Charles Babbage - The Analytical Engine

In 1832, Babbage abandoned work on his Difference Engine in favor of another project he considered to be far superior: a machine he called his Analytical Engine.

Babbage believed his Analytical Engine would solve the problems of the Differential Engine in both respects. First, he envisioned that this machine would be engineered to perform a limited range of arithmetic calculations. However, rather than having to reconfigure the machine to switch between these different calculations, Babbage planned to build his machine such that inserting a card with certain holes punched in it would trigger the appropriate mechanisms, causing the machine to perform the desired calculation. One pattern of holes would set off a chain reaction of mechanisms that caused the machine to perform addition, another set of holes would cause it to perform subtraction, and so on. Thus, given a series of punched cards, the machine could perform a whole sequence of the various types of calculations of which it was capable.

This idea of a mechanism with two possibilitiespunched or not punched— becomes a very important concept in computing.

Of course, since Babbage's cards were to be made of wood, there was no possibility of "pregnant chads," "dimpled chads," or "hanging chads." Two—and ONLY two!—possibilities.

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These pages were written by Steven H. VanderLeest and Jeffrey Nyhoff and edited by Nancy Zylstra
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