Unicode Explained

Definitions of Character Repertoires

The implementation of Unicode support is a long and mostly gradual process. Unicode

can be supported by programs on any operating systems, although some systems may

allow much easier implementation than others; this mainly depends on whether the

system uses Unicode internally so that support to Unicode is built in.

Even in circumstances where Unicode is supported in principle, the support usually

does not cover all Unicode characters. For example, an available font may cover some

part of Unicode that is only practically important in some area. When text data pro-

duced in one program is to be processed in another, we should be prepared for diffi-

culties with any unusual characters. For data transfer, it is essential to know which

Unicode characters the recipient is able to handle.

Thus, although Unicode contains a huge number of characters, not all of them can be

used safely. Among the 100,000 or so characters, usually only a small subset can be

used in a particular application and context without a serious risk of distorting infor-

mation.

Formally Defined Repertoires

Each character code, by itself, defines a character repertoire: the collection of characters

that can be represented in the code. In addition to this, subsets of such collections can

be defined.

A character repertoire is any collection of characters, without implying any particular

implementation ...