Palindrome Test and frequency

#include <stdio.h>
#include <string.h>

int is_palindrome(int start, int end, char *str)
{
    if (start>=end)
        return 1;
    if (str[start]!= str[end])
        return 0;
    return is_palindrome(++start,--end,str);
 }
 int frequency(int end, char *str, char c)
 {
    int fr=0;
    int i;
    for(i=0;i<end;i++)
        if(str[i]==c)
            fr+=1;
    return fr;
 }
int main()
{
    char str[20],c;
    printf("Enter the String.\n");
    fgets( str, sizeof( str ), stdin );
    if(is_palindrome(0, strlen(str)-2, str))
        printf("It's a palindrome!\n");
    else
        printf("It's not a palindrome! \n");
    printf("Enter the character you want to search for: ");
    scanf("%c",&c);
    printf("The frequency is %d",frequency((strlen(str)-1),str,c));
    return 0;
}
//Output
//Enter the String.
//ABBA
//It's a palindrome!
//Enter the character you want to search for: A
//The frequency is 2