The code segments you write for your Arduino are called sketches, and they are written in the C++ programming language.

Every sketch needs two “void” functions – these functions do not return any value. The first void function is setup () and this runs once, just after your Arduino is powered up. The second void function is a loop () and this runs continuously after the initial setup.

All your initialization steps need to run in the setup () function and the loop () is where you write the code you want to run repeatedly after setup.

A basic sketch looks like this:

void setup()
{

}

void loop()
{

}

Sample Code

You might notice that there's an LED on your board. This onboard LED is on pin number 13.

Enter the following code to

1. Create a variable called ledPin with an integer (int) type.
2. Call a special function called pinMode() in the setup to assign the LED as an output.
3. Call another special function called digitalWrite() to turn off the LED (and override the default flashing LED).

int ledPin = 13;

void setup()
{
pinMode(ledPin, OUTPUT);
}

void loop()
{
digitalWrite(ledPin, LOW);
}

Compile the code by clicking the “upload” arrow button in the application window. The LED will turn off.

Now, replace the LOW for HIGH in the digitalWrite() function and hit the “upload” arrow button again. The LED will turn on.