Chapter 1: Data Types, Variables, and Constants

C and C++ offer the programmer a rich assortment of built-in data types. Programmer-defined data types can be created to fit virtually any need. Variables can be created for any valid data type. Also, it is possible to specify constants of C/C++’s built-in types. In this section, various features relating to data types, variables, and constants are discussed.

The Basic Types

C89 defines the following elemental data types:

Type	Keyword
Character	char
Integer	int
Floating point	float
Double floating point	double
Valueless	void

To these, C99 adds the following:

Type	Keyword
Boolean (true/false)	_Bool
Complex	_Complex
Imaginary	_Imaginary

C++ defines the following basic types:

Type	Keyword
Boolean (true/false)	bool
Character	char
Integer	int
Floating point	float
Double floating point	double
Valueless	void
Wide character	wchar_t

As you can see, all versions of C and C++ provide the following five basic types: char, int, float, double, and void. Also notice that the keyword for the Boolean type is bool in C++ and _Bool in C99. No Boolean type is included in C89.

Several of the basic types can be modified using one or more of these type modifiers:

• signed

• unsigned

• short

• long

The type modifiers precede the type name that they modify. The basic arithmetic types, including modifiers, allowed by C and C++ are shown in the following table along with their guaranteed minimum ranges. Most compilers will exceed the minimums for one or more types. Also, if your computer uses two’s complement arithmetic (as most do), then the smallest negative value that can be stored by a signed integer will be one more than the minimums shown. For example, the range of an int for most computers is –32,768 to 32,767. Whether type char is signed or unsigned is implementation dependent.

Type	Minimum Range
char	–127 to 127 or 0 to 255
unsigned char	0 to 255
signed char	–127 to 127
int	–32,767 to 32,767
unsigned int	0 to 65,535
signed int	same as int
short int	same as int
unsigned short int	0 to 65,535
signed short int	same as short int
long int	–2,147,483,647 to 2,147,483,647
signed long int	same as long int
unsigned long int	0 to 4,294,967,295
long long int	–(263–1) to 263–1 (C99 only)
signed long long int	same as long long int (C99 only)
unsigned long long int	0 to 264–1 (C99 only)
float	6 digits of precision
double	10 digits of precision
long double	10 digits of precision
wchar_t	same as unsigned int

When a type modifier is used by itself, int is assumed. For example, you can specify an unsigned integer by simply using the keyword unsigned. Thus, these declarations are equivalent.

unsigned int i; // here, int is specified unsigned i; // here, int is implied