Instead of having to reduce design problems to equations, Jordan Kauffman shows that the Digigraphic Display Program system directly processes graphic data “input” by a user using a new object: the light pen or stylus which is developed from the optical gun. It allows drawing on a screen because by pressing the button on the stylus, the operator signals the computer to start and stop drawing a line. Data can be recalled at any time, and the “drawings” – light lines on a monitor – can be changed to different scales.