For compiling the source code you must follow these steps:
1) change directory and enter in lib:
   cd tutorial/lib
2) run make without parameters:
   make
3) in this way you have created the lib file "liboglprog.a"
4) now you can go in "exercises" or "examples/lectureXX":
   cd ../exercises
   or cd ../examples/lectureXX
5) Run make with file name as parameter (without extension .c), for example:
   make clearcolor
6) In theory, now there should be an executable file with the same
   name of the source file but without .c and you can run it.
   For example:
   ./clearcolor