POST(Power On Self Test)

Post (power on self test)

POST(Power on self test) is performed when the computer is started.

It is done to check the status of every device. Many communication, mobile phones and other devices

perform this test when they are power-on ed.

Bios does this test and gives a beep sound.

After POST , OS will be loaded and computer starts to run

Computer basic pheripherals

Mother board:

 

It is the most important device of a computer, it consist of all the connectors,

it is the circuit board which helps in communication of devices to processor and vice versa.

SMPS:

 

It is the power supply for mother board & processor .

It converts AC power into DC required to motherboard.

 HDD

it is memory unit of the computer, it is ROM of the computer, It comes in different types

HDD

SSD

magnetic tapes, etc...

it holds the OS. OS is loaded for storage devices to RAMs of the computer.




External devises:

Blue ray device will read Blue ray disk, and other DVDs & CDs,

RAM

RAM(Random access memory), are chips that help the system to store the data temperately for processing it at processor.

Processor

 

It is the brain of the computer, when ever data gets to the processor it is processed and sends the data to concerned device, data is taken form the RAM, .

Ethernet cable climping

CAT 5 or CAT 6 cable is requried for climping the Rjclips, in the CAT 5 or CAT 6 cable the are 4 pairs of wires, they are

green, green white

orange orange white

blue, bluewhite

brown, brown white

befor climping we need to follow colour code:

mentioned in the picture above. We need to climp by following the cloour code on both ends of the cable

ports of a computer

HDMI
 

High Definition multimedia interface, it is used to transfer multimedia content with out delay in transmission. It is used in Blue ray, projectors and other multimedia interfaces

 PS/2

 

This port came form IBM's personal system/2, this was replacement to DE-9 / RS port,

this port has 6-pins, it is used as a standard port for connecting Mouse & Keyboard

now USB is replacing these port.

 

 RJ45 port:

It is a standard socket used to communication in a network,

all switch and routers, desktops and other network devises uses RJ45 socket

a special cable(CAT 5, CAT 6) support this socket of RJ45.

SATA

serial ATA is a standard port used to connect storage devises such as hard disks, SSDs, external devices.

Using SATA data transfer rate is high that traditional ATA ports

 serial port:

 serial port was an historic port user for communication where the data is sent serially 1byet .
USB, Ethernet socket, modems, printers etc, where they connected using serial port 

USB:

This port is an industry standard post developed to gener computer connectivity,

it was developed in the year 1996, all the Keyboards, Mouse, Camera etc…

It has 4 pins 

 VGA

 

Video Graphic Array, is a general 15 pin port used for displaying on a monitor or projector ,

it is embedded in laptops, desktops, projectors, graphic adapters and other display devises

now HDMI port is replacing this port .

Firewall

Firewall:

A Firewall is a software program which prevents outside network entering to an intranet.

Basic firewall task are:

• Defend network resource
  
• give access to authorized network
  
• manage the follow of network traffic
  
• Record and report an network event
  
• and respond quick on any mishaps in network
  

for a group of users Software firewall is enough. But for larger network a hareware firewall is required,
Windows has a build in firewall called Windows Defender, for Linux there is build in package called Firewalld.

Network

Network:

In Computer world network plays an importunate role with out networking you would not

able to read this web page.Main work of network is to make computer connect to each

other and exchange data in the form of packets.

Network Topology:

Topology is the map which represent the connection among group of computers

in earlier days computers, network among them would be connected by following typologies.

Bus Topology:

Advantages:  

1) Easy to establish & make working

2) work good for small network

3) cost for establishing is less

Disadvantages:  

1) it is hard to troubleshoot the problem

2)Additional devices slows down the network

3)If main cable damages the complete network fails or split into two

Star Topology:

Advantages:

1)Easy to connect new nodes.

2)Monitoring network is easy

3)Fail user of any node in this topology does't effect other nodes

Disadvantages:

1) Too much dependency on central network device, if it fails whole network goes down

2) Using network devices will increase cost of network

3) adding new host to the network has limitation , its depends on network device

Mesh Topology
    

Advantages:

1)This Topology can handle high traffic, multiple transferd form different devices is posibble

2)if any node fails ther is no effect on the network

3)If There is any need of network changes, it can be done with out disrupting the netwok

Disadvantages:

1)Setting up this topolgy is very diffcult,

2)Cost of maintaining this topology is very costly

                         

Tree Topology:
         

Advantages:

1) adding or increasing the nodes is easy and can be done with out disturbing the network

2)the whole network is divided into segments, hence trouble shooting is easy

3)error detection is very easy

Disadvantages:

1)if the main cable brakes the complete network fails

2)As network grows, maintaing becoms diffcult

                                 

Hybrid Topology:

Advantages:                 

1) Its easy to increase the size of network by adding new components, without disturbing existing architecture.
2) Hybrid Network can be designed according to the requirements of the organization and by optimizing the available resources. Special care can be given to nodes where traffic is high as well as where chances of fault are high.

         
 Disadvantages:

1)Establishing this network is not easy, and designe is not easy

2)it requries many devices to connect among each other, and very costly

                         

Types of network:

LAN,WAN

These terms below will help you in understanding network.

Internet: it is a network of computers which communicate with each other from any part of the world .

Intranet: it is a small network of a group which communicate with each other where out side connection is not allowed

TCP/IP Model

TCP/IP:

Transmission control protocol and internet protocol is a network modle used in today's network.

It consist of Application layer, transport layer, internet layer, network access layer

Protocols used in TCP/IP:

application layer protocols used are telnet, ftp, smtp, DNS, HTTP etc…

Transport layer protocol used are TC &, UDP

TCP is a connection oriented protocol

it gives grantee of end to end delevary of packets

it is reliable protocol

UDP is a connection less protol

it dosent provide any guarantee of data delivery

this protocol used to streaming vedios audio files over network

network layer will assigne a logical address to the host network, with this the commnucaction is made.

physical layer it is an hardware unit which converts signals to packets of data. and viceversa. 

 

 

 

 

OSI referance model

OSI Model:

OSI means Open System Interconnection (Interface) or symply OSI model.

This is a standard is followed by every network device used in computmng.

Application Layer:

It is a interface between the end user & Application and the Network.

It deals with the software applications the is a user interface.

Presentation layer:

It negotiates data exchange format. It deals with representing the data for

eg: jpg, doc, etc.

Session Layer:

it allows the user to establish, manage and terminate the connection.

It handles the actual connection between the system and also perfoems the name resolvtion

Transport Layer:

it provides end to end reliable connection. It gives the gearentee of data delivery.

If a packet fails to reach the destination it notifies the sender, requesting another packet to the sender

Network Layer:

it routes the data through the larger internetwork. It defiens logical host address such as IP address it

gives the information about how & where the data should be defined

Data link Layer:

It determines access tot he netwokr media and specfies How the data bits are grouped into frames

it is divided into two sublayers

Physical Layer:

All physical equipment falls under this catogery, ie cables, NIC cards,

Data is transferred through signals.