Chapter 2. Variables and Basic Types

CONTENTS

Section 2.1 Primitive Built-in Types	34
Section 2.2 Literal Constants	37
Section 2.3 Variables	43
Section 2.4 const Qualifier	56
Section 2.5 References	58
Section 2.6 Typedef Names	61
Section 2.7 Enumerations	62
Section 2.8 Class Types	63
Section 2.9 Writing Our Own Header Files	67
Chapter Summary	73
Defined Terms	73

Types are fundamental to any program. They tell us what our data mean and what operations we can perform on our data.

C++ defines several primitive types: characters, integers, floating-point numbers, and so on. The language also provides mechanisms that let us define our own data types. The library uses these mechanisms to define more complex types such as variable-length character strings, vectors, and so on. Finally, we can modify existing types to form compound types. This chapter covers the built-in types and begins our coverage of how C++ supports more complicated types.

Types determine what the data and operations in our programs mean. As we saw in Chapter 1, the same statement

      i =i +j; 

can mean different things depending on the types of i and j. If i and j are integers, then this statement has the ordinary, arithmetic meaning of +. However, if i and j are Sales_item objects, then this statement adds the components of these two objects.

In C++ the support for types is extensive: The language itself defines a set of primitive types and ways in which we can modify existing types. It also provides a set of features that allow us to define our own types. This chapter begins our exploration of types in C++ by covering the built-in types and showing how we associate a type with an object. It also introduces ways we can both modify types and can build our own types.