Instant messaging (IM) is a type of online chat which offers real-time text transmission over the Internet. A LAN messenger operates in a similar way over alocal area network. Short messages are typically transmitted bi-directionally between two parties, when each user chooses to complete a thought and select "send". Some IM clients can use push technology to provide real-time text, which transmits messages character by character, as they are composed. More advanced instant messaging can add file transfer, clickable hyperlinks, Voice over IP, or video chat.
Non-IM types of chat include multicast transmission, usually referred to as "chat rooms", where participants might be anonymous or might be previously known to each other (for example collaborators on a project that is using chat to facilitate communication). Instant messaging systems tend to facilitate connections between specified known users (often using a contact list also known as a "buddy list" or "friend list"). Depending on the IM protocol, the technical architecture can be peer-to-peer (direct point-to-point transmission) or client-server (a central server retransmits messages from the sender to the receiver).
Though the term dates from the 1990s, instant messaging predates the Internet, first appearing on multi-user operating systems likeCompatible Time-Sharing System (CTSS) and Multiplexed Information and Computing Service (Multics)[1] in the mid-1960s. Initially, some of these systems were used as notification systems for services like printing, but quickly were used to facilitate communication with other users logged into the same machine. As networks developed, the protocols spread with the networks. Some of these used a peer-to-peerprotocol (e.g. talk, ntalk and ytalk), while others required peers to connect to a server (see talker and IRC). The Zephyr Notification Service(still in use at some institutions) was invented at MIT's Project Athena in the 1980s to allow service providers to locate and send messages to users. During the bulletin board system (BBS) phenomenon that peaked during the 1980s, some systems incorporated chat features which were similar to instant messaging; Freelancin' Roundtable was one prime example. The first[2] dedicated online chat service was the CompuServe CB Simulator in 1980,[3] created by CompuServe executive Alexander "Sandy" Trevor in Columbus, Ohio.
Early instant messaging programs were primarily real-time text, where characters appeared as they were typed. This includes the Unix"talk" command line program, which was popular in the 1980s and early 1990s. Some BBS chat programs (i.e. Celerity BBS) also used a similar interface. Modern implementations of real-time text also exist in instant messengers, such as AOL's Real-Time IM[4] as an optional feature.[5]
In the latter half of the 1980s and into the early 1990s, the Quantum Link online service for Commodore 64 computers offered user-to-user messages between concurrently connected customers, which they called "On-Line Messages" (or OLM for short), and later "FlashMail." (Quantum Link later became America Online and madeAOL Instant Messenger (AIM), discussed later). While the Quantum Link service ran on a Commodore 64, using only the Commodore's PETSCII text-graphics, the screen was visually divided into sections and OLMs would appear as a yellow bar saying "Message From:" and the name of the sender along with the message across the top of whatever the user was already doing, and presented a list of options for responding.[6] As such, it could be considered a type of graphical user interface (GUI), albeit much more primitive than the later Unix, Windows and Macintosh based GUI IM software. OLMs were what Q-Link called "Plus Services" meaning they charged an extra per-minute fee on top of the monthly Q-Link access costs.
Modern, Internet-wide, GUI-based messaging clients as they are known today, began to take off in the mid-1990s with PowWow, ICQ, and AOL Instant Messenger. Similar functionality was offered by CU-SeeMe in 1992; though primarily an audio/video chat link, users could also send textual messages to each other. AOL later acquired Mirabilis, the authors of ICQ; a few years later ICQ (now owned by AOL) was awarded two patents for instant messaging by the U.S. patent office. Meanwhile, other companies developed their own software; (Excite, MSN, Ubique, andYahoo!), each with its own proprietary protocol and client; users therefore had to run multiple client applications if they wished to use more than one of these networks. In 1998, IBM released IBM Lotus Sametime, a product based on technology acquired when IBM bought Haifa-based Ubique and Lexington-based Databeam.
In 2000, an open source application and open standards-based protocol called Jabber was launched. The protocol was standardized under the name Extensible Messaging and Presence Protocol(XMPP). XMPP servers could act as gateways to other IM protocols, reducing the need to run multiple clients. Multi-protocol clients can use any of the popular IM protocols by using additional local libraries for each protocol. IBM Lotus Sametime's November 2007 release added IBM Lotus Sametime Gateway support for XMPP.
As of 2010, social networking providers often offer IM abilities. Facebook Chat is a form of instant messaging, and Twitter can be thought of as a Web 2.0 instant messaging system.
Many instant messaging services offer video calling features, voice over IP and web conferencing services. Web conferencing services can integrate both video calling and instant messaging abilities. Some instant messaging companies are also offering desktop sharing, IP radio, and IPTV to the voice and video features.
The term "Instant Messenger" is a service mark of Time Warner and may not be used in software not affiliated with AOL in the United States. For this reason, in April 2007, the instant messaging client formerly named Gaim (or gaim) announced that they would be renamed "Pidgin".
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