Before microprocessors computers were built from small integrated circuits. Before that, individual transistors were wired together, and the very first stored-program computers used valves. The trend from 1971 onwards also holds true for all these preceding technologies, including famous names such as the Colossus and the Manchester Baby. Even the electro-mechanical Bell Calculator Model I, launched in 1940 and using relays, fits the trend. Only when we go back to the earlier purely mechanical calculators, do we find a slower but still exponential growth.