15

Chapter 4

Coded Character Sets And Encodings in

the World

Here major coded character sets and encodings are introduced. Note that you don't have to know

the detail of these character codes if you use LOCALE and

wchar_t

technology.

However, these knowledge will help you to understand why number of bytes, characters, and

columns should be counted separately, why

strchr()

and so on should not be used, why you

should use LOCALE and

wchar_t

technology instead of hard code processing of existing char 

acter codes, and so on so on.

These varieties of character sets and encodings will tell you about struggles of people in the world

to handle their own languages by computers. Especially, CJK people could not help working out

various technologies to use plenty of characters within ASCII based computer systems.

If you are planning to develop a text processing software beyond the fields which the LOCALE

technology covers, you will have to understand the following descriptions very well. These fields

include automatic detection of encodings used for the input file (Most of Japanese capable text

viewers such as

jless

and

lv

have this mechanism) and so on.

4.1 ASCII and ISO 646

ASCII is a CCS and also an encoding at the same time. ASCII is 7bit and contains 94 printable

characters which are encoded in the region of

0x21

0x7e

.

ISO 646 is the international standard of ASCII. Following 12 characters of

  0x23 (number),