The first functional computer program was written by Grace Murray Hopper (1906–1992), an admiral of the U.S. Navy. She wrote a program for the Mark I computer (developed in 1944), the first fully automatic calculator. During the 1950s Hopper directed the work that developed one of the most widely used computer programming languages, COBOL (Common Business Oriented Language). She is also credited with coining the slang term bug to refer to computer program errors. The story goes that her machine had broken down, and when she looked into the problem, she discovered a dead moth in the computer. As she removed it, she reportedly announced that she was “debugging the machine.” Hopper served the U.S. Navy for 43 years, from 1943 to 1986, and retired as its most senior officer. She was also a professor at Vassar College and a programmer for the Sperry Rand Corporation from 1959 to 1971. She is one of the pioneers of computer science.

The very first computer program written, though never used, was also by a woman: the English baroness Augusta Ada Byron (the poet Lord Byron’s daughter, born 1815) wrote it for Charles Babbage’s “analytical engine,” which was never completed, and so the program was not tested.