Computers And Internet

By Author: fed pats
Total Articles: 224
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Internet, a remarkable network that has spread all over the world with an amazing speed. We cannot
imagine life without it any more. Here is a short history of how the internet begun. At the very
beginning, the Internet was an experimental program for the American military, in the 60s. In this
project, the military paid for the costs involved in researching a network named Arpanet, which
connected universities and military bases. In 1974 the first independent communication hardware was
completed, in essence the first versions of TCP and IP, invented by Vincent Cerf and Robert Kahn. In the
80's the military network was transformed into a different network and Arpanet was
renamed "Internet."

The year 1990 marked the beginning of the Internet revolution: Tim Berners Lee created the World
Wide Web (WWW, Web, W3) with the intention of:

a. Having a method of attaching a name to all the computers on the Internet.
b. Having a method of presenting documents on different computers using the same programs.
c. Having a method of tying together parts of the same document ...
... or different documents, on the same
computer or using different computers.
d. The" Server Web" for document storage, the Internet representing today, a network of sub networks,

all connected to the server.
e. The"Browser", intended for the use of presenting documents on the server. Marc Andriessen created
the very first graphic Browser back in 1992; this browser's name was "Mozaic". Later on, it was known
as "Netscape".

The Internet can be described as an open system. Through "Open System" we understand that the
structure is no secret, meaning its creator has made the design detailed enough so that other people
can come along and make their own products. Other examples of open systems are UNIX and Linux.
Examples of privately owned systems are Microsoft Windows and Mac OS.

The primary function of the Internet is the exchange of data between computers; to accomplish this,
every computer of the Internet network has an IP address. The most common IP nowadays is the Ipv4.
In the Ipv4 the address of the computer is in a row of 32 bits (2 to the power of 4-bits); this is
represented by 4 octets, for example: 151.23.40.3. There is also a version that uses 128 bits (2 to the
power of 6 bits).

Most IP addresses of the Internet can go into 4 classifications:

1) The first bit in the 32 is, "0" and represents the class A; the next 7 bits show the network's address,
while the last 24 bits indicate the computer's address in the network.
2) The first 2 bits out of the 32 are "1 0" and they represent class B, the next 14 bits show the network's
address, while the last 16 indicate the computer that is on the network.
3) The first 3 bits out of the 32 are "1 1 0" and they represent class C, the next 21 bits show the
network's address, while the last 8 bits indicate the computer's address that is on the network.
4) The first 4 bits out of the 32 are "1 1 1 0" they represent class D, the next 28 bits are used to show a
single address which, in this case, is called a multicast address.

IP addresses are difficult to memorize in numeric format, that's why a method of attaching the name
through a domain system (the DNS-Domain Name System) was introduced. In essence, the DNS
represents a method of naming the computer (real or virtual) through a network based on TCP/IP (on a
type of Internet) using a hierarchy scheme.

Example: imap.des.kel.ac.uk is the name of the computer that is responsible for managing the electronic
mail (IMAP) from a certain department (des.kel) belonging to a sub network Internet (ac) in Great Britain
(uk). Every suffix from a name is called a domain. The relationship "des.kel.ac.uk < kel.ac.uk < ac.uk < uk"
where "