Interfacing 7 Segment with Parallel Port (Increment and Decrement)

7segment.c

#include <dos.h>
#define OUT 0x378
#define IN  0x379

int d1[10] = {0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x08,0x09};
int d2[10] = {0x00,0x10,0x20,0x30,0x40,0x50,0x60,0x70,0x80,0x90};

void display(int n){
  outportb(OUT,d2[n/10] | d1[n%10]);
  delay(100000);
}

int main(){
  int n = 0, p;
  display(0);
  
  while(1){
    p = inportb(IN);
    if (!(p & 0x10)){
      n++; if (n > 99) n = 0;
      display(n);
    } else if (!(p & 0x20)){
      n--; if (n < 0) n = 99;
      display(n);
    }
  }

  return 0;
}