Unit-1: Operating system lecture notes

Unit-1: Operating system lecture notes in Operating System uploaded at P.R.Engineering college

Unit-1: Operating system lecture notes in Operating System at P.R.Engineering college uploaded by P.R.Engineering college Staff in lecturenotes.net

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UNIT I:Introduction
 What is an Operating System?
 Mainframe Systems
 Desktop Systems
 Multiprocessor Systems
 Distributed Systems 
 Clustered System
 Real -Time Systems
 Handheld Systems
 Computing Environments
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 Components
1. Hardware – provides basic computing 
resources (CPU, memory, I/O devices).
2. Operating system – controls and coordinates 
the use of the hardware among the various 
application programs for the various users.
3. Applications programs – define the ways in 
which the system resources are used to solve 
the computing problems of the users 
(compilers, database systems, video games, 
business programs).
4. Users (people, machines, other computers). 
Abstract View of System Components
Operating System Definitions
 Resource allocator – manages and allocates 
resources.
 Control program – controls the execution of 
user programs and operations of I/O devices .
 Kernel – the one program running at all times 
(all else being application programs).
Mainframe Systems
 Reduce setup time by batching similar jobs
 Automatic job sequencing – automatically 
transfers control from one job to another. 
First rudimentary operating system.
 Resident monitor
 initial control in monitor 
 control transfers to job 
 when job completes control transfers pack 
to monitor[Introduction Unit I]
Operating Systems Page 2
Memory Layout for a Simple Batch 
System
Multiprogrammed Batch Systems
OS Features Needed for 
Multiprogramming
 I/O routine supplied by the system.
 Memory management – the system must 
allocate the memory to several jobs.
 CPU scheduling – the system must choose 
among several jobs ready to run.
 Allocation of devices.
Time-Sharing Systems–Interactive 
Computing 
 The CPU is multiplexed among several jobs 
that are kept in memory and on disk (the 
CPU is allocated to a job only if the job is in 
memory).
 A job swapped in and out of memory to the 
disk.
 On-line communication between the user and 
the system is provided; when the operating 
system finishes the execution of one 
command, it seeks the next “control 
statement” from the user’s keyboard.
 On-line system must be available for users to 
access data and code.
Desktop Systems
 Personal computers – computer system 
dedicated to a single user.
 I/O devices – keyboards, mice, display 
screens, small printers.
 User convenience and responsiveness.
 Can adopt technology developed for larger 
operating system’ often individuals have sole 
use of computer and do not need advanced 
CPU utilization of protection features.
 May run several different types of operating 
systems (Windows, MacOS, UNIX, Linux)[Introduction Unit I]
Operating Systems Page 3
Parallel Systems
 Multiprocessor systems with more than on 
CPU in close communication.
 Tightly coupled system – processors share 
memory and a clock; communication usually 
takes place through the shared memory.
 Advantages of parallel system: 
 Increased throughput
 Economical 
 Increased reliability
 graceful degradation
 fail-soft systems
 Symmetric multiprocessing (SMP)
 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
 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 Architecture
Distributed Systems
 Distribute the computation among several 
physical processors.
 Loosely coupled system – each processor has 
its own local memory; processors 
communicate with one another through 
various communications lines, such as highspeed buses or telephone lines.
 Advantages of distributed systems.
 Resources Sharing 
 Computation speed up – load sharing 
 Reliability
 Communications
 Requires networking infrastructure.
 Local area networks (LAN) or Wide area 
networks (WAN)
 May be either client-server or peer-to-peer 
systems.
General Structure of ClientServer
Clustered Systems
 Clustering allows two or more systems to
share storage.
 Provides high reliability.
 Asymmetric clustering: one server runs the 
application while other servers standby.[Introduction Unit I]
Operating Systems Page 4
 Symmetric clustering: all N hosts are running 
the application.
Real-Time Systems
 Often used as a control device in a dedicated 
application such as controlling scientific 
experiments, medical imaging systems, 
industrial control systems, and some display 
systems.
 Well-defined fixed-time constraints.
 Real-Time systems may be either hard or soft 
real-time.
 Hard real-time:
 Secondary storage limited or absent, data 
stored in short term memory, or read-only 
memory (ROM)
 Conflicts with time-sharing systems, not 
supported by general-purpose operating 
systems.
 Soft real-time
 Limited utility in industrial control of 
robotics
 Useful in applications (multimedia, virtual 
reality) requiring advanced operatingsystem features.
Handheld Systems
 Personal Digital Assistants (PDAs)
 Cellular telephones
 Issues:
 Limited memory
 Slow processors & Small display screens.
Migration of Operating-System Concepts and 
Features
Computing Environments
 Traditional computing
 Web-Based Computing
Operating-System Structures
 System Components

Title:
Unit-1: Operating system lecture notes

Subject:
Operating System

Institute:
P.R.Engineering college

Unit-1: Operating system lecture notes

Unit-1: Operating system lecture notes in Operating System uploaded at P.R.Engineering college

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