function KeineZahl(Wert)
{
 if(isNaN(Wert) == true)
 {
  alert(Wert + " ist keine Zahl!");
  return true;
 }
 else return false;
}

function calculate()
{

    if(KeineZahl(document.form.iuv.value))
     {
     document.form.iuv.focus();
      return false;
     }

  document.form.answer.value = printoutput(document.form.iuv.value,document.form.unit.options[document.form.unit.selectedIndex].text,document.form.unit.options[document.form.unit.selectedIndex].value,document.form.unit2.options[document.form.unit2.selectedIndex].text,document.form.unit2.options[document.form.unit2.selectedIndex].value);
}

function printoutput(iuv,unit1,con1,unit2,con2) {
var summe, p1, p2;

if (Temperature(unit1)) {

p1 = CToSI(parseFloat(iuv),unit1);
p2 = CFromSI(parseFloat(p1),unit2);

return (Math.round(p2*1000000)/1000000) }
else

 return (Math.round(iuv*con1*con2*1000000)/1000000)
}

function Temperature(Unit)
{
  if      (Unit == "Celsius")     return true
  else if (Unit == "Fahrenheit")  return true
  else if (Unit == "Kelvin")      return true
  else if (Unit == "Rankine")     return true
  else if (Unit == "Reaumure")    return true
  else
   return false;
}


function CToSI(Temp, TempUnit)
{
var f1;


  if      (TempUnit == "Celsius")     {f1= Temp + 273.15}
  else if (TempUnit == "Fahrenheit")  {f1 = 5.0/9.0 * (Temp + 459.67)}
  else if (TempUnit == "Kelvin")      {f1 = Temp}
  else if (TempUnit == "Rankine")     {f1 =  5.0/9.0 * Temp}
  else if (TempUnit == "Réaumure")    {f1 =  5.0/4.0 * Temp + 273.15}
  else { f1 = Temp}
   return f1
}


function CFromSI(Temp, TempUnit)
{
var f1;

  if      (TempUnit == "Celsius")    {f1= Temp - 273.15}
  else if (TempUnit == "Fahrenheit") {f1= 9.0/5.0 * Temp - 459.67}
  else if (TempUnit == "Kelvin")     {f1= Temp}
  else if (TempUnit == "Rankine")    {f1= 9.0/5.0 * Temp}
  else if (TempUnit == "Réaumure")   {f1= 4.0/5.0 * (Temp - 273.15)}
  else { f1 = Temp}
  return f1
}