CMC041 Operating Systems Architecture

1
CMC041Operating SystemsArchitecture

• Prof Cornelia Boldyreff and
• Adrian Wheal

2
Course Manifesto

• Summative and Integrative
• Draws on all aspects of I T
• Illustrates concepts in application
• Outward-looking
• Based on real-world case-studies
• Windows XP, UNIX, Linux and other OSs
• First-hand
• Keyed to your experiences and ours

3
Books

• Strongly recommended
• C Ritchie, Operating Systems, 4th ed, Thomson
• ISBN 0-826-464165
• 22.50 (or currently 16.79 from Amazon.co.uk)
• Other recommended books
• Tanenbaum, Modern Operating Systems
• Dietel and Dietel, Operating Systems
• Stallings, Operating Systems
• Silbershatz and Galvin, O S Concepts
• Note The editions in the library (even if not
  the latest) are fine!

4
Suggested Study Time
5
Assessment

• 5 Workshop tests 10 each
• Based on practical exercises and investigation
• Multiple choice format
• In-Class test 50
• After Easter
• Based on lectures and workshops
• Sample questions and mock test available before
  Easter

6
Course Overview

• What is an Operating System?
• Introduction to the course and to OSAs
• Development of Operating Systems
• History and types of Operating System
• Basic Concepts
• Systems Architecture
• The Concept of Process

7
Course Overview (cont)

• Process Management
• Memory Management
• Extending address space, Virtual Memory
• Inter-process Communication
• Deadlock
• Input-output systems
• File systems

8
Examples of OSs

• DOS
• Windows
• Windows NT
• Mac
• VMS
• OS/9
• Palm-OS

• UNIX
• OSF/1
• Linux
• UniPlus
• OS/360
• VM
• OS/2

9
What is an operating system?
Accounts
Student Records
Library Catalogue
Compilers
Database
Network
User Interface
Operating System
Firmware and Microprogramming
Computer Hardware
10
What is an operating system?

• What does an operating system do?
• Two approaches
• The Operating System as an Extended Machine
• Beautification Principle
• Top-down (user/application centred) view
• The Operating System as Resource Manager
• Bottom-up (machine centred) view

11
OS as Extended Machine

• OS hides the implementation details
• Example the file system of a computer vs direct
  programming of disk controller
• A Standardised Virtual Machine across different
  physical machines
• allows easy program distribution
• Computer appears more beautiful than its ugly
  hardware would alone

12
OS as a Resource Manager

• Allocates resources to users
• Disks, memory, network interfaces, timers,
  terminals/displays, laser printers, etc
• Whos using what? How is it shared?
• Maintains a multi-user illusion to several
  users
• Timesharing system has real multiple users
• Most systems allow several user programs

13
The Evolution of the O.S.

• 1st generation (1945-1955)
• Plugboards, valves, numerical work
• 2nd generation (1955-1965)
• Transistors, cards, punched tape, magtape
• Batch systems dominant
• 3rd generation (1965-1980)
• I.C.s and Multiprogramming
• OS360, VM, Multics, UNIX timesharing

14
Batch Jobs
EOJ
program data cards
RUN
LOAD
fortran program cards
FORTRAN
JOB 2,5 WHEAL
15
Key ideas of 3rd gen OS

• Multiprogramming
• Memory partitioned into several parts
• Different job in each partition
• Spooling
• Simultaneous Peripheral Operation On-line
• Timesharing
• Each user has interactive use
• Job pre-emption ensures fast response

16
Type of Operating System

• Single-user, single-processing
• Single-user, multi-processing
• Timesharing (Multi-user)
• Distributed (Multi-processor)
• Real-time
• Usually designed for control applications
• Require guaranteed response time
• Virtual Machine (VM)

17
4th Generation Systems (80-)

• Microcomputers
• PCs, Workstations
• Supercomputers
• Cray, CDC
• Multi-processor systems
• Distributed Systems
• Networks, client-server systems
• DOS, and UNIX dominant

18
The Digital PDP8

• Basic system
• 12-bit CPU
• 4096 word memory
• Teletype with reader/punch
• Available Software
• Paper-tape kit
• Diagnostics
• PAL (assembler)
• BASIC, 8K Fortran

The Classic PDP8 1965 price from 11,000
19
OS/8

• OS/8 developed from 1965-1977
• Needed only 8K
• Would run on disk or DECtape
• Design copied for CP/M (and DOS)
• Multos-8 offered multiple OS/8 VMs