host), a user would use a port number to select one of them. By default, WWW servers are on port 80. Other protocols have different ports (e.g., the default for FTP is 21). Most users never need to know about port numbers.Domain Name System (DNS). Another method used to help find an Internet address is the DNS. This system became a part of the Internet in the early 1980's. It is a distributed database that computers can use to find the IP address of any computer registered in the DNS database.The DNS works on a hierarchy where each organization has responsibility to manage their own part of the DNS and must provide name server computers, which provide the address information as requested. Therefore, when a computer needs to find the address of a particular computer, it goes one of the top level or root domain name server computers that are run by the Internet Authority and distributed around the world. These computers then direct the querying computer to the most appropriate name server to answer the query. These second level domain name server computers are usually responsible for the names for a particular class of domain name (com, edu, org) or for a country's domain names (au, uk, nz, sg).Now that you know what is an Internet address, we can look at client applications.What Client Applications Can be Used on the Internet?Useful client software applications that can be used on the Internet includeHypertextBrowsersE-mailHypertextHypertext provides the links between different documents and different document types. In a hypertext document, links from one place in the document to another are included with the text. By selecting a link, you are able to jump immediately to another part of the document or even to a different document. Moreover, in the WWW, links can go not only from one document to another but also from one computer to another.URLs provide the hypertext links between one document and another. Links can access a variet...
