A computer made of gears
Babbage first designed the Difference Engine to calculate mathematical tables. Then he came up with something far bolder: a machine with a “store” (memory), a “mill” (processing unit) and control by punched cards like those driving Jacquard looms. These are the principles of today's computers.
Ada Lovelace
In 1843 mathematician Ada Lovelace, daughter of the poet Byron, translated an article about the machine and added extensive notes. They included a procedure for calculating Bernoulli numbers, regarded as the first program. She was also the first to write that the machine could work not only with numbers but with music or symbols.
Built much later
In 1991 London's Science Museum built Difference Engine No. 2 from Babbage's plans. It worked exactly. Babbage was right; his era simply could not manufacture precise enough parts.