title: boolean expression in do while loop/c++
body: <p>I have a program to write: <em>write a program where user enters numbers until he enters 'e' or 'E'. All number entered by user sum and write on console.</em>
  So far, I write these, but I don't know how to break the loop when 'e' or 'E' is enter!? So, if anyone can help me with this. </p>
  
  <pre><code>#include&lt;iostream&gt;
  using namespace std;
  void main()
  {
      int sum=0, number=0;
  
      do
      {
          cout &lt;&lt; "Enter a number: \n";
          cin &gt;&gt; number;
          sum+=number;
  
      } while (don't know what to type here);
  
      cout &lt;&lt; "Sum =  " &lt;&lt; sum &lt;&lt; endl;
  
  }
  </code></pre>