Alt Graph Key, Compose Key, Dead Key
Difference between Alt Graph, Compose, Dead key?
They are used to insert special characters. The difference is how you press them.
- Hold down AltGraph and press another key to insert a character. For example, using US international layout, AltGraph+e inserts é.
- Press Compose, release it, press key or keys to insert a character. For example, Compose ' e for é.
- Dead key is similar to Compose key, but each limited to one specific accent mark. For example, dead´ e for é, dead¨ a for ä.
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:
- AltGraph+e inserts é
- AltGraph+c inserts ©
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 .
On the Mac, the ⌥ option key serve the same purpose as AltGraph. [see Mac Keyboard Viewer]
Compose Key
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
- Compose ' e inserts é
- Compose O c inserts ©
The Compose Key is on Sun Microsystem Type 6 Keyboard
Compose Key key has a Unicode symbol ⎄. [see Keyboard Symbols ⌘ ⏎ ⌫]
Dead Key
[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:
- é = e with acute mark
- à = a with grave mark
- ê = e with circumflex
- ñ = n with tilde
- ü = u with diaeresis
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:
- ① not holding down key is more ergonomic and more efficient. [see Ban Key Chords]
- ② key sequence allows far more possible characters. For example, AltGraph+e might produce é. You have 26 letters plus some punctuation keys, a total of about 40. With Compose key sequence, you can type Compose e ' to insert é. You are using 2 keys after the compose, so you have 40×40 = 1600 possibilities. [see How Many Keyboard Shortcuts Are There]
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.
