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

2. Chapter 3 Operating System Structures
An operating system can be viewed from several vantage points.
Services
Interfaces to users and programmers
Components and their interconnections
Ku-Yaw Chang
Chapter 3 Operating-System Structures

3. Chapter 3 Operating-System Structures
System Components
Operating-System Services
System Calls
System Programs
System Structures
Virtual Machines
System Design and Implementation
System Generation
Summary
Exercises
Ku-Yaw Chang
Chapter 3 Operating-System Structures

4. Chapter 3 Operating-System Structures
3.1 System Components
Common system components
Process Management
Main Memory Management
File Management
I/O System Management
Secondary Management
Networking
Protection System
Command-Interpreter System
Ku-Yaw Chang
Chapter 3 Operating-System Structures

5. Chapter 3 Operating-System Structures
3.1.1 Process Management
A process
A program in execution
Resources
CPU time
Memory
Files
I/O devices
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Chapter 3 Operating-System Structures

6. Chapter 3 Operating-System Structures
Process v.s. Program
A program by itself is not a process.
A program is a passive entity
Contents of a file stored on disk
A process is an active entity
A program counter specifies the next instruction to execute
A program spawns many processes as it runs.
Ku-Yaw Chang
Chapter 3 Operating-System Structures

7. Chapter 3 Operating-System Structures
Process Management
A computer
Consists of a collection of processes
Operating-system processes
User processes
Be executed concurrently, by multiplexing the CPU among them.
OS is responsible for
Creating and deleting both user and system processes
Suspending and resuming processes
Providing mechanisms for process synchronization
Providing mechanisms for process communication
Providing mechanisms for deadlock handling
(Chapters 4 through 7)
Ku-Yaw Chang
Chapter 3 Operating-System Structures

8. 3.1.2 Main-Memory Management
a large array of words or bytes, each with its own address.
a repository of quickly accessible data shared by the CPU and I/O devices.
a volatile storage device
OS is responsible for
Keeping track of which parts of memory are currently being used and by whom
Deciding which processes are to be loaded into memory when memory space becomes available
Allocating and deallocating memory space as needed
(Chapters 9 and 10)
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Chapter 3 Operating-System Structures

9. Chapter 3 Operating-System Structures
3.1.3 File Management
Physical Media
Magnetic tape
Magnetic disk
Optical disk
OS provides a uniform logical view of information storage – the file
Map files onto physical media
Access files via storage devices
A file
a collection of related information defined by its creator
represent programs (both source and object forms) and data
Directory (or folder)
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Chapter 3 Operating-System Structures

10. Chapter 3 Operating-System Structures
3.1.3 File Management
OS is responsible for
Creating and deleting files
Creating and deleting directories
Supporting primitives for manipulating files and directories
Mapping files onto secondary storage
Backing up files on stable (nonvolatile) storage media (Chapters 11 and 12)
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Chapter 3 Operating-System Structures

11. 3.1.4 I/O-System Management
The peculiarities of I/O devices are hidden from the bulk of the operating system itself by the I/O subsystem.
A memory-management component that includes buffering, caching, and spooling
A general device-driver interface
Drivers for specific hardware devices (Chapter 13)
Ku-Yaw Chang
Chapter 3 Operating-System Structures

12. 3.1.5 Secondary-Storage Management
Primary storage
Main memory
Secondary storage
Disks
Principal on-line storage medium
Source and destination of processing
OS is responsible for
Free-space management
Storage allocation
Disk scheduling (Chapter 14)
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Chapter 3 Operating-System Structures

13. Chapter 3 Operating-System Structures
3.1.6 Networking
A distributed system is a collection processors that do not share memory or a clock.
Each processor has its own local memory.
The processors in the system are connected through a communication network.
Communication takes place using a protocol.
A distributed system provides user access to various system resources.
Ku-Yaw Chang
Chapter 3 Operating-System Structures

14. Chapter 3 Operating-System Structures
3.1.6 Networking
Access to a shared resource allows
Computation speedup
Increased functionality
Increased data availability
Enhanced reliability
OSs usually generalize network access as a form of file access
Details are contained in the network interface’s device driver (Chapters 15 through 17)
Ku-Yaw Chang
Chapter 3 Operating-System Structures

15. Chapter 3 Operating-System Structures
3.1.7 Protection System
Protection
a mechanism for controlling access by programs, processes, or users to both system and user resources.
The protection mechanism must
distinguish between authorized and unauthorized usage
specify the controls to be imposed
provide a means of enforcement (Chapter 18)
Ku-Yaw Chang
Chapter 3 Operating-System Structures

16. 3.1.8 Command-Interpreter System
Interface between the user and the OS
Included in the kernel or as a special program
Control statements
Commands given to the OS
Shell
Also called control-card interpreter, or the command-line interpreter
To get the next command statement and execute it
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Chapter 3 Operating-System Structures

17. 3.1.8 Command-Interpreter System
Command statements
process creation and management
I/O handling
secondary-storage management
main-memory management
file-system access
protection
networking
Ku-Yaw Chang
Chapter 3 Operating-System Structures

18. Chapter 3 Operating-System Structures
System Components
Operating-System Services
System Calls
System Programs
System Structures
Virtual Machines
System Design and Implementation
System Generation
Summary
Exercises
Ku-Yaw Chang
Chapter 3 Operating-System Structures

19. 3.2 Operating-System Services
Common services
Program execution
to load a program into memory and to run it.
I/O operations
user programs cannot execute I/O operations directly
File-system manipulation
capability to read, write, create, and delete files.
Communications
exchange of information between processes
Implemented via shared memory or message passing.
Error detection
ensure correct computing by detecting errors in the CPU and memory hardware, in I/O devices, or in user programs.
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Chapter 3 Operating-System Structures

20. Chapter 3 Operating-System Structures
Additional Functions
Not for helping the user, but rather for ensuring efficient system operations.
Resource allocation
allocate resources to multiple users or multiple jobs running at the same time
Accounting
keep track of and record which users use how much and what kinds of computer resources for account billing or for accumulating usage statistics
Protection
ensure that all access to system resources is controlled
Ku-Yaw Chang
Chapter 3 Operating-System Structures

21. Chapter 3 Operating-System Structures
System Components
Operating-System Services
System Calls
System Programs
System Structures
Virtual Machines
System Design and Implementation
System Generation
Summary
Exercises
Ku-Yaw Chang
Chapter 3 Operating-System Structures

22. Chapter 3 Operating-System Structures
3.3 System Calls
System calls
The interface between a process and the OS
Assembly-language
Higher-level language
C, C++ and Perl
Modern Microsoft Windows platforms
Win32 API (application programmer interface)
Even simple programs may make heavy use of the operating system.
To read data from one file and to copy them to another file
Requiring a sequence of system calls
Details are hidden from the programmer
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Chapter 3 Operating-System Structures

23. Chapter 3 Operating-System Structures
3.3 System Calls
Pass parameters to the OS
In registers
Parameters may be more than registers
In a block or table in memory
The address is passed as a parameter in a register
Stack
Push parameters onto the stack by the program
Pop off the stack by operating system
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Chapter 3 Operating-System Structures

24. Passing of parameters as a table
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Chapter 3 Operating-System Structures

25. Chapter 3 Operating-System Structures
3.3 System Calls
Five major categories
Process control
File management
Device management
Information maintenance
Communications
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Chapter 3 Operating-System Structures

26. Chapter 3 Operating-System Structures
MS-DOS
At System Start-up
Running a Program
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27. UNIX running multiple programs
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Chapter 3 Operating-System Structures

28. Chapter 3 Operating-System Structures
3.3.5 Communication
Message Passing
Shared Memory
Ku-Yaw Chang
Chapter 3 Operating-System Structures

29. Chapter 3 Operating-System Structures
System Components
Operating-System Services
System Calls
System Programs
System Structures
Virtual Machines
System Design and Implementation
System Generation
Summary
Exercises
Ku-Yaw Chang
Chapter 3 Operating-System Structures

30. Chapter 3 Operating-System Structures
3.4 System Programs
System programs provide a convenient environment for program development and execution
File management
Status information
File modification
Programming language support
Program loading and execution
Communication
System utilities or application programs
To solve common problems, or perform common operations
Web browsers and word processors
Games
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Chapter 3 Operating-System Structures

31. Chapter 3 Operating-System Structures
3.4 System Programs
Command interpreter
The most important system program
Two approaches
The command interpreter contains the code to execute the command.
Implement most commands by system programs
Ku-Yaw Chang
Chapter 3 Operating-System Structures

32. Chapter 3 Operating-System Structures
System Components
Operating-System Services
System Calls
System Programs
System Structures
Virtual Machines
System Design and Implementation
System Generation
Summary
Exercises
Ku-Yaw Chang
Chapter 3 Operating-System Structures

33. Chapter 3 Operating-System Structures
To partition the task (OS) into small components (modules)
Not one monolithic system
Available approaches
Simple structure
Layered approach
Microkernels
Ku-Yaw Chang
Chapter 3 Operating-System Structures

34. Chapter 3 Operating-System Structures
3.5.1 Simple Structure
MS-DOS
written to provide the most functionality in the least space
not divided into modules
Although having some structure, its interfaces and levels of functionality are not well separated
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Chapter 3 Operating-System Structures

35. MS-DOS layer structure
Ku-Yaw Chang
Chapter 3 Operating-System Structures

36. Chapter 3 Operating-System Structures
3.5.1 Simple Structure
UNIX
Initially limited by hardware functionality
consists of two separable parts
The kernel
Everything below the system-call interface and above the physical hardware
Systems programs
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Chapter 3 Operating-System Structures

37. Chapter 3 Operating-System Structures
Unix System Structure
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Chapter 3 Operating-System Structures

38. Chapter 3 Operating-System Structures
3.5.2 Layered Approach
OS is broken into a number of layers (or levels)
Each built on top of lower layers
The bottom layer (layer 0) is the hardware
The highest layer (layer N) is the user interface
With modularity, layers are selected such that each uses functions (operations) and services of only lower-level layers.
Simplify debugging and system verification
Difficult to define each layer
Less efficient – overhead
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Chapter 3 Operating-System Structures

39. Chapter 3 Operating-System Structures
An OS layer
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Chapter 3 Operating-System Structures

40. Chapter 3 Operating-System Structures
OS/2 layer structure
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Chapter 3 Operating-System Structures

41. Chapter 3 Operating-System Structures
Windows NT
First release
A highly layer-oriented organization
Low performance (compared to Windows 95)
NT 4.0
Move layers from user space to kernel space
Closely integration
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Chapter 3 Operating-System Structures

42. Chapter 3 Operating-System Structures
3.5.3 Microkernels
Unix
Kernel became large and difficult to manage
Mach
Developed at Carnegie Mellon University in the mid-1980s
Use the microkernel approach
Removing non-essential components from the kernel
Implement them as system- and user-level programs
A smaller kernel
Main function
To provide a communication facility
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Chapter 3 Operating-System Structures

43. Chapter 3 Operating-System Structures
3.5.3 Microkernels
Benefits
easier to extend
easier to port to new architectures
more reliable (less code is running in kernel mode)
more secure
Examples
Tru64 UNIX – UNIX + Mach kernel
MacOS X – based on Mach kernel
QNX – a real-time OS
Windows NT ( a hybrid structure)
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Chapter 3 Operating-System Structures

44. Windows NT client-server structure
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Chapter 3 Operating-System Structures

45. Chapter 3 Operating-System Structures
System Components
Operating-System Services
System Calls
System Programs
System Structures
Virtual Machines
System Design and Implementation
System Generation
Summary
Exercises
Ku-Yaw Chang
Chapter 3 Operating-System Structures

46. Chapter 3 Operating-System Structures
3.6 Virtual Machines
A computer system is made up of layers
Hardware is the lowest
Virtual machines
take the layered approach to its logical conclusion
treat hardware and the operating system kernel as though they were all hardware
provide an interface identical to the underlying bare hardware.
The OS creates the illusion of multiple processes, each executing on its own processor with its own (virtual) memory.
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Chapter 3 Operating-System Structures

47. Chapter 3 Operating-System Structures
System Models
Non-virtual Machine
Virtual Machine
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Chapter 3 Operating-System Structures

48. Chapter 3 Operating-System Structures
3.6.1 Implementation
Difficult to implement
To provide an exact duplicate of the underlying machine
User mode
Monitor mode
Time – the major difference
I/O
Less time or more time
CPU
Multiprogrammed among many virtual machines
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Chapter 3 Operating-System Structures

49. Chapter 3 Operating-System Structures
3.6.2 Benefits
Provide complete protection of system resources
Each virtual machine is isolated from all other virtual machines.
Permits no direct sharing of resources.
A perfect vehicle for operating-systems research and development
System development is done on the virtual machine, instead of on a physical machine and so does not disrupt normal system operation.
Solve system compatibility problems
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Chapter 3 Operating-System Structures

50. Chapter 3 Operating-System Structures
3.6.3 Java
A very popular object-oriented language
By Sun Microsystems in late 1995
Consists of
A language specification
A large API library
A specification for a Java virtual machine(JVM)
A class loader
A class verifier
A Java interpreter
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Chapter 3 Operating-System Structures

51. Chapter 3 Operating-System Structures
3.6.3 Java
A Java program consists of one or more classes.
For each class, the Java compiler produce an architecture-neutral bytecode output (.class) file
Run on any implementation of the JVM
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Chapter 3 Operating-System Structures

52. Chapter 3 Operating-System Structures
Java virtual machine
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Chapter 3 Operating-System Structures

53. Chapter 3 Operating-System Structures
3.6.3 Java
Garbage collection
Reclaim memory from objects no longer in use and return it to the system
Just-in-time (JIT) compiler
Turn the architecture-neutral bytecodes to native machine language for the host computer
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Chapter 3 Operating-System Structures

54. Chapter 3 Operating-System Structures
System Components
Operating-System Services
System Calls
System Programs
System Structures
Virtual Machines
System Design and Implementation
System Generation
Summary
Exercises
Ku-Yaw Chang
Chapter 3 Operating-System Structures

55. 3.7 System Design and Implementation
A discussion about problems when designing and implementing an operating system
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Chapter 3 Operating-System Structures

56. Chapter 3 Operating-System Structures
3.7.1 Design Goals
User goals
should be convenient to use, easy to learn, reliable, safe, and fast.
System goals
should be easy to design, implement, and maintain, as well as flexible, reliable, error-free, and efficient.
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Chapter 3 Operating-System Structures

57. 3.7.2 Mechanisms and Policies
General software engineering principles are applicable to operating systems.
Separation of policy from mechanism
For flexibility
Mechanisms
How to do something
A general mechanism
Policies
What will be done
Change across places or over time
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Chapter 3 Operating-System Structures

58. 3.7.2 Mechanisms and Policies
Microkernel
Take the separation of mechanism and policy to one extreme
Apple Macintosh
Both mechanism and policy are encoded in the system
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59. Chapter 3 Operating-System Structures
3.7.3 Implementation
Traditionally written in assembly language, operating systems can now be written in higher-level languages.
Code written in a high-level language:
can be written faster.
is more compact.
is easier to understand and debug.
is easier to port (move to some other hardware)
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Chapter 3 Operating-System Structures

60. Chapter 3 Operating-System Structures
System Components
Operating-System Services
System Calls
System Programs
System Structures
Virtual Machines
System Design and Implementation
System Generation
Summary
Exercises
Ku-Yaw Chang
Chapter 3 Operating-System Structures

61. Chapter 3 Operating-System Structures
3.8 System Generation
Operating systems are designed to run on any of a class of machines.
must be configured for each specific computer site.
System generation (SYSGEN)
obtain information concerning the specific configuration of the hardware system.
From a given file
Ask the operator
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Chapter 3 Operating-System Structures

62. Chapter 3 Operating-System Structures
3.8 System Generation
Booting
starting a computer by loading the kernel.
Bootstrap program (bootstrap loader)
code stored in ROM that is able to locate the kernel, load it into memory, and start its execution.
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63. Chapter 3 Operating-System Structures
System Components
Operating-System Services
System Calls
System Programs
System Structures
Virtual Machines
System Design and Implementation
System Generation
Summary
Exercises
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Chapter 3 Operating-System Structures

64. Chapter 3 Operating-System Structures
Summary
P.89 – P.90
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65. Chapter 3 Operating-System Structures
System Components
Operating-System Services
System Calls
System Programs
System Structures
Virtual Machines
System Design and Implementation
System Generation
Summary
Exercises
Ku-Yaw Chang
Chapter 3 Operating-System Structures

66. Chapter 3 Operating-System Structures
Exercises
3.5
3.12
3.13
3.14
3.15
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Chapter 3 Operating-System Structures

67. The End