var op = false;
var eq = false;

function EnterNumber(Number)
{
  if (op == false) {
    document.getElementById("Formula").value += Number;
    document.getElementById("Answer").value += Number; }
  else {
    document.getElementById("Answer").value = Number;
    op = false;
    if (eq == true) {
      document.getElementById("Formula").value = Number;
      eq = false; }
    else {
      document.getElementById("Formula").value += Number; 
    }
  }
}

function EnterOperator(Operator)
{
  if (document.getElementById("Formula").value != "") {
    document.getElementById("Answer").value = 
      eval(document.getElementById("Formula").value);
    document.getElementById("Formula").value = 
      eval(document.getElementById("Formula").value) + Operator;
    op = true;
    eq = false;
  }
}

function EnterEqual()
{
  if (document.getElementById("Formula").value != "") {
    document.getElementById("Answer").value = 
      eval(document.getElementById("Formula").value);
    document.getElementById("Formula").value = 
      eval(document.getElementById("Formula").value);
    op = true;
    eq = true;
  }
}

function EnterClear()
{
  document.getElementById("Answer").value = "";
  document.getElementById("Formula").value = "";
  op = false;
  eq = false;
}