National Language Support Routines

Developer Guide and Reference

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ID 767251

Date 10/31/2024

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National Language Support Routines

Intel® Fortran provides a complete National Language Support (NLS) library of language-localization routines and multibyte-character routines. You can use these routines to write applications in many different languages.

In many languages, the standard ASCII character set is not enough because it lacks common symbols and punctuation (such as the British pound sign), or because the language uses a non-ASCII script (such as Cyrillic for Russian) or because the language consists of too many characters for each to be represented by a single byte (such as Chinese).

In the case of many non-ASCII languages, such as Arabic and Russian, an extended single-byte character set is sufficient. You need only change the language locale and codepage, which can be done at a system level or within your program. However, Eastern languages such as Japanese and Chinese use thousands of separate characters that cannot be encoded as single-byte characters. Multibyte characters are needed to represent them.

Character sets are stored in tables called code sets. There are three components of a code set: the locale, which is a language and country (since, for instance, the language Spanish may vary among countries), the codepage, which is a table of characters to make up the computer's alphabet, and the font used to represent the characters on the screen. These three components can be set independently. Each computer running Windows operating systems comes with many code sets built into the system, such as English, Arabic, and Spanish. Multibyte code sets, such as Chinese and Japanese, are not standard but come with special versions of the operating system (for instance, Windows NT-J comes with the Japanese code set).

The default code set is obtained from the operating system when a program starts up. When you install your operating system, you should install the system supplied code sets. Thereafter, they are always available. You can switch among them by:

Open the Control Panel (available from Settings)
Click the Regional Settings icon
Choose from the dropdown list of available locales (languages and countries).

When you select a new locale, it becomes the default system locale, and will remain the default locale until you change it. Each locale has a default codepage associated with it, and a default currency, number, and date format.

NOTE:

The default codepage does not change when you select a new locale until you reboot your computer.

You can change the currency, number, and date format in the International dialog box or the Regional Setting dialog box independently of the locale.

The locale determines the character set available to the user. The locale you select becomes the default for the NLS routines described in this section, but the NLS routines allow you to change locales and their parameters from within your programs. These routines are useful for creating original foreign-language programs or different versions of the same program for various international markets. Changes you make to the locale from within a program affect only the program. They do not change the system default settings.

The codepage you select, which can be set independently, controls the multibyte (MB routines) character routines described in this section. Only users with special multibyte-character code sets installed on their computers need to use MB routines. The standard code sets all use single-byte character code sets.

Note that in Intel Fortran source code, multibyte characters can be used only in character strings and source comments. They cannot be used within variable names or statements. Like program changes to the locale, program changes to codepages affect only the program, not the system defaults.

To access the routines, the following statement should be present in any program unit that uses NLS or MB routines:

USE IFNLS

Understand Single and Multibyte Character Sets on Windows

The ASCII character set defines the characters from 0 to 127 and an extended set from 128 to 255. Several alternative single-byte character sets, primarily European, define the characters from 0 to 127 identically to ASCII, but define the characters from 128 to 255 differently. With this extension, 8-bit representation is sufficient for defining the needed characters in most European-derived languages. However, some languages, such as Japanese Kanji, include many more characters than can be represented with a single byte. These languages require multibyte coding.

A multibyte character set consists of both one-byte and two-byte characters. A multibyte-character string can contain a mix of single and double-byte characters. A two-byte character has a lead byte and a trail byte. In a particular multibyte character set, the lead and trail byte values can overlap, and it is then necessary to use the byte's context to determine whether it is a lead or trail byte.

Parent topic: Optimization and Programming

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