There are mainly 2 types of Header files (also called Library files):
iostream.h :- the input(cin) and output(cout) commands are explained in this header file. So it cannot be removed.
conio.h :- the clear screen function[ clrscr()] is included in this header file. So it can be removed as per your requirement.
this is the best of my knowledge about C++. I am still a beginner.