Compatibility: DPMI 1.0+
Expects: AX    0504H
EBX   desired linear address or 0
ECX   size of block, in bytes (must not be 0)
EDX   flags:  bit 0: 1=create committed pages
0=create uncommitted pages
1-31: (reserved; should be 0)
                                                                  
Returns: CF    NC (clear) if successful; else AX = DPMI Error Code
EBX   linear address of allocated block
ESI   handle used to resize and free this block
                                                                  
Info: Allocates a block of page-aligned linear address space.  The base
address of the block may be specified by the client and the
allocated pages may be committed or uncommitted.

If EBX is 0 on entry, then the host can pick any available linear
addresses.

See Also: DPMI API
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INT 31H 0504H: Allocate Linear Memory Block