title: What is a "callback" in C and how are they implemented?
body: <p>From the reading that I have done, Core Audio relies heavily on callbacks (and C++, but that's another story).  </p>
  
  <p>I understand the concept (sort of) of setting up a function that is called by another function repeatedly to accomplish a task.  I just don't understand how they get set up and how they actually work.  Any examples would be appreciated.</p>