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A dead key is a special kind of a
modifier key In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes and development of both computer hardware , hardware and softwar ...
on a mechanical
typewriter A typewriter is a mechanical Mechanical may refer to: Machine * Mechanical system A machine is any physical system with ordered structural and functional properties. It may represent human-made or naturally occurring device molecular ...

typewriter
, or
computer keyboard A computer keyboard is a peripheral A peripheral or peripheral device is an auxiliary device used to put information into and get information out of the computer. The term peripheral device refers to all hardware components that are attached to ...

computer keyboard
, that is typically used to attach a specific
diacritic A diacritic (also diacritical mark, diacritical point, diacritical sign, or accent) is a glyph The term glyph is used in typography File:metal movable type.jpg, 225px, Movable type being assembled on a composing stick using pieces that ...
to a base
letter Letter, letters, or literature may refer to: Characters typeface * Letter (alphabet) A letter is a segmental symbol A symbol is a mark, sign, or word that indicates, signifies, or is understood as representing an idea, Object (philosophy ...
. The dead key does not generate a (complete)
character Character(s) may refer to: Arts, entertainment, and media Literature * ''Character'' (novel), a 1936 Dutch novel by Ferdinand Bordewijk * ''Characters'' (Theophrastus), a classical Greek set of character sketches attributed to Theophrastus M ...

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 has a dead key for the ''
grave accent The grave accent ( ` ) ( or ) is a diacritical A diacritic (also diacritical mark, diacritical point, diacritical sign, or accent) is a glyph added to a letter (alphabet), letter or to a basic glyph. The term derives from th ...

grave accent
'' (`), the French character ''à'' can be generated by first pressing and then , whereas ''è'' can be generated by first pressing and then . Usually, the diacritic itself can be generated as an isolated character by pressing the dead key followed by ''space''; so a plain grave accent can be typed by pressing and then .


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 ''
carriage A carriage is a private four-wheeled vehicle for people and is most commonly horse-drawn A horse-drawn vehicle is a mechanized piece of equipment pulled by one horse or by a team of horses. These vehicles typically had two or four wheels an ...
'') to move forward one space. So as to use a single diacritic, such as the
acute accent The acute accent, , is a diacritic A diacritic (also diacritical mark, diacritical point, diacritical sign, or accent) is a glyph The term glyph is used in typography File:metal movable type.jpg, 225px, Movable type being assembl ...

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 , 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), meaning it could be followed by any character that was to appear under the acute accent, producing an 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 or ), 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 mapping of the keyboard for the next keystroke, which activates a special keyboard
mode Mode ( la, modus meaning "manner, tune, measure, due measure, rhythm, melody") may refer to: Language * Grammatical mode In linguistics, grammatical mood is a Grammar, grammatical feature of verbs, used for signalling Modality (natural langua ...
rather than actually generating a modifier
character Character(s) may refer to: Arts, entertainment, and media Literature * ''Character'' (novel), a 1936 Dutch novel by Ferdinand Bordewijk * ''Characters'' (Theophrastus), a classical Greek set of character sketches attributed to Theophrastus M ...
. Instead of the normal letter, a precomposed variant, with the appropriate diacritic, is generated. Each combination of a diacritic and a base letter must be specified in the
character set Character encoding is the process of assigning numbers to Graphics, graphical character (computing), characters, especially the written characters of Language, human language, allowing them to be Data storage, stored, Data communication, transmit ...
and must be supported by the
font In metal A metal (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approxim ...

font
in use. There is no precomposed character to combine the acute accent with the letter ''q'', striking and then is likely to result in ´q, with the accent and letter as separate characters. However, in some systems, the invalid typing sequence may be discarded. (By using the
combining character In digital typography, combining characters are Character (computing), characters that are intended to modify other characters. The most common combining characters in the Latin script are the combining diacritic, diacritical marks (including co ...
s available in the
Unicode Unicode, formally the Unicode Standard, is an information technology Technical standard, standard for the consistent character encoding, encoding, representation, and handling of Character (computing), text expressed in most of the world's wri ...

Unicode
character set, it may be possible to generate a combination that more or less looks like a ''q'' with an acute accent (''q́''), but that technique is quite distinct from the dead key functionality. In addition, since a letter like ''q'' does not normally take accents, 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 on a font by font basis, since support for accenting in this way varies considerably.)


Chained dead keys

Unicode Unicode, formally the Unicode Standard, is an information technology Technical standard, standard for the consistent character encoding, encoding, representation, and handling of Character (computing), text expressed in most of the world's wri ...

Unicode
encoded over one hundred precomposed characters with two
diacritic A diacritic (also diacritical mark, diacritical point, diacritical sign, or accent) is a glyph The term glyph is used in typography File:metal movable type.jpg, 225px, Movable type being assembled on a composing stick using pieces that ...
s, for use in
Latin script Latin script, also known as Roman script, is an alphabetic An alphabet is a standardized set of basic written symbols A symbol is a mark, sign, or word In linguistics, a word of a spoken language can be defined as the smallest sequ ...

Latin script
for
Vietnamese Vietnamese may refer to: * Something of, from, or related to Vietnam, a country in Southeast Asia ** A citizen of Vietnam. See Demographics of Vietnam. * Vietnamese people, or Kinh people, a Southeast Asian ethnic group native to Vietnam ** Oversea ...

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. This ''chained dead key'' behavior is toggled by the ''dead key flag'', which is the fourth argument of the DEADTRANS function (after the base character code, the diacritic code, and the composed character code). If this flag is set to its default value zero, the composed character is inserted; if it is set to one, the composed character code is handled as another diacritic code like those due to dead key presses, and occurs typically as a second argument in other dead list entries. Chaining dead keys allows for compose key emulation by simply using the dead key feature. This may be performed either with proprietary keyboard editing software, or with driver development kits.


Dead keys on various keyboard layouts

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 QWERTY () is a keyboard layout, keyboard design for Latin-script alphabets. The name comes from the order of the first six Computer keyboard keys#Key types, keys on the top left letter row of the keyboard ( ). The QWERTY design is based on ...
does not have any dead keys, but the US-International keyboard layout, available on Windows and the
X Window System The X Window System (X11, or simply X) is a windowing system for bitmap displays, common on Unix-like A Unix-like (sometimes referred to as UN*X or *nix) operating system An operating system (OS) is system software that manages computer ...
, places some dead keys directly on similar-looking punctuation marks. Keyboards sold in most of the rest of the world have an
AltGr AltGr (also Alt Graph) is a modifier key found on many computer keyboards (rather than a second Alt key found on US keyboards). It is primarily used to type characters that are not widely used in the territory where sold, such as foreign cur ...
(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 MSX is a standardized home computer architecture, announced by Microsoft and ASCII Corporation on June 16, 1983. It was initially conceived by Microsoft as a product for the Eastern sector, and jointly marketed by Kazuhiko Nishi, then vice-pre ...

MSX
, often had a special key labeled ''dead key'', which in combination with the
CtrlCTRL or Ctrl may refer to several things: * Channel Tunnel Rail Link, a high-speed railway line opened in the 2000s in Britain * Control key, an input button present on most computer keyboards * CTRL (gene), a gene that in humans encodes the enzyme ...
and
Shift
Shift
keys could be used to add some of the diacritics commonly needed in the
Western Europe Western Europe is the western region of Europe Europe is a continent A continent is any of several large landmasses. Generally identified by convention (norm), convention rather than any strict criteria, up to seven geographical r ...

Western Europe
an languages (´, `, ˆ and ¨) 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 Option or Options may refer to: Computing *Option key, a key on Apple computer keyboards *Option type, a polymorphic data type in programming languages *Command-line option, an optional parameter to a command *OPTIONS, an Hypertext Transfer Prot ...
). In
Microsoft Word Microsoft Word is a word processing software developed by Microsoft Microsoft Corporation is an American multinational Multinational may refer to: * Multinational corporation, a corporate organization operating in multiple countries * ...
(and in most other text-input fields), using the
Control key In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes and development of both computer hardware , hardware and s ...

Control key
with a key that usually resembles the diacritic (e.g. ^ for a
circumflex The circumflex is a diacritic in the Latin script, Latin and Greek alphabet, Greek scripts that is used in the written forms of many languages and in various romanization and Transcription (linguistics), transcription schemes. It received its E ...
) acts as a dead key: On the
Macintosh The Macintosh (mainly Mac since 1998) is a family of personal computer A personal computer (PC) is a multi-purpose computer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be op ...

Macintosh
, many keyboard layouts employ dead keys. For example, when are first pressed simultaneously and then followed by , the result is ''á''. 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. However, some accented Latin letters less common in the major Western European languages, such as '' ŵ'' (used in
Welsh Welsh may refer to: Related to Wales * Welsh, referring or related to Wales * Welsh language, a Brittonic Celtic language of the Indo-European language family, indigenous to the British Isles, spoken in Wales ** Patagonian Welsh, a dialect of Wels ...
) or '' š'' (used in many
Eastern Europe Eastern Europe is the eastern region of Europe Europe is a continent A continent is any of several large landmasses. Generally identified by convention (norm), convention rather than any strict criteria, up to seven geographical reg ...

Eastern Europe
an languages), cannot be typed with the "US" layout. For users with US keyboards, access to many more diacritics is provided by the " US International" keyboard layout. Users with UK keyboards have a similar option with UK extended layout; many other national settings are available. In
AmigaOS AmigaOS is a family of proprietary native operating system An operating system (OS) is system software System software is software designed to provide a platform for other software. Examples of system software include operating systems like ...

AmigaOS
, dead keys are generated by pressing in combination with (acute), (grave), (circumflex), (tilde) or ( trema) (e.g., the ALT-F combination followed by the a key generates ''á'' and ALT-F followed by e generates ''é'', whereas ALT-G followed by a generates ''à'' and ALT-G followed by e generates ''è'').


See also

* * * * * * * *


References


External links


Microsoft Office Keyboard shortcuts for international characters
{{keyboard keys Computer keys Keyboard layouts