Difference Engine

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Difference Engine

(computer, history)
Charles Babbage's design for the first automatic mechanical calculator. The Difference Engine was a special purpose device intended for the production of mathematical tables. Babbage started work on the Difference Engine in 1823 with funding from the British Government. Only one-seventh of the complete engine, about 2000 parts, was built in 1832 by Babbage's engineer, Joseph Clement. This was demonstrated successfully by Babbage and still works perfectly. The engine was never completed and most of the 12,000 parts manufactured were later melted for scrap.

It was left to Georg and Edvard Schuetz to construct the first working devices to the same design which were successful in limited applications. The Difference Engine No. 2 was finally completed in 1991 at the Science Museum, London, UK and is on display there.

The engine used gears to compute cumulative sums in a series of registers: r[i] := r[i] + r[i+1]. However, the addition had the side effect of zeroing r[i+1]. Babbage overcame this by simultaneously copying r[i+1] to a temporary register during the addition and then copying it back to r[i+1] at the end of each cycle (each turn of a handle).

Difference Engine at the Science Museum.
This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)

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 $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, www.cbi.umn.edu)
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References in periodicals archive ?
"Charles Babbage, credited as the world's first computer pioneer, designed the "Difference Engine", of which Prince Albert had the opportunity to see a prototype in July 1843.
In 1823 he designed a machine known as the "difference engine" which was the forerunner of the modern electronic computer.
It was written by Ada Lovelace, who helped fellow mathematician Charles Babbage in inventing the world's first computer, the Difference Engine, in 1822.
The free exhibitions include Stephenson's Rocket, Puffing Billy (the oldest surviving steam locomotive), the first jet engine, a reconstruction of Crick and Watson's model of DNA, and Babbage's Difference Engine, a computer prototype.
In the 1830s, Charles Babbage built a Difference Engine (mechanical calculator) and then an Analytical Engine (a decimal digital computing device).
Babbage was already known for his design for a calculating machine, which he called a "Difference Engine," a reputation he would consolidate with his design for an "Analytical Engine" (1834).
Babbage, called by some "the father of the computer, had already invented what he called "the Difference Engine," also known as "the Thinking Machine," but he was now at work on a new version that he called "the Analytical Engine." The new machine, whose operation was controlled by a punched-card system, was to be much more advanced than the Difference Engine, and, as Essinger states, "able to do more than simply calculate mathematical tables." The key to the success of the Analytical System was the use of punched- cards.
Padua imagines a Pocket Universe in which Lovelace and Babbage work as partners and build the analytical engine, called here the Difference Engine, along with other things, and encounter all sorts of historical personages in their adventures.
It's the biggest collection of computer artefacts anywhere in the world, and it's not only a brilliant account of the progress of computing technology from Babbage's difference engine to the smartphone.
The Difference Engine received support from the likes of One North East, Sunderland and Middlesbrough councils, and launched with the ambition to propel ideas from the North East and further afield into fully fledged businesses.
The young Ada was tutored in maths and |after meeting Charles Babbage in 1833 at a party became fascinated by his analytical Difference Engine, forerunner of the modern electronic computer.

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