system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do TV shows 'play'?

When I'm watching TV, I'm obviously watching a pre-determined series of programs, but what is the process of getting them onto the television?
Does the channel transmit a 'playlist' every day, or every week, or does someone in a studio somewhere hit the play button when the ads finish?
I know that programs are sometimes cancelled at the last minute because a live sporting event has lasted longer than expected or whatever, so there is obviously a live 'controller', but is this someone who has to intervene, or someone (or a group of people) who is constantly in control of the transmissions?
gpt
Somewhere there is a big room called an MCR or Master Control Room (a bit like the place where Homer works in the nuclear plant) in which people control all that stuff. They have a kind of TV guide they're working from, which is much *much* more detailed than the one consumers see, and includes every commercial and trailer and station ID, to the second. Some of it is automated, and some of it is done by people clicking buttons and turning knobs. What makes it more complicated is Localisation, which means that there's one main channel showing the same movie across a wide geographical area, but in the ad breaks, different regions get different commercials.