计算机专业英语教程第版翻译

1Wehavelearnedthatallcomputershavesimilarcapabilitiesandperformessentiallythesamefunctions,althoughsomemightbefasterthanothers.Wehavealsolearnedthatacomputersystemhasinput,output,storage,andprocessingcomponents;thattheprocessoristhe“intelligence”ofacomputersystem;andthatasinglecomputersystemmayhaveseveralprocessors.Wehavediscussedhowdataarerepresentedinsideacomputersysteminelectronicstatescalledbits.Wearenowreadytoexposetheinnerworkingsofthenucleusofthecomputersystem—theprocessor.我们已经知道，全部计算机都具备相同能力，而且在本质上执行相同功效，尽管一些可能会比另一些快一点。我们也知道，一个计算机系统具备输入，输出，存放和处理部件；处理器是一个计算机系统智能关键，而且一个计算机系统能够有许多个处理器。我们已经讨论过怎样在计算机系统内部，用被称作“位”电子状态来表现数据，现在我们要弄明白计算机系统关键，即处理器，内在工作方式。Theinternaloperationofacomputerisinteresting,buttherereallyisnomysterytoit.Themysteryisinthemindsofthosewholistentohearsayandbelievescience-fictionwriter.Thecomputerisanonthinkingelectronicdevicethathastobepluggedintoanelectricalpowersource,justlikeatoasteroralamp.计算机内部操作很有意思，但确实没有什么神秘可言。所谓神秘只是存在于那些听信传闻和相信科幻小说作家人意识中。计算机就是一个没有思想需要接通电源电子设备而已，与烤面包机和台灯差不多。Literallyhundredsofdifferenttypesofcomputersaremarketedbyscoresofmanufacturers[1].Thecomplexityofeachtypemayvaryconsiderably,butintheendeachprocessor,sometimescalledthecentralprocessingunitorCPU,hasonlytwofundamentalsections:thecontrolunitandthearithmeticandlogicunit.Primarystoragealsoplaysanintegralpartintheinternaloperationofaprocessor.Thesethree—primarystorage,thecontrolunit,andthearithmeticandlogicunit—worktogether.Let’slookattheirfunctionsandtherelationshipsbetweenthem.不加夸大地讲，市场上有几百种不一样类型计算机在销售.每种电脑在复杂性上可能有很大区分，但归根结底,每种处理器，有时称为中央处理器即cpu，只有两个基本部分:控制单元和计算逻辑单元.主内存在处理器内部操作中也是一个不可缺乏部分.这三个部件--主内存，控制单元和计算逻辑单元--一起工作.然我们看看它们(各自)功效和它们之间联络。Unlikemagneticsecondarystoragedevices,suchastapeanddisk,primarystoragehasnomovingparts.Withnomechanicalmovement,datacanbeaccessedfromprimarystorageatelectronicspeeds,orclosetothespeedoflight.Mostoftoday’scomputersuseDRAM(DynamicRandom-AccessMemory)technologyforprimarystorage.Astate-of-the-artDRAMchipaboutoneeighththesizeofapostagestampcanstoreabout256,000,000bits,orover25,600,000charactersofdata!主存与其余辅助存放器（如：磁带、硬盘）不一样是，主存不含有运转部件。因为没有机械运转需要，主存种数据访问能够达成电子速度，或靠近于光速。当今计算机主存大多数使用DRAM（动态随机存取存放器）技术。现在最新工艺水平是：一块只有大约1/8张邮票大小DRAM芯片却能够存放大约256,000,000位，约25,6000,000个字符数据。Primarystorage,ormainmemory,providestheprocessorwithtemporarystorageforprogramsanddata.Allprogramsanddatamustbetransferredtoprimarystoragefromaninputdevice(suchasaVDT)orfromsecondarystorage(suchasadisk)beforeprogramscanbeexecutedordatacanbeprocessed.Primarystoragespaceisalwaysatapremium;therefore,afteraprogramhasbeenexecuted,thestoragespaceitoccupiedisreallocatedtoanotherprogramawaitingexecution.主存放器，也就是说内存，用于为处理器暂时存放程序和数据。全部程序和数据在被操作之前必须从输入设备（如VDT）或者辅助存放器转存到主存放器中。主存放器存放容量通常是相当有限，所以，在一个程序执行结束，它所占用存放空间必须被重新分配给其它正在等候执行操作程序。Figure1-1illustrateshowallinput/output(I/O)is“readto”or“writtenfrom”primarystorage.Inthefigure,aninquiry(input)ismadeonaVDT.Theinquiry,intheformofamessage,isroutedtoprimarystorageoverachannel(suchasacoaxialcable).Themessageisinterpreted,andtheprocessorinitiatesactiontoretrievetheappropriateprogramanddatafromsecondarystorage[3].Theprogramanddataare“loaded”,ormoves,toprimarystoragefromsecondarystorage.Thisisanondestructivereadprocess.Thatis,theprogramanddatathatarereadresideinbothprimarystorage(temporarily)andsecondarystorage(permanently).Thedataaremanipulatedaccordingtoprograminstructions,andareportiswrittenfromprimarystoragetoaprinter.图1-1描述了输入/输出设备与主存放器间读和写过程。在图中，VDT发出一个输入请求，请求是以消息模式经过通道（如同轴电缆）发送到主存放器。这个查询被解释，处理器发起操作从辅助存放器中调用适宜程序和数据。程序和数据从辅助存放器传送到主存放器中，这是一个非破坏性读取过程，也就是说，程序和数据同时存在于主存（暂时保留）和辅助存放器（永久保留）中。依照程序指令指示，处理器对数据进行操作，并从主存传送一份汇报到打印机。Aprograminstructionorapieceofdataisstoredinaspecificprimarystoragelocationcalledanaddress.Addressespermitprograminstructionsanddatatobelocated,accessed,andprocessed.Thecontentofeachaddressisconstantlychangingasdifferentprogramsareexecutedandnewdataareprocessed.程序指令和数据是存放在主存中一个特殊位置，称为地址空间。经过地址空间能够实现计算机对程序指令和数据定位、访问和处理。地址空间内容是经常改变，这是因为计算机一直在执行不一样程序和数据。Anothernameforprimarystorageisrandom-accessmemory,orRAM.Aspecialtypeofprimarystorage,calledread-onlymemory(ROM),cannotbealteredbytheprogrammer.ThecontentsofROMare“hard-wired”(designedintothelogicofthememorychip)bythemanufacturerandcanbe“readonly”.Whenyouturnonamicrocomputersystem,aprograminROMautomaticallyreadiesthecomputersystemforuse.ThentheROMprogramproducestheinitialdisplayscreenprompt.主存放器也称为随机存取存放器，或RAM。还有一个特殊主存放器，称为只读存放器（ROM），这种存放器不能被程序更改存放内容。ROM内容是被生产商经过硬件电路写入，而且不能被重写。当你开启计算机，ROM中一个程序会自动就绪等候计算机系统调用，然后在显示器中显示开机提醒。AvariationofROMisprogrammableread-onlymemory(PROM).PROMisROMintowhichyou,theuser,canload“read-only”programsanddata.OnceaprogramisloadedtoPROM,itisseldom,ifever,changed[4].However,ifyouneedtobeabletorevisethecontentsofPROM,thereisEPROM,erasablePROM.Beforeawriteoperation,allthestoragecellsmustbeerasedtothesameinitialstate.可编程只读存放器（PROM）是另一个ROM，它能够载入只读程序和数据，一旦载入，将不再改变。然而，若果你需要去修正PROM内容，能够使用可擦可编程只读存放器。 EPROM在进行一次写操作之前，全部存放单元必须被还原为同一初始状态。Amoreattractiveformofread-mostlymemoryiselectricallyerasableprogrammableread-onlymemory(EEPROM).Itcanbewrittenintoatanytimewithouterasingpriorcontents;onlythebyteorbytesaddressedareupdated.一个更吸引人可改写只读存放器是电可擦除可编程只读存放器(EEPROM)。它能够在任何时候写入，而且不会擦除以前内容；只会更新被寻址字节。TheEEPROMcombinestheadvantageofnonvolatilitywiththeflexibilityofbeingupdatableinplace[6],usingordinarybuscontrol,address,anddatalines.电可擦可编程存放器把非易失性优点和可更新、需要更新地方灵活性结合起来，修改时使用普通总线控制线、地址线和数据线。Anotherformofsemiconductormemoryisflashmemory(sonamedbecauseofthespeed).FlashmemoryisintermediatebetweenEPROMandEEPROMinbothcostandfunctionality.LikeEEPROM,flashmemoryusesanelectricalerasingtechnology.Anentireflashmemorycanbeerasedinoneorafewseconds,whichismuchfasterthanEPROM.Inaddition,itispossibletoerasejustblocksofmemoryratherthananentirechip.However,flashmemorydoesnotprovidebyte-levelerasure[7].LikeEPROM,flashmemoryusesonlyonetransistorperbit,andsoachievesthehighdensityofEPROM.另一个半导体记忆体是闪存（意味着速度快）。闪存在性价比上处于EPROM和EEPROM之间，它使用电擦写技术。整个闪存内容能够在一到几秒内被去除，这是远快于EPROM。另外，它还能够对部分记忆块而不是整个存放器进行去除。然而，闪存并不提供字节级擦除。像EPROM，闪存只使用一个晶体管每比特，所以能够实现高密度EPROM。CacheMemoryProgramanddataareloadedtoRAMfromsecondarystoragebecausethetimerequiredtoaccessaprograminstructionorpieceofdatafromRAMissignificantlylessthanfromsecondarystorage.ThousandsofinstructionsorpiecesofdatacanbeaccessedfromRAMinthetimeitwouldtaketoaccessasinglepieceofdatafromdiskstorage[8].RAMisessentiallyahigh-speedholdingareafordataandprograms.Infact,nothingreallyhappensinacomputersystemuntiltheprograminstructionsanddataaremovedtotheprocessor.Thistransferofinstructionsanddatatotheprocessorcanbetime-consuming,evenatmicrosecondspeeds.Tofacilitateanevenfastertransferofinstructionsanddatatotheprocessor,mostcomputersaredesignedwithcachememory.Cachememoryisemployedbycomputerdesignerstoincreasethecomputersystemthroughput(therateatwhichworkisperformed).程序和数据从辅助存放器装载到RAM中是因为对RAM中程序指令和数据访问时间要显著少于从辅助存放器访问。数以千条指令和数据能被访问而只需花费从硬盘访问一次数据时间。RAM是数据和程序主要高速存放区，实际上，计算机系统不会进行任何操作直到程序指令被传入处理器进行执行，这种指令和数据传输是需要花费时间，即使传输速度已经是以纳秒来计算了。为了能更加快速传输指令和数据，大多数计算机设计使用高速缓存。计算机设计者使用高速缓存来提升计算机系统总处理能力（工作效率）。LikeRAM,cacheisahigh-speedholdingareaforprograminstructionsanddata.However,cachememoryusesSRAM(StaticRAM)technologythatisabout10timesfasterthanRAMandabout100timesmoreexpensive.WithonlyafractionofthecapacityofRAM,cachememoryholdsonlythoseinstructionsanddatathatarelikelytobeneedednextbytheprocessor.Twotypesofcachememoryappearwidelyincomputers.ThefirstisreferredtoasinternalcacheandisbuiltintotheCPUchip.Thesecond,externalcache,islocatedonchipsplacedclosetotheCPUchip.Acomputercanhaveseveraldifferentlevelsofcachememory.Level1cacheisvirtuallyalwaysbuiltintothechip.Level2cacheusedtobeexternalcachebutisnowtypicallyalsobuiltintotheCPUlikelevel1cache.和RAM一样，高速缓存也是程序指令和数据高速存放区。然而，高速缓存使用静态RAM技术，这种技术比RAM在速度上要高出10倍，价格上高出100倍。cache只保留内存中那一小部分最有可能被处理器执行指令和数据。两种类型cache广泛应用于计算机，第一个被植入cpu中叫做内部高速存放，第二种是外部高速存放，它位于那些靠近cpu芯片中。一台计算机能够拥有几个不一样级别高速缓存。一级缓存实际上总是植入芯片中，二级缓存过去经常作为外部高速缓存，不过现在也像一级缓存植入cpu内部。2.1Opticallaserdisktechnologyeventuallymaymakemagnetic-diskandmagnetictapestorageobsolete.Withthistechnology,theread/writeheadusedinmagneticstorageisreplacedbytwolasers.Onelaserbeamwritestotherecordingsurfacebyscoringmicroscopicpitsinthedisk,andanotherlaserreadsthedatafromthelight-sensitiverecordingsurface.Alightbeamiseasilydeflectedtothedesiredplaceontheopticaldisk,soanaccessarmisnotneeded.光盘技术最终可能使磁盘和磁带存放淘汰。用这种技术，磁存放器所用读/写头被两束激光代替。一束激光经过在光盘上刻制微小凹点，对统计表面进行写；而另一束激光用来从光敏感统计表面读取数据。因为光束轻易被偏转到光盘上所需要位置，所以不需要存取臂。Opticallaserdisksarebecomingaveryinvitingoptionforusers.Theyarelesssensitivetoenvironmentalfluctuations,andtheyprovidemoredirect-accessstorageatacostthatismuchlesspermegabyteofstoragethanthemagnetic-diskalternative.Opticallaserdisktechnologyisstillemergingandhasyettostabilize;however,atpresenttherearethreemaincategoriesofopticallaserdisks.TheyareCD-ROM,recordableCD-RandrewritableCD-RW,andmagneto-opticaldisk.对用户而言，光盘正成为最有吸引力选择。它们(光盘)对环境改变不太敏感，而且它们以每兆字节比磁盘低得多存放器价格提供更多直接存取存放器。光盘技术仍在出现，而且还需要稳定；然而，现在有三种主要类型光盘。它们是CD-ROM、WORM盘和磁光盘。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，或紧密盘是设计来提升音乐录音重放质量光盘。为了制作一张CD，把音乐模拟声音转换成等价数字声音，而且存放在一张4.72英寸光盘上。在每张光盘上能够用数字格式（用20亿数字位）统计74分钟音乐。因为它巨大存放容量，计算机工业企业家们立刻认识到光盘技术潜力。实际上，任何能够被数字化东西都能存放在光盘上：数据、正文、声音、静止图象、音乐、图形和视频。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（读作C—D—ROM）是音频CD技术副产品。CD-ROM代表紧密盘—只读存放器。该名字隐含了它应用。只读光盘与(能长久播放)唱片一样，在工厂里“压制”并带着预先录好内容(如莎士比亚全集，或电影“飘”前30分钟部分)，分发出去。一旦光盘插入光盘驱动器，正文、视频图像等等就能读入主存进行处理或显示；然而，在只读光盘上数据是固定—它们不能被改变。当然，这是与磁盘读/写能力不一样。Thetremendousamountoflow-costdir-accessstoragemadepossiblebyopticallaserdiskshasopenedthedoortomanynewapplications.大量、低成本直接存取存放器（是光盘使之成为可能）已经打开了通向许多新应用大门。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都允许用户存放数据在光盘上，不过只有那些在可复写cd中数据能被擦除和重写。Cd-r光盘只能被写入一次。这俩种光盘看起来与只读cd光盘差不多。可统计cd管片通惯用于存放音乐文件，这么能够允许家庭用户制作高质量个人音乐唱片。Cd-rw光盘就像软盘那样能被重写和擦除。所以，他们是大容量文件存放另一个不错选择，同时也作为主盘在对cd-r光盘进行刻入之前（大多数可擦写光盘驱动器能够读取cd-rw和cd-r光盘，不过也有一些cd驱动器和cd-r驱动器不能读cd-rw光盘）。Cd-r和cd-rw驱动器也能够读cd-rom光盘，然而，cd将会被dvd所代替，一旦dvd技术完全成熟和标准化。Magneto-OpticalDiskMagneto-OpticaldiskofferspromisethatOpticallaserdiskswillbecomecommerciallyviableasaread-and-writestoragetechnology.The5and1/4inchdiskscanstoreupto1,000Mb.Atpresent,magneto-opticaldisksaretooexpensiveanddonotofferanywherenearthekindofreliabilitythatusershavecometoexpectofmagneticmedia.Inaddition,theaccesstimesarerelativelyslow,aboutthesameasalow-endWinchesterdisk.磁光盘有希望使得激光盘成为商业上可行读/写存放技术。5*1/4英寸磁光盘能够存放高达1000Mb。现在磁光盘太贵且根本未达成用户对磁介质所期望那种可靠性。另外，存取时间相对而言比较慢，大约与低级温彻斯特盘相同。Asopticallaserdisktechnologymaturestoreliable,cost-effective,read/writeoperation,iteventuallymaydominatesecondarystorageinthefutureasmagneticdisksandtypedotoday.伴随光盘技术成熟到可靠，性能价格合算，可读/可写，未来它最终会象现在磁盘、磁带那样统治二级存放器。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. 这个缩写影碟（数字化视频光盘或数字视频光盘），指是相对较新高容量光存放格式取决于光盘统计层和边数，能够从4.7GB持有以17GB，被使用。一个标准单层单面DVD能够存放4.7GB数据，一两个层次标准，增强了单面层到8.5GB。DVD可双面每件17GB最大存放。该DVD最初是存放标准全部内容两个小时电影，但现在还用于存放计算机数据和软件。DVD-ROM技术是被许多人视为对音乐CD，电脑光盘和人们购置和租赁预先录制家庭录影带后续，换句话说，只读产品。DVD-R是可统计DVD（就像CD-R那样）。用户能够对其进行一次写入。DVD-RW是可擦写（类似CD-RW），用户可擦除和重写磁盘数次。DVD-R和DVD-RW都是单面光盘。全部DVD驱动器能够同时播放电脑和音频CD。不过，不能在CD播放机上应用DVD光盘。DVDForumReceivesTopInformationTechnologyIndustryAwardforCreationofUnifiedSpecificationforNextMultimediaEraDVD论坛因建立下一代数字多媒体统一规范而取得最高信息技术工业奖TheDVDForumtodayannouncedthatithasreceivedthe1997PCMagazineAwardforTechnicalExcellenceinthecategoryof“Standards”,inrecognitionoftheForum’ssuccessfuldevelopmentofthedvd-romspecification.DVD论坛今天宣告，因该论坛成功制订了DVD-ROM规范而取得1997年PC杂志(制订标准)卓越技术奖。“Newstandardsareparticularlyimportant,sincetheypromisetobringhigherlevelsoftechnologyinnovationandmarketcompatibilitytotoday’stechnologyusers,”saidbyMichaelJ.Miller,editor-in-chiefofPCMagazine.”DVD-ROMisacompellingtechnologythatwaschosenbecauseit’safamiliarformatthatbringsawealthofnewcomputing,educational,gamingandentertainmentpossibilitiestotheuser.”“新标准尤其主要，因为它们承诺把更高级技术革新和市场兼容性带给今天技术用户，”PC杂志主编MichaelJ.Miller说，“DVD-ROM是被选出激发兴趣技术，因为它是一个熟悉格式，它把大量新计算、新教育、新游戏和新娱乐可能性带给用户。”IntheAwardcitationtoDVD-ROMtechnology,PCMagazinereferredtoDVDastheformatthatwill”replacetheCD-ROMastheprimarymeansofPCcontentdistribution.”Representativesofthreecompaniesinvolvedindevelopmentofthespecification,HitachiLtd.,MatsushitaElectricIndustrialCompany(Panasonic)andToshibaCorporation,acceptedtheawardonbehalfoftheDVDForuminaceremonyheldonNovember17atCOMDEX’97inLasVegas.在对DVD-ROM技术颁奖词中,PC杂志称，DVD将会“代替CD-ROM作为PC内容(即各种软件和资料)传输主要伎俩。”参加规范开发三个企业代表（日立，松下，东芝）以DVD论坛名义在11月7日，LasVegasCOMDEX'97举行庆贺仪式上接收该项奖。“ProductsbasedonspecificationsdefinedbytheDVDForumarenowshippinginvolumetotheworldwidecomputerandconsumerelectronicsmarkets,andtheAwardforTechnicalExcellenceaddstothemarket’svalidationofthesuccessofthestandardsprocess,”saidKojiHase,GeneralManageroftheDVDProductsDivisionatToshibaCorporationandafoundingmemberoftheDVDForum.”WeareextremelypleasedtoseetheworkoftheDVDForumrecognizedasoneofthekeytechnicalachievementsinthepersonalcomputerindustry,particularlyastheForumexpandsthescopeofitsworkwithalarge,globalmembershipin1998.”“基于DVD论坛定义规范产品现在正在大量运往世界各地计算机和电子产品市场，而且卓越技术奖增加了市场对成功制订标准认可，”东芝企业DVD产品部总经理和DVD论坛创办组员KojiHase说，“我们非常高兴地看到DVD论坛工作被公认为个人计算机工业中主要技术成就之一，尤其是在1998年与更大，全球会员扩大了它工作范围。”“ThemembersoftheDVDForumdevelopedtheDVD-ROMspecificationasthebesttechnicalapproachandalsothebestapproachforcustomersinthemarketplace,”saidSakonNagasaki,directoroftheDVDBusinessDevelopmentOfficeofMatsushitaElectricIndustrialCo.Ltd(Panasonic).“Acceptanceoftheformatillustrateshowstandards–makingeffortsadvancethegoalsoftheentireelectronicsindustry.”“DVD论坛组员把DVD-ROM规范开发作为最好技术方法和对市场上客户最好方法”松下有限企业DVD商业开发办公室主任SakonNagasaki说，“该格式接收说明了制订标准怎样加紧整个电子工业目标实现。”InadditiontoitsroleindevelopmentofDVD-ROMandDVD-Videostandards,theForumhasproposedtheformatforrecordableDVD,knownasDVD-R,andrewritableDVD,knownasDVD-RAM,tointernationalstandardsbodies.WorkisalsocontinuingondefinitionofaDVDAudiospecification.除了论坛在开发DVD-ROM和DVD-Video标准作用外，论坛也提出了可统计DVD格式，称为DVD-R和可重写DVD，称为DVD-RAM，并提交国际标准组织。定义DVD-Audio规范工作也正在继续着。 “ThemissonoftheDVDForumistodefineasmoothmigrationfromCDtoDVDtechnologybyworkingwiththewidestpossiblerepresentativegroupofmanufacturersandtechnologyend-usersintheconvergingindustriesofcomputersandcusumerelectronics,”saidDr.YoshitaTsunoda,amemberoftheExectiveStaffofHitachi,Ltd.AndChairmanoftheDVDForum’sDVD-RAMWorkingGroup.“ThedifferentworkinggroupshavealreadycompleteddefinitionofthreeseparateDVDtechnologystandards,andwehavebegunworkondevelopingnextgenerationspecificationsthatwillprovidecompatibleproductswellintothenextcentury.”“DVD论坛任务是，在汇共计算机工业和消费电子产品工业中，经过与最广泛代表性制造商与技术最终用户小组一起工作，确定从CD技术向DVD技术平滑过渡路径。”日立有限企业执行官之一和DVD论坛DVD-RAM工作组主席YoshitaTsunoda博士说，“不一样工作组已完成三个不一样DVD技术标准定义，而且我们已开始开发下一代规范工作，这些规范将很好地提供可兼容产品到下一世纪。”RecipientsofthePCMagazineAwardsforTechnicalExcellencearenamedbyateamofeditors,seniorcontributorsandPCLabspersonnelaftermonthsofevaluationanddiscussion.PCMagazine,thesponsoroftheTechnicalExcellenceAwards,isa1.175millioncirculationmagazinepublishedbyZiff-DavisInc.PcMagazineispublished22timesayearinprint,quarterlyonCD,andcontinuouslyontheWorldWideWeb(<>).PC杂志卓越技术奖取得者是由编辑、捐助者和PC试验室全体组员组成小组在几个月评价和讨论后提名。PC杂志，卓越技术奖主办者，是由Ziff-Davis企业出版、有1.175百万冊发行量杂志。PC杂志一年印刷出版22次，每季度出CD，而且连续地在环球网上。4.1Anoperatingsystemisthesoftwarewhichactsasaninterfacebetweenauserofacomputerandthecomputerhardware.操作系统是计算机用户和硬件软件接口。Thepurposeofanoperatingsystemistoprovideanenvironmentinwhichausermayexecuteprogram.操作系统目标是提供用户一个能够执行程序环境。Theprimarygoalofanoperatingsystemisthustomakethecomputersystemconvenienttouse.操作系统主要目标所以是使计算机系统便于使用。Asecondarygoalistousethecomputerhardwareinanefficientway.其次是高效地使用计算机硬件。Wecanviewanoperatingsystemasaresourceallocator.我们能够把操作系统看做是一个资源分配器。Acomputersystemhasmanyresourceswhichmayberequiredtosolveaproblem:CPUtime,memoryspace,filestorage,input/output(I/O)devices,andsoon.一个计算机系统拥有许多资源，所以需要去处理一些问题，如cpu时间，内存空间，文件存放，输入输出设备等。Theoperatingsystemactsasthemanageroftheseresourcesandallocatesthemtospecificprogramsandusersasnecessaryfortheirtasks.操作系统就像是资源管理员，把资源分配给特定程序和用户当它们工作需要时。Sincetheremaybemany,possiblyconflicting,requestsforresources,theo/smustdecidewhichrequestsareallocatedresourcestooperatethecomputersystemfairlyandefficiently.所以有可能会有很多有可能产生冲突资源请求，操作系统必须决定分配资源给哪个请求能使计算机系统合理和有效运行。Earlycomputerswere(physically)verylargemachinesrunfromaconsole.早期计算机是从控制台运行体积非常大机器。Theprogrammerwouldwriteaprogramandthenoperatetheprogramdirectlyfromtheoperator’sconsole.程序员要写一条程序然后直接从操作者控制台操作程序。Softwaresuchasassemblers,loaders,andcompilersimprovedontheconvenienceofprogrammingthesystem,butalsorequiredsubstantialset-uptime.象汇编程序、装入程序及编译程序这么软件使系统软件编程更方便，但同时也需要大量开启时间。Toreducethesetuptime,operatorswerehiredandsimilarjobswerebatchedtogether.[1]为了能降低这些准备时间，操作者就被雇佣，相同作业成批排在一起。Batchsystemsallowedautomaticjobsequencingbyaresidentmonitorandimprovedtheoverallutilizationofthecomputergreatly.批处理系统经过一个常驻内存监控程序允许自动作业定序。Thecomputernolongerhadtowaitforhumanoperation.这么计算机就无须再等候用户操作。CPUutilizationwasstilllow,however,becauseoftheslowspeedoftheI/OdevicesrelativetotheCPU.Offlineoperationofslowdeviceswastried.然而，CPU使用率依然不高，这是因为I/O设备处理速度较CPU慢造成。Bufferingwasanotherapproachtoimprovingsystemperformancebyoverlappingtheinput,output,andcomputationofasinglejob.缓冲机制是另一个提升系统系能方法，它将一条作业输入、输出和计算工作重合交织进行。Finally,spoolingallowedtheCPUtooverlaptheinputofonejobwiththecomputationandoutputofotherjobs.最终，伪脱机技术允许CPU将一条作业输入和其余作业计算输出交织进行。Spoolingalsoprovidesapoolofjobswhichhavebeenreadandarewaitingtoberun.伪脱机也为那些已经被读入而且还在等候运行作业提供一个作业池。Thisjobpoolsupportstheconceptofmultiprogramming.这个作业池支持一个叫做多程序设计概念。Withmultiprogramming,severaljobsarekeptinmemoryatonetime;theCPUisswitchedbackandforthbetweentheminordertoincreaseCPUutilizationandtodecreasethetotalrealtimeneededtoexecuteajob.在这种多程序设计技术中，多个作业能够同时存放在内存中；CPU在这些作业中往返切换控制，以至于增加CPU使用率和降低执行一条作业总时间。Multiprogramming,whichwasdevelopedtoimproveperformance,alsoallowstimesharing.多道程序设计被开发来提升性能，也允许分时。Time-sharedoperatingsystemsallowmanyusers(fromonetoseveralhundred)touseacomputersysteminteractiveatthesametime.分时操作系统允许多个用户（从一个到几百个）同时交互式地使用计算机系统。Asthesystemswitchesrapidlyfromoneusertothenext,eachuserisgiventheimpressionthathehashisowncomputer.因为系统快速地从一个用户切换到下一个用户，每一个用户被给予一个他拥有自己计算机印象。Otheroperatingsystemstypesincludereal-timesystemsandmultiprocessorsystems.其余操作系统类型包含实时系统和多处理机系统。Areal-timesystemisoftenusedascontrolde-viceinadedicatedapplication.实时系统通常被用作专用应用控制设备。Sensorsbringdatatothecomputer.传感器把数据带给计算机。Thecomputermustanalyzethedataandpossiblyadjustcontrolstomodifythesensorinputs.计算机必须分析数据，也可能调整控制去修改传感器输入。Systems,whichcontrolscientificexperiments,medicalcomputersystems,industrialcontrolsystems,andsomedisplaysystemsarereal-timesystems.控制科学试验，医学计算机系统，工业控制系统和一些显示系统等系统都是实时系统。Areal-timeoperatingsystemhaswell-definedfixedtimeconstraints．实时操作系统有定义明确固定时间约束。Processingmustbedonewithinthedefinedconstraints,orthesystemwillfail.处理必须在定义约束中完成，不然系统将失败。AmultiprocessorsystemhasmorethanoneCPU.多处理机系统有不只一个CPU。Theobviousadvantageswouldappeartobegreatercomputingpowerandreliability.显著优势好像是强大计算能力和可靠性。Therearevarioustypesofoperatingsystemsformultiprocessorsandmulticomputers.有各种各样操作系统用于多处理机和多计算机。ItismoreorlesspossibletodistinguishtwokindsofoperatingsystemsformultipleCPUsystems:Looselycoupled,suchasnetworkoperatingsystemanddistributedo/s,andtightlycoupled,suchasparallelo/s.这或多或少可能区分两种多CPU系统操作系统：松耦合，比如网络操作系统和分布式操作系统，和紧耦合，如并行操作系统。Asweshallsee,looselyandtightly-coupleds/wisroughtanalogoustolooselyandtight-coupledh/w.我们应该看到，松紧耦合软件大约类似于松紧耦合硬件。Theoperatingsystemmustensurecorrectoperationofthecomputersystem.操作系统必须确保改过计算机系统操作。Topreventuserprogramsfrominterferingwiththeproperoperationofthesystem,theh/wwasmodifiedtocreatetwomodes:usermodeandmonitormode[4].为了阻止用户程序干扰系统适当操作，硬件被修改成两种模式：用户模式和监控模式。Variousinstructions(suchasI/Oinstructionsandhaltinstructions)arepriviledgedandcanonlybeexecutedinmonitormode.许多指令（比如I/O指令和中止指令）是有特权，只能在监控模式下被执行。Thememoryinwhichthemonitorresidesmustalsobeprotectedfrommodificationbytheuser.监控程序所在内存也必须保护起来以防用户修改。Atimepreventsinfiniteloops.定时器能够预防死循环。Oncethesechanges(dualmode,privilegedinstructions,memoryprotection,timerinterrupt)havebeenmadetothebasiccomputerarchitecture,itispossibletowriteacorrectoperatingsystem.一旦这些对基本计算机体系结构改变（双模，权限指令，内存保护，定时器中止）被做到，这可能写成一个改进操作系统。《计算机专业英语教程》（第4版）5.1Internet因特网@Manynetworksexistintheworld,oftenwithdifferenthardwareandsoftware.许多网络通常会以不一样硬件和软件形式存在于世上。Peopleconnectedtoonenetworkoftenwanttocommunicatewithpeopleattachedtoadifferentone.attachedto隶属于连接了一个网络人经常想与隶属于一个不相同网络人交流。Thisdesirerequiresconnectingtogetherdifferent,andfrequentlyincompatiblenetworks,sometimesbyusingmachinescalledgatewaystomaketheconnectionandprovidethenecessarytranslation,bothintermsofhardwareandsoftware.Desire心愿frequently频繁地incompatible不兼容intermsof依照，在???方面这个要求把不一样和频繁不兼容网络连接在一起心愿，有时经过使用叫做网关机器去组成连接和提供必要转换，都依据硬件和软件来实现。AcollectionofinterconnectednetworksiscalledaninternetworkorjustInternet.Acollectionof...集合interconnected互连internetwork互连网络Internet因特网互连网络集合被称为互联网络或只是因特网。@AcommonformofInternetisacollectionofLANsconnectedbyaWAN.一个常见形式网络是经过一个广域网连接局域网集合。TheInternet(noteuppercaseI)meansaspecificworldwideinternetthatiswidelyusedtoconnectuniversities,governmentoffices,companies,andoflate,privateindividuals.Worldwide全世界note注意uppercase大写字母internet互联网oflate最近因特网（注意大写字母I）是一个特殊全世界互联网，被广泛用来连接大学，政府部门，企业和最近是私人。@By1995,thereweremultiplebackbones,hundredsofmid-level(i.e.regional)networks,tensofthousandsofL