Verbatim quotes from 2 official IB subject reports (2024–2023). Every quote is attributable to a specific paper and session — these are the things IB markers flag year after year.

Writing pseudocode algorithms

There were very few attempts at pseudocode questions indicating that the students were not well prepared for questions based on pseudocode.

— IB examiner, Paper 1 HL, May 2024 TZ1

Vague responses using everyday language instead of…

Students lost marks due to vagueness in their responses and not using the correct key terms. It is evident that these students did not learn definitions of computer science terms.

— IB examiner, Paper 1 HL, May 2023 TZ1

Not relating answers to the given scenario or context

Generic or rote learned answers are likely to only achieve partial marks. Theory should be taught iteratively and in a range of contexts.

— IB examiner, Paper 2, May 2024 TZ1

See how to avoid these in the Computer Science exam guide

About

About IB Computer Science

IB Computer Science is a Group 5 subject (counting as a science for many universities) covering computational thinking, system fundamentals, computer organisation, networks, object-oriented programming (OOP), abstract data structures, resource management, and control. HL students additionally cover databases, modelling and simulation, and further OOP concepts.

The subject emphasises algorithmic thinking and programming skills alongside theoretical concepts. Our archive includes IB Computer Science past papers and mark schemes covering both the current and legacy syllabi, with Paper 1 case study materials and Paper 2 programming questions.

Assessment

Exam Format

Paper 1 (SL: 1 hr 30 min / HL: 2 hr 10 min)

Short-answer and structured questions based on a pre-seen case study released several months before the exam.

Paper 2 (SL: 1 hr / HL: 1 hr 20 min)

Questions on programming, algorithms, and data structures. Requires pseudocode writing.

Paper 3 (HL only: 1 hr)

Questions on the HL extension topic (Databases, Modelling, OOP, or Web Science).

Levels

SL vs HL

IB Computer Science SL has two papers; HL adds a third paper on an extension topic. HL students study more advanced data structures and algorithms, and the HL option topics require deeper analytical skills.

Revision

Study Tips for IB Computer Science

✓Master IB pseudocode syntax — Paper 2 requires writing correct pseudocode, not a specific programming language.
✓Study the case study thoroughly before Paper 1 — questions reference specific details from it.
✓Practise trace tables for algorithms; this is a reliable way to gain marks in Paper 2.
✓Understand the differences between arrays, stacks, queues, linked lists, and binary trees.
✓Review OOP concepts: classes, objects, inheritance, polymorphism, and encapsulation.
✓For Paper 1, use the mark scheme language — generic answers often miss the specific point being awarded.
✓Work through at least 5 years of past Paper 2s to get comfortable with algorithm questions.

FAQs

Questions, answered.

Paper 2 requires writing pseudocode, not a specific programming language. However, learning Java or Python helps build the algorithmic thinking needed to succeed.

A pre-seen document released approximately 4 months before Paper 1. It describes a real-world scenario and Paper 1 questions are based on it.

For computer science or engineering degrees, HL is strongly preferred. SL is suitable if CS is a supporting subject rather than your intended degree.

IB CS uses IB pseudocode in exams. The IA (Internal Assessment) can be programmed in any language — Java, Python, and C++ are most common.

Extremely useful. Paper 1 questions are case-study specific, but Paper 2 question types (trace tables, algorithm writing, data structures) repeat across years.