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Essentials of Computer Systems


Admission requirements

Not applicable.


Modern computer systems consist of many abstraction layers and have the possibility to communicate with other systems in many ways. During this course, we take a journey through these layers and the communication mechanisms.

On the top layer of general purpose computers, phones, etc. we find applications, which are the interface between humans and the computer. That applications run smoothly and safely is ensured by an operating system. The operating system is our first part of the journey, during which we will see how operating systems schedule processes, connect applications with hardware and ensure a smooth operation of the computer.

The next part of the journey is how computer communicate with each other through networks. We start again from the perspective of an application and then make our way through the operating system all the way to how data is transported physically from one computer to another. This will allow us to see how data corruption and manipulation can be prevented.

In the final part of the journey, we go all the way down to the circuits underlying computer systems. Here, we will see how circuits are built, a CPU works and how we can make our own computer for special tasks. We end on the lowest level: the physical underpinnings of computers. Here we will see how transistors process the information we feed them all the way from the application down here.

This course focused on digital computer systems. However, students may choose to study other kinds of computing systems (analog, biological, etc.) if they align with the learning goals of the course.

Course objectives

The basic objectives of the course are to understand what digital computing systems comprise and how they are organised.

Specifically, you will understand

  • the role of abstraction and protocols in computer systems;

  • how operating systems, computer networks and computer architecture underpin the development and maintenance of digital computing systems;

  • one subject of choice in one these three areas in greater detail according to specific learning goals.

Moreover, you will put this knowledge to practice in a project with your chosen subject, again guided by specific learning goals provided during the course. Finally, you will learn how to work in teams, create and execute a project, present knowledge to others and guide other through the process of learning about your subject.


You will find the timetables for all courses and degree programmes of Leiden University in the tool MyTimetable (login). Any teaching activities that you have sucessfully registered for in MyStudymap will automatically be displayed in MyTimetable. Any timetables that you add manually, will be saved and automatically displayed the next time you sign in.

MyTimetable allows you to integrate your timetable with your calendar apps such as Outlook, Google Calendar, Apple Calendar and other calendar apps on your smartphone. Any timetable changes will be automatically synced with your calendar. If you wish, you can also receive an email notification of the change. You can turn notifications on in ‘Settings’ (after login).

For more information, watch the video or go the the 'help-page' in MyTimetable. Pleas note: Joint Degree students Leiden/Delft have to merge their two different timetables into one. This video explains how to do this.

Mode of instruction

The lectures will provide a comprehensive overview of the three main areas and the learning objectives of the course. In the initial segment of the lectures, we will delve into the first and second topics, and to evaluate your progress, an individual exam will be administered. Additionally, a multiple choice quiz will be provided to reinforce the learning goals covered in the first half of the lectures. Similarly, after completing the second segment of the course, a second exam will be conducted, encompassing the topics taught during this phase of the lectures. As an optional opportunity to enhance your final grade, you may choose to undertake small projects either individually or in groups.

Assessment method

The multiple choice quizzes provided with each presentation have to be taken by every student individually to complete the course.

The final grade is composed as follows.
1. Individual exam (middle of the course): 40%
2. Multiple choice quiz on first half of the content: 20%
3. Individual exam (second part of the course): 40%

Additionally, a bonus project could add 10% to the grading. The course is passed if all parts, have been completed. If the course is not passed, the individual exam (1 and 3) can be individually retaken. Should this not be sufficient to pass the course, an individual oral examination on one subject, chosen by the instructor, can be offered, but only a passing grade can be obtained in this way.

Reading list

Presentation material from the introductory lectures will be provided. The course is mainly based on the following books, the introductory chapters of which constitute the basic knowledge of the course.

The following books are not integral part of the course but may be used for further self-study.


From the academic year 2023-2024 on every student has to register for courses with the new enrollment tool MyStudymap. There are two registration periods per year: registration for the fall semester opens in July and registration for the spring semester opens in December. Please see this page for more information.

Please note that it is compulsory to register for every exam and retake. Not being registered for a course means that you are not allowed to participate in the final exam of the course.

Extensive FAQ on MyStudymap can be found here.


Communication will mainly happen through the Brightspace. Individual questions should be directed to a email provided in the first lecture

Education coordinator LIACS bachelors


Not applicable.