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redundant array independent memory redundant array independent memory raim design feature found certain computers main random access memory raim utilizes additional memory modules striping algorithms protect failure particular module keep memory system operating continuously raim similar concept redundant array independent disks raid protects failure disk drive case memory supports several dram device chipkills entire memory channel failures raim much robust parity checking ecc memory technologies protect many varieties memory failures july 22 2010 ibm introduced first high end computer server featuring raim zenterprise 196 z196 machine contains 3 tb usable raim-protected main memory 2011 business class model z114 introduced also supporting raim formal announcement letter offered additional information regarding implementation
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Computer architecture
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laurence hugh frost laurence hugh frost july 22 1902 – may 23 1977 rear admiral united states navy served director naval intelligence director national security agency frost graduated united states naval academy 1926 served various ships shore stations throughout 1920s 1930s commanding officer destroyer attacked german u-boat 4 september 1941 first attack germany united states warship world war ii occurred united states officially neutral three months america entered war decorated service world war ii frost assigned naval intelligence later saw combat commander cruiser korean war chief staff commander first fleet 1952 commanded destroyer flotilla four united states atlantic fleet 1955–1956 director naval intelligence 1956 1960 head naval intelligence tried change united states policy rebellion indonesia frost became director national security agency nsa november 1960 rank vice admiral held post 1962 holding posts beginning space race frost involved early decisions promote surveillance satellites navy elint program effort reduce tensions soon arrival nsa frost appointed robert f. rinehart chairman national security agency scientific advisory board specifically newest member board months experience fewer pre-acquired biases rinehart words according nsa 1962 vice admiral laurence frost unexpectedly transferred position gordon blake replacement final tour duty potomac river naval command frost retired 1964 papers preserved operational archives branch naval historical center washington d.c.. listed rear admiral john f. kennedy presidential library holds 11-page transcription oral interview gave 1970. portions remain closed career frost awarded navy distinguished service medal silver star one gold award star legion merit one gold award star combat v
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Computer security
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julia ward julia ward december 1900 – june 18 1962 founder central reference division national security agency nsa inducted cryptologic hall honor 2002 ward received a.b bryn mawr college 1923 ph.d bryn mawr college 1940 ward joined cryptologic service wwii worked signal security agency army cryptologic organization also worked librarian eventually built collection classified unclassified materials use analysts 1945 became deputy chief reference section within years turned section one known poorly organized section widely recognized highly respected 1949 ward named head collateral branch thereby becoming female branch head office operations 1955 ward promoted deputy chief nsa liaison foreign operations section ward inducted nsa cryptologic hall honor june 2002 national cryptologic museum baltimore md bryn mawr college plaque commemorate placement hall honor
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Computer security
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t-carrier t-carrier member series carrier systems developed bell laboratories digital transmission multiplexed telephone calls first version transmission system 1 t1 introduced 1962 bell system could transmit 24 telephone calls simultaneously single transmission line copper wire subsequent specifications carried multiples basic t1 1.544 mbit/s data rates t2 6.312 mbit/s 96 channels t3 44.736 mbit/s 672 channels others t-carrier hardware specification carrying multiple time-division multiplexed tdm telecommunications channels single four-wire transmission circuit developed bell laboratories ca 1957 first employed 1962 long-haul pulse-code modulation pcm digital voice transmission d1 channel bank t-carriers commonly used trunking switching centers telephone network including private branch exchange pbx interconnect points uses twisted pair copper wire analog trunks used employing one pair transmitting another pair receiving signal repeaters may used extended distance requirements digital t-carrier system carrier wave systems 12-channel carrier systems worked frequency division multiplexing call analog signal t1 trunk could transmit 24 telephone calls time used digital carrier signal called digital signal 1 ds-1 ds-1 communications protocol multiplexing bitstreams 24 telephone calls along two special bits framing bit frame synchronization maintenance-signaling bit t1 maximum data transmission rate 1.544 megabits per second europe rest world except japan standardized e-carrier system similar transmission system higher capacity directly compatible t-carrier existing frequency-division multiplexing carrier systems worked well connections distant cities required expensive modulators demodulators filters every voice channel connections within metropolitan areas bell labs late 1950s sought cheaper terminal equipment pulse-code modulation allowed sharing coder decoder among several voice trunks method chosen t1 system introduced local use 1961 later decades cost digital electronics declined point individual codec per voice channel became commonplace advantages digital transmission become entrenched common legacy system line rate speeds t1 means data circuit runs original 1.544 mbit/s line rate originally t1 format carried 24 pulse-code modulated time-division multiplexed speech signals encoded 64 kbit/s streams leaving 8 kbit/s framing information facilitates synchronization demultiplexing receiver t2 t3 circuit channels carry multiple t1 channels multiplexed resulting transmission rates 6.312 44.736 mbit/s respectively t3 line comprises 28 t1 lines operating total signaling rate 1.544 mbit/s possible get fractional t3 line meaning t3 line 28 lines turned resulting slower transfer rate typically reduced cost supposedly 1.544 mbit/s rate chosen tests done long lines chicago conducted underground test site typical bell system outside plant time accommodate loading coils cable vault manholes physically apart determined repeater spacing optimum bit rate chosen empirically—the capacity increased failure rate unacceptable reduced leave margin companding allowed acceptable audio performance seven bits per pcm sample original t1/d1 system later d3 d4 channel banks extended frame format allowing eight bits per sample reduced seven every sixth sample frame one bit robbed signaling state channel standard allow zero sample would produce long string binary zeros cause repeaters lose bit sync however carrying data switched 56 could long strings zeros one bit per sample set 1 jam bit 7 leaving 7 bits × 8,000 frames per second data detailed understanding rate 1.544 mbit/s divided channels follows explanation glosses t1 voice communications deals mainly numbers involved given telephone system nominal voiceband including guardband 4,000 hz required digital sampling rate 8,000 hz see nyquist rate since t1 frame contains 1 byte voice data 24 channels system needs 8,000 frames per second maintain 24 simultaneous voice channels frame t1 193 bits length 24 channels × 8 bits per channel 1 framing bit 193 bits 8,000 frames per second multiplied 193 bits yield transfer rate 1.544 mbit/s 8,000 × 193 1,544,000 initially t1 used alternate mark inversion ami reduce frequency bandwidth eliminate dc component signal later b8zs became common practice ami mark pulse opposite polarity previous one space level zero resulting three level signal however carried binary data similar british 23 channel systems 1.536 megabaud 1970s equipped ternary signal repeaters anticipation using 3b2t 4b3t code increase number voice channels future 1980s systems merely replaced european standard ones american t-carriers could work ami b8zs mode ami b8zs signal allowed simple error rate measurement bank central office could detect bit wrong polarity bipolarity violation sound alarm later systems could count number violations reframes otherwise measure signal quality allow sophisticated alarm indication signal system decision use 193-bit frame made 1958 allow identification information bits within frame two alternatives considered assign one extra bit b additional eight bits per frame 8-bit choice cleaner resulting 200-bit frame twenty-five 8-bit channels 24 traffic one 8-bit channel available operations administration maintenance oa chose single bit per frame reduce required bit rate 1.544 vs 1.6 mbit/s marketing worried 8 bits chosen oa function someone would try sell voice channel wind nothing soon commercial success t1 1962 t1 engineering team realized mistake one bit serve increasing demand housekeeping functions petitioned management change 8-bit framing flatly turned would make installed systems obsolete hindsight ten years later cept chose eight bits framing european e1 although feared extra channel sometimes appropriated voice data 1970s bell labs developed higher rate systems t1c sophisticated modulation scheme carried 3 mbit/s balanced pair cables could support t-2 carried 6.312 mbit/s requiring special low-capacitance cable foam insulation standard picturephone t-4 t-5 used coaxial cables similar old l-carriers used long lines td microwave radio relay systems also fitted high rate modems allow carry ds1 signal portion fm spectrum poor quality voice service later carried ds3 ds4 signals 1980s companies rlh industries inc. developed t1 optical fiber industry soon developed evolved multiplexed t1 transmission schemes ds1 signals interconnected typically central office locations common metallic cross-connect point known dsx-1 ds1 transported metallic outside plant cable signal travels conditioned cable pairs known t1 span t1 span +-130 volts dc power superimposed associated four wire cable pairs line span power line repeaters t1 niu t1 smartjacks t1 span repeaters typically engineered apart depending cable gauge 36 db loss requiring repeated span cable bridge taps load coils across pairs t1 copper spans replaced optical transport systems copper metallic span used t1 typically carried hdsl encoded copper line four wire hdsl require many repeaters conventional t1 spans newer two wire hdsl hdsl-2 equipment transports full 1.544 mbit/s t1 single copper wire pair approximately twelve thousand 12,000 feet 3.5 km 24 gauge cable used hdsl-2 employ multiple repeaters conventional four wire hdsl newer hdsl-4 systems one advantage hdsl ability operate limited number bridge taps tap closer hdsl transceiver two four wire hdsl equipment transmits receives cable wire pair compared conventional t1 service utilizes individual cable pairs transmit receive ds3 signals rare except within buildings used interconnections intermediate step multiplexed onto sonet circuit t3 circuit go repeaters customer orders ds3 usually receives sonet circuit run building multiplexer mounted utility box ds3 delivered familiar form two coax cables 1 send 1 receive bnc connectors ends twelve ds1 frames make single t1 superframe t1 sf t1 superframe composed two signaling frames t1 ds0 channels employ in-band signaling eighth bit written robbed full 64 kbit/s ds0 payload either logical zero one bit signify circuit signaling state condition hence robbed bit signaling restrict ds0 channel rate 56 kbit/s two twelve ds1 frames make t1 sf framed circuit t1 sf framed circuits yield two independent signaling channels b t1 esf framed circuits four signaling frames twenty four frame extended frame format yield four independent signaling channels b c 56 kbit/s ds0 channels associated digital data service dds services typically utilize eighth bit ds0 voice circuits employ b band signaling one exception switched 56kbit/s dds dds bit eight used identify dte request send rts condition switched 56 dds bit eight pulsed alternately set logical zero one transmit two state dial pulse signaling information sw56 dds csu/dsu digital end office switch use robbed-bit signaling america decreased significantly result signaling system 7 ss7 inter-office dial trunks ss7 full 64 kbit/s ds0 channel available use connection allows 64 kbit/s 128 kbit/s isdn data calls exist switched trunk network connection supporting t1 carrier entity optioned b8zs clear channel capable carriers price ds1 lines many different ways however boil two simple components local loop cost local incumbent charges transport signal end user central office otherwise known co point presence otherwise known pop carrier port cost access telephone network internet carrier network typically port price based upon access speed yearly commitment level loop based geography farther co pop loop costs loop price several components built including mileage calculation performed v/h coordinates standard gps coordinates telco piece local bell operating company—namely verizon inc. qwest—charge t-carriers different price per mile rates therefore price calculation two distance steps geomapping determination local price arrangements carriers utilize geographic pricing model described competitive local exchange carriers clecs telepacific integra telecom tw telecom windstream level 3 communications xo communications offer national pricing ds1 pricing model provider charges price every geography services national pricing outgrowth increased competition t-carrier market space commoditization t-carrier products providers adopted national pricing strategy may experience widely varying margins suppliers bell operating companies e.g. verizon inc. qwest maintain geographic pricing models albeit wholesale prices voice ds1 lines calculation mostly except port required internet access replaced ldu otherwise known long distance usage price loop determined voice-related charges added total short total price loop ldu x minutes used
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Internet protocols
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interrupts 65xx processors 65xx family microprocessors consisting mos technology 6502 derivatives wdc 65c02 wdc 65c802 wdc 65c816 csg 65ce02 handle interrupts similar fashion three hardware interrupt signals common 65xx processors one software interrupt instruction wdc 65c816 adds fourth hardware interrupt— useful implementing virtual memory architectures—and software interrupt instruction also present 65c802 intended use system coprocessor type e.g. floating point processor hardware interrupt signals active low follows detection signal causes processor enter system initialization period six clock cycles sets interrupt request disable flag status register loads program counter values stored processor initialization vector – commencing execution operating native mode 65c816/65c802 switched back emulation mode stay returned native mode software control detection signal well execution instruction cause overall sequence events order behavior 65c816 asserted differs respects description separately discussed note processor push accumulator index registers stack—code interrupt handler must perform task well restore registers termination interrupt processing necessary also note vector eight bit 65xx processors well 65c802/65c816 operating emulation mode operating native mode 65c802/65c816 provide separate vectors set interrupt request disable flag bit status register disable detection signal effect interrupts however see section instruction implemented wdc cmos processors additionally 65 c 02 65c816/65c802 operating emulation mode copy status register pushed stack flag set software interrupt cause interrupt cleared cause hence interrupt service routine must retrieve copy saved status register pushed onto stack check status flag order distinguish requirement eliminated operating 65c802/65c816 native mode due separate vectors two interrupt types 65c816 interrupt input intended provide means redirect program execution hardware exception detected page fault memory access violation hence processor response input asserted negated different and/or asserted also achieving correct operation response requires interrupt occur proper time machine cycle whereas requirement exists asserted valid memory cycle processor asserted and/or status outputs following sequence events occur address pushed stack aborted instruction rather contents program counter executing return interrupt following interrupt cause processor return aborted instruction rather next instruction would case interrupts order processor correctly respond abort system logic must assert negate input soon valid address placed bus determined address constitutes page fault memory access violation anomaly e.g. attempted execution privileged instruction hence logic must assert processor asserted signals also must remain asserted fall phase-two clock immediately released timing constraints observed abort interrupt handler may aborted causing registers and/or memory changed possibly-undefined manner nmos 6502 derivatives e.g. 6510 simultaneous assertion hardware interrupt line execution accounted design—the instruction ignored case also status decimal mode flag processor status register unchanged following interrupt kind behavior potentially result difficult locate bug interrupt handler decimal mode happens enabled time interrupt anomalies corrected cmos versions processor well-designed succinct interrupt handler interrupt service routine isr expeditiously service event causes interrupt without interfering way interrupted foreground task—the isr must transparent interrupted task although exceptions may apply specialized cases means isr must preserve microprocessor mpu state disturb anything memory supposed disturb additionally isr fully reentrant meaning two interrupts arrive close succession isr able resume processing first interrupt second one serviced reentrancy achieved using mpu hardware stack storage preserving mpu state means isr must assure whatever values mpu registers time interrupt isr terminates part preservation process automatically handled mpu acknowledges interrupt push program counter program bank 65c816/65c802 status register stack prior executing isr completion isr instruction executed mpu reverse process member 65xx family pushes registers stack isrs accumulator and/or index registers must preserved assure transparency later restored final steps prior executing case 65c816/65c802 consideration must given whether operated emulation native mode time interrupt latter may also necessary preserve data bank direct zero page registers guarantee transparency also 65c816 native mode operating system may well use different stack location application software means isr would preserve subsequently restore stack pointer complicating matters 65c816/65c802 sizes accumulator index registers may either 8 16 bits operating native mode requiring sizes preserved later restoration methods mpu state preserved restored within isr vary different versions 65xx family nmos processors e.g. 6502 6510 8502 etc one method accumulator index registers preserved accumulator pushed pulled stack therefore following isr entry code typical instruction necessary previously noted nmos versions 6502 clear decimal mode flag status register interrupt occurs accumulator index registers preserved isr use needed isr concluded work would restore registers resume interrupted foreground task following nmos code typical consequence instruction mpu return decimal mode state time interrupt 65c02 65c816/65c802 operating emulation mode require less code able push pull index registers without using accumulator intermediary also automatically clear decimal mode executing isr following typical upon finishing isr would reverse process previously stated little complexity 65c816/65c802 operating native mode due variable register sizes necessity accounting registers case index registers may pushed without regard sizes changing sizes automatically sets significant byte msb registers zero data lost pushed value restored provided index registers size pushed accumulator however really two registers designated pushing accumulator set 8 bits preserve could result loss transparency isr change way therefore accumulator must always set 16 bits pushed pulled isr using also efficient set index registers 16 bits pushing otherwise isr push extra copy status register restore register sizes prior pulling stack isrs following entry code achieve goal transparency code fragment symbol mos technology wdc standard assembly language syntax bitwise operand isr assigned stack location preservation stack pointer must occur memory pushes occurred—it apparent following code added sequence would handle requirement completion isr processes would reversed follows note upon executing 65c816/65c802 automatically restore register sizes interrupt occurred since pulling previously–saved status register sets clears register size bits time interrupt possible switch 65c816/65c802 native mode emulation mode within isr fraught peril addition forcing accumulator index registers 8 bits causing loss significant byte index registers entering emulation mode truncate stack pointer 8 bits relocate stack page 1 ram result stack existed time interrupt inaccessible unless also page 1 ram larger 256 bytes general mode switching servicing interrupt recommended procedure may necessary specific operating environments previously noted software interrupts may used variety ways implement system functions historical use assist patching proms bugs discovered system firmware typical technique often used firmware development arrange vector point unprogrammed patch area prom event bug discovered patching would accomplished blowing fuses address faulty instruction located thus changing instruction opcode upon executing resulting mpu would redirected patch area suitable patch code would written often patch area code started sniffing stack determine address bug encountered potentially allowing presence one patch prom use prom patching diminished eproms eeproms became commonly available another use software development debugging aid conjunction machine language monitor overwriting opcode directing hardware vector entry point monitor one cause program halt desired point allowing monitor take control time one may examine memory view processor register values patch code etc debugging advocated kuckes thompson facilitated liberally sprinkling one code instructions opcode replaced instructions without altering actual behaviour program debugged characteristic instructions processor treats either two byte instruction opcode following byte referred signature upon execution processor add two program counter prior pushing stack hence return interrupt executed interrupted program continue address immediately following signature used debugging device program counter may adjusted point signature order execution resume expected alternatively may inserted signature placeholder case program counter adjustment required fact double-increment program counter pushing stack facilitates technique treating supervisor call instructions found mainframe computers usual procedure treat signature operating system service index operating system handler would retrieve value program counter pushed stack decrement read resulting memory location get signature converting signature zero-based index simple lookup table consulted load program counter address proper service routine upon completion service routine instruction would used return control program made operating system call note signature may value whereas signature limited range use and/or request operating system service means user applications know entry address operating system function correct signature byte invoke desired operation hence relocation operating system memory break compatibility existing user applications also executing always vectors processor address simple code may used preserve registers stack prior turning control requested service however programming model result somewhat slower execution compared calling service subroutine primarily result stack activity occurs interrupt also interrupt requests disabled executing requiring operating system re-enable wait interrupt opcode instruction available wdc version 65c02 65c816/65c802 microprocessors mpu halts mpu places semi-catatonic state hardware interrupt kind occurs primary use low-power embedded systems mpu nothing expected event occurs minimal power consumption desired system waiting quick response required typical example code would make use follows code fragment mpu halt upon execution go low power consumption state despite interrupt requests irq disabled prior instruction mpu respond hardware interrupt waiting upon receipt interrupt mpu awaken one clock cycle resume execution instruction immediately following hence interrupt latency short 70 nanoseconds 14 megahertz resulting rapid response possible external event similar ways stop opcode instruction completely shuts mpu waiting single interrupt input executed mpu halts internal clock retain data registers enters low power state mpu brought state pulling reset input pin classified interrupt input low execution resume address stored locations hardware reset vector intended use low power embedded applications long periods time may elapse events require mpu attention processing required would used normal programming would result total cessation processing
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Computer architecture
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ourgrid ourgrid opensource grid middleware based peer-to-peer architecture ourgrid mainly developed federal university campina grande brazil run ourgrid instance named ourgrid since december 2004 anyone freely easily join gain access large amount computational power run parallel applications computational power provided idle resources participants shared way makes contribute get need currently platform used run application whose tasks i.e parts run single machine communicate among execution like simulations data mining searching figure 1.1 ourgrid main components ourgrid broker originally called mygrid scheduling component ourgrid solution machine running broker called home machine central point grid processing jobs acts grid coordinator scheduling execution tasks necessary data transfer grid machines due central role grid configuration management well job specification done home machine broker ourgrid user frontend provides support describe execute monitor jobs job processing done machines running ourgrid workers execution job broker gets workers on-demand associated peer broker role schedule tasks run workers deploy retrieve data to/from workers execution tasks ourgrid peer runs machine called peer machine main role peer organize provide worker machines belong administrative domain user perspective peer worker provider i.e. network service dynamically provides workers task execution administrative point view peer determines machines used workers ourgrid worker component runs machine available task execution worker provides necessary access functionality home machine also provides basic support instrumentation fault handling furthermore combined ourgrid peer allows use machines private networks practice computer connected internet used worker machine even lies different administrative domain behind firewall figure 1.1 administrative domains possibly using intranets illustrated rectangles containing workers encourage resource contribution network ourgrid uses resource allocation mechanism called network favours network favours autonomous reputation scheme rewards peers contribute way incentive peer contribute much possible system ourgrid community peer-to-peer resource sharing system focused providing resources bot applications central mission ourgrid community sharing done using network favours model model peer offers access idle resources community return work exceeds local capacity peer expects gain access idle resources participants system aims allow users bot applications easily obtain access use community computational resources dynamically forming on-demand large-scale grid peer community entity owns number resources occasionally needs computing power resources provide whenever peer needs power requests resources community whenever idle resources allocates one requesters guarantees quality service obtained idle resources donated community applications suitable ourgrid community status snapshot could seen
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Distributed computing architecture
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hardware description language computer engineering hardware description language hdl specialized computer language used describe structure behavior electronic circuits commonly digital logic circuits hardware description language enables precise formal description electronic circuit allows automated analysis simulation electronic circuit also allows synthesis hdl description netlist specification physical electronic components connected together placed routed produce set masks used create integrated circuit hardware description language looks much like programming language c textual description consisting expressions statements control structures one important difference programming languages hdls hdls explicitly include notion time hdls form integral part electronic design automation eda systems especially complex circuits application-specific integrated circuits microprocessors programmable logic devices due exploding complexity digital electronic circuits since 1970s see moore law circuit designers needed digital logic descriptions performed high level without tied specific electronic technology cmos bjt hdls created implement register-transfer level abstraction model data flow timing circuit two major hardware description languages vhdl verilog different types description dataflow behavioral structural example dataflow vhdl hdls standard text-based expressions structure electronic systems behaviour time like concurrent programming languages hdl syntax semantics include explicit notations expressing concurrency however contrast software programming languages hdls also include explicit notion time primary attribute hardware languages whose characteristic express circuit connectivity hierarchy blocks properly classified netlist languages used electric computer-aided design cad hdl used express designs structural behavioral register-transfer-level architectures circuit functionality latter two cases synthesizer decides architecture logic gate layout hdls used write executable specifications hardware program designed implement underlying semantics language statements simulate progress time provides hardware designer ability model piece hardware created physically executability gives hdls illusion programming languages precisely classified specification languages modeling languages simulators capable supporting discrete-event digital continuous-time analog modeling exist hdls targeted available certainly possible represent hardware semantics using traditional programming languages c++ operate control flow semantics opposed data flow although function programs must augmented extensive unwieldy class libraries generally however software programming languages include capability explicitly expressing time thus function hardware description languages introduction system verilog 2002 c++ integration logic simulator one ways use object-oriented programming hardware verification system verilog first major hdl offer object orientation garbage collection using proper subset hardware description language program called synthesizer logic synthesis tool infer hardware logic operations language statements produce equivalent netlist generic hardware primitives implement specified behaviour synthesizers generally ignore expression timing constructs text digital logic synthesizers example generally use clock edges way time circuit ignoring timing constructs ability synthesizable subset language make hardware description language first hardware description languages appeared late 1960s looking like traditional languages first lasting effect described 1971 c. gordon bell allen newell text computer structures text introduced concept register transfer level first used isp language describe behavior digital equipment corporation dec pdp-8 language became widespread introduction dec pdp-16 rt-level modules rtms book describing use least two implementations basic isp language ispl isps followed isps well suited describe relations inputs outputs design quickly adopted commercial teams dec well number research teams usa among nato allies rtm products never took commercially dec stopped marketing mid-1980s new techniques particular very-large-scale integration vlsi became popular separate work done 1979 university kaiserslautern produced language called karl kaiserslautern register transfer language included design calculus language features supporting vlsi chip floorplanning structured hardware design work also basis karl interactive graphic sister language abl whose name initialism block diagram language abl implemented early 1980s centro studi e laboratori telecomunicazioni cselt torino italy producing abled graphic vlsi design editor mid-1980s vlsi design framework implemented around karl abl international consortium funded commission european union late 1970s design using programmable logic devices plds became popular although designs primarily limited designing finite state machines work data general 1980 used devices design data general eclipse mv/8000 commercial need began grow language could map well 1983 data i/o introduced abel fill need design shifted vlsi first modern hdl verilog introduced gateway design automation 1985 cadence design systems later acquired rights verilog-xl hdl simulator would become de facto standard verilog simulators next decade 1987 request u.s. department defense led development vhdl vhsic hardware description language vhdl based ada programming language well experience gained earlier development isps initially verilog vhdl used document simulate circuit designs already captured described another form schematic files hdl simulation enabled engineers work higher level abstraction simulation schematic level thus increased design capacity hundreds transistors thousands introduction logic synthesis hdls pushed hdls background foreground digital design synthesis tools compiled hdl source files written constrained format called rtl manufacturable netlist description terms gates transistors writing synthesizable rtl files required practice discipline part designer compared traditional schematic layout synthesized rtl netlists almost always larger area slower performance circuit design skilled engineer using labor-intensive schematic-capture/hand-layout would almost always outperform logically-synthesized equivalent productivity advantage held synthesis soon displaced digital schematic capture exactly areas problematic rtl synthesis extremely high-speed low-power asynchronous circuitry within years vhdl verilog emerged dominant hdls electronics industry older less capable hdls gradually disappeared use however vhdl verilog share many limitations neither suitable analog mixed-signal circuit simulation neither possesses language constructs describe recursively-generated logic structures specialized hdls confluence introduced explicit goal fixing specific limitations verilog vhdl though none ever intended replace years much effort invested improving hdls latest iteration verilog formally known ieee 1800-2005 systemverilog introduces many new features classes random variables properties/assertions address growing need better test bench randomization design hierarchy reuse future revision vhdl also development expected match systemverilog improvements result efficiency gains realized using hdl majority modern digital circuit design revolves around designs begin set requirements high-level architectural diagram control decision structures often prototyped flowchart applications entered state diagram editor process writing hdl description highly dependent nature circuit designer preference coding style hdl merely 'capture language often beginning high-level algorithmic description c++ mathematical model designers often use scripting languages perl automatically generate repetitive circuit structures hdl language special text editors offer features automatic indentation syntax-dependent coloration macro-based expansion entity/architecture/signal declaration hdl code undergoes code review auditing preparation synthesis hdl description subject array automated checkers checkers report deviations standardized code guidelines identify potential ambiguous code constructs cause misinterpretation check common logical coding errors floating ports shorted outputs process aids resolving errors code synthesized industry parlance hdl design generally ends synthesis stage synthesis tool mapped hdl description gate netlist netlist passed back-end stage depending physical technology fpga asic gate array asic standard cell hdls may may play significant role back-end flow general design flow progresses toward physically realizable form design database becomes progressively laden technology-specific information stored generic hdl description finally integrated circuit manufactured programmed use essential hdl design ability simulate hdl programs simulation allows hdl description design called model pass design verification important milestone validates design intended function specification code implementation hdl description also permits architectural exploration engineer experiment design choices writing multiple variations base design comparing behavior simulation thus simulation critical successful hdl design simulate hdl model engineer writes top-level simulation environment called test bench minimum testbench contains instantiation model called device test dut pin/signal declarations model i/o clock waveform testbench code event driven engineer writes hdl statements implement testbench-generated reset-signal model interface transactions host–bus read/write monitor dut output hdl simulator — program executes testbench — maintains simulator clock master reference events testbench simulation events occur instants dictated testbench hdl reset-toggle coded testbench reaction model stimulus triggering events modern hdl simulators full-featured graphical user interfaces complete suite debug tools allow user stop restart simulation time insert simulator breakpoints independent hdl code monitor modify element hdl model hierarchy modern simulators also link hdl environment user-compiled libraries defined pli/vhpi interface linking system-dependent win32/linux/sparc hdl simulator user libraries compiled linked outside hdl environment design verification often time-consuming portion design process due disconnect device functional specification designer interpretation specification imprecision hdl language majority initial test/debug cycle conducted hdl simulator environment early stage design subject frequent major circuit changes hdl description also prototyped tested hardware — programmable logic devices often used purpose hardware prototyping comparatively expensive hdl simulation offers real-world view design prototyping best way check interfacing hardware devices hardware prototypes even running slow fpgas offer much shorter simulation times pure hdl simulation historically design verification laborious repetitive loop writing running simulation test cases design test chip designs grown larger complex task design verification grown point dominates schedule design team looking ways improve design productivity electronic design automation industry developed property specification language formal verification terms property factual statement expected assumed behavior another object ideally given hdl description property properties proven true false using formal mathematical methods practical terms many properties proven occupy unbounded solution space however provided set operating assumptions constraints property checker prove disprove certain properties narrowing solution space assertions model circuit activity capture document designer intent hdl code simulation environment simulator evaluates specified assertions reporting location severity violations synthesis environment synthesis tool usually operates policy halting synthesis upon violation assertion based verification still infancy expected become integral part hdl design toolset hdl grossly similar software programming language major differences programming languages inherently procedural single-threaded limited syntactical semantic support handle concurrency hdls hand resemble concurrent programming languages ability model multiple parallel processes flip-flops adders automatically execute independently one another change process input automatically triggers update simulator process stack programming languages hdls processed compiler often called synthesizer hdl case different goals hdls compiling refers logic synthesis process transforming hdl code listing physically realizable gate netlist netlist output take many forms simulation netlist gate-delay information handoff netlist post-synthesis placement routing semiconductor die generic industry-standard electronic design interchange format edif subsequent conversion jedec-format file hand software compiler converts source-code listing microprocessor-specific object code execution target microprocessor hdls programming languages borrow concepts features boundary becoming less distinct however pure hdls unsuitable general purpose application software development general-purpose programming languages undesirable modeling hardware yet electronic systems grow increasingly complex reconfigurable systems become increasingly common growing desire industry single language perform tasks hardware design software programming systemc example such—embedded system hardware modeled non-detailed architectural blocks black boxes modeled signal inputs output drivers target application written c c++ natively compiled host-development system opposed targeting embedded cpu requires host-simulation embedded cpu emulated cpu high level abstraction systemc models well suited early architecture exploration architectural modifications easily evaluated little concern signal-level implementation issues however threading model used systemc relies shared memory causing language handle parallel execution low-level models well level abstraction hdls compared assembly languages attempts raise abstraction level hardware design order reduce complexity programming hdls creating sub-field called high-level synthesis companies cadence synopsys agility design solutions promoting systemc way combine high-level languages concurrency models allow faster design cycles fpgas possible using traditional hdls approaches based standard c c++ libraries extensions allowing parallel programming found catapult c tools mentor graphics impulse c tools impulse accelerated technologies annapolis micro systems inc. corefire design suite national instruments labview fpga provide graphical dataflow approach high-level design entry languages systemverilog systemvhdl handel-c seek accomplish goal aimed making existing hardware engineers productive rather making fpgas accessible existing software engineers also possible design hardware modules using matlab simulink using mathworks hdl coder tool xilinx system generator xsg formerly accel dsp xilinx two widely used well-supported hdl varieties used industry verilog vhdl several projects exist defining printed circuit board connectivity using language based textual-entry methods
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Programming language topics
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business operating system software business operating system bos initially developed early cross-platform operating system originally produced intel 8080 motorola 6800 computers redeveloped actual businesses business models technology began subsequently zilog z80-based computers later microcomputers 1980s developed premium automated software solution investors asset managers alike cap ltd british company time one world largest information technology consulting firms developed bos cap designed bos bos applications platform-independence via management buyout mbo 1981 bos spun three interlinked companies mpsl microproducts software ltd looked sales marketing bos mppl microproducts programming ltd looked development bos various horizontal software packages microproducts training ltd. bos distributed global basis mainly united states british commonwealth variety independent mpsl-owned companies popular version implemented sage/stride 68000 family based computers sold well australia sage initially developed using ucsd pascal p-code fitted well basic bos design small bos dealer/distributor network command-line interface structure met demise graphical user interface operating systems became prevalent redevelopment 2013 integrated graphical user interface gui order provide simple use solution learned user input mpsl developed numerous products bos generally targeting horizontal markets leaving vertical markets i.e niche independent software vendors isv examples mpsl developed software include bos/finder database bos/planner spreadsheet bos/writer word processor bos/autoclerk report generation companies sold various bos accounting software suites uk united states uk bos accounting packages considered industry standard accountants bos applications initially compiled p-code interpreted ran bos p-code interpreter efficient programs even bos/writer word processor ran sufficiently fast satisfy users apart 2-kilobyte kb server computing /host kernel bos written bos/microcobol language based cobol system-level programming constructs added elements structured programming bore vague similarity pascal recent computing programming languages java re-introduced concept p-code virtual machines bos system evolved need programming asp.net developed quicker accessibility cloud computing harrell son took next steps bring bos back picture larger scale bos initially required 48 kb ram two 250 kb floppies though commonly deployed machines equipped 64 kilobytes ram hard drive computer 128 kb ram 10-megabyte mb hard drive could run many five concurrent users ibm pc xt came 1983 bos served eight concurrent dumb terminals time made bos attractive bos runs required ram serves 800,000 concurrent users paired cloud computing user-management tools 80 application programming interfaces mid-80 bos considered alternative even platform-specific operating systems machines pdp-11 vax new reemergence bos escalated number users requested entered pmm system may require consistent server updating despite command-line interface bos remains popular medium large organizations uk us
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Operating systems
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echoworx echoworx email encryption software company based toronto ontario canada offices hermosa beach california london uk certificate authority echoworx member microsoft root certificate program apple root certificate program echoworx operates several data centers including locations united states europe founded 2000 echoworx headed ceo president michael ginsberg formerly ceo certapay email money transfer technology company december 2005 one first telecommunications companies united states white-label provide echoworx encryption services subscribers verizon communications dow 30 company delivers broadband communication wireline wireless customers launched encrypted email products december 2005 british telecom leading provider communications solutions services operating 170 countries british telecom launched bt secure mail encrypted message exchange bt emx based public key infrastructure pki october 2007 messagelabs provider integrated messaging web security services launched echoworx policy based encryption later acquired symantec october 2008 apptix application service provider asp technology company providing hosted business services software service small medium-sized businesses provided apptix secure mail powered echoworx part hosted email security services portfolio launched service april 2010 hostway infrastructure-as-a-service provider partnered echoworx provide encryption services 2011 company original priority small business market evolved enterprise corporate market echoworx offers several products area email encryption products offered direct sales white-labelled product several partners major offerings include
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Computer security
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moblin moblin short 'mobile linux discontinued open source operating system application stack mobile internet devices mids netbooks nettops embedded devices built around intel atom processor builds designed minimize boot times power consumption netbook mid-centric operating system netbook/desktop version moblin supported chipsets based ssse3 instruction set core2 celeron processors oem support scarce hit all-time high 2009 acer replaced linpus linux moblin acer aspire one netbooks lg electronics chose moblin os 2.1 mobile internet device class smartphone lg gw990 dell also accepted orders ubuntu moblin remix canonical ltd. built moblin top ubuntu distribution base commercial products existed around moblin 2 prominently foxconn netbook inventech smartphone announced computex 2009 mandriva offered moblin v2 version mandriva distribution netbook owners consumer electronics show january 2010 msi novell announced suse moblin preloaded msi u135 netbook following release moblin version 2.1 first original equipment manufacturer oem sell fully supported intel atom processor-based netbook running moblin-based technology consumers demonstrated msi intel booths show addition samsung showed four netbooks preloaded suse moblin mobile world congress february 2010 announced moblin project would merging maemo create meego mobile software platform nokia stopped meego development switching windows phone 2011 intel also discontinued work join tizen project instead intel launched moblin.org site july 2007 significantly updated site april 2008 launch intel atom processor family intel developer forum shanghai custom software development kit sdk available site moblin 2 os specifically designed run intel atom processor netbook april 2009 intel turned moblin linux foundation subsequently moblin merged maemo becoming meego meego development also hosted linux foundation initially governed technical steering group overseen imad sousou intel nokia valtteri halla linux foundation canceled meego september 2011 favor tizen new finnish start-up jolla announced july 2012 meego community-driven successor mer would basis new operating system sailfish os slated launch smartphone 2013 linux collaboration summit april 2009 intel demonstrated moblin 2 alpha release load major components stack including graphics system start mere seconds may 19 2009 imad sousou announced release moblin v2.0 beta netbooks nettops developer testing moblin 2 core distribution based recent builds fedora distributions announce future support core moblin stack include linpus ubuntu second major release marked shift xfce desktop environment custom-built gnome mobile ui based openedhand clutter key piece maemo graphical environment built around x window system new ui also includes integrated gecko web browser register impressed interface noted presence quite apparent bugs described beta release moblin 2 closer alpha beta. moblin 2 interface designed netbook nettops built open source graphics technology clutter dri2 kms designed around toolbars panels available top screen
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Operating systems
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uninstaller uninstaller also called deinstaller variety utility software designed remove software parts computer opposite installer uninstallers useful primarily software components installed multiple directories software components might shared system uninstalled systems remain use generic uninstallers flourished 1990s due popularity shared libraries constraints then-current operating systems especially microsoft windows xp declining storage costs increasing capacity subsequently made reclaiming disk space less urgent end-user applications increasingly relied simpler installation architectures consolidate components facilitate removal typical uninstallers contain following components uninstall invented jack bicer working norton desktop windows symantec bicer came uninstall concept developed first uninstall program 1991 published march 23 1992 norton desktop windows v.20 see official readme.txt first software package ever include uninstaller shown uninstalling norton desktop section release norton desktop windows 2.0 ken spreitzer tester product symantec capitalized uninstall idea wrote first widely used pc program called uninstaller initially licensed microhelp february 1998 sold cybermedia microhelp published spreitzer program uninstaller version 1 1995 spreitzer told new york times royalties received microhelp uninstaller made millionaire age 30 tim o'pry president microhelp substantially rewrote code uninstaller version 2 became best-selling program
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Operating systems
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register keyword c programming language codice_1 reserved word keyword type modifier storage class hint codice_1 keyword deprecated c++ became reserved unused c++17 suggests compiler store declared variable cpu register faster location instead ram possible depending type cpu complexity program code optimize access variable hence improve execution time program c c++ keyword essentially ignored location variable declared codice_1 accessed codice_4 operator applied aside limitation codice_1 essentially meaningless modern compilers due optimization place variables register appropriate regardless whether hint given programming embedded systems codice_1 may still significant example microchip mplab xc32 compiler allows specify particular register keyword however discouraged favor compiler optimizations used codice_1 typically loop counters possibly frequently used variables code
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Programming language topics
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time-assignment speech interpolation telecommunication time-assignment speech interpolation tasi analog technique used certain long transmission links increase voice-transmission capacity tasi takes advantage fact typical person-person conversation speech single direction occurs approximately 40 time remaining time occupied pauses and/or silence statistical analysis demonstrated average voice channel usage 40 74 speech conversations could handled using 37 full duplex speech circuits thereby doubling potential revenue small capital outlay relative highly expensive cable e.g £12.5 million £263 million 2014 cost tat-1 cable tasi implemented tasi worked switching additional users onto voice channel temporarily idled original user stopped speaking original user resumes speaking user would turn switched channel happened idle speech detector function called voice activity detection clipping loss speech would occur conversations needed assigned available idle channel practice lasted least 17 ms whilst information required re-connect parties signalled tasi control circuits additional freezeout period lasting 0 500 ms would depend instantaneous loading voice circuits actual use delays presented problems typical conversations one issues using type technology users listening idled channel sometimes hear conversation switched onto generally sound heard low volume individual words distinguishable see also crosstalk similar phenomenon telecommunications another potential issue ensuring non-voice type circuits e.g music radio type circuits pauses would occur infrequently routed via tasi speech channels since could seriously degrade level service callers would encounter frequent clipped speech breaks conversation tasi invented bell labs early 1960s increase capacity transatlantic telephone cables one first applications requiring electronic switching voice circuits later digital circuit multiplication equipment included tasi feature distinct hardware
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Internet protocols
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netpc netpc standard diskless pcs developed microsoft intel competing standard network computer standard many ncs use intel cpus microsoft software network computer launched oracle corporation mid-1990s
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Distributed computing architecture
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mac os 9 mac os 9 ninth major release apple classic mac os operating system introduced october 23 1999 promoted apple best internet operating system ever highlighting sherlock 2 internet search capabilities integration apple free online services known itools improved open transport networking mac os 9 lacks protected memory full pre-emptive multitasking lasting improvements include introduction automated software update engine support multiple users apple discontinued development mac os 9 2001 transitioning future development mac os x final updates mac os 9 addressed compatibility issues mac os x running classic environment compatibility carbon applications 2002 world wide developers conference steve jobs began keynote address staging mock funeral os 9 apple billed mac os 9 including 50 new features heavily marketed sherlock 2 software introduced channels feature searching different online resources introduced quicktime-like metallic appearance mac os 9 also featured integrated support apple ’ suite internet services known itools later re-branded .mac mobileme replaced icloud included improved tcp/ip functionality open transport 2.5 features new mac os 9 include powerpc versions os x prior 10.5 include compatibility layer shell called classic enabling users run applications hardware requiring mac os 9 within os x achieved running mac os 9 without access finder inside os x requires mac os 9 installed computer even though computers run classic environment necessarily able boot mac os 9 mac os 9 applications run well classic demonstrate screen redraw problems lagging performance addition drivers software directly interact hardware fail work properly may 2002 apple worldwide developers conference san jose california steve jobs accompanied coffin held mock funeral announce apple stopped development mac os 9 mac os 9.2.2 released december 2001 final version mac os 9 classic mac os june 2005 jobs announced macintosh platform would transitioning intel x86 microprocessors developer documentation rosetta powerpc emulation layer revealed applications written mac os 8 9 would run x86-based macs classic environment remains powerpc version os x 10.4 however x86 versions os x support classic environment workaround intel-based macs mac os 9 emulated version 9.0.4 using sheepshaver powerpc emulator emulate versions newer 9.0.4 sheepshaver emulate memory management unit pearpc powerpc emulator support mac os 9 recently qemu added support emulating mac os 9 powerpc versions os x however mac os 9 longer supported apple retail copies still available several internet businesses varying prices although classed abandonware development ended still use upgrade os x due hardware limitations prefer os x. mac os 9 also popular choice retrocomputing hobbyists mac gamers also sometimes revert classic often via emulation native os 9 order play games supported os x example bugdom nanosaur oregon trail civilization ii marathon trilogy aside apple-branded hardware still maintained operated mac os 9 operated environments windows unix example aforementioned sheepshaver software designed use x86 platforms required actual powerpc processor present machine running similar hypervisor although provides powerpc processor support run mac os 9.0.4 emulate memory management unit updates mac os 9 include 9.0.4 9.1 9.2.1 9.2.2 mac os 9.0.4 collection bug fixes primarily relating usb firewire support mac os 9.1 included integrated cd burning support macintosh finder added new window menu finder switching open windows mac os 9.2 increased performance noticeably improved classic environment support mac os 9.2 officially supported g3 power macs could still installed certain unsupported powerpc models use third-party software mac os 9 helper
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Computer architecture
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time-division multiplexing time-division multiplexing tdm method transmitting receiving independent signals common signal path means synchronized switches end transmission line signal appears line fraction time alternating pattern used bit rate transmission medium exceeds signal transmitted form signal multiplexing developed telecommunications telegraphy systems late 19th century found common application digital telephony second half 20th century time-division multiplexing first developed applications telegraphy route multiple transmissions simultaneously single transmission line 1870s émile baudot developed time-multiplexing system multiple hughes telegraph machines 1944 british army used wireless set 10 multiplex 10 telephone conversations microwave relay far 50 miles allowed commanders field keep contact staff england across english channel 1953 24-channel tdm placed commercial operation rca communications send audio information rca facility broad street new york transmitting station rocky point receiving station riverhead long island new york communication microwave system throughout long island experimental tdm system developed rca laboratories 1950 1953 1962 engineers bell labs developed first d1 channel banks combined 24 digitized voice calls four-wire copper trunk bell central office analogue switches channel bank sliced 1.544 mbit/s digital signal 8,000 separate frames composed 24 contiguous bytes byte represented single telephone call encoded constant bit rate signal 64 kbit/s channel banks used fixed position temporal alignment one byte frame identify call belonged time-division multiplexing used primarily digital signals may applied analog multiplexing two signals bit streams transferred appearing simultaneously sub-channels one communication channel physically taking turns channel time domain divided several recurrent time slots fixed length one sub-channel sample byte data block sub-channel 1 transmitted time slot 1 sub-channel 2 time slot 2 etc one tdm frame consists one time slot per sub-channel plus synchronization channel sometimes error correction channel synchronization last sub-channel error correction synchronization cycle starts new frame starting second sample byte data block sub-channel 1 etc tdm extended time-division multiple access tdma scheme several stations connected physical medium example sharing frequency channel communicate application examples include circuit-switched networks public switched telephone network pstn desirable transmit multiple subscriber calls transmission medium effectively utilize bandwidth medium tdm allows transmitting receiving telephone switches create channels tributaries within transmission stream standard ds0 voice signal data bit rate 64 kbit/s tdm circuit runs much higher signal bandwidth permitting bandwidth divided time frames time slots voice signal multiplexed onto line transmitter tdm frame consists n voice frames line bandwidth n *64 kbit/s voice time slot tdm frame called channel european systems standard tdm frames contain 30 digital voice channels e1 american systems t1 contain 24 channels standards also contain extra bits bit time slots signaling synchronization bits multiplexing 24 30 digital voice channels called higher order multiplexing higher order multiplexing accomplished multiplexing standard tdm frames example european 120 channel tdm frame formed multiplexing four standard 30 channel tdm frames higher order multiplex four tdm frames immediate lower order combined creating multiplexes bandwidth n *64 kbit/s n 120 480 1920 etc three types synchronous tdm t1 sonet/sdh isdn plesiochronous digital hierarchy pdh developed standard multiplexing higher order frames pdh created larger numbers channels multiplexing standard europeans 30 channel tdm frames solution worked however pdh suffered several inherent drawbacks ultimately resulted development synchronous digital hierarchy sdh requirements drove development sdh sdh become primary transmission protocol pstn networks developed allow streams 1.544 mbit/s multiplexed order create larger sdh frames known synchronous transport modules stm stm-1 frame consists smaller streams multiplexed create 155.52 mbit/s frame sdh also multiplex packet based frames e.g ethernet ppp atm sdh considered transmission protocol layer 1 osi reference model also performs switching functions stated third bullet point requirement listed common sdh networking functions sdh network functions connected using high-speed optic fibre optic fibre uses light pulses transmit data therefore extremely fast modern optic fibre transmission makes use wavelength-division multiplexing wdm signals transmitted across fibre transmitted different wavelengths creating additional channels transmission increases speed capacity link turn reduces unit total costs statistical time-division multiplexing stdm advanced version tdm address terminal data transmitted together better routing using stdm allows bandwidth split one line many college corporate campuses use type tdm distribute bandwidth 10-mbit line entering network stdm used provide 178 terminals dedicated 56k connection 178 56k 9.96mb common use however grant bandwidth much needed stdm reserve time slot terminal rather assigns slot terminal requiring data sent received primary form tdm used circuit mode communication fixed number channels constant bandwidth per channel bandwidth reservation distinguishes time-division multiplexing statistical multiplexing statistical time-division multiplexing pure tdm time slots recurrent fixed order pre-allocated channels rather scheduled packet-by-packet basis dynamic tdma scheduling algorithm dynamically reserves variable number time slots frame variable bit-rate data streams based traffic demand data stream dynamic tdma used asynchronous time-division multiplexing atdm alternative nomenclature stdm designates synchronous time-division multiplexing older method uses fixed time slots
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Internet protocols
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ping sweep computing ping sweep method establish range ip addresses map live hosts classic tool used ping sweeps fping traditionally accompanied gping generate list hosts large subnets although recent version fping include functionality well-known tools ping sweep capability include nmap unix systems pinger software rhino9 windows nt many tools capability including hping simple nomad icmpenum solarwind ping sweep foundstone superscan also ping sweep tool windows mac linux android ios called fing made overlook soft pings detected protocol loggers like ippl
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Internet protocols
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ntfs reparse point ntfs reparse point type ntfs file system object available ntfs v3.0 found windows 2000 later versions reparse points provide way extend ntfs filesystem reparse point contains reparse tag data interpreted filesystem filter identified tag microsoft includes several default tags including ntfs symbolic links directory junction points volume mount points unix domain sockets also reparse points used placeholders files moved windows 2000 remote storage hierarchical storage system also act hard links n't limited point files volume point directories local volume general windows vista supports new symbolic link capability replaces windows 2000 windows xp junction points designed aid migration application compatibility unix operating systems unlike junction point symbolic link also point file remote smb network path additionally ntfs symbolic link implementation provides full support cross-filesystem links however functionality enabling cross-host symbolic links requires remote system also support effectively limits support windows vista later windows operating systems hard links use mft entry original file adding hard link creates new name attribute increases hard link count newly created file count equals one deleting hard link removes appropriate name decreases hard link count count goes zero system deletes file freeing allocated disk space releasing mft record name attributes independent deleting moving renaming file n't affect hard links volume mount points similar unix mount points root another file system attached directory ntfs allows additional file systems mounted without requiring separate drive letter codice_11 codice_12 volume mounted top existing directory another volume contents previously listed directory become invisible replaced content root directory mounted volume mounted volume could still drive letter assigned separately file system allow volumes mutually mounted volume mount points made either persistent remounted automatically system reboot persistent must manually remounted reboot mounted volumes may use file systems ntfs possibly security settings remapping access rights according remote file system policy directory junctions similar volume mount points reference directories file system instead volumes instance directory codice_13 directory junction attribute contains link codice_14 automatically refer directory codice_14 accessed user-mode application function conceptually similar symbolic links directories unix except target ntfs must always another directory typical unix file systems allow target symbolic link type file directory junctions created command codice_16 removed codice_17 console prompt persistent resolved server side share security realm local system domain parent volume mounted security settings contents content target directory however junction may distinct security settings unlinking directory junction delete files target directory directory junctions installed default windows vista compatibility previous versions windows codice_18 root directory system drive links codice_19 physical directory root directory volume however hidden default security settings set windows explorer refuse open within shell applications except local built-in system user local administrators group user accounts used system software installers additional security restriction probably made avoid users finding apparent duplicate files joined directories deleting error semantics directory junctions hardlinks reference counting used target contents even referenced container directory junctions soft links persist even target directory removed working limited form symbolic links additional restriction location target optimized version allowing faster processing reparse point implemented less overhead newer ntfs symbolic links resolved server side found remote shared directories symbolic links soft links introduced windows vista symbolic links resolved client side symbolic link shared target subject access restrictions client server symbolic links created either files created codice_20 directories created codice_21 unlike unix symbolic links semantic link must provided created link target however need exist available symbolic link created symbolic link accessed target checked availability ntfs also check correct type file directory return not-found error existing target wrong type also reference shared directories remote hosts files subdirectories within shared directories target mounted immediately boot temporarily demand opening openfile createfile api definition persistent ntfs volume created types symbolic links removed files using codice_22 command line prompt batch distributed link tracking allows applications track files shell shortcuts ole links even renamed moved another volume within machine domain workgroup tracking implemented system service uses object identifier oid index stored metafile application requests track file directory tracking service creates oid entry points file file rename copy move operation ntfs v3 volume also copies object id allows tracking service eventually find target file several directories different similar files files may identical content single instance storage allows identical files merged one file create references merged file sis consists file system filter manages copies modification merges files user space service groveler searches files identical need merging sis mainly designed remote installation servers may multiple installation images contain many identical files sis allows consolidated unlike example hard links file remains distinct changes one copy file leave others unaltered similar copy-on-write technique memory copying really done one copy modified hierarchical storage management means transferring files used period time less expensive storage media file next accessed reparse point file determines needed retrieves storage nss activex document storage technology since discontinued microsoft allowed activex documents stored multi-stream format activex uses internally nss file system filter loaded used process multiple streams transparently application file transferred non-ntfs formatted disk volume would also transfer multiple streams single stream windows 10 build 17063 stable release version 1803 microsoft introduced unix domain sockets windows realized using afunix.sys kernel driver new reparse point filesystem unix domain sockets common bsd linux systems since ages seen standard inter process communication systems therefore introduction windows allow simplified adoption code cross platform portability stuxnet part series win32 exploits uses ntfs junction points part overall mode operation
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Computer file systems
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list sparql implementations list shows notable triplestore apis storages implemented w3c sparql standard
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Web technology
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dan farmer dan farmer born april 5 1962 american computer security researcher programmer pioneer development vulnerability scanners unix operating systems computer networks farmer developed first software suite computer science student purdue university 1989 gene spafford one professors helped start project software called computer oracle password system cops comprises several small specialized vulnerability scanners designed identify security weaknesses one part unix operating system 1995 farmer wietse venema dutch programmer physicist developed second vulnerability scanner called security administrator tool analyzing networks satan published satan network administrators law enforcement personnel believed hackers would use identify break vulnerable computers consequently sgi terminated farmer employment within years use vulnerability scanners satan became accepted method auditing computer network security codeveloped titan vulnerability scanner brad powell matt archibald presented large installation system administration conference lisa 1998 farmer venema collaborated develop computer forensics suite called coroner toolkit later coauthored forensic discovery 2005 book computer forensics farmer co-founded elemental security dayne myers served corporation chief technical officer
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Computer security
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hi performance filesystem hi performance filesystem hfs file system used hp-ux operating system variant unix file system
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Computer file systems
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adtech company adtech ag german–american digital marketing company retails products manage serve evaluate online advertising campaigns including display video mobile formats company founded 1998 frankfurt germany acquired web portal aol may 15 2007 company merged oath inc. brand subsidiary verizon communications adtech founded 1998 frankfurt germany michael stusch michael schultheiß 2000 american internet holding company cmgi acquired controlling interest 80 adtech year adtech became private limited company based adforce inc. ’ technology adtech opened first data center frankfurt germany 1998 2001 adtech delivered ten billionth banner ad 2002 adtech supplied 100,000th advertising campaign delivered 100 million banners every day 2004 adforce technology replaced adtech ’ ad serving technology shortly second ad serving data center launched frankfurt may 16 2007 aol announced acquisition adtech ag adtech acquired provide aol ad serving platform enabling website publishers manage traffic report online advertising campaigns operating independent wholly owned subsidiary aol advertising.com division ad-serving platform aol advertising previously platform-a company november 2018 part oath inc. owned verizon communications adtech provides integrated ad serving platform product allows publishers advertisers agencies ad networks ability manage display video mobile digital advertising campaigns adtech ad server responds banner requests prompted user ’ browsers xml delivers specified end system — provision terminals must online open design adtech adservers allows implementation external technologies targeting adtech collaborates vendors nugg wunderloop fall 2007 adtech presented integrated suite display video mobile ad serving technologies digital publishers ad tech london ad tech new york collaboration technology partners lightningcast third screen media adtech merged new video mobile applications directly existing user interface reporting system according adtech digital advertisements distributed mobile devices type including mobile smart phones customers also able apply selective targeting options address advertiser needs since 2004 adtech interprets banner requests ad servers periodical web analyses europe adtech surveys document different aspects internet usage ranging browser trends click-through rates also serve reference professional articles trends digital marketing industry
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Web technology
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register file register file array processor registers central processing unit cpu modern integrated circuit-based register files usually implemented way fast static rams multiple ports rams distinguished dedicated read write ports whereas ordinary multiported srams usually read write ports instruction set architecture cpu almost always define set registers used stage data memory functional units chip simpler cpus architectural registers correspond one-for-one entries physical register file prf within cpu complicated cpus use register renaming mapping physical entry stores particular architectural register changes dynamically execution register file part architecture visible programmer opposed concept transparent caches register files may clubbed together register banks processors several register banks arm processors use arm register banks fast interrupt request x86 processors use context switching fast interrupt switching instruction decoder gprs register files one instruction issued existing processors support superscalar however context switching totally different mechanism arm register bank within registers modcomp later 8051-compatible processors use bits program status word select currently active register bank usual layout convention simple array read vertically single word line runs horizontally causes row bit cells put data bit lines run vertically sense amps convert low-swing read bitlines full-swing logic levels usually bottom convention larger register files sometimes constructed tiling mirrored rotated simple arrays register files one word line per entry per port one bit line per bit width per read port two bit lines per bit width per write port bit cell also vdd vss therefore wire pitch area increases square number ports transistor area increases linearly point may smaller and/or faster multiple redundant register files smaller numbers read ports rather single register file read ports mips r8000 integer unit example 9 read 4 write port 32 entry 64-bit register file implemented 0.7 µm process could seen looking chip arm length two popular approaches dividing registers multiple register files distributed register file configuration partitioned register file configuration principle operation could done 64-bit-wide register file many read write ports could done single 8-bit-wide register file single read port single write port however bit-level parallelism wide register files many ports allows run much faster thus operations single cycle would take many cycles fewer ports narrower bit width width bits register file usually number bits processor word size occasionally slightly wider order attach extra bits register poison bit width data word different width address—or cases 68000 even width—the address registers separate register file data registers basic scheme bit cell many optimizations possible register files make special provision prevent multiple write ports writing entry simultaneously instead instruction scheduling hardware ensures one instruction particular cycle writes particular entry multiple instructions targeting register issued one write enables turned crossed inverters take finite time settle write operation read operation either take longer return garbage common bypass multiplexers bypass written data read ports simultaneous read write entry commanded bypass multiplexers often part larger bypass network forwards results yet committed functional units register file usually pitch-matched datapath serves pitch matching avoids many busses passing datapath turn corners would use lot area since every unit must bit pitch every unit datapath ends bit pitch forced widest unit waste area units register files two wires per bit per write port bit lines must contact silicon every bit cell often set pitch datapath area sometimes saved machines multiple units datapath two datapaths side-by-side smaller bit pitch single datapath would case usually forces multiple copies register file one datapath alpha 21264 ev6 instance first large micro-architecture implement shadow register file architecture two copies integer register file two copies floating point register locate front end future scaled file contain 2 read 2 write port took extra cycle propagate data two context switch issue logic attempted reduce number operations forwarding data two greatly improved integer performance help reduce impact limited number gpr superscalar speculative execution design later adapted sparc mips later x86 implementation mips uses multiple register file well r8000 floating-point unit two copies floating-point register file four write four read ports wrote copies time context switch however support integer operation integer register file still remain one later shadow register file abandoned newer design favor embedded market sparc uses shadow register file architecture well high end line 4 copies integer register files future retired scaled scratched contain 7 read 4 write port 2 copies floating point register file unlike alpha x86 locate back end retire unit right order unit renaming register files load instruction instruction fetch decoding stage context switch needless design ibm uses mechanism many major microprocessors deeply merging register file decoder register file work independently decoder side involve context switch different alpha x86 register file serve dedicate decoder thread level example power8 8 instruction decoders 32 register files 32 general purpose registers 4 read 4 write port facilitate simultaneous multithreading instruction used cross register file lack context switch. x86 processor line typical pre-486 cpu individual register file general purpose register directly work decoder x87 push stack located within floating-point unit starting pentium typical pentium-compatible x86 processor integrated one copy single-port architectural register file containing 8 architectural registers 8 control registers 8 debug registers 8 condition code registers 8 unnamed based register one instruction pointer one flag register 6 segment registers one file one copy 8 x87 fp push stack default mmx register virtually simulated x87 stack require x86 register supplying mmx instruction aliases exist stack p6 instruction independently stored executed parallel early pipeline stages decoding micro-operations renaming out-of-order execution beginning p6 register files require additional cycle propagate data register files like architectural floating point located code buffer decoders called retire buffer reorder buffer oooe connected within ring bus 16 bytes register file still remains one x86 register file one x87 stack serve retirement storing x86 register file increased dual ported increase bandwidth result storage registers like debug/condition code/control/unnamed/flag stripped main register file placed individual files micro-op rom instruction sequencer inaccessible registers like segment register separated general-purpose register file except instruction pointer located scheduler instruction allocator order facilitate register renaming out-of-order execution x87 stack later merged floating-point register file 128-bit xmm register debuted pentium iii xmm register file still located separately x86 integer register files later p6 implementations pentium yonah introduced shadow register file architecture expanded 2 copies dual ported integer architectural register file consist context switch future retirered file scaled file using trick used integer floating point order solve register bottleneck exist x86 architecture micro op fusion introduced still 8 entries 32 bit architectural registers total 32 bytes capacity per file segment register instruction pointer remain within file though inaccessible program speculative file second file served scaled shadow register file without context switch scaled file store instruction independently instruction sse2/sse3/ssse3 require feature integer operation example instruction like pshufb pmaddubsw phsubw phsubd phsubsw phaddw phaddd phaddsw would require loading eax/ebx/ecx/edx register file though uncommon x86 processor take use another register file instruction time second file served scale retirered file pentium architecture still remains one dual-ported fp register file 8 entries mm/xmm shared three decoder fp register shadow register file shadow register file architecture including floating point function processor p6 architectural register file external locate processor backend retired opposite internal register file locate inner core register renaming/reorder buffer however core 2 within unit called register alias table rat located instruction allocator size register size retirement core 2 increased inner ring bus 24 bytes allow 3 instructions decoded extended register file dual ported one read/one write quad ported two read/two write register still remain 8 entries 32 bit 32 bytes including 6 segment register one instruction pointer unable access file code/instruction total file size expanded 16 entries x64 total 128 bytes size per file pentium pipeline port decoder increased 're located allocator table instead code buffer fp xmm register file also increase quad ported 2 read/2 write register still remain 8 entries 32 bit extended 16 entries x64 mode number still remain 1 shadow register file architecture including floating point/sse functions later x86 implementations like nehalem later processors integer floating point registers incorporated unified octa-ported six read two write general-purpose register file 8 8 32-bit 16 16 x64 per file register file extended 2 enhanced shadow register file architecture favorite executing hyper threading thread uses independent register files decoder later sandy bridge onward replaced shadow register table architectural registers much large yet advance physical register file decoding reorder buffer randered sandy bridge onward longer carry architectural register atom line modern simplified revision p5 includes single copies register file share thread decoder register file dual-port design 8/16 entries gprs 8/16 entries debug register 8/16 entries condition code integrated file however eight-entries 64 bit shadow based register eight-entries 64 bit unnamed register separated main gprs unlike original p5 design located execution unit file registers single-ported expose instruction like scaled shadow register file found core/core2 shadow register file made architectural registers bonnell due shadow register file architecture however file use renaming purpose due lack order execution found bonnell architecture also one copy xmm floating point register file per thread difference nehalem bonnell unified register file dedicated register file hyper threading instead bonnell uses separate rename register thread despite order similar bonnell larrabee xeon phi also one general-purpose integer register file larrabee 16 xmm register files 8 entries per file xeon phi 128 avx-512 register files containing 32 512-bit zmm registers vector instruction storage big l2 cache intel x86 lines n't register file internal design geode gx vortex86 many embedded processors n't pentium-compatible reverse-engineered early 80x86 processors therefore n't register file decoders gprs used individually pentium 4 hand register file decoder x86 gprs n't exist within structure due introduction physical unified renaming register file similar sandy bridge slightly different due inability pentium 4 use register naming attempting replace architectural register file skip x86 decoding scheme instead uses sse integer execution storage alu result sse2/sse3/ssse3 use mechanism well integer operation amd early design like k6 register file like intel support shadow register file architecture lack context switch bypass inverter necessary require register file function appropriately instead use separate gprs directly link rename register table oooe cpu dedicated integer decoder floating decoder mechanism similar intel pre-pentium processor line example k6 processor four int one eight-entries temporary scratched register file one eight-entries future register file one eight-entries fetched register file eight-entries unnamed register file two fp rename register files two eight-entries x87 st file one goes fadd one goes fmov directly link x86 eax integer renaming xmm0 register floating point renaming later athlon included shadow register front end scaled 40 entries unified register file order integer operation decoded register file contain 8 entries scratch register 16 future gprs register file 16 unnamed gprs register file later amd designs abandons shadow register design favored k6 architecture individual gprs direct link design like phenom three int register files two sse register files located physical register file directly linked gprs however scales one integer one floating-point bulldozer like early amd designs x86 manufacturers like cyrix via dm p sis used mechanism well resulting lack integer performance without register renaming in-order cpu companies like cyrix amd increase cache size hope reduce bottleneck amd sse integer operation work different way core 2 pentium 4 uses separate renaming integer register load value directly decode stage though theoretically need shorter pipeline intel sse implementation generally cost branch prediction much greater higher missing rate intel would take least two cycles sse instruction executed regardless instruction wide early amds implementations could execute fp int sse instruction set like intel implementation unlike alpha sparc mips allows one register file load/fetch one operand time would require multiple register files achieve superscale arm processor hand integrate multiple register files load/fetch instructions arm gprs special purpose instruction set arm isa require accumulator index stack/base points registers accumulator base/stack point used thumb mode gprs propagate store multiple instructions independently smaller code size small enough able fit one register architectural register act table shared decoder/instructions simple bank switching decoders major difference arm designs arm allows run general-purpose register quick bank switching without requiring additional register file superscalar despite x86 sharing mechanism arm gprs store data individually x86 confront data dependency three non-related instructions stored gprs per file small eight 32 bit mode 16 64 bit compared arm 13 32 bit 31 64 bit data impossible superscalar without multiple register files feed decoder x86 code big complex compared arm x86 front-ends become much larger much power hungry arm processor order competitive example pentium core 2 duo bay trail third-party x86 equivalent processors even became noncompetitive arm due dedicated register file architecture particularly amd cyrix via bring reasonable performance without register renaming order execution leave intel atom in-order x86 processor core mobile competition x86 nehalem processor merged integer floating point register one single file introduction large physical register table enhanced allocator table front-end renaming out-of-order internal core processors perform register renaming arrange functional unit write subset physical register file arrangement eliminate need multiple write ports per bit cell large savings area resulting register file effectively stack register files single write ports benefits replication subsetting read ports limit technique would place stack 1-write 2-read regfiles inputs functional unit since regfiles small number ports often dominated transistor area best push technique limit useful sparc isa defines register windows 5-bit architectural names registers actually point window much larger register file hundreds entries implementing multiported register files hundreds entries requires large area register window slides 16 registers moved architectural register name refer small number registers larger array e.g architectural register r20 refer physical registers 20 36 52 68 84 100 116 seven windows physical file save area sparc implementations implement 32-entry register file cell seven bits one read writeable external ports contents bits rotated rotation accomplishes single cycle movement register window wires accomplishing state movement local tremendous bandwidth possible little power technique used r10000 register renaming mapping file stores 6-bit virtual register number physical registers renaming file renaming state checkpointed whenever branch taken branch detected mispredicted old renaming state recovered single cycle see register renaming
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Computer architecture
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clsql clsql sql database interface common lisp created 2001 kevin m. rosenberg initially based substantially maisql package pierre r. mai orphaned onshore development marcus pearce ported uncommonsql package clsql provides commonsql-compatible api clsql clsql used query interface mysql postgresql odbc aodbc sqlite version 2 3 oracle oci
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Databases
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trigger list trigger list general meaning refers list whose items used initiate trigger certain actions united states person applies mortgage loan lender makes credit inquiry potential borrower national credit bureaus equifax experian transunion unless borrower opted credit bureaus put applicants onto trigger list leads persons interested new loans lists sold numerous lenders united states soon application applicant starts receiving offers parts country trigger lists contain significant amount personal financial information among buyers trigger lists lead generators resell filtered information borrowers e.g. people live certain area certain credit score federal trade commission considers market trigger lists legal business many people organizations national association mortgage brokers consider serious breach privacy lobby putting practice regulatory controls american consumers may opt-out trigger lists calling 1-888-5-optout 1-888-567-8688 zangger committee nuclear suppliers group maintain lists items may contribute nuclear proliferation nuclear non-proliferation treaty forbids members export items non-treaty members items said trigger countries responsibilities npt hence name
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Databases
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trusted computing base trusted computing base tcb computer system set hardware firmware and/or software components critical security sense bugs vulnerabilities occurring inside tcb might jeopardize security properties entire system contrast parts computer system outside tcb must able misbehave way would leak privileges granted accordance security policy careful design implementation system trusted computing base paramount overall security modern operating systems strive reduce size tcb exhaustive examination code base means manual computer-assisted software audit program verification becomes feasible term trusted computing base goes back john rushby defined combination kernel trusted processes latter refers processes allowed violate system access-control rules classic paper authentication distributed systems theory practice lampson et al define tcb computer system simply definitions clear convenient neither theoretically exact intended e.g network server process unix-like operating system might fall victim security breach compromise important part system security yet part operating system tcb orange book another classic computer security literature reference therefore provides formal definition tcb computer system words trusted computing base tcb combination hardware software controls work together form trusted base enforce security policy orange book explains words given piece hardware software part tcb designed part mechanism provides security computer system operating systems typically consists kernel microkernel select set system utilities example setuid programs daemons unix systems programming languages security features designed java e tcb formed language runtime standard library pointed consequence orange book definition boundaries tcb depend closely upon specifics security policy fleshed network server example even though say web server serves multi-user application part operating system tcb responsibility performing access control users usurp identity privileges sense definitely part tcb larger computer system comprises unix server user browsers web application words breaching web server e.g buffer overflow may regarded compromise operating system proper certainly constitutes damaging exploit web application fundamental relativity boundary tcb exemplified concept 'target evaluation 'toe common criteria security process course common criteria security evaluation one first decisions must made boundary audit terms list system components come scrutiny systems n't trusted computing base part design provide security secure insofar security provided external means e.g computer sitting locked room without network connection may considered secure depending policy regardless software runs david j. farber et al put nowiki n /nowiki computer system integrity lower layers typically treated axiomatic higher layers far computer security concerned reasoning security properties computer system requires able make sound assumptions importantly however barring reason believe otherwise computer able everything general von neumann machine obviously includes operations would deemed contrary simplest security policies divulging email password kept secret however barring special provisions architecture system denying computer could programmed perform undesirable tasks special provisions aim preventing certain kinds actions executed essence constitute trusted computing base reason orange book still reference design secure operating systems characterizes various security assurance levels defines mainly terms structure security features tcb outlined aforementioned orange book software portions trusted computing base need protect tampering effect due von neumann architecture implemented virtually modern computers since machine code processed another kind data read overwritten program barring special memory management provisions subsequently treated part tcb specifically trusted computing base must least prevent software written many modern cpus protection memory hosts tcb achieved adding specialized piece hardware called memory management unit mmu programmable operating system allow deny access specific ranges system memory programs run course operating system also able disallow programming programs technique called supervisor mode compared crude approaches storing tcb rom equivalently using harvard architecture advantage allowing security-critical software upgraded field although allowing secure upgrades trusted computing base poses bootstrap problems stated trust trusted computing base required make progress ascertaining security computer system words trusted computing base “ trusted ” first foremost sense trusted necessarily trustworthy real-world operating systems routinely security-critical bugs discovered attests practical limits trust alternative formal software verification uses mathematical proof techniques show absence bugs researchers nicta spinout open kernel labs recently performed formal verification sel4 member l4 microkernel family proving functional correctness c implementation kernel makes sel4 first operating-system kernel closes gap trust trustworthiness assuming mathematical proof free error due aforementioned need apply costly techniques formal verification manual review size tcb immediate consequences economics tcb assurance process trustworthiness resulting product terms mathematical expectation number bugs found verification review order reduce costs security risks tcb therefore kept small possible key argument debate preferring microkernels monolithic kernels aix materializes trusted computing base optional component install-time package management system
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Computer security
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tuvalu ship registry tuvalu ship registry body appointed government tuvalu register ships tuvalu flag ship registry launched 2004 located singapore operated tuvalu ship registry pte ltd ship registry managed behalf tuvalu government sovereign ventures sv pte ltd responsibilities registry include total 245 type bulk carrier 18 container ship 2 general cargo 36 oil tanker 27 162 2017 tuvalu entered international spotlight 2012 ships sailing flag iran registered tuvalu ship registry response european boycott iranian oil exports iran nuclear policy number oil tankers changed tuvalu flags according radio australia could lead unforeseen consequences small nation iranian vessels accepted tuvalu ship registry earlier flagged malta cyprus flags well-known reputable flags however upon understanding vessels actually sanctioned us eu government tuvalu took swift action instruct tuvalu ship registry de-register possible iranian-linked vessels 16 august 2012 iranian-linked vessels de-registered 21 september 2012 press releases actions taken tuvalu ship registry posted website iranian vessels later rumored gone flags tanzania mongolia others
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Databases
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operation europe path victory operation europe path victory released japan combat strategy video game multiple platforms one two players compete world war ii action ms-dos version game released north america object game fulfill one military objectives either axis allied forces players engage modern warfare around western europe eastern europe central europe north africa game uses abstract numbers figures map view saves concrete illustrations soldiers lock horns battlefield urban setting urban settings give traditional 1930s view housing office buildings provide extra protection units guarding however massive numbers crunch lack graphics help enhance number crunching ability game artificial intelligence way utilize nobunaga ambition video game engine simulating modern warfare general statistics completely randomized roulette system 84 different characters used generals including american television show combat examples non-fictional characters include adolf hitler josef stalin walter bedell smith weapons automatically replenished end scenario units built scratch must requested head brigade instead japanese version game 4 game modes campaign demonstration one player game 2 players game campaign mode player play germans starting mode invasion france german army continues fighting africa ending berlin defense officers gain experience every scenario retaining winning battle troops often replaced type one infantry artillery howitzers reactive artillery tanks self-propelled artillery armored infantry carriers mechanized units often give stronger instead weaker make losses battalion strong units although campaign mode directly available us version game still present game text translated needed graphics present formulas calculating quantity quality units operate allows game patched enable campaign mode reviewing snes version gamepro applauded intelligent ai stating even n't friend go head-to-head game still enjoyable challenging huge amount content arguing six scenarios essentially amount six complete games single cart though noting lack action gameplay would make unappealing average gamer concluded challenging strategy makes game serious ww ii buff without
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Computer architecture
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uninterruptible power supply uninterruptible power supply uninterruptible power source ups electrical apparatus provides emergency power load input power source mains power fails ups differs auxiliary emergency power system standby generator provide near-instantaneous protection input power interruptions supplying energy stored batteries supercapacitors flywheels on-battery run-time uninterruptible power sources relatively short minutes sufficient start standby power source properly shut protected equipment type continual power system ups typically used protect hardware computers data centers telecommunication equipment electrical equipment unexpected power disruption could cause injuries fatalities serious business disruption data loss ups units range size units designed protect single computer without video monitor around 200 volt-ampere rating large units powering entire data centers buildings world largest ups 46-megawatt battery electric storage system bess fairbanks alaska powers entire city nearby rural communities outages primary role ups provide short-term power input power source fails however ups units also capable varying degrees correcting common utility power problems manufacturers ups units categorize products accordance number power-related problems address three general categories modern ups systems on-line line-interactive standby ups one kilovolt-ampere 1 kva line-interactive standby variety usually less expensive large power units dynamic uninterruptible power supplies dups sometimes used synchronous motor/alternator connected mains via choke energy stored flywheel mains power fails eddy-current regulation maintains power load long flywheel energy exhausted dups sometimes combined integrated diesel generator turned brief delay forming diesel rotary uninterruptible power supply drups fuel cell ups developed recent years using hydrogen fuel cell power source potentially providing long run times small space offline/standby ups offers basic features providing surge protection battery backup protected equipment normally connected directly incoming utility power incoming voltage falls rises predetermined level sps turns internal dc-ac inverter circuitry powered internal storage battery ups mechanically switches connected equipment dc-ac inverter output switch-over time long 25 milliseconds depending amount time takes standby ups detect lost utility voltage ups designed power certain equipment personal computer without objectionable dip brownout device line-interactive ups similar operation standby ups addition multi-tap variable-voltage autotransformer special type transformer add subtract powered coils wire thereby increasing decreasing magnetic field output voltage transformer may also performed buck–boost transformer distinct autotransformer since former may wired provide galvanic isolation type ups able tolerate continuous undervoltage brownouts overvoltage surges without consuming limited reserve battery power instead compensates automatically selecting different power taps autotransformer depending design changing autotransformer tap cause brief output power disruption may cause upss equipped power-loss alarm chirp moment become popular even cheapest upss takes advantage components already included main 50/60 hz transformer used convert line voltage battery voltage needs provide two slightly different turns ratios one convert battery output voltage typically multiple 12 v line voltage second one convert line voltage slightly higher battery charging voltage multiple 14 v difference two voltages charging battery requires delta voltage 13–14 v charging 12 v battery furthermore easier switching line-voltage side transformer lower currents side gain buck/boost feature required two separate switches ac input connected one two primary taps load connected thus using main transformer primary windings autotransformer battery still charged bucking overvoltage boosting undervoltage transformer output low charge batteries autotransformers engineered cover wide range varying input voltages requires taps increases complexity expense ups common autotransformer cover range 90 v 140 v 120 v power switch battery voltage goes much higher lower range low-voltage conditions ups use current normal may need higher current circuit normal device example power 1000-w device 120 v ups draw 8.33 brownout occurs voltage drops 100 v ups draw 10 compensate also works reverse overvoltage condition ups need less current online ups batteries always connected inverter power transfer switches necessary power loss occurs rectifier simply drops circuit batteries keep power steady unchanged power restored rectifier resumes carrying load begins charging batteries though charging current may limited prevent high-power rectifier overheating batteries boiling electrolyte main advantage on-line ups ability provide electrical firewall incoming utility power sensitive electronic equipment online ups ideal environments electrical isolation necessary equipment sensitive power fluctuations although one time reserved large installations 10 kw advances technology permitted available common consumer device supplying 500 w less online ups may necessary power environment noisy utility power sags outages anomalies frequent protection sensitive equipment loads required operation extended-run backup generator necessary basic technology online ups standby line-interactive ups however typically costs much due much greater current ac-to-dc battery-charger/rectifier rectifier inverter designed run continuously improved cooling systems called double-conversion ups due rectifier directly driving inverter even powered normal ac current online ups typically static transfer switch sts increasing reliability hybrid rotary ups designs official designations although one name used utl double conversion demand style ups targeted towards high-efficiency applications still maintaining features protection level offered double conversion hybrid double conversion demand ups operates off-line/standby ups power conditions within certain preset window allows ups achieve high efficiency ratings power conditions fluctuate outside predefined windows ups switches online/double-conversion operation double-conversion mode ups adjust voltage variations without use battery power filter line noise control frequency ferroresonant units operate way standby ups unit however online exception ferroresonant transformer used filter output transformer designed hold energy long enough cover time switching line power battery power effectively eliminates transfer time many ferroresonant upss 82–88 efficient ac/dc-ac offer excellent isolation transformer three windings one ordinary mains power second rectified battery power third output ac power load dominant type ups limited around range units still mainly used industrial settings oil gas petrochemical chemical utility heavy industry markets due robust nature ups many ferroresonant upss utilizing controlled ferro technology may interact power-factor-correcting equipment result fluctuating output voltage ups may corrected reducing load levels adding linear type loads ups designed powering dc equipment similar online ups except need output inverter also ups battery voltage matched voltage device needs device power supply needed either since one power conversion steps eliminated increases efficiency run time many systems used telecommunications use extra-low voltage common battery 48 v dc power less restrictive safety regulations installed conduit junction boxes dc typically dominant power source telecommunications ac typically dominant source computers servers much experimentation 48 v dc power computer servers hope reducing likelihood failure cost equipment however supply amount power current would higher equivalent 115 v 230 v circuit greater current requires larger conductors energy lost heat laptop computer classic example pc dc ups built high voltage dc 380 v finding use data center applications allows small power conductors subject complex electrical code rules safe containment high voltages rotary ups uses inertia high-mass spinning flywheel flywheel energy storage provide short-term ride-through event power loss flywheel also acts buffer power spikes sags since short-term power events able appreciably affect rotational speed high-mass flywheel also one oldest designs predating vacuum tubes integrated circuits considered line since spins continuously normal conditions however unlike battery-based ups flywheel-based ups systems typically provide 10 20 seconds protection flywheel slowed power output stops traditionally used conjunction standby generators providing backup power brief period time engine needs start running stabilize output rotary ups generally reserved applications needing 10,000 w protection justify expense benefit advantages rotary ups systems bring larger flywheel multiple flywheels operating parallel increase reserve running time capacity flywheels mechanical power source necessary use electric motor generator intermediary diesel engine designed provide emergency power using transmission gearbox rotational inertia flywheel used directly start diesel engine running diesel engine used directly spin flywheel multiple flywheels likewise connected parallel mechanical countershafts without need separate motors generators flywheel normally designed provide high current output compared purely electronic ups better able provide inrush current inductive loads motor startup compressor loads well medical mri cath lab equipment also able tolerate short-circuit conditions 17 times larger electronic ups permitting one device blow fuse fail devices still continue powered rotary ups life cycle usually far greater purely electronic ups 30 years require periodic downtime mechanical maintenance ball bearing replacement larger systems redundancy system ensures availability processes maintenance battery-based designs require downtime batteries hot-swapped usually case larger units newer rotary units use technologies magnetic bearings air-evacuated enclosures increase standby efficiency reduce maintenance low levels typically high-mass flywheel used conjunction motor-generator system units configured case 3 motor generator synchronous/synchronous induction/synchronous motor side unit case nos 2 3 driven directly ac power source typically inverter bypass 6-step double-conversion motor drive 6-pulse inverter case 1 uses integrated flywheel short-term energy source instead batteries allow time external electrically coupled gensets start brought online case nos 2 3 use batteries free-standing electrically coupled flywheel short-term energy source smaller ups systems come several different forms sizes however two common forms tower rack-mount tower models stand upright ground desk shelf typically used network workstations desktop computer applications rack-mount models mounted standard 19-inch rack enclosures require anywhere 1u 12u rack units typically used server networking applications devices feature user interfaces rotate 90° allowing devices mounted vertically ground horizontally would found rack large business environments reliability great importance single huge ups also single point failure disrupt many systems provide greater reliability multiple smaller ups modules batteries integrated together provide redundant power protection equivalent one large ups n+1 means load supplied n modules installation contain n+1 modules way failure one module impact system operation many computer servers offer option redundant power supplies event one power supply failing one power supplies able power load critical point – power supply must able power entire server redundancy enhanced plugging power supply different circuit i.e different circuit breaker redundant protection extended yet connecting power supply ups provides double protection power supply failure ups failure continued operation assured configuration also referred 1+1 2n redundancy budget allow two identical ups units common practice plug one power supply mains power ups ups system placed outdoors specific features guarantee tolerate weather without effects performance factors temperature humidity rain snow among others considered manufacturer designing outdoor ups system operating temperature ranges outdoor ups systems could around −40 °c +55 °c outdoor ups systems either pole ground pedestal host mounted outdoor environment could mean extreme cold case outdoor ups system include battery heater mat extreme heat case outdoor ups system include fan system air conditioning system solar inverter pv inverter solar converter converts variable direct current dc output photovoltaic pv solar panel utility frequency alternating current ac fed commercial electrical grid used local off-grid electrical network critical bos–component photovoltaic system allowing use ordinary ac-powered equipment solar inverters special functions adapted use photovoltaic arrays including maximum power point tracking anti-islanding protection problem combination double-conversion ups generator voltage distortion created ups input double-conversion ups essentially big rectifier current drawn ups non-sinusoidal cause voltage ac mains generator also become non-sinusoidal voltage distortion cause problems electrical equipment connected power source including ups also cause power lost wiring supplying power ups due spikes current flow level noise measured percentage total harmonic distortion current thd classic ups rectifiers thd level around 25 –30 reduce voltage distortion requires heavier mains wiring generators twice large ups several solutions reduce thd double-conversion ups classic solutions passive filters reduce thd 5 –10 full load reliable big work full load present problems used tandem generators alternative solution active filter use device thd drop 5 full power range newest technology double-conversion ups units rectifier use classic rectifier components thyristors diodes uses high-frequency components instead double-conversion ups insulated-gate bipolar transistor rectifier inductor thd small 2 completely eliminates need oversize generator transformers without additional filters investment cost losses space power management pm requires basic computer-to-ups control methods intended one-to-one signaling single source single target example single ups may connect single computer provide status information ups allow computer control ups similarly usb protocol also intended connect single computer multiple peripheral devices situations useful single large ups able communicate several protected devices traditional serial usb control signal replication device may used example allows one ups connect five computers using serial usb connections however splitting typically one direction ups devices provide status information return control signals may permitted one protected systems ups ethernet increased common use since 1990s control signals commonly sent single ups multiple computers using standard ethernet data communication methods tcp/ip status control information typically encrypted example outside hacker gain control ups command shut distribution ups status control data requires intermediary devices ethernet switches serial multiplexers powered one ups systems order ups alerts reach target systems power outage avoid dependency ethernet infrastructure upss connected directly main control server using gsm/gprs channel also sms gprs data packets sent upss trigger software shut pcs reduce load three main types ups batteries valve regulated lead acid vrla flooded cell vla batteries lithium ion batteries run-time battery-operated ups depends type size batteries rate discharge efficiency inverter total capacity lead–acid battery function rate discharged described peukert law manufacturers supply run-time rating minutes packaged ups systems larger systems data centers require detailed calculation load inverter efficiency battery characteristics ensure required endurance attained lead–acid battery charged discharged initially affects reacting chemicals interface electrodes electrolyte time charge stored chemicals interface often called interface charge spreads diffusion chemicals throughout volume active material battery completely discharged e.g car lights left overnight next given fast charge minutes short charging time develops charge near interface battery voltage may rise close charger voltage charging current decreases significantly hours interface charge spread volume electrode electrolyte leading interface charge low may insufficient start car due interface charge brief ups self-test functions lasting seconds may accurately reflect true runtime capacity ups instead extended recalibration rundown test deeply discharges battery needed deep discharge testing damaging batteries due chemicals discharged battery starting crystallize highly stable molecular shapes re-dissolve battery recharged permanently reducing charge capacity lead acid batteries known sulfation also affects types nickel cadmium batteries lithium batteries therefore commonly recommended rundown tests performed infrequently every six months year multi-kilowatt commercial ups systems large easily accessible battery banks capable isolating testing individual cells within battery string consists either combined-cell battery units 12-v lead acid batteries individual chemical cells wired series isolating single cell installing jumper place allows one battery discharge-tested rest battery string remains charged available provide protection also possible measure electrical characteristics individual cells battery string using intermediate sensor wires installed every cell-to-cell junction monitored individually collectively battery strings may also wired series-parallel example two sets 20 cells situation also necessary monitor current flow parallel strings current may circulate strings balance effects weak cells dead cells high resistance shorted cells example stronger strings discharge weaker strings voltage imbalances equalized must factored individual inter-cell measurements within string battery strings wired series-parallel develop unusual failure modes due interactions multiple parallel strings defective batteries one string adversely affect operation lifespan good new batteries strings issues also apply situations series-parallel strings used ups systems also electric vehicle applications consider series-parallel battery arrangement good cells one becomes shorted dead way prevent subtle series-parallel string interactions using parallel strings using separate charge controllers inverters individual series strings even single string batteries wired series adverse interactions new batteries mixed old batteries older batteries tend reduced storage capacity discharge faster new batteries also charge maximum capacity rapidly new batteries mixed string new old batteries depleted string voltage drop old batteries exhausted new batteries still charge available newer cells may continue discharge rest string due low voltage energy flow may useful may wasted old cells resistance heating cells supposed operate within specific discharge window new cells capacity may cause old cells series string continue discharge beyond safe bottom limit discharge window damaging old cells recharged old cells recharge rapidly leading rapid rise voltage near fully charged state new cells capacity fully recharged charge controller detects high voltage nearly fully charged string reduces current flow new cells capacity charge slowly slowly chemicals may begin crystallize reaching fully charged state reducing new cell capacity several charge/discharge cycles capacity closely matches old cells series string reasons industrial ups management systems recommend periodic replacement entire battery arrays potentially using hundreds expensive batteries due damaging interactions new batteries old batteries within across series parallel strings
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Computer security
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xampp xampp free open-source cross-platform web server solution stack package developed apache friends consisting mainly apache http server mariadb database interpreters scripts written php perl programming languages since actual web server deployments use components xampp makes transitioning local test server live server possible xampp ease deployment means wamp lamp stack installed quickly simply operating system developer advantage number common add-in applications wordpress joomla also installed similar ease using bitnami term xampp apparent acronym however official acronym expansion specified apache friends website homepage header reads xampp apache mariadb php perl indicating abbreviation recursive acronym term unofficially broken follows mysql replaced mariadb 2015-10-19 beginning xampp versions 5.5.30 5.6.14 effectively altering meaning acronym letters p de facto interchangeable convention used apache friends website indicates first letter p short php latter letter p short perl xampp requires one zip tar 7z exe file downloaded run little configuration various components make web server required windows version xampp requires microsoft visual c++ 2017 redistributable xampp regularly updated latest releases apache mariadb php perl also comes number modules including openssl phpmyadmin mediawiki joomla wordpress self-contained multiple instances xampp exist single computer given instance copied one computer another xampp offered full standard version smaller version obvious characteristic xampp ease wamp webserver stack deployed instantiated later common packaged applications could easily installed provided bitnami officially xampp designers intended use development tool allow website designers programmers test work computers without access internet make easy possible many important security features disabled default xampp ability serve web pages world wide web special tool provided password-protect important parts package xampp also provides support creating manipulating databases mariadb sqlite among others xampp installed possible treat localhost like remote host connecting using ftp client using program like filezilla many advantages installing content management system cms like joomla wordpress also possible connect localhost via ftp html editor
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Web technology
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tcllib tcllib collection packages available tcl programming language tcllib distributed source code well pre-compiled binary formats tcllib supports variety common operating systems windows bsd unix linux tcllib includes implementations many common data structure algorithms linked list hash map tree graph
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Programming language topics
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michael franz michael franz american computer scientist best known pioneering work just-in-time compilation optimization artificial software diversity chancellor professor computer science donald bren school information computer sciences university california irvine uci professor electrical engineering computer science courtesy henry samueli school engineering uci director uci secure systems software laboratory fellow acm fellow ieee recipient ieee computer society technical achievement award humboldt prize graduated 27 ph.d.s primary advisor published 130 peer-reviewed articles holds 5 u.s patents also co-founder immunant inc. start-up company specializing software security born raised hamburg germany franz attended christianeum hamburg gordonstoun school elgin scotland eventually graduated christianeum accelerated high school diploma vorgezogenes abitur ahead rest class completing military service germany franz moved switzerland begin studies computer science eth zurich finishing diplom-ingenieur degree 1989 undergraduate years president eth computer science students association declining full fulbright scholarship would funded doctoral studies united states stayed eth began doctoral studies supervision turing award winner niklaus wirth completing doctor technical sciences degree 1994 following two years eth zurich senior research associate lecturer joined university california irvine assistant professor computer science january 1996 promoted associate professor 2001 full professor 2006 since 2007 held second appointment uci school engineering professor electrical engineering computer sciences courtesy 2016 awarded title chancellor professor franz well known pioneering advancing several research ideas quite unconventional proposed seem almost obvious hindsight doctoral dissertation entitled code generation on-the-fly key portable software proposed make software portable among different target computer architectures way using on-the-fly compilation compressed intermediate data structure load time two years later java programming language system launched took idea mainstream albeit using term just-in-time compilation instead term on-the-fly compilation franz used franz also one first academics realize javascript going huge time academic community ignoring javascript similar dynamic languages little scripting languages franz student andreas gal researched one would best tackle specific features dynamically typed language just-in-time compiler resulting technique trace tree compilation covered u.s. patent franz took idea brendan eich inventor javascript mozilla cto time collaborative project uci mozilla born eventually culminated tracemonkey javascript engine firefox recently franz one main drivers moving target defense movement cyber security pioneering compiler-generated software diversity defense mechanism software attacks inspired biodiversity nature imagine app store containing diversification engine multicompiler automatically generates unique version every program every user different versions program behave exactly way perspective end-user implement functionality subtly different ways result specific attack succeed small fraction targets attacker would require large number different attacks would way knowing priori specific attack succeed specific target equally importantly approach makes much difficult attacker generate attack vectors way reverse engineering security patches project attracted attention beyond academia coverage popular press ranging far economist wired magazine franz students hold u.s. patent underlying ideas
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Programming language topics
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powerpc e200 powerpc e200 family 32-bit power isa microprocessor cores developed freescale primary use automotive industrial control systems cores designed form cpu part system-on-a-chip soc designs speed ranging 600 mhz thus making ideal embedded applications e200 core developed mpc5xx family processors turn derived mpc8xx core powerquicc soc processors e200 adheres power isa v.2.03 well previous book e specification e200 core based microprocessors named mpc55xx mpc56xx/jpc56x scheme confused mpc52xx processors based powerpc e300 core april 2007 freescale ipextreme opened e200 cores licensing manufacturers continental ag freescale developing space tri-core e200 based processor designed electronic brake systems cars stmicroelectronics freescale jointly developed microcontrollers automotive applications based e200 mpc56xx/spc56x family e200 family consists six cores simple low-end complex high-end nature simplest core e200z0 features order four stage pipeline mmu cache fpu uses variable bit length vle part power isa uses 16-bit versions otherwise standard 32-bit powerpc book e isa thus reducing code footprint 30 single 32-bit amba 2.0v6 bus interface load/store unit pipelined 1-cycle load latency supports throughput one load store operation per cycle e200z0 used mpc5510 optional co-processor alongside e200z1 core making chip multicore processor e200z0 available co-processors e200 based processors well low end stand alone processors e200z1 four-stage single-issue pipeline branch prediction unit 8 entry mmu cache fpu use complete 32-bit powerpc isa well vle instructions uses dual 32-bit amba 2.0v6 bus interface load/store unit pipelined 1-cycle load latency supports throughput one load store operation per cycle e200z3 four-stage single-issue pipeline branch prediction unit 16 entry mmu simd capable fpu cache use complete 32-bit powerpc isa well vle instructions uses dual 64-bit amba 2.0v6 bus interface load/store unit pipelined 1-cycle load latency supports throughput one load store operation per cycle e200z4 five-stage dual-issue pipeline branch prediction unit 16 entry mmu signal processing extension spe simd capable single precision fpu 4 kilobyte 2/4-way set associative instruction l1 cache pseudo round-robin replacement algorithm data cache use complete 32-bit powerpc isa well vle instructions uses dual 64-bit bus amba 2.0v6 interface load/store unit pipelined 2-cycle load latency supports throughput one load store operation per cycle depending derivative may support spe lsp e200z6 seven-stage single-issue pipeline branch prediction unit 32 entry mmu signal processing extensions spe simd capable single-precision fpu 8-way set associative 32 kib unified data/instruction l1 cache use complete 32-bit powerpc isa well vle instructions uses single 64-bit bus amba 2.0v6 interface load/store unit pipelined 3-cycle load latency supports throughput one load store operation per cycle e200z7 ten-stage dual-issue pipeline branch prediction unit 32 entry mmu simd capable single-precision fpu 16-kb 4 way set-associative harvard instruction data l1 caches use complete 32-bit powerpc isa well vle instructions uses 32-bit bus amba 2.0v6 interface address bus 64-bit data bus plus attributes control bus load/store unit pipelined 3-cycle load latency supports throughput one load store operation per cycle depending derivative may support spe spe v1.1 spe v2
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Computer architecture
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static build static build compiled version program statically linked libraries computer science linking means taking one objects generated compilers assembling single executable program objects program modules containing machine code symbol definitions come two varieties linker program resolves references undefined symbols finding object defines symbol question replacing placeholders symbol address linkers take objects collection called library final program include whole library objects needed libraries diverse purposes exist one system libraries usually linked default modern operating system environments allow dynamic linking postponing resolving undefined symbols program run means executable still contains undefined symbols plus list objects libraries provide definitions loading program load objects/libraries well perform final linking dynamic linking offers three advantages statically built program dynamic linking occurs bindings done compile time static builds predictable behavior rely particular version libraries available final system commonly found forensic security tools avoid possible contamination malfunction due broken libraries examined machine flexibility permits upgraded library benefit dynamically-linked applications also prevent applications assume presence specific version particular library running correctly every application system must copy dynamic library ensure correct operation benefits dynamic linking moot another benefit static builds portability final executable file compiled longer necessary keep library files program references since relevant parts copied executable file result installing statically-built program computer user n't download install additional libraries program ready run
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Programming language topics
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dynamic site acceleration dynamic site acceleration dsa group technologies make delivery dynamic websites efficient manufacturers application delivery controllers content delivery networks cdns use host techniques accelerate dynamic sites including edge device either adc cdn capable tcp multiplexing placed web servers clients offload origin servers accelerate content delivery usually connection client server requires dedicated process lives origin duration connection clients slow connection occupies part origin server process stay alive server waiting complete request tcp multiplexing situation different device obtains complete valid request client sending origin request fully arrived offloads application database servers slower expensive use compared adcs cdns http built-in system cache control using headers etag expires last modified many cdns adcs claim dsa replaced system calling dynamic caching dynamic cache control gives options invalidate bypass cache standard http cache control purpose dynamic cache control increase cache-hit ratio website rate requests served cache served normal server due dynamic nature web 2.0 websites difficult use static web caching reason dynamic sites per definition personalized content different users regions example mobile users may see different content desktop users may see registered users may need see different content anonymous users see even among registered users content may vary widely often example social media websites static caching dynamic user-specific pages introduces potential risk serving irrelevant content 3rd party content wrong users identifier allowing caching system differentiate content url/get-request n't correctly varied appending user-specific tokens/keys dynamic cache control options configure caching cookie-based cache control allows serving content cache based presence lack specific cookies cookie stores unique identifier-key logged-in user device already implemented authenticating users upon execution page opens session dynamic caching system caches referred url well cookie keys allowing simply enable serving default caches anonymous users personalized caches logged-in users without forcing modify code make append additional user identifiers url like static caching system personalized content cached might queued edge device means system store list possible responses might needed future allowing readily served differs caching prefetched responses served especially useful accelerating responses third-party apis advertisements route optimization also known latency-based routing optimizes route traffic clients different origin servers order minimize latency route optimization done dns provider cdn route optimization comes measuring multiple paths client origin server recording fastest path path used serve content client specific geographical zone makes request although front-end optimization feo dsa describe group techniques improve online content delivery work different aspects overlaps on-the-fly data compression improved cache-control however key differences
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Web technology
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mysql archive mysql archive storage engine mysql relational database management system users use analytic storage engine create table “ archive ” data deleted table added archive engine uses compression strategy based zlib library packs rows using bit header represent nulls removes whitespace character type fields completed row inserted compression buffer flushed disk explicit flush table read closing table one current restrictions archive tables support indexes thus necessitating table scan select tasks archive tables however supported mysql query cache dramatically reduce response times archive table queries repetitively issued mysql examining index support archive tables upcoming releases engine acid compliant unlike oltp engines uses stream format disk block boundaries head archive file generated byte array representing data format contents file mysql 5.1 copy mysql frm file stored header archive file frm file represents definition table allows archive file restored mysql server archive file copied server despite use zlib archive files compatible gzio basis gzip tools uses azio system fork gzio archive differs mysql analytical engine myisam row level locking engine keeping constant version snapshot throughout single query making mvcc means archive lock concurrent bulk inserts bulk inserts performs interlaced insert unlike myisam order guaranteed users use archive_reader tool take online snapshot table change characteristics archive file create archive table specify following engine string mysql archive storage engine authored maintained brian aker introduced 2004 mysql 4.1
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Databases
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jeff waugh jeff waugh also known jdub australian free software open source software engineer known past prominence gnome ubuntu projects communities 2004 waugh hired mark shuttleworth early employee canonical ltd. member ubuntu project worked business development oscon 2005 waugh best evangelist google-o'reilly open source awards evangelism ubuntu gnome announced resignation canonical july 2006 focus fully work gnome project 2007 waugh then-wife pia waugh co-directors waugh partners australian open source consultancy launched 2006 waugh partners 2007 nsw state pearcey award young achievers work promoting free software australian ict industry 2008 waugh partner one laptop per child australia program 2008 pia waugh moved new career waugh later employers included bulletproof networks kounta waugh served number formal semi-formal positions free software development community projects waugh author python feed aggregator planet waugh married fellow open-source advocate community leader pia waugh 2011 wrote blog september 2011 occasion ruok day struggling depression since late teens contributing factor divorce felt overcome category living people category open source people category free software programmers category year birth missing living people category australian computer specialists category gnome developers category ubuntu operating system people category people sydney category australian bloggers
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Operating systems
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turbot business turbot turbot hq inc privately held software company headquartered united states turbot provides automated cloud governance controls enterprise cloud applications infrastructure turbot founded nathan wallace 2014 us corporation based nj 2016 company expanded virtual office across varying us states 2017 turbot announced expansion united kingdom turbot hq limited india turbot hq india private limited 2018 turbot expanded footprint multiple cities india started operations australia turbot hq private limited turbot provides real-time automated configuration control software-defined infrastructure cloud platforms turbot aws advanced technology partner multiple certified competencies security cloud management life sciences etc turbot also microsoft azure partner google cloud platform partner well member cloud native computing foundation linux foundation center internet security turbot varying consulting managed services technology integration partnerships providing varying use cases partners empower services capabilities turbot uses “ sandbox ” approach governance allows internal departments freedom explore adopt new software solutions adhering data protection regulations
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Distributed computing architecture
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wide area information server wide area information server wais client–server text searching system uses ansi standard z39.50 information retrieval service definition protocol specifications library applications z39.50:1988 search index databases remote computers developed late 1980s project thinking machines apple computer dow jones kpmg peat marwick wais adhere either standard osi framework adopting instead tcp/ip created unique protocol inspired z39.50:1988 wais protocol servers promoted thinking machines corporation tmc cambridge massachusetts tmc-produced wais servers ran massively parallel cm-2 connection machine sparc-based cm-5 mp supercomputers wais clients developed various operating systems windowing systems including microsoft windows macintosh next x gnu emacs character terminals tmc released free open source software version wais unix 1991 inspired wais project full-text databases emerging sgml projects z39.50 version 2 z39.50:1992 released unlike 1988 predecessor compatible superset international iso 10162/10163 standard advent z39.50:1992 termination support free wais thinking machines establishment wais inc commercial venture u.s. national science foundation funded clearinghouse networked information discovery retrieval cnidr promote internet search discovery systems open source standards cnidr created new free open-source wais first freewais based wais-8-b5 codebase tmc wholly new software suite isite based upon z39.50:1992 using isearch full-text search engine ulrich pfeifer norbert gövert computer science department university dortmund extended cnidr freewais code become freewais-sf structured fields main improvement ulrich pfeifer rewrote freewais-sf perl becoming wait inspired wais directory servers eliot christian usgs envisioned gils government information locator service gils based upon z39.50:1992 extensions became u.s. federal mandate part paperwork reduction act 1995 thinking machines corp provided service called directory servers wais server like information source except containing information wais servers internet wais server tmc wais code creates special record containing metadata plus common words describing indexed content record uploaded central server indexed along records public servers directory searched find servers might content relevant specific field interest model searching wais servers search became model gils peter deutsch whois++ distributed white pages directory two developers wais brewster kahle harry morris left thinking machines found wais inc menlo park california bruce gilliat wais inc. originally joint project apple computer peat markwick dow jones thinking machines 1992 presidential campaign ross perot used wais product campaign wide information system connecting field offices national office later perot systems adopted wais better access information corporate databases early clients environmental protection agency library congress department energy later wall street journal encyclopædia britannica wais inc sold aol may 1995 15 million following sale margaret st. pierre left wais inc start blue angel technologies wais variant formed basis metastar georgios papadopoulos left found atypon françois schiettecatte left human genome project johns hopkins hospital started fs-consult developed variant wais eventually became scienceserver later sold elsevier science kahle gilliat went found internet archive alexa internet public wais often used full-text search engine individual internet gopher servers supplementing popular veronica system searches menu titles gopher sites wais gopher share world wide web client–server architecture certain amount functionality wais protocol influenced largely z39.50 protocol designed networking library catalogs allows text-based search retrieval following search gopher provides free text search mechanism principally uses menus menu list titles user may pick one gopher space web containing many loops menu system gives user impression tree web data model similar gopher model except menus generalized hypertext documents cases simple file servers generate menus hypertext directly file structure server web hypertext model permits author freedom communicate options available reader include headings various forms list structure
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Internet protocols
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gamma group gamma group anglo-german technology company sells surveillance software governments police forces around world company strongly criticised human rights organisations selling finfisher software undemocratic regimes egypt bahrain following arab spring protests 2011 activists bahrain identified suspicious emails identified social engineering attempts persuade launch applications containing malicious software emails passed analysts identified malware would give finfisher access infected computers university toronto citizenlab conducted investigation gamma identified 33 likely government users finfisher 32 countries based presence finfisher master ip address country belonging specific government department 2014 gamma group hacked 40 gb dump information released detailing gamma 'client lists price lists source code details effectiveness finfisher malware user support documentation list classes/tutorials much details gamma capabilities found surveillance industry index despite hack extent negative publicity gamma activities finfisher reported gaining popularity around world numerous governments
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Computer security
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incr tcl incr tcl commonly stylised nowiki incr tcl /nowiki often abbreviated itcl set object-oriented extensions tcl programming language widely used among tcl community generally regarded industrial strength name pun c++ itcl implementations exist package may dynamically loaded tcl application well independent standalone language interpreter itcl allows namespaces used organizing commands variables example itcl like tcl built-in support integration c code itcl classes itcl follows copyright restrictions tcl/tk use copy modify even redistribute software without written agreement royalty provided keep copyright notices intact claim ownership software authors institutions retain ownership described license.terms files included standard distribution information please see incrtcl.sourceforge.net/itcl/copyright.html incr tcl ground chad smith published january 2000
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Programming language topics
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mp6 rise mp6 superpipelined superscalar microprocessor designed rise technology compete intel pentium line rise technology spent 5 years developing x86 compatible microprocessor finally introduced november 1998 low-cost low-power alternative super socket 7 platform allowed higher front-side bus speeds previous socket 7 made possible cpu manufacturers keep competing intel moved slot 1 platform mp6 made use mmx instruction set three mmx pipelines allowed cpu execute three mmx instructions single cycle three integer units made possible execute three integer instructions single cycle well fully pipelined floating point unit could execute two floating-point instructions per cycle improve performance core utilized branch prediction number techniques resolve data dependency conflicts according rise mp6 perform almost fast intel pentium ii frequencies despite innovative features real-life performance mp6 proved disappointing mainly due small l1 cache another reason rise mp6 pr 266 rating based upon old intel pentium mmx main competitors intel celeron 266 idt winchip 2-266 amd k6-2 266 delivered performance benchmarks applications celeron k6-2 actually worked 266 mhz winchip 2 pr rating based upon performance amd opponent announced 1998 chip never achieved widespread use rise quietly exited market december following year like competitors cyrix idt rise found unable compete intel amd silicon integrated systems sis licensed mp6 technology used sis 550 system-on-a-chip soc integrated mp6 cpu north south bridges sound video single chip sis 550 saw use compact pcs consumer devices dvd players sis 551 chip also marketed dm p vortex86 m6127d later dm p took mp6 design sis continues development vortex86 soc product line dm p signed agreement xcore allow rebrand chip xcore86
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Computer architecture
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vxinsight vxinsight knowledge mining tool developed sandia national laboratories institute scientific information allows user visualize relationship groups objects large databases 3d landscape hillier et al call pioneering study vxinsight used analyze gene expression i.e microarray data across number conditions c. elegans using vxinsight kim et al able cluster genes mounts coherent functions also able make novel observations finding distinct classes transposons tc3 mariner transposons appear differentially regulated development
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Databases
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in-database processing in-database processing sometimes referred in-database analytics refers integration data analytics data warehousing functionality today many large databases used credit card fraud detection investment bank risk management use technology provides significant performance improvements traditional methods traditional approaches data analysis require data moved database separate analytics environment processing back database spss ibm examples tools still today analysis database data resides eliminates costs time security issues associated old approach processing data warehouse though in-database capabilities first commercially offered mid-1990s object-related database systems vendors including ibm illustra/informix ibm oracle technology begin catch mid-2000s concept migrating analytics analytical workstation enterprise data warehouse first introduced thomas tileston presentation entitled “ cake eat accelerate data mining combining sas teradata ” teradata partners 2005 experience possibilities conference orlando fl september 18–22 2005 mr. tileston later presented technique globally 2006 2007 2008 point need in-database processing become pressing amount data available collect analyze continues grow exponentially due largely rise internet megabytes gigabytes terabytes petabytes “ big data ” one primary reasons become important collect process analyze data efficiently accurately also speed business accelerated point performance gain nanoseconds make difference industries additionally people industries use data answer important questions questions ask become complex demanding sophisticated tools precise results factors combination created need in-database processing introduction column-oriented database specifically designed analytics data warehousing reporting helped make technology possible three main types in-database processing translating model sql code loading c c++ libraries database process space built-in user-defined function udf out-of-process libraries typically written c c++ java registering database built-in udfs sql statement type in-database processing predictive model converted source language sql run database usually stored procedure many analytic model-building tools ability export models either sql pmml predictive modeling markup language sql loaded stored procedure values passed parameters model executed natively database tools use approach include sas spss r kxen c c++ udf libraries run process functions typically registered built-in functions within database server called like built-in function sql statement running process allows function full access database server ’ memory parallelism processing management capabilities functions must well-behaved negatively impact database engine type udf gives highest performance method olap mathematical statistical univariate distributions data mining algorithms out-of-process udfs typically written c c++ java running process run risk database engine run process space resources ’ expected performance in-process udf still typically registered database engine called standard sql usually stored procedure out-of-process udfs safe way extend capabilities database server ideal way add custom data mining libraries in-database processing makes data analysis accessible relevant high-throughput real-time applications including fraud detection credit scoring risk management transaction processing pricing margin analysis usage-based micro-segmenting behavioral ad targeting recommendation engines used customer service organizations determine next-best actions in-database processing performed promoted feature many major data warehousing vendors including teradata aster data systems acquired ibm netezza puredata systems db2 warehouse products iemc greenplum sybase paraccel sas exasol products offered vendors cwi monetdb ibm db2 warehouse offer users means write functions udfs extensions udxs enhance products capabilities fuzzy logix offers libraries in-database models used mathematical statistical data mining simulation classification modelling well financial models equity fixed income interest rate portfolio optimization in-database pioneers collaborates marketing teams institutionalize data mining analytic processes inside data warehouse fast reliable customizable consumer-behavior predictive analytics in-database processing one several technologies focused improving data warehousing performance others include parallel computing shared everything architectures shared nothing architectures massive parallel processing important step towards improving predictive analytics capabilities
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Databases
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preemption computing computing preemption act temporarily interrupting task carried computer system without requiring cooperation intention resuming task later time changes executed task known context switches normally carried privileged task part system known preemptive scheduler power preempt interrupt later resume tasks system given system design operations performed system may preemptible usually applies kernel functions service interrupts permitted run completion would tend produce race conditions resulting deadlock barring scheduler preempting tasks processing kernel functions simplifies kernel design expense system responsiveness distinction user mode kernel mode determines privilege level within system may also used distinguish whether task currently preemptible modern systems preemptive kernels designed permit tasks preempted even kernel mode examples systems solaris 2.0/sunos 5.0 windows nt linux kernel 2.6.x newer aix bsd systems netbsd since version 5 term preemptive multitasking used distinguish multitasking operating system permits preemption tasks cooperative multitasking system wherein processes tasks must explicitly programmed yield need system resources simple terms preemptive multitasking involves use interrupt mechanism suspends currently executing process invokes scheduler determine process execute next therefore processes get amount cpu time given time preemptive multitasking operating system kernel also initiate context switch satisfy scheduling policy priority constraint thus preempting active task general preemption means prior seizure high priority task instance seizes currently running task known preemptive scheduling term preemptive multitasking sometimes mistakenly used intended meaning specific referring instead class scheduling policies known time-shared scheduling time-sharing preemptive multitasking allows computer system reliably guarantee process regular slice operating time also allows system rapidly deal important external events like incoming data might require immediate attention one another process specific time processes grouped two categories waiting input output called i/o bound fully utilizing cpu cpu bound early systems processes would often poll busywait waiting requested input disk keyboard network input time process performing useful work still maintained complete control cpu advent interrupts preemptive multitasking i/o bound processes could blocked put hold pending arrival necessary data allowing processes utilize cpu arrival requested data would generate interrupt blocked processes could guaranteed timely return execution although multitasking techniques originally developed allow multiple users share single machine soon became apparent multitasking useful regardless number users many operating systems mainframes single-user personal computers no-user control systems like robotic spacecraft recognized usefulness multitasking support variety reasons multitasking makes possible single user run multiple applications time run background processes retaining control computer period time process allowed run preemptive multitasking system generally called time slice quantum scheduler run every time slice choose next process run length time slice critical balancing system performance vs process responsiveness time slice short scheduler consume much processing time time slice long processes take longer respond input interrupt scheduled allow operating system kernel switch processes time slices expire effectively allowing processor time shared number tasks giving illusion dealing tasks parallel simultaneously operating system controls design called multi-tasking system today nearly operating systems support preemptive multitasking including current versions windows macos linux including android ios earliest operating systems available home users featuring preemptive multitasking sinclair qdos 1984 amiga os 1985 ran motorola 68000-family microprocessors without memory management amiga os used dynamic loading relocatable code blocks hunks amiga jargon multitask preemptively processes flat address space early pc operating systems ms-dos pc dos support multitasking however alternative operating systems mp/m-86 1981 concurrent cp/m-86 support preemptive multitasking unix-like systems including minix coherent provided preemptive multitasking 1980s-era personal computers later dos versions natively supporting preemptive multitasking/multithreading include concurrent dos multiuser dos novell dos later called caldera opendos dr-dos 7.02 higher since concurrent dos 386 could also run multiple dos programs concurrently virtual dos machines earliest version windows support limited form preemptive multitasking windows 2.1x used intel 80386 virtual 8086 mode run dos applications virtual 8086 machines commonly known dos boxes could preempted windows 95 98 32-bit applications made preemptive running one separate address space 16-bit applications remained cooperative backward compatibility windows 3.1x protected mode kernel virtual device drivers ran preemptively 16-bit applications non-preemptive shared address space preemptive multitasking always supported windows nt versions os/2 native applications unix unix-like systems linux bsd macos vms os/360 many operating systems designed use academic medium-to-large business markets although plans upgrade cooperative multitasking found classic mac os preemptive model preemptive api exist mac os 9 although limited sense abandoned favor mac os x called macos hybrid old mac system style nextstep operating system based mach kernel derived part bsd always provided unix-like preemptive multitasking
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Operating systems
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list sip response codes session initiation protocol sip signalling protocol used controlling communication sessions voice ip telephone calls sip based around request/response transactions similar manner hypertext transfer protocol http transaction consists sip request one several request methods least one response sip requests responses may generated sip user agent user agents divided clients uacs initiate requests servers uases respond single user agent may act uac uas different transactions example sip phone user agent uac making call uas receiving one additionally devices act uac uas single transaction called back-to-back user agents b2buas sip responses specify three-digit integer response code one number defined codes detail status request codes grouped according first digit provisional success redirection client error server error global failure codes corresponding first digit 1–6 expressed example 1xx provisional responses code 100–199 sip response codes consistent http response codes although http response codes valid sip sip responses also specify reason phrase default reason phrase defined response code reason phrases varied however provide additional information provide text different language sip response codes corresponding reason phrases initially defined rfc 3261 rfc also defines sip parameters internet assigned numbers authority iana registry allow rfc provide response codes list includes sip response codes defined ietf rfcs registered sip parameters iana registry list also includes sip response codes defined obsolete sip rfcs specifically rfc 2543 therefore registered iana explicitly noted
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Internet protocols
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jordan antiquities database information system jordan antiquities database information system jadis computer database antiquities jordan first kind arab world established department antiquities 1990 cooperation american center oriental research amman sponsored united states agency international development jadis use 2002 superseded new system mega-j 10,841 antiquities registered database
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Databases
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qualis capes qualis brazilian official system purpose classifying scientific production maintained coordenadoria de aperfeiçoamento de pessoal de nível superior capes government agency linked brazilian ministry education qualis task classify evaluate academic means used production scientific publications post-graduate programs master theses doctoral dissertations classification occurs system grades per field evaluation depends level circulation local national international quality journal b c classification annually updated follows series criteria defined capes number issues indexation number publishing institutions impact factor based jcr etc grades called strata occur 1–8 scale a1 highest a2 b1 b2 b3 b4 b5 c — listed
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Databases
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thunderbyte antivirus thunderbyte anti-virus tbav early antivirus software product created dutchman frans veldman 1988 published company esass b.v mainly designed dos also versions supporting microsoft windows tbav known fast scan speed heuristics-based scanner codice_1 files tracking known-good file information originally thunderbyte used dedicated isa card provide protection operating system even loaded later software-only product released soon displaced hardware offering distributed shareware 1998 tbav sold norman asa discontinued thunderbyte product
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Computer security
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ekool ekool school management system used estonia covering 90 nation school network connecting pupils parents teachers involved estimated application used 28-30 estonians total name ekool means eschool estonian system usable teachers pupils parents exchange information time tables grades homework assignments similar features ekool created 2002 look world foundation cooperation companies private sector originally designed meet requirements four test schools rocca al mare school jüri gymnasium kuresaare gymnasium tallinn arte gymnasium since grown cover 90 estonian school network ekool started 2002 replace printed school diaries digital journals would enable parents students see grades homework assignments online pilot project launched specifications 4 schools rocca al mare school jüri gymnasium kuressaare gymnaasium tallinn arte gymnasium initial look world program ended 2005 turned private company koolitööde next years ekool mostly expanded estonian school system reaching 420 schools 2012 since 2014 ekool also supported mobile application allows students parents access information mobile phones however schools teachers still need use computer ekool accessed combination user-name password estonian id-card estonian mobile-id smart-id online bank identification ekool used various interest groups school personnel students parents extent local government overseeing school one user account person access functionalities different user groups user belongs schools personnel carries data entry process ekool latter used parties right access information among information schools provide parents students access information keep date side make easy school collect contact information parents students enter keep ekool updated using
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Distributed computing architecture
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volta microarchitecture volta codename gpu microarchitecture developed nvidia succeeding pascal first announced roadmap march 2013 however first product announced may 2017 architecture named 18th 19th century italian chemist physicist alessandro volta nvidia first chip feature tensor cores specially designed cores superior deep learning performance regular cuda cores architecture produced tsmc 12 nm finfet process first graphics card use datacentre tesla v100 e.g part nvidia dgx-1 system also used quadro gv100 titan v. mainstream geforce graphics cards based volta volta succeeded turing architecture architectural improvements volta architecture include following volta announced gpu microarchitecture within xavier generation tegra soc focusing self-driving cars nvidia annual gpu technology conference keynote 10th may 2017 nvidia officially announced volta microarchitecture along tesla v100 volta gv100 gpu built 12 nm process size using hbm2 memory 900 gb/s bandwidth nvidia officially announced nvidia titan v december 7 2017 nvidia officially announced quadro gv100 march 27 2018 volta also reported included summit sierra supercomputers used gpgpu compute volta gpus connect power9 cpus via nvlink 2.0 expected support cache coherency therefore improve gpgpu performance
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Computer architecture
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amdgpu amdgpu amd fully open source unified graphics driver linux amdgpu officially supports cards built upon gcn 1.2 higher support previous cards experimental may enabled kernel parameter amdgpu also optional closed-source component operates top open source amdgpu alternative 3d application support known amdgpu-pro
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Operating systems
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nokia e72 nokia e72 smartphone nokia eseries range manufactured finland nokia e72 announced june 15 2009 nokia connections 2009 event singapore successor nokia e71 based similar design form factor offers similar feature set nokia e72 business-oriented phone eseries devices standard features including mobile email calendar instant messaging among many others symbian-based s60 3rd edition feature pack 2 operating system nokia e72 new optical navi key feature addition standard d-pad used many nokia devices including nokia e71 – said improve ease scrolling menus emails internet browser images optical sensor addition series closely spaced buttons comparison predecessor nokia e72 said higher level performance likely due faster 600 mhz arm processor also includes 5-megapixel auto focusing camera changes improvements software-based including changes user interface built-in messaging application among others nokia e73 mode usa feature phone t-mobile usa support t-mobile uma service band iv support 3g different piece hardware internally e72 current firmware device 91.004 published 2 june 2012 check current firmware one may dial 0000 vertu constellation quest 2010 based e72 design
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Operating systems
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henry spencer henry spencer born 1955 canadian computer programmer space enthusiast wrote regex widely used software library regular expressions co-wrote c news usenet server program also wrote ten commandments c programmers coauthor david lawrence book managing usenet working university toronto ran first active usenet site outside u.s. starting 1981 records period eventually acquired google provide archive usenet 1980s first international usenet site run ottawa 1981 however generally remembered served merely read-only medium later 1981 spencer acquired usenet feed duke university brought utzoo online earliest public archives usenet date may 1981 result small size usenet youthful days spencer early involvement made well-recognised participant commemorated vernor vinge 1992 novel fire upon deep novel featured interstellar communications medium remarkably similar usenet author including spurious message headers one characters appeared solely postings modeled spencer slightly obliquely named also credited claim understand unix condemned reinvent poorly mid-december 2001 google unveiled improved usenet archives go decade deeper internet past millions posts company originally acquired bought existing archive called deja news 1981 1991 running zoology department computer system university toronto spencer copied 2 million usenet messages onto magnetic tapes 141 tapes wound university western ontario google michael schmidt tracked help david wiseman others got transferred onto disks google archives henry spencer helped geoff collyer write c news 1987 around time wrote non-proprietary replacement codice_1 unix library handling regular expressions made freely available api followed eighth edition research unix spencer library used many software packages including tcl mysql postgresql well adapted others including early versions perl circa 1993 spencer donated second version library 4.4bsd following posix standard regular expressions spencer technical lead frees/wan project implementing ipsec cryptographic protocol stack linux also wrote 'aaa amazing awk assembler one longest complex programs ever written awk programming language also developed 4 point font used entomologists labeling pinned insect specimens spencer founding member canadian space society served board directors several times since 1984 mission analysis planning launch orbits css canadian solar sail project defunct software architect canadian science microsatellite dedicated studying variable light stars extrasolar planets launched eurockot 2003 asteroid 117329 spencer named honour highly regarded space enthusiast familiar respected presence several space forums usenet internet 1983 2007 spencer posted 34,000 messages sci.space newsgroups knowledge space history technology corrected henry spencer virtual t-shirt award created reward anyone catch error fact
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Operating systems
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bill woodcock bill woodcock born august 16 1971 san francisco california united states executive director packet clearing house non-profit research institute dedicated understanding supporting internet traffic exchange technology policy economics bill entered field internet routing research 1989 serving network architect operations director international multiprotocol service-provision backbone network 1993 1994 woodcock one founders packet clearing house served current post executive director since 1997 time woodcock directly participated establishment three hundred public internet exchange points europe africa asia americas continues serve boards provide ongoing technical policy advice many institutions 1998 woodcock j.d falk model spam regulation became first anti-spam legislation world california law 17538.4 paved way jurisdictions woodcock successfully concluded telecommunications regulatory reform efforts several african countries woodcock director roles four companies areas satellite communications content distribution domain name service technology 2001 woodcock co-authored chuck goolsbee chuck woody fiendishly difficult mac-mgrs trivia quiz annual gathering member macintosh managers mailing list san francisco macworld expo date 50 questions remain unanswered twenty years together richard ford initially brita meng hosted annual inaptly named a/ux user group dinner conjunction mactivity macworld meetings woodcock current former packet clearing house representative afrinic apnic arin iepg isoc isp/c lacnic natoa ripe bill woodcock regular speaker afnog apia apnic apricot arin isoc ripe iepg ietf sanog nanog meetings served program committees nanog sanog pam apricot woodcock one estonia computer attacks unleashed bronze soldier tallinn incident assisted defense coordinated hillar aarelaid cert-ee wake itu december 2012 world conference international telecommunications characterized attempted take-over institutions internet governance woodcock published number secret itu budget documents acted point-person effort redirect usd 11m u.s. government funds itu contributions support multistakeholder model internet governance effort centered people petition web site received much favorable attention press internet governance community woodcock published work includes many pch white-papers 1993 mcgraw-hill book networking macintosh report anf appletalk tunneling architectures working group chaired 1993 1994 many articles network world macworld macweek connections networking journals periodicals addition principal author multicast dns ip anycast operator requirements infrastructure management methods ietf drafts early 1990s pioneered igp egp-based topological load-balancing techniques using ip anycast technology together mark kosters proposed 1996 montreal iepg root dns servers migrated ip anycast work provided basis upon root dns servers deployed since late 1990s 2010 2011 rick lamb previously built signing system places dnssec cryptographic signatures dns root zone woodcock built first global-scale fips 140-2 level 4 dnssec signing infrastructure locations singapore zurich san jose addition protocol development work woodcock developed networking products cisco agilent farallon
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Computer security
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world database happiness world database happiness web-based archive research findings subjective appreciation life database contains overview scientific publications happiness digest research findings database contains information happy people wide range circumstances 165 different nations happiness defined degree individual judges quality life whole favorably two 'components happiness distinguished hedonic level affect degree pleasant affect dominates contentment perceived realization wants world database happiness tool acquire overview ever-growing stream research findings happiness accumulation knowledge stagnates scientists capitalize earlier research investments medio 2013 database covered 19,000 scientific findings happiness 6000 distributional findings happy people another 13,000 correlational findings associated less happiness first findings date 1915 world database happiness often used popular media make lists happiest countries around globe example happy planet index aims chart sustainable happiness world combining data longevity happiness size ecological footprint citizens database clear conceptual focus includes research findings subjective enjoyment one ’ life whole thereby evades babel haunted study happiness ages side coin much interesting research left findings reported technical details measurement statistical analysis detail welcomed scholars makes information difficult digest lay-persons still another limitation available findings often contradictory makes hard draw firm conclusions causes happiness clear poor health separation unemployment lack social contact strongly negatively associated unhappiness another problem world database happiness number studies happiness increases high rate gets increasingly difficult offer complete overview research findings
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Databases
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jape software jape configurable graphical proof assistant originally developed richard bornat queen mary university london bernard sufrin university oxford allows user define logic decide view proofs much works variants sequent calculus natural deduction claimed jape popular program computer-assisted logic teaching involves exercises developing proofs mathematical logic program available mac unix windows operating systems written java programming language released gnu gpl
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Programming language topics
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unigine unigine proprietary cross-platform game engine developed russian software company unigine corp. apart use game engine mainly used enterprise area simulators virtual reality systems serious games visualization distinguishing feature unigine support large open worlds planet scale also advanced 3d renderer currently supports opengl 4 directx 11 updated unigine sdk released 3 months unigine engine also core technology lineup benchmarks cpu gpu power supply cooling system used overclockers technical media tom hardware linus tech tips pc gamer others unigine benchmarks also included part phoronix test suite benchmarking purposes linux systems first public release 0.3 version may 4 2005 unigine engine created scratch based engine last update released july 7 2014 initially started microsoft windows linux support platforms added later os x playstation 3 android ios experimental support webgl included official sdk unigine 1 support several graphical apis directx 9 directx 10 directx 11 opengl opengl es playstation 3 initial versions v0.3x opengl support 3 apis developers c++ c uniginescript proprietary scripting language similar с++ syntax custom shaders written glsl hlsl languages unigine 1 several features required professional simulators enterprise vr systems mostly support large virtual scenarios specific hardware often called serious games support large virtual worlds implemented via double precision coordinates 64-bit per axis zone-based background data streaming optional operations geographic coordinate system latitude longitude elevation instead x z video output sophisticated displays implemented via so-called multi-channel rendering network-synchronized image generation single large image several computers standard approach professional simulators system enabled support multiple output devices asymmetric projections e.g cave curved screens multiple projectors requiring image warping edge blending also supported also various types stereoscopic 3d output supported anaglyph separate images output nvidia 3d vision well vr hmd support oculus rift unigine 1 also supported multi-monitor output video-walls unigine renderer supports shader model 5.0 hardware tessellation directcompute well opencl together set post-processes including screen space ambient occlusion ssao real-time global illumination set built-in high-level objects like terrain grass water clouds unigine uses proprietary physics engine collision detection rigid body physics dynamical destruction objects rag doll cloth fluid buoyancy force fields time reverse pathfinding also implemented proprietary engine together basic ai components spatial triggers callbacks features includes interactive 3d gui video playback using theora codec 3d audio system based openal library wysiwyg scene editor unigineeditor originally released october 10 2015 unigine 2 features unigine 1 focus simulators enterprise use main differences transition forward rendering deferred rendering approach pbr shading introduction several new graphical technologies like geometry water multi-layered volumetric clouds ssrtgi voxel-based lighting introduction c api supported platforms microsoft windows linux os x support stopped starting 2.6 version unigine 2 supports following graphical apis directx 11 opengl 4.x 3 apis developers c++ c uniginescript supported shader languages hlsl glsl uusl unified unigine shader language proprietary ssrtgi screen space ray-traced global illumination rendering technology introduced 2.5 version presented siggraph 2017 real-time live event roots unigine frustum.org open source project initiated 2002 alexander frustum zaprjagaev co-founder along denis shergin ceo ex-cto unigine corp name unigine means universal engine unique engine november 25 2010 unigine corp announced competition support linux game development agreed give away free license unigine engine anyone willing develop release game linux native client would also grant team windows license competition ran december 10 2010 considerable number entries submitted due unexpected response unigine decided extend offer three best applicants getting full unigine licenses winners announced december 13 2010 developers selected kot-in-action creative artel previously developed steel storm gamepulp intend make puzzle platformer med-art previously worked 2019 company claimed 200 b2b customers worldwide primarily use unigine military virtual reality projects several notable projects include graphical benchmarks cad systems unigine engine used platform series benchmarks used determine stability pc hardware cpu gpu power supply cooling system extremely stressful conditions well overclocking
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Distributed computing architecture
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interrupt coalescing interrupt coalescing also known interrupt moderation technique events would normally trigger hardware interrupt held back either certain amount work pending timeout timer triggers used correctly technique reduce interrupt load order magnitude incurring relatively small latency penalties interrupt coalescing typically combined either hardware fifo direct memory access allow continued data throughput interrupts held back interrupt coalescing common feature modern network cards technique dates back early computer uarts 16550 uart chip used ibm pc serial interface time even servicing interrupt rates required low data rate serial data streams day taxing contemporary cpus interrupt coalescing also implemented without support hardware disabling interrupts interrupt controller using timer-based polling
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Computer architecture
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hash consing computer science particularly functional programming hash consing technique used share values structurally equal term hash consing originates implementations lisp attempt reuse cons cells constructed avoiding penalty memory allocation hash consing commonly implemented hash tables storing weak references may garbage-collected data stored therein contains references outside table hash consing shown give dramatic performance improvements—both space time—for symbolic dynamic programming algorithms interesting property hash consing two structures tested equality constant time turn improve efficiency divide conquer algorithms data sets contain overlapping blocks simple efficient suitable demonstration concept implementation memoizer means hash table weak references scheme
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Programming language topics
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security descriptor definition language security descriptor definition language sddl defines string format used describe security descriptor text string
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Computer security
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hp data protector hp data protector software automated backup recovery software single-server enterprise environments supporting disk storage tape storage targets provides cross-platform online backup data microsoft windows unix linux operating systems business- mission-critical applications hp data protector zero downtime backup leverages array-based solutions offload processing server perform backup operations copy production data hp data protector instant recovery retrieves data replicated images disk recovery specific points time hp data protector originated omniback last version use omniback name version 4.1 retired 2004 hewlett-packard acquired apollo computer 1989 latter already developed backup system entitled omniback network backup system available market time hp continued develop product omniback name purpose backing individual files raw disk partitions related distinct product omniback/turbo developed backing databases 1996 hp released omniback ii 2.0 merged omniback ii omniback/turbo single product although still impossible create single job would contain database file system backup windows nt port released version 2.3 version 2.55 released 1997 included support hp-ux ibm aix interim hewlett-packard withdrew development slovenia germany significant time spent delivering version 3.5.2 solaris complete however allowed quick ports tru64 linux version 5.0 omniback name dropped since product called hp openview storage data protector hp storageworks data protector product called hp data protector software hp announced release hp data protector 9.0 part adaptive backup recovery initiative may 2014 released july 2014 released july 2014 along two companion products hp data protector management pack hp backup navigator hp data protector architecture based concept cell network environment contains cell manager clients backup devices cell manager main system centrally controls manages cell contains database runs core software runs backup restore sessions writing session information database client system within cell clients backed require installation disk agent clients control backup restore data require installation media agent multi-site operations data protector manager managers mom allows local administrators control data backup restore providing centralized enterprise monitoring media management configuration multiple data protector cells grouped configured managed mom hp data protector offers data deduplication capabilities ability compare blocks data written backup device data blocks previously stored device data deduplication hp data protector allows disk-based data storage target storage tape drives used deduplication targets sequential nature opposed block-oriented nature disk-devices hp data protector supports backup restore virtual servers including protection whole virtual machine application data supported virtual environments include vmware windows 2008 hyper-v limited microsoft virtual server 2005 hp integrity virtual machines citrix xenserver support longer officially provided hp data protector includes automated key management software linear tape-open lto-4 encryption users choice client-based encryption data security use encryption functionality lto-4 later generation tape drives november 2009 hp began offering hp data protector notebook extension hp data protector notebook extension enables users back recover data working remotely offline hp data protector notebook extension data captured backed automatically time user changes creates receives file processes transparent user impact laptop desktop performance data stored temporarily local repository pending transfer network data vault full backup restore capabilities key features include end-user single-click recovery encryption compression techniques granular recovery extensions components sit inside applications provide operator application way triggering large restore selecting individual items need restored without requiring assistance backup administrator example vmware granular recovery extension appears extra item vsphere console vcenter lets vmware administrator restore vmdk file finally provides interface selecting files vmdk file sharepoint gre allows microsoft sharepoint administrators recover single document collection folder directly via sharepoint gui granular recovery sharepoint 2010 introduced version 7.0
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Computer security
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turnstile turnstile also called baffle gate turnstyle form gate allows one person pass time also made enforce one-way traffic people addition restrict passage people insert coin ticket pass similar thus turnstile used case paid access sometimes called faregate ticket barrier used purpose example access public transport pay toilet restrict access authorized people example lobby office building turnstiles originally used like forms stile allow human beings pass keeping sheep livestock penned use turnstiles modern applications credited clarence saunders used first piggly wiggly store turnstiles used wide variety settings including stadiums amusement parks mass transit stations office lobbies airports ski resorts factories power plants casinos business/revenue standpoint turnstiles give accurate verifiable count attendance security standpoint lead patrons enter single-file security personnel clear view patron enables security efficiently isolate potential trouble confiscate prohibited materials hand physical barriers become serious safety issue speedy evacuation needed requiring emergency exits bypass turnstiles persons disabilities may difficulties using turnstiles cases generally wide aisle gate manual gate may provided locations luggage expected line turnstiles may entirely formed wide aisle gates example heathrow terminals 2 3 underground station turnstiles often use ratchet mechanisms allow rotation stile one direction allowing ingress preventing rotation direction often designed operate payment made usually inserting coin token slot swiping tapping inserting paper ticket electronically-encoded card turnstiles often used counting numbers people passing gate even payment involved used extensively manner amusement parks order keep track many people enter exit park ride ride first major use turnstiles sporting venue hampden park glasgow scotland waist-high turnstiles often used fairs attractions arenas user inserts ticket pass slot barcode read access granted sensor determines speed user passes sets electric motor turn turnstile corresponding speed sometimes also referred half-height turnstiles fixed arm style traditionally popular type turnstile many variations style available including one designed accompanied matching ticket box one ticket box built styles designed allow entry payment actual coins tokens inserted others allow access valid barcode electronically read disadvantage type people jump turnstile happens commonly moscow metro mass transport systems russia optical turnstiles alternative traditional arm -style turnstile increasingly used locations physical barrier deemed unnecessary unaesthetic optical turnstiles generally use infrared beam count patrons recognize anyone attempting enter site without valid entry pass drop arm optical turnstile combination security tripod barrier turnstile fully optical turnstile lanes either single double arms access granted arms drop recesses cabinet arms drop way turnstile functions fully optical turnstile full-height turnstile larger version turnstile commonly high similar operation revolving door eliminates possibility inherent waist-high style someone jumping turnstile however type turnstile functions differently revolving door often allow someone come someone else goes also pejoratively known iron maiden torture device name high-wheel sometimes called rotogate especially chicago used unstaffed exits chicago l stations also used increasingly new york city subway stations since turn 21st century europe however rotogate refers different kind gate turnstile two types full height turnstiles high entrance/exit turnstile heet exit-only difference heet turnstiles rotate directions thus allowing two-way traffic exit-only turnstiles rotate one direction thus allowing one-way traffic exit-only turnstiles commonly used mass transit stations allow passengers exit system without interfering entering exit-only models also used enclosed areas theme parks zoos amusement parks allow visitors leave denying admission paid additionally single double tandem turnstiles contain two rotors side side frame allows throughput limited space tandems frequently narrow two single turnstiles placed side-by-side public transport systems soviet union common use turnstiles entrance subway stations first introduced moscow metro 7 november 1958 city buses commuter trains usually operated proof-of-payment system fare collection became pressing business post-soviet russia railway terminals high-traffic railway station moscow area nizhny novgorod elsewhere turnstiles installed early 2000s moscow authorities sought improve fare collection since enclosing bus tram stops providing fare gates feasible installed turnstiles inside city bus tram practice caused passenger complaints slowed boarding compared traditional honor system similar system use brazilian chilean city buses hong kong trams
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Computer security
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dynamic debugging technique dynamic debugging technique ddt name several debugger programs originally developed dec hardware initially known dec debugging tape distributed paper tape name pun insecticide i.e bug-killer ddt first version ddt developed mit pdp-1 computer 1961 newer versions newer platforms continued use name ported vendor platforms changing media name changed less dec-centric version ddt closely related odt names used several different debuggers generally debuggers odt name limited capabilities ddt debuggers early versions digital research cp/m cp/m-86 kept dec name ddt ddt-86 ddt-68k debugger however meaning dynamic debugging tool cp/m ddt later superseded symbolic instruction debugger sid zsid sid86 gemsid dr dos gem addition normal function debugger ddt also used top-level command shell mit operating system recent systems replaced pword implements restricted subset ddt functionality ddt could run debug eight processes called jobs time several sessions teco ddt could run recursively jobs could ddts could run another eight jobs eight jobs given unique names usual name original top-most ddt hactrn hack-tran thus guy l. steele famous filk poem parody edgar allan poe raven hactrn ddt dynamic debugging technique implemented decsystem-10 decsystem-20 allowed references symbols within programming debugged feature loaded symbols .exe executable file special version named sddt used symbols running monitor allowed system programmers peek inside
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Operating systems
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untouchables video game untouchables video game released ocean software 1989 zx spectrum amstrad cpc commodore 64 msx amiga dos later nes snes based film untouchables side-scrolling based loosely movie game plays significant parts film set chicago primary goal game take al capone henchmen eventually detain capone electronic gaming monthly gave super nes version 5.8 10 commenting title would better super scope compatible bit difficult use pad shooting sequences reviewer crash called game great stuff ocean brought chicago life atmospheric title tune 128k beautifully detailed graphics challenging gameplay add one addictive mean game sinclair user commented untouchables cracking conversion easily one successful accurate movie licenses date paul rand computer video games stated untouchables well thought package find niche people software collections ... buy wo n't disappointed games machine added six levels trigger-pumping fun suitable graphics give authentic twenties feel nice touches ... make untouchables winner
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Computer architecture
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network news transfer protocol network news transfer protocol nntp application protocol used transporting usenet news articles netnews news servers reading posting articles end user client applications brian kantor university california san diego phil lapsley university california berkeley wrote specification network news transfer protocol march 1986 contributors included stan o. barber baylor college medicine erik fair apple computer usenet originally designed based uucp network article transfers taking place direct point-to-point telephone links news servers powerful time-sharing systems readers posters logged computers reading articles directly local disk local area networks internet participation proliferated became desirable allow newsreaders run personal computers connected local networks resulting protocol nntp resembled simple mail transfer protocol smtp tailored exchanging newsgroup articles newsreader also known news client software application reads articles usenet either directly news server disks via nntp well-known tcp port 119 reserved nntp well-known tcp port 433 nnsp may used bulk transfer articles one server another clients connect news server transport layer security tls tcp port 563 often used sometimes referred nntps alternatively plain-text connection port 119 may changed use tls via codice_1 command october 2006 ietf released updates nntp codifies many additions made years since rfc 977 time ietf also released specifies use transport layer security tls via nntp starttls abortive attempt update nntp standard early 1990s specialized form nntp intended specifically use clients nnrp proposed protocol never completed fully implemented name persisted internetnews inn nnrpd program result subset standard nntp commands useful clients sometimes still referred nnrp
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Internet protocols
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in-memory database in-memory database imdb also main memory database system mmdb memory resident database database management system primarily relies main memory computer data storage contrasted database management systems employ disk storage mechanism in-memory databases faster disk-optimized databases disk access slower memory access internal optimization algorithms simpler execute fewer cpu instructions accessing data memory eliminates seek time querying data provides faster predictable performance disk applications response time critical running telecommunications network equipment mobile advertising networks often use main-memory databases imdbs gained lot traction especially data analytics space starting mid-2000s – mainly due multi-core processors address large memory due less expensive ram potential technical hurdle in-memory data storage volatility ram specifically event power loss intentional otherwise data stored volatile ram lost introduction non-volatile random access memory technology in-memory databases able run full speed maintain data event power failure simplest form main memory databases store data volatile memory devices devices lose stored information device loses power reset case imdbs said lack support durability portion acid atomicity consistency isolation durability properties volatile memory-based imdbs often support three acid properties atomicity consistency isolation many imdbs added durability via following mechanisms imdbs allow database schema specify different durability requirements selected areas database thus faster-changing data easily regenerated meaning system shut-down would need journaled durability though would replicated high availability whereas configuration information would flagged needing preservation storing data in-memory confers performance advantages expensive method data storage approach realising benefits in-memory storage limiting costs store frequently accessed data in-memory rest disk since hard distinction data stored in-memory stored disk systems dynamically update data stored based data usage approach subtly different caching recently accessed data cached opposed frequently accessed data stored in-memory flexibility hybrid approaches allow balance struck cloud computing industry terms data temperature hot data cold data emerged describe data stored respect hot data used describe mission-critical data needs accessed frequently cold data describes data needed less often less urgently data kept archiving auditing purposes hot data stored ways offering fast retrieval modification often accomplished in-memory storage always cold data hand stored cost-effective way accepted data access likely slower compared hot data descriptions useful concrete definition hot cold manufacturing efficiency provides another reason selecting combined in-memory/on-disk database system device product lines especially consumer electronics include units permanent storage others rely memory storage set-top boxes example devices require database system manufacturer adopt hybrid database system lower upper cost less customization code rather using separate in-memory on-disk databases respectively disk-less disk-based products first database engine support in-memory on-disk tables single database webdna released 1995 another variation involves large amounts nonvolatile memory server example flash memory chips addressable memory rather structured disk arrays database form memory combines fast access speed persistence reboots power losses
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Databases
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lanyon solutions lanyon solutions inc. privately owned software-as-a-service saas company provided cloud-based software manage meetings events travel lanyon software supported range clients including corporations hotels associations tradeshows convention visitor bureaus cvbs intermediaries meetings events travel space merged cvent 2017 lanyon solutions formed combination two companies active network business solutions group lanyon vista equity partners 2014 two acquisitions added passkey genieconnect 2014 nevertheless solutions services offered individual companies date back decades lanyon founded 1984 nick lanyon irving texas provider software focused corporate transient travel 2009 lanyon received 10 million funding frontier capital charlotte nc-based private equity company expand lanyon product customer sales support company purchased vista equity partners december 2012 signaling exit frontier capital investment company founded 1996 waltham ma-based passkey international provided hotel reservation technology hotels event planners april 2014 lanyon acquired passkey complemented lanyon existing event solutions included passkey groupmax technology enabled hotels destination marketing organizations drive revenue group reservations easing manual tasks associated managing group room blocks starcite founded 1999 spinoff mcgettigan partners company expanded focus desktop consolidation meetings technology acquiring attendee applications provider regweb 2002 attendee product provider b-there 2003 2006 starcite merged onvantage inc. formed merger seeuthere technologies plansoft 2004 bringing together two leaders meetings technology merged company took starcite name products included starcite mobile attendee attendee networking 1:1 meetings schedule meetings business intelligence meetings data analytics suite smm applications supplier database 2008 active network acquired boulder co-based regonline online registration company lindon ut-based wingateweb provided large enterprise event management software january 2012 active network acquired starcite 57.7 million form business solutions group offer smm event marketing software meetings events addition starcite smm business solutions group technology offering included activeworks conference conferences regonline online registration starcite supplier marketplace hotel venue sourcing september 2013 active network acquired vista equity partners 1 billion would return public company private status february 2014 lanyon paired active network business solutions group consolidated lanyon name genieconnect founded 2010 teams us uk apac previously known geniemobile march 2013 uk-based genieconnect offered enterprise-level mobile event technology products included smartconnect provides content based attendee app usage ibeacon-enabled audience response solution marketing track attendee behaviors send messages audiences omnistream event wall aggregate social event activity genieconnect mobile event technology used associations corporations exhibitors expo companies cisco live 2014 genieconnect achieved following results 11,000 attendee profiles updates 7,500 access interactive maps 167,00 plus favorited content mobile app received user rating 4.5 5 stars cisco post-event survey acquired lanyon december 2014 genieconnect mobile technology already integrated many lanyon existing solutions formed early 2014 merger active network business solutions group lanyon lanyon solutions expanded software offering focus several key mergers acquisitions company acquired group hotel reservations company passkey april 2014 mobile application company genieconnect december 2014 lanyon solutions relocated headquarters downtown dallas texas offices draper ut london uk philadelphia pa singapore singapore waltham lanyon serves meetings events travel industries variety software products businesses hotels lanyon large focus enterprise serving 80 fortune 100 10,000 small medium-sized businesses 100,000 hotels company solutions designed manage costs spend data related meetings hotels enabling hoteliers offer venues services corporations associations introduced 2013 lanyon smart events cloud solution brings together strategic meetings management event marketing technologies single solution smart events cloud solution includes products hoteliers lanyon provides rfp management software respond meetings transient erfps hotel booking systems product offerings include
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Distributed computing architecture
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command language command language language job control computing domain-specific interpreted language common examples command language shell batch programming languages languages used directly command line also automate tasks would normally performed manually command line share domain—lightweight automation—with scripting languages though command language usually stronger coupling underlying operating system command languages often either simple grammars syntaxes close natural language shallow learning curve many domain-specific languages
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Programming language topics
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compress compress unix shell compression program based lzw compression algorithm compared modern compression utilities gzip bzip2 compress performs faster less memory usage cost significantly lower compression ratio uncompress utility restore files original state compressed using compress utility files specified standard input uncompressed standard output up-coming posix single unix specification revision planned deflate algorithm used gzip format supported utilities files compressed compress typically given extension .z modeled earlier pack program used extension .z tar programs pipe data compress given command line option codice_1 tar program compress stores multiple files within one tape archive files returned original state using uncompress usual action uncompress merely create uncompressed copy file also restore timestamp attributes compressed file files produced compress systems uncompress supports 9- 16-bit compression lzw algorithm used compress patented sperry research center 1983 terry welch published ieee article algorithm 1984 failed note applied patent algorithm spencer thomas university utah took article implemented compress 1984 without realizing patent pending lzw algorithm gif image format also incorporated lzw compression way unisys later claimed royalties implementations gif joseph m. orost led team worked thomas et al create 'final 4.0 version compress published free software 'net.sources usenet group 1985. granted 1985 compress could used without paying royalties sperry research eventually merged unisys compress fallen favor particular user-groups makes use lzw algorithm covered unisys patent gzip bzip2 increased popularity linux-based operating systems due alternative algorithms along better file compression compress however maintained presence unix bsd systems us lzw patent expired 2003 public domain united states patents lzw worldwide also expired see graphics interchange format unisys lzw patent enforcement up-coming posix single unix specification revision planned deflate algorithm used gzip format supported utilities output binary consists bit groups bit group consists codes fixed amount bits 9-16 group except last aligned amount bits multiplied 8 right padded zeroes last group aligned 8 padded zeroes find information ncompress issue example want output 10 9 bit codes output 5 10 bit codes 2 bit groups 100 bits 50 bits first group aligned 72 right padded zeroes second group aligned 8 right padded zeroes need output 100 bits 44 zero bits 50 bits 6 zero bits actually bug lzw n't require alignment bug part original unix compress ncompress gzip even windows port exists 35 years application/x-compress files created using bug include output specification compress implementations writes random bits uninitialized buffer alignment bits guarantee alignment bits zeroes terms 100 compatibility decompressor ignore alignment bit values
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Computer file systems
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james dolan computer security expert james s. dolan july 20 1981 – december 27 2017 american computer security expert aaron swartz kevin poulsen co-developed securedrop widely used secure digital platform sources anonymously submit materials journalists dolan grew chester new york grew four sisters went school tuxedo park school considered gifted early age later moved brooklyn called home chester ny 1999 2006 dolan served marines two deployments iraq war worked data network specialist 2003 dolan served iii marine expeditionary force initial iraq war second deployment september 2004 march 2005 dolan served 4th civil affairs group fallujah one centers conflict time dolan fallujah operation phantom fury part second battle fallujah trevor timm freedom press foundation referenced dolan military service description dolan obituary wrote saying impact serving iraq often spoke motivating factor dolan cybersecurity work goal making metadata transparent accountable service iraq war dolan worked computer security large company 2012 side project job dolan helped develop open source securedrop initially known deaddrop 2013 poulsen dolan moved freedom press foundation ensure continued development adoption following death fellow developer aaron swartz dolan lead maintainer deaddrop freedom press foundation first employee performed outreach assisted installations news organizations included new yorker propublica washington post vice news among others 2015 dolan moved san diego california work head security classy american software company online fundraising platform designed nonprofit organizations position held time death dolan found dead brooklyn hotel december 2017 age 36 former colleagues speculate james died suicide fate swartz reportedly suffered ptsd time marines dolan second member securedrop team commit suicide gofundme fund set fellow marines establish james dolan memorial fund annually donate designated non-profit foundations projects name
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Computer security
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text template transformation toolkit microsoft text template transformation toolkit usually referred t4 template based text generation framework included visual studio t4 source files usually denoted file extension .tt t4 used developers part application tool framework automate creation text files variety parameters text files ultimately text format code example c xml html xaml t4 uses custom template format contain .net code string literals parsed t4 command line tool .net code compiled executed output executed code text file generated template t4 also completely run within .net applications via use texttransformation class eliminates need end user visual studio installed t4 used within microsoft asp.net mvc creation views controllers ado.net entity framework entity generation asp.net dynamic data also used outside microsoft projects subsonic t4 templating also supported monodevelop four types controls handed t4 template transformation engine microsoft often criticized lack tooling support t4 within visual studio ide relies third parties namely tangible engineering clarius consulting however later revisions included better tooling support
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Web technology
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wiper malware wiper class malware whose intention wipe hard drive computer infects piece malware referred wiper allegedly used attacks iranian oil companies 2012 international telecommunication union supplied kaspersky lab hard drives allegedly damaged wiper analysis sample alleged malware could found kaspersky discovered traces separate piece malware known flame shamoon malware contained disk wiping mechanism employed 2012 2016 malware attacks targeting saudi energy companies utilized commercial direct drive access driver known rawdisk original variant overwrote files portions image burning u.s. flag 2016 variant nearly identical except using image body alan kurdi instead wiping component used part malware employed lazarus group—a cybercrime group alleged ties north korea 2013 south korea cyberattack 2014 sony pictures hack sony hack also utilized rawdisk 2017 computers several countries—most prominently ukraine infected variant petya ransomware modified effectively act wiper malware infects master boot record payload encrypts internal file table ntfs file system although still demanded ransom found code significantly modified payload could actually revert changes ransom successfully paid
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Computer security
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interlock engineering interlock feature makes state two mechanisms functions mutually dependent may used prevent undesired states finite-state machine may consist electrical electronic mechanical devices systems applications interlock used help prevent machine harming operator damaging preventing one element changing state due state another element vice versa elevators equipped interlock prevents moving elevator opening doors prevents stationary elevator open doors moving although idiot proof strategies interlock confused simple safety switch example typical household microwave oven switch disables magnetron door opened interlock rather would considered interlock door locked magnetron magnetron prevented operating door open interlocks may include sophisticated elements curtains infrared beams photodetectors computer containing interlocking computer program digital analogue electronics simple switches locks trapped key interlocking method ensuring safety industrial environments forcing operator predetermined sequence using defined selection keys locks switches called trapped key works releasing trapping keys predetermined sequence control power isolated key released used grant access individual multiple doors example prevent access inside electric kiln trapped key system may used interlock disconnecting switch kiln door switch turned key held interlock attached disconnecting switch open kiln door switch first opened releases key key used unlock kiln door key removed switch interlock plunger interlock mechanically prevents switch closing power re-applied kiln kiln door locked releasing key key returned disconnecting switch interlock similar two-part interlock system used anywhere necessary ensure energy supply machine interrupted machine entered adjustment maintenance microprocessor architecture interlock hardware stalls pipeline inserts bubbles hazard detected hazard cleared one example hazard software program loads data system bus calls use data following cycle system loads take multiple cycles load-to-use hazard interlocks may strictly mechanical one form internal firearm safety blocks motion trigger sear and/or firing pin unless breech properly closed locked operation device press cutter hand fed workpiece hand removed use two buttons actuate device one hand greatly reduces possibility operation endangering operator system fool-proof systems often augmented use cable–pulled gloves worn operator retracted away danger area stroke machine major problem engineering operator safety tendency operators ignore safety precautions even outright disabling forced interlocks due work pressure factors therefore safeties require perhaps must facilitate operator cooperation many people use generators supplement power home business event main municipal power gone offline order safely transfer power source generator back main safety interlock often employed interlock consists one switches prevent main power generator power powering dwelling simultaneously without safeguard power sources running could cause overload condition generator power back-feed onto main could cause dangerous voltage reach lineman repairing main feed far outside building interlock device designed allow generator provide backup power way prevents main generator power connected time b allows circuit breakers operate normally without interference event overload condition interlock devices electrical systems employ mechanical device manage movement circuit breakers also allow use padlocks prevent someone accidentally activating main power system without authorization
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Computer architecture
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agris agris international system agricultural science technology global public domain database 9 million structured bibliographical records agricultural science technology became operational 1975 database maintained ciard content provided 150 participating institutions 65 countries agris search system allows scientists researchers students perform sophisticated searches using keywords agrovoc thesaurus specific journal titles names countries institutions authors information management flourished 1970s agris metadata corpus developed allow users free access knowledge available agricultural science technology agris developed international cooperative system serve developed developing countries advent internet along promises offered open access publishing growing awareness management agricultural science technology information would various facets standards methodologies interoperability facilitation knowledge exchange tools enable information management specialists process data information knowledge exchange across countries common interoperability criteria thus adopted implementation agris ap metadata accordingly created order allow exchange retrieval agricultural information resources agris covers wide range subjects related agriculture science technology including forestry animal husbandry aquatic sciences fisheries human nutrition extension content includes unique grey literature unpublished scientific technical reports theses conference papers government publications growing number around 20 bibliographical records corresponding full text document web easily retrieved google 5 december 2013 agris 2.0 released agris 2.0 time access agris repository provided agris search engine agris data converted rdf resulting linked dataset created 200 million triples agris also registered data hub http //thedatahub.org/dataset/agris agris partners contributing agris database use several formats exchanging data including simple dc oai-pmh systems agris ap format anyway adopted directly falling umbrella ciard joint initiative co-led cgiar gfar fao new agris aims promote sharing management agricultural science technology information use common standards methodologies incorporate web 2.0 features order make search experience comprehensive intuitive far-reaching possible users new agris furthermore new agris also leverage data infrastructure one ciard projects ciard ring acronym standing routemap information nodes gateways ring ciard ring project led gfar aims directory ard agricultural research development information services allow monitoring describing classifying existing services whilst benchmarking interoperability criteria ensure maximum outreach global availability
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Computer architecture
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messages apple messages instant messaging software application developed apple inc. macos ios watchos operating systems desktop messages application replaced ichat native os x instant messaging client release os x mountain lion july 2012 inherits majority ichat features messages also brings support imessage apple messaging service ios well facetime integration mobile version messages ios used iphone ipad also supports sms mms due replacing older text messaging text app since ios 3 users tell difference message via sms one sent imessage bubbles appear either green sms blue imessage apple released messages iphone built-in application iphone os 3.0 june 17 2009 replaced text application native messaging application since iphone inception change name due iphone gaining native support mms protocol addition previously available sms protocol even though iphone 3g newly released iphone 3gs original iphone received os 3.0 update original iphone left support mms citing hardware challenges messages also gained support sharing contacts using vcard standard big changes included support copy paste ability forward delete multiple messages time release iphone os 4.0 name later changed ios 4.0 2010 messages received minor upgrade among new features ability search within text messages much like search feature mail also added support displaying character count notify one gone standard sms character limit ios 4.0 also included support red exclamation mark appear app icon warn failure send message developers provided new api allowed add embedded messaging functionality apps ipad ipod touch gained support messages release ios 5.0 october 12 2011 unlike iphone supported sms mms imessage ipad ipod touch supported apple imessage protocol imessage users ios 5 could send text picture messages contacts wifi 3g ios 5 devices without using carrier quota addition user could start conversation one device continue another messages also introduced typing indication delivery read receipts imessage introduction notification center new sms mms imessages could seen lock screen pulling notification center ios 6 helped improve syncing multiple devices ipod touch ipad users could use iphone phone numbers send receive imessages earlier iphone users could receive imessages sent phone number ipad ipod touch addition users could add additional emails receive send messages device settings accessible settings application messages tab ios 6 also added share button apps like safari photos enabled users share links photos using sms/mms imessage without leaving app ios 7 messages received new user interface apple also allowed users see message post date swiping messages view right left ios 8 users send audio video messages holding record button group conversations users remove/add someone thread name thread share location thread view attachments turn disturb receive notifications specific thread part new continuity feature users use iphones relay send receive sms mms messages macs ipads ios 9 app received redesigned overlay sending audio clip well seeing contact photos list view iphone 6 later ios 10 app app store allowing user download third-party messages apps apps allow user send stickers play games within messages app app received new visual effects example chat bubbles sent loud gentle effect messages announced os x beta application february 16 2012 macs running mac os x 10.7 lion released conjunction developer preview apple to-be-released os mountain lion 10.8 beta discontinued december 12 2012 3 months release mountain lion full-version messages os x released july 25 2012 included mountain lion messages replaced ichat default im client since mac os x 10.2 addition supporting apple new imessage protocol messages os x retained support aim yahoo messenger google talk jabber messages unitizes newly added notification center notify incoming messages introduction new share button applications like safari finder preview gave users ability share links webpages photos files messages also supported dragging dropping files photos sharing messages also supports video calling apple facetime third-party im services supports release 10.8.2 messages os x gained ability send receive imessages using iphone phone number yosemite app redesigned look like app ios 7 8 part new continuity feature users able send receive sms mms messages iphones running ios 8 possibility reopen previous conversations removed embedded control font size character format within sent messages removed headlining feature ios 5 messages widely reviewed met fairly positive reviews dante cesa engadget review praised brilliance apple execution messages complimented way messages change earlier sms ui would automatically convert sms/mms imessage recipient registered imessage sms/mms stopped using service dan moren macworld also praise apple execution saying ... explain less technically savvy friends send free message instead sms done automatically feature widely praised anandtech praised apple technical achievements messages particularly imessage noted away sms character limits 140 160 helped eliminate messages sent received split two messages tests found apple actually prioritized using cellular networks send text messages opposed wifi networks spite possibly incurring data costs claimed data usage text based imessage small enough ignore especially considered cellular networks secure wifi protected picture video messages apple prioritized wifi given much higher data consumption compared text criticism messages relates imessage release ios 6 os x mountain lion 10.8.2 inability receive imessages sent one iphone phone number ipad ipod touch mac criticized feature addressed ios 6 iphones ipads ipod touches os x 10.8.2 macs messages also came fire due multiple cases apple icloud service going messages relies icloud send receive imessages using apple voiceover screen reader ios macos visually impaired users tap message read also navigate messages ui using voice utilizing siri messages enables one dictate send messages commands siri also able read new incoming messages default font size ios messages editable accessibility tab settings application
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Operating systems
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jsish javascript interpreter shell jsish jsi short scripting language designed use embedded systems language used primarily applications written c c++ using gnu tool-chains mingw provides windows compatibility jsi code compiles either c99 c++ c++ support native instead extern c jsi created embedded application replacement tcl jimtcl main goal provide embedded scripting using mostly standard syntax javascript opposed idiosyncratic ones used tcl lua python secondary goal data compatibility web browsers using json speed major goal life jsi started fork quad-wheel interpreter eventually major internal features tcl added current implementation nearly 10 times size original little original code remains jsi comes builtin support sqlite websocket self-hosting zip file-systems codice_1 executable unusual integrates self-mounting file system containing builtin utilities applications include debugger web-server latter used provide web user-interfaces debugger sqlite applications accessed via codice_1 command-line arguments jsi highly independent scripts extensions unusually robust due functions support duck typed-parameters implementation mature rich resilient development environment includes integrated logging asserts strict mode version 2.4 released december 2017 jsi considered feature-stable jsi implements version 5.1. ecmascript standard following deviations one major extension function definitions use types defaults
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Programming language topics
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corvision corvision fourth generation programming tool 4gl currently owned attunity inc. corvision developed cortex corporation vax/vms isam environment although cortex beta tested corvision-10 generated pcs corvision stayed anchored vms corvision-10 proved difficult hoped never released corvision traced back 1972 lou santoro mike lowery created inform newly formed time-sharing company standard information systems sis inform contained corvisions basic utility commands sort report list consolidate first users inform new england telephone polaroid temple barker sloan 1972 sis offices los angeles garden grove minneapolis chicago boston new york city district columbia charlotte raleigh atlanta phoenix 1976 1977 ken levitt dick berthold sis ported inform cdc-3600 pdp-11/70 ias called new tool inform-11 cortex founded 1978 sherm uchill craig hill mike lowery dick berthold market inform-11 inform-11 first used deliver 20-user order entry system eddie bauer deliver insurance processing system consolidated group trust 1981 1982 cortex received significant investment b. dick using new investment cortex ported inform digital equipment corporation new vax/vms adding compiled executables inform-11 promoted cortex digital pioneering rapid application development system 1984 jim warner encapsulated inform repository-based development tool called application factory inform process procedural language became known builder within application factory 1986 name application factory dropped favor name corvision 1986 1989 corvision experienced heyday quickly became known robust capable tool rapidly building significant multi-user applications addition relational database support attracted major accounts cortex quickly became international company 1992 corvision version 5 released query support unix query allowed read-only access users developers systems database backend seemed desirable facility allowing users create use throw away reports without calling developers nasty habit causing performance issues users often understand database structure could send large queries processing queues causing system-wide issues 1993 cortex started supported vesting digital new 64-bit alpha line 1994 international software group co. ltd. isg purchased cortex early 1987 cortex recognized growth popularity ibm pc supporting wikt diagrammatic editing menus data relationships corvision 1993 client-server version released widely adopted 1997 isg work corvision-10 herald rebirth corvision onto ibm pc platform stopped corvision-10 proving difficult port isg finally refused spend money now-dated system 1994 saw last innovative corvision release v5.11 extra-fee y2k release v5.12.2 marked end development corvision still exists handful companies yet found time money upgrade existing mainframe systems corvision runs vms environment stable search corvision developers contractors support ageing systems problem since around 1999 companies started appearing offering conversion tools convert builder code compiled visual basic java 2005 corvision guru michael lowery president order processing technologies attempted revive corvision franchise cv2vb process convert corvision applications .net applications using sql server cv2vb opt third generation corvision conversion replacement modeler/code generator commercial service former corvision clients information available cv2vb website brief explanation application development using corvison first step developing application corvision fill parameters control miscellaneous aspects concerning application-wide functions parameters fall five groupings follows usually default values parameters satisfactory corvision however allows setting changed time development parameters file wp accessed runtime latest setting always used corvision keeps information behind status screen up-to-date indicates current state development process left hand side indicates specification tasks need right hand side indicates generation tasks need changes additions specification cause changes dictionary datasets keys dictionary datasets keys screens reports menus corvision provides useful feature called field search field search allows investigate analyze use fields different aspects application allows developers assess impact changes made provide complete specification details hardcopy form corvision run reports option 80 different types report produced component specification reports csrs known also produced tentative unreferenced unresolved items key corvision procedures procedures corvision eventually become executable images .edo three types procedures essentially true consider procedure program fact procedure set instructions builder commands build program program builder actually called process program procedure therefore set builder commands instruct builder build process save program library compiled file .sav extension corvision keeps data structure files separate manipulated builder builder keeps structure file key structure file dataset used application process compiled data structures bound process time thus binding data structures takes place precise moment process compiled structure key structure files kept separate dataset definitions altered development major strength corvision allowing prototyping environment code data structures changed throughout development brought together compile time structure key structure files loaded process compiled done load file builder makes assumption data structures already loaded compiles process point compilation binds data structures code following files created following files also added following files created compiling
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Programming language topics
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qualified digital certificate context regulation eu 910/2014 eidas qualified digital certificate public key certificate issued qualified trust service provider ensures authenticity data integrity electronic signature accompanying message and/or attached data eidas defines several tiers electronic signatures used conducting public sector private transactions within across borders eu member states qualified digital certificate addition specific services provided qualified trust service provider required elevate status electronic signature considered qualified electronic signature using cryptography digital certificate also known public key certificate contains information link owner digital signature trust entity verifies authenticity content signed according eidas considered qualified digital certificate certificate must meet requirements provided annex regulation eu 910/2014 including limited need non-repudiation authentication electronic signatures originally addressed electronic signatures directive 1999/93/ec help facilitate secure transactions specifically occur across borders eu member states eidas regulation later replaced directive defined standards used creation qualified digital certificates trust service providers qualified digital certificate issued qualified trust service provider received authorization member state ’ supervisory body provide qualified trust services creating qualified electronic signatures provider must listed upon eu trust list otherwise permitted provide qualified digital certificates qualified trust services trust service provider required abide guidelines established eidas creating qualified digital certificate include court qualified electronic signature provided highest level probative value makes difficult refute authorship qualified electronic signature along qualified certificate given consideration handwritten signature used evidence legal proceedings validity qualified electronic signature created qualified certificate must accepted eu member states regardless member state signature produced parts world similar concepts created define standards electronic signatures switzerland digital signing standard zertes comparable standards address conformity regulation trust service providers product digital certificates united states nist digital signature standard dss provide comparable standard regulating qualified certificates would address non-repudiation signatory ’ qualified certificate amendment nist dss currently discussed would in-line eidas zertes handle trusted services
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Computer security
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logging service logging service laas architectural model centrally ingesting collecting type log files coming given source location servers applications devices etc files normalized filtered reformatting forwarding dependent systems processed “ native ” data managed displayed ultimately disposed according predesignated retention schedule based number criteria enterprise situation datacenter becomes hub log files normalization managed service provider msp environment log sources would coming applications outside enterprise still hosted managed msp needed model datacenter acts private cloud concept cloud computing provision logs various stakeholders within organization future forensics analysis identify risks patterns activity predict behaviors based data collected within logs becomes hub service stakeholders become beneficiaries centralized data form alerts reports periphery applications predictive analysis insight big data graphical display
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Distributed computing architecture
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amigabasic amigabasic interpreted basic programming language implementation amiga designed written microsoft amigabasic shipped amigaos versions 1.1 1.3 succeeded metacomco abasic included amigaos 1.0 1.1 superseded arexx rexx-style scripting language amigaos version 2.0 onwards amigabasic provided common basic language also attempted provide easy-to-use api amiga unique graphics sound capabilities object commands example made easy create moving objects – sprites bobs could drawn external drawing program object editor supplied amigabasic unusual feature language theoretically allowed calling handwritten assembly language subprograms however feature never worked bug failed align assembly language instructions correctly word boundary required amiga native mc68000 processor compute popular computer magazine published amigabasic still shipped included many amigabasic type programs articles typically implementations simple programs rudimentary games system file utilities desk accessories analog clocks address books amigabasic rendered obsolete incompatibilities amigaos 2.0 hardware successors motorola 68000 cpu incompatibilities due disregard programming guidelines set forth commodore however number third-party compiled basic languages released amiga could compile amigabasic programs minimal changes like a/c basic cursor see compiled basics continued work amigaos 2.0 compiled rather interpreted generally ran much faster original although amigabasic superseded arexx amigaos 2.0 two languages different functions capabilities hobbyist programmers changed time amigaos 2.0 release likely interested scripting existing third party applications writing new programs entirely scratch arexx seen better fitting needs basic along microsoft similar basic apple macintosh amigabasic first basic interpreter require line numbers adopting instead top-down approach executing lines code labels indicate goto instruction jump however programs contained line numbers able run line numbers simply treated labels purpose flow control also first microsoft interpreted language capable calling os functions dynamic libraries command library example codice_1 command invokes standard amiga graphics.library call functions go one better adding following line amiga say hello world using speech synthesis addition displaying screen
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Programming language topics
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heap feng shui computer security heap feng shui technique used exploits facilitate arbitrary code execution technique attempts manipulate layout heap making heap allocations carefully selected sizes named feng shui ancient chinese system aesthetics involves selection precise alignments space term general used describe variety techniques bypassing heap protection strategies paper often credited naming technique heap feng shui javascript used refer exploit dangling pointer aligned portion attacker-controlled chunk however also found usage capture flag events describe attacks exploit characteristics heap layout spacing chunks
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Computer security
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architecture windows nt architecture windows nt line operating systems produced sold microsoft layered design consists two main components user mode kernel mode preemptive reentrant multitasking operating system designed work uniprocessor symmetrical multiprocessor smp -based computers process input/output i/o requests use packet-driven i/o utilizes i/o request packets irps asynchronous i/o starting windows xp microsoft began making 64-bit versions windows available 32-bit versions operating systems programs subsystems user mode limited terms system resources access kernel mode unrestricted access system memory external devices kernel mode windows nt full access hardware system resources computer windows nt kernel hybrid kernel architecture comprises simple kernel hardware abstraction layer hal drivers range services collectively named executive exist kernel mode user mode windows nt made subsystems capable passing i/o requests appropriate kernel mode device drivers using i/o manager user mode layer windows nt made environment subsystems run applications written many different types operating systems integral subsystem operates system-specific functions behalf environment subsystems kernel mode stops user mode services applications accessing critical areas operating system access executive interfaces user mode subsystems deal i/o object management security process management kernel sits hardware abstraction layer executive provide multiprocessor synchronization thread interrupt scheduling dispatching trap handling exception dispatching kernel also responsible initializing device drivers bootup kernel mode drivers exist three levels highest level drivers intermediate drivers low-level drivers windows driver model wdm exists intermediate layer mainly designed binary source compatible windows 98 windows 2000 lowest level drivers either legacy windows nt device drivers control device directly plug play pnp hardware bus user mode made various system-defined processes dlls interface user mode applications operating system kernel functions called environment subsystem windows nt one implementing different api set mechanism designed support applications written many different types operating systems none environment subsystems directly access hardware access hardware functions done calling kernel mode routines four main environment subsystems win32 subsystem os/2 subsystem windows subsystem linux posix subsystem security subsystem deals security tokens grants denies access user accounts based resource permissions handles login requests initiates login authentication determines system resources need audited windows nt also looks active directory workstation service implements network redirector client side windows file print sharing implements local requests remote files printers redirecting appropriate servers network conversely server service allows computers network access file shares shared printers offered local system windows nt kernel mode full access hardware system resources computer runs code protected memory area controls access scheduling thread prioritization memory management interaction hardware kernel mode stops user mode services applications accessing critical areas operating system access user mode processes must ask kernel mode perform operations behalf x86 architecture supports four different privilege levels numbered 0 3 two extreme privilege levels used usermode programs run cpl 3 kernel runs cpl 0 two levels often referred ring 3 ring 0 respectively design decision done achieve code portability risc platforms support two privilege levels though breaks compatibility os/2 applications contain i/o privilege segments attempt directly access hardware code running kernel mode includes executive made many modules specific tasks kernel provides low-level services used executive hardware abstraction layer hal kernel drivers windows executive services make low-level kernel-mode portion contained file ntoskrnl.exe deals i/o object management security process management divided several subsystems among cache manager configuration manager i/o manager local procedure call lpc memory manager object manager process structure security reference monitor srm grouped together components called executive services internal name ex system services internal name nt i.e. system calls implemented level except call directly kernel layer better performance term service context generally refers callable routine set callable routines distinct concept service process user mode component somewhat analogous daemon unix-like operating systems kernel sits hal executive provides multiprocessor synchronization thread interrupt scheduling dispatching trap handling exception dispatching also responsible initializing device drivers bootup necessary get operating system running kernel performs almost tasks traditional microkernel strict distinction executive kernel prominent remnant original microkernel design historical design documentation consistently refers kernel component microkernel kernel often interfaces process manager level abstraction kernel never calls process manager way around save handful corner cases still never point functional dependence windows nt uses kernel-mode device drivers enable interact hardware devices drivers well defined system routines internal routines exports rest operating system devices seen user mode code file object i/o manager though i/o manager devices seen device objects defines either file device driver objects kernel mode drivers exist three levels highest level drivers intermediate drivers low level drivers highest level drivers file system drivers fat ntfs rely intermediate drivers intermediate drivers consist function drivers—or main driver device—that optionally sandwiched lower higher level filter drivers function driver relies bus driver—or driver services bus controller adapter bridge—which optional bus filter driver sits function driver intermediate drivers rely lowest level drivers function windows driver model wdm exists intermediate layer lowest level drivers either legacy windows nt device drivers control device directly pnp hardware bus lower level drivers directly control hardware rely drivers windows nt hardware abstraction layer hal layer physical hardware computer rest operating system designed hide differences hardware provide consistent platform kernel run hal includes hardware-specific code controls i/o interfaces interrupt controllers multiple processors however despite purpose designated place within architecture hal n't layer sits entirely kernel way kernel sits executive known hal implementations depend measure kernel even executive practice means kernel hal variants come matching sets specifically constructed work together particular hardware abstraction involve abstracting instruction set generally falls wider concept portability abstracting instruction set necessary handling several revisions x86 instruction set emulating missing math coprocessor performed kernel via hardware virtualization
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Computer architecture
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jackbe jackbe corporation privately held vendor enterprise mashup software real-time intelligence applications august 2013 jackbe acquired software ag jackbe flagship product enterprise mashup platform called presto used enterprise mashups business management dashboards real-time intelligence applications jackbe ’ main product presto enterprise mashup platform presto provides real-time intelligence functionality self-service on-demand data integration business dashboards jackbe launched cloud computing-based version presto product march 2010 hosted amazon ec2 jackbe launched mashup sites sharepoint mss july 2010 jackbe announced enterprise app depot 2010 platform creating internal application directories enterprise app depot aimed non-developers business users allowing create new business applications share applications users industry analyst joe mckendrick described enterprise app store cool idea zdnet
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Web technology
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nginx nginx like engine x stylized nginx nginx web server also used reverse proxy load balancer mail proxy http cache software created igor sysoev first publicly released 2004 company name founded 2011 provide support nginx plus paid software nginx free open-source software released terms bsd-like license large fraction web servers use nginx often load balancer march 2019 nginx company acquired f5 networks 670 million netcraft estimated nginx served 32 active websites ranked ranking first apache 29 top million websites neither ranked first ranked first 33 sources still estimate apache ahead overall according netcraft november 2016 web server survey nginx found second widely used web server across active sites 18.22 surveyed sites top million busiest sites 27.83 surveyed sites according w3techs used 37.7 top 1 million websites 49.7 top 100,000 websites 57.0 top 10,000 websites according builtwith used 38.2 top 10,000 websites growth within top 10k 100k 1 million segments increased 2018 survey docker usage found nginx commonly deployed technology docker containers wikipedia uses nginx ssl termination proxy openbsd release 5.2 1 november 2012 nginx became part openbsd base system providing alternative system fork apache 1.3 intended replace later replaced openbsd httpd 8 nginx deployed serve dynamic http content network using fastcgi scgi handlers scripts wsgi application servers phusion passenger modules serve software load balancer nginx uses asynchronous event-driven approach rather threads handle requests nginx modular event-driven architecture provide predictable performance high loads nginx default configuration file codice_1 features include upgrading executable configuration without client connections loss module-based architecture core third-party module support paid plus product includes additional features advanced load balancing access expanded suite metrics performance monitoring two versions nginx oss nginx nginx plus nginx plus offers additional features included oss nginx active health checks session persistence based cookies dns service discovery integration cache purging api appdynamic datalog dynatrace new relic plug-ins active-active ha config sync key-value store on-the-fly zero downtime updates upstream configurations key‑value stores using nginx plus api web application firewall waf dynamic module nginx written explicit goal outperforming apache web server box serving static files nginx uses dramatically less memory apache handle roughly four times many requests per second however performance boost comes cost decreased flexibility ability override systemwide access settings per-file basis apache accomplishes .htaccess file nginx feature built nginx also reputation harder install configure apache formerly adding third party modules nginx required recompiling application source modules statically linked partially overcome version 1.9.11 february 2016 addition dynamic module loading however modules still must compiled time nginx modules compatible system—some require older static linking process nginx generally considered less stable windows server linux apache equal support igor sysoev began development nginx 2002 originally nginx developed solve c10k problem fill needs websites including rambler search engine portal serving 500 million requests per day september 2008 nginx inc. founded july 2011 sysoev provide commercial products support software company principal place business san francisco california legally incorporated british virgin islands october 2011 nginx raised 3 million bv capital runa capital msd capital michael dell venture fund company announced commercial support options companies using nginx production nginx offered commercial support february 2012 paid nginx plus subscription august 2013 support packages focus installation configuration performance improvement etc support includes proactive notifications major changes security patches updates patches wordpress developer automattic inc. content delivery network provider maxcdn became funding partners update google spdy version 3.1 slated early 2014 nginx also offers consulting services assist customers custom configuration adding additional features october 2013 nginx raised 10 million series b investment round led new enterprise associates round included previous investors well aaron levie ceo founder box.com december 2014 nginx raised 20 million series b1 round led new enterprise associates participation e.ventures formerly bv capital runa capital index ventures nginx ceo gus robertson october 2017 nginx inc. announced general available nginx amplify saas providing monitoring analytics capabilities nginx september 2017 nginx announced api management tool nginx controller would build api gateway nginx plus june 2018 nginx raised 43 million series c funding round led goldman sachs accelerate application modernization digital transformation enterprises 11 march 2019 f5 networks acquired nginx
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Web technology
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plug compatible plug compatible refers hardware designed perform exactly like another vendor product term pcm refer term pcm originally applied manufacturers made replacements ibm peripherals later term used refer ibm-compatible computers rise pcm peripheral industry computing systems either many peripherals originally designed used specific central processing unit cpu term pcm originally applied manufacturers made replacements ibm peripherals first example plug compatible ibm subsystems tape drives controls offered telex beginning 1965 memorex 1968 first enter ibm plug-compatible disk followed shortly thereafter number suppliers cdc itel storage technology corporation boosted world largest user computing equipment directions ultimately plug-compatible products offered peripherals system main memory plug-compatible machine one designed backward compatible prior machine particular new computer system plug-compatible connectors protocol interfaces peripherals also binary-code compatibility—it runs software old system plug compatible manufacturer pcm company makes products one recurring theme plug-compatible systems ability bug compatible well forerunner system software interface problems successor must simulate problems otherwise new system may generate unpredictable results defeating full compatibility objective thus important customers understand difference bug feature latter defined intentional modification previous system e.g higher speed lighter weight smaller package better operator controls etc. original example pcm mainframes amdahl 470 mainframe computer plug-compatible ibm system 360 370 costing millions dollars develop ibm customer could literally remove 360 370 friday install amdahl 470 attach connectors peripherals channel interfaces new mainframe running software sunday night unfortunately system status indicators operators new system different introduced learning curve operators service technicians similar systems available comparex fujitsu hitachi large systems system vendors eventually left pcm market term may also used define replacement criteria components available multiple sources example plug-compatible cooling fan may need physical size shape also similar capability run voltage use similar power attach standard electrical connector similar mounting arrangements non-conforming units may re-packaged modified meet plug-compatible requirements adapter plate provided mounting different tool instructions supplied installation modifications would reflected bill materials components similar issues arise computer system interfaces competitors wish offer easy upgrade path general plug-compatible systems designed industry de facto standards rigorously defined environment large installed population machines benefit third-party enhancements plug compatible mean identical replacement however nothing prevents company developing follow-on products backward-compatible early products
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Computer architecture
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benchmark email benchmark email international internet-based service provider email marketing headquarters los alamitos ca company founded curt denise keller 2004 company offers various free paid editions benchmark member returnpath.net email sender provider coalition industry consortiums expansion international markets pursued company translating software english spanish french german chinese japanese portuguese italian establishing offices philippines japan china india spain taiwan italy among several countries recently website also launched french 2017 benchmark email named one 20 b2b technologies try 2017 forbes
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Distributed computing architecture
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relational data mining relational data mining data mining technique relational databases unlike traditional data mining algorithms look patterns single table propositional patterns relational data mining algorithms look patterns among multiple tables relational patterns types propositional patterns corresponding relational patterns example relational classification rules relational classification relational regression tree relational association rules several approaches relational data mining multi-relation association rules multi-relation association rules mrar new class association rules contrast primitive simple even multi-relational association rules usually extracted multi-relational databases rule item consists one entity several relations relations indicate indirect relationship entities consider following mrar first item consists three relations live nearby humid “ live place near city humid climate type also younger 20 health condition good ” association rules extractable rdbms data semantic web data
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Databases
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a/ux a/ux discontinued unix-based operating system apple computer custom integrated system 7 graphical interface application compatibility launched 1988 discontinued 1995 version 3.1.1 apple first official unix-based operating system a/ux requires select models 68k-based macintosh fpu paged memory management unit pmmu including macintosh ii se/30 quadra centris series predecessor macos variant unix currently bundled apple desktop computers described infoworld open systems solution macintosh heart operating system based unix system v release 2.2 includes additional features system v releases 3 4 bsd versions 4.2 4.3 posix system v interface definition svid compliant includes tcp/ip networking version 2 onward unix-compatible posix-compliant operating system made possible apple bid large contracts supply computers u.s. federal government institutes a/ux provides graphical user interface including familiar finder windows menus controls a/ux finder customized version system 7 finder adapted run unix process designed interact underlying unix file systems a/ux includes codice_1 terminal program offers command line interface underlying unix system x window system server application called macx terminal program also used interface system run x applications alongside finder alternatively user choose run fullscreen x11r4 session without finder apple compatibility layer allows a/ux run macintosh system 7.0.1 unix hybrid applications hybrid application uses functions macintosh toolbox unix system example run macintosh application calls unix system functions unix application calls macintosh toolbox functions quickdraw hypercard stack graphical frontend command-line unix application a/ux compatibility layer uses existing toolbox functions computer ’ rom function calls translated native unix system calls cooperatively multitasks macintosh apps single address space using token-passing system access toolbox a/ux includes utility called codice_2 similar tool name included macintosh programmer workshop assist users entering unix commands opening unix executable file finder opens dialog box allows user choose command-line options program using standard controls radio buttons check boxes display resulting command line argument user executing command program feature intended ease learning curve users new unix decrease user reliance unix manual a/ux utility allows user reformat third-party scsi drives way used macs era a/ux runs 68k-based macintoshes floating point unit fpu paged memory management unit pmmu even runs select models example quadra 840av apple fastest 68k macintosh run a/ux a/ux 1.0 announced february 1988 uniforum conference seven months behind schedule initially aimed existing unix customers universities vars. ref name= apple breaks unix market a/ux /ref system initially sold pre-installed macintosh ii although one could add larger monitor higher price purchase kit upgrading existing mac ii lower price third-party software announced system first release includes ingres database statview developer tools various productivity software packages based unix system v.2.2 additional features bsd unix networking support included tcp/ip appletalk nfs implementations developed unisoft base system gui running command line capable running single mac program time using system 6 interface although 10 existing mac software would run released 1989 a/ux 1.1 supplies basic gui system 6 finder chooser desk accessories control panels provisions unix x window system x11r3 gui draft 12 posix standard overall improved speed comparable low end sun workstation. ref name= a/ux release 1.1 supports x window /ref first posix compliant platform allowed apple join growing list industry heavyweights allowed us federal government burgeoning 6 billion bid market 1991 based aim alliance apple envisioned a/ux becoming basis drastically scaling concept macintosh system architecture application compatibility across computing industry personal enterprise markets apple formed new business division enterprise systems led director jim groff serve large businesses government higher education basing division upon maturing a/ux groff admitted apple major player unix market performed merely quiet marketing operating system fully intended become major player broad-based marketing objectives 1992 apple believed alliance ibm would merge a/ux aix system 7—thus ultimately scaling execution macintosh applications mac desktops ibm huge rs/6000 systems november 1991 apple launched a/ux 3.0 planning synchronize two ongoing release schedules a/ux system 7 time company also preannounced a/ux 4.0 expected release 1993 1994 announcement expounded upon historic technology partnership apple ibm expecting merge apple user-friendly graphical interface desktop applications market ibm highly scalable unix server market allowing two companies enter apple believed emerging general desktop open systems market upcoming a/ux 4.0 would target poweropen environment abi merge features ibm aix variant unix a/ux use osf/1 kernel open software foundation a/ux 3.0 would serve important migration path new system making unix system 7 applications compliant poweropen specification future a/ux 4.0 aix operating systems intended run variety ibm power powerpc hardware apple powerpc-based hardware april 1992 c2-level secure version a/ux released coincidentally aim alliance launched apple/ibm partner corporation taligent inc. one month earlier mission bringing pink market grandly universal operating system application framework contrary announcements apple eventually abandoned plans a/ux 4.0 never releasing product 1995 company withdrew taligent partnership poweropen discontinued 1996 discontinued two-year copland project intended become mac os 8 host taligent software 1996 1997 company deployed short-lived platform apple network server systems based upon powerpc hardware customized ibm aix operating system company overall failed operating system strategy left badly aged system 7 successor following apple 1996 acquisition next apple introduced 1999 mac os x server descendant unix-based nextstep operating system final release a/ux version 3.1.1 1995 apple abandoned a/ux platform completely 1996 a/ux 1.0 criticized 1988 infoworld review largely command-driven user interface unix variants rather graphical system 6 networking support praised though byte 1989 listed a/ux 1.1 among excellence winners byte awards stating could make unix multitasking operating system choice next decade challenge os/2 compared contemporary workstations unix vendors however macintosh hardware lacks features demand paging first two versions a/ux consequently suffer poor performance poor sales users also complained amount disk space uses standard macintosh though comparable unix system august 1992 issue infoworld author favorably reviewed a/ux 3.0 describing open systems solution macintosh heart apple finally gets unix right praised gui single-button point-and-click installer one year personal tech support graphical help dialogs user manuals saying a/ux defies stereotype unix difficult use easiest version unix learn list price much higher much weaker competing pc operating systems system 7 os/2 ms-dos windows 3.1 low compared prevailing proprietary unix licenses review found system speed acceptable great even fastest quadra 950 blaming software incomplete unix optimization found apple hardware though good value system price-performance ratio judged altogether uncompetitive sun sparcstation 2 reviewers thought unlikely users want buy macs run a/ux would awarded infoworld top score os proprietary macintosh hardware tony bove bove rhodes report generally complained f unix super-users compelling reason buy apple unix apple a/ux always way sell macs unix check-off item users a/ux requires specific raw hardware access execution a/ux within macintosh emulation software impossible 2014 introduction macintosh ii emulator named shoebill vintage a/ux users one central repository a/ux applications internet server nasa called jagubox administered jim jagielski also editor a/ux faq
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Operating systems
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system reconfiguration attacks system reconfiguration attacks modify settings user ’ pc malicious purposes example urls favorites file might modified direct users look-alike websites e.g. bank website url may changed “ bankofabc.com ” “ bancofabc.com ” بتعديل الإعدادات على جهاز الكمبيوتر الخاص بالمستخدم والهدف من هذا التعديل أهداف ضارة system reconfiguration attacks تقوم هجمات إعادة تهيئة النظام
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Computer security
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agnitum agnitum ltd founded 1999 st. petersburg russia software company 2000 agnitum hired 2 developers increased number staff people 20 2002 agnitum originally focused anti-trojan pc connections monitoring solutions targeted windows pcs users company known mostly personal firewall internet security products provider outpost firewall pro flagship product company released 2002 together freeware solution updated 2009 agnitum products mostly consumer-oriented taking account licensing agnitum products technologies several national security software publishers january 14 2016 agnitum confirmed official blog company acquired yandex december 2015 february 28 2017 final phase sale yandex agnitum site user forum shut agnitum established software producer 1999 st. petersburg russia two students baltic state technical university distributing software online shareware agnitum sold niche software entering 2002 pc firewalls market agnitum software become rather popular 2002 agnitum began formally implement international distribution strategy putting place agreements partners major european markets well germany italy spain poland 2003 2006 agnitum strengthened european american far east market positions personal firewall engine company became basis company products thus integrated several firms security solutions partnering security vendors provide personal firewall anti-spyware technologies 2003-2006 agnitum announced contracts anti-virus solutions vendors whole re-branded software part vendor suite sophos uk usa lavasoft sweden novell usa virusbuster hungary others 2006 agnitum criticized microsoft onecare firewall agnitum claimed leaks faced simplest attacks programs test firewalls leaks agnitum chief software architect posted less-than-glowing assessment microsoft windows firewall part company entry security software business 2006 agnitum entered strategic alliance virusbuster experienced anti-virus vendor hungary agnitum aimed enter market internet security suite solutions compete anti-virus vendors kaspersky zonelabs etc already integrated personal firewalls personal security solutions mostly personal anti-viruses additional spyware adware spam web content filtering engines 2007-2008 agnitum finally entered market anti-virus solutions anti-virus products began participating international domestic test labs tests virus bulletin vb100 anti-malware.ru anti-virus tests outpost firewall pro tested leaktests killtests independent research portals 2009 2010 agnitum released 2 freeware editions outpost software outpost firewall pro free edition outpost security suite free continue competition well-known zonealarm comodo free pc firewall vendors agnitum first software products anti-trojan tool tauscan pc connections monitoring tool jammer anti-trojan software tauscan occasionally achieved attention media received awards jammer focused detecting blocking attacks hackers prototype outpost personal firewall launched simultaneously “ free ” “ pro ” versions march 2002 march 2007 agnitum released free anti-spam plug-in filtering microsoft outlook outlook express mail supports bat since 2008 may 2007 agnitum released combined internet security suite solution — outpost security suite pro ossp proactive solution basis outpost firewall agnitum anti-spam licensed anti-virus combined agnitum anti-spyware october 2007 agnitum released microsoft vista-compatible outpost 2008 products outpost firewall pro began pass leak-tests kill-tests matousec transparent security firewall challenge project independent project proactive security software testing 2010 agnitum released extension freeware solution outpost security suite free include anti-virus anti-spyware anti-spam free internet security suite moment agnitum security products available following languages english german french spanish russian default also lot localized outpost software versions like italian polish hungarian japanese traditional simplified chinese korean turkish dutch brazilian portuguese agnitum firewall anti-spyware anti-virus engines became almost independent products several security companies licensing agnitum technologies integrate products list companies made publicity licensing novell novell os client security agent sophos corporate edition client agent bullguard internet security solution lavasoft personal firewall client agent cat/quickheal indian anti-virus solutions vendor total security solution
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Computer security
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system/34 basic ibm system/34 basic interpreter ibm system/34 midrange computer system/34 basic first offered 1978 contained many trappings basic program would encountered time period trs-80 many offerings seventies early eighties s/34 basic uses conventions longer standard modern basics line numbers support newer features while/wend do/enddo with/end procedures properties forth basic interpreters written seventies tended odd things odd ways example apple ii programmer could embed dos command program via print prefaced character string chr 4 peek poke could used various basics examine memory content change even create ad hoc machine language program run system/34 basic tends stay away odd conventions however programmer could call alarm buzzing sound made terminal via print chr 7 basic statements expected entered capital letters operator press cmd2 use lowercase basic interpreter convert non-comment keywords uppercase basic could useful midrange computing environment ibm added extensions language specific hardware software conventions ibm system/34 family workstn file support indexed direct sequential disk files ability open close multiple printer files load/save libraries fixed disk core basic statements functions commands used advanced ibm-supplied statements included error error-trapping statement allows basic suspend error might otherwise stop basic program running perform error-handling routine instead variants include suffixing oflow zdiv error types statement immediately trap errors option allows basic program meet special criteria sometimes basic much user space since s/34 programs limited 64k area called code space contains current user program must reside within user space therefore users could choose option lprec causes basic compute double-precision long numerics option sprec provides space single-precision short numerics programmers prefer matrix mathematics lowest-numbered index 0 others prefer 1 option base 0 option base 1 accomplish uses option rpg ii programs s/34 could call basic programs could using chain statement chain passes control current basic module named module bearing list arguments become variables new module loaded def fn allows definition user function basic named referred program fnend placed last statement function four ways format basic input output first unformatted print input heart content second print using s/34 basic incorporate constant string variable line number label third print fields input fields place 5250-type display fields crt immediate mode fourth using workstation file opened open x ws name= forth performing various combinations write read workstation file using sda-generated screen formats similar s/34 applications write read well print using input using direct basic line number label contains keyword image image statement contains decimals commas dollar signs dashes pound signs representation substituted numeric alphameric values 3540 image form statement denotes size variables read written save numeric value .00 99,999.99 use notation 2959 form n 7.2 label tag line follows 260 begin_calculations 270 x 1 12 280 x*1.08 290 next x desired statement gosub begin_calculations used instead gosub 260 open close write rewrite delete append already familiar cobol programmers describe actions taken access s/34 disk files using basic n't possible access every single type s/34 file include system files libraries folders every user-created s/34 file fixed record length fortran programs use variable record lengths suffice disk files opened sequentially index relatively record number file delete-capable records deleted using delete statement add record use write append specified open statement update use rewrite s/34 basic print printer device file must used default printer file called 255 always exists basic started printer name basic255 opens device default printer terminal begins basic session desired possible create different printer file numbered 1 254 use open x printer name= forth specifying columns device id parameters needed pageoflow keyword used trap page overflow condition printer versions basic allow programmer sort array s/34 basic n't provide function provide interesting remedy programmer define array number elements target array use aidx didx create ascending descending index element new array contain number representing ordinal sorted position target array america sixth element array first alphabetical order setting aidx would cause 1 contain value 6 writing basic program much fun rewriting program time use therefore authors basic allow programmers save program code library member replace changes made save prog1 pgmrlib causes current module saved subroutine member type r named prog1 user library named pgmrlib note system/34 files part libraries disk file named fnf001 open statement like one work open 3 name=fnf001 sequential input n't matter library used access file fnf001 renumber s/34 basic command used renumber statements internal references statement numbers immediately recalculated system/34 basic dangerous command called free typing free followed filename deletes file without trace work every user file unless conflict security in-use condition blocks system/34 basic another dangerous command called lock lock command make current program source code inaccessible reversible always save unlocked copy using lock 1983 ibm announced system/36 family midrange computers system/34 basic system/36 basic similar however machine code incompatibility makes impossible port subroutine member basic program systems
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Programming language topics
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freespire freespire community-driven linux distribution currently owned pc/open systems llc derived linspire composed mostly free open source software providing users choice including proprietary software including multimedia codecs device drivers application software freespire 1.0 based debian freespire 2.0 based ubuntu linspire bought xandros originally planned switch back debian future freespire releases january 1 2018 pc/open systems announced purchased linspire xandros released freespire 3.0 linspire 7 available 79.99 freespire 3.0 free august 2005 distribution live cd based linspire source pools named freespire hit web accident distribution created andrew betts produced released linspire inc. freespire confused users actual product linspire request linspire distribution adopted development codename squiggle began looking new name linspire back generated publicity offered users free linspire purchase price discounted 0 using coupon code freespire september 9 2005 squiggle os longer active development april 24 2006 linspire announced project named freespire new freespire distribution announced linspire president former ceo kevin carmony follows model fedora supported red hat community since 2003 novell also started similar community project name opensuse suse linux product line second half 2005 xandros acquired linspire/freespire summer 2008 xandros plans keep freespire community developed distribution similar opensuse fedora respective commercial distributions freespire 2.0.8 released 30 november 2007 based ubuntu 7.04 final release distribution revived 3.0 january 2018 distribution debian-based community-driven -supported project tied commercial linspire distribution freespire includes previously proprietary elements linspire click n run cnr client elements linspire licenses like windows media audio compatibility libraries remain proprietary closed source consequently two versions freespire one proprietary closed source libraries one called freespire oss edition includes mostly open-source components freespire number in-house programs written haskell ocaml iso image builder hardware detection autoconfiguration package autobuilder debian library also programs managing cgi
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Operating systems
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mdaemon mdaemon email server email server application groupware functions microsoft windows first released alt-n technologies 1996 mdaemon supports multiple client-side protocols including imap pop3 smtp/msa webmail caldav carddav optionally activesync mobile clients outlook connector outlook add-on mdaemon features include built-in spam filter heuristic bayesian analysis ssl tls encryption client-side server-side email attachment encryption public shared folder support mailing list support sharing groupware data calendar contacts tasks notes also basis mdaemon tech security gateway email servers according securityspace.com mail mx server survey june 2018 mdaemon provides approximately 1 percent known internet mail servers fifth largest installation base identified servers
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Internet protocols
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sun enterprise sun enterprise range unix server computers produced sun microsystems 1996 2001 line launched sun ultra enterprise series ultra prefix dropped around 1998 systems based 64-bit ultrasparc microprocessor architecture related contemporary ultra series computer workstations like ultra series run solaris various models single-processor entry-level servers large high-end multiprocessor servers produced enterprise brand phased favor sun fire model line 2001 onwards first ultrasparc-i-based servers produced sun launched 1995 ultraserver 1 ultraserver 2 server configurations ultra 1 ultra 2 workstations respectively later renamed ultra enterprise 1 ultra enterprise 2 consistency server models later joined ultra enterprise 150 comprises ultra 1 motherboard tower-style enclosure 12 internal disk bays 1998 sun launched server configurations ultrasparc-iii-based ultra 5 ultra 10 workstations called enterprise ultra 5s enterprise ultra 10s respectively sun enterprise 450 rack-mountable entry-level multiprocessor server launched 1997 capable four ultrasparc ii processors sun enterprise 250 two-processor version launched 1998 later joined enterprise 220r enterprise 420r rack-mount servers 1999 220r 420r models respectively based motherboards ultra 60 ultra 80 workstations 250 replaced sun fire v250 450 sun fire v880 220r superseded sun fire 280r 420r sun fire v480 1996 sun replaced sparcserver 1000e sparccenter 2000e models ultra enterprise 3000 4000 5000 6000 servers multiprocessor servers based common hardware architecture incorporating gigaplane packet-switched processor/memory bus ultrasparc-i ii processors high availability fault-tolerance features included x000 systems intended mission-critical applications 3000 model deskside server configurable six processors 10 internal disks 4000 rack-mount system 14 processors 5000 essentially 4000 rack cabinet 6000 cabinet-housed data center server 30 processors 1999 enterprise 3500 4500 5500 6500 models announced upgraded x000 systems faster gigaplane bus 100 mhz depending processor clock speed compared 83 mhz 3500 also differs 3000 additional gigaplane slot resulting increased maximum eight processors enterprise x500 series replaced sun fire 3800/4800/6800 line enterprise 10000 e10k starfire development code name also used marketing purposes high-end multiprocessor data center server capable configured 64 ultrasparc ii processors largely designed cray research business systems division successor cray superserver 6400 related sun earlier sun-4d architecture servers cray acquired silicon graphics 1996 division sold sun launched starfire ultra enterprise 10000 1997 starfire based around fault-tolerant gigaplane-xb processor/memory interconnect like x000 x500 series servers starfire incorporates many high-availability features including ability partitioned multiple domains booted individually run instance solaris also possible remove resources running domain short notice reassign freed resources domains domain granularity one cpu board single system may 1-16 single cpu board carry 4 processors 4gb ram 4 sbus io boards rare option replace 4 sbus boards dual pci boards starfire first server vendor exceed 2000 tpc-d 300 gb benchmark starfire systems used number high-profile customers dot-com boom notably ebay typically sold well 1 million fully configured system starfire contains one two controller modules connected via ethernet external computer system service processor ssp controller modules interface system centerplane via jtag control partitioning available cpus memory i/o devices one domains effect distinct computer system partitioned booted without original ssp contains encrypted keys issued manufacturer e10k preserved computer history museum mountain view starfire superseded sun fire 12k/15k models
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Computer architecture
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watchos watchos operating system apple watch developed apple inc based ios operating system many similar features released april 24 2015 along apple watch device runs watchos api called watchkit second version watchos 2 included support native third-party apps improvements released september 21 2015 third version watchos 3 released september 13 2016 emphasizing better performance including new watch faces stock apps fourth version watchos 4 released september 19 2017 fifth version watchos 5 released september 17 2018 adding third-party support new workouts along “ walkie-talkie ” feature sixth version watchos 6 announced june 3 2019 home screen rendered also known carousel composed circular application icons zoomed digital crown dragged launched touching display many apps miniaturized simplified versions ios counterparts prior watchos 3 glances provided fast access summarized view popular native third party applications used apple watch glances view opened swipe gesture watch face screen watchos 3 glances replaced redesigned control center much like one ios friends menu invoked side button acts dedicated dock apps different actions options appear depending user taps deep presses apple watch detects pressure-sensitive force touch display several years apple developing healthkit product bid change way people interact devices also conscious attempt penetrate lucrative healthcare wellness industry many observers believe hold huge growth opportunity apple confirmed jony ive apple chief designer interview said health crucial element apple watch since day inception developmental trajectory hardware watchos geared towards health-based capabilities ive pointed one primary apps shipped first watchos allowed users track communicate well encourage move exercise stand said many us phones us time ’ connected imagine something powerful times opportunities might present user opportunity phenomenal particularly ’ understand today terms technology capability headed.one recent updates watchos included applications keep users active also diagnose illnesses example app called deepheart deep learning network detect atrial fibrillation hypertension sleep apnea diabetes taps healthkit platform collect data particularly collected apple watch heart sensor watchos 5 first shown public san jose wwdc developer conference held apple instant watch-to-watch walkie-talkie mode first version watchos support first generation apple watch apple announced new version watchos contain features app store calculator tip tools audiobooks app apple voice memos app
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Operating systems
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ibm system/36 basic ibm system/36 basic interpreter ibm system/36 midrange computer system/36 basic first offered 1983 contained many trappings basic program would encountered time period ibm pc commodore 64 vic-20 trs-80 many offerings seventies early eighties s/36 basic uses conventions longer standard modern basics line numbers support newer features while/wend do/enddo with/end procedures properties forth basic interpreters written seventies tended odd things odd ways example apple ii programmer could embed command program via print prefaced character string chr 4 peek poke could used various basics examine memory content change even create ad hoc machine language program run system/36 basic tends stay away odd conventions however programmer could call alarm buzzing sound made terminal via print chr 7 basic statements expected entered capital letters operator press cmd2 use lowercase basic interpreter convert non-comment keywords uppercase basic could useful midrange computing environment ibm added extensions language specific hardware software conventions ibm system/36 family workstn file support indexed direct sequential disk files ability open close multiple printer files load/save libraries fixed disk core basic statements functions commands used advanced ibm-supplied statements included error error-trapping statement allows basic suspend error might otherwise stop basic program running perform error-handling routine instead variants include suffixing oflow zdiv error types statement immediately trap errors option allows basic program meet special criteria sometimes basic much user space since s/36 programs limited 64k area called code space contains current user program must reside within user space therefore users could choose option lprec causes basic compute double-precision long numerics option sprec provides space single-precision short numerics programmers prefer matrix mathematics lowest-numbered index 0 others prefer 1 option base 0 option base 1 accomplish uses option rpg ii programs s/34 s/36 could call basic programs could using chain statement chain passes control current basic module named module bearing list arguments become variables new module loaded def fn allows definition user function basic named referred program fnend placed last statement function four ways format basic input output first unformatted print input heart content second print using s/36 basic incorporate constant string variable line number label third print fields input fields place 5250-type display fields crt immediate mode fourth using workstation file opened open x ws name= forth performing various combinations write read workstation file using sda-generated screen formats similar s/36 applications write read well print using input using direct basic line number label contains keyword image image statement contains decimals commas dollar signs dashes pound signs representation substituted numeric alphameric values form statement denotes size variables read written save numeric value .00 99,999.99 use notation label tag line follows desired statement gosub begin_calculations used instead gosub 260 open close write rewrite delete append already familiar cobol programmers describe actions taken access s/36 disk files using basic n't possible access every single type s/36 file include system files libraries folders every user-created s/36 file fixed record length fortran programs use variable record lengths suffice disk files opened sequentially index relatively record number file delete-capable records deleted using delete statement add record use write append specified open statement update use rewrite s/36 basic print printer device file must used default printer file called 255 always exists basic started printer name basic255 opens device default printer terminal begins basic session desired possible create different printer file numbered 1 254 use open x printer name= forth specifying columns device id parameters needed pageoflow keyword used trap page overflow condition printer versions basic allow programmer sort array s/36 basic n't provide function provide interesting remedy programmer define array number elements target array use aidx didx create ascending descending index element new array contain number representing ordinal sorted position target array america sixth element array first alphabetical order setting didx would cause 6 contain value 1 writing basic program much fun rewriting program time use therefore authors basic allow programmers save program code library member replace changes made save prog1 pgmrlib causes current module saved subroutine member type r named prog1 user library named pgmrlib note system/36 files part libraries disk file named fnf001 open statement like one work n't matter library used access file fnf001 renumber s/36 basic command used renumber statements internal references statement numbers immediately recalculated system/36 basic dangerous command called free typing free followed filename deletes file without trace work every user file unless conflict security in-use condition blocks system/36 basic another dangerous command called lock lock command make current program source code inaccessible reversible always save unlocked copy using lock system/34 basic system/36 basic similar however machine code incompatibility makes impossible port subroutine member basic program systems see also square root 2 pi π solution solution published mainframes 1980s 1990s
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Programming language topics
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windows nt 4.0 windows nt 4.0 operating system part microsoft windows nt family operating systems released manufacturing july 31 1996 launched retail august 24 1996 microsoft primary business-oriented operating system introduction windows 2000 workstation server embedded editions sold editions feature graphical user interface similar windows 95 microsoft ended mainstream support windows nt 4.0 workstation june 30 2002 extended support june 30 2004 windows nt 4.0 server mainstream support ended december 31 2002 extended support december 31 2004 editions succeeded windows 2000 professional server respectively successor windows nt 3.51 windows nt 4.0 introduced user interface windows 95 windows nt family including windows shell file explorer known windows nt explorer time use nomenclature shell folders e.g computer also includes components introduced windows 95 internally windows nt 4.0 known shell update release sur many administrative tools notably user manager domains server manager domain name service manager still used old graphical user interfaces start menu windows nt 4.0 separated per-user shortcuts folders shared shortcuts folders separator line windows nt 4.0 includes enhancements microsoft plus windows 95 space cadet pinball table font smoothing showing window contents dragging high-color icons stretching wallpaper fit screen windows desktop update could also installed windows nt 4.0 update shell version install task scheduler windows nt 4.0 resource kit included desktop themes utility windows nt 4.0 preemptively multitasked 32-bit operating system designed work either uniprocessor symmetric multi-processor computers windows nt 4.0 last major release microsoft windows support alpha mips powerpc cpu architectures remained use businesses number years despite microsoft many efforts get customers upgrade windows 2000 newer versions also last release windows nt family branded windows nt although windows 2000 carried designation built nt technology although chief enhancement addition windows 95 shell several major performance scalability feature improvements core architecture kernel user32 com msrpc windows nt 4.0 also introduced concept system policies system policy editor important features server editions windows nt 4.0 include internet information services 2.0 microsoft frontpage 1.1 netshow services remote access service includes pptp server vpn functionality multi-protocol routing service new administrative wizards lite version network monitor utility shipped system management server enterprise edition introduced microsoft cluster server one significant difference previous versions windows nt graphics device interface gdi moved kernel mode rather user mode csrss process eliminated process-to-process context switch calling gdi functions resulting significant performance improvement windows nt 3.51 particularly graphical user interface however also mandated graphics printer drivers run kernel mode well resulting potential stability issues windows nt 4.0 first release microsoft windows include directx standard—version 2 shipped initial release windows nt 4.0 version 3 included release service pack 3 mid-1997 later versions directx released windows nt 4.0 however opengl supported used quake 3 unreal tournament early releases 4.0 numerous stability issues occur graphics printer vendors change drivers compatible kernel mode interfaces exported gdi change move gdi run process context caller prompted complaints nt workstation users real-time graphics performance change put considerable onus hardware manufacturers update device drivers windows nt 4.0 also included new windows task manager utility previous versions windows nt included task list utility shows applications currently desktop monitor cpu memory usage users forced use performance monitor task manager offers convenient way getting snapshot processes running system given time internet explorer 2 bundled windows nt 4 updated versions included service pack service pack 6 last service pack windows nt 4 included internet explorer 5.01 although also supports internet explorer 6.0 windows nt 4.0 upgraded ntvdm x86 emulation risc versions 286 486 sysprep introduced deployment tool windows nt 4.0 providing much greater stability windows 95 windows nt 4.0 less flexible desktop perspective much stability gained use protected memory hardware abstraction layer direct hardware access disallowed misbehaving programs terminated without needing computer restarted trade-off nt required much memory 32 mb normal desktop use 128 mb heavy 3d applications comparison consumer targeted products windows 95 nearly programs written windows 95 run windows nt many 3d games would partly limited directx support windows nt 4.0 third-party device drivers alternative access hardware directly poorly written drivers became frequent source infamous error known blue screen death bsod would require system restarted spite shipping year later windows 95 default plug play support device manager windows nt 4.0 greatly simplifies installation hardware devices although limited support could installed later many basic dos programs would run however graphical dos programs would run way accessed graphics hardware although windows nt 4.0 introduced application programming interface api defragmentation built-in defragmentation utility unlike windows 95 also windows nt 4.0 lacked usb support preliminary version would added oem editions windows 95 osr 2.1 difference nt family 9x family would remain release windows xp 2001 time apis — opengl directx — matured sufficiently efficient write common pc hardware hand hardware become powerful enough handle api processing overhead maximum amount supported physical random-access memory ram windows nt 4.0 4 gb maximum possible purely 32-bit x86 operating system comparison windows 95 fails boot computers approximately 480 mb memory like previous versions nt version 4.0 run multiple processor architectures windows 95 however run x86 windows nt 4.0 server included versions 4.0 4.5 backoffice small business server suite option pack available free-bundled cd starting around 1998 included iis 4.0 active server pages frontpage server extensions certificate server mts msmq cdonts internet authentication service ias indexing service microsoft management console 1.0 microsoft site server smtp nntp services new software several features distributed file system windows nt load balancing service wlbs delivered addons windows nt server 4.0 routing remote access service also downloadable feature replaced windows nt 4.0 separate ras multi-protocol routing services last version microsoft office compatible windows nt 4.0 office xp last version internet explorer compatible operating system internet explorer 6 sp1 service pack 6 6a required respectively windows nt 4.0 could directly upgraded windows 2000 windows xp professional windows nt 4.0 received seven service packs lifecycle well numerous service rollup packages option packs first service pack made available mips architecture service pack 3 final release powerpc architecture last full service pack service pack 6a sp6a service pack 7 planned one stage early 2001 became post sp6a security rollup full service pack released july 26 2001 16 months release windows 2000 nearly three months prior release windows xp addition bug fixes service packs also added multitude new features newer versions improvements internet information services public-key certificate authority functionality user accounts user profile improvements smart card support improved symmetric multiprocessing smp scalability clustering capabilities com support improvements user profile disk quotas event log service security configuration manager mmc snap-in ms-chapv2 ntlmv2 smb packet signing syskey boot improvements wins improvements routing remote access service rras pptp dcom/http tunneling improvements igmpv2 wmi active accessibility ntfs 3.0 support among others microsoft released five revisions windows nt 4.0 workstation server resource kit original release plus four supplements contained large number tools utilities desktops.exe allowed user multiple desktops well third-party software microsoft stopped providing security updates windows nt 4.0 workstation june 30 2004 windows nt 4.0 server december 31 2004 due major security flaws including microsoft security bulletin ms03-010 according microsoft could patched without significant changes core operating system according security bulletin due fundamental differences windows nt 4.0 windows 2000 successors infeasible rebuild software windows nt 4.0 eliminate vulnerability would require re-architecting significant amount windows nt 4.0 operating system ... would assurance applications designed run windows nt 4.0 would continue operate patched system june 2003 june 2007 127 security flaws identified patched windows 2000 server many may also affect windows nt 4.0 server however microsoft test security bulletins unsupported software
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Computer architecture
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renewables.ninja renewables.ninja web tool developed imperial college london eth zürich shows estimate amount energy could generated wind solar farms location model tested iain staffell codeveloper renewables.ninja centre environmental policy imperial college london stefan pfenninger eth zürich estimate productivity wind farms planned construction europe next 20 years german electrical supplier rwe using test models output
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Web technology
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christopher soghoian christopher soghoian born 1981 privacy researcher activist currently working senator ron wyden senator ’ senior advisor privacy cybersecurity 2012 2016 principal technologist american civil liberties union soghoian nephew sal soghoian former automation product manager apple inc. responsible applescript automator soghoian holds british us nationality received b.s james madison university computer science 2002 masters johns hopkins university security informatics 2005 phd indiana university informatics 2012 dissertation focused role third-party internet telecommunications service providers play facilitating law enforcement surveillance customers soghoian visiting fellow yale law school information society project ted senior fellow previously open society foundations fellow student fellow berkman center internet society harvard university soghoian research advocacy largely focused government surveillance research shed significant light use sophisticated surveillance technologies us law enforcement agencies exposing techniques public debate criticism august 2013 presentation hacker conference def con soghoian highlighted existence dedicated fbi team delivers malware computers mobile devices surveillance targets presentation soghoian stated discovered team reading heavily redacted government documents looking profiles ex-fbi contractors social network website linkedin october 2014 soghoian called attention fact fbi 2007 impersonated associated press effort deliver malware teenager washington state threatened bomb high school act deception strongly condemned leading news organizations including general counsel associated press february 2012 public speech soghoian criticized commercial market called zero-day security vulnerabilities topic yet receive significant attention mainstream press one month later soghoian quoted forbes lengthy article zero day market describing firms individuals sell software exploits “ modern-day merchants death ” selling “ bullets cyberwar. ” next several years several major media outlets published front-page stories industry often quotes soghoian criticizing providing hacking software governments december 2009 employee federal trade commission soghoian secretly audio recorded closed-door surveillance industry conference agency inspector general opened investigation soghoian conduct subsequently let go ftc recording executive sprint nextel revealed company created special website law enforcement agents obtain gps information subscribers website used process 8 million requests previous year recording subsequently cited alex kozinski chief judge ninth circuit court appeals u.s. v. pineda-moreno support view 1984 may come bit later predicted last june 2009 soghoian co-authored open letter google 37 prominent security privacy experts urging company protect privacy customers enabling https encryption default gmail cloud based services january 2010 google enabled https default users gmail subsequently products including search according google already considering https default soghoian recent years continued https advocacy calling news media law firms government agencies organizations encrypt websites may 2011 soghoian approached public relations firm burson-marsteller asked write anti-google op-ed criticizing company privacy issues associated social search product soghoian refused instead published email conversation subsequent investigation journalists revealed pr firm refused identify client soghoian retained facebook may 2011 soghoian filed complaint ftc claimed online backup service dropbox deceiving customers security services soon soghoian first publicly voiced concerns dropbox updated terms service privacy policy make clear company fact encrypt user data key known user company disclose users private data forced law enforcement agencies october 2010 soghoian filed complaint ftc claimed google intentionally leaking search queries sites users visited clicked link search results page two weeks later law firm filed class action lawsuit google practice lawsuit extensively quoted soghoian ftc complaint october 2011 google stopped leaking search queries sites users visited 2015 company settled search query leakage class action lawsuit 8.5 million dollars 2009 2010 worked us federal trade commission first ever in-house technical advisor division privacy identity protection ftc assisted investigations facebook twitter myspace netflix soghoian first gained public attention 2006 creator website generated fake airline boarding passes october 26 2006 soghoian created website allowed visitors generate fake boarding passes northwest airlines users could change boarding document name flight number city wished generator defaulted creating document osama bin laden soghoian claimed motivation website focus national attention ease passenger could evade no-fly lists information describing security vulnerabilities associated boarding pass modification widely publicized others including senator charles schumer d-ny security expert bruce schneier october 27 2006 then-congressman edward markey called soghoian arrest 2 october 28 2006 home raided agents fbi seize computers materials soghoian internet service provider voluntarily shut website received letter fbi claiming site posed national security threat october 29 2006 congressman markey issued revised statement stating soghoian go jail instead department homeland security put work fix boarding pass security flaws fbi closed criminal investigation november 2006 without filing charges tsa june 2007
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Computer security
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