What are the two types of requirements in software engineering?

In software engineering, requirements are the foundation of software design and development, describing what a system should do and how it should perform. These requirements are broadly categorized into two types:

1. Functional Requirements

Functional requirements describe the specific features, functions, and tasks that the software must perform to fulfill its intended purpose. They answer the question: "What should the system do?"

Characteristics

• Define specific actions, inputs, and outputs.
• Focus on user interactions and system behaviors.
• Include business rules, calculations, data processing, and user commands.

Examples

• The system must allow users to log in using a username and password.
• The software should generate monthly sales reports in PDF format.
• When a user places an order, the system must send a confirmation email.
• The application should provide search functionality for products by category or keyword.

2. Non-Functional Requirements

Non-functional requirements specify the quality attributes of the system, describing how the system should behave rather than what it should do. They answer the question: "How should the system perform?"

Characteristics

• Focus on system performance, usability, scalability, and reliability.
• Define constraints or benchmarks for the system.
• Impact the user experience and long-term system performance.

Examples

• The system must respond to user actions within 2 seconds (performance).
• The application should support up to 10,000 concurrent users (scalability).
• All data transmissions must be encrypted using industry-standard protocols (security).
• The system should have an uptime of 99.9% (reliability).

Why Both Types Are Important

• Functional requirements ensure the system delivers the expected functionality to users.
• Non-functional requirements ensure the system performs efficiently, securely, and reliably, meeting user satisfaction and operational goals.

Resources for Learning More

For a deeper dive into understanding and documenting requirements, explore Grokking System Design Fundamentals by DesignGurus.io: Learn More. Additionally, their blog Essential Software Design Principles You Should Know Before the Interview provides valuable insights: Read Blog.

By balancing functional and non-functional requirements, software engineers ensure the system is both useful and usable, meeting business goals and user needs effectively.