PURPOSE: To eliminate an error of a program and to operate an electronic computer efficiently by performing exclusive control automatically when plural programs access a common global area.

CONSTITUTION: A locking circuit 2 is connected to respective arithmetic controllers. When data in the global area 6 is made access, the address in an instruction is led out of an address extracting circuit 10 and inputted to a lock checking circuit 11. The circuit 11 inhibits a gate circuit 14 from being open until access to an address is completed when the address to be made access is in the global area 6 and by another controller 1. Further, when access to the global area 6 is possible and the address to be made access is not in the global area 6, a gate-on signal is outputted to the circuit 14. Therefore, only one arithmetic device 1 is permitted to be in access to the global area.