The document provides an introduction to operating systems, describing their definition, goals, and evolution over time. It discusses the main components of a computer system and outlines the key functions of an operating system, including resource management, process management, memory management, file management, I/O management, and protection. It also categorizes different types of operating systems such as single-user, network, distributed, real-time, mobile, and embedded operating systems.

1. OPERATING SYSTEMS
Introduction to ComputingCHAPTER # 9

2. Introduction to Computing 2Chapter # 9
Operating System Definition
 Operating Systems
 OS is a control program which manages computer
resources and allocate these resources among competing
tasks
 OS control and coordinates use of hardware among
applications for users
 OS is the interface between the hardware and software
environment
 OS is a program that acts as an intermediary between the
user and computer hardware

3. Introduction to Computing 3Chapter # 9
Operating System Goals
 Execute user programs and make solving user
problems easier
 Make the computer system convenient to use
 Use the computer hardware in an efficient manner

4. Introduction to Computing 4Chapter # 9
Computer System Overview
 From hardware and software point of view, a
computer system can be divided into six parts
 Application programs
 Compliers, editors, interpreters
 Operating system
 Machine language
 Microprogramming
 Physical devices

5. Introduction to Computing 5Chapter # 9
Computer System Overview

6. Introduction to Computing 6Chapter # 9
Computer System Overview
 Operating Systems
 OS is an integrated set of programs used to manage the
computer resources and its overall operations
 Provide a layer of services which manage the resources of
the hardware and permit the user to drive the system

7. Introduction to Computing 7Chapter # 9
Computer System Overview
 Operating Systems
 An operating system performs
 Resource Management
 CPU management
 Memory management
 File System management
 I/O management
 Resource Sharing
 Among Users
 Among CPUs
 Interfacing between hardware and users

8. Introduction to Computing 8Chapter # 9
Operating Systems Evolution
 In early systems the programs were entered by using a set of
switches to define memory address value
 The program was started by setting the program counter to
the first instruction word and pressing a start button
 The execution was progressed by displaying light on console
 The first step towards improvement was to reduce human
involvement in this process
 Offline input devices like cards or paper tape reader were
introduced later
 A program loader was established in Computer memory to
read program from input device and setup it in memory

9. Introduction to Computing 9Chapter # 9
Operating Systems Evolution
 Around 1960, a new computer called Atlas was developed
with the requirements of an operating system in mind
 Batch processing was applied to submit jobs in batches to the
computer
 Multiprogramming was introduced to run several programs at
the same time
 The processor should be kept busy for most of the time by switching its
attention from one program to another
 Fist time sharing system (support multiple interactive users)
was developed at MIT
 Mini Computer took place having multi-user OS

10. Introduction to Computing 10Chapter # 9
Types of Operating Systems
 With the passage of time operating systems are
divided into different categories. They can be
categories as follows
 Single User OS
 Network OS
 Distributed OS
 Multiprocessor OS
 Real-time OS
 Embedded OS

11. Introduction to Computing 11Chapter # 9
Single User Operating Systems
 These types of OS are used with modern computer systems referred as
Personal Computers
 Cheaper OS
 Easy to use
 May run several different types of operating systems (Windows, Mac
OS, UNIX, Linux)
 Supports multiple applications
 not dedicated for one type of application
 Have centralized resources
 Supports multimedia (images, text, graphics and audio/video)
 Example:
 Windows 98,ME
 Linux, Fedora, Mac OS

12. Introduction to Computing 12Chapter # 9
Network Operating Systems
 Network Operating Systems are used to connect more than
one computer
 User can login to a remote computer, to share its resources
 Network OS do not follow any transparency (e.g. location,
migration)
 Every operation has to be explicitly specified by the user
 User knows where his job is processing
 Examples:
 Windows NT
 Sun Solaris

13. Introduction to Computing 13Chapter # 9
Distributed Operating Systems
 Distribute computation among several physical processors
 Follows the transparencies
 Requires networking infrastructure
 Local area networks (LAN) or Wide area networks (WAN)
 May be either client-server or peer-to-peer systems
 Main features of Distributed System
 Resource sharing
 Computation speed up
 Reliability
 Communication

14. Introduction to Computing 14Chapter # 9
Distributed Operating Systems
 Two types of Distributed OS
 Tightly coupled DOS (Multiprocessor)
 Multiprocessor system
 Processor share memory
 Communication takes place through memory
 Loosely coupled DOS (Multicomputer)
 Single processor system
 Clusters of workstations
 Do not communicate via memory
 Communicate via high speed buses, telephone lines
 Examples:
 Windows 2000, XP, Vista, 7, 8
 Linux
 Unix

15. Introduction to Computing 15Chapter # 9
Multiprocessor Operating Systems
 These are actually distributed operating systems which run on
machines having more than one processor
 Communication is done via shared memory through message passing,
pipes etc.
 Microsoft Windows 2000 Profile
 Windows 2000 Professional supports 2 processors at same machine
 Windows 2000 Server supports 4 processors at same machine
 Windows Advanced Server supports 8 processors at same machine
 Windows 2000 Datacenter Server supports 16 processors at same
machine

16. Introduction to Computing 16Chapter # 9
Real-time Operating Systems
 These OS run on Real-time systems
 Very fast operating system
 Normally designed for a set of specific applications
 A real-time system is any information processing system
which has to respond to externally generated input stimuli
within a finite and specified period
 the correctness depends not only on the logical result but also the
time it was delivered
 failure to respond is as bad as the wrong response
 In a real time system emphasis is on timely execution of tasks
than speed of execution
 Often used as a control device in a dedicated application such
as controlling scientific experiments, medical imaging
systems, industrial control systems, and some display systems
 Real-Time systems may be either hard or soft real-time

17. Introduction to Computing 17Chapter # 9
Real-time Operating Systems
 Hard real-time system
 systems where it is absolutely imperative that responses occur within
the required deadline
 E.g. Flight control systems
 Secondary storage limited or absent, data stored in short term
memory, or read-only memory (ROM)
 Soft real-time system
 systems where deadlines are important but which will still function
correctly if deadlines are occasionally missed
 E.g. Data acquisition system
 Limited utility in industrial control of robotics
 Useful in applications (multimedia, virtual reality) requiring advanced
operating-system features

18. Introduction to Computing 18Chapter # 9
Mobile Operating System
 A mobile operating system, is the operating system that operates a
smart phone, tablet, PDA, or other digital mobile devices
 Modern mobile operating systems combine the features of a
personal computer operating system with some other features
 like touch screen, cellular, Bluetooth, Wi-Fi, GPS mobile navigation,
camera, video camera, speech recognition, voice recorder, music player,
Near field communication, personal digital assistant (PDA) and other
features
 Example includes
 Google Android
 Apple I OS
 Symbian
 Windows Mobile
 Blackberry OS

19. Introduction to Computing 19Chapter # 9
Embedded Operating Systems
 These operating systems are dedicated for devices
 These are normally built-in with devices
 Embedded operating systems are designed to be used in embedded
computer systems
 They are designed to operate on small machines like PDAs with less
autonomy
 They are able to operate with a limited number of resources
 They are very compact and extremely efficient by design
 Windows Mobile and I OS are some examples of embedded operating
systems
 Example:
 Mobile set OS
 PDA OS
 Issues:
 Limited memory
 Slow processors
 Small display screens

20. Introduction to Computing 20Chapter # 9
Operating System Management
 Process management
 Memory management
 File management
 I/O system management
 Secondary storage management

21. Introduction to Computing 21Chapter # 9
Process Management
 A process is a program in execution
 A process needs certain resources, including CPU time,
memory, files, and I/O devices, to accomplish its task
 The operating system is responsible for the following
activities in connection with process manager
 Process creation and termination
 Process suspension and resumption
 Provision of mechanisms for:
 process synchronization
 process communication

22. Introduction to Computing 22Chapter # 9Chapter # 2 22
Memory Management
 Memory is a large array of words or bytes, each with its own address
 It is a repository of quickly accessible data shared by the CPU and I/O
devices.
 Main memory is a volatile storage device
 It loses its contents in the case of system failure
 The operating system is responsible for the following activities in
connections with memory management:
 Keep track of which parts of memory are currently being used and by
whom
 Decide which processes to load when memory space becomes
available
 Allocate and deallocate memory space as needed

23. Introduction to Computing 23Chapter # 9Chapter # 2 23
File Management
 A file is a collection of related information defined by its
creator
 Commonly, files represent programs (both source and
object forms) and data
 The operating system is responsible for the following
activities in connections with file management:
 File creation and deletion
 Directory creation and deletion
 Support of primitives for manipulating files and directories
 Mapping files onto secondary storage
 File backup on stable (nonvolatile) storage media

24. Introduction to Computing 24Chapter # 9Chapter # 2 24
I/O System Management
 Operating system is responsible for I/O system
management
 The I/O system consists of:
 A buffer-caching system
 A general device-driver interface
 Drivers for specific hardware devices

25. Introduction to Computing 25Chapter # 9Chapter # 2 25
Secondary Storage Management
 Since main memory (primary storage) is volatile and too small
to accommodate all data and programs permanently, the
computer system must provide secondary storage to back up
main memory
 Most modern computer systems use disks as the principle on-
line storage medium, for both programs and data
 The operating system is responsible for the following
activities in connection with disk management:
 Free space management
 Storage allocation
 Disk scheduling

26. Introduction to Computing 26Chapter # 9
Operating System Services
 Program execution
 system capability to load a program into memory and to run it
 I/O operations
 since user programs cannot execute I/O operations directly, the
operating system must provide some means to perform I/O
 File-system manipulation
 program capability to read, write, create, and delete files
 Communications
 exchange of information between processes executing either on the
same computer or on different systems tied together by a network.
Implemented via shared memory or message passing

27. Introduction to Computing 27Chapter # 9
Operating System Services
 Error detection
 ensure correct computing by detecting errors in the CPU and memory
hardware, in I/O devices, or in user programs
 Resource allocation
 allocating resources to multiple users or multiple jobs running at the
same time
 Accounting
 keep track of and record which users use how much and what kinds of
computer resources for account billing or for accumulating usage
statistics
 Protection
 ensuring that all access to system resources is controlled

28. Introduction to Computing 28Chapter # 9Chapter # 2 28
System Protection
 Protection refers to a mechanism for controlling access by
programs, processes, or users to both system and user
resources
 The protection mechanism must
 distinguish between authorized and unauthorized access
 specify the controls to be imposed
 provide a means of enforcement

29. Introduction to Computing 29Chapter # 9
System Design Goals
 User goals
 Operating system should be convenient to use, easy to
learn, reliable, safe, and fast
 System goals
 Operating system should be easy to design, implement,
and maintain, as well as flexible, reliable, error-free, and
efficient

30. Introduction to Computing 30Chapter # 9
Operating System Implementation
 Traditionally written in assembly language, operating
systems can now be written in higher-level languages
like C or C++
 Code written in a high-level language:
 can be written faster
 is more compact
 is easier to understand and debug
 An operating system is far easier to port (move to some
other hardware) if it is written in a high-level language