DOS Fn 440eH: IOCTL Query Logical Drive Map
Expects: AX 440eH
BL drive number to be used (0=default, 1=A, 2=B, etc.)
Returns: AX error code if CF is set to CY
AL 00H: the drive has only one drive number (if no error)
01H-1aH: the drive number currently being used to refer to
this physical drive.
Info: This checks to see of a physical drive is currently acting as a
phantom floppy (or "logical drive") and if the alternate drive ID
is currently being used.
If CY is clear on return, then AL contains either 0 (no logical
mappings) or AL contains the alternative drive number that can
refer to this drive (1=A, 2=B. etc.).
Notes: ■ If fn 440fH (set logical drive map) has not been called, all
logical drive numbers will match the physical numbers.
■ The phantom floppy concept is used by DOS on systems which have
a single diskette drive. In that case, when you attempt to
access drive B, DOS prompts with:
Insert diskette for drive B.
Press any key when ready.
Programs may use this function to avoid using a logical ID and
thus, avoid having DOS issue this prompt.
■ Phantom floppies are also created by the Driver.Sys installable
See Also: Fn 44H (IOCTL)
Fn 440fH (set logical drive map)