Abstract: A host computer system employs a touch sensitive display screen (touchscreen) as an input device. A controller receives positional signals from the touchscreen and transmits positional digital values indicative of (X, Y) coordinates of the point of contact of a touch device upon the touchscreen. The touch device may take the form of a touch pen which is electrically coupled to the controller or a human finger. The controller responds to different commands from the host computer to transmit inputs entered only by finger, only by pen, or by both finger and pen. Additional commands from the computer cause the controller to take a variety of different actions, including resizing the active area on the touchscreen which may be touched by the touch device.