1-mark questions
About 6 × 1 mark · about 5 minutes in all
Multiple choice, tick boxes and one-word answers.
Assesses: AO1, AO2 (the split varies by question)
Marked: one mark for each correct point
Computer Science exam guide
Cambridge OCR GCSE (9–1) Computer Science (J277). Two written papers, each 80 marks in 1 hour 30 minutes and half of the GCSE, with no calculator. Paper 1 is on computer systems and ends with one 8-mark extended response. Paper 2 is on algorithms and programming, in two sections: Section A in any clear form, and Section B in Exam Reference Language or a programming language such as Python.
Paper 1: Computer systems
1 hour 30 minutes · 80 marks · 50% of the GCSE
Sections 1.1 to 1.6: systems architecture, memory and storage, networks, network security, systems software, and the impacts of digital technology. No calculator: show the working of any calculation. Every question must be answered, and the 8-mark question is marked with an asterisk (*).
Short and medium answers, then the extended response (80 marks)
Some short answers are calculations, such as a file size or a conversion, marked a step at a time.
2-mark questions
About 8 × 2 marks · about 16 minutes in all
State… / Identify… / Describe… / Explain… / Give one advantage…
Assesses: AO1, AO2 (the split varies by question)
Marked: one mark for each correct point
3-mark questions
About 2 × 3 marks · about 6 minutes in all
State… / Identify… / Describe… / Explain… / Give one advantage…
Assesses: AO1, AO2 (the split varies by question)
Marked: one mark for each correct point
Paper 1 exam skills · also: Units of data, Binary numbers, Images, Sound
4-mark questions
About 7 × 4 marks · about 28 minutes in all
State… / Identify… / Describe… / Explain… / Give one advantage…
Assesses: AO1, AO2 (the split varies by question)
Marked: one mark for each correct point
5-mark questions
About 2 × 5 marks · about 10 minutes in all
State… / Identify… / Describe… / Explain… / Give one advantage…
Assesses: AO1, AO2 (the split varies by question)
Marked: one mark for each correct point
6-mark questions
6 marks · about 6 minutes
State… / Identify… / Describe… / Explain… / Give one advantage…
Assesses: AO1, AO2 (the split varies by question)
Marked: one mark for each correct point
Extended response (*)
8 marks · about 12 minutes
Discuss… / Evaluate…
Assesses: AO2
Marked: The extended response (8 marks)
Paper 2: Computational thinking, algorithms and programming
1 hour 30 minutes · 80 marks · 50% of the GCSE
Sections 2.1 to 2.5: algorithms, programming fundamentals, robust programs, Boolean logic, and languages and IDEs. No calculator. All the code in the paper is printed in OCR Exam Reference Language.
Section A: concepts and algorithms (50 marks) (50 marks)
Answers can be in any clear form: pseudocode, a flowchart, bullet points, plain English, Exam Reference Language or Python. The logic matters, not the syntax. About 50 minutes.
1-mark questions
About 5 × 1 mark · about 5 minutes in all
Multiple choice, tick boxes and one-word answers.
Assesses: AO1, AO2 (the split varies by question)
Marked: one mark for each correct point
2-mark questions
About 3 × 2 marks · about 6 minutes in all
Short answers on the concepts, and completing, correcting or writing algorithms in any form.
Assesses: AO1, AO2, AO3 (the split varies by question)
Marked: one mark for each correct point
3-mark questions
About 4 × 3 marks · about 12 minutes in all
Short answers on the concepts, and completing, correcting or writing algorithms in any form.
Assesses: AO1, AO2, AO3 (the split varies by question)
Marked: one mark for each correct point
4-mark questions
About 4 × 4 marks · about 16 minutes in all
Short answers on the concepts, and completing, correcting or writing algorithms in any form.
Assesses: AO1, AO2, AO3 (the split varies by question)
Marked: one mark for each correct point
5-mark questions
5 marks · about 5 minutes
Short answers on the concepts, and completing, correcting or writing algorithms in any form.
Assesses: AO1, AO2, AO3 (the split varies by question)
Marked: one mark for each correct point
6-mark questions
6 marks · about 6 minutes
Short answers on the concepts, and completing, correcting or writing algorithms in any form.
Assesses: AO1, AO2, AO3 (the split varies by question)
Marked: one mark for each correct point
Section B: design, write, test and refine (30 marks) (30 marks)
Questions marked as needing it must be answered in OCR Exam Reference Language or a high-level language such as Python: pseudocode and plain English get no marks there, though minor syntax errors aren't penalised. Design questions can be answered in English, pseudocode or a flowchart, and test questions with test data, test plans and trace tables. About 40 minutes.
Design
4 marks · about 5 minutes
Design a solution: identify inputs, outputs and processes; choose data types; plan.
Assesses: AO3
Marked: one mark for each correct point
Paper 2 exam skills · also: Programming projects, Exam Reference Language
Write
6 marks · about 8 minutes
Write a program or sub-program in Exam Reference Language or Python.
Assesses: AO3
Marked: one mark for each correct point
Paper 2 exam skills · also: Programming projects, Exam Reference Language
Write a longer program
8 marks · about 11 minutes
Write a program or sub-program in Exam Reference Language or Python.
Assesses: AO3
Marked: one mark for each correct point
Paper 2 exam skills · also: Programming projects, Exam Reference Language
Test
6 marks · about 8 minutes
Give test data, a test plan or a trace table.
Assesses: AO3
Marked: one mark for each correct point
Paper 2 exam skills · also: Programming projects, Exam Reference Language
Refine
6 marks · about 8 minutes
Improve or correct a given program.
Assesses: AO3
Marked: one mark for each correct point
Paper 2 exam skills · also: Programming projects, Exam Reference Language
Suggested minutes are a guide: about a mark a minute, saving time on the 1-mark questions for Paper 1's 8-mark answer, and following OCR's advice of about 50 minutes on Paper 2's Section A and 40 on Section B. The numbers of each size of question are from the June 2025 papers, and change from year to year; Section B is laid out as the app's practice sets, one scenario through design, write, test and refine.
Assessment objectives
What examiners give marks for. Each question tests one or more of these.
| AO | What it means | Share of the GCSE | Assessed in |
|---|---|---|---|
| AO1 | Know and understand computer science: the key ideas, terms and principles, such as what each part of the CPU does. | 30% | Paper 1: 1-mark questions, 2-mark questions, 3-mark questions, 4-mark questions, 5-mark questions, 6-mark questions; Paper 2: 1-mark questions, 2-mark questions, 3-mark questions, 4-mark questions, 5-mark questions, 6-mark questions |
| AO2 | Apply that knowledge and understanding: use it in a new situation, such as choosing storage for a scenario or working out a file size. | 40% | Paper 1: 1-mark questions, 2-mark questions, 3-mark questions, 4-mark questions, 5-mark questions, 6-mark questions, Extended response (*); Paper 2: 1-mark questions, 2-mark questions, 3-mark questions, 4-mark questions, 5-mark questions, 6-mark questions |
| AO3 | Analyse problems and solve them computationally: make reasoned judgements, and design, write, test and refine programs. | 30% | Paper 2: 2-mark questions, 3-mark questions, 4-mark questions, 5-mark questions, 6-mark questions, Design, Write, Write a longer program, Test, Refine |
Levels
Examiners place an answer in a level, then choose a mark within it. The key words show what each level rewards.
The extended response (8 marks)
| Level | Marks | Key words | What it looks like |
|---|---|---|---|
| 3 | 6–8 | Thorough, consistent, well-developed | Thorough, accurate knowledge of a wide range of points, applied to the context all the way through. Both sides are weighed up, and the line of reasoning is clear and logically organised. |
| 2 | 3–5 | Reasonable, mostly applied | Reasonable knowledge of a range of points, mostly applied to the context, though some are underdeveloped or opportunities are missed. There's a line of reasoning with some structure. |
| 1 | 1–2 | Basic, limited | Basic knowledge, with some mistakes and little application to the context; points are asserted rather than supported, in an unstructured answer. |
Command words
The word that starts a question tells you what to do.
| Command words | What to do |
|---|---|
| State, give, identify, what | A short answer, such as a name or a value, with no explanation. |
| List, outline | Several brief points, or a short summary, without detail. |
| Define | The exact meaning of a term. |
| Describe, how | Say what something is like, or what happens, in detail. |
| Explain | Give reasons: say why or how, often with 'because' or 'so'. |
| Compare | Similarities and differences, mentioning both things in every point. |
| Justify | Give reasons that support your answer or choice. |
| Discuss, evaluate, analyse | Weigh up points on more than one side, such as strengths against limitations, and reach a supported judgement: the 8-mark question uses these. |
| Calculate, show, solve, convert | Work it out, writing every step: each step can earn a mark. |
| Complete, add, tick, order, label, annotate, draw | Fill in, choose or draw what's asked, such as a truth table, a trace table or a logic circuit. |
| Design | Plan a solution: its inputs, processes and outputs, or a structure diagram. |
| Write, rewrite, refine | Write code or an algorithm; write it again to improve it; or make it more efficient, fix it or add to it. |