Locale

The value LC_ALL(0x0) for category names the program’s entire locale
LC_CTYPE(char type) affects the behavior of
the character handling functions and the multibyte and wide character functions.
LC_NUMERIC affects the decimal-point character for the formatted input/output functions and the string conversion functions, as well as the
nonmonetary formatting information returned by the localeconv function

char *setlocale(int category, const char *locale_to_be_set):
A value of "C" for locale_to_be_set specifies the minimal environment for C translation(At program startup, the equivalent of setlocale(LC_ALL, "C"); is executed.).A value of "" specifies the locale-specific native environment.
If a pointer to a string is given for locale and the selection can be honored, the
setlocale function returns a pointer to the string associated with the specified
category for the new locale.