1. Operating Systems Dr. Raihan Ur Rasool BICSE-3 Credits: 3

2. 1.2 Operating System Concepts Contacts Office: Academic Block -II Phone 051-9280439 Ext 129 Office Hours: Monday 1000 – 1200 hrs email: dr.raihan@niit.edu.pk Exceptional meeting: Give me an email and get time.

3. 1.3 Operating System Concepts Course Outline 1.Introduction 2.Operating System Structures 3.Processes 4.Threads 5.CPU Scheduling 6.Process Synchronization 7.Deadlocks 8.Main Memory 9.Virtual Memory 10.File-System Interface 11.File-System Implementation 12.Mass-Storage Structure 13.I/O Systems

4. 1.4 Operating System Concepts Books n Text Books  Operating System Concepts, 7th Edition, by Avi Silberschatz, Peter Baer Galvin, Greg Gagne, published by John Wiley & Sons, Inc. ISBN 0-471-69466-5

5. 1.5 Operating System Concepts Books n Reference Books  Operating Systems by Williams Stallings F www.howstuffworks.com F www.whatis.com

6. 1.6 Operating System Concepts Evaluation One Hour Tests (OHT): 30% Assignments: 10% Quizzes: 5% Project: 10% End Semester Examination (ESE): 45%

7. 1.7 Operating System Concepts Policies Bring your own calculator, pen paper etc.. You will not be allowed to borrow anything from anyone during any test Must write your name and reference number (Merit No or Regn No) in a test No late work will be accepted (unless arrangements have been made in advance) Ask questions; participate actively in class You are allowed to talk to instructor only

8. 1.8 Operating System Concepts Policies You are responsible for what is covered in class – even if you don ’ t show up Deficiency in attendance may lead to termination or relegation You are encouraged to help each other with your homework assignments – but you must turn in your own work If you are found to be cheating, you will fail at least the assignment / test and perhaps the entire class

9. 1.9 Operating System Concepts Policies If you have any learning disabilities or special needs, please let me know in advance through email or personal meeting Check your email regularly for messages Quizzes are unannounced

10. 1.10 Operating System Concepts Chapter 1: Introduction What is an Operating System? Mainframe Systems Desktop Systems Multiprocessor Systems Distributed Systems Clustered System Real -Time Systems Handheld Systems Computing Environments

11. 1.11 Operating System Concepts What is an Operating System? A program that acts as an intermediary between a user of a computer and the computer hardware. Operating system goals:  Execute user programs and make solving user problems easier.  Make the computer system convenient to use. Use the computer hardware in an efficient manner. E.g.  Microsoft Windows 98/2000/XP  Linux (Different flavors, RedHat most popular)  Unix (FreeBSD Popular)  Solaris (Based on Unix, expensive but very reliable)  MacOS (Apple, Motorola 68K series)  Micro C Linux (Flavor of linux for Hand held devices)

12. 1.12 Operating System Concepts Computer System Components 1.Hardware – provides basic computing resources (CPU, memory, I/O devices). 2.Operating system – controls and coordinates the use of the hardware among the various application programs for the various users. 3.Applications programs – define the ways in which the system resources are used to solve the computing problems of the users (compilers, database systems, video games, business programs). 4.Users (people, machines, other computers).

13. 1.13 Operating System Concepts Operating System Definitions Resource allocator – manages and allocates resources.  Processor (CPU)  Memory  Disk Space  Modem, Network etc. Control program – controls the execution of user programs and operations of I/O devices.  C/C++ Programs  MS Office etc. Kernel – A program running at all the times (all else being application programs).  Always resident in RAM (Like soul of human)  E.g. Command.com in MS-DOS  In Windows system kernel is not just one program but it is a set of programs (We will look at Windows XP and Linux in a little more detail in future lectures)

14. 1.14 Operating System Concepts Abstract View of System Components OS – an environment provider

15. 1.15 Operating System Concepts Different Computer Systems Mainframe Systems  Batch Systems  Multiprogrammed Systems  Time-Sharing Systems Desktop Systems Multiprocessor Systems Distributed Systems

16. 1.16 Operating System Concepts Mainframe Systems First computers used to tackle commercial and engineering applications. 0 th Generation (1940’s) Very large computers (Size of a big room) Required a team to run / manage the whole system

17. 1.17 Operating System Concepts Batch Systems Mainframe Systems Reduced setup time by batching similar jobs  Batches were sorted and fed into the system by Operator.  E.g. Updating daily sales records in a database etc. Processed one program at a time and after finishing the program loaded another program from the same batch. Automatic job sequencing – automatically transfers control from one job to another. First basic operating system.

18. 1.18 Operating System Concepts Memory Layout for a Simple Batch System

19. 1.19 Operating System Concepts Card Reader Card Reader Batch Systems Card Reader CPU Printer

20. 1.20 Operating System Concepts Multiprogrammed Batch Systems Multiprogramming increases CPU utilization by organizing jobs so that the CPU always has one to execute – Early 1960 Job scheduling and CPU scheduling If Job 1 is being executed and then due to some reason it has to wait for some I/O Operation, then the CPU would automatically switch to Job 2 and would turn to Job 3 or Job 1 according to algorithm if job 2 has to perform I/O. Usually a process (program in the memory of CPU) has to perform I/O after a few calculations DISK Job1, Job 2, Job 3 … Job n

21. 1.21 Operating System Concepts Multiprogrammed Systems Mainframe DISK Job 1, Job 2,... Job n Operating System (OS) Job 1 Job 2 Job 3 Job 1 Job 2 Job 3

22. 1.22 Operating System Concepts OS Features Needed for Multiprogramming I/O routine supplied by the system. Memory management – the system must allocate the memory to several jobs. CPU scheduling – the system must choose among several jobs ready to run. Allocation of devices.

23. 1.23 Operating System Concepts Time-Sharing Systems–Interactive Computing The CPU is multiplexed among several jobs that are kept in memory and on disk (the CPU is allocated to a job only if the job is in memory). A job swapped in and out of memory to the disk. On-line communication between the user and the system is provided; when the operating system finishes the execution of one command, it seeks the next “control statement” from the user’s keyboard. On-line system must be available for users to access data and code.

24. 1.24 Operating System Concepts Desktop Systems Personal computers – computer system dedicated to a single user (1970’s). I/O devices – keyboards, mice, display screens, small printers. User convenience and responsiveness. Can adopt technology developed for larger operating system’ often individuals have sole use of computer and do not need advanced CPU utilization of protection features. May run several different types of operating systems (Windows, MacOS, UNIX, Linux, Solaris, BeOS)  90% share is for Microsoft Windows based OS  Linux is gaining popularity (Open source)

25. 1.25 Operating System Concepts Parallel Systems Multiprocessor systems with more than one CPU in close communication. Tightly coupled system – processors share memory and a clock; communication usually takes place through the shared memory. Advantages of parallel system:  Increased throughput  Economical  Increased reliability  graceful degradation  fail-soft systems

26. 1.26 Operating System Concepts Parallel Systems (Cont.) Symmetric multiprocessing (SMP)  Each processor runs an identical copy of the operating system.  Many processes can run at once without performance deterioration.  Most modern operating systems support SMP Asymmetric multiprocessing  Each processor is assigned a specific task; master processor schedules and allocates work to slave processors.  More common in extremely large systems

27. 1.27 Operating System Concepts Symmetric Multiprocessing Architecture

28. 1.28 Operating System Concepts Distributed Systems Distribute the computation among several physical processors. Loosely coupled system – each processor has its own local memory; processors communicate with one another through various communications lines, such as high- speed buses or telephone lines. Advantages of distributed systems.  Resources Sharing  Computation speed up – load sharing  Reliability  Communications

29. 1.29 Operating System Concepts Distributed Systems (cont) Requires networking infrastructure. Local area networks (LAN) or Wide area networks (WAN) May be either client-server or peer-to-peer systems.

30. 1.30 Operating System Concepts General Structure of Client-Server

31. 1.31 Operating System Concepts Clustered Systems Definition: Clustered computers which share storage and are closely linked via LAN networking. Advantages: high availability, performance improvement, etc. Clustering allows two or more systems to share storage. Provides high reliability. Asymmetric clustering: one server runs the application while other servers standby. Symmetric clustering: all N hosts are running the application.

32. 1.32 Operating System Concepts Real-Time Systems Definition: A real-time system is a computer system where a timely response by the computer to external stimuli is vital! Often used as a control device in a dedicated application such as controlling scientific experiments, medical imaging systems, industrial control systems, and some display systems. Well-defined fixed-time constraints. Real-Time systems may be either hard or soft real-time. Real-time means on-time instead of fast

33. 1.33 Operating System Concepts Real-Time Systems (Cont.) Hard real-time system: The system has failed if a timing constraint, e.g. deadline, is not met.  All delays in the system must be bounded.  Many advanced features are absent.  Secondary storage limited or absent, data stored in short term memory, or read-only memory (ROM)  Conflicts with time-sharing systems, not supported by general- purpose operating systems.  E.g. Robot manufacturing a car, Overhead crane loading and unloading at Sea Port, Computer interfacing of certain machines Soft real-time system: Missing a timing constraint is serious, but does not necessarily result in a failure unless it is excessive  A critical task has a higher priority.  Supported in most commercial OS.  Useful in applications (multimedia, virtual reality) requiring advanced operating-system features.

34. 1.34 Operating System Concepts Handheld Systems Personal Digital Assistants (PDAs) Cellular telephones Issues:  Slow processors  Battery Power  Limited memory  No virtual Memory, Small size  Small display screens  Web clipping,

35. 1.35 Operating System Concepts Migration of Operating-System Concepts and Features

36. 1.36 Operating System Concepts Computing Environments Traditional computing Web-Based Computing Embedded Computing

37. 1.37 Operating System Concepts End Of Lecture Next Lecture Computer System Operation I/O Structure Storage Structure Storage Hierarchy