• E-mail. You can send or receive electronic messages from anyone on the Internet. Anything that can be stored in text file can be mailed.

• File Transfer. The File Transfer Protocol (FTP) provides for the copying of files from one computer to another.

• Communication. You can communicate with the help of the Internet with one person or a group of persons simultaneously.

• Information.

On the Internet all addresses / domain names refer to «electronic Addresses», e.g.:

person-id@computer name.domain name

There is never blank space between the components of the Internet address. User ids need not be unique (id – identification), e.g. two people with the same name can have it as login name as long as they operate on separate domains. But the domain name of the computer must be unique, however:

austin@galaxi.isr.umd.edu, austin@euler.berkeley.edu

Austin is the person-id, «galaxy» and «euler» are computer names, «isr.umd.edu» and «berkeley.edu» are domain names. Domain names are composed of sub-domain names: esr, umd, edu.

The table summarizes commonly used sub-domain names:

Domain names meaning
Domain	Meaning
com	Commercial Organization
edu	Educational Organization
gov	Government
int	International Organization
mil	Military Organization
net	Networking Organization
org	Non-profit Organization
at	Austria
au	Australia
br	Brazil
ca	Canada
de	Germany (Deutschland)
dk	Denmark
fr	France
jp	Japan
nz	New Zealand
uk	United Kingdom (England, Scotland, Wales, Ireland)
ru	Russian Federation

In the computer address isr.umd.edu the sub-domain «edu» tells that the computer is located at an educational institution. The sub-domain name «umd» stands for the University of Maryland, and «isr» means the collection of computers at the Institute for System Research, at the University of Maryland.

If you want to send a message put down the word «mail» before the address.

Today computers are seen as indispensable tools not only for computation and typing but for communications. The merging of computation and communications is making essential changes to day-to-day business activities of engineers. Suppose an engineer belongs to a geographically dispersed team. He can:

• Use the Internet / E-mail for day-to-day communications.

• Conduct engineering analyses at remote sites.

• Share results among the team members.

• Participate joint ventures assembled over a network, and on-line bidding of projects etc.

The World Wide Web (WWW)

The World Wide Web dates back to March 1989, when Tim Bermers-Lee of the European Particle Physics Laboratory (known as CERN, a collective of European high-energy physics researchers) proposed the project to be used as a means of transporting research and ideas effectively throughout the organization. It was a goal of CERN’s since its members were located in a number of countries.

The initial project proposal outlined a simple system of using networked hypertext to transmit documents and communicate in the physics community. Hypertext is basically the same as regular text – it can be stored, read, searched or edited – with an important exception: hypertext contains connections with the text to other documents.

Although the early WWW system had as its goal the advancement of science and education, it is revolutionizing many elements of society, including commerce, politics, and literature.

Nobody owns the World Wide Web. People are responsible for the documents they author and make available publicly on the Web. Via the Internet hundreds of thousands of people around the world are making information available from their homes, schools, Universities, and workplaces.

Hypermedia combines hypertext and multimedia.

To find the necessary information over the Internet you must use a browser. The browser is a program which can send requests for documents to any Web server. A Web server is a program that, upon receipt of a request, sends the document requested back to the requesting client. Because the task of document storage is left to the server and the task of document presentation is left to the client, each program can concentrate on those duties and progress independently of each other.

Here is an example of how the process works:

1. Running a browser, the user selects a hyperlink in a piece of hypertext connecting to another document; e.g. it is «The History of Computers».

2. The browser uses the address associated with that hyperlink to connect to the Web server at a specified network address and asks for the document associated with «The History of Computers».

3. The server responds by sending the text and any other media within that text (pictures, sounds, or movies) to the browser, which it renders on the users screen.

The World-Wide Web is composed of thousands of these virtual transactions taking place per hour throughout the world, creating a web of information flow.

HTTP (HyperText Transfer Protocol) is the language that Web browsers and servers use to communicate with each other. HTTP defines how messages are formatted and transmitted, and what actions Web servers and browsers should take in response to various commands.

The other main standard that controls how the World-Wide Web works is HTML (HyperText Mark-up Language), which covers how Web pages are formatted and displayed. Every browser has the built-in ability to understand HTML.

The World-Wide Web uses what are called Uniform Resources Locators (URLs) to represent hypermedia links and links to network services within HTML documents. It’s possible to represent nearly any file or service on the Internet with a URL.

The first part of the URL (before the two slashes) specifies the method of access.

The second part is the address of the computer where the data or service is located. Further parts specify the names of files, the port to connect to, or the text to search for in a database.

A URL is always a single unbroken line with no space.

Sites that run World-Wide Web servers are typically named with a www at the beginning of the network address:

file://www.eit.com/picture.gif

It retrieves a picture and displays it.

ftp://www.xerox.com/pub/file.txt

It opens an FTP (File Transfer Protocol) connection to www.xerox.com and retrieves a text file.

Search Engines help you to locate documents containing specific titles, words or phrases. There are at least four good search engines: Altavista, Hotbot, Lycos, and Yahoo.

2. Exercises