Table of Contents
Advertisement
How theprogram works
Thisprogrambeginsby assigninga numberof printercommandsto BASIC
stringvariables(lines1000to 1060).Youcanfindmostof thesecommands
near the beginningof chapter7.
The WIDTH"LPT1:"255 statementin line 1080meansinfinitelinewidth.
It preventsthe IBM-PCfrom insertingunwantedcarriagemtums and line
feedsin graphicsdata.
Actualprintingbeginsin line 1090.Usingthe preassignedcommands,the
programprintssamplesofitsdifferentfonts,followedbysamplesoftheprint
pitches,then somedoubleand quadruple-sized printing.
Next comes the central attractionof the program: a line of text printed
fourteentimesinexpandingandcontractingloopsto giveabarreleffect.The
workis doneby fourprintercommands:a commandsettingtherightmargin
(line 1450);a centeringcommand(line 1470);a commandto vary the line
spacing(lines 1490and 1540);and a commandto micro-adjustthe space
betweencharacters(lines 1500and 1550).
Nextthepmgrarnreturnstonormalspacingandgivesa demonstration of the
printer'sword-processingabilities:italicprinting,bold printing,underlin-
ing, subscripts,etc.
The row of telephone symbols in the next printed line is created by
downloadingtwo new characterpatterns,whicharc printedin placeof the
character"<" (character60). Detailscan be foundin Chapter8.
Thefinalpartofthe programusesdotgraphicstoprintan"M&W"logo.The
dotpatternof thelogowasoriginallylaidouton graphpaper,thenconverted
to the datain lines 3180to 4640 withthe help of a calculator.Eachnumber
representseightvexticaldots. (See "Graphicscommands"in Chapter7 for
details.)
The patternis printedin three rows,each row is twenty-fourdots high and
240 dots wide.Line2040setsthe line spacingto 8/60inch so thatthe rows
will comect vertically.The loop in lines2050to 2130doesthe printingin
three passesof the printhead.
140
Advertisement
Table of Contents
