Abstract: A data communication system includes output devices, input devices allocated to users, and at least one host computer, wherein identical information is output at the output devices, the host computer transmits to the output devices further information allocated to the identical information, and data relating to the further information and input into the input devices are transmitted to the host computer. In this system, the host computer selects, in response to the data received from the input devices, one of the users or a subset of users, and transmits a selected message to the one user or subset of users.