Abstract: A system and method for inputting data to a single port of a host computer in parallel from a terminal keyboard and a graphic data digitizer. An adapter circuit includes inputs from the digitizer, the host computer and the terminal, outputs to the host computer and terminal and switching circuitry for routing signals from selected inputs to selected outputs, so that the use of the digitizer is transparent to the host computer. A microprocessor in the adapter circuit controls switching and, additionally, is programmed so that the digitizer, provided with menu images of keyboards, can mimic the function of the keyboard. The microprocessor memory contains a coordinates map of the menus, locatable as the user desires in the work area, which allows the user to access stored keyboard symbols and functions by using the digitizer.