LCID

LCID stands for Locale Identifier, a term used in Microsoft Windows and related technologies to specify a particular locale. A locale in this sense encompasses language, country or region, and a sorting order used for string comparison. LCIDs are used by various Windows APIs to tailor formatting of dates, times, numbers, currencies, and to control locale-specific sorting and resource selection.

Technical basics: an LCID is a 32-bit value. It encodes a language identifier (LANGID) in the low word and a sort order in the high word. The LANGID itself encodes the primary language and sublanguage for the locale. For example, 1033 (0x0409) corresponds to English—United States, while 2057 (0x0809) corresponds to English—United Kingdom. This structure allows applications and system components to refer to a locale with a single numeric identifier.

Usage in software: LCIDs are used by Windows functions such as GetUserDefaultLCID, GetSystemDefaultLCID, GetLocaleInfo, and SetThreadLocale to apply locale-specific behavior. In the .NET framework, the CultureInfo class exposes an LCID value, though many modern APIs prefer using the locale name (for example, "en-US") rather than the numeric identifier. LCIDs remain supported for backward compatibility and legacy code but are considered less robust for new development.

Relation to modern localization: While LCIDs persist for compatibility, contemporary practice favors standardized locale names and IETF language tags. These names are easier to map across platforms and reflect a broader approach to globalization, whereas LCIDs are Windows-centric and tied to older API conventions.