Charles Babbage (December 26, 1791 - October 18, 1871) was an English polymath. A mathematician, philosopher, inventor and mechanical engineer, he is best remembered for originating the concept of a digital programmable computer. Considered by some to be a "father of the computer", Babbage is credited with inventing the first mechanical computer that eventually led to more complex electronic designs, though all the essential ideas of modern computers are to be found in Babbage's analytical engine. His varied work in other fields has led him to be described as "pre-eminent" among the many polymaths of his century. In 1991, a perfectly functioning difference engine was constructed from Babbage's original plans. Built to tolerances achievable in the 19th century, the success of the finished engine indicated that Babbage's machine would have worked. He died in 1871 of renal inadequacy, secondary to cystitis, at the age of 79.