Block programming is a strategy of television and radio programmers. Block programming occurs when the television network schedules similar programs back-to-back. The concept is to provide similar programming to keep the viewers. Radio stations use it consistently: they program the same type of music for long periods of time. A notable example of block programming is NBC's "must-see-TV" Thursday evening, which is currently 2 hours of sitcoms and 1 hour of ER.