INT 21 - DOS 3.2+ - IOCTL - GENERIC BLOCK DEVICE REQUEST
        AX = 440Dh
        BL = drive number (00h=default,01h=A:,etc)
        CH = category code
            08h disk drive
            00h-7Fh reserved for Microsoft
            80h-FFh reserved for OEM/user-defined
        CL = function
            40h set device parameters
            41h write logical device track
            42h format and verify logical device track
            46h (DOS 4+) set volume serial number (see also AH=69h)
            47h (DOS 4+) set access flag
            60h get device parameters
            61h read logical device track
            62h verify logical device track
            66h (DOS 4+) get volume serial number (see also AH=69h)
            67h (DOS 4+) get access flag
            68h (DOS 5+) sense media type
        DS:DX -> (DOS) parameter block (see below)
        SI:DI -> (OS/2 comp box) parameter block (see below)
Return: CF set on error
            AX = error code (01h,02h) (see AH=59h)
        CF clear if successful
            DS:DX -> data block if CL=60h or CL=61h
Notes:  DOS 4.01 seems to ignore the high byte of the number of directory
          entries in the BPB for diskettes.
        functions 46h and 66h undocumented in DOS 4.x, documented for DOS 5.0
SeeAlso: AH=69h,INT 2F/AX=0802h,INT 2F/AX=122Bh

Format of parameter block for functions 40h, 60h:
Offset  Size    Description
 00h    BYTE    special functions
                bit 0 set if function to use current BPB, clear if Device
                        BIOS Parameter Block field contains new default BPB
                bit 1 set if function to use track layout fields only
                        must be clear if CL=60h
                bit 2 set if all sectors in track same size (should be set)
                bits 3-7 reserved
 01h    BYTE    device type
                00h  320K/360K disk
                01h  1.2M disk
                02h  720K disk
                03h  single-density 8-inch disk
                04h  double-density 8-inch disk
                05h  fixed disk
                06h  tape drive
                07h  (DOS 3.3+) 1.44M floppy
                08h  read/write optical disk
                09h  (DOS 5.0) 2.88M floppy
                0Ah  other type of block device
 02h    WORD    device attributes
                bit 0 set if nonremovable medium
                bit 1 set if door lock ("changeline") supported
                bits 2-15 reserved
 04h    WORD    number of cylinders
 06h    BYTE    media type
                for 1.2M drive
                    00h 1.2M disk (default)
                    01h 320K/360K disk
                always 00h for other drive types
 07h 31 BYTEs   device BPB (see AH=53h), bytes after BPB offset 1Eh omitted
 26h    WORD    number of sectors per track (start of track layout field)
                not used by function 60h
 28h  N word pairs: number,size of each sector in track

Format of parameter block for functions 41h, 61h:
Offset  Size    Description
 00h    BYTE    special functions (reserved, must be zero)
 01h    WORD    number of disk head
 03h    WORD    number of disk cylinder
 05h    WORD    number of first sector to read/write
 07h    WORD    number of sectors
 09h    DWORD   transfer address

Format of parameter block for functions 42h, 62h:
Offset  Size    Description
 00h    BYTE    reserved, must be zero (DOS <3.2)
                  bit 0=0: format/verify track
                        1: format status call (DOS 3.2+)
                  bits 1-7 reserved, must be zero
                on return (DOS 4.x):
                  bit 0: set if specified tracks, sectors/track supported
                  bit 1: set if function not supported by BIOS
                  bit 2: set if specified tracks, sectors/track not supported
                  bit 3: set if no disk in drive
 01h    WORD    number of disk head
 03h    WORD    number of disk cylinder

Format of parameter block for functions 46h, 66h:
Offset  Size    Description
 00h    WORD    info level (00h)
 02h    DWORD   disk serial number (binary)
 06h 11 BYTEs   volume label or "NO NAME    "
 11h  8 BYTEs   filesystem type "FAT12   " or "FAT16   " (CL=66h only)

Format of parameter block for functions 47h, 67h:
Offset  Size    Description
 00h    BYTE    special-function field (must be zero)
 01h    BYTE    disk-access flag, nonzero if access allowed by driver

Format of parameter block for function 68h:
Offset  Size    Description
 00h    BYTE    01h for default media type, 00h for any other media type
 01h    BYTE    02h for 720K, 07h for 1.44M, 09h for 2.88M