First Start Arduino Uno

Question

When I started connecting my Arduino Uno for first project: LED to pin 13, resistor, breadboard, USB connected to Windows Laptop, the orange on-board LED flashes every second and the LED on the breadboard did the same. What program is driving this? I had NOT uploaded any program. Please explain.

Answer 1

It is a preloaded sketch and will be overwritten when you upload your first sketch into the Arduino.

Typically it's the Arduino Blink sketch which can be found here:

https://www.arduino.cc/en/Tutorial/Blink

Which has the following (functional) content:

// 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);
}

// the loop function runs over and over again forever
void loop() {
  digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(1000);                       // wait for a second
  digitalWrite(LED_BUILTIN, LOW);    // turn the LED off by making the voltage LOW
  delay(1000);                       // wait for a second
}