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How theprogram works
Thisprogrambeginsby assigninga numberofprintercommandsto BASIC
stringvariables(lines1000to 1090).Youcanfindmostofthesecommands
nearthe beginningof chapter4.
TheWIDTH“LPT1:”255 statementin line 1110meansinfiite line width.
It preventsthe IBM-PCfrom insertingunwantedcarriagemtums andline
feeds in graphicsdata.
Actualprintingbeginsin line 1120.Usingthepreassignedcommands,the
programprintssamplesof its diffenmtfonts,includinga line showingall
stylesin italics,followedby samplesof theprintpitches,thensomedouble
and quadruple-sizedprinting.
Next comes the central attractionof the program: a line of text printed
fourteentimesinexpandingandcontractingloopstogiveabarreleffect.The
workisdonebyfourprintercommands:acommandsettingtherightmargin
(line 1400);a centeringcommand(line 1420);a commandto varythe line
spacing(lines 1440and 1490);and a commandto micro-adjustthe space
betweencharactm (lines 1450and 150Q).
Nexttheprogramnmmnstonormalspacingandgivesademonstrationofthe
printer’sword-processingabilities:bold printing,underlining,subscripts,
etc.
The row of automobilesin thenextprintedline is createdby downloading
two new characterpatterns,whichareprintedin placeof the character“e”
(character60). Detailscan be foundin Chapter5.
The finalpart of the programuses dot graphicsto print some“SW”logos
withvariousdensities.Thedotpatternofthelogowasoriginallylaidouton
graphpaper,then convertedto the datain lines2400to 2630withthe help
of a calculator.Eachnumber~presents eightverticaldots.(See“Graphics
commands”in Chapter4 for details.).
Thepatternis printedin four rows,each rowis eightdotshigh and65 dots
wide.Lines1800to 1850madthedotdataintoastringarrayvariablenamed
LOGO$.Line 1860setsthe line spacingto 8/72inch so thatthe rowswill
connectvertically.Theloop in lines 1870to 1960doestheprintingin four
passesof the printhead.
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