31. In this case a photosensor in the light pen was connected to the trigger line of the port. 32. Using a light pen , users could draw lines and arcs that could be related to each other using constraints. 33. Like the Atari XG-1 light gun, the Stack Light Rifle was treated by the hardware as a light pen . 34. Pens were once used in many computers instead of mice, from the earliest corded light pens of the 1950s. 35. The light pen allows the user to " draw ", to create images and to indicate, on the screen. 36. Witnesses will be able to mark or highlight documents with an electronic " light pen " during their testimony. 37. Together with light pens and trackballs, it was offered as an optional input device for their system since 1968. 38. Note that the light pen / light gun input device requires a conventional CRT using a scanning electron beam. 39. Similarly, graphics tablets and light pens can be used to input these gestures, however these are less common everyday. 40. In 1979, The Bookseller reported on " the light pen , or ` wand'that could read machine-readable codes on books ."
