<form name="smallcal">
<input type="text" size="20" name="calculator">
<input type="button" name="B1" value="Calculate" onclick="calculate()">
<input type="reset" name="B2" value="Reset">
Answer:<input type="text" size="20" name="answer">
</form>

<script>
function calculate()
{
document.smallcal.answer.value=
eval(document.smallcal.calculator.value)
}
</script>