The Digital Research Initiative
The University of North Carolina at Chapel Hill

Part One: Basic Computing/Networking Concepts

In order to effectively explain the technology behind the Internet, we should first look at some basic concepts.

What is a computer?

A computer is literally a machine that computes mathematical operations.

When one thinks of the most-common form of computer, the desktop PC, the fact that this device is essentially a very powerful calculator does not seem accurate. However, all of the functions that are performed by any computer, including a PC, are the result of mathematical operations. This is because computers represent information as 1's and 0's. It is the sequence and number of the 1's and 0's that tell a computer what letters, symbols, and numbers make up the data it stores as well as the instructions it is to complete. Everything that a computer does is the result of the deciphering 1's and 0's.

A more practical definition of a computer is that it is a device designed to process information and complete precise tasks. Just as large construction equipment is designed to complete tasks that are too difficult or time-consuming for human muscles, computers are designed to handle tasks that are too time-consuming or difficult for human brains.

This is not to say that computers can replace human brains, but that they are meant to be aides to human brains. Computers lack the will to do anything and are therefore unable to initiate tasks, which is why all computers require human instruction. Anytime a computer does anything, even when it seems to be acting on its own accord, it is acting because a human being provided instructions.

Physically, computers are generally a collection of very small electrical devices that reside on a common circuit board. These devices are called 'microchips.' Usually made of silicon, microchips contain millions of tiny transistors that are used to represent 1's (on) and 0's (off). Most microchips have specific purposes or contributions to the computer system, with the CPU being the main processor that controls all of the functions of the computer. Computers can be as large as entire buildings or as small as a dime. (Smaller computers are more limited in their abilities and applications.)

In order to process information, computers must have storage devices, both for short-term and long-term storage. Short-term storage is required for the computer to hold information for processing, and long-term storage is needed to keep the information while it's not being processed. A good example is the difference between a library and a hand. A person may hold a book in their hand while they are reading it, but while not in use that book is kept in the library, so the hand can be free for other projects. Short-term computer memory is usually provided by microchips that lose their data when the power is turned off. Long-term memory is generally kept on magnetic media, such as hard drives or floppy disks, and can hold data even when there is no power available.

As computers require human instruction, they must have either a communications port/method or a monitor with inputs such as a mouse and keyboard. A communications port/method allows for the computer to connect to another computer that has a display with inputs. Most desktop PCs have a display with inputs as well as several kinds of communication ports, including Serial ports, USB ports, Ethernet ports, and Parallel ports.

It is important to note that the words "USB," "Serial," "Ethernet," and "Parallel" refer the physical design of the receiver attached to the computer and to the cables that work with these receivers. For each of these receivers, the computer must have instructions (or "programs") that tell it how to send and receive data via these ports. Generally, these instructions are contained in the computer's "operating system," which is the collection of instructions that provide the foundation for the computer's functions. A real-world metaphor for an operating system is the education we receive in kindergarten and grade school. All of our advanced activities are based on the knowledge we were given in those years, just as all of a computer's advanced activities are dependent on the instructions in its operating system.

Human beings most often interact with computers by viewing their graphical output on computer monitors and inputting text and signals via a keyboard and mouse (There are other scenarios for blind or paralyzed users, such as audio inputs and outputs.). This interaction is how the activities of the computer have impact in the "real world," because this is when the data travels to the human society from the computer world.

For more information on the anatomy of computers, please see Computer Quiz and A Peek Inside Your Computer.

What is a computer network?

A computer network is a set of two or more computers that are able to communicate with each other.

As discussed above, computers often have communications ports, and it is through these communications ports that computers become members of networks. Generally, all of the computers of a single network are connected via the same type of communication port (i.e. all the computers on one network will be connected via Ethernet; it would be difficult for one network to have some computers connecting via USB and others connecting via Ethernet). Also note that the various types of communications ports mainly differ in the speed at which they can send and receive data, and thus networks are generally designed to utilize the fastest, most reliable communications ports available.

The purpose of a computer network is to enable computer users to share resources and data. For example, a company may need to allow its employees to work with a very large collection of documents. Rather than provide each employee's computer enough storage space to store this collection of documents, the company installs a large, central computer to store these documents and then all the employees' can access the collection on their computers via the company's network. The benefit is in the saved expense of the storage equipment, as well as the saved time in reconciling all of the changes the employees would have made to the collection of documents on their own computers.

More than just sharing storage space, computer networks allow users to share printers, multimedia equipment, and even experiences. Computer networks can operate like broadcast media where the users are an audience for a central resource such as a shared printer, or computer networks can operate as a conduit for conversation via the exchange of messages, sometimes in real-time and in multimedia formats.

Any operational computer network is set up so that the member computers use the same "protocol" to participate on the network. A "protocol" is the equivalent of the combination of language and custom in human society. Just as English-speaking humans utilize the word "hello" to initiate a conversation, computers have methods and expectations when communication with each other.

Network protocols also have "sub-protocols," which allow for specific activities on the network. For example, a network protocol allows two or more computers to converse with one another, and a file-sharing protocol allows these computers exchange files during the conversation. Sub-protocols provide the ability to make use of the network. A good example of a sub-protocol in the human world is the method for ordering food in a restaurant. English, combined with good manners, is the overall protocol that the customer is using, but it's the specific use of food/dining vocabulary and customs that allows the customer to have a meaningful conversation with the waiter. One would not receive a good meal if they threaten a waiter with violence or asked for a cardboard hat.

Computer networks are all applications of the OSI Seven-Layer Model, which is described in detail here on Webopedia.Com

What are clients and servers?

A "server" is a computer that provides data or services to one or more "client" computers via a network.

A computer is a server whenever it is configured to respond to requests by other computers via a network. Many computers are configured to respond with the current time when asked in a particular manner, and even providing this simple service means that these computers are servers.

Any computer than requests data or services from another is a client, even if that computer is also a server.

Returning to the restaurant example above, a waiter can be thought of as a human server while a customer is the human equivalent of a client. In one restaurant, a person may be a waiter/server, while that same person can travel to the restaurant down the street and become a customer/client.

As discussed above, computers require instruction on anything they do, and in order to function as a server, a computer must have "server software" to provide the instructions on its role. Likewise, a client computer must have "client software" to instruct it on requesting services from a server.

What are centralized and decentralized networks?

A "centralized" network is a network configured such that all of the client computers rely on one server computer for all of the services on the network. A "decentralized" network is a network that is configured such that multiple server computers provide the services used by the client computers.

The best example of a centralized network is one that is made up of "dumb terminals" that look to a mainframe computer. (These networks were common from the 1960's through the 1980's and are still in place today in many busniesses, especially newspapers and banks.) The dumb terminals get their name because they are computers that are unable to function independently of a server or an intermediate computer that carries requests to the server. The dumb terminals only provide a display and keyboard/mouse inputs to the server, and their purpose is to allow the users to interact with the server.

An example of a decentralized computer network is one in which the client computers utilize one server for sending text messages, another server for storing files, and another server for controlling a printer. The advantages of this configuration is increased reliability and speed. Since the burden of the required services is shared among multiple servers, each service can be provided in a more timely fashion, and there is less risk of overloading each server with too many requests. More importantly, if one server were to fail, the other servers can continue to provide their services, opposed to a centralized network that would be completely useless if it's one server were unavailable. This advantage grows significantly when the decentralized network is configured with redundant servers -- multiple servers providing each service. In this case, a server can fail, and clients will still have the opportunity to use the services it had offered.

The reliability advantage of decentralized networks is the inspiration that drove the development of the Internet. In the late 1960's, the United State Military decided to develop a decentralized network so that the country's entire computer network could not be destroyed with one nuclear bomb. The Internet is the ultimate decentralized network, and it continues to provide a valuable national security resource. For a more detailed history of the development of the Internet, please see Internet History.

Return to Intro | Part Two: What is the Internet?


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