Software Engineering - Old Questions

8. What do you mean by functional and non-functional requirements? Explain.

Functional Requirements

Functional requirements are the statements of services the system should provide, how the system should react to particular input, and how the system should behave in particular situation. The functional requirements for a system should describe what the system do. These requirements depend on the type of software being developed, the expected users of the software and the general approach taken by the organization when writing requirements. Each high level functional requirement may involve several interactions or dialogues between the system and the outside world. There are many ways of expressing functional requirements for e.g., natural language, a structured or formatted language with no rigorous syntax and formal specification language with proper syntax.

Non-Functional Requirements

Non-functional requirements are the requirements that are not directly concern with the specific function of the system. They define system properties and constraints like readability, response time and storage requirements. It describes how the system will do it. The process of specifying non-functional requirements requires the knowledge of functionality of system, as well as the knowledge of context within which the system will operate.