C program to find whether a string is palindrome without using inbuilt functions

PROGRAM:

#include<stdio.h>
int length(char[]);
void palindrome(char []);
int main()
{
    char str[50];
    printf("Enter a string\n");
    scanf("%s",str);
    palindrome(str);
    return 0;
}
void palindrome(char s1[])
{
    char s2[50];
    int i=0;
//Reversing the entered string
    while(s1[i]!='\0')
    {
        s2[length(s1)-1-i]=s1[i];
        i++;
    }
    s2[i]='\0';
//Comparing entered string with reversed string
    i=0;
    while(s1[i]!='\0')
    {
        if(s2[i]!=s1[i])
        {
            printf("Entered string %s is not a palindrome\n",s1);
            exit(0);
        }
        else
            i++;
    }
    printf("Entered string %s is a palindrome\n",s1);
}

//to find the length of entered string
int length(char str[])
{
    int i=0,count=0;
    while(str[i]!='\0')
    {
        ++i;
        ++count;
    }
    return count;
}

OUTPUT:

Enter a string
MADAM
Entered string MADAM is a palindrome