PURPOSE: To perform hot docking by informing the docking of a portable computer with a desk station to the portable computer before it is actually performed.

CONSTITUTION: When a computer 1 is set on the desk station 2, only communication connecters 13, 26 are connected with each other, and extended connectors 14, 28 are separated from each other. The desk station 2 issues a docking request command to the computer 1 via the communication connectors 13, 26. The computer 1 performs the processing of disconnection of a power source, etc., replying to the docking request command, and after that, issues a docking start command to the desk station 2 via the communication connectors 13, 26. The desk station 2 moves a second connector unit 27 by executing an automatic loading operating replying to the docking start command, then, connects the extended connectors 14 and 28 with each other.