Function 1Bh (27)        Get FAT Information for Current Drive

Gets disk characteristics and the media descriptor byte for the
current drive. (The media descriptor byte specifies the type of
drive.)

On entry:      AH         1Bh

Returns:       AL         Number of sectors per cluster
CX         Sector size in bytes
DX         Total number of disk clusters
DS:BX      Pointer to the media descriptor byte (FAT ID
byte)

                                                                          

  Media Descriptor (FAT ID) Byte

The media descriptor byte is limited to the values F0 through FF. This
range is no longer sufficient to provide unique identifiers for each
media type. The following values are defined:

FFh            Double-sided 5 1/4" floppy, 8 sectors
FEh            Single-sided 5 1/4" floppy, 8 sectors or
Single-sided 8" floppy, 26 sectors or
Single-sided 8" floppy, 8 sectors
FDh            Double-sided 5 1/4" floppy, 9 sectors or
Single-sided 8" floppy, 26 sectors
FCh            Single-sided floppy, 9 sectors per track
F9h            Double-sided 5 1/4" floppy, 15 sectors or
Double-sided 3 1/2" floppy, 9 sectors
F8h            Hard disk
F0h            Double-sided 3 1/2" floppy, 18 sectors or
Any other undefined media type

For more reliable information about media type, use Interrupt 25h to
read the BIOS Parameter Block (BPB) in the boot record.

                                                                          

Notes:         This function changes the current value of DS. To
ensure the stability of your program, it's best to
PUSH DS before calling this service.

To perform the same function for a drive other than
the default, use Function 1Ch.

See also: 1Ch
See also: 36h

1Bh (27) Get FAT Information for Current Drive