DOS Fn 4400H: IOCTL Query Device/File Flags

                                                         Compatibility: 2.0+ 
 Expects: AX    4400H
          BX    file handle  (device or disk file)
 Returns: AX    error code  if CF is set to CY
          DX    IOCTL device info (if no error)
    Info: Checks to see if a handle represents a device or a disk file and
          obtains information about that device or file.

          See IOCTL device info for a layout of the 16-bit return value.

          If the handle is a disk file:
            DX bit 7 is clear (0)
            DX bit 6 is set if the file is "dirty" (has been written to)
            DX bits 0-5 represent a drive number (0=A, 1=B, etc.)

          If the handle is a device:
            DX bit 7 is set (1)
            DX bits 0-6 are device information flags
            DX bits 8-15 are the same as bits 8-15 of the Device Attribute
              (the rDevAttr field of the driver's DevHdrRec structure).

   Notes: ■ This is often used to see if Standard I/O has been redirected.
            For instance, if handle 01H (standard output) represents a disk
            file rather than the CON device, you may wish to output
            different information and perhaps send some extra messages to
            handle 02H (Standard Error device).

See Also: Fn 44H (IOCTL)
          Fn 4401H (Set Device/File Flags)
          DOS Functions