operating system

Mr Satyendra Mohan Srivastava JIT Barabanki

Mr Satyendra Mohan Srivastava, JIT Barabanki

Chapter 1: Introduction What is Operating System Computer System Structure Diagrammatic representation of a Computer System Operating System: Viewpoints Few important points Classification of OS Computer startup OS Layered approach System component OS services

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Operating System

An Operating System is a program that acts as an intermediate b/w the computer hardware and the user of a computer

An Operating System is a program that manages the computer hardware

Operating system goalsConvenience for the userEfficiency

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Computer System Structure

Computer system is mainly divided into four components:• Hardware

Memory, CPU and I/O devices• Operating system

Coordinates and controls the use of hardware• Application programs

Word processors, web browsers, compilers, database systems and video games

• UsersMachines, people and other computers

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Operating System: Viewpoints

Operating System can be understood by following point of views:

User View System View

• USER VIEWUser emphasizes on ease of use, convenience, little on performance and none to resource utilization

• SYSTEM VIEWResource allocator - Hardware and SoftwareControl Program – Manages the execution of user programs(errors and improper use)

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computer hardware


Diagrammatic representation of a Computer System

User3

… Usern

User1

User2

operating system

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compiler assembler text editor … database system

system and application programs


Diagrammatic representation of a Computer System

User3

… Usern

User1

User2

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compiler assembler text editor … database system

system and application programs

operating system

computer hardware


Few Important Points

• Kernel is only program running all the time on the computer system• Other program will be an application program or system

program

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Classification of Operating System

Batch Systems

Interactive Systems Multiprogrammed Systems Time Sharing Systems

Desktop Systems

Multiprocessor Systems

Distributed Systems Client Server Systems Peer to Peer Systems

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Classification of Operating Systems Conti…

Real Time Systems

Clustered Systems

Interactive System

Multiuser System

Multithreaded System

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Batch System Job(Program, Data & Information) in job pool All job are kept in job pool Submit to the Job operator Operators together jobs(batch) as a group The output send back to appropriate program Disk technology allowed OS to keep all jobs on a disk OS perform job scheduling

Multiprogrammed System Goal: To maximize the CPU load Atleast one job needs to execute, CPU never sit idle Job Scheduling



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Time-Sharing or Multitasking System It is one of the extension of Multiprogramming The executable multiple jobs with short frequency time while running Minimum response time Resources are shared in many users CPU scheduling and Multiprogramming are mechanism for its

implementation

Multiprocessor or Parallel or Tightly coupled Systems More than one processor with shared bus, clock, peripheral devices Sometimes even memory Advanages: Increased throughput, Economy of sale, Increased

reliability



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Distributed System

Client-Server System Centralized systems act as server systems Server system satisfies the request generated by client

N/W

ClientClient Client Client

Server

Basic Client Server Architecture

Mr Satyendra Mohan Srivastava, JIT Barabanki05/01/23 14


Peer-to-Peer Systems Clustered System

Grouping of requirement

Real-Time System Rigid time requirement Type: Hard and Soft real-time system

Interactive System Provide interaction between Human and Computer system



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Multiuser System Concurrent access by multiple users

Multithreaded System A thread is a lightweight process A thread is a flow of execution Goal: Parallelism


Computer Startup Booting

The procedure or mechanism of starting a computer by loading Kernel

Bootstrap program

loaded at reboot or power-up stored in ROM or EPROM

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Operating System Structure Layered Approach

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Operating System is divided or broken down into levels (layers)

Built on top of lower layer

The bottom layer (lower layer 0) is hardware and the highest layer is the user interferences

The Data Structures and a set of routines at the top layer can invoke operations on lower layer

Each layer hides some operations, certain data structures and hardware from higher level layers


Operating System Structure Layered

Approach

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Hardware

Kernel

Program

Layered Architecture

Modularity Simplifies debugging(errors) System verification

Advantage:


System Component

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Process Management

Main Memory Management

File Management

I/O System Management

Secondary Memory Management

Networking

Protection System

Command Interpreter System


Operating System Services

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There are five type of services provided by operating system:

Program Execution

I/O Operations

File System manipulation

Communications

Error detection

Resource allocation

Accounting

Protection


Any Question….

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operating system

Engineering