Synopsis
#include <ctype.h>
int toupper(int c);
Description

toupper converts a lowercase letter to a corresponding uppercase letter.

If the argument c is a character for which islower is true, toupper returns the corresponding uppercase letter; otherwise, the argument is returned unchanged.

Portability

toupper conforms to ISO/IEC 9899:1990 (C90) and ISO/IEC 9899:1999 (C99).