Editing Compose key (section)

==History==
The Compose Character key<ref>{{cite web |url=http://www.wickensonline.co.uk/public-gallery/LK201/p1060628.html |title=p1060628 |website=WickensOnline |date=2007 |access-date=2015-07-07 |archive-url=https://web.archive.org/web/20150413081423/http://www.wickensonline.co.uk/public-gallery/LK201/p1060628.html |archive-date=2015-04-13 |url-status=dead }}</ref><ref>{{cite web |url=http://www.netbsd.org/docs/Hardware/Machines/DEC/LK201_large_keycodes.jpg |format=JPEG |title=LK201_large_keycodes.jpg |website=The NetBSD Project |access-date=2015-07-09}}</ref> was introduced by engineers at [[Digital Equipment Corporation]] (DEC) on the [[LK201]] keyboard, available since 1983 with the [[VT220]] terminal.<ref name="Appstorm">{{cite web |url=http://windows.appstorm.net/roundups/utilities-roundups/add-a-virtual-compose-key-to-your-pc/ |title=Add a Virtual Compose Key to Your PC |website=Windows.Appstorm |access-date=2015-07-07 |archive-date=2020-11-06 |archive-url=https://web.archive.org/web/20201106074437/http://windows.appstorm.net/roundups/utilities-roundups/add-a-virtual-compose-key-to-your-pc/ |url-status=dead }}</ref> The keyboard included an LED indicating that a Compose sequence is on-going.<ref>{{cite web |url=http://www.wickensonline.co.uk/public-gallery/LK201/p1060631.html |title=p1060631 |website=WickensOnline |date=2007 |access-date=2015-07-07 |archive-url=https://web.archive.org/web/20150413081428/http://www.wickensonline.co.uk/public-gallery/LK201/p1060631.html |archive-date=2015-04-13 |url-status=dead }}</ref> While the LK201 introduced the group of command keys between the alphanumerical block and the numerical keypad, and the "inverted T" arrangement of arrow keys, which have become standard,<ref>{{cite web |url=http://www.eldacur.com/~brons/NerdCorner/InverseT-History.html |title=Inverse-T History |last=Burrows |first=Jim |date=2009-09-21 |website=Nerd Corner |access-date=2015-07-09}}</ref> the compose key by contrast did not become a standard.

In 1987, [[Sun Microsystems]] released the [[Sun4]], the first dedicated Unix workstation that had a compose key.<ref name="Appstorm" /> On the keyboards of Sun Type 5 and 6 workstations, the Compose LED is placed in the keycap (see picture below).

[[ISO/IEC 9995]]-7 designed a graphical symbol for this key, in ISO/IEC 9995-7 as symbol 15 "Compose Character", and in ISO 7000 "Graphical symbols for use on equipment" as symbol ISO-7000-2021. This symbol is encoded in [[Unicode]] as {{unichar|2384|COMPOSITION SYMBOL}}.

Because [[Microsoft Windows]] and [[macOS]] do not support a compose key by default, the key does not exist on most keyboards designed for modern PC hardware. When software supports compose key behaviour, some other key is used. Common examples are the right-hand [[Windows key]], the {{key press|[[AltGr key|AltGr]]}} key, or one of the {{key press|Ctrl}} keys.<ref name="Earthwithsun.com">{{cite web|url=http://earthwithsun.com/questions/64178/compose-key-on-windows|title=Compose Key on Windows|website=Earthwithsun.com|archive-url=https://web.archive.org/web/20160303172349/http://earthwithsun.com/questions/64178/compose-key-on-windows|archive-date=2016-03-03|access-date=2015-07-07}}</ref> There is no keyboard LED or other physical indicator that a compose sequence is ongoing, though the OS may show some icon (such as the "Compose Character" symbol, below) on the user's text input field.

{{Gallery
| File:Compose key on LK201 keyboard.jpg | The compose key on a DEC LK201 keyboard is the leftmost key on the bottom row.
| File:Compose key on Sun Type 5c keyboard.jpg | The compose key and compose LED on Sun Type 5 and 5c keyboards is the second-rightmost key on the bottom row.
| File:ISO 7000 - Ref-No 2021.svg | ISO keyboard symbol for "Compose Character"
}}