Had it been built, the analytical engine of Charles Babbage would have been the first general-purpose computing machine, although, belonging to the mid-1800s, it would have been implemented mechanically rather than electronically. For many years, historians of computing have believed that the analytical engine was never built because the engineering techniques of the time could not support its construction (perhaps due to insufficiently precise manufacturing tolerances). In this view, the first general-purpose computing machine had to wait until the advent of electronic technology.

Recent evidence suggests that this view is inaccurate. Indeed, in 1991, a working model of the analytical engine was built, using only parts that could have been manufactured in the 1840s. The engineers responsible for building this working model argue that Babbage was unable to build the analytical engine not because of a lack of an appropriate implementing technology, but because of his inability to keep costs under control.

SOURCE: Swade, Doron. 1993. "Redeeming Charles Babbage's Mechanical Computer," Scientific American 261 (February):86–91.