Originally posted here by r4BBiT
I dont know what do Mahdi mean by that, are you thinking about modules or header files?
He means you have to write your own functions for opening a window i.e.. Then you can create 2 libraries with the same functions, 1 for windows and 1 for linux. That way your program can stay the same and it's just a case of recompiling and/or relinking to make it work on either of them.