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object-based spatial database object-based spatial database spatial database stores location objects object-based spatial model treats world surface littered recognizable objects e.g cities rivers exist independent locations objects simple polygons lines complex represent cities field-based data model sees world continuous surface features e.g elevation vary using object-based spatial database easier store additional attributes objects direction speed etc using attributes make easier answer queries like find tanks whose speed 10 km oriented north find enemy tanks certain region storing attributes objects provide better result presentation improved manipulation capabilities efficient way field-based data model information usually stored different layers harder extract different information various layers data model applied er germ model giser s.shekhar introduces direction spatial object presents solution object-direction-based queries common representations data model follow open-source software program adds support geographic objects postgresql object-relational database postgis follows simple features sql specification open geospatial consortium provides uml representation geographic applications represent concept field object provides way differentiate spatial relation simple association represents framework objects classes partitioned three kinds classes simple classes link classes path classes objects simple class one hand like objects models object type object identity attributes whose values either data type e.g integer string object type attribute may contain reference another object structure object basically tuple record hand objects simple class nodes database graph – whole database also viewed single graph objects link class like objects simple class additionally contain two distinguished references source target objects belonging simple classes makes edges database graph finally object path class like object simple class contains additionally list references node edge objects form path database graph represent data model store geographic information top eer model geis define input data model provide following data model geometry giser model geometry entity related spatial object relationship determines shape additional entities represent primitives points lines polygons proposed related models topology topology property belonging spatial object property remains unaltered even object deforms example road network two nodes network thus remain connected even path nodes changed road construction order represent topology basic primitives networks i.e. graphs partitions provided additional primitives added lines worboy model system support representation stored data oracle spatial component enterprise oracle 10g provides support stores object road top current implentend construction used network data model store geographic data nodes links graph representation node links set attributes example route object added database supports raster set vector representation
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Databases
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collision attack cryptography collision attack cryptographic hash tries find two inputs producing hash value i.e hash collision contrast preimage attack specific target hash value specified roughly two types collision attacks generally mathematically stated collision attack finds two different messages m1 m2 hash m1 hash m2 classical collision attack attacker control content either message arbitrarily chosen algorithm much like symmetric-key ciphers vulnerable brute force attacks every cryptographic hash function inherently vulnerable collisions using birthday attack due birthday problem attacks much faster brute force would hash n bits broken 2 time evaluations hash function efficient attacks possible employing cryptanalysis specific hash functions collision attack discovered found faster birthday attack hash function often denounced broken nist hash function competition largely induced published collision attacks two commonly used hash functions md5 sha-1 collision attacks md5 improved much 2007 takes seconds regular computer hash collisions created way usually constant length largely unstructured directly applied attack widespread document formats protocols however workarounds possible abusing dynamic constructs present many formats way two documents would created similar possible order hash value one document would shown authority signed signature could copied file malicious document would contain two different messages document conditionally display one subtle changes file extension collision attack chosen-prefix collision attack specific merkle–damgård hash functions case attacker choose two arbitrarily different documents append different calculated values result whole documents equal hash value attack much powerful classical collision attack mathematically stated given two different prefixes p1 p2 attack finds two appendages m1 m2 hash p1 ∥ m1 hash p2 ∥ m2 ∥ concatenation operation 2007 chosen-prefix collision attack found md5 requiring roughly 2 evaluations md5 function paper also demonstrates two x.509 certificates different domain names colliding hash values means certificate authority could asked sign certificate one domain certificate specially signature could used create new rogue certificate impersonate another domain real-world collision attack published december 2008 group security researchers published forged x.509 signing certificate could used impersonate certificate authority taking advantage prefix collision attack md5 hash function meant attacker could impersonate ssl-secured website man-in-the-middle thereby subverting certificate validation built every web browser protect electronic commerce rogue certificate may revokable real authorities could also arbitrary forged expiry time even though md5 known weak 2004 certificate authorities still willing sign md5-verified certificates december 2008 least one microsoft code-signing certificate still using md5 may 2012 flame malware successfully used new variation chosen-prefix collision attack spoof code signing components microsoft root certificate still used compromised md5 algorithm 2019 researchers found chosen-prefix collision attack sha-1 computing complexity 2 2 cost less 100,000 us dollars many applications cryptographic hash functions rely collision resistance thus collision attacks affect security example hmacs vulnerable attack useful attacker must control input hash function digital signature algorithms sign large amount data efficiently implementations use hash function reduce compress amount data needs signed constant size digital signature schemes often vulnerable hash collisions unless using techniques like randomized hashing usual attack scenario goes like 2008 researchers used chosen-prefix collision attack md5 using scenario produce rogue certificate authority certificate created two versions tls public key certificate one appeared legitimate submitted signing rapidssl certificate authority second version md5 hash contained flags signal web browsers accept legitimate authority issuing arbitrary certificates 2003 denial service dos attack described used hash collisions exploit worst-case runtime hash table lookups issue affected major programming languages used weaker hash functions
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Computer security
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plinian core plinian core set vocabulary terms used describe different aspects biological species information biological species information kinds properties traits related taxa—biological non-biological—are included thus instance terms pertaining descriptions legal aspects conservation management demographics nomenclature related resources incorporated plinian core aimed facilitate exchange information species upper taxa scope scope plinian core design requirements includes ease use self-contained able support data integration multiple databases ability handle different levels granularity core terms grouped current version follows plinian core started collaborative project instituto nacional de biodiversidad gbif spain 2005 series iterations elements defined implanted different projects resulted plinian core flat deprecated result new development impulse overcome 2012 new formal requirements additional input better support standard documentation well align processes tdwg world reference body biodiversity information standards new version plinian core v3.x.x defined provides flexibility fully represent information species variety scenarios new elements deal aspects ipr related resources referenced etc introduced elements already included better-defined documented partner development plinian core new phase incorporated university granada ug spain alexander von humboldt institute iavh colombia national commission knowledge use biodiversity conabio mexico university são paulo usp brazil plinian core task group within tdwg interest group species information constituted currently working development plinian core presented levels abstract model application profiles abstract model comprising abstract model schema xsd terms uris normative part comprehensive allows different levels granularity describing species properties taken menu choose terms level detail needed specific project subsets abstract model intended implemented specific projects application profiles aps besides containing part elements aps impose additional specifications included elements controlled vocabularies examples aps use follow plinian incorporates number elements already defined standards following table summarizes standards elements used plinian core
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Computer architecture
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darwin 4078 game takes place within gigantic spaceship virtually infinite capacity ability manipulate time space player must deal enigmatic creatures called evol consist pure energy need keep capsules order maintain existence world characters game designed resemble microscopic organisms appearance quick tricky movements player ship undergoes 10 types transformations throughout game offensive defensive maneuvers specific design sound effects used minimal different types sounds used according type shots speed sound resembling long scream results player ship hit returns weakest evolutionary state game designer graphic designer music composer tomo furukawa would go become vocalist band guniw tools player must progress 16 different levels defeating boss end level player controls ship using 8-way joystick 2 buttons one button targets enemies air targets enemies ground power player ship increases evolves two broad categories define enemies attack first type shoots forward direction constant speed second type shoots bullets travel different speeds depending distance player ship bullets travel quicker player farther away slower player close made staying away enemies would necessarily make easier avoid attacks game difficulty also change time enemies become stronger player ship evolves style continued game sequel player reaches 2,000,000 points gain bonus 2,000,000 points bonus 3,000,000 points reach 3,000,000 points bonus system allows player reach 10,000,000 points gaining 5,000,000 points game counter display digits ten millions destroying 16 ground enemies row desert level extends gameplay without insert additional credits biggest characteristic game evolution player ship ship starts form called beas evolves player collects evol capsules appear certain enemies killed player ship grows size strength evolves certain forms may difficult use effectively player must pace evolution properly order succeed 19 different evolutionary forms total ship attacks target airborne enemies gradually increase strength ship evolves attacks enemies ground improved way hitting airborne enemies certain number shots causes get knocked player ship dock enemies short period time knocked ship attacks enemies ground increase strength period however ground enemies killed power-up power-ups exist attacks enemies ground giant version zanzō knocked player use improve ground attack players must collect evol capsules frequently order advance strongest evolutionary forms failing collect capsules certain period time causes ship gradually devolve one level time however devolution timer stopped ship docked enemy character explained player ship devolves weakest form pister one rank beas hit enemy attack apply ship black deame suppurate forms farther ship evolutionary chain gets hit longer animation ship devolve though coming contact enemies normally results instant loss ship invincible devolution animation lasts player may kill enemies ramming player loses ship hit enemy attack weakest evolutionary form pister crash enemy ship devolving several evolutionary forms achieved gathering capsules mutation occurs player hit enemy attack certain evolutionary stage devolve time certain evolutionary stage ship attacks become highly stylized powerful used effectively reverse evolution another special form occurs player hit enemy attack specific set normal evolutions reverse evolutionary form black deame bat-like bears completely different appearance forms ship unaffected enemy attacks packs extraordinary amount firepower shoots numerous smaller versions main attack however player fails collect evol capsule allotted period time ship immediately devolves weakest form making transformation double-edged sword impossible maintain black deame form throughout game docking enemies since attack power powerful enemies die instantly rather knocked darwin 4078 ported 2nd generation msx 1987 hudson soft bore similar appearance arcade game b-wings nes game hector '87 sequel titled also written s.r.d released data east 1987 ported sega april 8 1990 sega mega drive darwin 4081 direct sequel game bears similarities darwin side-scrolling action game developed data east uses evolution system darwin 4081 numbered 4081 4th game used evolution system darwin 4078 s.r.d 4079 act-fancer 4080 similar games include bio-ship paladin upl bermuda triangle snk also feature ships change appearance power-ups
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Computer architecture
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mcst-r500s mcst r500s 32-bit system-on-a-chip developed moscow center sparc technologies mcst fabricated tsmc
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Computer architecture
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sensetalk sensetalk english-like scripting language derived hypertalk language used hypercard sensetalk originally developed scripting language within hypersense multimedia authoring application nextstep openstep platforms sensetalk resurfaced 2002 scripting language eggplant first commercial mac os x cross-platform gui testing application sensetalk english-like scripting language xtalk family derived hypertalk advanced programming language extensions number features distinguish sensetalk xtalk languages one inclusion lists property lists first class data structures another inclusion objects sensetalk treats script property list object encapsulating properties behaviors sensetalk include concept object classes instead treats every object equally object inherit behavior object objects multiple inheritance supported
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Programming language topics
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data event data event relevant state transition defined event schema typically event schemata described pre- post condition single set data items contrast eca event condition action considers event signal data event refers change signal describes specific state transitions referred eca conditions considering data events relevant data item state transitions allows defining complex event-reaction schemata database defining data event schemata relational databases limited attribute instance events object-oriented databases also support collection properties allows defining changes collections data events
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Databases
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shlomo argamon shlomo argamon american/israeli computer scientist forensic linguist currently tenured professor computer science director master data science program illinois institute technology chicago il shlomo argamon received b.s applied mathematics carnegie-mellon university m.phil ph.d. computer science yale university supervised drew mcdermott spent two years postdoctoral research fulbright foundation fellowship sarit kraus bar-ilan university ramat gan israel since late 1990s argamon worked primarily computational linguistic analysis non-denotational meaning including computational analysis language stylistics sentiment analysis metaphor analysis also published well-cited research active learning machine learning metalearning robotic mapping argamon best known work computational stylistics particularly author profiling together moshe koppel others shown statistical analysis word usage determine author age sex native language personality type high accuracy english-language texts work also shown textual features indicating differences male female authorship consistent languages across time also developed computational stylistic methods provide insights meaning stylistic differences one argamon key innovations purpose development computational stylistic analysis using systemic functional linguistics example together jeff dodick paul chase examined whether clear consistent differences scientific method experimental sciences historical sciences work showed using systemic functional features computational stylistic analysis provides evidence multiple scientific methodologies sorts posited previously philosophers science recently argamon pushed increased use linguistic analysis attribution cybersecurity attacks pointed linguistic attribution techniques often used good effect natural language texts arise different attack scenarios provided analyses high-profile cases sony pictures hack democratic national committee cyber attacks shadow brokers nsa leak 2013 argamon founded illinois institute technology master data science program currently directs program seeks teach students think real problems need solved simply find technical solutions argamon views data scientists sensemakers whose job merely produce analytic results help clients make sense complex uncertain fast-changing world rigorous analysis explanation data
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Computational linguistics
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fusion-io nvmfs sandisk/fusion-io nvmfs file system formerly known direct file system dfs accesses flash memory via virtual flash storage layer instead using traditional block layer api file system two main novel features first lays files directly large virtual storage address space second leverages virtual flash storage layer perform block allocations atomic updates result nvmfs performs better much simpler traditional unix file system similar functionalities additionally approach avoids log-on-log performance issues triggered log-structured file systems microbenchmark results show nvmfs deliver 94,000 i/o operations per second iops direct reads 71,000 iops direct writes virtualized flash storage layer top first-generation fusion-io iodrive direct access performance nvmfs consistently better ext3 platform sometimes 20 buffered access performance nvmfs also consistently better ext3 sometimes 149 application benchmarks show nvmfs outperforms ext3 7 250 requiring less cpu power additionally i/o latency lower nvmfs compared ext3 api used nvmfs access flash memory consists layer provides api called virtualized flash storage layer dfs paper responsibility layer perform block allocation wear leveling garbage collection crash recovery address translation also make address translation data structures persistent
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Computer file systems
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gretl gretl open-source statistical package mainly econometrics name acronym g nu r egression e conometrics ime-series l ibrary graphical user interface gui command-line interface written c uses gtk+ widget toolkit creating gui calls gnuplot generating graphs native scripting language gretl known hansl see also used together tramo/seats r stata python octave ox julia gretl output models latex files besides english gretl also available albanian basque bulgarian catalan chinese czech french galician german greek italian polish portuguese varieties romanian russian spanish turkish ukrainian gretl reviewed several times journal applied econometrics recently australian economic review review also appeared journal statistical software 2008 since journal featured several articles gretl used implement various statistical techniques gretl offers fully documented xml-based data format also import ascii csv databank eviews excel gnumeric gnu octave jmulti opendocument spreadsheets pcgive rats 4 sas xport spss stata files export stata gnu octave r csv jmulti pcgive file formats gretl scripting language called hansl recursive acronym hansl neat scripting language hansl turing-complete interpreted programming language featuring loops conditionals user-defined functions complex data structures considered domain-specific language econometrics like scientifically oriented programming languages matlab julia matrices supported natively primitive variable type gretl add-ons known function packages written hansl simple example hansl running code produces random number generation rng gretl examined tested yalta schreiber 2012 authors conclude results show rng related procedures gretl implemented soundly perform well three crush test suites testu01 due libre nature breadth econometric techniques contains gretl widely used teaching econometrics undergraduate level onwards datasets gretl format available several popular textbooks following list textbooks use gretl software choice addition free supplement hill griffiths lim principles econometrics wiley available
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Programming language topics
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atheos file system atheos file system afs originally used atheos operating system mbr partition id 0x2a part syllable syllable-based wave os operating system afs started exactly data structures file system bfs extended feature set many ways afs 64-bit journaled file system support file attributes file indexing soft deletions also partially supported
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Computer file systems
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tcp hole punching tcp nat traversal tcp hole punching sometimes nat punch-through occurs two hosts behind network address translation nat trying connect outbound tcp connections scenario particularly important case peer-to-peer communications voice-over-ip voip file sharing teleconferencing chat systems similar applications tcp hole punching experimental used nat traversal technique establishing tcp connection two peers behind nat device internet computer network nat traversal general term techniques establish maintain tcp/ip network and/or tcp connections traversing nat gateways following terms host client peer used almost interchangeably nat traversal tcp hole punching establishes bidirectional tcp connections internet hosts private networks using nat work types nats behavior standardized two hosts connecting tcp via outbound connections simultaneous tcp open case tcp state machine diagram availability tcp hole punching depends type computer port allocation used nat two peers behind nat connect via need know little bit one thing absolutely need know location peer remote endpoint remote endpoint data ip address port peer connect two peers b initiate tcp connections binding local ports pa pb respectively need know remote endpoint port mapped nat make connection peers behind nat discover public remote endpoint peer problem called nat port prediction tcp nat traversal hole punching techniques solve port prediction problem nat port allocation one two depending whether nats exhibit predictable non-predictable behavior possible perform tcp connection via tcp simultaneous open shown connection matrix representing different cases impact end-to-end communication methods used nats allow peers perform port prediction remote peer information one mapping guess value subsequent mappings tcp connection happen two steps first peers make connection third party learn mapping second step peers guess nat port mapping subsequent connections solves port prediction method requires making least two consecutive connections peer require use third party method work properly case carrier-grade nat lot subscribers behind ip addresses limited amount ports available allocating consecutive ports internal host might impractical impossible case port prediction trivial peers simply exchange port bound another communication channel udp dht making outbound connections tcp simultaneous open method requires one connection per peer require third party perform port prediction solution peers first connect third party server save port mapping value give peers port mapping value peer second step peers reuse local endpoint perform tcp simultaneous open unfortunately requires use so_reuseaddr tcp sockets use violates tcp standard lead data corruption used application protect data corruption assume port prediction already taken place one methods outlined peer knows remote peer endpoint peers make posix connect call peer endpoint tcp simultaneous open happen follows tcp simultaneous open work nat enough guarantee nats behave nicely respect tcp simultaneous open technique described works fine within cgn cgn also make use port overloading behavior means distinct internal endpoints port value mapped public endpoint break uniqueness quintuple result acceptable tcp port preservation also lead cases cgn ports overloaded issue protocol soundness port overloading tcp allows cgn fit hosts internally preserving tcp end-to-end communication guarantees
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Computer security
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semantic dictionary encoding semantic dictionary encoding sde preserves full semantic context source programs adding information used accelerating speed code generation sde forms code-generating loader form bytecode combined jit compiler code generation load time elementary form dictionary entries represent nodes directed acyclic graph dag describes actions program abstract syntax tree ast tabular form uses intermediate representation ir based encoded abstract syntax tree symbol table program
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Programming language topics
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openplay openplay name open-source cross-platform networking library created apple inc. openplay compiles runs classic mac os macos windows linux operating systems openplay high-level networking solution game applications known abstraction game player top automatically managed networking core version 2.0 includes netsprockets api mac os 9 netsprockets subset apple obsolete game sprockets
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Operating systems
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jacob t. schwartz jacob theodore jack schwartz january 9 1930 – march 2 2009 american mathematician computer scientist professor computer science new york university courant institute mathematical sciences designer setl programming language started nyu ultracomputer project founded new york university department computer science chairing 1964 1980 schwartz born bronx new york january 9 1930 ignatz hedwig schwartz attended stuyvesant high school went city college new york received b.s 1949 city college new york m.a 1949 ph.d. 1951 yale university research interests included theory linear operators von neumann algebras quantum field theory time-sharing parallel computing programming language design implementation robotics set-theoretic approaches computational logic proof program verification systems multimedia authoring tools experimental studies visual perception multimedia high-level software techniques analysis visualization bioinformatic data authored 18 books 100 papers technical reports also inventor artspeak programming language historically ran mainframes produced graphical output using single-color graphical plotter served chairman computer science department founded courant institute mathematical sciences new york university 1969 1977 also served chairman computer science board national research council former chairman national science foundation advisory committee information robotics intelligent systems 1986 1989 director darpa information science technology office darpa/isto arlington virginia jacob schwartz two daughters abby schwartz living new york city rachel fainman stage name rachel kane living winnipeg canada jack also two grandchildren adrienne fainman adam fainman
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Programming language topics
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kernel same-page merging computing kernel same-page merging abbreviated ksm also known kernel shared memory memory merging kernel feature makes possible hypervisor system share identical memory pages amongst different processes virtualized guests directly linked kernel-based virtual machine kvm use ksm merge memory pages occupied virtual machines ksm performs memory sharing scanning main memory finding duplicate pages detected duplicate pair merged single page mapped original locations page also marked copy-on-write cow kernel automatically separate one process modify data ksm originally intended run virtual machines one host sharing memory processes well virtual machines upon implementation different users found ksm also useful non-virtualized environments memory premium experimental implementation ksm red hat found 52 virtual instances windows xp 1 gb memory could run host computer 16 gb ram ksm merged linux kernel mainline kernel version 2.6.32 released december 3 2009 effective operating system kernel must find identical memory pages held different processes kernel also needs decide whether pages going update infrequently enough merging would efficient use processor resources concern although memory usage reduced cpu usage increased thus negating potential increases performance security also concern
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Operating systems
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cmu common lisp cmucl free common lisp implementation originally developed carnegie mellon university cmucl runs unix-like platforms including linux bsd experimental windows port well steel bank common lisp derived cmucl scieneer common lisp commercial derivative cmucl earliest implementation predates common lisp part spice lisp around 1980 1985 rob maclachlan started re-writing compiler would become python compiler cmucl ported unix workstations ibm pc rt mips sparc early cmucl releases support intel x86 architecture due lack registers cmucl strictly separated type-tagged immediate data types garbage collector would rely knowing one half cpu registers could hold tagged types half untagged types leave enough registers python backend cmu canceled project favor dylan implementation using cmucl compiler base maintenance taken group volunteers 1996 group making regular releases infrastructure around time port intel x86 architecture completed first running freebsd later linux problem lacking registers solved new conservative garbage collector new garbage collector accepts value type registers treats anything might pointer pointer purpose collecting moving target
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Programming language topics
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self-certifying file system computing self-certifying file system sfs global decentralized distributed file system unix-like operating systems also providing transparent encryption communications well authentication aims universal distributed file system providing uniform access available server however usefulness sfs limited low deployment sfs clients developed june 2000 doctoral thesis david mazières sfs client daemon implements sun network file system nfs protocol communicating operating system thus work operating system supports nfs including windows client manages connections remote file systems necessary acting kind protocol translation layer sfs server works similarly distributed file system servers exposing existing disk file system network specific sfs protocol unix-like systems sfs file systems usually found /sfs/hostname hostid sfs file system first accessed path connection server made directory created automounted primary motivation behind file system address shortcomings hardwired administratively configured distributed file systems larger organizations various remote file transfer protocols designed operate securely separate administrative realms example sfs one could store files single remote server access files securely transparently location stored locally without special privileges administrative cooperation running sfs client daemon available file systems found path regardless physical location implicitly authenticated path names — include public-key fingerprint server hence called self-certifying addition new perspective sfs also addresses commonly raised limitations distributed file systems example nfs smb clients rely server file system security policies nfs servers rely client computer authentication often complicates security one compromised computer could breach security entire organization nfs smb protocols also provide confidentiality encryption tamper resistance computers network without encapsulation layers ipsec unlike coda afs sfs provide local caching remote files thus dependent network reliability latency bandwidth
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Computer file systems
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ziilabs ziilabs global technology company producing line media-oriented application processors reference platforms enabling software series platforms named zms designed create products target range low-power consumer electronics embedded devices including android-based phones tablets ziilabs founded 1994 3dlabs became wholly owned subsidiary creative technology ltd 2002 january 2009 company re-branded ziilabs re-branding reflected 3dlabs focus supplying low-power media-rich application processors hardware platforms middleware rather 3d gpus previously case company announced first applications/media processor dms-02 2005 followed zms-05 zms-08 recently zms-20 zms-40 zms processors combine ziilabs ’ core asset stemcell computing array arm cores integrated peripheral functions create system chip soc 3dlabs company developed glint permedia gpus used personal workstation graphics cards 2002 company acquired intense3d group become vertically integrated graphics board vendor supplying workstation graphics card realizm brand 3dlabs stopped developing graphics gpus cards 2006 focus media processor business november 2012 creative technology limited announced entered agreement intel corporation intel license certain technology patents ziilabs inc. ltd acquire certain engineering resources assets related uk branch part 50 million deal ziilabs still wholly owned creative continues retain ownership stemcell media processor technologies patents continue supply support zms series chips customers company products include range arm-based zms processors feature so-called stemcell media processing architecture plus portfolio tablet reference platforms based in-house android board support package application software recent platform jaguar android reference tablet announced may 2011 core asset ziilabs zms chips seem array processing units called stemcells programmed perform media processing described 32-bit floating-point processing units likely form digital signal processor cores used accelerate various operations video codec 3d graphics handling zms processors handled programming array coprocessors job years number development platforms made introduced including zii development kits traditional large form factor systems
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Computer architecture
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windows aero windows aero backronym authentic energetic reflective open design language introduced windows vista operating system changes made aero interface affected many elements windows interface including incorporation new look along changes interface guidelines reflecting appearance layout phrasing tone instructions text applications windows aero force development windows vista windows 7 2012 development windows 8 windows server 2012 microsoft moved design language codenamed metro aero interface unveiled windows vista complete redesign windows interface replacing windows xp luna theme release windows vista beta 1 july 2005 little shown aero public leaked builds previous user interfaces plex featured longhorn builds 3683–4042 slate first featured lab06 compile build 4042 used development reset jade builds 4074 4094 microsoft started using aero theme public builds build 5048 first build full-featured aero build 5219 build 5270 released december 2005 contained implementation aero theme virtually complete according sources microsoft though number stylistic changes introduced operating system release windows aero incorporated following features windows vista windows aero revised windows 7 several ui changes touch friendly interface many new visual effects features including pointing device gestures windows 8 windows server 2012 adopted metro design language inherit elements aero aero glass theme replaced flatter solid colored theme transparency effects removed interface aside taskbar maintains transparency longer blur effect flip 3d also removed switches metro-style apps pre-release versions windows 8 used updated version aero glass flatter squared look glass theme ultimately removed final version first time since release windows 95 microsoft completely revised user interface guidelines covering aesthetics common controls buttons radio buttons task dialogs wizards common dialogs control panels icons fonts user notifications tone text used windows vista windows 7 computers meet certain hardware software requirements aero glass theme used default primarily incorporating various animation transparency effects desktop using hardware acceleration desktop window manager dwm personalize section added control panel windows vista users customize glass effects either opaque transparent change color tinted enabling aero glass also enables new features including enhanced alt-tab menu taskbar thumbnails live previews windows flip 3d window switching mechanism cascades windows 3d effect windows 7 features refinements aero glass including larger window buttons default minimize maximize close query revised taskbar thumbnails ability manipulate windows dragging top sides screen side make fill half screen top maximize ability hide windows hovering show desktop button taskbar ability minimize windows shaking one use dwm extension aero glass theme requires video card 128mb graphics memory least 64mb video ram 1gb system ram on-board graphics supporting pixel shader 2.0 wddm-compatible drivers aero glass also available windows 7 starter available limited extent windows vista home basic automatically disabled user detected running non-genuine copy windows windows server 2008 windows server 2008 r2 also support aero glass part desktop experience component disabled default wizard 97 prevailing standard wizard design visual layout functionality used windows 98 windows server 2003 well microsoft products time frame aero wizards replacement wizard 97 incorporating visual updates match aesthetics rest aero well changing interaction flow specifically notifications allow application operating system component icon notification area create pop-up window information event problem windows first introduced windows 2000 known colloquially balloons similar appearance speech balloons commonly seen comics balloons often criticized prior versions windows due intrusiveness especially regard interacted full-screen applications games entire application minimized bubble came notifications aero aim less intrusive gradually fading appearing full-screen application screensaver displayed—in cases notifications queued appropriate time larger icons multiple font sizes colors also introduced aero notification windows segoe ui typeface default font aero languages use latin greek cyrillic character sets default font size also increased 8pt 9pt improve readability segoe ui typeface prior windows 8 numeral zero 0 narrow capital letter wider windows 8 segoe ui keeps difference numeral one 1 top hook capital letter equal crown base windows 8 1 base crown base aero base icons designed iconfactory previously designed windows xp icons vista user experience guidelines also address issue tone writing text used aero user interface prior design guidelines microsoft done much address issue user interface text phrased way information requests presented user consistent parts operating system guidelines vista applications suggest messages present technically accurate advice concisely objectively positively assume intelligent user motivated solve particular problem specific advice includes use second person active voice e.g print photos camera avoidance words like please sorry thank
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Operating systems
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pkfix text-producing systems latex tex produce dvi files files written user files used moderate extent still post-processed tool called dvips converted dvi files postscript files understood many printers older versions dvips embedded bitmapped fonts represented letters symbols pictures fixed resolution instance 300 dpi files printed newer devices resolution 1200 dpi letters files bitmapped fonts display remarkably low quality jagged lines curves diagonals one solution problem substitute bitmapped fonts scalable fonts known among postscript users type 1 fonts remedy problem low quality printing one use heiko oberdiek utility called pkfix input pkfix postscript file generated dvips versions 5.58 newer output another postscript file time bitmapped fonts substituted scalable fonts possible technically speaking pkfix perl script searches postscript file comments bitmapped pk fonts introduced relatively recent dvips versions replaces corresponding type 1 fonts course simpler solution problem would reprocess latex/tex files recent tools fonts cases person given postscript file n't author document n't access source files worse source files may lost times
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Programming language topics
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single address space operating system computer science single address space operating system sasos operating system provides one globally shared address space processes
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Operating systems
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challenge–response authentication computer security challenge–response authentication family protocols one party presents question challenge another party must provide valid answer response authenticated simplest example challenge–response protocol password authentication challenge asking password valid response correct password clearly adversary eavesdrop password authentication authenticate way one solution issue multiple passwords marked identifier verifier ask passwords prover must correct password identifier assuming passwords chosen independently adversary intercepts one challenge–response message pair clues help different challenge different time example communications security methods unavailable u.s. military uses akac-1553 triad numeral cipher authenticate encrypt communications triad includes list three-letter challenge codes verifier supposed choose randomly random three-letter responses added security set codes valid particular time period ordinarily 24 hours interesting challenge–response technique works follows say bob controlling access resource alice comes along seeking entry bob issues challenge perhaps 52w72y alice must respond one string characters fits challenge bob issued fit determined algorithm known bob alice correct response might simple 63x83z character response one challenge real world rules would much complex bob issues different challenge time thus knowing previous correct response even n't hidden means communication used alice bob use challenge-response protocols also used assert things knowledge secret value captchas example sort variant turing test meant determine whether viewer web application real person challenge sent viewer distorted image text viewer responds typing text distortion designed make automated optical character recognition ocr difficult preventing computer program passing human non-cryptographic authentication generally adequate days internet user could sure system asking password really system trying access nobody likely eavesdropping communication channel observe password entered address insecure channel problem sophisticated approach necessary many cryptographic solutions involve two-way authentication user system must convince know shared secret password without secret ever transmitted clear communication channel eavesdroppers might lurking one way done involves using password encryption key transmit randomly generated information challenge whereupon end must return response similarly encrypted value predetermined function originally offered information thus proving able decrypt challenge instance kerberos challenge encrypted integer n response encrypted integer n 1 proving end able decrypt integer n variations hash function operates password random challenge value create response value encrypted hashed exchanges directly reveal password eavesdropper however may supply enough information allow eavesdropper deduce password using dictionary attack brute-force attack use information randomly generated exchange response different challenge guards possibility replay attack malicious intermediary simply records exchanged data retransmits later time fool one end thinking authenticated new connection attempt authentication protocols usually employ cryptographic nonce challenge ensure every challenge-response sequence unique protects man-in-the-middle attack subsequent replay attack impractical implement true nonce strong cryptographically secure pseudorandom number generator cryptographic hash function generate challenges highly unlikely occur sometimes important use time-based nonces weaken servers different time zones servers inaccurate clocks also important use time-based nonces synchronized clocks application vulnerable delayed message attack attack occurs attacker copies transmission whilst blocking reaching destination allowing replay captured transmission delay choosing easily accomplished wireless channels time-based nonce used limit attacker resending message restricted expiry time perhaps less one second likely effect upon application mitigating attack mutual authentication performed using challenge-response handshake directions server ensures client knows secret client also ensures server knows secret protects rogue server impersonating real server challenge–response authentication help solve problem exchanging session keys encryption using key derivation function challenge value secret may combined generate unpredictable encryption key session particularly effective man-in-the-middle attack attacker able derive session key challenge without knowing secret therefore able decrypt data stream avoid storage passwords operating systems e.g unix-type store hash password rather storing password authentication system need verify hash password entered matches hash stored password database makes difficult intruder get passwords since password stored difficult determine password matches given hash however presents problem many challenge-response algorithms require client server shared secret since password stored challenge-response algorithm usually use hash password secret instead password case intruder use actual hash rather password makes stored hashes sensitive actual passwords scram challenge-response algorithm avoids problem examples sophisticated challenge-response algorithms people consider captcha kind challenge-response authentication blocks spambots
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Computer security
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hobbit 1982 video game hobbit illustrated text adventure computer game released 1982 zx spectrum home computer based book hobbit j. r. r. tolkien developed beam software philip mitchell dr. veronika megler published melbourne house later converted home computers available time including commodore 64 bbc micro oric computers arrangement book publishers copy book included game sold parser advanced time used subset english called inglish released adventure games used simple verb-noun parsers allowing simple phrases like get lamp inglish allowed player type advanced sentences ask gandalf curious map take sword kill troll parser complex intuitive introducing pronouns adverbs viciously attack goblin punctuation prepositions allowing player interact game world ways previously possible many locations illustrated image based originals designed kent rees tape version save space image stored compressed format storing outline information flood filling enclosed areas screen slow cpu speed meant would take several seconds scene draw disk-based versions game used pre-rendered higher-quality images game innovative text-based physics system developed veronika megler objects including characters game calculated size weight solidity objects placed inside objects attached together rope damaged broken main character sitting barrel barrel picked thrown trapdoor player would go unlike works interactive fiction game also real time insofar period idleness causes wait command automatically invoked possibility events occurring result suppressed entering pause command stops events key pressed game cast non-player characters npcs entirely independent player bound precisely game rules loyalties strengths personalities affect behaviour always predicted character gandalf example would roam freely around game world fifty locations picking objects getting fights captured volatility characters coupled rich physics impossible-to-predict fighting system enabled game played many different ways though would also lead problems important character killed early numerous possible solutions hindsight game might regarded one first examples emergent gameplay also resulted however many bugs example development megler found animal npcs killed player arrived game documentation warned due immense size complexity game impossible guarantee ever completely error-free melbourne house issued version 1.1 fixes another bug resulted game unwinnable forcing release version 1.2 company never fixed bugs info 1985 rated hobbit commodore 64 three-plus stars five stating graphics pleasant show-stoppers game parser puzzles typical adventures today magazine concluded tolkien fans likely pleased title hobbit bestseller uk zx spectrum 1983 c64 bbc following year game 1983 golden joystick award best strategy game game also huge commercial success selling 100,000 copies first two years retail price £14.95 records sales figures article march 1985 estimated range 100,000 200,000 figure 500,000 copies possible making excellent candidate bestselling text adventure time challenged infocom ’ zork use images many locations opposed mostly text-only adventure games time flexibility inglish parser innovative independence non-player characters popularity tolkien work attributed game phenomenal success help players book called guide playing hobbit david elkan published 1984 developer beam software followed hobbit 1985 1987 shadows mordor game two lord rings 1989 crack doom would also reuse inglish sherlock 1986 parody game released crl boggit phrase game entered popular culture thorin sits starts singing gold also game mentioned nick montfort twisty little passages book exploring history form interactive fiction genre discworld noir references hobbit protagonist lewton discovers someone concealed wine barrel wonders brings mind phrases wait – time passes thorin sits starts singing gold
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Computer architecture
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pdf/vt pdf/vt international standard published iso august 2010 iso 16612-2 defines use pdf exchange format optimized variable transactional printing built top pdf/x-4 first variable-data printing vdp format ensures modern international color consortium-based icc color management use icc output intents adds notion encapsulated groups graphic objects support optimized efficient processing repeating text graphic image content introducing concept document part metadata dpm enables reliable dynamic management pages high volume transactional output hvto print data like record selection postage optimization based metadata pdf/vt-1 always consists self-contained file variants standard support use external graphic content pdf/vt-2 well streaming use multi-part mime packages pdf/vt-2s addition digital master vdp printing shared viewed interactively navigated human operators using normal pdf reader though completely accurate rendering requires pdf/x-4 pdf/vt conforming viewer number vendors announced support pdf/vt upon publication standard 2010 subsequent years various pdf/vt-consuming -producing products also reached market ubiquity pdf well fact pdf iso standard iso 32000-1:2008 clearly work favor pdf/vt nevertheless currently difficult predict industry pdf/vt adopted fast happen positioned vis-à-vis formats architectures variable data printing practical requirements benefits pdf/vt explained detail along related recommendations guide global graphics. ref name= dopdf/vtright /ref
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Programming language topics
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puma microarchitecture puma family 16h low-power microarchitecture amd apus succeeds jaguar second-generation version targets market belongs amd architecture family 16h beema line processors aimed low-power notebooks mullins targeting tablet sector puma cores use microarchitecture jaguar inherits design like jaguar puma core support following instruction sets instructions mmx sse sse2 sse3 ssse3 sse4a sse4.1 sse4.2 avx f16c clmul aes bmi1 movbe move big-endian instruction xsave/xsaveopt abm popcnt/lzcnt amd-v. amd released revision puma core puma+ part carrizo-l platform 2015 differences cpu microarchitecture unclear puma+ featured 2 4 cores 2.5ghz required newer fp4 socket
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Computer architecture
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oberon operating system oberon system modular single-user single-process multitasking operating system written programming language name originally developed late 1980s eth zürich oberon system unconventional visual text user interface instead conventional cli gui tui innovative time influenced design acme text editor plan 9 bell labs operating system oberon system still maintained also subsequently developed multi-process smp-capable bluebottle operating system zooming user interface oberon operating system originally developed part ns32032-based ceres workstation project written almost entirely since 2013 edition described entirely oberon programming language basic system designed implemented niklaus wirth jürg gutknecht design implementation fully documented book project oberon user interface programmers reference found martin reiser book oberon system later extended ported hardware team eth-zürich recognition popular magazines wirth gutknecht although active computer science professors referred 'part-time programmers book 'project oberon late 2013 couple months 80th birthday niklaus wirth published second edition project oberon details implementation oberon system using risc cpu design realized xilinx fpga board presented symposium organized 80th birthday ethz meantime several emulators version implemented according josef templ former member developer group eidgenössische technische hochschule zürich later member institut für systemsoftware johannes kepler university linz one versions v4 maintained genealogy different versions oberon system following oberon text user interface tui differentiated terminal user interface combines point-and-click convenience graphical user interface gui linguistic strength command line interface cli closely tied naming conventions oberon language text appearing almost anywhere screen edited therefore used command input commands activated middle-mouse click text fragment form module.command optionally followed parameters terminated command defined procedure empty argument list parameters command defined executing middle click must explicitly scanned retrieved procedure checks questions asked command execution sometimes called non-modal user interface ui nothing like command prompt required although radically different command line tui efficient powerful steep ascent early learning curve makes little bit difficult beginning questions asked deliberate design decision needs getting used editors ask user closing modified text case oberon system usage tui programming interface fully documented martin reiser book oberon system short introduction user interface found niklaus wirth home page later versions system oberon oberon v4 v4 short sometimes also referred linz-oberon oberon system 3 s3 sometimes also called eth-oberon spirit oberon enhanced basic interface different incompatible implementations buttons drop menus active elements v4 used purpose dedicated control character embedded normal text contrast system 3 extended kernel introducing persistent objects extensions include large set user interface elements mastering oberon user interface purely textual also called gadgets system s3 absolutely non-trivial therefore recommended proceed successful installation oberon system 3 andré fischers oberon system 3 tutorial expanded version tutorial published book print whole book available electronic form single user license every installed version system 3 windows linux native i.e also gadgets toolkit olr information get copy oberon companion may found section oberon wikibook similar user interfaces yet appear commonplace operating systems rob pike acme system plan 9 bell labs strongly inspired oberon tui whether worksheet interface macintosh programmer workshop influenced oberon tui vice versa difficult decide oberon system based wirth previous computer design lilith apple macintosh precursor lisa oberon system ceres precursor lilith roots inspired alto developed xerox parc v1 first usable version time oberon trilogy published major change text model together editor called write yielded v2 foreshadowed table section history major fork beginning 1990s v4 vs. system 3 group around jürg gutknecht introduced persistent objects object-libraries thereby extending kernel group around realized similar features introducing active elements mapped special character thereby extending fonts without changing kernel system 3 sometimes also called spirit oberon later renamed eth oberon whereas v4 sometimes also called linz oberon version oberon system 3 integrated microsoft windows os called plugin oberon version called oberon v4 see also history closer original operating system developed n. wirth j. gutknecht originally developed ethz h.p mössenböck went institut für systemsoftware johannes-kepler university linz jku development v4 moved also therefore v4 sometimes also called linz-oberon contrast eth-oberon recent version v4 extensions available jku oberon v4 appears orphaned almost changes since 2000 another repository v4 claudio nieder oberon v4 also shows difference different v4 implementations since 2013 page moved to/is mirrored sourceforge v4 closer would called integrated development environment operating system many extensions written v4 still available ftp server ssw jku documentation found web-pages information normally included packages given oberon special rich text format computer science department eth zurich recent years begun exploring active objects concurrency operating systems released early version new language active oberon new operating system first called aos — due copyright issues — called a2 and/or bluebottle available eth zurich source via internet native versions a2 i.e running bare hardware currently possible intel ia-32 x86-64 single- multi-processor systems strongarm cpu family versions running top another operating system available windows winaos unix unixaos linux linuxaos os-x darwinaos part industrial research project native systems group eth zurich developed application-specific operating system called stailaos based latest version oberon os targeted towards applications like real-time analytics high performance trading systems main memory based erp etc native oberon stands oberon system running bare hardware pc-native oberon version oberon operating system runs ia-32 x86-32 pc hardware never v4 native oberon every information section implicitly assumes system 3 native oberon minimal hardware requirements 133 mhz pentium 100mb hard disk vesa 2 graphics card resolution least 1024x768 pixel optionally 3com network card basic system runs single hd-floppy additional software installed network full installation includes gadgets gui written completely oberon programming language confusion caused fact exists version called lno acronym linux native oberon uses linux hardware abstraction layer hal goal compatible possible pc-native oberon versions oberon system i.e without native name partially modified interfaces low level modules 2015 peter matthias revitalized lno name olr oberon linux revival multi-platform distribution running seamlessly intel x86 risc-v mips arm runs nicely raspberry pi inexpensive chip computer tweaking adjusting group membership or/and permissions devices runs nicely tiny core linux olr interfaces linux kernel direct system calls olr currently mid 2017 misses network layer 2013 niklaus wirth paul reed completed re-implementation original oberon system digilent xilinx spartan 3 fpga starter board work included revision project oberon identified project oberon new edition 2013 system since ported xilinx spartan 6 fpga development board saanlima electronics 2015 paul reed collaborated victor yurkovsky creation oberonstation xilinx spartan 3-based computer designed specifically run oberon peter de wachter implemented emulator also ported java javascript michael schierl running modern browsers ported free pascal/ultibo markus greim andreas pirklbauer maintains experimental version extensions project oberon 2013 github a2 yet another name active object system 2003. br alo arm linux oberon lno family arm cpu. br aos active object system 2002. br bb blackbox component builder component pascal ide oberon microsystems. br bluebottle os another name active object system 2003. br cp component pascal dialect oberon family similar oberon-2. br etho oberon developed eidgenössische technische hochschule eth zürich. br fox compiler active oberon appearing aos a2 bluebottle br leo linux eth oberon etho 2.4.3 linux x86. br lno linux native oberon. br native oberon oberon running bare hardware rather atop another operating system. br olr oberon linux revival version uses linux hal runs x86 arm mips. br op2 portable oberon-2 compiler op2 developed port oberon onto commercially available platforms. br paco scope parallel compiler appears a2 compiles scope independent thread br risc5 cpu project oberon 2013 based upon wirth risc architecture confused risc-v. br unixaos unix-based aos. br winaos windows-based aos. br
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Operating systems
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impermium impermium cyber-security startup company based redwood city california provided anti-spam account protection services internet web sites 2014 company acquired google company founded 2010 mark risher vishwanath ramarao naveen jamal met managing anti-spam systems yahoo mail company protected 1.5 million sites worldwide including disqus livefyre pinterest squarespace tumblr attacks including fraudulent registrations login account hijacking malicious user-generated content forms social spam impermium received venture capital financing funds including accel partners greylock partners highland capital partners morado ventures social+capital partnership january 2014 google announced acquisition company merging team technology anti-spam group
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Computer security
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allwinner technology allwinner technology fabless semiconductor company designs mixed-signal systems chip soc company headquartered zhuhai guangdong china sales technical support office shenzhen guangdong logistics operations hong kong since founding 2007 allwinner released fifteen soc processors use android-based tablets well smartphones over-the-air ott boxes video camera systems car dvrs car media players 2012 2013 allwinner number one supplier terms unit shipments application processors android tablets worldwide according digitimes q4 2013 allwinner lost number one position terms unit shipments chinese market rockchip q2 2014 allwinner reported digitimes third largest supplier chinese market rockchip mediatek digitimes also projected allwinner fall number four position q4 2014 passed intel allwinner unit shipments continue decline series processors used mobile applications mainly referring tablet application 2011 company became arm processor licensee subsequently announced series arm cortex-a8 powered mobile application processors including a10 a13 a10s a12 used numerous tablets also pc-on-a-stick media center devices also adopted free hardware projects like cubieboard development board december 2012 allwinner announced availability two arm cortex-a7 mpcore powered products dual-core allwinner a20 quad-core allwinner a31 production a31 started september 2012 end products mostly high-end tablets chinese manufacturers appeared market early 2013 including onda v972 allwinner first make arm processor core available mass production march 2013 allwinner launched quad-core phablet processor a31s based quad-core cortex-a7 cpu architecture processor allows 3g 2g lte wifi bt fm gps agps nfc using minimum external components october 2013 allwinner released second dual-core a23 touted efficient dual core processor tablets a23 cpu frequency intended run 1.5 ghz june 2014 allwinner announced a33 quad-core soc pin compatible allwinner a23 new soc features four cortex-a7 cores 256 kb l1 cache 512 kb l2 cache mali-400 mp2 gpu new feature support openmax api allwinner positioned a33 entry-level tablets targeting quad-core tablets priced 30 60 july 2014 announced started mass production chip sell low 4 per unit april 2019 allwinner announced a50 28nm quad-core soc a50 features four cortex-a7 cores running 1.8ghz 512 kb l2 cache mali-400 mp2 gpu june 2017 allwinner announced a63 28nm quad-core soc apc 2017 conference a63 features four cortex-a53 cores running 1.8ghz 512 kb l2 cache mali-t760 mp2 gpu opengl es 3.2 support vpu 4k/6k vp9 h.265 h.264 4k 30fps video decoder h.264 hp encoder 1080p 30fps october 2013 allwinner disclosed upcoming octa-core a80 soc featuring four high-performance arm cortex-a15 four efficient arm cortex-a7 cpu cores big.little configuration june 30 2014 chinese brand onda officially released octa-core onda v989 tablet based allwinner a80 first allwinner a80-based tablet available consumers priced cny 1099 ~us 177 september 2014 allwinner announced allwinner a83t octa-core tablet processor packs eight highly energy-efficient cortex-a7 cores run simultaneously around 2.0 ghz also includes powervr gpu first tablet chip expected hit market q4 2014 april 2019 allwinner announced roadmap 2019 2020 feature a100 a200 a300 a301 soc allwinner a200 descrided “ ai blessing computational power ” f series processors based allwinner ’ melis os mainly used smart video radios video mp5 etc 2007 2011 allwinner introduced f-series processors including f10 f13 f18 f20 f1e200 f1c100 f20 series runs allwinner in-house operating system melis2.0 mainly used vehicle multimedia systems e-ink readers video intercom systems h-series introduced 2014 integrated application processors primarily targeted ott set-top box applications eg hdmi mini pcs gaming boxes etc allwinner launched a80 octa-core ott box solution targeting high-end ott box market launched allwinner h8 octa-core processor mid-range ott boxes recently launched quad-core allwinner h3 targeting us 35 50 ott box market r “ real-time series chip designed low power applications timing critical must done edge rather fog cloud chip also built redundancies meet industrial automotive standards processing r series chip applicable number different industries including industrial automation safe plcs power generation distribution healthcare automotive technology technology specifically r16 chip also utilised robotic vacuums smart speakers resulting longterm partnership cogobuy group ’ subsidiary ingdan cogobuy ’ preparatory k-system used basis add integrated slam modules allwinner chip ’ technical advantages patents cogobuy held allowed chip localisation edge computing required ai room mapping cleaning r40 r16 technology implemented number banana pi models r8 chip also used “ world ’ first nine dollar computer ” kickstarter project 2015 v-series video encoding processor targeting applications smart dvr ip camera smart home applications similar series soc adds support functions digital watermarking motion detection video scaling well cbr/vbr bit rate control mode july 2014 allwinner announced first 64-bit tablet processor hit market soon allwinner soc family includes a-series intended android os f-series intended company self-developed melis operating system a-series including a10 a20 a31 socs proprietary in-house designed multimedia co-processing dsp digital signal processing processor technology hardware accelerated video image audio decoding called cedarx subprocessing called cedarv video decoding cedara audio decoding able decode 2160p 2d 1080p 3d video main disadvantages cedarx technology associated libraries allwinner cedarx proprietary libraries clear usage license even source code versions available terms-of-use unknown open source software glue code multimedia frameworks gnu/linux systems could used middle-ware like example openmax vaapi a-series integrated application processors primarily targeting tablets well targeting mini pcs development boards tv boxes h-series introduced 2014 primarily targeted ott set-top box applications allwinner technology cooperates around ten independent design houses idhs based shenzhen china develop solutions based allwinner processors include inet technology worldchip digital technology sochip technology topwise communication chiphd technology highcharacter science technology wits technology ococci technology next huawen technology qi hao digital technology apart white-box market allwinner processors also found many brand products including hp msi zte noox gotab skyworth mele polaroid micromax archos texet ainol onda ramos teclast ployer readboy noah rf bmorn apical astro queo etc due low price a10 soc fact special rescue mode early availability u-boot linux kernel source several device makers allwinner socs popular among open-source software developers since least 2012 linux-sunxi community one active arm soc communities slightly older hardware minimal dependence firmware blobs since allwinner also official member linaro group nonprofit engineering consortium aimed developing open-source software arm architecture however noted contributions allwinner made linaro group form binary blobs clear violation gnu gpl license linux kernel uses december 2014 allwinner released android 5.0 sdk allwinner a33 quad-core solution allwinner accused multiple times violating gpl license providing linux/android kernel source code u-boot source using lgpl-licensed code within binary blobs etc allwinner also accused including backdoor published version linux kernel backdoor allows installed app full root access system may remnant debugging development process presents significant security risk devices using allwinner provided kernel
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Computer architecture
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internet citizen band internet citizen band better known icb early internet chat program associated protocol released 1989 icb typically served port 7326 first version icb program called forumnet fn written university kentucky staffer sean carrick casey widely used university kentucky georgia tech mit university new mexico stanford university mills college uc santa cruz uc berkeley fn based mud software program casey established protocol clients fn used realtime communications channel 1989 loma prieta earthquake internet access hard-hit santa cruz returned service reliable phone service march 1991 university kentucky changed policy shut fn server within 2 months new server created client software another fn user john atwood devries put online renamed icb new server code unrelated original server except common client software source used basis many icb servers follow 1995 2000 server code heavily rewritten stability additional features jon luini michel hoche-mong remains available icb.net web site icb still operation dedicated user base variety clients exist major operating systems icb features many standard chat program functions including channels private messages nickname registration common clients support tcl scripting commands functions clients principally icbm support scripting perl instead icb never supported multi-server shared groups number simultaneous users always somewhat limited comparison popular chat programs icb support transferring files multimedia via chat program however restrictive protocol small remote attack surface icb protocol 8-bit clean
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Internet protocols
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elementary key normal form elementary key normal form eknf subtle enhancement third normal form thus eknf tables 3nf definition happens one unique compound key overlap cases cause redundant information overlapping column table eknf elementary functional dependencies begin whole keys end elementary key attributes every full non-trivial functional dependency form x→y either x key part elementary key definition elementary functional dependency functional dependency x→a functional dependency x'→a also holds x strict subset x elementary key key x x→a elementary functional dependency attribute a. eknf defined carlo zaniolo 1982 example table whose highest normal form eknf see boyce–codd normal form achievability bcnf
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Databases
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win32s win32s 32-bit application runtime environment microsoft windows 3.1 3.11 operating systems allowed 32-bit applications run 16-bit operating system using call thunks beta version win32s available october 1992 version 1.10 released july 1993 simultaneously windows nt 3.1 win32s intended partial implementation win32 windows api existed early versions windows nt win32s signifies subset win32s lacked number windows nt functions including multi-threading asynchronous i/o newer serial port functions many gdi extensions generally limited win32s applications specifically designed win32s platform although standard win32 programs would work correctly including microsoft 3d pinball space cadet windows 95 included applets office 95 early versions internet explorer version 5 also win32s compatible although also existed 16-bit format generally 32-bit application compatible win32s use 16mb memory extended features directx win32s inherits many limitations win16 environment true win32 applications execute within private virtual address space whereas windows 3.x used address space shared among running applications application running win32s shared address space cooperative multitasking characteristics windows 3.1 consequently win32 application run win32s must contain relocation information technique named thunking fundamental implementation win32s well chicago-kernel operating systems windows 95 windows 98 windows however allowing user-level thunking greatly complicates attempts provide stable memory management memory protection system-wide basis well core kernel security—this allows poorly written applications undermine system stability win32s well chicago-kernel systems stability security windows nt offer partially based thunking illegal except thunks win16 win32—the cpu must remain protected mode times windows xp later 32-bit versions windows transparently provide virtual machine running win16 applications although feature removed 64-bit versions windows win32s-compatible applications could built using microsoft development tools well least borland c++ 4.x however several program compilation options dlls implicit windows nt 3.1 included application win32s microsoft ceased support win32s visual c++ version 4.2 released late 1996 win32s included implementation card game freecell example application couple years game became famous inclusion windows 95 dos game included level editor required win32s run editor used windows gui displaying large maps high-resolution graphic modes already handled windows ncsa mosaic web browser version 2 also required win32s win32s still found using web search engines pw1118.exe generally installation file used developers ensure installing ole require consistent clipboard handling many applications need made ole aware i.e setting ole server must reinstalled win32s also included early win32 programs
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Operating systems
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screenos screenos real-time embedded operating system netscreen range hardware firewall devices juniper networks beside transport level security screenos also integrates flow management applications december 2015 juniper networks announced found unauthorized code screenos since august 2012 two backdoors created would allow sophisticated hackers control firewall un-patched juniper netscreen products decrypt network traffic least one backdoors appeared likely effort governmental interest speculation security field whether nsa many security industry praised juniper transparent breach wired speculated lack details disclosed intentional use random number generator known security flaws could suggest planted intentionally 2011 leaked nsa document says gchq current exploit capability following screenos devices ns5gt n25 ns50 ns500 ns204 ns208 ns5200 ns5000 ssg5 ssg20 ssg140 isg 1000 isg 2000 exploit capabilities seem consistent program codenamed feedtrough
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Operating systems
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opentg opentg open-source implementation bulletin board system bbs software program written linux and/or unix written scratch jruby goal reproduce look feel functionality similar legacy bbs systems tag telegard maximus renegade written dos os/2 pre-internet communication era original code bbs used referenced order focus innovation unique capabilities august 17 2008 project founded chris tusa work toward version 1 code year later development branch known opentg/1 ended back-end configuration tool taken shape using ncurses library database abstraction using ruby-dbi postgresql backend database engine developer deemed version code failure due problems maintaining ncurses screen layouts sql queries dbi lessons learned upfront design planning iteration two known simply opentg heavy development code moved mri ruby jruby running openjdk latest code introduces status goal information available project homepage following listing software components used telegard/2 following tested operating system platforms used developers project founded currently led chris tusa hosted bitbucket uses mercirual source code control snapshots cloned github downloadable tarballs made available various intervals testing.. developers find information contributing project website
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Internet protocols
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2009 sidekick data loss sidekick data outage 2009 resulted estimated 800,000 smartphone users united states temporarily losing personal data emails address books photos mobile handsets computer servers holding data run microsoft brand phone affected danger hiptop also known sidekick connected via t-mobile cellular network time described biggest disaster cloud computing history sidekick smartphones originally produced danger inc. company bought microsoft february 2007 acquisition former danger staff absorbed mobile communications business mcb entertainment devices division microsoft worked future microsoft mobile phone platform known project pink however ex-danger employees soon left microsoft pursue things microsoft took running data servers data centers hosting customers data time lost friday october 2 2009 t-mobile sidekick phone users started noticing data service outages occurring outages lasted approximately two weeks october 10 2009 t-mobile announced personal information stored sidekick phones would permanently lost turned incorrect according financial times microsoft said data center acquired danger 18 months previously updated run microsoft technology company statement said mishap due confluence errors server failure hurt main backup databases supporting sidekick users t-mobile blamed microsoft loss data incident caused public loss confidence concept cloud computing plagued series outages data losses 2009 also problematic microsoft time trying convince corporate clients use cloud computing services azure phone october 14 2009 class action lawsuit launched microsoft t-mobile lawsuit alleged t-mobile microsoft promised safeguard important data customers possess apparently failed follow even basic data protection principles unthinkable day age class action lawsuit settled 2011 affected users compensated 35 t-mobile gift card 17.50 check payment 12 free downloadable items october 15 microsoft said able recover data would begin restore microsoft ceo steve ballmer disputed whether data loss instead describing outage ballmer said “ clear data loss however said incident good microsoft even data loss danger marketed application windows computers would back sidekick data onto user computer also allow changes made re-downloaded sidekick real-time users backup storage option able save data united states t-mobile marketed application one-time charge 10 immediately data restored users t-mobile incorporated sidekick storage website regular t-mobile backup site application user personal computer danger backup site t-mobile backup site could synchronized together
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Computer security
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ftrace ftrace abbreviated function tracer tracing framework linux kernel although original name function tracer came ftrace ability record information related various function calls performed kernel running ftrace tracing capabilities cover much broader range kernel internal operations various tracer plugins ftrace targeted different static tracepoints scheduling events interrupts memory-mapped i/o cpu power state transitions operations related file systems virtualization also dynamic tracking kernel function calls available optionally restrictable subset functions using globs possibility generate call graphs provide stack usage reports time ftrace used measure various latencies within linux kernel long interrupts preemption disabled ftrace-enabled linux kernel built enabling kernel configuration option entire runtime interaction ftrace performed readable writable virtual files contained specifically mounted debugfs file system result ftrace requires specialized userspace utilities operate however additional userspace utilities provide advanced features data recording analysis visualization examples utilities trace-cmd kernelshark internally ftrace relies gcc profiling mechanism prepend machine instructions compiled versions source-level kernel functions redirect execution functions ftrace trampolines tracer plugins perform actual tracing entry point instructions created gcc altered ftrace kernel booted varied later runtime ftrace nops actual jumps tracing trampolines depending tracing types options configured runtime ftrace developed primarily steven rostedt merged linux kernel mainline kernel version 2.6.27 released october 9 2008
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Operating systems
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robert škulj robert škulj born 1975 slovenian hacker discovered security hole banking e-commerce system called klik year 2002 offered nlb bank sell exploit trojan horse designed empty victim account countermeasures bank reacted denouncing pressing charges illegal breaking systems charges soon dropped court škulj announced intends sue bank state seizing software discovered dead august 2003 apartment city tržič apparently committing suicide shooting death cloud suspicion looms boris floricic death
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Computer security
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logparser logparser flexible command line utility initially written gabriele giuseppini microsoft employee automate tests iis logging intended use windows operating system included iis 6.0 resource kit tools default behavior logparser works like data processing pipeline taking sql expression command line outputting lines containing matches sql expression microsoft describes logparser powerful versatile tool provides universal query access text-based data log files xml files csv files well key data sources windows operating system event log registry file system active directory results input query custom-formatted text based output persisted specialty targets like sql syslog chart common use example selecting date time client username accessing aspx-files taken .log-files current directory
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Computer security
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kmldonkey kmldonkey graphical frontend mldonkey powerful p2p file sharing tool designed kde desktop key features kmldonkey 2.0.7 released together kde software compilation 4 within extragear-tarball
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Internet protocols
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ip fragmentation attack ip fragmentation attacks kind computer security attack based internet protocol ip requires data transmitted processed specifically invokes ip fragmentation process used partition messages service data unit sdu typically packet one layer network multiple smaller payloads fit within lower layer protocol data unit pdu every network link maximum size messages may transmitted called maximum transmission unit mtu sdu plus metadata added link layer exceeds mtu sdu must fragmented ip fragmentation attacks exploit process attack vector part tcp/ip suite internet protocol ip resides internet layer model ip responsible transmission packets network end points ip includes features provide basic measures fault-tolerance time live checksum traffic prioritization type service support fragmentation larger packets multiple smaller packets id field fragment offset support fragmentation larger packets provides protocol allowing routers fragment packet smaller packets original packet large supporting datalink frames ip fragmentation exploits attacks use fragmentation protocol within ip attack vector according kurose 2013 one type ip fragmentation attack attacker sends stream small fragments target host none offset zero target collapse attempts rebuild datagrams degenerate packets another attack involves sending overlapping fragments non-aligned offsets render vulnerable operating systems knowing causing crash ip packets encapsulated datalink frames therefore link mtu affects larger ip packets forces split pieces equal smaller mtu size accomplished several approaches three fields ip header used implement fragmentation reassembly identification flags fragment offset fields flags fragment offset specifies fragment position within original packet measured 8-byte units accordingly every fragment except last must contain multiple 8 bytes data obvious fragment offset hold 8192 2^13 units packet ca n't 8192 8 65,536 bytes data total length field ip header records total size including header data ip header least 20 bytes long maximum value fragment offset restricted 8189 leaves room 3 bytes last fragment ip internet connectionless fragments one packet may interleaved another destination identification field uniquely identifies fragments particular packet source system sets identification field packet unique value packets use source ip address destination ip address protocol values lifetime packet internet way destination distinguish incoming fragments belong unique packet buffer last fragment received last fragment sets fragment bit 0 tells receiving station start reassembling data fragments received following real-life fragmentation example following obtained using ethereal protocol analyzer capture icmp echo request packets simulate open terminal type ping ip_dest -n 1 -l 65000 results follows codice_1 note first fragment contains icmp header remaining fragments generated without icmp header two important points network infrastructure equipment routers load-balancers firewalls ids inconsistent visibility fragmented packets example device may subject initial fragment rigorous inspection auditing might allow additional fragments pass unchecked attacks may use fact evade detection placing incriminating payload data fragments devices operating full proxy mode generally susceptible subterfuge
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Computer security
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list tcp udp port numbers list tcp udp port numbers used protocols internet protocol suite operation network applications transmission control protocol tcp user datagram protocol udp needed one port full-duplex bidirectional traffic stream control transmission protocol sctp datagram congestion control protocol dccp also use port numbers usually use port numbers match services corresponding tcp udp implementation exist internet assigned numbers authority iana responsible maintaining official assignments port numbers specific uses however many unofficial uses well-known registered port numbers occur practice similarly many official assignments refer protocols never longer common use article lists port numbers associated protocols experienced significant uptake port numbers range 0 1023 0 2 − 1 well-known ports system ports used system processes provide widely used types network services unix-like operating systems process must execute superuser privileges able bind network socket ip address using one well-known ports range port numbers 1024 49151 2 2 2 − 1 registered ports assigned iana specific service upon application requesting entity systems registered ports used without superuser privileges range 49152–65535 2 2 2 − 1 contains dynamic private ports registered iana range used private customized services temporary purposes automatic allocation ephemeral ports
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Internet protocols
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pc-lisp pc-lisp implementation franz lisp dialect peter ashwood-smith version 2.11 released may 15 1986 current version may downloaded external link currently pc-lisp ported 32 64 bit linux mac windows note franz lisp dialect immediate portable successor version maclisp perhaps closest thing lisp steven levy book practical operate pc-lisp runs well dos emulators modern windows versions pc-lisp implements franz lisp dynamically scoped predecessor modern common lisp therefore historically important implementation session running following code demonstrates dynamic scoping franz lisp note pc-lisp implement codice_1 special form emacs lisp provides local variables instead variables algol-based language would call global first dialect lisp incorporate algol scoping rules called lexical scoping scheme although common lisp language also added feature another example showing use backquote power lisp differentiation example
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Programming language topics
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cybergraphx cybergraphx pronounced cybergraphics standard retargetable graphics api available amiga compatible systems developed thomas sontowski frank mariak later adopted phase5 use graphics cards many graphics card manufacturers offered hardware amiga compatible systems used well latest version cybergraphx v5 used morphos features include original cybergraphx software amigaos longer actively maintained cybergraphx v4 last release platform far aros implements cybergraphx v4 compatible api alternative rtg apis picasso 96 enhanced graphics system first used amigaos4 implements cybergraphx v4 api v5 extensions 2560×1600 running dual-link dvi example radeon 9650 256 mb
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Operating systems
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nokia e51 nokia e51 symbian os smartphone nokia announced 18 september 2007 replacement nokia e50 business-focused eseries line second nokia umts hsdpa dual band device phone available black silver bronze-coloured border backplate slim body made stainless steel 12 mm thick 100 g weight smallest nokia smartphone time yet still technologically capable like s60 devices time version without integrated camera also existed e51 highly acclaimed succeeded nokia e52 br
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Operating systems
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justniffer justniffer tcp packet sniffer log network traffic 'standard web server-like customized way also log response times useful tracking network services performances e.g web server application server etc. output format traffic easily customized example written python delivered official package stores transferred contents output directory separated domains means transferred files like html css javascript images sounds etc saved directory justniffer born help troubleshooting performance network tcp-based services http rtsp sip smtp imap pop ldap telnet etc collect low high level protocol performance information reconstructing tcp flow reliable way using portions linux kernel code uses slightly modified version libnids libraries already include modified version linux kernel code reusable way extended external scripts bash python executable generate logs customizable way man page justniffer explains options
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Computer security
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parasoft virtualize parasoft virtualize service virtualization product create deploy manage simulated test environments software development software testing purposes environments simulate behavior dependent resources unavailable difficult access difficult configure development testing simulates behavior dependent resources mainframes erp systems databases web services third-party information systems systems direct developer/tester control product used conjunction hardware/os virtualization provide developers testers resources need execute development testing tasks earlier faster completely technologies automating continuous testing used part continuous delivery continuous integration continuous release 2002 parasoft released technology create service implementation stubs emulate critical functionality made available testing. technology introduced parasoft soatest since 2002 technology extended intelligent stubs emulate behaviour running system allowing developer test services context application actual behaviour live running system. 2009 technology extended application behavior virtualization create copies applications back-end systems developer reference applications systems developing software technology extended released separate product 2011 parasoft created free community edition 2017 allows individual users small projects use service virtualization cost parasoft virtualize awarded 2012 jolt awards grand prize panel dr. dobb journal-appointed judges annual award showcases products jolted industry significance made task creating software faster easier efficient recent awards/recognitions received named leader functional test automation tools forrester functional test automation tools evaluation innovation technology leader voke service virtualization market mover array
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Web technology
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elastichosts elastichosts computer service provider based london england founded provides cloud computing service provided ten data centres united kingdom two sites netherlands united states four sites canada hong kong australia elastichosts privately held competes public cloud-infrastructure providers amazon elastic compute cloud rackspace cloud according ceo richard davies company aims provide servers set similar possible one would provision dedicated hosting exception customer self-serve time elastichosts eu hosting data centres uk ireland first public cloud service built linux kernel-based virtual machine rather xen api given good review rest perspective charges resources cpu memory disk network separate entities allowing customers build virtual machines widely different characteristics instead simply categorized ones small medium large instances elastichosts therefore licensees supported directly boxgrinder included fedora 15 may 2011 elastichosts cloud servers available ten data centres san jose los angeles dallas miami maidenhead uk portsmouth uk amsterdam toronto hong kong sydney elastichosts persistent storage based local host store however 2012 announced solid-state drives ssd instance sizes use storage area network instead directly attached raid arrays iscsi interconnects hosts 2011 ceo predicted greater demand storage elastichosts two types ipv4 addresses static dynamic allocated pools addresses static addresses kept account allocated account server time dynamic ones randomly allocated server specifically allocated static ip address guaranteed remain though remain lifespan instance shutdown virtual machine may may reallocate ip address elastichosts lock static ip server instance reallocated control panel reverse dns managed customer control panel elastichosts announced 14 april 2014 addition maintaining traditional cloud vm business releasing alternate type server based linux running within containers implementation similar chroot bsd jails uses advanced linux kernel control groups feature company deemed mature enough use basis new type cloud server launched name elastic containers claiming world first terms virtualization company currently offers versions debian ubuntu centos though nature containers run host linux kernel containers new technology cgroups features first begun added linux kernel 2007 companies docker inc. producing software uses virtualize applications claimed first time iaas provider used technology full operating system use various press articles focused newly released pay go billing option whereby container optionally billed actual usage opposed fixed instance size 15 minute increments common industry standard 1 hour time blocks cloud server rentals particular ceo claim customers could save 50 traditional costs using service analysts expressed confidence container based systems future cloud providers given fiercely competitive nature cloud pricing days ’ hard see containers ’ become dominant mechanism delivering cloud services though others wondered whether would actually pull customers dominating players market owen rogers senior analyst digital economics 451 research noted though “ interesting unique ” model give elastichosts advantage ... rest market ... still based virtual machines can¹t see changing overnight ” wondered whether ... consumers really care elastichosts ’ detailed – arguably fairer – method pricing bigger competitors slashing prices elastichosts acquired paragon internet group april 2016 paragon acquired host europe group late 2015 host europe group acquired godaddy december 2016 meaning elastichosts ultimately subsidiary godaddy
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Distributed computing architecture
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comspec comspec comspec one environment variables used dos os/2 windows normally points command line interpreter default command.com dos cmd.exe os/2 windows nt variable name written all-uppercase dos os/2 windows also supports lowercase environment variable names variable name comspec inside dos emulator ntvdm dos programs comspec cmd.exe variable contents displayed typing set comspec echo comspec command prompt environment variable default points full path command line interpreter also made different company different version
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Operating systems
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iris workspace iris workspace graphically organized iconic desktop environment allowed access irix file system along simplified system administration via system manager iris workspace used silicon graphics 4d1-3.0 irix 5.0 succeeded 1993 indigo magic desktop introduced irix 5.1 indy workstation
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Computer architecture
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socket 478 socket 478 also known mpga478 mpga478b 478-contact cpu socket used intel pentium 4 celeron series cpus socket 478 launched northwood core compete amd 462-pin socket athlon xp processors socket 478 intended replacement socket 423 willamette-based processor socket market short time socket 478 phased launch lga 775 2004 socket 478 used northwood pentium 4 celeron processors supported first prescott pentium 4 processors willamette celerons along several willamette-series pentium 4s socket 478 also supported newer prescott-based celeron processors early pentium 4 extreme edition processors 2 mib l3 cpu cache celeron processors also available socket 478 last cpus made socket intel mobile cpus available 478-pin packages fact operate range slightly differing sockets socket 479 socket socket p incompatible two socket 478 used combination ddr sdram socket pentium 4 celeron following mechanical maximum load limits exceeded heatsink assembly shipping conditions standard use load limits crack processor die make unusable see list intel chipsets pentium 4 chipsets
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Computer architecture
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qotd quote day qotd service member internet protocol suite defined rfc 865 indicated qotd concept predated specification qotd used mainframe sysadmins broadcast daily quote request user formally codified prior purposes well testing measurement purposes host may connect server supports qotd protocol either tcp udp port 17 keep quotes reasonable length rfc 865 specifies maximum 512 octets quote although sources indicate qotd service rarely enabled case often firewalled avoid 'pingpong attacks interest continues pre-existing purpose serving quotes seen web engine searches current testing measurement ip networks commonly done ping traceroute robust adaptations echo protocol rfc 862 predated attempt qotd standardization
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Internet protocols
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elegant degradation elegant degradation term used engineering describe occurs machines subject constant repetitive stress externally machine maintains appearance user appearing function properly internally machine slowly weakens time eventually unable withstand stress eventually breaks compared graceful degradation operational quality decrease breakdown may sudden term meaning varies depending context field may strictly considered exclusive engineering instance used mechanism food industry applied degradation lignin cellulose pentosan polymers among others concept also used extract chemicals elegant degradation paederus fuscipes obtain pederin hemiacetal pseuodopederin process degradation induced heat play name also used metaphor current state world
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Computer security
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objectivefs objectivefs distributed file system developed objective security corp posix-compliant file system built object store backend initially released aws s3 backend later implemented support google cloud storage object store devices released beta early 2013 first version officially released august 11 2013 objectivefs implements log structured file system top object stores amazon s3 google cloud storage object store devices posix compliant file system supports features dynamic file system size soft hard links unix attributes extended attributes unix timestamps users permissions limit file size atomic renames atomic file creation directory renames read write anywhere file named pipes sockets etc implements client-side encryption uses nacl crypto library algorithms like salsa20 poly1305 approach n't data-dependent branches data-dependency array indices protects cache timing attacks data encrypted leaving client stays encrypted rest motion one main difference objectivefs glusterfs/cephfs offloads storage cluster management cloud providers amazon/google objectivefs software runs server talks object store using s3 api software handles metadata multiple servers sharing files handles negotiation sharing servers also running objectivefs use cases scaling web servers mail servers content management services cms hybrid cloud. hybrid development environment laptop cloud
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Computer file systems
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koomey law koomey law describes trend history computing hardware half-century number computations per joule energy dissipated doubled every 1.57 years professor jonathan koomey described trend 2010 paper wrote fixed computing load amount battery need fall factor two every year half trend remarkably stable since 1950s r 98 2011 koomey re-examined data found 2000 doubling slowed every 2.6 years related slowing moore law ability build smaller transistors end around 2005 dennard scaling ability build smaller transistors constant power density difference two growth rates substantial doubling every year half results 100-fold increase efficiency every decade doubling every two half years yields 16-fold increase koomey wrote implications koomey law amount battery needed fixed computing load fall factor 100 every decade computing devices become smaller mobile trend may even important improvements raw processing power many applications furthermore energy costs becoming increasing factor economics data centers increasing importance koomey law slowing koomey law implications energy use information communications technology however computers run peak output continuously effect slowing may seen decade koomey writes exponential trend one eventually end ... decade energy use dominated power consumed computer active active power still hostage physics behind slowdown moore ’ law. koomey lead author article ieee annals history computing first documented trend time koomey published short piece ieee spectrum discussed mit technology review post erik brynjolfsson “ economics information ” blog economist online trend previously known digital signal processors named gene law name came gene frantz electrical engineer texas instruments frantz documented power dissipation dsps reduced half every 18 months 25 year period latest studies indicate koomey law slowed doubling every 2.6 years second law thermodynamics landauer principle irreversible computing continue made energy efficient forever 2011 computers computing efficiency 0.00001 assuming energy efficiency computing continue double every 1.57 years landauer bound reached 2048 thus 2048 koomey law longer hold landauer principle however applicable reversible computing 'beyond cmos future computing technologies as-yet undeveloped would represent entirely new efficiencies beyond koomey law
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Computer architecture
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nespos nespos open source information platform pleistocene humans providing detailed information important sites analytical results archaeological findings selection literary quotes moreover repository archaeologists paleoanthropologists exchange research results ideas protected wiki-based collaboration platform continuously growing sample 3d scanned human fossils artefacts nespos developed eu-funded project tnt designed interactive online database containing long run available anthropological archaeological data related neanderthals e.g computed tomography ct 3d surface scans neanderthal fossils artefacts well additional data like scanned literature images tables tnt specific targeted research innovation project eu “ digicult ” program facilitates research preservation work europe ’ artistic cultural treasures using modern technology involved project art+com company interactive media technology berlin pxp software austria gmbh e-business company austria hasso-plattner institute potsdam germany royal belgian institute natural sciences brussels university poitiers france natural history museum croatia neanderthal museum mettmann national geographic germany using wiki-functionality nespos users able upload data add comments colleagues ’ entries metadata search provides efficient tool content retrieval addition software 3d 2d visualisation digitised finds well geographic information excavation sites integrated part system since march 2006 nespos open scientific community 2008 nespos underwent updating open kinds data human evolution data homo erectus homo heidelbergensis australopithecus africanus already uploaded another huge updating process started april 2009 nespos open user important 3d-datasets stored spezialed space entered scientific members society visicore suite nespos 3d applications conjoint visual simulation collaborative rendering engine visicore suite provides archaeological visualisation annotation tools two main components artecore artefact exploration collaboration rendering engine provides toolset real-time 2d 3d visualisation routines examination remains ‘ virtual high resolution-representations geocore site mapping rendering engine provides mapbased geo information system presenting exploring editing archaeological excavation data real-time 3d perspective
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Web technology
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list x86 manufacturers x86-compatible processors designed manufactured sold number companies including past past past past
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Computer architecture
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abstract-type scheme-definition language asdl also common misspelling adsl abstract-type scheme-definition language asdl computer language developed part esprit project graspin basis generating language-based editors environments combines object-oriented type system syntax-directed translation schemes target-language interface
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Programming language topics
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xml enabled directory xml enabled directory xed framework managing objects represented using extensible markup language xml xed builds x.500 ldap directory services technologies xed originally designed 2003 steven legg enitiatives formerly eb2bcom adacel technologies daniel prager formerly deakin university xml enabled directory xed framework leverages existing lightweight directory access protocol ldap x.500 directory technology create directory service stores manages transmits extensible markup language xml format data maintaining interoperability ldap clients x.500 directory user agents duas x.500 directory system agents dsas main features xed xml enabled directory allows directory entries contain xml formatted data attribute values furthermore attribute syntax specified one variety xml schema languages directory understands directory server able perform data validation semantically meaningful matching xml documents parts behalf client applications making implementation xml-based applications easier faster xml applications also exploit directory traditional capabilities cross-application data sharing data distribution data replication user authentication user access control lowering cost building new xml applications xed implementations enitiatives viewds discovery server provides organisations fast scalable flexible directory system developed strictly adhering open standards features support x.500 ldap xed acp133 standards standards compliant viewds interface variety applications future
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Internet protocols
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cerberus ftp server cerberus ftp server windows-based ftp server support encrypted ftp sessions via ftps sftp well web client support via http https server exposes files using virtual file system supports user authentication via built-in users groups active directory ldap public key authentication server currently developed supported cerberus llc
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Internet protocols
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safersurf safersurf software product anonymous internet surfing aside offering web anonymity several features geolocation proxy service bypassing country restrictions safersurf runs centrally server n't need local installation safersurf created developed team nutzwerk german software company headquartered leipzig developing internet technologies obtained tüv certification 2005 2006 2007 2008 2009 tested wide range viruses false alarms safersurf provides various features safersurf released 2003 media praised speed hamburger abendblatt wrote surf ten times faster virus-free service offered company nutzwerk ... even slow modem connection data reaches goal faster ... pocket pc magazine wrote indeed assistance safersurf speed web pages display three times faster ... safersurf speed works independently isp internet connection standard modem isdn dsl mobile communications lan etc use media gave weight anonymity protection bild computer magazine tested several web anonymity programs cited reliable anonymization among advantages safersurf year macworld praised spam-filtering service
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Computer security
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inside–outside–beginning tagging iob format short inside outside beginning common tagging format tagging tokens chunking task computational linguistics ex named-entity recognition presented ramshaw marcus paper text chunking using transformation-based learning 1995 b- prefix tag indicates tag beginning chunk i- prefix tag indicates tag inside chunk b- tag used tag followed tag type without tokens tag indicates token belongs chunk another similar format widely used iob2 format iob format except b- tag used beginning every chunk i.e chunks start b- tag readable introduction entity tagging given bob carpenter blog post coding chunkers taggers 'bio plausibly synonym 'iob example iob format example iob2 format related tagging schemes sometimes include start/end consists tags b e used represent chunk containing single token chunks length greater equal two always start b tag end e tag tagging scheme include bioes/bilou e l denotes last ending character sequence denotes single element example bioes format
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Computational linguistics
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list songs singstar games playstation 2 following list singstar games released playstation 2 video game console tables list songs available game country availability indicated two-letter country codes games localised multiple markets songs either indicated present yes absent track list region first game series singstar released europe oceania 2004. twenty games singstar series released english-speaking territories including small number north america singstar games loosely based upon musical genres rock pop music singstar rocks singstar pop respectively artist-specific singstar games released featuring artists abba queen take die toten hosen kent mecano non-english releases table tracklist uk non-english releases tracklist uk releases tracklist uk releases tracklist uk australian new zealand game singstar catalogues
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Computer architecture
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trantor last stormtrooper trantor last stormtrooper video game zx spectrum commodore 64 msx amstrad cpc atari st released go label u.s. gold 1987 version ms-dos released keypunch software produced probe software team consisted david quinn nick bruty david perry released spain trantor erbe software game mix shoot 'em platform game mostly known large well-animated sprites bruty previously produced graphics within tight limits projects decided instead focus artwork keep aspects game simple fit constraints platforms player controls titular stormtrooper survivor destruction spaceship hence title gameplay revolves around exploring play-area collecting code-letters play-area consists several different floors explored freely via connecting lifts however trantor strict time limit levels infested various aliens small flying robots sap trantor strength touches fortunately trantor armed flamethrower destroy pests unfortunately fuel limited although re-fill fuel-points located many floors whenever trantor finds code-letter timer countdown reset counts finds another letter reason much gameplay race-against-time also lockers scattered around floors contain pick-ups assist trantor include hamburgers restore strength clocks reseting time finding code letter would game ends trantor energy runs timer reaches zero player performance shown percentage game completed along short comment comment nine percent fergus referring probe co-founder fergus mcgovern history trantor widely known short backstory included manual amstrad version game manual explains trantor served stormtrooper front lines interstellar war war trantor mistakenly killed infant flamethrower game action takes place trantor troubled mind fights fictional base attempting collect remnants soul enemies represent varying aspects psychosis player eventual death dooms trantor life despondency trantor unusual time featuring animated opening-sequence loading shown main options screen shows trantor ship animated radars slowly dropping shaft landing title character emerges seen beckon others join ship suddenly disintegrates leaving alone trantor generally received positive reviews sinclair giving 9/10 calling wonderful entertainment worth much asking price sinclair user tom dillon described main character animation realistic seen 8-bit computer gave game 10/10 crash hand said excellent presentation graphics conceal shallow gameplay gave overall 68
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Computer architecture
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biometrics use south african government biometric part attempts reduce incidences fraud corruption well deliver efficient services citizens south african government embarking program employing biometric identification systems certain programs instances south african government started implementing biometrics program following departments department agriculture head office pretoria identified need implement stringent system control mechanisms including financial system logging onto secure applications logging onto staff members personal workstations department applied strict password management policy different systems finance persal government standard salary payment system leave performance management etc regulated constant changing passwords resulted forgotten passwords lock-outs employees sitting next access one another passwords resulted downtime administrative burden staff pressing concerns increased opportunity costs also noticed unauthorized individuals after-hours access facilities department implemented fingerprint biometric reader computers eliminated passwords altogether furthermore readers also installed key access control points meant staff could n't log machines n't first gain access control points also meant staff could regulated hours supposed working allowed work system automatically logged computer 'clocked work area meant less wastage stricter security thus implementation biometric system ensures superior security measures ease use centralized databank access control information fact staff n't need carry access control instruments work except fingers part strive increase security reduce corruption within facilities department correctional services launched biometric security system august 2006 system included fingerprint access closed circuit television systems turnstile gates department recognized system would effective staff members would fully committed well-trained operating system included proactive monitoring form risk well acting promptly breach security take place system grounded principle fail-over case power loss unforeseen circumstances would switch fully functioning secondary site future foreseen improvements system include closed circuit television monitoring individual cell amongst others south africa approximately 48 million citizens one requires government-issued official identification booklet proof identity document needed public services also everyday actions renting dvd opening bank store account document based secure form identification individual fingerprint need undeniable process time consuming paper based resulted government archives contain 45 million paper files home affairs national identification system project known hanis implemented move away paper system would hanis replace existing system world class digital database also ensure real time processing verification accessibility every new existing fingerprint nec automatic fingerprint identification system afis selected offer solution south african government needed fingerprint recognition technologies host accuracy rate 99.9 system works fast process many 70,000 searches one day allows hanis produce largest citizen identification database world department home affairs however faced quite number challenges ensure successful complete implementation project data integrity compromised duplicated and/or missing data elements data inconsistency lack security around data stores led fraud corruption furthers contaminated data integrity relational linkages formalised different data-stores npr hanis edms shows little relational integrity immigration data stores based expired light-weight pc based technologies immigration visitor data shows integrated cohesive structure segmented data stores refugees deportation asylum seekers visitors visas movement control department working address issues benefits sight however paperless environment shorter queues reduction bureaucratic delays accuracy system dramatically reduce possibility identity theft fraud south african police service saps implemented biometric system 2001 secure integrated justice system ijs finger- palm prints convicted criminals captured automated fingerprint identification system afis – database used identity management idm used monitor criminals well track wanted criminals portable readers powered sagem morphotouch rapid technology used roadblocks around country identify wanted criminals bring justice afis implemented ideco group also completed hanis system discussed additional uses biometrics police services fingerprint readers fake fingerprint detection functionality access control departments secure sensitive information e.g forensic laboratories stolen vehicle departments etc. fingerprints also used sole method criminal record background checks commercial purposes – use name surname identification number much potential abuse system failure led much fraud full set fingerprints required criminal record check done individual companies want make use service called afiswitch enrolled afis service significantly faster turnaround time 48 hours opposed weeks traditional system checking criminal records south africa social assistance program government largest poverty alleviation intervention budget allocation approximately r100 billion provides social grants 15,8 million beneficiaries reduce levels deprivation enable participate economy budget vote speech 2 may 2012 minister social development bathabile dlamini conceded south african social security agency sassa incomplete information beneficiary details social grant system prone fraud misappropriation funds country social assistance touches high proportion citizens incorporates dealing enormous monetary amounts fraud misappropriation funds slap face truly need tolerated part strategy address problem sassa announced social assistance beneficiaries re-registered biometric enrollment system following enrollment biometric system analyse physical behavioural traits fingerprints iris face voice hand geometry verify identity beneficiary system allow effective authentication beneficiaries drastically reduce opportunities fraud sassa process implementing system phase 1 already completed biometric identification systems however fool proof accurately functioning systems rely two fundamental premises – permanence uniqueness relevant biometric trait certain furthermore may problems extracting biometric traits – example system environmental problems recent years significant growth biometric research resulted advancements field accurate cost effective secure robust biometric systems developed – hoped allow effective implementation system sassa main reasons implementing biometrics system south african government seem eradication crime corruption enhancing service delivery citizens country problems faced expected poor infrastructure lack funds perseverance however government able succeed efforts becoming effective use biometrics
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Databases
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tcp congestion control transmission control protocol tcp uses network congestion-avoidance algorithm includes various aspects additive increase/multiplicative decrease aimd scheme schemes slow start congestion window achieve congestion avoidance tcp congestion-avoidance algorithm primary basis congestion control internet per end-to-end principle congestion control largely function internet hosts network several variations versions algorithm implemented protocol stacks operating systems computers connect internet avoid congestive collapse tcp uses multi-faceted congestion-control strategy connection tcp maintains congestion window limiting total number unacknowledged packets may transit end-to-end somewhat analogous tcp sliding window used flow control tcp uses mechanism called slow start increase congestion window connection initialized timeout starts window small multiple maximum segment size mss size although initial rate low rate increase rapid every packet acknowledged congestion window increases 1 mss congestion window effectively doubles every round-trip time rtt congestion window exceeds slow-start threshold ssthresh algorithm enters new state called congestion avoidance congestion avoidance state long non-duplicate acks received congestion window additively increased one mss every round-trip time tcp congestion window one factors determines number bytes outstanding time congestion window maintained sender note confused sliding window size maintained receiver congestion window means stopping link sender receiver becoming overloaded much traffic calculated estimating much congestion link connection set congestion window value maintained independently host set small multiple mss allowed connection variance congestion window dictated aimd approach means segments received acknowledgments reach sender time constant added window size window reaches ssthresh congestion window increases linearly rate 1/ congestion window segment new acknowledgement received window keeps growing timeout occurs timeout system administrator may adjust maximum window size limit adjust constant added additive increase part tcp tuning flow data tcp connection also controlled use receive window advertised receiver comparing congestion window receive window sender determine much data may send given time slow start part congestion control strategy used tcp conjunction algorithms avoid sending data network capable forwarding avoid causing network congestion algorithm specified rfc 5681 although strategy referred slow start congestion window growth quite aggressive aggressive congestion avoidance phase slow start introduced tcp initial pre-congestion avoidance phase even faster slow start begins initially congestion window size cwnd 1 2 4 10 mss value congestion window size increased one acknowledgement ack received effectively doubling window size round-trip time transmission rate increased slow-start algorithm either loss detected receiver advertised window rwnd limiting factor ssthresh reached loss event occurs tcp assumes due network congestion takes steps reduce offered load network measurements depend exact tcp congestion avoidance algorithm used ssthresh reached tcp changes slow-start algorithm linear growth congestion avoidance algorithm point window increased 1 segment round-trip delay time rtt slow start assumes unacknowledged segments due network congestion acceptable assumption many networks segments may lost reasons poor data link layer transmission quality thus slow start perform poorly situations poor reception wireless networks slow start protocol also performs badly short-lived connections older web browsers would create many consecutive short-lived connections web server would open close connection file requested kept connections slow start mode resulted poor response time avoid problem modern browsers either open multiple connections simultaneously reuse one connection files requested particular web server connections however reused multiple third-party servers used web sites implement web advertising sharing features social networking services counter scripts web analytics additive increase/multiplicative decrease aimd algorithm closed-loop control algorithm aimd combines linear growth congestion window exponential reduction congestion takes place multiple flows using aimd congestion control eventually converge use equal amounts contended link fast retransmit enhancement tcp reduces time sender waits retransmitting lost segment tcp sender normally uses simple timer recognize lost segments acknowledgement received particular segment within specified time function estimated round-trip delay time sender assume segment lost network retransmit segment duplicate acknowledgement basis fast retransmit mechanism receiving packet e.g sequence number 1 receiver sends acknowledgement adding 1 sequence number i.e acknowledgement number 2 indicates sender receiver received packet number 1 expects packet number 2 suppose three subsequent packets lost next packets receiver sees packet numbers 5 6 receiving packet number 5 receiver sends acknowledgement still sequence number 2 receiver receives packet number 6 sends yet another acknowledgement value 2 duplicate acknowledgement occurs sender receives one acknowledgement sequence number 2 example sender receives several duplicate acknowledgements reasonably confident segment next higher sequence number dropped sender fast retransmit retransmit packet immediately without waiting timeout naming convention algorithms may originated 1996 paper kevin fall sally floyd following one possible classification according following properties well-known congestion avoidance mechanisms classified scheme follows tcp tahoe reno algorithms retrospectively named 4.3bsd operating system june 1986 first appeared named lake tahoe nearby city reno nevada tahoe algorithm first appeared 4.3bsd-tahoe made support cci power 6/32 tahoe minicomputer made available non-at licensees part 4.3bsd networking release 1 ensured wide distribution implementation improvements made 4.3bsd-reno subsequently released public networking release 2 later 4.4bsd-lite consider retransmission timeout rto duplicate acks packet loss events behavior tahoe reno differ primarily react duplicate acks tahoe reno ack times rto timeout slow start used algorithms reduce congestion window 1 mss mid-1990s tcp set timeouts measured round-trip delays based upon last transmitted packet transmit buffer university arizona researchers larry peterson lawrence brakmo introduced tcp vegas named largest nevada city timeouts set round-trip delays measured every packet transmit buffer addition tcp vegas uses additive increases congestion window comparison study various tcp congestion control algorithms tcp vegas appeared smoothest followed tcp cubic tcp vegas widely deployed outside peterson laboratory selected default congestion control method dd-wrt firmware v24 sp2 tcp new reno defined rfc 6582 obsoletes previous definitions rfc 3782 rfc 2582 improves retransmission fast-recovery phase tcp reno fast recovery every duplicate ack returned tcp new reno new unsent packet end congestion window sent keep transmit window full every ack makes partial progress sequence space sender assumes ack points new hole next packet beyond acked sequence number sent timeout timer reset whenever progress transmit buffer allows new reno fill large holes multiple holes sequence space much like tcp sack new reno send new packets end congestion window fast recovery high throughput maintained hole-filling process even multiple holes multiple packets tcp enters fast recovery records highest outstanding unacknowledged packet sequence number sequence number acknowledged tcp returns congestion avoidance state problem occurs new reno packet losses instead packets reordered 3 packet sequence numbers happens new reno mistakenly enters fast recovery reordered packet delivered ack sequence-number progress occurs end fast recovery every bit sequence-number progress produces duplicate needless retransmission immediately acked new reno performs well sack low packet error rates substantially outperforms reno high error rates tcp hybla aims eliminate penalization tcp connections incorporate high-latency terrestrial satellite radio link due longer round-trip times stems analytical evaluation congestion window dynamics suggests necessary modifications remove performance dependence rtt binary increase congestion control implementation tcp optimized congestion control algorithm high speed networks high latency called lfn long fat networks rfc 1072 bic used default linux kernels 2.6.8 2.6.18 cubic less aggressive systematic derivative bic window cubic function time since last congestion event inflection point set window prior event cubic used default linux kernels versions 2.6.19 3.2 agile-sd linux-based congestion control algorithm cca designed real linux kernel receiver-side algorithm employs loss-based approach using novel mechanism called agility factor af proposed mohamed a. alrshah et al increase bandwidth utilization high-speed short-distance networks low-bdp networks local area networks fiber-optic network especially applied buffer size small evaluated comparing performance compound-tcp default cca ms windows cubic default linux using ns-2 simulator improves total performance 55 term average throughput westwood+ sender-side modification tcp reno protocol stack optimizes performance tcp congestion control wireline wireless networks tcp westwood+ based end-to-end bandwidth estimation set congestion window slow start threshold congestion episode three duplicate acknowledgments timeout bandwidth estimated properly low-pass filtering rate returning acknowledgment packets rationale strategy simple contrast tcp reno blindly halves congestion window three duplicate acks tcp westwood+ adaptively sets slow start threshold congestion window takes account bandwidth used time congestion experienced tcp westwood+ significantly increases throughput wireless links fairness compared tcp reno/new reno wired networks compound tcp microsoft implementation tcp maintains two different congestion windows simultaneously goal achieving good performance lfns impairing fairness widely deployed windows versions since microsoft windows vista windows server 2008 ported older microsoft windows versions well linux tcp proportional rate reduction prr algorithm designed improve accuracy data sent recovery algorithm ensures window size recovery close possible slow start threshold tests performed google prr resulted 3–10 reduction average latency recovery timeouts reduced 5 prr available linux kernels since version 3.2 bottleneck bandwidth round-trip propagation time bbr tcp congestion control algorithm developed google 2016 congestion control algorithms loss-based rely packet loss signal lower rates transmission bbr like vegas model-based algorithm uses maximum bandwidth round-trip time network delivered recent flight outbound data packets build explicit model network cumulative selective acknowledgment packet delivery produces rate sample records amount data delivered time interval transmission data packet acknowledgment packet network interface controllers evolve megabit per second gigabit per second performance latency associated bufferbloat instead packet loss becomes reliable marker maximum throughput making latency/model-based congestion control algorithms provide higher throughput lower latency bbr reliable alternative popular loss-based algorithms like cubic implemented within youtube bbr yielded average 4 higher network throughput 14 countries bbr also available quic available linux tcp since linux 4.9 bbr efficient fast fairness non-bbr streams disputed google presentation shows bbr co-existing well cubic researchers like geoff huston hock bless zitterbart finds unfair streams scalable hock et al also found severe inherent issues increased queuing delays unfairness massive packet loss bbr implementation linux 4.9 soheil abbasloo et al authors c2tcp show bbr n't perform well dynamic environments cellular networks also shown bbr unfairness issue instance cubic flow default tcp implementation linux android macos coexists bbr flow network bbr flow dominate cubic flow get whole link bandwidth see figure 18 cellular controlled delay tcp c2tcp motivated lack flexible end-to-end tcp approach satisfy various qos requirements different applications without requiring changes network devices c2tcp aims satisfy ultra-low latency high bandwidth requirements applications virtual reality video conferencing online gaming vehicular communication systems etc highly dynamic environment current lte future 5g cellular networks c2tcp works add-on top loss-based tcp e.g reno newreno cubic bic ... makes average delay packets bounded desired delays set applications researchers nyu showed c2tcp outperforms delay/jitter performance various state-of-the-art tcp schemes instance showed compared bbr cubic westwood average c2tcp decreases average delay packets 250 900 700 respectively various cellular network environments c2tcp required installed server-side elastic-tcp proposed february 2019 mohamed a. alrshah et al increase bandwidth utilization high-bdp networks support recent applications cloud computing big data transfer iot etc linux-based congestion control algorithm cca designed linux kernel receiver-side algorithm employs loss-delay-based approach using novel mechanism called window-correlated weighting function wwf high level elasticity deal different network characteristics without need human tuning evaluated comparing performance compound-tcp default cca ms windows cubic default linux tcp-bbr default linux 4.9 google using ns-2 simulator testbed elastic-tcp significantly improves total performance term average throughput loss ratio delay recently soheil abbasloo et al proposed natcp network-assisted tcp controversial tcp design targeting mobile edge networks mec key idea natcp characteristics network known beforehand tcp would designed better way therefore natcp employs available features properties current mec-based cellular architectures push performance tcp close optimal performance natcp uses out-of-band feedback network servers located nearby feedback network includes capacity cellular access link minimum rtt network guides servers adjust sending rates preliminary results show natcp outperforms state-of-the-art tcp schemes least achieving 2x higher power defined gained throughput/delay natcp replaces traditional tcp scheme sender deal backward compatibility issue proposed another version called nacubic using nacubic sender use arbitrary tcp schemes however nacubic employs feedback received enforce cap final congestion window required tcp new reno commonly implemented algorithm sack support common extension reno/new reno others competing proposals still need evaluation starting 2.6.8 linux kernel switched default implementation new reno bic default implementation changed cubic 2.6.19 version freebsd uses new reno default algorithm however supports number choices per-flow product bandwidth latency increases regardless queuing scheme tcp becomes inefficient prone instability becomes increasingly important internet evolves incorporate high-bandwidth optical links tcp interactive itcp allows applications subscribe tcp events respond accordingly enabling various functional extensions tcp outside tcp layer tcp congestion schemes work internally itcp additionally enables advanced applications directly participate congestion control control source generation rate zeta-tcp detects congestions latency loss rate measures applies different congestion window backoff strategies based likelihood congestions maximize goodput also couple improvements accurately detect packet losses avoiding retransmission timeout retransmission accelerate/control inbound download traffic congestion control algorithms classified relation network awareness meaning extent algorithms aware state network consist three primary categories black box grey box green box black box algorithms offer blind methods congestion control operate binary feedback received upon congestion assume knowledge concerning state networks manage grey box algorithms use time-instances order obtain measurements estimations bandwidth flow contention knowledge network conditions green box algorithms offer bimodal methods congestion control measures fair-share total bandwidth allocated flow point system execution following algorithms require custom fields added tcp packet structure
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Internet protocols
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simple api grid applications simple api grid applications saga family related standards specified open grid forum define application programming interface api common distributed computing functionality saga specification distributed computing originally consisted single document gfd.90 released 2009 saga api strive replace globus similar grid computing middleware systems target middleware developers application developers background grid computing developers typically wish devote time goals minimize time spent coding infrastructure functionality api insulates application developers middleware specification services protocols interact scope saga rather api seeks hide detail service infrastructures may may used implement functionality application developer needs api aligns however middleware standards within open grid forum ogf saga api defined mechanism specify additional api packages expand scope saga core api defines number packages job management file management replica management remote procedure calls streams saga covers important frequently used distributed functionality supported available every major grid systems extreme science engineering discovery environment xsede egi futuregrid saga supports wide range distributed programming coordination models also easily extensible support new emerging middleware saga api standardised saga working group open grid forum based set use cases saga core api specification defines set general api principles 'saga look feel set api packages render commonly used grid programming patterns job management file management access replica management etc saga core specification also defines additional api packages defined relate core api 'look feel based number api extensions defined various states standardisation process saga specifications defined flavor idl thus object oriented language neutral different language bindings exist java c++ python point standardised nevertheless different implementations language bindings relatively coherent api definition particular different java implementations share abstract api classes 'look feel part saga core api specification covers following areas saga designed object oriented interface encapsulates related functionality set objects grouped functional namespaces called packages saga saga core implementation defines following packages overall architecture saga follows adaptor pattern software design pattern used translating one interface another saga translates calls api packages interfaces underlying middleware saga run-time system uses late binding decide run-time plug-in middleware adaptor load bind following table lists distributed middleware systems currently supported saga column labeled adaptor suite names collection release package set middleware adaptors provides support middleware system since saga interface definitions bound specific programming language several implementations saga standards exist different programming languages apart implementation language differ completeness terms standard coverage well support distributed middleware saga c++ first complete implementation saga core specification written c++ currently c++ implementation active development radical-saga light-weight python package implements parts ogf gfd.90 interface specification provides plug-ins different distributed middleware systems services radical-saga implements commonly used features gfd.90 based upon extensive use-case analysis focuses usability simple deployment real-world heterogeneous distributed computing environments application scenarios radical-saga currently implements job file management core apis well resource management api extension radical-saga provides plug-ins different distributed middleware systems services including support pbs sun grid engine ssh sftp others radical-saga used develop distributed applications frameworks run distributed cyber-infrastructure including xsede loni futuregrid clouds local clusters javasaga java implementation saga status javasaga remains uncertain import java.util.io int main int argc char** argv jsaga another java implementation saga core specification jsaga currently active development deshl deisa services heterogeneous management layer provides functionality submission management computational jobs within deisa deshl implemented set command-line tools on-top saga-inspired api implemented java back-end interfaces hila generic grid access client library part unicore system typical task distributed application submit job local remote distributed resource manager saga provides high-level api called job package following two simple examples show saga job package api used submit message passing interface mpi job remote globus gram resource manager c++ python work related saga project funded following grants nsf-che 1125332 cdi nsf-eps 1003897 lasigma nsf-oci 1007115 extenci previous grants include nsf-oci 0710874 hpcops nih grant number p20rr016456 uk epsrc grant number gr/d0766171/1 via omii-uk
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Distributed computing architecture
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mud mud originally multi-user dungeon later variants multi-user dimension multi-user domain multiplayer real-time virtual world usually text-based muds combine elements role-playing games hack slash player versus player interactive fiction online chat players read view descriptions rooms objects players non-player characters actions performed virtual world players typically interact world typing commands resemble natural language traditional muds implement role-playing video game set fantasy world populated fictional races monsters players choosing classes order gain specific skills powers objective sort game slay monsters explore fantasy world complete quests go adventures create story roleplaying advance created character many muds fashioned around dice-rolling rules dungeons dragons series games fantasy settings muds common many others science fiction settings based popular books movies animations periods history worlds populated anthropomorphic animals muds games designed educational purposes others purely chat environments flexible nature many mud servers leads occasional use areas ranging computer science research geoinformatics medical informatics analytical chemistry muds attracted interest academic scholars many fields including communications sociology law economics one time interest united states military using teleconferencing muds run hobbies free players may accept donations allow players purchase virtual items others charge monthly subscription fee muds accessed via standard telnet clients specialized mud clients designed improve user experience numerous games listed various web portals mud connector history modern massively multiplayer online role-playing games mmorpgs like everquest ultima online related virtual world genres social virtual worlds exemplified second life traced directly back mud genre indeed invention term mmorpg games style simply called graphical muds number influential mmorpg designers began and/or players raph koster brad mcquaid matt firor brian green involved early muds like mark jacobs j. todd coleman colossal cave adventure created 1975 crowther dec pdp-10 computer first widely used adventure game game significantly expanded 1976 woods also called adventure contained many features references including computer controlled dungeon master numerous dungeon crawlers created plato system university illinois american universities used plato beginning 1975 among pedit5 oubliette moria avathar krozair dungeon dnd crypt drygulch 1978-79 games heavily use various plato systems exhibited marked increase sophistication terms 3d graphics storytelling user involvement team play depth objects monsters dungeons inspired adventure group students mit summer 1977 wrote game pdp-10 minicomputer called zork became quite popular arpanet zork ported filename dungen dungeon fortran programmer working dec 1978 1978 roy trubshaw student university essex uk started working multi-user adventure game macro-10 assembly language dec pdp-10 named game mud multi-user dungeon tribute dungeon variant zork trubshaw greatly enjoyed playing trubshaw converted mud bcpl predecessor c handing development richard bartle fellow student university essex 1980 game revolved around gaining points till one achieved wizard rank giving character immortality special powers mortals mud better known essex mud mud1 later years ran university essex network became widely accessible guest account set allowed users janet british academic x.25 computer network connect weekends hours 2 8 weekdays became first internet multiplayer online role-playing game 1980 university connected internal network arpanet original mud game closed late 1987 reportedly pressure compuserve richard bartle licensed game left mist derivative mud1 similar gameplay remaining mud running university essex network becoming one first kind attain broad popularity mist ran machine hosted pdp-10 superseded early 1991 1985 saw origin number projects inspired original mud included gods ben laurie mud1 clone included online creation endgame became commercial mud 1988 mirrorworld tolkienesque mud started pip cordrey gathered people bbs ran create mud1 clone would run home computer neil newell avid mud1 player started programming mud called shades christmas 1985 mud1 closed holidays starting hobby shades became accessible uk commercial mud via british telecom prestel micronet networks scandal shades led closure micronet described indra sinha net-memoir cybergypsies time compunet started project named multi-user galaxy game science fiction alternative mud1 copy running system time one two programmers left compunet remaining programmer alan lenton decided rewrite game scratch named federation ii time federation existed mud officially launched 1989 federation ii later picked aol became known simply federation adult space fantasy federation later left aol run aol began offering unlimited service 1978 around time roy trubshaw wrote mud alan e. klietz wrote game called milieu using multi-pascal cdc cyber 6600 series mainframe operated minnesota educational computing consortium klietz ported milieu ibm xt 1983 naming new port scepter goth scepter supported 10 16 simultaneous users typically connecting modem first commercial mud franchises sold number locations scepter first owned run gambit minneapolis minnesota founded bob alberti gambit assets later sold interplay productions interplay eventually went bankrupt 1984 mark peterson wrote realm angmar beginning clone scepter goth 1994 peterson rewrote realm angmar adapting ms-dos basis many dial-in bbs systems renamed swords chaos years popular form mud hosted number bbs systems widespread internet access eliminated bbses 1984 mark jacobs created deployed commercial gaming site gamers world site featured two games coded designed jacobs mud called aradath later renamed upgraded ported genie dragon gate 4x science-fiction game called galaxy also ported genie peak site 100 monthly subscribers aradath galaxy genie shut late 1990s although dragon gate later brought america online finally released dragon gate closed february 10 2007 summer 1980 university virginia classmates john taylor kelton flinn wrote dungeons kesmai six player game inspired dungeons dragons used roguelike ascii graphics founded kesmai company 1982 1985 enhanced version dungeons kesmai island kesmai launched compuserve later 2-d graphical descendant legends kesmai launched aol 1996 games retired commercially 2000 popularity muds university essex tradition escalated usa late 1980s affordable personal computers 300 2400 bit/s modems enabled role-players log multi-line bulletin board systems online service providers compuserve time sometimes said mud stands multi undergraduate destroyer due popularity among college students amount time devoted them. published yehuda simmons 1989 first persistent game world kind without traditional hourly resets points-based puzzle solving progression systems avalon introduced equilibrium balance cooldowns skill-based player vs player combat concepts player-run governments player housing first popular mud codebase abermud written 1987 alan cox named university wales aberystwyth alan cox played original university essex mud gameplay heavily influenced abermud initially written b honeywell l66 mainframe gcos3/tss late 1988 ported c enabled spread rapidly many unix platforms upon release 1989 abermud popularity resulted several inspired works notable tinymud lpmud dikumud monster multi-user adventure game created richard skrenta vax written vms pascal publicly released november 1988 monster disk-based modifications game immediate monster pioneered approach allowing players build game world setting new puzzles creating dungeons players explore monster comprised 60,000 lines code lot features appeared designed allow colossal cave adventure work though never many network-accessible monster servers inspired james aspnes create stripped version monster called tinymud tinymud written c released late 1989 spawned number descendants including tinymuck tinymush tinymuck version 2 contained full programming language named muf multi-user forth mush greatly expanded command interface distance combat-oriented traditional muds said tinymud stood multi-user domain dimension along eventual popularity acronyms mud muck mush muse kind server led eventual adoption term mu* refer tinymud family ubermud untermud moo inspired tinymud direct descendants first version hourglass written yehuda simmons later daniel james debuted 1989 last london mud mega meets aptly named 'adventure '89 initially hosted iowa system initially written arm assembler acorn archimedes 440 1994 made leap venerable archimedes debian linux pc later red hat shifting ubuntu operating system remained ever since early version hourglass also ported pc named vortex ben maizels 1992 although written specifically avalon legend lives went spawn number games including avalon first age ran 1999-2014 defunct 1996 age thrones notably achaea dreams divine lands started life vortex prior moving rapture engine hourglass continues developed 2016 avalon legend lives currently 2901325 written words 2248374 lines game-code 2417900 instructions original game coming 1k 1989 compared 102gb january 2016 1989 lpmud developed lars pensjö hence lp lpmud pensjö avid player tinymud abermud wanted create world flexibility tinymud gameplay abermud order accomplish wrote nowadays known virtual machine called lpmud driver ran c-like lpc programming language used create game world pensjö interest lpmud eventually waned development carried others jörn amylaar rennecke felix dworkin croes tim beek hollebeek lars düning early 1990s lpmud one popular mud codebases descendants original lpmud include mudos dgd swlpc fluffos pike programming language latter work long-time lpmud developer fredrik profezzorn hübinette 1990 release dikumud inspired abermud led virtual explosion hack slash muds based upon code dikumud inspired numerous derivative codebases including circlemud merc rom smaug godwars original diku team comprised sebastian hammer tom madsen katja nyboe michael seifert hans henrik staerfeldt dikumud key influence early evolution mmorpg genre everquest created avid dikumud player brad mcquaid displaying diku-like gameplay verant developers made issue sworn statement actual dikumud code incorporated 1987 david whatley previously played scepter goth island kesmai founded simutronics tom susan zelinski year demonstrated prototype gemstone genie short-lived instance gemstone ii gemstone iii officially launched february 1990 gemstone iii became available aol september 1995 followed release dragonrealms february 1996 end 1997 gemstone iii dragonrealms become first second played games aol typical mud describe room area standing listing objects players non-player characters npcs area well exits carry task player would enter text command take apple attack dragon movement around game environment generally accomplished entering direction abbreviation player wishes move example typing north n would cause player exit current area via path north mud clients often contain functions make certain tasks within mud easier carry example commands buttons click order move particular direction pick item also tools available add hotkey-activated macros telnet mud clients giving player ability move around mud using arrow keys keyboard example many variations overall focus gameplay features muds distinct sub-groups formed used help categorize different game mechanics game genres non-game uses perhaps common approach game design muds loosely emulate structure dungeons dragons campaign focused fighting advancement role-playing muds restrict player-killing favor player versus environment conflict questing labeled hack slash muds may considered particularly appropriate since due room-based nature traditional muds ranged combat typically difficult implement resulting muds equipping characters mainly close-combat weapons style game also historically referred within mud genre adventure games video gaming whole developed meaning adventure game greatly odds usage muds restrict player versus player combat often abbreviated pk player killing accomplished hard coded restrictions various forms social intervention muds without restrictions commonly known pk muds taking step muds devoted solely sort conflict called pure pk muds first genocide 1992 genocide ideas influential evolution player versus player online gaming roleplaying muds generally abbreviated rp muds encourage enforce players act role playing characters times rp muds provide immersive gaming environment others provide virtual world game elements muds roleplay enforced game world heavily computer-modeled sometimes known roleplay intensive muds rpimuds many cases role-playing muds attempt differentiate hack slash types dropping mud name entirely instead using mux multi user experience mush multi user shared hallucination social muds de-emphasize game elements favor environment designed primarily socializing differentiated talkers retaining elements beyond online chat typically online creation community activity element role-playing often muds broadly defined contingents socializers roleplayers server software tinymud family mu* traditionally used implement social muds less-known mud variant talker variety online chat environment typically based server software like ew-too nuts early internet talkers lpmuds majority complex game machinery stripped away leaving communication commands first internet talker cat chat 1990 taking advantage flexibility mud server software muds designed educational purposes rather gaming chat micromuse considered first educational mud argued evolution role complete 1994 would make first many educational moos diversity university 1993 also first educational mud mud medium lends naturally constructionist learning pedagogical approaches mud institute tmi lpmud opened february 1992 gathering place people interested developing lpmud teaching lpc became clear lars pensjö lost interest project tmi focussed lpmud driver library driver evolving mudos tmi mudlib never officially released influential development libraries graphical mud mud uses computer graphics represent parts virtual world visitors prominent early graphical mud habitat written randy farmer chip morningstar lucasfilm 1985 graphical muds require players download special client game artwork range simply enhancing user interface simulating 3d worlds visual spatial relationships customized avatar appearances games meridian 59 everquest ultima online dark age camelot routinely called graphical muds earlier years runescape actually originally intended text-based mud graphics added early development however increase computing power internet connectivity late nineties shift online gaming mass market term graphical mud fell favor replaced mmorpg massively multiplayer online role-playing game term coined richard garriott 1997 within mud technical infrastructure mudlib concatenation mud library defines rules in-game world examples mudlibs include soph mudlib cdlib discworld mudlib lima mudlib lpuniversity mudlib morgengrauen mudlib nightmare mudlib tmi mudlib mud history preserved primarily community sites blogs mainstream sources journalistic repute late 1990s website called mud connector served central curated repository active muds 1995 independent reported 60,000 people regularly played 600 muds 170 muds three years prior independent also noted distinct patterns socialization within mud communities seraphina brennan massively wrote mud community decline 2009 sherry turkle developed theory constant use many cases overuse muds allows users develop different personalities environments uses examples dating back text-based muds mid-1990s showing college students simultaneously live different lives characters separate muds three time schoolwork students claimed way shut lives become part another reality turkle claims could present psychological problem identity today youths story tree short essay written raph koster regarding death legendmud player named karyn raising subject inter-human relationships virtual worlds observations mud-play show styles play roughly categorized achievers focus concrete measurements success experience points levels wealth explorers investigate every nook cranny game evaluate different game mechanical options socializers devote energy interacting players killers focus interacting negatively players permitted killing characters otherwise thwarting play players play one way play one way time exhibit diverse style according richard bartle people go part hero journey—a means self-discovery research suggested various factors combine muds provide users sense presence rather simply communication noun word mud variously written mud mud mud depending speaker context also used verb mud meaning play interact mud mudding referring act mudder naturally one muds compound words portmanteaux mudlist mudsex mudflation also regularly coined puns wet dirt meaning mud endemic example names rom rivers mud muck mush coffeemud codebases mud muddy waters
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Programming language topics
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zorin os zorin os personal computer operating system based ubuntu marketed operating system designed users new linux-based computer systems one operating system built-in features allows users change interface resemble microsoft windows mac os x also comes bundled wine playonlinux allowing users run windows software ease transition gaming zorin os creators distribute different versions operating system three versions ultimate education business version purchase current releases zorin os 15 ultimate zorin os 15 core new editions continue use debian-based linux kernel gnome interface zorin os fully graphical along graphical installer zorin os follows long-term releases main ubuntu system stability security zorin os comes repositories historically ubuntu repositories well zorin os ubuntu-based linux distribution distribution aims user-friendly fully compatible ubuntu base zorin os initially released 12.x series last version zorin os required users clean install 12.4 since able upgrade normal via systems update manager gnome lxde currently official desktop environments lxde tend used mainly lite editions desktop environments also available install repos due ubuntu-based zorin os like ubuntu-counterpart comes default uncomplicated firewall though enabled default zorin os praised intuitive familiar layouts functionality installation process
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Operating systems
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multi-simulation coordinator music multi-simulation coordinator software developed released incf royal institute technology kth school computer science communication stockholm sweden music designed interconnecting large scale neuronal network simulators either tools allows spike events continuous time series communicated applications cluster computer typical usage cases connecting models developed different simulators connecting parallel simulator post-processing tool music provides standardized software interface api top message-passing interface mpi communication among parallel applications large-scale computational neuroscience simulations enables transfer massive amounts event information continuous values one parallel application another including using different data allocation strategies design standard interface care taken allow easy adaptation existing simulators permit third-party development community-sharing reusable interoperable software tools parallel processing three simulators currently music interfaces moose neuron nest music software library documentation publicly available incf software center
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Distributed computing architecture
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mysql mysql s-q-l open-source relational database management system rdbms name combination name co-founder michael widenius daughter sql abbreviation structured query language mysql free open-source software terms gnu general public license also available variety proprietary licenses mysql owned sponsored swedish company mysql ab bought sun microsystems oracle corporation 2010 oracle acquired sun widenius forked open-source mysql project create mariadb mysql component lamp web application software stack others acronym linux apache mysql perl/php/python mysql used many database-driven web applications including drupal joomla phpbb wordpress mysql also used many popular websites including facebook flickr mediawiki twitter youtube mysql written c c++ sql parser written yacc uses home-brewed lexical analyzer mysql works many system platforms including aix bsdi freebsd hp-ux ecomstation i5/os irix linux macos microsoft windows netbsd novell netware openbsd opensolaris os/2 warp qnx oracle solaris symbian sunos sco openserver sco unixware sanos tru64 port mysql openvms also exists mysql server software client libraries use dual-licensing distribution offered gpl version 2 proprietary license support obtained official manual free support additionally available different irc channels forums oracle offers paid support via mysql enterprise products differ scope services price additionally number third party organisations exist provide support services including mariadb percona mysql received positive reviews reviewers noticed performs extremely well average case developer interfaces documentation mention feedback real world via web sites like good also tested fast stable true multi-user multi-threaded sql database server mysql created swedish company mysql ab founded david axmark allan larsson michael monty widenius original development mysql widenius axmark began 1994 first version mysql appeared 23 may 1995 initially created personal usage msql based low-level language isam creators considered slow inflexible created new sql interface keeping api msql keeping api consistent msql system many developers able use mysql instead proprietarily licensed msql antecedent additional milestones mysql development included work version 6 stopped sun microsystems acquisition mysql cluster product uses version 7 decision made jump version 8 next major version number 15 june 2001 nusphere sued mysql ab tcx datakonsult ab original authors michael monty widenius david axmark u.s district court boston breach contract tortious interference third party contracts relationships unfair competition 2002 mysql ab sued progress nusphere copyright trademark infringement united states district court nusphere allegedly violated mysql ab copyright linking mysql gpl'ed code nusphere gemini table without compliance license preliminary hearing judge patti saris 27 february 2002 parties entered settlement talks eventually settled hearing fsf commented judge saris made clear sees gnu gpl enforceable binding license october 2005 oracle corporation acquired innobase oy finnish company developed third-party innodb storage engine allows mysql provide functionality transactions foreign keys acquisition oracle press release mentioned contracts make company software available mysql ab would due renewal presumably renegotiation time 2006 mysql users conference april 2006 mysql ab issued press release confirmed mysql ab innobase oy agreed multi-year extension licensing agreement february 2006 oracle corporation acquired sleepycat software makers berkeley db database engine providing basis another mysql storage engine little effect berkeley db widely used dropped due lack use mysql 5.1.12 pre-ga release mysql 5.1 released october 2006 january 2008 sun microsystems bought mysql ab 1 billion april 2009 oracle corporation entered agreement purchase sun microsystems owners mysql copyright trademark sun board directors unanimously approved deal also approved sun shareholders u.s. government 20 august 2009 14 december 2009 oracle pledged continue enhance mysql done previous four years movement oracle acquisition mysql ab save mysql oracle started one mysql ab founders monty widenius petition 50,000+ developers users called upon european commission block approval acquisition time free software opinion leaders including pamela jones groklaw jan wildeboer carlo piana also acted co-counsel merger regulation procedure advocated unconditional approval merger part negotiations european commission oracle committed mysql server continue least 2015 use dual-licensing strategy long used mysql ab proprietary gpl versions available antitrust eu pressuring divest mysql condition approval merger revealed wikileaks us department justice request oracle pressured eu approve merger unconditionally european commission eventually unconditionally approved oracle acquisition mysql ab 21 january 2010 january 2010 oracle acquisition mysql ab monty widenius started gpl-only fork mariadb mariadb based code base mysql server 5.5 aims maintain compatibility oracle-provided versions mysql offered two different editions open source mysql community server proprietary enterprise server mysql enterprise server differentiated series proprietary extensions install server plugins otherwise shares version numbering system built code base major features available mysql 5.6 developers release minor updates mysql server approximately every two months sources obtained mysql website mysql github repository gpl license using storage engines default innodb mysql comply full sql standard implemented functionality including foreign key references check constraints parsed ignored storage engines mysql version 8.0.15 mysql 5.7 triggers limited one per action timing meaning one trigger defined executed insert operation one insert table triggers defined views mysql database inbuilt functions like unix_timestamp return 0 03:14:07 utc 19 january 2038 recently attempt solve problem assigned internal queue mysql built installed manually source code commonly installed binary package unless special customizations required linux distributions package management system download install mysql minimal effort though configuration often required adjust security optimization settings though mysql began low-end alternative powerful proprietary databases gradually evolved support higher-scale needs well still commonly used small medium scale single-server deployments either component lamp-based web application standalone database server much mysql appeal originates relative simplicity ease use enabled ecosystem open source tools phpmyadmin medium range mysql scaled deploying powerful hardware multi-processor server gigabytes memory however limits far performance scale single server 'scaling larger scales multi-server mysql 'scaling deployments required provide improved performance reliability typical high-end configuration include powerful master database handles data write operations replicated multiple slaves handle read operations master server continually pushes binlog events connected slaves event failure slave promoted become new master minimizing downtime improvements performance achieved caching results database queries memory using memcached breaking database smaller chunks called shards spread across number distributed server clusters logical backup tool included community enterprise editions mysql supports backing storage engines mysql enterprise backup hot backup utility included part mysql enterprise subscription oracle offering native innodb hot backup well backup storage engines oracle mysql offers high availability solution mix tools including mysql router mysql shell based group replication open source tools mariadb offers similar offer terms products mysql also run cloud computing platforms microsoft azure amazon ec2 oracle cloud infrastructure common deployment models mysql cloud graphical user interface gui type interface allows users interact electronic devices programs graphical icons visual indicators secondary notation opposed text-based interfaces typed command labels text navigation guis easier learn command-line interfaces clis require commands typed keyboard third-party proprietary free graphical administration applications front ends available integrate mysql enable users work database structure data visually well-known front ends command-line interface means interacting computer program user issues commands program typing successive lines text command lines mysql ships many command line tools main interface client mysql utilities set utilities designed perform common maintenance administrative tasks originally included part mysql workbench utilities stand-alone download available oracle percona toolkit cross-platform toolkit mysql developed perl percona toolkit used prove replication working correctly fix corrupted data automate repetitive tasks speed servers percona toolkit included several linux distributions centos debian packages available fedora ubuntu well percona toolkit originally developed maatkit late 2011 maatkit longer developed mysql shell tool interactive use administration mysql database supports javascript python sql modes used administration access purposes many programming languages language-specific apis include libraries accessing mysql databases include mysql connector/net integration microsoft visual studio languages c vb commonly used jdbc driver java addition odbc interface called mysql connector/odbc allows additional programming languages support odbc interface communicate mysql database asp coldfusion htsql url-based query method also ships mysql adapter allowing direct interaction mysql database web client via structured urls drivers exists languages like python node.js variety mysql forks exist including following
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Databases
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dragon quest video game dragon quest created yuji horii took inspiration previous role-playing games wizardry ultima 1983 game portopia serial murder case horii wanted create rpg would appeal wide audience people unfamiliar genre video games general tried place greater emphasis storytelling emotional involvement well simplify interface expose mostly western computer genre japanese console market manga artist dragon ball creator akira toriyama produced game artwork koichi sugiyama composed music north american version features numerous changes including battery-backed ram save games rather using password save system modified character sprites pseudo-elizabethan english style dialog dragon quest commercially successful japan 2 million copies sold release dragon warrior north america western countries less favorably received later western critics noted game shortcomings acknowledged importance genre fan-made rom hacks released substantial changes game game synthesized soundtrack orchestrated music performed numerous concerts whole dragon warrior credited establishing basic template japanese console rpgs followed dragon warrior role-playing video game gameplay mechanics described years release simplistic spartan players control young hero sets defeat known dragonlord starting game players presented menu allows begin new quest game continue previous quest change speed messages appear screen japanese version continuing quest requires players enter password north american nintendo entertainment system nes english version quest saved onto game cartridge battery-backup known game adventure log imperial scrolls honor english version also options delete duplicate saved quest players choose start new quest may give hero name wish either japanese kana english letters depending version hero name effect initial ability scores statistical growth course game stat falls one two categories one faster growth game determines path stat uses formula based kana letters character name. ref name= guide 6/105 /ref dragon warrior presents players clear objective start uses series smaller scenarios increase hero strength order achieve objective game begins king lorik chamber tantegel castle hero receives information dragonlord must defeat stolen balls light must retrieve receiving items gold hero sets quest much dragon warrior spent talking townspeople gathering information leads additional places events secrets players advised take notes hints future reference towns contain shops sell improved weapons armor general stores player may buy goods inns allow hero recover health magic shops offer keys purchase players may sell items half price shops provide weapons armor general goods hero status window shown whenever stops moving displaying current experience level lv number hit points hp magic points mp gold g experience points e safely progress next areas game players need accumulate experience points gold defeating enemies outside towns – overworld dungeons apart dragonlord castle physical restrictions players roam instead monsters increase difficulty players venture tantegel castle hero level increases players explore afield less risk enemies appear random encounters hero fights one opponent time encounter rate lowest fields increases forests hills battles turn-based fought first-person perspective hero remains off-screen combat players must defeat enemy reducing hp zero combat players four commands fight run spell item fight command causes hero attack enemy weapon bare fists weapon available attempt inflict damage run command hero attempts escape battle recommended hp low spell command casts magic example heal hero damage enemy item command uses herbs replenish hero hp combat hero loses hp takes damage display turns red hp low hp falls zero dies taken back king lorik resurrected loses half gold punishment hero succeeds defeating enemy gains experience points gold gains enough experience points experience level increases giving greater strength agility speed ability use magic spells every time spell used hero mp decreases different spells costing different amounts mp hp mp restored resting inn additionally non-player character replenish hero mp tantegel castle hero earns gold purchase better weapons armor items however players limited inventory space hold items must manage item collection conservatively caves hero explores dark require use torch radiant spell display temporary field vision around character english version players return king lorik point save quest japanese version battery backup players receive password return quest later time control pad may used move hero direction move flashing cursor menu displays additional buttons confirm cancel commands english version players use menu commands talk people check status search beneath feet use items take treasure chests open doors go stairs however game later remakes certain commands assigned buttons navigating stairs became automatic hero speed increased japanese version characters always face forward players must choose command direction perform action north american version hero turns face direction moving making direction selection unnecessary dragon warrior plot twist saving princess dragon n't even meet speak complete game dragon warrior sequel dragon quest ii prequel dragon quest iii comprise trilogy shared timeline story background begins kingdom alefgard shrouded permanent darkness brave warrior erdrick known loto game boy color gbc remake game defeated evil creature restored light land erdrick possession ball light used drive away enemies threatened kingdom erdrick handed ball light king lorik alefgard remained peaceful long time ball light kept winters short alefgard helped maintain peace prosperity region however one man shunned ball light radiance secluded mountain cave one day exploring cave extensive network tunnels man encountered sleeping dragon awoke upon entrance feared dragon would incinerate fiery breath dragon instead knelt obeyed commands man later discovered dragon became known dragonlord one day soul became corrupted learning magic dragonlord attacked tantegel castle nearby town breconnary fleet dragons set town fire riding large red dragon dragonlord descended upon tantegel castle stole ball light soon monsters began appear throughout entire land destroying everything paths much land became poisonous marshes least one destroyed town hauksness whose name erroneously transposed rimuldar adventurer handbook walkthrough never recovered remains ruins even time gameplay following day erdrick arrived tantegel castle speak king lorik offered help defeat dragonlord searching land clues dragonlord whereabouts erdrick found dragonlord lived island could accessed via magical bridge rainbow drop could generate venturing island erdrick never heard many years later king lorik xvi reign dragonlord attacked kingdom captured princess gwaelin many heroes tried rescue princess recover ball light dragonlord castle called charlock none succeeded prophet mahetta predicted one day descendant valiant erdrick shall come forth defeat dragonlord however descendant game hero arrives many people alefgard forgotten story erdrick remember consider myth believe mahetta prophecy king lorik starts mourn decline kingdom game begins player assumes role stranger arrives tantegel castle castle guard tells dragon captured princess holding captive distant cave determined rescue princess defeat dragonlord discovers ancient tablet hidden inside desert cave carved tablet message erdrick outlines hero needs follow erdrick footsteps defeat dragonlord hero eventually rescues princess gwaelin realizes order restore light alefgard must defeat dragonlord charlock castle hero collects series relics creates bridge reach charlock fights way castle finally confronting dragonlord point hero given dialogue choice – side dragonlord challenge players choose former game ends hero put sleep game freezes however gbc remake hero instead wakes bad dream players choose fight final battle hero dragonlord commences hero defeats dragonlord reclaims ball light eradicating monsters alefgard triumphantly returns tantegel castle king lorik offers kingdom reward hero turns offer instead wishes find kingdom accompanied princess gwaelin hero sets search new land sets stage events dragon warrior ii take place many years later tells story three hero descendants dragon warrior hero dragonlord two main characters major supporting characters king lorik king lars gbc remake daughter princess gwaelin lady lora two sages hero meets journey hero comes land beyond alefgard descendant legendary erdrick hero arrives appear warrior – arrives without weapons armor – ignorant situation populace thinks claim ability defeat dragonlord preposterous however king lorik sees ability give hope aids hero quest dragonlord dragon rules charlock castle visible tantegel castle game starting point soul became evil learning magic rumors say spy network knows everything happens alefgard seeks unlimited power destruction results rising tide evil throughout alefgard dragonlord wants enslave world army monsters controls yuji horii team chunsoft began developing dragon quest 1985 released japan 1986 famicom msx pc-9801 dragon quest released multiple platforms since initial release including mobile phones 2004 updated graphics similar eidansha boshu service center founded 1975 published tabloid magazines advertised real estate 1982 failing establish chain stores company founder yasuhiro fukushima transformed software company devoted gaming renamed enix find talent company fukushima held enix game hobby program contest competition styled manga competitions advertised computer manga magazines million prize winners winners koichi nakamura manga magazine shōnen jump editor yuji horii top winner horii designed tennis game love match tennis became enix first release believe would win motivated editor enjoyed games published horii articles later enix began creating games nes fukushima held another contest time nakamura cartoonish creative contest entry door door became enix first release nes horii earliest inspiration dragon quest 1983 pc visual novel portopia serial murder case – murder mystery adventure game bears similarities games mystery house zork particularly déjà vu horii wanted advance game storyline using dialogue portopia originally released japan nec pc-6001 later ported nes 1985 port enix second release system first game horii nakamura worked together horii redesigned interface port accommodate console limited controls added dungeon-crawling area detective explores portopia directly result dragon quest creation according 1up.com proving ground rpg menu-based command system portopia would later used dragon quest original idea dragon quest came development nes port portopia horii nakamura came across rpg wizardry macworld conference expo influence nes portopia dungeon crawl segments horii liked game depth visuals wanted create game similar wizardry expose mainly western-exclusive rpg genre japan expand genre past computer enthusiasts horii also cited ultima inspiration dragon quest gameplay specifically first-person random battles wizardry overhead perspective ultima rpg genre predominantly western limited pcs japanese gamers enjoyed home-grown games black onyx dragon slayer series alongside western rpg ports however horii nakamura enjoyed dungeon crawling statistical nature wizardry realized people would originally concern success super mario bros. greatly increased potential audience new famicom/nes game create dragon quest gameplay needed simplified according horii keyboard system much simpler using game controller still thought would really exciting player play alter ego game personally playing wizardry ultima time really enjoyed seeing self game order create rpg would appeal wide audience unfamiliar genre video games general horii wanted create new kind rpg rely previous experience dungeons dragons tabletop rpg require hundreds hours rote fighting could appeal kind gamer accomplish needed simplify system players associate hero thus game progressed hero would become stronger contrast games like super mario bros. character mario become progressively powerful game wanted build portopia place greater emphasis storytelling emotional involvement developed coming-of-age tale audiences could relate made use rpg level-building gameplay way represent horii believed famicom ideal platform dragon quest unlike arcade games players would worry spending money got game could continue playing left whenever player loses battle would immediately restored previous save point rather game ending returned main menu making game accessible also wanted include multiple player characters forced use one due memory constraints horii knew rpgs steeper learning curve video games time compensate implemented quick level-ups start game gave players clear final goal visible world map starting point dragonlord castle also provided series smaller scenarios order build player strength achieve final objective created open world blocked physically way except monsters easily kill unprepared players gamasutra described one earliest examples nonlinear gameplay horii used bridges signify changes difficulty implemented level progression high starting growth rate decelerates time contrasted random initial stats constant growth rates early editions dungeons dragons make game appeal larger audience manga artist creator dragon ball akira toriyama hired produce artwork dragon ball toriyama artwork features characters whose strength cunning transcend generations also includes humorous elements chibi style koichi sugiyama game music composer sought enix sugiyama sent pc game feedback questionnaire enix already well-known television composer upon seeing sugiyama feedback fukushima contacted confirm sugiyama television upon confirmation fukushima asked sugiyama compose score dragon quest game classical score sugiyama second video game composition wingman 2 sugiyama said took five minutes compose original opening theme noted difficulty adding personal touch short jingles past experience creating music television commercials helped according sugiyama composer three five seconds catch audience attention music theme jingles dragon quest remained relatively intact sequels coverage dragon quest north american localization first appeared nintendo fun club news winter 1988 issue – title changed dragon warrior title changed avoid infringing trademark wargame publisher simulations publications pen-and-paper rpg dragonquest article game featured images game japanese version erdrick original name roto dragonlord original name dragon king original name game starting location radatome castle briefly explained backstory basic gameplay elements comparing game legend zelda game later mentioned nintendo power pak watch preview section march 1989 mentioning dragon quest iii japanese release magazine premiere july 1988 issue mentioned change name dragon quest dragon warrior inspiration two japanese sequels release still distant time dragon warrior released north america nintendo america direction satoru iwata help horii august 1989 – months japanese release game released north america nearly three years original release japan graphics improved instead lengthy passwords kana characters north american version features battery-backed ram savegame akira toriyama artwork instruction booklets also changed reflect traditional tone found popular american based rpgs ultima series game character sprites changed face direction travel japanese versions sprites smaller face forwards requiring players choose direction actions menu spells given self-explanatory one-word titles instead made-up words japanese version locations renamed dialogue rewritten whimsical style comparable dragon ball style inspired elizabethan english sentences thy hit points decreased 1 nintendo also removed salacious humor religious connotations english-language version example japanese version town hero first buys keys woman offers sell puff-puff – japanese onomatopoeia girl rubbing breasts someone face juggling breasts north american version woman sells tomatoes term included game sequels well toriyama dragon ball series katsuya terada created artwork early dragon warrior articles nintendo power neither terada editing artwork instruction booklet followed toriyama work instead used settings character poses create alternate artwork american style japanese hero drawn super deformed manga style english version appearance based west template medieval hero june 1989 electronic gaming monthly quartermann speculated dragon warrior would nintendo big release north america christmas based series immense popularity japan especially dragon quest iii sales nintendo power provided three feature articles dragon warrior issues may october 1989 november–december 1989 issue includes strategy guide march–april 1990 issue nintendo power map game world poster super contra side also features dragon warrior text adventure late 1990 nintendo power gave free copies dragon warrior subscribers including 64-page explorer handbook full walkthrough game additional backstory mentioned original instruction booklet nintendo reportedly interested getting rid unsold copies game gave away subscribers time game cost approximately retail magazine subscription fee respectively adjusted inflation giveaway attracted nearly 500,000 new magazine subscribers many renewed subscription get game ultimately led success series western market enix remade dragon quest dragon quest ii one-cartridge compilation known dragon quest ii super famicom december 18 1993 remake sold 1.2 million copies japan 1998 enix released bs dragon quest super famicom satellaview extension exclusively japan latter consisted four one-hour scenarios players would download weekly schedule players tasked leveling character collecting medals completing scenario-specific conditions special events designed occur specific conditions real-time dragon warrior dragon warrior ii re-released part similar compilation gbc titled dragon warrior ii developed tose released enix september 23 1999 japan september 27 2000 north america uses entirely new translation discards pseudo-elizabethan english style uses names closer japanese version remake dragonlord changed dracolord erdrick changed loto several additional features added example players quicksave game anytime outside battle quicksave deleted standard saved game loaded players store gold future use bank case die menu streamlined monsters yield experience gold reduce amount time needed increase levels make saving in-game purchases faster 2004 game along sequel remade mobile phones japan version graphically based super famicom remake dragon quest iii famicom super famicom versions game together dragon quest ii dragon quest iii re-released dragon quest 25th anniversary collection compilation wii japan september 15 2011 compilation includes original copies games strategy guides original artwork material games development october 2013 square enix announced re-releasing dragon quest i–viii android ios november 2013 game released ios android mobile platforms japan release based 2004 mobile remake game united states europe mobile versions released september 11 2014 dragon warrior inspired related media form manga series adapted anime symphonic video game soundtrack manga series written chiaki kawamata junji koyanagi artwork kamui fujiwara published 1991 1997 monthly shōnen gangan enix compiled series 21 volumes later released compact disc 1994 released december 11 2009 playstation store part initial launch sony digital comic distribution 1996 anime movie based manga released videocassette square enix started publishing sequel series 2005. wrote first four volumes takashi umemura wrote last five yuji horii supervised manga kamui fujiwara contributed artwork dragon quest saga emblem roto takes place dragon warrior iii dragon warrior monsters possessed carmen king seven years kingdom fell hordes evil survivors prince arus army general daughter lunafrea meanwhile kingdom loran child born named jagan accordance demon lord imagine orders arus lunafrea set defeat monsters restore peace world sequel children inherit emblem takes place five years events dragon quest saga emblem roto world chaos young boy sets gather companions help save world evil koichi sugiyama composed directed music dragon warrior soundtrack included eight tracks rpgfan said foundation sugiyama career pieces arranged incorporated later dragon warrior games soundtracks music released variety formats first drama cd released enix july 19 1991 incorporated narrated story super famicom edition symphonic suite dragon quest published sony records january 12 1994 followed soundtrack featured orchestral versions tracks played london philharmonic orchestra original versions tunes game classical score considered revolutionary console game music soundtrack eight melodies approach set template rpg soundtracks released since hundreds organized similar manner orchestral albums dragon warrior ii combined symphonic suite dragon quest i•ii released sme visual works august 23 2000 king records reprinted october 7 2009 orchestral tracks released symphonic suite dragon quest album including orchestral versions game sound effects numerous live concerts featured performances game music many performances later released albums dragon quest concert suite dragon quest i•ii initial sales game low enix going lose money several shonen jump articles horii helped increase sales substantially people liked toriyama artwork sugiyama music book said richer exciting game music ever sounded game extremely popular japan became first series 2016 includes eleven games several spin-off series stand-alone titles 2 million copies sold japanese version dragon quest ii remake snes yielded 1.2 million copies sold japan 1989 soft catalog issue famicom tsūshin famitsu included dragon quest list best games time receiving best rpg best character design awards losing dragon quest iii overall grand prize best game time several years japanese release first english-language version dragon warrior garnered average reviews overall nintendo power ranked third five upon original release debuted 7 magazine bimonthly top 30 top nes games list november 1989 climbed 5 january 1990 remained 4 months dropped 11 may 14 july 16 september 1990 dropped list nintendo power awards 1989 game nominated best theme fun best overall failed win either category response japanese youths arrests waiting dragon quest iii release electronic gaming monthly quartermann said game special compared nes version recommended others play game instead english version seen commercial failure according chris kohler nintendo power subscription success allowed enix bring next three games said nintendo profited immensely dragon warrior subscription giveaway nintendo power essentially hundred-page monthly ad nintendo products thousands households game release regarded important history console rpg kohler noted toriyama sugiyama contributions game made dragon quest visually aurally exciting game play unique sophisticated gamespot named one fifteen influential titles video game history ign listed eighth best all-time nes game 2005 listed 92nd-best all-time video game 2007 listed game 29th best nintendo power rated dragon warrior 140th-best game made nintendo system top 200 games list 2006 ign reviewed game years later gave 7.8 10 rpgamer bill johnson gave 4 5 overall score nes localization received considerable praise adding extra characters depth story removal stylized dialogue gbc remake similarly lamented allgame declared despite enormous influence ... dragon warrior flawed game decent design ideas terribly enjoyable noting simplistic graphics slow pace poor sound seemingly primitive today standards dragon warrior features one-on-one combat limited item equipment array ten spells five towns five dungeons noting importance development rpg genre allgame reviewer kyle knight states taken merits enjoyable game play 1up.com explained series immensely popular first north america american console gamers used idea rpgs said would take decade genre flashy enough distract words made read gamecritics chi kong lui wrote game added realism video games added player perished dragon warrior suffer dire consequences losing progress precious gold element death evoked sense instinctive fear tension survival said allowed players identify main character much larger scale ign writer mark nix compared game seemingly archaic plot modern rpgs said noble blood means nothing society capitalist aristocratic militaristic damsels n't need rescuing – need battle axe magic tutoring field reviewing gamespy staff wrote many gamers dragon warrior first exposure console rpg recalling past staff member commented bill johnson compared dragon warrior modern rpgs noted game complete lack replay value due much requirement almost everything game must done beat difficulty johnson noted game historical importance said playing dragon warrior tough road walk reaching end instill new appreciation today rpg 2009 book vintage games contrasted dragon warrior 1986 nes title legend zelda said titles share common rpg elements zelda features fantasy setting magic level turn-based combat system dragon warrior features nintendo power said game historical significance greatest aspect noted playing dragon warrior days bit chore gamepro wrote favorite aspect game elizabethan-english dialogue disappointed removal gbc remake famitsu gave snes compilation remake dragon quest ii rating 35 40 satellaview remake given mixed overall positive review microgroup touches real-time event voicing appreciated implementation left much desired however medal collection nice way compete friends reviewer enjoyed game dragon warrior english remake part dual gbc cartridge dragon warrior ii received better reviews original garnering praise ign nintendo power gave 8 10 ign marc nix noted one interesting rpgs game boy color actually make american shores players feel frustrated played original lament changes new players feel game linear simple gamespot gave 9.6 10 citing great improvements sound quality appeal playing games succession gamerankings reports 82 overall score received rpgamer game boy color award year 2000 comparing nes counterpart rpgamer derek cavin awarded 3 5 wrote game average aspects particularly praised visual elements criticized game repetitiveness said short enough players finish game repetition becomes issue combined snes gbc remakes saw 1.94 million copies sold worldwide remakes good sales performances enix released dragon warrior iii gbc 2001 based previously unreleased snes update dragon quest iii english version square enix music online juan2darien reviewed game symphonic scores dragon quest suite dragon quest remix symphonic suite london philharmonic orchestra dragon quest ii symphonic suite london philharmonic orchestra remastered dragon quest symphonic suite tokyo metropolitan symphony orchestra comparing suites gave ratings ranging 7 9 10 found tokyo strings ensemble recording superior aforementioned symphonic suites music somewhat flat juan2darien acknowledged due source material praised koichi sugiyama orchestras efforts compose above-average piece despite limitation gamasutra kurt kalata also praised symphonies melody commenting overworld theme ... pretty simplistic grating actually sounds pretty beautiful played live orchestra dragon quest retsuden roto monshō – children inherit emblem sold well japan week august 26 september 1 2008 volume 7 ranked 9th japan selling 59,540 copies week february 24 march 2 2009 volume 8 ranked 19th japan selling 76,801 copies week october 26 november 1 2009 volume 9 ranked 16th japan selling 40,492 copies total 60,467 dragon warrior release noted notable turning point video game history game listed genre builder rpgs popularity japan synonymous rpgs game elements present previous rpg titles dragon warrior set template others almost elements became foundation nearly every later game genre gameplay narrative according shigeru miyamoto success dragon warrior changed nature video game development making scenario writers far important dragon warrior released many development techniques used intended compensate hardware limitations contemporary rpg developers continue use techniques despite technological advances made unnecessary dragon warrior introduced damsel-in-distress storyline many rpgs follow fresh plot twist saving princess formula game true objective revealed princess rescued game also introduced element romance player character given dialogue choice respond princess question whether loves romance since become commonplace feature genre game 2d graphic style used rpgs advent 3d graphics dragon warrior top-down perspective become dead giveaway rpg game featured elements still found rpgs ability obtain better equipment major quests intertwine minor subquests incremental spell system use hit points experience points medieval theme reviewers said final fantasy considered important due popularity attention north america dragon warrior laid fundamentals final fantasy based nintendo power november 2010 issue celebration nes 25th anniversary north america horii recalled making dragon warrior horiii fan basic rpg mechanics wanted simplify interfaces said many rpgs interfaces time complicated intimidated new users said dragon warrior simplified gameplay made game appealing people made franchise successful told nes lacked sufficient capacity rpgs motivated make one dragon quest became national phenomenon japan inspiring spinoff media figurines video game industry called japan national game horii linked shonen jump articles increased celebrity status become household name japan well known japan steven spielberg us contrast miyamoto creator super mario bros. legend zelda nearly well-known famitsu poll japanese public voted dragon quest seventh favorite game nes several clones glory heracles legend ghost lion mother inspired japanese version success mother shigesato itoi fan dragon warrior miyamoto detractor rpgs created rpg would subvert dragon warrior rpg template changing setting themes middle ages us dragon warrior along nes titles spawned many rom hacks recent years one notable hack includes super mario remix ii features new plot revised character sprites reflect mario series gameplay layout remain dragon warrior became popular japan asked draw 'slime japanese person likely draw shape similar game interpretation slime many aspects pop culture still reference dragon warrior video game music band descendants erdrick based austin texas named game main character april fools day 2012 google added dragon warrior -inspired 8-bit option google maps 2016 spin-off title dragon quest builders released alternate sequel first game story set 100 years consequences erdrick instead accepts dragonlord offer rule half world
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Computer architecture
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security switch security switch hardware device protect computers laptops smartphones similar devices unauthorized access operation distinct virtual security switch offers software protection security switches operated authorized user reason isolated devices order prevent unauthorized access possible bypass order prevent malicious manipulation primary purpose security switch provide protection cellphone surveillance eavesdropping malware spyware cyberwarfare laptop theft theft smartphones similar devices unlike protections techniques security switch provide protection even computer phone security already broken since access components accessible device software disconnect block peripheral device perform man middle operations like isolated encryption similar operations security switch s.s. used human presence detection since signals sent initiated human operator manipulated bypassed s.s. also used internet security hardware firewall concept security switch patented 2007 presented 35th ieee symposium security privacy
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Computer security
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martin roesch martin roesch founded sourcefire 2001 served chief technology officer company acquired cisco systems october 7 2013 roesch serves vice president chief architect cisco ’ security business group respected authority intrusion prevention detection technology forensics responsible technical direction product development efforts martin industry experience network security embedded systems engineering also author lead developer snort intrusion prevention detection system forms foundation sourcefire 3d system martin developed various network security tools technologies including intrusion prevention detection systems honeypots network scanners policy enforcement systems organizations gte internetworking stanford telecommunications inc. united states department defense martin interviewed industry expert multiple technology publications well print online news services msnbc wall street journal cnet zdnet scientific american also interviewed several books network intrusion detection analysts handbook intrusion signatures analysis maximum security hacking exposed others 2006 martin named one informationweek 18 innovators influencers one tech council maryland influential ctos maryland martin also recipient 2004 infoworld heroes innovator award well winning 2004 40 40 award baltimore business journal martin holds b.s electrical computer engineering clarkson university also author daemonlogger
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Computer security
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mirah programming language mirah formerly duby programming language based ruby language syntax local type inference hybrid static–dynamic type system pluggable compiler toolchain mirah created charles oliver nutter 'ruby-like language probably subset ruby syntax could compile solid fast idiomatic jvm bytecode word refers gemstone ruby javanese language play concept ruby java foster participation jruby project ruby community members nutter began explore possibility presenting ruby syntax static type model direct-to-native compiling context native meant mainly java virtual machine jvm mirah designed around possibility alternative backends object-oriented runtimes like common language runtime clr .net framework language needed look feel like ruby introduce new library dependencies jruby precludes jvm languages suffer performance penalty precludes writing ruby early versions mirah duby focused mostly mathematical performance dynamic programming languages often pay highest cost since evolved full jvm language several users real-world applications using core components mirah mostly pluggable compiler toolchain main elements chain phases last two need specific knowledge eventual target platform makes mirah suitable many backends also makes possible write language plug-ins mirah transformation phase apply supported backends equally simple pieces code jvm bytecode backend mirah compiler emits nearly instructions standard javac compilers mirah compiler ships standard library intent mirah users choose libraries want use perhaps write plugins mirah compiler support compiler rest explicit design goal avoid introducing requirement new external library standard library mirah whatever standard library current backend emphasis placed writing compiler plugins rather libraries extend enhance language mirah impose specific type system users instead relying whatever target backend provides jvm type system largely java type system type declarations refer jvm classes primitives interfaces mirah primarily statically-typed language support development allow dynamic typing also mechanism similar provided c 4 special dynamic type indicating dispatches variable value done dynamically dynamic type support currently planned java 7 higher using new codice_1 bytecode syntax mirah largely syntax ruby modifications support static typing outside differences mirah code generally looks like ruby code mirah development developers using mirah production applications limited scope dubious project running mirah google app engine provides way build apps mirah conventions familiar developers using ruby rails sinatra since everything compiled ahead-of-time mirah applications none initializing costs associated jruby dubious supports eruby erb simple datastore adapter uses syntax similar datamapper
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Programming language topics
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debian gnu/kfreebsd debian gnu/kfreebsd discontinued operating system released debian project used freebsd kernel gnu userland majority software debian gnu/kfreebsd built sources debian kernel packages freebsd k kfreebsd abbreviation kernel refers freebsd kernel discontinuing project debian maintained i386 amd64 ports last version debian kfreebsd debian 8 jessie rc3 debian gnu/kfreebsd created 2002 included debian 6.0 squeeze technology preview debian 7.0 wheezy official port debian gnu/kfreebsd discontinued officially supported platform debian 8.0 failed attract enough users justify burden rest project debian developers cited oss pf jails ndis zfs reasons interested freebsd kernel updated since debian 8 july 2019 however operating system continues maintained unofficially
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Operating systems
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so-net
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Web technology
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n.o.v.a near orbit vanguard alliance near orbit vanguard alliance better known n.o.v.a short action-adventure video game ipod apple products made apple gameloft released december 17 2009 ios webos one games containing gameloft live online gaming service later released playstation network playstation portable playstation 3 december 21 2010 five days release n.o.v.a 2 n.o.v.a legacy free download pay2progress game marketed remaster original n.o.v.a developed gameloft madrid actually locations original story completely removed released android google play store 2017 app store ios 2018 game hostiles known xenos similar metroid series well halo series n.o.v.a primarily first-person shooter one on-rails driving segment throughout game twelve levels players fight alien enemies known xenos game takes major cues sci-fi console shooters halo metroid series player use eight weapons resemble futuristic versions weapons found one gameloft previous works players use multiplayer n.o.v.a following ways indeterminate point future earth rendered uninhabitable humans animals unknown means therefore humans built satellites space order protect xenos created alliance called n.o.v.a near orbit vanguard alliance kal wardin n.o.v.a commander enjoying drink 2 soldiers come knock kal wakes training area tries head ship attacked xenos goes colonial frigate gone quiet time unknown reasons kal crashes ship inside air lock attacked raiders kal told self-destruct frigate explodes lands back earth meets later possible survivors frigate goes planet xenos yelena deleted pushes finds judger kal kills whole planet possibly explodes game well received critics metacritic score 94/100 based 9 reviews levi buchanan ign awarded game 9.0/10 calling best first-person shooter iphone right pocket gamer gave game 9/10 gold award slide play gave perfect 4/4 saying fans fpses n't let one slip halo ripoff packs lot great content tiny modestly-priced package high-definition version game released app store april 1 2010 however compatible apple ipad tablet pc july 21 2010 n.o.v.a along heavily updated iphone 4 includes gyroscope control hd 3d graphics compatible multitasking ios 4 august 31 2010 free version n.o.v.a hd released ipad remaster game called n.o.v.a legacy updated graphics weapon upgrade system power meter features released march 27 2017 sequel n.o.v.a developed published gameloft released itunes app store december 16 2010 titled game innovated many designs created first n.o.v.a added many new features 10-player online multiplayer matches retina display gyroscope support iphone 4 later may 10 2012 n.o.v.a 3 released app store also developed published gameloft added new features 2-man cars multiplayer updated graphics working in-house editor
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Operating systems
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privilege bracketing computer security privilege bracketing temporary increase software privilege within process perform specific function assuming necessary privileges last possible moment dismissing soon longer strictly necessary therefore ostensibly avoiding fallout erroneous code unintentionally exploits privilege merited example use principle least privilege defensive programming distinguished privilege separation much effective security measure separates privileged parts system unprivileged parts putting different processes opposed switching within single process
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Computer security
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port scanner port scanner application designed probe server host open ports application may used administrators verify security policies networks attackers identify network services running host exploit vulnerabilities port scan portscan process sends client requests range server port addresses host goal finding active port nefarious process majority uses port scan attacks rather simple probes determine services available remote machine portsweep scan multiple hosts specific listening port latter typically used search specific service example sql-based computer worm may portsweep looking hosts listening tcp port 1433 design operation internet based internet protocol suite commonly also called tcp/ip system network services referenced using two components host address port number 65536 distinct usable port numbers services use limited range port numbers port scanners scan common port numbers ports commonly associated vulnerable services given host result scan port usually generalized one three categories open ports present two vulnerabilities administrators must wary filtered ports tend present vulnerabilities forms port scanning rely assumption targeted host compliant rfc 793 transmission control protocol although case time still chance host might send back strange packets even generate false positives tcp/ip stack host non-rfc-compliant altered especially true less common scan techniques os-dependent fin scanning example tcp/ip stack fingerprinting method also relies types different network responses specific stimulus guess type operating system host running simplest port scanners use operating system network functions generally next option go syn feasible option described next nmap calls mode connect scan named unix connect system call port open operating system completes tcp three-way handshake port scanner immediately closes connection avoid performing denial-of-service attack otherwise error code returned scan mode advantage user require special privileges however using os network functions prevents low-level control scan type less common method noisy particularly portsweep services log sender ip address intrusion detection systems raise alarm syn scan another form tcp scanning rather using operating system network functions port scanner generates raw ip packets monitors responses scan type also known half-open scanning never actually opens full tcp connection port scanner generates syn packet target port open respond syn-ack packet scanner host responds rst packet closing connection handshake completed port closed unfiltered target instantly respond rst packet use raw networking several advantages giving scanner full control packets sent timeout responses allowing detailed reporting responses debate scan less intrusive target host syn scan advantage individual services never actually receive connection however rst handshake cause problems network stacks particular simple devices like printers conclusive arguments either way udp scanning also possible although technical challenges udp connectionless protocol equivalent tcp syn packet however udp packet sent port open system respond icmp port unreachable message udp port scanners use scanning method use absence response infer port open however port blocked firewall method falsely report port open port unreachable message blocked ports appear open method also affected icmp rate limiting alternative approach send application-specific udp packets hoping generate application layer response example sending dns query port 53 result response dns server present method much reliable identifying open ports however limited scanning ports application specific probe packet available tools e.g. nmap generally probes less 20 udp services commercial tools many 70 cases service may listening port configured respond particular probe packet ack scanning one unusual scan types exactly determine whether port open closed whether port filtered unfiltered especially good attempting probe existence firewall rulesets simple packet filtering allow established connections packets ack bit set whereas sophisticated stateful firewall might rarely used outdated nature window scanning fairly untrustworthy determining whether port opened closed generates packet ack scan checks whether window field packet modified packet reaches destination design flaw attempts create window size packet port open flagging window field packet 1 returns sender using scanning technique systems longer support implementation returns 0 window field labeling open ports closed since syn scans surreptitious enough firewalls general scanning blocking packets form syn packets fin packets bypass firewalls without modification closed ports reply fin packet appropriate rst packet whereas open ports ignore packet hand typical behavior due nature tcp ways inescapable downfall unusual scan types exist various limitations widely used nmap supports many internet service providers restrict customers ability perform port scans destinations outside home networks usually covered terms service acceptable use policy customer must agree isps implement packet filters transparent proxies prevent outgoing service requests certain ports example isp provides transparent http proxy port 80 port scans address appear port 80 open regardless target host actual configuration information gathered port scan many legitimate uses including network inventory verification security network port scanning however also used compromise security many exploits rely upon port scans find open ports send specific data patterns attempt trigger condition known buffer overflow behavior compromise security network computers therein resulting loss exposure sensitive information ability work threat level caused port scan vary greatly according method used scan kind port scanned number value targeted host administrator monitors host port scan often viewed first step attack therefore taken seriously disclose much sensitive information host despite probability port scan alone followed real attack small probability attack much higher port scan associated vulnerability scan inherently open decentralized architecture internet lawmakers struggled since creation define legal boundaries permit effective prosecution cybercriminals cases involving port scanning activities example difficulties encountered judging violations although cases rare time legal process involves proving intent commit break-in unauthorized access existed rather performance port scan 2006 uk parliament voted amendment computer misuse act 1990 person guilty offence makes adapts supplies offers supply article knowing designed adapted use course connection offence section 1 3 cma nevertheless area effect amendment blurred widely criticized security experts germany strafgesetzbuch § 202a b c also similar law council european union issued press release stating plan pass similar one albeit precise
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Computer security
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overlay programming general computing sense overlaying means process transferring block program code data main memory replacing already stored overlaying programming method allows programs larger computer main memory embedded system would normally use overlays limitation physical memory internal memory system-on-chip lack virtual memory facilities constructing overlay program involves manually dividing program self-contained object code blocks called overlays laid tree structure sibling segments depth level share memory called overlay region destination region overlay manager either part operating system part overlay program loads required overlay external memory destination region needed often linkers provide support overlays following example shows control statements instruct os/360 linkage editor link overlay program indented show structure segment names arbitrary statements define tree consisting permanently resident segment called root two overlays b loaded following end mod2 overlay consists two overlay segments aa ab execution time overlays b utilize memory locations aa ab utilize locations following end mod3 segments root given overlay segment called path business applications intended run platforms virtual memory developer platform design program memory constraint exist unless program working set exceeds available physical memory importantly architect focus problem solved without added design difficulty forcing processing steps constrained overlay size thus designer use higher-level programming languages allow programmer much control size e.g java c++ smalltalk still overlays remain useful embedded systems low-cost processors used embedded systems provide memory management unit mmu addition many embedded systems real-time systems overlays provide determinate response-time paging example space shuttle primary avionics system software pass uses programmed overlays even platforms virtual memory software components codecs may decoupled point loaded needed home computer era overlays popular operating system many computer systems ran lacked virtual memory little ram current standards — original ibm pc 16k 64k depending configuration overlays popular technique commodore basic load graphics screens order detect overlay already loaded flag variable could used several dos linkers 1980s supported overlays form nearly identical used 25 years earlier mainframe computers binary files containing memory overlays de facto standard extension .ovl file type used among others wordstar dbase enable dos office automation software package enable software inc.. gfa basic compiler able produce .ovl files
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Operating systems
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trips architecture trips microprocessor architecture designed team university texas austin conjunction ibm intel sun microsystems trips uses instruction set architecture designed easily broken large groups instructions graphs run independent processing elements design collects related data graphs attempting avoid expensive data reads writes keeping data high speed memory close processing elements prototype trips processor contains 16 elements trips hoped reach 1 tflop single processor papers published 2003 2006 computer programs consist series instructions stored memory processor runs program fetching instructions memory examining performing actions instruction calls early machines speed main memory generally order time basic operation within processor instance instruction adds two numbers might take three four instruction cycles fetching numbers memory might take one two cycles machines penalty data main memory instruction set architectures generally designed allow direct access instance add instruction might take value one location memory add value another store result third location introduction increasingly fast microprocessors cheap-but-slower dynamic ram changed equation dramatically modern machines fetching value main memory might take equivalent thousands cycles one key advances risc concept include processor registers earlier designs typically several dozen rather two three instructions formerly provided memory locations eliminated replaced ones worked registers loading data register explicit separate load action performed results explicitly saved back one could improve performance eliminating many memory instructions possible technique quickly reached limits since 1990s modern cpus added increasing amounts cpu cache increase local storage although cache slower registers since late 1990s performance gains mostly made use additional functional units allow instructions run parallel instance two addition instructions working different data run time effectively doubling speed program modern cpus generally dozens units integer math boolean logic floating point math long-data words others dealing memory housekeeping chores however programs work independent data instead use outputs one calculation input another limits set instructions run parallel factor based many instructions processor able examine on-the-fly level instruction parallelism quickly plateaued mid-2000s one attempt break limit long instruction word vliw concept vliw hands task looking instruction parallelism compiler removing processor theory allows entire program examined independent instructions sent processor order make maximal use functional units however proven difficult practice vliw processors become widely popular even case vliw another problem grown become issue traditional designs data instructions handled different parts cpu processing speeds low cause problems performance increased communication times one side chip registers functional units grows become significant fraction overall processing time gains performance registers distributed closer functional units trips processor based explicit data graph execution edge concept edge attempts bypass certain performance bottlenecks come dominate modern systems edge based processor able better understand instruction stream sent seeing linear stream individual instructions rather blocks instructions related single task using isolated data edge attempts run instructions block distributing internally along data need process compilers examine code find blocks code share information specific way assembled compiled hyperblocks fed cpu since compiler guaranteeing blocks specific interdependencies processor isolate code single functional unit local memory consider simple example adds two numbers memory adds result another value memory case traditional processor would notice dependency schedule instructions run one storing intermediate results registers edge processor interdependencies data code would noticed compiler would compile instructions single block block would fed along data needed complete single functional unit private set registers ensures additional memory fetching required well keeping registers physically close functional unit needs values code rely intermediate data would compiled separate hyperblocks course possible entire program would use data compilers also look instances data handed code effectively abandoned original block common access pattern case compiler still produce two separate hyperblocks explicitly encode handoff data rather simply leaving stored shared memory location processor see communications events schedule run proper order blocks considerable interdependencies re-arranged compiler spread communications order avoid bottlenecking transport effect change greatly increase isolation individual functional units edge processors limited parallelism capabilities compiler on-chip systems whereas modern processors reaching plateau four-wide parallelism edge designs scale much wider also scale deeper well handing blocks one unit another chain scheduled reduce contention due shared values university texas austin implementation edge concept trips processor tera-op reliable intelligently adaptive processing system trips cpu built repeating single basic functional unit many times needed trips design use hyperblocks loaded en-masse allows dramatic gains speculative execution whereas traditional design might hundred instructions examine possible scheduling functional units trips design thousands hundreds instructions per hyperblock hundreds hyperblocks examined leads greatly improved functional unit utilization scaling performance typical 4-issue superscalar design trips process three times many instructions per cycle traditional designs variety different types units integer floating point etc. allowing parallelism four-wide schedulers would otherwise allow however order keep units active instruction stream include different types instruction often case practice traditional cpus often lots idle functional units trips individual units general purpose allowing instruction run core avoid need carefully balance number different kinds cores also means trips design built number cores needed reach particular performance requirement single-core trips cpu simplified eliminated scheduler run set hyperblocks exactly like one hundreds cores slower better yet performance dependent types data fed meaning trips cpu run much wider variety tasks level performance instance traditional cpu fed math-heavy workload bog soon floating point units busy integer units lying idle fed data intensive program like database job floating point units lie idle integer units bog trips cpu every functional unit add performance every task every task run every unit designers refer polymorphic processor trips flexible regard developers suggested would even replace custom high-speed designs like dsps like trips dsps gain additional performance limiting data inter-dependencies unlike trips allowing limited workflow run trips would fast custom dsp workloads equally able run workloads time designers noted unlikely trips processor could used replace highly customized designs like gpus modern graphics cards may able replace outperform many lower-performance chips like used media processing reduction global register file also results non-obvious gains addition new circuitry modern processors meant overall size remained even move smaller process sizes result relative distance register file grown limits possible cycle speed due communications delays edge data generally local isolated well defined inter-core links eliminating large cross-chip delays means individual cores run higher speeds limited signaling time much shorter data paths combination two design changes effects greatly improves system performance goal produce single-processor system 1 tflops performance 2012 however 2008 gpus ati nvidia already exceeded 1 teraflop barrier albeit specialized applications traditional cpus contemporary 2007 mac pro using 2-core intel xeon perform 5 gflops single applications 2003 trips team started implementing prototype chip chip two complete cores one 16 functional units 4-wide 4-deep arrangement current implementation compiler constructs hyperblocks 128 instructions allows system keep 8 blocks flight time total 1,024 instructions per core basic design include 32 chips interconnected approaching 500 gflops
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Computer architecture
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higher-order differential cryptanalysis cryptography higher-order differential cryptanalysis generalization differential cryptanalysis attack used block ciphers standard differential cryptanalysis difference two texts used higher-order differential cryptanalysis studies propagation set differences larger set texts xuejia lai 1994 laid groundwork showing differentials special case general case higher order derivates lars knudsen year able show concept higher order derivatives used mount attacks block ciphers attacks superior standard differential cryptanalysis higher-order differential cryptanalysis notably used break kn-cipher cipher previously proved immune standard differential cryptanalysis block cipher maps formula_1-bit strings formula_1-bit strings fixed key thought function formula_3 standard differential cryptanalysis one interested finding pair input difference formula_4 output difference formula_5 two input texts difference formula_4 likely result output texts difference formula_5 i.e. formula_8 true many formula_9 note difference used xor usual case though definitions difference possible motivates defining derivative function formula_3 point formula_4 formula_12 using definition formula_13-th derivative formula_14 recursively defined formula_15 thus example formula_16 higher order derivatives defined many properties common ordinary derivative sum rule product rule importantly also taking derivative reduces algebraic degree function implement attack using higher order derivatives knowledge probability distribution derivative cipher needed calculating estimating distribution generally hard problem cipher question known low algebraic degree fact derivatives reduce degree used example cipher s-box function analysis known algebraic degree 8 9th order derivative must 0 therefore important cipher s-box function specific maximal close maximal degree defy attack cube attacks considered variant higher-order differential attacks works small low algebraic degree s-boxes small s-boxes addition xor operations
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Computer security
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sucuri sucuri company started daniel cid 2010 founder ossec project early premise sucuri provide webmasters tool provides visibility state security websites 2010 sucuri became private llc delaware dre armeda invited co-founder 2011 tony perez joined team third co-founder sucuri acquired godaddy march 2017 sucuri globally distributed company 100 employees across 27 different countries
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Computer security
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gyazmail gyazmail email client macos developed maintained japanese programmer goichi hirakawa supports pop3 imap smtp protocols handling multiple email accounts includes local mailboxes gyazmail based native macos cocoa written objective-c. gyazmail uses search function oniguruma regular expression library supports variety character encodings especially relevant asian languages version 1.0.1 released 2003
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Internet protocols
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distributed denial-of-service attacks root nameservers distributed denial-of-service attacks root nameservers internet events distributed denial-of-service attacks target one thirteen domain name system root nameserver clusters root nameservers critical infrastructure components internet mapping domain names ip addresses resource record rr data attacks root nameservers could theory impact operation entire global domain name system thus internet services use global dns rather specific websites however practice root nameserver infrastructure highly resilient distributed using inherent features dns result caching retries multiple servers zone fallback one fail recent years combination anycast load balancer techniques used implement thirteen nominal individual root servers globally distributed clusters servers multiple data centers particular caching redundancy features dns mean would require sustained outage major root servers many days serious problems created internet users even still numerous ways isps could set systems period mitigate even total loss root servers extended period time example installing copies global dns root zone data nameservers within network redirecting traffic root server ip addresses servers nevertheless ddos attacks root zone taken seriously risk operators root nameservers continue upgrade capacity ddos mitigation capabilities infrastructure resist future attacks effective attack dns might involve targeting top-level domain servers servicing .com domain instead root name servers alternatively man-in-the-middle attack dns poisoning attack could used though would difficult carry october 21 2002 attack lasting approximately one hour targeted 13 dns root name servers attackers sent many icmp ping packets using botnet servers however servers protected packet filters configured block incoming icmp ping packets sustain much damage little impact internet users february 6 2007 attack began 10:00 utc lasted twenty-four hours least two root servers g-root l-root reportedly suffered badly two others f-root m-root experienced heavy traffic latter two servers largely contained damage distributing requests root server instances anycast addressing icann published formal analysis shortly event due lack detail speculation incident proliferated press details released two intervals november 30 2015 december 1 2015 several root name servers received 5 million queries per second receiving valid queries single undisclosed domain name different domain next day source addresses spread throughout ipv4 space however may spoofed root server networks became saturated resulting timeouts however redundancy among root servers prevented downstream issues occurring incident february 12 2012 statement posted pastebin cited anonymous threatening attack root servers march 31 2012 protest sopa wallstreet irresponsible leaders beloved bankers starving world selfish needs sheer sadistic fun march 31 anonymous shut internet reads statement remember protest trying ‘ kill internet temporarily shutting hurts most…it may last one hour maybe maybe even days matter global known
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Computer security
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federation software theft federation software theft fast not-for-profit organisation formed 1984 aim eliminating copyright infringement software uk fast world first anti-piracy organisation work protecting copyrights software publishers initially concentrating lobbying parliament revise copyright law fast also prosecutes organisations individuals copyright infringement behalf members publicises legal penalties security risks prior agreement fast investors software not-for-profit organisation limited guarantee mission support advance professionalism software asset management related asset management enable individuals organisations improve effectiveness efficiency direct result work iso sam iso 19770 standard successfully launched may 2006 september 2008 fast investors software signed exclusive agreement operate federation name strengthen clarify advice given end user community relating best practice software asset management sam achieving cost efficient licence compliance new organisation operate name fast iis may 2008 fast iis launched initiative aim making easier end users manage software licensing requirements contain costs ensure effective software asset management software licence management encompassing compliance software industry research board sirb formed consultation five tier one software vendors fast iis remains not-for-profit organisation limited guarantee wholly owned members include software publishers resellers distributors sam practitioners law firms fast iis works champion professional management software protect members ’ rights since inception fast successfully lobbied changes software ip system uk eu dealings uk intellectual property office fast lobbying efforts brought amendments copyright act 1956 culminating software recognised literary work 2007 fast alliance ip theft successful pushing implementation section 107a copyright designs patents act 1988 ip crime measurement national policing safety plan
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Computer security
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page table page table data structure used virtual memory system computer operating system store mapping virtual addresses physical addresses virtual addresses used program executed accessing process physical addresses used hardware specifically ram subsystem page table key component virtual address translation necessary access data memory operating systems use virtual memory every process given impression working large contiguous sections memory physically memory process may dispersed across different areas physical memory may moved paged another storage typically hard disk drive process requests access data memory responsibility operating system map virtual address provided process physical address actual memory data stored page table operating system stores mappings virtual addresses physical addresses mapping also known page table entry pte cpu memory management unit mmu stores cache recently used mappings operating system page table called translation lookaside buffer tlb associative cache virtual address needs translated physical address tlb searched first match found tlb hit physical address returned memory access continue however match called tlb miss memory management unit operating system tlb miss handler typically look address mapping page table see whether mapping exists page walk one exists written back tlb must done hardware accesses memory tlb virtual memory system faulting instruction restarted may happen parallel well subsequent translation find tlb hit memory access continue page table lookup may fail two reasons physical memory full simple operation page written back physical memory page table tlb updated instruction restarted however physical memory full one pages physical memory need paged make room requested page page table needs updated mark pages previously physical memory longer mark page disk physical memory tlb also needs updated including removal paged-out page instruction restarted page page subject page replacement algorithms simplest page table systems often maintain frame table page table frame table holds information frames mapped advanced systems frame table also hold information address space page belongs statistics information background information page table holds mapping virtual address page address physical frame also auxiliary information page present bit dirty modified bit address space process id information amongst others secondary storage hard disk used augment physical memory pages paged physical memory disk present bit indicate pages currently present physical memory disk indicate treat different pages i.e whether load page disk page another page physical memory dirty bit allows performance optimization page disk paged physical memory read subsequently paged need written back disk since page changed however page written paged dirty bit set indicating page must written back backing store strategy requires backing store retain copy page paged memory dirty bit used backing store need large instantaneous total size paged-out pages moment dirty bit used times pages exist physical memory backing store operating systems single address space operating systems address space process id information necessary virtual memory management system knows pages associate process two processes may use two identical virtual addresses different purposes page table must supply different virtual memory mappings two processes done assigning two processes distinct address map identifiers using process ids associating process ids virtual memory pages also aid selection pages page pages associated inactive processes particularly processes whose main code page paged less likely needed immediately pages belonging active processes alternative tagging page table entries process-unique identifiers page table may occupy different virtual-memory page process page table becomes part process context implementation process page table paged whenever process longer resident memory several types page tables best suited different requirements essentially bare-bones page table must store virtual address physical address virtual address possibly address space information inverted page table ipt best thought off-chip extension tlb uses normal system ram unlike true page table necessarily able hold current mappings os must prepared handle misses would mips-style software-filled tlb ipt combines page table frame table one data structure core fixed-size table number rows equal number frames memory 4000 frames inverted page table 4000 rows row entry virtual page number vpn physical page number physical address data means creating collision chain see later search entries core ipt structure inefficient hash table may used map virtual addresses address space/pid information need index ipt collision chain used hash table known hash anchor table hashing function generally optimized coverage raw speed desirable course hash tables experience collisions due chosen hashing function may experience lot collisions usage entry table vpn provided check searched entry collision searching mapping hash anchor table used entry exists page fault occurs otherwise entry found depending architecture entry may placed tlb memory reference restarted collision chain may followed exhausted page fault occurs virtual address schema could split two first half virtual page number second half offset page major problem design poor cache locality caused hash function tree-based designs avoid placing page table entries adjacent pages adjacent locations inverted page table destroys spatial locality reference scattering entries operating system may minimize size hash table reduce problem trade-off increased miss rate normally one hash table contiguous physical memory shared processes per-process identifier used disambiguate pages different processes somewhat slow remove page table entries given process os may avoid reusing per-process identifier values delay facing alternatively per-process hash tables may used impractical memory fragmentation requires tables pre-allocated inverted page tables used example powerpc ultrasparc ia-64 architecture inverted page table keeps listing mappings installed frames physical memory however could quite wasteful instead could create page table structure contains mappings virtual pages done keeping several page tables cover certain block virtual memory example create smaller 1024-entry 4k pages cover 4m virtual memory useful since often top-most parts bottom-most parts virtual memory used running process top often used text data segments bottom stack free memory multilevel page table may keep smaller page tables cover top bottom parts memory create new ones strictly necessary smaller page tables linked together master page table effectively creating tree data structure need two levels possibly multiple ones virtual address schema could split three parts index root page table index sub-page table offset page multilevel page tables also referred hierarchical page tables mentioned creating page table structure contained mappings every virtual page virtual address space could end wasteful get around excessive space concerns putting page table virtual memory letting virtual memory system manage memory page table however part linear page table structure must always stay resident physical memory order prevent circular page faults look key part page table present page table present page table etc nested page tables implemented increase performance hardware virtualization providing hardware support page-table virtualization need emulate greatly reduced x86 virtualization current choices intel extended page table feature amd rapid virtualization indexing feature
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Operating systems
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boucher boucher case citation 2:06-mj-91 2009 wl 424718 federal criminal case vermont first directly address question whether investigators compel suspect reveal encryption passphrase password despite u.s. constitution fifth amendment protection self-incrimination magistrate judge held producing passphrase would constitute self-incrimination submission appeal district court government stated seek password encrypted hard drive sought force boucher produce contents encrypted hard drive unencrypted format opening drive grand jury district court judge agreed government holding given boucher initial cooperation showing content computer border agents producing complete contents would constitute self-incrimination late 2009 boucher finally gave password investigators found numerous images videos depicting sexual abuse children january 2010 boucher sentenced 3 years prison deported 17 december 2006 laptop computer defendant sebastien d. boucher born 1977 inspected crossed border canada united states derby line vermont laptop powered-up border crossed allowed contents browsed images containing child pornography allegedly seen immigration customs enforcement ice border agents seized laptop questioned boucher arrested complaint charging transportation child pornography violation 18 u.s.c 2252a 1 laptop subsequently powered-down laptop switched booted 29 december 2006 possible access entire storage capability laptop protected pgp disk encryption result investigators working us government unable view contents drive z allegedly contained illegal content grand jury subpoenaed defendant provide password encryption key protecting data november 29 2007 u.s. magistrate judge jerome niedermeier united states district court district vermont stated compelling boucher enter password forces produce evidence could used incriminate accordingly niedermeier quashed subpoena january 2 2008 united states appealed magistrate opinion district court sealed motion court docket case 2:06-mj-00091-wks-jjn-1 appeal heard u.s. district judge william k. sessions oral arguments scheduled april 30 2008 february 19 2009 judge sessions reversed magistrate ruling directed boucher provide unencrypted version z drive viewed ice agent
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Computer file systems
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canon v-20 canon v-20 msx microcomputer made japanese corporation canon innovative digital camera interface t-90/dmb-90 use canon t90 v-10 quite identical v-20 except less ram memory 16 kb white case
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Computer architecture
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jconsole jconsole graphical monitoring tool monitor java virtual machine jvm java applications local remote machine jconsole uses underlying features java virtual machine provide information performance resource consumption applications running java platform using java management extensions jmx technology jconsole comes part java development kit jdk graphical console started using jconsole command
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Programming language topics
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mlab mlab fully managed cloud database service hosts mongodb databases mlab runs cloud providers amazon google microsoft azure partnered platform-as-a-service providers may 2011 mlab secured 3 million first-round funding foundry group baseline ventures upfront ventures freestyle capital david cohen october 2012 mlab received follow-on investment 5 million shortly thereafter mlab named network world one 10 useful cloud databases along amazon web services google cloud sql microsoft azure rackspace others june 2014 mongodb inc. announced fully managed highly available mongodb-as-a-service add-on offering microsoft azure store offering delivered collaboration microsoft mlab february 2016 mlab changed name mongolab mlab expand new areas products october 2018 mlab announced acquired mongodb inc. citing reasons shared vision engineering culture engineers mlab invited join mongodb inc. mlab customers transitioned mongodb atlas instances acquisition expected close fourth quarter mongodb ’ fiscal year ending jan. 31 2019
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Distributed computing architecture
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clickjacking clickjacking classified user interface redress attack ui redress attack ui redressing malicious technique tricking user clicking something different user perceives thus potentially revealing confidential information allowing others take control computer clicking seemingly innocuous objects including web pages web browsers clickjacking browser security issue vulnerability across variety browsers platforms clickjacking also take place outside web browsers including applications clickjack takes form embedded code script execute without user knowledge clicking button appears perform another function clickjacking instance confused deputy problem wherein computer innocently fooled misusing authority 2002 noted possible load transparent layer web page user input affect transparent layer without user noticing however mainly ignored major issue 2008 2008 jeremiah grossman robert hansen discovered adobe flash player able clickjacked allowing attacker gain access computer without user knowledge term clickjacking coined jeremiah grossman robert hansen portmanteau words click hijacking attacks similar nature discovered focus term ui redressing changed describe category attacks rather clickjacking clickjacking takes advantage vulnerabilities present applications web pages allow attacker manipulate user computer example clickjacked page tricks user performing undesired actions clicking concealed link clickjacked page attackers load another page transparent layer unsuspecting users think clicking visible buttons actually performing actions invisible page hidden page may authentic page therefore attackers trick users performing actions users never intended way tracing actions attackers later users would genuinely authenticated hidden page clickjacking limited type though present forms classic clickjacking refers attacker uses hidden layers web pages manipulate actions user cursor resulting user mislead truly clicked user might receive email link video news item another webpage say product page amazon hidden top underneath play button news video user tries play video actually buys product amazon hacker send single click rely fact visitor logged amazon.com 1-click ordering enabled technical implementation attacks may challenging due cross-browser incompatibilities number tools beef metasploit project offer almost fully automated exploitation clients vulnerable websites clickjacking may facilitated may facilitate web attacks xss likejacking malicious technique tricking users website liking facebook page intentionally mean like term likejacking came comment posted corey ballou article like anything web safely one first documented postings explaining possibility malicious activity regarding facebook like button according article ieee spectrum solution likejacking developed one facebook hackathons like bookmarklet available avoids possibility likejacking present facebook like button nested clickjacking compared classic clickjacking works embedding malicious web frame two frames original harmless web page framed page displayed top window works due vulnerability http header codice_1 element value codice_2 web browser checks two aforementioned layers fact additional frames added two remaining undetected means attackers use benefit past google+ faulty version codice_1 attackers able insert frames choice using vulnerability present google image search engine image display frames present google+ well attacker-controlled frames able load restricted allowing attackers mislead whoever came upon image display page cursorjacking ui redressing technique change cursor location user perceives discovered 2010 eddy bordi researcher vulnerability.fr marcus niemietz demonstrated custom cursor icon 2012 mario heiderich hiding cursor jordi chancel researcher alternativ-testing.fr discovered cursorjacking vulnerability using flash html javascript code mozilla firefox mac os x systems fixed firefox 30.0 lead arbitrary code execution webcam spying second cursorjacking vulnerability discovered jordi chancel mozilla firefox mac os x systems fixed firefox 37.0 using flash html javascript code lead also spying webcam execution malicious addon allowing execution malware computer trapped user browserless clickjacking attackers utilize vulnerabilities programs replicate classic clickjacking without required use presence web browser method clickjacking mainly prevalent among mobile devices usually android devices especially due way toast notifications work toast notifications small delay moment notification requested moment notification actually displays on-screen attackers capable using gap create dummy button lies hidden underneath notification still clicked cookiejacking form clickjacking cookies stolen web browsers done tricking user dragging object seemingly appears harmless fact making user select entire content cookie targeted attacker acquire cookie data within filejacking attackers use web browser capability navigate computer access computer files order acquire personal data tricking user establishing active file server file folder selection window browsers use attackers access take files victims computers 2014 paper researcher carnegie mellon university found browsers refuse autofill protocol current login page different protocol time password saved password managers would insecurely fill passwords http version https-saved passwords managers protect iframe- redirection-based attacks exposed additional passwords password synchronization used multiple devices protection clickjacking including likejacking added mozilla firefox desktop mobile versions installing noscript add-on clearclick feature released 8 october 2008 prevents users clicking invisible redressed page elements embedded documents applets according google browser security handbook year 2008 noscript clearclick freely available product offers reasonable degree protection clickjacking protection newer cursorjacking attack added noscript 2.2.8 rc1 noclickjack web browser add-on browser extension adds client-side clickjack protection users google chrome mozilla firefox opera microsoft edge without interfering operation legitimate iframes noclickjack based technology developed guardedid noclickjack add-on free guardedid commercial product includes client-side clickjack protection users internet explorer without interfering operation legitimate iframes guardedid clickjack protection forces frames become visible guardedid teams web browser add-on noclickjack add protection google chrome mozilla firefox opera microsoft edge gazelle microsoft research project secure web browser based ie uses os-like security model limited defenses clickjacking gazelle window different origin may draw dynamic content another window screen space content draws opaque web site owners protect users ui redressing frame based clickjacking server side including framekiller javascript snippet pages want included inside frames different sources javascript-based protection unfortunately always reliable especially true internet explorer kind countermeasure circumvented design including targeted page inside iframe security=restricted element introduced 2009 internet explorer 8 new http header codice_1 offered partial protection clickjacking shortly adopted browsers safari firefox chrome opera header set website owner declares preferred framing policy values codice_5 codice_2 codice_7 prevent framing framing external sites allow framing specified site respectively addition advertising sites return non-standard codice_8 value intention allow framing content page equivalent setting x-frame-options 2013 x-frame-options header officially published rfc 7034 internet standard document provided informational purposes w3c content security policy level 2 recommendation provides alternative security directive frame-ancestors intended obsolete x-frame-options header security header like x-frame-options protect users clickjacking attacks using frame codice_9 directive content security policy introduced version 1.1 allow disallow embedding content potentially hostile pages using iframe object etc directive obsoletes x-frame-options directive page served headers frame-ancestors policy preferred browser.—although popular browsers disobey requirement example frame-ancestors policies
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Computer security
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high level architecture high-level architecture hla standard distributed simulation used building simulation larger purpose combining federating several simulations standard developed 90 ’ leadership us department defense later transitioned become open international ieee standard recommended standard within nato stanag 4603 today hla used number domains including defense security civilian applications architecture specifies following components together components form federation hla standard consists three parts hla initiated early 1990 ’ dr. anita k. jones director defense research engineering within us department defense gave defense modeling simulation office dmso task “ assuring interoperability reusability defense models simulations ” 1995 dmso formulated vision modeling simulation established modeling simulation masterplan included high-level architecture two protocols interoperability already existed distributed interactive simulation dis focusing real-time platform level simulation fixed object model aggregate level simulation protocol alsp focusing simulation aggregate time management ownership management flexible object models called confederation models purpose hla provide one unified standard would meet simulation interoperability requirements us dod components development hla based four prototypical federations platform prototype federation joint training protofederation analysis protofederation engineering prototype federation hla specification prototyped refined hla 1.3 finally released facilitate usage outside defense community hla transitioned ieee standard maintained simulation interoperability standards organization siso facilitate migration dis users federation object model corresponding fixed object model dis also developed real-time platform reference fom rpr fom following hla versions exist hla 1.3 published march 1998 dmso consists us dod also published interpretations hla 1.3 hla ieee 1516-2000 published 2000 ieee consists major improvements ieee 1516-2000 included xml-based fom detailed data type specifications well improved ddm design ieee 1516-2000 standard also complemented recommended development process well recommended vv process soon found 1516-2000 standard apis slightly different rti implementation siso produced standard alternate dynamic link compatible dlc c++ java apis dlc apis later merged main standard ieee 1516-2010 standard published august 2010 ieee commonly known hla evolved consists major improvements ieee 1516-2010 include modular foms incorporation dlc apis c++ java web services api fault tolerance machine-readable parts version hla xml schemas c++ java wsdl apis well fom/som samples downloaded ieee 1516 download area ieee web site full standards texts available extra cost siso members purchased ieee shop development new version hla started january 2016 siso currently ongoing hla standard consists three parts rti services defined hla interface specification grouped seven service groups addition services management object model mom provides services makes possible inspect adjust state federation programmatically rtis consist central rti component crc executable local rti components lrcs libraries used federates services provided c++ java api also using web services c++ java apis services invoked using calls instance rti ambassador class rti delivers information federate using callbacks delivered using calls instance federate ambassador class web services api defined using wsdl calls made callbacks fetched federate using web services requests responses service group descriptions focus key services exceptions advisories included purpose federation management services manage federation executions well federation-wide operations synchronization points save/restore one set federation management services manages connection rti federation execution set joined federates key services another set services relates synchronization points federation-wide events selected federates required complete operation initializing scenario execution continue key services yet another set service relates saving restoring federation execution save operation requires rti federate perform save internal state restore operation requires rti federate perform restore internal state key services save restore purpose declaration management services enable federates declare information wish publish send subscribe receive based object interaction classes fom rti uses information route updates interactions subscribing federates object class publishing subscribing performed specific set attributes interaction classes entire interaction including parameters published subscribed key services purpose object management services enable federates share information object instances exchange interactions object instance names reserved automatically generated federates register object instances specified object classes discovered subscribing federates attributes object instances updated updates reflected subscribing federates interactions sent interactions delivered subscribing federates key services objects attributes interactions purpose ownership management services dynamically manage federate simulates aspect object instance hla one federate allowed update given attribute given object instance federate considered owner attribute federate registers new object instance automatically owner attributes publishes cases attributes object instance may become unowned i.e owned federate ownership management provides services transferring ownership one several attributes runtime include federate divesting attribute another federate acquiring attribute two main patterns “ pull ” initiated acquiring federate “ push ” initiated divesting federate key services initiating “ pull ” ownership key services initiating “ push ” ownership object instances predefined attribute called hlaprivilegetodeleteobject owner attribute object instance allowed delete object instance ownership attribute transferred runtime using operations information exchange hla federation takes place real-time immediate receive order ro delivery messages unless hla time management enabled purpose hla time management guarantee causality correct consistent exchange time stamped messages updates interactions time stamp order tso matter federation executes real-time faster-than-real-time slower-than-real-time as-fast-as-possible important concepts hla time management logical time time axis hla starting zero logical time used time management timestamps operations logical time axis mapped scenario time federation example mapping let zero represent scenario time 8:00 1-jan-1066 let increment one represent one second scenario lookahead time interval specifying lowest time future federate produce messages federate fixed time step usually length time step granted federate granted allowed advance particular logical time rti time-stamped messages time delivered federate safely start calculating messages timestamp future timestamp may earlier granted time plus federates lookahead advancing federate finished producing data granted time plus lookahead may request advanced later time also means promises produce messages time stamp less requested time plus lookahead federate advancing state time regulating federate sends time stamped events considered time regulating since time advance federates may regulated time constrained federate receives time managed events considered time constrained since reception time stamped messages constrains time advance main principles hla time management example lookahead granted advancing least one federate federation performs pacing i.e correlates time advance requests real time clock federation may run real time scaled real time without pacing federation run fast possible used example monte carlo simulation key services include event driven simulation also possible federate request advanced next event using following service another important concept greatest available logical time galt greatest time federate granted depends time federates granted well lookahead galt federate specifies far federate granted without wait federates granted particularly interesting federate joins late time managed federation key services galt advanced services include order ensure proper interaction simulations way testing federate conformance defined involves ensuring every class interaction listed som particular federate used according usage described publishsubscribe publish subscribe none hla 1516-2010 instead single fdd describes entire fom specification describes fom modules merged form full fom default federation created merging hlastandardmim.xml fom module module provided federate creates federation standard mim mom initialization module contains mom classes basic default data types joining federate add one fom modules extend existing fom principle nothing changes federates call functions rti difference elements fom needed loaded managed addition federate joins late additional information exchange requirements added modular foms used hla rules describe responsibilities federations federates join ieee 1516 standard revised siso hla-evolved product development group approved 25-mar-2010 ieee standards activities board revised ieee 1516–2010 standard includes current dod standard interpretations edlc api extended version siso dlc api major improvements include hla current ieee 1516 version ancestor 1.3 version subject nato standardization agreement stanag 4603 modeling simulation modeling simulation architecture standards technical interoperability high level architecture hla base object model bom siso-std-003-2006 related standard siso provide better reuse composability hla simulations highly relevant hla developers provides way specify conceptual models map hla fom virtually means interconnecting distributed modeling simulation dm applications alternatives disadvantages hla exception regards distributed modeling simulation dm industry often used alternative hla distributed interactive simulation dis ieee 1278.1-2012 recently updated simulation protocol hla rti vendors also feature dis products middleware applications closely match hla features publish subscribe feature p see data distribution service dds shares many characteristics open on-the-wire protocol system interoperability hla message-oriented middleware defines set services provided c++ java api standardized on-the-wire protocol participants federation must use rti libraries provider usually also version order applications interoperate
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Distributed computing architecture
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carry-i carry-i model number ft-6200 intel 80286-based book-size diskless node produced flytech technology taiwan circa 1991 system bundled dr dos 5.0 australia system sold company hypec technology pty ltd
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Distributed computing architecture
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bounce rate bounce rate internet marketing term used web traffic analysis represents percentage visitors enter site leave bounce rather continuing view pages within site bounce rate calculated counting number single page visits dividing total visits represented percentage total visits bounce rate measure stickiness thinking effective website engage visitors deeper website encouraging visitors continue visit expressed percentage represents proportion single page visits total visits bounce rate visits access single page ÷ total visits website bounce rates used help determine effectiveness performance entry page generating interest visitors entry page low bounce rate means page effectively causes visitors view pages continue deeper web site high bounce rates typically indicate website good job attracting continued interest visitors means visitors view single pages without looking others taking form action within site specified time period interpretation bounce rate measure relevant website business objectives definitions conversion high bounce rate always sign poor performance sites objective met without viewing one page example websites sharing specific knowledge subject dictionary entry specific recipe bounce rate would meaningful determining conversion success contrast bounce rate e-commerce site could interpreted correlation purchase conversion rate providing bounces considered representative visits purchase made typically bounce rate e-commerce websites range 20 45 top performers operating 36 average bounce rate bounce occurs web site visitor views single page website visitor leaves site without visiting pages specified session-timeout occurs industry standard minimum maximum time visitor must leave order bounce occur rather determined session timeout analytics tracking software formula_1 visitor may bounce two exceptions 1 one-page website 2 offline value proposition compelling people would see one single webpage get information need leave commonly used session timeout value 30 minutes case visitor views page look another page leaves browser idle longer 30 minutes register bounce visitor continues navigate delay new session occur bounce rate single page number visitors enter site page leave within specified timeout period without viewing another page divided total number visitors entered site page contrast bounce rate web site number web site visitors visit single page web site per session divided total number web site visits site-wide bounce rate useful metric sites well-defined conversion steps requiring multiple page views may questionable value sites visitors likely find looking entry page type behavior common web portals referential content sites example visitor looking definition particular word may enter online dictionary site word definition page similarly visitor wants read specific news story may enter news site article written story example entry pages could bounce rate 80 thereby increasing site-wide average however may still considered successful
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Web technology
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marvin minsky marvin lee minsky august 9 1927 – january 24 2016 american cognitive scientist concerned largely research artificial intelligence ai co-founder massachusetts institute technology ai laboratory author several texts concerning ai philosophy marvin lee minsky born new york city eye surgeon father henry mother fannie zionist activist family jewish attended ethical culture fieldston school bronx high school science later attended phillips academy andover massachusetts served us navy 1944 1945 received b.a mathematics harvard university 1950 ph.d. mathematics princeton university 1954 mit faculty 1958 death joined staff mit lincoln laboratory 1958 year later john mccarthy initiated named mit computer science artificial intelligence laboratory toshiba professor media arts sciences professor electrical engineering computer science minsky inventions include first head-mounted graphical display 1963 confocal microscope 1957 predecessor today widely used confocal laser scanning microscope developed seymour papert first logo turtle minsky also built 1951 first randomly wired neural network learning machine snarc 1962 minsky published 7,4 turing machine able prove universal time simplest known universal turing machine record stood 40 years stephen wolfram published 2,5 universal turing machine 2002 book new kind science minsky wrote book perceptrons seymour papert attacking work frank rosenblatt became foundational work analysis artificial neural networks book center controversy history ai claim great importance discouraging research neural networks 1970s contributing so-called ai winter also founded several famous ai models book framework representing knowledge created new paradigm programming perceptrons historical practical book theory frames wide use minsky also wrote possibility extraterrestrial life may think like humans permitting communication early 1970s mit artificial intelligence lab minsky papert started developing came known society mind theory theory attempts explain call intelligence could product interaction non-intelligent parts minsky says biggest source ideas theory came work trying create machine uses robotic arm video camera computer build children blocks 1986 minsky published society mind comprehensive book theory unlike previously published work written general public november 2006 minsky published emotion machine book critiques many popular theories human minds work suggests alternative theories often replacing simple ideas complex ones recent drafts book freely available webpage minsky adviser stanley kubrick movie one movie characters victor kaminski named minsky honor minsky mentioned explicitly arthur c. clarke derivative novel name portrayed achieving crucial break-through artificial intelligence then-future 1980s paving way hal 9000 early 21st century 1952 minsky married pediatrician gloria rudisch together three children minsky talented improvisational pianist published musings relations music psychology minsky atheist signatory scientists open letter cryonics critic loebner prize conversational robots argued fundamental difference humans machines humans machines machines intelligence emerges interplay many unintelligent semi-autonomous agents comprise brain argued somewhere line computers become intelligent people hard predict fast progress would cautioned artificial superintelligence designed solve innocuous mathematical problem might decide assume control earth resources build supercomputers help achieve goal believed negative scenarios hard take seriously felt confident ai would go lot testing deployed minsky died cerebral hemorrhage age 88 minsky member alcor scientific advisory board believed cryonically preserved alcor presumably patient 144 whose cooling procedures began january 27 2016 2019 virginia giuffre named minsky one jeffrey epstein child trafficking clients unsealed deposition federal court minsky turing award greatest distinction computer science 1969 japan prize 1990 ijcai award research excellence 1991 benjamin franklin medal franklin institute 2001 2006 inducted fellow computer history museum co-founding field artificial intelligence creating early neural networks robots developing theories human machine cognition 2011 minsky inducted ieee intelligent systems ai hall fame significant contributions field ai intelligent systems 2014 minsky dan david prize artificial intelligence digital mind also awarded 2013 bbva foundation frontiers knowledge award information communication technologies category minsky affiliated following organizations
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Programming language topics
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link aggregation computer networking term link aggregation applies various methods combining aggregating multiple network connections parallel order increase throughput beyond single connection could sustain provide redundancy case one links fail link aggregation group lag combines number physical ports together make single high-bandwidth data path implement traffic load sharing among member ports group enhance connection reliability umbrella terms used describe method include port trunking link bundling ethernet/network/nic bonding channel bonding nic teaming umbrella terms encompass vendor-independent standards link aggregation control protocol lacp ethernet defined ieee 802.1ax previous ieee 802.3ad also various proprietary solutions link aggregation addresses two problems ethernet connections bandwidth limitations lack resilience regard first issue bandwidth requirements scale linearly ethernet bandwidths historically increased tenfold generation 10 megabit/s 100 mbit/s 1000 mbit/s 10,000 mbit/s one started bump bandwidth ceilings option move next generation could cost prohibitive alternative solution introduced many network manufacturers early 1990s combine two physical ethernet links one logical link via channel bonding solutions required manual configuration identical equipment sides aggregation second problem involves three single points failure typical port-cable-port connection either usual computer-to-switch switch-to-switch configuration cable either ports cable plugged fail multiple physical connections made many higher level protocols designed fail completely seamlessly network architects implement aggregation lowest three layers osi model regardless layer aggregation occurs possible balance network load across links however implementations take advantage methods provide failover well combining either occur multiple interfaces share one logical address i.e ip one physical address i.e mac address allows interface address former requires ends link use aggregation method performance advantages latter channel bonding differentiated load balancing load balancing divides traffic network interfaces per network socket layer 4 basis channel bonding implies division traffic physical interfaces lower level either per packet layer 3 data link layer 2 basis mid 1990s network switch manufacturers included aggregation capability proprietary extension increase bandwidth switches manufacturer developed method led compatibility problems ieee 802.3 group took study group create inter-operable link layer standard november 1997 meeting group quickly agreed include automatic configuration feature would add redundancy well became known link aggregation control protocol gigabit channel-bonding schemes use ieee standard link aggregation formerly clause 43 ieee 802.3 standard added march 2000 ieee 802.3ad task force nearly every network equipment manufacturer quickly adopted joint standard proprietary standards 802.3 maintenance task force report 9th revision project november 2006 noted certain 802.1 layers 802.1x security positioned protocol stack link aggregation defined 802.3 sublayer resolve discrepancy 802.3ax 802.1ax task force formed resulting formal transfer protocol 802.1 group publication ieee 802.1ax-2008 3 november 2008 within ieee specification link aggregation control protocol lacp provides method control bundling several physical ports together form single logical channel lacp allows network device negotiate automatic bundling links sending lacp packets peer directly connected device also implements lacp lacp features practical examples lacp works sending frames lacpdus links protocol enabled finds device end link also lacp enabled also independently send frames along links enabling two units detect multiple links combine single logical link lacp configured one two modes active passive active mode always send frames along configured links passive mode however acts speak spoken therefore used way controlling accidental loops long device active mode addition ieee link aggregation substandards number proprietary aggregation schemes including cisco etherchannel port aggregation protocol juniper aggregated ethernet avaya multi-link trunking split multi-link trunking routed split multi-link trunking distributed split multi-link trunking zte smartgroup huawei eth-trunk connectify speedify high-end network devices support kind link aggregation software-based implementations – *bsd lagg package linux bonding driver solaris dladm aggr etc – also exist many operating systems linux bonding driver provides method aggregating multiple network interface controllers nics single logical bonded interface two so-called nic slaves majority modern linux distributions come linux kernel linux bonding driver integrated loadable kernel module ifenslave network interface user-level control program pre-installed donald becker programmed original linux bonding driver came use beowulf cluster patches linux kernel 2.0 modes linux bonding driver network interface aggregation modes supplied parameters kernel bonding module load time may given command line arguments insmod modprobe command usually specified linux distribution-specific configuration file behavior single logical bonded interface depends upon specified bonding driver mode default parameter balance-rr linux team driver provides alternative bonding driver main difference team driver kernel part contains essential code rest code link validation lacp implementation decision making etc run userspace part teamd daemon link aggregation offers inexpensive way set high-speed backbone network transfers much data one single port device deliver link aggregation also allows network backbone speed grow incrementally demand network increases without replace everything deploy new hardware backbone installations install cabling fiber optic pairs initially necessary even immediate need additional cabling done labor costs higher cost cable running extra cable reduces future labor costs networking needs change link aggregation allow use extra cables increase backbone speeds little extra cost ports available balancing traffic network administrators often wish avoid reordering ethernet frames example tcp suffers additional overhead dealing out-of-order packets goal approximated sending frames associated particular session across link common implementations use l2 l3 hashes i.e based mac ip addresses ensuring flow always sent via physical link however may provide even distribution across links trunk single pairs hosts communicate i.e hashes provide little variation effectively limits client bandwidth aggregate single member maximum bandwidth per communication partner extreme one link fully loaded others completely idle reason even load balancing full utilization trunked links almost never reached real-life implementations advanced switches employ l4 hash i.e using tcp/udp port numbers may increase traffic variation across links – depending whether ports vary – bring balance closer even distribution multiple switches may utilized optimize maximum throughput multiple network switch topology switches configured parallel part isolated network two systems configuration switches isolated one another one reason employ topology isolated network many hosts cluster configured high performance example using multiple smaller switches cost effective single larger switch access beyond network required individual host equipped additional network device connected external network host additionally acts gateway network interfaces 1 3 computer cluster node example connected via separate network switches 1 3 network interfaces 1 3 computer cluster node b inter-connections network switches 1 3 linux bonding driver mode typically employed configurations type balance-rr balance-rr mode allows individual connections two hosts effectively utilize greater one interface bandwidth nics trunked together also provide network links beyond throughput one single nic example allows central file server establish aggregate 2-gigabit connection using two 1-gigabit nics teamed together note data signaling rate still 1gbit/s misleading depending methodologies used test throughput link aggregation employed microsoft windows server 2012 supports link aggregation natively previous windows server versions relied manufacturer support feature within device driver software intel example released advanced networking services ans bond intel fast ethernet gigabit cards.nvidia also supports teaming nvidia network access manager/firewall tool hp also teaming tool hp branded nics allow non-etherchanneled nic teaming support several modes etherchannel port aggregation including 802.3ad lacp addition basic layer-3 aggregation available least windows xp sp3 allows servers multiple ip interfaces network perform load balancing home users one internet connection increase connection speed sharing load interfaces broadcom offers advanced functions via broadcom advanced control suite bacs via teaming functionality basp broadcom advanced server program available offering 802.3ad static lags lacp smart teaming n't require configuration switches work possible configure teaming bacs mix nics different vendors long least one broadcom nics required capabilities create teaming linux freebsd netbsd openbsd macos opensolaris commercial unix distributions aix implement ethernet bonding trunking higher level hence deal nics different manufacturers drivers long nic supported kernel citrix xenserver vmware esx native support link-aggregation xenserver offers static lags well lacp vsphere 5.1 esxi supports static lags lacp natively virtual distributed switch microsoft hyper-v bonding teaming n't offered hyper-visor os-level above-mentioned methods teaming windows applies hyper-v well modes balance-rr balance-xor broadcast 802.3ad physical ports link aggregation group must reside logical switch scenarios leave single point failure physical switch links connected goes offline modes active-backup balance-tlb balance-alb also set two switches failover like modes cases active sessions may fail due arp problems restarted however almost vendors proprietary extensions resolve issue aggregate multiple physical switches one logical switch split multi-link trunking smlt protocol allows multiple ethernet links split across multiple switches stack preventing single point failure additionally allowing switches load balanced across multiple aggregation switches single access stack devices synchronize state across inter-switch trunk ist appear connecting access device single device switch block prevent packet duplication smlt provides enhanced resiliency sub-second failover sub-second recovery speed trunks 10 mbit/s 100 mbit/s 1,000 mbit/s 10 gbit/s operating transparently end-devices implementations ports used aggregation consist physical type copper ports 10/100/1000base‑t multi-mode fiber ports single-mode fiber ports however ieee standard requires link full duplex identical speed 10 100 1,000 10,000 mbit/s many switches phy independent meaning switch could mixture copper sx lx lx10 gbics maintaining phy usual approach possible aggregate 1000base-sx fiber one link 1000base-lx longer diverse path second link important thing speed 1 gbit/s full duplex links one path may slightly longer propagation time standard engineered cause issue aggregation mismatch refers matching aggregation type ends link switches implement 802.1ax standard support static configuration link aggregation therefore link aggregation similarly statically configured switches work fail statically configured switch device configured lacp ethernet interfaces channel bonding requires assistance ethernet switch host computer operating system must stripe delivery frames across network interfaces manner i/o striped across disks raid 0 array reason discussions channel bonding also refer redundant array inexpensive nodes rain redundant array independent network interfaces analog modems multiple dial-up links pots may bonded throughput bonded connections come closer aggregate bandwidth bonded links throughput routing schemes simply load-balance outgoing network connections links similarly multiple dsl lines bonded give higher bandwidth united kingdom adsl sometimes bonded give example 512kbit/s upload bandwidth 4 megabit/s download bandwidth areas access 2 megabit/s bandwidth docsis 3.0 3.1 specifications data cable tv catv systems multiple channels may bonded docsis 3.0 32 downstream 8 upstream channels may bonded typically 6 8mhz wide docsis 3.1 defines complicated arrangements involving aggregation level subcarriers larger notional channels broadband bonding type channel bonding refers aggregation multiple channels osi layers level four channels bonded wired links t-1 dsl line additionally possible bond multiple cellular links aggregated wireless bonded link previous bonding methodologies resided lower osi layers requiring coordination telecommunications companies implementation broadband bonding implemented higher layers done without coordination commercial implementations broadband channel bonding include see also mimo
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Internet protocols
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international symposium microarchitecture international symposium microarchitecture micro generally viewed top-tier academic conference computer architecture confused micro-conference
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Computer architecture
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pitfall pitfall video game designed david crane atari 2600 released activision 1982 player controls pitfall harry tasked collecting treasures jungle within 20 minutes avoiding obstacles hazards pitfall received positive reviews upon release one best-selling games atari 2600 four million copies sold top video game billboard charts year inspired numerous sequels ports across variety gaming consoles helped define side-scrolling platformer genre player controls character pitfall harry maze-like jungle attempt recover 32 treasures 20-minute time period along way players must maneuver numerous hazards including pits quicksand rolling logs fire rattlesnakes scorpions crocodiles harry may jump otherwise avoid obstacles climbing running swinging vines treasure includes bags money gold silver bars diamond rings range value 2000 5000 points 1000 point increments eight treasure type 32 total perfect score 114,000 achieved claiming 32 treasures without losing points points deducted either falling hole 100 points touching logs point loss depends long contact made log jungle tunnel harry access ladders found various points traveling though tunnel moves forward three screens time necessary order collect treasures within time limit however tunnels filled dead-ends blocked brick walls forcing player return surface one ladders try find way around thus wasting time tunnels also contain scorpions player loses life harry comes contact obstacle except logs falls tar pit quicksand waterhole mouth crocodile game ends either 32 treasures collected three lives lost time run pitfall created david crane programmer worked activision early 1980s november 2003 interview edge described 1979 developed technology display realistic running man 1982 searching suitable game use game technical achievements included non-flickering multicolored animated sprites system notoriously primitive graphics hardware innovative techniques used keep code space within 4k limit including polynomial counter create 256 screens within 50 bytes code swinging vines created repeatedly displaying atari one-pixel ball sprite different offsets several ports made computer systems msx commodore 64 atari 800 well home consoles colecovision intellivision versions pitfall ported home computers different names around 1983 one version 'trapfall ken kalish tom mix software tandy coco licensed sold part cuthbert series dragon 32 cuthbert jungle microdeal united kingdom version re-ported back computers like commodore 64 pitfall originally sold anyone scored 20,000 points could send activision picture television screen receive pitfall harry explorer club patch television commercial pitfall featured then-child actor jack black age 13 first tv role possibly great success raiders lost ark pitfall atari 2600 best-selling home video game 1982 first quarter 1983 mid-january 1983 top-selling game billboard chart seven weeks—much successful rival e.t atari paid 21 million license—and remained number one position 64 weeks row danny goodman creative computing video arcade games stated pitfall standout among dozens 2600 games announced summer 1982 consumer electronics show original cartridge vcs without arcade express reviewed atari 2600 version pitfall august 1982 stating may well best adventure game yet produced vcs giving score 8 10 electronic games june 1983 praised 2600 version superb graphics varied play-action goodman surprised intellivision version graphics greatly improved 2600 video games march 1983 criticized activision enhancing intellivision version graphics know graphics intellivision vcs improvements pitfall 2600 version pitfall awarded best adventure video game 4th annual arkie awards 2013 entertainment weekly listed one ten best atari 2600 games crane produced atari 2600 sequel 1983 pitfall series appeared nintendo entertainment system november 1987 form super pitfall reworking 1985 activision licensed pitfall sega made arcade version lost caverns game thoroughly remade first level resembling original pitfall second level resembling caverns pitfall ii later levels completely original version adapted sg-1000 pitfall produced commodore 64 apple ii home computers using garry kitchen gamemaker primarily demonstration game building software closer 16-bit platformers atari 2600 games made debut super nintendo entertainment system mega drive/genesis 1994 later appeared sega cd sega 32x consoles game ported windows 95 operating system atari jaguar 1995 recent re-release 2001 game boy advance mayan adventure includes original pitfall game easter egg 1998 featuring voice bruce campbell pitfall harry jr. released playstation game boy color without 3d designation 2004 fourth sequel released playstation 2 gamecube xbox game includes original pitfall pitfall ii games port lost expedition pitfall big adventure released wii september 23 2008 may 2010 pitfall released microsoft game room service xbox 360 console windows-based pcs also ported game room xbox live title windows phone february 2011 august 9 2012 activision released pitfall ios iphone ipad ipod touch december 21 activision released pitfall android free app version game departed 2d graphics seen original instead used 3d graphics gameplay also altered game endless runner style temple run month crane announced kickstarter jungleventure spiritual successor original games goal raise us 900,000 project failed reach target raising 31,207 crane said reason people thought asking much money everyone turned soon saw price pitfall generally viewed created side-scrolling platforming genre although scroll features games ability travel multiple levels play game also much longer atari 2600 games time typically lasted minutes due majority games ports arcade games short play time encouraged players spend money pitfall considered one influential games atari 2600 system introduced jungle setting video games many game mechanics used games like prince persia 1983 pitfall made animated television debut segment cbs saturday supercade cartoon lineup name pitfall harry basic plotline involved harry voiced robert ridgely niece rhonda voiced noelle north cowardly mountain lion quickclaw voiced kenneth mars exploring various locations hidden treasure one season pitfall harry frogger donkey kong jr. replaced kangaroo space ace
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Computer architecture
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weather apple weather preinstalled mobile app ipod touch iphone bundled ios since iphone os 1 app allows user see weather number selected cities locations added pressing list icon plus icon allows user type city name zip code postal code airport code locations removed tapping list icon swiping left location user wants delete weather app ios 8 updated use weather channel source information weather rather yahoo weather ios 10 later app removed home screen user wishes ios 12 information weather displayed ios device lock screen alarm set device ’ “ bedtime ” feature goes
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Operating systems
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