The program is what ultimately defines what plays in each zone on the screen. Each program is built upon a predefined layout . Each zone within the layout will have its own programming list, made up of content, media assets or even playlists and commands. The default behavior is for each zone to playback the content independent of each other zone, in a looping fashion (starting back at the beginning of the programming list once the playback reaches the end). The program also defines any synchronized playback between zones, conditional playback and events.