# Integer Constants

Integer constants are numbers used directly in a sketch, like `123`

. By default, these numbers are treated as int‘s but you can change this with the U and L modifiers (see below).

Normally, integer constants are treated as base 10 (decimal) integers, but special notation (formatters) may be used to enter numbers in other bases.

Base | Example | Formatter | Comment |

10 (decimal) | 123 | none | |

2 (binary) | B1111011 | leading ‘B’ | only works with 8 bit values (0 to 255) characters 0-1 valid |

8 (octal) | 0173 | leading ‘0’ | characters 0-7 valid |

16 (hexadecimal) | 0x7B | leading “0x” | characters 0-9, A-F, a-f valid |

Decimal is base 10. This is the common-sense math with which you are acquainted. Constants without other prefixes are assumed to be in decimal format.

Example:

`101 // same as 101 decimal ((1 * 10^2) + (0 * 10^1) + 1)`

Binary is base two. Only characters 0 and 1 are valid.

Example:

`B101 // same as 5 decimal ((1 * 2^2) + (0 * 2^1) + 1)`

The binary formatter only works on bytes (8 bits) between 0 (B0) and 255 (B11111111). If it is convenient to input an int (16 bits) in binary form you can do it a two-step procedure such as:

`myInt = (B11001100 * 256) + B10101010; // B11001100 is the high byte`

Octal is base eight. Only characters 0 through 7 are valid. Octal values are indicated by the prefix “0”

Example:

`0101 // same as 65 decimal ((1 * 8^2) + (0 * 8^1) + 1)`

Warning:

It is possible to generate a hard-to-find bug by (unintentionally) including a leading zero before a constant and having the compiler unintentionally interpret your constant as octal.

Hexadecimal (or hex) is base sixteen. Valid characters are 0 through 9 and letters A through F; A has the value 10, B is 11, up to F, which is 15. Hex values are indicated by the prefix “0x”. Note that A-F may be typed in upper or lower case (a-f).

Example:

`0x101 // same as 257 decimal ((1 * 16^2) + (0 * 16^1) + 1)`

### U & L formatters

By default, an integer constant is treated as an int with the attendant limitations in values. To specify an integer constant with another data type, follow it with:

- a
`'u'`

or`'U'`

to force the constant into an unsigned data format. Example:`33u`

- a
`'l'`

or`'L'`

to force the constant into a long data format. Example:`100000L`

- a
`'ul'`

or`'UL'`

to force the constant into an unsigned long constant. Example:`32767ul`

### See also

－ constants

－ #define

－ byte

－ int

－ unsigned int

－ long

－ unsigned long

*The text of the 86Duino reference is a modification of the Arduino reference, and is licensed under a Creative Commons Attribution-ShareAlike 3.0 License. Code samples in the reference are released into the public domain.*