c language check if the given string is a palindrome

// Example: check if string is a palindrome using c language

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#include <stdbool.h>

int main(int argc, char *argv[]) {
    char string1[20];
    int i, length;
    int flag = 0;

    printf("Enter a string:");
    scanf("%s", string1);

    length = strlen(string1);

    for(i=0;i < length ;i++){
        if(string1[i] != string1[length-i-1]){
            flag = 1;
            break;
       }
    }

    if (flag) {
        printf("%s is not a palindrome", string1);
    }
    else {
        printf("%s is a palindrome", string1);
    }
    return 0;
}