The moth in the machine

On a warm afternoon in 1947, a computer in Massachusetts stopped behaving. The cause, when they finally found it, was a moth. What the team did next is the part worth remembering.

The machine was the Harvard Mark II, a room-sized computer built from electromechanical relays. On 9 September 1947 it kept producing errors, and the operators went looking. Inside relay number 70, on panel F, they found a moth, caught between the contacts and stopping them from closing. They removed it, and then they did something lovely. They taped the moth into the logbook and wrote beside it: “First actual case of bug being found.”

An honest note, told properly

It is worth being accurate about the legend, because the truth is better than the tidy version. The word “bug”, meaning a fault in a machine, was already old by 1947. Engineers had used it for decades, and the team knew that. That is exactly why the note is a joke. It is the first time the bug was a literal insect. Grace Hopper, who worked on the Mark II, loved telling the story and did a great deal to make “debugging” part of how we all talk, even though the logbook itself was probably not in her hand. The moth and the page are now kept at the Smithsonian.

I am fond of this story for a reason that has nothing to do with insects. Faced with an odd, slightly embarrassing failure, the team did not quietly fix it and move on. They wrote down exactly what happened, kept the evidence, and made it easy for the next person to find. Time, location, component, cause, and the proof taped to the page. As incident reports go, it is close to perfect.

The taped moth is, in its way, the patron saint of good record-keeping. Keep the evidence, tell the truth, and let the next person find it.

The funny bit is not the point

An honest log is the difference between an organisation that learns and one that keeps relearning the same lesson at increasing cost. Most failures are far less charming than a moth in a relay. A loose fitting, a step skipped under time pressure, a reading that looked wrong and was. The discipline is identical. Notice it. Record it plainly. Keep what shows what happened. Make it findable, so the knowledge outlives the people who were there that day.

It is a humble habit, and an old one. A team of engineers in 1947 understood it well enough to laugh, and to write it down anyway. We could do worse than copy them.

References

1. Computer History Museum, “This Day in History, September 9: First instance of an actual computer bug being found”. computerhistory.org.
2. Smithsonian National Museum of American History, “Log Book With Computer Bug”. americanhistory.si.edu.
3. JSTOR Daily, “The Bug in the Computer Bug Story”. daily.jstor.org.

Shannon Hamming writes about how the working world keeps itself safe and honest: incident reporting, quality, ESG, compliance and the sensible use of technology in safety-critical work. Useful first, interesting always.