C Integer Constants

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 the letters 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