1. What is this ``Internet'' thing anyway?

A computer network is a collection of computers connected together so that they can exchange information. Each of the individual computers becomes much more flexible and useful as a result.

The Internet is a special kind of computer network. I will explain what is special about it, but first we need to understand a little of the history of how it was created.

Often the computers making up a network are located in the same local area--a school, office, hospital, university etc. In that case the network is called a local area network or LAN. Sometimes the network is extended to include computers at separate locations--perhaps connecting a sales office to a manufacturing plant. Then the network is called a wide area network or WAN.

The first computer networks, both LANs and WANs, were private and isolated from each other. They usually belonged to a single organisation. They made the activities of that organisation more efficient. However, when it was necessary to exchange information with other organisations, the private network did not help at all. Instead the information had to be printed out and then retyped for the other computer system, or perhaps stored on a magnetic tape or disk--if the other system could read the same kind of tape or disk, which was often not the case.

The obvious solution to these problems was to interconnect these separate networks to form one big network--an ``inter-network'' or internet for short. And that is precisely how the Internet (now with a capital ``I''!) came to be born.

The original Internet was an experimental project funded in the 1970s by the Defense Advanced Research Projects Agency (DARPA) in the US. In fact, the forerunner of the Internet as we now know it was called ARPANET.

This project explored the technical problems of interconnecting separate computer networks. One particular objective was to make the whole system robust and reliable even if individual communication links or computers were damaged. In fact, this was the chief military interest in the work. It is a tribute to the engineers and scientists who designed the original Internet that it is still operating remarkably reliably even though it now has tens of thousands of networks, containing millions of individual computers.

In the early days the Internet was confined to North America and connected a few tens of networks, mainly in universities and government organisations. It offered two main services:

• Electronic Mail: or e-mail. This simply means that people can compose letters on their computers and then post them ``electronically'' to each other. Similarly, each user has an Internet ``mailbox'' to receive their incoming electronic letters.

  This has a few advantages over traditional paper mail. Firstly, you don't need stamps, and you don't have to walk out to the postbox! Secondly, your letter can be delivered within a very short time of posting (as little as a few seconds). Finally, it is very easy to send the same letter to lots of people, instead of just one. I will discuss e-mail in much more detail in Chapter 4.

• Electronic Publishing: The idea here is that you can make information from your computer available to everyone else on the Internet. One of the most common uses of electronic publishing has been among academics--lecturers in universities--allowing them to share their research articles. This provided the motivation for much of the way publishing services have been developed on the Internet, so it is worth explaining this application in detail.

  Traditionally, academic researchers have published their work in printed journals. Academic libraries subscribe to many hundreds or even thousands of these journals. When a researcher needs to refer to one of these articles he checks his own university's library first; but if, as is often the case, it does not stock the particular journal, he would have to request a copy of the article by post from the author. Authors receive a number of free copies or ``offprints'' of their published articles for this purpose. But this whole system is very cumbersome and slow. It can take weeks or even months to get a copy of a needed article.

  But wait a moment: most articles and papers are prepared on computers now anyway, before being printed for submission to a journal. Would it not be possible to make this electronic version available for immediate access by anyone who wants it? Well, yes, it is possible and that is exactly the idea behind Electronic Publishing!

  Once an article is published ``electronically'', then anybody else can have it copied onto their own computer (via the Internet), and print it out on their local printer. This can be done in a few minutes, regardless of how far distant the computers are from each other, and without requiring the original author to be involved at all.

  The earliest form of electronic publishing on the Internet used a mechanism called file transfer protocol or FTP. This has now been largely displaced by a more sophisticated mechanism called hypertext transfer protocol or HTTP. HTTP underlies what is now called the World Wide Web. The Web is the collection of all information published electronically, by any mechanism, over the Internet. Fortunately you need not worry about the arcane technicalities of FTP or HTTP. You just need to understand the basic idea that the Web is a system for electronic publishing--a way for you to request all kinds of information, on all kinds of subjects, and to receive it more or less instantaneously.

  I will deal with the Web in detail in Chapter 3.

Although the Internet started as a research project, with a very limited number of partners involved, other organisations soon wanted to become connected as well. Major expansion of the Internet in the US was funded by the National Science Foundation. This eventually allowed the great majority of US universities to connect their own local area networks (LANs) to the Internet.

Similar academic and research networks were simultaneously being constructed in other countries of the world--such as the Joint Academic Research Network (JANET) in the UK, and the Higher Education Authority Network (HEANET) in Ireland. Initially these separate national networks tended to utilise slightly different and incompatible systems, making it difficult to join them together. But modern academic research usually involves international co-operation. This lack of completely compatible international connection was becoming a significant problem.

By the late 1980s it became clear that these networks would be much more useful if they were interconnected through a single compatible system. Since the US Internet was already the largest and best tested system in use, it was natural that other national networks began to adopt the same basic technologies, and interconnect with it. By the early 1990s the Internet existed as a single global network, interconnecting universities and other research organisations around the world. It was paid for by various national funding agencies, such as the Higher Education Authority in Ireland. It was not yet open to individual members of the general public, nor very widely used by commercial organisations.

The basic underlying technology that unites this global network has the rather cumbersome name of Transmission Control Protocol/Internet Protocol or (slightly less of a mouthful) TCP/IP. Fortunately, you need to know almost nothing about the intricacies of TCP/IP in order to actually use the Internet!

The beginnings of more popular interest in the Internet coincided with the development of the World Wide Web. The Web introduced two new key facilities on the Internet:

• Hyperlinks: This is a mechanism whereby one document can be electronically ``linked'' to another related one. So once you access an initial document it becomes very easy (at the proverbial ``touch of a button'') to access other related ones. These links can be visualised as connecting together documents all around the world into a single gigantic ``spider's web''.

• Multimedia: This simply means that electronically published documents are no longer restricted to be conventional text--characters and words that can be read or printed. Instead, ``documents'' on the Web can include diagrams, photographs, sounds, animations and even movie clips. This has been done in such a way that every type of document carries a standardised unique label that explains the correct way to ``view'' it--as text, audio or movie clip etc.--and this labelling scheme can be easily extended at any time to admit new types.

These new facilities were again inspired by the needs of the original Internet users--researchers publishing academic papers. These papers almost always refer to other earlier papers, and frequently need to include diagrams, photographs, or other media. But although the new facilities were inspired by these academic requirements, they have had a much wider effect. Quite suddenly, the Internet could be used in a much easier, more friendly, way. A user did not need to know arcane FTP commands to get a document--they could just ``point and click'' (point at a link to the document and click a button on their keyboard or mouse). Better still, the ``documents'' that are electronically published, or exchanged by e-mail, could now be in any kind of medium--text, music, photographs, anything at all. This opened up a much wider range of activities that could be done on the Internet, and triggered an explosion of interest--and an explosion of growth.

Which brings us to the Internet that we know today!

In just the last five years or so the Internet has very suddenly ceased to be an obscure and private toy for academics in ivory towers. Instead literally millions of ordinary people, and tens of thousands of organisations, from all around the world, have gone ``online'', by connecting to this global network. The ``Net'' has become a household word, and a regular subject for debate in magazines, newspapers and on television. People of all ages and all walks of life are using the Internet to exchange letters, postcards, snap shots and even movies. Companies, both long established and aggressive young upstarts, are offering a barrage of news, views, information and fiction, in every conceivable shape and form.

Many of these inhabitants of ``cyberspace''--the users of the Internet--want to sell you something. Others just want to play or to be entertained. Others again are using the Net to fight dictatorship, combat world poverty, or plead for the preservation of the tropical rain forests. The Internet now is all this and more, because it is a magnified image of the diversity of human society and communication across the globe. Whether you just want to search for package holiday bargains, or you intend to bring about World Peace, the Internet will allow you to make immediate contact with the information, the people, and the organisations that can make it happen.

So enough of this history: let's get you connected!