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From: platt@emory.uucp (Dan Platt)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Microsoft C 4.0 large models
Message-ID: <2195@emory.uucp>
Date: Thu, 6-Aug-87 00:27:16 EDT
Article-I.D.: emory.2195
Posted: Thu Aug  6 00:27:16 1987
Date-Received: Sat, 8-Aug-87 10:44:32 EDT
References: <3225@cucca.columbia.edu> <3320039@hpsrlc.HP.COM> <2190@emory.uucp> <4589@jade.BERKELEY.EDU>
Reply-To: platt@emory.UUCP (Dan Platt)
Distribution: world
Organization: Math & Computer Science, Emory University, Atlanta
Lines: 33
Keywords: Huge model...
Summary: Huge models

In article <4589@jade.BERKELEY.EDU> ehughes@violet.berkeley.edu () writes:
>On many DOS compilers, the allocated memory pool is taken from a single
>segment, i.e. 64K max.  This is true EVEN IN LARGE MODEL.  It is simply
>an outright laziness on the part of the library writers not to take
>this into consideration....

I would like to point out that the large pointers don't handle the 
problem of an element size exceeding 64k.  However, huge structure
types do allow a pointer to a structure whose size exceeds 64k.
There are huge pointer types, and it's possible to allocate a
simple linear array that exceeds 64k in size.  In this sense the
complaint isn't fair (also, there's a memory allocation routine for
huge pointers called halloc (huge_malloc) which handles the corresponding
job.  The command line parameter allowing huge compilation is /AH.
This works fine if the large memory library is there.

Also, it's possible to allocate square arrays that exceed 64k even though
you're using only the large model....  as follows:

...
	double **a;
	a= (double **)malloc(n*sizeof(double *));
	for(i=0;i<n;i++)a[i]=(double *)malloc(n*sizeof(double));
...

This will allocate an nxn array using only large model pointers,
so long as n*sizeof(double) < 64k (which is usually true since
in most dos machines around now there wouldn't be room for 64k * 64k
arrays.

Hope this is a useful clarification.

Dan