I moved from DevC++ to Codeblocks and I've come up with this code when I added a header file.

Code:
//Engine.h
#ifndef ENGINE_H_INCLUDED
#define ENGINE_H_INCLUDED
#endif // ENGINE_H_INCLUDED
In DevC++, I'm just including the file by using #include "Engine.h". I searched in google and still I didn't understand it. I have an Engine class in Engine.h and the functions in Engine.cpp. Can anyone explain this to me.