Entry: AH = 32h DL = drive number 0 = default, 1 = A, etc. Return: AL = Status 0FFh if invalid drive number, else DS:BX = Address of DOS Drive Parameter Block (DDPB).
Format of DOS Drive Parameter Block:
Offset Size Description 00h BYTE drive number (0 = A, etc.) 01h BYTE unit number within device driver 02h WORD number of bytes per sector 04h BYTE largest sector number in cluster (one less than sect/clust) 05h BYTE log base two of the cluster size 06h WORD number of reserved (boot) sectors 08h BYTE number of copies of the FAT 09h WORD number of root directory entries 0Bh WORD first data sector on medium 0Dh WORD largest possible cluster number (one more than # data clust) ---DOS 2.x--- 0Fh BYTE number of sectors in one FAT copy 10h WORD first sector of root directory 12h DWORD address of device driver for this drive 16h BYTE media descriptor byte for medium 17h BYTE FFh indicates block must be rebuilt 18h DWORD address of next device block, offset = FFFFh indicates last 1Ch WORD starting cluster of current directory (0 = root directory) 1Eh 64 BYTEs ASCIZ current directory path string ---DOS 3.x--- 0Fh BYTE number of sectors in one FAT copy 10h WORD first sector of root directory 12h DWORD address of device driver for this drive 16h BYTE media descriptor byte for medium 17h BYTE FFh = block must be rebuilt, 00h indicates block accessed 18h DWORD address of next device block, offset = FFFFh indicates last 1Ch WORD cluster at which to start search for free space when writing 1Eh WORD number of free clusters on drive, FFFFh = unknown ---DOS 4.0--- 0Fh WORD number of sectors in one FAT copy 11h WORD first sector of root directory 13h DWORD address of device driver for this drive 17h BYTE media descriptor byte for medium 18h BYTE FFh = block must be rebuilt, 00h indicates block accessed 19h DWORD address of next device block, offset = FFFFh indicates last 1Dh WORD cluster at which to start search for free space when writing 1Fh WORD number of free clusters on drive, FFFFh = unknown
Note: the OS/2 compatibility box supports this call except for the DWORD at 12h