Should every C or C++ file have an associated header file?

Question

Should every .C or .cpp file should have a header (.h) file for it?

Suppose there are following C files :

1. Main.C

2. Func1.C

3. <

Answer 1

I like putting interfaces into header files and implementation in cpp files. I don't like writing C++ where I need to add member variables and prototypes to the header and then the method again in the C++. I prefer something like:

module.h

struct IModuleInterface : public IUnknown
{
    virtual void SomeMethod () = 0;
}

module.cpp

class ModuleImpl : public IModuleInterface,
                   public CObject // a common object to do the reference
                                              // counting stuff for IUnknown (so we
                                              // can stick this object in a smart 
                                              // pointer).
{
    ModuleImpl () : m_MemberVariable (0)
    {
    }

    int m_MemberVariable;

    void SomeInternalMethod ()
    {
        // some internal code that doesn't need to be in the interface
    }

    void SomeMethod ()
    {
        // implementation for the method in the interface
    }

    // whatever else we need
};

I find this is a really clean way of separating implementation and interface.