AltGr is a modifier key on PC keyboards used to type many characters, primarily ones that are unusual for the locale of the keyboard layout, such as foreign currency symbols and accented letters. If a key has a third symbol on it (on the front vertical face or the bottom right of the key top, sometimes in a different colour), then AltGr is often the means of eliciting that symbol.

The meaning of "AltGr" is unclear. It is not explicitly given in many IBM PC technical reference manuals. The majority opinion holds that it is an abbreviation for "alternative graphics", although the specific function of the key has never had much to do with graphics (even with "graphics characters"). Some people hold that it is an abbreviation for "alternative group", denoting that whilst it is depressed an alternative group of characters is in effect for the keyboard. One minority opinion holds that it is an abbreviation for "accent grave", although the fact that its function is not actually limited solely to grave accents (and in some keyboard layouts has no relation to grave accents at all) and the letter "l" in "Alt" are both problematic for that hypothesis.

Originally, US PC keyboards (specifically: the US 101-key PC/AT keyboards) did not have an AltGr key, it being only relevant to non-US markets. (They simply had "left" and "right" Alt keys.) As those using such US keyboards increasingly needed the specific functionality of AltGr, a need to combat this deficiency in US keyboards arose. (Some of those who needed this were people using non-US software on systems with US keyboards.) Windows combats it by allowing all keystroke combinations involving AltGr to be duplicated by employing keystroke combinations using Ctrl+Alt in its place. It is for this reason that Ctrl-Alt should not be used as a modifier in Windows keyboard shortcuts (see external link below).

The function and usage of AltGr vary according to the exact keyboard layout, which in turn varies according to both the locale and the operating system. It is used extensively in French and Spanish to type the accented vowels áéíó and ú. In United Kingdom keyboard layouts, fewer symbols require the use of AltGr, but some of those few symbols, and thus the AltGr key, are almost as commonly used, by certain classes of users, as the symbols in French and in Spanish are.

The primary two symbols that involve the use of AltGr in UK keyboard layouts are the Euro currency symbol (€) and either the vertical bar ("pipe symbol", |) or broken vertical bar ("broken pipe symbol", ¦). The two latter symbols interchange places in UK keyboards according to the operating system in use. In OS/2, the "UK keyboard layout" (specifically: the UK166 layout) requires AltGr for the vertical bar and the broken vertical bar is a shifted key — which, coincidentally, matches the actual symbols that are printed on most UK keyboards; in Windows, the "UK keyboard layout" requires AltGr for the broken vertical bar and the vertical bar is a shifted key — the converse of what is usually printed on the keys; and in Linux, the "UK keyboard layout" does not have a simple keystroke combination for the broken vertical bar at all, producing the vertical bar for both key combinations.

See also

• Keyboard layout

External links

• Why Ctrl-Alt shouldn't be used as a shortcut modifier