C Pocket Reference

Integer Constants

Integer constants can be represented as ordinary decimal numbers, octal numbers, or hexadecimal numbers:

• A decimal constant (base 10) begins with a digit that is not 0; for example: 1024

• An octal constant (base 8) begins with a 0; for example: 012

• A hexadecimal constant (base 16) begins with the two characters 0x or 0X; for example: 0x7f, 0X7f, 0x7F, 0X7F. The hexadecimal digits A to F are not case-sensitive.

The type of an integer constant, if not explicitly specified, is the first type in the appropriate hierarchy that can represent its value.

For decimal constants, the hierarchy of types is:

int, long, unsigned long, long long(*).

For octal or hexadecimal constants, the hierarchy of types is:

int, unsigned int, long, unsigned long, long long(*), 
unsigned long long(*).

Thus, integer constants normally have type int. The type can also be explicitly specified by one of the suffixes L or l (for long), LL ^(*) or ll ^(*) (for long long ^(*)), and/or U or u (for unsigned). Table 1-6 provides some examples.

Table 1-6. Examples of integer constants

Decimal	Octal	Hexadecimal	Type
15	017	0xf	int
32767	077777	0x7FFF	int
10U	012U	0xAU	unsigned int
32768U	0100000U	0x8000u	unsigned int
16L	020L	0x10L	long
27UL	033ul	0x1BUL	unsigned long

The macros in Table 1-7 are defined to represent constants of an integer type with a given maximum or minimum width N (e. g., = 8, 16, 32, 64). Each of these macros takes a constant integer as its argument and is replaced ...