The horizontal smiley face, created by combining a colon, a dash and a closing bracket, is 25 years old today.

Scott Fahlman, research professor of computer science at Carnegie Mellon University, created the emoticon at 11:44am on 19 September 1982.

"Yes, I am the inventor of the sideways 'smiley face' (sometimes called an 'emoticon') that is commonly used in email, chat and newsgroup posts. Or at least I'm one of the inventors," Fahlman said on the Carnegie Mellon website.

The professor claims that the idea came to him because humorous comments posted on the university's bulletin boards were often misinterpreted.

"In at least one case, a humorous remark was interpreted by someone as a serious safety warning," he said.

"Various 'joke markers' were suggested, and in the midst of that discussion it occurred to me that the character sequence :-) would be an elegant solution, and one that could be handled by the ASCII-based computer terminals of the day. "

Fahlman said in the same post that he also suggested the use of :-( to indicate that a message was meant to be taken seriously, although that symbol quickly evolved into a marker for displeasure, frustration or anger.

Carnegie Mellon has now established an annual contest for students to create something that aids communication in technology.

The Smiley Award, which is sponsored by Yahoo, will present the winner with a $500 cash prize.