To:	ao950 AT FreeNet DOT Carleton DOT CA
Cc:	djgpp AT delorie DOT com
Subject:	Re: Ring 0? -semi off topic-
Message-ID:	<19970305.153413.6951.2.fwec@juno.com>
References:	<5fivnk$cfc AT freenet-news DOT carleton DOT ca>
From:	fwec AT juno DOT com (Mark T Logan)
Date:	Wed, 05 Mar 1997 15:36:30 EST

On 5 Mar 1997 05:18:44 GMT ao950 AT FreeNet DOT Carleton DOT CA (Paul Derbyshire)
writes:
>
>
>What exactly is "ring 0"? A page on optimizing code using CWSDPR0
>mentioned it. But it's not clear to me what it is. I assume it isn't a
>modem thing...:)
>--

If I'm wrong don't sue me, but this is what I know.

Under protected mode, different software is assigned a different ring
number,
or privelidge level.

Ring 0:  Operating systems Kernel.
Ring 1: systems services [the vector interrupt table?  correct me if I'm
wrong.] 
Ring 2: custom I/O extensions. [maybe MTMCDAE, the cd driver]
Ring 3: applications

Each ring can only access other rings which have a higher number. 
Therefore,
If your program has an uninitialized pointer, and you accidentally
overwrite the
block of memory which MSDOS.SYS (or maybe CWSDPMI, dos isn't protected
mode)
is occupying, you'll cause a GP.  In real mode, there is no ring
organization, and
if you wish, you can scramble dos and crash your computer if you like.


||          Fwec AT juno DOT com aka Mark Logan aka Gil Bates
||
|| This message was a work of fiction.  As such, all characters contained
in
|| said message are purely fictitious.  Any resemblence to actual
persons, living
|| or dead, is purely coincidental.

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