Exclamation mark
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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 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.[1]
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 times 4 times 3 times 2 times 1.