Following disputes over the Difference Engine and ultimate defunding by the government, Charles Babbage began work on a new calculating machine. This time, he called it the Analytical Engine, with the intent that the machine would be able to modify a calculation while the operation was already running. The operations that Babbage was trying to create would become the conceptual foundations for the modern computer, even though it would not be created and popularized for over a hundred years after the original theory.

Although the Analytical Engine was never built physically, Babbage had incredibly detailed plans for how the machine would work. In theory, the machine would be “programmed” using different punched cards that gave the machine a starting point for computing values. After hearing Babbage’s lectures and seeing figures about the Analytical Engine, Italian scientist Luigi Menabrea created a write-up of the project, which Babbage and another scientist suggested Lovelace translate the paper into English and expand upon it.

Lovelace’s appendixes are more than double the length of the original paper, and inside these appendixes rest her greatest contributions to the field of computer science. In her now-famous “Note G,” the final appendix, Lovelace explains in detail how the machine works through calculations of “Bernoulli” numbers, and how various quantities are “brought” forward, used to calculate, and then moved back. The table that she created to demonstrate this is often referred to as the very first computer program, although it is closer to what computer scientists would refer to today as “execution tracing” – showing a complete view of all the changes that were made.