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Skills that use Fluency

1. 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.

2. 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.

3. 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.

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