Arduino Data Types – Tutorial & Examples
In Arduino programming, variables are containers for storing data. Each variable has a data type
that defines the kind of values it can hold, such as numbers, text, or true/false values. Below are the
most common Arduino data types, with declaration examples and usage.
1. Data Types with Declarations & Usage
int - Used for integer numbers. Declaration: int counter; Example: int counter = 100;
unsigned int - Same as int but only positive numbers. Declaration: unsigned int distance;
Example: unsigned int distance = 50000; long - Stores very large integers. Declaration:
long population; Example: long population = 7000000L; float - Stores decimal
numbers. Declaration: float voltage; Example: float voltage = 3.75; double - Double
precision floating point. On Uno, same as float. Declaration: double pi; Example: double pi =
3.141592; char - Stores a single character (ASCII). Declaration: char letter; Example: char
letter = 'A'; byte - Stores numbers from 0 to 255. Declaration: byte value; Example: byte
value = 200; boolean - Stores true or false. Declaration: boolean ledState; Example:
boolean ledState = true; String - Stores text. Declaration: String name; Example:
String name = "Arduino";
2. Example Codes
// Integer and Boolean Example
int counter = 0;
boolean ledOn = true;
void setup() {
Serial.begin(9600);
}
void loop() {
counter++;
Serial.print("Counter: ");
Serial.println(counter);
if (ledOn) {
Serial.println("LED is ON");
} else {
Serial.println("LED is OFF");
}
delay(1000);
}
// Float Example
float voltage = 5.0;
float resistance = 220.0;
float current;
void setup() {
Serial.begin(9600);
}
void loop() {
current = voltage / resistance;
Serial.print("Current: ");
Serial.println(current);
delay(2000);
}
3. Arrays & Their Use
An array is a collection of variables of the same data type stored under one name. Arrays are
useful when you want to store multiple values, like sensor readings or pin numbers. Declaration:
int numbers[5]; Initialization: int numbers[5] = {10, 20, 30, 40, 50}; You can
access elements using their index (starting from 0).
// Array Example
int numbers[5] = {10, 20, 30, 40, 50};
void setup() {
Serial.begin(9600);
}
void loop() {
for (int i = 0; i < 5; i++) {
Serial.print("Value at index ");
Serial.print(i);
Serial.print(" = ");
Serial.println(numbers[i]);
}
delay(2000);
}
4. Quick Reference – Data Types Summary
Type Size (Bytes) Range Example
int 2 -32,768 to 32,767 int x = 25;
unsigned int 2 0 to 65,535 unsigned int u = 40000;
long 4 -2,147,483,648 to 2,147,483,647 long big = 100000L;
float 4 ±3.4028235E+38 float pi = 3.14;
double 4 (Uno) Same as float (Uno) double val = 2.71828;
char 1 -128 to 127 / ASCII char c = 'B';
byte 1 0 to 255 byte b = 200;
boolean 1 true/false boolean flag = true;
String varies text String s = "Hello";
