How to call a java script function on clicking Enter an Input field

Enter any thing in Text box then press Enter to execute

<form onSubmit='alerttest(this); return false'>       

 <input type="text">        

</form>





<script language="javascript">

  function alerttest()

  {

   alert("Executing jolly.exe !!!!");

   // function edited by Inderpreet singh

  }

</script>