title: Recursive algorithm to calculate square root
body: <p>I have a code that calculates the square root of a number the following way:</p>
  
  <pre><code>void f1(int,int);
  
  int main(){
      int i=1;
      int n;
      scanf("%d",&amp;n);
      f1(n,i);
      getch();
      return 0;
  }
  
  void f1(int n,int i){
      if((n*10000)-(i*i)&lt;=0)
          printf("%f",(double)i/100);
      else
          f1(n,i+1);
  }
  </code></pre>
  
  <p>I don't know why using <code>n*10000 - i*i</code>. Can someone explain this code please?</p>