THIS IS THE HTML FILE: 

<head>
JS Example of Forms
</head>

<body>


<SCRIPT>
<!--- Hide script from old browsers
function compute(f) {
        if (confirm("Are you sure?"))
                f.result.value = eval(f.expr.value)
        else
                alert("Please come back again.")
}
// end hiding from old browsers -->
</SCRIPT>
<FORM>
Enter an expression:
<INPUT TYPE="text" NAME="expr" SIZE=15 >
<INPUT TYPE="button" VALUE="Calculate" onClick="compute(this.form)">
<BR>
Result:
<INPUT TYPE="text" NAME="result" SIZE=15 >
</FORM>

</body>