Function of the opening of a film - Psycho (1960)

Function of the opening of a film - Psycho (1960)

The purpose of the opening scene in 'Psycho' (1960, directed by Alfred Hitchcock) is to set the scene of the film, show us what genre the film is and to introduce the two first characters. The film begins with the title sequence, with loud and fast music, creating a scary atmosphere, showing the audience the film is a horror. 
Once the title sequence is over, there is an establishing shot, with bold writing over the top saying 'Phoenix, Arizona', then 'Friday, December the eleventh' and finishing with 'two forty-three PM'. This allows the audience to know where the scene is set and what time of the day it is.
The camera then moves into a bedroom, where we see the first two characters. From their dialogue, we imagine they have an illicit relationship. We also get this impression from the fact Janet Leigh is in her underwear laying on the bed.

Overall, I think the opening of this film was created in this way to set the scene, just within the first 5 minutes it is clearly shown where the film is set, who the main characters are, and what the genre is.