1. Operating Systems: A Modern Perspective, Chapter 1

2. Operating Systems: A Modern Perspective, Chapter 1
Introduction
Operating Systems: A Modern Perspective, Chapter 1

3. Why Study Operating Systems?
Understand the model of operation
Easier to see how to use the system
Enables you to write efficient code
Learn to design an OS
Even so, OS is pure overhead of real work
Application programs have the real value to person who buys the computer
Operating Systems: A Modern Perspective, Chapter 1

4. Perspectives of the Computer
print
open()
start-printer
cut
malloc()
read-disk
send
save
fork()
track-mouse
Application
Software
Application
Software
Application
Software
System
Software
System
Software
System
Software
Hardware
Hardware
Hardware
End User
View
(b) Application
Programmer
View
(c) OS Programmer
View
Operating Systems: A Modern Perspective, Chapter 1

5. Operating Systems: A Modern Perspective, Chapter 1
System Software
Independent of individual applications, but common to all of them
Examples
C library functions
A window system
A database management system
Resource management functions
The OS
Operating Systems: A Modern Perspective, Chapter 1

6. Using the System Software
Application
Programmer
Software API
Command
Line
Interpreter
Loader
Window
System
Libraries
Libraries
Libraries
System Software
Compiler OS
Database
Management
System
Hardware
Operating Systems: A Modern Perspective, Chapter 1

7. Application Software, System Software, and the OS
Human-Computer Interface
Application Software
API
System Software
(More Abstract Resources)
OS Interface
Trusted OS
(Abstract Resources)
Software-Hardware Interface
Hardware Resources
Operating Systems: A Modern Perspective, Chapter 1

8. The OS as Resource Manager
Process: An executing program
Resource: Anything that is needed for a process to run
Memory
Space on a disk
The CPU
“An OS creates resource abstractions”
“An OS manages resource sharing”
Operating Systems: A Modern Perspective, Chapter 1

9. Operating Systems: A Modern Perspective, Chapter 1
Resource Abstraction
load(block, length, device);
seek(device, 236);
out(device, 9)
write(char *block, int len, int device,
int track, int sector) {
...
load(block, length, device);
seek(device, 236);
out(device, 9); }
write(char *block, int len, int device,int addr);
fprintf(fileID, “%d”, datum);
Operating Systems: A Modern Perspective, Chapter 1

10. Operating Systems: A Modern Perspective, Chapter 1
Disk Abstractions
Application
Programmer
OS Programmer
int fprintf(…) {
...
write(…) … }
void write() {
load(…);
seek(…)
out(…) }
load(…);
seek(…);
out(…);
(a) Direct Control
(b) write()
abstraction
(c) fprintf()
abstraction
Operating Systems: A Modern Perspective, Chapter 1

11. Operating Systems: A Modern Perspective, Chapter 1
Abstract Resources
User Interface
Application
Abstract Resources (API)
Middleware
OS Resources (OS Interface) OS
Hardware Resources
Operating Systems: A Modern Perspective, Chapter 1

12. Operating Systems: A Modern Perspective, Chapter 1
Abstract Machines
Abstract
Machines
Idea
Program
Result
Physical
Machine
Idea
Program
Result … … …
Idea
Program
Result
Operating Systems: A Modern Perspective, Chapter 1

13. Operating Systems: A Modern Perspective, Chapter 1
Resource Sharing
Space- vs time-multiplexed sharing
To control sharing, must be able to isolate resources
OS usually provides mechanism to isolate, then selectively allows sharing
How to isolate resources
How to be sure that sharing is acceptable
Concurrency
Operating Systems: A Modern Perspective, Chapter 1

14. Operating Systems: A Modern Perspective, Chapter 1
The OS as a Conductor
The OS coordinates the sharing and use of all the components in the computer
Operating Systems: A Modern Perspective, Chapter 1

15. Operating Systems: A Modern Perspective, Chapter 1
Multiprogramming
Abstract
Machine Pi
Abstract
Machine Pj
Abstract
Machine Pk …
OS Resource Sharing
Pi Memory
Pk Memory …
Pj Memory
Time-multiplexed
Physical Processor
Space-multiplexed
Physical Memory
Operating Systems: A Modern Perspective, Chapter 1

16. Operating Systems: A Modern Perspective, Chapter 1
Multiprogramming(2)
Technique for sharing the CPU among runnable processes
Process may be blocked on I/O
Process may be blocked waiting for other resource, including the CPU
While one process is blocked, another might be able to run
Multiprogramming OS accomplishes CPU sharing “automatically” – scheduling
Reduces time to run all processes
Operating Systems: A Modern Perspective, Chapter 1

17. How Multiprogramming Works
Process 1
Process 2
Process 3
Time-multiplexed CPU
Process 4
Space-multiplexed Memory
Operating Systems: A Modern Perspective, Chapter 1

18. Speeding Up the Car Wash
Vacuum
Inside
Wash
Dry
(a) The Sequential Car Wash
Vacuum
Inside
Wash
Dry
(b) The Parallel Car Wash
Operating Systems: A Modern Perspective, Chapter 1

19. Multiprogramming Performance
Pi’s Total Execution Time, ti
Time ti
(a) Pi’s Use of Machine Resources P1 P2 … Pi … PN
Time
(a) All Processes’ Use of Machine Resources
Using the processor
I/O operation
Operating Systems: A Modern Perspective, Chapter 1

20. Operating Systems: A Modern Perspective, Chapter 1
OS Strategies
Batch processing
Timesharing
Personal computer & workstations
Process control & real-time
Network
Distributed
Small computers
Operating Systems: A Modern Perspective, Chapter 1

21. Operating Systems: A Modern Perspective, Chapter 1
Batch Processing
Job 3
Job 19
Input Spooler
Output Spooler
Input Spool
Output Spool
Operating Systems: A Modern Perspective, Chapter 1

22. Operating Systems: A Modern Perspective, Chapter 1
Batch Processing(2)
Uses multiprogramming
Job (file of OS commands) prepared offline
Batch of jobs given to OS at one time
OS processes jobs one-after-the-other
No human-computer interaction
OS optimizes resource utilization
Batch processing (as an option) still used today
Operating Systems: A Modern Perspective, Chapter 1

23. A Shell Script Batch File
cc -g -c menu.c
cc -g -o driver driver.c menu.o
driver < test_data > test_out
lpr -PthePrinter test_out
tar cvf driver_test.tar menu.c driver.c test_data test_out
uuencode driver_test.tar driver_test.tar >driver_test.encode
Operating Systems: A Modern Perspective, Chapter 1

24. Operating Systems: A Modern Perspective, Chapter 1
Timesharing Systems
Abstract
Machines
Result
Physical
Machine
Command
Result
Command …
Result
Command
Operating Systems: A Modern Perspective, Chapter 1

25. Timesharing Systems(2)
Uses multiprogramming
Support interactive computing model (Illusion of multiple consoles)
Different scheduling & memory allocation strategies than batch
Tends to propagate processes
Considerable attention to resource isolation (security & protection)
Tend to optimize response time
Operating Systems: A Modern Perspective, Chapter 1

26. Operating Systems: A Modern Perspective, Chapter 1
Personal Computers
CPU sharing among one person’s processes
Power of computing for personal tasks
Graphics
Multimedia
Trend toward very small OS
OS focus on resource abstraction
Rapidly evolved to “personal multitasking” systems
Operating Systems: A Modern Perspective, Chapter 1

27. Process Control & Real-Time
Computer is dedicated to a single purpose
Classic embedded system
Must respond to external stimuli in fixed time
Continuous media popularizing real-time techniques
An area of growing interest
Operating Systems: A Modern Perspective, Chapter 1

28. Operating Systems: A Modern Perspective, Chapter 1
Networks
LAN (Local Area Network) evolution
3Mbps (1975)  10 Mbps (1980)  100 Mbps (1990)  1 Gbps (2000)
High speed communication means new way to do computing
Shared files
Shared memory
Shared procedures/objects
???
Operating Systems: A Modern Perspective, Chapter 1

29. Operating Systems: A Modern Perspective, Chapter 1
Distributed OS
Wave of the future
App
App
App
App
App
App
Distributed OS
Multiple Computers connected by a Network
Operating Systems: A Modern Perspective, Chapter 1

30. Operating Systems: A Modern Perspective, Chapter 1
Small Computers
PDAs, STBs, embedded systems became commercially significant
Have an OS, but
Not general purpose
Limited hardware resources
Different kinds of devices
Touch screen, no keyboard
Graffiti
Evolving & leading to new class of Oses
PalmOS, Pocket PC (WinCE), VxWorks, …
Operating Systems: A Modern Perspective, Chapter 1

31. Operating Systems: A Modern Perspective, Chapter 1
Evolution of Modern OS
Timesharing
Network OS
Memory Mgmt
PC & Wkstation
Client-Server Model
Scheduling
Batch
Protection
Protocols
System software
Real-Time
Human-Computer
Interface
Memory Mgmt
Protection
Scheduling
Scheduling
Files
Devices
Small Computer
Network storage,
Resource management
Modern OS
Operating Systems: A Modern Perspective, Chapter 1

32. Operating Systems: A Modern Perspective, Chapter 1
Examples of Modern OS
UNIX variants (e.g. Linux) -- have evolved since 1970
Windows NT/2K -- has evolved since 1989 (much more modern than UNIX
Win2K = WinNT, V5
Research OSes – still evolving …
Small computer OSes – still evolving …
Book provides Linux examples
This course will use Windows NT as the main example
Operating Systems: A Modern Perspective, Chapter 1

33. The Microsoft OS Family
Win32 API
Win32 API Subset
Win32 API SubSet
Windows CE
(Pocket PC)
Windows 95/98/Me
Windows NT/2000/XP
Operating Systems: A Modern Perspective, Chapter 1

34. Operating Systems: A Modern Perspective, Chapter 1
Microsoft Windows NT
Heavily window-oriented
Foundation behavior is windows-independent
We will focus on the foundation
Use only the “MS-DOS prompt” -- cmd.exe
OS API
NT Executive
NT User Interface
and Graphics
NT Kernel
Operating Systems: A Modern Perspective, Chapter 1

35. Operating Systems: A Modern Perspective, Chapter 1
Windows NT (cont)
OS API has text orientation (like UNIX)
Object-oriented implementation
Heavy use of threads
Broad spectrum of synchronization tools
Modern I/O system
Operating Systems: A Modern Perspective, Chapter 1

36. VxWorks Organization Applications VxWorks Runtime System
VxWorks Configurable
Core OS Extension
Wind Microkernel
Operating Systems: A Modern Perspective, Chapter 1

37. Windows CE Organization
Operating Systems: A Modern Perspective, Chapter 1