title: Why do we pass 0 as a parameter to "exit"?
body: <p>In the book <em>learn ruby the hard way</em>, I found a syntax to exit from the program:</p>
  
  <pre><code>Process.exit(0)
  </code></pre>
  
  <p>Why is the parameter <code>0</code> being passed in the <code>exit</code> method here even though it works if I pass another integer or do not pass any parameter? What is the significance of <code>0</code>?</p>