Converts a lowercase character to uppercase.
#include <ctype.h> int _toupper (int character);
The _toupper macro is equivalent to the toupper function except that its argument must be a lowercase letter (not uppercase, not EOF).
The _toupper macro should not be used with arguments that contain side-effect operations. For instance, the following example will not return the expected result:
d = _toupper (c++);
| x | The uppercase letter corresponding to the argument. |