The First Computer Bug Was an Actual Bug

While today's computer 'bugs' are frustrating flaws in software code, the earliest computer errors were often far more tangible. These pioneering machines, like the room-sized Harvard Mark II, were not built with microchips but with thousands of electromechanical relays—physical switches that clicked open and shut to perform calculations. This physical nature meant that malfunctions could be caused by environmental factors, including dust, temperature, or, in one famous instance, an insect intruder.

On September 9, 1947, operators tracing a fault in the Mark II discovered the culprit: a moth had become trapped between the contacts of a relay, preventing the circuit from closing. The team, which included computing pioneer Grace Hopper, carefully removed the insect and taped it into their logbook. Beneath it, they noted, 'First actual case of bug being found.' While the term 'bug' had been used by engineers for decades to describe technical glitches, this literal example cemented its place in the computing lexicon, giving rise to the now-ubiquitous term 'debugging' for the process of finding and fixing problems. The original logbook, complete with the moth, is now preserved at the Smithsonian National Museum of American History.