 The Internet is the huge network of computers that links many different types of computers all over the world.  It is a network of networks that shares common mechanism for addressing (identifying) computers and a common set of communication protocols for communications between two computers on the network.

 The Internet has its root in the ARPANET system of the Advanced Research Project Agency of the U.S. Department of Defense.  ARPANET was the first WAN and had only four sites in  The Internet evolved from the basic ideas of ARPANET for interconnecting computers and was initially used by research organizations and universities to share and exchange information.

 Personal computers or terminals were connected to a server.  The server was a mainframe, or connected to a mainframe computer.  The mainframe was connected to another mainframe of the company in another location via dedicated lines.  Only large companies could afford the expense and investment in equipment.

 In 1989, the U.S. Govt. lifted restrictions on the use of the internet and allowed it to be used for commercial purposes as well.  Since then, the Internet has rapidly grown to become the world’s largest network.

 Mainframes: - term for very large computers - used to handle large amount of data or complex processes - main advantage is reliability  Midrange: - medium sized, less expensive and smaller - usually a server  Micro-computer: - work stations with computing capabilities - single-users systems linked to form a network

7  Series of points or nodes interconnected by communication paths  Node is a connection point for transmitting data  Network can interconnect with other networks to form global networks

8  Facilitates resource sharing  Provides reliability  Cost effective  Provide a powerful medium across geographical divid e

9  Type of signal  Nature of connection  Types of physical links  Topology  Communication model  Geographical distance

10  Local area network (LAN): small area, share a single server  Metropolitan area network (MAN): a wider network, can bridge several LAN’s  Wide area network (WAN): a broader area covered, can include several MAN’s  Internet: a network of networks that covers the entire globe

11  Allows any two computers to communicate and exchange data.  The Internet transfers data packets among computers.  Each packet is identified by the sender address and a receiver address.  The sender´s computer transfers the data packet to another computer on the Internet, which transfers it to a chain of other computers until it reaches the final destination.

12  Internet uses TCP/IP, therefore every computer on the Internet has an IP address  IP address is numerical, separated by dots  Works with DNS: - com: for commercial purposes - net: for Internet Service Providers - org: for non-profit, non-commercial groups - gov: reserved for government - mil: reserved for military - int: reserved for international organizations

13  Technology first adopted to increase efficiency – doing the same tasks faster e.g. word processing instead of typing  Technology next adopted to increase effectiveness – doing tasks not only faster but better e.g. spreadsheets transformed finance and accounting (as well as science and other fields)