title: How to format a number using comma as thousands separator in C?
body: <p>In C, how can I format a large number from e.g. <code>1123456789</code> to <code>1,123,456,789</code>?</p>
  <p>I tried using <code>printf(&quot;%'10d\n&quot;, 1123456789)</code>, but that doesn't work.</p>
  <p>Could you advise anything? The simpler the solution the better.</p>