title: "if " and " #if "; which one is better to use
body: <p>I learned that <code>if</code> or <code>#if</code> can both be used for condition checks.
  As we can check conditions using <code>if</code>, why would we use preprocessor <code>#if</code>?</p>
  
  <p>What difference will it make to my code if I use <code>#if</code> instead of <code>if</code>?</p>
  
  <p>Which one is better to use and why?</p>