CHAPTER 7 Storage 4.ppt

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1、CHAPTER7StorageCDsandDVDsOpticalDisksCompactPermanentstorageOpticaldiskusereflectedlight.The1sand0sarerepresentedbyflatareascalledlandsandbumpyareascalledpits.TwocommontypesCD(650MBto1GB)DVD(4.7GBto17GB)2CompactDiscOpticalformatFrom650MBto1GBcapacityRotationspeedsvaryItdet

2、ermineshowfastdatacanbetransferredfromtheCD24Xor24-speedCDdrivecantransfer3.6MBpersecond.TypesReadonly:CD-ROMWriteonce:CD-RRewriteable:CD-RWPictureCDsandPhotoCDs3DigitalVersatileDiscDigitalVersatileDiskorDigitalVideoDisk(DVD)SimilartoCDs,butcanstoremoredataTypesReadonlyWri

3、teonceRewritableCD’sandDVD’sHistory:TheCompactDisc,andmorespecificallyaudiocompactdisc(CD-DA),wasintroducedtothemarketin1982(Japan)bythePhilipsandSonyCorporationsasanalternativetothevinyldiscandaudiocassette.Beethoven’s5thSymphonyestablishedthecapacityofthefirstaudioCD’s.5

4、CD’sandDVD’sHistory:(conti.)In1984bothcompaniesextendedthetechnologysoitcanbeusedtostoreandretrievedataandsotheCD-ROMwasborn.In1990againPhilipsandSonyexpandedthetechnologyandcreatedtherecordablecompactdisc(CD-R).Uptothen,theCD-ROMsweremanufacturedbyindustrialstampingwitham

5、astermadefromtheoriginal.6CD’sandDVD’sHistory:(conti.)In1991thePioneerCorporationbegandevelopmentofanewDigitalVideoDiscformat.Duringthistimesignificantadvancesinsoftwaredevelopment,specialtycompressionalgorithmsforvideoapplicationsweredevelopedsothattheCDdisksizecouldbemai

6、ntained.In1995Sonyleda9companyconsortiumtointroduceastandardforrecordableDVDs.Today,though,theDVDrecordableisnotstandardizedandtwotypesofsystemscoexists:DVD-RandDVD+R.7CD’sandDVD’sCDsandDVDsalthoughtheylookthesametheyarealldifferent.Oneachdiskisamediadescriptorthattellsthe

7、computerwhattypeofdiskitis.CD-RstechnicallyWORMs(WriteOnceReadMany)areoncewrittentooandareread-only.Approximatecapacityis80minutesofaudioor700MBofdata.CD-RWsarereadwriteable(orreusable)andwithpropersoftwarecanbeusedlikeafloppydisk.Approximatecapacityis74minutesofaudioor650

8、MBofdata.8CD’sandDVD’sCDFormats:CD-DA(CompactDisk–DigitalAudio),theoriginalformat,isavari