The document provides an introduction to operating systems, detailing their role as intermediaries between users and computer hardware and highlighting key functions such as executing programs and managing resources. It covers computer system organization, architecture, and various structures such as single and multiprocessor systems, as well as storage and I/O management. Additionally, it discusses the frameworks within operating systems, including middleware and the function of device drivers.

1. COURSE NAME : OPERATING
SYSTEM COURSE CODE :
381CCS-3
CHAPTER 1 : INTRODUCTION TO OPERATING
SYSTEM
REFERENCE DETAIL FOR CHAPTER 1
Topic Text Reference Chapter No. Page No
“Operating System
Introduction to Concepts”, 10th Edition, 3-7,
Operating Abraham SilberSchatz, Chapter 1 11-21,
System Peter Baer Galvin, 63-64
Greg Gagne, Wiley, 2018

2. 2
 Introduction
 What Operating System Do
 Computer System
Organization
 Storage structure
 I/O structure
 Computer System
Architecture
 Single Processor Systems
 Multi processor Systems
 Clustered Systems
 Distributed System
CHAPTER 1 : INTRODUCTION TO OPERATING SYSTEM

3. 1.1 INTRODUCTION
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1.1.1 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.

4.  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 – define the ways in which the system
resources are used to solve the computing problems of the
users
 W ord processors, compilers, web browsers, database
systems, video games
• Users
 People, machines, other computers
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1.1.2 COMPUTER SYSTEM
STRUCTURE

5. 1.1.3 ABSTRACT VIEW OF COMPONENTS OF
COMPUTER
Figure 1.1 Abstract view of the components of a computer system.
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6. 1.2 WHAT OPERATING SYSTEMS DO
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Depends on the Users point of view
 Users want convenience, ease of use and good performance
• Don’t care about resource utilization
 Mobile devices like smartphones and tablets 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
Ex : Embedded computers in devices and automobiles: Operating
systems and applications are designed primarily to run without user
intervention
Depends on System View Operating System is viewed as
 Resource Allocator : A computer system has many resources to solve
a problem like CPU time, memory space, storage space, I/O devices,
and so on. The operating system acts as the manager of these
resources.
 Control Program : controls the execution of user programs and
operations of I/O devices

7. 1.2.1 OPERATING SYSTEM DEFINITION
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 No universally accepted definition
 “The one program running at all times on the computer” is the
kernel, 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 additional services to application developers such
as databases, multimedia, graphics

8. 1.3 COMPUTER SYSTEM ORGANIZATION
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 Computer system consists of one or more CPUs and a number of device
controllers connect through common bus providing access to shared
memory
 Concurrent execution of CPUs and devices competing for memory cycles
 I/O devices and the CPU can execute concurrently
 Each device controller is in charge of a particular device type and has a
local buffer
 Operating systems have a device driver for each device controller to
manage it
 CPU moves data from/to main memory to/from local buffers
 I/O is from the device to local buffer of controller
 Device controller informs CPU that it has finished its operation by
causing an
interrupt.
Figure 1.2 A typical PC computer system

9. 1.3.1 STORAGE STRUCTURE
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Random access Memory (RAM) or Main Memory :
 Computers run most of their programs from this rewritable memory.
 It is the only large storage media that the CPU can access directly.
 Loses its content when power is turned off (Volatile).
 Main memory commonly is implemented in a semiconductor technology
called
dynamic random-access memory (DRAM).
BootStrap Program:
 It is Loaded at Power up or reboot.
 The first program to run on computer power-on and loads Operating System
Kernel and starts Execution
 Typically stored in ROM or EPROM, generally known as firmware
Secondary storage: Extension of main memory that provides large
nonvolatile (permanent) storage capacity
i) 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
ii) Non-volatile memory (NVM) devices
 Which provide storage for both programs and
data.

10. 1.3.1.1 STORAGE HIERARCHY
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 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
Figure 1.3 Storage-device hierarchy

11. 1.3.2 I/O STRUCTURE
 Two methods for handling I/O
After I/O starts, control returns to user program only upon I/O completion
• Wait instruction idles the CPU until the next interrupt
• Wait loop (contention for memory access)
• At most one I/O request is outstanding at a time, no
simultaneous I/O processing
After I/O starts, control returns to user program without waiting for I/O
completion
• System call – request to the OS to allow user to wait for I/O
completion
• Device-status table contains entry for each I/O device indicating its
type, address, and state
• OS indexes into I/O device table to determine device status and to
modify table
entry to include interrupt
Direct Memory Access Structure
• Used for high-speed I/O devices able to transmit information at
close to memory speeds
• Device controller transfers blocks of data from buffer storage

12. 1.4 COMPUTER SYSTEM ARCHITECTURE
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1. Single-Processor System
• Have only a single processor or CPU,
• Shared between users by dividing the CPU time into time-slices and
allocating one of these to each user in turn
• The time-slices are very short, giving each user the impression that
their programs are running continuously
2. Multiprocessor System(Parallel System)
• Parallel systems with more than one CPU in close communication
• Tightly coupled system – processors share memory and a clock;
communication usually takes place through the shared memory
Advantages
 Increased throughput
 Economy of scale
 Increased reliability – graceful degradation or fault tolerance

13. COMPUTER SYSTEM ARCHITECTURE(CONT…)
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Two types:
Asymmetric Multiprocessing
 Each processor is assigned a specific task.
 Master processor schedules and allocated work to slave
processors.
 More common in extremely large systems
Symmetric Multiprocessing
 each processor performs all tasks
 Each processor runs and identical copy of the operating system.
 Many processes can run at once without performance
deterioration.
 Most modern operating systems support SMP
Figure 1.4 Symmetric multiprocessing architecture.

14. COMPUTER SYSTEM ARCHITECTURE(CONT…)
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3. Clustered Systems
 Like multiprocessor systems, but multiple systems working together
 Usually sharing storage via a storage-area network (SAN)
provides a high-availability service which survives
failures Two types:
Asymmetric clustering
 has one machine in hot-standby mode and other is
running the applications.
 The hot-standby host machine does nothing but
monitor the active server.
 If that server fails, the hot-standby host becomes the
active serve
Symmetric clustering
 has multiple nodes running applications, monitoring
each other
 Efficient as it uses all of the available hardware.
 it does require that more than one application be
available to run.
Figure 1.5 General structure of a clustered system.

15. 1.5 DISTRIBUTED SYSTEM
 Loosely coupled system – each processor has its own local memory;
processors communicate with one another through various
communications lines, such as high-speed buses or telephone lines.
 Requires Networking
infrastructure Local Area
Network (LAN) Wide Area
Network (WAN)
Metropolitan Area Network
(MAN) Personal Area Network
(PAN)
 Network Operating System - provides features between systems across
network Communication scheme allows systems to exchange messages
Illusion of a single system
 Advantages
• Resources sharing
• Computation speed up – load sharing
• Reliability
• Communications
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