1. Outline Operating System Organization Operating System Examples
Basic functions
Factors in OS Design
Basic implementation considerations
Operating System Examples

2. Basic OS Responsibilities
Create an abstract machine environment
A nicer environment than bare hardware
Consists of multiple, autonomous abstract components
Coordinate the use of the components
Resource manager
Manage according to the policies of the machine’s administrator
4/28/2019
COP4610

3. Basic OS Functions Device management
Process, thread, and resource management
Memory management
File management
4/28/2019
COP4610

4. Device Management … Device-Independent Part Device-Dependent Device
4/28/2019
COP4610

5. Device Management – cont.
Application
Process
File
Manager
Device Controller
Command
Status
Data
Hardware Interface
System Interface
Device-Independent
Device-Dependent
4/28/2019
COP4610

6. Device Management – cont.
read(device, …);
Data
Device Controller
Command
Status
read driver
write driver 1 2 4 5
Hardware Interface
System Interface
Device Status Table
Device
Handler
Interrupt 6 7 8a 8b 9
4/28/2019
COP4610

7. Device Management – cont.
4/28/2019
COP4610

8. Life Cycle of an I/O Request
4/28/2019
COP4610

9. Process Management
4/28/2019
COP4610

10. Memory Management Process Manager Primary Memory Block Allocation
Virtual
Isolation &
Sharing
Storage
Devices
4/28/2019
COP4610

11. Memory Management – cont.
4/28/2019
COP4610

12. Memory Management – cont.
4/28/2019
COP4610

13. Memory Management – cont.
4/28/2019
COP4610

14. File System Management
4/28/2019
COP4610

15. Basic OS Functions – cont.
4/28/2019
COP4610

16. Basic OS Functions – cont.
Scheduler
IPC
Process/Thread
Admin
Synchronization
Memory
Allocation
Virtual
File
Management
Device
Resource
Deadlock
Protection
Mechanisms
Interrupt
Handler
4/28/2019
COP4610

17. Basic OS Functions – cont.
Application
Software
Other System
Other OS Functions
Kernel Functions
Nucleus Functions
Skeletal Nucleus
(a) Monolithic
(b) Modular
(c) Extensible
(d) Layered
4/28/2019
COP4610

18. Factors in OS Design Performance Protection and security Correctness
Maintainability
Commercial factors
Standard and open systems
4/28/2019
COP4610

19. Typical Computer at 1980 and 2000
4/28/2019
COP4610

20. Standard and Open Systems
A system consists of diverse computers, operating systems, and applications for problem solving
Strategies
Application integration
Portability
Interoperability
4/28/2019
COP4610

21. Java Virtual Machines
A further implementation of the virtual machine concept
It provides a virtual machine environment regardless of the hardware
Java programs can run on any machine that has a Java virtual machine
It provides attractive features in an open system environment
4/28/2019
COP4610

22. Dual-mode Operation Ensure proper operation of a computer system
Protect the operating system and all other programs and their data from any malfunctioning program
Protection is needed for any shared resource
Dual-mode provides a means of doing that
System operates in two modes
User mode
System mode
Privileged instructions
I/O instructions are privileged instructions
4/28/2019
COP4610

23. Dual-mode Operation – cont.
Supervisor mode
all instructions are legal
all addresses are absolute physical addresses (base and bound are not used)
User mode
instructions that modify control registers are illegal
all addresses must be less than bound and have base added to them
4/28/2019
COP4610

24. Privileged Instructions
Instructions that can only be executed in the supervisor mode are called supervisor, privileged, or protected instructions
I/O instructions are privileged instructions
A user program in user mode cannot perform its own I/O
Instruction to change the mode is a privileged instruction
Instruction to set the halt flag is a privileged instruction
4/28/2019
COP4610

25. Trap Instruction
4/28/2019
COP4610

26. Trap Instruction – cont.…
fork();
fork() {
trap N_SYS_FORK() }
sys_fork()
sys_fork() {
/* system function */
return;
Kernel
Trap Table
4/28/2019
COP4610

27. Kernels Kernels Extensions to the OS execute in user mode
Critical parts of OS that run in supervisor mode
Have access to other parts of the kernel
Trusted software
Extensions to the OS execute in user mode
4/28/2019
COP4610

28. Requesting Services from O.S.
Two techniques
System call
Message passing
4/28/2019
COP4610

29. How to Make a System Call – cont.
For the system
through a trap instruction which causes an interrupt
Hardware saves PC and current status information
Hardware changes mode to system mode
Hardware loads PC from system call interrupt vector location.
Execute the system call interrupt handler
return from the handler, restores PC and other saved status information
User process continues.
4/28/2019
COP4610

30. System Call Flow of Control
4/28/2019
COP4610

31. How to Make a System Call – cont.
Parameter passing
Through registers
System call number passed through register
Parameters are passed through registers
Returned value is also passed through a register to C/C++
Through a table in memory
Pass the address of the table in a register
Through the stack
Push the parameters on the stack by the user program
Pop the parameters off the stack by the O.S.
4/28/2019
COP4610

32. Requesting Services – cont.
Two techniques
System call
Message passing
4/28/2019
COP4610

33. Operating System Examples
UNIX
MACH
MS-DOS
Windows NT
OS/2
MacOS
4/28/2019
COP4610

34. UNIX One of the most popular operating systems
First version released in 1969
By Ken Thompson at Bell Lab
Widely used in universities and research organizations
Time-sharing system
Supports multiple processes
Disk files and I/O devices are treated similarly
4/28/2019
COP4610

35. History of UNIX Versions
4/28/2019
COP4610

36. Advantages of UNIX Written in a high-level language.
Distributed in source form.
Available on the web
Provided powerful operating-system primitives on an inexpensive platform.
Small size, modular, clean design.
4/28/2019
COP4610

37. UNIX Design Principles
Designed to be a time-sharing system
Has a simple standard user interface that can be replaced.
File system with multilevel tree-structured directories.
Files are supported by the kernel as unstructured sequences of bytes.
Supports multiple processes; a process can easily create new processes.
High priority given to making system interactive, and providing facilities for program development.
4/28/2019
COP4610

38. OS System Call Interface
UNIX System Structure
Libraries
Commands
Device Driver
Interactive User
Application
Programs
OS System Call Interface
Driver Interface …
Monolithic Kernel Module
Process Management
Memory Management
File Management
Device Mgmt Infrastructure
Trap Table
4/28/2019
COP4610

39. Windows NT
32-bit preemptive multitasking operating system for modern microprocessors.
Key goals for the system:
portability
security
POSIX compliance
multiprocessor support
extensibility
international support
compatibility with MS-DOS and MS-Windows applications.
Uses a micro-kernel architecture.
Available in two versions, Windows NT Workstation and Windows NT Server.
In 1996, more NT server licenses were sold than UNIX licenses
4/28/2019
COP4610

40. History of Windows NT
In 1988, Microsoft decided to develop a “new technology” (NT) portable operating system that supported both the OS/2 and POSIX APIs.
Originally, NT was supposed to use the OS/2 API as its native environment but during development NT was changed to use the Win32 API, reflecting the popularity of Windows 3.0.
4/28/2019
COP4610

41. Windows NT Design Principles
Extensibility — layered architecture.
NT executive, which runs in protected mode, provides the basic system services.
On top of the executive, several server subsystems operate in user mode.
Modular structure allows additional environmental subsystems to be added without affecting the executive.
4/28/2019
COP4610

42. Window NT Design Principles - Cont.
Portability — NT can be moved from one hardware architecture to another with relatively few changes.
Written in C and C++.
Processor-dependent code is isolated in a dynamic link library (DLL) called the “hardware abstraction layer” (HAL).
Reliability — NT uses hardware protection for virtual memory, and software protection mechanisms for operating system resources.
4/28/2019
COP4610

43. Window NT Design Principles - Cont.
Compatibility — applications that follow the IEEE (POSIX) standard can be complied to run on NT without changing the source code.
Performance — NT subsystems can communicate with one another via high-performance message passing.
Preemption of low priority threads enables the system to respond quickly to external events.
Designed for symmetrical multiprocessing.
International support — supports different locales via the national language support (NLS) API.
4/28/2019
COP4610

44. Windows NT Architecture
Layered system of modules.
Protected mode — HAL, kernel, executive.
User mode — collection of subsystems
Environmental subsystems emulate different operating systems.
Protection subsystems provide security functions.
4/28/2019
COP4610

45. Windows NT Architecture
4/28/2019
COP4610

46. Summary Basic functions of OS
Device management
Process and resource management
Memory management
File management
Several factors are important to OS design
Implementation considerations
Dual mode
OS examples
UNIX and Windows NT
4/28/2019
COP4610