机械式转轮.ppt

Introduction,Chapter0:Introduction,Computerscienceisthedisciplinethatseekstobuildascientificfoundationforsuchtopicsascomputerdesigncomputerprogramminginformationprocessingetc.Computerscienceprovidestheunderpinningsfortodayscomputerapplicationsaswellasthefoundationsfortomorrowsapplications.,Algorithms:Definitions,Algorithmasetofstepsthatdefineshowataskisperformed.Programarepresentationofanalgorithm.Programmingtheprocessofdevelopingaprogram.Softwareprograms+algorithms.Hardwaremachinery:whateverisntsoftware.,ComputerHistory,Whatiscomputer?,AnAbacus,OriginsofComputingMachines,EarlycomputingdevicesAbacus:positionsofbeadsrepresentnumbers,01600s-1800s機械式(轉輪),積體電路,積體電路可以分為以下幾類：小規模積體電路(SSI英文全名為Small-ScaleIntegration,幾十個邏輯閘以內)。中規模積體電路(MSI英文全名為Medium-ScaleIntegration,幾百個邏輯閘）。大規模積體電路(LSI英文全名為Large-ScaleIntegration,幾萬個邏輯閘）。超大規模積體電路(VLSI英文全名為Very-large-scaleintegration,幾十萬個邏輯閘以上）。甚大規模積體電路(ULSI英文全名為Ultra-LargeScaleIntegration,百萬個邏輯閘以上）。,EarlycomputingdevicesGear-basedmachines(1600s-1800s)PositionsofgearsrepresentnumbersBlaisePascal,WilhelmLeibniz,CharlesBabbage(progressionofflexibility),BlaisePascal1623-1662,FrancePascalMachineAdditionalgorithm,CharlesBabbagesMachine(1792-1871)PrintoutputvaluesonpaperProgrammableHisassistantAugustaAdaByronisoftenidentifiedtodayastheworldsfirstprogrammer.PunchedCardIdeafromJacquardLoomin1801,TheLondonScienceMuseumsreplica,AssembledafterhisdeathbyBabbagesson,usingpartsfoundinhislaboratory.,PunchedCards,Earlydatastorage:punchedcardsFirstusedinJacquardLoom(1801)tostorepatternsforweavingclothStoredprogramsinBabbagesAnalyticalEnginePopularthroughthe1970s,JacquardLoom,JacquardLoom,PunchedCards,Earlycomputers,Basedonmechanicalrelays(繼電器)1940:ModelK:StibitzatBellLaboratories1944:MarkI:HowardAikenandIBMatHarvardBasedonvacuumtubes(真空管)1937-1941:Atanasoff-BerryComputer(ABC)atIowaStateThefirst“computer”,NOCPU,DRAM1940s:Colossus:secretGermancode-breakerDecodeGermanmessagesduringthelatterpartofWorldWarII1940s:ENIAC:MauchlyKilobyte=210=1024“Mega-”normallymeans1,000,000;Megabyte=220=1,048,576“Giga-”normallymeans1,000,000,000;Megabyte=230=1,073,741,824,MassStorageSystems,Non-volatile;dataremainswhencomputerisoffUsuallymuchbiggerthanmainmemoryUsuallyrotatingdisksHarddisk,floppydisk,CD-ROMMuchslowerthanmainmemoryDataaccessmustwaitforseektime(headpositioning)Dataaccessmustwaitforrotationallatency,Figure1.9Adiskstoragesystem,Figure1.10CDstorageformat,Figure1.11Amagnetictapestoragemechanism,Files,File=theunitofdatastoredonamassstoragesystem.LogicalrecordandField=naturalgroupsofdatawithinafilePhysicalrecord=ablockofdataconformingtothephysicalcharacteristicsofthestoragedevice.Buffer=mainmemoryareasometimessetasideforassemblinglogicalrecordsorfieldsofafile,Figure1.12Logicalrecordsversusphysicalrecordsonadisk,Figure1.13Themessage“Hello.”inASCII,Representingtext,Eachprintablecharacter(letter,punctuation,etc.)isassignedauniquebitpattern.ASCII=7-bitvaluesformostsymbolsusedinwrittenEnglishtextUnicode=16-bitvaluesformostsymbolsusedinmostworldlanguagestodayISOproposedstandard=32-bitvalues,Representingnumericvalues,BinarynotationusesbitstorepresentanumberinbasetwoLimitationsofcomputerrepresentationsofnumericvaluesOverflowhappenswhenanumberistoobigtoberepresentedTruncationhappenswhenanumberisbetweentworepresentablenumbers,Figure1.14Thesoundwaverepresentedbythesequence0,1.5,2.0,1.5,2.0,3.0,4.0,3.0,0,Figure1.15Thebasetenandbinarysystems,Figure1.16Decodingthebinaryrepresentation100101,Figure1.17Analgorithmforfindingthebinaryrepresentationofapositiveinteger,Figure1.18ApplyingthealgorithminFigure1.15toobtainthebinaryrepresentationofthirteen,Figure1.19Thebinaryadditionfacts,Figure1.20Decodingthebinaryrepresentation101.101,RepresentingIntegers,UnsignedintegerscanberepresentedinbasetwoSignedintegers=numbersthatcanbepositiveornegativeTwoscomplementnotation=themostpopularrepresentationExcessnotation=anotherlesspopularrepresentation,Figure1.21Twoscomplementnotationsystems,Figure1.22Codingthevalue-6intwoscomplementnotationusingfourbits,Figure1.23Additionproblemsconvertedtotwoscomplementnotation,Figure1.24Anexcesseightconversiontable,Figure1.25Anexcessnotationsystemusingbitpatternsoflengththree,Figure1.26Floating-pointnotationcomponents,