Claims

1. Apparatus for control of a first computer (231) system responsive to callable programs (205) by a second computer system (233) connected by message transport means (210, 213) to the first computer system, characterized by 1. message providing means (227) in the second computer system for providing a call message (215) specifying a callable program in the first computer system to the message transport means, and 2. message interpretation means (211) in the frist computer system for receiving the call message from the message transport means and calling the callable program specified in the call message.

2. Control apparatus of claim 1 characterized in that the call message (215) further contains call data (239) for use in calling the specified callable program (205), and the message interpretation means (211) uses the call data (239) in calling the specified callable program.

3. Control apparatus of claim 1 or 2, characterized in that the message interpretation means (2t1) in the first computer system (231) provides a retum message (217) containing the result of the call of the callable program to the message transport means, and the message providing means (217) in the second computer system (233) receives the return message from the message transport means 4. Control apparatus of claim 3, characterized in that the message providing means (227) in the second computer system (233) is a processor means (221) executing a callable program (205); and the processor means executes a return operation after receiving the retum message (217).

5. Control apparatus of claim 3 or 4, characterized in that the retum message (217) further contains retum data (243).

6. Control apparatus of claim 5, characterized in that the message providing means (227) in the second computer system (233) is a processor means (221) executing a callable program (205), and the processor means provides the return data (243) to the calling program and executes a retum operation.

7. Control apparatus of any of claims l to 6, characterized in that the callable programs (205) include system programs.

8. Control apparatus of claim 1, characterized in that the callable programs (205) are subdivided into a plurality of sets of callable programs; the message interpretation means (211) is subdivided into message receiving means (751) and a plurality of server means (771, 773) corresponding to the plurality of sets of callable programs; the message providing means (227) further provides a server specifier message (607) specifying one of the server means prior to the call message; the message receiving means (751) responds to the server specifier message by slecting one of the server means (771, 773); and the selected server means responds to the call message by calling the specified callable program (205).

9. Control apparatus of claim 8, characterized in that the server means include system server means (773) for calling specified system programs and user server means (771) for calling specified user programs.

10. Apparatus for mutual control of a first computer system (301) responsive to first callable programs (311) and a second computer system (303) responsive to second callable programs (337), the first and second computer systems being connected by message transfer means (325), characterized by 1. first message providing means (317) in the first computer system for providing a first message (215) specifying one of the second callable programs to the transport means, 2 second message providing means (329) in the second computer system for providing a secopnd message (215) specifying one of the first callable programs to the transport means, 3. first message interpretation means (315) in the first computer system for receiving the second message from the transport means and invoking the first callable program specified therein, and 4. second message interpretation means (329) in the second computer system for receiving the first message from the transport means and invoking the second callable program specified therein.