计算机基本知识(第4课)

Chapter7ObjectivesDifferentiatebetweenstoragedevices

andstoragemediaDescribethecharacteristicsof

magneticdisks(磁盘)Describethecharacteristicsof

aharddiskDiscussvarioustypesofminiature(微型的),external(外部的),andremovableharddisksDescribethecharacteristics

ofopticaldiscs(光盘)DifferentiateamongCD-ROMs,

recordableCDs,rewritableCDs,DVD-ROMs,BD-ROMs,HDDVD-ROMs,recordableDVDs,andrewritableDVDsIdentifytheusesoftape(录音带)DiscussPCCards,ExpressCardmodules,andthevarioustypesofminiaturestoragemediaIdentifyusesofmicrofilm(微型胶卷)andmicrofiche(单片缩影胶片)NextStorageWhatis

storage?p.354-355Fig.7-1NextHoldsdata,instructions,andinformationforfutureuseStoragemedium

isphysicalmaterialusedforstorageAlsocalledsecondary(二次)storageStorageWhatis

capacity(容量)?p.356NextKilobyte(KB)1thousandMegabyte(MB)1millionGigabyte(GB)1billionTerabyte(TB)1trillionPetabyte(PB)1quadrillionNumberofbytes(characters)astoragemediumcanholdExabyte(EB)1quintillionZettabyte(ZB)1sextillionYottabyte(YB)1septillionStorageMedium

(floppydisks,Zipdisks,

harddisks,CDs)StorageHowdoesvolatility(易失性)compare?p.356NextNonvolatileStoragemediumisnonvolatile—contentsretainedwhenpowerisoffContents

retainedContentsavailabletouserMemory

(mostRAM)

(chipsonmotherboard)ScreenDisplayONOFFVolatileDisplaydisappearsDataand

instructionsavailabletouserDisplayappearsDataandinstructionserasedMemoryisvolatile—holdsdataandinstructionstemporarily(暂时的)WritingProcessoftransferring

itemsfrommemory

tostoragemediaStorageWhatisa

storagedevice?p.356NextReadingProcessoftransferring

itemsfromstorage

mediatomemoryHardwarethat

recordsand

retrievesitems

toandfrom

storagemediaFunctionsassource

ofinput

CreatesoutputFloppyDisk(软盘)SmallfilestobetransportedSecondaryStoragePrimaryStorageHardDiskFlashMemoryCards

andUSBFlashDrivesCDsandDVDsTapeItemswaitingtobeinterpreted

andexecutedbytheprocessorOperatingsystem,application

software,userdataandinformationDigitalpicturesorfiles

tobetransportedSoftware,backups,movies,musicBackupsMemory(mostRAM)Stores…TransferratesStorageWhatis

accesstime(存取时间)?p.357Fig.7-4TimeittakesstoragedevicetolocateitemonstoragemediumNextTimerequiredtodeliveritemfrommemorytoprocessorfaster

transfer

ratesslower

transfer

ratesMagneticDisksp.357Fig.7-5NextWhatare

tracks(磁道)

and

sectors(扇区)?FormattingpreparesdiskforuseTrack

isnarrowrecordingband

thatformsfull

circleondiskSector

storesupto

512bytes

ofdataPerpendicular(垂直的)recordingMagneticDisksWhatisa

harddisk?p.358Fig.7-6Nextharddiskmounted

insystemunitHigh-capacitystorageConsistsofseveralinflexible(坚硬的),circularplattersthatstoreitemselectronicallyComponentsenclosed(附在)inairtight(不透气的),sealed(密封的)caseforprotectionClicktoviewWebLink,

clickChapter7,ClickWebLink

fromleftnavigation,thenclickPerpendicularRecordingbelowChapter7Longitudinal(纵向的)recordingMagneticDisksWhatarecharacteristicsofaharddisk?p.359Fig.7-7NextSampleHardDiskCharacteristicsAdvertisedcapacity 500GBPlatters 4Read/writeheads 8Cylinders(柱面数) 16,383Bytespersecond 512Sectorspertrack 63Sectorsperdrive 973,773,168Revolutions(转数)perminute 7,200Transferrate 300MBpersecondAccesstime 8.5msactual

disk

capacityMagneticDisksHowdoesaharddiskwork?p.360Fig.7-8NextStep1.

Circuitboardcontrolsmovementofheadactuatorandasmallmotor(马达).Step2.

Smallmotorspins(旋转)platterswhilecomputerisrunning.Step3.

Whensoftwarerequestsadiskaccess,read/writeheadsdeterminecurrentornewlocationofdata.Step4.

Headactuatorpositionsread/writeheadarmsovercorrectlocationonplatterstoreadorwritedata.MagneticDisksWhatisa

cylinder(磁柱)?p.360Fig.7-9NextVertical(垂直的)section(截面)oftrackthroughallplattersSinglemovementofread/writeheadarmsaccessesallplatters

incylinderplatterread/write

headplattersidescylindertracksectorMagneticDisksWhatisa

headcrash(磁头划碰)?p.360-361Fig.7-10NextSpinningcreatescushionofairthatfloatsread/writeheadaboveplatterOccurswhenread/writeheadtouchesplattersurfaceAsmokeparticle(微粒),dustparticle,orhumanhaircouldrender(导致)driveunusableClearance(空隙)betweenheadandplatterisapproximately(大约)two-millionths(两百万分之一)ofaninchNextMagneticDisksWhatisa

diskcache(磁盘高速缓冲)?p.361Fig.7-11Portion(一部分)ofmemorythatprocessorusestostorefrequentlyaccesseditemssecondrequest

fordata—toharddiskfirstrequest

fordata—todiskcacheNextMagneticDisksWhatisRAID(磁盘冗余阵列)?p.362RedundantArrayofIndependentDisksConnectsmultiplesmallerdisksintoasingleunitthatactsasasinglelargeharddiskNextMagneticDisksWhatisaminiature(微型)harddisk?p.362Fig.7-13ProvidegreaterstoragecapacitiesthanflashmemorySmallerthannotebookcomputerharddisksApocketharddriveisaself-containedunitClicktoviewWeb

Link,clickChapter7,Click

WebLinkfromleft

navigation,thenclick

PocketHardDrives

belowChapter7MagneticDisksWhatare

externalharddisks

and

removableharddisks?p.363Fig.7-14NextExternalharddisk—freestanding(独立的)

harddiskthatconnectstosystemunitRemovableharddisk—harddisk

thatyouinsertandremove

fromharddiskdriveUsedtobackup(备份)ortransferfiles

SCSI(小型计算机系统接口)

controllersupportsuptofifteen

devicesincludingharddisks,CD

andDVDdrives,tapedrives,printers,

scanners,networkcardsSATA(SerialAdvancedTechnologyAttachment)(串行ATA接口规范)controllerusesserialsignalstotransferdata,instructions,andinformationMagneticDisksWhatisa

diskcontroller?p.363-364NextEIDE(Enhanced

Integrated

DriveElectronics)(增强型IDE接口)controllersupportsfourharddisks,providesconnectionsforCDandDVDdrivesChipandcircuitsthatcontroltransferofitemsfromdiskMagneticDisksWhatisonlinestorage?p.364-365Fig.7-15NextOtherscanbeauthorizedtoaccessyourdataServiceonWebthatprovidesstorageforminimalmonthlyfee(酬金)FilescanbeaccessedfromanycomputerwithWebaccessLargefilescanbedownloadedinstantaneously(即时)linkMagneticDisksWhatisa

floppydisk(软盘)?p.365Fig.7-16NextPortable,inexpensive(便宜的)storagemedium(alsocalleddiskette(磁盘))Thin,circular,flexible(柔韧的)filmenclosedin3.5”wideplasticshellPushthesamebutton

toclosethetray.OpticalDiscsWhatare

opticaldiscs?p.366Fig.7-17NextMostPCsincludeanopticaldiscdriveFlat,round,portablemetaldiscsmadeofmetal,plastic,andlacquer(漆)Canbereadonlyorread/writeInsertthedisc,

labelsideup.Pushthebuttonto

slideoutthetray.OpticalDiscsHowdoesalaserreaddataonanopticaldisc?p.367Fig.7-18Nextlaser

diodelaser

diodeprismprismlight-

sensing

diodelight-

sensing

diode01lenslenspitlanddisclabelStep1.

Laserdiodeshinesalightbeamtoward

disc.Step2.

Iflightstrikes

apit,itscatters.Iflightstrikesaland,itisreflectedbacktowarddiode.Step3.

Reflectedlightisdeflectedtoa

light-sensingdiode,whichsendsdigitalsignalsof1tocomputer.Absenceofreflectedlightisreadasdigitalsignalof0.OpticalDiscsHowisdatastoredonanopticaldisc?p.367Fig.7-19NextTypicallystoredinsingle

trackTrackdivided

intoevenly(平均的)

sized

sectors

thatstore

itemssingletrack

spiralstoedge

ofdiscdiscsectorsOpticalDiscsHowshouldyoucareforanopticaldisc?p.368Fig.7-20NextOpticalDiscsWhatisa

CD-ROM?p.369Fig.7-22NextCompact(坚实的)

disc

read-only

memoryCannoteraseormodifycontentsTypicallyholds650MBto1GBCommonlyusedtodistributemultimediaandcomplexsoftwareOpticalDiscsWhatisthedatatransferrateofaCD-ROMdrive?p.369Next75XRangesfrom

48Xto75X

orfaster75

150KBps=11,250KBps

or12.25MBps75Xis150KBps

(KBpersecond)48X:

48

150KBps=7,200KBps

or7.2MBpsOpticalDiscsWhatisa

PictureCD?p.370Fig.7-23NextFilmdevelopers

offer(提供)

PictureCD

serviceCanbe

modified(修改)

usingphoto

editingsoftwareStoresdigital

versionsof

rolloffilmStep3.

Athome,printimages

fromPictureCDon

yourink-jetphotoprinter.Atastore,printimagestoPictureCDatkiosk.Step1.

Dropofffilmtobedeveloped.MarkthePictureCDboxonthefilm-processingenvelope.Step2.

Whenyoupickupprintsandnegatives,aPictureCDcontainsdigitalimagesofeachphotograph.ClicktoviewWebLink,

clickChapter7,ClickWebLink

fromleftnavigation,thenclickPictureCDsbelowChapter7OpticalDiscsWhatare

CD-RsandCD-RWs?p.370-371NextMusthave

CDrecorder

orCD-RdriveCannoterase

disc’scontentsCD-R(compactdisc-recordable)—cdiscyoucanwriteononceCD-RW(compactdisc-rewritable)—ceerasablediscyoucanwriteon

multipletimesMusthave

CD-RWsoftware

and

CD-RWdriveOpticalDiscsVideo:GotYourVideoRightHereNextCLICKTOSTARTOpticalDiscsWhatisa

DVD-ROM

(digitalversatile(多功能)disc-ROMordigitalvideodisc-ROM)?p.372Fig.7-24NextMusthave

DVD-ROMdrive

orDVDplayertoreadDVD-ROMStoresdatabases,music,complexsoftware,andmoviesBlu-ray(蓝光)discshavestoragecapacityofupto100GBHD-DVDdiscs(高密度数字多功能光盘)havestoragecapacityofupto60GBUMDcanstoreupto1.8GBOpticalDiscsHowdoesaDVD-ROMstoredata?p.372-373Fig.7-25NextTwolayersofpitsareused,lowerlayerissemitransparent(半透明的)solasercanreadthroughSomearedouble-sidedManytypesofrecordableandrewritableDVDsareavailableDVD-RandDVD+RDVD-RWandDVD+RWTapeWhatis

tape?p.374Fig.7-27NextMagnetically(磁性的)coatedplasticribbon

capableofstoringlargeamounts

ofdataatlowcostPrimarilyusedforbackup(备份)TapeHowisdatastoredonatape?p.374NextSequential(按次序的)accessUnlikedirectaccess—usedonharddisks,CDs,andDVDs—whichcanlocate(指出)particular(特定的)itemimmediatelyReadsandwritesdataconsecutively(连贯的),likemusictapePCCardsandExpressCardModulesWhatare

PCCardsandExpressCardModules?p.374Figs.7-28NextAddscapabilitiestocomputerCredit-card(信用卡)-sizeddevicecommonlyusedinnotebookcomputersMiniatureMobileStorageMediaWhatis

miniature(微型的)mobilestoragemedia?p.375Fig.7-29NextStorageforsmallmobiledevicesMiniatureMobileStorageMediaWhatarecommontypesofflashmemorycards?p.376Fig.7-30NextCompactFlashSecureDigitalxDPictureCardMemoryStickMemoryStickPRODuoMiniatureMobileStorageMediap.377Fig.7-31NextHowdoesonetypeofflashmemorycardwork?MiniatureMobileStorageMediaWhatisa

USBFlashDrive?p.377Fig.7-32NextPlugsinaUSBportonacomputerormobiledeviceStoragecapacitiesupto64GBMayeventuallymakethefloppydiskobsolete(过时的)MiniatureMobileStorageMediaWhatisa

smartcard?p.378Fig.7-33NextStoresdataonmicroprocessor(微处理机)embeddedinsmallcardInput,process,output,andstoragecapabilitiesMicrofilmandMicroficheWhatare

microfilm

and

microfiche(单片缩影胶片)?p.379Fig.7-34NextImagesrecordedusing

computerou