Chapter 2. Introduction

6

which is valid only for ISO 8859 1. However, a majestic M17N software such as Mule can be

built using this approach.

Using this classification, let me consider the L10N, I18N, and M17N models from the program 

mer's point of view.

The L10N model can be realized only using his or her own knowledge on his or her language

(i.e. approach B). Since the motivation of L10N is usually to satisfy the programmer's own need,

extendability for the third languages is often ignored. Though L10N ed softwares are primarily

useful for people who speaks the same language to the programmer, it is sometimes useful for

other people whose coding system is similar to the programmer's. For example, a software which

doesn't recognize EUC JP but doesn't break EUC JP, will not break EUC KR also.

The main part of the I18N model is, in the case of a C program, achieved using standardized

locale technology and

gettext

. An locale approach is classified into I18N because functions

related to locale change their behavior by the current locales for six categories which are set by

setlocale()

. Namely, approach A is emphasized for I18N. For field where standardized meth 

ods are not available, however, approach B cannot be avoided. Even in such a case, the developers

should be careful so that a support for new languages can be easily added later even by other de 

velopers.

The M17N model can be achieved using international encodings such as ISO 2022 and Unicode.

Though you can hard code these encodings for your software (i.e. approach B), I recommend

to use standardized locale technology. However, using international encodings is not sufficient

to achieve the M17N model. You will have to prepare a mechanism to switch input methods.

You will also want to prepare an encoding guessing mechanism for input files, such as

jless

and

emacs

have. Mule is the best software which achieved M17N (though it does not use locale

technology).

2.2 Organization

Let's preview the contents of each chapter in this document.

As I wrote, this document will put stress on correct handling of characters and character codes

for users' native languages. To achieve this purpose, I will start the real contents of this docu 

ment by discussing basic important concepts on characters in `Important Concepts for Charac 

ter Coding Systems' on page

9

. Since this chapter includes many terminologies, all of you will

need to this chapter. The next chapter, `Coded Character Sets And Encodings in the World' on

page

15

, introduces many national and international standards of coded character sets and encod 

ings. I think almost of you can do without reading this chapter, since LOCALE technology will

enable us to develop international softwares without knowledges on these character sets and en 

codings. However, knowing about these standards will help you to understand the merit and

necessity of LOCALE technology.