The UI module contains UI components and is used to interact with a BlackBerry® device user. Typically, the UI module starts automatically when the user interacts with a custom message. For example, if the user highlights a custom message in the Messages application and clicks the trackpad or touches the touch screen, the UI module should start and display the message content. If the UI module is not running and the user attempts to open a custom message, the UI module starts automatically. The UI module can also let users reply to a message and compose a new message.