PURPOSE: To increase a data processing speed and to increase easily the number of memories by converting independently the operation mechanism of a transaction memory into hardware.

CONSTITUTION: A buffer memory consists totallly of a buffer memory 10 exclusive for transaction, CPU11 and main memory 12. The actuation of the memory 10 which is separated from the general-purpose memory 12 is started through the memory 12, communication line l1, CPU11, communication line l2 and a buffer memory starting part 101. A starting program stored to the memory 12 is read by the CPU11 and sent to the part 101 to start the memory 10. The line l3 is used when the data of a buffer memory 103 at the side of the memory 12. In this case, the part 101 can be omitted.