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macintosh se macintosh se personal computer designed manufactured sold apple computer inc. march 1987 october 1990 marked significant improvement macintosh plus design introduced apple time macintosh ii se retains compact macintosh form factor original macintosh computer introduced three years earlier uses design language used macintosh ii enhanced model se/30 introduced january 1989 sales original se continued macintosh se updated august 1989 include superdrive updated version called macintosh se fdhd later macintosh se superdrive macintosh se replaced macintosh classic similar model retained central processing unit form factor lower price point macintosh se introduced appleworld conference los angeles march 2 1987 se acronym system expansion notable new features compared similar predecessor macintosh plus se macintosh ii first apple computers since apple sold without keyboard instead customer offered choice new adb apple keyboard apple extended keyboard apple produced ten ses transparent cases prototypes promotional shots employees extremely rare command premium price collectors macintosh se shipped system 4.0 finder 5.4 version specific computer macintosh ii announced time shipped month later includes system 4.1 finder 5.5 readme file included installation disks se ii first place apple ever used term macintosh system software 1998 two versions retroactively given name macintosh system software 2.0.1 processor motorola 68000 8 mhz 8 mhz system bus 16-bit data path ram se came 1 mb ram standard expandable 4 mb logic board four 30-pin simm slots memory must installed pairs must 150 ns faster video 256 kb onboard video memory enabling 512x384 monochrome resolution built-in screen lower resolution storage se accommodate either one two floppy drives floppy drive hard drive after-market brackets designed allow se accommodate two floppy drives well hard drive however configuration supported apple addition external floppy disk drive may also connected making se macintosh besides macintosh portable could support three floppy drives though increased storage ram capacity optional internal hard drive rendered external drives less necessity predecessors single-floppy se models also featured drive-access light spot second floppy drive would hard-drive equipped models came 20 mb scsi hard disk battery soldered logic board 3.0 v 1/2aa lithium battery must present order basic settings persist power cycles macintosh se machines sat long time experienced battery corrosion leakage resulting damaged case logic board expansion processor direct slot logic board allows expansion cards accelerators installed se upgraded 50 mhz 5 mb micromac accelerators past accelerators also available sonnet allegro since installing card required opening computer case exposing user high voltages internal crt apple recommended authorized apple dealers install cards case sealed then-uncommon torx screws upgrades apple introduced macintosh se/30 january 1989 logic board upgrade sold apple dealers high-cost upgrade se consisting new se/30 motherboard case front internal chassis accommodate upgrade components easter egg macintosh se rom size increased 64 kb original mac 256 kb allowed development team include easter egg hidden roms jumping address 0x41d89a reading rom chips possible display four images engineering team introduced march 2 1987 introduced august 1 1989
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Computer architecture
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videntifier videntifier icelandic software company developed method quickly identify videos images automatic manner videntifier patented technology store fingerprints enormous amounts video content images identify reference material within seconds usually single frame enough identify entire video currently company headquartered reykjavik iceland office vilnius lithuania videntifier technologies founded september 2007 provides technology search track vast amounts multimedia data efficient manner previously company focused providing services police departments engaged locating illegal images videos seized computers company roots database laboratories reykjavik university later opened secondary lab irisa-cnrs rennes 2005 videntifier technologies received one top prizes austrian genius competition best business idea 2008 innovation award 2008 2008 videntifier technologies received golden egg award best new business idea iceland 2013 videntifier technologies signed agreement interpol provide advanced imaging technology effort child sexual abuse material
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Computer security
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grid file system grid file system computer file system whose goal improved reliability availability taking advantage many smaller file storage areas file systems contain three components grid file system would similar needs file systems designed appear single disk single computer manage entirely many new challenges arise grid scenario whereby single disk within grid capable handling requests data contained grid file storage utilizes layers redundancy achieve high level data protection inability lose data current means redundancy include replication parity checks redundancy implemented via raid array whereby multiple physical disks appear local computer single disk may include data replication and/or disk partitioning similarly grid file system would consist level redundancy either logical file level block level possibly including sort parity check across various disks present grid first foremost file table mechanism necessary additionally file table must include mechanism locating target/destination file within grid secondly mechanism working file data must exist mechanism responsible making file data available requests bittorrent technology parallel drawn grid file system torrent tracker search engine would file table torrent applications transmitting files would file data component rss feed like mechanism could utilized file table nodes indicate new files added table instigate replication similar components file system may incorporate similar technology distributed replication distributed data request/fulfillment systems file table file data capable addressed single entity i.e using virtual nodes cluster growth system could easily controlled simply deciding uses grid member would responsible file table file lookups and/or file data assuming exists method managing data replication assigning quotas etc autonomously within grid data could configured high availability regardless loss outage largest problem currently revolves around distributing data updates torrents support minimal hierarchy currently implemented either metadata torrent tracker strictly ui basic categorization updating multiple nodes concurrently assuming atomic transactions required presents latency updates additions usually point feasible additionally grid network based file system breaks traditional tcp/ip paradigms file system generally low level ring 0 type operations require complicated tcp/ip implementations introducing layers abstraction complication process creating grid file system examples high-available data include
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Computer file systems
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class computer programming object-oriented programming class extensible program-code-template creating objects providing initial values state member variables implementations behavior member functions methods many languages class name used name class template name default constructor class subroutine creates objects type objects generated instantiating class distinct concepts easily conflated object created constructor class resulting object called instance class member variables specific object called instance variables contrast class variables shared across class languages classes compile-time feature new classes declared run-time languages classes first-class citizens generally objects typically type similar languages class creates classes called metaclass casual use people often refer class object narrowly speaking objects type interface namely types member variables signatures member functions methods properties satisfy time class implementation specifically implementation methods create objects given type given implementation terms type theory class implementationa concrete data structure collection subroutineswhile type interface different concrete classes produce objects abstract type depending type system example type might implemented two classes fast small stacks scales poorly scales well high overhead small stacks similarly given class may several different constructors types generally represent nouns person place thing something nominalized class represents implementation example type might represent properties functionality bananas general classes would represent ways producing bananas say banana suppliers data structures functions represent draw bananas video game class could produce particular bananas instances class would objects type often single implementation type given case class name often identical type name classes composed structural behavioral constituents programming languages include classes programming construct offer support various class-related features syntax required use features varies greatly one programming language another class contains data field descriptions properties fields data members attributes usually field types names associated state variables program run time state variables either belong class specific instances class languages structure defined class determines layout memory used instances implementations possible example objects python use associative key-value containers programming languages support specification invariants part definition class enforce type system encapsulation state necessary able enforce invariants class behavior class instances defined using methods methods subroutines ability operate objects classes operations may alter state object simply provide ways accessing many kinds methods exist support varies across languages types methods created called programmer code special methods—such constructors destructors conversion operators—are created called compiler-generated code language may also allow programmer define call special methods every class implements realizes interface providing structure behavior structure consists data state behavior consists code specifies methods implemented distinction definition interface implementation interface however line blurred many programming languages class declarations define implement interface languages however provide features separate interface implementation example abstract class define interface without providing implementation languages support class inheritance also allow classes inherit interfaces classes derived example class inherits class b class b implements interface interface b class also inherits functionality constants methods declaration provided interface b languages support access specifiers interface class considered set public members class including methods attributes via implicit getter setter methods private members internal data structures intended depended external code thus part interface object-oriented programming methodology dictates operations interface class independent results layered design clients interface use methods declared interface interface places requirements clients invoke operations one interface particular order approach benefit client code assume operations interface available use whenever client access object buttons front television set interface electrical wiring side plastic casing press power button toggle television example particular television instance method represented button buttons together comprise interface television sets model would interface common form interface specification group related methods without associated implementation methods television set also myriad attributes size whether supports colour together comprise structure class represents full description television including attributes structure buttons interface getting total number televisions manufactured could static method television class method clearly associated class yet outside domain individual instance class static method finds particular instance set television objects another example following common set access specifiers although many object-oriented languages support access specifiers semantics may differ object-oriented design uses access specifiers conjunction careful design public method implementations enforce class invariants—constraints state objects common usage access specifiers separate internal data class interface internal structure made private public accessor methods used inspect alter private data access specifiers necessarily control visibility even private members may visible client external code languages inaccessible visible member may referred run-time example pointer returned member function attempt use referring name member client code prevented type checker various object-oriented programming languages enforce member accessibility visibility various degrees depending language type system compilation policies enforced either compile-time run-time example java language allow client code accesses private data class compile languages feature accessibility schemes addition design standalone classes programming languages may support advanced class design based upon relationships classes inter-class relationship design capabilities commonly provided compositional hierarchical classes composed classes thereby establishing compositional relationship enclosing class embedded classes compositional relationship classes also commonly known has-a relationship example class car could composed contain class engine therefore car engine one aspect composition containment enclosure component instances instance enclosing object contains component instances value components enclosing object similar lifetime components contained reference may similar lifetime example objective-c 2.0 class instance string object array object classes derived one existing classes thereby establishing hierarchical relationship derived-from classes base classes parent classes derived class child class subclass relationship derived class derived-from classes commonly known is-a relationship example class 'button could derived class 'control therefore button control structural behavioral members parent classes inherited child class derived classes define additional structural members data fields behavioral members methods addition inherit therefore specializations superclasses also derived classes override inherited methods language allows languages support multiple inheritance example java allows class implement multiple interfaces inherit one class multiple inheritance allowed hierarchy directed acyclic graph dag short otherwise tree hierarchy classes nodes inheritance relationships links classes level likely associated classes different levels levels hierarchy called layers levels abstraction example simplified objective-c 2.0 code iphone sdk example uitableview uiscrollview uiview uiresponder nsobject conceptually superclass superset subclasses example common class hierarchy would involve superclass would subclass subset relations set theory well i.e. squares rectangles rectangles squares common conceptual error mistake part relation subclass example car truck kinds vehicles would appropriate model subclasses vehicle class however would error model component parts car subclass relations example car composed engine body would appropriate model engine body subclass car object-oriented modeling kinds relations typically modeled object properties example class would property called would typed hold collection objects instances etc object modeling languages uml include capabilities model various aspects part kinds relations – data cardinality objects constraints input output values etc information utilized developer tools generate additional code beside basic data definitions objects error checking get set methods one important question modeling implementing system object classes whether class one superclasses real world actual sets would rare find sets n't intersect one set however systems flavors clos provide capability one parent run time introduces complexity many object-oriented community consider antithetical goals using object classes first place understanding class responsible handling message get complex dealing one superclass used carelessly feature introduce system complexity ambiguity classes designed avoid modern object-oriented languages smalltalk java require single inheritance run time languages multiple inheritance may useful modeling implementation however semantic web application objects multiple superclasses volatility internet requires level flexibility technology standards web ontology language owl designed support similar issue whether class hierarchy modified run time languages flavors clos smalltalk support feature part meta-object protocols since classes first-class objects possible dynamically alter structure sending appropriate messages languages focus strong typing java c++ allow class hierarchy modified run time semantic web objects capability run time changes classes rational similar justification allowing multiple superclasses internet dynamic flexible dynamic changes hierarchy required manage volatility although class-based languages commonly assumed support inheritance inheritance intrinsic aspect concept classes languages often referred object-based languages support classes yet support inheritance examples object-based languages include earlier versions visual basic object-oriented analysis uml association two classes represents collaboration classes corresponding instances associations direction example bi-directional association two classes indicates classes aware relationship associations may labeled according name purpose association role given end association describes role corresponding class example subscriber role describes way instances class person participate subscribes-to association class magazine also magazine subscribed magazine role association association role multiplicity describes many instances correspond instance class association common multiplicities 0..1 1..1 1..* 0..* specifies number instances many categories classes overlap language supports inheritance abstract class abstract base class abc class instantiated either labeled abstract simply specifies abstract methods virtual methods abstract class may provide implementations methods may also specify virtual methods via signatures implemented direct indirect descendants abstract class class derived abstract class instantiated abstract methods parent classes must implemented class derivation chain object-oriented programming languages allow programmer specify classes considered abstract allow instantiated example java c php keyword abstract used c++ abstract class class least one abstract method given appropriate syntax language pure virtual function c++ parlance class consisting virtual methods called pure abstract base class pure abc c++ also known interface users language languages notably java c support variant abstract classes called interface via keyword language languages multiple inheritance allowed class implement multiple interfaces class contain abstract publicly accessible methods concrete class class instantiated opposed abstract classes languages classes declared scopes global scope various types classes inner class class defined within another class relationship inner class containing class also treated another type class association inner class typically neither associated instances enclosing class instantiated along enclosing class depending language may may possible refer class outside enclosing class related concept inner types also known inner data type nested type generalization concept inner classes c++ example language supports inner classes inner types via typedef declarations another type local class class defined within procedure function limits references class name within scope class declared depending semantic rules language may additional restrictions local classes compared non-local ones one common restriction disallow local class methods access local variables enclosing function example c++ local class may refer static variables declared within enclosing function may access function automatic variables metaclasses classes whose instances classes metaclass describes common structure collection classes implement design pattern describe particular kinds classes metaclasses often used describe frameworks languages python ruby smalltalk class also object thus class instance unique metaclass built language common lisp object system clos non-subclassable classes allow programmers design classes hierarchies classes level hierarchy derivation prohibited stand-alone class may also designated non-subclassable preventing formation hierarchy contrast abstract classes imply encourage require derivation order used non-subclassable class implicitly concrete non-subclassable class created declaring class c java php example java class designated final non-subclassable classes may allow compiler compiled languages perform optimizations available subclassable classes open class one changed typically executable program changed customers developers often change classes typically change standard built-in ones ruby classes open python classes created runtime modified afterwards objective-c categories permit programmer add methods existing class without need recompile class even access source code languages special support mixins though language multiple inheritance mixin simply class represent is-a-type-of relationship mixins typically used add methods multiple classes example class might provide method called included classes share common parent languages supporting feature partial class class whose definition may split multiple pieces within single source-code file across multiple files pieces merged compile-time making compiler output non-partial class primary motivation introduction partial classes facilitate implementation code generators visual designers otherwise challenge compromise develop code generators manage generated code interleaved within developer-written code using partial classes code generator process separate file coarse-grained partial class within file thus alleviated intricately interjecting generated code via extensive parsing increasing compiler efficiency eliminating potential risk corrupting developer code simple implementation partial classes compiler perform phase precompilation unifies parts partial class compilation proceed usual benefits effects partial class feature include partial classes existed smalltalk name class extensions considerable time arrival .net framework 2 microsoft introduced partial classes supported c 2.0 visual basic 2005 winrt also supports partial classes simple example written visual basic .net shows parts class defined two different files compiled result two files written one like objective-c partial classes also known categories may even spread multiple libraries executables like following example key difference objective-c categories overwrite definitions another interface declaration categories n't equal original class definition first requires last instead .net partial class ca n't conflicting definitions partial definitions equal others foundation header file nsdata.h user-supplied library separate binary foundation framework header file nsdata+base64.h app yet another separate binary file source code file main.m dispatcher find methods called nsdata instance invoke correctly uninstantiable classes allow programmers group together per-class fields methods accessible runtime without instance class indeed instantiation prohibited kind class example c class marked static instantiated static members fields methods may instance constructors sealed unnamed class anonymous class class bound name identifier upon definition analogous named versus unnamed functions benefits organizing software object classes fall three categories object classes facilitate rapid development lessen semantic gap code users system analysts talk developers users using essentially vocabulary talking accounts customers bills etc object classes often facilitate rapid development object-oriented environments come powerful debugging testing tools instances classes inspected run time verify system performing expected also rather get dumps core memory object-oriented environments interpreted debugging capabilities developer analyze exactly program error occurred see methods called arguments arguments object classes facilitate ease maintenance via encapsulation developers need change behavior object localize change object component parts reduces potential unwanted side effects maintenance enhancements software re-use also major benefit using object classes classes facilitate re-use via inheritance interfaces new behavior required often achieved creating new class class inherit default behaviors data superclass tailor aspect behavior data accordingly re-use via interfaces also known methods occurs another object wants invoke rather create new kind object class method re-use removes many common errors make way software one program re-uses code another data type class usually considered compile-time construct language may also support prototype factory metaobjects represent run-time information classes even represent metadata provides access reflection facilities ability manipulate data structure formats run-time many languages distinguish kind run-time type information classes class basis information needed run-time dynamic languages make strict distinctions run-time compile-time constructs therefore may distinguish metaobjects classes example human metaobject representing class person instances class person created using facilities human metaobject
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Programming language topics
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fold higher-order function functional programming fold also termed reduce accumulate aggregate compress inject refers family higher-order functions analyze recursive data structure use given combining operation recombine results recursively processing constituent parts building return value typically fold presented combining function top node data structure possibly default values used certain conditions fold proceeds combine elements data structure hierarchy using function systematic way folds sense dual unfolds take seed value apply function corecursively decide progressively construct corecursive data structure whereas fold recursively breaks structure replacing results applying combining function node terminal values recursive results catamorphism versus anamorphism unfolds folds regarded consistently replacing structural components data structure functions values lists example built many functional languages two primitives list either empty list commonly called nil codice_1 constructed prefixing element front another list creating called cons node codice_2 resulting application codice_3 function written colon codice_4 haskell one view fold lists replacing nil end list specific value replacing cons specific function replacements viewed diagram another way perform structural transformation consistent manner order two links node flipped fed combining function pictures illustrate right left fold list visually also highlight fact codice_5 identity function lists shallow copy lisp parlance replacing cons codice_3 nil codice_7 change result left fold diagram suggests easy way reverse list codice_8 note parameters cons must flipped element add right hand parameter combining function another easy result see vantage-point write higher-order map function terms codice_9 composing function act elements codice_3 period operator denoting function composition way looking things provides simple route designing fold-like functions algebraic data types structures like various sorts trees one writes function recursively replaces constructors datatype provided functions constant values type provided values function generally referred catamorphism folding list codice_11 addition operator would result 15 sum elements list codice_11 rough approximation one think fold replacing commas list operation giving codice_13 example associative operation final result regardless parenthesization although specific way calculated different general case non-associative binary functions order elements combined may influence final result value lists two obvious ways carry either combining first element result recursively combining rest called right fold combining result recursively combining elements last one last element called left fold corresponds binary operator either right-associative left-associative haskell prolog terminology right fold sum would parenthesized codice_14 whereas left fold would parenthesized codice_15 practice convenient natural initial value case right fold used one reaches end list case left fold initially combined first element list example value 0 additive identity would chosen initial value giving codice_16 right fold codice_17 left fold multiplication initial choice 0 would n't work codice_18 identity element multiplication 1 would give us outcome codice_19 use initial value necessary combining function f asymmetrical types e.g codice_20 i.e type result different type list elements initial value must used type f result linear chain applications possible whether left- right-oriented determined types expected arguments combining function second argument must type result f could seen binary operation associates right vice versa function magma i.e symmetrical types codice_21 result type list elements type parentheses may placed arbitrary fashion thus creating tree nested sub-expressions e.g. codice_22 binary operation f associative value well-defined i.e. parenthesization although operational details calculated different significant impact efficiency f non-strict whereas linear folds node-oriented operate consistent manner node list tree-like folds whole-list oriented operate consistent manner across groups nodes one often wants choose identity element operation f initial value z initial value seems appropriate example one wants fold function computes maximum two parameters non-empty list get maximum element list variants codice_9 codice_24 use last first element list respectively initial value haskell several languages called codice_25 codice_26 1 making reference automatic provision initial element fact lists applied must least one element folds use type-symmetrical binary operation types arguments result must richard bird 2010 book proposes general fold function non-empty lists codice_27 transforms last element applying additional argument function value result type starting folding thus able use type-asymmetrical binary operation like regular codice_9 produce result type different list elements type using haskell example codice_24 codice_9 formulated equations list empty result initial value fold tail list using new initial value result applying f old initial value first element list empty result initial value z apply f first element result folding rest lists folded tree-like fashion finite indefinitely defined lists case codice_31 function avoid runaway evaluation indefinitely defined lists function codice_32 must always demand second argument value least and/or immediately see example presence lazy non-strict evaluation codice_9 immediately return application f head list recursive case folding rest list thus f able produce part result without reference recursive case right i.e. second argument rest result never demanded recursion stop e.g. allows right folds operate infinite lists contrast codice_24 immediately call new parameters reaches end list tail recursion efficiently compiled loop ca n't deal infinite lists — recurse forever infinite loop reached end list expression effect built codice_24 nested left-deepening codice_32-applications presented caller evaluated function codice_32 refer second argument first able produce part result without reference recursive case left i.e. first argument recursion would stop means codice_9 recurses right allows lazy combining function inspect list elements left conversely codice_24 recurses left allows lazy combining function inspect list elements right chooses e.g. reversing list also tail-recursive implemented using finite lists means left-fold reverse composed perform right fold tail-recursive way cf modification function codice_32 reverses order arguments i.e. tail-recursively building representation expression right-fold would build extraneous intermediate list structure eliminated continuation-passing style technique similarly codice_41 needed languages like haskell flipped order arguments combining function codice_24 unlike e.g. scheme order arguments used combining functions codice_24 another technical point case left folds using lazy evaluation new initial parameter evaluated recursive call made lead stack overflows one reaches end list tries evaluate resulting potentially gigantic expression reason languages often provide stricter variant left folding forces evaluation initial parameter making recursive call haskell codice_44 note apostrophe pronounced 'prime function codice_45 library one needs aware fact though forcing value built lazy data constructor wo n't force constituents automatically combined tail recursion folds approach efficiency loops ensuring constant space operation lazy evaluation final result impossible undesirable using haskell interpreter structural transformations fold functions perform illustrated constructing string infinite tree-like folding demonstrated e.g. recursive primes production unbounded sieve eratosthenes haskell function codice_46 operates ordered lists local manner efficiently produce set union codice_47 set difference finite lists e.g. merge sort duplicates-removing variety codice_48 could easily defined using tree-like folding function haskell 98 features mergesort|codice_49 duplicates-preserving variant codice_46 functions codice_51 codice_52 could defined folding language left fold right fold left fold without initial value right fold without initial value unfold notes category higher-order functions category recursion category programming language comparisons category articles example haskell code category articles example scheme code category iteration programming
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Programming language topics
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computer security computer security cybersecurity information technology security security protection computer systems theft damage hardware software electronic data well disruption misdirection services provide field becoming important due increased reliance computer systems internet wireless network standards bluetooth wi-fi due growth smart devices including smartphones televisions various devices constitute internet things due complexity terms politics technology cybersecurity also one major challenges contemporary world vulnerability weakness design implementation operation internal control vulnerabilities discovered documented common vulnerabilities exposures cve database exploitable vulnerability one least one working attack exploit exists vulnerabilities often hunted exploited aid automated tools manually using customized scripts secure computer system important understand attacks made threats typically classified one categories backdoor computer system cryptosystem algorithm secret method bypassing normal authentication security controls may exist number reasons including original design poor configuration may added authorized party allow legitimate access attacker malicious reasons regardless motives existence create vulnerability denial service attacks dos designed make machine network resource unavailable intended users attackers deny service individual victims deliberately entering wrong password enough consecutive times cause victims account locked may overload capabilities machine network block users network attack single ip address blocked adding new firewall rule many forms distributed denial service ddos attacks possible attack comes large number points – defending much difficult attacks originate zombie computers botnet range techniques possible including reflection amplification attacks innocent systems fooled sending traffic victim unauthorized user gaining physical access computer likely able directly copy data may also compromise security making operating system modifications installing software worms keyloggers covert listening devices using wireless mice even system protected standard security measures may able by-passed booting another operating system tool cd-rom bootable media disk encryption trusted platform module designed prevent attacks eavesdropping act surreptitiously listening private conversation typically hosts network instance programs carnivore narusinsight used fbi nsa eavesdrop systems internet service providers even machines operate closed system i.e. contact outside world eavesdropped upon via monitoring faint electromagnetic transmissions generated hardware tempest specification nsa referring attacks surfacing 2017 new class multi-vector polymorphic cyber threats surfaced combined several types attacks changed form avoid cyber security controls spread threats classified fifth generation cyber attacks phishing attempt acquire sensitive information usernames passwords credit card details directly users phishing typically carried email spoofing instant messaging often directs users enter details fake website whose look feel almost identical legitimate one fake website often ask personal information log-in passwords information used gain access individual real account real website preying victim trust phishing classified form social engineering privilege escalation describes situation attacker level restricted access able without authorization elevate privileges access level example standard computer user may able exploit vulnerability system gain access restricted data even become root full unrestricted access system social engineering aims convince user disclose secrets passwords card numbers etc example impersonating bank contractor customer common scam involves fake ceo emails sent accounting finance departments early 2016 fbi reported scam cost us businesses 2bn two years may 2016 milwaukee bucks nba team victim type cyber scam perpetrator impersonating team president peter feigin resulting handover team employees 2015 w-2 tax forms spoofing act masquerading valid entity falsification data ip address username order gain access information resources one otherwise unauthorized obtain several types spoofing including tampering describes malicious modification products so-called evil maid attacks security services planting surveillance capability routers examples employee behavior big impact information security organizations cultural concepts help different segments organization work effectively work effectiveness towards information security within organization ″exploring relationship organizational culture information security culture″ provides following definition information security culture ″isc totality patterns behavior organization contribute protection information kinds.″ andersson reimers 2014 found employees often see part organization information security effort often take actions ignore organizational information security best interests research shows information security culture needs improved continuously ″information security culture analysis change″ authors commented ″it never ending process cycle evaluation change maintenance.″ manage information security culture five steps taken pre-evaluation strategic planning operative planning implementation post-evaluation growth number computer systems increasing reliance upon individuals businesses industries governments means increasing number systems risk computer systems financial regulators financial institutions like u.s. securities exchange commission swift investment banks commercial banks prominent hacking targets cyber criminals interested manipulating markets making illicit gains web sites apps accept store credit card numbers brokerage accounts bank account information also prominent hacking targets potential immediate financial gain transferring money making purchases selling information black market in-store payment systems atms also tampered order gather customer account data pins computers control functions many utilities including coordination telecommunications power grid nuclear power plants valve opening closing water gas networks internet potential attack vector machines connected stuxnet worm demonstrated even equipment controlled computers connected internet vulnerable 2014 computer emergency readiness team division department homeland security investigated 79 hacking incidents energy companies vulnerabilities smart meters many use local radio cellular communications cause problems billing fraud aviation industry reliant series complex systems could attacked simple power outage one airport cause repercussions worldwide much system relies radio transmissions could disrupted controlling aircraft oceans especially dangerous radar surveillance extends 175 225 miles offshore also potential attack within aircraft europe pan-european network service newpens us nextgen program air navigation service providers moving create dedicated networks consequences successful attack range loss confidentiality loss system integrity air traffic control outages loss aircraft even loss life desktop computers laptops commonly targeted gather passwords financial account information construct botnet attack another target smartphones tablet computers smart watches mobile devices quantified self devices like activity trackers sensors cameras microphones gps receivers compasses accelerometers could exploited may collect personal information including sensitive health information wifi bluetooth cell phone networks devices could used attack vectors sensors might remotely activated successful breach increasing number home automation devices nest thermostat also potential targets large corporations common targets many cases aimed financial gain identity theft involves data breaches loss millions clients credit card details home depot staples target corporation recent breach equifax cyberattacks ordered foreign governments governments engage cyberwarfare intent spread propaganda sabotage spy targets many people believe russian government played major role us presidential election 2016 using twitter facebook affect results election medical records targeted use general identify theft health insurance fraud impersonating patients obtain prescription drugs recreational purposes resale although cyber threats continue increase 62 organizations increase security training business 2015 attacks financially motivated however example security firm hbgary federal suffered serious series attacks 2011 hacktivist group anonymous retaliation firm ceo claiming infiltrated group sony pictures attack 2014 motive appears embarrass data leaks cripple company wiping workstations servers vehicles increasingly computerized engine timing cruise control anti-lock brakes seat belt tensioners door locks airbags advanced driver-assistance systems many models additionally connected cars may use wifi bluetooth communicate onboard consumer devices cell phone network self-driving cars expected even complex systems carry security risk issues gained wide attention simple examples risk include malicious compact disc used attack vector car onboard microphones used eavesdropping however access gained car internal controller area network danger much greater – widely publicized 2015 test hackers remotely carjacked vehicle 10 miles away drove ditch manufacturers reacting number ways tesla 2016 pushing security fixes air cars computer systems area autonomous vehicles september 2016 united states department transportation announced initial safety standards called states come uniform policies government military computer systems commonly attacked activists foreign powers local regional government infrastructure traffic light controls police intelligence agency communications personnel records student records financial systems also potential targets largely computerized passports government id cards control access facilities use rfid vulnerable cloning internet things iot network physical objects devices vehicles buildings embedded electronics software sensors network connectivity enables collect exchange data – concerns raised developed without appropriate consideration security challenges involved iot creates opportunities direct integration physical world computer-based systems also provides opportunities misuse particular internet things spreads widely cyber attacks likely become increasingly physical rather simply virtual threat front door lock connected internet locked/unlocked phone criminal could enter home press button stolen hacked phone people could stand lose much credit card numbers world controlled iot-enabled devices thieves also used electronic means circumvent non-internet-connected hotel door locks medical devices either successfully attacked potentially deadly vulnerabilities demonstrated including in-hospital diagnostic equipment implanted devices including pacemakers insulin pumps many reports hospitals hospital organizations getting hacked including ransomware attacks windows xp exploits viruses data breaches sensitive data stored hospital servers 28 december 2016 us food drug administration released recommendations medical device manufacturers maintain security internet-connected devices – structure enforcement distributed generation systems risk cyber attack real according daily energy insider attack could cause loss power large area long period time attack could severe consequences natural disaster district columbia considering creating distributed energy resources der authority within city goal customers insight energy use giving local electric utility pepco chance better estimate energy demand d.c. proposal however would allow third-party vendors create numerous points energy distribution could potentially create opportunities cyber attackers threaten electric grid serious financial damage caused security breaches standard model estimating cost incident data available made public organizations involved several computer security consulting firms produce estimates total worldwide losses attributable virus worm attacks hostile digital acts general 2003 loss estimates firms range 13 billion worms viruses 226 billion forms covert attacks reliability estimates often challenged underlying methodology basically anecdotal security breaches continue cost businesses billions dollars survey revealed 66 security staffs believe senior leadership takes cyber precautions strategic priority however reasonable estimates financial cost security breaches actually help organizations make rational investment decisions according classic gordon-loeb model analyzing optimal investment level information security one conclude amount firm spends protect information generally small fraction expected loss i.e. expected value loss resulting cyber/information security breach physical security motivations breaches computer security vary attackers thrill-seekers vandals activists others criminals looking financial gain state-sponsored attackers common well resourced started amateurs markus hess hacked kgb recounted clifford stoll cuckoo egg additionally recent attacker motivations traced back extremist organizations seeking gain political advantage disrupt social agendas growth internet mobile technologies inexpensive computing devices led rise capabilities also risk environments deemed vital operations critical targeted environments susceptible compromise led series proactive studies migrate risk taking consideration motivations type actors several stark differences exist hacker motivation nation state actors seeking attack based ideological preference standard part threat modelling particular system identify might motivate attack system might motivated breach level detail precautions vary depending system secured home personal computer bank classified military network face different threats even underlying technologies use similar computer security countermeasure action device procedure technique reduces threat vulnerability attack eliminating preventing minimizing harm cause discovering reporting corrective action taken common countermeasures listed following sections security design alternately secure design means software designed ground secure case security considered main feature techniques approach include open security architecture organization defines security architecture design artifacts describe security controls security countermeasures positioned relate overall information technology architecture controls serve purpose maintain system quality attributes confidentiality integrity availability accountability assurance services techopedia defines security architecture unified security design addresses necessities potential risks involved certain scenario environment also specifies apply security controls design process generally reproducible key attributes security architecture state computer security conceptual ideal attained use three processes threat prevention detection response processes based various policies system components include following today computer security comprises mainly preventive measures like firewalls exit procedure firewall defined way filtering network data host network another network internet implemented software running machine hooking network stack case unix-based operating systems linux built operating system kernel provide real-time filtering blocking another implementation so-called physical firewall consists separate machine filtering network traffic firewalls common amongst machines permanently connected internet organizations turning big data platforms apache hadoop extend data accessibility machine learning detect advanced persistent threats however relatively organisations maintain computer systems effective detection systems fewer still organized response mechanisms place result reuters points companies first time report losing electronic theft data physical stealing assets primary obstacle effective eradication cyber crime could traced excessive reliance firewalls automated detection systems yet basic evidence gathering using packet capture appliances puts criminals behind bars vulnerability management cycle identifying remediating mitigating vulnerabilities especially software firmware vulnerability management integral computer security network security vulnerabilities discovered vulnerability scanner analyzes computer system search known vulnerabilities open ports insecure software configuration susceptibility malware beyond vulnerability scanning many organizations contract outside security auditors run regular penetration tests systems identify vulnerabilities sectors contractual requirement formal verification correctness computer systems possible yet common operating systems formally verified include sel4 sysgo pikeos – make small percentage market two factor authentication method mitigating unauthorized access system sensitive information requires something know password pin something card dongle cellphone piece hardware increases security unauthorized person needs gain access social engineering direct computer access physical attacks prevented non-computer means difficult enforce relative sensitivity information training often involved help mitigate risk even highly disciplined environments e.g military organizations social engineering attacks still difficult foresee prevent enoculation derived inoculation theory seeks prevent social engineering fraudulent tricks traps instilling resistance persuasion attempts exposure similar related attempts possible reduce attacker chances keeping systems date security patches updates using security scanner or/and hiring competent people responsible security statement ambiguous even systems developed competent people get penetrated effects data loss/damage reduced careful backing insurance hardware may source insecurity microchip vulnerabilities maliciously introduced manufacturing process hardware-based assisted computer security also offers alternative software-only computer security using devices methods dongles trusted platform modules intrusion-aware cases drive locks disabling usb ports mobile-enabled access may considered secure due physical access sophisticated backdoor access required order compromised covered detail one use term computer security refers technology used implement secure operating systems 1980s united states department defense dod used orange book standards current international standard iso/iec 15408 common criteria defines number progressively stringent evaluation assurance levels many common operating systems meet eal4 standard methodically designed tested reviewed formal verification required highest levels means uncommon example eal6 semiformally verified design tested system integrity-178b used airbus a380 several military jets software engineering secure coding aims guard accidental introduction security vulnerabilities also possible create software designed ground secure systems secure design beyond formal verification aims prove correctness algorithms underlying system important cryptographic protocols example within computer systems two many security models capable enforcing privilege separation access control lists acls capability-based security using acls confine programs proven insecure many situations host computer tricked indirectly allowing restricted file access issue known confused deputy problem also shown promise acls giving access object one person never guaranteed practice problems resolved capabilities mean practical flaws exist acl-based systems designers certain utilities must take responsibility ensure introduce flaws capabilities mostly restricted research operating systems commercial oss still use acls capabilities however also implemented language level leading style programming essentially refinement standard object-oriented design open source project area e language end-user widely recognized weakest link security chain estimated 90 security incidents breaches involve kind human error among commonly recorded forms errors misjudgment poor password management inability recognize misleading urls identify fake websites dangerous email attachments human component cyber risk particularly relevant determining global cyber risk organization facing security awareness training levels provides formal compliance regulatory industry mandates considered essential reducing cyber risk protecting individuals companies great majority cyber threats focus end-user represents profound cultural change many security practitioners traditionally approached cybersecurity exclusively technical perspective moves along lines suggested major security centers develop culture cyber awareness within organization recognizing security aware user provides important line defense cyber attacks responding forcefully attempted security breaches manner one would attempted physical security breaches often difficult variety reasons incident response organized approach addressing managing aftermath computer security incident compromise goal preventing breach thwarting cyberattack incident identified managed time intrusion typically escalates impactful event data breach system failure intended outcome computer security incident response plan limit damage reduce recovery time costs responding compromises quickly mitigate exploited vulnerabilities restore services processes minimize impact losses incident response planning allows organization establish series best practices stop intrusion causes damage typical incident response plans contain set written instructions outline organization response cyberattack without documented plan place organization may successfully detect intrusion compromise stakeholders may understand roles processes procedures escalation slowing organizations response resolution four key components computer security incident response plan illustrative examples different types computer security breaches given 1988 60,000 computers connected internet mainframes minicomputers professional workstations 2 november 1988 many started slow running malicious code demanded processor time spread computers – first internet computer worm software traced back 23-year-old cornell university graduate student robert tappan morris jr. said wanted count many machines connected internet 1994 hundred intrusions made unidentified crackers rome laboratory us air force main command research facility using trojan horses hackers able obtain unrestricted access rome networking systems remove traces activities intruders able obtain classified files air tasking order systems data furthermore able penetrate connected networks national aeronautics space administration goddard space flight center wright-patterson air force base defense contractors private sector organizations posing trusted rome center user early 2007 american apparel home goods company tjx announced victim unauthorized computer systems intrusion hackers accessed system stored data credit card debit card check merchandise return transactions 2010 computer worm known stuxnet reportedly ruined almost one-fifth iran nuclear centrifuges disrupting industrial programmable logic controllers plcs targeted attack generally believed launched israel united states – although neither publicly admitted early 2013 documents provided edward snowden published washington post guardian exposing massive scale nsa global surveillance also indications nsa may inserted backdoor nist standard encryption standard later withdrawn due widespread criticism nsa additionally revealed tapped links google data centres 2013 2014 russian/ukrainian hacking ring known rescator broke target corporation computers 2013 stealing roughly 40 million credit cards home depot computers 2014 stealing 53 56 million credit card numbers warnings delivered corporations ignored physical security breaches using self checkout machines believed played large role malware utilized absolutely unsophisticated uninteresting says jim walter director threat intelligence operations security technology company mcafee – meaning heists could easily stopped existing antivirus software administrators responded warnings size thefts resulted major attention state federal united states authorities investigation ongoing april 2015 office personnel management discovered hacked year earlier data breach resulting theft approximately 21.5 million personnel records handled office office personnel management hack described federal officials among largest breaches government data history united states data targeted breach included personally identifiable information social security numbers names dates places birth addresses fingerprints current former government employees well anyone undergone government background check believed hack perpetrated chinese hackers july 2015 hacker group known impact team successfully breached extramarital relationship website ashley madison created avid life media group claimed taken company data user data well breach impact team dumped emails company ceo prove point threatened dump customer data unless website taken permanently avid life media take site offline group released two compressed files one 9.7gb second 20gb second data dump avid life media ceo noel biderman resigned website remained functioning international legal issues cyber attacks complicated nature global base common rules judge eventually punish cyber crimes cyber criminals security firms agencies locate cybercriminal behind creation particular piece malware form cyber attack often local authorities take action due lack laws prosecute proving attribution cyber crimes cyber attacks also major problem law enforcement agencies computer viruses switch one country another one jurisdiction another – moving around world using fact n't capability globally police operations like internet someone given free plane tickets online criminals world use techniques dynamic dns fast flux bullet proof servers add difficulty investigation enforcement role government make regulations force companies organizations protect systems infrastructure information cyberattacks also protect national infrastructure national power-grid government regulatory role cyberspace complicated cyberspace seen virtual space remain free government intervention seen many today libertarian blockchain bitcoin discussions many government officials experts think government crucial need improved regulation mainly due failure private sector solve efficiently cybersecurity problem r. clarke said panel discussion rsa security conference san francisco believes industry responds threaten regulation industry n't respond threat follow hand executives private sector agree improvements necessary think government intervention would affect ability innovate efficiently daniel r. mccarthy analyzed public-private partnership cybersecurity reflected role cybersecurity broader constitution political order many different teams organisations exist including 14 april 2016 european parliament council european union adopted general data protection regulation gdpr eu 2016/679 gdpr became enforceable beginning 25 may 2018 provides data protection privacy individuals within european union eu european economic area eea gdpr requires business processes handle personal data built data protection design default gdpr also requires certain organizations appoint data protection officer dpo countries computer emergency response team protect network security since 2010 canada cyber security strategy functions counterpart document national strategy action plan critical infrastructure strategy three main pillars securing government systems securing vital private cyber systems helping canadians secure online also cyber incident management framework provide coordinated response event cyber incident canadian cyber incident response centre ccirc responsible mitigating responding threats canada critical infrastructure cyber systems provides support mitigate cyber threats technical support respond recover targeted cyber attacks provides online tools members canada critical infrastructure sectors posts regular cyber security bulletins operates online reporting tool individuals organizations report cyber incident inform general public protect online public safety canada partnered stop.think.connect coalition non-profit private sector government organizations launched cyber security cooperation program also run getcybersafe portal canadian citizens cyber security awareness month october public safety canada aims begin evaluation canada cyber security strategy early 2015 china central leading group internet security informatization established 27 february 2014 leading small group lsg communist party china headed general secretary xi jinping staffed relevant party state decision-makers lsg created overcome incoherent policies overlapping responsibilities characterized china former cyberspace decision-making mechanisms lsg oversees policy-making economic political cultural social military fields relate network security strategy lsg also coordinates major policy initiatives international arena promote norms standards favored chinese government emphasize principle national sovereignty cyberspace berlin starts national cyber defense initiative 16 june 2011 german minister home affairs officially opened new german ncaz national center cyber defense nationales cyber-abwehrzentrum located bonn ncaz closely cooperates bsi federal office information security bundesamt für sicherheit der informationstechnik bka federal police organisation bundeskriminalamt deutschland bnd federal intelligence service bundesnachrichtendienst mad military intelligence service amt für den militärischen abschirmdienst national organisations germany taking care national security aspects according minister primary task new organization founded 23 february 2011 detect prevent attacks national infrastructure mentioned incidents like stuxnet provisions cyber security incorporated rules framed information technology act 2000 national cyber security policy 2013 policy framework ministry electronics information technology meity aims protect public private infrastructure cyber attacks safeguard information personal information web users financial banking information sovereign data cert- nodal agency monitors cyber threats country post national cyber security coordinator also created prime minister office pmo indian companies act 2013 also introduced cyber law cyber security obligations part indian directors provisions cyber security incorporated rules framed information technology act 2000 update 2013 following cyber attacks first half 2013 government news media television station bank websites compromised national government committed training 5,000 new cybersecurity experts 2017 south korean government blamed northern counterpart attacks well incidents occurred 2009 2011 2012 pyongyang denies accusations 1986 computer fraud abuse act key legislation prohibits unauthorized access damage protected computers defined although various measures proposed – none succeeded 2013 executive order improving critical infrastructure cybersecurity signed prompted creation nist cybersecurity framework standardized government testing services general services administration gsa standardized penetration test service pre-vetted support service rapidly address potential vulnerabilities stop adversaries impact us federal state local governments services commonly referred highly adaptive cybersecurity services hacs listed us gsa advantage website see information penetration test standardized government penetration test services department homeland security dedicated division responsible response system risk management program requirements cybersecurity united states called national cyber security division division home us-cert operations national cyber alert system national cybersecurity communications integration center brings together government organizations responsible protecting computer networks networked infrastructure third priority federal bureau investigation fbi protect united states cyber-based attacks high-technology crimes along national white collar crime center nw3c bureau justice assistance bja part multi-agency task force internet crime complaint center also known ic3 addition specific duties fbi participates alongside non-profit organizations infragard criminal division united states department justice operates section called computer crime intellectual property section ccips charge investigating computer crime intellectual property crime specialized search seizure digital evidence computers networks 2017 ccips published framework vulnerability disclosure program online systems help organizations clearly describe authorized vulnerability disclosure discovery conduct thereby substantially reducing likelihood described activities result civil criminal violation law computer fraud abuse act 18 u.s.c § 1030 united states cyber command also known uscybercom tasked defense specified department defense information networks ensures security integrity governance government military infrastructure assets role protection civilian networks u.s. federal communications commission role cybersecurity strengthen protection critical communications infrastructure assist maintaining reliability networks disasters aid swift recovery ensure first responders access effective communications services food drug administration issued guidance medical devices national highway traffic safety administration concerned automotive cybersecurity criticized government accountability office following successful attacks airports claimed attacks airplanes federal aviation administration devoted funding securing systems board planes private manufacturers aircraft communications addressing reporting system concerns also raised future next generation air transportation system computer emergency response team name given expert groups handle computer security incidents us two distinct organization exist although work closely together growing concern cyberspace become next theater warfare mark clayton christian science monitor described article titled new cyber arms race future wars fought soldiers guns planes drop bombs also fought click mouse half world away unleashes carefully weaponized computer programs disrupt destroy critical industries like utilities transportation communications energy attacks could also disable military networks control movement troops path jet fighters command control warships led new terms cyberwarfare cyberterrorism united states cyber command created 2009 many countries similar forces critical voices question whether cybersecurity significant threat made cybersecurity fast-growing field concerned reducing organizations risk hack data breach according research enterprise strategy group 46 organizations say problematic shortage cybersecurity skills 2016 28 2015 commercial government non-governmental organizations employ cybersecurity professionals fastest increases demand cybersecurity workers industries managing increasing volumes consumer data finance health care retail however use term cybersecurity prevalent government job descriptions typical cyber security job titles descriptions include student programs also available people interested beginning career cybersecurity meanwhile flexible effective option information security professionals experience levels keep studying online security training including webcasts wide range certified courses also available united kingdom nationwide set cyber security forums known u.k cyber security forum established supported government cyber security strategy order encourage start-ups innovation address skills gap identified u.k government following terms used regards computer security explained
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Computer security
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desktop linux consortium desktop linux consortium dlc non-profit organization aims enhancing promoting use linux operating system desktop computers founded 4 february 2003
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Operating systems
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emdebian grip emdebian grip discontinued small-footprint linux distribution based compatible debian compared debian provides fine-grained control package selection size dependencies content enabling way creation small efficient debian packages use resource-limited embedded systems result reduced installation size one main benefits coming emdebian grip emdebian grip project terminated available updates planned new releases leaving version 3.1 based debian 7.1 wheezy longer supported latest stable release emdebian grip re-packs package files made available debian removing unneeded files man pages info documents documentation unwanted translation files emdebian grip debian distribution builder command package processes package compiled architectures supported debian generates equivalent emdebian grip package way binaries maintainer scripts dependencies original debian packages left untouched overall size installation footprint packages reduced packages created emdebian grip recompiled completely binary compatible debian result emdebian grip maintains much compatibility possible debian even possible mix emdebian debian packages even migrate existing debian system emdebian grip emdebian grip provides complete package repositories seven architectures i386 amd64 powerpc armhf armel mips mipsel included support standard debian tools like functional changes emdebian grip compared base debian releases since version 3.0 emdebian grip suites codenames include additional -grip suffix compared equivalent debian suites codenames july 13 2014 end-of-life notice posted project web site announced updates emdebian grip stopped leaving version 3.1 based debian 7.1 wheezy longer supported latest stable release main reasons stated cause ending project lack embedded devices provide support expandable storage much work involved preparing updates releasing new versions
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Computer architecture
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second-order co-occurrence pointwise mutual information computational linguistics second-order co-occurrence pointwise mutual information semantic similarity measure assess degree association two given words uses pointwise mutual information pmi sort lists important neighbor words two target words large corpus pmi-ir method used altavista advanced search query syntax calculate probabilities note near search operator altavista essential operator pmi-ir method however longer use altavista means implementation point view possible use pmi-ir method form new systems case algorithmic point view advantage using soc-pmi calculate similarity two words co-occur frequently co-occur neighboring words example british national corpus bnc used source frequencies contexts method considers words common lists aggregate pmi values opposite list calculate relative semantic similarity define pointwise mutual information function words formula_1 formula_3 tells us many times type formula_4 appeared entire corpus formula_5 tells us many times word formula_4 appeared word formula_7 context window formula_8 total number tokens corpus word formula_7 define set words formula_10 sorted descending order pmi values formula_7 taken top-most formula_12 words formula_13 set formula_10 contains words formula_15 rule thumb used choose value formula_12 formula_12-pmi summation function word defined respect another word word formula_21 respect word formula_22 formula_24 sums positive pmi values words set formula_25 also common words set formula_26 words function actually aggregates positive pmi values semantically close words formula_22 also common formula_21 list formula_29 value greater 1 formula_12-pmi summation function word formula_21 respect word formula_22 formula_33 formula_12-pmi summation function word formula_22 respect word formula_21 formula_37 respectively finally semantic pmi similarity function two words formula_21 formula_22 defined semantic word similarity normalized provides similarity score formula_43 formula_44 inclusively normalization semantic similarity algorithm returns normalized score similarity two words takes arguments two words formula_45 formula_46 maximum value formula_47 returned semantic similarity function sim returns similarity score 0 1 inclusively example algorithm returns 0.986 words cemetery graveyard formula_48 soc-pmi method
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Computational linguistics
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l2 syntactic complexity analyzer l2 syntactical complexity analyzer l2sca developed xiaofei lu pennsylvania state university computational tool produces syntactic complexity indices written english language texts along coh-metrix l2sca one extensively used computational tool compute indices second language writing development l2sca also widely utilised field corpus linguistics l2sca available single batch mode first provides possibility analyzing single written text 14 syntactic complexity indices latter allows user analyze 30 written texts simultaneously l2sca used numerous studies field second language writing development compute indices syntactic complexity l2sca also used various studies field corpus linguistics
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Computational linguistics
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kerio technologies kerio technologies inc. former technology company specializing collaboration software unified threat management small medium organizations founded 2001 kerio headquartered san jose california january 2017 gfi software acquired kerio kerio technologies incorporated 2001 first product winroute pro entered internet security market 1997 owned maintained tiny software february 1 2002 tiny software transferred sales development software kerio developers continued work kerio brand kerio main products early 2000s kerio personal firewall kerio winroute firewall company focused collaboration software kerio mailserver kerio discontinued personal firewall late 2005 acquired sunbelt software starting 2010 kerio mailserver renamed kerio connect kerio winroute kerio control kerio introduced kerio operator ip pbx system 2011 samepage file sharing collaboration software 2013 january 2017 kerio bought gfi software kerio connect kerio control kerio operator kerio cloud became gfi assets samepage part acquisition
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Computer security
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onefs distributed file system onefs file system parallel distributed networked file system designed isilon systems basis isilon scale-out storage platform onefs file system controlled managed onefs operating system freebsd variant data structures onefs file system maintain protection information means filesystem one file may protected +1 basic parity protection another may protected +4 resilient four failures yet another file may protected 2x mirroring feature referred flexprotect flexprotect also responsible automatically rebuilding data event failure protection levels available based number nodes cluster follow reed solomon algorithm blocks individual file spread across nodes allows entire nodes fail without losing access data file metadata directories snapshot structures quotas structures logical inode mapping structure based mirrored b+ trees block addresses generalized 64-bit pointers reference node drive blknum tuples native block size 8192 bytes inodes 512 bytes disk disks 512 byte sectors 8kb disks 4kb sectors one distinctive characteristic onefs metadata spread throughout nodes homogeneous fashion dedicated metadata servers piece metadata replicated every node address list root btree blocks inode mapping structure everything else found starting point following generalized 64-bit pointers nodes running onefs must connected together high performance low-latency back-end network optimal performance onefs 1.0-3.0 used gigabit ethernet back-end network starting onefs 3.5 isilon offered infiniband models 2007 mid-2018 nodes sold utilized infiniband back-end starting onefs 8.1.0 gen6 models isilon offers ethernet back-end network 10 gigabit 40 gigabit data metadata locking transaction group management allocation event traffic go back-end rpc system data metadata transfers zero-copy modification operations on-disk structures transactional journaled onefs equipped options accessing storage via nfs cifs/smb ftp http hdfs utilize non-local authentication active directory ldap nis capable interfacing external backup devices applications use ndmp protocol onefs file system proprietary file system managed controlled freebsd-derived onefs operating system zsh default login shell onefs operating system onefs presents specialized command set administer onefs file system specialized shell programs start letters isi notable exceptions isilon extensions freebsd codice_1 codice_2 programs
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Computer file systems
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gemini wing gemini wing arcade game created tecmo released 1987 vertically-scrolling shooter one two players control futuristic aircraft travelling numerous terrains shooting enemies animalistic insectoid design home conversions released zx spectrum commodore 64 amstrad cpc amiga atari st msx x68000
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Computer architecture
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powermapper powermapper web crawler automatically creates site map website using thumbnails web page number map styles available although cheaper standard edition fewer styles professional edition site maps displayed number different map styles arrange sites tree structure styles display thumbnails page others use text-only presentation map styles include site maps also exported xml sitemaps format use google yahoo msn search engines product received positive reviews infoworld 1.0 release 1997 subsequent reviews 4.0 release microsoft technet magazine websitetips.com also favorable list problems commonly encountered users provided vendor powermapper faq powermapper commercial licensed software uses serial numbers prevent unlicensed usage standard licensing per-user pooled floating licences also available extra cost
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Web technology
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boomerang attack cryptography boomerang attack method cryptanalysis block ciphers based differential cryptanalysis attack published 1999 david wagner used break coconut98 cipher boomerang attack allowed new avenues attack many ciphers previously deemed safe differential cryptanalysis refinements boomerang attack published amplified boomerang attack rectangle attack boomerang attack based differential cryptanalysis differential cryptanalysis attacker exploits differences input cipher plaintext affect resultant difference output ciphertext high-probability differential input difference produce likely output difference needed covers nearly cipher boomerang attack allows differentials used cover part cipher attack attempts generate so-called quartet structure point halfway cipher purpose say encryption action e cipher split two consecutive stages e e e e e plaintext message suppose two differentials two stages say e basic attack proceeds follows one attack kasumi block cipher used 3gpp related-key rectangle attack breaks full eight rounds cipher faster exhaustive search biham et al. 2005 attack requires 2 chosen plaintexts encrypted one four related keys time complexity equivalent 2 kasumi encryptions
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Computer security
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robocopy robocopy robust file copy command-line directory and/or file replication command microsoft windows robocopy functionally replaces xcopy options available part windows resource kit starting windows nt 4.0 first introduced standard feature windows vista windows server 2008 command robocopy robocopy noted capabilities beyond built-in windows copy xcopy commands including following requiring appropriate command-line options examples usage one option specified must separated spaces directory names non-standard characters spaces put double quotes usual command-line commands full reference see microsoft technet robocopy page robocopy syntax markedly different predecessors copy xcopy accepts folder names without trailing backslash source destination arguments file names wildcard characters codice_23 codice_24 valid source destination arguments files selected excluded using optional file filtering argument supports wildcards along various options example copy two files folder codice_25 codice_26 following syntax used copy pdf files codice_25 codice_26 files named copied folder selected copying fully qualified path names supported robocopy outputs screen optionally log file directories encounters alphabetical order directory preceded number files directory fulfill criteria copied directory yet exist target marked new dir directory empty /e option used contains files meeting criteria new directory created /nfl file names log option used files copied listed name directory end output table giving numbers directories files bytes table gives total number found source number copied includes directories marked new dir even copied number skipped already exist target number mismatches failed extras failed mean i/o error prevented file copied access denied also row time taken time spent failed files seems wrong column robocopy inter-packet gap ipg option allows control network bandwidth used session theory following formula expresses delay milliseconds required simulate desired bandwidth b kilobits per second network link available bandwidth b kbps formula_1 practice however experimentation usually required find suitable delay due factors nature volume traffic network methodology employed ipg option may offer level control provided bandwidth throttling technologies bits used windows update branchcache although robocopy command-line tool microsoft technet provides gui front-end called robocopy gui developed derk benisch systems engineer msn search group microsoft required .net framework 2.0 includes copy robocopy version xp026 non-microsoft guis robocopy ken tamaru microsoft developed copying program similar robocopy called richcopy available microsoft technet based robocopy offers similar features require .net framework note several versions robocopy show version number executing codice_35 command line version stored inside executable queried powershell example codice_36 inside windows explorer right-clicking robocopy.exe selecting properties clicking details tab
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Computer file systems
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packet generator packet generator packet builder type software generates random packets allows user construct detailed custom packets depending network medium operating system packet generators utilize raw sockets ndis function calls direct access network adapter kernel-mode driver useful testing implementations ip stacks bugs security vulnerabilities
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Computer security
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wxsqlite3 wxsqlite3 c++ wrapper around public domain sqlite 3.x database specifically designed use programs based wxwidgets library wxsqlite3 try hide underlying database contrary almost special features current sqlite version 3.18.0 supported like example creation user defined scalar aggregate functions since sqlite stores strings utf-8 encoding wxsqlite3 methods provide automatic conversion wxstrings utf-8 strings works best unicode builds wxwidgets ansi builds current locale conversion object wxconvcurrent used conversion to/from utf-8 special care taken external administration tools used modify database contents since tools operate unicode resp utf-8 mode since version 1.7.0 optional support key based database encryption 128 bit aes also included starting version 1.9.6 wxsqlite3 encryption extension compatible sqlite amalgamation source includes extension functions module support 256 bit aes encryption added version 1.9.8 since version 3.5.0 sqlite library integrated part wxsqlite3 since version 4.0.0 wxsqlite3 supports select encryption scheme runtime addition wxsqlite3 legacy schemes aes 128 bit aes 256 bit two encryption schemes namely sqleet aka chacha20 poly1305 sqlcipher aka aes 256 bit sha1/sha256/sha512 sqlcipher variants version 1 version 4 supported selected
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Databases
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spinning pinwheel spinning pinwheel variation mouse pointer arrow used apple macos indicate application busy officially macos human interface guidelines refers spinning wait cursor also known names including spinning beach ball spinning wheel death loading spinny spinning pizza death spod wristwatch first wait cursor early versions classic mac os apple hypercard first popularized animated cursors including black-and-white spinning quartered circle resembling beach ball beach-ball cursor also adopted indicate running script code hypertalk-like applescript cursors could advanced repeated hypertalk invocations set cursor busy wait cursors activated applications performing lengthy operations versions apple installer used animated counting hand cursor applications provided theme-appropriate custom cursors revolving yin yang symbol fetch running dog retrospect spinning tape pro tools tapping fingers apple provided standard interfaces animating cursors originally cursor utilities spincursor rotatecursor mac os 8 later appearance manager setanimatedthemecursor nextstep 1.0 used monochrome icon resembling spinning magneto-optical disk whose drive quite slow common reason wait cursor appear color support added nextstep 2.0 color versions icons added wait cursor updated reflect bright rainbow surface removable disks icon remained even later machines began using hard disk drives primary storage contemporary cd rom drives even slower 1x 150 kb/s arrival mac os x wait cursor often called spinning beach ball press presumably authors knowing next history relating hypercard wait cursor two-dimensional appearance kept essentially unchanged next rhapsody/mac os x server 1.0 otherwise user interface design resembling mac os 8/platinum theme mac os x 10.0/cheetah mac os x 10.1/puma introduced aqua user interface theme mac os x 10.2/jaguar gave cursor glossy rounded gumdrop look keeping os x interface elements os x 10.10 entire pinwheel rotates previously overlaying translucent layer moved os x 10.11 el capitan spinning wait-cursor design updated less shadowing brighter solid colors better match design user interface colors also turn spinning texture single-tasking operating systems like original macintosh operating system wait cursor might indicate computer completely unresponsive user input indicate response may temporarily slower usual due disk access changed multitasking operating systems system software 5 usually possible switch another application continue work individual applications could also choose display wait cursor long operations often able cancelled keyboard command transition mac os x macos apple narrowed wait cursor meaning display wait cursor controlled operating system application could indicate application infinite loop performing lengthy operation ignoring events application event queue receives events operating system example key presses mouse button clicks application takes longer 2 seconds process events event queue regardless cause operating system displays wait cursor whenever cursor hovers application windows meant indicate application temporarily unresponsive state application recover also may indicate part application entered unrecoverable state infinite loop time user may prevented closing resizing even minimizing windows affected application although moving window still possible os x well previously hidden parts window usually redrawn even application otherwise unresponsive one application unresponsive typically applications usable file system network delays another common cause default events actions initiate processed sequentially works well event involves trivial amount processing spinning wait cursor appearing operation complete processing takes long application appear unresponsive developers may prevent using separate threads lengthy processing allowing application main thread continue responding external events however greatly increases application complexity another approach divide work smaller packets use nsrunloop grand central dispatch instruments application comes mac os x developer tools along functions allows user monitor sample applications either responding performing lengthy operation time application respond spinning wait cursor activated instruments sample process determine code causing application stop responding information developer rewrite code avoid cursor activated apple guidelines suggest developers try avoid invoking spinning wait cursor suggest user interface indicators asynchronous progress indicator spinning wait cursor commonly referred spinning x death/doom common words phrases x replaced include
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Operating systems
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microsoft basic 1.0 basic 1.0 standard basic language thomson computers mo5 to7 etc reference entire range implementation microsoft basic basic-69 mo5 instruction set reduced double precision implemented interpreter fits 12 kb rom instead 16 kb to7 upgraded version produced name basic 128 to7-70 to9 mo5nr mo6 included dos new instructions to8/8d to9+ even upgraded version name basic 512 provided basic 1.0 interpreter recognizes usual commands for..next gosub..return if..then..else data read restore statements advanced instructions like on..goto on..gosub also possible used introduce children france programming 1980s three languages mainly taught lse basic logo school textbooks programs given basic 1.0 thomson sometimes exelbasic exelvision exl 100
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Programming language topics
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z80-rio z80-rio abbreviation z80 operating system relocatable modules i/o management general-purpose operating system developed zilog late 1970 various computer systems including z80 micro computer system mcz-1 series z80 development system zds mcz systems primarily used software development automation solutions rio designed facilitate development integration user programs production environment system provides modest environment minimum system support enhanced environment modest environment provides program debugger file manipulation capability floppy disk driver supporting eight disk drives basic console driver provision paper tape operation enhanced environment provides access rio executive system support utilities zilog floppy disk file system zdos zilog hard disk file system dfs also provides access number disk-resident software text editor macro assembler linker following list commands supported z80-rio udos z80-rio compatible clone veb robotron available number computers company 5120 pc 1715 based u880 processor latter clone zilog z80 udos also one operating systems available p8000 microcomputer system developed 1987 veb elektro-apparate-werke berlin-treptow „ friedrich ebert “ eaw german democratic republic ddr east germany
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Operating systems
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26-bit computer architecture 26-bit integers memory addresses data units 26 bits wide thus represent values 64 mega base 2 two examples computer processors featured 26-bit memory addressing certain second generation ibm system/370 mainframe computer models introduced 1981 several subsequent models 26-bit physical addresses 24-bit virtual addresses earlier models first generations arm processors data processing needs continued grow ibm customers faced challenges directly addressing larger memory sizes ended short-term emergency solution pair ibm second wave system/370 models 3033 3081 introduced 26-bit real memory addressing increasing system/370 amount physical memory could attached factor 4 previous 24-bit limit 16 mb ibm referred 26-bit addressing extended real addressing subsequent models also included 26-bit support however 2 years later ibm introduced 31-bit memory addressing expanding physical virtual addresses 31 bits system/370-xa models even popular 3081 upgradeable xa standard given 26-bit brief history state-of-the-art memory addressing available ibm model range given virtual addresses still limited 24 bits software exploitation 26-bit mode limited customers exploited 26-bit mode eventually adjusted applications support 31-bit addressing ibm dropped support 26-bit mode several years producing models supporting 24-bit 26-bit 31-bit modes 26-bit mode addressing mode ibm removed line mainframe computers descended system/360 addressing modes including 64-bit mode supported current model mainframes arm processor architecture 26-bit refers design used original arm processors program counter pc processor status register psr combined one 32-bit register r15 status flags filling high 6 bits program counter taking lower 26 bits fact program counter always word-aligned lowest two bits always zero allowed designers reuse two bits hold processor mode bits four modes allowed usr26 svc26 irq26 fiq26 contrast 32 possible modes available program status separated program counter recent arm architectures design enabled efficient program execution program counter status flags could saved restored single operation resulted faster subroutine calls interrupt response traditional designs would two register loads saves calling returning subroutine despite 32-bit alu word-length processors based arm architecture version 1 2 26-bit pc address bus consequently limited 64 mib addressable memory still vast amount memory time limitation architectures since included various steps away original 26-bit design arm architecture version 3 introduced 32-bit pc separate psr well 32-bit address bus allowing 4 gib memory addressed change pc/psr layout caused incompatibility code written previous architectures processor also included 26-bit compatibility mode used old pc/psr combination processor could still address 4 gb mode could execute anything address 0x3fffffc 64 mb mode used risc os running acorn risc pc utilise new processors retaining compatibility existing software arm architecture version 4 made support 26-bit addressing modes optional arm architecture version 5 onwards removed entirely
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Computer architecture
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normalized google distance normalized google distance ngd semantic similarity measure derived number hits returned google search engine given set keywords keywords similar meanings natural language sense tend close units normalized google distance words dissimilar meanings tend farther apart specifically normalized google distance ngd two search terms x n total number web pages searched google multiplied average number singleton search terms occurring pages f x f number hits search terms x respectively f x number web pages x occur formula_2 x viewed alike possible formula_3 x different two search terms x never occur together web page occur separately ngd infinite terms always occur together ngd zero example 9 april 2013 googling shakespeare gave 130,000,000 hits googling macbeth gave 26,000,000 hits googling shakespeare macbeth gave 20,800,000 hits number pages indexed google estimated number hits search term 25,270,000,000 hits assuming 1,000 search terms average page gives formula_4 hence shakespeare macbeth much alike according relative semantics supplied google normalized google distance derived earlier normalized compression distance namely objects given literally like literal four-letter genome mouse literal text macbeth shakespeare similarity objects given ncd simplicity take meaning object represented literal object objects also given name like 'the four-letter genome mouse 'the text macbeth shakespeare also objects given literally name acquire meaning contexts background common knowledge humankind like 'home red similarity names objects given ngd probabilities google search terms conceived frequencies page counts returned google divided number pages indexed google multplied average number search terms pages approximate actual relative frequencies search terms actually used society based premise relations represented normalized google distance approximately capture assumed true semantic relations governing search terms ngd world wide web google used text corpora wikipedia king james version bible oxford english dictionary together appropriate search engines following properties proved applications colors versus numbers primes versus non-primes given well randomized massive experiment using wordnet categories primes versus non-primes case wordnet experiment ngd method augmented support vector machine classifier experiments consist 25 positive examples 25 negative ones wordnet experiment consisted 100 random wordnet categories ngd method success rate 87.25 mean 0.8725 standard deviation 0.1169 rates agreement wordnet categories represent knowledge researchers phd entered rare see agreement less 75
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Computational linguistics
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hamlets software hamlets previously known ibm servlet-based content creation framework name open source system generating web-pages originally developed rené pawlitzek ibm defines hamlet servlet extension reads xhtml template files containing presentation using sax simple api xml dynamically adds content fly places template marked special tags ids using small set callback functions template compiler used accelerate hamlets hamlets provide easy-to-use easy-to-understand lightweight small-footprint servlet-based content creation framework facilitates development web-based applications hamlets framework supports also enforces complete separation content presentation
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Web technology
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louis hodes louis hodes june 19 1934 – june 30 2008 american mathematician computer scientist cancer researcher got phd hartley rogers thesis computability john mccarthy late 1950s early 1960s helped produce earliest implementations lisp marvin minsky early research visual pattern recognition lisp also credited idea initial implementation logic programming 1966 moved cancer-related research specifically national institutes health later national cancer institute turned interest visual pattern recognition medical imaging applications also worked efficient algorithms screening chemical compounds studying chemical carcinogenesis work models clustering chemical compounds pronounced milestone developmental therapeutics program national cancer institute revolutioniz ing selection compounds interest measuring novelty chemical structure comparing known compounds
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Programming language topics
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computational linguistics journal computational linguistics quarterly peer-reviewed open-access academic journal field computational linguistics published mit press association computational linguistics acl journal includes articles squibs book reviews established american journal computational linguistics 1974 david hays originally published microfiche 1978 george heidorn transformed print journal 1980 quarterly publication 1984 journal obtained current title open-access since 2009 according journal citation reports journal 2017 impact factor 1.319 following persons editors-in-chief
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Computational linguistics
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arora web browser arora discontinued free open-source web browser developed benjamin c. meyer arora available linux mac os x windows freebsd os/2 haiku genode operating system supported qt toolkit arora name palindrome browser features include tabbed browsing bookmarks browsing history smart location bar opensearch session management privacy mode download manager webinspector adblock several months meyer discontinued development arora due uncertainty strictures non-compete clauses employer finally july 2011 announced would longer contribute project another software developer bastien pederencino forked arora source code published variant called zbrowser renamed zeromus browser february 2013 may 2013 pederencino published another variant called bluelightcat february 2014 new patches released arora github project page linux distributions incorporating changes individual versions arora packages repositories
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Internet protocols
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books cryptography books cryptography published sporadically highly variable quality long time despite tempting though superficial paradox secrecy essence sending confidential messages — see kerckhoffs principle contrast revolutions cryptography secure communications since 1970s well covered available literature early example book cryptography roman work lost known references many early cryptographic works esoteric mystical and/or reputation-promoting cryptography mysterious much opportunity things least one work trithemius banned catholic church put index librorum prohibitorum black magic witchcraft many writers claimed invented unbreakable ciphers none though sometimes took long establish 19th century general standard improved somewhat e.g. works auguste kerckhoffs friedrich kasiski étienne bazeries colonel parker hitt william friedman early 20th century also wrote books cryptography authors others mostly abandoned mystical magical tone invention radio much military communications went wireless allowing possibility enemy interception much readily tapping landline increased need protect communications end world war cryptography literature began officially limited one exception american black chamber herbert yardley gave insight american cryptologic success stories including zimmermann telegram breaking japanese codes washington naval conference significant books cryptography include end world war ii early 1980s aspects modern cryptography regarded special concern governments military protected custom cases statute significant work published cryptography period undoubtedly david kahn codebreakers published time mid-1960s virtually information modern practice cryptography available kahn said ninety percent content previously unpublished book caused serious concern nsa despite lack coverage specific modern cryptographic practice much failing prevent book published nsa staff informed even acknowledge existence book asked us military mere possession copy cryptographic personnel grounds considerable suspicion perhaps single greatest importance book impact next generation cryptographers whitfield diffie made comments interviews effect
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Computer security
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jim gettys jim gettys born 15 october 1953 american computer programmer involved multiple computer related projects gettys worked dec cambridge research laboratory january 2009 vice president software one laptop per child project working software olpc xo-1 2009 2014 worked alcatel-lucent bell labs since 2010 gettys core member group investigating bufferbloat effect performance internet one original developers x window system mit worked x.org served board directors served gnome foundation board directors worked world wide web consortium w3c editor http/1.1 specification internet engineering task force draft standard gettys helped establish handhelds.org community development linux handheld devices traced one main goals olpc review overhaul much standard linux software order make run faster consume less memory power context pointed common fallacy among programmers today storing computed values memory preferable recomputing values later claims often false current hardware given fast cpus long time takes recover potential cache miss holds bsc degree mit earth planetary sciences course 12 — eaps 1997 internet plumber year award behalf group worked http/1.1 gettys one keepers flame usenix 1999 lifetime achievement award behalf x window system community large
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Operating systems
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ultra machine translation system ultra machine translation system created five languages japanese chinese spanish english german computing research laboratory 1991 ultra universal language translator machine translation system developed computing research laboratory translate five languages japanese chinese spanish english german uses artificial intelligence well linguistic logic programming methods main goal system robust cover general language simple use uses bidirectional parsers/generators system language-independent system intermediate representation means takes account needs expression expression one main elements language uses relaxation techniques provide best translation used x window user interface users paste sentence source window chose target language press translate tool translates source text taking consideration said said said lexical entries system two parts ultra works intermediate representation language systems transfer takes place language systems independent independent systems gives extra benefit adding another language disrupt existing language translations developers david farwell yorick wilks created ir interlingual representation base analyzing generating expressions analyzed many different types communications business letters documents emails compare communication style ultra looks best words kinds information good forms equivalents expression target language
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Computational linguistics
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sdlbasic sdlbasic multiplatform interpreter basic using sdl libraries interpreter core based wxbasic interpreter useful people familiar ansi-basic interpreters curious needing sdl library features coding development using ide possible create executable sdlbasic development started december 2002 author vroby roberto viola got idea using sdl libraries wxbasic core instead wxwidgets libraries major releases 2004 2005 2007 2012 prior 2005 text editor used write program code 2005 ide added 2012 package split ide interpreter although ide could used run code main download site sourceforge support site online documentation forum moved changed maintainer found link added altervista.org original author still contributes forum may 22 2008 sdlbasic ported sony playstation portable allows play games use applications coded sdlbasic recently someone qj forums released update version 0.7 included video output slim sdlbasic open source freely available terms gnu general public licence
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Programming language topics
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unix system laboratories inc. v. berkeley software design inc. usl v. bsdi lawsuit brought united states 1992 unix system laboratories berkeley software design inc regents university california intellectual property related unix operating system culmination unix wars case settled court 1994 judge expressed doubt validity usl intellectual property novell time bought usl university agreeing litigate berkeley software distribution bsd suit roots computer systems research group csrg university california berkeley license source code unix bell labs students operating systems research csrg modified extended unix csrg made several releases modified operating system beginning 1978 blessing berkeley software distribution bsd contained copyrighted unix source code available organizations source code license unix students faculty csrg audited software code tcp/ip stack removing intellectual property released general public 1988 net/1 bsd license became apparent berkeley csrg would soon close students faculty csrg began effort remove remaining code bsd replace effort resulted public release net/2 1991 bsd license net/2 contained enough code nearly complete unix-like system csrg believed contained intellectual property berkeley software design bsdi obtained source net/2 filled missing pieces ported intel i386 computer architecture bsdi sold resulting bsd/386 operating system could ordered 1-800-its-unix drew ire agree bsdi claim bsd/386 free intellectual property unix system laboratories subsidiary filed suit bsdi new jersey april 1992 suit later amended include regents university california lawsuit usl alleged grounds usl asked court preliminary injunction would bar bsdi distributing net/2 software case decided hearing bsdi contended using sources freely distributed university california plus six additional files bsdi accepted liability six files refused account files distributed university california judge agreed bsdi argument told usl restate complaint based solely six files would dismiss rather narrow claim usl chose sue bsdi university california requested preliminary injunction distribution net/2 1993 judge dickinson r. debevoise denied preliminary injunction grounds usl valid copyright 32v could show obvious trade secret works published u.s. january 1 1978 march 1 1989 subject provisions 17 u.s.c § 405 required copyright owner properly affix copyright notice work order claim copyright protection released v32 1978 omitted notice thousands copies failed copyright 32v 1992 1993 days dismissal preliminary injunction university filed countersuit usl california claiming usl failed credit university use bsd code system v required software license contract university demanded usl forced reprint documentation appropriate due credit added notify licensees oversight run full-page advertisements major publications wall street journal fortune magazine informing public omission 1993 soon uc filed countersuit usl purchased novell novell ceo ray noorda favored settlement reached 1994 salient points 18,000 files berkeley distribution three removed 70 modified show usl copyright notices condition settlement usl would file lawsuits users distributors upcoming 4.4bsd-lite release
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Operating systems
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first-class citizen programming language design first-class citizen also type object entity value given programming language entity supports operations generally available entities operations typically include passed argument returned function modified assigned variable concept first- second-class objects introduced christopher strachey 1960s actually define term strictly contrasted real numbers procedures algol first second class objects algol real number may appear expression assigned variable either may appear actual parameter procedure call procedure hand may appear another procedure call either operator common case one actual parameters expressions involving procedures whose results procedures thus sense procedures algol second class citizens—they always appear person never represented variable expression except case formal parameter ... robin popplestone gave following definition items certain fundamental rights 1990s raphael finkel proposed definitions second third class values definitions widely adopted simplest scalar data types integer floating-point numbers nearly always first-class many older languages arrays strings first-class assigned objects passed parameters subroutine example neither fortran iv c supports array assignment passed parameters position first element actually passed—their size lost c appears support assignment array pointers fact simply pointers array first element carry array size languages data types first-class objects though object-oriented languages classes first-class objects instances metaclasses languages support continuations goto-labels objects let alone first-class objects many programming languages support passing returning function values applied arguments whether suffices call function values first-class disputed authors require possible create new functions runtime call 'first-class result functions c first-class objects instead sometimes called second-class objects still manipulated fashions via function pointers smalltalk functions methods first-class objects like smalltalk classes since smalltalk operators etc methods also first-class objects languages java php explicit reflection subsystem allow access internal implementation structures even though accessible manipulable way ordinary objects
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Programming language topics
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directory-based cache coherence computer engineering directory-based cache coherence type cache coherence mechanism directories used manage caches place snoopy methods due scalability snoopy bus-based methods scale poorly due use broadcasting methods used target performance scalability directory systems full bit vector format possible cache line memory bit used track whether every individual processor line stored cache full bit vector format simplest structure implement least scalable sgi origin 2000 uses combination full bit vector coarse bit vector depending number processors directory entry must 1 bit stored per processor per cache line along bits tracking state directory leads total size required number processors ×number cache lines storage overhead ratio number processors cache block size×8 observed directory overhead scales linearly number processors may fine small number processors implemented large systems size requirements directory becomes excessive example block size 32 bytes 1024 processors storage overhead ratio becomes 1024/ 32×8 400 coarse bit vector format similar structure full bit vector format though rather tracking one bit per processor every cache line directory groups several processors nodes storing whether cache line stored node rather line improves size requirements expense bus traffic saving processors per node × total lines bits space thus ratio overhead replacing number processors number processor groups bus request made cache line one processor group directory broadcasts signal every processor node rather caches contain leading unnecessary traffic nodes n't data cached case directory entry uses 1 bit group processors cache line example full bit vector format consider 1 bit 8 processors group storage overhead 128/ 32×8 =50 significant improvement full bit vector format cache stores small subset blocks main memory particular time hence entries directory belong uncached blocks sparse directory format wastage reduced storing cached blocks directory.consider processor cache size 64kb block size 32 bytes main memory size 4mb maximum number entries directory sparse directory format 2048 directory entry blocks memory number entries directory 131072 thus evident storage improvement provided sparse directory format significant format directory decentralised distributed among caches share memory block different caches share memory block arranged form binary tree cache accesses memory block first root node memory block root node information head sharing counter field sc sc field number caches share block cache entry pointers next sharing caches known l-chd r-chd condition directory binary tree number balanced i.e number nodes left sub tree must equal one greater number nodes right subtree subtrees also number balanced format memory holds directory pointer latest cache accessed block cache pointer previous cache accessed block processor sends write request block memory processor sends invalidations chain pointers directory cache block replaced need traverse list order change directory increases latency order prevent doubly linked lists widely used cached copy pointers previous next cache accesses block limited pointer format uses set number pointers track processors caching data new processor caches block free pointer chosen pool point processor options handling cases number sharers exceeds number free pointers one method invalidate one sharers using pointer new requestor though costly cases block large number readers lock another method separate pool free pointers available blocks method usually effective number blocks shared large number processors normally large
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Computer architecture
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trusted client computing trusted client device program controlled user service restrictions designed prevent use ways authorized provider service client device vendors trust sell consumers trust examples include video games played computer network content scramble system css dvds trusted client software considered fundamentally insecure security broken one user break trivially copyable available others computer security specialist bruce schneier states average user anything works need complex security software skilled attacker hand nothing works trusted client hardware somewhat secure complete solution trusted clients attractive business form vendor lock-in sell trusted client loss charge would otherwise economically viable associated service one early example radio receivers subsidized broadcasters restricted receiving radio station modern examples include video recorders forced law include macrovision copy protection dvd region code system region-coded video game consoles technically knowledgeable consumers manufacturers frequently bypass limiting features trusted clients — simple replacement fixed tuning capacitor early locked radios successful decss cryptographic attack css 1999 manufacturers resorted legal threats via digital millennium copyright act similar laws prevent circumvention varying degrees success however nature internet enables crack discovered published virtually impossible remove trusted computing aims create computer hardware assists implementation restrictions software attempts make circumvention restrictions difficult
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Computer security
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imagenet imagenet project large visual database designed use visual object recognition software research 14 million images hand-annotated project indicate objects pictured least one million images bounding boxes also provided imagenet contains 20,000 categories typical category balloon strawberry consisting several hundred images database annotations third-party image urls freely available directly imagenet though actual images owned imagenet since 2010 imagenet project runs annual software contest imagenet large scale visual recognition challenge ilsvrc software programs compete correctly classify detect objects scenes challenge uses trimmed list one thousand non-overlapping classes 30 september 2012 convolutional neural network cnn called alexnet achieved top-5 error 15.3 imagenet 2012 challenge 10.8 percentage points lower runner made feasible due utilization graphics processing units gpus training essential ingredient deep learning revolution according economist suddenly people started pay attention within ai community across technology industry whole 2015 alexnet outperformed microsoft deep cnn 100 layers imagenet 2015 contest ai researcher fei-fei li began working idea imagenet 2006 time ai research focused models algorithms li wanted expand improve data available train ai algorithms 2007 li met princeton professor christiane fellbaum one creators wordnet discuss project result meeting li went build imagenet starting word-database wordnet using many features assistant professor princeton li assembled team researchers work imagenet project used amazon mechanical turk help classification images presented database first time poster 2009 conference computer vision pattern recognition cvpr florida imagenet crowdsources annotation process image-level annotations indicate presence absence object class image tigers image tigers image object-level annotations provide bounding box around visible part indicated object imagenet uses variant broad wordnet schema categorize objects augmented 120 categories dog breeds showcase fine-grained classification one downside wordnet use categories may elevated would optimal imagenet people interested lady gaga ipod mini rare kind diplodocus 2012 imagenet world largest academic user mechanical turk average worker identified 50 images per minute ilsvrc aims follow footsteps smaller-scale pascal voc challenge established 2005 contained 20,000 images twenty object classes order democratize imagenet fei-fei li proposed pascal voc team collaboration beginning 2010 research teams would evaluate algorithms given data set compete achieve higher accuracy several visual recognition tasks resulting annual competition known imagenet large scale visual recognition challenge ilsvrc ilsvrc uses trimmed list 1000 image categories classes including 90 120 dog breeds classified full imagenet schema 2010s saw dramatic progress image processing around 2011 good ilsvrc classification error rate 25 2012 deep convolutional neural net called alexnet achieved 16 next couple years error rates fell percent 2012 breakthrough combined pieces dramatic quantitative improvement marked start industry-wide artificial intelligence boom 2015 researchers microsoft reported cnns exceeded human ability narrow ilsvrc tasks however one challenge organizers olga russakovsky pointed 2015 programs identify images belonging one thousand categories humans recognize larger number categories also unlike programs judge context image 2014 fifty institutions participated ilsvrc 2015 baidu scientists banned year using different accounts greatly exceed specified limit two submissions per week baidu later stated fired team leader involved would establish scientific advisory panel 2017 29 38 competing teams greater 95 accuracy 2017 imagenet stated would roll new much difficult challenge 2018 involves classifying 3d objects using natural language creating 3d data costly annotating pre-existing 2d image dataset expected smaller applications progress area would range robotic navigation augmented reality
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Databases
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phone phone online service companion mobile client application microsoft service launched october 6 2009 provided free mobile phone back-up solution wirelessly synchronizing contacts calendar appointments tasks text messages browser favorites photos music video documents password-protected online portal users could access manage information service also enabled photo sharing markets set features dealing lost phone sold premium package requiring one-time fee phone supported windows mobile os versions 6.0 6.1 6.5 available globally 25 languages service used windows live id authentication windows live server infrastructure storing user information june 8 2011 microsoft announced phone would discontinued sync phones ending august 7 2011 website access data ending october 6 2011 data contacts calendar entries text messages photos moved skydrive since rebranded onedrive microsoft announced launched beta version phone mobile world congress february 16 2009 approximately 200,000 users 200 countries beta tested service scalability features service offered following free features phone offers set premium features event lost phone features include premium features available users free service as-needed basis sold package requiring one-time fee 4.99 us package meant activated phone portal phone lost stolen long device turned connectivity package includes 7-day access 3 ring 3 map 1 lock 1 erase premium package initially free charge trial since december 2009 package supplied one free activation used time premium package available united states canada mexico united kingdom germany france italy spain portugal denmark netherlands greece poland finland norway sweden brazil australia japan singapore taiwan
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Distributed computing architecture
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sable sable xml markup language used annotate texts speech synthesis defines tags control written words numbers sentences audibly reproduced computer sable developed informal joint project sun microsystems bell labs university edinburgh initial letters make word sable initiative combine three previous speech synthesis markup languages ssml stml jsml sable used festival speech synthesis system development sable appears stopped 2010 reached status formal standard recommended specification
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Computational linguistics
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tournament gods sid enters tournament shortly crowned champion fallen angel aquross infects hideous disease requires steal life energy angels constant pain relief lies drug kills pain causes sexual urges denied sid must defeat evil aquross condensed single 35-minute episode released us subtitled white-cassette vhs pink pineapple studio mike toole comparing ova gor find interesting chris beveridge commented video strange piece good fun moments english japanese
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Computer architecture
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n-version programming n -version programming nvp also known multiversion programming multiple-version dissimilar software method process software engineering multiple functionally equivalent programs independently generated initial specifications concept n -version programming introduced 1977 liming chen algirdas avizienis central conjecture independence programming efforts greatly reduce probability identical software faults occurring two versions program aim nvp improve reliability software operation building fault tolerance redundancy general steps n -version programming n -version programming applied software switching trains performing flight control computations modern airliners electronic voting save system detection zero-day exploits among uses
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Computer architecture
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microsoft yahei microsoft yahei sans-serif gothic typeface created founder electronics monotype corporation commission microsoft hinting font undertaken monotype imaging cjk ideographic characters designed founder electronics foundry senior designer li qi 齐立 development began 2004 microsoft commissioned beijing founder electronics co. ltd. cleartype font use simplified chinese version windows vista default font ideographs yahei based previous sans-serif font family designer made early 1990s like yahei feature flared stroke terminals changes prototype fonts include redesigning hook stroke longer end addition 'foot ending stroke terminal readjusting black white proportions glyphs introduction dents stroke path outlines intersect stroke path outlines flattening diagonal dot stroke top top glyph yahei optimized screen use font family originally includes two fonts regular bold weights named codice_1 'microsoft yahei bold separate file codice_2 opentype features include vertical writing microsoft yahei distributed windows since windows vista default user interface font language set simplified chinese aims legible simsun predecessor used cleartype also included simplified chinese version microsoft office 2007 downloading installing simplified chinese cleartype fonts windows xp microsoft also makes microsoft yahei available windows xp font file contains 20,902 original cjk unified ideographs code points specified unicode plus approximately 80 code points defined standardization administration china supports gbk character set localized glyphs semilight semibold heavy weight fonts introduced windows 10 redstone 4 spring creators update microsoft yahei ui version microsoft yahei alternate character design reduced line height introduced windows 8 part microsoft yahei update microsoft yahei ui included ttc file along microsoft yahei founder electronics versions fonts released various character sets depending family gb2312-80 simplified chinese characters gb12345-90 traditional chinese characters gbk simplified traditional chinese characters big-5 hong kong taiwan region gb18030-2000 includes gbk big-5 characters mapped unicode cjk unified ideographs extension fzlantinghei 方正兰亭黑 founder electronics variant based microsoft yahei latin glyphs changed resemble arial fzlantinghei-db fzlantinghei-b correspond font weights yahei yahei bold respectively family includes 14 font styles 10 weights 3 widths condensed extended widths h width r weights released character set fonts include gb2312-80 gb12345-90 gbk big-5 gb18030-2000 fzlantinghei 方正兰亭刊黑 based fzlantinghei designed printing family includes 1 font styles 1 weight 1 width font weight equal el middle width fzlantinghei released character set fonts include gb2312-80 gb12345-90 gbk fzlantingyuan 方正兰亭圆 based fzlantinghei rounded terminals corners elimination 'foot stroke terminals latin glyphs changed lowercase g less like arial designers included cui yan han chunli zhang zhang shao wei yan yao li xueying wang ji jie zhao yue yuan family includes 9 font styles 9 weights h eb b db1 db r l el 1 width medium released character set fonts include gb2312-80 gb12345-90 gbk fzlantinghei bronze prize 2009 dfa design asia award
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Operating systems
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computer display standard computer display standards combination aspect ratio display size display resolution color depth refresh rate associated specific expansion cards video connectors monitors various computer display standards display modes used history personal computer often combination aspect ratio specified width-to-height ratio display resolution specified width height pixels color depth measured bits per pixel refresh rate expressed hertz associated screen resolution refresh rate display adapter earlier display adapters simple frame-buffers later display standards also specified extensive set display functions software controlled interface beyond display modes vesa industry organization defined several standards related power management device identification ergonomics standards set tco number common resolutions used computers descended original ibm pc supported families personal computers de facto standards usually originated one manufacturer reverse-engineered others though vesa group co-ordinated efforts several leading video display adapter manufacturers video standards associated ibm-pc-descended personal computers shown diagram table alongside early macintosh makes comparison early 1990s onwards manufacturers moved pc display standards thanks widely available affordable hardware although common standard prefixes super ultra indicate specific modifiers base standard resolutions several others prefixes also often combined wqxga whuxga levels stacking hindered consideration towards readability decline added x especially even defined hierarchy value s/x/u/+ modifiers
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Computer architecture
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olivier danvy olivier danvy french computer scientist specializing programming languages partial evaluation continuations professor yale-nus college singapore danvy received phd degree université paris vi 1986 notable number scientific papers acknowledge help writing nature editor declan butler reports analysis acknowledgments nearly one third million scientific papers reports danvy thanked person computer science danvy quoted stunned find name top list ascribing position series coincidences multidisciplinary well travelled part international phd programme networker belongs university department long tradition many international visitors
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Programming language topics
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sap netweaver application server sap netweaver application server sap web application server component sap netweaver works web application server sap products abap application servers including message server represent application layer multitier architecture abap-based sap system application servers execute abap applications communicate presentation components database also using message server architecture sap web application server separated 5 areas sap netweaver accept multiple forms authentication sap netweaver application server connectivity layer supports https required encrypted communications via secure socket layer possible enable ssl using sap cryptographic library company running traditional sap systems uses rfc diag protocols secure network communications required encrypted communications well
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Web technology
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orlov block allocator orlov block allocator algorithm define particular file reside given file system blockwise speed disk operations scheme named creator grigoriy orlov first posted brief description implementation openbsd technique later used bsd fast filesystem kernel variants performance file system dependent many things one crucial factors filesystem lays files disk general best keep related items together linux ext2 ext3 filesystems instance tried spread directories cylinders disk imagine setting system users home directories /home first-level directories within /home i.e home directories numerous users placed next may space left contents directories user files thus end placed far directories contain performance suffers spreading directories disc allows files directory remain less contiguous number and/or size grows situations causes excessive spreading data disc surface essentially orlov algorithm tries spread top-level directories assumption unrelated directories created root directory filesystem considered top-level directories theodore ts added special inode flag allows system administrator mark directories top-level directories well /home lives root filesystem people set systems way simple codice_1 command make system treat top-level directory creating directory top-level directory orlov algorithm tries put cylinder group parent little care taken however ensure directory contents also able fit cylinder group many inodes blocks available group directory placed different cylinder group resources available result hopefully much better locality files truly related likely accessed together orlov block allocator shown offer performance gains workloads traverse directory trees freebsd one benchmark result ext3 new allocator seems posted results promising time required traverse linux kernel tree reduced roughly 30 orlov scheme needs rigorous benchmarking also needs serious stress testing demonstrate performance degrade filesystem changed time
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Computer file systems
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communications toolbox communications toolbox generally shortened comm toolbox ctb suite application programming interfaces libraries device drivers classic mac os implemented wide variety serial network communication protocols using ctb one could write application would seamlessly work appletalk modem variety connections developers could also write plug-in communications modules known tools allowing ctb-aware application use connection method ctb notoriously slow buggy received mixed support developers examples applications using simple tasks common many target uses like terminal emulators almost always ran faster designed target single connection type avoid ctb ctb based shared library concept era mac os include shared library system instead ctb wrote driver manager layer communications resource manager resource manager responsible installing managing various drivers tools provided various functions within ctb system three primary types tools associated manager connection manager handled communications drivers opened channels remote services terminal manager managed tools implemented character conversion command string interpretation needed support sort terminal emulator file transfer manager sort file transfer protocol applications could use managers ctb typical terminal emulator would use connecting tool selected connection manager another terminal manager periodically using file transfer manager user request case common terminal emulators like versaterm macterminal however another application might use one say connection manager set communications quickmail eudora well-known examples applications typically used gui elements supplied managers handle user interaction could also enumerate tools provide custom gui perhaps best known tool apple modem tool provided serial communications drivers well system storing setup commands connection initiated using modem tool link modem opened commands sent link established dialling modem tool also indicative problems ctb general slow lacking features quickly became outdated modem speeds improved saw little development effort support 1.5 version addressing problems released 1993 even finding proved difficult update needed support higher speeds 28kbit/s modems become common apple also produced simple serial tool appletalk tools additional connection methods tty vt102 tools terminal emulation text xmodem tools file transfers third party tools common supporting connections including teleport modem plugged apple desktop bus thus required custom drivers apple x.25 isdn tools variety examples
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Operating systems
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chomski pattern parsing virtual machine previously called 'chomski noam chomsky pp pattern parser also provisional name refer command line computer language utility interpreter language used parse transform text patterns formal mathematical languages utility reads input files character character sequentially applying operation specified via command line pp script outputs line developed 2006 c language pp derived number ideas syntax elements sed command line text stream editor pattern-parser language uses many ideas taken sed unix stream editor example sed includes two virtual variables data buffers known pattern space hold space two variables constitute extremely simple virtual machine chomski language virtual machine augmented several new buffers registers along number commands manipulate buffers parsing virtual machine includes tape data structure well stack data structure along workspace equivalent sed pattern space number buffers lesser importance virtual machine designed specifically apt parsing formal languages parsing process traditionally involves two phases lexical analysis phase formal grammar phase lexical analysis phase series tokens generated tokens used input set formal grammar rule chomski virtual machine uses stack hold tokens uses tape structure hold attributes parse tokens pp script two phases lexing parsing combined one script file series command words used manipulate different data structures virtual machine purpose pp tool parse transform text patterns text patterns conform rules provided formal language include many context free languages whereas traditional unix tools awk sed grep etc process text one line time use regular expressions search transform text pp tool processes text one character time use context free grammars transform compile text however common unix philosophy pp tool works upon plain text streams encoded according locale local computer produces output another plain text stream allowing pp tool used part standard pipeline motivation creation pp tool chomski virtual machine allow writing parsing scripts rather resort traditional parsing tools lex yacc following example shows typical use pp pattern parser -e option indicates pattern parse expression follows script c multiline comments /* ... */ deleted input stream pattern parser tool designed used filter pipeline example generate data make small change replacing x however functionality currently available pp tool also includes comprehensive script viewer debugger read piped standard input several commands put together file called example substitute.pss applied using -f option read commands file besides substitution forms simple processing possible example following uses accumulator-increment command a+ count commands count number lines file complex pp constructs possible allowing serve simple highly specialised programming language pp two flow control statements apart test structures codice_1 codice_2 codice_3 etc namely .reparse .restart commands jump back parse label labels permitted idea chomski arose limitations regular expression engines use line line paradigm limitations parsing nested text patterns regular expressions chomski evolved natural progression grep sed command development began approximately 2006 continues sporadically pattern parsing script language general purpose programming language like sed designed limited type usage currently support unicode strings since current implementation uses standard c character arrays since virtual machine behind pattern parser language considerably complex sed necessary able debug scripts facility currently provided within 'pp executable
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Programming language topics
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tradervoice tradervoice underlying technology pool supports real time communications brokers bankers following move electronic banking 90's key suppliers industry alphabetical order
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Internet protocols
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frisk software international frisk software international icelandic software company developed f-prot antivirus f-prot aves antivirus anti-spam service name derived initial letters personal name patronymic friðrik skúlason founder company founded 1993 acquired commtouch known cyren 2012 frisk software competes antivirus industry avast avira eset f-secure kaspersky mcafee panda security sophos symantec among others f-prot antivirus one oldest antivirus products first release 1989 world first heuristic engine sold home corporate packages editions windows linux bsd corporate versions microsoft exchange solaris certain ibm eservers linux bsd versions available home users free charge virus definition updates free 30-day trial versions platforms downloaded f-prot aves specifically targeted towards corporate users company also produced genealogy program called espólín púki spellchecker additional features summer 2012 frisk acquired cyren israeli-american provider security products friðrik skúlason joined cyren vice-president antivirus technologies f-prot antivirus antivirus product developed frisk software international available related versions several platforms available microsoft windows microsoft exchange server linux bsd solaris aix ibm eservers *nix scanning engine used f-prot provides signature based detection capability heuristics low use computer resources 1991 f-prot antivirus dos became world first heuristic behavior scanner f-prot dos since discontinued frisk software international allows others develop applications based scanning engine use sdk specifically released many software vendors use f-prot antivirus engine including suse sdk known today commtouch antivirus sdk friðrik skúlason also sometimes known frisk founder frisk software international one founding members caro computer antivirus research organization originally developed f-prot antivirus computer support work subsequently started company many years technical editor virus bulletin
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Computer security
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brown clustering brown clustering hard hierarchical agglomerative clustering problem based distributional information proposed peter brown vincent della pietra peter desouza jennifer lai robert mercer typically applied text grouping words clusters assumed semantically related virtue embedded similar contexts natural language processing brown clustering ibm clustering form hierarchical clustering words based contexts occur proposed peter brown vincent della pietra peter desouza jennifer lai robert mercer ibm context language modeling intuition behind method class-based language model also called cluster -gram model i.e one probabilities words based classes clusters previous words used address data sparsity problem inherent language modeling jurafsky martin give example flight reservation system needs estimate likelihood bigram shanghai without seen training set system obtain good estimate cluster shanghai city names make estimate based likelihood phrases london beijing denver brown groups items i.e. types classes using binary merging criterion based log-probability text class-based language model i.e probability model takes clustering account thus average mutual information ami optimization function merges chosen incur least loss global mutual information result output thought binary tree perhaps helpfully sequence merges terminating one big class words model general form hidden markov model reduced bigram probabilities brown solution problem mi defined finding clustering maximizes likelihood data computationally expensive approach proposed brown et al greedy heuristic work also suggests use brown clusterings simplistic bigram class-based language model given cluster membership indicators tokens text probability word instance given preceding word given criticised limited utility ever predicts common word class restricted word types reflected low relative reduction perplexity found using model brown works examined trigrams approaches brown clustering problem brown clustering proposed generates fixed number output classes important choose correct number classes task-dependent cluster memberships words resulting brown clustering used features variety machine-learned natural language processing tasks generalization algorithm published aaai conference 2016 including succinct formal definition 1992 version also general form core concept classes considered merging necessarily represent final number classes output altering number classes considered merging directly affects speed quality final result known theoretical guarantees greedy heuristic proposed brown et al february 2018 however clustering problem framed estimating parameters underlying class-based language model possible develop consistent estimator model mild assumptions
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Computational linguistics
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windows forms windows forms winforms graphical gui class library included part microsoft .net framework mono framework providing platform write rich client applications desktop laptop tablet pcs seen replacement earlier complex c++ based microsoft foundation class library offer comparable paradigm acts platform user interface tier multi-tier solution microsoft connect event december 4 2018 microsoft announced releasing windows forms open source project github released mit license release windows forms become available projects targeting .net core framework however framework still available windows platform mono incomplete implementation winforms remains cross-platform implementation future development microsoft succeeded winforms xaml based gui entry using frameworks wpf uwp however drag drop placement gui components manner similar winforms still provided xaml replacing root xaml element page/window canvas ui-control making change user build window similar fashion winforms directly dragging dropping components using visual studio gui xaml provided drag drop placement backwards compatibility canvas control xaml controls similar winform controls 1-to-1 backwards compatible perform similar functions similar appearance properties methods different enough require remapping one api another windows forms application event-driven application supported microsoft .net framework unlike batch program spends time simply waiting user something fill text box click button windows forms provides access native windows user interface common controls wrapping existent windows api managed code help windows forms .net framework provides comprehensive abstraction win32 api visual basic mfc windows forms similar microsoft foundation class mfc library developing client applications provides wrapper consisting set c++ classes development windows applications however provide default application framework like mfc every control windows forms application concrete instance class visual elements windows forms class library derive control class provides minimal functionality user interface element location size color font text well common events like click drag/drop control class also docking support let control rearrange position parent microsoft active accessibility support control class also helps impaired users use windows forms better besides providing access native windows controls like button textbox checkbox listview windows forms added controls activex hosting layout arrangement validation rich data binding controls rendered using gdi+ like abstract window toolkit awt equivalent java api windows forms early easy way provide graphical user interface components .net framework windows forms built existing windows api controls merely wrap underlying windows components methods allow direct access win32 callbacks available non-windows platforms .net framework 2.0 windows forms gained richer layout controls office 2003 style toolstrip controls multithreading component richer design-time data binding support well clickonce web-based deployment release .net 3.0 microsoft released second parallel api rendering guis windows presentation foundation wpf based directx together gui declarative language called xaml question-and-answer session build 2014 conference microsoft explained windows forms maintenance mode new features added bugs found would still fixed recently improved high-dpi support various windows forms controls introduced updates .net framework version 4.5 mono project led xamarin formerly ximian novell create ecma standard compliant .net compatible set tools mono support system.windows.forms .net 2.0 announced complete also system.windows.forms 2.0 works natively mac os x however system.windows.forms actively developed mono full compatibility .net achieved possible microsoft system.windows forms mainly wrapper around windows api methods allow direct access win32 callbacks available platforms windows
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Operating systems
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socket p intel socket p mpga478mn mobile processor socket replacement core microarchitecture chips core 2 duo launched may 9 2007 part santa rosa platform merom penryn processors front-side bus fsb cpus install socket p run 400 533 667 800 1066 mt/s adapting multiplier frequency cpu throttle save power given socket p cpus support eist except celeron support eist socket p 478 pins electrically pin-compatible socket socket 478 socket p also known 478-pin micro fcpga μfcpga-478 plastic grid printed mpga478mn
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Computer architecture
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embedded c embedded c set language extensions c programming language c standards committee address commonality issues exist c extensions different embedded systems historically embedded c programming requires nonstandard extensions c language order support exotic features fixed-point arithmetic multiple distinct memory banks basic i/o operations 2008 c standards committee extended c language address issues providing common standard implementations adhere includes number features available normal c fixed-point arithmetic named address spaces basic i/o hardware addressing embedded c uses syntax semantics standard c e.g. main function variable definition datatype declaration conditional statements switch case loops functions arrays strings structures union bit operations macros etc technical report published 2004 second revision 2006
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Programming language topics
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network centric product support network centric product support ncps early application internet things iot computer architecture developed leverage new information technologies global networks assist managing maintenance support supply chain complex products made one complex systems mobile aircraft fleet fixed location assets building systems accomplished establishing digital threads connecting physical deployed subsystem design digital twins virtual model embedding intelligence networked micro-web servers also function computer workstation within subsystem component i.e engine control unit aircraft controller enabling 2-way communications using existing internet technologies communications networks thus allowing extension product lifecycle management plm system mobile deployed product subsystem level real time ncps considered support flip side network-centric warfare approach goes beyond traditional logistics aftermarket support functions taking complex adaptive system management approach integrating field maintenance logistics unified factory field environment evolution began insights gained cdr dave loda usnr network centric warfare-based fleet battle experimentation us naval warfare development command nwdc late 1990s later lead commercial research efforts ncps aviation united technologies corporation interaction mit auto-id labs epcglobal air transport association america ata spec 100/ispec 2200 consortium pioneering emerging machine machine internet things iot architecture contributed evolution ncps simply put architecture extends existing world wide web infrastructure networked web servers product subsystem controller level using systems engineering system systems nested approach core embedded dual function webserver/computer workstation connected product controller test ports used retrofit applications integrated directly controller new products hence providing access operational cycles sensor information clustered internet addressable node allows local remote access ability host remotely reconfigurable software collect process data mated subsystem controller onboard pull computing resources throughout network establish localized wireless world wide web around product securely connected mechanic web browser-equipped handheld independent greater world wide web well seamlessly integrate global networks external wireless communications available thus creating data digital twins factory connecting deployed product usage product lifecycle constantly updated digital threads allows integrated approach enables offline online updates occur legacy systems usually require human physically connect laptop system controller telematic solution manually collect data carry back location later transferred factory restricted webserver-based download sites offboard analysis architecture also enables communications micro-webservers computer cluster i.e aircraft higher level clusters internet portal managed fleet flight operations managers thus enabling access data resources personnel factory engineers remote office computers world wide web stated previously system operates asynchronously always connected world wide web function rather simply operates locally synchronizes two-way information relevant subsystem acting gateway telecommunications board connects gateways within network airborne ground as-needed basis communications available accomplished wireless lan network satellite cellular network wireless wired communications capabilities security network critical architecture utilize standard web security protocols public-key cryptography embedded hardware encryption devices extension world wide web architecture product important understand decisions manufacturing spare parts scheduling flights factory oem airline operator functions driven primarily happens product field rate wear impending failure primarily predicting rate wear hence impact operations forecasting producing spare parts future critical optimizing operations involved managing complex system fleet aircraft vehicles fixed location products accomplished manner example coupled technologies rfid system could track parts factory aircraft board continue read configuration subsystem ’ replaceable tagged parts map configuration hours run duty cycles process/communicate projected wear rate world wide web back operator factory way mechanical wear rates future failures predicted accurately forecasting spare parts manufacturing shipment significantly improved called prognostics health monitoring phm become possible recent years advent electronic controllers recent evolutionary step aircraft support maintenance management began individual processes prior world war ii solidified manual tracking system support aircraft fleets korean war support mechanic comes local wireless access technical information stored remotely updated board micro-webserver component relevant product service bulletins factory updates fault code driven intelligent 3d computer game-like maintenance procedures social media applications sharing product issues maintenance procedure improvements field include collaborative 2-way voice text image communications note architecture utilized system requires monitoring trending include mobile medical applications monitoring functionality human systems subject equipped data sensors original micro-webserver component i. e. onboard unit key enabling ncps architecture first prototyped demonstrated 2001 david loda enzo macchia sam quadri bjorn stickling united technologies pratt whitney division initially tested board fairchild-dornier 328 later avcraft 328 regional jet january 2002 introduced public demonstrated farnborough air show july 2002 prototype form 2004 flight certified product offering marketed united technologies dtu later fast data management units service number aircraft helicopter fleets similar complex systems approach completely different application successfully embodied eisenhower interstate highway system though transported ncps information cars trucks network centric product support net-centric product support architectural concept merely connects major avenues already existing global communications internet mobile product extending maintenance supply chain processes integrated product centric system real time feedback loop designers factory maintainers product performance reliability example gain information particular engine mobile aircraft efficient send inquiry engine directly host information generated relevant system well synchronize twin remote database access queuing engine system communications examples applied include shipping containers automobiles spacecraft appliances human medical monitoring complex product sensors subsystems require maintenance support monitoring many organizations beginning see value netcentric also spelled net-centric approach managing complex systems including network centric operations industry consortium ncoic association leading aerospace defense contractors network centric warfare arena network centric thinking aircraft operations including network enabled operations neo demonstrations also figure prominently commercial next generation air transportation system nextgen approach made us government revamping air transportation management 21st century
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Computer architecture
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global information grid-bandwidth expansion global information grid bandwidth expansion gig-be program major united states department defense dod net-centric transformational initiative executed disa part global information grid project gig-be created ubiquitous bandwidth-available environment improve national security intelligence surveillance reconnaissance information assurance well command control gig-be disa leveraged dod existing end-to-end information transport capabilities significantly expanding capacity reliability select joint staff-approved locations worldwide gig-be achieved full operational capability foc december 20 2005 program provided increased bandwidth diverse physical access approximately 87 critical sites continental united states conus us pacific command pacom us european command eucom locations interconnected via expanded gig core gig-be provides secure robust optical terrestrial network delivers high-speed classified unclassified internet protocol ip services key operating locations worldwide assistant secretary defense networks information integration asd/nii vision color every base physically diverse network access optical mesh upgrades backbone network regional/man upgrades needed color every base implies every site oc-192 10 gigabits per second usable ip dedicated site extensive component integration operational testing implementation began middle 2004 fiscal year extended calendar year 2005 initial implementation concentrated six sites used proof initial operational capability ioc achieved september 30 2004 gig-be program office conducted detailed site surveys approximately 87 joint staff-approved locations parallel implementation conus overseas gig-be program office completed final operational test evaluation fot e 54 operational sites october 7 2005 december 20 2005 gig-be program achieved milestone full operational capability gig-be awarded saic 2001 877 million contract development instantiation maintenance gig-be network saic instantly divided equipment tasks subcontracts subcontracts follows representatives marty meehan d-mass jim saxton r-nj expressed concern selection process contractor lead gig-be effort say handled irresponsibly reason expressed meehan spokesperson kimberly abbott whole bidding process n't fair open could contractor government led decision process saic contract eventually handed large subset engineering light meehan stress questioning competence winners two congressman delivered letter dod regarding contract issue slowly forgotten
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Distributed computing architecture
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uwe schöning uwe schöning born 28 december 1955 german computer scientist known research computational complexity theory schöning earned ph.d. university stuttgart 1981 supervision wolfram schwabhäuser professor institute theoretical informatics university ulm schöning introduced low high hierarchies structural complexity theory 1983 schöning later showed 1988 paper hierarchies play important role complexity graph isomorphism problem schöning developed 1993 monograph köbler toran 1999 focs paper schöning showed walksat randomized algorithm previously analyzed 2-satisfiability papadimitriou good expected time complexity although still exponential applied worst-case instances 3-satisfiability np-complete constraint satisfaction problems time fastest guaranteed time bound 3sat subsequent research built idea develop even faster algorithms schöning also inventor pedagogical programming languages loop goto described textbook theoretische informatik kurz gefasst schöning author editor many books computer science including research articles include
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Programming language topics
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zooko wilcox-o'hearn zooko wilcox-o'hearn born bryce wilcox may 13 1974 phoenix arizona american colorado-based computer security specialist cypherpunk ceo zcash known tahoe least-authority file store tahoe-lafs secure decentralized fault-tolerant filesystem released gpl tgppl licenses creator transitive grace period public licence tgppl wilcox-o'hearn designer multiple network protocols incorporate concepts self-contained economies secure reputation systems member development team zrtp blake2 cryptographic hash function zooko triangle named wilcox-o'hearn described schema relates three desirable properties identifiers 2001 founder ceo least authority enterprises boulder colorado developer mojonation p2p system lead developer follow-on mnet network developer simplegeo furthermore zooko part founding team launched zcash 2016
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Computer security
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georgia softworks georgia softworks gsw privately held software development company headquartered dawsonville georgia united states company creates data communications systems telecommunications applications commercial emphasis ssh/telnet server microsoft windows georgia softworks markets reliability product suite features designed industrial applications company claims supplied first ssh server using digital certificate authentication internet information server-like certificate user account mapping established 1991 georgia softworks started custom software development company specializing data communications telecommunications applications company needed reliable telnet connectivity windows nt features correctly displayed characters proper function key operation alt-key operation time telnet widely available unix frequently utilized windows commercial environments georgia softworks developed gsw telnet server windows named foundation product universal terminal server designed different protocols could installed requirements determined gsw added features telnet server mouse operation file transfer telnet connection successful in-house use uts commercialized georgia softworks developed major features uts logon scripts feature eventually evolved global per user per ip address certificate based logon scripts features included client device failure detection graceful termination session saver automatic logon session monitoring shadowing team services technology georgia softworks developed commercialized fips 140-2 compliant ssh2 server client software designed run top uts product platform georgia softworks resellers end users every continent except antarctica across variety industries including government automobile manufactures schools oil companies airlines pharmaceutical medical food beverage nasa many
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Computer security
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pop-up ad pop-up ads pop-ups forms online advertising world wide web pop-up graphical user interface gui display area usually small window suddenly appears pops foreground visual interface pop-up window containing advertisement usually generated javascript uses cross-site scripting xss sometimes secondary payload uses adobe flash also generated vulnerabilities/security holes browser security variation pop-up window pop-under advertisement opens new browser window active window pop-unders interrupt user immediately appear user closes covering window making difficult determine website created pop-up ads originated tripod.com webpage hosting site late 1990s javascript provided capability web page open another window ethan zuckerman claims used capability launch advertisements separate windows response complaints advertisers ads appearing pages sexual content zuckerman later apologized unforeseen nuisance pop-up ads evolved web development design technologies allow author associate item pop-up action including cancel innocent looking button bad experiences apprehensive possible damage may cause users click interact item inside pop-up window whatsoever may leave site generated block pop-ups opera first major browser incorporate tools block pop-up ads mozilla browser later improved blocking pop-ups generated page loads early 2000s major web browsers except internet explorer let users block unwanted pop-ups almost completely 2004 microsoft released windows xp sp2 added pop-up blocking internet explorer modern browsers provide pop-up blocking tools third-party tools add features ad filtering users websites web applications continuously experience unwanted pop ads course normal interaction web browser ordinarily users respond dismissing pop-up close cancel feature window hosting pop-up typical response authors pop-up advertising depend create on-screen buttons controls look similar close cancel option user chooses one simulated cancel options however button performs unexpected unauthorized action opening new pop-up downloading unwanted file user system hover ad in-page pop-up uses dhtml combine banner ad pop-up window appears front browser screen javascript imposes advertisement webpage transparent layer advertisement appear variety forms example advertisement contain adobe flash animation links advertiser site advertisement also look like regular window pop-up blockers block ad part webpage blocked third-party ad blockers adblock adblock plus using custom style sheets urls sometimes redirected advertisement pages url redirection urls sometimes opened new tab content old background tab replaced advertisement page url redirection times switches tab user advertisement tab adblock plus ublock noscript block redirects pop-under ads similar pop-up ads ad window appears hidden behind main browser window rather superimposed front pop-up ads became widespread intrusive often taking whole computer screen many users would immediately close pop-up ads appeared site without looking pop-under ads immediately impede view content remain unnoticed user closes minimizes main browser window pop-under ad involves two javascript functions introduced 1997 netscape 2.0b3 browser modern web publishers advertisers use create window front users screen load advertisement send behind screen modern browsers allow codice_1 execute called user interaction e.g. mouse click event handler non-interactive calls timer callback load events etc codice_1 result new window blocked bypass restriction pop-under ads trigger mouse click event listener attached directly document document body enables catching mouse click events consumed click event handlers calling codice_1 without blocked example user selects text mouse click triggers mouse click handler attached document pop-under opens using code notice techniques bypass codice_1 call restriction hijacking mouse clicks exitexchange.com filed patent 2000 subset pop-under advertising called exit pop years controversy numerous articles pop-under patent patent awarded united states patent trademark office uspto april june 2008 respective patent numbers patent 7,386,555 related method opening exit pop toolbar software application computing device whereas patent 7,353,229 covers method used open exit pop embedded script found within media file e.g. javascript code web page copyright aspects pop-up advertising discussed wikipedia articles derivative works transformativeness articles contain illustrations links examples pop-up advertising
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Computer security
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geomesa geomesa open-source distributed spatio-temporal index built top bigtable-style databases using implementation geohash algorithm written scala geomesa capable ingesting indexing querying billions geometry features using highly parallelized index scheme geomesa builds top open source geo osg libraries implements geotools datastore interface providing standardized access feature collections well implementing geoserver plugin google announced geomesa supported google cloud bigtable hosted nosql service release blog post may 2015 geomesa also supports bigtable-derivative implementations apache accumulo apache hbase geomesa implements z-order curve via custom geohash implementation combine three dimensions geometry time i.e latitude/longitude/timestamp single-dimension lexicographic key space provided accumulo
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Distributed computing architecture
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ragic ragic online database management system marketed platform service model online database creation application interface similar spreadsheet additional functionality includes cloud capabilities linking database sheets collaboration generating reports query builder allows users find information integration file storage services like dropbox productivity tools like evernote ragic enables business users familiar spreadsheets build database apps without programming developers make use http api server-side javascript perform complex operations
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Distributed computing architecture
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macvswindows mac vs windows formerly xvsxp online operating system comparison wiki run james scariati michael moriarty site longer active domains point spam blogs site compares competing operating systems windows vista mac os x v10.5 100 different topics site explicitly includes out-of-the-box experience os well freely released updates manufacturer unique feature site many os comparison sites features forum encourage readers voice concerns comments site well suggestions additions site originally launched march 2003 dan pouliot scope site explicit also concerns creative professional site originally intended advocate os x virtue fair comparison windows xp pouliot acknowledged fair comparison difficult relied debates within site online forum refine expand site pdf version site available pouliot reports downloaded 250,000 times launch site time pdf removed january 2005 site almost closed january 2005 including brief period xvsxp converted pay site pouliot time decided needed move change ownership negotiated november 2005 site officially changed hands current owners james scariati michael moriarty rewrite site began renewed objective unbiased comparison point view changed away first person content considered editorial nature removed site officially relaunched march 2006 sporting refreshed look updated sections well format reportedly designed ease updating due upcoming releases operating systems windows vista mac os x v10.5 june 20 2007 xvsxp.com owners announced moving new website mac vs. windows www.macvswindows.com one main new features introduced new website transition wiki model owners stated even current comparison large amount work truly objective comparison aspects platform would require team full-time employees addition current 1 10 scoring system viewed definitive subjective review also compounded final score page option weigh scores based user concerns e.g security given much weight icons criticism xvsxp lodged continued delays providing coverage windows side comparison june 10 2007 site still fails show data windows vista seven months vista ’ release manufacturing rtm even though one xvsxp admins acknowledged four months ago vista released initial acknowledgement february 8 2007 vista came three months went rtm
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Operating systems
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traditional knowledge digital library traditional knowledge digital library tkdl indian digital knowledge repository traditional knowledge especially medicinal plants formulations used indian systems medicine set 2001 collaboration council scientific industrial research csir ministry ayush objective library protect ancient traditional knowledge country exploitation biopiracy unethical patents documenting electronically classifying per international patent classification systems apart non-patent database serves foster modern research based traditional knowledge simplifies access vast knowledge remedies practices 2010 transcribed 148 books ayurveda unani siddha yoga public domain 34 million pages information translated five languages — english german french spanish japanese data 80,000 formulations ayurveda 1,000,000 unani 12,000 siddha already put tkdl plus signed agreements leading international patent offices european patent office epo united kingdom trademark patent office ukpto united states patent trademark office protect traditional knowledge biopiracy giving patent examiners international patent offices access tkdl database patent search examination issue biopiracy unethical bioprospecting made headlines government india successfully revoked limited turmeric basmati rice patents granted united states patent trademark office uspto neem patent granted european patent office epo late 1990s soon patent claims came light india ’ vast traditional medicine knowledge existed languages like sanskrit hindi arabic persian urdu tamil making inaccessible examiners international patent offices verify claims experience prompted department ayush government india create task force experts areas traditional medicine systems india i.e. ayurveda unani siddha yoga patent examiners experts scientists technical officers creation traditional knowledge digital library tkdl initiated 2001 tasks included example transcribing sanskrit shlokas describe ayurvedic formulation text using traditional knowledge resource classification tkrc devised purpose easily understandable patent examiner anywhere world reason entire 34 million pages text available english german french spanish japanese database project reached completion 2006 government allowed access library international patent offices including european patent office epo japan uk subject non-disclosure clause allows patent examiners evaluate patent applications stop attempts patent traditional knowledge new inventions agreements signed epo february 2009 united kingdom trademark patent office ukpto january 2010 u.s. patent trademark office uspto summit meeting us president barack obama prime minister manmohan singh also january 2010 patent examiners getting access tkdl database legal cases regarding unethical patent claims taken years vast expenditure case could avoided another project include data relating 1,500 postures yoga began 2008 new reports large number false gurus yoga masters attempted patent ancient knowledge countries example 131 yoga-related patents traced us alone 2007 uproar parliament media government india took issue uspto thereafter team yoga gurus nine schools working government officials 200 scientists council scientific industrial research csir scanned 35 ancient texts including hindu epics mahabharata bhagwad gita patanjali yoga sutras register native pose end 2009 1500 asanas added 2010 union environment minister jairam ramesh stated eight years 34 million pages information collected estimated cost rs 7 crore least 36 cases identified epo 40 cases uspto using tkdl future project people ’ register biodiversity set government document protect traditional knowledge passed oral tradition india ’ national biodiversity act 2002
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Databases
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queued sequential access method ibm mainframe operating systems queued sequential access method qsam access method read write datasets sequentially qsam available os/360 os/vs2 mvs z/os related operating systems qsam used devices naturally sequential punched card readers punches line printers data devices could also addressed directly magnetic disks qsam offers device independence extent possible api calls used different devices qsam is—as name says—queued specific context meaning buffered deblocking reads blocking writes allows programs read write logical records within physical blocks data opposed less advanced basic sequential access method bsam allows programs access physical blocks data provides support accessing logical records within blocks indeed qsam manages truncated final blocks truncated embedded blocks completely transparently user qsam application program interface compared interface offered open read write close calls using file handles operating systems unix windows
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Operating systems
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clu programming language clu programming language created massachusetts institute technology mit barbara liskov students 1974 1975 find extensive use introduced many features used widely seen step development object-oriented programming oop key contributions include abstract data types call-by-sharing iterators multiple return values form parallel assignment type-safe parameterized types type-safe variant types also notable use classes constructors methods without inheritance syntax clu based algol starting point new language designs key addition concept cluster clu type extension system root language name cluster clusters correspond generally concept class oo language similar syntax instance clu syntax cluster implements complex numbers cluster module encapsulates components except explicitly named clause correspond public components class recent oo languages cluster also defines type named outside cluster case complex_number representation type rep hidden external clients cluster names global namespace mechanism provided group clusters allow created locally inside clusters clu perform implicit type conversions cluster explicit type conversions change abstract type representation universal type procedure force check object certain type objects may mutable immutable latter base types integers booleans characters strings another key feature clu type system iterators return objects collection serially one another iterators offer identical application programming interface api matter data used thus iterator collection codice_1s used interchangeably array codice_2s distinctive feature clu iterators implemented coroutines value provided caller via yield statement iterators like clu common feature many modern languages c ruby python though recently often referred generators clu also includes exception handling based various attempts languages exceptions raised using codice_3 handled codice_4 unlike languages exception handling exceptions implicitly resignaled calling chain also unlike languages provide exception handling exceptions clu considered part ordinary execution flow considered normal efficient typesafe way break loops return functions allows direct assignment return values except conditions apply exceptions neither caught resignaled explicitly immediately converted special failure exception typically terminates program clu often credited first language type-safe variant types called oneofs language ml final distinctive feature clu parallel assignment multiple assignment one variable appear left hand side assignment operator instance writing codice_5 would exchange values codice_6 codice_7 way functions could return several values like codice_8 parallel assignment though multiple return values predates clu appearing cpl 1963 named simultaneous assignment clu popularized often credited direct influence leading parallel assignment later languages objects clu program live heap memory management automatic clu supports type parameterized user-defined data abstractions first language offer type-safe bounded parameterized types using structure clauses express constraints actual type arguments clu influenced many languages many ways approximate chronological order include clu ada major inspirations c++ templates clu exception handling mechanisms influenced later languages like c++ java sather python c include iterators first appeared clu perl lua took multiple assignment multiple returns function calls clu python ruby borrowed several concepts clu call sharing yield statement multiple assignment
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Programming language topics
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dafny dafny imperative compiled language targets c supports formal specification preconditions postconditions loop invariants loop variants language combines ideas primarily functional imperative paradigms includes limited support object-oriented programming features include generic classes dynamic allocation inductive datatypes variation separation logic known implicit dynamic frames reasoning side effects dafny created rustan leino microsoft research previous work developing esc/modula-3 esc/java spec dafny used widely teaching features regularly software verification competitions e.g vstte'08 vscomp'10 cost'11 verifythis'12 dafny designed provide simple introduction formal specification verification used widely teaching dafny builds boogie intermediate language uses z3 automated theorem prover discharging proof obligations dafny provides methods implementation may side-effects functions use specification pure methods consist sequences statements following familiar imperative style whilst contrast body function simply expression side-effecting statements method e.g assigning element array parameter must accounted noting parameters mutated codice_1 clause dafny also provides range immutable collection types including sequences e.g codice_2 sets e.g codice_3 maps codice_4 addition mutable arrays e.g codice_5 provided dafny supports proofs imperative programs based ideas hoare logic following illustrates many features dafny including use preconditions postconditions loop invariants loop variants method max arr array int returns max int examples computes maximum element array method precondition postcondition given codice_6 codice_7 clauses respectively likewise loop invariant loop variant given codice_8 codice_9 clauses respectively treatment loop invariants dafny differs traditional hoare logic variables mutated loop treated information known prior loop discarded information required prove properties variables must expressed explicitly loop invariant contrast variables mutated loop retain information known beforehand following provides illustrates method sumandzero ns array int returns sum nat fails verification dafny establish codice_10 holds assignment precondition intuitively codice_11 holds loop since codice_12 nop however assignment causes dafny treat codice_13 mutable variable drop information known loop verify program dafny either remove redundant assignment codice_12 add loop invariant codice_15 dafny additionally employs limited static analysis infer simple loop invariants possible example would seem loop invariant codice_16 also required variable codice_17 mutated within loop whilst underlying logic require invariant dafny automatically infers hence omitted source level dafny includes features support use proof assistant whilst proofs simple properties within codice_18 codice_19 shown unusual tools nature dafny also allows proof properties one codice_18 another common proof assistant proofs often inductive nature dafny perhaps unusual employing method invocation mechanism applying inductive hypothesis following illustrates datatype list nil link data int next list function sum l list int predicate isnatlist l list ghost method natsumlemma l list n int requires isnatlist l n == sum l ensures n 0 codice_21 proves useful property codice_22 codice_23 i.e codice_24 use codice_25 encoding lemma theorems standard dafny recursion employed induction typically structural induction case analysis performed using codice_26 statements non-inductive cases often discharged automatically verifier must also complete access contents codice_18 codice_28 order unroll necessary implications used conjunction access modifiers specifically hiding contents codice_18 using codice_30 modifier limit properties established
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Programming language topics
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structured program theorem structured program theorem also called böhm–jacopini theorem result programming language theory states class control flow graphs historically called charts context compute computable function combines subprograms three specific ways control structures structured chart subject constraints may however use additional variables form bits stored extra integer variable original proof order keep track information original program represents program location construction based böhm programming language p′′ theorem typically credited 1966 paper corrado böhm giuseppe jacopini david harel wrote 1980 böhm–jacopini paper enjoyed universal popularity particularly proponents structured programming harel also noted due rather technical style 1966 böhm–jacopini paper apparently often cited read detail reviewing large number papers published 1980 harel argued contents böhm–jacopini proof usually misrepresented folk theorem essentially contains simpler result result traced inception modern computing theory papers von neumann kleene harel also writes generic name proposed h.d mills structure theorem early 1970s version theorem replaces original program control flow single global codice_1 loop simulates program counter going possible labels flowchart boxes original non-structured program harel traced origin folk theorem two papers marking beginning computing one 1946 description von neumann architecture explains program counter operates terms loop harel notes single loop used folk version structured programming theorem basically provides operational semantics execution flowchart von neumann computer another even older source harel traced folk version theorem stephen kleene normal form theorem 1936 donald knuth criticized form proof results pseudocode like one pointing structure original program completely lost transformation similarly bruce ian mills wrote approach spirit block structure style language simulating von neumann machine produce behavior spaghetti code within confines block-structured language prevent spaghetti proof böhm jacopini paper proceeds induction structure flow chart employed pattern matching graphs proof böhm jacopini really practical program transformation algorithm thus opened door additional research direction böhm–jacopini proof settle question whether adopt structured programming software development partly construction likely obscure program improve contrary signalled beginning debate edsger dijkstra famous letter go statement considered harmful followed 1968 academics took purist approach böhm–jacopini result argued even instructions like codice_2 codice_3 middle loops bad practice needed böhm–jacopini proof thus advocated loops single exit point purist approach embodied pascal programming language designed 1968–1969 mid-1990s preferred tool teaching introductory programming classes academia edward yourdon notes 1970s even philosophical opposition transforming unstructured programs structured ones automated means based argument one needed think structured programming fashion get go pragmatic counterpoint transformations benefited large body existing programs among first proposals automated transformation 1971 paper edward ashcroft zohar manna direct application böhm–jacopini theorem may result additional local variables introduced structured chart may also result code duplication latter issue called loop half problem context pascal affected problems according empirical studies cited eric s. roberts student programmers difficulty formulating correct solutions pascal several simple problems including writing function searching element array 1980 study henry shapiro cited roberts found using pascal-provided control structures correct solution given 20 subjects subject wrote incorrect code problem allowed write return middle loop 1973 s. rao kosaraju proved possible avoid adding additional variables structured programming long arbitrary-depth multi-level breaks loops allowed furthermore kosaraju proved strict hierarchy programs exists nowadays called kosaraju hierarchy every integer n exists program containing multi-level break depth n rewritten program multi-level breaks depth less n without introducing additional variables kosaraju cites multi-level break construct bliss programming language multi-level breaks form codice_4 keyword actually introduced bliss-11 version language original bliss single-level breaks bliss family languages n't provide unrestricted goto java programming language would later follow approach well simpler result kosaraju paper program reducible structured program without adding variables contain loop two distinct exits reducibility defined kosaraju loosely speaking computing function using primitive actions predicates original program possibly using different control flow structures narrower notion reducibility böhm–jacopini used inspired result section vi highly-cited paper introduced notion cyclomatic complexity thomas j. mccabe described analogue kuratowski theorem control flow graphs cfg non-structured programs say minimal subgraphs make cfg program non-structured subgraphs good description natural language mccabe actually found four graphs independent appearing subgraphs meaning necessary sufficient condition program non-structured cfg subgraph one subset three four graphs also found non-structured program contains one four sub-graphs must contain another distinct one set four latter result helps explain control flow non-structured program becomes entangled popularly called spaghetti code mccabe also devised numerical measure given arbitrary program quantifies far ideal structured program mccabe called measure essential complexity mccabe characterization forbidden graphs structured programming considered incomplete least dijkstra structures considered building blocks 1990 quite proposed methods eliminating gotos existing programs preserving structure various approaches problem also proposed several notions equivalence stricter simply turing equivalence order avoid output like folk theorem discussed strictness chosen notion equivalence dictates minimal set control flow structures needed 1988 jacm paper lyle ramshaw surveys field point well proposing method ramshaw algorithm used example java decompilers java virtual machine code branch instructions targets expressed offsets high-level java language multi-level codice_2 codice_6 statements ammarguellat 1992 proposed transformation method goes back enforcing single-exit 1980s ibm researcher harlan mills oversaw development cobol structuring facility applied structuring algorithm cobol code mills transformation involved following steps procedure note construction improved converting cases selection statement subprocedures material yet covered
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Programming language topics
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optimizing compiler computing optimizing compiler compiler tries minimize maximize attributes executable computer program common requirements minimize program execution time memory requirement power consumption last two popular portable computers compiler optimization generally implemented using sequence optimizing transformations algorithms take program transform produce semantically equivalent output program uses fewer resources and/or executes faster shown code optimization problems np-complete even undecidable practice factors programmer willingness wait compiler complete task place upper limits optimizations compiler implementer might provide optimization generally cpu- memory-intensive process past computer memory limitations also major factor limiting optimizations could performed factors optimization rarely produces optimal output sense fact optimization may impede performance cases rather heuristic methods improving resource usage typical programs techniques used optimization broken among various scopes affect anything single statement entire program generally speaking locally scoped techniques easier implement global ones result smaller gains examples scopes include addition scoped optimizations two general categories optimization following instance local machine dependent optimization set register 0 obvious way use constant 0 instruction sets register value constant less obvious way xor register compiler know instruction variant use many risc machines instructions would equally appropriate since would length take time many microprocessors intel x86 family turns xor variant shorter probably faster need decode immediate operand use internal immediate operand register potential problem xor may introduce data dependency previous value register causing pipeline stall however processors often xor register special case cause stalls large extent compiler optimization techniques following themes sometimes conflict optimization techniques primarily designed operate loops include data-flow optimizations based data-flow analysis primarily depend certain properties data propagated control edges control flow graph include optimizations intended done transforming program special form called static single assignment see ssa form every variable assigned one place although function without ssa effective ssa many optimizations listed sections also benefit special changes register allocation although many also apply non-functional languages either originate easily implemented particularly critical functional languages lisp ml interprocedural optimization works entire program across procedure file boundaries works tightly intraprocedural counterparts carried cooperation local part global part typical interprocedural optimizations procedure inlining interprocedural dead code elimination interprocedural constant propagation procedure reordering usual compiler needs perform interprocedural analysis actual optimizations interprocedural analyses include alias analysis array access analysis construction call graph interprocedural optimization common modern commercial compilers sgi intel microsoft sun microsystems long time open source gcc criticized lack powerful interprocedural analysis optimizations though improving another open source compiler full analysis optimization infrastructure open64 due extra time space required interprocedural analysis compilers perform default users must use compiler options explicitly tell compiler enable interprocedural analysis expensive optimizations early history compilers compiler optimizations good hand-written ones compiler technologies improved good compilers typically generate code good enough generally longer warrant much higher effort program hand-optimized code assembly language except special cases risc cpu architectures even vliw hardware compiler optimization key obtaining efficient code risc instruction sets compact hard human manually schedule combine small instructions get efficient results indeed architectures designed rely compiler writers adequate performance however optimizing compilers means perfect way compiler guarantee program source code fastest smallest possible equivalent compiled program output compiler fundamentally impossible would solve halting problem assuming turing completeness may proven considering call function foo function returns nothing side effects i/o modify global variables live data structures etc. fastest possible equivalent program would simply eliminate function call however function foo fact return program call foo would different program without call optimizing compiler determine solving halting problem additionally number practical issues optimizing compiler technology moreover optimization algorithms complicated especially used compile large complex programming languages bugs introduce errors generated code cause internal errors compilation compiler errors kind disconcerting user especially case since may clear optimization logic fault case internal errors problem partially ameliorated fail-safe programming technique optimization logic compiler coded failure trapped warning message issued rest compilation proceeds successful completion work improve optimization technology continues one approach use so-called post-pass optimizers commercial versions date back mainframe software late 1970s tools take executable output optimizing compiler optimize even post pass optimizers usually work assembly language machine code level contrast compilers optimize intermediate representations programs performance post-pass compilers limited fact much information available original source code always available processor performance continues improve rapid pace memory bandwidth improves slowly optimizations reduce memory bandwidth requirements even cost making processor execute relatively instructions become useful examples already mentioned include loop nest optimization rematerialization early compilers 1960s often primarily concerned simply compiling code correctly efficiently – compile times major concern one earliest notable optimizing compilers bliss 1970 described design optimizing compiler 1975 late 1980s optimizing compilers sufficiently effective programming assembly language declined co-evolved development risc chips advanced processor features instruction scheduling speculative execution designed targeted optimizing compilers rather human-written assembly code
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Programming language topics
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strozzi nosql strozzi nosql shell-based relational database management system initialized developed carlo strozzi runs unix-like operating systems others compatibility layers e.g. cygwin windows file name nosql merely reflects fact express queries using structured query language nosql rdbms distinct circa-2009 general concept nosql databases typically non-relational unlike nosql rdbms strozzi nosql released gnu gpl nosql uses operator-stream paradigm number operators perform unique function passed data stream used supplied unix input/output redirection system pipe system result calculation passed operators unix pipes run memory efficient way implementation nosql development led carlo strozzi latest perhaps active line implementations stream-operator database design originally described evan shaffer rod manis robert jorgensen 1991 unix review article associated paper implementations include perl-based rdb commercial version original authors called /rdb starbase version added astronomical data operators john roll harvard smithsonian astrophysical observatory strengths dealing pipe data implementations mixture awk programming languages usually c perl concept originally described 1991 unix review article later expanded paper see reference well book unix relational database management nosql along similar stream-operator databases well-suited number fast analytical database tasks significant advantage keeping tables ascii text form allowing many powerful text processing tools used adjunct database functions popular tools use nosql include python perl awk shell scripts using ubiquitous unix text processing tools cut paste grep sort uniq etc nosql written mostly interpretive languages slowing actual process execution ability use ordinary pipes filesystems means extremely fast many applications using ram filesystems heavily leveraging pipes mostly memory-based many implementations reasons avoiding sql follows contrast rdbms nosql full power unix application development usage user interface uses unix shell necessary learn set new commands administer database view nosql database set files similar user file scripting type database language used besides unix shell shell-nature encourages casual use database makes use familiar resulting formal use words nosql set shell routines access normal files operating system retrieve information particular employee query sql might look like since document-oriented nosql database often retrieves pre-connected document representing entire employee query might look like stream-operator paradigm differs conventional sql since nosql db relational possible map nosql operators sql equivalents
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Databases
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emerald isle video game emerald isle text adventure game level 9 computing released 1984 plane crashed struck storm bermuda triangle sole occupant escaped parachute finds unknown island inhabited strange peoples creatures game standard text adventure limited graphics platforms
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Computer architecture
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processor design processor design design engineering task creating processor key component computer hardware subfield computer engineering design development implementation electronics engineering fabrication design process involves choosing instruction set certain execution paradigm e.g vliw risc results microarchitecture might described e.g vhdl verilog microprocessor design description manufactured employing various semiconductor device fabrication processes resulting die bonded onto chip carrier chip carrier soldered onto inserted socket printed circuit board pcb mode operation processor execution lists instructions instructions typically include compute manipulate data values using registers change retrieve values read/write memory perform relational tests data values control program flow cpu design divided design following components cpus designed high-performance markets might require custom optimized application specific see designs items achieve frequency power-dissipation chip-area goals whereas cpus designed lower performance markets might lessen implementation burden acquiring items purchasing intellectual property control logic implementation techniques logic synthesis using cad tools used implement datapaths register files clocks common logic styles used cpu design include unstructured random logic finite-state machines microprogramming common 1965 1985 programmable logic arrays common 1980s longer common device types used implement logic include cpu design project generally major tasks re-designing cpu core smaller die-area helps shrink everything photomask shrink resulting number transistors smaller die improves performance smaller transistors switch faster reduces power smaller wires less parasitic capacitance reduces cost cpus fit wafer silicon releasing cpu size die smaller cpu core keeps cost allows higher levels integration within one very-large-scale integration chip additional cache multiple cpus components improving performance reducing overall system cost complex electronic designs logic verification effort proving design bugs dominates project schedule cpu key cpu architectural innovations include index register cache virtual memory instruction pipelining superscalar cisc risc virtual machine emulators microprogram stack variety proposed including reconfigurable logic clockless cpus computational ram optical computing benchmarking way testing cpu speed examples include specint specfp developed standard performance evaluation corporation consumermark developed embedded microprocessor benchmark consortium eembc commonly used metrics include may tradeoffs optimizing metrics particular many design techniques make cpu run faster make performance per watt performance per dollar deterministic response much worse vice versa several different markets cpus used since markets differ requirements cpus devices designed one market cases inappropriate markets vast majority revenues generated cpu sales general purpose computing desktop laptop server computers commonly used businesses homes market intel ia-32 64-bit version x86-64 architecture dominate market rivals powerpc sparc maintaining much smaller customer bases yearly hundreds millions ia-32 architecture cpus used market growing percentage processors mobile implementations netbooks laptops since devices used run countless different types programs cpu designs specifically targeted one type application one function demands able run wide range programs efficiently made cpu designs among advanced technically along disadvantages relatively costly high power consumption 1984 high-performance cpus required four five years develop scientific computing much smaller niche market revenue units shipped used government research labs universities 1990 cpu design often done market mass market cpus organized large clusters proven affordable main remaining area active hardware design research scientific computing high-speed data transmission systems connect mass market cpus measured units shipped cpus embedded machinery telephones clocks appliances vehicles infrastructure embedded processors sell volume many billions units per year however mostly much lower price points general purpose processors single-function devices differ familiar general-purpose cpus several ways embedded cpu family largest number total units shipped 8051 averaging nearly billion units per year 8051 widely used inexpensive design time roughly zero widely available commercial intellectual property often embedded small part larger system chip silicon cost 8051 low us 0.001 implementations use 2,200 logic gates take 0.0127 square millimeters silicon 2009 cpus produced using arm architecture instruction set 32-bit instruction set arm architecture first arm chip designed one half years 5 human years work time 32-bit parallax propeller microcontroller architecture first chip designed two people 10 human years work time 8-bit avr architecture first avr microcontroller conceived designed two students norwegian institute technology 8-bit 6502 architecture first mos technology 6502 chip designed 13 months group 9 people 32 bit berkeley risc risc ii architecture first chips mostly designed series students part four quarter sequence graduate courses design became basis commercial sparc processor design decade every student taking 6.004 class mit part team—each team one semester design build simple 8 bit cpu 7400 series integrated circuits one team 4 students designed built simple 32 bit cpu semester undergraduate courses require team 2 5 students design implement test simple cpu fpga single 15-week semester multititan cpu designed 2.5 man years effort considered relatively little design effort time 24 people contributed 3.5 year multititan research project included designing building prototype cpu embedded systems highest performance levels often needed desired due power consumption requirements allows use processors totally implemented logic synthesis techniques synthesized processors implemented much shorter amount time giving quicker time-to-market
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Computer architecture
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silverplatter silverplatter information inc. one first companies produce commercial reference databases cd-roms founded 1983 united kingdom béla hatvany walt winshall explicit intention using cd technology publish data thus provide alternative searching databases magnetic tape format ron rietdyk company first president firm started 1986 small building newton lower falls massachusetts company began experimenting four databases eric lisa psyclit embase 1987 company 12 databases revenues approximately 6m competing cd plus ovid technologies aries cambridge scientific abstracts dialog company offered libraries wide range cd-roms next years company expanded academic base medical business health safety cd publishing 1989 firm launched multiplatter system networking cd-roms across local area network 1991 introduced searching data held company site erl electronic reference library system providing hard disk access databases via dxp protocol last proved successful 500 sites using firm technology 1997 year company grown 75m revenues 250 databases 2001 silverplatter sold wolters kluwer reputed price 113m forms part ovid technologies wolters kluwer subsidiary
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Databases
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memory management operating systems operating systems memory management function responsible managing computer primary memory memory management function keeps track status memory location either allocated free determines memory allocated among competing processes deciding gets memory receive much allowed memory allocated determines memory locations assigned tracks memory freed unallocated updates status distinct application memory management process manages memory assigned operating system single allocation simplest memory management technique computer memory usually exception small portion reserved operating system available single application ms-dos example system allocates memory way embedded system running single application might also use technique system using single contiguous allocation may still multitask swapping contents memory switch among users early versions music operating system used technique partitioned allocation divides primary memory multiple memory partitions usually contiguous areas memory partition might contain information specific job task memory management consists allocating partition job starts unallocating job ends partitioned allocation usually requires hardware support prevent jobs interfering one another operating system ibm system/360 used lock-and-key technique systems used base bounds registers contained limits partition flagged invalid accesses univac 1108 storage limits register separate base/bound sets instructions data system took advantage memory interleaving place called bank bank separate memory modules partitions may either static defined initial program load ipl boot time computer operator dynamic automatically created specific job ibm system/360 operating system multiprogramming fixed number tasks mft example static partitioning multiprogramming variable number tasks mvt example dynamic mvt successors use term region distinguish dynamic partitions static ones systems partitions may relocatable using hardware typed memory like burroughs corporation b5500 base bounds registers like pdp-10 ge-635 relocatable partitions able compacted provide larger chunks contiguous physical memory compaction moves in-use areas memory eliminate holes unused areas memory caused process termination order create larger contiguous free areas systems allow partitions swapped secondary storage free additional memory early versions ibm time sharing option tso swapped users single time-sharing partition paged allocation divides computer primary memory fixed-size units called page frames program virtual address space pages size hardware memory management unit maps pages frames physical memory allocated page basis address space appears contiguous usually paged memory management job runs address space however single address space operating systems run processes within single address space ibm runs processes within large address space ibm os/vs2 svs ran jobs single 16mib virtual address space paged memory demand-paged system move pages required primary secondary memory segmented memory memory management technique provide user program linear contiguous address space segments areas memory usually correspond logical grouping information code procedure data array segments require hardware support form segment table usually contains physical address segment memory size data access protection bits status swapped swapped etc segmentation allows better access protection schemes memory references relative specific segment hardware permit application reference memory defined segment possible implement segmentation without paging without paging support segment physical unit swapped memory required paging support pages usually unit swapping segmentation adds additional level security addresses segmented system usually consist segment id offset relative segment base address defined offset zero intel ia-32 x86 architecture allows process 16,383 segments 4gib ia-32 segments subdivisions computer linear address space virtual address space provided paging hardware multics operating system probably best known system implementing segmented memory multics segments subdivisions computer physical memory 256 pages page 1k 36-bit words size resulting maximum segment size 1mib 9-bit bytes used multics process could 4046 segments rollout/rollin computer operating system memory management technique entire non-shared code data running program swapped auxiliary memory disk drum free main storage another task programs may rolled demand end or…when waiting long event rollout/rollin commonly used time-sharing systems user think time relatively long compared time swap unlike virtual storage—paging segmentation rollout/rollin require special memory management hardware however unless system relocation hardware memory map base bounds registers program must rolled back original memory locations rollout/rollin largely superseded virtual memory rollout/rollin optional feature os/360 multiprogramming variable number tasks mvt rollout/rollin allows temporary dynamic expansion particular job beyond originally specified region job needs space rollout/rollin attempts obtain unassigned storage job use unassigned storage another job rolled -- i.e. transferred auxiliary storage -- region may used first job released first job additional storage available either 1 unassigned storage source 2 receive job transferred back main storage rolled note rollin/rollout os/360 used batch jobs rollin occur jobstep borrowing region terminates
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Operating systems
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galaksija basic galaksija basic basic interpreter galaksija build-it-yourself home computer yugoslavia partially based code taken trs-80 level 1 basic creator believed microsoft basic extensive modifications galaksija basic—such include rudimentary array support video generation code cpu absence dedicated video circuitry generally improvements programming language—is said left much flow-control floating point code remaining original core implementation interpreter fully contained 4 kib rom 1 computer original mainboard reserved slot extension rom b 2 added commands features built-in zilog z80 assembler core implementation rom 1 contained 3 special symbols 32 keywords extended basic features rom b 2 contained one extra reserved symbol 22 extra keywords
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Programming language topics
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data segment computing data segment often denoted .data portion object file corresponding virtual address space program contains initialized static variables global variables static local variables size segment determined size values program source code change run time data segment read-write since values variables altered run time contrast read-only data segment segment .rodata contains static constants rather variables also contrasts code segment also known text segment read-only many architectures zero-initialized data variables constants instead bss segment historically able support memory address spaces larger native size internal address register would allow early cpus implemented system segmentation whereby would store small set indexes use offsets certain areas intel 8086 family cpus provided four segments code segment data segment stack segment extra segment segment placed specific location memory software executed instructions operated data within segments performed relative start segment allowed 16-bit address register would normally able access 64 kb memory space access 1 mb memory space segmenting memory space discrete blocks specific tasks carried programming languages day concept still widely use within modern programming languages computer program memory largely categorized two sections read-only read-write distinction grew early systems holding main program read-only memory mask rom prom eeprom systems became complex programs loaded media ram instead executing rom idea portions program memory modified retained became .text .rodata segments program remainder could written divided number segments specific tasks code segment also known text segment simply text portion object file corresponding section program virtual address space contains executable instructions stored generally read-only fixed size .data segment contains global static variables pre-defined value modified variables defined within function thus accessed anywhere defined function defined static retain address across subsequent calls examples c include values variables initially stored within read-only memory typically within .text copied .data segment start-up routine program note example variables declared within function would default stored local stack frame bss segment also known uninitialized data usually adjacent data segment bss segment contains global variables static variables initialized zero explicit initialization source code instance variable defined codice_1 would contained bss segment heap area commonly begins end .bss .data segments grows larger addresses heap area managed malloc calloc realloc free may use brk sbrk system calls adjust size note use brk/sbrk single heap area required fulfill contract malloc/calloc/realloc/free may also implemented using mmap/munmap reserve/unreserve potentially non-contiguous regions virtual memory process virtual address space heap area shared threads shared libraries dynamically loaded modules process stack area contains program stack lifo structure typically located higher parts memory stack pointer register tracks top stack adjusted time value pushed onto stack set values pushed one function call termed stack frame stack frame consists minimum return address automatic variables also allocated stack stack area traditionally adjoined heap area grew towards stack pointer met heap pointer free memory exhausted large address spaces virtual memory techniques tend placed freely still typically grow converging direction standard pc x86 architecture stack grows toward address zero meaning recent items deeper call chain numerically lower addresses closer heap architectures grows opposite direction interpreted languages offer similar facility data segment notably perl ruby languages including line codice_2 perl codice_3 ruby old perl marks end code segment start data segment contents prior line executed contents source file line available file object codice_4 perl e.g. codice_5 codice_6 ruby considered form document file literal
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Operating systems
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csc version 6.0 center internet security critical security controls version 6.0 released october 15 2015 consists
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Computer security
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parisa tabriz parisa tabriz american computer security expert works google director engineering chose title security princess due experience hacking internet security desire less staid whimsical title business card 2012 forbes magazine included top 30 people 30 watch technology industry list tabriz appears protagonist intrepid innovator book ara star engineer komal singh parisa tabriz born iranian father doctor american mother nurse polish-american descent grew suburbs chicago older sister two brothers neither parents computer literate tabriz n't encounter world computing first year university tabriz initially enrolled university illinois urbana–champaign study engineering soon became interested computer science instead completed bachelor master degrees university research wireless networking security attacks privacy-enhancing technologies co-authoring papers advisor nikita borisov also active member student club interested website security joined website hacked introduced field internet security tabriz offered summer internship google security team college joined company months graduation 2007 preparing attend conference tokyo google decided use job title security princess business card rather conventional information security engineer since sounded less boring considered ironic career tabriz trained google staff interested learning security worked youth expose diverse set people field computer security 2013 tabriz took responsibility security google chrome 2018 response rsa conference one non-male keynote speaker line-up 20 tabriz co-founded security advocates conference oursa five days pulled together speaker line-up consisting speakers under-represented backgrounds 14 speakers women
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Computer security
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lock screen lock screen computer user interface element used various operating systems regulate immediate access device requiring user perform certain action order receive access entering password using certain button combination performing certain gesture using device touchscreen lock functions pc operating systems utilize login screen lock screens mobile devices often provide functionality beyond unlocking phone notifications emails text messages date time display shortcuts certain applications mobile operating system run smartphones tablets typically use gesture based lock-screen phones manufactured neonode unlocked swiping right touchscreen apple ios used iphone ipad lines utilized similar unlock mechanism ios 10 on-screen slider slid right beginning ios 5 sliding direction sends user directly camera app ios 7 slider widget removed part larger overhaul ios interface users could swipe point screen lock screen also displays clock notifications provides audio playback controls ios 10 made major changes lock screen removing swiping gesture accessing home screen requiring touch home button swiping still used access camera well additional page left widgets iphone x uses swipe gesture access home screen authenticated physical home button first android use gesture-based lock screen electing require user press phone menu button android 2.0 new gesture-based lock screen introduced displaying two icons one unlocking phone one setting volume mode activated dragging relevant icon center screen curve similarly rotary dial android 2.1 rotary dial replaced two tabs either end screen android 3.0 introduced new design ball padlock icon dragged outside circular area 4.0 option unlock straight camera provided 4.1 adds ability unlock google search screen dragging android 4.2 makes additional changes lock screen allowing users add widgets pages accessible lock screen swiping left edge screen camera accessed similar manner swiping right edge screen android also allows devices locked using password passcode pattern grid 9 circles fingerprint sensing facial recognition android distributions manufacturers typically use different lock screen designs stock android utilizes newer versions htc sense used metallic ring dragged bottom screen unlock phone also allows users launch apps dragging respective shortcut icon ring instead recent samsung devices lock screen involves dragging direction location screen touchwiz nature devices galaxy iii s4 also accompanied visual effect pond ripple lens flare similarly htc lock screen app shortcuts dragged bottom screen unlock directly apps may contain adware hijacks default lock screen replace one displays advertising november 2017 google play store officially banned non-lock screen apps monetizing lock screen windows nt offered ability users lock computers displaying login window requires active user password entered re-gain access system since windows xp lock function also bound keyboard shortcut windows 8 lock screen re-designed closer resemble used mobile operating systems users choose distinct wallpaper use lock screen also displays clock calendar events notifications apps screen dragged upwards mouse touchscreen unlock device windows 10 maintains design whilst adding ability use cortana voice assistant lock screen support slide shows windows spotlight service retrieve daily wallpapers optionally receive promotional suggestions related wallpaper screen locking functionality also built screensaver systems unix-like operating systems xscreensaver gnome-screensaver apple holds several patents related sliding lock screen used ios devices granted 2010 2011 describing system involves continuously dragging image certain point unlock device part ongoing patent wars numerous companies surrounding patents related mobile devices apple asserted patents several patent infringement lawsuits outside united states competing vendors apple lawsuits samsung netherlands htc united kingdom led failure courts ruled patents invalid citing similar lock screen n1 mobile phone manufactured swedish company neonode prior art apple design british court specifically ruled apple lock screen obvious improvement neonode n1 due additional visual feedback on-screen slider graphic unlike n1 displayed written instruction explaining gesture early work touchscreen technology university maryland human – computer interaction lab also cited prior art particular 1991 touchscreen slider developed catherine plaisant january 2012 apple permanent injunction german court ruled motorola mobility violated patents recent devices although motorola xoom tablet ruled infringed patent however apple warned would required put bond insurance allow injunction take effect potential sales ban result would limited germany
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Computer security
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dapper orm dapper object-relational mapping orm product microsoft .net platform provides framework mapping object-oriented domain model traditional relational database purpose relieve developer significant portion relational data persistence-related programming tasks dapper free open source software distributed dual license either apache license 2.0 mit license following key features dapper
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Databases
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autonumber autonumber type data used microsoft access tables generate automatically incremented numeric counter may used create identity column uniquely identifies record table one autonumber allowed table data type called counter access 2.0 three forms autonumbers generated default size autonumber 4-byte long integer size used start+increment random autonumbers replication id autonumbers codice_1 property field changed long integer codice_2 autonumber long integer codice_3 property determines whether start+increment random form values property take increment random default autonumber type start+increment counter start value 1 increment 1 although many instances autonumber field appear contains row count deletion rows table example cause autonumber fields re-numbered instead leaves holes numbering similarly transaction add row table begun later aborted autonumber assigned row re-used default start+increment form start value 1 increment 1 suitable circumstances reasons choose form trade-offs default start increment values might reveal information table desired reveal people viewing individual table rows example using autonumber field customer id might reveal information desirable reveal say customer number 6 one example occasion start value autonumber field raised customer number 6 say autonumber field value 10006 using random values desirable cases would unfortunate possible guess next values assigned new rows table usage rare however common problem autonumber fields encountered tables replicated multiple users using multiple replicas table likely end assigning values autonumber fields new rows add causing replication conflicts replicas merged problem addressed two ways first possible use replication ids autonumbers replication ids guids unique across replicas low probability collision second access creates table replicas automatically changes autonumbers start+increment form random form following data definition language ddl query creates autonumber field start value increment query resets counter alternative method resetting counter drop column re-add side effect renumbering existing rows table
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Databases
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mystery house mystery house adventure game released on-line systems 1980 designed written illustrated roberta williams programmed ken williams apple ii mystery house first graphical adventure game first game produced on-line systems company would evolve sierra on-line one earliest horror video games game starts near abandoned victorian mansion player soon locked inside house option explore mansion contains many interesting rooms seven people tom plumber sam mechanic sally seamstress dr. green surgeon joe grave-digger bill butcher daisy cook initially player search house order find hidden cache jewels however terrible events start happening dead bodies people begin appearing becomes obvious murderer loose house player must discover become next victim end 1970s ken williams sought set company enterprise software market-dominating apple ii computer one day took teletype terminal house work development accounting program looking catalogue found game called colossal cave adventure buying game introduced wife roberta played finished colossal cave adventure began search something similar found market underdeveloped roberta decided could write conceived plot mystery house taking inspiration agatha christie novel none recognizing knew programming needed someone else code game convinced husband help ken agreed borrowed brother apple ii computer write game roberta suggested adding graphical scenes otherwise text-based game would make interesting players pair bought versawriter machine allowed users trace line drawing convert digital drawing roberta drew seventy scenes game ken found however resulting digital drawings large fit 5¼-inch floppy disk stored images game instructions program redraw lines scenes rather static images well writing better version versawriter scanning software resulting game text-based adventure depiction character location displayed text game code completed days finished may 5 1980 pair took advertisement micro magazine on-line systems mass-produced ziploc bags containing floppy disk sheet instructions sold 24.95 williams surprise roberta initially considered hobby project sold 10,000 copies mail-order including 1982 rerelease sierraventure line game sold 80,000 units world-wide making one best-selling computer games time computer gaming world 1996 ranked fourth magazine list innovative computer games gamepro named mystery house 51st important game time 2007 introducing visual component adventure games featuring graphics time computer games though game often considered first adventure game use graphics dungeon crawl role-playing video games already using graphics prior release applying graphics adventure game however unprecedented previous story-based adventure games entirely text-based mystery house success led williams create hi-res adventures brand note game hi-res adventure 1 follow-on success next game wizard princess pair moved game development full-time on-line systems incorporated 1980 sierra on-line game later released public domain 1987 part sierra seventh anniversary celebration japan several different adventure games title mystery house released 1982 microcabin released mystery house unrelated inspired on-line systems game name following year japanese company starcraft released enhanced remake on-line systems mystery house realistic art work depiction blood nec pc-6001 pc-8801 mystery house ii msx released sequel microcabin mystery house japanese versions mystery house sold 50,000 units including 30,000 copies msx 20,000 copies pc-6001 pc-8001 pc-8801 pc-9801 fm-7 x1 computers mystery house satirized 1982 adventure game prisoner 2 one location game spooky house whereupon arrival player told killed ken —that ken williams—and must seek absolution murder elements game later reintroduced sierra on-line game colonel bequest 1989
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Computer architecture
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morgan marquis-boire morgan marquis-boire new zealand-born hacker journalist security researcher late 2017 accused multiple sexual assaults director security first look media contributing writer intercept research security surveillance censorship front pages new york times washington post covered news media including bbc news bloomberg wall street journal der spiegel work tracking digital component ongoing syrian civil war book black code inside battle cyberspace marquis-boire previously served advisor freedom press foundation special advisor electronic frontier foundation eff advisor united nations interregional crime justice research institute marquis-boire resigned september 2017 position technical advisory group citizen lab multi-disciplinary advanced research laboratory university toronto citizen lab later disclosed resignation received allegation 2014 sexual assault involving marquis-boire profiled wired cnn süddeutsche zeitung tages anzeiger one wired italy top 50 people 2014 march 2015 named young global leader marquis-boire born new zealand began hacking teenager name headhntr holds bachelor degree political science university auckland marquis-boire conducted research blue coat systems palo alto company provides internet blocking monitoring solutions reports include devices wander mistake planet blue coat redux 2013 planet blue coat mapping global censorship surveillance tools 2013 research covered news media including front page washington post new york times globe mail jakarta post following publication reports blue coat systems announced would longer provide “ support updates services ” software syria april 2013 us government bureau industry security imposed fine usd 2.8 million emirati company responsible purchasing filtering products blue coat exporting syria without license marquis-boire conducted research global proliferation targeted surveillance software toolkits including finfisher hacking team finfisher suite remote intrusion surveillance software developed munich-based gamma international gmbh marketed sold exclusively law enforcement intelligence agencies uk-based gamma group 2012 morgan marquis-boire bill marczak provided first public identification finfisher software marquis-boire collaborators done investigations finfisher including revealing use bahraini activists analyzing variants finfisher suite target mobile phone operating systems uncovering targeted spying campaigns political dissidents malaysia ethiopia documenting finfisher command control servers 36 countries research informed responses civil society organizations pakistan mexico united kingdom mexico local activists politicians collaborated demand investigation state ’ acquisition surveillance technologies uk led crackdown sale software worries misuse repressive regimes hacking team milan italy-based company provides intrusion surveillance software called remote control system rcs law enforcement intelligence agencies marquis-boire collaborators mapped rcs network endpoints 21 countries provided evidence rcs used target human rights activist united arab emirates moroccan media organization independent news agency run members ethiopian diaspora following publication reports eff privacy international took legal action related allegations ethiopian government compromised computers ethiopian expatriates us uk 23rd usenix security symposium marquis-boire researchers released paper governments hack opponents look actors technology examining government targeting activists opposition members ngos observed bahrain syria united arab emirates 2012 2017 marquis-boire reported digital campaigns targeting syrian activists eff citizen lab many findings translated arabic disseminated along recommendations detecting removing malware work cover businessweek covered new york times al jazeera wired december 31 2013 marquis-boire gave interview covering work npr radio show things considered 2012 gave presentation use targeted malware attacks arab spring black hat briefings las vegas covered use malware campaigns purposes digital surveillance espionage libya syria bahrain morocco iran released paper eva galperin eff targeting vietnamese diaspora malware attacks detailed ongoing state-sponsored hacking campaign targeting prominent bloggers academics journalists marquis-boire given interviews wake global surveillance disclosures die zeit international business times dazed named al jazeera media trends watch 2015 shane huntley marquis-boire co-authored paper government targeting journalists media organizations presented black hat singapore 2014 paper reported 21 world top 25 media organizations targeted state-sponsored hacking april 2015 marquis-boire spoke western regional conference society professional journalists san francisco california presented paper entitled data security beginners black hat usa 2015 held las vegas august marquis-boire presented paper entitled big game hunting peculiarities nation-state malware research marquis-boire presented paper entitled security humans privacy coercion resistant design strange loop conference st. louis missouri september 2015 may 2016 state surveillance episode hbo series vice along edward snowden ron wyden september 2017 marquis-boire resigned position senior researcher citizen lab october organization cut ties informed accused sexually assaulting individual 2014 cyber dialogue event eff also released statement saying marquis-boire longer associated november verge published report specific claims assault rape second article contained claims including alleged quotes chat extracts marquis-boire admits drunkenly sexually assaulted raped women — exact number currently determining number women quoted articled sexually assaulted raped least ten
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Computer security
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tegra tegra system chip soc series developed nvidia mobile devices smartphones personal digital assistants mobile internet devices tegra integrates arm architecture central processing unit cpu graphics processing unit gpu northbridge southbridge memory controller onto one package early tegra socs designed efficient multimedia processors recent models emphasize performance gaming machine learning applications without sacrificing power efficiency tegra apx 2500 announced february 12 2008 tegra 6xx product line revealed june 2 2008 apx 2600 announced february 2009 apx chips designed smartphones tegra 600 650 chips intended smartbooks mobile internet devices mid first product use tegra microsoft zune hd media player september 2009 followed samsung m1 microsoft kin first cellular phone use tegra however phone app store tegra power provide much advantage september 2008 nvidia opera software announced would produce version opera 9.5 browser optimised tegra windows mobile windows ce mobile world congress 2009 nvidia introduced port google android tegra january 7 2010 nvidia officially announced demonstrated next generation tegra system-on-a-chip nvidia tegra 250 consumer electronics show 2010 nvidia primarily supports android tegra 2 booting arm-supporting operating systems possible devices bootloader accessible tegra 2 support ubuntu gnu/linux distribution also announced nvidia developer forum nvidia announced first quad-core soc february 2011 mobile world congress event barcelona though chip codenamed kal-el branded tegra 3 early benchmark results show impressive gains tegra 2 chip used many tablets released second half 2011 january 2012 nvidia announced audi selected tegra 3 processor in-vehicle infotainment systems digital instruments display processor integrated audi entire line vehicles worldwide beginning 2013 process iso 26262-certified summer 2012 tesla motors began shipping model electric high performance sedan contains two nvidia tegra 3d visual computing modules vcm one vcm powers 17-inch touchscreen infotainment system one drives 12.3-inch digital instrument cluster march 2015 nvidia announced tegra x1 first soc graphics performance 1 teraflop announcement event nvidia showed epic games unreal engine 4 elemental demo running tegra x1 october 20 2016 nvidia announced nintendo upcoming switch hybrid home/portable game console powered tegra hardware march 15 2017 techinsights revealed nintendo switch powered tegra x1 model t210 second generation tegra soc dual-core arm cortex-a9 cpu ultra low power ulp geforce gpu 32-bit memory controller either lpddr2-600 ddr2-667 memory 32kb/32kb l1 cache per core shared 1mb l2 cache tegra 2 cortex a9 implementation include arm simd extension neon version tegra 2 soc supporting 3d displays soc uses higher clocked cpu gpu tegra 2 video decoder largely unchanged original tegra limited support hd formats lack support high-profile h.264 particularly troublesome using online video streaming services common features tegra 3 codenamed kal-el functionally soc quad-core arm cortex-a9 mpcore cpu includes fifth companion core nvidia refers variable smp architecture cores cortex-a9s companion core manufactured low-power silicon process core operates transparently applications used reduce power consumption processing load minimal main quad-core portion cpu powers situations tegra 3 first tegra release support arm simd extension neon gpu tegra 3 evolution tegra 2 gpu 4 additional pixel shader units higher clock frequency also output video 2560×1600 resolution supports 1080p mpeg-4 avc/h.264 40 mbit/s high-profile vc1-ap simpler forms mpeg-4 divx xvid tegra 3 released november 9 2011 common features tegra 4 codenamed wayne announced january 6 2013 soc quad-core cpu includes fifth low-power cortex a15 companion core invisible os performs background tasks save power power-saving configuration referred variable smp architecture operates like similar configuration tegra 3 geforce gpu tegra 4 evolution predecessors however numerous feature additions efficiency improvements implemented number processing resources dramatically increased clock rate increased well 3d tests tegra 4 gpu typically several times faster tegra 3 additionally tegra 4 video processor full support hardware decoding encoding webm video 1080p 60mbit/s 60fps along tegra 4 nvidia also introduced i500 optional software modem based nvidia acquisition icera reprogrammed support new network standards supports category 3 100mbit/s lte later updated category 4 150mbit/s common features pixel shaders vertex shaders pixel pipelines tegra 4i codenamed grey announced february 19 2013 hardware support audio video formats using cortex-a9 cores instead cortex-a15 tegra 4i low-power variant tegra 4 designed phones tablets unlike tegra 4 counterpart tegra 4i also integrates icera i500 lte/hspa+ baseband processor onto die common features pixel shaders vertex shaders pixel pipelines nvidia ’ tegra k1 codenamed logan features arm cortex-a15 cores 4+1 configuration similar tegra 4 nvidia 64-bit project denver dual-core processor well kepler graphics processing unit support direct3d 12 opengl es 3.1 cuda 6.5 opengl 4.4/opengl 4.5 vulkan nvidia claims outperforms xbox 360 ps3 whilst consuming significantly less power support adaptive scalable texture compression late april 2014 nvidia shipped jetson tk1 development board containing tegra k1 soc running ubuntu linux unified shaders texture mapping units render output units december 2015 web page wccftech.com published article stating tesla going use tegra k1 based design derived template nvidia visual computing module vcm driving infotainment systems providing visual driving aid respective vehicle models time news found similar successor clear confirmation later place combination multimedia auto pilot system vehicle models nvidia tegra x1 codenamed erista features four arm cortex-a57 cores four arm cortex-a53 cores well maxwell-based graphics processing unit supports adaptive scalable texture compression contrary initial belief nvidia use eight cores arm big.little configuration instead devices utilizing tegra x1 always show four arm cortex-a57 cores available four arm cortex-a53 cores accessed operating system used automatically low power scenarios determined cpu nvidia tegra x2 codenamed parker features nvidia custom general-purpose armv8-compatible core denver 2 well code-named pascal graphics processing core gpgpu support chips made using finfet process technology using tsmc 16 nm finfet+ manufacturing process recent tegra soc xavier named comic book character professor x announced 28 september 2016 march 2019 released contains 7 billion transistors 8 custom armv8 cores volta gpu 512 cuda cores open sourced tpu tensor processing unit called dla deep learning accelerator able encode decode 8k ultra hd 7680×4320 users configure operating modes 10w 15w 30w tdp needed die size 350 mm nvidia confirmed fabrication process 12 nm finfet ces 2018 linux kernel mailing list tegra194 based development board type id p2972-0000 got reported board consists p2888 compute module p2822 baseboard nvidia announced next-gen soc codename orin resembling name aquaman comic hero march 27 2018 gpu technology conference 2018 presentations already indicate design two orin chips planned par performance pegasus board four chips supposed formed two xavier chips two gpu chips factor five performance xavier orin seems indicated nowiki /nowiki pixel shaders vertex shaders since kepler unified shaders used nvidia distributes proprietary device drivers tegra oems part linux tegra formerly l4t development kit newer powerful devices tegra family supported nvidia vibrante linux distribution vibrante comes larger set gnu/linux tools plus several nvidia provided libraries acceleration area data processing especially image processing driving safety automated driving level deep learning neuronal networks make e.g heavy use cuda capable accelerator blocks via opencv make use neon vector extensions arm cores due different business needs geforce line graphics cards nvidia one embedded partners avionic design gmbh germany also working submitting open-source drivers tegra upstream mainline linux kernel nvidia co-founder ceo laid tegra processor roadmap using ubuntu unity gpu technology conference 2013 end 2018 evident nvidia employees contributed substantial code parts make t186 t194 models run hdmi display audio upcoming official linux kernel 4.21 q1 2019 thus positively affected software modules open source nouveau closed source nvidia graphics drivers along nvidia proprietary cuda interface drive px2 board announced qnx rtos support april 2016 gpu technology conference socs platforms comparable specifications e.g audio/video input output processing capability connectivity programmability entertainment/embedded/automotive capabilities certifications power consumption
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Computer architecture
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icwatch icwatch public database mainly linkedin profiles people united states intelligence community database created transparency toolkit hosted wikileaks publication global surveillance disclosures 2013 revealed code names surveillance projects including marina mainway discovered linkedin profiles individuals intelligence community mentioned code names well additional ones transparency toolkit took advantage automated collection linkedin profiles mentioning code names collating searchable database name icwatch play icreach alleged top-secret surveillance-related search engine created united states national security agency nsa september 11 attacks initial commit git repository lookingglass made august 23 2014 lookingglass search tool built use icwatch icwatch launched may 6 2015 day transparency toolkit group created icwatch presented conference launch database contained information 27,000 linkedin profiles mid-may 2015 transparency toolkit began receiving requests individuals removed icwatch including death threats following threats well distributed denial-of-service attacks made site wikileaks began hosting website database end may 2015 may 20 2015 number profiles icwatch increased almost 140,000 august 2016 techcrunch reported linkedin suing 100 unnamed individuals scraped linkedin website named icwatch possible target database tracks 100,000 profiles linkedin indeed public sources database searched using company location industry parameters intelligence workers discovered profiles national security agency working contractors project also revealed possible trends employment intelligence community instance number people claiming work sigint databases … increased dramatically years since 2008 small decline starting 2013 m. c. mcgrath transparency toolkit believes workers part pretty normal people ian paul pc world voiced concern safety individuals listed database
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Computer security
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dexos dexos 32-bit operating system written x86 assembly designed coders want direct access hardware including cpu graphics well-commented code documentation licensed free use license commercial non-commercial use written maintained craig bamford voluntary developers around world dexos two modes interaction graphical user interface gui command line interface available user boot version 5.0 dexos fasm port text editor image viewer full tcp/ip stack many games web server support sound ethernet cards programs following list commands supported dexos command line
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Operating systems
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complex instruction set computer complex instruction set computer cisc computer single instructions execute several low-level operations load memory arithmetic operation memory store capable multi-step operations addressing modes within single instructions term retroactively coined contrast reduced instruction set computer risc therefore become something umbrella term everything risc large complex mainframe computers simplistic microcontrollers memory load store operations separated arithmetic instructions modern risc processor therefore much complex say modern microcontroller using cisc-labeled instruction set especially complexity electronic circuits also number instructions complexity encoding patterns typical differentiating characteristic risc designs use uniform instruction length almost instructions employ strictly separate load/store-instructions examples instruction set architectures retroactively labeled cisc system/360 z/architecture pdp-11 vax architectures data general nova many others well known microprocessors microcontrollers also labeled cisc many academic publications include motorola 6800 6809 68000-families intel 8080 iapx432 x86-family zilog z80 z8 z8000-families national semiconductor 32016 ns320xx-line mos technology 6502-family intel 8051-family others designs regarded borderline cases writers instance microchip technology pic labeled risc circles cisc others 6502 6809 described risc-like although complex addressing modes well arithmetic instructions operate memory contrary risc-principles risc philosophy became prominent many computer architects tried bridge so-called semantic gap i.e. design instruction sets directly support high-level programming constructs procedure calls loop control complex addressing modes allowing data structure array accesses combined single instructions instructions also typically highly encoded order enhance code density compact nature instruction sets results smaller program sizes fewer slow main memory accesses time early 1960s onwards resulted tremendous saving cost computer memory disc storage well faster execution also meant good programming productivity even assembly language high level languages fortran algol always available appropriate indeed microprocessors category sometimes still programmed assembly language certain types critical applications 1970s analysis high-level languages indicated complex machine language implementations determined new instructions could improve performance instructions added never intended used assembly language fit well compiled high-level languages compilers updated take advantage instructions benefits semantically rich instructions compact encodings seen modern processors well particularly high-performance segment caches central component opposed embedded systems fast complex expensive memories inherently limited size making compact code beneficial course fundamental reason needed main memories i.e. dynamic ram today remain slow compared high-performance cpu core many designs achieved aim higher throughput lower cost also allowed high-level language constructs expressed fewer instructions observed always case instance low-end versions complex architectures i.e using less hardware could lead situations possible improve performance using complex instruction procedure call enter instruction instead using sequence simpler instructions one reason architects microcode writers sometimes over-designed assembly language instructions including features could implemented efficiently basic hardware available could instance side effects conventional flags setting register memory location perhaps seldom used done via ordinary non duplicated internal buses even external bus would demand extra cycles every time thus quite inefficient even balanced high-performance designs highly encoded relatively high-level instructions could complicated decode execute efficiently within limited transistor budget architectures therefore required great deal work part processor designer cases simpler typically slower solution based decode tables and/or microcode sequencing appropriate time transistors components limited resource also left fewer components less opportunity types performance optimizations circuitry performs actions defined microcode many cisc processors processor many ways reminiscent structure early cpu designs early 1970s gave rise ideas return simpler processor designs order make feasible cope without relatively large expensive rom tables and/or pla structures sequencing and/or decoding first retroactively risc- labeled processor ibm 801 ibm watson research center mid-1970s tightly pipelined simple machine originally intended used internal microcode kernel engine cisc designs also became processor introduced risc idea somewhat larger public simplicity regularity also visible instruction set would make easier implement overlapping processor stages pipelining machine code level i.e level seen compilers however pipelining level already used high performance cisc supercomputers order reduce instruction cycle time despite complications implementing within limited component count wiring complexity feasible time internal microcode execution cisc processors hand could less pipelined depending particular design therefore less akin basic structure risc processors modern context complex variable-length encoding used typical cisc architectures makes complicated still feasible build superscalar implementation cisc programming model directly in-order superscalar original pentium out-of-order superscalar cyrix 6x86 well known examples frequent memory accesses operands typical cisc machine may limit instruction level parallelism extracted code although strongly mediated fast cache structures used modern designs well measures due inherently compact semantically rich instructions average amount work performed per machine code unit i.e per byte bit higher cisc risc processor may give significant advantage modern cache based implementation transistors logic plas microcode longer scarce resources large high-speed cache memories limited maximum number transistors today although complex transistor count cisc decoders grow exponentially like total number transistors per processor majority typically used caches together better tools enhanced technologies led new implementations highly encoded variable length designs without load-store limitations i.e non-risc governs re-implementations older architectures ubiquitous x86 see well new designs microcontrollers embedded systems similar uses superscalar complexity case modern x86 solved converting instructions one micro-operations dynamically issuing micro-operations i.e indirect dynamic superscalar execution pentium pro amd k5 early examples allows fairly simple superscalar design located fairly complex decoders buffers giving speak best worlds many respects technique also used ibm z196 later z/architecture microprocessors terms cisc risc become less meaningful continued evolution cisc risc designs implementations first highly tightly pipelined x86 implementations 486 designs intel amd cyrix ibm supported every instruction predecessors achieved maximum efficiency fairly simple x86 subset little typical risc instruction set i.e without typical risc load-store limitations intel p5 pentium generation superscalar version principles however modern x86 processors also typically decode split instructions dynamic sequences internally buffered micro-operations helps execute larger subset instructions pipelined overlapping fashion also facilitates advanced extraction parallelism code stream even higher performance contrary popular simplifications present also academic texts ciscs microcoded complex instructions cisc became catch-all term meaning anything load-store risc architecture number instructions complexity implementation instructions define cisc fact arithmetic instructions also perform memory accesses compared small 8-bit cisc processor risc floating-point instruction complex cisc even need complex addressing modes 32 64-bit risc processors may well complex addressing modes small 8-bit cisc processors pdp-10 pdp-8 intel 80386 intel 4004 motorola 68000 system z mainframe burroughs b5000 vax zilog z80000 mos technology 6502 vary wildly number sizes formats instructions number types sizes registers available data types hardware support operations like scanning substring arbitrary-precision bcd arithmetic transcendental functions others 8-bit addition subtraction cisc category load-operate instructions load and/or store memory contents within instructions perform actual calculations instance pdp-8 8 fixed-length instructions microcode cisc instructions work powerpc 230 instructions vaxes complex internals like register renaming reorder buffer risc minimal cisc 8 instructions clearly cisc combines memory access computation instructions
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Computer architecture
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load-balanced switch load-balanced switch switch architecture guarantees 100 throughput central arbitration cost sending packet across crossbar twice load-balanced switches subject research large routers scaled past point practical central arbitration internet routers typically built using line cards connected switch routers supporting moderate total bandwidth may use bus switch high bandwidth routers typically use sort crossbar interconnection crossbar output connects one input information flow every output simultaneously crossbars used packet switching typically reconfigured tens millions times per second schedule configurations determined central arbiter example wavefront arbiter response requests line cards send information one another perfect arbitration would result throughput limited maximum throughput crossbar input output example traffic coming line cards b destined line card c maximum traffic cards b process together limited c. perfect arbitration shown require massive amounts computation scales much faster number ports crossbar practical systems use imperfect arbitration heuristics islip computed reasonable amounts time load-balanced switch related load balancing switch refers kind router used front end farm web servers spread requests single website across many servers shown figure right load-balanced switch n input line cards rate r connected n buffers link rate r/n buffers turn connected n output line cards rate r links rate r/n buffers center partitioned n virtual output queues input line card spreads packets evenly n buffers something clearly without contention buffer writes packets single buffer-local memory combined rate r. simultaneously buffer sends packets head virtual output queue output line card rate r/n card output line card clearly forward packets line contention buffer load-balanced switch acts shared-memory switch load-balanced switch essentially way scale shared-memory switch cost additional latency associated forwarding packets rate r/n twice stanford group investigating load-balanced switches concentrating implementations number buffers equal number line cards one buffer placed line cards two interconnection meshes actually mesh supplying rate 2r/n every pair line cards basic load-balanced switch architecture require buffers placed line cards number buffers line cards one interesting property load-balanced switch although mesh connecting line cards buffers required connect every line card every buffer requirement mesh act non-blocking crossbar connections responsive traffic pattern connection far simpler centrally arbitrated crossbar two packets destined output arrive back-to-back one line card spread two different buffers could two different occupancies packets could reordered time delivered output although reordering legal typically undesirable tcp perform well reordered packets adding yet latency buffering load-balanced switch maintain packet order within flows using local information one algorithm foff fully ordered frames first foff additional benefits removing vulnerability pathological traffic patterns providing mechanism implementing priorities stanford university tiny tera project see abrizio introduced switch architecture required least two chip designs switching fabric crossbar slice arbiter upgrading arbiter include load-balancing combining devices could reliability cost throughput advantages since line cards load-balanced switch need physically near one another one possible implementation use entire continent- global-sized backbone network interconnection mesh core routers line cards implementation suffers latencies increased twice worst-case transmission latency number intriguing advantages
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Internet protocols
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stop-and-wait arq stop-and-wait arq also referred alternating bit protocol method telecommunications send information two connected devices ensures information lost due dropped packets packets received correct order simplest automatic repeat-request arq mechanism stop-and-wait arq sender sends one frame time special case general sliding window protocol transmit receive window sizes equal one greater one respectively sending frame sender n't send frames receives acknowledgement ack signal receiving valid frame receiver sends ack ack reach sender certain time known timeout sender sends frame timeout countdown reset frame transmission behavior basic example stop-and-wait however real-life implementations vary address certain issues design typically transmitter adds redundancy check number end frame receiver uses redundancy check number check possible damage receiver sees frame good sends ack receiver sees frame damaged receiver discards send ack—pretending frame completely lost merely damaged one problem ack sent receiver damaged lost case sender n't receive ack times sends frame receiver two copies frame n't know second one duplicate frame next frame sequence carrying identical data another problem transmission medium long latency sender timeout runs frame reaches receiver case sender resends packet eventually receiver gets two copies frame sends ack one sender waiting single ack receives two acks may cause problems assumes second ack next frame sequence avoid problems common solution define 1 bit sequence number header frame sequence number alternates 0 1 subsequent frames receiver sends ack includes sequence number next packet expects way receiver detect duplicated frames checking frame sequence numbers alternate two subsequent frames sequence number duplicates second frame discarded similarly two subsequent acks reference sequence number acknowledging frame stop-and-wait arq inefficient compared arqs time packets ack data received successfully twice transit time assuming turnaround time zero throughput channel fraction could solve problem one send one packet time larger sequence number use one ack set done go-back-n arq selective repeat arq
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Internet protocols
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azure data lake azure data lake scalable data storage analytics service service hosted azure microsoft public cloud azure data lake service released november 16 2016 azure data lake built learnings technologies cosmos microsoft ’ internal big data system cosmos used store process data applications azure adcenter bing msn skype windows live cosmos features sql-like query engine called scope upon u-sql built users store structured semi-structured unstructured data produced applications including social networks relational data sensors videos web apps mobile desktop devices single azure data lake store account store trillions files single file greater petabyte size azure data lake analytics parallel on-demand job service parallel processing system based microsoft dryad solution dryad represent arbitrary directed acyclic graphs dags computation data lake analytics provides distributed infrastructure dynamically allocate de-allocate resources customers pay services use azure data lake analytics uses apache yarn central part apache hadoop govern resource management deliver operations across hadoop clusters microsoft azure data lake store supports application uses open apache hadoop distributed file system hdfs standard using data lake analytics users develop run parallel data transformation processing programs u-sql query language combines sql c u-sql designed evolution declarative sql language native extensibility user code written c u-sql uses c data types c expression language
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Distributed computing architecture
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formation z taking place year 2701 player controls robot transform aero fighter mission stop alien super weapon reaching earth robot may move forwards backwards jump aero fighter may travel anywhere screen limited fuel combination two must used avoid obstacles well destroy on-screen enemies extra points
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Computer architecture
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peter garza peter garza born august 6 1960 united states computer forensics expert cybercrime investigator special agent naval criminal investigative service peter garza conducted first court-ordered internet wiretap united states investigating julio cesar ardita el griton hacking case ardita charged u.s. justice department using compromised user accounts harvard university hack government university computer systems u.s. abroad ardita pleaded guilty may 19 1998 united states district court massachusetts unlawfully intercepting electronic communications damaging files military computer systems garza founded evidentdata inc. private sector consulting firm specializing computer forensics electronic discovery expert consulting 1999 evidentdata acquired first advantage left 2009 form data forté garza continues involved many high-profile civil cases gave expert testimony regarding altered electronic documents case beckman coulter inc. v. dovatron international inc. resulted 934 million jury award testified regarding critical deleted recoverable data case steinberg moorad dunn inc. v. dunn brought sports agent leigh steinberg former partner david dunn resulted 45 million jury award peter garza earned master science information systems claremont graduate university 2001 also developed taught graduate course computer forensics california state polytechnic university pomona
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Computer security
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object description language object description language odl original interface definition language created microsoft specifying interfaces used ole automation superset omg idl microsoft provided utility codice_1 compile odl files odl merged microsoft interface definition language
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Operating systems
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list linux containers linux containers implementations operating system-level virtualization linux operating system several implementations exist based virtualization isolation resource management mechanisms provided linux kernel notably linux namespaces cgroups include
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Operating systems
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clear channel assessment attack clear channel assessment attack queensland attack physical layer dos attack wi-fi networks attack focuses need wireless network receive clear channel assessment function within csma/ca determine whether wireless medium ready able receive data transmitter may start sending attack makes appear airwaves busy basically puts entire system hold attack works 802.11b effective ofdm-based protocols 802.11g 802.11a however hybrid 802.11b/g access points hinder 802.11g network 802.11b network attacked attack originally discovered researchers queensland university technology information security research center thus name queensland attack comes signal telling system airwaves busy course sent attacker nic placing continuous transmit mode attack set use intersil prism test utility prismtestutil322.exe
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Computer security
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mol-360 mol-360 mid-level systems programming language ibm system/360 family computers based algol data structure supported language arrays support floating point data allows direct access processor registers inline assembly language mol-360 used system development corporation sdc develop adept time-sharing system similar language mol940 written sds 940 computer system
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Programming language topics
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secure environment computing secure environment system implements controlled storage use information event computing data loss secure environment used protect personal and/or confidential data often secure environments employ cryptography means protect information secure environments employ cryptographic hashing simply verify information altered since last modified
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Computer security
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hareraiser hareraiser computer game originally released 1984 uk home computer platforms released two parts prelude finale prize worth £30,000 offer game could solved game released acorn electron amstrad cpc bbc micro model b commodore 64 commodore vic-20 ex dragon 32 msx oric atmos 48k sinclair zx spectrum 1984 £8.95 part game takes form series graphical screens depicting grass sky trees occasional text clues interaction pressing cursor keys follow hare moves across screen disappears one sides hints puzzle solved may case text position trees sun clouds elements different screen interpreted way solvers prelude would also buy solve finale could enter competition locate prize bejewelled 18 carat golden hare pendant featured cover golden hare previously prize solving book masquerade british artist kit williams buried secret location ampthill park bedfordshire object game solve clues book would lead successful treasure-hunter location golden prize several sources state erroneously hareraiser based masquerade fact thing apart prize two common feature hare haresoft founded dugald thompson controversial winner masquerade business partner john guard haresoft claimed game released two parts make fun enable competitors ages participate sinclair user magazine however suggested simply make money haresoft stated additional clue revealed harrods tv personality anneka rice nature clue remains unknown whether rice even revealed clue game sell well haresoft went liquidation hareraiser never solved hare sold sotheby auction creditors 1988 although given guide price £3,000–6,000 fact exceed haresoft stated value selling £31,900 although rumoured sold early 1990s whereabouts unknown 20 years july 2009 appeal made bbc radio 4 current owner granddaughter got touch kit williams reunited hare bbc tv documentary game awarded 3/10 sinclair user reviewer richard price struggling find reason play game except sincere need get rich norwich gaming festival 2017 comedian computer game historian stuart ashen described showed game play called worst game ever revealing solution videogame predecessor discovered via cheating ashen stated believed puzzle intentionally designed unsolvable haresoft would lose art piece golden hare
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Computer architecture
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imp programming language imp early systems programming language developed edgar t. irons late 1960s early 1970s unlike systems programming languages imp even though designer refers language based algol imp excludes many defining features language supporting non-algol-like one syntax extensibility compiler imp existed early 1965 used programming cdc 6600 time-sharing system use institute defense analyses since 1967 although compiler slower comparable ones non-extensible languages used practical production work imp compilers developed cdc-6600 cray pdp-10 pdp-11 computers important imp versions imp65 imp70 imp72 imp allows programmer extend syntax although specific means provided add new datatypes structures achieve syntax-extensibility imp uses powerful parse algorithm based syntax graph several connectivity matrices programmer may add new bnf productions graph imp72 syntax extended means extended-bnf syntax statements included source program mechanism powerful allowed implementation language i.e. imp72 source file consisting entirely syntax statements input trivial compiler initially able translate simplest case syntax statement also simple form syntax statement looks like macro casual user basically syntax statement augmented bnf production associated semantics added right example add construct described following bnf semantics codice_1 translate codice_2 programmer would need insert following imp statement semantic-part also contain calls semantic routines following syntax statement semantic part statement consists call semantic routine codice_3 arguments octal constant codice_4 semantic routine call codice_5 codice_6 object top stack moment production invoked codice_3 semantic routine respectively takes arguments pdp-10 machine language opcode register object object produces object whose value result executing designated machine instruction using address field object last argument specific example opcode codice_4 designates codice_9 instruction thus result syntax statement compile code compute absolute value codice_6 imp language used nsa homegrown time-sharing system known folklore
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Programming language topics
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htcondor htcondor open-source high-throughput computing software framework coarse-grained distributed parallelization computationally intensive tasks used manage workload dedicated cluster computers farm work idle desktop computersso-called cycle scavenging htcondor runs linux unix mac os x freebsd microsoft windows operating systems htcondor integrate dedicated resources rack-mounted clusters non-dedicated desktop machines cycle scavenging one computing environment htcondor developed htcondor team university wisconsin–madison freely available use htcondor follows open-source philosophy licensed apache license 2.0 htcondor makes use unused computing time leaving computers turned use htcondor increase energy consumption associated costs starting version 7.1.1 htcondor hibernate wake machines based user-specified policies feature previously available via third-party software htcondor formerly known condor name changed october 2012 resolve trademark lawsuit htcondor scheduler software used distribute jobs first draft assembly human genome way example nasa advanced supercomputing facility nas htcondor pool consists approximately 350 sgi sun workstations purchased used software development visualization email document preparation etc workstation runs daemon watches user i/o cpu load workstation idle two hours job batch queue assigned workstation run daemon detects keystroke mouse motion high non-htcondor cpu usage point job removed workstation placed back batch queue htcondor run sequential parallel jobs sequential jobs run several different universes including vanilla provides ability run batch ready programs standard universe target application re-linked htcondor i/o library provides remote job i/o job checkpointing htcondor also provides local universe allows jobs run submit host world parallel jobs htcondor supports standard message passing interface parallel virtual machine goux et al 2000 addition master worker mw library extremely parallel tasks htcondor-g allows htcondor jobs use resources direct control mostly used talk grid cloud resources like pre-ws ws globus nordugrid arc unicore amazon elastic compute cloud also used talk batch systems like torque/pbs lsf support sun grid engine currently development part egee project htcondor supports drmaa job api allows drmaa compliant clients submit monitor htcondor jobs saga c++ reference implementation provides htcondor plug-in adaptor makes htcondor job submission monitoring available via saga python c++ apis htcondor features include dagman provides mechanism describe job dependencies
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Distributed computing architecture
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sas software sas previously statistical analysis system software suite developed sas institute advanced analytics multivariate analysis business intelligence data management predictive analytics sas developed north carolina state university 1966 1976 sas institute incorporated sas developed 1980s 1990s addition new statistical procedures additional components introduction jmp point-and-click interface added version 9 2004 social media analytics product added 2010 sas software suite mine alter manage retrieve data variety sources perform statistical analysis sas provides graphical point-and-click user interface non-technical users advanced options sas language sas programs data steps retrieve manipulate data proc steps analyze data step consists series statements data step executable statements result software taking action declarative statements provide instructions read data set alter data appearance data step two phases compilation execution compilation phase declarative statements processed syntax errors identified afterwards execution phase processes executable statement sequentially data sets organized tables rows called observations columns called variables additionally piece data descriptor value proc step consists proc statements call upon named procedures procedures perform analysis reporting data sets produce statistics analyses graphics 300 procedures one contains substantial body programming statistical work proc statements also display results sort data perform operations sas macros pieces code variables coded referenced perform repetitive tasks sas data published html pdf excel formats using output delivery system first introduced 2007 sas enterprise guide sas point-and-click interface generates code manipulate data perform analysis automatically require sas programming experience use sas software suite 200 components sas components include development sas began 1966 north carolina state university re-hired anthony barr program analysis variance regression software would run ibm system/360 computers project funded national institute health originally intended analyze agricultural data improve crop yields barr joined student james goodnight developed software statistical routines two became project leaders 1968 barr goodnight integrated new multiple regression analysis variance routines 1972 issuing first release sas project lost funding according goodnight nih wanted fund projects medical applications goodnight continued teaching university salary 1 access mainframe computers use project funded university statisticians southern experiment stations following year john sall joined project 1973 contributed software econometrics time series matrix algebra another early participant caroll g. perkins contributed sas early programming jolayne w. service jane t. helwig created sas first documentation first versions sas named year released 1971 sas 71 published limited release used ibm mainframes main elements sas programming data step common procedures proc step following year full version released sas 72 introduced merge statement added features handling missing data combining data sets 1976 barr goodnight sall helwig removed project north carolina state incorporated sas institute inc. sas re-designed sas 76 open architecture allowed compilers procedures input infile statements improved could read data formats used ibm mainframes generating reports also added put file statements ability analyze general linear models also added format procedure allowed developers customize appearance data 1979 sas 79 added support cms operating system introduced datasets procedure three years later sas 82 introduced early macro language append procedure sas version 4 limited features made sas accessible version 5 introduced complete macro language array subscripts full-screen interactive user interface called display manager 1985 sas rewritten c programming language allowed sas multivendor architecture allows software run unix ms-dos windows previously written pl/i fortran assembly language 1980s 1990s sas released number components complement base sas sas/graph produces graphics released 1980 well sas/ets component supports econometric time series analysis component intended pharmaceutical users sas/ph-clinical released 1990s food drug administration standardized sas/ph-clinical new drug applications 2002 vertical products like sas financial management sas human capital management called cfo vision hr vision respectively also introduced jmp developed sas co-founder john sall team developers take advantage graphical user interface introduced 1984 apple macintosh shipped first time 1989 updated versions jmp released continuously 2002 recent release 2016 sas version 6 used throughout 1990s available wider range operating systems including macintosh os/2 silicon graphics primos sas introduced new features dot-releases 6.06 6.09 user interface based windows paradigm introduced support sql added version 7 introduced output delivery system ods improved text editor ods improved upon successive releases example output options added version 8 number operating systems supported reduced unix windows z/os linux added sas version 8 sas enterprise miner released 1999 2002 text miner software introduced text miner analyzes text data like emails patterns business intelligence applications 2004 sas version 9.0 released dubbed project mercury designed make sas accessible broader range business users version 9.0 added custom user interfaces based user role established point-and-click user interface sas enterprise guide software primary graphical user interface gui customer relationship management crm features improved 2004 sas interaction management 2008 sas announced project unity designed integrate data quality data integration master data management sas institute inc v world programming ltd lawsuit developers competing implementation world programming system alleging infringed sas copyright part implementing functionality case referred united kingdom high court justice european court justice 11 august 2010 may 2012 european court justice ruled favor world programming finding functionality computer program programming language protected copyright free version introduced students 2010 sas social media analytics tool social media monitoring engagement sentiment analysis also released year sas rapid predictive modeler rpm creates basic analytical models using microsoft excel introduced year jmp 9 2010 added new interface using r programming language jmp add-in excel following year high performance computing appliance made available partnership teradata emc greenplum 2011 company released enterprise miner 7.1 company introduced 27 data management products october 2013 october 2014 updates 160 others 2015 sas global forum announced several new products specialized different industries well new training software sas many releases since 1972 since release 9.3 sas/stat release numbering 2011 sas largest set products line customer intelligence numerous sas modules web social media marketing analytics may used profile customers prospects predict behaviors manage optimize communications sas also provides sas fraud framework framework primary functionality monitor transactions across different applications networks partners use analytics identify anomalies indicative fraud sas enterprise grc governance risk compliance provides risk modeling scenario analysis functions order manage visualize risk compliance corporate policies also sas enterprise risk management product-set designed primarily banks financial services organizations sas products monitoring managing operations systems collectively referred sas management solutions sas collects data various assets performance utilization creates reports analyses sas performance management products consolidate provide graphical displays key performance indicators kpis employee department organizational level sas supply chain intelligence product suite offered supply chain needs forecasting product demand managing distribution inventory optimizing pricing also sas sustainability management set software forecast environmental social economic effects identify causal relationships operations impact environment ecosystem sas product sets specific industries government retail telecommunications aerospace marketing optimization high-performance computing sas also offers free university edition downloaded anyone used non commercial use first announcement regarding free university edition seems appeared newspapers 28 may 2014 hence said university edition available freely since 2005 article journal marriage family comparing statistical packages sas competitors stata spss alan c. acock wrote sas programs provide extraordinary range data analysis data management tasks difficult use learn spss stata meanwhile easier learn better documentation less capable analytic abilities though could expanded paid spss free stata add-ons acock concluded sas best power users occasional users would benefit spss stata comparison university california los angeles gave similar results competitors revolution analytics alpine data labs advertise products considerably cheaper sas 2011 comparison doug henschen informationweek found start-up fees three similar though admitted starting fees necessarily best basis comparison sas business model weighted heavily initial fees programs instead focusing revenue annual subscription fees according idc sas largest market-share holder advanced analytics 35.4 percent market 2013 fifth largest market-share holder business intelligence bi software 6.9 share largest independent vendor competes bi market conglomerates sap businessobjects ibm cognos spss modeler oracle hyperion microsoft power bi sas named gartner leader quadrant data integration tool business intelligence analytical platforms study published 2011 bmc health services research found sas used 42.6 percent data analyses health service research based sample 1,139 articles drawn three journals
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