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Difference Engine

An early calculator designed by Charles Babbage and subsidized by the British government. Employing wheels and rods, which others had experimented with earlier, the project was started in 1821 but failed its test in 1833. Babbage then turned his attention to the Analytical Engine and completely abandoned the Difference Engine by 1842. Although never completed, it did improve the precision of Britain's machine-tool industry. In 1991, the National Museum of Science and Technology built a working model of the Difference Engine.

In 1879, Babbage's son reassembled a section of the Difference Engine from parts, and in 1995, Christie's auction in London auctioned off that section to the Power House Museum in Sydney for USD $282,000. The other known sections are owned by Harvard and Cambridge Universities. See Analytical Engine.

The Difference Engine
This impression from a woodcut was printed in 1853 showing a portion of the Difference Engine that was built in 1833. Babbage later turned his attention to the Analytical Engine. It, too, was never finished. (Image courtesy of Charles Babbage Institute, University of Minnesota,

Analytical Engine

A programmable calculator designed by British scientist Charles Babbage. After his Difference Engine failed its test in 1833, Babbage started the design of the Analytical Engine in 1834. Developed in spurts due to lack of funds and constant redesign, a trial model was finally built in 1871, the year Babbage died. Although never completed, it was a major advance in computing because it contained the principles of the stored program computer. For example, it provided a conditional statement that would branch somewhere else in the program based on the value being tested. The parts of the Engine that were actually built did work however.

Babbage's colleague and close friend, Augusta Ada Byron, the Countess of Lovelace and daughter of the poet Lord Byron, explained the machine's concepts to the public. Her programming notes survived, making her the first official computing machine programmer in the world. The Ada programming language was named after her. See analytical database engine, Difference Engine and Mark I.

Analytical Engine
Programming the Analytical Engine might have been a bit more tedious than programming one of today's computers. (Image courtesy of Charles Babbage Institute, University of Minnesota,

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