struc MediaRequest              ; Device-Driver function 01h
 mrLength       db ?            ; Length of structure, in bytes
 mrUnit         db ?            ; Not used
 mrFunction     db ?            ; Function number (01h)
 mrStatus       dw ?            ; Status
 mrReserved     db 8 dup (?)    ; Reserved
 mrMediaID      db ?            ; INPUT:  current media descriptor
 mrReturn       db ?            ; OUTPUT: media changed -1|0|1=yes|?|no
 mrVolumeID     dd ?            ; OUTPUT: address of volume id.
ends                            ; = 19d bytes