FILE ALLOCATION TABLE (FAT)
Allocatesspaceonthediskforfiles,oneclusteratatime;locksoutunusableclusters; identifiesunused(free)area;andlistsafile’slocation.WithtwoFAT’spresent,the secondcopyensuresconsistencyandprotectsagainstlossofdataifoneofthesectorson thefirstFATisdamaged.
FLUX CHANGES PER INCH
Synonymouswithfrpi(fluxreversalsperinch).OnlyinMFMrecordingdoes1fci
FORMAT
FORMATTED CAPACITY
Theactualcapacityavailabletostoredatainamassstoragedevice.Theformatted capacityisthegrosscapacity,lessthecapacitytakenupbytheoverheaddatausedin formattingthesectors.
FREQUENCY MODULATION
Arecordingcode.Afluxreversalatthebeginningofacelltimerepresentsclockbit;a “1”bitisafluxreversalatthecenterofthecelltime,anda“0”bitisanabsenceofa fluxreversal.
FREQUENCY RESPONSE
Ameasureofhoweffectivelyacircuitordevicetransmitsthedifferentfrequencies appliedtoit.Indiskandtapedrivesthisreferstotheread/writechannel.Indisk drives,itcanalsorefertothedynamicmechanicalcharacteristicsofapositioning system.
G
GIGABYTE (GB)
Onebillionbytes(onethousandmegabytes)or109.
H
HARD ERROR
Anerrorthatisnotabletobeovercomebyrepeatedreadingsandrepositioningmeans.
HARD SECTORED
Atechniquewhereadigitalsignalindicatesthebeginningofasectoronatrack.Thisis contrastedtosoftsectoring,wherethecontrollerdeterminesthebeginningofasector bythereadingofformatinformationfromthedisk.
HEAD
Theelectromagneticdevicethatwrite(records),reads(playsback),anderasesdataona magneticmedia.Itcontainsareadcore(s)and/orawritecore(s)and/orerasecore(s) whichis/areusedtoproduceorreceivemagneticflux.Sometimesthetermisall inclusivetomeanthecarriageassemblywhichincludesthesliderandflexure.
HEAD CRASH
Theinadvertenttouchingofadiskbyaheadflyingoverthedisk(maydestroya portionofthemediaand/orthehead).
HEAD DISK ASSEMBLY (HDA)
Themechanicalportionofarigid,fixeddiskdrive.Itusuallyincludesdisks,heads, spindlemotor,andactuator.
HEAD LOADING ZONE
HEAD POSITIONER
Alsoknownasactuator,amechanismthatmovesthearmsthatcarryread/writeheads tothecylinderbeingaccessed.
I
INDEX
Similartoadirectory,butusedtoestablishaphysicaltologicalcrossreference.Usedto updatethephysicaldiskaddress(tracksandsectors)offilesandtoexpediteaccesses.
GLOSSARY
INSIDE DIAMETER
Thesmallestradialpositionusedfortherecordingandplaybackoffluxreversalsona magneticdisksurface.
INITIALIZATION
Applyinginputpatternsorinstructionstoadevicesothatalloperationalparametersare ataknownvalue.
INPUT
Dataenteringthecomputertobeprocessed;alsousercommands.
INPUT/OUTPUT (I/O)
Theprocessofenteringdataintoorremovingdatafromacomputersystemora peripheraldevice.
INTELLIGENT PERIPHERAL
Aperipheraldevicethatcontainsaprocessorormicroprocessortoenableittointerpret andexecutecommands.
INTERFACE
Thedatatransmitters,datareceivers,logic,andwiringthatlinkonepieceofcomputer equipmenttoanother,suchasadiskdrivetoacontrolleroracontrollertoasystem bus.
INTERFACE STANDARD
Theinterfacespecificationsagreedtobyvariousmanufacturerstopromoteindustry- wideinterchangeabilityofproductssuchasadiskdrive.Interfacestandardsgenerally reduceproductcosts,allowsbuyerstopurchasefrommorethanonesource,andallow fastermarketacceptanceofnewproducts.
INTERLEAVE
Anorderingofphysicalsectorstobeskippedbetweenlogicalsectorsonyourhard disk.
I/O PROCESSOR
Intelligentprocessororcontrollerthathandlestheinput/outputoperationsofa computer.
INTERRUPT
Asignal,usuallyfromasubsystemtoacentralprocessingunit,tosignifythatan operationhasbeencompletedorcannotbecompleted.
J
JUMPER
Asmallpieceofplasticthatslidesoverpairsofpinsthatprotrudefromthecircuitboard ontheharddrivetomakeanelectricalconnectionandactivateaspecificoption.
K
KILOBYTE (KB)
Aunitofmeasureofapproximately1,000bytes.(However,becausecomputer memoryispartitionedintosizesthatareapoweroftwo,akilobyteisreally1,024 bytes.)
L
LANDING ZONE OR LZONE
ThecylindernumbertowhereParkHeadsmovetheread/writeheads.
LATE BIT
Abitthatisinthelatehalfofthedatawindow.
LATE WINDOW
Adatawindowthathasbeenshiftedinalatedirectiontofacilitatedatarecovery.
LATENCY
Adelayencounteredinacomputerwhenwaitingforaspecificresponse.Inadisk drivethereisbothseeklatencyandrotationallatency.Thetimerequiredforthe addressedsectortoarriveundertheheadaftertheheadispositionedoverthecorrect track.Itisaresultofthedisk’srotationalspeedandmustbeconsideredindetermining thediskdrive’stotalaccesstime.
LOGIC
Electroniccircuitrythatswitchesonandoff(“1”and“0”)toperformfunctions.
GL – 3
