nonsense, and so tiny you could hardly read it? Chances are there was somebody at your shoulder insisting that every single spit and comma had to be accurate or the thing wouldn’t work.

For most of us, telling computers precisely what to do is a relatively new experience. But programmers have been taking care over spits and commas for half a century - although sometimes not as much care as they might have.

The Mariner unmanned probes were built to carry out the earliest explorations of neighbouring planets, in this case, Venus. Mariner 1 was not only the great-great-grandmother of today’s Spirit on Mars mission, but was the first interplanetary spacecraft ever.

Or at least that’s how it was shaping up at 4.21 on a July morning in 1962.

That’s when the probe blasted off on its historic journey from Cape Canaveral. But at 4.25, its delivery vehicle had a change of heart. To the dismay of controllers, it flipped over and began an unscheduled nose dive.

Fearing that it would plunge into shipping lanes or, even worse, a populated area, Nasa officials decided to blow both rocket and probe to smithereens. But while this painful decision was taken in an instant, identifying the cause of the disaster took a little longer. Not until the following summer did a report to the House Committee on Science and Astronautics reveal a mistake in a computer program had sealed the fate of Mariner 1.

First, there was a problem with a radio guidance system. At that point an inboard computer should have taken over. But the program had never been put to the test, because the radio system had always functioned perfectly. And when it was put to the test I The investigators’ report went straight to the point. “Omission of hyphen in data editing”, it said, “caused computer to swing automatically into a series of unnecessary course-correction signals which threw spacecraft off course so that it had to be destroyed.”

So remember, it’s “http colon forward slash forward slash . . .”