Arduino programming

We will now take a step back, and look at the first line of code.

// the setup function runs once when you press reset or power the board
void setup() {
  // initialize digital pin LED_BUILTIN as an output.
  pinMode(LED_BUILTIN, OUTPUT);
}

We see that the

pinMode

statement is included in a structure like this:

void setup() {
...
}

These structures are called functions. In an Arduino sketch, these are the two basic sections: the setup() function and the loop() function.

void setup() {
...
}

void loop() {
...
}

Whatever is inside setup() happens once in the beginning of the program execution, followed by loop() which repeats over and over.