The exclamation mark, !, also sometimes referred to as the exclamation point (American English), is a punctuation mark usually used after an interjection or exclamation to indicate strong feelings or to show emphasis. The exclamation mark often marks the end of a sentence, for example: "Watch out!". Similarly, a bare exclamation mark (with nothing before or after) is often established in warning signs.
The exclamation mark is often used in writing to make a character seem as though they are shouting and/or excited/surprised. It can also be used in fiction writing for a person who is doing the same thing but in real life.
Graphically, the exclamation mark is represented by variations on the theme of a full stop point with a vertical line above.
One theory of its origin posits derivation from a Latin exclamation of joy, namely io, analogous to "hurray"; the modern graphical representation is believed to have originated in the Middle Ages; medieval copyists wrote the Latin word io at the end of a sentence, to indicate expression of joy. Over time, the i moved above the o; that o first became smaller, and (with time) a dot.[2][page needed][3][page needed][better source needed]
The exclamation mark was first introduced into English printing in the 15th century to show emphasis, and was called the "sign of admiration or exclamation"[4] or the "note of admiration" until the mid-17th century;[5] "admiration" referred to that word's Latin-language sense, of wonderment.
Many pre-computer age typewriters did not have the exclamation mark. Instead the user typed a full stop and then backspaced and overtyped an apostrophe. Such typewriters often lacked a '1' key as well (the user typed a lower-case 'L'). That is why the exclamation point is usually shift+1 as both were added at the same time.[citation needed]