The Computron and the Selectron, antediluvian ancestors of solid-state integrated circuits, were vacuum-tube versions of the microprocessor and memory chip. “The idea was to make a single tube which could multiply two numbers and add a third number to the product, the numbers being expressed in digital binary code,” Rajchman explains. “A number of electron beams emanating from a single central cathode were deflected each by three electrodes, corresponding respectively to a digit of the multiplier, a digit of the multiplicand, and a ‘carry-over’ digit…. In effect, the tube was made by
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