计算机专业英语第3章

1第3章

SoftwareKnowledge

3.1OperatingSystem3.2DataStructures3.3ProgrammingLanguage3.4专业英语应用模块23.1OperatingSystem

Whatexactlydoesanoperatingsystemdo?Basically,itperformsanumberofsupportfunctions.

Allmodernoperatingsystemsaremultitaskingandcanrunseveralprocessessimultaneously.InmostcomputersthereisonlyoneCPU,soamultitaskingoperatingsystemcreatestheillusionofseveralprocessesrunningsimultaneouslyontheCPU.

Operatingsystemscanusevirtualmemorytorunprocessesthatrequiremoremainmemorythanisactuallyavailable.Withthistechnique,spaceontheharddriveisusedtomimictheextramemoryneeded.3MainContentsoftheTextIntroductionResourceallocationandrelatedfunctions

ControlofI/OOperations

OSstructure

Resourceallocationcriteriadependonwhetheraresourceisasystemresourceorauser-createdresource.Twopopularstrategiesforresourceallocationare:Partitioningofresources;Allocationfromapool.45TofacilitateexecutionofI/Ooperations,mostoperatingsystemshaveastandardsetofcontrolinstructionstohandletheprocessingofallinputandoutputinstructions.Thesestandardinstructions,referredtoastheInput/OutputControlSystem(IOCS),areanintegralpartofmostoperatingsystems.TheysimplifythemeansbywhichallprogramsbeingprocessedmayundertakeI/Ooperations.6OSdesignstronglydependsontwofactors:architecturalfeaturesofthecomputeronwhichitoperates,andfeaturesofitsapplicationdomain.ThedependenceonthesetwofactorsposesobviousdifficultiesinusinganOSoncomputerswithdifferentarchitecturesanddifferentapplicationdomains.7Inearlyoperatingsystems,thisapproachfacedseveraldifficultiesduetothemonolithicstructureoftheOS.Thus,operatingsystemsdidnotprovidecleaninterfacesbetweenthearchitecturespecificandarchitectureindependentpartsoftheircode.HencethetotalportingeffortwasdeterminedbythetotalsizeofOScode,ratherthanbythesizeofitsarchitecturespecificpart.8KeyWords

allot分配concurrently同时发生地considerable相当的，重要的constraint强制，约束criteria标准critical批评的，临界的domain领域，范围embody使具体化entrust信托，委托illusion幻影，幻想integral整体的mechanism机制，机理9KeyWords

mimic 模拟，模仿monolithic整体的，完全统一的partition分割perceive感知，认知perceptible 可察觉的，感觉得到的primitive 原始的，基本的privilege特权suspend 暂停，挂起undergo经历utilization利用10Notes

[1]Themostcommonmechanismusedtocreatethisillusionistimeslicemultitasking,wherebyeachprocessisrunindividuallyforafixedperiodoftime.译文：产生这种错觉的最常用机制是时间分割多任务处理，以每个过程各自运行固定的一段时间的方式来实现的。过去分词短语usedtocreatethisillusion作定语，修饰mechanism；由whereby引导的是非限制性定语从句。whereby：bymeansofwhich，以…方式；凭借。11Notes

[2]Theprocessesappeartorunsimultaneouslybecausetheuser’ssenseoftimeismuchslowerthantheprocessingspeedofthecomputer.译文：由于用户的时间感觉比计算机的处理速度要慢得多，所以几个程序看起来是同时执行的。本句中由“because”引导原因状语从句，“…muchslowerthan…”是比较结构。12Notes

[3]Operatingsystemscanusevirtualmemorytorunprocessesthatrequiremoremainmemorythanisactuallyavailable.译文：实际可用空间不够时，为了运行那些需要更多主存储空间的程序，操作系统可以利用虚拟存储器。本句中，torunprocesses…到句末为目的状语；由that引导的定语从句修饰和限定processes；than后面省略了主语that(that意指mainmemory)。13Notes

[4]Boththepartitioningandthepool-basedallocationapproachescanbeusedtomanagethememoryresource.译文：资源分区和基于资源池的分配方式都适用于存储器资源管理。本句的主语是由并列的两部分组成，即“Boththepartitioningandthepool-basedallocationapproaches”，并且用被动态表示客观性。

14Notes

[5]Takingadvantageofthisfacility,datareadfromonelocationmaybedistributedthroughoutcomputerizedsystem.译文：利用这一功能，读自某一设备的数据可以分布贯穿整个计算机处理系统。现在分词短语Taking…做伴随状语；过去分词短语readfromonelocation作定语，修饰主语data。15ReadingMaterial——LinuxOperatingSystem

Linuxisanoperatingsystemthatwasinitiallycreatedasahobbybyayoungstudent,LinusTorvaids,attheUniversityofHelsinkiinFinland.LinuxisanimplementationoftheUnixdesignphilosophy,whichmeansthatitisamulti-usersystem.Linuxisopen.Thismeansthatallprogrammersanduserscanhaveaccesstothesourcecodeaswellastherighttomodifyit.16ReadingMaterial——LinuxOperatingSystemLinuxisavailableinseveralformats.InordertogetabetterunderstandingofthewayyourLinuxsystemworks,orhowtocustomizeittosuityourneeds,youshouldreadtheHOWTOdocuments.Linuxisoneofthemorestableoperatingsystemsavailabletoday.173.2DataStructures

Datastructuresorganizedatainwaysthatmakealgorithmsmoreefficient.Forexample,considersomeofthewayswecanorganizedataforsearchingit.Datastructuresprovideamoreunderstandablewaytolookatdata;thus,theyofferalevelofabstractioninsolvingproblems.

Datastructuresarereusablebecausetheytendtobemodularandcontext-free.Theyaremodularbecauseeachhasaprescribedinterfacethroughwhichaccesstodatastoredinthedatastructureisrestricted.

18MainContentsoftheTextAnintroductiontodatastructures

Datastructuresandalgorithms

Datatype

19Anydatastructureisdesignedtoorganizedatatosuitaspecificpurposesothatitcanbeaccessedandworkedwithinappropriateways.Incomputerprogramming,adatastructuremaybeselectedordesignedtostoredataforthepurposeofworkingonitwithvariousalgorithms.20Algorithmsanddatastructurescanbespecifiedinanyadequatelypreciselanguage.Englishandothernaturallanguagesaresatisfactoryifusedwithcaretoavoidambiguitybutmoreprecisemathematicallanguagesandprogramminglanguagesaregenerallypreferred.21Ifweprovideasetofpossibledatavaluesandasetofoperationsthatactonthevalues,wecanthinkofthecombinationasadatatype.Letuslookattwoclassesofdatatypes.Wewillcallanydatatypewhosevalueswechoosetoconsideratomicanatomicdatatype.Oftenwechoosetoconsiderintegerstobeatomic.22Wewillcallanydatatypewhosevaluesarecomposedofcomponentelementsthatarerelatedbysomestructureastructureddatatype,ordatastructure.Inotherwords,thevaluesofthesedatatypesaredecomposable,andwemustthereforebeawareoftheirinternalconstruction.23（1）ClassesofdatatypesAtomicdatatypes(valuesarenotdecomposable).DataStructures(valuesaredecomposable).（2）DataStructure—AdatatypewhosevaluesCanbedecomposedintoasetofcomponentdataelementseachofwhichiseitheratomicoranotherdatastructure.Includeasetofassociationsorrelationships(structure)involvingthecomponentelements.24KeyWords

Abstraction 抽象，摘要adequately 足够地，适当地arithmetic 算术，算法attribute 属性considerably 非常地，很decompose 分解equivalent 相等的，同等的essential 重要的，本质的gracefully 优美地heap 堆ingredient 组成，成分25KeyWords

irrelevant 不恰当的，不相干的modular有标准组件的property 性质，属性recipe 食谱reusability 可再使用地seemingly 外观上地，表面上地simplistic 过分简单化的superfluous 多余的，过剩的terminate 结束，终止26Notes

[1]Datastructuresarecontext-freebecausetheycanbeusedwithanytypeofdataandinavarietyofsituationsorcontexts.译文：因为数据结构能用于任何类型的数据，并用于多种环境中，所以数据结构与使用环境无关。本句中的“because”引导原因状语从句。27Notes

[2]Generaldatastructuretypesincludethearray,thefile,therecord,thetable,thetree,andsoon.译文：一般的数据结构类型包括数组、文件、记录、表、树等。本句中的“thearray,thefile,therecord,thetable,thetree,andsoon”是宾语，其中包含若干项并列部分。28Notes

[3]Oneoftheartsofcomputerprogrammingistosuppressunnecessarydetailoftheproblemandofthecomputerused.译文：计算机程序设计的艺术之一就是消除一个问题中和所用计算机不必要的细节。本句中的表语是不定式结构，“oftheproblemandofthecomputerused”是定语，修饰“detail”。29Notes

[4]Theessenceofadatatypeisthatitattemptstoidentifyqualitiescommontoagroupofindividualsorobjectsthatdistinguishitasanidentifiableclassorkind.译文：数据类型的本质是标识一组个体或目标所共有的特性，这些特性把该组个体作为可识别的种类。本句由两个复合句构成，均由“that”引导。第一个“that”引导表语从句；第二个“that”引导限定性定语从句，修饰“qualities”，“it”代表“agroupofindividualsorobjects”。30Notes

[5]Adatastructureisadatatypewhosevaluesarecomposedofcomponentelementsthatarerelatedbysomestructure.译文：数据结构是一种数据类型，其值是由与某些结构有关的组成元素所构成的。由“whose”引导的限定性定语从句修饰“adatatype”，“that”引导的限定性定语从句修饰“componentelements”。31ReadingMaterial—StacksandQueues

Theendofastackatwhichentriesareinsertedanddeletediscalledthetopofthestack.Theotherendissometimescalledthestack’sbase.Toreflectthefactthataccesstoastackisrestrictedtothetopmostentry,weusespecialterminologywhenreferringtotheinsertionanddeletionoperations.Theprocessofinsertinganobjectonthestackiscalledapushoperation,andtheprocessofdeletinganobjectiscalledapopoperation.Thuswespeakofpushinganentryontoastackandpoppinganentryoffastack.

32ReadingMaterial—StacksandQueuesQueuesoccurfrequentlyineverydaylifeandarethereforefamiliartous.

Therearemanyapplicationsofthefirst-in/first-out(FIFO)protocolofqueuesincomputing.Forexample,thelineofinput/output(I/O)requestswaitingforaccesstoadiskdriveinamulti-usertime-sharingsystemmightbeaqueue.Thelineofcomputingjobswaitingtoberunonacomputersystemmightalsobeaqueue.ThejobsandI/Orequestsareservicedinorderoftheirarrival,thatis,thefirstinisthefirstout.

333.3ProgrammingLanguage

Aprogramminglanguagerepresentsaspecialvocabularyandasetofgrammaticalrulesforinstructingacomputertoperformspecifictasks.Broadlyspeaking,itconsistsofasetofstatementsorexpressionsunderstandabletobothpeopleandcomputers.34MainContentsoftheTextMachineLanguageAssemblyLanguageHigh-LevelLanguagesC++andObject-OrientedProgrammingEncapsulationandDatahidingInheritanceandReusePolymorphism35Anexecutableprogramisasequenceofextremelysimpleinstructionsknownasmachinecode.Machinecodeinstructionsarebinary—thatis,sequencesofbits(0sand1s).36Lyingbetweenmachinelanguagesandhigh-levellanguagesareassemblylanguages,whicharedirectlyrelatedtoacomputer’smachinelanguage.Inotherwords,ittakesoneassemblycommandtogenerateeachmachinelanguagecommand.Machinelanguagesconsistentirelyofnumbersandarealmostimpossibleforhumanstoreadandwrite.37Onceanassembly-languageprogramiswritten,itisconvertedtoamachine-languageprogrambyanotherprogramcalledanassembler.Assemblylanguageisfastandpowerfulbecauseofitscorrespondencewithmachinelanguage.38Ahigh-levelprogramminglanguageisameansofwritingdown,informalterms,thestepsthatmustbeperformedtoprocessagivensetofdatainauniquelydefinedway.Thehigh-levellanguagesareoftenorientedtowardaparticularclassofprocessingproblems.39Inahigh-levellanguagewewouldexpecttofindfacilitiestodothefollowing:structuretheprogram;definedataelements,givethemaname,sizeandtypes;processdataelements(arithmetic/Boolean/transfer);controlflowofprogram(test,branch);allowcommonlyusedprogramtobeusedrepeatedly(loops,subroutines,procedures);allowinput/outputofdata.40C++isahighlyportablelanguage,andtranslatorsforitexistonmanydifferentmachinesandsystems.C++compilersarehighlycompatiblewithexistingCprogramsbecausemaintainingsuchcompatibilitywasadesignobjective.C++fullysupportsobject-orientedprogramming,includingthefourpillarsofobject-orienteddevelopment:encapsulation,datahiding,inheritance,andpolymorphism.41KeyWords

accelerator加速器assembler汇编程序，汇编器carburetor化油器，汽化器encapsulation封装executable可执行的，可实行的facility容易，便利，工具inheritance继承injection注满，充满42KeyWords

morph变种，形态orthogonal正交的，互相垂直的pillar台柱，栋梁polymorphism多态性，多形性roughly粗略地scratch凑合的，随意的subclass子类subroutine子程序terseness简洁，简练turbocharger涡轮增压器43Notes

[1]Becausethesenumbersarenotunderstoodeasilybyhumans,computerinstructionsusuallyarenotwritteninmachinecode.译文：由于这些数字令人难以理解，所以计算机指令通常不是用机器码来写的。本句中由“Because”引导原因状语从句，主句用被动语态。44Notes

[2]Itisageneral-purposeandmorecomprehensiveapplicationsprogramminglanguagedevelopedbyEjarneStroustrupatBellLaboratory.译文：它是由贝尔实验室的EjarneStroustrup开发的一种通用的、更完整的应用程序设计语言。本句中的“It”指C语言，表语是并列的两部分，“developedby…”是过去分词短语作定语，修饰“language”。45Notes

[3]Unlikeotherobject-orientedlanguages,suchasSmalltalk,C++isanextensionofanexistinglanguagewidelyusedonmanymachines.译文：不像其他的面向对象语言，如Smalltalk语言，C++是现有语言的一种扩展，它广泛地用于很多种机器。本句中的“Unlikeotherobject-orientedlanguages”是状语，“suchasSmalltalk”是同位语。46Notes

[4]C++supportsthepropertiesofencapsulationanddatahidingthroughthecreationofuser-definedtypes,calledclasses.译文：C++通过创建称为类的用户定义类型而支持封装和数据隐藏的属性。本句中的“throughthecreationofuser-definedtypes”是状语，而“calledclasses”是同位语。47Notes

[5]Thisnewsubclassissaidtoderivefromtheexistingtypeandissometimescalledaderivedtype.译文：这个新的子类从已存在类派生而来，可称为派生类。这是一个并列句，主语是“Thisnewsubclass”，本句使用被动语态。48ReadingMaterial——SoftwareEngineeringSoftwareengineeringistheapplicationoftools,methods,anddisciplinestoproduceandmaintainanautomatedsolutiontoareal-worldproblem.Theoverallobjectiveofsoftwareengineeringistogivethereaderasenseoftheflowofeventsinanintegratedsystemandsoftware