Alt Graph Key, Compose Key, Dead Key

By Xah Lee. Date: . Last updated: .
sun keyboard ret
The ◆ Meta, ⎄ Compose, AltGr keys, on Sun Microsystem's Type 6 Keyboard

What is the difference between Alt Graph key, Compose key, Dead key?

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

〔►see Accent Marks: Trema, Umlaut, Macron, Circumflex, and All That

Alt Graph Key

The Alt Graph key, usually labeled “AltGr”. This key is a modifier key. It is for inserting special characters. Press 【AltGr+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's 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 AltGr if you set your keyboard layout to one of European layouts.

Mac keyboard viewer us int 2017  41373
Mac keyboard viewer, with ⌥ option key down, US International layout, 2017. Those colored orange are prefix keys, allowing you to type accented characters such as {é ü ô}.

On the Mac, the ⌥ option key serve the same purpose as AltGr. 〔►see Mac Keyboard Viewer and Unicode

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's Type 6 Keyboard and usually on unix “workstation” keyboards of 1980s.

Compose Key key has a Unicode symbol . 〔►see Unicode Keyboard Symbols ⌘ ⏎ ⌫

Dead Key

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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 AltGr 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, and All That

Emacs has over 1k keybinding, including a full set of keys for AltGr, ⎄ Compose, and dead keys. 〔►see List of Emacs Default Keybinding

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

AltGr and ⎄ Compose serves the same purpose. The only difference is that one is a modifier key, you need to hold it 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.

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  13. Alt Graph Key, Compose Key, Dead Key