1. MODERN OPERATING SYSTEMS Third Edition ANDREW S. TANENBAUM Chapter 1 Introduction Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

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 Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

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. Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

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. Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

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 Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

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 Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

15. 1 st : 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. 2 nd : 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. 2 nd : 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. Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

20. 3 rd : IC and Multiprogramming OS/360: a dinosaur stuck in a tar pit  Aims to adapts 1401/7904, covers all trades of life  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. 3 rd : ICs and Multiprogramming Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

22. 3 rd : Ics and Multiprogramming Problems:  3 rd 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. 3 rd : 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. 4 th : personal computers Computers have performance similar to 3 rd generation, but prices drastically different CP/M  First disk-based OS 1980, IBM PC, Basic Interpreter, DOS, MS- DOS GUI--Lisa—Apple: user friendly MS-DOS with GUI– Win95/98/me— winNT/xp…

25. Summary 4 generations OS Develops with hardware and user needs Multi-user, multi-programming, time-sharing

26. Computer Hardware Review Figure 1-6. Some of the components of a simple personal computer. Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

27. 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, priority, mode…

28. CPU Pipelining Figure 1-7. (a) A three-stage pipeline. (b) A superscalar CPU. Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

29. CPU Pipeline Accelerate the execution Cause headaches to OS/compiler writers For superscalar: instructions are often executed out of order

30. 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 Chips Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

31. Figure 1-9. A typical memory hierarchy. The numbers are very rough approximations. Memory (1) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

32. 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

33. 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. Memory (2) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

34. 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

35. 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

36. Figure 1-11. (a) The steps in starting an I/O device and getting an interrupt. I/O Devices Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

37. I/O devices Two parts: a controller and a device Controller: to provide a simpler interface to OS Device driver: talks to controller, give commands and accepts response Busy waiting/interrupt/DMA

38. Buses Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

39. Booting the Computer BIOS—basic input/output system  On the parentboard, 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

40. 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 Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

41. Processes Address spaces Files Input/Output Protection The shell Ontogeny recapitulates phylogeny Large memories Protection hardware Disks Virtual memory Operating System Concepts Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

42. 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

43. Processes 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. Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

44. 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

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

46. 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 (2) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

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

48. 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

49. 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

50. 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

51. 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

52. 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

53. 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

56. Figure 1-19. A stripped-down shell. A Simple Shell Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

57. Figure 1-20. Processes have three segments: text, data, and stack. Memory Layout Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

58. Figure 1-21. (a) Two directories before linking /usr/jim/memo to ast’s directory. (b) The same directories after linking. Linking Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

59. 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

60. 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

61. 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

62. 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

63. Figure 1-26. Structure of the MINIX 3 system. Microkernels Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639

64. 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

65. 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

66. 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

67. 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

68. 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

69. 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

70. 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