Path: utzoo!utgpu!water!watmath!clyde!rutgers!mit-eddie!husc6!cmcl2!nrl-cmf!ames!pasteur!ucbvax!sdcsvax!ucsdhub!esosun!seismo!uunet!portal!cup.portal.com!ROBERT_C_TELLEFSON
From: ROBERT_C_TELLEFSON@cup.portal.com
Newsgroups: comp.sys.ibm.pc
Subject: Re: EXEC call (was: Re: shell script program for pc)
Message-ID: <2638@cup.portal.com>
Date: 21 Jan 88 19:03:38 GMT
References: <288@dbase.UUCP> <5589@eecae.UUCP> <555@srs.UUCP>
Organization: The Portal System (TM)
Lines: 27
XPortal-User-Id: 1.1001.2624

>In article <5589@eecae.UUCP> driscoll@eecae.UUCP (Mike Driscoll) writes:
>>  Actually, it (the On Command shell) resides on top of command.com's
>>resident portion, which contains DOS's ONLY loader.  Any program using
>>the DOS exec call needs this loader.
>Not quite true.
>    1. Bare PC-DOS (without COMMAND.COM) can load .COM programs via EXEC.
>       That's how COMMAND.COM is probably loaded.
>    2. Microsoft's MS-DOS Programmer's Reference Manual 3.1 states that
>       only IBM's version (PC-DOS, not generic MS-DOS) has the .EXE loader
>       in (the transient portion of) COMMAND.COM.  IBM wanted it that way to
>       save memory.

The DOS (MS or PC) Exec function (4b hex) may be called by any
application to load and execute a .com or .exe file without command.com's
participation.  This is how command.com executes programs entered at the
command line. 

My company produces a shell capable of replacing command.com, in which case,
command.com plays no part in executing programs.  Note that command.com
is required for execution of .bat files.

Robert 'Bob' Tellefson           UUCP:  tellefson@cup.portal.com
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