The first computer bug was a moth

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The use of the word “bug” for a flaw or an error in computer software or hardware is generally attributed to an actual moth that caused the Harvard Mark II computer to malfunction. Though the story is true, “bug” has been around for a much longer time.

It had been used originally to describe defects and faults in mechanical devices. For instance, the word appeared in a letter dated 1878 that the great inventor Thomas Alva Edison wrote to his associate.

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First actual case of bug being found – The Harvard Mark II moth

But it was Grace Hopper, one of the first programmers of the Harvard Mark I, who popularised the word in the field of computers. When engineers traced the cause of errors on the Harvard Mark II computer, they found an actual bug – a moth – trapped in the relay. The insect was preserved, taped on the 9th September 1947 page of the computer’s log book.

The first computer bug - a moth trapped in the relay of the Harvard Mark II computer

One of the engineers, Bill Burke, knew the use of the term in engineering and wrote “First actual case of bug being found.” Though we understand the humour, we also know it really wasn’t the first occurrence of a ‘bug’.

However, Grace Hopper was quite fond of the story and related it often. This probably led to the increase in popularity of the word and its association in the computer field.


And on similar lines, removing that moth from the Harvard Mark II relay also wasn’t the first case of “debugging”. The Oxford English Dictionary mentions the use of the word in 1945 in the context of aircraft engines.

Anyway, I like the story of the Harvard Mark II moth and agree with Bill Burke that it is the first case of reported a computer bug. Removing that moth from the relay would also count as he first case of ‘computer debugging’.

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