### The Default POSIX C Locale

The default POSIX C locale is prebuilt into the runtime library. It conforms to US English conventions.

The POSIX C locale is defined as though it was built with a charmap file with an MB_CUR_MAX value of 2. The codeset name for the nl_langinfo and getsyntx functions is IBM-850.

The following is true of the POSIX C locale:

1. It is the default locale.
2. Issuing setlocale(category, "") has the following effect:
   - Locale-related environment variables are checked to determine which locales to use to set the category specified.
   - If no non-null environment variable is present, then it is the equivalent of having issued setlocale(category, "C"). That is, the locale chosen is the C locale definition, and querying the locale with setlocale(category, NULL) returns "C" as the locale name.

Internationalization

Make Your Program International

Definition of the POSIX C Locale
Locale Categories
Locale-Sensitive Interfaces