What is the Internet?

LAN vs. WAN

Hosts and Terminals

First, within the Internet, each separate computer is called a host. You may also see a computer referred to as a node. Here is why. If you draw a diagram of points and lines to represent the connections within a network, each computer will be a point and each connection will be a line. In the part of mathematics that deals with such diagrams, each such point is called a "node". Network specialists have borrowed this term to refer to any computer that is connected to a network. Thus "node" is a more technical synonym for "host".

The second meaning of the word "host" has to do with how certain computer systems are set up.
In general, there are two ways you might use a computer. You might have it all to yourself, or you might share it. Single-user computers, especially the more powerful ones, are often called workstations.

The multi-user systems are often referred to as host computers.
A large mainframe computer can act as a host for hundreds of users at the same time. More commonly, a smaller computer, perhaps one that looks no larger than a PC, will act as a host for a small group of users.

When you have your own computer, you interact by using the keyboard, screen, and a mouse. These devices are part of the computer. With a multi-user computer, each person has his or her own terminal to use. A terminal has a keyboard, screen, perhaps a mouse, and not much more. All the terminals are connected to the host, which provides the computing power for everybody.

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Client and Server Systems

On the internet, hardware is normally not visible, and the terms "client" and "server" usually refer to the programs that ask for and provide services, respectively.

For example, many Internet sites provide a service called a "Gopher". When you use a Gopher, two different programs are involved. First, there is the program that provides your interface. This is the program that interprets your keystrokes, displays the menus, and generally makes sure your requests are carried out. This program is called the Gopher client.

The other program is the one that supplies whatever it is the Gopher client has requested on your behalf. This program is called the Gopher server.

The beauty of this system is that the client and server programs do not necessarily run on the same computer. All of the Internet services make use of this client/server relationship. Learning how to use the Internet actually means learning how to use each of the client programs. Thus, in order to use an internet service, you must understand:

• How to start the clinet program for that service
• How to tell the client program which server to use
• Which commands you must use with that type of client

What is TCP/IP?

Internet Addressing

The way to understand a domain name is to look at the sub-domains from right to left. The name is constructed so that each sub-domain tells you something about the "node". The rightmost sub-domain, called the top-level domain, is the most general. As you read to the left, the sub-domains become more specific.
The following is the examples of the commonly used organizational top-level domains and geographical top-level domains:

Domain	Meanings
Organizational:
com	commercial organization
edu	educational institution
gov	government
int	international organization
mil	military
net	networking organization
org	non-profit organization
geographical:
at	Austria
au	Australia
ca	Canada
ch	Switzerland
cn	China
de	Germany
dk	Denmark
es	Spain
fr	France
gr	Greece
ie	Republic of Ireland
jp	Japan
nz	New Zealand
uk	United Kingdom
us	United States

So far, we have talked about Internet addresses in which each sub-domain is a name. However, underneath the socially acceptable veneer of this system lies a typical computer trick: the real Internet addresses are actually numbers, not names.

Names, of course, are easier for people to use, but every time you use a domain address, your system has to turn it into a number, although the details are hidden from you. The numeric version of an address is called an IP(Internet Protocol) address

The part of the Internet that keeps track of addresses is called the Domain Name System or DNS. DNS is a TCP/IP service that is called upon to translate domain names to and from IP addresses. Fortunately, it is all done behind the scenes, and there is no reason to bother with the details. In rare cases, it may be that your system has trouble understanding a domain address. If it happens, the IP address may work better.

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Uniform Resource Locator

This information is called a URL or Uniform Resource Locator. Within the Internet, every resource can be described by a URL. The first part of a URL specifies what type of resources is being described, the next part shows the address of the resource.
The following are common resource types:

http://	Hyper text transfer protocal
ftp://	file transfer protocal
gopher://	gopher
telnet://	telnet
news://	news group
files://	local files
wais://	wide area information system

Detailed information is available.
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Acronyms used on the Internet

Smileys used on the Internet

The following are commonly used smileys:

Smileys	Meaning
:-)	smiling
:-D	laughing
;-)	winking
:-(	frowning
:-I	indifferent
:-#	smiley with braces
:-{)	smiley with a mustache
{:-)	smiley with a toupe
:-X	my lips are sealed
=:-)	punk rocker
=:-(	real punk rockers don't smile

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Ritsumeikan University
Last updated: 98.3.26