Provide feedback of where the user is and where the system is at any point in time.
The type of feedback to display depends on the response time
indeterminate spinner, fractional progress bar, TaxAct step process wizard
Space constraints and current status should be presented to the user if they need to be aware
Gmail storage capacity, Evernote upload allowance
Show and highlight changes or the need to save changes.
A stop light is a good example of a system communicating action in dual coding - by using color and placement, it makes it faster to recognize and is usable to both normal sighted users and the color impaired. The Google Calendar notification below could be enhanced with dual coding if both color and icon were used. The Amazon gift card redemption message uses the dual coding well.
Let the user know what can or should happen next.
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