Irc (Internet Relay Chat)
Internet Relay Chat is a Unix-based Internet chat system that was created in 1988 by Jarkko Oikarinen of Finland. There was an earlier Unix-based program on the Internet called Talk--this program would connect two users at one time who were both logged in to their Unix accounts, possibly on different systems. A "talk window" appeared on a regular Unix shell, with a horizontal line that partitioned the window into two halves. Each user would see whatever he typed in one half, and whatever the other person typed in the other half. Although Talk was a successful program and remains installed on many systems, its utility was limited--it did not allow for the transfer of files during talk sessions, and more importantly, it did not afford a way to connect more than two users together at one time.
The IRC program that Oikarinen created solved these problems in a big way. Users now had to connect to a server, and the various IRC servers would connect with one another using regular Internet communication protocols. Users could communicate with one another through the servers. While each server had limits on how many users it would allow to sign on to it, there was no limit on the number of users who could be on IRC as a whole.
IRC has been used in many countries (within a few years of its creation, it had already been used in over 60), and is virtually synonymous with a multi-user online chat system, where users can congregate in specific "channels," each devoted to a certain topic. Any user may create a channel, except if a channel by that very name already exists. A creator of a channel comes in with privileges, and may invite others, or give other people "ops"--operator privileges--within the channel. Only an op can kick people and ban them from the channel, or change settings on a channel (such as by making a channel private and invite-only). An op can also give ops to other users.
IRC first became internationally famous during the 1991 Persian Gulf war, during which time wire service updates about the conflict and the situation in the U.S. and in the Gulf states were all posted to a single IRC channel, so that users who were online at the time could get virtually live updates from many different news sources. Next to CNN, this IRC channel was the most important source of live information. A similar situation occurred later the same year during the coup against Soviet leader Mikhail Gorbachev, and also during the coup against the Russian leader Boris Yeltsin in September 1993. Thus, although IRC had been intended as a source of leisure, it did prove to have its serious uses as well.
IRC is a client-server system in the classical sense—each user runs an IRC client, and there are servers that need to be accessed. The client passes messages on to the server, and the servers pass messages on to one another. Various types of client software exist, and it is possible for a user to download and install one of them. Unfortunately, many of the client programs that are freely available on the Net are known to contain Trojan horses (special backdoor features that enable an outsider to gain control over the client or the system running the client) and other forms of nefarious loopholes, so many sysadmins are wary of allowing users to install arbitrary IRC clients on their system. If installing a client, it is a good idea to peruse the source code carefully (if one is an expert programmer) to check whether it has any traps, and then compile and install the client oneself. Otherwise, one would need to verify in some other way that the client one is considering using is really clean and harmless.
Another type of IRC entity that is of interest to users is an IRC bot. A "bot" is a computer program, usually running under user's name or id, which exhibits specified behavior. For example, a bot can be programmed to repeat the Message Of The Day (MOTD) upon receipt of a particular command. Likewise, a bot can be used to manage a channel, by keeping ops, giving ops only to known and recognized users, and removing and banning offending users. Unfortunately, as bots can be used as tools to exert power, they are often sources of conflict, and can be used to "hack" or break into other people's channels, removing their ops and causing mayhem. For this reason, many servers do not allow users to run bots. A bot that is borrowed from another user will also likely contain a hook that its creator can use to control it; only bots that one has oneself coded from scratch could be called reliable. In general, one does not need bots to enjoy IRC, and only a very questionable set of priorities would cause one to spend time coding bots to break into other people's channels--after all, there is nothing really to be gained.
IRC is a good source for learning about common problems with the Internet, such as netsplits (when one set of servers is logically separated from the other, by being unable to communicate) and lag (delay in message transmission). These problems exist on the Internet always, but IRC makes users aware of them, and makes users appreciate their significance.
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