计算机专业英语论文

《专业英语》课程作业学生姓名学号院系专业任课教师二Ｏ一五年六月2一、英译中（英文科技资料翻译）原文：Anoperatingsystemisthesoftwarewhichactsasaninterfacebetweenauserofacomputerandthecomputerhardware.Thepurposeofanoperatingsystemistoprovideanenvironmentinwhichausermayexecuteprogram.Theprimarygoalofanoperatingsystemisthustomakethecomputersystemconvenienttouse.Asecondarygoalistousethecomputerhardwareinanefficientway.Wecanviewanoperatingsystemasaresourceallocator.Acomputersystemhasmanyresourceswhichmayberequiredtosolveaproblem:CPUtime,memoryspace,filestorage,input/output(I/O)devices,andsoon.Theoperatingsystemactsasthemanageroftheseresourcesandallocatesthemtospecificprogramsandusersasnecessaryfortheirtasks.Sincetheremaybemany,possiblyconflicting,requestsforresources,theo/smustdecidewhichrequestsareallocatedresourcestooperatethecomputersystemfairlyandefficiently.Multimediameans,fromtheuser’sperspective,thatcomputerinformationcanberepresentedthroughaudioand/orvideo,inadditiontotext,image,graphicsandanimation.Theintegrationofthesemediaintothecomputerprovidesadditionalpossibilitiesfortheuseofcomputationalpowercurrentlyavailable(e.g.,forinteractivepresentationofhugeamountsofinformation).Furthermore,thesedatacanbetransmittedthoughcomputerandtelecommunicationnetworks,whichimpliesapplicationsintheareasofinformationdistributionandcooperativework.Multimediaprovidesthepossibilityforaspectrumofnewapplications,manyofwhichareinplacetoday.Amultimediasystemdistinguishesitselffromothersystemsthroughseveralproperties.Weelaborateonthemostimportantpropertiessuchascombinationofthemedia,media-independence,computercontrolandintegration.Noteveryarbitrarycombinationofmediajustifiestheusageofthetermmultimedia.Asimpletextprocessingprogramwithincorporatedimagesisoftencalledamultimediaapplicationbecausetwomediaareprocessedthroughoneprogram.Butoneshouldtalkaboutmultimediaonlywhenbothcontinuousanddiscretemediaareutilized.Atextprocessingprogramwithincorporatedimagesisthereforenotamultimediaapplication.Animportantaspectofdifferentmediaistheirlevelofindependencefromeachother.Ingeneral,thereisarequestforindependenceofdifferentmedia,butmultimediamayrequireseverallevelsofindependence.Ontheonehand,acomputer-controlledvideorecorderstoresaudioandvideoinformation,butthereisaninherentlytightconnectionbetweenthetwotypesofmedia.Both3mediaarecoupledtogetherthroughthecommonstoragemediumofthetape.Ontheotherhand,forthepurposeofpresentations,thecombinationofDATrecorder(DigitalAudioTape)signalsandcomputer-availabletextsatisfiestherequestformedia-independence.Earlycomputerswere(physically)verylargemachinesrunfromaconsole.Theprogrammerwouldwriteaprogramandthenoperatetheprogramdirectlyfromtheoperator’sconsole.Softwaresuchasassemblers,loaders,andcompilersimprovedontheconvenienceofprogrammingthesystem,butalsorequiredsubstantialset-uptime.Toreducethesetuptime,operatorswerehiredandsimilarjobswerebatchedtogether.Batchsystemsallowedautomaticjobsequencingbyaresidentmonitorandimprovedtheoverallutilizationofthecomputergreatly.Thecomputernolongerhadtowaitforhumanoperation.CPUutilizationwasstilllow,however,becauseoftheslowspeedoftheI/OdevicesrelativetotheCPU.Offlineoperationofslowdeviceswastried.Bufferingwasanotherapproachtoimprovingsystemperformancebyoverlappingtheinput,output,andcomputationofasinglejob.Finally,spoolingallowedtheCPUtooverlaptheinputofonejobwiththecomputationandoutputofotherjobs.Spoolingalsoprovidesapoolofjobswhichhavebeenreadandarewaitingtoberun.Thisjobpoolsupportstheconceptofmultiprogramming.Withmultiprogramming,severaljobsarekeptinmemoryatonetime;theCPUisswitchedbackandforthbetweentheminordertoincreaseCPUutilizationandtodecreasethetotalrealtimeneededtoexecuteajob.Multiprogramming,whichwasdevelopedtoimproveperformance,alsoallowstimesharing.Time-sharedoperatingsystemsallowmanyusers(fromonetoseveralhundred)touseacomputersysteminteractiveatthesametime.Asthesystemswitchesrapidlyfromoneusertothenext,eachuserisgiventheimpressionthathehashisowncomputer.Otheroperatingsystemstypesincludereal-timesystemsandmultiprocessorsystems.Areal-timesystemisoftenusedascontroldeviceinadedicatedapplication.Sensorsbringdatatothecomputer.Thecomputermustanalyzethedataandpossiblyadjustcontrolstomodifythesensorinputs.Systems,whichcontrolscientificexperiments,medicalcomputersystems,industrialcontrolsystems,andsomedisplaysystemsarereal-timesystems.Areal-timeoperatingsystemhaswell-definedfixedtimeconstraints．Processingmustbedonewithinthedefinedconstraints,orthesystemwillfail.AmultiprocessorsystemhasmorethanoneCPU.Theobviousadvantageswouldappeartobegreatercomputingpowerandreliability.Therearevarioustypesofoperatingsystemsformultiprocessorsandmulticomputers.ItismoreorlesspossibletodistinguishtwokindsofoperatingsystemsformultipleCPUsystems:Looselycoupled,suchasnetworkoperatingsystemanddistributedo/s,andtightlycoupled,suchasparallelo/s.Asweshallsee,looselyand4tightly-coupleds/wisroughtanalogoustolooselyandtight-coupledh/w.Theoperatingsystemmustensurecorrectoperationofthecomputersystem.Topreventuserprogramsfrominterferingwiththeproperoperatio