[CyMonk]

It actually goes back to mechanical typewriters, which were limited to 70 to 90 characters per line. Commonly used punch cards also had 80 columns. Both were the inspiration for the 80 characters in computer terminals.

[rsolva]

Weeel, actually! ... It dates back to the early days of the printing press, and has been a general convention since then.

Rules can be broken, but not without consequence.