Int 21/AH=20h

AH = 20h

Return:
AL = 00h

Note: Corresponds to the CP/M BDOS function "get/set default user (sublibrary) number", which is meaningless under MS-DOS

See Also: AH=18h - AH=1Dh - AH=1Eh - AX=4459h

Category: DOS Kernel - Int 21h - D