Tag Archives: arduino

Arduino Variable Types Explained

Here’s something for reference.
I can never find just quite the succinct reference to Arduino Variable types. Nowhere could i find a list of minimum and maximum values, the bits, and the memory used by each variable type.

Neither was there any clear definition of meaning of ‘unsigned’, which just means no plus or minus signs in this type – that is all numbers positive. This increases the highest number that can be stored in the same memory. (thank me in the comments).

Usage Variable type Bits Min value Max value Ram usage Comments
common boolean 8 TRUE FALSE 1 byte
common byte 8 0 255 1 byte
char 8 -128 127 1 byte  A single ‘character’ e.g. ‘a’ is a single char.  Represented by chr(65) or the binary: 01000001
word 16 0 65535 2 byte
common int 16 -32768 32767 2 byte
unsigned long 32 0 4,294,967,295 4 byte
common long 32 -2,147,483,648 2,147,483,647 4 byte
common float 32 -3.4028235E+38 3.4028235E+38 4 byte
The below types are only included for compatibility or further study.
redundant unsigned char 8 0 255  1 byte use byte instead
redundant unsigned int 16 0 65535  2 bytes use word instead
redundant double 32 -3.4028235E+38  3.4028235E+38  4 bytes use float instead
The below types are special types (see arduino.cc)
special string variable  1 byte + x An array of chars
(used for storing strings to modify)
special enum variable  N/A Like boolean but custom fixed set of values allowed instead of TRUE/FALSE.
special struct variable  N/A Public sub variables
(as if you’d made a public class)
special pointer  N/A I’ll be honest, I wasn’t sure the use of this one. Here for completeness though!
Source: https://learn.sparkfun.com/tutorials/data-types-in-arduino
Source: https://playground.arduino.cc/Code/DatatypePractices
Remark: “Unsigned” means no negative sign. This increases the range of positive numbers available.
Remark: Unsigned variables that exceed their capacity roll over back to zero. This could be useful to iterate through arrays of limited length

PPS If anyone can figure out how to properly format this table so it looks nice, with ‘center’ aligned text, please let me know wordpress was being frustrating!

(The formatting css is in the source, see the table tag)