計算機(jī)專業(yè)英語第4版-Software Knowledge

SoftwareKnowledge3.1OperatingSystem3.2DataStructures3.3ProgrammingLanguage3.4專業(yè)英語應(yīng)用模塊13.1OperatingSystemOperatingsystemsareeithersingle-taskingormultitasking.Allmodernoperatingsystemsaremultitaskingandcanrunseveralprocessessimultaneously.InmostcomputersthereisonlyoneCPU,soamultitaskingoperatingsystemcreatestheillusionofseveralprocessesrunningsimultaneouslyontheCPU.2Operatingsystemscanusevirtualmemorytorunprocessesthatrequiremoremainmemorythanisactuallyavailable.Withthistechnique,spaceontheharddriveisusedtomimictheextramemoryneeded.Accessingtheharddriveismoretime-consumingthanaccessingmainmemory,however,soperformanceofthecomputerslows.31．ResourceAllocationandRelatedFunctionsTheresourceallocationfunctionallocatesresourcesforusebyauser’scomputation.ResourcescanbedividedintosystemprovidedresourceslikeCPUs,memoryareasandI/Odevices,oruser-createdresourceslikefileswhichareentrustedtotheOS.Resourceallocationcriteriadependonwhetheraresourceisasystemresourceorauser-createdresource.Allocationofsystemresourcesisdrivenbyconsiderationsofefficiencyofresourceutilization.4AnOScanusearesourcetableasthecentraldatastructureallocation.Thetablecontainsanentryforeachresourceunitinthesystem.TheCPUcanbesharedinasequentialmanneronly.Henceonlyoneprogramcanexecuteatanytime.Otherprogramsinthesystemhavetowaittheirturn.Itisoftenimportanttoprovidefairservicetoallprogramsinthesystem.52．ControlofI/OOperationsAsaccessisoftennecessarytoaparticulardevicebeforeI/Ooperationsmaybegin,theoperatingsystemmustcoordinateI/Ooperationsandthedevicesonwhichtheyareperformed.TofacilitateexecutionofI/Ooperations,mostoperatingsystemshaveastandardsetofcontrolinstructionstohandletheprocessingofallinputandoutputinstructions.Thesestandardinstructions,referredtoastheInput/OutputControlSystem(IOCS),areanintegralpartofmostoperatingsystems.63．OSStructureOSdesignstronglydependsontwofactors:Architecturalfeaturesofthecomputeronwhichitoperates,andfeaturesofitsapplicationdomain.Dependenceonarchitecturalfeaturesiscausedbytheneedtoexercisecompletecontroloverallfunctionalunitsofthesystem.Hence,theOSneedstoknowtheaddressingstructure,interruptstructure,I/Oorganizationandmemoryprotectionfeaturesofthecomputersystem.7Operatingsystemsdidnotprovidecleaninterfacesbetweenthearchitecturespecificandarchitectureindependentpartsoftheircode.HencethetotalportingeffortwasdeterminedbythetotalsizeofOScode,ratherthanbythesizeofitsarchitecturespecificpart.8allot 分配concurrently 同時considerable 相當(dāng)?shù)?，重要的constraint 強(qiáng)制，約束criteria 標(biāo)準(zhǔn)critical 批評的，臨界的domain 領(lǐng)域，范圍embody 使具體化9entrust 信托，委托illusion 幻影，幻想integral 整體的mechanism 機(jī)制，機(jī)理mimic 模擬，模仿monolithic 整體的，完全統(tǒng)一的partition 分割10perceive 感知，認(rèn)知perceptible

可察覺的，感覺得到的Primitive

原始的，基本的privilege 特權(quán)suspend

暫停，掛起undergo 經(jīng)歷utilization 利用11[1]Themostcommonmechanismusedtocreatethisillusionistimeslicemultitasking,wherebyeachprocessisrunindividuallyforafixedperiodoftime.譯文：用于產(chǎn)生這種現(xiàn)象的最常用機(jī)制是時間分割多任務(wù)處理，以每個過程各自運行固定的一段時間的方式來實現(xiàn)。過去分詞短語“usedtocreatethisillusion”作定語，修飾“mechanism”；由“whereby”引導(dǎo)的是非限制性定語從句?！皐hereby”：bymeansofwhich，以……方式；憑借。12[2]Theprocessesappeartorunsimultaneouslybecausetheuser’ssenseoftimeismuchslowerthantheprocessingspeedofthecomputer.譯文：由于用戶的時間感覺比計算機(jī)的處理速度要慢得多，故幾個程序看起來是同時執(zhí)行的。本句中由“because”引導(dǎo)原因狀語從句，“…muchslowerthan…”是比較結(jié)構(gòu)。13[3]Operatingsystemscanusevirtualmemorytorunprocessesthatrequiremoremainmemorythanisactuallyavailable.譯文：實際可用空間不夠時，為了運行那些需要更多主存儲空間的程序，操作系統(tǒng)可以利用虛擬存儲器。本句中，“torunprocesses”到句末為目的狀語；由“that”引導(dǎo)的定語從句修飾和限定“processes”；“than”后面省略了主語that(that意指mainmemory)。14[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器資源管理。本句的主語是由并列的兩部分組成的，即“Boththepartitioningandthepool-basedallocationapproaches”，并且用被動態(tài)表示客觀性。15[5]Takingadvantageofthisfacility,datareadfromonelocationmaybedistributedthroughoutcomputerizedsystem.譯文：利用這一功能，讀自某一位置的數(shù)據(jù)可以分布貫穿整個計算機(jī)處理系統(tǒng)。現(xiàn)在分詞短語“Taking…”作伴隨狀語；過去分詞短語“readfromonelocation”作定語，修飾主語data。16LinuxOperatingSystemLinuxisanoperatingsystemthatwasinitiallycreatedasahobbybyayoungstudent,LinusTorvalds,attheUniversityofHelsinkiinFinland.TherearenowhundredsofcompaniesandorganizationsandanequalnumberofindividualsthathavereleasedtheirownversionsofoperatingsystemsbasedontheLinuxkernel.17LinuxisanimplementationoftheUNIXdesignphilosophy,whichmeansthatitisamulti-usersystem.Thishasmanyadvantages.Whetheroneuserisrunningseveralprogramsorseveralusersarerunningoneprogram,Linuxiscapableofmanagingthetraffic.Linuxisopen.Thismeansthatallprogrammersanduserscanhaveaccesstothesourcecodeaswellastherighttomodifyit.Thismeansmanygoodthingsfortheuser.Itmeanshigher-qualitysoftware,moreefficientandlesspronetocrash.18Linuxisoneofthemorestableoperatingsystemsavailabletoday.Thisisdueinlargeparttothefactthatitwaswrittenbyprogrammerswhowerewritingforotherprogrammersandnotforthecorporatesystem.Linuxperformswellformostapplications.However,theperformanceisnotoptimalunderheavynetworkload.193.2DataStructuresDatastructuresorganizedatainwaysthatmakealgorithmsmoreefficient.Forexample,considersomeofthewayswecanorganizedataforsearchingit.Datastructuresprovideamoreunderstandablewaytolookatdata;thus,theyofferalevelofabstractioninsolvingproblems.20Forexample,bystoringdatainastack,wecanfocusonthingsthatwedowithstacks,suchaspushingandpoppingelements,ratherthandetailsofhowtoimplementeachoperation.Inotherwords,datastructuresletustalkaboutprogramsinalessprogrammaticway.

Datastructuresarereusablebecausetheytendtobemodularandcontext-free.Theyaremodularbecauseeachhasaprescribedinterfacethroughwhichaccesstodatastoredinthedatastructureisrestricted.21Fromthepointofviewofdecidingwhichdatastructureshouldrepresentthatattributesofobjectsinaspecificclass,theemphasisthattheobject-orientedapproachplacesonabstractionisveryimportanttothesoftwaredevelopmentprocess.Abstractionmeanshidingunnecessarydetails.22DataStructuresandAlgorithmsAdatastructureisaspecializedformatfororganizingandstoringdata.Generaldatastructuretypesincludethearray,thefile,therecord,thetable,thetree,andsoon.Anydatastructureisdesignedtoorganizedatatosuitaspecificpurposesothatitcanbeaccessedandworkedwithinappropriateways.Incomputerprogramming,adatastructuremaybeselectedordesignedtostoredataforthepurposeofworkingonitwithvariousalgorithms.23Algorithmsanddatastructurescanbespecifiedinanyadequatelypreciselanguage.Englishandothernaturallanguagesaresatisfactoryifusedwithcaretoavoidambiguitybutmoreprecisemathematicallanguagesandprogramminglanguagesaregenerallypreferred.Givenaproblemtosolve,weselectordesignabstractdatastructurestostorethedataandalgorithmstomanipulatethem.Adatastructureisaninstanceofadatatype.24DataTypeTheessenceofadatatypeisthatitattemptstoidentifyqualitiescommontoagroupofindividualsorobjectsthatdistinguishitasanidentifiableclassorkind.Ifweprovideasetofpossibledatavaluesandasetofoperationsthatactonthevalues,wecanthinkofthecombinationasadatatype.25Therearetwoessentialingredientstoanyobjectthatcanbedecomposed—itmusthavecomponentelementsanditmusthavestructure,therulesforrelatingorfittingtheelementstogether.（1）Classesofdatatypes

Atomicdatatypes(valuesarenotdecomposable).

DataStructures(valuesaredecomposable).26（2）DataStructure—Adatatypewhosevalues

Canbedecomposedintoasetofcomponentdataelements,eachofwhichiseitheratomicoranotherdatastructure.

Includeasetofassociationsorrelationships(structure)involvingthecomponentelements.27abstraction 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，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28ingredient 組成，成分irrelevant 不恰當(dāng)?shù)模幌喔傻膍odular 標(biāo)準(zhǔn)組件的property 性質(zhì)，屬性recipe 食譜reusability 可再使用性seemingly 外觀上地，表面上地simplistic 過分簡單化的superfluous 多余的，過剩的terminate 結(jié)束，終止29[1]Datastructuresarecontext-freebecausetheycanbeusedwithanytypeofdataandinavarietyofsituationsorcontexts.譯文：因為數(shù)據(jù)結(jié)構(gòu)能用于任何類型的數(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)境無關(guān)。本句中的“because”引導(dǎo)原因狀語從句。30[2]Generaldatastructuretypesincludethearray,thefile,therecord,thetable,thetree,andsoon.譯文：一般的數(shù)據(jù)結(jié)構(gòu)類型包括數(shù)組、文件、記錄、表、樹等。本句中的“thearray,thefile,therecord,thetable,thetree,andsoon”是賓語，其中包含若干項并列部分。31[3]Oneoftheartsofcomputerprogrammingistosuppressunnecessarydetailoftheproblemandofthecomputerused.譯文：計算機(jī)程序設(shè)計的藝術(shù)之一就是消除問題和所用計算機(jī)的不必要細(xì)節(jié)。本句中的表語是不定式結(jié)構(gòu)，“oftheproblemandofthecomputerused”是定語，修飾“detail”。32[4]Theessenceofadatatypeisthatitattemptstoidentifyqualitiescommontoagroupofindividualsorobjectsthatdistinguishitasanidentifiableclassorkind.譯文：數(shù)據(jù)類型的本質(zhì)是標(biāo)識一組個體或目標(biāo)所共有的特性，這些特性把該組個體作為可識別的種類。本句由兩個復(fù)合句構(gòu)成，均由“that”引導(dǎo)。第一個“that”引導(dǎo)表語從句；第二個“that”引導(dǎo)限定性定語從句，修飾“qualities”。“it”代表“agroupofindividualsorobjects”。33[5]Adatastructureisadatatypewhosevaluesarecomposedofcomponentelementsthatarerelatedbysomestructure.譯文：數(shù)據(jù)結(jié)構(gòu)是一種數(shù)據(jù)類型，其值是由與某些結(jié)構(gòu)有關(guān)的組成元素構(gòu)成的。由“whose”引導(dǎo)的限定性定語從句修飾“adatatype”?！皌hat”引導(dǎo)的限定性定語從句修飾“componentelements”。34StacksandQueuesAstackisalistinwhichallinsertionsanddeletionsareperformedatthesameendofthestructure.Aconsequenceofthisrestrictionisthatthelastentryenteredwillalwaysbethefirstentryremoved—anobservationthatleadstostacksbeingknownasLast-In,First-Out(LIFO)structures.Theendofastackatwhichentriesareinsertedanddeletediscalledthetopofthestack.Theotherendissometimescalledthestack’sbase.35Toimplementastackstructureinacomputer’smemory,itiscustomarytoreserveablockofcontiguousmemorycellslargeenoughtoaccommodatethestackasitgrowsandshrinks.Determiningthesizeofthisblockcanoftenbeacriticaldecision.Iftoolittleroomisreserved,thestackultimatelyexceedstheallottedstoragespace;iftoomuchroomisreserved,memoryspacewillbewasted.36Queuesoccurfrequentlyineverydaylifeandarethereforefamiliartous.Themainfeatureofqueuesisthattheyfollowafirst-come/first-servedrule.TherearemanyapplicationsoftheFirst-In/First-Out(FIFO)protocolofqueuesincomputing.Forexample,thelineofInput/Output(I/O)requestswaitingforaccesstoadiskdriveinamulti-usertime-sharingsystemmightbeaqueue.37Acommonsolutionistosetasideablockofmemoryforthequeue,startthequeueatoneendoftheblock,andletthequeuemigratetowardtheotherendoftheblock.Then,whenthetailofthequeuereachestheendoftheblock,wemerelystartinsertingadditionalentriesbackattheoriginalendoftheblock,whichbythistimeisvacant.383.3ProgrammingLanguageAprogramminglanguagerepresentsaspecialvocabularyandasetofgrammaticalrulesforinstructingacomputertoperformspecifictasks.Broadlyspeaking,itconsistsofasetofstatementsorexpressionsunderstandabletobothpeopleandcomputers.39MachineLanguageComputerprogramsthatcanberunbyacomputer’soperatingsystemarecalledexecutables.Anexecutableprogramisasequenceofextremelysimpleinstructionsknownasmachinecode.Theseinstructionsarespecifictotheindividualcomputer’sCPUandassociatedhardware.40AssemblyLanguageLyingbetweenmachinelanguagesandhigh-levellanguagesareassemblylanguages,whicharedirectlyrelatedtoacomputer’smachinelanguage.Inotherwords,ittakesoneassemblycommandtogenerateeachmachinelanguagecommand.Assemblylanguageshavethesamestructureandsetofcommandsasmachinelanguages,buttheyenableaprogrammertousenamesinsteadofnumbers.41High-LevelLanguagesAhigh-levelprogramminglanguageisameansofwritingdown,informalterms,thestepsthatmustbeperformedtoprocessagivensetofdatainauniquelydefinedway.Itmaybearnorelationtoanygivencomputerbutdoesassumethatacomputerisgoingtobeused.Thehigh-levellanguagesareoftenorientedtowardaparticularclassofprocessingproblems.42Inahigh-levellanguagewewouldexpecttofindfacilitiestodothefollowing:

structuretheprogram;

definedataelements,givethemaname,sizeandtypes;

processdataelements(arithmetic/Boolean/transfer);

controlflowofprogram(test,branch);

allowcommonlyusedprogramtobeusedrepeatedly(loops,subroutines,procedures);

allowinput/outputofdata.43C++andObject-OrientedProgrammingC++isbasedonC.ItisanewversionofC.C++retainsmuchofC,includingarichoperatorset,nearlyorthogonaldesign,terseness,andextensibility.C++isahighlyportablelanguage,andtranslatorsforitexistonmanydifferentmachinesandsystems.C++fullysupportsobject-orientedprogramming,includingthefourpillarsofobject-orienteddevelopment:encapsulation,datahiding,inheritance,andpolymorphism.44EncapsulationandDatahidingThepropertyofbeingaself-containedunitiscalledencapsulation.Withencapsulation,wecanaccomplishdatahiding.Datahidingisthehighlyvaluedcharacteristicthatanobjectcanbeusedwithouttheuserknowingorcaringhowitworksinternally.45InheritanceandReuseC++supportstheideaofreusethroughinheritance.Anewtype,whichisanextensionofanexistingtype,canbedeclared.Thisnewsubclassissaidtoderivefromtheexistingtypeandissometimescalledaderivedtype.46PolymorphismC++supportstheideathatdifferentobjectsdo“therightthing”throughwhatiscalledfunctionpolymorphismandclasspolymorphism.Polymeansmany,andmorphmeansform.Polymorphismreferstothesamenametakingmanyforms.47accelerator 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，可實行的facility 容易，便利，工具inheritance 繼承injection 注滿，充滿morph 變種，形態(tài)48orthogonal 正交的，互相垂直的pillar 臺柱，棟梁polymorphism 多態(tài)性，多形性roughly 粗略地scratch 湊合的，隨意的subclass 子類subroutine 子程序terseness 簡潔，簡練turbocharger 渦輪增壓器49[1]Becausethesenumbersarenotunderstoodeasilybyhumans,computerinstructionsusuallyarenotwritteninmachinecode.譯文：因為這些數(shù)字令人難以理解，所以計算機(jī)指令通常不是用機(jī)器碼來寫的。本句中由“Because”引導(dǎo)原因狀語從句，主句用被動語態(tài)。50[2]Itisageneral-purposeandmorecomprehensiveapplicationsprogramminglanguagedevelopedbyBjarneStroustrupatBellLaboratory.譯文：它是由貝爾實驗室的BjarneStroustrup開發(fā)的一種通用的、更完整的應(yīng)用程序設(shè)計語言。本句中的“It”指C語言，表語是并列的兩部分，“developedby…”是過去分詞短語作定語，修飾“l(fā)anguage”。51[3]Unlikeotherobject-orientedlanguages,suchasSmalltalk,C++isanextensionofanexistinglanguagewidelyusedonmanymachines.譯文：不像其他的面向?qū)ο笳Z言，如Smalltalk語言，C++是現(xiàn)有語言的一種擴(kuò)展，它廣泛地用于很多種機(jī)器。本句中的“Unlikeotherobject-orientedlanguages”是狀語，“suchasSmalltalk”是同位語。52[4]C++supportsthepropertiesofencapsulationanddatahidingthroughthecreationofuser-definedtypes,calledclasses.譯文：C++通過創(chuàng)建稱為類的用戶定義類型而支持封裝和數(shù)據(jù)隱藏的屬性。本句中的“throughthecreationofuser-definedtypes”是狀語，而“calledclasses”是同位語。53[5]Thisnewsubclassissaidtoderivefromtheexistingtypeandissometimescalledaderivedtype.譯文：這個新的子類從已存在類派生而來，可稱為派生類。這是一個并列句，主語是“Thisnewsubclass”，本句使用被動語態(tài)。54SoftwareEngineeringSoftwareengineeringistheapplicationoftools,methods,anddisciplinestoproduceandmaintainanautomatedsolutiontoareal-worldproblem.Itrequirestheidentificationofaproblem,acomputertoexecuteasoftwareproduct,andanenvironment(composedofpeople