To make a main program reproduce contents by controlling an external AD device via 1394 at the time of reproducing and executing a program composed of a plurality of media, and also to protect the contents without reproducing the program at the time of the other operation.

The program existing in the media on a control device reproduces the contents by transmitting a control command to a controlled device via the 1394. At this time, the controlled device adds a keycode kept by the contents, compares the keycode, and reproduces the contents only when this contents is controlled by the program which this contents belongs to.