Language and Country/Region Strings
The locale argument to the setlocale function takes the following form:
locale "lang[_country_region[.code_page]]" | ".code_page" | "" | NULL
This appendix lists the language strings and Country/Region strings available to setlocale. All Country/Region and language codes currently supported by the Win32 NLS API are supported by setlocale. For information on code pages, see Code Pages.