<meta charset="utf-8">
<script>
function linebreak(){
document.write("<br>");
}
function show(text){
document.write(text);
linebreak();
}
alert("Programa que mostra todos os números de 20 a 0!");
var twenty = 20;
while (twenty >= 0 && twenty <= 20){
show(twenty);
twenty = twenty - 1;
}
show("FIM!");
</script>
