Java Reference
In-Depth Information
tricalandElectronicsEngineers(IEEE)andtheAmericanNationalStan-
dardsInstitute(ANSI)formallyapprovedmathematicalstandardsfor
digitalcomputers.
Sinceelectronictechnologyisbasedonbi-stablecomponents,thebi-
narynumbersystemhasbeenalmostuniversallyadoptedforcomputer
data.Datastoredinprocessorregisters,inmagneticmedia,inopticalde-
vices,orinpunchedtape,isencodedinbinary.Theprogrammerandthe
machineoperatoroftenignorethephysicalcharacteristicsofthestorage
medium,sinceabinarynumbercanberepresentedbyholesinastripof
papertape,bymagneticchargesonamylar-coateddisk,byvoltagelevels
inanintegratedcircuitmemorycell,orbythedepthofminutecraterson
thesurfaceoftheCD.
Computer word size
Inelectronicdevicesstatesarerepresentedbyabinarydigit.Circuitde-
signersgroupseveralindividualcellstoformaunitofstoragethatholds
severalbits.Inaparticularmachinethebasicunitofdatastorageiscalled
the
wordsize
.
Table20-1
liststhewordsizeofsomehistoricalcomputer
systems.
Table 20-1
Computer Word Size in Historical Systems
COMPUTER FAMILY
WORD SIZE
TRS 80 Microcomputers (Z80 processor)
8 bits
Apple Microcomputers (6502 processor)
Original PC and other microcomputers
16 bits
equipped with Intel 8086, 8088 or 80286 CPU
DEC PDP 11
PS/2 line and other PCs equipped with
32 bits
the Intel 80386, 486, or Pentium
IBM 360/370 series
IBM 303X, 308X series
DEC VAX 11
Prime computers
DEC 10
36 bits
UNIVAC
Honeywell
CDC 6000
60 bits
CDC 7000
CDC CYBER series
