Star Micronics 8 Series - The ASCII table

Theimportantthingtorealizeisthatthere’smorethanonewaytoshowthe
samenumericvalue.Computerprogrammers,forexample,occasionallyuse
thehexadecimalsystembecauseit’s so compact.(Programmersoftenjust
say“hex”.)Thisbinarynumber:
101001011111110100110111111011010010110100001001
looksquiteabittidierwhenitiswrittenasA5FD37ED2D09,whichmeans
thesamething.
TheASCII table
Wheredoes the Star LaserPrinter8 get the charactersand instructionsit
needsto print in the first place?It gets them from yourcomputer,which
sendsa streamof textandcommandsto yourprinter.
Theprogramin yourcomputerthatcontrolseverythingsentto theprinter
(calledthe printer driver) will usuallybe includedwith your computer
programsrsuchasyourwordprocessor.Butthecommandscouldalsocome
fromaprogramyou’vewritten,perhapsinBASIC,aprogramminglanguage
thatusescommonEnglishwords.
Internally,computemand printersuse only the binarynumbersystemto
representboth commandsand all the alphabetic,numericand otherkey-
boardsymbols.Nearlyallof thosemachinesusethe sameschemeto code
thosesymbols,theAmericanStandardsCodefor InformationInterchange
(ASCII). ‘
Anexample:inourfamiliardecimalsystem,binary01001010addsuptothe
number 74. Dependingon which program your printer is using, it can
interpretthatbinarystring01001010aseitherthenumber74orthesymbol
J. TheprinterstoresthesymbolJ atposition74 in a tablein itsmemory.
Thateight-bitbinarystring,orbyte,canbebrokenintotwohalves.Theleft
orhigh-orderpartcontaining0100is calledthezoneportion;therightpart
holdingthe1010iscalledthedigitspdion. Andinthehexadecimalnumber
system,the zone and digit parts of that byte are representedas 4 and A
respectively(lookthemup in thelist above).
SothelaserprinterunderstandsthesymbolJ as 01001010,whichwecan
alsorepresentas the decimalnumber74 or the hexadecimalnumber4A.
We’veprintedthisbyteverticallyandhorizontallybelow,showinghowit
addsup to decimal74 andhex 4A.
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