View source for Alt key

{{short description|Computer key}}
{{more citations needed|date=January 2008}}
[[File:Alt - Lenovo.jpg|thumb|The '''Alt''' key  on a Lenovo laptop keyboard]]
[[File:ISO 7000 - Ref-No 2105.svg|thumb|upright=0.6|ISO keyboard symbol for “Alternate”]]
The '''Alt key''' {{keypress|Alt}} (pronounced {{IPAc-en|ɔː|l|t}} {{respell|AWLT}} or {{IPAc-en|ʌ|l|t}} {{respell|ULT}}) on a computer keyboard is used to change (alternate) the function of other pressed keys. Thus, the Alt key is a [[modifier key]], used in a similar fashion to the [[Shift key]]. For example, simply pressing ''A'' will type the letter 'a', but holding down the Alt key while pressing ''A'' will cause the [[computer]] to perform an {{key press|Alt|A}} function, which varies from [[Computer program|program]] to program. The international standard [[ISO/IEC 9995]]-2 calls it ''Alternate key''. The key is located on either side of the [[space bar]], but in non-US PC keyboard layouts, rather than a second Alt key, there is an '[[AltGr key|Alt Gr]]' key to the right of the space bar. Both placements are in accordance with ISO/IEC 9995-2.  With some [[keyboard mapping]]s (such as [[US-International]]), the right Alt key can be reconfigured to function as an [[AltGr]] key although not engraved as such.

The standardized keyboard symbol for the Alt key, {{keypress|⎇}} (which may be used when the usual Latin lettering "Alt" is not preferred for labeling the key) is given in [[ISO/IEC 9995]]-7 as symbol 25, and in ISO 7000 ''"Graphical symbols for use on equipment"'' as symbol ISO-7000-2105. This symbol is encoded in [[Unicode]] as {{unichar|2387|alternative key symbol}}. [[Mac (computer)|Macintosh]] keyboards equate the Alt key with the {{key top|Option}} key, which has its own symbol, similar to that of the ISO standard.

The Alt key should not be confused with the Altmode key (sometimes also labelled Alt) on some Teletype and ASCII terminals, which is a synonym for the [[Escape character#ASCII escape character|ASCII escape character]].

==Evolution==
The Alt key has come to replace the [[Meta key]] of the old MIT keyboards. In their original function, both Alt and Meta would set the high [[bit]] of the signal generated by the key to 1 (for example, A generates 01000001 while {{key press|Alt|A}} generates 11000001). However, in modern software, due to the requirement for all bits to be used for post-ASCII 8-bit character sets, Alt no longer works in such a way.

[[File:AppleAlt.jpg|thumb|right|The Alt key on an Apple keyboard]]

Since the 1990s, Alt has been printed on the [[Option key]] ({{key top|Opt}}) on most Mac keyboards. As of 2017, the newest Apple keyboards do not contain the Alt label. Alt is used in non-Mac software, such as non-macOS Unix and Windows programs, but in macOS it is always referred to as the Option key. The Option key's behaviour in macOS differs slightly from that of the Windows Alt key (it is used as a modifier rather than to access pull-down menus, for example).

==Alt key combinations==
The {{key press|Alt}} key is well known as part of the key combinations:

*{{key press|Ctrl|Alt|Delete}} may restart the computer (its original function); in some operating systems it brings up a [[task manager]] - see [[Control-Alt-Delete]].
*{{key press|Alt|Cmd|Esc}} (often referred to as {{key press|Cmd|Opt|Esc}}.) brings up the [[Force Quit]] window in [[Apple Inc.|Apple's]] [[macOS]], see [[Option key]].
*{{key press|Ctrl|Alt|Backspace}} usually causes the X [[display server]] to shut down or to restart, see [[Control-Alt-Backspace]].
*{{key press|Alt|F4}} closes the current window (or shuts down the computer if the desktop is in the foreground) on most windowing systems.
*{{key press|Alt|Shift}} switches between language layouts.
*{{key press|Alt|Tab}} switches between the currently opened windows on most windowing systems, often referred to as [[alt-tab]]bing.
*{{key press|Alt|Enter}} allows for a new line when Enter performs another command. (This is also done by {{key press|Shift|Enter}} in other programs.) For example, in a word processor, this creates a [[Newline|line break]] rather than a [[Newline#Unicode|paragraph break]].
*Holding <kbd>Alt</kbd> while dragging the mouse over a [[hyperlink]] selects it as if it were solid text. On [[Linux]], this is done using <kbd>Super</kbd>+<kbd>Alt</kbd>. (The Linux [[Super key (keyboard button)|"Super" key]] is physically the same as the [[Windows key]].)
*When only holding <kbd>Alt</kbd> while dragging with the mouse on Linux ([[X Window System]]), the [[Window (computing)|window]] is moved.

==Alt key for special characters==
===Windows===
In [[Microsoft Windows]], holding down the Alt key while typing in numbers (often referred to as [[Alt code]]s) on the [[NumPad|numeric keypad]] allows the user to type special characters not normally available on the keyboard. For example, holding down Alt while typing 0225 ({{key press|Alt|0}}{{key press|2}}{{key press|2}}{{key press|5}}) on the numeric keypad will result in {{char|á}}, the character at 225 in the (Western Latin) [[code page 1252]]. These extended keyboard characters are useful for persons using foreign languages, mathematics, currency symbols, business use, etc. Some computers work the same if the [[Num Lock key]] is on.

===macOS===
On a [[Macintosh]], the Alt key is called the [[Option key]]. It is not used to enter numeric character codes. Instead, keyboard letters and numbers are used. The diagram below shows the special characters a US Mac keyboard will produce when the Option key is pressed.<ref>[https://web.archive.org/web/20091208035043/http://www.recordpc.com/how-to-find-symbols-and-characters-on-the-mac How to find symbols and characters on the Mac – Record PC] - via [[Archive.org]]</ref>

The highlighted orange keys show the accents available from the combination of the {{key press|Alt}} key and the keyboard characters {{key press|e}} {{key press|i}} {{key press|u}} (on the top letters row) and {{key press|`}} {{key press|n}} (on the bottom letters row). The accent then can be applied to associated letters both lower and uppercase. The additional characters a Mac will produce are a combination of both the {{key press|Option}} key and the {{key press|Shift}} key pressed down together. With this combination pressed the keyboard will now produce a different set or an uppercase version of the previous set in some cases.

==Alt key pressed alone==
When a user presses the {{key press|Alt}} key by itself on [[Microsoft Windows]], that moves keyboard focus to the menu bar of the application having keyboard focus, and the key is not delivered to the application. In that state, another press of the {{key press|Alt}} key will be delivered to the application.

On other platforms, for example [[Ubuntu (operating system)|Ubuntu]], the {{key press|Alt}} key pressed by itself may invoke another application and not be delivered to the application having keyboard focus. In Ubuntu 16.04, pressing the key opens the HUD, which is an input field that lets the user perform menu commands such as opening a file, or creating a new file.<ref>[https://wiki.ubuntu.com/Unity/HUD Unity/HUD - Ubuntu Wiki]</ref>

==See also==
* [[Table of keyboard shortcuts]]
* [[Control-Alt-Delete]]
* [[Modifier key]]
* [[Alt code]]
* [[Option key]]

==References==
{{reflist}}

{{Keyboard}}
{{keyboard keys}}

{{DEFAULTSORT:Alt Key}}
[[Category:Computer keys]]