Instant messaging (IM) allows real-time text communication between users over the internet or other networks. While similar to online chat, IM connects known contacts via buddy lists rather than allowing communication between anonymous users. IM was developed in the 1960s on early computer systems and gained popularity in the 1990s with services like AOL Instant Messenger. Today many social networks and platforms integrate IM capabilities.

1. Definition Definition IM falls under the umbrella term online chat , as it is a real-time text-based networked communication system, but is distinct in that it is based on clients that facilitate connections between specified known users (often using "Buddy List", "Friend List" or "Contact List"), whereas online 'chat' also includes web-based applications that allow communication between (often anonymous) users in a multi-user environment.

2. Overview Instant messaging (IM) is a collection of technologies used for real-time text-based communication between two or more participants over the Internet, or other types of networks. Of importance is that online chat and instant messaging differs from other technologies such as e-mail due to the perceived synchronicity of the communications by the users –chat happens in real-time. Some systems permit messages to be sent to people not currently 'logged on' ( offline messages ), thus removing some of the differences between IM and e-mail (often done by sending the message to the associated e-mail account). IM allows effective and efficient communication, allowing immediate receipt of acknowledgment or reply. In many cases instant messaging includes additional features which can make it even more popular. For example, users can see each other by using webcams, or talk directly for free over the Internet using a microphone and headphones or loudspeakers. Many client programs allow file transfers as well, although they are typically limited in the permissible file-size. It is typically possible to save a text conversation for later reference. Instant messages are often logged in a local message history, making it similar to the persistent nature of e-mails.

3. History Instant messaging predates the Internet, first appearing on multi-user operating systems like CTSS and Multics 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 in to the same machine.[ citation needed ] As networks developed, the protocols spread with the networks. Some of these used a peer-to-peer protocol (e.g. talk, ntalk and ytalk), while others required peers to connect to a server (see talker and IRC). 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.

4. In the last half of the 1980s and into the early 1990s, the Quantum Link online service for Commodore 64 computers offered user-to-user messages between currently connected customers which they called "On-Line Messages" (or OLM for short). (Quantum Link later became America Online and made AOL 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 up 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. As such, it could be considered a sort of GUI, albeit much more primitive than the later Unix, Windows and Macintosh based GUI IM programs. 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.

5. 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 type messages to each other. AOL later acquired Mirabilis, the creators 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 applications (Excite, MSN, Ubique, and Yahoo), 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.

6. In the current era, social networking providers often offer IM capabilities. Many instant messaging services offer video calling features, Voice Over IP (VoIP) and web conferencing services. Web conferencing services can integrate both video calling and instant messaging capabilities. 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, the instant messaging client formerly known as Gaim or gaim announced in April 2007 that they would be renamed "Pidgin".

7. Compliance risks In addition to the malicious code threat, the use of instant messaging at work also creates a risk of non-compliance to laws and regulations governing the use of electronic communications in businesses. In the United States alone there are over 10,000 laws and regulations related to electronic messaging and records retention.The better-known of these include the Sarbanes-Oxley Act, HIPAA, and SEC 17a-3.

8. Clarification from the Financial Industry Regulatory Authority ("FINRA") was issued to member firms in the financial services industry in December, 2007, noting that "electronic communications", "email", and "electronic correspondence" may be used interchangeably and can include such forms of electronic messaging as instant messaging and text messaging.Changes to Federal Rules of Civil Procedure, effective December 1, 2006, created a new category for electronic records which may be requested during discovery in legal proceedings. Most countries around the world also regulate the use of electronic messaging and electronic records retention in similar fashion to the United States. The most common regulations related to IM at work involve the need to produce archived business communications to satisfy government or judicial requests under law. Many instant messaging communications fall into the category of business communications that must be archived and retrievable.

9. User base October 2006 1 million total Meebo September 2006 1 million active (daily) Mail.ru Agent June 2007 1 million total IMVU unknown iChat December 2009 40 million total (licensed, entitled users in enterprises) IBM Lotus Sametime May 2009 Over 6 million active (majority in Poland) Gadu-Gadu mobile and PC Gizmo5 October 2006, including 4 million mobile users 35 million total eBuddy January 2006 >100 million total September 2006 53 million active AIM Date/source User count Service

10. Facebook statistics Claimed 400 million users Facebook unknown users. Chat within Gmail, iGoogle, and orkut, All on the web, PC and Mac Google Talk 17 Jan 2008 248 million active registered Yahoo global users (refers to ALL Yahoo users not Instant Messaging users) Yahoo! Messenger May 2010 16 million total Xfire June 2009 330 million active Windows Live Messenger (previously MSN Messenger ) December 2008 >550,000 VZOchat 29 Oct 2009 990 million total registered accounts. (majority in China) 29 Oct 2009 440 million active accounts (includes users with multiple accounts). (majority in China) 29 Oct 2009 61.3 million peak online (majority in China) Tencent QQ April 2008 309 million total October 2009 19 million peak online Skype February 2007. Note that these users are part of the IRC user base, messaging user base consists of a few hundred users 1 million active (daily) (majority in Brazil) PSYC August 2006 3.3 million unique visitors per month Paltalk

11. 資料來源 http://en.wikipedia.org/wiki/Instant_messaging