A combination of C and Tcl/Tk is an easy and powerful way to make graphical controls for your devices. Tcl/Tk gives you a flexible set of commands for creating the graphical interface, while C lets you execute the low-level commands necessary to get at the serial port. This technique is good for making a wide variety of computer programs, for robotics and other things. Personally, we have been using four variations of it: the one you saw in this demo, programs for interfacing with a stepper motor controller and a nanometer-precision piezo controller, and even a jukebox for playing music from our mp3 collection! We hope you find it as useful as we have.