INT 2Fh... (47)          Multiplex Interrupt                         Overview

    Defines a general interface between two processes. Applications using
    this interrupt must define specific functions and parameters.
    Functions currently defined by DOS include the resident portions of
    PRINT, ASSIGN, SHARE, and APPEND.

       On entry:      AH         Multiplex number
                      AL         Function to be performed by multiplex handler

       Returns:       AX         Error code

  --------------------------------------------------------------------------

    A multiplex handlers is referenced by its "multiplex number," in the
    AH register. The choice of multiplex number is arbitrary; you may
    assign any number to your routine between 80h and FFh; 0 through 7Fh
    are reserved for use by DOS.

    The function to be performed by the multiplex handler is specified in
    AL. Other registers may hold other parameters, as needed (see the
    separate descriptions of the multiplex handlers implemented by DOS).

    All multiplex handlers must define a call for AL = 0 (Get Installed
    State). AL values of F8h to FFh are reserved by DOS.

    Multiplex Handlers Implemented or Reserved by DOS

               AH       1h      Resident part of PRINT
                        2h      Resident part of ASSIGN
                       10h      Resident part of SHARE
                       B7h      Resident part of APPEND

    All other values from AH = 0 to AH = 7Fh are reserved by DOS.

    Interrupt 2Fh is available in DOS versions 3.1 and later.