Epson Apex-80 - Manual (Page 117)

Some computer systems change one or more codes when sending
them from BASIC to the printer. The ability of the Apex80 to dump
in hexadecimal lets you determine which codes are creating problems
for your system.
A hex printout of a program shows you exactly what the printer is
receiving, regardless of what the computer is sending. The following
test program lets you check to see which codes, if any, are problems for
your computer system.
10 FOR X=0 TO 255
20 LPRINT CHR$(X);
30
NEXT X
Put the printer in data dump mode and then run the program.
Remember to press the ON/OFF LINE button to make the Apex80 print
the final line. Then compare your printout with the list of hex codes in
order in Appendix B. If any are skipped or repeated, you know that
your BASIC language changes some codes before it sends them to the
printer.
For example, the line below is the first line of the printout of the test
program run on a system that changes hex 09, which is the code for
horizontal tabbing, to several 20s, the code for a space. Therefore, you
know that if you use this system, you must be careful about sending a
decimal 9 (hex 09).
0000 00 01 02 03 04 05 06 07 08 20 20 20 20 20 20 20 . . . . . . . . . .
The data dumping capability can help you solve problems quickly.
Appendix B can help you translate the hex codes to ASCII
equivalents.
Coding Solutions
Once you’ve determined that a code creates problems for your
printing, either by trial and error or by using the data dumping
capability of the Apex80, you can start overcoming them.
Because each computer system deals with ASCII codes differently, it
is impossible to provide solutions for all potential problems in one
appendix. It may help, however, to be aware of some generic problems
and some ways to handle them.
C-6 Problem Solving and Maintenance