Allocates a block of memory, using DOS service 0x48.
#include <dos.h>
#include <errno.h>
unsigned _dos_allocmem( unsigned size, unsigned *seg );
| size | Block size to allocate | |
| seg | Return buffer for segment descriptor |
The _dos_allocmem function uses DOS service 0x48 to allocate a block of memory size paragraphs long. (A paragraph is 16 bytes.) Allocated blocks are always paragraph aligned. The segment descriptor for the initial segment of the new block is returned in the word that seg points to. If the request cannot be satisfied, the maximum possible size (in paragraphs) is returned in this word instead.
If successful, the _dos_allocmem returns 0. Otherwise, it returns the DOS error code and sets errno to ENOMEM, indicating insufficient memory or invalid arena (memory area) headers.
Standards:None
16-Bit:DOS
32-Bit:None
_alloca, calloc functions, _dos_freemem, _dos_setblock, _halloc, malloc functions
/* DALOCMEM.C: This program allocates 20 paragraphs of memory, increases
* the allocation to 40 paragraphs, and then frees the memory space.
*/
#include <dos.h>
#include <stdio.h>
void main( void )
{
unsigned segment;
unsigned maxsize;
/* Allocate 20 paragraphs */
if( _dos_allocmem( 20, &segment ) != 0 )
printf( "allocation failed\n" );
else
printf( "allocation successful\n" );
/* Increase allocation to 40 paragraphs */
if( _dos_setblock( 40, segment, &maxsize ) != 0 )
printf( "allocation increase failed\n" );
else
printf( "allocation increase successful\n" );
/* free memory */
if( _dos_freemem( segment ) != 0 )
printf( "free memory failed\n" );
else
printf( "free memory successful\n" );
}
allocation successful
allocation increase successful
free memory successful