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From: hwfe@ur-tut (Harlan Feinstein)
Newsgroups: comp.lang.c,comp.arch
Subject: Re: Self-modifying code
Keywords: self-modifying code, generate-and-execute
Message-ID: <2314@ur-tut.UUCP>
Date: 19 Jul 88 06:04:50 GMT
References: <3353@cognos.UUCP> <619@goofy.megatest.UUCP> <429@uwovax.uwo.ca> <5254@june.cs.washington.edu> <12357@ut-sally.UUCP> <5262@june.cs.washington.edu>
Reply-To: hwfe@tut.cc.rochester.edu.UUCP (Harlan Feinstein)
Organization: Univ. of Rochester Computing Center
Lines: 12

Reasons for writing self-modifying code have been scarce, and have basically
centered around speed reasons.  Speed is not the only reasons why someone
would want to write s-m code.  I've seen a program for the IBM PC called 
PC-LOCK that prohibits one from accessing the hard disk without providing
a password.  The install and de-install programs are self-modifying to 
make tracing them all but impossible.  

One time last summer I changed my password right before the weekend, and
wouldn't you know it, come Monday I had no clue as to what the password was.
I tried all kinds of disassembly and debug tracing to no avail.  Hence, another
reasons for self-modifying code.

--harlan