Computer Science units & topics
Tap a unit to see its topics. Every topic has free notes, a diagram, quizzes and flashcards.
GCSE Computer Science revision covers both theory and programming. You need to understand how computers work (hardware, networks, data representation), how to write and trace algorithms, and how to apply computational thinking to solve problems. It's the only GCSE where you need to write actual code in the exam, making it unique among all subjects.
AQA GCSE Computer Science (8525) has two papers. Paper 1 is Computational Thinking and Programming Skills (1 hour 30 minutes, on-screen exam where you write and trace code). Paper 2 is Computing Concepts (1 hour 45 minutes, written exam covering theory). Paper 1 requires you to write Python code, trace algorithms, and debug programs. Paper 2 covers data representation, networks, cybersecurity, and ethical issues.
Tap a unit to see its topics. Every topic has free notes, a diagram, quizzes and flashcards.
A simple, proven loop that works for every topic on this page — and beats re-reading your notes every time.
Whether your exam is on-screen or on paper, you need to write code without syntax highlighting or error messages. Practise writing short programs on paper: a function that validates an email address, a loop that finds the largest number in a list, a program that reads a CSV file. Then desk-check your code by hand to find bugs.
Data representation questions appear on every GCSE Computer Science paper. Practise converting between binary, denary, and hexadecimal until it's automatic. Also practise binary addition (including overflow), binary shifts, and calculating image file sizes from resolution and colour depth. These are procedural skills — pure practice makes them reliable marks.
Don't just memorise what bubble sort does — trace through it with a specific list of numbers, step by step, using a trace table. The exam will ask you to trace an algorithm, show the state of variables at each step, or predict the output. If you've only read about the algorithm, you'll struggle. If you've traced it 10 times, you'll be fine.
Theory answers in GCSE Computer Science need precise technical language. 'The CPU processes stuff' gets zero marks. 'The ALU (Arithmetic Logic Unit) performs calculations and logical comparisons on data' gets full marks. Mark schemes show you the exact wording examiners expect. Read them before attempting your own answers.
Wherever you are in your GCSEs, here's the best place to pick up Computer Science.
Just starting GCSE content? Begin with the first unit — it underpins almost everything else in the Computer Science course.
Start from the beginningWorking through the course? Follow the units in order and learn one new topic at a time, testing as you go.
Browse all unitsExams approaching? Focus on the high-frequency topics examiners ask most, and drill them with quizzes and past questions.
See top exam topicsPrepWise covers 60 GCSE Computer Science topics across AQA, Edexcel and OCR. Each topic includes revision notes, exam-style questions, and flashcards.
Yes. All 60 topics, 949+ exam-style questions, and 779 flashcards are free during alpha. No card required, no trial period.
PrepWise covers AQA, Edexcel and OCR for GCSE Computer Science. You can select your board during setup and the content, questions, and daily plan adapt to your specification.
GCSE Computer Science tests both theory and programming. The highest-frequency topics are data representation (binary, hex), computer networks (protocols, topologies), algorithms (searching and sorting), programming constructs (sequence, selection, iteration), and Boolean logic. SQL and pseudocode appear regularly in both AQA and OCR papers.
For students and parents — from Year 10 through to exam day
GCSE Computer Science revision covers both theory and programming. You need to understand how computers work (hardware, networks, data representation), how to write and trace algorithms, and how to apply computational thinking to solve problems. It's the only GCSE where you need to write actual code in the exam, making it unique among all subjects.
AQA GCSE Computer Science (8525) has two papers. Paper 1 is Computational Thinking and Programming Skills (1 hour 30 minutes, on-screen exam where you write and trace code). Paper 2 is Computing Concepts (1 hour 45 minutes, written exam covering theory). Paper 1 requires you to write Python code, trace algorithms, and debug programs. Paper 2 covers data representation, networks, cybersecurity, and ethical issues.
The biggest challenge in GCSE Computer Science revision is that it combines a theoretical subject (how computers work) with a practical skill (programming). Students who are good at programming sometimes struggle with the binary and networking theory, while students who learn the theory well may struggle to write code under exam conditions. Both skills need regular practice.
GCSE Computer Science specifications differ between boards, particularly in programming language requirements and practical assessment. Make sure your GCSE Computer Science revision covers the right content for your board.
Two papers: Paper 1 is an on-screen exam testing programming skills in Python (or another language your school chose). Paper 2 is a written exam covering theory. AQA's on-screen exam is distinctive — you actually write and test code during the exam. The non-exam assessment (NEA) is a programming project completed in class but does not count toward the final grade (it's a requirement to sit the exam).
Two papers: Computer Systems (1 hour 30 minutes) and Computational Thinking, Algorithms and Programming (1 hour 30 minutes). OCR covers similar theory but organises topics differently. Their Paper 2 includes pseudocode questions and algorithm design. The programming project is also a non-exam assessment requirement. OCR tends to test more structured algorithm design questions.
Two papers: Principles of Computer Science and Application of Computational Thinking. Edexcel includes more on emerging technologies, artificial intelligence, and environmental impact in their theory paper. Their programming questions use flowcharts and pseudocode alongside actual code. The exam format is entirely written (not on-screen like AQA).
A complete gcse computer science revision plan from Year 10 through to the final exam — with advice for students and tips for parents at every stage.
GCSE Computer Science revision starts with getting comfortable with programming. Write code every week — even simple programs. Practise converting between binary, hexadecimal, and denary until it's automatic. Learn the key data representation concepts: binary addition, binary shifts, character encoding (ASCII/Unicode), and image representation (pixels, colour depth, resolution). These are fundamental and come up on every exam. Parents: if your child has a computer at home, encourage them to code outside class. Free platforms like Replit let them practise Python without installing anything.
Year 11 covers networks, cybersecurity, algorithms, and more advanced programming. Start practising tracing algorithms by hand — follow the code line by line, tracking variable values in a trace table. This skill is worth significant marks in the exam. Learn the common sorting algorithms (bubble sort, merge sort, insertion sort) and searching algorithms (linear search, binary search) well enough to trace them, write them, and compare their efficiency.
Audit your GCSE Computer Science knowledge across both papers. For Paper 1, can you write Python code for: input validation, string manipulation, file handling, arrays/lists, and functions? For Paper 2, can you convert between number bases, explain network protocols, describe cybersecurity threats, and discuss ethical issues? Any gaps here need focused revision. Practise SQL queries — SELECT, FROM, WHERE — as these commonly appear and are free marks if you know the syntax.
Your Computer Science mock will reveal whether you can code under pressure. If you froze on programming questions, you need more practice writing code by hand (or on-screen under timed conditions). If you lost marks on theory, identify which topics — data representation and networks are usually the weakest areas. After mocks, spend time on Boolean logic (AND, OR, NOT truth tables and logic gates) — it's a topic students often skip but it appears on every Paper 2.
Do full GCSE Computer Science past papers. For Paper 1, practise writing programs on paper — in the exam you may need to write code without running it, so you need to desk-check your own work. For Paper 2, focus on the topics worth the most marks: data representation (binary, hex, ASCII, image/sound representation), network hardware and protocols, and cybersecurity (types of attack, prevention methods). Make sure you can explain the fetch-decode-execute cycle and the purpose of each CPU component.
Final GCSE Computer Science revision should cover both theory recall and programming fluency. Test yourself on: binary/hex conversions, truth tables, network topologies, SQL syntax, and common algorithms. For programming, write small programs daily — input validation loops, search functions, file read/write operations. Don't forget ethical and environmental topics — these are often the last questions on Paper 2 and students frequently leave them blank or write vaguely.
Whether your exam is on-screen or on paper, you need to write code without syntax highlighting or error messages. Practise writing short programs on paper: a function that validates an email address, a loop that finds the largest number in a list, a program that reads a CSV file. Then desk-check your code by hand to find bugs.
Data representation questions appear on every GCSE Computer Science paper. Practise converting between binary, denary, and hexadecimal until it's automatic. Also practise binary addition (including overflow), binary shifts, and calculating image file sizes from resolution and colour depth. These are procedural skills — pure practice makes them reliable marks.
Don't just memorise what bubble sort does — trace through it with a specific list of numbers, step by step, using a trace table. The exam will ask you to trace an algorithm, show the state of variables at each step, or predict the output. If you've only read about the algorithm, you'll struggle. If you've traced it 10 times, you'll be fine.
Theory answers in GCSE Computer Science need precise technical language. 'The CPU processes stuff' gets zero marks. 'The ALU (Arithmetic Logic Unit) performs calculations and logical comparisons on data' gets full marks. Mark schemes show you the exact wording examiners expect. Read them before attempting your own answers.
These come straight from examiner reports — the mistakes that cost students marks every year.
Writing pseudocode in a real programming language syntax, or writing code when pseudocode is asked for. Read the question: 'Write an algorithm' usually means pseudocode, 'Write a program' means actual code.
Forgetting to include data types in trace tables — the examiner wants to see whether a variable holds a string, integer, float, or boolean.
In binary questions, not showing working. Write out the place values (128, 64, 32, 16, 8, 4, 2, 1) every time — it prevents errors and shows method for marks.
In network questions, confusing protocols with hardware. TCP/IP is a protocol (rules), a router is hardware (physical device). Mixing these up loses marks.
Writing vague answers about ethical issues — 'it could be bad for privacy' gets nothing. 'Facial recognition systems collect biometric data without consent, which violates GDPR Article 6 and could enable mass surveillance' gets full marks.
As parents of GCSE students ourselves, we know how hard it is to support revision without being overbearing. Here's what actually helps with gcse computer science revision at home.
GCSE Computer Science is part theory, part practical programming skill. Both need practice. If your child can explain how a network works but can't write a simple Python program, they'll struggle on Paper 1. If they can code but can't do binary conversions, they'll lose marks on Paper 2.
Encourage your child to code outside of class. It doesn't have to be GCSE-related — building a simple game, automating something, or following a tutorial all build the fluency needed for the exam. The key skill is comfort with writing code, not memorising syntax.
Computer Science has a lower pass rate than most GCSEs because it genuinely requires both understanding and skill. Regular practice — even 15 minutes of coding or 10 binary conversion questions — makes a real difference over time.
If your child is doing the AQA on-screen exam, make sure they've practised coding in the actual exam environment. Ask their teacher if they can access practice papers in the same format — coding on paper vs on-screen feels very different.
60 topics, all aligned to your exam board — learn, quiz and test your way through them.
Start revising free →