Physics, and transistors in computers

The spectacular success of the transistor in making a steady stream of increasingly powerful and affordable digital computers available through the 50 years since its invention is well known. Yet in spite of this remarkable record the same fifty years has witnessed a continuing series of proposals for replacing the transistor in computing systems with some other device. The tunnel diode and Josephson devices are notable examples. Some of these proposals have attracted many millions of pounds of industry and government support. Yet none has had any effect on computing technology. The problem of the many alternatives is that they do not use quantitative standard signals to represent digits; in other words, they are not truly digital.