.. _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>`_