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1、VisualBasicforApplications(VBA)isanimplementationofMicrosoft'sevent-drivenprogramminglanguageVisualBasic6,andassociatedintegrateddevelopmentenvironment(IDE),whichisbuiltintomostMicrosoftOfficeapplications.VBAenablesdeveloperstobuilduserdefinedfunctions,automateproc
2、esses,andaccessWin32andotherlowlevelfunctionalitythroughDLLs.ItwasalsobuiltintoOfficeapplicationsuptoversion2004forApple'sMacOSX,otherMicrosoftapplicationssuchasMicrosoftMapPointandMicrosoftVisio;aswellasbeingatleastpartiallyimplementedinsomeotherapplicationssuchas
3、AutoCAD,WordPerfectandArcGIS.Itsupersedesandexpandsonthecapabilitiesofearlierapplication-specificmacroprogramminglanguagessuchasWord'sWordBasic,andcanbeusedtocontrolmanyaspectsofthehostapplication,includingmanipulatinguserinterfacefeatures,suchasmenusandtoolbars,an
4、dworkingwithcustomuserformsordialogboxes.VBAcanalsobeusedtocreateimportandexportfiltersforvariousfileformats,suchasODF.Asitsnamesuggests,VBAiscloselyrelatedtoVisualBasicandusestheVisualBasicRuntime,butcannormallyonlyruncodewithinahostapplicationratherthanasastandal
5、oneapplication.Itcan,however,beusedtocontroloneapplicationfromanotherusingOLEAutomation.Forexample,itisusedtoautomaticallycreateaWordreportfromExceldata,inturnautomaticallycollectedbyExcelfrompolledobservationsensors.VBAisfunctionallyrichandflexiblebutitdoeshavesom
6、eimportantlimitations,suchasrestrictedsupportforfunctionpointerswhichareusedascallbackfunctionsintheWindowsAPI.Ithastheabilitytouse(butnotcreate)(ActiveX/COM)DLLs,andlaterversionsaddsupportforclassmodules.LanguageCodewritteninVBAiscompiled[1]toaproprietaryintermedi
7、atelanguagecalledP-code(packedcode)[2],whichisstoredbythehostingapplications(Access,Excel,Word,PowerPoint))asaseparatestreaminStructuredstoragefiles(e.g.,.docor.xls)independentofthedocumentstreams.Theintermediatecodeisthenexecuted[1]byavirtualmachine(hostedbythehos
8、tingapplication).DespiteitsresemblancetomanyoldBASICdialects(particularlyMicrosoftBASIC,fromwhichitisindirectlyderived),VBAisnotcompatiblewithany
