To automatically select an optimum operation mode according to the current network environment of the network computer.

It is checked first whether or not an NC server is in the same TCP/IP network with a network computer(NC) (step S11). When the NC server is in the network, all execution environment is obtained basically from the NC server and a mode (network mode or office mode) for operation is automatically selected. When the NC server is not in the same network, on the other hand, it is checked whether or not a DHCP(dynamic host configuration protocol) server is in the same network with the NC (step S13) and when so, a remote connection mode or remote office mode wherein operation can be started in remote network environment is selected.