The extension file is a chance to add some extra facilities to NASPEN. I
have included a printer driver for a centronics driven RX80. The main reason
for this was that I found I had three program modules fighting over the print
format if I used the built-in POLYDOS routines. It also gave the opportunity
to invent a way of putting control sequences to printer. The main problem is
that Naspen will not store an “escape” character, because this code is used to
terminate a Naspen command. I have used a “Control D” which can be stored in
with the text, to replace the “escape”. This means that most if not all of the
print-modes of the EPSON RX80 can be switched on and off, at will, by embedded
“escape” strings. A further addition of the extension file is that the system
can be restarted by a NAS-SYS “EB000” command which warm-starts NASPEN. The
overlay file will have been lost, because the “Exec” overlay will have been
loaded by the return to POLYDOS but it is not required once the main Naspen
programs have been loaded and cold-started the first time. The warm start
proved most necessary with the disk system, because it is easy to call a wrong
file-name, or one that already exists. Either of these errors will blast you
back into POLYDOS command level. (Rather like a touch of the snakes and
ladders.) Obviously a rather more sophisicated file handling routine would
allow for default file extensions and would automatically overwrite an
existing file, renaming the existing version as a “.BK” backup version. The
fun of getting that going is all yours!! An even more useful addition would be
to toggle the screen with some unused memory and allow the operator to view
the disk directories whilst in Naspen.
Some further minor changes were made to Naspen to indicate differences
from the original prom version, the title was changed to read “NASPEN PDOS4”.
The initialisation routine was changed to give 32000 bytes free instead of the
original 11000. Although this is supposed to slow down the operation of some
commands, I have not found it as big a disadvantage as the space restriction.
There are a few points to take note of before committing your epic novel,
or autobiography to “Polypen”. DON’T use the “NP” extension for any other
files. I use the extension “nt” for my Naspen text files. Remember to patch
the printer reflection on your files before you submit them to “Polypen”. The
disk save routines save all memory from 1000H.
To avoid compromising copyright on the PolyDos listing I have not
included the comments. If you have bought PolyDos you will have a manual which
explains all. I was amazed by the ease with which I managed to effect these
changes, and it speaks volumes for the quality of the manual that the first
successful assembly of the file-writing routine worked first time. (For a
comparison note how many non-Digital Research textbooks are recommended for
CP/M tinkerers ).
Subject to probable change the following items should appear in the
of 80-BUS News, a special ‘back-from-holiday’ issue !
Is there any truth in the rumour that Dave Hunt, Aunt Agatha and Lawrence all
went away together?