大學(xué)專業(yè)英語(yǔ)Unit-3-Section-A-xiaodan

ComputerEnglish

(FourthEdition)Unit3ComputerLanguageandProgramming

SectionAProgrammingLanguage廈門(mén)理工學(xué)院陳丹波ProgrammingLanguage－IntroductionI.IntroductionProgramminglanguages,incomputerscience,aretheartificiallanguagesusedtowriteasequenceofinstructions(acomputerprogram)thatcanberunbyacomputer.Similartonaturallanguages,suchasEnglish,programminglanguageshaveavocabulary,grammar,andsyntax.Asequence一系列Vocabulary詞匯Syntax句法I.引言在計(jì)算機(jī)科學(xué)中，編程語(yǔ)言是用于編寫(xiě)可由計(jì)算機(jī)運(yùn)行的一系列指令（計(jì)算機(jī)程序）的人工語(yǔ)言。與英語(yǔ)等自然語(yǔ)言相類似，編程語(yǔ)言有詞匯、語(yǔ)法和句法。

ProgrammingLanguage－IntroductionHowever,naturallanguagesarenotsuitedforprogrammingcomputersbecausetheyareambiguous,meaningthattheirvocabularyandgrammaticalstructuremaybeinterpretedinmultipleways.然而，自然語(yǔ)言不適合為計(jì)算機(jī)編程，因?yàn)樗鼈儠?huì)引起歧義，也就是說(shuō)它們的詞匯和語(yǔ)法的結(jié)構(gòu)可能被用多種方式進(jìn)行解釋Suitfor適合于Ambiguous模糊的，含糊的Grammatical語(yǔ)法的Thelanguagesusedtoprogram

computersmusthavesimplelogicalstructures,andtherulesfortheirgrammar,spelling,andpunctuation

mustbeprecise.ProgrammingLanguage－IntroductionProgram編程Spelling拼寫(xiě)Punctuation標(biāo)點(diǎn)符號(hào)用于計(jì)算機(jī)編程的語(yǔ)言必須有簡(jiǎn)單的邏輯結(jié)構(gòu)，它們的語(yǔ)法、拼寫(xiě)和標(biāo)點(diǎn)符號(hào)的規(guī)則必須精確。ProgrammingLanguage－IntroductionProgramminglanguagesvarygreatlyintheirsophistication

andintheirdegreeofversatility.Someprogramminglanguagesarewrittentoaddress

aparticularkindofcomputingproblemorforuseonaparticularmodelofcomputersystem.

Vary:變化的,差異的Sophistication復(fù)雜性,復(fù)雜Versatility通用性,多用性address處理,操作編程語(yǔ)言在復(fù)雜性和通用程度上差異很大。一些編程語(yǔ)言是為了處理特定類型的計(jì)算問(wèn)題或?yàn)榱擞糜谔囟ㄐ吞?hào)的計(jì)算機(jī)系統(tǒng)而編寫(xiě)的。ProgrammingLanguage－IntroductionForinstance,programminglanguagessuchasFORTRANandCOBOLwerewrittentosolvecertaingeneraltypesofprogrammingproblems—FORTRANforscientificapplications,andCOBOLforbusinessapplications.

例如，F(xiàn)ORTRAN和COBOL等編程語(yǔ)言是為解決某些普遍的編程問(wèn)題類型而編寫(xiě)的——FORTRAN是為了科學(xué)領(lǐng)域的應(yīng)用，而COBOL是為了商業(yè)領(lǐng)域的應(yīng)用。ProgrammingLanguage－Introduction

Althoughtheselanguagesweredesignedtoaddressspecificcategoriesofcomputerproblems,theyarehighlyportable,meaningthattheymaybeusedtoprogrammanytypesofcomputers.Portable:輕便的,可攜帶的盡管這些語(yǔ)言旨在處理特定類型的計(jì)算機(jī)問(wèn)題，但它們具有很高的可移植性，也就是說(shuō)它們可以用來(lái)為多種類型的計(jì)算機(jī)編程O(píng)therlanguages,suchasmachinelanguages,aredesignedtobeusedbyonespecificmodelofcomputersystem,orevenbyonespecificcomputerincertainresearchapplications.Themostcommonlyusedprogramminglanguagesarehighlyportableandcanbeusedtoeffectivelysolvediversetypesofcomputingproblems.LanguageslikeC,PASCAL,andBASICfallintothiscategory。ProgrammingLanguage－IntroductionDiverse不同的,區(qū)別的Fallintothiscategory屬于這一類型其他的語(yǔ)言，如機(jī)器語(yǔ)言，是為一種特定型號(hào)的計(jì)算機(jī)系統(tǒng)，甚至是一臺(tái)特定的計(jì)算機(jī)，在某些研究領(lǐng)域的使用而編寫(xiě)的.最常用的編程語(yǔ)言具有很高的可移植性，可以用于有效地解決不同類型的計(jì)算問(wèn)題。像C、PASCAL和BASIC這樣的語(yǔ)言就屬于這一范疇ProgrammingLanguage－LanguageTypes

Ⅱ.LanguageTypes

Programminglanguagescanbeclassifiedaseitherlow-levellanguagesorhigh-levellanguages.Low-levelprogramminglanguages,ormachinelanguages,arethemostbasictypeofprogramminglanguagesandcanbeunderstooddirectlybyacomputer.Machinelanguages

differdependingonthemanufacturerandmodelofcomputer.Classify：分類，分等級(jí)Differ不同的語(yǔ)言類型

編程語(yǔ)言可分為低級(jí)語(yǔ)言和高級(jí)語(yǔ)言。低級(jí)編程語(yǔ)言或機(jī)器語(yǔ)言，是編程語(yǔ)言中最基礎(chǔ)的類型，可以被計(jì)算機(jī)直接理解。機(jī)器語(yǔ)言視計(jì)算機(jī)制造商與型號(hào)不同而有所區(qū)別High-levellanguagesareprogramminglanguagesthatmustfirstbetranslatedintoamachinelanguagebeforetheycanbeunderstoodandprocessedbyacomputer.高級(jí)語(yǔ)言是必須首先翻譯成機(jī)器語(yǔ)言計(jì)算機(jī)才能理解和處理的編程語(yǔ)言ProgrammingLanguage－LanguageTypesProgrammingLanguage－LanguageTypesExamplesofhigh-levellanguagesareC,C++,PASCAL,andFORTRAN.

Assemblylanguages

areintermediatelanguages

thatareveryclosetomachinelanguagesanddonothavetheleveloflinguisticsophisticationexhibitedbyotherhigh-levellanguages,butmuststillbetranslatedintomachinelanguage.Assembly匯編Linguistic:語(yǔ)言學(xué)的，語(yǔ)言的intermediate：中間的，中級(jí)的C、C++、PASCAL和FORTRAN都是高級(jí)語(yǔ)言的例子。匯編語(yǔ)言是中級(jí)語(yǔ)言，非常接近于機(jī)器語(yǔ)言，沒(méi)有其他高級(jí)語(yǔ)言所表現(xiàn)出的語(yǔ)言復(fù)雜程度，但仍然得翻譯成機(jī)器語(yǔ)言。ProgrammingLanguage－LanguageTypes1.MachineLanguagesInmachinelanguages,instructionsarewrittenassequencesof1sand0s,calledbits,thatacomputercanunderstanddirectly.Aninstructioninmachinelanguagegenerallytellsthecomputerfourthings:1.機(jī)器語(yǔ)言在機(jī)器語(yǔ)言中，指令被寫(xiě)成計(jì)算機(jī)能夠直接理解的1和0（稱作位）序列。一條機(jī)器語(yǔ)言的指令一般告訴計(jì)算機(jī)4件事：ProgrammingLanguage－LanguageTypes

（1）到計(jì)算機(jī)主存（隨機(jī)存儲(chǔ)器）的什么位置去找一兩個(gè)數(shù)字或簡(jiǎn)單的數(shù)據(jù)片；（2）要執(zhí)行的簡(jiǎn)單操作，如將兩個(gè)數(shù)字相加；（3）在主存的什么位置存放該簡(jiǎn)單操作的結(jié)果；（4）到什么位置去找下一條要執(zhí)行的指令(1)wheretofindoneortwonumbersorsimplepiecesofdatainthemaincomputermemory(RandomAccessMemory,orRAM),(2)asimpleoperationtoperform,suchasaddingthetwonumberstogether,(3)whereinthemainmemorytoputtheresultofthissimpleoperation,and(4)wheretofindthenextinstructiontoperform.ProgrammingLanguage－LanguageTypes

Whileallexecutableprogramsareeventuallyreadbythecomputerinmachinelanguage,theyarenotallprogrammedinmachinelanguage.Itisextremelydifficulttoprogramdirectlyinmachinelanguagebecausetheinstructionsaresequencesof1sand0s.Atypicalinstructioninamachinelanguagemightread1001011001011andmeanaddthecontentsofstorageregister

AtothecontentsofstorageregisterB.Executable可執(zhí)行的Register寄存器盡管所有的可執(zhí)行程序最終都是以機(jī)器語(yǔ)言的形式被計(jì)算機(jī)讀入的，但它們并非都是用機(jī)器語(yǔ)言編寫(xiě)的。直接用機(jī)器語(yǔ)言編程極端困難，因?yàn)橹噶钍?和1的序列。一條典型的機(jī)器語(yǔ)言指令可能寫(xiě)成1001011001011，意思是把存儲(chǔ)寄存器A的內(nèi)容加到存儲(chǔ)寄存器B的內(nèi)容中。ProgrammingLanguage－LanguageTypes

Statement語(yǔ)句2.高級(jí)語(yǔ)言

高級(jí)語(yǔ)言是相對(duì)復(fù)雜的一系列語(yǔ)句，它們使用來(lái)自人類語(yǔ)言的詞匯和句法。高級(jí)語(yǔ)言比匯編語(yǔ)言或機(jī)器語(yǔ)言類似于正常的人類語(yǔ)言，因此用之來(lái)編寫(xiě)復(fù)雜的程序比較容易。2.High-LevelLanguagesHigh-levellanguagesarerelativelysophisticatedsetsofstatements

utilizingwordsandsyntaxfromhumanlanguage.Theyaremoresimilartonormalhumanlanguagesthanassemblyormachinelanguagesandarethereforeeasiertouseforwritingcomplicatedprograms.ProgrammingLanguage－LanguageTypesTheseprogramminglanguagesallowlargerandmorecomplicatedprogramstobedevelopedfaster.However,high-levellanguagesmustbetranslatedintomachinelanguagebyanotherprogramcalledacompiler

beforeacomputercanunderstandthem.Forthisreason,programswritteninahigh-levellanguagemaytakelongertoexecuteanduseupmorememorythanprogramswritteninanassemblylanguage.Compiler編譯器Forthisreason因此Useup占用這些編程語(yǔ)言可以更快地開(kāi)發(fā)更大和更復(fù)雜的程序。然而，高級(jí)語(yǔ)言必須由稱為編譯器的另外一種程序翻譯成機(jī)器語(yǔ)言，計(jì)算機(jī)才能理解它們。因?yàn)檫@個(gè)原因，與用匯編語(yǔ)言編寫(xiě)的程序相比較，用高級(jí)語(yǔ)言編寫(xiě)的程序可能運(yùn)行時(shí)間長(zhǎng)，占用內(nèi)存多。ProgrammingLanguage－LanguageTypes3.AssemblyLanguagesComputerprogrammersuseassemblylanguagestomakemachine-languageprogramseasiertowrite.Inanassemblylanguage,eachstatementcorrespondsroughlytoonemachinelanguageinstruction.Anassemblylanguagestatementiscomposedwiththeaidofeasytoremembercommands.Roughly粗糙的,大致的Withtheaidof借助于3.匯編語(yǔ)言計(jì)算機(jī)程序員通過(guò)使用匯編語(yǔ)言，使機(jī)器語(yǔ)言程序比較容易編寫(xiě)。在匯編語(yǔ)言中，每個(gè)語(yǔ)句大致對(duì)應(yīng)于一條機(jī)器語(yǔ)言指令。一條匯編語(yǔ)言的語(yǔ)句是借助于易于記憶的命令編寫(xiě)的。ProgrammingLanguage－LanguageTypesThecommandtoaddthecontentsofthestorageregisterAtothecontentsofstorageregisterBmightbewrittenADDB,Ainatypicalassemblylanguagestatement.Typical典型的在一個(gè)典型的匯編語(yǔ)言語(yǔ)句中，把存儲(chǔ)寄存器A的內(nèi)容加到存儲(chǔ)寄存器B的內(nèi)容中這一命令，可能寫(xiě)成ADDB,A。ProgrammingLanguage－LanguageTypesAssemblylanguagessharecertainfeatureswithmachinelanguages.Forinstance,itispossibletomanipulatespecificbitsinbothassemblyandmachinelanguages.Programmersuseassemblylanguageswhenitisimportanttominimizethetimeittakestorunaprogram,becausethetranslationfromassemblylanguagetomachinelanguageisrelativelysimple.Minimize最小化,盡量減少匯編語(yǔ)言與機(jī)器語(yǔ)言具有某些共同的特征。例如，對(duì)特定的位進(jìn)行操控，用匯編語(yǔ)言和機(jī)器語(yǔ)言都是可行的。當(dāng)盡量減少程序的運(yùn)行時(shí)間很重要時(shí)，程序員就使用匯編語(yǔ)言，因?yàn)閺膮R編語(yǔ)言到機(jī)器語(yǔ)言的翻譯相對(duì)簡(jiǎn)單。ProgrammingLanguage－LanguageTypesAssemblylanguagesarealsousedwhensomepartofthecomputerhastobecontrolleddirectly,suchasindividualdotsonamonitorortheflowofindividualcharacterstoaprinter.Dot點(diǎn)Character字符匯編語(yǔ)言也用于計(jì)算機(jī)的某個(gè)部分必須被直接控制的情況，如監(jiān)視器上的單個(gè)點(diǎn)或者單個(gè)字符向打印機(jī)的流動(dòng)。ProgrammingLanguage－ClassificationofHigh-LevelLanguages

III.ClassificationofHigh-LevelLanguages

High-levellanguagesarecommonlyclassifiedasprocedure-oriented,functional,object-oriented,orlogiclanguages.Themostcommonhigh-levellanguagestodayareprocedure-orientedlanguages.Classification分類,歸類Procedure過(guò)程,程序Orient定向的,面向的III.高級(jí)語(yǔ)言的分類語(yǔ)言高級(jí)通常分為面向過(guò)程語(yǔ)言、函數(shù)式語(yǔ)言、面向?qū)ο笳Z(yǔ)言或邏輯語(yǔ)言。當(dāng)今最常見(jiàn)的高級(jí)語(yǔ)言是面向過(guò)程語(yǔ)言。

ProgrammingLanguage－ClassificationofHigh-LevelLanguagesIntheselanguages,oneormorerelatedblocksofstatementsthatperformsomecompletefunctionaregroupedtogetherintoaprogrammodule,orprocedure,andgivenanamesuchas“procedureA.”

Ifthesamesequenceofoperationsisneededelsewhereintheprogram,asimplestatementcanbeusedtoreferbacktotheprocedure.

Programmodule程序模塊Referbackto調(diào)回,找回在這種語(yǔ)言中，執(zhí)行某個(gè)完整功能的一個(gè)或多個(gè)相關(guān)的語(yǔ)句塊組成一個(gè)程序模塊或過(guò)程，而且被給予諸如“過(guò)程A”一類名稱。如果在程序的其他地方需要同樣的操作序列，可以使用一個(gè)簡(jiǎn)單的語(yǔ)句調(diào)回這個(gè)過(guò)程。ProgrammingLanguage－ClassificationofHigh-LevelLanguagesInessence,aprocedureisjustamini-program.Alargeprogramcanbeconstructedbygroupingtogetherproceduresthatperformdifferenttasks.Procedurallanguages

allowprogramstobeshorterandeasierforthecomputertoread,buttheyrequiretheprogrammertodesigneachproceduretobegeneralenoughtobeusedindifferentsituations.Essence本質(zhì),實(shí)質(zhì)Procedurallanguage過(guò)程語(yǔ)言General一般的,通用的實(shí)質(zhì)上，一個(gè)過(guò)程就是一個(gè)小型程序。一個(gè)大型程序可以通過(guò)將執(zhí)行不同任務(wù)的過(guò)程組合在一起而構(gòu)成。過(guò)程語(yǔ)言使程序變得比較短，而且比較容易被計(jì)算機(jī)讀取，但要求程序員將每個(gè)過(guò)程都設(shè)計(jì)得足夠通用，能用于不同的情況。ProgrammingLanguage－ClassificationofHigh-LevelLanguagesFunctionallanguages

treatprocedureslikemathematicalfunctionsandallowthemtobeprocessedlikeanyotherdatainaprogram.Thisallowsamuchhigherandmorerigorous

levelofprogramconstruction.Functionallanguage函數(shù)式語(yǔ)言Rigorous嚴(yán)格的,嚴(yán)密的函數(shù)式語(yǔ)言像對(duì)待數(shù)學(xué)函數(shù)一樣對(duì)待過(guò)程，并允許像處理程序中的任何其他數(shù)據(jù)一樣處理它們。這就使程序構(gòu)造在更高、更嚴(yán)密的水平上得以實(shí)現(xiàn)。ProgrammingLanguage－ClassificationofHigh-LevelLanguagesFunctionallanguagesalsoallowvariables—symbolsfordatathatcanbespecifiedandchangedbytheuserastheprogramisrunning—tobegivenvaluesonlyonce.Thissimplifiesprogrammingbyreducingtheneedtobeconcernedwiththeexactorderofstatementexecution,sinceavariabledoesnothavetoberedeclared,orrestated,eachtimeitisusedinaprogramstatement.Variable變量Simplify使簡(jiǎn)化Restate重新說(shuō)明函數(shù)式語(yǔ)言也允許變量——在程序運(yùn)行過(guò)程中可以被用戶指定和更改的數(shù)據(jù)符號(hào)——只被賦值一次。這樣，通過(guò)減少對(duì)語(yǔ)句執(zhí)行的確切順序給予關(guān)注的必要性，就簡(jiǎn)化了編程，因?yàn)橐粋€(gè)變量沒(méi)有必要每次在一個(gè)程序語(yǔ)句中用到，都重新聲明或重新說(shuō)明。ProgrammingLanguage－ClassificationofHigh-LevelLanguagesManyoftheideasfromfunctionallanguageshavebecomekeypartsofmanymodernprocedurallanguages.Object-orientedlanguagesareoutgrowthsoffunctionallanguages.Inobject-orientedlanguages,thecodeusedtowritetheprogramandthedataprocessedbytheprogramaregroupedtogetherintounitscalledobjects.Outgrowth發(fā)展結(jié)果來(lái)自函數(shù)式語(yǔ)言的許多思想已經(jīng)成為許多現(xiàn)代過(guò)程語(yǔ)言的關(guān)鍵部分。面向?qū)ο笳Z(yǔ)言是函數(shù)式語(yǔ)言的發(fā)展結(jié)果。在面向?qū)ο笳Z(yǔ)言中,用來(lái)編寫(xiě)程序的代碼和由程序處理的數(shù)據(jù)，組合成叫做對(duì)象的單元ProgrammingLanguage－ClassificationofHigh-LevelLanguagesObjectsarefurthergroupedintoclasses,whichdefinetheattributesobjectsmusthave.AsimpleexampleofaclassistheclassBook.ObjectswithinthisclassmightbeNovelandShortStory.Class類Attribute屬性,特性對(duì)象進(jìn)一步組合成類，而類則定義對(duì)象必須具有的屬性。類的一個(gè)簡(jiǎn)單例子就是書(shū)這個(gè)類。這個(gè)類中的對(duì)象可能是小說(shuō)和短篇小說(shuō)ProgrammingLanguage－ClassificationofHigh-LevelLanguagesObjectsalsohavecertainfunctionsassociatedwiththem,calledmethods.Thecomputeraccessesanobjectthroughtheuseofoneoftheobject’smethods.Themethodperformssomeactiontothedataintheobjectandreturnsthisvaluetothecomputer.對(duì)象還有某些與其相關(guān)的功能，稱為方法。計(jì)算機(jī)通過(guò)使用一個(gè)對(duì)象的某種方法來(lái)訪問(wèn)該對(duì)象。方法對(duì)對(duì)象中的數(shù)據(jù)執(zhí)行某種操作，然后將值返回給計(jì)算機(jī)。ProgrammingLanguage－ClassificationofHigh-LevelLanguagesClassesofobjectscanalsobefurthergroupedintohierarchies,inwhichobjectsofoneclasscaninheritmethodsfromanotherclass.Thestructureprovidedinobject-orientedlanguagesmakesthemveryusefulforcomplicatedprogrammingtasks.

Hierarchy階層inherit:繼承,遺傳對(duì)象的類也可進(jìn)一步組合成層，而在層中一個(gè)類的對(duì)象可繼承另一個(gè)類的方法。面向?qū)ο笳Z(yǔ)言提供的這種結(jié)構(gòu)，使該語(yǔ)言對(duì)于復(fù)雜的編程任務(wù)非常有用。ProgrammingLanguage－ClassificationofHigh-LevelLanguagesLogiclanguagesuselogicastheirmathematicalbase.Alogicprogramconsistsofsetsoffactsandif-thenrules,whichspecifyhowonesetoffactsmaybededuced

fromothers,forexample:IfthestatementXistrue,thenthestatementYisfalse.Deduce推斷,推導(dǎo)邏輯語(yǔ)言將邏輯用作其數(shù)學(xué)基礎(chǔ)。邏輯程序由事實(shí)組和“如果―則”規(guī)則構(gòu)成，“如果―則”規(guī)則具體說(shuō)明一組事實(shí)如何可以從其他事實(shí)組中推斷出來(lái)，例如：如果X語(yǔ)句為真，則Y語(yǔ)句為假。ProgrammingLanguage－ClassificationofHigh-LevelLanguagesIntheexecutionofsuchaprogram,aninputstatementcanbelogicallydeducedfromotherstatementsintheprogram.Manyartificialintelligenceprogramsarewritteninsuchlanguages.在這樣一個(gè)程序的執(zhí)行過(guò)程中，一條輸入語(yǔ)句可以按照邏輯從程序中的其他語(yǔ)句推斷出來(lái)。許多人工智能程序使用這種語(yǔ)言編寫(xiě)。ProgrammingLanguage－LanguageStructureandComponents

IV.

LanguageStructureandComponents

Programminglanguagesusespecifictypesofstatements,orinstructions,toprovidefunctionalstructuretotheprogram.Astatementinaprogramisabasicsentencethatexpressesasimpleidea—itspurposeistogivethecomputerabasicinstruction.IV.語(yǔ)言結(jié)構(gòu)與成分編程語(yǔ)言使用特定類型的語(yǔ)句或指令，來(lái)給程序提供功能結(jié)構(gòu)。程序中的一個(gè)語(yǔ)句是表達(dá)一個(gè)簡(jiǎn)單想法的基本句子——它的目的是給計(jì)算機(jī)一條基本指令。

ProgrammingLanguage－LanguageStructureandComponentsStatementsdefinethetypesofdataallowed,howdataaretobemanipulated,andthewaysthatproceduresandfunctionswork.Programmersusestatementstomanipulatecommoncomponentsofprogramminglanguages,suchasvariablesandmacros

(mini-programswithinaprogram).Macros宏mini-programs小程序語(yǔ)句定義所允許的數(shù)據(jù)類型、數(shù)據(jù)如何處理以及過(guò)程和函數(shù)的工作方式。程序員使用語(yǔ)句來(lái)操控編程語(yǔ)言的常見(jiàn)成分，如變量和宏（程序中的小程序段）。ProgrammingLanguage－LanguageStructureandComponentsStatementsknownasdatadeclarations

givenamesandpropertiestoelementsofaprogramcalledvariables.Variablescanbeassigneddifferentvalueswithintheprogram.

Declaration：

聲明property:財(cái)產(chǎn),特性Assign賦予數(shù)據(jù)聲明語(yǔ)句給稱為變量的那些程序元素以名稱和屬性。變量在程序中可以賦予不同的值.Thepropertiesvariablescanhavearecalledtypes,andtheyincludesuchthingsaswhatpossiblevaluesmightbesavedinthevariables,howmuchnumericalaccuracyistobeusedinthevalues,andhowonevariablemayrepresentacollectionofsimplervaluesinanorganizedfashion,suchasatableorarray.ProgrammingLanguage－LanguageStructureandComponentsacollectionof一組fashion方式Table表格array數(shù)組變量可以具有的屬性稱為類型，它們包括：變量中能保存哪些可能的值；這些值中使用何種程度的數(shù)值精度；以及一個(gè)變量可以如何以有組織結(jié)構(gòu)的方式——如以表或數(shù)組的形式——表示一組比較簡(jiǎn)單的值ProgrammingLanguage－LanguageStructureandComponentsInmanyprogramminglanguages,akeydatatypeisapointer.Variablesthatarepointersdonotthemselveshavevalues;instead,theyhaveinformationthatthecomputercanusetolocatesomeothervariable—thatis,theypointtoanothervariable.Pointer指針在許多編程語(yǔ)言中，一個(gè)關(guān)鍵的數(shù)據(jù)類型是指針。指針變量本身沒(méi)有值，而是含有計(jì)算機(jī)可以用來(lái)查找某個(gè)其他變量的信息——也就是說(shuō)，它們指向另一個(gè)變量。ProgrammingLanguage－LanguageStructureandComponentsAnexpression

isapieceofastatementthatdescribesaseriesofcomputationstobeperformedonsomeoftheprogram’svariables,suchasX+Y/Z,inwhichthevariablesareX,Y,andZandthecomputationsareadditionanddivision.Expression表達(dá)式Division除法一個(gè)表達(dá)式是語(yǔ)句的一段，用于描述要對(duì)一些程序變量執(zhí)行的一系列計(jì)算操作，如X+Y/Z，其中X、Y和Z為變量，加法和除法是計(jì)算操作。ProgrammingLanguage－LanguageStructureandComponentsAnassignmentstatement

assignsavariableavaluederivedfromsomeexpression,whileconditional

statements

specifyexpressionstobetestedandthenusedtoselectwhichotherstatementsshouldbeexecutednext.Assignment賦值derivedfrom來(lái)自,衍生于一個(gè)賦值語(yǔ)句給一個(gè)變量賦予來(lái)自某個(gè)表達(dá)式的值，而條件語(yǔ)句則指定要被測(cè)試、然后用于選擇接下來(lái)應(yīng)該執(zhí)行那些其他語(yǔ)句的表達(dá)式。ProgrammingLanguage－LanguageStructureandComponentsProcedureandfunctionstatements

definecertainblocksofcodeasproceduresorfunctionsthatcanthenbereturnedtolaterintheprogram.Thesestatementsalsodefinethekindsofvariablesandparameters

theprogrammercanchooseandthetypeofvaluethatthecodewillreturnwhenanexpressionaccessestheprocedureorfunction.Function函數(shù)Parameter參數(shù)過(guò)程和函數(shù)語(yǔ)句將某些代碼塊定義為以后可在程序中回調(diào)的過(guò)程或函數(shù)。這些語(yǔ)句也定義程序員可選的變量和參數(shù)種類，以及當(dāng)表達(dá)式訪問(wèn)過(guò)程或函數(shù)時(shí)代碼所返回的值的類型。ProgrammingLanguage－LanguageStructureandComponentsManyprogramminglanguagesalsopermitminitranslationprogramscalledmacros.Macrostranslatesegmentsofcodethathavebeenwritteninalanguagestructuredefinedbytheprogrammerintostatementsthattheprogramminglanguageunderstands.Minitranslation小翻譯Segments段,塊許多編程語(yǔ)言也容許叫做宏的小翻譯程序。宏將那些用程序員定義的語(yǔ)言結(jié)構(gòu)編寫(xiě)的代碼段翻譯成編程語(yǔ)言可以理解的語(yǔ)句。ProgrammingLanguage－History

V.

History

Programmingl