Operating Systems I
Principal lecturer: Dr Steven Hand
Taken by: Part IA (50% option), Part IA (25% option), Part IA (Maths with Computer Science)
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
The course comprises 12 lectures given T/T/S at 12:00 in the Cockroft
Lecture theatre, starting Thursday 22nd April. The course divides into
three main parts as follows:
Part I. Computer Organisation
Part II. Operating Systems
- 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 III. OS Case Studies
- Introduction to Operating Systems.
Abstract view of an operating system. OS Evolution:
Dual-mode operation. Protecting I/O, memory, CPU.
Kernels and micro-kernels.
- Processes and Scheduling.
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. Comparison. Software segments.
- 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.
- 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.
- 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.
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 notes are available on-line in
postscript, 1up, PDF, 1up, or
gzipped poscript, 2up) formats.
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) since this is not well represented
in the past exam questions. These were prepared by Dr Tim Harris in
2002, but remain valid. They are available in
ps.gz and pdf
Supervisors: note that a section of the first part of the course
includes additional material not for examination and not covered in
lectures. However you may wish to go over this with interested students.
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 vitual memory management and process synchronization
issues are not relevant to this course, being topics covered in subsequent
- 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 (2000). Inside Windows 2000.
Microsoft Press (3rd ed.).
Feedback is welcome at any time: either through the on-line comment
system, by e-mail to me or
through any of the other channels available.