Computer Science


The Computer Science Tripos (CST) has a number of options in year 1. At first these may seem confusing, but they are there to provide ways in which students can select a route into the subject that best suits their background and experience. All CST students spend 50% of their time in the first year taking Papers 1 and 2 of the CST, covering hardware, software, operating systems, algorithms and some of the mathematics that lies behind all of these. The content of the remaining 50% depends on the option followed:

The CST 75% option: This option suits students who wish to concentrate their studies on computer science to the maximum extent possible, without incorporating material from related subjects. A student following this option will spend a further 25% of their time in the first year taking Paper 3 of the CST, and the remaining 25% of their time completing a mathematics course that is held in common with other subjects.

The CST 50% option: This option allows students to study a further subject in addition to computer science in their first year. A further 25% of their time is spent on a mathematics course that is held in common with other subjects, leaving the final 25% a free choice from a number of possibilities: Physics, Earth Sciences, Chemistry, Physiology, or Evolution and Behaviour (all experimental science subjects from the Natural Sciences Tripos (NST)). Students take paper 3 of the CST in their second year.

The Computer Science with Mathematics option: Students following this option fill the remaining 50% of their time taking Papers 1 and 2 from the main Mathematics Tripos, covering vectors and matrices, differential equations, probability, and analysis. It should be noted that a very high level of mathematical preparation will be expected of those wishing to take this route, but that it is intended as a route into second year computer science and students will not normally be able to switch to the full Mathematics Tripos at the end of the first year.

Option selection

Applicants should indicate on their application if they intend to read the Computer Science with Mathematics option. If selecting one of the remaining options it is not necessary to choose a specific option until the first week of the first term. It will not normally be possible to switch to the Computer Science with Mathematics option if this was not the option applied for.

Computer Science in other subjects

The CST options described above are aimed at those wanting to become graduates in Computer Science. Alternatively, there is a Computer Science option in the first year of the Natural Sciences Tripos, where computer science accounts for 25% of the work in the first year (Paper 1 of the CST covering programming, algorithms and numerical methods). In addition, students take two natural science subjects and the common mathematics course for scientists. This can be a good route for students whose core interests are in one of the physical sciences, but who would appreciate some exposure to university-level computer science in their first year.  It will not normally be possible to switch to the Computer Science Tripos from this route.

Optional Fourth Year

It is possible to apply to continue studying Computer Science into a fourth year, provided a sufficiently high standard is achieved in the third year examination. The course then leads to the MEng degree in addition to the BA achieved in the three year course. If necessary – for example in dealing with your funding body – it would be wise to indicate that the length of the course is four years, or three/four years, to allow for all possibilities.

Further information on the CST Tripos

Please see for further information hosted by the Computer Laboratory website.  In particular, you can find information here on the detailed structure of later years in the CST.

CST in Trinity

Trinity’s Directors of Studies in Computer Science are: Dr Sean Holden, whose research interests include machine learning, Bayesian inference, and artificial intelligence, and Professor Frank Stajano, whose research interests include systems security, privacy in the electronic society, and ubiquitous computing.

Student rooms provide network connections allowing access to email, the web and all major computing facilities around the University. There are also well-equipped computer rooms which provide access to scanners, laser printers and where the bulk of the machines can be re-set to run either Windows or Linux.

Interview and written test

Candidates shortlisted for an interview will also sit the Computer Science Admissions Test (CSAT) – a written test that has been jointly designed by Directors of Studies from various Colleges.  The test will be followed by a 45-minute interview with a Director of Studies and another Computer Scientist. Information on the CSAT, including sample papers, can be found at

Preparatory on-line course

Before arriving in October successful candidates will be required to complete an online pre-arrival course, and an acceptable performance may be used as a prerequisite for following the 75% CST option in the first year.


Each of the options described above has specific A-level requirements. Conditional offers for the CST will typically be A*A*A including Mathematics and two other science subjects (preferably Physics and Further Mathematics); we may also ask for a high grade in a relevant subject taken at only AS level.

In addition to these requirements, applicants selecting the Computer Science with Mathematics option should note that the entry requirements are particularly rigorous: they will need to offer at least AS-level Further Mathematics, A2-level Further Mathematics would be desirable, and it is very likely that any offer made would require the attainment of specified STEP results.

Comparable conditions are set for those taking the IB and other school-leaving examinations.  The annual intake is normally between 6 and 8.

Teaching Staff

  • Dr Sean Holden
  • Dr Frank Stajano

Admissions Assessment

All applicants for Computer Science are required are required to take the Computer Science Admissions Test (CSAT) at interview, if interviewed.

Assessment format

  • CSAT Maths-based problems (120 minutes)

You do not need to register or be registered in advance for the assessment at interview – the College will provide details of arrangements in the emails inviting applicants to interview.

Further details about the format of the assessment and preparatory materials can be found on the written assessments page.

Please note that your performance in the assessment at interview will not be considered in isolation, but will be taken into account alongside the other elements of your application.


Applications received 58
Offers made 12
Applications received 68
Offers made 10
Applications received 74
Offers made 11
Applications received 97
Offers made 17