Date   : Sun, 08 Apr 1984106:04:00-PST
From   : Kevin W. Rudd <kevinw@Su-Dsn.ARPA>
Subject: cpm vs cpm-plus

having just scanned an article which mentions how to do a bug fix
to an existing distribution public domain program, i have noticed
what could be to many a very confusing issue.  this has to do with
how to put the patched software back to disk.

in cpm the solution is to use ddt to patch the software and then to
exit ddt back to the ccp and use the cpm SAVE command (having decoded
the size of the program from the ddt (or sid) logon message).

there is one problem with this approach with cpm-plus (aka cpm3) --
it won't work.  cpm-plus has a pre-execution save command which, upon
return to the system from the next run program, prompts you for the
address range to be saved and to what file.  easier to use, perhaps, but
much different in actual useage.  it could be used in a similar wa,
perhaps, but i have not tried it.  instead, one may use the W commad in
sid (as supplied by dri) -- it will write the program to a file or will
write a user supplied address range to a file as well.  there is a problm
in the default address range as it uses the address of the last loaded
module end location as the end location to save rather than the greatest
end location...  oooopppppssssss.  just what we expect frm dri though...

unfortunately, there is no easy solution to how to give instructions to
people to patch programs.  perhaps it would be better to have some kind
of program editor which will take a patch file and process it.  this program
would be written to work in a cpm or a cpm-plus system and would alleviate
any potential confusion which may arise from people trying to follow
instructions (or to determine which of several instructions) blindly.

  -- K