Functional Requirement & Non-Functional Requirements

A functional requirement defines a function that a system or system component must be able to perform. Probably the easiest way to explain ‘non-functional’ requirements is that they specify all the remaining requirements not covered by the functional requirements. Non-functional requirements specify the system’s ‘quality characteristics’ or ‘quality attributes’. Requirements also known as quality. Two products could have the same functions but their attributes can make them entirely different products. A Rolls Royce has more or less the same functionality as a Lada but many different attributes!