A pen-shaped sensing device is provided for sensing coded data disposed which is substantially invisible to the average unaided human eye on a surface. The device has a region identity sensor configured to sense, when the sensing device is positioned or moved relative to a region of the surface, and using at least some of the coded data, region identity data indicative of an identity of the region, and a transmitter configured to transmit the sensed region identity data to the computer system to a computer system.