An exclamation mark or exclamation point (!) is used at the end of a sentence to express surprise, disgust, admiration, etc., or to add emphasis to a command. In formal writing, however, it is rarely used.
In C and similar computer programming languages, it is used to represent "logical not" and in a pair with an equals sign (=) to represent is not equal to, e.g. if (a != b) means if a is not equal to b.
In mathematics, the exclamation mark is typically used to represent the factorial of a whole number, n, as n!. For example, 5! can be read as "5 factorial", which means 5 x 4 x 3 x 2 x 1.
- Truss, Lynne. Eats, Shoots and Leaves: The Zero Tolerance Approach to Punctuation. 2003, Gotham Books.
- National Punctuation Day - The Exclamation Point,nationalpunctuationday.com