INT 21 - DOS 1+ - NULL FUNCTION FOR CP/M COMPATIBILITY
AH = 1Dh
Return: AL = 00h
Note:   corresponds to the CP/M BDOS function "get bit map of read-only
drives", which is meaningless under MSDOS
SeeAlso: AH=1Eh,AH=20h,AX=4459h

See also: 2118

211D - DOS 1+ - NULL FUNCTION FOR CP/M COMPATIBILITY