C Integer Constants
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An "integer constant" is a decimal (base 10), octal (base 8), or hexadecimal (base 16) number that represents an integral value. Use integer constants to represent integer values that cannot be changed.
Syntax
integer-constant:
decimal-constant integer-suffix opt
octal-constant integer-suffix opt
hexadecimal-constant integer-suffix opt
decimal-constant:
nonzero-digit
decimal-constant digit
octal-constant:
0
octal-constant octal-digit
hexadecimal-constant:
0x hexadecimal-digit
0X hexadecimal-digit
hexadecimal-constant hexadecimal-digit
nonzero-digit: one of
1 2 3 4 5 6 7 8 9
octal-digit: one of
0 1 2 3 4 5 6 7
hexadecimal-digit: one of
0 1 2 3 4 5 6 7 8 9
a b c d e f
A B C D E F
integer-suffix:
unsigned-suffix long-suffix opt
long-suffix unsigned-suffix opt
unsigned-suffix: one of
u U
long-suffix: one of
l L
64-bit integer-suffix:
i64
Integer constants are positive unless they are preceded by a minus sign (–). The minus sign is interpreted as the unary arithmetic negation operator. (See Unary Arithmetic Operators for information about this operator.)
If an integer constant begins with 0x or 0X, it is hexadecimal. If it begins with the digit 0, it is octal. Otherwise, it is assumed to be decimal.
The following lines are equivalent:
0x1C /* = Hexadecimal representation for decimal 28 */
034 /* = Octal representation for decimal 28 */
No white-space characters can separate the digits of an integer constant. These examples show valid decimal, octal, and hexadecimal constants.
/* Decimal Constants */
10
132
32179
/* Octal Constants */
012
0204
076663
/* Hexadecimal Constants */
0xa or 0xA
0x84
0x7dB3 or 0X7DB3