中文（繁體）
中文（简体）
English
IB Computer Science Paper 1: Keywords and Boundary Cases
Keywords in short answers, boundary cases in code
Paper 1 works through short answers and code analysis, and length follows the marks: two marks take two keywords, four marks take two keywords with a sentence each. Code answers need working logic plus the three boundary cases, empty input, a single element and an out-of-range index, since mark schemes award them separately.
How is IB Computer Science Paper 1 assessed, and what does each part carry?
Paper 1 (Theme A + case study): SL 50 marks (A 38 + B 12) (SL 35%／HL 40%); Paper 2 (Theme B computational thinking): SL 50 marks (HL 80) (SL 35%／HL 40%)
Assessment at a glance (2027)
| Component | Content | Weighting | Duration |
|---|---|---|---|
| Paper 1 (Theme A + case study) | SL 50 marks (A 38 + B 12) | SL 35%／HL 40% | SL 1 h 15 min / HL 2 h |
| Paper 2 (Theme B computational thinking) | SL 50 marks (HL 80) | SL 35%／HL 40% | SL 1 h 15 min / HL 2 h |
IB Computer Science Paper 1 drilling technique: answer the command term exactly (outline gives the shape, explain gives mechanism plus consequence); show every step of binary/hex conversion (method marks survive); Section B case-study answers must cite specifics from the scenario – generic answers score nothing. Paper 3 no longer exists from 2027.
What each paper is actually testing
| Paper | Drill focus | How marks are lost |
|---|---|---|
| Paper 1 (Theme A + case study) | concepts + case study analysis | Short answer longer than the marks require yet carrying one keyword. |
| Paper 2 (Theme B computational thinking) | tracing + coding + databases | Code with no empty-input or range check, losing the whole boundary strand. |
What is each IB Computer Science Paper 1 paper really testing, and what should you drill?
Paper 1 (Theme A + case study): concepts + case study analysis; Paper 2 (Theme B computational thinking): tracing + coding + databases
Drill order: by topic, then by year, then the mark scheme
| Step | What you do | Why |
|---|---|---|
| 1. By topic | Work through each topic, starting with the paper that allows least help (no calculator / closed book) | Exposes what is genuinely not understood |
| 2. By year | Whole papers to time, one or two a week | Trains pace, stamina and question selection |
| 3. Mark scheme | Go through the marking scheme question by question and log the scoring steps you missed | Most lost marks are written wrong, not thought wrong |
Should drilling go by topic first or by year?
By topic first, then whole papers by year, then the mark scheme. The first third of the time goes topic by topic (8-10 years of the same topic back to back), the middle switches to timed whole papers, and the last fortnight only redoes the recurring errors from your log.
A 12-week drilling timetable
| Week | Phase | What to do |
|---|---|---|
| Weeks 1-3 | By topic: foundation | Topic by topic, starting with the easiest marks, building habits and recall |
| Weeks 4-6 | By topic: core | 8-10 years of the same topic back to back, errors classified by topic |
| Weeks 7-8 | By topic: advanced and electives | Elective and higher-order topics, now under time pressure |
| Weeks 9-10 | By year: timed papers | One full paper a week, timed, no reference materials |
| Week 11 | Mark scheme work | Question by question against the marking scheme; list the scoring steps you omitted |
| Week 12 | Plug holes and simulate | Only the recurring errors from your log, then one full exam simulation |
Subject-specific weighting for this timetable: Weeks 1-3: keyword lists per topic, three to five compulsory terms with the marks each earns. Weeks 4-6: ten short answers a time with sentence count tied to marks. Weeks 7-9: code drills, three boundary questions asked before every answer plus a short test note. Weeks 10-12: two timed papers a week, the last ten minutes on indentation and variable declarations.
Use it properly: this is not a checklist to finish. Every week must keep time for redoing errors, or from week 9 you will be repeating the same batch.
Pacing
| Paper | Time | Suggested split |
|---|---|---|
| Paper 1 (Theme A + case study) | SL 1 h 15 min / HL 2 h | about 55 min Section A, 20 min Section B |
| Paper 2 (Theme B computational thinking) | SL 1 h 15 min / HL 2 h | includes an algorithmic-thinking question with no code |
How should the time be split inside each IB Computer Science Paper 1 paper?
Paper 1 (Theme A + case study): about 55 min Section A, 20 min Section B; Paper 2 (Theme B computational thinking): includes an algorithmic-thinking question with no code
The drilling mistakes that cost the most marks
| Mistake | What it looks like | What actually happens | Instead |
|---|---|---|---|
| Binary conversion without steps | Final answer only | Show each 4-bit grouping | method marks |
| Generic case-study answer | Theory only | Must cite scenario specifics | cite the scenario |
| Command terms treated alike | Outline written long | Outline gives only the shape | answer the command term |
| Still drilling Paper 3 | Using legacy material | Paper 3 removed from 2027 | only Papers 1 and 2 |
The error log and the mark scheme
Three columns: the question and the answer written; the keyword or boundary case missed; whether the fault was conceptual, syntactic or careless. A boundary case missed twice means writing that test set out in full the following week.
How many years should you drill?
Paper 1 has kept its pattern and marking style for years, so five to seven years covers the main demands; revised-syllabus topics need the official samples and subject guide, with older items kept for concept practice.
How many years of past papers is enough?
Paper 1 has kept its pattern and marking style for years, so five to seven years covers the main demands; revised-syllabus topics need the official samples and subject guide, with older items kept for concept practice.
Frequently asked questions
Is this page a mock paper or a drilling guide?
This is the IB Computer Science Paper 1 drilling guide: assessment structure, drill order, a 12-week timetable, pacing, common mark losses and the error-log method. For questions with answers, use the IB Computer Science Paper 1 mock papers linked under Related.
By topic or by year first?
By topic. Eight to ten years of the same topic back to back is what exposes repeating errors; going straight to whole papers just repeats the same batch under time pressure.
How should the error log be written?
Do not copy out questions. Per error record four things: question reference, which step failed (concept, wording, calculation), what the mark scheme requires, and the correct action next time.
Does a longer short answer score more?
No. Marks follow keywords, and off-target length earns nothing while eating time from the code questions; match sentences to marks, two for two, four for four.
How much is lost when logic works but empty input is unhandled?
The boundary marks, often two or three of the question total; asking empty, single and out-of-range before moving on is cheaper than repairing later.
Official references
| Resource | What to use it for |
|---|---|
| IB Computer Science curriculum update (IBO) | Confirm the Paper 1/2 marks and times |
| https://www.tutorzone.com.hk/en-ib-psychology-paper-1-mock-2027/ | IB Psychology Paper 1 drilling mock |
Related: IB Computer Science Paper 2 drilling mock (Theme B) · IB Computer Science drill guide (two-paper order, 75-minute pacing) · practice area · IB Physics drilling mock
Next step: find a tutor / register as a tutor
After drilling, the hard part is telling a conceptual error from a writing error. Tell us the year group, the school and your available times, and TutorZone will match you with a tutor who knows the HKEAA assessment requirements.
Demand for tutors in this subject is steady, and those who can explain the marking scheme and where marks are won are especially sought after. Register free; you pay only when a match succeeds.