After the Vassar math professor convinced the Navy to let her join up at the age of 37, she went to work on the Mark I computer at Harvard University and set about learning how to make the supercomputer work better than anybody else had. When Hopper first laid eyes on the Mark I, she was enamored: “Gee, that’s the prettiest gadget I ever saw,” she recalled thinking. At one point, Hopper reportedly plucked a pesky moth out of the machine and taped it into her notes, potentially inventing the term "debugging." Hopper didn’t know what her work would be used for at the time, but over three months with the Mark I, she solved an incredibly difficult calculation for the Manhattan Project : figuring out how to make a sphere collapse on itself and where on that sphere to apply pressure in order to make it work. Her solution was the key to making the atomic bomb explode properly. Even so, after the war ended, Hopper wasn’t allowed to become a professor at Harvard — then a guys-only club — nor continue in the Navy (ditto). So, instead:Hopper found a job working for an early computer company and quickly realized none of the small computers being developed could talk to each other. Recognizing that most people in America can’t understand anything about math (guilty), she advocated turning symbolic computer language into plain English. She was laughed off. She later playfully made fun of her doubters in a speech. “I’ve driven a large number of people at least partially nuts,” she said. “After all, insisting on talking to computers in plain English was a totally ridiculous idea, and you couldn’t do that. Except it worked.” The language she helped develop, known as COBOL, made up 70% of all actively used code by the year 2000.