with DOS/4GW? - Open Watcom

DOS Programming Guide
void main()
{
/* Need a far pointer to use the screen selector */
char far *ptr;
int i;
}
/* Make a far pointer to screen memory */
ptr = MK FP( PL SCREEN SELECTOR, 0 );
for( i = 0; i < SCREEN SIZE - 1; i++ ) {
*ptr = ’*’;
ptr += 2 * sizeof( char );
}
It is also possible to map screen memory into your near memory using Phar Lap system calls.
Please refer to the chapter entitled "386|DOS-Extender System Calls" in Phar Lap’s
386|DOS-Extender Reference Manual for details.
5.3 How do I get information about free memory in the
32-bit environment?
Under a virtual memory system, programmers are often interested in the amount of physical
memory they can allocate. Information about the amount of free memory that is available is
always provided under a DPMI host, however, the manner in which this information is
provided may differ under various environments. Keep in mind that in a multi-tasking
environment, the information returned to your task from the DPMI host can easily become
obsolete if other tasks allocate memory independently of your task.
5.3.1 Getting Free Memory Information under DOS/4GW
DOS/4GW provides a DPMI interface through interrupt 0x31. This allows you to use DPMI
service 0x0500 to get free memory information. The following program illustrates this
procedure.
22 How do I get information about free memory in the 32-bit environment?