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.

〔see Accent Marks: Trema, Umlaut, Macron, Circumflex〕

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

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

Compose is a better design, because:

• Not holding down key is more ergonomic and more efficient. 〔see Ban Key Chords〕
• 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 key 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.