Important Notice

The pages on this site contain documentation for very old MS-DOS software, purely for historical purposes. If you're looking for up-to-date documentation, particularly for programming, you should not rely on the information found here, as it will be woefully out of date.

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     Through an Int 2Fh multiplex handler, a TSR can communicate its
     location in memory to a calling program. This allows the calling
     program to
 
        ■ Verify the TSR's presence in memory
        ■ Read or write resident data
        ■ Deinstall the TSR from memory
 
     DOS version 2.0 does not provide a Multiplex Interrupt except when
     the print spooler PRINT is resident. A program that sets up a
     multiplex handler under version 2.0 must first inspect the Int 2Fh
     vector. If the vector is null, the handler must terminate with an
     IRET to avoid passing control to a nonexistent routine.
     Furthermore, if PRINT is used under version 2.0, it must be
     installed before all other programs that chain to Int 2Fh.
                                    -♦-