A device is connectable to a computer and recognized by the computer as a USB multi function device capable of functioning as a USB storage device and an additional device. The device includes a mode switching section configured to switch the device to one of a first mode and a second mode in which an access from the computer to a USB storage device is permitted and prohibited, respectively. When the device is in the first mode, the device accesses the physical storage area of the data storage section. When the device is in the second mode, the device transmits a pseudo response to the computer. The pseudo response indicates that no storage medium is mounted to the data storage section. When a particular data string different from the standard data string is received, the device accesses a file through a file system provided in the device.