Integer Types

Integers are numbers with no fractional part, such as 2, 98, –5286, and 0. There are lots of integers, assuming that you consider an infinite number to be a lot, so no finite amount of computer memory can represent all possible integers. Thus, a language can represent only a subset of all integers. Some languages offer just one integer type (one type fits all!), but C++ provides several choices. This gives you the option of choosing the integer type that best meets a program’s particular requirements. This concern with matching type to data presages the designed data types of OOP.

The various C++ integer types differ in the amount of memory they use to hold an integer. A larger block of memory can represent a larger range in integer values. Also some types (signed types) can represent both positive and negative values, whereas others (unsigned types) can’t represent negative values. The usual term for describing the amount of memory used for an integer is width. The more memory a value uses, the wider it is. C++’s basic integer types, in order of increasing width, are char, short, int, long, and, with C++11, long long. Each comes in both signed and unsigned versions. That gives you a choice of ten different integer types! Let’s look at these integer types in more detail. Because the char type has some special properties (it’s most often used to represent characters instead of numbers), this chapter covers the other types first.