A global computer network is a set of computers connected together for the purpose of sharing resources. The most common resource. The most common resource shared today is connection to the internet. Other shared resources can include a printer or a file server. The  internet itself can be considered a  computer network. A global computer network is a set of one or more interconnected computers and a set of hardware devices.

Need of Networking

1. Resource Sharing- All programs, data and peripherals are available to anyone on the network irrespective of the physical location of the resource and the user.

2. High Reliability- A file could be replicated on two or three machines, so if one of them is unavailable (hardware crash), the other copies could be available 

3. Cost Factor-personal computers (PC’s) have a much better price/performance ratio than micro ones.
4. Communication Medium-A file that was updated/modified on a network, can be seen by the other user on the network immediately.

Network Applications

1. Sharing of data, programs and peripherals
2. Access to remote programs.
3. Access to remote databases.
4. Value-added communication facilities.

Advantages of Network

1. Speed- Sharing and transferring files within Networks are very rapid. Thus saving time, while maintaining the integrity of the file.
2. Security- Sensitive files and programs on a network are passwords protected so no illegal copying of programs is there.
3. Centralized Software Management– Software can be loaded on one computer eliminating that need to spend time installing on independent computers.
4. Resource Sharing- Resources such as printers,fax machines and moderns can be shared. Therefore it is cheaper to have these on many systems.

      5.Improve Communications- E-mail acids in personal and professional communications. Electronic mail on a LAN can enable staff to communicate within the building without having not to leave their desk.

Disadvantages of Network

1. Cabling can be expensive to install and replace.
2. A fault with the server will prevent the whole network from working.
3. Security measures are needed to restrict access to the network.
4. WANs are vulnerable to hackers and viruses.
5. Server faults stop applications being available.
6. Network faults can cause loss of data and resources.
7. User work dependent upon network.
8. Could degrade in performance.
9. Resources could be located too far from users.
10. Network management can become difficult for very large networks.