An information processing system has a power supply section which detects a predetermined potential applied to a USB terminal and supplying the potential as a source potential, an information detection section which detects the predetermined information supplied to the USB terminal, and a processing section which executes, subsequent to the detection of the predetermined potential, the encoding process or the decoding process in accordance with at least the operating information supplied from the operation key arranged on the body and in accordance with the predetermined information supplied to the USB terminal after detection of the predetermined information. The recording and reproducing operation can be performed with the operating key on the body with power supplied only from the USB terminal.