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Epic failures: 11 infamous software bugs

By Matt Lake
September 9, 2010 06:00 AM ET

Mariner 1's five-minute flight

On July 22, 1962, the first spacecraft of NASA's Mariner program blasted off on a mission to fly by Venus. The booster did its job, taking the spacecraft from its Cape Canaveral launchpad, but after a few minutes, Mariner 1 began to yaw off course. The guidance system failed to correct the trajectory, and guidance commands failed to correct it manually.

As the rocket veered off toward North Atlantic shipping lanes, the range safety officer did the only thing he could do: blow the thing up. Four minutes and 55 seconds into the mission, the Mariner 1 exploded.

NASA was already suffering from Sputnik envy, and the Mariner 1 incident was another international embarrassment for the agency. The postmortem of this debacle revealed what NASA described as "improper operation of the Atlas airborne beacon equipment" -- though later it came out that the mistranscription of a single punctuation mark by an engineer caused the mission's fatal software error.

In his 1968 book The Promise of Space, Arthur C. Clarke described the mission as "wrecked by the most expensive hyphen in history."

That may not be strictly accurate. Although NASA did mention a hyphen in some of its reports of the incident, it appears that the agency was simplifying the story for a nontechnical audience.

A more widely accepted account is that the punctuation mark was a superscript bar over a radius symbol, handwritten in a notebook. In rocket science, the overbar signifies a smoothing function, so the formula should have calculated the smoothed value of the time derivative of a radius.

Without the smoothing function, even minor variations of speed would trigger the corrective boosters to kick in. The automobile driving equivalent would be to yank the steering wheel in the opposite direction of every obstacle in the driver's field of vision.

But few people know what an overbar is, and since it looks like a hyphen, that's how most people tell the story.

After the sidebar: Forty seconds of Ariane-5

Moth in the machine: Debugging the origins of 'bug'

It's an oft-repeated tale that the grande dame of military computing, computer scientist and U.S. Navy Rear Admiral Grace Hopper, coined the terms bug and debug after an incident involving Harvard University's Mark II calculator.

The story goes like this:

On Sept. 9, 1945, a Harvard technical team looked at Panel F and found something unusual between points in Relay 70. It was a moth, which they promptly removed and taped in the log book. Grace Hopper added the caption, "First actual case of bug being found," and that's the first time anyone used the word bug to describe a computer glitch. Naturally, the term debugging followed.

Yes, it's an oft-repeated tale, but it's got more bugs in it than Relay 70 ever had.

For one thing, Harvard's Mark II came online in summer of 1947, two years after the date attributed to this story. For another thing, you don't use a line like "First actual case of bug being found" if the term bug isn't already in common use. The comment doesn't make sense in that context, except as an example of engineer humor. And although Hopper often talked about the moth in the relay, she did not make the discovery or the log entry.

The core facts of the story are true -- including the date of Sept. 9 and time of 15:45 hours -- but that's not how this meaning of the word bug entered the lexicon. Inventors and engineers had been talking about bugs for more than a century before the moth-in-the-relay incident. Even Thomas Edison used the word. Here's an excerpt from a letter he wrote in 1878 to Theodore Puskas, as cited in The Yale Book of Quotations (2006):

'Bugs' -- as such little faults and difficulties are called -- show themselves and months of intense watching, study and labor are requisite before commercial success or failure is certainly reached.

Word nerds trace the word bug to an old term for a monster -- it's a word that has survived in obscure terms like bugaboo and bugbear and in a mangled form in the word boogeyman. Like gremlins in machinery, system bugs are malicious. Anyone who spends time trying to get all the faults out of a system knows how it feels: After a few hours of debugging, any problems that remain are hellspawn, mocking attempts to get rid of them with a devilish glee.

And that's the real origin of the term bug. But the tale of the moth in the relay is worth retelling anyway.

Infamous software bugs



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