AQA A Level Computer Science 7517 — What You Need to Know

AQA A Level Computer Science (specification 7517) is a demanding but rewarding qualification that develops both deep theoretical understanding and genuine programming ability. This guide covers everything you need to know about the specification, assessment structure, and how to achieve the highest grades.

Assessment Structure

AQA 7517 has three components:

Component	Name	Weighting	Format
Paper 1	Computer Systems	40%	2 hr 30 min written exam
Paper 2	Algorithms and Programming	40%	2 hr 30 min written exam
NEA	Non-Exam Assessment (Coursework)	20%	Programming project

The two written papers each carry 100 marks. The NEA is marked internally and moderated by AQA.

Paper 1: Computer Systems

Paper 1 is the broader theoretical paper. It covers the entire computer systems side of the specification.

4.1 Fundamentals of Data Representation

This is foundational — everything else builds on it.

Number systems: binary, denary, hexadecimal — and conversion between them
Binary arithmetic: addition, subtraction using two’s complement
Negative numbers: sign-magnitude and two’s complement
Floating point: normalisation, mantissa, exponent, precision vs range trade-off
Character encoding: ASCII, Unicode (UTF-8, UTF-16, UTF-32)
Images: pixels, bit depth, resolution, colour depth, calculating file size
Sound: sampling, sample rate, bit depth, Nyquist theorem
Compression: lossy vs lossless, run-length encoding, Huffman coding

Examiner tip: Floating point normalisation is consistently poorly answered. The mantissa must start with 0.1 (for positive) or 1.0 (for negative) in sign-magnitude. Practice many examples.

4.2 Fundamentals of Computer Systems

Hardware and software: relationship between them
The role of the operating system: process scheduling, memory management, virtual memory, paging, segmentation
Boolean algebra: AND, OR, NOT, NAND, NOR, XOR; De Morgan’s laws; Karnaugh maps for simplification
Logic gates and circuits: drawing, truth tables, simplification

4.3 Fundamentals of Computer Organisation and Architecture

Internal hardware components: CPU structure, buses (data, address, control), registers
The stored program concept (Von Neumann)
Fetch-decode-execute cycle in detail
Performance factors: cores, clock speed, cache levels, pipelining
Assembly language and machine code: instruction sets, addressing modes (immediate, direct, indirect, indexed)
I/O: interrupts, interrupt service routines, polling vs interrupt-driven I/O

4.4 Consequences of Uses of Computing

Privacy and data protection
Ethical issues in AI and automation
Environmental impact
Equality, diversity and inclusion in computing

4.5 Fundamentals of Communication and Networking

Serial and parallel transmission, synchronous and asynchronous
Bit rate, baud rate, bandwidth — and the difference between them
Error detection: parity bits, checksums, CRC
Networking: topologies, protocols, the TCP/IP stack
IP addressing: IPv4, IPv6, subnetting (CIDR notation)
Network security: symmetric/asymmetric encryption, digital certificates, TLS/SSL
The internet: HTTP/HTTPS, DNS, FTP, SMTP, POP3, IMAP

4.6 Fundamentals of Databases

Relational databases: tables, records, fields, primary keys, foreign keys
Entity-relationship diagrams (ERDs)
Normalisation: 1NF, 2NF, 3NF — know how to normalise a table
SQL: SELECT, FROM, WHERE, ORDER BY, GROUP BY, HAVING, JOIN, INSERT, UPDATE, DELETE
ACID properties: atomicity, consistency, isolation, durability
Transaction processing and concurrency control
Big Data: the 3 Vs (volume, velocity, variety), distributed processing

4.7 Big Data

What constitutes Big Data
Distributed processing: map-reduce, Hadoop
Machine learning basics

4.8 Fundamentals of Functional Programming

This is a topic many students find completely new:

Functional programming paradigm: functions as first-class objects, immutability, no side effects
Higher-order functions: map, filter, reduce
Lambda expressions (anonymous functions)
Recursion in the functional style
Function composition

AQA uses Haskell-inspired notation in exam questions, though you don’t need to write Haskell — you need to understand the concepts and trace through examples.

Paper 2: Algorithms and Programming

Paper 2 is more practical and applied. Expect longer questions requiring you to write, trace, and analyse code.

4.9 Fundamentals of Communication and Networking (overlap)

Some networking theory from Paper 1 topics may appear in Paper 2 questions — protocols in practice.

4.10 Fundamentals of Algorithms

Complexity: time complexity, Big O notation — O(1), O(log n), O(n), O(n log n), O(n²)
Standard algorithms: linear search, binary search, bubble sort, insertion sort, merge sort, quicksort
Graph algorithms: Dijkstra’s shortest path, A* search, depth-first search (DFS), breadth-first search (BFS)
Tree algorithms: pre-order, in-order, post-order traversal
Optimisation: the Travelling Salesman Problem — heuristic methods

4.11 Fundamentals of Data Structures

Arrays: 1D, 2D, 3D
Records / structs
Lists, queues, stacks — operations and implementations
Linked lists — singly and doubly linked
Trees: binary trees, binary search trees
Graphs: directed, undirected, weighted — adjacency matrix vs adjacency list
Hash tables: hash functions, collision handling

4.12 Systematic Approach to Problem Solving

Decomposition and stepwise refinement
Structure diagrams

4.13 Fundamentals of Programming

Procedural programming: sequence, selection, iteration, subprograms
Object-oriented programming (OOP): classes, objects, encapsulation, inheritance, polymorphism
File handling: sequential, random access
Recursion: base case, recursive step, stack frames
Exception handling: try/except blocks

The NEA: Non-Exam Assessment

The NEA is worth 20% (75 marks) and is a significant opportunity to secure marks before the exam.

What the NEA involves

You must complete an individual programming project that demonstrates:

Analysis: defining a problem, identifying stakeholder requirements, feasibility
Design: structure charts, algorithms (pseudocode/flowcharts), data structures, UI design
Implementation: a working program in your chosen language
Testing: test plan, evidence of testing, evaluation of results
Evaluation: how well the solution meets the original requirements, limitations

Choosing a project

The best NEA projects:

Are achievable within the time available
Have a clear real-world purpose and identifiable stakeholder
Allow you to demonstrate complex programming techniques (OOP, file I/O, database integration, recursion)
Can be meaningfully tested

Avoid projects that are too simple — a quiz app or a calculator will not demonstrate enough complexity. Avoid projects that are too ambitious — unfinished projects score poorly.

Mark band breakdown

Section	Marks
Analysis	9
Design	15
Implementation	32
Testing	12
Evaluation	7

Implementation is by far the largest section. A working, complex program with good code quality is essential.

Examiner tip: Many students lose marks in Analysis by failing to identify a real stakeholder and gathering actual requirements from them. Document a real conversation or questionnaire.

Recommended Languages

AQA accepts any programming language. The most common choices are:

Python: best for beginners, excellent library support, clean syntax
Java: strong OOP features, widely used in industry
C#: excellent for GUI applications with Windows Forms or WPF

Python is the most popular choice and there’s no disadvantage to using it — the implementation marks are for complexity and skill, not language choice.

Revision Strategy

Paper 1 focus areas

Allocate extra time to: floating point, Boolean algebra, SQL, functional programming, networking protocols, and normalisation — these are where the hardest marks are.

Paper 2 focus areas

Practice writing algorithms in pseudocode under timed conditions. Trace through Dijkstra’s algorithm and merge sort multiple times until you can do them confidently.

Using past papers

AQA past papers and mark schemes are available on their website from 2017 onwards. The 2022 and 2023 papers are particularly good practice as they reflect the current question style.

Getting Help

If you’re struggling with the NEA, particular Paper 1 topics, or algorithm questions, book a 1-to-1 session with Gareth — who has experience marking AQA papers and supporting students through every stage of the NEA.

Students regularly move up multiple grade boundaries and from the bottom NEA mark bands to the highest with targeted support.