void setup() {
  // put your setup code here, to run once:
volatile char *dir1;
dir1 = 0x30;             //directon reg for port f
*dir1 = 0xff;             //port f as output
volatile char *dir2;
dir2 = 0x107;               //direction reg for port k
*dir2 = 0x00;             // port k as input
volatile char *dir3;
dir3 = 0x21;               //direction reg for port a 
*dir3 = 0xff;               //port a as output

}

void loop() {
  // put your main code here, to run repeatedly:
  volatile long j;
  volatile int i,x;
volatile char *row;
row = 0x31;
volatile char *col;
col = 0x106;
volatile char *seg;
seg = 0x22;

while(1)
{
for(i=0;i<4;i++)
{
  *row = 1 << i;
 
  if(*row == 1)

 {
   x = *col;
    if(x == 0x01) *seg = 0x06;
  for(j=0;j<1000;j++);
   if(x == 0x02) *seg = 0x5b;
  for(j=0;j<1000;j++);
   if(x == 0x04) *seg = 0x4f;
  for(j=0;j<1000;j++);
   if(x == 0x08) *seg = 0x77;
  for(j=0;j<1000;j++);*seg = 0;}

 if(*row == 2)
 {
   x = *col;
   if(x == 0x01) *seg = 0x66;
  for(j=0;j<1000;j++);
   if(x == 0x02) *seg = 0x6d;
  for(j=0;j<1000;j++); 
  if(x == 0x04) *seg = 0x7d;
  for(j=0;j<1000;j++); 
  if(x == 0x08) *seg = 0x7f;
  for(j=0;j<1000;j++);  *seg = 0;}
  
   if(*row == 4)
 {
   x = *col;
  
  if(x == 0x01) *seg = 0x07;
  for(j=0;j<1000;j++); 
  if(x == 0x02) *seg = 0x7f;
  for(j=0;j<1000;j++);
   if(x == 0x04) *seg = 0x6f;
  for(j=0;j<1000;j++);
     if(x == 0x08) *seg = 0x39;
  for(j=0;j<1000;j++);  *seg = 0;} 
      
        if(*row == 8)
 {
   x = *col;
  
  if(x == 0x01) *seg = 0x49;
  for(j=0;j<1000;j++); 
  if(x == 0x02) *seg = 0x3f;
  for(j=0;j<1000;j++);
   if(x == 0x04) *seg = 0x36;
  for(j=0;j<1000;j++);
     if(x == 0x08) *seg = 0x3f;
  for(j=0;j<1000;j++);  *seg = 0;} 

    }
   
  }
}