British Informatics Olympiad: Complete Guide

Editorial overview

The British Informatics Olympiad (BIO) is the UK's national competition for students who want to test themselves on programming problems rather than school-style coding exercises. It is organised as a school-based first round followed by an invitational final in Cambridge, and it also forms part of the selection route for the UK's teams at the International Olympiad in Informatics (IOI), the European Girls' Olympiad in Informatics (EGOI) and the Western European Olympiad in Informatics (WEOI).

That combination gives BIO a distinctive character. Entry to the first round is open to eligible students and does not require a previous qualifying result, but the skill demand rises quickly. The paper is designed so that students with some programming experience can make progress while stronger contestants can be separated by algorithmic insight, implementation quality and the number of test cases they can handle. The official evaluation on CompeteMap reflects that contrast: the entry requirement is light, while the skill demand and preparation load are substantial, with national-selection and international-recognition outcomes.

BIO is not simply a faster version of a beginner coding contest. It asks students to translate a problem into an algorithm, reason about constraints, write a program, test it and improve it. The strongest preparation therefore combines programming fluency with mathematical problem solving and careful debugging.

What is the British Informatics Olympiad?

BIO was founded in 1995 as a non-profit competition intended to encourage active interest in information technology and give strong students an opportunity to compete internationally. The official BIO site describes it as an annual computer-programming competition for secondary schools and sixth-form colleges.

The competition is coordinated through schools or colleges. Students do not need to be studying Computer Science, and the official entry information notes that some successful contestants have been self-taught. This is important for families: a student may have the right ability even if their school does not offer a formal programming course, but the school still needs an adult contact to enter and supervise the first round.

Eligibility and entry

The official rules for BIO 2026 state that the competition is open to students under 19 who are studying full-time at a secondary or further-education establishment in mainland Britain. Entries are coordinated by the teacher in charge at the school or college.

Students in Northern Ireland and the Republic of Ireland should not assume that the British BIO is the correct national route. The BIO rules point to similar competitions for those jurisdictions. Families should check the relevant local organiser and national selection policy rather than entering the wrong pathway.

The first round is not a parent-entry online contest. The teacher registers the school or college, estimates the number of students and arranges the sitting. The school also marks the scripts using the organiser's mark scheme and submits the results for students to be considered for the final.

Entry has historically been free, supported by sponsorship, but dates and administrative arrangements can change. For the next cycle, check the official BIO website and the current rules before planning around a particular deadline.

The BIO pathway

The route is best understood as three connected stages.

Stage 1: School first round

The first round is a three-hour paper taken in school. The 2026 rules describe three programming questions supplemented by written problems. Students may use a computer and any programming language for the programming tasks, but the paper is not a simple automatic online judge: the answer includes programs, written answers and specified test results, and the teacher marks the work using the published scheme.

The purpose of the first round is both access and selection. Students can experience an olympiad-style problem without travelling to a university, while the organisers can identify contestants whose solutions show enough promise for the final.

Stage 2: Cambridge final

The strongest first-round contestants are invited to the final at Churchill College, Cambridge, normally during the Easter holiday. The 2026 rules specify the best 15 first-round competitors, together with additional students taking part for a place on the EGOI team. The final uses written and programming problems and is expected to run in a Linux environment with C/C++ available.

The final is not just a ceremony for students who have already solved the hardest first-round question. It tests whether a contestant can work for longer under more standardised conditions, produce robust programs and make sound algorithmic decisions without the support of a classroom setting. Food and accommodation are covered under the published 2026 rules; families should confirm the arrangements for the relevant year.

Stage 3: international teams

The final is also the selection point for the UK's IOI, EGOI and WEOI teams. The four top BIO finalists form the British IOI team, subject to the current rules and eligibility requirements. Other final results are used to select the EGOI and WEOI teams and reserves.

The progression is therefore:

School registration -> BIO first round -> Cambridge final -> IOI / EGOI / WEOI selection

There is no requirement to win a separate junior contest before entering BIO. However, reaching the international team stage requires success through the BIO selection process and compliance with the relevant international eligibility rules.

What does the first round actually test?

The first round is built around problems rather than a fixed school syllabus. A student may need to use simulation, greedy reasoning, counting, graph ideas, dynamic programming, search, data structures or mathematical observation. The paper can reward partial progress: a program that solves small cases or an easier subtask may earn useful marks even if it does not solve the full constraint range.

Students should therefore read the constraints carefully. They are not decorative numbers. A solution that is correct for 100 inputs may be unusable for 100,000. A strong contestant asks:

• What is the input size?
• What time complexity is likely to pass?
• Can the problem be simplified into subtasks?
• Is there a pattern, invariant or monotonic property?
• What cases will break a greedy or brute-force approach?
• How can the program be tested before submission?

This is why BIO feels different from writing a small app. The objective is not primarily to create a user interface or demonstrate a language feature. It is to find a correct and efficient method under constraints.

Who is BIO suitable for?

BIO is a strong fit for students who enjoy puzzles, algorithms and turning an abstract idea into a working program. It can suit:

• students who already solve competitive programming problems;
• students who enjoy mathematics but want an algorithmic outlet;
• self-taught programmers who do not take Computer Science at school;
• students who like debugging and improving a solution after it fails;
• students considering Computer Science, Mathematics, Engineering or related degrees.

It is less suitable as a first-ever coding experience if the student has not yet learned variables, loops, functions, arrays and basic debugging. That does not mean a beginner should avoid it forever. It means the first goal should be building the foundations needed to understand a problem and test a program independently.

How to prepare

1. Build one reliable language foundation

For the first round, any language may be used under the rules, but students should choose one language they can write and debug comfortably. For the Cambridge final, the published 2026 rules identify Linux and C/C++ as the expected environment. Students aiming for the final should eventually become comfortable with the final's environment rather than relying on an unfamiliar language on the day.

The foundation should include input and output, arithmetic, strings, arrays, loops, functions, sorting, basic recursion, sets or maps, and file or standard-input habits appropriate to the contest environment.

2. Learn to reason from constraints

Before coding, estimate the scale of the problem. A quadratic algorithm may be fine for a few thousand items and impossible for a million. Students should practise writing a one-line complexity estimate for every solution.

3. Work through past BIO problems

The official BIO problem archive contains past questions, and BIO Helper provides a grader and model solutions for many round-one problems. These resources are especially useful because they show the style of the competition and allow students to practise partial scoring and test-driven debugging.

Use them in stages:

1. solve without help;
2. identify the largest subtask you can handle;
3. inspect the constraints and mark scheme;
4. read a solution only after recording your own idea;
5. reimplement the solution from memory;
6. change the examples and test edge cases.

Reading code is not the same as acquiring the algorithm. The student should be able to explain why the method works and what input would expose a weaker approach.

4. Practise partial solutions

BIO rewards useful progress. Students should learn to submit or test a simple correct solution first, then improve it. This develops a better contest habit than spending the whole session searching for a perfect idea while having no working baseline.

5. Add timed sessions gradually

Start untimed so that algorithm selection can be discussed. Then use a 45- or 60-minute problem session, followed by a full three-hour paper closer to the competition. After each session, review not only wrong answers but also time lost to reading, coding, testing and debugging.

A twelve-week preparation structure

The exact topics should follow the student's errors, not a fashionable checklist. A student who knows graph terminology but cannot test a simple program needs more implementation discipline, not another advanced topic.

What the school needs to do well

Because BIO is school-coordinated, students should ask early:

• Who is the teacher in charge?
• Does the school register all interested students or run an internal selection?
• Which programming language and computers are available?
• Can the first round be supervised for the full three hours?
• What is the internal deadline for registering interest?
• How will student programs and written answers be stored and marked?

If a school has not entered before, a student can approach a Computing, Mathematics or ICT teacher with the official rules and a simple request: “Could the school register for BIO and supervise a first round? I can help identify interested students and share the official information.” This is more useful than asking the school to create an entire training programme immediately.

BIO compared with other coding competitions

BIO sits in a particular part of the landscape. UK Bebras and The Raspberry Pi Foundation Coding Challenge can help students discover computational thinking and problem solving. BIO moves further toward algorithm design, implementation and national-team selection. A student does not need to complete those earlier competitions to enter BIO, but they may provide useful preparation.

The progression is not a single mandatory ladder. A student can move from general coding challenges to BIO, learn through online programming platforms, or begin directly with BIO past problems if they have the necessary foundations. The important question is whether the student is building the skills BIO actually tests.

Common mistakes

Learning language syntax instead of problem solving

Knowing more library functions will not replace the ability to model a problem and reason about constraints.

Ignoring written explanations

The first round includes written elements. Students should practise explaining an algorithm, not only submitting code.

Starting with the hardest final problems

The official first round is the correct entry point for most students. Build confidence with accessible problems, then increase the difficulty.

Copying model solutions

A copied program can pass a test while the student still cannot identify the key idea. Reimplement and modify the solution after reading it.

Treating the final as automatic after a good school paper

The final is a new selection stage. Students invited to Cambridge should expect different conditions, Linux and C/C++ expectations, and longer-form algorithmic pressure.

Key Takeaways

• BIO is the UK's national programming competition and part of the route to IOI, EGOI and WEOI selection.
• Eligible students can enter the first round without a prior qualifying result, but entry is coordinated through a school or college.
• The first round is a three-hour, three-question paper with programming and written components.
• The strongest first-round contestants progress to a Cambridge final; the final selects international teams.
• BIO tests algorithmic reasoning, implementation, constraints, testing and debugging rather than school syllabus recall alone.
• Students do not need to study Computer Science, but they do need reliable programming foundations and a willingness to solve unfamiliar problems.
• Use official past papers, mark schemes and graders to practise partial solutions and explain why algorithms work.
• The website Evaluation describes BIO as light to enter but demanding in skill and preparation, with national-selection and international-recognition outcomes.
• Always check the current year's official rules for eligibility, registration dates, language and final arrangements.