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bulposcor bulgarian part speech-annotated corpus bulposcor bulgarian български пос анотиран корпус булпоскор morphologically annotated general monolingual corpus written language item text assigned grammatical tag bulposcor created department computational linguistics institute bulgarian language bulgarian academy sciences consists 174 697 lexical items bulposcor compiled structured brown corpus bulgarian sampling 300+ word-excerpts expanded sentence boundary original bcb files way preserve bcb overall structure annotation process consists primary stage automatically assigning tags bulgarian grammar dictionary stage manual resolving morphological ambiguities.the disambiguated corpus consists 174,697 lexical units bulposcor search interface koeva sv gramatichen rechnik na balgarskiya ezik.opisanie na koncepciyata za organizaciyata na lingvistichnite danni grammatical dictionary bulgarian в български език 6 1998 с 49-58 koeva sv. sv leseva i. stoyanova e. tarpomanova m. todorova bulgarian tagged corpora proceedings fifth international conference formal approaches south slavic balkan languages 18–20 october 2006 sofia bulgaria pp 78–86 todorova maria rositsa dekova balgarski pos anotiran korpus – osobenosti na gramatichnata anotaciya bulgarian pos annoted corpus – specifics grammatical annotation в езикови ресурси и технологии за български език състав и научн ред св коева д. благоева т. тинчев софия академично издателство „ марин дринов “ 2014
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Computational linguistics
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trusted platform module trusted platform module tpm also known iso/iec 11889 international standard secure cryptoprocessor dedicated microcontroller designed secure hardware integrated cryptographic keys trusted platform module tpm conceived computer industry consortium called trusted computing group tcg standardized international organization standardization iso international electrotechnical commission iec 2009 iso/iec 11889 tcg continued revise tpm specifications last revised edition tpm main specification version 1.2 published march 3 2011 consisted three parts based purpose second major version tpm however tcg released tpm library specification 2.0 builds upon previously published tpm main specification latest edition released september 29 2016 several errata latest one dated january 8 2018 trusted platform module provides computer programs use tpm authenticate hardware devices since tpm chip unique secret rsa key burned produced pushing security hardware level provides protection software-only solution united states department defense dod specifies new computer assets e.g. server desktop laptop thin client tablet smartphone personal digital assistant mobile phone procured support dod include tpm version 1.2 higher required disa stigs technology available dod anticipates tpm used device identification authentication encryption device integrity verification primary scope tpm assure integrity platform context integrity means behave intended platform computer device regardless operating system ensure boot process starts trusted combination hardware software continues operating system fully booted applications running responsibility assuring said integrity using tpm firmware operating system example unified extensible firmware interface uefi use tpm form root trust tpm contains several platform configuration registers pcrs allow secure storage reporting security relevant metrics metrics used detect changes previous configurations decide proceed good examples found linux unified key setup luks bitlocker privatecore vcage memory encryption see example tpm use platform integrity trusted execution technology txt creates chain trust could remotely attest computer using specified hardware software full disk encryption utilities dm-crypt bitlocker use technology protect keys used encrypt computer storage devices provide integrity authentication trusted boot pathway includes firmware boot sector operating systems often require authentication involving password means protect keys data systems authentication mechanism implemented software access prone dictionary attacks since tpm implemented dedicated hardware module dictionary attack prevention mechanism built effectively protects guessing automated dictionary attacks still allowing user sufficient reasonable number tries without level protection passwords high complexity would provide sufficient protection application use tpm chip uses exist give rise privacy concerns physical presence feature tpm addresses concerns requiring bios-level confirmation operations activating deactivating clearing changing ownership tpm someone physically present console machine starting 2006 many new laptops sold built-in tpm chip future concept could co-located existing motherboard chip computers device tpm facilities could employed cellphone pc either lpc bus spi bus used connect tpm chip tcg certified tpm chips manufactured infineon technologies nuvoton stmicroelectronics assigned tpm vendor ids advanced micro devices atmel broadcom ibm infineon intel lenovo national semiconductor nationz technologies nuvoton qualcomm rockchip standard microsystems corporation stmicroelectronics samsung sinosun texas instruments winbond five different types tpm 2.0 implementations tpm 2.0 addresses many use cases similar features details different tpm 2.0 backward compatible tpm 1.2 tpm 2.0 policy authorization includes 1.2 hmac locality physical presence pcr adds authorization based asymmetric digital signature indirection another authorization secret counters time limits nvram values particular command command parameters physical presence permits anding oring authorization primitives construct complex authorization policies tcg faced resistance deployment technology areas authors see possible uses specifically related trusted computing may raise privacy concerns concerns include abuse remote validation software manufacturerand user owns computer systemdecides software allowed run possible ways follow actions taken user recorded database manner completely undetectable user truecrypt disk encryption utility well derivative veracrypt support tpm original truecrypt developers opinion exclusive purpose tpm protect attacks require attacker administrator privileges physical access computer attacker physical administrative access computer circumvent tpm e.g. installing hardware keystroke logger resetting tpm capturing memory contents retrieving tpm-issued keys condemning text goes far claim tpm entirely redundant veracrypt publisher reproduced original allegation changes replacing truecrypt veracrypt private endorsement key fundamental security tpm circuit never made available end-user private key must known hardware chip manufacturer manufacture time otherwise would able burn key circuit guarantees private key kept manufacturer shared government agencies anyone access private endorsement key would able forge chip identity break security chip provides thus security tpm relies entirely manufacturer authorities country hardware produced 2010 christopher tarnovsky presented attack tpms black hat briefings claimed able extract secrets single tpm able 6 months work inserting probe spying internal bus infineon sle 66 cl pc 2015 part snowden revelations revealed 2010 us cia team claimed internal conference carried differential power analysis attack tpms able extract secrets october 2017 reported code library developed infineon widespread use tpms contained vulnerability known roca allowed rsa private keys inferred public keys result systems depending upon privacy keys vulnerable compromise identity theft spoofing cryptosystems store encryption keys directly tpm without blinding could particular risk types attacks passwords factors would meaningless attacks extract encryption secrets currently tpm used nearly pc notebook manufacturers primarily offered professional product lines tpm implemented several vendors also hybrid types example tpm integrated ethernet controller thus eliminating need separate motherboard component
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Computer security
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liberty basic liberty basic lb commercial computer programming language integrated development environment ide interpreter developed smalltalk recognizes dialect basic programming language runs 16- 32-bit windows os/2 liberty basic written carl gundel published first release company shoptalk systems 1992 progressed steadily since last published update software june 2018 current version v4.5.1 though liberty basic share limitations design advanced programming provides introductory integrated development environment ide moderate advanced users windows os/2 dlls available current version runs microsoft windows wine linux alpha testing liberty basic v5.0 underway versions run microsoft windows mac os x linux raspberry pi well liberty basic compile native code instead compiles code written ide encrypted file extension tkn file executed exe file carries file name although may change release version 5 liberty basic allows programming style similar dos basics run console mode using default main window displays formatted text accepts user input also supports gui-based event-driven programming using several types windows may contain standard controls buttons menus textboxes etc central idea creating liberty basic model handling windows syntax file handling example liberty basic help file open command opens communication device disk file window dynamic link library serial communications port “ device ” open data also commands control device “ printed ” type device set commands sent way recent versions lb word print may dropped print statement making syntax even simpler simplicity heart liberty basic beginning makes easier learn cost perhaps limiting functionality two data types supported lb4.03 numeric string type declarations required variable sign end name string variable otherwise numeric plan lb5 support types user defined types well purpose making calls api 3rd party dlls struct additional types necessary dll data structure currently supported array arrays one two dimensions supported lb5 may support arrays user-defined types examples language hello world program program display pop-up message box words hello world program display input box running another application using liberty basic printing multiplication table 5 form gnu/liberty basic compiler collection glbcc anthony liguori set tools compile liberty basic programs runs windows linux systems project updated since 2001 2011 alternative windows implementation liberty basic lb booster lbb became available although substantially compatible liberty basic 4 language syntax lbb developed entirely independently richard russell written bbc basic lbb offers typically increased execution speed smaller self-contained executables additional capabilities however lbb 100 compatible lb4 whilst many programs run without modification may need adapted even unsuitable running lbb
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Programming language topics
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rmdir computing codice_1 codice_2 command remove empty directory various operating systems available unix e.g macos solaris aix hp-ux unix-like e.g freebsd linux dos dr flexos ibm os/2 microsoft windows reactos operating systems ms-dos command available versions 2 later dr dos 6.0 also includes implementation command also available open source ms-dos emulator dosbox kolibrios numerical computing environments matlab gnu octave include codice_1 function similar functionality normal usage straightforward name_of_directory corresponds name directory one wishes delete options command -p unix removes parent directories also empty example first remove baz/ bar/ finally foo/ thus removing entire directory tree specified command argument rmdir remove directory empty unix rm command remove directory contents recursively example normal usage identical unix-like operating systems equivalent command ms-dos earlier non-nt-based versions microsoft windows deleting non-empty directories deltree later version windows windows based nt kernel xp vista 7 8 server 2003/2008 case insensitive like earlier predecessors unless two files name different case exist case sensitivity applies selecting file use case match either file one may chosen windows two files named different case sensitivity allowed either windows services unix installed windows registry settings set allow example security risk using rd/rmdir two directories name different case sensitivities exist one contains valid data and/or programs contains incriminating materials and/or malware rd/rmdir gets executed without regard case sensitivity windows chooses legitimate folder delete folder left undesired one windows uses folder instead previously legitimate one execute programs one may led believe contains legitimate data
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Computer file systems
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cloudsoft monterey cloudsoft monterey platform service paas software developed cloudsoft corp provide intelligent application mobility across multiple cloud computing environments supported vcloud amazon ec2 gogrid well private clouds using jclouds cloud api application written java using equinox osgi framework configuration dsls written groovy main components eclipse based development studio tool plugin developers management console monterey management network nodes run mobile application logic
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Distributed computing architecture
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csi-dos csi-dos operating system created samara soviet elektronika bk-0011m elektronika bk-0011 microcomputers csi-dos support earlier bk-0010 csi-dos used unique file system supported color graphics video mode system supported hard floppy drives well ram disks computer memory also included software work ay-3-8910 ay-3-8912 music co-processors covox speech thing number games demos designed specially system system also included turbo vision-like application programming interface api allowing simpler design user applications graphical file manager called x-shell
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Operating systems
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data transfer project data transfer project dtp open-source initiative features data portability multiple online platforms project launched introduced google july 20 2018 currently partnered facebook microsoft twitter apple project formed google data liberation front 2017 hoping provide platform could allow individuals move online data different platforms without need downloading re-uploading data ecosystem achieved extracting different files various available apis released online platforms translating codes could compatible platforms july 20 2018 joint project announced source code uploaded github mainly written google microsoft engineers july 30 2019 apple announced joining project allowing data portability icloud
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Computer architecture
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link access procedure frame relay wide area network computing link access procedure frame relay lapf part network communications protocol ensures frames error free executed right sequence lapf formally defined international telecommunication union standard q.922 derived ibm synchronous data link control protocol layer 2 protocol ibm systems network architecture developed around 1975 itu used sdlc basis develop lapf frame relay environment along equivalents lapb x.25 protocol stack lapm v.42 protocol lapd isdn protocol stack frame relay local management interface lmi messages carried variant lapf frames lapf corresponds osi model data link layer
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Internet protocols
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architecture control networks architecture control networks acn suite network protocols control entertainment technology equipment particularly used live performance large-scale installations example lighting audio special effects equipment acn maintained entertainment services technology association first official release ansi standard e1.17-2006 entertainment technology architecture control networks standard subsequently revised released ansi e1.17-2010 acn initially designed layered top udp/ip therefore run ip transports including standard inexpensive ethernet 802.11 wi-fi networks acn defines common protocol architecture two major network protocols sdt dmp device description language ddl number ‘ e1.17 profiles interoperability ’ known epi interoperability profiles define elements acn architecture must used particular context achieve interoperability example providing specific values ranges timing parameters used particular network environment breakdown acn sub-protocols interoperability profiles small pieces criticized making acn hard read understand makes architecture highly modular cleanly layered allowed many pieces operated contexts replaced revised without changing pieces example dmp operated tcp well sdt defined initial standard ddl adapted little change describe devices accessed dmx512 ansi e1.31/streaming acn several interoperability profiles seen major revision replacement without disturbing parts standard common architecture specification defines format nested protocol data units pdus rather similar tlv encoding used main protocols defines minimal root layer protocol used splice higher level protocols lower level transport defines root layer protocol using pdu format use udp/ip session data transport sdt reliable multicast transport protocol operates udp/ip used group peers within network sessions deliver messages individually group messages delivery ordered messages may selectively sent reliably unreliably message-by-message basis reliability important data avoiding time resource overhead reliability mechanism beneficial others reliability mechanism also provides online status component detect connection broken sdt provides high degree fine tuning trade-off latency reliability levels resource requirements availability large numbers concurrent sessions means powerful tool grouping managing components whose functions related whose communication requirements similar device management protocol dmp represents device set addressable properties represent current desired state monitoring control controller achieved setting examining values properties avoid inefficiencies polling addition simply reading property values using get-property message dmp provides subscription mechanism whereby device asynchronously send event messages subscribed controllers value property changes dmp expects connections provide reliability set-property event messages form large part operational bandwidth show situation require explicit acknowledgement dmp level e1.17 standard majority systems sdt provides reliability dmp also operated using tcp provide reliable connections size bits representation read/write accessibility function property dmp device determined protocol defines mechanism read and/or write property value instead information must either provided externally device description written ddl limited cases may pre-programmed fore-knowledge specific device types device description language ddl allows machine parsable description interface capabilities device defined description interpreted controller may automatically configure controlling device description provides address property mapping information necessary dmp operate also contain huge amount information functionality capabilities semantics device extensible format allows controller extract features needs specific context skipping information relevant needs ddl xml based language descriptions contained small number xml documents normal acn systems description device may downloaded device however descriptions may also distributed ways internet download since description valid devices type controllers typically maintain cache descriptions devices commonly encounter interoperability profiles epis provided ansi e1.17 initial service discovery system allocation multicast addresses used udp ipv4 udp port allocation multicasting ip address assignment conformant systems protocol timeouts specific environments epis conform acn architecture developed outside ansi e1.17 standard see due modular nature acn easy extend major protocol ansi e1.31 known streaming acn sacn developed organization uses root layer pdu format acn transport data dmx512 data ip networks acn compatible transport number interoperability profiles developed standardized plasa include ansi e1.30-3-2009 time reference acn systems using sntp ntp ansi e1.30-4-2010 defines use ddl describe devices controlled using dmx512 streaming acn early open-source implementation acn released openacn available sourceforge ported wide range platforms limited scope implement ddl support recent much complete implementation c 'acacian includes features ddl support yet another open source acn project codeplex implemented c aims provide full managed code implementation includes code several related protocols e1.31 streaming dmx acn supported linux arm i386 x86-64 macintosh powerpc i386 x86-64 open lighting architecture rust implementation e1.31 found github acn deployed proprietary implementations number companies including use electronic theatre controls etc basis 'net3 branded networked control infrastructure shure inc. control wireless microphones
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Internet protocols
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avg technologies avg technologies cz s.r.o czech security software company headquartered brno founded 1991 jan gritzbach tomáš hofer wholly owned subsidiary avast since 2016 company develops antivirus software internet security services avg antivirus corporate offices europe israel brazil canada united states 2 february 2015 200 million active users used avg software products services include internet security performance optimization personal privacy identity protection applications july 2016 avast announced intended acquire avg acquisition completed 30 september 2016 avast avg operated single company since 3 october 2016 retaining two separate brands company founded brno czech republic jan gritzbach tomáš hofer 1991 grisoft /c/ software spol r. o.. owned jan gritzbach 2001 jan gritzbach decided sell grisoft benson oak capital acquisitions holding company grisoft inc. based wilmington delaware used transaction 2002 company renamed grisoft s.r.o.. three years later benson oak sold 65 share company intel capital enterprise investors us 52 million holding company grisoft holdings b.v. based amsterdam netherlands later grisoft international b.v. gradually became main company 19 april 2006 grisoft acquired german company ewido networks anti-spyware software manufacturer incorporated ewido features new versions avg software 6 november 2006 microsoft announced avg security products would available directly windows security center windows vista since 7 june 2006 avg software also used optional component gfi mailsecurity produced gfi software 5 december 2007 grisoft announced acquisition exploit prevention labs developer linkscanner safe surfing technology 2008 grisoft s.r.o renamed avg technologies cz s.r.o grisoft international b.v. avg technologies n.v.. change made increase effectiveness marketing activities january 2009 avg announced plans acquire sana security finalized plans integrate sana technologies free consumer product avg anti-virus still consideration according jr smith avg chief executive sana security developed technologies currently licensed symantec 5 october 2009 ta associates announced bought minority stake avg technologies us 200 million april 2010 avg announced appointed security industry veteran yuval ben-itzhak senior vice president engineering ben-itzhak became chief technology officer later year 9 june 2010 avg announced acquisition north carolina-based walling data north america security software distribution distributed avg offerings across united states since 2001 10 november 2010 avg announced acquisition tel aviv-based droidsecurity company specializes field mobile security solutions android devices upon completion acquisition droidsecurity become wholly owned subsidiary avg droidsecurity ceo co-founder eran pfeffer become general manager avg ’ mobile solutions team december 2010 avg released mandatory-install update 2011 version antivirus software caused thousands 64 bit windows vista windows 7 computers become completely inoperable avg since released fix attempts repair computers bricked installing update affected users watch following video avg official youtube page resolve issue 28 january 2011 dangerous rogue appeared interface graphics resemble previous version software uses sophisticated social engineering deceive users infect systems malware also portrays so-called emergency mode internet explorer exist genuine application 1 december 2011 avg technologies announced acquisition bsecure technologies inc. bsecure leading provider proprietary cloud-based technology internet filtering industry since 2001 endorsed software provider family online safety 2011 group restructured avg technologies holdings b.v. founded avg technologies cz s.r.o avg technologies n.v. subsidiaries 7 february 2012 avg technologies n.v. listed new york stock exchange 12 june 2013 avg technologies announced acquisition level platforms 8 march 2013 jr smith ceo tendered resignation avg eight years ceo leading company successful ipo nyse delivering eight quarters successive high-growth 30 july 2013 avg technologies announced gary kovacs company new ceo november 2014 avg technologies announced acquisition norman safeground asa oslo-based company known norman suite security products avg technologies announced may 2015 acquisition privax uk based company owner hidemyass vpn service september 2015 company announced acquisition location labs company personal security products four major us cellular carriers 7 july 2016 avast announced intended acquire avg technologies purchase price 25.00 per share cash total around 1.3 billion acquisition completed 30 september 2016 avast avg operate single company monday 3 october 2016 company delisted new york stock exchange 20 august 2010 avg entered partnership moka5 secure desktop virtualisation solutions partnership adds critical security layer virtual desktop marketplace enterprise companies turning desktop virtualization secure solution bringing computer byoc work home initiatives employees 1 july 2010 avg partnered opera software provide malware security web browser opera protection added existing fraud protection technology netcraft phishtank haute secure july 2011 avg joined forces israeli company zbang launch multimi free windows ipad app integrates e-mail social media multimedia one interface avg provides linkscanner app checking link sent e-mail shared social network found via search december 2012 avg yahoo partnered secure search toolbar september 2013 avg partnered facebook launch facebook privacy application avg crowd control may 2012 avg technologies issued copyright claim referred 'takedown request youtube video 1987 pop song never gon na give performed british singer rick astley video october 2015 150 million views 300,000 comments uploaded 2007 restored within 24 hours youtube video name refers internet meme commonly referred 'rickrolling someone pranks others tricking going video avg browser add-on avg secure search criticized adware since frequently bundled software often mistakenly installed exhibits malware-like behavior avg secure search also advertised users free versions avg products although add-on offers legitimate malware-blocking capabilities default behavior changing internet browser default search engine homepage new tab page avg secure search reminiscent potentially unwanted program pup problems uninstalling add-on widely reported add-on could potentially make internet browser vulnerable attacks
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Computer security
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analytica software analytica visual software package developed lumina decision systems creating analyzing communicating quantitative decision models modeling environment interesting way combines hierarchical influence diagrams visual creation view models intelligent arrays working multidimensional data monte carlo simulation analyzing risk uncertainty optimization including linear nonlinear programming design especially influence diagrams treatment uncertainty based ideas field decision analysis computer language notable combining declarative non-procedural structure referential transparency array abstraction automatic dependency maintenance efficient sequencing computation analytica models organized influence diagrams variables objects appear nodes various shapes diagram connected arrows provide visual representation dependencies analytica influence diagrams may hierarchical single module node diagram represents entire submodel hierarchical influence diagrams analytica serve key organizational tool visual layout influence diagram matches natural human abilities spatially level abstraction people able take far information model structure organization glance possible less visual paradigms spreadsheets mathematical expressions managing structure organization large model significant part modeling process substantially aided visualization influence diagrams influence diagrams also serve tool communication quantitative model created final results computed often case understanding results obtained various assumptions impact results far important specific numbers computed ability target audience understand aspects critical modeling enterprise visual representation influence diagram quickly communicates understanding level abstraction normally appropriate detailed representations mathematical expressions cell formulae detail desired users drill increasing levels detail speeded visual depiction model structure existence easily understandable transparent model supports communication debate within organization effect one primary benefits investing quantitative model building interested parties able understand common model structure debates discussions often focus directly specific assumptions cut cross-talk therefore lead productive interactions within organization influence diagram serves graphical representation help make models accessible people different levels analytica uses index objects track dimensions multidimensional arrays index object name list elements two multidimensional values combined example expression revenue expenses multidimensional analytica repeats profit calculation dimension recognizes dimension occurs values treats dimension calculation process called intelligent array abstraction unlike programming languages inherent ordering dimensions multidimensional array avoids duplicated formulas explicit loops common sources modeling errors simplified expressions made possible intelligent array abstraction allow model accessible interpretable transparent another consequence intelligent array abstraction new dimensions introduced removed existing model without requiring changes model structure changes variable definitions example creating model model builder might assume particular variable example discount_rate contains single number later constructing model user might replace single number table numbers perhaps discount_rate broken country economic_scenario new divisions may reflect fact effective discount rate international divisions company different rates applicable different hypothetical scenarios analytica automatically propagates new dimensions results depend upon discount_rate example result net present value become multidimensional contain new dimensions essence analytica repeats calculation using discount rate possible combination country economic_scenario flexibility important exploring computation tradeoffs level detail computation time available data overall size dimensionality parametric spaces adjustments common models fully constructed way exploring what-if scenarios overall relationships variables incorporating uncertainty model outputs helps provide realistic informative projections uncertain quantities analytica specified using distribution function evaluated distributions sampled using either latin hypercube monte carlo sampling samples propagated computations results sampled result distribution summary statistics viewed directly mean fractile bands probability density function pdf cumulative distribution function cdf analytica supports collaborative decision analysis probability management use sipmath tm standard system dynamics approach simulating behaviour complex systems time deals feedback loops time delays behaviour entire system dynamic function analytica allows definition variables cyclic dependencies feedback loops expands influence diagram notation normally allow cycles least one link cycle includes time lag depicted gray influence arrow distinguish standard black arrows without time lags analytica includes general language operators functions expressing mathematical relationships among variables users define functions libraries extend language analytica several features programming language designed make easy use quantitative modeling visual programming language users view programs models influence diagrams create edit visually adding linking nodes declarative language meaning model declares definition variable without specifying execution sequence required conventional imperative languages analytica determines correct efficient execution sequence using dependency graph referentially transparent functional language execution functions variables side effects i.e changing variables analytica array programming language operations functions generalize work multidimensional arrays analytica used policy analysis business modeling risk analysis areas analytica applied include energy health pharmaceuticals environmental risk emissions policy analysis wildlife management ecology climate change technology defense strategic financial planning r planning portfolio management financial services aerospace manufacturing environmental health impact assessment analytica software runs microsoft windows operating systems three editions professional enterprise optimizer functions cost purchased users interested building models free edition available called analytica free 101 allows build medium moderate sized models 101 user objects.. free 101 also allows view models 101 objects change inputs compute results enables free sharing models review capable non-free power player enables users save inputs utilize database connections analytica cloud player allows share models web lets users access run via web browser recent release analytica version 5.1 released may 2018 analytica predecessor called demos grew research tools policy analysis max henrion phd student later professor carnegie mellon university 1979 1990 henrion founded lumina decision systems 1991 brian arnold lumina continued develop software apply environmental public policy analysis applications lumina first released analytica product 1996
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Programming language topics
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file transfer protocol file transfer protocol ftp standard network protocol used transfer computer files client server computer network ftp built client-server model architecture using separate control data connections client server ftp users may authenticate clear-text sign-in protocol normally form username password connect anonymously server configured allow secure transmission protects username password encrypts content ftp often secured ssl/tls ftps replaced ssh file transfer protocol sftp first ftp client applications command-line programs developed operating systems graphical user interfaces still shipped windows unix linux operating systems many ftp clients automation utilities since developed desktops servers mobile devices hardware ftp incorporated productivity applications html editors original specification file transfer protocol written abhay bhushan published 16 april 1971 1980 ftp ran ncp predecessor tcp/ip protocol later replaced tcp/ip version june 1980 october 1985 current specification several proposed standards amend example february 1994 enables firewall-friendly ftp passive mode june 1997 proposes security extensions september 1998 adds support ipv6 defines new type passive mode ftp may run active passive mode determines data connection established cases client creates tcp control connection random usually unprivileged port n ftp server command port 21 modes updated september 1998 support ipv6 changes introduced passive mode time updating extended passive mode server responds control connection three-digit status codes ascii optional text message example 200 200 ok means last command successful numbers represent code response optional text represents human-readable explanation request e.g need account storing file ongoing transfer file data data connection aborted using interrupt message sent control connection transferring data network four data representations used text files different format control record structure options provided features designed facilitate files containing telnet asa data transfer done three modes ftp software also implements deflate-based compressed mode sometimes called mode z command enables mode described internet draft standardized ftp login uses normal username password scheme granting access username sent server using user command password sent using pass command sequence unencrypted wire may vulnerable network sniffing attack information provided client accepted server server send greeting client session commence server supports users may log without providing login credentials server may authorize limited access sessions host provides ftp service may provide anonymous ftp access users typically log service 'anonymous lower-case case-sensitive ftp servers account prompted user name although users commonly asked send email address instead password verification actually performed supplied data many ftp hosts whose purpose provide software updates allow anonymous logins ftp normally transfers data server connect back client port command sent client problematic nats firewalls allow connections internet towards internal hosts nats additional complication representation ip addresses port number port command refer internal host ip address port rather public ip address port nat two approaches solve problem one ftp client ftp server use pasv command causes data connection established ftp client server widely used modern ftp clients another approach nat alter values port command using application-level gateway purpose http essentially fixes bugs ftp made inconvenient use many small ephemeral transfers typical web pages ftp stateful control connection maintains current working directory flags transfer requires secondary connection data transferred passive mode secondary connection client server whereas default active mode connection server client apparent role reversal active mode random port numbers transfers firewalls nat gateways hard time ftp http stateless multiplexes control data single connection client server well-known port numbers trivially passes nat gateways simple firewalls manage setting ftp control connection quite slow due round-trip delays sending required commands awaiting responses customary bring control connection hold open multiple file transfers rather drop re-establish session afresh time contrast http originally dropped connection transfer cheap http subsequently gained ability reuse tcp connection multiple transfers conceptual model still independent requests rather session ftp transferring data connection control connection idle transfer takes long firewall nat may decide control connection dead stop tracking effectively breaking connection confusing download single http connection idle requests normal expected connections dropped time-out common web browsers retrieve files hosted ftp servers although may support protocol extensions ftps ftp—rather http—url supplied accessible contents remote server presented manner similar used web content full-featured ftp client run within firefox form extension called fireftp ftp url syntax described taking form codice_1 bracketed parts optional example url nowiki ftp //public.ftp-servers.example.com/mydirectory/myfile.txt /nowiki represents file myfile.txt directory mydirectory server public.ftp-servers.example.com ftp resource url nowiki ftp //user001 secretpassword private.ftp-servers.example.com/mydirectory/myfile.txt /nowiki adds specification username password must used access resource details specifying username password may found browsers documentation e.g. firefox internet explorer default web browsers use passive pasv mode easily traverses end-user firewalls variation existed different browsers treat path resolution cases non-root home directory user ftp designed secure protocol many security weaknesses may 1999 authors listed vulnerability following problems ftp encrypt traffic transmissions clear text usernames passwords commands data read anyone able perform packet capture sniffing network problem common many internet protocol specifications smtp telnet pop imap designed prior creation encryption mechanisms tls ssl common solutions problem include ftp ssh practice tunneling normal ftp session secure shell connection ftp uses multiple tcp connections unusual tcp/ip protocol still use particularly difficult tunnel ssh many ssh clients attempting set tunnel control channel initial client-to-server connection port 21 protect channel data transferred ftp software either end sets new tcp connections data channels thus confidentiality integrity protection otherwise necessary ssh client software specific knowledge ftp protocol monitor rewrite ftp control channel messages autonomously open new packet forwardings ftp data channels software packages support mode include explicit ftps extension ftp standard allows clients request ftp sessions encrypted done sending auth tls command server option allowing denying connections request tls protocol extension defined implicit ftps outdated standard ftp required use ssl tls connection specified use different ports plain ftp ssh file transfer protocol chronologically second two protocols abbreviated sftp transfers files similar command set users uses secure shell protocol ssh transfer files unlike ftp encrypts commands data preventing passwords sensitive information transmitted openly network interoperate ftp software trivial file transfer protocol tftp simple lock-step ftp allows client get file put file onto remote host one primary uses early stages booting local area network tftp simple implement tftp lacks security advanced features offered robust file transfer protocols file transfer protocol tftp first standardized 1981 current specification protocol found simple file transfer protocol first protocol abbreviated sftp defined proposed unsecured file transfer protocol level complexity intermediate tftp ftp never widely accepted internet assigned historic status ietf runs port 115 often receives initialism sftp command set 11 commands support three types data transmission ascii binary continuous systems word size multiple 8 bits implementation binary continuous protocol also supports login user id password hierarchical folders file management including rename delete upload download download overwrite download append summary ftp reply codes may returned ftp server codes standardized ietf reply code three-digit value first digit used indicate one three possible outcomes — success failure indicate error incomplete reply second digit defines kind error third digit reply code used provide additional detail categories defined second digit
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Internet protocols
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castlecops castlecops volunteer security community focused making internet safer place services public free including malware rootkit cleanup infected computers malware phish investigations terminations searchable database lists malware file hashes targeted spammers throughout existence fought back using legal means defeat education collaborative information sharing among castlecops formerly known computer cops name change 2005 highest priorities achieved training volunteer staff anti-malware phishing rootkit academies additional services including castlecops forums news reviews continuing education castlecops consistently worked industry experts law enforcement reach ultimate goal securing safe smart computing experience everyone online castlecops reached five-year anniversary february 2007 accolades well-known computer security industry pundits players december 24 2008 website announced things come end castlecops ceased exist yet undisclosed reason later reported founder paul laudanski offered job microsoft however domain name remained active ever since albeit content order prevent purchased criminals castlecops malware databases well known security circles already moved systemlookup.com demise site
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Computer security
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jean-loup gailly jean-loup gailly author gzip wrote compression code portable archiver info-zip tools compatible pkzip archiver ms-dos worked zlib collaboration mark adler prefers write hyphenated first name j l ell capitalized wrote chapter fractal image compression mark nelson data compression book 1990 1995 designed real-time executive chorusos microkernel 1999 2001 cto mandrakesoft 2006 2014 worked google tech lead manager
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Operating systems
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saber software saber general purpose simulation program synopsys inc originally developed analogy inc. bought avanti corporation 2000 bought synopsys inc. saber began single-kernel analog simulation technology brought vhdl-ams verilog-ams spice saber-mast language single environment saber coupled digital simulators via calaveris algorithm
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Programming language topics
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authorization authorization function specifying access rights/privileges resources related information security computer security general access control particular formally authorize define access policy example human resources staff normally authorized access employee records policy usually formalized access control rules computer system operation system uses access control rules decide whether access requests authenticated consumers shall approved granted disapproved rejected resources include individual files item data computer programs computer devices functionality provided computer applications examples consumers computer users computer software hardware computer access control computer systems networks rely access policies access control process divided following phases policy definition phase access authorized policy enforcement phase access requests approved disapproved authorization function policy definition phase precedes policy enforcement phase access requests approved disapproved based previously defined authorizations modern multi-user operating systems include access control thereby rely authorization access control also uses authentication verify identity consumers consumer tries access resource access control process checks consumer authorized use resource authorization responsibility authority department manager within application domain often delegated custodian system administrator authorizations expressed access policies types policy definition application e.g form access control list capability policy administration point e.g xacml basis principle least privilege consumers authorized access whatever need jobs older single user operating systems often weak non-existent authentication access control systems anonymous consumers guests consumers required authenticate often limited authorization distributed system often desirable grant access without requiring unique identity familiar examples access tokens include keys certificates tickets grant access without proving identity trusted consumers often authorized unrestricted access resources system must verified access control system make access approval decision partially trusted guests often restricted authorization order protect resources improper access usage access policy operating systems default grant consumers full access resources others opposite insisting administrator explicitly authorizes consumer use resource even access controlled combination authentication access control lists problems maintaining authorization data trivial often represents much administrative burden managing authentication credentials often necessary change remove user authorization done changing deleting corresponding access rules system using atomic authorization alternative per-system authorization management trusted third party securely distributes authorization information public policy authorization feature trusted systems used security social control banking authorization hold placed customer account purchase made using debit card credit card publishing sometimes public lectures freely available texts published without approval author called unauthorized texts example 2002 'the theory everything origin fate universe collected stephen hawking lectures published without permission per copyright law
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Computer security
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anti-computer forensics anti-computer forensics sometimes counter forensics general term set techniques used countermeasures forensic analysis anti-forensics recently recognized legitimate field study within field study numerous definitions anti-forensics abound one widely known accepted definitions comes marc rogers purdue university rogers uses traditional crime scene approach defining anti-forensics attempts negatively affect existence amount and/or quality evidence crime scene make analysis examination evidence difficult impossible conduct abbreviated definition given scott berinato article entitled rise anti-forensics anti-forensics technology approach criminal hacking summed like make hard find impossible prove found neither author takes account using anti-forensics methods ensure privacy one personal data anti-forensics methods often broken several sub-categories make classification various tools techniques simpler one widely accepted subcategory breakdowns developed dr. marcus rogers proposed following sub-categories data hiding artifact wiping trail obfuscation attacks cf computer forensics processes tools attacks forensics tools directly also called counter-forensics within field digital forensics much debate purpose goals anti-forensic methods common conception anti-forensic tools purely malicious intent design others believe tools used illustrate deficiencies digital forensic procedures digital forensic tools forensic examiner education sentiment echoed 2005 blackhat conference anti-forensic tool authors james foster vinnie liu stated exposing issues forensic investigators work harder prove collected evidence accurate dependable believe result better tools education forensic examiner also counter-forensics significance defence espionage recovering information forensic tools serves goals spies equally well investigators data hiding process making data difficult find also keeping accessible future use obfuscation encryption data give adversary ability limit identification collection evidence investigators allowing access use common forms data hiding include encryption steganography various forms hardware/software based data concealment different data hiding methods makes digital forensic examinations difficult different data hiding methods combined make successful forensic investigation nearly impossible one commonly used techniques defeat computer forensics data encryption presentation gave encryption anti-forensic methodologies vice president secure computing paul henry referred encryption forensic expert nightmare majority publicly available encryption programs allow user create virtual encrypted disks opened designated key use modern encryption algorithms various encryption techniques programs make data virtually impossible read without designated key file level encryption encrypts file contents leaves important information file name size timestamps unencrypted parts content file reconstructed locations temporary files swap file deleted unencrypted copies encryption programs ability perform number additional functions make digital forensic efforts increasingly difficult functions include use keyfile full-volume encryption plausible deniability widespread availability software containing functions put field digital forensics great disadvantage steganography technique information files hidden within another file attempt hide data leaving plain sight steganography produces dark data typically buried within light data e.g. non-perceptible digital watermark buried within digital photograph experts argued use steganography techniques widespread therefore n't given lot thought experts agree steganography capability disrupting forensic process used correctly according jeffrey carr 2007 edition technical mujahid bi-monthly terrorist publication outlined importance using steganography program called secrets mujahideen according carr program touted giving user capability avoid detection current steganalysis programs use steganography conjunction file compression forms data hiding involve use tools techniques hide data throughout various locations computer system places include memory slack space hidden directories bad blocks alternate data streams hidden partitions one well known tools often used data hiding called slacker part metasploit framework slacker breaks file places piece file slack space files thereby hiding forensic examination software another data hiding technique involves use bad sectors perform technique user changes particular sector good bad data placed onto particular cluster belief forensic examination tools see clusters bad continue without examination contents methods used artefact wiping tasked permanently eliminating particular files entire file systems accomplished use variety methods include disk cleaning utilities file wiping utilities disk degaussing/destruction techniques disk cleaning utilities use variety methods overwrite existing data disks see data remanence effectiveness disk cleaning utilities anti-forensic tools often challenged believe completely effective experts n't believe disk cleaning utilities acceptable disk sanitization base opinions current dod policy states acceptable form sanitization degaussing see national industrial security program disk cleaning utilities also criticized leave signatures file system wiped cases unacceptable widely used disk cleaning utilities include dban srm bcwipe total wipeout killdisk pc inspector cyberscrubs cybercide another option approved nist nsa cmrr secure erase uses secure erase command built ata specification file wiping utilities used delete individual files operating system advantage file wiping utilities accomplish task relatively short amount time opposed disk cleaning utilities take much longer another advantage file wiping utilities generally leave much smaller signature disk cleaning utilities two primary disadvantages file wiping utilities first require user involvement process second experts believe file wiping programs n't always correctly completely wipe file information widely used file wiping utilities include bcwipe r-wipe clean eraser aevita wipe delete cyberscrubs privacysuite disk degaussing process magnetic field applied digital media device result device entirely clean previously stored data degaussing rarely used anti-forensic method despite fact effective means ensure data wiped attributed high cost degaussing machines difficult average consumer afford commonly used technique ensure data wiping physical destruction device nist recommends physical destruction accomplished using variety methods including disintegration incineration pulverizing shredding melting purpose trail obfuscation confuse disorient divert forensic examination process trail obfuscation covers variety techniques tools include log cleaners spoofing misinformation backbone hopping zombied accounts trojan commands one widely known trail obfuscation tools timestomp part metasploit framework timestomp gives user ability modify file metadata pertaining access creation modification times/dates using programs timestomp user render number files useless legal setting directly calling question files credibility another well known trail-obfuscation program transmogrify also part metasploit framework file types header file contains identifying information .jpg would header information identifies .jpg .doc would information identifies .doc transmogrify allows user change header information file .jpg header could changed .doc header forensic examination program operating system conduct search images machine would simply see .doc file skip past anti-forensic tools focused attacking forensic process destroying data hiding data altering data usage information anti-forensics recently moved new realm tools techniques focused attacking forensic tools perform examinations new anti-forensic methods benefited number factors include well documented forensic examination procedures widely known forensic tool vulnerabilities digital forensic examiners heavy reliance tools typical forensic examination examiner would create image computer disks keeps original computer evidence tainted forensic tools hashes created forensic examination software verify integrity image one recent anti-tool techniques targets integrity hash created verify image affecting integrity hash evidence collected subsequent investigation challenged use chassis intrusion detection feature computer case sensor photodetector rigged explosives self-destruction anti-forensic methods rely several weaknesses forensic process including human element dependency tools physical/logical limitations computers reducing forensic process susceptibility weaknesses examiner reduce likelihood anti-forensic methods successfully impacting investigation may accomplished providing increased training investigators corroborating results using multiple tools
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Computer security
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url shortening url shortening technique world wide web uniform resource locator url may made substantially shorter still direct required page achieved using redirect links web page long url example url shortened url shortened often redirect domain name shorter original one friendly url may desired messaging technologies limit number characters message example sms reducing amount typing required reader copying url print source making easier person remember intention permalink november 2009 shortened links url shortening service bitly accessed 2.1 billion times uses url shortening beautify link track clicks disguise underlying address although disguising underlying address may desired legitimate business personal reasons open abuse url shortening service providers found spam blacklists use redirect services sites trying bypass blacklists websites prevent short redirected urls posted several reasons use url shortening often regular unshortened links may aesthetically unpleasing many web developers pass descriptive attributes url represent data hierarchies command structures transaction paths session information result urls hundreds characters long contain complex character patterns urls difficult memorize type-out distribute result long urls must copied-and-pasted reliability thus short urls may convenient websites hard copy publications e.g printed magazine book latter often requiring long strings broken multiple lines case e-mail software internet forums truncated twitter instant-messaging services limit number characters message carry however twitter shortens links automatically using url shortening service need use separate url shortening service shorten urls tweet services using url shortener allow linking web pages would otherwise violate constraint shortening services generate urls human-readable although resulting strings longer generated length-optimized service finally url shortening sites provide detailed information clicks link receives simpler setting equally powerful server-side analytics engine unlike latter require access server urls encoded two-dimensional barcodes qr code often shortened url shortener order reduce printed area code allow printing lower density order improve scanning reliability websites create short links make sharing links via instant messaging easier make cheaper send via sms done online web pages url shortening service batch demand may require use api well-known websites set url shortening services use example twitter t.co google g.co godaddy x.co url shortening every long url associated unique key part top-level domain name example key redirection treated equally redirection instruction sent browser contain header http status 301 moved permanently 302 found 307 temporary redirect 308 permanent redirect several techniques implement url shortening keys generated base 36 assuming 26 letters 10 numbers case character sequence alternatively uppercase lowercase letters differentiated character represent single digit within number base 62 26 26 10 order form key hash function made random number generated key sequence predictable users may propose custom keys example shortened protocols capable shortened 2011 although protocols http https ftp ftps mailto mms rtmp rtmpt ed2k pop imap nntp news ldap gopher dict dns addressed services url shortener typically urls supported security reasons combat attacks like xss session hijacking url shortening services support forwarding mailto urls alternative address munging avoid unwanted harvest web crawlers bots may sometimes done using short captcha-protected urls common makers url shorteners usually register domain names less popular esoteric top-level domains order achieve short url catchy name often using domain hacks results registration different url shorteners myriad different countries leaving relation country domain registered url shortener shortened links top-level domains countries libya .ly samoa .ws mongolia .mn malaysia .my liechtenstein .li used well many others cases political cultural aspects country charge top-level domain may become issue users owners usually case services may record inbound statistics may viewed publicly others many providers shortened urls claim never expire always implied small print —there contract breached free service regardless promises — permanent url necessarily good thing security implications obsolete short urls remain existence may circulated long cease point relevant even extant destination sometimes short url useful simply give someone telephone conversation one-off access file download longer needed within couple minutes url shorteners offer time-limited service expire specified period services available include ordinary easy-to-say word url lifetime 5 minutes 24 hours creation url expire specified date specified period creation very-short-lived url 5 characters typing smartphone restriction creator total number uses url password protection microsoft security brief recommends creation short-lived urls reasons explicitly security rather convenience early reference us patent 6957224 describes ... system method computer program product providing links remotely located information network remotely connected computers uniform resource locator url registered server shorthand link associated registered url associated shorthand link url logged registry database request received shorthand link registry database searched associated url shorthand link found associated url url fetched otherwise error message returned patent filed september 2000 patent issued 2005 us patent applications made public within 18 months filing another reference url shortening 2001 first notable url shortening service tinyurl launched 2002 popularity influenced creation least 100 similar websites although simply domain alternatives initially twitter automatically translated urls longer twenty-six characters using tinyurl although began using bit.ly instead 2009 later developed url shortening service t.co 14 august 2009 wordpress announced wp.me url shortener use referring wordpress.com blog post november 2009 shortened links bit.ly accessed 2.1 billion times around time bit.ly tinyurl widely used url-shortening services one service tr.im stopped generating short urls 2009 blaming lack revenue-generating mechanisms cover costs twitter default use bit.ly shortener questioning whether shortening services could profitable url shortening longer term resumed time closed shortest possible long-term urls generated nanourl december 2009 2011 associated top-level .to tonga domain form represents sequence random numbers letters 14 december 2009 google announced service called google url shortener goo.gl originally available use google products google toolbar feedburner extensions google chrome 21 december 2009 google introduced youtube url shortener youtu.be september 2010 google url shortener became available via direct interface goo.gl service provides analytics details qr code generator 30 march 2018 google announced turning support goo.gl coming weeks replacing firebase dynamic links although existing goo.gl links continue function main advantage short link fact short looks neat clean easily communicated entered without error limited extent may obscure destination url though easily discoverable may advantageous disadvantageous irrelevant short link expires terminated security advantages short urls often circumvent intended use top-level domains indicating country origin domain registration many countries requires proof physical presence within country although redirected url guarantee url shortening may utilized spammers illicit internet activities result many removed online registries shut web hosts internet service providers according tonic corporation registry .to domains serious keeping domains spam free may remove url shortening services registry service abused addition u.nu made following announcement upon closing operations google url-shortener discussion group frequently included messages frustrated users reporting specific shortened urls disabled reported spam study may 2012 showed 61 url shorteners shut 614 1002 common cause cited abuse spammers convenience offered url shortening also introduces potential problems led criticism use services short urls example subject linkrot shortening service stops working urls related service become broken legitimate concern many existing url shortening services may sustainable business model long term late 2009 internet archive started 301 works projects together twenty collaborating companies initially whose short urls preserved project shortened internet links typically use foreign country domain names therefore jurisdiction nation libya instance exercised control .ly domain october 2010 shut vb.ly violating libyan pornography laws failure predict problems url shorteners investment url shortening companies may reflect lack due diligence websites prevent short redirected urls posted april 2009 tinyurl reported blocked saudi arabia yahoo answers blocks postings contain tinyurls wikipedia accept links url shortening services articles reddit community strongly discourages subreddits outright bans url shortening services link submissions disguise origin domain name whether link previously submitted reddit legitimate reasons use link shorteners reddit link submissions sites adf.ly use number advertising techniques including interstitial advertising generate revenue may deter readers short url obscures target address used redirect unexpected site examples rickrolling redirecting shock sites affiliate websites short url allow blacklisted urls accessed bypassing site blocks facilitates redirection user blacklisted scam pages pages containing malware xss attacks tinyurl tries disable spam-related links redirecting zonealarm however warned users tinyurl may unsafe website known distribute spyware tinyurl countered problem offering option view link destination using shortened url ability installed browser via tinyurl website requires use cookies destination preview may also obtained prefixing word preview tinyurl url example destination revealed entering url shortening services provide similar destination display security professionals suggest users check short url destination accessing following instance shortening service cli.gs compromised exposing millions users security uncertainties several web applications display destination url shortened url url shortening services filter links bad-site screening services google safe browsing many sites accept user-submitted content block links however certain domains order cut spam reason known url redirection services often added spam blacklists another privacy problem many services shortened url format small enough vulnerable brute-force search many people use url shorteners share links private content fact many web services like google maps offered automatic generation shortened links driving directions reveal personal information like home addresses sensitive destinations like clinics specific diseases including cancer mental diseases addiction treatment centers abortion providers correctional juvenile detention facilities payday car-title lenders gentlemen ’ clubs etc short urls although making easier access might otherwise long url user-space isp server add additional layer complexity process retrieving web pages every access requires requests least one dns lookup though may cached one http/https request thereby increasing latency time taken access page also risk failure since shortening service may become unavailable another operational limitation url shortening services browsers resend post bodies redirect encountered overcome making service reverse proxy elaborate schemes involving cookies buffered post bodies techniques present security scaling challenges therefore used extranets internet-scale services open source commercial scripts also available redirecting shortening links usually written php web application plugin one popular applications wordpress scripts avoid many issues shortening services keep domain name part shortened link made private
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Web technology
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bulnet bulgarian wordnet bulnet lexical semantic network bulgarian following princeton wordnet pwn framework implements traditional semantic networks whose structure consists nodes relations nodes bulnet started within eu-funded project balkanet multilingual semantic network balkan languages directed construction synchronized semantic databases following balkan languages bulgarian greek romanian serbian turkish expansion czech lexical-semantic network balkanet completion development bulgarian wordnet continued within nationally funded projects bulnet lexical-semantic network bulgarian 2005-2010 language e-resources processing tools 2011-2013 latter co-funded project cesar central south-east european resources information communication technologies policy support programme call cip ict-psp-2010-4 currently bulgarian wordnet comprises 80,000 april 15 2015 synonym sets distributed nine parts speech nouns verbs adjectives adverbs pronouns prepositions conjunctions particles interjections words included bulgarian wordnet selected according different criteria main ones frequency analysis word occurrences large text corpora taking account number occurrences citation forms wordforms well inclusion synsets already featuring wordnets languages synsets correspond high-frequency word senses found parallel corpora synonym set synset encodes relation equivalence number lexical items literals least one explicitly represented synset unique meaning specified value sense pertain one part speech specified value pos represent one lexical meaning specified value def synset linked counterpart pwn 3.0 means unique identification number id common synsets balkan languages marked common concepts subsets bcs monolingual database synset linked least one synset intralingual relation non-obligatory information may also encoded examples usage stylistic peculiarities morphological syntactic properties author last edit details large number relations encoded bulgarian wordnet effectively illustrates language semantic derivational richness offers diverse opportunities numerous applications multilingual database bulgarian electronic semantic database offers linguistic solutions semantic level options synonym selection queries semantic relations word language lexical system antonymy holonymy etc explanatory definition queries translation equivalents lexical item bulgarian wordnet electronic multilingual dictionary synonym sets along explanatory definitions sets semantic relations words language hydra os-independent system designed wordnet development validation exploration program enables users browse edit number monolingual wordnets time individual wordnets synchronised equivalent synonym sets synsets may viewed explored parallel
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Computational linguistics
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javapoly javapoly library polyfills native jvm support within modern web browser allows websites import java libraries call directly javascript even user java installed computer unlike gwt teavm attempt compile subset java javascript javapoly actually executes java bytecode instructions means javapoly run almost java library including libraries use threads shared memory locking primitives 64-bit integers javapoly designed optimize performance taking advantage native jvms available running node.js javapoly always use native jvm thereby utilize native capabilities like multi-core support otherwise unavailable javascript applications similarly javapoly take advantage native java support within web browser support available suitable alternatives detected javapoly call doppio vm provides execution support legacy browsers
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Programming language topics
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open power template open power template web template engine written php 5 common strategy designing web application separation application logic i.e data processing presentation displaying data opt tool implementing separation presentation layer represented templates text files html code extra instructions controlling data substitution opt uses dedicated xml template language writing templates general-purpose domain-specific language primarily designed support simplify template-specific problems set declarative instructions instead implementing rendering algorithms statements like imperative programming template designer specifies expected result features aims ease costs efforts associated software development maintenance library provides object-oriented api based solutions popular frameworks first member bigger project open power libs built upon small opl core library provides basic features project started november 2004 template engine discussion board project inspired smarty later failed library became independent july 2006 version 1.0.0 released offered template language smarty-like syntax small set declarative instructions january 2007 developers release version 1.1.0 brings notable improvements pagination support tree rendering january 2008 developers form open-source programming team invenzzia develop opt php projects time development open power template 2.0 began last version 1.1 branch released may 2008 group focused opt 2.0 development new library went beta-stage december first stable version released july 2009 opt 2.0 template language xml application allows manipulate xhtml document structure features built-in xml parser reconfigured parse certain html documents plain text content since templates separated application logic need least two files first one contains presentation code xml template second one generates data configures library
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Web technology
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primefaces primefaces open-source user interface ui component library javaserver faces-based applications created turkish company primetek informatics initial development primefaces started late 2008 predecessor primefaces yui4jsf library set jsf components based yui javascript library yui4jsf got cancelled favor primefaces early 2009 since release primefaces strongly supported oracle particularly within netbeans world packt publishing publish books technology
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Programming language topics
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bootsplash bootsplash also known bootscreen graphical representation boot process operating system bootsplash simple visualisation scrolling boot messages console also present graphics combinations unlike splash screens bootsplash necessarily designed marketing purposes enhance experience user eye candy provide user messages added advantage color-coding facility diagnose state system versions microsoft windows feature boot screen loaded startup process extra third-party utilities possible replace default windows boot screen custom images text and/or animations windows vista default boot screen represented green indeterminate progress indicator boot screen changed displays static image aurora text starting windows vista enabling gui boot option within windows system configuration utility msconfig.exe microsoft would update aurora image throughout lifecycle operating system starting first service pack altered match image displayed operating system hibernation screen windows 7 change boot screen although possible third-party utilities extremely risky may cause system unable boot also hidden aurora bootscreen removed
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Operating systems
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frees/wan frees/wan free secure wide-area networking free software project implemented reference version ipsec network security layer linux project goal ubiquitous opportunistic encryption internet traffic realized although contribute general internet encryption project founded john gilmore administered duration hugh daniel john ioannidis angelos keromytis started codebase outside united states america prior autumn 1997 technical lead project henry spencer later michael richardson ike keying daemon pluto maintained d. hugh redelmeier ipsec kernel module klips maintained richard guy briggs sandy harris main documentation person project later claudia schmeing final frees/wan version 2.06 released 22 april 2004 earlier version 2.04 forked form two projects openswan strongswan openswan since 2012 forked libreswan
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Internet protocols
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system management mode system management mode smm sometimes called ring -2 reference protection rings operating mode x86 central processor units cpus normal execution including operating system suspended alternate software system usually resides computer firmware hardware-assisted debugger executed high privileges first released intel 386sl initially special sl versions required smm intel incorporated smm mainline 486 pentium processors 1993 amd implemented intel smm am386 processors 1991 available later microprocessors x86 architecture smm special-purpose operating mode provided handling system-wide functions like power management system hardware control proprietary oem designed code intended use system firmware applications software general-purpose systems software main benefit smm offers distinct easily isolated processor environment operates transparently operating system executive software applications order achieve transparency smm imposes certain rules smm entered smi system management interrupt processor executes smm code separate address space made inaccessible operating modes cpu firmware initially system management mode used implementing advanced power management apm features however time bios manufacturers relied smm functionality like making usb keyboard work real mode uses system management mode system management mode also abused run high-privileged rootkits demonstrated black hat 2008 2015 smm entered via smi system management interrupt invoked entering smm processor looks first instruction address smbase smbase register content 8000h default 38000h using registers cs 3000h eip 8000h cs register value 3000h due use real mode memory addresses processor smm case cs internally appended 0h rightmost end design operating system override disable smi due fact target malicious rootkits reside including nsa implants individual code names specific hardware like souffletrough juniper networks firewalls j-series routers company dell hp proliant servers improperly designed insufficiently tested smm bios code make wrong assumptions work properly interrupting modes like pae 64-bit long mode according documentation linux kernel around 2004 buggy implementations usb legacy support feature common cause crashes example motherboards based intel e7505 chipset since smm code smi handler installed system firmware bios os smm code may expectations hardware settings incompatible different ideas advanced programmable interrupt controller apic set operations smm take cpu time away applications operating system kernel hypervisor effects magnified multicore processors since smi causes cores switch modes also overhead involved switching smm since cpu state must stored memory smram write-back caches must flushed destroy real-time behavior cause clock ticks get lost windows linux kernels define ‘ smi timeout ’ setting period within smm handlers must return control operating system ‘ hang ’ ‘ crash ’ smm may disrupt behavior real-time applications constrained timing requirements logic analyzer may required determine cpu entered smm checking state smiact pin cpu recovering smi handler code analyze bugs vulnerabilities secrets requires logic analyzer disassembly system firmware
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Computer security
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xsan xsan apple inc. storage area network san clustered file system macos xsan enables multiple mac desktop xserve systems access shared block storage fibre channel network xsan file system installed computers read write storage volume time xsan complete san solution includes metadata controller software file system client software integrated setup management monitoring tools xsan normal features expected enterprise shared disk file system including support large files file systems multiple mounted file systems meta data controller failover fault tolerance support multiple operating systems xsan based stornext file system made quantum corporation stornext file system xsan file system share file system layout protocol talking meta data server also seem share common code base close development based new features developed file systems xsan website claims complete interoperability stornext file system xsan completely interoperable quantum ’ stornext file system even provide clients windows linux unix platforms direct fibre channel block-level access data xsan-managed storage pool quantum corporation claims complete interoperability apple ’ xsan promise raid allows xsan xserve raid support aix hp-ux irix red hat linux suse linux mac os x solaris windows clients including support 64 bit windows windows vista command line tools xsan begin letters cv stand centravision – original name file system xsan clients use tcp ports 49152–65535 tcp/63146 frequently showing log files xsan file system uses several logical storages distribute information two main classes information appear xsan user data files file system metadata folders file names file allocation information configurations use different storages data metadata file system supports dynamic expansion distribution data metadata areas january 4 2005 apple announced shipping xsan may 2006 apple released xsan 1.2 support volume sizes nearly 2 petabytes august 7 2006 apple announced xsan 1.4 available intel-based macintosh computers universal binary supports file system access control lists december 5 2006 apple released xsan 1.4.1 october 18 2007 apple released xsan 1.4.2 resolves several reliability compatibility issues february 19 2008 apple released xsan 2 first major update introduces multisan completely redesigned administration tools 2.1 introduced june 10 2008 2.1.1 introduced october 15 2008 2.2 released september 14 2009 july 20 2011 apple released xsan 2.3 included mac os x lion first version xsan included macos august 25 2011 apple released xsan 2.2.2 brought along several reliability fixes july 25 2012 apple released xsan 3 included os x mountain lion october 17 2014 apple released xsan 4 os x yosemite september 20 2016 apple released xsan 5 macos sierra macos server 5.2
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Computer file systems
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cdemu cdemu free open-source virtual drive software designed emulate optical drive optical disc including cd-roms dvd-roms linux operating system cdemu available official repositories debian ubuntu fedora linux release available via official ppa ubuntu copr fedora linux cdemu consists software portable operating systems supported glib exceptions kernel module clients rely d-bus communication cdemu originally designed robert penz justus schwartz patch mplayer allowed mounting .cue/.bin files patch completed realized simplicity wrote module linux kernel originally cdemu named virtual cd name previously trademarked owners trademark requested use name june 2007 development cdemu 0.8 ceased rewrite developed instead work done rok mandeljc new version cdemu took another approach emulation much possible userspace june 2008 considered mostly stable version 2.0.0 cdemu supports following image formats emulator endeavors follow mmc-3 standard scsi optical drives closely possible ensuring realistic accurate emulation optical media emulated cdemu mounted within linux cdemu support cd subchannels cd-text isrc，mcn ecc/edc dpm/rmps also support limited number encrypted compressed image formats developers working supporting many major formats encourage users submit patches end alternative linux programs available repositories debian ubuntu fedora linux
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Computer architecture
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deep freeze software deep freeze faronics software application available microsoft windows macos operating systems allows system administrators protect core operating system configuration files workstation server restoring computer back saved configuration time computer restarted also known reboot restore software deep freeze also protect computer harmful malware since automatically deletes rather longer sees downloaded files computer restarted advantage using deep freeze uses system resources thus slow computer performance greatly disadvantage provide real-time protection therefore infected computer would restarted order remove malware deep freeze protects workstations fresh-booted state deep freeze prevents permanent tampering protected hard drives/partitions across reboots user activity restarts limited program example deep freeze prevent application installation user install modified version web browser seemingly harmless unknowing user designed secretly send users passwords server connected internet workaround deep freeze configured restart user logout shutdown chosen period inactivity restart/shutdown scheduled time attempt ensure installations retained rebooting system returns system original unmodified state deep freeze protect operating system hard drive upon installed computer booted another medium another bootable partition internal hard drive external hard drive usb device optical media network server cases user would real access contents supposedly frozen system windows-based computer scenario may prevented configuring cmos nonvolatile bios memory workstation boot hard drive protected password-protecting cmos normal precaution public access computers precaution would lock pc case shut physical lock tiedown cable system prevent access motherboard jumpers deep freeze protect hard drive partitions larger 2 tb capacity using ntfs
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Computer security
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elephantdrive elephantdrive storage virtualization service used primarily online backup tool also remote access service/collaboration tool service runs windows mac platforms allows users create simple automated rules protecting data moving elephantdrive account elephantdrive makes use infrastructure-on-demand part architecture one first popular examples applications built amazon s3 simple storage service elephantdrive initially utilized amazon s3 tool datacenter migration quickly moved production infrastructure elephantdrive first major breakthrough came conjunction 2008 closing early cloud storage provider aol property xdrive service offered free tool migrating files xdrive platform simplifying process switching providers company turned focus network attached storage nas space designing deploying cloud storage optimized run natively nas devices series partnerships hardware makers initial partnership netgear storage product line readynas systems form co-branded embedded cloud backup service called readynas vault additional cloud storage nas integration launched hardware makers qnap thecus opted use elephantdrive brand opposed vault co-branding
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Computer security
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nemesis operating system nemesis operating system designed university cambridge university glasgow swedish institute computer science citrix systems nemesis conceived multimedia uses mind microkernel environment application typically implemented number processes servers performing work behalf one client leads enormous difficulty accounting resource usage kernel-based system multimedia applications spend time kernel leading similar problems guiding principle design nemesis structure operating system way majority code could execute application process nemesis therefore extremely small lightweight kernel performed operating system functions shared libraries executed user process isas nemesis supports include x86 intel i486 pentium pentium pro pentium ii alpha arm strongarm sa-110 nemesis also runs evaluation boards 21064 21164
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Operating systems
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veriexec veriexec file-signing scheme netbsd operating system introduces special device node /dev/veriexec signature list loaded kernel list contains file paths together hashes expected file type direct executables indirect scripts file shared libraries regular files kernel verifies contents signed files hashes opened exec open system call veriexec enabled level 0 kernel simply warn signature mismatches level 1 prevent access mismatched files level 2 prevents signed files overwritten deleted highest level 3 kernel allow unsigned files accessed
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Operating systems
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konversation konversation internet relay chat irc client built kde platform free software released terms gnu general public license konversation currently maintained kde extragear network module means release cycle independent main kde applications default irc client many prominent linux distributions opensuse kde spin fedora kubuntu konversation supports ipv6 connections offers ssl server support supports blowfish encryption also supports identity management multiple server connections using separate identities different servers display multiple servers channels one window konversation features automatic utf-8 detection support different encodings different channels also features optional on-screen display osd message notifications save bookmarks channels servers konversation supports colors text decorations themable nicklist icons konversation also scriptable using shell scripts via d-bus includes support aliases action system automatic events also identifies different users conversation window choosing random color user
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Internet protocols
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davix davix live cd based slackware purposes computer security operations distribution focuses data analysis visualization davix stands data analysis visualization linux first live cd integrate many visualization tools long-term goal distribution provide good set tools supporting complete process visual data analysis jan monsch began work cd december 2007 discussions raffael marty january 2008 jan agreed produce cd applied security visualization based list utilities raffael discussed book davix contains collection 25 free tools data processing visualization examples tools davix cd ships 15 chapter manual covers davix use customization examples screenshots additionally utilities system documentation pages davix cd based slax computer information security visualization form visualization computer graphics enterprise environments computer security information generated large volumes become difficult analyze without visual context using davix security engineer visually spot anomalies network traffic changes ip sources/destinations network protocols application protocols traffic patterns frequency volume davix released black hat briefings/def con august 2008
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Operating systems
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ml programming language ml meta language general-purpose functional programming language roots lisp characterized lisp types known use polymorphic hindley–milner type system automatically assigns types expressions without requiring explicit type annotations ensures type safetythere formal proof well-typed ml program cause runtime type errors ml provides pattern matching function arguments garbage collection imperative programming call-by-value currying used heavily programming language research one languages completely specified verified using formal semantics types pattern matching make well-suited commonly used operate formal languages compiler writing automated theorem proving formal verification features ml include call-by-value evaluation strategy first-class functions automatic memory management garbage collection parametric polymorphism static typing type inference algebraic data types pattern matching exception handling ml uses static scoping rules ml referred impure functional language although encourages functional programming allow side-effects like languages lisp unlike purely functional language haskell like programming languages ml uses eager evaluation meaning subexpressions always evaluated though lazy evaluation achieved use closures thus one create use infinite streams haskell expression indirect ml strengths mostly applied language design manipulation compilers analyzers theorem provers general-purpose language also used bioinformatics financial systems ml developed robin milner others early 1970s university edinburgh whose syntax inspired iswim historically ml conceived develop proof tactics lcf theorem prover whose language pplambda combination first-order predicate calculus simply-typed polymorphic lambda calculus ml metalanguage today several languages ml family three prominent standard ml sml ocaml f ideas ml influenced numerous languages like haskell cyclone nemerle ats elm following examples use syntax standard ml ml dialects ocaml f differ small ways factorial function expressed pure ml describes factorial recursive function single terminating base case similar descriptions factorials found mathematics textbooks much ml code similar mathematics facility syntax part definition shown optional describes types function notation e read expression e type instance argument n assigned type integer int fac n int result applying fac integer n also type integer function fac whole type function integer integer int int fac accepts integer argument returns integer result thanks type inference type annotations omitted derived compiler rewritten without type annotations example looks like function also relies pattern matching important part ml programming note parameters function necessarily parentheses separated spaces function argument 0 zero return integer 1 one cases second line tried recursion executes function base case reached implementation factorial function guaranteed terminate since negative argument causes infinite descending chain recursive calls robust implementation would check nonnegative argument recursing follows problematic case n negative demonstrates use ml exception system function improved writing inner loop tail-recursive style call stack need grow proportion number function calls achieved adding extra accumulator parameter inner function last arrive following function reverses elements list precisely returns new list whose elements reverse order compared given list implementation reverse correct clear inefficient requiring quadratic time execution function rewritten execute linear time following efficient though less easy-to-read style notably function example parametric polymorphism consume lists whose elements type return lists type modules ml system structuring large projects libraries module consists signature file one structure files signature file specifies api implemented like c header file java interface file structure implements signature like c source file java class file example following define arithmetic signature implementation using rational numbers imported interpreter 'use command interaction implementation allowed via signature functions example possible create 'rat data object directly via code 'structure block hides implementation detail outside ml standard libraries implemented modules way
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Programming language topics
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multiprocessor specification multiprocessor specification mps x86 architecture open standard describing enhancements operating systems firmware allow work x86-compatible processors multi-processor configuration mps covers advanced programmable interrupt controller apic architectures version 1.1 specification released april 11 1994 version 1.4 specification released july 1 1995 added extended configuration tables improve support multiple pci bus configurations improve expandability linux kernel freebsd known support intel mps utility called 'mptable used examine mps table motherboards since newer machines support advanced configuration power interface acpi subsumes mps functionality mps part supplanted acpi mps still useful machines operating systems support acpi
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Computer architecture
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global information grid global information grid gig all-encompassing communications project united states department defense defined globally interconnected end-to-end set information capabilities collecting processing storing disseminating managing information demand warfighters policy makers support personnel gig includes owned leased communications computing systems services software including applications data security services associated services national security systems non-gig information technology includes stand-alone self-contained embedded connected enterprise network new definition removes references national security systems defined section 5142 clinger-cohen act 1996 new definition removes references gig providing capabilities operating locations bases posts camps stations facilities mobile platforms deployed sites lastly definition removes part definition discusses interfaces coalition allied non-department defense users systems dod use term gig undergoing changes department deals new concepts cyberspace operations gig 2.0 joint staff j6 initiative department defense information enterprise die gig managed construct known netops netops defined operational framework consisting three essential tasks situational awareness sa command control c2 commander cdr united states strategic command usstratcom coordination dod global netops community employs operate defend gig ensure information superiority department defense information enterprise defined dod information resources assets processes required achieve information advantage share information across department defense mission partners includes network-centric warfare ncw doctrine represents fundamental shift military culture away compartmentalized war machines toward interconnected units operating cohesively tenets network centric warfare enterprise level forging new paths components military communicate ease logistics burdens improve communication combat effectiveness war fighter decrease instances confusion-related fratricide accelerate trend minimizing collateral damage hasten flow business warfighter situational awareness would improved tremendously linking sees overhead satellite sees fog war would lifted seamless communication unit members site detection devices commanders operating behind line improved coordination may also assist delivering appropriate firepower tangible assets first responders domestic attacks natural disasters worldwide
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Distributed computing architecture
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wolf frameworks wolf frameworks web application designing development platform service based india united states represented via partners worldwide founded 2006 cloud computing infrastructure offered company enables users design deliver cross platform saas applications without writing technical code wolf 100 ajax xml .net based enables building mashable interoperable web applications using browser internet connection knowledge modelling business
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Distributed computing architecture
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geospatial authentication software package designed allow authentication determining rover is/are within set boundaries specific area access critical geospatial information using gps signal structures means authenticate mobile devices network wirelessly real-time developed advantage lies system allows designated geospatial boundaries areas server geospatial authentication software two parts — server client server software virtual private network vpn developed linux operating system using perl programming language server stand-alone vpn server combined applications services client software gui windows ce software mobile graphical software allows users authenticate network purpose client software pass needed satellite information server authentication work done stacey d. lyle geospatial research innovation design nasa ’ stennis space center
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Computer security
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rtp control protocol rtp control protocol rtcp sister protocol real-time transport protocol rtp basic functionality packet structure defined rfc 3550 rtcp provides out-of-band statistics control information rtp session partners rtp delivery packaging multimedia data transport media data primary function rtcp provide feedback quality service qos media distribution periodically sending statistics information transmitted octet packet counts packet loss packet delay variation round-trip delay time participants streaming multimedia session application may use information control quality service parameters perhaps limiting flow using different codec typically rtp sent even-numbered udp port rtcp messages sent next higher odd-numbered port rtcp provide flow encryption authentication methods mechanisms may implemented example secure real-time transport protocol srtp defined rfc 3711 rtcp provides basic functions expected implemented rtp sessions rtcp reports expected sent participants even multicast session may involve thousands recipients traffic increase proportionally number participants thus avoid network congestion protocol must include session bandwidth management achieved dynamically controlling frequency report transmissions rtcp bandwidth usage generally exceed 5 total session bandwidth furthermore 25 rtcp bandwidth reserved media sources times large conferences new participants receive cname identifiers senders without excessive delay rtcp reporting interval randomized prevent unintended synchronization reporting recommended minimum rtcp report interval per station 5 seconds stations transmit rtcp reports often every 5 seconds rtcp distinguishes several types packets sender report receiver report source description goodbye addition protocol extensible allows application-specific rtcp packets standards-based extension rtcp extended report packet type introduced rfc 3611 large-scale applications internet protocol television iptv long delays minutes hours rtcp reports may occur rtcp bandwidth control mechanism required control congestion see protocol functions acceptable frequencies usually less one per minute affords potential inappropriate reporting relevant statistics receiver cause evaluation media sender inaccurate relative current state session methods introduced alleviate problems rtcp filtering rtcp biasing hierarchical aggregation hierarchical aggregation also known rtcp feedback hierarchy optimization rtcp feedback model aim shift maximum number users limit together quality service qos measurement rtcp bandwidth constant takes 5 session bandwidth therefore reporting interval qos depends among others number session members large sessions become high minutes even hours however acceptable interval 10 seconds reporting bigger values would cause time-shifted inaccurate reported status current session status optimization made sender could even negative effect network qos conditions hierarchical aggregation used source-specific multicast single source allowed i.e iptv another type multicast could any-source multicast suitable large-scale applications huge number users modern iptv systems use hierarchical aggregation feedback target new type member firstly introduced internet draft draft-ietf-avt-rtcpssm-13 hierarchical aggregation method extended functionality function member receive receiver reports rr see rtcp retransmit summarized rr packets so-called receiver summary information rsi sender case single level hierarchy
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Internet protocols
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picolisp picolisp programming language dialect language lisp runs operating systems including linux others portable operating system interface posix compliant prominent features simplicity minimalism built one internal data type cell language level programmer use three different data types numbers symbols lists represented cells differentiated bits end cell free open-source software released mit license x11 functions accept arbitrary types numbers arguments macros needed rare cases implemented using quote function picolisp include lisp lambda function quote function changed return arguments unevaluated codice_1 first special feature intrinsic create read update delete crud functioning persistent symbols first-class citizens objects loaded database files automatically accessed written back modified applications written using class hierarchy entities relations features include prolog engine database engine database queries distributed databases inlining c language functions native c function calls child process management interprocess communication browser graphical user interface gui internationalization localization 1980s picolisp began development macintosh used commercial application development since ported dos sco unix since 1993 used mainly linux mid-1990s database functions added first versions written mix c assembly language 1999 first rewrite scratch done fully c. 2002 version released gnu general public license gnu gpl 2010 changed mit/x11 license 2009 64-bit version released another rewrite time written generic assembly turn implemented picolisp version adds support coroutines december 2010 java version named ersatz picolisp released september 2014 burger announced pilmcu project picolisp development listserv effort george orais implement picolisp hardware directly summer 2016 development pilbox picolisp box – generic android app allowing write apps pure picolisp – started still developed maintained
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Programming language topics
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foundation network relayware formerly foundation network vendor partner relationship management prm solutions delivers businesses internet using software service model foundation network founded 1997 former business consultant technologist simon wallace-jones later year company secured first global customer 3com network infrastructure vendor april 2008 foundation network announced release relayware 8 next-generation prm software foundation network became relayware 2010 established headquarters redwood shores california usa
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Distributed computing architecture
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robert harper computer scientist robert william bob harper jr. computer science professor carnegie mellon university works programming language research harper made major contributions design standard ml programming language lf logical framework harper named acm fellow 2005 awarded honor contributions type systems programming languages 2003–2008 harper hosted progressive talk show left wrct-fm fellow host carnegie mellon university school computer science faculty member danny sleator
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Programming language topics
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esoteric programming language esoteric programming language sometimes shortened esolang programming language designed test boundaries computer programming language design proof concept software art hacking interface another language particularly functional programming procedural programming languages joke use esoteric distinguishes languages programming languages working developers use write software usually esolang creators intend language used mainstream programming although esoteric features visuospatial syntax inspired practical applications arts languages often popular among hackers hobbyists usability rarely goal esoteric programming language designers—often design leads quite opposite usual aim remove replace conventional language features still maintaining language turing-complete even one computational class unknown earliest still canonical example esoteric language intercal designed 1972 woods james m. lyon stated intention unlike programming language authors familiar parodied elements established programming languages day fortran cobol assembly language many years intercal represented paper copies intercal manual language revival 1990 implementation c unix stimulated wave interest intentional design esoteric computer languages 1993 wouter van oortmerssen created false small stack-oriented programming language syntax designed make code inherently obfuscated confusing unreadable also compiler 1024 bytes inspired urban müller create even smaller language now-infamous brainfuck consists eight recognized characters along chris pressey befunge like false two-dimensional instruction pointer brainfuck one best-supported esoteric programming languages canonical examples minimal turing tarpits needlessly obfuscated language features brainfuck related p′′ family turing machines turing tarpit turing-complete programming language computable function could theoretically written impractically difficult esoteric languages may described turing tarpits especially aim minimize number language features method encoding programs substring encoding instruction single instruction always includes two sequential phases choosing operation executing list operations may either static—as remorse thrat—or dynamic—as remorse4ever example based remorse thrat paradigm language fall number categories categories used get general understanding way specific language operates include imperative languages brainfuck instructions describe change data functional languages unlambda data code less interchangeable execution repeated application functions results functions rewriting languages thue transformation functions applied initial state funge esoteric programming language models programs metric spaces coordinate systems often necessarily cartesian execute instructions located points program space moving instruction pointer position vector indicates currently executing instruction space different instructions determine direction instruction pointer moves consequently sequence instructions executed current official standard behaviour programming languages funge-98 specification specification generalisation semantics befunge programming language two-dimensional toroidal topology languages adhere closely standard unefunge one-dimensional trefunge three-dimensional sometimes called funges distant relatives differ significant respects referred fungeoids one instruction set computer machine supports one operation deterministic language one given current state program next state always predicted true nondeterministic language languages deterministic languages befunge supply built-in randomization instruction moreover languages java2k randomized instructions thus getting even trivial programs reliable output often monumental outright impossible task nondeterministic languages used explore large search spaces grammars exhaustive search impractical random text generators dada engine rmutt examples kind nondeterminstic language esoterically nondeterministic algorithms employed theoretical investigation hypercomputation characteristic examples esoteric programming languages arnoldc esoteric programming language based one-liners arnold schwarzenegger following hello world programmed arnoldc showtime talk hand hello world terminated asciidots esoteric programming language based ascii art language dots represented periods codice_1 travel ascii art paths undergo operations example code golf counter 1/ befunge allows instruction pointer roam multiple dimensions code example following program displays hello world pushing characters reverse order onto stack printing characters loop circulates clockwise instructions codice_2 codice_3 codice_4 codice_5 codice_6 codice_7 binary lambda calculus designed algorithmic information theory perspective allow densest possible code minimal means featuring 29 byte self interpreter 21 byte prime number sieve 112 byte brainfuck interpreter brainfuck designed extreme minimalism leads obfuscated code programs containing eight distinct characters following program outputs hello world chef david morgan-mar stack-oriented programming language designed make programs look like cooking recipes programs consist title list variables data values list stack manipulation instructions joking design principle states program recipes generate valid output easy prepare delicious morgan-mar notes example hello world program 101 eggs 111 cups oil would produce lot food one person false stack-based language single-character commands variables example 3 1 calculated evaluating λ x → x 1 3 fim++ object-oriented programming language based television show fim++ programs read like plain english style show 'friendship reports following program prints hello world fim++ supports many modern language features interfaces inheritance importing files uniquely variable names contain spaces fim++ dear princess celestia hello world today learned say hello world said hello world say hello world faithful student twilight sparkle fractran program ordered list positive fractions together initial positive integer input formula_1 program run multiplying integer formula_1 first fraction formula_3 list formula_4 integer integer formula_1 replaced formula_4 rule repeated fraction list produces integer multiplied formula_1 program halts fractran invented mathematician john conway .gertrude named gertrude stein designed gerson kurz enable programs vaguely resemble poetry programs golfscript consist lists items pushed onto stack encountered exception variables code blocks value case code executed grass functional programming language uses characters codice_8 codice_9 codice_4 thus programs grass said look like ascii art grass grass formal specification based untyped lambda calculus secd machine grass confused grass different programming language intercal short compiler language pronounceable acronym created 1972 parody satirize aspects various programming languages time jsfuck esoteric programming style javascript code written using six characters codice_11 codice_12 codice_13 codice_14 codice_15 codice_16 unlike brainfuck requires compiler interpreter jsfuck valid javascript code meaning jsfuck programs run web browser engine interprets javascript lolcode designed resemble speech lolcats following hello world example lolcode frequently criticized esoteric rather ordinary procedural language unusual vocabulary lollipop church esoteric programming language programs look like russian guide books lollipop church designed shakila tayefeh 7 april 2019 following hello world example gulfoffinland hello world malbolge 8th circle hell designed difficult esoteric programming language among features code self-modifying design effect instruction depends address memory modiscript esoteric programming language entirely consists quotes indian prime minister narendra modi speeches language follows many ideologies import rule importation code allowed consistent make india campaign following code prints mandir wahin banayenge mitrooon bjp governed state hai sp opposition hai agar ye sach hai nahi toh achhe din aa gaye piet language designed david morgan-mar whose programs bitmaps look like abstract art compilation guided pointer moves around image one continuous coloured region next procedures carried pointer exits region 20 colours behaviour specified 18 colourful colours ordered 6-step hue cycle 3-step brightness cycle black white ordered exiting colourful colour entering another one performed procedure determined number steps change hue brightness black entered pointer tries enter black region rules choosing next block changed instead possible rules tried program terminates regions outside borders image also treated black white perform operations allows pointer pass behaviour colours 20 specified left compiler interpreter variables stored memory signed integers single stack specified procedures deal operations stack others input/output rules compilation pointer moves piet named dutch painter piet mondrian originally intended name mondrian already taken pikachu esoteric programming language developed nilabhro datta whose programs look like dialect pikachu stated purpose easily usable pikachu programs written language readable writable pikachu end pikachu makes use 3 valid syntax elements codice_17 codice_18 codice_19 rockstar designed creating computer programs also song lyrics heavily influenced lyrical conventions 1980s hard rock power ballads dynamically typed turing-complete following example line code multiplies value codice_20 codice_21 stores codice_22 shakespeare designed make programs look like shakespearean plays example following statement declares point program reached via goto-type statement train completely visual programming language looks like wooden train set engines threads train cars memory cargo cars variables train contains multiple data types including blocks numbers colors dinosaurs stations operate cargo e.g increment decrement add subtract catapult type specific wyes direct flow trains include greater less prompt random magic tunnels allow creation functions unlike programming languages distinction code memory output train program state defined arrangement train pieces unlambda minimalist functional programming language based ski calculus combined first-class continuations imperative i/o input usually requiring use continuations whitespace uses whitespace characters space tab return ignoring characters reverse many traditional languages distinguish different whitespace characters treating tab space also allows whitespace programs hidden source code programs languages like c. ~ath esoteric programming language used humans trolls webcomic homestuck name spoken tilde ath pun til death known insufferable work despite relative simplistic syntax language compile using infinite loops context story capability import change objects wide library author universe wide range combined inability interact anything short lifespan leads files tied long-term events deaths characters universes ~ath also sensitive color text written accepts unusual characters one ~ath program shown story uses command called bifurcate split program red text blue text another ~ath program contains character appears animated flickering billiard ball ~ath code simplest language code deviating pattern compile cultural context esolangs studied people like geoff cox writes esolangs shift attention command control toward cultural expression refusal seeing esolangs similar code art code poetry mez breeze mezangelle daniel temkin describes brainfuck refusing ease boundary human expression assembly code thereby taking us ludicrous journey logic exposing inherent conflict human thinking computer logic connects programming within esolang performing event score fluxus movement playing rules logic code makes point view language clear
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Programming language topics
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wmlscript wmlscript procedural programming language dialect javascript used wml pages part wireless application protocol wap wmlscript client-side scripting language similar javascript like javascript wmlscript used tasks user input validation generation error message dialog boxes etc wmlscript based ecmascript european computer manufacturers association script javascript standardized version thus syntax wmlscript similar javascript fully compatible despite syntactical similarities two different languages wmlscript objects array javascript hand allows declare include external functions scripts wmlscript optimised low power devices compiled language
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Programming language topics
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reval company reval software company reval ’ cloud-based software provides clients tools manage cash financial risks company headquartered new york city regional offices emea apac reval led ceo chairman co-founder jiro okochi reval founded 1999 jiro okochi woo song 2009 company acquired fxpress corporation leading treasury software provider fortune 1000 2011 acquired european treasury management provider ecofinance 2012 2013 reval global finance magazine treasury cash management award best financial risk management solution.in october 2016 reval acquired ion investment group little kids rock lkr leading nonprofit provider free musical instruments teacher trainings u.s. public schools appointed jiro okochi new york area board directors spearhead fundraising efforts lkr ’ new york metro area program
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Distributed computing architecture
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yoix computer programming yoix high-level general-purpose interpreted dynamic programming language yoix interpreter implemented using standard java technology without add-on packages requires sun-compliant jvm operate initially developed labs researchers internal use available free open source software since late 2000 1998 java technology still emerging swing toolkit add-on package interruptible i/o regular expressions printf capability yet features java web start developed moreover java scripting languages largely non-existent time groovy jruby yet invented jython created late 1997 browsers 1998 limited feature sets unstable production use 8-hour shift still fighting skirmishes browser wars environment yoix technology created response pressing need reliable easy distribute maintain gui front-end mission-critical application developed within namely global fraud management system day monitors tracks fraud activity related voice traffic expanding networks wireline wireless ip yoix technology first released public late 2000 open source initiative common public license v1.0 yoix name came partially fox hunting cry encouragement hounds partially echo another familiar four-letter name ends ix partially avoid many false-positives google search yoix technology provides pure java programming language implementation general purpose dynamic programming language developed researchers labs syntax grammar easy learn familiar c programming language java end-user yoix application indistinguishable java application application developer yoix provide simpler coding experience working java directly much like writing perl code simpler writing c code yoix language object oriented language makes use 165 object types provide access standard java classes yoix interpreter built entirely using java technology means yoix applications cross-platform gui-capable network thread friendly yet yoix developers find insulated complex error-prone parts coding functionality directly java use reflection access java functionality thus adds value simplifying access functionality also improving application reliability coding java glitches complicated java features one-time behind-the-scenes yoix language includes safe pointers addressing declarations global local variables addition supporting native user functions users add builtin functions written java two central elements yoix design borrowed postscript language dictionaries language components permissions-protected dictionaries exposed system components homage tcl language exposure philosophy also given though direct influence another key yoix design element involves pointers addressing pointers pointer arithmetic yoix language syntactically similar found c language yoix implementation prevents using pointer outside bounds addition address operator always produces valid usable result overall yoix design attempted make language easy learn programmers experienced c java languages yoix distribution includes yoix web application instant template ywait software framework building yoix web application yoix web application resides web server downloaded piecemeal run-time as-needed basis yoix interpreters running client machines model analogous familiar model client web browsers downloading website piecemeal as-needed run-time permits simple efficient distribution maintenance applications relies ubiquitous web server yoix interpreter building web application using ywait framework requires standard unix tools available modern operating systems linux mac os x microsoft windows help add-on packages u/win client side ywait-based application relies yoix interpreter thus platform independent running wherever java runs yoix software development philosophy aims keep things simple eschewing popular tendency multiple embedded specialized languages ywait framework permits easy incremental screen development simple logical source tree hierarchy development yoix web application reduced basics command prompt text editor ide enthusiasts may nonplussed small beautiful approach software development highly effective practice addition role tool building gui applications yoix technology supports several modes data visualization data visualization module called ydat yoix data analysis tool included public yoix distribution since release 2.1.2 ydat uses data manager component coordinate data display filtering among several visualization components include event plot graph drawing pane histogram filters tabular detail ydat able display graphs generated graphviz graph drawing layout tool another open source tool freely available labs ydat highly configurable yoix language level image screenshot yoix ydat instantiation example used analyze vehicle auction transactions yoix technology provides good support graph drawing addition graph display mentioned part ydat module data types yoix language support building manipulating traversing graph structures native yoix functions support dot language output built-in dot language parser facilitate interaction graphviz layout engines ychart data visualization toolkit added yoix distribution release 2.2.0 ychart allows one organize display cells data two interactive ychart applications contained yoix distribution periodic table elements unicode chart program demonstrate using ychart variable width cells might occur schedule also available yoix distribution yoix distribution also includes yoix package called byzgraf rendering basic data plots line charts histograms statistical box plots currently implemented yoix language interpreted means example probably right choice computationally intensive applications unless one codes computations java module extension similarly excessive looping also display limitations interpreted language focus language interactive standalone client/server gui data visualization applications yoix technology free software licensed open source initiative common public license yoix registered trademark inc.. 1 extract html directives home page write standard output 2 build display gui two buttons titled frame i.e. window also titled border one button pops message pressed quits example window sized automatically fit components additional code calculates location put center screen making visible 3 code shown used generate yoix logo image png format seen language description box near top page command-line arguments allow size image specified well select png image output display on-screen window
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Programming language topics
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nokia n73 nokia n73 smartphone announced nokia 25 april 2006 part nseries started shipping 24 july n73 succeeded n70 packed numerous multimedia features features 3.2 megapixel autofocus camera front camera then-large 2.4 inch display stereo speakers relatively slim pocketable size form runs symbian v9.1 s60 3rd edition became one top selling nseries devices 2006 2007 high popularity helped nokia sales 'multimedia phones grow 28 year-on-year q3 2007 according nokia top selling line n70 n95 common nokia 'nseries 'eseries phones time late 2006 n73 comes loaded many software applications including contacts messaging picture video galleries music player visual fm radio realplayer im client wap browser full web browser based khtml/webkit microsoft office document viewer pdf viewer adobe flash lite viewer games majority applications support background execution example one may listen music browsing internet may switch write text message e-mail without close applications exception newer sony ericsson phones like k550 w610 smartphones typically limited way example music player run background java applications well symbian s60 release 3 applications installed removed phone user using either nokia pc suite software included phone installer application phone n73 uses database system supplied 'gallery applications permanently run background order reduce seek operation times databases updated locally device means supported image video audio files placed almost anywhere file system browsed easily case mp3 audio files id3 tag e.g 'album 'artist etc. notably nokia supports firmware upgrades n73 made user via module nokia pc suite directly over-the-air besides original edition nokia released three variants n73 addition basic n73 nokia subsequently released n73 'music edition 'multimedia button keypad replaced button starts music player phone music edition also includes 2gb memory card phone completely black music player music edition supports album art visualisations regular n73 music player application stays background time even music played later firmware versions application terminated prevents music edition remote control working application started using phone keypad 'n73 internet edition essentially music edition retaining 'multimedia button function rather dedicated 'music button 'n73 internet edition available middle east north africa nokia also released another model n73 called 'n73 special edition middle east north africa phone released muslim holy month ramadan 2007 phone hardware editions n73 comes pre-loaded islamic applications phone completely white nokia also released n73 special edition indonesia without pre-loaded islamic applications three versions n73 appear updated software update 26 june 2007 updates standard n73 music player version music edition enhanced music player detailed keeping 'multimedia button function essentially making internet edition 2008 updates standard features nokia maps application installed default requires external bluetooth gps receiver nokia lifeblog ptt search applications carried previous updates plus addition nokia mobile tv application also installed default requires external nokia mobile tv receiver su-33w application available n77 camera much improved earlier firmware update phone takes 27 seconds boot compared 42 previous versions also n73 20 mb ram available boot little change users may able install n-gage application modified work n73 making better compared multimedia keypad rather single usage button features music player like supports album art visualizations enhanced control interface also available start screen menu key pressed hold phone boots also recent uk nokia poster campaigns black version phone advertised without term 'music edition o2 uk shop sells n73 silver/plum black black version multimedia button rather music button
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Operating systems
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modulation electronics telecommunications modulation process varying one properties periodic waveform called carrier signal modulating signal typically contains information transmitted radio systems 20th century used frequency modulation fm amplitude modulation radio broadcast modulator device performs modulation demodulator sometimes detector demod device performs demodulation inverse modulation modem modulator–demodulator perform operations aim analog modulation transfer analog baseband lowpass signal example audio signal tv signal analog bandpass channel different frequency example limited radio frequency band cable tv network channel aim digital modulation transfer digital bit stream analog communication channel example public switched telephone network bandpass filter limits frequency range 300–3400 hz limited radio frequency band analog digital modulation facilitate frequency division multiplexing fdm several low pass information signals transferred simultaneously shared physical medium using separate passband channels several different carrier frequencies aim digital baseband modulation methods also known line coding transfer digital bit stream baseband channel typically non-filtered copper wire serial bus wired local area network aim pulse modulation methods transfer narrowband analog signal example phone call wideband baseband channel schemes bit stream another digital transmission system music synthesizers modulation may used synthesize waveforms extensive overtone spectrum using small number oscillators case carrier frequency typically order much lower modulating waveform see frequency modulation synthesis ring modulation synthesis analog modulation modulation applied continuously response analog information signal common analog modulation techniques include digital modulation analog carrier signal modulated discrete signal digital modulation methods considered digital-to-analog conversion corresponding demodulation detection analog-to-digital conversion changes carrier signal chosen finite number alternative symbols modulation alphabet simple example telephone line designed transferring audible sounds example tones digital bits zeros ones computers may however communicate telephone line means modems representing digital bits tones called symbols four alternative symbols corresponding musical instrument generate four different tones one time first symbol may represent bit sequence 00 second 01 third 10 fourth 11 modem plays melody consisting 1000 tones per second symbol rate 1000 symbols/second 1000 baud since tone i.e. symbol represents message consisting two digital bits example bit rate twice symbol rate i.e 2000 bits per second similar technique used dial-up modems opposed dsl modems according one definition digital signal modulated signal digital signal according another definition modulation form digital-to-analog conversion textbooks would consider digital modulation schemes form digital transmission synonymous data transmission would consider analog transmission fundamental digital modulation techniques based keying qam in-phase signal one example cosine waveform quadrature phase signal q example sine wave amplitude modulated finite number amplitudes summed seen two-channel system channel using ask resulting signal equivalent combination psk ask methods phases frequencies amplitudes assigned unique pattern binary bits usually phase frequency amplitude encodes equal number bits number bits comprises symbol represented particular phase frequency amplitude alphabet consists formula_1 alternative symbols symbol represents message consisting n bits symbol rate also known baud rate formula_2 symbols/second baud data rate formula_3 bit/second example alphabet consisting 16 alternative symbols symbol represents 4 bits thus data rate four times baud rate case psk ask qam carrier frequency modulated signal constant modulation alphabet often conveniently represented constellation diagram showing amplitude signal x-axis amplitude q signal y-axis symbol psk ask sometimes also fsk often generated detected using principle qam q signals combined complex-valued signal jq j imaginary unit resulting called equivalent lowpass signal equivalent baseband signal complex-valued representation real-valued modulated physical signal so-called passband signal rf signal general steps used modulator transmit data receiver side demodulator typically performs common digital communication systems design modulator demodulator must done simultaneously digital modulation schemes possible transmitter-receiver pair prior knowledge data encoded represented communications system digital communication systems modulator transmitter demodulator receiver structured perform inverse operations non-coherent modulation methods require receiver reference clock signal phase synchronized sender carrier signal case modulation symbols rather bits characters data packets asynchronously transferred opposite coherent modulation common digital modulation techniques msk gmsk particular cases continuous phase modulation indeed msk particular case sub-family cpm known continuous-phase frequency shift keying cpfsk defined rectangular frequency pulse i.e linearly increasing phase pulse one-symbol-time duration total response signaling ofdm based idea frequency-division multiplexing fdm multiplexed streams parts single original stream bit stream split several parallel data streams transferred sub-carrier using conventional digital modulation scheme modulated sub-carriers summed form ofdm signal dividing recombining help handling channel impairments ofdm considered modulation technique rather multiplex technique since transfers one bit stream one communication channel using one sequence so-called ofdm symbols ofdm extended multi-user channel access method orthogonal frequency-division multiple access ofdma multi-carrier code division multiple access mc-cdma schemes allowing several users share physical medium giving different sub-carriers spreading codes different users two kinds rf power amplifier switching amplifiers class amplifiers cost less use less battery power linear amplifiers output power however work relatively constant-amplitude-modulation signals angle modulation fsk psk cdma qam ofdm nevertheless even though switching amplifiers completely unsuitable normal qam constellations often qam modulation principle used drive switching amplifiers fm waveforms sometimes qam demodulators used receive signals put switching amplifiers automatic digital modulation recognition intelligent communication systems one important issues software defined radio cognitive radio according incremental expanse intelligent receivers automatic modulation recognition becomes challenging topic telecommunication systems computer engineering systems many civil military applications moreover blind recognition modulation type important problem commercial systems especially software defined radio usually systems extra information system configuration considering blind approaches intelligent receivers reduce information overload increase transmission performance obviously knowledge transmitted data many unknown parameters receiver signal power carrier frequency phase offsets timing information etc. blind identification modulation made fairly difficult becomes even challenging real-world scenarios multipath fading frequency-selective time-varying channels two main approaches automatic modulation recognition first approach uses likelihood-based methods assign input signal proper class another recent approach based feature extraction term digital baseband modulation digital baseband transmission synonymous line codes methods transfer digital bit stream analog baseband channel a.k.a lowpass channel using pulse train i.e discrete number signal levels directly modulating voltage current cable serial bus common examples unipolar non-return-to-zero nrz manchester alternate mark inversion ami codings pulse modulation schemes aim transferring narrowband analog signal analog baseband channel two-level signal modulating pulse wave pulse modulation schemes also allow narrowband analog signal transferred digital signal i.e. quantized discrete-time signal fixed bit rate transferred underlying digital transmission system example line code modulation schemes conventional sense since channel coding schemes considered source coding schemes cases analog-to-digital conversion techniques analog-over-analog methods analog-over-digital methods
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Internet protocols
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diablo data systems diablo data systems division xerox created acquisition diablo systems inc. us 29 million 1972 company founded 1969 george e. comstock charles l. waggoner others company best known hytype hytype ii diablo 630 daisywheel printers also produced hard disk drives resold dec rk02 rk03 removable disk drives used xerox manufactured xerox alto computer
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Databases
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supplemental access control supplemental access control sac set security features defined icao protecting data contained electronic travel documents e.g electronic passports sac specifies password authenticated connection establishment pace protocol supplements improves icao basic access control bac pace like bac prevents two types attacks implementation pace begins third generation electronic passports eu members must implement pace electronic passports end 2014 states sake global interoperability must implement pace without implementing bac inspection systems implement pace use supported mrtd chip thus important global interoperability achieved make enhancement reliable document verification process achieve interoperability called interoperability tests results last test focusing sac describe current state implementation field version 1.1 april 2014 icao supplemental access control technical report introduces chip authentication protocol alternative active authentication integrates pace achieving new protocol chip authentication mapping pace-cam allows faster execution separate protocols
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Computer security
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transcendent memory transcedent memory linux kernel feature representing class memory unknown dynamically variable size addressable indirectly kernel configured either persistent ephemeral meaning around might disappear without warning still fast enough synchronously accessible
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Operating systems
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apparmor mobile apparmor mobile division cutcom software inc. builds custom mobile safety apps emergency notification systems university college institutions canada united states australia company founded 2002 based toronto ontario canada apparmor partner institutions include university guelph university nevada reno queen university dalhousie university jacksonville university wilfrid laurier university apparmor safety apps include features push notifications location tracking click-to-call capability
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Computer security
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programmable macro language programmable macro language pml domain specific language developed aveva enable customisation plant marine design products pml file-based interpreted language enables application developer design microsoft windows form-based add-ins included within aveva product plant design management system pdms pml originated computer-aided design centre cadcentre established cambridge uk 1967 uk ministry technology cadcentre later became aveva carried great deal early pioneering cad research early staff members went become prominent worldwide cad community brothers dick martin newell cadcentre arguably important single factor transformation cambridge one world high technology centers within years late 1970s early 1980s pml language facilitates customisation plant design management system pdms system may used industries marine offshore onshore oil gas chemical process plants mining currently three iterations pml language following pml code prints classic hello world string pdms command window define function helloworld endfunction code defines new pml function called helloworld takes parameters returns value simply assigns string 'hello world local variable calls p command print text command window within pdms order example work code placed inside file called helloworld.pmlfnc extension mandatory filename function name pml case sensitive file placed inside directory pdms searches pml code initialization process
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Programming language topics
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yuuguu yuuguu desktop sharing web conferencing application software company behind yuuguu ltd. founded anish kapoor philip hemsted yuuguu acquired july 2010 via-vox ltd. holding company powwownow conference call company yuuguu offers cross network instant messaging real time collaboration instant screen sharing web conferencing remote support yuuguu desktop client cross-platform also web-based browser client may 2009 yuuguu added integration skype client
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Web technology
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h.323 h.323 recommendation itu telecommunication standardization sector itu-t defines protocols provide audio-visual communication sessions packet network h.323 standard addresses call signaling control multimedia transport control bandwidth control point-to-point multi-point conferences widely implemented voice videoconferencing equipment manufacturers used within various internet real-time applications gnugk netmeeting widely deployed worldwide service providers enterprises voice video services ip networks part itu-t h.32x series protocols also address multimedia communications isdn pstn ss7 3g mobile networks h.323 call signaling based itu-t recommendation q.931 protocol suited transmitting calls across networks using mixture ip pstn isdn qsig isdn call model similar isdn call model eases introduction ip telephony existing networks isdn-based pbx systems including transitions ip-based pbxs within context h.323 ip-based pbx might gatekeeper call control element provides service telephones videophones device may provide facilitate basic services supplementary services call transfer park pick-up hold first version h.323 published itu november 1996 emphasis enabling videoconferencing capabilities local area network lan quickly adopted industry means transmitting voice communication variety ip networks including wans internet see voip years h.323 revised re-published enhancements necessary better enable voice video functionality packet-switched networks version backward-compatible previous version recognizing h.323 used communication lans wans within large carrier networks title h.323 changed published 1998 title since remained unchanged packet-based multimedia communications systems current version h.323 approved 2009 one strength h.323 relatively early availability set standards defining basic call model also supplementary services needed address business communication expectations h.323 first voip standard adopt internet engineering task force ietf standard real-time transport protocol rtp transport audio video ip networks h.323 system specification describes use several itu-t ietf protocols protocols comprise core almost h.323 system many h.323 systems also implement protocols defined various provide supplementary services support deliver functionality user recommendations addition itu-t recommendations h.323 implements various ietf request comments rfcs media transport media packetization including real-time transport protocol rtp h.323 utilizes itu-defined codecs codecs defined outside itu codecs widely implemented h.323 equipment include h.323 terminals providing video communications shall capable encoding decoding video according h.261 qcif h.323 terminals shall audio codec shall capable encoding decoding speech according itu-t rec g.711 terminals shall capable transmitting receiving a-law μ-law support audio video codecs optional h.323 system defines several network elements work together order deliver rich multimedia communication capabilities elements terminals multipoint control units mcus gateways gatekeepers border elements collectively terminals multipoint control units gateways often referred endpoints h.323 uses tcp port number 1720 elements required least two terminals required order enable communication two people h.323 deployments gatekeeper employed order among things facilitate address resolution terminals h.323 network fundamental elements h.323 system devices users would normally encounter might exist form simple ip phone powerful high-definition videoconferencing system inside h.323 terminal something referred protocol stack implements functionality defined h.323 system protocol stack would include implementation basic protocol defined itu-t recommendation h.225.0 h.245 well rtp protocols described diagram figure 1 depicts complete sophisticated stack provides support voice video various forms data communication reality h.323 systems implement wide array capabilities logical arrangement useful understanding relationships multipoint control unit mcu responsible managing multipoint conferences composed two logical entities referred multipoint controller mc multipoint processor mp practical terms mcu conference bridge unlike conference bridges used pstn today significant difference however h.323 mcus might capable mixing switching video addition normal audio mixing done traditional conference bridge mcus also provide multipoint data collaboration capabilities means end user placing video call h.323 mcu user might able see participants conference hear voices gateways devices enable communication h.323 networks networks pstn isdn networks one party conversation utilizing terminal h.323 terminal call must pass gateway order enable parties communicate gateways widely used today order enable legacy pstn phones interconnect large international h.323 networks presently deployed services providers gateways also used within enterprise order enable enterprise ip phones communicate service provider users pstn gateways also used order enable videoconferencing devices based h.320 h.324 communicate h.323 systems third generation 3g mobile networks deployed today utilize h.324 protocol able communicate h.323-based terminals corporate networks gateway devices gatekeeper optional component h.323 network provides number services terminals gateways mcu devices services include endpoint registration address resolution admission control user authentication forth various functions performed gatekeeper address resolution important enables two endpoints contact without either endpoint know ip address endpoint gatekeepers may designed operate one two signaling modes namely direct routed gatekeeper routed mode direct routed mode efficient widely deployed mode mode endpoints utilize ras protocol order learn ip address remote endpoint call established directly remote device gatekeeper routed mode call signaling always passes gatekeeper latter requires gatekeeper processing power also gives gatekeeper complete control call ability provide supplementary services behalf endpoints h.323 endpoints use ras protocol communicate gatekeeper likewise gatekeepers use ras communicate gatekeepers collection endpoints registered single gatekeeper h.323 referred “ zone ” collection devices necessarily associated physical topology rather zone may entirely logical arbitrarily defined network administrator gatekeepers ability neighbor together call resolution happen zones neighboring facilitates use dial plans global dialing scheme dial plans facilitate “ inter-zone ” dialing two endpoints separate zones still communicate border elements peer elements optional entities similar gatekeeper manage endpoints directly provide services described ras protocol role border peer element understood via definition administrative domain administrative domain collection zones control single person organization service provider within service provider network may hundreds thousands gateway devices telephones video terminals h.323 network elements service provider might arrange devices zones enable service provider best manage devices control logical arrangement city taken together zones within service provider network would appear another service provider administrative domain border element signaling entity generally sits edge administrative domain communicates another administrative domain communication might include things access authorization information call pricing information important data necessary enable communication two administrative domains peer elements entities within administrative domain less help propagate information learned border elements throughout administrative domain architecture intended enable large-scale deployments within carrier networks enable services clearinghouses diagram figure 2 provides illustration administrative domain border elements peer elements gatekeepers h.323 defined binary protocol allows efficient message processing network elements syntax protocol defined asn.1 uses packed encoding rules per form message encoding efficient message encoding wire overview various communication flows h.323 systems address remote endpoint resolved endpoint use h.225.0 call signaling order establish communication remote entity h.225.0 messages simplest form h.323 call may established follows figure 3 example endpoint ep left initiated communication gateway right gateway connected call called party reality call flows often complex one shown calls utilize fast connect procedures defined within h.323 established 2 3 messages endpoints must notify gatekeeper gatekeepers used call call concluded device send release complete message endpoints required notify gatekeeper gatekeepers used call ended endpoints use ras protocol order communicate gatekeeper likewise gatekeepers use ras communicate peer gatekeepers ras fairly simple protocol composed messages namely endpoint powered generally send gatekeeper request grq message discover gatekeepers willing provide service gatekeepers respond gatekeeper confirm gcf endpoint select gatekeeper work alternatively possible gatekeeper predefined system ’ administrative setup need endpoint discover one endpoint determines gatekeeper work try register gatekeeper sending registration request rrq gatekeeper responds registration confirm rcf point endpoint known network make place calls endpoint wishes place call send admission request arq gatekeeper gatekeeper resolve address either locally consulting another gatekeeper querying network service return address remote endpoint admission confirm message acf endpoint place call upon receiving call remote endpoint also send arq receive acf order get permission accept incoming call necessary example authenticate calling device ensure available bandwidth call figure 4 depicts high-level communication exchange two endpoints ep two gatekeepers gk call initiated necessarily fully connected endpoints may initiate h.245 call control signaling order provide extensive control conference h.245 rather voluminous specification many procedures fully enable multipoint communication though practice implementations implement minimum necessary order enable point-to-point voice video communication h.245 provides capabilities capability negotiation master/slave determination opening closing logical channels i.e. audio video flows flow control conference control support unicast multicast communication allowing size conference theoretically grow without bound functionality provided h.245 capability negotiation arguably important enables devices communicate without prior knowledge capabilities remote entity h.245 enables rich multimedia capabilities including audio video text data communication transmission audio video text h.323 devices utilize itu-defined codecs codecs defined outside itu codecs widely implemented h.323 equipment include h.245 also enables real-time data conferencing capability protocols like t.120 t.120-based applications generally operate parallel h.323 system integrated provide user seamless multimedia experience t.120 provides capabilities application sharing t.128 electronic whiteboard t.126 file transfer t.127 text chat t.134 within context conference h.323 device initiates communication remote h.323 device h.245 communication established two entities terminal capability set tcs message first message transmitted side sending tcs message h.323 entities h.245 exchanges attempt determine device master slave process referred master/slave determination msd important master call settles disputes two devices example endpoints attempt open incompatible media flows master takes action reject incompatible flow capabilities exchanged master/slave determination steps completed devices may open logical channels media flows done simply sending open logical channel olc message receiving acknowledgement message upon receipt acknowledgement message endpoint may transmit audio video remote endpoint typical h.245 exchange looks similar figure 5 exchange messages two endpoints ep figure would transmitting audio direction number message exchanges numerous important purpose nonetheless takes time reason h.323 version 2 published 1998 introduced concept called fast connect enables device establish bi-directional media flows part h.225.0 call establishment procedures fast connect possible establish call bi-directional media flowing two messages like figure 3 fast connect widely supported industry even devices still implement complete h.245 exchange shown perform message exchange parallel activities noticeable delay calling called party voice internet protocol voip describes transmission voice using internet packet switched networks itu-t recommendation h.323 one standards used voip voip requires connection internet another packet switched network subscription voip service provider client analogue telephone adapter ata voip phone soft phone service provider offers connection voip services pstn service providers charge monthly fee additional costs calls made using voip two enterprise locations would necessarily require voip service provider example h.323 widely deployed companies wish interconnect remote locations ip using number various wired wireless technologies videoconference videoteleconference vtc set telecommunication technologies allowing two locations interact via two-way video audio transmissions simultaneously basically two types videoconferencing dedicated vtc systems required components packaged single piece equipment desktop vtc systems add-ons normal pc transforming vtc devices simultaneous videoconferencing among three remote points possible means multipoint control unit mcu mcu bridges ip isdn-based videoconferencing due price point proliferation internet broadband particular strong spurt growth use h.323-based ip videoconferencing h.323 accessible anyone high speed internet connection dsl videoconferencing utilized various situations example distance education telemedicine video relay service business h.323 used industry enable large-scale international video conferences significantly larger typical video conference one widely attended annual event called megaconference
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Internet protocols
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web services modeling language wsml web service modeling language formal language provides syntax semantics web service modeling ontology wsmo words wsml provides means formally describe wsmo elements ontologies semantic web services goals mediators wsml based logical formalisms description logic first-order logic logic programming
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Web technology
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data synchronization data synchronization process establishing consistency among data source target data storage vice versa continuous harmonization data time fundamental wide variety applications including file synchronization mobile device synchronization e.g. pdas synchronization also useful encryption synchronizing public key servers tools available file synchronization version control cvs subversion etc distributed filesystems coda etc mirroring rsync etc attempt keep sets files synchronized however version control file synchronization tools deal modifications one copy files several theoretical models data synchronization exist research literature problem also related problem slepian–wolf coding information theory models classified based consider data synchronized problem synchronizing unordered data also known set reconciliation problem modeled attempt compute symmetric difference formula_1 two remote sets formula_2 formula_3 b-bit numbers solutions problem typified case two remote strings formula_4 formula_5 need reconciled typically assumed strings differ fixed number edits i.e character insertions deletions modifications data synchronization process reducing edit distance formula_4 formula_5 ideal distance zero applied filesystem based synchronizations data ordered many practical applications discussed referenced sometimes possible transform problem one unordered data process known shingling splitting strings shingles fault-tolerant systems distributed databases must able cope loss corruption part data first step usually replication involves making multiple copies data keeping date changes made however necessary decide copy rely loss corruption instance occurs simplest approach single master instance sole source truth changes replicated instances one instances becomes new master old master fails paxos raft complex protocols exist solve problems transient effects failover two instances thinking master time secret sharing useful failures whole nodes common moves synchronization explicit recovery process part read read data requires retrieving encoded data several different nodes corrupt out-of-date data may present nodes approach may also benefit use error correction code dhts blockchains try solve problem synchronization many nodes hundreds billions
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Computer architecture
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gestigon gestigon stylized gestigon software development company founded september 2011 sascha klement erhardt barth thomas martinetz company develops software solutions gesture control body tracking based 3d depth data gestigon developing augmented reality automotive solutions audi renault volkswagen company also working ar/vr headsets well consumer electronics smart home devices march 2017 gestigon acquired valeo french automotive supplier sascha klement worked student assistant ph.d. student professors thomas martinetz erhardt barth developing software solutions based time-of-flight sensors university lübeck since 2002 together founded gestigon 2011 seed-funding high-tech gründerfonds mittelständische beteiligungsgesellschaft schleswig-holstein local business angels march 2012 moritz von grotthuss joined company advisor later became ceo considered late-founder month gestigon received innovation award cebit 2012 one 15 startups receive award 276 candidates january 2013 gestigon participated ces las vegas later year also techcrunch disrupt new york city next year visteon volkswagen used gestigon gestures solutions products presented ces 2014 cebit 2014 “ cebit innovation award ” public displays gestigon technologies include audi ces 2015 ces 2016 volkswagen infineon gestigon launched virtual reality solution carnival techcrunch disrupt san francisco september 2015 using oculus rift different depth sensors first demo using mobile device done ces 2015 gestigon partnered several companies develop hardware solutions especially depth sensors provide sensing solutions 2015 gestigon partnered inuitive 3d computer vision image processors developer create vr unit system presented ces 2016 assembled oculus rift development kit july 2015 gestigon closed series financing round nbr technology ventures gmbh primary investor headed fabian von kuenheim financing round company received additional investments high-tech gründerfonds vorwerk direct selling ventures march 2017 gestigon developed software recognizes driving gestures gestigon develops software works 3d sensors recognize human gestures poses biometrical features real time gecko feature tracker developed company tracks individual measuring biometric features flamenco software finger hand gesture control gestigon developed carnival sdk software augmented reality virtual reality allows users see use hands virtual interfaces gestigon solutions based skeleton recognition software recognizes body parts 3d data making recognition faster accurate software sensor agnostic work based data depth module using time-of-flight- stereo- structured light technologies
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Distributed computing architecture
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mac address media access control address mac address device unique identifier assigned network interface controller nic communications within network segment used network address ieee 802 network technologies including ethernet wi-fi bluetooth within open systems interconnection osi model mac addresses used medium access control protocol sublayer data link layer typically represented mac addresses recognizable six groups two hexadecimal digits separated hyphens colons separator see notational conventions mac address may referred burned-in address also known ethernet hardware address hardware address physical address confused memory physical address network node multiple nics must unique mac address sophisticated network equipment multilayer switch router may require one permanently assigned mac addresses mac addresses often assigned manufacturer network interface cards stored hardware card read-only memory firmware mechanism mac address typically includes manufacturer organizationally unique identifier oui mac addresses formed according principles two numbering spaces based extended unique identifiers eui managed institute electrical electronics engineers ieee eui-48 replaces obsolete term mac-48 eui-64 original ieee 802 mac address comes original xerox network systems ethernet addressing scheme 48-bit address space contains potentially 2 281,474,976,710,656 possible mac addresses ieee manages allocation mac addresses originally known mac-48 refers eui-48 identifiers ieee target lifetime 100 years 2080 applications using eui-48 space restricts applications accordingly ieee encourages adoption plentiful eui-64 non-ethernet applications distinction eui-48 mac-48 identifiers name application mac-48 used address hardware interfaces within existing 802-based networking applications eui-48 used 802-based networking also used identify devices software example bluetooth ieee considers mac-48 obsolete term eui-48 used cases addition eui-64 numbering system originally encompassed mac-48 eui-48 identifiers simple translation mechanism translations since deprecated individual address block iab inactive registry activity replaced ma-s ma-s previously named oui-36 registry product january 1 2014 iab uses oui ma-l ma-l registry previously named oui registry term oui still use calling registry belonging ieee registration authority concatenated 12 additional ieee-provided bits total 36 bits leaving 12 bits iab owner assign 4096 individual devices iab ideal organizations requiring 4096 unique 48-bit numbers eui-48 unlike oui allows assignee assign values various different number spaces example eui-48 eui-64 various context-dependent identifier number spaces individual address block could used assign eui-48 identifiers potential uses based oui iabs allocated reserved remain property ieee registration authority also noted 2007 september 2012 oui value 00:50 c2 used iab assignments september 2012 value 40 d8:55 used owners already assigned iab may continue use assignment another registry called ma-m mac addresses medium ma-m assignment block provides 2 eui-48 identifiers 2 eui-64 identifiers means first 28 bits ieee assigned bits first 24-bits assigned ma-m block oui assigned ieee reassigned addresses either universally administered addresses uaa locally administered addresses laa universally administered address uniquely assigned device manufacturer first three octets transmission order identify organization issued identifier known organizationally unique identifier oui remainder address three octets eui-48 five eui-64 assigned organization nearly manner please subject constraint uniqueness locally administered address assigned device network administrator overriding burned-in address universally administered locally administered addresses distinguished setting second-least-significant bit first octet address bit also referred u/l bit short universal/local identifies address administered bit 0 address universally administered 1 address locally administered example address first octet 06 hex binary form 00000110 second-least-significant bit 1 therefore locally administered address another example uses locally administered addresses decnet protocol mac address ethernet interface changed decnet software reflects decnet network address xx.yy host eliminates need address resolution protocol since mac address decnet host simply determined least significant bit address first octet 0 zero frame meant reach one receiving nic type transmission called unicast unicast frame transmitted nodes within collision domain modern wired setting collision domain usually length ethernet cable two network cards wireless setting collision domain receivers detect given wireless signal switch know port leads given mac address switch forward unicast frame ports except originating port action known unicast flood node matching hardware mac address accept frame network frames non-matching mac-addresses ignored unless device promiscuous mode least significant bit first octet set 1 frame still sent however nics choose accept based criteria matching mac address example based configurable list accepted multicast mac addresses called multicast addressing ieee built several special address types allow one network interface card addressed one time examples group addresses opposed individual addresses least significant bit first octet mac address distinguishes individual addresses group addresses bit set 0 individual addresses set 1 group addresses group addresses like individual addresses universally administered locally administered following network technologies use eui-48 identifier format every device connects ieee 802 network ethernet wifi eui-48 address common networked consumer devices pcs smartphones tablet computers use eui-48 addresses eui-64 identifiers used broadcast networks ethernet mac address expected uniquely identify node segment allows frames marked specific hosts thus forms basis link layer osi layer 2 networking upon upper layer protocols rely produce complex functioning networks many network interfaces support changing mac address unix-like systems command utility ifconfig may used remove add link address aliases instance active ifconfig directive may used netbsd specify attached addresses activate hence various configuration scripts utilities permit randomization mac address time booting establishing network connection changing mac addresses necessary network virtualization mac spoofing practiced exploiting security vulnerabilities computer system modern operating systems apple ios android especially mobile devices designed randomize assignment mac address network interface scanning wireless access points avert tracking systems internet protocol ip networks mac address interface corresponding ip address may queried address resolution protocol arp ipv4 neighbor discovery protocol ndp ipv6 relating osi layer 3 addresses layer 2 addresses according edward snowden us national security agency system tracks movements mobile devices city monitoring mac addresses avert practice apple started using random mac addresses ios devices scanning networks vendors followed quickly mac address randomization scanning added android starting version 6.0 windows 10 linux kernel 3.18 actual implementations mac address randomization technique vary largely different devices moreover various flaws shortcomings implementations may allow attacker track device even mac address changed instance probe requests elements timing random mac addresses used researchers confirmed possible link real identity particular wireless mac address using wireless access points ssid-hidden mode network cloaking mobile wireless device may disclose mac address traveling even mac addresses associated ssids device already connected configured send part probe request packets alternative modes prevent include configuring access points either beacon-broadcasting mode probe-response ssid mode modes probe requests may unnecessary sent broadcast mode without disclosing identity previously-known networks standard ieee 802 format printing eui-48 addresses human-friendly form six groups two hexadecimal digits separated hyphens transmission order e.g form also commonly used eui-64 e.g conventions include six groups two hexadecimal digits separated colons e.g three groups four hexadecimal digits separated dots e.g transmission order standard notation also called canonical format mac addresses written transmission order least significant bit byte transmitted first used output codice_1 codice_2 codice_3 commands example however since ieee 802.3 ethernet ieee 802.4 token bus send bytes octets wire left-to-right least significant bit byte first ieee 802.5 token ring ieee 802.6 fddi send bytes wire significant bit first confusion may arise address latter scenario represented bits reversed canonical representation example address canonical form would transmitted wire bits codice_4 standard transmission order least significant bit first token ring networks would transmitted bits codice_5 most-significant-bit first order latter might incorrectly displayed referred bit-reversed order non-canonical form msb format ibm format token ring format explained
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Internet protocols
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comparison object-relational database management systems comparison object-relational database management systems ordbmss system least features object-relational database vary widely completeness approaches taken following tables compare general technical information please see individual products articles information unless otherwise specified footnotes comparisons based stable versions without add-ons extensions external programs information fundamental ordbmses features implemented natively information data types implemented natively
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Databases
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hijackthis hijackthis also hijackthis hjt free open-source tool detect malware adware microsoft windows originally created merijn bellekom later sold trend micro program notable quickly scanning user computer display common locations malware rather relying database known spyware hijackthis used primarily diagnosis malware remove detect spyware—as uninformed use removal facilities cause significant software damage computer browser hijacking cause malware installed computer february 16 2012 trend micro released hijackthis source code open source available sourceforge site hijackthis generate plain-text logfile detailing entries finds entries fixed hijackthis inexperienced users advised exercise caution seek help using latter option except small whitelist known safe entries hijackthis discriminate legitimate unwanted items hijackthis attempts create backups files registry entries fixes used restore system event mistake common use post logfile forum experienced users help decipher entries need removed automated tools also exist analyze saved logs attempt provide recommendations user clean entries automatically use tools however generally discouraged specialize manually dealing hijackthis logs consider tools dangerous inexperienced users neither accurate reliable enough substitute consulting trained human analyst later versions hijackthis include additional tools task manager hosts-file editor alternate-data-stream scanner 2002 2003 entrepreneur glenn bluff owner computer hope uk made several attempts buy hijackthis led joint development hijackpro professional version hijackthis built-in capabilities kill processes similar killbox hijackpro 2.3 million downloads illegal download site 2003 2004 found sites claiming hijackthis free hijackpro sold touchstone software phoenix technologies 2007 integrated driveragent.com along glenn bluff company drivermagic.com
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Computer security
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eighteenth century collections online eighteenth century collections online ecco digital collection books published great britain 18th century gale education publishing company united states assembled collection digitally scanning microfilm reproductions 136,291 titles documents scanned 2002 added second collection ecco ii january 2014 ecco ii comprises 46,607 titles far 2,231 texts released free public work university michigan ’ text creation partnership rather ocr rekey texts tag tei aim enable improved access fraction collection making sgml/xml text editions 10,000 books addition free version subscription access also offered text analytic tools available subset text analysis portal research project one text creation partners university oxford converted public domain texts free publicly accessible versions accordance text encoding initiative p5 guidelines makes available variety file formats including html epub via oxford text archive cross-search also available proquest subscribe early english books online ecco
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Databases
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fruux fruux cross-platform synchronization service operated fruux company behind popular open source project sabredav service enables users synchronize address book contacts calendar events tasks bookmarks notes apple computers devices web app also allows manage contacts calendars tasks browser fruux synchronization uses encrypted ssl transfers fruux supports conflict resolution helps users data changed one computer choose correct dataset fruux runs entirely amazon web services infrastructure company uses amazon elastic load balancing amazon elastic compute cloud amazon ec2 amazon elastic block store amazon ebs run nginx web servers amazon simple storage service amazon s3 fruux ’ choice versioned application code backup storage addition fruux uses amazon relational database service amazon rds manage central databases amazon simple email service ses highly scalable bulk transactional email-sending service service similar services icloud plaxo fruux supports synchronization mainly contacts calendar events items wide array devices services company recently announced launch calendar syncing ios caldav capable devices also offering contact synchronization ios carddav capable devices company released device management layer may 2012 working special offering teams another distinguishing feature recently released calendar sharing feature allows users invite people calendars possibility set individual permissions gives first glimpse future team offering fruux secured six-figure seed round march 2012 led high-tech gründerfonds
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Distributed computing architecture
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john herivel john william jamieson herivel 29 august 1918 – 18 january 2011 british science historian former world war ii codebreaker bletchley park codebreaker concerned cryptanalysis enigma herivel remembered chiefly discovery soon dubbed herivel tip herivelismus herivelismus consisted idea herivel tip method establishing whether applied using herivel square based herivel insight habits german operators enigma cipher machine allowed bletchley park easily deduce part daily key brief critical period may 1940 herivel tip conjunction cillies another class operator error main technique used solve enigma war herivel became academic studying history philosophy science queen university belfast particularly isaac newton joseph fourier christiaan huygens retirement wrote autobiographical account work bletchley park entitled herivelismus german military enigma john herivel born belfast attended methodist college belfast 1924 1936 1937 awarded kitchener scholarship study mathematics sidney sussex college cambridge supervisor gordon welchman welchman recruited herivel government code cypher school gc cs bletchley park welchman worked alan turing newly formed hut 6 section created solve army air force enigma herivel aged 21 arrived bletchley 29 january 1940 briefed enigma alan turing tony kendrick time herivel started work bletchley park hut 6 limited success enigma-enciphered messages mostly luftwaffe enigma network known red working alongside david rees another cambridge mathematician recruited welchman nearby elmers school testing candidate solutions working plugboard settings process slow however herivel determined find method improve attack would spend evenings trying think ways intercepted morse coded messages enciphered germans ’ enigma electro-mechanical rotor cipher machine implemented polyalphabetic cipher main model use 1940 three rotors set electrical pathway keyboard lampboard pressing key caused one lamp light right-most rotor advance one letter position changed electrical pathway pressing key caused different letter light one 26 positions notch right-most rotor engaged middle rotor two rotors advanced together similarly middle rotor would engage left-most rotor giving long period sequence repeated 26 × 26 × 26 17,576 ring rotor contained notch caused next rotor advance could set one 26 positions three rotors selected set five giving 60 different ways mounting rotors machine however germans laid rule rotor position successive days previous days rotors positions known number reduced 32 enigma machine worked reciprocally identical machine identical settings would fed enciphered letters show deciphered letters lampboard hut 6 enigma replica machines logically identical machines germans using decipher intercepted messages required selection rotors ring settings plugboard connections known time first three letters prelude message used indicator tell receiving operator letters appear windows particular message herivel insight february 1940 lazy german code clerks might give away enigma ring settings ringstellung first message day several lazy clerks first message grundstellung would random would clustering around ringstellung insight became known herivel tip needed time luftwaffe doubly-enciphering message keys techniques zygalski sheets could used may 1940 germans stopped doubly-enciphered keys methods becoming ineffective bletchley park started using herivel tip break luftwaffe traffic continued main method bombe delivered august 1940 rotors positioning ring containing notch changed daily settings defined codebook common operators network start day messages sent received enigma operators implemented day rotor selection ring settings selected three rotors adjusted ring settings could done rotors mounted axle inserted machine possible adjust ring settings loaded rotors moving spring-loaded retaining pin right turning rotor display specified letter herivel thought likely least operators would adjust rings mounted rotors machine set alphabet rings closed lid operator moved rotors well away positions displayed three letters ring setting windows operators herivel great insight came one evening february 1940 relaxing front landlady fire stressed lazy operators set rings rotors machine might left ring setting near top used three letters first message day transmitted message sending operator would follow standard procedure september 1938 would use initial position encrypt indicator send clear followed message key enciphered setting ground setting gkx example would use enigma rotors set gkx encrypt message setting might choose rtq might encrypt llp may 1940 encrypted message setting repeated makes difference herivel insight operator would turn rotors rtq encrypt actual message thus preamble message would unencrypted ground setting gkx followed encrypted message setting llp receiving enigma operator could use information recover message setting decrypt message ground setting gkx example chosen random herivel reasoned operators lazy hurry otherwise pressure might simply use whatever rotor setting currently showing machine first message day operator set ring settings rotors already inside machine rotor position currently showing machine could well ring setting close situation occurred example gkx would ring setting close polish cryptographers used idea pc bruno phoney war day insight herivel colleagues agreed idea possible way enigma hut 6 began looking effect predicted herivel tip arranged first messages day transmitting station sent early plotted indicators grid termed herivel square example shown rows columns grid labelled alphabet first indicator first message day received station network entered grid done finding column corresponding first letter row corresponding second letter entering third letter cell row column intersected example gkx would recorded entering x cell column g row k. herivel tip suggested would cluster entries close together cluster around gkx example would narrow options ring settings 17,576 small set possibilities perhaps 6 30 could tested individually effect predicted herivel immediately show enigma traffic however bletchley park continue rely different technique get enigma method perforated sheets passed polish cryptologists situation changed 1 may 1940 germans changed indicating procedure rendering perforated sheet method obsolete hut 6 suddenly unable decrypt enigma fortunately codebreakers pattern predicted herivel tip began manifest soon 10 may germans invaded netherlands belgium david rees spotted cluster indicators 22 may air force message sent 20 may decoded first since change procedure although herivel tip provided enigma ring settings provide parts enigma key rotor order plugboard settings luftwaffe key time chose 5 rotors 60 possible rotor orders addition might 8 10 plugboard connections means 6 26 letters permuted plugboard codebreakers use methods find remaining portions enigma key herivel tip used combination another class operator mistake known cillies solve settings decipher messages herivel tip used several months specialised codebreaking machines designed alan turing so-called bombes ready use gordon welchman wrote herivel tip vital part breaking enigma bletchley park importance contribution herivel singled introduced winston churchill visit bletchley park also taught enigma cryptanalysis party americans assigned hut 6 intensive two-week course herivel later worked administration newmanry section responsible solving german teleprinter ciphers using machine methods colossus computers assistant head section mathematician max newman 2005 researchers studying set enigma-encrypted messages world war ii noted occurrence clustering predicted herivel tip messages august 1941 end war herivel taught mathematics school year found could handle rumbustious boys joined queen university belfast became reader history philosophy science one students supervised actor simon callow said published books articles isaac newton joseph fourier christiaan huygens publications include 1978 retired oxford became fellow souls college retirement published died oxford 2011 survived daughter josephine herivel
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Computer security
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timenavigator atempo time navigator also known tina backup recovery solution atempo major unix linux windows mac os platforms supported
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Computer security
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carbanak carbanak apt-style campaign targeting limited financial institutions claimed discovered 2014 russian/uk cyber crime company kaspersky lab said used steal money banks microsoft windows malware said introduced targets via phishing emails hacker group said stolen 900 million dollars 140 billion dollars reports banks thousand private customers criminals able manipulate access respective banking networks order steal money variety ways instances atms instructed dispense cash without locally interact terminal money mules would collect money transfer swift network criminals ’ accounts kaspersky said carbanak group went far alter databases pump balances existing accounts pocketing difference unbeknownst user whose original balance still intact intended targets primarily russia followed united states germany china ukraine according kaspersky lab one bank lost 7.3 million atms programmed spew cash certain times henchmen would collect separate firm 10 million taken via online platform kaspersky lab helping assist investigations countermeasures disrupt malware operations cybercriminal activity investigations provide technical expertise analyzing infection vectors malicious programs supported command control infrastructure exploitation methods fireeye published research tracking activities referring group fin7 including sec-themed spear phishing campaign proofpoint also published research linking group bateleur backdoor expanded list targets u.s.-based chain restaurants hospitality organizations retailers merchant services suppliers others beyond initial financial services focus march 26th 2018 europol claimed arrested mastermind carbanak associated cobalt cobalt strike group alicante spain investigation led spanish national police cooperation law enforcement multiple countries well private cybersecurity companies group campaigns appear continued however hudson bay company breach using point sale malware recently attributed group controversy exists around carbanak attacks seemingly described several months earlier report internet security companies group-ib russia fox-it netherlands dubbed attack anunak anunak report shows also greatly reduced amount financial losses according statement issued fox-it release new york times article compromise banks outside russia match research also interview conducted russian newspaper kommersant controversy claims kaspersky lab group-ib come light group-ib claims banks outside russia ukraine hit activity outside region focused point sale systems reuters issued statement referencing private industry notification issued fbi usss united states secret service claiming received reports carbanak affected financial sector two representative groups us banking industry fs-isac aba american bankers association interview bank technology news say us banks affected
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Computer security
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globalenglish globalenglish corporation american technology company founded 1997 reece duca stephen patrick martin rice used owned pearson plc bought back management globalenglish provides on-demand enterprise solutions support global business performance effective business english communication company headquartered silicon valley california company announced pending acquisition pearson plc lse pson may 2012 all-cash transaction officially acquired pearson july 5 2012.. november 10 2016 company acquired pearson management
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Distributed computing architecture
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icy application icy discontinued package manager jailbroken iphone ipod touch originally created maintained ripdev allows users browse download mobile apps range sources apps available download free requiring purchase downloading including software created ripdev kate apps downloaded directly iphone ipod touch generally located codice_1 directory place apple native apps located icy project closed october 24 2009 source code released mit license icy installer taken two development teams weamdev infini-dev icy intended alternative cydia source unofficial apps since development installer.app created nullriver discontinued purpose developing icy create package manager used apt method used cydia therefore making icy compatible cydia sources faster lightweight cydia icy project closed october 24 2009 source code released mit license icy project picked weamdev latest version beta 2.3 support ios 7 group called infini dev also taken project reviving icy created version ripdev source code called icy version 1.5.1 icy 1.4.7 added support ipad development member sammy guichelaar icy development halted early 2014 support ios 9 infini-dev dropped icy support order support installer x package manager legacy devices
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Computer security
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machine code machine code computer program written machine language instructions executed directly computer central processing unit cpu instruction causes cpu perform specific task load store jump alu operation one units data cpu registers memory machine code strictly numerical language intended run fast possible may regarded lowest-level representation compiled assembled computer program primitive hardware-dependent programming language possible write programs directly machine code tedious error prone manage individual bits calculate numerical addresses constants manually reason programs rarely written directly machine code modern contexts may done low level debugging program patching especially assembler source available assembly language disassembly overwhelming majority practical programs today written higher-level languages assembly language source code translated executable machine code utilities compilers assemblers linkers important exception interpreted programs translated machine code however interpreter may seen executor processor performing instructions source code typically consists directly executable machine code generated assembly high-level language source code machine code definition lowest level programming detail visible programmer internally many processors use microcode optimise transform machine code instructions sequences micro-ops generally considered machine code per se every processor processor family instruction set instructions patterns bits physical design correspond different commands machine thus instruction set specific class processors using mostly architecture successor derivative processor designs often include instructions predecessor may add additional instructions occasionally successor design discontinue alter meaning instruction code typically needed new purposes affecting code compatibility extent even nearly completely compatible processors may show slightly different behavior instructions rarely problem systems may also differ details memory arrangement operating systems peripheral devices program normally relies factors different systems typically run machine code even type processor used processor instruction set may instructions length may variable-length instructions patterns organized varies strongly particular architecture often also type instruction instructions one opcode fields specifies basic instruction type arithmetic logical jump etc actual operation add compare fields may give type operand addressing mode addressing offset index actual value constant operands contained instruction called immediates machines individual instructions explicit operands accumulator machine combined left operand result implicit accumulator arithmetic instructions architectures 8086 x86-family accumulator versions common instructions accumulator regarded one general registers longer instructions stack machine operands implicit stack special purpose instructions also often lack explicit operands cpuid x86 architecture writes values four implicit destination registers instance distinction explicit implicit operands important code generators especially register allocation live range tracking parts good code optimizer track implicit well explicit operands may allow frequent constant propagation constant folding registers register assigned result constant expression freed replacing constant code enhancements computer program list instructions executed central processing unit program execution done order cpu executing solve specific problem thus accomplish specific result simple processors able execute instructions one another superscalar processors capable executing variety different instructions program flow may influenced special 'jump instructions transfer execution instruction numerically following one conditional jumps taken execution continues another address execution continues next instruction depending condition much readable rendition machine language called assembly language uses mnemonic codes refer machine code instructions rather using instructions numeric values directly example zilog z80 processor machine code codice_1 causes cpu decrement codice_2 processor register would represented assembly language codice_3 mips architecture provides specific example machine code whose instructions always 32 bits long general type instruction given op operation field highest 6 bits j-type jump i-type immediate instructions fully specified op r-type register instructions include additional field funct determine exact operation fields used types rs rt rd indicate register operands shamt gives shift amount address immediate fields contain operand directly example adding registers 1 2 placing result register 6 encoded load value register 8 taken memory cell 68 cells location listed register 3 jumping address 1024 computer architectures machine code implemented even fundamental underlying layer called microcode providing common machine language interface across line family different models computer widely different underlying dataflows done facilitate porting machine language programs different models example use ibm system/360 family computers successors dataflow path widths 8 bits 64 bits beyond nevertheless present common architecture machine language level across entire line using microcode implement emulator enables computer present architecture entirely different computer system/360 line used allow porting programs earlier ibm machines new family computers e.g ibm 1401/1440/1460 emulator ibm s/360 model 40 machine code generally different bytecode also known p-code either executed interpreter compiled machine code faster direct execution exception processor designed use particular bytecode directly machine code case java processors machine code assembly code sometimes called native code referring platform-dependent parts language features libraries harvard architecture computer architecture physically separate storage signal pathways code instructions data today processors implement separate signal pathways performance reasons implement modified harvard architecture support tasks like loading executable program disk storage data executing harvard architecture contrasted von neumann architecture data code stored memory read processor allowing computer execute commands point view process code space part address space code execution stored multitasking systems comprises program code segment usually shared libraries multi-threading environment different threads one process share code space along data space reduces overhead context switching considerably compared process switching pamela samuelson wrote machine code unreadable united states copyright office identify whether particular encoded program original work authorship however us copyright office allow copyright registration computer programs program machine code sometimes decompiled order make functioning easily understandable humans cognitive science professor douglas hofstadter compared machine code genetic code saying looking program written machine language vaguely comparable looking dna molecule atom atom
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Computer architecture
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uniform type identifier uniform type identifier uti text string used software provided apple inc. uniquely identify given class type item apple provides built-in utis identify common system objects – document image file types folders application bundles streaming data clipping data movie data – allows third party developers add utis application-specific proprietary uses support utis added mac os x 10.4 operating system integrated spotlight desktop search technology uses utis categorize documents one primary design goals utis eliminate ambiguities problems associated inferring file content mime type filename extension type creator code utis use reverse-dns naming structure names may include ascii characters a-z a-z 0-9 hyphen period unicode characters u+007f colons slashes prohibited compatibility macintosh posix file path conventions utis support multiple inheritance allowing files identified number relevant types appropriate contained data one difficulties maintaining user-accessible operating system establishing connections data types applications processes effectively use data example file contains picture data particular compression format opened processed applications capable handling picture data applications must able identify compression type used order extract work data early computer systems – particularly dos variants versions windows – file associations maintained file extensions three four character code following file name instructs system open file particular applications beginning system 1 macintosh operating systems attached type codes creator codes part file metadata four-character codes designed specify application created file creator code specific type file type code applications could easily open process file data however type creator codes extended flexibility system — particular type file restricted opening particular application — suffered many problems file extensions type creator codes could lost files transferred across non-macintosh systems unix-based servers plethora type codes made identification problematic addition classic mac os recognize file extensions leading unrecognized file errors files transferred dos/windows systems openstep formed basis mac os x used extensions early versions mac os x followed suit led controversy users developers coming os x next windows origins advocating continued use file extensions coming classic mac os urging apple replace supplement file extensions type creators file identification types exist example mime types used identifying data transferred web however apple uti system designed create flexible file association system would describe data hierarchically allow better categorization searching standardize data descriptions across contexts provide uniform method expanding data types instance public.jpeg public.png utis inherit public.image uti allowing users search narrowly jpeg images png images broadly kind image merely changing specificity uti used search application developers design new data types easily extend utis available example new image format developed company may uti com.company.proprietary-image specified inherit public.image type apple macos continues support forms file association contains utilities translating use utis preference available apple maintains public domain set base data types utis utis associated base utis conformance system similar class inheritance utis conform utis share basic types general application works data general uti able work data uti conforms general uti basic public utis apple hierarchy follows utis even used identify file type identifiers dynamic utis created needed applications prefix dyn take form uti-compatible wrapper around otherwise unknown filename extension mime type ostype apple provides large collection system-declared uniform type identifiers third-party applications add utis database maintained macos exporting utis declared within application package new utis declared conform existing system utis declarations associate new utis file extensions exported declaration alone provide operating system enough information enable new functions enabling quick look new file types get uti given file use mdls meta data list part spotlight command terminal
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Operating systems
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archivemount archivemount fuse-based file system unix variants including linux purpose mount archives e.g tar tar.gz etc mount point read written file system makes accessing contents archive may compressed transparent programs without decompressing
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Computer file systems
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black bag operation black bag operations black bag jobs covert clandestine entries structures obtain information human intelligence operations usually entails breaking entering denied areas tactics techniques procedures associated black bag operations lock picking safe cracking key impressions fingerprinting photography electronic surveillance including audio video surveillance mail manipulation flaps seals forgery host related skills term black bag refers small bag burglars carry tools black bag operations federal bureau investigation fbi agents entered offices targeted individuals organizations photographed information found records practice used fbi 1942 1967 july 1966 fbi director j. edgar hoover ordered practice discontinued use black bag jobs fbi declared unconstitutional united states supreme court 19 june 1972 plamondon case united states v. u.s. district court 407 u.s. 297 fbi still carries numerous black bag entry-and-search missions search covert target investigation informed search took place investigation involves criminal matter judicial warrant required national security cases operation must approved foreign intelligence surveillance court example 1947 american spy elizabeth bentley defected soviet underground started talking fbi fbi broke brooklyn hotel black-bag job verify background – look anything otherwise found nothing ordinary bentley learned dodge intrusions earliest days underground learned determine enemy agents discovered secret documents possession leave apartment careful put black trunk tie thin black thread around would know tampered absence cia used black-bag operations steal cryptography secrets foreign government offices outside united states practice preceding u.s. intelligence organisations dates back least far 1916
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Computer security
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geom raid5 geom_raid5 storage module created freebsd operating system facilitates raid5 functionality without need hardware raid controller geom_raid5 allows storage large amounts data protected disk failure providing good throughput performance like freebsd storage modules geom_raid5 utilizes geom framework built kernel loadable module kld allows run inside freebsd kernel module compiled freebsd release 5 newer releases geom_raid5 also incorporated freenas operating system dedicated network attached storage author arne woerner released software bsd license making geom_raid5 osi-compliant open source software geom_raid5 distinguishes providing advanced features high performance theoretical maximum write speed speed slowest disk · number disks 1 latest version able achieve 80 theoretical maximum huge contrast software raid5 solutions sometimes achieve less 10 throughput combined significantly higher cpu utilization reason huge difference lies geom_raid5 design order write data raid5 volume data must often first read order calculate parity information protects data loss case single disk failure using request combining full stripe block 'collected read longer required means harddrive heads need change position every time write data contiguously theoretically full speed course works sequential transfers sometimes even filesystem write contiguously using request combining geom_raid5 manages outperform software raid5 solution date capable reaching write-speeds associated hardware raid5 budget-level x86 hardware currently module finalized stable version released author release information design disclose benchmarks particular benchmarks showing geom_raid5 performance versus zfs raid-z long-awaited users various incarnations geom raid5 exist trade speed memory usage stable version slower variants certain cases uses memory deliver better transfer rates memory usage speed tng pp uses less memory tng slower uses memory original geom_raid5 driver faster also claimed pp code best cleanest three
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Operating systems
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cain abel software cain abel often abbreviated cain password recovery tool microsoft windows recover many kinds passwords using methods network packet sniffing cracking various password hashes using methods dictionary attacks brute force cryptanalysis attacks cryptanalysis attacks done via rainbow tables generated winrtgen.exe program provided cain abel cain abel maintained massimiliano montoro sean babcock virus scanners browsers e.g chrome 20.0.1132.47 detect cain abel malware avast detects win32 cain-b tool classifies potentially dangerous program microsoft security essentials detects win32/cain 4_9_14 classifies tool program potentially unwanted behavior even cain install directory well word cain added avast exclude list real-time scanner known stop cain functioning however latest version avast longer blocks cain
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Computer security
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ginga middleware ginga middleware specification nipo-brazilian digital tv system sbtvd portuguese sistema brasileiro de tv digital ginga also itu-t recommendation iptv services also considered itu-t recommendations cable broadcast services itu-t j.200 recommendation series rec itu-t j.200 rec itu-t j.201 rec itu-t j.202 terrestrial broadcast services itu-r bt.1889 itu-r bt.1699 itu-r bt.1722 ginga developed based set standardized technologies mainly innovations developed brazilian researchers current reference implementation released gpl license ginga divided two main integrated subsystems allow development applications following two different programming paradigms subsystems called ginga-ncl declarative ncl applications ginga-j imperative java applications case brazilian terrestrial digital tv system digital tv systems following definitions abnt standards ginga middleware abnt 15606 ginga-j required supported fixed receivers optional portable receivers iptv services following h.761 itu-t recommendation ginga-ncl subsystem required terminal type ginga developed telemídia lab pontifical catholic university rio de janeiro puc-rio lavid federal university paraíba ufpb
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Distributed computing architecture
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asus zen ui asus zen ui stylized asus zenui front-end touch interface developed asus partners featuring full touch user interface current version zenui 6 zenui used asus android phones tablet computers available licensing external parties zenui also comes asus-made apps preloaded like zenlink pc link share link party link remote link zenui made debut asus zenfone series asus memopad 7 me176c asus padfone mini 2014 zenui asus made front-end interface android phones tablets called asus waveshare ui asus waveshare ui front-end touch interface developed asus partners waveshare ui used asus android phones tablet computers available licensing external parties waveshare ui originally released asus padfone hybrid smartphone/tablet later used asus products last gadget use waveshare ui asus memo pad hd 7 asus zenui updated google play store preloaded apps preloaded apps
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Operating systems
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kaō kaō huāyā stylized signature mark used east asia place true signature kaō first appeared china tang dynasty began used japan heian period though use became far less widespread edo period continue used even contemporary politicians famous people reading identification individual kaō often requires specialist knowledge whole books devoted topic published often used japanese swordsmith sword tang nakago
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Computer security
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mongrel web server mongrel open-source software http library web server written ruby zed shaw used run ruby web applications presents standard http interface makes layering servers front possible using web proxy load balancer combination instead use conventional methods employed run scripts fastcgi scgi communicate made possible integrating custom high-performance http request parser implemented using ragel mongrel first web server used twitter inspired node.js according ryan dahl shaw subsequently created mongrel2 open-source language agnostic web server successor mongrel server one popular configuration run apache http server 2.2 load balancer using mod_proxy_balancer conjunction several mongrel instances mongrel instance would run separate tcp port configured via mongrel_cluster management utility 2010 twitter notable instance configuration switched unicorn mongrel capable serving ruby rails powered sites without requiring web servers though single-threaded application configuration unsuitable light loads original author zed shaw left ruby rails-scene releases mongrel stopped current release 1.1.5 longer able install ruby versions higher 1.9.2 recommended rails 3 fix use much older 1.2.0-pre2 release mongrel n't stable new maintained server called thin uses mongrel parser mongrel also forked unicorn puma essentially parser
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Web technology
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linuxlive usb creator linuxlive usb creator free microsoft windows program creates live usb systems installed images supported linux distributions
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Operating systems
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cray cray inc. american supercomputer manufacturer headquartered seattle washington also manufactures systems data storage analytics several cray supercomputer systems listed top500 ranks powerful supercomputers world cray manufactures products chippewa falls wisconsin founder seymour cray born raised company also offices bloomington minnesota numerous sales service engineering r locations around world company predecessor cray research inc. cri founded 1972 computer designer seymour cray seymour cray went form spin-off cray computer corporation ccc 1989 went bankrupt 1995 cray research bought sgi next year cray inc. formed 2000 tera computer company purchased cray research inc. business sgi adopted name acquisition may 17 2019 hewlett packard enterprise announced agreement buy cray inc. 1.3 billion seymour cray began working computing field 1950 joined engineering research associates era saint paul minnesota helped create era 1103 era eventually became part univac began phased left company 1960 years former era employees set control data corporation cdc initially worked cdc headquarters minneapolis grew upset constant interruptions managers eventually set lab home town chippewa falls wisconsin 85 miles east cray string successes cdc including cdc 6600 cdc 7600 cdc ran financial difficulties late 1960s development funds cray follow-on cdc 8600 became scarce told project would put hold 1972 cray left form company cray research inc copying previous arrangement cray kept research development facilities chippewa falls put business headquarters minneapolis company first product cray-1 supercomputer major success significantly faster computers time first system sold within month us 8.8 million seymour cray continued working time cray-2 though ended marginally faster cray x-mp developed another team company cray soon left ceo position become independent contractor started new vlsi technology lab cray-2 boulder colorado cray laboratories 1979 closed 1982 undaunted cray later headed similar spin-off 1989 cray computer corporation ccc colorado springs worked cray-3 project—the first attempt major use gallium arsenide gaas semiconductors computing however changing political climate collapse warsaw pact end cold war resulted poor sales prospects ultimately one cray-3 delivered number follow-on designs never completed company filed bankruptcy 1995 ccc remains began cray final corporation src computers inc. cray research continued development along separate line computers originally lead designer steve chen cray x-mp chen departure cray y-mp cray c90 cray t90 developed original cray-1 architecture achieved much greater performance via multiple additional processors faster clocks wider vector pipes uncertainty cray-2 project gave rise number cray-object-code compatible crayette firms scientific computer systems scs american supercomputer supertek perhaps one firm firms mean compete cray therefore attempted less expensive slower cmos versions x-mp release cos operating system scs cft fortran compiler also considered national labs lanl/llnl developed ctss operating system well joining broader trend toward adoption unixes series massively parallel computers thinking machines kendall square research intel supercomputing systems division ncube maspar meiko scientific took 1980s high performance market first cray research denigrated approaches complaining developing software effectively use machines difficult – true complaint era illiac iv becoming less day cray eventually realized approach likely way forward started five-year project capture lead area plan result dec alpha-based cray t3d cray t3e series left cray remaining supercomputer vendor market besides nec 2000 sites cray installation considered member exclusive club cray operators cray computers considered quite prestigious crays extremely expensive machines number units sold small compared ordinary mainframes perception extended countries well boost perception exclusivity cray research marketing department promotional neckties made mosaic tiny national flags illustrating club cray-operating countries new vendors introduced small supercomputers known minisupercomputers opposed superminis late 1980s early 1990s out-competed low-end cray machines market convex computer series well number small-scale parallel machines companies like pyramid technology alliant computer systems particularly popular one vendor supertek whose s-1 machine air-cooled cmos implementation x-mp processor cray purchased supertek 1990 sold s-1 cray xms machine proved problematic meanwhile not-yet-completed s-2 y-mp clone later offered cray y-mp el later becoming el90 series started sell reasonable numbers 1991–92—to mostly smaller companies notably oil exploration business line evolved cray j90 eventually cray sv1 1998 december 1991 cray purchased assets floating point systems another minisuper vendor moved file server market sparc-based model 500 line smp machines scaled 64 processors ran modified version solaris operating system sun microsystems cray set cray research superservers inc. later cray business systems division sell system cray s-mp later replacing cray cs6400 spite machines powerful available applied appropriate workloads cray never successful market possibly due foreign existing market niche ccc building cray-3/sss went chapter 11 march 1995 cray research merged silicon graphics sgi february 1996 time industry highly critical move noting little overlap two companies either markets technology founder seymour cray died result traffic accident later year sgi immediately sold superservers business sun quickly turned ultrasparc-based starfire project development extremely successful enterprise 10000 range servers sgi use number cray technologies attempt move graphics workstation market supercomputing key among use cray-developed hippi data-bus details interconnects used t3 series sgi long-term strategy merge high-end server line cray product lines two phases code-named sn1 sn2 sn standing scalable node sn1 intended replace t3e sgi origin 2000 systems later became sn-mips sgi origin 3000 architecture sn2 originally intended unify high-end/supercomputer product lines including t90 single architecture goal never achieved sgi divested cray business sn2 name later associated sn-ia sgi altix 3000 architecture sgi ownership one new cray model line sv1 launched 1998 clustered smp vector processor architecture developed j90 technology sgi set separate cray research business unit august 1999 preparation detachment march 2 2000 unit sold tera computer company tera computer company renamed cray inc. deal closed april 4 tera merger tera mta system relaunched cray mta-2 commercial success shipped two customers cray inc. also unsuccessfully badged nec sx-6 supercomputer cray sx-6 acquired exclusive rights sell sx-6 u.s. canada mexico 2002 cray inc. announced first new model cray x1 combined architecture vector mpp supercomputer previously known sv2 x1 end result earlier sn2 concept originated sgi years may 2004 cray announced one partners u.s. department energy fastest-computer-in-the-world project build 50 teraflops machine oak ridge national laboratory cray sued 2002 isothermal systems research patent infringement suit claimed cray used isr patented technology development cray x1 lawsuit settled 2003 november 2004 cray x1 maximum measured performance 5.9 teraflops 29th fastest supercomputer world since x1 superseded x1e faster dual-core processors october 4 2004 company announced cray xd1 range entry-level supercomputers use dual-core 64-bit amd opteron cpus running linux system previously known octigabay 12k cray acquisition company xd1 provided one xilinx virtex ii pro field-programmable gate array fpga node four opteron processors fpgas could configured embody various digital hardware designs could augment processing input/output capabilities opteron processors furthermore fpga contains pair powerpc 405 processors add already considerable power single node cray xd1 although moderately successful eventually discontinued 2004 cray completed red storm system sandia national laboratories red storm become jumping-off point string successful products eventually revitalized cray supercomputing red storm processors clustered 96 unit cabinets theoretical maximum 300 cabinets machine design speed 41.5 teraflops red storm also included innovative new design network interconnects dubbed seastar destined centerpiece succeeding innovations cray cray xt3 massively parallel supercomputer became commercialized version red storm similar many respects earlier t3e architecture like xd1 using amd opteron processors cray xt4 introduced 2006 added support ddr2 memory newer dual-core future quad-core opteron processors utilized second generation seastar2 communication coprocessor also included option fpga chips plugged directly processor sockets unlike cray xd1 required dedicated socket fpga coprocessor august 8 2005 peter ungaro appointed ceo ungaro joined cray august 2003 vice president sales marketing made cray president march 2005 november 13 2006 cray announced new system cray xmt based mta series machines system combined multi-threaded processors used original tera systems seastar2 interconnect used xt4 reusing asics boards cabinets system software used comparatively higher volume xt4 product cost making specialized mta system reduced second generation xmt scheduled release 2011 first system ordered swiss national supercomputing center cscs 2006 cray announced vision products dubbed adaptive supercomputing first generation systems dubbed rainier project used common interconnect network seastar2 programming environment cabinet design i/o subsystem systems included existing xt4 xmt second generation launched xt5h allowed system combine compute elements various types common system sharing infrastructure xt5h combined opteron vector multithreaded fpga compute processors single system april 2008 cray intel announced would collaborate future supercomputer systems partnership produced cray cx1 system launched september year deskside blade server system comprising 16 dual- quad-core intel xeon processors either microsoft windows hpc server 2008 red hat enterprise linux installed 2009 largest computer system cray delivered xt5 system national center computational sciences oak ridge national laboratories system 224,000 processing cores dubbed jaguar fastest computer world measured linpack benchmark speed 1.75 petaflops surpassed tianhe-1a october 2010 first system exceed sustained performance 1 petaflops 64-bit scientific application may 2010 cray xe6 supercomputer announced cray xe6 system core new gemini system interconnect new interconnect included true global-address space represented return t3e feature set successful cray research product successful follow-on xt3 xt4 xt5 products first multi-cabinet xe6 system shipped july 2010 next generation cascade systems designed make use future multicore and/or manycore processors vendors intel nvidia cascade scheduled introduced early 2013 designed use next-generation network chip follow-on gemini code named aries early 2010 cray also introduced cray cx1000 rack-mounted system choice compute-based gpu-based smp-based chassis cx1 cx1000 product lines sold late 2011 2011 cray announced cray xk6 hybrid supercomputer cray xk6 system capable scaling 500,000 processors 50 petaflops peak performance combines cray gemini interconnect amd multi-core scalar processors nvidia tesla gpgpu processors october 2012 cray announced cray xk7 supports nvidia kepler gpgpu announced ornl jaguar system would upgraded xk7 renamed titan capable 20 petaflops titan world fastest supercomputer measured linpack benchmark introduction tianhe-2 2013 substantially faster 2011 cray also announced awarded 188m us blue waters contract university illinois ibm pulled delivery system delivered 2012 largest system date terms cabinets general-purpose x86 processors cray ever delivered november 2011 cray sonexion 1300 data storage system introduced signaled cray entry high performance storage business product used modular technology lustre file system 2011 cray launched openacc parallel programming standard organization however 2019 cray announced deprecating openacc support openmp april 2012 cray inc. announced sale interconnect hardware development program related intellectual property intel corporation 140 million november 9 2012 cray announced acquisition appro international inc. california-based privately held developer advanced scalable supercomputing solutions currently 3 provider top100 supercomputer list appro builds world advanced high performance computing hpc cluster systems 2012 cray opened subsidiary china may 17 2019 hewlett packard enterprise hpe announced purchasing cray 1.4 billion approximately 35 per share deal expected close first quarter hpe fiscal year 2020 ends january 31 2020
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Computer architecture
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offline private key protocol offline private key protocol opkp cryptographic protocol prevent unauthorized access back archive data protocol results public key used encrypt data offline private key later used decrypt data protocol based three rules regarding key offline private key comply rules offline private key protocol uses method asymmetric key wrapping protocol provide rules strength encryption methods keys used security protocol depends actual cryptographic implementation used combination strong encryption methods protocol provide extreme security initially archiving creating backup session file restore backed archived data
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Computer security
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offline private key offline private key cryptographic key stored network-connected medium key used decrypt archive backup data key result offline private key protocol printed form key trusted paper key
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Computer security
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source mage source mage linux distribution package installed source code automatically downloaded compiled installed source mage descended sorcerer source mage name suggests source-based linux distribution instead delivering binaries users source code compiled method allows greater control software precompiled distributions ubuntu individual dependencies selected deselected saving valuable hard drive space freeing ram cpu cycles instance openssh compiled without support x11 sharing one choose set cflags cxxflags ldflags specific situation using source-based distribution one way unlock full performance computer many binary distros compile software wide audience particular group users specific processor source mage spell cast latest stable release downloaded developer site rather source mage allows up-to-date system unlike gentoo another popular source-based distribution maintains customized cache packages smgl changes little possible packages fit bare standards filesystem hierarchy standard immune kind errors resulting distribution developers tampering 2000 kyle sallee released linux distribution named sorcerer gnu/linux due several issues 2002 chuck s. mead forked sorcerer lunar linux soon afterwards kyle sallee took sorcerer gnu/linux offline remaining sorcerer gnu/linux development team brought back online continued development month later kyle sallee brought version sorcerer back online new license prevented forking dropping gnu/linux name consequently request sallee sorcerer gnu/linux team renamed project source mage source mage tagline linux advanced may well magic commands sorcerous theme package called spell package management program called sorcery install package user must cast spell casting spell consists downloading source code already downloaded checking dependencies casting necessary compiling program installing set available spells called grimoire uninstall package user must dispel spell source mage established distribution commitment source mage social contract establishes basic rules similar though identical debian first part contract ensures freedom source mage source mage restrict user choice software free software installing source mage involves first creating minimal installation kernel run gcc c compiler network connection basic tools support downloading compiling source code enables system download compile install components compilation results tailored specific system source mage-maintained code designed presume minimal system base system n't explicitly require c++ compiler gcc 4.x+ replaced besides posix-compliant tools core components require bash sed either gawk mawk instead heavyweight languages like perl python makes source mage suitable small installation
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Operating systems
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vulnerability discovery model vulnerability discovery model vdm uses discovery event data software reliability models predicting thorough presentation vdm techniques available numerous model implementations available mcmcbayes open source repository several vdm examples include
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Computer security
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khalil sehnaoui khalil sehnaoui belgian-lebanese information security consultant specialises middle-east founder managing partner beirut-based krypton security also member chaos computer club ccc europe largest association hackers co-founded managing partner security firm krypton security helps test companies security strengths weaknesses potential loopholes online report published april 6 2016 sehnaoui listed one top 100 influencers information security sehnaoui often called upon comment media information security matters sehnaoui born beirut parents marwan sehnaoui mouna bassili sehnaoui 23 may 1975 grew living paris france beirut lebanon father president lebanese order malta mother middle-east painter attended college stanislas paris well collège louise wegman beirut following earned ba management universite saint joseph beirut well masters economics sehnaoui featured guardian video series power privacy 2015 may 2017 sehnaoui went viral twitter internet tweeting getting revenge loud rude customers coffee shop customers loud rude waiters voluble conversation perfect new business name retaliation sehnaoui registered domain name tweeted according mashable twitter users praised sehnaoui act digital savagery sehnaoui also featured national geographic 2017 series breakthrough produced ron howard brian grazer season 2 episode 2 cyber-terror episode offered exclusive look inside shadowy world hackers good battles evil security world stake episode follows “ white-hat ” hackers jayson street darren kitchen khalil sehnaoui security specialists combine clever coding “ mission impossible ” -style “ social engineering. ” 2019 sehnaoui featured amongst 70 information security professionals book called tribe hackers collection industry career personal insights cybersecurity luminaries book quickly rose 1 spot new releases amazon computer security encryption category 2015 controversy sehnaoui identified silent circle warrant canary removed site sehnaoui also prominently featured video series guardian privacy risks often called upon comment recent information security news founding information security firm attempted improve patient representation lebanese insurance industry starting january 2016 reports islamic state allegedly built new android app called alrawi exchanging encrypted messages based claims online counter-terrorism firm ghost security group gsg claim quickly reprinted newsweek fortune techcrunch among others sehnaoui one security specialists helped debunk myth tool showing bad media mock-up try get attention july 2018 arrested alleged piracy several lebanese companies government institutions detention illegal legal vacuum lebanese laws cybercrime released questioned charges brought
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Computer security
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array access analysis computer science array access analysis compiler analysis used decide read write access patterns elements portions arrays major data type manipulated scientific programs array define/use analysis whole array insufficient aggressive compiler optimizations auto parallelization array privatization array access analysis aims obtain knowledge portions even elements array accessed given code segment basic block loop even procedure level array access analysis largely categorized exact reference-list-based summary methods different tradeoffs accuracy complexity exact methods precise costly terms computation space storage summary methods approximate computed quickly economically typical exact array access analysis include linearization atom images summary methods divided array sections bounded regular sections using triplet notation linear-constraint methods data access descriptors array region analysis
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Programming language topics
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light web browser light formerly known firefox light free open-source web browser based firefox light available windows os x linux operating systems differs firefox built performance achieves removing several firefox built components including crash reporter safe browsing spell checker development tools support various types video audio media
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Internet protocols
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byzantine foothold byzantine foothold unclassified code name related united states department defense effort within larger cyber initiative framework specifically aimed curbing preventing foreign intrusions computer networks us federal agencies said threat related ongoing efforts chinese hackers peoples liberation army public documentation available would prove case twenty largest american military-industrial contractors also invited participate program highly potent hacker attack detected booz allen corp although us government sees largest cyber espionage effort arrests made specific cyber intruder identified public information available state on-going investigation related intrusion
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Computer security
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multigrainmalware new sophisticated point-of-sale memory-scraping malware called “ multigrain ” discovered april 17 2016 fireeye inc. security company multigrain malware comes family newposthings malware malware similar newposthings frameworkpos bernhardpos malware known previously notorious malware multigrain uses luhn algorithm validate credit debit card details pos malware infects computer blocks hypertext transfer protocol http file transfer protocol ftp traffic monitors data exfiltration exfiltrates scraped information credit debit card via domain name server dns sends collected payment card information 'command control server server multigrain targets specifically windows point sale system multi.exe executable file multigrain gets pos system multi.exe deletes without leaving trace
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Computer security
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s3 graphics s3 graphics ltd commonly referred s3 american computer graphics company company perhaps best known virge much improved successor savage 3d chrome series struggling competition 3dfx interactive ati nvidia height 3d accelerator wars graphics portion company spun new joint effort via technologies new company focused mobile graphics market became major player space company purchased htc 2011 although primarily mobile technology company still produce graphics accelerators home computers s3 chrome brand name s3 founded incorporated january 1989 dado banatao ronald yara march 5 1993 s3 began initial public offering 2,000,000 shares common stock nasdaq several profitable years independent startup company struggling transition integrated 3d cards s3 remodeled consumer electronics company sold core graphics division joint venture via technologies 323 million joint venture s3 graphics continues develop market chipsets based s3 graphics technology reformed company carried substantial cash pile profitable trio see days successful investment umc taiwanese semiconductor foundry november 15 2000 s3 changed name sonicblue nasdaq stock symbol sblu new business model focused digital media information appliance opportunities graphics division sold via technologies s3 graphics replaytv rio govideo brands developed sonicblue march 21 2003 sonicblue filed chapter 11 bankruptcy s3 graphics first developed graphic cores via igp chipset years later began produce graphics accelerators home computers chrome brand name include deltachrome gammachrome chrome s27 chrome 440gtx july 6 2011 announced htc corporation would buy via technologies stake s3 graphics thus becoming majority owner s3 graphics s3 produces graphics cards primarily pcs earlier products trio range 2d later 3d functionality added virge savage cards recently s3 chipsets sold integrated via northbridge parts however units also available pci-e chrome 440 series supports directx 10.1 hd blu-ray video 3d acceleration powerful enough run today games moderate settings latest graphics card chrome 530gt supports directx 10.1 opengl 3.0 hd-dvd hd blu-ray video playback gpgpu acceleration image processing using s3fotopro video color correction video encoding transcoding scientific research game physics engineering analysis financial analysis signal processing media chipsets formation 1989 took s3 two years develop world first single-chip graphical user interface gui accelerator integrated functionality enabled attractive pricing solid features competitive prices remained hallmark s3 strategy s3 notable product range s3 trio 2d chipset remains one best selling graphics chipsets time updated number timely revisions time s3 managed keep series one step ahead competition however trio 2d range mid 1990s consumers oems started demand 3d functionality graphics cards internally s3 failed recognise transition quickly enough rush s3 virge range 3d cards cheap popular oems reason performance drivers poor enthusiasts even nicknamed graphics decelerators integrated modern style 3d feature produced s3 savage series graphics cards notably pioneered s3tc proprietary metal api subsequently adopted microsoft royalty industry standard texture compression directx savage also introduced motion compensation engine quality video scaler well hardware alpha-blended sub-picture blending first however 3d performance savage cards never quite enough take significant market share poor yields meant actual clock speeds 30 lower projected development transform lighting engine implementation flawed became apparent s3 integrated 2d technology longer enough ensure overall success chipset s3 could continued development savage cards likely resolved outstanding issues instead 2001 s3 management decided sell core business via 323 million subsequently savage derived chips turned numerous via motherboard chipsets integrated north bridge solution twister unichrome recent discrete derivations carried brand names deltachrome gammachrome manner s3 derived chips held onto 10 share overall pc graphics market sonicblue american consumer electronics company resulting 1999 merger computer peripheral maker diamond multimedia graphics chipset maker s3 incorporated november 2000 combined company changed name sonicblue changed focus graphics chipsets computer peripherals consumer electronics rio line mp3 players january 2001 graphics chipset business sold joint venture sonicblue via called s3 graphics later year company bought replaytv maker pvr systems sensory science corporation company selling dual-deck dvd/vcr systems govideo brand name march 21 2003 sonicblue filed chapter 11 bankruptcy protection sold main product lines april 16 2003 holdings parent company denon ltd. marantz japan inc. purchased virtually operating assets sonicblue produces replaytv rio units new subsidiary digital networks north america dnna inc last piece company effectively sold late 2003 best data acquired diamond supra modem business along rights diamond multimedia name use new video card division august 2005 company said would discontinue making mp3 players licensed digital audio software technology chipmaker sigmatel month
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Computer architecture
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mongrel2 mongrel2 open-source language agnostic web server written zed shaw successor shaw mongrel server server supports http flash xmlsockets websockets long polling connections mongrel2 described language agnostic meaning prefer specific programming language another server documentation says shaw began working server june 2010 released version 1.0 software september 1 2010 mongrel2 nothing common original mongrel webserver except using http parser
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Web technology
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interpreter directive interpreter directive computer language construct systems better described aspect system executable file format used control interpreter parses interprets instructions computer program unix linux unix-like operating systems first two bytes file characters constitute magic number hexadecimal 23 21 ascii values often referred shebang prefix first line script remainder line command usually limited max 14 introduced usually 80 characters 2016 file system permissions script file include execute permission bit user invoking filename often found command search path used tell operating system interpreter usually program implements scripting language use execute script contents may batch commands might intended interactive use example would /bin/bash meaning run script bash shell found /bin directory systems files may use magic number interpreter directives
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Operating systems
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pic microcontrollers pic usually pronounced pick family microcontrollers made microchip technology derived pic1650 originally developed general instrument microelectronics division name pic initially referred peripheral interface controller currently expanded programmable intelligent computer first parts family available 1976 2013 company shipped twelve billion individual parts used wide variety embedded systems early models pic read-only memory rom field-programmable eprom program storage provision erasing memory current models use flash memory program storage newer models allow pic reprogram program memory data memory separated data memory 8-bit 16-bit latest models 32-bit wide program instructions vary bit-count family pic may 12 14 16 24 bits long instruction set also varies model powerful chips adding instructions digital signal processing functions hardware capabilities pic devices range 6-pin smd 8-pin dip chips 144-pin smd chips discrete i/o pins adc dac modules communications ports uart i2c even usb low-power high-speed variations exist many types manufacturer supplies computer software development known mplab x assemblers c/c++ compilers programmer/debugger hardware mplab pickit series third party open-source tools also available parts in-circuit programming capability low-cost development programmers available well high-production programmers pic devices popular industrial developers hobbyists due low cost wide availability large user base extensive collection application notes availability low cost free development tools serial programming re-programmable flash-memory capability original pic intended used general instrument new cp1600 16-bit central processing unit cpu whilst people considered cp1600 good cpu poor i/o performance 8-bit pic developed 1975 improve performance overall system offloading i/o tasks cpu pic used simple microcode stored rom perform tasks although term risc used time shares common features risc designs 1985 general instrument sold microelectronics division new owners cancelled almost everything time mostly out-of-date pic however upgraded internal eprom produce programmable channel controller 2001 microchip introduced flash programmable devices full production commencing 2002 today huge variety pics available various on-board peripherals serial communication modules uarts motor control kernels etc program memory 256 words 64k words word one assembly language instruction varying length 8 16 bits depending specific pic micro family pic picmicro registered trademarks microchip technology generally thought pic stands peripheral interface controller although general instruments original acronym initial pic1640 pic1650 devices programmable interface controller acronym quickly replaced programmable intelligent computer microchip 16c84 pic16x84 introduced 1993 first microchip cpu on-chip eeprom memory 2013 microchip shipping one billion pic microcontrollers every year pic micro chips designed harvard architecture offered various device families baseline mid-range families use 8-bit wide data memory high-end families use 16-bit data memory latest series pic32mz 32-bit mips-based microcontroller instruction words sizes 12-bit pic10 pic12 14-bit pic16 24-bit pic24 dspic binary representations machine instructions vary family shown pic instruction listings within families devices may designated picnncxxx cmos picnnfxxx flash c devices generally classified suitable new development actively promoted microchip program memory c devices variously described otp rom eeprom october 2016 otp product classified production pic16hv540 c devices quartz windows erasure general longer available devices feature 12-bit wide code memory 32-byte register file tiny two level deep call stack represented pic10 series well pic12 pic16 devices baseline devices available 6-pin 40-pin packages generally first 7 9 bytes register file special-purpose registers remaining bytes general purpose ram pointers implemented using register pair writing address fsr file select register indf indirect f register becomes alias addressed register banked ram implemented bank number selected high 3 bits fsr affects register numbers 16–31 registers 0–15 global affected bank select bits limited register space 5 bits 4 rarely read registers assigned addresses written special instructions codice_1 codice_2 rom address space 512 words 12 bits may extended 2048 words banking codice_3 codice_4 instructions specify low 9 bits new code location additional high-order bits taken status register note call instruction includes 8 bits address may specify addresses first half 512-word page lookup tables implemented using computed codice_4 assignment pcl register table codice_6 instructions baseline core support interrupts i/o must polled enhanced baseline variants interrupt support four-level call stack pic10f32x devices feature mid-range 14-bit wide code memory 256 512 words 64-byte sram register file 8-level deep hardware stack devices available 6-pin smd 8-pin dip packages two pins unused one input three i/o pins available complex set interrupts available clocks internal calibrated high-frequency oscillator 16 mhz choice selectable speeds via software 31 khz low-power source devices feature 14-bit wide code memory improved 8-level deep call stack instruction set differs little baseline devices two additional opcode bits allow 128 registers 2048 words code directly addressed additional miscellaneous instructions two additional 8-bit literal instructions add subtract mid-range core available majority devices labeled pic12 pic16 first 32 bytes register space allocated special-purpose registers remaining 96 bytes used general-purpose ram banked ram used high 16 registers 0x70–0x7f global important special-purpose registers including status register holds ram bank select bits global registers fsr indf low 8 bits program counter pcl pc high preload register pclath master interrupt control register intcon pclath register supplies high-order instruction address bits 8 bits supplied write pcl register 11 bits supplied codice_4 codice_3 instruction sufficient address available rom space 17 series never became popular superseded pic18 architecture however see clones 17 series recommended new designs availability may limited users improvements earlier cores 16-bit wide opcodes allowing many new instructions 16-level deep call stack pic17 devices produced packages 40 68 pins 17 series introduced number important new features significant limitation ram space limited 256 bytes 26 bytes special function registers 232 bytes general-purpose ram awkward bank-switching models supported 2000 microchip introduced pic18 architecture unlike 17 series proven popular large number device variants presently manufacture contrast earlier devices often programmed assembly c become predominant development language 18 series inherits features instructions 17 series adding number important new features ram space 12 bits addressed using 4-bit bank select register 8-bit offset instruction additional access bit instruction selects bank 0 =0 bank selected bsr =1 1-level stack also available status wreg bsr registers saved every interrupt may restored return interrupts disabled may also used subroutine call/return setting bit appending fast instruction auto increment/decrement feature improved removing control bits adding four new indirect registers per fsr depending indirect file register accessed possible postdecrement postincrement preincrement fsr form effective address adding w fsr advanced pic18 devices extended mode available makes addressing even favorable compiled code pic18 devices still developed 2017 fitted cip core independent peripherals 2001 microchip introduced dspic series chips entered mass production late 2004 microchip first inherently 16-bit microcontrollers pic24 devices designed general purpose microcontrollers dspic devices include digital signal processing capabilities addition although still similar earlier pic architectures significant enhancements features dspics programmed c using microchip xc16 compiler formerly called c30 variant gcc instruction rom 24 bits wide software access rom 16-bit words even words hold least significant 16 bits instruction odd words hold significant 8 bits high half odd words reads zero program counter 23 bits wide least significant bit always 0 22 modifiable bits instructions come two main varieties important operations add xor shifts etc allowing forms first like classic pic instructions operation specified f register i.e first 8k ram single accumulator w0 destination select bit selecting updated result w registers memory-mapped f operand may w register second form conventional allowing three operands may 16 w registers destination one sources also support addressing modes allowing operand memory pointed w register november 2007 microchip introduced pic32mx family 32-bit microcontrollers based mips32 m4k core device programmed using microchip mplab c compiler pic32 mcus variant gcc compiler first 18 models currently production pic32mx3xx pic32mx4xx pin pin compatible share peripherals set pic24fxxga0xx family 16-bit devices allowing use common libraries software hardware tools today starting 28 pin small qfn packages high performance devices ethernet usb otg full family range mid-range 32-bit microcontrollers available pic32 architecture brought number new features microchip portfolio including november 2013 microchip introduced pic32mz series microcontrollers based mips m14k core pic32mz series include 2015 microchip released pic32mz ef family using updated mips m5150 warrior m-class processor 2017 microchip introduced pic32mz da family featuring integrated graphics controller graphics processor 32mb ddr2 dram june 2016 microchip introduced pic32mm family specialized low-power low-cost applications pic32mm features core-independent peripherals sleep modes 500 na 4 x 4 mm packages pic32mm microcontrollers use mips technologies m4k 32-bit mips32 processor meant low power consumption limited 25 mhz key advantage support 16bits instructions mips making program size much compact 40 microchip introduced pic32mk family 2017 specialized motor control industrial control industrial internet things iiot multi-channel applications pic architecture characterized multiple attributes distinction memory space register space ram serves job memory registers ram usually referred register file simply registers pics set registers function general-purpose ram special-purpose control registers on-chip hardware resources also mapped data space addressability memory varies depending device series pic devices banking mechanism extend addressing additional memory later series devices feature move instructions cover whole addressable space independent selected bank earlier devices register move achieved accumulator implement indirect addressing file select register fsr indirect register indf used register number written fsr reads writes indf actually register pointed fsr later devices extended concept post- pre- increment/decrement greater efficiency accessing sequentially stored data also allows fsr treated almost like stack pointer sp external data memory directly addressable except pic18 devices high pin count code space generally implemented on-chip rom eprom flash rom general provision storing code external memory due lack external memory interface exceptions pic17 select high pin count pic18 devices pics handle address data 8-bit chunks however unit addressability code space generally data space example pics baseline pic12 mid-range pic16 families program memory addressable wordsize instruction width i.e 12 14 bits respectively contrast pic18 series program memory addressed 8-bit increments bytes differs instruction width 16 bits order clear program memory capacity usually stated number single-word instructions rather bytes pics hardware call stack used save return addresses hardware stack software-accessible earlier devices changed 18 series devices hardware support general-purpose parameter stack lacking early series greatly improved 18 series making 18 series architecture friendly high-level language compilers pic instructions vary 35 instructions low-end pics 80 instructions high-end pics instruction set includes instructions perform variety operations registers directly accumulator literal constant accumulator register well conditional execution program branching operations bit setting testing performed numbered register bi-operand arithmetic operations always involve w accumulator writing result back either w operand register load constant necessary load w moved another register older cores register moves needed pass w changed high-end cores pic cores skip instructions used conditional execution branching skip instructions skip bit set skip bit set cores pic18 unconditional branch instructions conditional jumps implemented conditional skip opposite condition followed unconditional branch skips also utility conditional execution immediate single following instruction possible skip instructions example instruction sequence skip skip b c execute c true b false 18 series implemented shadow registers registers save several important registers interrupt providing hardware support automatically saving processor state servicing interrupts general pic instructions fall five classes architectural decisions directed maximization speed-to-cost ratio pic architecture among first scalar cpu designs still among simplest cheapest harvard architecture instructions data come separate sources simplifies timing microcircuit design greatly benefits clock speed price power consumption pic instruction set suited implementation fast lookup tables program space lookups take one instruction two instruction cycles many functions modeled way optimization facilitated relatively large program space pic e.g 4096 × 14-bit words 16f690 design instruction set allows embedded constants example branch instruction target may indexed w execute retlw named return literal w. interrupt latency constant three instruction cycles external interrupts synchronized four-clock instruction cycle otherwise one instruction cycle jitter internal interrupts already synchronized constant interrupt latency allows pics achieve interrupt-driven low-jitter timing sequences example video sync pulse generator longer true newest pic models synchronous interrupt latency three four cycles following stack limitations addressed pic18 series still apply earlier cores paged program memory two page sizes worry one call goto another computed goto typically used table lookups example pic16 call goto 11 bits addressing page size 2048 instruction words computed gotos add pcl page size 256 instruction words cases upper address bits provided pclath register register must changed every time control transfers pages pclath must also preserved interrupt handler several commercial compilers available 2008 microchip released c compilers c18 c30 line 18f 24f 30/33f processors 2013 microchip offers xc series compilers use mplab x microchip eventually phase older compilers c18 recommends using xc series compilers new designs risc instruction set pic assembly language code make overall flow difficult comprehend judicious use simple macros increase readability pic assembly language example original parallax pic assembler spasm macros hide w make pic look like two-address machine macro instructions like codice_17 move data address address b codice_18 add data address data address b also hides skip instructions providing three-operand branch macro instructions codice_19 compare b jump dest equal pic devices generally feature within series still many device variants depending hardware resources chip features first generation pics eprom storage almost completely replaced chips flash memory likewise original 12-bit instruction set pic1650 direct descendants superseded 14-bit 16-bit instruction sets microchip still sells otp one-time-programmable windowed uv-erasable versions eprom based pics legacy support volume orders microchip website lists pics electrically erasable otp uv erasable windowed versions chips ordered f picmicro part number generally indicates picmicro uses flash memory erased electronically conversely c generally means erased exposing die ultraviolet light possible windowed package style used exception rule pic16c84 uses eeprom therefore electrically erasable l name indicates part run lower voltage often frequency limits imposed parts designed specifically low voltage operation within strict range 3 3.6 volts marked j part number parts also uniquely i/o tolerant accept 5 v inputs microchip provides freeware ide package called mplab x includes assembler linker software simulator debugger also sell c compilers pic10 pic12 pic16 pic18 pic24 pic32 dspic integrate cleanly mplab x free versions c compilers also available features free versions optimizations disabled 60 days several third parties develop c language compilers pics many integrate mplab and/or feature ide fully featured compiler picbasic language program pic microcontrollers available melabs inc. mikroelektronika offers pic compilers c basic pascal programming languages graphical programming language flowcode exists capable programming 8- 16-bit pic devices generating pic-compatible c code exists numerous versions free demonstration complete professional edition proteus design suite able simulate many popular 8 16-bit pic devices along circuitry connected pic schematic program simulated developed within proteus mplab development tool devices called programmers traditionally used get program code target pic pics microchip currently sells feature icsp circuit serial programming and/or lvp low voltage programming capabilities allowing pic programmed sitting target circuit microchip offers programmers/debuggers mplab pickit series mplab icd4 mplab real ice current programmers debuggers professional engineering pickit 3 low-cost programmer debugger line hobbyists students many higher end flash based pics also self-program write program memory process known bootloading demo boards available small bootloader factory programmed used load user programs interface rs-232 usb thus obviating need programmer device alternatively bootloader firmware available user load onto pic using icsp programming bootloader onto pic user reprogram device using rs232 usb conjunction specialized computer software advantages bootloader icsp faster programming speeds immediate program execution following programming ability debug program using cable many programmers pic microcontrollers ranging extremely simple designs rely icsp allow direct download code host computer intelligent programmers verify device several supply voltages many complex programmers use pre-programmed pic send programming commands pic programmed intelligent type programmer needed program earlier pic models mostly eprom type support in-circuit programming third party programmers range plans build self-assembly kits fully tested ready-to-go units simple designs require pc low-level programming signalling typically connect serial parallel port consist simple components others programming logic built typically use serial usb connection usually faster often built using pics control newer pic devices feature icd in-circuit debugging interface built cpu core allows interactive debugging program conjunction mplab ide mplab icd mplab real ice debuggers communicate interface using icsp interface debugging system comes price however namely limited breakpoint count 1 older devices 3 newer devices loss i/o exception surface mount 44-pin pics dedicated lines debugging loss on-chip features devices on-chip debug support due cost lack pins larger chips also debug module debug devices special -icd version chip mounted daughter board provides dedicated ports required debug chips able operate one type chip use selectable jumpers daughter board allows broadly identical architectures feature chip peripheral devices replaced single -icd chip example 12f690-icd function one six different parts features one five chip peripherals microchip offers three full in-circuit emulators mplab ice2000 parallel interface usb converter available newer mplab ice4000 usb 2.0 connection recently real ice usb 2.0 connection tools typically used conjunction mplab ide source-level interactive debugging code running target pic projects may utilize real time operating systems freertos avix rtos urtos salvo rtos similar libraries task scheduling prioritization open source project serge vakulenko adapts 2.11bsd pic32 architecture name retrobsd brings familiar unix-like operating system including onboard development environment microcontroller within constraints onboard hardware parallax produced series picmicro-like microcontrollers known parallax sx currently discontinued designed architecturally similar pic microcontrollers used original versions basic stamp sx microcontrollers replaced pic several subsequent versions product parallax sx 8-bit risc microcontrollers using 12-bit instruction word run fast 75 mhz 75 mips include 4096 12-bit words flash memory 262 bytes random access memory eight bit counter support logic software library modules emulate i²c spi interfaces uarts frequency generators measurement counters pwm sigma-delta a/d converters interfaces relatively easy write existing modules modified get new features russian pkk milandr produces microcontrollers using pic17 architecture 1886 series program memory consists 64kb flash memory 1886ve2u 8kb eeprom 1886ve5u 1886ве5у 1886ve5u 1886ве5у 1886ve7u 1886ве7у specified military temperature range -60 °c +125 °c hardware interfaces various parts include usb i2c spi well a/d d/a converters 1886ve3u 1886ве3у contains hardware accelerator cryptographic functions according gost 28147-89 even radiation-hardened chips designations 1886ve8u 1886ве8у 1886ve10u 1886ве10у elan microelectronics corp. taiwan make line microcontrollers based pic16 architecture 13-bit instructions smaller 6-bit ram address space holtek semiconductor make large number cheap microcontrollers low 8.5 cents quantity 14-bit instruction set strikingly similar pic16 many ultra-low-cost otp microcontrollers asian manufacturers found low-cost consumer electronics based pic architecture modified form clones target baseline parts pic16c5x/pic12c50x microchip attempted sue manufacturers copying particularly egregious without success
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Computer architecture
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concurrency control information technology computer science especially fields computer programming operating systems multiprocessors databases concurrency control ensures correct results concurrent operations generated getting results quickly possible computer systems software hardware consist modules components component designed operate correctly i.e. obey meet certain consistency rules components operate concurrently interact messaging sharing accessed data memory storage certain component consistency may violated another component general area concurrency control provides rules methods design methodologies theories maintain consistency components operating concurrently interacting thus consistency correctness whole system introducing concurrency control system means applying operation constraints typically result performance reduction operation consistency correctness achieved good possible efficiency without reducing performance reasonable levels concurrency control require significant additional complexity overhead concurrent algorithm compared simpler sequential algorithm example failure concurrency control result data corruption torn read write operations comments concurrency control database management systems dbms e.g. bernstein et al 1987 weikum vossen 2001 transactional objects related distributed applications e.g. grid computing cloud computing ensures database transactions performed concurrently without violating data integrity respective databases thus concurrency control essential element correctness system two database transactions executed time overlap access data e.g. virtually general-purpose database system consequently vast body related research accumulated since database systems emerged early 1970s well established concurrency control theory database systems outlined references mentioned serializability theory allows effectively design analyze concurrency control methods mechanisms alternative theory concurrency control atomic transactions abstract data types presented lynch et al 1993 utilized theory refined complex wider scope less utilized database literature classical theory theory pros cons emphasis insight extent complementary merging may useful ensure correctness dbms usually guarantees serializable transaction schedules generated unless serializability intentionally relaxed increase performance cases application correctness harmed maintaining correctness cases failed aborted transactions always happen many reasons schedules also need recoverability abort property dbms also guarantees effect committed transactions lost effect aborted rolled back transactions remains related database overall transaction characterization usually summarized acid rules databases become distributed needed cooperate distributed environments e.g. federated databases early 1990 cloud computing currently effective distribution concurrency control mechanisms received special attention concept database transaction atomic transaction evolved order enable well understood database system behavior faulty environment crashes happen time recovery crash well understood database state database transaction unit work typically encapsulating number operations database e.g. reading database object writing acquiring lock etc abstraction supported database also systems transaction well defined boundaries terms program/code executions included transaction determined transaction programmer via special transaction commands every database transaction obeys following rules support database system i.e. database system designed guarantee transactions runs concept atomic transaction extended years become business transactions actually implement types workflow atomic however also enhanced transactions typically utilize atomic transactions components transactions executed serially i.e. sequentially overlap time transaction concurrency exists however concurrent transactions interleaving operations allowed uncontrolled manner unexpected undesirable results may occur high-performance transactional systems need run transactions concurrently meet performance requirements thus without concurrency control systems neither provide correct results maintain databases consistently main categories concurrency control mechanisms different categories provide different performance i.e. different average transaction completion rates throughput depending transaction types mix computing level parallelism factors selection knowledge trade-offs available category method chosen provide highest performance mutual blocking two transactions one blocks results deadlock transactions involved stalled reach completion non-optimistic mechanisms blocking prone deadlocks resolved intentional abort stalled transaction releases transactions deadlock immediate restart re-execution likelihood deadlock typically low blocking deadlocks aborts result performance reduction hence trade-offs categories many methods concurrency control exist implemented within either main category major methods many variants cases may overlap combined major concurrency control types utilized conjunction methods include common mechanism type database systems since early days 1970s strong strict two-phase locking ss2pl also called rigorous scheduling rigorous 2pl special case variant two-phase locking 2pl commitment ordering co pessimistic spite long name historical reasons idea ss2pl mechanism simple release locks applied transaction transaction ended ss2pl rigorousness also name set schedules generated mechanism i.e. ss2pl rigorous schedules ss2pl rigorousness property concurrency control mechanisms firstly need operate correctly i.e. maintain transaction integrity rules related concurrency application-specific integrity rule scope transactions running concurrently thus integrity entire transactional system correctness needs achieved good performance possible addition increasingly need exists operate effectively transactions distributed processes computers computer networks subjects may affect concurrency control recovery replication correctness common major goal concurrency control mechanisms generating schedules serializability property without serializability undesirable phenomena may occur e.g. money may disappear accounts generated nowhere serializability schedule means equivalence resulting database values serial schedule transactions i.e. transactions sequential overlap time thus completely isolated concurrent access two transactions data possible serializability considered highest level isolation among database transactions major correctness criterion concurrent transactions cases compromised relaxed forms serializability allowed better performance e.g. popular snapshot isolation mechanism meet availability requirements highly distributed systems see eventual consistency application correctness violated relaxation e.g. relaxation allowed money transactions since relaxation money disappear appear nowhere almost implemented concurrency control mechanisms achieve serializability providing conflict serializablity broad special case serializability i.e. covers enables serializable schedules impose significant additional delay-causing constraints implemented efficiently comment general area systems term recoverability may refer ability system recover failure incorrect/forbidden state within concurrency control database systems term received specific meaning concurrency control typically also ensures recoverability property schedules maintaining correctness cases aborted transactions always happen many reasons recoverability abort means committed transaction schedule read data written aborted transaction data disappear database upon abort parts incorrect database state reading data violates consistency rule acid unlike serializability recoverability compromised relaxed case since relaxation results quick database integrity violation upon aborts major methods listed provide serializability mechanisms none general form automatically provides recoverability special considerations mechanism enhancements needed support recoverability commonly utilized special case recoverability strictness allows efficient database recovery failure excludes optimistic implementations e.g. strict co sco optimistic implementation semi-optimistic ones comment note recoverability property needed even database failure occurs database recovery failure needed rather needed correctly automatically handle transaction aborts may unrelated database failure recovery fast technological development computing difference local distributed computing low latency networks buses blurring thus quite effective utilization local techniques distributed environments common e.g. computer clusters multi-core processors however local techniques limitations use multi-processes threads supported multi-processors multi-cores scale often turns transactions distributed ones need span multi-processes cases local concurrency control techniques scale well database systems become distributed started cooperate distributed environments e.g. federated databases early 1990s nowadays grid computing cloud computing networks smartphones transactions become distributed distributed transaction means transaction spans processes may span computers geographical sites generates need effective distributed concurrency control mechanisms achieving serializability property distributed system schedule see distributed serializability global serializability modular serializability effectively poses special challenges typically met regular serializability mechanisms originally designed operate locally especially due need costly distribution concurrency control information amid communication computer latency known general effective technique distribution commitment ordering disclosed publicly 1991 patented commitment ordering commit ordering co raz 1992 means transactions chronological order commit events kept compatible respective precedence order co require distribution concurrency control information provides general effective solution reliable high-performance scalable distributed global serializability also heterogeneous environment database systems transactional objects different concurrency control mechanisms co indifferent mechanism utilized since interfere transaction operation scheduling mechanisms control determines order commit events thus co enables efficient distribution mechanisms also distribution mix different local mechanisms achieving distributed global serializability existence solution considered unlikely 1991 many experts also later due misunderstanding co solution see quotations global serializability important side-benefit co automatic distributed deadlock resolution contrary co virtually techniques combined co prone distributed deadlocks also called global deadlocks need special handling co also name resulting schedule property schedule co property chronological order transactions commit events compatible respective transactions precedence partial order ss2pl mentioned variant special case co thus also effective achieve distributed global serializability also provides automatic distributed deadlock resolution fact overlooked research literature even co publication well strictness thus recoverability possessing desired properties together known efficient locking based implementations explains ss2pl popularity ss2pl utilized efficiently achieve distributed global serializability since 1980 become de facto standard however ss2pl blocking constraining pessimistic proliferation distribution utilization systems different traditional database systems e.g. cloud computing less constraining types co e.g. optimistic co may needed better performance comments unlike serializability distributed recoverability distributed strictness achieved efficiently straightforward way similarly way distributed co achieved database system applied locally employ vote ordering strategy two-phase commit protocol 2pc raz 1992 page 307 mentioned distributed ss2pl including distributed strictness recoverability distributed commitment ordering serializability automatically employs needed vote ordering strategy achieved globally employed locally local database system known utilized many years matter fact locality defined boundary 2pc participant raz 1992 design concurrency control mechanisms often influenced following subjects systems prone failures handling recovery failure must properties generated schedules dictated concurrency control mechanism may affect effectiveness efficiency recovery example strictness property mentioned section recoverability often desirable efficient recovery high availability database objects often replicated updates replicas database object need kept synchronized may affect way concurrency control done e.g. gray et al 1996 multitasking operating systems especially real-time operating systems need maintain illusion tasks running top running time even though one tasks really running given moment due limitations hardware operating system running multitasking fairly simple tasks independent however several tasks try use resource tasks try share information lead confusion inconsistency task concurrent computing solve problem solutions involve locks similar locks used databases risk causing problems deadlock solutions non-blocking algorithms read-copy-update
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Databases
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global relay global relay technology services company providing software-as-a-service electronic message archiving e.g. email archiving instant messaging compliance supervision solutions focus highly regulated industries global relay privately held employee controlled outside venture funding global relay founded 1999 warren roy duff reid eric parusel company developed one first cloud email archiving services use records management tool architecture design construction industries several years later company realized perfect technology wrong industry company shifted focus financial sector began selling archiving services broker-dealers investment advisors hedge funds banks email electronic messages increasingly became standard methods business communication new market emerged secure way retain messages business legal regulatory purposes beginning 2001 accounting scandals major us corporations enron worldcom arthur andersen brought regulatory compliance issues sharper focus financial firms also public companies wake scandals regulators sec financial industry regulatory authority finra formerly nasd well newly introduced sarbanes-oxley legislation began requiring financial firms system electronic message recordkeeping supervision — paper records global relay built customer base combining technology compliance legal audit/ediscovery services company gained widespread adoption among banks investment advisors broker-dealers hedge funds private equity firms 2007 global relay entered worldwide exclusive partnership thomson reuters archiving compliance thomson reuters messenger eikon new message types adopted financial industry global relay developed ability capture retain compliance public instant messaging aol instant messenger yahoo messenger msn messenger googletalk first message type followed bloomberg messaging mobile messaging blackberry android sms blackberry pin call logs ice chat cme/pivot social media linkedin twitter facebook integrations well company archiving system built in-house global relay development teams global relay markets global relay archive compliance necessity tool boost end-user productivity since company acquisition mobile software firm 2008 released apps every major mobile platform including iphone ipad blackberry android — allowing users find retrieve archived messages location global relay strategy future centers upon transition offering back office tools message archiving also providing front office communication services global relay message company cloud-based enterprise platform instant messaging collaboration designed meet regulatory requirements finance industry global relay also process developing next generation core archiving product provide increased scalability capacity process index messaging data companies hundreds thousands users additional key component global relay competitive strategy construction data centers allowing global relay fully control components technology stack including software workstations servers data centers property global relay 4-megawatt west coast data center located north vancouver british columbia capacity 200 racks 5000 servers environmentally friendly facility employs evaporative cooling technology eliminate need mechanical air conditioning thereby dramatically reducing electricity usage global relay significant player cloud-based messaging archiving industries recent articles cite client base 18,000 including 22 world 25 biggest banks 61 us hedge funds.1,2 revenue growth last five years rapid global relay ranked 197th fastest-growing software company north america 2012 data security paramount global relay financial customer base company annually engages kpmg provide independent verification security reliability internal controls january 2012 global relay announced five-year 1-million commitment become title sponsor operator global relay gastown grand prix 2016 global relay gastown grand prix professional cycling criterium race vancouver british columbia november 2012 global relay introduced global relay bridge gap philanthropic fund support up-and-coming canadian cyclists global relay pledged 400,000 four years support cyclists ages 19 25 providing funding coaching travel equipment five veteran professional canadian riders board members global relay bridge gap ryan anderson andrew pinfold routley svein tuft erinne willock
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Distributed computing architecture
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glyder 2 glyder 2 ios adventure game developed glu mobile released december 16 2009 game rating 93 metacritic based 5 critic reviews appsmile said replay value high game perfect killing minutes hours. slidetoplay wrote glyder 2 must flight game enthusiasts want take easy without pinned red-flashing control panel seating area full screaming passengers. pocketgameruk said glyder 2 one-way ticket fantastic gameplay combination self-motivated exploration dynamic goals ensuring first class flight. 148apps said technically game fantastic graphics great controls responsive well done soundtrack fantastic real hick-up found occasional heavy frame dropping mushroom world sporelle. toucharcade said glyder 2 delivers fanciful aerial questing experience iphone ipod touch like forerunner highly enjoyable game challenging time relaxing.
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Operating systems
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computer security conference computer security conference convention individuals involved computer security generally serve meeting places system network administrators hackers computer security experts common activities hacker conventions may include general security conferences might held non-profit/not-for-profit/for-profit professional associations individuals informal group individuals security product vendor companies hacker conference also known hacker con convention hackers serve meeting places phreakers hackers security professionals actual events time-spans details various themes conventions depends specific convention attended also perceived reputation typically actual details given convention couched mild secrecy due legality certain panels well willingness attendees explain law enforcement less computer-savvy individuals see hacker definition controversy common topics include wardriving lockpicking corporate network security personal rights freedoms new technologies well general 'geek motifs may also contests general collaborative events hackathons one facet hacker conferences tends differentiate many hackercons general computer security conferences evolution conference badge many conferences use fairly standard paper/plastic badge identify attendees name many hacker con evolved use non-traditional badges electronic pcb led lcd screens include wifi advanced often hidden functionality include games identify individual sometimes promoting group identity regional/local group affiliation spurred creation so-called badgelife different individuals organizations local hacker groups may design create sell otherwise distribute separate badge attendees wear addition conference badge badges may purchased may earned completing challenge conference one rarest desirable badges defcon black badge use badges traditionally associated defcon use spread conferences
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Computer security
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miguel de icaza miguel de icaza born november 23 1972 mexican-american programmer best known starting gnome mono xamarin projects de icaza born mexico city studied mathematics national autonomous university mexico unam dropped getting degree work came family scientists father physicist mother biologist started writing free software 1992 one earliest pieces software wrote linux midnight commander file manager text-mode file manager also one early contributors wine project worked david s. miller linux sparc port wrote several video network drivers port well libc ports platform later worked extending linux mips run sgi indy computers wrote original x drivers system ingo molnar wrote original software implementation raid-1 raid-5 drivers linux kernel summer 1997 interviewed microsoft job internet explorer unix team work sparc port lacked university degree required obtain work h-1b visa said interview tried persuade interviewers free ie code even netscape browser de icaza started gnome project federico mena august 1997 create completely free desktop environment component model linux unix-like operating systems also created gnome spreadsheet program gnumeric 1999 de icaza along nat friedman co-founded helix code gnome-oriented free software company employed large number gnome hackers 2001 helix code later renamed ximian announced mono project led de icaza goal implement microsoft new .net development platform linux unix-like platforms august 2003 ximian acquired novell de icaza vice president developer platform may 2011 de icaza started xamarin replace monotouch mono android novell bought attachmate projects abandoned shortly afterwards xamarin novell reached agreement xamarin took development sales products february 2016 xamarin announced acquired microsoft one month later microsoft build conference announced mono project would relicensed mit visual studio would include xamarin even free versions without restrictions xamarin sdks would opensourced de icaza endorsed microsoft office open xml ooxml document standard disagreeing lot widespread criticism open source free-software community also developed mono – free open-source alternative microsoft .net framework – gnome raised much disagreement due patents microsoft holds .net framework de icaza criticized richard stallman software freedom day 2009 labeled traitor free software community icaza responded blog stallman remark believes world possibility open discussions ways improve pool open source free software august 2012 de icaza criticized linux desktop killed apple de icaza specifically criticized generally developer-focused culture lack backward compatibility fragmentation among various linux distributions march 2013 de icaza announced personal blog regularly used macos instead linux desktop computing 2014 joined anders hejlsberg stage announcements .net foundation open sourcing microsoft c compiler serves board directors .net foundation miguel de icaza received free software foundation 1999 award advancement free software mit technology review innovator year award 1999 named one time magazine 100 innovators new century september 2000 early 2010 received microsoft mvp award march 2010 named fifth powerful voices open source mindtouch de icaza cameo appearances 2001 motion pictures antitrust code married brazilian maria laura soares da silva maria laura de icaza 2003 de icaza critical actions state israel towards palestinians middle east blogged subject de icaza granted us citizenship january 2015
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Operating systems
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seqlock seqlock short sequential lock special locking mechanism used linux supporting fast writes shared variables two parallel operating system routines semantics stabilized version 2.5.59 present 2.6.x stable kernel series seqlocks developed stephen hemminger originally called frlocks based earlier work andrea arcangeli first implementation x86-64 time code needed synchronize user space possible use real lock reader-writer consistent mechanism avoids problem writer starvation seqlock consists storage saving sequence number addition lock lock support synchronization two writers counter indicating consistency readers addition updating shared data writer increments sequence number acquiring lock releasing lock readers read sequence number reading shared data sequence number odd either occasion writer taken lock data read may changed sequence numbers different writer changed data read either case readers simply retry using loop read even sequence number reader never blocks may retry write progress speeds readers case data modified since acquire lock would traditional read-write lock also writers wait readers whereas traditional read-write locks leading potential resource starvation situation number readers writer must wait readers two factors seqlocks efficient traditional read-write locks situation many readers writers drawback much write activity reader slow might livelock readers may starve also noted technique work data contains pointers writer could invalidate pointer reader already followed case using read-copy-update synchronization preferred first applied system time counter updating time interrupt updates time day may many readers time operating system internal use applications writes relatively infrequent occur one time bsd timecounter code instance appears use similar technique one subtle issue using seqlocks time counter impossible step debugger retry logic trigger time debugger slow enough make read race occur always
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Computer architecture
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can4linux can4linux open source linux-kernel device driver development started mid 1990s philips 82c200 controller stand alone chip isa board at-can-mini 1995 first version created use bus linux laboratory automation project linux lab project fu berlin increasing spread field bus technology automation especially embedded devices growth linux area leads growing importance device drivers base higher layer protocols like canopen j1939 devicenet besides nxp sja1000 successor first supported controller philips 82c200 intel 82527 development powerful microcontrollers integrated controllers capable run linux operating system intensified since 2005 examples development serve freescale coldfire processors arm models atmel freescale also stand-alone controller mcp2515 connected via spi bus br list supported controllers available can4linux project site latest version virtual mode implemented allows applications communicate without hardware using device driver software layer mode already includes support new frame format called fd allows data frame length 64 byte application software opens device descriptor gets back file descriptor using file descriptor standard operating system functions like codice_1 codice_2 used exchange frames nodes bus following code example puts frame bus afterwards waits frame transmitted another node examples available can4linux project site can4linux compiled way allows one process access controller hardware reading writing frames bus beside real application processes like data loggers diagnosis processes access bus
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Operating systems
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