Allocates an alternate map register set for use with Int 67H Function 5BH Subfunctions 00H and 01H. The contents of the currently active map registers are copied into the newly allocated alternate map registers in order to provide an initial context when they are selected.
Call with:
AH = 5BH
AL = 03H
Returns:
If function successful
AH = 00H
BL = alternate map register set number or zero, if no alternate
sets are available
If function unsuccessful
AH = error code
Note:
This function is intended for use by operating systems only and can be disabled by the operating system at any time.