Hi all. I'm new in 3d programming but i've also use "allegro" in c++. I'see there're lot of difference from the 2D game programming,the 3d is more complicated of 2D. So,when i programmed in 2D i created all the code in the same .cpp file,but now,with 3d,i think it's impossible... What i've to do for program a game? Create lot of file .cpp? Ex: -main file; -IA file; -level file; Or exist other ways? Really thanks. Ps:sorry for bad english.

It is always a good idea to split your project into seperate files
even if it is a *simple* 2d game.
It is just a matter of convenience c++ actually allows you to write an entire
program in a single file.
As to how you split them: I guess most people generally create a file for each
class they have.
For starting with 3d I suggest you look here(a bit outdated).

Ok,thanks for the answer