0:504h                   Phantom drive flag

Length: 1 byte

Reports the status of a single-drive system when mimicking a two-drive

system.

Examination of this byte will reveal the current status of the single

drive installed on a one drive system. By using this byte, a

programmer can avoid the message 'Insert disk for drive B:' when

working with a single-drive system.

                  Value              Meaning

00h           Acting as drive A

01h           Acting as drive B

FFh           Acting as drive A

Although the last value, FFh, is undocumented, FFh means the drive

letter has not been determined yet, so using the drive as drive A will

work correctly.

To determine if only one drive is installed, use the equipment list

(see INT 11h).

Prev:     0:501h Reserved

See also: INT 11h

Next:     0:505h Reserved