PURPOSE: To change system definition contents without using an SDCL batch read command and an SDCL batch write command relating to a system definition instruction system in a controlling arithmetic unit.

CONSTITUTION: At the time of changing the system definition contents stored in a storage means 2, a definition instruction is written in an executable definition instruction execution unit 8 and is transferred to the controlling arithmetic unit 1. Then, when the controlling arithmetic unit 1 prepares an entry table 3 and the definition instruction execution unit 8 written in the storage means 2 is detected, a reproduction request storage means 4 stores the reproduction request of a definition instruction file and reproduces the definition instruction file by using an SDCL instruction after searching is ended. Further, the system definition contents of the reproduced definition instruction file 9 are read from the storage means 2 by referring to the entry table 3 and are extended inside the controlling arithmetic unit 1.