First things first — Ada Lovelace was a champion for Charles Babbage's calculating machine, the Analytical Engine, when no one else was. She is celebrated for having the foresight that an instrument of this kind had endless practical and scientific uses, including the ability to create graphics and compose complex music.
Looking at how much technology is integrated into our lives today, she was absolutely right. Ada also devised a way for how the Analytical Engine could calculate Bernoulli numbers, a plan that is now considered the first "computer program." And because she published the source code of this program, she is also considered the world's first open source programmer.
