Arduino – Variables and Datatypes

Table of Contents

Arduino Variables

In programming, values that are stored for further processing are named with a single word called a variable. The value of a variable can change continuously or be changed by the program. The variable name should be chosen in such a way that it is easily readable and understandable within the program. In addition, a variable also has a data type that defines the value range.

The Variable must be declared before being used. So the data type, the variable name and the value of the variable are set. If no value is specified, the variable value is set to 0.

datatype Variable_Name = Value;

Example:

int motorSpeed = 255;

Comprehensible variable names such as motorSpeed or temperatureSensor improve the readability of the program

Arduino Datatypes

A data type describes the value range and the possible operations of a variable. Since the data types of the variables require different amounts of memory, you must be aware of exactly which possible values a variable defined can have when creating the program: Is it only a digital state with the values yes and no or can the variable hold an entire text? The data type must be selected accordingly. The most important data types and their value ranges for creating Arduino programs are listed below:

Data type	Value range	Memory requirement	Explanations/Notes	Examples
boolean	true/false	1 byte	Value for Yes/No or On/Off,	boolean machineStatus = true;
int	-32,768 to 32,767	2 bytes	Integer values for values without decimal places	int potiValue = 1023;
unsigned int	0 to 4,294,967,295	2 bytes	Integer for positive values without decimal places	int tempValue = -5;
byte	0 to 255	1 byte	Low values (and correspondingly small memory requirements)	byte brightnessLED = 126;
word	Unsigned 16-bit or 32-bit	16-bit on Atmega boards. 32-bit on Due and Zero	Be aware of processor used	word value = 1500;
long	-2,147,483,648 to 2,147,483,647	4 bytes	Integer numbers with big values	long offset = -15362;
unsigned long	0 to 4,294,967,295	4 bytes	Unsigned Integer numbers with big values	unsigned long secondsPassed = 45379;
float	-3.4028235E+38 to 3.4028235E+38	4 bytes	Values with decimal places	float voltageValue = 3.3;
double	-3.4028235E+38 to 3.4028235E+38	4 bytes	-3.4028235E+38 to 3.4028235E+38	double distanceGPS= 722.54;
char	-128 to 127	1 byte	Value for storing one character	char charR = ‘R’;
unsigned char	0 to 255	1 byte	Usually used with numbers having range 0 to 255	unsigned char charNumber = 255;
string	length depends on definition	depends on need	Strings like texts or several characters	string brand[ ] = “ROBOSANS”;
array	size depends to definition	Depends on array size	store values in variables with table form like e.g. lists of ports or configuration values	int portsPWM[ ] = {3,5,6,9,10,11};

Arduino Datatypes