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Chapter 4. Digital Electronics

First and foremost, the computer is a thinking machine—and that implies all sorts of preposterous nonsense. The thinking machine could be a devious device, hatching plots against you as it sits on your desk. A thinking machine must work the same unfathomable way as the human mind, something so complicated that in thousands of years of attempts by the best geniuses, no one has yet satisfactorily explained how it works. A thinking machine has a brain, so you might suppose that opening it up and working inside it is brain surgery, and the electronic patient is likely to suffer irreversible damage at the hands of an unskilled operator.

But computers don't think—at least not in the same way you and I do or Albert Einstein did. The computer has no emotions or motivations. The impulses traveling through it are no odd mixture of chemicals and electrical activity, of activation and repression. The computer deals in simple pulses of electricity, well understood and carefully controlled. The intimate workings of the computer are probably better understood than the seemingly simple flame that inhabits the internal combustion engine inside your car. Nothing mysterious lurks inside the thinking machine called the computer.

What gives those electrical pulses their thinking power is a powerful logic system that allows electrical states to represent propositions and combinations of them. Engineers and philosophers tailored this logic system to precisely match the capabilities of a computer while, at the same time, approximating the way you think and express yourself—or at least how they thought you would think and express yourself. When you work with a computer, you bend your thoughts to fit into this clever logical system; then the computer manipulates your ideas with the speed and precision of digital electronics.

This logic system doesn't deal with full-fledged ideas such as life, liberty, and the pursuit of happiness. It works at a much smaller level, dealing with concepts no more complex than whether a light switch is on or off. But stacking those tiny logical operations together in more and more complex combinations, building them layer after layer, you can approach an approximation of human language with which to control the thoughts of the computer. This language-like control system is the computer program, the software that makes the computer work.

The logic and electronics of computer circuitry are intimately combined. Engineers designed the electronics of computers exactly to suit the needs of binary logic. Through that design, your computer comes to life.

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