var fjoldi = 0;
var stafli = new Array();

function frumstillaStafla(){
  fjoldi = 0;
}

function push(){
  stafli[fjoldi] = document.all['stak'].value;
  document.all['stak'].value = "";
  fjoldi++;
  birtaStafla();
}

function pop(){
  if (fjoldi > 0){
	document.all['stak'].value = stafli[--fjoldi];
	birtaStafla();
  }
  else {
    parent.frames['nedri'].document.close();
    parent.frames['nedri'].document.write("Staflinn er tómur!"); 
  }
}

function birtaStafla(){
  parent.frames['nedri'].document.close();
  if (fjoldi == 0) {parent.frames['nedri'].document.write(" ");}
  for (i=0; i<fjoldi; i++){
    parent.frames['nedri'].document.write(stafli[i], "<br>");    
  }
}