title: Difference between return values NULL and zero
body: <p>What is the difference between <code>return NULL</code> and <code>return 0</code> in C? </p>
  
  <p>Yes, I know that <code>0</code> is a number and <code>NULL</code> is a void. But I don't understand the purpose of the two in context of programming. </p>
  
  <p>Also I believe <code>return 0</code> doesn't return the number <code>0</code> to calling function, but returns <code>void</code>. So what difference would it make if the statements <code>return NULL</code> and <code>return 0</code> are interchanged?</p>