CBSE Class 8 Computer Science Chapter 2

CBSE Class VIII Computer Science Chapter 2 – Computer Communication

Communication media connects resources to share information among users. Communication media is classified into two types: Guided media and Unguided media. In guided media, the computers are connected with each other through cables. Examples of guided communication are twisted pair cable, coaxial cable and fiber optic cable. In unguided media, the computers are connected with each other through waves. Examples of unguided communication are microwave, radio and satellite etc. 

Computer network is formed according to size, complexity and their geographical spread. It is mainly classified into three types: Local Area Network (LAN), Metropolitan Area Network (MAN) and Wide Area Network (WAN). LAN connects nodes over a short distance. MAN connects nodes over an area larger than a LAN but smaller than a WAN. WAN connects nodes over large geographical areas. Network topology defines the way to group computers to form a network. The commonly used topologies are bus, ring and star. In bus topology, the nodes are connected to a single backbone cable by a transceiver. In ring topology, each node is connected by the other to form a circular ring. In star topology, each node is connected to a central switch or hub.  

The data transmission mode defines the direction of the flow of information transmitted from one place to another place. The three modes of data transmission are: simplex mode, half-duplex mode and full-duplex mode. In simplex mode, the data transmission is unidirectional. In half-duplex mode, the data transmission can take place in both directions but in one direction at a time. In full-duplex mode, the data transmission can take place in both directions simultaneously.