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How the program works
This program begins by assigning a number of printer commands to BASIC
string variables (lines 1000 to 1090). You can find most of these commands
near the beginning of chapter 4.
The WIDTH "LPTl:" 255 statement in line 1110 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 1120. Using the preassigned commands, the
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program prints samples of its different font styles, including a line showing
all styles in italics, followed by samples of the print pitches, then some
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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 1460); a centering command (line 1480); a command to vary the line
spacing (lines 1500 and 1550); and a command to micro-adjust the space
between characters (lines 1510 and 1560).
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Next the program returns to normal spacing and gives a demonstration of the
printer's word-processing abilities: bold printing, underlining, subscripts,
etc.
The row of telephone symbols in the next printed line is created by down-
loading two new character patterns, which are printed in place of the
character "<" (character 60). Details can be found in Chapter 5.
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 2570 to 4030 with the help of a calculator. Each number
represents eight vertical dots. (See "Graphics commands" in Chapter 4 for
details.)
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The pattern is printed in three rows, each 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.
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