Today marks Ada Lovelace Day, a six-year-old annual celebration of women in so-called STEM (Science, Technology, Engineering and Mathematics) fields named after a 19th-century mathematician and writer. But who is she – and why is she so important?

Well, the fact that you’re reading this on a computer (and the fact that #AdaLovelaceDay is trending on Twitter) owes a debt to Lovelace, who is often considered to be the first computer programmer – before computers even really existed.

Born in 1815, Lovelace was the only legitimate child of poet Lord Byron, though her parents separated a month after her birth and she never met her father. Her mother Anabella encouraged Ada’s interest in maths and science over the arts to avoid what she saw as Byron’s “madness”, but Ada looked up to him and described her work as “poetical science”.

Portrait of Ada by British painter Margaret Sarah Carpenter (1836)

Eventually, her work led to a friendship and working relationship with Charles Babbage, the creator of the earliest mechanical computers including the Analytical Engine – and the man with whom Lovelace made history.

You see, Lovelace wrote a paper in the 1840s imagining the potential of Babbage’s machines, including the idea that they could compose music and the original computer algorithm (you’re welcome, Google), now widely considered to be the world’s first computer program. You can read some of Lovelace's ideas below.

[The Analytical Engine] might act upon other things besides number, were objects found whose mutual fundamental relations could be expressed by those of the abstract science of operations, and which should be also susceptible of adaptations to the action of the operating notation and mechanism of the engine...

Supposing, for instance, that the fundamental relations of pitched sounds in the science of harmony and of musical composition were susceptible of such expression and adaptations, the engine might compose elaborate and scientific pieces of music of any degree of complexity or extent.

Sadly, Lovelace never got to try out her ideas after falling out with Babbage and dying young, but she went on to inspire early computer pioneers including a certain Alan Turing (who found her paper during his research). Turing is of course the mathematician whose codebreaking computer helped end the Second World War, and is widely considered to be the father of computer science and artificial intelligence.

Alan Turing, left; and as played by Benedict Cumberbatch in his biopic The Imitation Game, right

If you’re looking to celebrate Ada Lovelace Day, then you could do a lot worse than checking out Hannah Fry’s BBC4 documentary Calculating Ada: The Countess of Computing, which is still available on BBC iPlayer until Saturday.

Watch the documentary here, or read our review below.

Presenter Hannah Fry with the Analytical Engine

Ada Lovelace was remarkable in a number of ways, be it her famous parentage or her struggle in the male-dominated field of Victorian mathematics – but the focus of this engaging programme is on her extraordinary vision for what the earliest computers could achieve.

As enthusiastic presenter Hannah Fry explains, Ada saw a deeper potential in the basic mechanical number-crunchers that existed at the time.

Her work went on to inspire other computer pioneers like Turing, but sadly Ada never got the chance to try out her ideas fully. As Fry reveals, she may have had a little more of her father’s self-destructive tendencies in her than anyone realised…