TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

Affiliated to Institution of G.G.S.IP.U, Delhi

OPERATING SYSTEM

PAPER CODE - BCA 301

Charanpreet Kaur

Assistant Professor

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

• To introduce an operation System and describe the functionalities of Operating System.

• To Understand the services provided by an operating system.

OBJECTIVES OF THE SUBJECT

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

• Introduction: What is an Operating System, Simple Batch Systems, Multiprogrammed Batches systems, Time-Sharing Systems, Personal-computer systems, Parallel systems, Distributed Systems, Real-Time Systems.

• Memory Management: Background, Logical versus Physical Address space, swapping, Contiguous allocation, Paging, Segmentation.

• Virtual Memory: Demand Paging, Page Replacement, Page-replacement Algorithms, Performance of Demand Paging, Allocation of Frames, Thrashing, Other Considerations.

OVERVIEW OF THE SYLLABUS 1st Unit

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

• Processes: Process Concept, Process Scheduling, Operation on Processes.

• CPU Scheduling: Basic Concepts, Scheduling Criteria, Scheduling Algorithms, Multiple-Processor Scheduling.

• Process Synchronization: Background, The Critical-Section Problem, Synchronization Hardware, Semaphores, Classical Problems of Synchronization.

2nd Unit

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

• Deadlocks: System Model, Deadlock Characterization, Methods for Handling Deadlocks, Deadlock Prevention, Deadlock Avoidance, Deadlock Detection, Recovery from Deadlock

• Device Management: Techniques for Device Management, Dedicated Devices, Shared Devices, Virtual Devices; Input or Output Devices, Storage Devices, Buffering, Secondary-Storage Structure, Disk Structure, Disk Scheduling, Disk Management, Swap-Space Management, Disk Reliability

3rd Unit

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

• Information Management: Introduction, A Simple File System, General Model of a File System, Types of File System File-System Interface: File Concept, Access Methods, Directory Structure, Protection: Goals of protection, Domain of protection, Access rights, Consistency Semantics Security: Authentication, Program threats, System threats, Encryption.

4th Unit

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

INTRODUCTION

What is an Operating System?

A program that acts as an intermediary between a user of a computer and the computer hardware.

It provide a pleasant and effective interface between the user and the hardware.

It uses the computer hardware in an efficient manner.

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

Operating System is a program that controls execution of application programs.

Hardware

O.S

System and application programs

USERS

Abstract View of Computer system

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

• Hardware:- It includes CPU, the memory, input output(I/O) devices and provides the basic computing resources for the system.

• Application Programs:- It includes Word Processors, Spreadsheets, compilers, web browsers and define the ways in which these resources are used to solve users computing problems.

• Operating System:- coordinates its use among the various application programs for the various users.

• Users:- They are the end users who interact with the system.

Abstract View Of an Operating System

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

An operating system performs basic tasks such as:

controlling and allocating memory

process management

controlling input and output devices

facilitating networking

managing file systems

command interpretation

WHAT DOES AN OPERATING SYSTEM DO?

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

• It is the control module of an operating system.

• It is the one which loads first and remains in the main memory.

• All the critical functions are implemented by the kernel.

• It is that part of an OS which directly interacts with the hardware.

KERNEL OF AN OPERATING SYSTEM

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

• It provides the mechanism for creation and deletion of processes.

• It provides process scheduling, memory management, I/O management.

• It provides mechanism for synchronization of processes.

• It provides mechanism for IPC (Inter Process Communication)

Functions of Kernel

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

Some Examples of Operating System

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

1. BATCH PROCESSING SYSTEMS

• In Batch processing same type of jobs batch (BATCH- a

set of jobs with similar needs) together and execute at a time.

• The OS was simple, its major task was to transfer control from one job to the next.

• The job was submitted to the computer operator in form of punch cards. At some later time the output appeared.

EVOLUTION OF OPERATING SYSTEM

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

• For example:- imagine that the operator received one FORTRAN, one PASCAL and another FORTRAN program. If he runs in the same order, he would have to set up first the FORTRAN environment, then set up the PASCAL environment and finally again load the settings for running the FORTRAN program.

• However, if he runs the two FORTRAN programs as a batch, he needs to set up only once the FORTRAN environment, thus saving the operator’s time.

BATCH PROCESSING SYSTEMS

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

• Multiprogramming is a technique to execute number of programs simultaneously by a single processor.

• In Multiprogramming, number of processes reside in main memory at a time.

• The OS picks and begins to executes one of the jobs in the main memory.

• If any I/O wait happened in a process, then CPU switches from that job to another job.

• Hence CPU in not idle at any time.

2. MULTIPROGRAMMING SYSTEMS

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

• Advantages:-

Efficient memory utilization

Throughput increases

CPU is never idle, so performance increases.

Supports multiple simultaneous interactive users.

MULTIPROGRAMMING SYSTEMS

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

• Multiprocessing is the use of two or more central processing units (CPUs) within a single computer system.

• The term refers to the ability of a system to support more than one processor and the ability to allocate tasks between them.

• A multiprocessor is a computer system having two or more processing units (multiple processors) each sharing main memory and peripherals, in order to simultaneously process programs.

3. MULTIPROCESSING SYSTEMS

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

MULTIPROCESSING OPERATING SYSTEM

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

Types of Multiprocessing Systems:-

1. Symmetric Multiprocessor System

2. Asymmetric Multiprocessor System

Symmetric Multiprocessor System

All the CPU’s are essentially identical and perform identical functions.

CPU 1 CPU 2

CPU 3 CPU 4

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

Asymmetric Multiprocessor System

Different processors do different tasks; one may be a Master and it may control other CPU’s.

(MASTER)

CPU 3

CPU 1

CPU 3 CPU 2

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

• Time sharing, or multitasking, is a logical extension of multiprogramming.

• Multiple jobs are executed by switching the CPU between them.

• In this, the CPU time is shared by different processes, so it is called as “Time sharing Systems”.

• Time slice is defined by the OS, for sharing CPU time between processes.

• A time shared system allows many users to share the computer simultaneously.

4. TIME SHARING SYSTEMS

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

• A distributed environment refers to the collection of autonomous systems, capable of communicating and cooperating with each other through the network, are connected to each other through LAN/WAN.

• A distributed OS is the one that looks to its users like an ordinary centralized OS but runs on multiple independent CPU’s.

• It allows users to access remote resources in the same manner as they do with local resources.

5. DISTRIBUTED SYSTEMS

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

• If there are no. of sites connected, then it allows resource sharing in a distributed system.

• There is computation speed up.

• Reliability is also better.

• Communication is also easy is these systems.

Advantages

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

• A real-time operating system (RTOS) is an operating system (OS) intended to serve real-time application requests. It must be able to process data as it comes in, typically without buffering delays.

• A real time OS has a well defined and fixed time constraint.

• A primary objective of RTOS is to provide quick event response times and thus meet the scheduling deadlines.

• For example:- Air traffic control systems, medical imaging systems, industrial control systems, etc.

4. REAL TIME SYSTEMS

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

• A system consisting of more than one processor and sharing resources like bus, clock, memory, I/O devices is a parallel system.

• A single CPU may be slow therefore, many CPU’s may parallely execute a single given problem.

• These systems reduce the time required for job execution and increase the CPU throughput.

5. PARALLEL SYSTEMS

TRINITY INSTITUTE OF PROFESSIONAL STUDIES Sector – 9, Dwarka Institutional Area, New Delhi-75

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