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linux kernel library linux kernel library project started octavian purdila university politehnica bucharest ixia sponsored laboratories ixlabs project goal use linux kernel linkable library non-static functions kernel called external program first application use lkl lklftpd ftp daemon serves files disk images containing file system supported linux kernel
Computer architecture
ibm spufi sql processor using file input database facility invented ibm interfacing db2 system accessed within tso ispf db2i primary option menu spufi allows direct input sql commands tso environment rather embedded within program set spufi defaults unlikely changed values similar across installations typical example shown although essentially interactive tool spufi operates using pair datasets dataset z/os equivalent file operating systems main spufi screen one specifies input dataset output dataset specified reused repeatedly user moves main screen standard ispf editor opened input dataset point user enter required sql statements using familiar editor exiting editor main spufi screen reappears user moves time contents input dataset executed results placed output dataset ispf editor opened read-only browse mode output user reads results interactive use spufi continues around steps summary cycle spufi uses normal datasets commands output possible pre-populate commands operate output accessing datasets independently spufi tool using datasets also means possibly-complicated set sql commands persist session session rather lost user exits tool simple query comments typical result type query output dataset contains resultant rows case select along additional details like number rows affected sql query sqlcode returned execution sql query case sql errors details error given db2 developer guide craig mullins sams publishing
Databases
peter g. neumann peter gabriel neumann born 1932 computer-science researcher worked multics operating system 1960s edits risks digest columns acm software engineering notes communications acm founded acm sigsoft fellow acm ieee aaas 1950 1958 neumann studied harvard university 1961 granted ph.d. completing fulbright scholarship germany 1958–1960 student harvard two-hour breakfast albert einstein 8 november 1952 discussing simplicity design neumann worked bell labs 1960 1970 worked sri international menlo park california since 1971 risks mailing list neumann best known provably secure operating system psos neumann worked dorothy e. denning 1980s develop computer intrusion detection system known ides model later computer security software neumann long served moderator risks digest member accurate project neumann founding editor acm software engineering notes sen fellow acm
Computer security
mastering internet mastering internet mti mass surveillance project led british communications intelligence agency government communications headquarters gchq budgeted £1 billion according reports register sunday times early may 2009 contracts total value £200m already awarded suppliers responding reports gchq issued press release countering claims mass surveillance stating gchq developing technology enable monitoring internet use phone calls britain target everyone uk however 2013 mass surveillance disclosures revealed gchq gathers raw information without filtering communications british citizens web part mastering internet programme mastering internet mti project british government part interception modernisation programme imp system described 2009 register sunday times replacement scrapped plans single central database involving thousands dpi black boxes various internet service providers association gchq base cheltenham funded single intelligence account budget £1.6 bn including £200m contract lockheed martin contract bae systems detica 2013 system capable copying signals 200 fibre-optic cables physical points entry great britain early 2007 john adams chief canada intelligence agency communications security establishment told parliament canada plans five eyes master internet cooperation nsa allies 2013 guardian provided specific details financial contributions made u.s. national security agency nsa mastering internet part five eyes alliance several english-speaking western democracies according documents leaked edward snowden nsa paid gchq £17.2 million towards running programme
Computer security
nat friedman nathaniel dourif friedman born august 6 1977 american technology executive 1996 freshman massachusetts institute technology friedman befriended miguel de icaza linuxnet irc network friedman created discuss linux intern microsoft friedman worked iis web server mit studied computer science mathematics graduated bachelor science 1999 friedman co-founded ximian originally called international gnome support helix code de icaza develop applications infrastructure gnome project de icaza started aim producing free software desktop environment company later bought novell 2003 novell friedman chief technology strategy officer open source january 2010 launched hula project began release components novell netmail open source tenure novell began effort migrate 6,000 employees away microsoft windows suse linux microsoft office openoffice.org friedman final project departure work suse studio sabbatical friedman created hosted podcast called hacker medley may 2011 friedman de icaza together founded xamarin friedman made ceo company created offer commercial support mono project de icaza initiated ximian provide free software implementation microsoft .net software stack xamarin focused continuing develop mono monodevelop marketing cross-platform xamarin sdk developers targeting mobile computing devices video game consoles 2016 friedman became employee microsoft upon acquisition xamarin rose position corporate vice president developer services june 2018 announcement microsoft 7.5 billion acquisition github companies simultaneously announced friedman would become github new ceo github co-founder then-current ceo chris wanstrath leading search wanstrath replacement since august 2017 friedman assumed role ceo 29th october 2018
Operating systems
jdom jdom open-source java-based document object model xml designed specifically java platform take advantage language features jdom integrates document object model dom simple api xml sax supports xpath xslt uses external parsers build documents jdom developed jason hunter brett mclaughlin starting march 2000 part java community process jsr 102 though effort since abandoned suppose file foo.xml contains xml document one parse xml file tree java objects jdom like case want create document object file input stream create document object element converse one construct tree elements generate xml file following example
Programming language topics
active directory federation services active directory federation services ad fs software component developed microsoft run windows server operating systems provide users single sign-on access systems applications located across organizational boundaries uses claims-based access-control authorization model maintain application security implement federated identity claims-based authentication involves authenticating user based set claims user identity contained trusted token token often issued signed entity able authenticate user means trusted entity claims-based authentication part active directory services ad fs identity federation established two organizations establishing trust two security realms federation server one side accounts side authenticates user standard means active directory domain services issues token containing series claims user including identity side resources side another federation server validates token issues another token local servers accept claimed identity allows system provide controlled access resources services user belongs another security realm without requiring user authenticate directly system without two systems sharing database user identities passwords practice user might typically perceive approach follows ad fs integrates active directory domain services using identity provider ad fs interact ws-* saml 2.0-compliant federation services federation partners
Operating systems
orthogonal frequency-division multiplexing telecommunications orthogonal frequency-division multiplexing ofdm method encoding digital data multiple carrier frequencies ofdm developed popular scheme wideband digital communication used applications digital television audio broadcasting dsl internet access wireless networks power line networks 4g mobile communications coded orthogonal frequency-division multiplexing cofdm forward error correction convolutional coding time/frequency interleaving applied signal transmitted done overcome errors mobile communication channels affected multipath propagation doppler effects cofdm introduced alard 1986 digital audio broadcasting eureka project 147 practice ofdm become used combination coding interleaving terms cofdm ofdm co-apply common applications ofdm frequency-division multiplexing fdm scheme used digital multi-carrier modulation method ofdm introduced chang bell labs 1966 numerous closely spaced orthogonal subcarrier signals overlapping spectra emitted carry data demodulation based fast fourier transform algorithms ofdm improved weinstein ebert 1971 introduction guard interval providing better orthogonality transmission channels affected multipath propagation subcarrier signal modulated conventional modulation scheme quadrature amplitude modulation phase-shift keying low symbol rate maintains total data rates similar conventional single-carrier modulation schemes bandwidth main advantage ofdm single-carrier schemes ability cope severe channel conditions example attenuation high frequencies long copper wire narrowband interference frequency-selective fading due multipath without complex equalization filters channel equalization simplified ofdm may viewed using many slowly modulated narrowband signals rather one rapidly modulated wideband signal low symbol rate makes use guard interval symbols affordable making possible eliminate intersymbol interference isi use echoes time-spreading analog television visible ghosting blurring respectively achieve diversity gain i.e signal-to-noise ratio improvement mechanism also facilitates design single frequency networks sfns several adjacent transmitters send signal simultaneously frequency signals multiple distant transmitters may re-combined constructively sparing interference traditional single-carrier system following list summary existing ofdm-based standards products details see usage section end article ofdm-based multiple access technology ofdma also used several 4g pre-4g cellular networks mobile broadband standards next generation wlan advantages disadvantages listed discussed characteristics principles operation section conceptually ofdm specialized frequency-division multiplexing fdm method additional constraint subcarrier signals within communication channel orthogonal one another ofdm subcarrier frequencies chosen subcarriers orthogonal meaning cross-talk sub-channels eliminated inter-carrier guard bands required greatly simplifies design transmitter receiver unlike conventional fdm separate filter sub-channel required orthogonality requires subcarrier spacing formula_1 hertz seconds useful symbol duration receiver-side window size k positive integer typically equal 1 stipulates carrier frequency undergoes k complete cycles per symbol period previous carrier therefore n subcarriers total passband bandwidth b ≈ n ·δ f hz orthogonality also allows high spectral efficiency total symbol rate near nyquist rate equivalent baseband signal i.e near half nyquist rate double-side band physical passband signal almost whole available frequency band used ofdm generally nearly 'white spectrum giving benign electromagnetic interference properties respect co-channel users ofdm requires accurate frequency synchronization receiver transmitter frequency deviation subcarriers longer orthogonal causing inter-carrier interference ici i.e. cross-talk subcarriers frequency offsets typically caused mismatched transmitter receiver oscillators doppler shift due movement doppler shift alone may compensated receiver situation worsened combined multipath reflections appear various frequency offsets much harder correct effect typically worsens speed increases important factor limiting use ofdm high-speed vehicles order mitigate ici scenarios one shape subcarrier order minimize interference resulting non-orthogonal subcarriers overlapping example low-complexity scheme referred wcp-ofdm weighted cyclic prefix orthogonal frequency-division multiplexing consists using short filters transmitter output order perform potentially non-rectangular pulse shaping near perfect reconstruction using single-tap per subcarrier equalization ici suppression techniques usually increase drastically receiver complexity orthogonality allows efficient modulator demodulator implementation using fft algorithm receiver side inverse fft sender side although principles benefits known since 1960s ofdm popular wideband communications today way low-cost digital signal processing components efficiently calculate fft time compute inverse-fft fft transform take less time symbol example dvb-t means computation done less -point fft may approximated computational demand approximately scales linearly fft size double size fft needs double amount time vice versa comparison intel pentium iii cpu 1.266 ghz able calculate fft using fftw intel pentium 1.6 ghz intel core duo 3.0 ghz one key principle ofdm since low symbol rate modulation schemes i.e. symbols relatively long compared channel time characteristics suffer less intersymbol interference caused multipath propagation advantageous transmit number low-rate streams parallel instead single high-rate stream since duration symbol long feasible insert guard interval ofdm symbols thus eliminating intersymbol interference guard interval also eliminates need pulse-shaping filter reduces sensitivity time synchronization problems cyclic prefix transmitted guard interval consists end ofdm symbol copied guard interval guard interval transmitted followed ofdm symbol reason guard interval consists copy end ofdm symbol receiver integrate integer number sinusoid cycles multipaths performs ofdm demodulation fft standards ultrawideband interest transmitted power cyclic prefix skipped nothing sent guard interval receiver mimic cyclic prefix functionality copying end part ofdm symbol adding beginning portion effects frequency-selective channel conditions example fading caused multipath propagation considered constant flat ofdm sub-channel sub-channel sufficiently narrow-banded i.e. number sub-channels sufficiently large makes frequency domain equalization possible receiver far simpler time-domain equalization used conventional single-carrier modulation ofdm equalizer multiply detected subcarrier fourier coefficient ofdm symbol constant complex number rarely changed value fundamental level simpler digital equalizers better require fewer operations translates fewer round-off errors equalizer round-off errors viewed numerical noise inevitable differential modulation dpsk dqpsk applied subcarrier equalization completely omitted since non-coherent schemes insensitive slowly changing amplitude phase distortion sense improvements fir equalization using ffts partial ffts leads mathematically closer ofdm ofdm technique easier understand implement sub-channels independently adapted ways varying equalization coefficients switching different qam constellation patterns error-correction schemes match individual sub-channel noise interference characteristics subcarriers ofdm symbols may carry pilot signals measurement channel conditions i.e. equalizer gain phase shift subcarrier pilot signals training symbols preambles may also used time synchronization avoid intersymbol interference isi frequency synchronization avoid inter-carrier interference ici caused doppler shift ofdm initially used wired stationary wireless communications however increasing number applications operating highly mobile environments effect dispersive fading caused combination multi-path propagation doppler shift significant last decade research done equalize ofdm transmission doubly selective channels ofdm invariably used conjunction channel coding forward error correction almost always uses frequency and/or time interleaving frequency subcarrier interleaving increases resistance frequency-selective channel conditions fading example part channel bandwidth fades frequency interleaving ensures bit errors would result subcarriers faded part bandwidth spread bit-stream rather concentrated similarly time interleaving ensures bits originally close together bit-stream transmitted far apart time thus mitigating severe fading would happen travelling high speed however time interleaving little benefit slowly fading channels stationary reception frequency interleaving offers little benefit narrowband channels suffer flat-fading whole channel bandwidth fades time reason interleaving used ofdm attempt spread errors bit-stream presented error correction decoder decoders presented high concentration errors decoder unable correct bit errors burst uncorrected errors occurs similar design audio data encoding makes compact disc cd playback robust classical type error correction coding used ofdm-based systems convolutional coding often concatenated reed-solomon coding usually additional interleaving top time frequency interleaving mentioned two layers coding implemented choice reed-solomon coding outer error correction code based observation viterbi decoder used inner convolutional decoding produces short error bursts high concentration errors reed-solomon codes inherently well suited correcting bursts errors newer systems however usually adopt near-optimal types error correction codes use turbo decoding principle decoder iterates towards desired solution examples error correction coding types include turbo codes ldpc codes perform close shannon limit additive white gaussian noise awgn channel systems implemented codes concatenated either reed-solomon example mediaflo system bch codes dvb-s2 system improve upon error floor inherent codes high signal-to-noise ratios resilience severe channel conditions enhanced information channel sent return-channel based feedback information adaptive modulation channel coding power allocation may applied across subcarriers individually subcarrier latter case particular range frequencies suffers interference attenuation carriers within range disabled made run slower applying robust modulation error coding subcarriers term dmt denotes ofdm-based communication systems adapt transmission channel conditions individually subcarrier means so-called bit-loading examples adsl vdsl upstream downstream speeds varied allocating either fewer carriers purpose forms rate-adaptive dsl use feature real time bitrate adapted co-channel interference bandwidth allocated whichever subscriber needs ofdm primary form considered digital modulation technique multi-user channel access method since used transferring one bit stream one communication channel using one sequence ofdm symbols however ofdm combined multiple access using time frequency coding separation users orthogonal frequency-division multiple access ofdma frequency-division multiple access achieved assigning different ofdm sub-channels different users ofdma supports differentiated quality service assigning different number subcarriers different users similar fashion cdma thus complex packet scheduling media access control schemes avoided ofdma used ofdma also candidate access method ieee 802.22 wireless regional area networks wran project aims designing first cognitive radio-based standard operating vhf-low uhf spectrum tv spectrum multi-carrier code division multiple access mc-cdma also known ofdm-cdma ofdm combined cdma spread spectrum communication coding separation users co-channel interference mitigated meaning manual fixed channel allocation fca frequency planning simplified complex dynamic channel allocation dca schemes avoided ofdm-based wide-area broadcasting receivers benefit receiving signals several spatially dispersed transmitters simultaneously since transmitters destructively interfere limited number subcarriers whereas general actually reinforce coverage wide area beneficial many countries permits operation national single-frequency networks sfn many transmitters send signal simultaneously channel frequency sfns use available spectrum effectively conventional multi-frequency broadcast networks mfn program content replicated different carrier frequencies sfns also result diversity gain receivers situated midway transmitters coverage area increased outage probability decreased comparison mfn due increased received signal strength averaged subcarriers although guard interval contains redundant data means reduces capacity ofdm-based systems broadcasting systems deliberately use long guard interval order allow transmitters spaced farther apart sfn longer guard intervals allow larger sfn cell-sizes rule thumb maximum distance transmitters sfn equal distance signal travels guard interval — instance guard interval 200 microseconds would allow transmitters spaced 60 km apart single frequency network form transmitter macrodiversity concept used dynamic single-frequency networks dsfn sfn grouping changed timeslot timeslot ofdm may combined forms space diversity example antenna arrays mimo channels done ieee 802.11 wireless lan standards ofdm signal exhibits high peak-to-average power ratio papr independent phases subcarriers mean often combine constructively handling high papr requires non-linearity signal chain cause intermodulation distortion linearity requirement demanding especially transmitter rf output circuitry amplifiers often designed non-linear order minimise power consumption practical ofdm systems small amount peak clipping allowed limit papr judicious trade-off consequences however transmitter output filter required reduce out-of-band spurs legal levels effect restoring peak levels clipped clipping effective way reduce papr although spectral efficiency ofdm attractive terrestrial space communications high papr requirements far limited ofdm applications terrestrial systems crest factor cf db ofdm system n uncorrelated subcarriers cf crest factor db subcarrier cf 3.01 db sine waves used bpsk qpsk modulation example dvb-t signal 2k mode composed 1705 subcarriers qpsk-modulated giving crest factor 35.32 db many crest factor reduction techniques developed dynamic range required fm receiver dab require comparison extra bit per sample increases dynamic range performance communication system measured terms power efficiency bandwidth efficiency power efficiency describes ability communication system preserve bit error rate ber transmitted signal low power levels bandwidth efficiency reflects efficiently allocated bandwidth used defined throughput data rate per hertz given bandwidth large number subcarriers used bandwidth efficiency multicarrier system ofdm using optical fiber channel defined factor 2 two polarization states fiber formula_9 symbol rate giga symbol per second gsps formula_10 bandwidth ofdm signal saving bandwidth using multicarrier modulation orthogonal frequency division multiplexing bandwidth multicarrier system less comparison single carrier system hence bandwidth efficiency multicarrier system larger single carrier system 1 dbm increase receiver power get 76.7 improvement bandwidth efficiency using multicarrier transmission technique section describes simple idealized ofdm system model suitable time-invariant awgn channel ofdm carrier signal sum number orthogonal subcarriers baseband data subcarrier independently modulated commonly using type quadrature amplitude modulation qam phase-shift keying psk composite baseband signal typically used modulate main rf carrier formula_11 serial stream binary digits inverse multiplexing first demultiplexed formula_12 parallel streams one mapped possibly complex symbol stream using modulation constellation qam psk etc. note constellations may different streams may carry higher bit-rate others inverse fft computed set symbols giving set complex time-domain samples samples quadrature-mixed passband standard way real imaginary components first converted analogue domain using digital-to-analogue converters dacs analogue signals used modulate cosine sine waves carrier frequency formula_13 respectively signals summed give transmission signal formula_14 receiver picks signal formula_15 quadrature-mixed baseband using cosine sine waves carrier frequency also creates signals centered formula_16 low-pass filters used reject baseband signals sampled digitised using analog-to-digital converters adcs forward fft used convert back frequency domain returns formula_12 parallel streams converted binary stream using appropriate symbol detector streams re-combined serial stream formula_18 estimate original binary stream transmitter formula_12 subcarriers used subcarrier modulated using formula_20 alternative symbols ofdm symbol alphabet consists formula_21 combined symbols low-pass equivalent ofdm signal expressed formula_23 data symbols formula_12 number subcarriers formula_25 ofdm symbol time subcarrier spacing formula_26 makes orthogonal symbol period property expressed formula_28 denotes complex conjugate operator formula_29 kronecker delta avoid intersymbol interference multipath fading channels guard interval length formula_30 inserted prior ofdm block interval cyclic prefix transmitted signal interval formula_31 equals signal interval formula_32 ofdm signal cyclic prefix thus low-pass signal either real complex-valued real-valued low-pass equivalent signals typically transmitted baseband—wireline applications dsl use approach wireless applications low-pass signal typically complex-valued case transmitted signal up-converted carrier frequency formula_13 general transmitted signal represented ofdm used key features common ofdm-based systems presented following table ofdm used adsl connections follow ansi t1.413 g.dmt itu g.992.1 standards called discrete multitone modulation dmt dsl achieves high-speed data connections existing copper wires ofdm also used successor standards adsl2 adsl2+ vdsl vdsl2 g.fast adsl2 uses variable subcarrier modulation ranging bpsk 32768qam adsl terminology referred bit-loading bit per tone 1 15 bits per subcarrier long copper wires suffer attenuation high frequencies fact ofdm cope frequency selective attenuation narrow-band interference main reasons frequently used applications adsl modems ofdm used many powerline devices extend digital connections power wiring adaptive modulation particularly important noisy channel electrical wiring medium speed smart metering modems prime g3 use ofdm modest frequencies 30–100 khz modest numbers channels several hundred order overcome intersymbol interference power line environment ieee 1901 standards include two incompatible physical layers use ofdm itu-t g.hn standard provides high-speed local area networking existing home wiring power lines phone lines coaxial cables based phy layer specifies ofdm adaptive modulation low-density parity-check ldpc fec code ofdm extensively used wireless lan man applications including ieee 802.11a/g/n wimax ieee 802.11a/g/n operating 2.4 5 ghz bands specifies per-stream airside data rates ranging 6 54 mbit/s devices use ht mode added 802.11n top 20 mhz per-stream rate increased 72.2 mbit/s option data rates 13.5 150 mbit/s using 40 mhz channel four different modulation schemes used bpsk qpsk 16-qam 64-qam along set error correcting rates 1/2–5/6 multitude choices allows system adapt optimum data rate current signal conditions ofdm also used wimedia/ecma-368 standard high-speed wireless personal area networks 3.1–10.6 ghz ultrawideband spectrum see multiband-ofdm much europe asia adopted ofdm terrestrial broadcasting digital television dvb-t dvb-h t-dmb radio eureka 147 dab digital radio mondiale hd radio t-dmb directive european commission television services transmitted viewers european community must use transmission system standardized recognized european standardization body standard developed codified dvb project digital video broadcasting dvb framing structure channel coding modulation digital terrestrial television customarily referred dvb-t standard calls exclusive use cofdm modulation dvb-t widely used europe elsewhere terrestrial digital tv ground segments digital audio radio service sdars systems used xm satellite radio sirius satellite radio transmitted using coded ofdm cofdm word coded comes use forward error correction fec question relative technical merits cofdm versus 8vsb terrestrial digital television subject controversy especially european north american technologists regulators united states rejected several proposals adopt cofdm-based dvb-t system digital television services instead opted 8vsb vestigial sideband modulation operation one major benefits provided cofdm rendering radio broadcasts relatively immune multipath distortion signal fading due atmospheric conditions passing aircraft proponents cofdm argue resists multipath far better 8vsb early 8vsb dtv digital television receivers often difficulty receiving signal also cofdm allows single-frequency networks possible 8vsb however newer 8vsb receivers far better dealing multipath hence difference performance may diminish advances equalizer design cofdm also used radio standards digital audio broadcasting dab standard digital audio broadcasting vhf frequencies digital radio mondiale drm standard digital broadcasting shortwave medium wave frequencies 30 mhz drm+ recently introduced standard digital audio broadcasting vhf frequencies 30 174 mhz usa uses alternate standard proprietary system developed ibiquity dubbed hd radio however uses cofdm underlying broadcast technology add digital audio medium wave fm broadcasts digital radio mondiale hd radio classified in-band on-channel systems unlike eureka 147 dab digital audio broadcasting uses separate vhf uhf frequency bands instead band-segmented transmission orthogonal frequency division multiplexing bst-ofdm system proposed japan isdb-t isdb-tsb isdb-c broadcasting systems improves upon cofdm exploiting fact ofdm carriers may modulated differently others within multiplex forms cofdm already offer kind hierarchical modulation though bst-ofdm intended make flexible 6 mhz television channel may therefore segmented different segments modulated differently used different services possible example send audio service segment includes segment composed number carriers data service another segment television service yet another segment—all within 6 mhz television channel furthermore may modulated different parameters example audio data services could optimized mobile reception television service optimized stationary reception high-multipath environment ultra-wideband uwb wireless personal area network technology may also use ofdm multiband ofdm mb-ofdm uwb specification advocated wimedia alliance formerly multiband ofdm alliance mboa wimedia alliance two merged one competing uwb radio interfaces fast low-latency access seamless handoff orthogonal frequency division multiplexing flash-ofdm also referred f-ofdm based ofdm also specified higher protocol layers developed flarion purchased qualcomm january 2006 flash-ofdm marketed packet-switched cellular bearer compete gsm 3g networks example 450 mhz frequency bands previously used nmt-450 c-net c450 1g analogue networks mostly decommissioned europe licensed flash-ofdm operators finland license holder digita began deployment nationwide 450 wireless network parts country since april 2007 purchased datame 2011 february 2012 datame announced would upgrade 450 mhz network competing cdma2000 technology slovak telekom slovakia offers flash-ofdm connections maximum downstream speed 5.3 mbit/s maximum upstream speed 1.8 mbit/s coverage 70 percent slovak population flash-ofdm network switched majority slovakia 30 september 2015 t-mobile germany used flash-ofdm backhaul wi-fi hotspots deutsche bahn ice high speed trains 2005 2015 switching umts lte american wireless carrier nextel communications field tested wireless broadband network technologies including flash-ofdm 2005 sprint purchased carrier 2006 decided deploy mobile version wimax based scalable orthogonal frequency division multiple access sofdma technology citizens telephone cooperative launched mobile broadband service based flash-ofdm technology subscribers parts virginia march 2006 maximum speed available 1.5 mbit/s service discontinued april 30 2009 ofdm become interesting technique power line communications plc area research wavelet transform introduced replace dft method creating orthogonal frequencies due advantages wavelets offer particularly useful noisy power lines instead using idft create sender signal wavelet ofdm uses synthesis bank consisting formula_36-band transmultiplexer followed transform function receiver side analysis bank used demodulate signal bank contains inverse transform followed another formula_36-band transmultiplexer relationship transform functions example w-ofdm uses perfect reconstruction cosine modulated filter bank pr-cmfb extended lapped transform elt used wavelet tf thus formula_42 formula_43 given two functions respective inverses used modulate demodulate given input sequence case dft wavelet transform creates orthogonal waves formula_47 formula_48 ... formula_49 orthogonality ensures interfere sent simultaneously receiver formula_50 formula_51 ... formula_52 used reconstruct data sequence w-ofdm evolution standard ofdm certain advantages mainly sidelobe levels w-ofdm lower results less ici well greater robustness narrowband interference two properties especially useful plc lines n't shielded em-noise creates noisy channels noise spikes comparison two modulation techniques also reveals complexity algorithms remains approximately
Internet protocols
windows driver model computing windows driver model wdm also known one point win32 driver model framework device drivers introduced windows 98 windows 2000 replace vxd used older versions windows windows 95 windows 3.1 well windows nt driver model wdm drivers layered stack communicate via i/o request packets irps microsoft windows driver model unified driver models windows 9x windows nt product lines standardizing requirements reducing amount code needed written wdm drivers run operating systems earlier windows 98 windows 2000 windows 95 windows nt 4.0 windows 3.1 conforming wdm drivers binary compatible source-compatible across windows 98 windows 98 second edition windows windows 2000 windows xp windows server 2003 windows vista backwards compatibility x86-based computers wdm drivers designed forward-compatible wdm driver run version windows newer driver initially written would mean driver take advantage new features introduced new version wdm generally backward-compatible wdm driver guaranteed run older version windows example windows xp use driver written windows 2000 make use new wdm features introduced windows xp however driver written windows xp may may load windows 2000 wdm exists intermediary layer windows 2000 kernel-mode drivers introduced increase functionality ease writing drivers windows although wdm mainly designed binary source compatible windows 98 windows 2000 may always desired specific drivers developed either operating system windows drivers model wdm devices microsoft implements approach kernel mode drivers unique windows operating systems wdm implements layered architecture device drivers every device computer served stack drivers however every driver stack chain isolate hardware independent features driver beneath drivers stack need interact directly one another wdm defines architecture device procedures range devices display network card known network driver interface specification ndis ndis architecture layered network drivers include lower-level drivers manage hardware upper-level drivers implement network data transport transmission control protocol tcp wdm defines three types device drivers driver stacks given device contain types device drivers three wdm device driver types bus driver every bus mainboard one bus driver primary responsibility identification devices connected bus responding plug play events microsoft provide bus drivers part operating system pci pnpisa scsi usb firewire function driver principal driver device provides operational interface device handling read write operations function drivers written device vendors interaction hardware depend specific bus driver present windows operating system filter driver driver optional modify behaviour device input output requests drivers implemented lower-level upper-level filter drivers function drivers bus drivers often implemented driver/minidriver pairs practice either class/miniclass port/miniport pair bus drivers devices attached bus implemented class drivers hardware-agnostic support operations certain type device windows operating systems include number class drivers kbdclass.sys driver keyboards miniclass drivers hand supplied vendor device support device specific operations particular device given class port drivers support general input/output i/o operations peripheral hardware interface core functionality port drivers mandated operating system windows operating systems integrate variety port drivers example i8042prt.sys port driver 8042 microcontroller connects ps/2 keyboards mainboard peripheral bus miniport drivers like miniclass drivers supplied hardware vendors support device specific operations peripheral hardware connected port mainboard driver processes i/o request device corresponding object loaded main memory device object created windows operating system associated device class device objects contain structures type device_object store pointers driver run time pointers used locate driver dispatch routine member functions wdm driver stack filter driver device object known upper filter receive i/o request packet irp device i/o manager upper filter driver serve request locate object driver one step driver stack irp passed driver stack calling function iocalldrive processed function driver device object also known functional device object function driver device object turn may pass irp lower filter another filter device object irp may passed bus driver operates physical device object bus driver object bottom driver stack interacts hardware abstraction layer part windows operating system kernel allows windows operating systems run variety processors different memory management unit architectures variety computer systems different i/o bus architectures execution irp finished driver objects stack returns request back i/o manager result status flag wdm framework developed microsoft simplify communication operating system drivers inside kernel windows operating systems drivers implemented dynamic link libraries .dll .sys files wdm compliant drivers must follow rules design initialisation plug-and-play power management memory allocation practice wdm driver programmers reuse large pieces code building new object orientated drivers means drivers wdm stack may contain residual functionality documented specifications drivers passed microsoft quality test digitally signed microsoft microsoft hardware compatibility tests driver development kit include reliability stress tests device driver designed specific hardware component may allow another device function basic functionality hardware device class similar functionality video card class example allows microsoft basic display adapter driver work wide variety video cards however installing wrong driver device mean full functionality device used may result poor performance destabilization windows operating system hardware device vendors may release updated device drivers particular windows operating systems improve performance add functionality fix bugs device working expected latest device drivers downloaded vendor website installed device drivers designed particular windows operating system versions device drivers previous version windows may work correctly versions many device drivers run kernel mode installing drivers previous operating system version may destabilise windows operating system migrating computer higher version windows operating system therefore requires new device drivers installed hardware components finding date device drivers installing windows 10 introduced complications migration process common device driver compatibility issues include 32-bit device driver required 32-bit windows operating system 64-bit device driver required 64-bit windows operating system 64-bit device drivers must signed microsoft run kernel mode unrestricted access computer hardware operating systems prior windows 10 microsoft allowed vendors sign 64-bit drivers assuming vendors undertaken compatibility tests however windows 10 64-bit drivers need signed microsoft therefore device vendors submit drivers microsoft testing approval driver installation package includes files .inf directory files package need installed otherwise installation device driver may fail operating system versions windows 10 files necessary driver installation included package requirement consistently enforced device driver installers user interface gui often requiring user configuration input absence user interface mean installation device driver successful besides windows 10 device drivers allowed include user interface network driver interface specification ndis 10.x used network devices windows 10 operating system network device drivers windows xp use ndis 5.x may work subsequent windows operating systems performance reasons network device drivers implement ndis 6.0 higher similarly wddm driver model windows vista replaces xpdm used graphics drivers device manager control panel applet microsoft windows operating systems allows users view control hardware attached computer allows users view modify hardware device properties also primary tool manager device drivers windows driver model significant improvement vxd windows nt driver model used criticised driver software developers significantly following also number concerns quality documentation samples microsoft provided issues microsoft released new set frameworks top wdm called windows driver frameworks wdf formerly windows driver foundation includes kernel-mode driver framework kmdf user-mode driver framework umdf windows vista supports pure wdm newer wdf kmdf also available download windows xp even windows 2000 umdf available windows xp
Operating systems
simulationx simulationx cae software application running microsoft windows physical simulation technical systems developed sold esi iti gmbh dresden germany mid 1980s veb mikromat dresden developed program dos design controlled feed axis systems perform hydraulic calculations 1993 iti gmbh founded former mikromat employees 1990 introduced simulation tool microsoft windows designed dynamic calculations drive systems iti-sim 1 release iti-sim 2 1995 software also allowed fluid simulations 2002 newly developed application simulationx based object-oriented description language modelica introduced market year 2007 iti-sim version 3.8 completely replaced simulationx since beginning 2016 iti belongs esi group operates name esi iti gmbh simulation models created basis discrete network approach means system broken logical parts linked specific connections sub-systems represented preconfigured custom model elements organized domain-specific custom model libraries sub-models parameterized connected models created either graphical user interface using modelica command lines model libraries obtained modular packages software producer various libraries available basic models corresponding physical domains well libraries advanced models specific applications industries depending objective user choose 1d 2d 3d model elements respect modeling simulation parameterization requirements modelica-based third-party custom-built libraries also integrated simulationx simulationx libraries include simulationx supports modelica modeling language simulate individually created realistic sub- models models modelica standard library ones purely based modelica language definition executed simulationx provides open comprehensive cax-interfaces external programs different purposes applications e.g cae vehiclesim carsim bikesim trucksim cad solid edge unigraphics nx solidworks creo elements/pro autodesk inventor catia v5 cam computer-aided optimization e.g isight modefrontier optimus optislang optiy fea/fem abaqus ansys comsol multiphysics msc nastran cfd co-simulation provides general interface used link simulationx cae tools predefined setups particular realizations msc.adams simpack matlab/simulink fluent cadmould etc. coupling ensures data exchange tools simulation software tools holistic structural system analysis equilibrium computation natural frequencies vibration modes input-output analysis linking simulation model databases available com interface allows communication simulationx windows applications user-defined batch runs embedded simulation parameter studies optimizations code-export features support generation c source code seamless model integration hardware-in-the-loop hil applications rapid control prototyping functional mock-up virtual machine throughout stages modern system design processes engineers scientists work variety seamlessly integrated tools connection simulationx real-time testing simulation platforms labview ni veristand dspace etas labcar scale-rt heavily increases productivity design cycle shortens time-to-market new products simulationx supports creation import functional mock-up units defined functional mock-up interface standard development started modelisar project standardized interfaces facilitate platform-independent exchange simulation models increase flexibility connection external simulation tools models simulationx used designing modeling analyzing dynamic behavior complex mechatronic systems well virtual tests many industries research education including automotive sector railway shipbuilding heavy machinery mining power generation building technology aerospace defense mechanical engineering medical engineering oil gas precision instruments home appliances well consumer electronics simulationx widely used education research worldwide
Programming language topics
wizard oz 1985 video game wizard oz illustrated text adventure game developed published windham classics apple ii commodore 64 ms-dos msx 1985 adaptation books wonderful wizard oz marvelous land oz wizard oz positively received press including ii computing ahoy commodore power play
Computer architecture
distributed common ground system distributed common ground system dcgs system produces military intelligence multiple military branches u.s. air force use system produces intelligence collected u-2 dragonlady rq-4 global hawk mq-9 reaper mq-1 predator previous system similar use deployable ground station dgs first deployed july 1994 subsequent version dgs developed 1995 2009 although officially designated weapons system consists computer hardware software connected together computer network devoted processing dissemination information images 480th intelligence surveillance reconnaissance wing air combat command operates maintains usaf system plan envisioned 1998 develop interoperable systems army navy addition air force 2006 version 10.6 deployed air force version known dcgs-a developed army 2010 report general michael t. flynn program intended use cloud computing easy use ipad soldiers years commonly using april 2011 project manager colonel charles wells announced version 3 army system code named griffin deployed us war afghanistan january 2012 united states army communications-electronics research development engineering center hosted meeting based dcgs-a early experience brought together technology providers hope developing integrated systems using cloud computing open architectures compared previously specialized custom-built systems major contractor lockheed martin computers supplied silicon graphics international chippewa falls wisconsin office software known analyst notebook originally developed i2 limited included dcgs-a ibm acquired i2 2011 us army personnel reported using palantir technologies product improve ability predict locations improvised explosive devices april 2012 report recommending study initial success palantir software rated easy use flexibility wide number data sources dcgs-a july 2012 congressman duncan d. hunter california state palantir based complained us dod obstacles wider use although limited test august 2011 test evaluation command recommended deployment operation problems dcgs-a included baseline system operationally effective reboots average every 8 hours set improvements identified november 2012 press reported shortcomings uncovered general genaro dellarocco tests ambitious goal integrating 473 data sources 75 million reports proved challenging spending estimated 2.3 billion army system alone may 2013 politico reported palantir lobbyists anonymous returning veterans continued advocate use software despite interoperability limits particular members special forces us marines required use official army system similar stories appeared publications army representatives major general mary a. legere citing limitations various systems congressman hunter member house armed services committee required review program two members congress sent open letter secretary defense leon panetta senate defense appropriations subcommittee included testimony army chief staff general ray odierno 130th engineer brigade united states found system unstable slow friendly major hindrance operations equivalent system united states navy planned initial deployment 2015 within shipboard network called consolidated afloat networks enterprise services canes 2016 early testing announced 2009 aboard aircraft carrier portion software distributed data framework dcgs integration backbone dib version 4 submitted open-source software repository codice foundation github framework new dib version 4 replacing legacy dib portal ozone widget framework interface written java programming language distributed common ground system-army dcgs-a united states army primary system post data process information disseminate intelligence surveillance reconnaissance isr information threat weather terrain echelons dcgs-a provides commanders ability task battle-space sensors receive intelligence information multiple sources august 17 2011 upi article quoted i2 chief executive officer robert griffin commented dcgs-a best-of-breed approach development article detailed army contracting i2 analyst notebook software open architecture analyst notebook supports army strategy employ integrate best-of-breed solutions across industry meet dynamic needs users face field daily basis february 1 2012 article army web page quoted mark kitz dcgs-a technical director dcgs-a uses latest cloud technology rapidly gather collaborate share intelligence data multiple sources deliver common operating picture dcgs-a able rapidly adapt changing operational environments leveraging iterative development model open architecture allowing collaboration multiple government industry academic partners july 2012 article signal magazine monthly publication armed forces communications electronics association promoted dcgs-a taking advantage technological environments young soldiers familiar article quoted dcgs-a program manager col. charles wells systems benefits article also included lockheed martin dcgs-a program manager milwaukee journal sentinel published article may 4 2012 wisconsin-located companies helping dcgs-a cloud computing technology article promoted speed cloud computing processes intelligence cost savings analyzing data field u.s. army released 2011 army posture statement march 2 included statement dcgs-a dcgs-a connects tactical operational theater-level commanders hundreds intelligence intelligence-related data sources classification levels allows focus efforts entire isr community information requirements ground commanders describe dcgs-a unwieldy unreliable hard learn difficult use supporting alternative software palantir technologies palantir software supports small unit situational awareness sufficiently funded support broader role dcgs-a fulfills
Distributed computing architecture
underground underground one biggest hacking conferences middle east europe series events dedicated information security held warsaw prague 2009 underground organised germany conference focused security aim show participants defend improve security lectures conducted byol bring laptop mode aimed participants brought computers therefore actively participate sessions attendees able boot machines test networks using techniques described lecturers try defend attacks performed others underground website
Computer security
dictionary scottish architects dictionary scottish architects publicly available online database provides biographical information architects known worked scotland 1840 1980 lists works launched 2006 compiled team led professor david walker emeritus professor school art history university st andrews database includes known works architects based scotland scottish works english irish architects included database available free charge managed fully funded historic environment scotland replaced historic scotland 2015
Databases
heap overflow heap overflow heap overrun type buffer overflow occurs heap data area heap overflows exploitable different manner stack-based overflows memory heap dynamically allocated application run-time typically contains program data exploitation performed corrupting data specific ways cause application overwrite internal structures linked list pointers canonical heap overflow technique overwrites dynamic memory allocation linkage malloc meta data uses resulting pointer exchange overwrite program function pointer typical example older versions linux two buffers allocated next heap writing beyond boundary first buffer allows overwriting meta data second buffer setting in-use bit zero second buffer setting length small negative value allows null bytes copied program calls free first buffer attempt merge two buffers single buffer happens buffer assumed freed expected hold two pointers fd bk first 8 bytes formerly allocated buffer bk gets written fd used overwrite pointer accidental overflow may result data corruption unexpected behavior process uses affected memory area operating systems without memory protection could process system deliberate exploit may result data specific location altered arbitrary way arbitrary code executed example microsoft jpeg gdi+ buffer overflow vulnerability could allow remote execution code affected machine ios jailbreaking often uses heap overflows gain arbitrary code execution usually kernel exploits achieve ability replace kernel one jailbreak provides buffer overflows primarily three ways protect heap overflows several modern operating systems windows linux provide implementation three since version 2.3.6 gnu libc includes protections detect heap overflows fact example checking pointer consistency calling unlink however protections prior exploits almost immediately shown also exploitable addition linux included support aslr since 2005 although pax introduced better implementation years also linux included support nx-bit since 2004 microsoft included protections heap resident buffer overflows since april 2003 windows server 2003 august 2004 windows xp service pack 2 mitigations safe unlinking heap entry header cookies later versions windows vista server 2008 windows 7 include removal commonly targeted data structures heap entry metadata randomization expanded role heap header cookie randomized heap base address function pointer encoding termination heap corruption algorithm variation normal data execution prevention dep aslr also help mitigate attack
Computer security
ubot studio ubot studio web browser automation tool allows users build scripts complete web-based actions data mining web testing social media marketing scripts created via command window inside ubot studio browser compiled separate executable files “ internet bots ” run computer called “ infrastructural piece botting world ” ubot studio developed seth turin media inc. first released 2009 ubot studio web automation product designed internet marketing automation advanced versions ubot studio contain drag-and-drop user interface designer bots image recognition task scheduler ability automate non web-based applications 2013 company introduced api creation plugins allow addition non-standard functionality software 2015 company released ubot studio stealth new browser using cef framework additional features
Programming language topics
waterfox waterfox open-source web browser x64 arm64 systems intended speedy ethical maintain support legacy extensions dropped firefox forked official releases windows including portable version macos linux android waterfox based firefox compiled using various compilers using intel math kernel library streaming simd extensions 3 advanced vector extensions linux builds built clang waterfox continuing support long-standing xul xpcom add-on capability firefox removed version 57 features waterfox currently waterfox first released march 27 2011 64-bit windows mac build introduced may 14 2015 release version 38.0 linux build introduced december 20 2016 release version 50.0 android build first introduced version 55.2.2 version 29.0 released july 22 2015 build ios may 7 2019 68.0a1 first alpha version next generation waterfox released may 12 2015 november 12 2015 waterfox exclusive charity search engine called storm ecosia default search engine bing search engine default one
Internet protocols
akamai technologies akamai technologies inc. american content delivery network cdn cloud service provider headquartered cambridge massachusetts united states akamai content delivery network one world largest distributed computing platforms responsible serving 15 30 web traffic company operates network servers around world rents capacity servers customers want websites work faster distributing content locations close user user navigates url akamai customer browser redirected one akamai copies website akamai technologies entered 1998 mit 50k competition business proposition based research consistent hashing selected one finalists august 1998 developed working prototype help jonathan seelig randall kaplan began taking steps incorporate company late 1998 early 1999 group business professionals joined founding team notably paul sagan former president new media time inc. george conrades former chairman chief executive officer bbn corp. senior vice president u.s. operations ibm conrades became chief executive officer akamai april 1999 led company start-up sustained profitability positive free cash-flow turning reins sagan 2005 company launched commercial service april 1999 listed nasdaq stock market october 29 1999 july 1 2001 akamai added russell 3000 index russell 2000 index september 11 2001 co-founder daniel m. lewin died stabbing flight september 11th attacks age 31 lewin aboard american airlines flight 11 first plane crash world trade center 2005 paul sagan named chief executive officer akamai sagan worked differentiate akamai competitors expanding company breadth services leadership company grew 1.37 billion revenues sagan served chief executive officer co-founder current ceo tom leighton elected position 2013 akamai headquarters kendall square started technology square expanded multiple buildings cambridge center consolidating offices purpose-built building 145 broadway late 2019 early 2020 akamai intelligent platform distributed cloud computing platform operates worldwide network 240,000 servers deployed 120 countries servers reside 1,500 world networks gathering real-time information traffic congestion trouble spots akamai server equipped proprietary software uses complex algorithms process requests nearby users serve requested content content delivery process begins user submitting request browser user enters url dns request triggered ip address retrieved ip address browser contact web server directly subsequent requests content delivery network structure domain name url translated mapping system ip address edge server serve content user akamai delivers web content intelligent platform transparently mirroring elements html css software downloads media objects customers servers akamai server automatically picked depending type content user network location receiving content akamai server close user allows faster download times less vulnerability network congestion akamai claims provide better scalability delivering content last-mile servers close end-users avoiding middle-mile bottleneck internet download delivery product line includes http downloads large downloadable objects customizable application consumers analytics tools metrics monitor report download process addition using akamai servers akamai delivers content end-users computers form peer-to-peer networking users request download large files served system prompts download install akamai netsession interface download manager used reduce download time increase quality however software operates merely download manager delivering content internet user computer also peer-to-peer server delivering content cached user computer users computers akamai network operations command center nocc used proactive monitoring troubleshooting servers global akamai network nocc provides real time statistics akamai web traffic traffic metrics update automatically provide view internet traffic conditions akamai servers customer websites state internet report quarterly report akamai releases based data gathered intelligent platform provides global internet statistics connection speed broadband adoption attack traffic network connectivity mobile connectivity akamai ’ data visualization tools display data moving across internet real-time viewers able see global web conditions malicious attack traffic internet connectivity addition net usage indices monitor global news consumption industry specific traffic mobile trends akamai also offers internet visualization application allows users view real-time data mobile device october 9 2013 akamai announced open initiative 2013 akamai edge conference open allows customers partners develop customize way interact akamai intelligent platform key components open include system development operations integration real-time big data integration single-point user interface akamai technologies owns 60 domains primary domains uses include july 21 1999 macworld expo new york apple akamai announced strategic partnership build apple new media network quicktime tv qtv based quicktime streaming server companies later announced apple made 12.5 million investment company previous month apple continues use akamai primary content delivery network wide range applications including software downloads apple website quicktime movie trailers itunes store september 1999 microsoft akamai formed strategic relationship incorporate windows media technology akamai freeflow service well facilitate porting freeflow product windows platform relationship exists day microsoft azure offers akamai along verizon options standard cdn service arabic news network al-jazeera customer march 28 2003 april 2 2003 akamai decided end relationship network english-language managing editor claimed due political pressure june 2008 newsmarket teamed akamai accelerate dynamic content applications global media ahead beijing olympics bbc iplayer uses akamai stream recorded live programs focused xml playlist entire china central television website cctv.com including streaming video hosted akamai edge servers since late 2009 hulu uses akamai hosting video mit opencourseware utilizes akamai edgesuite content delivery network trend micro uses akamai housecall antivirus application valve corporation steam software service uses akamai content delivery network storing screenshots icons uploaded users akamai provided streaming services espn star india course icc cricket world cup 2011 rackspace cloud files use akamai content delivery network cdn storing customer files customers include adobe systems airbnb amd autotrader.com cos espn great courses hewlett-packard hilton worldwide ibm j. c. penney mtv networks nasa national academy recording arts sciences nbc sports pearson education red bull gmbh red hat sony playstation yahoo august 2017 nintendo launched new game console mobile gaming application simultaneously around world via akamai media delivery solutions one akamai patents covers method delivering electronic data using content delivery network internet web site proprietors content providers contract akamai deliver web sites content individual internet users patented method permits large files video music files stored akamai servers accessed servers internet users increases speed internet users access content web sites unfortunately akamai patent written way called permitted actions multiple persons entities—such content provider customer company providing cdn service akamai competitor limelight chose operate allegedly infringing service manner—it performed steps patented process customers performed so-called tagging step interpretation patent law time akamai decided sue limelight patent infringement method patent could held infringed single actor performed steps court therefore overturned 40 million jury verdict akamai favor akamai initially lost case even taking supreme court supreme court returned case united states court appeals federal circuit however invitation re-evaluate rule chose steps method performed single actor infringement remand federal circuit considered matter en banc active judges circuit modified rule held patent could also directly infringed alleged infringer conditions participation activity receipt benefit upon performance step steps patented method establishes manner timing performance basis federal circuit reinstated 40 million jury verdict said akamai presented substantial evidence demonstrating limelight conditions customers use content delivery network upon customers performance steps limelight perform considered substantial change patent law discussion case see akamai techs. inc. v. limelight networks inc. national security agency federal bureau investigation reportedly used facebook akamai content delivery network cdn collect information facebook users report appears show intelligence analysts intercepting communications facebook cdn provider indicate akamai complicit process according researchers universities cambridge california-berkeley university college london international computer science institute-berkeley akamai blocking access web sites visitors using tor feature known 'network lists optional implemented customers akamai legitimate feature common many major vendors provide network security feeds emerging threats provides feed free
Distributed computing architecture
obfuscation software software development obfuscation deliberate act creating source machine code difficult humans understand like obfuscation natural language may use needlessly roundabout expressions compose statements programmers may deliberately obfuscate code conceal purpose security obscurity logic implicit values embedded primarily order prevent tampering deter reverse engineering even puzzle recreational challenge someone reading source code done manually using automated tool latter preferred technique industry architecture characteristics languages may make easier obfuscate others c c++ perl programming language examples languages easy obfuscate writing reading obfuscated source code brain teaser number programming contests reward creatively obfuscated code international obfuscated c code contest obfuscated perl contest types obfuscations include simple keyword substitution use non-use whitespace create artistic effects self-generating heavily compressed programs according nick montfort techniques may include short obfuscated perl programs may used signatures perl programmers japhs another perl hacker winning entry international obfuscated c code contest written ian phillipps 1988 subsequently reverse engineered thomas ball c program compiled run generate 12 verses 12 days christmas contains strings required poem encoded form within code non-winning entry year next example illustrates creative use whitespace generates mazes arbitrary length ansi-compliant c compilers n't allow constant strings overwritten avoided changing *m 3 omitting m= following example óscar toledo gutiérrez best show entry 19th ioccc implements 8080 emulator complete terminal disk controller capable booting cp/m-80 running cp/m applications example japh slowly displays text another perl unix hacker multiple characters time delays explanation found python examples found official python programming faq elsewhere several advantages automated code obfuscation made popular widely useful across many platforms platforms java android .net decompiler reverse-engineer source code executable library main advantage automated code obfuscation helps protect trade secrets intellectual property contained within software making reverse-engineering program difficult economically unfeasible advantages might include helping protect licensing mechanisms unauthorized access shrinking size source code possibly shrinking size executable decompilation sometimes called man-at-the-end attack based traditional cryptographic attack known man-in-the-middle run-time interpreted languages commonly known script like older versions basic programs execute faster take less ram use single letter variable names avoid comments contain blank characters brief shorter faster obfuscation make reading writing reverse-engineering program difficult time-consuming necessarily make impossible anti-virus software avg antivirus also alert users land site code manually obfuscated one purposes obfuscation hide malicious code however developers may employ code obfuscation purpose reducing file size increasing security average user may expect antivirus software provide alerts otherwise harmless piece code especially trusted corporations feature may actually deter users using legitimate software variety tools exist perform assist code obfuscation include experimental research tools created academics hobbyist tools commercial products written professionals open-source software also exist deobfuscation tools attempt perform reverse transformation although majority commercial obfuscation solutions work transforming either program source code platform-independent bytecode used java .net also work directly compiled binaries debate whether illegal skirt copyleft software licenses releasing source code obfuscated form cases author less willing make source code available issue addressed gnu general public license requiring preferred form making modifications made available gnu website states obfuscated 'source code real source code count source code
Computer security
citizen lab citizen lab interdisciplinary laboratory based munk school global affairs university toronto canada founded directed professor ronald deibert citizen lab studies information controls—such network surveillance content filtering—that impact openness security internet pose threats human rights citizen lab collaborates research centres organizations individuals around world uses mixed methods approach combines computer-generated interrogation data mining analysis intensive field research qualitative social science legal policy analysis methods citizen lab founding partner opennet initiative 2002–2013 information warfare monitor 2002–2012 projects organization also developed original design psiphon censorship circumvention software spun lab private canadian corporation psiphon inc. 2008 citizen lab research outputs made global news headlines around world including front page exclusives new york times washington post globe mail tracking ghostnet 2009 researchers uncovered suspected cyber espionage network 1,295 infected hosts 103 countries high percentage high-value targets including ministries foreign affairs embassies international organizations news media ngos seminal study one first public reports reveal cyber espionage network targeted civil society government systems around world shadows cloud 2010 researchers documented complex ecosystem cyber espionage systematically compromised government business academic computer network systems india offices dalai lama united nations several countries million dollar dissident published august 2016 researchers discovered ahmed mansoor one uae five human rights defender united arab emirates targeted software developed israeli cyber war company nso group using chain zero-day exploits operators spyware attempted get mansoor click link socially engineered text message would given access everything phone prior releases report researchers contacted apple released security update patched vulnerabilities exploited spyware operators citizen lab number awards work first canadian institution win macarthur foundation ’ macarthur award creative effective institutions 2014 canadian institution receive new digital age grant 2014 google executive chairman eric schmidt past awards include electronic frontier foundation pioneer award 2015 canadian library association advancement intellectual freedom canada award 2013 canadian committee world press freedom press freedom award 2011 canadian journalists free expression ’ vox libera award 2010 according january 24 2019 ap news report citizen lab researchers targeted international undercover operatives citizen lab independent government corporate interests financial support citizen lab come ford foundation open society institute social sciences humanities research council canada international development research centre idrc canada centre global security studies university toronto ’ munk school global affairs john d. catherine t. macarthur foundation donner canadian foundation open technology fund walter duncan gordon foundation citizen lab received donations software support palantir technologies virustotal oculus info inc citizen lab ’ targeted threats research stream seeks gain better understanding technical social nature digital attacks civil society groups political context may motivate citizen lab conducts ongoing comparative analysis growing spectrum online threats including internet filtering denial-of-service attacks targeted malware targeted threats reports covered number espionage campaigns information operations tibetan community diaspora phishing attempts made journalists human rights defenders political figures international investigators anti-corruption advocates mexico prominent human rights advocate focus government surveillance united arab emirates citizen lab researchers collaborators like electronic frontier foundation also revealed several different malware campaigns targeting syrian activists opposition groups context syrian civil war many findings translated arabic disseminated along recommendations detecting removing malware citizen lab ’ research threats civil society organizations featured front page businessweek covered al jazeera forbes wired among international media outlets group reports work analyzing spyware used target opposition figures south america triggered death threats september 2015 members group received pop-up said opennet initiative tested internet filtering 74 countries found 42 them—including authoritarian democratic regimes—implement level filtering citizen lab continued research area internet censorship lab iclab project aimed developing new systems methods measuring internet censorship collaborative effort citizen lab professor phillipa gill group stony brook university department computer science professor nick feamster network operations internet security group princeton university citizen lab studies censorship surveillance implemented popular applications including social networks instant messaging search engines previous work includes investigations censorship practices search engines provided google microsoft yahoo chinese market along domestic chinese search engine baidu 2008 nart villeneuve found tom-skype chinese version skype time collected stored millions chat records publicly accessible server based china 2013 citizen lab researchers collaborated professor jedidiah crandall ph.d. student jeffrey knockel university new mexico reverse engineering tom-skype sina uc another instant messaging application used china team able obtain urls encryption keys various versions two programs downloaded keyword blacklists daily work analyzed one year half data tracking keyword lists examined social political contexts behind content lists analyzed times list updated including correlations current events current research focuses monitoring information controls popular chinese microblogging service sina weibo chinese online encyclopedias mobile messaging applications popular asia asia chats project utilizes technical investigation censorship surveillance assessment use storage user data comparison terms service privacy policies applications first report released project examined regional keyword filtering mechanisms line applies chinese users analysis popular cellphone app called smart sheriff citizen lab german group cure53 asserted app represented security hole betrayed privacy children meant protect parents south korean law required cellphones sold 18 contain software designed protect children smart sheriff popular government approved app—with 380,000 subscribers citizen lab/cure53 report described smart sheriff security holes catastrophic citizen lab conducts groundbreaking research global proliferation targeted surveillance software toolkits including finfisher hacking team nso group finfisher suite remote intrusion surveillance software developed munich-based gamma international gmbh marketed sold exclusively law enforcement intelligence agencies uk-based gamma group 2012 morgan marquis-boire bill marczak provided first public identification finfisher software citizen lab collaborators done extensive investigations finfisher including revealing use bahraini activists analyzing variants finfisher suite target mobile phone operating systems uncovering targeted spying campaigns political dissidents malaysia ethiopia documenting finfisher command control servers 36 countries citizen lab finfisher research informed inspired responses civil society organizations pakistan mexico united kingdom mexico example local activists politicians collaborated demand investigation state acquisition surveillance technologies uk led crackdown sale software worries misuse repressive regimes hacking team milan italy-based company provides intrusion surveillance software called remote control system rcs law enforcement intelligence agencies citizen lab collaborators mapped rcs network endpoints 21 countries revealed evidence rcs used target human rights activist united arab emirates moroccan citizen journalist organization independent news agency run members ethiopian diaspora following publication hacking team targeting ethiopian journalists electronic frontier foundation privacy international took legal action related allegations ethiopian government compromised computers ethiopian expatriates united states uk 2018 citizen lab released investigation global proliferation internet filtering systems manufactured canadian company netsweeper inc using combination publicly available ip scanning network measurement data technical tests identified netsweeper installations designed filter internet content operational networks 30 countries focused 10 past histories human rights challenges afghanistan bahrain india kuwait pakistan qatar somalia sudan uae yemen websites blocked countries include religious content political campaigns media websites particular interest netsweeper ‘ alternative lifestyles ’ category appears one principal purposes blocking non-pornographic lgbtq content including offered civil rights advocacy organizations hiv/aids prevention organizations lgbtq media cultural groups citizen lab called government agencies abandon act filtering lgbt content since 2016 citizen lab published number reports pegasus spyware mobile devices developed nso group israeli-based cyber intelligence firm citizen lab ten part series nso group ran 2016 2018 august 2018 report timed coordinate amnesty international in-depth report nso group 2017 group released several reports showcased phishing attempts mexico used nso group technology products used multiple attempts gain control mobile devices mexican government officials journalists lawyers human rights advocates anti-corruption workers operations used sms messages bait attempt trick targets clicking links nso group exploit infrastructure clicking links would lead remote infection target phone one case son one journalists—a minor time—was also targeted nso purports sell products governments also came group focus prominent uae human rights defender ahmed mansoor mobile phone targeted report attempts showed first time ios zero day exploits wild prompted apple release security update ios 9.3.5 affecting 1 billion apple users worldwide citizen lab research surveillance software featured front pages washington post new york times covered extensively news media around world including bbc bloomberg cbc slate salon citizen lab research commercial surveillance technologies resulted legal policy impacts december 2013 wassenaar arrangement amended include two new categories surveillance systems dual use control list— intrusion software ip network surveillance systems wassenaar arrangement seeks limit export conventional arms dual-use technologies calling signatories exchange information provide notification export activities goods munitions included control lists amendments december 2013 product intense lobbying civil society organizations politicians europe whose efforts informed citizen lab research intrusion software like finfisher surveillance systems developed marketed blue coat systems citizen lab studies commercial market censorship surveillance technologies consists range products capable content filtering well passive surveillance citizen lab developing refining methods performing internet-wide scans measure internet filtering detect externally visible installations url filtering products goal work develop simple repeatable methodologies identifying instances internet filtering installations devices used conduct censorship surveillance citizen lab conducted research companies blue coat systems netsweeper smartfilter major reports include devices wander mistake planet blue coat redux 2013 pakistan stand guard thee analysis canada-based netsweeper ’ role pakistan ’ censorship regime 2013 planet blue coat mapping global censorship surveillance tools 2013 research covered news media around world including front page washington post new york times globe mail jakarta post following 2011 publication behind blue coat investigations commercial filtering syria burma blue coat systems officially announced would longer provide support updates services software syria december 2011 u.s. department commerce bureau industry security reacted blue coat evidence imposed 2.8 million fine emirati company responsible purchasing filtering products blue coat exporting syria without license citizen lab netsweeper research cited pakistani civil society organizations bytes bolo bhi public interest litigation pakistani government formal complaints high commission embassy canada pakistan citizen lab examines transparency accountability mechanisms relevant relationship corporations state agencies regarding personal data surveillance activities research investigated use artificial intelligence canada immigration refugee systems co-authored international human rights program university toronto faculty law analysis ongoing encryption debates canadian context co-authored canadian internet policy public interest clinic close look consumer personal data requests canada summer 2017 government canada introduced new national security legislation bill c-59 national security act proposed significantly change canada national security agencies practices including canada signals intelligence agency communications security establishment since bill first proposed range civil society groups academics called significant amendments proposed act co-authored paper citizen lab canadian internet policy public interest clinic represented detailed comprehensive analysis cse-related reforms date analysis produced help members parliament journalists researchers lawyers civil society advocates engage effectively issues included parliamentary committee debates highlighted dozens media reports citizen lab active participant various global discussions internet governance internet governance forum icann united nations government group experts information telecommunications since 2010 citizen lab helped organize annual cyber dialogue conference hosted munk school global affairs ’ canada centre convenes 100 individuals countries around world work government civil society academia private enterprise effort better understand pressing issues cyberspace cyber dialogue participatory format engages attendees moderated dialogue internet security governance human rights conferences around world including high-level meeting hague-based scientific council government policy swedish government stockholm internet forum taken themes inspired discussions cyber dialogue citizen lab contributes field building supporting networks researchers advocates practitioners around world particularly global south citizen lab developed regional networks activists researchers working information controls human rights past ten years networks asia opennet asia commonwealth independent states opennet eurasia middle east north africa support international development research centre idrc citizen lab launched cyber stewards network 2012 consists south-based researchers advocates practitioners analyze impact cybersecurity policies practices local regional international level project consists 24 partners across asia sub-saharan africa latin america middle east north africa including 7iber opennet centre internet society citizen lab staff also work local partners educate train at-risk communities example 2013 collaborated tibet action institute hold public awareness events dharamshala india exiled tibetan community cyber espionage campaigns winter 2013 citizen lab conducted digital security training session russian investigative journalists sakharov center moscow citizen lab work often cited media stories relating digital security privacy controls government policy human rights technology since 2006 featured 24 front-page stories publications including new york times washington post globe mail international herald tribune since 2013 citizen lab hosted summer institute monitoring internet openness rights annual research workshop munk school global affairs university toronto brings together researchers practitioners academia civil society private sector working internet openness security rights collaborations formed clsi workshops led publication high impact reports internet filtering zambia security audit child monitoring apps south korea analysis great cannon attack tool china used large scale distributed-denial service attacks github greatfire.org according report ap news journalist raphael satter citizen lab researchers reported october israeli nso group surveillance software used spy inner circle jamal khashoggi murder targeted turn international undercover operatives citizen lab october report revealed nso signature spy software placed iphone saudi dissident omar abdulaziz one khashoggi ’ confidantes months abdulaziz said saudi arabia spies used hacking software reveal khashoggi private criticisms saudi royal family said played major role death march 2019 new york times reported citizen lab target uae contractor darkmatter
Computer security
advice programming aspect functional programming advice describes class functions modify functions latter run certain function method procedure applied given join point program following taken discussion mailing list aosd-discuss pascal costanza contributed following term advice goes back term advising introduced warren teitelman phd thesis 1966 quote chapter 3 thesis advising found way bbn lisp later xerox parc interlisp also found way flavors first object-oriented extension lisp developed mit subsumed notion method combination since method combination macros closely related also interesting note first macro system described 1963 three years warren teitelman phd thesis practical use advice functions generally modify otherwise extend behavior functions easily modified extended emacspeak emacs-addon makes extensive use advice must modify thousands existing emacs modules functions produce audio output blind corresponding visual presentation would infeasible copy redefine produce audio output addition normal outputs emacspeak programmers define advice functions run another emacs example suppose one corrected misspelled word ispell one wanted re-spellcheck entire buffer codice_1 offers functionality even spellchecked word used thousand times one could track definition codice_1 copy one .emacs write additional functionality tedious prone broken-ness .emacs version get sync actual ispell elisp module even works home one wants fairly simple run another command codice_1 runs using advice functions done simply form advices part c classes late 1970s early 1980s namely functions called codice_4 codice_5 defined class called respectively member functions class however dropped c++ advices part common lisp object system clos codice_6 codice_7 codice_8 methods combined primary method standard method combination common lisp implementations provide advice functionality addition standard method combination clos extensions lispworks supports advising functions macros clos methods emacslisp added advice-related code version 19.28 1994 gregor kiczales comments follows
Programming language topics
claims-based identity claims-based identity common way applications acquire identity information need users inside organization organizations internet also provides consistent approach applications running on-premises cloud claims-based identity abstracts individual elements identity access control two parts notion claims concept issuer authority claim statement one subject person organization makes another subject example statement name group buying preference ethnicity privilege association capability subject making claim claims provider claims packaged one tokens issued issuer provider commonly known security token service sts name claims-based identity confusing first seems like misnomer attaching concept claims concept identity appears combining authentication determination identity authorization identified subject may may however closer examination reveals case claims subject subject application receiving incoming claim map is/is claims may/may rules application traditional systems often confusion differences similarities user is/is user may/may claims-based identity makes distinction clear distinction user is/is user may/may clarified possible authentication user is/is claims handled third party third party called security token service better understand concept security token service consider analogy night club doorman doorman wants prevent under-age patrons entry facilitate requests patron present driver license health insurance card identification token issued trusted third party security token service provincial state vehicle license department health department insurance company nightclub thus alleviated responsibility determining patron age trust issuing authority course make judgment authenticity token presented two steps completed nightclub successfully authenticated patron regard claim legal drinking age continuing analogy nightclub may membership system certain members may regular vip doorman might ask another token membership card might make another claim member vip case trusted issuing authority token would probably club membership card makes claim patron vip club react accordingly translating authenticated vip membership claim permission patron permitted sit exclusive lounge area served free drinks note uses term authentication include claims acquisition difference authentication limited binding user information contained user target site attribute data claim required complete authentication privacy concerns become important ability digital entities authenticate users without access personal attributes becomes increasingly important claims-based identity potential simplify authentication logic individual software applications applications n't provide mechanisms account creation password creation reset furthermore claims-based identity enables applications know certain things user without interrogate user determine facts facts claims transported envelope called secure token claims-based identity greatly simplify authentication process user n't sign multiple times multiple applications single sign creates token used authenticate multiple applications web sites addition certain facts claims packaged token user tell individual application facts repeatedly instance answering similar questions completing similar forms
Computer security
david sayre david sayre march 2 1924 – february 23 2012 american scientist credited early development direct methods protein crystallography diffraction microscopy also called coherent diffraction imaging working ibm part initial team ten programmers created fortran later suggested use electron beam lithography fabrication x-ray fresnel zone plates international union crystallography awarded sayre ewald prize 2008 unique breadth contributions crystallography range seminal contributions solving phase problem complex physics imaging generic objects x-ray diffraction microscopy ... sayre born new york city completed bachelor degree physics yale university age 19 working mit radiation laboratory earned ms degree auburn university 1948 1949 moved oxford wife anne colquhoun married 1947 sayre completed doctoral studies dorothy hodgkin group 1951 time sayre discovered equation named based concept atomicity although key direct methods still use today sayre share 1985 chemistry nobel prize awarded discovery also around time sayre inspired claude shannon recent work suggested short paper crystallographic phase problem could solved easily one could measure intensities higher density imposed bragg law insight widely seen initial spark lead recent lensless imaging techniques back united states david sayre worked structure determination carcinogen molecule lab peter friedlander university pennsylvania philadelphia structure determination program wrote ibm 701 attracted attention john backus hired part initial team programmers developed high-level programming language fortran sayre remain ibm retirement 1990 early 1970s sayre became interested x-ray microscopy suggested use newly developed electron beam lithography apparatus ibm produce fresnel zone plates type x-ray lens widely used synchrotron facilities '80s came back goal achieving lensless imaging pursued rest life
Programming language topics
incapsula imperva incapsula cloud-based application delivery platform uses global content delivery network provide web application security ddos mitigation content caching application delivery load balancing failover services incapsula founded 2009 gur shatz marc gaffan company origins imperva nyse impv american-based cyber security firm owned 85 incapsula spun imperva 2009 reported growing rate 50 per quarter august 2013 company lost 1.7 million second quarter year february 2014 imperva bought remaining part incapsula became product line within parent company october 2013 incapsula credited protected one internet largest attacks website september 24 2013 attack said lasted nine hours 100gbit/s traffic peak attack btc china bitcoin yuan trading platform december 2016 incapsula reported defended largest ddos attack ever recorded peaked 650gbit/s 200mpps incapsula multiple features used security performance websites incapsula waf protects websites cross site scripting illegal resource access owasp top 10 threats sql injections web 2.0 threats including academic web archiving comment spam fake registrations malicious bots referrer spam site scraping works changing website domain name system dns record route website traffic incapsula incapsula filters malicious attacks bots website scrapers incapsula also content delivery network caches websites server network speed website load time cached information returned server closest end user order provide fast page loads also eliminates slow response central servers due heavy server traffic incapsula launched tool named backdoor protect 2013 tool reported detect block malicious backdoors webshells tool works comparing website traffic database known backdoors later year company announced login-protect two factor authentication feature integrated addition products incapsula also announced 2013 would implementing layer 7 load balancing capabilities 2011 incapsula chosen one top 10 companies participate rsa conference innovation sandbox year finalist red herring top 100 north america award 2013 incapsula named 1 best cloud based security cdn werockyourweb 2017 forrester wave ddos service providers named imperva leader top scores current offering strategy evaluated ddos service providers
Computer security
edubuntu edubuntu previously known ubuntu education edition official derivative ubuntu operating system designed use classrooms inside schools homes communities edubuntu developed collaboration teachers technologists several countries edubuntu built top ubuntu base incorporates ltsp thin client architecture several education-specific applications aimed users aged 6 18 designed easy installation ongoing system maintenance included edubuntu linux terminal server project many applications relevant education including gcompris kde edutainment suite sabayon profile manager pessulus lockdown editor edubuntu menueditor libreoffice gnome nanny italc edubuntu cds previously available free charge shipit service available download dvd format edubuntu default gui unity gnome still available unity default gui since release 12.04 since release 7.10 kde also available edubuntu kde 2010 edubuntu qimo 4 kids project working providing qimo within edubuntu done would fitted cd primary goal edubuntu enable educator limited technical knowledge skills set computer lab on-line learning environment hour less effectively administer environment principal design goals edubuntu centralized management configuration users processes together facilities working collaboratively classroom setting equally important gathering together best available free software digital materials education according statement goals official edubuntu website aim put together system contains best free software available education make easy install maintain also aims allow low income environments maximize utilisation available older equipment first edubuntu release coincided release ubuntu 5.10 codenamed breezy badger 2005-10-13 8.04 hardy heron release edubuntu given name ubuntu education edition changed add-on standard ubuntu installation instead installable livecd version 9.10 onwards edubuntu changed available full system dvd instead add-on cd edubuntu also installable via selection edubuntu packages distributions using official ubuntu repositories ubuntu kubuntu mainly since 14.04 edubuntu become lts-only edubuntu announced skip 16.04 lts update plan staying 14.04 due lack contributors
Operating systems
iptables rope rope programming language allows developers write extensions iptables/netfilter components linux using simple scripting language based reverse polish notation scriptable iptables match module used identify whether ip packets passed match particular set criteria rope started life project make string match module iptables stronger evolved fairly quickly open-ended scriptable packet matching mechanism
Programming language topics
news news network extensible window system discontinued windowing system developed sun microsystems mid-1980s originally known sundew primary authors james gosling david s. h. rosenthal news interpreter based postscript later display postscript although two projects otherwise unrelated extending allow interaction multiple contexts support windows like postscript news could used complete programming language unlike postscript news could used make complete interactive programs mouse support gui news started implementing postscript interpreter running cooperative multitasking fashion since unlike postscript printer news would displaying number postscript programs time one screen also added complete view hierarchy based viewports known canvases synchronous event distribution system supporting events interests threads monitors like view system guis news included concept tree embedded views along events passed instance mouse click would generate event would passed object directly mouse pointer say button object respond event object button would receive message news included complete model events including timers automatic events input queues devices mice keyboards functionality required full interaction input handling system designed provide strong event synchronization guarantees possible asynchronous protocols like x support user interface widgets news expanded original postscript stack-based language complete object oriented oo programming style inheritance eliminated need external oo language build complete application since additions implemented extensions postscript possible write simple postscript code would result running onscreen interactive program two popular demonstration programs onscreen clock required two pages code program drew pair eyes followed cursor moved around screen eyeball program shown siggraph 1988 inspiration later well-known x application xeyes news included several libraries user interface elements widgets written news widgets ran behaviour news interpreter required communications outside program news code widget demanded example toggle button display routine query button state pressed change display accordingly button postscript code also react mouse clicks changing state pressed pressed vice versa happen windowing server without interaction client program mouse released button event sent handling sophisticated x window system server model report mouse pushed mouse mouse released events client figure event button switch state finally instruct server display new state client server machine interactions must travel network results delay responding news architecturally similar called ajax except news coherently best example library tnt news toolkit sun released 1989 sun also shipped earlier lite toolkit intended example purposes making small programs although adoption never widespread several companies licensed news adapted various uses open look version framemaker desktop publishing program developed frame technology corp. funding mainly sun microsystems nsa one commercial products ran news hyperlook developed arthur van hoff turing institute interactive application design system hopkins developed news version simcity built hyperlook commercial drawing program altsys virtuoso produced news port freehand additional functionality took advantage postscript environment unfortunately sun announced end support news virtuoso became ready ship compared x news vastly powerful also slower especially local connections c api low level difficult use news programs tended entirely written postscript another factor popularity sun charged fee license news source code mit x11 code free cost first versions news emulated x10 protocol translating calls news postscript speed problems plus existence programs relied exact pixel results x10 calls obsolescence x10 forced sun release x11/news hybrid called xnews ran x11 server parallel postscript interpreter seriously degraded news interpreter performance considered good x11 server either sun also implemented open look user interface specification several toolkits news toolkit tnt open look toolkit written postscript ran news server olit built xt x intrinsics base motif xview used apis sun earlier sunview window system clear open look lost motif popularity adobe acquired framemaker sun stopped supporting news products news simply vanished
Programming language topics
yoper yoper linux—your operating system—was linux distribution pcs i686 pentium pro higher processor types intended use personal computers server used hardware recognition tools known knoppix defining feature distribution set custom optimisations intended make fastest out-of-the-box distribution project founded andreas girardet later maintained tobias gerschner distribution scratch-built opposed modifying one popular distributions create new distribution yoper discontinued operationally dismantled december 31 2012
Operating systems
amazon aurora amazon aurora relational database service developed offered amazon web services beginning october 2014 aurora available part amazon relational database service rds aurora offered mysql compatible service upon release added postgresql compatibility october 2017 became possible stop start aurora clusters september 2018 august 2018 amazon began offer serverless version 2019 developers aurora sigmod systems award fundamentally redesigning relational database storage cloud environments aurora automatically allocates database storage space 10-gigabyte increments needed maximum 64 terabytes aurora offers automatic six-way replication chunks across multiple locations improved availability fault-tolerance aurora provides users performance metrics query throughput latency provides fast database cloning amazon designed aurora compatible mysql meaning tools querying managing mysql databases command-line client mysql workbench graphical user-interface used mysql options features available amazon aurora compatible mysql 5.6 5.7 supports innodb storage engine amazon claims fivefold performance improvements benchmarking tests mysql hardware due tightly integrating database engine ssd-based virtualized storage layer purpose-built database workloads reducing writes storage system minimizing lock contention eliminating delays created database process threads independent tests shown aurora performs better competing technologies combinations workload instance type
Databases
fabasoft fabasoft ag software manufacturer headquartered linz upper austria company established 1988 helmut fallmann leopold bauernfeind name fabasoft acronym fallmann bauernfeind software fiscal year fabasoft ag commences april 1 number employees respective reporting date march 31 increased recent years 100 staff 2003 185 2004 203 2005 corporate revenue also increased eur 16.94 million 2003/2004 fiscal year eur 21.85 million 2004/2005 eur 25.3 million 2005/2006 fiscal year 2006/2007 fiscal year revenue decreased eur 21.2 million eur 21.6 million recorded 2007/2008 fiscal year 2008/2009 fabasoft ag recorded revenue eur 20.02 million fiscal year 2009/2010 sales revenue eur 23.3 million fabasoft ag stocks listed prime standard frankfurt stock exchange since october 4 1999 fabasoft certified according iso 9001 iso 20000 iso 27001 type ii
Distributed computing architecture
ucoz ucoz free web hosting built-in content management system modules ucoz cms used together build fully featured website separately e.g online shopping platform blog webforum etc july 10 2015 one half million websites created ucoz system ucoz among top sites russian-speaking users according alexa internet initially basis service development formed combined experience several developers consisted previous work different services polls free guestbooks importantly professional cms script wocatalog pro 29 october 2005 almost year development ucoz announced russian version system june 2007 english version system officially announced august — german version currently ucoz also available azeri spanish french arabic hungarian romanian swedish polish portuguese partially hebrew latvian ukrainian georgian languages january 2013 yandex 4th largest search engine world announced transfer ucoz project narod 2nd largest free website hosting platform russian internet merger increased ucoz market share substantially company already market leader merger ucoz backed mail.ru group headquarters moscow russia offices sankt petersburg rostov kazan cherkassy ukraine saas system ucoz features type platform like closed source code availability running server-side scripts like javascript also unavailability running databases possible within web 3.0 paas concept balanced great number built-in system capabilities also system fully html5 css3 compatible
Web technology
astron belt astron belt アストロンベルト early laserdisc video game form third-person space combat rail shooter released arcades 1983 sega japan licensed bally midway release united states developed 1982 commonly cited first laserdisc game game unveiling 1982 amoa show chicago marked beginning laserdisc fever videogame industry release japan following year marked first commercial release laserdisc game however release united states delayed due several hardware software bugs time dragon lair beaten public release astron belt however first laserdisc game released europe arcade game available upright cockpit cabinets latter illuminated buttons control panel larger 25 monitor upright used standard 19 vibrating seat astron belt ported msx home system player controls lone spacecraft mission singlehandedly take entire enemy armada enemy fighters ships shoot player mines objects must shot avoided game divided waves end wave command ship must destroyed later waves enemy fighters move shoot aggressively shots accurate waves take place open space others require player battle enemies flying narrow trenches tunnels player timer beginning game unlimited number lives available length timer adjusted machine operator normally 60 seconds timer expires player given limited number additional lives lives lost game ends background videos used game mixture original artwork borrowed material addition scenes created specifically game designers also incorporated footage three science fiction movies battle beyond stars message space astron belt used one four laserdisc players either pioneer ld-v1000 ld-v1001 hitachi vip-9500sg vip-9550 two different versions laser disc also pressed single-sided version pioneer double-sided version sega however discs information may used four players running sega laserdisc hardware game combines pre-rendered laserdisc footage real-time 2d computer graphics plane real-time graphics plane overlaid imitating matting technique crt monitor scans horizontally across screen fed information laserdisc point fed information computer graphics system information coming laserdisc stops creating black mask sprite inserted uses collision detection system laserdisc sprite planes interact frame laserdisc footage coded hit detection spot stored rom memory zilog z80 cpu reads number laserdisc frame checks laserdisc hit spots shots fired player coordinates correspond instructs laserdisc player display explosion sequence sections player must navigate walls walls laserdisc footage also coded use collision detection astron belt responsible starting interactive movie laserdisc craze shown 1982 amoa show one laserdisc games inspired dragon lair sega bally midway released sequel called starblazer also known galaxy ranger 1984 controls similar gameplay astron belt one machine could converted simply changing laserdisc game roms sound board
Computer architecture
list game middleware middleware games piece software integrated game engine handle specialized aspect physics graphics networking ai pathfinding collisions physics animation sound
Distributed computing architecture
x32 abi x32 abi application binary interface abi one interfaces linux kernel allows programs take advantage benefits x86-64 instruction set larger number cpu registers better floating-point performance faster position-independent code shared libraries function parameters passed via registers faster syscall instruction using 32-bit pointers thus avoiding overhead 64-bit pointers though x32 abi limits program virtual address space 4 gib also decreases memory footprint program making pointers smaller allow run faster fitting data cache best results testing 181.mcf spec cpu 2000 benchmark x32 abi version 40 faster x86-64 version average x32 5–8 faster spec cpu integer benchmarks compared x86-64 speed advantage x86-64 spec cpu floating-point benchmarks running userspace consists mostly programs compiled ilp32 mode also principal access 64-bit cpu instructions uncommon especially field classic risc chips example solaris operating system sparc x86-64 linux side sparc powerpc linux distributions aurora sparc linux debian also ship ilp32 userspace underlying reason somewhat expensive nature lp64 code like shown x86-64 regard x32 abi extends ilp32-on-64bit concept x86-64 platform several people discussed benefits x86-64 abi 32-bit pointers years since athlon 64 release 2003 notably donald knuth 2008 little publicly visible progress towards implementing mode august 27 2011 hans peter anvin announced linux kernel mailing list h. j. lu working x32-abi day linus torvalds replied concern use 32-bit time values x32 abi could cause problems future use 32-bit time values would cause time values overflow year 2038 following request developers x32 abi changed time values 64-bit presentation linux plumbers conference september 7 2011 covered x32 abi x32 abi merged linux kernel 3.4 release support added gnu c library version 2.16 december 2018 considered deprecate x32 abi happened march 2019
Computer architecture
garuda garuda global access resource using distributed architecture india grid computing initiative connecting 17 cities across country 45 participating institutes nationwide project include iits c-dac centers major institutes india garuda collaboration science researchers experimenters nationwide grid computational nodes mass storage scientific instruments aims provide technological advances required enable data compute intensive science 21st century one garuda ’ important challenges strike right balance research daunting task deploying innovation complex scientific engineering endeavors undertaken today department information technology dit government india funded centre development advanced computing c-dac deploy nationwide computational grid garuda proof concept poc phase ended march 2008 17 cities across country connected aim bring “ grid ” networked computing research labs industry april 2008 foundation phase progress aim include users ’ applications providing service oriented architecture improving network stability upgrading grid resources garuda assist accelerate india ’ drive turn substantial research investment tangible economic benefits main monitoring centre also called garuda monitoring management centre set c-dac knowledge park bangalore point whole grid extended even europe monitored managed c-dac young scientists india garuda uses national knowledge network network backbone garuda adopted pragmatic approach using existing grid infrastructure web services technologies deployment grid tools services garuda based judicious mix in-house developed components globus toolkit gt industry grade open source components foundation phase garuda based stable version gt4 resource management scheduling garuda based deployment industry grade schedulers hierarchical architecture cluster level scheduling achieved load leveler aix platforms torque linux clusters garuda portal provides user interface grid resources hides complexity grid users allows submission sequential parallel jobs also provides job accounting facilities problem solving environment pse domains bio-informatics community atmospheric model support entire cycle problem solving specific domains supporting problem formulation algorithm selection numerical simulation solution visualization
Distributed computing architecture
embedded sql embedded sql method combining computing power programming language database manipulation capabilities sql embedded sql statements sql statements written inline program source code host language embedded sql statements parsed embedded sql preprocessor replaced host-language calls code library output preprocessor compiled host compiler allows programmers embed sql statements programs written number languages cobol fortran differs sql-derived programming languages n't go discrete preprocessors pl/sql t-sql sql standards committee defined embedded sql standard two steps formalism called module language defined embedded sql standard derived module language sql standard defines embedding sql embedded sql language sql queries embedded referred host language popular host language c. host language c embedded sql example called pro*c oracle sybase database management systems ecpg postgresql database management system sql may also embedded languages like php etc ibm db2 version 9 linux unix windows supports embedded sql c c++ java cobol fortran rexx although support fortran rexx deprecated mimer sql linux openvms windows support embedded sql raima database manager 14.0 supports embedded sql c/c++ sql pl sap sybase ase 15.7 supports embedded sql c cobol part software developer kit sybase sap sybase sql anywhere supports embedded sql c c++ part sql anywhere database management system sql anywhere sap sybase iq supports embedded sql c c++ part sybase iq database management system sybase iq
Databases
database management library database management library dbl relational database management system rdbms contained c++ programming library dbl source code available terms gnu general public license dbl fully developed within two weeks holiday programming project aims easy simple use c++ programming dbl library becomes integral part application program unlike client–server model database management systems standalone process application program communicates application software uses dbl functionality function calls basic program creates simple database however task must done usually done dbl command-line interface int main database db mydatabase class stores database name tables main functions useful functions use class database class stores table name structure columns table main functions useful functions use class table class stores columns table data stored data file main functions useful functions use class row class stores column value column main functions useful functions use class storage class stores name structure column main functions class stores indexes table main functions useful functions use class index dbl command-line interface program one create database table add columns table besides operations printing
Databases
motorola single board computers motorola single board computers motorola production line computer boards embedded systems three different lines mvme68k mvmeppc mvme88k first version board appeared 1988 motorola still makes boards last one mvme3100 netbsd supports module families mvme147 mvme162 mvme167 mvme172 mvme177 openbsd supports mvme141 mvme165 mvme188 mvme197 boards
Computer architecture
cloud operating system cloud browser-based operating system created good os llc los angeles-based corporation company initially launched linux distribution called gos heavily based ubuntu third incarnation cloud simplified operating system ran web browser providing access variety web-based applications allowed user perform many simple tasks without booting full-scale operating system simplicity cloud could boot seconds operating system designed netbooks mobile internet devices pcs mainly used browse internet cloud user quickly boot main os cloud continues booting main os background combining browser basic operating system allows use cloud computing applications data live run internet instead hard drive cloud installed used together operating systems act standalone operating system used standalone operating system hardware requirements relatively low 2009 cloud officially available built gigabyte m912 touch screen netbook early reviews compared operating system user interface os x noted similarity browser google chrome although actually based modified mozilla firefox browser
Distributed computing architecture
digital signal 1 digital signal 1 ds1 sometimes ds-1 t-carrier signaling scheme devised bell labs ds1 primary digital telephone standard used united states canada japan able transmit 24 multiplexed voice data calls telephone lines e-carrier used place t-carrier outside united states canada japan south korea ds1 logical bit pattern used physical t1 line practice terms ds1 t1 often used interchangeably t1 refers primary digital telephone carrier system used north america t1 one line type pcm t-carrier hierarchy t1 describes cabling signal type signal regeneration requirements carrier system signal transmitted t1 line referred ds1 signal consists serial bits transmitted rate 1.544 mbps type line code used called alternate mark inversion ami digital signal designation classification digital bit rates digital multiplex hierarchy used transport telephone signals one location another ds-1 communications protocol multiplexing bitstreams 24 telephone calls along two special bits framing bit frame synchronization maintenance-signaling bit transmitted digital circuit called t1 t1 maximum data transmission rate 1.544 megabits per second ds1 telecommunication circuit multiplexes 24 ds0s twenty-four ds0s sampled 8,000 times per second one 8bit pcm sample dso per ds1 frame consume 1.536 mbit/s bandwidth one framing bit adds 8 kbit/s overhead total 1.544 mbit/s calculated follows ds1 full-duplex circuit concurrently transmitting receiving 1.544 mbit/s frame synchronization necessary identify timeslots within 24-channel frame synchronization takes place allocating framing 193rd bit results 8 kbit/s framing data ds1 8-kbit/s channel used transmitting equipment overhead 1.536 mbit/s actually passed user two types framing schemes superframe sf extended superframe esf superframe consists twelve consecutive 193-bit frames whereas extended superframe consists twenty-four consecutive 193-bit frames data due unique bit sequences exchanged framing schemes compatible two types framing sf esf use 8 kbit/s framing channel different ways connectivity refers ability digital carrier carry customer data either end cases connectivity may lost one direction maintained cases terminal equipment i.e. equipment marks endpoints ds1 defines connection quality received framing pattern alarms normally produced receiving terminal equipment framing compromised three defined alarm indication signal states identified legacy color scheme red yellow blue red alarm indicates alarming equipment unable recover framing reliably corruption loss signal produce red alarm connectivity lost toward alarming equipment knowledge connectivity toward far end yellow alarm also known remote alarm indication rai indicates reception data framing pattern reports far end red alarm alarm carried differently sf d4 esf d5 framing sf framed signals user bandwidth manipulated bit two every ds0 channel shall zero resulting loss payload data transmitting yellow alarm undesirable resolved esf framed signals using data link layer repeating 16-bit pattern consisting eight 'ones followed eight 'zeros shall transmitted continuously esf data link may interrupted period exceed 100-ms per interruption types alarms transmitted duration alarm condition least one second blue alarm also known alarm indication signal ais indicates disruption communication path terminal equipment line repeaters dcs signal received intermediary equipment produces unframed all-ones signal receiving equipment displays red alarm sends signal yellow alarm far end framing intermediary interfaces equipment report ais alarm indication signal ais also called ones data framing pattern alarm states also lumped term carrier group alarm cga meaning cga connectivity digital carrier failed result cga condition varies depending equipment function voice equipment typically coerces robbed bits signaling state result far end properly handling condition applying often different state customer equipment connected alarmed equipment simultaneously customer data often coerced 0x7f pattern signifying zero-voltage condition voice equipment data equipment usually passes whatever data may present leaving customer equipment deal condition additionally voice t1s two main types so-called plain inband t1s pri primary rate interface carry voice telephone calls similar fashion pris commonly used call centers provide 23 actual usable telephone lines known b channels bearer also 24th line known channel data carries line signaling information special channel carries caller id cid automatic number identification ani data required channel type usually b bearer channel call handle dialed number identification service dnis info requested channel number request response inband t1s also capable carrying cid ani information configured carrier sending dtmf *ani*dnis* however pris handle efficiently inband t1 seemingly slight advantage due 24 lines available make calls opposed pri 23 channel inband t1 must perform setup tear-down call pri uses 24th channel data channel perform overhead operations 23 channels including cid ani although inband t1 24 channels 23 channel pri set calls faster due dedicated 24th signalling channel channel name t1 came carrier letter assigned technology 1957 digital systems first proposed developed decided skip q r use time division naming system ended letter designated fiber networks destined successors t1 system networks called t1c t2 t3 t4 commercial success disappeared quickly signals would carried systems called ds1 ds2 ds3 ds4 carried t1 infrastructure ds-1 means digital service – level 1 signal sent—as opposed network delivers originally 24 digitized voice channels t1 since practice naming networks ended letter terms t1 ds1 become synonymous encompass plethora different services voice data clear-channel pipes line speed always consistent 1.544 mbit/s payload vary greatly dark fiber dark fiber refers unused fibers available use dark fiber still available sale wholesale market metro wide area links may available markets city pairs dark fiber capacity typically used network operators build sonet dense wavelength division multiplexing dwdm networks usually involving meshes self-healing rings also used end-user enterprises expand ethernet local area networks especially since adoption ieee standards gigabit ethernet 10 gigabit ethernet single-mode fiber running ethernet networks geographically separated buildings practice known wan elimination ds1c digital signal equivalent two digital signal 1 extra bits conform signaling standard 3.152 mbit/s circuit capacities still use today early days digital data transmission 3-mbit/s data rate used link mainframe computers together physical side circuit called t1c t1/e1 protocol implemented line interface unit silicon semiconductor chip contains decoder/encoder loop backs jitter attenuators receivers drivers additionally usually multiple interfaces labeled dual quad octal etc. depending upon number transceiver chip primary purpose retrieve information line i.e. conductive line transverses distance receiving pulses converting signal subjected noise jitter interference clean digital pulse interface chip
Internet protocols
maze galious sequel konami msx game knightmare majou densetsu original game overhead vertical scrolling shooter maze galious side-view flick-screen platform game player controls popolon aphrodite entering evil priest galious castle free yet-to-be-born son pampas priest evil clutches able control popolon aphrodite means player switch two characters slightly different abilities example popolon push stones open heavy doors hand aphrodite survives longer water shoot projectiles either character die visit shrine pay resurrection unlike typical platform games characters survive damage hit point bars game several types enemies strengths weaknesses monsters immune frontal attacks vulnerable fire ten different bosses fought defeating boss give player key used unlock doors boss areas in-game saving provided giving player encoded password
Computer architecture
stacki stacki computer cluster software product company stackiq released open-source software stackiq originally named clustercorp founded 2006 first product commercial version linux distribution called rocks cluster distribution originally based san jose california co-founders included mason katz chief executive tim mcintire 2011 company re-incorporated stackiq moved la jolla district san diego california round venture capital funding april october 2014 raised 6 million located solana beach california august 2016 pervez choudhry replaced mcintire chief executive product called stackiq cluster manager renamed stackiq boss february 2015 stacki works several servers time takes long provision number servers system allows installations via preboot execution environment pxe supports “ servers boot network ” “ servers spreadsheet ” method installations servers installed isolated network stacki tool called insert-ethers run grab machine boots network add stacki commencing installation needed servers installed shared network loading spreadsheet machines install tells stacki ones install stacki uses database manage variables use installation variables defined individual server installation type globally manipulated via spreadsheets command line networking example managed variables machine configured multiple network cards multiple networks varying routes open/closed ports stacki released june 2015 stackiq company acquired teradata june 30 2017 undisclosed amount
Distributed computing architecture
mysql cluster mysql cluster technology providing shared-nothing clustering auto-sharding mysql database management system designed provide high availability high throughput low latency allowing near linear scalability mysql cluster implemented ndb ndbcluster storage engine mysql ndb stands network database mysql cluster designed around distributed multi-master acid compliant architecture single point failure mysql cluster uses automatic sharding partitioning scale read write operations commodity hardware accessed via sql non-sql nosql apis internally mysql cluster uses synchronous replication two-phase commit mechanism order guarantee data written multiple nodes upon committing data contrast usually referred mysql replication two copies known replicas data required guarantee availability mysql cluster automatically creates “ node groups ” number replicas data nodes specified user updates synchronously replicated members node group protect data loss support fast failover nodes also possible replicate asynchronously clusters sometimes referred mysql cluster replication geographical replication typically used replicate clusters data centers disaster recovery reduce effects network latency locating data physically closer set users unlike standard mysql replication mysql cluster geographic replication uses optimistic concurrency control concept epochs provide mechanism conflict detection resolution enabling active/active clustering data centers starting mysql cluster 7.2 support synchronous replication data centers supported multi-site clustering feature mysql cluster implemented fully distributed multi-master database ensuring updates made application sql node instantly available nodes accessing cluster data node accept write operations data within mysql cluster ndb tables automatically partitioned across data nodes system done based hashing algorithm based primary key table transparent end application clients connect node cluster queries automatically access correct shards needed satisfy query commit transaction mysql cluster able support cross-shard queries transactions users define partitioning schemes allows developers add “ distribution awareness ” applications partitioning based sub-key common rows accessed high running transactions ensures data used complete transactions localized shard thereby reducing network hops mysql cluster allows datasets larger capacity single machine stored accessed across multiple machines mysql cluster maintains indexed columns distributed memory non-indexed columns also maintained distributed memory maintained disk in-memory page cache storing non-indexed columns disk allows mysql cluster store datasets larger aggregate memory clustered machines mysql cluster writes redo logs disk data changes well check pointing data disk regularly allows cluster consistently recover disk full cluster outage redo logs written asynchronously respect transaction commit small number transactions lost full cluster fails however mitigated using geographic replication multi-site cluster discussed current default asynchronous write delay 2 seconds configurable normal single point failure scenarios result data loss due synchronous data replication within cluster mysql cluster table maintained memory cluster access disk storage write redo records checkpoints writes sequential limited random access patterns involved mysql cluster achieve higher write throughput rates limited disk hardware compared traditional disk-based caching rdbms checkpointing disk in-memory table data disabled per-table basis disk-based persistence n't needed mysql cluster designed single point failure provided cluster set correctly single node system piece hardware fail without entire cluster failing shared disk san required interconnects nodes standard ethernet gigabit ethernet infiniband sci interconnects mysql cluster stores tables data nodes rather mysql server multiple interfaces available access database part commercial mysql cluster cge mysql cluster manager tool designed simplify creation administration mysql cluster cge database automating common management tasks including on-line scaling upgrades backup/restore reconfiguration mysql cluster manager also monitors automatically recovers mysql server application nodes management nodes well mysql cluster data nodes mysql cluster uses three different types nodes processes generally expected node run separate physical host vm cloud instance although common co-locate management nodes mysql servers best practice recommended co-locate nodes within node group single physical host would represent single point failure mysql cluster version numbers longer tied mysql server example recent version mysql cluster 7.5 even though based on/contains server component mysql 5.7 higher versions mysql cluster include features lower versions plus new features older versions longer development currently available versions evaluation purposes possible run mysql cluster single physical server production deployments minimum system requirements 3 x instances hosts configurations follows tips recommendations deploying highly performant production grade clusters found mysql cluster evaluation guide guide optimizing performance mysql cluster database mysql ab acquired technology behind mysql cluster alzato small venture company started ericsson ndb originally designed telecom market high availability high performance requirements mysql cluster based ndb storage engine since integrated mysql product first release mysql 4.1 mysql cluster licensed gplv2 license commercial support available part mysql cluster cge also includes non-open source addons mysql cluster manager mysql enterprise monitor addition mysql enterprise security mysql enterprise audit
Distributed computing architecture
alcatel one touch fire alcatel one touch fire one first generation smartphones preinstalled firefox os open-source mobile operating system developed mozilla phone developed marketed alcatel mobile phones lower-cost entry-level smartphone specific latin american european countries brazil chile colombia mexico peru uruguay venezuela latin america germany greece hungary italy montenegro poland serbia europe mobile network operators carried phone include congstar germany cosmote greece movistar chile mexico peru uruguay venezuela t-mobile montenegro macedonia telcel mexico telenor serbia montenegro telecom italia mobile italy vivo brazil one touch fire variation earlier android-based smartphone alcatel one touch t'pop unlike one touch fire one touch t'pop uses arm cortex-a9 cpu powervr sgx531 gpu also incorporates home back push-buttons distinct cosmetics differences one touch fire sold three color schemes mozilla orange apple green pure white two model numbers one touch fire 4012a 4012x support different cellular network standards frequency bands different countries 4012a quadband gsm radio communicate 850 900 1800 1900 mhz umts radio capable 850 1900 2100 mhz communication 4012x umts radio communicates 900 2100 mhz consequently 4012x lower specific absorption rate 4012a 4012x succeeded one touch fire c one touch fire e one touch fire s. 2019 alcatel one touch fire still little resale value worldwide due discontinuation firefox os fared well hardly considered collector item
Operating systems
public computer public computer public access computer various computers available public areas places public computers may available libraries schools facilities run government public computers share similar hardware software components personal computers however role function public access computer entirely different public access computer used many different untrusted individuals throughout course day computer must locked secure intentional unintentional abuse users typically n't authority install software change settings personal computer contrast typically used single responsible user customize machine behavior preferences public access computers often provided tools pc reservation system regulate access world first public access computer center marin computer center california co-founded david annie fox 1977 see also computer kiosk kiosk special type public computer using software hardware modifications provide services place kiosk example movie ticket kiosk found movie theater kiosks usually secure browser zero access desktop many kiosks may run linux however atms kiosk designed depositing money often run windows xp united states canada almost public libraries computers available use patrons though libraries keep users timed allow others get turns keep library less busy users often allowed print documents created using computers though sometimes small fee u.s. government given money many school boards purchase computers educational applications schools may multiple computer labs contain computers students use usually internet access machines schools put blocking service limit websites students able access include educational resources google addition controlling content students viewing putting blocks also help keep computers safe preventing students downloading malware threats however effectiveness content filtering systems questionable since easily circumvented using proxy websites virtual private networks weak security systems merely knowing ip address intended website enough go school computers often advanced operating system security prevent tech-savvy students inflicting damage i.e windows registry editor task manager etc disabled microsoft windows machines schools advanced tech services may also install locked bios/firmware make kernel-level changes operating system eradicating chances unauthorized activity
Computer security
gr8bit gr8bit educational 8-bit computer hardware software platform upon users experiment computer electronics simpler computer architecture compared modern mainstream electronics created eugeny brychkov licensed msx licensing corporation age labs announced 2011 launch msx kit called gr8bit do-it-yourself computer learning purposes licensed msx licensing corporation kit priced 499 includes necessary components assemble working msx2 compatible computer except atx chassis power supply floppy drive hard disk ps/2 keyboard monitor also comes assembly operational manuals supplement compiled vendor community support
Computer architecture
pac-mania pac-mania would gain highly-positive critical reception uniqueness gameplay nominated best coin-op conversion year golden joystick awards 1987 although would lose taito operation wolf game would go sell 1,412 arcade cabinets north america end 1987 grossing around 2.82 million 6.22 million adjusted inflation pac-mania would ported several home consoles computers including atari st msx2 sega genesis nintendo entertainment system last published tengen several pac-man namco video game collections would also include game ports wii virtual console ios mobile phones also produced pac-mania isometric maze game player controls pac-man yellow circular creature must eat pellets stage avoiding five colored ghosts blinky pinky inky clyde sue eating large power pellets cause ghosts turn blue flee allowing pac-man eat bonus points send house middle stage clearing stage pellets allow pac-man move next new game ability jump ghosts allowing pac-man evade capture ghosts later areas game introduce two new ghosts green ghost funky steel gray ghost spunky also ability jump pac-man still jump funky impossible jump spunky eating certain number pellets cause bonus items appear middle stage pac-man eat points items increase pac-man movement speed double point values blue ghosts pac-mania arrived 8-bit systems 1988 favourable home conversion appeared commodore 64 conversions designed ported teque software otherwise known peter harrap monty mole shaun hollingworth ex-gremlin games published grandslam entertainment full screen 32-colour commodore amiga version released 1988 highly rated x68000 version acorn archimedes 16-bit atari st conversion ran 55 screen area used 16 colours pac-mania later ported nintendo entertainment system 1990 sega genesis 1991 tengen version unlicensed neither port released japan genesis port outsourced sculptured software recently port atari ste based st version modified take advantage ste features developed entertainment weekly gave game b- game runner-up category best coin-op conversion year golden joystick awards behind operation wolf arcade version pac-mania appeared namco museum volume 5 2001 namco museum release namco museum 50th anniversary namco museum virtual arcade 2001 one games included pac-man collection game boy advance later 2002 arcade version re-released included unlockable bonus pac-man world 2 2007 pac-mania also released namco museum remix pac pal pac n roll super pac-man non-pac-man games re-released 2010 part follow-up compilation namco museum megamix along 17 namco arcade games six remix games five appeared namco museum remix 2010 design pac-man ghosts pac-mania appear pac-man championship edition dx game released app app store ios devices pac-mania also re-released part pac-man arcade party arcade machine 2010 pac-man 30th anniversary february 2014 included pac-man museum playstation 3 xbox 360 windows pc via steam 2018 included pac-man pixel bash arcade cabinet along pac-man different namco games music pac-man park later used pac-man ghostly adventures power theme pac show version pac-man theme along block town music would remixed used super smash bros. nintendo 3ds wii u
Computer architecture
cross-zone scripting cross-zone scripting browser exploit taking advantage vulnerability within zone-based security solution attack allows content scripts unprivileged zones executed permissions privileged zone i.e privilege escalation within client web browser executing script vulnerability could common attack scenario involves two steps first step use cross-zone scripting vulnerability get scripts executed within privileged zone complete attack perform malicious actions computer using insecure activex components type vulnerability exploited silently install various malware spyware remote control software worms onto computers browsing malicious web page four well known zones internet explorer zones explained detail use security zones internet explorer also additional hidden zone local intranet trusted sites local computer usually configured privileged zones cross-zone scripting attacks designed jump internet zone privileged zone type exploit attempts execute code security context local computer zone following html used illustrate naive non-working attempt exploitation explanation html code attempts get attack.gif loaded cache using img src reference script src tag used attempt executing script local computer zone addressing local file cache consider scenario computer considers intranet.example.com part local intranet zone successfully cross zone scripted well-known example 2f bug internet explorer 6 discovered following url executed trusted sites permission listed trusted site
Computer security
object database object database database management system information represented form objects used object-oriented programming object databases different relational databases table-oriented object-relational databases hybrid approaches object databases considered since early 1980s object-oriented database management systems oodbmss also called odbms object database management system combine database capabilities object-oriented programming language capabilities oodbmss allow object-oriented programmers develop product store objects replicate modify existing objects make new objects within oodbms database integrated programming language programmer maintain consistency within one environment oodbms programming language use model representation relational dbms projects way contrast maintain clearer division database model application usage web-based technology increases implementation intranets extranets companies vested interest oodbmss display complex data using dbms specifically designed store data objects gives advantage companies geared towards multimedia presentation organizations utilize computer-aided design cad object-oriented databases designed work well object-oriented programming languages delphi ruby python javascript perl java c visual basic .net c++ objective-c smalltalk others jade programming languages oodbmss use exactly model object-oriented programming languages object database management systems grew research early mid-1970s intrinsic database management support graph-structured objects term object-oriented database system first appeared around 1985. notable research projects included encore-ob/server brown university exodus university wisconsin–madison iris hewlett-packard ode bell labs orion microelectronics computer technology corporation mcc vodak gmd-ipsi zeitgeist texas instruments orion project published papers efforts kim mcc compiled best papers book published mit press early commercial products included gemstone servio logic name changed gemstone systems gbase graphael vbase ontologic additional commercial products entered market late 1980s mid 1990s included itasca itasca systems jasmine fujitsu marketed computer associates matisse matisse software objectivity/db objectivity inc. objectstore progress software acquired excelon originally object design incorporated ontos ontos inc. name changed ontologic technology merged several companies acquired informix turn acquired ibm poet fastobjects versant acquired poet software versant object database versant corporation voss logic arts jade jade software corporation products remain market joined new open source commercial products intersystems caché object database management systems added concept persistence object programming languages early commercial products integrated various languages gemstone smalltalk gbase lisp vbase cop voss virtual object storage system smalltalk much 1990s c++ dominated commercial object database management market vendors added java late 1990s recently c starting 2004 object databases seen second growth period open source object databases emerged widely affordable easy use entirely written oop languages like smalltalk java c versant db4o db4objects dts/s1 obsidian dynamics perst mcobject available dual open source commercial licensing object databases based persistent programming acquired niche application areas engineering spatial databases telecommunications scientific areas high energy physics molecular biology another group object databases focuses embedded use devices packaged software real-time systems object databases also offer kind query language allowing objects found using declarative programming approach area object query languages integration query navigational interfaces biggest differences products found attempt standardization made odmg object query language oql access data faster object retrieved directly without search following pointers another area variation products way schema database defined general characteristic however programming language database schema use type definitions multimedia applications facilitated class methods associated data responsible correct interpretation many object databases example gemstone voss offer support versioning object viewed set versions also object versions treated objects right object databases also provide systematic support triggers constraints basis active databases efficiency database also greatly improved areas demand massive amounts data one item example banking institution could get user account information provide efficiently extensive information transactions account information entries etc object data management group consortium object database object-relational mapping vendors members academic community interested parties goal create set specifications would allow portable applications store objects database management systems published several versions specification last release odmg 3.0 2001 major object database object-relational mapping vendors claimed conformance odmg java language binding compliance components specification mixed 2001 odmg java language binding submitted java community process basis java data objects specification odmg member companies decided concentrate efforts java data objects specification result odmg disbanded 2001 many object database ideas also absorbed implemented varying degrees object-relational database products 2005 cook rai rosenberger proposed drop standardization efforts introduce additional object-oriented query apis rather use oo programming language i.e. java .net express queries result native queries emerged similarly microsoft announced language integrated query linq dlinq implementation linq september 2005 provide close language-integrated database query capabilities programming languages c vb.net 9 february 2006 object management group omg announced granted right develop new specifications based odmg 3.0 specification formation object database technology working group odbt wg odbt wg planned create set standards would incorporate advances object database technology e.g. replication data management e.g. spatial indexing data formats e.g. xml include new features standards support domains object databases adopted e.g. real-time systems work odbt wg suspended march 2009 subsequent economic turmoil late 2008 odb vendors involved effort decided focus resources elsewhere january 2007 world wide web consortium gave final recommendation status xquery language xquery uses xml data model ideas developed originally object databases found way xquery xquery intrinsically object-oriented popularity xml xquery engines compete object databases vehicle storage data complex variable hold conveniently relational database xquery also allows modules written provide encapsulation features provided object-oriented systems xquery v1 xpath v2 extremely complex foss software implementing standards 10 years publication compared xpath v1 xslt v1 xml fit community demands open format since early 2000s json gained community adoption popularity applications surpassing xml 2010s jsoniq query-analog xquery json sharing xquery core expressions operations demonstrated functional equivalence json xml formats context main strategy oodbms maintainers retrofit json databases using internal data type january 2016 postgresql 9.5 release first foss oodbms offer efficient json internal datatype jsonb complete set functions operations basic relational non-relational manipulations object database stores complex data relationships data directly without mapping relational rows columns makes suitable applications dealing complex data objects many-to-many relationship accessed use pointers pointers linked objects establish relationships another benefit oodbms programmed small procedural differences without affecting entire system
Databases
email authentication email authentication validation collection techniques aimed providing verifiable information origin email messages validating domain ownership message transfer agents mta participated transferring possibly modifying message original base internet email simple mail transfer protocol smtp feature forged sender addresses emails practice known email spoofing widely used phishing email spam various types fraud combat large number competing email authentication proposals developed fairly recently three widely adopted – spf dkim dmarc results validation used automated email filtering assist recipients selecting appropriate action article cover user authentication email submission retrieval early 1980s simple mail transfer protocol smtp designed provided real verification sending user system problem email systems run trusted corporations universities since commercialization internet early 1990s spam phishing crimes increasingly involve email email authentication necessary first step towards identifying origin messages thereby making policies laws enforceable hinging domain ownership stance emerged early 2000 implies coarse-grained authentication given domains appear right part email addresses sign fine-grain authentication user level achieved means pretty good privacy s/mime present digital identity needs managed individual smtp defines message transport message content thus defines mail envelope parameters envelope sender header except trace information body message std 10 define smtp envelope std 11 define message header body formally referred internet message format smtp defines trace information message saved header using following two fields mail user agent mua knows outgoing mail smtp server configuration mta relay server typically determines server connect looking mx mail exchange dns resource record recipient domain name path depicted left reconstructed ground trace header fields host adds top header receives message important realize first lines top header usually trusted recipient fact lines written machines recipient administrative management domain admd act upon explicit mandate contrast lines prove involvement b well purported author mua could counterfeit created c. codice_1 field shown epoch-making piece header codice_2 written e mail delivery agent mda based message envelope additional trace fields designed email authentication populate top header normally messages sent author admd go directly destination mx b → figures sender admd add authentication tokens message goes boxes common cases schematized follows spf allows receiver check email claimed come specific domain comes ip address authorized domain administrators usually domain administrator authorize ip addresses used outbound mtas including proxy smarthost ip address sending mta guaranteed valid transmission control protocol establishes connection checking remote host reachable receiving mail server receives codice_3 smtp command soon connection set codice_4 beginning message contain domain name spf verifier queries domain name system dns matching spf record exists specify ip addresses authorized domain administrator result pass fail intermediate result systems generally take account anti-spam filtering dkim checks message content deploying digital signatures rather using digital certificates keys signature-verification distributed via dns way message gets associated domain name dkim-compliant domain administrator generates one pairs asymmetric keys hands private keys signing mta publishes public keys dns dns labels structured codice_5 selector identifies key pair codice_6 fixed keyword followed signing domain name publication occurs authority domain admd injecting message smtp transport system signing mta creates digital signature covers selected fields header body beginning signature cover substantive header fields codice_7 codice_8 codice_9 codice_10 added message header trace field number relays receive forward message every hop signature verified retrieving public key dns long intermediate relays n't modify signed parts message dkim-signatures remain valid dmarc allows specification policy authenticated messages built top two existing mechanisms sender policy framework spf domainkeys identified mail dkim allows administrative owner domain publish policy dns records specify mechanism dkim spf employed sending email domain check codice_7 field presented end users receiver deal failures reporting mechanism actions performed policies range methods proposed either deprecated yet gained widespread support included sender id certified server validation domainkeys adsp allows specification policy messages signed author domain message go dkim authentication first adsp demand punishing treatment message signed author domain —as per codice_7 header field adsp record codice_13 published dns label codice_14 adsp designed domains heavily abused phishing similar fraud may want forgo mail facilities mailing lists non delivery reports happen remain unsigned exchange cut abuse adsp demoted historic november 2013 vbr adds vouch already authenticated identity method requires globally recognized authorities certify reputation domains sender apply reference vouching authority reference accepted published dns branch managed authority vouched sender add codice_15 header field messages sends also add dkim signature use authentication method spf receiver validating sender identity verify vouch claimed codice_15 looking reference applications avoid using method means authentication nevertheless often carried results written codice_1 header field besides tcp information required smtp specification ip reverse confirmed looking ip address name found indication ip set properly dns reverse resolution range ip addresses delegated admd uses remain managed network provider latter case useful identity related message obtained rfc 8601 defines trace header field codice_18 receiver record results email authentication checks carried multiple results multiple methods reported field separated semicolons wrapped appropriate example following field purportedly written codice_19 reports spf dkim results first token field name codice_19 id authentication server token known authserv-id receiver supporting rfc 8601 responsible remove rename false header claiming belong domain downstream filters get confused however filters still need configured know identities domain may use mail user agent mua slightly harder learn identities trust since users receive email multiple domains—e.g. multiple email addresses -— domains could let codice_18 fields pass looked neutral way malicious sender forge authserv-id user would trust message arrived different domain legitimate codice_18 typically appears codice_1 field domain message relayed additional codice_1 fields may appear top header message got transferred internally servers belonging trusted admd internet assigned numbers authority maintains registry email authentication parameters parameters need registered though example local policy values designed site internal use correspond local configuration need registration hand header field meant report results based data already present message data retrieved third parties global reputation systems compliant rfc 7601 example attempt register add dnswl results field rejected basis
Computer security
web services discovery web services discovery provides access software systems internet using standard protocols basic scenario web service provider publishes service web service consumer uses service web service discovery process finding suitable web services given task publishing web service involves creating software artifact making accessible potential consumers web service providers augment service endpoint interface interface description using web services description language wsdl consumer use service universal description discovery integration uddi xml-based registry business internet services provider explicitly register service web services registry uddi publish additional documents intended facilitate discovery web services inspection language wsil documents service users consumers search web services manually automatically implementation uddi servers wsil engines provide simple search apis web-based gui help find web services web services may also discovered using multicast mechanisms like ws-discovery thus reducing need centralized registries smaller networks current uddi search mechanism focus single search criterion business name business location business category service type name business identifier discovery url fact business solution normal search multiple uddi registries wsil documents aggregate returned result using filtering ranking techniques ibm modularized federated web services discovery engine 2001 released technology ibm business explorer web services be4ws universal description discovery integration uddi pronounced platform-independent extensible markup language protocol includes xml-based registry businesses worldwide list internet mechanism register locate web service applications uddi open industry initiative sponsored organization advancement structured information standards oasis enabling businesses publish service listings discover define services software applications interact internet uddi originally proposed core web service standard designed interrogated soap messages provide access web services description language wsdl documents describing protocol bindings message formats required interact web services listed directory uddi written august 2000 time authors vision world consumers web services would linked providers public private dynamic brokerage system vision anyone needing service credit card authentication would go service broker select service supporting desired soap service interface meeting criteria world publicly operated uddi node broker would critical everyone consumer public open brokers would return services listed public discovery others service producer getting good placement brokerage—by relying metadata authoritative index categories—would critical effective placement uddi included web services interoperability ws-i standard central pillar web services infrastructure uddi specifications supported publicly accessible universal business registry naming system built around uddi-driven service broker uddi widely adopted designers hoped ibm microsoft sap announced closing public uddi nodes january 2006 group defining uddi oasis universal description discovery integration uddi specification technical committee voted complete work late 2007 closed september 2010 microsoft announced removing uddi services future versions windows server operating system instead capability would moved biztalk server 2013 microsoft announced deprecation uddi services biztalk server 2016 microsoft remove uddi services biztalk server uddi systems commonly found inside companies used dynamically bind client systems implementations however much search metadata permitted uddi used relatively simple role uddi business registration consists three components white pages give information business supplying service includes name business description business potentially multiple languages using information possible find service information already known example locating service based provider name contact information business also provided example businesses address phone number information dun bradstreet yellow pages provide classification service business based standard taxonomies include standard industrial classification sic north american industry classification system naics united nations standard products services code unspsc geographic taxonomies single business may provide number services may several yellow pages describing service associated one white page giving general information business green pages used describe access web service information service bindings information related web service address service parameters references specifications interfaces information related directly web service includes e-mail ftp corba telephone details service web service may multiple bindings defined wsdl description service may multiple green pages binding need accessed differently uddi nodes servers support uddi specification belong uddi registry uddi registries collections one nodes soap xml-based protocol exchange messages requester provider web service provider publishes wsdl uddi requester join using soap
Web technology
whois whois pronounced phrase query response protocol widely used querying databases store registered users assignees internet resource domain name ip address block autonomous system also used wider range information protocol stores delivers database content human-readable format current iteration whois protocol drafted internet society documented elizabeth feinler team created resource directory arpanet responsible creating first whois directory early 1970s feinler set server stanford network information center nic acted directory could retrieve relevant information people entities team created domains feinler suggestion domains divided categories based physical address computer process registration established nowiki rfc 920 /nowiki whois standardized early 1980s look domains people resources related domain number registrations registration done one organization time one centralized server used whois queries made looking information easy time emergence internet arpanet organization handled domain registrations defense advanced research projects agency darpa united states government created 1958 responsibility domain registration remained darpa arpanet became internet 1980s uunet began offering domain registration service however simply handled paperwork forwarded darpa network information center nic national science foundation directed management internet domain registration would handled commercial third-party entities internic formed 1993 contract nsf consisting network solutions inc. general atomics general atomics contract canceled several years due performance issues 20th century whois servers highly permissive would allow wild-card searches whois query person last name would yield individuals name query given keyword returned registered domains containing keyword query given administrative contact returned domains administrator associated since advent commercialized internet multiple registrars unethical spammers permissive searching longer available december 1 1999 management top-level domains tlds com net org assigned icann time tlds converted thin whois model existing whois clients stopped working time month later self-detecting common gateway interface support program could operate web-based whois lookup external tld table support multiple whois servers based tld request eventually became model modern whois client 2005 many generic top-level domains early 1980s also many country-code top-level domains led complex network domain name registrars registrar associations especially management internet infrastructure become internationalized performing whois query domain requires knowing correct authoritative whois server use tools whois proxy searches become common 2003 ietf committee formed create new standard looking information domain names network numbers cross registry information service protocol crisp january 2005 july 2006 working name proposed new standard internet registry information service iris initial ietf proposed standards rfcs iris status rfcs group worked found ietf tools site march 2009 crisp ietf working group concluded final rfc 5144 published group note ietf crisp working group confused number resource organization nro team name consolidated rir iana stewardship proposal team crisp team 2013 ietf acknowledged iris successful replacement whois primary technical reason appeared complexity iris non-technical reasons deemed lie areas upon ietf pass judgment meanwhile arin ripe ncc managed serve whois data via restful web services charter drafted february 2012 provided separate specifications number registries first name registries follow working group produced five proposed standard documents informational document whois protocol origin arpanet nicname protocol based name/finger protocol described nowiki rfc 742 /nowiki 1977 nicname/whois protocol first described nowiki rfc 812 /nowiki 1982 ken harrenstien vic white network information center sri international whois originally implemented network control program ncp found major use tcp/ip suite standardized across arpanet later internet protocol specification following original quote command line server query normally single name specification i.e name resource however servers accept query consisting question mark return description acceptable command line formats substitution wild-card formats also exist e.g. appending full-stop period query name returns entries beginning query name modern internet whois services typically communicated using transmission control protocol tcp servers listen requests well-known port number 43 clients simple applications establish communications channel server transmit text record name resource queried await response form sequence text records found database simplicity protocol also permits application command line interface user query whois server using telnet protocol 2014 june icann published recommendation status codes extensible provisioning protocol epp domain status codes whois lookups traditionally performed command line interface application many alternative web-based tools exist whois sister protocol called referral whois rwhois whois database consists set text records resource text records consists various items information resource associated information assignees registrants administrative information creation expiration dates two data models exist storing resource information whois database thick thin model whois information stored looked according either thick thin data model thick model usually ensures consistent data slightly faster queries since one whois server needs contacted registrar goes business thick registry contains important information registrant entered correct data privacy features used obscure data registration information retained thin registry contact information might available could difficult rightful registrant retain control domain whois client understand deal situation would display full information registrar unfortunately whois protocol standard determining distinguish thin model thick model specific details records stored vary among domain name registries top-level domains including com net operate thin whois requiring domain registrars maintain customers data global top-level registries including org operate thick model country-code top-level registry national rules first applications written whois information system command-line interface tools unix unix-like operating systems i.e solaris linux etc. whois client server software distributed free open-source software binary distributions included unix-like systems various commercial unix implementations may use proprietary implementation example solaris 7 whois command line client passes phrase given argument directly whois server various free open source examples still found sites sourceforge.net however modern whois tools implement command line flags options -h option access specific server host default servers preconfigured additional options may allow control port number connect displaying additional debugging data changing recursion/referral behavior like tcp/ip client-server applications whois client takes user input opens internet socket destination server whois protocol manages transmission query reception results advent world wide web especially loosening network solutions monopoly looking whois information via web become quite common present popular web-based whois-queries may conducted arin ripe apnic early web-based whois clients merely front-ends command-line client resulting output gets displayed web page little clean-up formatting currently web based whois clients usually perform whois queries directly format results display many clients proprietary authored domain name registrars need web-based clients came fact command-line whois clients largely existed unix large computing worlds microsoft windows macintosh computers whois clients installed default registrars find way provide access whois data potential customers many end-users still rely clients even though command line graphical clients exist home pc platforms microsoft provides sysinternals suite includes whois client cost also many sites owned registrars internet-related companies support main tld remain free web-based whois sites incomplete support tld ip search cpan several perl modules available work whois servers many current fully function current 2005 whois server infrastructure however still much useful functionality derive including looking numbers registrant contacts whois servers operated regional internet registries rir queried directly determine internet service provider responsible particular resource records registries cross-referenced query arin record belongs ripe return placeholder pointing ripe whois server lets whois user making query know detailed information resides ripe server addition rirs servers commercial services exist routing assets database used large networks e.g. large internet providers acquired isps several rir areas currently standard determining responsible whois server dns domain though number methods common use top-level domains tlds whois lookups require searching procuring domain registrar display domain owner details normally contact information resources assignee returned however registrars offer private registration case contact information registrar shown instead registry operators wholesalers meaning typically provide domain name services large number retail registrars turn offer consumers private registration identity wholesale registrar may returned case identity individual well retail registrar may hidden example whois data returned individual resource holder result whois query example.com referral whois rwhois extension original whois protocol service rwhois extends concepts whois scalable hierarchical fashion potentially creating system tree-like architecture queries deterministically routed servers based hierarchical labels reducing query primary repository information lookups ip address allocations often limited larger classless inter-domain routing cidr blocks e.g. /24 /22 /16 usually regional internet registries rirs domain registrars run rwhois whois servers although rwhois intended run even smaller local internet registries provide granular information ip address assignment rwhois intended replace whois providing organized hierarchy referral services one could connect rwhois server request look-up automatically re-directed correct server however technical functionality place adoption rwhois standard weak rwhois services typically communicated using transmission control protocol tcp servers listen requests well-known port number 4321 rwhois first specified nowiki rfc 1714 /nowiki 1994 network solutions specification superseded 1997 rfc 2167 referral features rwhois different feature whois server refer responses another server rwhois also implements one criticism whois lack full access data parties realtime access complete databases others cite competing goal domain privacy criticism although problem strongly mitigated domain privacy services currently internet corporation assigned names numbers icann broadly requires mailing address phone number e-mail address owning administrating domain name made publicly available whois directories registrant domain owner contact details address telephone number easily accessible anyone queries whois server however policy enables spammers direct marketers identity thieves attackers loot directory personal information people although icann exploring changing whois enable greater privacy lack consensus among major stakeholders type change made domain registrars offer private registrations also known domain privacy contact information registrar shown instead customer offer private registration many registrars risk mitigated studies shown spammers harvest plain-text email addresses whois servers reason whois servers websites offering whois queries implemented rate-limiting systems web-based captcha limited amounts search queries per user ip address whois requirements conflict general data protection regulation gdpr effective european union 25 may 2018 places strict regulations processing publication personally identifiable information icann stated november 2017 would reprimand noncompliance contractual obligations related handling registration data registrars provide alternative solutions compliance rules whois requirements updated take gdpr account whois protocol written international audience mind whois server and/or client determine text encoding effect query database content many servers originally using us-ascii internationalization concerns n't taken consideration much later might impact usability usefulness whois protocol countries outside usa case internationalized domain names responsibility client application perform translation domain name native language script dns name punycode cases registrant domain owner identity public anyone easily confirm status domain via whois case private registrations ascertaining registration information may difficult registrant acquired domain name wants verify registrar completed registration process three steps may required provides confidence retailer actually registered name registrar goes business failure registerfly 2007 rightful domain holder privacy-protected registrations may difficulty regaining administration his/her domain name registrants using private registration attempt protect using registrar places customer data escrow third party icann requires every registrant domain name given opportunity correct inaccurate contact data associated his/her domain reason registrars required periodically send holder contact information record verification provide guarantee accuracy information registrant provided inaccurate information whois generated policy issues united states federal government noted whois creates privacy issue also tied free speech anonymity however whois important tool law enforcement officers investigating violations like spam phishing track holders domain names result law enforcement agencies sought make whois records open verified expert working group ewg internet corporation assigned names numbers icann recommended 24 june 2013 whois scrapped recommends whois replaced system keeps information secret internet users discloses information permissible purposes icann list permissible purposes includes domain-name research domain-name sale purchase regulatory enforcement personal data protection legal actions abuse mitigation although whois key tool journalists determining disseminating certain information internet use whois free press included icann ’ proposed list permissible purposes ewg collected public input initial report 13 september 2013 final report issued 6 june 2014 without meaningful changes recommendations icann process re-inventing whois working icann whois beta
Internet protocols
hao123 hao123 online listings portal baidu.. portuguese thai version hao123 accused internet hijacking installing virus inserts hao123 onto desktop malicious browser hijacker often installs without user consent installed difficult remove hao123 uses windows service registry browser parameters modify browser default setting prevent removed uninstalled adding back windows service also sniffs user internet traffic illegally forces users visit website improve website traffic ranking reason hao123 considered malware many anti-virus programs
Computer security
blackpos malware blackpos interprocess communication hook malware type point-of-sale malware spyware program specifically designed installed point sale pos system scrape data debit credit cards different normal memory-scraping malware scrapes data needs filters extract target data specifically hooks track information thus called interprocess communication hook malware gets installed looks pos.exe file system parses content track 1 track 2 financial card data scraped data encoded base64 algorithm stored magnetic strip back card encoded data moved second machine smb blackpos malware involved target corporation data breach 2013 blackpos program first surfaced early 2013 affected many australian american canadian companies target marcus neiman incorporated point-of-sale systems companies virus also known 'reedum 'kaptoxa originally created 23 year-old rinat shabayev later developed 17-year-old sergey taraspov better known online name 'ree4 original version blackpos sold online black market forums taraspov around 2000 became cheaper readily available source code malware leaked onto web blackpos infects computers running windows operating systems credit card readers connected part pos system pos system computers easily infected date operating systems antivirus programs prevent security breaches computer database systems weak administration login credentials blackpos standard memory-scraping malware exception virus limited pos.exe files infected pos system desired pos system infected malware pinpoints process corresponded card reader steals payment card track 1 track 2 data information stored magnetic strip payment cards system memory stolen information cloned onto blank credit cards sold black market use used personal reasons results consumer personal information compromised usable anyone access information unlike pos malware vskimmer blackpos offline data extraction method captured information uploaded remote server online makes easier hackers need proximity infected systems retrieve consumer information furthermore hackers may try hide virus detection programming blackpos send stolen information certain time frames mask traffic information creates normal work hours making seem nothing suspicious going blackpos used steal customer information businesses worldwide well-known attack occurred back 2013 mega-store chain target thanksgiving break november 2013 target pos system infected blackpos malware mid-december mega-store became aware breach security hackers able get target systems compromising company web server uploading blackpos software target pos systems result attack 40 million customer credit debit card information 70 million addresses phone numbers names personal information stolen mainframes end 1800 u.s. target stores affected malware attack target however business affected software neiman marcus another well-known retailer affected well computer database said infected early july 2013 fully contained january 2014 breach believed involve 1.1 million credit debit cards span several months although credit debit card information compromised neiman marcus issued statement saying social security numbers birthdates affected among things companies ups wendy home depot also claimed affected blackpos well although reports state breaches caused malware virus two ways detect blackpos activity pos systems based malware works first strategy detect blackpos uses fact first 15 characters stolen track data always consists digits result limited amount combinations produced means predictable pattern followed addition encoding outputs 000 999 result string always begin “ m1 ” “ mf ” “ mh ” “ ml ” “ t1 ” “ tf ” “ th ” “ tl ” “ sh ” “ sl ” second way identify blackpos network activity dropping file specific location using fixed filename format example given security intelligence checks file path name matches format written \windows\twain_32\*_*_*_*.txt strategy demonstrated following opensignature rule alert tcp 445 msg kaptoxa file write detected flow to_server established content smb|a2| content \\|00|w|00|i|00|n|00|d|00|o|00|w|00|s|00|\\|00|t|00|w|00|a|00|i|00|n|00|_|00|3|00|2|00|\\ pcre /.*_.*_.*_ *\.|00|t|00|x|00|t/ sid:1 prevention according pci security council businesses keep malware prevention software updated frequently lower chance infection addition system logs regularly checked irregular activity within servers well monitoring large data files sent unknown sources companies also require login credentials updated regularly provide instructions create safer secure passwords
Computer security
unisoft unisoft corporation american software developer established 1981 originally focused development unix ports various computer architectures based millbrae california builds standardization conformance testing applications digital television market unisoft founded october 5 1981 emeryville california original business unix development soon recognized one early implementers unix emerging 16-bit microcomputer market 1989 completed 225 unix implementations various hardware platforms estimated 65 ports unisoft port version 7 unix first operating system sun microsystems sun-1 workstations servers also developed apple inc. unix variant a/ux apple macintosh ii 1991 company moved current offices millbrae california unisoft shifted focus television industry 1997 order address standards compliant software market works solely development testing broadcast tools digital television
Operating systems
web services inspection language ws-inspection web service specification discovery documents developed joint effort microsoft ibm ws-inspection lists groups web services endpoints xml format currently standards used purpose microsoft disco expected ws-inspection eventually replace standards become universally accepted discovery standard web services
Web technology
kurumin kurumin linux live cd operating system based debian main features advanced hardware auto-detection inherited knoppix portuguese user interface main goal ease use release 7.0 size disk image approximately 603 mb version ng 8.06 based ubuntu 8.04 released june 24 2008 discontinued january 29 2009 name comes tupi word kurumi means boy usage letter k instead usual portuguese spelling curumi curumim brings line kde kurumin default desktop environment well knoppix late 2007 morimoto said project would halted scope reduced november 2008 project officially discontinued distribution sports open-source control center named clicaaki roughly clickhere features series shell scripts kommander-based panels magic icons install software included live cd icons one configure wide range networking options control center also provides access synaptic package manager clicaaki control panel shortcuts scripts also perform tasks like downloading installing free games apps divided categories short description work differences control panel also includes scripts downloading automatically configuring drivers 3d video cards ati nvidia difficult task novice users another feature distro support many winmodems including official packages drivers debian repository also scripts automate tasks compiling configuring necessary modules features kurumin spread gnu/linux operating system brazil level never seen
Operating systems
graph-based access control graph-based access control gbac declarative way define access rights task assignments recipients content information systems access rights granted objects like files documents also business objects like account also used assignment agents tasks workflow environments organizations modeled specific kind semantic graph comprising organizational units roles functions well human automatic agents i.a persons machines compared approaches like role-based access control attribute-based access control main difference gbac access rights defined using organizational query language instead total enumeration foundations gbac go back research project named cocosorg configurable cooperation system english language please see bamberg university cocosorg organization represented semantic graph formal language used specify agents access rights workflow environment within c-org-project hof university institute information systems iisys approach extended features like separation duty access control virtual organizations subject-oriented access control graph-based access control consists two building blocks organizational graph divided type instance level instance level node types organizational units functional units agents basic structure organization defined using called structural relations define part relations functional units organizational units well mapping agents functional units additionally specific relationship types like deputyship informed_by types extended modeler relationships context sensitive usage predicates type level organizational structures described general manner consists organizational unit types functional unit types relationship types instance level type definitions used create new instances reuse organizational knowledge case exceptions reading see gbac query language used define agents certain characteristics abilities following table shows usage query language context access control matrix first query means managers working company six months read financial report well managers classified flag readfinancialreport daily financial report written manager controlling department clerks department enabled writefinancialreport==true gbac first implemented cocos environment within organizational server cocosorg c-org-project extended sophisticated features like separation duty access control distributed environments also cloud-based implementation ibm bluemix platform implementations server takes query client system resolves set agents set sent back calling client response clients file systems database management systems workflow management systems physical security systems even telephone servers
Computer security
point-to-point tunneling protocol point-to-point tunneling protocol pptp obsolete method implementing virtual private networks pptp many well known security issues pptp uses tcp control channel generic routing encapsulation tunnel encapsulate ppp packets many modern vpns use various forms udp functionality pptp specification describe encryption authentication features relies point-to-point protocol tunneled implement security functionalities pptp implementation ships microsoft windows product families implements various levels authentication encryption natively standard features windows pptp stack intended use protocol provide security levels remote access levels comparable typical vpn products specification pptp published july 1999 rfc 2637 developed vendor consortium formed microsoft ascend communications today part nokia 3com others pptp proposed ratified standard internet engineering task force pptp tunnel instantiated communication peer tcp port 1723 tcp connection used initiate manage gre tunnel peer pptp gre packet format non standard including new acknowledgement number field replacing typical routing field gre header however normal gre connection modified gre packets directly encapsulated ip packets seen ip protocol number 47 gre tunnel used carry encapsulated ppp packets allowing tunnelling protocols carried within ppp including ip netbeui ipx microsoft implementation tunneled ppp traffic authenticated pap chap ms-chap v1/v2 pptp subject many security analyses serious security vulnerabilities found protocol known vulnerabilities relate underlying ppp authentication protocols used design mppe protocol well integration mppe ppp authentication session key establishment summary vulnerabilities eap-tls seen superior authentication choice pptp however requires implementation public-key infrastructure client server certificates may viable authentication option remote access installations networks use pptp apply additional security measures deemed completely inappropriate modern internet environment time means negating aforementioned benefits protocol point matter slice using pptp lose-lose scenario
Internet protocols
tippingpoint trend micro tippingpoint ’ intrusion prevention system ips deals threat protection combining new application-level security practical user awareness inbound/outbound messaging inspection capabilities scalable ngips protects user ’ applications network data new threats tippingpoint ngips protects user ’ network sophisticated attacks tippingpoint functions part trend micro security previously tippingpoint division hp part enterprise security group american software company roots traced back 1999 focused network security products particularly intrusion prevention systems networks tippingpoint acquired 3com corporation 2005 run autonomous security-focused division 2005 2010 april 12 2010 hp completed acquisition 3com september 2011 tippingpoint within hp networking networking division hp transferred hp software division september 2013 hp announced entered next-generation firewall market new line tippingpoint firewalls new line extends tippingpoint existing intrusion prevention system ips appliances traditional stateful packet filtering application control company founded january 1999 name shbang texas co-founders john f. mchale kent savage first chief executive kenneth a. kalinoski business develop sell internet appliances may 1999 company changed name netpliance november released i-opener low-cost computer intended used browsing world wide web 2000 las vegas engineer ken segler discovered method install alternative operating system device 2001 company fined federal trade commission 100,000 sales billing practices 2002 company discontinued operations internet appliance business focus network security products new name tippingpoint ceo savage replaced chairman board mchale mchale stepped 2004 however remained chairman board position filled kip mcclanahan former ceo broadjump january 2005 tippingpoint acquired network equipment company 3com 442 million operating division 3com led james hamilton tippingpoint president later replaced alan kessler 3com acquired computer manufacturer hewlett-packard april 2010 approximately 2.7 billion oct 21 2015 tippingpoint acquired trend micro approximately 300 million
Databases
smp/e smp/e system modification program/extended tool designed manage installation software products z/os system track modifications products smp/e manages multiple software versions helps apply patches updates ptfs facilitates orderly testing necessary reversion previous state allows trial run pseudo-installation verify actual installation work keeps audit security records assure approved software updates occur otherwise provides highly evolved centralized control software installation z/os although possible design ship software products install z/os without smp/e mainframe administrators prefer smp/e-enabled products least non-trivial packages using smp/e typically requires working knowledge job control language jcl although products supply sample jcl rigorous software management discipline associated smp/e typically extends product documentation well ibm vendors supplying standardized program directory manual software product precisely aligns smp/e work processes program directory provides detailed information pre-requisites co-requisites example use smp/e manage system updates helps ensure system integrity making sure system consistent state changes state properly audited previously called smp system modification program smp/e evolved osmp os maintenance program os/360 smp version 4 major revision new syntax smp/e introduced mvs introduced use vsam datasets concept extended ibm operating systems dos/vs maintain system history program mshp vm/sp ses virtual machine serviceability enhancements staged vmses/e ibm non-ibm software assigned least one seven character fmid function module id identifies piece software release number first fmid called base fmid example db2 version 9 base fmid hdb9910 separately installable features also fmids called dependent fmids relate way base product db2 english language panels version 9 dependent fmid jdb9910 software package composed elements individual components object files mod macros mac sample programs samp etc csi consolidated software inventory dataset containing information smp/e needs track contents distribution target libraries csi contains metadata identifying installed fmids elements id recent update pointers associated libraries sysmod system modification modification system includes sysmod assigned seven character sysmod id uniquely identify sysmod installed id recorded csi entry element added replaced called rmid replacement module id simple declarative language called mcs modification control statements provides information smp/e identifying sysmod providing information install sysmod prefixed number mcs statements example identify apar fix ptf supply sysmod id identify applicable fmid etc prerequisites prereqs sysmods required installed second installed corequisites coreqs two sysmods must installed together none installed without others sysmod supersedes sups another functionally replaces first prereq coreq sup information provided mcs requisite chain sequence sysmods directly indirectly identified requisites given sysmod example prereq b b prereq c b requisite chain c need installed c although necessarily separate run smp/e requisite chains frequently become extremely involved comprise hundreds sysmods holddata set mcs statements indicate specific sysmods contain errors require manual processing outside scope smp/e installed user required take action fix problem possible installing held sysmods smp/e manages two types libraries target libraries tlibs contain executable code information used run system originally limited number target libraries sys1.linklib executable programs sys1.maclib standard macros etc. 2012 software product usually set target libraries distribution libraries dlibs contain master copy element system product fmid set distribution libraries normally used smp/e libraries os/360 successors unlike directories unix usually contain one type format data software package may object libraries mod ispf panels pnl macro libraries mac many smp/e single large program runs batch job series ispf panels used interactively build smp/e job stream based user input one common sequence steps called receive-apply-accept commands used step smp/e receive command processes sysmods source outside smp previously might put tape distributed ibm roughly monthly recently might collection sysmods downloaded internet receive process uses mcs create entry csi sysmod marking status received stores mcs information actual sysmod data reject command used delete sysmods received status apply command installs one received sysmods appropriate target libraries sysmods applied selected various criteria example single sysmod selected sysmod id sysmods received group selected sourceid un-applied sysmods received applied requisite chains specified sysmods checked sysmods without proper requisites hold status superseded flagged errors installed commonly smp/e instructed also automatically apply requisites receive status minimize errors sysmods installed status changed applied csi apply check used check sysmods installed without actually performing installation restore command used remove applied sysmod accepted accept command installs sysmods permanently distribution libraries marks status accepted csi normally accept done sysmods known performing correctly next apply service way smp/e undo accept operation except delete installation libraries including csis start installation smp/e large complex program features datasets added every release major smp/e datasets
Operating systems
squashfs squashfs compressed read-only file system linux squashfs compresses files inodes directories supports block sizes 4 kib 1 mib greater compression several compression algorithms supported squashfs also name free software licensed gpl accessing squashfs filesystems squashfs intended general read-only file-system use constrained block-device memory systems e.g embedded systems low overhead needed squashfs used live cd versions arch linux debian fedora gentoo linux linux mint salix ubuntu embedded distributions openwrt dd-wrt router firmware also used chromecast system partitions android nougat often combined union mount filesystem unionfs overlayfs aufs provide read-write environment live linux distributions takes advantage squashfs high-speed compression abilities ability alter distribution running live cd distributions debian live mandriva one puppy linux salix live slax use combination appimage project aims create portable linux applications uses squashfs creating appimages snappy package manager also uses squashfs .snap file format squashfs also used linux terminal server project splashtop tools unsquashfs mksquashfs ported windows nt – windows 8.1 7-zip also supports squashfs squashfs initially maintained out-of-tree linux patch initial version 1.0 released 23 october 2002 2009 squashfs merged linux mainline part linux 2.6.29 process backward-compatibility code older formats removed since squashfs kernel space code maintained linux mainline tree user space tools remain project sourceforge page original version squashfs used gzip compression although linux kernel 2.6.34 added support lzma lzo compression linux kernel 2.6.38 added support lzma2 compression used xz linux kernel 3.19 added support lz4 compression support zstandard added linux kernel 4.14 linux kernel 2.6.35 added support extended file attributes
Computer file systems
pc protector pc protector rogue antivirus program part windows police pro windows antivirus pro family program tries block type microsoft program anti-virus anti-malware suite program says protect computer program protect use firewall data like malware pc protector tries steal privacy asking credit card data use money much says spend anti-malware like malwarebytes antimalware might able remove virus pc protector uses windows filenames hide program name way track extra svchost.exe running user profile task manager processes may find svchost.exe common files may open pc protector would hijack windows registry modify web browser loading feature hijack registry make web page load saying unsafe web page show virus alert alert claims must purchase pc protector program also install browser helper object would hijack search results feature modifies windows host file dns hijacker dns hijacking pc protector secure purchase pc protector many different actions pc protector many different blocked executable .exe files pc protector blocks computer user using
Computer security
name resolution semantics text extraction semantics text extraction name resolution refers ability text mining software determine actual person actor object particular use name refers also referred entity resolution example text mining field software frequently needs interpret following text john gave edward book stood called john come back room sentences software must determine whether pronoun refers john edward first sentence software must also determine whether john referred second sentence john first sentence third person whose name also happens john examples apply almost languages english frequently type name resolution also used across documents example determine whether george bush referenced old newspaper article president united states george h. w. bush person george bush mentioned separate news article years later man running president george w bush many people may name analysts software must take account substantially information name determine whether two identical references george bush actually refer specific entity person name/entity resolution text extraction semantics notoriously difficult problem part many cases sufficient information make accurate determination numerous partial solutions exist rely specific contextual clues found data currently known general solution problem sometimes referred name disambiguation digital libraries author disambiguation examples software might provide name resolution benefits see also
Computational linguistics
apache phoenix apache phoenix open source massively parallel relational database engine supporting oltp hadoop using apache hbase backing store phoenix provides jdbc driver hides intricacies nosql store enabling users create delete alter sql tables views indexes sequences insert delete rows singly bulk query data sql phoenix compiles queries statements native nosql store apis rather using mapreduce enabling building low latency applications top nosql stores phoenix began internal project company salesforce.com need support higher level well understood sql language originally open-sourced github 28 jan 2014 became top-level apache project 22 may 2014 apache phoenix included hortonworks distribution hdp 2.1 available part cloudera labs part hadoop ecosystem
Databases
verbmobil verbmobil long-term interdisciplinary language technology esp machine translation research project aim develop system recognize translate produce natural utterances thus translate spontaneous speech robustly bidirectionally german/english german/japanese verbmobil research carried 1993 2000 funded germany federal ministry research technology bundesministerium für forschung und technologie total 116m deutschmarks roughly 60m euros industry partners daimlerchrysler siemens philips contributed additional 52 million dm 26m euros verbmobil ii project tübingen university created semi-automatically annotated treebanks german japanese english spontaneous speech tüba-d/s contains ca 38,000 sentences 360,000 words tüba-e/s contains ca 30,000 sentences 310,000 words tüba-j/s contains ca 18,000 sentences 160,000 words
Computational linguistics
active oberon active oberon general purpose programming language developed 1996-1998 group around niklaus wirth jürg gutknecht swiss federal institute technology eth zürich extension programming language oberon extensions aim implementing active objects expressions parallelism compared predecessors oberon oberon-2 active oberon adds objects object-centered access protection local activity control system-guarded assertions preemptive priority scheduling changed syntax methods aka type-bound procedures oberon terminology objects may active means may threads processes operating system a2 aka bluebottle especially kernel synchronizes coordinates different active objects unlike java c objects may synchronized signals directly conditions simplifies development concurrent programs fork active oberon zonnon
Programming language topics
chain industry standard ceced convergence working group defined new platform called chain ceced home appliances interoperating network defines protocol interconnecting different home appliances single multibrand system allows control automation basic appliance-related services home e.g. remote control appliance operation energy load management remote diagnostics automatic maintenance support appliances downloading updating data programs services possibly internet
Computer architecture
name resolution programming languages programming languages name resolution resolution tokens within program expressions intended program components expressions computer programs reference variables data types functions classes objects libraries packages entities name context name resolution refers association not-necessarily-unique names intended program entities algorithms determine identifiers refer specific contexts part language definition complexity algorithms influenced sophistication language example name resolution assembly language usually involves single simple table lookup name resolution c++ extremely complicated involves programming languages name resolution performed either compile time runtime former called static name resolution latter called dynamic name resolution somewhat common misconception dynamic typing implies dynamic name resolution however static typing imply static name resolution example erlang dynamically typed static name resolution static name resolution catches compile time use variables scope preventing programmer errors languages dynamic scope resolution sacrifice safety flexibility typically set get variables scope runtime example python interactive repl however relying dynamic name resolution code discouraged python community feature also may removed later version python examples languages use static name resolution include c c++ e erlang haskell java pascal scheme smalltalk examples languages use dynamic name resolution include lisp dialects perl php python rebol tcl masking occurs identifier used different entities overlapping lexical scopes level variables rather names known variable shadowing identifier variable x masks identifier variable x two conditions met outer variable x said shadowed inner variable x example parameter foo shadows local variable foo common pattern name masking cause complications function overloading due overloading happening across scopes languages notably c++ thus requiring overloaded functions redeclared explicitly imported given namespace programming languages lexical scoping reflect variable names α-conversion α-renaming used make name resolution easy finding substitution makes sure variable name masks another name containing scope alpha-renaming make static code analysis easier since alpha renamer needs understand language scoping rules example code within point constructor class variables x shadowed local variables name might alpha-renamed new version masking immediately obvious uses correspond declarations
Programming language topics
macintosh quadra 840av macintosh quadra 840av personal computer designed manufactured sold apple computer inc. july 1993 july 1994 introduced alongside centris 660av av model numbers signifying video input output capabilities well enhanced audio 840av mini tower form factor quadra 800 faster motorola 68040 processor quadra 840av discontinued shortly introduction powerpc-based power macintosh power macintosh 8100/80av provided functionality form factor albeit significantly higher price point 7100/66av priced comparably 840av iivx-style desktop case time introduction 40 mhz motorola 68040 cpu interleaved ram made fastest macintosh available topping nominally higher-end quadra 950 quadra 800 7 mhz remains fastest quadra fastest 68k macintosh time since later high-end macintoshes powerpc-based power macintoshes 840av also mac use 40 mhz-clocked 68040 also sports faster 66.7 mhz dsp 3210 digital signal processor chip compared 55 mhz variant 660av on-board dsp primarily intended speed audio/video processing although mac programs made use due complexity programming 840av relative centris/quadra 660av marked number firsts macintosh family first macintoshes include on-board 16-bit 48 khz stereo audio playback recording capability well s-video composite video input output improve video playback two separate frame buffers used one standard graphics one specifically video enabled live video input displayed scalable window within macintosh user interface also first personal computers supported speech recognition plaintalk out-of-the-box apple geoport telecom adapter kit introduced av macs added many dsp-based telecommunication functions modem fax telephony quadra 840av came similar case earlier macintosh quadra 800 housing chassis power supply internal storage assemblies front rear panels changed power button moved back internally 840av significantly different apart faster processor logic board lacks 800 processor direct slot second adb port dav slot line nubus slot new geoport also unlike 800 8 mib fixed ram 840av memory simms reason minimum amount memory lower way 840av deals memory dram different machines generation quadra 700 800 950 4 8 16 32 mb 72-pin 60ns simms may installed 128 mb sizes mixed however quadra 840av support 1 mb 2 mb 64 mb simms 840av 660av first macintosh computers operate 32-bit mode times toggled back 24-bit mode may useful using early nubus cards conform 24-bit addressing new av machines first ship standard internal cd-rom drive earlier quadra centris models available built-in cd-rom drive optional extras operating system installation package came cd-rom rather series floppy disks whenever cd-rom drive included hidden quicktime video included original quadra 840av/centris 660av install first cd-rom shows jubilant cyclone tempest design team midst celebrating accomplishment video cyclone 840av prototype logic board shown logic board fitted 25 mhz 68040 number rework wires conspicuously daughter card nicknamed karma audio video input/output ports located notably audio video ports card front-facing positioned though would protrude opening lower front case easily accessible user according member team av card feature omitted enough room case coinciding introduction av macs apple introduced apple audiovision 14 display featuring easily accessible audio input audio output video input ports could fed adc adapter cable connected rear av ports av macs later power macintosh 6100 7100 8100 returned av card concept later abandoned 7500/8500 series machines re-introduced wings av personality card power macintosh g3 gossamer artemis machines stored inside spare rom space two jpeg images quadra 840av development team early quadra 840av logic boards featured 2 mb rom simm slot located ram simm slots originally planned 840av rom would contain bootable image system 7 within larger 4 mb rom space code-named supermario apple dropped idea 840av shipped later revisions 840av logic board included 2 mb rom soldered onto logic board
Computer architecture
flintstones 1988 video game flintstones 1988 video game based 1960s television series flintstones game developed teque software development published grandslam entertainments game released europe 1988 amiga amstrad cpc atari st commodore 64 msx2 zx spectrum version sega master system released 1991 version flintstones features identical gameplay game contains four levels story begins fred flintstone finishing work rock quarry exclaiming yabba dabba doo game spoken line dialogue achieved speech synthesis remainder game character interactions done speech balloons fred wants bowl barney rubble bowling alley fred wife wilma tells must paint living room first arrival mother playing fred player must paint room also preventing young daughter pebbles scribbling walls player paintbrush squirrel stopping pebbles squirrel sometimes runs away must captured second level fred must race bowling alley avoiding rocks road hitting rock results vehicle losing wheel requiring player search replacement get back road third level played bowling game fred barney two players taking turns final level fred returns home discovers pebbles missing house finds climbing construction site competes barney rescue avoiding nuts bolts practice mode allows player explore area rendition theme music television series created ben daglish present throughout game except zx spectrum version games machine criticized bowling level long-winded restacking pins bowl – taking realism far magazine praised music noted graphics could challenge tv cartoon concluded patience flintstones could provide amusing generally tough challenge magazine noted atari st version identical amiga version except slightly poorer sound reviewing amstrad cpc commodore 64 zx spectrum versions games machine wrote version retained impressive cartoon-like graphics difficult gameplay earlier versions magazine wrote commodore version moves fair rate spectrum amstrad cpc versions slow enough cause frustration chris jenkins computer video games praised graphics sound considered bowling level poorest portion game jenkins concluded game polished professional product deserves seen john butters atari st user praised music sound called graphics immaculate concluded game soon became frustrating rather addictive andy richards also atari st user praised music sound gameplay graphics one reviewer st action wrote painting level clever infuriating taxing bowling scene could thoughtfully designed another reviewer st action wrote sluggish controls slow speed make painting scene unbelievably tedious sadly bowling scene anything worse lot time wasted player resets pins whilst barney bowls means sitting waiting turn nothing program recommend paul glancey zzap 64 wrote commodore 64 version poor sprites feeble backgrounds coupled grating rendition flintstones theme tune create bad impression frustrating controls painting section enthrall sub-games dated – paint collect game '88 – basic tenth frame bowling n't encourage player reach final section tv licences work rarely flintstones certainly n't paul sumner also zzap 64 wrote neither fred barney resembled television counterparts praised sound music sumner wrote gameplay little difficult first due mainly slightly unresponsive control perseverance reap reward though personally found game difficult warrant extensive play
Computer architecture
dnsbl domain name system-based blackhole list dnsbl real-time blackhole list rbl effort stop email spamming blacklist locations internet reputed send email spam locations consist ip addresses often used publish addresses computers networks linked spamming mail server software configured reject flag messages sent site listed one lists term blackhole list sometimes interchanged term blacklist blocklist dnsbl software mechanism rather specific list policy dozens dnsbls existence use wide array criteria listing delisting addresses may include listing addresses zombie computers machines used send spam internet service providers isps willingly host spammers sent spam honeypot system since creation first dnsbl 1998 operation policies lists frequently controversial internet advocacy occasionally lawsuits many email systems operators users consider dnsbls valuable tool share information sources spam others including prominent internet activists objected form censorship addition small number dnsbl operators target lawsuits filed spammers seeking lists shut first dnsbl real-time blackhole list rbl created 1997 first border gateway protocol bgp feed paul vixie dnsbl eric ziegast part vixie mail abuse prevention system maps dave rand abovenet first subscriber first version rbl published dnsbl rather list networks transmitted via bgp routers owned subscribers network operators could drop tcp/ip traffic machines used send spam host spam supporting services website inventor technique later commonly called dnsbl eric ziegast employed vixie enterprises term blackhole refers networking black hole expression link network drops incoming traffic instead forwarding normally intent rbl sites using would refuse traffic sites supported spam — whether actively sending spam ways address would listed rbl volunteers maps staff would attempt repeatedly contact persons responsible get problems corrected effort considered important blackholing network traffic also meant spammers spam supporting isps could delay put rbl long periods discussions went later rbl also released dnsbl form paul vixie encouraged authors sendmail mail software implement rbl support clients allowed mail software query rbl reject mail listed sites per-mail-server basis instead blackholing traffic soon advent rbl others started developing lists different policies one first alan brown open relay behavior-modification system orbs used automated testing discover list mail servers running open mail relays—exploitable spammers carry spam orbs controversial time many people felt running open relay acceptable scanning internet open mail servers could abusive 2003 number dnsbls came denial-of-service attacks dos since party admitted attacks discovered responsible purpose matter speculation however many observers believe attacks perpetrated spammers order interfere dnsbls operation hound shutting august 2003 firm osirusoft operator several dnsbls including one based spews data set shut lists suffering weeks near-continuous attack technical specifications dnsbls came relatively late rfc5782 uniform resource identifier uri dnsbl dnsbl lists domain names sometimes also ip addresses found clickable links contained body spams generally found inside legitimate messages uri dnsbls created determined much spam made past spam filters short time frame first use spam-sending ip address point sending ip address first listed major sending-ip-based dnsbls many cases elusive spams contain links domain names ip addresses collectively referred uris uri already spotted previously caught spam uri found non-spam e-mail therefore spam filter extracts uris message checks uri dnsbl spam blocked even sending ip spam yet listed sending ip dnsbl three major uri dnsbls oldest popular surbl surbl created volunteers surbl started second major uri dnsbl uribl 2008 another long-time surbl volunteer started another uri dnsbl ivmuri spamhaus project provides spamhaus domain block list dbl describe domains found spam messages dbl intended uribl rhsbl checked domains message envelope headers domains urls message bodies unlike uribls dbl lists domain names ip addresses since spamhaus provides lists ip addresses uri dnsbls often confused rhsbls right hand side bls different uri dnsbl lists domain names ips found body message rhsbl lists domain names used reply-to e-mail address rhsbls debatable effectiveness since many spams either use forged addresses use addresses containing popular freemail domain names gmail.com yahoo.com hotmail.com uri dnsbls widely used rhsbls effective used majority spam filters operate dnsbl requires three things domain host nameserver domain list addresses publish possible serve dnsbl using general-purpose dns server software however typically inefficient zones containing large numbers addresses particularly dnsbls list entire classless inter-domain routing netblocks large resource consumption using software designed role domain name server role-specific software applications designed specifically servers role dns blacklist hard part operating dnsbl populating addresses dnsbls intended public use usually specific published policies listing means must operated accordingly attain sustain public confidence mail server receives connection client wishes check client dnsbl let say dnsbl.example.net less following looking address dnsbl thus similar looking reverse-dns differences dnsbl lookup uses rather ptr record type uses forward domain dnsbl.example.net rather special reverse domain in-addr.arpa informal protocol addresses returned dnsbl queries match dnsbls return address 127.0.0.0/8 ip loopback network address 127.0.0.2 indicates generic listing addresses block may indicate something specific listing—that indicates open relay proxy spammer-owned host etc details see rfc 5782 uri dnsbl query rhsbl query fairly straightforward domain name query prepended dns list host follows dnslist.example.com dns list host example.net queried domain generally record returned name listed different dnsbls different policies dnsbl policies differ one another three fronts addition different types listed entities ip addresses traditional dnsbls host domain names rhsbls uris uribls wide range semantic variations lists listing means list maintainers divided issues whether listings seen statements objective fact subjective opinion lists best used result definitive taxonomy dnsbls names defined e.g yellow nobl varieties widespread use names widespread use recognized many spam control specialists end-users organizations concerns regarding concept dnsbls specifics created used criticisms include despite criticisms people object principle mail-receiving sites able reject undesired mail systematically one person john gilmore deliberately operates open mail relay gilmore accuses dnsbl operators violating antitrust law number parties electronic frontier foundation peacefire raised concerns use dnsbls isps one joint statement issued group including eff peacefire addressed stealth blocking isps use dnsbls spam-blocking techniques without informing clients spammers pursued lawsuits dnsbl operators similar grounds
Computer security
livecode livecode formerly revolution metacard cross-platform rapid application development runtime environment inspired hypercard features transcript formerly metatalk programming language belongs family xtalk scripting languages like hypercard hypertalk environment introduced 2001 revolution development system based metacard engine technology runtime revolution later acquired metacard corporation 2003 platform macworld annual editor choice award best development software 2004 revolution renamed livecode fall 2010 livecode developed sold runtime revolution ltd. based edinburgh scotland march 2015 company renamed livecode ltd. unify company name product april 2013 free/open source version 'livecode community edition 6.0 published successful crowdfunding campaign kickstarter code base re-licensed made available free open source software version april 2013 livecode runs ios android os x windows 95 windows 10 raspberry pi several variations unix including linux solaris bsd used mobile desktop server/cgi applications ios iphone ipad version released december 2010 first version deploy web released 2009 widely used hypercard/hypertalk clone one runs major operating systems developer release v.8 announced new york march 12 2015 major enhancement product includes new separate development language known livecode builder capable creating new object classes called widgets earlier versions set object classes fixed could enhanced via use ordinary procedural languages c. new language runs ide departure transitional x-talk paradigm permits typing variables two environments fully integrated apart ability create new objects development livecode proceeds normal way within established ide second crowdfunding campaign bring html5 livecode reached funding goals nearly 400,000 usd july 31 2014 livecode developer release 8.0 dp4 august 31 2015 first include standalone deployment option html5 livecode software creates applications run many supported environments using compile-free workflow computer code livecode play across multiple devices platforms livecode uses high level english-like programming language called transcript dynamically typed transcript compile-free workflow generates code self-documenting easy casual programmers comprehend example following script executed system clock 9:00:00 ten lines loaded first text field denoted field 1 seen notes livecode natural english-like syntax easy beginners learn variables typeless typed compile time based purely context makes language simple read maintain relatively minimal loss speed language contains advanced features including associative arrays regular expressions multimedia support variety sql databases tcp/ip libraries livecode engine supports several common image formats including bmp png gif jpeg anti-aliased vector graphics html-style text hyperlinks chained behaviors embedded web browsers accessing higher-level functions designed straightforward livecode around 1,900 built-in language terms keywords may extended external libraries written c lower level languages livecode project files binary-compatible across platforms inherit platform look-and-feel behaviors buttons scroll bars progress bars menus behave expected target platform without intervention part one authoring livecode application compiling livecode standalone produces single executable file minimum size ~1.5mb platform targeted separate runtime necessary wikipedia article hypercard contains detailed discussion basics similar development environment scripting language modern livecode vast superset former hypercard yet retains simplicity livecode includes number features missing original hypercard program including multiple platform deployment communication external devices many fundamental language extensions livecode toolkit compared hypercard ability access internet-based text media resources allows creation internet-enabled desktop applications ios android targets available versions note complete linux requirements 4.5.x-6.x following
Programming language topics
lfe programming language lisp flavored erlang lfe functional concurrent garbage collected general-purpose programming language lisp dialect built core erlang erlang virtual machine beam lfe builds erlang provide lisp syntax writing distributed fault-tolerant soft real-time non-stop applications lfe also extends erlang support metaprogramming lisp macros improved developer experience feature-rich read–eval–print loop repl lfe actively supported recent releases erlang oldest version erlang supported r14 initial work lfe began 2007 robert virding started creating prototype lisp running erlang work focused primarily parsing exploring implementation might look like version control system used time tracking exact initial dates somewhat problematic virding announced first release lfe erlang questions mail list march 2008 release lfe limited handle recursive codice_1s codice_2s codice_3 codice_4 also support lisp shell initial development lfe done version r12b-0 erlang dell xps laptop robert virding stated several reasons started lfe programming language like lisp lfe expression-oriented language unlike non-homoiconic programming languages lisps make little syntactic distinction expressions statements code data written expressions lfe brought homoiconicity erlang vm lfe list data type written elements separated whitespace surrounded parentheses example list whose elements integers atom values implicitly typed respectively two integers lisp-specific data type called symbolic atom need declared seen example lfe expressions written lists using prefix notation first element list name form i.e. function operator macro remainder list arguments lfe-erlang operators used way expression evaluates 42 unlike functions erlang lfe arithmetic operators lisp variadic n-ary able take number arguments lfe lambda like common lisp also however lambda-match account erlang pattern-matching abilities anonymous function calls section represent complete comparison erlang lfe give taste erlang lfe erlang lfe idiomatic functional style erlang lfe erlang lfe using cons literal instead constructor form erlang lfe erlang lfe calls erlang functions take form module function arg1 ... argn using recursion define ackermann function defun ackermann composing functions message-passing erlang light-weight processes defmodule messenger-back multiple simultaneous http requests
Programming language topics
windows cardspace windows cardspace codenamed infocard microsoft now-canceled client software identity metasystem cardspace instance class identity client software called identity selector cardspace stores references users digital identities presenting users visual information cards cardspace provides consistent ui designed help people easily securely use identities applications web sites accepted resistance phishing attacks adherence kim cameron 7 laws identity goals design information card-enabled application website wishes obtain information user application website requests particular set claims user cardspace ui appears switching display cardspace service displays user stored identities visual i-cards user selects infocard use cardspace software contacts issuer identity obtain digitally signed xml token contains requested information cardspace also allows users create personal also known self-issued information cards contain one 14 fields identity information full name address etc transactions may require managed infocard issued third party identity provider makes claims person behalf bank employer government agency windows cardspace built top web services protocol stack open set xml-based protocols including ws-security ws-trust ws-metadataexchange ws-securitypolicy means technology platform supports ws-* protocols integrate cardspace order accept information cards website developer simply needs declare html codice_1 tag specifies claims website demanding user implement code decrypt returned token extract claim values identity provider wants issue tokens must provide means user obtain managed card provide security token service sts handles ws-trust requests returns appropriate encrypted signed token identity provider wish build sts able obtain one variety vendors including pingidentity bmc sun microsystems microsoft siemens well companies organizations cardspace identity metasystem upon based token-format-agnostic cardspace compete directly internet identity architectures like openid saml ways three approaches identity seen complementary indeed information cards used today signing openid providers windows live id accounts saml identity providers kinds services ibm novell planned support higgins trust framework provide development framework includes support information cards web services protocol stack thus including cardspace within broader extensible framework also supporting identity-related technologies saml openid microsoft initially shipped windows cardspace .net framework 3.0 runs windows xp windows server 2003 windows vista installed default windows vista well windows 7 available free download xp server 2003 via windows update updated version cardspace shipped .net framework 3.5 windows 7 cardspace technology used new credential manager management storage saved user credentials february 15 2011 microsoft announced windows cardspace 2.0 would shipped microsoft currently working replacement called u-prove
Web technology
captive ntfs captive ntfs discontinued open-source project within linux programming community started jan kratochvíl driver wrapper around original microsoft windows ntfs file system driver using parts reactos code taking approach captive ntfs aimed provide safe write support ntfs partitions release ntfs-3g free ntfs driver full write support january 26 2006 jan kratochvíl released version 1.1.7 package version restores compatibility recent linux kernels replacing obsolete lufs linux userland file system module fuse file system userspace linux 2.6.14 included official linux kernel captive ntfs requires ntfs.sys distributed legal reasons either obtained installed windows system computers ntfs partitions likely extracted certain microsoft service packs
Computer file systems
nonstop server computers nonstop series server computers introduced market 1976 tandem computers inc. beginning nonstop product line followed hewlett-packard integrity nonstop product line extension nonstop systems based integrated hardware/software stack hp also developed nonstop os operating system nonstop systems extent self-healing circumvent single points failure equipped almost redundant components mainline component fails system automatically falls back backup systems often used banks stock exchanges telecommunication providers enterprises requiring extremely high uptime originally introduced 1976 tandem computers inc. line later owned compaq 1997 hewlett-packard since 2003 2005 current product line hp integrity nonstop tns/e servers based intel itanium microprocessors introduced 2014 first systems nonstop x tns/x running intel x86 chip introduced early nonstop applications specifically coded fault-tolerance requirement removed 1983 introduction transaction monitoring facility tmf handles various aspects fault tolerance system level nonstop os message-based operating system designed fault tolerance works process pairs ensures backup processes redundant cpus take case process cpu failure data integrity maintained takeovers transactions data lost corrupted operating system whole branded nonstop os includes guardian layer low-level component operating system so-called oss personality runs atop layer implements unix-like interface components os use operating system application designed support fault tolerant hardware operating system continually monitors status components switching control necessary maintain operations also features designed software allow programs written continuously available programs accomplished using pair processes one process performs primary processing serves hot backup receiving updates data whenever primary reaches critical point processing primary stop backup steps resume execution using current transaction systems support relational database management systems like nonstop sql hierarchical databases enscribe hp integrity nonstop computers line fault-tolerant server computers based intel itanium processor platform optimized transaction processing average availability levels 99.999 observed nonstop systems feature massively parallel processing mpp architecture provide linear scalability cpu systems expanded 4000 cpus runs copy os shared-nothing architecture — share nothing arrangement also known loosely coupled multiprocessing diminishing returns occur processors added see amdahl law due integrated hardware/software stack single system image even largest configurations system management requirements nonstop systems rather low deployments single production server complex server farm customers also backup server remote location disaster recovery standard products keep data production backup server sync hence fast takeover data loss also disaster situation production server disabled destroyed hp also developed data warehouse business intelligence server line hp neoview based nonstop line acted database server providing nonstop os nonstop sql lacked transaction processing functionality original nonstop systems line retired longer marketed january 24 2011
Computer architecture
identity column identity column column also known field database table made values generated database much like autonumber field microsoft access sequence oracle concept important database science many rdbms systems implement type generated key although terminology identity column differs primary key values managed server usually modified many cases identity column used primary key however always case common misconception identity column enforce uniqueness however case want enforce uniqueness column must include appropriate constraint microsoft sql server options seed starting value increment default seed increment 1. often useful necessary know identity value generated insert command microsoft sql server provides several functions identity provides last value generated current connection current scope ident_current tablename provides last value generated regardless connection scope created example
Databases
branch predictor computer architecture branch predictor digital circuit tries guess way branch e.g if–then–else structure go known definitively purpose branch predictor improve flow instruction pipeline branch predictors play critical role achieving high effective performance many modern pipelined microprocessor architectures x86 two-way branching usually implemented conditional jump instruction conditional jump either taken continue execution first branch code follows immediately conditional jump taken jump different place program memory second branch code stored known certain whether conditional jump taken taken condition calculated conditional jump passed execution stage instruction pipeline see fig 1 without branch prediction processor would wait conditional jump instruction passed execute stage next instruction enter fetch stage pipeline branch predictor attempts avoid waste time trying guess whether conditional jump likely taken taken branch guessed likely fetched speculatively executed later detected guess wrong speculatively executed partially executed instructions discarded pipeline starts correct branch incurring delay time wasted case branch misprediction equal number stages pipeline fetch stage execute stage modern microprocessors tend quite long pipelines misprediction delay 10 20 clock cycles result making pipeline longer increases need advanced branch predictor first time conditional jump instruction encountered much information base prediction branch predictor keeps records whether branches taken taken encounters conditional jump seen several times base prediction history branch predictor may example recognize conditional jump taken often taken every second time branch prediction branch target prediction branch prediction attempts guess whether conditional jump taken branch target prediction attempts guess target taken conditional unconditional jump computed decoding executing instruction branch prediction branch target prediction often combined circuitry static prediction simplest branch prediction technique rely information dynamic history code executing instead predicts outcome branch based solely branch instruction early implementations sparc mips two first commercial risc architectures used single-direction static branch prediction always predict conditional jump taken always fetch next sequential instruction branch jump evaluated found taken instruction pointer get set non-sequential address cpus evaluate branches decode stage single cycle instruction fetch result branch target recurrence two cycles long machine always fetches instruction immediately taken branch architectures define branch delay slots order utilize fetched instructions advanced form static prediction presumes backward branches taken forward branches backward branch one target address lower address technique help prediction accuracy loops usually backward-pointing branches taken often taken processors allow branch prediction hints inserted code tell whether static prediction taken taken intel pentium 4 accepts branch prediction hints feature abandoned later intel processors static prediction used fall-back technique processors dynamic branch prediction dynamic predictors sufficient information use motorola mpc7450 g4e intel pentium 4 use technique fall-back static prediction decisions made compile time execution program dynamic branch prediction uses information taken taken branches gathered run-time predict outcome branch using random pseudorandom bit pure guess would guarantee every branch 50 correct prediction rate improved worsened reordering instructions simplest static prediction assume take compilers reorder instructions get better 50 correct prediction also would make timing much nondeterministic superscalar processors mips r8000 alpha 21264 alpha 21464 ev8 fetch line instructions pointer next line next-line predictor handles branch target prediction well branch direction prediction next-line predictor points aligned groups 2 4 8 instructions branch target usually first instruction fetched initial instructions fetched wasted assuming simplicity uniform distribution branch targets 0.5 1.5 3.5 instructions fetched discarded respectively since branch generally last instruction aligned group instructions taken branch delay slot discarded assuming uniform distribution branch instruction placements 0.5 1.5 3.5 instructions fetched discarded discarded instructions branch destination lines add nearly complete fetch cycle even single-cycle next-line predictor 1-bit saturating counter essentially flip-flop records last outcome branch simple version dynamic branch predictor possible although accurate 2-bit saturating counter state machine four states branch evaluated corresponding state machine updated branches evaluated taken change state toward strongly taken branches evaluated taken change state toward strongly taken advantage two-bit counter scheme one-bit scheme conditional jump deviate twice done past prediction changes example loop-closing conditional jump mispredicted rather twice original non-mmx intel pentium processor uses saturating counter though imperfect implementation spec'89 benchmarks large bimodal predictors saturate 93.5 correct every branch maps unique counter predictor table indexed instruction address bits processor fetch prediction every instruction instruction decoded two-level branch predictor also referred correlation-based branch predictor uses two-dimensional table counters also called pattern history table table entries two-bit counters codice_1 statement executed three times decision made third execution might depend upon whether previous two taken scenarios two-level adaptive predictor works efficiently saturation counter conditional jumps taken every second time regularly recurring pattern predicted well saturating counter two-level adaptive predictor remembers history last n occurrences branch uses one saturating counter possible 2 history patterns method illustrated figure 3 consider example n 2 means last two occurrences branch stored two-bit shift register branch history register four different binary values 00 01 10 11 zero means taken one means taken pattern history table contains four entries per branch one 2 4 possible branch histories entry table contains two-bit saturating counter type figure 2 branch branch history register used choosing four saturating counters use history 00 first counter used history 11 last four counters used assume example conditional jump taken every third time branch sequence 001001001 ... case entry number 00 pattern history table go state strongly taken indicating two zeroes comes one entry number 01 go state strongly taken indicating 01 comes zero case entry number 10 entry number 11 never used never two consecutive ones general rule two-level adaptive predictor n-bit history predict repetitive sequence period n-bit sub-sequences different advantage two-level adaptive predictor quickly learn predict arbitrary repetitive pattern method invented t.-y yeh yale patt university michigan since initial publication 1991 method become popular variants prediction method used modern microprocessors local branch predictor separate history buffer conditional jump instruction may use two-level adaptive predictor history buffer separate conditional jump instruction pattern history table may separate well may shared conditional jumps intel pentium mmx pentium ii pentium iii local branch predictors local 4-bit history local pattern history table 16 entries conditional jump spec'89 benchmarks large local predictors saturate 97.1 correct global branch predictor keep separate history record conditional jump instead keeps shared history conditional jumps advantage shared history correlation different conditional jumps part making predictions disadvantage history diluted irrelevant information different conditional jumps uncorrelated history buffer may include bits branch many branches may use two-level adaptive predictor scheme better saturating counter scheme large table sizes rarely good local prediction history buffer must longer order make good prediction size pattern history table grows exponentially size history buffer hence big pattern history table must shared among conditional jumps two-level adaptive predictor globally shared history buffer pattern history table called gshare predictor xors global history branch pc gselect concatenates global branch prediction used amd processors intel pentium core core 2 silvermont-based atom processors alloyed branch predictor combines local global prediction principles concatenating local global branch histories possibly bits program counter well tests indicate via nano processor may using technique agree predictor two-level adaptive predictor globally shared history buffer pattern history table additional local saturating counter outputs local global predictors xored give final prediction purpose reduce contentions pattern history table two branches opposite prediction happen share entry pattern history table agree predictor used first version intel pentium 4 later abandoned hybrid predictor also called combined predictor implements one prediction mechanism final prediction based either meta-predictor remembers predictors made best predictions past majority vote function based odd number different predictors scott mcfarling proposed combined branch prediction 1993 paper spec'89 benchmarks predictor good local predictor predictors like gshare use multiple table entries track behavior particular branch multiplication entries makes much likely two branches map table entry situation called aliasing turn makes much likely prediction accuracy suffer branches multiple predictors beneficial arrange predictor different aliasing patterns likely least one predictor aliasing combined predictors different indexing functions different predictors called gskew predictors analogous skewed associative caches used data instruction caching conditional jump controls loop best predicted special loop predictor conditional jump bottom loop repeats n times taken n-1 times taken conditional jump placed top loop taken n-1 times taken conditional jump goes many times one way way detected loop behavior conditional jump predicted easily simple counter loop predictor part hybrid predictor meta-predictor detects whether conditional jump loop behavior indirect jump instruction choose among two branches processors specialized indirect branch predictors newer processors intel amd predict indirect branches using two-level adaptive predictor kind instruction contributes one bit history buffer zec12 later z/architecture processors ibm support instruction preload branch predictor entry given instruction branch target address constructed adding contents general-purpose register immediate displacement value processors without mechanism simply predict indirect jump go target last time function normally return called return instruction indirect jump reads target address call stack many microprocessors separate prediction mechanism return instructions mechanism based so-called return stack buffer local mirror call stack size return stack buffer typically 4 16 entries trade-off fast branch prediction good branch prediction sometimes dealt two branch predictors first branch predictor fast simple second branch predictor slower complicated bigger tables override possibly wrong prediction made first predictor alpha 21264 alpha ev8 microprocessors used fast single-cycle next-line predictor handle branch target recurrence provide simple fast branch prediction next-line predictor inaccurate branch resolution recurrence takes long cores two-cycle secondary branch predictors override prediction next-line predictor cost single lost fetch cycle intel core i7 two branch target buffers possibly two branch predictors machine learning branch prediction using lvq multi-layer perceptrons called neural branch prediction proposed lucian vintan lucian blaga university sibiu one year later developed perceptron branch predictor neural branch predictor research developed much daniel jimenez 2001 first perceptron predictor presented feasible implement hardware first commercial implementation perceptron branch predictor amd piledriver microarchitecture main advantage neural predictor ability exploit long histories requiring linear resource growth classical predictors require exponential resource growth jimenez reports global improvement 5.7 mcfarling-style hybrid predictor also used gshare/perceptron overriding hybrid predictors main disadvantage perceptron predictor high latency even taking advantage high-speed arithmetic tricks computation latency relatively high compared clock period many modern microarchitectures order reduce prediction latency jimenez proposed 2003 fast-path neural predictor perceptron predictor chooses weights according current branch path rather according branch pc many researchers developed concept a. seznec m. monchiero d. tarjan k. skadron v. desmet akkary et al. k. aasaraai michael black etc state-of-the-art branch predictors using perceptron predictor see intel championship branch prediction competition intel already implements idea one ia-64 simulators 2003 amd ryzen multi-core processor infinity fabric samsung exynos processor include perceptron based neural branch predictor ibm 7030 stretch designed late 1950s pre-executes unconditional branches conditional branches depended index registers conditional branches first two production models implemented predict untaken subsequent models changed implement predictions based current values indicator bits corresponding today condition codes stretch designers considered static hint bits branch instructions early project decided misprediction recovery provided lookahead unit stretch part stretch reputation less-than-stellar performance blamed time required misprediction recovery subsequent ibm large computer designs use branch prediction speculative execution ibm 3090 1985 two-bit predictors introduced tom mcwilliams curt widdoes 1977 lawrence livermore national lab s-1 supercomputer independently jim smith 1979 cdc microprogrammed processors popular 1960s 1980s beyond took multiple cycles per instruction generally require branch prediction however addition ibm 3090 several examples microprogrammed designs incorporated branch prediction burroughs b4900 microprogrammed cobol machine released around 1982 pipelined used branch prediction b4900 branch prediction history state stored back in-memory instructions program execution b4900 implements 4-state branch prediction using 4 semantically equivalent branch opcodes represent branch operator type opcode used indicated history particular branch instruction hardware determines branch prediction state particular branch needs updated rewrites opcode semantically equivalent opcode hinted proper history scheme obtains 93 hit rate others granted scheme vax 9000 announced 1989 microprogrammed pipelined performs branch prediction first commercial risc processors mips r2000 r3000 earlier sparc processors trivial not-taken branch prediction use branch delay slots fetched one instruction per cycle execute in-order performance loss later r4000 uses trivial not-taken branch prediction loses two cycles taken branch branch resolution recurrence four cycles long branch prediction became important introduction pipelined superscalar processors like intel pentium dec alpha 21064 mips r8000 ibm power series processors rely one-bit simple bimodal predictors dec alpha 21264 ev6 uses next-line predictor overridden combined local predictor global predictor combining choice made bimodal predictor amd k8 combined bimodal global predictor combining choice another bimodal predictor processor caches base choice bimodal predictor counters bits l2 cache otherwise used ecc result effectively large base choice predictor tables parity rather ecc instructions l2 cache parity design sufficient since instruction suffering parity error invalidated refetched memory alpha 21464 ev8 cancelled late design minimum branch misprediction penalty 14 cycles use complex fast next-line predictor overridden combined bimodal majority-voting predictor majority vote bimodal two gskew predictors 2018 catastrophic security vulnerability called spectre made public google project zero researchers affecting virtually modern cpus vulnerability involves extracting private data leftover data caches branch mispredictions
Computer architecture
snatcher video game snatcher cyberpunk graphic adventure game developed published konami written designed hideo kojima first released 1988 pc-8801 msx2 japan snatcher set future east asian metropolis humanoid robots dubbed snatchers discovered killing humans replacing society player takes role gillian seed amnesiac joins snatcher hunting agency hoping help remember past gameplay takes place primarily menu-based interface player choose examine items search rooms speak characters explore semi-open world perform actions kojima wanted snatcher cinematic feel setting story heavily influenced science fiction films especially blade runner cyberpunk works akira terminator development pc versions took twice long average game time even kojima asked trim half initial story game released positive reviews poor sales garnered cult following remade role-playing game called sd snatcher msx2 1990 followed remake original adventure game using cd-rom technology released pc engine super cd-rom² system 1992 looking provide interactive experience gamers west konami developed sega cd version snatcher specifically north america europe 1994 although released poor commercial reception sega cd version received mostly positive reviews cinematic presentation mature themes uncommon games time snatcher retrospectively acclaimed one best adventure cyberpunk games time identified foundation themes kojima explored later metal gear series game significant inspiration goichi suda worked kojima produce radio drama prequel sdatcher english version snatcher never rereleased despite desire fans snatcher graphic adventure game visual novel elements player takes role protagonist gillian seed investigates hunts snatchers dangerous humanoid robots disguised humans roaming neo kobe city game visuals static images animations display top screen point-and-click interface actions made text menu commands move look investigate game puzzles dialogue trees simple lending emphasis linear storytelling sometimes character panels shown main graphics window conversations convey facial expressions game allows exploration semi-open world handful action segments player shoots enemies dispersed across 3x3 grid sega cd version supports justifier light gun packaged lethal enforcers segments snatcher set mid-21st century fifty years biological weapon known lucifer-alpha killed much world population neo kobe city metropolis artificial island eastern asia humanoid robots dubbed snatchers recently discovered killing humans donning skin disguise replacing society neo kobe government closes city outside world establishes junker task force hunt snatchers player takes role gillian seed amnesiac remember past somehow related snatchers starts working junker hopes hunting snatchers bring past light gillian seed arrives junker headquarters introduced chief cunningham receives robot navigator named metal gear junker engineer harry benson metal gear receives distress call jean-jack gibson junker agent gillian travels metal gear find pair snatchers killed try pursue snatchers forced make quick escape factory explodes gillian begins searching identity snatchers murdered jean-jack searching house speaking informant gillian identifies pair suspects hunting snatchers nearly killed saved random hajile snatcher bounty hunter random joins gillian metal gear travel hospital jean-jack identified suspicious investigation learn abandoned several years harbors secret basement find skeletons snatcher victims among find chief cunningham meaning junker chief snatcher snatchers attack group random distracts allow gillian metal gear escape back junker headquarters gillian kills chief speaks harry briefly dies mortally wounded chief immediately gillian receives call estranged wife jamie telling held kremlin gillian metal gear travel abandoned church resembling kremlin find jamie held captive scientist named elijah modnar explains gillian past father jamie involved secret experiment taken soviet union 50 years prior cold war create snatchers designed kill replace world leaders giving soviets power gillian cia agent spying project married jamie child harry benson gillian jamie placed cryogenic sleep elijah released lucifer-alpha atmosphere pair saved army lost memories due extended period time frozen become corrupt power elijah reveals intends snatchers wipe replace humanity proof mankind follies also reveals random anti-snatcher created late father based elijah appearance memories presents deactivated body point random reactivates holds elijah bay allowing gillian jamie escape metal gear activates orbital weapon destroys snatcher base killing elijah random learned larger snatcher factory moscow gillian prepares embark mission hope finally destroying snatcher menace rekindling romance jamie snatcher created hideo kojima working konami heavily influenced blade runner 1982 works cinema wanted develop game similar style game pitched cyberpunk adventure kojima found difficult explain meaning cyberpunk konami trademark department phone game originally titled junker name sounded similar existing mahjong game title new order also considered kojima like final name previous game metal gear 1987 also named enemy game development began kojima character designer tomiharu kinoshita treated project like making film anime rather game expanded form small team konami half size needed typical famicom game allowed work closely quickly game filled science fiction culture references skirt copyright laws kojima told kinoshita make gillian similar katsuhiro otomo director science fiction film akira 1988 team never aimed game mature atmosphere naturally progressed direction addition fourth wall breaking dialogue game kojima wanted print secret message heat-activated scent floppy disks could noticed warming disk drive konami approve idea year half snatcher half completed originally kojima planned six chapters told trim two team wanted create third chapter already allowed development schedule forced end game cliffhanger development took two three times longer average game difficulties memory constraints prompted staff take break development time kojima began explore concepts later game policenauts 1994 originally snatcher going pc-8801 exclusive also developed msx2 request konami pc-8801 version supports fm stereo sounds via pc-8801 sound board ii expansion card msx2 version came special cartridge provided expanded soundscape beyond platform default capabilities extra ram featuring different music track arrangements expansion cartridge raised price msx2 version beyond pc-8801 version reverse platform typically cheaper retail game pricing quantity music sound greater games time required larger usual sound team neither platform capable accurately synthesizing speech sound effects used represent character dialogue snatcher released pc-8801 november 26 1988 msx2 december year players began asking home console version soon release game large required several floppy disks cd-rom systems considered opposed systems ran rom cartridges pc engine super cd-rom² system available chosen host snatcher console port port first time development team worked cd technology team added third act version decision criticized internally others believed game already long enough using cd technology enabled add recorded speech high quality background music artist satoshi yoshioka created graphics version kojima wanted visuals appear cinematic possible yoshioka pulled inspiration blade runner terminator 1984 alien 1979 replicate hollywood-style special effects used custom drawing application konami create character graphics including facial expressions conversations found gillian expressions difficult animate due complexities characterization trial version called pilot disk released august 7 1992 covers beginning first act also contains supplemental content character introductions preview trailer select music tracks full version released october 23 1992 reportedly sold well pc engine game releasing first game sega cd lethal enforcers 1992 konami wanted bring interactive experience system western players considered making game full motion video like night trap 1992 thought may difficult ultimately decided localize port snatcher also gave snatcher developers opportunity improve upon pc engine version still completely satisfied although sega cd could display 64 colors simultaneously compared pc engine 256 team used software techniques increase 112 modified palettes compromise several scenes censored otherwise altered sega cd release woman breasts covered 14-year-old girl shown standing naked shower obscured age changed 18 options allowed gillian engage behaviors related sexual harassment removed toned allowed sniff panties stare breasts audio robot becomes aroused watching pornographic film cut entirely violence altered except one scene partially dead dog twitching innards made completely dead twitching fearing copyright issues united states clientele bar changed kamen rider alien characters konami characters feeling third act movie-like konami added interactivity additional forks choices additionally player graded well solved mysteries dates events game also moved five years still occur near future compensate late release game translated scott hards supervision jeremy blaustein konami japan translation took two three months seven voice actors recorded two half hours dialogue 26 different characters large amount text included game translation expensive konami felt difficult part porting process according blaustein kojima involved sega cd port likely working policenauts time snatcher released december 1994 europe january 1995 north america according blaustein sold couple thousand copies united states ultimately commercial failure poor sales attributed late release sega cd lifespan snatcher released japan 1996 time 32-bit game consoles playstation version released january 26 followed sega saturn version march 29 pc-8801 msx2 versions received positive reviews japan attained cult following commercially successful pc engine version also attained following japan part gore famicom tsushin gave 33 40 commending cinematic quality game still listed reader best 20 list two years release sega saturn magazine found sega saturn version faithful port pc engine version snatcher arrived west sega cd received praise story cinematic presentation mature themes cinematic told mature story gamers familiar time mean machines sega felt snatcher substantial adventure games calling one involved storyboards backgrounds video game game writing generally lauded videogames game players felt juvenile humor sometimes conflicted otherwise serious tone reviewer gamefan called one longest involving games played long time wrote never played – nay experienced – game moving dramatic gore-riddled ma-17 adult magazine praised konami retaining mature content mean machines sega believed snatcher presentation heightened use cd-rom technology supported digitized voices high quality graphics critics praised english voice acting writing though next generation thought konami could contracted better actors graphics criticized computer video games dated videogames generic magazines discussed graphics positive light gamepro liked japanese anime style graphics felt combined writing drew players story however reviewer criticized music calling old-fashioned cyberpunk adventure mean machines sega compared positively john carpenter-style incidental themes critics felt game slow moving times rewarded patient players gamepro wrote rewards patience persistence plodding ultimate future games felt game linear leaned heavily illusion choice story could advanced completing tasks certain order mean machines sega felt puzzles challenging game considerably longer substantial rise dragon 1990 another cyberpunk adventure game computer video games felt gun shooting sections weak disappointing snatcher called one best adventure games best cyberpunk games time continued receive praise story presentation waypoint wrote narrative visuals hold contrast sega cd cyberpunk adventure games kotaku called science fiction cornucopia liked game explored topics human existence fear machines replacing humans felt game heavily influenced science fiction films including blade runner terminator akira invasion body snatchers 1956 publications also picked inspirations especially blade runner retro gamer felt ironic game cinematic games using full motion video destructoid enjoyed plot complained interface allgame wrote text-based menu driven games like snatcher become tedious felt storyline graphics made snatcher worth time critics discussed snatcher setting stage kojima later works 1up.com felt game demonstrated love film cerebral affair efforts ingenuity attention detail helped make game especially noteworthy game informer wrote snatcher foreshadowed kojima use science fiction explore philosophy sex human condition metal gear solid snatcher remains one kojima renowned games often overshadowed metal gear solid series snatcher obtained cult following influence science fiction works including project itoh novel genocidal organ 2015 adventure game kojima expressed interest reviving snatcher capacity explained time work project would welcome another director lead according project never feasible business perspective 2011 said sequel would need sell half million copies make sense financially kojima left konami 2015 game remains property company expressed interest reviving either rerelease sequel game lack availability modern platforms surprised critics believed would play well nintendo ds 3ds following footsteps successful graphic adventures platforms like sega cd version remains sole release western territories demand driven prices copies secondary market making emulation reasonable option players japanese copies far cheaper game text-based nature makes difficult non-japanese readers japanese pc engine version included turbografx-16 mini fans experimented porting game systems demo early part game made virtual boy 2015 complete stereoscopic 3d effects pcm music another fan experimented porting dreamcast remixed soundtrack retouched visuals snatcher first translation project jeremy blaustein went translate kojima metal gear solid 1998 blaustein launched crowdfunding campaign kickstarter steampunk adventure game titled blackmore 2014 game directed blaustein former snatcher staff making parts team meet funding goal snatcher remade role-playing game called sd snatcher msx2 released 1990 sd stands super deformed japanese media another way reference chibi character designs game plays top-down perspective player controls gillian ventures environment player encounters enemy field game shifts first-person battle mode player must shoot enemies using one many different guns different parts enemy targeted different weapons varying abilities ranges outside key plot points game significantly changes locations explored events transpired original game also concludes story similar manner cd-rom versions like msx2 version snatcher sd snatcher shipped expanded sound cartridge translated dutch-based group oasis 1993 making one earliest documented fan translations episodic radio drama prequel sdatcher released 2011 collaboration kojima game designer goichi suda suda credited snatcher along works yu suzuki igniting interest video games asked kojima wanted make new game together project lead radio drama announced 2007 script written suda music composed akira yamaoka worked suda grasshopper manufacture studio worked silent hill series original snatcher artist satoshi yoshioka promotional illustrations first act released september new acts released every week november year distributed free later sold cds later translated fans
Computer architecture
reliability availability serviceability reliability availability serviceability ras computer hardware engineering term involving reliability engineering high availability serviceability design phrase originally used international business machines ibm term describe robustness mainframe computers computers designed higher levels ras many features protect data integrity help stay available long periods time without failure data integrity uptime particular selling point mainframes fault-tolerant systems ras originated hardware-oriented term systems thinking extended concept reliability-availability-serviceability systems general including software note distinction reliability availability reliability measures ability system function correctly including avoiding data corruption whereas availability measures often system available use even though may functioning correctly example server may run forever ideal availability may unreliable frequent data corruption physical faults temporary permanent transient intermittent faults typically handled detection correction e.g. ecc codes instruction replay see permanent faults lead uncorrectable errors handled replacement duplicate hardware e.g. processor sparing passing uncorrectable error high level recovery mechanisms successfully corrected intermittent fault also reported operating system os provide information predictive failure analysis example hardware features improving ras include following listed subsystem fault-tolerant designs extended idea making ras defining feature computers applications like stock market exchanges air traffic control system crashes would catastrophic fault-tolerant computers e.g. see tandem computers stratus technologies tend duplicate components running lock-step reliability become less popular due high cost high availability systems using distributed computing techniques like computer clusters often used cheaper alternatives
Computer architecture
william j. barry william john barry born 1943 ireland one leading phoneticians germany came germany early years mainly educated university kiel renowned german phonetician klaus j. kohler 1992 appointed chair phonetics saarland university principal research areas speech synthesis rhythm segmental structures application linguistics questions pronunciation learning speech-language pathology speech technology general william j. barry innovative productive research close cooperation institute computational linguistics saarland university well german research center artificial intelligence also saarbruecken made saarbruecken institute phonetics outstanding pillar science europe 2007 w. j. barry held chair 16th international congress phonetic sciences icphs became emeritus professor 2008 barry currently council member international phonetic association editor phonus journal publications resulted cooperation researchers
Computational linguistics
fdformat fdformat name two unrelated programs
Computer file systems
unlink unix unix-like operating systems unlink system call command line utility delete files program directly interfaces system call removes file name gnu systems directories like rm rmdir file name last hard link file file deleted soon program open also appears php node.js perl standard libraries form unlink built-in function like unix utility also used delete files delete file named foo one could type php one could use following function perl syntax identical php syntax save parentheses node.js almost others
Computer architecture
mediatek mediatek inc. taiwanese fabless semiconductor company provides chips wireless communications high-definition television handheld mobile devices like smartphones tablet computers navigation systems consumer multimedia products digital subscriber line services well optical less disc drives headquartered hsinchu taiwan company 25 offices worldwide third largest fabless ic designer worldwide 2016 since founding 1997 mediatek creating chipsets global market mediatek also provides customers reference designs mediatek originally unit united microelectronics corporation umc tasked designing chipsets home entertainment products 28 may 1997 unit spun incorporated mediatek inc. listed taiwan stock exchange tsec 2454 code 23 july 2001 company started designing chipsets optical drives subsequently expanded chips dvd players digital tvs mobile phones smartphones tablets general mediatek strong record gaining market share displacing competitors entering new markets company launched division design products mobile devices 2004 seven years later taking orders 500 million mobile system-on-chip units per annum included products feature phones smart devices providing extensive system engineering assistance company allowed many smaller companies new entrants enter mobile phone market previously dominated large often vertically integrated corporations long broadly entrenched telecommunications industry mobile chip market quickly became main growth driver company mobile world congress 2014 mediatek unveiled new brand “ everyday genius ” dubbing term “ super-mid market ” vision aiming make smartphones accessible affordable wider market november 2014 1500 mobile models accounting 700 million units shipped globally 2014 using mediatek chips company posted revenues us 5.3 billion first half 2014 nearly much whole 2013 revenue growth however partly due revenue recognition acquisition mstar became effective beginning 2014 2005 mediatek acquired inprocomm wireless semiconductor design company producing 802.11a b a/g chips september 10 2007 mediatek announced intention buy analog devices cellular radio baseband chipset divisions us 350 million acquisition finalised january 11 2008 5 may 2011 mediatek acquired ralink technology corporation gaining products expertise wi-fi technology mobile non-mobile applications well wired dsl ethernet connectivity 11 april 2012 mediatek acquired coresonic global producer digital signal processing products based linköping sweden coresonic became wholly owned subsidiary mediatek europe 22 june 2012 mediatek announced would acquire rival taiwanese chipset designer mstar semiconductor inc. held strong market share position digital television chips initial phase deal saw mediatek taking 48 percent stake option purchase remaining stake later date following merger mediatek mstar delayed antitrust concerns china south korea finalized 1 february 2014 mediatek financial results subject variation financial success different product lines fluctuated mediatek relatively strong sales 2009/2010 based strong market position feature phone chipsets smartphone tablet products contributed mediatek sales income increase 2013 revenue recognition acquisition mstar semiconductor became effective february 2014 well continuing strong position smartphone tablet solutions main reasons sales growth seen 2014 2014 smartphone chips accounted approximately 50–55 revenue followed digital home products 25–30 includes digital television chips tablet chips 5–10 feature phone chips 5–10 wi-fi products 5–10 mediatek started shipping chips integrated 4g lte baseband volume second half 2014 later largest competitor qualcomm additional cost separate baseband chip required every 4g handset made mediatek offerings expensive prompted larger customers like alcatel one touch zte choose competing socs like qualcomm snapdragon 400 410 platforms negatively affecting mediatek revenue stream mediatek stock trading taiwan stock exchange symbol mediatek often followed industry-first strategy differentiate competition mt8135 system-on-chip soc tablets announced july 2013 industry first chip implement new arm big.little technology heterogeneous multi-processing variant mt8135 used amazon kindle fire hd tablet models also november 20 2013 mediatek launched mt6592 soc first system-on-chip soc eight cpu cores could used simultaneously contrast competing socs eight physical cores subset could active given time true octa-core trademark registered emphasize difference marketing materials 7 january 2014 mediatek announced development world first multimode receiver wireless charging contrast existing implementations compatible inductive resonant charging resulting mt3188 wireless charging chip certified power matters alliance wireless power consortium announced february 24 2014 25 february 2014 mediatek announced industry first five-in-one wireless chip soc mt6630 supports 802.11a/b/g/n/ac wifi bluetooth ant+ gps fm radio mediatek collaborated google first ultra hd tv platform android tv resulting development mt5595 digital television soc product first shipped lcd tv models made sony list devices using mediatek socs armv5 list devices using mediatek socs armv7 dual core list devices using mediatek socs armv7 quad core list devices using mediatek socs armv7 hexa core list devices using mediatek socs armv8 quad core list devices using mediatek socs armv8 octa core list devices using mediatek tablet processors consumer electronics show january 2015 mediatek announced mt2601 wearable devices based google ’ android wear software according mediatek small size allows fewer components lower current consumption compared chipsets market chip includes dual-core arm cortex-a7 cpu arm mali-400 mp gpu allows display resolutions qhd 960x540 combined mt6630 chip wireless connectivity mediatek mt2621 mt2625 two soc build lte nb-iot modems mt2625 launched 29 june 2017 mt2621 added 24 november mt6630 2014 five-in-one combo wireless soc integrating dual-band 802.11a/b/g/n/ac advanced wi-fi direct miracast support bluetooth 4.1 ant+ tri-band gps fm transceiver intended paired chips like mt6595 octa-core smartphone processor features integrated 4g modem built-in wi-fi/bluetooth/gps/fm functionality could also used tablets conjunction stand-alone application processor global navigation satellite system gnss modules result merger ralink mediatek added wireless network interface controllers ieee 802.11-standards socs mips cpus product portfolio consumer electronics show january 2015 mediatek announced mt5595 new digital television soc support google android tv platform adopted sony new lcd tv models
Computer architecture
link-local multicast name resolution link-local multicast name resolution llmnr protocol based domain name system dns packet format allows ipv4 ipv6 hosts perform name resolution hosts local link included windows vista windows server 2008 windows 7 windows 8 windows 10 also implemented systemd-resolved linux llmnr defined rfc 4795 responding queries responders listen udp port 5355 following link-scope multicast address responders also listen tcp port 5355 unicast address host uses respond queries
Internet protocols
real-time recovery information technology real-time recovery ability recover piece infrastructure server infrastructure failure human-induced error time frame minimal impact business operations real-time recovery focuses appropriate technology restores thus reducing recovery time objective rto minutes recovery point objectives rpo within 15 minutes ago minimizing test recovery objectives tro ability test validate backups occurred correctly without impacting production systems real-time recovery new market segment backup recovery disaster recovery market addresses challenges companies historically faced regards protecting importantly recovering data real-time recovery solution must contain minimum following attributes ability restore server minutes totally different virtual environment within 5 minutes ago require use additional agents options modules accomplish must able restore files seconds reason anyone backups able restore must perform sector level backups every 5 minutes ability self-heal broken incremental chain backups part image set get corrupted deleted must deliver improved recoverability data files databases data loss classified three broad categories data servers either physical hosts servers running guest servers within virtualization platform combination common customer environment mixture virtual physical servers attention detail must given approach protecting data servers regular intervals distinct advantages selecting technology virtual physical independent would limit number technologies organizations get trained skilled purchase deploy manage maintain ideal world reduce complexity managing multiple products protect physical virtual infrastructure reap rewards technology gets installed operating system level ensures consistency environment either physical virtual eliminates api compatibility disk volume structure limitations e.g raw mapped devices vmfs prior selecting realtime recovery strategy real-time recovery rtr solution disaster recovery planner refer organization business continuity plan indicate key metrics recovery point objective rpo recovery time objective recovery time objective various business processes process run payroll generate order e-mail etc. metrics specified business processes must mapped underlying systems infrastructure support processes recovery time objective recovery point objective metrics mapped infrastructure dr planner determine suitable recovery strategy system important note however business ultimately sets budget therefore rto rpo metrics need fit available budget business unit heads would like zero data loss zero time loss cost associated level protection historically made high availability solutions impractical unaffordable benefit implementing real-time recovery solution investment substantially reduced traditional tape based backup products
Computer security
dreamwidth dreamwidth online journal service based livejournal codebase code fork original service set ex-livejournal staff denise paolucci mark smith born desire new community based open access transparency freedom respect dreamwidth announced 11 june 2008 went open beta 30 april 2009 part features similar livejournal users journals may post entries webpage users may comment dreamwidth also provides shared group journals called communities areas dreamwidth differs significantly livejournal include following initially dreamwidth accounts could created invite code december 2011 invite codes turned originally experimental temporary measure significant increase spam accounts servers adjusted handle load invite codes turned back start new year planned new users still create account without use invite code free accounts limited features paid accounts exist two levels paid premium paid additional features time open beta launch limited number seed accounts also available response criticisms livejournal friending system dreamwidth split user relationships two parts subscriptions access control users may subscribe users journals grant access users read locked entries separate actions dreamwidth terminology reflects split instance friends page renamed reading page custom friends groups split access filters reading filters dreamwidth provides greater interoperability livejournal-based sites including ability import journal another site crosspost multiple sites greater functionality users log via openid addition search facilities brought livejournal paid account users search journal introduced 24 july 2009 livejournal initially free advertisements gradually incorporated 2017 ads shown non-paid readers pages dreamwidth remains free advertisements following features available livejournal available dreamwidth despite lack features dreamwidth acclaimed strong community transparency dreamwidth based upon free open-source server software designed run livejournal written primarily perl majority dreamwidth code available gpl sites use unlike many social networking sites using livejournal codebase insanejournal deadjournal dreamwidth code fork removing unwanted features advertising adding new ones described founders site rejected advertising model intrusive instead implemented payment system users purchase add-on premium features 2009 oscon presentation saw dreamwidth identified highly unusual among open-source projects number women development team 75 developers female compared around 1.5 field whole paolucci smith also spoke linux.conf.au 2010 dreamwidth development model invited speak web 2.0 expo oscon techniques dreamwidth accepted gsoc mentoring organization summer 2010 allotted seven students worked variety projects athena also known afuna fu introduced site first paid employee 7 april 2010 7 september 2010 mark smith announced stepped back dreamwidth front line moved work stumbleupon still owner dreamwidth along denise however following positive reactions dreamwidth diversity statement model inclusiveness various projects followed suit including python diversity list dreamfish
Web technology
emm386 name emm386 used expanded memory managers microsoft ms-dos ibm pc dos digital research dr-dos created expanded memory using extended memory intel 80386 cpus also emm386.exe available freedos emm386.exe map memory unused blocks upper memory area uma allowing device drivers tsrs loaded high preserving conventional memory technique probably first appeared development cemm included compaq ms-dos 3.31 1987 microsoft version first appeared built-in windows/386 2.1 1988 standalone emm386.sys ms-dos 4.01 1989 flexible emm386.exe version appeared ms-dos 5.0 1991 expanded memory managers emm386 uses processor virtual 8086 mode forces memory accesses made dos applications go processors mmu introduced 386 page table entries used mmu configured emm386 map certain regions upper memory areas extended memory obtained emm386 extended memory manager himem.sys technique enabled ems expanded memory well umbs appear dos applications memory upper area fact mapped physical memory locations beyond 1mb temporarily shuts windows session 386 enhanced mode windows protected mode kernel taking role windows uses gemmis api take memory management emm386.exe global emm import specification gemmis supported via document available select number memory-manager vendors windows/386 paging import specification memory managers implemented gemmis api ones include emm386.exe quarterdeck qemm386.sys dosbox builtin dos notably missing freedos memory managers freedos memory managers himemx.exe jemm386.exe jemmex.exe implement gemmis api windows fails start running conjunction jemmxxx since windows fails take memory management role windows windows 98 windows 95 windows workgroups 3.1x windows 3.xx fail jemmxxx displaying jemmxx possible run windows 3.x windows workgroups 3.1x limited capabilities forcing windows use standard mode i.e using 80286 protected mode 80386 enhanced mode three conditions required note windows standard mode limited functionality lacks virtual memory skips 386enh section system.ini device drivers 386enh loaded
Computer architecture
compute node linux compute node linux cnl runtime environment based linux kernel cray xt3 cray xt4 cray xt5 cray xt6 cray xe6 cray xk6 supercomputer systems based suse linux enterprise server cnl forms part cray linux environment systems running cnl ranked 3rd 6th 8th among fastest supercomputers world
Computer architecture
mks vir mks_vir formerly mks_vir – polish antivirus program created marek sell 1987 original reason creation software solutions existing market times satisfy author needs first versions dos distributed floppy disks apexim company marek sell worked updates issued monthly sent mail initially software delivered users personalized – main screen contained serial number data license owner despite program often used without license popularity confirmed appearing trojan horses impersonating program updates issued yet later together full version software demo versions issued allowed use program week educational reasons program contained descriptions operation viruses including demonstrations graphical sound effects 3.99 version lexicon viruses popular poland 1996 became winner third edition teraz polska contest 1996 mks company created marek sell became program producer website program bbs created company continued development program death author 2004 versions microsoft windows unix created online scanner based activex technology became available software website bankruptcy mks company 2011 property receiver sold rights mks_vir trademark arcabit company created years earlier former mks employees reactivated mks_vir product free antivirus application officially arcabit company resigned distribution support software 2014 march 1 although released brand new version may 2018 program versions
Computer security
voat voat inc open source news aggregator social networking service registered community members submit content text posts direct links registered users vote submissions content entries organized areas interest called subverses website described several media outlets including quartz new york times new york us uk editions wired hub alt-right voat site hosts aggregated content discussion forums according wired voat aesthetically functionally similar reddit like reddit voat collection entries submitted registered users themed categories called subverses voat similar bulletin board system unlike reddit voat emphasized looser content restrictions ad-revenue sharing program voat written c programming language reddit written python january 2017 new yorker article voat described descendant 2chan 4chan 8chan users compete shock value verge described site imzy dark twin indirect products gamergate culture war name voat play words 'goat 'vote site mascot goat website uses colombian top level domain .co registered november 2014 founded april 2014 whoaverse website hobby project atif colo known voat atko student pursuing bsc later joined justin chastain known puttitout website labelled alternative reddit focus freedom expression december 2014 whoaverse changed name voat ease use february 2015 following accusations censorship reddit voat claimed seen “ large influx ” new users reddit early june 2015 reddit banned five subreddits harassment—the largest around 150,000 subscribers—many users reddit began create accounts voat influx new participants temporarily overloaded site causing downtime voat germany-based web hosting service host europe precursor webfusion shut service june 2015 alleged voat publicizing incitement people well abusive insulting youth-endangering content well illegal right-wing extremist content voat founder attributed shutdown political correctness voat also payments frozen paypal due sexually oriented materials services voat shut four subverses response two hosted sexualized images minors jailbait website continued accept donations bitcoin able continue functioning moved different hosting provider website continued experience downtime due ongoing distributed denial service ddos attack rendering 700,000 unique visitors unable access site early july 2015 following dismissal popular administrator reddit another influx reddit members registered voat leading traffic caused voat experience downtime developers website subsequently approached venture capitalists interested investing project also july voat alongside wikileaks subject bitcoin dust attack ddos attacks bitcoin attack slowed payment processing websites ddos attack launched july 12 unsuccessful due cloudflare services although side effect rendering third-party voat apps incapable functioning august 2015 voat became incorporated united states colo explained post announcing incorporation u.s. law far beats every candidate country ’ researched november 2016 users relocated voat reddit banned pizzagate conspiracy theory subreddit citing doxing harassment concerns january 2017 colo resigned ceo voat citing lack time available devote site colo replaced ceo chastain may 2017 chastain ran fundraising campaign announcing voat might shut due lack money november 2017 reddit incel community moved voat incel community banned reddit september 12 2018 reddit banned several subreddits dedicated discussing qanon conspiracy theory stating violated rules prohibiting inciting violence harassment dissemination personal information caused many q anon posters migrate voat
Web technology
jape linguistics computational linguistics jape java annotation patterns engine component open-source general architecture text engineering gate platform jape finite state transducer operates annotations based regular expressions thus useful pattern-matching semantic extraction many operations syntactic trees produced natural language parsers jape version cpsl – common pattern specification language jape grammar consists set phases consists set pattern/action rules phases run sequentially constitute cascade finite state transducers annotations left-hand-side lhs rules consist annotation pattern description right-hand-side rhs consists annotation manipulation statements annotations matched lhs rule may referred rhs means labels attached pattern elements dhaval thakker taha osman phil lakin jape grammar tutorial http //gate.ac.uk/sale/thakker-jape-tutorial/gate 20jape 20manual.pdf
Computational linguistics
user-mode driver framework user-mode driver framework umdf device-driver development platform first introduced microsoft windows vista operating system also available windows xp facilitates creation drivers certain classes devices standard device drivers difficult write must handle wide range system device states particularly multithreaded software environment badly written device drivers cause severe damage system e.g. bsod data corruption since standard drivers high privileges accessing kernel directly user-mode driver framework insulates kernel problems direct driver access instead providing new class driver dedicated application programming interface user level interrupts memory management error occurs new framework allows immediate driver restart without impacting system particularly useful devices intermittently connected system support hot swapping via bus technology usb firewire according microsoft umdf drivers simpler write debug kernel-mode drivers however umdf would used performance-intensive highly stateful devices first version umdf shipped part windows media player version 10 2004-10-12 code-named crescent designed support media transfer protocol driver public interfaces documentation provided later microsoft decided turn umdf device driver development platform umdf driver dll based microsoft component object model com however umdf use com loading unloading controlling concurrency uses com programming pattern example exploiting com iunknown interface startup umdf calls dllgetclassobject get pointer iclassfactory interface driver uses createinstance method iclassfactory interface create instance driver callback object driver object instance framework-provided iwdfdriver interface driver provides set callbacks via idriverentry com interface main entry point driver customization
Operating systems
auslogics antivirus auslogics antivirus antivirus software application intended protect user computer viruses spyware keyloggers cyber threats program also check computer vulnerability status provide privacy controls real-time virus protection encryption instant messaging program made used computers run microsoft windows operating system application version 14 latest writing article february 2012 supporting windows xp vista 7 program published auslogics software pty ltd australian-based company specializes maintenance software computers run microsoft windows operating system started 2008 company gained recognition two highly rated products – auslogics boostspeed auslogics disk defrag 2009 company partnered sony vaio develop part sony vaio care software installed vaio laptops desktop pc ’ 2011 auslogics premier elite partner status intel software partner program december 2011 comparative test performed independent antivirus software certification authority virus bulletin auslogics antivirus received vb100 award placed among top 10 programs 54 antivirus packages included test reactive proactive rap detection rates near 100 chart published virus bulletin program also received editor pick award software informer rated 5 stars download3000.com reviewed freedownloadscenter.com among program advantages reviewers cite easy-to-use configuration wizard settings levels novice intermediate advanced users high detection rates gaming mode feature main drawback mentioned reviews lengthy installation process
Computer security
tiny core linux tiny core linux tcl minimal linux operating system focusing providing base system using busybox fltk developed robert shingledecker distribution notable small size 11 16 mb minimalism additional functions provided extensions tiny core linux free open source software licensed gnu general public license version 2 tiny core 16 mb recommended option new users wired network connection includes base core system dynamic fltk/flwm graphical user interface core 11 mb also known micro core linux smaller variant tiny core without graphical desktop though additional extensions added create system graphical desktop environment dcore 12 mb core made debian ubuntu compatible files uses import sce package format self-contained package format tiny core distribution since 5.x series corepure64 notable port core x86_64 architecture core plus 106 mb installation image distribution composed tiny core additional functionality notably wireless support non-us keyboard support picore raspberry pi port core minimal configuration tiny core needs least 46 mb ram order run core requires least 28 mb ram minimum cpu i486dx recommended configuration pentium 2 cpu 64 mb ram recommended tiny core developers describe tcl nomadic ultra small graphical desktop operating system capable booting cdrom pendrive frugally hard drive version 2.8.1 core designed run primarily ram three distinct modes operation
Operating systems
aura battler dunbine dunbine set byston well parallel world resembles countryside medieval europe kingdoms ruled monarchs castles armies unicorn-riding cavalry armed swords crossbows little winged creatures called ferario flying offering help hindrance depending mood main draw series insect-like aura battlers used population byston well fight wars fighting suits powered powerful energy called aura life energy certain people strong enough aura-energy act power-supply mecha making aura warriors series aired nagoya tv february 5 1983 january 21 1984 totaling 49 episodes three-episode anime ova sequel new story aura battler dunbine also known tale neo byston well released 1988 series later dubbed adv films released dvd north america along original japanese version 2003 however quickly became print 2018 available digital purchase now-defunct daisuki site sentai filmworks licensed series series followed shō zama suddenly finds pulled world byston well vehicular incident one rivals byston well located another dimension located sea land populated dragons castles knights powerful robots known aura battlers shō discovered possess powerful aura drafted byston well conflict pilot lavender-colored dunbine tomino creations dunbine cast populated nordic-looking military types elaborate costumes one side young japanese hero caught middle freedom fighters side beautiful female warriors abound sides hero falls main female lead romances cut across battle lines non-stop battles elaborate fighting craft land air cast pilot aura battlers although lots standard airships smaller fighters large warships well also typical tomino style large number named characters die tragically throughout series dunbine characters mecha storyline elements make appearances quite games super robot wars series banpresto notably first series banpresto gone make spinoff series taking place different universes alpha series impact however dunbine made appearances latter titles recently making something comeback first returning ux followed almost immediately operation extend bx gives recent use story dunbine units also appeared another century episode series first sequel another century episode 2 many units dunbine series included compared amount first game large part plot shō marvel piloting bilbine dunbine respectively also acquire unique team attack another century episode 3 story plot involve dunbine player unit continues appear bilbine shares combination attack nanajin wings rean also world set byston well first three games produced family soft msx 2000 title released playstation bandai new story aura battler dunbine also known tale neo byston well three episode anime ova released 1988 sequel tv series dunbine set roughly 700 years events show also second show set fictional medieval land byston well followed garzey wing wings rean directed toshifumi takizawa samurai 7 700 years passed since great war involving aura machines ended attempt conquer byston well black knight rabaan kidnaps princess nation baran-baran – nation said hold legendary treasure rabaan also captures shion young hunter shion princess remul escape rabaan castle return homeland find baran-baran treasure actually powerful aura battler sirbine riding sirbine shion fights rabaan evil forces
Computer architecture
wondermedia wondermedia fabless soc company headquartered taipei taiwan subsidiary via technologies notable creating low cost processors used large number chinese android windows ce-based devices soc designs collectively called wondermedia prizm platform based reference implementations provided arm holdings
Computer architecture
intersection type type theory intersection type assigned values assigned two given types particular value assigned type formula_1 type formula_2 value assigned intersection type formula_3 intersection type system generally ranges values two types overlap value belonging intersection two ranges assigned intersection type two types value safely passed argument functions expecting either two types example java class implements interfaces therefore object type safely passed functions expecting argument type functions expecting argument type intersection types composite data types similarly product types used assign several types object however product types assigned tuples tuple element assigned particular product type component comparison underlying objects intersection types necessarily composite restricted form intersection types refinement types intersection types useful describing overloaded functions example type functions taking number argument returning number type functions taking string argument returning string intersection two types used describe overloaded functions one based type input given contemporary programming languages including ceylon flow java scala typesript whiley see comparison languages intersection types use intersection types combine interface specifications express ad hoc polymorphism complementing parametric polymorphism intersection types may used avoid class hierarchy pollution cross-cutting concerns reduce boilerplate code shown typescript example type theoretic study intersection types referred intersection type discipline remarkably program termination precisely characterized using intersection types microsoft typescript supports intersection types improving expressivity type system reducing potential class hierarchy size demonstrated follows following program code defines classes method returning object either type additionally function resp requires object type resp argument //produces eggs //produces milk //produces random number //requires egg function eategg egg egg //requires milk function drinkmilk milk milk following program code defines ad hoc polymorphic function invokes member function given object function two type annotations namely connected via intersection type constructor specifically applied argument type returns object type type applied argument type returns object type type ideally applicable object possibly chance method //given chicken produces egg given cow produces milk let animaltofood chicken egg cow milk finally following program code demonstrates type safe use definitions var chicken new chicken var cow new cow var randomnumbergenerator new randomnumbergenerator console.log randomnumbergenerator.produce //0.2626353555444987 //console.log animaltofood randomnumbergenerator //error argument type 'randomnumbergenerator assignable parameter type 'cow' console.log eategg animaltofood chicken //i ate egg //console.log eategg animaltofood cow //error argument type 'milk assignable parameter type 'egg' console.log drinkmilk animaltofood cow //i drank milk //console.log drinkmilk animaltofood chicken //error argument type 'egg assignable parameter type 'milk' program code following properties minimalistic example realized using inheritance instance deriving classes base class however larger setting could disadvantageous introducing new classes class hierarchy necessarily justified cross-cutting concerns may outright impossible example using external library imaginably example could extended following classes may require additional classes interfaces specifying whether produce method available whether produce method returns food whether produce method used repeatedly overall may pollute class hierarchy minimalistic example already shows duck typing less suited realize given scenario class contains method object valid argument example realized using duck typing instance introducing new field classes signifying objects corresponding type valid arguments however would increase size respective classes especially introduction methods similar also non-local approach respect example realized using function overloading instance implementing two methods typescript solution almost identical provided example programming languages java require distinct implementations overloaded method may lead either code duplication boilerplate code example realized using visitor pattern would require animal class implement method accepting object implementing interface adding non-local boilerplate code function would realized method implementation unfortunately connection input type result type would difficult represent one hand intersection types used locally annotate different types function without introducing new classes interfaces class hierarchy hand approach requires possible argument types result types specified explicitly behaviour function specified precisely either unified interface parametric polymorphism duck typing verbose nature intersection types unfavorable therefore intersection types considered complementary existing specification methods dependent intersection type denoted formula_4 dependent type type formula_2 may depend term variable formula_6 particular term formula_7 dependent intersection type formula_4 term formula_7 type formula_1 type formula_11 formula_11 type results replacing occurrences term variable formula_6 formula_2 term formula_7 scala supports type declarations object members allows type object member depend value another member called path-dependent type example following program text defines scala trait witness used implement singleton pattern trait witness trait witness declares member assigned type value member value assigned value type t. following programm text defines object booleanwitness instance trait witness object booleanwitness defines type boolean value value true example executing system.out.println booleanwitness.value prints true console object booleanwitness extends witness let formula_16 type specifically record type objects member formula_17 type formula_1 example object booleanwitness assigned dependent intersection type formula_19 reasoning follows object booleanwitness member assigned type boolean value since boolean type object booleanwitness type formula_20 additionally object booleanwitness member value assigned value true type boolean since value booleanwitness.t boolean object booleanwitness type formula_21 overall object booleanwitness intersection type formula_22 therefore presenting self-reference dependency object booleanwitness dependent intersection type formula_19 alternatively minimalistic example described using dependent record types comparison dependent intersection types dependent record types constitute strictly specialized type theoretic concept intersection type family denoted formula_24 dependent type type formula_2 may depend term variable formula_6 particular term formula_7 type formula_24 term formula_29 type formula_1 term formula_7 type formula_32 notion also called implicit pi type observing argument formula_29 kept term level
Programming language topics
distributed data flow distributed data flow also abbreviated distributed flow refers set events distributed application protocol distributed data flows serve purpose analogous variables method parameters programming languages java represent state stored communicated layer software unlike variables parameters represent unit state resides single location distributed flows dynamic distributed simultaneously appear multiple locations within network time distributed flows natural way modeling semantics inner workings certain classes distributed systems particular distributed data flow abstraction used convenient way expressing high-level logical relationships parts distributed protocols distributed data flow satisfies following informal properties formally represent event distributed flow quadruple form x k v x location e.g. network address physical node event occurs time happens k version sequence number identifying particular event v value represents event payload e.g. arguments passed method call distributed flow possibly infinite set quadruples satisfies following three formal properties addition flows number additional properties
Distributed computing architecture