Operating System
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Objectives
Objective
The purpose of this course is to provide an understanding of operating systems to
students so they will be able to understand the terminology surrounding and
describing operating systems. Students will become familiar with the kinds of
abstractions provided by general purpose operating systems that facilitate the
development of user applications. Also they will become familiar with the typical
internal policies and mechanisms implemented by operating systems and how they
impact system performance.
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Description
Description
This course is an introduction to the theory and practice behind modern operating
systems. Topics will include what an operating system does, system calls and
interfaces, processes, concurrent programming, resource scheduling and
management, virtual memory, deadlocks and security.
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Course Outline
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Course Administration
Text & Reference Books:
Operating System Concepts Eighth Edition Abraham Silberschatz, the Peter
Gaivin, Greg Gagne
Modern Operating System Third Edition ANDREW S. TANENBAUM
Abraham Silberschatz, the Peter Gaivin, Greg Gagne, Applied Operating System
Concepts (practical concept of the operating system)., John Wiley & Sons,
Inc.2000 (Beijing: Higher Education Press .2001,5)
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Class Policies
Marks Distribution
Marks Head
Total
Frequency
Total
Exempted
Marks
/Frequency
Total Marks
/Head
Quiz
3
0
5
15
Assignment
3
0
5
15
Final Paper
1
0
30+10(Viva)
40
Mid Term Paper
1
0
25+5(Viva)
30
Total Marks
100
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Class Rules
• No usage of cell phones and cells should be on silent mode.
• Discipline during the lecture
• Be on time
• Attendance ( No more absentees than 3)
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Let’s Start
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Basic components of a computer system:
place of OS
•
A computer system can be divided into
four components
– Hardware – provides basic computing
resources
• CPU, memory, I/O devices
– Operating system
• Controls and coordinates use
of hardware among various
applications and users
– Application programs –solve the
problems of the users: use system
resources
• Word processors, compilers, web
browsers, database systems,
video games
– Users
• People, machines, other
computers
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Purpose of a Computer System
• Computer systems consist of software and
hardware that are combined to provide a tool to
solve specific problems in an efficient manner
• Execute programs
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Computer System Hardware
Integer
Unit
Control
Unit
Keyboard
Mouse
CD
Floating Point
Unit
Cache
Processor
System Bus
HD
Mem
Bus
RAM/ROM
Printer
Monitor
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Operating System
• OS is the one program running all times on the computer.
• Kernel: running all the time; having most of the functionality
• Everything else: either a system program or an application program
The kernel is the essential center of
a computer operating system (OS).
It is the core that provides basic
services for all other parts of the OS. It
is the main layer between the OS and
hardware, and it helps with process
and memory management, file
systems, device control and
networking.
system
programs
+ you can install
other applications
kernel
(Some
application
programs)
OS CD
System programs: programs that are associated with the operating system
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What is OS?
An operating system (OS) is a collection of software that manages
computer hardware resources and provides common services for
computer programs. The operating system is a vital component of the
system software in a computer system.
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What OS Do?
An Operating System (OS) is an interface between a computer user and computer
hardware. An operating system is a software which performs all the basic tasks like file
management, memory management, process management, handling input and output, and
controlling peripheral devices such as disk drives and printers.
Some popular Operating Systems include Linux Operating System, Windows Operating
System, VMS, OS/400, AIX, z/OS, etc.
Following are some of important functions of an operating System.
• Memory Management
• Processor Management
• Device Management
• File Management
• Security
• Control over system performance
• Job accounting
• Error detecting aids
• Coordination between other software and users
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Applications of OS
Following are some of the important activities that an Operating System performs −
•Security − By means of password and similar other techniques, it prevents unauthorized
access to programs and data.
•Control over system performance − Recording delays between request for a service and
response from the system.
•Job accounting − Keeping track of time and resources used by various jobs and users.
•Error detecting aids − Production of dumps, traces, error messages, and other debugging
and error detecting aids.
•Coordination between other softwares and users − Coordination and assignment of
compilers, interpreters, assemblers and other software to the various users of the computer
systems.
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What is Open Source Operating System?
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Open source refers to the computer software or applications where the owners
or copyright holders allow the users or third party to see, use and provide the
right to modify the source code of the product.
An Open-source Operating System is the Operating System in which source
code is visible publically and editable. The generally known Operating
Systems like Microsoft’s Windows, Apple’s iOS and Mac OS, are closed
Operating system.
Closed Operating Systems are built with numerous codes and complex
programming and that is called source code. This source code is kept secret
by the respective companies (owners) and inaccessible to third parties. By
doing so, they ensure the safety and secure the Operating System and
computer from any threats.
In the case of an Open Source Operating system, everyone can access and
edit the source code.
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Pros and Cons of Open Source Operating
Systems:
Pros:
Cost-efficient – Most of the Open Source OS is free. And some of them are available at a very cheap
rate than the commercial closed products.
• Reliable and efficient – Most of them are monitored by thousands of eyes since the source code is
public. So if there is any vulnerability or bugs, they are fixed by the best developers around the world
• Flexibility- The great advantage is you can customize it as per your need. And there is creative freedom.
Cons:
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Security risk – Though the bugs are identified, there is a risk of attacks as the source code is available
to the attackers.
Complicated – It is not user-friendly as the closed ones. You need to have the minimum technical
knowledge to use this software
No support – If you meet with the problem, then there is no customer support to help you out.
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Some Free and Open Source OS
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Ubuntu-Linux-based OS
Linux Lite-Linux-based OS
Fedora-Linux-based OS
Linux Mint-Linux-based OS
Solus-Linux-based OS
Xubuntu-Unix-based OS
Chrome OS-Chromium and Linux
React OS(No Linux and Unix involved)
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Computer Startup
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Bootstrap program is loaded at power-up or reboot
– Typically stored in ROM or EPROM,
– Initializes all aspects of the system
– Locate and Load operating system kernel and starts execution
Kernel runs and make the system ready for running applications
– Kernel is always ready to run (always in memory)
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Computer system operation:
I/O and device interaction
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I/O devices and the CPU can execute concurrently
Each device controller has a local buffer
– Data movement (I/O) between device and local buffer
– Data movement between memory and local buffer (by CPU)
Device controller informs CPU that it has finished its current operation or it
has something by causing an interrupt
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Computer System Organization
• Computer-system operation
– One or more CPUs, device controllers connect through common bus
providing access to shared memory
– Concurrent execution of CPUs and devices competing for memory cycles
Network
cable
Network
adapter
Bus
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Storage Structure
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Main memory – CPU can access directly
Secondary storage – extension of main
memory that provides large nonvolatile
storage capacity
– Magnetic disks
• platters
• The disk controller determines the
interaction between the device and
the computer
Main
Memory
CPU
Disk
Controller
Spinning
Disk
secondary
storage
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Storage Hierarchy
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Storage systems organized in hierarchy
– Speed, Cost, Volatility
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