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Posting-Version: version B 2.10.2 9/18/84; site looking.UUCP
Path: utzoo!watmath!looking!syncro
From: syncro@looking.UUCP (Tom Haapanen)
Newsgroups: net.micro.pc
Subject: Re: Segment Registers -- 8086/80286
Message-ID: <592@looking.UUCP>
Date: Sat, 28-Jun-86 20:19:22 EDT
Article-I.D.: looking.592
Posted: Sat Jun 28 20:19:22 1986
Date-Received: Sun, 29-Jun-86 07:22:07 EDT
References: <165@sci.UUCP> <146@apr.UUCP> <494@ubvax.UUCP> <1851@gitpyr.UUCP> <140@ima.UUCP>
Reply-To: @looking.UUCP (Tom Haapanen)
Organization: Looking Glass Software Ltd. Waterloo, Ontario
Lines: 26
Keywords: 286 segment registers

In article <140@ima.UUCP> johnl@ima.UUCP (John R. Levine) writes:
>>> ... and if you ever plan on writing programs for the i80286, don't
>>> "normalize" pointers.

>>So how will one compare pointers?  If you can't normalize them, two pointers
>>could reference the same address, but not contain the same values. ...

>Not likely.  The 286 is a genuine segmented architecture (as opposed to the
>8086 which is an unsatisfactory approximation.)  The operating system
>controls where each segment is mapped.  Unless you have a strange
>operating system, you can assume that the contents of different segments are
>disjoint, so that if two pointers point into different segments, they're not
>pointing at the same thing.

Ummm, if you ask DOS to allocate memory for you, it returns a *segment* 
address, and you are to assume zero offset (see DOS function calls 48 and
49).  Now, unless you are allocating in 64K-sized chunks, the segments
won't likely be disjoint.  I am no great fan of DOS, but I'm not sure I'd
call it *strange* in net.micro.pc...

--
\tom haapanen					looking glass software ltd.
syncro@looking.UUCP				waterloo, ontario, canada
watmath!looking!syncro				(519) 884-7473

"These opinions are solely mine, although even I would like to deny them..."