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1、DataRepresentationChapter2天津大学软件学院2.1DATATYPES(数据类型)Datatodaycomeindifferentformssuchasnumbers,text,images,audio,andvideo.Peopleneedtoprocessallthesedatatypes.Thecomputerindustryusestheterm “multimedia”todefineinformationthatcontainsnumbers,text,imag
2、es,audio,andvideo.number：数值text：文本image：图像audio：音频Video：视频Multimedia:多媒体AnalogandDigital(模拟和数字)InformationComputersarefinite（有限的）.Computermemoryandotherhardware（硬件）deviceshaveonlysomuchroomtostoreandmanipulateacertainamountofdata.Thegoalofdatareprese
3、ntation（数据表示）istorepresentenoughoftheworldtosatisfyourcomputationalneedsandoursensesofsightandsound.AnalogandDigitalInformationInformationcanberepresentedinoneoftwoways:analogordigital.AnalogdataAcontinuousrepresentation,analogoustotheactualinformati
4、onitrepresents.DigitaldataAdiscreterepresentation,breakingtheinformationupintoseparateelements.AnalogandDigitalInformationAmercurythermometerexemplifiesanalogdataasitcontinuallyrisesandfallsindirectproportiontothetemperature.Digitaldisplaysonlyshowdi
5、screte（离散的）information.2.2DATAINSIDETHECOMPUTERAlldatatypesfromoutsideacomputeraretransformedintoauniformrepresentationwhenstoredinacomputerandthentransformedbackwhenleavingthecomputer.Thisuniversalformatiscalledabitpattern（位组合格式）.BIT（位）Abit(binarydi
6、git)isthesmallestunitofdatathatcanbestoredinacomputer;itiseither0or1.BITPATTERN（位组合格式）Abitpatternisasequence,orasitissometimescalled,astringofbitsthatcanrepresentasymbol.e.g.BYTE（字节）Abitpatternoflength8iscalledabyte.Examplesofbitpatterns2.3REPRESENTI
7、NGDATATEXT（文本）Apieceoftextinanylanguageisasequenceofsymbolsusedtorepresentanideainthatlanguage.Youcanrepresenteachsymbolwithabitpattern.Inotherwords,textsuchas“BYTE”,whichismadeoffoursymbols,canberepresentedas4bitpatterns,eachpatterndefiningasinglesy
8、mbol.Howmanybitsareneededinabitpatterntorepresentasymbolinalanguage?Thelengthofthebitpatternthatrepresentsasymbolinalanguagedependsonthenumberofsymbolsusedinthatlanguage.Moresymbolsmeanalongerbitpattern.Therelationshipisnotlinear;itislogarithmic.Ifyo
