← GCSE Computer Science

D01 3.3.1 Number bases: decimal, binary, hexadecimal; why hex is used

Currently Developing · last touched 2026-10-23

Ask cold next session with no sentence shown; listen for the four-bits/fewer-digits fact before the so-what.

Every change

WhenChangeEvidenceSession
2026-10-23Developing → Developing23 Oct: why-hex taught as one sentence ('one hex digit stands for four binary digits, so shorter'); said back from memory, fact then so-what. Prompted in the same session, not a cold check.session 136
2026-10-21Developing → Developingpaper #10 Q11: 1/2, loss=technique — 'easier to write, fewer mistakes', no fact; third cold 1/2 (19 Oct cold 1/2, framed 2/2)session 127
2026-10-20Developing → Developing19 Oct cold, 2-mark why-hex: 'less chance of mistakes and easier to type' 1/2, no fewer-digits fact; 2/2 inside a sentence frame. 2/2 cold on 16 Oct did not hold three days later. Stays developing.session 117
2026-10-16Gap → DevelopingSession 114, 16 Oct, cold, no cue, first item; bar: 2-mark points-marked explain. 'one hex digit stands for four binary bits, so a number has far fewer digits in hex than in binary so it harder to make mestakes' - fact and consequence, 2/2 unaided, typed. Previously 1/2 cold on 6, 13 and 15 Oct after teaching and framed confirms. Developing bar met unaided: gap -> developing, one level.standalone
2026-10-15Gap → Gap15 Oct, cold, no cue, 2nd item; bar: 2-mark points-marked explain. 'easer to type and they make less mistakes': 1/2 (consequences, no fewer-digits fact). No storage idea for a 2nd cold day (13, 15 Oct). Frame 'Hex uses ___ than binary' -> 'less space on the page' at once; model sentence shown. Below the bar cold: stays gap.session 108
2026-10-13Gap → GapSession 102, 13 Oct, cold, no cue; bar: 2-mark points-marked explain. 'so its easyer to write add send to each othor': 1/2 (a consequence for people; no fewer-digits fact). No 'store' or 'memory'. One-blank frame 'Hex uses ___ digits than binary' -> 'less' at once. Up from 0/2 cold on 6 Oct; below the bar cold: stays gap.standalone
2026-10-06Gap → Gap6 Oct, cold, first item, no cue; bar: 2-mark points-marked explain. 'because it is easery to send to others' 0/2. With 'fact, then so-what': harder to make mistakes, plus 'both binary and hexadecimal take up the same amount of space', 1/2 (consequence, no fact). One-blank frame: 'hex uses less digits than binary, so it is harder to make mistakes', 2/2 inside the frame. No storage idea. Below the bar cold: stays gap.session 79
2026-10-05Gap → Gap5 Oct, cold, no notes, before any teaching; bar: 2-mark points-marked explain. 'Does hex make the computer use less memory' -> no. Why -> computers only work in binary, hex is easier for people (own sentence). 2-mark why-hex with only the cue 'fact, then so-what': fewer mistakes plus 'easier for them to store' = 1/2 (consequence; no fewer-digits fact; 'store' not credited). Frame 'hex uses ___ than binary' -> 'less digets'. Joined 2/2 sentence shown by the tutor. Not moved: proposed developing.session 73
2026-10-02Gap → Gap2 Oct, why hex is used; bar: 2-mark points-marked explain. Frame 'so people ___' restated the point, no consequence; either/or (more or fewer mistakes) right. Open 2-mark cold: storage idea again, 0/2; 'does AC use less memory' -> yes after an analogy. Switches picture built: no / 8 / own sentence that hex takes the same space / 'still stored as binary', confirm 2/2. Open 2-mark again 0/2; guided join 1/2 ('easier to write down'). Below the bar: stays gap.session 68
2026-10-01Gap → Gap1 Oct, why hex is used. Open question drew the storage misconception (easier to store, can store more), corrected. Narrowed: one hex digit replaces 4 bits; 8 and 2 digits to copy; the 8-digit one gives more chances to slip, 3/3. 2-mark sentence frame: 'uses less space on paper' plus 'the pc can only store binary': point present, consequence absent, 1/2. Follow-up 'so people ___' set, not answered at the stop. Below the bar: stays gap.session 61
2026-09-29Not started → GapCorrection (parent rule, 29 Sep): a topic touched and answered below the bar cannot stay notstarted → gap. Session 58, 29 Sep: 'why does each column double' off-target to the open form; why-255 explain about 1/2 after a prompt (doubling row and sum absent). Why hex is used untaught. notstarted → gap.standalone
2026-09-29Not started → Not started29 Sep: 'why does each column double' answered off-target to the open form ('you can show more numbers'), corrected: two symbols per box. Why-255 explain 1/2 after prompt: 'all ones, add them together' present, doubling row and the sum absent. Why hex is used not yet taught.session 58
2026-09-28Not started → Not startedPlacement Q2 skipped. 0/1, 28 Sep. Untaught.session 53

In papers

AttemptPaperQMarksNote
Exam practice — week 43 · lang, lit, cs — GCSE Computer Science sectionexam-skills #10111/2Two consequences, no fact; fewer-digits fact absent. 1/2 cold again (19 Oct: 1/2 cold, 2/2 framed). loss=technique.
Placement — Computer Science paper 2 (theory) — GCSE Computer Science sectionexam-skills #220/1skip. 0/1. D01 untaught.

Materials

Craig'n'Dave: Number bases
Decimal, binary and hexadecimal.
video
Craig'n'Dave: Why hexadecimal is used in computer science
The 'why hex' half of D01, which is a written answer, not a calculation.
video
Teach-ICT: Binary
Written back-up on number bases.
notes
Teach-ICT: Hexadecimal
Why hexadecimal is used — material for the written answer.
notes
PMT: Fundamentals of Data Representation (notes and questions)
Free, no login. Retrieval layer after teaching.
practice
AQA 8525 specification v1.3 (first teaching Sept 2025, exams June 2027 onwards)
THE document to teach to. Sections 3.1–3.8 are the syllabus; the right-hand 'additional information' column gives the depth limits. Verified 5 Sep 2026.
notes
AQA Summary of changes (8525), June 2025 — what was removed for 2027
Removed: Von Neumann as a named model, optical storage, LAN topologies, Ethernet, Wi-Fi, UDP, FTP, alternative link-layer names. Void these questions on any 2022–2026 paper.
notes
AQA 8525 overview page (specs, teaching guides, sample papers)
Stable entry point if any file link below dies. Lists both spec versions and the 2027 sample materials.
other
AQA subject-specific vocabulary (first exam 2027)
The terminology examiners expect. Use for retrieval starters and to check definitions in written answers.
notes
AQA Notes and guidance: Pseudo-code (8525/1)
Every algorithm in a question paper uses this pseudo-code. She must READ it fluently; she need not write in it.
notes
AQA Notes and guidance: Python (8525/1)
The exact Python style AQA uses in question papers and mark schemes. Use if Python 3 is the chosen language.
notes
AQA Notes and guidance: C# (8525/1)
The exact C# style AQA uses in question papers and mark schemes. Use if C# is the chosen language.
notes
AQA Notes and guidance: VB.NET (8525/1)
The exact VB.NET style AQA uses in question papers and mark schemes. Use if VB.NET is the chosen language.
notes
AQA Notes and guidance: 8525/1 Marking guidance (coded solutions)
FOR THE MARKER. AQA's examiner rulebook: logic over syntax, indentation rules per language, design marks, meaningful variable names, typing rules, records. Read before marking any code question. Verified 5 Sep 2026.
notes
Specimen Paper 1 (Python) 8525B/1 — sample assessment materials
Official specimen, 90 marks, 2h. Paper 1 content unchanged for 2027, so fully usable. Handwrite the code answers.
paper
Specimen Paper 1 (VB.NET) 8525C/1 — sample assessment materials
VB.NET variant of the same specimen. The C# variant (8525A/1) is on the AQA assessment-resources page.
paper
Specimen Paper 1 mark scheme (all three languages) 8525/1
Mark against the section for her language only. Shows the 'Mark A/B/C' feature-marking and 'max N if any errors' caps.
paper
Sample Paper 2 question paper — Sample set 1 (first exam 2027) 8525/2
The ONLY official Paper 2 on the 2027 content. Use as the first full Paper 2 mock. 90 marks, 1h45.
paper
Sample Paper 2 mark scheme — Sample set 1 (first exam 2027) 8525/2
Contains the level-of-response band descriptors and flags the Von Neumann question as no longer asked from 2027.
paper
June 2023 Paper 2 question paper 8525/2 (legacy spec)
LEGACY: void any question on Von Neumann, optical storage, topologies, Ethernet, Wi-Fi, UDP, FTP and reduce the maximum before marking.
paper
June 2023 Paper 1 (VB.NET) question paper 8525/1C (legacy spec)
Paper 1 is unaffected by the 2027 changes. The 1A (C#) and 1B (Python) variants of the same paper are on the AQA past-paper finder.
paper
June 2023 Paper 1 mark scheme 8525/1 (all languages)
Covers 1A, 1B and 1C. Note the examiner 'I.' (ignore) lists — the compile tolerance in practice.
paper
June 2023 Paper 1 examiner report 8525/1
What real candidates got wrong. Key lines: design marks exist even for wrong code; attempt every coding question; the indentation grids are misused.
notes
June 2022 Paper 1 mark scheme 8525/1 (all languages)
Legacy but Paper 1 content is unchanged. Question paper via the past-paper finder.
paper
AQA past-paper finder (2022–2024 papers, mark schemes, examiner reports, modified papers)
Search 8525. The most recent series (2025, 2026) are login-gated for about a year — ask the exam centre. 2027 is the first series on the new content.
other
AQA 8525 assessment resources page
The file list renders in-browser only. Filter by 'Sample papers' for the C# specimen (8525A/1).
other
AQA GCSE grade boundaries — June 2024 (contains 8525A/B/C rows, out of 180)
Legacy proxy only. The tracker holds the 8525C row. Look up 8525A or 8525B here once the language is chosen. No 2027 boundaries exist until August 2027.
other
AQA GCSE subject grade boundaries — June 2025
Most recent legacy series. Directional only.
other
AQA GCSE exam timetable May/June 2027 (version 1.0)
8525/1A/1B/1C Monday 10 May 2027 am; 8525/2 Wednesday 19 May 2027. Confirm with the centre.
other
AQA private candidates page
PARENT: the centre must sign the Practical Programming Statement (spec 5.1) and declare the Paper 1 language at entry. Confirm both in writing early.
other