软件生命周期计算机程序科技文献翻译SectionAComputerProgram(计算机程序)SectionBSoftwareLifeCycle(软件生命周期)英文原文：ComputerProgramⅠ.IntroductionAcomputerprogramisasetofinstructionsthatdirectsacomputertoperformsomeprocessingfunctionorcombinationfunctions.Fortheinstructionstobecarriedout,acomputermustexecuteaprogram,thatis,thatisthecomputerreadstheprogram,andthenfollowsthestepsencodedintheprograminapreciseorderuntilcompletion.Aprogramcanbeexecutedmanydifferenttimes,witheachexecutionyieldingapotentiallydifferentresultdependingupontheoptionsanddatathattheusergivesthecomputer.Programfallintotwomajorclasses:applicationprogramandoperatingsystems.Anapplicationprogramisonethatcarriesoutsomefunctiondirectlyforauser,suchaswordprocessingorgameplaying.Anoperatingsystemisaprogramthatmanagesthecomputerandthevariousresourcesanddevicesconnectedtoit,suchasRAM(randomaccessmemory),harddrives,monitors,keyboards,printers,andmodems,sothattheymaybeusedbyotherprogram.ExamplesofoperatingsystemsareDOS,WindowsXP,OS/2,andUNIX.Ⅱ.ProgramDevelopmentSoftwaredesignerscreatenewprogrambyusingspecialapplicationsprograms,oftencalledutilityprogramsordevelopmentprograms.Aprogrammerusesanothertypeofprogramcalledatexteditortowritethenewprograminaspecialnotationcalledprogramminglanguage.Withthetexteditor,theprogrammercreatesatextfile,whichisanorderedlistofinstructions,alsocalledprogramsourcefile.Theindividualinstructionsthatmakeupthesourcefilearecalledsourcecode.Atthispoint,aspecialapplicationprogramtranslatesthesourcecodeintomachinecodelanguage,orobjectcode–aformatthattheoperatingsystemswillrecognizeasaproperprogramandbeabletoexecute.Threetypesofapplicationprogramstranslatefromsourcecodetoobjectcode:compilers,interpreters,andassemblers.Thethreeoperatedifferentlyandondifferenttypesofprogramminglanguages,buttheyservethesamepurposeoftranslatingfromaprogramminglanguageintomachinelanguage.Acompilertranslatestextfileswritteninahigh-levelprogramminglanguage-suchasFORTRAN,C,orPascal–fromthesourcecodetotheobjectcodeallatonce,ThisdiffersfromtheapproachtakenbyinterpretedlanguagesuchasBASIC,inwhichaprogramintranslatedintoobjectcodestatementbystatementaseachinstructionisexecuted.Theadvantagetointerpretedlanguageisthattheycanbeginexecutingtheprogramimmediatelyinsteadofhavingtowaitingforallthesourcecodetobecompiled.Changescanalsobemadetotheprogramfairlyquicklywithouthavingwaitingforittobecompiledagain.Thedisadvantageofinterpretedlanguageisthattheyareslowtoexecute,sincetheentireprogrammusttranslatedoneinstructionatatime,eachtimeprogramisrun.Ontheotherhand,compiledlanguagearecompiledonlyonceandthuscanbeexecutedbythecomputermuchmorequicklythaninterpretedlanguages,Forthisreason,compiledlanguagesaremorecommonandalmostalwaysusedinprofessionalandscientificapplications.Anothertypeoftranslatoristheassembler,whichisusedforprogramsorpartsofprogramswritteninassemblylanguage.Assemblylanguageisanotherprogramminglanguage,butitismuchmoresimilartomachinelanguagethanothertypeofhigh-levellanguage.Inassemblylanguage,asinglestatementcanusuallybetranslatedintoasingleinstructionofmachinelanguage.Today,assemblylanguageisrarelyusedtowrittenentireprogram,butisinsteadmostoftenusedwhentheprogrammerneedstodirectlycontrolsomeaspectofthecomputer’sfunction.Programsareoftenwrittenasasetofsmallerpieces,witheachpiecerepresentingsomeaspectoftheoverallap...
