Fontlab TransType Pro 3.0.2 Manuel d'utilisateur télécharger pdf (Page 103)

A p p e nd i x A

Basics o f Digital Fo nt Or ganiz atio n

Digital fonts consist of glyphs (drawings) of characters (letters of

alphabets/scripts) organized (encoded) in a particular arrangement.

Because there are many different languages and scripts each alphabet has

its own arrangement (codepage) which allows a computer to know where

to find a particular character, retrieve the glyph, and either print or display

it for the computer user.

The most familiar “encoding” to most North Americans and Western

Europeans is alphabetic order. Dictionaries, thesauri, membership lists,

databases, etc. all use this “encoding” to organize their contents. Font

encodings are a bit more complicated, because they must include not only

the letters of the alphabet (which must be represented in both their

uppercase and lowercase forms) but also punctuation, symbols, and

typographic necessities (like spaces of various sizes). Early in the history of

computing a standard “font” of 256 characters was decided upon because

that was the number that could be addressed by one byte of data.

Of course as soon as a few more alphabets were added it became obvious

that 256 characters was not nearly enough. Many different arrangements

were used and it looked like every country would have its own – some

several. Thus Unicode was born. Unicode is a two-byte font encoding that

has room for about 64,000 characters. All known scripts of the world are (or

are being) included in Unicode. While even 64000 characters is beginning

to look like it may not be enough, it seems that it will be adequate for the

immediate future.

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Fontlab TransType Pro 3.0.2 Manuel d'utilisateur Page 103