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Free A-Level Computer Science guide
A useful design lets another reader understand how the proposed solution will meet the requirements. Explain decisions and interactions rather than collecting diagrams without a purpose.
Content owner: Michael Print · Written for A-Level learners · Checked against official specifications
Trace each important requirement into a design decision. Define what each component receives, what it returns, what data it owns and what happens when an operation fails. A test plan records how the design will be checked.
These are fictional teaching exercises. Your assessed project must be your own work. Follow your centre's supervision and authentication rules and OCR section 4e: permitted AI assistance must be acknowledged and its effect made clear; copied output cannot establish your own knowledge, understanding or ability.
OCR H446 · 3.2.1–3.2.3
Useful foundations
By the end, you should be able to
A contract might say: checkConflict receives a candidate booking and existing bookings, and returns conflicting identifiers without changing either input. Keeping the check separate from saving makes it easier to test and reuse. State assumptions, such as all dates being converted to a consistent representation.
Load records
Supply the existing booking data.
Validate input
Check the candidate booking’s format and valid interval.
Check overlaps
Return the identifiers of same-room intervals that conflict.
Save accepted booking
Store only valid candidates with no conflicts.
Display result
Explain acceptance or give enough detail to recover from rejection.
Show inputs, outputs and interactions. A box labelled “validation” alone is too vague to implement.
Describe the logic that does substantive work. A conflict check first selects records for the same room, then compares intervals. Explain why it detects a booking contained inside another, not just equal starting times. Use pseudocode, structured English or a clear diagram consistently.
Define fields, types and relationships in your fictional design, including key constraints and validation. A record might contain bookingId, roomId, start and end. Reject start >= end. Decide how missing files, invalid values and duplicate identifiers are handled.
Choose a list or indexed structure with reference to expected operations and scale.
Sketch the user's task rather than only the visual appearance. Show where an error is reported, how entered values are preserved, and how a conflicting booking is identified. Feedback should help a person recover without guessing.
Justify navigation, labels and input controls from analysis. A colour change alone is insufficient for an error message. Include a written cue and focus on readable presentation. Describe inputs, outputs and any accessibility or resource constraints relevant to the users.
Choose normal, boundary and invalid cases for each important requirement. Derive expected outcomes from the requirement, not from running your current implementation and copying its output. Include integration tests for interactions such as validation followed by saving and reloading.
A test plan may evolve when the design changes, but record why. A requirement-to-test mapping exposes gaps: a searchable interface does not prove that saved data survives a restart.
| Existing interval | Candidate | Expected |
|---|---|---|
| 10:00–11:00 | 10:15–10:30 | Reject: contained overlap |
| 10:00–11:00 | 11:00–12:00 | Accept: adjacent |
| 10:00–11:00 | 10:30–11:30, other room | Accept: different room |
| 10:00–11:00 | 12:00–11:00 | Reject: invalid interval before conflict check |
Worked example
4 original questions total 14 marks. Attempt each before opening the independently written indicative marking guidance.
Define a contract for a function that finds conflicting booking identifiers without saving a booking. [4]
Indicative answer
Explain why comparing only the start times cannot detect every interval overlap. [3]
Indicative answer
Give one normal, one boundary and one invalid test for the fictional conflict checker, each with an expected outcome. [3]
Indicative answer
Explain two ways to make a conflict error easier for users to recover from. [4]
Indicative answer
This guide addresses OCR H446 3.2.1–3.2.3. Check your examination year and the complete specification for the assessment scope.
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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