Palindrome in C

https://www.testdome.com/questions/c/palindrome/7285?visibility=1&skillId=11

A palindrome is a word that reads the same backward or forward.

Write a function that checks if a given word is a palindrome. Character case should be ignored. If the given word is a palindrome, the function should return 1; otherwise it should return 0.

For example, is_palindrome("Deleveled") should return 1 as character case should be ignored resulting with "deleveled" which is a palindrome since it reads same backward and forward.

I tried below code, it is working fine. But i am confused how can i handle character case. Please help.

#include <stdlib.h>
#include <stdio.h>

int is_palindrome(char *str)
{
    int l = 0;
    int h = strlen(str) - 1;

    while (h > l)
    {
        if (str[l++] != str[h--])
        {
            return 1;
        }
    }
    exit(0);
}

#ifndef RunTests
int main()
{
    char *str = "Deleveled";
    printf("%d", is_palindrome(str));
}
#endif