# 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-suffixopt
octal-constant integer-suffixopt

decimal-constant:
nonzero-digit
decimal-constant digit

octal-constant:
0
octal-constant octal-digit

0x 0X

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

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-suffixopt
unsigned-suffix long-long-suffix
unsigned-suffix 64-bit-integer-suffix
long-suffix unsigned-suffixopt
long-long-suffix unsigned-suffixopt
64-bit-integer-suffix

unsigned-suffix: one of
u U

long-suffix: one of
l L

long-long-suffix: one of
ll LL

64-bit-integer-suffix: one of
i64 I64

The i64 and I64 suffixes are Microsoft-specific.

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 integer constants are equivalent:

``````28
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 some valid decimal, octal, and hexadecimal constants.

``````    /* Decimal Constants */
int                 dec_int    = 28;
unsigned            dec_uint   = 4000000024u;
long                dec_long   = 2000000022l;
unsigned long       dec_ulong  = 4000000000ul;
long long           dec_llong  = 9000000000LL;
unsigned long long  dec_ullong = 900000000001ull;
__int64             dec_i64    = 9000000000002I64;
unsigned __int64    dec_ui64   = 90000000000004ui64;

/* Octal Constants */
int                 oct_int    = 024;
unsigned            oct_uint   = 04000000024u;
long                oct_long   = 02000000022l;
unsigned long       oct_ulong  = 04000000000UL;
long long           oct_llong  = 044000000000000ll;
unsigned long long  oct_ullong = 044400000000000001Ull;
__int64             oct_i64    = 04444000000000000002i64;
unsigned __int64    oct_ui64   = 04444000000000000004uI64;