A computer system, including data-processing equipment and a freely movable input device, wherein the input device contains at least one position change sensor from which information can be sent to the data-processing equipment and wherein the data-processing equipment can also capture information about the absolute position of the input device. Information about the absolute position of the input device can be captured by the data-processing equipment as a result of the fact that the data-processing equipment is in data communication with a light-sensitive, position-sensitive input surface and the input device emits a light beam, the point of incidence of which on the input surface can be detected by the latter.