What is a network?

A network is simply two or more computers linked together. It allows users to share not only data files and software applications, but also hardware like printers, high-speed modems and other components resources such as fax.
Most networks link computers within a limited area - within a department, an office, or a building. These are called Local Area Network, or LANs. But networks can link computers across the world, so you can share information with someone on the other side of the world as easily as sharing with a person at the next desk. When networks are linked together in this way, they are called Wide Area Networks, or WANs.
Networks increase productivity by allowing workers to share information easily without printing, copying, telephoning, or posting. They also save money by sharing peripherals such as printers.

Network topologies

There are different ways a local network (LAN) can operate. The three most common configurations are Token Ring, Bus and Star.

On a Token Ring network, all devices are (PCs, printers, file servers, etc.) are connected to the same circuit, forming a continuous loop or ring. A token - a piece of software - circulates continuously along the ring, and is read through an adaptor card in each machine as the token passes by. A computer can only send a message or document on the network if it has the token; when it has finished, it passes the token to the next device. If a cable breaks or one of the computers fails, the whole network will be affected.

The limitation of the Token Ring is that only one computer may send send data at a time.

A Bus network consists of one common cable to which all the devices are connected. The two ends of the cable are not joined. Each device is able to send a message to another device when it is sure that no other signals are being transmitted. Too many messages can slow down the network speed. When two devices send messages at the same time, there is a collision and the messages need to be sent again. If a computer fails, or we remove one from the network, it won't affect the other computers.

In a Star network configuration, all devices are connected to a central station, called the Star Controller. The central station functions as a switching center. Computers cannot pass messages directly to one another; instead, they have to communicate via the central station which prevents messages from colliding. This means that more than one computer can send a message at the same time. If the central station fails, the whole network will fail.

PREDICTIING CONSEQUENCES: CONDITIONAL CLAUSES

When you want to talk about a possible situation and its consequences, you use a conditional sentence. Here we examine TWO TYPES of conditionals:

1. First Conditional (possible situation):

If  A  happens                                 B will happen
(simple present)                             (will + verb)

e.g. If you click on the speaker icon, you’ll get a piece of dialogue from the movie.

a. When the verb to be is used in the main clause, the base form be is used after will.

e.g. If you hire a fast Internet provider, your phone bills will be lower.

b. The negative form of will is won’t (will + not).

c. In the main clause, we can also have a modal (can, may), an imperative, or a present tense verb.

2. Second Conditional (unlikely situation):

If A happened                      B would happen
(simple past)                         (would + verb)

If I had money, I would invest in a blue-ray player.

a. ATTENTION: when used in the if-clause, the verb be becomes were for all persons.
If I were you, I wouldn’t give my password to that guy.

b. When the verb to be is used in the main clause, the base form be is used after would.
If I were you, I would be very happy.

Other modals (could, should, might) may appear in the main clause.
Ex. If I had enough money, I could buy an upgrade kit.

Note: You need to learn some past tense forms of the verbs to use the second conditional correctly.