1. Unit 1_Introduction to OS.pptx

Faculty Name- Aishwarya
aishwarya@inurture.co.in
Operating system principles-CSC433

UNIT -I INTRODUCTION TO OPERATING SYSTEM
UNIT -II
UNIT -III
UNIT -IV
UNIT -V
PROCESS MANAGEMENT
Process Synchronization and Deadlocks
MEMORY MANAGEMENT AND FILE-SYSTEM
INTRODUCTION TO DISTRIBUTED SYSTEMS

UNIT–I INTRODUCTION TO OPERATING SYSTEM
Computer System organization, Computer System architecture,
Operating System structure, Operating System operations, Process
management, Memory management, Storage management, Protection
and security, Special-purpose systems, Computing environments,
Operating System Services, User interface, System calls, System
programs, Operating System design and implementation, Operating
System structure, Operating System generation, System boot- Case
Study.

 Microsoft Windows
 Apple macOS
 Ubuntu
 Linux
 Chrome OS
 Red Hat
 Fedora
 CentOS
 FreeBSD
x
Examples of Operating System
 Google's Android OS
 Apple iOS
 Windows Phone OS
 Series 40 (Nokia)
 Symbian OS (Nokia)
 BlackBerry OS
 Bada – Samsung
 MeeGo OS (Nokia and Intel)

x
Examples of Operating System

x
Examples of Operating System with Market Share
OS Name Share
Windows 40.34
Android 37.95
iOS 15.44
Mac OS 4.34
Linux 0.95
Chrome OS 0.14
Windows Phone OS 0.06

 In the Computer System (Hardware and Software), Hardware can only
understand machine code (in the form of 0’s and 1’s).
x
Operating System

x
Structure of a Computer System

A Computer System consists of:
1. Users  People who are using the Computer. (Machine)
2. Application Programs  Compilers, Databases, Games, Video player,
Web Browsers, Word Processors etc.
3. System Programs  Shells, Editors, Compilers, etc.
4. Operating System  A special program which acts as an interface
between user and hardware.
5. Hardware  CPU, Disks, Memory, I/O etc.
x
Structure of a Computer System

What is an Operating System?
 A program that acts as an intermediary between a user of a
computer and the computer hardware
 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

Computer System Structure
Computer system can be divided into four components:
•provides basic computing resources
CPU Hardware – Memory, I/O devices
•Operating system-
Controls and coordinates use of hardware among various applications
and users
•Application programs – define the ways in which the system resources are
used to solve the computing problems of the users
Word processors, compilers, web browsers, database systems, video
games
•Users
People, machines, other computers

Abstract View of Components of Computer

User View
1. System is designed for one user to monopolize its resources.
• The goal is to maximize the work (or play) that the user is
performing.
• In this case/ the operating system is designed mostly for ease of
use, with some attention paid to performance and none paid to
resource utilization –how various hardware and software
resources are shared.

User view
2. A user sits at a terminal connected to a mainframe or a
minicomputer. Other users are accessing the same computer
through other terminals.
• These users share resources and may exchange information.
• The operating system in such cases is designed to maximize
resource utilization- to assure that all available CPU time,
memory, and I/0 are used efficiently and that no individual user
takes more than her fair share.

User view
• 3. In some cases, users sits at workstations connected to networks of
other workstations and servers. These users have dedicated
resources at their disposal, but they also share resources such as
networking and servers- file , compute, and print servers.
• Therefore, their operating system is designed to compromise
between individual usability and resource utilization.

System View
• The operating system is the program most intimately involved with
the hardware. In this context, we can view an operating system as
a resource allocation.
• A computer system has many resources that may be required to
solve a problem: CPU time, memory space, file-storage space, I/0
devices, and so on.
• A slightly different view of an operating system emphasizes the
need to control the various I/0 devices and user programs. An
operating system is a control program

System View
• A control program manages the execution of user programs to
prevent errors and improper use of the computer. It is especially
concerned with the operation and control of I/O devices

What Operating Systems Do
Depends on the point of view:
Users want convenience, ease of use and good performance
•Don’t care about resource utilization
But shared computer such as mainframe or minicomputer
must keep all users happy
•Operating system is a resource allocator and control
program making efficient use of HW and managing execution
of user programs

What Operating Systems Do (Cont.)
Users of dedicate systems such as workstations have dedicated
resources but frequently use shared resources from servers
Mobile devices like smartphones and tables are resource poor,
optimized for usability and battery life
•Mobile user interfaces such as touch screens, voice recognition
Some computers have little or no user interface, such as
embedded computers in devices and automobiles: ex- IoT devices
•Run primarily without user intervention

Operating System Definition
No universally accepted definition
“The one program running at all times on the computer” is the
kernel, which is part of the operating system
Everything else is either
•A system program (ships with the operating system, but not part of the
kernel) , or
•An application program, all programs not associated with the operating
system
Today’s OSes for general purpose and mobile computing also include
middleware – a set of software frameworks that provide addition services to
application developers such as databases, multimedia, graphics

Overview of Computer System Structure

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

Computer Startup
Bootstrap program is loaded at power-up or
reboot
Typically stored in ROM or EPROM, generally
known as firmware
Initializes all aspects of system
Loads operating system kernel and starts
execution

Storage Definition and Notation
• A bit is a basic unit of computer storage. It can contain one of two
values: zero and one.
• Storage in a computer is based on collections of bits
• Given enough bits, it is amazing how many things a computer can
represent: numbers, letters, images, movies, sounds, documents,
and programs, to name a few.
• A Byte is 8 bits, and on most computers it is smallest convenient
chunk of storage.
• kilobyte: 1024bytes; megabyte: 1024^2 bytes; gigabyte: 1024^3
bytes

Storage Structure
Main memory – only large storage media that the CPU
can access directly
•Typically, volatile
•Typically, random-access memory in the form of
Dynamic Random-access Memory (DRAM)
Secondary storage – extension of main memory that
provides large nonvolatile storage capacity

Storage Structure (Cont.)
Hard Disk Drives (HDD) – rigid metal or glass platters
covered with magnetic recording material
•Disk surface is logically divided into tracks, which are
subdivided into sectors
•The disk controller determines the logical interaction
between the device and the computer
Non-volatile memory (NVM) devices– faster than hard
disks, nonvolatile
•Various technologies
•Becoming more popular as capacity and performance
increases, price drops

Storage Hierarchy
Storage systems organized in hierarchy
•Speed
•Cost
•Volatility
Caching – copying information into faster storage
system; main memory can be viewed as a cache for
secondary storage
Device Driver for each device controller to manage I/O
•Provides uniform interface between controller and
kernel

How a Modern Computer Works
A von Neumann architecture

Operating-System Operations
Bootstrap program – simple code to initialize the system,
load the kernel
Kernel loads
Starts system daemons (services provided outside of the
kernel)
Kernel interrupt driven (hardware and software)
•Hardware interrupt by one of the devices
•Software interrupt (exception or trap):
Software error (e.g., division by zero)
Request for operating system service – system call
Other process problems include infinite loop,
processes modifying each other or the operating
system

System Calls
• System calls provide an interface to the services made available
by an operating system.
• These calls are generally available as routines written in C and
C++, although certain low-level tasks (for example, tasks where
hardware must be accessed directly) may have to be written using
assembly-language instructions.
• The first input that the program will need is the names of the two
files: the input file and the output file
• System calls is a programmatic way in which a computer program
request a service from kernel of the operating system.

The handling of a user application invoking
the open() system call

Types of System Calls
Process control
•create process, terminate process
•end, abort
•load, execute
•get process attributes, set process attributes
•wait for time
•wait event, signal event
•allocate and free memory
•dump memory if error
•Debugger for determining bugs, single step execution
•Locks for managing access to shared data between processes

File management
• create file, delete file
• open, close file
• read, write, reposition
• get and set file attributes
Device management
• request device, release device
• read, write, reposition
• get device attributes, set device attributes
• logically attach or detach devices
Types of System Calls (Cont.)

Information maintenance
• get time or date, set time or date
• get system data, set system data
• get process, file, or device attributes
• set process, file, or device attributes
Communications
• create, delete communication connection
• send, receive messages
• transfer status information
• attach or detach remote devices

• Protection provides a mechanism for controlling access to the
resources provided by a computer system. Historically, protection
was a concern only on multi programmed computer systems with
several users.
• System calls providing protection include set permission() and get
permission(), which manipulate the permission settings of resources
such as files and disks. The allow user() and deny user() system calls
specify whether particular users can—or cannot—be allowed access
to certain resources.

Single Processor System
• In Single Processor System, there is one main CPU capable of
executing a general purpose instruction set, including instructions
from user programs.

Multi processor Systems
• Multiprocessor systems (also known as parallel systems or
multicore systems) have begun to dominate the landscape of
computing.
• Such systems have two or more processors in close
communication, sharing the computer bus and sometimes the
clock, memory, and peripheral devices. Multiprocessor systems
first appeared prominently appeared in servers and have since
migrated to desktop and laptop systems

Multiprocessor systems have three main
advantages:
• Increased throughput. By increasing the number of processors,
we expect to get more work done in less time. The speed-up ratio
with N processors is not N, however; rather, it is less than N.
• Economy of scale. Multiprocessor systems can cost less than
equivalent multiple single-processor systems, because they can
share peripherals, mass storage, and power supplies
• Increased reliability. If functions can be distributed properly
among several processors, then the failure of one processor will
not halt the system, only slow it down

1. Unit 1_Introduction to OS.pptx

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1. Unit 1_Introduction to OS.pptx