LOCALE_IDIALINGCODE and LOCALE_ICOUNTRY
Country/region code, based on international phone codes, also referred to as IBM country/region codes. The maximum number of characters allowed for this string is six, including a terminating null character.
Windows 10 added LOCALE_IDIALINGCODE as a more accurately-named synonym for LOCALE_ICOUNTRY. We encourage you to use the new name in order to improve code readability.