Mike Bohan, age 13, of Nashville, Tennessee, for his question:
How does an adding machine work?
This handy little gadget looks like an up date invention of the modern world. Its working parts are concealed neatly under its outer casing of metal and plastic. This adding machine is a humble relative of the great digital computer. But it is based on a simple and very, very ancient idea.
Math problems can be tough enough to strain the brain of a genius. But before a person can tackle even the simplest of such problems, he must be snne of his arithmetic. These basic skills use various methods of multiplying and dividing but all arithmetic boils down to the two simple operations of adding and subtracting. This is why adding is the basic number skill. And a machine that can add also can subtract and also should be able to divide and multiply. If it does the ,job fast and accurately, it can save an enormous amount of wear and tear on the human brain.
People figured out how to count and they invented various number systems before the dawn of history. Thousands of years ago, merchants and traders began keeping accounts and, to do so they invented the first adding machine. It was a simple gadget called the abacus. It was a counting frame, designed in several different forms. The abacus was so good that many Oriental countries still use it. In fact, some years ago, an abacus expert challenged a modern computer and won.
The first adding machine was the ancient abacus and the most modern adding machine cannot improve upon its basic principle. Way back in the 1600s, the French mathematician Blaise Pascal was figuring out the theory of probability. His interest in the behavior of liquids led him to invent the hydraulic press. Pascal also invented an adding machine. A few years later, Baron von Leibnitz of Germany invented the binary system used in most modern computers. Leibnitz also invented an improved adding machine.
These adding machines of the Middle Ages had faster working mechanical parts. But they worked on the same principle as the ancient abacus. The same basic idea is used to make our most modern adding machines. The reliable old abacus may be a simple rectangular frame, enclosing nine parallel wires or pegs, one for each digit from 0 to 9. Each peg holds 10 movable beads. A bead on the second peg is worth ten on the first peg. The 10 third row beads are worth one on the fourth row. The beads can be moved and counted in either direction to do the two basic skills of adding and subtracting. .
Leibnitz invented a mechanical stepped wheel to do the counting in his adding machine. A modern machine still uses the same type of wheel, along with a more refined system of gears and gadgets. When you push its numbered buttons, its moving parts mechanically do the basic counting for adding or 'subtracting.
Commercial adding machines have been made and marketed since the 1820s. Their main fob is to add columns of figures fast and accurately. As it counts and computes, it types its figures onto a roll of paper. Its parts may be moved by a hand crank. But an up date adding machine needs only human hands to press its numbered buttons. It has an electric motor to move the mechanical parts that do the necessary counting of basic arithmetic. If you press the right buttons, the right answer is tapped out in neatly typed figures.