The exclamation mark or exclamation point is a punctuation mark usually used after an interjection or exclamation to indicate strong feelings or high volume, and often marks the end of a sentence. Similarly, an exclamation mark is often used in warning signs. Other uses include, In mathematics it denotes the factorial operation, at the beginning of an expression to denote logical negation, e. g. A means the logical negation of A, also called not A. Graphically the exclamation mark is represented as a stop point with a vertical line above. One theory of its origin is that it is derived from a Latin exclamation of joy, the modern graphical representation is believed to have been born in the Middle Ages. Medieval copyists wrote the Latin word io at the end of a sentence to indicate joy, over time, the i moved above the o, and the o became smaller, becoming a point. The exclamation mark did not have its own dedicated key on standard manual typewriters before the 1970s, instead, one typed a period, backspaced, and typed an apostrophe. In the 1950s, secretarial dictation and typesetting manuals in America referred to the mark as bang, appeared in dialogue balloons to represent a gun being fired, although the nickname probably emerged from letterpress printing. This bang usage is behind the names of the interrobang, an unconventional character, and a shebang line. In the printing world, the mark can be called a screamer, a gasper. In hacker culture, the mark is called bang, shriek, or, in the British slang known as Commonwealth Hackish. For example, the password communicated in the spoken phrase Your password is em-nought-pee-aitch-pling-en-three is m0ph. n3, the exclamation mark is common to languages using the Latin alphabet, although usage varies slightly between languages. The exclamation mark was adopted in languages written in other scripts, such as Greek, Russian, Arabic, Hebrew, Chinese, Korean, Japanese and Devanagari. A sentence ending in an exclamation mark may be an exclamation, or an imperative, or may indicate astonishment or surprise, They were the footprints of a gigantic hound. Exclamation marks are occasionally placed mid-sentence with a similar to a comma, for dramatic effect, although this usage is obsolescent, On the walk. Informally, exclamation marks may be repeated for emphasis. The exclamation mark is used in conjunction with the question mark. This can be in protest or astonishment, a few writers replace this with a single, nonstandard punctuation mark, the interrobang, which is the combination of a question mark and an exclamation mark
Trilingual billboard in Barcelona (detail), showing the initial exclamation mark for Spanish, but not for Catalan (top line) and English.
New Zealand road sign warning of a "cattle stop" (cattle grid/cattle guard)
This Action Comics cover from 1959 ends every sentence with an exclamation point or question mark. Often, few or no periods would be used in the entire book.