PURPOSE: To protect an area to be inhibited from writing of data precisely by setting up a flag bit for displaying whether data writing in said area is to be permited or not in accordance with the area having a fixed size.
CONSTITUTION: When the IPL of a control program to a storage device 2 is ended, the end is informed to a flag writing control part 4 by a signal S and an address control part 1 generates an address in an area to be inhibited from writing. The data concerned are stored in a register 5. At that time, the control part 4 generates a flag, stores the flag in a flag setting part 6 and rewrites the flag on the formed address position in the storage device 2. Consequently, the flag is displayed in a flag display part 3 corresponding to the address concerned. After repeating said operation and ending the writing of all flags, the status is informed to the control program by a signal E and the system is opened. Then, the data writing to the storage device 2 is inhibited by the contents of a flag detecting part 7.
SATOU MASAO
KABEMOTO AKIRA
