void time_delay(void);

int main(void)
{
  // Configure PORTS Direction PORTF to Output, PORTK to Input
  volatile char *dirf, *dirk;
  dirf = (char *) 0x30;
  *dirf = 0xFF;

  dirk = (char *) 0x107;
  *dirk = 0x00;
     
  // Setup input register of PORTK and output register of PORTF
  volatile char *outf, *ink;
  outf = (char*) 0x31;
  ink = (char*) 0x106;

  // Declare a volatile variable to store values read from PORTK
  volatile char x = 0;

  // Array containing seven segment values to display 0 to 9
  unsigned char sev_seg[] = {0x3F, 0x06, 0x5B, 0x4F, 0x66, 0x6D,
                             0x7D, 0x07, 0x7F, 0x67};
  unsigned char size = (unsigned char) sizeof(sev_seg)/sizeof(sev_seg[0]);

  volatile char i = size - 1;
  
  while (1)
  {
  /* Initially display 9.
When switch 2 is pressed every time decrement by 1 */

      if (i >= 0)
        *outf = sev_seg[i];
      else
        i = size - 1;

      x = *ink;

    if (x & 0x02) // check if switch 2 is pressed. If true, decrement i
    {
      time_delay(); // delay for switch debouncing
     i--;
    }
  }
}

void time_delay(void)
{
  volatile long del = 0;
  while (del++ < 100000);
}