int timer = 100;  //delay time for blinking
int ledPin;      // variable to set the ouput pin
void setup()
{
  //loop to initialize the pin mode of digital pins 2 to 7
  for (ledPin = 2; ledPin < 8; ledPin++)
  {
    pinMode (ledPin, OUTPUT);
  } // end loop
} // end of setup()

void loop()
{
  //for loop to blink from pin 2 through to pin 7 with a delay time mentioned in timer
  for (ledPin = 2; ledPin < 8; ledPin++)
  {
    digitalWrite (ledPin, HIGH);
    delay (timer);
    digitalWrite (ledPin, LOW);
  }// end of for loop

  //for loop to blink from pin 7 through to pin 2 with a delay time mentioned in timer
  for (ledPin = 7; ledPin >= 2; ledPin--)
  {
    digitalWrite (ledPin, HIGH);
    delay (timer);
    digitalWrite (ledPin, LOW);
  } // end for loop
} // end program