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How theprogram works
ThisprogrambeginsbyassigninganumberofprintercommandstoBASIC
stringvariables(lines1000to 1070).Youcanfmdmostofthesecommands
nearthe beginningof chapter7.
TheWIDTH“LPT1:“255statementinline 1090meansintlnitelinewidth.
It preventsthe IBM-PCfrominsertingunwantedcarriagereturnsandline
feedsin graphicsdata.
Actualprintingbeginsin line 1100.Usingthepreassignedcommands,the
pmgramprintssamplesofitsdiffemntfonts,followedbysarnplesoftheprint
pitches,then somedoubleandquadruple-sizedprinting.
Next comes the central attractionof the program:a line of text printed
fourteentimesinexpandingandcontractingloopstogiveabarreleffect.The
woxicisdonebyfourprintercommands:acommandsettingtherightmargin
(line 1370);a centeringcommand(line 1390);a commandto varytheline
spacing(l”mes1410and 1460);and a commandto micro-adjustthe space
betweencharactem(lines 1420and 1470).
Nexttheprogramreturnstonormalspacingandgivesademonstrationofthe
printer’sword-processingabilities:italicprinting,boldprinting,underlin-
ing,subscripts,etc.
Therowofcarsymbolsinthenextprintedlineiscreatedbydownloadingtwo
new characterpatterns, which are printed in place of the character“<”
(character60).Detailscanbe foundin Chapter8.
‘l%efinalpartoftheprogramusesdotgraphicstopnntsome“SW’’logos with
variousdensities.
The dot pattern of the logo was originallylaid out on graphpaper, then
eonvertedtothedatainlines2400to2670withthehelpofacalculator.Each
number~presentseightverticaldots.(See’’Graphicscommands”inChapter
7 fordetails.)
Thepatternis printedin fourrows,eacheightdotshighand 65 dotswide.
Lines 1770to 1840~ad the dot data into a string array variablenamed
LOGO$.Line 1850setstheline spacingto 8fl’2inchso thatthe rowswill
connectvertically.Theloopinlines1860to 1940andlines1960to 2040do
theprintingin fourpassesoftheprinthead.
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