Computer Science — Year 3 to GCSE

66 lessons, each with practice questions, a printable worksheet and an end-of-chapter test. Free to browse.

• Two's Complement & Negative Binary Years 10–11 · Storing negative whole numbers in a fixed byte using the two's complement system.
• Data Transmission Years 9–11 · How data is broken into packets and sent along wires as serial or parallel, simplex,…
• Error Detection & Correction Years 10–11 · Spotting and fixing transmission errors with parity, parity blocks, checksums, echo…
• Logic Gates & Circuits Years 10–11 · The six logic gates, their symbols and truth tables, and building and reading logic…
• Validation, Verification & Testing Years 9–11 · Checking data is sensible with validation, checking it was entered correctly with…
• Computational Thinking Years 6–9 · Solving problems the way a programmer does: decomposition, pattern recognition and…
• Pseudocode & Flowcharts Years 6–9 · Planning algorithms with plain-English pseudocode and with standard flowchart shapes.
• Searching Algorithms Years 8–11 · Comparing linear search (check every item) with binary search (repeatedly halve a sorted…
• Sorting Algorithms Years 8–11 · How bubble, insertion and merge sort put a list in order, and why their speeds differ.
• Trace Tables & Efficiency Years 10–11 · Using trace tables to follow variables step by step, and describing how an algorithm's…
• Variables, Data Types & Operators Years 6–10 · How programs remember values in named variables, the main data types, and the operators…
• Selection (IF statements) Years 6–10 · How programs make decisions with IF, ELSE and ELSE IF, and how to trace which branch runs.
• Iteration (Loops) Years 7–11 · Repeating code with count-controlled FOR loops and condition-controlled WHILE and REPEAT…
• Arrays & Lists Years 8–11 · Storing many values under one name, reading and changing them by zero-based index, and…
• Strings Years 8–11 · How programs store, measure, slice and join text using zero-based indexing and core…
• Functions & Procedures Years 8–11 · Named, reusable subprograms: the difference between functions and procedures, and how…
• Files & Data Years 9–11 · Storing data permanently in text files: open/read/write/close, file modes, and how…
• Databases & SQL Years 10–11 · Organising data in database tables of records and fields, and using SQL (SELECT, FROM,…
• Binary Numbers Years 7–11 · How computers count using only 0 and 1, and how to convert between denary and 8-bit…
• Binary Arithmetic & Shifts Years 9–11 · Adding 8-bit binary numbers with carries and overflow, and using binary shifts to…
• Hexadecimal Years 8–11 · Base-16 as a compact shorthand for binary, and converting between hex, binary and denary.
• Characters (ASCII & Unicode) Years 8–11 · How characters are stored as number codes using ASCII, and why Unicode is needed for the…
• Images & Bitmaps Years 8–11 · How bitmap images store pixels, and how resolution and colour depth determine file size.
• Sound Years 9–11 · How analogue sound is sampled into binary, and how sample rate and bit depth affect…
• Compression Years 10–11 · Why files are compressed, the difference between lossy and lossless, and how run-length…
• Inside the CPU Years 8–11 · The von Neumann architecture, the fetch-decode-execute cycle, and the registers that…
• CPU Performance Years 9–11 · How clock speed, number of cores and cache size each affect how fast a CPU gets work done.
• Memory Years 8–11 · RAM, ROM, cache and virtual memory: what each stores, whether it is volatile, and how…
• Secondary Storage Years 8–11 · Magnetic, solid-state and optical storage: how each works and the trade-offs of speed,…
• System Software Years 8–11 · The jobs of an operating system, the utility programs that maintain a computer, and the…
• Boolean Logic & Logic Gates Years 10–11 · The AND, OR and NOT logic gates, their symbols, and how to build and read truth tables.
• Networks & Topologies Years 8–11 · How computers are connected: LANs and WANs, star and mesh topologies, and the…
• The Internet & Protocols Years 7–11 · How data crosses the internet: packets, the TCP/IP protocols, DNS name lookups,…
• Wired & Wireless Networks Years 8–11 · Comparing Ethernet and Wi-Fi: speed, reliability and security, the role of encryption…
• Cyber Security Threats Years 7–11 · Common threats to computer systems: malware types, phishing and social engineering, SQL…
• Protecting Systems Years 8–11 · Defences that keep systems safe: firewalls, encryption, authentication and 2FA,…
• Ethics, Law & the Environment Years 6–11 · The legal, ethical and environmental side of computing: data-protection, computer-misuse…
• Artificial Intelligence Years 9–11 · How machine learning lets computers learn from examples, why all of today's AI is…
• Blockchain Years 10–11 · How a blockchain works as a shared, append-only chain of hashed blocks, why tampering is…
• Data Structures Years 10–11 · Beyond simple arrays: records, 2D arrays, lists, stacks (LIFO) and queues (FIFO), and…
• Defensive Design & Testing Years 10–11 · Anticipating misuse with input validation and authentication, and testing with normal,…
• Translators & Language Levels Years 10–11 · High-level vs low-level languages, machine code and assembly, and the translators…
• Cryptography Years 10–11 · Why we encrypt data, the Caesar/substitution cipher and the idea of a key, and the…
• Cloud Computing Years 9–11 · How the cloud lets you use someone else's computers and storage over the internet, the…
• Internet of Things (IoT) Years 9–11 · How everyday objects gain sensors and internet connections, the sense-send-decide-act…
• Robotics & Automation Years 8–11 · How a robot follows the sense-think-act loop using sensors and actuators, what…
• Quantum Computing Years 10–11 · How a quantum computer uses qubits that can be in superposition (0 and 1 at once)…
• Big Data & Data Science Years 10–11 · What makes data 'big' through the 3 Vs of Volume, Velocity and Variety, where big data…
• How the Web Works Years 6–10 · The web versus the internet, URLs and DNS, the client-server request-response cycle, and…
• HTML & CSS Basics Years 7–11 · HTML tags and elements provide a page's structure and content; CSS rules of selector,…
• Web Design Years 7–11 · What makes a good website: clear navigation, consistent layout, accessibility,…
• Recursion Years 10–11 · A function that calls itself, using a base case to stop and a recursive case that…
• Object-Oriented Programming Years 10–11 · OOP bundles data (attributes) and behaviour (methods) into objects; a class is a…
• JavaScript Basics Years 9–11 · The three layers of a web page (HTML structure, CSS style, JavaScript behaviour);…
• Forms & User Input Years 9–11 · HTML forms collect input from users; input types such as text, password, checkbox, radio…
• Publishing a Website Years 6–10 · Turning your local HTML, CSS and JS files into a live site: uploading them to an…
• Front-end & Back-end Years 10–11 · The front-end is what the user sees and interacts with in the browser (HTML, CSS, JS);…
• Algorithms: Clear Step-by-Step Instructions (Year 3–4) Years 3–4 · An algorithm is a set of clear steps, in the right order, that tells someone (or a…
• Debugging: Finding & Fixing Mistakes (Year 4–5) Years 4–5 · A bug is a mistake in your steps. Debugging means testing your steps, spotting where…
• Block Coding: Sequences & Events (Year 3–4) Years 3–4 · Learn how a program is a list of commands the computer does in order, how a sprite…
• Loops: Making Code Repeat (Year 4–5) Years 4–5 · Learn how a loop repeats commands so you don't write them many times, use 'repeat 4…
• Selection: Making Choices with 'if' (Year 5) Year 5 · Learn how selection lets a program choose what to do, how 'if … then …' works, and how a…
• Staying Safe Online (Year 3–4) Years 3–4 · Learn to keep your private information safe, ask a trusted adult before signing up or…
• Being Kind & Honest Online (Year 4–6) Years 4–6 · Learn to show good character online: use kind words, know what to do if you see someone…
• How the Internet Helps Us (Year 4–5) Years 4–5 · Discover what the internet is in simple terms, the useful things it lets us do, why we…
• Collecting & Sorting Data (Year 3–5) Years 3–5 · Data is information. We can collect it with a survey or tally, sort and group it (like…