Constants And Internal Representation

ANSI C acknowledges that the size and numeric range of the basic data types (and their various permutations) are implementation-specific and usually derive from the architecture of the host computer. For CodeGear C++, the target platform is the IBM PC family (and compatibles), so the architecture of the Intel 80x86 and the Pentium family of microprocessors governs the choices of internal representations for the various data types.

The following tables list the sizes and resulting ranges of the data types. Internal representation of numerical types shows how these types are represented internally.

32-bit data types, sizes, and ranges

Type	Size (bits)	Range	Sample applications

unsigned char	8	0 <= X <= 255	Small numbers and full PC character set
char	8	-128 <= X <= 127	Very small numbers and ASCII characters
short int	16	-32,768 <= X <= 32,767	Counting, small numbers, loop control
unsigned int	32	0 <= X <= 4,294,967,295	Large numbers and loops
int	32	-2,147,483,648 <= X <= 2,147,483,647	Counting, small numbers, loop control
unsigned long	32	0 <= X <= 4,294,967,295	Astronomical distances
enum	32	-2,147,483,648 <= X <= 2,147,483,647	Ordered sets of values
long	32	-2,147,483,648 <= X <= 2,147,483,647	Large numbers, populations
float	32	1.18 ( 10^-38 < \|X\| < 3.40 ( 10^38	Scientific (7-digit) precision)
double	64	2.23 ( 10^-308 < \|X\| < 1.79 ( 10^308	Scientific (15-digit precision)
long double	80	3.37 ( 10^-4932 < \|X\| < 1.18 ( 10^4932	Financial (18-digit precision)