The importantthingto realizeis thatthere’smorethanone wayto showthe samenumericvalue.Computerprogrammers,forexample,occasionallyuse the hexadecimalsystembecauseit’s so compact.(Programmersoftenjust say “hex”.)This binarynumber:
101001011111110100110111111011010010110100001001
looksquiteabittidierwhenitis writtenasA5FD37ED2D09,whichmeans the same thing.
The ASCII table
Where does the Star LaserPrinter8 get the charactersand instructionsit needs to print in the first place? It gets them from your computer,which sendsa streamof text and commandsto yourprinter.
The programin your computerthat controlseverythingsent to the printer (called the printer driver) will usually be included with your computer programsrsuchas yourwordprocessor.Butthecommandscouldalsocome froma programyou’vewritten,perhapsin BASIC,aprogramminglanguage that uses commonEnglishwords.
Internally,computemand printersuse only the binary number system to representboth commandsand all the alphabetic,numeric and other key- board symbols.Nearlyall of thosemachinesuse the same schemeto code those symbols,the AmericanStandardsCodefor InformationInterchange
(ASCII). ‘
Anexample:in ourfamiliardecimalsystem,binary01001010addsup tothe number 74. Dependingon which program your printer is using, it can interpretthatbinarystring01001010as eitherthenumber74 or the symbol J. The printer storesthe symbolJ at position74 in a table in its memory.
So the laser printerunderstandsthe symbolJ as 01001010, which we can also representas the decimalnumber74 or the hexadecimalnumber4A. We’veprintedthis byteverticallyand horizontallybelow,showinghow it addsup to decimal74 and hex 4A.
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