title: Input function & Symbol?
body: <p>My friend showed me this code, he asked me what is the &amp; sign in the input parameter?</p>
  
  <pre><code>#include&lt;iostream&gt;
  using namespace std;
  
  void f(int &amp; i, int j) {
  i++;
  j++;
  }
  int main() {
  int i=1, j=2;
  f(i, j);
  cout &lt;&lt; ( i + j );
  system ("pause");
  return 0;
  }
  </code></pre>
  
  <p>p.s What is the &amp; sign?</p>