Alternatively referred to as a hash, hash-mark, number, number key, number sign, or a pound (not to be confused with the pounds sterling "£"), the octothorpe is the symbol above the number 3 on a United States qwerty keyboard with two horizontal lines crossing two vertical lines ( # ). Some common examples of how this symbol may be used include using it before a number, e.g. #1, in hashtags, e.g. #computer, and in programming to identify a nonexecutable statement.
Also see: Keyboard definitions,