Question

What is the difference between functional and nonfunctional requirements and give examples of each?

Answer 1

Requirements analysis is very important method that allows the performance of a system or software project to be evaluated. Requirements are typically categorized into two types: Functional and Non-functional requirements.

Functional Requirements: These are the requirements that the end user explicitly needs as the system 's fundamental facilities. All these functions must be integrated as part of the contract into the framework. They are shown or specified as input, operation and expected output to be provided to the device. In theory, the specifications indicated by the consumer are, unlike the non-functional requirements, directly visible inside the final product.

Non-functional requirements: These are essentially the quality limitations which the system must meet under the Project Agreement. The priority or degree of implementation of these factors varies from one project to another. They are often referred to as non-behavioral requirements.

They basically deal with issues like:

• Portability
• Reliability
• Security
• Maintainability
• Reusability
• Flexibility
• Scalability
• Performance

FUNCTIONAL REQUIREMENTS	NON FUNCTIONAL REQUIREMENTS
The device or component is specified by a functional requirement.	The quality attribute of the software system is specified by a non-functional requirement.
It specifies “What should the software system do?”	It places constraints on “How should the software system fulfill the functional requirements?”
The user shall define the functional requirement.	The non-functional requirement is defined by the technical people, e.g. Architect, technical administrators and software developers.
It is mandatory.	It is not mandatory.
It is captured in use case.	It is captured as a quality attribute.
Defined at a component level.	Applied to a system as a whole.
Helps you check the functionality of the software.	Help you check the software 's performance.
Functional Testing like System, Integration, End to End, API testing, etc are done.	Non-Functional Testing like Performance, Stress, Usability, Security testing, etc are done.
Usually easy to define.	Usually more difficult to define.
Example 1) User authentication when signing into the device. 2) System shutdown in case of a cyber attack. 3) A Verification-email is sent to user whenever he/she registers for the first time on some software system.	Example 1) Emails should be sent with a latency of no greater than 12 hours from such an activity. 2) The processing of each request should be done within 10 seconds 3) The site should load in 3 seconds when the number of simultaneous users are > 10000