00 LED blink

This blinks LED connected to PIN 13 in Arduino UNO board every 1 second

Circuit diagram

(credits: https://www.circuito.io/)

Here, you can connect resistor and LED to board directly without breadboard. If you do not have LED, replace 5 with 13 in the code below which will make the on-board LED blink.

Code

void setup() {
  pinMode(5, OUTPUT);
}

void loop() {
  digitalWrite(5, HIGH); // Turn LED on
  delay(1000);            // Wait 1 second
  digitalWrite(5, LOW);  // Turn LED off
  delay(1000);            // Wait 1 second
  }