What Are Functional Requirements?
In software development, functional requirements determine the functions an entire application or just one of its components should perform. A function consists of three steps: data input – system behavior – data output. It can calculate, manipulate data, carry out business processes, establish user interaction, or do any other tasks.
In other words, a functional requirement is WHAT an application must or must not do after some data input.
Functional requirements are important as they show software developers how the system is intended to behave. If the system doesn’t meet functional requirements it means that it doesn’t work properly.
What Are Non-Functional Requirements?
Non-functional requirements determine the performance standards and quality attributes of software, e.g. system usability, effectiveness, security, scalability, etc.
While functional requirements determine what the system does, non-functional requirements describe HOW the system does it. For example, a web application must handle more than 15 million users without any decline in its performance, or a website must not load more than 3 seconds.
If an app doesn’t meet non-functional requirements, it continues to perform its basic functions, however, it won’t be able to provide a great user experience.
Non-functional requirements are important as they help software developers to define the system abilities and constraints that are essential for developing high-quality software. Therefore, non-functional requirements are as important as functional requirements for successful product adoption.
Why Is the Difference Between Functional and Non-Functional Requirements Important?
Well-defined functional and non-functional requirements help software developers to build the product that exactly corresponds to the client’s needs. However, is it really necessary to know the difference between functional and non-functional requirements?
The main reason to know the difference between functional and non-functional requirements is that they define the scope of work for a project. Software developers need to keep up with this scope to develop an application within its timeframe and budget.