Charles Babbage, (1791 – 1871), was an English mathematician, philosopher, inventor and mechanical engineer who originated the concept of a programmable computer. 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. Difference Engine No. 2, built faithfully to the original drawings, consists of 8,000 parts, weighs five tons, and measures 11 feet long, an astonishingly complex device for the 19th century. Considered a "father of the computer", Babbage is credited with inventing the first mechanical computer that eventually led to more complex designs. An identical Engine completed in March 2008 is on display at the Computer History Museum in Mountain View, California.