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Washington, D.C.

Grace Hopper's Bug

A computer bug so primitive it was an actual insect. 

On September 9, 1947, Harvard’s Mark II Aiken Relay computer was malfunctioning. After rooting through the massive machine to find the cause of the problem, Admiral Grace Hopper, who worked in the Navy’s engineering program at Harvard, found the bug. It was an actual insect.

The incident is recorded in Hopper’s logbook alongside the offending moth, taped to the logbook page: “15:45 Relay #70 Panel F (moth) in relay. First actual case of bug being found.”

Grace Hopper had been a keen mathematician her entire life, but it wasn’t until she enlisted in the Navy during WWII that she got a chance to unleash her skills. Originally turned away from the Women’s Naval Reserves because at 34 she was considered too old and too small, Hopper persisted and eventually came to work at Harvard. She was one of the top minds in computer science, pioneering early compilers that translated computer source code into English, not to mention the fact that she became the Navy’s first female admiral.

The “bug” and the page it’s attached to reside at the Smithsonian’s Museum of American History in Washington, D.C. Though the moth anecdote is often falsely credited with the creation of the computing terms “bug” and “debug” (these were actually used as early as Edison), it accurately provides a glimpse of the wit and cleverness of Admiral Grace Hopper.

Know Before You Go

Note: The computer bug is currently not on display.