How to do separate compilation

• Break up a C++ program from Object-Oriented perspective. Break up a program into 3 files:
  1. a header file ( "classname.h") -- contains class definition
  2. an implementation file ("classname.cpp") -- contains member function definitions
  3. an application file ("app.cpp") -- contains main

      

• For each file, you need to put necessary lines to make things work.
  1. Header file needs macro guard (by preprocessor directives) which wraps the class definition. They are need to avoid duplicate definition.

     // filename: myclass.h
     
     // macro guard
     #ifndef MYCLASS_H
     #define MYCLASS_H
     
     class MyClass
     {
        ...
     };
     
     #endif     // end of macro guard

  2. Implementation file needs to #include the header file. For user defined header file, you enclose it by " ".

     // filename: myclass.cpp
     
     #include "myclass.h"        // include header file
     
     MyClass::MyClass()
     { ... }

  3. Application file must #include the header file(s) of the class(s).

     // filename: app1.cpp
     
     #include <iostream>
     using namespace std;
     
     #include "myclass.h"        // include header file
     
     int main()
     {
        ...
        return 0;
     }

• Separate compilation -- Instruction is here.