void setup() {
  // put your setup code here, to run once:
  volatile char *dirf,*dirk,x;
  volatile char *outf,*ink;

  dirf = 0x30;   dirk = 0x107;
  outf = 0x31;   ink = 0x106;

  *dirf = 0x01;  // to make only 1 bit as output // setting as output 
  *dirk = 0x00; // making all input
   
   while(1) //always in the loop
   {
    x = *ink;  //read
    if(x == 0x01)   //if x is 1 and only 1
       *outf = 0x02;   //when switch is pressed make it 1 // here 0b00000010 //also try 0x03 or 0b00000011 
    else
      *outf = 0x00;   //otherwise 0
   } 
}

void loop() {
  // put your main code here, to run repeatedly:

}