PURPOSE: To ensure the change of priority by reporting a phenomenon of the highest priority and rewriting the contents of a priority table in case a transfer request of phenomena is given from a computer main body based on the contents of the table and a phenomenon register.

CONSTITUTION: The priority is decided for each of phenomena produced at random and these priorities are registered to a priority table 2 in a style suitable to the high-speed processing. A central processing unit 3 starts its working with a request given from a computer main body to set only the bit having the highest priority based on the contents of a phenomenon memory register 1 and the table 2 and informs the output result to the computer main body. As a result, it is possible to cope with a high processing speed and the change of the priority or the number of phenomena just by maintaining the table 2 only.