# : Java Glossary

Names

# is officially called the octothorpe, from its eight points or possibly representing eight fields. In Twitter, it is called a hash tag. There, it is used to mark a keyword in a post. On a telephone keypad, it is called the pound key. I think this goes back to the days of the mechanical typewriter where shift-3 gave you either £ or # depending on the model. It is sometimes called the number sign. It looks similar to the musical sharp (♯).

Uses

In HTML (Hypertext Markup Language) it is used in hex entities such as ♯ or decimal entities such as ♯. It is used in Unix to introduce the name of an interpreter for a given script. e.g. #!/usr/bin/perl In Python, it introduces a comment. It has no special significance in Java.