What is a Computer Network?
Computer networks can be interpreted as 2 or more autonomous computers that are connected to one another through network communication media, to share information, data and also existing resources.

The main purpose of a computer network is sharing resources (read: resources), where a computer can utilize the resources owned by other computers that are in the same network.
The development of computer data and network communication technology today is no longer limited to computers. Various communication technology devices that are present are currently developing in line with the development of computer technology, many of which integrate computer devices such as microprocessors, memory displays, storage, and communication technology into them even though this technology was developed for computers that we can currently use in technology computer network.

A computer network consists of:

– minimum of two computers
– network card (network interface card / NIC) on each computer
-medium connection, which connects one computer’s network card to another computer, commonly referred to as a data transmission medium, can be either wired or wireless or wireless (wireless such as radio, microwave, satellite, etc.).
– Network operating system software (NOSS) which functions to manage network systems, for example: Microsoft Windows 2000 server, Microsoft Windows NT, Novell Netware, Linux, and so on.
– interconnection equipment such as Hubs, Bridges, Switches, Routers, Gateways, if the network is formed the wider the range

• Source. This device has the duty to generate or determine the data to be transmitted; for example a telephone or personal computer.
• Transmitter. Usually, data is generated by the source system and is not directly transmitted directly in the form as the data was created. A transmitter will transform and encode the information in the form of electromagnetic signals that can be propagated on the transmission system. For example, a modem takes a bit stream from a computer and transforms it into analog signals that can be propagated on the telephone network.
• Transmission System. This can be in the form of transmission media or communication lines or a complex network that connects source and destination.
• Receiver. The receiver receives signals from the transmission system and converts them into a form recognized by the destination device. For example, a modem will receive analog signals coming from a network or transmission line and convert them into digital streams.
• Destination. Is the final goal of sending data that receives data from the receiver.

How is the Data Communicated?

The picture above is another perspective of the data communication model (figure a). To facilitate understanding, we take the example of sending electronic mail.
Suppose the input and transmitter devices are components of a personal computer (PC). A user on a PC will send a message to another user. This user will activate the electronic mail package on the PC and type messages through the keyboard (input device). The character string created will be stored in the main memory buffer. This PC is connected to a transmission medium, such as a cable or telephone via an I / O device (transmitter), for example a transceiver or modem. The message will be transferred to the transmitter as a line of voltage [g (t)] which represents the bits in the cable or communication bus. Transmitter is connected directly to the medium and converts the coming flow [g (t)] to a signal [s (t)] which allows it to be transmitted / propagated.