The removable-media function is supported only under MS-DOS versions 3.0 and later and only on block devices; in character-device drivers it should do nothing except set the done flag. This function is called only if bit 11 is set in the device attribute word in the device header.
The removable-media function is called with
RH + 1 BYTE Unit code
RH + 2 BYTE Command code = 15 (0FH)
It returns
RH + 3 WORD Status:
If busy bit = 1, medium nonremovable
If busy bit = 0, medium removable