Dr.Khaled Kh. Sharaf

Faculty Of Computers

And Information

Technology

First Term

2019- 2020

Operating System

Overview

Suppose you work as a manager in a company

• Where is your location in the company's organizational

structure

• So what tasks do you must to do?

• What role will you play within the company's

organizational hierarchy?

• Is there a need to company

manager? And why?

So the operating system

acts as a manager

Overview

Overview

An operating system is the most important software that

runs on a computer.

It manages the computer's memory and processes, as well

as all of its software and hardware.

It also allows you to communicate with the computer

without knowing how to speak the computer's language.

Without an operating system, a computer is useless.

The operating system acts as an intermediary between the

user of a computer and the computer hardware.

The purpose of an operating system is to provide an

Environment in which a user can execute programs in

a convenient and efficient manner.

Overview

Internally, operating systems vary greatly in their

makeup, since they are organized along many different

lines.

The design of a new operating system is a major task.

It is important that the goals of the system be well

defined before the design begins.

These goals form the basis for choices among various

algorithms and strategies.

Because an operating system is large and complex, it must

be Created piece by piece.

Each of these pieces should be a well-delineated portion

of the system, with carefully defined inputs, outputs,

and functions.

Overview

Overview

Overview

Definition

An operating system is

a program that acts as

an interface between

the user and the

computer hardware

and controls the

execution of all kinds

of programs.

Overview

Overview

Your computer's operating system (OS) manages all

of the software and hardware on the computer.

Most of the time, there are several different

computer programs running at the same time, and

they all need to access your computer's central

processing unit (CPU), memory, and storage.

The operating system coordinates all of this to

make sure each program gets what it needs.

The operating system's job

Overview

Operating systems usually come pre-loaded on any

computer you buy. Most people use the operating

system that comes with their computer, but it's

possible to upgrade or even change operating

systems. The three most common operating systems

for personal computers are Microsoft Windows,

macOS, and Linux.

Modern operating systems use a graphical user

interface, or GUI (pronounced gooey).

Types of operating systems

Overview

A GUI lets you use your mouse to click icons,

buttons, and menus, and everything is clearly

displayed on the screen using a combination of

graphics and text.

Types of operating systems

Overview

Types of operating systems

Each operating system's GUI has a different look and

feel, so if you switch to a different operating system

it may seem unfamiliar at first. However, modern

operating systems are designed to be easy to use, and

most of the basic principles are the same.

Overview

Microsoft Windows

Microsoft created the Windows operating system in the

mid-1980s. There have been many different versions of

Windows, but the most recent ones are Windows 10

(released in 2015), Windows 8 (2012), Windows 7 (2009),

and Windows Vista (2007). Windows comes pre-loaded on

most new PCs, which helps to make it the most popular

operating system in the world.

Overview

macOS

macOS (previously called OS X) is a line of operating systems created by Apple. It comes preloaded on all

Macintosh computers, or Macs. Some of the specific

versions include Mojave (released in 2018), High Sierra

(2017), and Sierra (2016).

According to

StatCounter Global Stats,

macOS users account for

Less than 10% of global

operating systems—much

lower than the percentage

of Windows users

(more than 80%).

One reason for this is that Apple computers tend to be

more expensive.

However, many people do prefer the look and feel of

macOS over Windows.

Overview

Linux

Linux (pronounced LINN-ux) is a family of open-source

operating systems, which means they can be modified and

distributed by anyone around the world. This is

different from proprietary software like Windows, which

can only be modified by the company that owns it. The

advantages of Linux are that it is free, and there are

many different distributions—or versions—you can choose

from.

According to StatCounter

Global Stats, Linux users

account for less than 2%

of global operating systems.

However, most servers run

Linux because it's

relatively easy to

customize.

Overview

Operating systems for mobile devices

The operating systems we've been talking about so far

were designed to run on desktop and laptop computers.

Mobile devices such as phones, tablet computers, and MP3

players are different from desktop and laptop computers,

so they run operating systems that are designed

specifically for mobile devices.

Examples of mobile operating systems include Apple iOS

and Google Android.

Overview

Operating systems for mobile devices

In the screenshot below you can see iOS running on an

iPad.

Operating systems

for mobile devices

generally aren't as

fully featured as

those made for

desktop and laptop

computers, and they

aren't able to run

all of the same

software.

However, you can still do a lot of things with them,

like watch movies, browse the Web, manage your calendar,

and play games.

Topics:

1. Introduction

2. Process Management

3. Memory Management

4. Storage Management

5. Protection and Security

Overview

A process can be thought of as a program in execution.

A process will need certain resources—such as CPU time,

memory, files, and I/O devices—to accomplish its task.

These resources are allocated to the process either when

it is created or while it is executing.

A process is the unit of work in most systems. Systems

consist of a collection of processes:

• operating-system processes execute system code

• user processes execute user code

All these processes may execute concurrently.

Processor Management

Overview

Although traditionally a process contained only a single

thread of control as it ran, most modern operating

systems now support processes that have multiple threads.

The operating system is responsible for several important

aspects of process and thread management:

• The creation and deletion of both user and system

processes.

• The scheduling of processes.

• The provision of mechanisms for synchronization,

communication, and deadlock handling for processes.

Processor Management Cont.

Overview

Main objectives:

• To introduce the notion of a process—a program in

execution, which forms the basis of all computation.

• To describe the various features of processes,

including scheduling, creation, and termination.

• To explore interprocess communication using shared

memory and message passing.

• To describe communication in client–server systems.

Processor Management Cont.

Overview

The main purpose of a computer system is to execute

programs.

These programs, together with the data they access, must

be at least partially in main memory during execution.

To improve both the utilization of the CPU and the speed

of its response to users, a general-purpose computer must

keep several processes in memory.

Many memory-management schemes exist, reflecting various

approaches, and the effectiveness of each algorithm

Depends on the situation.

Selection of a memory-management scheme for a system

depends on many factors, especially on the hardware

design of the system. Most algorithms require hardware

support.

Memory Management

Overview

Main objectives:

• To provide a detailed description of various ways of

organizing Memory hardware.

• To explore various techniques of allocating memory to

processes.

• To discuss in detail how paging works in contemporary

computer systems.

Memory Management Cont.

Overview

Since main memory is usually too small to accommodate all

the data and programs permanently, the computer system

must provide secondary storage to back up main memory.

Modern computer systems use disks as the primary on-line

storage medium for information (both programs and data).

The file system provides the mechanism for on-line storage

of and access to both data and programs residing on

the disks.

A file is a collection of related information defined by

its creator.

The files are mapped by the operating system onto physical

devices.

Storage Management

Overview

Files are normally organized into directories for ease

of use.

The devices that attach to a computer vary in many aspects

• Some devices transfer a character or a block of

characters at a time.

• Some can be accessed only sequentially, others randomly.

• Some transfer data synchronously, others asynchronously.

• Some are dedicated,

• Some shared.

They can be read-only or read–write. They vary greatly in

speed.

In many ways, they are also the slowest major component

of the computer.

Storage Management Cont.

Overview

Because of all this device variation, the operating

system needs to provide a wide range of functionality to

applications, to allow them to control all aspects of

the devices.

One key goal of an operating system’s I/O subsystem is to

provide the simplest interface possible to the rest of

the system. Because devices are a performance bottleneck,

another key is to optimize I/O for maximum concurrency.

Storage Management Cont.

Overview

Main objectives:

• To describe the physical structure of secondary storage

devices and its effects on the uses of the devices.

• To explain the performance characteristics of

mass-storage devices.

• To evaluate disk scheduling algorithms.

• To discuss operating-system services provided for mass

storage, including RAID.

Storage Management Cont.

Overview

Protection mechanisms control access to a system by

limiting the types of file access permitted to users.

In addition, protection must ensure that only processes

that have gained proper authorization from the operating

system can operate on memory segments, the CPU, and other

resources.

Protection is provided by a mechanism that controls the

access of programs, processes, or users to the resources

defined by a computer system. This mechanism must provide

a means for specifying the controls to be imposed,

together with a means of enforcing them.

Protection and Security

Overview

Security ensures the authentication of system users

to protect the integrity of the information stored in the

system (both data and code), as well as the physical

resources of the computer system.

The security system prevents unauthorized access,

malicious destruction or alteration of data, and

accidental introduction of inconsistency.

Protection and Security Cont.

Overview

Main objectives:

• To discuss the goals and principles of protection in

a modern computer system.

• To explain how protection domains, combined with an

access matrix, are used to specify the resources

a process may access.

• To examine capability- and language-based protection

systems.

Protection and Security Cont.

Overview

The intention of operating systems and their functions,

introduction to various operating systems and their

tools, knowledge and use of the basic concepts of the

common operating systems of most computers, such as

organizing the processor, memory management, file

organization, virtual memory scheduling processors,

Kernel system and feeding system.

Course description

Overview

• To introduce the notion of a process—a program in

execution, which forms the basis of all computation.

• To describe the various features of processes,

including scheduling, creation, and termination.

• To explore interprocess communication using shared

memory and message passing.

• To describe communication in client–server systems.

• To provide a detailed description of various ways of

organizing Memory hardware.

• To explore various techniques of allocating memory to

processes.

• To discuss in detail how paging works in contemporary

computer systems.

Course Objectives

Overview

• To describe the physical structure of secondary storage

devices and its effects on the uses of the devices.

• To explain the performance characteristics of

mass-storage devices.

• To evaluate disk scheduling algorithms.

• To discuss operating-system services provided for mass

storage, including RAID.

• To discuss the goals and principles of protection in

a modern computer system.

• To explain how protection domains, combined with an

access matrix, are used to specify the resources

a process may access.

• To examine capability- and language-based protection

systems.

Course Objectives Cont.

Overview

Semester Teaching plan

Overview

Week Topics No

1 Course syllabus and course overview,

operating System

1.

2 Introduction 2.

3,4,5 Process Management 3.

6,8,9 Memory Management 4.

7 Midterm Exam 5.

10,11,12 Storage Management 6.

13,14 Protection and Security 7.

15 Review 8.

16 Final Exam 9.

Overview

Marks Task No

10 Quizzes, Home works 1

20 Midterm Exam 2

10 Lab 4

60 Final Exam 5

Evaluation tasks

Text book:

OPERATING SYSTEM CONCEPTS, ABRAHAM SILBERSCHATZ,

PETER BAER GALVIN,GREG GAGNE

NINTH EDITION

Course materials

Overview

Finally

I wish you good luck