Provide Effective Feedback and Guidance and Assistance 599

Step 9: Provide Effective Feedback and Guidance and Assistance 599

–– When a long operation is completed, present an acknowledgment that it is completed. • A significantly changed screen appearance. • An auditory tone.

–– If an operation is very time-consuming

• Consider breaking the operation into subtasks and providing progress indica-

tors for each subtask. • Allow users to start a new activity while waiting.

Long, invisible operations: –– When an operation not visible to the user is completed, present an acknowledg-

ment that it is completed. • A message. • An auditory tone.

Progress indicator: –– A long rectangular bar that is initially empty but filled as the operation proceeds.

• Dynamically fill the bar. • Fill it with a color or shade of gray. • Fill it from left to right or bottom to top.

Percent complete message: –– A message that indicates the percent of the operation that is complete. –– Useful if a progress indicator takes too long to update.

Elapsed time message: –– A message that shows the amount of elapsed time that the operation is consum-

ing. –– Useful if • The length of the operation is not known in advance. • A particular part of the operation will take an unusually long time to com-

plete.

Web page downloads: –– For pages requiring download times greater that 5 seconds, give the user some-

thing to do while waiting. • Quickly present, at the top of the downloading page, an image, text or links.

–– Advise of long download times. –– Warn of “Time Outs.”

Elapsing time is in the eye of the beholder. What is important is perceived passing time, not actual time as measured by a clock. Dealing with time delays involves pro- viding feedback that the system is truly working, and that the system’s processing will

be completed at some foreseeable and predictable time. Dealing with time delays also involves diverting people’s attention away from a delay by engaging them in some meaningful interim activities.

Button clicks . Acknowledge all button clicks by visual or aural feedback within

one-tenth of a second. This assures the user that a requested action has been received by the system.

600 Part 2: The User Interface Design Process

Waits of up to 10 seconds . If an operation takes 10 seconds or less to complete, pre- sent a “busy” signal until the operation is finished. An hourglass pointer is the customary signal. A “Please wait...” message can be presented to indicate that more complex processing is occurring or has been delayed. When the process is finished, provide an indication that the user may proceed.

Waits of 10 seconds to 1 minute . If an operation takes longer than 10 seconds to complete, display a rolling barber’s pole or other large animated object. Additionally, present a progress indicator, percent complete message, or elapsed time message. When the process is finished, provide an indication that the user may proceed.

Waits over 1 minute . For waits exceeding 1 minute, present an estimate of the length of the wait. If the length is unknown, an educated guess is better than a “Don’t Know” or no estimate at all. A time estimate allows the user to decide what to do next — wait, go to lunch, or start some other task. For these waits, dis- play a progress indicator, percent complete message, or elapsed time message. If an operation is very time-consuming, consider breaking the operation into sub- tasks and providing progress indicators for each subtask. Also, allow users to start a new activity while waiting so a delay will not be unproductive. Also, con- sider offering engaging text messages to keep users informed and entertained while they are waiting for process completion. Provide a clear indication of when the process is finished, significantly changing the screen’s appearance so the change may be recognized from some distance away. Also, include an auditory tone to attract the user’s attention back to the screen.

Long, invisible operations . When a long operation not visible to the user is com- pleted, present an acknowledgment message that it is completed. For example, upon completion of a search with no positive results, “Search complete, Jones not found” might be displayed. Also provide an auditory signal, because the user’s attention may be directed to another part of the screen, or entirely away from the screen.

Progress indicator . A progress indicator is a long rectangular bar that is initially empty but filled as the operation proceeds. Dynamically fill the bar with a color or shade of gray. Fill all bars from left to right or bottom to top. A progress indi- cator is shown in Figure 9.1.

Figure 9.1: Processing progress indicator.