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By:RahmaAlhajri

I.TChapter #2

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Operating System

Operating System: a Master Set of programs whichperform certain functions/operations.

e.g. O.S depends upon the nature & configuration ofcomputing devices.

{ Macintosh, Windows, Cos, Unicos, Linux, Unix ..etc}

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Functions of O.S

Functions of Operating System:1. Booting.2.User Interface.3.Memory Management.4.Resource Management.

5.Input/Output Management.6.Task Management.

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1. Booting

.It refers to Starting of Computer

Booting: is Loading of operating system into Mainmemory.{From Hard-disk into RAM}.

its done by 2 processes:1.Diagnostic Routine.

-In this routine the devices/memory are checked for

errors.2.Boot Strapping.

-After D.R the loading of operating system into memorytakes place. {KERNAL}=Main component of O.S

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2. User Interface

User interactive medium through which usercommunicate with O.S

Main Types:1. Command driven interface.

2. Menu driven interface.3. Graphical User interface. (GUI)

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1) Command driven interface: (main core)

-User use command to perform any action.

e.g. C:\>dir\p (command in DOS/ disk operating system)

--This command is telling the O.S to open all directions page-wise.

e.g. C:\>copy*.* -- to copy everything in C.

drive Systemprompt

command

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2) Menu driven interface:

-In this type of interface the commands are givenin the form of Menu so that user can choose thecommand for any action.

e.g.

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3) GUI :

Desktop.(main screen in rectangular form having graphics/colors, icons..etc)

Icons. (pictorial form of any command)

Menus. (List of commands)

Colors.

Graphics.

Animation

User Friendly.(Easy to use)

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KERNAL:is the main program of O.S which manage allthe processes related to CPU. its a resident program whichstays in M.M.

=>

it acts like a traffic police officer which manages & organize the

process & coordinate with CPU.

Swapping:The exchanging of data or programs amonghard-disk & Main-memory.

O.S divides M.M into 2 parts:

1. Foreground Memory:- contains programs of high-priority.

2.Background Memory:- contains programs of less-priority.

3. Memory Management

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4. Resource Management

The operating system manages all the internal &external resources of computer.

e.g. Spooling: it refers to printing.

-if there is a printer on a network & many users

want to print, all the requests will be stored in amemory known as buffer in a queue, Thisprocess is known as Spooling

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5. Input & Output

management

All the input & output devices are managed byoperating system, some operating system useplug & play routine for installing new devices.

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Task ManagementUser can perform many tasks at the same time, O.S handles thesetasks by certain methodologies. i.e.:

1.Multi Tasking:one user can perform many tasks on one CPU at the same time.

2.Multi programing: one or more than one user perform one or more than oneprogram at the same time on one CPU.its event driven, where interrupt is generated by, for the event & cpu returns tothe program.

3.Time Sharing: one or more than one user perform one or more than oneprogram at the same time on one CPU.its Time driven, where all programs are given time-slice.(its used for tele-communication servers)

4.Multi Processing: one or more than one user use many cpus for one or morethan one program. -The program is split into Chunks & CPUs are processing these chunks separately.

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What is the difference between:

1. Main-Memory 2. Secondary-Memory 3. Register

e.g. RAM

on Motherboard

e.g. Hard-disk, CD

on Separate Memory

e.g. Cache Memory

located on cpu chip

Volatile Non-Volatile Volatile

Size: Bigger Size: Biggest Size: Smaller

Faster Fast Fastest

Expensive Less Expensive Most Expensive

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Networking

A communication system between computingdevices in order to share data & resources.

Types of Networks:

1) LAN. (Local Area Network). -can be among several devices in the same place.

2) MAN. (Metropolitan Area Network).-Among computing devices within a city.

3) WAN. (Wide Area Network).-A network of networks globally. e.g. internet.

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Modes of Transmission

1. Simplex. -Sender sends data & Receiver receives data only. -e.g. { T.V & Radio }.

2. Half-duplex. -Sender sends data & Receiver receives data, also &receiver can send the data & Sender can receive the data.But one at a time. -e.g. { Walke-Talke & Fax }

3. Full-duplex. -Sender can send & receive data, Receiver can also send &receive data. Both at the same time.

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