The World Wide Web

The new possibilities, which result from the connecting of computers, has first been recognized in military and scientific institutions. But only with the appearance of applications, that allow a simple and intuitive access to a multitude of connected information, the network in the form of the ``World Wide Web'' became a mass medium.

As important as the actual computers and cables is a common language, which allows to establish connections and to exchange data, a protocol. The protocol of the internet is called TCP/IP.

Internet: the collection of connected computers all over the world that communicate via the TCP/IP protocol.

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An important part of the TCP/IP protocol is a number, which denotes a sender or receiver uniquely, the IP address. For simplicity of usage these numbers are translated into names (so called domain names), which have the following form:

COMPUTERNAME.SUBNET.NET.DOMAIN  
  

COMPUTERNAME denotes the computer itself, SUBNET is a subdivision of NET, and DOMAIN a global division of all subnets world wide. According to the size of a net (i.e. number of connected computers) SUBNET can be missing or divided further.

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The address

hp56.rz.tu-harburg.de

means:

hp56	computer name
rz	subnet
tu-harburg	net
de	domain

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Special domains (or ``top level domains'') exist for many countries and (for historical reasons) for special organizations in the USA. Often one can infer the geographical position of a computer from its domain name.

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top level domain	meaning
de	Germany
fr	France
uk	Great Britain
jp	Japan
edu	University in the USA
gov	US government
com	companies (sometimes world wide)

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The communication via the TCP/IP protocol is usually hidden from the user. Important are the high level applications or internet services.

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Some important internet services:

e-mail

private messages between persons

news

bulletin boards, which can be read locally or world wide, mostly with open access.

ftp

transfer of files (documents, programs) between computers

telnet

remote access to a computer

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With the growth of the internet it became difficult to find specific informations. Scientists at the european research center CERN created a pioneering system that allows the integration of different kinds of documents with arbitrary links: the World Wide Web (WWW).

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Basic elements of the WWW are:

1. a protocol for the transfer of very diverse data from a source computer (the WWW server) to the computer of the user, i.e. the Hypertext Transfer Protocol, or http),
2. a language that allows to describe the content of a document, including references to other doucuments (HTML),
3. an application that displays HTML documents and allows to follow links easily, even to documents on different servers (the browser).