Operating systems and related system software such as hypervisors form the basis of today's computer systems. The design and implementation of the core parts of system software can have significant impact not only on the performance of a computer system, but also on other aspects such a safety, security, and energy efficiency. Thus, the design and implementation of operating systems is a highly relevant topic for students working in all areas of computer science, from small embedded systems to large virtualized Cloud infrastructures.

This module concentrates on the central part ("kernel") of an operating system, i.e. the part of the system running in a privileged processor mode that interacts directly with hardware. Based on seminal publications, students will investigate different architectures of kernels, such as monolithic, micro- and exokernels, hypervisors and also unikernels. Mechanisms and policies of operating systems will be analyzed with respect to their functional as well as non-functional properties. The analysis of mechanisms dependent on a specific processor architecture will be explained using the modern and open RISC-V processor architecture.

A central part of this module will consist of code reading and the development of pieces of code for a small operating system. Different aspects of operating system functionality will be demonstrated through existing code. Constraints of, extension possibilities for, as well as alternative approaches to implement a given functionality will be discussed; this discussion will then form the basis for the implementation of a given feature in the practical exercises. An example for this is the discussion of file systems; here, features of a given traditional inode-based file system will be discussed and analyzed and alternative implementations, such as log-structured file systems, will be investigated and implemented in a basic form.