What is the primary purpose of the Observer pattern in system design?

The Observer pattern is predominantly utilized in system design to facilitate loose coupling between modules. This design pattern allows an object, known as the subject, to maintain a list of dependents, referred to as observers, that are notified of any state changes in the subject. By employing this pattern, observers can react to changes without needing to know the details of the subject's implementation, promoting a more modular architecture.

This decoupling is significant because it permits changes to be made in one component of the system without necessitating alterations in others. For instance, if an observer’s behavior needs to be modified or a new observer type is added, the subject does not need to change, thus supporting easier maintenance and scalability.

The other options, while relevant in their contexts, do not specifically capture the essence of the Observer pattern. For instance, enforcing a single access point to shared resources pertains more to the Singleton pattern, while providing a unified interface aligns with the Adapter pattern. Creating new instances without specifying exact classes closely relates to the Factory pattern rather than the Observer pattern. Each of those patterns serves a different purpose and addresses distinct design challenges within object-oriented design.