void setup() {
  // put your setup code here, to run once:

  //F is output port // K is input port

  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) == 0x01)
       *outf = 0x01;   //when switch is pressed make it 1  //0x01 means 0b00000001 => bit 0 is ON or Output
    else
      *outf = 0x00;   //otherwise 0
   } 
}

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

}