Check Given String is Palindrome or not in C++

This code is very simple and easy to write and run. To write this program first get input from use and revers this number, in next step compare output with original number, if both are same it means input number by user is palindrome otherwise not palindrome number. Check Given String is Palindrome or not in C++

#include <iostream>
using namespace std;
int main(){
char string1[20];
int i, length;
int flag = 0;

cout << "Enter a string: "; cin >> string1;

length = strlen(string1);

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

if (flag) {
cout << string1 << " is not a palindrome" << endl;
}
else {
cout << string1 << " is a palindrome" << endl;
}
system("pause");
return 0;
}