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access the network, it’s offline. A computer can be offline for several reasons. The computer can be turned off, the user may have disabled the network connection, the computer may be broken, the cable that connects it to the network can be unplugged, or a wad of gum can be jammed into the disk drive.

       Up, down: When a computer is turned on and working properly, it’s up. When a computer is turned off, broken, or being serviced, it’s down. Turning off a computer is sometimes called taking it down. Turning it back on is sometimes called bringing it up.

       Local, remote: A resource such as a disk drive is local if it resides in your computer. It’s remote if it resides in another computer somewhere else on your network.

       Internet: The Internet is a huge amalgamation of computer networks strewn about the entire planet. Networking the computers in your home or office so that they can share information with one another and connecting your computer to the worldwide Internet are two separate but related tasks.

Why Bother with a Network?

      Frankly, computer networks are a bit of a pain to set up. So, why bother? Because the benefits of having a network outweigh the difficulties of setting one up.

You don’t have to be a PhD to understand the benefits of networking. In fact, you learned everything you need to know in kindergarten: Networks are all about sharing. Specifically, networks are about sharing three things: files, resources, and programs.

      Accessing the Internet

      Probably the main reason most small business and home networks exist is to allow everyone to access the Internet through a single shared Internet connection. In Figure 1-1, you can see that the wireless router is connected to the Internet. By sharing this connection, all the computers on the network, whether wireless or via cables, can access the Internet through the wireless router.

      It’s important to note that nearly all wireless routers also contain a built-in firewall. The firewall helps protect the computers on the network from the imminent dangers of the Internet. The moment you connect a home or office network to the Internet, cybercriminals will begin trying to break into your network and try to trick you into divulging sensitive information, such as the password to your bank account.

      

Never — and I mean never — allow any computer to connect directly to the Internet without a firewall in place.

      Sharing files

      Networks enable you to share information with other computers on the network. Depending on how you set up your network, you can share files with your network friends in several different ways. You can send a file from your computer directly to a friend’s computer by attaching the file to an email message and then mailing it. Or you can let your friend access your computer over the network so that your friend can retrieve the file directly from your hard drive. Yet another method is to copy the file to a disk on another computer and then tell your friend where you put the file so that your friend can retrieve it later. One way or the other, the data travels to your friend’s computer over the network cable and not on a CD or DVD or flash drive, as it would in a sneakernet.

      Sharing resources

      You can set up certain computer resources — such as hard drives or printers — so that all computers on the network can access them. For example, the printer in Figure 1-1 is a shared resource, which means that anyone on the network can use it. Without the network, Marge, Lisa, and Bart would have to buy their own printers.

Hard drives can be shared resources, too. In fact, you must set up a hard drive as a shared resource to share files with other users. Suppose that Lisa wants to share a file with the Bart, and a shared folder has been set up on Homer’s computer. All Lisa has to do is copy his file to the shared folder in Homer’s computer and tell the Bart where she put it. Then, when the Bart gets around to it, he can copy the file from Homer’s computer to his own.

      Sharing programs

      Instead of keeping separate copies of programs on each person’s computer, put programs on a drive that everyone shares. For example, if ten computer users all use a particular program, you can purchase and install ten copies of the program, one for each computer. Or you can purchase a ten-user license for the program and then install just one copy of the program on a shared drive. Each of the ten users can then access the program from the shared hard drive.

      

Remember that purchasing a single-user copy of a program and then putting it on a shared network drive — so that everyone on the network can access it — is illegal. If five people use the program, you need to either purchase five copies of the program or purchase a network license that specifically allows five or more users.

      

That being said, many software manufacturers sell their software with a concurrent usage license, which means that you can install the software on as many computers as you want, but only a certain number of people can use the software at any given time. Usually, special licensing software that runs on one of the network’s server computers keeps track of how many people are currently using the software. This type of license is frequently used with more specialized (and expensive) software, such as accounting systems or computer drafting systems.

      Another common method for software vendors to license their software is through a monthly or yearly subscription. You just give them your credit card number, and they give you the right to use the software. You need a working Internet connection so that the software can confirm that you have a valid subscription each time you run the software.

      Another benefit of networking is that networks enable computer users to communicate with one another over the network. The most obvious way networks allow computer users to communicate is by passing messages back and forth, using email or instant-messaging programs. Networks also offer other ways to communicate: For example, you can hold online meetings over the network. Network users who have inexpensive video cameras (webcams) attached to their computers can have videoconferences. You can even play a friendly game of Hearts over a network — during your lunch break, of course.

Servers and Clients

      The network computer that contains the hard drives, printers, and other resources that are shared with other network computers is a server. This term comes up repeatedly, so you have to remember it. Write it on the back of your left hand.

      Any computer that’s not a server is a client. You have to remember this term, too. Write it on the back of your right hand.

      Only two kinds of computers are on a network: servers and clients. Look at your left hand and then look at your right hand. Don’t wash your hands until you memorize these terms.

      The distinction between servers and clients in a network has parallels in sociology — in effect, a sort of class distinction between the “haves” and “have-nots” of computer resources:

       Usually, the most powerful and expensive computers in a network are the servers. There’s a good technical reason: All users on the network share the server’s resources.

       The cheaper and less-powerful computers in a network are the clients. Clients are the computers used by individual users for everyday work. Because clients’ resources don’t have to be shared, they don’t have to be as fancy. (The exception to this rule is if the users do work that requires powerful desktop computers — for example, engineering design or video processing.)

       Most

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