Unicode Explained

use a small set of such letters, perhaps just two or three—e.g., ä, ö, and ü in German.

However, if there are many different combinations of a letter and diacritic marks, it is

more practical to include keys that correspond to the diacritic marks.

Many keyboard designs contain auxiliary keys for typing characters with diacritic

marks. The key might have the characters ´ and ` (acute accent and grave accent)

engraved onto it, for example. Hitting such a key has no visible effect as such, but when

followed by a letter, it might add an accent on the letter. Thus, on a Spanish keyboard,

as was illustrated in Figure 2-2, you would press the ´ key, and then the “O” key to

type ó.

Such an auxiliary key is often called a dead key, since just pressing it causes nothing; it

works only in combination with some other key. You press it before pressing a letter

key, not simultaneously. A more official name for a dead key is modifier key.

A dead key itself may be affected by a Shift key. Thus, Shift-´ followed by “a” might

produce à, and Shift-´ Shift-A would then produce À. Moreover, even AltGr might

affect a dead key. On a normal Finnish keyboard, there is a dead key with the dieresis

(¨) and the circumflex (^) above it (i.e., as “upper case,” to be generated using the Shift

key) and the tilde (~) below or left to it. This means that on such a keyboard, the AltGr

key is needed for producing a letter ...