c语言程序设计课件ppt（英文）c program language 之8 file

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1、ChapterSevenFileContentsIntroduction1Open/closefile2Read/writefile3Checkthestateoftheopeningfile4Thelocationofthefilepointer54ChapterSevenHowtogetthedatawhilerunaprogram?Wherewilltheresultin?Howcaninputtheresultofaprogramtoanotherprogram?IntroductionTheproc

2、edureofClanguageEditLinkCreatetheprogramtextCompileCompileitsuccessfullyLinkittotheCfunctionlibraryChapterSevenIntroductionprogramformatoutputcharacteroutputstringoutputinitializationassignmentinputfromkeyboardmemorymemoryformatinputcharacterinputstringinpu

3、tQuestionReaddatafromafileWritedatatoafileChapterSevenIntroductionFileisthegatherofrelatedinformationsavedinmemorydevice(assistantmemory)OSmanagessysteminfilesProcessingfilesmeansfileinput/outprocessing.Procedure1openfile2fileread/write3closefile.Interfacei

4、nput/outdevicesaretreatedasfilesinC.Fileaccessingmethods:1)BufferedI/O(orstreamI/O)2)UnbufferedI/O(orlow-levelI/O)ChapterSevenIntroductionBuffered(temporarystoragelocation)We’lldiscussBufferedI/OinourlectureInbufferedI/O,---openacommunicationareainRAMDISkPR

5、OGRAMOutputfilebufferInputfilebufferTherearetwowaystodealwithfile:BinaryfileASCIIfilestreamChapterSevenIntroductionstreamStreamistheabstractoffileusedtodealwithfile.TherearetwokindsofstreamsinC.ThecharacterisASCIIcode.oneASCIIcodeoccupiesonebyte,newline‘’

6、isendofline.Afterread/writeacharacterfrom/toASCIIfile,thefpincreasesautomaticallytoguaranteetheread/writesequences.TextstreamBinarystreamStoringdatatodiskintheformthesameasinRAM.Example:10000Inbinaryfile,use2bytesInASCIIfile,use5bytesChapterSevenOpen/closef

7、ileHowtomagangeafileinC?PointerOperationsopenfile（loadfile）operatefileusingfunctionsclosefile（removefilefrommemory）BDFACEAfilesystemcreatanewfiledeleteanoldoneread/writeaccessafilebyitsnamemanagethememoryfileusedlimittheuser’srightChapterSevenOpen/closefile

8、Filepointer,pointstoastructurethatcontainsinformationaboutthefile,suchasthelocationofabuffer,thecurrentcharacterpositioninthebuffer,whetherthefileisbeingreadorwritten,andwhethererrorsorendoffilehaveocc