C++ header files and classes

I have a class Stack with a header file Stack.h which uses up another class with a header file Activity.h

I have a third class ActivityManager which uses up both the Stack and the Activity class.If I run the program and add in both Activity.h and Stack.h to the #include list I get a compilation error:Activity.h is defined 2 times in the script.How do I solve this issue?

You can use the pragma once idiom or some of the other methods shown on that page.

From a C standpoint, I would use #ifndef <Some variable defined in the header you are trying to include>.