At its most basic, the Internet is the ultimate network of networks. It connects millions of computers via telephone lines, and they talk to each other using a common or set of rules. This is called Transmission Control Protocol/Internet Protocol, but is usually shortened to the much easier to remember TCP/IP.
These conventions determine how files, text, sound, video and pictures are sent and received, and when you log on, your computer is making a connection to over a quarter of a century of digital history.
The Internet arose out of the US defence industry during the Cold War paranoia of the 1960s, by which time computers had become an important and expensive part of processing information. In 1969 the Department of Defense funded the networking project (named after its Advanced Research Projects Administration, or ARPA). The aim was to link together researchers in order to share information, and maximise computer use across research projects. The proposed network would also have the potential to turn into a military communications infrastructure, so it had to be dispersed rather than centralised - if one site took a hit in a nuclear war the whole system would be able to keep functioning.
To do this, it used packet switching. This was pioneered by English scientist Donald Davies in 1965. Communications are broken into small "packets" of data (1,024 bits), which find their own ways to the destination. If any section of the network is down, they reroute themselves along other lines and through other nodes. Once the final packet arrives at their ultimate destination, they reassemble themselves into the original communication.
That's still how information goes out over the Internet. Whether it's an email message or the component parts of a Web page, the data from the host (or server) computer is broken down into small pieces, then sent via phone lines and reassembled in the receiver's computer (or client).
Arpanet, the forerunner of the Internet, was born in 1969, with the first four sites (or "nodes") in California and Utah. By 1971, this had grown to 30 nodes. In the 1980s, ARPA handed over the running of the expanding network to the US National Science Foundation, and NSFNET with its high-speed telecommunications lines, became the network "backbone". That eventually metamorphosed into the Internet as we know it today.
But the Internet was to remain a relatively closed-off world of research communities, government organisations and university students until the early 1990s. British researcher Tim BernersLee, based at the CERN physics laboratory in Switzerland, had written a paper in 1989 suggesting a simple method for the thousands of scientists around the world who were involved in the project to share documents more efficiently.
He proposed a system - in hypertext some words or phrases or "hot" areas are to other related text, - and he dubbed this new system the World Wide Web. Web pages would be held on servers, and through a new protocol called (or HyperText Transfer Protocol - the same HTTP that you see at the beginning of Web addresses), client on users' computers would understand how to build the page up.
The Web truly began to take off with Mosaic, the first widelyused graphical browser (which later evolved into Netscape Navigator and Microsoft's rival Internet Explorer). It turned the text-based Internet into a more easily-accessible, visual world, based on a Macintosh-like graphical interface. Within less than half a decade it has attracted tens of millions of new users to the Internet, creating an entirely new industry and mass medium.
Karlin Lillington is at: karlin@indigo.ie