Zork

Zork is a text-based adventure game, first released in 1977 by developers Tim Anderson, Marc Blank, Bruce Daniels, and Dave Lebling for the PDP-10 mainframe computer. It was expanded by the original developers and others as Infocom and split into three titles—Zork I: The Great Underground Empire, Zork II: The Wizard of Frobozz, and Zork III: The Dungeon Master—which were released commercially for a variety of personal computers beginning in 1980. In the game, the player explores the abandoned Great Underground Empire in search of treasure. The game is composed of hundreds of areas, and the player moves between these areas and interacts with objects in them by typing commands which are interpreted by the game's natural language input system. The program acts as a narrator, describing the player's location and the results of the player's attempted actions. It has been described as the most famous piece of interactive fiction.

The original game, developed between 1977 and 1979 at the Massachusetts Institute of Technology (MIT), was inspired by Colossal Cave Adventure (1976), the first well-known example of interactive fiction and the first well-known adventure game. The developers wanted to make a similar game that was able to understand more complicated sentences than Adventure's two-word commands. They and several other staff and students at the MIT computer center founded Infocom in 1979 to develop software programs, and Blank and Joel Berez created a way to run a smaller portion of Zork on a microcomputer. The parts of Zork were Infocom's first products. The first episode was published by Personal Software in 1980, after which Infocom purchased back the rights and self-published all three episodes beginning in late 1981.

Zork was a massive success for Infocom, with sales increasing for years as the market for personal computers expanded. The first episode sold over 38,000 copies in 1982, and around 150,000 copies in 1984. Collectively, all three episodes sold more than 680,000 copies through 1986, making up over a third of Infocom's sales in the time period. Several more games in the Zork series were released beginning in 1987, as well as books and gamebooks. Reviews of the episodes were very positive, with several reviewers calling them the best adventure game to date. It is regarded as one of the greatest games of all time, based on its prevalence on such lists by critics. Later historians have noted the game as having a large influence on the adventure game genre of the time, and along with Adventure influencing the MUD genre and through it the more recent massively multiplayer online role-playing game genre. In 2007, Zork was named to a list of the ten most important video games of all time, which formed the start of the game canon at the Library of Congress.

Zork is a text-based adventure game wherein the player explores the ruins of the Great Underground Empire (GUE) to find treasure. The player must explore the varied locations and solve puzzles by using items that they find to obtain the treasures and leave the underground empire. The player types in commands to move their character through the locations, interact with objects in the cave, pick up items to put into their inventory, and perform other actions. These commands can be one- or two-word commands like "get lantern" or can be more complex sentences like "put the lamp and sword in the case". The allowable commands are contextual to the area, or room, the player is in; for example, "get lamp" only has an effect if there is a lamp in the area. There are hundreds of rooms, each of which has a name such as "West of House" and a description, and may contain objects, obstacles, or creatures. The program acts as a narrator, describing to the player their location and the results of certain actions. If the game does not understand the player's commands, it asks for the player to retype their actions. The program's replies are typically in a sarcastic, conversational tone, much as a Dungeon Master would use in leading players in a tabletop role-playing game.