title: Implementation of ceil() and floor()
body: <p>Just curious how are these implemented. I can't see where I would start. Do they work directly on the <code>float</code>'s/<code>double</code>'s bits?</p>
  
  <p>Also where can I find the source code of functions from math.h? All I find are either headers with prototypes or files with functions that call other functions from somewhere else.</p>
  
  <p><strong>EDIT</strong>: Part of the message was lost after editing the title. What I meant in particular were the <code>ceil()</code> and <code>floor()</code> functions. </p>