struc LogDeviceRequest          ; Device-Driver functions 17h, 18h
 ldrLength      db ?            ; Length of structure, in bytes
 ldrUnit        db ?            ; INPUT:  unit number for drive to check
                                ; OUTPUT: active drive number
 ldrFunction    db ?            ; Function number (17h or 18h)
 ldrStatus      dw ?            ; Status
 ldrReserved    db 8 dup (?)    ; Reserved
ends                            ; = 13d bytes