User Guide

Editing Fonts
69
Character Identification in FontLab
I n FontL ab th er e a r e f o u r m o d e s o f c h a r a c t e r a n d g l y p h i d e n t i f i c a t i o n :
1. Names mode. This mode historically is used in Type 1 fonts. An
interesting point is that Names mode may have two different
applications: it may be used to reference glyphs or characters. In the
latter case all referenced characters must have a one-to-one
relationship between character and glyph, so there is no difference
between referencing the character and the glyph. Tables that are used
to reference glyphs or characters in Names mode are called Encoding
Tables. There are two kinds of these tables: a mapping encoding table
references characters in Type 1 fonts and is based on one of the Adobe
standards; while a definition encoding table references glyphs and has
no relation to characters. This is sometimes useful in managing a font
at the design stage.
2. Codepages mode. This is a character-identification method – a
special table of Unicode indexes is used to map a subset of characters
to the top part of the Font Window table. This table, called a codepage,
may use one or two bytes to represent a character mapping record.
Two-byte codepages are used to reference characters in Far-East fonts:
Chinese, Japanese, Korean or Traditional Vietnamese.
3. Unicode Ranges mode. Unicode is a two-byte standard so it
potentially can cover 65,536 characters (not taking into account the
extension methods implemented in the Unicode 3.1 standard). This is a
huge code space and to manage it most efficiently it is divided into
several ranges. Usually a range is designed to cover a single script, like
Cyrillic, Armenian or Thai. The Unicode Ranges mode references
characters.
4. Index mode. This is the simplest glyph identification mode: all
glyphs are sorted in their sequential numerical order in the collection
of glyphs.