DOS apps and XP (was: Now *that* was strange...)

[Jay R. Ashworth]

On Sun, Oct 22, 2006 at 09:31:53PM -0400, Kenneth Brody wrote:
> Quoting Fairlight (Sat, 21 Oct 2006 23:14:52 -0400):
> > At Sat, Oct 21, 2006 at 11:08:51PM -0400 or thereabouts,
> [...]
> > > It includes cmd.exe *and* command.com, and I'm pretty sure they're
> > > different programs.
> >
> > They are.  command.com is 16bit DOS and cmd.com is 32bit.  But Ken said
> > there's an actual emulator involved that is neither of these.  I have
> > yet to have time away from other research and sundry to check and see
> > what he's talking about or how to get into it, but it sounds interesting.
> 
> You "get into it" by running a 16-bit DOS app.  Windows will automatically
> load the emulator (ntvdm.exe) and run the program using it.
> 
> To demonstrate:
> 
>     start / run / cmd.exe
> 
> Press Ctrl-Alt-Del to bring up the task manager.  Sort the list by image
> name for ease of searching.  Note that there is no ntvdm.exe listed. (At
> least there should be, unless you have a command window open which has
> run a 16-bit DOS app.)  Now, type "command.com".  Note that ntvdm.exe is
> now listed.  Type "exit" to leave command.com.  (The ntvdm.exe should
> still be listed.)  Type "exit" to leave cmd.exe.  Note that both the
> cmd.exe and ntvdm.exe items disappear.

So cmd.exe is a native program, and command.com is itself a 16-bit app
that runs in a dos box.  Interesting point; hadn't thought about it
that way...

Cheers,
-- jra
-- 
Jay R. Ashworth                                                jra at baylink.com
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