Compatibility: 2.0+
Expects: AH    1bH
Returns: DS:BX address of a FAT ID byte (might indicate disk type)
DX    total clusters (allocation units) on the disk
AL    sectors per cluster
CX    bytes per sector
Info: Returns information on the size and type of the default disk.

Disk size in bytes = (DX * AL * CX)

Find free space with DOS Fn 36h Disk Free or 32h Disk Info

Warning: Notice that this changes the value of DS segment register.

Versions: DOS 1.x held the FAT in memory and returned DS:BX => FAT
DOS 2.0+ may retain only a portion of the FAT in memory.

See Also: Fns 1cH  36H  32H
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DOS Fn 1bH: Get Drive Info (current disk)