There is no doubt that the Internet has changed the way we communicate. For many of us, e-mail has virtually replaced traditional letters and even telephone calls as the choice for correspondence. Every day, billions of e-mail messages are sent out. E-mail has been the most rapidly adopted form of communication ever known. In less than two decades, it has gone from obscurity to mainstream dominance.

America Online's Instant Messenger (AIM) program is one of the most popular instant messaging utilities available.

In our fast-paced world, sometimes even the rapid response of e-mail is not fast enough. You have no way of knowing if the person you are sending e-mail to is online at that particular moment or not. Also, if you are sending multiple e-mails back and forth with the same person, you normally have to click through a few steps to read, reply and send the e-mail. This is why instant messaging (IM) has gained popularity.

Instant messaging allows you to maintain a list of people that you wish to interact with. You can send messages to any of the people in your list, often called a buddy list or contact list, as long as that person is online. Sending a message opens up a small window where you and your friend can type in messages that both of you can see.

Most of the popular instant-messaging programs provide a variety of features:

• Instant messages - Send notes back and forth with a friend who is online
• Chat - Create your own custom chat room with friends or co-workers
• Web links - Share links to your favorite Web sites
• Images - Look at an image stored on your friend's computer
• Sounds - Play sounds for your friends
• Files - Share files by sending them directly to your friends
• Talk - Use the Internet instead of a phone to actually talk with friends
• Streaming content - Real-time or near-real-time stock quotes and news

In this edition of HowStuffWorks, you will learn about the history of instant messaging and how it works. You will also learn what the major IM programs are, what makes them different from each other and what the future holds for IM.

Background
Before the Internet became popular, a lot of people were already online through the use of bulletin boards and online services. A bulletin board is comparable to a single, isolated Web site that you reach using special communications software and a modem. You create an entry in the software for the bulletin board that contains the board's direct phone number and any special parameters for connecting to the computer hosting the bulletin board. Once connected to the board, you normally use a series of menus to navigate through the board's contents. To reach another board, you have to disconnect from the first board and dial up to the other one.

Major online services, such as America Online (AOL), Prodigy and CompuServe, were the main way that ordinary people could connect and communicate with each other online. Think of an online service as a very sophisticated bulletin board. Whereas most small bulletin boards use standard communications software, online services provide a complete application that includes the communications software necessary to connect to their service. This application also includes the actual interface that you use once you are online and connected to the service. This allows the online service to create a very sophisticated and targeted experience for their users.

Probably one of the biggest attractions of the online service model is the community that it builds. AOL is considered the pioneer of the online community. AOL provides its users with the ability to talk in real-time with each other while they are online through the use of chat rooms and instant messages. A chat room is software that allows a group of people to type in messages that are seen by everyone in the "room," while instant messages are basically a chat room for just two people.

In the early 1990s, as people began to spend increasing amounts of time on the Internet, creative software developers designed software that could reproduce some of the aspects of an online service. Chat-room software was developed and set up on Web servers, used by sites like TalkCity.

Instant messaging really exploded on the Internet scene in November 1996. That's when Mirablis, a company founded by four Israeli programmers, introduced ICQ, a free instant-messaging utility that anyone could use.

ICQ
ICQ, a combination of letters that is shorthand for the phrase "I seek you," is a real-time tool that uses a software application, called a client, that resides on your computer. The client communicates with an ICQ server whenever you are online and the client is running.

ICQ was one of the first available IM programs.

Look at the steps below to understand exactly what happens with ICQ.

1. You go to the download page (www.icq.com) for ICQ and get a copy of the free software client for your computer.
2. You install the software and open the client.
3. The client tries to connect to the ICQ server. It uses a proprietary protocol, ICQ v5, for communication.
4. Once the client is connected to the server, you can enter your name and password to log in to the server. If this is your first time on, you can sign up for an account and immediately begin using it. When the server verifies your name and password, you are logged in.
5. The client sends the server the connection information (IP address and number of the port assigned to the ICQ client) of the computer you are using. It also provides the user with the names of everyone in your ICQ contacts list.
6. The server creates a temporary file that has the connection information for you and the list of your contacts. It then checks to see if any of the users in your contact list are currently logged in.
7. If the server finds any of your contacts logged in, it sends a message back to the ICQ client on your computer with the connection information for that user. The ICQ server also sends your connection information to the people in your contact list that are signed on.
8. When your ICQ client gets the connection information for a person in your contact list, it changes the "status" of that person to "Online."

The ICQ message window provides more details about your session than other IM utilities do.

9. You click on the name of a person in your contact list who is online, and a window opens that you can enter text into. You enter a message and click "Send" to communicate with that person.
10. Because your ICQ client has the IP address and port number for the computer of the person that you sent the message to, your message is sent directly to the ICQ client on that person's computer. In other words, the ICQ server is not involved at this point. All communication is directly between the two clients.
11. The other person gets your "instant message" and responds. The ICQ window that each of you see on your respective computers expands to include a scrolling dialog of the conversation. Each person's instant messages appears in this window on both computers.
12. When the conversation is complete, you close the message window. Eventually, you go offline and exit ICQ. When this happens, your ICQ client sends a message to the ICQ server to terminate the session. The ICQ server sends a message to the ICQ client of each person on your contact list that is currently online to indicate that you have logged off. Finally, the ICQ server deletes the temporary file that contained the connection information for your ICQ client. In the ICQ clients of your contacts that are online, your name moves to the "Offline" status section.

While some of the details vary between utilities, the basic steps outlined above for ICQ apply to all of the other IM utilities on the market today. ICQ is still very popular. In fact, Mirablis was acquired in June 1998 by AOL, and ICQ became part of the suite of online services that AOL owns.

AIM
Not long after ICQ established the popularity of IM, AOL decided to enter the fray. Within a very short time, AOL Instant Messenger (AIM) supplanted ICQ as the leading IM utility.

Like all of the other major IM utilities, AIM uses a proprietary protocol that is not understood by other instant-messaging services. A key reason why AIM is so popular is that it allows AOL members to communicate with non-members -- other IM utilities have not been able to provide this link between AOL and the rest of the Internet. With more than 20 million subscribers to AOL, this is no small matter. In fact, one of the provisions of the recent AOL-Time Warner merger was that other services be allowed access to the AOL community and AIM protocol.

Customizing AIM is easy.

It is important to note that instant messaging is not considered a secure way to communicate. Messages and connection information are maintained on servers controlled by the provider of the IM utility that you use. Most utilities do provide a certain level of encryption, but they are not so secure that you should send any confidential information through the system. There have been reported cases of IM user logs being captured and used by nefarious sorts.

More IM Utilities
Although AIM and ICQ are the leaders in the IM race, there are several other worthy entrants. Microsoft's MSN Messenger, like other IM programs, allows you to talk with another MSN Messenger user just like you would over the telephone. You and the person you wish to talk to must each have a sound card, microphone and speakers to use this feature.

Detail of the MSN menu bar

Another IM utility that has been around for a while is Yahoo! Messenger. The interesting thing about Yahoo! Messenger is how well it integrates with other Yahoo! content and services. There are several utilities, such as Odigo and Omni, that combine various services. Odigo allows you to combine AIM, ICQ and Yahoo! Messenger contact lists. Omni lets you combine the functionality of AIM, ICQ, MSN Messenger and Yahoo! Messenger, plus file-sharing utilities, all in one program!

Yahoo!

The future of instant messaging is very bright. All of the utilities described in this article continue to be updated by their owners. And the Internet Engineering Task Force (IETF) is developing a standard protocol for instant messaging, called the Instant Messaging and Presence Protocol. Business users are discovering that instant messaging allows them to have virtual conferences and collaborate on projects very easily. In other words, if you have not tried IM, you're missing out on a whole new world of communication.