[support] what is the simplest way to set text in a textfield on select events

Hi All Say in a D7 form, I have a choice (of type select) and a textfield. Say when I select different items in choice, I want the textfield shoudl show the text of seected choice item. I know it can be done using AJAX. Is there anyother simple way to do this. If so can somebody guide me. Thanks kamal necs, ble