title: C++ `long long` variable type
body: <p>I am now studying about writing binary files. I've seen this question on StackOverflow. And the author says, in his code </p>
  
  <pre><code>const unsigned long long size = 1ULL*1024ULL*1024ULL;
  </code></pre>
  
  <p>I don't actually know what are the <code>ULL symbols</code>. Could anybody give me some documentation about it? I have searched on Google, and everything I get is more documentation about writing files...</p>