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# Language Reference

See the extended reference for more advanced features of the Arduino languages and the libraries page for interfacing with particular types of hardware.

Arduino programs can be divided in three main parts: structure, values (variables and constants), and functions. The Arduino language is based on C/C++.

## Structure

An Arduino program run in two parts:

- void setup()
- void loop()

setup() is preparation, and loop() is execution. In the setup section, always at the top of your program, you would set pinModes, initialize serial communication, etc. The loop section is the code to be executed -- reading inputs, triggering outputs, etc.

- Variable Declaration
- Function Declaration
  - void

#### Control Structures

- if
- if...else
- for
- switch case
- while
- do... while
- break
- continue
- return

#### Further Syntax

- ; (semicolon)
- {} (curly braces)
- // (single line comment)
- /* */ (multi-line comment)

#### Arithmetic Operators

- = (assignment operator)
- + (addition)
- - (subtraction)
- * (multiplication)
- / (division)
- % (modulo)

#### Comparison Operators

- == (equal to)
- != (not equal to)
- < (less than)
- > (greater than)
- <= (less than or equal to)
- >= (greater than or equal to)

#### Boolean Operators

- && (and)
- || (or)
- ! (not)

#### Compound Operators

- ++ (increment)
- -- (decrement)
- += (compound addition)
- -= (compound subtraction)
- *= (compound multiplication)
- /= (compound division)

## Variables

Variables are expressions that you can use in programs to store values, such as a sensor reading from an analog pin.

#### Constants

Constants are particular values with specific meanings.

- HIGH | LOW
- INPUT | OUTPUT
- true | false

- Integer Constants

#### Data Types

Variables can have various types, which are described below.

- boolean
- char
- byte
- int
- unsigned int
- long
- unsigned long
- float
- double
- string
- array

## Reference

- ASCII chart

## Functions

Digital I/O

- pinMode(pin, mode)
- digitalWrite(pin, value)
- int digitalRead(pin)

Analog I/O

- int analogRead(pin)
- analogWrite(pin, value) - PWM

Advanced I/O

- shiftOut(dataPin, clockPin, bitOrder, value)
- unsigned long pulseIn(pin, value)

Time

- unsigned long millis()
- delay(ms)
- delayMicroseconds(us)

Math

- min(x, y)
- max(x, y)
- abs(x)
- constrain(x, a, b)
- map(value, fromLow, fromHigh, toLow, toHigh)
- pow(base, exponent)
- sqrt(x)

Trigonometry

- sin(rad)
- cos(rad)
- tan(rad)

Random Numbers

- randomSeed(seed)
- long random(max)
- long random(min, max)

Serial Communication

Used for communication between the Arduino board and a computer or other devices. This communication happens via the Arduino board's serial or USB connection and on digital pins 0 (RX) and 1 (TX). Thus, if you use these functions, you cannot also use pins 0 and 1 for digital i/o.

- Serial.begin(speed)
- int Serial.available()
- int Serial.read()
- Serial.flush()
- Serial.print(data)
- Serial.println(data)

Didn't find something? Check the extended reference or the libraries.

Reference Home

Corrections, suggestions, and new documentation should be posted to the Forum.

The text of the Arduino reference is licensed under a Creative Commons Attribution-ShareAlike 3.0 License. Code samples in the reference are released into the public domain.

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