Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!uunet!mcsun!sunic!dkuug!harald.ruc.dk!jba
From: jba@harald.ruc.dk (Jan B. Andersen)
Newsgroups: comp.arch
Subject: Self-modifying CP/M code
Message-ID: <174@harald.UUCP>
Date: 16 Oct 89 09:55:15 GMT
References: <6481@pt.cs.cmu.edu> <9175@etana.tut.fi> <1619@atanasoff.cs.iastate.edu> <672@sce.carleton.ca>
Organization: RUC - Roskilde University Center, Denmark
Lines: 13

cassel@sce.carleton.ca (Ron Casselman) writes:

>The program would copy itself to a different
>part of memory and change all address references as it did so. It would
>then load a second program into the original location. (all programs
>under CP/M started at a fixed location). The second program would then
>begin to run. Sorry I cannot remember any more details as to the purpose
>of this self-modifying code.

Sounds like the CP/M debugger to me (name ??). I believe that self-modifying
code is quite common in small single-processes OS's, but except for very
special cases (like I/O drivers which someone has mentioned) I think it
should be avoided at all cost.