In order to protect a library's interface file from being included multiple times, we always put in three special preprocessor directives. Show a skeleton/template of what this looks like here.
What is the symbol/name being defined here? (I.E. What does it represent in this process of precluding multiple header file inclusion? How do you come up with it s there a simple pattern we can follow? Make sure I know what it is in the context of your sample above.)