Students experiment to construct a 4bit CPU

Researchers say it's important to learn the flow of signals in a computer. However, in most classroom lectures, learning is done for each signal, not for each bit. So we devised an experiment that could learn bit-by-bit electrical signals.The students conducted four 3-hour experiments and built a 4-bit Central processing unit (hereinafter CPU) by inserting Integrated Circuits(hereinafter IC) and switches on the breadboard. Students assemble CPUs in pairs and run programs. The experiment started in 2007 and has been improved year by year to make it even better. In this paper, we report the contents of the experiment and the results of the improvement.