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arduino:constants:integerconstants [2013/02/15 20:45] (current)
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 +======Integer Constants   ======
 +
 +Integer constants are numbers used directly in a sketch, like //123//.  By default, these numbers are treated as [[arduino:data_types:int|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.  
 +
 +
 +<code arduino>
 +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    
 +</code>
 +
 +
 +**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:<code arduino>
 +101     // same as 101 decimal   ((1 * 10^2) + (0 * 10^1) + 1)
 +</code>
 +\\
 +
 +**Binary** is base two.  Only characters 0 and 1 are valid. 
 +
 +Example:<code arduino>
 +B101    // same as 5 decimal   ((1 * 2^2) + (0 * 2^1) + 1)
 +</code>
 +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:
 +
 +<code arduino>
 +myInt = (B11001100 * 256) + B10101010;    // B11001100 is the high byte
 +</code>
 +
 +
 +**Octal** is base eight.  Only characters 0 through 7 are valid. Octal values are indicated by the prefix "0"
 +
 +Example:
 +<code arduino>
 +0101    // same as 65 decimal   ((1 * 8^2) + (0 * 8^1) + 1) </code>
 +->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:
 +<code arduino>
 +0x101   // same as 257 decimal   ((1 * 16^2) + (0 * 16^1) + 1)
 +</code>
 +
 +
 +
 +==== U & L formatters   ====
 +
 +By default, an integer constant is treated as an [[arduino:data_types:int|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   ====
 +* [[arduino:constants:Constants]]
 +* [[arduino:further_syntax:define|#define]]
 +* [[arduino:data_types:byte|byte]]
 +* [[arduino:data_types:int|int]]
 +* [[arduino:data_types:unsignedint| unsigned int]]
 +* [[arduino:data_types:long|long]]
 +* [[UnsignedLong | unsigned long]]
 +
 +
 +Source: arduino.cc
  
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arduino/constants/integerconstants.txt · Last modified: 2013/02/15 20:45 (external edit)

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