What is a functional requirement?
Refers mainly to the expected function of the product. Product or system features, or what the program does is what the functional requirements are. Definitely it is easier to determine the functional requirements than the non-functional because they are almost obvious.
What is a non-functional requirement?
These requirements refer mainly to the attributes that include performance, security, usability, etc. Developers usually miss these requirements because they focus mainly on the functional requirements. When addressing incorrectly these non-functional requirements, the system actually fails. For example, the lack of usability or performance can lead to frustration or system problems. This is why non-functional requirements are so important for a system to succeed.
To be more precise, in software engineer, functional requirements define the functions of the system, is the description of the feature required. It also includes description of the required functions. Some examples of functional requirements are calculations, technical details, data manipulation and processing.
Non-Functional requirements focus on quality factors and effectiveness. These factors are what give value to the software and make the functional requirements function appropriately.
Sqa.org.uk. (2016). Functional and Non-Functional Requirements. [online] Available at:http://www.sqa.org.uk/e-learning/SDM03CD/page_02.htm [Accessed 13 Sep. 2016].
SearchSoftwareQuality. (2016). Functional vs non-functional requirements, what is the difference?. [online] Available at:http://searchsoftwarequality.techtarget.com/answer/Functional-vs-non-functional-requirements-what-is-the-difference [Accessed 13 Sep. 2016].
