INVERTED EXCLAMATION MARK. Other uses include: In mathematics, it denotes the factorial operation. Several computer languages use ! at the beginning of an expression to denote logical negation.
In order to make communication easier, in 1754, the second edition of the Ortografa de la Real Academia (the Spanish equivalent of the Oxford English Dictionary) established the rule of adding an upside-down question and exclamation mark at the start of the sentence to questions and exclamations.