《計算機專業(yè)英語》課件第16章

EvolutionofC#and.NET

ProgrammingLanguages

Inthe1940sprogrammerstoggledswitchesonthefrontofcomputerstoenterprogramsanddataintomemory.Thatishowprogrammingbegan.1Evenwhentheymovedtopunching0sand1soncardsandreadingthecardsintomemory,itcouldnothavebeenmuchfuntobeaprogrammer.Codingwasverytediousandpronetoerror.Inthe1950sassemblylanguagesreplacedthebinarynotationbyusingmnemonicsymbolstorepresenttheinstructionsforthecomputer.SymbolssuchasMVwereusedtorepresentmovingthecontentsofonevalueinmemorytoanothermemorylocation.Assemblylanguagesweredesignedtomaketheprogrammer’sjobeasierbyusingthesemnemonicsymbolsinsteadofbinarynumbers.However,theinstructionsdependedontheparticularCPUarchitecture.Statementstoperformthesametaskdifferedfromcomputertocomputer.Assemblylanguagesarestillconsideredlow-levelprogramminglanguages.AsyoucanseefromFigure16-1,thesetypesofinstructionsarenoteasytoreadorunderstand.TheyarenotconsideredclosetotheEnglishlanguage,ashigh-levelprogramminglanguagessuchasCandJavaare.Fig.16-1Assemblylanguageinstructiontoaddtwovalues

High-levellanguagescameintoexistenceinthe1950swithFORTRAN(FormulaTranslator)andlaterCOBOL(CommonBusinessOrientedLanguage).Theselanguageswereconsideredhigh-levellanguagebecausetheyweredesignedtobeaccessibletohumans—easytoreadandwrite,andclosetotheEnglishlangrage.Overtheyearssincethen,morethan2,000high-levellanguageshavecomeintoexistence.Somehavegonebythewayside,whileothershaveevolvedandarestillwidelyusedtoday.

SomeofthemorenoteworthyhighlevelprogramminglanguagesareC,C++,VisualBasic,Java,andnowC#.C++isanextensionofC,whichactuallyevolvedfromBCPLandBin1973.DennisRitchieiscreditedwithdevelopingtheCprogramminglanguages;BjarneStroustrupatBellLabsisconsideredthefatherofC++forhisdesignworkintheearly1980s.C++includesfeaturesthatenabledprogrammerstoperformobject-orientedprogramming.C++isusedheavilyinthecomputerindustrytoday.

Smalltalk,consideredapureobjectorientedlanguage,wasdevelopedattheXeroxPaloAltoResearchCenter(PARC).2VisualBasic,introducedin1991,derivedfromtheBASIC(BeginnersAllPurposeSymbolicCode)programminglanguage,alanguagedevelopedinthe1960s.TheearlierversionsofVisualBasicdidnotfacilitatedevelopmentusinganobject-orientedapproach.EarlierversionsofVisualBasicdid,however,facilitateeasycreationofWindows-basedgraphicaluserinterfaces(GUIs).VisualBasichasbeenusedforagreatdealofapplicationdevelopmentbecauseofthis.

Java

Javawasintroducedin1995andwasoriginallycalledOak.Itwasoriginallydesignedtobealanguageforintelligentconsumer-electronicdevicessuchasapplianceandmicrowaveovens.3Insteadofbeingusedforthatpurpose,thebusinesscommunityusedJavamostheavilyforWebapplicationsbecauseofthenatureofthebytecode,whichenabledmachineindependentlanguagecompiling.4Sincethebytecodedoesnottargetanyparticularcomputerplatformandmustbeconvertedtothelanguageofthesystemrunningtheapplication,thisfacilitatesdevelopmentofcodethatrunsonmanytypesofcomputers.

C#

C#isoneofthenewestprogramminglanguages.ItconformscloselytoCandC++,butmanydevelopersconsideritakintoJava.Thereareanumberofsimilaritiesbetweenthelanguages.Ithastherapidgraphicaluserinterface(GUI)featuresofpreviousversionsofVisualBasic,theaddedpowerofC++,andobjectorientedclasslibrariessimilartoJava.C#wasdesignedfromscratchbyMicrosofttoworkwiththenewprogrammingparadigm,.NET,andwasthelanguageusedmostheavilyforthedevelopmentofthe.NETFrameworkclasslibraries.C#canbeusedtodevelopanytypeofsoftwarecomponentincludingmobileapplications,dynamicWebpages,databaseaccesscomponents,Windowsdesktopapplications,Webservices,andconsole-basedapplications.

.NET

WhenyouthinkaboutC#,youshouldalsounderstanditsrelationshipto.NET..NETisanenvironmentinwhichprogramsrunandwasdesignedtobeanewprogrammingparadigm.5Itisnotanoperatingsystem,butratheralayerbetweentheoperatingsystemandotherapplications.Assuch,itprovidesaplatformfordevelopingandrunningcodethatiseasytouse.Microsoftstatedthatthevisionfor.NETwastoprovideanewprogrammingplatformandasetofdevelopmenttools.Theintentwasfordeveloperstobeabletobuilddistributedcomponent-basedapplications.Bytheyear2000,whenMicrosoftunveiled.NET,manydevelopershadalreadyexperienced.NETduetothemassivemarketingcampaignofMicrosoft.

Beforeitsofficialannouncementin2000,.NETwasindevelopmentforoverthreeyears.Microsoftdistributedanumberofbetaversionsbeforetheofficialrelease.Abedaversionisaworkingversionthathasnotbeenfullytestedandmaystillcontainbugsorerrors.6ItwasnotuntilFebruary2002thatMicrosoftfinallyreleasedthefirstversionofVisualStudio.NET,theIntegratedDevelopmentEnvironment(IDE)fordevelopingC#applications.VisualBasic.NET,VisualC++.NET,VisualJ#.NET,andVisualC#.NETallusethissamedevelopmentenvironment.7IncludedinVisualStudioaretoolsfortypingprogramstatements,andcompiling,executing,anddebuggingapplications.

Multi-languageIndependence

.NETsupportsdevelopmentusinganumberofprogramminglanguages:VisualBasic,C#,J#,C++,andanumberofthirdpartylanguages.AllthecodefromeachofthelanguagescompilestothecommonMicrosoftIntermediateLanguage(IL).

TheIntermediateLanguageiseasilyobtainedinVisualStudiousingatoolcalledILDasm,whichstandsforIntermediateLanguageDisassembler.ThissameIntermediateLanguagewouldbeproducedwhethertheprogramwerewritteninC#,VisualBasic,oranyother.NETsupportedlanguages.Thismakesnewerlanguagesmoreinteroperablethanearlierlanguages,whichmeansthatoneapplicationcanbedividedupandwritteninmorethanonelanguage.PartoftheapplicationmightbedevelopedusingC++andanotherportiondevelopedusingC#.Whentheyarecompiled,theytranslatetoacommonIL.

Thefollowinglistdescribessomeofthecommonfeaturesofthe.NETsupportedlanguages.

NewFrameworkBaseClasses

The.NETFrameworkhasaclasslibrary,whichprovidesaverylargecollectionofover2,500reusabletypes(classes)availabletoany.NETlanguage.

DynamicWebPagesandWebServices

.NETwaswrittenwiththeInternetinmind;thus,deployingapplicationsoverIntranetortheInternetbecomesanordinary,day-to-dayoperation.8Usinganewtechnology,ASP.NET,assetofcomponentscalledADO.NET,andhavingXMLsupport,makesiteasiertoaccessrelationaldatabasesandotherdatasourcesaswellastoimportandexportdatathroughtheWeb.

ScalableComponentDevelopment

9.NETnotonlyfacilitatesobject-orienteddevelopment,butittakesdesignonestepfurther.With.NET,truecomponentbaseddevelopmentcanbeperformedbetterandeasierthaninthepast.Segmentsofcode,createdasseparateentities,canbestoredindependently,combined,andreusedinmanyapplications.Thatisthebeautybehind.NET.10.NETprovidesarelativelyseamlesswayforclientprogramstousecomponentsbuiltusingdifferentlanguages.With.NET,component-baseddevelopmentcanbecomeareality.NewWordstoggle

vt.切換punchvt.沖孔,打孔；n.沖孔機,沖床,打孔機tediousadj.單調(diào)乏味的,沉悶的,冗長乏味的architecturen.體系結(jié)構(gòu)accessibleadj.易接近的,可到達的,易受影響的,可理解的creditn.信任,信用,聲望,榮譽,［財務］貸方,銀行存款;vt.相信,信任,把……歸給facilitatevt.(不以人作主語的)使容易,使便利,推動,幫助,使容易,促進bytecoden.字節(jié)碼akinadj.同族的,類似的scratchn.擦除；adj.可擦除的frameworkn.構(gòu)架,框架,結(jié)構(gòu)componentbasedadj.基于組件的access

v.訪問,存取consolen.控制臺distributevt.分發(fā),分配,散布,分布,分類,分區(qū);v.分發(fā)distributedadj.分布式的unveilvt.使公諸于眾,揭開,揭幕,除去……的面紗;vi.顯露,除去面紗compilevt.編譯,編輯,匯編interoperableadj.可互用的,相互作用的,相互配合的deployv.展開,配置daytodayadj.日常的,逐日的assetn.資產(chǎn),有用的東西seamlessadj.無縫合線的,無傷痕的PhrasesandExpressions

assemblylanguage匯編語言binarynotation二進制記數(shù)法mnemonicsymbol助記符comeintoexistence開始存在,成立FORTRAN(formulatranslator)FORTRAN語言,公式翻譯程序語言COBOL(commonbusinessorientedlanguage)面向商業(yè)的通用語言beaccessibleto是……能夠接近的overtheyearssincethen自從那時以后的幾年中Basic［Bootstrap］CombinedProgrammingLanguage(BCPL)基本［自展］組合程序設(shè)計語言objectorientedprogramming面向?qū)ο蟪绦蛟O(shè)計,面向?qū)ο缶幊碳夹g(shù)derivefrom得自,由來,衍生BASIC(beginnersallpurposesymbolicinstructioncode)BASIC語言(初學者通用指令碼)GUIs(graphicaluserinterfaces)圖形用戶界面mobileapplication移動應用程序IDE(integrateddevelopmentenvironment)集成開發(fā)環(huán)境programstatement程序語句IL(intermediatelanguage)中間語言ILDasm(intermediatelanguagedisassembler)中間語言反匯編程序divideup分割clientprogram客戶程序TheExplanationofDifficultStatements

1.Evenwhentheymovedtopunching0sand1soncardsandreadingthecardsintomemory,itcouldnothavebeenmuchfuntobeaprogrammer.

分析:“Evenwhen”譯為“即使當”;“itcouldnothavebeenmuchfuntobeaprogrammer”表示虛擬。

句意:程序員改成在卡片上打孔來代表0和1,并將卡片上的內(nèi)容讀入內(nèi)存,即使這樣,成為一個程序員也沒有很多樂趣。

2.VisualBasic,introducedin1991,derivedfromtheBASIC(BeginnersAllPurposeSymbolicCode)programminglanguage,alanguagedevelopedinthe1960s.

分析:“introduced”是過去分詞短語作定語,修飾“VisualBasic”,可以將其還原成定語從句“whichwasintroducedin1991”;“alanguagedevelopedinthe1960s”是之前的“theBASICprogramminglanguage”的同位語,都是介詞“from”的賓語;“developedinthe1960s”作為過去分詞修飾“alanguage”。句意:VisualBasic1991年被提出,由在20世紀60年代開發(fā)的BASIC語言發(fā)展而來。

3.Insteadofbeingusedforthatpurpose,thebusinesscommunityusedJavamostheavilyforWebapplicationsbecauseofthenatureofthebytecode,whichenabledmachineindependentlanguagecompiling.

分析:“Insteadof”解釋為“替代……”;定語從句“whichenabledmachineindependentlanguagecompiling”修飾“thenature”。

句意:然而,Java并未被用于這種用途,商業(yè)團體廣泛地使用Java開發(fā)Web應用程序,是因為字節(jié)碼自身的特點,即能使獨立于機器的語言進行編譯。

4.Sincethebytecodedoesnottargetanyparticularcomputerplatformandmustbeconvertedtothelanguageofthesystemrunningtheapplication,thisfacilitatesdevelopmentofcodethatrunsonmanytypesofcomputers.

分析:“since”引導原因狀語從句;“runningtheapplication”是現(xiàn)在分詞短語修飾“system”,還原成定語從句是“thesystemwhichrunstheapplication”。

句意:因為字節(jié)碼不是針對任何一個特殊的計算機平臺并且必須被轉(zhuǎn)化成為運行這個應用程序的系統(tǒng)的語言,所以這些促進了能在很多種計算機中運行的代碼的發(fā)展。

5.Itisnotanoperatingsystem,butratheralayerbetweentheoperatingsystemandotherapplications.

分析:“not...but...”解釋為“不是……而是……”。

句意:它不是一個操作系統(tǒng),而是位于操作系統(tǒng)和其它應用程序之間的一個層。

6.ItwasnotuntilFebruary2002thatMicrosoftfinallyreleasedthefirstversionofVisualStudio.NET,theIntegratedDevelopmentEnvironment(IDE)fordevelopingC#applications.

分析:“notuntil”譯為“直到……才……”;此句為強調(diào)句型;“theIntegratedDevelopmentEnvironment(IDE)fordevelopingC#applications”是“thefirstversionofVisualStudio.NET”的同位語。

句意:直到2002年的2月Microsoft才最終發(fā)布了VisualStudio.NET的第一代版本,這是開發(fā)C#應用程序的一個完整的開發(fā)環(huán)境。

7.IncludedinVisualStudioaretoolsfortypingprogramstatements,andcompiling,executing,anddebuggingapplications.

分析:整個句子采用倒裝語序。正常語序為“Toolsfortypingprogramstatements,andcompiling,executing,anddebuggingapplicationsareincludedinVisualStudio.”

句意:在VisualStudio中包含了鍵入編程語句、編譯、執(zhí)行和調(diào)試應用軟件的工具。

8.Usinganewtechnology,ASP.NET,assetofcomponentscalledADO.NET,andhavingXMLsupport,makesiteasiertoaccessrelationaldatabasesandotherdatasourcesaswellastoimportandexportdatathroughtheWeb.

分析:“it”作為形式賓語指代不定式“toaccessrelationaldatabasesandotherdatasourcesaswellastoimportandexportdatathroughtheWeb”。

句意:使用一種新技術(shù)——ASP.NET,使用叫做ADO.NET的組件資源,并且具有XML的支持,使能夠較容易地訪問關(guān)系數(shù)據(jù)庫和其它數(shù)據(jù)資源,并且能容易地通過網(wǎng)絡(luò)輸入輸出數(shù)據(jù)。

9..NETnotonlyfacilitatesobject-orienteddevelopment,butittakesdesignonestepfurther.

分析:“notonly...but(also)...”譯為“不僅……而且……”。句意:.NET不僅促進了面向?qū)ο蟮拈_發(fā),而且使設(shè)計更進一步。

10..NETprovidesarelativelyseamlesswayforclientprogramstousecomponentsbuiltusingdifferentlanguages.

分析:過去分詞“built”修飾“components”,表示被動,理解為“被創(chuàng)建的”;現(xiàn)在分詞短語“usingdifferentlanguages”修飾“components”,譯為“使用不同語言的”。句意:.NET為客戶程序提供了一個相對完美的方式去使用不同語言創(chuàng)建的組件。Exercises

Ⅰ.Fillintheblanksaccordingtothetext:(1)Inthe1950sassemblylanguagesreplacedthebinarynotationbyusing______________torepresenttheinstructionsforthecomputer.(2)C++includesfeaturesthatenabledprogrammerstoperform______________.(3)Insteadofbeingusedforthatpurpose,thebusinesscommunityusedJavamostheavilyforWebapplicationsbecauseofthenatureofthebytecode,whichenabled______________.(4)C#hastherapid______________featuresofpreviousversionsofVisualBasic,theaddedpowerofC++,andobjectorientedclasslibrariessimilartoJava.(5)ItwasnotuntilFebruary2002thatMicrosoftfinallyreleasedthefirstversionofVisualStudio

.NET,______________fordevelopingC#applications.Ⅱ.Decidewhethereachofthefollowingstatementsistrueorfalseaccordingtothetext:(1)Assemblylanguagesweredesignedtomaketheprogrammer’sjobeasierbyusingbinarynumbersinsteadofthesemnemonicsymbols.(2)Inthe1950s,highlevellanguagescameintoexistence,suchasFORTRAN(FormulaTranslator)andlaterCOBOL(CommonBusinessOrientedLanguage).Theselanguageswereeasytoreadandwrite,andclosetotheEnglishlanguage.(3)TheearlierversionsofVisualBasicfacilitateddevelopmentusinganobject-orientedapproach.(4)ItwasoriginallydesignedtobealanguageforWebapplicationsbecauseofthenatureofthebytecode,whichenabledmachineindependentlanguagecompiling.(5)C#wasdesignedfromscratchbyMicrosofttoworkwiththenewprogrammingparadigm,Java,andwasthelanguageusedmostheavilyforthedevelopmentoftheJavaFrameworkclasslibraries.Ⅲ.Rewritethefollowingsentences,usingproperformsofinversion:(1)Someofitscompoundsaremuchmoreimportantthantheelementitself.(2)Hissurprisewassogreatthathealmostranaway.(3)HehadreadthebookonEinstein’sgeneralrelativitymanyatime.(4)Thehousewassobigthatitwasnecessarytodestroypartofthewallsnearthefateinorderthatitshouldhaveroomtoenter.(5)Alastingpeacewillbeestablishedintheareaonlyifbothsidesaccepttheagreement.Ⅳ.TranslatethefollowingparagraphintoChinese:

Encryptionisusedtoensuretheconfidentiality,integrityandauthenticityofthetwoendpointsintheprivatenetwork.TheInternetKeyExchange(IKE),anapplicationlayerprotocol,authenticateseachpeerinanIPsectransaction.IKEnegotiatessecuritypolicy,determiningwhichalgorithmmaybeusedtosetupthetunnel.Italsohandlestheexchangeofsessionkeysusedforthatonetransaction.

NetworksthatuseIPsectosecuredatatrafficcanautomaticallyauthenticatedevicesbyusingdigitalcertificates,whichverifytheidentitiesofthetwouserwhoaresendinginformationbackandforth.IPseccanbeidealwaytosecuredatainlargenetworksthatrequiresecureconnectionsamongmanydevices.ReadingMaterials

InternetProtocolSecurity(Ⅰ)

WhiletheInternetisinherentlyinsecure,businessesstillneedtopreservetheprivacyofdataasittravelsoverthenetwork.Tohelpdothat,theInternetEngineeringTaskForceaninternationalgroupofnetworkdesigners,operators,vendorsandresearchersconcernedwiththeevolutionofInternetarchitecturehasdevelopedasuiteofprotocolscalledInternetProtocolSecurity(IPsec).

IPseccreatesastandardplatformtodevelopsecurenetworksandelectronictunnelsbetweentwomachines.SecuretunnelingviaIPseccreatescircuit-likeconnectionsinanetworkthroughwhichdatapacketscanmove.Italsoencapsulateseachdatapacketinanewpacketthatcontainstheinformationnecessarytosetup,maintainandteardownthetunnelwhenit’snolongerneeded.

Encryptionisusedtoensuretheconfidentiality,integrityandauthenticityofthetwoendpointsintheprivatenetwork.TheInternetKeyExchange(IKE),anapplicationlayerprotocol,authenticateseachpeerinanIPsectransaction.IKEnegotiatessecuritypolicy,determiningwhichalgorithmmaybeusedtosetupthetunnel.Italsohandlestheexchangeofsessionkeysusedforthatonetransaction.

NetworksthatuseIPsectosecuredatatrafficcanautomaticallyauthenticatedevicesbyusingdigitalcertificates,whichverifytheidentitiesofthetwouserswhoaresendinginformationbackandforth.IPseccanbeidealwaytosecuredatainlargenetworksthatrequiresecureconnectionsamongmanydevices.NewWordsandExpressionsinherentlyadj.固有的IPsec(internetprotocolsecurity)因特網(wǎng)安全協(xié)議electronictunnels電子隧道encryptionn.加密IKE:(internetkeyexchange)因特網(wǎng)密匙交換applicationlayerprotocol應用層協(xié)議transactionn.交易negotiatevi./vt.商議,談判authenticatevt.認證,證明……為真Questions(1)WhodevelopIPsec?(2)WhatisEncryptionusedtoensure?InternetProtocolSecurity(Ⅱ)

UsersdeployingIPseccansecuretheirnetworkinfrastructurewithoutaffectingtheapplicationson