Fatto generale: 80 is a common limit for the characters per line in computing (derived from the number of columns in IBM cards).
Fatto matematico: 80 is a ménage number, and is a Harshad number number in base 10.
Trivia: 80 is the standard TCP/IP port number used for HTTP connections.
Data storica: March 20th is the day in 1951 that Fujiyoshida, a city located in Yamanashi Prefecture, Japan, in the center of the Japanese main island of Honshū is founded.