In this chapter, you learned that linked lists are collections of data items that are “linked up in a chain.” You also learned that a program can perform insertions and deletions anywhere in a linked list (though our implementation performed insertions and deletions only at the ends of the list). We demonstrated that the stack and queue data structures are constrained versions of lists. For stacks, you saw that insertions and deletions are made only at the top. For queues, you saw that insertions are made at the tail and deletions are made from the head. We also presented the binary tree data structure. You saw a binary search tree that facilitated high-speed searching and sorting of data and efficient duplicate elimination. You learned how to create these data structures for reusability (as templates) and maintainability. In the next chapter, we study various searching and sorting techniques and implement them as function templates.