The computer should acknowledge every entry immediately.
Additional Information:
For every entry action by the user, there should be some obvious reaction from the computer. The absence of computer response is not an acceptable means of indicating that an entry is being processed. 'Immediately' as used in this guideline must be interpreted in relation to the response time requirements of different dialogue types. For example, execution of a requested transaction might produce an immediately apparent result, as when a user requests NEXT PAGE and the next page is displayed. A message might indicate completion of a transaction, as when a user requests a printout at a remote facility and the computer displays a confirming message "RAD WASTE file has been sent to printer;" or, a message might indicate that execution is in progress or deferred, as when a user enters data and the computer displays an interim message "RAD WASTE file is being updated." A message might indicate that the control entry requires correction or confirmation, as when a user requests a file display and the computer displays an error message "RAD WASTE file not recognized." In a menu selection context, it may suffice simply to highlight the selected option label (e.g., by brightening or inverse video) when that would provide an unambiguous acknowledgment.