functional requirements

Functional requirements are the desired operations of a program, or system as defined in software development and systems engineering. The systems in systems engineering can be either software electronic hardware or combination software-driven electronics.

Functional requirements are a part of requirements analysis (also known as requirements engineering), which is an interdisciplinary field of engineering that concerns the design and maintenance of complex systems. Functional requirements describe the desired end function of a system operating within normal parameters, so as to assure the design is adequate to make the desired product and the end product reaches its potential of the design in order to meet user expectations.

The requirements in requirement engineering help direct the development of the engineered product. Typically, a functional requirement is a basic functionality or desired behavior documented clearly and quantitatively. Requirements engineering ideas may be applied to more or less complex items. For example, when outlining the functional requirements for a jar, a functional requirement would be that it holds a fluid and have a threaded top for a lid to seal the jam for better preservation. When a product fails functional requirements, it usually means the product is of low quality and possibly entirely useless.

Functional requirements in systems engineering are complemented by technical requirements, which are also known as non-functional requirements. Technical requirements define what is required to deliver the desired function or behavior from a system to a user’s standards. Technical requirements can be performance factors, accessibility, versatility, logging, control and  backup.

Functional requirements may be considered met even when the non-functional requirements are not. This can still mean that the product is unusable, such as in the consideration of performance requirements.