Officers' quarters was the designation given to the staterooms on Constitution-class starships that were reserved for the officers. A typical quarter was segregated into a sleeping and working area. Directional signs gave information as to where the officers' quarters were located, along with the room numbers. In post-refit Constitution-class starships, sonic showers were added to the rooms. These quarters were located on Deck 5. (TOS: "Where No Man Has Gone Before"; Star Trek: The Motion Picture)
The first mention of officers' quarters was in "Where No Man Has Gone Before" where a directional sign was seen with this label. Through the run of the series, there were a handful of other directional signs for these quarters. The first and only dialogue reference to these quarters was in the first movie.
In these quarters, there was a door that lead to an unseen room. In a deleted scene from "The Corbomite Maneuver", this was revealed to be a closet. [1]
In the shooting script for the first movie, the officers' quarters were located on Deck 4.