1,500 websites compromised mostly european region traffic websites infected mebroot reach 50,000 100,000 views per day
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Computer security
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inverse symbolic calculator inverse symbolic calculator online number checker established july 18 1995 peter benjamin borwein jonathan michael borwein simon plouffe canadian centre experimental constructive mathematics burnaby canada user input number calculator use algorithm search calculate closed-form expressions suitable functions roots near number hence calculator great importance working numerical areas experimental mathematics isc contains 54 million mathematical constants plouffe inverter opened 1998 contains 214 million newer version tables 3.702 billion entries june 19 2010 exists 2016 plouffe released portable version plouffe inverter containing 3 billion entries
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Databases
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lunar pool lunar pool known japan video game combines pool pocket billiards aspects miniature golf created developed compile nintendo entertainment system msx stage differently shaped pool table object knock ball pocket using cue ball sixty levels choose friction table adjustable thus lunar reference title along moon-related background imagery within game japanese lunar ball appeared famicom clone systems pirated multi-game cartridges power player super joy iii released wii north american virtual console october 22 2007 lunar pool played boards different shapes wherein player shoot cue ball knock colored balls pockets player fails pocket least one colored ball three consecutive turns player lose one life also player pockets cue ball loses life player pockets colored balls level consecutively without failure player get perfect remark bonus points added player score lunar pool either played alone another player computer game played another player computer players take turns shooting cue ball one player fails knock least one colored balls pocket pockets cue ball opponent turn
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Computer architecture
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ghostbusters 1984 video game ghostbusters licensed game activision based movie name designed david crane produced brad fregger released several home computer platforms 1984 later video game console systems including atari 2600 master system nes primary target platform commodore 64 programmer initial version game adam bellin versions game released usa except amstrad cpc version released europe msx version released europe south america japan early 1984 ghostbusters movie nearing completion tom lopez vice president activision product development contacted columbia pictures obtain license ghostbusters video game columbia gave activision specific rules requests design content game stipulating finished quickly possible order released movie peak popularity activision forced complete programming work six weeks contrast usual several months development time game activision time rough concept driving/maze game called car wars decided build ghostbusters game effort paid movie game proved huge successes player sets ghost busting franchise city rising psychokinetic pk energy level ability purchase equipment traps upgrade vehicle player negotiates grid representing city need stop roamers reaching temple zuul causes pk energy level jump player moves city block flashing red game mode switches overhead view player vehicle driving location player must move left right vacuum stray ghosts avoid cars player moves screen slimer ghost must guided two proton streams ghost trap ghost successfully captured player income increases aim 10,000 time city pk level reaches 9999 stay-puff marshmallow man appear wreak havoc city thereby ending game versions e.g commodore 64 version first successful game player given account number stores amount money player end game allowed purchasing expensive items use faster cars traps etc. order win games player required earned money initial account balance one earliest uses passwords used 'save game feature home computers versions game feature sampled rendition ghostbusters cry start movie theme song c64 atari 8bit versions produced within game using patented form compression similar adpcm ess electronic speech systems without requiring external hardware produce speech pcjr/tandy port feature antic may 1985 called ghostbusters first adaptation capture feel theme movie based ... enjoyable play edge 2007 called ghostbusters dauntingly good noting despite action sequences expected licensed title game polished intelligently-paced strategic business simulation ernie hudson said kids really hated commodore 64 game thought sucked 1985 print shop reportedly two widely pirated commodore 64 programs ii computing listed ghostbusters eighth magazine list top apple ii games late 1985 based sales market-share data activision best-selling commodore game late 1987 amstrad cpc zx spectrum versions game included 1986 compilation sold million 3 along fighter pilot rambo kung-fu master game also released story far volume iv december 1989 hollywood collection december 1990 knocked daley thompson decathlon top uk spectrum sales chart ghostbusters ported ibm pcjr tandy 1000 1985 due timing-sensitive raster effects game uses incompatible tandy machines 1000/1000a 1000hx 1000ex use 4.77mhz 8088 cpu nes version created association works later changed name bits laboratory version panned critics gamers fans alike monotonous gameplay sloppy controls lack connection original film game also released nintendo entertainment system 1988 1986 japan master system 1987 versions featured added gameplay ghostbusters sneak marshmallow man played like conventional vertical scrolling platform game actually climb stairs get roof however nes version ghostbusters could fire weapons trap ghosts instead sneak floors contrast master system version ghostbusters able shoot ghosts proton streams temporarily make go away nes version considered difficult reason end nes version final screen states conglaturation completed great game prooved justice culture go rest heroes version extremely negatively received critics monotonous gameplay poor graphics sound well unfair difficulty particularly stairway
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Computer architecture
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language-based security computer science language-based security lbs set techniques may used strengthen security applications high level using properties programming languages lbs considered enforce computer security application-level making possible prevent vulnerabilities traditional operating system security unable handle software applications typically specified implemented certain programming languages order protect attacks flaws bugs application ’ source code might vulnerable need application-level security security evaluating applications behavior respect programming language area generally known language-based security use large software systems scada taking place around world computer systems constitute core many infrastructures society relies greatly infrastructure water energy communication transportation rely fully functionally working computer systems several well known examples critical systems fail due bugs errors software shortage computer memory caused lax computers crash hundreds flights delayed april 30 2014 traditionally mechanisms used control correct behavior software implemented operating system level operating system handles several possible security violations memory access violations stack overflow violations access control violations many others crucial part security computer systems however securing behavior software specific level even stronger security achieved since lot properties behavior software lost compilation significantly difficult detect vulnerabilities machine code evaluating source code compilation theory implementation programming language also considered vulnerabilities uncovered developers keep making mistakes instead relying programmers memories strive produce tools codify known common security vulnerabilities integrate directly development process — d. evans d. larochelle 2002 using lbs security software increased several areas depending techniques used common programming errors allowing buffer overflows illegal information flows occur detected disallowed software used consumer also desirable provide proof consumer security properties software making consumer able trust software without receive source code self checking errors compiler taking source code input performs several language specific operations code order translate machine readable code lexical analysis preprocessing parsing semantic analysis code generation code optimization commonly used operations compilers analyzing source code using theory implementation language compiler attempt correctly translate high-level code low-level code preserving behavior program compilation programs written type-safe language java source code must type-check successfully compilation type-check fails compilation performed source code needs modified means given correct compiler code compiled successfully type-checked source program clear invalid assignment errors information value code consumer provides degree guarantee program crash due specific error goal lbs ensure presence certain properties source code corresponding safety policy software information gathered compilation used create certificate provided consumer proof safety given program proof must imply consumer trust compiler used supplier certificate information source code verified figure illustrates certification verification low-level code could established use certifying compiler software supplier gains advantage reveal source code consumer left task verifying certificate easy task compared evaluation compilation source code verifying certificate requires limited trusted code base containing compiler verifier main applications program analysis program optimization running time space requirements power consumption etc program correctness bugs security vulnerabilities etc. program analysis applied compilation static analysis run-time dynamic analysis language-based security program analysis provide several useful features type checking static dynamic monitoring taint checking control-flow analysis information flow analysis described set tools used analyze information flow control program order preserve confidentiality integrity regular access control mechanisms come short decoupling right access information right disseminate flow model goes beyond access matrix model ability specify secure information flow practical system needs access flow control satisfy security requirements — d. denning 1976 access control enforces checks access information concerned happens example system two users alice bob alice file secret.txt allowed read edited prefers keep information system also exists file public.txt free read edit users system suppose alice accidentally downloaded malicious program program access system alice bypassing access control check secret.txt malicious program copies content secret.txt places public.txt allowing bob users read constitutes violation intended confidentiality policy system noninterference property programs leak reveal information variables higher security classification depending input variables lower security classification program satisfies noninterference produce output whenever corresponding input lower variables used must hold every possible value input implies even higher variables program different values one execution another visible lower variables attacker could try execute program satisfy noninterference repeatedly systematically try map behavior several iterations could lead disclosure higher variables let attacker learn sensitive information example systems state whether program satisfies noninterference evaluated compilation assuming presence security type systems security type system kind type system used software developers order check security properties code language security types types variables expressions relate security policy application programmers may able specify application security policy via type declarations types used reason various kinds security policies including authorization policies access control capabilities information flow security security type systems formally related underlying security policy security type system sound programs type-check satisfy policy semantic sense example security type system information flow might enforce noninterference meaning type checking reveals whether violation confidentiality integrity program vulnerabilities low-level code bugs flaws lead program state behavior program undefined source programming language behavior low-level program depend compiler runtime system operating system details allows attacker drive program towards undefined state exploit behavior system common exploits insecure low-level code lets attacker perform unauthorized reads writes memory addresses memory addresses either random chosen attacker approach achieve secure low-level code use safe high-level languages safe language considered completely defined programmers manual bug could lead implementation-dependent behavior safe language either detected compile time lead well-defined error behavior run-runtime java accessing array bounds exception thrown examples safe languages c haskell scala compilation unsafe language run-time checks added low-level code detect source-level undefined behavior example use canaries terminate program discovering bounds violations downside using run-time checks bounds-checking impose considerable performance overhead memory protection using non-executable stack and/or heap also seen additional run-time checks used many modern operating systems general idea identify sensitive code application data analyzing source code done different data separated placed different modules assuming module total control sensitive information contains possible specify leave module example cryptographic module prevent keys ever leaving module unencrypted certifying compilation idea producing certificate compilation source code using information high-level programming language semantics certificate enclosed compiled code order provide form proof consumer source code compiled according certain set rules certificate produced different ways e.g proof-carrying code pcc typed assembly language tal main aspects pcc summarized following steps example certifying compiler touchstone compiler provides pcc formal proof type- memory safety programs implemented java tal applicable programming languages make use type system compilation object code carry type annotation checked ordinary type checker annotation produced many ways similar annotations provided pcc limitations however tal handle security policy may expressed restrictions type system include memory safety control flow among others
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Computer security
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goagent goagent gnu gpl open-source cross-platform network access software mainly written python supports windows os x linux linux-based os like android openwrt uses google app engine servers provide users free proxy service gain access blocked information normally used web browsers goagent eventually shut request chinese law enforcement project called xx-net claims reborn goagent first release january 2015
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Web technology
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series 40 series 40 often shortened s40 software platform application user interface ui software nokia broad range mid-tier feature phones well vertu line luxury phones one world widely used mobile phone platforms found hundreds millions devices nokia announced 25 january 2012 company sold 1.5 billion series 40 devices used smartphones nokia primarily uses windows phone 2012 symbian however 2012 2013 several series 40 phones asha line 308 309 311 advertised smartphones although actually support smartphone features like multitasking fully fledged html browser 2014 microsoft acquired nokia mobile phones business part licensing agreement company microsoft mobile allowed use nokia brand feature phones series 40 range however july 2014 company memo revealed microsoft would end future production series 40 devices replaced series 30+ series 40 underlying operating system called intelligent system architecture isa also called nokia operating system nos series 40 introduced 1999 release nokia 7110 96 × 65 pixel monochrome display first phone come wap browser years s40 ui evolved low-resolution ui high-resolution color ui enhanced graphical look third generation series 40 became available 2005 introduced support devices resolutions high qvga 240×320 possible customize look feel ui via comprehensive themes 2012 nokia asha mobile phones 200/201/210 302/306/305/308/310/311 303 311 released used series 40 final feature phone running series 40 nokia 515 2013 running 6th edition series 40 provides communication applications telephone internet telephony voip messaging email client pop3 imap4 capabilities web browser media applications camera video recorder music/video player fm radio phonebook personal information management pim applications calendar tasks basic file management like series 60 provided applications gallery folders subfolders gallery also default location files transferred bluetooth placed user-installed applications series 40 generally mobile java applications flash lite applications also supported mostly used screensavers integrated web browser access web content service provider xhtml/html gateway latest version series 40 called series 40 6th edition introduced new browser based webkit open source components webcore javascriptcore new browser delivers support html 4.01 css2 javascript 1.5 ajax also like higher-end series 60 series 40 run uc browser web browser enhance user web browsing experience latest feature phones asha lineup come nokia xpress browser uses proxy servers compress optimize web pages similar fashion opera mini support syncml synchronization address book calendar notes external services present however many s40 phones synchronization settings must sent via ota text message series 40 embedded software platform open software development via standard de facto content application development technologies supports java midlets i.e java midp cldc technology provide location communication messaging media graphics capabilities s40 also supports flash lite applications
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Operating systems
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nebula computing platform nebula federal cloud computing platform originated nasa ames research center moffett field california nebula project run acits 2 contract originally held perot systems nebula hosted many advanced research projects one application open sourced nasa developed nebula project 'nova became one two founding projects openstack project ames internet exchange aix formerly mae-west one original nodes internet major peering location tier 1 isps well home e root name servers aix provides connectivity nebula cloud enabling 10gige connections nisn nebula-project uses variety free open-source software
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Distributed computing architecture
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dataplow san file system san file system sfs high-performance clustered file system created company dataplow sfs enables fast access shared files located shared storage area network san -attached storage devices sfs utilizes high-speed scalable data transfers inherent storage area networks general-purpose file system wide variety environments including scientific computing finance healthcare entertainment defense broadcast aerospace supported linux solaris os x windows supports san-based block-level storage protocols including fibre channel iscsi interoperability security specifications limits
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Computer file systems
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encryption cryptography encryption process encoding message information way authorized parties access authorized encryption prevent interference denies intelligible content would-be interceptor encryption scheme intended information message referred plaintext encrypted using encryption algorithm – cipher – generating ciphertext read decrypted technical reasons encryption scheme usually uses pseudo-random encryption key generated algorithm principle possible decrypt message without possessing key well-designed encryption scheme considerable computational resources skills required authorized recipient easily decrypt message key provided originator recipients unauthorized users symmetric-key schemes encryption decryption keys communicating parties must key order achieve secure communication example symmetric key german military enigma machine key settings day allies figured machine worked able decipher information encoded within messages soon could discover encryption key given day transmissions public-key encryption schemes encryption key published anyone use encrypt messages however receiving party access decryption key enables messages read public-key encryption first described secret document 1973 encryption schemes symmetric-key also called private-key although published subsequently work diffie hellman published journal large readership value methodology explicitly described method became known diffie hellman key exchange publicly available public key encryption application called pretty good privacy pgp written 1991 phil zimmermann distributed free charge source code purchased symantec 2010 regularly updated encryption long used militaries governments facilitate secret communication commonly used protecting information within many kinds civilian systems example computer security institute reported 2007 71 companies surveyed utilized encryption data transit 53 utilized encryption data storage encryption used protect data rest information stored computers storage devices e.g usb flash drives recent years numerous reports confidential data customers personal records exposed loss theft laptops backup drives encrypting files rest helps protect physical security measures fail digital rights management systems prevent unauthorized use reproduction copyrighted material protect software reverse engineering see also copy protection another somewhat different example using encryption data rest encryption also used protect data transit example data transferred via networks e.g internet e-commerce mobile telephones wireless microphones wireless intercom systems bluetooth devices bank automatic teller machines numerous reports data transit intercepted recent years data also encrypted transmitted across networks order protect eavesdropping network traffic unauthorized users conventional methods deleting data permanently storage device involve overwriting whole content zeros ones patterns – process take significant amount time depending capacity type medium cryptography offers way making erasure almost instantaneous method called crypto-shredding example implementation method found ios devices cryptographic key kept dedicated 'effaceable storage key stored device setup offer full confidentiality protection case unauthorized person gains physical access device encryption important tool sufficient alone ensure security privacy sensitive information throughout lifetime applications encryption protect information rest transit leaving sensitive data cleartext potentially vulnerable improper disclosure processing cloud service example homomorphic encryption secure multi-party computation emerging techniques compute encrypted data techniques general turing complete incur high computational and/or communication costs response encryption data rest cyber-adversaries developed new types attacks recent threats encryption data rest include cryptographic attacks stolen ciphertext attacks attacks encryption keys insider attacks data corruption integrity attacks data destruction attacks ransomware attacks data fragmentation active defense data protection technologies attempt counter attacks distributing moving mutating ciphertext difficult identify steal corrupt destroy encryption protect confidentiality messages techniques still needed protect integrity authenticity message example verification message authentication code mac digital signature authenticated encryption algorithms designed provide encryption integrity protection together standards cryptographic software hardware perform encryption widely available successfully using encryption ensure security may challenging problem single error system design execution allow successful attacks sometimes adversary obtain unencrypted information without directly undoing encryption see example traffic analysis tempest trojan horse integrity protection mechanisms macs digital signatures must applied ciphertext first created typically device used compose message protect message end-to-end along full transmission path otherwise node sender encryption agent could potentially tamper encrypting time creation secure encryption device correct keys tampered endpoint device configured trust root certificate attacker controls example attacker inspect tamper encrypted data performing man-in-the-middle attack anywhere along message path common practice tls interception network operators represents controlled institutionally sanctioned form attack countries also attempted employ attacks form control censorship even encryption correctly hides message content tampered rest transit message length form metadata still leak sensitive information message well-known crime breach attacks https side-channel attacks relied information leakage via length encrypted content example traffic analysis broad class techniques often employs message lengths infer sensitive implementation traffic flows many messages aggregate padding message payload encrypting help obscure cleartext true length cost increasing ciphertext size introducing bandwidth overhead messages may padded randomly deterministically approach different tradeoffs encrypting padding messages form padded uniform random blobs purbs practice guaranteeing cipher text leaks metadata cleartext content leaks asymptotically minimal formula_1 information via length
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Computer security
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status register status register flag register condition code register ccr collection status flag bits processor examples registers include flags register x86 architecture flags program status word psw register ibm system/360 architecture z/architecture application program status register apsr arm cortex-a architecture status register hardware register contains information state processor individual bits implicitly explicitly read and/or written machine code instructions executing processor status register lets instruction take action contingent outcome previous instruction typically flags status register modified effects arithmetic bit manipulation operations example z bit may set result operation zero cleared nonzero classes instructions may also modify flags indicate status example string instruction may indicate whether instruction terminated found match/mismatch found end string flags read subsequent conditional instruction specified action depending processor jump call return occurs flags indicate specified result earlier instruction cpu architectures mips alpha use dedicated flag register others implicitly set and/or read flags machines either pass implicit status information instructions pass explicitly selected general purpose register status register may often fields well specialized flags interrupt enable bits similar types information interrupt status thread currently executing preserved later recalled storing current value status register along program counter active registers machine stack reserved area memory list common cpu status register flags implemented almost modern processors processors status register also contains flags status flags enable instruction act based result previous instruction pipelined processors superscalar speculative processors create hazards slow processing require extra hardware work around long instruction word processors dispense status flags single instruction performs test indicates outcome test take action compare b jump c equal result test saved subsequent instructions another alternative status register processor instructions deposit status information general-purpose register program requests mips amd 29000 dec alpha risc-v examples architectures provide comparison instructions store comparison result general-purpose register single bit numeric value 0 1 conditional branches act based value general-purpose register usually comparison instructions test equality signed/unsigned magnitude test conditions program uses equivalence formula example mips carry bit program performing multiple-word addition test whether single-word addition registers overflowed testing whether sum lower operand codice_1 instruction sets codice_2 1 0 based specified comparison two operands general-purpose register codice_2 used status register govern conditional jump rather possible value 1 indicating carry low-order addition added high-order word scheme becomes less convenient adding three words two additions computing codice_4 either may generate carry must detected two codice_1 instructions fortunately two carries may added without risk overflow situation stabilizes five instructions per word added
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Computer architecture
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beos api beos api often called api inc. application programming interface required write graphical native applications beos hence derivatives haiku zeta api divided number kits collect related classes together bear relation library contains supporting code almost entirely c++ third-party bindings classes python tiny subset classes mostly storage kit related perl application kit contains basic classes required launch beos application well support global clipboard inter-application internal messaging timers rosters functions seen required support graphical application application kit classes supported libbe.so storage kit provides methods manipulating files creating managing symlinks way file open/save panels graphical applications well dealing file system attributes storage kit classes mostly libtracker.so tracker native file manager os interface kit provides large collection widgets building graphical applications main window class dialogue boxes including font handling rendering control majority libbe.so comprises kit kernel kit provides threading semaphores ability access system information also libbe.so support kit provides advanced functions readily fall another kit assisted memory allocation list support network kit provides either rudimentary beos r5 lower almost complete beos dano higher implementation berkeley sockets bind well native functions based nettle c++ networking library libnet.so provides berkeley sockets r5 later replaced common libsocket/libbind.so nomenclature libnetapi r5 later replaced libbnetapi provides modified version nettle mail kit provides native email format well way use system fetch receive email using standard protocols pop3 smtp mail kit supported libmail.so translation kit provides method whereby images plain text formats handled addons allowing applications support one format native intermediate one save/load addon-supported format api also allows video audio translation library although superseded beos r4 immediately disabled translation kit supported libtranslation.so media kit provides audio video input/output abstraction layer based pluggable addons well handling sound mixing audio video format translation media related functions media kit functions supported libmedia.so midi kit provides midi hardware input output abstraction well software synthesiser provided headspace beos r5 libmidi.so provides old beos r3 era midi api libmidi2.so provides r4+ api game kit provides number sound formats suited computer game audio output well ability run full-screen applications use video overlays opengl kit provides implementation opengl well supporting classes allow use native applications beos r5 supported opengl version 1.1 software accelerated although kit hardware-neutral fact outperformed many hardware implementations running competing platforms could deliver similar latency/bandwidth performance due underlying inefficiencies design implementation device kit provides platform-abstracted direct hardware access serial parallel ports well beboxs infamous geekport locale kit provides classes localize applications different languages timezones number formatting conventions etc kit found haiku implementation beos api services kit provides lightweight direct connection web services kit found haiku implementation beos api web kit provides means rendering web pages fork apple webkit kit found haiku implementation beos api package kit provides means package management kit found haiku implementation beos api majority api reimplemented haiku open-source beos replacement although effort catch intervening years since beos r5 additional functionality added ranging large changes mail kit support imap encrypted connections multiple accounts move opengl 1.5 support via mesa 3d alternative systems attempted draw inspiration syllable beos api making attempts provide base port applications private port much api microsoft windows later linux using gtk+ done gobe software enable port gobe productive office suite platforms beos originally developed entire api stage beos revision 3 documented two paper books developer guide advanced topics released o'reilly media inc imprint 1997/8 addition digital representation provided updated beos 2007 access co ltd owners inc intellectual property released text creative commons licence
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Operating systems
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akismet akismet spam filtering service filters spam comments trackbacks contact form messages filter works combining information spam captured participating sites using spam rules block future spam akismet offered automattic company behind wordpress.com launched october 25 2005 akismet said captured 100 billion spam comments pings october 2013 founder automattic matt mullenweg decided create akismet mother could blog safety 2005 discussions deal comment spam plug-ins available mullenweg first attempt javascript plug-in modified comment form hid fields within hours launch spammers downloaded figured worked bypassed late 2005 mullenweg launched akismet plug-in wordpress akismet stands automatic kismet way dealing spam aggregate crowd-sourced spam-fighting tool time someone posts comment participating website akismet checks comments database spam deleted spam gets user marks spam comment added database pool spam comments widens making akismet increasingly effective time akismet originally developed integrate plug-in wordpress akismet plug-in included default wordpress builds since version 2.0 activated wordpress.com-hosted blogs public akismet api resulted third-party plug-ins platforms one official akismet plug-in release open source internet forum software discourse use akismet necessary obtain api key key necessary site communicate akismet servers released terms gnu general public license akismet plug-in free software although code akismet system nature algorithm used released akismet service free personal use march 2016 commercial plans start 5/month
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Computer security
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google cloud connect google cloud connect free cloud computing plug-in windows microsoft office 2003 2007 2010 automatically store synchronize microsoft word document powerpoint presentation excel spreadsheet google docs google docs microsoft office formats google doc copy automatically updated time microsoft office document saved microsoft office documents edited offline synchronized later online google cloud sync maintains previous microsoft office document versions allows multiple users collaborate working document time google cloud connect discontinued april 30 2013 according google cloud connect features available google drive google cloud connect could automatically manually synchronize changes made microsoft office 2003 2007 2010 document google docs documents secured private access one user shared specific people collaboration made public anyone previous document versions retrieved
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Distributed computing architecture
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comm100 live chat comm100 live chat free basic live support software product offered via saas software service model enables businesses organizations communicate website visitors real time improve conversions sales customer satisfaction first version comm100 live chat released august 5 2009 october 2011 comm100 live chat featured apps month techrepublic scott lowe company hit 200,000 registered business users mark october 2012 january 2013 comm100 live chat released version 7.0 features salesforce integration re-designed operator console month comm100 live chat ranked top 3 2013 best enterprise chat software category toptenreviews zero downtime upgrade comm100 live chat made possible march 2013 comm100 live chat consists 3 parts web chat window operator console control panel totally web-based version works major web browsers chrome ie firefox safari opera etc major operating systems windows mac linux operator console also cross-platform compatible desktop app apps mobile devices iphone ipad android blackberry key features comm100 live chat include comm100 live chat offers plugins integrations following
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Distributed computing architecture
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heaps law linguistics heaps law also called herdan law empirical law describes number distinct words document set documents function document length called type-token relation formulated v number distinct words instance text size n k β free parameters determined empirically english text corpora typically k 10 100 β 0.4 0.6 law frequently attributed harold stanley heaps originally discovered mild assumptions herdan–heaps law asymptotically equivalent zipf law concerning frequencies individual words within text consequence fact type-token relation general homogenous text derived distribution types heaps law means instance text gathered diminishing returns terms discovery full vocabulary distinct terms drawn heaps law also applies situations vocabulary set distinct types attributes collection objects example objects could people types could country origin person persons selected randomly selecting based country origin heaps law says quickly representatives countries proportion population become increasingly difficult cover entire set countries continuing method sampling
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Computational linguistics
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epictetus database client epictetus free cross-platform multi-database administration tool used jvm run epictetus distributed freeware antilogic software discontinued since 2009
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Databases
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endace endace ltd privately owned network monitoring company based new zealand founded 2001 provides network visibility network recording products large organizations company listed london stock exchange 2005 delisted 2013 acquired emulex 2016 endace spun emulex currently private company october 2016 intercept revealed endace clients intelligence agencies including british gchq known conducting massive surveillance network communications moroccan dgst likewise known mass surveillance citizens endace founded dag project school computing mathematical sciences university waikato new zealand first cards designed university intended measure latency atm networks 2006 endace transitioned component manufacturer appliance manufacturer managed infrastructure provider company sells network visibility fabrics based range network recorders large corporations government agencies endace first new zealand company list london alternative investment market floated mid-june 2005 move without controversy poor share price performance early years seeming failure attract broad enough shareholder base lent weight criticism endace focused initially developing local profile via nzx rather pushing overseas investment via london aim endace headquartered auckland new zealand r centre hamilton new zealand offices australia united states great britain dag project grew academic research waikato university found software measurements atm cells packets unsatisfactory reasons accuracy lack certainty packet loss research group set developing hardware generate better quality recordings hardware subsequent iterations introduced two fundamental innovations hardware timestamping hardware accounting packet loss conventionally packet cell given timestamp host machine kernel i.e software kernel driver notified new packet arrived approach results poor quality timestamps several reasons among considerable latency jitter packet arriving network interface receipt kernel driver uncertainty caused interrupt coalescing wherein one host interrupt signifies arrival several packets poor quality limits research usefully done network performance related fields solve dag generates timestamps hardware close network interface possible obviate latency jitter problems caused interrupt coalescing hardware capable much greater accuracy precision software-generated timestamps precision comes freedom custom hardware assign many bits timestamp required accuracy assured reference external time source gps accurate ± 40 nanoseconds contrast accuracy ntp kernel clocks corrected internet order milliseconds 100,000 times less accurate depending conditions involved dag produces 64 bit timestamps fixed-point format 32 fractional bits giving potential precision formula_1 seconds 233 picoseconds actual precision offered varies particular model dag oldest giving 24 fractional bits 60 nanoseconds better precisions offered dags higher bandwidth networks timestamp derived free-running clock provided crystal oscillator accuracy crystals drift temperature age dag solution use direct digital synthesis using 1 hz pulse-per-second output many gps receivers provide reference clock mechanism described §5.5.3 stephen donnelly phd thesis also describes detail pre-commercial era models dag crucially academically significant contribution dag ability use external reference globally synchronised gps makes possible one-way time-of-flight measurements immense interest academic researchers packets flowing two points internet neither guaranteed follow path direction guaranteed timing characteristics direction outside academic world timestamp accuracy commercial applications enforcement compliance law eu markets financial instruments directive 2004 almost important timestamp accuracy guaranteeing 100 cell packet capture loss unavoidable knowing packets lost important analysing packet trace important able compensate lost packets calculating inter-arrival times commercial nics keep count dropped packets ca n't indicate packets lost dag prepends header amongst things indicates many packets dropped packet previously accepted packet dag also engineered deliver recorded packets host greatest possible efficiency together interstitial loss counter makes dag appealing surveillance applications interstitial loss counter also finds application forensics prosecutor needs able prove record complete october 2016 intercept published article showing endace customers include intelligence agencies including gchq canadian australian intelligence agencies dgst morocco ’ domestic surveillance agency edward snowden documents shown gchq installed massive surveillance network communications uk using over-sea cable europe north america
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Computer security
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recruitee recruitee software service saas functions talent acquisition platform formerly known applicant tracking system ats includes careers site editor employer branding plugin sourcing personnel job board integration email calendar synchronization within 4 months public launch august 2015 recruitee attracted 1000 small medium-sized enterprises smes recruiting agencies worldwide 2011 perry oostdam met pawel smoczyk founder2be social network helps aspiring entrepreneurs find co-founder working remotely netherlands poland put together first product mobile activation game called georun 2014 oostdam smoczyk pivoted business built recruitee frustration hassles hiring believe hiring team effort founders hr alone launch recruitee quickly became popular got undisclosed amount seed funding september 1 2015 board members include dutch entrepreneurs robert pijselman luc brandts november 2015 recruitee announced partnership rockstart accelerator amsterdam recruitee set talent pool let applicants apply job openings startups affiliated rockstart recruitee current clients include vice magazine usabilla vlisco users customize hiring pipeline job opening users drag drop candidates profiles different stages move along hiring process users post job openings free paid job boards recruitee users bulk upload résumés synchronize emails calendars recruitee users send bulk emails candidates users import potential candidates websites using recruitee sourcing extension google chrome firefox users make careers sites showcase employer branding like company team culture
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Distributed computing architecture
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mediabrowser mediabrowser mediabrowser.com inc. internet browser branding company started 2000 mark c. brown made specially branded versions internet explorer various company brands themes branded web browsers made mediabrowser require internet explorer 5 higher supported windows operating systems december 5 2001 mediabrowser.com inc. went bankrupt shut site branded web browsers windows 95 windows xp internet explorer 5.0 higher windows media player 6.4 higher macromedia flash 4.0 higher also 486 mhz higher processor 32 mb ram 5 mb free hard drive space active internet connection due compatibility issues mediabrowser compatible windows vista windows 7 however run windows xp compatibility mode upon new installation mediabrowser branded browser user required register web browser using mediabrowser online registration form asked name address etc 12 years old mediabrowser shut registration process broken registration form hosted defunct web site therefore users would able use unless modified value windows registry branding consisted various brand images background navigation buttons splash screen links specific web pages related brand company mediabrower also space ads display bottom web browser mediabrowser microtron also included every mediabrowser branding display brand-related video content user late 2000 video game company nintendo partnered mediabrowser make branded browsers new upcoming video games first two browsers released upcoming pokémon gold silver video games mario tennis retailers gave cd-rom copies branded pokémon gs browser anyone pre-ordered copy pokémon gold silver special promotion later 2001 browsers released branded nintendo games paper mario nintendo power branded browser released well mediabrowser.com inc. went bankrupt december 5 2001 chapter 7 filing due company debts 2.49 million various unpaid loans web site containing branded web browsers pulled nintendo posted notice downloads page stating nintendo custom browsers currently unavailable date return keep checking nintendo.com downloads page updates thanks
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Internet protocols
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allocate-on-flush allocate-on-flush also called delayed allocation file system feature implemented hfs+ xfs reiser4 zfs btrfs ext4 feature also closely resembles older technique berkeley ufs called block reallocation blocks must allocated hold pending writes disk space appended data subtracted free-space counter actually allocated free-space bitmap instead appended data held memory must flushed storage due memory pressure kernel decides flush dirty buffers application performs unix sync system call example effect batching together allocations larger runs delayed processing reduces cpu usage tends reduce disk fragmentation especially files grow slowly also help keeping allocations contiguous several files growing time used conjunction copy write zfs convert slow random writes fast sequential writes
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Computer file systems
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panorama database engine panorama database engine development environment macintosh microsoft windows one first applications available mac os 1984 panorama database software apple inc. macintosh microsoft windows product provue development according owner jim rea provue oldest third-party software company apart microsoft developing software macintosh personal computer panorama claim fame databases creates ram-based making extremely fast said disk speeds os application memory caching improved speed benefit becomes less less evident years go panorama popular filemaker main competitor though outlasted many similar products lacks conforming standard application conventions makes potential customisation incorporating powerful scripting language current version mac 6.0 snow leopard compatible intel cpu native windows 5.5 six years development time successor panorama x released november 2017
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Databases
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equals sign etymology word equal latin word æqualis meaning uniform identical equal aequus level even symbol universally accepted mathematics equality first recorded welsh mathematician robert recorde whetstone witte 1557 original form symbol much wider present form book recorde explains design gemowe lines meaning twin lines latin gemellus auoide tediouſe repetition theſe woordes equalle ſette doe often woorke vſe paire paralleles gemowe lines one lengthe thus bicauſe noe .2. thynges moare equalle avoid tedious repetition words equal set often work use pair parallels gemowe lines one length thus 2 things equal according scotland university st andrews history mathematics website symbol '= immediately popular symbol || used æ œ latin word aequalis meaning equal widely used 1700s mathematics equals sign used simple statement fact specific case x 2 create definitions let x 2 conditional statements x 2 … express universal equivalence codice_1 first important computer programming language use equals sign original version fortran fortran designed 1954 implemented 1957 fortran serves assignment operator codice_2 sets value codice_3 2 somewhat resembles use mathematical definition different semantics expression following evaluated first may refer previous value codice_3 example assignment codice_5 increases value codice_3 2 rival programming-language usage pioneered original version algol designed 1958 implemented 1960 algol included relational operator tested equality allowing constructions like codice_7 essentially meaning conditional usage mathematics equals sign reserved usage usages remained common different programming languages early 21st century well fortran used assignment languages c perl python awk descendants used equality assignment pascal family ada eiffel apl languages languages basic pl/i used equals sign mean assignment equality distinguished context however languages one meanings different character often sequence characters used meaning following algol languages use equality use assignment although apl special character set uses left-pointing arrow fortran equality operator possible compare expression zero using arithmetic statement fortran iv released 1962 since used four characters .eq test equality language b introduced use == meaning copied descendant c later languages means assignment equals sign also used defining attribute–value pairs attribute assigned value php triple equals sign codice_8 denotes value type equality meaning two expressions evaluate equal values also data type instance expression codice_9 true codice_10 number 0 integer value whereas false boolean value javascript semantics codice_8 referred equality without type coercion however javascript behavior codice_12 described simple consistent rules expression codice_9 true codice_14 false even though sides codice_12 act boolean context reason sometimes recommended avoid codice_12 operator javascript favor codice_8 ruby equality codice_12 requires operands identical type e.g codice_9 false codice_8 operator flexible may defined arbitrarily given type example value type codice_21 range integers codice_22 codice_23 false since types different range vs. integer however codice_24 true since codice_8 codice_21 values means inclusion range note semantics codice_8 non-symmetric e.g codice_28 false since interpreted mean codice_29 rather codice_30 equals sign also used grammatical tone letter orthographies budu congo-kinshasa krumen mwan dan ivory coast unicode character used tone letter u+a78a different mathematical symbol u+003d possibly unique case equals sign european usage person name specifically double-barreled name pioneer aviator alberto santos-dumont also known often used double hyphen resembling equals sign two surnames place hyphen also seems personally preferred practice display equal respect father french ethnicity brazilian ethnicity mother instead double hyphen equals sign sometimes used japanese separator names ojibwe readily-available equal sign keyboard used substitute double hyphen linguistic interlinear glosses equals sign conventionally used mark clitic boundaries equals sign placed clitic word clitic attached chemical formulas two parallel lines denoting double bond commonly rendered using equals sign recent years equals sign used symbolize lgbt rights symbol used since 1995 human rights campaign lobbies marriage equality subsequently united nations free equal promotes lgbt rights united nations symbols used denote items approximately equal include following symbol used denote inequation items equal slashed equals sign ≠ u+2260 2260 alt+x microsoft windows latex done \neq command programming languages limiting 7-bit ascii character set typeable characters use codice_31 codice_32 codice_33 codice_34 codice_35 codice_36 represent boolean inequality operator triple bar symbol ≡ u+2261 latex \equiv often used indicate identity definition also represented u+225d ≝ u+2254 ≔ congruence relation modular arithmetic symbol ≅ often used indicate isomorphic algebraic structures congruent geometric figures equality truth values i.e bi-implication logical equivalence may denoted various symbols including ⇔ additional symbols unicode related equals sign include equals sign sometimes used incorrectly within mathematical argument connect math steps non-standard way rather show equality especially early mathematics students example one finding sum step step numbers 1 2 3 4 5 one might incorrectly write structurally shorthand notation incorrect part equality different value interpreted strictly says implies correct version argument would difficulty results subtly different uses sign education early arithmetic-focused grades equals sign may operational like equals button electronic calculator demands result calculation starting algebra courses sign takes relational meaning equality two calculations confusion two uses sign sometimes persists university level related
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Programming language topics
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browser security browser security application internet security web browsers order protect networked data computer systems breaches privacy malware security exploits browsers often use javascript — sometimes cross-site scripting xss — sometimes secondary payload using adobe flash security exploits also take advantage vulnerabilities security holes commonly exploited browsers including mozilla firefox google chrome opera microsoft internet explorer safari web browsers breached one following ways browser may aware breaches may show user safe connection made whenever browser communicates website website part communication collects information browser order process formatting page delivered nothing else malicious code inserted website content worst-case scenario website specifically designed host malicious code vulnerabilities specific particular browser allow malicious code run processes within browser application unintended ways remember one bits information website collects browser communication browser identity- allowing specific vulnerabilities exploited attacker able run processes visitor machine exploiting known security vulnerabilities allow attacker gain privileged access browser n't already running privileged access infected system order perform even greater variety malicious processes activities machine even victim whole network breaches web browser security usually purpose bypassing protections display pop-up advertising collecting personally identifiable information pii either internet marketing identity theft website tracking web analytics user using tools web bugs clickjacking likejacking facebook like button targeted http cookies zombie cookies flash cookies local shared objects lsos installing adware viruses spyware trojan horses gain access users personal computers via cracking malware including online banking theft using man-in-the-browser attacks vulnerabilities web browser software minimized keeping browser software updated sufficient underlying operating system compromised example rootkit subcomponents browsers scripting add-ons cookies particularly vulnerable confused deputy problem also need addressed following principle defence depth fully patched correctly configured browser may sufficient ensure browser-related security issues occur example rootkit capture keystrokes someone logs banking website carry man-in-the-middle attack modifying network traffic web browser dns hijacking dns spoofing may used return false positives mistyped website names subvert search results popular search engines malware rsplug simply modifies system configuration point rogue dns servers browsers use secure methods network communication help prevent attacks perimeter defenses typically firewalls use filtering proxy servers block malicious websites perform antivirus scans file downloads commonly implemented best practice large organizations block malicious network traffic reaches browser topic browser security grown point spawning creation entire organizations browser exploitation framework project creating platforms collect tools breach browser security ostensibly order test browsers network systems vulnerabilities although part browser per se browser plugins extensions extend attack surface exposing vulnerabilities adobe flash player adobe acrobat reader java plugin activex commonly exploited malware may also implemented browser extension browser helper object case internet explorer browsers like google chrome mozilla firefox block—or warn users of—insecure plugins august 2009 study social science research network found 50 websites using flash also employing flash cookies yet privacy policies rarely disclosed user controls privacy preferences lacking browsers cache history delete functions affect flash player writing local shared objects cache user community much less aware existence function flash cookies http cookies thus users deleted http cookies purged browser history files caches may believe purged tracking data computers fact flash browsing history remains well manual removal betterprivacy addon firefox remove flash cookies adblock plus used filter specific threats flashblock used give option allowing content otherwise trusted sites charlie miller recommended install flash computer security conference cansecwest several security experts also recommend either install adobe flash player block contents web page arbitrary controlled entity owning domain named displayed address bar https used encryption used secure attackers access network changing page contents en route presented password field web page user supposed look address bar determine whether domain name address bar correct place send password example google single sign-on system used e.g youtube.com user always check address bar says nowiki https //accounts.google.com /nowiki inputting password un-compromised browser guarantees address bar correct guarantee one reason browsers generally display warning entering fullscreen mode top address bar would normally fullscreen website make fake browser user interface fake address bar attempts market hardware-based browsers running non-writable read-only file systems data stored device media overwritten presenting clean executable time loads first device zeusgard secure hardware browser released late 2013 zeusgard website functional since mid-2016 another device icloak® stik icloak website provides complete live os completely replaces computer entire operating system offers two web browsers read-only system icloak provide tor browser anonymous browsing well regular firefox browser non-anonymous browsing non-secured web traffic using https example could still subject man-in-the-middle alteration network traffic-based manipulations livecds run operating system non-writable source typically come web browsers part default image original livecd image free malware software used including web browser load free malware every time livecd image booted one effective ways browse web safely use browser patches avoid cross-origin resource sharing vulnerability example patches provided webkit-based browsers browsing world wide web least-privilege user account i.e without administrator privileges limits ability security exploit web browser compromising whole operating system internet explorer 4 later allows blacklisting whitelisting activex controls add-ons browser extensions various ways internet explorer 7 added protected mode technology hardens browser application security sandboxing feature windows vista called mandatory integrity control google chrome provides sandbox limit web page access operating system suspected malware sites reported google confirmed google flagged hosting malware certain browsers third-party extensions plugins available harden even latest browsers older browsers operating systems whitelist-based software noscript block javascript adobe flash used attacks privacy allowing users choose sites know safe adblock plus also uses whitelist ad filtering rules subscriptions though software filtering list maintainers come controversy by-default allowing sites pass pre-set filters us-cert recommends block flash using noscript modern web browsers undergo extensive fuzzing uncover vulnerabilities chromium code google chrome continuously fuzzed chrome security team 15,000 cores microsoft edge internet explorer microsoft performed fuzzed testing 670 machine-years product development generating 400 billion dom manipulations 1 billion html files
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Computer security
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openinsight openinsight database application development tool revelation technologies first released 1992 current version 10.0.1 released march 2018 openinsight windows-based development tool contains database type post-relational database known multivalue database openinsight contains tools creating database applications run windows workstations windows linux novell networks browser-based applications tools include limited table builder database manager editor debugger programming language forms designer creating data entry forms user interface tools reporting tools deployment tools openinsight programming language called basic+ extension dialect basic programming language openinsight applications use data revelation software built-in database use data sql databases rocket software rocket u2 databases well tigerlogic d3 database
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Databases
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callback verification callback verification also known callout verification sender address verification technique used smtp software order validate e-mail addresses common target verification sender address message envelope address specified smtp dialogue mail mostly used anti-spam measure since large percentage e-mail spam generated forged sender mfrom addresses spam detected checking whether forging resulted invalid address using method related technique call forwards secondary firewall mail exchanger verify recipients primary mail exchanger domain order decide whether address deliverable receiving mail server verifies sender address verifying parts sender address domain name part character local part part character first step establish successful smtp connection mail exchanger sender address mail exchanger found looking mx records domain dns zone second step query exchanger make sure accepts address valid one done way sending email address however process stopped mail exchanger accepts rejects recipient address steps receiving mail server would take bounce mail back sender however case mail sent smtp commands sent equivalently mail rcpt commands replaced vrfy command however vrfy command required supported usually disabled modern mtas techniques technically compliant relevant smtp rfcs rfc 5321 however rfc 2505 best current practice recommends default disabling vrfy command prevent directory harvest attacks one widespread interpretation implies mail from/rcpt pair commands also respond way stated rfcs documentation postfix exim caution use technique mention many limitations smtp callbacks particular many situations either ineffective causes problems systems receive callbacks problems caused originating systems violating stretching limits rfcs verification problems reflecting problems back senders like unintentionally used invalid addresses rejection null sender greylisting example delay caused verifying recipient closely related delay caused originator many cases turn helps originator system detect problems fix like unintentionally able receive valid bounces several problems reduced caching verification results particular systems give useful information rejecting rcpt time catch-all e-email etc remembered future call backs systems need made also results positive negative specific e-mail addresses remembered mtas like exim caching built
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Computer security
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cache language model cache language model type statistical language model occur natural language processing subfield computer science assign probabilities given sequences words means probability distribution statistical language models key components speech recognition systems many machine translation systems tell systems possible output word sequences probable improbable particular characteristic cache language model contains cache component assigns relatively high probabilities words word sequences occur elsewhere given text primary means sole use cache language models speech recognition systems understand good idea statistical language model contain cache component one might consider someone dictating letter elephants speech recognition system standard non-cache n-gram language models assign low probability word elephant rare word english speech recognition system contain cache component person dictating letter may annoyed time word elephant spoken another sequence words higher probability according n-gram language model may recognized e.g. tell plan erroneous sequences deleted manually replaced text elephant time elephant spoken system cache language model elephant still probably misrecognized first time spoken entered text manually however point system aware elephant likely occur – estimated probability occurrence elephant increased making likely spoken recognized correctly elephant occurred several times system likely recognize correctly every time spoken letter completely dictated increase probability assigned occurrence elephant example consequence machine learning specifically pattern recognition exist variants cache language model single words also multi-word sequences occurred previously assigned higher probabilities e.g. san francisco occurred near beginning text subsequent instances would assigned higher probability cache language model first proposed paper published 1990 ibm speech-recognition group experimented concept group found implementation form cache language model yielded 24 drop word-error rates first hundred words document dictated detailed survey language modeling techniques concluded cache language model one new language modeling techniques yielded improvements standard n-gram approach caching results show caching far useful technique perplexity reduction small medium training data sizes development cache language model generated considerable interest among concerned computational linguistics general statistical natural language processing particular recently interest applying cache language model field statistical machine translation success cache language model improving word prediction rests human tendency use words bursty fashion one discussing certain topic certain context frequency one uses certain words quite different frequencies one discussing topics contexts traditional n-gram language models rely entirely information small number four three two words preceding word probability assigned adequately model burstiness recently cache language model concept originally conceived n-gram statistical language model paradigm adapted use neural paradigm instance recent work continuous cache language models recurrent neural network rnn setting applied cache concept much larger contexts yielding significant reductions perplexity another recent line research involves incorporating cache component feed-forward neural language model fn-lm achieve rapid domain adaptation
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Computational linguistics
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iamus computer iamus computer cluster half-cabinet encased custom shell located universidad de málaga powered melomics technology composing module iamus takes 8 minutes create full composition different musical formats although native representation obtained whole system less second average iamus composes full pieces contemporary classical music iamus opus one created october 15 2010 first fragment professional contemporary classical music ever composed computer style rather attempting emulate style existing composers previously done david cope iamus first full composition hello world premiered exactly one year creation opus one october 15 2011 four iamus works premiered july 2 2012 broadcast live school computer science universidad de málaga part events included alan turing year compositions performed event later recorded london symphony orchestra creating album iamus new scientist reported first complete album composed solely computer recorded human musicians commenting authenticity music stephen smoliar critic classical music san francisco examiner commented primary act making music engaged performers listener responds performers ... interesting documents generated iamus capacity challenge creative talents performing musicians
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Distributed computing architecture
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transactional ntfs transactional ntfs abbreviated txf component introduced windows vista present later versions microsoft windows operating system brings concept atomic transactions ntfs file system allowing windows application developers write file-output routines guaranteed either succeed completely fail completely major operating system components including system restore task scheduler windows update rely txf stability development windows vista winfs also relied txf storing files due complexity various nuances developers need consider part application development microsoft considered deprecating txf application programming interfaces apis future version windows microsoft strongly recommended developers investigate using alternatives rather adopting transactional ntfs api platform may available future versions windows transactional ntfs allows files directories created modified renamed deleted atomically using transactions ensures correctness operation series file operations done transaction operation committed operations succeed case failure entire operation roll back fail transactional ntfs implemented top kernel transaction manager windows kernel component introduced windows vista provides transactioning objects kernel ntfs file system already supports journaling low-level operations writing block data transactional ntfs expands capability include exception read operations using transactional ntfs transactions encrypting file system files supported windows vista service pack 1 windows server 2008
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Operating systems
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synaptic software synaptic gtk-based graphical user interface apt package manager used debian linux distribution derivatives synaptic usually used systems based deb packages also used systems based rpm packages used install remove upgrade software packages add repositories also following features package manager enables user install upgrade remove software packages install remove package user must search navigate package mark installation removal changes applied instantly user must first mark changes apply synaptic development funded conectiva asked alfredo kojima employee write graphical front-end apt continuing work initiated creation apt rpm back-end apt-rpm
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Operating systems
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tss-8 tss-8 discontinued time-sharing operating system co-written witcraft john everett digital equipment corporation 1967 dec also referred timeshared-8 edusystem 50 operating system ran 12-bit pdp-8 computer released 1968 timesharing system like ibm call/os implemented language variants also supported dec focal developed specifically pdp 8/e provided algebraic language also desk calculator mode
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Operating systems
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william jolitz william frederick jolitz born february 22 1957 commonly known bill jolitz american software programmer best known developing 386bsd operating system 1989 1994 along wife lynne jolitz jolitz received ba computer science uc berkeley wife reside los gatos california children rebecca benjamin sarah
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Operating systems
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lynx software technologies lynx software technologies inc. formerly lynuxworks san jose california software company founded 1988 lynx software technologies specializes secure virtualization open reliable real-time operating system rtos originally known lynx real-time systems company changed name lynuxworks 2000 acquiring merging isdcorp integrated software devices corporation nine-year-old embedded systems company strong linux background may 2014 company changed name lynx software technologies representation company ’ forward direction lynxos rtos family products lynxsecure hypervisor continued gain increased traction current customers markets new internet connected embedded world lynx software technologies created technology successfully deployed thousands designs millions products made leading communications industrial transportation avionics aerospace/defense consumer electronics companies 1989 lynxos company flagship real-time operating system selected use nasa/ibm space station freedom project lynx software technologies operating systems also used medical industrial communications systems around world lynx software technologies held private 2000 company filed registration statement initial public offering later withdrew plans due unfavourable economic conditions lynxos company real-time operating system unix-compatible posix-compliant features predictable worst-case response time preemptive scheduling real-time priorities romable kernel memory locking lynxos 7.0 marketed military grade general purpose multi-core hard real-time operating system intended developers embed security features design process rather adding security features development security used protect user accessible also machine machine m2m based embedded devices utilizing access control lists audit quotas local trusted path account management trusted menu manager openpam 2000 lynx software technologies released first embedded linux distribution bluecat linux 1.0 specialized paravirtualized linux embedded systems virtualization 2003 company introduced lynxos-178 real-time operating system specialized version lynxos geared toward avionics applications require certification industry standards do-178b lynxos-178 commercial off-the-shelf cots rtos fully satisfies objectives do-178b level specification meets requirements integrated modular avionics developers lynxsecure hypervisor bare metal type 1 separation kernel released 2005 lynxsecure programmable processor partitioning system uses hardware virtualization capabilities modern multi-core processors isolate computing resources lynx software technologies patents lynxos technology include patent 5,469,571 operating system architecture using multiple priority light weight kernel task-based interrupt handling november 21 1995 patent 5,594,903 operating system architecture reserved memory space resident program code identified file system name space january 14 1997
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Operating systems
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