計(jì)算機(jī)專(zhuān)業(yè)英語(yǔ)第3章

1第3章

SoftwareKnowledge

3.1OperatingSystem3.2DataStructures3.3ProgrammingLanguage3.4專(zhuān)業(yè)英語(yǔ)應(yīng)用模塊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同時(shí)發(fā)生地considerable相當(dāng)?shù)?，重要的constraint強(qiáng)制，約束criteria標(biāo)準(zhǔn)critical批評(píng)的，臨界的domain領(lǐng)域，范圍embody使具體化entrust信托，委托illusion幻影，幻想integral整體的mechanism機(jī)制，機(jī)理9KeyWords

mimic 模擬，模仿monolithic整體的，完全統(tǒng)一的partition分割perceive感知，認(rèn)知perceptible 可察覺(jué)的，感覺(jué)得到的primitive 原始的，基本的privilege特權(quán)suspend 暫停，掛起undergo經(jīng)歷utilization利用10Notes

[1]Themostcommonmechanismusedtocreatethisillusionistimeslicemultitasking,wherebyeachprocessisrunindividuallyforafixedperiodoftime.譯文：產(chǎn)生這種錯(cuò)覺(jué)的最常用機(jī)制是時(shí)間分割多任務(wù)處理，以每個(gè)過(guò)程各自運(yùn)行固定的一段時(shí)間的方式來(lái)實(shí)現(xiàn)的。過(guò)去分詞短語(yǔ)usedtocreatethisillusion作定語(yǔ)，修飾mechanism；由whereby引導(dǎo)的是非限制性定語(yǔ)從句。whereby：bymeansofwhich，以…方式；憑借。11Notes

[2]Theprocessesappeartorunsimultaneouslybecausetheuser’ssenseoftimeismuchslowerthantheprocessingspeedofthecomputer.譯文：由于用戶(hù)的時(shí)間感覺(jué)比計(jì)算機(jī)的處理速度要慢得多，所以幾個(gè)程序看起來(lái)是同時(shí)執(zhí)行的。本句中由“because”引導(dǎo)原因狀語(yǔ)從句，“…muchslowerthan…”是比較結(jié)構(gòu)。12Notes

[3]Operatingsystemscanusevirtualmemorytorunprocessesthatrequiremoremainmemorythanisactuallyavailable.譯文：實(shí)際可用空間不夠時(shí)，為了運(yùn)行那些需要更多主存儲(chǔ)空間的程序，操作系統(tǒng)可以利用虛擬存儲(chǔ)器。本句中，torunprocesses…到句末為目的狀語(yǔ)；由that引導(dǎo)的定語(yǔ)從句修飾和限定processes；than后面省略了主語(yǔ)that(that意指mainmemory)。13Notes

[4]Boththepartitioningandthepool-basedallocationapproachescanbeusedtomanagethememoryresource.譯文：資源分區(qū)和基于資源池的分配方式都適用于存儲(chǔ)器資源管理。本句的主語(yǔ)是由并列的兩部分組成，即“Boththepartitioningandthepool-basedallocationapproaches”，并且用被動(dòng)態(tài)表示客觀性。

14Notes

[5]Takingadvantageofthisfacility,datareadfromonelocationmaybedistributedthroughoutcomputerizedsystem.譯文：利用這一功能，讀自某一設(shè)備的數(shù)據(jù)可以分布貫穿整個(gè)計(jì)算機(jī)處理系統(tǒng)。現(xiàn)在分詞短語(yǔ)Taking…做伴隨狀語(yǔ)；過(guò)去分詞短語(yǔ)readfromonelocation作定語(yǔ)，修飾主語(yǔ)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 足夠地，適當(dāng)?shù)豠rithmetic 算術(shù)，算法attribute 屬性considerably 非常地，很decompose 分解equivalent 相等的，同等的essential 重要的，本質(zhì)的gracefully 優(yōu)美地heap 堆ingredient 組成，成分25KeyWords

irrelevant 不恰當(dāng)?shù)模幌喔傻膍odular有標(biāo)準(zhǔn)組件的property 性質(zhì)，屬性recipe 食譜reusability 可再使用地seemingly 外觀上地，表面上地simplistic 過(guò)分簡(jiǎn)單化的superfluous 多余的，過(guò)剩的terminate 結(jié)束，終止26Notes

[1]Datastructuresarecontext-freebecausetheycanbeusedwithanytypeofdataandinavarietyofsituationsorcontexts.譯文：因?yàn)閿?shù)據(jù)結(jié)構(gòu)能用于任何類(lèi)型的數(shù)據(jù)，并用于多種環(huán)境中，所以數(shù)據(jù)結(jié)構(gòu)與使用環(huán)境無(wú)關(guān)。本句中的“because”引導(dǎo)原因狀語(yǔ)從句。27Notes

[2]Generaldatastructuretypesincludethearray,thefile,therecord,thetable,thetree,andsoon.譯文：一般的數(shù)據(jù)結(jié)構(gòu)類(lèi)型包括數(shù)組、文件、記錄、表、樹(shù)等。本句中的“thearray,thefile,therecord,thetable,thetree,andsoon”是賓語(yǔ)，其中包含若干項(xiàng)并列部分。28Notes

[3]Oneoftheartsofcomputerprogrammingistosuppressunnecessarydetailoftheproblemandofthecomputerused.譯文：計(jì)算機(jī)程序設(shè)計(jì)的藝術(shù)之一就是消除一個(gè)問(wèn)題中和所用計(jì)算機(jī)不必要的細(xì)節(jié)。本句中的表語(yǔ)是不定式結(jié)構(gòu)，“oftheproblemandofthecomputerused”是定語(yǔ)，修飾“detail”。29Notes

[4]Theessenceofadatatypeisthatitattemptstoidentifyqualitiescommontoagroupofindividualsorobjectsthatdistinguishitasanidentifiableclassorkind.譯文：數(shù)據(jù)類(lèi)型的本質(zhì)是標(biāo)識(shí)一組個(gè)體或目標(biāo)所共有的特性，這些特性把該組個(gè)體作為可識(shí)別的種類(lèi)。本句由兩個(gè)復(fù)合句構(gòu)成，均由“that”引導(dǎo)。第一個(gè)“that”引導(dǎo)表語(yǔ)從句；第二個(gè)“that”引導(dǎo)限定性定語(yǔ)從句，修飾“qualities”，“it”代表“agroupofindividualsorobjects”。30Notes

[5]Adatastructureisadatatypewhosevaluesarecomposedofcomponentelementsthatarerelatedbysomestructure.譯文：數(shù)據(jù)結(jié)構(gòu)是一種數(shù)據(jù)類(lèi)型，其值是由與某些結(jié)構(gòu)有關(guān)的組成元素所構(gòu)成的。由“whose”引導(dǎo)的限定性定語(yǔ)從句修飾“adatatype”，“that”引導(dǎo)的限定性定語(yǔ)從句修飾“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匯編程序，匯編器carburetor化油器，汽化器encapsulation封裝executable可執(zhí)行的，可實(shí)行的facility容易，便利，工具inheritance繼承injection注滿(mǎn)，充滿(mǎn)42KeyWords

morph變種，形態(tài)orthogonal正交的，互相垂直的pillar臺(tái)柱，棟梁polymorphism多態(tài)性，多形性roughly粗略地scratch湊合的，隨意的subclass子類(lèi)subroutine子程序terseness簡(jiǎn)潔，簡(jiǎn)練turbocharger渦輪增壓器43Notes

[1]Becausethesenumbersarenotunderstoodeasilybyhumans,computerinstructionsusuallyarenotwritteninmachinecode.譯文：由于這些數(shù)字令人難以理解，所以計(jì)算機(jī)指令通常不是用機(jī)器碼來(lái)寫(xiě)的。本句中由“Because”引導(dǎo)原因狀語(yǔ)從句，主句用被動(dòng)語(yǔ)態(tài)。44Notes

[2]Itisageneral-purposeandmorecomprehensiveapplicationsprogramminglanguagedevelopedbyEjarneStroustrupatBellLaboratory.譯文：它是由貝爾實(shí)驗(yàn)室的EjarneStroustrup開(kāi)發(fā)的一種通用的、更完整的應(yīng)用程序設(shè)計(jì)語(yǔ)言。本句中的“It”指C語(yǔ)言，表語(yǔ)是并列的兩部分，“developedby…”是過(guò)去分詞短語(yǔ)作定語(yǔ)，修飾“l(fā)anguage”。45Notes

[3]Unlikeotherobject-orientedlanguages,suchasSmalltalk,C++isanextensionofanexistinglanguagewidelyusedonmanymachines.譯文：不像其他的面向?qū)ο笳Z(yǔ)言，如Smalltalk語(yǔ)言，C++是現(xiàn)有語(yǔ)言的一種擴(kuò)展，它廣泛地用于很多種機(jī)器。本句中的“Unlikeotherobject-orientedlanguages”是狀語(yǔ)，“suchasSmalltalk”是同位語(yǔ)。46Notes

[4]C++supportsthepropertiesofencapsulationanddatahidingthroughthecreationofuser-definedtypes,calledclasses.譯文：C++通過(guò)創(chuàng)建稱(chēng)為類(lèi)的用戶(hù)定義類(lèi)型而支持封裝和數(shù)據(jù)隱藏的屬性。本句中的“throughthecreationofuser-definedtypes”是狀語(yǔ)，而“calledclasses”是同位語(yǔ)。47Notes

[5]Thisnewsubclassissaidtoderivefromtheexistingtypeandissometimescalledaderivedtype.譯文：這個(gè)新的子類(lèi)從已存在類(lèi)派生而來(lái)，可稱(chēng)為派生類(lèi)。這是一個(gè)并列句，主語(yǔ)是“Thisnewsubclass”，本句使用被動(dòng)語(yǔ)態(tài)。48ReadingMaterial——SoftwareEngineeringSoftwareengineeringistheapplicationoftools,methods,anddisciplinestoproduceandmaintainanautomatedsolutiontoareal-worldproblem.Theoverallobjectiveofsoftwareengineeringistogivethereaderasenseoftheflowofeventsinanintegratedsystemandsoftware