What is Computer Network? Is Internet a CN?

Definition:

A computer network is a group of computer systems and other computing hardware devices that are linked together through communication channels to facilitate communication and resource-sharing among a wide range of users. 

The connection need not be via a copper wire; fiber optics, microwaves, infrared, and communication satellites can also be used. Networks come in many sizes, shapes and forms.

Some Misconception:

Although it may sound strange to some people, neither the Internet nor the World Wide Web is a computer network.

 The Internet is not a single network but a network of networks and the Web is a distributed system that runs on top of the Internet.

 

There is considerable confusion in the literature between a computer network and a distributed system. The key distinction is that in a distributed system, a collection of independent computers appears to its users as a single coherent system. Usually, it has a single model or paradigm that it presents to the users. Often a layer of software on top of the operating system, called middle ware, is responsible for implementing this model. A well-known example of a distributed system is the World Wide Web, in which everything looks like a document (Web page). 

In a computer network, this coherence, model, and software are absent. Users are exposed to the actual machines, without any attempt by the system to make the machines look and act in a coherent way. If the machines have different hardware and different operating systems, that is fully visible to the users. If a user wants to run a program on a remote machine, he [] has to log onto that machine and run it there. 

Thus, the distinction between a network and a distributed system lies with the software (especially the operating system), rather than with the hardware.