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The moth myth – aka the world's first computer bug

9 August 2022
Grace Hopper (1906-1992)

I’m going to take you back to 1947. To Harvard University, where a huge, US Navy-financed, electromechanical computer called the Harvard Mark II – also known as the Aiken* Relay Calculator – was malfunctioning.

One of the leading engineers working in the Navy’s program, Admiral Grace Hopper, investigated. And found the bug; an actual insect. It had become trapped and was disrupting the electronics.

Someone (possibly Hopper but maybe not) recorded the incident in the logbook along with the actual moth, taped to the page. Gritty!

A faded piece of graph paper contains handwritten notes, dated 9/9. Notes include: "15:45 Relay #70 Panel F moth in relay". Next to this is a very yellowed piece of tape which has been used to stick a (presumably dead) moth to the page
Credit: US Navy

It’s a popular misconception that this was how ‘bug’ started being used to mean a flaw or glitch. In fact, Thomas Edison reported ‘bugs’ in his designs as early as the 1800s. But Hopper's moth does seem to be the first recorded case of a computer bug.

– Thanks to Euan for highlighting this story

Further reading about Grace Hopper:

Grace Hopper's bug (Atlas Obscura)

Grace Hopper – The Navy And Computers (Smithsonian Institute)

World's First Computer Bug (National Geographic)

*I can't help but point out the name of the computer – the Aiken Relay Calculator – which was built and programmed by Howard Aiken and Grace Hopper 🤦‍♀️

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