title: Why does isdigit() return 2048 if true?
body: <p>Can anybody explain why does <code>isdigit</code> return <code>2048</code> if true? I am new to <code>ctype.h</code> library.</p>
  
  <pre><code>#include &lt;stdio.h&gt;
  #include &lt;ctype.h&gt;
  int main() {
    char c = '9';
    printf ("%d", isdigit(c));
    return 0;
  }
  </code></pre>