User Guide

FontLab 4
78
Codepages
Codepages are tables that map character codes (one byte long) to the
Unicode indexes. Depending on the size of the page, these tables may have
256 or 65,536 records, one for each possible character code. Long
codepages are called double-byte codepages and are primarily used to
represent codes used in Chinese, Japanese, Korean or Vietnamese
languages.
Codepages are necessary because we need to somehow encode text written
in different languages in the one-byte code space. So when we have a text
file encoded according to some codepage, we use the codepage table to find
which characters were used in this text. We may have two different texts
with the same code 192 (decimal), but in one case it may mean the Russian
‘A’ and in the other case it may mean ‘À’ (Agrave).
Codepages are used not only to identify characters, but also to simplify text
sorting, conversion of lowercase to uppercase characters, spell-checking
and in many other applications where it is necessary to know which
characters are used in the text.