南开大学现代物流研究中心.ppt

01040203Today’scomputersarebasedonintegratedcircuits(chips),eachofwhichincludesmillionsofsubminiaturetransistorsEachtransistorcanbeineitheran“on”or“off”positionThe“on-off”statesoftransistorsareusedtostoreonebinarydigit,orbit(representedinthebinarynumbersystembya0ora1)Combinationsofbitscanbeusedtostorenumbers,characters,andmultimediafilesAnswerComputerSystemComponentsTheEvolutionofComputerHardwareFirstgeneration(1946to1956)VacuumtubesSecondgeneration(1957to1963)TransistorsThirdgeneration(1964to1979)IntegratedcircuitsFourthgeneration(1980topresent)Largerscaleintegratedcircuits(LSI,VLSI,ULSI,andGSI)Fifthgeneration?NumberRepresentationandProcessingNumbersmaybestoredinlogicalgroupingsofbits(usually16or32)Theymaybestoredasintegersorasfloating-pointnumbersThefirstbitmaybeusedtoindicatethesign(positiveornegative)TheALUusessixsimpleoperations–add,subtract,multiply,divide,compare,anddeterminewhetheranumberispositive,negative,orzeroNumbersmayberepresentedinbinary,decimal,orhexadecimalformatsCharacterRepresentationAsufficientnumberofbitstorepresentspecificcharacters(letters,numericalcharacters,andspecialsymbols)isknownasabyte,usually8bitsBecauseabithasonlytwostates,0or1,thebitscomprisingabytecanrepresentanyof28,or256,uniquecharactersThetwomostcommonlyusedcodingschemesare:Formicrocomputers-theAmericanNationalStandardCodeforInformationInterchange(ASCII),pronounced“ask-ee”Formainframecomputers–theExtendedBinaryCodedDecimalInterchangeCode(EBCDIC),pronounced“ebsa-dick”Whymaythisnotworkforallhumanlanguages?AbstractThenextinformationrevolutioniswellunderway.Butitisnothappeningwhereinformationscientists,informationexecutives,andtheinformationindustryingeneralarelookingforit.Itis