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From: brownc@utah-cs.UUCP (Eric C. Brown)
Newsgroups: net.micro
Subject: Re: Re: DOS EXEC FUNCTION CALL
Message-ID: <3465@utah-cs.UUCP>
Date: Sun, 8-Sep-85 01:02:56 EDT
Article-I.D.: utah-cs.3465
Posted: Sun Sep  8 01:02:56 1985
Date-Received: Tue, 10-Sep-85 02:59:52 EDT
References: <1267@brl-tgr.ARPA> <11416@styx.UUCP>
Reply-To: brownc@utah-cs.UUCP (Eric C. Brown)
Organization: Univ of Utah CS Dept
Lines: 20

In article <11416@styx.UUCP> jlt@styx.UUCP (John L. Thomas) writes:
>> when you return back to TURBO all your stack and data is garbage. The
>> solution is to push all your necessary registers and then save the SS
>> and SP in a location in your code segment.
>
>Just to clear up a ?minor? point of confusion:
>How could the return from interrupt have happened if the SS:SP is garbage?
>In fact, the restoration of CS:IP comes from the return, which requires
>that SS:SP be correct.
>
Well, actually, according to a note in the Zenith MS-DOS 2.0 Programmer's
Utility Package, all registers (including the stack) are altered because
control is returned from the executed program, not the system.  My guess
is that the 2.0 Exec function sets up the program exit address of the 
called program to point back to the calling program.

Eric C. Brown
brownc@utah-cs
...{ihnp4, decvax}!utah-cs!brownc
Execute Programs, not People!