PURPOSE: To speed up the data processing, by mounting a duel port memory and an I/O processor to each input and output module and using this dual port memory as a part of the main memory for the whole system.

CONSTITUTION: An address bus inputted and outputted to a CPU module C is provided with a main memory module M1, an auxiliary memory M2 and a memory module system to which input/output modules A11WA1N such as various interface modules and control modules are connected. The modules A11W A1N are provided with a dual port memory M3 functioned as a part of the memory M1 and an I/O processor P. The speed-up of data processing can be made by freely accessing the memory M3 with the CPU and the processor P as the main memory.