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Elementary Data Structures

In all the earlier chapters, we have used data structures along with our examples. While
you should therefore be somewhat familiar with them, they need to be systematically
studied. There are endless alternatives to the ways that data are stored, and so there is a
potential for disorder. Before you get into a crisis due to the general disarray of your data
and then convince yourself of the need for data structures, we want you to have the tools
needed to handle that crisis. In this chapter, we systematically cover the data structures
that are most useful in microcomputer systems.
The first section discusses what a data structure is in more detail. Indexable
structures, including the frequently used vector, are discussed in the second section. The
third section discusses sequential structures, which include the string and the stack
structures. The linked list is briefly discussed next, only to give you an idea of what it
is, while the conclusions summarize the chapter with recommendations for further
reading on data structures.
At the end of this chapter, you should be able to use simple data structures, such as
vectors and strings, with ease. You should be able to handle deques and their derivatives,
stacks and queues, and you should know a linked list structure when you see one. This
chapter should provide you with the tools that you need to handle most of the problems
that cause confusion when storing data in your microcomputer programs.

10.1 What a Data Structure Is

In previous chapters, we described a data structure as the way data are stored in memory.
While this description was adequate for those earlier discussions, we now want to be
more precise. A data structure is more or less the way data are stored and accessed. This
section expands on this definition.
A data structure is an abstract idea that is used as a reference for storing data. It is
like a template for a drawing. For example, a vector is a data structure that we have used
since Chapter 3. Several sets of data can be stored in a vector in the same program and
the same "template" is used to store each set. You may write or see a program that uses
vectors that have five 1-byte elements. While writing another program, you may
recognize the need for a vector that has five 1-byte elements and, by using the same

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