4xLEDs.ino

int led1 = 12;
int led2 = 27;
int led3 = 33;
int led4 = 15;

void setup() 
{
  // put your setup code here, to run once:
  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT);
  pinMode(led3, OUTPUT);
  pinMode(led4, OUTPUT);

}

void loop() 
{
  // put your main code here, to run repeatedly:
  digitalWrite(led1,HIGH);
  digitalWrite(led2,HIGH);
  digitalWrite(led3,HIGH);
  digitalWrite(led4,HIGH);
  delay(500);

  digitalWrite(led1,LOW);
  digitalWrite(led2,LOW);
  digitalWrite(led3,LOW);
  digitalWrite(led4,LOW);
  delay(500);

}