void setup() {
  // put your setup code here, to run once:
  volatile char *dirf,*dirk;
  dirf=0x30; dirk=0x107;
  *dirf=0xff; *dirk=0xff;
}

void loop() {
  // put your main code here, to run repeatedly:
  volatile char *outf,*outk;
  outk=0x108; outf=0x31;
  *outk=0x0d;//the dig1,...dig4 all are like control pins, to make the particular
  //number's place ON. We have to make the pins control pins 0, in order to turn ON that
  //particular bit, because the current flows from (+)ve to (-)ve,i.e., 5V--->0V.
  *outf=0x3f;
}