Ada Lovelace

Lovelace translated an Italian engineer's article on Charles Babbage's proposed Analytical Engine in 1843 and added her own notes, three times longer than the original article, that included a step by step method for the engine to compute Bernoulli numbers, often cited as the first published algorithm written for a machine. Her notes also argued the engine could manipulate any symbols following defined rules, not just numbers, anticipating that a computer could work with music or images as well as arithmetic. The Analytical Engine was never built in her lifetime, so her algorithm was never run, and historians have debated how much of the mathematical content in the notes was hers alone versus developed jointly with Babbage; the surviving correspondence between them shows substantial original contribution on her part.