What distinguishes functional requirements from non-functional requirements?

Functional requirements are primarily concerned with what a system must do; they specify the behaviors, functions, and activities the system should perform. This includes the transformations of inputs into outputs, business rules, and interactions necessary for the functionality of the system. By defining system operations, functional requirements outline the expected behaviors and functionalities that users will interact with or that will be processed by the system.

For example, functional requirements would detail specific functionalities such as processing a customer order, generating reports, or allowing user authentication. These requirements guide the development team in ensuring that the system meets user needs and business objectives.

In contrast, the other options misunderstand the nature of functional requirements. Performance is typically associated with non-functional aspects of the system, while user interactions—though relevant—are just one aspect among many that define functional requirements. Similarly, addressing limitations pertains to constraints or non-functional requirements that specify how well a system operates or under what conditions. Thus, focusing on system operations encapsulates the essence of functional requirements well.