 # 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

```
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.
```101     // same as 101 decimal   ((1 * 10^2) + (0 * 10^1) + 1)
```
Binary is base two. Only characters 0 and 1 are valid.
```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"
```

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).
```

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