I'm afraid you'll need to be a little bit more specific about your problem.
Could you perhaps tell us a little bit more about the problem?
If you want to have multiple .cpp files, you need to compile them together with main.cpp.
Also, you need a .h file containing the definitions of your functions/classes so you can include it in your main.cpp:
I mean when I write the class in a separate file .seprate the interface from the implementation ..the output dosen't appear ..my teacher said that I'm not save it in the same directory and I don't understand what she means