[工学]计算机导论-讲稿

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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,images,audio,andvideo.number：数值

2、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.Thegoalofdatarepresentation（数据表示）istorepresentenoughoftheworldtosatisfyour

3、computationalneedsandoursensesofsightandsound.AnalogandDigitalInformationInformationcanberepresentedinoneoftwoways:analogordigital.AnalogdataAcontinuousrepresentation,analogoustotheactualinformationitrepresents.DigitaldataAdiscreterepresentation,breakingtheinformationupintosep

4、arateelements.AnalogandDigitalInformationAmercurythermometerexemplifiesanalogdataasitcontinuallyrisesandfallsindirectproportiontothetemperature.Digitaldisplaysonlyshowdiscrete（离散的）information.2.2DATAINSIDETHECOMPUTERAlldatatypesfromoutsideacomputeraretransformedintoauniformrep

5、resentationwhenstoredinacomputerandthentransformedbackwhenleavingthecomputer.Thisuniversalformatiscalledabitpattern（位组合格式）.BIT（位）Abit(binarydigit)isthesmallestunitofdatathatcanbestoredinacomputer;itiseither0or1.BITPATTERN（位组合格式）Abitpatternisasequence,orasitissometimescalled,as

6、tringofbitsthatcanrepresentasymbol.e.g.BYTE（字节）Abitpatternoflength8iscalledabyte.Examplesofbitpatterns2.3REPRESENTINGDATATEXT（文本）Apieceoftextinanylanguageisasequenceofsymbolsusedtorepresentanideainthatlanguage.Youcanrepresenteachsymbolwithabitpattern.Inotherwords,textsuchas“BY

7、TE”,whichismadeoffoursymbols,canberepresentedas4bitpatterns,eachpatterndefiningasinglesymbol.Howmanybitsareneededinabitpatterntorepresentasymbolinalanguage?Thelengthofthebitpatternthatrepresentsasymbolinalanguagedependsonthenumberofsymbolsusedinthatlanguage.Moresymbolsmeanalon

8、gerbitpattern.Therelationshipisnotlinear;itislogarithmic.Ifyo