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cerner ccl cerner ccl cerner command language cerner corporation fourth-generation programming language expressed cerner discern explorer solution ccl patterned structured query language sql cerner millennium health information technology solutions use ccl/discern explorer select insert update delete cerner millennium database ccl allows programmer fetch data oracle database display user wants see features like record structure subroutines allows us get data database manipulate storing temporary structure execute particular section code required using subroutine complete ccl cerner command language provided cerner corporation discern explorer provides several applications used create execute analyze ad hoc queries reports programs applications provide flexibility skill set needed build programs design reports discern explorer programs written using visualexplorer.exe discernvisualdeveloper.exe dvdev operating system command-line editor text editor explorermenu.exe em used execute discern explorer programs demand exploreranalyzer.exe ea allows users analyze system resources used rdbms queries ccl hello world examples call echo hello world go drop program helloworld2 go drop program helloworld3 go drop program jcmclass1a go
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Programming language topics
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pygame pygame cross-platform set python modules designed writing video games includes computer graphics sound libraries designed used python programming language pygame originally written pete shinners replace pysdl development stalled community project since 2000 released open source free software gnu lesser general public license pygame uses simple directmedia layer sdl library intention allowing real-time computer game development without low-level mechanics c programming language derivatives based assumption expensive functions inside games abstracted game logic making possible use high-level programming language python structure game features sdl n't include vector math collision detection 2d sprite scene graph management midi support camera pixel-array manipulation transformations filtering advanced freetype font support drawing applications using pygame run android phones tablets use pygame subset android pgs4a sound vibration keyboard accelerometer supported android regular competition called pyweek write games using python usually necessarily pygame community created many tutorials pygame
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Operating systems
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google desktop google desktop computer program desktop search capabilities created google linux apple mac os x microsoft windows systems allowed text searches user email messages computer files music photos chats web pages viewed ability display google gadgets user desktop sidebar september 2011 google announced would discontinue number products including google desktop reason given last years ’ huge shift local cloud-based storage computing well integration search gadget functionality modern operating systems people instant access data whether online offline goal google desktop product discontinued january 2008 google desktop featured following functionality prominent feature google desktop sidebar holds several common gadgets resides one side desktop sidebar available windows linux versions google desktop sidebar comes pre-installed following gadgets like windows taskbar google desktop sidebar set auto-hide mode appear user moves mouse cursor towards side resides auto-hide default sidebar always take 1/6 – 1/9 screen depending screen resolution windows forced resize however sidebar resized take less space users disable always top feature options auto-hide feature sidebar temporarily overlaps maximized windows another feature comes sidebar alerts sidebar minimized new email news displayed pop-up window windows taskbar searching sidebar deskbar floating deskbar google desktop displays quick find window window filled six default relevant results user computer results update user types allows use without open another browser window deskbars boxes enable searching directly desktop web results open browser window selected computer results displayed quick find box see deskbar either fixed deskbar sits windows taskbar floating deskbar may positioned anywhere desktop google desktop includes plugins allow indexing searching contents local microsoft outlook ibm lotus notes mozilla thunderbird email databases outside client applications built-in search functions lotus notes local databases indexed searching google desktop email indexing feature also integrated google web-based email service gmail index search email messages gmail accounts desktop gadgets interactive mini-applications placed anywhere user desktop – docked sidebar – show new email weather photos personalized news google offers gallery pre-built gadgets download official website developers google offers sdk official blog anyone wants write gadgets plug-ins google desktop automated system creates developer hierarchy called google desktop hall fame programmers advance based gadgets number popularity sdk also allows third-party applications make use search facilities provided google desktop search example file manager directory opus offers integrated google desktop search support even though desktop search programs search files meta data google desktop windows one uses title tag results lists files linux shows meta-data html files pdf files programs use file names results lists use title tag gives significantly better user experience since metadata titles present written ordinary language file names less communicative title meta data missing file google desktop reverts use filename google desktop originally developed bring google search technology desktop google desktop received much attention may allow reverse engineering google proprietary search algorithm centrally administered version integrates user experience vendor appliance exists well google desktop officially discontinued september 14 2011 february 2007 yair amit watchfire found series vulnerabilities google desktop could allow malicious individual achieve remote persistent access sensitive data cases full system control well significant impact ease exploitation forced google change google desktop logic google desktop version 5 many privacy civil liberties groups electronic frontier foundation eff concerns personal information people computers could readily copied users hard drives google desktop version 3 contains certain features raise serious security privacy concerns specifically share across computers feature introduces ability search content desktop desktop greatly increases risk users privacy google desktop v.3 set allow search across computers files indexed computer copied google servers potential information stored computers accessed others enable feature google desktop v. 3 computers seriously considered eff advises using feature also confidential data work home computers enable feature privacy laws company policies could violated installation feature specifically sb 1386 hipaa ferpa glba sarbanes-oxley far reaching concerns arise around packaging end user license agreement – specifically level intrusion local machine disclaimers users implicitly agree future changes license agreement without actually able see immediately issues microsoft outlook indexing deleted email listings removed required re-installing google desktop new archived mail listed several versions released patch outlook indexing first half 2009 large number google desktop users reported product stopped indexing suddenly index file reached approximately 4gb size full uninstall including manually deleting indexes reinstall would fix problem temporarily problem would recur index file reached 4gb problem resolved google desktop search version 5.9 currently google desktop index email contacts outlook 2010 default google desktop index email thunderbird 3
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Internet protocols
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scramble formation game player controls red propeller-driven airplane flying city tokyo able shoot capture red smaller planes follow player formation player choose 3 formations first able shoot air-to-air air-to-ground projectiles second air-to-air larger area third air-to-ground larger area well gameplay player react accordingly threats quickly decide one 3 formation types adequate one given moment game divided areas depicting key places tokyo shinjuku akasaka ginza clearly defined levels points player faced giant mothership shot hitting engines port released msx 2 home computer 1987
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Computer architecture
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database molecular motions database macromolecular motions molmovdb bioinformatics database software-as-a-service tool attempts categorize macromolecular motions sometimes also known conformational change originally developed mark b. gerstein werner krebs nat echols molecular biophysics biochemistry department yale university since introduction late 1990s peer-reviewed papers database received thousands citations database mentioned news articles major scientific journals book chapters elsewhere users search database particular motion either protein name protein data bank id number typically however users enter database via protein data bank often provides hyperlink molmovdb entry proteins found databases database includes web-based tool morph server allows non-experts animate visualize certain types protein conformational change generation short movies system uses molecular modelling techniques interpolate structural changes two different protein conformers generate set intermediate structures hyperlink pointing morph results emailed user morph server originally primarily research tool rather general molecular animation tool thus offered limited user control rendering animation parameters color point view original methods sometimes required fair amount cpu time completion since initial introduction 1996 database associated morph server undergone development try address shortcomings well add new features normal mode analysis research grounds subsequently developed alternative systems moviemaker university alberta bioinformatics vendor dnastar incorporated morphs database commercial protean3d product connection dnastar authors database immediately clear
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Distributed computing architecture
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knowledgeman knowledgeman early computer database management system created micro data base systems lafayette indiana knowledgeman introduced 1983 pc-sized version company mainframe computing database software knowledgeman promoted users dbase faster database using sophisticated computing power macro language sql structured query language allowed reports spreadsheet interface statistical graphics i.e. pie charts bar charts etc knowledgeman designed david bartkus knowledgeman first database management system ported mainframe system also first written 16-bit pc processor knowledgeman first separate database engine command interface something microsoft access lauded decade later micro data base systems developed graphical user interface knowledgeman frequently called kman 1985 although popular developers preferred use software command line interface 1986 introduced guru expert system incorporated knowledgeman database graphical user interface mid-1990s knowledgeman folded guru 2004 micro data base systems folded product line taken savitar corporation savitar folded 2008 besides uses business computing knowledgeman used archaeologists including neanderthal site france remains new amsterdam new york city elsewhere physicists fermilab wide range domains
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Programming language topics
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brian lamacchia brian a. lamacchia computer security specialist lamacchia best known work massachusetts institute technology establishing mit pgp key server first key centric pki implementation see wide-scale use lamacchia wrote first web interface pgp key server lamacchia currently works microsoft director security cryptography microsoft research previously director security cryptography microsoft extreme computing group played leading role design xkms security architecture .net palladium designed led development team .net security architecture security architect palladium most-referenced work .net framework played leading role design w3c xmldsig xkms standards particular author versions 1.0 1.1 2.0 xmldsig contributor xkms coauthor oasis standard ws-security lamacchia earned s.b. s.m. ph.d. degrees mit 1990 1991 1996 respectively primary community activity involvement seattle international film festival treasurer 2013 currently president
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Computer security
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apache ojb apache objectrelationalbridge ojb object/relational mapping tool allows transparent persistence java objects relational databases released april 6 2005 january 16 2011 apache objectrelationalbridge retired ojb open source project lightweight easy use requiring simply configure two files implement persistence layer easy integrate existing application generate code allows use different patterns persistence owner persistencebroker api jdo object data management group odmg ojb uses xml based object/relational mapping mapping resides dynamic metadata layer manipulated runtime simple meta-object-protocol mop change behaviour persistence kernel least two files required configure ojb ojb.properties repository.xml mapping 1-1 relationship example two tables person account case person account vice versa
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Web technology
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specfs unix-like computer systems specfs short special filesystem physical network file system mount point either simply filesystem layer access device special files hosted regular filesystems
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Computer file systems
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certified penetration testing engineer certified penetration testing engineer c pte internationally recognized cyber security certification administered united states-based information security company mile2 accreditation maps committee national security systems 4013 education certification c pte certification considered one five core cyber security certifications obtaining c pte certification requires proven proficiency knowledge five key information security elements penetration testing data collection scanning enumeration exploitation reporting c pte certification one several information assurance accreditations recognized u.s. national security agency certification also approved u.s. department homeland security national initiative cyber security studies careers nicss u.s.-based national security systems committee online exam c pte accreditation lasts two hours consists 100 multiple choice questions
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Computer security
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m2001 m2001 modular educational mathematical programming language developing presenting mathematical algorithms modern discrete classical continuous mathematics m2001 built semantic framework based category theory syntax similar pascal modula-2 designed purely pedagogic use efficiency ease implementation far less important development generality range application created play important role forming formal algorithmic foundation first-year college math students based multi-layered datatyping scheme m2001 includes collection eight computational types another six structured types two respectively collections mathematical classes abstract classes built latter encompassing commonly used abstract data types computer science lower two layers m2001 typing scheme based earlier experimental called cat programming language modular mathematical programming language ronald e. prather
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Programming language topics
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dns leak dns leak refers security flaw allows dns requests revealed isp dns servers despite use vpn service attempt conceal although primary concern vpn users also possible prevent proxy direct internet users vulnerability allows isp well on-path eavesdroppers see websites user may visiting possible browser dns requests sent isp dns server directly sent vpn occurs certain types vpns e.g split-tunnel vpns traffic still sent local network interface even vpn active starting windows 8 microsoft introduced smart multi-homed named resolution altered way windows 8 handled dns requests ensuring dns request could travel across available network interfaces computer general consensus new method domain name resolution accelerated time required dns look-up completed also exposed vpn users dns leaks connected vpn endpoint computer would longer use dns servers assigned vpn service instead dns request would sent available interfaces thus dns traffic would travel vpn tunnel expose user default dns servers websites exist allow testing determine whether dns leak occurring dns leaks addressed number ways websites may report false positive test results advisable always check result manually making sure note country provider ip home isp something different foreign may always easy know whether one using set dns whether dns leaks safest way verify via one online dns leak tests sometimes isp may already using one public dns servers default setting public one may show difference servers isp may collecting data case safest change different dns test dns leaks example isp using google public dns using may wise try cloudflare dns see leaks google dns
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Computer security
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jungle disk jungle disk name online backup software service privately held data security company suite products also includes network protection service email archiving one first backup services use cloud storage amazon s3 2009 acquired rackspace service added rackspace cloud files name word association amazon rainforest jungle disk common shorthand hard disk drive jungle disk backup monthly subscription software service supports laptops desktops servers microsoft windows macos linux operating systems data backed online disk using either continuous backup aka sync scheduled back selected files folders everything system data accessed software client web browser mobile devices running android ios also provides webdav server integration applications customers protect data using aes-256 encryption key even jungle disk employees access records subscription includes 10 gigabytes storage pay-as-you-go additional data jungle disk founded atlanta dave wright 2006 october 22 2008 jungle disk entered agreement acquired rackspace hosting inc. rackspace purchased jungle disk order expand cloud hosting services acquisition integration dave left rackspace found solidfire jungle disk relocated san antonio 2010 pace development slowed rackspace focused cloud infrastructure software platform became openstack 2013 rackspace revived jungle disk customer support going ticket service include phone chat ticketing january 5 2016 jungle disk spun rackspace us inc. privately held company headquartered san antonio tx december 5 2017 jungle disk announced acquired safetynet first backup quickbooks online jobber march 6 2018 jungle disk announced acquired teampassword password manager connected teams simplify password management security addition teampassword jungle disk product portfolio gives small businesses data security tool help generate secure unique passwords share access applications services enabling users productive work collaboration jungle disk raised 11 million equity 2016 part spin-off rackspace investors include number san antonio family offices january 18th 2017 jungle disk announced tripled growth capital additional funding existing investors december 7 2016 jungle disk tech-onomic impact award 2016 tech titans awards presented san antonio business journal january 31 2017 jungle disk named one ten finalists 'the best cloud storage file sharing providers businesses 2017 pc magazine march 2017 jungle disk named 'top 10 cloud storage solution provider cloud technology insights may 23 2017 jungle disk named one five finalists 'best cloud backup services businesses pc magazine tied second scoring affordable price large margin may 11 2018 jungle disk named one lifewire list 21 online backup services jungle disk client software receive update 2012-2014 part cloud office portfolio new version released december 2015 june 3 2011 colin percival owner tarsnap competitor jungle disk identified two potential weaknesses jungle disk security
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Computer security
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application virtualization application virtualization also known process virtualization software technology encapsulates computer programs underlying operating system executed fully virtualized application installed traditional sense although still executed application behaves runtime like directly interfacing original operating system resources managed isolated sandboxed varying degrees context term virtualization refers artifact encapsulated application quite different meaning hardware virtualization refers artifact abstracted physical hardware full application virtualization requires virtualization layer application virtualization layers replace part runtime environment normally provided operating system layer intercepts disk operations virtualized applications transparently redirects virtualized location often single file application remains unaware accesses virtual resource instead physical one since application working one file instead many files spread throughout system becomes easy run application different computer previously incompatible applications run side-by-side examples technology windows platform include application virtualization allows applications run environments suit native application example wine allows microsoft windows applications run linux application virtualization reduces system integration administration costs maintaining common software baseline across multiple diverse computers organization lesser integration protects operating system applications poorly written buggy code cases provides memory protection ide-style debugging features may even run applications written correctly example applications try store user data read-only system-owned location feature assists implementation principle least privilege removing requirement end-users administrative privileges order run poorly written applications allows incompatible applications run side-by-side time minimal regression testing one another isolating applications operating system security benefits well exposure application automatically entail exposure entire os application virtualization also enables simplified operating system migrations applications transferred removable media computers without need installing becoming portable software application virtualization uses fewer resources separate virtual machine computer programs virtualized examples include applications require device driver form integration os 16-bit applications need run shared memory space anti-virus programs applications require heavy os integration windowblinds stylexp difficult virtualize moreover software licensing application virtualization bears great licensing pitfalls mainly application virtualization software virtualized applications must correctly licensed application virtualization address file registry-level compatibility issues legacy applications newer operating systems applications n't manage heap correctly execute windows vista still allocate memory way regardless whether virtualized reason specialist application compatibility fixes shims may still needed even application virtualized technology categories fall application virtualization include
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Computer security
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check point ipso check point ipso operating system 'check point firewall appliance security devices based freebsd numerous hardening features applied ip ipso refers ipsilon networks company specialising ip switching acquired nokia 1997 2009 check point acquired nokia security appliance business including ipso nokia ipso version 6.2 fork freebsd 6 two systems called ipso-sx ipso-lx linux-based check point offers three lines security appliances one based ipso 6.x one based operating system called secureplatform latest based gaia platform rhel4 based ipso notable features firsts include ipso sb originally derived ipsilon networks freebsd 2.1-stable cross-compiled freebsd 2.2.6-release 3.5-release platforms major components ipso versions 2.x sold ipsilon networks part atm tag-switching solutions originally pioneered ipso 3.0 onwards designed host check point firewall-1 third party packages ipso 3.0 3.9 spanned 1999 2005 adding many features significant performance hardware refinements recognizably administrator ipso 4.0 designed major update internally numbered ipso 3.10 however check point software unable process two-digit dot version also included refresh voyager html interface point javascript frames avoided order facilitate use lynx command line interface together resulted renumbered 4.0 ipso 4.1 ipso 4.2 incremental releases ipso 4.2 gain source-based routing last scheduled new feature new development continue ipso 6.x ipso 5.0 build 056 released 2009 vsx r65 support ip appliance ipso 6.0 announced nokia relation ip2450 ip690 hardware based freebsd 6.x primary advantage ipso 4.x improved memory management performance scheduling threading posix-compliance operating system features ipso 6.0.7 released 2009 ip690 ip2450 corexl multi-core support ipso 6.1 contains enhancements freebsd 6.x without corexl support step change nokia advertised ipso 4.2 6.07 6.1 run alongside period time check point acquired nokia ip appliance business 6.07 6.1 development branches merged combined 6.2 recent version ipso 6.2mr6 released february 2017 nokia offered ipso 7 actually ipso lx discontinued 7.2 2008 acquiring nokia ip appliance business check point announced project gaia combine ipso secure platform first release expected 2011
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Operating systems
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loren kohnfelder loren kohnfelder best known mit s.b bscse thesis written may 1978 describing practical means applying public key cryptography secure network communications kohnfelder thesis introduced terms 'certificate 'certificate revocation list well introducing numerous concepts established important parts public key infrastructure x.509 certificate specification provides basis ssl s/mime modern pki implementations based kohnfelder thesis also co-creator praerit garg stride model security threats widely used threat modeling
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Computer security
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coroner toolkit coroner toolkit tct suite free computer security programs dan farmer wietse venema digital forensic analysis suite runs several unix-related operating systems freebsd openbsd bsd/os sunos/solaris linux hp-ux tct released terms ibm public license parts tct used aid analysis data recovery computer disasters tct superseded sleuth kit although tsk partially based tct authors tct accepted official successor tct
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Computer security
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unica nettracker unica nettracker web analytics application processes web log files unica nettracker first released 1996 sane solutions sold unica corporation current version december 2006 7.1.0 unica announce end-of-life end-of-support december 31 2011 nettracker processes log files virtually format using custom log definition logs processed web servers proxy servers streaming media servers ftp servers well processing log files nettracker use page tag data augment log file data nettracker stores processed log files internal database based upon sqlite
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Web technology
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health insurance portability accountability act health insurance portability accountability act 1996 hipaa kennedy–kassebaum act ref name= atchinson/fox /ref enacted 104th united states congress signed president bill clinton 1996 created primarily modernize flow healthcare information stipulate personally identifiable information maintained healthcare healthcare insurance industries protected fraud theft address limitations healthcare insurance coverage act consists five titles title hipaa protects health insurance coverage workers families change lose jobs title ii hipaa known administrative simplification provisions requires establishment national standards electronic health care transactions national identifiers providers health insurance plans employers title iii sets guidelines pre-tax medical spending accounts title iv sets guidelines group health plans title v governs company-owned life insurance policies five sections act known titles title hipaa regulates availability breadth group health plans certain individual health insurance policies amended employee retirement income security act public health service act internal revenue code title requires coverage also limits restrictions group health plan place benefits preexisting conditions group health plans may refuse provide benefits relation preexisting conditions either 12 months following enrollment plan 18 months case late enrollment title allows individuals reduce exclusion period amount time creditable coverage enrolling plan significant breaks coverage creditable coverage defined quite broadly includes nearly group individual health plans medicare medicaid significant break coverage defined 63-day period without creditable coverage along exception allowing employers tie premiums co-payments tobacco use body mass index title also requires insurers issue policies without exclusion leaving group health plans creditable coverage see exceeding 18 months renew individual policies long offered provide alternatives discontinued plans long insurer stays market without exclusion regardless health condition health care plans exempted title requirements long-term health plans limited-scope plans like dental vision plans offered separately general health plan however benefits part general health plan hipaa still applies benefits example new plan offers dental benefits must count creditable continuous coverage old health plan towards exclusion periods dental benefits alternate method calculating creditable continuous coverage available health plan title 5 categories health coverage considered separately including dental vision coverage anything 5 categories must use general calculation e.g. beneficiary may counted 18 months general coverage 6 months dental coverage beneficiary general health plan covered dental 6 months prior application date since limited-coverage plans exempt hipaa requirements odd case exists applicant general group health plan obtain certificates creditable continuous coverage independent limited-scope plans dental apply towards exclusion periods new plan include coverages hidden exclusion periods valid title e.g. accident covered must occurred beneficiary covered exact health insurance contract clauses must acted upon health plan also must re-written comply hipaa title ii hipaa establishes policies procedures maintaining privacy security individually identifiable health information outlines numerous offenses relating health care establishes civil criminal penalties violations also creates several programs control fraud abuse within health-care system however significant provisions title ii administrative simplification rules title ii requires department health human services hhs increase efficiency health-care system creating standards use dissemination health-care information rules apply covered entities defined hipaa hhs covered entities include health plans health care clearinghouses billing services community health information systems health care providers transmit health care data way regulated hipaa per requirements title ii hhs promulgated five rules regarding administrative simplification privacy rule transactions code sets rule security rule unique identifiers rule enforcement rule hipaa privacy rule composed national regulations use disclosure protected health information phi healthcare treatment payment operations covered entities effective compliance date privacy rule april 14 2003 one-year extension certain small plans hipaa privacy rule regulates use disclosure protected health information phi held covered entities generally health care clearinghouses employer-sponsored health plans health insurers medical service providers engage certain transactions regulation hhs extended hipaa privacy rule independent contractors covered entities fit within definition business associates phi information held covered entity regarding health status provision health care health care payment linked individual interpreted rather broadly includes part individual medical record payment history covered entities must disclose phi individual within 30 days upon request also must disclose phi required law reporting suspected child abuse state child welfare agencies covered entities may disclose protected health information law enforcement officials law enforcement purposes required law including court orders court-ordered warrants subpoenas administrative requests identify locate suspect fugitive material witness missing person covered entity may disclose phi certain parties facilitate treatment payment health care operations without patient express written authorization disclosures phi require covered entity obtain written authorization individual disclosure case covered entity discloses phi must make reasonable effort disclose minimum necessary information required achieve purpose privacy rule gives individuals right request covered entity correct inaccurate phi also requires covered entities take reasonable steps ensuring confidentiality communications individuals example individual ask called work number instead home cell phone numbers privacy rule requires covered entities notify individuals uses phi covered entities must also keep track disclosures phi document privacy policies procedures must appoint privacy official contact person responsible receiving complaints train members workforce procedures regarding phi individual believes privacy rule upheld file complaint department health human services office civil rights ocr however according wall street journal ocr long backlog ignores complaints complaints privacy violations piling department health human services april 2003 november 2006 agency fielded 23,886 complaints related medical-privacy rules yet taken enforcement actions hospitals doctors insurers anyone else rule violations spokesman agency says closed three-quarters complaints typically found violation provided informal guidance parties involved however july 2011 ucla agreed pay 865,500 settlement regarding potential hipaa violations hhs office civil rights investigation showed 2005 2008 unauthorized employees repeatedly without legitimate cause looked electronic protected health information numerous uclahs patients january 2013 hipaa updated via final omnibus rule updates included changes security rule breach notification portions hitech act significant changes related expansion requirements include business associates covered entities originally held uphold sections law addition definition significant harm individual analysis breach updated provide scrutiny covered entities intent disclosing breaches previously unreported previously organization needed proof harm occurred whereas organizations must prove harm occurred protection phi changed indefinite 50 years death severe penalties violation phi privacy requirements also approved hipaa privacy rule may waived natural disaster case hurricane harvey 2017 see privacy section health information technology economic clinical health act hitech act privacy rule requires medical providers give individuals access phi individual requests information writing typically using provider form purpose provider 30 days provide copy information individual individual may request information electronic form hard-copy provider obligated attempt conform requested format providers using electronic health record ehr system certified using cehrt certified electronic health record technology criteria individuals must allowed obtain phi electronic form providers encouraged provide information expediently especially case electronic record requests individuals right access health-related information including health condition treatment plan notes images lab results billing information explicitly excluded private psychotherapy notes provider information gathered provider defend lawsuit providers charge reasonable amount relates cost providing copy however charge allowable providing data electronically certified ehr using view download transfer feature required certification delivered individual electronic form individual may authorize delivery using either encrypted un-encrypted email delivery using media usb drive cd etc. may involve charge direct messaging secure email technology common use healthcare industry possibly methods using un-encrypted email individual must understand accept risks privacy using technology information may intercepted examined others regardless delivery technology provider must continue fully secure phi system deny delivery method poses additional risk phi system individual may also request writing phi delivered designated third party family care provider individual may also request writing provider send phi designated service used collect manage records personal health record application example patient request writing ob-gyn provider digitally transmit records latest pre-natal visit pregnancy self-care app mobile phone according interpretations hipaa hospitals reveal information phone relatives admitted patients instances impeded location missing persons asiana airlines flight 214 san francisco crash hospitals reluctant disclose identities passengers treating making difficult asiana relatives locate one instance man washington state unable obtain information injured mother janlori goldman director advocacy group health privacy project said hospitals overcautious misapplying law times reports suburban hospital bethesda md. interpreted federal regulation requires hospitals allow patients opt included hospital directory meaning patients want kept directory unless specifically say otherwise result patient unconscious otherwise unable choose included directory relatives friends might able find goldman said hipaa intended make health care system united states efficient standardizing health care transactions hipaa added new part c titled administrative simplification title xi social security act supposed simplify healthcare transactions requiring health plans engage health care transactions standardized way hipaa/edi provision scheduled take effect october 16 2003 one-year extension certain small plans however due widespread confusion difficulty implementing rule cms granted one-year extension parties january 1 2012 newer versions asc x12 005010 ncpdp d.0 become effective replacing previous asc x12 004010 ncpdp 5.1 mandate asc x12 005010 version provides mechanism allowing use icd-10-cm well improvements july 1 2005 medical providers file electronically file electronic claims using hipaa standards order paid hipaa hipaa-covered health plans required use standardized hipaa electronic transactions see 42 usc § 1320d-2 45 cfr part 162 information found final rule hipaa electronic transaction standards 74 fed reg 3296 published federal register january 16 2009 cms website key edi x12 transactions used hipaa compliance edi health care claim transaction set 837 used submit health care claim billing information encounter information except retail pharmacy claims see edi retail pharmacy claim transaction sent providers health care services payers either directly via intermediary billers claims clearinghouses also used transmit health care claims billing payment information payers different payment responsibilities coordination benefits required payers regulatory agencies monitor rendering billing and/or payment health care services within specific health care/insurance industry segment example state mental health agency may mandate healthcare claims providers health plans trade professional medical health care claims electronically must use 837 health care claim professional standard send claims many different business applications health care claim slight derivations cover claims involving unique claims institutions professionals chiropractors dentists etc edi retail pharmacy claim transaction ncpdp telecommunications standard version 5.1 used submit retail pharmacy claims payers health care professionals dispense medications either directly via intermediary billers claims clearinghouses also used transmit claims retail pharmacy services billing payment information payers different payment responsibilities coordination benefits required payers regulatory agencies monitor rendering billing and/or payment retail pharmacy services within pharmacy health care/insurance industry segment edi health care claim payment/advice transaction set 835 used make payment send explanation benefits eob send explanation payments eop remittance advice make payment send eop remittance advice health insurer health care provider either directly via financial institution edi benefit enrollment maintenance set 834 used employers unions government agencies associations insurance agencies enroll members payer payer healthcare organization pays claims administers insurance benefit product examples payers include insurance company healthcare professional hmo preferred provider organization ppo government agency medicaid medicare etc organization may contracted one former groups edi payroll deducted another group premium payment insurance products 820 transaction set making premium payment insurance products used order financial institution make payment payee edi health care eligibility/benefit inquiry 270 used inquire health care benefits eligibility associated subscriber dependent edi health care eligibility/benefit response 271 used respond request inquiry health care benefits eligibility associated subscriber dependent edi health care claim status request 276 transaction set used provider recipient health care products services authorized agent request status health care claim edi health care claim status notification 277 transaction set used healthcare payer authorized agent notify provider recipient authorized agent regarding status health care claim encounter request additional information provider regarding health care claim encounter transaction set intended replace health care claim payment/advice transaction set 835 therefore used account payment posting notification summary service line detail level notification may solicited unsolicited edi health care service review information 278 transaction set used transmit health care service information subscriber patient demographic diagnosis treatment data purpose request review certification notification reporting outcome health care services review edi functional acknowledgement transaction set 997 transaction set used define control structures set acknowledgments indicate results syntactical analysis electronically encoded documents although specifically named hipaa legislation final rule necessary x12 transaction set processing encoded documents transaction sets grouped functional groups used defining transactions business data interchange standard cover semantic meaning information encoded transaction sets final rule security standards issued february 20 2003 took effect april 21 2003 compliance date april 21 2005 covered entities april 21 2006 small plans security rule complements privacy rule privacy rule pertains protected health information phi including paper electronic security rule deals specifically electronic protected health information ephi lays three types security safeguards required compliance administrative physical technical types rule identifies various security standards standard names required addressable implementation specifications required specifications must adopted administered dictated rule addressable specifications flexible individual covered entities evaluate situation determine best way implement addressable specifications privacy advocates argued flexibility may provide much latitude covered entities software tools developed assist covered entities risk analysis remediation tracking standards specifications follows hipaa covered entities providers completing electronic transactions healthcare clearinghouses large health plans must use national provider identifier npi identify covered healthcare providers standard transactions may 23 2007 small health plans must use npi may 23 2008 effective may 2006 may 2007 small health plans covered entities using electronic communications e.g. physicians hospitals health insurance companies forth must use single new npi npi replaces identifiers used health plans medicare medicaid government programs however npi replace provider dea number state license number tax identification number npi 10 digits may alphanumeric last digit checksum npi contain embedded intelligence words npi simply number additional meaning npi unique national never re-used except institutions provider usually one institution may obtain multiple npis different sub-parts free-standing cancer center rehab facility february 16 2006 hhs issued final rule regarding hipaa enforcement became effective march 16 2006 enforcement rule sets civil money penalties violating hipaa rules establishes procedures investigations hearings hipaa violations many years prosecutions violations march 2013 u.s. dept health human services hhs investigated 19,306 cases resolved requiring changes privacy practice corrective action noncompliance determined hhs entities must apply corrective measures complaints investigated many different types businesses national pharmacy chains major health care centers insurance groups hospital chains small providers 9,146 cases hhs investigation found hipaa followed correctly 44,118 cases hhs find eligible cause enforcement example violation started hipaa started cases withdrawn pursuer activity actually violate rules according hhs website following lists issues reported according frequency common entities required take corrective action voluntary compliance according hhs listed frequency title iii standardizes amount may saved per person pre-tax medical savings account beginning 1997 medical savings account msa available employees covered employer-sponsored high deductible plan small employer self-employed individuals title iv specifies conditions group health plans regarding coverage persons pre-existing conditions modifies continuation coverage requirements also clarifies continuation coverage requirements includes cobra clarification title v includes provisions related company-owned life insurance employers providing company-owned life insurance premiums prohibiting tax-deduction interest life insurance loans company endowments contracts related company also repeals financial institution rule interest allocation rules finally amends provisions law relating people give united states citizenship permanent residence expanding expatriation tax assessed deemed giving u.s. status tax reasons making ex-citizens names part public record creation quarterly publication individuals chosen expatriate enactment privacy security rules caused major changes way physicians medical centers operate complex legalities potentially stiff penalties associated hipaa well increase paperwork cost implementation causes concern among physicians medical centers august 2006 article journal annals internal medicine detailed concerns implementation effects hipaa hipaa restrictions researchers affected ability perform retrospective chart-based research well ability prospectively evaluate patients contacting follow-up study university michigan demonstrated implementation hipaa privacy rule resulted drop 96 34 proportion follow-up surveys completed study patients followed heart attack another study detailing effects hipaa recruitment study cancer prevention demonstrated hipaa-mandated changes led 73 decrease patient accrual tripling time spent recruiting patients tripling mean recruitment costs addition informed consent forms research studies required include extensive detail participant protected health information kept private information important addition lengthy legalistic section privacy may make already complex documents even less user-friendly patients asked read sign data suggest hipaa privacy rule currently implemented may negative impacts cost quality medical research dr. kim eagle professor internal medicine university michigan quoted annals article saying privacy important research also important improving care hope figure right complexity hipaa combined potentially stiff penalties violators lead physicians medical centers withhold information may right review implementation hipaa privacy rule u.s. government accountability office found health care providers uncertain legal privacy responsibilities often responded overly guarded approach disclosing information ... necessary ensure compliance privacy rule reports uncertainty continue period immediately prior enactment hipaa privacy security acts medical centers medical practices charged getting compliance early emphasis potentially severe penalties associated violation many practices centers turned private for-profit hipaa consultants intimately familiar details legislation offered services ensure physicians medical centers fully compliance addition costs developing revamping systems practices increase paperwork staff time necessary meet legal requirements hipaa may impact finances medical centers practices time insurance companies medicare reimbursement also declining education training healthcare providers paramount correct implementation hipaa privacy security acts effective training must describe statutory regulatory background purpose hipaa general summary principles key provisions privacy rule.although hipaa training course tailored towards roles employees attending course vital elements included although hipaa fits 1996 public law 104-191 health insurance portability accountability act references title ii privacy rule often stated health information privacy portability act hippa usa federal state county government sectors governmental agencies issued corrective followups regarding hippa hipaa according us department health human services office civil rights april 2003 january 2013 received 91,000 complaints hipaa violations 22,000 led enforcement actions varying kinds settlements fines 521 led referrals us department justice criminal actions examples significant breaches protected information hipaa violations include according koczkodaj et al. 2018 total number individuals affected since october 2009 173,398,820 differences civil criminal penalties summarized following table
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Computer security
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nokia e71 nokia e71 smartphone introduced may 2008 eseries range qwerty keyboard targeting business users worldwide runs symbian os v9.2 series 60 3rd edition second generation feature pack 1 nokia e71 succeeded nokia e61/61i models building base design form factor enhancing feature set nokia e71 well received highly popular often considered one nokia finest devices superseded nokia e72 2009 primary 3.15 mp 2048x1536 pixels autofocus led flash video qvga 15fps secondary videocall camera pre-installed several open source developers well paid third party developers created software various functions utilities car headsets power colors grey steel white red black e71 currently sold mainland china wi-fi 802.11b/g wlan networking back mounted camera 3g also excluded licenses 3g mainland china approved early 2009 reduction price phones lacking features firmware update bring back hardware missing e71 sold macau hong kong lack features software bundled chinese version slightly different also qq client along chinese specific programs e71 received highly positive critical reception widely praised battery life software features like push email slim design hardware including keyboard trusted reviews reviewer gave 5 stars 5 cnet uk wrote n't like camera think rest pretty close perfect techradar called terrific device well thought package listing lack 3.5 mm headphone jack disadvantage publications dubbed blackberry killer iphone killer
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Operating systems
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ole automation microsoft windows applications programming ole automation later renamed simply automation inter-process communication mechanism created microsoft based subset component object model com intended use scripting languages – originally visual basic – used several languages windows automation objects required implement idispatch interface provides infrastructure whereby applications called automation controllers access manipulate i.e set properties call methods shared automation objects exported applications supersedes dynamic data exchange dde older mechanism applications control one another dde ole automation automation controller client application exporting automation objects server contrary name automation objects necessarily use microsoft ole although automation objects used ole environments confusion roots microsoft earlier definition ole previously less synonym com ensure interoperability automation interfaces limited use subset com types specifically automation interfaces must use safearray instead raw com arrays automation-compatible com servers however rely in-built ole marshalling implementation avoids need additional proxy/stub projects marshalling out-of-process automation designed ease scripting mind controllers often provide languages visual basic applications end users allowing control automation objects via scripts automation objects often written conventional languages c++ c++ attributes used simplify development languages visual basic borland delphi also provides convenient syntax automation hides complexity underlying implementation order automate application developer automation controller must know object model employed target application exporting activation objects requires developer target application publicly document object model development automation controllers without knowledge target application object model difficult impossible complications automation components usually provided type libraries contain metadata classes interfaces features exposed object library interfaces described microsoft interface definition language type libraries viewed using various tools microsoft ole/com object viewer codice_1 part microsoft platform sdk object browser visual basic version 6 visual studio .net type libraries used generate proxy pattern/stub code interoperating com platforms microsoft .net java instance .net framework sdk includes tools generate proxy .net dll access automation objects using early binding information interfaces extracted type library late binding via idispatch mapped .net reflection api built-in .net-to-com bridge called com interop java lacks built-in com support toolsets like jacob jsegue generate proxy source code consisting two parts set java classes c++ source java native interface dll type libraries solutions work windows another java based j-interop library enables interoperability com components without jni using dcom wire protocol msrpc works non-windows platforms also microsoft publicly documented object model applications microsoft office software developers also documented object models applications object models presented automation controllers type libraries interfaces described odl automation available variety languages including limited
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Operating systems
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pdp-10 digital equipment corporation pdp-10 later marketed decsystem-10 mainframe computer family manufactured beginning 1966 discontinued 1983 1970s models beyond marketed decsystem-10 name especially tops-10 operating system became widely used pdp-10 architecture almost identical dec earlier pdp-6 sharing 36-bit word length slightly extending instruction set improved hardware implementation aspects instruction set unusual notably byte instructions operated bit fields size 1 36 bits inclusive according general definition byte contiguous sequence fixed number bits pdp-10 machine made time-sharing common features made common fixture many university computing facilities research labs 1970s notable harvard university aiken lab mit ai lab project mac stanford sail computer center corporation ccc eth zir carnegie mellon university main operating systems tops-10 tenex used build early arpanet reasons pdp-10 looms large early hacker folklore projects extend pdp-10 line eclipsed success unrelated vax superminicomputer cancellation pdp-10 line announced 1983 original pdp-10 processor ka10 introduced 1968 uses discrete transistors packaged dec flip-chip technology backplanes wire wrapped via semi-automated manufacturing process cycle time 1 μs add time 2.1 μs 1973 ka10 replaced ki10 uses transistor–transistor logic ttl ssi joined 1975 higher-performance kl10 later faster variants built emitter-coupled logic ecl microprogrammed cache memory kl10 performance 1 megaflops using 36-bit floating point numbers matrix row reduction slightly faster newer vax-11/750 although limited memory smaller less expensive model ks10 introduced 1978 using ttl am2901 bit-slice components including pdp-11 unibus connect peripherals ks marketed decsystem-2020 dec entry distributed processing arena introduced world lowest cost mainframe computer system ka10 maximum main memory capacity virtual physical 256 kilowords equivalent 1152 kilobytes supplied dec include paging hardware memory management consisted two sets protection relocation registers called base bounds registers allows half user address space limited set section main memory designated base physical address size allows model separate read-only shareable code segment normally high segment read-write data/stack segment normally low segment used tops-10 later adopted unix ka10 machines first mit later bolt beranek newman bbn modified add virtual memory support demand paging ka10 weighed 10/50 top-of-the-line uni-processor ka machine time pa1050 software package introduced two ka10 models uniprocessor 10/40 dual-processor 10/55 ki10 later processors offer paged memory management also support larger physical address space 4 megawords ki10 models include 1060 1070 1077 latter incorporating two cpus original kl10 pdp-10 also marketed decsystem-10 models 1080 1088 etc use original pdp-10 memory bus external memory modules module context meant cabinet dimensions roughly wxhxd 30 x 75 x 30 capacity 32 256 kwords magnetic core memory picture right hand side introduction shows six cabinets processors used decsystem-20 2040 2050 2060 2065 commonly incorrectly called kl20 use internal memory mounted cabinet cpu 10xx models also different packaging come original tall pdp-10 cabinets rather short ones used later decsystem-20 differences 10xx 20xx models cosmetic real 10xx systems 20-style internal memory i/o 20xx systems 10-style external memory i/o bus particular arpanet tops-20 systems i/o bus an20 imp interface i/o bus device could run either tops-10 tops-20 microcode thus corresponding operating system later model b version 2060 processors removed 256 kiloword limit virtual address space allowing use 32 sections 256 kilowords along substantial changes instruction set model model b kl10 processors thought different cpus first operating system took advantage model b capabilities tops-20 release 3 user mode extended addressing offered tops-20 release 4 tops-20 versions release 4.1 would run model b. tops-10 versions 7.02 7.03 also use extended addressing run 1090 1091 model b processor running tops-20 microcode final upgrade kl10 mca25 upgrade 2060 2065 1091 1095 gave performance increases programs run multiple sections ks10 design crippled model even though necessary data paths needed support model b architecture present doubt intended segment market greatly shortened ks10 product life frontend processors computers extend functionality systems connected kl class machines started without assistance pdp-11/40 frontend computer installed every system pdp-11 booted dual-ported rp06 disk drive alternatively 8 floppy disk drive dectape commands given pdp-11 start main processor typically booted rp06 disk drive pdp-11 pdp-11 performs watchdog functions main processor running networking remote job entry rje accomplished via pdp-11/34a frontend dec used terms dn60 d60spl ks system uses similar boot procedure 8080 cpu loads microcode rm03 rm80 rp06 disk magnetic tape starts main processor 8080 switches modes operating system boots controls console remote diagnostic serial ports i/o architecture 20xx series kl machines based dec bus design called massbus many attributed success pdp-11 dec decision make pdp-11 unibus open architecture dec reverted prior philosophy kl making massbus unique proprietary consequently aftermarket peripheral manufacturers made devices massbus dec chose price massbus devices notably rp06 disk drive substantial premium comparable ibm-compatible devices compuserve one designed alternative disk controller could operate massbus connect ibm style 3330 disk subsystems two models tape drives supported tm10 magnetic tape control subsystem mix eight could supported providing seven-track /or nine-track devices tu20 tu30 came 9 track b 7 track versions aforementioned tape drives could read/write from/to 200 bpi 556 bpi 800 bpi ibm-compatible tapes tm10 magtape controller available two submodels first pdp-6s model kl-10s user-mode instruction set architecture largely section covers architecture multi-section extended addressing covered decsystem-10/decsystem-20 processor reference manual pdp-10 36-bit words 18-bit word addresses supervisor mode instruction addresses correspond directly physical memory user mode addresses translated physical memory earlier models give user process high low memory addresses 0 top bit used one base register higher addresses used another segment contiguous later architectures paged memory access allowing non-contiguous address spaces cpu general-purpose registers also addressed memory locations 0-15 16 general-purpose 36-bit registers right half registers register 0 may used indexing instructions operate pairs registers pc word consists 13-bit condition register plus 5 always zero bits left half 18-bit program counter right half condition register records extra bits results arithmetic operations e.g overflow accessed instructions two operational modes supervisor user mode besides difference memory referencing described supervisor-mode programs execute input/output operations communication user-mode supervisor-mode done unimplemented user operations uuos instructions defined hardware trapped supervisor mechanism also used emulate operations may hardware implementations cheaper models major datatypes directly supported architecture two complement 36-bit integer arithmetic including bitwise operations 36-bit floating-point halfwords extended 72-bit floating point supported special instructions designed used multi-instruction sequences byte pointers supported special instructions word structured count half pointer half facilitates use bounded regions memory notably stacks instruction set symmetrical every instruction consists 9-bit opcode 4-bit register code 23-bit effective address field consists turn 1-bit indirect bit 4-bit register code 18-bit offset instruction execution begins calculating effective address adds contents given register non-zero offset indirect bit 1 fetches word calculated address repeats effective address calculation effective address zero indirect bit reached resulting effective address used instruction either fetch memory contents simply constant thus example movei a,3 c adds 3 18 lower bits register c puts result register without touching memory three main classes instruction arithmetic logical move conditional jump conditional skip may side effects also several smaller classes arithmetic logical move operations include variants operate immediate-to-register memory-to-register register-to-memory register-and-memory-to-both memory-to-memory since registers may addressed part memory register-to-register operations also defined variants useful though well-defined example add operation variants addi add 18-bit mmediate constant register addm add register contents emory location addb add b oth add register contents memory also put result register elaborate example hlrom h alf l eft r ight nes emory takes left half register contents places right half memory location replaces left half memory location ones halfword instructions also used linked lists hlrz lisp car operator hrrz cdr conditional jump operations examine register contents jump given location depending result comparison mnemonics instructions start jump jumpa meaning jump always jump meaning jump never – consequence symmetric design instruction set contains several no-ops jump example jumpn loc jumps address loc contents register non-zero also conditional jumps based processor condition register using jrst instruction ka10 ki10 jrst faster jumpa standard unconditional jump jrst conditional skip operations compare register memory contents skip next instruction often unconditional jump depending result comparison simple example camn loc compares contents register contents location loc skips next instruction equal elaborate example tlce loc read test left complement skip equal using contents loc mask selects corresponding bits left half register bits e qual zero skip next instruction case replace bits boolean complement smaller instruction classes include shift/rotate instructions procedure call instructions particularly notable stack instructions push pop corresponding stack call instructions pushj popj byte instructions use special format indirect word extract store arbitrary-sized bit fields possibly advancing pointer next unit original pdp-10 operating system simply called monitor later renamed tops-10 eventually pdp-10 system renamed decsystem-10 early versions monitor tops-10 formed basis stanford waits operating system compuserve time-sharing system time pdp-10 operators began running operating systems assembled major components developed outside dec. example main scheduler might come one university disk service another commercial timesharing services compuserve on-line systems ols rapidata maintained sophisticated inhouse systems programming groups could modify operating system needed businesses without dependent dec others also strong user communities decus users share software developed bbn developed alternative operating system tenex fairly quickly became de facto standard research community dec later ported tenex kl10 enhanced considerably named tops-20 forming decsystem-20 line mit developed ctss compatible time-sharing system run ibm 709 later modified ibm 7094 system also developed incompatible timesharing system run pdp-6 later modified pdp-10 naming related since ibm dec/pdp hardware different i.e incompatible despite 36-bit cpu name selected tom knight play ctss name tymshare developed tymcom-x derived tops-10 using page-based file system like tops-20 1971 1972 researchers xerox parc frustrated top company management refusal let buy pdp-10 xerox bought scientific data systems sds 1969 wanted parc use sds machine instead group led charles p. thacker designed constructed two pdp-10 clone systems named maxc pronounced max honour max palevsky sold sds xerox use maxc also backronym multiple access xerox computer maxc ran modified version tenex third-party attempts sell pdp-10 clones relatively unsuccessful see foonly systems concepts xkl one largest collections decsystem-10 architecture systems ever assembled compuserve peak operated 200 loosely coupled systems three data centers columbus ohio compuserve used systems 'hosts providing access commercial applications compuserve information service first systems bought dec dec abandoned pdp-10 architecture favor vax compuserve pdp-10 customers began buying plug compatible computers systems concepts january 2007 compuserve operating small number pdp-10 architecture machines perform billing routing functions main power supplies used kl-series machines inefficient compuserve engineers designed replacement supply used half energy compuserve offered license design kl supply dec free dec would promise new kl bought compuserve would efficient supply installed dec declined offer another modification made pdp-10 compuserve engineers replacing hundreds incandescent indicator lamps ki10 processor cabinet led lamp modules cost conversion easily offset cost savings electricity use reduced heat labor needed replace burned-out lamps digital followed step world picture right hand side shows light panel mf10 memory contemporary ki10 cpu item part computer museum populated leds 2008 demonstration purposes similar banks indicator lamps kl ks processors pdp-10 eventually eclipsed vax superminicomputer machines descendants pdp-11 dec recognized pdp-10 vax product lines competing decided concentrate software development effort profitable vax pdp-10 product line cancellation announced 1983 including cancelling ongoing jupiter project produce new high-end pdp-10 processor despite project good shape time cancellation minnow project produce desktop pdp-10 may prototyping stage event spelled doom technical cultures spawned original jargon file 1990s become something badge honor among old-time hackers cut one teeth pdp-10 pdp-10 assembly language instructions ldb dpb load/deposit byte live functions programming language common lisp see references section lisp article 36-bit word size pdp-6 pdp-10 influenced programming convenience 2 lisp pointers 18 bits one word crowther created adventure prototypical computer adventure game pdp-10 daglow created first computer baseball game 1971 dungeon 1975 first role-playing video game pdp-10 walter bright originally created empire pdp-10 roy trubshaw richard bartle created first mud pdp-10 zork written pdp-10 infocom used pdp-10s game development testing bill gates paul allen originally wrote altair basic using intel 8080 emulator running pdp-10 harvard university founded microsoft shortly software simulation historical computers simh contains module emulate ks10 cpu windows unix-based machine copies dec original distribution tapes available downloads internet running tops-10 tops-20 system may established also available simh ken harrenstien klh10 software unix-like systems emulates kl10b processor extended addressing 4 mw memory ks10 processor 512 kw memory kl10 emulation supports v.442 kl10 microcode enables run final versions tops-10 tops-20 ks10 emulation supports v.262 microcode final version ks10 dec v.130 microcode final versions ks tops-10 tops-20
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Computer architecture
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densify densify privately held software company based markham ontario canada company provides machine learning analytics services related public cloud utilization billing data deliver savings corporate cloud bill densify co-founded andrew hillier riyaz somani jayanti parmar 1999 2005 gerry smith – previously executive vice president governance solutions compuware corporation joined new ceo company formerly known cirba inc. changed name densify june 2017 delivered service densify patented optimization engine collects analyzes data cloud computing services environments combined advisory services cloud experts report cost explore usage patterns project future trends densify compatible amazon web services microsoft azure google cloud platform hybrid cloud environments densify also introduced complimentary ec2 assessment service help aws users identify risk reduction cost saving opportunities april 2017 idc recognized densify innovator multi-cloud management june 2017 ema research selected densify ema top 3 product stating densify delivers better application performance highest asset utilization lowest cloud spend without requiring special training september 2017 densify awarded best vmworld 2017 gold award recognized impressive find justin warren forbes january 2018 densify rated 9.5/10 zdnet.com recent product review 2018 densify acknowledged leader forrester wave™ report cloud cost monitoring optimization
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Distributed computing architecture
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apt package manager advanced package tool apt free-software user interface works core libraries handle installation removal software debian ubuntu related linux distributions apt simplifies process managing software unix-like computer systems automating retrieval configuration installation software packages either precompiled files compiling source code apt collection tools distributed package named apt significant part apt defined c++ library functions apt also includes command-line programs dealing packages use library three programs codice_1 codice_2 codice_3 commonly used examples apt simple ubiquitous apt package important priority current debian releases therefore included default debian installation apt considered front-end codice_4 friendlier older codice_5 front-end codice_4 performs actions individual packages apt manages relations especially dependencies well sourcing management higher-level versioning decisions release tracking version pinning apt often hailed one debian best features debian developers attribute strict quality controls debian policy major feature apt way calls codice_4 — topological sorting list packages installed removed calls codice_4 best possible sequence cases utilizes codice_9 options codice_4 however unable calculate avoid reason codice_4 requires action forced user indicates one packages installed package name phrased name portion package fully qualified filename instance debian system libc6 would argument provided codice_12 notably apt automatically gets installs packages upon indicated package depends necessary original distinguishing characteristic apt-based package management systems avoided installation failure due missing dependencies type dependency hell another distinction remote repository retrieval packages apt uses location configuration file codice_13 locate desired packages might available network removable storage medium example retrieve also obtain information available installed packages apt provides command options override decisions made apt-get conflict resolution system one option force particular version package downgrade package render dependent software inoperable user must careful finally codice_14 mechanism allows user create alternative installation policy individual packages user specify packages posix regular expression apt searches cached list packages lists dependencies must installed updated apt retrieves configures installs dependencies automatically triggers treatment deferred actions usage modes apt apt-get facilitate updating installed packages include codice_19 apt configuration folders files apt-config apt configuration query program codice_20 shows configuration apt relies concept repositories order find software resolve dependencies apt repository directory containing packages along index file specified networked cdrom location debian project keeps central repository 25,000 software packages ready download installation number additional repositories added apt sources.list configuration file codice_13 queried apt graphical front-ends often allow modifying codice_29 simply apt-setup package repository specified like system installation packages repository installed without specifying source kept up-to-date automatically addition network repositories compact discs storage media usb keydrive hard disks ... used well using apt-cdrom adding codice_33 source list file apt-cdrom specify different folder cd-rom using codice_34 option i.e hard disk usb keydrive debian cds available download contain debian repositories allows non-networked machines upgraded also one use apt-zip problems may appear several sources offer package systems possibly conflicting sources use apt pinning control sources preferred apt pinning feature allows administrators force apt choose particular versions packages may available different versions different repositories allows administrators ensure packages upgraded versions may conflict packages system sufficiently tested unwelcome changes order pins apt preferences file codice_35 must modified although graphical front-ends often make pinning simpler several front-ends apt exist provide advanced installation functions intuitive interfaces include apt front-ends apt front-ends list dependencies packages installed upgraded ask administrator packages recommended suggested newly installed packages installed automatically install dependencies perform operations system removing obsolete files packages original effort led apt-get program dselect replacement project known codename deity project commissioned brian white debian release manager time first functional version apt-get called dpkg-get intended test program core library functions would underpin new ui much original development apt done irc records lost 'deity creation team mailing list archives include major highlights deity name abandoned official name project due concerns religious nature name apt name eventually decided considerable internal public discussion ultimately name proposed irc accepted finalized mailing lists apt introduced 1998 original test builds circulated irc first debian version included debian 2.1 released 9 march 1999 end original goal deity project replacing dselect user interface ui failure work ui portion project abandoned ui directories removed cvs system first public release apt-get response apt dselect method command line utility great positive development efforts focused maintaining improving tool much later several independent people built uis top libapt-pkg eventually new team picked project began build new features released version 0.6 apt introduced secure apt feature using strong cryptographic signing authenticate package repositories apt originally designed front-end dpkg work debian codice_36 packages version apt modified also work rpm package manager system released apt-rpm fink project ported apt mac os x package management tasks apt also available opensolaris apt-file command packaged separately apt find package includes specific file list files included package remote repositories
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Operating systems
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integrated test facility integrated test facility itf creates fictitious entity database process test transactions simultaneously live input used incorporate test transactions normal production run system advantage periodic testing require separate test processes however careful planning necessary test data must isolated production data moreover itf validates correct operation transaction application ensure system operated correctly integrated test facility considered useful audit tool audit uses programs compare processing using independently calculated data involves setting dummy entities application system processing test production data entity means verifying processing accuracy
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Databases
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endgame inc endgame provides cyber operations platform supporting detection exploitation mitigation cyber-threats endgame started executives iss internet security systems endgame started 2008 chris rouland executives previously worked cia iss october 2010 saw investment 29 million usd raised bessemer ventures columbia capital kleiner perkins caufield byers kpcb techoperators company offers commercial web-based malware detection services defensive digital security intelligence big data analysis software february 2011 company announced partnerships hewlett-packard ibm use endgame ip reputation intelligence service within hp tippingpoint digital vaccine service ibm managed services offerings month emails sent hb gary endgame leaked revealed company sold zero-day vulnerabilities 2014 endgame moved away zero-day exploitations identifying protecting consumers potential cyber threats endgame offers services companies within financial services industry consumer technology companies software company collects information data sources accessed consumers identifying potential security threats december 2012 endgame announced appointment nathaniel fick chief executive officer replacing chris rouland former marine author bestseller one bullet away fick previously ceo center new american security independent nonpartisan national security defense policy research institution remains operating partner bessemer venture partners march 2013 endgame closed 23 million series b equity financing stated purpose fund growth existing federal customer base well expand commercial market round led new investor paladin capital group multi-stage private equity firm included participation existing investors bessemer venture partners columbia capital kleiner perkins caufield byers techoperators endgame initially became known providing cyber intelligence us agencies national security agency 2013 expanded financial commercial clients within private sector raising additional 30 million funding investment edgemore capital top tier capital partners savano capital partners endgame offers defensive analytics company network servers data exploits endgame acquired onyxware 2014 florida-based mobile security technology company provides applications detecting third-party network threats november 2014 endgame boasts approximately 100 employees endgame board directors led christopher darby president ceo in-q-tel independent strategic investment firm supporting missions intelligence community endgame announced march 2013 kenneth minihan former director national security agency managing director paladin also joined board directors april 2014 james n. miller former secretary defense policy appointed board advisers niloofar howe appointed chief strategy officer jamie butler serves chief scientist jon brody senior vice president marketing jim tosh vice president engineering
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Computer security
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meta-circular evaluator computing meta-circular evaluator mce meta-circular interpreter mci interpreter defines feature interpreted language using similar facility interpreter host language example interpreting lambda application may implemented using function application meta-circular evaluation prominent context lisp self-interpreter meta-circular interpreter interpreted language nearly identical host language two terms often used synonymously dissertation corrado böhm describes design self-hosting compiler self-interpreter meta-circular interpreter host language also language interpreted self-interpreter displays universal function language question helpful learning certain aspects language self-interpreter provide circular vacuous definition language constructs thus provides little insight interpreted language semantics example evaluation strategy addressing issues produces general notion definitional interpreter combination existing language implementation meta-circular interpreters provide baseline system extend language either upwards adding features downwards compiling away features rather interpreting also useful writing tools tightly integrated programming language sophisticated debuggers language designed meta-circular implementation mind often suited building languages general even ones completely different host language many languages one meta-circular implementations partial list languages meta-circular implementation designed bottom grouped chronological order languages meta-circular implementation via third parties
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Programming language topics
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macintosh lc macintosh lc personal computer designed manufactured sold apple computer inc. october 1990 march 1992 first macintosh lc family lc introduced macintosh classic repackaging older macintosh plus macintosh iisi new entry-level machine macintosh ii series offered half price macintosh ii significantly lesser performance overall creation lc prompted apple desire produce product could sold school boards price apple ii designed inexpensive manufacturing five major components robots could assemble computer 2400 list price new 600 12-inch color display 3500 less expensive macintosh ii long apple iie card introduced lc apple officially announced retirement ii company wanted focus sales marketing efforts lc original macintosh lc introduced october 1990 initial shipments dealers following december january replaced macintosh lc ii largely built around motorola 68030 processor lc uses pizza box case processor direct slot pds nubus slots 16 mhz 68020 microprocessor lacks floating-point coprocessor although one could added via pds lc 16-bit data bus major performance bottleneck 68020 32-bit cpu lc memory management chipset places limit 10 mb ram matter much installed lc shipped 256 kb vram supporting display resolution 512×384 pixels 8-bit color vram upgradeable 512 kb supporting display resolution 512×384 pixels 16-bit color 640×480 pixels 8-bit color lc commonly purchased apple 12 rgb monitor fixed resolution 512×384 pixels form factor exactly matching width lc chassis giving two together near all-in-one appearance apple 13 640×480 trinitron display also available list price 999 cost almost much lc introduction lc lowest resolution supported color macs 640×480 many programs written color macintosh ii family computers assumed minimum unusable lower resolution several years software developers add support smaller screen resolution order guarantee software would run lcs well color classics use resolution overall general performance machine disappointing due crippling data bus bottleneck making run far slower 16 mhz 68020-based macintosh ii 1987 identical processor ran almost twice fast one difference mac ii mac lc latter socket 68851 mmu therefore could take advantage system 7 virtual memory features standard configuration included floppy drive 40 mb 80 mb hard drive version available education market apple ii card pds slot two floppy drives hard drive lc final macintosh model allow dual internal floppy drives lc macs day featured built-in networking serial port using localtalk ethernet also available option via single pds slot single expansion slot limitation multifunction cards available combining ethernet functionality mmu fpu socket apple iie card pds slot offered bundle education models lcs card allowed lc emulate apple iie combination low-cost color macintosh apple iie compatibility intended encourage education market transition aging apple ii models macintosh platform instead new low-cost ibm pc compatibles despite lc minimal video specs 12 monitor lc supports card switched 560×384 resolution better compatibility iie 280×192 high-resolution graphics essentially doubled introduced october 15 1990
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Computer architecture
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xilleon xilleon brand family socs combining low-power cpu asics accelerated video decompression functions major worldwide broadcast networks including pal ntsc secam atsc targeting digital television i.e products like set-top boxes integrated digital television digital television adapters smart tvs etc. xilleon-branded socs revealed next generation avivo named unified video decoder uvd based xilleon video processor provide hardware decoding h.264 vc-1 video codec standards amd trueaudio amd unified video decoder uvd based cadence tensilica xtensa processor originally licensed ati technologies inc. 2004 owner brand xilleon ati technologies later advanced micro devices broadcom amd announced completion acquisition ati technologies third quarter 2006 xilleon products would sold amd brand amd xilleon august 25 2008 xilleon line sold semiconductor company broadcom new line xilleon video processors flat panel lcd tvs named xilleon panel processors four models 410 411 420 421 announced ces 2008 supporting 1080p video resolution featuring technology advanced motion estimation motion compensation frame rate conversion technology based enhanced phase-plane correlation technology converts 24 60 hz input video signals 100 120 hz refresh rates used lcd tvs creating additional frames form smoother motion amd signed agreement divx inc. allow several future xilleon video processors implement hardware divx video decoding divx certification january 2008 however result company restructuring amd divested digital tv chipset business starting second quarter 2008
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Computer architecture
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comparison ipv6 support operating systems comparison operating systems regard support ipv6 protocol
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Operating systems
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china economic databases china economic databases ced project china studies center national chengchi university taiwan collects publishes information china economic development support scholarly research ced available chinese english ced designed scholars students interested study development economy china anyone able add information platform submitting relevant material ced sponsored center china studies national chengchi university taiwan supported taiwan ministry education project launched december 2003 currently directed dr. chen-yuan tung professor graduate institute development studies national chengchi university currently ten databases 1 china economic literature index database china economic literature database celd currently collects data 47 chinese periodicals 22 english sources additionally online databases ssci econlit used keep database up-to-date information celd range topics including macroeconomics capital investment regional development economical reform trade taiwan mainland china chinese foreign trade renminbi exchange economical globalization financial policy financial reform search function also available ease data collecting currently celd approximately 3,000 papers july 2007 2 china economic experts database 3 china economic books database china economic books database cebd main purpose form comprehensive listing books topic china ’ economy cebd includes titles world including english chinese traditional simplified titles subjects books cebd include china economic globalization regional economy international trade rmb exchange rate domestic economic development financial market industry development commerce investment overall economic policy evaluation analysis every book cebd listed relevant search info author/editor ’ name publisher publication date isbn key word classification full listing cebd data sources found 4 china economic websites database china economic websites database collects relevant websites categorizes easy use according various aspects china economy 5 china economic government reports database china economic policy reports database ceprd platform holds economic policy reports chinese government white papers database currently lists reports since 2000 english chinese range content included national development plans agricultural policy monetary policy system reform policy financial market supervision policy commercial investment reports economical operation reports balance payment reports reports listed according policy name issuing unit date issued content summary source along full text linking download capabilities complete list sources please see following link 6 china economic analysis reports database china economic reports database cerd offers reports related indicators china ’ economy gdp cpi investment import export volumes reports published biweekly monthly annually therefore cerd constantly updated reports listed along title publishing institution content abstract 7 china economic conference database china economic conference database cecd offers information upcoming conferences related china ’ economy aims set platform scholars communicate issues china ’ economy also advertise promote conferences information includes theme conference date venue sponsor agenda conference link 8 china economic call papers database china economic call papers database related conference database providing up-to-date info upcoming current calls papers related forthcoming conferences dealing china economy 9 renminbi database renminbi rmb database focused relevant materials towards rmb research content includes rmb reports academic journals books research papers policy reports research meetings syllabus within sub-databases china economic databases platform 10 opencourseware ocw project gathers syllabi related course materials promote research learning field china economy february 2008 ocw site approaching 100 courses schools harvard yale johns hopkins peking university 1 china economic database e-paper english-language publications bi-weekly china economic databases e-paper available online e-paper gives updates recent journals books people republic china government white papers policy reports china economic analysis monthly published online reports recent macroeconomic developments e-paper china economic analysis monthly available traditional simplified chinese 2 china economic analysis monthly monthly publication provides indepth look china economy featuring graphs text various sectors china economy valuable tool scholars currently publication text chinese 3 china economic world ranking report china economic world ranking report gives clear overview china position world economy currently report available chinese however ranking tables listed english chinese
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Databases
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xybots xybots 1987 third-person shooter arcade game atari games xybots two players control major rock hardy captain ace gunn must travel 3d maze fight series robots known xybots whose mission destroy mankind game features split screen display showing gameplay bottom half screen information player status current level top half designed ed logg originally conceived sequel previous title gauntlet game well received reviewers lauding game various features particularly cooperative multiplayer aspect despite met limited financial success attributed unique control scheme involves rotating joystick turn player character xybots ported various personal computers atari lynx handheld versions nintendo entertainment system sega genesis/mega drive announced never released emulated versions arcade game later released part various compilations starting midway arcade treasures 2 2004 two players navigate corridors either rock hardy ace gunn battling enemy xybots laser gun seeking cover enemy fire behind various objects attempting reach level exit certain levels players face large boss xybot players move using joystick also rotates turn player character lower half screen shows gameplay area players upper half split map current level status display player display shows player remaining energy replenished collecting energy pods within levels energy also purchased shops levels using coins dropped defeated xybots player also purchase power-ups shops including extra armor increased speed strength firepower along maze enemy maps concept game born attempt designer ed logg engineer/technician doug snyder create first-person video game without specialized hardware 2005 logg recalled trouble controls game building controls worked game design getting players realize could rotate joystick turn in-game characters difficulties logg unsure game would enter mass production originally logg envisioned game second sequel gauntlet titled gauntlet iii catacombs however marketing department atari games want make another gauntlet game made change title logg co-programmer bob flannagan eventually settled theme based major havoc previous atari arcade game upon release game positively reviewed drew favorable comparisons berzerk gauntlet maze-like stages shooting gameplay game various features including cooperative gameplay praised computer video games games machine citing aspects made game addictive commodore user also cited two-player game highlight saying real appeal team game mate running place covering dividing destroying robots maze lending one another gold coins shop ed logg recalled 2005 game financial success gamestm wrote xybots overlooked arcades due complex controls tricky gameplay lack earnings arcades reason sequel ever developed retrospect wrote game ahead time offered unique experience similar games era unable match xybots ported various contemporary computers msx commodore 64 amstrad zx spectrum atari st commodore amiga received ports 1991 atari games subsidiary tengen released version game portable atari lynx version sega genesis/mega drive tengen announced 1990 winter consumer electronics show alongside ports atari games titles paperboy hard drivin latter two games released system xybots planned nintendo entertainment system port tengen also went unreleased acquired rights atari games arcade library parent company williams midway released arcade version xybots part 2004 console compilation midway arcade treasures 2 well midway arcade treasures deluxe edition microsoft windows.the arcade version also saw release psp part midway arcade treasures extended play dissolution midway 2009 warner bros. interactive entertainment picked rights midway arcade titles releasing xybots playstation 3 xbox 360 part midway arcade origins various platforms lego dimensions midway arcade level pack
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Computer architecture
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volume serial number volume serial number serial number assigned disk volume tape volume originated 1950s mainframe computer operating systems os/360 line human-configurable maximum length six characters uppercase must start letter identifies volume system unique manner example sysres often used system residence volume fat ntfs file systems volume serial number feature used determine disk present drive detect exchanged another one identification system created microsoft ibm development os/2 introduced ms-dos 4.01 1988 volume serial number 32-bit number determined date time real-time clock current computer time disk formatting previously method used discern whether disk swapped identified reading drive volume label much similar concept os/360 however even time volume label required unique optional therefore many users given disks meaningful name old method failed
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Computer file systems
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funtouch os funtouchos operating system created vivo fork google operating system android major difference android funtouch os latter includes features unavailable former features include customizable gestures communication drawer bottom top swipe security centre lock screen resize options long screen shot eye protection changing warmer color temperature others funtouch os respects looks similar ios made apple list funtouchos releases
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Operating systems
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ethernut ethernut open source hardware software project use embedded-ethernet-system currently four different reference designs exist ethernut 1 ethernut 2 ethernut 3 ethernut 5 available ready use boards reference designs share set interfaces designs mainly differ used microcontroller ethernut 1 2 8-bit avr ethernut 3 5 32-bit arm available memory size since ethernut 3 board mmc slot available ethernut 5 also includes usb host device interfaces rise idea internet things different groups people different aims started around 2000 developing embedded systems would able integrate existing tcp/ip networks limited resources mostly 8-bit embedded systems rarely reached exceeded 64 kb main memory imposed great challenge year 2000 british developer dave hudson released source code real-time operating system integrated tcp/ip stack named liquorice another challenge suitable hardware kind development nearly non-existing nearly network controllers time used pci-bus interface complex small microcontrollers one still-in-production controllers isa-bus interface also recommended new designs used together atmega103 microcontroller create single board computer layout board released bsd license one early open hardware projects one year hudson ceased work project source code liquorice used software foundation new ethernut project aimed integrate software hardware development first versions released avr freaks board project switched sourceforge 2002 open source operating system boards called nut/os modular real-time operating system licensed bsd license characteristics nut/os supported popular ssl/tls libraries wolfssl embedded security ethernut project implements network stack called nut/net implements substantial protocol socket api use nut/os programs supported protocols configuring nut/os nut/net quite simple download source packages nut/os configurator executed build needed libraries selected hardware configuration application programmers use nut/os nut/net libraries write software beside nut/os libraries application programmer use standard c libraries programming languages c used c++ mostly supported well additionally lua interpreter exists lua scripts executed interactively runtime board multitude simple sample applications exists easy introduction nut/os following architectures supported actively maintained research group distributed systems eth zurich developed distributed sensor network nodes based avr sensor nodes communicate via bluetooth system software open source btnut bluetooth stack used btnut stack based nut/os system extends nut/os functionality bluetooth access functions although btnut stack developed mainly btnode sensor nodes easily ported applications according german manufacturer egnite gmbh 33.000 ethernut boards sold state december 2013 several manufacturers compatible hardware achatz electronics netherlands proconx australia propox poland soc robotics canada hw group s.r.o czech republic thermotemp embedded-it germany beside nut/os operating system used base btnode sensor network eth zurich
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Operating systems
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h. d. moore h moore network security expert open source programmer hacker developer metasploit framework penetration testing software suite founder metasploit project served chief research officer boston based security firm rapid7 provider security data analytics software cloud solutions remained chief architect metasploit framework departure rapid7 2016 since leaving rapid7 moore joined atredis partners vice president research development founded critical research corporation software firm develops rumble network discovery referred industry famous white hat hacker moore developed security software utilities united states department defense teenager founded metasploit project summer 2003 goal becoming public resource exploit code research development known work warvox axman metasploit decloaking engine rogue network link detection tools. started month browser bugs mobb initiative 2006 experiment fast-paced vulnerability discovery full disclosure started month bugs project meme resulted number web browser patches improved security measures moore discovered involved discovery number critical security vulnerabilities metasploit framework development platform creating security tools exploits framework used network security professionals perform penetration testing system administrators verify patch installations product vendors perform regression testing security researchers worldwide framework written ruby programming language includes components written c assembly language october 2009 metasploit project acquired rapid7 metasploit framework continues free rapid7 added commercial edition called metasploit express acquisition project hd moore became chief security officer rapid7 remaining chief architect metasploit warvox software suite exploring classifying auditing telephone systems unlike normal wardialing tools warvox processes raw audio call use modem directly model allows warvox find classify wide range interesting lines including modems faxes voice mail boxes pbxs loops dial tones ivrs forwarders using signal processing techniques axman activex fuzzing engine goal axman discover vulnerabilities com objects exposed internet explorer since axman web-based security changes browser also affect results fuzzing process metasploit decloaking engine system identifying real ip address web user regardless proxy settings using combination client-side technologies custom services vulnerabilities exploited tool properly configured tor setup result identifying information exposed rogue network link detection tools designed detect unauthorized outbound network links large corporate networks tools send spoofed tcp syn icmp echo requests original destination ip encoded packet read back external listening host moore work gained praise antagonism industry companies microsoft credited discovering vulnerabilities yet criticism metasploit similar tools due capacity used criminal purposes instead offensive security criticism fallen upon moore moore warned us law enforcement involvement critical.io scanning project according moore though 're always chasing bad guys – good guys never ahead 're ones wrote exploits often found wild defenders generally following black hats
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Computer security
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x-agent x-agent xagent spyware malware program designed collect transmit hacked files machines running windows linux ios android servers operated hackers employs phishing attacks program designed hop device device 2016 crowdstrike identified android variant malware first time claimed malware targeted members ukrainian military distributing infected version app control d-30 howitzer artillery ukrainian army denied crowdstrike report stated losses howitzer artillery pieces nothing stated cause slovakian computer security company eset obtained x-agent source code 2015 described inner workings report released october 2016 washington dc grand jury indictment resulting robert mueller investigation russian election interference charges agents russian gru moscow developed customized monitored x-agent malware used hack dccc democratic congressional campaign committee dnc democratic national committee networks beginning around april 2016 item 15 end page 4 beginning page 5
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Operating systems
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debian system debian system 2005 non-fiction book written martin krafft deals exclusively debian gnu/linux detailing internal workings book mostly experienced users seeking in-depth technical knowledge rather beginners author native language german decided write debian de facto language english book written publication open source press later licensed co-publication starch press english version thus released two different isbns due popular demand book later translated german japanese french chinese translation works languages planned
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Operating systems
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cabal software haskell cabal common architecture building applications libraries aids packaging distribution software packages contained haskell platform cabal introduced simplify packaging haskell software modules added glasgow haskell compiler version 6.4 default package manager along ghc internal manager ghc-pkg actual binary cabal library cabal developed different packages throughout development gained additional features sandboxes allow escape so-called cabal hell see cabalizing process making library written haskell programming language conformant requirements cabal library infrastructure cabalizing may required library initially developed without taking requirements consideration developed prior introduction cabal haskell community cabal packages provide standard set metadata build process thus possible develop tools upload cabal packages cpan-like community repository software hackage even allow automated downloading compilation installation desired packages hackage since cabal uses global package repository default version conflicts dependencies lead cabal hell state certain packages get installed without re-installing already existing ones therefore breaking packages although version 1.18 introduced sandboxes improved dependency hell non-proper use sandboxes could still lead problems since packages hackage might build version boundaries dependencies loose result stable less bleeding edge variant hackage called stackage created fp complete
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Operating systems
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kiki kaikai set feudal japan player must assume role shinto shrine maiden named sayo-chan must use o-fuda scrolls ohari gohei wand defeat number renegade spirits monsters japanese mythology game noteworthy using traditional fantasy setting genre otherwise filled science fiction motifs game follows adventures sayo-chan young shinto shrine maiden living feudal japan one night sayo-chan fanning ceremonial fire visited seven lucky gods warn great impending danger suddenly band mischievous youkai appear kidnap gods quickly retreating faraway mountain range sayo-chan determined help gods sets journey across countryside confronts number strange creatures japanese mythology including obake yurei defeating several powerful youkai leaders sayo must battle leader ancient serpent orochi kiki kaikai overhead multi-directional shooter game requires player move four directions various levels attacking harmful enemies approach screen sayo-chan player attack either throwing special o-fuda scrolls eight separate directions swinging purification rod directly front techniques upgraded finding special paper slips left defeated enemies either enhance power improve range sayo damaged coming contact enemy hit knocked must resume level preset continuation point end level player must face powerful boss monster takes several attacks defeat difficult normal enemies several hidden items found attacking objects sayo purification rod used either enhance attack grant player points certain number points gained player gain another life additional chance complete level player lives exhausted number match screen appears random 3-digit number 50-base increments 100 150 200 250 last three digits player total score match number displayed granted free game game ends family computer disk system version kiki kaikai introduced gameplay changes original arcade version including new levels enemies well limiting number times player may use sayo-chan ranged o-fuda attack along second playable character miki-chan another shrine maiden designated player two character though several additional ports would made years one would rely basic game mechanics kiki kaikai originally created 1986 taito game designer hisaya yabusaki pulling inspiration tales japanese mythology well several top-down arcade shooters popular era game put conventional spin usually technologically driven science-fiction shoot 'em titles time utilizing action game elements player free move screen choose instead forced forward normal scrolling shooter fashion similar earlier released game commando style presentation kiki kaikai described taito lovely action game offering exotic asian atmosphere shortly game japanese debut bootleg version called knight boy released arcades various countries version though officially licensed taito exact duplicate original kiki kaikai altered title screen contained new gameplay elements features kiki kaikai ported numerous home consoles personal computer systems since original arcade release game first home version released msx2 february 10 1987 minor gameplay adjustments august 28 1987 version disk system released entitled kiki kaikai dotouhen added two-player support new playable character miki-chan pc engine version released three years later march 27 1990 largely based previous disk system instalment game made jump consoles june 12 2003 taito developed java-based version kiki kaikai mobile phones called kiki kaikai bizarre world port programmed mediakite appeared may 14 2004 windows-based pcs web-based game service launched taito japanese website later year courtesy ezweb kiki kaikai also made available along various classic taito titles number compilations would appear japanese-only taito memories vol 1 playstation 2 july 28 2005 taito pocket memories playstation portable 2006 game would officially released english first time part taito legends 2 playstation 2 pc xbox released north america may 2007 later taito legends power-up playstation portable kiki kaikai soundtrack composed hisayoshi ogura reflective traditional japanese folk music mostly utilizing woodwind string instruments like shamisen electronic beat music originally presented mono format composed entirely synth-based chiptunes standard audio development system older video game hardware exclusive game soundtrack never released commercially music game featured 1987 album taito game music catalog number 28xa-110 published alfa music single track medley song later presented individualized tracks 2002 re-release taito game music scdc-00156 time published sci-tron digital content kiki kaikai garnered harsh reviews long initial release gamespot considers games one taito sleepier titles overall less quality classic games like bubble bobble double dragon latter licensed technos u.s. game graphics though unique time produced preserve well allgame remarking get initial amusement game smiling ghosts comical skeletons 'll find graphics dull controls seen simplistic yet responsive though game levels found monotonous like ninja warriors kiki kaikai one-off work 1992 taito allowed natsume release kiki kaikai nazo kuro mantle would known pocky rocky north american release natsume would follow pocky rocky 2 years later would help altron release pocky rocky becky modern continuation kiki kaikai kiki kaikai 2 originally development playstation 2 console starfish entertainment set 2006 release canceled early development reemerge unlicensed spiritual successor title kiki kai world later became heavenly guardian published protagonist game design well ghost enemies would later become heavy influences characters reimu hakurei equivalent ghost enemies respectively touhou project games pc-98 sayo-chan kiki kaikai appeared one microgames
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Computer architecture
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av-test av-test independent organization evaluates rates antivirus security suite software microsoft windows android operating systems according variety criteria every month researchers publish results testing list products awarded certification organisation based magdeburg germany 2013 security specialist ceo security company kaspersky lab eugene kaspersky criticized av-test changing certification process
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Computer security
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commodore basic commodore basic also known pet basic dialect basic programming language used commodore international 8-bit home computer line stretching pet 1977 c128 1985 core based 6502 microsoft basic shares many characteristics 6502 basics time applesoft basic commodore licensed basic microsoft pay royalties basis jack tramiel turned bill gates offer 3 per unit fee stating 'm already married would pay 25,000 perpetual license commodore took source code flat-fee basic developed internally 8-bit home computers commodore 128 v7.0 microsoft copyright notice displayed however microsoft built easter egg version 2 upgrade commodore basic proved provenance typing obscure command codice_1 would result codice_2 appearing screen easter egg well-obfuscated—the message show disassembly interpreter popular commodore 64 came basic v2.0 rom despite computer released pet/cbm series version 4.0 64 intended home computer pet/cbm series targeted business educational use built-in programming language presumed heavily used saved manufacturing costs v2 fit smaller roms convenient feature commodore rom-resident basic interpreter kernal full-screen editor although commodore keyboards featured two cursor keys alternated direction shift key held screen editor allowed users enter direct commands input edit program lines anywhere screen line prefixed line number tokenized stored program memory lines beginning number executed pressing key whenever cursor happened line marked significant upgrade program entry interfaces compared common home computer basics time typically used line editors invoked separate codice_3 command copy cursor truncated line cursor position also capability saving named files device including cassette – popular storage device days pet one remained use throughout lifespan 8-bit commodores inexpensive form mass storage systems supported filenames diskette made saving multiple files devices difficult user one systems note recorder counter display location file inaccurate prone error pet basic 2.0 files cassettes could requested name device would search filename reading data sequentially ignoring non-matching filenames file system also supported powerful record structure could loaded saved files commodore cassette data recorded digitally rather less expensive less reliable analog methods used manufacturers therefore specialized datasette required rather standard tape recorder adapters available used analog digital converter allow use standard recorder cost little less datasette command may used optional parameter load program memory address contained first two bytes file bytes discarded retained memory parameter used program load start basic program area widely differs machines commodore basic variants supplied codice_4 codice_5 commands worked like counterparts applesoft basic loading saving bitmaps specified memory locations pet support relocatable programs command always load first two bytes contained program file created problem trying load basic programs saved commodore machines would load higher address pet basic expected program workarounds move programs proper location program saved cbm-ii machine way load pet modifying first two bytes disk sector editor cbm-ii series basic program area 0 would result pet attempting load zero page locking like original microsoft basic interpreter based commodore basic slower native machine code test results shown copying 16 kilobytes rom ram takes less second machine code compared minute basic execute faster interpreter programmers started using various techniques speed execution one store often-used floating point values variables rather using literal values interpreting variable name faster interpreting literal number since floating point default type commands faster use floating point numbers arguments rather integers speed important programmers converted sections basic programs 6502 6510 assembly language loaded separately file poked memory data statements end basic program executed basic using codice_6 command either direct mode program execution speed machine language great game waiting user input programmers could poll reading selected memory locations c6 64 d0 128 denoting size keyboard queue delay halt execution commodore basic keywords could abbreviated entering first unshifted keypress shifted keypress next letter set high bit causing interpreter stop reading parse statement according lookup table meant statement high bit set accepted substitute typing entire command however since basic keywords stored memory single byte tokens convenience statement entry rather optimization default uppercase-only character set shifted characters appear graphics symbol e.g command codice_7 could abbreviated codice_8 resembled codice_9 onscreen commands two letters long cases longer cases like ambiguity unshifted letters command needed codice_10 codice_11 required codice_12 commands abbreviated form either due brevity ambiguity commands example command codice_13 abbreviation spelling collided separate codice_14 keyword located nearer beginning keyword lookup table heavily used codice_15 command single codice_16 shortcut common microsoft basic dialects abbreviating commands shifted letters unique commodore basic abbreviating keywords possible fit code single line line lengths usually limited 2 4 screen lines depending specific machine allowed slight saving overhead store otherwise necessary extra program lines nothing basic commands tokenized took 1 byte two case several commands basic 7 basic 10 memory matter way entered long lines could difficult edit codice_17 command displayed entire command keyword extending program line beyond 2 4 screen lines could entered program memory unique feature commodore basic use control codes perform tasks clearing screen positioning cursor within program invoked either issuing command x corresponds control code issued example control code clear screen pressing key question quote marks thus pressing following quote mark cause basic display visual representation control code case reversed heart acted upon program execution directly printing control codes uses less memory executes faster invoking function comparison implementations basic typically dedicated commands clear screen move cursor basic 3.5 proper commands clearing screen moving cursor program lines commodore basic require spaces anywhere command always display one line number statement e.g. common write programs spacing feature added conserve memory since tokenizer never removes space inserted keywords presence spaces results extra codice_18 bytes tokenized program merely skipped execution spaces line number program statement removed tokenizer program lines 80 characters total machines machines 40 column text would cause line wrap around next line screen vic-20 22 column display program lines could occupy many four basic 7.0 commodore 128 increased limit program line 160 characters four 40-column lines two 80-column lines using abbreviations instead possible fit even line basic 7.0 displays error user enters program line 160 characters length earlier versions produced error simply display ready prompt two lines line length exceeded line number counted number characters program line five digit line number result four fewer characters allowed one digit number order execution commodore basic lines determined line numbering instead followed order lines linked memory program lines stored memory singly linked list line number pointer containing address beginning next program line tokenized code line program entered basic would constantly reorder program lines memory line numbers pointers ascending order however program entered manually altering line numbers pointers poke commands could allow out-of-order execution even give line line number early days basic used commercially software protection technique discourage casual modification program line numbers range 0 65520 take five bytes store regardless many digits line number although execution faster fewer digits putting multiple statements line use less memory execute faster variable names significant 2 characters thus variable names codice_19 codice_20 codice_21 refer variable commodore basic also supports bitwise operators although feature part core microsoft 6502 basic code usually omitted implementations applesoft basic native number format commodore basic like parent ms basic floating point contemporary basic implementations used one byte characteristic exponent three bytes mantissa accuracy floating point number using three-byte mantissa 6.5 decimal digits round-off error common 6502 implementations microsoft basic utilized 40-bit floating point arithmetic meaning variables took five bytes store four byte mantissa one byte exponent unlike 32-bit floating point found basic-80 8080/z80 implementations microsoft basic supported integer double precision variables 6502 implementations floating point although commodore basic supports signed integer variables denoted percent sign range -32768 32767 practice used array variables serve function conserving memory limiting array elements two bytes array 2000 elements occupy 10,000 bytes declared floating point array 4000 declared integer array denoting variable integer simply causes basic convert back floating point slowing program execution wasting memory percent sign takes one additional byte store since also applies integer arrays programmer avoid using unless large arrays used would exceed available memory stored floating point also possible memory locations 32767 address defined signed integer period used place number 0 thus instead instead execute slightly faster statement used start machine language programs added commodore original microsoft basic code featured usr function invoking machine language routines automatically loads cpu registers values c64 varies machines -- used pass data machine language routines means calling kernal functions basic example clears screen since commodore 8-bit machines c128 automatically boot disk software usual technique include basic stub like begin program execution possible automatically start software loading require user type statement done piece code hooks basic ready vector versions microsoft basic array declared statement automatically set ten elements practice 11 since array elements counted 0 larger arrays must declared basic display error program run array re-dimensioned program unless variables wiped via clr statement numeric arrays automatically filled zeros created may momentary delay program execution large array dimensioned string variables represented tagging variable name dollar sign thus variables codice_22 codice_23 codice_24 would understood distinct array variables also considered distinct simple variables thus refer variable size string array merely refers many strings stored array size element allocated dynamically unlike implementations microsoft basic commodore basic require string space reserved start program unlike 8-bit machines apple ii commodore machines built-in clock initialized 0 power updated every tick pia/via/ted/cia timer thus 60 times per second assigned two system variables basic contain current time ti read-only modified result syntax error message may used set time via six number string error results using string six numbers clock reliable method timekeeping since stops whenever interrupts turned done kernal routines accessing iec ieee port pet port slow clock update ticks function commodore basic use clock generate random numbers accomplished however relatively limited use numbers 0 255 returned otherwise works implementations microsoft basic pseudo-random sequence used via fixed 5-byte seed value stored power memory locations c64 location differs machines number higher 0 generate random number amalgamated value included function seed value updated 1 time rnd function executed negative number goes point sequence current seed value specified number since true random number generation impossible statement typical c64 c128 utilize sid chip white noise channel random numbers basic 2.0 notoriously suffered extremely slow garbage collection strings garbage collection automatically invoked time function executed many string variables arrays manipulated course program clearing take hour worst conditions also possible abort garbage collection basic scan run/stop key performing routine basic 4.0 introduced improved garbage collection system back pointers later implementations commodore basic also function basic 2.0 suffered another technical flaw handle signed numbers 32768 thus function invoked c64 38k basic memory negative amount free basic memory displayed adding 65535 reported number obtain correct amount free memory pet vic-20 never 32k total memory available basic limitation become apparent c64 developed function basic 3.5 7.0 corrected problem basic 7.0 also split two functions one display free basic program text memory display free variable memory many basic extensions released commodore 64 due relatively limited capabilities native basic 2.0 one popular extensions dos wedge included commodore 1541 test/demo disk 1 kb extension basic added number disk-related commands including ability read disk directory without destroying program memory features subsequently incorporated various third-party extensions popular epyx fastload cartridge basic extensions added additional keywords make easier code sprites sound high-resolution graphics like simons basic although basic 2.0 lack sound graphics features frustrating many users critics argued ultimately beneficial since forced user learn machine language limitations basic 2.0 c64 led use built-in rom machine language basic load file designated memory location filename drive device number would read call location would specified x registers load routine would called disk magazine c64 loadstar venue hobbyist programmers shared collections proto-commands basic called command modern programming point view earlier versions commodore basic presented host bad programming traps programmer issues derived microsoft basic virtually every home computer basic era suffered similar deficiencies every line microsoft basic program assigned line number programmer common practice increment numbers value 5 10 100 make inserting lines program editing debugging easier bad planning meant inserting large sections program often required restructuring entire code common technique start program low line number jump table body program structured sections starting designated line number like 1000 2000 large section needed added could assigned next available major line number inserted jump table later basic versions commodore platforms included command well auto line numbering command would automatically select insert line numbers according selected increment addition variables treated global variables clearly defined loops hard create often causing programmer rely command later rectified basic 3.5 addition commands flag variables often needed created perform certain tasks earlier basics commodore also lack debugging commands meaning bugs unused variables hard trap structures standard part z80 microsoft basics added basic 3.5 unavailable earlier versions commodore basic common home computers commodore machines booted directly basic interpreter basic file programming commands could entered direct mode load execute software program execution halted using run/stop key variable values would preserved ram could printed debugging 128 even dedicated second 64k bank variable storage allowing values persist codice_25 codice_26 command issued along advanced screen editor included commodore basic gave programming environment repl-like feel programmers could insert edit program lines screen location interactively building program contrast business-oriented operating systems time like cp/m ms-dos typically booted command line interface programming language required platforms loaded separately versions commodore basic included disk-specific codice_27 codice_28 commands version built commodore 64 lacked requiring user specify disk drive device number typically 8 9 standard codice_29 command otherwise defaulted tape another omission commodore 64s basic 2.0 codice_30 command display disk contents without clearing main memory 64 viewing files disk implemented loading program listed showed directory pseudo basic program file block size line number effect overwriting currently loaded program addons like dos wedge overcame rendering directory listing direct screen memory list cbm basic versions chronological order successively added features
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Programming language topics
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heroku heroku cloud platform service paas supporting several programming languages one first cloud platforms heroku development since june 2007 supported ruby programming language supports java node.js scala clojure python php go reason heroku said polyglot platform features developer build run scale applications similar manner across languages heroku acquired salesforce.com 2010 212 million heroku initially developed james lindenbaum adam wiggins orion henry supporting projects compatible ruby programming platform known rack prototype development took around six months later heroku faced drawbacks lack proper market customers many app developers used tools environment jan 2009 new platform launched built almost scratch three-month effort october 2009 byron sebastian joined heroku ceo december 8 2010 salesforce.com acquired heroku wholly owned subsidiary salesforce.com july 12 2011 yukihiro matz matsumoto chief designer ruby programming language joined company chief architect ruby month heroku added support node.js clojure september 15 2011 heroku facebook introduced heroku facebook present heroku supports redis databases addition standard postgresql name heroku portmanteau heroic haiku japanese theme nod matz creating ruby name pronounced similarly “ widening ” japanese though creators heroku want name project particular meaning japanese language chose invent name applications run heroku typically unique domain typically applicationname.herokuapp.com used route http requests correct dyno application containers dynos spread across dyno grid consists several servers heroku git server handles application repository pushes permitted users heroku services hosted amazon ec2 cloud-computing platform
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Distributed computing architecture
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gun.smoke gun.smoke 1985 vertical scrolling shooter arcade game capcom wild west-themed game designed yoshiki okamoto gun.smoke centers character named billy bob nes version bounty hunter vicious criminals wild west red dead revolver first installment red dead series spiritual successor gun.smoke gun.smoke similar 1942 commando also developed capcom differences game scrolling shooter screen scrolls upward automatically players three ways shoot using three buttons left right center shooting player also change way gunman shoots button combinations player dies getting shot struck enemies getting caught obstacle bottom screen player collect special items including horse protection three hits get killed obstacle boots speed movement bullets faster shots rifles longer shot range items found shooting barrels rifles boots bullets stock five items add score points include stars bottles bags dragonflies cows two items watch yashichi 1up cattle skull reduces billy power note two versions gun.smoke released license america romstar one fixed sequence bosses third sixth levels swapped roy followed wolf chief pig joe followed ninja version also removes boss rundown gun.smoke ported many systems game later ported nintendo entertainment system family computer disk system 1988 objective free town hicksville band criminals known wingates order capture dangerous henchmen stage player must retrieve wanted sign said henchman otherwise impossible clear stage nes version also different music game main character bounty hunter named billy bob even though nes version stayed true gameplay arcade version major changes done although virtually identical nes version fds version featured several differences soundtrack arcade version composed ayako mori august 25 1986 alfa records released limited edition soundtrack featuring music arcade version well two unused tracks catalog number capcom game music – 28xa-94
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Computer architecture
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spoonwep/wpa spoonwep/wpa gui uses aircrack-ng autonomously crack wep wpa keys tool included so-called network-scrounging cards chinese usb wi-fi adapters promise internet access free
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Computer security
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interoperation engineering interoperation setup ad hoc components methods make two systems work together combined system partial functionality certain time possibly requiring human supervision perform necessary adjustments corrections contrasts interoperability theoretically permits number systems compliant given standard work together long time smoothly unattended combined system full functionality standard another definition interoperation services effectively combining multiple resources domains ... requires interoperability interoperation usually performed systems combined designed standardization example legacy systems standard compliance expensive difficult immature interoperation may use following mechanisms components methods area data processing interoperation may also use following components methods
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Computer architecture
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pipeline unix unix-like computer operating systems pipeline mechanism inter-process communication using message passing pipeline set processes chained together standard streams output text process stdout passed directly input stdin next one first process completed second started executed concurrently concept pipelines championed douglas mcilroy unix ancestral home bell labs development unix shaping toolbox philosophy named analogy physical pipeline key feature pipelines hiding internals ritchie thompson 1974 turn allows clarity simplicity system article anonymous pipes data written one process buffered operating system read next process uni-directional channel disappears processes completed differs named pipes messages passed pipe named making file remains processes completed standard shell syntax anonymous pipes list multiple commands separated vertical bars pipes common unix verbiage example list files current directory retain lines output containing string view result scrolling page user types following command line terminal codice_1 produces process output stdout piped input stdin process grep key likewise process less process takes input previous process produces output next process via standard streams codice_2 tells shell connect standard output command left standard input command right inter-process communication mechanism called anonymous pipe implemented operating system pipes unidirectional data flows pipeline left right widely used unix shells special syntax construct creation pipelines usage one writes commands sequence separated ascii vertical bar character codice_2 reason often called pipe character shell starts processes arranges necessary connections standard streams including amount buffer storage default standard error streams stderr processes pipeline passed pipe instead merged directed console however many shells additional syntax changing behavior csh shell instance using codice_4 instead codice_2 signifies standard error stream also merged standard output fed next process bourne shell also merge standard error codice_4 since bash 4.0 using codice_7 well redirect different file commonly used simple pipelines shell connects series sub-processes via pipes executes external commands within sub-process thus shell direct processing data flowing pipeline however possible shell perform processing directly using so-called mill pipemill since codice_8 command used mill results initial command construct generally looks something like pipemill may perform intended body loop includes commands codice_9 codice_10 read codice_11 loop first iteration program let call drain read remaining output codice_12 loop terminate results depending specifics drain couple possible ways avoid behavior first drains support option disable reading codice_11 e.g codice_14 alternatively drain need read input codice_11 something useful given codice_16 input pipelines created program control unix codice_17 system call asks operating system construct new anonymous pipe object results two new opened file descriptors process read-only end pipe write-only end pipe ends appear normal anonymous file descriptors except ability seek avoid deadlock exploit parallelism unix process one new pipes generally call codice_18 create new processes process close end pipe using producing consuming data alternatively process might create new thread use pipe communicate named pipes may also created using codice_19 codice_20 presented input output file programs invoked allow multi-path pipes created especially effective combined standard error redirection codice_21 unix-like systems processes pipeline started time streams appropriately connected managed scheduler together processes running machine important aspect setting unix pipes apart pipe implementations concept buffering example sending program may produce 5000 bytes per second receiving program may able accept 100 bytes per second data lost instead output sending program held buffer receiving program ready read data next program pipeline reads buffer linux size buffer 65,536 bytes 64kib open source third-party filter called bfr available provide larger buffers required tools like netcat socat connect pipes tcp/ip sockets pipeline concept invented douglas mcilroy first described man pages version 3 unix mcilroy noticed much time command shells passed output file one program input another ideas implemented 1973 one feverish night wrote mcilroy ken thompson added codice_17 system call pipes shell several utilities version 3 unix next day mcilroy continued saw unforgettable orgy one-liners everybody joined excitement plumbing mcilroy also credits thompson codice_2 notation greatly simplified description pipe syntax version 4 idea eventually ported operating systems dos os/2 microsoft windows beos often notation although developed independently unix pipes related preceded 'communication files developed ken lochner 1960s dartmouth time sharing system tony hoare communicating sequential processes csp mcilroy pipes developed robot icon apple automator also uses pipeline concept chain repetitive commands together holds pipe homage original unix concept feature unix borrowed operating systems taos ms-dos eventually became pipes filters design pattern software engineering
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Operating systems
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null session null session anonymous connection inter-process communication network service windows-based computers service designed allow named pipe connections may used attackers remotely gather information system
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Computer security
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instruction pipelining computer science instruction pipelining technique implementing instruction-level parallelism within single processor pipelining attempts keep every part processor busy instruction dividing incoming instructions series sequential steps eponymous pipeline performed different processor units different parts instructions processed parallel allows faster cpu throughput would otherwise possible given clock rate may increase latency due added overhead pipelining process central processing units cpus driven clock clock pulse need thing rather logic cpu directs successive pulses different places perform useful sequence many reasons entire execution machine instruction happen pipelining effects happen time made dependent steps instruction example one clock pulse latches value register begins calculation take time value stable outputs register calculation complete another example reading instruction memory unit done time instruction writes result memory unit number dependent steps varies machine architecture example pipeline made deeper greater number dependent steps given step implemented simpler circuitry may let processor clock run faster pipelines may called superpipelines processor said fully pipelined fetch instruction every cycle thus instructions conditions require delays inhibit fetching new instructions processor fully pipelined seminal uses pipelining illiac ii project ibm stretch project though simple version used earlier z1 1939 z3 1941 pipelining began earnest late 1970s supercomputers vector processors array processors one early supercomputers cyber series built control data corporation main architect seymour cray later headed cray research cray developed xmp line supercomputers using pipelining multiply add/subtract functions later star technologies added parallelism several pipelined functions working parallel developed roger chen 1984 star technologies added pipelined divide circuit developed james bradley mid-1980s pipelining used many different companies around world pipelining limited supercomputers 1976 amdahl corporation 470 series general purpose mainframe 7-step pipeline patented branch prediction circuit today pipelining innovations implemented instruction unit microprocessors model sequential execution assumes instruction completes next one begins assumption true pipelined processor situation expected result problematic known hazard imagine following two register instructions hypothetical processor processor 5 steps listed initial illustration instruction 1 would fetched time execution would complete instruction 2 would fetched would complete first instruction might deposit incremented number r5 fifth step register write back second instruction might get number r5 copy r6 second step instruction decode register fetch time seems first instruction would incremented value code invokes hazard writing computer programs compiled language might raise concerns compiler could designed generate machine code avoids hazards early dsp risc processors documentation advises programmers avoid dependencies adjacent nearly adjacent instructions called delay slots declares second instruction uses old value rather desired value example processor might counter-intuitively copy unincremented value declares value uses undefined programmer may unrelated work processor meantime ensure correct results programmer may insert nops code partly negating advantages pipelining pipelined processors commonly use three techniques work expected programmer assumes instruction completes next one begins branch normal instruction sequence often involves hazard unless processor give effect branch single time cycle pipeline continue fetching instructions sequentially instructions allowed take effect programmer diverted control another part program conditional branch even problematic processor may may branch depending calculation yet occurred various processors may stall may attempt branch prediction may able begin execute two different program sequences eager execution assuming branch taken discarding work pertains incorrect guess processor implementation branch prediction usually makes correct predictions minimize performance penalty branching however branches predicted poorly may create work processor flushing pipeline incorrect code path begun execution resuming execution correct location programs written pipelined processor deliberately avoid branching minimize possible loss speed example programmer handle usual case sequential execution branch detecting unusual cases using programs gcov analyze code coverage lets programmer measure often particular branches actually executed gain insight optimize code right generic pipeline four stages fetch decode execute write-back top gray box list instructions waiting executed bottom gray box list instructions execution completed middle white box pipeline execution follows pipelined processor may deal hazards stalling creating bubble pipeline resulting one cycles nothing useful happens illustration right cycle 3 processor decode purple instruction perhaps processor determines decoding depends results produced execution green instruction green instruction proceed execute stage write-back stage scheduled purple instruction stalled one cycle fetch stage blue instruction due fetched cycle 3 stalled one cycle red instruction bubble blue ovals illustration processor decode circuitry idle cycle 3 execute circuitry idle cycle 4 write-back circuitry idle cycle 5 bubble moves pipeline cycle 6 normal execution resumes everything one cycle late take 8 cycles cycle 1 8 rather 7 completely execute four instructions shown colors
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Computer architecture
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pl/i pl/i programming language one pronounced procedural imperative computer programming language developed published ibm designed scientific engineering business system programming used academic commercial industrial organizations since introduced 1960s still used pl/i main domains data processing numerical computation scientific computing system programming supports recursion structured programming linked data structure handling fixed-point floating-point complex character string handling bit string handling language syntax english-like suited describing complex data formats wide set functions available verify manipulate 1950s early 1960s business scientific users programmed different computer hardware using different programming languages business users moving autocoders via comtran cobol scientific users programmed general interpretive programme gip fortran algol george others ibm system/360 announced 1964 delivered 1966 designed common machine architecture groups users superseding existing ibm architectures similarly ibm wanted single programming language users hoped fortran could extended include features needed commercial programmers october 1963 committee formed composed originally three ibmers new york three members share ibm scientific users group propose extensions fortran given constraints fortran unable embarked design new programming language based loosely algol labeled npl acronym conflicted uk national physical laboratory replaced briefly mppl multipurpose programming language 1965 pl/i roman numeral first definition appeared april 1964 ibm took npl starting point completed design level first compiler could written npl definition incomplete scope detail control pl/i language vested initially new york programming center later ibm uk laboratory hursley share guide user groups involved extending language role ibm process controlling language pl/i projects experience defining large language showed need formal definition pl/i project set 1967 ibm laboratory vienna make unambiguous complete specification led turn one first large scale formal methods development vdm fred brooks credited ensuring pl/i character data type language first specified detail manual pl/i language specifications c28-6571 written new york 1965 superseded pl/i language specifications gy33-6003 written hursley 1967 ibm continued develop pl/i late sixties early seventies publishing gy33-6003 manual manuals used multics group early implementers first compiler delivered 1966 standard pl/i approved 1976 goals pl/i evolved early development language competitiveness cobol record handling report writing required language scope usefulness grew include system programming event-driven programming additional goals pl/i achieve goals pl/i borrowed ideas contemporary languages adding substantial new capabilities casting distinctive concise readable syntax many principles capabilities combined give language character important meeting language goals language designed things programmers summary extracted ansi pl/i standard ansi pl/i general-purpose subset standard pl/i program consists set procedures written sequence statements codice_5 construct used include text sources program translation statement types summarized groupings give overview language standard uses organization names may declared represent data following types either single values aggregates form arrays lower-bound upper-bound per dimension structures comprising nested structure array scalar variables codice_6 type comprises attributes base scale precision scale factor codice_7 type encoded within codice_8 mode specified separately codice_9 applied real imaginary parts values computed expressions written using specific set operations builtin functions may applied aggregates well single values together user-defined procedures likewise may operate return aggregate well single values assignment statement assigns values one variables reserved words pl/i statement terminated semi-colon maximum length statement implementation defined comment may appear anywhere program space permitted preceded characters forward slash asterisk terminated characters asterisk forward slash i.e statements may label-prefix introducing entry name codice_10 codice_11 statements label name condition prefix enabling disabling computational condition e.g codice_12 entry label names may single identifiers identifiers followed subscript list constants codice_13 sequence statements becomes group preceded codice_4 statement followed codice_15 statement groups may include nested groups begin blocks codice_16 statement specifies group single statement codice_17 part codice_18 part see sample program group unit iteration begin block codice_19 may contain declarations names internal procedures local block procedure starts codice_11 statement terminated syntactically codice_15 statement body procedure sequence blocks groups statements contains declarations names procedures local procedure codice_22 procedure on-unit single statement block statements written executed one conditions occur computational condition input/output condition one conditions declaration identifier may contain one following attributes need mutually consistent current compilers kednos micro focus particularly ibm implement many extensions standardized version language ibm extensions summarised implementation sub-section compiler later although extensions common compilers lack current standard means compatibility guaranteed language standardization began april 1966 europe ecma tc10 1969 ansi established composite language development committee nicknamed kludge later renamed x3j1 pl/i standardization became joint effort ecma tc/10 ansi x3j1 subset gy33-6003 document offered joint effort ibm became base document standardization major features omitted base document multitasking attributes program optimization e.g codice_27 codice_28 proposals change base document voted upon committees event committees disagreed chairs initially michael marcotty general motors c.a.r hoare representing icl resolve disagreement addition ibm honeywell cdc data general digital equipment prime computer burroughs rca univac served x3j1 along major users eastman kodak mitre union carbide bell laboratories various government university representatives development language occurred standards bodies continuing improvements structured programming internal consistency omission obscure contentious features language development neared end x3j1/tc10 realized number problems document written english text discussion single item might appear multiple places might might agree difficult determine omissions well inconsistencies consequently david beech ibm robert freiburghouse honeywell milton barber cdc m. donald maclaren argonne national laboratory craig franklin data general lois frampton digital equipment editor d.j andrews ibm undertook rewrite entire document producing one complete chapters standard couched formal definition using pl/i machine specify semantics first possibly programming language standard written semi-formal definition pl/i general-purpose subset subset-g standard issued ansi 1981 revision published 1987 general purpose subset widely adopted kernel pl/i implementations pl/i first implemented ibm hursley laboratories united kingdom part development system/360 first production pl/i compiler pl/i f compiler os/360 operating system built john nash team hursley uk runtime library team managed i.m nobby clarke pl/i f compiler written entirely system/360 assembly language release 1 shipped 1966 os/360 real-memory environment compiler designed systems little 64 kilobytes real storage – f 64 kb s/360 parlance fit large compiler 44 kilobytes memory available 64-kilobyte machine compiler consists control phase large number compiler phases approaching 100 phases brought memory disk one time handle particular language features aspects compilation phase makes single pass partially-compiled program usually held memory aspects language still designed pl/i f implemented omitted later releases pl/i record i/o shipped pl/i f release 2 list processing functions based variables pointers areas offsets locate-mode i/o first shipped release 4 major attempt speed pl/i code compete fortran object code pl/i f release 5 substantial program optimization do-loops facilitated reorder option procedures version pl/i f released tss/360 timesharing operating system system/360 model 67 adapted ibm mohansic lab ibm la gaude lab france developed language conversion programs convert fortran cobol algol programs pl/i f level pl/i pl/i compiler using 16 kilobytes memory developed ibm germany dos/360 low end operating system implements subset pl/i language requiring strings arrays fixed extents thus simplifying run-time environment reflecting underlying operating system lacks dynamic storage allocation controlled storage class shipped within year pl/i f. compilers implemented several groups early 1960s multics project mit one first develop operating system high-level language used early pl/i epl subset dialect pl/i implementation language 1964 epl developed bell labs mit douglas mcilroy robert morris others influential multics pl/i compiler source compiler technology used number manufacturers software groups honeywell pl/i compiler series 60 implementation full ansi x3j1 standard pl/i optimizer checkout compilers produced hursley support common level pl/i language aimed replace pl/i f compiler checkout compiler rewrite pl/i f bsl ibm pl/i-like proprietary implementation language later pl/s performance objectives set compilers shown ibm presentation bcs compilers produce identical results checkout compiler used debug programs would submitted optimizer given compilers entirely different designs handling full pl/i language goal challenging achieved pl/i optimizing compiler took pl/i f compiler ibm workhorse compiler 1970s 1990s like pl/i f multiple pass compiler 44 kilobyte design point entirely new design unlike f compiler perform compile time evaluation constant expressions using run-time library reducing maximum memory compiler phase 28 kilobytes second-time around design succeeded eliminating annoyances pl/i f cascading diagnostics written s/360 macro assembler team led tony burbridge worked pl/i f. macros defined automate common compiler services shield compiler writers task managing real-mode storage allowing compiler moved easily memory models gamut program optimization techniques developed contemporary ibm fortran h compiler deployed optimizer equaled fortran execution speeds hands good programmers announced ibm s/370 1970 shipped first dos/360 operating system august 1971 shortly afterward os/360 first virtual memory ibm operating systems os/vs1 mvs vm/cms developers unaware shoehorning code 28 kb sections ibm poughkeepsie finally ready ship virtual memory support os/360 supported batch programming environments tso cms could run interactively compiler went many versions covering mainframe operating systems including operating systems japanese plug-compatible machines pcms compiler superseded ibm pl/i os/2 aix linux z/os pl/i checkout compiler colloquially checker announced august 1970 designed speed improve debugging pl/i programs team led brian marks three-pass design cut time compile program 25 taken f compiler run interactive terminal converting pl/i programs internal format h-text format interpreted checkout compiler run-time detecting virtually types errors pointers represented 16 bytes containing target address description referenced item thus permitting bad pointer use diagnosed conversational environment error detected control passed user inspect variables introduce debugging statements edit source program time debugging capability mainframe programming environments developed functions offered compiler withdrawn 1990s perhaps commercially successful implementation aside ibm digital equipment 1988 release ansi pl/i 1987 subset implementation strict superset ansi x3.4-1981 pl/i general purpose subset provides features new ansi x3.74-1987 pl/i general purpose subset front end designed robert freiburghouse code generator implemented dave cutler managed design implementation vax/vms runs vms vax alpha tru64 uniprise systems inc. responsible compiler late 1960s early 1970s many us canadian universities establishing time-sharing services campus needed conversational compiler/interpreters use teaching science mathematics engineering computer science dartmouth developing basic pl/i popular choice concise easy teach ibm offerings unsuitable number schools built subsets pl/i interactive support examples compiler developed cornell university teaching dialect called pl/c unusual capability never failing compile program use extensive automatic correction many syntax errors converting remaining syntax errors output statements language almost pl/i implemented ibm pl/c fast compiler plago created polytechnic institute brooklyn used simplified subset pl/i language focused good diagnostic error messages fast compilation times computer systems research group university toronto produced sp/k compilers supported sequence subsets pl/i called sp/1 sp/2 sp/3 ... sp/8 teaching programming programs ran without errors sp/k compilers produced results contemporary pl/i compilers ibm pl/i f compiler ibm checkout compiler cornell university pl/c compiler examples pl0 p. grouse university new south wales plum marvin zelkowitz university maryland. pluto university toronto major revamp pl/i ibm santa teresa california launched entirely new compiler 1992 initial shipment os/2 included ansi-g features many new pl/i features subsequent releases covered additional platforms mvs vm os/390 aix windows -although support windows since withdrawn continued add functions make pl/i fully competitive languages offered pc particularly c c++ areas overtaken corresponding ibm language environment supports inter-operation pl/i programs database transaction systems programs written c c++ cobol compiler supports data types needed intercommunication languages pl/i design principles retained withstood major extension comprising several new data types new statements statement options new exception conditions new organisations program source resulting language compatible super-set pl/i standard earlier ibm compilers major topics added pl/i latest series pl/i compilers z/os called enterprise pl/i z/os leverage code generation latest z/architecture processors z14 z13 zec12 zbc12 z196 z114 via use archlvl parm control passed compilation second high level language supported z/os language environment xl c/c++ first enterprise cobol v5 last codice_30 new computational data type ordinal facilities like pascal e.g codice_39 addition name internal values accessible via built-in functions built-in functions provide access ordinal value predecessor successor codice_40 see allows additional codice_33s declared composed pl/i built-in attributes codice_42 locator data type similar codice_43 data type strongly typed bind particular data structure codice_44 operator used select data structure using handle codice_34 attribute equivalent codice_46 early pl/i specifications permits several scalar variables arrays structures share storage unit occupies amount storage needed largest alternative attributes added new string-handling functions added centre text edit using picture format trim blanks selected characters head tail text codice_63 codice_64 right codice_65 codice_66 functions compound assignment operators la c e.g codice_67 codice_68 codice_69 codice_70 added codice_71 equivalent codice_72 additional parameter descriptors attributes added omitted arguments variable length argument lists codice_73 attribute declares identifier constant derived specific literal value restricted expression parameters codice_74 pass address codice_37 pass value attributes codice_76 codice_77 attributes prevent unintended assignments codice_78 obviates need contrived construct codice_79 codice_40 introduces user-specified names e.g codice_81 combinations built-in attributes e.g codice_82 thus codice_83 creates codice_33 name codice_81 alias set built-in attributes fixed binary 31.0 codice_31 applies structures members provides codice_33 name set structure attributes corresponding substructure member declarations use structure declaration generalisation codice_88 attribute codice_89 statement exit loop codice_90 continue next iteration loop codice_56 codice_57 options iterative groups package construct consisting set procedures declarations use unit variables declared outside procedures local package use codice_93 codice_94 codice_95 storage procedure names used package also local made external means codice_96 option codice_97 codice_98 executed on-unit terminates execution on-unit raises condition procedure called current one thus passing control corresponding on-unit procedure codice_99 condition handles invalid operation codes detected pc processor well illegal arithmetic operations subtraction two infinite values codice_100 condition provided intercept conditions specific on-unit provided current procedure codice_101 condition raised codice_102 statement unable obtain sufficient storage number vendors produced compilers compete ibm pl/i f optimizing compiler mainframes minicomputers 1970s 1980s target usually emerging ansi-g subset pl/i implementations developed mainframes late 1960s mini computers 1970s personal computers 1980s 1990s although main use mainframes pl/i versions dos microsoft windows os/2 aix openvms unix widely used business data processing system use writing operating systems certain platforms complex powerful systems built pl/i sas system initially written pl/i sas data step still modeled pl/i syntax pioneering online airline reservation system sabre originally written ibm 7090 assembler s/360 version largely written using sabretalk purpose built subset pl/i compiler dedicated control program pl/i used write executable formal definition interpret ibm system network architecture pl/i fulfill supporters hopes would displace fortran cobol become major player mainframes remained minority significant player definitive explanation trends 1970s 1980s militated success progressively reducing territory pl/i enjoyed competitive advantage first nature mainframe software environment changed application subsystems database transaction processing cics ims oracle system 370 application generators became focus mainframe users application development significant parts language became irrelevant need use corresponding native features subsystems tasking much input/output fortran used application areas confining pl/i cobol territory users stayed cobol pc became dominant environment program development fortran cobol pl/i became minority languages overtaken c++ java like second pl/i overtaken system programming field ibm system programming community ready use pl/i instead ibm developed adopted proprietary dialect pl/i system programming – pl/s success pl/s inside ibm c outside ibm unique pl/i strengths system programming became less valuable third development environments grew capabilities interactive software development made unique pl/i interactive debugging strengths less valuable fourth cobol fortran added features structured programming character string operations object orientation reduced pl/i relative advantages mainframes substantial business issues stake ibm hardware competitors little gain much lose success pl/i compiler development expensive ibm compiler groups in-built competitive advantage many ibm users wished avoid locked proprietary solutions early support pl/i vendors best avoid pl/i article uses pl/i standard reference point language features number features significance early implementations standard offered non-ibm compilers de facto language continued grow standard ultimately driven developments personal computer multi tasking implemented pl/i f optimizer newer aix z/os compilers comprised data types codice_104 codice_105 codice_106 codice_107 fork codice_108 join codice_109 codice_110s record i/o statements codice_111 statement unlock locked records codice_112 files event data identify particular event indicate whether complete 1 b incomplete 0 b task data items identify particular task process indicate priority relative tasks first ibm compile time preprocessor built ibm boston advanced programming center located cambridge mass shipped pl/i f compiler codice_5 statement standard rest features dec kednos pl/i compilers implemented much set features ibm additions ibm continued add preprocessor features compilers preprocessor treats written source program sequence tokens copying output source file acting token encountered following compile time statement executed identifier token encountered identifier codice_114d codice_115d assigned compile time value identifier replaced value tokens added output stream require action e.g codice_116 values activated compile time expressions thus compile time variable codice_117 could declared activated assigned using codice_118 subsequent occurrences codice_117 would replaced codice_120 data type supported codice_121 integers codice_122 strings varying length maximum length structure statements simple statements also may label-list feature allowed programmers use identifiers constants e.g product part numbers mathematical constants superseded standard named constants computational data conditional compiling iterative generation source code possible compile-time facilities supported standard several manufacturers implemented facilities structured programming additions made pl/i standardization accepted standard features codice_133 exit iterative codice_4 codice_135 codice_136 added codice_4 case statement general form codice_138 br features included dec pl/i pl/i f offered debug facilities put forward standard implemented others notably check variable-list condition prefix codice_139 on-condition codice_140 option ibm optimizing checkout compilers added additional features appropriate conversational mainframe programming environment e.g codice_141 condition several attempts made design structure member type could one several datatypes codice_46 early ibm growth classes programming theory approaches became possible pl/i base codice_34 codice_33 etc added several compilers pl/i conceived single-byte character world support japanese chinese language becoming essential developments international code pages character string concept expanded accommodate wide non-ascii/ebcdic strings time date handling overhauled deal millennium problem introduction datetime function returned date time one 35 different formats several date functions deal conversions days seconds though language easy learn use implementing pl/i compiler difficult time-consuming language large pl/i needed subsets vendors could produce users master resolved ansi g published compile time facilities unique pl/i took added implementation effort additional compiler passes pl/i compiler two four times large comparable fortran cobol compilers also much slower—supposedly offset gains programmer productivity anticipated ibm first compilers written argue pl/i unusually hard parse pl/i keywords reserved programmers use variable procedure names programs original pl/i f compiler attempts auto-correction encounters keyword used incorrect context often assumes variable name leads cascading diagnostics problem solved later compilers effort needed produce good object code perhaps underestimated initial design language program optimization needed compete excellent program optimization carried available fortran compilers unusually complex owing side effects pervasive problems aliasing variables unpredictable modification occur asynchronously exception handlers may provided statements unseen callers together make difficult reliably predict program variables might modified runtime typical use however user-written error handlers codice_145 often make assignments variables spite aforementioned difficulties ibm produced pl/i optimising compiler 1971 pl/i contains many rarely-used features multitasking support ibm extension language add cost complexity compiler co-processing facilities require multi-programming environment support non-blocking multiple threads processes operating system compiler writers free select whether implement features undeclared variable default declared first occurrence—thus misspelling might lead unpredictable results implicit declaration different fortran programs pl/i f however attribute listing enables programmer detect misspelled undeclared variable many programmers slow move cobol fortran due perceived complexity language immaturity pl/i f compiler programmers sharply divided scientific programmers used fortran business programmers used cobol significant tension even dislike groups pl/i syntax borrowed cobol fortran syntax instead noticing features would make job easier fortran programmers time noticed cobol syntax opinion business language cobol programmers noticed fortran syntax looked upon scientific language cobol fortran programmers viewed bigger version language somewhat intimidated language disinclined adopt another factor pseudo -similarities cobol fortran algol pl/i elements looked similar one languages worked differently pl/i frustrations left many experienced programmers jaundiced view pl/i often active dislike language early unix fortune file contained following tongue-in-cheek description language speaking someone delved intricacies pl/i sure real men could written machine-hogging cycle-grabbing all-encompassing monster allocate array free middle third sure multiply character string times bit string assign result float decimal go ahead free controlled variable procedure parameter reallocate passing back overlay three different types variable memory location anything say write recursive macro well real men use rescan could language obviously designed written real men intended real man use positive side full support pointers data types including pointers structures recursion multitasking string handling extensive built-in functions pl/i indeed quite leap forward compared programming languages time however enough persuade majority programmers shops switch pl/i pl/i f compiler compile time preprocessor unusual outside lisp world using target language syntax semantics e.g compared c preprocessor directives pl/i provides several 'storage classes indicate lifetime variables storage managed codice_146 codice_94 simplest implement codice_93 indicates memory allocated initialized load-time done cobol working-storage early fortran default codice_22 variables pl/i default storage class codice_150 variables codice_151 similar block-structured languages influenced algol like auto storage class c language default storage allocation pascal local-storage ibm cobol storage codice_151 variables allocated upon entry codice_153 procedure on-unit declared compiler runtime system allocate memory stack frame contain housekeeping information variable declared codice_154 code set initial value executed time care required manage use initialization properly large amounts code executed initialize variables every time scope entered especially variable array structure storage codice_151 variables freed block exit codice_156 codice_94 variables used retain variables contents invocations procedure block codice_95 storage also managed using stack pushing popping allocations stack managed programmer using codice_102 codice_160 statements storage codice_94 variables managed using codice_162 instead stack allocations independent lifetimes addressed codice_163 codice_43 variables codice_23 attribute used declare programmer-defined heaps data allocated freed within specific area area deleted read written unit several ways accessing allocated storage different data declarations well defined safe used safely careful programming inherently unsafe and/or machine dependent passing variable argument parameter reference allows argument allocated storage referenced using parameter codice_166 attribute e.g codice_167 allows part variable storage used different consistent declaration language definition includes codice_46 attribute later renamed codice_34 allow different definitions data share storage supported many early ibm compilers usages safe machine independent record i/o list processing produce situations programmer needs fit declaration storage next record item knowing type data structure based variables pointers key programs data structures must designed appropriately typically using fields data structure encode information type size fields held preceding structure constraints current one encoding preceding structure program needs allocate based variable declaration matches current item using expressions extents needed type size information kept current structure self defining structures type-defining fields must ahead type dependent items place every version data structure codice_103-option used self-defining extents e.g string lengths codice_171 codice_172 used allocate instances data structure self-defining structures typing codice_173 fields placed ahead real data records data set items list data structures organised way handled safely machine independent way pl/i implementations except pl/i checkout compiler keep track data structure used storage first allocated codice_94 declaration used pointer storage access storage inherently unsafe machine dependent however usage become important pointer arithmetic typically adding certain amount known address contentious subject computer science addition problem wild references buffer overruns issues arise due alignment length data types used particular machines compilers many cases pointer arithmetic might needed involve finding pointer element inside larger data structure codice_175 function computes pointers safely machine independently pointer arithmetic may accomplished aliasing binary variable pointer codice_176 relies pointers length codice_177 integers aligned boundaries prevalence c free easy attitude pointer arithmetic recent ibm pl/i compilers allow pointers used addition subtraction operators giving simplest syntax compiler options disallow practices safety machine independence paramount pl/i designed programs ran batch mode possible intervention programmer terminal exceptional condition division zero would abort program yielding hexadecimal core dump pl/i exception handling via on-units allowed program stay control face hardware operating system exceptions recover debugging information closing gracefully program became properly debugged exception handling could removed disabled level control became less important conversational execution became commonplace computational exception handling enabled disabled condition prefixes statements blocks including on-units procedures – e.g codice_178 operating system exceptions input/output storage management always enabled on-unit single statement codice_179-block introduced codice_180 executing statement enables condition specified e.g. codice_181 exception condition occurs condition enabled on-unit condition executed on-units inherited call chain block procedure on-unit activated on-units established invoking activation inherited new activation may over-ridden another codice_180 reestablished codice_183 exception simulated using codice_184 – e.g help debug exception handlers dynamic inheritance principle on-units allows routine handle exceptions occurring within subroutines uses on-unit effect condition raised standard system action taken often raise codice_25 condition system action reestablished using codice_186 option codice_180 conditions possible complete executing on-unit return point interrupt e.g. codice_188 conditions resume normal execution conditions codice_189 codice_25 condition raised attempted on-unit may terminated codice_191 preventing return point interrupt permitting program continue execution elsewhere determined programmer on-unit needs designed deal exceptions occur on-unit codice_192 statement allows nested error trap error occurs within on-unit control might pass operating system system dump might produced computational conditions continue execution mentioned pl/i codice_193 i/o statements relatively simple syntax offer options many situations end-of-file record transmission errors occur record read written instead complexities handled on-units various file conditions approach adopted codice_23 sub-allocation codice_23 condition existence exception handling on-units effect optimization variables inspected altered on-units values variables might otherwise kept registers statements may need returned storage statements discussed section implementation issues
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Programming language topics
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focal programming language focal interpreted programming language resembling joss name acronym formulating on-line calculations algebraic language largely creation richard merrill focal initially written largest impact pdp-8 computers made digital equipment corporation dec merrill wrote original 1968 classic focal-69 interpreters pdp-8 dec described focal joss-like language like early versions basic focal complete programming environment requiring operating system mumps commands could practice abbreviated single letter alphabet creative choices words used make command uniquely defined leading character digital made available several european-language versions command words translated target language focal ran low-end pdp-8 systems even systems 4k words 6k bytes memory lacking mass storage focal interpreter written assembly language typically used 3k 12-bit words leaving somewhat limiting 1k words hold user program variables system upgraded adding one extra 4k banks memory focal could use extra memory either single user split extra memory across several time-sharing users focal made extensive use interrupt-driven terminal i/o could keep four teleprinters busy without pause memory space precious storing textual error messages focal used clever workaround error messages instead displayed start address error-managing routine floating-point number example focal-69 implementation division zero error managed code starting memory address octal 4333 division zero program line numbered codice_1 produced error message codice_2 codice_3 represents memory page 28 plus offset 73 words focal sites error number error message list posted near terminals comparisons focal basic inevitable since languages common minicomputers era focal lacked inherent support strings data elements could assigned variables generally thought serious deficiency compared string capabilities basics deficiency serious utterly crippling might sound surprising amount string usage focal programs devoted formatting user output since focal output character-stream-oriented outputting two strings sequentially could sometimes substitute concatenating procedural tools could written performing complex formatted output limited amount string input could done program could ask simple yes/no questions really kludge example one typed hello input statement focal would convert h 8 interpret e starting exponent would try compute 8 llo power would take several seconds cpu time result value 0.76593020e+103 particularly helpful response generally agreed focal efficient use resources comparable basic systems typical machine day often 6 24 kilobytes magnetic-core memory focal could handle larger complex programming tasks basic focal pdp-8 implementation used floating point representation represented numbers four 12-bit words thirty-six bits mantissa twelve bits exponent allowed significantly higher precision significantly wider range values low-end programming systems made reasonable choice serious numerical work high precision good choices default decimal output formatting meant difficulties binary-to-decimal rounding evident beginning users coca-cola corporation used customized version focal called coke focal later implemented pdp-7 pdp-9 pdp-10 pdp-11 pdp-12 pdp-5 linc-8 focal manual showed add commands focal parser many sites added specialized commands operating custom hardware digital equipment computer users society collected many patches enhancements focal even major enhanced offshoots focal focal-w added many features including better mass storage file i/o even virtual variable memory russia saw use late early 1990s mass-produced home computers electronika bk series focal15 v6b program takes year birth calculates year a.f focal born program lines focal program grouped line groups line numbers within group first line program line 01.10 line 10 group 01 line numbers targets goto statements ask statement prompts attached teleprinter input type statement outputs text teleprinter multiple items output teleprinter appending item comma exclamation mark causes linefeed carriage return sent set statement assigns value variable value result expression conditional statement receive three line numbers parameters arithmetic program branches first linenumber result expression parentheses less zero second result zero third result zero go command focal begins run program focal prompts single asterisk beginning line expecting input
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Programming language topics
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berkeley r-commands berkeley r-commands suite computer programs designed enable users one unix system log issue commands another unix computer via tcp/ip computer network r-commands developed 1982 computer systems research group university california berkeley based early implementation tcp/ip protocol stack internet csrg incorporated r-commands unix operating system berkeley software distribution bsd r-commands premiered bsd v4.1 among programs suite remote copy remote execution remote login remote shell remote r-commands significant innovation became de facto standards unix operating systems wider public adoption internet inherent security vulnerabilities became problem beginning development secure shell protocols applications 1995 adoption entirely supplanted deployment use r-commands telnet networked systems original berkeley package provides rlogin also features rcp remote-copy allowing files copied network rsh remote-shell allowing commands run remote machine without user logging share hosts.equiv .rhosts access-control scheme although connect different daemon rshd enables user log another server via computer network using tcp network port 513. rlogin also name application layer protocol used software part tcp/ip protocol suite authenticated users act physically present computer rfc 1282 defined states rlogin facility provides remote-echoed locally flow-controlled virtual terminal proper flushing output rlogin communicates daemon rlogind remote host rlogin similar telnet command customizable able connect unix-like hosts rsh opens shell remote computer without login procedure connected user execute commands remote computer shell command-line interface rsh passes input output standard streams sends standard output user console network standard input standard flow tcp port 514 standard error flows different tcp port rsh daemon rshd opens like rsh rexec enables user run shell commands remote computer however unlike rsh server rexec server rexecd requires login authenticates users reading username password unencrypted network socket rexec uses tcp port 512. rcp copy file directory local system remote system remote system local system one remote system another command line arguments cp rcp similar rcp remote files prefixed name remote system unix copy command cp rcp overwrites existing file name target unlike cp provides mechanism warning user overwriting target file like rsh rcp uses tcp port 514 command lists users logged local unix system rwho lists users logged multi-user unix systems local network rwho daemon rwhod maintains database status unix systems local network daemon database also used ruptime program command shows long unix system running since last restart requests status report computers local network returns uptime report computer respond within time limit ruptime reports system information tracked stored daemon rwhod also used rwho command r-commands involve user authentication rcp rexec rlogin rsh share several serious security vulnerabilities due problems r-commands fell relative disuse many unix linux distributions longer including default many networks formerly relied rlogin telnet replaced ssh rlogin-equivalent slogin
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Internet protocols
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miller columns miller columns also known cascading lists browsing/visualization technique applied tree structures columns allow multiple levels hierarchy open provide visual representation current location closely related techniques used earlier smalltalk browser independently invented mark s. miller 1980 yale university technique used project xanadu datapoint next datapoint miller generalized technique browse directed graphs labeled nodes arcs cases technique appropriate structures high degree large fanout low-degree structures outline editors graph viewers effective miller columns well known today “ columns view ” mode mac os x finder well browser view itunes columns finder descend directly nextstep file viewer use miller columns going back 1986 gnustep project continues offer miller column browser closely follows next approach bringing advantages column browser linux bsd operating systems large tree structures ipod browsing categories audio file tag attributes reminiscent column browsing although one column visible time many software music players implement tag browsing feature utilizes miller columns miller columns several issues usability standpoint
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Operating systems
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mips-3d mips-3d extension mips v instruction set architecture isa added 13 new instructions improving performance 3d graphics applications instructions improved performance reducing number instructions required implement four common 3d graphics operations vertex transformation clipping transformation lighting vertex transformation clipping perspective division normalization
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Computer architecture
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job file table job file table jft dos data structure program segment prefix psp starts psp offset 0x18 20 bytes long open file handle dos stores index system file table sft file handle returned codice_1 codice_2 similar functions simply index jft dos stored sft entry index file device program opened program starts first 5 entries jft preconnected standard devices handles marked closed setting value entry 0xff standard devices initialised follows handles 0-2 connected console device program execution get modified closed redirected like handle size jft psp limited 20 bytes originally 15 files 20-5 standard devices could open time ms-dos 2.0 extended job file table introduced allowed 254 files opened ms-dos 3.30 size jft modified call codice_3
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Operating systems
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leon leon meaning lion 32-bit cpu microprocessor core based sparc-v8 risc architecture instruction set designed sun microsystems originally designed european space research technology centre estec part european space agency esa gaisler research described synthesizable vhdl leon dual license model lgpl/gpl floss license used without licensing fee proprietary license purchased integration proprietary product core configurable vhdl generics used system-on-a-chip soc designs research commercial settings leon project started european space agency esa late 1997 study develop high-performance processor used european space projects objectives project provide open portable non-proprietary processor design capable meet future requirements performance software compatibility low system cost another objective able manufacture single event upset seu tolerant sensitive semiconductor process maintain correct operation presence seus extensive error detection error handling functions needed goals detect tolerate one error register without software intervention suppress effects single event transient set errors combinational logic leon family includes first leon1 vhsic hardware description language vhdl design used leonexpress test chip developed 0.25 μm technology prove fault-tolerance concept second leon2 vhdl design used processor device at697 atmel f various system-on-chip devices two leon implementations developed esa gaisler research part cobham aeroflex gaisler developed third leon3 design announced availability fourth generation leon leon4 processor leon processor implemented programmable logic fpga manufactured asic section subsequent subsections focus leon processors soft ip cores summarise main features processor version infrastructure processor packaged referred leon distribution processors leon series based sparc-v8 risc architecture leon2 -ft five-stage pipeline later versions seven-stage pipeline leon2 leon2-ft distributed system-on-chip design modified using graphical configuration tool leon2 -ft design extended re-used designs structure emphasise re-using parts design building blocks enable designers easily incorporate new ip cores design standard leon2 -ft distribution includes following support cores leon3 leon3ft leon4 cores typically used together grlib ip library leon2 distributions contain one design used several target technologies grlib contains several template designs fpga development boards asic targets modified using graphical configuration tool similar one leon2 distribution leon/grlib package contains larger number cores compared leon2 distributions also include plug play extension on-chip amba bus ip cores available grlib include design flow documentation leon fpga available manufacturer third party resources term leon2/leon2-ft often refer leon2 system-on-chip design leon2 processor core together standard set peripherals available leon2 -ft distribution later processors leon series used wide range designs therefore tightly coupled standard set peripherals leon3 leon4 name typically refers processor core leon/grlib used refer complete system-on-chip design leon2 following characteristics leon2-ft processor single event upset fault tolerant ft version leon2 processor flip-flops protected triple modular redundancy internal external memories protected edac parity bits special licence restrictions apply ip distributed european space agency among satellites processor used esa intermediate experimental vehicle ixv 2015 china chang e 4 lunar lander leon3 synthesisable vhdl model 32-bit processor compliant sparc v8 architecture model highly configurable particularly suitable system-on-a-chip soc designs full source code available gnu gpl license allowing use purpose without licensing fee leon3 also available proprietary license allowing used proprietary applications several differences two leon2 processor models leon3 leon3 includes smp support seven-stage pipeline leon2 support smp five-stage pipeline leon3ft fault-tolerant version standard leon3 sparc v8 processor designed operation harsh space environment includes functionality detect correct single event upset seu errors on-chip ram memories leon3ft processor supports functionality standard leon3 processor adds following features following features standard leon3 processor supported leon3ft leon3ft core distributed together special ft version grlip ip library netlist distribution possible fpga implementation called leon3ft-rtax proposed critical space applications january 2010 fourth version leon processor released release following new features real-time operating systems support leon core currently rtlinux pikeos ecos rtems nucleus threadx opencomrtos vxworks per port gaisler research lynxos also per port gaisler research pok free arinc653 implementation released bsd licence ork+ open-source real-time kernel high-integrity real-time applications ravenscar profile
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Computer architecture
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conversational monitor system conversational monitor system cms – originally cambridge monitor system simple interactive single-user operating system cms originally developed part ibm cp/cms operating system went production use 1967 cms part ibm vm family runs ibm mainframe computers vm first announced 1972 still use today z/vm cms runs guest operating system private virtual machine created vm control program control program plus cms together create multi-user time-sharing operating system cms originally developed part ibm cp/cms operating system time acronym meant cambridge monitor system also console monitor system 1972 ibm released vm/370 operating system re-implementation cp/cms system/370 announcement also added virtual memory hardware system/370 series unlike cp/cms vm/370 supported ibm vm went series versions still use today z/vm distinct versions releases cms platform remained still quite recognizable close descendant original cms version running cp-40 many key user interface decisions familiar today users already made 1965 part cp-40 effort see cms cp-40 examples vm cp/cms checkered histories ibm vm one ibm strategic operating systems primarily os dos families suffered ibm political infighting time-sharing versus batch processing goals conflict cp/cms originally released unsupported system vm often limited development support resources within ibm exceptionally strong user community first established self-support days cp/cms remaining active launch vm made substantial contributions operating system mitigated difficulties running ibm operating system cms intrinsic part vm/cms architecture established cp/cms cms user control private virtual machine – simulated copy underlying physical computer – cms runs stand-alone operating system approach remained consistent years based details cms interacts virtual machine environment found vm cp/cms articles cms originally built stand-alone operating system capable running bare machine though course nobody would choose however cms longer run outside vm environment provides hypervisor interface needed various critical functions cms provides users environment running applications batch jobs managing data files creating debugging applications cross-platform development communicating systems users cms still development wide use today users log vm providing userid password boot virtual machine done issuing command ipl cms ipl initial program load traditional ibm jargon booting machine though normally done automatically user personal customization done standard shell script file named profile exec sets user-specified environmental defaults disks libraries accessed cms started era teletype-style paper terminals later glass teletype dumb terminals late 1970s however vm users connecting via full-screen terminals – particularly ibm 3270 ubiquitous transaction processing terminal ibm mainframes 3270 played strategic role ibm product line making selection natural choice large data centers day many manufacturers eventually offered bisync terminals emulated 3270 protocol 3270s local buffer storage processing capabilities generally dealt entire screen data time handled editing tasks locally transmitted set fields entire page enter key program function key pfk pressed 3270 family incorporated smart control units concentrators network processing elements communicating mainframe dedicated circuits relatively high speeds via bisync synchronous data transmission protocol mainframe-oriented communication technologies provided capabilities taken granted modern communication networks device addressing routing error correction support variety configurations multipoint multidrop topologies historical note 3270 approach differed lower-cost dumb terminals period point-to-point asynchronous commercial time-sharing users important segment early cp/cms vm sites relied devices could connect via 300- 1200 bit/s modems normal voice-grade telephone circuits installing dedicated circuit 3270 often practical economical timely 3270 block-oriented approach consistent ibm batch- punched card-oriented view computing particularly important ibm mainframes day unlike contemporary minicomputers ibm mainframes equipped character-at-a-time interrupts dumb terminal support relied terminal control units ibm 270x see ibm 3705 memorex 1270 asynchronous terminal controllers assembled line characters fixed maximum length return key pressed typing many characters would result error familiar situation users day data centers include equipment except needed dial-up access 3270 approach preferred block-oriented terminals like 3270 made practical implement screen-oriented editors mainframes – opposed line-oriented editors previous norm important advantage contemporary minicomputers character-oriented systems availability via 3270 warmly welcomed gulf developed 3270 world focused page-oriented mainframe transaction processing especially via cics asynch terminal world focused character-oriented minicomputers dial-up timesharing asynchronous terminal vendors gradually improved products range smart terminal features usually accessed via escape sequences however devices rarely competed 3270 users ibm maintained dominance mainframe data center hardware purchase decisions viewed retrospect major philosophical divergence block-oriented character-oriented computing asynchronous terminal controllers 3270s provided mainframe block-oriented interactions – essentially made terminal input look like card reader approach preferred ibm led development entirely different user interface paradigms programming strategies character-oriented systems evolved differently difference apparent comparing atomic transaction approach dominant cics interactive stream-oriented style unix vm/cms evolved somewhere extremes cms command-driven stateful interactive environment rather adopting cics approach stateless transaction-oriented interface yet cms responds page- line-at-a-time interaction instead character interrupts cms earned good reputation efficient good human factors ease use relative standards time course prior widespread use graphical user interface environments commonly used today uncommon hundreds later thousands concurrent cms interactive users vm mainframe sub-second response times common 'trivial functions vm/cms consistently outperformed mvs ibm operating systems terms support simultaneous interactive users many cms users programmed languages cobol fortran pl/i c/370 apl scripting language rexx vm/cms often used development platform production systems ran ibm operating systems mvs cms users worked commercial software packages focus nomad spss sas one time cms also major environment e-mail office productivity important product ibm profs later renamed officevision two commonly used cms tools editor xedit rexx programming language products ported platforms widely used outside mainframe environment see vm operating system vm-related sources source citations
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Operating systems
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apple pascal apple pascal implementation pascal apple ii apple iii computer series based ucsd pascal like ucsd pascal implementations ran operating system apple pascal operating system derivative ucsd p-system graphical extensions originally released apple ii august 1979 apple dos 3.2 apple pascal pioneered number features would later incorporated dos 3.3 well others would seen introduction prodos apple pascal software package also included disk maintenance utilities assembler meant complement apple built-in monitor assembler fortran compiler written silicon valley software sunnyvale california compiling p-code pascal also available apple pascal operating system introduced new disk format instead dividing disk 256-byte sectors dos 3.2 apple pascal divides blocks 512 bytes each.. p-system also introduced different method saving retrieving files apple dos files saved available sector os could find regardless location time could lead file system fragmentation slowing access disk apple pascal attempted rectify saving consecutive blocks disk innovations introduced file system included introduction timestamp feature previously file name basic type size would shown disks could also named first time limitations p-system included new restrictions naming files writing files consecutive blocks also created problems time free space tended become fragmented store new files utility called krunch included package consolidate free space biggest problem apple pascal system big fit one floppy disk meant system one floppy disk drive frequent disk swapping needed system needed least two disk drives order use operating system properly br br
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Operating systems
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calculus constructions mathematical logic computer science calculus constructions coc type theory created thierry coquand serve typed programming language constructive foundation mathematics second reason coc variants basis coq proof assistants variants include calculus inductive constructions adds inductive types calculus co inductive constructions adds coinduction predicative calculus inductive constructions removes impredicativity coc higher-order typed lambda calculus initially developed thierry coquand well known top barendregt lambda cube possible within coc define functions integers integers well integers types types types types integers coc strongly normalizing although impossible prove property within coc since implies consistency gödel incompleteness theorem impossible prove within system coc developed alongside coq proof assistant features added possible liabilities removed theory became available coq variants coc used proof assistants matita calculus constructions considered extension curry–howard isomorphism curry–howard isomorphism associates term simply typed lambda calculus natural-deduction proof intuitionistic propositional logic calculus constructions extends isomorphism proofs full intuitionistic predicate calculus includes proofs quantified statements also call propositions term calculus constructions constructed using following rules words term syntax bnf calculus constructions five kinds objects calculus constructions allows proving typing judgments read implication valid judgments calculus constructions derivable set inference rules following use formula_7 mean sequence type assignments formula_8 use k mean either p t. shall write formula_9 mean result substituting term formula_10 free variable formula_11 term formula_6 inference rule written form means 1. formula_16 3. formula_17 4. formula_18 5. formula_19 calculus constructions basic operators logical operator forming propositions formula_20 however one operator sufficient define logical operators basic data types used computer science defined within calculus constructions note booleans naturals defined way church encoding however additional problems arise propositional extensionality proof irrelevance
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Programming language topics
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amy koch amy t. koch born october 8 1971 american politician former majority leader minnesota senate represented portions hennepin wright counties koch first female senate majority leader state history also regular commentator minnesota local media koch grew buffalo minnesota graduating buffalo high school 1990 briefly attending concordia college moorhead minnesota koch joined united states air force 1992 serving military koch met former husband christopher gave birth daughter rachel koch studied russian defense language institute california assigned national security agency fort meade maryland graduated honors stages military training received joint service commendation medal contribution intelligence community receiving honorable discharge air force 1996 koch returned buffalo minnesota attended st cloud state university earned bachelor degree 1999 managed expanded family power utility service company next years koch received mba capella university 2009 koch volunteered adult leader 4-h served vice chair st. francis xavier parish council well liaison education advisory board 2016 koch began working political strategist hylden advocacy law minneapolis koch part owner hbk properties llc buffalo 2013 koch bought maple lake bowl bowling alley north home buffalo mn koch owned operated bowling alley sold summer 2016 leaving military returning minnesota koch became active local republican politics addition serving local party unit board koch actively volunteered former congressman mark kennedy former secretary state mary kiffmeyer koch first elected minnesota senate 2005 special election replacing mark ourada resigned months earlier re-elected 2006 2010 koch former assistant minority leader first woman serve majority leader minnesota senate first republican since party affiliation inheriting 6.2 billion budget deficit 2011 koch helped integrate 20 new members caucus negotiated budget deficit turned surplus december 15 2011 surprise announcement koch said would resign post majority leader minnesota senate republican state senators indicated koch inappropriate relationship staffer whose identity would later confirmed former state senate aide michael brodkorb koch later apologized seek re-election another term minnesota senate
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Computer security
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ophcrack ophcrack free open-source gpl licensed program cracks windows log-in passwords using lm hashes rainbow tables program includes ability import hashes variety formats including dumping directly sam files windows computers ophcrack crack passwords within minutes rainbow tables lm hashes provided free developers default ophcrack bundled tables allows crack passwords longer 14 characters using alphanumeric characters available free download four windows xp tables four windows vista tables objectif sécurité even larger tables purchase intended professional use larger rainbow tables ntlm hash cracking windows vista/windows 7 ophcrack also available live cd distributions automate retrieval decryption cracking passwords windows system one live cd distribution available windows xp lower well another windows vista windows 7 live cd distributions ophcrack built slitaz gnu/linux starting version 2.3 ophcrack also cracks ntlm hashes necessary generation lm hash disabled default windows vista password longer 14 characters case lm hash stored starting version 3.7.0 source code moved sourceforge gitlab
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Computer security
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general-purpose computing graphics processing units general-purpose computing graphics processing units gpgpu rarely gpgp use graphics processing unit gpu typically handles computation computer graphics perform computation applications traditionally handled central processing unit cpu use multiple video cards one computer large numbers graphics chips parallelizes already parallel nature graphics processing addition even single gpu-cpu framework provides advantages multiple cpus offer due specialization chip essentially gpgpu pipeline kind parallel processing one gpus cpus analyzes data image graphic form gpus operate lower frequencies typically many times number cores thus gpus process far pictures graphical data per second traditional cpu migrating data graphical form using gpu scan analyze create large speedup gpgpu pipelines developed beginning 21st century graphics processing e.g. better shaders pipelines found fit scientific computing needs well since developed direction principle arbitrary boolean function including addition multiplication mathematical functions built-up functionally complete set logic operators 1987 conway game life became one first examples general purpose computing using early stream processor called blitter invoke special sequence logical operations bit vectors general-purpose computing gpus became practical popular 2001 advent programmable shaders floating point support graphics processors notably problems involving matrices and/or vectors especially two- three- four-dimensional vectors easy translate gpu acts native speed support types scientific computing community experiments new hardware began matrix multiplication routine 2001 one first common scientific programs run faster gpus cpus implementation lu factorization 2005 early efforts use gpus general-purpose processors required reformulating computational problems terms graphics primitives supported two major apis graphics processors opengl directx cumbersome translation obviated advent general-purpose programming languages apis sh/rapidmind brook accelerator followed nvidia cuda allowed programmers ignore underlying graphical concepts favor common high-performance computing concepts newer hardware vendor-independent offerings include microsoft directcompute apple/khronos group opencl means modern gpgpu pipelines leverage speed gpu without requiring full explicit conversion data graphical form language allows code running cpu poll gpu shader return values create gpgpu framework opencl dominant open general-purpose gpu computing language open standard defined khronos group opencl provides cross-platform gpgpu platform additionally supports data parallel compute cpus opencl actively supported intel amd nvidia arm platforms khronos group also standardised implemented sycl higher-level programming model opencl single-source domain specific embedded language based pure c++11 dominant proprietary framework nvidia cuda nvidia launched cuda 2006 software development kit sdk application programming interface api allows using programming language c code algorithms execution geforce 8 series later gpus programming standards parallel computing include opencl vendor-independent openacc openhmpp mark harris founder gpgpu.org coined term gpgpu created xcelerit designed accelerate large existing c++ c code-bases gpus minimal effort provides simplified programming model automates parallelisation manages devices memory compiles cuda binaries additionally multi-core cpus accelerators targeted source code openvidia developed university toronto 2003-2005 collaboration nvidia. created altimesh compiles common intermediate language cuda binaries supports generics virtual functions debugging profiling integrated visual studio nsight available visual studio extension visual studio marketplace microsoft introduced directcompute gpu computing api released directx 11 api. created quantalea introduces native gpu computing capabilities microsoft .net language f c alea gpu also provides simplified gpu programming model based gpu parallel-for parallel aggregate using delegates automatic memory management matlab supports gpgpu acceleration using parallel computing toolbox matlab distributed computing server third-party packages like jacket gpgpu processing also used simulate newtonian physics physics engines commercial implementations include havok physics fx physx typically used computer video games close metal called stream amd gpgpu technology ati radeon-based gpus c++ accelerated massive parallelism c++ amp library accelerates execution c++ code exploiting data-parallel hardware gpus due trend increasing power mobile gpus general-purpose programming became available also mobile devices running major mobile operating systems google android 4.2 enabled running renderscript code mobile device gpu apple introduced proprietary metal api ios applications able execute arbitrary code apple gpu compute shaders computer video cards produced various vendors nvidia amd ati cards vendors differ implementing data-format support integer floating-point formats 32-bit 64-bit microsoft introduced shader model standard help rank various features graphic cards simple shader model version number 1.0 2.0 3.0 etc. pre-directx 9 video cards supported paletted integer color types various formats available containing red element green element blue element sometimes another alpha value added used transparency common formats early fixed-function limited programmability graphics i.e. including directx 8.1-compliant gpus sufficient also representation used displays important note representation certain limitations given sufficient graphics processing power even graphics programmers would like use better formats floating point data formats obtain effects high dynamic range imaging many gpgpu applications require floating point accuracy came video cards conforming directx 9 specification directx 9 shader model 2.x suggested support two precision types full partial precision full precision support could either fp32 fp24 floating point 32- 24-bit per component greater partial precision fp16 ati radeon r300 series gpus supported fp24 precision programmable fragment pipeline although fp32 supported vertex processors nvidia nv30 series supported fp16 fp32 vendors s3 graphics xgi supported mixture formats fp24 implementations floating point nvidia gpus mostly ieee compliant however true across vendors implications correctness considered important scientific applications 64-bit floating point values double precision float commonly available cpus universally supported gpus gpu architectures sacrifice ieee compliance others lack double-precision efforts occurred emulate double-precision floating point values gpus however speed tradeoff negates benefit offloading computing onto gpu first place operations gpu operate vectorized fashion one operation performed four values example one color r1 g1 b1 modulated another color r2 g2 b2 gpu produce resulting color r1*r2 g1*g2 b1*b2 one operation functionality useful graphics almost every basic data type vector either 2- 3- 4-dimensional examples include vertices colors normal vectors texture coordinates many applications put good use higher performance vector instructions termed single instruction multiple data simd long available cpus originally data simply passed one-way central processing unit cpu graphics processing unit gpu display device time progressed however became valuable gpus store first simple complex structures data passed back cpu analyzed image set scientific-data represented 2d 3d format video card understand gpu access every draw operation analyze data forms quickly whereas cpu must poll every pixel data element much slowly speed access cpu larger pool random-access memory even worse case hard drive slower gpus video cards typically contain smaller amounts expensive memory much faster access transferring portion data set actively analyzed gpu memory form textures easily readable gpu forms results speed increase distinguishing feature gpgpu design ability transfer information bidirectionally back gpu cpu generally data throughput directions ideally high resulting multiplier effect speed specific high-use algorithm gpgpu pipelines may improve efficiency especially large data sets and/or data containing 2d 3d imagery used complex graphics pipelines well scientific computing fields large data sets like genome mapping two- three-dimensional analysis useful especially present biomolecule analysis protein study complex organic chemistry pipelines also vastly improve efficiency image processing computer vision among fields well parallel processing generally heavily optimized pipelines yielded speed increases several hundred times original cpu-based pipeline one high-use task simple example would gpu program collects data average lighting values renders view either camera computer graphics program back main program cpu cpu make adjustments overall screen view advanced example might use edge detection return numerical information processed image representing outlines computer vision program controlling say mobile robot gpu fast local hardware access every pixel picture element image analyze average first example apply sobel edge filter convolution filter second much greater speed cpu typically must access slower random-access memory copies graphic question gpgpu fundamentally software concept hardware concept type algorithm piece equipment specialized equipment designs may however even enhance efficiency gpgpu pipelines traditionally perform relatively algorithms large amounts data massively parallelized gigantic-data-level tasks thus may parallelized even via specialized setups rack computing many similar highly tailored machines built rack adds third layer many computing units using many cpus correspond many gpus bitcoin miners used setups high-quantity processing historically cpus used hardware-managed caches earlier gpus provided software-managed local memories however gpus increasingly used general-purpose applications state-of-the-art gpus designed hardware-managed multi-level caches helped gpus move towards mainstream computing example geforce 200 series gt200 architecture gpus feature l2 cache fermi gpu 768 kib last-level cache kepler gpu 1.5 mib last-level cache maxwell gpu 2 mib last-level cache pascal gpu 4 mib last-level cache gpus large register files allow reduce context-switching latency register file size also increasing different gpu generations e.g. total register file size maxwell gm200 pascal gpus 6 mib 14 mib respectively comparison size register file cpus small typically tens hundreds kilobytes several research projects compared energy efficiency gpus cpus fpgas gpus designed specifically graphics thus restrictive operations programming due design gpus effective problems solved using stream processing hardware used certain ways following discussion referring vertices fragments textures concerns mainly legacy model gpgpu programming graphics apis opengl directx used perform general-purpose computation introduction cuda nvidia 2007 opencl vendor-independent 2008 general-purpose computing apis new gpgpu codes longer necessary map computation graphics primitives stream processing nature gpus remains valid regardless apis used see e.g. gpus process independent vertices fragments process many parallel especially effective programmer wants process many vertices fragments way sense gpus stream processors processors operate parallel running one kernel many records stream stream simply set records require similar computation streams provide data parallelism kernels functions applied element stream gpus vertices fragments elements streams vertex fragment shaders kernels run element read input perform operations write output permissible multiple inputs multiple outputs never piece memory readable writable arithmetic intensity defined number operations performed per word memory transferred important gpgpu applications high arithmetic intensity else memory access latency limit computational speedup ideal gpgpu applications large data sets high parallelism minimal dependency data elements variety computational resources available gpu fact program substitute write texture output instead framebuffer done either render texture rtt render-to-backbuffer-copy-to-texture rtbctt recent stream-out common form stream take gpgpu 2d grid fits naturally rendering model built gpus many computations naturally map grids matrix algebra image processing physically based simulation since textures used memory texture lookups used memory reads certain operations done automatically gpu compute kernels thought body loops example programmer operating grid cpu might code looks like gpu programmer specifies body loop kernel data loop invoking geometry processing sequential code possible control flow program using if-then-else statements various forms loops flow control structures recently added gpus conditional writes could performed using properly crafted series arithmetic/bit operations looping conditional branching possible recent gpus allow branching usually performance penalty branching generally avoided inner loops whether cpu gpu code various methods static branch resolution pre-computation predication loop splitting z-cull used achieve branching hardware support exist map operation simply applies given function kernel every element stream simple example multiplying value stream constant increasing brightness image map operation simple implement gpu programmer generates fragment pixel screen applies fragment program one result stream size stored output buffer computations require calculating smaller stream possibly stream 1 element larger stream called reduction stream generally reduction performed multiple steps results prior step used input current step range operation applied reduced one stream element remains stream filtering essentially non-uniform reduction filtering involves removing items stream based criteria scan operation also termed parallel prefix sum takes vector stream data elements arbitrary associative binary function '+ identity element input a0 a1 a2 a3 ... exclusive scan produces output a0 a0 a1 a0 a1 a2 ... inclusive scan produces output a0 a0 a1 a0 a1 a2 a0 a1 a2 a3 ... require identity exist first glance operation may seem inherently serial efficient parallel scan algorithms possible implemented graphics processing units scan operation uses e.g. quicksort sparse matrix-vector multiplication scatter operation naturally defined vertex processor vertex processor able adjust position vertex allows programmer control information deposited grid extensions also possible controlling large area vertex affects fragment processor perform direct scatter operation location fragment grid fixed time fragment creation altered programmer however logical scatter operation may sometimes recast implemented another gather step scatter implementation would first emit output value output address immediately following gather operation uses address comparisons see whether output value maps current output slot dedicated compute kernels scatter performed indexed writes gather reverse scatter scatter reorders elements according map gather restore order elements according map scatter used dedicated compute kernels gather may performed indexed reads shaders performed texture-lookups sort operation transforms unordered set elements ordered set elements common implementation gpus using radix sort integer floating point data coarse-grained merge sort fine-grained sorting networks general comparable data search operation allows programmer find given element within stream possibly find neighbors specified element gpu used speed search individual element instead used run multiple searches parallel mostly search method used binary search sorted elements variety data structures represented gpu following areas gpus used general purpose computing gpgpu usage bioinformatics † expected speedups highly dependent system configuration gpu performance compared multi-core x86 cpu socket gpu performance benchmarked gpu supported features may kernel kernel performance comparison details configuration used view application website speedups per nvidia in-house testing isv documentation ‡ q=quadro gpu t=tesla gpu nvidia recommended gpus application check developer isv obtain certification information
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Computer architecture
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enstratius enstratius formerly enstratus cloud computing infrastructure management platform intended address governance issues associated deploying systems public private hybrid clouds twenty public private clouds supported well configuration management tools chef puppet enstratius supports saas on-premises deployment models company originally formed 2008 enstratus networks spin-off marketing software maker valtira software forming backbone enstratus set cloud management tools valtira developed support cloud operations company announced publicly minnedemo conference february 2009 began accepting on-demand accounts co-founders david bagley george reese enstratius moved focus purely security wider problem governance multiple cloud computing environments 2010 enstratius spun part intellectual property open source project hosted github apache license called dasein cloud dasein cloud java abstraction api enstratius uses talk clouds supports company raised series financing 4.5 million november 2011 el dorado ventures vesbridge partners citrix march 2013 enstratus networks changed name enstratius inc. enstratius headquartered eden prairie minnesota remote workers across united states offices auckland new zealand edinburgh scotland may 2013 company acquired dell two weeks later dell discontinued cloud computing service june 2016 dell shifted enstratius product line support-only continue support customers longer selling cloud management platform
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Distributed computing architecture
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advanced programming unix environment advanced programming unix environment computer programming book w. richard stevens describing application programming interface unix family operating systems book illustrates unix application programming c programming language first edition book published addison-wesley 1992 covered programming two popular families unix operating system berkeley software distribution particular 4.3 bsd 386bsd unix system v particularly svr4 book covers system calls operations single file descriptors special calls like ioctl operate file descriptors operations files directories covers stdio section c standard library parts library needed several chapters concern apis control processes process groups daemons inter-process communication signals one chapter devoted unix terminal control another pseudo terminal concept libraries like termcap curses build atop stevens adds three chapters giving concrete examples unix programming implements database library communicates postscript printer modem book cover network programming subject stevens 1990 book unix network programming subsequent three-volume tcp/ip illustrated stevens died 1999 leaving second edition incomplete increasing popularity technical diversification unix derivatives largely compatible systems like linux environment code coverage stevens original became increasingly outdated working stevens unfinished notes stephen a. rago completed second edition addison-wesley published 2005 added support freebsd linux sun solaris apple darwin added coverage multithreaded programming posix threads second edition features foreword dennis ritchie unix-themed dilbert strip scott adams book widely lauded well written well crafted comprehensive received hearty recommendation linux journal review osnews describes one best tech books ever published review second edition
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Operating systems
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tree command computing codice_1 recursive directory listing command program produces depth-indented listing files available unix unix-like systems well dos digital research flexos ibm/toshiba 4690 os pts-dos freedos ibm os/2 microsoft windows reactos arguments codice_1 lists files current directory directory arguments given codice_1 lists files directories found given directories turn upon completion listing files directories found codice_1 returns total number files directories listed options change characters used output use color output command available ms-dos versions 3.2 later ibm pc dos releases 2 later dr dos 6.0 includes implementation command tree unix utility developed steve baker freedos version developed dave dunfield reactos version developed asif bahrainwala three implementations licensed gpl
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Computer file systems
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database audit database auditing involves observing database aware actions database users database administrators consultants often set auditing security purposes example ensure without permission access information access
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Databases
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ben wizner ben wizner born 1971 american lawyer writer civil liberties advocate american civil liberties union since july 2013 lead attorney nsa whistleblower edward snowden wizner born 1971 new connecticut grew campus yale university father stephen wizner professor law yale law school mother dean described drawn social justice work least early high school graduating harvard college 1993 worked organization provided legal assistance homeless near-homeless people new york university school law planned work legal services impoverished communities capital punishment cases graduating clerked judge stephen reinhardt united states court appeals ninth circuit wizner began working american civil liberties union los angeles august 2001 initially focusing prison reform following september 11 attacks wizner focus shifted civil liberties issues relating u.s. national security around 2004 moved aclu headquarters new york city argued legal cases relating airport security government watchlists surveillance practices targeted killing extraordinary rendition torture made several trips guantanamo bay detention camp many cases wizner took dismissed later commented worst days believed ... n't litigation traditional sense n't trying get court something creating record ... people would able look back decide whether right decision disastrous decision starting 2005 wizner represented khalid el-masri german citizen arrested travelling macedonia suspicion links al qaeda held cia black site afghanistan five months despite evidence wrong person el-masri suit dismissed u.s. grounds state secrecy though cia ultimately admitted making mistake report released u.s. senate european court human rights ruled macedonia case 2011 wizner became director aclu speech privacy technology project wizner adjunct professor new york university school law contributor website lawfare written time freedom press foundation several media outlets testified u.s. congress regularly appeared television news analysis programs including democracy meet press politicking larry king 2013 edward snowden contacted journalist glenn greenwald filmmaker laura poitras longtime acquaintances wizner releasing classified information nsa programs poitras consulted wizner travelling meet snowden hong kong greenwald later put wizner contact snowden july 2013 snowden stranded transit zone moscow passport revoked u.s. government wizner snowden exchanged encrypted communications time snowden legal team also includes jesselyn radack advocate whistleblowers wolfgang kaleck european attorney attorneys expertise criminal asylum law team works pro bono ensure snowden continued freedom ability contribute public conversation began disclosures wizner describes gatekeeper media requests snowden said believes snowden return u.s. eventually wizner called snowden case work lifetime traditional legal work means previously spent decade trying bring cases u.s. intelligence agencies cases often dismissed lack standing snowden revelations verizon delivering metadata u.s. government aclu standing sue wizner defended right privacy critical use extensive surveillance enforce law highlighted role lawbreaking positive social change pointing lgbt civil rights movement drug prohibition areas illegal activities contributed positive changes law public opinion speaking u.s. intelligence apparatus said nsa uniquely evil uniquely capable wizner forcefully defended snowden calls punishment stating broke law public good noting elected officials held criminally liable torture human rights violations since 9/11 following april 2019 arrest wikileaks founder julian assange london ecuadorian embassy ben wizner said authorities prosecute assange violating u.s. secrecy laws would set especially dangerous precedent u.s. journalists routinely violate foreign secrecy laws deliver information vital public interest
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Computer security
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libvirt libvirt open-source api daemon management tool managing platform virtualization used manage kvm xen vmware esxi qemu virtualization technologies apis widely used orchestration layer hypervisors development cloud-based solution libvirt c library bindings languages notably python perl ocaml ruby java javascript via node.js php libvirt programming languages composed wrappers around another class/package called libvirtmod libvirtmod implementation closely associated counterpart c/c++ syntax functionality various virtualization programs platforms use libvirt virtual machine manager others provide graphical interfaces popular command line interface virsh higher level tools ovirt gnome boxes uses libvirt development libvirt backed red hat significant contributions organisations individuals libvirt available linux distributions remote servers also accessible apple microsoft windows clients
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Operating systems
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bondwell-2 bondwell-2 early laptop personal computer running cp/m operating system introduced bondwell 1985 came zilog z80 cpu clocked 4 mhz 64 kb ram 4 kb rom 3.5 floppy disk drive highly unusual cp/m system os largely outmoded time 3.5 drives introduced model 2 main attraction price 995 usd also included micropro complete line cp/m software including wordstar also unusually cp/m system bondwell-2 capable displaying bitmapped graphics flip-up lcd display resolution 640x200 pixels 80x25 text characters 300 baud modem available option
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Operating systems
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bc programming language bc basic calculator often referred bench calculator arbitrary-precision calculator language syntax similar c programming language bc typically used either mathematical scripting language interactive mathematical shell typical interactive usage typing command codice_1 unix command prompt entering mathematical expression whereupon output bc work arbitrary precision actually defaults zero digits decimal point expression yields surprise new bc users unaware fact option bc sets default scale digits decimal point 20 adds several additional mathematical functions language bc first appeared version 6 unix 1975 written robert morris lorinda cherry bell labs bc preceded dc earlier arbitrary-precision calculator written authors dc could arbitrary-precision calculations reverse polish notation rpn syntax inconvenient users therefore bc written front-end dc bc simple compiler single yacc source file hundred lines converted new c-like bc syntax dc postfix notation piped results dc 1991 posix rigorously defined standardized bc two implementations standard survive today first traditional unix implementation front-end dc survives unix plan 9 systems second free software gnu bc first released 1991 philip a. nelson gnu implementation numerous extensions beyond posix standard longer front-end dc bytecode interpreter posix standardized bc language traditionally written program dc programming language provide higher level access features dc language without complexities dc terse syntax form bc language contains single-letter variable array function names standard arithmetic operators well familiar control-flow constructs codice_2 codice_3 codice_4 c. unlike c codice_5 clause may followed codice_6 functions defined using codice_7 keyword values returned using codice_8 followed return value parentheses codice_9 keyword optional c used declare variable local function numbers variable contents arbitrary-precision numbers whose precision decimal places determined global codice_10 variable numeric base input interactive mode output program constants may specified setting reserved codice_11 input base codice_12 output base variables output generated deliberately assigning result calculation variable comments may added bc code use c codice_13 codice_14 start end comment symbols following posix bc operators behave exactly like c counterparts modulus operators codice_15 codice_16 behave exactly like c counterparts global codice_10 variable set 0 i.e calculations integer-only otherwise computation done appropriate scale codice_18 defined codice_19 examples operators superficially resemble c bitwise exclusive-or operators fact bc integer exponentiation operators particular note use codice_20 operator negative numbers follow c operator precedence codice_21 gives answer 4 bc rather −4 bitwise boolean conditional operators available posix bc codice_22 function calculating square roots posix bc built-in mathematical function functions available external standard library codice_23 function determining precision codice_10 variable argument codice_25 function determining number significant decimal digits argument also built-in bc standard math library defined -l option contains functions calculating sine cosine arctangent natural logarithm exponential function two parameter bessel function j standard mathematical functions including inverse trigonometric functions constructed using see external links implementations many functions -l option changes scale 20 things modulo may work unexpectedly example writing codice_26 command codice_27 outputs 0 writing codice_28 codice_26 command codice_27 output 1 plan 9 bc identical posix bc additional codice_31 statement gnu bc derives posix standard includes many enhancements entirely separate dc-based implementations posix standard instead written c. nevertheless fully backwards compatible posix bc programs run unmodified gnu bc programs gnu bc variables arrays function names may contain one character operators included c notably codice_5 clause may followed codice_6 output achieved either deliberately assigning result calculation variable posix way using added codice_31 statement furthermore codice_35 statement allows interactive input number running calculation addition c-style comments codice_36 character cause everything next new-line ignored value last calculation always stored within additional built-in codice_37 variable following logical operators additional posix bc available use conditional statements within codice_5 statement note however still equivalent bitwise assignment operations functions available gnu bc inherited posix functions provided standard gnu distribution since bc codice_20 operator allows integer power right one first functions bc user might write power function floating-point exponent assume standard library included /* function return integer part x */ calculate pi using builtin arctangent function bc -lq scale=10000 4*a 1 atan 1 45 degrees pi/4 radians syntax bc similar c published numerical functions written c often translated bc quite easily immediately provides arbitrary precision bc example journal statistical software july 2004 volume 11 issue 5 george marsaglia published following c code cumulative normal distribution double phi double x necessary changes accommodate bc different syntax realizing constant 0.9189 ... actually log 2*pi /2 translated following gnu bc code define phi x bc used non-interactively input pipe useful inside shell scripts example contrast note bash shell performs integer arithmetic e.g one also use here-string idiom bash ksh csh
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Programming language topics
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pipeline computing computing pipeline also known data pipeline set data processing elements connected series output one element input next one elements pipeline often executed parallel time-sliced fashion amount buffer storage often inserted elements computer-related pipelines include operating systems may provide unix-like syntax string several program runs pipeline implement latter simple serial execution rather true pipelining — namely waiting program finish starting next one pipelining commonly used concept everyday life example assembly line car factory specific task — installing engine installing hood installing wheels — often done separate work station stations carry tasks parallel different car car one task performed moves next station variations time needed complete tasks accommodated buffering holding one cars space stations and/or stalling temporarily halting upstream stations next station becomes available suppose assembling one car requires three tasks take 20 10 15 minutes respectively three tasks performed single station factory would output one car every 45 minutes using pipeline three stations factory would output first car 45 minutes new one every 20 minutes example shows pipelining decrease latency total time one item go whole system however increase system throughput rate new items processed first one since throughput pipeline better slowest element designer try divide work resources among stages take time complete tasks car assembly example three tasks took 15 minutes instead 20 10 15 minutes latency would still 45 minutes new car would finished every 15 minutes instead 20 ideal circumstances processing elements synchronized take amount time process item received element released previous one single clock cycle way items flow pipeline constant speed like waves water channel wave pipelines synchronization buffering needed stages besides storage needed data items generally buffering pipeline stages necessary processing times irregular items may created destroyed along pipeline example graphics pipeline processes triangles rendered screen element checks visibility triangle may discard invisible may output two triangular pieces partly hidden buffering also needed accommodate irregularities rates application feeds items first stage consumes output last one buffer two stages may simply hardware register suitable synchronization signalling logic two stages stage stores data item register sends data available signal next stage b b used data responds data received signal stage halts waiting signal storing next data item register stage b halts waiting data available signal ready process next item stage provided yet processing times element variable whole pipeline may often stop waiting element previous ones consume items input buffers frequency pipeline stalls reduced providing space one item input buffer stage multiple-item buffer usually implemented first-in first-out queue upstream stage may still halted queue gets full frequency events decrease buffer slots provided queuing theory tell number buffer slots needed depending variability processing times desired performance stage takes may take much longer others sped designer provide two processing elements carry task parallel single input buffer single output buffer element finishes processing current data item delivers common output buffer takes next data item common input buffer concept non-linear dynamic pipeline exemplified shops banks two cashiers serving clients single waiting queue applications processing item stage may depend results effect processing previous item x later stage b pipeline case stage correctly process item item x cleared stage b situation occurs often instruction pipelines example suppose arithmetic instruction reads contents register supposed modified earlier instruction x let stage fetches instruction operands b stage writes result specified register stage tries process instruction instruction x reaches stage b register may still contain old value effect would incorrect order handle conflicts correctly pipeline must provided extra circuitry logic detects takes appropriate action strategies include pipelined system typically requires resources circuit elements processing units computer memory etc one executes one batch time stages share resources buffering additional synchronization logic may needed elements moreover transfer items separate processing elements may increase latency especially long pipelines additional complexity cost pipelining may considerable dependencies processing different items especially guess-and-backtrack strategy used handle indeed cost implementing strategy complex instruction sets motivated radical proposals simplify computer architecture risc vliw compilers also burdened task rearranging machine instructions improve performance instruction pipelines
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Computer architecture
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pascal programming language pascal imperative procedural programming language designed niklaus wirth small efficient language intended encourage good programming practices using structured programming data structuring named honor french mathematician philosopher physicist blaise pascal pascal developed pattern algol 60 language wirth involved process improve language part algol x efforts proposed version known algol w. accepted algol x process bogged 1968 wirth decided abandon algol x process improve algol w releasing pascal 1970 pascal became successful 1970s notably burgeoning minicomputer market compilers also available many microcomputers field emerged late 1970s widely used teaching language university-level programming courses 1980s also used production settings writing commercial software period displaced c programming language late 1980s early 1990s unix-based systems became popular especially release c++ derivative known object pascal designed object-oriented programming developed 1985 used apple computer borland late 1980s later developed delphi microsoft windows platform extensions pascal concepts led languages modula-2 oberon much history computer language design 1960s traced algol 60 language algol developed 1950s explicit goal able clearly describe algorithms included number features structured programming remain common languages day shortly introduction 1962 wirth began working dissertation helmut weber euler programming language euler based algol syntax many concepts derivative primary goal add dynamic lists types allowing used roles similar lisp language published 1965 time number problems algol identified notably lack standardized string system group tasked maintaining language begun algol x process identify improvements calling submissions wirth tony hoare submitted conservative set modifications add strings clean syntax considered minor worth using new standard algol wirth wrote compiler language became known algol w. algol x efforts would go choose dramatically complex language algol 68 complexity language led considerable difficulty producing high-performance compilers widely used industry left opening newer languages pascal influenced algol w efforts explicit goals producing language would efficient compiler run-time allow development well-structured programs useful teaching students structured programming generation students used pascal introductory language undergraduate courses one early successes language introduction ucsd pascal version ran custom operating system could ported different platforms key platform apple ii saw widespread use led use pascal becoming primary high-level language used development apple lisa later macintosh parts original macintosh operating system hand-translated motorola 68000 assembly language pascal sources typesetting system tex donald e. knuth written web original literate programming system based dec pdp-10 pascal successful commercial applications like adobe photoshop written macintosh programmer workshop pascal applications like total commander skype macromedia captivate written delphi object pascal apollo computer used pascal systems programming language operating systems beginning 1980 variants pascal also used everything research projects pc games embedded systems newer pascal compilers exist widely used work lisa larry tesler began corresponding wirth idea adding object oriented extensions language led initially clascal introduced 1983 lisa program faded replaced mac version known object pascal created introduced macintosh 1985 part macapp application framework became apple primary development language early 1990s object pascal extensions added turbo pascal release version 5.5 1989 years object pascal became basis delphi system microsoft windows still used developing windows applications cross-compile code systems free pascal open source cross-platform alternative wirth intention create efficient language regarding compilation speed generated code based structured programming recently popularized concept promoted book algorithms data structures programs pascal roots algol 60 language also introduced concepts mechanisms top algol scalars arrays enabled programmers define complex structured datatypes also made easier build dynamic recursive data structures lists trees graphs important features included records enumerations subranges dynamically allocated variables associated pointers sets make possible meaningful pascal strong typing objects means one type data converted interpreted another without explicit conversions similar mechanisms standard many programming languages today languages influenced pascal development simula 67 wirth algol w. pascal like many programming languages today unlike languages c family allows nested procedure definitions level depth also allows kinds definitions declarations inside subroutines procedures functions enables simple coherent syntax complete program syntactically nearly identical single procedure function except heading one three keywords first pascal compiler designed zürich cdc 6000 series mainframe computer family niklaus wirth reports first attempt implement fortran 1969 unsuccessful due fortran inadequacy express complex data structures second attempt implemented c-like language scallop max engeli translated hand r. schild pascal boot-strapping operational mid-1970 many pascal compilers since similarly self-hosting compiler written pascal compiler usually capable recompiling new features added language compiler ported new environment gnu pascal compiler one notable exception written c. first successful port cdc pascal compiler another mainframe completed welsh quinn queen university belfast qub 1972 target icl 1900 series compiler turn parent pascal compiler information computer systems ics multum minicomputer multum port developed – view using pascal systems programming language – findlay cupples cavouras davis working department computing science glasgow university thought multum pascal completed summer 1973 may first 16-bit implementation completely new compiler completed welsh et al qub 1977 offered source-language diagnostic feature incorporating profiling tracing type-aware formatted postmortem dumps implemented findlay watt glasgow university implementation ported 1980 icl 2900 series team based southampton university glasgow university standard pascal model implementation also based compiler adapted welsh hay manchester university 1984 check rigorously conformity bsi 6192/iso 7185 standard generate code portable abstract machine first pascal compiler written north america constructed university illinois donald b. gillies pdp-11 generated native machine code propagate language rapidly compiler porting kit created zurich included compiler generated code virtual stack machine i.e code lends reasonably efficient interpretation along interpreter code – pascal-p system p-system compilers termed pascal-p1 pascal-p2 pascal-p3 pascal-p4 pascal-p1 first version pascal-p4 last come zurich version termed pascal-p1 coined fact many different sources pascal-p existed compiler redesigned enhance portability issued pascal-p2 code later enhanced become pascal-p3 intermediate code backward compatible pascal-p2 pascal-p4 backward compatible pascal-p4 compiler/interpreter still run compiled systems compatible original pascal however accepts subset pascal language pascal-p5 created outside zurich group accepts full pascal language includes iso 7185 compatibility ucsd pascal branched pascal-p2 kenneth bowles utilized create interpretive ucsd p-system ucsd p-system one three operating systems available launch original ibm personal computer ucsd pascal used intermediate code based byte values thus one earliest byte code compilers pascal-p1 pascal-p4 rather based cdc 6600 60 bit word length compiler based pascal-p4 compiler created native binaries released ibm system/370 mainframe computer australian atomic energy commission called aaec pascal compiler abbreviation name commission apple computer created lisa pascal lisa workshop 1982 ported compiler apple macintosh mpw 1985 1985 larry tesler consultation niklaus wirth defined object pascal extensions incorporated lisa pascal mac pascal compilers 1980s anders hejlsberg wrote blue label pascal compiler nascom-2 reimplementation compiler ibm pc marketed names compas pascal polypascal acquired borland renamed turbo pascal turbo pascal became hugely popular thanks aggressive pricing strategy one first full-screen ides fast turnaround time seconds compile link run written highly optimized entirely assembly language making smaller faster much competition 1986 anders ported turbo pascal macintosh incorporated apple object pascal extensions turbo pascal extensions added back pc version turbo pascal version 5.5 time microsoft also implemented object pascal compiler turbo pascal 5.5 large influence pascal community began concentrating mainly ibm pc late 1980s many pc hobbyists search structured replacement basic used product also began adopted professional developers around time number concepts imported c let pascal programmers use c-based api microsoft windows directly extensions included null-terminated strings pointer arithmetic function pointers address-of operator unsafe typecasts turbo pascal derivatives units module concepts modular languages however provide nested module concept qualified import export specific symbols super pascal variant added non-numeric labels return statement expressions names types tmt pascal first borland-compatible compiler 32-bit dos protected mode os/2 win32 operating systems tmt pascal language first one allow function operator overloading universities wisconsin-madison zürich karlsruhe wuppertal developed pascal-sc pascal-xsc extensions scientific computation compilers aimed programming numerical computations development pascal-sc started 1978 supporting iso 7185 pascal level 0 level 2 support added later stage pascal-sc originally targeted z80 processor later rewritten dos x86 68000 pascal-xsc various times ported unix linux sunos hp-ux aix microsoft/ibm dos emx os/2 windows operating systems operates generating intermediate c source code compiled native executable pascal-sc language extensions adopted gnu pascal pascal sol designed around 1983 french team implement unix-like systems named sol standard pascal level-1 parametrized array bounds definition allowed alternative keywords predefined identifiers french language included extensions ease system programming e.g equivalent lseek sol team later moved chorusos project design distributed operating system ip pascal implementation pascal programming language using micropolis dos moved rapidly cp/m-80 running z80 moved 80386 machine types 1994 exists today windows/xp linux implementations 2008 system brought new level resulting language termed pascaline pascal calculator includes objects namespace controls dynamic arrays along many extensions generally features functionality type protection c implementation also compatible original pascal implementation standardized iso 7185 pascal original form purely procedural language includes traditional array algol-like control structures reserved words else case ranging single statement begin-end statements block pascal also data structuring constructs included original algol 60 types like records variants pointers enumerations sets procedure/pointers constructs part inherited inspired simula 67 algol 68 niklaus wirth algol w suggestions c. a. r. hoare pascal programs start program keyword list external file descriptors parameters ref name= iso/iec 7185:1990 6.10 pascal iso 7185:1990 6.10 /ref required turbo pascal etc follows main block bracketed begin end keywords semicolons separate statements full stop i.e. period ends whole program unit letter case ignored pascal source example source code use simple hello world program type pascal several popular programming languages defines variable way defines range values variable capable storing also defines set operations permissible performed variables type predefined types range values allowed except boolean implementation defined functions provided data conversions conversion codice_1 codice_2 following functions available codice_3 rounds integer using banker rounding codice_4 rounds towards zero programmer freedom define commonly used data types e.g byte string etc terms predefined types using pascal type declaration facility example subranges ordinal data type simple type except real also made contrast programming languages time pascal supports set type set fundamental concept modern mathematics may used many algorithms feature useful may faster equivalent construct language support sets example many pascal compilers executes faster sets non-contiguous values particularly useful terms performance readability examples involve sets small domains improved performance usually achieved compiler representing set variables bit vectors set operators implemented efficiently bitwise machine code operations types defined types using type declarations complex types constructed simple types shown example pascal files sequences components every file buffer variable denoted f^ procedures get reading put writing move buffer variable next element read introduced read f x x f^ get f write introduced write f x f^ x put f type text predefined file char buffer variable could used inspecting next character used check digit reading integer leads serious problems interactive programs early implementations solved later lazy i/o concept jensen wirth pascal strings represented packed arrays chars therefore fixed length usually space-padded pascal supports use pointers variable nodeptr pointer data type node record pointers used declared forward declaration exception rule things must declared used create new record assign value 10 character fields b record initialise pointer c null pointer nil pascal statements would could also done using statement follows inside scope statement b refer subfields record pointer nodeptr record node pointer type pnode linked lists stacks queues created including pointer type field c record unlike many languages feature pointers pascal allows pointers reference dynamically created variables anonymous allow reference standard static local variables pointers also must associated type pointer one type compatible pointer another type e.g pointer char compatible pointer integer helps eliminate type security issues inherent pointer implementations particularly used pl/i c. also removes risks caused dangling pointers ability dynamically deallocate referenced space using dispose function effect free library function found c means risk dangling pointers entirely eliminated languages java c provide automatic garbage collection entirely eliminate related problem memory leaks restrictions lifted newer dialects pascal structured programming language meaning flow control structured standard statements usually without 'goto commands pascal structures programs procedures functions procedures functions nested depth 'program construct logical outermost block default parameters passed value 'var precedes parameter name passed reference procedure function declarations goto labels constants types variables procedures functions must order ordering requirement originally intended allow efficient single-pass compilation however dialects embarcadero delphi strict ordering requirement declaration sections relaxed pascal adopted many language syntax features algol language including use semicolon statement separator contrast languages pl/i c etc use semicolon statement terminator semicolon needed end keyword record type declaration block case statement keyword repeat statement else keyword statement presence extra semicolon permitted early versions pascal however addition algol-like empty statements 1973 revised report later changes language iso 7185:1983 allow optional semicolons cases semicolon still permitted immediately else keyword statement else follows single statement statement sequence case nested ifs semicolon used avoid dangling else problem inner else outer putatively terminating nested semicolon – instead terminates clauses instead explicit codice_5 block must used several pascal compilers interpreters available general use 1983 language standardized international standard iec/iso 7185 several local country specific standards including american ansi/ieee770x3.97-1983 iso 7185:1983 two standards differed iso standard included level 1 extension conformant arrays array boundaries array known run time ansi allow extension original wirth version language 1989 iso 7185 revised iso 7185:1990 correct various errors ambiguities found original document iso 7185 stated clarification wirth 1974 language detailed user manual report jensen wirth also notable adding conformant array parameters level 1 standard level 0 pascal without conformant arrays addition made request c. a. r. hoare approval niklaus wirth precipitating cause hoare wanted create pascal version nag numerical algorithms library originally written fortran found possible without extension would allow array parameters varying size similar considerations motivated inclusion iso 7185 facility specify parameter types procedural functional parameters niklaus wirth referred 1974 language standard example differentiate machine specific features cdc 6000 compiler language documented pascal report second part pascal users manual report large machines mainframes minicomputers pascal originated standards generally followed ibm pc ibm pcs borland standards turbo pascal delphi greatest number users thus typically important understand whether particular implementation corresponds original pascal language borland dialect ibm pc versions language began differ advent ucsd pascal interpreted implementation featured several extensions language along several omissions changes many ucsd language features survive today including borland dialect 1990 extended pascal standard created iso/iec 10206 identical technical content ref name= iso/ansi identical /ref ieee/ansi 770x3.160-1989 2019 support extended pascal freepascal compiler planned niklaus wirth zurich version pascal issued outside eth two basic forms cdc 6000 compiler source porting kit called pascal-p system pascal-p compiler left several features full language required bootstrap compiler example procedures functions used parameters undiscriminated variant records packing dispose interprocedural gotos features full compiler omitted ucsd pascal professor kenneth bowles based pascal-p2 kit consequently shared several pascal-p language restrictions ucsd pascal later adopted apple pascal continued several versions although ucsd pascal actually expanded subset pascal pascal-p kit adding back standard pascal constructs still complete standard installation pascal early 1990s alan burns geoff davies developed pascal-fc extension pl/0 niklaus book 'algorithms+data structures=programs several constructs added use pascal-fc teaching tool concurrent programming semaphores monitors channels remote-invocation resources able demonstrate concurrency compiler output kind p-code could executed virtual machine virtual machine simulated normal – fair – environment could also simulate extreme conditions unfair mode borland turbo pascal written anders hejlsberg written assembly language independent ucsd zurich compilers however adopted much subset extensions ucsd compiler probably ucsd system common pascal system suitable developing applications resource-limited microprocessor systems available time shrink-wrapped turbo pascal version 3 later incarnations including borland object pascal delphi non-borland near-compatibles became popular programmers including shareware authors swag library pascal code features large amount code written versions delphi mind software products compilers ide/rapid application development rad category pascal generated wide variety responses computing community critical complimentary popular 1980s early 1990s implementations pascal closely followed wirth initial definition language widely criticized unsuitable use outside teaching brian kernighan popularized c language outlined notable criticisms pascal early 1981 article pascal favorite programming language serious problem described array sizes string lengths part type possible write function would accept variable-length arrays even strings parameters made unfeasible write example sorting library kernighan also criticized unpredictable order evaluation boolean expressions poor library support lack static variables raised number smaller issues also stated language provide simple constructs escape knowingly forcibly ignore restrictions limitations general complaints sources noted scope declarations clearly defined original language definition sometimes serious consequences using forward declarations define pointer types record declarations led mutual recursion identifier may may used enumeration list another difficulty like algol 60 language allow procedures functions passed parameters predefine expected type parameters kernighan criticisms directly addressed article pascal programming language bill catambay specifically myth 6 pascal serious programmers despite initial criticisms pascal continued evolve kernighan points apply versions language enhanced suitable commercial product development borland turbo pascal kernighan predicted article extensions fix issues incompatible compiler compiler since early 1990s however varieties seem condensed two categories iso borland-like extended pascal addresses many early criticisms supports variable-length strings variable initialization separate compilation short-circuit boolean operators default codice_6 clauses case statements
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Programming language topics
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powerbook 170 powerbook 170 released apple inc. 1991 along powerbook 100 powerbook 140 identical form factor 140 high end original powerbook line featuring faster 25 mhz motorola 68030 processor floating point unit fpu expensive significantly better quality active matrix display replaced powerbook 180 1992 though powerbook 100 direct descendant macintosh portable based internal architecture 170 portable direct successor no-compromise portable version desktop macintosh 170 includes virtually features incorporated original portable comparable desktop day smaller sleeker case design initiated suitable replacement portable features first generation 170 include reduced space external video port internal rom pds expansion slots indeed apple canceled external monitor adapter portable shortly announced instead relying numerous third party providers solutions still applicable 170 fcc regulations day prevented real use pds expansion slot restricting external connections powerbook 180 replacement would address external video less year later expansion slots would return macintosh portables three years later powerbook 500 series form pcmcia cards 170 also dropped external floppy disk port macintosh classic ii still one made provision second internal floppy disk port feature also missing rest desktop line time overall roughly equivalent features performance powerful macintosh iici desktop laptop 170 introduced system 7.0.1 specifically support new power management unique hardware features however due ram prices 1991 combined already high list price 170 like 100 140 2 megabytes mb ram soldered directly onto logicboard critics felt restrictive use system 7 since localized versions system 7 yet available worldwide japanese 6.0.7 kanjitalk version apple system software modified support three new powerbooks released version j-6.0.7.1 result version unofficially adapted use standard 6.0.7 allowing many users run system 6 powerbooks rather upgrading on-board ram expensive proprietary ram card 6 mb card us 899 170 shipped additional 2 mb ram card already installed less problem however 4 mb minimum recommended ram size use system 7 practical use ram disk battery power-saving feature though released time powerbook 140 powerbook 100 140 170 designed entirely apple 100 miniaturized sony full-sized macintosh portable result 170 represents first powerbook created apple 100 actually representing first design improvements though internal architecture oldest series
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Computer architecture
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inca internet inca internet corporation also known nprotect corporation sells computer software inca internet founded young heum joo current ceo president inca internet 2000 offers anti-virus anti-spyware game security unified corporate security headquartered seoul republic korea inca internet selected one deloitte technology fast 50 korea 2007 deloitte technology fast 500 asia pacific 2007 inca internet information security company based republic korea develops 'nprotect line computer security products young heum joo founded company january 31 2000 currently ceo president company currently holds 70 market share information security korean financial institutions 90 game portal security public company limited shares young hem joo largest stockholder followed jaic japan meespierson netherlands major investors include jaic japan largest independent venture capital firm kdb korea development bank main business areas inca internet include online pc security services financial institutions internet business corporations online game corporations among others online game security solutions united pc security solution corporate internal security b2c business online anti-virus normal internet users inca internet one first application service provider asp companies online pc security industry products widely used korean japanese financial institutions public institutions worldwide on-line game companies inca internet awarded ir52 jang yeong-sil award regarded highest reputable award korean industrial technology field acquired iso 9000 certificate tuvit certification institution affiliated german rwtuv group inca internet information security company korea included deloitte technology fast500 asia pacific 2007 inca internet currently client companies 23 countries total 200 million users 170 countries inca internet first entered market january 2000 acquired global patent 'nprotect netizen first program provide real-time client pc information security service inca internet developed strong corporation independent technology leading korean japanese security market financial electronic commerce industry inca internet first founded internet usage fast spread ill-intended cyber attack pattern diversification user niche various complicated malware started show limit single one-time purchase security solutions hw-based information security products since inca internet quickly adjusted information security market trend provided end-user based user friendly pc security solution optimized today internet environment since december 2005 inca internet located within guro digital complex largest industrial complex korea played pivotal role economic growth korea referred miracle han contributing 10 national exports 1970s futuristic industrial hub centering research development advanced information technology knowledge industries relocation great synergy effect inca internet many corporations located benefited information sharing partnerships inca internet nprotect products apply saas software service model first company security industry provide internet banking security online since spread saas model pc security web security company currently holds 70 market share information security korean financial institutions 90 game portal security internationally inca internet mainly provides security solutions china japan south-east asia europe companies jcb card ufj tokyo star bank among corporations using inca internet protection online game security system asp based pc security anti-virus solution unified solution web security programs widely used korean internet environment depend activex microsoft windows internet banks korea need programs law users using linux mac os x browsers operating systems besides internet explorer microsoft windows access online banks functions run kernel level os versions windows use uac user account control windows vista windows 7 higher unable run smoothly moreover program crash kernel x64 windows system input devices especially usb keyboard conjunction nprotect caused reason nprotect netizen nprotect personal nprotect keycrypt programs used mostly internet banking korea programmed terminate processes associated banking processes terminated indiscriminately deemed threat thus may compromise system stability programs also inject existing processes startup sometimes collide anti-viruses problematically korean banks update program every time inca releases update
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Computer security
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interchangeable parts interchangeable parts parts components practical purposes identical made specifications ensure nearly identical fit assembly type one part freely replace another without custom fitting filing interchangeability allows easy assembly new devices easier repair existing devices minimizing time skill required person assembly repair concept interchangeability crucial introduction assembly line beginning 20th century become important element modern manufacturing missing important industries interchangeability parts achieved combining number innovations improvements machining operations invention several machine tools slide rest lathe screw-cutting lathe turret lathe milling machine metal planer additional innovations included jigs guiding machine tools fixtures holding workpiece proper position blocks gauges check accuracy finished parts electrification allowed individual machine tools powered electric motors eliminating line shaft drives steam engines water power allowing higher speeds making modern large scale manufacturing possible modern machine tools often numerical control nc evolved cnc computerized numeric control microprocessors became available methods industrial production interchangeable parts united states first developed nineteenth century term american system manufacturing sometimes applied time distinction earlier methods within decades methods use various countries american system term historical reference rather current industrial nomenclature evidence use interchangeable parts traced back two thousand years carthage first punic war carthaginian ships standardized interchangeable parts even came assembly instructions akin tab slot b marked east asia warring states period later qin dynasty bronze crossbow triggers locking mechanisms mass-produced made interchangeable late 18th century french general jean-baptiste vaquette de gribeauval promoted standardized weapons became known système gribeauval issued royal order 1765 focus time artillery muskets handguns one accomplishments system solid cast cannons bored precise tolerances allowed walls thinner cannons poured hollow cores however cores often center wall thickness determined size bore standardized boring allowed cannons shorter without sacrificing accuracy range tighter fit shells also allowed standardization shells 18th century devices guns made one time gunsmiths unique manner one single component firearm needed replacement entire firearm either sent expert gunsmith custom repairs discarded replaced another firearm 18th early 19th centuries idea replacing methods system interchangeable manufacture gradually developed development took decades involved many people gribeauval provided patronage honoré blanc attempted implement système gribeauval musket level around 1778 honoré blanc began producing first firearms interchangeable flint locks although carefully made craftsmen blanc demonstrated front committee scientists muskets could fitted flint locks picked random pile parts muskets interchangeable locks caught attention thomas jefferson efforts honoré blanc jefferson ambassador france 1785 jefferson tried persuade blanc move america successful wrote american secretary war idea returned usa worked fund development president george washington approved idea 1798 contract issued eli whitney 12,000 muskets built new system louis de tousard fled french revolution joined u.s. corp artillerists 1795 wrote influential artillerist manual stressed importance standardization numerous inventors began try implement principle blanc described development machine tools manufacturing practices required would great expense u.s ordnance department years trying achieve interchangeability firearms produced cost manufacture 1853 evidence interchangeable parts perfected federal armories led savings ordnance department freely shared techniques used outside suppliers us eli whitney saw potential benefit developing interchangeable parts firearms united states military july 1801 built ten guns containing exact parts mechanisms disassembled united states congress placed parts mixed pile help reassembled firearms right front congress much like blanc done years congress captivated ordered standard united states equipment use interchangeable parts removed problems earlier eras concerning difficulty impossibility producing new parts old equipment one firearm part failed another could ordered firearm would discarded catch whitney guns costly handmade skilled workmen charles fitch credited whitney successfully executing firearms contract interchangeable parts using american system historians merritt roe smith robert b. gordon since determined whitney never actually achieved interchangeable parts manufacturing family arms company however death mass production using interchangeable parts first achieved 1803 marc isambard brunel cooperation henry maudslay simon goodrich management contributions brigadier-general sir samuel bentham inspector general naval works portsmouth block mills portsmouth dockyard hampshire england time napoleonic war height royal navy state expansion required 100,000 pulley blocks manufactured year bentham already achieved remarkable efficiency docks introducing power-driven machinery reorganising dockyard system marc brunel pioneering engineer maudslay founding father machine tool technology developed first industrially practical screw-cutting lathe 1800 standardized screw thread sizes first time collaborated plans manufacture block-making machinery proposal submitted admiralty agreed commission services 1805 dockyard fully updated revolutionary purpose-built machinery time products still built individually different components total 45 machines required perform 22 processes blocks could made three different sizes machines almost entirely made metal thus improving accuracy durability machines would make markings indentations blocks ensure alignment throughout process one many advantages new method increase labour productivity due less labour-intensive requirements managing machinery richard beamish assistant brunel son engineer isambard kingdom brunel wrote ten men aid machinery accomplish uniformity celerity ease formerly required uncertain labour one hundred ten 1808 annual production reached 130,000 blocks equipment still operation late mid-twentieth century eli terry using interchangeable parts using milling machine early 1800 ward francillon horologist concluded study terry already accomplished interchangeable parts early 1800 study examined several terry clocks produced 1800-1807 parts labeled interchanged needed study concluded clock pieces interchangeable first mass production using interchangeable parts america eli terry 1806 porter contract called production 4000 clocks three years contract terry crafted four-thousand wooden gear tall case movements time annual average dozen unlike eli whitney terry manufactured products without government funding terry saw potential clocks becoming household object use milling machine terry able mass-produce clock wheels plates dozen time jigs templates used make uniform pinions parts could assembled using assembly line crucial step toward interchangeability metal parts taken simeon north working miles eli terry north created one world first true milling machines metal shaping done hand file diana muir believes north milling machine online around 1816 muir merritt roe smith robert b. gordon agree 1832 simeon north john hall able mass-produce complex machines moving parts guns using system entailed use rough-forged parts milling machine milled parts near-correct size filed gage hand aid filing jigs historians differ question whether hall north made crucial improvement merrit roe smith believes done hall muir demonstrates close personal ties professional alliances simeon north neighboring mechanics mass-producing wooden clocks argue process manufacturing guns interchangeable parts probably devised north emulation successful methods used mass-producing clocks may possible resolve question absolute certainty unless documents unknown surface future skilled engineers machinists many armory experience spread interchangeable manufacturing techniques american industries including clockmakers sewing machine manufacturers wilcox gibbs wheeler wilson used interchangeable parts 1860 late adopt interchangeable system singer corporation sewing machine 1870s reaper manufacturer mccormick harvesting machine company 1870s–1880s several large steam engine manufacturers corliss mid-1880s well locomotive makers typewriters followed years later large scale production bicycles 1880s began use interchangeable system decades true interchangeability grew scarce difficult achievement everyday capability throughout manufacturing industries 1950s 1960s historians technology broadened world understanding history development people outside academic discipline knew much topic recently 1980s 1990s academic knowledge began finding wider audiences recently 1960s alfred p. sloan published famous memoir management treatise years general motors even longtime president chair largest manufacturing enterprise ever existed knew little history development say nowiki /nowiki henry m. leland believe one mainly responsible bringing technique interchangeable parts automobile manufacturing … called attention eli whitney long started development interchangeable parts connection manufacture guns fact suggests line descent whitney leland automobile industry one better-known books subject first published 1984 enjoyed readership beyond academia david a. hounshell american system mass production 1800–1932 development manufacturing technology united states principle interchangeable parts flourished developed throughout 19th century led mass production many industries based use templates jigs fixtures applied semi-skilled labor using machine tools augment later largely replace traditional hand tools throughout century much development work done creating gauges measuring tools calipers micrometers standards screw threads processes scientific management principle interchangeability remained constant introduction assembly line beginning 20th century interchangeable parts became ubiquitous elements manufacturing interchangeability relies parts dimensions falling within tolerance range common mode assembly design manufacture long part reaches assembly within tolerance mating parts totally random value reasons already discussed earlier another mode assembly called selective assembly gives randomness capability trade-off value two main areas application benefit economically selective assembly tolerance ranges tight quite held reliably making total randomness unavailable tolerance ranges reliably held fit finish final assembly maximized voluntarily giving randomness makes available ideally desirable either case principle selective assembly parts selected mating rather mated random parts inspected graded separate bins based end range fall violate falling within high low end range usually called heavy light violating high low end range usually called oversize undersize examples given french vierck provide one-paragraph description selective assembly aptly summarizes concept one might ask parts must selected mating makes selective assembly different oldest craft methods fact significant difference selective assembly merely grades parts several ranges within range still random interchangeability quite different older method fitting craftsman mated set parts specifically filed fit part specific unique counterpart contexts application requires extremely tight narrow tolerance ranges requirement may push slightly past limit ability machining processes stamping rolling bending etc stay within range cases selective assembly used compensate lack total interchangeability among parts thus pin must sliding fit hole free sloppy dimension may spec 'd 12.00 +0 −0.01 mm pin 12.00 +.01 −0 hole pins came oversize say pin 12.003mm diameter necessarily scrap mated counterparts also came oversize say hole 12.013mm true matching size parts size counterparts inherent example product application 12 mm dimension require extreme accuracy desired fit parts require good precision see article accuracy precision allows makers cheat little total interchangeability order get value manufacturing effort reducing rejection rate scrap rate sound engineering decision long application context support example machines intention future field service parts-replacing nature rather simple replacement whole unit makes good economic sense lowers unit cost products impede future service work example product might benefit approach could car transmission expectation field service person repair old transmission instead simply swap new one therefore total interchangeability absolutely required assemblies inside transmissions would specified anyway simply general principle except certain shaft required precision high cause great annoyance high scrap rates grinding area decent accuracy required long fit hole good every case money could saved saving many shafts scrap bin examples like one common real commerce conceivably could mostly separation concerns part complex system expected give performance make limiting assumptions parts system car transmission example separation concerns individual firms customers accept lack freedom options others supply chain example car buyer view car manufacturer within rights assume field-service mechanic ever repair old transmission instead replacing customer expects decision preserved make later repair shop based option less expensive time figuring replacing one shaft cheaper replacing whole transmission logic always valid reality might better customer total ownership cost pay lower initial price car especially transmission service covered standard warranty 10 years buyer intends replace car anyway pay higher initial price car preserve option total interchangeability every last nut bolt shaft throughout car going taken advantage anyway commerce generally chaotically multivariate logic prevail total interchangeability ends specified achieved even adds expense needless holistic view commercial system may avoided extent customers experience overall value minds detect appreciate without understand logical analysis thus buyers amazingly affordable car surprisingly low initial price probably never complain transmission field-serviceable long never pay transmission service lifespan ownership analysis important manufacturer understand even lost customer carve competitive advantage marketplace accurately predict cut corners ways customer never pay thus could give lower transmission unit cost however must sure transmissions using reliable replacement covered long warranty expense main area application selective assembly contexts total interchangeability fact achieved fit finish final products enhanced minimizing dimensional mismatch mating parts consider another application similar one 12 mm pin say example precision important produce desired fit accuracy also important 12 mm pin must interact something else accurately sized 12 mm implications example rejection rate lowered parts must fall within tolerance range scrapped savings salvaging oversize undersize parts scrap however still one bit value selective assembly mated pairs close identical sliding fit possible opposed tighter fits looser fits—all sliding varying resistance example product might benefit approach could toolroom-grade machine tool accuracy highly important also fit finish
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Computer architecture
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outwit hub outwit hub web data extraction software application designed automatically extract information online local resources recognizes grabs links images documents contacts recurring vocabulary phrases rss feeds converts structured unstructured data formatted tables exported spreadsheets databases first version released 2010 version 8.0 released june 2019 program includes mozilla-based browser side bar gives access number views pre-set extractors web pages textual documents broken different constituents presented tables views application navigate series links sequences search engine results pages extract information elements organize tables export various formats predefined extractors allow collect structured tables lists feeds custom scrapers also created extract data less structured page elements regular expressions included scrapers well parts application define variable recognition markers although outwit hub presented tool non-technical users fact application n't use document object model structure extractions prevents visual point grab data scraping forces user wants create custom scrapers define markers source code page advantage approach however allows precise definition extraction masks html nodes faster execution document object model tree n't need rendered browser extraction time program exists two versions standalone application mozilla firefox add-on include identical features limited free version downloaded publisher site shareware enterprise edition application includes advanced extraction automation features specific large volume extractions sending series automatically generated http post queries uploading scraped data ftp servers
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Web technology
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program segment prefix program segment prefix psp data structure used dos systems store state program resembles zero page cp/m operating system psp following structure psp often used get command line arguments dos program example command foo.exe /a /f executes foo.exe arguments '/a '/f segment address psp passed ds register program executed also determined later using int 21h function 51h int 21h function 62h either function return psp address register bx alternatively .com programs loaded offset 100h one address psp directly using offsets listed offset 000h points beginning psp 0ffh points end etc example following code displays command line arguments dos 1.x necessary cs code segment register contain segment psp program termination thus standard programming practice involved saving ds register stack program start since ds register loaded psp segment terminating program retf instruction would pop saved segment value stack jump address 0 psp contained int 20h instruction executable .com file procedure unnecessary program could terminated merely direct int 20h instruction else calling int 21h function 0 however programmer still ensure cs register contained segment address psp program termination thus dos 2.x higher program termination accomplished instead int 21h function 4ch require cs register contain segment value psp
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Operating systems
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powerpc e300 powerpc e300 family 32-bit powerpc microprocessor cores developed freescale primary use system-on-a-chip soc designs speed ranging 800 mhz thus making ideal embedded applications e300 superscalar risc core 16/16 32/32 kb l1 data/instruction caches four-stage pipeline load/store system register branch prediction integer unit optional double precision fpu e300 core completely backwards compatible g2 powerpc 603e cores derives e300 core cpu part several soc processors freescale
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Computer architecture
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uninitialized variable computing uninitialized variable variable declared set definite known value used value predictable one programming error common source bugs software common assumption made novice programmers variables set known value zero declared true many languages true potential error languages c use stack space variables collection variables allocated subroutine known stack frame computer set aside appropriate amount space stack frame usually simply adjusting value stack pointer set memory new state typically efficiency concerns therefore whatever contents memory time appear initial values variables occupy addresses simple example c final value codice_1 undefined answer must 10 assumes started zero may may true note example variable codice_2 initialized zero first clause codice_3 statement another example dealing structs code snippet codice_4 contains variables describing information student function codice_5 leaks memory fails fully initialize members codice_6 take closer look beginning codice_7 codice_8 codice_9 initialized initialization codice_10 codice_11 members incorrect length codice_10 codice_11 character arrays less 16 bytes codice_14 fail fully initialize entire 16 bytes memory reserved members hence codice_15'ing resulted struct codice_16 leak stack memory caller case even variable implicitly initialised default value like 0 typically correct value initialised mean correct value default one however default initialisation 0 right practice pointers arrays pointers since makes invalid actually initialised correct value c variables static storage duration initialized explicitly initialized zero null pointers uninitialized variables frequent cause bugs kind bug particularly serious may reproducible instance variable may remain uninitialised branch program cases programs uninitialized variables may even pass software tests uninitialized variables powerful bugs since exploited leak arbitrary memory achieve arbitrary memory overwrite gain code execution depending case exploiting software utilizes address space layout randomization often required know base address software memory exploiting uninitialized variable way force software leak pointer address space used bypass aslr uninitialized variables particular problem languages assembly language c c++ designed systems programming development languages involved design philosophy conflicts performance safety generally resolved favor performance programmer given burden aware dangerous issues uninitialized variables languages variables often initialized known values created examples include even languages uninitialized variables allowed many compilers attempt identify uninitialized variables report compile-time errors
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Programming language topics
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symbolic linguistic representation symbolic linguistic representation representation utterance uses symbols represent linguistic information utterance information phonetics phonology morphology syntax semantics symbolic linguistic representations different non-symbolic representations recordings use symbols represent linguistic information rather measurements typical kind symbolic linguistic representation phonetic transcription symbolic linguistic representations frequently used computational linguistics
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Computational linguistics
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security event manager security event management sem related sim siem computer security disciplines use data inspection tools centralize storage interpretation logs events generated software running network acronyms sem sim siem sometimes used interchangeably generally refer different primary focus products practice many products area mix functions often overlap – many commercial vendors also promote terminology many systems applications run computer network generate events kept event logs logs essentially lists activities occurred records new events appended end logs occur protocols syslog snmp used transport events occur logging software host events generated better sems provide flexible array supported communication protocols allow broadest range event collection beneficial send events centralized sem system following reasons although centralised logging existed long time sems relatively new idea pioneered 1999 small company called e-security still evolving rapidly key feature security event management tool ability analyse collected logs highlight events behaviors interest example administrator super user logon outside normal business hours may include attaching contextual information host information value owner location etc identity information user info related accounts referenced event like first/last name workforce id manager name etc forth contextual information leveraged provide better correlation reporting capabilities often referred meta-data products may also integrate external remediation ticketing workflow tools assist process incident resolution better sems provide flexible extensible set integration capabilities ensure sem work customer environments sems often sold help satisfy u.s. regulatory requirements sarbanes-oxley pci-dss glba one major problems sem space difficulty consistently analyzing event data every vendor indeed many cases different products one vendor uses different proprietary event data format delivery method even cases standard used part chain like syslog standards n't typically contain enough guidance assist developers generate events administrators gather correctly reliably consumers analyze effectively attempt combat problem couple parallel standardization efforts underway first open group updating circa 1997 xdas standard never made past draft status new effort dubbed xdas v2 attempt formalize event format including data included events expressed xdas v2 standard include event delivery standards standards development dmtf may provide wrapper addition mitre also midst standardization effort called cee somewhat broader scope – attempts define event structure well delivery methods
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Computer security
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macintosh lc ii macintosh lc ii personal computer designed manufactured sold apple computer inc. march 1992 march 1993 lc ii update original macintosh lc replacing motorola 68020 processor 68030 increasing onboard memory 4 mb lc ii priced 1,699 usd fully 800 less original lc introduced september 1992 apple introduced macintosh performa family consumer-oriented computers lc ii repackaged performa 400 lc ii replaced macintosh lc iii early 1993 lc ii discontinued north america two new performa models 405 430 introduced place october performa 400 405 430 discontinued new lc ii-based model called performa 410 introduced became apple new entry-level computer lc ii continued sold markets time lc ii apple highest-selling macintosh product 1992 lc ii retains original lc 16-bit system bus 10 mb ram limit making performance roughly earlier model main benefit 68030 processor lc ii onboard paged memory management unit system 7 uses enable new virtual memory feature apple opted get quick update lc door instead spending additional time required full architectural update happened following year macintosh lc iii lc ii sold time macintosh iisi 800 expensive lc ii 10 mb memory limit 16-bit data bus mono audio output iisi also includes nubus expansion slot lc ii lacks powered via button keyboard unlike lc range power switch back unit case lc ii retains predecessor pizza box form factor design updated lc ii production run auto-inject floppy drive substituted manual-inject unit revised front bezel longer featured horizontal indentation aligning floppy drive defining characteristic snow white design language logic board lc ii retains much original lc logic board design including 16-bit data path 10 mb memory limit limitations limited machine ability take full advantage 68030 cpu storage lc ii shipped one floppy drive standard options 40 80 mb hard drives original lc two internal floppy drive connectors lc ii one 5 lc units sold two floppy drives internal hard disks becoming common 1992 second connector removed video lc ii logic board one video ram slot filled 256 kb simm standard high-end configuration shipped 512 kb simm instead vram simms original lc supported lc ii upgrades apple sold 599 upgrade kit replaced lc ii logic board lc iii introduced march 23 1992 introduced september 4 1992 introduced april 12 1993 introduced october 18 1993
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Computer architecture
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libipq libipq development library iptables userspace packet queuing libipq provides api communicating ip_queue libipq deprecated favour newer libnetfilter_queue linux kernel-2.6.14 onwards libipq used widely deployed applications interface linux kernel-space iptables packet filter
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Operating systems
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comm100 comm100 comm100 network corporation provider customer service communication products products available saas software service company serves 200,000 businesses around globe company founded 3 july 2009 vancouver british columbia canada first product comm100 live chat introduced 5 august 2009 company reached 100,000 registered business users milestone april 2011 company products services offered free christmas 2011 may 2013 company joined m3aawg supporter 2013 comm100 silver winner best biz awards international year company provides suite business communication tools customer service marketing two popular products comm100 live chat live support software allows users track chat website visitors real time comm100 email marketing bulk email software helps users send opt-in email newsletters subscribers products developed microsoft technologies asp.net microsoft sql server iis internet information services etc
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Distributed computing architecture
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four horsemen infocalypse four horsemen infocalypse term internet criminals imagery internet criminals play four horsemen apocalypse refers types criminals use internet facilitate crime consequently jeopardize rights honest internet users appear exact definition horsemen usually described terrorists drug dealers pedophiles organized crime sources use slightly different descriptions generally refer types criminals term coined timothy c. may 1988 referred child pornographers terrorists drug dealers etc discussing reasons limited civilian use cryptography tools among famous cypherpunk faq states term seems used less often discussions online criminal activity often discussions negative chilling effects activity regular users daily experiences online also used frequently describe political tactic think children message mailing list states four supposed threats may used individually depending circumstances aj 2013 director safe internet league voluntary censorship group russia claimed pedophiles perverts drug dealers “ creeps ” using tor anonymity software reason software outlawed list mention terrorists money-launderers directly use catch-all phrase creeps potentially includes 2015 uk conservative party claimed proposed “ new communications data legislation strengthen ability disrupt terrorist plots criminal networks organised child grooming gangs ” echoing child pornographers terrorists drug dealers etc quote timothy c. may later 2015 gamma group released statement claiming surveillance technology used terrorist threats drug cartels major organised crime paedophile rings justification concerns used target opposition politicians media groups uganda money-laundering treated major organised crime quote matches closely list given cypherpunk faq
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Computer security
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automated essay scoring automated essay scoring aes use specialized computer programs assign grades essays written educational setting method educational assessment application natural language processing objective classify large set textual entities small number discrete categories corresponding possible grades—for example numbers 1 6 therefore considered problem statistical classification several factors contributed growing interest aes among cost accountability standards technology rising education costs led pressure hold educational system accountable results imposing standards advance information technology promises measure educational achievement reduced cost use aes high-stakes testing education generated significant backlash opponents pointing research computers yet grade writing accurately arguing use purposes promotes teaching writing reductive ways i.e teaching test historical summaries aes trace origins field work ellis batten page 1966 argued possibility scoring essays computer 1968 published successful work program called project essay grade™ peg™ using technology time computerized essay scoring would cost-effective page abated efforts two decades eventually page sold peg measurement incorporated 1990 desktop computers become powerful widespread aes practical possibility early 1982 unix program called writer workbench able offer punctuation spelling grammar advice collaboration several companies notably educational testing service page updated peg ran successful trials early 1990s peter foltz thomas landauer developed system using scoring engine called intelligent essay assessor™ iea iea first used score essays 1997 undergraduate courses product pearson educational technologies used scoring within number commercial products state national exams intellimetric® vantage learning aes engine development began 1996 first used commercially score essays 1998 educational testing service offers e-rater® automated essay scoring program first used commercially february 1999 jill burstein team leader development ets criterion online writing evaluation service uses e-rater engine provide scores targeted feedback lawrence rudner done work bayesian scoring developed system called betsy bayesian essay test scoring system results published print online commercial system incorporates betsy yet leadership howard mitzel sue lottridge pacific metrics developed constructed response automated scoring engine crase® currently utilized several state departments education u.s. department education-funded enhanced assessment grant pacific metrics ’ technology used large-scale formative summative assessment environments since 2007 measurement inc. acquired rights peg 2002 continued develop 2012 hewlett foundation sponsored competition kaggle called automated student assessment prize asap 201 challenge participants attempted predict using aes scores human raters would give thousands essays written eight different prompts intent demonstrate aes reliable human raters competition also hosted separate demonstration among 9 aes vendors subset asap data although investigators reported automated essay scoring reliable human scoring claim substantiated statistical tests vendors required tests performed precondition participation moreover claim hewlett study demonstrated aes reliable human raters since strongly contested including randy e. bennett norman o. frederiksen chair assessment innovation educational testing service major criticisms study five eight datasets consisted paragraphs rather essays four eight data sets graded human readers content rather writing ability rather measuring human readers aes machines true score average two readers scores study employed artificial construct resolved score four datasets consisted higher two human scores disagreement last practice particular gave machines unfair advantage allowing round datasets beginning basic procedure aes start training set essays carefully hand-scored program evaluates surface features text essay total number words number subordinate clauses ratio uppercase lowercase letters—quantities measured without human insight constructs mathematical model relates quantities scores essays received model applied calculate scores new essays recently one mathematical model created isaac persing vincent ng evaluates essays features also argument strength evaluates various features essay agreement level author reasons adherence prompt topic locations argument components major claim claim premise errors arguments cohesion arguments among various features contrast models mentioned model closer duplicating human insight grading essays various aes programs differ specific surface features measure many essays required training set significantly mathematical modeling technique early attempts used linear regression modern systems may use linear regression machine learning techniques often combination statistical techniques latent semantic analysis bayesian inference method assessment must judged validity fairness reliability instrument valid actually measures trait purports measure fair effect penalize privilege one class people reliable outcome repeatable even irrelevant external factors altered computers entered picture high-stakes essays typically given scores two trained human raters scores differed one point third experienced rater would settle disagreement system easy way measure reliability inter-rater agreement raters consistently agree within one point training may fault rater consistently disagrees whichever raters look essays rater probably needs training various statistics proposed measure inter-rater agreement among percent agreement scott π cohen κ krippendorf α pearson correlation coefficient r spearman rank correlation coefficient ρ lin concordance correlation coefficient percent agreement simple statistic applicable grading scales scores 1 n usually 4 ≤ n ≤ 6 reported three figures percent total number essays scored exact agreement two raters gave essay score adjacent agreement raters differed one point includes exact agreement extreme disagreement raters differed two points expert human graders found achieve exact agreement 53 81 essays adjacent agreement 97 100 inter-rater agreement applied measuring computer performance set essays given two human raters aes program computer-assigned scores agree one human raters well raters agree aes program considered reliable alternatively essay given true score taking average two human raters scores two humans computer compared basis agreement true score researchers reported aes systems fact better human page made claim peg 1994 scott elliot said 2003 intellimetric typically outperformed human scorers aes machines however appear less reliable human readers kind complex writing test current practice high-stakes assessments gmat always scored least one human aes used place second rater human rater resolves disagreements one point aes criticized various grounds yang et al mention overreliance surface features responses insensitivity content responses creativity vulnerability new types cheating test-taking strategies several critics concerned students motivation diminished know human read writing among telling critiques reports intentionally gibberish essays given high scores march 12 2013 humanreaders.org launched online petition professionals machine scoring student essays high-stakes assessment within weeks petition gained thousands signatures including noam chomsky cited number newspapers including new york times number education technology blogs petition describes use aes high-stakes testing trivial reductive inaccurate undiagnostic unfair secretive detailed summary research aes petition site notes research findings show one—students parents teachers employers administrators legislators—can rely machine scoring essays ... machine scoring measure therefore promote authentic acts writing petition specifically addresses use aes high-stakes testing says nothing possible uses resources automated essay scoring proprietary
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Computational linguistics
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postgresql postgresql also known postgres free open-source relational database management system rdbms emphasizing extensibility technical standards compliance designed handle range workloads single machines data warehouses web services many concurrent users default database macos server also available linux freebsd openbsd windows postgresql features transactions atomicity consistency isolation durability acid properties automatically updatable views materialized views triggers foreign keys stored procedures postgresql developed postgresql global development group diverse group many companies individual contributors postgresql developers pronounce postgresql abbreviated postgres ubiquitous support sql standard among relational databases originally named postgres name post ingres refers project origins rdbms originated university california berkeley review postgresql core team announced 2007 product would continue use name postgresql postgresql evolved ingres project university california berkeley 1982 leader ingres team michael stonebraker left berkeley make proprietary version ingres returned berkeley 1985 began post-ingres project address problems contemporary database systems become increasingly clear early 1980s turing award 2014 projects techniques pioneered new project postgres aimed add fewest features needed completely support data types features included ability define types fully describe relationships – something used widely maintained entirely user postgres database understood relationships could retrieve information related tables natural way using rules postgres used many ideas ingres code starting 1986 published papers described basis system prototype version shown 1988 acm sigmod conference team released version 1 small number users june 1989 followed version 2 re-written rules system june 1990 version 3 released 1991 re-wrote rules system added support multiple storage managers improved query engine 1993 number users began overwhelm project requests support features releasing version 4.2 june 30 1994 – primarily cleanup – project ended berkeley released postgres mit license variant enabled developers use code use time postgres used ingres-influenced postquel query language interpreter could interactively used console application named monitor 1994 berkeley graduate students andrew yu jolly chen replaced postquel query language interpreter one sql query language creating postgres95 monitor also replaced psql yu chen announced first version 0.01 beta testers may 5 1995 version 1.0 postgres95 announced september 5 1995 liberal license enabled software freely modifiable july 8 1996 marc fournier hub.org networking services provided first non-university development server open-source development effort participation bruce momjian vadim b. mikheev work began stabilize code inherited berkeley 1996 project renamed postgresql reflect support sql online presence website postgresql.org began october 22 1996 first postgresql release formed version 6.0 january 29 1997 since developers volunteers around world maintained software postgresql global development group project continues make releases available free open-source software postgresql license code comes contributions proprietary vendors support companies open-source programmers postgresql manages concurrency multiversion concurrency control mvcc gives transaction snapshot database allowing changes made without affecting transactions largely eliminates need read locks ensures database maintains acid principles postgresql offers three levels transaction isolation read committed repeatable read serializable postgresql immune dirty reads requesting read uncommitted transaction isolation level provides read committed instead postgresql supports full serializability via serializable snapshot isolation ssi method postgresql includes built-in binary replication based shipping changes write-ahead logs wal replica nodes asynchronously ability run read-only queries replicated nodes allows splitting read traffic among multiple nodes efficiently earlier replication software allowed similar read scaling normally relied adding replication triggers master increasing load postgresql includes built-in synchronous replication ensures write transaction master waits least one replica node written data transaction log unlike database systems durability transaction whether asynchronous synchronous specified per-database per-user per-session even per-transaction useful workloads require guarantees may wanted data slow performance due requirement confirmation transaction reaching synchronous standby standby servers synchronous asynchronous synchronous standby servers specified configuration determines servers candidates synchronous replication first list actively streaming used current synchronous server fails system fails next line synchronous multi-master replication included postgresql core postgres-xc based postgresql provides scalable synchronous multi-master replication licensed license postgresql related project called postgres-xl postgres-r yet another fork bidirectional replication bdr asynchronous multi-master replication system postgresql tools repmgr make managing replication clusters easier several asynchronous trigger-based replication packages available remain useful even introduction expanded core abilities situations binary replication full database cluster inappropriate postgresql includes built-in support regular b-tree hash table indexes four index access methods generalized search trees gist generalized inverted indexes gin space-partitioned gist sp-gist block range indexes brin addition user-defined index methods created although quite involved process indexes postgresql also support following features postgresql schema holds objects except roles tablespaces schemas effectively act like namespaces allowing objects name co-exist database default newly created databases schema called public schemas added public schema n't mandatory setting determines order postgresql checks schemas unqualified objects without prefixed schema default set refers currently connected database user default set database role level session parameter freely changed even multiple times client session affecting session non-existent schemas listed search_path silently skipped objects lookup new objects created whichever valid schema one presently exists appears first search_path.schema outline database wide variety native data types supported including addition users create data types usually made fully indexable via postgresql indexing infrastructures – gist gin sp-gist examples include geographic information system gis data types postgis project postgresql also data type called domain data type optional constraints defined creator domain means data entered column using domain conform whichever constraints defined part domain data type represents range data used called range types discrete ranges e.g integer values 1 10 continuous ranges e.g. time 10:00 11:00 built-in range types available include ranges integers big integers decimal numbers time stamps without time zone dates custom range types created make new types ranges available ip address ranges using inet type base float ranges using float data type base range types support inclusive exclusive range boundaries using characters respectively e.g. represents integers starting including 4 including 9 range types also compatible existing operators used check overlap containment right etc new types almost objects inside database created including tables set inherit characteristics parent table data child tables appear exist parent tables unless data selected parent table using keyword i.e adding column parent table cause column appear child table inheritance used implement table partitioning using either triggers rules direct inserts parent table proper child tables feature fully supported yet – particular table constraints currently inheritable check constraints not-null constraints parent table automatically inherited children types constraints unique primary key foreign key constraints inherited inheritance provides way map features generalization hierarchies depicted entity relationship diagrams erds directly postgresql database postgresql link systems retrieve data via foreign data wrappers fdws take form data source file system another relational database management system rdbms web service means regular database queries use data sources like regular tables even join multiple data-sources together postgresql several interfaces available also widely supported among programming language libraries built-in interfaces include libpq postgresql official c application interface ecpg embedded c system external interfaces include procedural languages allow developers extend database custom subroutines functions often called stored procedures functions used build database triggers functions invoked modification certain data custom data types aggregate functions procedural languages also invoked without defining function using command sql level languages divided two groups procedures written safe languages sandboxed safely created used user procedures written unsafe languages created superusers allow bypassing database security restrictions also access sources external database languages like perl provide safe unsafe versions postgresql built-in support three procedural languages addition postgresql allows procedural languages loaded database extensions three language extensions included postgresql support perl python tcl external projects add support many languages including java javascript pl/v8 r ruby others triggers events triggered action sql data manipulation language dml statements example insert statement might activate trigger checks values statement valid triggers activated either insert update statements triggers fully supported attached tables triggers per-column conditional update triggers target specific columns table triggers told execute set conditions specified trigger clause triggers attached views using instead condition multiple triggers fired alphabetical order addition calling functions written native pl/pgsql triggers also invoke functions written languages like pl/python pl/perl postgresql provides asynchronous messaging system accessed notify listen unlisten commands session issue notify command along user-specified channel optional payload mark particular event occurring sessions able detect events issuing listen command listen particular channel functionality used wide variety purposes letting sessions know table updated separate applications detect particular action performed system prevents need continuous polling applications see anything yet changed reducing unnecessary overhead notifications fully transactional messages sent transaction sent committed eliminates problem messages sent action performed rolled back many connectors postgresql provide support notification system including libpq jdbc npgsql psycopg node.js used external applications rules allow query tree incoming query rewritten query re-write rules attached table/class re-write incoming dml select insert update and/or delete one queries either replace original dml statement execute addition query re-write occurs dml statement parsing query planning postgresql server process-based threaded uses one operating system process per database session multiple sessions automatically spread across available cpus operating system starting postgresql 9.6 many types queries also parallelized across multiple background worker processes taking advantage multiple cpus cores client applications use threads create multiple database connections thread postgresql manages internal security per-role basis role generally regarded user role log group role roles members permissions granted revoked object column level also allow/prevent creation new objects database schema table levels postgresql security label feature extension sql standards allows additional security bundled loadable module supports label-based mandatory access control mac based security-enhanced linux selinux security policy postgresql natively supports broad number external authentication mechanisms including gssapi sspi kerberos peer ident certificate methods also use specified map file lists users matched authentication system allowed connect specific database user methods specified cluster host-based authentication configuration file pg_hba.conf determines connections allowed allows control user connect database connect ip address ip address range domain socket authentication system enforced whether connection must use transport layer security tls postgresql claims high complete conformance sql standard one exception handling unquoted identifiers like table column names postgresql folded – internal – lower case characters whereas standard says unquoted identifiers folded upper case thus equivalent according standard many informal performance studies postgresql done performance improvements aimed improving scalability began heavily version 8.1 simple benchmarks version 8.0 version 8.4 showed latter 10 times faster read-only workloads least 7.5 times faster read write workloads first industry-standard peer-validated benchmark completed june 2007 using sun java system application server proprietary version glassfish 9.0 platform edition ultrasparc t1-based sun fire server postgresql 8.2 result 778.14 specjappserver2004 jops standard compares favourably 874 jops standard oracle 10 itanium-based hp-ux system august 2007 sun submitted improved benchmark score 813.73 specjappserver2004 jops standard system test reduced price price/performance improved 84.98/jops 70.57/jops default configuration postgresql uses small amount dedicated memory performance-critical purposes caching database blocks sorting limitation primarily older operating systems required kernel changes allow allocating large blocks shared memory postgresql.org provides advice basic recommended performance practice wiki april 2012 robert haas enterprisedb demonstrated postgresql 9.2 linear cpu scalability using server 64 cores matloob khushi performed benchmarking postgresql 9.0 mysql 5.6.15 ability process genomic data performance analysis found postgresql extracts overlapping genomic regions eight times faster mysql using two datasets 80,000 forming random human dna regions insertion data uploads postgresql also better although general searching ability databases almost equivalent postgresql available following operating systems linux recent distributions windows windows 2000 sp4 later compilable e.g visual studio recent 2017 version freebsd openbsd netbsd macos os x aix hp-ux solaris unixware officially tested dragonfly bsd bsd/os irix openindiana opensolaris openserver tru64 unix unix-like systems could also work modern support postgresql works following instruction set architectures x86 x86-64 windows operating systems supported windows ia-64 itanium external support hp-ux powerpc powerpc 64 s/390 s/390x sparc sparc 64 armv8-a 64-bit older arm 32-bit including older armv6 raspberry pi mips mipsel pa-risc also known work alpha dropped 9.5 m68k m32r ns32k vax beyond possible build postgresql unsupported cpu disabling spinlocks open source front-ends tools administering postgresql include number companies offer proprietary tools postgresql often consist universal core adapted various specific database products tools mostly share administration features open source tools offer improvements data modeling importing exporting reporting notable organizations products use postgresql primary database include notable vendors offer postgresql software service
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Databases
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macintosh 128k macintosh 128k originally released apple macintosh original apple macintosh personal computer beige case consisted crt monitor came keyboard mouse handle built top case made easier computer lifted carried initial selling price 2,495 macintosh introduced now-famous 370,000 television commercial ridley scott 1984 aired cbs third quarter super bowl xviii january 22 1984 sales macintosh strong initial release january 24 1984 reached 70,000 units may 3 1984 upon release successor macintosh 512k rebranded macintosh 128k computer model number heart computer motorola 68000 microprocessor running connected 128 kb ram shared processor display controller boot procedure operating system routines contained additional rom chip apple offer ram upgrades unlike apple ii source code listings macintosh system roms offered ram macintosh consisted sixteen 4164 64k×1 drams 68000 video controller took turns accessing dram every four cpu cycles display frame buffer 68000 unrestricted access dram vertical horizontal blanking intervals arrangement reduced overall performance cpu much 35 code display logic often blocked cpu access ram caused computer run slower several competitors despite nominally high clock rate mac 128s 512s commonly equipped micron-branded 4164 ram chips cost reasons however micron quality control poor chips common failure point built-in display one-bit black-and-white crt fixed resolution 512×342 pixels establishing desktop publishing standard 72 ppi expansion networking achieved using two non-standard rs-422 de-9 serial ports named printer modem support hardware handshaking external floppy disk drive could added using proprietary connector 19-pin d-sub keyboard mouse used simple proprietary protocols allowing third-party upgrades original keyboard arrow keys numeric keypad function keys intentional decision apple keys common older platforms thought addition keys would encourage software developers simply port existing applications mac rather design new ones around gui paradigm later apple would make numeric keypad available macintosh 128k keyboard sold newer macintosh plus model would include numeric keypad arrow keys still function keys apple lisa mouse single button standard headphones could also connected monaural jack apple also offered 300 1200 bit/s modems originally released apple ii line initially printer available apple imagewriter dot matrix printer designed produce 144 dpi wysiwyg output mac 72 dpi screen eventually laserwriter printers capable connected using appletalk apple built-in networking system macintosh contained single 400 kb single-sided -inch floppy disk drive dedicating space internal mechanical storage mac os disk-based beginning ram conserved startup disk could still temporarily ejected ejecting root filesystem remained unusual feature classic mac os system 7 one floppy disk sufficient store system software application data files created application indeed 400 kb drive capacity larger pc xt 360 kb 5.25-inch drive however sophisticated work environments time required separate disks documents system installation due memory constraints 128 kb original macintosh fact floppies could hold 400 kb users frequently swap disks floppy drive reason external floppy drives frequently used macintosh external disk drive mechanically identical internal one piggybacking controller popular add-on us 495 third-party hard drives considerably expensive usually connected slower serial port specified apple though manufacturers chose use faster nonstandard floppy port 128k use original macintosh file system storage unit include fan relying instead convection cooling made quiet operation steve jobs insisted macintosh ship without fan persisted introduction macintosh se 1987 allegedly source many common costly component failures first four macintosh models enough problem prompt introduction third-party external cooling fan fan unit fitted inside macintosh carrying-handle slot produced forced draft computer existing ventilation holes macintosh shipped first system finder application known public system 1.0 formally known system 0.97 finder 1.0 original macintosh saw three upgrades discontinued apple recommends system 2.0 finder 4.2 system 3.2 finder 5.3 maximum system 4.0 officially dropped support macintosh 128k distributed 800 kb floppy disks could used 128k applications macpaint macwrite bundled mac programs available included macproject macterminal microsoft word programming languages available time included macbasic macpascal macintosh 68000 development system macintosh also came manual unique guided tour cassette tape worked together guided tour diskette tutorial macintosh bundled applications since new macintosh users never used mouse much less manipulated graphical user interface computer released january 1984 simply apple macintosh following release macintosh 512k september expanded memory 128 kb 512 kb original macintosh re-branded macintosh 128k nicknamed thin mac new 512k model nicknamed fat mac functionally closed systems macintosh macintosh 128k technically two different computers re-badged 128k containing completely redesigned logic board easily accommodate 128 kb 512 kb ram configurations manufacturing though ram still permanently soldered logic board new design allowed easier though unsanctioned third-party upgrades 512 kb addition newer models contained 1984 revision b rom accommodate changes 400 kb floppy disk drive system software contains support unreleased macintosh 256k increased ram 512k vitally important macintosh finally allowed powerful software applications then-popular program microsoft multiplan however apple continued market 128k year entry-level computer mid-level 512k high-end lisa claiming could easily expanded user ever need ram jobs stated customization really mostly software ... options computers mac unlike apple ii macintosh 128k need slots described costly requiring larger size power upgradable user apple service centers permitted open case accessories external maccharlie added ibm pc compatibility provision adding internal storage ram upgrade cards however macintosh engineers objected jobs ideas secretly developed workarounds example macintosh supposed 17 address lines motherboard enough support 128k system ram design team added additional two address lines without jobs knowledge making possible expand computer 512k although actual act upgrading system ram difficult required piggybacking additional ram chips overtop onboard 4164 chips september 1984 months complaints mac inadequate ram apple released official 512k machine although always planned beginning steve jobs maintained user desired ram mac 128 provided simply pay extra money mac 512 rather upgrade computer mac 512 released apple rebranded original model macintosh 128k modified motherboard allow easier ram upgrades improving hard-wired ram thus required motherboard replacement priced similarly new computer third-party chip replacement upgrade expensive would void apple warranty difficulty fitting software limited free memory coupled new interface event driven programming model discouraged software vendors supporting leaving 128k relatively small software library whereas macintosh plus lesser extent macintosh 512k compatible much later software 128k limited specially crafted programs stock mac 128k original 64k rom neither compatible apple external 800 kb drive hfs apple hard disk 20 mac 128k upgraded newer 128k rom called macintosh 128ke use internal external 800 kb drives hfs well hd20 print appleshare network neither file sharing limited ram early 1985 much macintosh software required 512k memory apple sold official memory upgrade macintosh 128k included motherboard replacement effectively making macintosh 512k price us 995 additionally apple offered 800 kb floppy disk drive kit including updated 128k roms finally mac 128k could upgraded macintosh plus swapping logic board well case back accommodate slightly different port configuration optionally adding macintosh plus extended keyboard kits could purchased alone together time partial full upgrade macintosh 128k upgrades required performed professional apple technicians reportedly refused work macintosh upgraded 512k without apple official upgrade us 700 much expensive 300 third-party versions original macintosh unusual included signatures macintosh division early 1982 molded inside case names peggy alexio colette askeland bill atkinson steve balog bob belleville mike boich bill bull matt carter berry cash debi coleman george crow donn denman christopher espinosa bill fernandez martin haeberli andy hertzfeld joanna hoffman rod holt bruce horn hap horn brian howard steve jobs larry kenyon patti king daniel kottke angeline lo ivan mach jerrold manock mary ellen mccammon vicki milledge mike murray ron nicholson jr. terry oyama benjamin pang jef raskin ed riddle brian robertson dave roots patricia sharp burrell smith bryan stearns lynn takahashi guy bud tribble randy wigginton linda wilkin steve wozniak pamela wyman laszlo zidek macintosh 128/512k models also included easter eggs os rom user went system debugger typed codice_1 graphic reading stolen apple computers would appear upper left corner screen designed prevent unauthorized cloning macintosh numerous apple ii clones appeared many simply stole apple copyrighted system roms steve jobs allegedly planned macintosh clone appeared market court case happened could access easter egg computer prove using pirated macintosh roms macintosh se would later augment easter egg slideshow 4 photos apple design team codice_2 entered erik sandberg-diment new york times january 1984 stated macintosh presages revolution personal computing although preferring larger screens calling lack color mistake praised refreshingly crisp clear display lack fan noise unsure whether would become second standard big blue ronald rosenberg boston globe wrote february euphoria macintosh change america computes anyone tries pint-size machine gets hooked features gregg williams byte month found hardware software design predicted would imitated copied impressive criticized lack standard second disk drive predicted computer would popularize 3½-inch floppy disk drive standard macintosh would improve apple reputation delay ibm domination personal computer market williams concluded macintosh important development computers last five years brings us one step closer ideal computer appliance follow-up article may 1984 issue byte williams added initial reaction macintosh strongly overpoweringly favorable traditional computer users see mouse windows desktop metaphor silly useless frills others outraged lack color graphics users impressed machine capabilities still people expressed concern relatively small 128k-byte ram size lack computer language sent part basic unit inconvenience single disk drive jerry pournelle also byte added macintosh bargain get heavily discounted price offered faculty students favored 24 universities macintosh consortium noted however macintosh attracted people previously hated computers ... apparently something mice pull-down menus icons appeal people previously intimidated like
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Computer architecture
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t.37 t.37 itu standard deals sending fax messages using email also referred ifax internet fax store-forward-fax fax machine supporting t.37 send fax email address converting document tiff-f image attaching email using mime format sending document using smtp destination fax receives email prints attached document interface regular fax machines
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Internet protocols
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gnome ranger gnome ranger text adventure game level 9 released 1987 followed sequel titled ingrid back gnome ingrid bottomlow displeased family un-gnomelike behaviour going university getting education teleported village faulty scroll must find way back.. game standard text adventure limited graphics platforms comes short novella peter mcbride gnettlefield journal explaining ingrid predicament setting background story gameplay similar earlier level 9 adventure knight orc uses game engine kaos player must explore settings collecting useful items interacting various non-player characters solve puzzles problems game takes place three areas characterized non-player characters ingrid meet first contains characters animal nature second vegetable nature third mineral nature
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Computer architecture
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millicode computer architecture millicode higher level microcode used implement instruction set computer millicode runs top microcoded instructions uses instructions implement complex instructions visible user system implementation millicode requires special processor mode called millimode provides set registers possibly special instructions invisible user ibm invented concept term millicode system/390 9672-g4 processor 1997 following cited advantages millicode i370 code capitol chipset used es/9370 models similar millicode written combination system/370 instructions code access special hardware features
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Computer architecture
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macintosh 512k macintosh 512k personal computer designed manufactured sold apple computer inc. september 1984 april 1986 first update original macintosh 128k virtually identical previous macintosh differing primarily amount built-in random-access memory increased memory turned macintosh business-capable computer gained ability run software mac 512k originally shipped macintosh system 1.1 able run versions mac os system 4.1 replaced macintosh 512ke macintosh plus support mac 512k discontinued september 1 1998 like macintosh 128k 512k contained motorola 68000 connected 512 kb dram 16-bit data bus though memory quadrupled could upgraded large increase earned nickname fat mac 64 kb rom chip boosts effective memory 576 kb offset display 22 kb framebuffer shared dma video controller shared arrangement reduces cpu performance 35 shared revised logic board re-badged macintosh 128k previously called macintosh streamlined manufacturing resolution display 512x342 apple sold memory upgrade macintosh 128k 995 initially reduced price 256k dram prices fell months later applications macpaint macwrite still bundled mac soon model released several applications became available including macdraw macproject macintosh pascal others particular microsoft excel written specifically macintosh required minimum 512 kb ram solidified macintosh serious business computer models enhanced rom also supported apple switcher allowing cooperative multitasking among necessarily applications laserwriter printer became available shortly 512k introduction well number pad mic tablet keyboard mouse basic mouse much utilized apple built-in networking scheme localtalk allows sharing devices among several users 512k oldest macintosh capable supporting apple appleshare built-in file sharing network introduced 1987 expanded memory 512k allowed better handle large word-processing documents make better use graphical user interface generally increased speed 128k model original 512k could accept macintosh system software version 4.1 system software 5 possible used hard disk 20 updated version replaced macintosh 512k debuted macintosh 512k enhanced april 1986 differed original 512k 800 kb floppy disk drive improved rom macintosh plus exception new model number m0001e otherwise cosmetically identical stock 512k could also use 800 kb floppy disk drive well hard disk 20 first hard disk manufactured apple exclusively use 512k required special system file required 512k e loaded improved rom code ram thus reducing available ram uses apple offered upgrade kit replaced floppy disk drive roms essentially turning 512k e one oem upgrade replaced logicboard rear case entirely macintosh plus original macintosh 512k designed slots upgrade boards hard-disk controller internal upgrades available 512k general computer us 2,795 hyperdrive hard drive plug directly 68000 processor socket upgrades included snap-on scsi cards ram upgrades 2 mb
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Computer architecture
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c dynamic memory allocation c dynamic memory allocation refers performing manual memory management dynamic memory allocation c programming language via group functions c standard library namely c++ programming language includes functions however operators provide similar functionality recommended language authors still myriad situations using codice_1 applicable garbage collection code performance-sensitive code combination codice_2 codice_3 may required instead higher-level codice_4 operator many different implementations actual memory allocation mechanism used available performance varies execution time required memory c programming language manages memory statically automatically dynamically static-duration variables allocated main memory usually along executable code program persist lifetime program automatic-duration variables allocated stack come go functions called return static-duration automatic-duration variables size allocation must compile-time constant except case variable-length automatic arrays required size known run-time example data arbitrary size read user disk file using fixed-size data objects inadequate lifetime allocated memory also cause concern neither static- automatic-duration memory adequate situations automatic-allocated data persist across multiple function calls static data persists life program whether needed many situations programmer requires greater flexibility managing lifetime allocated memory limitations avoided using dynamic memory allocation memory explicitly flexibly managed typically allocating free store informally called heap area memory structured purpose c library function codice_2 used allocate block memory heap program accesses block memory via pointer codice_2 returns memory longer needed pointer passed codice_7 deallocates memory used purposes platforms provide library calls allow run-time dynamic allocation c stack rather heap e.g codice_8 memory automatically freed calling function ends c dynamic memory allocation functions defined codice_9 header codice_10 header c++ creating array ten integers automatic scope straightforward c however size array fixed compile time one wishes allocate similar array dynamically following code used computes number bytes ten integers occupy memory requests many bytes codice_2 assigns result pointer named codice_19 due c syntax pointers arrays used interchangeably situations codice_2 might able service request might return null pointer good programming practice check program longer needs dynamic array must eventually call codice_7 return memory occupies free store memory set aside codice_2 initialized may contain cruft remnants previously used discarded data allocation codice_2 elements array uninitialized variables command codice_24 return allocation already cleared realloc resize amount memory pointer points example pointer acting array size formula_1 want change array size formula_2 use realloc note realloc must assumed changed base address block i.e failed extend size original block therefore allocated new larger block elsewhere copied old contents therefore pointers addresses within original block also longer valid codice_2 returns void pointer codice_26 indicates pointer region unknown data type use casting required c++ due strong type system whereas case c. lack specific pointer type returned codice_2 type-unsafe behaviour according programmers codice_2 allocates based byte count type different c++ new operator returns pointer whose type relies operand see c type safety one may cast see type conversion pointer specific type advantages disadvantages performing cast improper use dynamic memory allocation frequently source bugs include security bugs program crashes often due segmentation faults common errors follows implementation memory management depends greatly upon operating system architecture operating systems supply allocator malloc others supply functions control certain regions data dynamic memory allocator often used implement codice_2 operator codice_4 c++ implementation allocator commonly done using heap data segment allocator usually expand contract heap fulfill allocation requests heap method suffers inherent flaws stemming entirely fragmentation like method memory allocation heap become fragmented sections used unused memory allocated space heap good allocator attempt find unused area already allocated memory use resorting expanding heap major problem method heap two significant attributes base beginning heap virtual memory space length size heap requires enough system memory fill entire length base never change thus large areas unused memory wasted heap get stuck position small used segment exists end heap could waste amount address space lazy memory allocation schemes often found linux operating system large heap necessarily reserve equivalent system memory first write time reads non-mapped memory pages return zero granularity depends page size doug lea developed dlmalloc doug lea malloc general-purpose allocator starting 1987 gnu c library glibc uses ptmalloc allocator based dlmalloc memory heap allocated chunks 8-byte aligned data structure contains header usable memory allocated memory contains 8 16 byte overhead size chunk usage flags unallocated chunks also store pointers free chunks usable space area making minimum chunk size 16 bytes 32-bit systems 24/32 depends alignment bytes 64-bit systems unallocated memory grouped bins similar sizes implemented using double-linked list chunks pointers stored unallocated space inside chunk requests 256 bytes smallbin request simple two power best fit allocator used free blocks bin block next highest bin split two requests 256 bytes mmap threshold recent versions dlmalloc use in-place bitwise trie algorithm free space left satisfy request dlmalloc tries increase size heap usually via brk system call requests mmap threshold largebin request memory always allocated using mmap system call threshold usually 256 kb mmap method averts problems huge buffers trapping small allocation end expiration always allocates entire page memory many architectures 4096 bytes size since freebsd 7.0 netbsd 5.0 old codice_2 implementation phkmalloc replaced jemalloc written jason evans main reason lack scalability phkmalloc terms multithreading order avoid lock contention jemalloc uses separate arenas cpu experiments measuring number allocations per second multithreading application shown makes scale linearly number threads phkmalloc dlmalloc performance inversely proportional number threads openbsd implementation codice_2 function makes use mmap requests greater size one page entire allocation retrieved using codice_52 smaller sizes assigned memory pools maintained codice_2 within number bucket pages also allocated codice_52 call codice_7 memory released unmapped process address space using codice_56 system designed improve security taking advantage address space layout randomization gap page features implemented part openbsd codice_52 system call detect use-after-free bugs—as large memory allocation completely unmapped freed use causes segmentation fault termination program hoard allocator whose goal scalable memory allocation performance like openbsd allocator hoard uses codice_52 exclusively manages memory chunks 64 kilobytes called superblocks hoard heap logically divided single global heap number per-processor heaps addition thread-local cache hold limited number superblocks allocating superblocks local per-thread per-processor heap moving mostly-empty superblocks global heap reused processors hoard keeps fragmentation low achieving near linear scalability number threads every thread local storage small allocations large allocations mmap sbrk used tcmalloc malloc developed google garbage-collection local storage dead threads tcmalloc considered twice fast glibc ptmalloc multithreaded programs operating system kernels need allocate memory application programs implementation codice_2 within kernel often differs significantly implementations used c libraries however example memory buffers might need conform special restrictions imposed dma memory allocation function might called interrupt context necessitates codice_2 implementation tightly integrated virtual memory subsystem operating system kernel codice_2 relatives strong impact performance program uncommon override functions specific application custom implementations optimized application allocation patterns c standard provides way operating systems found various ways exploiting dynamic linking one way simply link different library override symbols another employed unix system v.3 make codice_2 codice_7 function pointers application reset custom functions largest possible memory block codice_2 allocate depends host system particularly size physical memory operating system implementation theoretically largest number maximum value held codice_65 type implementation-dependent unsigned integer representing size area memory c99 standard later available codice_66 constant codice_67 although guaranteed iso c usually c library implementations shipping various operating systems compilers may come alternatives extensions standard codice_2 package notable among
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Operating systems
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light weight kernel threads light weight kernel threads lwkt computer science term dragonflybsd particular lwkts differ normal kernel threads preempt normal kernel threads according matt dillon dragonflybsd creator
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Operating systems
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big v telecom big v telecom indian cloud telephony company serves direct clients also works partnership network franchises company first incubated tata elxsi 2013 part 140 billion tata group based pune india big v telecom founded keshor daga 2008 flagship product yocc contact centre 2012 part company corporate social responsibility drive big v telecom established call anna virtual contact centre anti-corruption activist anna hazare indian anti-corruption movement 2012 big v telecom partnered western central railways providing 131 railway enquiry number firm also partnered bsnl providing value added services maharashtra august 2015 firm launched product named voter first propagated india first voter engagement issue resolution application custom built politicians interact constituents download android ios stores reports suggest voter first name sub-division big v telecom firm name appear app stores instead politician apps appear respective names picture identity mobile app firm past also partnered tv18 commoditycontrol.com providing on-spot updates commodity rates via phone calls consumers self-funded company recently announced looking venture capital funding expansion within outside india ndtv profit business services excellence award innovative franchise business service sector 2010 aegis graham bell award innovative managed services 2012 tata elxsi takes big v telecom incubator programme tata elxsi incubates big v telecom tata elxsi picks big v telecom first startup new incub te program tata elxsi sets business incubator cloud telephony firm big v telecom looking raise 6.5m funding big v telecom incubated tata elxsi expands footprints delhi/ncr big v telecom incubated tata elxsi expands footprints delhi/ncr big v telecom incubated tata elxsi expands footprints delhi/ncr
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Distributed computing architecture
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chinese national vulnerability database chinese national vulnerability database cnnvd people republic china nstional vulnerability database maintained chinese ministry state security
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Computer security
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ballerina programming language ballerina general-purpose programming language features optimized network distributed applications easy write modify suitable application programmers open source project started 2015 architects wso2 code-based alternative configuration-based integration tools eai esb workflow products ballerina various constructs geared toward cloud-native development including support modern data formats protocols reliability distributed transactions apis event streams simple hello world service depicted // start service navigate directory contains // .bal file execute ballerina run command import ballerina/http import ballerina/log service hello new http listener 9090 print “ hello world ” parallel using workers import ballerina/io public function main
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Programming language topics
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mohamed elnoby mohamed abdelbasset elnouby famous egyptian programmer information security specialist one famous white hat arabic hackers start point 2013 penetrated discovered vulnerabilitya facebook resulted website gave reward focused name many arabic global media channels paid big attention also discovered many vulnerabilities many famous global websites like google yahoo amazon adobe others honored effort plus adding name add value hall fame list white hat security experts 20 global websites founder member chief technonogy officer google business community upper egypt ex general moderator arabic version foursquare app facebook added name hall fame list white hat security experts 2013 2014 2015 2016 row born 1988 esna qena upper egypt graduated faculty tourism hotels elmenia university started working programming computer networks field since 1999 code name facebook symbiansymoh worked many organizations like s3geeks cooperated volunteering works like arabization famous social media website twitter also worked general moderator arabic version foursquare app working freelance programmer chief technonogy officer google business community upper egypt took first step penetration hacking others computers stealing accounts turned moral hacker call white hat hacker start point discovering vulnerability famous website facebook got financial reward plus adding name honor list white hat security experts continued discovering vulnerabilities till got 5 ones processes vulnerabilities discovery global websites continued till got 22 websites famous hunter vulnerabilities rewards
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Computer security
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memory protection memory protection way control memory access rights computer part modern instruction set architectures operating systems main purpose memory protection prevent process accessing memory allocated prevents bug malware within process affecting processes operating system protection may encompass accesses specified area memory write accesses attempts execute contents area attempt access unowned memory results hardware fault called segmentation fault storage violation exception generally causing abnormal termination offending process memory protection computer security includes additional techniques address space layout randomization executable space protection segmentation refers dividing computer memory segments reference memory location includes value identifies segment offset within segment x86 architecture multiple segmentation features helpful using protected memory architecture x86 architecture global descriptor table local descriptor tables used reference segments computer memory pointers memory segments x86 processors also stored processor segment registers initially x86 processors 4 segment registers cs code segment ss stack segment ds data segment es extra segment later another two segment registers added – fs gs paging memory address space divided equal-sized blocks called pages using virtual memory hardware page reside location computer physical memory flagged protected virtual memory makes possible linear virtual memory address space use access blocks fragmented physical memory address space computer architectures support paging also use pages basis memory protection page table maps virtual memory physical memory page table usually invisible process page tables make easier allocate additional memory new page allocated anywhere physical memory impossible application access page explicitly allocated every memory address either points page allocated application generates interrupt called page fault unallocated pages pages allocated application addresses application point view page fault may necessarily indicate error page faults used memory protection operating system may manage page table way reference page previously swapped disk causes page fault operating system intercepts page fault loads required memory page application continues fault occurred scheme known virtual memory allows in-memory data currently use moved disk storage back way transparent applications increase overall memory capacity systems page fault mechanism also used executable space protection w^x memory protection key mpk mechanism divides physical memory blocks particular size e.g. 4 kib associated numerical value called protection key process also protection key value associated memory access hardware checks current process protection key matches value associated memory block accessed exception occurs mechanism introduced system/360 architecture available today system z mainframes heavily used system z operating systems subsystems system/360 protection keys described associated physical addresses different protection key mechanism used architectures hewlett-packard/intel ia-64 hewlett-packard pa-risc associated virtual addresses allow multiple keys per process itanium pa architectures translations tlb entries keys itanium access ids pa associated running process several protection key registers 16 itanium 4 hp/pa translation selected virtual address key compared protection key registers match plus possible checks access permitted none match fault exception generated software fault handler desired check missing key larger list keys maintained software thus protection key registers inside processor may treated software-managed cache larger list keys associated process pa 15–18 bits key itanium mandates least 18 keys usually associated protection domains libraries modules etc x86 protection keys architecture allows tagging virtual addresses user pages 16 protection keys pages tagged protection key constitute protection domain new register contains permissions associated protection domain load store operations checked page table permissions protection key permissions associated protection domain virtual address allowed permissions allow access protection key permissions set user space allowing applications directly restrict access application data without os intervention since protection keys associated virtual address protection domains per address space processes running different address spaces use 16 domains simulation use monitoring program interpret machine code instructions computer architectures instruction set simulator provide memory protection using segmentation-like scheme validating target address length instruction real time actually executing simulator must calculate target address length compare list valid address ranges holds concerning thread environment dynamic memory blocks acquired since thread inception plus valid shared static memory slots meaning valid may change throughout thread life depending upon context may sometimes allowed alter static block storage sometimes depending upon current mode execution may may depend storage key supervisor state generally advisable use method memory protection adequate facilities exist cpu takes valuable processing power computer however generally used debugging testing purposes provide extra fine level granularity otherwise generic storage violations indicate precisely instruction attempting overwrite particular section storage may storage key unprotected storage capability-based addressing method memory protection unused modern commercial computers method pointers replaced protected objects called capabilities created using privileged instructions may executed kernel process authorized effectively lets kernel control processes may access objects memory need use separate address spaces context switches commercial products used capability based security plessey system 250 ibm system/38 intel iapx 432 architecture keykos capability approaches widely used research systems eros combex darpa browser used conceptually basis virtual machines notably smalltalk java currently darpa-funded cheri project university cambridge working create modern capability machine also supports legacy software dynamic tainting technique protecting programs illegal memory accesses memory allocated runtime technique taints memory corresponding pointer using taint mark taint marks suitably propagated program executes checked every time memory address accessed pointer p taint marks associated p differ execution stopped illegal access reported sparc m7 processors higher implement dynamic tainting hardware oracle markets feature silicon secured memory ssm previously branded application data integrity adi lowrisc cpu design includes dynamic tainting name tagged memory protection level particular implementation may measured closely adheres principle minimum privilege different operating systems use different forms memory protection separation although memory protection common mainframes many minicomputer systems 1960s true memory separation used home computer operating systems os/2 risc os released 1987 prior systems lack protection even used form interprocess communication sending pointer processes possible processes access system memory windows 9x family operating systems operating systems implement memory protection include unix-like systems codice_1 system call used control memory protection
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Operating systems
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lga 1150 lga 1150 also known socket h3 microprocessor socket used intel central processing units cpus built haswell microarchitecture socket also used haswell successor broadwell microarchitecture successor lga 1155 succeeded lga 1151 2016 motherboards lga 1150 socket support varying video outputs vga dvi hdmi depending model intel clear video technology intel platform controller hub pch lga 1150 cpus codenamed lynx point intel xeon processors socket lga 1150 use intel c222 c224 c226 chipsets 4 holes fastening heatsink motherboard placed square lateral length 75 mm intel sockets lga 1156 lga 1155 lga 1150 lga 1151 cooling solutions therefore interchangeable may 12 2014 intel announced release two 9-series chipsets h97 z97 differences new features two chipsets compared h87 z87 counterparts following motherboards based h97 z97 chipsets available purchase day chipsets announced
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Computer architecture
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