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GCSEAQA

Computer Science

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What an Algorithm Is (Step-by-Step Instructions)

Fundamentals of algorithms (AQA)

Algorithm vs Program (Same Idea, Different Thing)

Fundamentals of algorithms (AQA)

Decomposition: Breaking a Problem into Sub-Problems

Fundamentals of algorithms (AQA)

Abstraction: Removing Unnecessary Detail

Fundamentals of algorithms (AQA)

A Systematic Approach to Solving Problems

Fundamentals of algorithms (AQA)

Writing Algorithms in Pseudocode

Fundamentals of algorithms (AQA)

Curriculum Modules

What an Algorithm Is (Step-by-Step Instructions)Algorithm vs Program (Same Idea, Different Thing)Decomposition: Breaking a Problem into Sub-Problems Abstraction: Removing Unnecessary Detail A Systematic Approach to Solving Problems Writing Algorithms in Pseudocode Representing Algorithms with Flowcharts Representing Algorithms with Program Code Inputs, Processes and Outputs in an Algorithm Spotting Inputs, Processes and Outputs in Given Pseudocode Tracing an Algorithm with a Trace Table Determining What a Simple Algorithm Does (Purpose)Why Different Algorithms Can Solve the Same Problem Comparing Algorithms by Time Efficiency (Faster vs Slower)Linear Search: How It Works (Mechanics)Linear Search: Tracing Step-by-Step Binary Search: Why the Data Must Be Sorted Binary Search: How It Works (Mechanics)Binary Search: Tracing Step-by-Step Linear vs Binary Search: Advantages and Disadvantages Merge Sort: Splitting a List into Halves Merge Sort: Merging Two Sorted Lists Merge Sort: Tracing a Full Example Bubble Sort: Swapping Adjacent Items Bubble Sort: Passes, Comparisons and Swaps Bubble Sort: Tracing a Full Example Merge Sort vs Bubble Sort: Advantages and Disadvantages

Integer, Real and Boolean Data Types Character and String Data Types Choosing the Right Data Type for a Variable Variables and Assignment (Storing and Updating Values)Constants and Why They’re Useful Meaningful Identifier Names (Readable Code)Sequence: Running Statements in Order Selection: IF, ELSEIF, ELSE Decisions Nested Selection (IF Inside IF)Count-Controlled Iteration (FOR Loops)Condition-Controlled Iteration (WHILE / REPEAT UNTIL)Avoiding Infinite Loops (Correct Conditions)Arithmetic Operators: +, -, *, /, DIV, MOD Order of Operations in Expressions Relational Operators: =, ≠, <, >, ≤, ≥Building Conditions with Relational Operators Boolean Operators: AND, OR, NOT Combining Boolean Conditions (With Brackets)One-Dimensional Arrays: Indexes and Bounds Iterating Through a 1D Array Two-Dimensional Arrays: Rows, Columns and Indexes Iterating Through a 2D Array (Nested Loops)Records: Fields Inside a Single Data Item Arrays of Records (Lists of Structured Items)Input from a User (Keyboard / Form Input)Output to a User (Screen / Console Output)String Length and String Indexing Substrings and String Slicing Concatenating Strings Converting Between Characters and Character Codes Random Number Generation (Range and Use Cases)Using Randomness in Algorithms (Games / Sampling)Subroutines: Why We Use Them (Decomposition in Code)Procedures vs Functions (Return Values)Passing Parameters into a Subroutine Using Return Values from Functions Local vs Global Variables (Scope Basics)Data Validation: Presence, Length and Range Checks Data Validation: Format Checks (e.g. Type/Pattern)Authentication: Usernames, Passwords and Access CAPTCHA: Why It’s Used and What It Stops Common Programming Errors: Syntax vs Logic Testing Strategies: Normal, Boundary and Erroneous Test Data Debugging: Finding and Fixing Errors from Test Results

Decimal, Binary and Hexadecimal Bases Why Computers Use Binary Bit Patterns: Same Bits, Different Meanings (Text/Image/Sound/Number)Why Hexadecimal Is Useful in Computing Binary Place Value (8-bit Numbers 0–255)Writing Decimal Numbers (0–255) in Binary Hex Place Value and Hex Digits (0–F)Writing Decimal Numbers (0–255) in Hex Converting Binary to Decimal Converting Decimal to Binary Converting Binary to Hex (Nibble Grouping)Converting Hex to Binary (Nibble Expansion)Converting Decimal to Hex Converting Hex to Decimal Bits and Bytes (b vs B)Decimal Prefixes: kB, MB, GB, TB (Powers of 10)Comparing File Sizes Using Prefixes Adding Two Binary Numbers (With Carry)Adding Three Binary Numbers (Column Rules)Logical Shifts Left and Right (8-bit)Using Shifts for Multiply/Divide by Powers of 2 What a Character Set Is 7-bit ASCII: Using an Encoding Table Unicode: Why It Exists and Its Advantages over ASCII Converting Characters to Codes (Using a Given Table)Converting Codes to Characters (Using a Given Table)Pixels and How a Bitmap Image Is Stored Image Resolution and Colour Depth Calculating Image File Size (Resolution × Colour Depth)How Changing Resolution Affects Image Quality and File Size How Changing Colour Depth Affects Image Quality and File Size Sampling Sound: From Analogue to Digital Sampling Rate and Sample Resolution (Bit Depth)How Sampling Choices Affect Sound Quality Calculating Sound File Size (Rate × Resolution × Time)Why Data Compression Is Used Lossy vs Lossless Compression (What Changes, What Doesn’t)Run-Length Encoding: Creating Compressed Data Run-Length Encoding: Decompressing Back to Original Huffman Coding: Frequency Tables and Idea Huffman Coding: Building/Using a Huffman Tree Huffman Coding: Calculating Bits Saved

Hardware vs Software (What Each Means)How Hardware and Software Work Together Boolean Values: True/False as 1/0 The NOT Gate: Truth Table and Meaning The AND Gate: Truth Table and Meaning The OR Gate: Truth Table and Meaning The XOR Gate: Truth Table and Meaning Logic Gates with Three Inputs (Truth Tables)Drawing Logic Circuits Using Gate Symbols Reading a Logic Circuit to Produce a Truth Table Combining Logic Gates into Larger Circuits Boolean Expressions from Logic Circuits Logic Circuits from Boolean Expressions System Software vs Application Software The Purpose of an Operating System OS Management: Memory, Processor, Devices and Users Utility Software: What It Is and Examples Low-Level vs High-Level Programming Languages Machine Code: What It Is and Why It’s Processor-Specific Assembly Language: What It Is and Why It’s Used Translators: Compiler, Interpreter and Assembler Compiler vs Interpreter (Key Differences)What Main Memory Does in a Computer System CPU Components: ALU, Control Unit and Clock Registers and Their Role (No Specific Registers Needed)Buses: What They Are and Why They Matter The Fetch-Decode-Execute Cycle (Full Cycle)What Affects CPU Performance: Clock Speed What Affects CPU Performance: Cores and Cache RAM vs ROM (Volatile vs Non-Volatile)Cache and Registers: Why They Exist Main Memory vs Secondary Storage Why Secondary Storage Is Needed Magnetic Storage: How It Stores Data Solid State Storage: How It Stores Data (High Level)Magnetic vs Solid State: Pros and Cons Cloud Storage: What It Means Cloud Storage vs Local Storage: Pros and Cons Embedded Systems: What They Are Embedded vs Non-Embedded Systems (Examples)

What a Computer Network Is Advantages of Using Networks Disadvantages and Risks of Networks PAN: What It Is (Bluetooth Only)LAN: What It Is (Size and Ownership)WAN: What It Is (The Internet as a WAN)Wired vs Wireless Networks (Key Differences)Wireless vs Wired: Advantages and Disadvantages Copper vs Fibre Cabling (When Each Is Appropriate)What a Network Protocol Is IP: Addressing and Routing (Purpose)TCP: Reliable Transmission (Purpose)HTTP: How Web Pages Are Transferred (Purpose)HTTPS: What Changes Compared to HTTP (Purpose)SMTP: Sending Email (Purpose)IMAP: Retrieving Email (Purpose)Why Network Security Matters Authentication on Networks (Users and Permissions)Encryption on Networks (Protecting Data in Transit)Firewalls: What They Do and How Rules Work MAC Address Filtering: Allowing/Blocking Devices Layering Security Methods Together (Defence in Depth)The TCP/IP 4-Layer Model: Names of the Layers Application Layer: What Happens Here Transport Layer: What Happens Here Internet Layer: What Happens Here Link Layer: What Happens Here Which Protocols Sit in Which TCP/IP Layer

What Cyber Security Means The Main Purposes of Cyber Security Social Engineering: What It Is Blagging (Pretexting): How It Works Phishing: How It Works (Email/SMS)Shouldering (Shoulder Surfing): How It Works Protecting Against Social Engineering (Practical Behaviours)Malware: What It Is (Umbrella Term)Computer Viruses: How They Spread and Harm Trojans: Disguised Malware and Its Risks Spyware: Monitoring Users and Stealing Data Protecting Against Malware (Practical Steps)Pharming: Redirecting Traffic to Fake Websites Weak/Default Passwords: Why They’re Dangerous Misconfigured Access Rights: How They Create Risks Removable Media Threats (e.g. Infected USBs)Unpatched/Outdated Software: Why It’s a Threat Penetration Testing: What It Is Used For Pen Testing: Internal Attack Simulation Pen Testing: External Attack Simulation Biometrics for Security (Especially Mobile Devices)Password Systems (Strong Password Practice)CAPTCHA and Automated Attack Prevention Email Confirmations for Identity Checking Automatic Software Updates as Protection

What a Database Is What a Relational Database Is Tables, Records and Fields (Core Vocabulary)Data Types in Databases (Why They Matter)Primary Keys: Unique Identifiers Foreign Keys: Linking Tables Together Reducing Redundancy and Inconsistency with Relational Design SELECT: Choosing Which Fields to Show FROM: Choosing Which Table(s) to Use WHERE: Filtering Records by a Condition ORDER BY: Sorting Results ASC and DESC Writing Queries Using Two Tables (Maximum)INSERT INTO: Adding a New Record UPDATE: Editing Existing Data Safely with WHERE DELETE: Deleting Records Safely with WHERE

What “Ethical Impact” Means in Digital Technology What “Legal Impact” Means in Digital Technology What “Environmental Impact” Means in Digital Technology Privacy: What People Expect and Why It Matters Security vs Privacy: The Core Trade-Off (Safety vs Access)Evaluating a Scenario: Stakeholders, Benefits and Risks Cyber Security Impacts: Protection, Surveillance and Harm Mobile Technologies: Location Tracking and Personal Data Wireless Networking: Convenience vs Eavesdropping Risks Cloud Storage: Data Ownership, Access and Jurisdiction Issues Cloud Storage: Reliability, Outages and Dependency Risks Hacking (Unauthorised Access): Harm, Motivations and Consequences Wearable Tech: Health Data, Consent and Data Sharing Computer-Based Implants: Safety, Consent and Data Security Autonomous Vehicles: Safety, Liability and Decision-Making Ethics Environmental Costs: Energy Use of Devices and Data Centres Environmental Costs: E-waste and Product Lifecycles Key UK Digital Laws (Overview: Data, Access, Copyright, Info Rights)

Designing a Program to Meet a Brief Writing a Program in a Text-Based High-Level Language Testing a Program Systematically Refining a Program Based on Test Evidence Using Programming Tasks to Build Exam-Ready Skills What the Practical Programming Statement Confirms (Opportunity to Practise)Avoiding Malpractice in Practical Programming Evidence

Community Lessons

Tracing an Algorithm with a Trace Table

Tracing an Algorithm with a Trace Table

What an Algorithm Is (Step-by-Step Instructions)

What an Algorithm Is (Step-by-Step Instructions)

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