Functional vs non-functional requirements in Software Engineering - Practice Questions

Challenge - 5 Problems

🧠 Conceptual

intermediate

Identify the Functional Requirement

Which of the following is an example of a functional requirement for a banking app?

A The app must allow users to transfer money between accounts.

B The app should load within 2 seconds on a 4G network.

C The app must be available 99.9% of the time.

D The app interface should be easy to navigate for new users.

💡 Hint

Functional requirements describe what the system should do.

Functional requirements specify specific behaviors or functions of the system, such as money transfer. The other options describe qualities or constraints, which are non-functional.

📋 Factual

intermediate

Definition of Non-Functional Requirements

What do non-functional requirements primarily describe in a software system?

A Specific tasks the system must perform.

B The user interface design details.

C The programming language used to build the system.

D The qualities and constraints like performance and security.

💡 Hint

Think about qualities like speed, reliability, and security.

Non-functional requirements describe how the system performs and constraints it must meet, such as speed, security, and usability.

🚀 Application

advanced

Classify Requirements for a Website

Given these requirements for an e-commerce website, classify each as functional (F) or non-functional (NF):

• Users can add items to a shopping cart.
• The website must load within 3 seconds.
• Users can create and manage their accounts.
• The website must be accessible on mobile devices.

Which option correctly pairs the requirements?

A Add to cart - F, Load time - F, Manage accounts - NF, Mobile access - NF

B Add to cart - F, Load time - NF, Manage accounts - F, Mobile access - NF

C Add to cart - NF, Load time - F, Manage accounts - NF, Mobile access - F

D Add to cart - NF, Load time - NF, Manage accounts - F, Mobile access - F

💡 Hint

Functional requirements describe actions users can perform. Non-functional describe qualities like speed and accessibility.

Adding items and managing accounts are functions the system must perform. Loading speed and mobile accessibility are qualities, so non-functional.

🔍 Analysis

advanced

Impact of Non-Functional Requirements

Why are non-functional requirements critical to the success of a software product?

A They describe the marketing strategy for the product.

B They define the core features users interact with directly.

C They ensure the system meets quality standards like reliability and usability.

D They specify the programming language and tools to be used.

💡 Hint

Think about qualities that affect user satisfaction and system stability.

Non-functional requirements ensure the system is reliable, usable, and performs well, which are essential for user satisfaction and product success.

❓ Comparison

expert

Distinguishing Functional and Non-Functional Requirements

Consider the following statements about software requirements:

1. Functional requirements describe what the system should do.
2. Non-functional requirements describe how the system performs its functions.
3. Functional requirements are always measurable.
4. Non-functional requirements can include constraints like security and performance.

Which of these statements are correct?

A Only 1, 2, and 4 are correct.

B Only 1 and 4 are correct.

C Only 2 and 3 are correct.

D All 1, 2, 3, and 4 are correct.

💡 Hint

Consider if functional requirements are always measurable and the role of non-functional requirements.

Statements 1, 2, and 4 are true. Functional requirements describe what the system does. Non-functional describe how it performs and include constraints. Functional requirements are not always measurable.

Practice

1. Which of the following best describes a functional requirement in software engineering?

easy

A. The look and feel of the user interface

B. A measure of how fast the system responds

C. A feature that specifies what the system should do

D. The hardware needed to run the software

Solution

1. Step 1: Understand the definition of functional requirements

   Functional requirements describe specific behaviors or functions the system must perform.

2. Step 2: Match the option to the definition

   A feature that specifies what the system should do states a feature specifying what the system should do, which matches the definition.

3. Final Answer:

   A feature that specifies what the system should do -> Option C

4. Quick Check:

   Functional requirement = What system does [OK]

Hint: Functional = what system does, Non-functional = how it does [OK]

Common Mistakes:

• Confusing functional with non-functional requirements
• Thinking performance is a functional requirement
• Mixing hardware needs with software functions

2. Which of the following is an example of a non-functional requirement?

easy

A. The system must allow users to reset their password

B. The system should respond to user input within 2 seconds

C. The system must save user data to a database

D. The system must support login with username and password

Solution

1. Step 1: Identify non-functional requirements

   Non-functional requirements describe how the system performs, such as speed or reliability.

2. Step 2: Evaluate each option

   The system should respond to user input within 2 seconds specifies response time, which is a performance measure and thus non-functional.

3. Final Answer:

   The system should respond to user input within 2 seconds -> Option B

4. Quick Check:

   Non-functional = performance or behavior [OK]

Hint: Look for speed, usability, or reliability for non-functional [OK]

Common Mistakes:

• Choosing features as non-functional requirements
• Confusing functional actions with performance measures
• Ignoring timing or quality aspects

3. Consider this statement: "The system shall encrypt all user data before saving." What type of requirement is this?

medium

A. Functional requirement

B. Non-functional requirement

C. Neither functional nor non-functional

D. Both functional and non-functional

Solution

1. Step 1: Analyze the statement's action

   Encrypting data is a specific action the system must perform, describing what it does.

2. Step 2: Classify the requirement type

   Since it describes a function (encryption), it is a functional requirement.

3. Final Answer:

   Functional requirement -> Option A

4. Quick Check:

   Encryption = system function = functional [OK]

Hint: If it describes a system action, it's functional [OK]

Common Mistakes:

• Thinking encryption is a performance or quality aspect
• Confusing security features with non-functional requirements
• Selecting 'both' without clear reasoning

4. A software team wrote this requirement: "The system must be user-friendly." What is the main issue with this requirement?

medium

A. It describes a functional requirement incorrectly

B. It is a security requirement

C. It is a hardware requirement, not software

D. It is too vague and not measurable

Solution

1. Step 1: Understand the requirement's nature

   "User-friendly" describes a quality but is subjective and lacks clear criteria.

2. Step 2: Identify the problem

   Requirements must be clear and measurable; this one is vague and cannot be tested easily.

3. Final Answer:

   It is too vague and not measurable -> Option D

4. Quick Check:

   Good requirements = clear + measurable [OK]

Hint: Vague terms mean poor requirements [OK]

Common Mistakes:

• Assuming all non-functional requirements are clear
• Confusing vague qualities with functional features
• Ignoring measurability in requirements

5. A project requires the system to handle 1000 users simultaneously and respond within 1 second. Which combination correctly classifies these requirements?

hard

A. "Handle 1000 users simultaneously" is functional; "respond within 1 second" is non-functional

B. "Handle 1000 users simultaneously" is non-functional; "respond within 1 second" is functional

C. Both are functional requirements

D. Both are non-functional requirements

Solution

1. Step 1: Analyze "handle 1000 users simultaneously"

   This describes a specific system function to support multiple users at once, which is a functional requirement.

2. Step 2: Analyze "respond within 1 second"

   This describes a performance measure, how fast the system reacts, so it is non-functional.

3. Final Answer:

   "Handle 1000 users simultaneously" is functional; "respond within 1 second" is non-functional -> Option A

4. Quick Check:

   Function = what system does; Performance = how system performs [OK]

Hint: Capacity = functional; speed = non-functional [OK]

Common Mistakes:

• Classifying capacity as non-functional
• Mixing performance with system capabilities
• Ignoring the difference between function and quality