#define F_CPU 8000000  //Define clcok speed as 1Mhz
int main(void)
{
  DDRA = 0b10000000;  //set PA7as output & all other pins as input  
    while (1) //Repeat the below actions continuously
    {
    PORTA |= (1<<7);// Set PA7 high (Make LED ON)
    _delay_ms(3000);//delay of 1 sec
    PORTA &= ~(1<<7);// Set PA7 low (Make LED OFF)
    _delay_ms(3000);//delay of 1 sec
  }
}