The Internet is primarily a means of communication. The computer is used to establish that communication. Since the late 1960s, people have been working on connecting computers with each other. These connections can be made with a cable. Or one can use the public telephone network. This is how we came to what the Internet is today: a gigantic network of interconnected computers. Any point in this network can communicate with any other point.

When using the telephone network, one must have a means of transmitting signals from one computer to another. A modem is used for this. This unit converts digital signals from the computer into (analog) audio signals (Modulation). These signals are then sent over the telephone line. On the other hand, the same modem converts the signals back into digital form (Demodulation).
The physical form of a modem can be a separate box that is connected to a serial port of the computer.
It can also be a plug-in card that plugs into a free slot on the computer's motherboard.
The modems communicate at speeds of 56 Kbps (kilobits per second) or higher. This speed is much higher with current internet service providers.

The main activity of the computers connected to the Internet is to receive and forward data. This is referred to as data transmission.
To make this exchange of data run smoothly, a series of rules or protocols have been drawn up.
TCP/IP (Transfer (or Transmission) Control Protocol/Internet Protocol) is therefore a collection of protocols that ensure the exchange of data packets.

The IP protocol takes care of the transmission of the packets between sender and receiver. It uses an address to reach each computer.
An IP address (version 4) is a number made up of 32 bits. This number is divided into 4 units (of 8 bits) separated by a period (For example: 194.7.1.4).
Each element of the Internet network has a unique IP address. In order to be able to easily assign these addresses to each element, an address is composed of a network number and a computer number.
All computers are divided into 3 classes:
Class A networks : with a network number with a first number group from 1 to 127. These are large-scale networks (eg IBM, AT&T,...) to which a very large number of computers are connected.
Class B networks : with a network number with a first digit group between 128 and 191. This address type is mainly used in universities. Up to 65,000 terminals or computers can be connected.
Class C Networks: With a network number with a first digit group between 192 and 223. This is mainly intended for smaller networks with up to 255 computers.

Those digit groups are not easy to use for the user. That is why an addressing system has been created with domain names. Such a domain name consists of the name of the computer, the name of the organization and the name of the zone (for example: www.skynet.be).
For the zone one uses the country names (eg be = Belgium, nl = Netherlands, de = Germany,...) or a user category (eg com = commercial activity, edu = educational institution, gov = government institution).
The name of the computer is usually the name of the service provided (eg www or ftp).
Since the network only works with digital IP addresses, a translation system has been developed. In every network there is a computer that maintains the address translation tables (the Domain Names Server or DNS).

To access the Internet one has to turn to an Internet access provider or Internet Access Provider (IAP) (or Internet Service Provider (ISP) because of the many services they offer). This commercial company has a permanent connection to the Internet and sells Internet access to users. It takes care of the development of its own network to which users log in.

These two protocols make it possible to establish a temporary IP connection. SLIP (Serial Line Internet Protocol) and PPP (Point to Point Protocol) are offered by most Access Providers.
The SLIP or PPP program provides the different steps to be taken to establish an Internet connection:
• checking the presence of a modem;
• dialing the telephone number;
• establishing a communication with a SLIP or PPP access terminal or computer (after the modems agree on the communication speed and protocols);
• carrying out the admission procedure (filling in name and password);
• initialization of the IP services, after which you are assigned an IP address.
Once these steps have been successfully completed, you are part of the Internet. You are then online.