C toupper() function

C toupper(int c)

The toupper() function is used to translate lowercase characters to uppercase characters. The function is defined in the ctype.h header file.


int toupper(int ch);

toupper() Parameters:

Name Description Required /Optional
ch Argument ch represents a lowercase letter. Required

Return value from toupper()

  • Upon successful completion, toupper() returns the uppercase letter corresponding to the argument passed; otherwise returns the argument unchanged.

Example: C toupper() function

#include <stdio.h>
#include <ctype.h>
int main() {
    char ch;
     printf("Convert lower case to upper case:\n");
    ch = 'M';
    printf("%c -> %c", ch, toupper(ch));

    ch = 'k';
    printf("\n%c -> %c", ch, toupper(ch));
    ch = 'y';
    printf("\n%c -> %c", ch, toupper(ch));
    ch = 'w';
    printf("\n%c -> %c", ch, toupper(ch));
    return 0;


Convert lower case to upper case:
M -> M
k -> K
y -> Y
w -> W

C Programming Code Editor:

Contribute your code and comments through Disqus.

Previous C Programming: C tolower()

Follow us on Facebook and Twitter for latest update.

C Programming: Tips of the Day

What is the static function in C ?

Making a function static hides it from other translation units, which helps provide encapsulation.


int f1(int);        /* prototype */
static int f2(int); /* prototype */

int f1(int foo) {
    return f2(foo); /* ok, f2 is in the same translation unit */
                    /* (basically same .c file) as f1         */

int f2(int foo) {
    return 42 + foo;


int f1(int); /* prototype */
int f2(int); /* prototype */

int main(void) {
    f1(10); /* ok, f1 is visible to the linker */
    f2(12); /* nope, f2 is not visible to the linker */
    return 0;

Ref : https://bit.ly/3CI9ebJ

We are closing our Disqus commenting system for some maintenanace issues. You may write to us at reach[at]yahoo[dot]com or visit us at Facebook