Programs in English
During the war she programmed the Harvard Mark I computer. She later came up with the idea that a person could write a program in a language resembling English, and the computer would translate it into machine code itself. Many colleagues didn't believe it would work. In 1952 she built the A-0 compiler, and later the FLOW-MATIC language, from which COBOL (1959) was derived.
The first "bug"
In 1947 her team found a moth in a relay of the Mark II computer, causing a fault. They taped it into their logbook with a note that this was the first actual case of a "bug" being found. The word bug for a fault had been used before, but this story made it famous, and Hopper loved to tell it.
COBOL lives on
Programs written in COBOL still process a large share of banking and government systems today. It was because of them that the world worried about the Y2K problem before the year 2000.