void setup() {
  // Set up the direction register and output register pointers
  volatile char *dir, *dirk, *ink, *outf;
  
  dir = (volatile char *) 0x30;   // Data direction register for output (7-segment)
  dirk = (volatile char *) 0x107; // Data direction register for switch
  ink = (volatile char *) 0x106;  // Input register (switch input)
  outf = (volatile char *) 0x31;  // Output register for 7-segment display
  
  *dir = 0xFF;   // Set the 7-segment display port as output
  *dirk = 0x00;  // Set the switch port as input
}

void loop() {
  volatile char *ink = (volatile char *) 0x106;  // Input register (switch input)
  volatile char *outf = (volatile char *) 0x31;  // Output register (7-segment display)
  
  // Array holding the 7-segment values for numbers 0 to 9
  char segmentMap[10] = {
    0x3F, // 0
    0x06, // 1
    0x5B, // 2
    0x4F, // 3
    0x66, // 4
    0x6D, // 5
    0x7D, // 6
    0x07, // 7
    0x7F, // 8
    0x6F  // 9
  };
  
  int i = 0; // Counter to track current number displayed
  char prevSwitchState = 0x00; // To store previous state of the switch
  
  while(1) {
    char switchState = *ink; // Read the switch input
    
    // Check if the switch is pressed (switchState == 0x01) and it was not previously pressed
    if (switchState == 0x01 && prevSwitchState == 0x00) {
      *outf = segmentMap[i];  // Output the corresponding 7-segment code
      i = (i + 1) % 10;       // Increment to the next digit, and wrap around after 9
      prevSwitchState = 0x01; // Set previous state to pressed
    } else if (switchState == 0x00) {
      prevSwitchState = 0x00; // Set previous state to not pressed when switch is released
    }
    
    // Simple delay for debouncing (you may adjust or use a proper debouncing technique)
    for (long n = 0; n < 100000; n++);
  }
}