計(jì)算機(jī)專業(yè)英語教程第版翻譯

1Wehavelearnedthatallcomputershavesimilarcapabilitiesandperformessentiallythesamefunctions,althoughsomemightbefasterthanothers.Wehavealsolearnedthatacomputersystemhasinput,output,storage,andprocessingcomponents;thattheprocessoristhe“intelligence”ofacomputersystem;andthatasinglecomputersystemmayhaveseveralprocessors.Wehavediscussedhowdataarerepresentedinsideacomputersysteminelectronicstatescalledbits.Wearenowreadytoexposetheinnerworkingsofthenucleusofthecomputersystem—theprocessor.我們已經(jīng)知道，全部計(jì)算機(jī)都具備相同能力，而且在本質(zhì)上執(zhí)行相同功效，盡管一些可能會(huì)比另一些快一點(diǎn)。我們也知道，一個(gè)計(jì)算機(jī)系統(tǒng)具備輸入，輸出，存放和處理部件；處理器是一個(gè)計(jì)算機(jī)系統(tǒng)智能關(guān)鍵，而且一個(gè)計(jì)算機(jī)系統(tǒng)能夠有許多個(gè)處理器。我們已經(jīng)討論過怎樣在計(jì)算機(jī)系統(tǒng)內(nèi)部，用被稱作“位”電子狀態(tài)來表現(xiàn)數(shù)據(jù)，現(xiàn)在我們要弄明白計(jì)算機(jī)系統(tǒng)關(guān)鍵，即處理器，內(nèi)在工作方式。Theinternaloperationofacomputerisinteresting,buttherereallyisnomysterytoit.Themysteryisinthemindsofthosewholistentohearsayandbelievescience-fictionwriter.Thecomputerisanonthinkingelectronicdevicethathastobepluggedintoanelectricalpowersource,justlikeatoasteroralamp.計(jì)算機(jī)內(nèi)部操作很有意思，但確實(shí)沒有什么神秘可言。所謂神秘只是存在于那些聽信傳聞和相信科幻小說作家人意識(shí)中。計(jì)算機(jī)就是一個(gè)沒有思想需要接通電源電子設(shè)備而已，與烤面包機(jī)和臺(tái)燈差不多。Literallyhundredsofdifferenttypesofcomputersaremarketedbyscoresofmanufacturers[1].Thecomplexityofeachtypemayvaryconsiderably,butintheendeachprocessor,sometimescalledthecentralprocessingunitorCPU,hasonlytwofundamentalsections:thecontrolunitandthearithmeticandlogicunit.Primarystoragealsoplaysanintegralpartintheinternaloperationofaprocessor.Thesethree—primarystorage,thecontrolunit,andthearithmeticandlogicunit—worktogether.Let’slookattheirfunctionsandtherelationshipsbetweenthem.不加夸大地講，市場(chǎng)上有幾百種不一樣類型計(jì)算機(jī)在銷售.每種電腦在復(fù)雜性上可能有很大區(qū)分，但歸根結(jié)底,每種處理器，有時(shí)稱為中央處理器即cpu，只有兩個(gè)基本部分:控制單元和計(jì)算邏輯單元.主內(nèi)存在處理器內(nèi)部操作中也是一個(gè)不可缺乏部分.這三個(gè)部件--主內(nèi)存，控制單元和計(jì)算邏輯單元--一起工作.然我們看看它們(各自)功效和它們之間聯(lián)絡(luò)。Unlikemagneticsecondarystoragedevices,suchastapeanddisk,primarystoragehasnomovingparts.Withnomechanicalmovement,datacanbeaccessedfromprimarystorageatelectronicspeeds,orclosetothespeedoflight.Mostoftoday’scomputersuseDRAM(DynamicRandom-AccessMemory)technologyforprimarystorage.Astate-of-the-artDRAMchipaboutoneeighththesizeofapostagestampcanstoreabout256,000,000bits,orover25,600,000charactersofdata!主存與其余輔助存放器（如：磁帶、硬盤）不一樣是，主存不含有運(yùn)轉(zhuǎn)部件。因?yàn)闆]有機(jī)械運(yùn)轉(zhuǎn)需要，主存種數(shù)據(jù)訪問能夠達(dá)成電子速度，或靠近于光速。當(dāng)今計(jì)算機(jī)主存大多數(shù)使用DRAM（動(dòng)態(tài)隨機(jī)存取存放器）技術(shù)?，F(xiàn)在最新工藝水平是：一塊只有大約1/8張郵票大小DRAM芯片卻能夠存放大約256,000,000位，約25,6000,000個(gè)字符數(shù)據(jù)。Primarystorage,ormainmemory,providestheprocessorwithtemporarystorageforprogramsanddata.Allprogramsanddatamustbetransferredtoprimarystoragefromaninputdevice(suchasaVDT)orfromsecondarystorage(suchasadisk)beforeprogramscanbeexecutedordatacanbeprocessed.Primarystoragespaceisalwaysatapremium;therefore,afteraprogramhasbeenexecuted,thestoragespaceitoccupiedisreallocatedtoanotherprogramawaitingexecution.主存放器，也就是說內(nèi)存，用于為處理器暫時(shí)存放程序和數(shù)據(jù)。全部程序和數(shù)據(jù)在被操作之前必須從輸入設(shè)備（如VDT）或者輔助存放器轉(zhuǎn)存到主存放器中。主存放器存放容量通常是相當(dāng)有限，所以，在一個(gè)程序執(zhí)行結(jié)束，它所占用存放空間必須被重新分配給其它正在等候執(zhí)行操作程序。Figure1-1illustrateshowallinput/output(I/O)is“readto”or“writtenfrom”primarystorage.Inthefigure,aninquiry(input)ismadeonaVDT.Theinquiry,intheformofamessage,isroutedtoprimarystorageoverachannel(suchasacoaxialcable).Themessageisinterpreted,andtheprocessorinitiatesactiontoretrievetheappropriateprogramanddatafromsecondarystorage[3].Theprogramanddataare“l(fā)oaded”,ormoves,toprimarystoragefromsecondarystorage.Thisisanondestructivereadprocess.Thatis,theprogramanddatathatarereadresideinbothprimarystorage(temporarily)andsecondarystorage(permanently).Thedataaremanipulatedaccordingtoprograminstructions,andareportiswrittenfromprimarystoragetoaprinter.圖1-1描述了輸入/輸出設(shè)備與主存放器間讀和寫過程。在圖中，VDT發(fā)出一個(gè)輸入請(qǐng)求，請(qǐng)求是以消息模式經(jīng)過通道（如同軸電纜）發(fā)送到主存放器。這個(gè)查詢被解釋，處理器發(fā)起操作從輔助存放器中調(diào)用適宜程序和數(shù)據(jù)。程序和數(shù)據(jù)從輔助存放器傳送到主存放器中，這是一個(gè)非破壞性讀取過程，也就是說，程序和數(shù)據(jù)同時(shí)存在于主存（暫時(shí)保留）和輔助存放器（永久保留）中。依照程序指令指示，處理器對(duì)數(shù)據(jù)進(jìn)行操作，并從主存?zhèn)魉鸵环輩R報(bào)到打印機(jī)。Aprograminstructionorapieceofdataisstoredinaspecificprimarystoragelocationcalledanaddress.Addressespermitprograminstructionsanddatatobelocated,accessed,andprocessed.Thecontentofeachaddressisconstantlychangingasdifferentprogramsareexecutedandnewdataareprocessed.程序指令和數(shù)據(jù)是存放在主存中一個(gè)特殊位置，稱為地址空間。經(jīng)過地址空間能夠?qū)崿F(xiàn)計(jì)算機(jī)對(duì)程序指令和數(shù)據(jù)定位、訪問和處理。地址空間內(nèi)容是經(jīng)常改變，這是因?yàn)橛?jì)算機(jī)一直在執(zhí)行不一樣程序和數(shù)據(jù)。Anothernameforprimarystorageisrandom-accessmemory,orRAM.Aspecialtypeofprimarystorage,calledread-onlymemory(ROM),cannotbealteredbytheprogrammer.ThecontentsofROMare“hard-wired”(designedintothelogicofthememorychip)bythemanufacturerandcanbe“readonly”.Whenyouturnonamicrocomputersystem,aprograminROMautomaticallyreadiesthecomputersystemforuse.ThentheROMprogramproducestheinitialdisplayscreenprompt.主存放器也稱為隨機(jī)存取存放器，或RAM。還有一個(gè)特殊主存放器，稱為只讀存放器（ROM），這種存放器不能被程序更改存放內(nèi)容。ROM內(nèi)容是被生產(chǎn)商經(jīng)過硬件電路寫入，而且不能被重寫。當(dāng)你開啟計(jì)算機(jī)，ROM中一個(gè)程序會(huì)自動(dòng)就緒等候計(jì)算機(jī)系統(tǒng)調(diào)用，然后在顯示器中顯示開機(jī)提醒。AvariationofROMisprogrammableread-onlymemory(PROM).PROMisROMintowhichyou,theuser,canload“read-only”programsanddata.OnceaprogramisloadedtoPROM,itisseldom,ifever,changed[4].However,ifyouneedtobeabletorevisethecontentsofPROM,thereisEPROM,erasablePROM.Beforeawriteoperation,allthestoragecellsmustbeerasedtothesameinitialstate.可編程只讀存放器（PROM）是另一個(gè)ROM，它能夠載入只讀程序和數(shù)據(jù)，一旦載入，將不再改變。然而，若果你需要去修正PROM內(nèi)容，能夠使用可擦可編程只讀存放器。 EPROM在進(jìn)行一次寫操作之前，全部存放單元必須被還原為同一初始狀態(tài)。Amoreattractiveformofread-mostlymemoryiselectricallyerasableprogrammableread-onlymemory(EEPROM).Itcanbewrittenintoatanytimewithouterasingpriorcontents;onlythebyteorbytesaddressedareupdated.一個(gè)更吸引人可改寫只讀存放器是電可擦除可編程只讀存放器(EEPROM)。它能夠在任何時(shí)候?qū)懭?，而且不?huì)擦除以前內(nèi)容；只會(huì)更新被尋址字節(jié)。TheEEPROMcombinestheadvantageofnonvolatilitywiththeflexibilityofbeingupdatableinplace[6],usingordinarybuscontrol,address,anddatalines.電可擦可編程存放器把非易失性優(yōu)點(diǎn)和可更新、需要更新地方靈活性結(jié)合起來，修改時(shí)使用普通總線控制線、地址線和數(shù)據(jù)線。Anotherformofsemiconductormemoryisflashmemory(sonamedbecauseofthespeed).FlashmemoryisintermediatebetweenEPROMandEEPROMinbothcostandfunctionality.LikeEEPROM,flashmemoryusesanelectricalerasingtechnology.Anentireflashmemorycanbeerasedinoneorafewseconds,whichismuchfasterthanEPROM.Inaddition,itispossibletoerasejustblocksofmemoryratherthananentirechip.However,flashmemorydoesnotprovidebyte-levelerasure[7].LikeEPROM,flashmemoryusesonlyonetransistorperbit,andsoachievesthehighdensityofEPROM.另一個(gè)半導(dǎo)體記憶體是閃存（意味著速度快）。閃存在性價(jià)比上處于EPROM和EEPROM之間，它使用電擦寫技術(shù)。整個(gè)閃存內(nèi)容能夠在一到幾秒內(nèi)被去除，這是遠(yuǎn)快于EPROM。另外，它還能夠?qū)Σ糠钟洃泬K而不是整個(gè)存放器進(jìn)行去除。然而，閃存并不提供字節(jié)級(jí)擦除。像EPROM，閃存只使用一個(gè)晶體管每比特，所以能夠?qū)崿F(xiàn)高密度EPROM。CacheMemoryProgramanddataareloadedtoRAMfromsecondarystoragebecausethetimerequiredtoaccessaprograminstructionorpieceofdatafromRAMissignificantlylessthanfromsecondarystorage.ThousandsofinstructionsorpiecesofdatacanbeaccessedfromRAMinthetimeitwouldtaketoaccessasinglepieceofdatafromdiskstorage[8].RAMisessentiallyahigh-speedholdingareafordataandprograms.Infact,nothingreallyhappensinacomputersystemuntiltheprograminstructionsanddataaremovedtotheprocessor.Thistransferofinstructionsanddatatotheprocessorcanbetime-consuming,evenatmicrosecondspeeds.Tofacilitateanevenfastertransferofinstructionsanddatatotheprocessor,mostcomputersaredesignedwithcachememory.Cachememoryisemployedbycomputerdesignerstoincreasethecomputersystemthroughput(therateatwhichworkisperformed).程序和數(shù)據(jù)從輔助存放器裝載到RAM中是因?yàn)閷?duì)RAM中程序指令和數(shù)據(jù)訪問時(shí)間要顯著少于從輔助存放器訪問。數(shù)以千條指令和數(shù)據(jù)能被訪問而只需花費(fèi)從硬盤訪問一次數(shù)據(jù)時(shí)間。RAM是數(shù)據(jù)和程序主要高速存放區(qū)，實(shí)際上，計(jì)算機(jī)系統(tǒng)不會(huì)進(jìn)行任何操作直到程序指令被傳入處理器進(jìn)行執(zhí)行，這種指令和數(shù)據(jù)傳輸是需要花費(fèi)時(shí)間，即使傳輸速度已經(jīng)是以納秒來計(jì)算了。為了能更加快速傳輸指令和數(shù)據(jù)，大多數(shù)計(jì)算機(jī)設(shè)計(jì)使用高速緩存。計(jì)算機(jī)設(shè)計(jì)者使用高速緩存來提升計(jì)算機(jī)系統(tǒng)總處理能力（工作效率）。LikeRAM,cacheisahigh-speedholdingareaforprograminstructionsanddata.However,cachememoryusesSRAM(StaticRAM)technologythatisabout10timesfasterthanRAMandabout100timesmoreexpensive.WithonlyafractionofthecapacityofRAM,cachememoryholdsonlythoseinstructionsanddatathatarelikelytobeneedednextbytheprocessor.Twotypesofcachememoryappearwidelyincomputers.ThefirstisreferredtoasinternalcacheandisbuiltintotheCPUchip.Thesecond,externalcache,islocatedonchipsplacedclosetotheCPUchip.Acomputercanhaveseveraldifferentlevelsofcachememory.Level1cacheisvirtuallyalwaysbuiltintothechip.Level2cacheusedtobeexternalcachebutisnowtypicallyalsobuiltintotheCPUlikelevel1cache.和RAM一樣，高速緩存也是程序指令和數(shù)據(jù)高速存放區(qū)。然而，高速緩存使用靜態(tài)RAM技術(shù)，這種技術(shù)比RAM在速度上要高出10倍，價(jià)格上高出100倍。cache只保留內(nèi)存中那一小部分最有可能被處理器執(zhí)行指令和數(shù)據(jù)。兩種類型cache廣泛應(yīng)用于計(jì)算機(jī)，第一個(gè)被植入cpu中叫做內(nèi)部高速存放，第二種是外部高速存放，它位于那些靠近c(diǎn)pu芯片中。一臺(tái)計(jì)算機(jī)能夠擁有幾個(gè)不一樣級(jí)別高速緩存。一級(jí)緩存實(shí)際上總是植入芯片中，二級(jí)緩存過去經(jīng)常作為外部高速緩存，不過現(xiàn)在也像一級(jí)緩存植入cpu內(nèi)部。2.1Opticallaserdisktechnologyeventuallymaymakemagnetic-diskandmagnetictapestorageobsolete.Withthistechnology,theread/writeheadusedinmagneticstorageisreplacedbytwolasers.Onelaserbeamwritestotherecordingsurfacebyscoringmicroscopicpitsinthedisk,andanotherlaserreadsthedatafromthelight-sensitiverecordingsurface.Alightbeamiseasilydeflectedtothedesiredplaceontheopticaldisk,soanaccessarmisnotneeded.光盤技術(shù)最終可能使磁盤和磁帶存放淘汰。用這種技術(shù)，磁存放器所用讀/寫頭被兩束激光代替。一束激光經(jīng)過在光盤上刻制微小凹點(diǎn)，對(duì)統(tǒng)計(jì)表面進(jìn)行寫；而另一束激光用來從光敏感統(tǒng)計(jì)表面讀取數(shù)據(jù)。因?yàn)楣馐p易被偏轉(zhuǎn)到光盤上所需要位置，所以不需要存取臂。Opticallaserdisksarebecomingaveryinvitingoptionforusers.Theyarelesssensitivetoenvironmentalfluctuations,andtheyprovidemoredirect-accessstorageatacostthatismuchlesspermegabyteofstoragethanthemagnetic-diskalternative.Opticallaserdisktechnologyisstillemergingandhasyettostabilize;however,atpresenttherearethreemaincategoriesofopticallaserdisks.TheyareCD-ROM,recordableCD-RandrewritableCD-RW,andmagneto-opticaldisk.對(duì)用戶而言，光盤正成為最有吸引力選擇。它們(光盤)對(duì)環(huán)境改變不太敏感，而且它們以每兆字節(jié)比磁盤低得多存放器價(jià)格提供更多直接存取存放器。光盤技術(shù)仍在出現(xiàn)，而且還需要穩(wěn)定；然而，現(xiàn)在有三種主要類型光盤。它們是CD-ROM、WORM盤和磁光盤。CD-ROMIntroducedin1980,theextraordinarilysuccessfulCD,orcompactdisk,isanopticallaserdiskdesignedtoenhancetherecordedreproductionofmusic.TomakeaCDrecording,theanalogsoundsofmusicaretranslatedintotheirdigitalequivalentsandstoredona4.72-inchopticallaserdisk.Seventy-fourminutesofmusiccanberecordedoneachdiskindigitalformatby2billiondigitalbits.Withitstremendousstoragecapacity,computer-industryentrepreneursimmediatelyrecognizedthepotentialofopticallaserdisktechnology.Ineffect,anythingthatcanbedigitizedcanbestoredonopticallaserdisk:data,text,voice,stillpictures,music,graphics,andvideo.1980年引入，非常成功CD，或緊密盤是設(shè)計(jì)來提升音樂錄音重放質(zhì)量光盤。為了制作一張CD，把音樂模擬聲音轉(zhuǎn)換成等價(jià)數(shù)字聲音，而且存放在一張4.72英寸光盤上。在每張光盤上能夠用數(shù)字格式（用20億數(shù)字位）統(tǒng)計(jì)74分鐘音樂。因?yàn)樗薮蟠娣湃萘?，?jì)算機(jī)工業(yè)企業(yè)家們立刻認(rèn)識(shí)到光盤技術(shù)潛力。實(shí)際上，任何能夠被數(shù)字化東西都能存放在光盤上：數(shù)據(jù)、正文、聲音、靜止圖象、音樂、圖形和視頻。CD-ROM(pronouncedcee-dee-ROM)isaspinoffofaudioCDtechnology.CD-ROMstandforcompactdisk-readonlymemory.Thenameimpliesitsapplication.CD-ROMdisks,likelong-playingrecordalbums,are“pressed”atthefactoryanddistributedwiththeirprerecordedcontents(forexample,thecompleteworksofShakespeareorthefirst30minutesofGonewiththewind).Onceinsertedintothediskdrive,thetext,videoimages,andsooncanbereadintoprimarystorageforprocessingordisplay;however,thedataonthediskarefixed—theycannotbealtered.Thisisincontrast,ofcourse,totheread/writecapabilityofmagneticdisks.CD-ROM（讀作C—D—ROM）是音頻CD技術(shù)副產(chǎn)品。CD-ROM代表緊密盤—只讀存放器。該名字隱含了它應(yīng)用。只讀光盤與(能長(zhǎng)久播放)唱片一樣，在工廠里“壓制”并帶著預(yù)先錄好內(nèi)容(如莎士比亞全集，或電影“飄”前30分鐘部分)，分發(fā)出去。一旦光盤插入光盤驅(qū)動(dòng)器，正文、視頻圖像等等就能讀入主存進(jìn)行處理或顯示；然而，在只讀光盤上數(shù)據(jù)是固定—它們不能被改變。當(dāng)然，這是與磁盤讀/寫能力不一樣。Thetremendousamountoflow-costdir-accessstoragemadepossiblebyopticallaserdiskshasopenedthedoortomanynewapplications.大量、低成本直接存取存放器（是光盤使之成為可能）已經(jīng)打開了通向許多新應(yīng)用大門。CD-RANDCD-RWCD-RandCD-RWbothallowusertostoredataoncompactdiscs,butonlydataonrewriteableCDscanbeerasedandoverwritten.CD-Rdiscscanonlybewrittentoonce.BothtypesofdiscslookverysimilartoCD-ROMdiscs.RecordableCDsarecommonlyusedtostoremusicfiles,allowinghomeuserstomakehigh-qualitypersonalizedmusicCDs.CD-RWdiscscanbewrittentoanderasedsimilartofloppydisk.Consequently,theyareagoodalternativeforlargefilestorage,aswellasforcreatinga“master”discbeforeburningaCD-Rdiscs(mostCD-RWdrivescanwritetobothCD-RWandCD-Rdiscs,butsomeCDandCD-RdrivescannotreadCD-RWdiscs).CD-RandCD-RWdrivesalsoreadCD-ROMdiscs.However,CDswillbeeclipsedBYDVDs,oncethattechnologybecomesimprovedandstandardized.CD-R和CD-RW都允許用戶存放數(shù)據(jù)在光盤上，不過只有那些在可復(fù)寫cd中數(shù)據(jù)能被擦除和重寫。Cd-r光盤只能被寫入一次。這倆種光盤看起來與只讀cd光盤差不多?？山y(tǒng)計(jì)cd管片通慣用于存放音樂文件，這么能夠允許家庭用戶制作高質(zhì)量個(gè)人音樂唱片。Cd-rw光盤就像軟盤那樣能被重寫和擦除。所以，他們是大容量文件存放另一個(gè)不錯(cuò)選擇，同時(shí)也作為主盤在對(duì)cd-r光盤進(jìn)行刻入之前（大多數(shù)可擦寫光盤驅(qū)動(dòng)器能夠讀取cd-rw和cd-r光盤，不過也有一些cd驅(qū)動(dòng)器和cd-r驅(qū)動(dòng)器不能讀cd-rw光盤）。Cd-r和cd-rw驅(qū)動(dòng)器也能夠讀cd-rom光盤，然而，cd將會(huì)被dvd所代替，一旦dvd技術(shù)完全成熟和標(biāo)準(zhǔn)化。Magneto-OpticalDiskMagneto-OpticaldiskofferspromisethatOpticallaserdiskswillbecomecommerciallyviableasaread-and-writestoragetechnology.The5and1/4inchdiskscanstoreupto1,000Mb.Atpresent,magneto-opticaldisksaretooexpensiveanddonotofferanywherenearthekindofreliabilitythatusershavecometoexpectofmagneticmedia.Inaddition,theaccesstimesarerelativelyslow,aboutthesameasalow-endWinchesterdisk.磁光盤有希望使得激光盤成為商業(yè)上可行讀/寫存放技術(shù)。5*1/4英寸磁光盤能夠存放高達(dá)1000Mb?，F(xiàn)在磁光盤太貴且根本未達(dá)成用戶對(duì)磁介質(zhì)所期望那種可靠性。另外，存取時(shí)間相對(duì)而言比較慢，大約與低級(jí)溫徹斯特盤相同。Asopticallaserdisktechnologymaturestoreliable,cost-effective,read/writeoperation,iteventuallymaydominatesecondarystorageinthefutureasmagneticdisksandtypedotoday.伴隨光盤技術(shù)成熟到可靠，性能價(jià)格合算，可讀/可寫，未來它最終會(huì)象現(xiàn)在磁盤、磁帶那樣統(tǒng)治二級(jí)存放器。DVDsTheacronymDVD(fordigitalversatiledisc,ordigitalvideodisc)refertoarelativelynewhigh-capacityopticalstorageformatthatcanholdfrom4.7GBto17GB,dependingonthenumberofrecordinglayersanddiscssidesbeingused.Astandardsinglelayered,single-sidedDVDcanstore4.7GBofdata;atwo-layeredstandardenhancesthesingle-sidelayerto8.5GB.DVDcanbedouble-sidedwithamaximumstorageof17GBperdisc.TheDVDwasinitiallydevelopedtostorethefullcontentsofastandardtwo-hourmovie,butisnowalsousedtostorecomputerdataandsoftware.DVD-ROMtechnologyisseenbymanyasthesuccessortomusicCDs,computerCD-ROMs,andprerecordedVHSvideotapethatpeoplebuyandrentforhomeviewing-inotherwords,read-onlyproducts.DVD-RisDVDrewritable(similartoCD-W).Theusercanwritetothediskonlyonce.DVD-RWisDVDrecordable(similartoCD-RW).Theusercaneraseandrewritetothediskmultipletimes.Onlyone-sideddiskscanbeusedforbothDVD-Randdvd-rw.MostDVDdrivescanplaybothcomputerandaudioCDs,butyoucan’tplayDVDsinaCDdrive. 這個(gè)縮寫影碟（數(shù)字化視頻光盤或數(shù)字視頻光盤），指是相對(duì)較新高容量光存放格式取決于光盤統(tǒng)計(jì)層和邊數(shù)，能夠從4.7GB持有以17GB，被使用。一個(gè)標(biāo)準(zhǔn)單層單面DVD能夠存放4.7GB數(shù)據(jù)，一兩個(gè)層次標(biāo)準(zhǔn)，增強(qiáng)了單面層到8.5GB。DVD可雙面每件17GB最大存放。該DVD最初是存放標(biāo)準(zhǔn)全部?jī)?nèi)容兩個(gè)小時(shí)電影，但現(xiàn)在還用于存放計(jì)算機(jī)數(shù)據(jù)和軟件。DVD-ROM技術(shù)是被許多人視為對(duì)音樂CD，電腦光盤和人們購(gòu)置和租賃預(yù)先錄制家庭錄影帶后續(xù)，換句話說，只讀產(chǎn)品。DVD-R是可統(tǒng)計(jì)DVD（就像CD-R那樣）。用戶能夠?qū)ζ溥M(jìn)行一次寫入。DVD-RW是可擦寫（類似CD-RW），用戶可擦除和重寫磁盤數(shù)次。DVD-R和DVD-RW都是單面光盤。全部DVD驅(qū)動(dòng)器能夠同時(shí)播放電腦和音頻CD。不過，不能在CD播放機(jī)上應(yīng)用DVD光盤。DVDForumReceivesTopInformationTechnologyIndustryAwardforCreationofUnifiedSpecificationforNextMultimediaEraDVD論壇因建立下一代數(shù)字多媒體統(tǒng)一規(guī)范而取得最高信息技術(shù)工業(yè)獎(jiǎng)TheDVDForumtodayannouncedthatithasreceivedthe1997PCMagazineAwardforTechnicalExcellenceinthecategoryof“Standards”,inrecognitionoftheForum’ssuccessfuldevelopmentofthedvd-romspecification.DVD論壇今天宣告，因該論壇成功制訂了DVD-ROM規(guī)范而取得1997年P(guān)C雜志(制訂標(biāo)準(zhǔn))卓越技術(shù)獎(jiǎng)?！癗ewstandardsareparticularlyimportant,sincetheypromisetobringhigherlevelsoftechnologyinnovationandmarketcompatibilitytotoday’stechnologyusers,”saidbyMichaelJ.Miller,editor-in-chiefofPCMagazine.”DVD-ROMisacompellingtechnologythatwaschosenbecauseit’safamiliarformatthatbringsawealthofnewcomputing,educational,gamingandentertainmentpossibilitiestotheuser.”“新標(biāo)準(zhǔn)尤其主要，因?yàn)樗鼈兂兄Z把更高級(jí)技術(shù)革新和市場(chǎng)兼容性帶給今天技術(shù)用戶，”PC雜志主編MichaelJ.Miller說，“DVD-ROM是被選出激發(fā)興趣技術(shù)，因?yàn)樗且粋€(gè)熟悉格式，它把大量新計(jì)算、新教育、新游戲和新娛樂可能性帶給用戶?！盜ntheAwardcitationtoDVD-ROMtechnology,PCMagazinereferredtoDVDastheformatthatwill”replacetheCD-ROMastheprimarymeansofPCcontentdistribution.”Representativesofthreecompaniesinvolvedindevelopmentofthespecification,HitachiLtd.,MatsushitaElectricIndustrialCompany(Panasonic)andToshibaCorporation,acceptedtheawardonbehalfoftheDVDForuminaceremonyheldonNovember17atCOMDEX’97inLasVegas.在對(duì)DVD-ROM技術(shù)頒獎(jiǎng)詞中,PC雜志稱，DVD將會(huì)“代替CD-ROM作為PC內(nèi)容(即各種軟件和資料)傳輸主要伎倆?！眳⒓右?guī)范開發(fā)三個(gè)企業(yè)代表（日立，松下，東芝）以DVD論壇名義在11月7日，LasVegasCOMDEX'97舉行慶賀儀式上接收該項(xiàng)獎(jiǎng)。“ProductsbasedonspecificationsdefinedbytheDVDForumarenowshippinginvolumetotheworldwidecomputerandconsumerelectronicsmarkets,andtheAwardforTechnicalExcellenceaddstothemarket’svalidationofthesuccessofthestandardsprocess,”saidKojiHase,GeneralManageroftheDVDProductsDivisionatToshibaCorporationandafoundingmemberoftheDVDForum.”WeareextremelypleasedtoseetheworkoftheDVDForumrecognizedasoneofthekeytechnicalachievementsinthepersonalcomputerindustry,particularlyastheForumexpandsthescopeofitsworkwithalarge,globalmembershipin1998.”“基于DVD論壇定義規(guī)范產(chǎn)品現(xiàn)在正在大量運(yùn)往世界各地計(jì)算機(jī)和電子產(chǎn)品市場(chǎng)，而且卓越技術(shù)獎(jiǎng)增加了市場(chǎng)對(duì)成功制訂標(biāo)準(zhǔn)認(rèn)可，”東芝企業(yè)DVD產(chǎn)品部總經(jīng)理和DVD論壇創(chuàng)辦組員KojiHase說，“我們非常高興地看到DVD論壇工作被公認(rèn)為個(gè)人計(jì)算機(jī)工業(yè)中主要技術(shù)成就之一，尤其是在1998年與更大，全球會(huì)員擴(kuò)大了它工作范圍?！薄癟hemembersoftheDVDForumdevelopedtheDVD-ROMspecificationasthebesttechnicalapproachandalsothebestapproachforcustomersinthemarketplace,”saidSakonNagasaki,directoroftheDVDBusinessDevelopmentOfficeofMatsushitaElectricIndustrialCo.Ltd(Panasonic).“Acceptanceoftheformatillustrateshowstandards–makingeffortsadvancethegoalsoftheentireelectronicsindustry.”“DVD論壇組員把DVD-ROM規(guī)范開發(fā)作為最好技術(shù)方法和對(duì)市場(chǎng)上客戶最好方法”松下有限企業(yè)DVD商業(yè)開發(fā)辦公室主任SakonNagasaki說，“該格式接收說明了制訂標(biāo)準(zhǔn)怎樣加緊整個(gè)電子工業(yè)目標(biāo)實(shí)現(xiàn)?！盜nadditiontoitsroleindevelopmentofDVD-ROMandDVD-Videostandards,theForumhasproposedtheformatforrecordableDVD,knownasDVD-R,andrewritableDVD,knownasDVD-RAM,tointernationalstandardsbodies.WorkisalsocontinuingondefinitionofaDVDAudiospecification.除了論壇在開發(fā)DVD-ROM和DVD-Video標(biāo)準(zhǔn)作用外，論壇也提出了可統(tǒng)計(jì)DVD格式，稱為DVD-R和可重寫DVD，稱為DVD-RAM，并提交國(guó)際標(biāo)準(zhǔn)組織。定義DVD-Audio規(guī)范工作也正在繼續(xù)著。 “ThemissonoftheDVDForumistodefineasmoothmigrationfromCDtoDVDtechnologybyworkingwiththewidestpossiblerepresentativegroupofmanufacturersandtechnologyend-usersintheconvergingindustriesofcomputersandcusumerelectronics,”saidDr.YoshitaTsunoda,amemberoftheExectiveStaffofHitachi,Ltd.AndChairmanoftheDVDForum’sDVD-RAMWorkingGroup.“ThedifferentworkinggroupshavealreadycompleteddefinitionofthreeseparateDVDtechnologystandards,andwehavebegunworkondevelopingnextgenerationspecificationsthatwillprovidecompatibleproductswellintothenextcentury.”“DVD論壇任務(wù)是，在匯共計(jì)算機(jī)工業(yè)和消費(fèi)電子產(chǎn)品工業(yè)中，經(jīng)過與最廣泛代表性制造商與技術(shù)最終用戶小組一起工作，確定從CD技術(shù)向DVD技術(shù)平滑過渡路徑。”日立有限企業(yè)執(zhí)行官之一和DVD論壇DVD-RAM工作組主席YoshitaTsunoda博士說，“不一樣工作組已完成三個(gè)不一樣DVD技術(shù)標(biāo)準(zhǔn)定義，而且我們已開始開發(fā)下一代規(guī)范工作，這些規(guī)范將很好地提供可兼容產(chǎn)品到下一世紀(jì)?！盧ecipientsofthePCMagazineAwardsforTechnicalExcellencearenamedbyateamofeditors,seniorcontributorsandPCLabspersonnelaftermonthsofevaluationanddiscussion.PCMagazine,thesponsoroftheTechnicalExcellenceAwards,isa1.175millioncirculationmagazinepublishedbyZiff-DavisInc.PcMagazineispublished22timesayearinprint,quarterlyonCD,andcontinuouslyontheWorldWideWeb(<>).PC雜志卓越技術(shù)獎(jiǎng)取得者是由編輯、捐助者和PC試驗(yàn)室全體組員組成小組在幾個(gè)月評(píng)價(jià)和討論后提名。PC雜志，卓越技術(shù)獎(jiǎng)主辦者，是由Ziff-Davis企業(yè)出版、有1.175百萬冊(cè)發(fā)行量雜志。PC雜志一年印刷出版22次，每季度出CD，而且連續(xù)地在環(huán)球網(wǎng)上。4.1Anoperatingsystemisthesoftwarewhichactsasaninterfacebetweenauserofacomputerandthecomputerhardware.操作系統(tǒng)是計(jì)算機(jī)用戶和硬件軟件接口。Thepurposeofanoperatingsystemistoprovideanenvironmentinwhichausermayexecuteprogram.操作系統(tǒng)目標(biāo)是提供用戶一個(gè)能夠執(zhí)行程序環(huán)境。Theprimarygoalofanoperatingsystemisthustomakethecomputersystemconvenienttouse.操作系統(tǒng)主要目標(biāo)所以是使計(jì)算機(jī)系統(tǒng)便于使用。Asecondarygoalistousethecomputerhardwareinanefficientway.其次是高效地使用計(jì)算機(jī)硬件。Wecanviewanoperatingsystemasaresourceallocator.我們能夠把操作系統(tǒng)看做是一個(gè)資源分配器。Acomputersystemhasmanyresourceswhichmayberequiredtosolveaproblem:CPUtime,memoryspace,filestorage,input/output(I/O)devices,andsoon.一個(gè)計(jì)算機(jī)系統(tǒng)擁有許多資源，所以需要去處理一些問題，如cpu時(shí)間，內(nèi)存空間，文件存放，輸入輸出設(shè)備等。Theoperatingsystemactsasthemanageroftheseresourcesandallocatesthemtospecificprogramsandusersasnecessaryfortheirtasks.操作系統(tǒng)就像是資源管理員，把資源分配給特定程序和用戶當(dāng)它們工作需要時(shí)。Sincetheremaybemany,possiblyconflicting,requestsforresources,theo/smustdecidewhichrequestsareallocatedresourcestooperatethecomputersystemfairlyandefficiently.所以有可能會(huì)有很多有可能產(chǎn)生沖突資源請(qǐng)求，操作系統(tǒng)必須決定分配資源給哪個(gè)請(qǐng)求能使計(jì)算機(jī)系統(tǒng)合理和有效運(yùn)行。Earlycomputerswere(physically)verylargemachinesrunfromaconsole.早期計(jì)算機(jī)是從控制臺(tái)運(yùn)行體積非常大機(jī)器。Theprogrammerwouldwriteaprogramandthenoperatetheprogramdirectlyfromtheoperator’sconsole.程序員要寫一條程序然后直接從操作者控制臺(tái)操作程序。Softwaresuchasassemblers,loaders,andcompilersimprovedontheconvenienceofprogrammingthesystem,butalsorequiredsubstantialset-uptime.象匯編程序、裝入程序及編譯程序這么軟件使系統(tǒng)軟件編程更方便，但同時(shí)也需要大量開啟時(shí)間。Toreducethesetuptime,operatorswerehiredandsimilarjobswerebatchedtogether.[1]為了能降低這些準(zhǔn)備時(shí)間，操作者就被雇傭，相同作業(yè)成批排在一起。Batchsystemsallowedautomaticjobsequencingbyaresidentmonitorandimprovedtheoverallutilizationofthecomputergreatly.批處理系統(tǒng)經(jīng)過一個(gè)常駐內(nèi)存監(jiān)控程序允許自動(dòng)作業(yè)定序。Thecomputernolongerhadtowaitforhumanoperation.這么計(jì)算機(jī)就無須再等候用戶操作。CPUutilizationwasstilllow,however,becauseoftheslowspeedoftheI/OdevicesrelativetotheCPU.Offlineoperationofslowdeviceswastried.然而，CPU使用率依然不高，這是因?yàn)镮/O設(shè)備處理速度較CPU慢造成。Bufferingwasanotherapproachtoimprovingsystemperformancebyoverlappingtheinput,output,andcomputationofasinglejob.緩沖機(jī)制是另一個(gè)提升系統(tǒng)系能方法，它將一條作業(yè)輸入、輸出和計(jì)算工作重合交織進(jìn)行。Finally,spoolingallowedtheCPUtooverlaptheinputofonejobwiththecomputationandoutputofotherjobs.最終，偽脫機(jī)技術(shù)允許CPU將一條作業(yè)輸入和其余作業(yè)計(jì)算輸出交織進(jìn)行。Spoolingalsoprovidesapoolofjobswhichhavebeenreadandarewaitingtoberun.偽脫機(jī)也為那些已經(jīng)被讀入而且還在等候運(yùn)行作業(yè)提供一個(gè)作業(yè)池。Thisjobpoolsupportstheconceptofmultiprogramming.這個(gè)作業(yè)池支持一個(gè)叫做多程序設(shè)計(jì)概念。Withmultiprogramming,severaljobsarekeptinmemoryatonetime;theCPUisswitchedbackandforthbetweentheminordertoincreaseCPUutilizationandtodecreasethetotalrealtimeneededtoexecuteajob.在這種多程序設(shè)計(jì)技術(shù)中，多個(gè)作業(yè)能夠同時(shí)存放在內(nèi)存中；CPU在這些作業(yè)中往返切換控制，以至于增加CPU使用率和降低執(zhí)行一條作業(yè)總時(shí)間。Multiprogramming,whichwasdevelopedtoimproveperformance,alsoallowstimesharing.多道程序設(shè)計(jì)被開發(fā)來提升性能，也允許分時(shí)。Time-sharedoperatingsystemsallowmanyusers(fromonetoseveralhundred)touseacomputersysteminteractiveatthesametime.分時(shí)操作系統(tǒng)允許多個(gè)用戶（從一個(gè)到幾百個(gè)）同時(shí)交互式地使用計(jì)算機(jī)系統(tǒng)。Asthesystemswitchesrapidlyfromoneusertothenext,eachuserisgiventheimpressionthathehashisowncomputer.因?yàn)橄到y(tǒng)快速地從一個(gè)用戶切換到下一個(gè)用戶，每一個(gè)用戶被給予一個(gè)他擁有自己計(jì)算機(jī)印象。Otheroperatingsystemstypesincludereal-timesystemsandmultiprocessorsystems.其余操作系統(tǒng)類型包含實(shí)時(shí)系統(tǒng)和多處理機(jī)系統(tǒng)。Areal-timesystemisoftenusedascontrolde-viceinadedicatedapplication.實(shí)時(shí)系統(tǒng)通常被用作專用應(yīng)用控制設(shè)備。Sensorsbringdatatothecomputer.傳感器把數(shù)據(jù)帶給計(jì)算機(jī)。Thecomputermustanalyzethedataandpossiblyadjustcontrolstomodifythesensorinputs.計(jì)算機(jī)必須分析數(shù)據(jù)，也可能調(diào)整控制去修改傳感器輸入。Systems,whichcontrolscientificexperiments,medicalcomputersystems,industrialcontrolsystems,andsomedisplaysystemsarereal-timesystems.控制科學(xué)試驗(yàn)，醫(yī)學(xué)計(jì)算機(jī)系統(tǒng)，工業(yè)控制系統(tǒng)和一些顯示系統(tǒng)等系統(tǒng)都是實(shí)時(shí)系統(tǒng)。Areal-timeoperatingsystemhaswell-definedfixedtimeconstraints．實(shí)時(shí)操作系統(tǒng)有定義明確固定時(shí)間約束。Processingmustbedonewithinthedefinedconstraints,orthesystemwillfail.處理必須在定義約束中完成，不然系統(tǒng)將失敗。AmultiprocessorsystemhasmorethanoneCPU.多處理機(jī)系統(tǒng)有不只一個(gè)CPU。Theobviousadvantageswouldappeartobegreatercomputingpowerandreliability.顯著優(yōu)勢(shì)好像是強(qiáng)大計(jì)算能力和可靠性。Therearevarioustypesofoperatingsystemsformultiprocessorsandmulticomputers.有各種各樣操作系統(tǒng)用于多處理機(jī)和多計(jì)算機(jī)。ItismoreorlesspossibletodistinguishtwokindsofoperatingsystemsformultipleCPUsystems:Looselycoupled,suchasnetworkoperatingsystemanddistributedo/s,andtightlycoupled,suchasparallelo/s.這或多或少可能區(qū)分兩種多CPU系統(tǒng)操作系統(tǒng)：松耦合，比如網(wǎng)絡(luò)操作系統(tǒng)和分布式操作系統(tǒng)，和緊耦合，如并行操作系統(tǒng)。Asweshallsee,looselyandtightly-coupleds/wisroughtanalogoustolooselyandtight-coupledh/w.我們應(yīng)該看到，松緊耦合軟件大約類似于松緊耦合硬件。Theoperatingsystemmustensurecorrectoperationofthecomputersystem.操作系統(tǒng)必須確保改過計(jì)算機(jī)系統(tǒng)操作。Topreventuserprogramsfrominterferingwiththeproperoperationofthesystem,theh/wwasmodifiedtocreatetwomodes:usermodeandmonitormode[4].為了阻止用戶程序干擾系統(tǒng)適當(dāng)操作，硬件被修改成兩種模式：用戶模式和監(jiān)控模式。Variousinstructions(suchasI/Oinstructionsandhaltinstructions)arepriviledgedandcanonlybeexecutedinmonitormode.許多指令（比如I/O指令和中止指令）是有特權(quán)，只能在監(jiān)控模式下被執(zhí)行。Thememoryinwhichthemonitorresidesmustalsobeprotectedfrommodificationbytheuser.監(jiān)控程序所在內(nèi)存也必須保護(hù)起來以防用戶修改。Atimepreventsinfiniteloops.定時(shí)器能夠預(yù)防死循環(huán)。Oncethesechanges(dualmode,privilegedinstructions,memoryprotection,timerinterrupt)havebeenmadetothebasiccomputerarchitecture,itispossibletowriteacorrectoperatingsystem.一旦這些對(duì)基本計(jì)算機(jī)體系結(jié)構(gòu)改變（雙模，權(quán)限指令，內(nèi)存保護(hù)，定時(shí)器中止）被做到，這可能寫成一個(gè)改進(jìn)操作系統(tǒng)。《計(jì)算機(jī)專業(yè)英語教程》（第4版）5.1Internet因特網(wǎng)@Manynetworksexistintheworld,oftenwithdifferenthardwareandsoftware.許多網(wǎng)絡(luò)通常會(huì)以不一樣硬件和軟件形式存在于世上。Peopleconnectedtoonenetworkoftenwanttocommunicatewithpeopleattachedtoadifferentone.attachedto隸屬于連接了一個(gè)網(wǎng)絡(luò)人經(jīng)常想與隸屬于一個(gè)不相同網(wǎng)絡(luò)人交流。Thisdesirerequiresconnectingtogetherdifferent,andfrequentlyincompatiblenetworks,sometimesbyusingmachinescalledgatewaystomaketheconnectionandprovidethenecessarytranslation,bothintermsofhardwareandsoftware.Desire心愿frequently頻繁地incompatible不兼容intermsof依照，在???方面這個(gè)要求把不一樣和頻繁不兼容網(wǎng)絡(luò)連接在一起心愿，有時(shí)經(jīng)過使用叫做網(wǎng)關(guān)機(jī)器去組成連接和提供必要轉(zhuǎn)換，都依據(jù)硬件和軟件來實(shí)現(xiàn)。AcollectionofinterconnectednetworksiscalledaninternetworkorjustInternet.Acollectionof...集合interconnected互連internetwork互連網(wǎng)絡(luò)Internet因特網(wǎng)互連網(wǎng)絡(luò)集合被稱為互聯(lián)網(wǎng)絡(luò)或只是因特網(wǎng)。@AcommonformofInternetisacollectionofLANsconnectedbyaWAN.一個(gè)常見形式網(wǎng)絡(luò)是經(jīng)過一個(gè)廣域網(wǎng)連接局域網(wǎng)集合。TheInternet(noteuppercaseI)meansaspecificworldwideinternetthatiswidelyusedtoconnectuniversities,governmentoffices,companies,andoflate,privateindividuals.Worldwide全世界note注意uppercase大寫字母internet互聯(lián)網(wǎng)oflate最近因特網(wǎng)（注意大寫字母I）是一個(gè)特殊全世界互聯(lián)網(wǎng)，被廣泛用來連接大學(xué)，政府部門，企業(yè)和最近是私人。@By1995,thereweremultiplebackbones,hundredsofmid-level(i.e.regional)networks,tensofthousandsofL