LNF Cymru Literacy and numeracy for Wales

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GCSE Computer Science

Numeracy is heavy and specific: learners convert between denary, binary and hexadecimal, add in binary, work with base 2 storage units, calculate image, sound and compressed file sizes and routing costs, and reason with truth tables and DIV and MOD. Literacy centres on close reading of the Unit 2 scenario and requirements, precise technical vocabulary, short and extended judgement answers in Unit 1, and code annotation and test commentaries. The single biggest thing Key Stage 3 should build is fluent place value in base 2 and base 16, so that storage and file size calculations become routine.

First taught
September 2025
Amount of literacy work
Medium
Amount of numeracy work
High
Specification
Open the WJEC specification (PDF)
How this GCSE is assessed
  • Unit 1: Understanding Computer Science: Digital examination 1 hour 30 minutes, 50%, 80 marks
  • Unit 2: Computer Programming: On-screen examination based on a pre-released brief, 2 hours, 50%, 80 marks, set and marked by WJEC

The literacy and numeracy skills in this GCSE

  1. Reading a scenario, its requirements and given code

    Assessed: In the exam

    Learners analyse a set of requirements from the pre-released scenario and read, evaluate and extend given Python code. They sit the examination with a clean copy of the brief and no notes, so close reading and recall of the scenario matter.

    Literacy: Reading strategies, Understanding, response and analysis

    Getting pupils ready

    Year 7
    Pupils highlight the must-have features in a short written brief for a class quiz program and turn them into a numbered checklist before they start coding.
    Year 8
    Pupils read a one-page scenario for a school canteen ordering app, underline each requirement and write three questions a programmer would need to ask the client.
    Year 9
    Pupils read a short given Python program alongside its brief, annotate which lines meet each requirement and note one requirement the code does not yet meet.
    Show the specification wording and the LNF statements

    Where it is in the specification: Unit 2, Section 2.1.1 Investigation, page 23

    “analyse a set of requirements”
    Progression step 3

    • I can use a range of strategies for finding information, e.g. skimming for gist, scanning for detail.

    • I can read closely, identifying and noting features of texts, e.g. introduction, sequence, illustrations, formality, key vocabulary.

    • I can show understanding of and use the main ideas and significant details in different texts on the same topic.

    Progression step 4

    • I can read, with concentration, printed and digital texts that are new to me and update, broaden and deepen my understanding of information, ideas and issues.

    • I can use a range of strategies, e.g. speed reading, close reading, annotation, prediction, to skim texts for gist, key ideas and themes, and scan for detailed information.

    • I can read closely, follow up and use additional material in texts to extend my understanding.

    Progression step 5

    • I can read and analyse a range of unseen, printed and digital texts with concentration and independence.

    • I can use a range of strategies, e.g. speed reading, close reading, annotation, prediction, to skim texts for gist, key ideas and themes, and scan for detailed information, extracting and commenting maturely on key ideas and themes.

    • I can read closely, analysing the content, language and impact of texts to deepen my understanding.

  2. Extended answers on legal, ethical, social and environmental impact

    Assessed: In the exam

    Unit 1 includes short and extended answers, and the legal, social, ethical, environmental and professional dimensions run through every topic. AO3 asks learners to make reasoned judgements, for example on e-waste, privacy or AI.

    Literacy: Planning and organising for different purposes, audiences and context, Connectives and syntax

    Getting pupils ready

    Year 7
    Pupils write one paragraph on whether old mobile phones should be recycled rather than thrown away, using the connectives because, however and therefore.
    Year 8
    Pupils write two linked paragraphs giving one advantage and one disadvantage of facial recognition cameras in shops, each backed by an example.
    Year 9
    Pupils plan and write a 300 word balanced answer on whether AI chatbots should be allowed for homework, ending with a reasoned judgement.
    Show the specification wording and the LNF statements

    Where it is in the specification: Unit 1, Overview of unit, page 9; Section 3.1, page 28

    “consider the broad legal, social, ethical, environmental and professional consequences relevant to the use of technology”
    Progression step 3

    • I can adapt my writing style and structure to suit the audience, purpose and context, e.g. suitable balance between facts and viewpoints, a precise conclusion.

    • I can use paragraphs and make links between them.

    • I can use an increasing range of connectives to organise my ideas in sentences, paragraphs and whole texts.

    Progression step 4

    • I can use summary, discussion of issues, detailed explanations and logic when covering a topic.

    • I can organise and construct my writing effectively, connecting and developing my ideas for a range of different contexts.

    • I can use a range of connectives specifically when organising my ideas in whole texts for different purposes.

    Progression step 5

    • I can write extended pieces which include detailed evidence and information for different purposes and audiences within and across different disciplines.

    • I can convey objectivity and impartiality on complex topics, using a range of linguistic devices.

    • I can organise writing in an appropriate form, ensuring content is detailed within and between paragraphs or sections, developing and sustaining ideas coherently.

  3. Technical vocabulary and acronyms

    Assessed: In the exam

    Learners must recall and use precise technical terms and a long list of acronyms (CPU, ALU, RAM, TCP, HTTPS, DNS and more) and show understanding of software development terminology. Identifiers in code must also be spelt consistently to work.

    Literacy: Vocabulary, spelling, grammar

    Getting pupils ready

    Year 7
    Pupils build a Computer Science glossary of hardware words such as processor, input, output and storage, and spell each from memory in a weekly five-word quiz.
    Year 8
    Pupils expand acronyms such as CPU, RAM, ROM and USB and use each one correctly in a sentence about a real device in the classroom.
    Year 9
    Pupils rewrite a vague answer such as 'the computer gets faster' using precise terms like clock speed, cores and cache, correcting any misspelt terms.
    Show the specification wording and the LNF statements

    Where it is in the specification: Unit 2, Section 2.4.2 Refinement and evaluation, page 26

    “demonstrate an understanding of the technical terminology/concepts used during software development”
    Progression step 3

    • I can use varied, appropriate and precise vocabulary including area of learning and experience/discipline-specific words for different purposes.

    • I can use strategies to correctly spell polysyllabic, complex and irregular words in the context of each area of learning and experience.

    Progression step 4

    • I have experienced a range of area of learning and experience/discipline-specific and general academic vocabulary, and can use them in my own communication.

    • I can use a variety of strategies and resources to spell familiar and unfamiliar vocabulary and area of learning and experience/discipline-specific words correctly.

    Progression step 5

    • I can use a range of discipline-specific and general academic vocabulary accurately and precisely.

    • I can use strategies to spell discipline-specific and general academic words in appropriate contexts.

  4. Annotating code, writing test commentaries and refining

    Assessed: In the exam

    Learners annotate code so a competent third party can follow it, present test outcomes with commentaries, and explain and evaluate the changes they make when refining a solution. Test plans must use typical, extreme and erroneous data.

    Literacy: Proofreading, editing and improving, Planning and organising for different purposes, audiences and context, Vocabulary, spelling, grammar

    Getting pupils ready

    Year 7
    Pupils add comments to their Scratch or Python game explaining what each part does, then swap with a partner who checks the comments make sense without running the code.
    Year 8
    Pupils complete a test table for a number-guessing program using typical, extreme and wrong inputs and write one sentence explaining each result.
    Year 9
    Pupils fix a bug in a given Python program and write a short commentary saying what went wrong, what they changed and how they retested it.
    Show the specification wording and the LNF statements

    Where it is in the specification: Unit 2, Sections 2.3.1 and 2.4.1, pages 25 to 26

    “present test outcomes with detailed and informed commentaries”
    Progression step 3

    • I can reflect on, edit and redraft to improve the quality of my expression, and use a range of strategies to ensure greater clarity.

    • I can explore different ways to plan, draft and present my work appropriately.

    • I can present my work appropriately in digital contexts.

    Progression step 4

    • I can improve writing through independent review and redrafting.

    • I can select and use appropriate strategies to plan and develop my writing for different purposes and audiences.

    • I can present my work appropriately in digital contexts using appropriate digital conventions, e.g. thumbnails, language preferences.

    Progression step 5

    • I can improve the content, structure and accuracy of my writing through critical reflection, review and editing, responding constructively to feedback.

    • I can summarise confidently, adapting style and form for the reader or intended audience and purpose for writing.

    • I can understand and use formal conventions of language in a range of purposes, making effective use of reference tools and accuracy aids.

  5. Discussing the impact of computing and AI

    Assessed: Taught, but not assessed

    The specification expects discussion of the impact of the latest AI tools and collaborative teamwork, and Appendix A ticks speaking and listening for both units. These experiences are not directly assessed.

    Literacy: Collaborative talk, Questioning, Clarity and vocabulary, Purpose

    Getting pupils ready

    Year 7
    Pupils take roles such as parent, pupil and headteacher in a short group discussion on screen time rules, building on each other's points.
    Year 8
    Pupils pair program a Scratch task as driver and navigator, swapping every ten minutes and explaining each choice aloud using the correct terms.
    Year 9
    Pupils hold a structured class debate on whether AI should mark coursework, using evidence from two short articles and responding to the other side.
    Show the specification wording and the LNF statements

    Where it is in the specification: Opportunities for integration of learning experiences, page 27

    “engage in discussions about the potential impacts of the latest Artificial Intelligence (AI)”
    Progression step 3

    • I can explore challenging or contentious issues through a variety of authentic contexts, including sustaining a role.

    • I can ask and answer questions, building on and developing the ideas of others in group discussions.

    • I can express issues and ideas clearly using area of learning and experience/discipline-specific vocabulary and examples.

    Progression step 4

    • I can use talk in a range of authentic contexts to explore challenging or contentious issues.

    • I can sustain a convincing point of view, anticipating and responding to other perspectives.

    • I have experienced a range of area of learning and experience/discipline-specific and general academic vocabulary, and can use them in my own communication.

    Progression step 5

    • I can confidently and consistently explore challenging or contentious issues through sustaining roles in formal situations, contexts and purposes.

    • I can organise talk effectively to critically evaluate and respond to what I have heard, read or seen.

    • I can use a range of discipline-specific and general academic vocabulary in my own communication.

  6. Converting between denary, binary and hexadecimal

    Assessed: In the exam

    Learners convert between denary, binary and hexadecimal, perform binary addition, use arithmetic shifts and explain overflow and underflow. All of this rests on secure place value and powers of 2.

    Numeracy: The number system, Calculation, Relationships within the number system, Conceptual understanding, Fluency, Logical reasoning

    Getting pupils ready

    Year 7
    Pupils use binary place-value cards from 128 down to 1 to make their age and house number, write each as 8-bit binary and check by adding the place values.
    Year 8
    Pupils add two 8-bit binary numbers in columns, convert the answer to denary to check it, and explain in one sentence what happens when a ninth bit is needed.
    Year 9
    Pupils convert web colour codes such as FF8800 from hexadecimal to denary and binary, and show that a left shift of one place doubles a binary number.
    Show the specification wording and the LNF statements

    Where it is in the specification: Unit 1, Section 1.2.1, page 13

    “convert between, denary, binary and hexadecimal counting systems”
    Progression step 3

    • I can read and write numbers to 1 million and numbers to 3 decimal places.

    • I can add and subtract numbers using whole numbers and decimals.

    • I can use a range of strategies to check calculations including the use of inverse operations, equivalent calculations and the rules of divisibility.

    Progression step 4

    • I can use powers and understand the importance of powers of 10.

    • I can represent a concept in different ways, flowing between different representations including verbal, concrete, visual, digital and abstract.

    • I can use the four operations and the connections between them, e.g. apply division as the inverse of multiplication.

    Progression step 5

    • I can represent a concept in different ways, flowing between different representations including verbal, concrete, visual, digital and abstract.

    • I can use firmly established, memorable and usable facts and techniques in order to apply the most efficient methods.

    • I can verify and prove results and solutions.

  7. Data storage units and capacity

    Assessed: In the exam

    Learners must know the base 2 storage units from bit and nibble to petabyte, where each step is 1,024 not 1,000, and calculate the capacity needed to store data.

    Numeracy: Measurement, Calculation, The number system, Relationships within the number system, Communicating with symbols, Fluency, Conceptual understanding

    Getting pupils ready

    Year 7
    Pupils order bit, nibble, byte, kilobyte, megabyte and gigabyte on a class washing line and work out how many bits are in one kilobyte.
    Year 8
    Pupils work out how many 3 MB photos fit on a 16 GB memory stick, first estimating with 1,000 and then calculating with 1,024, and explain the difference.
    Year 9
    Pupils total the file sizes in a sample project folder, convert the total into the most sensible unit and judge whether it fits their school network storage allowance.
    Show the specification wording and the LNF statements

    Where it is in the specification: Unit 1, Section 1.2.1, pages 13 to 14

    “the relationship between data storage units using the base 2 prefixes”
    Progression step 3

    • I can convert metric units of length to smaller units, e.g. cm to mm, m to cm, km to m.

    • I can multiply numbers and decimals by a multiple of 10, e.g. 15 x 30, 1.4cm x 20.

    • I can read and write numbers to 1 million and numbers to 3 decimal places.

    Progression step 4

    • I can use the common units of measure, convert between related units of the metric system and carry out calculations.

    • I can use powers and understand the importance of powers of 10.

    • I can read and write numbers of any size.

    Progression step 5

    • I can use appropriate notation, symbols and units of measurement, including compound measures.

    • I can use firmly established, memorable and usable facts and techniques in order to apply the most efficient methods.

    • I can interpret answers within the context of the problem and consider whether answers, including calculator, analogue and digital displays, are sensible.

  8. Calculating file sizes for images and sound

    Assessed: In the exam

    Learners calculate the storage needed for graphics from dimensions and colour depth, and for sound from sampling rate, bit depth and length, then convert the result into suitable units.

    Numeracy: Shape and space, Calculation, Strategic competence, Measurement, Communicating with symbols

    Getting pupils ready

    Year 7
    Pupils draw an 8 by 8 pixel icon on squared paper using four colours, find the number of pixels as an area and work out that each pixel needs 2 bits.
    Year 8
    Pupils use width times height times colour depth to calculate the file size of their pixel art in bits and bytes, then predict what doubling the colour depth does.
    Year 9
    Pupils record a 10 second sound clip in Audacity, calculate its size from sample rate, bit depth and length, and compare their answer with the saved file size.
    Show the specification wording and the LNF statements

    Where it is in the specification: Unit 1, Section 1.2.1, page 13

    “how to calculate the storage requirements for graphics using different dimensions, bit depths and colour depths.”
    Progression step 3

    • I can find areas by counting squares, progressing to calculating the area of squares and rectangles using formulae.

    • I can multiply 2- and 3-digit numbers by a 2-digit number.

    • I can prioritise and organise the relevant steps needed to complete the task or reach a solution.

    Progression step 4

    • I can demonstrate an understanding of the relationship between a formula representing a measurement and the units used.

    • I can use the order of operations including brackets and powers.

    • I can prioritise and organise the relevant steps needed to complete the task or reach a solution.

    Progression step 5

    • I can recognise, model and apply the underlying mathematical structures and ideas within problems, in order to formulate and solve them.

    • I can refine methods of recording calculations.

    • I can understand and use a variety of compound measures.

  9. Compression ratios and file size reduction

    Assessed: In the exam

    Learners calculate compression ratios and the reduction in file size after lossy or lossless compression, and judge whether the saving is worth the loss of quality.

    Numeracy: Calculation, Relationships within the number system, Conceptual understanding, Logical reasoning

    Getting pupils ready

    Year 7
    Pupils run-length encode rows of their pixel art, for example 5 white then 3 black, and count how many characters they save compared with listing every pixel.
    Year 8
    Pupils zip a folder of text files, record the size before and after, and write the saving as a ratio in its simplest form.
    Year 9
    Pupils save one photo as PNG and at three JPEG quality settings, calculate the percentage reduction for each and explain which methods are lossy.
    Show the specification wording and the LNF statements

    Where it is in the specification: Unit 1, Section 1.2.1, page 14

    “calculation of compression ratios and the reduction in file sizes following compression.”
    Progression step 3

    • I can use ratio and proportion to calculate quantities.

    • I can calculate a percentage, fraction and decimal of any quantity with a calculator where appropriate.

    • I can use equivalence of fractions, decimals and percentages to compare proportions.

    Progression step 4

    • I can express one quantity as a percentage of another.

    • I can calculate a percentage increase or decrease.

    • I can use equivalence of fractions, decimals and percentages to select the most appropriate one for a calculation.

    Progression step 5

    • I can use multipliers as an efficient method when working with percentages, e.g. multiply by 1.2 to increase an amount by 20%.

    • I can interpret answers within the context of the problem and consider whether answers, including calculator, analogue and digital displays, are sensible.

    • I can explain results and procedures precisely using appropriate mathematical language.

  10. Logical operators, truth tables and computing operators

    Assessed: In the exam

    Learners use AND, OR, NOT and XOR in truth tables to solve problems, and apply the relational operators and integer division (DIV and MOD) set out in Appendix B when tracing and writing algorithms.

    Numeracy: Logical reasoning, Communicating with symbols, Calculation

    Getting pupils ready

    Year 7
    Pupils complete AND and OR truth tables for a burglar alarm that sounds only when it is switched on and a door is open, then test it with switch cards.
    Year 8
    Pupils use DIV and MOD to turn a number of seconds into minutes and seconds for a Scratch quiz timer, checking three answers by hand.
    Year 9
    Pupils write conditions using >=, <= and <> for a cinema ticket price program and complete a truth table showing which ages each condition accepts.
    Show the specification wording and the LNF statements

    Where it is in the specification: Unit 1, Section 1.6.1, page 19; Appendix B, pages 34 to 35

    “the use of logical operators in truth tables to solve problems”
    Progression step 3

    • I can justify my procedures and predictions.

    • I can use appropriate notation, symbols and units of measurement.

    • I can use mental strategies to recall multiplication tables up to 10 x 10 and use to solve division problems.

    Progression step 4

    • I can justify my procedures, predictions and conjectures.

    • I can use appropriate notation, symbols and units of measurement, including compound measures.

    • I can use the four operations and the connections between them, e.g. apply division as the inverse of multiplication.

    Progression step 5

    • I can construct and develop a mathematical argument.

    • I can use appropriate notation, symbols and units of measurement, including compound measures.

    • I can explain results and procedures precisely using appropriate mathematical language.

  11. Calculating the cost of routing data

    Assessed: In the exam

    Learners calculate the cost of routing data across a network by adding link costs along possible routes and comparing the totals to find the cheapest.

    Numeracy: Strategic competence, Calculation, Fluency

    Getting pupils ready

    Year 7
    Pupils find the cheapest route for a message between rooms on a school map where each corridor has a cost, adding the totals for three routes.
    Year 8
    Pupils list every route between two routers on a six-node network diagram with decimal link costs, add each total and circle the lowest.
    Year 9
    Pupils recalculate the cheapest route when one link on a network diagram fails and write a sentence justifying their new choice with the totals.
    Show the specification wording and the LNF statements

    Where it is in the specification: Unit 1, Section 1.3.1, page 15

    “cost calculation of routing data on a network.”
    Progression step 3

    • I can select, trial and evaluate a variety of possible approaches and break problems into a series of tasks.

    • I can add and subtract numbers using whole numbers and decimals.

    • I can select and apply appropriate checking strategies.

    Progression step 4

    • I can select, trial and evaluate a variety of possible approaches and break complex problems into a series of tasks.

    • I can use efficient written methods to add and subtract numbers and decimals of any size, including a mixture of large and small numbers with differing numbers of decimal places.

    • I can select and apply appropriate checking strategies.

    Progression step 5

    • I can select, trial and evaluate a variety of possible approaches and break complex problems into a series of tasks.

    • I can prioritise and organise the relevant steps needed to complete the task or reach a solution.

    • I can select and apply appropriate checking strategies.

Good to know

Links with other GCSEs

Place value, powers, ratio and percentage reduction are taught in Mathematics, so agreeing shared language (for example 'column value' and 'simplest form') with the Mathematics department in Years 7 to 9 will help pupils transfer these skills to binary and file size work.

Source: WJEC GCSE Computer Science specification, teaching from 2025, for award from 2027, Version 3, September 2025.