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1、1Chapter1IntroductiontoComputers,Programs,andJava2ObjectivesTounderstandcomputerbasics,programs,andoperatingsystems(§§1.2–1.4).TodescribetherelationshipbetweenJavaandtheWorldWideWeb(§1.5).TounderstandthemeaningofJavalanguagespecification,API,JDK,andI
2、DE(§1.6).TowriteasimpleJavaprogram(§1.7).Todisplayoutputontheconsole(§1.7).ToexplainthebasicsyntaxofaJavaprogram(§1.7).Tocreate,compile,andrunJavaprograms(§1.8).TousesoundJavaprogrammingstyleanddocumentprogramsproperly(§1.9).Toexplainthedifferencesbe
3、tweensyntaxerrors,runtimeerrors,andlogicerrors(§1.10).TodevelopJavaprogramsusingNetBeans(§1.11).TodevelopJavaprogramsusingEclipse(§1.12).3WhatisaComputer?AcomputerconsistsofaCPU,memory,harddisk,floppydisk,monitor,printer,andcommunicationdevices.4CPUT
4、hecentralprocessingunit(CPU)isthebrainofacomputer.Itretrievesinstructionsfrommemoryandexecutesthem.TheCPUspeedismeasuredinmegahertz(MHz),with1megahertzequaling1millionpulsespersecond.ThespeedoftheCPUhasbeenimprovedcontinuously.IfyoubuyaPCnow,youcange
5、tanIntelPentium4Processorat3gigahertz(1gigahertzis1000megahertz).5MemoryMemoryistostoredataandprograminstructionsforCPUtoexecute.Amemoryunitisanorderedsequenceofbytes,eachholdseightbits.Aprogramanditsdatamustbebroughttomemorybeforetheycanbeexecuted.A
6、memorybyteisneverempty,butitsinitialcontentmaybemeaninglesstoyourprogram.Thecurrentcontentofamemorybyteislostwhenevernewinformationisplacedinit.6HowDataisStored?Dataofvariouskinds,suchasnumbers,characters,andstrings,areencodedasaseriesofbits(zerosand
7、ones).Computersusezerosandonesbecausedigitaldeviceshavetwostablestates,whicharereferredtoaszeroandonebyconvention.Theprogrammersneednottobeconcernedabouttheencodinganddecodingofdata,whichisperformedautomaticallybythesystembasedontheencodingscheme.The
8、encodingschemevaries.Forexample,character‘J’isrepresentedby01001010inonebyte.Asmallnumbersuchasthreecanbestoredinasinglebyte.Ifcomputerneedstostorealargenumberthatcannotfitintoasinglebyte,itusesanumberofadjacentbytes.Notwodatacanshareorsplitasamebyte