Computer Science (3 Years) [BSc]

Operating Systems

Unit code: COMP25111
Credit Rating: 10
Unit level: Level 2
Teaching period(s): Semester 1
Offered by School of Computer Science
Available as a free choice unit?: N



Additional Requirements

Students who are not from the School of Computer Science must have permission from both Computer Science and their home School to enrol.


This course unit assumes that students are familiar with the idea that their applications programs run on some sort of 'box'. The intention is to peel back another layer to see how the system software - and in a few cases the associated hardware - conspire to run that application safely and securely, despite the hardware itself - processors, memory, filestore etc. - differing from case to case.  It also seeks to illuminate the services a typical operating system provides, some of which will probably be unfamiliar, in a practical way.

To support this material there will also be some revision of (or an introduction to, for a few students) some architectural features and enough material on the C language to enable someone already familiar with (say!) Java to be able to poke around the machine.


An operating system is typically the 'lowest' layer of software in a computer.  It provides an abstracted interface so that applications can run on diverse hardware without modification and it provides security which prevents misbehaving software from crashing the hardware or disturbing other tasks which may be running simultaneously.

This course unit provides an introduction to the major principles of implementation of an operating system and some experience in how these features may be exploited by the 'higher' software layers. Note that this module is currently undergoing major redevelopment and modernisation and, whilst the principles will not change, some of the details both in the syllabus and teaching methods may differ in the autumn.

Teaching and learning methods


22 in total, 2 per week


11 hours in total, 1 hour weekly sessions

Assessment breakdown
Exam:  85%
Mid-term test:  5%
Coursework:  10%

Learning outcomes

Learning outcomes are detailed on the COMP25111 course unit syllabus page on the School of Computer Science's website for current students.

Employability skills

  • Analytical skills
  • Problem solving
  • Research
  • Other

Assessment methods

  • Written exam - 90%
  • Practical skills assessment - 10%



  • Overview; abstraction layers; purpose.


  • Basic C programming and pointers
  • Memory map and structure
  • Virtual memory, paging; caches et alia.
  • Processes & threads


  • Protection, priority, real-time constraints
  • Scheduling, context switching

Device management

  • Ownership, protection
  • Polling, Interrupts, DMA

File systems

  • File organisation; types; security

Multiprocessors, hypervisors and future stuff

Recommended reading

COMP25111 reading list can be found on the School of Computer Science website for current students.

Feedback methods

The intention is to automate as much feedback as possible by providing many small 'exercises' to illuminate the various concepts.  Some exercises may only take a few minutes - at least for those who grasp the concept immediately - others a bit longer but wherever feasible misconceptions will be highlighted immediately and more 'goes' provided.  There is a strong intent to keep the assessment elements as minimal as sensible during the duration of the course. 

Scheduled'laboratories' are intended to support the on-line systems which will be available at all times; they are not for generating marks.

Lectures and other material are intended to guide one sensible path through the various interdependent topics.

Inevitably, there will also be an examination at the end of the semester.

Study hours

  • Assessment written exam - 2 hours
  • Lectures - 24 hours
  • Practical classes & workshops - 11 hours
  • Independent study hours - 63 hours

Teaching staff

James Garside - Unit coordinator

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