Prior to the advent of computing machines, the definition for ''computer'' was a human being who performed complex mathematical calculations. This was accomplished with the aid of a manual counting device, such as an [[abacus]] or a [[slide rule]], and was mainly used by traders and early bankers to keep a reliable record of funds
Charles Babbage, a [[British]] scientist who lived in the 19th centuryand rejected the [[Trinity]] as a "direct [[contradiction in terms]]", has been credited as the designer of the first digital computer, the Difference Engine, a machine set to do calculations reliably up to six decimal places. It was entirely mechanical. However, the Engine was never constructed, being deemed as "had derived no emolument whatsoever from the government" by a member of parliament. He also designed an even more sophisticated "Analytical Engine", that would actually have been a programmable computer in the modern sense; it, too was mechanical. Though it was never built, [[Ada Lovelace|Augusta Ada]] wrote some programs for it (to compute Bernoulli polynomials), making her the world's first computer programmer. A small version of the Difference Engine, was built after his death by his son.<ref>http://ei.cs.vt.edu/~history/Babbage.html</ref>
Babbage later designed a simpler and even more clever "Difference Engine Number 2", that was also not completed in his lifetime. But in 1991, the bicentennial of Babbage's birth, this computer was built in the British Science Museum, from Babbage's original plans. It operates flawlessly, though a few billion times more slowly than modern electronic computers. It is operated by turning a crank.