The Story Of The First Computer Bug

First computer bug
   Reading time 3

The Story Of The First Computer Bug

The story goes that On September 9, 1947, a team of computer scientists and engineers reported the world’s first computer bug.

The massive (and I’m talking massive – It weighed 25 short tons (2,000 pounds/ton) and occupied over 4,000 square feet of floor space) Mark II Aiken Relay Calculator which was undergoing final testing for the U.S. Navy, at Harvard University stopped functioning properly. When completed it will run ordnance calculations for the U.S. Navy.

The Mark II, also known as the Aiken Relay Calculator, was an electromechanical computer built under the direction of Howard Aiken at Harvard University and completed in 1947. It was financed by the United States Navy and used for ballistic calculations at Naval Proving Ground Dahlgren. Howard Aiken and Grace Hopper worked together to build and program the Mark II. (source)

The contract to build the Mark II was signed with Harvard in February 1945, after the successful demonstration of the Mark I in 1944. It was completed and debugged in 1947, and delivered to the US Navy Proving Ground at Dahlgren, Virginia (Now Naval Surface Warfare Center, Dahlgren Division) in March 1948, becoming fully operational by the end of that year.

Hopper at the UNIVAC I console, c. 1960
Hopper at the UNIVAC I console, c. 1960

On September 9, 1947, at 1545 hours (3:45 p.m. for you non-military types), technicians discovered why it stopped calculating properly. A moth had become trapped between one of the machine’s 17,000 electrical relays. (Relay #70 of Panel F). Navy personnel assigned to the Bureau of Ordnance Computation Project at Harvard University preserved the insect in the daily log, noting that it was “the first actual case of a bug being found” in a computer. The log entry was made by the U.S. Navy Lt. (j.g.) Grace Hopper, didn’t actually find the moth, but she is credited with it as it was her logbook entry that is now famous.

Thomas Edison letter mentioning a "bug"
Thomas Edison letter mentioning a "bug"

In 1988, the log, with the moth still taped by the entry, was in the Naval Surface Warfare Center Computer Museum at Dahlgren, Virginia (I started working at Dahlgren in 2004).

Today the sheet is kept at the National Museum of American History of the Smithsonian Institution in Washington.

Dahlgren Lab Log book with moth taped in it
Dahlgren Lab Log book with moth taped in it
Close up of the log book
Log book with moth taped in it - from the "It's Alive In The Lab" blog

The story was once the million-dollar question o ‘Who Wants to Be a Millionaire?’ March 23rd, 2000, 25-year-old Joe Trela, the customer service representative for a computer company, became the third contestant to win the big prize. He was asked “Which insect shorted out an early supercomputer and inspired the term “computer bug”?” Asked to choose between a moth, roach, fly, or Japanese beetle, he correctly identified the moth as the culprit.

If it’s a good idea, go ahead and do it. It’s much easier to apologize than it is to get permission.
— Grace Hopper

Average Joe

Avatar photo

Welcome to the Average Joe Weekly blog. This is basically my place on the web where I can help spread some of the knowledge that I have accumulated over the years. I served 10+ years in the Marine Corps on Active Duty, but that was some 25 years ago.

Avatar photo

By Average Joe

Welcome to the Average Joe Weekly blog. This is basically my place on the web where I can help spread some of the knowledge that I have accumulated over the years. I served 10+ years in the Marine Corps on Active Duty, but that was some 25 years ago.

Leave a comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.