Grace Hopper was a computer scientist and U.S. Navy officer who helped invent an early programming language that let computers understand words instead of just numbers. She once found a real moth stuck inside a computer, and the word "bug" for a computer error stuck around ever since. The Navy kept recalling her out of retirement for her expertise, and she finally retired for good in 1986 as a rear admiral at age 79 — then the oldest serving officer in the entire U.S. Navy — remembered as one of the pioneers who made modern computer programming possible.