AQA 8525

AQA GCSE Computer Science

Every section of the AQA 8525 specification, from 3.1 fundamentals of algorithms through to 3.8 impacts, written to AQA's own conventions: AQA pseudo-code, AQA's decimal units, and Huffman and RLE worked through in full.

Start the first topic Practice papers Printable worksheets

23Topics

230Quiz questions

323Exam marks

Grade 9Target grade

Your route to Grade 9

Revision works when it has an order. Follow these stages rather than opening topics at random.

Know which board you are sitting

AQA and OCR cover similar computer science but they are not interchangeable. AQA uses its own pseudo-code, counts a kilobyte as 1000 bytes, examines star and bus topologies rather than star and mesh, and requires Huffman coding and run length encoding in detail. Work from the right course and none of that catches you out.

Read a topic once, then close it

Write down everything you can remember before you look again. What you cannot produce from memory is what you have not learned yet, and rereading will never show you the difference.

Score full marks on the knowledge check

Ten questions per topic with an explanation for every answer. Anything below ten out of ten is a signal to go back to that section rather than to move on.

Write the exam answers before reading the model

Every topic ends with exam-style questions marked against real mark scheme points. Produce your answer first. Reading a model answer feels productive and teaches you very little until you have attempted one yourself.

Practise the calculations until they are automatic

Number bases, binary addition and shifts, file sizes, Huffman savings. These are the most reliable marks on Paper 1 and they are entirely method. Use the tools on this site until you stop having to think about them.

Sit whole papers to time, then fix what you dropped

Paper 1 is 2 hours of computational thinking and programming, Paper 2 is 1 hour 45 of computing concepts. Mark honestly, list every mark you lost and why, and revise from that list rather than from the specification.

Paper 1 4 topics

3.1 Fundamentals of Algorithms

What an algorithm is, how to express one in pseudo-code and as a flowchart, and the four searching and sorting algorithms AQA names.

3.1.1Computational ThinkingWhat AQA means by an algorithm, why a program is not the same thing, and how decomposition and abstraction turn a problem you cannot see the end of into one you can actually code.3.1.1Representing AlgorithmsAQA pseudo-code written the way AQA writes it, the six flowchart symbols and what each one is for, and a method for trace tables that does not fall apart under time pressure.3.1.2, 3.1.3Efficiency and Searching AlgorithmsWhat efficiency actually means for an algorithm, how linear and binary search work step by step, and the exact conditions under which each one is the right choice.3.1.4Sorting AlgorithmsBubble sort and merge sort traced pass by pass, why merge sort wins on large lists, and how to answer the compare question without repeating yourself.

Paper 1 5 topics

3.2 Programming

Everything from data types and the three constructs to arrays, files, subroutines, robust programming and the languages themselves.

3.2.1 to 3.2.5Programming FundamentalsData types, variables and constants, every operator AQA can ask about, and the three programming constructs that between them can express any algorithm ever written.3.2.6 to 3.2.9Data Structures, Strings and FilesArrays and records, every string operation AQA can ask for, reading and writing text files, and generating random numbers, with the traps that cost marks in each.3.2.10 to 3.2.11Subroutines and Structured ProgrammingProcedures and functions, parameters and return values, local and global scope, and why breaking a program into named pieces is the difference between code you can maintain and code you cannot.3.2.12Robust and Secure ProgrammingValidation, authentication, defensive design and testing, plus the three kinds of error and how to find each one, written around the idea that a program must survive users who do the wrong thing.3.2.13Classification of Programming LanguagesHigh and low level languages, machine code and assembly language, and the three translators, with a clear account of why anyone would still write low level code today.

Paper 2 6 topics

3.3 Fundamentals of Data Representation

Number bases and units, binary arithmetic and shifts, characters, images, sound, and compression including Huffman and run length encoding.

3.3.1 to 3.3.2Number Bases and Units of InformationWhy computers use binary at all, how to convert between denary, binary and hexadecimal in both directions, and the units of information using AQA's decimal convention.3.3.3Binary Arithmetic and ShiftsAdding binary numbers with carries, recognising overflow, and binary shifts, including exactly what happens to the bits that fall off the end.3.3.4Character EncodingCharacter sets, ASCII and Unicode, why the codes for letters and digits are in order, and why the character '7' is not the number 7.3.3.5Representing ImagesHow a bitmap stores a picture as numbers, what resolution and colour depth actually control, why metadata is needed, and every step of an image file size calculation.3.3.6Representing SoundHow an analogue wave becomes a stream of numbers, what sample rate and sample resolution each control, and how to calculate a sound file size without losing a mark on the conversions.3.3.7Data Compression, Huffman and RLEWhy compression matters, the difference between lossy and lossless, and full worked methods for both Huffman coding and run length encoding, including how to calculate the saving.

Paper 2 3 topics

3.4 Computer Systems

Hardware and software, the operating system and utilities, Boolean logic, and the architecture of the processor itself.

3.4.1 and 3.4.3Hardware, Software and the Operating SystemWhat separates hardware from software, the four jobs an operating system does that nothing else can, and the utility programs that keep a machine usable.3.4.2Boolean LogicNOT, AND, OR and XOR, how to build and read a logic circuit diagram, and a reliable method for completing the truth table of a combined circuit without guessing.3.4.4Systems ArchitectureThe von Neumann architecture, every register named in the specification, the fetch execute cycle in full, the three factors affecting CPU performance and what an embedded system actually is.

Paper 2 2 topics

3.5 Fundamentals of Computer Networks

Local and wide area networks, star and bus topologies, wired against wireless, every named protocol, and why networking is layered.

3.5.1 to 3.5.2Computer Networks and TopologiesLocal and wide area networks, star and bus topologies compared properly, wired against wireless, and the three ways a wireless network is secured.3.5.3 to 3.5.4Protocols and LayersEvery protocol named in the specification and what each one is actually for, why TCP and UDP are different jobs rather than rivals, and what layering buys you.

Paper 2 1 topics

3.6 Cyber Security

Social engineering and malicious code threat by threat, and every method of detection and prevention in the specification.

3.6Cyber SecuritySocial engineering and malware named threat by threat, plus every detection and prevention method in the specification, with the reason each one works.

Paper 2 1 topics

3.7 Relational Databases and SQL

Tables, records, fields and keys, why data is split across linked tables, and writing SQL that would actually run.

3.7Relational Databases and SQLTables, records, fields, primary and foreign keys, why splitting data across related tables removes whole categories of error, and every SQL statement the specification requires.

Paper 2 1 topics

3.8 Ethical, Legal and Environmental Impacts

The four Acts, software licensing, the impacts of the technologies AQA names, and how to structure the extended answer.

3.8Ethical, Legal and Environmental ImpactsThe four Acts you must be able to name, open source against proprietary licensing, and how to structure the extended answer that carries the most marks on the paper.