Functional requirements specify the inputs, behavior and outputs in a given software system or the components. They may include calculations, methodologies, technical requirements, processes and data manipulation. These specifications define how the system functions and its intentions. The concept may also include nonfunctional requirements or quality requirements, such as performance, security and reliability. However, functional requirements specify the system itself, whereas the nonfunctional requirements specify the system architecture.
When designing a system, the designer/programmer should follow a functional requirement specification document. It should specify:
- The type of data that should be entered.
- The operations performed on each screen.
- The workflows (Illustrations and descriptions).
- User and System Requirements.