A locale is a collection of language-related, user preference information represented as a list of values. Each system has at least one installed locale and usually has many locales from which the user may choose. Each locale has a unique locale identifier (LCID), a 32-bit value that consists in part of a language identifier. The language identifier is a standard international numeric abbreviation for a country or geographical region.
The system assigns a locale to each thread. Initially, the system assigns the system default locale to the thread. This default locale is set by the user when the system is installed or through the International applet of the Control Panel. If a thread is run in a process belonging to a user, the system assigns the user default locale to the thread. An application can override either default by using the the SetThreadLocale function to explicitly set the locale for a thread.
There are two predefined locale identifiers: LOCALE_SYSTEM_DEFAULT, which identifies the system default locale, and LOCALE_USER_DEFAULT, which identifies the locale of the current user. An application can retrieve the current locale identifiers by using the GetSystemDefaultLCID and GetUserDefaultLCID functions. Similarly, an application can retrieve the current language identifiers by using the GetSystemDefaultLangID and GetUserDefaultLangID functions.
An application can retrieve specific information about any available language or locale. This can be important for handling language- and locale-specific strings. An application can retrieve information about a locale by using the GetLocaleInfo function. Each element of locale information has a unique LCTYPE value that identifies a specific information type. Applications use these values to retrieve the information they need.
All LCTYPE values are mutually-exclusive, so only one type of information can be retrieved at a time. An exception is the LOCALE_NOUSEROVERRIDE which can be used to bypasses user overrides and retrieve the system default values for the requested locale.
Locale information is always stored and manipulated as a null-terminated string. No binary data is allowed; any numeric values must be specified as text. Each type of information has a particular format. Also, several of types are linked together, such that changing one changes the value of the other as well.
Although a given locale identifier may be supported, it is not available for use by an application unless it is also installed.