Alt Graph Key, Compose Key, Dead Key

By Xah Lee. Date: . Last updated: .
Sun Microsystems Type 6 keyboard meta
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. DEC VT220 Terminal, 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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