Ahad, 27 Jun 2010

Virus H1N1


Influenza A (H1N1) virus is a subtype of influenza A virus and was the most common cause of human influenza (flu) in 2009. Some strains of H1N1 are endemic in humans and cause a small fraction of all influenza-like illness and a small fraction of all seasonal influenza. H1N1 strains caused a few percent of all human flu infections in 2004–2005.[1] Other strains of H1N1 are endemic in pigs (swine influenza) and in birds (avian influenza).
In June 2009, the World Health Organization declared the new strain of swine-origin H1N1 as a pandemic. This strain is often called swine flu by the public media. This novel virus spread worldwide and had caused about 17,000 deaths by the start of 2010.

Ahad, 20 Jun 2010


In computer networking, topology refers to the layout of connected devices.
Network topology is defined as the interconnection of the various elements (links, nodes, etc.) of a computer network.[1][2] Network Topologies can be physical or logical. Physical Topology means the physical design of a network including the devices, location and cable installation. Logical topology refers to the fact that how data actually transfers in a network as opposed to its physical design.
Topology can be considered as a virtual shape or structure of a network. This shape actually does not correspond to the actual physical design of the devices on the computer network. The computers on the home network can be arranged in a circle shape but it does not necessarily mean that it presents a ring topology.
Any particular network topology is determined only by the graphical mapping of the configuration of physical and/or logical connections between nodes. The study of network topology uses graph theory. Distances between nodes, physical interconnections, transmission rates, and/or signal types may differ in two networks and yet their topologies may be identical.
A Local Area Network (LAN) is one example of a network that exhibits both a physical topology and a logical topology. Any given node in the LAN has one or more links to one or more nodes in the network and the mapping of these links and nodes in a graph results in a geometrical shape that may be used to describe the physical topology of the network. Likewise, the mapping of the data flow between the nodes in the network determines the logical topology of the network. The physical and logical topologies may or may not be identical in any particular network.

Network architecture is the design of a communications network. It is a framework for the specification of a network's physical components and their functional organization and configuration, its operational principles and procedures, as well as data formats used in its operation.
In computing, the network architecture is a characteristics of a computer network. The most prominent architecture today is evident in the framework of the Internet, which is based on the Internet Protocol Suite.
In telecommunication, the specification of a network architecture may also include a detailed description of products and services delivered via a communications network, as well as detailed rate and billing structures under which services are compensated.
In distinct usage in distributed computing, network architecture is also sometimes used as a synonym for the structure and classification of distributed application architecture, as the participating nodes in a distributed application are often referred to as a network. For example, the applications architecture of the public switched telephone network (PSTN) has been termed the Advanced Intelligent Network. There are any number of specific classifications but all lie on a continuum between the dumb network (e.g., Internet) and the intelligent computer network (e.g., the telephone network). Other networks contain various elements of these two classical types to make them suitable for various types of applications. Recently the context aware network, which is a synthesis of the two, has gained much interest with its ability to combine the best elements of both.

Computer Network


A computer network, often simply referred to as a network, is a collection of computers and devices connected by communications channels that facilitates communications among users and allows users to share resources with other users. Networks may be classified according to a wide variety of characteristics. This article provides a general overview of types and categories and also presents the basic components of a network.

Rabu, 28 April 2010

Format Hardisk

1
When you format a computer hard drive you will lose everything that is on the drive. Therefore, it is very important to back up anything you might want later. Additionally, if you are going to be formatting and installing XP you need to make sure you have the discs for any applications or third party hardware you use since you will need to re-install your programs and drivers after re-installing Windows.
Step 2
Take a moment to think of anything that you have on the computer that you wouldn't want to lose. Generally, you probably want everything in your My Documents folder, and you also want to save things like your favorites or bookmarks from your Web browser. Remember that each user on the computer has his or her own My Documents folder, Desktop items and Favorites/Bookmarks.
Step 3
Save everything to a CD, DVD or a hard drive that you won't be formatting.
Formatting a Secondary Hard Drive
Step 1
Right-Click on the "My Computer" icon either on your desktop or in the Start Menu and select "Manage."
Step 2
A new window titled "Computer Management" comes up. Select "Storage" from the left hand side by clicking it once, then select "Disk Management(local)" from the right side by double-clicking it.
Step 3
Now in the lower part of the main frame (right side) of the window you should see a nice visual of all your hard drives. Each line is a different drive. Each box on a line (with a colored bar at the top and a size displayed in MB or GB) is a partition on the drive. Partitions are separations of space on a drive. Unless you are doing something specific that requires multiple partitions, you only want one partition per drive.
Step 4
First you must delete any existing partitions on the drive you are going to format. Do this by right-clicking on the partition's box and selecting "Delete Partition..." Since you already know that you will be deleting everything on the drive, and have already backed everything up, you can safely say yes to any warning the computer presents you with.
Step 5

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If there are multiple partitions make sure you have saved everything off them since they might each have different drive letters (i.e. "D:" or "F:"). Then repeat the above step for each of them. If you only want to format one partition that is OK and you can continue to the next step without deleting the other partitions.
Step 6
The box for the drive to be formatted should now have a black bar at the top of it and should say "Unallocated" under its size (see picture). Right click on it and select "New Partition..." The New Partition Wizard comes up.
Step 7
In the New Partition Wizard click next. On the next page make sure "Primary Partition" is selected and click next. Now make the size equal to the maximum (it should already be set to it), and click next again. On the next page the computer will automatically choose the first available drive letter for the new drive. However, if you like you can choose another drive letter from the drop-down menu, and then click next.
Step 8
Finally the New Partition Wizard asks if you would like to format the new partition and if so what format. Choose "NTFS" as it is faster and more secure. Leave the "Allocation unit size" as "Default." In the "Volume label" field enter whatever name you want the drive to have. Simple is better. Avoid using spaces. Lastly, if the drive is brand new and has never been used before check the "Perform a quick format" box. If the drive has been used before leave this box unchecked. Leave the "Enable file and folder compression" box unchecked and click next. Then on the next page click finish.
Step 9
The wizard will now spend a little while formatting the drive. On old or large drives this may take a while. Do not close the "Computer Management" window until it finishes. You will know it is done when the word under the size of the drive changes from "Formatting" to "Healthy" and the name and drive letter you chose for the new drive show up. After it is finished you can proceed to use your newly formatted drive.

Installation Antivirus


Reboot your system: ’Tis better to have a clean-running system that’s not teetering on the edge of a crash because too many days have passed since the last reboot. (That’s especially a problem on older Windows systems such as Windows 95, Windows 98, or Windows ME.)
Stop all of your other programs: This includes all of the clutter in your systray, half of which you probably don’t need or use anyway.
Read all the way through the antivirus program installation and/or upgrade instructions: Wouldn’t you just hate yourself if Step 46 said to do something that’s really hard to do without a specific preparation that’s only mentioned in Step 46? (I’m not much of a cook, and many times I’ve regretted not reading the recipe all the way through before starting, only to find that I lacked some important ingredient or didn’t have enough time to prepare.)
Take notes: Write down some of the essential things along the way — you may wish you had those little tidbits of data later. A few examples include the name of the directory where you installed the software, and the installation options that you chose.
·Take your time: If you hurry, you’re more likely to skip an important step or make a mistake. It’s more important to install your antivirus software correctly than quickly. You have to live with the results, probably for a long time. Quality doesn’t take shortcuts, and neither should you.
Consider getting help: If installing software feels as intimidating as rebuilding an automobile engine or programming a VCR, then consider having a PC expert help you out, or at least watch over your shoulder and tactfully refrain from snickering to him- or herself.