The Binary Number System and ASCII Code
A very useful and fun tool in working with the Arduino is the serial monitor. Using the USB PC connection and the serial monitor feature of the IDE makes it unbelievably easy to use the on-screen serial monitor for both troubleshooting and creating entertaining game programs with minimal electronic interfacing. The IDE serial monitor function is bidirectional so that you can both transmit and receive data and see it in real time on the PC screen.