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From: mason@gargoyle.UChicago.EDU (Tony Mason)
Newsgroups: comp.sys.ibm.pc,comp.lang.c
Subject: Re: Assigning to Pointers
Message-ID: <642@gargoyle.UChicago.EDU>
Date: Thu, 30-Apr-87 10:35:01 EDT
Article-I.D.: gargoyle.642
Posted: Thu Apr 30 10:35:01 1987
Date-Received: Sat, 2-May-87 09:05:57 EDT
References: <3537@vrdxhq.UUCP> <2248@tekgvs.TEK.COM>
Reply-To: mason@gargoyle.uchicago.edu.UUCP (Tony Mason)
Organization: U. of Chicago, Computer Science Dept.
Lines: 41
Xref: mnetor comp.sys.ibm.pc:3650 comp.lang.c:1988

>>This may be a dumb question, but could someone please explain
>>to me how I assign an absolute address to a pointer to an array?
>>...
>>I'm using MSC 4.0
>>
>You have to remember that addresses of "far" data structures are longs and
>not ints.
>
>For SMALL or MEDIUM memory models (i.e., one data segment), you can say
>
>int far *aa[];	/* aa is a far pointer to an array of ints */
                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Unless my understanding of C (and of those around me) has just gone out the
window, that is an array of far pointers to integers. To make the delcaration
fit the comment it should be:

int far *aa; /* aa is a far pointer to an array of ints */

Now you just use integer arithmetic to acces elements in the array (eg.
*(aa + 4) would be the fifth integer in the array).

To make the comment match the declaration :

int far *aa[]; /* aa is an array of far pointers to integers */

Now, to access an integer, you would use something like *aa[4] to access the
integer pointed at by the fifth element of the pointer array.

Finally, if you use the undefined array size syntax, you are defining
something that must be external (or in a function declaration list).  Whether
or not the compiler should accept this at all is quite suspect (at least to
me) without an extern in front.  As for using far, that is only necessary
when you are using (1) any model with restricted data size AND (2) accessing
a data structure outside the normal data segment.  In line with the type of
question asked, this is probably NOT what was being asked.  I think the
confusion in this case was with pointer declarations, not access problems.

Tony Mason
Univ. of Chicago, Dept. of C.S.
ARPA: mason@gargoyle.uchicago.edu
UUCP: ...ihnp4!gargoyle!mason