DOS Fn 440fH: IOCTL Set Logical Drive Map

                                                         Compatibility: 3.2+ 
 Expects: AX    440eH
          BL    drive in question (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)
                else: drive number currently being used to refer to this
                physical drive.
    Info: This tells the device driver that its "drive alias" will be used
          in subsequent read/write access.

   Notes: ■ 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 ell that driver that the
            "disk for drive B" is already in place--and thus avoid having
            DOS issue this prompt.

          ■ Phantom floppies are also created by the Driver.Sys installable
            device driver.

See Also: Fn 44H (IOCTL)
          Fn 440eH (query logical drive map)
          DOS Functions