“It’s the ‘Hey, you! Listen to me’ key,” says Jack Dennerlein of the Harvard School of Public Health. According to Dennerlein, an expert on how humans interact with computers, the escape key helped drive the computer revolution of the 1970s and ’80s. “It says to the computer: ‘Stop what you’re doing. I need to take control.’ ” In other words, it reminds the machine that it has a human master. If the astronauts in “2001: A Space Odyssey” had an ESC key, Dennerlein points out, they could have stopped the rogue computer Hal in an instant.

The key was born in 1960, when an I.B.M. programmer named Bob Bemer was trying to solve a Tower of Babel problem: computers from different manufacturers communicated in a variety of codes. Bemer invented the ESC key as way for programmers to switch from one kind of code to another. Later on, when computer codes were standardized (an effort in which Bemer played a leading role), ESC became a kind of “interrupt” button on the PC — a way to poke the computer and say, “Cut it out.”

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Why “escape”? Bemer could have used another word — say, “interrupt” — but he opted for “ESC,” a tiny monument to his own angst. Bemer was a worrier. In the 1970s, he began warning about the Y2K bug, explaining to Richard Nixon’s advisers the computer disaster that could occur in the year 2000. Today, with our relatively stable computers, few of us need the panic button. But Bob Frankston, a pioneering programmer, says he still uses the ESC key. “There’s something nice about having a get-me-the-hell-out-of-here key.”