Abstract: A memory control method includes a first step of managing control information in each of memory blocks constituting the memory, the control information joining the memory blocks in a chain according to the frequency of data erasures occurring in each of the memory blocks; and a second step of determining, on the basis of the control information, a memory block that should be a transfer destination of write data.

Abstract: In a magnetic disc device, track bytes are added to a record which is to be stored in a cylinder of a magnetic disc in order to utilize additional magnetic disc devices of a different type in the same manner as the first-mentioned magnetic disc device. The magnetic disc device provides track byte check device which checks track bytes read from the record for errors, stores the track bytes in a track byte register when they are correct, and, if the stored track bytes are re-read, utilizes the correct contents stored in the track byte register as the track bytes of the record.