title: How does this program duplicate itself?
body: <p>This code is from Hacker's Delight. It says this is the shortest such program in C and is 64 characters in length, but I don't understand it:</p>
  
  <pre><code>    main(a){printf(a,34,a="main(a){printf(a,34,a=%c%s%c,34);}",34);}
  </code></pre>
  
  <p>I tried to compile it. It compiles with 3 warnings and no error.</p>