PURPOSE: To allow a supervisor to perform task processing by an attach instruction and a call instruction by providing a table stored with instruction of the supervisor and also providing a function which stores a post instruction in the table successively to attach instruction processing.

CONSTITUTION: A task A,1 requests the supervisor to perform task generation. The supervisor 2 receives this request at a reception part 3 to inform a control part 4 that the request is the attach instruction, and registers the attach instruction in the table 5 and operates a task control block 6 to put a task B,7 in operation. The control part 4 stores a post instruction by said operation as a substitute for the attach instruction in the table 5. Therefore, the generated task is performed according to the post instruction to eliminate the need for a judgement for discriminating between the task generation and task communication. When the call instruction is generated for the task A,1, the reception part 3 registers it in the table 5, and a task control block 6 is operated to call a task B,7.