H446 · 1.1.1(a–e)
Processor architecture and performance
Connect registers and buses to assembly, then explain clock speed, cache, cores and pipelining.
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Free A-Level Computer Science guide
Find the ideas you need in the H446 specification, practise with worked examples and original questions, and see which topics still need resources.
Content owner: Michael Print · Written for A-Level learners · Checked against official specifications
Choose the paper and topic you want to revise. Read the explanation, trace the worked example, then attempt the questions before opening the marking guidance.
This index maps all 24 numbered examined topic sections and the four project phases. A linked guide covers a stated part of a topic; it does not mean the whole specification section is complete.
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The same format as the existing guides: a direct explanation, worked examples, common mistakes and original practice with indicative answers. Workshop clips can be added when a suitable tutor recording exists.
H446 · 1.1.1(a–e)
Connect registers and buses to assembly, then explain clock speed, cache, cores and pipelining.
H446 · 1.1.2(a–c), 1.1.3(a–d)
Compare RISC, CISC and GPUs; select input, output and storage for a stated problem.
H446 · 1.2.1(a–b), (e–h)
Explain OS services, OS types, paging, segmentation, virtual memory, firmware, drivers and virtual machines.
H446 · 1.2.1(c–d)
Trace an ISR and compare all five OCR scheduling approaches with exact timelines.
H446 · 1.2.2(a–f)
Choose software and follow source code through compilation, linking and loading.
H446 · 1.2.3(a–c)
Choose waterfall, agile, XP, spiral or RAD and practise following/designing algorithms.
H446 · 1.2.4(a–e); appendix 5d LMC instruction set
Choose programming approaches, trace Little Man Computer programs and resolve four addressing modes.
H446 · 1.3.3(a–e)
Follow a web request through DNS, TCP/IP and network hardware, then evaluate switching and security.
H446 · 1.3.4(a–d); appendix 5d HTML, CSS and JavaScript scope
Build a small HTML/CSS/JavaScript page and reason about client/server processing, indexing and link ranking.
H446 · 1.3.1(a–d). Original teaching examples; no exam-board questions are reproduced.
Choose the right operation, trace lossless compression and explain how keys and hashes are used.
H446 · 1.3.2(a–f), with the SQL baseline in appendix 5d. Explicitly labelled SQL extensions provide additional practical depth.
Follow dependencies from a flat table to 3NF, query related records and reason about concurrent changes.
H446 · 1.4.1(a–f,i). Real-number representation and character sets continue in the companion guide.
Keep bit width and representation explicit while converting, calculating, shifting and masking.
H446 · 1.4.1(g–h,j), with fixed point as a comparison. OCR's clarification uses two's-complement mantissa and exponent; this teaching format is not IEEE 754.
Decode signed mantissas, align exponents for arithmetic and separate Unicode characters from their byte encodings.
H446 · 1.4.2(a,c), covering arrays up to three dimensions, records, lists and tuples. Python examples state where language behaviour differs from a fixed array.
Choose a collection by what its positions mean, then create, traverse, insert and remove data safely.
H446 · 1.4.2(b–c), directed/undirected graphs and hash tables. Traversal supports later graph algorithms; pathfinding is taught separately.
Represent connections, traverse without revisiting vertices and handle collisions without losing keyed data.
H446 · 1.4.3(a–d). Textual gate connections and tables accompany original two-, three- and four-variable reasoning.
Translate a rule into logic, simplify with named laws and group a four-variable map correctly across its edges.
H446 · 1.4.3(e), using logic diagrams expressed as named connections and complete truth/state tables. The D-type example is explicitly positive-edge-triggered.
Separate sum from carry and instantaneous combinational outputs from clocked stored state.
H446 · 1.5.1(a–d)
Apply data protection, computer misuse, copyright and investigatory powers to computing scenarios.
H446 · 1.5.2 (all nine listed issue areas)
Evaluate automation, AI, privacy, censorship, the environment and inclusive design with balanced scenario answers.
H446 · 2.1.2(a–d)
Identify inputs, outputs and preconditions; weigh caching and reusable components.
H446 · 2.1.4(a–c), 2.1.5(a–b)
Follow decision points and reason about tasks that can overlap.
H446 · 2.2.1(a), (c–e)
Trace control structures, scope, parameters and modular programs; use debugging tools.
H446 · 2.2.2(a–f)
Choose methods for solvable problems, from divide and conquer to backtracking and modelling.
H446 · 2.2.1(b)
Trace calls and returns, identify a base case and compare recursion with iteration.
H446 · 2.3.1(b–d)
Compare time and space requirements and explain how growth affects algorithm choice.
H446 · 2.3.1(f) — sorting
Trace three sorting methods and compare their requirements and costs.
H446 · 2.3.1(e); supporting 1.4.2
Build a binary search tree and trace depth-first post-order and breadth-first traversal.
H446 · 2.3.1(f) — pathfinding
Update tentative distances, reconstruct a shortest path and use a heuristic carefully.
H446 · 2.1.1(a–d), 2.1.3(a–d); reinforces 2.2.2(c,e)
Compare models with reality and design ordered subprocedures with clear inputs, outputs and assumptions.
H446 · 2.2.2(f): data mining, performance modelling, pipelining and visualisation
Apply the remaining named computational methods with original basket-pattern calculations, performance predictions, pipeline schedules and visualisation choices.
H446 · 1.2.4(e), 2.2.1(f)
Trace inheritance, overriding, super and a common method interface using an original runnable Python ticket example.
H446 · 1.4.2(b–c), 2.3.1(e): singly linked-list operations
Create, traverse, search, insert into and delete from a singly linked list, including empty and head-node cases.
H446 · 1.4.2(b–c), 2.3.1(e): array-based stack and queue operations
Implement stack and FIFO queue operations in fixed arrays with explicit empty/full rules, count and circular wraparound.
H446 · 2.2.1(a,d–e), 2.3.1(a); reinforces 2.3.1(b)
Design an original stock-reordering algorithm, trace a rounding bug, use debugger evidence and select useful test cases.
H446 · 2.2.2(f): backtracking and heuristics; reinforces 2.2.1(b), 2.3.1(a–b)
Trace a complete choose-check-recurse-undo search and compare exact search ordering with an approximate greedy rule.
H446 · 2.2.1(a,d), 2.3.1(a); Appendix 5d, printed pages 33–36; supporting inline CSS from 1.3.4(a) and Appendix 5d page 39
Translate OCR string, file, loop and parameter conventions accurately into executable code.
H446 · 3.1.1–3.1.4
Investigate a suitable problem, consult stakeholders and define justified, measurable success criteria.
H446 · 3.2.1–3.2.3
Connect decomposition, algorithms, data structures, interfaces and test planning to analysed requirements.
H446 · 3.3.1–3.3.2
Develop in justified increments and document tests, failures, fixes and retests as they happen.
H446 · 3.4.1–3.4.4
Use final tests and feedback to judge success criteria, usability, limitations and justified future development.
Paper 1 · Component 01
Explore processors, data representation, software, networks, databases and the wider effects of computing.
OCR H446 · 1.1.1
Topic guides · see each guide's scope
OCR H446 · 1.1.2
Topic guides · see each guide's scope
OCR H446 · 1.1.3
Topic guides · see each guide's scope
OCR H446 · 1.2.1
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OCR H446 · 1.2.2
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OCR H446 · 1.2.3
Topic guides · see each guide's scope
OCR H446 · 1.2.4
Topic guides · see each guide's scope
OCR H446 · 1.3.1
Topic guides · see each guide's scope
OCR H446 · 1.3.2
Topic guides · see each guide's scope
OCR H446 · 1.3.3
Topic guides · see each guide's scope
OCR H446 · 1.3.4
Topic guides · see each guide's scope
OCR H446 · 1.4.1
Topic guides · see each guide's scope
OCR H446 · 1.4.2
Topic guides · see each guide's scope
OCR H446 · 1.4.3
Topic guides · see each guide's scope
OCR H446 · 1.5.1
Topic guides · see each guide's scope
OCR H446 · 1.5.2
Topic guides · see each guide's scope
Paper 2 · Component 02
Choose from algorithm and programming topics, including the AS recap and A-Level programming guides. The recap includes selected H046 topics; the references below identify the H446 requirements.
OCR H446 · 2.1.1
Topic guides · see each guide's scope
OCR H446 · 2.1.2
Topic guides · see each guide's scope
OCR H446 · 2.1.3
Topic guides · see each guide's scope
OCR H446 · 2.1.4
Topic guides · see each guide's scope
OCR H446 · 2.1.5
Topic guides · see each guide's scope
OCR H446 · 2.2.1
Topic guides · see each guide's scope
OCR H446 · 2.2.2
Topic guides · see each guide's scope
OCR H446 · 2.3.1
Topic guides · see each guide's scope
Component 03 · Independent project guidance
The project guides explain the process through fictional teaching exercises. Apply the skills to your own work and follow your centre's assessment and AI guidance.
OCR H446 · 3.1
Topic guides · see each guide's scope
OCR H446 · 3.2
Topic guides · see each guide's scope
OCR H446 · 3.3
Topic guides · see each guide's scope
OCR H446 · 3.4
Topic guides · see each guide's scope
Additional specifications · Growing libraries
Reuse shared computing explanations, then study these supplements for additional requirements. They are a starting set, rather than complete coverage of either board. Cambridge guides use the 2027–2029 syllabus and identify relevant 2026 differences; check your examination year.
AQA 7517 · AQA 7517: 4.12.1.1–4.12.1.5, 4.12.2.1, 4.12.3.1
Apply AQA function types, first-class functions, partial application, composition, map, filter, fold and head/tail list operations.
AQA 7517 · AQA 7517: 4.4.2.1–4.4.2.4, 4.4.3.1
Trace accepting FSMs and Mealy outputs, interpret the required set mathematics, translate simple regexes and use BNF/syntax diagrams.
AQA 7517 · AQA 7517: 4.4.4.1–4.4.4.7, 4.4.5.1
Trace a one-way infinite-tape machine, interpret transition rules, compare growth and distinguish tractability from non-computability.
Cambridge International 9618 · 9618 (2027–2029): 10.3, 13.2, 20.2; Paper 4 practical scope
Read, append and update records; distinguish file organisation/access and handle specific failures.
Cambridge International 9618 · 9618 (2027–2029): 6.2; supporting transmission context from 2.1/14.1; ARQ is an explicitly labelled extension
Work with parity, block parity, checksums and check digits, then distinguish detection from retransmission.
Cambridge International 9618 · 9618 (2027–2029): 7.1 AI applications/impact; 18.1 graphs, neural networks, learning categories, backpropagation and regression
Compare supervised, unsupervised, reinforcement and deep learning, with regression and error-update examples.
Each specification requirement needs a checked explanation, an example that demonstrates the method and original practice with answers. Larger topics need several guides and mixed questions; the number of pages alone is not a measure of coverage.
Once OCR coverage is established, the same core explanations can support AQA 7517 and Cambridge International 9618. Each board will have its own verified topic mapping, required depth, terminology, pseudocode conventions and extra material.
Checked on 10 October 2026 against OCR H446, version 3.0 (April 2026). Check the qualification page and your examination year when using the library.
These are independently written explanations and practice questions. CompSciTutoring.co.uk is not affiliated with or endorsed by an examination board. The marking guidance is indicative; always check the syllabus for your examination year.
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