The API is managed by a singleton object of type TimetableManager. The single instance of this object is created by a call to the static function TimetableManager::Create() which creates the global state managed by the API. The instance returned by TimetableManager::Create() can be used to call API functions that depend on global state only, as well as to create new user sessions.

User sessions are represented by objects of type UserSession. A new user session can be created using the TimetableManager::StartSession() API function, which returns a UserSession object. A UserSession object can be used to create course loads associated with that session.

Course loads are represented by objects of type CourseLoad. New course loads associated with a user session can be created by calling NewCourseLoad() or OpenCourseLoad() on the UserSession object. The CourseLoad object has methods for interacting with the course load, such as selecting courses and generating timetales. A course load is freed when its CourseLoad object's destructor is called.

A session ends when its UserSession object's destructor gets called. The API client should ensure that any CourseLoad objects associated with the session are destroyed before the UserSession object is destroyed.

As mentioned above, API functions can be classified based on what type of state they depend on. This is expressed in the following coding conventions: