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From: kpk@gitpyr.UUCP (Kevin P. Kleinfelter)
Newsgroups: net.micro.pc
Subject: Re: Segment Registers -- 8086/80286
Message-ID: <1851@gitpyr.UUCP>
Date: Wed, 4-Jun-86 08:56:28 EDT
Article-I.D.: gitpyr.1851
Posted: Wed Jun  4 08:56:28 1986
Date-Received: Sat, 7-Jun-86 02:21:13 EDT
References: <165@sci.UUCP> <146@apr.UUCP> <494@ubvax.UUCP>
Organization: Georgia Institute of Technology
Lines: 22
Keywords: 286 segment registers

In article <494@ubvax.UUCP>, skip@ubvax.UUCP writes:
> In article <146@apr.UUCP> las@apr.UUCP (Larry Shurr) writes:
> > ...
> ... and if you ever plan on writing programs for the i80286, don't
> "normalize" pointers.  To paraphrase some Microsoft documentation:
> 
> 	When a program loads a segment register on an 8086, it is
> 	actually loading a displacement value.  On the 80286, what
> 	is loaded is actually a segment number indexing to an entry
> 	in the master segment table.  The actual displacement value
> 	is loaded from that table.  There is NO relation between
> 	segment N and segment N+1 (ie N+1:0 != N:10h).
>
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.  In
a language such as Pascal, equality is a valid test on pointers.  In a language
such as Modula-2, pointer arithmetic is valid.  How can items such as these
be implemented without normalization of pointers?

                                 Confused,
                                 Kevin Kleinfelter (kpk@gitpyr.UUCP)