🚀 go-pugleaf

In article <1992Nov5.053551.20533@emr1.emr.ca> jagrant@emr1.emr.ca (John Grant) writes:
>In article <1992Nov5.031544.5264@sequent.com> furballs@sequent.com (Paul Penrod) writes:
>[stuff deleted]
>
>>Almost right, but you forgot something.
>>
>>In your data declarations, if you do not specifically specify the
>>keyword far, then the declaration is left in the default data
>>segment, which can be a problem if you have more than 64k of global
>>data. Granted, DS is referenced by a far pointer, but you are still
>>limited to 64k per data segment, eventhough you can reference upto
>>1 megabyte of data and 1 meg of code. This is because the far
>>pointers in the LARGE model are not normalized 32 bit, but
>>segment:offset 20 bit pointers. 
>>
>I am writing my first app, and I am using large model (BC++ 3.1). I haven't
>used either 'far' or 'FAR' so far.  I have just let pointers default to far as
>provided by the large model.  Ok, presumably I will eventually hit the
>64k limit for data in my app sooner or later.  What do I do then?
>Are you saying I can get more than 64k data storage by explicitly using the
>'far' declaration?  Does that give me 'another' 64k data segment?
>
By explicitly declaring a variable, array, pointer, structure, etc.
to be far the compiler forces it into another data segment, thus
you can achieve more than 64k of TOTAL global storage by this
method. If you want to have arrays or structures that explicity
store > 64k of data in one instance then you have to use the HUGE
model, which, under the Borland Compiler, makes use of 32 nit
normalized pointers. By normalized, they mean a linear 32 bit
address that refers to only one place in memory. Under the segment
offset method, several variations of the segment:offset address can
point to the exact physical location in memory.

If you have the Borland C++ 3.0 or 3.1 compiler, look on page 344
to 346 of the Programmer's Guide and it does give a good, albeit
cursory explaination of pointers and how those versions of the
compiler handle them and the advantages, plus drawbacks to each.

Good Luck...

...Paul


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