toupper - convert a char to uppercase
toupper, tolower, toupper_l, tolower_l - convert uppercase or lowercase
#include <ctype.h>
int toupper(char c);
Think of this function as taking a char as input.
#include <ctype.h>
int toupper(int c);
int tolower(int c);
int toupper_l(int c, locale_t locale);
int tolower_l(int c, locale_t locale);Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
This function converts c to uppercase.
These functions convert lowercase letters to uppercase, and vice versa.
If c is a lowercase letter, toupper()
returns its uppercase equivalent, if an uppercase representation exists
in the current locale. Otherwise, it returns c. The
toupper_l() function performs the same task, but uses
the locale referred to by the locale handle locale.
If c is an uppercase letter, tolower()
returns its lowercase equivalent, if a lowercase representation exists
in the current locale. Otherwise, it returns c. The
tolower_l() function performs the same task, but uses
the locale referred to by the locale handle locale.
If c is neither an unsigned char value nor
EOF, the behavior of these functions is undefined.
The behavior of toupper_l() and
tolower_l() is undefined if locale is the
special locale object LC_GLOBAL_LOCALE (see
duplocale(3)) or is not a valid locale object
handle.
If c is a lowercase letter (a through z), this function returns its uppercase equivalent (A through Z). If c is not a lowercase letter, this function returns c itself.
The value returned is that of the converted letter, or c if
the conversion was not possible.
#include <cs50.h>
#include <ctype.h>
#include <stdio.h>
int main(void)
{
char c = get_char("Input: ");
printf("Output: %c\n", toupper(c));
}