PURPOSE: To flexibly deal with the changes of addresses, etc., and to improve the diversion properties of a process input/output control system by performing an access of the input/output data between the processes through a user program and in response to the physical address of each printed board.

CONSTITUTION: A process input/output control part 6 outputs the output request data to an external device 3 via a printed board 4 while analyzing the request parameter received from a user program. The part 6 also informs the user program of the data given from a sensor 2 via the board 4. Then, the user program inputs and outputs the data given from each process based on a control table 5 for logical/physical addresses and data types and with use of the logical address that can have an access to the one-word data corresponding to the physical address of the board 4. Furthermore, the user program can request plural logical addresses at one time and contains an invalid NOP address in order to directly use the data 8 and 10 transmitted to and received from a host device 7 respectively.