Opearating System

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  • Opearating System

    1. 1. Chapter 13 Operating Systems: An Overview The Architecture of Computer Hardware and Systems Software: An Information Technology Approach 3rd Edition, Irv Englander John Wiley and Sons ©2003 Wilson Wong, Bentley College Linda Senne, Bentley College
    2. 2. Chapter 13 13-2 Integrated Computer Environment
    3. 3. Chapter 13 13-3 Operating System – Basic Services  Programs that accept commands and requests from a user and a user’s program  Manages, loads, and executes programs  Manages hardware resources of the computer  Act as an interface between the user and the system
    4. 4. Chapter 13 13-4 Operating System – Additional Services  Provides interfaces for the user and the user’s programs  File support services  I/O support services  Means of starting the computer  Bootstrapping or booting the computer  Initial Program Load (IPL)  Handles all interrupt processing  Network services  Provides tools and services for concurrent processing
    5. 5. Chapter 13 13-5 Additional Services Required by Concurrent Processing  Allocates resources such as memory, CPU time, and I/O devices to programs  Protects users and programs from each other and provides for inter-program communication  Provides feedback to the system administrators to permit performance optimization of the computer system
    6. 6. Chapter 13 13-6 OS Parts  Memory Resident  Always loaded in memory  Commonly called the kernel  Contains essential services required by other parts of the operating system and applications.  Typically responsible for managing memory management, processes and tasks, and secondary storage  Memory Non-resident  Applications  Infrequently used programs, software tools, and commands  Bootstrap program  Diskless workstations or thin clients  Programs, including the OS, are located on another computer on the network
    7. 7. Chapter 13 13-7 OS Degree of Activity  Interactive  Also known as conversational systems  Batch processing  User submits programs or jobs for processing  Little to no user interaction  Event driven  Interrupts or service requests
    8. 8. Chapter 13 13-8 Hardware and the OS  A hardware platform may support a variety of operating systems  An operating system may work on a variety of platforms  A standard operating system that works on different hardware  Provides program and file portability  Enables user efficiency through recognizable interface  Is implemented through a systems programming language like C or C++ as opposed to assembly language
    9. 9. Chapter 13 13-9 Single Job Processing  Only one program is loaded into memory and executed  Example: MS-DOS  Memory resident components  Command interface shell  I/O routines, including BIOS  File management system  User program in control
    10. 10. Chapter 13 13-10 Single Job Processing Disadvantages  Lack of security  Programs can overwrite the resident OS  Programs can write directly to I/O devices  System provides minimum memory management and no scheduling  CPU is often idle awaiting the completion of I/O operations
    11. 11. Chapter 13 13-11 Concurrent Operations  Multitasking (multiprogramming) vs. multiprocessing which implies multiple CPUs  Concurrent processing vs. simultaneous processing
    12. 12. Chapter 13 13-12 Achieving Multitasking  While one program is waiting for I/O to take place, another program is using the CPU to execute instructions.  Time-slicing. The CPU may be switched rapidly back and forth between different programs  Dispatching is the process of selecting which program to run at any given instant
    13. 13. Chapter 13 13-13 Services and Facilities  Command processor  File management system  I/O control system  Process control management and inter-process communication  Memory management  Scheduling system  Secondary storage management  System protection management  Network management, communication support, and communication interfaces  System Administration
    14. 14. Chapter 13 13-14 User Interface and Command Execution Services  Types of user interfaces  CLI - Command Line Interface  GUI - Graphical User Interface  Menu environment  Shell  User interface and command processor that interacts with the kernel  UNIX: C, Bourne and Korn shells  Command Languages  IBM Mainframes – JCL  MS Windows – BAT files, Windows Scripting Host  UNIX – shell scripts
    15. 15. Chapter 13 13-15 File Management  File - logical unit of storage  Basic file management system provides  Directory structures for each I/O device  Tools to copy and move files  Information about each file in the system and the tools to access that information  Security mechanisms to protects files and control access  Additional file management features  Backup, emergency retrieval and recovery  File compression  Transparent network file access  auditing
    16. 16. Chapter 13 13-16 I/O Services and Process Control Management  I/O services  Startup configuration  Device drives that implement interrupts and provide other techniques for handling I/O  Plug and play: hot swapping, hot plugging  Process control management  A process is an executing program  A thread is an individually executable part of a process  Interprocess messaging services  Example: a pipe in UNIX or DOS that is a temporary software connection between two programs or commands
    17. 17. Chapter 13 13-17 Memory Management  Keeps track of memory  Identifies programs loaded into memory  Amount of space each program uses  Available remaining space  Prevents programs from reading and writing memory outside of their allocated space  Maintains queues of waiting programs  Allocates memory to programs that are next to be loaded  Deallocates a program’s memory space upon program completion
    18. 18. Chapter 13 13-18 Scheduling  High-level scheduling  Placed in queue based on level of priority and eventually executed  Dispatching  Actual selection of processes that will be executed at any given time  Preemptive – uses clock interrupts  Non-preemptive – program voluntarily gives up control  Context switching  Transfer control to the process that is being dispatched  Nonpreemptive: program voluntarily gives up control  Preemptive: uses clock interrupt for multitasking  Processing requirements  CPU vs. I/O bound
    19. 19. Chapter 13 13-19 Secondary Storage and Security  Secondary storage management  Optimizes completion of I/O tasks for efficient disk usage  Combination of hardware and software  Security and protection services  Protect OS from users  Protect users from other users  Prevent unauthorized entry to system  Prevent unauthorized system use by authorized users
    20. 20. Chapter 13 13-20 Network and Communication Services  TCP-IP protocol suite  Locate and connect to other computers  Access files, I/O devices, and programs from remote systems  Support distributed processing  Network Applications  Email, remote login, Web services, streaming multimedia, voice over IP telephony, VPN  Interface between communication software and OS I/O control system that provides network access
    21. 21. Chapter 13 13-21 System Administration Support  System configuration and setting group configuration policies  Adding and deleting users  Modifying user privileges  System security  Files systems management  Network administration  Backups  Software installations and upgrades  OS installations (system generation), patches, and upgrades  System tuning and optimization
    22. 22. Chapter 13 13-22 Types of Operating Systems  Single user, single tasking  Single user, multitasking  Multi-user, multitasking  Distributed systems  Processing power distributed among computers in a cluster or network  Network servers  Real-time systems  Embedded systems
    23. 23. Chapter 13 13-23 Bootstrapping  Execution begins with bootstrap loader (mini-loader, IPL) stored in ROM  Looks for OS program in a fixed location  Loads OS into RAM  Transfers control to starting location of OS  Loader program in OS used to load and execute user programs
    24. 24. Chapter 13 13-24 Bootstrapping  Cold vs. warm boot (does not retest the system)

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