IPhone : Universal iOS app file managing

I have written universal app and am not sure about code/file management. For example, I use file A (.h and .m) on iPhone app and file B (.h and .m) on iPad. If I export IPA file, I think both file A and file B will be there for both iPhone and iPad. Can I manage to exclude file A for iPad? It is also same for images. I have some images that is only used in iPhone. How can I exclude that?