PURPOSE: To simplify the device, by providing a plurality of page alteration display sections for a table in a TLB device, checking the 2nd display section when the content of the TLB is revised, and rewriting the 1st display section based on the content.

CONSTITUTION: A TLB9 has an alteration bit C' as a pair of a virtual and a real address, and the bit C' is set to "1", when write is made to a page in service of the address conversion. The TLB has the same page correspondence as the storage key as the hardware and performs the detection and recording of page write generation to the hardware of the TLB primarily, and the R, C bit recording is formed for the storage key with the firmware simply. The alteration bit C' is set to "1" with a logical sum AND 12 between a write control output from a decoder 10 and the TLB table retrieval output, when the execution of an instruction 4 includes the write access.