US Patent 7346730 Mobile electronic device

In a memory, first and second data areas are set as an area which stores one data item and a management area which stores determination information used to determine which one of the first and second data areas stores the newest data is additionally set. In the process of writing data into the memory, data is written into one of the data areas which stores data determined not to be the newest data based on the determination information and identification information is updated when the data writing process is correctly terminated.