title: Why is my string of type `bytes`?
body: <p>According to <em>Real World OCaml</em>, the type of <code>"abc"</code> should be <code>string</code>. But actually in my <code>utop</code> REPL, it's of type <code>bytes</code>.</p>
  
  <p>I've already opened <code>Core.Std</code>. Why is that?</p>
  
  <p>(The version of <code>OCaml</code> is <code>4.02.2</code>; <code>Core</code> is <code>112.24.01</code>; <code>utop</code> is <code>1.18</code>.)</p>