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series 90 software platform series 90 formerly hildon platform mobile phones uses symbian os developed nokia collaboration psion released 2003 going platform nokia 7700 cancelled eventually make market nokia 7710 nokia discontinued series 90 platform merged technology s60 although one production series 90 device made form gui continued nokia hildon user interface maemo shipped nokia internet tablets series 90 completely incompatible series 60 s60 uiq popular platforms symbian smartphones however applications nokia series 80 communicator devices – nokia 9300 – function series 90 essentially series 90 development psion eikon gui used series 5 series 5mx revo netpad series 7 netbook machines modified controlled entirely touchscreen supplemented 77x0 seven hardware buttons rocker-dial nokia 7700 never released on-screen keyboard text input 7710 added basic handwriting recognition applications single menu tree accessible title bar top screen exit quit option apps button bar added right hand side screen resembling nokia communicator smartphones
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Operating systems
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fast virtual disk fast virtual disk better known fvd virtualization-oriented disk image file format developed ibm qemu virtualization platform differs existing paravirtualization-centric virtual disk image formats design emphasizes lack contention separation concerns host guest kernels duduplication filesystem block layer storage management fvd written either directly physical logical blockstore avoiding host filesystem overheads regular host file system file strives maintain similarity raw disk layouts eliminate host filesystem disk image compression overheads minimize metadata-related overheads
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Computer file systems
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cleancode email cleancode email also known cleancode email simply email simple command line software utility sending smtp email portable enough compile run linux os x bsd solaris cygwin perhaps unix-like operating systems upon installing cleancode email codice_1 executable binary becomes available program offers features sending email via smtp supports smtp auth via login plain mechanisms mime attachments address book encryption transport via tls message via pgp digital signatures via pgp easily used sending email command line via shell scripts software packages lack modern features helps cleancode email stand fast efficient helpful tool system administrators unix-like environments intentional purpose first developed cleancode email started september 2001 currently still maintained developed original author dean jones
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Internet protocols
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spread toolkit spread toolkit computer software package provides high performance group communication system resilient faults across local wide area networks spread functions unified message bus distributed applications provides highly tuned application-level multicast group communication point point support spread services range reliable messaging fully ordered messages delivery guarantees toolkit consists messaging server client libraries many software development environments including c/c++ libraries without thread support java class used applets applications interfaces perl python ruby interfaces many software environments provided third parties typical operation computer cluster runs instance spread server client applications connect locally server process spread servers turn communicate pass messages subscriber applications also configured clients distributed across network communicate spread server process one host spread toolkit developed spread concepts llc much support distributed systems networks lab dsn johns hopkins university experimental networked systems lab george washington university partial funding provided defense advanced research projects agency darpa national security agency nsa bindings spread toolkit exist many languages platforms
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Distributed computing architecture
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synack synack american technology company based redwood city california synack ’ business includes vulnerability intelligence platform automates discovery exploitable vulnerabilities reconnaissance turns company ’ freelance hackers create vulnerability reports clients synack founded 2013 former nsa agents jay kaplan mark kuhr synack uses network freelance security analysts hackers 50 countries check vulnerability security problems synack also developed hydra platform built spot vulnerabilities look out-of-date software clients first form hydra went live october 21 2015 april 24 2014 company announced secured series funding kleiner perkins caufield byers google ventures allegis capital derek smith shape security february 2015 company raised 25 million series b funding april 11 2017 reported synack raised 21 million microsoft ventures hewlett packard enterprise singtel prior investors ggv capital gv kleiner perkins caufield byers also took part funding round bringing total money raised company 55 million since founding april 11 2017 company 100 employees well growing network freelance hackers cnbc named synack cnbc disruptor company three times row 2015 2017
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Computer security
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avnu alliance avnu alliance consortium professional automotive consumer electronics industrial manufacturing companies working together establish certify interoperability open audio video bridging avb time-sensitive networking tsn standards alliance works member companies certify avb tsn products interoperability manufacturers may use avnu logo certified products every avb-compliant device submitted certification avnu alliance lack avnu logo necessarily imply device incompatible avnu-certified devices institute electrical electronics engineers ieee formed 1963 merger american institute electrical engineers founded 1884 institute radio engineers founded 1912 two organizations merged rise electronics many interests beginning overlap 1980 ieee started project 802 create standards local area network lan applications 1985 802.3 became official standard ethernet cable-based data transmission system originally developed xerox 1970s audio video bridging name given set technical standards developed ieee audio video bridging task group ieee 802.1 standards committee committee developed original technical standards avb way simplify audio video streaming use ethernet cable rather complicated approach traditionally taken using array analog one-way single-purpose point-to-point cables avnu alliance launched august 25 2009 create certification processes based avb standards would ensure interoperability founding members include broadcom cisco systems harman international intel xilinx august 2013 alliance includes 60 members worldwide represent cross-section companies 2012 avnu alliance announced formation avnu automotive avb gen2 council aaa2c committee automotive industry experts collectively identify automotive requirements future development second generation avb standards april 2013 forum launched avnu alliance broadcast advisory council aabac assess improve avb requirements broadcast industry created participation avnu alliance members network technologists broadcasters aabac also intends promote use avb broadcast applications avnu alliance chairman president rick kreifeldt harman international avnu alliance invites industry companies participate collaborate efforts improve audio/video quality members create broad array products including cars semiconductors loudspeakers consoles microphones 2012 avnu alliance created single set open standards avb uses certify devices guarantee interoperability since january 2012 avnu alliance worked test house university new hampshire interoperability laboratory unh-iol test interoperability provide validation certified products avnu certification testing officially began unh-iol february 2013 unh-iol neutral independent testing service works audio/video industry consortiums including ethernet alliance wi-fi alliance ipv6 forum provide third-party verification lower costs collaborative testing help guide industry acceptance technology standard technology ecosystem supporting accelerating development avnu certified products matured include standards-compliant silicon devices fpga ip open-source software also 3rd-party avb certification services coveloz avb certification service product submitted avnu alliance certification tested 400 pages conformance requirements combine ieee 802.1 standard requirements additional requirements developed avnu issues product may reported manufacturer fixing outstanding issues manufacturer submit product avnu official approval permission use avnu certification logo product accompanying marketing efforts february 2014 avnu alliance announced first certified products series avb switches extreme networks passed conformance tests bear avnu-certified logo extreme networks summit x440 series stackable switches extend benefits extremexos software intended professional av applications allowing data audio video co-exist single standards-based network avnu alliance goal make easier implement network systems promoting adoption ieee 802.1 1722 1733 avb standards automotive professional consumer electronics markets ensuring avb products different manufacturers would able interconnect seamlessly along ensuring interoperability adoption ieee 802.1 related ieee 1722 ieee 1733 avb standards various networks would reduce technical issues synching glitches delays improving content streaming capabilities alliance industry standards improved ethernet technology making simpler add enhanced performance capabilities audio/video networks bringing costs using lighter cheaper cable easier set able carry larger amount information regularly used networking environments 2018 avnu alliance announced milan initiative define implementation details media formats clocking redundancy device control provide certification testing program ensure devices different vendors interoperable within common device profiles milan specification based following ieee standards specification requires media clocking based ieee 1722 crf clock reference format sample rate 48 khz optionally 96 192 khz audio stream format based ieee 1722 32-bit standard aaf audio format 8 channels per stream optionally 24 32 bit high capacity format 56 64 channels redundancy providedcwith two independent logical networks every endpoint seamless switchover mechanism avdecc defines operations discover device addition removal retrieve device entity model connect disconnect streams manage device connection status remote control devices alliance members represent variety facets automotive technology growing complexity in-vehicle audio/video systems increasing number in-vehicle applications infotainment safety multiple cameras testing ensure interoperability increasingly important automotive market automotive systems multiple applications require interoperability work properly 2013 avnu alliance works genivi alliance jaspar alliance standardize in-vehicle ethernet requirements ieee avb task group developed series enhancements provide highly-reliable delivery low latency synchronized audio video technology enables construction affordable high performance professional media networks ieee avb task force developed improvements ethernet order improve audio/video networking avnu certifies avb products ensure interoperability video interoperability specifications pro market currently development meyer sound noted adopting avnu alliance ethernet standards assist development first avb-capable loudspeaker named cal stands column array loudspeaker completed 2013 improvements ethernet developed ieee avb task force also benefit desiring distribute digital content among multiple devices home networks 2013 avnu alliance began establish testing requirements avb interoperability specifications reliable time-synced av streaming ethernet wireless networks residential applications
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Computer architecture
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sasl programming language sasl st andrews static language alternatively st andrews standard language purely functional programming language developed david turner university st andrews 1972 based applicative subset iswim 1976 turner redesigned reimplemented non-strict lazy language form foundation turner later languages krc miranda sasl appears untyped whereas miranda polymorphic types burroughs corporation used sasl write compiler operating system
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Programming language topics
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location-based authentication location-based authentication special procedure prove individual identity authenticity appearance simply detecting presence distinct location enable location-based authentication special combination objects required basic requirement safe location-based authentication well defined separation locations well equally well defined proximity applying individual location offered technical solution simple location-based authentication includes method limiting granted access presence hence terminating granted authentication leave defines mandate either include new additional procedure
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Computer security
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apache axis apache axis apache extensible interaction system open-source xml based web service framework consists java c++ implementation soap server various utilities apis generating deploying web service applications using apache axis developers create interoperable distributed computing applications axis development takes place auspices apache software foundation using java version axis two ways expose java code web service easiest one use axis native jws java web service files another way use custom deployment custom deployment enables customize resources exposed web services see also apache axis2 jws files contain java class source code exposed web service main difference ordinary java file jws file file extension another difference jws files deployed source code compiled class files following example expose methods add subtract class calculator axis servlet deployed need copy jws file axis directory server work using apache tomcat container case using another web container custom war archive creation required jws web service accessible using url nowiki http //localhost:8080/axis/calculator.jws /nowiki running custom configuration apache tomcat different container url might different custom web service deployment requires specific deployment descriptor called wsdd web service deployment descriptor syntax used specify resources exposed web services current version 1.3 supports web service exposed using axis generate wsdl file automatically accessing web service url wsdl appended example implementing deploying simple web-service c++ version axis found axis-cpp tutorial link reference section steps necessary information individual steps go directly tutorial
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Web technology
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flapjax flapjax programming language built atop javascript provides spreadsheet-like dataflow computation style functional reactive programming making easy create reactive web pages without burden callbacks potentially inconsistent mutation flapjax thought two ways either library use regular javascript programs new language compiler converts generic javascript either case resulting programs run regular web browser addition flapjax comes persistent storage simple api masks complexity using ajax along sharing access-control server data flapjax compiler written haskell
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Programming language topics
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lexra lexra semiconductor intellectual property core company based waltham massachusetts founded 1997 began developing licensing semiconductor intellectual property cores implemented mips architecture except four unaligned load store lwl lwr swl swr instructions lexra implement instructions necessary good performance modern software silicon graphics owned patent originally granted mips computer systems inc. implementing unaligned loads stores risc processor lexra wish pay high license fee permission use patent lexra licensed soft cores unlike arm ltd time lexra probably first semiconductor intellectual property core company 1998 silicon graphics spun mips technologies inc. semiconductor ip licensing company would compete directly lexra mips technologies sued lexra claiming trademark infringement lexra claims compatibility mips i. lexra mips technologies settled dispute agreeing public statements lexra would clearly state implement unaligned loads stores 1999 mips technologies sued lexra time infringing patents unaligned loads stores though lexra processor designs implement unaligned loads stores possible emulate functionality unaligned loads stores long series instructions opinion lexra ability emulate function unaligned loads stores software predated grant patent question could viewed infringement hardware patent reasonable interpretation also much earlier mips technologies processor ibm mainframes supported unaligned memory operations earlier ibm processors unaligned memory operations partial access registers available microcode instruction set architecture aspects earlier ibm processors posed much greater threat patent invalidation mips technologies compared seemingly vacuous mips technologies infringement claim lexra protracted second lawsuit combined downturn semiconductor industry business forced lexra settlement mips technologies included mips technologies paying lexra large sum money granting lexra license technologies exchange lexra exiting ip business lexra failed networking communications fabless semiconductor chip company ceased operations january 2003 5.5 years lexra implemented ten processor designs licensed nine ip cores lexra first lexra also enhanced mips architecture extensions greatly enhanced performance digital signal processing dsp algorithms
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Computer architecture
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self-signed certificate cryptography computer security self-signed certificate identity certificate signed entity whose identity certifies term nothing identity person organization actually performed signing procedure technical terms self-signed certificate one signed private key typical public key infrastructure pki arrangements digital signature certificate authority ca attests particular public key certificate valid ca one root keys certificates associated public keys trust anchors use special type self-signed certificates establishing trust ca root certificate dependent upon procedures beyond checking digital signature ca based pki system ca must trusted parties usually accomplished placing ca certificates whitelist trusted certificates example web browsers developers may use procedures specified ca/browser forum private ca certificate may placed firmware embedded system trust issues entity accepting new self-signed certificate similar issues entity trusting addition new ca certificate parties self-signed pki must establish trust using procedures outside pki confirm accurate transfer public keys e.g compare hash band many subtle differences ca signed self-signed certificates especially amount trust placed security assertions certificate cas verify identity person issue certificate example us military issues common access cards person multiple forms id ca attest identity values like including signed certificate entity validates certificate trust information certificate extent trust ca signed implication security procedures ca used verify attested information self-signed certificate contrast trust values certificate complicated entity possesses signing key always generate new certificate different values example validity dates self-signed certificate might trusted entity could always create sign new certificate contained valid date range values self-signed certificate trusted following conditions true values out-of-band verified self-signed formally trusted method verify self-signed certificate changed trusted example procedure trusting self-signed certificate includes manual verification validity dates hash certificate incorporated white list certificate presented entity validate first verify hash certificate matches reference hash white-list match indicating self-signed certificate one formally trusted certificate validity dates trusted special treatment x.509 certificate fields self-signed certificate found rfc 3280 least two reasons self-signed certificate based pki may decreased overall risk first also shared private pki systems avoid problems trusting third parties may improperly sign certificates self-signed certificate transactions usually present far smaller attack surface eliminating complex certificate chain validation ca revocation checks like crl ocsp revocation self-signed certificates differs ca signed certificates self-signed certificate nature revoked ca revocation self-signed certificate accomplished removing whitelist trusted certificates essentially revoking trust ca failure revoke self-signed certificate may allow attacker already gained access monitor inject data connection spoof identity private key compromised cost self-signed certificates created free using wide variety tools including openssl java keytool adobe reader apple keychain certificates bought major cas often cost around hundred dollars per year december 2015 mozilla foundation launched let encrypt allows one obtain domain-validated certificate free speed deploy self-signed certificates require two parties interact e.g securely trade public keys using ca requires ca certificate holder interact holder public key validate authenticity ca root certificate customization self-signed certificates easier customize example larger key size contained data metadata etc
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Computer security
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pre-play attack field security engineering pre-play attack cryptographic attack attacker prepares attack advance carrying simulated transaction pretending device attacked repeats attack second time real device time likely carry series operations simulation technique relies able guess content transaction advance something usually made possible poor choice unpredictability within system name play replay attack pre-play attacks effective chances success slim
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Computer security
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source command codice_1 unix command evaluates file following command list commands executed current context frequently current context terminal window user typing commands interactive session source command abbreviated dot codice_2 bash similar posix-ish shells however acceptable c shell command first appeared bash scripts run using codice_3 syntax rather run executable command e.g. contain change directory codice_4 command user intends left directory script complete contain export command user wants modify environment current shell another usage situation script file execute permission passing script filename desired shell run script subshell current context
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Operating systems
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commonloops commonloops common lisp object-oriented programming system acronym reminiscent earlier lisp oo system loops interlisp-d system early programming language extended common lisp include object-oriented programming functionality dynamic object system differs oop facilities found static languages c++ java like new flavors commonloops supported multiple inheritance generic functions method combination commonloops also supported multi-methods made use metaobjects commonloops new flavors primary ancestors clos commonloops supported portable implementation known portable commonloops pcl ran common lisp implementations day
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Programming language topics
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time-based authentication time-based authentication special procedure prove individual identity authenticity appearance simply detecting presence scheduled time day within scheduled time interval distinct location enable time-based authentication special combination objects required makes sense define starting time time span without constraints location granting access known without defining distinct location access shall granted basic requirement safe time based authentication well defined separation locations well equally well defined proximity applying individual location
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Computer security
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motorola 68000 motorola 68000 'sixty-eight-thousand also called m68k motorola 68k sixty-eight-kay 16/32-bit cisc microprocessor introduced 1979 motorola semiconductor products sector design implements 32-bit instruction set 32-bit registers 32-bit internal data bus address bus 24-bits use memory segmentation made popular programmers internally uses 16-bit data alu two additional 16-bit alus used mostly addresses 16-bit external data bus reason motorola referred 16/32-bit processor one first widely available processors 32-bit instruction set running relatively high speeds era 68k popular design 1980s widely used new generation personal computers graphical user interfaces including apple macintosh commodore amiga atari st many others competed primarily intel 8088 found ibm pc easily outperformed 68k 8088 pushed designs like zilog z8000 niche markets made motorola major player cpu space 68k soon expanded additional family members implementing full 32-bit alus part growing motorola 68000 series original 68k generally software forward-compatible rest line despite limited 16-bit wide external bus 40 years production 68000 architecture still use motorola first widely-produced cpu motorola 6800 although capable design eclipsed powerful designs like zilog z80 less powerful faster designs like mos 6502 sales prospects 6800 dimmed motorola began totally new design replace became motorola advanced computer system silicon project macss begun 1976 macss aimed develop entirely new architecture without backward compatibility 6800 ultimately retain bus protocol compatibility mode existing 6800 peripheral devices version 8-bit data bus produced however designers mainly focused future forward compatibility gave 68000 design head start later 32-bit instruction set architectures instance cpu registers 32 bits wide though self-contained structures processor operate 32 bits time macss team drew heavily influence minicomputer processor design pdp-11 vax systems similarly microcode-based mid 1970s 8-bit microprocessor manufacturers raced introduce 16-bit generation national semiconductor first imp-16 pace processors 1973–1975 issues speed intel worked advanced 16/32-bit intel iapx 432 alias 8800 since 1975 intel 8086 since 1976 introduced 1978 became really widespread form almost identical 8088 ibm pc years later arriving late 16-bit arena afforded new processor transistors roughly 40,000 active versus 20,000 active 8086 32-bit macroinstructions acclaimed general ease use original mc68000 fabricated using hmos process 3.5 µm feature size formally introduced september 1979 initial samples released february 1980 production chips available counter november initial speed grades 4 6 8 mhz 10 mhz chips became available 1981 12.5 mhz chips june 1982 16.67 mhz 12f version mc68000 fastest version original hmos chip produced late 1980s 68k instruction set particularly well suited implement unix 68000 successors became dominant cpus unix-based workstations including sun workstations apollo/domain workstations 68000 also used mass-market computers apple lisa macintosh amiga atari st 68000 used microsoft xenix systems well early netware unix-based server 68000 used first generation desktop laser printers including original apple inc. laserwriter hp laserjet 1982 68000 received minor update isa support virtual memory conform popek goldberg virtualization requirements updated chip called 68010 also added new loop mode sped small loops increased overall performance 10 clock speeds extended version exposed 31 bits address bus also produced small quantities 68012 support lower-cost systems control applications smaller memory sizes motorola introduced 8-bit compatible mc68008 also 1982 68000 8-bit data bus smaller 20-bit address bus 1982 motorola devoted attention 68020 88000 projects several companies second-source manufacturers hmos 68000 included hitachi hd68000 shrank feature size 2.7 µm 12.5 mhz version mostek mk68000 rockwell r68000 signetics scn68000 thomson/sgs-thomson originally ef68000 later ts68000 toshiba tmp68000 toshiba also second-source maker cmos 68hc000 tmp68hc000 encrypted variants 68000 hitachi fd1089 fd1094 store decryption keys opcodes opcode data battery-backed memory used certain sega arcade systems including system 16 prevent piracy illegal bootleg games 68hc000 first cmos version 68000 designed hitachi jointly introduced 1985 motorola version called mc68hc000 hitachi hd68hc000 68hc000 eventually offered speeds 8–20 mhz except using cmos circuitry behaved identically hmos mc68000 change cmos greatly reduced power consumption original hmos mc68000 consumed around 1.35 watts ambient temperature 25 °c regardless clock speed mc68hc000 consumed 0.13 watts 8 mhz 0.38 watts 20 mhz unlike cmos circuits hmos still draws power idle power consumption varies little clock rate apple selected 68hc000 use macintosh portable motorola replaced mc68008 mc68hc001 1990 chip resembled 68hc000 respects data bus could operate either 16-bit 8-bit mode depending value input pin reset thus like 68008 could used systems cheaper 8-bit memories later evolution 68000 focused modern embedded control applications on-chip peripherals 68ec000 chip scm68000 core expanded address bus 32 bits removed m6800 peripheral bus excluded move sr instruction user mode programs 1996 motorola updated standalone core fully static circuitry drawing 2 µw low-power mode calling mc68sec000 motorola ceased production hmos mc68000 mc68008 1996 spin-off company freescale semiconductor still producing mc68hc000 mc68hc001 mc68ec000 mc68sec000 well mc68302 mc68306 microcontrollers later versions dragonball family 68000 architectural descendants 680x0 cpu32 coldfire families also still production recently sendai fab closure 68hc000 68020 68030 68882 parts discontinued leaving 68sec000 production succeeded true 32-bit microprocessors 68000 used core many microcontrollers 1989 motorola introduced mc68302 communications processor introduction 68000 first used high-priced systems including multiuser microcomputers like wicat 150 early alpha microsystems computers sage ii iv tandy trs-80 model 16 single-user workstations hewlett-packard hp 9000 series 200 systems first apollo/domain systems sun microsystems sun-1 corvus concept graphics terminals like digital equipment corporation vaxstation 100 silicon graphics iris 1000 1200 unix systems rapidly moved capable later generations 68k line remained popular market throughout 1980s mid-1980s falling production cost made 68000 viable use personal home computers starting apple lisa macintosh followed commodore amiga atari st sharp x68000 hand sinclair ql microcomputer commercially important utilisation 68008 along derivatives icl one per desk business terminal helix systems missouri united states designed extension swtpc ss-50 bus ss-64 produced systems built around 68008 processor adoption risc x86 displaced 68000 series desktop/workstation cpu processor found substantial use embedded applications early 1980s quantities 68000 cpus could purchased less 30 usd per part video game manufacturers used 68000 backbone many arcade games home game consoles atari food fight 1982 one first 68000-based arcade games others included sega system 16 capcom cp system cps-2 snk neo geo late 1980s 68000 inexpensive enough power home game consoles sega mega drive/genesis console also sega cd attachment sega cd system three cpus two 68000s 1993 multi-processor atari jaguar console used 68000 support chip although developers used primary processor due familiarity 1994 multi-processor sega saturn console used 68000 sound co-processor much mega drive/genesis uses z80 co-processor sound and/or purposes certain arcade games steel gunner others based namco system 2 use dual 68000 cpu configuration systems triple 68000 cpu configuration also exist galaxy force others based sega board along quad 68000 cpu configuration used jaleco one 68000 sound lower clock rate compared 68000 cpus games big run cisco heat fifth 68000 different clock rate compared 68000 cpus additionally used jaleco arcade game wild pilot i/o processing 68000 also saw great success embedded controller early 1981 laser printers imagen imprint-10 controlled external boards equipped 68000 first hp laserjet—introduced 1984—came built-in 8 mhz 68000 printer manufacturers adopted 68000 including apple introduction laserwriter 1985 first postscript laser printer 68000 continued widely used printers throughout rest 1980s persisting well 1990s low-end printers 68000 also saw success field industrial control systems among systems benefited 68000 derivative microprocessor families programmable logic controllers plcs manufactured allen-bradley texas instruments subsequently following acquisition division ti siemens users systems accept product obsolescence rate domestic users entirely likely despite installed 20 years ago many 68000-based controllers continue reliable service well 21st century number digital oscilloscopes 80s 68000 used waveform display processor models including lecroy 9400/9400a also use 68000 waveform math processor including addition subtraction multiplication division two waveforms/references/waveform memories digital oscilloscopes using 68000 including 9400/9400a also perform fft functions waveform 683xx microcontrollers based 68000 architecture used networking telecom equipment television set-top boxes laboratory medical instruments even handheld calculators mc68302 derivatives used many telecom products cisco 3com ascend marconi cyclades others past models palm pdas handspring visor used dragonball derivative 68000 alphasmart uses dragonball family later versions portable word processors texas instruments uses 68000 high-end graphing calculators ti-89 ti-92 series voyage 200 early versions used specialized microcontroller static 68ec000 core later versions use standard mc68sec000 processor modified version 68000 formed basis ibm xt/370 hardware emulator system 370 processor 68000 24-bit external address bus two byte-select signals replaced a0 24 lines therefore address 16 mb physical memory byte resolution address storage computation uses 32 bits internally however 8 high-order address bits ignored due physical lack device pins allows run software written logically flat 32-bit address space accessing 24-bit physical address space motorola intent internal 32-bit address space forward compatibility making feasible write 68000 software would take full advantage later 32-bit implementations 68000 instruction set however prevent programmers writing forward incompatible software 24-bit software discarded upper address byte used purposes addressing could fail 32-bit 68000 implementations example early pre-7.0 versions apple mac os used high byte memory-block master pointers hold flags locked purgeable later versions os moved flags nearby location apple began shipping computers 32-bit clean roms beginning release 1989 mac iici 68000 family stores multi-byte integers memory big-endian order cpu eight 32-bit general-purpose data registers d0-d7 eight address registers a0-a7 last address register stack pointer assemblers accept label sp equivalent a7 good number registers time many ways small enough allow 68000 respond quickly interrupts even worst case 8 data registers d0–d7 7 address registers a0–a6 needed saved 15 registers total yet large enough make calculations fast could done entirely within processor without keeping partial results memory note exception routine supervisor mode also save user stack pointer a7 would total 8 address registers however dual stack pointer a7 supervisor-mode a7 design 68000 makes normally unnecessary except task switch performed multitasking system two types registers mildly annoying times hard use practice reportedly allowed cpu designers achieve higher degree parallelism using auxiliary execution unit address registers 68000 comparison arithmetic logic operations set bit flags status register record results use later conditional jumps bit flags zero z carry c overflow v extend x negative n extend x flag deserves special mention separate carry flag permits extra bit arithmetic logic shift operations separated carry flow-of-control linkage designers attempted make assembly language orthogonal instructions divided operations address modes almost address modes available almost instructions 56 instructions minimum instruction size 16 bits many instructions addressing modes longer include additional address mode bits cpu later whole family implements two levels privilege user mode gives access everything except privileged instructions interrupt level controls supervisor privilege gives access everything interrupt always becomes supervisory supervisor bit stored status register visible user programs advantage system supervisor level separate stack pointer permits multitasking system use small stacks tasks designers allocate memory required hold stack frames maximum stack-up interrupts cpu recognizes seven interrupt levels levels 1 5 strictly prioritized higher-numbered interrupt always interrupt lower-numbered interrupt status register privileged instruction allows one set current minimum interrupt level blocking lower equal priority interrupts example interrupt level status register set 3 higher levels 4 7 cause exception level 7 level triggered non-maskable interrupt nmi level 1 interrupted higher level level 0 means interrupt level stored status register visible user-level programs hardware interrupts signalled cpu using three inputs encode highest pending interrupt priority separate encoder usually required encode interrupts though systems require three hardware interrupts possible connect interrupt signals directly encoded inputs cost additional software complexity interrupt controller simple 74ls148 priority encoder may part vlsi peripheral chip mc68901 multi-function peripheral used atari st range computers sharp x68000 also provided uart timer parallel i/o exception table interrupt vector table interrupt vector addresses fixed addresses 0 1023 permitting 256 32-bit vectors first vector reset consists two vectors namely starting stack address starting code address vectors 3 15 used report various errors bus error address error illegal instruction zero division chk chk2 vector privilege violation block privilege escalation reserved vectors became line 1010 emulator line 1111 emulator hardware breakpoint vector 24 starts real interrupts spurious interrupt hardware acknowledgement level 1 level 7 autovectors 16 trap vectors reserved vectors user defined vectors since minimum starting code address vector must always valid reset systems commonly included nonvolatile memory e.g rom starting address zero contain vectors bootstrap code however general purpose system desirable operating system able change vectors runtime often accomplished either pointing vectors rom jump table ram use bank switching allow rom replaced ram runtime 68000 meet popek goldberg virtualization requirements full processor virtualization single unprivileged instruction move sr allows user-mode software read-only access small amount privileged state 68000 also unable easily support virtual memory requires ability trap recover failed memory access 68000 provide bus error exception used trap save enough processor state resume faulted instruction operating system handled exception several companies succeed making 68000-based unix workstations virtual memory worked using two 68000 chips running parallel different phased clocks leading 68000 encountered bad memory access extra hardware would interrupt main 68000 prevent also encountering bad memory access interrupt routine would handle virtual memory functions restart leading 68000 correct state continue properly synchronized operation main 68000 returned interrupt problems fixed next major revision 68k architecture release mc68010 bus error address error exceptions push large amount internal state onto supervisor stack order facilitate recovery move sr instruction made privileged new unprivileged move ccr instruction provided use place user mode software operating system trap emulate user-mode move sr instructions desired standard addressing modes plus access status register later models special registers instructions dot-letter suffixes permitting operations occur 8-bit bytes .b 16-bit words .w 32-bit longs .l like many cpus era cycle timing instructions varied depending source operand example unsigned multiply instruction takes 38+2n clock cycles complete n equal number bits set operand create function took fixed cycle count required addition extra code multiply instruction would typically consume extra cycles bit n't set original multiplication operand instructions dyadic operation source destination destination changed notable instructions 68ec000 low-cost version 68000 slightly different pinout designed embedded controller applications 68ec000 either 8-bit 16-bit data bus switchable reset processors available variety speeds including 8 16 mhz configurations producing 2,100 4,376 dhrystones processors floating-point unit difficult implement fpu coprocessor mc68881/2 one ec series lacks necessary coprocessor instructions 68ec000 used controller many audio applications including ensoniq musical instruments sound cards part midi synthesizer ensoniq sound boards controller provided several advantages compared competitors without cpu board processor allowed board configured perform various audio tasks mpu-401 midi synthesis mt-32 emulation without use tsr program improved software compatibility lowered cpu usage eliminated host system memory usage motorola 68ec000 core later used m68k-based dragonball processors motorola/freescale also used sound controller sega saturn game console controller hp jetdirect ethernet controller boards mid-1990s laserjet printers 68000 assembly code subroutine named copies null-terminated string 8-bit characters destination string converting alphabetic characters lower case subroutine establishes call frame using register a6 frame pointer kind calling convention supports reentrant recursive code typically used languages like c c++ subroutine retrieves parameters passed stack loops reading ascii character single byte string checking whether capital alphabetic character converting lower-case character otherwise leaving writing character string finally checks whether character null character repeats loop otherwise restores previous stack frame a6 register returns note string pointers registers a0 a1 auto-incremented iteration loop contrast code stand-alone function even restrictive version ams ti-89 series calculators kernel-independent values looked tables files libraries executing system calls exception processing minimal registers used need save valid historical julian dates 1 march 1 ad gregorian ones less two dozen operations calculates day number compatible iso 8601 called three inputs stored corresponding locations
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Computer architecture
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ultrasparc iii ultrasparc iii code-named cheetah microprocessor implements sparc v9 instruction set architecture isa developed sun microsystems fabricated texas instruments introduced 2001 operates 600 900 mhz succeeded ultrasparc iv 2004 gary lauterbach chief architect presented '97 microprocessor forum probable introduction date ultrasparc iii 1999 would competed digital equipment corporation alpha 21264 intel itanium merced case delayed 2001 despite late awarded analysts choice award best server/workstation processor 2001 microprocessor report multiprocessing features ultrasparc iii in-order superscalar microprocessor ultrasparc iii designed shared memory multiprocessing performance several features aid achieving goal integrated memory controller dedicated multiprocessing bus fetches four instructions per cycle instruction cache decoded instructions sent dispatch unit six time dispatch unit issues instructions appropriate execution units depending operand resource availability execution resources consisted two arithmetic logic units alus load store unit two floating-point units one alus execute simple integer instructions loads two floating point units also equal one execute simple instructions adds executes multiplies divides square roots ultrasparc iii split primary instruction data caches instruction cache capacity 32 kb data cache capacity 64 kb four-way set-associative 32-byte cache line external l2 cache maximum capacity 8 mb accessed via dedicated 256-bit bus operating 200 mhz peak bandwidth 6.4 gb/s cache built synchronous static random access memory clocked frequencies 200 mhz l2 cache tags located on-die enable clocked microprocessor clock frequency increases bandwidth accessing cache tags enabling ultrasparc scale higher clock frequencies easily part increased bandwidth cache tags used cache coherency traffic required multiprocessor systems ultrasparc iii designed used maximum capacity l2 cache 8 mb l2 cache tags 90 kb size external interface consists 128-bit data bus 43-bit address bus operating 150 mhz data bus used access memory memory microprocessors shared i/o devices ultrasparc integrated memory controller implements dedicated 128-bit bus operating 150 mhz access 4 gb local memory integrated memory controller used reduce latency thus improve performance unlike ultrasparc microprocessors use feature reduce cost ultrasparc iii consisted 16 million transistors 75 contained caches tags initially fabricated texas instruments c07a process complementary metal–oxide–semiconductor cmos process 0.18 µm feature size six-levels aluminium interconnect 2001 fabricated 0.13 µm process aluminium interconnects enabled operate 750 900 mhz die packaged using controlled collapse chip connection method first sun microprocessor unlike microprocessors bonded way majority solder bumps placed peripheral ring instead distributed across die packaged 1,200-pad land grid array lga package ultrasparc iii cu code-named cheetah+ development original ultrasparc iii operated higher clock frequencies 1002 1200 mhz die size 232 mm fabricated 0.13 µm 7-layer copper metallization cmos process texas instruments packaged 1,368-pad ceramic lga package ultrasparc iiii code named jalapeno derivative ultrasparc iii workstations low-end one four processor servers introduced 2003 operates 1064 1593 mhz on-die l2 cache integrated memory controller capable four-way multiprocessing glue-less system bus optimized function contains 87.5 million transistors 178.5 mm die fabricated texas instruments 0.13 µm seven-layer metal copper cmos process low-k dielectric ultrasparc iiii unified 1 mb l2 cache operates half microprocessor clock frequency six-cycle latency two-cycle throughput load use latency 15 cycles tag store protected parity data ecc every 64-byte cache line 36 ecc bits enabling correction one-bit errors detection error within four bits cache four-way set-associative 64-byte line size physically indexed tagged uses 2.76 µm sram cell consists 63 million transistors on-die memory controller supports 256 mb 16 gb 133 mhz ddr-i sdram memory accessed via 137-bit memory bus 128 bits data 9 ecc memory bus peak bandwidth 4.2 gb/s microprocessor designed support four-way multiprocessing jbus used connect four microprocessors 128-bit address data multiplexed bus operates one half one third microprocessor clock frequency ultrasparc iiii+ code-named serrano development ultrasparc iiii scheduled introduction second half 2005 cancelled year favor ultrasparc iv+ ultrasparc t1 ultrasparc t2 cancellation known 31 august 2006 improvements higher clock frequencies range 2ghz larger 4mb on-die l2 cache support ddr-333 sdram new 90nm process ultrasparc iii family processors succeeded ultrasparc iv series ultrasparc iv combined two ultrasparc iii cores onto single piece silicon offered increased clock rates cpu packaging nearly identical offering difference single pin simplifying board manufacturing system design systems used ultrasparc iii processors could accept ultrasparc iv cpu board upgrades
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Computer architecture
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telephony service provider telephony service provider defined microsoft tapi specification software interface physical telephony device modem accessed programmatically perform actions dialing phone number logging call tsps thought tapi specific driver telephony device example windows 10 supplies
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Operating systems
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execute direct access program ibm mainframe operating systems execute direct access program xdap pseudo access method accessing direct access datasets block block basis xdap specifically described os system programmer guide existing blocks may read updated dataset may created extended using xdap purpose true access method required xdap may coexist bsam bpam several os components implemented way programmer responsible computing full direct access block identifier mbbcchhr system algorithms available calculating mbbcchhr ttrn system data form track capacity tables available calculating ttrn block number direct access device type later versions os facilitate accessing large capacity devices using trkaddr macro list execute forms xdap supported whereby prototype form called list form expanded data functional form called execute form expanded instructions xdap also supported conventionally case two forms combined expanded inline data instructions use list execute forms facilitates development re-enterable programs xdap results excp supervisor call executed hence execute channel program excp implicitly embedded within xdap iob sole parameter excp included data structure within xdap macro expansion channel command words xdap must reference opened dcb full direct access identifier dcb may opened input output input output inout outputs must update writes existing blocks xdap support format writes bsam bpam available executing format writes writes add new blocks dataset i.e initial additional block particularly final block iobspsvc flag logically iob sam pam svc flag available causes sequential access methods appendages bypassed enhancement first implemented svs retrofitted previous versions os significantly facilitated processing dataset already opened bsam bpam using xdap otherwise certain pre-svs sam pam appendages could cause random supervisor storage overlays presented certain xdap channel programs ibm guarantee system security data integrity pre-svs systems obvious circumvention utilize xdap channel programs also utilize rps rps-type xdap channel programs confusing sam pam appendages thereby leading random supervisor storage overlays
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Operating systems
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inline expansion computing inline expansion inlining manual compiler optimization replaces function call site body called function inline expansion similar macro expansion occurs compilation without changing source code text macro expansion occurs prior compilation results different text processed compiler inlining important optimization complicated effects performance rule thumb inlining improve speed minor cost space excess inlining hurt speed due inlined code consuming much instruction cache also cost significant space survey modest academic literature inlining 1980s 1990s given jones marlow 1999 inline expansion similar macro expansion compiler places new copy function place called inlined functions run little faster normal functions function-calling-overheads saved however memory penalty function inlined 10 times 10 copies function inserted code hence inlining best small functions called often c++ member functions class defined within class definition inlined default need use inline keyword otherwise keyword needed compiler may ignore programmer ’ attempt inline function mainly particularly large inline expansion used eliminate time overhead excess time function called typically used functions execute frequently also space benefit small functions enabling transformation optimizations without inline functions compiler decides functions inline programmer little control functions inlined giving degree control programmer allows use application-specific knowledge choosing functions inline ordinarily function invoked control transferred definition branch call instruction inlining control drops directly code function without branch call instruction compilers usually implement statements inlining loop conditions loop bodies need lazy evaluation property fulfilled code compute loop conditions loop bodies inlined performance considerations another reason inline statements context functional programming languages inline expansion usually followed beta-reduction transformation programmer might inline function manually copy paste programming one-time operation source code however methods controlling inlining see preferable precipitate bugs arising programmer overlooks possibly modified duplicated version original function body fixing bug inlined function direct effect optimization improve time performance eliminating call overhead cost worsening space usage due duplicating function body code expansion due duplicating function body dominates except simple cases thus direct effect inline expansion improve time cost space however primary benefit inline expansion allow optimizations improved scheduling due increasing size function body better optimization possible larger functions ultimate impact inline expansion speed complicated due multiple effects performance memory system primarily instruction cache dominates performance modern processors depending specific program cache inlining particular functions increase decrease performance impact inlining varies programming language program due different degrees abstraction lower-level imperative languages c fortran typically 10–20 speed boost minor impact code size abstract languages significantly important due number layers inlining removes extreme example self one compiler saw improvement factors 4 55 inlining direct benefits eliminating function call primary benefit inlining however optimizations allows optimizations cross function boundaries done without requiring interprocedural optimization ipo inlining performed additional intra procedural optimizations global optimizations become possible enlarged function body example done without inlining require significantly complicated compiler linker case caller callee separate compilation units conversely cases language specification may allow program make additional assumptions arguments procedures longer make procedure inlined preventing optimizations smarter compilers glasgow haskell compiler track naive inlining loses information benefit inlining memory system direct cost inlining increased code size due duplicating function body call site however always namely case short functions function body smaller size function call caller including argument return value handling trivial accessor methods mutator methods getters setters function used one place case duplicated thus inlining may minimized eliminated optimizing code size often case embedded systems inlining also imposes cost performance due code expansion due duplication hurting instruction cache performance significant prior expansion working set program hot section code fit one level memory hierarchy e.g. l1 cache expansion longer fits resulting frequent cache misses level due significant difference performance different levels hierarchy hurts performance considerably highest level result increased page faults catastrophic performance degradation due thrashing program failing run last rare common desktop server applications code size small relative available memory issue resource-constrained environments embedded systems one way mitigate problem split functions smaller hot inline path fast path larger cold non-inline path slow path inlining hurting performance primarily problem large functions used many places break-even point beyond inlining reduces performance difficult determine depends general precise load subject manual optimization profile-guided optimization similar issue code expanding optimizations loop unrolling also reduces number instructions processed decrease performance due poorer cache performance precise effect inlining cache performance complicated small cache sizes much smaller working set prior expansion increased sequentiality dominates inlining improves cache performance cache sizes close working set inlining expands working set longer fits cache dominates cache performance decreases cache sizes larger working set inlining negligible impact cache performance changes cache design load forwarding offset increase cache misses compilers use variety mechanisms decide function calls inlined include manual hints programmers specific functions together overall control via command-line options inlining done automatically many compilers many languages based judgment whether inlining beneficial cases manually specified via compiler directives typically using keyword compiler directive called codice_1 typically hints inlining desired rather requiring inlining force hint varying language compiler typically compiler developers keep performance issues mind incorporate heuristics compilers choose functions inline improve performance rather worsening cases compiler decided inline particular function performing inlining operation usually simple depending whether compiler inlines functions across code different languages compiler inlining either high-level intermediate representation like abstract syntax trees low-level intermediate representation either case compiler simply computes arguments stores variables corresponding function arguments inserts body function call site linkers also function inlining linker inlines functions may inline functions whose source available library functions see link-time optimization run-time system inline function well run-time inlining use dynamic profiling information make better decisions functions inline java hotspot compiler simple example inline expansion performed hand source level c programming language inlining inlining note example actual c application would preferable use inlining language feature parameterized macros inline functions tell compiler transform code way next section lists ways optimize code assembler macros provide alternative approach inlining whereby sequence instructions normally generated inline macro expansion single macro source statement zero parameters one parameters might option alternatively generate one-time separate subroutine containing sequence processed instead inlined call function example range different heuristics explored inlining usually inlining algorithm certain code budget allowed increase program size aims inline valuable callsites without exceeding budget sense many inlining algorithms usually modeled knapsack problem decide callsites valuable inlining algorithm must estimate benefit -- i.e expected decrease execution time commonly inliners use profiling information frequency execution different code paths estimate benefits addition profiling information newer jit compilers apply several advanced heuristics traditionally languages c inline expansion accomplished source level using parameterized macros use true inline functions available c99 provides several benefits approach many compilers also inline expand recursive functions recursive macros typically illegal bjarne stroustrup designer c++ likes emphasize macros avoided wherever possible advocates extensive use inline functions inline expansion optimization since eliminates overhead calls much important enabling transformation compiler expands function body context call site—often arguments may fixed constants—it may able variety transformations possible example conditional branch may turn always true always false particular call site turn may enable dead code elimination loop-invariant code motion induction variable elimination c example previous section optimization opportunities abound compiler may follow sequence steps new function looks like complete inline expansion always possible due recursion recursively inline expanding calls terminate various solutions expanding bounded amount analyzing call graph breaking loops certain nodes i.e. expanding edge recursive loop identical problem occurs macro expansion recursive expansion terminate typically resolved forbidding recursive macros c c++ many compilers aggressively inline functions wherever beneficial although lead larger executables aggressive inlining nevertheless become desirable memory capacity increased faster cpu speed inlining critical optimization functional languages object-oriented programming languages rely provide enough context typically small functions make classical optimizations effective many languages including java functional languages provide language constructs inline functions compilers interpreters often perform aggressive inline expansion languages provide constructs explicit hints generally compiler directives pragmas ada programming language exists pragma inline functions functions common lisp may defined inline codice_1 declaration haskell compiler ghc tries inline functions values small enough inlining may noted explicitly using language pragma c c++ codice_1 keyword functions compiler directive – specifying inlining desired required – also changes visibility linking behavior visibility change necessary allow function inlined via standard c toolchain compilation individual files rather translation units followed linking linker able inline functions must specified header visible marked codice_1 avoid ambiguity multiple definitions
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Programming language topics
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exception handling syntax exception handling syntax set keywords and/or structures provided computer programming language allow exception handling separates handling errors arise program operation ordinary processes syntax exception handling varies programming languages partly cover semantic differences largely fit language overall syntactic structure languages call relevant concept 'exception handling others may direct facilities still provide means implement commonly error handling uses codice_1 block errors created via codice_2 statement significant variation naming syntax some_error exception raise some_error raise some_error memory -- specific diagnostic message ada.exceptions ada.text_io procedure foo begin exception -- start exception handlers end foo assembly languages macro instruction interrupt address available particular system intercept events illegal op codes program check data errors overflow divide zero ibm univac mainframes stxit macro digital equipment corporation rt11 systems trap vectors program errors i/o interrupts dos certain interrupt addresses microsoft windows specific module calls trap program errors print_error echo error trap print_error exit list signals trap tempfile= mktemp trap rm tempfile exit ./other.sh || echo warning failed echo oops echo never printed one set trap multiple errors responding signal syntax like error goto/gosub structure used basic quite different modern exception handling basic one global handler whereas modern exception handling exception handlers stacked error goto handler open somefile.txt input 1 close 1 print file opened successfully end handler print file exist end resume may used instead returns control original position common way implement exception handling standard c use setjmp/longjmp functions enum some_exception 1 exception jmp_buf state int main void two types exist example seh c programming language int filterexpression exception_pointers* ep int main void public static void main int main try c++ resource acquisition initialization technique used clean resources exceptional situations c++ intentionally support outer braces method optional cfscript try catch e finally //cf9+ /cfscript adobe coldfusion documentation cftry /cftry adobe coldfusion documentation added standard syntax cfml dialects railo lucee allow codice_3 statement statement returns processing start prior codice_4 block cfscript example try catch e tag-syntax example cftry /cftry import std.stdio // writefln int main clause resource acquisition initialization technique used clean resources exceptional situations type ecustom class exception // exceptions children class exception raise exception.create 'message raise exception.createfmt 'message values value1 value2 // see sysutils.format parameters raise ecustom.createcustom x try // finally finally end try catch end haskell special syntax exceptions instead /// interface provided functions import prelude hiding catch import control.exception instance exception int instance exception double main prints analogy c++ using namespace std int main another example catch \ex purely functional code one error condition exists type may sufficient instance haskell class default complex error propagation achieved using monads similar functionality using supported try catch exampleexception ee finally try catch error finally handler-case unwind-protect lua uses codice_5 codice_6 functions codice_6 taking function act codice_8 block function foo x end function attempt arg end attempt hello attempt nil attempt foo 42 print success end pcall else end print done -- always executed nsexception *exception nsexception exceptionwithname myexception throw exception try catch someexception *se catch nsexception *ne catch id ue finally exception myexception string int exceptions carry value let perl mechanism exception handling uses throw exception wrapped inside block special variable contains value passed however scoping issues make correctly quite ugly error failed failed perl 5.005 added ability throw objects well strings allows better introspection handling types exceptions eval pseudo-signal trapped handle calls suitable exception handling since global however used convert string-based exceptions third-party packages objects local sig __die__ sub forms shown sometimes fail global variable changed exception thrown checked statement happen multi-threaded environments even single-threaded environments code typically called destruction object resets global variable checking code following example shows way avoid problem see cost able use return values eval several modules comprehensive perl archive network cpan expand basic mechanism // exception handling available php versions 5 greater try catch firstexceptionclass exception catch secondexceptionclass exception finally exception handling available powerbuilder versions 8.0 trap exception try catch exception1 catch exception2 exception3etc catch f none try except ioerror except catch exceptions else executed exceptions raised finally clean-up actions always executed trycatch specialerror=function e error=function e rebol error exception try 1 0 probe disarm exception print attempt divide 1 0 example func function throw exception catch example sophisticated func function throw named error exception catch/name sophisticated 'moniker signal halt begin rescue someerror rescue anothererror error rescue else ensure end try new exceptions may created using function e.g. create exception called subclass exceptions may generated using throw statement throw arbitrary s-lang objects code might throw exception general mechanism provided message exceptions normal objects subclass throw one creating instance sending message e.g. handling mechanism normal message implemented thrown exception passed parameter handling block closure queried well potentially sending allow execution flow continue exception handling supported since swift 2. enum myexception errortype func somefunc throws catch myexception.foo let let catch catch err since tcl 8.6 also try command try ok res opt trap listpattern1 err opt trap listpattern2 err opt error err opt finally new try error resume next .catch error goto 0 select case .number end select end *** try class *** class try end class new try error resume next .catch error goto 0 select case .number end select end *** try class *** private mstrdescription string private mlnghelpcontext long private mstrhelpfile string private mlnglastdllerror long private mlngnumber long private mstrsource string public sub catch end sub public property get source string end property public property get number long end property public property get lastdllerror long end property public property get helpfile string end property public property get helpcontext long end property public property get description string end property try catch ex exception condition catch ex exceptiontype catch ex exception finally end try http //wiki.visual-prolog.com/index.php title=language_reference/terms try-catch-finally try catch traceid finally end try public static void main args _args
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Programming language topics
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frank w. lewis frank waring lewis august 25 1912 – november 18 2010 american cryptographer cryptic crossword compiler puzzles printed nation 60 years total 2,962 puzzles leonard bernstein kurt vonnegut katha pollitt listed among fans puzzles lewis born august 25 1912 salt lake city utah father england lewis attended secretarial school university utah later earned degree absentia passed federal civil service test earned master degree music catholic university america washington d.c washington lewis worked government secretarial jobs world war ii lewis approached col. william f. friedman head u.s. army cryptography section looking smart people lewis hired civilian helped break code used coordinate japanese ships war joined national security agency nsa awarded decoration exceptional civilian service war department nsa may person two medals much work remains classified 1969 retired wife caribbean relocated massachusetts eruption montserrat volcano died november 18 2010 age 98 survived wife 74 years sylvia née shosteck six children lewis discovered british-style cryptic crosswords stationed war bletchley park code-breaking station england lewis took nation puzzle setter 1947 nation started running puzzles every week instead weekly starting 2008 public outcry great resumed printing puzzles weekly lewis published last puzzle nation december 2009 magazine began reprinting old ones lewis death magazine continued reprint old puzzles searched new puzzle setter
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Computer security
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grub search engine grub open source distributed search crawler platform users grub could download peer-to-peer grubclient software let run computer idle time client indexed urls sent back main grub server highly compressed form collective crawl could theory utilized indexing system one proposed wikia search grub able quickly build large snapshot asking thousands clients crawl analyze small portion web wikia released entire grub package open source software license however old grub clients functional anymore new clients found wikia wiki project started 2000 kord campbell igor stojanovski ledio ago oklahoma city intellectual property rights acquired grub january 2003 1.3 million cash stock looksmart short time original team continued working project releasing several new versions software albeit closed license operations grub shut late 2005 july 27 2007 jimmy wales announced wikia inc. for-profit company developing open source search engine wikia search acquired grub looksmart july 17 50,000 day site reactivated currently updated
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Web technology
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ldap account manager ldap account manager web application managing various account types ldap directory written php contrast tools likephpldapadmin focus account based give user abstract view directory aims allow people little technical background manage ldap data base application licensed gnu general public license extended version available commercial license ldap account manager lam project founded february 2003 first developers michael dürgner roland gruber tilo lutz leonhard walchshäusl goal create application manage samba software accounts time samba supported ldap 2.x releases version 3 alpha stage gui manage lam version 0.4.10 samba accounts could managed year 2004 project started develop plugin architecture support account types first stable release new code lam 0.5.0 september 2005 commercial variant lam pro since 1.0.4 supports user self-service e.g change password telephone number ... also supports additional ldap objects e.g zarafa kerberos ppolicy ... important account types supported lam samba unix zarafa ppolicy user define profiles account types set default values account information exported pdf files also possibility create users via file upload also includes tree view phpldapadmin access raw ldap attributes lam translated 16 languages supported account types commercial version also includes user self-service allows users edit data register accounts reset passwords
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Databases
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maintenance operations protocol maintenance operation protocol mop used utility services uploading downloading system software remote testing problem diagnosis proprietary protocol digital equipment corporation mop frames one following commands
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Operating systems
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operating systems design implementation operating systems design implementation computer science textbook written andrew s. tanenbaum help albert s. woodhull includes tanenbaum minix free unix-like operating system designed teaching purposes publisher prentice hall 1987 source code minix included part original 719 pages text later versions three editions also included loadable disks minix
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Operating systems
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qct quanta cloud technology qct provider data center hardware cloud solutions used hyperscale data center operators facebook rackspace conjunction parent company quanta computer qct sells approximately one every seven server manufactured world qct early contributor open compute project non-profit organization launched facebook engineers open source designs data center products qct manufactured facebook servers among first designs project addition headquarters taoyuan taiwan qct offices san jose seattle beijing hangzhou tokyo qct us subsidiary quanta computer established may 2012 manufacture servers end users course 2012 qct also added storage hardware networking switches portfolio became hardware provider cloud market 2013 qct added rack systems product portfolio 2015 qct partnered software vendors offer software-defined hyper-converged infrastructure solutions variety cloud environments public private hybrid 2004 2012 qct became early contributor open compute project ocp ocp solution provider qct designs builds delivers ocp servers data centers 2015 qct opened two cloud solutions centers demonstrate hyper-converged software hyperscale hardware april 2015 qct cloud solution center taiwan october 2015 opened one fremont california mike yang serves general manager qct qct received editors ’ choice award top 5 vendors watch 2014 hpcwire readers ’ editors ’ choice awards
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Distributed computing architecture
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mos technology 6502 mos technology 6502 typically sixty-five-oh-two six-five-oh-two 8-bit microprocessor designed small team led chuck peddle mos technology introduced 1975 6502 considerable margin least expensive microprocessor market initially sold less one-sixth cost competing designs larger companies motorola intel caused rapid decreases pricing across entire processor market along zilog z80 sparked series projects resulted home computer revolution early 1980s popular home video game consoles computers atari 2600 atari 8-bit family apple ii nintendo entertainment system commodore 64 atari lynx bbc micro others used 6502 variations basic design soon 6502 introduction mos technology purchased outright commodore international continued sell microprocessor licenses manufacturers early days 6502 second-sourced rockwell synertek later licensed companies cmos form developed western design center 6502 family continues widely used embedded systems estimated production volumes hundreds millions 6502 designed many engineers designed motorola 6800 microprocessor family motorola started 6800 microprocessor project 1971 tom bennett main architect chip layout began late 1972 first 6800 chips fabricated february 1974 full family officially released november 1974 john buchanan designer 6800 chip rod orgill later 6501 assisted buchanan circuit analyses chip layout bill mensch joined motorola june 1971 graduating university arizona age 26 first assignment helping define peripheral ics 6800 family later principal designer 6820 peripheral interface adapter pia motorola engineers could run analog digital simulations ibm 370-165 mainframe computer bennett hired chuck peddle 1973 architectural support work 6800 family products already progress contributed many areas including design 6850 acia serial interface motorola target customers established electronics companies hewlett-packard tektronix trw chrysler may 1972 motorola engineers began visiting select customers sharing details proposed 8-bit microprocessor system rom ram parallel serial interfaces early 1974 provided engineering samples chips customers could prototype designs motorola total product family strategy focus price microprocessor reducing customer total design cost offered development software timeshare computer exorciser debugging system onsite training field application engineer support intel motorola initially announced 360 price single microprocessor actual price production quantities much less motorola offered design kit containing 6800 six support chips 300 peddle would accompany sales people customer visits found customers put high cost microprocessor chips lower price ic chip size would shrink chips could produced silicon wafer could done removing inessential features 6800 using newer fabrication technology depletion-mode mos transistors peddle team members started outlining design improved feature reduced size microprocessor time motorola new semiconductor fabrication facility austin texas difficulty producing mos chips mid-1974 beginning year-long recession semiconductor industry also many mesa arizona employees displeased upcoming relocation austin motorola semiconductor products division management overwhelmed problems showed interest peddle low-cost microprocessor proposal chuck peddle frustrated motorola management missing new opportunity november 1975 interview motorola chairman robert galvin agreed said choose right leaders semiconductor products division division reorganized management replaced new group vice-president john welty said semiconductor sales organization lost sensitivity customer needs could n't make speedy decisions peddle began looking outside motorola source funding new project found small semiconductor company pennsylvania august 1974 chuck peddle bill mensch rod orgill harry bawcom ray hirt terry holdt wil mathys left motorola join mos technology mike james joined later seventeen chip designers layout people 6800 team seven left 30 40 marketers application engineers system engineers 6800 team december gary daniels transferred 6800 microprocessor group tom bennett want leave phoenix area daniels took microprocessor development austin first project depletion-mode version 6800 cut chip area nearly half doubled speed faster parts available july 1976 followed 6802 added 128 bytes ram on-chip clock oscillator circuit mos technology formed 1969 three executives general instrument mort jaffe mclaughlin john paivinen produce metal-oxide-semiconductor mos integrated circuits allen-bradley supplier electronic components industrial controls acquired majority interest 1970 company designed fabricated custom ics customers developed line calculator chips august 19 1974 former motorola employees moved mos technology headquarters valley forge pennsylvania goal design produce low cost microprocessor embedded applications target wide possible customer base would possible microprocessor low cost—and semiconductor business chip size determined cost size goal required n-channel depletion-load mos transistors advanced process mos technology calculator chips used john paivinen able fabrication process ready june 1975 chuck peddle rod orgill wil mathys designed initial architecture new processors would two microprocessors 6501 would plug socket motorola 6800 6502 would work 6800 family peripherals on-chip clock oscillator processors would run 6800 software different instruction set different registers mostly different addressing modes september 1975 article edn magazine gives summary design mos technology 650x family represents conscious attempt eight former motorola employees worked development 6800 system put part would replace outperform 6800 yet undersell benefit hindsight gained 6800 project mos technology team headed chuck peddle made following architectural changes motorola cpu… second b accumulator omitted 16-bit 6800 index register 8-bit offset instruction replaced two 8-bit index registers 8-bit 16-bit offset three-state control eliminated address bus outputs clock generator included chip address bus always active vma valid-memory address output eliminated 8080-type rdy signal single-cycle stepping added chip high level design turned drawings transistors interconnects mos technology layout manual process done color pencils vellum paper layout consisted thousands polygon shapes six different drawings one layer semiconductor fabrication process rod orgill responsible 6501 design assisted john buchanan motorola 6800 bill mensch 6502 designer 6820 peripheral interface adapter pia motorola harry bawcom mike james sydney-anne holt helped layout size goal 6502 chip 153 x 168 mils 3.9 x 4.3 mm area 16.6 mm time technical literature would state length width chip mils 0.001 inch smaller chip area means chips per silicon wafer greater yield defects generally randomly uniformly scattered across wafer area chips per wafer smaller ratio defective chips total wafer chips original 6800 chips intended 180 x 180 mils layout completed 212 x 212 mils 5.4 x 5.4 mm area 29.0 mm first 6502 chips 168 x 183 mils 4.3 x 4.7 mm area 19.8 mm rotate right instruction ror work first silicon instruction temporarily omitted published documents next iteration design shrank chip fixed rotate right instruction included revised documentation mos technology microprocessor introduction quite different traditional months-long product launch first run new integrated circuit normally used internal testing shared select customers engineering samples chips often minor design defect two corrected production begins chuck peddle goal sell first run 6501 6502 chips attendees wescon trade show san francisco beginning september 16 1975 peddle effective spokesman mos technology microprocessors extensively covered trade press one earliest full-page story mcs6501 mcs6502 microprocessors july 24 1975 issue electronics magazine stories also ran ee times august 24 1975 edn september 20 1975 electronic news november 3 1975 byte november 1975 microcomputer digest november 1975 advertisements 6501 appeared several publications first week august 1975 6501 would sale wescon 20 september 1975 advertisements included 6501 6502 microprocessors 6502 would cost 25 mos technology arrived wescon found exhibitors permitted sell anything show floor rented macarthur suite st. francis hotel directed customers purchase processors suite processors stored large jars imply chips production readily available customers know bottom half jar contained non-functional chips chips 20 25 documentation package additional 10 users encouraged make photocopies documents inexpensive way mos technology distribute product information processors supposed 56 instructions rotate right ror instruction work correctly chips preliminary data sheets listed 55 instructions reviews byte edn noted lack ror instruction next revision layout fixed problem may 1976 datasheet listed 56 instructions peddle wanted every interested engineer hobbyist access chips documentation semiconductor companies wanted deal serious customers example signetics introducing 2650 microprocessor advertisements asked readers write information company letterhead 6501/6502 introduction print wescon enormous success downside extensive press coverage got motorola attention october 1975 motorola reduced price single 6800 microprocessor 175 69 300 system design kit reduced 150 came printed circuit board november 3 1975 motorola sought injunction federal court stop mos technology making selling microprocessor products also filed lawsuit claiming patent infringement misappropriation trade secrets motorola claimed seven former employees joined mos technology create company microprocessor products motorola billion-dollar company plausible case lawyers october 30 1974 motorola filed numerous patent applications microprocessor family granted twenty-five patents first june 1976 second bill mensch july 6 1976 6820 pia chip layout patents covered 6800 bus peripheral chips interfaced microprocessor motorola began making transistors 1950 portfolio semiconductor patents allen-bradley decided fight case sold interest mos technology back founders four former motorola engineers named suit chuck peddle mathys bill mensch rod orgill named inventors 6800 patent applications discovery process motorola found one engineer mike james ignored peddle instructions brought 6800 design documents mos technology march 1976 independent mos technology running money settle case agreed drop 6501 processor pay motorola 200,000 return documents motorola contended confidential companies agreed cross-license microprocessor patents may motorola dropped price single 6800 microprocessor 35 november commodore acquired mos technology legal troubles behind mos still left problem getting developers try processor prompting chuck peddle design mdt-650 microcomputer development terminal single-board computer another group inside company designed kim-1 sold semi-complete could turned usable system addition 3rd party computer terminal compact cassette drive much amazement kim-1 sold well hobbyists tinkerers well engineers targeted related rockwell aim 65 control/training/development system also well software aim 65 based mdt another roughly similar product synertek sym-1 one first public uses design apple microcomputer introduced 1976 6502 next used commodore pet apple ii released 1977 later used atari 8-bit family acorn atom home computers bbc micro commodore vic-20 designs home computers business ohio scientific oric 6510 direct successor 6502 digital i/o port tri-state address bus cpu utilized best-selling commodore 64 home computer commodore floppy disk drive 1541 processor own—it 6502 another important use 6500 family video games first make use processor design atari vcs later renamed atari 2600 vcs used offshoot 6502 called 6507 fewer pins result could address 8 kb memory millions atari consoles would sold mos processor another significant use nintendo entertainment system famicom 6502 used nes second source version ricoh partial system-on-a-chip lacked binary-coded decimal mode added 22 memory-mapped registers on-die hardware sound generation joypad reading sprite list dma called 2a03 ntsc consoles 2a07 pal consoles difference memory divider ratio lookup table audio sample rates processor produced exclusively nintendo atari lynx used 4 mhz version chip 65sc02 1980s popular electronics magazine elektor/elektuur used processor microprocessor development board junior computer 6502 little-endian 8-bit processor 16-bit address bus original versions fabricated using process technology chip advertised die size area 16.6 mm internal logic runs speed external clock rate despite low clock speeds typically neighborhood 1 2 mhz 6502 performance competitive contemporary cpus using significantly faster clocks partly due simple state machine implemented combinational clockless logic greater extent many designs two-phase clock supplying two synchronizations per cycle thereby control whole machine -cycle directly typical instructions might take half many cycles complete 6502 contemporary designs like simple cpus era dynamic nmos 6502 chip sequenced microcode rom uses pla occupied 15 chip area instruction decoding sequencing 8-bit microprocessors chip limited overlapping fetching execution low clock frequency moderated speed requirement memory peripherals attached cpu 50 clock cycle available memory access due asynchronous design fraction varied strongly among chip versions critical time affordable memory access times range original nmos 6502 minimalistically engineered efficiently manufactured therefore cheap—an important factor getting design wins price-sensitive game-console home-computer markets like precursor 6800 6502 registers 6502 registers include one 8-bit accumulator register two 8-bit index registers x 7 processor status flag bits p 8-bit stack pointer 16-bit program counter pc compares typical design era z80 eight general-purpose 8-bit registers combined four 16-bit ones order make somewhat lack registers 6502 included zero-page addressing mode uses one address byte instruction instead two needed address full 64 kb memory provides fast access first 256 bytes ram using shorter instructions chuck peddle said interviews specific intention allow first 256 bytes ram used like registers stack address space memory page 01 i.e address range 0100– 01ff 256–511 software access stack done via four implied addressing mode instructions whose functions push pop pull accumulator processor status register stack also used subroutine calls via jsr jump subroutine rts return subroutine instructions interrupt handling chip uses index stack registers effectively several addressing modes including fast direct page zero page mode similar found pdp-8 accesses memory locations addresses 0 255 single 8-bit address saving cycle normally required fetch high-order byte address —code 6502 uses zero page much code processors would use registers 6502-based microcomputers operating system os uses zero page leaving handful locations user addressing modes also include implied 1-byte instructions absolute 3 bytes indexed absolute 3 bytes indexed zero-page 2 bytes relative 2 bytes accumulator 1 indirect x indirect 2 immediate 2 absolute mode general-purpose mode branch instructions use signed 8-bit offset relative instruction branch numerical range −128..127 therefore translates 128 bytes backward 127 bytes forward instruction following branch 126 bytes backward 129 bytes forward start branch instruction accumulator mode uses accumulator effective address need operand data immediate mode uses 8-bit literal operand indirect modes useful array processing looping 5/6 cycle indirect mode 8-bit register added 16-bit base address read zero page located single byte following opcode register therefore index register sense used hold actual index opposed x register 6800 base address directly stored immediate offset could added incrementing index register walk array byte-wise takes two additional cycles less frequently used indirect x mode effective address operation found zero page address formed adding second byte instruction contents x register using indexed modes zero page effectively acts set 128 additional though slow address registers 6502 capable performing addition subtraction binary binary-coded decimal placing cpu bcd mode codice_1 set flag instruction results decimal arithmetic codice_2 would result 00 carry c flag set binary mode codice_3 clear flag operation would result 9a carry flag cleared atari basic bcd mode seldom used home-computer applications see article simple characteristic example 6502 assembly language 6502 instruction operation codes opcodes eight-bits long general form aaabbbcc aaa cc define opcode bbb defines addressing mode instance consider codice_4 instruction performs bitwise bits accumulator another value instruction opcode form 000bbb01 bbb may 010 immediate mode value constant 001 zero page fixed address 011 absolute address pattern absolute number exceptions however apply allows one easily deconstruct opcode values back assembler mnemonics majority instructions handling edge cases special-purpose code 256 possible opcodes available using 8-bit pattern original 6502 uses 151 organized 56 instructions possibly multiple addressing modes depending instruction addressing mode opcode may require zero one two additional bytes operands hence 6502 machine instructions vary length one three bytes operand stored 6502 customary little-endian format 65c816 16-bit cmos version 6502 also supports 24-bit addressing results instructions assembled three-byte operands also arranged little-endian format remaining 105 opcodes undefined original design instructions low-order 4-bits nibble 3 7 b f used providing room future expansion likewise 2xxx column single entry codice_5 remaining 25 empty slots distributed empty slots used 65c02 provide new instructions well variations existing ones new addressing modes fxxx instructions initially left free allow 3rd party vendors add instructions later versions 65c02 standardized set bit fiddling instructions developed rockwell semiconductor 6502 assembly language statement consists three-character instruction mnemonic followed operands instructions take separate operand target single register based addressing mode combine target register instruction mnemonic assembler uses codice_6 opposed codice_7 increment x register processor non-maskable interrupt nmi input edge sensitive means interrupt triggered falling edge signal rather level implication feature wired-or interrupt circuit readily supported however also prevents nested nmi interrupts occurring hardware makes nmi input inactive often control nmi interrupt handler simultaneous assertion nmi irq maskable hardware interrupt lines causes irq ignored however irq line remains asserted servicing nmi processor immediately respond irq irq level sensitive thus sort built-in interrupt priority established 6502 design break flag processor different flag bits flag setting resetting testing instructions affected php plp instructions exists stack brk php always write 1 irq nmi always write 0 input pin asserted set processor overflow status bit deasserting clear overflow bit however used high-speed polling device driver poll hardware three cycles using branch-on-overflow-clear codice_8 instruction branches example commodore 1541 commodore floppy disk drives use technique detect without delay whether serializer ready accept provide another byte disk data obviously great care must used device driver associated system design spurious assertion overflow bit could ruin arithmetic processing several variants nmos 6502 mos technology 6512 6513 6514 6515 rely external clock instead using internal clock generator like 650x e.g 6502 used advantage designs clocks could run asymmetrically increasing overall cpu performance 6512 used bbc micro b+64 western design center designed currently produces w65c816s processor 16-bit static-core successor 65c02 greatly enhanced features w65c816s newer variant 65c816 core apple ii computer basis ricoh 5a22 processor powered popular super nintendo entertainment system w65c816s incorporates minor improvements 65c816 make newer chip exact hardware-compatible replacement earlier one currently available electronics distributors november 2017 w65c816s rated 14-megahertz operation western design center also designed produced 65c802 65c816 core 64-kilobyte address space 65 c 02 pin-compatible package 65c802 could retrofitted 6502 board would function 65c02 power-up operating emulation mode 65c816 two-instruction sequence would switch 65c802 native mode operation exposing 16 bit accumulator index registers well 65c816 enhanced features 65c802 widely used new designs almost always built around 65c816 resulting 65c802 production discontinued following 6502 assembly language source code subroutine named codice_10 copies null-terminated character string one location another converting upper-case letter characters lower-case letters string copied source string converted source stored destination 6502 several bugs quirks accounted programming
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Computer architecture
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mos technology 65xx mos technology 65xx series family 8-bit microprocessors mos technology based motorola 6800 introduced ca 1975 65xx family included 6502 used home computers commodore pet vic-20 apple ii atari 800 british bbc micro 6501 6502 40-pin dip packages 6503 6504 6505 6507 28-pin dip versions reduced chip circuit board cost 28-pin versions pin count reduced leaving high-order address pins various combinations function pins making functions unavailable typically 12 pins omitted three n.c. pins one two vss pins one clock pins sync pin s.o pin either maskable interrupt nmi four most-significant address lines a12–a15 12 pins omitted reduce pin count 40 28 omission four address pins reduces external addressability 4 kb 64 kb 6502 though internal pc register effective address calculations remain 16-bit 6507 omits interrupt pins order include address line a12 providing 8 kb external addressability interrupt capability 6507 used popular atari 2600 video game console design divides 8 kb memory space half allocating lower half console internal ram peripherals upper half game cartridge™ atari 2600 cartridges 4 kb address limit capacity limit unless cartridge contains bank switching circuitry one popular 6502 based computer commodore 64 used modified 6502 cpu 6510 unlike 6503–6505 6507 6510 40-pin chip adds internal hardware 8-bit parallel i/o port mapped addresses 0000 0001 6508 another chip like 6510 adds internal hardware 256 bytes sram 8-bit i/o port featured 6510 though chips reduced pin counts compared 6502 need 8 new pins added parallel i/o port case address lines among 8 removed pins
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Computer architecture
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q*bert q*bert arcade game developed published north american market gottlieb 1982 2d action game puzzle elements uses isometric graphics create pseudo-3d effect objective level game change color every cube pyramid making q*bert on-screen character hop top cube avoiding obstacles enemies players use joystick control character game conceived warren davis jeff lee lee designed title character original concept developed implemented davis q*bert developed project name cubes q*bert well-received arcades among critics game gottlieb successful video game among recognized brands golden age arcade games ported numerous platforms game success resulted sequels use character likeness merchandising appearances lunch boxes toys animated television show q*bert character became known swearing – incoherent phrase made synthesized speech generated sound chip speech balloon nonsensical characters appear collides enemy game developed period columbia pictures owned gottlieb intellectual rights q*bert remained columbia even divested gottlieb assets 1984 therefore rights owned sony pictures entertainment since parent sony acquired columbia 1989 q*bert appeared disney computer-animated film wreck-it ralph license sony later appeared columbia live-action film pixels 2015 q*bert action game puzzle elements played axonometric third-person perspective convey three-dimensional look game played using single diagonally mounted four-way joystick player controls q*bert starts game top pyramid made 28 cubes moves hopping diagonally cube cube landing cube causes change color changing every cube target color allows player progress next stage beginning jumping every cube enough advance later stages cube must hit twice reach target color times cubes change color every time q*bert lands instead remaining target color reach elements combined subsequent stages jumping pyramid results character death player impeded several enemies introduced gradually game collision purple enemies fatal character whereas green enemies removed board upon contact colored balls occasionally appear second row cubes bounce downward contact red ball lethal q*bert contact green one immobilizes on-screen enemies limited time multicolored floating discs either side pyramid serve escape danger particularly coily q*bert jumps disc transports top pyramid coily close pursuit character jump q*bert fall death awarding bonus points causes enemies balls screen disappear though start return seconds points awarded color change 25 defeating coily flying disc 500 remaining discs end stage higher stages 50 100 catching green balls 100 slick sam 300 bonus points also awarded completing screen starting 1,000 first screen level 1 increasing 250 subsequent completion 5,000 level 4 extra lives granted reaching certain scores set machine operator programmer warren davis wrote inspired pattern hexagons implemented fellow gottlieb developer mad planets designer kan yabumoto different telling initial concept began artist jeff lee drew pyramid cubes inspired m. c. escher lee believed game could derived artwork created orange armless main character character jumped along cubes shot projectiles called mucus bombs tubular nose enemies enemies included blue creature later changed purple named wrong way orange creature later changed green named sam lee drawn similar characters since childhood inspired characters comics cartoons mad magazine artist ed big daddy roth q*bert design later included speech balloon string nonsensical characters lee originally presented joke warren davis hired work game protector noticed lee ideas asked could use practice programming randomness gravity game mechanics thus added balls bounce pyramid top bottom davis still learning program game mechanics wanted keep design simple also believed games complex control schemes frustrating wanted something could played one hand accomplish davis removed shooting changed objective saving protagonist danger davis worked game one night gottlieb vice president engineering ron waxman noticed suggested change color cubes game character landed davis implemented unique control scheme four-way joystick rotated 45° match directions q*bert jumping staff members gottlieb urged conventional orientation davis stuck decision davis remembered started programming april 1982 project put schedule actual product several months later mos technology 6502 chip operates 894 khz generates sound effects speech synthesizer votrax generates q*bert incoherent expressions audio system uses 128 b random-access memory 4 kb erasable programmable read memory store sound data code implement like gottlieb games sound system thoroughly tested ensure would handle daily usage retrospect audio engineer david thiel commented testing minimized time available creative designing thiel tasked using synthesizer produce english phrases game however unable create coherent phrases eventually chose string together random phonemes instead thiel also believed incoherent speech good fit q*bert speech balloon following suggestion technician rick tighe pinball machine component included make loud sound character falls pyramid sound generated internal coil hits interior cabinet wall foam padding added area contact cabinet developers decided softer sound better matched fall rather loud knocking sound cost installing foam however expensive padding omitted gottlieb staff difficulty naming game aside project name cubes untitled development process staff agreed game named main character disagreed name lee title initial concept— snots boogers —was rejected list suggestions compiled company employees according davis vice president marketing howie rubin championed title although staff members argued silly would impossible pronounce early test models produced title units artwork meeting hubert suggested staff member thought combining cubes hubert cubert art director richard tracy changed name q-bert hyphen later changed asterisk retrospect davis expressed regret asterisk prevented name becoming common crossword term wildcard character search engines development neared production stage q*bert underwent location tests local arcades preliminary title widely distributed according jeff lee oldest written record attesting game playable public location brunswick bowling alley dates back september 11 1982 gottlieb also conducted focus groups designers observed players one-way mirror control scheme received mixed reaction play testing players adapted quickly others found frustrating initially davis worried players would adjust different controls players would unintentionally jump pyramid several times reaching game ten seconds players however became accustomed controls playing several rounds game different responses controls prompted davis reduce game level difficulty—a decision would later regret copyright claim registered united states copyright office gottlieb february 10 1983 cites date publication q*bert october 18 1982 video games reported game sold directly arcade operators public showing amoa show held november 18–20 1982 gottlieb offered machines 2600 per unit q*bert gottlieb fourth video game q*bert gottlieb video game gathered huge critical commercial success selling around 25,000 arcade cabinets cabaret cocktail versions game later produced machines since become collector items rarest cocktail versions game first introduced wider industry audience november 1982 amoa show immediately received favorably press video games placed q*bert first list top ten hits describing unusual exciting game show stating operator dared walk away without buying least one coin slot reported gottlieb game q*bert one stars show predicted game well contemporaneous reviews equally enthusiastic focused uniqueness gameplay audiovisual presentation roger c. sharpe electronic games considered potential arcade award winner coin-op game year praising innovative gameplay outstanding graphics william brohaugh creative computing video arcade games described game all-round winner many strong points praised variety sound effects graphics calling colors vibrant brohaugh lauded q*bert inventiveness appeal stating objective interesting unique michael blanchet electronic fun suggested game might push pac-man spotlight 1983 neil tesser video games also likened q*bert japanese games like pac-man donkey kong due focus characters animation story lines well absence violence computer video games magazine praised game graphics colors electronic games awarded q*bert innovative coin-op game year video game player called funniest game year among arcade games 1983 q*bert continues widely recognized significant part video game history author steven kent gamespy william cassidy considered q*bert one memorable games time author david ellis echoed similar statements calling classic favorite 1up.com jeremy parish kim wild retro gamer magazine described game difficult yet addictive author john sellers also called q*bert addictive praised sound effects three-dimensional appearance graphics cassidy called game unique challenging attributed challenge part control scheme ign jeremy dunham believed controls poorly designed describing unresponsive struggle nonetheless considered game addictive main character also received positive press coverage edge magazine attributed success game title character stated players could easily relate q*bert particularly swore computer video games however considered swearing negative character appealing cassidy believed game appeal lay main character described q*bert cute personality made stand comparison popular video game characters authors high score referred q*bert ultra-endearing alien hopmeister cutest game character 1982 1982 amoa show parker brothers secured license publish home conversions q*bert arcade game parker first published port atari 2600 end 1983 company also advertised versions atari 5200 intellivision colecovision atari 8-bit computer family commodore vic-20 texas instruments ti-99/4a commodore 64 release commodore 64 version noted lag behind others appeared 1984 parker brothers also translated game stand-alone tabletop electronic game uses vfd screen since become rare collector item q*bert also published parker brothers philips videopac europe tsukuda original othello multivision japan ultra games nes north america initial home port atari 2600 widespread system time met mixed reactions video games warned buyers atari 2600 version may find little disappointed criticized lack music removing characters ugg wrongway system troubles handle character sprites screen steady performance later mark brownstein magazine favor game still cited presence fewer cubes game pyramidal layout pretty poor control negatives richardson electronic games noted lack audiovisual qualities counter-intuitive controls commended gameplay stating game comes much closer source inspiration surface evaluation indicates randi hacker electronic fun computers games called sterling adaption 2008 however ign levi buchanan rated fourth worst arcade port atari 2600 mostly due lack jumping animations enemies instead pop instantly adjacent cube making impossible know direction travel land entertainment weekly called q*bert one top ten games atari 2600 2013 saying port lost cool isometric perspective none addictive gameplay home versions well-received exceptions colecovision version electronic fun computers games noted q*bert aficionados disappointed marc brownstein video games called one best authorized versions warren davis also considered colecovision version accurate port arcade mark brownstein judged atari 5200 version inferior colecovision due imprecision atari 5200 controller noted tend grow video games determined intellivision version worst available ports criticizing system controller inadequate game antic magazine david duberman called atari 8-bit version one finest translations arcade game home computer format arthur leyenberger creative computing listed runner-up best arcade adaptation system praising faithful graphics sound movement playability softline critical criticizing atari version controls lack swearing magazine concluded home computer game n't sense style one arcades ... execution n't 1984 magazine readers named game fifth-worst atari program 1983 computer games called c64 version absolutely terrific translation almost totally duplicates arcade game aside lack synthesized speech stand-alone tabletop awarded stand-alone game year electronic games 2003 version java-based mobile phones announced sony pictures mobile reviewers generally acknowledged faithful port arcade original criticized controls modojo robert falcon stated diagonal controls take time adapt cell phone traditional directions michael french pocket gamer concluded ca n't escape fact n't exactly fit mobile graphics certainly spruced-up sound effects timeless ... really little perfect conversion airgamer criticized gameplay monotonous difficulty frustrating contrast wireless gaming review called one best mobile retro roundup february 22 2007 q*bert released playstation 3 playstation network features upscaled filtered graphics online leaderboard players post high-scores sixaxis motion controls game received mixed reception dunham gerstmann enjoy motion controls said title nostalgic players eurogamer.net richard leadbetter judged game elements simplistic repetitive make worthwhile 2007 contrast parish considered title worth purchasing citing addictive gameplay according jeremy parish q*bert one higher-profile titles classic era describing q*bert legacy jeff gerstmann gamespot referred game rare arcade success 2008 guinness world records ranked behind 16 arcade games terms technical creative cultural impact though successful creators game receive royalties gottlieb program place time davis lee nonetheless expressed pride game continuing remembered fondly q*bert became one merchandised arcade games behind pac-man although according john sellers nearly successful franchise donkey kong character likeness appears various items including coloring books sleeping bags frisbees board games wind-up toys stuffed animals flyer distributed 1983 gottlieb claimed 125 licensed products however north american video game crash 1983 depressed market game popularity began decline 1984 years following release q*bert inspired many games similar concepts magazines video games computer games commented trend features q*bert -like games 1984 listed mr cool sierra on-line frostbite activision q-bopper accelerated software juice tronix quick step imagic flip flop boing first star software pharaoh pyramid master control software pogo joe screenplay rabbit transit starpath games inspired q*bert titles identified q*bert -like games include cubit micromax j-bird orion software uk bouncer acornsoft hubert blaby computer games pogo ocean spellbound beyond vector hopper kristof tuts 1983 q*bert adapted animated cartoon part saturday supercade cbs features segments based video game characters golden age video arcade games saturday supercade produced ruby-spears productions q*bert segments 1983 1984 show set united states 1950s era town called q-burg stars q*bert high school student altered include arms hands jacket sneakers shoots black projectiles nose calls slippy dew make enemies slip characters frequently say puns add letter q words q*bert themes characters appear essential 2012 3d disney computer-animated film wreck-it ralph 2015 sony film pixels 2014 q*bert makes cameo appearance radioshack super bowl xlviii commercial '80s called q*bert seen played 1984 film moscow hudson starring robin williams 1993 ibm pc role-playing game features segment player solve pyramid puzzle homage q*bert 2009 action-adventure game q*bert arcade cabinet seen ghostbusters headquarters game referenced several animated television series family guy futurama simpsons robot chicken mad south park november 28 1983 rob gerhardt reached record score 33,273,520 points q*bert marathon held almost 30 years george leutz brooklyn new york played one game q*bert eighty-four hours forty-eight minutes february 14–18 2013 richie knucklez arcade flemington new jersey scored 37,163,080 points doris self credited guinness world records oldest competitive female gamer set tournament record score 1,112,300 q*bert 1984 age 58 record surpassed drew goins june 27 1987 score 2,222,220 self continually attempted regain record death 2006 november 18 2012 george leutz broke q*bert tournament world record live kong 2 event 1up arcade bar denver colorado leutz scored 3,930,990 points eight hours earning 1.5 million points first life beating self score using single life leutz score verified twin galaxies video ends score 3.7 million points 1,500,000 points previous record believing original game easy davis initiated development faster harder challenging q*bert also known fhmc q*bert 1983 increases difficulty introduces q*bertha adds bonus round however project canceled game never entered production davis released fhmc q*bert rom image sqbert.zip onto web december 1996 gottlieb also released pinball game q*berts quest based arcade version features two pairs flippers x formation audio arcade gottlieb produced fewer 900 units several video game sequels released years reach level success original first titled q*bert qubes shows copyright 1983 title screen whereas instruction manual cites 1984 copyright manufactured mylstar electronics uses hardware original game features q*bert introduces new enemies meltniks shoobops rat-a-tat-tat player navigates protagonist around plane cubes avoiding enemies jumping cube causes rotate changing color visible sides cube goal match line cubes target sample later levels require multiple rows match though part popular franchise game release hardly noticed parker brothers showcased home versions q*bert qubes winter consumer electronics show january 1985 q*bert qubes ported colecovision atari 2600 konami distributed original q*bert japanese arcades 1983 produced game title q*bert msx computers 1986 released japan europe however main character little dragon mechanics based q*bert qubes contrary mylstar arcade game 50 stages different pattern cubes addition known rule extensions later stages competitive 2-player mode assigns side different pattern players score points either completing pattern first pushing board 1992 handheld game developed realtime associates published jaleco 1992 features 64 boards different shapes q*bert 3 snes also developed realtime associates released 1992 jeff lee creator q*bert character also worked graphics game q*bert 3 features gameplay similar original like game boy game larger levels varying shapes addition enemies first game introduces several new enemies frogg top hat derby published ntvic q*bert playable character game ntvic started contest electronic gaming monthly magazine consisting three questions game reader answer questions mail egm first winner answer questions correctly first prize consisting snes console copy q*bert 3 copy strike gunner s.t.g snes egm t-shirt first five contestants came second place latter two prizes 2004 sony pictures released sequel adobe flash titled q*bert 2004 containing faithful rendition original arcade game along 50 levels use new board layouts six new visual themes q*bert deluxe ios devices initially released rendition arcade game later received updates themes stages q*bert 2004 2005 sony pictures released q*bert 2005 download windows flash browser applet featuring 50 different levels july 2 2014 gonzo games sideline amusement announced q*bert rebooted released steam ios android versions playstation 3 playstation 4 playstation vita released february 17 2015 north america february 18 2015 europe released february 12 2016 xbox one according mark caplan vice president consumer products worldwide marketing distribution sony pictures entertainment release motivated renewed interest q*bert part due cameo recent wreck-it ralph animated feature film q*bert rebooted contains port classic arcade game alongside new playing mode uses hexagonal shapes increasing number possible movement directions six additionally 'rebooted mode features new enemy types including boxing glove punches q*bert levels treasure chest tries avoid game 5 different stage designs spread across 40 levels contain three rounds bonus round completed 5 lives gems collected unlock different skins q*bert character completing levels multiple times reaching specific time score goals awarded stars enable access levels
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Computer architecture
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mos technology 6510 mos technology 6510 8-bit microprocessor designed mos technology modified form successful 6502 6510 widely used commodore 64 home computer variants primary change 6502 addition 8-bit general purpose i/o port although six i/o pins available common version 6510 addition address bus could made tristate c64 extra i/o pins processor used control computer memory map bank switching controlling three four signal lines datasette tape recorder electric motor control key-press sensing write data lines read data line went another i/o chip possible writing correct bit pattern processor address 01 completely expose almost full 64 kb ram c64 leaving rom i/o hardware exposed except processor i/o port data directional register 1985 mos produced 8500 hmos version 6510 process modification virtually identical nmos version 6510 8500 originally designed use modernised c64 c64c however 1985 limited quantities 8500s found older nmos-based c64s finally made official debut 1987 appearing motherboard using new 85xx hmos chipset 7501/8501 variant 6510 introduced 1984 compared 6510 variant extends number i/o port pins 6 8 omits pins non-maskable interrupt clock output.. used commodore c16 c116 plus/4 home computers i/o port controlled datasette also cbm bus interface main difference 7501 8501 cpus manufactured slightly different processes 7501 manufactured hmos-1 8501 hmos-2 2 mhz-capable 8502 variant used commodore 128 cpus opcode compatible including undocumented opcodes commodore 1551 disk drive used 6510t version 6510 eight i/o lines nmi rdy signals available
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Computer architecture
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visi visicorp visi short-lived highly influential graphical user interface-based operating environment program ibm compatible personal computers running ms-dos although visi never popular steep minimum system requirements day major influence later development microsoft windows spring 1981 personal software cash-flush ever-increasing sales visicalc corporate directors sat planned future directions ed esber introduced concept family products could sold together technical perspective none products similar anything name instance use visiplot visicalc data numbers plotted exported raw format re-imported dan fylstra led technical discussion sorts actions user would need able accomplish order products truly integrated decided three key concepts one universal data exchange would supported set common data structures used programs another common consistent interface users would re-learn ui moved one program another finally fylstra concerned time needed move one program another long useful – user needing quickly look something visidex would save exit visicalc look information quit re-launch visicalc process made quicker simpler july 1981 xerox announced xerox star advanced workstation computer featuring graphical user interface point well known secret apple computer working low-cost computer gui would later released apple lisa personal software president terry opdendyk knew two-man team texas working gui arranged scott warren dennis abbe visit personal software headquarters sunnyvale california demonstrated version smalltalk programming language running trs-80 microcomputer seriously underpowered machine task personal software extremely impressed contract soon signed work project quasar started almost immediately name shortly thereafter changed visi play vision retained visi naming experimental port ill-fated apple iii completed november development work shifted dec vax cross-compilers number different machines early 1982 personal software changed name visicorp betting much future success company visi visi many features modern gui included become common many years later fully mouse-driven used bit-mapped display text graphics included on-line help allowed user open number programs window visi however include graphical file manager visi also demanded hard drive order implement virtual memory system used fast switching time hard drives expensive piece equipment tom powers visicorp new vp marketing pushed system demonstrated fall comdex show 1982 others company worried product ready shipping showing early would leave potential customers distributors upset n't ready soon another concern visiword released show worry might lost shuffle demonstrations comdex huge success many viewers told simply movie watching bill gates speculated pc fact simply terminal real machine like vax became one talked-about products industry however huge success led number serious problems separate june july 1983 byte articles company mentioned late summer 1983 release visi development continued visicorp entity process self-destruction terry opdendyk president hand-picked early venture capital investors extremely autocratic management style led departure many key executives late 1981 eventual release visi product management company left notably mitch kapor charge visicalc development ed esber roy folk visi product marketing manager among others referred corporate civil war mitch kapor departure would prove devastating company however kapor developer visiplot visitrend pressing development greatly improved spreadsheet succeed visicalc opdendyk uninterested time visicorp visicalc developers impasse visicalc growing increasingly outdated kapor decided leave executives pressed clause forbidding kapor work integrated spreadsheet opdendyk could n't bothered exclaiming kapor spaghetti programmer denigrating abilities kapor would go release lotus 1-2-3 became major competitor visicalc 1983 end year sales cut half combined exodus major portions senior executive staff ongoing battle visicalc developers visicorp soon serious financial difficulty hopes company future placed visi october 31 1983 infoworld article titled finally visi flatly stated ... publisher putting product computer store shelves ... visi scheduled available last week october november 14 1983 issue said visicorp released visi however july 2 1984 issue says time visi actually shipped december 16 1983 ... pc magazine reported february 7 1984 issue still n't received product commercially available form operating system known visi applications manager released december 1983 sold 495 requiring mouse another 250 main disadvantage visi extremely high system requirements 1982 standards needed 512 kilobytes ram hard disk time pcs shipped 64k-128k ibm yet offer hard disk pc ibm first model hard drive pc xt n't ship march 1983 third-party drives however available time typically 5mb units connected floppy controller treated operating system oversized floppy disk subdirectory support brought total cost running visi 7500 three-quarters cost apple lisa press continued laud product going far claim represented end operating systems end-users less impressed however due high cost required hardware also general slowness system market computers generally used one two tasks usually business related whole purpose visi seriously diluted january 1984 apple computer released macintosh much fanfare although macintosh seriously lacking software faster cheaper included one feature visi lacked graphical file manager finder although n't compete directly visi really pc product nevertheless demonstrated gui could indeed fast relatively inexpensive visi failed deliver adding release problems bill gates took page visicorp book announced product microsoft windows would available may 1984 muddied waters significantly notably claimed would similar feature set n't require hard disk cost 250 windows released even longer delay visi shipping november 1985 lacking features forced visi demand hard drive eight visicorp employees still developing visi visicorp sold source code control data mid-1984 raise cash sued software arts continuing sell software sales apparently slow february 1985 visicorp responded lowering price basic os 99 knowing anyone purchasing would also need buy applications bundled three 990 improved situation somewhat sales still far projections certainly helping company stave problems due lotus 1-2-3 following declining visicalc sales low revenues visi november 1985 company merged paladin software new company kept paladin name visicorp line visiproducts history official system requirements visi work newer pcs requires compatible mouse hard disk partition 15mb fat12 file system supported addition revectors irqs used pc/ats later visionxt.exe requires modifications prevent graph applications functioning properly visi required mouse systems-compatible mice microsoft-compatible pc mice time became standard introduced later may 1983 visi used two mouse drivers first loaded text mode made mouse registers accessible embedded driver translated coordinates cursor position internal driver built-in subroutine visionxt.exe required mouse systems pc-mouse pointing device compatible microsoft mouse standard writing visi applications required unix development environment visi targeted toward high-end expensive pc workstations visi applications written subset c visic third-party could ported core software visihost visimachine virtual machine visionxt.exe ibm pc dos version unix never occurred 1984 visicorp assets sold control data corporation making working copies original floppy disks using modern methods difficult protected using pre-created bad sectors methods floppy disk identification
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Operating systems
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motorola 68020 motorola 68020 sixty-eight-oh-twenty sixty-eight-oh-two-oh six-eight-oh-two-oh 32-bit microprocessor motorola released 1984 successor motorola 68010 succeeded motorola 68030 lower cost version also made available known 68ec020 keeping naming practices common motorola designs 68020 usually referred 020 pronounced oh-two-oh oh-twenty 68020 32-bit internal external data address buses compared early 680x0 models 16-bit data 24-bit address buses 68020 alu also natively 32-bit could perform 32-bit operations one clock whereas 68000 took two clocks minimum due 16-bit alu newer packaging methods allowed '020 feature external pins without large size earlier dual in-line package method required 68ec020 lowered cost 24-bit address bus 68020 produced speeds ranging 12 mhz 33 mhz 68020 added many improvements 68010 including 32-bit arithmetic logic unit alu 32-bit external data address buses extra instructions additional addressing modes 68020 68030 proper three-stage pipeline though 68010 loop mode sped loops effectively tiny instruction cache held two short instructions thus little used 68020 replaced proper instruction cache 256 bytes first 68k series processor feature true on-chip cache memory previous 68000 68010 processors could access word 16-bit long word 32-bit data memory word-aligned located even address 68020 alignment restrictions data access naturally unaligned accesses slower aligned accesses required extra memory access 68020 coprocessor interface supporting eight coprocessors main cpu recognizes f-line instructions four significant opcode bits one uses special bus cycles interact coprocessor execute instructions two types coprocessors defined floating point units mc68881 mc68882 fpus paged memory management unit mc68851 pmmu one pmmu used cpu principle multiple fpus could used cpu commonly done coprocessor interface asynchronous possible run coprocessors different clock rate cpu multiprocessing support implemented externally use rmc pin indicate indivisible read-modify-write cycle progress processors hold memory accesses cycle complete software support multiprocessing included tas cas cas2 instructions multiprocessor system coprocessors could shared cpus avoid problems returns coprocessor bus error address error exceptions generally necessary multiprocessor system cpus model fpus model well new instructions included minor improvements extensions supervisor state several instructions software management multiprocessing system removed 68060 support high-level languages get used much removed future 680x0 processors bigger multiply 32×32→64 bits divide 64÷32→32 bits quotient 32 bits remainder instructions bit field manipulations 68000 'supervisor mode meet popek goldberg virtualization requirements due single instruction 'move sr unprivileged sensitive 68010 later made privileged better support virtualization software new addressing modes added scaled indexing another level indirection many pre-existing modes added quite bit flexibility various indexing modes operations though intended new modes made 68020 suitable page printing laser printers early 1990s 68ec020 core 68020 small 256-byte direct-mapped instruction cache arranged 64 four-byte entries although small still made significant difference performance many applications resulting decrease bus traffic particularly important systems relying heavily dma 68020 used apple macintosh ii macintosh lc personal computers sun 3 workstations commodore amiga 1200 hewlett-packard 8711 series network analyzers later members hp 9000/300 family alpha microsystems am-2000 also 68020 alternative upgrade sinclair ql computer 68008 super gold card interface miracle systems amiga 2500 a2500ux shipped a2620 accelerator using 68020 68881 floating point unit 68851 memory management unit 2500ux shipped amiga unix requiring '020 '030 processor number digital oscilloscopes mid-80s late-90s used 68020 including lecroy 9300 series higher end models including c suffix models used powerful 68ec030 9300 models 68020 processor upgraded 68ec030 change cpu board earlier lecroy 9400 series models excluding 9400/9400a used 68000 along certain tektronix tds series models.. hp 54520 54522 54540 54542 also use 68020 together 68882 math coprocessor also processor used board tgv trains decode signalling information sent trains rails used flight control radar systems eurofighter typhoon combat aircraft nortel networks dms-100 telephone central office switch also used 68020 first microprocessor supernode computing core information instructions architecture see motorola 68000 68ec020 lower cost version motorola 68020 main difference two 68ec020 24-bit address bus rather 32-bit address bus full 68020 thus able address 16 mb memory commodore amiga 1200 computer amiga cd32 games console used cost-reduced 68ec020 namco system 22 taito f3 arcade boards also used processor atari jaguar ii prototype also featured replace 68000 original atari jaguar console also found use laser printers apple used laserwriter iiɴᴛx kodak used ektaplus 7016ps dataproducts used lzr 1260 2014 rochester electronics re-established manufacturing capability 68020 microprocessor still available today
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Computer architecture
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address book server address book server dates back several years inclusion feature share contacts 10.6 server product based sync services synchronised contacts network macintosh computers thus allowing contacts present local address book manner contacts server friendly web interface used provide access windows linux remote users product confused address book server included snow leopard server 10.6 unlike apple offering address book server offers features web interface supports 10.4 10.5 10.6 10.7 address book server consists two separate components one server side package requires installation dedicated server client components installs panel system preferences installed server publish presence local network using bonjour accessed via safari bookmarks client requires basic configuration enabled contacts calendar events synchronised published server published records accessed via server web interface stage clients also enabled synchronise local records server basic setup address book server consist clients periodically synchronising server synchronisation changes entire data set fetched form server via sync services compared local records present server differences local records received form server sent back server update central database details address book server available website project abandoned 2010 longer undergoing development
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Internet protocols
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cratedb cratedb distributed sql database management system integrates fully searchable document oriented data store open-source written java based shared nothing architecture designed high scalability includes components facebook presto apache lucene elasticsearch netty cratedb project started jodok batlogg open source contributor creator contributed open source initiative vorarlberg lovely systems dornbirn software open source clustered database used fast text search analytics company called crate.io raised first round financing april 2014 4m round march 2016 2.5m round january 2017 dawn capital draper esprit speedinvest sunstone capital june 2014 crate.io judge choice award gigaom structure launchpad competition october 2014 win techcrunch disrupt europe london cratedb 1.0 released december 2016. reported one million downloads cratedb 2.0 enterprise edition released may 2017 cratedb language sql uses document-oriented approach nosql style databases software uses sql parser facebook presto query analysis distributed query engine elasticsearch lucene used transport protocol cluster discovery netty asynchronous event driven network application framework cratedb offers automatic data replication self-healing clusters high availability cratedb includes built-in administration interface command line interface crate shell – crash allows interactive queries python client advanced features sqlalchemy integration
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Databases
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digital self-defense digital self-defense use self-defense strategies internet users ensure digital security say protection confidential personal electronic information internet security software provides initial protection setting firewall well scanning computers malware viruses trojan horses worms spyware however information risk includes personal details birthdates phone numbers bank account schooling details sexuality religious affiliations email addresses passwords information often openly revealed social networking sites leaving internet users vulnerable social engineering possibly internet crime mobile devices especially wi-fi allow information shared inadvertently digital self-defense requires internet users take active part guarding personal information four key strategies frequently suggested assist protection computer security context referring internet security software ongoing security private information requires frequent updating virus spyware definitions ongoing developments malicious software interfere copy private information practice utilising one email account separate personal business usage recreational usage strategy commonly used manage personal privacy free ready availability email accounts sites yahoo google hotmail allows protection personal identity use different names identify email account throw-away accounts discarded replaced providing another level protection username required set email accounts open accounts various official commercial recreational social networking sites many cases email address may also utilised username usernames correlate personal information names nicknames risk ones cryptic anonymous particularly social recreational sites password mandatory security measure accompanies usernames use personal data construct passwords i.e family members ’ names pet ’ names birth dates increases risk confidential information easier crack long complicated passwords password strength key strategy protecting personal information password weak strong weak password cutekittens strong password lacpas56ikms according microsoft ideal password least 14 characters length letters punctuation symbols numbers complexity added inclusion uppercase letters social networking sites offer greater security risks personal electronic information sensitive private confidential information personal identifiers routinely used create public profiles many websites give options suppress amount personal information revealed customisation privacy settings however privacy settings reset changes website occur
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Computer security
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windows dvd maker windows dvd maker dvd authoring utility developed microsoft first released 2007 windows vista utility allows users create dvd slideshows videos playback media devices dvd player comparable apple idvd released 2001 dvd maker removed windows 8 windows dvd maker first reported paul thurrott windows hardware engineering conference 2003 thurrott stated windows vista known codename longhorn would support dvd movie creation independent application shell information accompanied additional reports windows vista would support major dvd packet writing formats mount rainier would also eliminate staging burning steps writing optical media—files copied recordable media would instead written immediately latter functionality exposed via live file system windows dvd maker available home premium enterprise ultimate editions windows vista well home premium professional enterprise ultimate editions windows 7 simple aero wizard-style user interface takes user process creating dvd-video first step involves importing video files arranging play proper order windows dvd maker automatically splits videos scenes accessed special scene selection page dvd menu next step animated dvd menus added compilation windows dvd maker also add slide show pictures musical accompaniment transition effects many similar transition effects available windows movie maker users also customize font button styles application show interactive preview dvd look act like burned example users navigate dvd menus testing windows dvd maker designed encode video background process reduced scheduling priority ensure computer remains responsive compilation process
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Operating systems
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hp integral pc hp integral pc hp 9807a portable unix workstation computer system produced hewlett-packard launched 1985 based motorola 68000 microprocessor running 8 mhz ran early version hp-ux operating system integral pc mains-powered portable computer 9-inch amber electroluminescent display resolution 512×255 pixels 80×28 characters also incorporated 710 kb 3.5 floppy disk drive hp thinkjet ink-jet printer standard memory capacity 256 kb rom plus 512 kb ram expandable 1.5 mb expansion slots hp-ib bus also included mechanical design based ideas de facto standard hp-85 concept upright portable computer system integrated printer floppy screen followed several companies century within integral pc cpu ram rom memory management i/o buffering system timing keyboard interface integrated single logic-board peripheral units 14 connections built using independent boards board smaller letter sized sheet make easier check boards board contains timer i/o-board two connections optional addons keyboard-interface human interface link hp-hil power supply checked tested independently graphics processor integral pc gpu custom made could drive electroluminescence display nearly every kind monitor processor provides graphical subsystem simple use drive bitmapped display gpu able draw lines rectangles alphanumerical characters hardware additionally provides hardware cursor display-ram-interface electroluminescence-display based thin-film-technique developed hp companies integral pc unusual hp-ux operating system kernel resided rom also included hp windows graphical user interface personal applications manager pam hp-ux commands utilities supplied separately floppy disk add rom provides hp-basic using rom integral pc ready run basic simply switching system
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Computer architecture
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swift programming language swift general-purpose multi-paradigm compiled programming language developed apple inc. ios macos watchos tvos linux z/os swift designed work apple cocoa cocoa touch frameworks large body existing objective-c code written apple products built open source llvm compiler framework included xcode since version 6 released 2014 apple platforms uses objective-c runtime library allows c objective-c c++ swift code run within one program apple intended swift support many core concepts associated objective-c notably dynamic dispatch widespread late binding extensible programming similar features safer way making easier catch software bugs swift features addressing common programming errors like null pointer dereferencing provides syntactic sugar help avoid pyramid doom swift supports concept protocol extensibility extensibility system applied types structs classes apple promotes real change programming paradigms term protocol-oriented programming similar traits swift introduced apple 2014 worldwide developers conference wwdc underwent upgrade version 1.2 2014 major upgrade swift 2 wwdc 2015 initially proprietary language version 2.2 made open-source software apache license 2.0 december 3 2015 apple platforms linux version 3.0 syntax swift went significant evolution core team making source stability focus later versions first quarter 2018 swift surpassed objective-c measured popularity swift 4.0 released 2017 introduced several changes built-in classes structures code written previous versions swift updated using migration functionality built xcode swift 5 released march 2019 introduced stable binary interface apple platforms allowing swift runtime incorporated apple operating systems source compatible swift 4 development swift started july 2010 chris lattner eventual collaboration many programmers apple swift took language ideas objective-c rust haskell ruby python c clu far many others list june 2 2014 apple worldwide developers conference wwdc application became first publicly released app written swift beta version programming language released registered apple developers conference company promise final version swift would source code compatible test version apple planned make source code converters available needed full release swift programming language free 500-page manual also released wwdc available ibooks store official website swift reached 1.0 milestone september 9 2014 gold master xcode 6.0 ios swift 1.1 released october 22 2014 alongside launch xcode 6.1 swift 1.2 released april 8 2015 along xcode 6.3 swift 2.0 announced wwdc 2015 made available publishing apps app store september 21 2015 swift 3.0 released september 13 2016 swift 4.0 released september 19 2017 swift 4.1 released march 29 2018 swift first place loved programming language stack overflow developer survey 2015 second place 2016 december 3 2015 swift language supporting libraries debugger package manager open sourced apache 2.0 license runtime library exception swift.org created host project source code hosted github easy anyone get code build even create pull requests contribute code back project december 2015 ibm announced swift sandbox website allows developers write swift code one pane display output another swift sandbox deprecated january 2018 wwdc 2016 apple announced ipad exclusive app named swift playgrounds intended teach people code swift app presented 3d video game-like interface provides feedback lines code placed certain order executed january 2017 chris lattner announced departure apple new position tesla motors swift project lead role going team veteran ted kremenek wwdc 2019 apple announced swiftui provides framework declarative ui structure design across apple platforms swift alternative objective-c language employs modern programming-language theory concepts strives present simpler syntax introduction described simply objective-c without c default swift expose pointers unsafe accessors contrast objective-c uses pointers pervasively refer object instances also objective-c use smalltalk-like syntax making method calls replaced dot-notation style namespace system familiar programmers common object-oriented oo languages like java c swift introduces true named parameters retains key objective-c concepts including protocols closures categories often replacing former syntax cleaner versions allowing concepts applied language structures like enumerated types enums cocoa cocoa touch environments many common classes part foundation kit library included nsstring string library using unicode nsarray nsdictionary collection classes others objective-c provided various bits syntactic sugar allow objects created on-the-fly within language created objects manipulated object calls instance objective-c concatenating two nsstrings required method calls similar swift many basic types promoted language core manipulated directly instance strings invisibly bridged nsstring foundation imported concatenated codice_1 operator allowing greatly simplified syntax prior example becoming swift supports five access control levels symbols codice_2 codice_3 codice_4 codice_5 codice_6 unlike many object-oriented languages access controls ignore inheritance hierarchies codice_6 indicates symbol accessible immediate scope codice_5 indicates accessible within file codice_4 indicates accessible within containing module codice_3 indicates accessible module codice_2 classes methods indicates class may subclassed outside module important new feature swift option types allow references values operate manner similar common pattern c pointer may refer value may null implies non-optional types result null-pointer error compiler ensure possible optional types created codice_12 mechanism—to make integer nullable one would use declaration similar codice_13 c swift also includes syntactic sugar allowing one indicate variable optional placing question mark type name codice_14 variables constants marked optional either value underlying type codice_15 optional types wrap base type resulting different instance codice_16 codice_17 fundamentally different types latter common codice_18 codice_16 access value inside assuming nil must unwrapped expose instance inside performed codice_20 operator case codice_20 operator unwraps codice_22 expose instance inside allowing method call made codice_22 nil null-pointer error occurs annoying practice swift also includes concept optional chaining test whether instance nil unwrap non-null case runtime calls codice_24 codice_22 nil suppressing error normally requires programmer test whether codice_26 nil proceeding origin term chaining comes common case several method calls/getters chained together instance reduced codice_27 syntax circumvents pyramid doom swift 2 introduced new keyword codice_28 cases code stop executing condition unmet using codice_28 three benefits syntax act codice_30 statement primary benefit inferring non-nullability codice_30 statement requires case codice_28 assumes case based condition provided also since codice_28 contains scope exception codice_34 closure codice_35 presented unwrapped optional guard super-scope lastly codice_28 statement test fails swift requires codice_34 exit current method loop ensuring codice_35 never accessed codice_15 performed keywords codice_40 codice_41 codice_42 codice_43 objective-c weakly typed allowed method called object time method call failed default handler runtime returned nil meant unwrapping testing needed equivalent statement objective-c would return nil could tested however also demanded method calls dynamic introduces significant overhead swift use optionals provides similar mechanism testing dealing nils way allows compiler use static dispatch unwrapping action called defined instance wrapper versus occurring runtime dispatch system many object-oriented languages objects represented internally two parts object stored block data placed heap data structure |heap name handle object represented pointer computer programming |pointer objects passed methods copying value pointer allowing underlying data heap accessed anyone copy contrast basic types like integers floating point values represented directly handle contains data pointer data passed directly methods copying styles access termed pass-by-reference case objects pass-by-value basic types concepts advantages disadvantages objects useful data large like description window contents document cases access data provided copying 32- 64-bit value versus copying entire data structure however smaller values like integers size pointers typically one word computer architecture |word advantage passing pointer versus passing value also pass-by-reference inherently requires dereferencing operation produce noticeable overhead operations typically used basic value types like mathematics similarly c contrast oo languages swift offers built-in support objects using either pass-by-reference pass-by-value semantics former using codice_44 declaration latter using codice_45 structs swift almost features classes methods implementing protocols using extension mechanisms reason apple terms data generically instances versus objects values structs support inheritance however programmer free choose semantics appropriate data structure application larger structures like windows would defined classes allowing passed around pointers smaller structures like 2d point defined structs pass-by-value allow direct access internal data dereference performance improvement inherent pass-by-value concept swift uses types almost common data types including codice_46 codice_47 types normally represented objects like codice_16 codice_49 using value types result significant performance improvements user applications well ensure even largest structs cause performance penalty handed swift uses copy write objects copied program attempts change value means various accessors effect pointer data storage data physically stored one instance memory level application values separate physical separation enforced copy write needed key feature objective-c support categories methods added extend classes runtime categories allow extending classes in-place add new functions need subclass even access original source code example might add spell checker support base codice_50 class means instances nsstring application gain spell checking system also widely used organizational technique allowing related code gathered library-like extensions swift continues support concept although termed extensions declared keyword codice_51 unlike objective-c swift also add new properties accessors types enums extant instances another key feature objective-c use protocol_ object-oriented_programming protocols known modern languages interfaces protocols promise particular class implements set methods meaning objects system call methods object supporting protocol often used modern oo languages substitute multiple inheritance although feature sets entirely similar common example protocol cocoa codice_52 protocol defines one method codice_53 implements object copying deep copy|deep copying objects objective-c languages implementing protocol concept programmer ensure required methods implemented class swift adds ability add methods using extensions use generic programming generics implement combined allow protocols written support wide variety instances also extension mechanism used add protocol conformance object list protocol definition example protocol might declared called codice_54 ensures instances conform protocol implement codice_55 method returns codice_16 swift declared code like protocol added string access base class source swift like many modern languages supporting interfaces protocols used types means variables methods defined protocol instead specific type matter sort instance codice_57 compiler ensure conforms protocol thus code safe syntax also means collections based protocols also like codice_58 swift treats structs classes similar concepts extensions protocols extensively used swift runtime provide rich api based structs instance swift uses extension add codice_59 protocol many basic types like strings arrays allowing compared codice_60 operator concrete example features interact seen concept default protocol implementations function defines method works instance conforming codice_59 providing equals function instance class struct automatically gains implementation simply conforming codice_59 many instances gain codice_59 base implementations generic extensions basic objects runtime gain equals equals code combination protocols defaults protocol inheritance extensions allows many functions normally associated classes inheritance implemented value types properly used lead dramatic performance improvements significant limits api concept widely used within swift apple begun calling protocol-oriented programming language suggest addressing many problem domains normally solved though classes inheritance using protocols structs instead swift uses runtime extant objective-c system requires ios 7 macos 10.9 higher swift objective-c code used one program extension c c++ also contrast c c++ code used directly swift objective-c c wrapper must created swift c++ case objective-c swift considerable access object model used subclass extend use objective-c code provide protocol support converse true swift class subclassed objective-c. aid development programs re-use extant code xcode 6 higher offers semi-automated system builds maintains bridging header expose objective-c code swift takes form additional header file simply defines imports objective-c symbols needed project swift code point swift refer types functions variables declared imports though written swift objective-c code also use swift code directly importing automatically maintained header file objective-c declarations project swift symbols instance objective-c file mixed project called myapp could access swift classes functions code codice_64 symbols available mechanism however—use swift-specific features like generic types non-object optional types sophisticated enums even unicode identifiers may render symbol inaccessible objective-c swift also limited support attributes metadata read development environment necessarily part compiled code like objective-c attributes use codice_65 syntax currently available set small one example codice_66 attribute marks given value code outlet available use within interface builder ib outlet device binds value on-screen display object code swift uses automatic reference counting arc memory management|manage memory apple used require manual memory management objective-c introduced arc 2011 allow easier memory allocation deallocation one problem arc possibility creating reference counting reference cycle|strong reference cycle objects reference way reach object started following references e.g references b b references causes become leaked memory never released swift provides keywords codice_67 codice_68 prevent strong reference cycles typically parent-child relationship would use strong reference child-parent would use either codice_67 reference parents children unrelated codice_68 child always parent parent may child weak references must optional variables since change become codice_15 closure within class also create strong reference cycle capturing self references self references treated weak unowned indicated using capture list key element swift system ability cleanly debugged run within development environment using read–eval–print loop repl giving interactive properties common scripting abilities python traditional system programming languages repl enhanced new concept swift playgrounds|playgrounds interactive views running within xcode environment respond code debugger changes on-the-fly swift playgrounds|playgrounds allow programmers add swift code along markdown documentation code changes time regard ranged input value view used timeline assistant demonstrate output animated way addition xcode debugging features swift development including breakpoints step step statements well ui element placement breakdowns app developers apple says swift industrial-quality programming language expressive enjoyable scripting language many features introduced swift also well-known performance safety trade-offs apple implemented optimizing compiler|optimizations reduce overhead swift similar c various ways also similarities objective-c differences objective-c include since language open-source prospects ported web web frameworks already developed ibm kitura perfect server framework |perfect vapor server-side swift |vapor official server apis work group also started apple members swift developer community playing central role second free implementation swift targets cocoa api |cocoa microsoft common language infrastructure .net framework|.net java software platform |java android operating system |android platform exists part elements compiler remobjects software category apple inc. software category computer-related introductions 2014 category object-oriented programming languages category pattern matching programming languages category programming languages category programming languages created 2014 category software using apache license category statically typed programming languages category systems programming languages
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Programming language topics
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composer software composer application-level package manager php programming language provides standard format managing dependencies php software required libraries developed nils adermann jordi boggiano continue manage project began development april 2011 first released march 1 2012 composer strongly inspired node.js npm ruby bundler project dependency solving algorithm started php-based port opensuse libzypp satsolver composer runs command line installs dependencies e.g libraries application also allows users install php applications available packagist main repository containing available packages also provides autoload capabilities libraries specify autoload information ease usage third-party code composer offers several parameters including example composer.json generated following command different authorized versions libraries defined
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Operating systems
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voms voms acronym used virtual organization membership service grid computing structured simple account database fixed formats information exchange features single login expiration time backward compatibility multiple virtual organizations database manipulated authorization data defines specific capabilities roles users administrative tools used administrators assign roles capability information database command-line tool allows users generate local proxy credential based contents voms database credential includes basic authentication information standard grid proxy credentials contain also includes role capability information voms server voms-aware applications use voms data make authentication decisions regarding user requests voms originally developed european datagrid enabling grids e-science projects maintained italian national institute nuclear physics infn voms also acronym voucher management system used providing recharge management services prepaid systems telecom service providers typically external voucher management systems used intelligent network based prepaid systems
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Distributed computing architecture
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nitrosecurity nitrosecurity inc. privately held united states-based provider security information event management siem technology nitrosecurity headquarters located portsmouth new hampshire usa sales offices throughout united states united kingdom primary software engineering development siem products idaho falls idaho acquired mcafee 2011 engineering siem products continue developed mcafee idaho falls 2010 inc. magazine rated nitrosecurity 523 inc. 5,000 list fastest-growing companies nitrosecurity develops security information event management siem tools identify correlate remediate information security threats product names nitroview esm nitroview elm nitroview adm nitroview dbm nitroguard ips
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Computer security
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modern operating systems modern operating systems book written andrew tanenbaum version target implementation book 4th edition published march 2014 modern operating systems mostly known mos popular book across globe includes fundamentals operating system small amounts code written autonomous c language mos describes many scheduling algorithms
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Operating systems
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fabrik inc. fabrik inc. manufacturer external hard drives digital content management software services fabrik said third largest supplier external storage products north america 2007 headquartered san mateo offices santa ana culver city california company sells external hard drives online backup software bundled product consumers small business users audio/video a/v content creation professionals company also hosts free online digital content management sharing site joggle fabrik product lines include simpletech g-technology joggle fabrik ultimate backup fabrik founded web-based software company august 2005 former maxtor executives mike cordano keyur patel anaal udaybabu designed brand identity on-the-web storage following month company disclosed completion series funding 4.1 million followed 8 million series b funding july 2006 14.3 million february 2007 may 2007 company received 24.9 million funding bringing total 51.3 million funding february 2006 fabrik partnered maxtor acquired seagate 2005 develop maxtor fusion network-attached storage nas device built organizing sharing digital files late 2006 company launched myfabrik.com organized stored digital media online february 2007 company acquired consumer business simpletech inheriting simpletech product line external hard drives consumers small businesses january 2008 fabrik acquired g-technology inherited suite external hard drives mac creative pro photography a/v markets including firewire esata usb scsi fibre channel storage products fabrik acquisitions introduction joggle demo conference january 2008 created four brands simpletech g-technology joggle fabrik ultimate backup simpletech g-technology products still branded maintained separate online website entities february 23 2009 hitachi global storage technologies announced agreed acquire fabrik point fabrik revenue year 2009 estimated 350m 400m range growing 40 yearly basis april 6 2009 hitachi global storage technologies completed acquisition formed core hitachi gst new branded business division following acquisition subsidiary branded g-technology hitachi company simpletech products external hard drives mainstream consumers small business users includes portable external hard drives desktop external hard drives simpletech products come bundled free local backup software online backup capabilities simpletech drive 100 percent recyclable enclosure several energy resource efficiency features company claims drive world eco-friendly resource conscious external hard drive original design simpletech portable external storage product line inspired ferrari design team pininfarina fabrik started free online digital content management site called joggle early 2008 web site searches video photos music user computer external hard drive online communities networking sites automatically consolidates single online organizing sharing tool company also pure online backup approach fabrik ultimate backup data backed remote servers using 128-bit ssl blowfish encryption
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Computer security
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kemp inc kemp inc. founded 2000 bethpage new york operates application delivery controller industry company builds load balancing products balances user traffic multiple application servers physical virtual cloud environment 2010 kemp opened european headquarters limerick ireland edison ventures kennet partners orix venture finance invested 16 million company research development sales marketing early 2012 april 2014 kemp announced investment limerick operations expand 30 positions 80 kemp recognized visionary 2015 gartner magic quadrant application delivery controllers 2016 2019 kemp purchased private equity firm mill point capital kemp software company develops load balancing application delivery software built linux operating system sold loadmaster brand 2017 40,000 customer deployments loadmaster need high availability scalability security visibility applications enables customers scale operations delivering applications layer 4 7 load balancing enhanced performance secure access loadmaster software-based load balancer adc available virtualized appliance well cloud including azure aws others kemp main product loadmaster load balancer built proprietary software platform called lmos enables run almost platform kemp loadmaster appliance virtual loadmaster vlm deployed hyper-v vmware bare metal public cloud kemp available azure top 15 deployed applications well aws vmware vcloud air 2013 kemp announced adding pre-authorization single sign-on sso persistent logging product range tmg alternative kemp ’ dns based global site load balancer gslb enables customers provide availability scaling resilience applications geographically distributed including data center environments private clouds multi-public cloud environments azure aws well hybrid environments applications deployed across public private cloud capabilities provided geo loadmaster similar hosted services dyn dns march 2014 kemp announced availability microsoft azure cloud platform first 3rd party load balancer available vlm azure loadmaster virtual load balancer may 2016 kemp launched centralized application monitoring reporting product called kemp 360 central™ allows network application administrators view state different load balancers application delivery controllers views include throughput users transactions per second product allows users connect 3rd party devices like f5 nginx haproxy time launching kemp 360 central kemp also announced general release 360 vision monitors health applications 360 vision monitors patterns application data statistics able provide pre-emptive health alerts designed prevent application outages march 2015 kemp launched free version loadmaster software called free loadmaster fully featured load balancer shares commercial product features including full layer 4 layer 7 load balancing reverse proxy web content caching compression non-commercial waf web application firewall 20mbps kemp announced launched world first software defined network sdn ready adaptive load balancer september 2014 kemp announced joining opendaylight open source sdn project kemp introduced service mesh part offering 2018 listed company watch techtarget
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Computer security
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motorola 68030 motorola 68030 sixty-eight-oh-thirty 32-bit microprocessor motorola 68000 family released 1987 68030 successor motorola 68020 followed motorola 68040 keeping general motorola naming cpu often referred 030 pronounced oh-three-oh oh-thirty 68030 features 273,000 transistors on-chip instruction data caches 256 bytes also on-chip memory management unit mmu built floating-point unit fpu 68881 faster 68882 floating point unit chips could used 68030 lower cost version 68030 motorola 68ec030 also released lacking on-chip mmu commonly available 132 pin qfp 128 pin pga packages poorer thermal characteristics qfp package limited full 68030 qfp variant 33 mhz pga 68030s included 40 mhz 50 mhz versions also small supply qfp packaged ec variants microarchitecture 68030 basically 68020 core additional 256 byte data cache process shrink added burst mode caches four longwords placed cache without cpu intervention motorola used process shrink pack hardware die case mmu mostly completely compatible external 68851 integration mmu made cost-effective 68020 external mmu also allowed 68030 access memory one cycle faster 68020/68851 combo however 68030 switch synchronous asynchronous buses without reset 68030 also lacks 68020 instructions increases performance ≈5 reducing power draw ≈25 compared 68020 68030 used 68020 bus case performance similar 68020 derived however 68030 provides additional synchronous bus interface used accelerates memory accesses 33 compared equally clocked 68020 finer manufacturing process allowed motorola scale full-version processor 50 mhz ec variety topped 40 mhz 68030 used many models apple macintosh ii commodore amiga series personal computers next cube later alpha microsystems multiuser systems descendants atari st line atari tt atari falcon also used unix workstations sun microsystems sun-3x line desktop workstations earlier sun3 used 68020 laser printers nortel networks dms-100 telephone central office switch recently 68030 core also adapted freescale microcontroller embedded applications lecroy used 68ec030 certain models 9300 series digital oscilloscopes including “ c ” suffix models high performance 9300 series models along mega waveform processing hardware option 68020-based 9300 series models 68ec030 low cost version 68030 difference two 68ec030 omits on-chip memory management unit mmu thus essentially upgraded 68020 68ec030 used cpu low-cost model amiga 4000 number cpu accelerator cards commodore amiga line computers also used cisco systems 2500 series router small-to-medium enterprise computer internetworking appliance 50 mhz speed exclusive ceramic pga package plastic '030 stopped 40 mhz
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Computer architecture
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arch linux arm arch linux arm port arch linux arm processors design philosophy simplicity full control end user like parent operating system arch linux aims unix-like goal minimalism complete user control however make arch linux difficult linux beginners requires knowledge responsibility operating system arch linux arm based arch linux minimalist linux distribution first released march 11 2002 idea making single official port arch linux devices arm processors born members arch linux plugapps archmobile development teams notably mike staszel went found arch linux arm project kevin mihelich currently arch linux arm primary developer arch linux arm community-developed software development user support provided fully volunteer effort donations also unlike community-supported operating systems ubuntu arch linux arm relatively small user base making user participation development especially important arch linux arm rolling release cycle i.e new software packaged released bleeding edge release cycle small frequent package updates differs release cycles linux distributions debian focus large scheduled releases packages proven stable unlike arch linux aimed x86-64 cpus arch linux arm aimed low- high-end arm cpus low end support armv5 platforms like plug computers oxnas-based armv6 pogoplugs arch linux arm also supports many single-board computers raspberry pi beagleboard higher end support however arch linux arm run device supports armv5te armv6h armv7 armv8 instruction sets list officially supported platforms see archlinuxarm.org platforms page list unofficial community-supported devices see archlinuxarm.org community-supported devices forum arch linux arm gained popularity lightweight linux distribution 2014 growing popularity among single-board computer hobbyists arch linux arm also known good community support
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Computer architecture
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euler software euler euler mathematical toolbox eumatht free open-source numerical software package contains matrix language graphical notebook style interface plot window euler designed higher level math calculus optimization statistics software handle real complex interval numbers vectors matrices produce 2d/3d plots uses maxima symbolic operations software compilable windows unix linux versions contain computer algebra subsystem euler math toolbox originated 1988 program atari st. time title program simply euler turned unspecific internet main aim program create tool testing numerical algorithms visualize results demonstrate mathematical content classroom euler math toolbox uses matrix language similar matlab system development since 1970s main developer euler rené grothmann mathematician catholic university eichstätt-ingolstadt germany 2007 euler married maxima computer algebra system symbolic expressions functions added communicate maxima reach good degree integration numerical euler core euler core numerical system written c/c++ handles real complex interval values matrices types available data types sparse compressed matrices long accumulator exact scalar product strings strings used expressions file names etc based core additional functions implemented euler matrix language interpreted programming language style advanced basic dialect euler contains libraries statistics exact numerical computations interval inclusions differential equations stiff equations astronomical functions geometry clean interface consists text window graphics window text window contains fully editable notebooks graphics window graphics output graphics added notebook window exported various formats png svg wmf clipboard graphic types include line bar point plots 2d 3d including anaglyph plots 3d surfaces 3d plots euler api use open raytracer pov-ray euler handles symbolic computations via maxima loaded separate process communicating euler pipes two programs exchange variables values indeed maxima used various euler functions e.g newton method assist computation derivatives taylor expansions integrals moreover maxima called definition time euler function latex used within euler display formulas export formulas html either generated latex images mathjax used special export option exports graphics svg euler also includes tiny c compiler allows subroutines c compiled included via windows dll euler lot similarity matlab free clones gnu octave compatible
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Programming language topics
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motorola 68060 motorola 68060 sixty-eight-oh-sixty 32-bit microprocessor motorola released 1994 successor motorola 68040 highest performing member 68000 series two derivatives produced 68lc060 68ec060 lc low-cost version without fpu ec embedded controller without mmu fpu 68060 design led joe circello 68060 shares architectural features p5 pentium similar superscalar in-order dual instruction pipeline configuration instruction decoder breaks complex instructions simpler ones execution however significant difference 68060 fpu pipelined therefore three times slower pentium floating point applications contrast integer multiplications bit shifting instructions significantly faster 68060 68060 ability execute simple instructions address generation unit agu thereby supply result two cycles alu development 68060 large amounts commercial compiled code analyzed clues instructions would best candidates performance optimization pentium 68060 perform better mixed code pentium decoder issue fp instruction every opportunity hence fpu superscalar alus 68060 non-pipelined fpu accept instruction issued one decoder means optimizing 68060 easier rules prevent fp instructions issued whenever convenient programmer well understood instruction latencies however properly optimized scheduled code pentium fpu capable double clock clock throughput 68060 fpu 68060 last development 68000 family general purpose use abandoned favor powerpc chips saw use late-model amiga machines amiga accelerator cards well atari st clones falcon accelerator board ct60/ct63/ct60e latter created 2015 late models alpha microsystems multiuser computers migration x86 apple inc. unix world moved onto various risc platforms time 68060 available 68060 introduced 50 mhz motorola 0.6 µm manufacturing process years later shrunk 0.42 µm clock speed raised 66 mhz 75 mhz developments basic core continue intended embedded systems combined number peripheral interfaces reduce overall complexity power requirements design number chips different sets interfaces sold names coldfire dragonball model numbers even second-to-last digit 68000 68020 68040 68060 reserved major revisions 680x0 core architecture model numbers odd second-to-last digit 68010 68030 reserved upgrades architecture previous chip 68050 68070 ever produced motorola example motorola 68010 obscure 68012 68000 improvements loop instruction ability suspend continue instruction event page fault enabling use virtual memory appropriate mmu hardware however major overhauls core architecture similarly motorola 68030 represents process improvement 68020 mmu small data cache 256 bytes moved on-chip 68030 released speed ratings 50 mhz jump 68000/68010 68020/68030 however represents major overhaul innumerable individual changes time 68060 production motorola abandoned development 68000 family favor powerpc 68060 last 68000 family processor motorola signetics philips produced 68000-based variant somewhat confusingly named 68070 contains modestly-improved 68000 cpu simple on-chip mmu i²c bus controller came long 68060 used principally embedded processor consumer electronics items notably cd-i consoles 68060 history american broadcast television graphics chyron max maxine series television character generators use 68060 main processor character generators fixture many american television networks affiliate stations desktops 68060 used variants amiga 4000t produced amiga technologies available third party upgrade amiga models also used amiga clone draco non-linear video system q60 extended sinclair ql design similarly slowest start ultimate pace 68k architecture capabilities 68060-based motherboards—at 66 mhz full 68060 non-fpu 68lc060 option overclocked 80 mhz—are 100 times faster sinclair ql running operating systems 68060 used nortel meridian 1 option 51 61 81 large office pbx systems powering cp3 cp4 core processor boards pair boards sporting 68060 could used make pbx fault tolerant logical application previous meridian 1 cores used motorola chips nortel later changed architecture use intel processors motorola vanguard 6560 multiprotocol router uses 50 mhz 68ec060 processor motorola mvme-17x force computer sys68k vmebus systems use 68060 cpu 68ec060 version motorola 68060 microprocessor intended embedded controllers ec differs 68060 neither fpu mmu makes less expensive draws less power 68lc060 low cost version motorola 68060 microprocessor fpu makes less expensive draws less power atc address translation cache
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Computer architecture
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history computer clusters history computer clusters best captured footnote greg pfister search clusters “ virtually every press release dec mentioning clusters says ‘ dec invented clusters ... ’ ibm invent either customers invented clusters soon could fit work one computer needed backup date first unknown would surprising 1960s even late 1950s. ” formal engineering basis cluster computing means parallel work sort arguably invented gene amdahl ibm 1967 published come regarded seminal paper parallel processing amdahl law amdahl law describes mathematically speedup one expect parallelizing given otherwise serially performed task parallel architecture article defined engineering basis multiprocessor computing cluster computing primary differentiator whether interprocessor communications supported inside computer example customized internal communications bus network outside computer commodity network consequently history early computer clusters less directly tied history early networks one primary motivations development network link computing resources creating de facto computer cluster packet switching networks conceptually invented rand corporation 1962 using concept packet switched network arpanet project succeeded creating 1969 arguably world first commodity-network based computer cluster linking four different computer centers something cluster right probably commodity cluster arpanet project grew internet—which thought mother computer clusters union nearly compute resources including clusters happen connected also established paradigm use computer clusters world today—the use packet-switched networks perform interprocessor communications processor sets located otherwise disconnected frames development customer-built research clusters proceeded hand hand networks unix operating system early 1970s tcp/ip xerox parc project created formalized protocols network-based communications hydra operating system built cluster dec pdp-11 minicomputers called c.mmp carnegie mellon university 1971 however circa 1983 protocols tools easily remote job distribution file sharing defined largely within context bsd unix implemented sun microsystems hence became generally available commercially along shared filesystem first commercial clustering product arcnet developed datapoint 1977 arcnet commercial success clustering per se really take digital equipment corporation released vaxcluster product 1984 vax/vms operating system arcnet vaxcluster products supported parallel computing also shared file systems peripheral devices idea provide advantages parallel processing maintaining data reliability uniqueness vaxcluster vmscluster still available openvms systems hp running alpha itanium systems two noteworthy early commercial clusters tandem himalaya circa 1994 high-availability product ibm s/390 parallel sysplex also circa 1994 primarily business use history commodity computer clusters would complete without noting pivotal role played development parallel virtual machine pvm software 1989 open source software based tcp/ip communications enabled instant creation virtual supercomputer—a high performance compute cluster—made tcp/ip connected systems free-form heterogeneous clusters built top model rapidly achieved total throughput flops greatly exceeded available even expensive big iron supercomputers pvm advent inexpensive networked pcs led 1993 nasa project build supercomputers commodity clusters 1995 beowulf cluster—a cluster built top commodity network specific purpose supercomputer capable performing tightly coupled parallel hpc computations—was invented spurred independent development grid computing named entity although grid-style clustering around least long unix operating system arpanet whether clusters used named
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Distributed computing architecture
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malvertising malvertising portmanteau malicious advertising use online advertising spread malware typically involves injecting malicious malware-laden advertisements legitimate online advertising networks webpages online advertisements provide solid platform spreading malware significant effort put order attract users sell advertise product advertising content inserted high-profile reputable websites malvertising provides malefactors opportunity push attacks web users might otherwise see ads due firewalls safety precautions like malvertising attractive attackers 'can easily spread across large number legitimate websites without directly compromising websites malvertising fairly new concept spreading malware even harder combat work way webpage spread system unknowingly interesting thing infections delivered malvertising require user action like clicking compromise system exploit vulnerabilities website server hosted ... infections delivered malvertising silently travel web page advertisements able expose millions users malware even cautious growing rapidly 2012 estimated nearly 10 billion ad impressions compromised malvertising attackers wide reach able deliver attacks easily advertisement networks companies websites difficulty diminishing number malvertising attacks suggests attack vector ’ likely disappear soon websites web publishers unknowingly incorporate corrupted malicious advertisement page computers become infected pre-click post click misconception infection happens visitors begin clicking malvertisement examples pre-click malware include embedded main scripts page drive-by-downloads malware also auto-run case auto redirects user automatically taken different site could malicious malware also found delivery ad – clean ad malware pre post click build design still infected whilst called malicious code hide undetected user idea coming way post-click malvertisement example user clicks ad visit advertised site instead directly infected redirected malicious site sites trick users copying viruses spyware usually disguised flash files popular web redirection often built online advertising spread malware often successful users expect redirection happen clicking advertisement redirection taking place needs co-opted order infect user computer malvertising often involves exploitation trustworthy companies attempting spread malware place clean advertisements trustworthy sites first order gain good reputation later insert virus spyware code behind ad mass virus infection produced remove virus thus infecting visitors site time period identities responsible often hard trace making hard prevent attacks stop altogether ad network infrastructure complex many linked connections ads click-through destinations malvertisements infect vulnerable computer even user never clicks normal-appearing advertisement 2007/2008 first recorded sighting malvertising late 2007 early 2008 threat based vulnerability adobe flash something continued day – see later affected number platforms including myspace excite rhapsody 2009 online edition new york times magazine found serving ad part larger click fraud scam created botnet network malware infected computers nicknamed bahama botnet went used carry click fraud pay per click ads web banner feed new york times hacked weekend september 11 14 causing readers see advertisements telling systems infected trying trick installing rogue security software computers according spokeswoman diane mcnulty culprit approached newspaper national advertiser provided apparently legitimate ads week ads switched virus alert malvertisement afterwards new york times suspended third-party advertisements address problem even posted advice readers regarding issue technology blog 2010 malvertising takes marketing analysts clickz noted online trust alliance ota identified billions display ads across 3500 sites carrying malware year online trust alliance formed cross industry anti-malvertising task force 2011 spotify malvertising attack used blackhole exploit kit – one first instances drive-by download user ’ even click ad become infected malware according bluecoat security systems report 2011 saw increase 240 malvertising based malicious sites 2012 symantec includes malvertising section internet security threat report 2013 looked back landscape 2012 symantec used scanning software across series websites detected half infected malvertising 2012 la times hit massive malvertising attack used blackhole exploit kit infect users seen part general campaign malvertising hit large news portals – strategy carried subsequent years attacks huffingtonpost.com ny times 2013 major malvertising campaign waged yahoo.com one largest ad platforms monthly visits 6.9 billion malware exploit based commonly used web attack cross-site scripting xss number three top ten web attacks types identified open web application security project owasp attack infected users machines ransomware ‘ cryptowall ’ type malware extorts money users encrypting data placing ransom 1000 bitcoins paid 7 days decrypt data 2014 2014 major malvertising campaigns doubleclick zedo ad networks various news portals including times israel hindustan times affected previous attacks cybercrime involved cryptowall malware infection spate malvertising believed brought 1 million ransom money infecting 600,000 computers 2015 mcafee threat report february 2015 said malvertising growing quickly mobile platforms 2015 malvertising campaigns ebay answers.com talktalk.co.uk wowhead.com among others campaigns involved breaches ad networks including doubleclick engage bdr also report possibly first political malvertising campaign pro-russian activists based botnet forced users machines visit bogus sites generated ad revenue activists users also ended several pro-russian propaganda videos several popular websites news sources victims malvertising malicious advertisements placed webpages widgets unknowingly including horoscope.com new york times london stock exchange spotify onion visiting websites affected malvertising users risk infection many different methods used injecting malicious advertisements programs webpages several precautions people take lessen chances getting tricked advertisements commonly used programs adobe flash player adobe reader flaws exploited become vulnerable attacks important avoid least keep date users also download anti-virus software protects threats removes malicious software systems users also push companies websites scan advertisements making active webpages users also use ad blocking software avoid downloading malware contained advertisements specific browser extension alerting malvertising campaigns
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Computer security
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motorola 68040 motorola 68040 sixty-eight-oh-forty 32-bit microprocessor motorola released 1990 successor 68030 followed 68060 68050 keeping general motorola naming 68040 often referred simply '040 pronounced oh-four-oh oh-forty apple macintosh computers 68040 introduced macintosh quadra named chip fastest 68040 processor clocked 40 mhz used quadra 840av expensive models short-lived macintosh centris line also used 68040 cheaper quadra centris macintosh performa used 68lc040 68040 also used personal computers amiga 4000 amiga 4000t well number workstations alpha microsystems servers hp 9000/400 series later versions next computer 68040 first 680x0 family member on-chip floating-point unit fpu thus included functionality previously required external chips namely fpu memory management unit mmu added 68030 also split instruction data caches 4 kilobytes fully pipelined six stages unfortunately 68040 ran transistor budget limit early design mmu take many transistors—indeed die cpu actually saved transistors—the fpu certainly motorola 68882 external fpu known high performance unit motorola wish risk integrators using lc version 68882 instead profitable full rc unit information motorola multiprocessing model 680x0 series see motorola 68020 fpu 68040 thus made incapable ieee transcendental functions supported 68881 68882 used popular fractal generating software time little else motorola floating point support package fpsp emulated instructions software interrupt exception handler heavy use transcendental functions caused severe performance penalties heat always problem throughout 68040 life delivered four times per-clock performance 68020 68030 chip complexity power requirements came large die large caches affected scaling processor never able run clock rate exceeding 40 mhz 50 mhz variant planned canceled overclocking enthusiasts reported success reaching 50 mhz using 100 mhz oscillator instead 80 mhz part novel technique adding oversized heat sinks fans 68040 offered features intel 80486 clock-for-clock basis could significantly outperform intel chip integer floating point instructions however 80486 ability clocked significantly faster without suffering overheating problems late 1991 higher-end macintosh desktop lineup transitioned '040 apple unable offer newer processor top-of-the-line powerbooks early 1994 powerbooks restricted 68030s several years macworld reviewers conceded best choice power users pc-compatible texas instruments 80486 notebook rather top-of-the-line powerbook 180 versions 68040 created specific market segments including 68lc040 removed fpu 68ec040 removed fpu mmu motorola intended ec variant embedded use embedded processors 68040 time need power 68040 ec variants 68020 68030 continued common designs motorola produced several speed grades 16 mhz 20 mhz parts never qualified xc designation used prototyping samples 25 mhz 33 mhz grades featured across whole line around 2000 40 mhz grade full 68040 planned 50 mhz grade canceled exceeded thermal design envelope information instructions architecture see motorola 68000 68ec040 version motorola 68040 microprocessor intended embedded controllers ec differs 68040 neither fpu mmu makes less expensive draws less power 68ec040 used cisco switch supervisor engine heart models 2900 2948g 2980g 4000 4500 5000 5500 6000 6500 7600 68lc040 low cost version motorola 68040 microprocessor fpu makes less expensive draws less power although cpu fits feature chart like motorola 68030 continues include 68040 caches pipeline thus significantly faster 68030 mask revisions 68lc040 contained bug prevents chip operating correctly software fpu emulator used according motorola errata chip mask set 2e71m later contain bug new mask introduced mid-1995 converted 68lc040 chip mc status buggy revisions typically found 68lc040-based apple macintosh computers chips mask set 2e23g used lc 475 confirmed faulty fault relates pending writes lost f-line exception triggered 68040 update microcode manner modern x86 chips means way use software requires floating-point functionality replace buggy 68lc040 later revision full 68040 atc address translation cache
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Computer architecture
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bigfix inc bigfix inc. american company focusing managing networked desktop mobile server computers origins personal computer self-help application company ’ products expanded on-demand endpoint management services include asset inventory/discovery security vulnerability detection remediation software distribution information technology compliance reporting patch management software license management security policy enforcement endpoint device power consumption management founded 1997 bigfix inc. headquartered emeryville california july 1 2019 hcl technologies completed acquisition bigfix ibm previously acquired bigfix undisclosed amount ibm changed name bigfix product ibm tivoli endpoint manager tem shortened name ibm endpoint manager iem 2013 ibm changed name back ibm bigfix july 7 2015 bigfix inc. founded david hindawi david donoho april 1997 emeryville california company ’ initial product user self-service system management application marketed oem pc manufacturers 2002 company developed bigfix software company-wide networked desktop mobile server computer management shifted focus company consumer enterprise markets initial uses centered security patch management identified significant pain point time enterprise departments 2007 bigfix expanded specific management areas security threat suppression bigfix endpoint protection enterprise security configuration management bigfix security configuration vulnerability management enterprise systems management bigfix systems lifecycle management 2009 bigfix entered exclusive partnership trend micro markets included banking financial services manufacturing government education healthcare customers included pitney bowes stanford university suntrust bank miami-dade county public schools us department energy july 20 2010 ibm acquired bigfix inc. approximately 400 million integrated bigfix product tivoli software portfolio new name ibm tivoli endpoint manager tem march 5 2013 ibm tivoli endpoint manager renamed ibm became ibm endpoint manager iem july 7 2015 ibm changed name ibm endpoint manager back ibm bigfix december 7 2018 hcl technologies announced acquisition ibm bigfix acquisition closed july 1 2019
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Computer security
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openstep openstep defunct object-oriented application programming interface api specification legacy object-oriented operating system basic goal offering nextstep-like environment non-nextstep operating systems openstep principally developed next sun microsystems allow advanced application development sun operating systems specifically solaris next produced version openstep mach-based unix stylized openstep well version windows nt software libraries shipped openstep superset original openstep specification including many features original nextstep taligent considered venerable competitor operating system object markets microsoft cairo least consideration even without product releases either taligent theoretical newness often compared next older mature commercially established platform sun microsystems held exploratory meetings taligent deciding upon building object application framework openstep partnership next preemptive move taligent cairo bud tribble founding designer macintosh nextstep sunsoft vice president object products lead decision included 10 million investment sun next deal described first unadulterated piece good news next community last four years openstep api created result 1993 collaboration next sun microsystems allowing cut-down version nextstep operating system object layers run sun solaris operating system specifically solaris sparc-based hardware openstep effort strip away portions nextstep depended mach next-specific hardware present resulted smaller system consisted primarily display postscript objective-c runtime compilers majority nextstep objective-c libraries included basic operating system lower-level display system steve jobs said ahead today race far ... 1996 cairo close behind taligent far behind sun ceo scott mcnealy said insurance policy made firm one-company one-architecture decision like taligent getting trophy spouse signing hp first draft api published next mid 1994 later year released openstep compliant version nextstep openstep supported several platforms well sun sparc systems next submitted openstep specification industry object standards bodies official openstep api published september 1994 first split api foundation application kit first use ns prefix early versions nextstep use nx prefix contain application kit relying standard unix libc types low-level data structures openstep remained next primary operating system product purchased apple computer 1997 openstep combined technologies existing classic mac os produce mac os x. iphone ipad ios also descendant openstep targeted touch devices sun originally adopted openstep environment intent complementing sun corba-compliant object system solaris neo formerly known project doe providing object-oriented user interface toolkit complement object-oriented corba plumbing port involved integrating openstep appkit display postscript layer sun x11 server making appkit tolerant multi-threaded code project doe inherently heavily multi-threaded implementing solaris daemon simulate behavior mach ports extending sunpro c++ compiler support objective-c using next objc runtime writing x11 window manager implement nextstep look feel much possible integrating next development tools project builder interface builder sunpro compiler order provide complete end-user environment sun also ported nextstep-3.3 versions several end-user applications including mail.app preview.app edit.app workspace manager dock openstep corba parts products later split neo released late 1995 without openstep environment march 1996 sun announced joe product integrate neo java sun shipped beta release openstep environment solaris july 22 1996 made freely available download august 1996 non-commercial use sale september 1996 openstep/solaris shipped sparc architecture openstep differs nextstep various ways openstep api specification defines three major components foundation kit software framework application kit gui graphics front-end display postscript 2d graphics system drawing windows graphics screen standardization openstep also allowed creation several new library packages delivered openstep platform unlike operating system whole packages designed run stand-alone practically operating system idea use openstep code basis network-wide applications running across different platforms opposed using corba system primary among packages portable distributed objects pdo pdo essentially even stripped version openstep containing foundation kit technologies combined new libraries provide remote invocation little code unlike openstep defined operating system applications would run pdo libraries compiled application creating stand-alone native application particular platform pdo small enough easily portable versions released major server vendors mid-1990s next staff took writing solutions various corba magazine articles lines code whereas original article would fill several pages even though using pdo required installation considerable amount supporting code objective-c libraries pdo applications nevertheless considerably smaller similar corba solutions typically one-half one-third size similar d'ole provided types services presented resulting objects com objects goal allowing programmers create com services running high-powered platforms called microsoft windows applications instance one could develop high-powered financial modeling application using d'ole call directly within microsoft excel d'ole first released ole communicated applications running single machine pdo enabled next demonstrate excel talking microsoft applications across network microsoft able implement functionality dcom another package developed openstep enterprise objects framework eof tremendously powerful time object-relational mapping product eof became popular enterprise market notably financial sector openstep caused something minor revolution next first operating system nextstep sophisticated mach-unix based operating system originally ran next motorola 68k-based workstations ported run 32-bit intel x86-based ibm-compatible personal computers pa-risc-based workstations hewlett-packard sparc-based workstations sun microsystems next completed implementation openstep existing mach-based os called openstep mach 4.0 july 1996 4.1 december 1996 4.2 january 1997 intents nextstep 4.0 still retained flagship nextstep technologies dps unix underpinnings user interface characteristics like dock shelf retained classic nextstep user interface styles openstep mach improved comparison nextstep 3.3 vastly improved driver support – however environment actually write drivers changed introduction object-oriented driverkit openstep mach supported intel x86-based pc sun sparc workstations next 68k-based architectures hp pa-risc version dropped versions continued run underlying mach-based os used nextstep openstep mach became next primary os 1995 used mainly intel platform addition complete openstep implementation system delivered complete set nextstep libraries backward compatibility easy thing openstep due library versioning openstep suffer bloat addition openstep mach port sparc sun next developed openstep compliant set frameworks run sun solaris operating system developing solaris openstep sun lost interest openstep shifted attention toward java virtual machine development environment java served direct competitor openstep next also delivered implementation running top windows nt 4.0 called openstep enterprise often abbreviated ose unintentional demonstration true nature portability programs created openstep specification programs openstep mach could ported ose little difficulty allowed existing customer base continue using tools applications running windows many process switching never clean match ui perspective probably due openstep routing window graphics display postscript server—which also ported windows—ose nevertheless managed work fairly well extended openstep commercial lifespan openstep ose two revisions one major one never released next purchased apple 1997 acquiring next apple intended ship rhapsody reworked version openstep mach mac standard pcs rhapsody openstep mach copland appearance mac os 8 support java apple technologies including colorsync quicktime could regarded openstep 5 two developer versions rhapsody released known developer preview 1 2 ran limited subset intel powerpc hardware mac os x server 1.0 first commercial release operating system delivered exclusively powerpc mac hardware replacing display postscript windowserver quartz responding developers including better backward compatibility classic mac os applications addition carbon apple released mac os x mac os x server starting version 10.0 mac os x named macos macos primary programming environment essentially openstep certain additions xml property lists url classes internet connections macos ports development libraries tools called cocoa macos since become single popular desktop unix-like operating system world although macos longer openstep compliant operating system gnustep free software implementation next libraries began time nextstep predating openstep openstep ose purchased apple effectively ended commercial development implementing openstep platforms gnustep ongoing open source project aiming create portable free software implementation cocoa/openstep libraries gnustep also features fully functional development environment reimplementations newer innovations macos cocoa framework well extensions api
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Operating systems
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plexil plexil plan execution interchange language open source technology automation created currently development nasa plexil programming language representing plans automation 2006 vandi verma one several co-writers plexil used automation technologies nasa k10 rover mars curiosity rover percussion drill deep space habitat habitat demonstration unit edison demonstration smallsat networks ladee autonomy operating system aos procedure automation international space station plexil executive execution engine implements plexil interfaced using provided software framework external systems controlled and/or queried plexil used demonstrate automation technologies targeted future nasa space missions binaries documentation widely available open source sourceforge.net fundamental programming unit plexil node node data structure formed two primary components set conditions drive execution node another set specifies node accomplishes execution hierarchical composition nodes called plan plan tree divided nodes close root high level nodes leaf nodes represent primitive actions variable assignments sending commands external system node types september 2008 nasa implemented seven types nodes node states node one state nodes transitions
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Programming language topics
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video acceleration api video acceleration api va api royalty-free api well implementation free open-source library libva distributed mit license va api implemented device drivers offer end-user software vlc media player gstreamer access available video acceleration hardware purevideo libva-vdpau driver implements va api terms vdpau unified video decoder api enables provides access hardware-accelerated video processing using hardware graphics processing units gpu accelerate video encoding decoding offloading processing central processing unit cpu va api video decode/encode interface platform window system independent primarily targeted direct rendering infrastructure dri x window system unix-like operating systems including linux freebsd solaris android however potentially also used direct framebuffer graphics sub-systems video output accelerated processing includes support video decoding video encoding subpicture blending rendering va api specification originally designed intel gma graphics media accelerator series gpu hardware specific purpose eventually replacing xvmc standard default unix multi-platform equivalent microsoft windows directx video acceleration dxva api today api longer limited intel-specific hardware gpus hardware manufacturers freely use open standard api hardware accelerated video processing hardware without paying royalty fee main motivation va api enable hardware-accelerated video decode various entry-points vld idct motion compensation deblocking prevailing coding standards today mpeg-2 mpeg-4 asp/h.263 mpeg-4 avc/h.264 h.265/hevc vc-1/wmv3 extending xvmc considered due original design mpeg-2 motioncomp made sense design interface scratch fully expose video decode capabilities today gpus january 17 2012 va api natively supported va api currently supports video codecs official mainline version note exactly video codecs supported depends hardware driver capabilities video decoding post-processing processes offloaded accelerated device drivers gpu hardware supports current interface window system independent potentially used graphics sub-systems dri direct rendering infrastructure x window system direct framebuffer work third-party drm direct rendering manager libraries nutshell scheme pass various types data buffers application gpu decoding encoding compressed bit-stream
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Internet protocols
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butler sql butler sql now-defunct sql-based database server classic mac os everyware development much history partnered another everyware product tango built dynamic database pages sql data product eventually ended pervasive software although longer sold butler introduced take advantage new mac os component known data access manager dam similar concept odbc allowing end-user client programs access various data sources dam however worked lower level odbc contain inherent query language address concern single dam program might want work different back-end databases apple used second system known data access language dal variant sql included additional flow-control data manipulation instructions dal queries converted target database using adaptor server butler written natively support dal variant sql use dam internally support networking avoided several intermediary layers would required use queries database servers butler 2.0 released may 1996 added direct odbc links well butler suffered performance problems due single-user nature mac os particular file access single-threaded multitasking coordinated applications operating system
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Databases
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sgi visual workstation sgi visual workstation series workstation computers designed manufactured sgi unlike product lines used 64-bit mips risc architecture line used intel pentium ii iii processors shipped windows nt 4.0 windows 2000 operating system lieu irix however visual workstation 320 540 models deviated architecture ibm-compatible pcs using sgi arcs firmware instead traditional bios internal components adapted mips-based products proprietary components made incompatible internal hardware designed standard pcs hence unable run versions microsoft windows especially windows 9x contrast remaining models line standard pcs using via technologies chipsets nvidia video cards standard components two series visual workstations based intel processors first series 320 540 used sgi arcloader prom cobalt video chipset remainder essentially standard pc 320 540 use unified memory architecture uma memory system shares video system memory runs speed allows 80 percent system ram applied video memory allocation static however adjusted via profile 320 540 also use onboard cobalt video adapter sgi proprietary graphics chipset firmware used systems prom enables booting graphical subsystem os loaded regard resemble irix/mips line sgi computers sgi o2 320 540 also stand firewire ieee 1394 ports onboard composite/s-video capture usb keyboards mice differ 320 dual pentium ii/iii-capable 1gb maximum system ram 540 quad pentium iii xeon-capable 2gb maximum system ram computers use proprietary dimm module essentially ecc sdram pc-100 package one-half normal size maximum memory per module 96mb sgi 320 twelve memory slots firewire ports built 320 never functioned sgi distributed orange micro firewire cards year production commenced lieu fixing firewire ports 320 540 limited pci slots albeit two 66 mhz one 33 mhz slot operated 3.3v step 5v slots used manufacturers limits number accessories added visual workstations built compete new intel processor based workstations considerably cheaper sgi line mips workstations little standard pcs use many parts also available aftermarket 320 540 visual workstations shipped originally microsoft windows nt 4.0 due arcloader prom custom hardware abstraction layer hal windows necessary windows 2000 last release included required sgi-specific hal sgi ceased supporting visual workstation series installation later windows versions xp unsupported 230 330 550 also supported windows nt 2000 addition sgi offered systems pre-loaded release 6.2 red hat linux distribution systems letter l appended model numbers various sgi enhancements particular 320 540 visual workstations often out-perform intel pcs similar configuration graphically-intensive memory bound applications however due hefty upgrade costs non-standard components cost effective purchase entire new higher-spec non-sgi pc rather purchase upgrades visual workstation visual workstations support conventional crt monitors vga display connectors 230 330 550 models use nvidia quadro cards also support dvi sgi 320 540 models shipped groundbreaking stylistically matched 1600sw lcd display using openldi display connector requires accessory flat panel adapter sgi o2 also supports 1600sw adapter model numbers visual workstations visual workstations initially equipped either single pentium ii pentium iii processor dual smp pentium iii processors 540 550 models support xeon implementation pentium series could support four xeons smp configuration two 550 although sgi visual workstation ever released cpu running higher 700 mhz hobbyists able run faster processors sgi 320 limit dual 1 ghz pentium iii processors single 1.4 ghz celeron dual 1 ghz processors require specific model cpu intended intel servers voltage regulator prom revision motherboard also correct setup work single processors powerleap pl-ip3t slocket adapter tualatin 1.4 ghz celeron processor limit straight bolt-in installation tualatin core gives modern processor powerleap adapter handles voltage regulation cpu sgi 540 reported handle 900 mhz quad xeon processors fastest pentium 3 xeons 100 mhz front side bus speed 540 230 330 550 models essentially standard pcs capabilities upgrade limits pcs time 230 330 based via chipsets used socket 370 processors conventional sdram 550 used slot 2 xeon processors intel 840 chipset rdram three models generic pc bios generic pc memory non-differentiated parts video cards systems used nvidia agp cards based quadro 2 chipset differ aftermarket quadros drivers
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Computer architecture
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object access method object access method oam access method z/os designed storage large numbers large files images number distinguishing features e.g compared vsam oam used conjunction db2 example use case oam would storing medical images db2 database running z/os oam created 1980s prototype product insurance company replace microfiche initially oam supported optical storage magnetic disks 1990s support magnetic tape added 2011 support added storage objects z/os unix file system—either zfs nfs 1990s object access method used canadian intellectual property office store documents related patent processing
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Operating systems
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hyper-threading hyper-threading officially called hyper-threading technology ht technology abbreviated htt ht intel proprietary simultaneous multithreading smt implementation used improve parallelization computations multiple tasks performed x86 microprocessors first appeared february 2002 xeon server processors november 2002 pentium 4 desktop cpus later intel included technology itanium atom core series cpus among others processor core physically present operating system addresses two virtual logical cores shares workload possible main function hyper-threading increase number independent instructions pipeline takes advantage superscalar architecture multiple instructions operate separate data parallel htt one physical core appears two processors operating system allowing concurrent scheduling two processes per core addition two processes use resources resources one process available another process continue resources available addition requiring simultaneous multithreading smt support operating system hyper-threading properly utilized operating system specifically optimized furthermore intel recommends htt disabled using operating systems unaware hardware feature hyper-threading technology form simultaneous multithreading technology introduced intel concept behind technology patented sun microsystems architecturally processor hyper-threading technology consists two logical processors per core processor architectural state logical processor individually halted interrupted directed execute specified thread independently logical processor sharing physical core unlike traditional dual-processor configuration uses two separate physical processors logical processors hyper-threaded core share execution resources resources include execution engine caches system bus interface sharing resources allows two logical processors work efficiently allows logical processor borrow resources stalled logical core assuming logical cores associated physical core processor stalls waiting data sent finish processing present thread degree benefit seen using hyper-threaded multi core processor depends needs software well operating system written manage processor efficiently hyper-threading works duplicating certain sections processor—those store architectural state—but duplicating main execution resources allows hyper-threading processor appear usual physical processor extra logical processor host operating system htt-unaware operating systems see two physical processors allowing operating system schedule two threads processes simultaneously appropriately execution resources would used current task processor without hyper-threading especially processor stalled hyper-threading equipped processor use execution resources execute another scheduled task processor may stall due cache miss branch misprediction data dependency technology transparent operating systems programs minimum required take advantage hyper-threading symmetric multiprocessing smp support operating system logical processors appear standard separate processors possible optimize operating system behavior multi-processor hyper-threading capable systems example consider smp system two physical processors hyper-threaded total four logical processors operating system thread scheduler unaware hyper-threading treat four logical processors two threads eligible run might choose schedule threads two logical processors happen belong physical processor processor would become extremely busy would idle leading poorer performance possible scheduling threads onto different physical processors problem avoided improving scheduler treat logical processors differently physical processors sense limited form scheduler changes required numa systems first published paper describing known hyperthreading general purpose computer stanford ph.d. dissertation 1973 denelcor inc. introduced multi-threading heterogeneous element processor hep 1982 hep pipeline could hold multiple instructions process one instruction given process allowed present pipeline point time instruction given process block pipe instructions processes would continue pipeline drained us patent technology behind hyper-threading granted kenneth okin sun microsystems november 1994 time cmos process technology advanced enough allow cost-effective implementation intel implemented hyper-threading x86 architecture processor 2002 foster mp-based xeon also included 3.06 ghz northwood-based pentium 4 year remained feature every pentium 4 ht pentium 4 extreme edition pentium extreme edition processor since previous generations intel processors based core microarchitecture hyper-threading core microarchitecture descendant p6 microarchitecture used iterations pentium since pentium pro pentium iii celeron covington mendocino coppermine tualatin-based pentium ii xeon pentium iii xeon models intel released nehalem core i7 november 2008 hyper-threading made return first generation nehalem contained four cores effectively scaled eight threads since two- six-core models released scaling four twelve threads respectively earlier intel atom cores in-order processors sometimes hyper-threading ability low power mobile pcs low-price desktop pcs itanium 9300 launched eight threads per processor two threads per core enhanced hyper-threading technology next model itanium 9500 poulson features 12-wide issue architecture eight cpu cores support eight virtual cores via hyper-threading intel xeon 5500 server chips also utilize two-way hyper-threading according intel first hyper-threading implementation used 5 die area comparable non-hyperthreaded processor performance 15–30 better intel claims 30 performance improvement compared otherwise identical non-simultaneous multithreading pentium 4 tom hardware states cases p4 running 3.0 ghz ht even beat p4 running 3.6 ghz ht turned intel also claims significant performance improvements hyper-threading-enabled pentium 4 processor artificial-intelligence algorithms overall performance history hyper-threading mixed one beginning one commentary high-performance computing november 2002 notes hyper-threading improve performance mpi applications depending cluster configuration importantly nature application running cluster performance gains vary even negative next step use performance tools understand areas contribute performance gains areas contribute performance degradation result performance improvements application-dependent however running two programs require full attention processor actually seem like one programs slows slightly hyper-threading technology turned due replay system pentium 4 tying valuable execution resources equalizing processor resources two programs adds varying amount execution time pentium 4 prescott xeon nocona processors received replay queue reduces execution time needed replay system completely overcomes performance penalty according november 2009 analysis intel performance impacts hyper-threading result increased overall latency case execution threads result significant overall throughput gains vary application words overall processing latency significantly increased due hyper-threading negative effects becoming smaller simultaneous threads effectively use additional hardware resource utilization provided hyper-threading similar performance analysis available effects hyper-threading used handle tasks related managing network traffic processing interrupt requests generated network interface controllers nics another paper claims performance improvements hyper-threading used interrupt handling first ht processors released many operating systems optimized hyper-threading technology e.g windows 2000 linux older 2.4 2006 hyper-threading criticised energy inefficiency example specialist low-power cpu design company arm stated simultaneous multithreading smt use 46 power ordinary dual-core designs furthermore claimed smt increases cache thrashing 42 whereas dual core results 37 decrease intel disputed claim stating hyper-threading highly efficient uses resources would otherwise idle underutilised 2010 arm said might include simultaneous multithreading future chips however rejected favor 2012 64-bit design 2013 intel dropped smt favor out-of-order execution silvermont processor cores found gave better performance better power efficiency lower number cores smt 2017 revealed intel skylake kaby lake processors bug implementation hyper-threading could cause data loss microcode updates later released address issue 2019 coffee lake intel began move away including hyper-threading mainstream core i7 desktop processors except highest-end core i9 parts pentium gold gpus also started recommending disabling hyper-threading new cpu vulnerability attacks revealed could mitigated disabling ht may 2005 colin percival demonstrated malicious thread pentium 4 use timing attack monitor memory access patterns another thread shares cache allowing theft cryptographic information potential solutions include processor changing cache eviction strategy operating system preventing simultaneous execution physical core threads different privileges 2018 openbsd operating system disabled hyper-threading order avoid data potentially leaking applications software caused foreshadow/l1tf vulnerabilities 2019 set vulnerabilities led security experts recommending disabling hyperthreading devices
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Computer architecture
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dam busters video game dam busters combat flight simulator set world war ii published u.s. gold 1984 loosely based real life operation chastise 1955 film game released 1984 colecovision commodore 64 1985 apple ii ms-dos msx zx spectrum 1986 amstrad cpc nec pc-9801 choose three different night missions increasingly difficult three goal successfully bomb dam practice run approach bomb dam without obstacles two missions feature various enemies overcome start either french coast british airfield flight control every aspect bomber seven crew positions pilot front gunner tail gunner bomb aimer navigator engineer squadron leader leaving positions unattended event could spell death person position rendering useless encounters must evade enemies plan approach set variables speed height timing etc execute successful bombing sometimes becomes necessary deal emergencies engine fires en route target expect encounter attacks enemy aircraft barrage balloons flak enemy searchlights events like flash along border screen indictating key press take station need assistance example flying enemy search lights 'll need man gunner station shoot lights ground left unattended expect flak enemy aircraft start damaging bomber begin final run target presented custom bombing sights made famous story toggle bomb shown animation bomb bouncing along lake hitting hitting target dam info rated dam busters commodore 64 three-plus stars five stating lacks depth variability game like silent service better average graphics play features computer gaming world gave dam busters two five points overview world war ii simulations stating product graphics 'feel make much game enough simulation
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Computer architecture
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raft computer science raft consensus algorithm designed alternative paxos meant understandable paxos means separation logic also formally proven safe offers additional features raft offers generic way distribute state machine across cluster computing systems ensuring node cluster agrees upon series state transitions number open-source reference implementations full-specification implementations go c++ java scala named reliable replicated redundant fault-tolerant raft byzantine fault tolerant algorithm nodes trust elected leader raft achieves consensus via elected leader server raft cluster either leader follower candidate precise case election leader unavailable leader responsible log replication followers regularly informs followers existence sending heartbeat message follower timeout typically 150 300 ms expects heartbeat leader timeout reset receiving heartbeat heartbeat received follower changes status candidate starts leader election raft implements consensus leader approach cluster one one elected leader fully responsible managing log replication servers cluster means leader decide new entries placement establishment data flow servers without consulting servers leader leads fails disconnects case new leader elected consensus problem decomposed raft two relatively independent subproblems listed existing leader fails start algorithm new leader needs elected case new term starts cluster term arbitrary period time server new leader needs elected term starts leader election election completed successfully i.e single leader elected term keeps going normal operations orchestrated new leader election failure new term starts new election leader election started candidate server server becomes candidate receives communication leader period called election timeout assumes acting leader anymore starts election increasing term counter voting new leader sending message servers requesting vote server vote per term first-come-first-served basis candidate receives message another server term number least large candidate current term candidate election defeated candidate changes follower recognizes leader legitimate candidate receives majority votes becomes new leader neither happens e.g. split vote new term starts new election begins raft uses randomized election timeout ensure split votes problem resolved quickly reduce chance split vote servers wo n't become candidates time single server timeout win election become leader sends heartbeat messages servers followers become candidates leader responsible log replication accepts client requests client request consists command executed replicated state machines cluster appended leader log new entry requests forwarded followers appendentries messages case unavailability followers leader retries appendentries messages indefinitely log entry eventually stored followers leader receives confirmation majority followers entry replicated leader applies entry local state machine request considered committed event also commits previous entries leader log follower learns log entry committed applies entry local state machine ensures consistency logs servers cluster ensuring safety rule log matching respected case leader crash logs left inconsistent logs old leader fully replicated cluster new leader handle inconsistency forcing followers duplicate log followers leader compare log log follower find last entry agree delete entries coming critical entry follower log replace log entries mechanism restore log consistency cluster subject failures raft guarantees safety properties first four rules guaranteed details algorithm described previous section state machine safety guaranteed restriction election process rule ensured simple restriction candidate ca n't win election unless log contains committed entries order elected candidate contact majority cluster given rules logs committed means every committed entry going present least one servers candidates contact raft determines two logs carried two distinct servers up-to-date comparing index term last entries logs logs last entry different terms log later term up-to-date logs end term whichever log longer up-to-date raft request candidate voter includes information candidate log log up-to-date candidate log voter denies vote candidate implementation ensures state machine safety rule follower crashes appendentries vote requests sent servers fail failures handled servers trying indefinitely reach downed follower follower restarts pending requests complete request already taken account failure restarted follower ignore timing critical raft elect maintain steady leader time order perfect availability cluster stability ensured respecting timing requirement algorithm broadcasttime « electiontimeout « mtbf typical number values 0.5ms 20ms broadcasttime implies set electiontimeout somewhere 10ms 500ms take several weeks months single server failures means values right stable cluster work https //groups.google.com/forum/ topic/raft-dev/95rzqptgpmu
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Computer architecture
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bit test codice_1 x86 assembly language instruction stands bit test added x86 instruction set 80386 processor codice_1 copies bit given register carry flag example copy third least significant bit eax carry flag codice_3 bit test set operates also sets bit register codice_4 bit test reset resets codice_5 bit test complement flips
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Computer architecture
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mark zbikowski mark zibo joseph zbikowski born march 21 1956 former microsoft architect early computer hacker started working company years inception leading efforts ms-dos os/2 cairo windows nt 2006 honored 25 years service company third employee reach milestone bill gates steve ballmer designer ms-dos executable file format headers file format start initials ascii characters 'mz 0x4d 0x5a zbikowski born detroit michigan 1956 attending roeper school known roeper city country school 1961 1974 developed interest mathematics computers 8th-grade performance michigan mathematics prize competition led invitation nsf-funded summer program oakland university became friends microsoft steve ballmer jeff sachs zbikowski pursued computer science harvard a.b 1978 yale s.m 1979 active universities gilbert sullivan performing groups ballmer recruited zbikowski joined microsoft 1981 march 1982 replaced tim paterson development lead manager microsoft ms-dos 2.0 position held dos 4.0 first major contributions addition hierarchical directory structure dos 2.0 installable device drivers march 1985 1991 architecture team os/2 development manager file systems device drivers technical advisor paul maritz breakthrough concept installable file system os/2 attributed following demise microsoft/ibm joint development agreement architect development manager key contributor cairo working jim allchin later anthony short led cairo object file system content index efforts 1996 cairo migrated standalone product technology source zbikowski worked lou perazzoli windows nt kernel focusing performance size becoming architect development manager nt file systems 1998 2001 zbikowski candidate director harvard alumni association zbikowski retired microsoft june 2006 due interest education became affiliated 2007 university washington lecturer computer science engineering department college engineering mark zbikowski affiliated following companies __notoc__
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Operating systems
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xgrid xgrid proprietary program distributed computing protocol developed advanced computation group subdivision apple inc allows networked computers contribute single task provides network administrators method creating computing cluster allows exploit previously unused computational power calculations divided easily smaller operations mandelbrot maps setup xgrid cluster achieved next cost xgrid client pre-installed computers running mac os x 10.4 mac os x 10.7 xgrid client included mac os x 10.8 xgrid controller job scheduler xgrid operation also included within mac os x server free download apple apple kept command-line job control mechanism minimalist providing api develop sophisticated tools built around program employs communication protocol layered top schema communicate nodes communication protocol interfaces beep infrastructure network application protocol framework computers discovered xgrid system computers mac os x xgrid service enabled automatically added list available computers use processing tasks initiating computer sends complete instructions job processing controller controller splits task small instruction packets known tasks design xgrid system consists small packets transferred xgrid-enabled computers network computers nodes execute instructions provided controller return results controller assembles individual task results whole job results returns initiating computer apple modeled design xgrid zilla program distributed next openstep operating system application programming interface api apple owned rights company also opted provide client version mac os x command-line functions little flexibility giving mac os x server version xgrid gui control panel full set features xgrid original concept traced back zilla.app found openstep operating system created next late 1980s zilla first distributed computing program released end-user operating system used idle screen-saver motif design feature since found widely used projects seti home distributed.net zilla national computerworld smithsonian award science category 1991 ease use good design apple acquired zilla along rest next 1997 later used zilla inspiration xgrid first beta version xgrid released january 2004 several organizations adopted xgrid large international computing networks one example xgrid cluster macresearch openmacgrid scientists request access large amounts processing power run tasks related research another defunct xgrid stanford project used range computers stanford university campus around world perform biochemical research pre-release promotional piece macworld cited xgrid among unix features 10 things know tiger calling handy work huge amounts experimental data render complex animations xgrid introduction 2004 infoworld noted 'preview grade technology would directly benefit xserve g5 launch later year infoworld commentator ephraim schwartz also predicted xgrid opening move apple entry enterprise computing market apple discontinued xgrid os x v10.8 mountain lion along dependent services podcast producer xgrid protocol uses beep network framework communicate nodes network system infrastructure includes three types computers communicate protocol one client communicates calculation next controller starts segregates calculation finally agents process allocated part calculation computer act one three components time xgrid protocol provides basic infrastructure computers communicate involved processing specified calculation xgrid targeted towards time consuming computations easily segregated smaller tasks sometimes called embarrassingly parallel tasks includes monte carlo calculations 3d rendering mandelbrot maps within xgrid protocol three types messages passed computers cluster requests notifications replies requests must responded recipient reply notifications require reply replies responses sent messages identified name type request/notification/reply contents message encapsulated beep message beep msg acknowledged receipt empty reply rpy xgrid leverage beeps message/reply infrastructure received message requires response merely generates independent beep message containing reply xgrid messages encoded dictionaries key/value pairs converted xml sent across beep network architecture xgrid system designed around job based system controller sends agents jobs agents return responses actual computation controller executes xgrid system known job job contains files required complete task successfully input parameters data files directories executables and/or shell scripts files included xgrid job must able executed either simultaneously asynchronously benefits running job xgrid lost job completes controller set notify client task completion failure example email client leave network tasks running also monitor job status demand querying controller although track ongoing progress individual tasks controller central correct function xgrid node responsible distribution supervision coordination tasks agents program running controller assign reassign tasks handle individual agent failures demand number tasks assigned agent depend two factors number agents xgrid number processors node number agents xgrid determines controller assign tasks tasks may assigned simultaneously large number agents queued small number agents node one processor detected xgrid controller may assign one task per processor occurs number agents network lower number tasks controller complete xgrid layered upon blocks extensible exchange protocol beep ietf standard comparable http focus two-way multiplexed communication found peer-to-peer networks beep turn uses xml define profiles communicating multiple agents single network internet connection possible access xgrid command line xgrid graphical user interface program bundled mac os x server march 2009 available online much efficient way administering xgrid system originally xgrid agent included mac os x version 10.4 installations gui reserved users mac os x server decision limited efforts computer community embrace platform eventually apple released mac os x server administration tools public included xgrid administration application bundled mac os x server despite lack graphical controller interface standard non-server mac os x distribution possible set xgrid controller via command line tools codice_1 codice_2 xgrid controller daemon running administration grid apple xgrid admin tool possible applications visualhub provided xgrid controller capability user interfaces
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Distributed computing architecture
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psos real-time operating system psos portable software silicon real time operating system rtos created 1982 alfred chao developed/marketed first part life company software components group scg 1980s psos rapidly became rtos choice embedded systems based motorola 68000 family architecture written 68000 assembler highly optimised start also modularised early support os-aware debugging plug-in device drivers tcp/ip stacks language libraries disk subsystems later came source-level debugging multi-processor support networking extensions 1991 software components group acquired integrated systems inc. isi developed psos restyled psos+ microprocessor families rewriting greater part c. attention also paid supporting successively integrated development environments culminating prism+ july 1994 integrated systems acquired digital research modular real-time multi-tasking operating system flexos novell 1995 integrated systems offered psosystem/nest package novell embedded systems technology nest february 2000 integrated systems inc. acquired wind river systems originators rival rtos vxworks despite initial reports psos support would continue development halted wind river announced plans 'convergence version vxworks support psos system calls releases psos made nxp semiconductors acquired psos trimedia wind river continued support os trimedia vliw core march 2000 rival company express logic released evaluation kit psos+ users designed provide migration path threadx rtos august 2000 mapusoft technologies inc. came psos os changer porting kit smoothly move software multiple os linux vxworks includes ide api optimization along profiling tool measure api timing target boards www.mapusoft.com august 2007 rowebots former partner scg isi open sourced psos+ compatible version called reliant available wish upgrade without applications changes xenomai project supports psos+ apis others traditional rtos apis linux-based real-time framework allow existing industrial applications migrate easily gnu/linux-based environment keeping stringent real-time guarantees another open sourced alternative rtems support various apis including classic api compatible psos posix api compared gnu/linux rtems closer match psos applications due lower memory footprint strict realtime behaviour popular ssl/tls libraries wolfssl still support psos
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Operating systems
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soap-over-udp soap-over-udp oasis standard covering publication soap messages udp transport protocol providing one-way request-response message patterns
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Web technology
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linked data page linked data page web page explicitly describes one things objects via hyperdata links unlike traditional web page hypertext links hyperdata links expose properties attributes relationships property values associated things page linked data pages created hand generated dynamically via linked data server user agent single reference uri iri thing needed experience power serendipitous data discovery offered linked data page typical web page endowed links explicitly describe anything links simply expose unqualified associations documents web put differently linked data pages reveal explicit properties things basic web pages loosely anything requiring human interpretation reasoning order attain clarity
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Web technology
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prodigal computer system prodigal proactive discovery insider threats using graph analysis learning computer system predicting anomalous behavior among humans data mining network traffic emails text messages server log entries part darpa anomaly detection multiple scales adams project initial schedule two years budget 9 million uses graph theory machine learning statistical anomaly detection high-performance computing scan larger sets data quickly past systems amount data analyzed range terabytes per day targets analysis employees within government defense contracting organizations specific examples behavior system intended detect include actions nidal malik hasan wikileaks source chelsea manning commercial applications may include finance results analysis five serious threats per day go agents analysts operators working counterintelligence
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Computer security
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zero page zero page series memory addresses beginning computer address space page whose starting address zero size page depends context significance zero-page memory versus higher addressed memory highly dependent machine architecture example motorola 6800 mos technology 6502 processor families treat first 256 bytes memory specially whereas many processors actual size zero page bytes determined microprocessor design older designs often equal largest value referenced processor indexing registers example aforementioned 8-bit processors 8-bit index registers page size 256 bytes therefore zero page extends address 0 address 255 early computers including pdp-8 zero page special fast addressing mode facilitated use temporary storage data compensated relative shortage cpu registers pdp-8 one register zero page addressing essential unlike modern hardware 1970s computer ram fast faster cpu thus made sense registers use main memory extended pool extra registers since memory location within zero page 16-bit address bus computer may addressed single byte faster 8-bit data bus machines access location rather non-zero page location example mos technology 6502 one general purpose register accumulator result used zero page extensively many instructions coded differently zero page non-zero page addresses two instructions accomplish thing load value memory location 00 .a register accumulator however first instruction two bytes long requires three clock cycles complete second instruction three bytes length requires four clock cycles execute obviously difference execution time could significantly improve performance repetitive code zero page addressing mostly historical significance since developments integrated circuit technology made adding registers cpu less expensive cpu operations much faster ram accesses computer architectures still reserve beginning address space purposes though instance intel x86 systems reserve first 512 words address space interrupt table run real mode similar technique using zero page hardware related vectors employed arm architecture leading badly written programs infamous ofla behaviour program tries read information unintended memory area winds mistaking executable code text vice versa especially problem zero page area used store system jump vectors firmware tricked storing data fact quite contrary zero page original preferential use modern operating systems freebsd linux microsoft windows actually make zero page inaccessible trap uses null pointers useful null pointers method used represent value reference points nothing since code operating reference written assuming reference actually refers valid structure value catching case reference points nothing use since sure sign bug 8-bit cp/m zero page used communication running program operating system see zero page cp/m information
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Operating systems
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http header injection http header injection general class web application security vulnerability occurs hypertext transfer protocol http headers dynamically generated based user input header injection http responses allow http response splitting session fixation via set-cookie header cross-site scripting xss malicious redirect attacks via location header http header injection relatively new area web-based attacks primarily pioneered amit klein work request/response smuggling/splitting
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Computer security
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shell computing computing shell user interface access operating system services general operating system shells use either command-line interface cli graphical user interface gui depending computer role particular operation named shell outermost layer around operating system kernel cli shells require user familiar commands calling syntax understand concepts shell-specific scripting language example bash also easily operated via refreshable braille display provide certain advantages screen readers graphical shells place low burden beginning computer users characterized easy use since also come certain disadvantages gui-enabled operating systems also provide cli shells operating systems provide various services users including file management process management running terminating applications batch processing operating system monitoring configuration operating system shells direct interfaces underlying kernel even shell communicates user via peripheral devices attached computer directly shells actually special applications use kernel api way used application programs shell manages user–system interaction prompting users input interpreting input handling output underlying operating system much like read–eval–print loop repl since operating system shell actually application may easily replaced another similar application operating systems addition shells running local systems different ways make remote systems available local users approaches usually referred remote access remote administration initially available multi-user mainframes provided text-based uis active user simultaneously means text terminal connected mainframe via serial line modem remote access extended unix-like systems microsoft windows unix-like systems secure shell protocol usually used text-based shells ssh tunneling used x window system–based graphical user interfaces guis microsoft windows remote desktop protocol used provide gui remote access since windows vista powershell remote used text-based remote access via wmi rpc ws-management operating system shells fall one two categories command-line graphical command line shells provide command-line interface cli operating system graphical shells provide graphical user interface gui possibilities although common include voice user interface various implementations text-based user interface tui cli relative merits cli- gui-based shells often debated command-line interface cli operating system shell uses alphanumeric characters typed keyboard provide instructions data operating system interactively example teletypewriter send codes representing keystrokes command interpreter program running computer command interpreter parses sequence keystrokes responds error message recognize sequence characters may carry program action loading application program listing files logging user many others operating systems unix large variety shell programs different commands syntax capabilities operating systems single style command interface commodity operating systems ms-dos came standard command interface third-party interfaces also often available providing additional features functions menuing remote program execution application programs may also implement command-line interface example unix-like systems telnet program number commands controlling link remote computer system since commands program made keystrokes data sent remote computer means distinguishing two required escape sequence defined using either special local keystroke never passed always interpreted local system program becomes modal switching interpreting commands keyboard passing keystrokes data processed feature many command-line shells ability save sequences commands re-use data file contain sequences commands cli made follow typed user special features cli may apply carrying stored instructions batch files script files used repeatedly automate routine operations initializing set programs system restarted batch mode use shells usually involves structures conditionals variables elements programming languages bare essentials needed purpose others sophisticated programming languages conversely programming languages used interactively operating system shell purpose-built program command-line shell may offer features command-line completion interpreter expands commands based characters input user command-line interpreter may offer history function user recall earlier commands issued system repeat possibly editing since commands operating system typed user short command names compact systems representing program options common short names sometimes hard user recall early systems lacked storage resources provide detailed on-line user instruction guide graphical shells desktop shells provide means manipulating programs based graphical user interface gui allowing operations opening closing moving resizing windows well switching focus windows graphical shells may included desktop environments come separately even set loosely coupled utilities graphical user interfaces develop metaphor electronic desktop data files represented paper documents desk application programs similarly graphical representations instead invoked command names graphical shells typically build top windowing system case x window system wayland shell consists x window manager wayland compositor respectively well one multiple programs providing functionality start installed applications manage open windows virtual desktops often support widget engine case macos quartz could thought windowing system shell consists finder dock systemuiserver mission control modern versions microsoft windows operating system use windows shell shell windows shell provides familiar desktop environment start menu task bar well graphical user interface accessing file management functions operating system older versions also include program manager shell 3.x series microsoft windows fact shipped later versions windows 95 nt types least windows xp interfaces windows versions 1 2 markedly different desktop applications also considered shells long use third-party engine likewise many individuals developers dissatisfied interface windows explorer developed software either alters functioning appearance shell replaces entirely windowblinds stardock good example former sort application litestep emerge desktop good examples latter interoperability programmes purpose-designed software lets windows users use equivalents many various unix-based guis discussed well macintosh equivalent os/2 presentation manager version 3.0 run os/2 programmes conditions using os/2 environmental subsystem versions windows nt shell also used loosely describe application software built around particular component web browsers email clients analogy shells found nature also sometimes referred wrappers expert systems shell piece software empty expert system without knowledge base particular application
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Operating systems
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matlab matlab matrix laboratory multi-paradigm numerical computing environment proprietary programming language developed mathworks matlab allows matrix manipulations plotting functions data implementation algorithms creation user interfaces interfacing programs written languages including c c++ c java fortran python although matlab intended primarily numerical computing optional toolbox uses mupad symbolic engine allowing access symbolic computing abilities additional package simulink adds graphical multi-domain simulation model-based design dynamic embedded systems 2018 matlab 3 million users worldwide matlab users come various backgrounds engineering science economics cleve moler chairman computer science department university new mexico started developing matlab late 1970s designed give students access linpack eispack without learn fortran soon spread universities found strong audience within applied mathematics community jack little engineer exposed visit moler made stanford university 1983 recognizing commercial potential joined moler steve bangert rewrote matlab c founded mathworks 1984 continue development rewritten libraries known jackpac 2000 matlab rewritten use newer set libraries matrix manipulation lapack matlab first adopted researchers practitioners control engineering little specialty quickly spread many domains also used education particular teaching linear algebra numerical analysis popular amongst scientists involved image processing matlab application built around matlab scripting language common usage matlab application involves using command window interactive mathematical shell executing text files containing matlab code variables defined using assignment operator codice_1 matlab weakly typed programming language types implicitly converted inferred typed language variables assigned without declaring type except treated symbolic objects type change values come constants computation involving values variables output function example simple array defined using colon syntax initial codice_2 increment codice_2 terminator instance defines variable named codice_4 assigns new value existing variable name codice_4 array consisting values 1 3 5 7 9 array starts 1 initial value increments step previous value 2 increment value stops reaches avoid exceeding 9 terminator value increment value actually left syntax along one colons use default value 1. assigns variable named codice_6 array values 1 2 3 4 5 since default value 1 used incrementer indexing one-based usual convention matrices mathematics although programming languages c c++ java matrices defined separating elements row blank space comma using semicolon terminate row list elements surrounded square brackets parentheses used access elements subarrays also used denote function argument list sets indices specified expressions 2:4 evaluates 2 3 4 example submatrix taken rows 2 4 columns 3 4 written square identity matrix size n generated using function eye matrices size zeros ones generated functions zeros ones respectively transposing vector matrix done either function transpose adding prime dot matrix without dot matlab perform conjugate transpose matlab functions accept matrices apply element example codice_7 multiply every element j 2 reduce element modulo n matlab include standard loops similar applications r using vectorized notation often produces code faster execute code excerpted function magic.m creates magic square odd values n matlab function codice_8 used generate square matrices j containing 1 n matlab structure data types since variables matlab arrays adequate name structure array element array field names addition matlab supports dynamic field names field look-ups name field manipulations etc. unfortunately matlab jit support matlab structures therefore simple bundling various variables structure come cost creating matlab function name file match name first function file valid function names begin alphabetic character contain letters numbers underscores functions often case sensitive matlab supports elements lambda calculus introducing function handles function references implemented either .m files anonymous/nested functions matlab supports object-oriented programming including classes inheritance virtual dispatch packages pass-by-value semantics pass-by-reference semantics however syntax calling conventions significantly different languages matlab value classes reference classes depending whether class handle super-class reference classes value classes method call behavior different value reference classes example call method alter member object object instance reference class example simple class provided put file named hello.m executed following commands matlab supports developing applications graphical user interface gui features matlab includes guide gui development environment graphically designing guis also tightly integrated graph-plotting features example function plot used produce graph two vectors x code produces following figure sine function matlab program produce three-dimensional graphics using functions surf plot3 mesh matlab graphical user interfaces programmed gui design environment guide tool matlab call functions subroutines written programming languages c fortran wrapper function created allowing matlab data types passed returned mex files matlab executables dynamically loadable object files created compiling functions since 2014 increasing two-way interfacing python added libraries written perl java activex .net directly called matlab many matlab libraries example xml sql support implemented wrappers around java activex libraries calling matlab java complicated done matlab toolbox sold separately mathworks using undocumented mechanism called jmi java-to-matlab interface confused unrelated java metadata interface also called jmi official matlab api java added 2016 alternatives mupad based symbolic math toolbox available mathworks matlab connected maple mathematica libraries also exist import export mathml matlab proprietary product mathworks users subject vendor lock-in although matlab builder products deploy matlab functions library files used .net java application building environment future development still tied matlab language toolbox purchased separately evaluation license requested mathworks sales department requires detailed information project matlab evaluated granted often evaluation license valid two four weeks student version matlab available home-use license matlab simulink subset mathwork toolboxes substantially reduced prices reported european union eu competition regulators investigating whether mathworks refused sell licenses competitor regulators dropped investigation complainant withdrew accusation evidence wrongdoing found matlab number competitors commercial competitors include mathematica tk solver maple idl also free open source alternatives matlab particular gnu octave scilab freemat sagemath intended mostly compatible matlab language julia programming language also initially used matlab-like syntax among languages treat arrays basic entities array programming languages apl fortran 90 higher s-lang well statistical languages r s. also libraries add similar functionality existing languages it++ c++ perl data language perl ilnumerics .net numpy/scipy/matplotlib python scilua/torch lua sciruby ruby numeric.js javascript gnu octave unique alternatives treats incompatibility matlab bug see matlab compatibility gnu octave theory octave thus superset matlab language practice octave implement matlab functionality number release number version reported concurrent license manager program flexlm complete list changes matlab official toolboxes consult matlab release notes several easter eggs exist matlab include hidden pictures jokes example typing spy used generate picture spies spy vs spy displays image dog typing randomly outputs philosophical answer commands include penny toilet image life every easter egg appears every version matlab
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Programming language topics
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safenet safenet inc. information security company based belcamp maryland united states acquired august 2014 french security company gemalto safenet products marketed safenet product brand include solutions enterprise authentication data encryption key management safenet software monetization products sold gemalto sentinel brand safenet notably one largest suppliers encryption technology united states government 8 august 2014 gemalto announced signed definitive agreement acquire 100 share capital safenet vector capital us 890 million debt free/cash free basis subsequent acquisition gemalto french rival thales group completed 2 april 2019 former rainbow technologies subsidiary safenet government solutions llc formerly safenet mykotronx still based torrance california offices irvine california columbia maryland company founded 1979 myko enterprises changed name mykotronx inc 1987 merged safenet part safenet merger rainbow 2004 safenet government solutions llc operationally merged safenet lines two organizations intentionally blurred due financial reasons safenet government solutions longer considered subsidiary safenet government solutions llc provides infosec comsec technology us government firm indefinite-delivery indefinite-quantity contract kiv-7 line commercial off-the-shelf cryptographic devices provide protection digital voice communications top secret used agencies nsa nro products include kov-14 fortezza plus pc card developed part nsa nssi program used secure terminal equipment previously developed clipper chip 2009 vector capital acquired aladdin knowledge systems placed safenet annotation 'under common management 2010 two companies officially merged
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Computer security
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caspio caspio privately held global software company headquartered santa clara california offices ukraine poland philippines founded frank zamani 2000 caspio provides non-technical business professionals ability create database-centric web applications without coding caspio founder ceo frank zamani worked microsoft developer late 1990s vision enable organizations build custom cloud applications ease fraction time cost versus traditional software development “ wanted build tool business users create applications without coding ” zamani said “ time lot people said ’ done ’ going stop me. ” today caspio powers 1 million applications 100 countries research projects global low-code development platform market size grow us 4.32 billion 2017 us 27.23 billion 2022 compound annual growth rate cagr 44.49 forecast period
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Distributed computing architecture
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mtr software traceroute originally named matt traceroute mtr computer program combines functions traceroute ping programs one network diagnostic tool mtr probes routers route path limiting number hops individual packets may traverse listening responses expiry regularly repeat process usually per second keep track response times hops along path original matt traceroute program written matt kimball 1997 roger wolff took maintaining mtr renamed traceroute october 1998 mtr licensed terms gnu general public license gpl works modern unix-like operating systems normally works text console also optional gtk+-based graphical user interface gui mtr relies internet control message protocol icmp time exceeded type 11 code 0 packets coming back routers icmp echo reply packets packets hit destination host mtr also user datagram protocol udp mode invoked -u command line pressing u key curses interface sends udp packets time live ttl field ip header increasing one probe sent toward destination host udp mode used mtr relies icmp port unreachable packets type 3 code 3 destination reached mtr also supports ipv6 works similar manner instead relies icmpv6 messages tool often used network troubleshooting showing list routers traversed average round-trip time well packet loss router allows users identify links two given routers responsible certain fractions overall latency packet loss network help identify network overuse problems example shows mtr running linux tracing route host machine example.lan web server yahoo p25.www.re2.yahoo.com across level 3 communications network additional example shows recent version mtr running freebsd mpls labels displayed default -e switch used command line e key pressed curses interface winmtr windows gui application functionally equivalent mtr originally developed appnor msp s.r.l maintained white-tiger although similar winmtr shares common code mtr console version mtr exist windows fewer features mtr platforms
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Computer security
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australian rock database australian rock database website searchable online database listed details australian rock music artists albums bands producers record labels established 2000 swedish national magnus holmgren developed interest australian music visiting exchange student information database entries initially gleaned chris spencer zbig nowara paul mchenry australian rock 3rd ed 1993 ian mcfarlane encyclopedia australian rock pop 1999 australian government former website culture recreation listed australian rock database resource australian rock music
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Databases
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terminology-oriented database terminology-oriented database terminology-oriented database management system conceptual extension object-oriented database implements concepts defined terminology model compared object-oriented databases terminology-oriented database requires minor conceptual extensions schema level supporting set relations super-set subset intersection etc weak-typed collections shared inheritance data model terminology-oriented database high-level terminology-oriented database provides facilities transforming terminology model provided subject area experts completely database schema target schema might database schema object-oriented database well relational database schema even xml schema typically terminology-oriented databases bound specific database type since information content stored object-oriented databases relational databases identical data terminology-oriented database stored theoretically type database well xml file thus terminology-oriented databases may support several database systems storing application data terminology databases contain terms vocabularies become valuable ontologies turn ontologies help process associated triples complex predicates thus going deeper hierarchies keys rdbms semantic mapping also enhance performance
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Computational linguistics
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lliurex lliurex project generalitat valenciana whose objective introduction new technologies information communication based free software education system valencian community linux distribution used 110,000 pcs schools valencia region
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Operating systems
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haptik haptik enterprise conversational al platform based mumbai india founded 2013 platform reaches 30 million devices monthly processed billion messages far technology infrastructure employs blend artificial intelligence natural language processing machine learning haptik founded aakrit vaish swapan rajdev university illinois engineering alumni august 2013 march 2014 company launched first product haptik app chat-based personal assistant lets users get things done android ios platforms india september 2014 platform powered 125 chat experts helped users queries time evolved full-blown conversational commerce app 2 million downloads 15 million app installs company launched life insurance chat-bot hdfc life baap bot fathers day august 2015 dan roth university illinois joined haptik board advisers make platform underlying nlp technology layer smarter year haptik became official personal assistant mumbai city fc also provided customer support chat-bot swipe telecom may 2016 company growing 20 percent month-on-month chat volume downloads user addition put together technology perspective 25 percent responses already automated platform november 2017 company launched full-scale enterprise level bot management platform including analytics dashboard company partnered amazon pay hdfc life ola cabs uber times internet mumbai city fc coca-cola ziman zomato bookmyshow cleartrip goibibo urbanclap via.com dineout flipkart run campaigns haptik app march 2018 company partnered amazon web services aws offer al-enabled conversational solutions customers india haptik entered strategic partnership combinator-backed leena ai provide enterprises types bot solutions haptik repertoire chatbot customers india includes samsung future group kfc dream11 sharekhan edelweiss tokio club mahindra iifl among others haptik also built assistants toi samsung ziman akancha harassment online cyber safety initiative haptik one world largest conversational ai platforms october 2017 times india app incorporated haptik virtual personal assistant service sprite exclusive brand partner samsung second partner uses haptik power ‘ assistant ’ service pre-installed samsung galaxy s7 galaxy s7 edge india haptik built scalable support bot dream11 helped online handle 8x volume without large support staff ipl 2018 april times internet acquired majority stake company invested 11.2 million business haptik raised 11.2m series b funding round times internet april 2016 earlier company received funding 1 million kalaari capital september 2014 haptik app chat-based personal assistant allowing users set reminders book cab flight tickets recharge phones pay utility bills find places vicinity web check-in uses artificial intelligence ai machine learning deliver fast precise results platform successful forging alliances technology humans haptik utilizes skill set human resources customer service help train bots reported deccan chronicle platform app runs uses artificial intelligence al machine learning deliver fast precise results haptik open sourced proprietary named entity recognition system powers chatbots behind haptik app chatbot summit held berlin june 26 2017
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Operating systems
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fail-stop fail-stop subset computer language one semantics original except case exceptional condition arises fail-stop subset must report exceptional condition whenever superset language reports one may additionally report exceptional condition cases fail-stop languages often used computer systems correctness important since easier make systems fail-fast example operator many programming languages associative possibility floating-point overflow repairing languages fail fast commonly assumed properties hold makes much easier write verify correct code many widely used programming languages code might reduce bank account value deposited amount old account value large causing overflowed value assigned new_bank_account_value fail-stop language treats overflow exceptional condition either correct terminate exceptional condition
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Computer security
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programmer key programmer key interrupt button button switch macos-era macintosh systems jumps machine code monitor symbol button ⎉ 68000 family based macintosh computers interrupt request also sent holding command key striking power key keyboard effect also simulated 68000 environment mac os nanokernel powerpc machines classic environment plastic insert came macintosh 128k macintosh 512k macintosh plus computers could attached exterior case used press interrupt button located motherboard modern mac hardware longer includes interrupt button mac os x operating system integrated debugging options addition mac os x protected memory blocks direct patching system memory order better secure system
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Computer architecture
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firewalk computing firewalking technique developed mike schiffman david goldsmith utilizes traceroute techniques ttl values analyze ip packet responses order determine gateway acl access control list filters map networks active reconnaissance network security analysis technique attempts determine layer 4 protocols specific firewall allow firewalk software tool performs firewalking protect firewall gateway firewalking one block icmp time exceeded messages
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Computer security
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cert coordination center cert coordination center cert/cc coordination center computer emergency response team cert software engineering institute sei non-profit united states federally funded research development center cert/cc researches software bugs impact software internet security publishes research information findings works business government improve security software internet whole first organization kind cert/cc created pittsburgh november 1988 darpa direction response morris worm incident cert/cc part cert division software engineering institute 150 cybersecurity professionals working projects take proactive approach securing systems cert program partners government industry law enforcement academia develop advanced methods technologies counter large-scale sophisticated cyber threats cert program part software engineering institute sei federally funded research development center ffrdc carnegie mellon university main campus pittsburgh cert registered trademark carnegie mellon university 2003 department homeland security entered agreement carnegie mellon university create us-cert us-cert national computer security incident response team csirt united states america cooperation often causes confusion cert/cc us-cert related two organizations distinct entities general us-cert handles cases concern us national security whereas cert/cc handles general cases often internationally cert/cc coordinates information us-cert computer security incident response teams licensed use name “ cert. ” organizations license cert name carnegie mellon university organizations independent entities established countries operated cert/cc cert/cc established first organization promoting cooperating information exchange various national certs private product security psirts research work cert/cc split several different work areas key capabilities products listed cert/cc works directly software vendors private sector well government agencies address software vulnerabilities provide fixes public process known coordination cert/cc promotes particular process coordination known responsible coordinated disclosure case cert/cc works privately vendor address vulnerability public report published usually jointly vendor security advisory extreme cases vendor unwilling resolve issue contacted cert/cc typically discloses information publicly 45 days since first contact attempt software vulnerabilities coordinated cert/cc may come internal research outside reporting vulnerabilities discovered outside individuals organizations may reported cert/cc using cert/cc vulnerability reporting form depending severity reported vulnerability cert/cc may take action address vulnerability coordinate software vendor cert/cc regularly publishes vulnerability notes cert knowledgebase vulnerability notes include information recent vulnerabilities researched coordinated individuals organizations may mitigate vulnerabilities vulnerability notes database meant comprehensive cert/cc provides number free tools security research community tools offered include following cert/cc periodically offers training courses researchers organizations looking establish psirts cert coordination center summer 2014 cert research funded us federal government key de-anonymization tor anonymity network information subpoenaed cert fbi used take silkroad 2.0 fall fbi denied paying deanonymize users cmu denied receiving funding compliance government subpoena despite indirectly contributing taking numerous illicit websites arrest least 17 suspects research raised multiple issues cmu said statement november 2015 ... university time time served subpoenas requesting information research performed university abides rule law complies lawfully issued subpoenas receives funding compliance even though motherboard reported neither fbi cmu explained authority first learned research subpoenaed appropriate information past sei also declined explain nature particular research response press inquiries saying thanks inquiry practice comment law enforcement investigations court proceedings
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Computer security
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mongoose web server mongoose cross-platform embedded web server networking library functions including tcp http client server websocket client server mqtt client broker much small size software enables internet-connected device function web server mongoose available gpl v2 commercial licenses mongoose built top mongoose embedded library used implementation restful services serve web gui embedded devices create rpc frameworks e.g json-rpc mongoose cross-platform application used windows macintosh os linux qnx ecos free rtos android ios via application programming interface api mongoose embedded programs mongoose written c. mongoose used several companies various industries functions mongoose include august 2013 license changed mit license dual gplv2/commercial licensing scheme license change mongoose forked different forks eventually diverged significantly new features added
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Web technology
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comparison mysql database engines comparison available database engines mysql database management system dbms database engine storage engine underlying software component dbms uses create read update delete crud data database
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Databases
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spacetime software spacetime also known spacetime3d 3d graphical user interface displays web pages 3d tabbed stack interface available online flash application free desktop software download microsoft windows operating system technology presented 2008 ces tradeshow ceo eddie bakhash began working spacetime 1993 product debuted beta june 4 2007 day release san jose mercury news noted software advanced 3-d navigation system 've seen n't make dizzy except thoughts could become software capabilities compared current browsing 3d technologies techcrunch comment spacetime pure eye candy sort like second life meets firefox online version spacetime features ability search google google images wikipedia youtube desktop application released beta form june 4 2007 currently available windows 2000 xp vista systems mac os x version planned 2008 yet come fruition spacetime developers currently working port product opengl framework order support linux unix operating systems using search engines including google google images yahoo yahoo image ebay flickr spacetime loads first ten results stack pages beta browser received mixed reviews katherine boehret wall street journal stated though ’ still rely google basic searches visual search save time turn searching fun process jack m. germain technewsworld described spacetime delivers promise save time provide revolutionary online searching stating continue use 3-d searching environment though fun work edward n. albro pcworld gave beta browser 2.5/5 stating visual results make searches easier basic browsing spacetime appeal browser buggy slow basic browsing
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Internet protocols
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labview laboratory virtual instrument engineering workbench labview system-design platform development environment visual programming language national instruments graphical language named g confused g-code originally released apple macintosh 1986 labview commonly used data acquisition instrument control industrial automation variety operating systems oss including microsoft windows various versions unix linux macos latest versions labview labview 2019 labview nxg 3.1 released may 2019 programming paradigm used labview sometimes called g based data availability enough data available subvi function subvi function execute execution flow determined structure graphical block diagram labview-source code programmer connects different function-nodes drawing wires wires propagate variables node execute soon input data become available since might case multiple nodes simultaneously labview execute inherently parallel multi-processing multi-threading hardware exploited automatically built-in scheduler multiplexes multiple os threads nodes ready execution labview integrates creation user interfaces termed front panels development cycle labview programs-subroutines termed virtual instruments vis vi three components block diagram front panel connector pane last used represent vi block diagrams calling vis front panel built using controls indicators controls inputs allow user supply information vi indicators outputs indicate display results based inputs given vi back panel block diagram contains graphical source code objects placed front panel appear back panel terminals back panel also contains structures functions perform operations controls supply data indicators structures functions found functions palette placed back panel collectively controls indicators structures functions referred nodes nodes connected one another using wires e.g. two controls indicator wired addition function indicator displays sum two controls thus virtual instrument run either program front panel serving user interface dropped node onto block diagram front panel defines inputs outputs node connector pane implies vi easily tested embedded subroutine larger program graphical approach also allows nonprogrammers build programs dragging dropping virtual representations lab equipment already familiar labview programming environment included examples documentation makes simple create small applications benefit one side also certain danger underestimating expertise needed high-quality g programming complex algorithms large-scale code important programmer possess extensive knowledge special labview syntax topology memory management advanced labview development systems offer ability build stand-alone applications furthermore possible create distributed applications communicate client–server model thus easier implement due inherently parallel nature g. applications labview usually designed using well-known architectures known design patterns common design patterns graphical labview applications listed table labview includes extensive support interfacing devices instruments camera devices users interface hardware either writing direct bus commands usb gpib serial using high-level device-specific drivers provide native labview function nodes controlling device labview includes built-in support ni hardware platforms compactdaq compactrio large number device-specific blocks hardware measurement automation explorer max virtual instrument software architecture visa toolsets national instruments makes thousands device drivers available download ni instrument driver network idnet labview includes compiler produces native code cpu platform aids performance graphical code translated executable machine code compiler labview syntax strictly enforced editing process compiled executable machine code requested run upon saving latter case executable source code merged single file executable runs help labview run-time engine contains pre-compiled code perform common tasks defined g language run-time engine reduces compiling time provides consistent interface various operating systems graphic systems hardware components etc run-time environment makes code portable across platforms generally labview code slower equivalent compiled c code although differences often lie program optimization inherent execution speed many libraries large number functions data acquisition signal generation mathematics statistics signal conditioning analysis etc. along numerous functions integration filters specialized abilities usually associated data capture hardware sensors enormous addition labview includes text-based programming component named mathscript added functions signal processing analysis mathematics mathscript integrated graphical programming using script nodes uses syntax compatible generally matlab labview inherently concurrent language easy program multiple tasks performed parallel via multithreading example done easily drawing two parallel loops connecting two separate nodes great benefit test system automation common practice run processes like test sequencing data recording hardware interfacing parallel due longevity popularity labview language ability users extend functions large ecosystem third party add-ons developed via contributions community ecosystem available labview tools network marketplace free paid labview add-ons low-cost labview student edition aimed educational institutions learning purposes also active community labview users communicate several electronic mailing lists email groups internet forums national instruments provides low cost labview home bundle edition labview proprietary product national instruments unlike common programming languages c fortran labview managed specified third party standards committee american national standards institute ansi institute electrical electronics engineers ieee international organization standardization iso etc many users criticised tendency freeze crash simple tasks often requiring software shut restarted small applications still start run-time environment large slow task tends restrict labview monolithic applications examples might tiny programs grab single value hardware used scripting language overhead run-time environment render approach impractical labview g language non-textual software tools versioning side-by-side diff comparison version code change tracking applied manner textual programming languages additional tools make comparison merging code source code control versioning tools subversion cvs perforce ability zoom enlarge vi hard see large high-resolution monitor practice however n't problem good programming practice means creating subroutines sub-vis keeping block diagram uncluttered relatively small 2005 starting labview 8.0 major versions released around first week august coincide annual national instruments conference ni week followed bug-fix release following february 2009 national instruments began naming releases year released bug-fix termed service pack example 2009 service pack 1 released february 2010 2017 national instruments moved annual conference may released labview 2017 alongside completely redesigned labview nxg 1.0 built windows presentation foundation wpf openg well lava code repository lavacr serve repositories wide range open source labview applications libraries sourceforge labview listed one possible languages code written vi package manager become standard package manager labview libraries similar purpose ruby rubygems perl cpan although provides graphical user interface similar synaptic package manager vi package manager provides access repository openg libraries labview tools exist convert mathml g code national instruments also offers product named measurement studio offers many test measurement control abilities labview set classes use microsoft visual studio allows developers harness labview strengths within text-based .net framework national instruments also offers labwindows/cvi alternative ansi c programmers applications need sequencing users often use labview teststand test management software also national instruments ch interpreter c/c++ interpreter embedded labview scripting tril centre ireland biomobius platform dsp robotics flowstone dsp also use form graphical programming similar labview limited biomedical robotics industries respectively labview direct node modefrontier multidisciplinary multi-objective optimization design environment written allow coupling almost computer-aided engineering tool part process workflow description virtually driven optimization technologies available modefrontier
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Programming language topics
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mount rainier packet writing mount rainier mrw format writable optical discs provides packet writing defect management goal replacement floppy disk named mount rainier volcano near seattle washington united states mount rainier used drives explicitly support part scsi/mmc work atapi works standard cd-r cd-rw dvd+/-r dvd+/-rw media physical format mrw disk managed drive firmware remaps physical drive blocks virtual defect-free space thus host computer see physical format disk sequence data blocks capable holding filesystem time needed disk formatting shortened one minute background formatting capabilities drive formatting allocates sectors end disk defect management defective sectors recorded table lead-in administrative area copy table lead-out host computer perspective mrw disc provides defect-free block-accessible device upon host supported filesystem may written filesystems may fat32 ntfs etc. preferred format usually udf 1.02 file format widely supported mrw-formatted cd-rw udf filesystem gives approximately 500 mb free space mt rainier allows write access disc within seconds insertion spin-up even background formatting sequence taking place technology user would wait formatting complete writing data new disc even possible read write mrw disks without mrw-compatible drive remapper device driver needed example easywrite reader windows alternative mrw physically format disc udf 1.5 higher using spared build achieved use specialized packet writing software operating systems support udf versions 1.5 mrw capabilities overlap somewhat udf 1.5+ advantages mrw udf 1.5+ include advantage udf 1.5+ mrw include mount rainier implemented natively windows vista windows 7 linux built-in mrw support since kernel version 2.6.2 2004 amiga os4 supports natively since first beta appeared 2004 support reading format also added mac os x operating systems n't support mrw natively notably windows xp prior versions need third-party software read write mrw-formatted discs tend packet writing utilities allow native udf filesystems written optical media optical disk software isobuster support mount rainier non-mr drives easywrite logo marketing symbol created philips cd drives mount rainier compatible cd-mrw stands compact disc – mount rainier read/write
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Computer file systems
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autoit autoit freeware programming language microsoft windows earliest release primarily intended create automation scripts sometimes called macros microsoft windows programs since grown include enhancements programming language design overall functionality scripting language autoit 1 2 statement-driven designed primarily simulating user interaction version 3 onward autoit syntax similar found basic family languages form autoit general-purpose third-generation programming language classical data model variant data type store several types data including arrays autoit automation script converted compressed stand-alone executable run computers autoit interpreter installed wide range function libraries known udfs user defined functions also included standard available website add specialized functionality autoit also distributed ide based free scite editor compiler help text fully integrated provide de facto standard environment developers using autoit autoit typically used produce utility software microsoft windows automate routine tasks systems management monitoring maintenance software installation also used simulate user interaction whereby application driven via automated form entry keypresses mouse clicks things autoit script autoit also used low-cost laboratory automation applications include instrument synchronisation alarm monitoring results gathering devices cnc routers 3d-printers also controlled developers autoit originally released source code gnu general public license gpl practice discontinued beginning version 3.2.0 august 2006 following terms gpl code version 3.1 used create fork autohotkey project community continuing develop release code gpl
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Programming language topics
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lnfs lnfs plan 9 file system enabling use long filenames filesystems support similar umsdos file system linux
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Computer file systems
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cybersecurity information sharing act cybersecurity information sharing act cisa 113th congress 114th congress united states federal law designed improve cybersecurity united states enhanced sharing information cybersecurity threats purposes law allows sharing internet traffic information u.s. government technology manufacturing companies bill introduced u.s. senate july 10 2014 passed senate october 27 2015 opponents question cisa value believing move responsibility private businesses government thereby increasing vulnerability personal private information well dispersing personal private information across seven government agencies including nsa local police text bill incorporated amendment consolidated spending bill u.s. house december 15 2015 signed law president barack obama december 18 2015 cybersecurity information sharing act introduced july 10 2014 113th congress able pass senate intelligence committee vote 12-3 bill reach full senate vote end congressional session bill reintroduced 114th congress march 12 2015 bill passed senate intelligence committee vote 14-1 senate majority leader mitch mcconnell r-ky attempted attach bill amendment annual national defense authorization act blocked 56-40 reaching necessary 60 votes include amendment mitch mcconnell hoped bring bill senate-wide vote week august 3–7 unable take bill summer recess senate tentatively agreed limit debate 21 particular amendments manager amendment set time limits debate october 2015 us senate took bill back following legislation concerning sanctuary cities main provisions bill make easier companies share personal information government especially cases cyber security threats without requiring information sharing bill creates system federal agencies receive threat information private companies respect privacy bill includes provisions preventing sharing personal data irrelevant cyber security personal information get removed sharing procedure used variety ways shared cyber threat indicators used prosecute cyber crimes may also used evidence crimes involving physical force sharing national intelligence threat data among public private partners hard problem one care national intelligence threat sharing nits project intended innovative solution hard problem altogether nits innovative useful first ensure nits trustworthy private partners must indemnified indemnification takes act congress literally underlying impediment fulsome cooperation among buyers sellers peers within supply chain indemnification indemnification needed secure industry partners legal responsibility actions unfortunately congressional refusal offer indemnification remains impediment real collaboration least qualified immunity accorded immunity individuals performing tasks part government actions cisa received support advocacy groups including united states chamber commerce national cable telecommunications association financial services roundtable number business groups also opposed bill including computer communications industry association well individual companies twitter yelp apple reddit bsa software alliance appeared initially supportive cisa sending letter july 21 2015 urging senate bring bill debate september 14 2015 bsa published letter support amongst things cyber threat information sharing legislation addressed congress signed board members adobe apple inc. altium autodesk ca technologies datastax ibm microsoft minitab oracle salesforce.com siemens symantec prompted digital rights advocacy group fight future organize protest cisa following opposition campaign bsa stated letter expressed support cyber threat sharing legislation general endorse cisa pending cyber threat sharing bill particular bsa later stated opposed cisa current form computer communications industry association another major trade group including members google amazon.com cloudflare netflix facebook red hat yahoo also announced opposition bill proponents cisa include bill main cosponsors senators dianne feinstein d-ca richard burr r-nc senators announced opposition cisa including ron wyden d-or rand paul r-ky bernie sanders i-vt senator ron wyden d-or objected bill based classified legal opinion justice department written early george w bush administration obama administration states rely legal justification laid memo wyden made repeated requests us attorney general declassify memo dating least far back 2010 office inspector general report cited memo legal justification fbi warrantless wire-tapping program august 4 2015 white house spokesman eric schultz endorsed legislation calling senate take bill soon possible pass united states department homeland security initially supported bill jeh johnson secretary dhs calling bill move forward september 15 however august 3 letter senator al franken d-mn deputy secretary dhs alejandro mayorkas expressed desire connections brokered dhs given department charter protect executive branch networks letter dhs found issue direct sharing information government agencies advocating instead dhs sole recipient cyberthreat information allowing scrub private information addition department homeland security published privacy impact assessment detailing internal review proposed system handling incoming indicators industry privacy advocates opposed version cybersecurity information sharing act passed senate october 2015 left intact portions law said made amenable surveillance actual security quietly stripping several remaining privacy protections cisa criticized advocates internet privacy civil liberties electronic frontier foundation american civil liberties union compared criticized cyber intelligence sharing protection act proposals 2012 2013 passed united states house representatives pass senate united kingdom government policy cyber security scottish government information sharing
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Computer security
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tkhtml tkhtml discontinued open-source browser engine written c using tk widget toolkit used primarily html viewer 3 hv3 minimalist web browser version 1 written using xf application builder functionality reasons part rewritten 2006 announced public build tkhtml alpha 10 passed acid2 test run tkhtml tcl/tk framework needed installed standard wish interpreter needed replaced wwwish interpreter use wysiwyg previewing function
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Web technology
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redis redis remote dictionary server in-memory data structure project implementing distributed in-memory key-value database optional durability redis supports different kinds abstract data structures strings lists maps sets sorted sets hyperloglogs bitmaps streams spatial indexes project mainly developed salvatore sanfilippo sponsored redis labs open-source software released bsd 3-clause license name redis means remote dictionary server redis project began salvatore sanfilippo nicknamed antirez original developer redis trying improve scalability italian startup developing real-time web log analyzer encountering significant problems scaling types workloads using traditional database systems sanfilippo began prototype first proof concept version redis tcl later sanfilippo translated prototype c language implemented first data type list weeks using project internally success sanfilippo decided open source announcing project hacker news project began get traction among ruby community github instagram among first companies adopting sanfilippo hired vmware march 2010 may 2013 redis sponsored pivotal software vmware spin-off june 2015 development became sponsored redis labs.. october 2018 redis 5.0 released introducing redis stream new data structure allows storage multiple fields string values automatic time-based sequence single key redis made popular idea system considered time store cache using design data always modified read main computer memory also stored disk format unsuitable random access data reconstruct data back memory system restarts time redis provides data model unusual compared relational database management system rdbms user commands describe query executed database engine specific operations performed given abstract data types hence data must stored way suitable later fast retrieval without help database system form secondary indexes aggregations common features traditional rdbms redis implementation makes heavy use fork system call duplicate process holding data parent process continues serve clients child process creates copy data disk according monthly db-engines rankings redis often popular key-value database redis also ranked 4 nosql database user satisfaction market presence based user reviews popular nosql database containers 1 nosql database 2015 ranking website stackshare.io voted loved database stack overflow developer survey 2017 2018 2019 since version 2.6 redis features server-side scripting language lua many programming languages redis language bindings client side including actionscript c c++ c chicken clojure common lisp crystal dart elixir erlang go haskell haxe io java javascript node.js julia lua objective-c ocaml perl php pure data python r racket ruby rust scala smalltalk swift tcl several client software programs exist languages redis maps keys types values important difference redis structured storage systems redis supports strings also abstract data types type value determines operations called commands available value redis supports high-level atomic server-side operations like intersection union difference sets sorting lists sets sorted sets data types supported based redis modules api redis module redisjson implements ecma-404 javascript object notation json data interchange standard native data type redis typically holds whole dataset memory versions 2.4 could configured use refer virtual memory dataset stored disk feature deprecated persistence redis achieved two different methods first snapshotting dataset asynchronously transferred memory disk regular intervals binary dump using redis rdb dump file format alternatively journaling record operation modifies dataset added append-only file aof background process redis rewrite append-only file background avoid indefinite growth journal journaling introduced version 1.1 generally considered safer approach default redis writes data file system least every 2 seconds less robust options available needed case complete system failure default settings seconds data would lost redis supports master-replica replication data redis server replicate number replicas replica may master another replica allows redis implement single-rooted replication tree redis replicas configured accept writes permitting intentional unintentional inconsistency instances publish/subscribe feature fully implemented client replica may subscribe channel receive full feed messages published master anywhere replication tree replication useful read write scalability data redundancy durability data needed in-memory nature redis allows perform well compared database systems write every change disk considering transaction committed redis operates single process single-threaded double-threaded rewrites aof append-only file thus single redis instance use parallel execution tasks stored procedures redis introduced clustering april 2015 release version 3.0 cluster specification implements subset redis commands single-key commands available multi-key operations commands related unions intersections restricted keys belonging node commands related database selection operations unavailable redis cluster scale 1,000 nodes achieve acceptable write safety continue operations nodes fail due nature database design typical use cases session caching full page cache message queue applications leaderboards counting among others large companies twitter using redis amazon web services offering redis portfolio microsoft offering redis cache azure companies used redis created commercial offerings around february 21 2019 redis labs relicensed redis modules redis source available license source-available arrangement prohibits users selling software redis modules formerly licensed affero general public license
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Distributed computing architecture
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guardian analytics guardian analytics american privately held company headquartered mountain view california provides behavioral analytics machine learning technology preventing banking fraud established 2005 products based anomaly detection monitor financial transactions 2012 guardian analytics together mcafee dissected us 78 million cyber attack titled operation high roller 2013 guardian analytics listed among top 10 influencers banking information security september 2016 nearly 430 financial institutions using guardian analytics products mitigate fraud risk rely company stop sophisticated criminal attacks guardian analytics offers fraud prevention services financial institutions general architecture includes two main components first component risk engine merges analytics behavior-based models user create probabilistic profile individual recognizing anomalous behavior possible identify fraudulent activity loss occurs risk engine dynamically adapts user behavior able detect new fraud attacks second component visual analytics data browser used financial institutions monitor investigate resolve potential fraud accessing collected data visual interface shows risk scores underlying contextual information facilitate analysis investigation guardian analytics able detect fraudulent activities account takeover account reconnaissance fraudulent wire ach bill pay transactions guardian analytics specific type threat protect cyber attacks phishing vishing man browser software transparent account holders require action side guardian analytics markets several services targeting particular types financial interactions guardian analytics marketed software service deployed company sas 70 type ii certified environment frauddesk fraud monitoring managed service
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Computer security
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simmon simmon simulation monitor proprietary software testing system developed late 1960s ibm product test laboratory poughkeepsie n.y designed then-new line system/360 computers vehicle testing software ibm developing architecture simmon first described ibm simsymp 1968 symposium held rye new york simmon hypervisor similar ibm cp-40 system independently developed cambridge scientific center time chief difference cp-40 simmon supported single virtual machine testing single guest program running cp-40 supported many virtual machines time-sharing production work cp-40 evolved many stages present vm/cms operating system simmon useful test vehicle many years simmon designed dynamically include independently developed programs test tools testing target guest program simmon kernel maintained control hardware guest coordinated invocation test tools two modes operation provided mode instruction guest program simulated without ever passing control directly guest instruction set simulator simmon unusual simulated architecture running i.e ibm system/360/370 order magnitude slower interrupt mode allowed close attention operation guest would mode used various instruction trace test tools interrupt mode a/k/a bump mode constrained guest program run user program state simmon kernel handling hardware interrupts simulating privileged instructions guest attempted execute mode could used example test tool simulate hardware device test tools developed use simmon error generation test test tool developed test device support error recovery ibm pcp primary control program operating system developed used novel efficient table-driven finite state machine fsm inject simulated errors verify operating system followed detailed specifications actions taken attempt recovery table driven fsm aspect granted u.s. patent mapper confused unisys product name statistical performance analysis tool operated allowing program test run interrupt mode also used system timer periodically interrupt addresses tested program interrupted recorded later summarized tabulated form map showing density interrupts memory addresses result resembled nuclear scintigraphy images showing parts program frequently used test conditions hotspots instruction trace tool written help identify performance problem areas ibm mft operating system branch trace data written tape summarized report took form listing similar storage dump program entry points exit points identified including frequency use instruction sequence data identified memory management component consuming 20 cpu resources used justify task force try improve performance specific test tool distorted timing relationships running simmon found number problems particularly input/output sections unless simmon tool put place normalize delay i/o events would appear guest program happening unnaturally quickly programs test -- so-called guest programs -- capable stand-alone operation bare hardware simmon provided services test tools guest programs tested using simmon
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Computer architecture
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ronja ronja reasonable optical near joint access free-space optical communication system originating czech republic developed karel kulhavý twibright labs released 2001 transmits data wirelessly using beams light ronja used create 10 mbit/s full duplex ethernet point-to-point link estimated 1000 2000 links built worldwide range basic configuration device consists receiver transmitter pipe optical head mounted sturdy adjustable holder two coaxial cables used connect rooftop installation protocol translator installed house near computer switch range extended doubling tripling transmitter pipe building instructions blueprints schematics published gnu free documentation licence free software tools used development author calls level freedom user controlled technology ronja project twibright labs building instructions written inexperienced builder mind basic operations like drilling soldering etc. explained several techniques – drilling templates detailed checks soldering testing procedures – employed minimize errors critical places help speed work printed circuit boards downloadable ready manufacture instructions fabhouse people previous experience building electronics reported mailing list device ran first try 154 installations worldwide registered gallery technical data pictures brightest variant lumileds hpwt-bd00-f4000 led 130 mm diameter cheap chinese magnifying glass lenses range 1.4 km less bright easier buy e4000 variant hpwt-bd00 yields 1.3 km speed always 10 mbit/s full duplex regardless distance definition clear visibility transmitter receiver essential beam obscured way link stop working typically problems may occur conditions snow dense fog one device weighs 15.5 kg requires 70 hours building time requires ability set full duplex manually network card switch take advantage full duplex since n't support autonegotiation must plugged directly pc switch using integral 1 ethernet cable complete ronja system made 2 transceivers 2 optical transmitters 2 optical receivers assembled individually combination complete system layout shown block diagram usual approach fso free space optics preamplifiers employ transimpedance amplifier transimpedance amplifier sensitive broadband high-speed device featuring feedback loop fact means layout plagued stability problems special compensation pin diode capacitance must performed therefore n't allow selection wide range cheap pin photodiodes varying capacitances ronja however uses feedbackless design pin high working electrical resistance 100 kilohms together total input capacitance roughly 8 pf 5 pf pin 3 pf input mosfet cascode makes device operate passband 6 db/oct slope low pass formed pin working resistance total input capacitance signal immediately amplified remove danger contamination signal noise compensation 6 db/oct slope done derivator element programming pins ne592 video amplifier surprisingly flat characteristic obtained pin diode equipped 3 kω working resistor operate flat band mode range reduced 30 due thermal noise 3 kω resistor hsdl4220 infrared led originally unsuitable 10 mbit/s operation bandwidth 9 mhz 10 mbit/s manchester-modulated systems need bandwidth around 16 mhz operation usual circuit current drive would lead substantial signal corruption range reduction therefore twibright labs developed special driving technique consisting driving led directly 15-fold 74ac04 gate output parallel rf voltage applied current-unlimited directly led large capacitors voltage keep nominal led average current 100ma varies temperature component tolerances ac-bypassed current sense resistor put series led feedback loop measures voltage resistor keeps preset level varying supply voltage 74ac04 gates therefore nominally digital 74ac04 operating structured power cmos switch completely analog mode way led junction flooded cleared carriers quickly possible basically short circuit discharge pushes speed led maximum makes output optical signal fast enough range/power ratio faster red hpwt-bd00-f4000 led side effects brutal driving technique 1 led overshoots beginning longer 5 mhz/1 mhz impulses 2x brightness measured adverse effect range 2 blocking ceramic capacitor bank backing 74ac04 switching array crucial correct operation charging discharging led done short circuit dimensioning bank causes leading trailing edges optical output grow longer ronja twister electronic interface free space optical datalink based counter shift register chips part ronja design effectively optical ethernet transceiver without optical drive part original design superseded twister2 logic circuit remained one doctoral dissertation 10 master bachelor theses three high school graduation exams one high school vocational activity 18 master bachelor theses one university semester project cite ronja czech technical university built 120 educational link buildings two faculties teaching students practically fso one czech private university dedicates page textbook ronja additional 12 journal conference university articles based largely ronja soderberg studying ronja sociologically writes arguably first project vindicated methods licensing schemes free software development applied practices open hardware development pulled state-of-the-art technology without backing universities firms ronja project whole toolchain built strictly upon free tools source files provided free gpl allows anyone enter development start manufacture invest technology without entry costs costs normally include software licence costs time investment resolution compatibility issues proprietary applications costs intellectual property licence negotiations decision conceive project way inspired observed organizational efficiency free software christmas 2001 ronja became world first 10 mbit/s free space optics device free sources examples tools used development
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Internet protocols
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commit charge computing commit charge term used microsoft windows operating systems describe total amount virtual memory guaranteed processes fit physical memory page file systems pagefile may thought maximum potential pagefile usage systems pagefile still counted virtual address space must remain physical memory ram times accessed windows task manager utility windows xp server 2003 performance tab shows three counters related commit charge program process explorer reports set values labeling total current additionally providing percentages peak current towards limit value commit charge increases program opened used goes program closed also change already-running programs allocate free private virtual memory example virtualalloc virtualfree apis task manager utility windows xp windows server 2003 graphical displays labeled pf usage page file usage history despite labels reflect pagefile contents total current commit charge height graph area corresponds commit limit show much actually written pagefile maximum potential pagefile usage amount pagefile would used current contents ram removed windows 2000 windows nt 4.0 displays labeled mem usage actually show commit charge commit limit similar displays task manager windows vista later changed reflect usage physical memory task manager processes display process contribution total commit charge shown vm size column windows xp server 2003 value labeled commit size windows vista later total commit charge always larger sum values total includes system-wide allocations paged pool display mem usage column windows xp server 2003 working set memory column windows vista later shows process current working set count physical memory ram rather virtual address space represents subset process virtual address space valid meaning referenced without incurring page fault commit charge process include major contributions process virtual address space mapped files reason process working set portion address space referenced without incurring page fault may larger contribution total commit charge total commit charge inclusive total memory physical virtual actually use commit limit may increased either creating additional pagefiles pagefile expansion enabled expanding existing one operating system expand pagefile automatically possible total commit charge approaches limit event popup window displayed stating system running low virtual memory system ever runs completely commit charge total reaches limit popup window displayed stating system virtual memory may become extremely sluggish even nonresponsive closing programs user still able point decreases total commit charge may thereby free system
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Operating systems
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security service security service secaas business model service provider integrates security services corporate infrastructure subscription basis cost effectively individuals corporations provide total cost ownership considered secaas inspired software service model applied information security type services require on-premises hardware avoiding substantial capital outlays security services often include authentication anti-virus anti-malware/spyware intrusion detection penetration testing security event management among others outsourced security licensing delivery boasting multibillion-dollar market secaas provides users internet security services providing protection online threats attacks ddos constantly searching access points compromise websites demand use cloud computing skyrockets users vulnerable attacks due accessing internet new access points secaas serves buffer persistent online threats cloud security alliance csa organization dedicated defining raising awareness secure cloud computing csa defined following categories secaas tools created series technical implementation guidance documents help businesses implement understand secaas categories include secaas typically offered several forms security service offers number benefits including secaas number deficiencies make insecure many applications individual security service request adds least one across-the-'net round-trip counting installer packages four opportunities hacker intercept conversation secaas makes security handling uniform security breach one request security broken requests broadest attack surface also multiplies rewards incentive hacker value gained effort dramatically increased factors especially tailored resources nation/state-sponsored hacker biggest challenge secaas market maintaining reputation reliability superiority standard non-cloud services secaas whole seemingly become mainstay cloud market cloud-based website security ’ cater businesses specific requirements must properly assessed individual needs business cater end consumers afford keep data loose vulnerable hacker attacks heaviest part secaas educating businesses since data biggest asset businesses cios ctos take care overall security company
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Computer security
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