Guide to Oxbridge Computer Science Interviews

Receiving Your Invitation to Interview

Receiving an invitation to interview at Oxford or Cambridge is a significant achievement. Typically, invitations are sent out in late November or early December, so it can be a little wait between applying and receiving your invitation. This means that it can be a good idea to start preparing for potential interviews before you’ve been invited, since there’s likely to be less than a month between receiving a formal invitation and attending the interview itself. Notification of your invitation (or not) will come in a letter or email from an Oxford or Cambridge college. This could be the college you applied to, or another college (either different from the one you applied to or any college if you submitted an open application). If you applied to a specific college and are invited to interview elsewhere, do not take this as any kind of sign reflecting your chances at acceptance - it is all part of the normal reallocation process that Oxford and Cambridge use to ensure that the best applicants across the university are accepted.

The date and time of your interview(s) (or at least those which the college has organised at present - but more on that later) will be specified in the correspondence you receive from the college along with your invitation, so no need to worry about organising that. Oxford have already published their rough interview timetable (i.e. windows in which various subjects can expect their interviews to take place), but this can always change so it’s good to remain a little flexible. Most interviews in the 2023-2024 cycle will be held online again this year, with the exception of specific Cambridge applicants (UK-based applicants to Gonville & Caius, King’s, Pembroke, Peterhouse, Selwyn, and Trinity Colleges). If you are asked to interview in person, the details of this will be made clear in your invitation from the College.

Turning Up to Your Interview (Online)

1. Technical Preparation

Since the COVID-19 pandemic, online interviews are still being used at both Oxford and Cambridge (with the exception of the Cambridge applicants listed above). This makes the interview easier in certain manners (you won’t have to travel, you are able to remain in the comfort of your own home, etc.), but it also presents additional potential issues in that you are responsible for ensuring you have a reliable technical set up. In the lead up to the interview, ensure that you have access to a stable internet connection, a functioning camera (either built into a laptop or computer, or a separate webcam), and a quiet, well-lit environment. Be sure to check this all with plenty of time to spare (e.g. the week or some days before) so that, should an issue arise, you’ve got plenty of time to address it.

If you are worried about not having access to the appropriate equipment or the right atmosphere in which to conduct a successful interview, we suggest asking your school if they have a classroom or quiet space and some equipment you could use.

2. Dress Appropriately
Even for online interviews, it is a good idea to dress smartly. Present yourself professionally, just as you would in person, but ensure that you are also comfortable (remember that if you’re interviewing over a webcam you can always keep on your favourite slippers!). We’re not saying that you need to wear a full suit and tie, but maybe don’t keep on your pyjamas or a stained hoodie; interviews are all about showing your intent, and dressing respectfully is the first step to showing that you mean business.

3. Practice Video Interviews
If you're not used to video interviews, practice with friends or mentors to get comfortable with the format. It can be easy to think of talking over video meetings to be just the same as in person, but the process can actually feel very different. Chances are most of us have learned to interact over online video chat over the course of the COVID-19 pandemic, but it’s always good to get a little practice in order to refresh your memory. We also recommend practising video calls from your chosen location (either with someone else or just to yourself) to make sure that nothing inappropriate can be seen in the background!

Turning Up to Your Interview (In Person)

1. Arrive Early
If your interview is in person, make sure you arrive early. This will give you time to settle your nerves and familiarise yourself with the surroundings. Punctuality shows that you are serious about performing well in your interviews, as well as ensuring that you’re not rushing and flustered when you arrive (something which can easily carry on into the interview itself and affect your performance).

2. Dress Smartly
Wear appropriate attire for the occasion. You don't need to be overly formal, but looking well-presented (whilst trying your best to maintain comfort) is essential. Remember that these are your potential future professors and/or tutors, so think about what is appropriate to where to class or in a professional setting when dressing for your interview; first impressions (in all regards) are important!

3. Bring Necessary Documents
Make sure that if the college or department specify any documents, you have brought them with you. It may not be necessary, but you might also like to consider bringing a copy of your personal statement with you when you travel to Oxford or Cambridge for the interview process. It is highly likely that interviewers will ask questions building from the content of the statement, so making sure that you’re on top of the content therein is crucial to a good performance.

How Many Interviews Will I Have?

The number of interviews you will be asked to attend varies by course and college. Some applicants may have two or more interviews, while others might have only one. It's crucial to check the specific requirements for your chosen course and college. It is also common to have two interviews scheduled from the beginning: one with your college and one with the department.

In addition to the interviews you have scheduled from the start, it is also possible that, during the interview window, you will have further interviews scheduled. This is usually because other colleges have decided to cast their net wider, and are considering you for a position at their college instead of the one who invited you to interview. These interviews will be conducted by new interviewers, so there is no separate preparation you will need to undertake. It’s also important to remember that being invited to other interviews in no way indicates that you have a higher or lower chance of being accepted: It’s just part of the university’s way of making sure they get the most talented Computer Science applicants from across the applicant pool.

Answering Questions Based on Your Personal Statement

Be prepared to discuss your personal statement in detail during the interview. Examiners may ask questions related to what you've written, so make sure you understand every aspect of your statement. We recommend reading through your personal statement regularly in the lead up to interviews to ensure that you know its contents inside and out! It can also be useful, if you have time, to read, watch, or listen back on the key sources you reference in your statement, especially since it can be some time between initially consulting them and attending the interview itself. Remember that interviewers will be well-versed in key literature relating to your subject, and so may well be familiar with any resources you reference, meaning that you need to know them in detail (or at least the key arguments within that you find interesting) to be able to discuss them in an academic setting.

A useful exercise can be to think about the key ideas or resources in your personal statement critically just to yourself. Maybe write them down and produce a spider diagram of thoughts, opinions, or interesting linking ideas you have relating to them? Thinking in a creative and open-minded way about the content of your Personal Statement can be a good way to prepare yourself for the questions interviewers might ask. We also recommend sitting down with a parent, friend, or mentor to explain and discuss the big issues identified in your Personal Statement. Don’t worry if nobody close to you is familiar with the topic; sometimes explaining an idea to someone new can be the best way of solidifying it in your own mind!

Pre-Interview Admissions Assessments (For Cambridge Computer Science Applicants)

If you’re applying to the Computer Science course at Cambridge at Peterhouse or Trinity Colleges, you will be required to sit an admissions assessment as part of the interviewing process. There is no admin or registration attached to this assessment, and all the relevant details relating to it will be communicated to you by the college when you are invited to interview.

The Computer Science Aptitudes Test is a 100 minute paper made up of several sections of questions, from which students can answer the subsets of questions that they feel most comfortable answering. Section A features 8 questions and Section B features 12 questions, with Section B being more challenging and the questions worth more marks. A student’s best 5 questions in each section are considered and the points contribute to their final score.

Even though these tests are based on skills rather than particular subject knowledge, they can absolutely still be prepared for! We recommend going through past papers to practise applying your skills to unseen materials and responding in timed conditions as per the real test. Our Computer Science Aptitudes Test guide is a great place to start for tips and tricks on how to prepare.

Analysing Unseen Materials as Part of the Interview

Often in Oxbridge-style interviews, applicants are given a piece of unseen material and asked to discuss it as part of the interview. This could be a text extract, a piece of data, an image, or a problem to solve. In the case of Computer Science interviews, interviewers may provide you with a problem sheet to work on. They will most likely provide you with this just before the interview and ask you to discuss your answers in the interview itself. 

The key to such a task is to approach it as systematically as possible. Reading the problems carefully, making notes as you work it out, and thinking about possible discussion points as you go through it can all be crucial to your performance in the interview. Remember that subjects are broad and there is a good chance you will be unfamiliar with the content or specific context of the material in question; this is not a problem! The exercise is not intended to assess how much you know about the wider subject, but rather your application of principles you have learned in your studies so far to new materials. 

What Do I Do If I Don't Know the Answer to a Question?

It's okay not to have all the answers. If you encounter a question that stumps you, the key is not to panic. Take a deep breath, ask for clarification if needed, and attempt to work through the problem logically. Interviewers often want to see how you handle challenging situations and think on your feet. For more guidance on how to handle unknown questions in an interview situation, read our tips for answering an unexpected Oxford and Cambridge interview question.

Example Questions

Below are some past interview questions asked to applicants for Computer Science (and its combination subjects) during their Oxford and Cambridge interviews. Use them to get a feel for what is asked during an interview and to prepare your strategy for responding.

Computer Science (Oxford and Cambridge):

• Tell me about binary searches and their efficiency.
• What are the possible ways of making a secure transfer?
• What is the fundamental difference between a spreadsheet and a database?
• What is the fundamental difference between a spreadsheet and a database?
• What factors contribute to the accuracy of the Global Positioning System (GPS)?
• How would you ensure security between two people, A and B?

Computer Science and Philosophy (Oxford):

• What is the relevance of philosophy in science as opposed to everyday life?
• Write an algorithm to find all factors of a number.
• How would you define infinity?

How to Prepare for an Oxbridge-Style Interview 

Given that the interview is designed to test, in large part, your creativity and thinking skills, it is unsurprisingly quite difficult to think of how to prepare. As we talked about before, the first step we recommend is to go through your personal statement and review any key sources so that you’re happy to discuss questions relating to them (since they are the questions you can most rely on cropping up). When it comes to preparing for unexpected or unknown questions, there are a whole host of ways that you can exercise your ability to deal with them. To delve into these recommendations in closer detail, read our dedicated interview preparation top tips blog, where our expert mentors have collated their 14 most useful tips for interview preparation.