C++ strings: taking string input, pointer to string, Using OOP

Write a C++ program that prompts the user to enter the string and outputs the length of the characters entered. (Use pointers to calculate the length of the string). 
Source Code:

#include <iostream>

using namespace std;

int main()

{

   char string[1000], *ptr;

   int i=0 ;

      cout << "Enter Any string  : "<<endl;

   cin>>string;

   ptr = string;

   while (*ptr != '\0')

   {

      i++;

      ptr++;

   }

   cout << "Length of String : " << i<<endl;

   return 0;

}
output: