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1 OPERATING SYSTEMS Lecturer: Szabolcs Mikulas Office: B38B URL: Textbook: A.S.

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Presentation on theme: "1 OPERATING SYSTEMS Lecturer: Szabolcs Mikulas Office: B38B URL: Textbook: A.S."— Presentation transcript:

1 1 OPERATING SYSTEMS Lecturer: Szabolcs Mikulas Office: B38B URL: Textbook: A.S. Tanenbaum, Modern Operating Systems, Second edition, Prentice Hall, 2001, ISBN

2 2 OUTLINE 1. Introduction 2. Processes and threads 3. Deadlock 4. Memory management 5. Input/output 6. File systems 7. Multimedia operating systems 8. Multiple processor systems 9. Security UNIX and Windows are to be used as running case studies.

3 3 Introduction Chapter What is an operating system 1.2 History of operating systems 1.3 The operating system zoo 1.4 Computer hardware review 1.5 Operating system concepts 1.6 System calls 1.7 Operating system structure

4 4 Introduction A computer system consists of –hardware –system programs –application programs

5 5 What is an Operating System It is an extended, or virtual, machine –provides a simple, high-level abstraction, i.e., hides the messy details which must be performed –presents user with a virtual machine, easier to use –provides services; programs obtain these by system calls It is a resource manager –provides orderly and controlled allocation for programs in terms of time and space, multiplexing

6 6 History of Operating Systems First generation –vacuum tubes, plug boards Second generation –transistors, batch systems Third generation 1965 – 1980 –ICs and multiprogramming Fourth generation 1980 – present –personal computers

7 7 Second Generation Early batch system –bring cards to 1401 –read cards to tape –put tape on 7094 which does computing –put tape on 1401 which prints output

8 8 Second Generation (2) Structure of a typical FMS job – 2 nd generation

9 9 Third Generation Third generation: Multiprogramming Timesharing MULTICS => UNIX

10 10 Fourth Generation Fourth generation (1980- ) - Personal computers MS-DOS, Graphical User Interface (GUI), Windows, Network and distributed OSs

11 11 The Operating System Zoo Mainframe operating systems Server operating systems Multiprocessor operating systems Personal computer operating systems Real-time operating systems Embedded operating systems Smart card operating systems

12 12 Computer Hardware Review Components of a simple personal computer Monitor Bus

13 13 Processors (a) A three-stage pipeline (b) A superscalar CPU

14 14 Memory Typical memory hierarchy –numbers shown are rough approximations

15 15 Hard Disk Structure of a disk drive

16 16 Base-Limit Pairs One base-limit pair and two base-limit pairs

17 17 Interrupt (a) Steps in starting an I/O device and getting interrupt (b) How the CPU is interrupted (a)(b)

18 18 Pentium System Structure of a large Pentium system

19 19 Processes Program in execution Address space: list of memory locations for read and write - code, data, stack Process table: one entry for each process, contains:list of open files, state UID etc. Communication, scheduling

20 20 A Process Tree A created two child processes, B and C B created three child processes, D, E, and F

21 21 Deadlock (a) A potential deadlock. (b) An actual deadlock. Read-write example

22 22 Main Memory Holds executing programs Multiple programs - protection Large programs - virtual memory

23 23 File System File system for a university department

24 24 Files Abstract model of device independent files Hierarchy, directories, operations Absolute and relative path names - root and working directory Special files (for I/O devices): –block s.f. –character s.f. Security

25 25 Mounting Before mounting, –files on floppy are inaccessible After mounting floppy on b, –files on floppy are part of file hierarchy

26 26 Pipe Two processes connected by a pipe e.g. sort

27 27 System Calls Interface between OS and user programs (to perform privileged operations) Machine dependent, but procedure libraries

28 28 Steps in Making a System Call There are 11 steps in making the system call read (fd, buffer, nbytes)

29 29 Some System Calls For Process Management

30 30 Some System Calls For File Management

31 31 Some System Calls For Directory Management

32 32 Some System Calls For Miscellaneous Tasks

33 33 Shell A stripped down shell: while (TRUE) {/* repeat forever */ type_prompt( );/* display prompt */ read_command (command, parameters)/* input from terminal */ if (fork() != 0) {/* fork off child process */ /* Parent code */ waitpid( -1, &status, 0);/* wait for child to exit */ } else { /* Child code */ execve (command, parameters, 0);/* execute command */ }

34 34 Link Link(/usr/jim/memo,/usr/ast/note) (a) Two directories before linking /usr/jim/memo to ast's directory (b) The same directories after linking

35 35 Mount mount(/dev/fd0,/mnt,0) (a) File system before the mount (b) File system after the mount

36 36 Windows System Calls Some Win32 API calls

37 37 Monolithic System Simple structuring model for a monolithic system

38 38 Layered System Structure of the THE operating system MULTICS - concentric rings

39 39 Virtual Machines Structure of VM/370 with CMS CMS: Conversational Monitor System VM: Virtual Machine Monitor - multiprogramming MS-DOS on Pentium JVM

40 40 Exokernels Similar to VM, but Restriction to allocated resources No need for remap

41 41 Client-Server Model Microkernel handles communication provides low-level resource management Cf. Mechanism versus policy

42 42 C-S Model in a DS The client-server model in a distributed system

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