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GCSE Computer Science revision
Explore GCSE Computer Science through clear explanations, worked examples and an organised topic guide for OCR J277 and AQA 8525 examinations from 2027.
Start with a topic you find difficult. Follow what changes in each worked example, explain the mechanism in your own words, then practise using the notation and command words expected by your exam board.
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Choose your board
OCR GCSE Computer Science J277
Explore computer systems, computational thinking, algorithms and programming for OCR J277. Follow the specification references and distinguish the language used in a question from the Python you use to practise.
Explore OCR J277 topics →Choose your board
AQA GCSE Computer Science 8525 — exams from 2027
Explore algorithms, programming and computing concepts for the AQA 8525 specification assessed from 2027. Topic pages identify the AQA requirements and label useful extensions separately.
Explore AQA 8525 (2027+) topics →Systems architecture
Processor components, CPU registers, performance factors, embedded systems and the fetch-decode-execute cycle.
- The Fetch Cycle
How the CPU collects the next instruction
- Decode and Execute
How an instruction becomes an action
- CPU Performance
Clock speed, cores and cache
- Embedded Systems
Identify the dedicated computer inside a larger device and explain how its inputs, memory, processor and outputs serve that task.
Memory and storage
Primary memory, secondary storage, capacity, units, compression and selecting suitable storage technologies.
- Computer Memory
RAM, ROM and cache inside the computer
- Secondary Storage
How computers keep data without power
- Virtual Memory
What happens when RAM runs out
Data representation
Binary and hexadecimal numbers, text, images, sound, arithmetic and the representation limits of finite data.
- Data Units
From bits and bytes to real storage hardware
- Number Systems and Conversions
Use place value to move accurately between denary, eight-bit binary and hexadecimal without changing the quantity.
- Character Encoding
How characters become binary
- Binary Arithmetic and Shifts
Follow carries and fixed-width bit movement, then check the result using place value and the selected board's requirements.
- Bitmap Image Representation
Read a pixel grid and colour codes, distinguish dimensions from colour depth, and calculate uncompressed image data.
- Digital Sound Representation
See how measurements of a wave become binary samples and how rate, resolution and duration determine uncompressed size.
- Data Compression
Decide what information must survive compression, then apply the methods and calculations required by your exam board.
Networks and protocols
Network types, hardware, topologies, layers, addressing and the protocols that coordinate communication.
- Network Organisation
LANs, WANs, clients and servers
- Network Devices
How data crosses a real network
- Network Identity and Connections
How devices are identified and connected
- Protocol Layers
How data moves through four network layers
- The Web Address Journey
How a URL finds the right server
- How the Internet Works
What happens after you type a URL
- Network Performance
Explain bandwidth, shared demand and bottlenecks using a school network, and choose improvements that address the actual limitation.
Cyber security
Threats, vulnerabilities, social engineering, malicious software and proportionate prevention and detection methods.
- Cyberattack Methods
How attacks enter and what they can change
Algorithms
Decomposition, abstraction, searching, sorting, trace tables and evaluating alternative computational solutions.
- Computational Thinking
Turn a complex problem into a solvable model
- Representing and Tracing Algorithms
Read pseudocode, flowcharts and trace tables as one state story
- Searching Algorithms
Know when and how linear and binary search move
- Sorting Algorithms
Trace comparisons, passes and merges without skipping states
- Comparing and Improving Algorithms
Compare the whole job, including preparation
Programming fundamentals
Variables, selection, iteration, data structures, subprograms, validation, testing and robust program construction.
- Variables, Data Types and Operators
Follow values, types and expressions as program state changes
- Selection and Iteration
Control which statements run and how repetition stops
- Strings, Arrays and Records
Store and update structured collections precisely
- Subprograms and Modular Programs
Build clear interfaces from parameters, local state and returned values
- Files, Data Records and SQL
Move persistent data safely through files, records and queries
- Testing and Defensive Programming
Choose revealing tests and handle unexpected input safely
Boolean logic
Logic gates, truth tables, Boolean expressions and reasoning about combinations of digital conditions.
- Logic Gates and Truth Tables
Turn Boolean gate rules into complete truth-table evidence
- Combined Logic Circuits
Trace intermediate signals before calculating the final output
- Boolean Expressions and Circuit Design
Translate requirements, expressions and circuits without changing their grouping
Software and languages
Operating systems, utilities, translators, language levels and the development tools used to build programs.
- Operating Systems
How software manages the whole computer
- Utility Software
Tools that protect, maintain and optimise
- Programming Language Levels
Distinguish high-level source from machine-specific instructions and justify language characteristics without a coding course.
- Program Translators
Follow source through compilation or interpretation, keep build time separate from running time and understand each tool's limits.
- Integrated Development Environments
Match IDE facilities to editing, translating, running and investigating a program; distinguish tool support from proof of correctness.
Impacts of digital technology
Ethical, legal, cultural, environmental and privacy consequences of developing and using digital systems.
- UK Computer Law and Software Permissions
How law shapes the use of data and software
- Impacts of Digital Technology
Explain concrete benefits and harms for different people, consider privacy and the environment, and reach a supported judgement.
Choose the support you need
Start with an explanation when the mechanism is unclear. Use topic practice to apply it to exam questions, then an original mock to check what you can do independently. The full activities and your saved progress are available in your learner account.
Build your practical programming
Use the theory explanations alongside practical programming. Python courses provide a structured route from first programs to GCSE problems, and the books offer a separate way to study the same skills.
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