A cellular phone. The cellular phone comprises a connector, a first memory module, a second memory module, and a controller. The connector is used for physically connecting the cellular phone to an external device. The first memory module stores phone data. The second memory module stores application data received from the external device. The controller determines whether the connector is connected to the external device. If the connector is not connected to the external device, access right of both the first and second memory modules is granted exclusively to the cellular phone. If the connector is connected to the external device, access right of the first memory is granted exclusively to the cellular phone, and access right of the second memory module is granted exclusively to the external device.