C++ Primer, Fifth Edition

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Part I: The Basics

Contents

Every widely used programming language provides a common set of features, which differ in detail from one language to another. Understanding the details of how a language provides these features is the first step toward understanding the language. Among the most fundamental of these common features are

  • Built-in types such as integers, characters, and so forth
  • Variables, which let us give names to the objects we use
  • Expressions and statements to manipulate values of these types
  • Control structures, such as if or while, that allow us to conditionally or repeatedly execute a set of actions
  • Functions that let us define callable units of computation

Most programming languages supplement these basic features in two ways: They let programmers extend the language by defining their own types, and they provide library routines that define useful functions and types not otherwise built into the language.

In C++, as in most programming languages, the type of an object determines what operations can be performed on it. Whether a particular expression is legal depends on the type of the objects in that expression. Some languages, such as Smalltalk and Python, check types at run time. In contrast, C++ is a statically typed language; type checking is done at compile time. As a consequence, the compiler must know the type of every name used in the program.

C++ provides a set of built-in types, operators to manipulate those types, and a small set of statements for program flow control. These elements form an alphabet from which we can write large, complicated, real-world systems. At this basic level, C++ is a simple language. Its expressive power arises from its support for mechanisms that allow the programmer to define new data structures. Using these facilities, programmers can shape the language to their own purposes without the language designers having to anticipate the programmers’ needs.

Perhaps the most important feature in C++ is the class, which lets programmers define their own types. In C++ such types are sometimes called “class types” to distinguish them from the types that are built into the language. Some languages let programmers define types that specify only what data make up the type. Others, like C++, allow programmers to define types that include operations as well as data. A major design goal of C++ is to let programmers define their own types that are as easy to use as the built-in types. The Standard C++ library uses these features to implement a rich library of class types and associated functions.

The first step in mastering C++—learning the basics of the language and library—is the topic of Part I. Chapter 2 covers the built-in types and looks briefly at the mechanisms for defining our own new types. Chapter 3 introduces two of the most fundamental library types: string and vector. That chapter also covers arrays, which are a lower-level data structure built into C++ and many other languages. Chapters 4 through 6 cover expressions, statements, and functions. This part concludes in Chapter 7, which describes the basics of building our own class types. As we’ll see, defining our own types brings together all that we’ve learned before, because writing a class entails using the facilities covered in Part I.