INT 21,32 - Get Pointer to Drive Parameter Table (Undocumented)
AH = 32h DL = drive (0=default, 1=A:, 2=B:, 3=C:, ...) on return: AL = FF if the drive number in DL was invalid DS:BX = address of drive parameter table (DPT) - available since DOS 2.0 - used by DOS commands CHKDSK and RECOVER - forces a media check, which clears byte DS:[BX+17h] or DS:[BX+18h] in the Drive Parameter Table - actually accesses the disk, causing a critical error if a disk error occurs - can be used to determine if a drive is SUBST'ed by comparing DS:[BX+1] and DS:[BX] for a match. If not equal, then the drive is possibly SUBST'ed (though not guaranteed, this may also indicate a Bernoulli box) - can be used to determine if a drive is a RAM disk; if the disk is NOT removable and (DS:[BX+1] == 0), then the disk is a RAM disk (see IOCTL,0 bit number 0Bh to determine if the disk is removable)