INT 2fH 1683H: Get Current Virtual Machine ID

                                                      Compatibility: Win 3.x 
 Expects: AX    1683H
 Returns: BX    virtual machine identifier
    Info: DOS programs and device drivers can use this service to learn
          which virtual machine (e.g., DOS session) is running.  This is
          handy if your TSR maintains separate data or execution contexts
          for each VM or DOS session.

          Windows typically runs in VM 0001H (but that's not guaranteed in
          the future).  Also, Windows may need to recycle VM IDs, so you
          are supposed to monitor for VM starts and terminations (though it
          is not obvious how to do so).

See Also: INT 2fH 16xxH: Enh386 Windows Services & Notifications
          INT 2fH: Multiplex Interrupt
          DOS Functions