Ada Lovelace

Ada Lovelace was born in 1815 and named Agusta Ada Byron. As in Lord Byron. You know, the poet and crazy dude. She was his only legitimate child. Byron, being something of a jerk, was disappointed she wasn't a boy.

Ada's mum, fed up with high romance, poetry, and the other stuff Byron spouted, countered with a very unusual education for young Ada; it was long on science and math, and short on the subjects usually taught to girls in that era, namely literature and painting. She (Ada, not her mum) had migraines and other health problems, and so spent a lot of her childhood doing math and other tutored subjects.

In 1833, she met Charles Babbage. He was busy working on his 'difference engine', essentially a mechanical calculator. This, a photo from the innards of one built, gives you an idea:

(Image from Wiki commons.)

Metallurgy and machining being what they were in the 1830s, Babbage's machine was never built in his lifetime. The design was solid, though; eventually it was built, and it does work.

In the early 1840s, Ada became acquainted with the concept of the engine, and corresponded with Babbage on the subject, and related topics. In her notes, there is a program she wrote, that calculated Bernoulli Numbers, a sequence important in number theory. Basically, while everyone else, including Babbage himself, saw the Difference Engine as a way to do arithmetic quickly and easily, Ada saw the big picture and the possibilities beyond. In other words - she got the idea of the computer. The program she wrote, when finally put into the working Difference Engine built years after her death, worked just fine.

Ada Lovelace is considered by many to be the world's first programmer, code monkey, or computer geek. Depending on who you ask. Her notes, translations, and mathematical work were vital to the early history of computing. She was writing programs for Babbages Analytical Engine that would have worked. Meaning she was writing useful code for a computer whose hardware never ran.

Not too many people can do that.