Virus

Computer Virus:

A computer virus is program that may disturb the normal working of a computer system. Virus attaches itself to files stored on floppy disks, email attachments and hard disks. A file containing a virus is called infected file.

The virus cannot damage computer hardware. It may cause many damages to a computer system. A virus can:

• Damage data or software on the computer.
• It can delete some or all files on the computer system.
• It can destroy all data by formatting hard drive.
• It may display a political or false message every few times.

Desktop Icon

Detail of Desktop Icon:

Desktop icon detail are following:.

1. Icon

Icons are little pictures that represent different programs or saved items. Double-clicking on the icon accesses the information icons represent.

2. My Document:

It is the default storage folder for your files that you create. When you save or open a file, Microsoft Windows initially opens the My Documents dialog box. At this time you can navigate to where you want to save your file

3. My Computer:

It displays information about your computer, such the contents of your computer drives and which printers you have installed. It also allows you to find, view and organize files.

4. Recycle Bin:

This is where you place files you no longer need. Your computers data files should be tidied up regularly and any unwanted files deleted from the system. Any file you delete from your hard drive will be placed first in Recycle Bin.

5. Window:

Each application opened will appear in its own window, or its own little section of the screen. Windows can be moved and resized so that you can operate many different applications at the same time.

6. Dialog box:

When you ask the computer to do certain commands, such as to save your work, the computer will need more information from you, and this will appear in a dialog box. These boxes contain options and commands for the computer execute.

7. Start Menu:

In the lower left hand corner of the windows screen is the start button. When you click on the button a menu will appear, which we will call the Star menu. This menu gives you access to all the different parts and functions of the computer.

8. Task Bar:

At the very bottom of the screen is a horizontal bar called the task bar. This bar contains the Start button, shortcuts to various programs minimized programs, and another section of shortcuts that includes sound volume, printers and the time.

9. Tab Menu:

Tab Menus, which are often present in dialogue boxes, are menus that represent many different “pages” of information. To access each page click on the tab at the top of the dialog box

Mesh Topology

Mesh Topology:

In mesh topology, every device in the network is physically connected to every other device in the network. A message can sent on different possible paths from source to destination. Mesh topology provides improved performance and reliability. Mesh networks are not used much in local area networks. It is mostly used in wide area networks.

Advantages:

1. The use of dedicated link guarantees that each connection can carry its own data load. It eliminates traffic problem
2. If one link becomes unusable, it does not harm the entire system
3. It is easy to troubleshoot.

Disadvantages:

1. A full mesh network can be very expensive
2. It is difficult to install and reconfigure.

Tree Topology

Tree Topology.

A tree topology combines the characteristics of bus and star topologies. It consists of different groups of computers attached in star topology. The groups are then connected to a bus backbone cable. It is used for the extension of an existing network.

Advantages:

1. It provides point to point writing for individual segments.
2. It is supported by several hardware and software vendors.

Disadvantages:

1. Overall length of each segment is limited by the type of cabling used.
2. If the backbone is breaks, the entire segment  goes down
3. It is more difficult to configure and wire than other topologies.

RingTopology

    Ring Topology

In ring topology, each computer is connected to next computer and last connected to the first computer. Thus, a ring of computers is formed.

Working of ring topology:

Each computer receives message from previous computer and transmit it to the next computer. The message flow in one direction. The message is speed around the ring until it reaches the connect destination computer.

Advantages:

1. It is less expensive than star topology
2. Every computer has equal access to the network.

Disadvantage:

1. Failure of one computer in the ring can affect the whole network
2. It is difficult to troubleshoot.
3. Adding or removing computers affect the whole network

Star Topology

       Star Topology

All computers in star topology are connected with central device called hub. It is mostly use in client server networks.

Working of star topology:

The sending computer sends the data to hub. The hub send the data to receiving computer. Each computer in star topology communicate with hub.

Advantages:

1. It is easy to maintain and modify network.
2. Adding or removing computers can be done without disturbing the network.
3. Finding faults becomes very simple.
4. Single computer failure does not bring down the hole network.
5. It is more flexible than other topology.

Disadvantages:

1. If central hub fails, the entire network breaks down
2. It requires a large length of cable to connect computers.
3. It is more expensive.

Bus Topology

     Bus Topology

In bus topology, all computers connected to communication medium. This medium is central wire known as bus. The terminator is used at end of a bus to absorb signals.

Advantages:

It is simple and easy to use.

It requires small length of cable to connect computer.

It is less expensive

If one node fail, it does not affect the rest of the network.

It is easy to extend bus.

Disadvantages:

It is difficult troubleshoot

It only supports small number of computers.

The network speed slows down as the number of computer increases.