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How the program works
This program begins by assigning a number of printer commands to BASIC
string variables (lines 1000to 1060).You can find most of these commands
near the beginning of chapter 8.
TheWIDTH "LPT1 :" 255 statement in line 1080 means infinite line width.
It prevents the IBM-PC from inserting unwanted carriage returns and line
feeds in graphics data.
Actual printing begins in line 1090. Using the preassigned commands, the
program prints samples of its different fonts, followed by samples of the print
pitches, then some double and quadruple-sized printing.
Next comes the central attraction of the program: a line of text printed
fourteen times in expanding and contracting loops to give a barrel effect. The
work is done by four printer commands: a command setting the right margin
(line 1400); a centering command (line 1420); a command to vary the line
spacing (lines 1440 and 1490); and a command to micro-adjust the space
between characters (lines 1450 and 1500).
Next the program returns to normal spacing and gives a demonstration of the
printer's word-processing abilities: italic printing, bold printing, underlin-
ing, subscripts. etc.
The row of telephone symbols in the next printed line is created by
downloading two new character patterns, which are printed in place of the
character "<" (character 60). Details can be found in Chapter 9.
The final part of the program uses dot graphics to print an "M&W" logo. The
dot pattern of the logo was originally laid out on graph paper, then converted
to the data in lines 3180 to 4640 with the help of a calculator. Each number
represents eight vertical dots. (See "Graphics commands" in Chapter 8 for
details.)
The pattern is printed in three rows, each row is twenty-four dots high and
240 dots wide. Line 1990 sets the line spacing to 8/60 inch so that the rows
will connect vertically. The loop in lines 2000 to 2080 does the printing in
three passes of the print head.
The printout sample with this program is shown in page 7.
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