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object language object language language object study various fields including logic linguistics mathematics theoretical computer science language used talk object language called metalanguage object language may formal natural language mathematical logic linguistics make use metalanguages languages describing nature languages mathematical logic object language usually formal language language metalanguage used describe object language called language object discussion using metalanguage instance someone says french say bonjour greet someone uses english metalanguage describe object language french two ways term object language used computing language object formal specification language object goal compiler interpreter computer languages object languages metalanguage specification written computer science referred specification language backus–naur form one earliest used specification languages compilers written using systems like lex yacc rules programmer writes look much like formal specification considered implementation instead many programming language implementations strictly specifications adding features making implementation-dependent design decisions basic level computers act given limited set instructions understood cpus earliest computers meant programmers sometimes composed actual 1 0 program since requires considerable programmer training patience create instructions later computer languages gone great lengths simplify programmer task example high level programming language may allow programmer assign value variable without specifying memory location cpu instruction context high level programming language source language translated compiler object code cpu read directly object code object language varies depending cpu given instructions object language context means something akin object programmer trying achieve source language object languages viewed formal logical languages compiler interpret source target language different computer science use interpreted language meaning one compiled object language context synonymous target language object language translation often machine language kind language assembly language object language compilation usually machine language term object file come mean file containing machine instructions sometimes translated program simply called object object language also confused object-oriented language type computer programming language changes programmer environment convenient objects used something similar drag-and-drop fashion symbol idea abstraction concept tokens may marks configuration marks form particular pattern although term symbol common use refers times idea symbolized times marks piece paper chalkboard used express idea formal languages studied mathematics logic term symbol refers idea marks considered token instance symbol formal languages used mathematical logic computer science well-formed formula simply formula idea abstraction concept expressed using symbols formation rules also called formal grammar particular formal language say string symbols formula_1 well-formed formula respect given formal grammar formula_2 equivalent saying formula_1 belongs language generated formula_2 formal system formal language together deductive system consists set inference rules and/or axioms formal system used derive one expression one expressions previously expressed system expressions called axioms case previously supposed true theorems case derived formal system may formulated studied intrinsic properties may intended description i.e model external phenomena theorem symbol string symbols derived using formal system string symbols logical consequence axioms rules system formal proof derivation finite sequence propositions called well-formed formulas case formal language axiom follows preceding sentences sequence rule inference last sentence sequence theorem formal system concept natural deduction generalization concept proof theory set sentences formal language
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Programming language topics
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buffer overflow protection buffer overflow protection various techniques used software development enhance security executable programs detecting buffer overflows stack-allocated variables preventing causing program misbehavior becoming serious security vulnerabilities stack buffer overflow occurs program writes memory address program call stack outside intended data structure usually fixed-length buffer stack buffer overflow bugs caused program writes data buffer located stack actually allocated buffer almost always results corruption adjacent data stack could lead program crashes incorrect operation security issues typically buffer overflow protection modifies organization stack-allocated data includes canary value destroyed stack buffer overflow shows buffer preceding memory overflowed verifying canary value execution affected program terminated preventing misbehaving allowing attacker take control buffer overflow protection techniques include bounds checking checks accesses allocated block memory go beyond actually allocated space tagging ensures memory allocated storing data contain executable code overfilling buffer allocated stack likely influence program execution overfilling buffer heap stack contains return addresses active function calls however similar implementation-specific protections also exist heap-based overflows several implementations buffer overflow protection including gnu compiler collection llvm microsoft visual studio compilers stack buffer overflow occurs program writes memory address program call stack outside intended data structure usually fixed-length buffer stack buffer overflow bugs caused program writes data buffer located stack actually allocated buffer almost always results corruption adjacent data stack cases overflow triggered mistake often cause program crash operate incorrectly stack buffer overflow type general programming malfunction known buffer overflow buffer overrun overfilling buffer stack likely derail program execution overfilling buffer heap stack contains return addresses active function calls stack buffer overflow caused deliberately part attack known stack smashing affected program running special privileges accepts data untrusted network hosts example public webserver bug potential security vulnerability allows attacker inject executable code running program take control process one oldest reliable methods attackers gain unauthorized access computer typically buffer overflow protection modifies organization data stack frame function call include canary value destroyed shows buffer preceding memory overflowed provides benefit preventing entire class attacks according researchers performance impact techniques negligible stack-smashing protection unable protect certain forms attack example protect buffer overflows heap sane way alter layout data within structure structures expected modules especially shared libraries data structure buffer impossible protect canaries thus programmers must careful organize variables use structures canaries canary words known values placed buffer control data stack monitor buffer overflows buffer overflows first data corrupted usually canary failed verification canary data therefore alert overflow handled example invalidating corrupted data canary value confused sentinel value terminology reference historic practice using canaries coal mines since would affected toxic gases earlier miners thus providing biological warning system canaries alternately known cookies meant evoke image broken cookie value corrupted three types canaries use terminator random random xor current versions stackguard support three propolice supports terminator random canaries terminator canaries use observation buffer overflow attacks based certain string operations end string terminators reaction observation canaries built null terminators cr lf -1 result attacker must write null character writing return address avoid altering canary prevents attacks using codice_1 methods return upon copying null character undesirable result canary known even protection attacker could potentially overwrite canary known value control information mismatched values thus passing canary check code executed soon specific processor return-from-call instruction random canaries randomly generated usually entropy-gathering daemon order prevent attacker knowing value usually logically possible plausible read canary exploiting canary secure value known need know it—the buffer overflow protection code case normally random canary generated program initialization stored global variable variable usually padded unmapped pages attempting read using kinds tricks exploit bugs read ram cause segmentation fault terminating program may still possible read canary attacker knows get program read stack random xor canaries random canaries xor-scrambled using part control data way canary control data clobbered canary value wrong random xor canaries vulnerabilities random canaries except read stack method getting canary bit complicated attacker must get canary algorithm control data order re-generate original canary needed spoof protection addition random xor canaries protect certain type attack involving overflowing buffer structure pointer change pointer point piece control data xor encoding canary wrong control data return value changed pointer control data return value changed without overflowing canary although canaries protect control data altered clobbered pointers protect data pointers function pointers especially problem overflowed execute shellcode called bounds checking compiler-based technique adds run-time bounds information allocated block memory checks pointers run-time c c++ bounds checking performed pointer calculation time dereference time implementations approach use either central repository describes allocated block memory fat pointers contain pointer additional data describing region point tagging compiler-based hardware-based requiring tagged architecture technique tagging type piece data memory used mainly type checking marking certain areas memory non-executable effectively prevents memory allocated store data containing executable code also certain areas memory marked non-allocated preventing buffer overflows historically tagging used implementing high-level programming languages appropriate support operating system tagging also used detect buffer overflows example nx bit hardware feature supported intel amd arm processors stack-smashing protection first implemented stackguard 1997 published 1998 usenix security symposium stackguard introduced set patches intel x86 backend gcc 2.7 stackguard maintained immunix linux distribution 1998 2003 extended implementations terminator random random xor canaries stackguard suggested inclusion gcc 3.x gcc 2003 summit proceedings never achieved 2001 2005 ibm developed gcc patches stack-smashing protection known propolice improved idea stackguard placing buffers local pointers function arguments stack frame helped avoid corruption pointers preventing access arbitrary memory locations redhat engineers identified problems propolice though 2005 re-implemented stack-smashing protection inclusion gcc 4.1 work introduced -fstack-protector flag protects vulnerable functions -fstack-protector-all flag protects functions whether need 2012 google engineers implemented -fstack-protector-strong flag strike better balance security performance flag protects kinds vulnerable functions -fstack-protector every function providing better performance -fstack-protector-all available gcc since version 4.9 fedora packages compiled -fstack-protector since fedora core 5 -fstack-protector-strong since fedora 20 packages ubuntu compiled -fstack-protector since 6.10 every arch linux package compiled -fstack-protector since 2011 arch linux packages built since use -fstack-protector-strong stack protection used packages debian freebsd base system since 8.0 stack protection standard certain operating systems including openbsd hardened gentoo dragonfly bsd stackguard propolice protect overflows automatically allocated structures overflow function pointers propolice least rearrange allocation order get structures allocated function pointers separate mechanism pointer protection proposed pointguard available microsoft windows compiler suite microsoft implements buffer overflow protection since version 2003 command-line switch enabled default since version 2005 using disables protection stack-smashing protection turned compiler flag codice_2 clang supports three buffer overflow detectors namely addresssanitizer -fsanitize=address -fsanitize=bounds safecode systems different tradeoffs terms performance penalty memory overhead classes detected bugs stack protection standard certain operating systems including openbsd intel c c++ compiler supports stack-smashing protection options similar provided gcc microsoft visual studio fail-safe c open-source memory-safe ansi c compiler performs bounds checking based fat pointers object-oriented memory access invented mike frantzen stackghost simple tweak register window spill/fill routines makes buffer overflows much difficult exploit uses unique hardware feature sun microsystems sparc architecture deferred on-stack in-frame register window spill/fill detect modifications return pointers common way exploit hijack execution paths transparently automatically protecting applications without requiring binary source modifications performance impact negligible less one percent resulting gdb issues resolved mark kettenis two years later allowing enabling feature following event stackghost code integrated optimized openbsd/sparc normal buffer allocation x86 architectures similar architectures shown buffer overflow entry show modified process pertains stackguard function called stack frame created stack frame built end memory beginning stack frame placed top stack closest beginning memory thus running end piece data stack frame alters data previously entered stack frame running end stack frame places data previous stack frame typical stack frame may look return address reta placed first followed control information ctli c function may contain many different per-call data structures piece data created call placed stack frame order thus ordered end beginning memory hypothetical function stack frame hypothetical situation ten bytes written array 13 character array excess overflow integer pointer integer control information finally return address overwriting pointer made reference position memory causing read arbitrary address overwriting reta function made execute code attempts return either existing functions ret2libc code written stack overflow nutshell poor handling unbounded strcpy calls may allow attacker control program influencing values assigned directly goal buffer overflow protection detect issue least intrusive way possible done removing harms way placing sort tripwire canary buffer buffer overflow protection implemented change compiler possible protection alter structure data stack frame exactly case systems propolice function automatic variables rearranged safely arrays allocated first stack frame places integer integer pointer memory stack frame becomes impossible move ctli reta without breaking produced code another tactic employed extra piece information called canary cnry placed buffers stack frame buffers overflow canary value changed thus effectively attack program attacker must leave definite indication attack stack frame end every function instruction continues execution memory address indicated reta instruction executed check cnry ensures altered value cnry fails test program execution ended immediately essence deliberate attacks inadvertent programming bugs result program abort canary technique adds instructions overhead every function call automatic array immediately dynamic buffer allocation dynamic buffer deallocation overhead generated technique significant work though unless canary remains unchanged attacker knows determine value canary may simply copy usually difficult arrange intentionally highly improbable unintentional situations position canary implementation specific always buffers protected data varied positions lengths varied benefits
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Computer security
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agnes meyer driscoll agnes meyer driscoll july 24 1889 – september 16 1971 known miss aggie madame x american cryptanalyst world war world war ii born geneseo illinois 1889 driscoll moved family westerville ohio 1895 father gustav meyer taken job teaching music otterbein college 1909 donated family home anti-saloon league recently moved headquarters westerville home later donated westerville public library home anti-saloon league museum westerville local history center driscoll attended otterbein college 1907 1909 1911 received bachelor arts degree ohio state university majored mathematics physics studied foreign languages statistics music fluent english french german latin japanese earliest days college student pursued technical scientific studies graduation moved amarillo texas lived 1911 1918 worked director music military academy later chair mathematics department local high school june 22 1918 one year america entered world war driscoll enlisted united states navy – america started allowing women enlist recruited highest possible rank chief yeoman stint postal cable censorship office assigned code signal section director naval communications war ended made use option continue working post civilian except two-year hiatus worked private firm would remain leading cryptanalyst u.s. navy 1949 1920 continuing work navy driscoll studied riverbank laboratories geneva illinois fellow code breakers including william f. friedman elizebeth smith friedman worked known also worked american black chamber run herbert yardley first u.s. peacetime code-breaking agency set break codes used diplomatic correspondence efforts limited manual systems involved also emerging machine technology time applied making breaking ciphers first days code signal section co-developed one u.s. navy cipher machines cm cipher machine would become standard enciphering device navy 1920s recognition work united states congress awarded driscoll 15,000 split widow machine coinventor william greshem 1923 inventor edward hebern creator fledgling hebern electric code company attempting create secure rotor-driven cipher machine driscoll left navy test machine failed deliver secure encryption system agnes returned navy spring 1924 august 1924 married michael driscoll washington d.c. lawyer driscoll alongside lieutenant joseph rochefort broke japanese navy manual code red book code 1926 three years work helped broke blue book code 1930 early 1935 agnes driscoll led attack japanese m-1 cipher machine also known u.s. orange machine used encrypt messages japanese naval attaches around world 1939 made important inroads jn-25 japanese fleet operational code used important messages successfully solved cipher component 5-num system used number groups substitutes words numbers encrypted digital cipher navy could read standard format messages weather reports bulk messages remained discovered work later developed exploited attack pearl harbor rest pacific war provided advance warning japanese attack midway atoll would unable take part work october 1940 transferred team working break german naval enigma cipher period driscoll mentored following naval cryptographers getting work jn-25 started driscoll transferred new group attacked german enigma ciphers using catalog approach similar rainbow tables almost two years work new assignment driscoll team unable make progress solving german device partly due unwillingness use machine support mathematical approach also refused help british code breakers bletchley park traveled united states advise besides u.s. u.k. communicate effectively approach fruitless tried british determined unlikely work ultimately work superseded us-uk cryptologic exchanges 1942–43 1943 worked team break japanese cipher coral broken two months later although driscoll said little influence project 1945 appears worked attacking russian ciphers driscoll part navy contingent joined new national cryptologic agencies firstly armed forces security agency 1949 national security agency 1952 armed forces security agency may contributed attacking cipher called venona 1946 retirement national security agency filled number positions advanced ranks senior leadership retired armed forces security agency 1959 died 1971 buried arlington national cemetery 2000 inducted national security agency hall honor 2017 ohio historical marker placed front meyer home westerville honoring agnes meyer driscoll achievements
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Computer security
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phpldapadmin phpldapadmin web app administering lightweight directory access protocol ldap servers written php programming language licensed gnu general public license application available 14 languages supports utf-8 encoded directory strings project began fall 2002 dave smith student brigham young university byu lead developer needed robust web application manage ldap servers originally phpldapadmin called davedap august 2003 name changed phpldapadmin since time software downloaded approximately 150 times per day commonly used throughout world two developers contributed code base xavier renard uwe ebel xavier focused ldif imports/exports samba software integration uwe focused internationalizing application spring 2005 deon george took maintenance phpldapadmin due long period starting 2016 new pull requests merged master project releases made several forks exist implement new compatibilities functionality since spring 2019 new development going many pull requests merged project restoring compatibility recent php releases following linux distributions include phpldapadmin official software repositories available extra packages enterprise linux epel repository allowing managed installation distributions red hat enterprise linux fedora centos scientific linux included m23 software distribution system manages distributes software debian ubuntu kubuntu xubuntu linux mint fedora centos opensuse distributions also available repositories freebsd openbsd solaris
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Databases
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open relay behavior-modification system open relay behavior-modification system orbs created run alan brown new zealand one first dns-based blackhole lists dnsbl means internet domain may publish list ip addresses database easily queried automatically computer programs internet orbs list used blacklist ip addresses open mail relays third-party mail servers spammers relay messages thus attempt obfuscate source spam orbs list controversial number reasons many people felt methods orbs employed scan internet open mail servers could abusive orbs used probes test open relays without permission sometimes claimed testing networks continued even asked orbs stop others claimed relayed spam n't stop either cases tests interfered mail servers causing delays especially servers assigned hundreds ip addresses related testing regime excessive eyes number email administrators brown policy adding servers unable test list whether actually open relays also matter dispute another complaint open relays never sent spam listed without notice false listings orbs also alleged particularly brown engaged legal dispute listed party website created 2001 brad baker called stoporbs.org offer assistance mail administrators listed orbs blacklist reasons open relays many administrators felt listing servers reasons advertised open relays list reliable supposed purpose orbs created run alan brown new zealand shut 2001 due brown health money issues two lawsuits brought companies listed orbs xtra actrix refused remove companies listed orbs blocked probes kept relaying spam brown forced sell internet service provider manawatu internet services cover expenses state companies listed inappropriately brown also defamation lawsuit brought o'brien v brown court ruled brown made defamatory comments patrick o'brien ceo domainz .nz domain registrar comments made domainz discussion group brown offered chance apologize made additional defamatory comments following o'brien victory awarding 42,000 brown claimed net worth 500 said lawyer several groups cached lists retested open relays replaced orbs running open relay became even bigger problem dnsbls listing open relays got effective spammers shifted insecure proxy servers internet society new zealand council seats subsequently domainz board filled rebel members elections july 2000 o'brien departed run singapore internet registry
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Computer security
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fedora unity fedora unity community project build comprehensive concise websites content provide fedora users contributors quality information submissions project covered open publication license options unless otherwise noted order allow submission fedora documentation project fedora unity project produces iso images i386 x86_64 architectures available jigdo downloads containing slipstreamed installation media last release fedora 12 re-spins-20100303 released march 19 2010 re-spin isos based officially released fedora 12 installation media include updates released march 3 2010
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Operating systems
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filzip filzip freeware file archiver program microsoft windows platform written philipp engel free author request donations help cost development reward work march 2019 new version released since version 3.0.6 filzip presumed unmaintained software development program localized twenty languages filzip supports seven different archive formats allowing user add extract files archives include zip bh cab jar lha lzh tar gzip handful formats supported extraction including ace arc arj rar zoo files within formats viewed without explicitly unpacking removed renamed within archive zip files may spanned written number files fixed maximum size placed removable media program integration create self-extracting executable archives redistribution without licensing fees cnet rated 4/5 stars wrote easy program operation sets freeware file compression tool apart crowded genre
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Computer file systems
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sox operating system sox name unix clone developed scratch brazil late 1980s computadores e sistemas brasileiros s/a cobra tecnologia leadership ivan da costa marques certified unix-compatible x/open unisoft early 1989 sox one first re-implementation unix fully independent passed x/open verification tests one ever completed 100 outside united states sox designed run cobra minicomputers part brazilian informatics policy aimed achieve technological independence united states despite technical success sox came late cobra largely lost support sox development stopped soon certified government decided instead allow import unix system v release 4.0
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Operating systems
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webfinger webfinger protocol specified internet engineering task force ietf allows discovery information people things identified uri information person might discovered via acct uri example uri looks like email address webfinger specified discovery protocol openid connect protocol allows one easily log various sites internet webfinger protocol used federated social networks gnu social statusnet diaspora discover users federated nodes pods well remotestorage protocol historical note name webfinger derived old arpanet finger protocol different protocol designed http protocol payload represented json
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Internet protocols
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anti-spam techniques various anti-spam techniques used prevent email spam unsolicited bulk email technique complete solution spam problem trade-offs incorrectly rejecting legitimate email false positives opposed rejecting spam false negatives – associated costs time effort cost wrongfully obstructing good mail anti-spam techniques broken four broad categories require actions individuals automated email administrators automated email senders employed researchers law enforcement officials number techniques individuals use restrict availability email addresses goal reducing chance receiving spam sharing email address among limited group correspondents one way limit chance address harvested targeted spam similarly forwarding messages number recipients n't know one another recipient addresses put bcc field recipient get list recipients email addresses email addresses posted webpages usenet chat rooms vulnerable e-mail address harvesting address munging practice disguising e-mail address prevent automatically collected way still allow human reader reconstruct original email address nowiki no-one example.com /nowiki might written no-one example dot com instance related technique display part email address image jumbled text order characters restored using css common piece advice reply spam messages spammers may simply regard responses confirmation email address valid similarly many spam messages contain web links addresses user directed follow removed spammer mailing list – treated dangerous case sender addresses often forged spam messages responding spam may result failed deliveries – may reach completely innocent third parties businesses individuals sometimes avoid publicising email address asking contact come via contact form webpage – typically forwards information via email forms however sometimes inconvenient users able use preferred email client risk entering faulty reply address typically notified delivery problems contact forms drawback require website appropriate technology many modern mail programs incorporate web browser functionality display html urls images avoiding disabling feature help avoid spam may however useful avoid problems user opens spam message offensive images tracked web bugs targeted javascript attacks upon security vulnerabilities html renderer mail clients automatically download display html images attachments fewer risks clients configured display default email user may sometimes need give address site without complete assurance site owner use sending spam one way mitigate risk provide disposable email address — address user disable abandon forwards email real account number services provide disposable address forwarding addresses manually disabled expire given time interval expire certain number messages forwarded disposable email addresses used users track whether site owner disclosed address security breach systems use ham passwords ask unrecognised senders include email password demonstrates email message ham spam message typically email address ham password would described web page ham password would included subject line email message appended username part email address using plus addressing technique ham passwords often combined filtering systems let messages identified ham tracking spammer isp reporting offense lead spammer service terminated criminal prosecution unfortunately difficult track spammer online tools spamcop network abuse clearinghouse assist always accurate historically reporting spam way played large part abating spam since spammers simply move operation another url isp network ip addresses many countries consumers may also forward unwanted deceptive commercial email authorities e.g us email address spam uce.gov maintained us federal trade commission ftc similar agencies countries large number applications appliances services software systems email administrators use reduce load spam systems mailboxes general attempt reject block majority spam email outright smtp connection stage accept message typically analyze content – may decide quarantine categorised spam number systems developed allow domain name owners identify email authorized many systems use dns list sites authorized send email behalf many proposals spf dkim dmarc widely supported growing adoption directly attacking spam systems make much harder spoof addresses common technique spammers also used phishing types fraud via email method may used internet service providers specialized services enterprises combat spam require unknown senders pass various tests messages delivered strategies termed challenge/response systems checksum-based filter exploits fact messages sent bulk identical small variations checksum-based filters strip everything might vary messages reduce remains checksum look checksum database distributed checksum clearinghouse collects checksums messages email recipients consider spam people button email client click nominate message spam checksum database message likely spam avoid detected way spammers sometimes insert unique invisible gibberish known hashbusters middle messages make message unique checksum email servers expect never communicate particular countries receive great deal spam therefore use country-based filtering – technique blocks email certain countries technique based country origin determined sender ip address rather trait sender large number free commercial dns-based blacklists dnsbls allow mail server quickly look ip incoming mail connection reject listed administrators choose scores dnsbls reflects different policies list sites known emit spam others list open mail relays proxies others list isps known support spam spam/phishing messages contain url entice victims clicking thus popular technique since early 2000s consists extracting urls messages looking databases spamhaus domain block list dbl surbl uribl many spammers use poorly written software unable comply standards legitimate control computer using send spam zombie computer setting tighter limits deviation rfc standards mta accept mail administrator reduce spam significantly also runs risk rejecting mail older poorly written configured servers greeting delay – sending server required wait received smtp greeting banner sends data deliberate pause introduced receiving servers allow detect deny spam-sending applications wait receive banner temporary rejection – greylisting technique built fact smtp protocol allows temporary rejection incoming messages greylisting temporarily rejects messages unknown senders mail servers – using standard 4xx error codes compliant mtas proceed retry delivery later many spammers spambots downside legitimate messages first-time senders experience delay delivery helo/ehlo checking – says smtp server may verify domain name argument ehlo command actually corresponds ip address client however verification fails server must refuse accept message basis systems however configured invalid pipelining – several smtp commands allowed placed one network packet pipelined example email sent cc header several smtp rcpt commands might placed single packet instead one packet per rcpt command smtp protocol however requires errors checked everything synchronized certain points many spammers send everything single packet since care errors efficient mtas detect invalid pipelining reject email sent way nolisting – email servers given domain specified prioritized list via mx records nolisting technique simply adding mx record pointing non-existent server primary i.e lowest preference value – means initial mail contact always fail many spam sources retry failure spammer move next victim legitimate email servers retry next higher numbered mx normal email delivered brief delay quit detection – smtp connection always closed quit command many spammers skip step spam already sent taking time properly close connection takes time bandwidth mtas capable detecting whether connection closed correctly use measure trustworthy system another approach simply imitation mta gives appearance open mail relay imitation tcp/ip proxy server gives appearance open proxy spammers probe systems open relays/proxies find host attempt send mail wasting time resources potentially revealing information origin spam sending entity operates honeypot system may simply discard spam attempts submit dnsbls store analysis spamassassin policyd-weight others use various tests spam assigns numerical score test message scanned patterns applicable scores tallied total fixed value message rejected flagged spam ensuring single spam test flag message spam false positive rate greatly reduced outbound spam protection involves scanning email traffic exits network identifying spam messages taking action blocking message shutting source traffic primary impact spam spam recipients sending networks also experience financial costs wasted bandwidth risk ip addresses blocked receiving networks outbound spam protection stops spam also lets system administrators track spam sources network remediate – example clearing malware machines become infected virus participating botnet ptr dns records reverse dns used number things including content filtering techniques rely specification lists words regular expressions disallowed mail messages thus site receives spam advertising herbal viagra administrator might place phrase filter configuration mail server would reject message containing phrase header filtering looks header email contains information origin destination content message although spammers often spoof fields header order hide identity try make email look legitimate many spoofing methods detected violation rfc 5322 standard header formed also serve basis rejecting message since large percentage spam forged invalid sender addresses spam detected checking address valid mail server try verify sender address making smtp connection back mail exchanger address creating bounce stopping email sent callback verification various drawbacks 1 since nearly spam forged return addresses nearly callbacks innocent third party mail servers unrelated spam 2 spammer uses trap address sender address receiving mta tries make callback using trap address mail command receiving mta ip address blacklisted 3 finally standard vrfy expn commands used verify address exploited spammers mail administrators enable leaving receiving smtp server effective way validate sender email address smtp proxies allow combating spam real time combining sender behavior controls providing legitimate users immediate feedback eliminating need quarantine spamtrapping seeding email address spammers find normal users email address used sender must spammer black listed example email address spamtrap example.org placed source html web site way n't displayed web page human visitors website would see spammers hand use web page scrapers bots harvest email addresses html source code would find address spammer later sends address spamtrap knows highly likely spammer take appropriate action statistical bayesian filtering set requires administrative maintenance per se instead users mark messages spam nonspam filtering software learns judgements thus matched end user needs long users consistently mark/tag emails respond quickly changes spam content statistical filters typically also look message headers considering content also peculiarities transport mechanism email software programs implement statistical filtering include bogofilter dspam spambayes assp crm114 email programs mozilla mozilla thunderbird mailwasher later revisions spamassassin tarpit server software intentionally responds extremely slowly client commands running tarpit treats acceptable mail normally known spam slowly appears open mail relay site slow rate spammers inject messages mail facility depending server internet speed tarpit slow attack factor around 500 many systems simply disconnect server n't respond quickly eliminate spam however legitimate email systems also deal correctly delays fundamental idea slow attack perpetrator waste time without significant success organization successfully deploy tarpit able define range addresses protocols ports deception process involves router passing supported traffic appropriate server sent contacts sent tarpit examples tarpits include labrea tarpit honeyd smtp tarpits ip-level tarpits variety techniques email senders use try make sure send spam failure control amount spam sent judged email receivers often cause even legitimate email blocked sender put dnsbls since spammer accounts frequently disabled due violations abuse policies constantly trying create new accounts due damage done isp reputation source spam many isps web email providers use captchas new accounts verify real human registering account automated spamming system also verify credit cards stolen accepting new customers check spamhaus project rokso list background checks malicious person easily attempt subscribe another user mailing list — harass make company organisation appear spamming prevent modern mailing list management programs gnu mailman listserv majordomo qmail ezmlm support confirmed opt-in default whenever email address presented subscription list software send confirmation message address confirmation message contains advertising content construed spam address added live mail list unless recipient responds confirmation message email senders typically type anti-spam checks email coming users customers inward email coming rest internet protects reputation could otherwise harmed case infection spam-sending malware receiving server initially fully accepts email later determines message spam non-existent recipient generate bounce message back supposed sender however often case spam sender information incoming email forged unrelated third party bounce message backscatter spam reason generally preferable rejection incoming email happen smtp connection stage 5xx error code sending server still connected case sending server report problem real sender cleanly firewalls routers programmed allow smtp traffic tcp port 25 machines network supposed run mail transfer agents send email practice somewhat controversial isps block home users especially isps allow blocking turned upon request email still sent computers designated smart hosts via port 25 smart hosts via email submission port 587 network address translation used intercept port 25 smtp traffic direct mail server enforces rate limiting egress spam filtering commonly done hotels cause email privacy problems well making impossible use starttls smtp-auth port 587 submission port n't used machines suddenly start sending lots email may well become zombie computers limiting rate email sent around typical computer question legitimate email still sent large spam runs slowed manual investigation done monitoring spam reports places spamcop aol feedback loop network abuse clearinghouse domain abuse mailbox etc. isps often learn problems seriously damage isp reputation mail servers blacklisted malicious software human spam senders often use forged addresses sending spam messages control may enforced smtp servers ensure senders use correct email address field outgoing messages email users database user record email address smtp server must check email address field outgoing message address belongs user credentials supplied smtp authentication field forged smtp error returned email client e.g email address trying send isps webmail providers either acceptable use policy aup terms service tos agreement discourages spammers using system allows spammer terminated quickly violations 2000 onwards many countries enacted specific legislation criminalize spamming appropriate legislation enforcement significant impact spamming activity legislation provides specific text bulk emailers must include also makes legitimate bulk email easier identify increasingly anti-spam efforts led co-ordination law enforcement researchers major consumer financial service companies internet service providers monitoring tracking email spam identity theft phishing activities gathering evidence criminal cases analysis sites spamvertised given piece spam often followed domain registrars good results several approaches proposed improve email system since spamming facilitated fact large volumes email inexpensive send one proposed set solutions would require senders pay cost order send email making prohibitively expensive spammers anti-spam activist daniel balsam attempts make spamming less profitable bringing lawsuits spammers artificial intelligence techniques deployed filtering spam emails artificial neural networks algorithms bayesian filters methods use probabilistic methods train networks examination concentration frequency words seen spam versus legitimate email contents channel email new proposal sending email attempts distribute anti-spam activities forcing verification probably using bounce messages back-scatter occur first email sent new contacts spam subject several research conferences including
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Computer security
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openmoko linux openmoko linux operating system smartphones developed openmoko project based ångström distribution comprising various pieces free software main targets openmoko linux openmoko neo 1973 neo freerunner furthermore efforts port system mobile phones openmoko linux developed 2007 2009 openmoko inc development discontinued financial problems afterwards development software openmoko phones taken community continued various projects including shr qtmoko hackable1 openmoko linux uses linux kernel gnu libc x.org server plus graphical user environment built using efl toolkit gtk+ toolkit qt toolkit illume window manager previously matchbox window manager openembedded build framework opkg package management system used create maintain software packages different approach android everything except linux webkit java language inside android seems non-standard applications targeted android must substantially rewritten largely portable many existing gnu/linux desktop apps easily ported openmoko however limited computational power screen resolution require substantial reworking existing applications order render usable finger-oriented small-screen environment
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Operating systems
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eia-530 currently known tia-530-a often called eia-530 rs-530 balanced serial interface standard generally uses 25-pin connector originally created telecommunications industry association finalized 1987 revision finalized 1992 specification defines cable dte dce devices used conjunction eia-422 eia-423 define electrical signaling characteristics tia-530 calls common 25 pin connector displaced similar eia-449 also uses eia-422/423 larger 37-pin connector two types interchange circuits signals leads dce dte defined tia-530 category uses balanced characteristics eia-422 category ii unbalanced eia-423 interchange circuits category exception local loopback pin 18 remote loopback pin 21 test mode pin 25 category ii tia-530 originally used category circuits commonly called data set ready dce ready pins 6 22 data terminal ready dte ready pins 20 23 revision changed interchange circuits category ii para 4.3.6 4.3.7 standard added ring indicator pin 22 pin 23 grounded tia-530-a confusion revisions led many incorrect wiring diagrams interface manufacturers still adhere original tia-530 standard care taken ensure devices standard connecting avoid complications
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Internet protocols
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compaq presario presario series desktop computers notebooks compaq presario family computers launched consumer marketplace september 1993 mid-1990s compaq began manufacturing pc monitors part presario brand series all-in one units containing pc monitor case also released although hp acquired compaq 2002 presario name used compaq brand discontinued 2013 hp due marketability issues all-in-one computers containing pc monitor unit mvx00 fpx00 monitors designed sold series 3 designed compaq towers retained original spaceship shape second generation compaq presario towers except smoked-black plastic flip-up doors slightly squatter design rounded generation 2 presario towers lacked smoked plastic easy access door usb audio ports behind black smoked cd bezel covers fp meant flat panel display one first offered home pc 1x25 monitors paired presario 4500 4600 4800 series 2 designed compaq presarios originators rocket ship shape tower faceplate monitors shared design cues split lower bezel ran middle like towers meant match rare set monitors fx series built-in speakers subwoofer three extra usb ports designed go 4800 series presario multimedia towers—specifically 4830 4882 black like fx monitor monitors came jbl pro speakers could mount side monitor fx exception built-in jbl pro powered speakers subwoofer rear casing
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Computer architecture
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gigamon gigamon privately held network visibility traffic monitoring technology vendor formerly traded publicly owned elliott management headquartered santa clara california gigamon 371 employees december 27 2014 743 employees april 2017 company proprietary products manipulate route traffic various application performance network management analysis compliance security tools gigamon founded 2004 gigamon systems llc company went public new york stock exchange june 11 2013 initial public offering june 12 2013 investors bought 6.75 million shares priced 19 generating 128 million sales gigamon officials rang closing bell new york stock exchange february 24 2016 january 2018 company acquired elliott management corporation qatar investment authority qia 1,6 billion us gigamon develops physical virtual network visibility technologies including network tap aggregation products traffic manipulation applications visibility fabric nodes
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Computer security
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daniel p. friedman daniel paul friedman born 1944 professor computer science indiana university bloomington indiana research focuses programming languages prominent author field david wise friedman wrote highly influential paper lazy programming specifically lazy streams icalp 1976 paper entitled cons evaluate arguments one first publications pushing exploration programming style potentially infinite data structures form programming employs computational effects though programs may diverge 1970s friedman wise explored topic depth also considered extensions world parallel computing 1980s friedman turned study scheme programming language explored use macros defining programming languages eugene kohlbecker matthias felleisen bruce duba co-introduced notion hygienic macros 1986 lfp paper still widely cited today christopher t. haynes mitchell wand simultaneously studied nature continuation objects uses possibilities constraining following friedman felleisen introduced lambda calculus continuations control operators work spawned work semantics connections classical logic computation practical extensions continuations friedman also prolific textbook author first textbook little lisper dates back 1974 still print fourth edition called little schemer felleisen friedman felleisen wrote three little books 1990s little mler seasoned schemer little java patterns friedman also lead author essentials programming languages textbook programming languages changed landscape language textbooks 1980s shifting focus surveys languages study principles via series interpreters today textbooks topic tend follow organization employing operational semantics type theory instead interpreters like little lisper essentials programming languages long-living book third edition recently friedman resumed work little series reasoned schemer william e. byrd oleg kiselyov explaining logic programming via extension scheme little prover carl eastlund introducing inductive proofs way determine facts computer programs daniel p. friedman author co-author following books
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Programming language topics
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hdclone hdclone disk cloning backup application miray software supports copying storage devices sector-by-sector well file-by-file allows create physical logical identical copy supported x86 x64 computer architectures windows desktop versions xp 10 windows server versions 2003 2016 hdclone offered free download pay version may also purchased data cd license model freemium price policy hdclone home users professional users hdclone offered seven languages website focuses german english several hundred thousand users worldwide sold 140 countries primary aim hdclone cloning storage devices creating restoring storage device images generally possible start hdclone directly windows stand-alone boot media boot media possible implement bare-metal restore windows hdclone offers command-line interface allows automatic control e.g combination windows task scheduler enterprise edition possible write 16 storage devices separate tool miray virtual disk possible mount images windows virtual drives order access content hdclone offered several editions free edition free charge offers basic functionality cloning creating respectively restoring images additional functionalities higher editions must purchased additional functions include others depending edition hdclone following additional software modules hdclone supports edition-dependent following functionalities listed file systems possible make usb drive optical medium bootable order start hdclone independently windows also allows copy operating systems hdclone executable file ca n't started uses either miray symobi linux host operating system symobi proprietary real-time operating system miray software sole base starting hdclone via boot media first 5 years hdclone 3.5 symobi based message-oriented operating system µnos based real-time kernel sphere µnos version 0.92 officially presented 1 august 2001 intermediately sphere sp 2.0 released 14 may 2002 symobi presented first time version 1.2 systems fair munich year 2006 following year version 1.4 multi-core support 32 processor cores separate tool miray virtual disk possible mount hdclone created images windows virtual drives allows access contained data via windows explorer depending edition possible mount 1 7 images time optionally permanently writeable content mounted image changed changes stored overlay functions differential image may also included restoring respective image 31 march 2003 hdclone version 1.0 announced 25 april 2003 hdclone officially presented hdclone started stand-alone product required boot media start five years version 3.6 also possible start hdclone directly windows however parallel writing multiple storage devices already realised enterprise edition one year 2010 came version 3.9 command-line interface automatic control year miray virtual disk added separate tool version 4.0 allowed open hdclone images virtual storage devices first time four years version 5.0 equipped support sata hot plugging since 2017 possible use linux additional host operating system stand-alone boot media hdclone 7 various german computer magazines like pc magazin computerbild com computerwoche chip published tips use hdclone duplicating hard disk drive content internationally hdclone mainly described via digital journalism free edition praised german computer magazines clear simple user interface recommended copying small hard disk drives criticized limited left functionalities available paid versions reduced data transfer rate mentioned regard time time reports highlight practice boot media allows using hdclone independently installed operating system hdclone mentioned example disk cloning software international books international books use hdclone also case example disk cloning software detailed description
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Computer security
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master/slave technology master/slave model communication one device process unidirectional control one devices systems master selected group eligible devices devices acting role slaves context motor control master/slave configuration used load sharing purposes two identical motors connected two different drives coupled common load one drive defined master configured running speed-control mode whereas defined slave configured running torque-control mode terminology often replaced something different terms master slave allude practice slavery one alternative databases primary replica used documentation ibm microsoft engine yard amazon web services/amazon relational database service acm well python django drupal couchdb redis mediawiki still uses master configuration management tool salt uses terms master minion december 2017 internet systems consortium decided allow words primary secondary substitute master/slave terminology dns server software bind 2003 county los angeles california asked manufacturers suppliers contractors stop using master slave terminology products county made request based cultural diversity sensitivity los angeles county following outcries request county los angeles issued statement saying decision nothing request following controversy global language monitor found term master/slave egregious example political correctness 2004 named politically incorrect term year
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Distributed computing architecture
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binary large object binary large object blob collection binary data stored single entity database management system blobs typically images audio multimedia objects though sometimes binary executable code stored blob database support blobs universal blobs originally big amorphous chunks data invented jim starkey dec describes thing ate cincinnati cleveland whatever 1958 steve mcqueen movie referring blob later terry mckiever marketing person apollo felt needed acronym invented backronym basic large object informix invented alternative backronym binary large object data type definition introduced describe data originally defined traditional computer database systems particularly large store practically time field database systems first defined 1970s 1980s data type became practical disk space became cheap definition gained popularity ibm db2 term used nosql databases especially key-value store databases redis name blob borrowed deep learning software caffe represent multi-dimensional arrays world free open-source software term also borrowed refer proprietary device drivers distributed without source code exclusively binary code use term binary blob common even though first letter blob abbreviation already stands binary depending implementation culture around usage concept might alternately referred basic large object binary data type
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Databases
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bootx apple bootx software-based bootloader designed developed apple inc. use company macintosh computer range bootx used prepare computer use loading required device drivers starting-up mac os x booting kernel powerpc macintoshes running mac os x 10.2 operating system later versions using bootrom read-only memory rom computer chip containing openfirmware graphical bootsplash shown briefly compatible macintosh computers grey apple logo spinning cursor appears startup sequence program freely available part darwin operating system open-source apple public source license bootx superseded another nearly identical bootloader named codice_1 extensible firmware interface rom release intel-based mac older macintoshes dating 1983 1998 utilized basic bootloader bootloader solely rom chip varying sizes 4 megabytes mb contained computer code boot computer run mac os operating system known macintosh toolbox old world rom differs greatly design modern macintosh generally use hard drive large capacity store operating system bootloader used macintosh computers mid-1998 advent imac series macintoshes firmware updated rom reduced size 1 mb called bootrom remainder rom moved file codice_2 mac os system folder stored hard drive rom used full implementation openfirmware standard contained bootrom named new world rom 2001 release mac os x 10.0 codice_2 file replaced codice_4 bootloader file 2002 release mac os x 10.2 historical happy mac start-up picture replaced grey apple logo introducing intel mac 2006 bootrom replaced near identical extensible firmware interface rom although apple still calls bootrom codice_1 file make boot loader appealing operating system developers apple added features allow flexibility booting process network boot using tftp load mach-o elf formatted kernels bootx also boot hfs hfs+ ufs ext2 formatted volumes boot loader manipulated startup holding various key combinations alter booting process functions include verbose mode achieved holding command v key startup replaces default apple logo text-based information boot process single user mode achieved holding command depending operating system may boot basic command-line text-based version operating system facilitate maintenance recovery action rom also set require password access technical functions using openfirmware interface powerpc-based macintoshes boot process starts activation bootrom basic macintosh rom performs power self test test hardware essential startup passing test startup chime played control computer passed openfirmware openfirmware initializes random access memory memory management unit hardware necessary rom operation openfirmware checks settings stored nvram builds list devices device tree gathering stored fcode information completion task bootx takes startup process configuring keyboard display claiming reserving memory various purposes checking see various key combinations pressed process completed bootx displays grey apple logo spins spinning wait cursor proceeds load kernel kernel extensions start kernel
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Operating systems
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multics multics multiplexed information computing service influential early time-sharing operating system based concept single-level memory virtually modern operating systems heavily influenced multics – often unix created people worked multics – either directly linux macos indirectly windows nt initial planning development multics started 1964 cambridge massachusetts originally cooperative project led mit project mac fernando corbató along general electric bell labs developed ge 645 computer specially designed first one delivered mit january 1967 multics conceived commercial product general electric became one honeywell albeit successfully due many novel valuable ideas multics significant impact computer science despite faults multics numerous features intended ensure high availability would support computing utility similar telephone electricity utilities modular hardware structure software architecture used achieve system could grow size simply adding appropriate resource computing power main memory disk storage separate access control lists every file provided flexible information sharing complete privacy needed multics number standard mechanisms allow engineers analyze performance system well number adaptive performance optimization mechanisms multics implemented single-level store data access discarding clear distinction files called segments multics process memory memory process consisted solely segments mapped address space read write process simply used normal central processing unit cpu instructions operating system took care making sure modifications saved disk posix terminology every file codice_1ed however multics concept process memory separate memory used hold mapped-in files unix memory system part segment appeared file system included temporary scratch memory process kernel stack etc one disadvantage size segments limited 256 kilowords 1 mib due particular hardware architecture machines multics ran 36-bit word size index registers used address within segments half size 18 bits extra code used work files larger called multisegment files days one megabyte memory prohibitively expensive large databases later huge bitmap graphics limit rarely encountered another major new idea multics dynamic linking running process could request segments added address space segments could contain code could execute allowed applications automatically use latest version external routine called since routines kept segments dynamically linked process first tried begin execution since different processes could use different search rules different users could end using different versions external routines automatically equally importantly appropriate settings multics security facilities code segment could gain access data structures maintained different process thus interact application running part daemon another process user process simply performed normal procedure-call instruction code segment dynamically linked code segment implemented operation associated daemon code segment could modify data maintained used daemon action necessary commence request completed simple procedure return instruction returned control user process user code multics also supported extremely aggressive on-line reconfiguration central processing units memory banks disk drives etc could added removed system continued operating mit system early software development done common practice split multiprocessor system two separate systems off-hours incrementally removing enough components form second working system leaving rest still running original logged-in users system software development testing could done second system components second system added back main user system without ever shut multics supported multiple cpus one earliest multiprocessor systems multics first major operating system designed secure system outset despite early versions multics broken repeatedly led work made system much secure prefigured modern security engineering techniques break-ins became rare second-generation hardware base adopted hardware support ring-oriented security multilevel refinement concept master mode multics first operating system provide hierarchical file system file names could almost arbitrary length syntax given file directory could multiple names typically long short form symbolic links directories also supported multics first use now-standard concept per-process stacks kernel separate stack security ring also first command processor implemented ordinary user code – idea later used unix shell also one first written high-level language multics pl/i burroughs mcp system written algol 1964 multics developed initially ge-645 mainframe 36-bit system ge computer business including multics taken honeywell 1970 around 1973 multics supported honeywell 6180 machines included security improvements including hardware support protection rings bell labs pulled project 1969 people worked went create unix system multics development continued mit general electric honeywell continued system development 1985 80 multimillion-dollar sites installed universities industry government sites french university system several installations early 1980s honeywell stopped supporting multics users migrated systems like unix 1985 multics issued certification b2 level secure operating system using trusted computer system evaluation criteria national computer security center ncsc division nsa first operating system evaluated level multics distributed 1975 2000 groupe bull europe bull hn information systems inc. united states 2006 bull sas open sourced multics versions mr10.2 mr11.0 mr12.0 mr12.1 mr12.2 mr12.3 mr12.4 mr12.5 last known multics installation running natively honeywell hardware shut october 30 2000 canadian department national defence halifax nova scotia canada 2006 bull hn released source code mr12.5 final 1992 multics release mit system available open-source software exception optional pieces tcp/ip 2014 multics successfully run current hardware using simulator 1.0 release simulator available release 12.6f multics accompanies 1.0 release emulator adds new features including command line recall editing using video system peter h. salus author book covering unix early years stated one position multics tried much versatile flexible operating system failed miserably position however widely discredited computing community many multics technical innovations used modern commercial computing systems permanently resident kernel multics system derided day large complex 135 kb code comparison linux system 2007 might occupied 18 mb first mit ge-645 512 kilowords memory 2 mib truly enormous amount time kernel used moderate portion multics main memory entire system including operating system complex pl/1 compiler user commands subroutine libraries consisted 1500 source modules averaged roughly 200 lines source code compiled produce total roughly 4.5 mib procedure code fairly large standards day multics compilers generally optimised code density cpu performance example using small sub-routines called operators short standard code sequences makes comparison object code size modern systems less useful high code density good optimisation choice multics multi-user system expensive main memory design features multics greatly influenced unix operating system originally written two multics programmers ken thompson dennis ritchie superficial influence multics unix evident many areas including naming commands internal design philosophy quite different focusing keeping system small simple correcting deficiencies multics high resource demands limited computer hardware time name unix originally unics pun multics u unix rumored stand uniplexed opposed multiplexed multics underscoring designers rejections multics complexity favor straightforward workable approach smaller computers garfinkel abelson cite alternative origin peter neumann bell labs watching demonstration prototype suggested pun name unics – pronounced eunuchs – castrated multics although dennis ritchie said denied ken thompson transcribed 2007 interview peter seibel refers multics overdesigned overbuilt everything close unusable massachusetts institute technology still claim monstrous success clearly n't admitted however things liked enough multics actually take hierarchical file system shell — separate process replace process prime computer operating system primos referred multics shoebox william poduska founder company poduska later moved found apollo computer whose aegis later domain/os operating systems sometimes called multics matchbox extended multics design heavily networked graphics workstation environment stratus vos operating system stratus computer stratus technologies strongly influenced multics external user interface internal structure bear many close resemblances older project high-reliability availability security features multics extended stratus vos support new line fault tolerant computer systems supporting secure reliable transaction processing stratus vos directly-related descendant multics still active development production usage today protection architecture multics restricting ability code one level system access resources another adopted basis security features icl vme operating system literature contains large number papers multics various components fairly complete list available multics bibliography page important and/or informative ones listed
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Operating systems
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marcus j. ranum marcus j. ranum born november 5 1962 new york city new york united states computer network security researcher credited number innovations firewalls including building first internet email server whitehouse.gov domain intrusion detection systems held technical leadership positions number computer security companies faculty member institute applied network security marcus ranum born new york city graduated gilman school baltimore maryland attending johns hopkins university obtained bachelor arts psychology 1985 ranum helped design implement digital equipment corporation secure external access link seal later altavista firewall regarded first commercial bastion host firewall 1990 left dec work trusted information systems tis chief scientist development manager internet security products tis ranum became responsible whitehouse.gov internet email site charged responsibility ranum advocated whitehouse.com domain registered well despite advice registered government later registered adult entertainment provider tis developed tis internet firewall toolkit fwtk grant darpa tis worked v-one chief scientist extensively involved company ipo three months ipo ranum formed company network flight recorder nfr served ceo three years stepping cto role ranum later left nfr consult trusecure joining tenable network security cso addition various full-time positions ranum also held board advisory positions nfr security protego networks fortify software ranum spoken usenix audiences lisa 1997 1999 tutorial lisa 2000 keynote 2002 2003 tutorial spoke full disclosure black hat security briefings 2000 recently ranum spoken interop 2005 2007 cansecwest 2010 secure360 2011 previously taught courses sans institute ranum work cited least 15 published u.s. patents well numerous computer network security articles books ranum cited author eponymous law ca n't solve social problems software marcus co-authored series face articles bruce schneier appeared approximately bi-monthly information security magazine since july 2006 ranum one number editors sans newsbites semiweekly email newsletter currently ranum lives morrisdale pennsylvania hobbies include photography firearms maintains active stock photography account deviantart wrote essay oleg volk pro-firearms site www.a-human-right.com marcus ranum also interviewed digital artist brandon pence nwflaa read 2 parts part 1 part 2 atheist maintaining blog freethought blogs network
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Computer security
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pyspark apache spark open-source distributed general-purpose cluster-computing framework released support python spark pyspark provides interface programming entire clusters implicit data parallelism fault tolerance following sub-packages provided following classes marked core classes sample code may look like follows
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Distributed computing architecture
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xquery xquery xml query query functional programming language queries transforms collections structured unstructured data usually form xml text vendor-specific extensions data formats json binary etc. language developed xml query working group w3c work closely coordinated development xslt xsl working group two groups share responsibility xpath subset xquery xquery 1.0 became w3c recommendation january 23 2007 xquery 3.0 became w3c recommendation april 8 2014 xquery 3.1 became w3c recommendation march 21 2017 xquery functional side effect-free expression-oriented programming language simple type system summed kilpeläinen xquery provides means extract manipulate data xml documents data source viewed xml relational databases office documents xquery contains superset xpath expression syntax address specific parts xml document supplements sql-like flwor expression performing joins flwor expression constructed five clauses named let order return language also provides syntax allowing new xml documents constructed element attribute names known advance xml-like syntax used cases expressions referred dynamic node constructors available constructs defined expressions within language arbitrarily nested language based xquery xpath data model xdm uses tree-structured model information content xml document containing seven kinds nodes document nodes elements attributes text nodes comments processing instructions namespaces xdm also models values sequences singleton value considered sequence length one items sequence either xml nodes atomic values atomic values may integers strings booleans full list types based primitive types defined xml schema features updating xml documents databases full text search capability part core language defined add-on extension standards xquery update facility 1.0 supports update feature xquery xpath full text 1.0 supports full text search xml documents xquery 3.0 adds support full functional programming functions values manipulated stored variables passed higher-order functions dynamically called sample xquery code lists unique speakers act shakespeare play hamlet encoded hamlet.xml xquery constructs performing computations expressions statements even though keywords appear suggest statement-like behaviors execute function expression within body evaluated value returned thus write function double input value one simply writes write full query saying 'hello world one writes expression style common functional programming languages examples xquery used although xquery initially conceived query language large collections xml documents also capable transforming individual documents capabilities overlap xslt designed expressly allow input xml documents transformed html formats xslt 2.0 xquery standards developed separate working groups within w3c working together ensure common approach appropriate share data model xdm type system function library include xpath 2.0 sublanguage two languages however rooted different traditions serve needs different communities xslt primarily conceived stylesheet language whose primary goal render xml human reader screen web web template language paper xquery primarily conceived database query language tradition sql two languages originate different communities xslt stronger handling narrative documents flexible structure xquery stronger data handling example performing relational joins xslt 1.0 appeared recommendation 1999 whereas xquery 1.0 became recommendation early 2007 result xslt still much widely used languages similar expressive power though xslt 2.0 many features missing xquery 1.0 grouping number date formatting greater control xml namespaces many features planned xquery 3.0 comparison must take account fact xslt 1.0 xslt 2.0 different languages xslt 2.0 particular heavily influenced xquery move strong typing schema-awareness usability studies shown xquery easier learn xslt especially users previous experience database languages sql attributed fact xquery smaller language fewer concepts learn fact programs concise also true xquery orthogonal expression used syntactic context contrast xslt two-language system xpath expressions nested xslt instructions vice versa xslt currently stronger xquery applications involve making small changes document example deleting note elements applications generally handled xslt use coding pattern involves identity template copies nodes unchanged modified specific templates modify selected nodes xquery equivalent coding pattern though future versions possible tackle problems using update facilities language development xquery 1.0 lacked kind mechanism dynamic binding polymorphism remedied introduction functions first-class values xquery 3.0 absence capability starts become noticeable writing large applications writing code designed reusable different environments xslt offers two complementary mechanisms area dynamic matching template rules ability override rules using codice_1 make possible write applications multiple customization layers absence facilities xquery 1.0 deliberate design decision consequence xquery amenable static analysis essential achieve level optimization needed database query languages also makes easier detect errors xquery code compile time fact xslt 2.0 uses xml syntax makes rather verbose comparison xquery 1.0 however many large applications take advantage capability using xslt read write modify stylesheets dynamically part processing pipeline use xml syntax also enables use xml-based tools managing xslt code contrast xquery syntax suitable embedding traditional programming languages java see xquery api java c necessary xquery code also expressed xml syntax called xqueryx xqueryx representation xquery code rather verbose convenient humans easily processed xml tools example transformed xslt stylesheets two major extensions xquery developed w3c reached recommendation status extensions xquery 1.0 work taking forward work xquery 3.0 abandoned lack resources work xquery 3.0 published recommendation 8 april 2014 xquery 3.1 recommendation february 2017 scripting procedural extension xquery designed never completed expath community group develops extensions xquery related standards xpath xslt xproc xforms following extensions currently available jsoniq extension xquery adds support extract transform data json documents jsoniq superset xquery 3.0 published creative commons attribution-sharealike 3.0 license exquery project develops standards around creating portable xquery applications following standards currently available portions borrowed permission books xml hacks o'reilly media xquery o'reilly media previous version based article
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Programming language topics
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dragon knight ii dragon knight ii ドラゴンナイトii fantasy-themed eroge role-playing video game dragon knight franchise originally developed published elf corporation 1990-1991 japan first sequel original dragon knight game 1989 game erotic dungeon crawler young warrior takeru fights lift witch curse turned girls monsters following commercial critical success dragon knight ii elf followed dragon knight iii knights xentar 1991 censored remake dragon knight ii published nec avenue 1992 dragon knight ii available japanese gameplay system changed much since first dragon knight game still standard dungeon crawler first-person view perspective 2d graphics player spends time navigating dungeon-like mazes fighting enemies progress made mazes become complicated first game aid player form mini-map grid coordinates player also visit shops converse non-hostile npcs game starts one player character takeru two characters join later game battle system also undergone minor changes still features turn-based battles mostly randomly generated fights better balanced first game player attack defend use spells items deal various types female enemies berserker banshee catgirl centaur elf harpy ninja mummy werewolf fought one time enemies actually girls transformed monsters whenever player character fights one subdued enemy loses clothing later enemies revert normal self gratitude offer sex protagonist cutscene censored console versions also one boss beat end characters voice actors include taverner totani koji weaponsmith yukitoshi hori old witch hiroyuki sato apothecary witch isamu tanonaka rem lisa hatayama mei noriko namiki messiah natsuko yamada merumo mayumi horikawa cherry akiko sato orchid azusa nakao mami kaori ohara hamy minako takenouchi rika tomomi uesaka monami masami suzuki mischa mihoko fujiwara tanya yasuko kajimura nadia yuki kato bunny junko shimakata mimi yoko asada paula naomi matamura betty yumiko sakita marie mayumi seto lina mayumi shigeno eve megumi kanba nina naoko nakamura lara yasuko hirayama game narrated kaneto shiozawa vagabond youth hero first dragon knight takeru yamato wanders small town phoenix finds terrorized devoid young men phoenix ruled group powerful wicked witches destroyed all-male dragon knights three years events game woman known mesaanya arrived phoenix first appeared friendly gained villagers trust healer revealed true colors took witch tower forbade love men women next morning takeru arrival sees town changed mesaanya steals set seven evil-sealing holy scriptures takeru delivered used possesses young maiden named kate also kidnaps 28 village girls turns minions guard witch tower reluctantly takeru decides enter tower collect scriptures break curse ultimate goal takeru defeat witch supposed wait top tower also needs rescue girls one one course game takeru joined burly merchant named baan originally sent phoenix mysterious spell-casting priestess named sophia also meets rescues kate fiancé young man neighboring town went first rescue kate without combat experience disappeared eventually bewitched girls saved time find mesaanya since witch throne room empty kate also found looking takeru learns witches conquered help special-metal falcon sword genji armor capable resisting magic searching artifacts party descends hidden dungeon town graveyard baan reveals ancestor fought witches killed queen mesaanya ancestor twist ending sophia true identity revealed really disguised mesaanya along magic blast gravely wounds baan shocked takeru revealed son god legendary armor set god could use wraps around decisive duel mesaanya slain kate finally freed spell peace restored village quest completed takeru spends night kate marry leaving adventures game originally released 1990-1991 msx2 nec pc-8801 nec pc-9801 x68000 computer systems enhanced pc engine port removed sexually explicit content added voice acting new graphics developed tamtam released nec avenue 1992 among controversies first erotic game officially published video game console two soundtracks released japan nec avenue dragon knight ii fantastic remix ドラゴンナイト ii ファンタスティック・リミックス october 1991 dragon knight ii pc engine world ドラゴンナイト ii ～ｐｃエンジンワールド 1992 distributed nippon columbia like predecessor dragon knight ii commercial success game placed third msx magazine msx soft top 30 best-selling chart may 1991 even one year later remained 28th place pc engine version fifth pc engine fan chart august 1992 magazine review gave highly positive score 90 famitsu gave score 24/40 electronic gaming monthly egm reported dragon knight ii became sleeper hit japanese role-playing fans made popular fact noticeably different rpgs game opted lots women instead beasts slight characteristics monsters predicting action scantily clad women attack sequel really entice japanese market egm also included game tons interesting people meet 1993 ranking top ten hottest video game babes second place pc engine fan listed mesaanya sophia kate among sexiest female characters pc engine games takeru renamed desmond west returns hero 1991 sequel dragon knight iii titled knights xentar highly rewritten western-localized versions phoenix takeru celebrity former witch tower renamed tower takeru honor revisited sequel fully recovered baan rejoins fight demons kate romantically met takeru uses falcon sword genji armor baan marries marie one girls dragon knight ii
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Computer architecture
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national transportation communications intelligent transportation system protocol national transportation communications intelligent transportation system protocol ntcip family standards designed achieve interoperability interchangeability computers electronic traffic control equipment different manufacturers nticp around 20 years increasingly use smart city initiatives suppliers technology example riders want know next bus arrive stop using apps use ntcip siemens initiatives seattle elsewhere future ntcip used two way communication vehicles traffic signals ability buses control traffic lights done sinwaves protocol product joint standardization project guided joint committee ntcip composed six representatives national electrical manufacturers association nema american association state highway transportation officials aashto institute transportation engineers ite joint committee turn formed 14 technical working groups develop maintain standards initiated produced 50 standards information reports project receives funding contract united states department transportation usdot part wider effort develop comprehensive family intelligent transportation system standards nema initiated development ntcip 1992 early 1993 us federal highway administration fhwa brought together transportation industry representatives discuss obstacles installing field equipment new intelligent transportation systems representatives said number one priority need industry-wide standard data communications protocol since nema transportation section members already started work new industry standard offered expedite expand scope activities key objectives new ntcip protocol interchangeability similar roadside devices interoperability different types devices communications channel 1996 fhwa suggested partnership standards developing organizations expand user industry involvement aashto ite signed agreement nema establish joint committee ntcip work together developing maintaining ntcip standards ntcip enabled center field communication command/control equipment different manufacturers specified procured deployed tested ntcip communications standards field devices listed corresponding ntcip document number shown parentheses center center c2c communication involves peer-to-peer communications computers involved information exchange real-time transportation management many-to-many network type communication similar internet center request information provide information number centers example center center communications two traffic management centers exchange real-time information inventory status traffic control devices allows center system know timing plan example center system running allow traffic signal coordination across center geographic boundaries examples type communication include ntcip communications standards center center communications listed corresponding ntcip document number shown parentheses ntcip coordinated information level standards development organizations development center-to-center application profiles supports ite traffic management data dictionary ite tmdd ieee 1512 incident management ieee 1512 apta transit communications interface profiles apta tcip sae j2354 advanced traveler information systems standards ntcip framework based primarily open standards internet engineering task force ietf world wide web consortium w3c iso plus ntcip data dictionary standards specific task device communications layered modular approach communications standards used represent data communications two computers electronic devices ntcip refers “ levels ” ntcip rather “ layers ” distinguish hierarchical architecture applied defined open system interconnection reference model osi model iso internet engineering task force ietf five ntcip levels information level application level transport level subnetwork level plant level figure used permission shows structure ntcip information application transport subnetwork plant levels ensure working system deployers select specify least one ntcip protocol profile level discussion level ntcip standards apply level follows ntcip framework preclude combinations beyond expressly indicated diagram
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Internet protocols
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cbasic cbasic compiled version basic programming language written cp/m operating system gordon eubanks 1976–1977 enhanced version basic-e. basic-e eubank master thesis project developed pl/m eubanks gary kildall new cp/m operating system men naval postgraduate school monterey california basic-e based basic compiler originally written gary kildall 1974 developed public expense basic-e public domain could marketed exclusively seymour rubinstein marketing director imsai contacted eubanks asked create saleable version contract imsai 8080 microcomputer eubanks developed cbasic spare time still naval officer stationed submarine uss george washington vallejo california retained joint ownership program imsai sold program company compiler systems acquired digital research 1981 basic-e early versions cbasic compiled source code intermediate p-code file executed separate run-time interpreter program cbasic could execute minimum 24 kb memory line numbers program source optional unless needed label program jump cbasic proved popular incorporated 14-digit binary-coded decimal bcd math eliminated mbasic rounding errors sometimes troublesome accounting cbasic2 adds following features infoworld 1980 described cbasic primary language development commercial cp/m applications developers widespread familiarity basic ability distribute royalty-free binaries without source code cbasic owners magazine stated language become popular despite serious drawbacks including required preprocessor interpreted source code making debugging difficult slow speed incompatible changes jerry pournelle said may 1983 digital research practically ruin ed eubanks cbasic manual acquiring company new edition much better
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Programming language topics
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pre-shared key cryptography pre-shared key psk shared secret previously shared two parties using secure channel needs used build key shared secret key derivation function typically used systems almost always use symmetric key cryptographic algorithms term psk used wi-fi encryption wired equivalent privacy wep wi-fi protected access wpa method called wpa-psk wpa2-psk also extensible authentication protocol eap known eap-psk cases wireless access points ap clients share key characteristics secret key determined system uses system designs require keys particular format password passphrase hexadecimal string secret used systems involved cryptographic processes used secure traffic systems crypto systems rely one keys confidentiality one particular attack always possible keys brute force key space search attack sufficiently long randomly chosen key resist practical brute force attack though principle attacker sufficient computational power see password strength password cracking discussion unavoidably however pre-shared keys held parties communication compromised one end without knowledge anyone several tools available help one choose strong passwords though network connection inherently unsafe one general know anyone may eavesdropping interaction choosing keys used cryptographic algorithms somewhat different pattern whatsoever avoided pattern may provide attacker lower effort attack brute force search implies random key choice force attackers spend much effort possible difficult principle practice well general rule software except cryptographically secure pseudorandom number generator csprng avoided
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Computer security
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ingres database ingres database commercially supported open-source sql relational database management system intended support large commercial government applications ingres database fully open source global community contributors however actian corporation announced april 2018 acquired hcl technologies controls development ingres makes certified binaries available download well providing worldwide support ingres began research project university california berkeley starting early 1970s ending 1985 original code like projects berkeley available minimal cost version bsd license ingres spawned number commercial database applications including sybase microsoft sql server nonstop sql number others postgres post ingres project started mid-1980s later evolved postgresql acid compatible fully transactional including ddl statements part lisog open-source stack initiative 1973 system r project getting started ibm research team released series papers describing system building two scientists berkeley michael stonebraker eugene wong became interested concept reading papers started relational database research project already raised money researching geographic database system berkeley economics group called ingres interactive graphics retrieval system decided use money fund relational project instead used seed new much larger project decided re-use original project name new project became university ingres funding stonebraker approached darpa obvious funding source computing research development time darpa office naval research onr turned already funding database research elsewhere stonebraker introduced idea agencies help colleagues eventually obtained modest support nsf three military agencies air force office scientific research army research office navy electronic systems command thus funded ingres developed mid-1970s rotating team students staff ingres went evolution similar system r early prototype 1974 followed major revisions make code maintainable ingres disseminated small user community project members rewrote prototype repeatedly incorporate accumulated experience feedback users new ideas research project ended 1985 ingres remained largely similar ibm system r concept based largely dec machines unix vax/vms unlike system r ingres source code available tape modest fee 1980 1,000 copies distributed primarily universities many students u.c berkeley universities used ingres source code worked various commercial database software systems berkeley students jerry held later karel youseffi moved tandem computers built system evolved nonstop sql tandem database system re-implementation ingres technology evolved system ran effectively parallel computers included functionality distributed data distributed execution distributed transactions last fairly difficult components system first released late 1970s 1989 system could run queries parallel product became fairly famous one systems scales almost linearly number processors machine adding second cpu existing nonstop sql server almost exactly double performance tandem later purchased compaq started re-write 2000 product hewlett-packard early 1980s ingres competed head-to-head oracle two products widely regarded leading hardware-independent relational database implementations comparable functionality performance market share pricing many commentators considered ingres perhaps marginally superior product around 1985 however ingres steadily lost market share one reason oracle aggressive marketing another increasing recognition sql preferred relational query language ingres originally provided different language quel conversion sql delivered ingres version 6 took three years losing valuable time race robert epstein chief programmer project berkeley formed britton lee inc. along students ingres project paula hawthorn michael ubell joined later eric allman later epstein founded sybase sybase 2 product behind oracle time 1980s 1990s informix came nowhere took 1997 sybase product line also licensed microsoft 1992 rebranded microsoft sql server relationship soured late 1990s today sql server outsells sybase wide margin several companies used ingres source code produce products successful company named relational technology inc. rti founded 1980 stonebraker wong another berkeley professor lawrence a. rowe rti renamed ingres corporation late 1980s company ported code dec vax/vms commercial operating system dec vax computers also developed collection front-end tools creating manipulating databases e.g. reporterwriters forms entry update etc application development tools time much source rewritten add functionality example multiple-statement transactions sql b-tree access method date/time datatypes etc improve performance example compiled queries multithreaded server company purchased ask corporation november 1990 founders left company next several months 1994 ask/ingres purchased computer associates continued offer ingres variety brand names example openingres ingres ii advantage ingres 2004 computer associates released ingres r3 open source license code includes dbms server utilities character-based front-end application-development tools essence code everything except openroad windows 4gl gui-based development environment november 2005 garnett helfrich capital partnership computer associates created new company called ingres corporation provided support services ingres openroad connectivity products february 2006 ingres corporation released ingres 2006 gnu general public licence ingres 9.3 released october 7 2009 limited release targeted new application development linux windows ingres 10 released october 12 2010 full release supporting upgrade earlier versions product available 32-bit 64-bit linux 32-bit microsoft windows open-source community initiatives ingres included community bundles – alliances open-source providers projects alfresco jaspersoft hibernate apache tomcat eclipse enable ingres provide platform technology open-source technologies established ingres carleton university series open source boot camps held 2008 work open-source communities projects introduce university college students staff concepts realities open source involvement includes global ingres university alliances ingres engineering summit ingres janitors project several memberships open-source initiatives ingres icebreaker appliance combines ingres database linux operating system enabling people simultaneously deploy manage database operating system ingres café consolidated application foundation eclipse created team developers carleton university integrated environment helps software architects accelerate simplify java application development ingres geospatial community-based project create industry-standards-compliant geospatial storage features ingres dbms words storing map data providing powerful analysis functions within dbms november 2010 garnett helfrich capital acquired last 20 equity ingres corp already september 22 2011 ingres corporation became actian corporation focused action apps use ingres vectorwise rdbms systems postgres project started mid 1980s address limitations existing database-management implementations relational model primary among inability let user define new domains types combinations simpler domains see relational model explanation term domain project explored ideas including incorporation write-once media e.g. optical disks use massive storage e.g. never delete data inferencing object-oriented data models implementation also experimented new interfaces database application programs e.g. portals sometimes referred fat cursors resulting project named postgres aimed introducing minimum number features needed add complete types support included ability define types also ability fully describe relationships – time widely used maintained entirely user postgres database understood relationships could retrieve information related tables natural way using rules 1990s stonebraker started new company commercialize postgres name illustra company technology later purchased informix ingres 11 released 18 april 2017 known actian x hybrid database
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Databases
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dualshock dualshock originally dual shock trademarked dualshock dual shock line gamepads vibration-feedback analog controls developed sony interactive entertainment playstation family systems dualshock introduced japan november 1997 launched north american market may 1998 first introduced secondary peripheral original playstation updated version playstation console included controller sony subsequently phased digital controller originally included console well sony dual analog controller 28 million dualshock controllers sold brand name excluding bundled controllers dualshock analog controller scph-1200 controller capable providing vibration feedback based onscreen actions taking place game game supports well analog input two analog sticks name derives use two dual vibration motors shock motors housed within handles controller left one larger powerful one right allow varying levels vibration dualshock differs nintendo 64 rumble pak respect rumble pak uses single motor rumble pak also uses batteries power vibration function corded varieties dualshock use power supplied playstation however third party dualshock-compatible controllers use batteries instead playstation power supply rumble feature dualshock similar one featured first edition japanese dual analog controller feature removed shortly controller released dualshock like predecessor dual analog controller two analog sticks unlike earlier controller dualshock analog sticks feature textured rubber grips rather smooth plastic tips recessed grooves found dual analog controller dualshock also features two additional buttons compared dual analog l3 r3 triggered depressing analog sticks differences dual analog dualshock include longer grips/handles slightly different l2/r2 buttons dualshock controller widely supported shortly launch new titles including spyro dragon tekken 3 included support vibration feature dual analog sticks capcom re-released resident evil director cut resident evil 2 support controller added newer versions games designed dual analog vibration capability porsche challenge crash bandicoot 2 also work many games took advantage presence two motors provide vibration effects stereo including gran turismo playstation port quake ii released 1999 playstation hit ape escape became first game explicitly require dualshock/dual-analog-type controllers gameplay requiring use analog sticks 2000 ps one remodeled version original playstation released slightly redesigned dualshock controller scph-110 similar first one except color white instead gray middle controller ps one logo instead playstation naming buttons analog sticks cord brighter previous one connector semi-circle shape round edge also came colors dualshock also compatible playstation 2 use connector protocol however certain ps2 games utilize dualshock 2 analog buttons bouncer compatible dualshock dualshock fully forwards compatible playstation 2 console used play playstation games playstation 2 computer entertainment system announced dualshock 2 analog controller scph-10010 included almost exactly externally previous dualshock analog controller however minor cosmetic changes different screw positioning one fewer screw blue dualshock 2 logo added top controller connector square dualshock cable connector black rather grey standard controller black colors came later rather grey original dualshock analog sticks also noticeably stiffer original dualshock internally dualshock 2 lighter buttons except analog mode start select l3 r3 buttons readable analog values pressure-sensitive dualshock 2 made available various colors black satin silver ceramic white slate grey ocean blue emerald green crimson red candy pink original playstation forward compatible dualshock 2 playstation 3 backward compatible dualshock dualshock 2 use third party peripherals connect controller console via usb port however dualshock dualshock 2 work properly games require sixaxis functionality heavy rain announced 2007 tokyo game show dualshock 3 wireless controller scph-98050/cechzc2 gamepad playstation 3 replaces sixaxis wireless controller originally released earlier versions console dualshock 3 nearly identical previous sixaxis version adds haptic feedback – also known force feedback – capabilities found dualshock dualshock 2 sony settled patent infringement lawsuit immersion march 2007 following lengthy legal battle settlement cleared way incorporating missing rumble feature sixaxis lacked vibration function motion-sensing capabilities dualshock 3 used simultaneously without one interfering like sixaxis also usb mini-b port charging also used psp go via bluetooth though controller psp go must registered using ps3 console dualshock 3 identified dualshock 3 sixaxis markings also weighs 40 predecessor sixaxis weighed rear markings indicate original dualshock 3 draws 300 current 3.7 v power consumption 1.11 w order magnitude increase 30 current 3.7 v 0.111 w listed sixaxis however current drawn constantly maximum current rumble active main power source internal 3.7 v li-ion battery tentatively capable storing 570 mah provides 30 hours continuous gaming full charge third party replacement batteries also available like sixaxis dualshock 3 comes instructions remove replace battery dualshock 3 also draw power usb cable via usb mini-b connector top controller allows controller used battery low also used charging battery connected via usb controller communicates console usb cable rather bluetooth along release 'slim model ps3 sony released new version dualshock 3 a1 uses 5.0 v 500 connected still contains 3.7 v battery revision dualshock 3 away additional plastic brackets l1/r1 buttons l2/r2 triggers increasing controller rigidity indicator lights soldered directly board comes slightly revised color schemes dualshock 3 compatible standard usb mini-b cable many usb chargers official charging cables available sony include official cable usb 2.0 cable pack wall charger ac adapter charging kit third-party usb charger used must act usb host device rather simply providing power appropriate pins since sixaxis dualshock 3 require host signal wake begin charging sony representative confirmed april 2 2008 original sixaxis controller would officially discontinued release force-feedback enabled dualshock 3 mid-april 2008 sixaxis longer produced 2008 dropped stock retailers dualshock 3 made available various colors black satin silver ceramic white classic white metallic blue deep red pink jungle green olive candy blue light blue urban camouflage three-color digital camouflage crimson red transparent red cosmic blue transparent blue colors made available markets times additional colors also made available alongside limited edition consoles including gun-metal grey cloud black dark grey limited edition baseball themed dualshock 3 controller released march 8 2011 coincide release another color metallic gold became available june 2012 limited edition europe north america sold exclusively gamestop october 2012 limited edition controller available uk part console bundle coincide launch game americas game controller bundle november 1 2013 sony announced new see-through crystal model dualshock 3 controller japan dualshock 4 cuh-zct1 playstation 4 controller similar dualshock 3 several new features one new feature built-in two-point capacitive touch pad front controller clicked controller supports motion detection via three-axis gyroscope three-axis accelerometer vibration includes non-removable rechargeable 3.7 v 1000 mah lithium-ion battery charged system rest mode weighs dimensions also lacks sony logo front due touchpad place top gamepad features light bar three leds illuminate different colors used identify players matching colors characters controlling game provide enhanced feedback immersion changing patterns colors reaction gameplay example grand theft auto v player wanted police light bar flashes red blue also used conjunction playstation camera judge positions movements multiple players light bar developed playstation vr controller features several input output connectors stereo headset jack 3.5 mm omtp trrs connector micro-usb port extension port charged via microusb dedicated charging station console even console also includes mono speaker like wii remote second major controller video game history feature dualshock 4 features following buttons ps button share button options button directional buttons action buttons triangle circle cross square shoulder buttons r1/l1 triggers r2/l2 analog stick click buttons l3/r3 touch pad click button mark several changes dualshock 3 previous playstation controllers start select buttons merged single options button dedicated share button allows players upload screenshots videos gameplay experiences joysticks triggers redesigned based developer input ridged surface joysticks featuring outer ring surrounding convex dome caps dualshock 4 buttons differ slightly functionality dualshock 3 l1 l2 r1 r2 buttons pressure-sensitive change functionality dualshock 2 3 likely due fact games utilize buttons well due used competitors controllers including wii u xbox one playstation 3 forward compatible dualshock 4 originally via microusb cable firmware update 4.60 ps3 added wireless connectivity however motion vibration functions supported start select buttons longer present options share buttons respectively replace sony initially released dualshock 4 estimated around 10 wear issues rubber surface left analog stick exhibited excessive wear tearing short-term use january 2014 sony issued statement acknowledging issue small percentage controllers early september 2016 sony confirmed second generation dualshock 4 controllers known dualshock v2 cuh-zct2 hosts slight improvements original dualshock 4 including usb communication longer battery life ability see light bar top touchpad released september 15 2016 initial controller version light bar permanently illuminated bright-colored light potential light pollution darkened playing rooms well interest extending battery life led inquiries whether light bar could switched users required game sony executive shuhei yoshida initially responded negative july 2013 though videogame developers option disable light game early 2014 company announced future update would allow light bar dimmed enabled system update 1.70 april 2014 original dualshock 4 cuh-zct1 available jet black glacier white urban camouflage wave blue black back magma red black back gold silver steel black newer dualshock 4 cuh-zct2 currently available jet black glacier white green camouflage blue camouflage wave blue blue back magma red red back gold silver sunset orange crystal red crystal blue crystal steel black midnight blue metallic copper alpine green berry blue also dualshock 4 exclusive least initially console bundles like 20th anniversary edition gun metal metal gear solid v star wars battlefront monster hunter world god war gran turismo sport days play marvel spider-man 500 million limited edition ps4 pro dualshock controller given emmy award peripheral development technological impact video game controllers national academy television arts sciences january 8 2007 sony initially reported sixaxis received award issuing correction
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Computer architecture
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domain-key normal form domain-key normal form dk/nf normal form used database normalization requires database contains constraints domain constraints key constraints domain constraint specifies permissible values given attribute key constraint specifies attributes uniquely identify row given table domain/key normal form achieved every constraint relation logical consequence definition keys domains enforcing key domain restraints conditions causes constraints met thus avoids non-temporal anomalies reason use domain/key normal form avoid general constraints database clear domain key constraints databases easily test domain key constraints attributes general constraints however would normally require special database programming form stored procedures often trigger variety expensive maintain expensive database execute therefore general constraints split domain key constraints much easier build database domain/key normal form convert lesser databases may contain numerous anomalies however successfully building domain/key normal form database remains difficult task even experienced database programmers thus domain/key normal form eliminates problems found databases tends costly normal form achieve however failing achieve domain/key normal form may carry long-term hidden costs due anomalies appear databases adhering lower normal forms time third normal form boyce–codd normal form fourth normal form fifth normal form special cases domain/key normal form either functional multi-valued join dependencies converted super keys domains normal forms unconstrained domain constraints satisfied however transforming higher normal form domain/key normal form always dependency-preserving transformation therefore always possible violation dknf occurs following table constraint linking wealthy person type net worth dollars even though deduce one constraint dictates eccentric millionaire evil millionaire net worth 1,000,000 999,999,999 inclusive eccentric billionaire evil billionaire net worth 1,000,000,000 higher constraint neither domain constraint key constraint therefore rely domain constraints key constraints guarantee inconsistent wealthy person type net worth dollars combination make way database dknf violation could eliminated altering wealthy person type domain make consist two values 'evil 'eccentric wealthy person status millionaire billionaire implicit net worth dollars useful information lost relationships impossible express foreign keys obvious violations dknf example parent id attribute points one several referenced tables depending second parent type attribute violates dknf
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Databases
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iphone x iphone x roman numeral x pronounced ten smartphone designed developed marketed apple inc eleventh generation iphone announced september 12 2017 alongside iphone 8 iphone 8 plus steve jobs theater apple park campus release date – november 3 2017 – marked iphone series tenth anniversary iphone x intended showcase apple considered technology future using glass stainless-steel form factor beze-less design shrinking bezels chin unlike many android phones first iphone use oled screen offer wireless charging home button replaced new type password authentication called face id using advanced technologies scan user face unlock device face-recognition capability also enabled emojis animated following user expression animoji bezel-less design iphone user interaction changed significantly using gestures navigate operating system rather home button used previous iphones time november 2017 launch price tag us 999 also made expensive iphone ever even higher prices internationally due additional local sales import taxes iphone x received mixed reviews display build quality universally praised camera also scored positively tests phone received particularly polarized reception due sensor housing notch top screen introduction all-new authentication method notch heavily mocked users social media although app developers responded either neutrally positively changes brought user experience apps games reviewers mixed reactions condemning others acknowledging unusual first moments use getting accustomed presence face id facial recognition praised simple setup criticized requiring direct eyes screen though option disabled within system preferences along iphone 6s plus variant iphone se iphone x discontinued september 12 2018 following announcement new iphone xs iphone xs max iphone xr devices result shelf life 10 months iphone x shortest ever tenure flagship device history iphone november 22 2018 apple reportedly resumed production iphone x due weak sales successors iphone x remains discontinued february 2019 apple started selling refurbished models 769 technology behind iphone x development five years far back 2012 rumors drastic iphone redesign began circulating around time iphone 7 announcement third quarter 2016 intensified homepod firmware leak july 2017 suggested apple would shortly release phone nearly bezel-less design lack physical home button facial recognition new features near-final development version ios 11 operating system also leaked september 2017 confirming new design features august 31 2017 apple invited journalists september 12 press event first public event held steve jobs theater company new apple park campus cupertino california iphone x unveiled keynote us 999 starting price expensive iphone launch price price even higher international markets due currency fluctuations import fees sales taxes unlocked version phone made available purchase united states december 5 2017 april 2018 federal communications commission divulged images unreleased gold-colored iphone x model opposed space gray silver color options iphone x ships divulged initial plans release gold option device however put hold due production issues apple released revised b model iphone x fixed nfc issues users japan china america iphone x 5.8-inch oled color-accurate screen supports dci-p3 wide color gamut srgb high dynamic range contrast ratio 1,000,000:1 super retina display true tone technology found ipad pro uses ambient light sensors adapt display white balance surrounding ambient light although iphone x feature promotion technology used displays second-generation ipad pro display delivers refresh rate 120hz sample touch input 120hz oled screen technology known negative trend burn-in effects particular elements consistently screen long periods time leave faint trace even new images appear apple acknowledged oled screens excluded issue writing support document also expected behavior greg joswiak apple vice president product marketing told tom guide oled panels apple used iphone x engineered avoid oversaturation colors using oled panels typically results made color adjustments subpixel -level refinements crisp lines round corners out-of-warranty servicing damages relating manufacturing defects screen repairs iphone x cost us 279 damage repairs cost us 549 iphone x two color options silver space gray sides phone composed surgical-grade stainless steel improve durability front back made glass design intended ip67 water dust resistant iphone x contains apple a11 bionic system-on-chip also used iphone 8 8 plus six-core processor two cores optimized performance 25 faster a10 fusion processor along four cores optimized efficiency 70 faster previous generation also features first apple-designed graphics processing unit neural engine powers artificial intelligence accelerator face id replaces touch id authentication system facial recognition sensor consists two parts romeo module projects 30,000 infrared dots onto user face juliet module reads pattern pattern sent secure enclave a11 bionic chip confirm match phone owner face default system work eyes closed effort prevent unauthorized access requirement disabled settings iphone x two cameras rear one 12-megapixel wide-angle camera f/1.8 aperture support face detection high dynamic range optical image stabilization capable capturing 4k video 24 30 60 frames per second 1080p video 30 60 120 240 frames per second secondary telephoto lens features 2× optical zoom 10× digital zoom aperture f/2.4 optical image stabilization portrait mode capable producing photos specific depth-of-field lighting effects also quad-led true tone flash 2× better light uniformity front phone 7-megapixel truedepth camera f/2.2 aperture features face detection hdr capture 1080p video 30 frames per second 720p video 240 frames per second exclusively allows use animoji animated emojis placed top user face intelligently react user facial expressions iphone x also supports qi-standard wireless charging tests conducted macrumors iphone x charging speed varies significantly depending types cables powerbanks adapters wireless chargers used due different screen layout ios developers required update apps make full use additional screen real estate changes include rounded corners sensor notch top screen indicator area bottom accessing home screen apple published human interface guidelines document explain areas focus discouraged developers attempting mask call special attention new changes additionally text within app needs configured properly reference face id rather touch id authentication technology used iphone x anticipation release phone major apps quickly updated support new changes brought iphone x though required changes cause delayed app updates major apps traditional home button found previous devices iphone lineup removed entirely replaced touch-based gestures wake device users tap display use side button access home screen users must swipe bottom display access multitasking window users must swipe similarly method accessing home screen stop finger middle screen causing app carousel appear iphone x rear camera received overall rating 97 dxomark camera testing company short highest score 99 awarded samsung galaxy s9+ smartphone google pixel 2 received rating 98 consumer reports non-profit independent organization aiming write impartial reviews consumer products ranked iphone x iphone 8 iphone 8 plus well samsung galaxy s8 s8+ note 8 due less durability shorter battery life although praised x camera highest-rated smartphone camera ever tested nilay patel verge praised display calling polished tight clean bright colorful criticized repeated lack headphone jack device fragility despite apple claims durability sensor notch calling ugly patel highlighted fact apps required updates fit new screen writing popular apps received updates time review resulting apps huge black borders resembling iphone 8 especially criticized positioning sensor notch holding phone landscape mode causing notch go somewhat forgettable element top status bar giant interruption side screen cameras given positive feedback maintaining detail low-light patel particularly praised animoji calling probably single best feature iphone x writing work work incredibly well finally wrote face id whole foundation iphone x stated generally works great though acknowledging occasional misstep users must actively move phone closer face compensate specifically criticized limited range face id authentication working holding phone 25–50 centimeters away face chris velazco engadget also praised display writing experience sensor notch goes weird first noticeable due action videos usually happening center build quality given particular acclaim called beautifully made device construction seamlessly connects front back glass stainless-steel frame velazco noted new gesture-based interaction takes time getting used particularly control center moved bottom top right display camera processor performance battery life also given positive thoughts heavily negative review dennis green business insider significantly criticized impossible one-handed use iphone x writing new gestures use phone swiping top access notifications control center work using phone one hand due able reach top review sparked outrage among twitter users many used condescending tones green reasoned n't know whether anger directed toward loyalty apple justify choice spend 1,000 phone obvious much criticism came people never used phone macworld roman loyola praised face id authentication system writing setup process easy system integration seamless touch id fingerprint authentication past said loyola note half-second slower unlocking time touch id well needing look directly screen making impossible unlock phone next user desk face id raised concerns regarding possibility law enforcement accessing individual phone pointing device user face united states senator al franken asked apple provide information security privacy face id day announcement apple responding highlighting recent publication security white paper knowledge base detailing answers inconsistent results shown testing face id identical twins tests showing system managing separate two tests failed however despite apple promise increased security face id compared touch id fingerprint authentication system multiple media reports indicating otherwise verge noted courts united states granted different fifth amendment rights united states constitution biometric unlocking systems opposed keycodes keycodes considered testimonial evidence based contents users thoughts whereas fingerprints considered physical evidence suspects ordered unlock phones via fingerprint many attempts break face id sophisticated masks attempted though failed week iphone x released vietnamese security firm bkav announced blog post successfully created 150 mask tricked face id though wired noted bkav technique proof-of-concept rather active exploitation risk technique requiring detailed measurement digital scan iphone owner face putting real risk danger targets espionage world leaders additionally reuters reported early november 2017 apple would share certain facial data users third-party app developers precise selfie filters fictional game characters mirror real-world user facial expressions although developers required seek customer permission allowed sell data others create profiles users use data advertising limited rough map rather full capabilities still get access 50 kinds facial expressions american civil liberties union aclu center democracy technology raised privacy questions apple enforcement privacy restrictions connected third-party access apple maintaining app store review processes effective safeguards rough map facial data third-parties access also enough unlock device according reuters however overall idea letting developers access sensitive facial information still satisfactorily handled according jay stanley senior policy analyst aclu stanley telling reuters privacy issues around use sophisticated facial recognition technology unlocking phone overblown … real privacy issues access third-party developers much debate iphone x revolved around design sensor housing dubbed notch media top display outline described visually disgusting element verge posted report focusing public criticism people mocking apple odd design choice every reviewer equally negative opinions third-party ios developers interviewed ars technica said despite work restructuring design elements apps notch cause problems even arguing notch good push simplify designs two weeks iphone x release apple approved notch remover app app store places black bars across top home screen make notch visually disappear approval done despite company user interface guidelines discouraging developers specifically masking design iphone x first device notch–both essential phone sharp aquos s2 announced display notch–but iphone x arguably popularized november 2017 early adopters new phone reported experiencing activation issues certain cellular carriers notably announced within hours issue fixed end spokesperson verizon carrier told media none customers affected despite reports problems november 2017 iphone x users reported reddit device screen would become unresponsive experiencing rapid temperature drops apple released ios 11.1.2 update november 16 2017 fixing issue forbes contributor gordon kelly reported march 2018 1,000 users experienced problems using camera flash cold weather problem still persisting ios 11.3 beta 1 apple engaged legal battle qualcomm allegedly anti-competitive practices dual-sourcing cellular modem chips reduce reliance semiconductor manufacturer starting iphone 7 2016 apple used half qualcomm modem chips half intel professional measurement tests performed wireless signal testing firm cellular insights indicated previous-gen iphone 7 qualcomm chips outperform intel lte download speeds 67 faster weak signal conditions resulting sources recommending purchase unlocked iphone x one bought cellular carrier verizon order get models featuring faster qualcomm modem additionally cnet reported september 2017 new iphone models including x 8 8 plus ability connect next-generation wireless lte data connection despite 10 new android devices including flagships main smartphone competitor samsung capability apple new smartphones support lte advanced theoretical peak speed 500 megabits per second android models ability connect gigabit lte allowing theoretical speeds 1 gigabit per second doubling apple speed releasing iphone x japan china customers experienced issues related phone nfc trying access public transit smart card readers april 2018 apple released revision iphone x included vastly improved nfc chip solved problem nfc reader errors cases previously around 1 3 nfc attempts would fail initial reports issue also affected users america
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Operating systems
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data item data item describes atomic state particular object concerning specific property certain time point collection data items object time forms object instance table row type complex information broken elementary data items atomic state data items identified object property p time value v function p v f p values typically represented symbols like numbers texts images sounds videos others values necessarily atomic complexity value depends complexity property time component looking databases xml files object usually identified object name type object identifier part data properties defined columns table row properties object instance tags xml often time explicitly expressed attribute applying complete data set data collections provide time instance level time series column level even attribute/property level
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Databases
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symantec online backup symantec online backup online remote backup service provides businesses system backing storing computer files internet released february 2008 symantec protection network platform symantec online backup example cloud computing saas software service sales symantec online backup discontinued january 2010
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Computer security
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defensive computing defensive computing form practice computer users help reduce risk computing problems avoiding dangerous computing practices primary goal method computing able anticipate prepare potentially problematic situations prior occurrence despite adverse conditions computer system mistakes made users achieved adherence variety general guidelines well practice specific computing techniques strategies defensive computing could divided two categories network security backup restoration data users put computers risk accessing internet networks use either allows others gain access user system important information implementing certain strategies defensive users aim reduce risk associated network access firewall collection security measures protects computer harmful inbound outbound traffic internet prevents unauthorized access computer systems security measures integrated form special software runs autonomously either individual computer systems externally built software within routers modems firewall software protect computers sending unauthorized harmful outbound traffic important defensive computing strategy seek implement quality firewall software filters inbound outbound traffic basic strategy defensive computer users install use anti-malware software firewalls may completely protect computer malicious software may able get firewall onto system anti-malware anti-virus anti-phishing email filtering software offer protection harmful software reside within computer amount malicious software available internet steadily increasing important defensive users use anti-malware effective easily updated order combat new strains malicious software developed side anti malware contains serious vulnerabilities malware could use vulnerabilities anti-malware launch malicious code anti-malware works scanning files network connections known signatures signatures never date able scan network connections encryptions ssl/tls need bypassed even broken anti-malware software monitoring emails anti-malware opens attachments analysis bug scanner used starting point malware attackers need send malware mailbox scanned automatically questionable malware scanners even useful ex mozilla developer rober o'callahan writes blog anti malware software disabled except windows defender important aspect defensive computing users skeptical data access via internet malicious software exist multitude different forms many misleading general computer users even anti-malware software defensive users think critically information access reduce chances downloading spreading malicious software strategies include scanning email attachments prior opening manually filtering suspicious emails inboxes users aware persuasive subject lines headings emails address may actually contain malicious software spam mislead users false advertisement resulting identity theft defensive users scan files download prior opening also configure computers show file extensions revealing potentially dangerous files appear harmless skepticism also applied websites visited users emails users led false advertisements also malicious software unknowingly downloaded infect computer visiting certain website despite efforts defensive computer user loss important data occur due malware power outages equipment failure general misuse although loss data completely prevented defensive users take steps minimize amount data lost restore systems previous state defensive strategy unintentional data loss regular backup important files users make multiple copies important data store either computer another device compact disc external hard drive users also upload important files internet provided access internet storage services operating systems give users option performing procedure restores computer predetermined state option available user obtain appropriate restoration software system event system failure serious case data loss user restore lost changed files remove malicious files previously exist
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Computer security
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xenix xenix discontinued version unix operating system various microcomputer platforms licensed microsoft corporation late 1970s santa cruz operation sco later acquired exclusive rights software eventually replaced sco unix known sco openserver mid-to-late 1980s xenix common unix variant measured according number machines installed microsoft chairman bill gates said 1996 long time microsoft highest-volume unix license bell labs developer unix part regulated bell system could sell unix directly end customers instead licensed software others microsoft expected unix would operating system future personal computers became powerful enough purchased license version 7 unix 1978 announced august 25 1980 would make available 16-bit microcomputer market microsoft able license unix name company gave original name microsoft called xenix universal operating environment sell xenix directly end users licensed software oems ibm intel management systems development tandy altos sco siemens sinix ported proprietary computer architectures 1981 microsoft said first version xenix close original unix version 7 source pdp-11 later versions incorporate fixes improvements company stated intended port operating system zilog z8000 series digital lsi-11 intel 8086 80286 motorola 68000 possibly numerous processors provide microsoft full line system software products including basic languages first port z8001 16-bit processor first customer ship january 1981 central data corporation illinois followed march 1981 paradyne corporation z8001 product first 8086 port altos computer systems non-pc-compatible 8600-series computers first customer ship date q1 1982 intel sold complete computers xenix intel system 86 brand specific models 86/330 86/380x also offered individual boards made computers isbc brand included processor boards like isbc 86/12 also mmu boards isbc 309 first intel xenix systems shipped july 1982 tandy doubled xenix installed base made trs-xenix default operating system trs-80 model 16 68000-based computer early 1983 largest unix vendor 1984 seattle computer products also made pc-incompatible 8086 computers bundled xenix like gazelle ii used s-100 bus available late 1983 early 1984 also port ibm system 9000 sco initially worked pdp-11 port v7 called dynix struck agreement microsoft joint development technology exchange xenix 1982 1984 port 68000-based apple lisa 2 jointly developed sco microsoft first shrink-wrapped binary product sold sco 1983 oem directory microsoft said difficulty porting various 8086 z8000-based machines lack standardized memory management unit protection facilities hardware manufacturers compensated designing hardware ensuing complexity made extremely difficult impossible small manufacturer develop computer capable supporting system xenix scratch xenix kernel must custom-tailored new hardware environment generally available port unmapped intel 8086/8088 architecture done santa cruz operation around 1983 sco xenix pc xt shipped sometime 1984 contained enhancement 4.2bsd also supported micnet local area networking later 286 version xenix leveraged integrated mmu present chip running 286 protected mode 286 xenix accompanied new hardware xenix oems example sperry pc/it ibm pc clone advertised capable supporting eight simultaneous dumb terminal users version xenix 2.0 still based version 7 unix version 3.0 upgraded unix system iii code base 1984 intel manual xenix 286 noted xenix kernel 10,000 lines time followed system v.2 codebase xenix 5.0 a.k.a xenix system v microsoft hopes xenix become preferred choice software production exchange company stated 1981 microsoft referred ms-dos single-user single-tasking operating system advised customers wanted multiuser multitasking support buy xenix planned time improve ms-dos would almost indistinguishable single-user xenix xedos would also run 68000 z8000 lsi-11 would upwardly compatible xenix byte 1983 described multi-user ms-dos future microsoft chris larson described ms-dos 2.0 xenix compatibility second important feature company advertised dos xenix together listing shared features single-user os multi-user multi-tasking unix-derived operating system promising easy porting started selling system v however breakup bell system microsoft believing could compete unix developer decided abandon xenix decision immediately transparent led term vaporware agreed ibm develop os/2 xenix team together best ms-dos developers assigned project 1987 microsoft transferred ownership xenix sco agreement left microsoft owning slightly less 20 sco amount prevented companies disclose exact amount event sco ipo microsoft eventually lost interest os/2 well company based high-end strategy windows nt 1987 sco ported xenix 386 processor 32-bit chip securing knowledge microsoft insiders microsoft longer developing xenix xenix system v release 2.3.1 introduced support i386 scsi tcp/ip sco xenix system v/386 first 32-bit operating system available market x86 cpu architecture microsoft continued use xenix internally submitting patch support functionality unix 1987 trickled code base xenix sco unix microsoft said used xenix sun workstations vax minicomputers extensively within company late 1988 internal microsoft email transport done xenix-based 68000 systems 1995–1996 company moved exchange server product sco released sco unix higher-end product based system v.3 offering number technical advances xenix xenix remained product line meantime sun microsystems completed merge xenix bsd sunos system v.3 system v release 4 last version sco xenix/386 system v.2.3.4 released 1991 aside unix base xenix incorporated elements bsd notably vi text editor supporting libraries termcap curses kernel featured original extensions microsoft notably file locking semaphores userland microsoft added visual shell menu-driven operation instead traditional unix shell limited form local networking serial lines rs-232 ports possible micnet software supported file transfer electronic mail although uucp still used networking via modems oems often added modifications xenix system trusted xenix variant initially developed ibm name secure xenix later versions trusted xenix name developed trusted information systems incorporated bell-lapadula model multilevel security multilevel secure interface stu-iii secure communications device stu-iii connection would made available applications running privilege level key loaded stu-iii evaluated formal methods achieved b2 security rating dod trusted computer system evaluation criteria—the second highest rating ever achieved evaluated operating system version 2.0 released january 1991 version 3.0 april 1992 version 4.0 september 1993 still use late 1995
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Operating systems
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westgrid westgrid government-funded infrastructure program started 2003 mainly western canada provides institutional research faculty students access high performance computing distributed data storage using combination grid networking collaboration tools westgrid one four partners within umbrella organization compute canada westgrid 14 partner institutions across four provinces british columbia alberta saskatchewan manitoba participating institutions include westgrid also works partnership province optical regional advanced network westgrid network partners include
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Distributed computing architecture
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lena foundation lena developer advanced technology programs accelerate language development children 0-3 close opportunity gaps nonprofit organization uses technology system comprises lena device patented processing software secure cloud-based data access technology used cornerstone programs aimed increasing interactive talk children caregivers implemented community organizations around world lena system also used researchers universities harvard mit brown university stanford university hospitals research institutions used study subjects language builds children brains autism child language acquisition communication deaf hard hearing families lena research foundation nonprofit organization created 2009 donation assets infoture inc. terrance terry judith judi paul also majority owners renaissance learning inc. rli founder renaissance learning terry paul became familiar achievement gap caused differences home language environments 1998 read meaningful differences everyday lives young american children betty hart ph.d. todd risley ph.d. based data gathered intensive longitudinal study meaningful differences revealed number adult words spoken children birth three predicted almost variance children language ability iq age three terry realized help advanced speech recognition technology could streamline data acquisition process provide parents tool easy use could thoroughly chart child natural language environment called lena “ language environment analysis ” 2004 terry started infoture inc. hired team scientists engineers scientific advisors conduct research development work lena system infoture launched pilot version lena system february 2006 february 2009 pauls donated assets infoture gift 2 million create lena research foundation nonprofit organization january 2018 organization updated name lena adopted tagline building brains early talk lena organizational goals based science shows talk conversational engagements child experiences first four years life better academics society based research harvard university showing interactive talk children caregivers one important factors affecting early brain development new research mit published february 2018 confirmed conversational turns responsible activation broca area children lena several programs designed encourage interactive talk children caregivers including programs aimed parents childcare providers home visitors growing body research shows early childhood contains critical periods tasks language acquisition meaning first three years once-in-a-lifetime opportunity development early childhood development drives success school life fostering cognitive skills like attentiveness self-regulation motivation sociability interactive talk — specifically conversational turns — proved key factor stimulating brain growth important years according center developing child harvard university additionally longitudinal research lena found amount conversation children experience ages 18-24 months related iq verbal comprehension language skills adolescence investing early children lead huge social economic gains research shown investments young children lead reductions criminal activity later life 13 percent returns investment annually positive effects last several generations lena stands language environment analysis lena technology provides 25 different metrics natural language environment children including estimates percentile scores adult words spoken child conversational turns child vocalizations system also generates automatic expressive language developmental age percentile score based child voiceprint parent places lena device children lena vest records entire day child sound environment device connected computer special software processes recording data metrics including child exposure verbal stimulation number child utterances information pediatricians child height weight system also generates percentile scores comparing child vocalizations children age lena start program parents uses regular feedback lena system plus 13 weekly group sessions help improve home language environment since introduction 2015 lena start implemented school districts library systems types organizations huntsville ala. san mateo county calif. ames iowa longmont co. minneapolis minn. sites across country texas children hospital first regional healthcare center adopt model lena grow professional development program teachers work early childhood classrooms according lena website lena ’ talk reports teachers focus primarily conversational turns strong measure interactive talk training teachers increase conversational turns important children spend 60 percent time childcare program first piloted escambia county florida launching sites around country lena home supplement existing parent coaching curriculums typically home visitors facilitate use lena system help parents track progress towards increasing interactive talk homes lena sp version lena designed researchers language professionals use lena developmental snapshot based 52-question parent survey assesses expressive receptive language skills provides estimate child developmental age 2 months 36 months
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Computational linguistics
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palm v palm v personal digital assistant made palm computing division 3com functionally similar predecessor palm iii series pdas distinguished sleek design anodized aluminum finish built-in rechargeable battery first palm device palm v design created design firm ideo palm v series succeeded palm m500 series battery contacts back unit short circuited data stored device erased data held kind memory required power retaining data enthusiasts able fix issue adding diode one battery contacts charging device diode open short-circuit diode blocked short circuiting current
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Computer architecture
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brendan eich brendan eich born july 4 1961 american technologist creator javascript programming language co-founded mozilla project mozilla foundation mozilla corporation served mozilla corporation chief technical officer briefly chief executive officer ceo brave software brendan eich grew palo alto attended ellwood p. cubberley high school graduated class 1979 eich received bachelor degree mathematics computer science santa clara university received master degree 1985 university illinois urbana-champaign eich started career silicon graphics working seven years operating system network code worked three years microunity systems engineering writing microkernel dsp code first mips r4000 port gcc started work netscape communications corporation april 1995 eich originally joined intending put scheme browser netscape superiors insisted language ’ syntax resemble java result language much functionality scheme object orientation self syntax java first version completed ten days order accommodate navigator 2.0 beta release schedule called mocha renamed livescript september 1995 later javascript month eich continued oversee development spidermonkey specific implementation javascript navigator early 1998 eich co-founded mozilla project jamie zawinski others creating mozilla.org website meant manage open-source contributions netscape source code served mozilla chief architect aol bought netscape 1999 aol shut netscape browser unit july 2003 eich helped spin mozilla foundation august 2005 serving lead technologist member board directors mozilla foundation eich became chief technical officer newly founded mozilla corporation meant mozilla foundation for-profit arm eich continued mozilla spidermonkey module javascript engine passed ownership 2011 march 24 2014 eich promoted ceo mozilla corporation gary kovacs john lilly ellen siminoff resigned mozilla board prior appointment anonymously expressing disagreements eich strategy desire ceo experience mobile industry employees mozilla foundation separate organization mozilla corporation tweeted calls resignation reference donation 1,000 california proposition 8 called banning same-sex marriage california eich stood decision fund campaign wrote blog sorry “ causing pain ” pledged promote equality mozilla activists created online campaign eich online dating site okcupid automatically displaying message firefox users information eich donation suggesting users switch different browser although giving link continue firefox others mozilla corporation spoke blogs favor board members wanted stay company different role april 3 2014 eich resigned ceo left mozilla personal blog posted present circumstances effective leader eich ceo brave software internet security company raised 2.5 million early funding angel investors january 20 2016 company released developer versions open-source brave web browser blocked ads trackers included micropayments system offer users choice viewing selected ads paying websites display brave software eich co-created basic attention token bat cryptocurrency designed use brave browser bat launched ico may 31 2017 raised 35 million
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Programming language topics
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streaker video game streaker arcade adventure game published mastertronic bulldog label 1987 game runs amstrad cpc msx sinclair zx spectrum hero game carlin naked man mugged stripped needs find clothes carlin town planet zuggi resembles town earth many ways locations including hotel cafe supermarket chemist shop streaker finds clothes able enter locations game fully dressed game arcade adventure somewhere puzzle-based adventure game action game gameplay controlled nested menu system mastertronic spellbound multitude items game many used seem purpose streaker pick keys open doors eat food items raise hunger levels needs solve number simple puzzles aspects life zuggi similar earth number fantastic elements world example streaker may teleport beam transfer using number different coloured beamers teleport streaker location corresponding beampad beampads moved streaker good way avoid thieves nice touches include streaker ability advance time acquiring stopwatch game played real time often need wait particular location open save load options appearing streaker picks tape recorder streaker quest made difficult presence number thieves steal streaker clothes contact cause lose life naked clothes may regained thieves finding offering thief item wants thieves follows despite rather unusual aim game seem prurient content therein 1980s young children occasionally unwittingly perplexed embarrassed teachers telling spent evening playing streaker
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Computer architecture
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aleste 2 aleste 2 アレスタ２ scrolling shooter video game developed released compile msx2 1989 exclusively japan sequel aleste first game aleste series feature recurring series heroine ellinor later appeared musha aleste aleste 2 along compile shooters also released now-defunct woomb service 2009 projectegg released game digitally windows also english game takes place year 2039 two decades super computer dia51 attacked decimated earth long restoration period earth invaded race alien plant-like humanoids called vagand intent finding new food source earth first attack earth vagand destroys earth space cruiser commanded previous earth hero ray waizen plan invade earth challenged newest version aleste piloted daughter ray yuri waizen ellinor vowed avenge father death personally kill vagand leader gaizel retro gamer included among top ten msx games three aleste titles msx computers worth seeking chose aleste 2 looks superb allows select weapons start game first title canon feature reoccurring protagonist ellinor
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Computer architecture
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client certificate cryptography client certificate type digital certificate used client systems make authenticated requests remote server client certificates play key role many mutual authentication designs providing strong assurances requester identity
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Computer security
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erik meijer computer scientist erik meijer born 18 april 1963 curaçao dutch computer scientist entrepreneur tie-dye enthusiast 2000 early 2013 software architect microsoft headed cloud programmability team founded applied duality inc. 2013 associate professor utrecht university since 2015 director engineering facebook received ph.d. nijmegen university 1992 meijer research included areas functional programming particularly haskell compiler implementation parsing programming language design xml foreign function interfaces work microsoft included c visual basic linq volta reactive programming framework reactive extensions .net 2009 recipient microsoft outstanding technical leadership award 2007 outstanding technical achievement award member c team meijer lived netherlands antilles age 14 father retired job family moved back netherlands 2011 erik meijer appointed part-time professor cloud programming within software engineering research group delft university technology also member acm queue editorial board since 2013 also honorary professor programming language design school computer science university nottingham associated functional programming laboratory early 2013 erik meijer left microsoft started applied duality incorporated period worked hack language facebook rxjava library netflix dart language google christmas 2014 erik meijer diagnosed chronic myelogenous leukemia suffered close death experience hospitalized teaches course mooc provider coursera called principles reactive programming course edx called introduction functional programming
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Programming language topics
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arcserve arcserve provider data protection replication recovery solutions enterprise mid-market businesses arcserve founded 1983 cheyenne software software vendor ca technologies known computer associates acquired cheyenne 1996 continued develop market arcserve product brand arcserve first developed product used back software programs ensure data network could lost major function first release automatically copy information system mishaps power failures equipment malfunctions would destroy erase early nineties arcserve became cheyenne flagship product massive growth sales cheyenne brought improved version core program arcserve 1993 began distribution original equipment manufacturers oems mid-nineties cheyenne continued release series new arcserve products tailored specifically different market segments macintosh windows users software vendor ca technologies known computer associates acquired cheyenne 1996 continued develop market arcserve product brand august 2014 arcserve became independent company marlin equity partners acquired business ca technologies released first product named arcserve unified data protection udp arcserve provides largest independent software vendor isv developed backup software products market supports wide variety platforms applications arcserve unified data protection udp offered fully integrated software set-and-forget virtual physical appliances arcserve r cloud april 26 2017 arcserve announced acquisition email archiving technology named arcserve udp archiving july 11 2017 arcserve announced acquisition zetta cloud-based disaster recovery solutions provider offers direct-to-cloud draas baas arcserve udp cloud direct
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Computer security
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microsoft windows microsoft windows group several graphical operating system families developed marketed sold microsoft family caters certain sector computing industry active microsoft windows families include windows nt windows iot may encompass subfamilies e.g windows server windows embedded compact windows ce defunct microsoft windows families include windows 9x windows mobile windows phone microsoft introduced operating environment named windows november 20 1985 graphical operating system shell ms-dos response growing interest graphical user interfaces guis microsoft windows came dominate world personal computer pc market 90 market share overtaking mac os introduced 1984 apple came see windows unfair encroachment innovation gui development implemented products lisa macintosh eventually settled court microsoft favor 1993 pcs windows still popular operating system however 2014 microsoft admitted losing majority overall operating system market android massive growth sales android smartphones 2014 number windows devices sold less 25 android devices sold comparison however may fully relevant two operating systems traditionally target different platforms still numbers server use windows comparable competitors show one third market share similar end user use recent version windows pcs tablets smartphones embedded devices windows 10 recent version server computers windows server version 1903 specialized version windows also runs xbox one video game console microsoft developer windows registered several trademarks denote family windows operating systems target specific sector computing industry 2014 following windows families actively developed following windows families longer developed term windows collectively describes several generations microsoft operating system products products generally categorized follows history windows dates back 1981 microsoft started work program called interface manager announced november 1983 apple lisa macintosh name windows windows 1.0 released november 1985 windows 1.0 compete apple operating system achieved little popularity windows 1.0 complete operating system rather extends ms-dos shell windows 1.0 program known ms-dos executive components included calculator calendar cardfile clipboard viewer clock control panel notepad paint reversi terminal write windows 1.0 allow overlapping windows instead windows tiled modal dialog boxes may appear windows microsoft sold included windows development libraries c development environment included numerous windows samples windows 2.0 released december 1987 popular predecessor features several improvements user interface memory management windows 2.03 changed os tiled windows overlapping windows result change led apple computer filing suit microsoft alleging infringement apple copyrights windows 2.0 also introduced sophisticated keyboard shortcuts could make use expanded memory windows 2.1 released two different versions windows/286 windows/386 windows/386 uses virtual 8086 mode intel 80386 multitask several dos programs paged memory model emulate expanded memory using available extended memory windows/286 spite name runs intel 8086 intel 80286 processors runs real mode make use high memory area addition full windows-packages runtime-only versions shipped early windows software third parties made possible run windows software ms-dos without full windows feature set early versions windows often thought graphical shells mostly ran top ms-dos use file system services however even earliest windows versions already assumed many typical operating system functions notably executable file format providing device drivers timer graphics printer mouse keyboard sound unlike ms-dos windows allowed users execute multiple graphical applications time cooperative multitasking windows implemented elaborate segment-based software virtual memory scheme allows run applications larger available memory code segments resources swapped thrown away memory became scarce data segments moved memory given application relinquished processor control windows 3.0 released 1990 improved design mostly virtual memory loadable virtual device drivers vxds allow windows share arbitrary devices multi-tasked dos applications windows 3.0 applications run protected mode gives access several megabytes memory without obligation participate software virtual memory scheme run inside address space segmented memory provides degree protection windows 3.0 also featured improvements user interface microsoft rewrote critical operations c assembly windows 3.0 first microsoft windows version achieve broad commercial success selling 2 million copies first six months windows 3.1 made generally available march 1 1992 featured facelift august 1993 windows workgroups special version integrated peer-to-peer networking features version number 3.11 released sold along windows 3.1 support windows 3.1 ended december 31 2001 windows 3.2 released 1994 updated version chinese version windows 3.1 update limited language version fixed issues related complex writing system chinese language windows 3.2 generally sold computer manufacturers ten-disk version ms-dos also simplified chinese characters basic output translated utilities next major consumer-oriented release windows windows 95 released august 24 1995 still remaining ms-dos-based windows 95 introduced support native 32-bit applications plug play hardware preemptive multitasking long file names 255 characters provided increased stability predecessors windows 95 also introduced redesigned object oriented user interface replacing previous program manager start menu taskbar windows explorer shell windows 95 major commercial success microsoft ina fried cnet remarked time windows 95 finally ushered market 2001 become fixture computer desktops around world microsoft published four oem service releases osr windows 95 roughly equivalent service pack first osr windows 95 also first version windows bundled microsoft web browser internet explorer mainstream support windows 95 ended december 31 2000 extended support windows 95 ended december 31 2001 windows 95 followed release windows 98 june 25 1998 introduced windows driver model support usb composite devices support acpi hibernation support multi-monitor configurations windows 98 also included integration internet explorer 4 active desktop aspects windows desktop update series enhancements explorer shell also made available windows 95 may 1999 microsoft released windows 98 second edition updated version windows 98 windows 98 se added internet explorer 5.0 windows media player 6.2 amongst upgrades mainstream support windows 98 ended june 30 2002 extended support windows 98 ended july 11 2006 september 14 2000 microsoft released windows millennium edition last dos-based version windows windows incorporated visual interface enhancements windows nt-based counterpart windows 2000 faster boot times previous versions however required removal ability access real mode dos environment removing compatibility older programs expanded multimedia functionality including windows media player 7 windows movie maker windows image acquisition framework retrieving images scanners digital cameras additional system utilities system file protection system restore updated home networking tools however windows faced criticism speed instability along hardware compatibility issues removal real mode dos support pc world considered windows one worst operating systems microsoft ever released 4th worst tech product time november 1988 new development team within microsoft included former digital equipment corporation developers dave cutler mark lucovsky began work revamped version ibm microsoft os/2 operating system known nt os/2 nt os/2 intended secure multi-user operating system posix compatibility modular portable kernel preemptive multitasking support multiple processor architectures however following successful release windows 3.0 nt development team decided rework project use extended 32-bit port windows api known win32 instead os/2 win32 maintained similar structure windows apis allowing existing windows applications easily ported platform also supported capabilities existing nt kernel following approval microsoft staff development continued windows nt first 32-bit version windows however ibm objected changes ultimately continued os/2 development first release resulting operating system windows nt 3.1 named associate windows 3.1 released july 1993 versions desktop workstations servers windows nt 3.5 released september 1994 focusing performance improvements support novell netware followed windows nt 3.51 may 1995 included additional improvements support powerpc architecture windows nt 4.0 released june 1996 introducing redesigned interface windows 95 nt series february 17 2000 microsoft released windows 2000 successor nt 4.0 windows nt name dropped point order put greater focus windows brand next major version windows nt windows xp released october 25 2001 introduction windows xp aimed unify consumer-oriented windows 9x series architecture introduced windows nt change microsoft promised would provide better performance dos-based predecessors windows xp would also introduce redesigned user interface including updated start menu task-oriented windows explorer streamlined multimedia networking features internet explorer 6 integration microsoft .net passport services modes help provide compatibility software designed previous versions windows remote assistance functionality retail windows xp marketed two main editions home edition targeted towards consumers professional edition targeted towards business environments power users included additional security networking features home professional later accompanied media center edition designed home theater pcs emphasis support dvd playback tv tuner cards dvr functionality remote controls tablet pc edition designed mobile devices meeting specifications tablet computer support stylus pen input additional pen-enabled applications mainstream support windows xp ended april 14 2009 extended support ended april 8 2014 windows 2000 microsoft also changed release schedules server operating systems server counterpart windows xp windows server 2003 released april 2003 followed december 2005 windows server 2003 r2 lengthy development process windows vista released november 30 2006 volume licensing january 30 2007 consumers contained number new features redesigned shell user interface significant technical changes particular focus security features available number different editions subject criticism drop performance longer boot time criticism new uac stricter license agreement vista server counterpart windows server 2008 released early 2008 july 22 2009 windows 7 windows server 2008 r2 released rtm release manufacturing former released public 3 months later october 22 2009 unlike predecessor windows vista introduced large number new features windows 7 intended focused incremental upgrade windows line goal compatible applications hardware windows vista already compatible windows 7 multi-touch support redesigned windows shell updated taskbar home networking system called homegroup performance improvements windows 8 successor windows 7 released generally october 26 2012 number significant changes made windows 8 including introduction user interface based around microsoft metro design language optimizations touch-based devices tablets all-in-one pcs changes include start screen uses large tiles convenient touch interactions allow display continually updated information new class apps designed primarily use touch-based devices changes include increased integration cloud services online platforms social networks microsoft onedrive formerly skydrive xbox live services windows store service software distribution new variant known windows rt use devices utilize arm architecture update windows 8 called windows 8.1 released october 17 2013 includes features new live tile sizes deeper onedrive integration many revisions windows 8 windows 8.1 subject criticism removal start menu september 30 2014 microsoft announced windows 10 successor windows 8.1 released july 29 2015 addresses shortcomings user interface first introduced windows 8 changes pc include return start menu virtual desktop system ability run windows store apps within windows desktop rather full-screen mode windows 10 said available update qualified windows 7 sp1 windows 8.1 windows phone 8.1 devices get windows 10 application windows 7 windows 8.1 windows update windows 7 february 2017 microsoft announced migration windows source code repository perforce git migration involved 3.5 million separate files 300 gigabyte repository may 2017 90 percent engineering team uses git 8500 commits 1760 windows builds per day multilingual support built windows since windows 3 language keyboard interface changed region language control panel components supported input languages input method editors automatically installed windows installation windows xp earlier files east asian languages chinese right-to-left scripts arabic may need installed separately also said control panel third-party imes may also installed user feels provided one insufficient needs interface languages operating system free download languages limited certain editions windows language interface packs lips redistributable may downloaded microsoft download center installed edition windows xp later translate windows interface require certain base language language windows originally shipped used languages emerging markets full language packs translates complete operating system available specific editions windows ultimate enterprise editions windows vista 7 editions windows 8 8.1 rt except single language require specific base language commonly used popular languages french chinese languages downloaded download center available optional updates windows update service except windows 8 interface language installed applications affected changes windows interface language availability languages depends application developers windows 8 windows server 2012 introduces new language control panel interface input languages simultaneously changed language packs regardless type downloaded central location pc settings app windows 8.1 windows server 2012 r2 also includes counterpart settings page changing interface language also changes language preinstalled windows store apps mail maps news certain microsoft-developed apps remote desktop limitations language packs however still effect except full language packs installed edition except single language caters emerging markets windows nt included support several different platforms x86-based personal computer became dominant professional world windows nt 4.0 predecessors supported powerpc dec alpha mips r4000 although platforms implement 64-bit computing operating system treated 32-bit however windows 2000 successor windows nt 4.0 dropped support platforms except third generation x86 known ia-32 newer 32-bit mode client line windows nt family still runs ia-32 although windows server line ceased supporting platform release windows server 2008 r2 introduction intel itanium architecture ia-64 microsoft released new versions windows support itanium versions windows xp windows server 2003 released time mainstream x86 counterparts windows xp 64-bit edition released 2005 last windows client operating systems support itanium windows server line continues support platform windows server 2012 windows server 2008 r2 last windows operating system support itanium architecture april 25 2005 microsoft released windows xp professional x64 edition windows server 2003 x64 editions support x86-64 simply x64 eighth generation x86 architecture windows vista first client version windows nt released simultaneously ia-32 x64 editions x64 still supported edition windows 8 known windows rt specifically created computers arm architecture arm still used windows smartphones windows 10 tablets windows rt updated starting windows 10 fall creators update later includes support pcs arm architecture windows ce officially known windows embedded compact edition windows runs minimalistic computers like satellite navigation systems mobile phones windows embedded compact based dedicated kernel dubbed windows ce kernel microsoft licenses windows ce oems device makers oems device makers modify create user interfaces experiences windows ce provides technical foundation windows ce used dreamcast along sega proprietary os console windows ce core windows mobile derived successor windows phone 7 based components windows ce 6.0 r3 windows ce 7.0 windows phone 8 however based nt-kernel windows 8 windows embedded compact confused windows xp embedded windows nt 4.0 embedded modular editions windows based windows nt kernel xbox os unofficial name given version windows runs xbox one specific implementation emphasis virtualization using hyper-v three operating systems running consisting core operating system second implemented games windows-like environment applications microsoft updates xbox one os every month updates downloaded xbox live service xbox subsequently installed using offline recovery images downloaded via pc windows 10-based core replaced windows 8-based one update new system sometimes referred windows 10 xbox one onecore xbox one system also allows backward compatibility xbox 360 xbox 360 system backwards compatible original xbox 2017 microsoft announced would start using git open source version control system created linus torvalds microsoft previously used proprietary version control system called source depot microsoft began integrate git team foundation server 2013 windows continued rely source depot however decision came complexity windows codebase especially well suited decentralized nature linux development git originally created manage git repository contains complete history files proved unworkable windows developers cloning repository takes several hours microsoft working new project called virtual file system git vfsforgit address challenges according net applications tracks use operating systems devices active web windows used operating-system family personal computers july 2017 close 90 usage share including personal computers kinds e.g. desktops laptops mobile devices windows oses accounted 35.24 usage share july 2017 compared android highest 41.24 ios 13.22 macos 4.64 according statcounter tracks use operating systems use devices active web windows used less half market developing countries also developed ones—such united states use windows desktops plurality operating system fallen 46.18 united kingdom ireland numbers easiest monthly numbers find track real use may mirror installed base sales numbers recent years devices consistent server numbers next section terms number devices shipped operating system installed smartphones windows phone third-most-shipped os 2.6 android 82.8 ios 13.9 second quarter 2015 according idc across pcs mobile devices 2014 windows oses second-most-shipped 333 million devices 14 android 1.2 billion 49 ahead ios macos combined 263 million 11 use latest version windows 10 exceeded windows 7 globally since early 2018 developed countries japan australia us windows 10 already popular version since early 2017 usage share windows serversthose running web servers also kinds servers 33.6 consumer versions windows originally designed ease-of-use single-user pc without network connection security features built outset however windows nt successors designed security including network multi-user pcs initially designed internet security mind much since first developed early 1990s internet use less prevalent design issues combined programming errors e.g buffer overflows popularity windows means frequent target computer worm virus writers june 2005 bruce schneier counterpane internet security reported seen 1,000 new viruses worms previous six months 2005 kaspersky lab found around 11,000 malicious programs—viruses trojans back-doors exploits written windows microsoft releases security patches windows update service approximately month usually second tuesday month although critical updates made available shorter intervals necessary versions windows including windows 2000 sp3 windows xp updates automatically downloaded installed user selects result service pack 2 windows xp well service pack 1 windows server 2003 installed users quickly otherwise might windows 9x series offered option profiles multiple users concept access privileges allow concurrent access true multi-user operating systems addition implemented partial memory protection accordingly widely criticised lack security windows nt series operating systems contrast true multi-user implement absolute memory protection however lot advantages true multi-user operating system nullified fact prior windows vista first user account created setup process administrator account also default new accounts though windows xp limited accounts majority home users change account type fewer rights – partially due number programs unnecessarily required administrator rights – home users ran administrator time windows vista changes introducing privilege elevation system called user account control logging standard user logon session created token containing basic privileges assigned way new logon session incapable making changes would affect entire system logging user administrators group two separate tokens assigned first token contains privileges typically awarded administrator second restricted token similar standard user would receive user applications including windows shell started restricted token resulting reduced privilege environment even administrator account application requests higher privileges run administrator clicked uac prompt confirmation consent given including administrator credentials account requesting elevation member administrators group start process using unrestricted token leaked documents published wikileaks codenamed vault 7 dated 2013–2016 detail capabilities cia perform electronic surveillance cyber warfare ability compromise operating systems microsoft windows august 2019 computer experts reported bluekeep security vulnerability potentially affects older unpatched microsoft windows versions via program remote desktop protocol allowing possibility remote code execution may include related flaws collectively named dejablue affecting newer windows versions i.e. windows 7 recent versions well addition experts reported microsoft security vulnerability based legacy code involving microsoft ctf ctfmon ctfmon.exe affects windows versions older windows xp version recent windows 10 versions patch correct flaw currently available windows versions windows nt 3 based file system permission system referred agdlp accounts global local permissions file permissions applied file/folder form 'local group 'global groups members global groups hold groups users depending different windows versions used system varies vendor products linux netware due 'static allocation permission applied directory file folder however using process aglp/agdlp/agudlp allows small number static permissions applied allows easy changes account groups without reapplying file permissions files folders january 6 2005 microsoft released beta version microsoft antispyware based upon previously released giant antispyware february 14 2006 microsoft antispyware became windows defender release beta 2 windows defender freeware program designed protect spyware unwanted software windows xp windows server 2003 users genuine copies microsoft windows freely download program microsoft web site windows defender ships part windows vista 7 windows 8 windows defender microsoft security essentials combined single program named windows defender based microsoft security essentials borrowing features user interface although enabled default turned use another anti-virus solution windows malicious software removal tool optional microsoft safety scanner two free security products offered microsoft windows 10 anniversary update microsoft introduced limited periodic scanning feature allows windows defender scan detect remove threats third-party anti-virus software missed advanced threat protection service introduced enterprise users new service uses cloud service detect take actions advanced network attacks article based report symantec internetnews.com described microsoft windows fewest number patches shortest average patch development time five operating systems monitored last six months 2006 study conducted kevin mitnick marketing communications firm avantgarde 2004 found unprotected unpatched windows xp system service pack 1 lasted four minutes internet compromised unprotected also unpatched windows server 2003 system compromised connected internet 8 hours computer running windows xp service pack 2 compromised aol national cyber security alliance online safety study october 2004 determined 80 windows users infected least one spyware/adware product much documentation available describing increase security microsoft windows products typical suggestions include deploying microsoft windows behind hardware software firewall running anti-virus anti-spyware software installing patches become available windows update owing operating system popularity number applications released aim provide compatibility windows applications either compatibility layer another operating system standalone system run software written windows box include
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Operating systems
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google neural machine translation google neural machine translation gnmt neural machine translation nmt system developed google introduced november 2016 uses artificial neural network increase fluency accuracy google translate gnmt improves quality translation applying example based ebmt machine translation method system learns millions examples gnmt proposed architecture system learning first tested hundred languages supported google translate large end-to-end framework system learns time create better natural translations gnmt capable translating whole sentences time rather piece piece gnmt network undertake interlingual machine translation encoding semantics sentence rather memorizing phrase-to-phrase translations google brain project established 2011 secretive google x research lab google fellow jeff dean google researcher greg corrado stanford university computer science professor andrew ng ng ’ work led biggest breakthroughs google stanford september 2016 research team google announced development google neural machine translation system gnmt november google translate began using neural machine translation nmt preference previous statistical methods smt used since october 2007 proprietary in-house smt technology google translate nmt system uses large artificial neural network capable deep learning using millions examples gnmt improves quality translation using broader context deduce relevant translation result rearranged adapted approach grammatically based human language gnmt proposed architecture system learning first tested hundred languages supported google translate gnmt create universal interlingua rather aimed commonality found many languages considered interest psychologists linguists computer scientists new translation engine first enabled eight languages english french german spanish portuguese chinese japanese korean turkish 2016 march 2017 three additional languages enabled russian hindi vietnamese along thai support added later support hebrew arabic also added help google translate community month mid april 2017 google netherlands announced support dutch european languages related english support added nine indian languages viz hindi bengali marathi gujarati punjabi tamil telugu malayalam kannada end april 2017 list language translation pairs supported google translate neural machine translation nmt model july 2017 languages currently support translation english gnmt system said represent improvement former google translate able handle zero-shot translation directly translates one language another example japanese korean google translate previously first translated source language english translated english target language rather translating directly one language another currently non-english language pairs supported
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Computational linguistics
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playstation 2 technical specifications playstation 2 technical specifications describe various components playstation 2 ps2 video game console sixth-generation hardware playstation 2 video game console consists various components heart console configuration central processing unit cpu custom risc processor known emotion engine operates 294 mhz 300 mhz later consoles cpu heavily relies integration two vector processing units known vpu0 vpu1 graphics synthesizer floating-point unit fpu order render 3d graphics components system dvd-rom optical drive dualshock 2 controller provide software user control input playstation 2 software distributed cd-rom dvd-rom addition console play audio cds dvd movies backwards compatible original playstation games accomplished inclusion original playstation cpu also serves ps2 i/o processor ps2 also supports limited functionality original playstation memory cards controllers ps2 dualshock 2 controller upgraded version playstation dualshock analog face shoulder d-pad buttons replacing digital buttons original like predecessor dualshock 2 controller features force feedback technology standard playstation 2 memory card 8 mb capacity uses sony magicgate encryption requirement prevented production memory cards third parties purchase magicgate license memory cards without encryption used store playstation game saves playstation games would unable read write card – card could used backup variety non-sony manufactured memory cards available playstation 2 allowing larger memory capacity standard 8 mb however use unsupported compatibility guaranteed memory cards 128 mb storage space console also features usb ieee 1394 expansion ports compatibility usb ieee 1394 devices dependent software supporting device example ps2 bios boot iso image usb flash drive operate usb printer machine operating system include functionality contrast gran turismo 4 tourist trophy programmed save screenshots usb mass storage device print images certain usb printers playstation 2 hdd installed via expansion bay back console required play certain games notably popular final fantasy xi replaced powerpc-based deckard iop 4 mb sdram starting scph-7500x
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Computer architecture
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google app runtime chrome android runtime chrome arc discontinued compatibility layer sandboxing technology running android applications desktop laptop computers isolated environment allowed applications safely run web browser independent user operating system near-native speeds since discontinued google developed another method run android apps chrome os devices android runtime chrome partially open-sourced project development google announced sundar pichai google i/o 2014 developer conference limited beta consumer release september 2014 duolingo evernote sight words vine android applications made available chrome web store installation chromebook devices running os version 37 higher development google taking place behind closed doors individual repository commits code reviews issue tracking kept internal company open sourced parts arc licensed bsd-style license limited beta consumer release september 2014 duolingo evernote sight words vine android applications made available chrome web store installation chromebook devices running os version 37 higher october 2014 three apps added cloudmagic onefootball podcast addict march 2015 anandtech reported vlc media player added coming months april 1 2015 google released arc welder chrome packaged app providing arc runtime application packager intended give android developers preview upcoming technology chance test android apps chrome platform arc builds upon google native client native client platform extended posix-compatible layer top nacl integrated runtime pepper apis emulate linux environment foundation android phone allows running almost unchanged dalvik vm sandboxed environment arc uses chrome permission system android one according security evaluation meng xu arc apps may communicate installed chrome extensions files stored underlying operating system might open avenues various attacks threats mitigated heavily sandboxed environment arc second half 2014 developer tools documentation released google several community efforts arc appeared vlad filippov maintains archon unofficial distribution arc runtime installed non-chromebook computers developer also maintains javascript nodejs tool automate packaging android apps use arc developers created user-friendly tools beyond chromeos-apk simplify packaging applications arcon runtime first chrome packaged app called twerk android application arcon packager used named chrome apk packager name changed google request active reddit community maintains list android apps work arcon runtime vlad filippov published guide run opera mini inside chromium browser reception mostly positive developers expressed confusion wide scale competing development platforms google offers web apps chrome packaged apps android apps delivered arc google responded fully committed platforms encourage developers choose one fits best
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Computer security
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wirth law wirth law adage computer performance states software getting slower rapidly hardware becoming faster adage named niklaus wirth discussed 1995 article plea lean software wirth attributed saying martin reiser preface book oberon system wrote hope progress hardware cure software ills however critical observer may observe software manages outgrow hardware size sluggishness observers noted time indeed trend becoming obvious early 1987 states two contributing factors acceptance ever-growing software rapidly growing hardware performance customers ignorance features essential versus nice-to-have enhanced user convenience functionality supposedly justify increased size software wirth argues people increasingly misinterpreting complexity sophistication details cute essential hidden cost result calls creation leaner software pioneered development oberon software system developed 1986 1989 based nothing hardware primary goal show software developed fraction memory capacity processor power usually required without sacrificing flexibility functionality user convenience law restated 2009 attributed larry page founder google referred page law first use name attributed sergey brin google i/o conference 2009 common forms use names leading hardware software companies 1990s intel microsoft ceos andy grove bill gates intel giveth microsoft taketh away andy giveth bill taketh away gates law speed software halves every 18 months variant wirth law borrowing name bill gates co-founder microsoft observation speed commercial software generally slows 50 every 18 months thereby negating benefits moore law could occur variety reasons featuritis code cruft developer laziness management turnover whose design philosophy coincide previous manager may law named david may variant stating software efficiency halves every 18 months compensating moore law
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Computer architecture
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quite c quite c nqc programming language application programming interface api native bytecode compiler toolkit lego mindstorms cybermaster lego spybotics systems based primarily c language specific limitations maximum number subroutines variables allowed differ depending version firmware rcx language invented david baum released two books subject simple test program written nqc rcx motor connected output port could look like thus motor go full speed two seconds turned nqc legal tournaments sanctioned first number teams complained far without success nqc compilers integrated development environments ides available many platforms including microsoft windows mac os x linux beos dos one bricx command center compiler sources ide sources
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Programming language topics
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adam leventhal programmer adam leventhal born 1979 united states american software engineer one three authors dtrace dynamic tracing facility solaris 10 sun microsystems latest os allows users observe debug tune system behavior real time available public since november 2003 dtrace since used find opportunities performance improvements production environments adam joined solaris kernel development team graduating cum laude brown university 2001 b.sc math computer science 2006 adam dtrace colleagues chosen gold winners wall street journal technology innovation awards contest panel judges representing industry well research academic institutions year sun microsystems acquired oracle corp leventhal announced leaving company served chief technology officer delphix 2010 2016
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Operating systems
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bonnell microarchitecture bonnell cpu microarchitecture used intel atom processors execute two instructions per cycle like many x86 microprocessors translates x86 instructions cisc instructions simpler internal operations sometimes referred micro-ops effectively risc style instructions prior execution majority instructions produce one micro-op translated around 4 instructions used typical programs producing multiple micro-ops number instructions produce one micro-op significantly fewer p6 netburst microarchitectures bonnell microarchitecture internal micro-ops contain memory load memory store connection alu operation thus similar x86 level powerful micro-ops used previous designs enables relatively good performance two integer alus without instruction reordering speculative execution register renaming side effect speculative execution invulnerability meltdown spectre bonnell microarchitecture therefore represents partial revival principles used earlier intel designs p5 i486 sole purpose enhancing performance per watt ratio however hyper-threading implemented easy i.e low-power way employ whole pipeline efficiently avoiding typical single thread dependencies 2 march 2008 intel announced new single-core atom z5xx series processor code-named silverthorne used ultra-mobile pcs mobile internet devices mids supersede stealey a100 a110 processor 47 million transistors 25 mm die allowing extremely economical production ~2500 chips single 300 mm diameter wafer atom z500 processor dual-thread performance equivalent predecessor stealey outperform applications use simultaneous multithreading sse3 run 0.8 2.0 ghz tdp rating 0.65 2.4 w dip 0.01 w idle feature 32 kb instruction l1 24 kb data l1 caches 512 kb l2 cache 533 mt/s front-side bus processors manufactured 45 nm process 2 march 2008 intel announced lower-power variants diamondville cpu named atom n2xx intended use nettops classmate pc like predecessors single-core cpus hyper-threading n270 tdp rating 2.5 w runs 1.6 ghz 533 mhz fsb n280 clock speed 1.66 ghz 667 mhz fsb 22 september 2008 intel announced new 64-bit dual-core processor unofficially code-named dual diamondville branded atom 330 used desktop computers runs 1.6 ghz fsb speed 533 mhz tdp rating 8 w. dual core consists two diamondville dies single substrate 2009 nvidia used atom 300 geforce 9400m chipset mini-itx form factor motherboard ion platform although atom processor relatively low-power x86 microprocessor many chipsets commonly used dissipate significantly power example atom n270 commonly used netbooks mid-2010 tdp rating 2.5 w intel atom platform uses 945gse express chipset specified maximum tdp 11.8 w processor responsible relatively small portion total power dissipated individual figures 2.5 w n270 processor 6 w 945gse chipset 3.3 w 82801gbm i/o controller intel also provides us15w system controller hub-based chipset combined tdp less 5 w together atom z5xx silverthorne series processors used ultra-mobile pcs mids though manufacturers released ultra-thin systems running processors e.g sony vaio x initially atom motherboards consumer market featured intel 945gc chipset uses 22 watts early 2009 manufacturers offering lower-power motherboards 945gse us15w chipset atom n270 n280 z5xx series cpu 21 december 2009 intel announced n450 d510 d410 cpus integrated graphics new manufacturing process resulted 20 reduction power consumption 60 smaller die size intel gma 3150 45 nm shrink gma 3100 hd capabilities included on-die gpu netbooks using new processor released 11 january 2010 major new feature longer battery life 10 hours 6-cell systems generation atom codenamed pineview used pine trail platform intel pine trail-m platform utilizes atom processor codenamed pineview-m platform controller hub codenamed tiger point graphics memory controller moved processor paired tiger point pch creates power-efficient 2-chip platform rather 3-chip one used previous-generation atom chipsets 1 march 2010 intel introduced n470 processor running 1.83 ghz 667 mhz fsb tdp rating 6.5 w. new atom n4xx chips became available 11 january 2010 used netbook nettop systems includes integrated single-channel ddr2 memory controller integrated graphics core also features hyper-threading manufactured 45 nm process new design uses half power older menlow platform reduced overall power consumption size makes platform desirable use smartphones mobile internet devices d4xx d5xx series support x86-64 bit instruction set ddr2-800 memory rated embedded use series integrated graphics processor built directly cpu help improve performance models targeted nettops low-end desktops support speedstep atom d510 dual-core processor runs 1.66 ghz 1 mb l2 cache tdp rating 13 w. single-core atom d410 runs 1.66 ghz 512 kb l2 cache tdp rating 10 w. tunnel creek embedded atom processor used queens bay platform topcliff pch lincroft z6xx whitney point pch included oak trail tablet platform oak trail intel atom platform based moorestown platforms include lincroft microprocessor use two distinct input/output platform controller hubs i/o-pch codenamed langwell whitney point respectively oak trail presented 11 april 2011 released may 2011 z670 processor part oak trail platform delivers improved video playback faster internet browsing longer battery life without sacrificing performance according intel oak trail includes support 1080p video decoding well hdmi platform also improved power efficiency allows applications run various operating systems including android meego windows stellarton tunnel creek cpu altera field programmable gate array fpga sodaville consumer electronics atom soc groveland consumer electronics atom soc 32 nm shrink bonnell called saltwell intel released third-generation cedar trail platform consisting range cedarview processors nm10 southbridge chip based 32 nm process technology fourth quarter 2011 intel stated improvements graphics capabilities including support 1080p video additional display options including hdmi displayport enhancements power consumption enable fanless designs longer battery life cedar trail platform includes two new cpus 32 nm-based n2800 1.86 ghz n2600 1.6 ghz replace previous generation pineview n4xx n5xx processors cpus also feature integrated gpu supports directx 9 addition netbook platform two new cedarview cpus nettops d2500 d2700 released 25 september 2011 early march 2012 n2800-based intel dn2800mt motherboard started become available due use netbook processor mini-itx motherboard reach idle power consumption low 7.1 w. penwell atom soc part medfield mid/smartphone platform berryville consumer electronics atom soc cloverview atom soc part clover trail tablet platform december 2012 intel launched 64-bit centerton family atom cpus designed specifically use bordenville platform servers based 32 nm saltwell architecture centerton adds features previously unavailable atom processors intel vt virtualization technology support ecc memory briarwood atom soc designed server platform
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Computer architecture
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saml 1.1 security assertion markup language saml xml standard exchanging authentication authorization data security domains saml product oasis organization security services technical committee saml 1.1 ratified oasis standard september 2003 critical aspects saml 1.1 covered detail official documents samlcore samlbind new saml probably read introductory saml topic first samloverview document oasis prior saml 1.1 saml 1.0 adopted oasis standard november 2002 saml undergone one minor v1.1 one major revision v2.0 since v1.0 relatively simple protocol saml 1.0 historical interest however since us federal e-authentication initiative adopted saml 1.0 core technology versions 1.0 1.1 saml similar see samldiff specific differences two standards article concentrates saml 1.1 since important standard upon many standards implementations depend warning implementers deployers note well code examples article non-normative illustration purposes consult oasis saml specifications normative requirements saml assertions contain statements service providers use make access control decisions instance authentication statements assert service provider principal indeed authenticate identity provider particular time using particular method authentication information principal may disclosed authentication statement authentication statement example e-mail address principal asserted service provider e-mail address example suffice large number situations cases however additional information needed service provider make access control decision example suppose students allowed access scholarships data attribute statement indicate whether principal affiliation student service provider uses allow deny access resp scholarships application attributes often obtained ldap directory consistent representations attributes across security domains crucial example showing student might obtain access scholarships application service provider functioning policy enforcement point policy decision point situations may preferable associate policy decision point identity provider case service provider passes uri identity provider asserts authorization decision statement dictates whether principal allowed access secured resource given uri three statement types mutually exclusive example authentication statements attribute statements may included single assertion shown precludes need make subsequent round trips service provider identity provider saml protocol simple request-response protocol saml requester sends saml codice_1 element responder similarly saml responder returns saml codice_2 element requester bindings profiles needed affect message exchange detailed following sections saml 1.1 formally defines one protocol binding saml soap binding compatible saml 1.1 implementation must implement saml soap http synchronous protocol binding transport mechanisms besides http permitted provided protocol-independent aspects saml soap binding observed see section 3.1.2 samlbind saml 1.1 soap binding built top version 1.1 soap numbering purely coincidental saml requester wraps saml codice_1 element within body soap message similarly saml responder returns saml codice_2 element within body returned soap message error responder returns soap fault code instead saml markup must included soap body saml 1.1 define saml-specific soap headers requester free insert soap headers wishes although none required recall soap 1.1 codice_5 http header must included http request although value may empty saml requester may give following value codice_5 header saml responder must depend value however secure connection required saml requests responses situations message integrity confidentiality required http ssl 3.0 tls 1.0 server-side certificate required saml responder may return 403 forbidden response refuses respond saml requester responder must return 500 internal server error response event soap error soap fault element must included well otherwise 200 ok response returned even presence saml processing error response include saml codice_7 element soap body general profiles describe use cases message exchanges required ultimately transfer assertions identity provider service provider saml 1.1 specifies two web browser sso profiles browser/post profile relies push operation passes sso assertion value browser using http post say identity provider pushes assertion service provider browser/artifact profile employs pull mechanism profile essentially passes sso assertion identity provider service provider reference browser using http redirect subsequently dereferenced via back-channel exchange i.e. service provider pulls assertion identity provider using saml soap http profiles support cross-domain single sign-on sso specification define additional profiles particular saml 1.1 support profile secure web service message support single logout profile saml 1.1 profiles begin inter-site transfer service managed identity provider principal arrives transfer service first place dictated specification see sections 4.1 4.2 samloverview possible scenarios practice client accessing secured resource service provider redirected inter-site transfer service identity provider precise sequence steps needed accomplish outlined saml 1.1 see section 4.3 samloverview rough ideas along lines scenario thoroughly addressed saml 2.0 visiting inter-site transfer service principal transferred assertion consumer service service provider exactly principal transferred inter-site transfer service assertion consumer service depends profile used case browser/artifact profile redirect used case browser/post profile client issues post request without user intervention expedite processing assertion consumer service two separate urls specified endpoint locations may recorded metadata files exactly identity provider obtains trusted metadata file otherwise determines trusted endpoint locations particular service provider scope respect saml 1.1 note conforming saml 1.1 identity provider must provide inter-site transfer service similarly saml 1.1 service provider must provide assertion consumer service saml 1.1 browser/post profile specifies following four 4 steps terminology used original specification modified slightly conform saml 2.0 specification message flow begins request directed idp principal via http user agent requests inter-site transfer service identity provider codice_8 desired resource service provider say nowiki https //sp.example.com/home /nowiki words following get request issued user agent ssl/tls profile specify url transfer service codice_9 parameter obtained user agent inter-site transfer service returns html document containing codice_10 element codice_9 parameter preserved step 1 value codice_12 parameter base64 encoding saml codice_2 element following saml response must digitally signed identity provider important assumed principal already established security context identity provider otherwise inter-site transfer service would unable provide authentication statement saml codice_2 element user agent requests assertion consumer service service provider values codice_9 codice_12 parameters taken html form step 2 note automate submission form following line javascript may appear anywhere page assumes course page contains single codice_10 element codice_18 assertion consumer service consumes saml codice_2 element creates security context service provider redirects user agent target resource saml 1.1 browser/artifact profile specifies following six 6 steps terminology used original specification modified slightly conform saml 2.0 specification message flow begins request directed idp principal via http user agent requests inter-site transfer service identity provider codice_8 desired resource service provider say nowiki https //sp.example.com/home /nowiki words following get request issued user agent ssl/tls profile specify url transfer service codice_9 parameter obtained user agent principal redirected assertion consumer service service provider following response returned user agent codice_22 reference assertion identity provider willing provide upon request important assumed principal already established security context identity provider otherwise inter-site transfer service would unable provide authentication statement user agent requests assertion consumer service service provider codice_8 codice_22 words following get request issued user agent ssl/tls assertion consumer service service provider begins back-channel exchange artifact resolution service identity provider saml soap message bound http post request codice_22 previously sent identity provider service provider steps 2 3 identity provider completes back-channel exchange responding saml assertion bound saml soap message case authentication statement includes codice_26 containing principal e-mail address assertion consumer service parses saml codice_2 element creates security context service provider redirects user agent target resource
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Computer security
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intel 8259 intel 8259 programmable interrupt controller pic designed intel 8085 intel 8086 microprocessors initial part 8259 later suffix version upward compatible usable 8086 8088 processor 8259 combines multiple interrupt input sources single interrupt output host microprocessor extending interrupt levels available system beyond one two levels found processor chip 8259a interrupt controller isa bus original ibm pc ibm pc 8259 introduced part intel mcs 85 family 1976 8259a included original pc introduced 1981 maintained pc/xt introduced 1983 second 8259a added introduction pc/at 8259 coexisted intel apic architecture since introduction symmetric multi-processor pcs modern pcs begun phase 8259a favor intel apic architecture however anymore separate chip 8259a interface still provided platform controller hub southbridge chipset modern x86 motherboards main signal pins 8259 follows eight interrupt input request lines named irq0 irq7 interrupt request output line named intr interrupt acknowledgment line named inta d0 d7 communicating interrupt level vector offset connections include cas0 cas2 cascading 8259s eight slave 8259s may cascaded master 8259 provide 64 irqs 8259s cascaded connecting int line one slave 8259 irq line one master 8259 three registers interrupt mask register imr interrupt request register irr in-service register isr irr maintains mask current interrupts pending acknowledgement isr maintains mask interrupts pending eoi imr maintains mask interrupts sent acknowledgement end interrupt eoi operations support specific eoi non-specific eoi auto-eoi specific eoi specifies irq level acknowledging isr non-specific eoi resets irq level isr auto-eoi resets irq level isr immediately interrupt acknowledged edge level interrupt trigger modes supported 8259a fixed priority rotating priority modes supported 8259 may configured work 8080/8085 8086/8088 8086/8088 interrupt controller provide interrupt number data bus interrupt occurs interrupt cycle 8080/8085 issue three bytes data bus corresponding call instruction 8080/8085 instruction set 8259a provides additional functionality compared 8259 particular buffered mode level-triggered mode upward compatible programming 8259 conjunction dos microsoft windows introduced number confusing issues sake backwards compatibility extends far back original pc introduced 1981 first issue less root second issue dos device drivers expected send non-specific eoi 8259s finish servicing device prevents use 8259 eoi modes dos excludes differentiation device interrupts rerouted master 8259 slave 8259 second issue deals use irq2 irq9 introduction slave 8259 pc/at slave 8259 int output connected master ir2 irq2 line isa bus originally connected ir2 rerouted ir1 slave thus old irq2 line generates irq9 cpu allow backwards compatibility dos device drivers still set irq2 handler installed bios irq9 redirects interrupts original irq2 handler pc bios thus also dos traditionally maps master 8259 interrupt requests irq0-irq7 interrupt vector offset 8 int08-int0f slave 8259 pc/at later interrupt requests irq8-irq15 interrupt vector offset 112 int70-int77 done despite first 32 int00-int1f interrupt vectors reserved processor internal exceptions ignored design pc reason reserved vectors exceptions operating systems map least master 8259 irqs used platform another interrupt vector base offset since operating systems allow changes device driver expectations 8259 modes operation auto-eoi may used especially important modern x86 hardware significant amount time may spent i/o address space delay communicating 8259s also allows number optimizations synchronization critical sections multiprocessor x86 system 8259s since isa bus support level triggered interrupts level triggered mode may used interrupts connected isa devices means pc/xt pc/at compatible systems 8259 must programmed edge triggered mode mca systems devices use level triggered interrupts interrupt controller hardwired always work level triggered mode newer eisa pci later systems edge/level control registers elcrs control mode per irq line effectively making mode 8259 irrelevant systems isa buses elcr programmed bios system startup correct operation elcrs located 0x4d0 0x4d1 x86 i/o address space 8-bits wide bit corresponding irq 8259s bit set irq level triggered mode otherwise irq edge triggered mode 8259 generates spurious interrupts response number conditions first irq line deasserted acknowledged may occur due noise irq lines edge triggered mode noise must maintain line low state 100 ns noise diminishes pull-up resistor returns irq line high thus generating false interrupt level triggered mode noise may cause high signal level systems intr line system sends acknowledgment request 8259 nothing resolve thus sends irq7 response first case generate spurious irq7 similar case occur 8259 unmask irq input de-assertion properly synchronized many systems irq input deasserted i/o write processor n't wait write reaches i/o device processor continues unmasks 8259 irq irq input deasserted 8259 assert intr time processor recognizes intr issues acknowledgment read irq 8259 irq input may deasserted 8259 returns spurious irq7 second master 8259 irq2 active high slave 8259 irq lines inactive falling edge interrupt acknowledgment second case generate spurious irq15 rare pc/xt isa system one 8259 controller pc/at later systems two 8259 controllers master slave irq0 irq7 master 8259 interrupt lines irq8 irq15 slave 8259 interrupt lines labels pins 8259 ir0 ir7 irq0 irq15 names isa bus lines 8259s attached
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Computer architecture
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macintosh iifx macintosh iifx personal computer designed manufactured sold apple computer inc. march 1990 april 1992 introduction cost depending configuration fastest macintosh available time iifx powerful 68030-based macintosh ii family replaced top apple lineup macintosh quadra 1991 last apple computer released designed using snow white design language dubbed wicked fast product manager frank casanova – came apple apollo computer boston massachusetts boston term wicked commonly used denote anything extreme – iifx runs clock rate 40 megahertz 32 kb level 2 cache six nubus slots includes number proprietary asics coprocessors designed speed machine chips require system-specific drivers 40 mhz speed refers main logic board clock bus motorola 68030 cpu computer motorola 68882 fpu machine eight ram slots maximum 128 mb ram enormous amount time iifx features specialized high-speed 80 ns ram using 64-pin dual-ported simms contemporary macintosh models use 30-pin simms extra pins separate path allow latched read write operations also possible use parity memory modules iifx stock 68k macintosh support along special versions macintosh iici logic board total 8 ram slots must populated four time 1 4 16 mb chips results maximum memory amount 128 mb iifx includes two special dedicated processors floppy disk operations sound adb serial communications i/o chips feature pair 10 mhz embedded 6502 cpus cpu family used apple ii machines iifx uses scsi hard disk interface previous macintosh models since macintosh plus iifx requires special black-colored scsi terminator external drives first introduced iifx offered configurations introduced may 15 1990
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Computer architecture
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theodore ts theodore yue tak ts 曹子德 born 1968 software engineer mainly known contributions linux kernel particular contributions file systems primary developer maintainer e2fsprogs userspace utilities ext2 ext3 ext4 filesystems maintainer ext4 file system ts graduated mit degree computer science 1990 worked mit information systems department 1999 time project leader kerberos v5 team 1994 ts created codice_1 linux device node corresponding kernel driver linux unix first kernel interface provided high quality cryptographic random numbers user programs codice_1 works without access hardware random number generator allowing user programs depend upon existence separate daemons codice_3 take random numbers hardware make accessible via codice_1 since creation codice_1 codice_6 become standard interfaces unix linux bsd macos systems mit ts went work va linux systems two years late 2001 joined ibm worked improvements linux kernel performance scalability working real-time kernel ibm ts joined linux foundation late 2007 two-year fellowship initially served chief platform strategist becoming chief technology officer 2008 ts also served treasurer usenix 2008 chaired annual linux kernel developers summit 2010 ts moved google saying would working kernel file system storage stuff ts debian developer maintaining several packages mostly filesystem-related ones including e2fsprogs since march 2003 member security area directorate internet engineering task force one chairs ipsec working group one founding board members free standards group ts awarded free software foundation 2006 award advancement free software
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Operating systems
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intersystems intersystems corporation privately held vendor software systems technology high-performance database management rapid application development integration healthcare information systems vendor products include intersystems iris data platform caché database management system intersystems ensemble integration platform healthshare healthcare informatics platform trakcare healthcare information system sold outside united states intersystems based cambridge massachusetts company earned 644 million 2017 intersystems founded 1978 phillip t. terry ragon current ceo 2018 firm one original vendors m-technology aka mumps systems product called ism years acquired several mumps implementations dtm data tree 1993 dsm digital 1995 msm micronetics 1998 making intersystems dominant technology vendor firm eventually started combining features products one called openm consolidated technologies product caché 1997 time stopped new development legacy m-based products although company stills supports existing customers launched ensemble integration platform 2003 healthshare scalable health informatics platform 2006 2007 intersystems purchased trakhealth australian vendor trakcare modular healthcare information system based intersystems technology may 2011 firm launched globals free database based multi-dimensional array storage technology used caché september 2011 intersystems purchased siemens health services shs france parent company siemens september 2017 intersystems announced intersystems iris data platform company said combines database management capabilities together interoperability analytics well technologies sharding performance company products include largest customer intersystems epic leading health records vendor like intersystems epic privately held rooted older programming language called mumps developed mass general hospital 1960s founders coded first products turned outside investors preferring maintain control said zina moukheiber forbes profile 2013 large customers include u.s. department veterans affairs partners healthcare cleveland clinic national health services england scotland wales european space agency credit suisse august 14 2008 boston globe reported intersystems filing lawsuit microsoft corporation another tenant cambridge mass. headquarters seeking prevent microsoft expanding building intersystems also filed lawsuit building owner equity office partners subsidiary blackstone group contending conspired microsoft lease space intersystems rights sought drive rents process 2010 ceo terry ragon led coalition cambridge called save skyline protest city zoning change would allowed signs top commercial buildings partly response microsoft desire put sign top shared building disputes eventually settled microsoft intersystems agreed put low signs front building street level
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Databases
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csound csound computer programming language sound also known sound compiler audio programming language precisely audio dsl called csound written c opposed predecessors free software available lgpl csound originally written mit barry vercoe 1985 based earlier system called music 11 turn followed music-n model initiated max mathews bell labs development continued throughout 1990s 2000s led john fitch university bath first documented version 5 release version 5.01 march 18 2006 many developers contributed notably istvan varga gabriel maldonado robin whittle richard karpen michael gogins matt ingalls steven yi richard boulanger victor lazzarini developed many years currently nearly 1700 unit generators one greatest strengths completely modular extensible user csound closely related underlying language structured audio extensions mpeg-4 saol csound takes two specially formatted text files input orchestra describes nature instruments score describes notes parameters along timeline csound processes instructions files renders audio file real-time audio stream output orchestra score files may unified single structured file using markup language tags csd file filename extension .csd simple example unified csound data file produces wave file containing one-second sine wave tone 1 khz sample rate 96 khz many programming languages writing long programs csound eased using integrated environment editing previewing testing debugging one officially supported csoundqt many features automatic code insertion integrated documentation browser integrated widgets graphically controlling parameters realtime plus button playing code version 5.01 released march 18 2006 – 20 years csound first release csound 5 available binary source code linux microsoft windows mac os x sourceforge csound project much improved expanded compared original software effectively made software library api variety front ends developed addition basic c api also python java lisp tcl c++ among bindings like one haskell allows control csound purely functional environment use plug-ins allows additional capabilities without modifications csound code possibility write user-defined opcodes extensions original language ladspa dssi supported vst support removed real-time performance midi added 1990s another addition support fltk widgets graphical interface components sliders knobs etc controlling real-time audio integration custom graphical interfaces written python csound 6 development since features hashed csound conference held 2011 hanover csound 6 released july 2013 available github csound 6 also available android major new features csound 6 include development csound 6 led john ffitch steven yi victor lazzarini currently csound score note events generated real time opposed instruments definable compile time csound first starts csound 6 limitation removed set sound processors defined compiled load time individual processing objects spawned destroyed real time input audio processed real time output generated also real time note events triggered based osc communications within instrument instance spawned midi entered stdin typing terminal sending textual statements another program use csound 5 live performance tool augmented variety third-party software live event sheet within csoundqt used modify score real-time addition interfaces programming languages used script csound paper detailing use csound qt pure data real-time musical synthesis presented 2012 linux audio conference ounk project attempts integrate python csound csoundac provides way algorithmic composition python using csound backend audivation csound live packages various opcodes max/msp wrappers suitable use ableton live csound also available mobile systems ios android csound5 chosen audio/music development system olpc project xo-1 laptop platform
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Programming language topics
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saml 2.0 security assertion markup language 2.0 saml 2.0 version saml standard exchanging authentication authorization data security domains saml 2.0 xml-based protocol uses security tokens containing assertions pass information principal usually end user saml authority named identity provider saml consumer named service provider saml 2.0 enables web-based cross-domain single sign-on sso helps reduce administrative overhead distributing multiple authentication tokens user saml 2.0 ratified oasis standard march 2005 replacing saml 1.1 critical aspects saml 2.0 covered detail official documents samlcore samlbind samlprof samlmeta 30 individuals 24 companies organizations involved creation saml 2.0 particular special note liberty alliance donated identity federation framework id-ff specification oasis became basis saml 2.0 specification thus saml 2.0 represents convergence saml 1.1 liberty id-ff 1.2 shibboleth 1.3 assertion package information supplies zero statements made saml authority saml assertions usually made subject represented codice_1 element saml 2.0 specification defines three different kinds assertion statements created saml authority saml-defined statements associated subject three kinds statements defined follows important type saml assertion so-called bearer assertion used facilitate web browser sso example short-lived bearer assertion issued identity provider nowiki https //idp.example.org/saml2 /nowiki service provider nowiki https //sp.example.com/saml2 /nowiki assertion includes authentication assertion codice_2 attribute assertion codice_3 presumably service provider uses make access control decision prefix codice_4 represents saml v2.0 assertion namespace note example codice_5 element contains following child elements words assertion encodes following information assertion b07b804c-7c29-ea16-7300-4f3d6f7928ac issued time 2004-12-05t09:22:05z identity provider nowiki https //idp.example.org/saml2 /nowiki regarding subject 3f7b3dcf-1674-4ecd-92c8-1544f346baf8 exclusively service provider nowiki https //sp.example.com/saml2 /nowiki authentication statement particular asserts following principal identified codice_9 element authenticated time 2004-12-05t09:22:00z means password sent protected channel likewise attribute statement asserts principal identified codice_9 element staff member institution following protocols specified samlcore important protocols—the authentication request protocol—is discussed detail saml 1.1 web browser sso profiles idp-initiated unsolicited codice_15 element transmitted identity provider service provider via browser prefix codice_16 denotes saml protocol namespace saml 2.0 however flow begins service provider issues explicit authentication request identity provider resulting authentication request protocol significant new feature saml 2.0 principal entity acting principal behalf wishes obtain assertion containing authentication statement codice_17 element transmitted identity provider codice_17 element implicitly requests assertion containing authentication statement evidently issued service provider nowiki https //sp.example.com/saml2 /nowiki subsequently presented identity provider via browser identity provider authenticates principal necessary issues authentication response transmitted back service provider via browser saml message transmitted one entity another either value reference reference saml message called artifact receiver artifact resolves reference sending codice_19 request directly issuer artifact responds actual message referenced artifact suppose example identity provider sends following codice_19 request directly service provider via back channel response service provider returns saml element referenced enclosed artifact protocol forms basis http artifact binding bindings supported saml 2.0 outlined bindings specification samlbind web browser sso http redirect binding http post binding commonly used example service provider may use http redirect send request identity provider uses http post transmit response example illustrates entity choice binding independent partner choice binding saml protocol messages carried directly url query string http get request since length urls limited practice http redirect binding suitable short messages codice_17 message longer messages e.g containing signed encrypted saml assertions saml responses usually transmitted via bindings http post binding saml requests responses transmitted via http redirect codice_22 codice_23 query string parameter respectively sent message deflated without header checksum base64-encoded url-encoded order upon receipt process reversed recover original message example encoding codice_17 message yields message formatted readability may signed additional security practice data contained codice_17 codice_26 contains sp id codice_27 agreed idp sp beforehand via manual information exchange via saml metadata case signing request security constraint codice_17 contains information known idp beforehand assertion consumer service url signing request recommended security purposes following example service provider identity provider use http post binding initially service provider responds request user agent document containing xhtml form value codice_22 parameter base64-encoding codice_17 element transmitted identity provider via browser sso service identity provider validates request responds document containing another xhtml form value codice_23 parameter base64 encoding codice_15 element likewise transmitted service provider via browser automate submission form following line javascript may appear anywhere xhtml page assumes course first form element page contains samlresponse containing codice_33 element codice_34 http artifact binding uses artifact resolution protocol saml soap binding http resolve saml message reference consider following specific example suppose service provider wants send codice_17 message identity provider initially service provider transmits artifact identity provider via http redirect next identity provider sends codice_19 request artifactresolverequest shown earlier directly service provider via back channel finally service provider returns codice_37 element containing referenced codice_17 message course flow go direction well identity provider may issue artifact fact common see example double artifact profile example later topic general saml 2.0 artifact defined follows samlbind thus saml 2.0 artifact consists three components two-byte codice_39 two-byte codice_40 arbitrary sequence bytes called codice_41 three pieces information concatenated base64-encoded yield complete artifact codice_39 uniquely identifies artifact format saml 2.0 predefines one artifact type 0x0004 codice_40 reference particular artifact resolution endpoint managed artifact issuer may either idp sp mentioned earlier codice_41 determined type definition meat artifact format type 0x0004 artifact defined follows thus type 0x0004 artifact size 44 bytes unencoded codice_45 arbitrary sequence bytes although practice codice_45 sha-1 hash issuer entityid codice_47 random sequence bytes references saml message artifact issuer willing produce on-demand example consider hex-encoded type 0x0004 artifact look closely see codice_39 0x0004 codice_40 0x0000 front artifact next 20 bytes sha-1 hash issuer entityid nowiki https //idp.example.org/saml2 /nowiki followed 20 random bytes base64-encoding 44 bytes see artifactresolverequest example saml 2.0 saml 1.1 primary use case still web browser sso scope saml 2.0 broader previous versions saml suggested following exhaustive list profiles although number supported profiles quite large profiles specification samlprof simplified since binding aspects profile factored separate bindings specification samlbind saml 2.0 specifies web browser sso profile involving identity provider idp service provider sp principal wielding http user agent service provider four bindings choose identity provider three leads twelve 12 possible deployment scenarios outline three deployment scenarios one common scenarios service provider sends saml request idp sso service using http-redirect binding identity provider returns saml response sp assertion consumer service using http-post binding message flow begins request secured resource service provider 1 request target resource sp principal via http user agent requests target resource service provider service provider performs security check behalf target resource valid security context service provider already exists skip steps 2–7 service provider may use kind mechanism discover identity provider used e.g. ask user use preconfigured idp etc 2 redirect idp sso service service provider generates appropriate samlrequest relaystate redirects browser idp sso service using standard http 302 redirect codice_50 token opaque reference state information maintained service provider value codice_22 parameter deflated base64-encoded url-encoded value codice_17 element samlrequest may signed using sp signing key typically however necessary 3 request sso service idp user agent issues get request sso service identity provider values codice_22 codice_50 parameters provided redirect sso service identity provider processes codice_17 element url-decoding base64-decoding inflating request order performs security check user valid security context identity provider identifies user mechanism details omitted 4 respond xhtml form sso service validates request responds document containing xhtml form value codice_50 parameter preserved step 3 value codice_23 parameter base64 encoding following codice_15 element 5 request assertion consumer service sp user agent issues post request assertion consumer service service provider values codice_23 codice_50 parameters taken xhtml form step 4 6 redirect target resource assertion consumer service processes response creates security context service provider redirects user agent target resource 7 request target resource sp user agent requests target resource service provider 8 respond requested resource since security context exists service provider returns resource user agent relatively simple deployment saml 2.0 web browser sso profile samlprof service provider sp identity provider idp use http post binding message flow begins request secured resource sp 1 request target resource sp principal via http user agent requests target resource service provider service provider performs security check behalf target resource valid security context service provider already exists skip steps 2–7 2 respond xhtml form service provider responds document containing xhtml form codice_50 token opaque reference state information maintained service provider value codice_22 parameter base64 encoding following codice_17 element codice_17 element inserted xhtml form first base64-encoded 3 request sso service idp user agent issues post request sso service identity provider values codice_22 codice_50 parameters taken xhtml form step 2 sso service processes codice_17 element url-decoding base64-decoding inflating request order performs security check user valid security context identity provider identifies user details omitted 4 respond xhtml form sso service validates request responds document containing xhtml form value codice_50 parameter preserved step 3 value codice_23 parameter base64 encoding following codice_15 element 5 request assertion consumer service sp user agent issues post request assertion consumer service service provider values codice_23 codice_50 parameters taken xhtml form step 4 6 redirect target resource assertion consumer service processes response creates security context service provider redirects user agent target resource 7 request target resource sp user agent requests target resource service provider 8 respond requested resource since security context exists service provider returns resource user agent complex deployment saml 2.0 web browser sso profile samlprof service provider sp identity provider idp use http artifact binding artifacts delivered respective endpoints via http get message flow begins request secured resource sp 1 request target resource sp principal via http user agent requests target resource service provider service provider performs security check behalf target resource valid security context service provider already exists skip steps 2–11 2 redirect single sign-on sso service idp service provider redirects user agent single sign-on sso service identity provider codice_50 parameter codice_74 parameter appended redirect url 3 request sso service idp user agent requests sso service identity provider codice_75 opaque reference state information maintained service provider codice_76 saml artifact issued step 2 4 request artifact resolution service sp sso service dereferences artifact sending codice_19 element bound saml soap message artifact resolution service service provider value codice_78 element saml artifact transmitted step 3 5 respond saml authnrequest artifact resolution service service provider returns codice_37 element containing codice_17 element bound saml soap message sso service identity provider sso service processes codice_17 element performs security check user valid security context identity provider identifies user details omitted 6 redirect assertion consumer service sso service identity provider redirects user agent assertion consumer service service provider previous codice_50 parameter new codice_74 parameter appended redirect url 7 request assertion consumer service sp user agent requests assertion consumer service service provider codice_75 token value step 3 codice_85 saml artifact issued step 6 8 request artifact resolution service idp assertion consumer service dereferences artifact sending codice_19 element bound saml soap message artifact resolution service identity provider value codice_78 element saml artifact transmitted step 7 9 respond saml assertion artifact resolution service identity provider returns codice_37 element containing codice_15 element bound saml soap message assertion consumer service service provider 10 redirect target resource assertion consumer service processes response creates security context service provider redirects user agent target resource 11 request target resource sp user agent requests target resource service provider 12 respond requested resource since security context exists service provider returns resource user agent saml 2.0 identity provider discovery profile introduces following concepts hypothetical example common domain let suppose example uk example.co.uk example deutschland example.de belong virtual organization example global alliance example.com example domain example.com common domain example uk example deutschland presence domain uk.example.com de.example.com resp. common domain cookie secure browser cookie scoped common domain browser user cookie stores history list recently visited idps name value cookie specified idp discovery profile samlprof successful act authentication idp requests common domain cookie writing service service appends idp unique identifier common domain cookie sp receives unauthenticated request protected resource requests common domain cookie reading service discover browser user recently used idp assertion query/request profile general profile accommodates numerous types so-called queries using following saml 2.0 elements saml soap binding often used conjunction queries attribute query perhaps important type saml query often requester acting behalf principal queries identity provider attributes give example query issued principal directly note codice_26 codice_97 case sometimes called attribute self-query identity provider might return following assertion wrapped codice_15 element shown contrast bearerassertion shown earlier assertion longer lifetime corresponding lifetime x.509 certificate principal used authenticate identity provider moreover since assertion signed user push assertion relying party long user prove possession corresponding private key hence name holder-of-key relying party assured assertion authentic quite literally metadata makes saml work work well let look important uses metadata metadata ensures secure transaction identity provider service provider metadata trust information encoded implementation proprietary manner sharing trust information facilitated standard metadata saml 2.0 provides well-defined interoperable metadata format entities leverage bootstrap trust process identity provider publishes data codice_101 element note following details entity descriptor definition identity provider manages sso service supports saml web browser sso profile specified samlprof see example identity provider described codice_107 element shown next section sso service identity provider described codice_107 element previous metadata element describes sso service identity provider note following details element noted beginning section values codice_112 attributes used service provider route saml messages minimizes possibility rogue identity provider orchestrating man-in-the-middle attack like identity provider service provider publishes data codice_101 element note following details entity descriptor definition service provider manages assertion consumer service supports saml web browser sso profile specified samlprof see example service provider described codice_133 element shown next section assertion consumer service contained codice_133 element note following details codice_133 metadata element noted beginning section values codice_112 attributes used identity provider route saml messages minimizes possibility rogue service provider orchestrating man-in-the-middle attack previous examples codice_101 element shown digitally signed practice however multiple codice_101 elements grouped together codice_159 element single digital signature entire aggregate note following details codice_159 element typically metadata aggregates published trusted third parties called federations vouch integrity metadata aggregate note metadata aggregates large composed hundreds even thousands entities per aggregate primary references secondary references deprecated references
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Computer security
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chown command chown abbreviation change owner used unix unix-like operating systems change owner file system files directories unprivileged regular users wish change group membership file may use chgrp ownership file system may altered super-user user give away ownership file even user owns similarly member group change file group id group chown name_of_new_owner file_name
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Operating systems
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file descriptor unix related computer operating systems file descriptor fd less frequently fildes abstract indicator handle used access file input/output resource pipe network socket file descriptors form part posix application programming interface file descriptor non-negative integer generally represented c programming language type negative values reserved indicate value error condition unix process except perhaps daemon expect three standard posix file descriptors corresponding three standard streams traditional implementation unix file descriptors index per-process maintained kernel turn indexes system-wide table files opened processes called table records mode file resource opened reading writing appending possibly modes also indexes third table called inode table describes actual underlying files perform input output process passes file descriptor kernel system call kernel access file behalf process process direct access file inode tables linux set file descriptors open process accessed path codice_1 pid process identifier unix-like systems file descriptors refer unix file type named file system well regular files includes directories block character devices also called special files unix domain sockets named pipes file descriptors also refer objects normally exist file system anonymous pipes network sockets file data structure c standard i/o library usually includes low level file descriptor object question unix-like systems overall data structure provides additional abstraction instead known file handle following lists typical operations file descriptors modern unix-like systems functions declared codice_2 header codice_3 header instead function used perform various operations file descriptor depending command argument passed commands get set attributes associated file descriptor including series new operations file descriptors added many modern unix-like systems well numerous c libraries standardized future version posix codice_4 suffix signifies function takes additional first argument supplying file descriptor relative paths resolved forms lacking codice_4 suffix thus becoming equivalent passing file descriptor corresponding current working directory purpose new operations defend certain class tocttou attacks unix file descriptors behave many ways capabilities passed processes across unix domain sockets using codice_6 system call note however actually passed reference open file description mutable state file offset file status access flags complicates secure use file descriptors capabilities since programs share access open file description interfere use changing offset whether blocking non-blocking example operating systems specifically designed capability systems rarely mutable state associated capability unix process file descriptor table example c-list
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Computer file systems
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nadim kobeissi nadim kobeissi computer science researcher specialized applied cryptography professor new york university paris campus author cryptocat open-source encrypted web chat client kobeissi also known speaking publicly internet censorship internet surveillance kobeissi born beirut lebanon studied lebanese american university beirut 2008–2009 graduated degree philosophy concordia university montreal 2013 kobeissi ph.d. student studying applied cryptography french institute research computer science automation inria france 2015 2018 kobeissi primary author cryptocat project discontinued 2019 2015 kobeissi became active researching formal verification cryptographic protocols december 2018 defended ph.d. thesis formal verification real-world cryptographic protocols implementations vérification formelle des protocoles et des implementations cryptographiques 2010 kobeissi early supporter bradley manning support network organized march montreal december year support wikileaks ran wikileaks mirror site defended wikileaks various canadian news publications 2011 2012 kobeissi hosted chomp.fm radio program internet activism ran weekly montreal ckut-fm radio station show included guests electronic frontier foundation eff security researcher bruce schneier journalist glenn greenwald 2013 kobeissi led effort known skype open letter brought together forty organizations including electronic frontier foundation reporters without borders open technology institute calling microsoft skype release transparency reports regarding skype monitoring surveillance effort successful microsoft released first transparency report shortly letter published
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Computer security
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superscalar processor superscalar processor cpu implements form parallelism called instruction-level parallelism within single processor contrast scalar processor execute one single instruction per clock cycle superscalar processor execute one instruction clock cycle simultaneously dispatching multiple instructions different execution units processor therefore allows throughput number instructions executed unit time would otherwise possible given clock rate execution unit separate processor core processor multi-core processor execution resource within single cpu arithmetic logic unit flynn taxonomy single-core superscalar processor classified sisd processor single instruction stream single data stream though single-core superscalar processor supports short vector operations could classified simd single instruction stream multiple data streams multi-core superscalar processor classified mimd processor multiple instruction streams multiple data streams superscalar cpu typically also pipelined superscalar pipelining execution considered different performance enhancement techniques former executes multiple instructions parallel using multiple execution units whereas latter executes multiple instructions execution unit parallel dividing execution unit different phases superscalar technique traditionally associated several identifying characteristics within given cpu seymour cray cdc 6600 1966 often mentioned first superscalar design 1967 ibm system/360 model 91 another superscalar mainframe motorola mc88100 1988 intel i960ca 1989 amd 29000-series 29050 1990 microprocessors first commercial single-chip superscalar microprocessors risc microprocessors like first superscalar execution risc architectures free transistors die area used include multiple execution units risc designs faster cisc designs 1980s 1990s except cpus used low-power applications embedded systems battery-powered devices essentially general-purpose cpus developed since 1998 superscalar p5 pentium first superscalar x86 processor nx586 p6 pentium pro amd k5 among first designs decode x86-instructions asynchronously dynamic microcode-like micro-op sequences prior actual execution superscalar microarchitecture opened dynamic scheduling buffered partial instructions enabled parallelism extracted compared rigid methods used simpler p5 pentium also simplified speculative execution allowed higher clock frequencies compared designs advanced cyrix 6x86 simplest processors scalar processors instruction executed scalar processor typically manipulates one two data items time contrast instruction executed vector processor operates simultaneously many data items analogy difference scalar vector arithmetic superscalar processor mixture two instruction processes one data item multiple execution units within cpu thus multiple instructions processing separate data items concurrently superscalar cpu design emphasizes improving instruction dispatcher accuracy allowing keep multiple execution units use times become increasingly important number units increased early superscalar cpus would two alus single fpu later design powerpc 970 includes four alus two fpus two simd units dispatcher ineffective keeping units fed instructions performance system better simpler cheaper design superscalar processor usually sustains execution rate excess one instruction per machine cycle merely processing multiple instructions concurrently make architecture superscalar since pipelined multiprocessor multi-core architectures also achieve different methods superscalar cpu dispatcher reads instructions memory decides ones run parallel dispatching one several execution units contained inside single cpu therefore superscalar processor envisioned multiple parallel pipelines processing instructions simultaneously single instruction thread available performance improvement superscalar techniques limited three key areas existing binary executable programs varying degrees intrinsic parallelism cases instructions dependent executed simultaneously cases inter-dependent one instruction impacts either resources results instructions codice_1 run parallel none results depend calculations however instructions codice_2 might runnable parallel depending order instructions complete move units number simultaneously issued instructions increases cost dependency checking increases extremely rapidly exacerbated need check dependencies run time cpu clock rate cost includes additional logic gates required implement checks time delays gates research shows gate cost cases may formula_1 gates delay cost formula_2 formula_3 number instructions processor instruction set formula_4 number simultaneously dispatched instructions even though instruction stream may contain inter-instruction dependencies superscalar cpu must nonetheless check possibility since assurance otherwise failure detect dependency would produce incorrect results matter advanced semiconductor process fast switching speed places practical limit many instructions simultaneously dispatched process advances allow ever greater numbers execution units e.g. alus burden checking instruction dependencies grows rapidly complexity register renaming circuitry mitigate dependencies collectively power consumption complexity gate delay costs limit achievable superscalar speedup roughly eight simultaneously dispatched instructions however even given infinitely fast dependency checking logic otherwise conventional superscalar cpu instruction stream many dependencies would also limit possible speedup thus degree intrinsic parallelism code stream forms second limitation collectively limits drive investigation alternative architectural changes long instruction word vliw explicitly parallel instruction computing epic simultaneous multithreading smt multi-core computing vliw burdensome task dependency checking hardware logic run time removed delegated compiler explicitly parallel instruction computing epic like vliw extra cache prefetching instructions simultaneous multithreading smt technique improving overall efficiency superscalar processors smt permits multiple independent threads execution better utilize resources provided modern processor architectures superscalar processors differ multi-core processors several execution units entire processors single processor composed finer-grained execution units alu integer multiplier integer shifter fpu etc may multiple versions execution unit enable execution many instructions parallel differs multi-core processor concurrently processes instructions multiple threads one thread per processing unit called core also differs pipelined processor multiple instructions concurrently various stages execution assembly-line fashion various alternative techniques mutually exclusive—they frequently combined single processor thus multicore cpu possible core independent processor containing multiple parallel pipelines pipeline superscalar processors also include vector capability
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Computer architecture
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secure network programming secure network programming snp prototype first secure sockets layer designed built networking research laboratory university texas austin led simon s. lam work published 1994 usenix summer technical conference project authors 2004 acm software system award work began 1991 theoretical investigation networking research laboratory formal meaning protocol layer satisfying upper interface specification service provider lower interface specification service consumer networking research laboratory received grant national security agency june 1991 investigate apply theory modules interfaces security verification time three well-known authentication systems built mit kerberos developed dec spx ibm kryptoknight systems suffered common drawback namely export clean easy-to-use interface could readily used internet applications example would take tremendous amount effort “ kerberize ” existing distributed application toward goal secure network programming masses inventors snp conceived secure sockets high-level abstraction suitable securing internet applications 1993 designed built prototype snp designed application sublayer top sockets snp provides user interface closely resembling sockets resemblance design security could retrofitted existing socket programs minor modifications also sublayer carefully designed implementation thoroughly debugged easily used internet application uses sockets end-to-end communications natural idea hindsight 1993 novel major departure mainstream network security research time snp secure sockets support stream datagram semantics security guarantees i.e. data origin authenticity data destination authenticity data integrity data confidentiality many ideas design choices snp found subsequent secure sockets layers including placing authenticated communication endpoints application layer use public key cryptography authentication handshake protocol establishing session state including shared secret use symmetric key cryptography data confidentiality managing contexts credentials secure sockets layer paper presented june 8 1994 usenix summer technical conference includes system design together performance measurement results prototype implementation clearly demonstrate practicality secure sockets layer snp invented secure sockets internet applications general independently concurrently design development http protocol world-wide web still infancy 1993 subsequent secure socket layers ssl netscape tls ietf re-implemented several years later using key ideas first presented snp enabled secure e-commerce browsers servers today many internet applications including email use https consists http running secure sockets layer
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Computer security
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dead code computer programming dead code section source code program executed whose result never used computation execution dead code wastes computation time memory result dead computation may never used may raise exceptions affect global state thus removal code may change output program introduce unintended bugs compiler optimizations typically conservative approach dead code removal ambiguity whether removal dead code affect program output programmer may aid compiler matter making additional use static and/or inline functions enabling use link-time optimization example although division ix iy computed never used throw exception division zero occurs therefore removal dead code may change output program dead code elimination form compiler optimization dead code removed program dead code analysis performed using live variable analysis form static code analysis data flow analysis contrast unreachable code analysis based control flow analysis dead code elimination technique class optimizations unreachable code elimination redundant code elimination large programming projects sometimes difficult recognize eliminate dead code particularly entire modules become dead test scaffolding make appear code still live times contract language require delivery code even code longer relevant ides xcode visual studio 2010 eclipse galileo ability locate dead code compiling stage optimization techniques seek remove dead code implementation extreme forms optimization size may sometimes desirable deliberately introduce carefully shape seemingly dead code allows fold otherwise unrelated code sections together thereby reduce combined size extra code effectively harm first path execution code used carry actions necessary alternative paths execution sections code may become dead code functional level seen artificially introduction harmless/useful side-effects reduction redundancy code also used opcode level order allow usage shorter instructions would possible folding code sequences without concerted introduction side-effects caused dead code
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Programming language topics
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long instruction word long instruction word vliw refers instruction set architectures designed exploit instruction level parallelism ilp whereas conventional central processing units cpu processor mostly allow programs specify instructions execute sequence vliw processor allows programs explicitly specify instructions execute parallel design intended allow higher performance without complexity inherent designs traditional means improve performance processors include dividing instructions substeps instructions executed partly time termed pipelining dispatching individual instructions executed independently different parts processor superscalar architectures even executing instructions order different program out-of-order execution methods complicate hardware larger circuits higher cost energy use processor must make decisions internally methods work contrast vliw method depends programs providing decisions regarding instructions execute simultaneously resolve conflicts practical matter means compiler software used create final programs becomes far complex hardware simpler many means parallelism processor executes every instruction one i.e. non-pipelined scalar architecture may use processor resources inefficiently yielding potential poor performance performance improved executing different substeps sequential instructions simultaneously termed pipelining even executing multiple instructions entirely simultaneously superscalar architectures improvement achieved executing instructions order different occur program termed out-of-order execution three methods raise hardware complexity executing operations parallel processor must verify instructions interdependencies example first instruction result used second instruction input execute time second instruction execute first modern out-of-order processors increased hardware resources schedule instructions determine interdependencies contrast vliw executes operations parallel based fixed schedule determined programs compiled since determining order execution operations including operations execute simultaneously handled compiler processor need scheduling hardware three methods described require thus vliw cpus offer computing less hardware complexity greater compiler complexity superscalar cpus superscalar designs number execution units invisible instruction set instruction encodes one operation superscalar designs instruction width 32 bits fewer contrast one vliw instruction encodes multiple operations least one operation execution unit device example vliw device five execution units vliw instruction device five operation fields field specifying operation done corresponding execution unit accommodate operation fields vliw instructions usually least 64 bits wide far wider architectures example following instruction super harvard architecture single-chip computer sharc one cycle floating-point multiply floating-point add two autoincrement loads fits one 48-bit instruction codice_1 since earliest days computer architecture cpus added several arithmetic logic units alus run parallel superscalar cpus use hardware decide operations run parallel runtime vliw cpus use software compiler decide operations run parallel advance complexity instruction scheduling moved compiler complexity hardware reduced substantially similar problem occurs result parallelizable instruction used input branch modern cpus guess branch taken even calculation complete load instructions branch architectures even start compute speculatively cpu guesses wrong instructions context need flushed correct ones loaded takes time led increasingly complex instruction-dispatch logic attempts guess correctly simplicity original reduced instruction set computing risc designs eroded vliw lacks logic thus lacks energy use possible design defects negative aspects vliw compiler uses heuristics profile information guess direction branch allows move preschedule operations speculatively branch taken favoring likely path expects branch branch takes unexpected way compiler already generated compensating code discard speculative results preserve program semantics vector processor single instruction multiple data simd cores combined vliw architecture fujitsu fr-v microprocessor increasing throughput speed concept vliw architecture term vliw invented josh fisher research group yale university early 1980s original development trace scheduling compiling method vliw developed graduate student new york university vliw notion prescheduling execution units instruction-level parallelism software well established practice developing horizontal microcode fisher innovations involved developing compiler could target horizontal microcode programs written ordinary programming language realized get good performance target wide-issue machine would necessary find parallelism beyond generally within basic block also developed region scheduling methods identify parallelism beyond basic blocks trace scheduling method involves scheduling likely path basic blocks first inserting compensating code deal speculative motions scheduling second likely trace schedule complete fisher second innovation notion target cpu architecture designed reasonable target compiler compiler architecture vliw processor must codesigned inspired partly difficulty fisher observed yale compiling architectures like floating point systems fps164 complex instruction set computing cisc architecture separated instruction initiation instructions saved result needing complex scheduling algorithms fisher developed set principles characterizing proper vliw design self-draining pipelines wide multi-port register files memory architectures principles made easier compilers emit fast code first vliw compiler described ph.d. thesis john ellis supervised fisher compiler named bulldog yale mascot fisher left yale 1984 found startup company multiflow along cofounders john o'donnell john ruttenberg multiflow produced trace series vliw minisupercomputers shipping first machines 1987 multiflow vliw could issue 28 operations parallel per instruction trace system implemented mix medium-scale integration msi large-scale integration lsi large-scale integration vlsi packaged cabinets technology obsoleted grew cost-effective integrate components processor excluding memory one chip multiflow early catch following wave chip architectures began allow multiple-issue cpus major semiconductor companies recognized value multiflow technology context compiler architecture subsequently licensed firms cydrome company producing vliw numeric processors using emitter-coupled logic ecl integrated circuits timeframe late 1980s company like multiflow failed years one licensees multiflow technology hewlett-packard josh fisher joined multiflow demise bob rau founder cydrome also joined hp cydrome failed two would lead computer architecture research hewlett-packard 1990s along systems time 1989–1990 intel implemented vliw intel i860 first 64-bit microprocessor first processor implement vliw one chip processor could operate simple risc mode vliw mode early 1990s intel introduced i860 risc microprocessor simple chip two modes operation scalar mode vliw mode vliw mode processor always fetched two instructions assumed one integer instruction floating-point i860 vliw mode used extensively embedded digital signal processor dsp applications since application execution datasets simple well ordered predictable allowing designers fully exploit parallel execution advantages enabled vliw vliw mode i860 could maintain floating-point performance range 20-40 double-precision mflops high value time processor running 25-50mhz 1990s hewlett-packard researched problem side effect ongoing work pa-risc processor family found cpu could greatly simplified removing complex dispatch logic cpu placing compiler compilers day far complex 1980s added complexity compiler considered small cost vliw cpus usually made multiple risc-like execution units operate independently contemporary vliws usually four eight main execution units compilers generate initial instruction sequences vliw cpu roughly manner traditional cpus generating sequence risc-like instructions compiler analyzes code dependence relationships resource requirements schedules instructions according constraints process independent instructions scheduled parallel vliws typically represent instructions scheduled parallel longer instruction word incorporates individual instructions results much longer opcode termed long specify executes given cycle examples contemporary vliw cpus include trimedia media processors nxp formerly philips semiconductors super harvard architecture single-chip computer sharc dsp analog devices c6000 digital signal processor dsp family texas instruments st200 family stmicroelectronics based lx architecture designed josh fisher hp lab paolo faraboschi mppa manycore family kalray contemporary vliw cpus mainly successful embedded media processors consumer electronic devices vliw features also added configurable processor cores system-on-a-chip soc designs example tensilica xtensa lx2 processor incorporates technology named flexible length instruction extensions flix allows multi-operation instructions xtensa c/c++ compiler freely intermix 32- 64-bit flix instructions xtensa processor one-operation risc instructions 16 24 bits wide packing multiple operations wide 32- 64-bit instruction word allowing multi-operation instructions intermix shorter risc instructions flix allows soc designers realize vliw performance advantages eliminating code bloat early vliw architectures infineon carmel dsp another vliw processor core intended soc uses similar code density improvement method called configurable long instruction word cliw outside embedded processing markets intel itanium ia-64 explicitly parallel instruction computing epic elbrus 2000 appear examples widely used vliw cpu architectures however epic architecture sometimes distinguished pure vliw architecture since epic advocates full instruction predication rotating register files long instruction word encode non-parallel instruction groups vliws also gained significant consumer penetration graphics processing unit gpu market though nvidia amd since moved risc architectures improve performance non-graphics workloads ati technologies ati advanced micro devices amd terascale microarchitecture graphics processing units gpus vliw microarchitecture december 2015 first shipment pcs based vliw cpu elbrus-4s made russia silicon technology allowed wider implementations execution units built compiled programs earlier generation would run wider implementations encoding binary instructions depended number execution units machine transmeta addressed issue including binary-to-binary software compiler layer termed code morphing crusoe implementation x86 architecture mechanism advertised basically recompile optimize translate x86 opcodes runtime cpu internal machine code thus transmeta chip internally vliw processor effectively decoupled x86 cisc instruction set executes intel itanium architecture among others solved backward-compatibility problem general mechanism within multiple-opcode instructions bit field allocated denote dependency prior vliw instruction within program instruction stream bits set compile time thus relieving hardware calculating dependency information dependency information encoded instruction stream allows wider implementations issue multiple non-dependent vliw instructions parallel per cycle narrower implementations would issue smaller number vliw instructions per cycle another perceived deficiency vliw designs code bloat occurs one execution unit useful work thus must execute operation nop instructions occurs dependencies code instruction pipelines must allowed drain later operations proceed since number transistors chip grown perceived disadvantages vliw diminished importance vliw architectures growing popularity especially embedded system market possible customize processor application system-on-a-chip embedded vliw products available several vendors including fr-v fujitsu bsp15/16 pixelworks st231 stmicroelectronics trimedia nxp semiconductors ceva-x dsp ceva jazz dsp improv systems silicon hive texas instruments tms320 dsp line evolved c6xxx family look like vliw contrast earlier c5xxx family
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Computer architecture
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smithproject smithproject open source cfml script engine smith project initiated youngculture ag based need migrate large coldfusion based web application java-based engine cfml engines include adobe coldfusion new atlanta bluedragon lucee railo coral web builder
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Programming language topics
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windows startup process windows startup process process microsoft windows series operating systems initializes windows versions 1.01 windows 2.11 system loaded codice_1 executed loaded codice_2 codice_3 codice_4 codice_5 along configuration settings file codice_6 default shell ms-dos executive modules codice_7 codice_8 codice_9 fonts various device drivers codice_10 codice_11 codice_12 incorporated codice_2/codice_3 codice_4/codice_5 windows 3.x 95/98/me boot loader phase handled ms-dos boot phase codice_17 codice_18 executed along configuration settings files codice_6 codice_20 virtual device drivers also loaded startup process commonly loaded registry codice_21 codice_20 file system configuration files device drivers loaded 16-bit modules codice_23 codice_7 codice_9 loaded 32-bit dlls codice_26 codice_27 codice_28 loaded 32-bit vxd message server msgsrv32 starts codice_29 responsible loading network logon client client microsoft networks microsoft family logon windows logon user logging windows startup sound played shell usually codice_30 loaded boot section codice_20 file startup items loaded versions windows 9x except also possible load windows booting dos prompt typing win command line switches used win command codice_32 switch windows boots safe mode codice_33 switch windows boots safe mode networking latter switch works properly windows 95 windows 3.1 additional options available codice_34 starts windows 386 enhanced mode codice_35 starts windows standard mode startup sound added windows 3.1 windows nt boot loader called ntldr responsible accessing file system boot drive starting ntoskrnl.exe loading boot-time device drivers memory boot system drivers loaded kernel system thread starts session manager subsystem smss.exe turn starts winlogon loads graphical identification authentication library user successfully logged machine winlogon following windows 95/98/me also possible run program user logs using runservicesonce runservices keys windows nt replaced services.exe program able load set system services user logs additionally english-language versions windows startup folder called startup instead startup win9x due minimally restricted environment operating systems program add startup registry key system folder method frequently used malware sequence booting windows vista later versions different previous version windows uses nt kernel operating system boot loader vista called winload.exe invoked windows boot manager additionally gina use versions windows nt since 3.1 entirely replaced credential providers
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Operating systems
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addressing mode addressing modes aspect instruction set architecture central processing unit cpu designs various addressing modes defined given instruction set architecture define machine language instructions architecture identify operand instruction addressing mode specifies calculate effective memory address operand using information held registers and/or constants contained within machine instruction elsewhere computer programming addressing modes primarily interest write assembly languages compiler writers note generally accepted way naming various addressing modes particular different authors computer manufacturers may give different names addressing mode names different addressing modes furthermore addressing mode one given architecture treated single addressing mode may represent functionality another architecture covered two addressing modes example complex instruction set computer cisc architectures digital equipment corporation dec vax treat registers literal immediate constants another addressing mode others ibm system/360 successors reduced instruction set computer risc designs encode information within instruction thus latter machines three distinct instruction codes copying one register another copying literal constant register copying contents memory location register vax single mov instruction term addressing mode subject different interpretations either memory address calculation mode operand accessing mode first interpretation instructions read memory write memory add literal register considered addressing mode second interpretation allows machines vax use operand mode bits allow register literal operand first interpretation applies instructions load effective address addressing modes listed divided code addressing data addressing computer architectures maintain distinction architectures allow almost addressing modes used context instructions shown purely representative order illustrate addressing modes necessarily reflect mnemonics used particular computer different computer architectures vary greatly number addressing modes provide hardware benefits eliminating complex addressing modes using one simpler addressing modes even though requires extra instructions perhaps extra register proven much easier design pipelined cpus addressing modes available simple ones risc architectures five simple addressing modes cisc architectures dec vax dozen addressing modes quite complicated ibm system/360 architecture three addressing modes added system/390 addressing modes particular addressing mode required usually encoded within instruction code e.g ibm system/360 successors risc lots addressing modes specific field often set aside instruction specify addressing mode dec vax allowed multiple memory operands almost instructions reserved first bits operand specifier indicate addressing mode particular operand keeping addressing mode specifier bits separate opcode operation bits produces orthogonal instruction set even computer many addressing modes measurements actual programs indicate simple addressing modes listed account 90 addressing modes used since measurements based code generated high-level languages compilers reflects extent limitations compilers used instruction set architectures intel x86 ibm/360 successors load effective address instruction performs calculation effective operand address instead acting memory location loads address would accessed register useful passing address array element subroutine may also slightly sneaky way calculations normal one instruction example using instruction addressing mode base+index+offset detailed allows one add two registers constant together one instruction |jump| address effective address absolute instruction address address parameter modifications |jump| offset jump relative effective address pc-relative instruction address offset parameter added address next instruction offset usually signed allow reference code instruction particularly useful connection jumps typical jumps nearby instructions high-level language statements reasonably short measurements actual programs suggest 8 10 bit offset large enough 90 conditional jumps roughly ±128 ±512 bytes another advantage pc-relative addressing code may position-independent i.e loaded anywhere memory without need adjust addresses versions addressing mode may conditional referring two registers jump reg1=reg2 one register jump unless reg1=0 registers implicitly referring previously-set bit status register see also conditional execution |jumpvia| reg effective address register indirect instruction address specified register example a7 access content address register a7 effect transfer control instruction whose address specified register many risc machines well cisc ibm system/360 successors subroutine call instructions place return address address register—the register-indirect addressing mode used return subroutine call nop execute following instruction cpu executing sequential instruction immediately executes following instruction sequential execution considered addressing mode computers instructions cpu architectures sequential instructions instructions sequential instructions cpu designers often add features deliberately sacrifice performance instructions—branch instructions—in order make sequential instructions run faster conditional branches load pc one 2 possible results depending condition—most cpu architectures use addressing mode taken branch sequential execution taken branch many features modern cpus -- instruction prefetch complex pipelineing out-of-order execution etc -- maintain illusion instruction finishes next one begins giving final results even though exactly happens internally basic block sequential instructions exhibits temporal spatial locality reference cpus use sequential execution program counter extremely rare cpus instruction always specifies address next instruction cpus instruction pointer holds specified address program counter provision incrementing cpus include drum memory computers ibm 650 secd machine rtx 32p computing architectures go much attempting bypass von neumann bottleneck using variety alternatives program counter computer architectures conditional instructions arm longer instructions 64-bit mode conditional load instructions x86 cases make conditional branches unnecessary avoid flushing instruction pipeline instruction 'compare used set condition code subsequent instructions include test condition code see whether obeyed ignored |skipeq| reg1| reg2| skip next instruction reg1=reg2 skip addressing may considered special kind pc-relative addressing mode fixed +1 offset like pc-relative addressing cpus versions addressing mode refer one register skip reg1=0 registers implicitly referring previously-set bit status register cpus version selects specific bit specific byte test skip bit 7 reg12 0 unlike conditional branches skip instruction never needs flush instruction pipeline though may need cause next instruction ignored mul reg1| reg2| reg3| reg1 reg2 reg3 addressing mode effective address considered addressing mode computers example operands registers result placed register sometimes referred 'base plus displacement' offset usually signed 16-bit value though 80386 expanded 32 bits offset zero becomes example register indirect addressing effective address value base register many risc machines register 0 fixed value zero register 0 used base register becomes example absolute addressing however small portion memory accessed 64 kilobytes offset 16 bits 16-bit offset may seem small relation size current computer memories 80386 expanded 32-bit could worse ibm system/360 mainframes unsigned 12-bit offset however principle locality reference applies short time span data items program wants access fairly close addressing mode closely related indexed absolute addressing mode example 1 within subroutine programmer mainly interested parameters local variables rarely exceed 64 kb one base register frame pointer suffices routine class method object-oriented language second base register needed points attributes current object self high level languages example 2 base register contains address composite type record structure offset used select field record records/structures less 32 kb size add reg1| reg2| constant reg1 reg2 constant addressing mode effective address considered addressing mode computers constant might signed unsigned example codice_1 move immediate hex value feedabba register d0 instead using operand memory value operand held within instruction dec vax machine literal operand sizes could 6 8 16 32 bits long andrew tanenbaum showed 98 constants program would fit 13 bits see risc design philosophy clear carry bit implied addressing mode also called implicit addressing mode x86 assembly language explicitly specify effective address either source destination sometimes either source destination effective address sometimes implied opcode implied addressing quite common older computers mid-1970s computers typically single register arithmetic could performed—the accumulator accumulator machines implicitly reference accumulator almost every instruction example operation b c done using sequence load b add c store -- destination accumulator implied every load add instruction source accumulator implied every store instruction later computers generally one general purpose register ram location could source destination arithmetic—and later computers need addressing mode specify source destination arithmetic among x86 instructions use implicit registers one operands results multiplication division counting conditional jump many computers x86 avr one special-purpose register called stack pointer implicitly incremented decremented pushing popping data stack source destination effective address implicitly address stored stack pointer many 32-bit computers 68000 arm powerpc one register could used stack pointer—and use register autoincrement indirect addressing mode specify registers used pushing popping data stack current computer architectures e.g ibm/390 intel pentium contain instructions implicit operands order maintain backwards compatibility earlier designs many computers instructions flip user/system mode bit interrupt-enable bit etc implicitly specify special register holds bits simplifies hardware necessary trap instructions order meet popek goldberg virtualization requirements—on system trap logic need look operand final effective address opcode cpus designed every operand always implicitly specified every instruction -- zero-operand cpus load reg address requires space instruction quite large address often available cisc machines variable-length instructions x86 risc machines special load upper literal instruction places 16- 20-bit constant top half register used base register base-plus-offset addressing mode supplies low-order 16 12 bits combination allows full 32-bit address load reg |index| address also requires space instruction quite large address address could start array vector index could select particular array element required processor may scale index register allow size array element note less base-plus-offset addressing mode except offset case large enough address memory location example 1 within subroutine programmer may define string local constant static variable address string stored literal address instruction offset—which character string use iteration loop—is stored index register example 2 programmer may define several large arrays globals class variables start array stored literal address perhaps modified program-load time relocating loader instruction references offset—which item array use iteration loop—is stored index register often instructions loop re-use register loop counter offsets several arrays load reg base|index| base register could contain start address array vector index could select particular array element required processor may scale index register allow size array element could used accessing elements array passed parameter load reg base|index| offset base register could contain start address array vector records index could select particular record required offset could select field within record processor may scale index register allow size array element load reg base|index| base register could contain start address array vector data structure index could contain offset one particular array element required addressing mode dynamically scales value index register allow size array element e.g array elements double precision floating-point numbers occupying 8 bytes value index register multiplied 8 used effective address calculation scale factor normally restricted power two shifting rather multiplication used load reg1 base| computers distinct addressing mode many computers use base plus offset offset value 0 example a7 load reg base determining effective address value base register incremented size data item accessed example a7 would access content address register a7 increase address pointer a7 1 usually 1 word within loop addressing mode used step elements array vector high-level languages often thought good idea functions return result side effects lack side effects makes program understanding validation much easier addressing mode side effect base register altered subsequent memory access causes error e.g page fault bus error address error leading interrupt restarting instruction becomes much problematic since one registers may need set back state instruction originally started least two computer architectures implementation problems regard recovery interrupts addressing mode used load reg base| determining effective address value base register decremented size data item accessed within loop addressing mode used step backwards elements array vector stack implemented using mode conjunction previous addressing mode autoincrement see discussion side-effects autoincrement addressing mode addressing modes mentioned article could extra bit indicate indirect addressing i.e address calculated using mode fact address location typically complete word contains actual effective address indirect addressing may used code data make implementation pointers references handles much easier also make easier call subroutines otherwise addressable indirect addressing carry performance penalty due extra memory access involved early minicomputers e.g dec pdp-8 data general nova registers limited addressing range 8 bits hence use memory indirect addressing almost way referring significant amount memory load reg1 base=pc offset pc-relative addressing mode used load register value stored program memory short distance away current instruction seen special case base plus offset addressing mode one selects program counter pc base register cpus support pc-relative data references cpus include mos 6502 derivatives used relative addressing branch instructions instructions used mode jumps used variety addressing modes x86-64 architecture 64-bit armv8-a architecture pc-relative addressing modes called rip-relative x86-64 literal armv8-a motorola 6809 also supports pc-relative addressing mode pdp-11 architecture vax architecture 32-bit arm architectures support pc-relative addressing pc register file addressing mode used compiler typically places constants literal pool immediately immediately subroutine uses prevent accidentally executing constants instructions addressing mode always fetches data memory stores data memory sequentially falls execute next instruction effective address points data confused pc-relative branch fetch data store data memory instead branches instruction given offset effective address points executable instruction addressing modes listed used 1950–1980 period longer available current computers list means complete many interesting peculiar addressing modes used time time e.g absolute-minus-logical-or two three index registers word size larger address word referenced memory-indirect addressing could indirect flag set indicate another memory indirect cycle flag referred indirection bit resulting pointer tagged pointer indirection bit tagging whether direct pointer indirect pointer care needed ensure chain indirect addresses refer one get infinite loop trying resolve address ibm 1620 data general nova hp 2100 series nar 2 multi-level memory indirect could enter infinite address calculation loop memory indirect addressing mode nova influenced invention indirect threaded code dec pdp-10 computer 18-bit addresses 36-bit words allowed multi-level indirect addressing possibility using index register stage well computers registers regarded occupying first 8 16 words memory e.g icl 1900 dec pdp-10 meant need separate add register register instruction – one could use add memory register instruction case early models pdp-10 cache memory tight inner loop loaded first words memory fast registers addressable installed ran much faster would magnetic core memory later models dec pdp-11 series mapped registers onto addresses input/output area primarily intended allow remote diagnostics confusingly 16-bit registers mapped onto consecutive 8-bit byte addresses dec pdp-8 minicomputer eight special locations addresses 8 15 accessed via memory indirect addressing locations would automatically increment use made easy step memory loop without needing use registers handle steps data general nova minicomputer 16 special memory locations addresses 16 31 accessed via memory indirect addressing 16 23 would automatically increment use 24 31 would automatically decrement use data general nova motorola 6800 family mos technology 6502 family processors internal registers arithmetic logical instructions mostly performed values memory opposed internal registers result many instructions required two-byte 16-bit location memory given opcodes processors one byte 8 bits length memory addresses could make significant part code size designers processors included partial remedy known zero page addressing initial 256 bytes memory 0000 – 00ff a.k.a. page 0 could accessed using one-byte absolute indexed memory address reduced instruction execution time one clock cycle instruction length one byte storing often-used data region programs could made smaller faster result zero page used similarly register file many systems however resulted high utilization zero page memory area operating system user programs limited use since free space limited zero page address mode enhanced several late model 8-bit processors including wdc 65816 csg 65ce02 motorola 6809 new mode known direct page addressing added ability move 256-byte zero page memory window start memory offset address 0000 new location within first 64 kb memory csg 65ce02 allowed direct page moved 256-byte boundary within first 64 kb memory storing 8-bit offset value new base page b register motorola 6809 could direct page dp register wdc 65816 went step allowed direct page moved location within first 64 kb memory storing 16-bit offset value new direct register result greater number programs able utilize enhanced direct page addressing mode versus legacy processors included zero page addressing mode similar scaled index addressing except instruction two extra operands typically constants hardware checks index value bounds another variation uses vector descriptors hold bounds makes easy implement dynamically allocated arrays still full bounds checking computers special indirect addressing modes subfields within words ge/honeywell 600 series character addressing indirect word specified either 6-bit 9-bit character fields within 36-bit word dec pdp-10 also 36-bit special instructions allowed memory treated sequence fixed-size bit fields bytes size 1 bit 36 bits one-word sequence descriptor memory called byte pointer held current word address within sequence bit position within word size byte instructions existed load store bytes via descriptor increment descriptor point next byte bytes split across word boundaries much dec software used five 7-bit bytes per word plain ascii characters one bit per word unused implementations c use four 9-bit bytes per word since 'malloc function c assumes size int multiple size char actual multiple determined system-dependent compile-time operator sizeof elliott 503 elliott 803 apollo guidance computer used absolute addressing index registers thus indirect jumps jumps registers supported instruction set instead could instructed add contents current memory word next instruction adding small value next instruction executed could example change codice_2 codice_3 thus creating effect indexed jump note instruction modified on-the-fly remains unchanged memory i.e self-modifying code value added next instruction large enough could modify opcode instruction well instead address
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Computer architecture
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third manifesto third manifesto 1995 christopher j date hugh darwen proposal future database management systems response two earlier manifestos purpose theme manifestos avoid object-relational impedance mismatch object-oriented programming languages relational database management systems third manifesto proposes maintain relational model databases support objects user-defined types major theme manifesto explain inadequacies existing relational database management systems shortcomings relational database model per se rather implementation decisions systems sql query language systems use manifesto describes alternative sql named d. specification desirable characteristics database language rather specific syntax grammar describes family languages rather particular language however example particular member hypothetical family called tutorial described detail including significant portions grammar several partial implementations exist including
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Databases
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clamwin free antivirus clamwin free antivirus free open-source antivirus tool windows provides graphical user interface clam antivirus engine firefox extensions allow users process downloaded files clamwin clamwin free antivirus scans demand automatically scan files read written non-affiliated projects clam sentinel winpooch add-ons provide real-time scanning capability clamwin clamwin free antivirus virus database updated automatically detects connection internet small balloon tip appears taskbar icon indicating completion status update process retries establish connection server fails download updates first time historically clamwin free antivirus suffered poor detection rates scans slow less effective antivirus programs example 2009 clamwin free antivirus failed detect almost half trojan horses password stealers malware av-test zoo malware samples 1–21 june 2008 test performed virus.gr clamwin free antivirus version 0.93 detected 54.68 threats ranked 37th 49 products tested best scored 99 10 august-05 september 2009 test performed virus.gr clamwin free antivirus version 0.95.2 detected 52.48 threats ranked 43 55 products tested best scored 98.89 6 september 2011 cnet gave clamwin free antivirus rating excellent 4 5 stars
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Computer security
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battle cross 1982 video game battle cross shoot 'em arcade game released omori electric 1982 player controls fighter spacecraft moving around screen shooting enemies
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Computer architecture
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media resource control protocol media resource control protocol mrcp communication protocol used speech servers provide various services speech recognition speech synthesis clients mrcp relies another protocol real time streaming protocol rtsp session initiation protocol sip establishing control session audio streams client server mrcp uses similar style clear-text signaling http many internet protocols message contains 3 sections first-line header body first line indicates type message well information response codes header contains number lines format nowiki header data /nowiki body whose length specified header contains details message like http mrcp uses request usually issued client response model responses may simply acknowledge receipt request give information regarding processing example mrcp client may request send audio data processing say speech recognition server could respond message containing suitable port number send data since mrcp support audio data specifically would handled protocol real-time transport protocol rtp mrcp protocol version 2 approved rfc version 2 uses sip managing sessions audio streams server clients whereas version 1 specify underlying protocol mrcp adopted wide range commercial speech servers microsoft speech server lumenvox speech engine neospeech speech engine/server nuance recognizer vocalizer sestek tts sestek call steering well commercial interactive voice response software blueworx voice response
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Internet protocols
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itk itk framework building mega-widgets using incr tcl object system mega-widgets high-level widgets like file browser tab notebook act like ordinary tk widgets constructed using tk widgets component parts without write c code effect mega-widget looks acts exactly like tk widget considerably easier implement
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Programming language topics
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microsoft bob microsoft bob microsoft software product released march 11 1995 discontinued early 1996 program intended provide user-friendly interface windows 3.1x windows 95 windows nt operating systems supplanting windows program manager microsoft bob presented screens showing house rooms user could go containing familiar objects corresponding computer applications—for instance desk pen paper checkbook items case clicking pen paper would open word processor cartoon dog named rover cartoon characters provided guidance using speech balloons rover others later returned windows xp search companions upon release microsoft bob criticized media gain wide acceptance users resulted discontinuation microsoft bob released march 1995 windows 95 released although widely publicized prior date codename utopia project leader bob karen fries microsoft researcher design based research professors clifford nass byron reeves stanford university melinda gates wife bill gates marketing manager product microsoft originally purchased domain name bob.com boston-area techie bob antia later traded bob kerstein windows2000.com domain name bob included various office suite programs finance application word processor user interface designed simplify navigational experience novice computer users similar early graphical shells like jane main interface portrayed inside house different rooms corresponding common real-world room styles kitchen family room room contains decorations furniture well icons represent applications bob offers user option fully customizing entire house user full control decorating room add remove reposition objects user also add remove rooms house change destinations door also feature bob offers multiple themes room designs decorations contemporary postmodern applications built bob represented matching decorations – example clicking clock opens calendar pen paper represent word processor user also add shortcuts applications computer shortcuts display icon inside various styles decorations boxes picture frames released right internet beginning become popular bob offered email client user could subscribe mci mail dial-up email account price 5.00 per month send 15 emails per month email limited 5000 characters additional email limit reached additional 45 cents toll-free phone number called set account bob features assistants cartoon characters intended help user navigate virtual house perform tasks main interface within built-in applications edition microsoft bob bundled gateway 2000 computer around 1995 gateway edition contained gateway branding login screen along additional rooms backgrounds seen retail version one additional room attic contained box gateway 2000 computer along additional rooms icons appeared default new rooms bob one microsoft visible product failures despite discontinued windows 95 released microsoft bob continued severely criticized reviews popular media 2017 melinda gates acknowledged software needed powerful computer people back bob received 7th place pc world magazine list 25 worst tech products time number one worst product decade cnet.com spot list 50 worst inventions published time magazine called bob overly cutesy operating system designed around clippy microsoft steve ballmer mentioned bob example situation decided succeeded let stop microsoft employee raymond chen wrote article encrypted copy bob included windows xp install cds take space slow downloading illegal copies tech journalist harry mccracken called story delightfully urban legend-y tale noted similarities april fools day joke claiming bob hidden windows vista rover software dog mascot reappeared windows xp file search function typeface comic sans created used microsoft bob microsoft
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Operating systems
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nix package manager nix cross-platform package management system utilizes purely functional deployment model software installed unique directories generated cryptographic hashes dependencies software included within hash solving problem dependency hell novel approach package management promises generate reliable reproducible portable packages nix packages defined lazy functional programming language specifically designed package management dependencies tracked directly language special values called derivations installed nix lazily nix keeps track references automatically installed packages garbage collected package depends cost greater storage requirements upgrades nix guaranteed atomic efficiently rolled back also enables multiple users safely install software system without administrator privileges nix full support linux safely installed side-by-side existing package manager macos also officially supported nixos linux distribution using nix consistently every piece software system including linux kernel
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Operating systems
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code segment computing code segment also known text segment simply text portion object file corresponding section program virtual address space contains executable instructions term segment comes memory segment historical approach memory management succeeded paging program stored object file code segment part file loader places program memory may executed various memory regions allocated particular pages corresponding segments object files segments needed run time example code segment object file loaded corresponding code segment memory code segment memory typically read-only fixed size embedded systems usually placed read-only memory rom without need loading code segment read-only particular architecture allows self-modifying code fixed-position position independent code may shared memory several processes segmented paged memory systems memory region code segment may placed heap stack order prevent heap stack overflows overwriting
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Operating systems
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printer command language printer command language commonly referred pcl page description language pdl developed hewlett-packard printer protocol become de facto industry standard originally developed early inkjet printers 1984 pcl released varying levels thermal matrix page printers hp-gl/2 pjl supported later versions pcl pcl occasionally incorrectly said abbreviation printer control language actually another term page description language pcl levels 1 5e/5c command-based languages using control sequences processed interpreted order received consumer level pcl data streams generated print driver pcl output also easily generated custom applications hp introduced pcl 6 around 1995 hp laserjet 4000 series printers consists pcl 6 enhanced architecture altered modular easily modified future hp printers prints complex graphics faster reduces network traffic higher quality early implementations hp market pcl 6 well thus causing confusion terminology pcl xl renamed pcl 6 enhanced many third-party products still use older term products may claim pcl 6 compliant may include pcl 5 backward compatibility pcl 6 enhanced primarily generated printer drivers windows cups due structure compression methodology custom applications rarely use directly pcl 6 enhanced stack-based object-oriented protocol similar postscript however restricted binary encoding opposed postscript sent either binary code plain text plain-text commands code examples shown pcl programming documentation meant compiled utility like hp jetasm sent printer pcl 6 enhanced designed match drawing model windows gdi way windows printer driver simply passes gdi commands little modification leading faster return-to-application times microsoft extended concept next-generation xps format printer implementations xps developed new idea comparable display postscript apple quartz contrast gdi printers compressed bitmap sent printer jetready printers clj 3500/3550/3600 use undocumented extensions otherwise mandate class 3.0 inputs pjl printer job language introduced hp laserjet iiisi pjl adds job level controls printer language switching job separation environment commands status readback device attendance file system commands
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Programming language topics
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raima database manager raima database manager rdm acid-compliant embedded database management system designed use embedded systems applications rdm designed utilize multi-core computers networking local wide area on-disk in-memory storage management rdm provides support multiple application programming interfaces apis low-level c api c++ sql native odbc jdbc ado.net labview rdm highly portable available windows linux unix several real-time embedded operating systems source-code license also available rdm support non-sql record cursor level database access sql database design manipulation capabilities non-sql features important resource-restricted embedded system environments high performance small footprint priority sql important providing widely-known standard database access method small enough footprint embedded systems environments raima inc. originally released rdm 1984 called db_vista one first microcomputer network model database management systems designed exclusively use c language applications companion product called db_query introduced 1986 first sql-like query report writing utility network model database db_vista derivative dbms designed provide high-performance transaction-processing client-server sql dbms called raima database server rds released 1993 first dbms provided odbc api native sql interface also first sql system incorporated use network model ddl features soon thereafter rds renamed velocis 2001 rdm server version 8.4 rdm server released 2012 uninterrupted development rdm also known rdm embedded continued recent feature additions including database mirroring use support highly available ha systems database replication multi-version concurrency read-only transactions multiple transactional file server access encryption sql designed specifically use embedded systems applications version 12.0 rdm released 2013 also 2013 rdm introduced first on-platform sql dbms available use national instruments labview graphical programming language named national instruments labview embedded tools network product year version 14.0 rdm released q3/16 rdm v. 14.0 contains all-new data storage engine optimized specifically working in-memory resident data sets new in-memory database imdb allows significant performance gains reduction processing requirements compared older in-memory on-disk implementations version 14.1 rdm released q1/18 new release focuses ease use portability speed raima new file format develop deploy anywhere performance increased 50-100 depending use case compared previous rdm releases raima extended improved sql support snapshots geospatial functionality version 14.1 consolidates source code lines features raima database manager rdm server one source code rdm 14.1 includes major features updated in-memory support snapshots r-tree support compression encryption sql sql pl platform independence—develop deploy anywhere rmd 14.1 includes portability options direct copy paste permit development deployment different target platforms regardless architecture byte order release includes streamlined interface cursor-based extended sql support stored procedures support sql pl also supports odbc c c++ ado.net c jdbc java supported development environments include microsoft visual studio apple xcode eclipse wind river workbench redesigned optimized database file format architecture maintains acid compliance data safeguards separate formats in-memory on-disk hybrid storage file formats hide hardware platform specifics e.g. byte ordering download packages include examples rdm speed performance benchmarks transactional file server tfs software component within rdm system maintains safe multi-user transactional updates set files responds page requests tfserver utility links tfs allow run separate utility allowing users run rdm distributed computing environment tfs may also linked directly application avoid rpc overhead calling separate server modes operation dynamic ddl encryption additional sql data types data providers drivers interoperability different “ tree ” support snapshots circular tables support database limitations data types supported non-sql core ddl features sql ddl features rdm transactional file server tfs specializes serving managing database files given medium tfs set functions called rdm runtime manage sharing database files among one runtime library instances normal multi-user configuration tfs functions wrapped server process called tfserver standard tcp/ip used make connection whether runtime library tfserver computer different computers however computer faster shared-memory protocol available default figure shows one rdm client runtime may connections multiple tfservers one tfserver may used multiple client runtimes applications using rdm runtime tfservers locations processes invisible processes may one computer may different computers provides opportunities true distributed processing tfserver considered “ database controller ” much way disk controller manages storage device tfs initialized root directory stored files managed tfs one computer multiple disk controllers recommended one tfserver assigned controller facilitates parallelism one computer especially multiple cpu cores also present complete application system may multiple tfservers running one computer multiple computers networked together tfserver able run parallel others allowing performance scale accordingly tfs functions used rdm runtime programmer visibility calls made functions made available runtime library three forms descriptive reasons call tfsr tfst tfss rdm database union feature provides unified view multiple identically structured databases since rdm allows highly distributed data storage processing feature provides mechanism unifying distributed data giving appearance single large database simple illustration consider widely distributed database organization headquarters seattle branch offices boston london mumbai office owns maintains employee records locally headquarters also performs reporting entire organization database location structure identical others although fully contained database location also considered partition larger global database case partitioning based geographical location mechanism querying distributed database simple programmer database opened partitions referenced together symbols “ ” individual partition names partitioning unified queries also used scaling performance consider database operation begins lookup record ’ primary key “ database ” composed four partitions stored multi-core computer different disks controlled different disk controllers requirement scheme divides primary key among four partitions scheme modulo primary key application quickly determines partition store record read record since multiple cpu cores run multiple processes applications tfss four partitions accessible parallel four controllers permit processing capacity four times larger single-core single-disk single-partition configuration rdm allows database content encrypted transported across network written database files rdm encryption supports rijndael/aes encryption algorithm 128- 192- 256-bit keys based application-specified encryption key database mirroring rdm reproduces exact byte-for-byte copy master database onto mirrored slave database database mirroring important database feature applications require high availability ha tfserver fail reason application ha monitor automatically switch mirrored tfserver rdm provides synchronous mirroring transaction committed master tfserver also securely committed mirror tfserver rdm also provides set ha support api functions called application ha monitor monitor operational status tfservers mirroring also used support maintaining multiple copies database updates made master readers directed one mirrored slaves order distribute many possible database readers across multiple computers situation necessary master wait slave confirm successful commit transaction mirroring process run asynchronously rdm database mirroring requires master mirrored databases maintained computer/operating system platforms due released q2/18 replication similar mirroring really intended ha support transferring likely portions one database master another database slave replication designed work databases necessarily maintained platform slave databases rdm-managed databases 3rd-party dbms rdm replication includes support multiple master single slave selective replication circular table data—important embedded computers devices edge data grid status condition monitoring occurs status data stored master circular table replicated central control system maintaining permanent history device statuses made available variety time series analyses rdm also provides database change notification api library allows slave access master replication logs without data stored managed database allows example master store device control information database replicated device notification api order efficiently control device operation rdm sql programming language sql pl based ansi/iso sql persistent stored modules psm specification iso/iec 90756-4:2011 +2012 provides high-level language stored procedures functions written compiled called within rdm sql system rdm sql designed specifically use embedded systems applications important features rdm sql include rdm provides application programming interfaces allow application development variety programming languages rdm ported wide variety computers operating systems packages available following platforms rdm 14.1 consists two packages rdm 14.1 core rdm 14.1 enterprise rdm based applications used today major industries including aerospace defense automotive business automation financial government industrial automation medical telecommunication sampling rdm users includes following
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Databases
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versus io versus online comparison tool mobile phones tablets cameras camcorders cities versus aims 1 destination help users make informed buying decisions world ’ first multi-language all-algorithm big data driven content provider generating fully automated natural text keen focus user interface comparison platform turns raw data natural language simplifies complexity using versus consumers able view results simple clear format without ‘ information overload ’ ultimately allowing users digest complex product data quickly efficiently versus plans add additional 640 categories include real estate motorcycles food credit cards banks plastic surgeons even people unlike similar sites comparisons include user reviews strictly based technical specifications screen resolution processing power site presents results pointing one prefer product service launched april 2012 german startup urge io currently available 18 languages claims 500k monthly visits 60 page-view growth rate monthly basis
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Web technology
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community cloud community cloud computing collaborative effort infrastructure shared several organizations specific community common concerns security compliance jurisdiction etc whether managed internally third-party hosted internally externally controlled used group organizations shared interest costs spread fewer users public cloud private cloud cost savings potential cloud computing realized
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Distributed computing architecture
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cisco systems cisco systems inc. american multinational technology conglomerate headquartered san jose california center silicon valley cisco develops manufactures sells networking hardware telecommunications equipment high-technology services products numerous acquired subsidiaries opendns webex jabber jasper cisco specializes specific tech markets internet things iot domain security energy management cisco stock added dow jones industrial average june 8 2009 also included p 500 index russell 1000 index nasdaq-100 index russell 1000 growth stock index cisco systems founded december 1984 leonard bosack sandy lerner two stanford university computer scientists pioneered concept local area network lan used connect geographically disparate computers multiprotocol router system time company went public 1990 cisco market capitalization 224 million end dot-com bubble year 2000 cisco 500 billion market capitalization cisco systems founded december 1984 sandy lerner director computer facilities stanford university graduate school business lerner partnered husband leonard bosack charge stanford university computer science department computers cisco initial product roots stanford university campus technology early 1980s students staff stanford including bosack used technology campus link school computer systems talk one another creating box functioned multiprotocol router called blue box blue box used software originally written stanford research engineer william yeager due underlying architecture ability scale well yeager well-designed invention became key cisco early success 1985 bosack stanford employee kirk lougheed began project formally network stanford campus adapted yeager software became foundation cisco ios despite yeager claims denied permission sell blue box commercially july 11 1986 bosack lougheed forced resign stanford university contemplated filing criminal complaints cisco founders theft software hardware designs intellectual properties 1987 stanford licensed router software two computer boards cisco addition bosack lerner lougheed greg satz programmer richard troiano handled sales completed early cisco team company first ceo bill graves held position 1987 1988 1988 john morgridge appointed ceo name cisco derived city name san francisco company engineers insisted using lower case cisco early years logo intended depict two towers golden gate bridge february 16 1990 cisco systems went public market capitalization 224 million listed nasdaq stock exchange august 28 1990 lerner fired upon hearing news husband bosack resigned protest couple walked away cisco 170 million 70 committed charity although cisco first company develop sell dedicated network nodes one first sell commercially successful routers supporting multiple network protocols classical cpu-based architecture early cisco devices coupled flexibility operating system ios allowed keeping evolving technology needs means frequent software upgrades popular models time cisco 2500 managed stay production almost decade virtually unchanged company quick capture emerging service provider environment entering sp market product lines cisco 7000 cisco 8500 1992 1994 cisco acquired several companies ethernet switching kalpana grand junction notably mario mazzola crescendo communications together formed catalyst business unit time company envisioned layer 3 routing layer 2 ethernet token ring switching complementary functions different intelligence architecture—the former slow complex latter fast simple philosophy dominated company product lines throughout 1990s 1995 john morgridge succeeded john chambers internet protocol ip became widely adopted mid-to-late 1990s cisco introduced products ranging modem access shelves as5200 core gsr routers making major player market late march 2000 height dot-com bubble cisco became valuable company world market capitalization 500 billion july 2014 market cap us 129 billion still one valuable companies perceived complexity programming routing functions silicon led formation several startups determined find new ways process ip mpls packets entirely hardware blur boundaries routing switching one juniper networks shipped first product 1999 2000 chipped away 30 cisco sp market share response cisco later developed homegrown asics fast processing cards gsr routers catalyst 6500 switches 2004 cisco also started migration new high-end hardware crs-1 software architecture ios-xr part rebranding campaign 2006 cisco systems adopted shortened name cisco created human network advertising campaign efforts meant make cisco household brand—a strategy designed support low-end linksys products future consumer products traditional business side cisco continued develop routing switching security portfolio quickly growing importance ethernet also influenced company product lines limits ios aging crescendo architecture also forced cisco look merchant silicon carrier ethernet segment resulted new asr9000 product family intended consolidate company carrier ethernet subscriber management business around ezchip-based hardware ios-xr throughout mid-2000s cisco also built significant presence india establishing globalization centre east bangalore 1 billion cisco also expanded new markets acquisition—one example 2009 purchase mobile specialist starent networks cisco continued challenged domestic alcatel-lucent juniper networks overseas competitors huawei due lower-than-expected profit 2011 cisco reduced annual expenses 1 billion company cut around 3,000 employees early-retirement program accepted buyout planned eliminate many 10,000 jobs around 14 percent 73,400 total employees curtailment 2011 analyst call cisco ceo john chambers called several competitors name including juniper hp july 24 2012 cisco received approval eu acquire nds tv software developer us 5 billion 2013 cisco sold linksys home-router unit belkin international inc. signaling shift sales businesses rather consumers july 23 2013 cisco systems announced definitive agreement acquire sourcefire 2.7 billion august 14 2013 cisco systems announced would cut 4,000 jobs workforce roughly 6 starting 2014 end 2013 cisco announced poor revenue due depressed sales emerging markets caused economic uncertainty fears national security agency planting backdoors products april 2014 cisco announced funding early-stage firms focus internet things investment fund allocated investments iot accelerators startups alchemist accelerator ayla networks evrythng later year company announced laying another 6,000 workers 8 global workforce part second restructuring november 4 2014 cisco announced investment stratoscale may 4 2015 cisco announced ceo chairman john chambers would step ceo july 26 2015 remain chairman chuck robbins senior vice president worldwide sales operations 17-year cisco veteran announced next ceo july 23 2015 cisco announced divesture television set-top-box cable modem business technicolor sa 600 million division originally formed cisco 6.9 billion purchase scientific atlanta deal came part cisco gradual exit consumer market part effort cisco new leadership focus cloud-based products enterprise segments cisco indicated would still collaborate technicolor video products november 19 2015 cisco alongside arm holdings dell intel microsoft princeton university founded openfog consortium promote interests development fog computing january 2016 cisco invested velocloud software-defined wan sd-wan start-up cloud offering configuring optimizing branch office networks cisco contributed velocloud 27 million series c round led march capital partners february 2017 cisco launched cloud-based secure internet gateway called cisco umbrella provide safe internet access users n't use corporate networks vpns connect remote data centers immediately reporting fourth quarter earnings 2017 cisco price-per-share value jumped 7 earnings per share ratio increased 60 61 cents per share due part cisco outperformance analyst expectations september 2017 chambers announced would step executive chairman role end term board december 2017 december 11 2017 robbins elected succeed chambers executive chairman retaining role ceo chambers given title chairman emeritus reuters reported cisco systems inc ’ csco.o product revenue russia grew 20 percent 2017 ahead cisco ’ technology product revenue growth so-called bric countries brazil china india may 1 2018 cisco systems agreed buy ai-driven business intelligence startup accompany 270 million june 2018 cisco systems ranked 444th forbes global 2000 list 221.3 billion market cap fiscal year 2017 cisco reported earnings us 0.1 billion annual revenue us 49.3 billion increase 2.8 previous fiscal cycle cisco shares traded 43 per share market capitalization valued us 213.2 billion september 2018 low net income fiscal year 2018 attributed one time tax charge allowed cisco bring back capital overseas cisco used money able bring back lower tax rate fund share buybacks acquisitions cisco acquired variety companies spin products talent company 1995–1996 company completed 11 acquisitions several acquisitions stratacom biggest deals industry occurred internet boom 1999 company acquired cerent corporation start-up company located petaluma california us 7 billion expensive acquisition made cisco date acquisition scientific atlanta larger 1999 cisco also acquired stake 1 billion kpmg consulting enable establishing internet firm metrius founded keyur patel fuse several acquired companies grown 1bn+ business units cisco including lan switching enterprise voice internet protocol voip platform webex home networking latter came result cisco acquiring linksys 2003 2010 supplemented new product line dubbed cisco valet cisco announced january 12 2005 would acquire airespace us 450 million reinforce wireless controller product lines cisco announced january 4 2007 would buy ironport deal valued us 830 million completed acquisition june 25 2007 ironport best known ironport antispam senderbase email reputation service email security appliances accordingly ironport integrated cisco security business unit ironport senderbase renamed sensorbase take account input database cisco devices provide sensorbase allows devices build risk profile ip addresses therefore allowing risk profiles dynamically created http sites smtp email sources cisco announced march 15 2012 would acquire nds group 5bn transaction completed july 30 2012 recent merger deals cisco bought starent networks mobile packet core company moto development group product design consulting firm helped develop cisco flip video camera also 2010 cisco became key stakeholder e-skills week march 2011 cisco completed acquisition privately held network configuration change management software company pari networks although many buy-ins crescendo networks 1993 tandberg 2010 resulted acquisition flagship technology cisco many others failed—partially completely instance 2010 cisco occupied meaningful share packet-optical market revenues still par us 7 billion price tag paid 1999 cerent acquired technologies flip pure digital saw product lines terminated january 2013 cisco systems acquired israeli software maker intucell around 475 million cash move expand mobile network management offerings month cisco systems acquired cognitive security company focused cyber threat protection cisco also acquired solvedirect cloud services march 2013 ubiquisys mobile software april 2013 cisco acquired cyber-security firm sourcefire october 2013 june 16 2014 cisco announced completed acquisition threatgrid company provided dynamic malware analysis threat intelligence technology june 17 2014 cisco announced intent acquire privately held tail-f systems leader multi-vendor network service orchestration solutions traditional virtualized networks april 2 2015 cisco announced plans buy embrane software-defined networking startup deal give cisco embrane software platform provides layer 3–7 network services things firewalls vpn termination server load balancers ssl offload may 7 2015 cisco announced plans buy tropo cloud api platform simplifies addition real-time communications collaboration capabilities within applications june 30 2015 cisco acquired privately held opendns company best known dns service adds level security monitoring domain name requests august 6 2015 cisco announced completed acquisition privately held maintenancenet us-based company best known cloud-based contract management platform serviceexchange month cisco acquired pawaa privately held company bangalore india provides secure on-premises cloud-based file-sharing software september 30 2015 cisco announced intent acquire privately held portcullis computer security uk-based company provides cybersecurity services enterprise clients government sectors october 26 2015 cisco announced intent acquire parstream privately held company based cologne germany provides analytics database allows companies analyze large amounts data store near real time anywhere network october 27 2015 cisco announced would acquire lancope company focuses detecting threat activity 452.5 million cash-and-equity deal june 28 2016 cisco announced intent acquire cloudlock privately held cloud security company founded 2011 three israeli military veterans 293 million deal expected close first quarter 2017 august 2016 cisco announced getting closer making deal acquire springpath startup whose technology used cisco hyperflex systems cisco already owns undisclosed stake hyper-converged provider january 2017 cisco announced would acquire appdynamics company monitors application performance 3.7 billion acquisition came one day appdynamics set ipo january 26 2017 cisco founded innovation alliance germany eleven companies bringing together 40 sites 2,000 staff provide small businesses germany expertise august 1 2017 cisco completed acquisition viptela inc. 610 million cash assumed equity awards viptela privately held software-defined wide area network sd-wan company based san jose ca october 23 2017 cisco systems announced would acquiring broadsoft 1.9 billion entrench cloud communication collaboration area 2017 cisco systems shares mainly held institutional investors vanguard group blackrock state street corporation others cisco products services focus upon three market segments—enterprise service provider midsize small business cisco provides products services across five major technology areas networking including ethernet optical wireless mobility security collaboration including voice video data data center internet things cisco grown increasingly popular asia-pacific region last three decades dominant vendor australian market leadership across market segments uses australian office one main headquarters asia-pacific region offering diverse product portfolio long-term stability integration sustainable competitive advantage cisco became major provider voice ip enterprises moving home user market acquisitions scientific atlanta linksys scientific atlanta provides voip equipment cable service providers time warner cablevision rogers communications upc others linksys partnered companies skype microsoft yahoo integrate consumer voip services wireless cordless phones cisco partners offer cloud-based services based cisco virtualized unified computing system ucs part cisco unified services delivery solution includes hosted versions cisco unified communications manager ucm cisco unified contact center cisco unified mobility cisco unified presence cisco unity connection unified messaging cisco webex meeting center part tactical operations initiative cisco maintains several network emergency response vehicles nerv s. vehicles maintained deployed cisco employees natural disasters public crises vehicles self-contained provide wired wireless services including voice radio interoperability voice ip network-based video surveillance secured high-definition video-conferencing leaders first responders crisis areas 3 mbit/s bandwidth via 1.8-meter satellite antenna nervs based cisco headquarters sites san jose california research triangle park north carolina allowing strategic deployment north america become fully operational within 15 minutes arrival high-capacity diesel fuel-tanks allow largest vehicles run 72 hours continuously nerv deployed incidents october 2007 california wildfires hurricanes gustav ike katrina 2010 san bruno gas pipeline explosion tornado outbreaks north carolina alabama 2011 hurricane sandy 2012 tactical operations team maintains deploys smaller portable communication kits emergencies outside north america 2010 team deployed assist earthquake recovery haiti christchurch new zealand 2011 deployed flooding brazil well response 2011 earthquake tsunami japan 2011 cisco received innovation preparedness award american red cross silicon valley chapter development use vehicles disasters cisco systems also sponsors line professional certifications cisco products four five path network designers levels certification entry ccent associate ccna/ccda professional ccnp/ccdp expert ccie/ccde recently architect ccar ccde previous well nine different paths routing switching design industrial network network security service provider service provider operations storage networking voice datacenter wireless number specialist technician sales datacenter certifications also available cisco also provides training certifications via portal called cisco networking academy qualifying schools become members cisco networking academy provide ccna level level courses cisco academy instructors must ccna certified ccai certified instructor cisco often finds involved technical education 10,000 partnerships 65 countries cisco academy program operates many exotic locations example march 2013 cisco announced interest myanmar investing two cisco networking academies yangon mandalay channel partner network cisco products including ip phones telepresence seen movies tv series company featured documentary film something ventured premiered 2011 cisco 2002–03 recipient ron brown award u.s. presidential honor recognize companies exemplary quality relationships employees communities cisco included part fortune 100 best companies work ranking 20 2011 according report technology consulting firm lexinnova cisco one leading recipients network security-related patents largest portfolio within companies 6,442 security-related patents 2015 class action lawsuit filed april 20 2001 accused cisco making misleading statements relied purchasers cisco stock insider trading cisco denied allegations suit august 18 2006 cisco liability insurers directors officers paid plaintiffs us 91.75 million settle suit december 11 2008 free software foundation filed suit cisco regarding cisco failure comply gpl lgpl license models make applicable source code publicly available may 20 2009 cisco settled lawsuit complying fsf licensing terms making monetary contribution fsf cisco criticized involvement censorship people republic china according author ethan gutmann cisco telecommunications equipment providers supplied chinese government surveillance internet infrastructure equipment used block internet websites track online activities china cisco stated customize develop specialized unique filtering capabilities enable governments block access information sells equipment china sells worldwide wired news uncovered leaked confidential cisco powerpoint presentation detailed commercial opportunities golden shield project internet control may 2011 group falun gong practitioners filed lawsuit alien tort statute alleging cisco knowingly developed customized product assist chinese government prosecution abuse falun gong practitioners lawsuit dismissed september 2014 united states district court northern district california decision appealed united states court appeals ninth circuit september 2015 october 2007 employees cisco brazilian unit arrested charges imported equipment without paying import duties response cisco stated import directly brazil instead use middlemen december 1 2008 multiven filed antitrust lawsuit cisco systems inc. multiven complaint alleges cisco harmed multiven consumers bundling tying bug fixes/patches updates operating system software maintenance services smartnet may 2010 cisco accused person filed antitrust suit british-nigerian technology entrepreneur peter alfred-adekeye hacking pressured us government extradite canada cisco settled antitrust lawsuit two months alfred-adekeye arrest making software updates available multiven customers cisco linksys e2700 e3500 e4500 devices reported remotely updated firmware version forces users register cloud service allows cisco monitor network use ultimately shut cloud service account thus render affected router unusable according german magazine der spiegel nsa developed jetplow gaining access asa series 5505 5510 5520 5540 5550 500-series pix firewalls cisco chief security officer addressed allegations publicly denied working government weaken cisco products exploitation implement security back doors document included trove national security agency files released glenn greenwald book place hide details agency tailored access operations tao unit nsa employees intercept servers routers network gear shipped organizations targeted surveillance install covert firmware onto delivered trojan horse systems described nsa manager “ productive operations tao pre-position access points hard target networks around world. ” cisco denied allegations customer document saying information included specific cisco products supply chain intervention implant techniques new security vulnerabilities cisco general counsel also said cisco work government including united states government weaken products allegations reported prompted company ceo express concern president united states march 2014 cisco systems sued patent infringement spherix says 43 billion cisco sales infringe old nortel patents owned spherix officials spherix saying wide range cisco products switches routers infringe 11 former nortel patents company owns january 2008 cisco announced investment 10 million three years towards job creation technology sector development palestinian territories according cisco project cooperation palestinian authority president mahmoud abbas ramallah-based exalt technologies handles software development cisco outsources palestinian territories
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Computer security
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sky force sky force vertically scrolling shoot 'em video game series created polish video game developer infinite dreams inc.. gameplay reminiscent capcom 19xx series seibu kaihatsu raiden series featuring weapon upgrade system large end stage bosses first title series originally released symbian pocket pc 2004 ported palm webos 2005 ios 2009 android 2010 first game series entirely sprite-based 2d game game received near perfect rating ign gave score 9.5 10 second outing initially released symbian pocket pc palm webos 2006 later released ios 2009 iphone ios 7 2010 psp 2011 psp version sky force reloaded simply named sky force 2d graphics style first title combined 3d polygon objects like destructible towers received remake mobile 2016 pc playstation 4 xbox one versions released 2017 also nintendo switch version released 2018 psp version game received metascore 69 100 metacritic based 6 reviews third part series released 2014 ios android free-to-play game third part series 2d graphics first two titles entirely replaced polygonal 3d graphics ios version game received favorable metascore 83 100 composed 8 reviews title windows version sky force 2014 released steam 2015 apple tv 4 2016 released playstation 3 playstation 4 playstation vita via playstation network summer 2016 version f2p improved upgrade system game received favorable review hardcore gamer gave score 4 5
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Operating systems
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deferred deep linking deferred deep linking one aspect mobile deep linking describes principle deep linking app yet installed case deep linking deferred application installed user implies clicking otherwise invoking deep link causes common use case drive installs linking functionality not-yet-installed app provides user incentive install deferred deep linking allows mobile developers mobile marketers deliver seamlessly automated user experience whether app previously installed improving conversion rates user retention currently industry standard deferred deep linking various platform providers offer differing levels support platforms real support majority option roll-your-own approach general approach provide mechanism url parameters passed around app store ie received source linking application click stored passed destination linked-to application installed launched major technical challenge solve approach identifying click caused install correct url parameters passed newly-installed app tying clicks installs family technologies known attribution
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Web technology
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rsts/e rsts multi-user time-sharing operating system initially developed evans griffiths hart boston acquired digital equipment corporation dec part hewlett packard pdp-11 series 16-bit minicomputers first version rsts rsts-11 version 1 implemented 1970 dec software engineers developed tss-8 time-sharing operating system pdp-8 last version rsts rsts/e version 10.1 released september 1992 rsts-11 rsts/e usually referred rsts article generally use shorter form kernel rsts programmed assembly language macro-11 compiled installed disk using cilus program running dos-11 operating system rsts booted extended version basic programming language dec called basic-plus system software cusps operating system including programs resource accounting login logout managing system written basic-plus 1970 1973 rsts ran 56k bytes magnetic core memory 64 kilobytes including memory-mapped i/o space would allow system 16 terminals maximum 17 jobs maximum program size 16k bytes end 1973 dec estimated 150 licensed systems running rsts 1973 memory management support included rsts rsts/e newer dec pdp-11/40 pdp-11/45 minicomputers pdp-11/20 supported rsts-11 introduction memory management newer pdp-11 computers meant machines able address four times amount memory 18-bit addressing 256k bytes also paved way developers separate user mode processes core kernel 1975 memory management support updated newer 22-bit addressable pdp-11/70 rsts systems could expanded use much two megabytes memory running 63 jobs rts ccl concepts introduced although compiled sysgen multi-terminal service introduced would allow single job ability control multiple terminals 128 total large-message send/receive interprocess communication became sophisticated efficient august 1,200 licensed systems 1977 installation process rsts longer dependent dos-11 rsts kernel could compiled rt-11 rts formatted kernel file rt-11 silus copied system disks computer time-sharing basic-plus rts well rt-11 rsx-11 teco third party rtss ran user mode processes independent rsts kernel systems manager could decide bootstrap phase rts run systems default kbm 3,100 licensed systems 1978 final memory management update included machines could support 22bit addressing rsts could use maximum amount memory available pdp-11 4 megabytes support also included supervisory mode made rsts first dec operating system capability decnet also supported well remote diagnostics field service technicians rdc colorado springs colorado dec subscription service end decade 5,000 licensed systems 1981 support separate instruction data space users unibus machines pdp-11/44 pdp-11/45 pdp-11/55 pdp-11/70 provided extension memory constraints individual program compiling programs use separate instruction data space would soon give program 64 kb instructions 64 kb buffering data dcl rts included well support newer revision decnet iii 1983 rsts/e v8.0-06 included support smallest 18-bit pdp-11 sold dec micropdp-11 pre-generated kernel cusps included distribution make installation micropdp-11 easier dec sold pre-generated version micropdp-11 microrsts reduced price however users needed purchase full version need generate kernel file system upgraded given designation rsts directory structure 1 rds1 previous versions rsts file system given designation rds0 newer file system designed support 1700 user accounts thought well 10,000 licensed users least equal number unlicensed users 1985 1989 rsts became mature product version 9 revisions dcl installed primary rts file system upgraded rds1.2 support new user account features passwords encrypted using modified des algorithm instead limited six 6 characters stored dec radix-50 format version 9 non-user system account project group zero designation 0,1 accounts project number 1 privileged unlike root account unix systems version 9 released additional accounts could created project zero multiple privileges could individually set account support lat protocol included well ability run newest version decnet iv network enhancements gave user connected terminal decserver ability communicate rsts machine easily could vax running vms dcl command structure dec operating systems also contributed familiar look feel another pseudo command file processor based vms features dcl command file processor fully supported integrated rsts extensive changes dcl monitor dcl executes command files part job therefore pseudo keyboard forcing commands keyboard necessary atpk 1994 dec sold pdp-11 software business mentec digital continued support pdp-11 customers short period assistance mentec staff issue ip rights digital later compaq later still hewlett packard straightforward much mis-information pervaded hobbyist user community digital mentec granted no-cost license anyone non-commercial hobby purpose use specific non-current versions several operating systems developed pdp-11 use specific pdp-11 emulator known simh emulators versions pdp software released use authorized disk images authorized operating systems may found internet along simh emulator ibm pc class computers thus possible hobbyist run rsts/e personal computer using software emulation fast faster originally ran real hardware standard complement documentation manuals accompanies rsts distribution consists least 11 large three-ring binders collectively known orange wall one small three-ring binder containing rsts/e quick reference guide paperback copy introduction basic aa-0155b-tk 11 three-ring binders contains volume 1 general information installation volume 2 system management volume 3 system usage volume 4 utilities volume 4a utilities volume 4b utilities volume 5 basic-plus volume 6 system programming volume 7 macro programming volume 7a macro programming volume 8 rms last software product description dec outlined following topics major features rsts/e version 10.1 rsts uses serial communication connection interact operator connection might local computer terminal 20 current loop interface rs-232 interface either local serial port remote connection via modem ethernet connection utilizing decnet lat many 128 terminals using multi-terminal service could connect rsts system running maximum 63 jobs depending processor used amount memory disk space system load rsts systems nowhere near many terminals users could also submit jobs run batch mode also batch program called atpk allowed users run series commands imaginary terminal pseudo-terminal semi-interactive mode similar batch commands ms-dos users connected system typing login command hello logged-out terminal pressing return actually typing command logged-out terminal simply started login program interpreted command one commands allowed used user yet logged logged associated program command chained otherwise message please say hello printed terminal prior version 9 user could also initiate 1 line login however left password screen anyone behind view examples follow one could determine status terminal command responses printed command interpreter logged-in user communicating basic-plus kbm given prompt ready user logged given prompt bye user would log supplying ppn number password user numbers consisted project number would equivalent group number unix comma programmer number numbers range 0 254 special exceptions specifying account project programmer number enclosed brackets typical user number could 10,5 project 10 programmer 5 2,146 254,31 200,220 etc user running system program logged system manager enabled ppn number 0,0 would appear systat cusp ** ** thus valid account number every project programmer number 0 usually reserved group account could referenced special symbol one user number 20,103 reference file name beginning would refer file stored account user number 20,0 feature would useful educational environments programmer number 0 could issued instructor class individuals students given accounts project number instructor could store account files marked shared project number would students class two special classes project numbers existed project number 0 generally reserved system software prior version 9 1 project 0 account named 0,1 programmers project number 1 privileged accounts equivalent single account root unix systems except account numbers 1,0 1,254 privileged accounts version 9 released account could granted specific privileges systems manager account 0,1 used store operating system file run-time library systems certain system files relating booting system author comments appear right bold dir command installed ccl equivalent run command direct program 0,1 account number directory name operating system storage account would referred project number 0 programmer number 1 numbers shown file represent size disk blocks block 512 bytes 1/2 kilobyte k c indicates file contiguous stored one file without separated pieces similar files microsoft windows system drive defragmented p indicates specially protected deleted even privileged user unless p bit cleared separate command numbers brackets like 40 represent protections file always displayed decimal protections indicate file may seen user users programmer number file read may altered another user whether file may executed ordimary user giving additional privileges protection codes similar r w x protections unix similar operating systems bsd linux code 60 equivalent private file code 63 private non-deletable file 40 public file library files kept account 1,1 usually referenced logical name lb account 1,2 system startup account much like unix system starting root contains system cusps could referenced prefixing cusp name dollar sign used account 1,3 1,4 1,5 account 1,1 also special privilege account user logged account permitted execute poke system call put values memory system thus account number 1,1 closest equivalent root unix-based systems one features rsts means execution programs environment used run various environments allowed programming basic-plus enhanced basic-plus-2 traditional programming languages cobol fortran environments separate one could start program one environment system would switch different environment running different program return user original environment started environments referred rts term command line interface rtss kbm prior version 9 systems manager needed define rts system would start one would execute compiled programs systems manager may also install special ccl commands take precedence kbm commands exception dcl ccl analogous shortcut program windows system symbolic link unix-based systems ccls installed memory-resident command either startup dynamically system running system manager i.e permanent like disk file logged user switch environments type language statements basic-plus programming language issue run commands specific programs issue special command called ccl execute program command options rsts systems managers generated kernel include control-t one line status option could tell program running rts program using much memory program taking much could expand much memory rts using programs written basic-plus ran basic rts allowed 32k bytes memory 64k total language interpreted different keyword internally converted unique byte code variables data indexed stored separately within memory space internal byte-code format known pcode interactive save command issued basic plus rts simply saved working memory area disk file .bac extension although format undocumented two electronic engineering undergraduates southampton university uk nick de smith david garrod developed decompiler could reverse engineer bac files original basic plus source complete original line numbers variable names subsequently worked dec rest memory used basic rts one wrote programs language permitted true binary executables basic-plus-2 fortran-iv macro assembler amount memory available would 56k 8k allocated rts standard basic-plus prompt ready response example starting version 9 dcl became primary startup rts even though ability execute binary programs became possible advent disappearing rsx rts see dcl incorporated recent versions dec operating systems rsx-11 rt-11 vms later openvms compatibility standard dcl prompt dollar sign example programs written rsx rts cobol macro assembler later releases basic-plus-2 could utilize maximum amount memory available binary program 56k due requirements rts needing top 8k use rsts version 7 later allowed rsx rts included kernel making completely disappear user address space thus allowing 64k bytes memory user programs programs got around limitations amount available memory using libraries permissible complicated overlay strategies calling programs chaining passing commands shared memory area called core common among practices rsx default kbm standard rsx prompt logged logged mcr monitor console routine sign example rt-11 rts emulated single job version rt-11 distribution like rsx emulation rt-11 occupied top 8k memory leaving bottom 56k cusps programs written fortran-iv macro assembler rt-11 default kbm standard rt-11 prompt logged logged sign example teco editor implemented rts maximize amount memory available editing buffer also first implemented rsts v5b release general purpose runtime systems rsx rt11 teco rts distributed rsts contain built-in kbm user would start teco like program running teco program teco.tec teco affine qedit direct ancestors first unix-based text editor ed rsts systems used ccl create file make filespec edit file teco filespec run teco program mung filespec data following program example teco could used calculate pi currently set 20 digits user typed unrecognised command system boot option prompt init.sys startup utility message type 'help help displayed user subsequently typed 'help including quotes prompt response amusing anyway ... followed actual help message one nice features system manager could compile kernel rotating display pattern gave illusion 2 snakes chasing around console lights normal kernel would give illusion 1 snake moving right left data lights across bottom system manager also compiled lights object module would see additional snake moving left right address lights across top accomplished using supervisory mode versions prior 9.0 rsx also similar display pattern would appear 2 snakes playing chicken would run center console command 'make allowed user make text file automatically enter teco text editor user typed 'make love system created file called 'love typed back 'not war kevin herbert later working dec added undocumented feature 90 allow user enter ^f see list open files user process complete blocks use file sizes beginning version 9.0 undocumented feature would allow system manager change display system date rsts became first operating system would display system date set numbers representing stardate commonly known tv series system industries bought source license rsts implement enhancement called simacs simultaneous machine access allowed special disk controller set semaphore flag disk access allowing multiple writes files rsts system disk shared multiple pdp-11 rsts systems feature implemented system industries controllers attached many dec computers designed dr. albert chu worked system industries required many changes way access disks accomplished rsts operating system fips file information processing system system handled i/o access single-threaded rsts allow disk access stall another machine active access block required fips could timeout request go next request 'come back stalled one round robin fashion code allow written philip hunt working system industries milipitas ca eventually worked digital equipment new england area late 1980s early '90s 1981 evans griffiths hart marketed ross/v product ross/v allowed user mode processes rsts cusps rtss user programs ability run unmodified vms vax-11 machines code emulation handled kernel processes would normally handled rsts kernel running pdp-11 original basic-plus language carried versions rsts subcontracted evans griffiths hart inc. fixed price 10,500 rsts applications run pdp-11 emulator information see pdp-11 rsts originally called btss name changed btss rtss product name btss marketed honeywell simple typing mistake changed name rtss rsts addition new memory management support ability install memory pdp-11/40 pdp-11/45 led another name change rsts-11 became rsts/e computer bureaus sometimes deployed user-11 rsts/e-based data management
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Operating systems
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mbrola mbrola speech synthesis software worldwide collaborative project mbrola project web page provides diphone databases large number spoken languages mbrola software complete speech synthesis system languages text must first transformed phoneme prosodic information mbrola format separate software e.g espeakng necessary mbrola project started 1995 tcts lab faculté polytechnique de mons belgium scientific project obtain set speech synthesizers many languages possible first release mbrola software 1996 provided freeware non-commercial non-military application licenses created voice databases differ also mostly non-commercial non-military use due free usage non-commercial applications mbrola alternative choice private/home users de facto speech synthesis engine espeakng linux workstations mostly used commercial solutions e.g speaking time clocks boarding notifications ports terminals etc initial development voice databases updates support mbrola software ceased gradually closed-source binaries fell behind development recent hardware operating systems deal mbrola development team decided release mbrola open source software october 24 2018 source code released github gnu affero general public license january 23 2019 tool called mbrolator released provide creation mbrola database wav files license mbrola software uses mbrola multi-band resynthesis overlap add algorithm speech generation although diphone-based quality mbrola synthesis considered higher diphone synthesisers preprocesses diphones imposing constant pitch harmonic phases enhances concatenation slightly degrading segmental quality mbrola time-domain algorithm similar psola implies low computational load synthesis time unlike psola however mbrola require preliminary marking pitch periods feature made possible develop mbrola project around mbrola algorithm many speech research labs companies individuals around world provided diphone databases many languages voices notable omissions chinese
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Computational linguistics
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kernel virtual address space kernel virtual address space kva virtual memory area linux kernel threads reside second part virtual address space occupied user virtual address space contain user threads
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Operating systems
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lisp 2 lisp 2 programming language proposed 1960s successor lisp largely lisp-like semantics algol 60-like syntax today mostly remembered syntax fact many features beyond early lisps early lisps many limitations including limited data types slow numerics use fully parenthesized notation also considered problem inventor lisp john mccarthy expected issues addressed later version called notionally lisp 2 hence name lisp 1.5 successor earliest lisp lisp 2 joint project system development corporation information international inc. intended ibm built an/fsq-32 military computer development later shifted ibm 360/67 digital equipment corporation pdp-6 project eventually abandoned
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Programming language topics
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affix grammar finite lattice linguistics affix grammars finite lattice agfl formalism notation context-free grammars finite set-valued features acceptable linguists many different schools agfl-project aims development technology natural language processing available gnu gpl
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Computational linguistics
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benild joseph benild joseph born 15 may 1992 indian cyber security researcher tedx speaker white hat hacker currently president information systems security association issa india chapter advisory board member cybersecurity ventures featured book hacking hacker authored roger grimes silicon india magazine listed one top 8 ethical hackers india benild joseph born wayanad kerala studied infant jesus english medium school interest technology prompted mother send computer institute later learnt programming coding penchant towards technology led hacking working ebay tesco citigroup law enforcement agencies government organizations india helping dealing cyber threats safeguarding digital assets
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Computer security
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block allocation map computer file systems block allocation map data structure used track disk blocks considered use blocks may also referred allocation units clusters cp/m used block allocation map directory directory entry could list 8 16 blocks depending disk format allocated file file used blocks additional directory entries would needed thus single file could multiple directory entries benefit method possibility use sparse files declaring large file size allocating blocks actually used detriment method disk may free space unallocated blocks data appended file directory entries used commodore dos used similarly named significantly different block availability map
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Computer file systems
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ansi-sparc architecture ansi-sparc architecture ansi-sparc stands american national standards institute standards planning requirements committee abstract design standard database management system dbms first proposed 1975 ansi-sparc model however never became formal standard mainstream dbms systems fully based tend exhibit full physical independence prevent direct user access conceptual level idea logical data independence widely adopted objectives three-level architecture separate user view three levels three level architecture aim enabling users access data personalised view distancing internal level external level means users need know data physically stored database level separation also allows database administrator dba change database storage structures without affecting users views three different types schema corresponding three levels ansi-sparc architecture overall description database called database schema
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Databases
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playstation 2 homebrew homebrew playstation 2 refers independent development video games consumers playstation 2 video game console sony released linux-based operating system ps2 package also includes keyboard mouse ethernet adapter hdd currently sony online store states linux kit longer sale north america however july 2005 european version still available kit boots installing proprietary interface run-time environment region-coded dvd european north america kits work ps2 respective regions europe australia ps2 came free yabasic interpreter bundled demo disc time allows simple programs created ps2 end-user included failed attempt circumvent uk tax defining console computer contained certain software port netbsd project blackrhino gnu/linux alternative debian-based distribution also available ps2 using homebrew programs e.g 'sms media player possible listen various audio file formats mp3 oma ogg vorbis aac flac ac3 watch various video formats divx/xvid mpeg1 mpeg2 mpeg4-asp avi container using console media played device connected console i.e external usb/firewire/thumb drive/hard disk drive fat32 internal hard disk early revision consoles optical cd-r w /dvd±r w disks modded systems patched disks network shares windows network ps2 host protocol homebrew programs launched directly memory card unmodified consoles using certain software takes advantage long known used exploit dealing boot part ee/iop process independence recent development may 2008 called free mcboot allows homebrew programs launched without trigger disc required older exploit also allows use homebrew unmodded systems without functional disc drive however installation exploit individual memory card requires either already exploited/modded system order launch installer boot image load app loads elf files network adapter hard drive also required copying one memory card another work newer exploit work newest ps2s scph-9000x model bios 2.30 work models prior newest versions free mcboot version 1.90 newer also ability install boot sony non-sony hdds using fat ps2 network adapter support called free hdboot fhdb minor issues possible game entirely hdd without needing use optical disc drive physical memory card homebrew programs used play patched backups original ps2 dvd games unmodified consoles install retail discs installed hard drive older models esr hd loader hd advance open ps2 loader homebrew emulators older computer gaming systems developed ps2
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Computer architecture
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dave cutler david neil dave cutler sr. born march 13 1942 american software engineer designer developer several operating systems computer industry operating systems microsoft windows nt digital equipment corporation rsx-11m vaxeln vms openvms cutler born lansing michigan grew dewitt michigan graduating olivet college michigan 1965 went work dupont cutler holds least 20 patents affiliate professor computer science department university washington cutler avid auto racing driver competed atlantic championship 1996 2002 scoring career best 8th milwaukee mile 2000 cutler member adelphic alpha pi fraternity olivet college michigan cutler first exposure computers came tasked perform computer simulations model one dupont customers using ibm gpss-3 language ibm model 7044 work led interest computers operating systems worked cutler left dupont pursue interest computer systems beginning digital equipment corporation 1971 worked famous mill facility maynard massachusetts april 1975 digital began hardware project code-named star design 32-bit virtual address extension pdp-11 june 1975 cutler together dick hustvedt peter lipman appointed technical project leaders software project code-named starlet develop totally new operating system star family processors two projects tightly integrated beginning three technical leaders starlet project together three technical leaders star project formed blue ribbon committee digital produced fifth design evolution programs design featured simplifications memory management process scheduling schemes earlier proposals architecture accepted star starlet projects culminated development vax-11/780 superminicomputer vax/vms operating system respectively digital began working new cpu using risc design principles 1986 cutler working dec decwest facility bellevue washington selected head prism project develop company ’ risc machine operating system code named mica embody next generation design principles compatibility layer unix vms risc machine based ecl technology one three ecl projects digital undertaking time funding research development r costs multiple ecl projects yielding products would ultimately compete strain three ecl projects vax 9000 one directly commercialized primarily early successes pmax advanced development project need differing business models prism canceled 1988 favor pmax prism later surfaced basis digital alpha family computer systems cutler known disdain things unix sardonic nature showed vms versus unix debates digital early 1980s expressed low opinion unix process input/output model reciting get byte get byte get byte byte byte tune finale rossini william tell overture cutler left digital microsoft october 1988 led development windows nt later worked targeting windows nt digital 64-bit alpha architecture based prism design windows 2000 demise windows alpha demise digital instrumental porting windows amd new 64-bit amd64 architecture officially involved windows xp pro 64-bit windows server 2003 sp1 64-bit releases moved working microsoft live platform august 2006 dave cutler awarded prestigious status senior technical fellow microsoft 2008 professional developers conference microsoft announced azure services platform cloud-based operating system microsoft developing conference keynote cutler mentioned lead developer project along amitabh srivastava spokesperson microsoft confirmed cutler longer working windows azure joined xbox team information provided cutler role working within team may 2013 microsoft announced xbox one console cutler mentioned worked development host os portion system running inside new gaming device apparently work focused creating optimized version microsoft hyper-v host os specifically designed xbox one
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Operating systems
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maya embedded language maya embedded language mel scripting language used simplify tasks autodesk 3d graphics software maya tasks achieved maya gui achieved mel well certain tasks available gui mel offers method speeding complicated repetitive tasks well allowing users redistribute specific set commands others may find useful mel syntactically similar perl tcl provides memory management dynamic array-allocation offers direct access functions specific maya majority standard maya commands default mel scripts saved maya program files directory mel fairly limited compared mainstream scripting languages mel primarily language meant journal maya session thus lacks many advanced features associative arrays python added maya alternative mel maya 8.5 still mel offers advantages python mel often criticized lack programming features object orientation practice however mel used metaprogramming language mel instructs maya node architecture solve problem since nodes form actual computational core maya using robust readily apparent programming method would inefficient approach many ways mel complements maya api somewhat clear boundaries allocated tasks makes mel harder learn fully understand tools designed using mel scripts generally come following categories example script copies selected object path maya also offers expression language super-set mel results nodes executed part maya dependency graph expressions developed maya expression editor allow scripts trigger maya evaluates scene file change time simulate complex behaviors perform useful tasks
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Programming language topics
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bpo security information security emerged significant concern banks mobile phone companies businesses use call centers business process outsourcing bpo instances theft personal data reported call centers britain financial services authority examined standards india april 2005 banking code standards board audited eight india-based call centres 2006 handling million calls per month uk examinations extend africa-based call centres staffed workers indian origin bcsb report stated customer data subject level security uk high risk complex processes subject higher levels scrutiny similar activities onshore india nasscom said take breach security extremely seriously assist police probe three identifiable types illicit activities concerning fraud emanating call centers items 1 2 mostly subject police action call centres use internal procedures minimise risk mitigation measures include limited
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Computer security
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applescript editor applescript editor formerly recently known script editor code editor applescript scripting language included classic mac os macos applescript editor provides basic debugging capabilities save applescripts plain text .applescript compiled script .scpt script bundle .scptd application .app applescript editor also handles script dictionary files allowing user see scripting classes commands available scriptable application installed computer prior mac os x 10.3 script editor developed using carbon 10.3 introduced new script editor written using cocoa applescript editor known script editor mac os x 10.6 also os x 10.10 renamed back script editor likely introduction javascript automation
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Programming language topics
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ibm informix ibm informix product family within ibm information management division centered several relational database management system rdbms offerings informix products originally developed informix corporation whose informix software subsidiary acquired ibm 2001 april 2017 ibm hcl technologies products platforms division agreed long-term 15-year partnership co-develop support market product ibm continued active development marketing key informix products current version 12.10 forms basis several product editions variation capacity functionality informix database used many high transaction rate oltp applications retail finance energy utilities manufacturing transportation sectors recently server enhanced support data warehouse workloads informix server supports object-relational model permitted ibm offer extensions support data types part sql standard widely used time series spatial extensions provide data type support language extensions permit high performance domain specific queries efficient storage datasets based time series spatial data current version ibm informix 12.10 code-named centaurus development major enhancements made previous releases adding built-in index compression integration json collections support mongodb json drivers server enhancement permitting database objects partitioned across multiple servers cluster grid aka sharding queries optionally return data locally connected server instance entire grid sql heterogeneous clusters fully supported several deployment options available including provide high levels data redundancy fault tolerance feature marketed ibm informix flexible grid informix offered number editions including free developer editions editions small mid-sized business editions supporting complete feature set designed used support largest enterprise applications also advanced data warehouse edition informix version includes informix warehouse accelerator uses combination newer technologies including in-memory data tokenization deep compression columnar database technology provide extreme high performance business intelligence data warehouse style queries informix timeseries unique feature database system allows efficient fast manipulation time series data generated devices smart electric meters found financial trading systems time stamped stock 'ticks type data well suited storage use normal sql supported style data organization unique among ibm database products apple mac environment supported informix since version 11.7 ibm several database products capabilities overlap areas informix often compared ibm major database product db2 offered mainframe zseries platform well unix linux speculation ibm would combine informix db2 database products proven unfounded ibm instead continued expand variety database products offers netezza data warehouse appliance cloudant nosql database ibm described approach market providing workload optimized systems informix generally considered optimized environments low database administration including use embedded database long track record supporting high transaction rates providing uptime characteristics needed mission critical applications manufacturing lines reservation systems informix widely deployed retail sector low administration overhead makes useful in-store deployments ability deeply embed informix gateways routers timeseries support small footprint low administration requirements informix also targeted internet-of-things solutions many data-handling requirements handled gateways embed informix connect sensors devices internet april 2017 ibm announced outsourcing development informix indian specialists hcl number ibm employees working informix would also move hcl part arrangement ibm continue market sell informix customers addition products based version 12.1 engine ibm informix family also includes number legacy database products still supported market include informix online informix standard edition se informix c-isam products simpler smaller footprint database engines also frequently embedded third party applications collectively products often referred informix classics ibm informix family also includes client-side development environment client-sdk supports number different environments including .net windows developers variety protocols unix linux environments ibm long-term plans informix db2 databases sharing technology although ibm continually denied fusion two products ibm training includes complete set core data servers training courses apply informix courses delve many essential informix concepts fundamentals advanced sql topics part ibm academic initiative ibm offering informix software documentation training higher education institutions worldwide new informix campus program ibm offering inclusive package informix materials college faculty called informix box offers hands-on labs powerpoints use lessons recorded training teachers dvds class material vmware virtual appliance images well t-shirts students users groups remain active belgium croatia france germany united states many countries iiug international informix users group acts federation user groups provides numerous services members
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Databases
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basho technologies basho technologies distributed systems company developed key-value nosql database technology riak object storage system built upon riak platform called riak cs basho developer riak open source distributed database offers high availability fault tolerance operation simplicity scalability riak enterprise commercial version database offered basho project sponsor advanced multi-data center replication enterprise support riak key value store system collect unstructured data store objects buckets queried also highly scalable able distribute server cluster add new servers needed maintaining high availability riak written erlang language gives system built-in support distribution across server cluster fault tolerance ability absorb new hardware added cluster without disrupting operations following demise basho company assets purchased bet365 previously closed source components riak_repl multi-data-centre replication released open-source github.com basho also offered riak cloud storage cs open source multi-tenant cloud storage database built riak platform integrated private clouds public clouds amazon web services aws used enterprises power internal private clouds startups amazon-compatible api download service riak cs includes large object support s3-compatible api authentication multi-tenancy per-user reporting operational model adding capacity visual interface monitoring metrics riak 1.0 released september 2011 featured secondary indexes riak pipe riak search integration lager leveldb support riak 1.1 released early 2012 included numerous changes riak core new ownership claim algorithm riak kv improvements mapreduce improvements august 2012 riak 1.2 released riak enterprise 1.2 added ssl encryption better balancing granular control replication across multiple data centers march 2013 basho released portions riak cs code open source basho also announced commercial version riak cs enterprise adding multi-datacenter replication monitoring tools 24x7 support riak 1.4 featured pn-counters database first distributed data type pn-counters eventually consistent incremented decremented node across cluster compact binary data format reduces storage overheads connected small objects large bucket names riak cs 1.4 provides compatibility openstack openstack object storage swift ceph object stores increased scalability riak 2.0 released september 2014 includes support new data types tunable consistency search integration apache solr riak 2.1 released april 2015 focused performance simplification developers system administrators basho technologies founded january 2008 earl galleher former executive vice president akamai technologies antony falco former vp product management technical services akamai 2011 donald j. rippert long time cto accenture joined basho president ceo bobby patrick former cmo gxs digex joined cmo late 2012 rippert left basho gregory collins took ceo basho march 2014 collins stepped adam wray former ceo tier 3 became new ceo basho time basho cto justin sheehy chief architect original riak author andy gross left company dave mccrory former svp engineering warner music group took cto mccrory well known creating concept data gravity theory describes difficulty relocating large volumes data due physical restrictions bandwidth 2012 basho announced ricon two-day distributed systems conference developers basho hosted ricon west ricon east 2012 2013 hosted single ricon conference 2014 2015 basho recognized dbta 100 companies matter data crn big data 100 data management 2017 basho put receivership
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Distributed computing architecture
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emc networker emc networker formerly legato networker enterprise-level data protection software product unifies automates backup tape disk-based flash-based storage media across physical virtual environments granular disaster recovery cross-platform support provided linux windows macos netware openvms unix environments deduplication backup data provided integration dell emc data domain dd boost storage solutions central networker server manages datazone contains backup clients networker storage nodes access backup media platforms supported core networker server aix hp-ux pa-risc itanium linux fully featured x86 x86-64 itanium client powerpc zlinux macos client solaris sparc x64 sgi irix client tru64 windows java based networker management console nmc software bundled networker distribution provides user interface functions client configuration policy settings schedules monitoring reports daily operations deduplicated non-deduplicated backups core networker software backs client file systems operating system environment add-on database application modules provide backup services products oracle db2 sap lotus informix sybase well microsoft exchange server sharepoint sql server client backup data sent remote networker storage node stored locally attached device use dedicated storage node additionally networker supports client direct backups allowing clients back directly shared devices bypassing storage node processes networker snapshot management automates generation point-in-time data snapshots cloning supported storage arrays emc vnx xtremio symmetrix ndmp module used client-less backups nas filers like isilon emc vnx netapp vmware virtual machines directly backed either installing networker client virtual machine networker vmware protection solution leverages vproxys perform application consistent image filesystem backups networker also supports backup recovery microsoft windows server hyper-v virtual servers using volume shadow copy services interface support protects parent child partitions guests well applications running within virtual machines networker came emc acquisition legato october 2003 legato founded 1988 four individuals worked together sun microsystems jon kepecs bob lyon joe moran russell sandberg networker unix first introduced 1990
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Computer security
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