C++ doesn't have any standard graphic libraries. You can though use SFML, SDl , OpenGl , Directx , ect...I would suggest SFML though it has good documentations and is fairly simple(if you know basics of c++).
Also AFAIK graphics.h was a really old library from borland and is a c library I could be wrong though.
i use borland turbo c++ 5.02 and whenever i try to use graphics.h, it says that it is not supported on windows platform and moreover mine version of turbo c++ is not compatible w/ dosbox.
i think it was used back with dos.h but i could be wrong. i would use one of the libs glib mentioned and in addition there is alos qt, allegro, and the win32 api (which only use if you dont want to go cross platform)