Compound interest

< html >
< head >
< script >
<!-- Original :  Paul Hartmann (guycroft@clara.co.uk) -->
<!-- Web Site :  http : //www.guycroft.clara.net -->
<!-- Begin
var princ;
var ratepc;
var years;
var rate;
var power;
function calcAmt(frm) {
princ = eval (frm.pr.value);
ratepc = eval (frm.rt.value);
years = eval (frm.yr.value);
rate = ratepc / 100;
power = Math .pow((1 + rate), years);
frm.amt.value = Math .round(princ * power * 100) / 100;
frm.inter.value = Math .round((frm.amt.value - princ) * 100) / 100;
}
function checkInput(frm) {
if (rate == 0 || rate > .3) {
window.alert ( "Are you sure that the interest rate is " + ratepc + "%?" );
frm.rt.focus();
}
if (years == 0 || years > 30) {
window.alert ( "Are you sure that the term is " + years + " years?" );
frm.yr.focus();
   }
}
//  End -->
</ script >

</ head >

< body Background = .. / graphics / grayback.jpg >
< center >< BR >< BR >< BR >
< form method = get name = frm >
Principal < input type = text name = pr size = 10 maxlength = 10 onChange = calcAmt( this .form) >
Rate < input type = text name = rt size = 6 maxlength = 6 onChange = calcAmt( this .form) >

Years < input type = text name = yr size = 5 maxlength = 5 onChange = calcAmt( this .form) >
< br >
< br >
< input type = button name = calc value = "Calculate" size = 10 onClick = checkInput( this .form); calcAmt( this .form); >
< input type = reset value = "Clear" >
< br >
< br >
Amount < input type = text name = amt size = 10 >
Interest < input type = text name = inter size = 10 >
</ form >

</ center >
</ BODY >
</ html >

//Thanks to David Pye for his JavaScript Vault contribution.