What are functional and nonfunctional requirements?

In the context of software engineering and system development, both functional and nonfunctional requirements play crucial roles in defining the characteristics and behavior of a system. Here are the definitions and explanations for both:

1. Functional Requirements:
   • Definition: Functional requirements specify what the system should do. They define specific behavior or functions that the system should exhibit, often described in terms of services, tasks, or operations that the system must perform.
   • Examples:
     • User authentication: The system should allow users to log in using a username and password.
     • Data validation: The system should validate user input to ensure it meets specified criteria.
     • Report generation: The system should generate monthly sales reports for managers.
   • Key Points:
     • Functional requirements focus on the specific functionalities and features of the system.
     • They describe the interactions between the system and its users or other systems.
2. Nonfunctional Requirements:
   • Definition: Nonfunctional requirements, also known as quality attributes or “ilities,” specify how the system should behave or perform in terms of qualities such as usability, reliability, performance, and security.
   • Examples:
     • Performance: The system should respond to user requests within 2 seconds.
     • Security: The system should encrypt sensitive user data stored in the database.
     • Usability: The user interface should be intuitive and easy to navigate.
   • Key Points:
     • Nonfunctional requirements define system attributes such as performance, reliability, security, and scalability.
     • They focus on qualities or characteristics of the system rather than specific functionalities.

Correct Answer: In an interview setting, it’s important to provide clear and concise definitions for both functional and nonfunctional requirements, along with examples to illustrate each concept. Additionally, highlighting the importance of both types of requirements in ensuring the success of a software project is essential. Here’s a concise answer:

“Functional requirements define what the system should do, specifying its specific functionalities or features, such as user authentication or report generation. On the other hand, nonfunctional requirements specify how the system should behave in terms of qualities like performance, security, and usability. For instance, a functional requirement might state that the system should allow users to log in, while a nonfunctional requirement could specify that the system must respond to user requests within a certain timeframe. Both types of requirements are crucial for ensuring the overall effectiveness and quality of the software solution.”