The computer symbol for "not serious" or now more generally "happiness," made up of a colon, dash and a right parenthesis, was born into existence at 11:44 a.m. on September 19, 1982, after it was posted on an online bulletin board by Carnegie Mellon computer scientist Scott Fahlman.
"If someone made a sarcastic remark, a few readers would fail to get the joke, and each of them would post a lengthy diatribe in response," the New York Daily News quoted Fahlman, as writing, in a post on Carnegie Mellon's website about the invention of the sideways smile.
"The problem caused some of us to suggest (only half seriously) that maybe it would be a good idea to explicitly mark posts that were not to be taken seriously," he added.
"In the midst of that discussion it occurred to me that the character sequence :-) would be an elegant solution ... So I suggested that," he said.
Fahlman also suggested the reverse, what has come to be known as a sad face, by using the other parenthesis marker.
"This convention caught on quickly around Carnegie Mellon, and soon spread to other universities and research labs via the primitive computer networks of the day," he wrote.
Still on staff at Carnegie Mellon, Fahlman is modest about his invention, which he says he's never profited from.
"I probably was not the first person ever to type these three letters in sequence, perhaps even with the meaning of 'I'm just kidding' and perhaps even online. But I do believe that my 1982 suggestion was the one that finally took hold, spread around the world, and spawned thousands of variations," Fahlman wrote.