Lesson 1 · Study skills
Getting Started
See how algorithms, programming, data, systems, networks and cybersecurity fit together.
Free Lessons -> GCSE / Key Stage 4 -> Computer Science
GCSE Computer Science
GCSE Computer Science lessons
Build confidence with computational thinking, algorithms, programming, data, systems, networks, cybersecurity, databases and computing impacts.
50 lessons availableComplete GCSE sequenceSelf-contained lessons
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Lesson 2 · Algorithms
Computational Thinking
Break problems into parts, ignore irrelevant details, spot patterns and design a solution.
Lesson 3 · Algorithms
Algorithms and Flowcharts
Represent solutions using ordered steps, structured pseudocode and clear flowchart decisions.
Lesson 4 · Algorithms
Trace Tables
Follow an algorithm line by line and record how variables change.
Lesson 5 · Programming
Input, Processing, Output
Separate what a program receives, what it does and what it displays or returns.
Lesson 6 · Programming
Sequence, Selection, Iteration
Use ordered instructions, decisions and loops to control how a program runs.
Lesson 7 · Programming
Variables and Data Types
Store values using clear variable names and choose suitable data types for each value.
Lesson 8 · Programming
Operators and Expressions
Use arithmetic, comparison and logical operators to build expressions in programs.
Lesson 9 · Programming
Boolean Logic
Combine true or false conditions using AND, OR and NOT.
Lesson 10 · Programming
Count-controlled Loops
Use count-controlled loops when the number of repeats is known.
Lesson 11 · Programming
Condition-controlled Loops
Use condition-controlled loops when repetition depends on a true or false test.
Lesson 12 · Programming
Lists, Arrays, Strings
Store multiple values, read indexed positions and handle text as character data.
Lesson 13 · Programming
Subroutines
Split programs into named reusable blocks, and distinguish procedures from functions.
Lesson 14 · Programming
Validation and Verification
Check whether input is sensible and whether copied data matches the original source.
Lesson 15 · Programming
Testing and Debugging
Use test data, expected results and debugging steps to find and fix programming errors.
Lesson 16 · Data representation
Binary and Denary
Convert between denary numbers and binary using powers of two place values.
Lesson 17 · Data representation
Hexadecimal
Use hexadecimal as a compact way to write binary numbers in groups of four bits.
Lesson 18 · Data representation
Binary Arithmetic and Storage
Add binary numbers, recognise overflow and convert between common storage units.
Lesson 19 · Data representation
Character Sets
Explain how computers represent characters using binary codes in character sets.
Lesson 20 · Data representation
Bitmap Images
Describe bitmap images using pixels, resolution, colour depth and file-size calculations.
Lesson 21 · Data representation
Sound Sampling
Explain how analogue sound is sampled and how sample rate and resolution affect quality and file size.
Lesson 22 · Data representation
Compression
Compare lossy and lossless compression and choose the right method for a scenario.
Lesson 23 · Computer systems
CPU Cycle
Describe the role of the CPU and the stages of the fetch-decode-execute cycle.
Lesson 24 · Computer systems
Memory and Storage
Compare RAM, ROM, cache and secondary storage by purpose, speed, capacity and volatility.
Lesson 25 · Computer systems
Embedded Systems
Identify embedded systems and explain how dedicated hardware and software control specific tasks.
Lesson 26 · Computer systems
Operating Systems
Explain core operating system roles and distinguish them from utility software tasks.
Lesson 27 · Computer systems
Translators
Explain why source code must be translated and compare compilers, interpreters and assemblers.
Lesson 28 · Computer systems
Performance Factors
Explain how CPU, memory, storage and software factors combine to affect computer performance.
Lesson 29 · Networks
Network Types
Compare LANs, WANs, client-server, peer-to-peer and common topology ideas.
Lesson 30 · Networks
Network Hardware
Match routers, switches, wireless access points, NICs and transmission media to network roles.
Lesson 31 · Networks
Protocols and DNS
Explain how protocols, IP addressing, DNS and HTTP(S) work together when a web page loads.
Lesson 32 · Networks
Packets and Routing
Describe how data is split into packets, routed across networks and reassembled by the receiving device.
Lesson 33 · Cybersecurity
Cybersecurity Threats
Identify common cybersecurity threats and explain how they can affect users, data and systems.
Lesson 34 · Cybersecurity
Malware
Compare malware types and describe common attack methods such as brute force and denial of service.
Lesson 35 · Cybersecurity
Social Engineering
Explain how attackers manipulate people and how users can spot and reduce phishing risks.
Lesson 36 · Cybersecurity
Authentication
Explain authentication, authorisation and encryption, including why MFA and secure keys matter.
Lesson 37 · Cybersecurity
Security Measures
Choose appropriate firewalls, updates, backups, access levels and user training for security scenarios.
Lesson 38 · Data and databases
Databases and Keys
Describe relational database tables, records, fields, primary keys and foreign keys.
Lesson 39 · Data and databases
SQL SELECT
Read and write simple SQL SELECT queries using SELECT, FROM and WHERE.
Lesson 40 · Data and databases
SQL Filtering
Use conditions, sorting and simple aggregate functions to answer database questions.
Lesson 41 · Impacts of computing
Privacy and Ethics
Explain privacy, legal and ethical issues including personal data, consent, copyright and computer misuse.
Lesson 42 · Impacts of computing
Environmental Impacts
Evaluate energy use, e-waste, cloud computing and sustainable choices in digital systems.
Lesson 43 · Impacts of computing
AI and Automation
Discuss benefits and risks of automation, AI systems, bias and unequal access to technology.
Lesson 44 · Programming
Robust Programs
Design programs that validate inputs, handle errors and fail safely without confusing the user.
Lesson 45 · Programming
File Handling
Explain how programs read, write and append files so data persists after the program ends.
Lesson 46 · Algorithms
Searching and Sorting
Compare linear search, binary search and common sorting algorithms using clear step-by-step reasoning.
Lesson 47 · Algorithms
Algorithm Efficiency
Reason about algorithm efficiency by comparing steps, input size and practical trade-offs.
Lesson 48 · Programming
Project Practice
Plan, code, test and explain a small GCSE-style programming solution using sensible structure.
Lesson 49 · Revision
Algorithms Revision
Use a calm routine for algorithm, trace, pseudocode, programming and testing questions.
Lesson 50 · Revision
Systems Revision
Revise systems, networks, cybersecurity, databases and impacts with precise terms and scenario links.