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:
- It is the default locale.
- 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