A multiplayer video game is one which more than one person can play in the same game environment at the same time. Unlike most other games, computer and video games are often single-player activities that pit the player against preprogrammed challenges and/or AI-controlled opponents, which often lack the flexibility and ingenuity of regular human thinking.
Multiplayer components allow players to enjoy interaction with other individuals, be it in the form of partnership, competition or rivalry, and provide them with a form of social communication that is almost always missing in single-player oriented games. In a variety of different multiplayer game types, players may individually compete against two or more human contestants, work cooperatively with a human partner(s) in order to achieve a common goal, supervise activities of other players, or engage in a game type that incorporates any possible combination of the above. Examples of better-known multiplayer gametypes include deathmatch and team deathmatch, MMORPG-associated forms of PvP and Team PvE, capture the flag, domination (competition over control of resources), co-op, and various objective-based modes, often expressed in terms of "assault/defend a control point". Multiplayer games typically require the players to share resources of a single game system or use networking technologies that allow players to play together over greater distances.
The first known examples of massively multi-player real time games based around real time networking were developed on the PLATO system starting around 1973. Important multiuser games developed on this system included Empire from 1973 and Spasim from 1974. The latter was a pioneering first-person shooter.
The first large scale serial sessions based around a single computer were STAR (based on the series Star Trek), OCEAN (a battle of ships, submarines and helicopters with multiple players divided up between the two combating cities) and CAVE (based on Dungeons and Dragons), created by Christopher Caldwell (with art work and suggestions by Roger Long and some assembly coding by Robert Kenney) in 1975 on the University of New Hampshire's DECsystem-1090. The University's computer system had hundreds of terminals connected via serial lines through cluster PDP-11s for student, teacher and staff access. The games worked by having one instance of the program running on each terminal (for each player), sharing a segment of shared memory (known as the "High segment" in the OS TOPS-10).
Due to their popularity, the games were frequently banned by the University's Computer Services since they could easily take up all available RAM and cycles.
STAR was based on the original single-user turn oriented BASIC program STAR written by Michael O'Shaughnessy at UNH in 1974.
Digital Equipment Corporation soon distributed another multi-user version of Star Trek called Decwars though not featuring real-time screen updating. Decwars was widely distributed to universities with DECsystem-10s.
In 1981, Cliff Zimmerman wrote a more detailed homage to Star Trek in Macro-10 for DECsystem-10s and -20s using VT100 series graphics. "VTtrek" pitted 4 Federation players against 4 Klingons in a three dimensional universe
MIDI Maze was an early first-person shooter released in 1987 for the Atari ST. It was unique in featuring network multiplayer through the MIDI interface long before mainstream Ethernet and Internet play became commonplace. It is considered the first multiplayer 3D shooter on a mainstream system and the first major network multiplayer action game, with support for as many as 16 players. It was followed up by ports to various platforms in 1991 under the title Faceball 2000, including the Game Boy and Super NES, making it possibly the first handheld and multiplatform first-person shooter and an early console example of the genre. 
In modern computer games, the word multiplayer usually implies that the players play together by connecting multiple computers via a network, usually either a LAN or the Internet. This form of multiplayer is sometimes called "netplay" to refine the meaning. The first popular videogaming title to release a LAN version was Doom in 1993, when the first network version of the game allowed a total of four simultaneous gamers. Playing networked multiplayer games via LAN often eliminates problems common in Internet play, such as lag and anonymity of players. As a result, multiplayer games usually are the focus of LAN parties. Play-by-email games are multiplayer games that use email as the method of communication between computers. Other turn-based variations which do not require players to be online at the same time are Play-by-post gaming and Play-by-Internet. Some online games are "massively multiplayer" games, which means that a large number of players participate simultaneously. The two major genres are MMORPG (massively multiplayer online role-playing game) such as World of Warcraft or EverQuest and MMORTS (massively multiplayer online real-time strategy).
Some networked multiplayer games do not even feature a single-player mode. For example, MUDs and massively multiplayer online games, such as RuneScape are multiplayer games by definition. First-person shooters have become very popular multiplayer games and games like Battlefield 1942 and Counter-Strike gained their fame despite not featuring extensive (or any) single-player plot or gameplay. The biggest MMOG in the world is Lineage out of South Korea with 14 million registered gamers which is played in several mostly Asian countries. The biggest Western MMOG in 2008 is World of Warcraft with over 10 million registered gamers worldwide. This category of games currently requires multiple machines to connect to each other over the Internet, but before the Internet became popular, MUDs were played on time-sharing computer systems, and games such as Doom were played on a LAN.
Gamers often refer to latency by the term ping, which measures round-trip network communication delays (by the use of ICMP packets). For example, a player on a DSL connection with a 50 ms "ping" will be able to react faster to game events than a modem user with 350 ms average latency. Another popular complaint is packet loss and choke, which can render a player unable to "register" their actions with the server. In first-person shooters, this problem usually manifests itself in the problem of bullets appearing to hit the enemy, but the enemy taking no damage. Note that the player's connection is not the only factor; the entire network path to the server is relevant, and some servers are slower than others. While latency is frequently complained about, many players believe a lack of finesse and decent tactics is more damaging than a slow connection in most games. Major and frequent variations in latency, however, can be another story; these can make it very difficult to properly play the game.
Starting with Sega Dreamcast in 2000, game consoles have also begun to support network gaming, over both the internet and LANs. Many mobile phones and handheld consoles also offer wireless gaming through Bluetooth or similar technologies.
As in all games, some players choose to cheat and gain an unfair advantage in online multiplayer games. This is often done by exploiting bugs, glitches or design limitations in the software. Games companies try to prevent cheating in a number of ways. Technologically, they use software such as PunkBuster or RSVP First which continually verifies that the game being played is unaltered. Games companies can also demand a subscription fee for access to the game network which is non-refundable, so they can effectively fine cheaters for cheating. They may also issue "patches" to the users of a certain game (usually via internet download) that effectively fix glitches in the code that cheaters often exploit to their advantage.
Even with the use of anti-cheat software, the FPS games are notorious for having the most cheats, which can sometimes turn people away from that type of game. This may be due in part because both clients and servers are run on private systems instead of on company owned servers. One of the most infamously hacked games is the original Diablo, a role-playing game with an online component. Another game is Aliens versus Predator 2 where hackers change memory variables to alter the game's programming.
Also another common method of cheating is in RTS games, where players are able to unlock game database files, and edit variables in them which often provide infinite amounts of a certain resource, unit, etc. For example, in Age of Mythology, which also suffers from the ajax hack, in which case players spawn the Ajax from the SPC campaign, it is not uncommon to find people exploiting the ESO game system to give them unlimited resources, then attacking before any other player is ready.
In modern console games, arcade games, and personal computer games, multiplayer usually implies that the players play together by using several controllers plugged into the same game system. Home console games often use split-screen so that each player has an individual view of the action (important for genres such as the first person shooter), although most arcade games and some console games (ranging from Pong to Super Smash Bros. Brawl) make use of a single play area for all players.
Single-system games may also involve several gamers taking turns playing on the same system using the same input devices, usually called hotseat. Examples of hotseat games include the Worms series and perhaps a game of Horse in Tony Hawk's Pro Skater or Matt Hoffman's BMX spin-off.
As many game consoles now support online or network gaming, split-screen is often supported in combination with these multi-system modes. For example, in a network or Internet game of Halo 3 on an Xbox 360 or Warhawk on the Playstation 3, four players may be playing in split-screen on each console in the network, for a total of 16 players in Halo 3, or 32 players in Warhawk.
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