1. Operating System Concepts
Ku-Yaw Chang
Assistant Professor, Department of Computer Science and Information Engineering
Da-Yeh University

2. Chapter 1 Introduction An Operating System (OS)
A program that manages the computer hardware
Provides a basis for application programs
Acts as an intermediary between a user of a computer and the computer hardware
Some operating systems are designed to be
Convenient
Efficient
Some combination of the above
Ku-Yaw Chang
Chapter 1 Introduction

3. Chapter 1 Introduction To understand how they have developed
Trace the development of operating systems
Operating system variations
Parallel systems
Real-time systems
Embedded systems
Ku-Yaw Chang
Chapter 1 Introduction

4. Chapter 1 Introduction What is an Operating System? Mainframe Systems
Desktop Systems
Multiprocessor Systems
Distributed Systems
Clustered System
Real-Time Systems
Handheld Systems
Feature Migration
Computing Environments
Summary
Exercises
Ku-Yaw Chang
Chapter 1 Introduction

5. 1.1 What Is an Operating System?
A computer system can be divided into:
The hardware
The operating system
The application programs
The users
Ku-Yaw Chang
Chapter 1 Introduction

6. Abstract view of the components of a computer system
Ku-Yaw Chang
Chapter 1 Introduction

7. 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).
Ku-Yaw Chang
Chapter 1 Introduction

8. Two Viewpoints 1.1.1 User ViewPC
Monopolize its resources
Maximize the work
Designed for ease of use - convenient
Mainframe or minicomputer
Terminal
Share resources and may exchange information
Maximize resource utilization – efficient
Workstation
Compromise between individual usability and resource utilization
Embedded computer
Little or no user view
Ku-Yaw Chang
Chapter 1 Introduction

9. Two Viewpoints 1.1.2 System View
Resource allocator
manages and allocates resources.
Control program
controls the execution of user programs and operations of I/O devices .
Kernel
the one program running at all times (all else being application programs)
Ku-Yaw Chang
Chapter 1 Introduction

10. 1.1.3 System Goals Tradeoffs
Convenience
Efficiency
Operating systems have also evolved over time.
Graphical User Interfaces (GUIs)
Ku-Yaw Chang
Chapter 1 Introduction

11. Chapter 1 Introduction What is an Operating System? Mainframe Systems
Desktop Systems
Multiprocessor Systems
Distributed Systems
Clustered System
Real-Time Systems
Handheld Systems
Feature Migration
Computing Environments
Summary
Exercises
Ku-Yaw Chang
Chapter 1 Introduction

12. 1.2 Mainframe Systems
First computers used to tackle many commercial and scientific applications
Batch systems
Multiprogrammed Systems
Time-Sharing Systems
Ku-Yaw Chang
Chapter 1 Introduction

13. 1.2.1 Batch Systems Early computer
Physically enormous machine run from a console
Input devices
Card readers
Tape drives
User prepared a job and submitted it to the computer operator
At some time later, the output appeared.
Output devices
Line Printer
Tape drives
Card punches
Ku-Yaw Chang
Chapter 1 Introduction

14. 1.2.1 Batch Systems First rudimentary operating system
Always resident in memory
To speed up processing
Batch similar jobs
Automatic job sequencing – transfers control from one job to another
Introduction of disk technology
Keep all jobs on disk
Job scheduling
Ku-Yaw Chang
Chapter 1 Introduction

15. Memory Layout for a Simple Batch System
Ku-Yaw Chang
Chapter 1 Introduction

16. 1.2.2 Multiprogrammed Systems
Increase CPU utilization
Keep several jobs in memory simultaneously
CPU is multiplexed among them.
Ku-Yaw Chang
Chapter 1 Introduction

17. Memory Layout for a Multiprogramming System
Ku-Yaw Chang
Chapter 1 Introduction

18. 1.2.2 Multiprogrammed Systems
Job scheduling
All the jobs enter the system are kept in the job pool
Processes residing on disk awaiting for allocation of main memory
If there is not enough room for all the jobs, the system must choose among them.
CPU scheduling
If several jobs are ready to run at the same time, the system must choose among them.
Ku-Yaw Chang
Chapter 1 Introduction

19. 1.2.3 Time-Sharing Systems Multiprogrammed, batch systems
Utilize system resources effectively
CPU, memory, peripheral devices
Do not provide user interaction with computer system.
Time-sharing (Multitasking) system
A logical extension of multiprogramming
Switch CPU among multiple jobs frequently
The user can interact with each program while it is running.
Ku-Yaw Chang
Chapter 1 Introduction

20. 1.2.3 Time-Sharing Systems Response time
The amount of time it takes to start responding (not output that response)
An interactive (hands-on) computer system
Direct communication
The response time should be short – typically with 1 second or so.
Ku-Yaw Chang
Chapter 1 Introduction

21. 1.2.3 Time-Sharing Systems A time-sharing system
Allow many users to share the computer simultaneously
Switch rapidly from one user to the next
Give each user the impression that the entire computer system is dedicated to his/her use
Ku-Yaw Chang
Chapter 1 Introduction

22. 1.2.3 Time-Sharing Systems
Multiprogramming and time sharing systems are the central themes of modern operating systems
Process and Thread concepts
Virtual / Physical memory
File system
Ku-Yaw Chang
Chapter 1 Introduction

23. Chapter 1 Introduction What is an Operating System? Mainframe Systems
Desktop Systems
Multiprocessor Systems
Distributed Systems
Clustered System
Real-Time Systems
Handheld Systems
Feature Migration
Computing Environments
Summary
Exercises
Ku-Yaw Chang
Chapter 1 Introduction

24. 1.3 Desktop Systems Personal computers (PCs)
Computer system dedicated to a single user.
Appear in the 1970s
Maximizing user convenience and responsiveness
Instead of maximizing CPU and peripheral utilization
May run several different types of operating systems (Windows, MacOS, UNIX, Linux)
Ku-Yaw Chang
Chapter 1 Introduction

25. Chapter 1 Introduction What is an Operating System? Mainframe Systems
Desktop Systems
Multiprocessor Systems
Distributed Systems
Clustered System
Real-Time Systems
Handheld Systems
Feature Migration
Computing Environments
Summary
Exercises
Ku-Yaw Chang
Chapter 1 Introduction

26. 1.4 Multiprocessor Systems
More than one CPU in close communication
Also known as parallel systems or tightly coupled systems
Processors share
Computer bus
Clock
Main Advantages
Increased throughput
Economy of scale
Increased reliability
graceful degradation
fault tolerant
Memory
Peripheral devices
Ku-Yaw Chang
Chapter 1 Introduction

27. 1.4 Multiprocessor Systems
Symmetric multiprocessing (SMP)
Each processor runs an identical copy of the operating system.
Many processes can run simultaneously without performance deterioration.
Most modern operating systems support SMP.
Asymmetric multiprocessing
Each processor is assigned a specific task; master processor schedules and allocated work to slave processors.
More common in extremely large systems
Ku-Yaw Chang
Chapter 1 Introduction

28. Symmetric Multiprocessing Architecture
Ku-Yaw Chang
Chapter 1 Introduction

29. Chapter 1 Introduction What is an Operating System? Mainframe Systems
Desktop Systems
Multiprocessor Systems
Distributed Systems
Clustered System
Real-Time Systems
Handheld Systems
Feature Migration
Computing Environments
Summary
Exercises
Ku-Yaw Chang
Chapter 1 Introduction

30. 1.5 Distributed Systems Depends on network functionality
TCP/IP is the most common network protocol
Local-area network (LAN)
Within a room, a floor, or a building
Wide-area network (WAN)
Between buildings, cities, or countries
Metropolitan-area network (MAN)
Buildings within a city
Small-area network (SAN)
Short distance of several feet : BlueTooth
Ku-Yaw Chang
Chapter 1 Introduction

31. 1.5.1 Client-Server Systems
Centralized systems
Terminals
Supplanted by PCs
Server systems
Satisfy requests generated by client systems
Two categories (broadly)
Compute-server systems
File-server systems
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Chapter 1 Introduction

32. General Structure of a Client-Server System
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Chapter 1 Introduction

33. 1.5.2 Peer-to-Peer 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.
Network operating system
Provide features such as file sharing across the network
Ku-Yaw Chang
Chapter 1 Introduction

34. Chapter 1 Introduction What is an Operating System? Mainframe Systems
Desktop Systems
Multiprocessor Systems
Distributed Systems
Clustered System
Real-Time Systems
Handheld Systems
Feature Migration
Computing Environments
Summary
Exercises
Ku-Yaw Chang
Chapter 1 Introduction

35. 1.6 Clustered Systems
Gather multiple CPUs to accomplish computational work
Provide high availability
General accepted definition
Clustered computers share storage and are closely linked via LAN networking
Ku-Yaw Chang
Chapter 1 Introduction

36. 1.6 Clustered Systems Asymmetric clustering Symmetric clustering
one server runs the application while other servers standby.
Symmetric clustering
all N hosts are running the application.
Ku-Yaw Chang
Chapter 1 Introduction

37. 1.6 Clustered Systems Parallel clusters Clustering over a WAN
Multiple hosts to access the same data on the shared storage
Most OSs lack such support
Clustering over a WAN
Global clusters – the machines could be anywhere in the world
Cluster technology is rapidly changing.
Storage-Area-Networks (SANs)
Ku-Yaw Chang
Chapter 1 Introduction

38. Chapter 1 Introduction What is an Operating System? Mainframe Systems
Desktop Systems
Multiprocessor Systems
Distributed Systems
Clustered System
Real-Time Systems
Handheld Systems
Feature Migration
Computing Environments
Summary
Exercises
Ku-Yaw Chang
Chapter 1 Introduction

39. 1.7 Real-Time Systems Well-defined, fixed time constraints
Processing must be done within the defined constraints, or the system will fail.
Often used as a control device in a dedicated application
Weapon systems
Medical imaging systems
Industrial control systems
Ku-Yaw Chang
Chapter 1 Introduction

40. Two Flavors Hard real-time system Soft real-time system
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
Soft real-time system
Limited utility in industrial control of robotics
Useful in applications (multimedia, virtual reality) requiring advanced operating-system features
Ku-Yaw Chang
Chapter 1 Introduction

41. Chapter 1 Introduction What is an Operating System? Mainframe Systems
Desktop Systems
Multiprocessor Systems
Distributed Systems
Clustered System
Real-Time Systems
Handheld Systems
Feature Migration
Computing Environments
Summary
Exercises
Ku-Yaw Chang
Chapter 1 Introduction

42. 1.8 Handheld Systems Personal Digital Assistants (PDAs)
Palm
Cellular telephones
Limited size
Small amount of memory
Slow processor
Small display screens
Ku-Yaw Chang
Chapter 1 Introduction

43. Chapter 1 Introduction What is an Operating System? Mainframe Systems
Desktop Systems
Multiprocessor Systems
Distributed Systems
Clustered System
Real-Time Systems
Handheld Systems
Feature Migration
Computing Environments
Summary
Exercises
Ku-Yaw Chang
Chapter 1 Introduction

44. Migration of OS Concepts and Features
Ku-Yaw Chang
Chapter 1 Introduction

45. Chapter 1 Introduction What is an Operating System? Mainframe Systems
Desktop Systems
Multiprocessor Systems
Distributed Systems
Clustered System
Real-Time Systems
Handheld Systems
Feature Migration
Computing Environments
Summary
Exercises
Ku-Yaw Chang
Chapter 1 Introduction

46. 1.10 Computing Environments
Traditional computing
Web-based computing
Embedded computing
Ku-Yaw Chang
Chapter 1 Introduction

47. Chapter 1 Introduction What is an Operating System? Mainframe Systems
Desktop Systems
Multiprocessor Systems
Distributed Systems
Clustered System
Real-Time Systems
Handheld Systems
Feature Migration
Computing Environments
Summary
Exercises
Ku-Yaw Chang
Chapter 1 Introduction

48. Summary
P.23 – P.24
Ku-Yaw Chang
Chapter 1 Introduction

49. Chapter 1 Introduction What is an Operating System? Mainframe Systems
Desktop Systems
Multiprocessor Systems
Distributed Systems
Clustered System
Real-Time Systems
Handheld Systems
Feature Migration
Computing Environments
Summary
Exercises
Ku-Yaw Chang
Chapter 1 Introduction

50. Exercises
1.3
1.4
1.5
1.9
1.10
Ku-Yaw Chang
Chapter 1 Introduction

51. The End