Laser Printer User Manual

Theimportantthingto realizeisthatthere’smorethanonewayto showthe

samenumericvalue.Computerprogrammers,forexample,occasionallyuse

thehexadecimalsystembecauseit’s so compact.(Programmersoftenjust

say“hex”.)Thisbinarynumber:

10100101111111010011011111101101OO1O11O1OOOO1OO1

looksquiteabittidierwhenitiswrittenasA5FD37ED2D09,whichmeans

the samething.

1.2.2TheASCII table

Wheredoes the Star LaserPrinter4 get the charactersand instructionsit

needsto print in the first place’?It getsthem fmm yourcomputer,which

sendsa streamof textandcommandsto yourprinter.

The programin yourcomputerthatcontrolseverythingsentto the printer

(called the printer driver) will usuallybe includedwith your computer

programs;suchasyourwordprocessor.Butthecommandscouldalsocome

fromaprogramyou’vewritten,perhapsinBASIC,aprogramminglanguage

thatuses commonEnglishwords.

Internally,computemand printersuse only the binarynumbersystemto

representboth commandsand all the alphabetic,numericand other key-

boardsymbols.Nearlyallof thosemachinesuse the sameschemeto code

thosesymbols,the AmericanStandardsCodefor InformationInterchange

(ASCII).

Anexample:inourfamiliardecimalsystem,binary01001010addsuptothe

number 74. Dependingon which program your printer is using, it can

interpretthatbinarystring01001010aseitherthenumber74orthesymbol

J. The printerstoresthe symbolJ atposition74in a tablein itsmemory.

Thateight-bitbinarystring,orbyte,canbebrokenintotwohalves.Theleft

or high-orderpartcontaining0100is calledthezoneportion;the rightpart

holdingthe 1010iscalledthedigitsportion.Andinthehexadecimalnumber

system,the zone and digit parts of that byte are representedas 4 and A

respectively(lookthemup in thelist above).

So the laserprinterunderstandsthesymbolJ as 01001010, whichwe can

also representas the decimalnumber74 or the hexadecimalnumber4A.

We’veprintedthisbyteverticallyandhorizontallybelow,showinghowit

addsup to decimal74 andhex4A.