Understanding Functional and Non-Functional Requirements in Software Development

Understanding Functional and Non-Functional Requirements in Software Development

To make a successful product, both functional and non-functional requirements is essential in the software development. Together, these two requirements serve different purposes of the software that meets user needs and performs well under expected conditions.

What Are Functional Requirements?

The functional requirements will describe, what exactly the systems should do. The functions, features and operations that the software support will be specified by it. And also, these requirements directly tied to the users interaction and business processes.

Examples of Functional Requirements:

  • User Authentication: The system must allow users to log in with a username and password.
  • Data Management: Users should be able to create, read, update, and delete records in a database.
  • Payment Processing: The software must process credit card payments securely.

Functional Requirements are often documented using:

  • Use Cases: Descriptions of how users will interact with the system.
  • User Stories: Brief statements that describe a feature from an end-user perspective.
  • System Requirements Specifications (SRS): Detailed documentation of all functional requirements.

What Are Non-Functional Requirements?

This particular non-functional requirements define how the system performs the certain level of functions. The main focus of them is on system quality attributes and operational capabilities ensuring that the software runs efficiently and effectively.

Examples of Non-Functional Requirements:

  • Performance: The system should handle 10,000 transactions per second.
  • Usability: The interface should be intuitive and easy to navigate for users.
  • Reliability: The system must have an uptime of 99.9%.
  • Security: Data must be encrypted at rest and in transit.
  • Scalability: The system should support an increasing number of users without performance degradation.

Non-functional requirements are often categorized into:

  • Performance Requirements: Related to the speed and responsiveness of the system.
  • Security Requirements: Ensuring the system is protected against threats.
  • Usability Requirements: How easy it is for users to interact with the system.
  • Reliability Requirements: Ensuring the system is dependable and consistent.
  • Maintainability Requirements: How easy it is to update and fix the system.

Why Both Requirements Are Important

Balance: Both types of requirements are crucial. Functional requirements ensure the system does what it’s supposed to do, while non-functional requirements ensure it does so efficiently and reliably.

User Satisfaction: Meeting functional requirements ensures that the user’s needs are met. Addressing non-functional requirements enhances the user experience by making the software reliable, fast, and easy to use.

Quality Assurance: Non-functional requirements are key to ensuring the software’s quality. They help in setting performance benchmarks and reliability standards.

How to Gather Requirements

  1. Stakeholder Interviews: Discuss needs and expectations with users, clients, and other stakeholders.
  2. Surveys and Questionnaires: Collect input from a broader audience to understand user requirements.
  3. Document Analysis: Review existing documentation to identify required functionalities.
  4. Workshops: Conduct collaborative sessions with stakeholders to gather and refine requirements.
  5. Prototyping: Create prototypes to visualize and validate requirements early in the development process.

Documenting Requirements

  1. Use Clear and Concise Language: Avoid ambiguity by being specific and straightforward.
  2. Prioritize Requirements: Rank requirements based on their importance and impact on the project.
  3. Use Diagrams and Models: Visual aids like flowcharts, wireframes, and UML diagrams help clarify complex requirements.
  4. Maintain Traceability: Trace each requirement back to its source and link it to related requirements and design elements.
  5. Regular Reviews and Updates: Continuously review and update requirements as the project evolves to ensure they remain relevant and accurate.


Knowing and understanding the accurate both functional and non-functional requirements is critical for the success of any software development project. Functional requirements will ensure that the software performs the necessary tasks, while non-functional requirements guarantee that it performs well under all conditions. Balancing these requirements, teams can develop high-quality software that meets the needs of the user and stands up to the real-world demands. For expert guidance, contact the Krify team.

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