Editing Dead key

{{short description|Special kind of modifier keyboard key}}
{{more citations needed|date=March 2015}}
A '''dead key''' is a special kind of [[modifier key]] on a mechanical [[typewriter]], or [[computer keyboard]], that is typically used to attach a specific [[diacritic]] to a base [[letter (alphabet)|letter]].<ref>{{cite web|url=http://www.merriam-webster.com/dictionary/dead%20key |title=Dead Key &#124; Definition of Dead Key by Merriam-Webster |publisher=Merriam-webster.com |access-date=2017-05-01}}</ref> The dead key does not generate a (complete) [[grapheme|character]] by itself, but modifies the character generated by the key struck immediately after. Thus, a dedicated key is not needed for each possible combination of a diacritic and a letter, but rather only one dead key for each diacritic is needed, in addition to the normal base letter keys.

For example, if a [[keyboard mapping]] (such as [[US international]]) has a dead key for the [[circumflex]],  {{char|^}}, the character {{char|â}} can be generated by first pressing {{keypress|^}} and then {{keypress|a}}.<ref>The Unicode Standard, version 8.0.0, ch.05, §12 Strategies for Handling Nonspacing Marks: Keyboard Input | https://www.unicode.org/versions/Unicode8.0.0/ch05.pdf#G1076</ref>  <!-- please do not add more examples, one is plenty to illustrate the point. -->

Usually, the diacritic itself can be generated as a free-standing character by pressing the dead key followed by ''space''; so a [[caret]] (free-standing circumflex) can be typed by pressing {{keypress|^}} and then {{keypress|Space}}.

==Mechanical typewriters==
[[File:Idazmakina.jpg |thumb|Spanish typewriter (QWERTY keyboard) with dead keys for acute, circumflex, diaeresis and grave accents.]]
{{see also|Tilde#Role of mechanical typewriters}}
The dead key is  mechanical in origin, and "dead" means without movement. On mechanical typebar typewriters, all characters are of equal width. As a key is pressed, a metal typebar strikes the character onto an inked ribbon, transferring ink to the paper, and a mechanism is triggered which causes the paper (inserted in a ''[[typewriter carriage|carriage]]'') to move forward one space. To use a single diacritic, such as the [[acute accent]], with multiple foundation characters (such as ''á, é, í, ó, ú'') the decision was made to create a new character, the acute accent or diacritic {{char|´}}, which did not exist in typesetting as of that date. Due to a change in the mechanism, striking the key containing the accent did not advance the paper (the key was "dead" or non-[[spacing character|spacing]]), meaning it could be followed by any character that was to appear under the acute accent, producing an [[overstrike|overstruck]] character. This second key moved the paper carriage forward.

Note that with mechanical keyboards, the acute accent could be followed by any character, to create new combinations such as ''q'' with acute accent.

==Electronic keyboards==
A dead key is different from a typical modifier key (such as {{keypress|[[AltGr key|AltGr]]}} or {{keypress|[[Option key|Option]]}}), in that rather than being pressed and held while another key is struck, the dead key is ''pressed and released'' before striking the key to be modified. In some computer systems, there is no indication to the user that a dead key has been struck, so the key appears dead (nothing immediately happens), but in some text-entry systems, the diacritic is displayed, along with an indication that the system is waiting for another keystroke to complete the typing sequence.

Computers, however, work differently. The dead key temporarily changes the [[keyboard layout|mapping of the keyboard]] for the next keystroke, which activates a special keyboard [[mode (user interface)|mode]] rather than actually generating a modifier [[character (computing)|character]]. Instead of the normal letter, a [[precomposed character|precomposed]] variant, with the appropriate diacritic, is generated. Each combination of a diacritic and a base letter must be specified in the [[character set]] and must be supported by the [[computer font]] in use.

There is no precomposed character to combine the acute accent with the letter {{char|q}}, striking {{keypress|´}} and then {{keypress|q}} is likely to result in {{char|´q}}, with the accent and letter as separate characters. However, in most systems, the invalid typing sequence may be discarded.{{efn|By using the [[combining character]]s available in the [[Unicode]] character set, it may be possible to generate a combination that more or less looks like a {{char|q}} with an acute accent ({{char|q́}}), but that technique is quite distinct from the dead key functionality. In addition, since a letter like ''q'' does not normally take accents, computer font makers may not include the font attributes necessary for a combining accent to be applied successfully or in an attractive way. It is necessary to test this usage in context, since support for accenting in this way varies considerably. Furthermore, files generated in this way may not be useful since it is not possible to guarantee that all recipients have the required fonts installed.}}

==Chained dead keys==

[[Unicode]] encoded over one hundred [[Precomposed character|precomposed&nbsp;characters]] with two [[diacritic]]s, for use in [[Latin script]] for [[Vietnamese language|Vietnamese]] and a number of other languages. For convenience, they are generated on most keyboards supporting them, by pressing the two corresponding deadkeys in any order, followed by the letter key. Therefore, these dead keys are ''chained'', which means that the second keystroke does not trigger any insertion, the system being still awaiting another key press.

Chaining dead keys allows for [[Compose key|compose&nbsp;key]] emulation by simply using the dead key feature. This may be performed either with proprietary keyboard editing software,<ref>{{cite web|url=http://www.kbdedit.com/manual/dead_chained.html |title=Chained dead keys |publisher=Kbdedit.com |access-date=2017-05-01}}</ref> or with driver development kits.<ref>{{cite web|url=https://www.microsoft.com/en-us/download/details.aspx?id=11800 |title=Download Windows Driver Kit Version 7.1.0 from Official Microsoft Download Center |publisher=Microsoft.com |date=2010-02-26 |access-date=2017-05-01}}</ref>

==Dead keys on various keyboard layouts==
{{Main|Keyboard layout|QWERTY|AZERTY|QWERTZ}}

A key may function as a dead key by default, and many non-English keyboard layouts in particular have dead keys directly on the keyboard. The basic [[US keyboard]] does not have any dead keys, but the [[US-International|US-International keyboard layout]], available on Windows and the [[X Window System]], places some dead keys directly on similar-looking punctuation marks. Keyboards sold in most of the rest of the world have an [[AltGr key|AltGr]] (Alternative graphic) key, which gives the ability to modify some letters directly and turns others into dead keys (depending on keyboard setting). Old computer systems, such as the [[MSX]], often had a special key labeled ''dead key'', which in combination with the [[Ctrl key|Ctrl]] and [[Shift key|Shift]] keys could be used to add some of the diacritics commonly needed in the [[Western Europe]]an languages (<code>´</code>, <code>`</code>, <code>ˆ</code> and <code>¨</code>) to vowels that were typed subsequently.

In the absence of a default dead key, even a normal printing key can temporarily be altered to function as a dead key by simultaneously holding down another modifier key (typically AltGr or [[Option key|Option]]). In [[Microsoft Word]] (and in most other text-input fields), using the [[Control key]] with a key that usually resembles the diacritic (e.g. <code>^</code> for a [[circumflex]]) acts as a dead key.<ref>{{cite web |title=How do I get letters with accent marks in Microsoft Word? |url=https://www.computerhope.com/issues/ch000657.htm |website=www.computerhope.com |access-date=21 February 2019 |language=en}}</ref> On the [[Mac (computer)|Macintosh]], many keyboard layouts employ dead keys. For example, when {{key press|Option|i}} are first pressed simultaneously and then followed by {{key press|a}}, the result is ''â''.<ref>{{Cite web |title=Enter characters with accent marks on Mac |url=https://support.apple.com/en-gb/guide/mac-help/mh27474/mac |access-date=2024-01-21 |website=Apple Support |language=en}}</ref> On a Macintosh, pressing one of these Option-key combinations creates the accent and highlights it, then the final character appears when the key for the base character is pressed.{{citation needed |date=January 2023}}

However, some accented Latin letters less common in the major Western European languages, such as ''[[ŵ]]'' (used in [[Welsh language|Welsh]]) or ''[[š]]'' (used in many [[Central Europe]]an languages), cannot be typed with the "US" layout. For users with US keyboards, access to many more diacritics is provided by the "[[QWERTY#US-International|US International]]" keyboard layout. Users with UK keyboards have a similar option with [[QWERTY#United Kingdom (Extended) Layout|UK extended]] layout; many other national settings are available.

In [[AmigaOS]], dead keys are generated by pressing {{key press|Alt}} in combination with {{key press|F}} (acute), {{key press|G}} (grave), {{key press|H}} (circumflex), {{key press|J}} (tilde) or {{key press|K}} ([[Diaeresis (diacritic)|trema]]) (e.g., the {{key press|Alt|F}} combination followed by the {{key press|a}} key generates ''á'' and {{key press|Alt|F}} followed by {{key press|e}} generates ''é'', whereas {{key press|Alt|F}} followed by {{key press|a}} generates ''à'' and {{key press|Alt|G}} followed by {{key press|e}} generates ''è'').<ref>{{Cite book | author=Commodore-Amiga, Inc. | title=AMIGA ROM Kernel Reference Manual LIBRARIES | year=1992 | pages=823–827 | publisher=Addison-Wesley | isbn=0-201-56774-1}}</ref>

==See also==

* {{Annotated link |AltGr key}}
* {{Annotated link |Bucky bit}}
* {{Annotated link |Combining character}}
* {{Annotated link |Compose key}}
* {{Annotated link |Modifier key}}
* {{Annotated link |Precomposed character}}
* {{Annotated link |Sticky keys}}
* {{Annotated link |Alt code|Windows Alt keycodes}}

==Notes==
{{notelist}}

==References==
{{Reflist}}

==External links==
*[https://support.office.com/en-us/article/keyboard-shortcuts-for-international-characters-108fa0c1-fb8e-4aae-9db1-d60407d13c35 Microsoft Office Keyboard shortcuts for international characters]

{{keyboard keys}}

[[Category:Computer keys]]
[[Category:Keyboard layouts]]