The computer organizing a transaction must identify its intended destination with a unique address. Every computer on the Internet has a 4-part numeric address, called the IP (Internet Protocol) address. The IP address contains routing information that identifies destination location. Each of the four parts is a number between 0 and 255, so an IP address looks like this: 108.64.125.116.

Computers have no trouble working with such numbers, but humans are not so skilled. Therefore, computers connected to the Internet use an address system called a Domain Name System (DNS), where and address uses words instead of numbers.

DNS address have two parts: an user name, followed by a domain that identifies the type of institution that uses the address, such as .com for commercial or .edu for schools, colleges, and universities. Microsoft’s DNS address is Microsoft.com and Google’s DNS address is google.com. Within the United States, the last three letters of the domain usually tell the types of institution. The following table lists the most common types.

Domains	Types of organization
.com	(Business) Commercial
.edu	Educatonal
.gov	US Government
.mil	US Military
.net	Gateway or host
.org	Other organization

Large institutions and big corporations may divide their domain address into smaller sub-domains. A business with many branches might have a sub-domain for each office. Sub-domains may be broken into even smaller sub-domains, like: du.bangla.net. Outside the United States, domains usually identify the county in which the system is located, such as .in for India, .jp for Japan, .ca for Canada or .fr for France. A geographic domain address may include a sub-domain. An example could be: www.telemagazine.ac.uk.

DNS and IP address identify individual computers. A single computer might have many users, each of whom must have an account. Some of the largest domains may have huge number of different user names. When a message is sent to a person that person’s user name is the address identifies the recipient. The standard format is: the user name first, “at” symbol @, and finally the DNS address. Therefore, Imran’s e-mail address might be: Imran@titas.com.

Electronic-mail:

The most common use of the Internet is for the e-mail. Anyone with an e-mail account can send messages to other users of the Internet. Most e-mail programs also permit users to attach data files and program files to messages. E-mail is not a live connection between the sender of a message and its recipient. There is always a delay between the sending time of a message and its arrival time at the distention. Sometimes that delay is just a few seconds, but it is always there.

When a message is sent the computer presses it to a post office server, which identifies the destination address and passes it through the Internet to a mail server, where the message is stored in a mailbox until the recipient looks for it. The sender computer creates the message and sends it to a local post office server. The post office server passes the message through the Internet to the recipient’s mail server which passes it to the recipient’s computer. E-mail programs generally combine the following features.

• A text editor for writing and editing messages.
• Arrangements for storing names and e-mail addresses.
• Ability to send messages to a post office server.
• Ability to get messages from a mail server.
• A manager that organizes and stores the sent and received messages.

There is an e-mail program included in Windows 98 and many others are available separately. One of the most popular e-mail programs is Eudora, which exists in versions for both Windows and Macintosh operating systems. Besides one-to-one, Internet e-mail is also used for one-to-many, in which the same message goes to a list of names.