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From: bambi@kirk.nmg.bu.oz (David J. Hughes)
Newsgroups: comp.sys.ibm.pc.programmer
Subject: Re: .SYS (device drivers) that are actually .EXEs?
Message-ID: <1145@kirk.nmg.bu.oz>
Date: 4 Jul 90 22:39:20 GMT
References: <4237@jato.Jpl.Nasa.Gov>
Organization: Network Management Group, Bond University, Australia
Lines: 38

From article <4237@jato.Jpl.Nasa.Gov>, by kaleb@mars.jpl.nasa.gov (Kaleb Keithley):
> In article <141@qmsseq.imagen.com> pipkins@imagen.com (Jeff Pipkins) writes:
>>
>>In MS-DOS versions < 3.0, the EXEC function call (EXE loader) was actually
>>a part of COMMAND.COM.  Because COMMAND.COM is not loaded until after
> 
> Wrong!  I just whipped out the M'soft Encyclopedia, and the EXEC function
> call has been there all along.  Maybe you're thinking of that short lived
> abortion known as DOS 1.0.

To coin a phrase - "Wrong !".  It is in fact true that the EXEC call
"has been there all along" but that was not the statement made by Jeff.
His statement implied that the code that supported the EXEC function was
implemented within command.com.  

This is quite a true statement.  What Jeff meant to say was that in 
versions of DOS earlier than 3.0, the EXEC function call was implemented 
within the *** transient *** portion of the command processor.  This is 
only the case for IBM DOS 2.x.  I cannot imagine why you would place the 
EXEC routine in the transient section as it is quite legal for an 
application to stomp all over the transient part of command.com and then
issue an EXEC - but IBM did it that way.

They must have realised the problem - as IBM DOS 3.x did not work in
this way (neither did MS DOS 2.x).  All this information and more can
found in Dave Williams Shareware "Dos Technial Information" manual.  A
must for any DOS sysprog (but UNIX is more fun anyway :-)



bambi
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| David J. Hughes   (AKA bambi)	 |   bambi@kowande.bu.oz.au                  |
| Systems Programmer		 |   bambi@kowande.bu.oz.au@uunet.uu.net     |
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