How to Answer Computer Science Exam Questions — A Guide to Command Words

One of the most common reasons students lose marks in Computer Science exams is not because they don’t know the answer — it’s because they misread the command word and write the wrong type of answer.

A “state” question expects one fact. Writing two paragraphs earns you one mark and wastes three minutes.

An “evaluate” question expects advantages, disadvantages and a conclusion. Writing one advantage scores 1 out of 6.

This guide explains exactly what each command word means, how many marks to aim for per point, and shows you the difference between a weak and strong answer — with real Computer Science examples.

---

Why command words matter

Every question in an AQA, OCR or Cambridge Computer Science exam begins with a command word. The examiners choose these words deliberately to tell you:

1. How much to write — one word, one sentence, or several paragraphs?
2. What type of answer — facts, reasons, comparisons, or a judgement?
3. How many marks — the mark allocation tells you how many points are needed

Golden rule: match your answer to the command word AND the mark allocation. If a question says “explain [2 marks]”, you need one explained point. If it says “evaluate [8 marks]”, you need multiple arguments and a conclusion.

---

STATE / GIVE / IDENTIFY / NAME

What it means: Give a brief, direct factual answer. No explanation, no reasoning. One or two words or a short phrase.

Marks: Usually 1 mark per point. If it says “state two”, give exactly two — not one, not three.

How much to write: One line per mark.

---

Question: State two characteristics of a LAN. [2]

❌ Weak answer:

“A LAN is a network used in schools and offices. It connects all the computers together so they can share files and printers and communicate with each other.”

This is far too long and doesn’t clearly identify two distinct characteristics. The examiner has to hunt for the points.

✅ Strong answer:

1. A LAN covers a small geographical area such as a single building or site.
2. A LAN is typically owned and managed by one organisation.

Two clear points, one per line. Done.

---

Question: Name the register that holds the address of the next instruction to be fetched. [1]

❌ Weak answer:

“The Program Counter stores the next address that needs to be fetched from memory so that the CPU knows where to go next in the program.”

Correct, but far too long for a 1-mark name question.

✅ Strong answer:

Program Counter (PC)

---

DEFINE

What it means: Give a precise, technical meaning of a specific term. More than just “stating” — you need to capture what makes the term distinct.

Marks: Usually 1–2 marks. A definition mark scheme often has a “correct definition” worth 1 mark and “with example” worth the second mark.

How much to write: One to two sentences maximum.

---

Question: Define the term ‘abstraction’ in the context of computational thinking. [2]

❌ Weak answer:

“Abstraction means simplifying things.”

Too vague. Any concept could be described as “simplifying things”.

✅ Strong answer:

Abstraction is the process of removing unnecessary or irrelevant detail from a problem [1], focusing only on the information needed to solve it — for example, a map abstracts away the texture of the road surface but keeps the routes between locations [1].

---

DESCRIBE

What it means: Give details of what something is, how it works, or what it does. More than just naming — you need features, steps or characteristics. But you don’t need to say why.

Marks: Typically 2–4 marks. Aim for one clear point per mark.

How much to write: Several sentences; use bullet points or numbered steps if describing a process.

---

Question: Describe how a cache memory works. [3]

❌ Weak answer:

“Cache is a type of memory that makes the computer faster.”

This only earns 1 mark at most — it’s barely more than a name.

✅ Strong answer:

Cache is a small, fast memory located between the CPU and main RAM [1]. When the CPU needs data, it checks the cache first — if the data is there (a cache hit), it is returned very quickly [1]. If the data is not in the cache (a cache miss), it is fetched from the slower RAM and then stored in the cache for future use [1].

Three distinct points, each earning a mark.

---

Question: Describe the steps of the Fetch stage of the FDE cycle. [3]

✅ Strong answer:

1. The address held in the Program Counter (PC) is copied to the Memory Address Register (MAR). [1]
2. The instruction stored at that memory address is retrieved and copied to the Memory Data Register (MDR). [1]
3. The PC is incremented to point to the next instruction. [1]

Using a numbered list makes it clear and easy to mark. Include register names — the mark scheme specifically rewards them.

---

EXPLAIN

What it means: State a point AND give a reason, cause or consequence. The keyword is why or how. “Because” is your best friend.

Marks: Usually 2–4 marks. An explained point = fact + reason = 2 marks. An unexplained fact scores just 1.

How much to write: One or two sentences per mark pair — fact + “because/therefore/this means that”.

---

Question: Explain why binary search is more efficient than linear search for large sorted datasets. [2]

❌ Weak answer:

“Binary search is faster.”

This is an assertion with no explanation. 0 marks.

❌ Another weak answer:

“Binary search has a time complexity of O(log n) and linear search has O(n).”

Better — but still no explanation of why or what this means in practice.

✅ Strong answer:

Binary search halves the remaining search space with each comparison [1], so for a list of 1,024 items it takes at most 10 comparisons rather than up to 1,024 for linear search [1].

Fact + consequence = full marks.

---

Question: Explain why virtual memory can slow down a computer. [2]

✅ Strong answer:

When RAM is full, the OS uses hard drive space as virtual memory [1]. Because hard drives are far slower to access than RAM, retrieving data from virtual memory takes significantly longer, causing the overall system to slow down [1].

---

Question: Explain two advantages of using a compiler rather than an interpreter. [4]

Advantage 1: The compiled program can be run without the compiler being present [1], which means it can be distributed to users who do not have a development environment installed [1].

Advantage 2: A compiled program typically runs faster than an interpreted one [1], because the translation to machine code happens once at compile time rather than line by line during execution [1].

Each advantage: one fact + one reason = 2 marks each.

---

COMPARE

What it means: Identify both similarities AND differences between two things. A comparison that only lists differences scores half marks. Use comparative language (“whereas”, “in contrast”, “both”, “however”).

Marks: Usually 4–6 marks. Aim for 2–3 points of comparison.

How much to write: A paragraph, or a short structured response using “both / whereas / however”.

---

Question: Compare TCP and UDP as transport layer protocols. [4]

❌ Weak answer:

“TCP is reliable and UDP is not. TCP is used for web browsing and UDP is used for streaming. TCP has error checking and UDP doesn’t.”

Three differences, but no similarities and no comparison language. Also slightly thin on explanation.

✅ Strong answer:

Both TCP and UDP are transport layer protocols that break data into segments for transmission [1]. However, TCP is connection-oriented — it establishes a connection before transmitting and guarantees reliable, ordered delivery with error checking and retransmission [1], whereas UDP is connectionless and offers no delivery guarantee, making it faster but less reliable [1]. TCP is therefore preferred for web browsing and file transfers where accuracy is critical, while UDP is better suited to video streaming and online gaming where speed matters more than occasional lost packets [1].

Two similarities + two differences, with context = 4 marks.

---

JUSTIFY

What it means: Give reasons to support a choice, decision or recommendation. You’re defending a position. Include reasons why your choice is better, often referencing the specific scenario.

Marks: Usually 2–4 marks. One reason + development per 2 marks.

---

Question: A small business needs to store large video files. Justify the use of an HDD rather than an SSD. [2]

✅ Strong answer:

HDDs provide a much higher storage capacity per pound than SSDs [1], which is important for a small business storing large video files on a limited budget — an HDD would allow them to store significantly more footage for the same cost [1].

The justification links the technical point to the specific scenario (budget, video files, small business).

---

EVALUATE

What it means: Consider the advantages AND disadvantages (or multiple perspectives) of something, then reach a conclusion or judgement. This is the highest-order command word and requires the most structured response.

Marks: Usually 6–9 marks. Aim for 2–3 advantages, 2–3 disadvantages, and a conclusion.

How much to write: Several paragraphs. Use PEE (Point, Evidence, Explanation) for each argument.

---

Question: Evaluate the use of open source software compared to proprietary software. [6]

✅ Strong answer structure:

Advantages of open source:

Open source software is free to use, which significantly reduces licensing costs for organisations [P]. A school, for example, could deploy LibreOffice on hundreds of computers with no per-seat licensing fees [E], saving thousands of pounds annually that could be spent on hardware or support [E].

The source code is publicly available, meaning security vulnerabilities can be spotted and fixed by the global community more quickly [P]. This can result in faster patch releases than proprietary alternatives [E].

Disadvantages of open source:

However, open source software often lacks dedicated customer support [P]. If a critical bug affects a business operation, they may have to rely on community forums rather than a professional support team, potentially causing costly downtime [E].

Furthermore, there may be compatibility issues with proprietary formats [P], for instance, an open source office suite may not render complex Microsoft Word documents perfectly, causing problems when sharing files with clients [E].

Conclusion:

Overall, open source software is a strong choice for cost-sensitive organisations with technical staff capable of managing it. For businesses that rely on specialist software or require guaranteed support contracts, proprietary software may be more appropriate despite the higher cost.

Why this scores full marks: multiple arguments each side, specific examples, and a conclusion that makes a judgement.

---

DISCUSS

What it means: Similar to evaluate, but often more open-ended. Present different viewpoints, arguments for and against. A conclusion is expected but may be less definitive than evaluate.

Marks: 6–9 marks, same structure as evaluate.

Tip: “Discuss” is common for ethical and social issues topics. Always acknowledge counterarguments.

---

Question: Discuss the ethical issues surrounding the collection of personal data by social media companies. [6]

Structure to aim for:

1. Argument in favour (benefits to users — targeted content, personalised experience)
2. Counter-argument (privacy concerns, data breaches, selling data to third parties)
3. Second argument in favour (safety — detecting harmful content)
4. Second counter-argument (surveillance capitalism, algorithmic manipulation)
5. Balanced conclusion referring to relevant legislation (GDPR)

---

CALCULATE / SHOW YOUR WORKING

What it means: Perform a numerical calculation. Always show your working — even if your final answer is wrong, you can earn method marks.

Marks: Usually 2–3 marks. One mark often for the method/formula, one for correct substitution, one for correct answer.

---

Question: Calculate the file size of a 640 × 480 pixel image with a colour depth of 24 bits. Give your answer in kilobytes. [3]

✅ Strong answer:

File size = width × height × colour depth [1] = 640 × 480 × 24 = 7,372,800 bits [1] = 7,372,800 ÷ 8 = 921,600 bytes = 921,600 ÷ 1024 = 900 KB [1]

Always write the formula first, then substitute, then calculate step by step. If you write just “900 KB” with no working, you risk scoring 0 if you’ve made an arithmetic error somewhere.

---

TRACE / COMPLETE THE TRACE TABLE

What it means: Follow the execution of the given code line by line, recording the value of each variable at each step.

Marks: Usually 1 mark per correctly completed row or column.

---

Question: Trace the following code and complete the trace table.

total = 0
for i in range(1, 5):
    total = total + i
print(total)

i	total
—	0
1	1
2	3
3	6
4	10

Output: 10

Tips:

• Go through the code exactly as Python would — don’t skip steps
• Update one cell at a time; don’t try to do multiple iterations in your head
• Cross out and rewrite rather than scribble — examiners must be able to read it

---

WRITE CODE / DESIGN AN ALGORITHM

What it means: Write working code (usually Python or pseudocode) that solves the described problem. You’re being tested on programming ability, not just knowledge.

Marks: Usually 4–8 marks, awarded for: correct logic, correct syntax, appropriate use of constructs (loops, selection, functions).

Tips:

• Write comments to explain your thinking — the examiner can give credit even if a line has a minor syntax error
• Indent correctly — Python syntax errors from indentation lose marks
• Test your code mentally with an example before you finish

---

Question: Write a Python function that takes a list of integers and returns the largest value. Do not use the built-in max() function. [4]

✅ Strong answer:

def find_largest(numbers):
    largest = numbers[0]          # start with first element [1]
    for num in numbers:           # loop through all elements [1]
        if num > largest:         # compare each to current largest [1]
            largest = num
    return largest                # return the result [1]

Each mark corresponds to a key programming construct: initialisation, loop, comparison, return.

---

DRAW / LABEL / COMPLETE THE DIAGRAM

What it means: Produce or complete a visual representation — logic circuit, flowchart, state transition diagram, network diagram, etc.

Marks: Awarded per correct component. Diagrams must be neat and clearly labelled.

Tips:

• Use a ruler for straight lines
• Label all components (gate names, state names, node labels)
• Check arrows point the correct direction

---

Quick reference summary

Command word	What you need	Marks per point
State / Give / Name / Identify	One fact, no explanation	1 mark per point
Define	Precise technical meaning	1–2 marks
Describe	Features, steps or characteristics	1 mark per clear point
Explain	Fact + reason (use “because”)	2 marks per explained point
Compare	Similarities AND differences	1–2 marks per comparison
Justify	Reasons supporting a choice with context	2 marks per justified point
Evaluate / Discuss	Advantages + disadvantages + conclusion	6–9 marks total
Calculate	Show formula → substitution → answer	3 marks (method + working + answer)
Trace	Correct variable values at each step	1 mark per correct row
Write code	Working program with correct constructs	1 mark per key construct

---

The five most common ways students lose easy marks

1. Ignoring the command word — writing an explanation when “state” was asked; writing a list when “evaluate” was asked
2. Not matching answer length to marks — a 6-mark question answered in two lines; a 1-mark question answered in a paragraph
3. Assertions without evidence — “Binary search is better” with no explanation of why or by how much
4. Vague vocabulary — “the computer is faster” instead of “the CPU can access data in fewer clock cycles because…”
5. No conclusion on evaluate/discuss — losing 2 marks for not making a final judgement

---

A template for extended answers (6+ marks)

For any “evaluate”, “discuss” or “assess” question:

Point 1 (for): [Make the argument clearly] Explain: [Why this is significant — use “because/therefore/this means that”] Example: [Specific, relevant example from the scenario or real world]

Point 2 (for): …

Counter-argument 1 (against): [Present the opposing view] Explain: [Why this is a valid concern]

Counter-argument 2 (against): …

Conclusion: “Overall, [position] because [most important reason], although [acknowledge the strongest counter-argument].”

Practice makes perfect. Use the Question Bank on CompSci Tutoring to practise answering exam questions and see how your responses compare to the mark scheme — with instant AI feedback on your answers.