The document discusses the history and concepts of modern operating systems. It covers four generations of operating systems: 1) Vacuum tubes (1945-1955): Large, slow computers that were programmed and operated directly by engineers. 2) Transistors and batch systems (1955-1965): Systems managed by professional operators using punch cards. Programs were run in batches. 3) Integrated circuits and multiprogramming (1965-1980): OS/360 introduced techniques like multiprogramming and spooling to improve efficiency. Timesharing systems like Multics provided interactive use. 4) Personal computers (1980-present): Lower-cost systems led to popular OS like CP/M, DOS, and

1. MODERN OPERATING SYSTEMS
Third Edition
ANDREW S. TANENBAUM
Chapter 1
Introduction

2. Outline
 What is an operating system
 The history of Operating System
 Hardware of operating system
 Important concepts of Operating System

3. What Is An Operating System
A modern computer consists of:
• One or more processors
• Main memory
• Disks
• Printers
• Various input/output devices
Managing all these components requires a layer of
software – the operating system

4. What is an Operating System?
 A modern computer is very complex.
 Networking
 Disks
 Video/audio card
 ….
 It is impossible for every application programmer to
understand every detail
 A layer of computer software is introduced to provide a
better, simpler, cleaner model of the resources and
manage them

5. What Is An Operating System
Figure 1-1. Where the operating system fits in.

6. What is an Operating System?
 Users use various OS
 Windows, Linux, Mac OS etc.
 User interacts with shell or GUI
 part of OS?
 they use OS to get their work done
 Is device driver part of OS?

7. What is an Operating System?
 On top of hardware is OS
 Most computers have two modes of operation:
 Kernel mode and user mode
 OS runs in kernel mode, which has complete access to all
hardware and can execute any instruction
 Rest of software runs in user mode, which has limited
capability
 Shell or GUI is the lowest level of user mode software

8. What is an operating system?
 Two functions:
 From top to down: provide application programmers a
clean abstract set of resources instead of hardware ones
 From down to top: Manage these hardware resources

9. The Operating System as an Extended
Machine
Figure 1-2. Operating systems turn ugly hardware into beautiful
abstractions.

10. As an extended machine
 Abstraction:
 CPU—process
 Storage –- files
 Memory– address space
 4 types of people:
 Industrial engineer: design hardware
 Kernel designer
 Application programmer: OS’s user
 End users

11. The Operating System as a Resource
Manager
• Allow multiple programs to run at the same time
• Manage and protect memory, I/O devices, and
other resources
• Includes multiplexing (sharing) resources in two
different ways:
• In time
• In space

12. As a resource manager
 Modern OS runs multiple programs of multiple users at
the same time
 Imagine what would happen if several programs want to
print at the same time?
 How to account the resource usage of each process?
 Resources can be multiplexed:
 How to ensure fairness and efficiency?

13. summary
 Operating system is a software
 Is a complex software
 Runs in kernel mode
 Manages hardware
 Provide a friendly interface for application programmer

14. History of Operating Systems
Generations:
• (1945–55) Vacuum Tubes
• (1955–65) Transistors and Batch Systems
• (1965–1980) ICs and Multiprogramming
• (1980–Present) Personal Computers

15. 1st: vacuum tubes
 Large and slow
 Engineers design, build, operate and maintain the
computer
 All programming is done with machine language, or by
wiring circuits using cables
 insert plugboards into the computer and operate
 The work is mainly numerical calculations

16. 2nd: transistors and batch
systems
 Also called mainframes
 Computers are managed by professional operators
 Programmers use punch card to run programs;
operators operate (load compiler, etc ) and
collect output to the user
 Complains soon come:
 Human Operation between computer operation
 Lead to batch system
 Collect a batch of jobs in the input room, then read
them into a magnetic tape; the same for output

17. 2nd: Transistors and Batch Systems (1)
Figure 1-3. An early batch system.
(a) Programmers bring cards to 1401.
(b)1401 reads batch of jobs onto tape.
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

18. Transistors and Batch Systems (2)
Figure 1-3. (c) Operator carries input tape to 7094.
(d) 7094 does computing. (e) Operator carries output tape to
1401. (f) 1401 prints output.
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

19. Transistors and Batch Systems (4)
Figure 1-4. Structure of a typical FMS job.

20. 3rd: IC and Multiprogramming
 OS/360:
 However, OS/360 introduces several key techniques
 Multi-programming: solve the problem of CPU idling
 Spooling: simultaneous peripheral operation on line
 Whenever a job finishes, OS load a new job from disk to the
empty-partition

21. Figure 1-5. A multiprogramming system
with three jobs in memory.
3rd: ICs and Multiprogramming

22. 3rd: Ics and Multiprogramming
 Problems:
 3rd generation OS was well suited for big scientific
calculations and massive data processing
 But many programmers complain a lot… for not be able to
debug quickly…. Why?
 And the solution to this problem would be….?
 Timesharing:
 A variant of multiprogramming
 Provide both fast interactive service but also fits big batch
work

23. 3rd: IC and Multiprogramming
 A system to be remembered: MULTICS
 A machine that would support hundreds of simultaneous
timesharing users– like the electricity system (like a web
server nowadays)
 Introduces many brilliant ideas but enjoys no commercial
success
 Its step-child is the well-known and time-honored UNIX
 System V/ FreeBSD, MINIX, Linux

24. 4th: personal computers
 Computers have performance similar to 3rd generation,
but prices drastically different
 4 generations OS
 Develops with hardware and user needs
 Multi-user, multi-programming, time-sharing
 CP/M (Control Program for Microcomputers)
 First disk-based OS
 1980, IBM PC, Basic Interpreter, DOS, MS-DOS
 GUI--Lisa—Apple: user friendly
 MS-DOS with GUI– Win95/98/me— win NT/ windows XP…

25. Computer Hardware Review
Figure 1-6. Some of the components
of a simple personal computer.

26. Hardware: processor
 Brain of computer
 Fetches instruction from memory and execute
 Cycle of CPU:
 fetch, decode, execute
 CPU has registers to store variable and temporary result:
load from memory to register; store from register to
memory
 Program counter: next instruction to fetch
 Stack pointer: the top of the current stack
 PSW: program status word (The program status word (PSW)
is an IBM System/360 architecture and successors control
register which performs the function of a status register
and program counter in other architectures, and more),
priority, mode…

27. CPU Pipelining
Figure 1-7. (a) A three-stage pipeline. (b) A superscalar CPU.
 Accelerate the execution
 Cause headaches to OS/compiler writers
 For superscalar: instructions are often executed out of
order

28. Figure 1-8. (a) A quad-core chip with a shared L2 cache.
(b) A quad-core chip with separate L2 caches.
Multithreaded and Multicore
(Multiprocessor) Chips

29. Figure 1-9. A typical memory hierarchy.
The numbers are very rough approximations.
Memory

30. Memory
 Memory is where computer fetch and store data, ideally,
it should be both chip/large
 The best people can do, is to construct a memory
hierarchy
 Cache lines:
 Memory divided into cache lines; the mostly used ones are
stored in caches
 Cache hit, cache miss
 Cache: whenever there is disparity in usage or speed; used
to improve performance
 Questions when dealing with cache:
 When to put a new item into the cache.
 Which cache line to put the new item in.
 Which item to remove from the cache when a slot is
needed.
 Where to put a newly evicted item in the larger memory.

31. Figure 1-10. Structure of a disk drive.
Disks
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

32. Disks
 Cheap and large: two orders better than RAM
 Slow: three orders worse than RAM
 Mechanical movement to fetch data
 One or more platter—rotate– rpm
 Information is stored on concentric circles
 Arm, track, cylinder, sector
 Disk helps to implement Virtual Memory
 When no enough memory is available, disks are used as
the storage, and memory as cache

33. Figure 1-11. (a) The steps in starting an I/O device and getting an interrupt.
I/O Devices
 a Two parts: a controller and a device
 Controller: to provide simpler interface to OS
 Device driver: talks to controller, give commands and accepts
response
 Busy waiting/interrupt/DMA

34. Booting the Computer
 BIOS—basic input/output system
 On the motherboard, low-level I/O software
 Checks RAM, keyboard and other basic devices
 Determine the boot device: floppy, CD-ROM, disk
 First sector of the boot-device is read into memory
 The sector contains program to check which partition is
active
 Then a secondary boot-loader is read into memory and
reads in operating system from the active partition

35. The Operating System Zoo
• Mainframe operating systems
• Server operating systems
• Multiprocessor operating systems
• Personal computer operating systems
• Handheld operating systems
• Embedded operating systems
• Sensor node operating systems
• Real-time operating systems
• Smart card operating systems

36. • Processes
• Address spaces
• Files
• Input / Output
• Protection
• The shell
• Ontogeny recapitulates phylogeny
• Large memories
• Protection hardware
• Disks
• Virtual memory
Operating System Concepts

37. Processes
 Process
 Address space: 0-4G; executable
program, program’s data, and its
stack
 Other resources like: registers,
files, alarms, related processes,
and other information
 A process is fundamentally a
container that holds information
for a program to run
Figure 1-13. A process tree. Process A created two child
processes, B and C. Process B created three
child processes, D, E, and F.

38. Address Space
 The memory used by a process, in concept
 MOS allows multiple processes in memory
simultaneously
 Some processes need more memory than physically
available– virtual memory

39. Figure 1-14. A file system for a university department.
Files
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

40. Figure 1-15. (a) Before mounting, the files on the CD-ROM are not accessible.
(b) After mounting, they are part of the file hierarchy.
Files
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

41. Figure 1-16. Two processes connected by a pipe.
Files
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

42. System calls
 System calls is the interface users contact with OS and
hardware
 System calls vary from system to system, but the
underlying concepts are similar

43. Figure 1-17. The 11 steps in making the system call
read(fd, buffer, nbytes).
System Calls
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

44. Figure 1-18. Some of the major POSIX system calls.
System Calls for Process Management
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

45. Figure 1-18. Some of the major POSIX system calls.
System Calls for File Management (1)
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

46. Figure 1-18. Some of the major POSIX system calls.
System Calls for File Management (2)
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

47. Figure 1-18. Some of the major POSIX system calls.
Miscellaneous System Calls
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

49. Figure 1-20. Processes have three segments:
text, data, and stack.
Memory Layout

50. Figure 1-21. (a) Two directories before linking /usr/jim/memo to
ast’s directory. (b) The same directories after linking.
Linking

51. Figure 1-22. (a) File system before the mount.
(b) File system after the mount.
Mounting
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

52. Figure 1-23. The Win32 API calls that roughly correspond
to the UNIX calls of Fig. 1-18.
Windows Win32 API
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

53. Monolithic systems – basic structure:
• A main program that invokes the requested
service procedure.
• A set of service procedures that carry out the
system calls.
• A set of utility procedures that help the service
procedures.
Operating Systems Structure
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

54. Figure 1-25. Structure of the THE operating system.
Layered Systems
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

55. Figure 1-26. Structure of the MINIX 3 system.
Microkernels

56. Figure 1-27. The client-server model over a network.
Client-Server Model
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

57. Figure 1-29. (a) A type 1 hypervisor. (b) A type 2 hypervisor.
Virtual Machines (2)
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

58. • The C language
• Header files
• Large programming projects
• The model of run time
The World According to C
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

59. World according to C
 Operating systems are large C programs consisting of
many pieces written by many programmers
 C language
 Data types, variables, control statements…
 Header files: declaration, definition, macros…
 For a large programming project

60. Figure 1-30. The process of compiling C and header files to
make an executable.
The Model of Run Time
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

61. Large programming projects
 C preprocessor:
 Gets the header, expand macros, handling conditional
compilation
 Compiler
 .c -.o
 Linker
 Combine all .o to an executable program; traditionally
a.out

62. Gcc: preprocess-assemble-
compile-link
 gcc -E hello.c –o hello.i
 gcc -S hello.i -o hello.s
 gcc -c hello.s –o hello.o
 gcc hello.o –o hello
 ldd hello
