Abstract: A user interface system for providing pen based input to large display screens includes a portable computer supporting both a wireless transmitter and a small pen input screen. A computer is connected to a large display screen having an area substantially larger than an area of the small pen input screen of the portable computer. A wireless receiver is connected to the computer and configured to receive wireless communications from the portable computer. An input mapping module is used for controlling user defined output on the large display screen in response to user defined input from the small pen input screen of the portable computer. The input mapping module has a selectable first mode for positioning graphical output to fall within a bounding box movable about the large display screen in response to pen movement on the small pen input screen.