There is provided a method of, and interface system for, enabling a user to instruct a computer system to perform an operation by interacting with graphical information and coded data printed on a first interface surface using a sensing device which generates indicating data indicative of the operation by sensing the coded data. In the method, and interface system, the computer system receives the indicating data from the sensing device, the computer system performs the operation indicated by the indicating data, and in response to performing the operation, a second interface surface is printed with graphical information relating to the performed operation and coded data.