First computer "bug" is found

9th September 1947
First computer "bug" is found

On September 9th 1947, one of the team of engineers working on Harvard University’s Mark II computer recorded the first actual computer "bug" — a moth stuck between the relays in the machine. Logged at 15:45 hours, the remains of the errant insect are taped to the page with the words:

“first actual case of a bug being found.”

Computing pioneer Grace Hopper was member of the Harvard Mark II team, but the Smithsonian Institution notes that the log book was probably not Hopper's. However, it was likely that she helped make the incident famous.

Even though the word "bug" was already in use to mean a small fault, having been used by Thomas Edison in an 1878 letter, the log book story has helped popularize the use of the term in the digital age, along with the related phrase "debug".

Related information:


  • Harvard Mark II computer's log book entry containing the "bug"
    Credit: U.S. Naval Historical Center Online Library Photograph NH 96566-KN

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