How the program works
This program beginsby assigning anumberof printer commands toBASIC stringvariables
(lines 1000to 1050).You can find most of these commands near the beginning of chapter
6.
The WIDTH “LPT1:“ 255 statement in line 1070means infinite line width. It prevents the
IBM-PC from inserting unwanted carriage returns and line feeds in graphics data.
Actual printing begins in line 1080.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 1340); a centering command (line
1360);acommand to vary the line spacing (lines 1380and 1430);and acommand to micro-
adjust the space between characters (lines 1390 and 1440).
Next the program returns to normal spacing and gives a demonstration of the printer’s
word-processing abilities: italic printing, bold printing, underlining, 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 7.
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 2800
to 4260 with the help of a calculator. Each number represents eight vertical dots. (See
“Graphics commands” in Chapter 6 for details.)
The pattern is printed in three rows, each row is twenty-four dots high and 240 dots wide.
Line 1870setsthe linespacing to 8/60inch so thatthe rows willconnect vertically. The loop
in lines 1880to 1960 does the printing in three passes of the print head.
Chapter8 MS-DOS AND YOUR PRINTER 85
