title: define and initialize array for stdin, stdout and stderr
body: <p>Below is a copy of some code from the book "The C Programming Language, Second Edition" by K&amp;R. I have no idea how these <code>stdin</code>, <code>stdout</code>, <code>stderr</code> can be defined and initialized as this way. Please help me with an explanation.</p>
  
  <pre><code>FILE _iob[OPEN_MAX] = {
      {0, (char *) 0, (char *) 0, _READ, 0},
      {0, (char *) 0, (char *) 0, _WRITE, 1},
      {0, (char *) 0, (char *) 0, _WRITE | _UNBUF, 2}
  };
  </code></pre>