Epson LQ-860 User Manual page 125

The letter s represents the command that you wish to change the
assignment for (K, L, Y, or Z) and m is the number of the graphics
option that you want to assign to it. For example, to change the
ESC K command to use the CRT I graphics option, the command in
BASIC is:
LPRINT CHR$ (27);"?";"K";CHR$(4)
This is a quick way to change the aspect ratio of the design that you
are printing. Changing the graphics option will change the width
without changing the height. You should, however, make this
change with caution.
If you change one of the 8-pin graphics options to a 24-pin graphics
option without changing the program that supplies the graphics
data, you will print garbage (if the program prints at all).
Remember, the 24-pin graphics options require three times as much
graphics data as the 8-pin graphics options.
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Software and Graphics