The computer models described in this book have all been built, tested and operated by pupils of the Grammar Technical School, Spennymoor. The aim, initially, was to provide an enjoyable out-of-school activity which would also have a bearing on some of the modern applications of mathematics. However, far more than this has been achieved. Those taking part in the projects have not only experienced some of the thrills and frustrations of research work but also gained an insight into modern electronic circuits. In addition, those not taking an active part have had the opportunity to see an operate working models which give an insight into the high-speed world of electronics. All this helps to breed a confidence which cannot be achieved in any other way. The models range from a cheap mechanical model through a logic demonstration board to a high-speed computer model. All the electronic models are based on the NOR logic element and no advanced knowledge of electronics is necessary to construct them and none at all to operate them.