toupper()

#include <ctype.h>
int toupper(int ch);

tolower() converts any lower-case character in the range from a to z into an upper-case character from A to Z.

If ch is a lower-case character, the corresponding upper-case letter. Otherwise, ch is returned (unchanged).

isalnum(), isalpha(), iscntrl(), isdigit(), isgraph(), islower(), isprint(), ispunct(), isspace(), isupper(), and isxdigit(),

tolower()