External storage

Explanation

CommonexternalstorageofPCsarefloppydiskstorage,harddiskstorage,opticaldiskstorageWait.Therearetwotypesofdisks:floppydisksandharddisks.Therearethreetypesofopticaldiscs:CD-ROM,write-onceopticaldiscWORMandrewritableopticaldiscMO.

Introduction

Therearemanytypesofmemory,whichcanbedividedintomainmemoryandauxiliarymemoryaccordingtotheiruse.Mainmemoryisalsocalledinternalmemory(memoryforshort),andauxiliarymemoryisalsocalledexternalmemory(Referredtoasexternalstorage).Themostprominentfeatureoftheinternalmemoryisthefastaccessspeed,butthecapacityissmall,andthepriceisexpensive;theexternalmemoryischaracterizedbythelargecapacity,lowprice,buttheaccessspeedisslow.Theinternalmemoryisusedtostoretheprogramsanddatathatareneededimmediately;theexternalmemoryisusedtostorethetemporarilyunusedprogramsanddata.Informationisfrequentlyexchangedbetweeninternalstorageandexternalstorage.Externalstorageisusuallymagneticmediaoropticaldiscs,suchasharddisks,floppydisks,tapes,CDs,etc.,whichcanstoreinformationforalongtimeanddonotrelyonelectricitytostoreinformation.However,drivenbymechanicalcomponents,thespeedismuchslowerthanthatoftheCPU.

Floppydisk:Thefloppydiskusesasoftpolyestermaterialtomakeaprototypefilm,andthetwosurfacesarecoatedwithmagneticmaterials.Thecommonlyusedfloppydiskhasadiameterof3.5inchesandastoragecapacityof1.44MB.Thefloppydiskusesafloppydiskdrivetoreaddata.

Udisk:Udiskisalsocalled"flashdisk",whichcanstoredatathroughtheUSBportofthecomputer.Comparedwithfloppydisks,Udiskshavereplacedfloppydisksduetotheirsmallsize,largestoragecapacityandconvenientportability.

HardDisk:Theharddiskiscomposedofaluminumalloyoriginaldiskscoatedwithmagneticmaterials,andeachharddiskiscomposedofseveralmagneticdisks.

Tapestorage:MagnetictapeisalsocalledsequentialaccessstorageSAM.Ithasalargestoragecapacity,butthesearchspeedisveryslow,andisgenerallyonlyusedasadatabackupstorage.Thereare3typesoftapedrivesusedincomputersystems:reel-to-reeltapedrives,datastreamtapedrivesandspiralscantapedrives.

CD-ROMstorage:CD-ROMreferstoadiscthatusesopticalmethodsforinformationstorage.Itappliesopticalstoragetechnology,thatis,usingalasertowriteinformationonacertainmedium,andthenusingthelasertoreadtheinformation.Discstoragecanbedividedinto:CD-ROM,CD-R,CD-RW,andDVD-ROM,etc.

Type

Floppydisks,harddisks,opticaldisks,Udisks,andtapesareallexternalstorage.

FromtheworkingprincipleofvonNeumann'sstoredprogramandthecompositionofthecomputer,thecomputerisdividedintoarithmeticunit,controller,memoryandinput/outputdevice.Thememoryherereferstothememory,andtheharddiskBelongstoinput/outputdevices.

TheprogramcodeanddatarequiredforCPUoperationscomefromthememory,andthethingsinthememorycomefromtheharddisk,sotheharddiskdoesnotdirectlydealwiththeCPU.

Comparedwithmemory,harddiskisexternalstorage.

Memoryisusedtostoredata.Thememoryhashigh-speedcacheandmemory.TheinternalstorageofthecomputerandtheexternalstorageareexternalstoragesimilartoUdisk.

Theinternalmemoryisfastandexpensive,andthecapacityissmall.Thedatainthememorywillbelostafterapowerfailure.(ROMisnotlostwhenpowerisoff)

Externalmemoryhaslowunitprice,largecapacity,slowspeed,anddatawillnotbelostafterpoweroff.

PerformanceIndicators

HardDisk

●Capacity-usuallyreferredtoasthecapacityreferstothetotalcapacityoftheharddisk,generallytheunitdefinedbytheharddiskmanufactureris1GB=1000MB,Thesystemdefines1GB=1024MB,sotherewillbeasituationwherethenominalvalueontheharddiskisgreaterthantheformattedcapacity.Thisisconsideredanindustrypracticeandisnormal.

●Thecapacityofasinglediscreferstoadisc.Thenumberofbytesthatcanbestored,thesingle-diskcapacityofaharddiskisgenerallymorethan20GB.Withtheincreaseofthesingle-diskcapacityoftheharddisk,thetotalcapacityoftheharddiskcanreachhundredsofGorevenafewterabytes(commerciallypurchasedharddiskcapacity)Ifitis1TB,itmayactuallyonlybe1000GBinsteadof1024GB.Inthetruesense,1TB=1024GB.).

Rotationspeed-Rotationspeedreferstotherotationspeedofthemotorspindleintheharddisk,andtheunitisRPM(revolutionsperminute).Rotationspeedisoneofthedeterminantsoftheinternaltransmissionrateoftheharddisk,anditsspeedisveryslow.Toalargeextent,itdeterminesthespeedoftheharddisk,anditisalsoanimportantcriteriontodistinguishthegradeoftheharddisk.Atpresent,thegeneralharddiskspeedis5400rpmand7200rpm.Thehighestspeedcanreachmorethan10,000rpm.

●ThehighestinternalTransmissionrate-Thisisthetransmissionrateoftheouterringoftheharddisk.Itreferstothehighestdatatransmissionratebetweenthemagneticheadandthehigh-speeddatacache,inMB/s.Theperformanceofthehighestinternaltransmissionrateisrelatedtotheharddiskspeedandthestoragedensityofthedisk.(Singlediskcapacity)isdirectlyrelated.

●AverageseektimeAverageseektimereferstothetimeittakesfortheharddiskheadtomovetothetrackwherethedataislocated,inmilliseconds(ms),theaverageoftheharddiskTheseektimeisgenerallylessthan9milliseconds.Theshortertheaverageseektime,thehigherthecapacityoftheharddisktoreaddata.

Udisk

●Theoreticaldatareadingspeed:18MB/s

●Theoreticaldatawritingspeed:17MB/s

●Nodriverinstallation(exceptforwindows98)

●Noadditionalpowersupply,onlyUsbbustogetpower

●Largecapacity,manyvarieties

●Withwriteprotectionswitchtopreventfilesfrombeingerased,antivirus

●LEDindicatorlightindicationWorkingstatus

●Smallsizeandlightweight:about20g

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