Broadcast programming or scheduling is the practice of organizing television or radio programs in a daily, weekly, or season-long schedule. Modern broadcasters use broadcast automation to regularly change the scheduling of their programs to build an audience for a new show, retain that audience, or compete with other broadcasters' programs. In the United Kingdom, this is known as TV listings. Television scheduling strategies are employed to give programs the best possible chance of attracting and retaining an audience. They are used to deliver programs to audiences when they are most likely to want to watch them and deliver audiences to advertisers in the composition that makes their advertising most likely to be effective (Ellis 2000 p. 136). Digitally based broadcast programming mechanisms are known as electronic program guides (EPG). At a micro level, scheduling is the minute planning of the transmission; what to broadcast and when, ensuring that every second of airtime is covered.