Function 19h (25)        Get Current Disk

Gets the drive number of the current default drive.

On entry:      AH         19h

Returns:       AL         Number of default drive (A = 0, B = 1, etc.)

                                                                          

Note:          The drive numbers returned by this function are one
less than the drive numbers used by many functions;
many functions use 0 for the default drive and start
with A = 1 (rather than A = 0).

See also: 0Eh

19h (25) Get Current Disk