Thursday, June 27, 2019
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Day 1: Introduction To Operating System Concepts

Introduction To Operating System Concepts – What Operating System Do? , Computer System Organisation, Operating System Operation, Definitions.

What Is an Operating System?

A Program (Or) A Software Which  Acts As An Intermediary Between A User Of A Computer And The Computer Hardware.

Operating System Goals

  • To Execute User Programs
  • To Make Solving User Problems Easier
  • To Make The Computer System Convenient To Use
  • To Use The Computer Hardware And Resources In An Efficient Manner

Operating System Is A Manager That Need To Use All The Resources To Perform Management Duties.

User View

Extended Machine That Lower Level Details

System View

Resource Allocator



Resource Component Of A Limited Availability Necessary For Effective Operation

Process Active Program

Dead Lock – A Situation In Which Two Or More Competing Actions Are Each Waiting For The Other To Furnish, And Thus Neither Ever Does.

Buffer – Area Of Memory That Stores Data

Cache – Area Of Fast Memory That Stores Copies Of Data

what is the difference between cache and buffer?

Buffer Is A Area Of Memory That Stores Data And Cache Is Area Of Fast Memory That Stores Copies Of Data.

OS Kernel – Contains Basic Functions(one process active all the time)

Everything Else Is Either A System Program(Ships With The Operating System) Or An Application Program.

Interrupt – Change In Flow Of Execution, Operating Systems Are Interrupt Driven.

Volatile Storage – Volatile Memory Is A Computer Storage That Only Maintains Its Data While The Device Is Powered, Most(Random Access Memory) Used For Primary Storage In Personal Computers Is Volatile Memory.

Persistent/Non-Volatile Storage – Non- Volatile Storage Is A Type Of Computer Memory That Can Retrieve Stored Information Even After Having Been Power Cycled. In Contrast, Volatile Memory Needs Constant Power In Order To Retain Data.


Computer System Organisation

  • One Or More CPU’s Device Controllers Connect Through Common Bus Providing Access To Shared Memory.

  • Concurrent Execution Of CPU’s And Device Competing For Memory Cycles
  • I/O Devices And The CPU Can Execute Concurrently
  • Each Device Controller Is In Charge Of A Particular Device Type
  • Each Device Controller Has A Local Buffer
  • 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


Interrupt Transfers Control To The Interrupt Service Routine

Interrupt Architecture Must Save The Address The Interrupted Instruction

A Trap Or Exception Is A Software Generated Interrupt Caused Either By An Error Or A User Request




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