Date   : Mon,  9 Apr 1984 12:44:11-MST,1658;000000000000
From   : "Robert L. Krawitz" <ZZZ.RLK%MIT-OZ@MIT-MC.ARPA>
Subject: MDMLNK - Patching MDM7xx and other files without DDT or SID

In response to both your questios:

1)  A .com file is simply a binary file containing a Z-80 (or 8080)
machine-language program.  It should cold start at 100H.

2)  Yes, there is a standard relocatable format.  It is not in the .com
file, however.  The hex file ("object" file produced by the assembler)
is what you want.  Original Intel hex format doesn't define the
necessary extensions, but there is a standard extension.  Unfortunately,
I do not remembe the proper format, but I shall look it up.  It is
consistent with the Intel hex, and an Intel loader will load the
program, without the relocating information.  It is not difficult to
patch -- I've done it before.  As usual, what is required is that the
jumps be re-calculated -- patching the hex file won't do that.  If you
don't have a hex file, patching something is difficult.  Of course, you
could write a program to recalculate jumps, but you have to be careful
not to munge data.

                               Robert