title: Why/when do I need a 'clean' target?
body: <p>Sometimes it seems like not a new executable is built, even though I need one, but I don't understand why. For example, when I change a Makefile, but there is already an executable, and when I execute 'make' it doesn't create an updated executable.</p>
  
  <p>Isn't the whole purpose of Makefiles so that I don't need to worry about that stuff anymore? </p>