<< Previous Message Main Index Next Message >>
<< Previous Message in Thread This Month Next Message in Thread >>
Date   : Tue, 17 Nov 1992 07:54:32 GMT
From   : munnari.oz.au!uniwa!cujo!cc.curtin.edu.au!nmurrayr@tcgould.tn.cornell.edu (Ron Murray)
Subject: Re: ZMODEM for CP/M ???

In article <1992Nov2.085522.22309@cc.tut.fi>, kent@cc.tut.fi (Kentt{l{
Marko) writes:

> I'd like to have ZMODEM documentation or source (ZMP doesn't come with
> so if any of you have it, just E-mail it to kent@ee.tut.fi, please.

   I've been promising for some time to release the zmp/rzmp sources, but
it's one of those things I just don't seem to have got around to yet! I'm
currently looking into a Windows version for PCs, so I just rooted out the
sources again. I'll try and post them in the next week or so. Be warned though
that it may not be easy to recompile zmp from the sources: I had to resort to
a few fiddles to get it to compile and run in what is, after all, a rather
restrictive environment for that sort of thing (I had only about 54k of TPA).
I was able to get it to go only by using a particular compiler, which isn't
all that common.

   There were several reasons why I didn't release the sources with zmp in
the first place: mostly, I guess, I didn't want 156 different versions of
zmp floating around (we all learned an awful lot from SD!). In these days
of PCs, Macs and "shareware", I'm more worried about someone else making
money from my code (and, of course, that of Hal Maney, who wrote Hmodem,
from which [r]zmp was derived). Perhaps releasing it all under the GPL will
help: has anyone got any suggestions on this? (Please note that any Windows
port of zmp will be released under much the same conditions as cp/m zmp was:
free to non-commercial users).

   The Zmodem specs, which you should try and get if you intend to write a
program using Zmodem, are probably in Simtel-20's zmodem directory. Try
"yzmodem.arc" and possibly "zmodem810.zip" as well.

> JMODEM would be even better...

   You may have problems with jmodem in a cp/m environment. If memory serves
me right (it's been a long time, and I don't have the docs with me), it's
basically xmodem with an impossibly large (for cp/m) packet size: up to about
14k, I believe. (The Zmodem-like protocol in Fidonet mail systems has a similar
problem, in case you wonder why I never added that capability to Foodo). It
wasn't possible to add jmodem to zmp for this reason: simple lack of memory.
(You may notice that zmp receives files in chunks of up to 16k: if these
chunks are less than 16k, then that's all the memory you have free in your
system with zmp running). It may be possible to get jmodem running by
re-coding the whole lot in assembler, or cutting down on other things, but
the real question is: why bother? Zmodem is probably more efficient under
all but the best conditions.


 Ron Murray
 Internet: nmurrayr@cc.curtin.edu.au
     Are we having fun yet?    -- Garfield

End of INFO-CPM Digest V92 Issue #135
<< Previous Message Main Index Next Message >>
<< Previous Message in Thread This Month Next Message in Thread >>