Why three segments?
Segments will be used to reduce the clutter in the code.
Segments will also make the program easier to test (and to debug if need be) and to modify later if needed.
The setup segments will contain code for getting the actors and the props ready for "lights, camera, and action."
The setup and closing segments will also contain code for creating special effects used to transition from one scene to the next.
The action segments will contain the code that carries the story line.