function calc_sum(){
  num1 = document.frm1['num1'].value
  num2 = document.frm1['num2'].value
  cal0 = document.frm1['cal0'].value;
  if ((num1 == "") || (num2 == "")) {
    alert("数値は必ず入力してください。");
    return false;
  }
  if (cal0 == "+") sum1 = eval(num1) + eval(num2);
  if (cal0 == "-") sum1 = eval(num1) - eval(num2);
  if (cal0 == "*") sum1 = eval(num1) * eval(num2);
  if (cal0 == "/") sum1 = eval(num1) / eval(num2);
  document.frm1['num3'].value = sum1;
  return false;
}
function reset_exe(){
  sum1 = "";
  if (confirm('リセットします。')){
    document.frm1['num1'].value = "";
    document.frm1['num2'].value = "";
    document.frm1['num3'].value = sum1;
  }
}