Date: Thu, 14 May 1998 16:15:24 +0300 (IDT)
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
To: Graeme Fenwick <gfenwick AT primex DOT co DOT uk>
cc: djgpp AT delorie DOT com
Subject: Re: Looking for help with MSDOS AUTOEXEC & CONFIG
In-Reply-To: <355ac9a8.0@scooby.nildram.co.uk>
Message-ID: <Pine.SUN.3.91.980514160356.1637C-100000@is>
MIME-Version: 1.0
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On Thu, 14 May 1998, Graeme Fenwick wrote:

> 1) What are the differences between "genuine" MSDOS, Win95's DOS in a window
> (via Start menu) and rebooting Win95 into MSDOS mode?

Too long a story to explain in a message, IMHO.  You can easily get away 
by thinking that the first two are identical.  The third is mostly the 
same as the other two, except that Windows leaves a small stub behind, to 
be able to restart itself when you exit the DOS mode.

> 2) Do books on the newer MSDOSs apply to DOS under W95 in general?

Yes.

> 3) AUTOEXEC.BAT is a file that simply executes the list of commands
> contained within on booting, or running the DOS window- right (or wrong)?

The first part is right.  It only runs at boot time, not every time a DOS 
box is started.  (I mean the AUTOEXEC.BAT that is common to the entire 
system, not the ones customized for shortcuts.)

> And assuming I haven't configured a special DOS shortcut with its own
> AUTOEXEC, does it run for all DOS Windows when launched?

No, AUTOEXEC.BAT only runs once, when your system boots.  

It seems that you think Windows runs DOS anew in every DOS box.  This is
incorrect.  Windows just creates another virtual machine, and copies into
that machine the DOS memory, including any TSRs and device drivers loaded
by CONFIG.SYS and AUTOEXEC.BAT during bootstrap, from the ``master copy''
of DOS which loaded before Windows.  (Actually, ``copies'' is inaccurate: 
Windows fiddles the memory page directories so that the same memory is 
mapped into all of the virtual machines.  But you can think about this as 
a copy.)

> And I'm guessing CONFIG.SYS tells the system where to find any device
> drivers...

It also includes system-wide directives like FILES= etc.

> 4) Does SET PATH tell DOS where to search for a certain command, say gcc,
> and if so, how do I get DOS to look in two different paths for a program
> (since it seems I can't do two SET PATHs)?

PATH is a list of directories separated by a semi-colon:

   set PATH=C:\DOS;C:\WINDOWS;C:\NUPROGS\djgpp\gnu\emacs

DOS and Windows look for every program in all those directories in 
sequence, from left to right.  The current directory is checked before 
PATH, so in a sence you could think that "." is always prepended to the 
value of PATH.