#define TRUE 1
#define FALSE 0
const int numLEDs=4;
const int GPIO_Pins[]={1,3,8,12}; //store all pin number in the array
const int blinkRate = 500; // in milliseconds
static bool flag = TRUE; // cannot be const as it has to toggle between true and false
void setup() {
  // put your setup code here, to run once:
  //int led ; variable name can be called anything
  for(int led=0;led<numLEDs;led++)
  {
    pinMode(GPIO_Pins[led],OUTPUT);
    //ARRAY at index LED is initalised in the for loop with each iteration
  }
}
void loop() {
  // put your main code here, to run repeatedly:
  //initially FLAG is TRUE
  for(int led=0;led<numLEDs;led++)
  {
    //user defined function
    controlLEDs(led,flag); //function call
  }
  delay(blinkRate);//500 milli seconds delay
  flag = !flag; //FLAG = FALSE (inversion of previous reading)
  //goes back to the beginning on loop() function and the for loop starts from 0 again
}
void controlLEDs(int led,bool state)
{
  if(state==TRUE)
    digitalWrite(GPIO_Pins[led],HIGH);
  else
    digitalWrite(GPIO_Pins[led],LOW);
}