How to install Zwinky????

NOTE: Zwinky for Firefox is not supported by some webmail programs including Yahoo! Mail and MSN Hotmail. Excite, iWon and MyWay webmail accounts, as well as most IM programs, do support Zwinky for Firefox. Download Instructions Installing Zwinky for Firefox is easy! Just follow the following steps: 1) You should momentarily see a pop-up box. 2) Click on the "OK" button to save the Zwinky installation program to your Desktop. 3) If you see a "Downloads" pop-up dialog box, click on the "X" in the upper right corner of the box to close the window. 4) After the download ends, click on the "ZwinkySetup2.3.50.22.ZJfox000.exe" installation program on your Desktop. 5) Zwinky for Firefox should now be installed on your computer. The next time you start your browser, you will see the Zwinky icon above your search box. 6) Click on these icons in your browser to use your newly installed products. It's that simple! Note: To use Zwinky your PC must be running Windows 98, Windows 2000, or Windows XP. For more details, see Zwinky Help.

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UNIX

Uniplexed Information and Computig Systems


UNIX is an operating system which was first developed in the 1960s, and has been under constant development ever since. By operating system, we mean the suite of programs which make the computer work. It is a
* Portability
* Hierarchical file structure
* multi-user,
* multi-tasking system for servers, desktops and laptops.
UNIX systems also have a graphical user interface similar to Microsoft Windows which provides an easy to use environment. However, knowledge of UNIX is required for operations which aren't covered by a graphical program, or for when there is no windows interface available.
UNIX is an open source operating system.That means user has the freedom to
-develop softwares,
-same copy can use to install unix in several computers
-there is no licence to agree

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Wide Area Networks

A wide area network, or WAN, spans a large geographical area, often a country or continent. It contains a collection of machines intended for running user programs.

We will follow traditional usage and call these machines hosts. The hosts are connected by a communication subnet, or just subnet for short. The hosts are owned by the customers (e.g., people's personal computers), whereas the communication subnet is typically owned and operated by a telephone company or Internet service provider. The job of the subnet is to carry messages from host to host, just as the telephone system carries words from speaker to listener. Separation of the pure communication aspects of the network (the subnet) from the application aspects (the hosts), greatly simplifies the complete network design.
In most wide area networks, the subnet consists of two distinct components: transmission lines and switching elements. Transmission lines move bits between machines. They can be made of copper wire, optical fiber, or even radio links. Switching elements are specialized computers that connect three or more transmission lines. When data arrive on an incoming line, the switching element must choose an outgoing line on which to forward them. These switching computers have been called by various names in the past; the name router is now most commonly used.

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Metropolitan Area Networks(MAN)

A metropolitan area network, or MAN, covers a city. The best-known example of a MAN is the cable television network available in many cities. This system grew from earlier community antenna systems used in areas with poor over-the-air television reception. In these early systems, a large antenna was placed on top of a nearby hill and signal was then piped to the subscribers' houses.

At first, these were locally-designed, ad hoc systems. Then companies began jumping into the business, getting contracts from city governments to wire up an entire city.

The next step was television programming and even entire channels designed for cable only. Often these channels were highly specialized, such as all news, all sports, all cooking, all gardening, and so on. But from their inception until the late 1990s, they were intended for television reception only.
Starting when the Internet attracted a mass audience, the cable TV network operators began to realize that with some changes to the system, they could provide two-way Internet service in unused parts of the spectrum. At that point, the cable TV system began to morph from a way to distribute television to a metropolitan area network.

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Broadcast networks

Broadcast networks can be further divided into

• static
• dynamic depending on how the channel is allocated.Dynamic allocation methods for a common channel are either centralized or decentralized.

In the centralized channel allocation method, there is a single entity, for example a bus arbitration unit, which determines who goes next. It might do this by accepting requests and making a decision according to some internal algorithm. In the decentralized channel allocation method, there is no central entity; each machine must decide for itself whether to transmit. You might think that this always leads to chaos, but it does not.A typical static allocation would be to divide time into discrete intervals and use a round-robin algorithm, allowing each machine to broadcast only when its time slot comes up. Static allocation wastes channel capacity when a machine has nothing to say during its allocated slot.

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Local Area Networks

Local area networks, generally called LANs, are privately-owned networks within a single building or campus of up to a few kilometers in size. They are widely used to connect personal computers and workstations in company offices and factories to share resources (e.g., printers) and exchange information.
LANs are distinguished from other kinds of networks by three characteristics:

(1) their size,
(2) their transmission technology,
(3) their topology.


LANs are restricted in size, which means that the worst-case transmission time is bounded and known in advance. Knowing this bound makes it possible to use certain kinds of designs that would not otherwise be possible. It also simplifies network management.
LANs may use a transmission technology consisting of a cable to which all the machines are attached, like the telephone company party lines once used in rural areas. Traditional LANs run at speeds of 10 Mbps to 100 Mbps, have low delay (microseconds or nanoseconds), and make very few errors. Newer LANs operate at up to 10 Gbps.
Various topologies are possible for broadcast LANs. .

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