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In article <1992Jul29.125835.14342@msc.cornell.edu> revesz@msc.cornell.edu (Peter Revesz) writes:
>Hi, Netters,
>
>My global data is basicly in structures. To avoid
>compile-time error message (global data >64 Kb) I have
>to make all global far.
>
>How to make a struct far?
>
>This way:
>
>struct one {
>    int far a[100];
>    double far b[2000];
>} one;
>
>or this way:
>
>struct two {
>    int a[100];
>    double b[2000];
>} far two;
>
>
>or this way?
>
>struct three {
>    int far a[100];
>    double far b[2000];
>} far three;
>
>
>Which the proper way to create far structs?
>Any help will be appreciated.
>
>Peter Revesz
>
>revesz@msc.cornell.edu

> Hi, Netters,
> 
> My global data is basicly in structures. To avoid
> compile-time error message (global data >64 Kb) I have
> to make all global far.
> 
> How to make a struct far?
> 
> This way:
> 
> struct one {
>     int far a[100];
>     double far b[2000];
> } one;
>
This won't work - the data being delcared is static, which will still
result in the same error message.

> or this way:
> 
> struct two {
>     int a[100];
>     double b[2000];
> } far two;
> 
> 
> or this way?
> 
> struct three {
>     int far a[100];
>     double far b[2000];
> } far three;
> 
> 
> Which the proper way to create far structs?
> Any help will be appreciated.
> 

How about:

struct foo {
	int *a;
	double *b;
} bar;
    .
    .
    .
    if ((bar.a = calloc(sizeof(int),100)) == NULL)
        .
        .
        .
    if ((bar.b = calloc(sizeof(double),2000)) == NULL)
        .
        .
        .


For one thing the far keyword is not portable, and is implementation dependant.
the meathod I have showed you is portable, and will work with ANSI C.


In 8086 real mode and 80286 protected mode, the processor's maximum memory
allocation unit is a 64K segment. (except in huge model where the compiler
generates the code necessary to 'tile' segments). When you compile your code,
static data goes in a single segment, DGROUP. If, at compile time, the static
data consists of pointers rather than the actual arrays, then the DGROUP
is smaller. If you are compiling under medium or large memory models,
you can allocate almost 64K per item, provided there is enough available
memory on the far heap. If you are using the compact, or small models,
you can add the far keyword in front of your pointer declarations and use
farcalloc (or farmalloc) to get memory.



Hope this helps ....


Steve

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