7.4.1.11 The isupper functionļ
Synopsis
#include <ctype.h>
int isupper(int c);
Description
The isupper function tests for any character that is an uppercase letter or is one of a locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or isspace is true. In the āCā locale, isupper returns true only for the uppercase letters (as defined in 5.2.1).