Alt Graph Key, Compose Key, Dead Key

By Xah Lee. Date: . Last updated: .
sun keyboard ret
The Meta, Compose, AltGraph keys, on Sun Microsystem Type 6 Keyboard

Difference between Alt Graph, Compose, Dead key?

They are used to insert special characters. The difference is how you press them.

[see Accent Marks: Trema, Umlaut, Macron, Circumflex]

Alt Graph Key

The Alt Graph key, usually labeled “AltGr”. This key is a modifier key. It is for inserting special characters. Press AltGraph+key to insert a special char.

For example, when using US international layout:

This key is on some European keyboards. It's also on Sun Microsystem Type 6 Keyboard .

Which character is inserted with what key is dependent on the keyboard layout. [see International Keyboard Layouts]

On Windows, the right Alt becomes AltGraph if you set your keyboard layout to one of European layouts .

macOS 10.15.5 keyboard viewer 2020-07
MacOS Keyboard Viewer. macOS 10.15.5, 2020-07-25. Hold ⌥option down to type Unicode symbols. Those colored orange are prefix keys, allowing you to type accented characters such as é ü ô. You can make it insert emoji. [see macOS: Create Custom Keyboard Layout]

On the Mac, the ⌥option key serve the same purpose as AltGraph. [see Mac Keyboard Viewer]

Compose Key

compose key on lk201 keyboard 0574
Compose key on LK201 keyboard

The Compose Key key is also for inserting special characters. But it is used in a different way than Alt Graph key.

The Compose Key is used as a starting key of a key sequence. Press Compose Key first (and release it), then type other keys, to insert a special char. For example

The Compose Key is on Sun Microsystem Type 6 Keyboard

Compose Key key has a Unicode symbol . [see Keyboard Symbols ⌘ ⏎ ⌫]

Dead Key

french keyboard layout 2017 04 30
French (AZERTY) keyboard layout. Red are a dead keys. image source
jelly comb keyboard french azerty 11754
French AZERTY keyboard. The ^ and ¨ (to the right of P) are dead keys.

[see French Keyboard Layout]

Dead key is a special key similar to Compose key. It is used for inputting chars with diacritic marks, such as:

You press the dead key first, then type a letter.

Many European language layout have both AltGraph key and dead keys. See: International Keyboard Layouts .

On the Mac, ⌥option+e is a software dead key. It adds the acute mark to any letter typed after.

[see Accent Marks: Trema, Umlaut, Macron, Circumflex]

Emacs has over 1k keybinding, including a full set of keys for AltGraph, Compose, and dead keys. [see A Curious Look at Emacs's One Thousand Keybindings]

Which is Better Design? Alt Graph, Compose, or Dead Key?

AltGraph and Compose serves the same purpose. The only difference is that you need to holdAltGraph down.

Compose is a better design, because:

Dead key has a special place. That is, if there are a few special characters that are used very frequently, having a dead key for them is more efficient than using Compose. For example, suppose in your language the characters é and ú and í occur frequently. If you add dedicated keys for them, that would be expensive, because keys space is limited. Using Compose, you might press Compose ' e. Using Dead key, you just press dead ' e. Of course, you will need a extra physical key on your keyboard for each possible accent mark. But, if there's just a few specific symbol that you need to input frequently, it's good to have one dedicated dead key for it.

In general, keyboard should just have a Compose key.

Keyboard Keys Topic

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