Vysvětlení
CommonexternalstorageofPCsarefloppydiskstorage,harddiskstorage,opticaldiskstorageWait.Therearetwotypesofdisks:floppydisksandharddisks.Therearethreetypesofopticaldiscs:CD-ROM,write-onceopticaldiscWORMandrewritableopticaldiscMO.
Úvod
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.
Pevný disk: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.
Typ
Diskety, pevné disky, optické disky, Udisky a pásky jsou skutečným externím úložištěm.
FromtheworkingprincipleofvonNeumann'sstoredprogramandthecompositionofthecomputer,thecomputerisdividedintoarithmeticunit,controller,memoryandinput/outputdevice.Thememoryherereferstothememory,andtheharddiskBelongstoinput/outputdevices.
TheprogramcodeanddatarequiredforCPUoperationscomefromthememory,andthethingsinthememorycomefromtheharddisk,sotheharddiskdoesnotdirectlydealwiththeCPU.
Ve srovnání s pamětí, pevným diskem s externím úložištěm.
Memoryisusedtostoredata.Thememoryhashigh-speedcacheandmemory.TheinternalstorageofthecomputerandtheexternalstorageareexternalstoragesimilartoUdisk.
Theinternalmemoryisfastandexpensive,andthecapacityissmall.Thedatainthememorywillbelostafterapowerfailure.(ROMisnotlostwhenpowerisoff)
Externalmemoryhaslowunitprice,largecapacity,slowspeed,anddatawillnotbelostafterpoweroff.
Výkonnostní indikátory
Pevný disk
●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
●Teoretická rychlost čtení dat: 18 MB/s
●Teoretická rychlost zápisu dat: 17 MB/s
●Instalace Nodriveru (kromě Windows98)
●Žádný přídavný zdroj napájení, pouze USB pro získání napájení
●Velká kapacita, mnoho druhů
●Withwriteprotectionswitchtopreventfilesfrombeingerased,antivirus
●LEDindikátorlightindikacePracovnístav
●Malá velikost a lehká: asi 20 g