Function 440Fh (68-15)   IOCTL: Set Logical Drive                     DOS 3.2

Sets the drive letter used most recently to refer to a device that has
more than one drive letter.

On entry:      AH         44h
AL         0Fh
BL         Drive number (0=default, 1=A, etc.)

Returns:       AL         00h of only one letter is assigned to the
block device
Highest letter assigned to block device
(1 = A, 2 = B, etc.)
AX         Error code if CF is set

                                                                          

Some block devices use more than one drive letter to refer to the same
device.  For example, the floppy disk drive on a system with only one
floppy disk drive can be referred to as either A: or B:.  This
function sets the drive letter used most recently to refer to a drive.

Notes:         Function 440Eh can be used to get the most recent
drive letter used to refer to a device.

If you issue an I/O operation using a drive letter
other than the most recently used drive letter, DOS
will issue a message "Insert diskette for...".  You
can avoid this message by changing the current drive
letter before issuing any I/O function calls.

See also: 44h
See also: 440Eh

440Fh (68-15) IOCTL: Set Logical Drive >= DOS 3.2