title: Pintos test cases : Why are some written in c and some in ck file extension?
body: <p>In <code>pintos/src/tests/threads</code>, some of the tests are written in c, while some written in perl (ck file), and the other tests have both c and ck files.</p>
  
  <p>two questions :</p>
  
  <ol>
  <li><p>Is .ck extension used for perl scripts? For some reason, I am not getting satisfiable explanation about the .ck extension.</p></li>
  <li><p>Why is some written in c and others written in ck?</p></li>
  </ol>