int d=0;

void setup() {
  // put your setup code here, to run once:
  DDRD=0b11111111;
//  DDRD=0xFF; // The code is the same as above (this is in hexadecimal)
  PORTD=0b00000001;
  DDRB=0b00000000;
  PORTB=0b00000011;

}

void loop() {
  // put your main code here, to run repeatedly:
  
  //if (PORTD==0x80) 
  if ((PINB&0b00000001)==0)
  {
    d=1;
  }

  if ((PINB&0b00000011)==0)
  {
    d=0;
  }

  if (PORTD==0x01) 
  {
    d=0;
  }

  if (d==0) 
  {
    PORTD=PORTD<<1;
  }

  if (d==1) 
  {
    PORTD=PORTD>>1;
  } 
  delay(1000);
}