void setup() {
  // put your setup code here, to run once:
   volatile char *dir;
   dir = 0x30;
   *dir = 0xFF;
}

void loop() {
  // put your main code here, to run repeatedly:
  volatile char *out;
  out = 0x31;
  *out = 0x00;  //where ever there is 0 => it is ON in COMMON ANODE CONDITION //try 0x00 or 0b00000000 or 0xFF or 0b11111111 //try 0xFF all 1 i.e; 0b11111111
}