Star Micronics 4 manual TheASCII table

The importantthingto realizeis thatthere’smorethanone wayto showthe samenumericvalue.Computerprogrammers,forexample,occasionallyuse the hexadecimalsystembecauseit’s so compact.(Programmersoftenjust say “hex”.)This binarynumber:

1010010111111101001101101101OO1O11O1OOOO1OO1

looksquiteabittidierwhenitiswrittenasA5FD37ED2D09, whichmeans the same thing.

1.2.2 TheASCII table

Where does the Star LaserPrinter4 get the charactersand instructionsit needs to print in the first place’?It gets them fmm your computer,which sends a streamof text and commandsto yourprinter.

The programin your computerthat controlseverythingsent to the printer (called the printer driver) will usually be included with your computer programs;suchas yourwordprocessor.Butthe commandscouldalsocome froma programyou’vewritten,perhapsin BASIC,aprogramminglanguage that uses commonEnglishwords.

Internally,computemand printersuse only the binary number system to representboth commandsand all the alphabetic,numericand other key- board symbols.Nearly all of thosemachinesuse the same schemeto code those symbols,the AmericanStandardsCodefor InformationInterchange (ASCII).

Anexample:in ourfamiliardecimalsystem,binary01001010addsupto the 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.

Thateight-bitbinarystring,or byte,canbe brokenintotwohalves.The left or high-orderpart containing0100is calledthe zoneportion;the rightpart holdingthe 1010iscalledthedigitsportion.Andinthehexadecimalnumber system, the zone and digit parts of that byte are representedas 4 and A respectively(lookthem up in the list above).

So the laser printerunderstandsthe symbolJ as 01001010, whichwe can also representas the decimalnumber74 or the hexadecimalnumber4A. We’veprintedthis byte verticallyand horizontallybelow,showinghow it addsup to decimal74 and hex 4A.

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