PURPOSE: To allow data control system to execute processing corresponding to the urgency or the like of various data by allocating priority levels to respective groups of data queues.

CONSTITUTION: The data queues A to J to be used for respective operation programs are divided into groups I to IV and the priority levels corresponding to processing priority are allocated to respective groups of these data queues, and these levels are a high level and a low level for instance. Namely, the processing priority level is allocated to each group of plural data queues and data in the data queue in the higher priority level are processed with priority. When a higher priority level is set up in a fault program or the like requiring urgent processing, the program can be immediately processed without generating a queue time.