Realizing the high error rate in the calculation of mathematical tables, he decided to find a method by which they could be calculated by machine, which would not suffer the errors, fatigue and boredom of human calculators. To this end, he was given a grant by the British Government to build such a machine, which he called the Difference Engine. Construction started on this machine, but it was not completed, as he realised that the basic mechanisms could be generalised to an all-purpose calculating machine, programmable by a punched card mechanism like that of a Jacquard loom; this machine, which existed only as plans, was called the Analytical engine.
While great efforts were expended in trying to create a working model, the internal friction and gearing available at the time were not good enough for the models to be completed. Partly because of the effort expended in gearmaking for these machines, the British had superior machinery for the next few decades, and this contributed to the qualitative superiority of British navy in the first world war.
Although his two computing projects were never completed in his lifetime, his ideas on their operation show them to be the forerunner of modern computers. Parts of his uncompleted mechanisms are on display in the London Science Museum. In 1991, working from Babbage's original plans, a Difference Engine was completed, and functioned perfectly.
- Ada Byron, Countess of Lovelace, described and programmed the analytical engine
- McTutor biography of Babbage