A data control apparatus includes an extension devices interface to which a plurality of extension devices are connectable, a program memory provided on each of the plurality of extension devices and configured to secure a program, and an overwriting device provided on at least one of the plurality of extension devices and configured to overwrite the program stored in the program memory. The extension devices interface includes a download communicator configured to download extension device control programs from the extension devices interface to the extension devices connected to the extension devices interface.