Ada Lovelace has been called the world's first computer programmer. What she did was write the world’s first machine algorithm for an early computing machine that existed only on paper. Of course, someone had to be the first, but Lovelace was a woman, and this was in the 1840s. Lovelace was a brilliant mathematician, thanks in part to opportunities that were denied most women of the time.

Ada Byron was a teenager when she met Cambridge mathematics professor Charles Babbage, who had invented the Difference Engine, a mechanical computer designed to produce mathematical tables automatically and error-free. Babbage never built the actual machine due to personal setbacks and financing difficulty. By 1834 he had moved on to design his Analytical Engine, the first general purpose computer, which used punch cards for input and output. This machine also lacked financing and was never built. (Babbage's Difference Engine was finally constructed in 1985–2002, and it worked.)

An original model of part of the Analytical Engine. Photograph by Bruno Barral (ByB)

Babbage was impressed with the brilliant young woman, and they corresponded for years, discussing math and computing as he developed the Analytical Engine. In 1842, Babbage gave a lecture on the engine at the University of Turin. Luigi Menabrea, a mathematician (and future Italian prime minister), transcribed the lecture in French. Ada, now in her late 20s and known as Countess of Lovelace, was commissioned to translate the transcript into English. Lovelace added her own notes to the lecture, which ended up being three times as long as the actual transcript. It was published in 1843

Lovelace's notes made it clear that she understood the Analytical Engine as well as Babbage himself, and furthermore, she understood how to make it do the things computers do. She suggested the data input that would program the machine to calculate Bernoulli numbers, which is now considered the first computer program. But more than that, Lovelace was a visionary: she understood that numbers could be used to represent more than just quantities, and a machine that could manipulate numbers could be made to manipulate any data represented by numbers. She predicted that machines like the Analytical Engine could be used to compose music, produce graphics, and be useful to science. Of course, all that came true—in another 100 years. 

Babbage was so impressed with Lovelace's contributions, he dubbed her "The Enchantress of Numbers."

How did a young woman get the opportunity to show the world her talents in the 19th century? Mathematical intelligence was not the only thing Ada Lovelace had going for her. Her potential for intelligence probably came genetically, as she was the daughter of the poet Lord Byron and his first wife Anne Isabella Noel Byron. Both were privileged members of the aristocracy, and both were gifted and well educated. The marriage broke up shortly after Ada was born.

Lady Byron, who studied literature, science, philosophy, and, most unusual for a woman, mathematics, was determined that Ada not follow in her father's footsteps. Instead of art and literature, Ada was tutored in mathematics and science. Ada excelled in all her studies, and her interests were wide ranging. Ada became a baroness in 1835 when she married William King, 8th Baron King; the two had three children. In 1838, she became Countess of Lovelace when her husband was elevated to Earl of Lovelace. Her pedigree and peerage alone would have landed Lovelace in the history books, but her accomplishments in mathematics made her a pioneer of not only computing, but of women in science.

Lovelace died of cancer in 1852, when she was only 36. More than 150 years later, we remember her contributions to science and engineering in the celebration of Ada Lovelace Day on October 13. First celebrated in 2009 (in March), it is a day set aside to learn about women in science, technology, engineering, and mathematics.