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How theprogram works
Thisprogrambeginsby assigninga numberof printercommandsto BASIC
stringvariables(lines1000to 1070).Youcanfindmostof thesecommands
near the begiming of chapter4.
The WIDTH"LPT1:"255 statementin line 1090meansinfiniteline width.
It preventsthe IBM-PCfrom insertingunwantedcarriagereturnsand line
feeds in graphicsdata.
Actualprintingbeginsin line 1100.Usingthe preassignedcommands,the
programprints samplesof its differentfonts, followedby samplesof the
print pitches,then somedoubleand quadruple-sized printing.
Next comes the central attractionof the program: a line of text printed
fourteentimesin expandingandcontracting loopstogiveabarreleffect.The
workis doneby fourprintercommands:a commandsettingtherightmargin
(line 1370);a centeringcommand(line 1390);a commandto vary the line
spacing(lines 1410and 1460);and a commandto micro-adjustthe space
betweencharactem(lines 1420and 1470).
Nexttheprogramreturnstonormalspacingandgivesa demonstration ofthe
printer'sword-processingabilities:italicprinting,bold printing,underlin-
ing, subscripts,etc.
The row of automobilesin the nextprintedline is createdby downloading
two new characterpatterns,whichare printedin placeof the character"<"
(character60). Detailscan be foundin Chapter5.
The finalpart of the programuses dot graphicsto print some"SW" logos
withvariousdensities.Thedotpatternof thelogowasoriginallylaid outon
graphpaper,then convertedto the datain lines 2370to 2630with the help
of a calculator.Each numberrepresentseightverticaldots. (See "Graphics
commands"in Chapter4 for details.)
The patternis printedin four rows,each eightdots high and 65 dots wide.
Lines 1800 to 1870 read the dot data into a string array variablenamed
LOGO$.Line 1880sets the line spacingto 8/72inch so that tie rows will
connectvertically.The loop in lines 1890to 1990doesthe printingin four
passesof the print head.
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