<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
 <HEAD>  <TITLE> New Document </TITLE> </HEAD>
 <script>
  function ff(){
   var str ='v.value = ' + v.value;
//   alert(str);
   eval(str);
  }
</script>
 <BODY>
<input id=v  value="0"><br>
<input id=b  type=button value="  =   " onclick="ff();">


 </BODY>
</HTML>