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.. _arduino-integerconstants:
Integer Constants
=================
Integer constants are numbers used directly in a sketch, like
``123``. By default, these numbers are treated as
`int <http://arduino.cc/en/Reference/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 syted 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 <http://arduino.cc/en/Reference/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 <http://arduino.cc/en/Reference/Constants>`_
- `#define <http://arduino.cc/en/Reference/Define>`_
- `byte <http://arduino.cc/en/Reference/Byte>`_
- `int <http://arduino.cc/en/Reference/Int>`_
- `unsigned int <http://arduino.cc/en/Reference/UnsignedInt>`_
- `long <http://arduino.cc/en/Reference/Long>`_
- `unsigned long <http://arduino.cc/en/Reference/UnsignedLong>`_
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