Block programming

Block programming is an age-old strategy of programmers. Block programming occurs when the channel schedules similar programs back to back. The concept is to provide similar programming to keep the viewers glued to your channel. Radio stations use it consistently: they program the same type of music for an entire daypart. Early radio used to air soap operas in the daytime, children's programs after school, and comedies, dramas, and music programs in the evening hours. Consider NBC's "must-see-TV" Thursday evenings, 2 hours of sitcoms and 1 hour of ER.

Source: Dr. Michael Porter, Chair of Communications at the University of Missouri - Columbia