Introduction
Paper 1 is the heart of IB Computer Science. Whether you’re sitting SL (1 hour 15 minutes) or HL (2 hours), this exam makes up a huge share of your final grade: 35% at SL and 40% at HL. Unlike Paper 2, which leans more on theory and applied contexts, Paper 1 is a problem-solving paper. You’ll be asked to read, write, and interpret code — usually in Java or Python — while applying computational thinking skills.
The question is: what should you focus on if you want the highest return on your revision time? This guide will break down the core Paper 1 topics, explain why they matter, and show you how to revise them effectively in your final days before the exam.
Quick Start Checklist for Paper 1
- Decide on your exam language: Java or Python (stick to one).
- Revise algorithm templates for sorting, searching, and recursion.
- Practice past Paper 1 questions under timed conditions.
- Review the IB command terms — knowing how to “explain” vs. “describe” matters.
- Prioritize clarity in pseudocode — examiners reward logical structure.
The Core Paper 1 Topics
1. Programming Fundamentals
- Variables, constants, and data types.
- Input/output handling.
- Casting and type conversion.
- Common errors (logic vs syntax).
👉 Why it matters: Almost every Paper 1 starts with fundamental coding tasks. Weakness here can cause you to lose easy marks.
2. Control Structures
- If/else statements.
- Loops (for, while, nested).
- Boolean logic.
👉 How to revise: Write small programs that combine loops and conditions — IB loves problems that test both at once.
3. Arrays and Data Structures
- 1D and 2D arrays.
- Basic operations: insert, delete, traverse.
- Stacks and queues (HL especially).
👉 Pro tip: Practice tracing array algorithms step by step. Many students miscount iterations under exam stress.
4. Algorithms
- Searching: linear search, binary search.
- Sorting: bubble sort, selection sort, insertion sort.
- Recursion basics.
👉 These algorithms appear year after year. Even if you can’t write them perfectly, you should recognize their structure and explain time complexity at a basic level.
5. String Manipulation
- Substrings, concatenation, trimming.
- Converting between characters and numbers.
- Searching within strings.
👉 In Python, know your string methods; in Java, practice using .substring() and .charAt().
6. Object-Oriented Programming (HL)
- Classes, objects, methods.
- Inheritance and polymorphism.
- Encapsulation (private vs public).
👉 HL students: Be prepared to design small class structures and explain relationships.
7. Tracing and Debugging Code
- Dry-run code segments.
- Spot off-by-one errors in loops.
- Identify logic mistakes.
👉 IB loves to give broken code and ask you to fix or explain it.
Paper 1 Exam Strategies
Practice Pseudocode, Not Just Code
IB doesn’t care if your syntax matches exactly — they care about logic. Clear pseudocode can often score full marks.
Master Command Terms
- Explain = “make the examiner understand.”
- Outline = “give key points only.”
- Evaluate = “consider pros and cons.”
Knowing these can save you wasted time.
Don’t Over-Engineer
Paper 1 solutions are often simpler than they look. Stick to the basics: loops, arrays, conditions.
Work Step-by-Step
When tracing an algorithm, make a table to track variable changes. This avoids silly mistakes.
How to Revise Effectively in 3 Days
- Day 1: Drill programming fundamentals and algorithms. Write pseudocode for all sorting/searching algorithms from memory.
- Day 2: Practice Paper 1 past questions on arrays, loops, and string handling.
- Day 3: Do one timed Paper 1 under exam conditions, then review every mistake.
Frequently Asked Questions
1. Do I need to memorize algorithms word-for-word?
No. Examiners want to see you understand the structure and logic, not that you’ve memorized exact code. If you can write pseudocode that logically works, you’ll score.
2. Should I choose Java or Python for Paper 1?
Stick with the one you’ve practiced most in class. Both are accepted, but consistency is more important than switching last minute.
3. How much OOP comes up in Paper 1?
For HL, OOP is significant — expect at least one question testing classes and methods. For SL, OOP is less emphasized but can still appear in applied coding problems.
4. Are past papers enough to revise Paper 1?
Yes, but combine them with targeted notes. Past papers train your exam technique, while RevisionDojo’s notes ensure you understand the core syllabus content.
5. What’s the best way to avoid silly mistakes?
Always trace your own code before finalizing. Many marks are lost to off-by-one errors or forgetting to reset a variable.
Conclusion
Paper 1 rewards students who focus on fundamentals and practice. By mastering core algorithms, practicing pseudocode, and training under timed conditions, you can pick up the majority of available marks.
If you only revise a handful of topics, make sure they include arrays, sorting/searching algorithms, control structures, and string handling. For HL, add object-oriented programming.
To boost your revision, check out IB Computer Science Notes for concise explanations, and don’t miss our guide on How to Get a 7 in IB Computer Science. Pair these with daily past paper practice, and Paper 1 will feel far more manageable.
