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System Management Concepts: Operating System and Devices

National Language Support Overview

National Language Support (NLS) provides commands and Standard C Library subroutines for a single worldwide system base. An internationalized system has no built-in assumptions or dependencies on language-specific or cultural-specific conventions such as:

All information pertaining to cultural conventions and language is obtained at process run time.

The following capabilities are provided by NLS to maintain a system running in an international environment:

Localization of Information

An internationalized system processes information correctly for different locations. For example, in the United States, the date format, 9/6/1990, is interpreted to mean the sixth day of the ninth month of the year 1990. The United Kingdom interprets the same date format to mean the ninth day of the sixth month of the year 1990. The formatting of numerical and monetary data is also country-specific, for example, the U.S. dollar and the U.K. pound. A locale is defined by these language-specific and cultural-specific conventions for processing information.

All locale information must be accessible to programs at run time so that data is processed and displayed correctly for your cultural conventions and language. This process is called localization; it consists of developing a database containing locale-specific rules for formatting data and an interface to obtain the rules. For more information about localization, see "Locale Overview" .

Separation of Messages from Programs

To facilitate translations of messages into various languages and to make the translated messages available to the program based on a user's locale, it is necessary to keep messages separate from the programs and provide them in the form of message catalogs that a program can access at run time. To aid in this task, commands and subroutines are provided by the message facility. For more information, see "Message Facility Overview" .

Conversion between Code Sets

A character is any symbol used for the organization, control, or representation of data. A group of such symbols used to describe a particular language make up a character set. A code set contains the encoding values for a character set. It is the encoding values in a code set that provide the interface between the system and its input and output devices.

Historically, the effort was directed at encoding the English alphabet. It was sufficient to use a 7-bit encoding method for this purpose because the number of English characters is not large. To support larger alphabets, such as the Asian languages (for example, Chinese, Japanese, and Korean), additional code sets were developed that contained multibyte encodings.

The following code sets are supported:

As more code sets are supported, it becomes important not to clutter programs with the knowledge of any particular code set. This is known as code set independence . To aid in code set independence, NLS supplies converters that translate character encoding values found in different code sets. Using these converters, a system can accurately process data generated in different code set environments. For more information, see "Converters Overview" .

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