731: Mainline

To design the header and link classes, you need to answer the following questions:

• What member variables do you need for the pointers involved?
• What member functions do you need to create lists, to add new list elements, and to access existing elements?
• Which member variables and member functions should be private, which should be protected, and which should be public?

For the moment, you can defer the private–protected–public question by making all member variables and member functions public. Later, with all the answers to the other questions behind you, you can make the adjustments that sensibly allocate the member variables and member functions to the appropriate portions of the class definitions.