Depends. What operating system? For MS-Windows, do you want to use pure win32 api functions? If yes, here is a tutorial. But there are a lot easier ways to write gui programs nowdays. Two of them is CLR/C++ Windows Forms, and C# instead of C.
If you are thinking *nix, then look into low-level X11R6 (there are lots of books on that) or Motief. Again, C++ gives you more and easier options, sich as wxWidgets.