Which statement best distinguishes functional requirements from non-functional requirements?

Which statement best distinguishes functional requirements from non-functional requirements?

• A. Functional requirements specify the tasks the system must perform.
• B. Non-functional requirements specify the exact data models used.
• C. Functional requirements are optional and not testable.
• D. Non-functional requirements describe user interface layout only.

Answer: (A)

Functional requirements specify the tasks the system must perform. They describe the concrete functions, features, and behaviors the system must deliver in response to user actions or business rules. Non-functional requirements describe how the system performs those tasks, focusing on attributes like performance, reliability, security, usability, and maintainability. The option is best because it clearly captures the primary distinction: it states what the system must do, not how it should be constrained or how well it should run. The other statements don’t fit because data models are design choices about structure and storage, not a blanket non-functional attribute; functional requirements aren’t typically described as optional or untestable, since they define verifiable behaviors the system must exhibit; and non-functional requirements cover more than just user interface layout, including performance, security, availability, scalability, and other quality attributes.

Functional requirements specify the tasks the system must perform. They describe the concrete functions, features, and behaviors the system must deliver in response to user actions or business rules. Non-functional requirements describe how the system performs those tasks, focusing on attributes like performance, reliability, security, usability, and maintainability. The option is best because it clearly captures the primary distinction: it states what the system must do, not how it should be constrained or how well it should run.

The other statements don’t fit because data models are design choices about structure and storage, not a blanket non-functional attribute; functional requirements aren’t typically described as optional or untestable, since they define verifiable behaviors the system must exhibit; and non-functional requirements cover more than just user interface layout, including performance, security, availability, scalability, and other quality attributes.