In a camera system, if software is rewritten in accordance with the change in hardware structure, compatibility between the hardware and the software is determined, thereby avoiding a problem, such as an inoperable condition or a breakdown of a component. The camera system includes a camera body operated in accordance with programs stored in a program storage circuit and a peripheral for rewriting at least a part of the programs. The camera body comprises a data storage circuit which stores structure data of the camera. The peripheral comprises a communication circuit for receiving the structure data of the camera and a control circuit for determining whether the programs should be rewritten based on the structure data.