Allocate Linear Memory Block

Call With

AX = 0504H
EBX = desired page-aligned linear address of memory block, or zero if linear address unspecified
ECX = size of block (bytes, must be nonzero)
EDX = flags

Bit	Significance
0	0 = create uncommitted pages
	1 = create committed pages
1-31	reserved, should be zero

if function unsuccessful
Carry flag = set
AX = error code

8001H	unsupported function (16-bit host)
8012H	linear memory unavailable
8013H	physical memory unavailable
8014H	backing store unavailable
8016H	handle unavailable
8021H	invalid value (ECX = 0)
8025H	invalid linear address (EBX not page aligned)

Notes

• A DPMI 1.0 host that is 16-bit only will not support this function.

• A 16-bit client of a 32-bit DPMI 1.0 host can use this function.

• The allocated block is always page-aligned. If a specific linear address is not requested (EBX = 0), the DPMI host allocates the memory block at any available page-aligned linear address. If a specific linear address is requested (EBX nonzero), the host either allocates the block at the specified address or returns error code 8012H (linear memory unavailable).

• Int 31H Function 0501H, which can also be used to allocate linear memory blocks, does not necessarily page-align its blocks and does not have the ability to create uncommitted pages or allocate a block at a specific linear address.