INFORMATION PROCESSOR

PURPOSE:To inhibit a reading in a device except for a device used at the time of writing without forcing an operator to execute a special operation by automatically writing information inherent in each device to a medium and automatically executing a check also at the time of reading. CONSTITUTION:A writing means to write data to a medium 5 and a checking means 4 to execute the check with the data of a reading means 2 to read the data are provided. Information is read from a specific part 6 of the medium when the medium 5 is mounted to the device to write the information red from a device switch 1 in the specific part 6 after the format completion of the medium 5, the information is compared with the information read from the device switch 1, and a processing which is a processing continuation incapability is executed at the time of a non-coincidence. Thus, the secrecy holding of a data file can be executed.