1 Operating Systems: Principles and Practice Cpr E 308

2 What is an Operating System? It is the code that {Linux, Sun, Microsoft} provide The code which makes the computer crash ….. Copyright © 2002 Thomas W. Doeppner. All rights reserved.

3 Introduction A computer system consists of –hardware –system programs –application programs

4 What is an Operating System? It is an extended machine –Hides the messy details which must be performed –Presents user with a virtual machine, easy to use abstractions It is a resource manager –Each program gets time with the resource –Each program gets space on the resource

5 Hardware Resources

6 Floppy Disk I/O Anybody who directly communicates with the floppy disk controller must deal with: Physical address on disk (disk block) The data recording format Turn on/off the motor Error detection/correction

7 Abstractions Hardware –Disks –Processors –Network –Monitor –Keyboard –Mouse Operating System –Files –Threads of control –Communication –Windows, graphics –Input (files) –Locator Copyright © 2002 Thomas W. Doeppner. All rights reserved.

8 Program vs Process A process is a program in execution –Program is a piece of code –Process has “state” (what could this state be?) There could be multiple processes all simultaneously executing the same program

9 Multiple Processes Coordinate accesses and sharing of resources Sharing in time – CPU cycles Sharing in space – Memory

10 Memory Sharing Process 1 Process 2 Operating System Process 3 Physical memory

11 Single Processor Sharing Each process gets a “virtual processor” Virtual processor Real processor Copyright © 2002 Thomas W. Doeppner. All rights reserved.

12 Multi Processor Systems Virtual processor Copyright © 2002 Thomas W. Doeppner. All rights reserved.

13 Deadlocks (a) A potential deadlock. (b) an actual deadlock.

14 What is an Operating System? It is an extended machine –Hides the messy details which must be performed –Presents user with a virtual machine, easier to use It is a resource manager –Each program gets time with the resource –Each program gets space on the resource

15 History of Computer Hardware First generation –vacuum tubes, plug boards Second generation –transistors, batch systems Third generation 1965 – 1980 –ICs and multiprogramming Fourth generation 1980 – present –personal computers

16 History of Operating systems (1) Vacuum Tubes –No operating system –Programmers supplied all the code –All programs in machine language

17 History of Operating Systems (2) Early batch system –bring cards to 1401 –read cards to tape –put tape on 7094 which does computing –put tape on 1401 which prints output –Use of high level languages

18 History of Operating Systems (3) Third Generation Computers Multiprogramming system

19 History of Operating Systems(4) Third Generation –Multics (GE, Bell Labs, MIT) –OS/360 (IBM) –Unix (Thompson and Ritchie, Bell Labs) Originally written for DEC PDP-11 Source code released to universities “Portable” Enhanced by Berkeley (BSD)

20 PC/Workstation Operating Systems Apple Macintosh (GUIs) Microsoft DOS, Windows Sun OS, Solaris (Unix based) 1987: Tanenbaum writes OS text and toy OS “Minix” 1992: Linus Torvalds releases Linux 0.12 (building on Minix) 2001: Windows XP

21 Course Info Text: “Modern Operating Systems” by Andrew S. Tanenbaum, 2 nd edition Website WebCT to handle grades, discussions

22 Labs Weekly labs Check your section Labs begin next week

23 The Workload Programming Labs – 30% 2 Projects – 15% 3-4 home works Quizzes based on homeworks – 10% Two exams (mid-term 15% and final 30%)

24 Collaboration Labs should be done individually (unless otherwise specified) –Not allowed to use work done by other students –Not allowed to get answers directly in any form (ex: from the web) Cases of cheating will be dealt with severely