title: Interesting project to learn C?
body: <p>I have some basic knowledge of C (and a bit more of C++). I got a copy of K&amp;R, and I want to use it to help me dig deeper into the language. What is a good idea that will involve using most of C's features and standard library? Also, what important differences between C89 and C99 should I be aware of?</p>
  
  <p><b>EDIT:</b> Forgot to mention, this should be mostly doable for a beginner. I'm not asking for a programming tutorial; rather, something mid-scale. I understand that OS stuff is one of C's main purposes, but wouldn't that be too complicated?</p>
  
  <p>Also, reading and answering questions is always a good idea, but I want to get some actual practice, make a program that will do stuff.</p>