1. Supercomputer

1. Wide Area Networks (WAN) have a national or global reach. With satellite technology, WANs can connect nodes that have no physical connection to one another. The Internet is the best example of a WAN — a global network of networks.
2. Metropolitan Area Networks (MAN) have a larger geographical range, connecting nodes in separate buildings within a few miles of each other. Cellular phone systems are good examples of MANs. In order to have national coverage, the cellular company connects all of its MANs into a larger network, known as a WAN.
3. Local Area Networks (LAN) connect nodes that are in close physical proximity to each other — in the same office or building for example. Most of the examples we use throughout this lesson refer to LANs. 2 forms of LANs are as follows:
1. Client/server LAN: consists of microcomputers requesting data and service (clients) and powerful computers supplying data and service (servers).
2. Peer-to-peer LAN: there is no server; PCs on a network communicate with each other directly.
4. Intranets and Extranets
Intranets and extranets are special types of networks that use the same technology as the World Wide Web. Data is stored on servers and is communicated via the TCP/IP protocol. If the Internet is the global village, then intranets and extranets are private, gated communities within that village. As an authorized user, you can access the intranet or extranet through your regular browser, but if you aren't an authorized user, you won't be able to get past the gate.
Intranets are commonly used for internal communications in corporations or educational institutions. Strictly speaking, an intranet does not allow any access from the outside Internet. Only computers connected to the internal network can connect to the intranet. Once you allow authorized external users to connect to an intranet, it becomes an extranet. An extranet is still restricted, but allows access by certain networks, computers, or individual users.
5. Command line interface, graphical user interface (GUI)
1. The user interface is the display screen that enables user interaction with the computer via keyboard or via the mouse, which has an onscreen pointer. You send commands to the operating system through the user interface. Early operating systems such as MS-DOS and UNIX used a command line interface to send commands. With a command line interface, the user types instructions to the operating system. Because command line operating systems understand only certain commands, they can be difficult to learn and require some programming skills.