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WJEC A-Level Computer Science: complete guide to the five units and the exams

A complete guide to WJEC A-Level Computer Science (Wales). Covers the five units (Fundamentals, Practical Programming, Programming and System Development, Computer Architecture Data Communication and Applications, and the Software Development project), how the written, on-screen and non-exam assessments are structured, and how to study each unit for top grades.

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WJEC A-Level Computer Science (Wales) is a two-year course with an AS year and an A2 year, assessed by written papers, an on-screen practical examination and a non-exam assessment programming project. It follows the 2015 WJEC specification. This page is the index: below is a map of the five units, the assessment structure, and how to study each one.

The five WJEC Computer Science units

The specification organises the content into five units. Units 1 and 2 are the AS content and first year; Units 3, 4 and 5 are the A2 content.

Unit 1 Fundamentals of Computer Science: Data representation, data structures, logical operations, algorithms, principles of programming, software and systems, hardware and architecture, organisation of data, communication and the internet, and security, integrity and the law. Examined by an AS written paper.
Unit 2 Practical Programming to Solve Problems: The application of programming skills to solve set problems, assessed by an on-screen practical examination. It applies the programming principles of Unit 1 rather than adding new theory.
Unit 3 Programming and System Development: Advanced data structures and algorithms, Boolean simplification and Karnaugh maps, programming paradigms, the systems development life cycle, system design, testing and maintenance, data transmission and networks, and data security and integrity. Examined by an A2 written paper.
Unit 4 Computer Architecture, Data, Communication and Applications: Hardware and communication, advanced data representation and floating point, organisation of data with normalisation to third normal form and big data, low-level programs and addressing modes, applications including artificial intelligence and machine learning, and the impact of computing. Examined by an A2 written paper.
Unit 5 Software Development: A substantial programming project, assessed as non-exam assessment, in which you analyse a problem and design, implement, test, document and evaluate a working solution. It draws together the skills of Units 1 to 4.

Assessment structure

WJEC A-Level Computer Science is assessed by written papers, an on-screen examination and a non-exam assessment. A calculator is not required, but precise calculation by hand is.

Unit 1 Fundamentals of Computer Science - AS written paper, 25 per cent of the A level.
Unit 2 Practical Programming to Solve Problems - AS on-screen examination, 15 per cent of the A level.
Unit 3 Programming and System Development - A2 written paper, 20 per cent of the A level.
Unit 4 Computer Architecture, Data, Communication and Applications - A2 written paper, 20 per cent of the A level.
Unit 5 Software Development - A2 non-exam assessment programming project, 20 per cent of the A level.

AS results (Units 1 and 2) count towards the full A level. Always confirm exact paper lengths and mark totals from the current WJEC specification.

How to study WJEC Computer Science

Computer Science rewards precise definitions, confident calculation and tracing, and genuine programming fluency.

Work from the specification statements. Each statement is a checklist; written questions are written from them.
Drill the calculations and traces. Binary and two's complement, floating point and normalisation, address-bus width, tree traversals, Karnaugh maps and addressing modes must be automatic.
Learn definitions and contrasts. Mark schemes reward exact wording and clear distinctions (compiler versus interpreter, validation versus verification, inheritance versus polymorphism).
Programme regularly. The on-screen exam (Unit 2) and the project (Unit 5) are practical; fluency comes only from writing and debugging code.
Practise balanced impact answers. The ethical, legal, social and environmental questions in Unit 4 reward two-sided, reasoned judgement.

The five units, topic by topic

Each unit has a topic-level overview with worked exam questions and cross-links, plus dot-point answer pages for the specification statements:

Unit 1: Fundamentals of Computer Science
Unit 2: Practical Programming to Solve Problems
Unit 3: Programming and System Development
Unit 4: Computer Architecture, Data, Communication and Applications
Unit 5: Software Development

For the official specification

WJEC publishes the full specification, past papers, mark schemes and non-exam assessment guidance at wjec.co.uk. Always revise from the current specification and WJEC's own past papers, because question style is board-specific.

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Common questions about Computer Science

How is WJEC A-Level Computer Science structured?

WJEC A-Level Computer Science is a two-year course with an AS year and an A2 year, following the 2015 WJEC specification used in Wales. The AS comprises Unit 1 (Fundamentals of Computer Science), a written paper, and Unit 2 (Practical Programming to Solve Problems), an on-screen examination. The A2 adds Unit 3 (Programming and System Development) and Unit 4 (Computer Architecture, Data, Communication and Applications), both written papers, and Unit 5 (Software Development), a non-exam assessment programming project. AS results count towards the full A level.

What are the WJEC A-Level Computer Science assessments?

There are five units. Unit 1 Fundamentals of Computer Science is an AS written paper (25 per cent of the A level). Unit 2 Practical Programming to Solve Problems is an AS on-screen examination (15 per cent). Unit 3 Programming and System Development is an A2 written paper (20 per cent). Unit 4 Computer Architecture, Data, Communication and Applications is an A2 written paper (20 per cent). Unit 5 Software Development is a non-exam assessment programming project (20 per cent). Always confirm exact timings and mark totals from the current WJEC specification.

What is the difference between WJEC and Eduqas Computer Science?

WJEC is the awarding body for Wales, while Eduqas (part of WJEC) offers a closely related specification for England. The two share much of the same content and heritage, but the qualification you sit, the unit arrangements and the administrative details depend on your centre and country. This guide covers the WJEC (Wales) AS/A level specification. Always revise from the current WJEC specification and WJEC's own past papers and mark schemes, because question style is board-specific.

How much programming is in WJEC A-Level Computer Science?

A great deal. Unit 2 is an on-screen practical programming examination, and Unit 5 is a substantial programming project assessed as non-exam assessment, so two of the five units are practical. The written units also assess programming concepts: algorithm design, the control structures, subroutines and parameters, recursion, data structures, programming paradigms including object-oriented programming, and low-level assembly language. Regular programming practice is essential, not optional.

How should I structure my WJEC A-Level Computer Science revision?

Work unit by unit against the specification statements, because written questions are written directly from them. Drill the calculations and traces that recur (binary and two's complement, floating point and normalisation, address-bus width, tree traversals, Karnaugh maps, addressing modes) until they are automatic, and learn definitions precisely because mark schemes reward exact wording. Programme regularly for the on-screen exam and the project, and practise balanced, two-sided answers for the impact questions in Unit 4.

What topics are most heavily examined in WJEC Computer Science?

Across the written papers, data representation (binary, hexadecimal, two's complement, floating point and normalisation) and algorithms (searching, sorting, efficiency and tree traversals) recur constantly, as do the fetch-execute cycle, logic and Karnaugh maps, databases and normalisation, networking and protocols, and the ethical, legal, social and environmental impact of computing. Programming concepts, including object-oriented programming and low-level assembly with addressing modes, are also central. Use the unit overviews and dot-point pages to target each.