In this chapter, we saw that an abstract data type or ADT is an abstraction of a data structure. It is a contract that an underlying data structure is supposed to adhere to. The contract involves different operations on the data structure and their specific behavior. We then saw a few simple ADTs as examples. These ADTs are, however, extremely useful as we will see in the course of this book when we encounter other algorithms. Abstraction allows different implementations of the structures. We will also see more ADTs in the course of this book and their implementations.

In the next chapter, we will take a detour into a new area of algorithms called functional programming. Remember that an algorithm is a sequence of steps that may be followed to achieve a desired processing; it turns out that there is another way of looking at it, which we will explore in the next chapter.