Operating System Overview: Understanding the Role of an OS in Managing Computer Resources, Exercises of Operating Systems

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Dr.Khaled Kh. Sharaf

Faculty Of Computers And Information Technology

First Term 2019- 2020

Operating System

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

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

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.

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

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

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.

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.

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 MP 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.

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.

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

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.

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

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.