A nonvolatile memory stores encrypted data, which is obtained by linking and encrypting program data, in which combined data is compressed, and first information data indicating the number of programs contained in the combined data, and second information data indicating the size of each program. A CPU reads the encrypted data from the nonvolatile memory and decrypts the read encrypted data to restore the program data, the first information data and the second information data, after which the program data is decompressed to restore the combined data that is then stored in RAM. The CPU also creates a program management table for managing the respective programs based on the first and second information data, and stores the program management table in the RAM. The present invention is applicable to microcomputers.