AltGr

AltGr (also Alt Graph, Alt Graphic, Alt Graphics, Alt Grammar, Alt Car, or Right Alt) is a modifier key found on some computer keyboards and is primarily used to type characters that are unusual for the locale of the keyboard layout, such as currency symbols and accented letters. On a typical, IBM-compatible PC keyboard, the AltGr key, when present, takes the place of the right-hand Alt key. In OS X, the Option key has functions similar to the AltGr key.

AltGr is used similarly to the Shift key: it is held down when another key is struck in order to obtain a character other than the one that the latter normally produces. AltGr and Shift can also sometimes be combined to obtain yet another character. For example, on the US-International keyboard layout, the C key can be used to insert four different characters:

The meaning of the key's abbreviation is not explicitly given in many IBM PC compatible technical reference manuals. However, IBM states that AltGr is an abbreviation for alternate graphic, and Sun keyboards label the key as Alt Graph.

AltGr was originally introduced as a means to produce box-drawing characters, also known as pseudographics, in text user interfaces. These characters are, however, much less useful in graphical user interfaces, and rather than alternate graphic the key is today used to produce alternate graphemes.

Originally, US PC keyboards (specifically, the US 101-key PC/AT keyboards) did not have an AltGr key because that was relevant to only non-US markets; they simply had "left" and "right" Alt keys.

The right Alt key is usually an equivalent of the AltGr key because both the right Alt key and the AltGr key share the same scancode and are indistinguishable by software. However, on some keyboards it may not be the case, i.e. the keyboard has two Alt keys, each of which acts as the left Alt key. On compact keyboards like those of netbooks, the right Alt key may be missing altogether. To allow the specific functionality of AltGr when typing non-English text on such keyboards, Windows allows it to be emulated by pressing the Alt key together with the Control key:

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