Date:	Fri, 14 Mar 1997 22:09:20 -0600 (CST)
From:	"Colin W. Glenn" <cwg01 AT gnofn DOT org>
To:	"'OpenDOS newsgroup'" <opendos AT mail DOT tacoma DOT net>
Subject:	Re: [opendos] IOSYS Magic?
In-Reply-To:	<199703140753.IAA17825@math.amu.edu.pl>
Message-ID:	<Pine.GSO.3.95.970314215949.16822E-100000@sparkie.gnofn.org>
MIME-Version:	1.0
Sender:	owner-opendos AT mail DOT tacoma DOT net

On Fri, 14 Mar 1997, Mark Habersack wrote:
> On 13 Mar 97 (at 19:49) Colin W. Glenn became famous by saying:
> > To those familar with how the kernel works, I got a question:
> > 
> > Does the kernel set anything special up before loading the shell?  Does the

> Yes. The shell is special in that it is being loaded in two parts - each of 
> them in a specific region of memory. The resident portion goes low in the 
> memory, right after the kernel code (with an exception when DOS is loaded up 
> or high - the the shell goes there as well) while the transient portion is 
> pushed up towards the end of TPA to protect it from being overwritten too 

Command.com does this itself, says so in the DOS Programmer's reference,
pages 56-57.  I psuedo-quote:

After completing the initialization process, SYSINIT closes all file
handles, opens CON for STDIN STDOUT STDERR, PRN as STDLIST, AUX as STDAUX.
It then calls upon DOS EXEC to load and execute COMMAND.COM or (shell)..

When COMMAND.COM is loaded, it immediately relocates part of itself in
high memory.  The low-memory section of C.C (the resident section)
contains code for INT's 22h, 23h, 24h....

End psuedo-quote.

> > shell have to meet certain requirements to be a shell?  Can a shell have a
> I'm not sure, but I suspect the answer is yes. From what I investigated, 
> M$-DOG kernel does some undocummented calls into the shell on load time. 

How can the kernel make undocumented calls into (shell)?

> Besides try to set *any* program as a shell?

fraid not, not daring enough.

> > Inquiring minds need to know!
> Inquiring minds join together! ;-)

Just watch out for brain bruises. ;)

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