PURPOSE: To improve performance for executing a pipe line by setting a following executable instruction to a pipe line register together and executing the instruction when a certain instruction is locked concerning the pipe-line control system.

CONSTITUTION: Pipe line registers PR1-PRn are provided and in the case of successively setting instructions to these registers and executing them, a flag provided at the pipe line register PR2 is set to ON when the instructions set to the pipe line registers PR1 and PR2 can be simultaneously executed. When the instruction is set to the pipe line register PRn and locked during the execution, the set flag is propagated and when it is turned on, the instruction of the pipe line register PRn is set together to this pipe line register PRn so as to continue the processing.