Operating System

 Operating system

®   Operating system is system software that controls and manages overall operation of computer and acts as a mediator between User and computer hardware.

®   It provides interface to user and platform for other application

®   First OS: GM NAA I/O by Generals Motors in 1981

®   Examples: windows OS, MAC OS, android, IOS, Linux, Unix, etc

Function of Operating system

1.    Memory management

®   Keeps track of RAM, how much memory is used and how much is unused

®   Allocates memory required to any program

2.  Process management

®   Creates or deletes the process as required

®   Keeps track of processor and status of process

3.  File management

®   Perform file related task such as saving, updating and naming files

®   Handle files permission

4.  Device Management

®   Recognize and manages to any device connected to computer to makes it functionality

5.   Security

®   Protect computer system from unauthorized access

6.  Error detecting and handling

®   Monitors the overall computer system to detect error and avoid the malfunctioning of the computer

Others functions are

®   Command interpretation

®   Communication

®   Resource Management

®   I/O management

Types of Operating system

1.    Based on interface

a.   CLI (Command Line Interface)

·  Works with commands

·  E.g. DOS

b.   GUI (Graphical User Interface)

·  Works with graphical symbols or icons

·  E.g. Windows

2.  Based on User

a.   Single user

·  Only one user can work at a time

·  E.g. DOS, Windows

b.   Multiuser

·  More than one user can work at a time

·  E.g. Linux, Unix, Windows server

3.  Based on task

a.   Single task

·  Only one task can run at a time

·  E.g. DOS

b.   Multitask

·  More than one task can run at a time

·  E.g. Windows

Other types of Operating system

·        Embedded OS

®   OS that comes embedded with hardware which is kept by manufacturer company at the time of manufacture

®   E.g. Android in cell phone, OS in ATM and Traffic light, etc

·        Networking OS

®   Multiuser OS in server that controls and manages other computer in network

®   E.g. Linux, Unix, Windows Server

·        Real-time OS

®   OS that responds instantly after giving the command

®   E.g. Process control, Military system software, OS in aircraft, etc

 

DOS

®   Stands for Disk Operating System

®   Single user, single task, CLI based operating system

®   Developed by Microsoft Corporation in 1981

Naming rule

®   Primary name cannot have more than 8 characters

®   Extension(secondary name) should have 3 characters

®   0-9, a-z and different symbol are used in file name

®   / \ : * “ < > ? are not allowed in file name

®   File name is not case sensitive

File

®   A collection of related data or program record stored as unit with a single name

Types of file

1.    Data file

®   Collection of data/instruction used by computer program

®   Extension: .dat

2.  Program file

®   Executable file of any program

®   Extension: .exe, .msi

3.  Information file

®   File created by computer user and stored in computer for further use

®   Created by different program in computer

®   Having different extension based on program

                               i.   Word document: .docx

                              ii.   Image: .jpg, .png

                            iii.   Audio: .mp3

                             iv.   Video: .mp4, .mkv

4.  System file

®   Files loaded while booting computer

                               i.   DOS.sys

®   Provides interface for user to work

                              ii.   Command.Com

®   Interprets user commands

®   Contain different commands to perform different task

                            iii.   IO.sys

®   Control input and output in computer