Computer Laboratory > Teaching > Course material 2008–09 > Operating Systems I


Operating Systems I

Principal lecturer: Dr Steven Hand
Taken by: Part IA CST
Past exam questions


The overall aim of this course is to provide a general understanding of how a computer works. This includes aspects of the underlying hardware as well as the structure and key functions of the operating system. Case studies will be used to illustrate and reinforce fundamental concepts.


The course comprises 17 lectures given M/W/F at 12:00 in the Hopkinson Lecture Theatre, starting in Michaelmas on Wednesday 5th November, and resuming in Lent term on Monday 19th January. The course divides into three main parts as follows:

Part I. Computer Organisation

  • Computer Foundations. History: from vacuum tubes to VLSI. Von Neumann architecture. Hardware/software layers and languages.

  • Operation of a Simple Computer. Overview: processors, memory, buses, devices. Memory: concepts, structures, hierarchy. Processor: control and execution units. ALU and computer arithmetic. Logical and Conditional Operations. Branches. Memory access. Data representation: (integers), text, reals, compound structures, instructions. Fetch-Execute Cycle Revisited.

  • Input/Output. General I/O architecture. Example devices. Buses: general operation, hierarchy, synchronous versus asynchronous. Interrupts. Direct Memory Access. Review of Part I.
Part II. Operating Systems

  • Introduction to Operating Systems. Abstract view of an operating system. OS Evolution: multi-programming, time-sharing. Dual-mode operation. Protecting I/O, memory, CPU. Kernels and micro-kernels.

  • Processes and Scheduling. Job/process concepts. Scheduling basics: CPU-I/O interleaving, (non-)preemption, context switching. Scheduling algorithms: FCFS, SJF, SRTF, priority scheduling, round robin. Combined schemes.

  • Memory management. Processes in memory. Logical addresses. Partitions: static versus dynamic, free space management, external fragmentation. Segmented memory. Paged memory: concepts, internal fragmentation, page tables. Demand paging/segmentation. Replacement strategies: OPT, FIFO, LRU (and approximations), NRU, LFU/MFU, MRU. Working set schemes.

  • I/O Subsystem. General structure. Polled mode versus interrupt-driven I/O. Application I/O interface: block and character devices, buffering, blocking versus non-blocking I/O. Other issues: caching, scheduling, spooling, performance.

  • File Management. File concept. Directory and storage services. File names and meta-data. Directory name-space: hierarchies, DAGs, hard and soft links. File operations. Access control. Existence and concurrency control.
Part III. OS Case Studies

  • Unix case study. History. General structure. Unix file system: file abstraction, directories, mount points, implementation details. Processes: memory image, life cycle, start of day. The shell: basic operation, commands, standard I/O, redirection, pipes, signals. Character and block I/O. Process scheduling.

  • Windows NT case study. History. Design principles. Overall architecture. HAL. Kernel: objects, processes, threads, scheduling. Executive: object manager and object namespace, process manager, VM manager, I/O manager. File-System. Security System.


At the end of the course students should be able to
  • describe the fetch-execute cycle of a simple computer with reference to the control and execution units
  • understand the different types of information which may be stored within a computer memory
  • explain the concepts of process, address space, and file
  • compare and contrast various CPU scheduling algorithms
  • understand the differences between segmented and paged memories, and be able to describe the advantages and disadvantages of each
  • compare and contrast polled, interrupt-driven and DMA-based access to I/O devices

Supervisions and Revision

The handouts are available on-line:
  • handout-1 (computer organization) [1up or 2up]
  • handout-2 (MIPS assembly) [2up]
  • handout-3 (OS intro, processes, memory management) [1up] or [2up]
  • handout-4 (I/O, filing systems) [1up] or [2up]
  • handout-5 (case studies) [1up] or [2up]
For the MIPS assembly section of the course it is strongly recommended that you get a copy of SPIM, the MIPS simulator. Versions are available for linux, mac OS X, or windows from The same page has a list of additional resources towards the end, and you should be able to find a number of other sites with tutorial info or example programs. It is of course best to learn by doing, so get programming!

In previous years, there was a second course in Part IB which covered additional topics in operating systems. Some parts of this have been incorporated into the current Part 1A course, but some others were not (due to space constraints). For interested students, I've put the old Part IB notes here, as well as a short document which expands on some of the aspects therein here. Please feel free to read these yourselves and/or discuss them with your supervisor.

The past exam questions are also online and are useful for exam practice, or for assigning supervision work. Note that the course was substantially revised in 1998/99, and so many questions prior to to 1999 are not relevant; some exceptions are 1998 P1Q4 and 1998 P1Q11. There is also a set of additional questions for the first part of the course (computer organisation) which were prepared by Dr Tim Harris in 2002. They are available in ps.gz and pdf formats.

Finally, one of the PhD students in the systems research group has put together a set of sample / revision questions which cover all parts of the course. You can find them here.

Recommended books

There are a large number of books covering the various topics in this course; a selection are listed below. One caveat regarding operating systems texts; many details of process synchronization issues are not relevant to this course, being a topic covered in subsequent lecture series.
  • Tanenbaum, A.S. (1990). Structured Computer Organisation. Prentice-Hall (3rd ed).
  • Patterson, D. &; Hennessy, J. (1998). Computer Organisation and Design. Morgan Kaufmann (2nd ed.).
  • Bacon, J. & Harris, T (2003). Operating Systems. Addison-Wesley (3rd ed).
  • Silberschatz, A., Peterson, J.L. &; Galvin, P.C. (1998). Operating Systems Concepts. Addison-Wesley (5th or 6th ed).
  • Leffler, S. (1989). The Design and Implementation of the 4.3BSD Unix Operating System. Addison-Wesley.
  • Solomon, D. & Russinovich, M. Inside Windows 2000. Microsoft Press (3rd ed.), 2000, or Windows Internals, Microsoft Press (4th ed.), 2005.

Useful Links


Feedback is welcome at any time: either through the on-line feedback system, by e-mail to me or through any of the other channels available.