1. Thanks to Silberschatz, Galvin and Gagne  2002 1.1 Operating System Concepts Chapter 1: Introduction n What is an Operating System? n Mainframe Systems n Desktop Systems n Multiprocessor Systems n Distributed Systems n Clustered System n Real -Time Systems n Handheld Systems n Computing Environments

2. Thanks to Silberschatz, Galvin and Gagne  2002 1.2 Operating System Concepts What is an Operating System? n A program that acts as an intermediary between a user of a computer and the computer hardware. n Operating system goals: F Execute user programs and make solving user problems easier. F Make the computer system convenient to use. n The operating system must ensure the correct operation of the computer system. F Hardware must provide appropriate mechanisms. n Use the computer hardware in an efficient manner.

3. Thanks to Silberschatz, Galvin and Gagne  2002 1.3 Operating System Concepts Computer System Components 1. Hardware n Provides basic computing resources (CPU, memory, I/O devices). 2. Operating system n Controls and coordinates the use of the hardware among the various application programs for the various users. 3. Applications programs n Define the ways in which the system resources are used to solve the computing problems of the users (compilers, database systems, …). 4.Users (people, machines, …).

4. Thanks to Silberschatz, Galvin and Gagne  2002 1.4 Operating System Concepts Abstract View of System Components

5. Thanks to Silberschatz, Galvin and Gagne  2002 1.5 Operating System Concepts Operating System Definitions 1. Resource allocator F Manages and allocates resources F Regarding efficiency and fairness 2. Control program F Controls the execution of user programs and operations of I/O devices F Preventing errors and improper use of the computer 3. Kernel F The one program running at all times (all else being application programs).

6. Thanks to Silberschatz, Galvin and Gagne  2002 1.6 Operating System Concepts Chapter 1: Introduction n What is an Operating System? n Mainframe Systems F Batch Systems F Multiprogrammed Systems F Time Sharing Systems n Desktop Systems n Multiprocessor Systems n Distributed Systems n Clustered System n Real -Time Systems n Handheld Systems n Computing Environments

7. Thanks to Silberschatz, Galvin and Gagne  2002 1.7 Operating System Concepts Mainframe Systems n Reduce setup time by batching similar jobs n Automatic job sequencing F automatically transfers control from one job to another. First rudimentary operating system. n Operating system always resident in memory F initials control F control transfers to job F when job completes control transfers back

8. Thanks to Silberschatz, Galvin and Gagne  2002 1.8 Operating System Concepts Memory Layout for a Simple Batch System

9. Thanks to Silberschatz, Galvin and Gagne  2002 1.9 Operating System Concepts Multiprogrammed Batch Systems n Increases CPU utilization by organizing jobs so that the CPU always has one to execute. n Several jobs are kept in main memory at the same time, and the CPU is multiplexed among them.

10. Thanks to Silberschatz, Galvin and Gagne  2002 1.10 Operating System Concepts OS Features Needed for Multiprogramming n I/O routine supplied by the system. n Memory management F the system must allocate the memory to several jobs. n CPU scheduling F the system must choose among several jobs ready to run. n Allocation of devices.

11. Thanks to Silberschatz, Galvin and Gagne  2002 1.11 Operating System Concepts Time-Sharing Systems n The CPU is multiplexed among several jobs. F Jobs are kept in memory and on disk F The CPU is allocated to a job only if the job is in memory. n A job swapped in and out of memory to the disk. n On-line communication between the user and the system is provided. F When the operating system finishes the execution of one command, it seeks the next “control statement” from the user’s keyboard. n On-line system must be available for users to access data and code.

12. Thanks to Silberschatz, Galvin and Gagne  2002 1.12 Operating System Concepts OS Features Needed for Time-Sharing n Time Sharing requires features needed by Multiprogramming, and also… F Memory management and protection F Virtual Memory F File System F Disk Management F Mechanisms for job synchronization and communication F A solution for the deadlock problem

13. Thanks to Silberschatz, Galvin and Gagne  2002 1.13 Operating System Concepts Chapter 1: Introduction n What is an Operating System? n Mainframe Systems n Desktop Systems n Multiprocessor Systems n Distributed Systems n Clustered System n Real -Time Systems n Handheld Systems n Computing Environments

14. Thanks to Silberschatz, Galvin and Gagne  2002 1.14 Operating System Concepts Desktop Systems n Typically Personal computers F computer system dedicated to a single user. n Main goals: user convenience and responsiveness. n Doesn’t require all the technologies developed for larger operating systems F often individuals have sole use of computer and do not need advanced CPU utilization and protection features. n May run several different types of operating systems (Windows, MacOS, UNIX, Linux)

15. Thanks to Silberschatz, Galvin and Gagne  2002 1.15 Operating System Concepts Chapter 1: Introduction n What is an Operating System? n Mainframe Systems n Desktop Systems n Multiprocessor Systems n Distributed Systems n Clustered System n Real -Time Systems n Handheld Systems n Computing Environments

16. Thanks to Silberschatz, Galvin and Gagne  2002 1.16 Operating System Concepts Multiprocessor Systems n Also known as parallel systems or tightly coupled systems. n Multiprocessor systems with more than one CPU in close communication. n Processors share memory and a clock; communication usually takes place through the shared memory. n Advantages of parallel systems: F Increased throughput F Economical F Increased reliability 4 graceful degradation 4 fail-soft systems

17. Thanks to Silberschatz, Galvin and Gagne  2002 1.17 Operating System Concepts Multiprocessor Systems (Cont.) n Symmetric multiprocessing (SMP) F Each processor runs an identical copy of the operating system. F Many processes can run at once without performance downfall. F Most modern operating systems support SMP n Asymmetric multiprocessing F Each processor is assigned a specific task; master processor schedules and allocated work to slave processors. F More common in extremely large systems

18. Thanks to Silberschatz, Galvin and Gagne  2002 1.18 Operating System Concepts Symmetric Multiprocessing Architecture

19. Thanks to Silberschatz, Galvin and Gagne  2002 1.19 Operating System Concepts Chapter 1: Introduction n What is an Operating System? n Mainframe Systems n Desktop Systems n Multiprocessor Systems n Distributed Systems n Clustered System n Real -Time Systems n Handheld Systems n Computing Environments

20. Thanks to Silberschatz, Galvin and Gagne  2002 1.20 Operating System Concepts Distributed Systems n Distribute the computation among several physical processors. n Loosely coupled system F each processor has its own local memory F processors communicate with one another through various communication lines, such as high-speed buses or telephone lines. n Advantages of distributed systems. F Resource Sharing F Computation speed up (Load sharing) F Reliability

21. Thanks to Silberschatz, Galvin and Gagne  2002 1.21 Operating System Concepts Distributed Systems (cont) n Requires networking infrastructure. n Local area networks (LAN) or Wide area networks (WAN) n May be either client-server or peer-to-peer systems. n General Structure of Client-Server:

22. Thanks to Silberschatz, Galvin and Gagne  2002 1.22 Operating System Concepts Chapter 1: Introduction n What is an Operating System? n Mainframe Systems n Desktop Systems n Multiprocessor Systems n Distributed Systems n Clustered System n Real -Time Systems n Handheld Systems n Computing Environments

23. Thanks to Silberschatz, Galvin and Gagne  2002 1.23 Operating System Concepts Clustered Systems n Clustered computers share storage and are closely linked via LAN networking. n Differ from parallel systems in a sense that they are composed of two or more individual systems coupled together. n Clustering provides high reliability. n Asymmetric clustering: one server runs the application while other servers monitor the active server (hot standby mode). n Symmetric clustering: all N hosts are running the application.

24. Thanks to Silberschatz, Galvin and Gagne  2002 1.24 Operating System Concepts Chapter 1: Introduction n What is an Operating System? n Mainframe Systems n Desktop Systems n Multiprocessor Systems n Distributed Systems n Clustered System n Real -Time Systems n Handheld Systems n Computing Environments

25. Thanks to Silberschatz, Galvin and Gagne  2002 1.25 Operating System Concepts Real-Time Systems n Often used as a control device in a dedicated application F controlling scientific experiments, medical imaging systems, industrial control systems, … n A real-time system has well-defined fixed-time constraints. F Processing must be done within the defined system constraints or the system will fail. n Real-Time systems may be either hard or soft real-time.

26. Thanks to Silberschatz, Galvin and Gagne  2002 1.26 Operating System Concepts Hard Real-Time Systems n Guarantees that critical tasks will be completed on time. n To achieve this, all the delays in the system must be bounded. F Secondary storage limited or absent, data stored in short term memory, or read-only memory (ROM) F Memory is located on nonvolatile storage devices. 4 Resist electric outage n Conflicts with time-sharing systems, not supported by general-purpose operating systems.

27. Thanks to Silberschatz, Galvin and Gagne  2002 1.27 Operating System Concepts Soft Real-Time Systems n Critical real-time task gets priority over other tasks and retains that priority until it completes. n The operating system kernel delays need to be bounded. F A real-time task cannot wait indefinitely for the kernel to run it. n Lack of deadline support F Limited utility in industrial control of robotics F Useful in applications (multimedia, virtual reality) requiring advanced operating-system features.

28. Thanks to Silberschatz, Galvin and Gagne  2002 1.28 Operating System Concepts Chapter 1: Introduction n What is an Operating System? n Mainframe Systems n Desktop Systems n Multiprocessor Systems n Distributed Systems n Clustered System n Real -Time Systems n Handheld Systems n Computing Environments

29. Thanks to Silberschatz, Galvin and Gagne  2002 1.29 Operating System Concepts Handheld Systems n Personal Digital Assistants (PDAs) n Cellular telephones n Issues: F Limited memory F Slow processors F Small display screens.

30. Thanks to Silberschatz, Galvin and Gagne  2002 1.30 Operating System Concepts Migration of Operating-System Concepts and Features

31. Thanks to Silberschatz, Galvin and Gagne  2002 1.31 Operating System Concepts Chapter 1: Introduction n What is an Operating System? n Mainframe Systems n Desktop Systems n Multiprocessor Systems n Distributed Systems n Clustered System n Real -Time Systems n Handheld Systems n Computing Environments

32. Thanks to Silberschatz, Galvin and Gagne  2002 1.32 Operating System Concepts Computing Environments n Traditional computing F Personal Computers F Organization Networks F … n Web-Based Computing n Embedded Computing F Embedded computers F Run embedded real-time operating systems F Tend to have very specific tasks

33. Thanks to Silberschatz, Galvin and Gagne  2002 1.33 Operating System Concepts Exercises n Answer these exercises n Teaching Assistance and its classes.