Function  32h  Read DOS Disk Block 
 *   Retrieve the pointer to the drive parameter block for a drive  
entry   AH      32h 
	DL      drive (0=default, 1=A:, etc.).  
return	AL	00h	if drive is valid
		0FFh    if drive is not valid 
	DS:BX	pointer to DOS Drive Parameter Table. Format of block:
		Bytes   Type        Value 
		00h     byte    Drive: 0=A:, 1=B:, etc. 
		01h     byte    Unit within drive (0, 1, 2, etc.) 
		02h-03h word    Bytes per sector 
		04h     byte    Sectors per cluster - 1 
		05h     byte    Cluster to sector shift (i.e., how far to shift- 
			        left the bytes/sector to get bytes/cluster) 
		06h-07h word    Number of reserved (boot) sectors 
		08h     byte    Number of FATs 
		09h-0Ah word    Number of root directory entries 
		0Bh-0Ch word    Sector # of 1st data. Should be same as # of  
			        sectors/track. 
		0Dh-0Eh word    # of clusters + 1 (=last cluster #) 
		0Fh     byte    Sectors for FAT 
		10h-11h word    First sector of root directory 
  (note 3)	12h-15h dword	Address of device\drivers header for drive
Function  32h  Read DOS Disk Block
return	DS:BX	pointer to DOS Drive Parameter Table. Format of block:
                Bytes   Type        Value 
                16h     byte    Media Descriptor Byte for this drive
		17h     byte    0FFh indicates block must be rebuilt 
			        (DOS 3.x) 00h indicates block device has  
			        been accessed 
		18h-1Bh dword   address of next DOS Disk Block (0FFFFh means  
			        last in chain) 
		22h     byte    Current Working Directory (2.0 only) (64 bytes) 
note 1) Use [BX+0D] to find no. of clusters (1000H, 16-bit FAT; if not, 12-bit 
	(exact dividing line is probably a little below 1000h to allow for 
	bad sectors, EOF markers, etc.) 
     2) Short article by C.Petzold, PC Magazine  Vol.5,no.8, and the article 
	"Finding Disk Parameters" in the May 1986 issue of PC Tech Journal. 
     3) This call is mostly supported in OS/2 1.0's DOS Compatibility Box. The 
	dword at 12h will not return the address of the next device driver when 
	in the Compatibility Box. 
     4) used by CHKDSK