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Publisher(s)Personal Software
Designer(s)Tim Anderson
Marc Blank
Dave Lebling
Bruce Daniels
Release1977 (PDP-10)
1980 (Zork I)
1981 (Zork II)
1982 (Zork III)
Genre(s)Text adventure

Zork is an interactive fiction computer game. It was originally developed by four members of the MIT Dynamic Modelling Group — Tim Anderson, Marc Blank, Bruce Daniels, and Dave Lebling — between 1977 and 1979 for the DEC PDP-10 mainframe computer.[1][2][3] The four founded the company Infocom in 1979 and released Zork as a commercial game for personal computers, split into three parts due to memory limits of personal computers compared to the mainframe system. The three titles released commercially were Zork: The Great Underground Empire – Part I in 1980 (later known as Zork I), Zork II: The Wizard of Frobozz in 1981, and Zork III: The Dungeon Master in 1982.[4] The game has since been ported to numerous systems.

Zork was directly inspired by the first text adventure game, Colossal Cave Adventure, written in 1975. Zork distinguished itself in its genre as an especially rich game, in terms of both the quality of the storytelling and the sophistication of its text parser, which was not limited to simple verb-noun commands ("hit troll"), but recognized some prepositions and conjunctions ("hit the troll with the Elvish sword").[5]



Zork is set in "the ruins of an ancient empire lying far underground". The player is a nameless adventurer "who is venturing into this dangerous land in search of wealth and adventure". The goal is to return from exploring the "Great Underground Empire" (GUE, for short) alive and with all treasures needed to complete each adventure,[6] ultimately inheriting the title of Dungeon Master. The dungeons are stocked with many novel creatures, objects, and locations, among them the ferocious but light-fearing grues, zorkmids (the GUE's currency), and Flood Control Dam #3—all of which are referenced by subsequent Infocom text adventures.

FrobozzCo International is a fictional monopolistic conglomerate from the game.[6] FrobozzCo products are littered throughout all Zork games, often to humorous effect.

Several treasures and locations in Zork reveal that there used to be a large aristocratic family called the Flatheads, who reigned supreme over the GUE. There were twelve rulers from this family, one of whom, King Mumberthrax the Insignificant, had twelve sons of his own, who are referenced in the book The Lives of the Twelve Flatheads.[6] With the exception of his first son and successor, Lord Dimwit Flathead, Mumberthrax's children are named after historical figures. For example, in Zork II, one treasure is a portrait of "J. Pierpont Flathead".

In each game, there are several light sources the player can pick up and use, among them a battery-powered brass lantern and a pair of candles, which both have a limited lifespan, as well as a torch that never expires. The player must be carrying at least one light source at all times when exploring the dark areas of the games,[6] or else, if they continue navigating through the dark, the player will be caught and devoured by a carnivorous grue, ending the adventure in defeat. The exception to this rule occurs when the player must use a spray can of grue repellent to navigate dark areas where a light source cannot be brought.


The original MIT version of Zork (also called Dungeon) combines plot elements from all three of the following games, which were made available for commercial sale.

Zork I: The Great Underground Empire[edit]

The game takes place in the Zork calendar year 948 GUE (although the passage of time is not notable in gameplay). The player steps into the deliberately vague role of an "adventurer". The game begins near a white house in a small, self-contained area. Although the player is given little instruction, the house provides an obvious point of interest.

Zork II: The Wizard of Frobozz[edit]

The player begins in the Barrow from Zork I armed only with the trusty brass lantern and the elvish sword of great antiquity from before. The objective of the game is not initially clear, but the player is pursued throughout by the titular wizard.

Zork III: The Dungeon Master[edit]

The player begins at the bottom of the Endless Stair from Zork II.

Zork III is somewhat less of a straightforward treasure hunt than previous installments. Instead, the player—in the role of the same "adventurer" played in Zork I and Zork II—must demonstrate worthiness to assume the role of the Dungeon Master.


In the Zork games, the player is not limited to verb-noun commands, such as "take lamp", "open mailbox", and so forth. Instead, the parser supports more sophisticated sentences such as "put the lamp and sword in the case", "look under the rug", and "drop all except lantern".[7] The game understands many common verbs, including "take", "drop", "examine", "attack", "climb", "open", "close", "count", and many more. The games also support commands to the game directly (rather than taking actions within the fictional setting of the game) such as "save" and "restore", "script" and "unscript" (which begin and end a text transcript of the game text), "restart", and "quit".[6]

You could modify the amount of information displayed on screen, in each room, and subsequent return to the same room, by commands "brief," "superbrief" and "verbose." "brief" would give a moderate room or item description on the initial visit, and a bare minimum on subsequent visits, "Superbrief" would only give a room title for each and every visit, while "verbose" would supply "Maximum Verbosity" by giving all available information in each room, or item thereof, or revisit thereafter.[6]


Colossal Cave[edit]

The first adventure game, Colossal Cave Adventure, was written by Will Crowther in FORTRAN on the DEC PDP-10 at BBN in 1975. Colossal Cave is a basic treasure hunt that takes place in an analog of Mammoth Cave. The game uses a simple two-word parser that later adventure games imitated. PDP-10 users quickly spread Colossal Cave around their community, including a Stanford University computer used by Don Woods in 1976. Woods contacted Crowther and received his permission to make an improved version which also spread to many locations, including the PDP-10 systems at MIT.[8]

Zork and Dungeon[edit]

4.3 BSD from the University of Wisconsin, running Zork and displaying the introductory leaflet for "Dungeon"

Dave Lebling, a member of the Dynamic Modelling Group (DM) at MIT's Laboratory for Computer Science,[9] recalled that after Colossal Cave reached MIT, "For a couple of weeks, dozens of people were playing the game and feeding each other clues ... Everyone was asking you in the hallway if you had gotten past the snake yet." In the spring of 1977, wanting to play more such games—and believing that they could improve on Colossal Cave—Lebling, Marc Blank, and Tim Anderson decided to write one in MDL (referred to as "muddle")[10] on their PDP-10 running the ITS operating system. Muddle is a LISP-based system that provided powerful string manipulation, so while the two games are similar in using text commands for input and exploration, Zork is much more advanced technically, allowing longer and more specific commands. Zork also uses a completely new map that was designed in multiple areas with their own stories and self-contained puzzles, whereas Cave is purely exploratory. While Colossal Cave has been referred to as a simulation of Mammoth Cave, Zork has been described as a simulation of Colossal Cave,[11] but much more sophisticated; The Boston Globe in 1984 stated that "Zork bore about the same relationship to Adventure as the splashiest arcade games do to the little white light that bounced through the primitive Pong".[10]

By the summer of 1977 the DM group's game was runnable, although only about one-half its final 1 MB size. The team's members, now referring to themselves as the "imps" ("implementers"), continued to add new sections to the map. The game initially ran only on ITS, but a port of muddle to TENEX was available, which the imps adapted to run on TOPS-20 after they were granted an account on a machine running it. This version became widely available on ARPANET, and a mailing list dedicated to the game appeared. During the fall the final sections were added, along with the D&D-inspired combat system, and the game was essentially complete.[9] The imps continued working on the game over the next year, adding areas and puzzles, with major development completed by the fall of 1978. The last addition was not made until February 1979 but development continued on bug fixes and touchups, with the last mainframe release in January 1981.[9]

The word "Zork" is a nonsense word, often used by MIT hackers as the name for any unfinished program until they were ready to be installed on the system.[10][2][12][13] With the game complete, in 1978 the imps renamed the game Dungeon; by this time it was popular among gamers. That year the developers received notice from TSR Hobbies, the publishers of Dungeons and Dragons, claiming the game violated their trademark; the name was changed back to Zork.[9][14]

Fortran port[edit]

While being developed at DM, the game's source code was protected by encrypting the files and patching the machine's copy of ITS to not allow access to the directory containing the source code. Digital Equipment Corporation programmer Ted Hess[15] repatched the OS to allow access to the directory, copied the source directory to a TOPS-20 machine, and used a brute-force attack to decrypt the files. Bob Supnik, also at DEC, used the decrypted source to create a Fortran IV port, which allowed the game to run on the smaller PDP-11.[4][16] Supnik released his version in January 1978,[17] which was ported to many platforms. The source for these versions were taken in the era when the original game was still known as Dungeon.[9][14] The Fortran version of Dungeon was widely available on DEC VAXen, being one of the most popular items distributed by DECUS,[12] and incorporated features and changes from the original muddle version. In the late 1980s the Fortran version was extensively rewritten for VAX Fortran and became fully compatible with the last MDL release. It has one extra joke: an impassable entrance to the Mill, a reference to DEC's Maynard, Massachusetts headquarters. It also has a gdt command (game debugging technique, a reference to the DDT debugger) which enables the player to move any object (including the player) to any room. Use of gdt requires answering a random question requiring deep knowledge of the game. The game's response to a wrong answer ("A booming voice says 'Wrong, cretin!' and you notice that you have turned into a pile of dust") appears in many "fortune cookie" databases.

The Fortran version was also included in the distribution media for some Data General operating systems. It was used as an acceptance test to verify that the OS had been correctly installed. Being able to compile, link, and run the program demonstrated that all of the run-time libraries, compiler, and link editor were installed in the correct locations.

A Fortran version was running in an IBM 370 port in the Constituyentes Atomic Center, Argentina, around 1984.

Infocom forms[edit]

In 1979 three of the four original imps founded Infocom as a general programming firm.[9] Two other members of the DM team, Joel Berez and Marc Blank, convinced the founders that it was possible to sell Zork commercially on new personal computers. Such systems, however, did not support MDL, usually did not have a Fortran compiler, and used floppy disk systems storing about 180 kB or even using cassette tapes for storage.[4] Berez and Blank came up with the idea of creating a new computer programming language, "Zork Implementation Language" or "ZIL", which would run within a virtual machine known as the Z-machine. The Z-machine would be ported to various platforms in shells known as the "Z-machine Interpreter Program" or ZIP. Using rented time on a TOPS-20 machine, they built the first ZIP in 1979.[4]

To solve the problem of storage space, they first considered using data compression but decided to remove sections of the game until it would fit on a floppy disk. Dave Lebling drew a circle on the Zork map so it contained about half of the original map, about 100 or so locations including everything above ground and a large section surrounding the Round Room. The map was modified to make it more logical and seal off exits that led to no longer-existing areas.[4]

Berez became the president of Infocom. The new game was running on TOPS-20 ZIP and a new PDP-11 version of the Z-machine by the end of 1979. Scott Cutler created a TRS-80 version of ZIP in early 1980, and in February the company demonstrated Zork to Personal Software (PS), the distributors of VisiCalc and likely the first software distribution firm for microcomputers. PS agreed to distribute the game in June.

Sales begin[edit]

Zork being played on a Kaypro computer

PS had no interest in the PDP-11 version so Infocom retained the distribution rights; it became the first official sale for the company in November 1980, when it shipped a copy on 8-inch floppy along with a hand-copied version of the manual. Sales of the TRS-80 version through PS began the next month, selling 1,500 copies over the next nine months. Bruce Daniels' Apple II version began sales in February 1981 and PS sold 6,000 copies by September.[4]

After Zork began shipping, Lebling began converting the remaining half of the map to ZIL. It was divided into two parts, both modified from the original, to be released as Zork II and Zork III.[4] While Zork I is very similar to the first half of the original game, the sequels are very different from the second half; for example, in II the player cannot return to the white house.[18] Zork II was offered to PS in April and licensed in June 1981, but Infocom worried about PS's commitment to the game. Although the company did not know, sales of VisiCalc were so strong that PS began discontinuing other software to become VisiCorp. Infocom took over distribution in October, releasing both the renamed Zork I and Zork II in November 1981.[4]

In 1982 the company completed the port of Zork III and wrote new ZIPs for Commodore 64, the Atari 8-bit family, the CP/M systems, and the IBM PC. Zork III shipped on all platforms in the fall of 1982.[4]

When Zork became a commercial product at Infocom, Infocom agreed that if an Infocom copyright notice was put on the Fortran version, noncommercial distribution would be allowed. It, and C translations thereof, have been included in several Linux distributions.[citation needed]


The Zork series was very successful. Infocom sold more than 250,000 copies of the first three games by 1984,[10] and more than 680,000 copies through 1986, or about one third of Infocom's total game sales.[19] As of 1993, two million copies had been sold.[20]

In 1996, Next Generation listed all the text adventure installments of the series collectively as number 38 on their "Top 100 Games of All Time", praising their AI, puzzles, humor, and writing. They further argued that "text adventures in general, and Zork in particular, can offer a greater variety of puzzles, more explorable areas, and better plot development than graphic adventures." [emphasis in original][21]

In 1999, Next Generation listed the Zork series as number 48 on their "Top 50 Games of All Time", commenting that, "Never mind the great writing or humorous tone that Zork and its direct descendants products, the puzzles that the Zork series offers have yet to be matched by most modern adventure games".[22]


Zork I's sales surprised Infocom by rising, not falling, over time; many dealers sold the game as an essential accessory to those purchasing new computers.[23] It was the best-selling game of 1982, with 32,000 copies sold by the first half of that year;[24][25] almost 100,000 copies in 1983;[26] more than 150,000 copies in 1984, comprising more than 20% of Infocom's sales that year;[23] and a total of 378,987 copies by 1986.[19] It was so popular that a hint book was printed in invisible ink to guide players through the world without unnecessary spoilers.[27]

Zork II sold 173,204 copies by 1986.[19] Zork III sold 129,232 copies by 1986.[19]



The Enchanter trilogy:

Games that take place somewhere in the Zork universe:

The Zork Anthology comprises the original Zork Trilogy plus:

The Zork Quest series:

  • Zork Quest: Assault on Egreth Castle (1988, Infocom, interactive computer comic book)
  • Zork Quest: The Crystal of Doom (1989, Infocom, interactive computer comic book)

After a five-year hiatus, the following games were produced:

The Enchanter trilogy and Wishbringer occupy somewhat unusual positions within the Zork universe. Enchanter was originally developed as Zork IV; Infocom decided to instead release it separately, however, and it became the basis of a new trilogy. (In each trilogy, there is a sense of assumed continuity; that is, the player's character in Zork III is assumed to have experienced the events of Zork I and Zork II. Similarly, events from Enchanter are referenced in Sorcerer and Spellbreaker; but the Enchanter character is not assumed to be the same one from the Zork trilogy. In fact, in Enchanter the player's character encounters the Adventurer from Zork, who helps the player's character solve a puzzle in the game.) Although Wishbringer was never officially linked to the Zork series, the game is generally agreed to be "Zorkian" due to its use of magic and several terms and names from established Zork games.

Sorcerer contains two puzzles from the original mainframe Zork (the long slide and sending for the brochure) that were not included in any of Zork I, II, and III.[4]

An MMO adventure game in the series was later released:

Compilations and adaptations[edit]

Among the games bundled in The Lost Treasures of Infocom, published in 1991 by Activision under the Infocom brand, were the original Zork trilogy, the Enchanter trilogy, Beyond Zork and Zork Zero. A second bundle published in 1992, The Lost Treasures of Infocom II, contained Wishbringer and ten other non-Zork-related games. Activision's 1996 compilation, Classic Text Adventure Masterpieces of Infocom, includes all the text-based Zork games; the Zork and Enchanter trilogies, Wishbringer, Beyond Zork and Zork Zero. Activision briefly offered free downloads of Zork I as part of the promotion of Zork: Nemesis, and Zork II and Zork III as part of the promotion for Zork Grand Inquisitor, as well as a new adventure: Zork: The Undiscovered Underground.

Four gamebooks, written by S. Eric Meretzky and taking place in the Zork universe, were published in 1983-4 by Tor Books in the US and Canada, and Puffin in the UK: The Forces of Krill (1983), The Malifestro Quest (1983), The Cavern of Doom (1983), Conquest at Quendor (1984). Together, these are known as the Zork books.

Infocom adapted the games into a series of books. Of six novels published as "Infocom Books" by Avon Books between 1988 and 1991, four were directly based on Zork: Wishbringer by Craig Shaw Gardner (1988), Enchanter by Robin W. Bailey (1989), The Zork Chronicles by George Alec Effinger (1990) and The Lost City of Zork by Robin W. Bailey (1991).

In 1996 Threshold Entertainment acquired the rights to Zork and announced plans to create a Zork movie and live action TV series.[28][29] However, neither was produced.

Zork I is featured in Activision's 2010 game Call of Duty: Black Ops as an Easter egg. In the main menu of the game, the player can get up from a chair and find a computer. Typing "zork" into this computer will start Zork I. Zork I is fully playable within Call of Duty: Black Ops. Zork was also featured in the book version of Ready Player One by Ernest Cline as the challenge to find the Jade key.


Two parody games were also released, in 1988 titled Pork: The Great Underground Sewer System,[30] and in 1989 Pork 2: The Gizzard of Showbiz.[31]

Source code[edit]

The MDL programming language source code of a 1977 version of the original Zork was recovered from tapes and published on Github by the MIT Libraries Department of Distinctive Collections (DDC) on May 5, 2020.[32]


  1. ^ "The making of Zorkl", Retro Gamer, Imagine Publishing (77): 32–33, May 2010
  2. ^ a b Tim Anderson (Winter 1985), "The History of Zork – First in a series", The New Zork Times, 4 (1): 7–11, archived from the original (PDF) on 2006-04-27
  3. ^ "Dave Lebling on the Genesis of the Adventure Game – and the Creation of Zork", US Gamer, August 2014
  4. ^ a b c d e f g h i j Tim Anderson (Spring 1985), "The History of Zork – Second in a series", The New Zork Times, 4 (3): 4–5, archived from the original (PDF) on 2006-04-27
  5. ^ Liddil, Bob (February 1981). "Zork, The Great Underground Empire". BYTE. Vol. 6, no. 2. pp. 262–264. Retrieved 18 October 2013.
  6. ^ a b c d e f Dave Lebling & Marc Blank (1984), Zork Trilogy Instruction Manual. (PDF), Infocom
  7. ^ Lebling, P David (December 1980). "Zork and the Future of Computerized Fantasy Simulations". BYTE. Vol. 5, no. 12. pp. 172–182.
  8. ^ Adams, Rick. "Here's where it all began..."
  9. ^ a b c d e f Tim Anderson (Spring 1985), "The History of Zork – Second in a series", The New Zork Times, 4 (2): 3–5, archived from the original (PDF) on 2006-04-27
  10. ^ a b c d Dyer, Richard (1984-05-06). "Masters of the Game". The Boston Globe. Archived from the original on 1997-06-07.
  11. ^ Barton, Matt (28 June 2007). "The History Of Zork". Gamasutra.
  12. ^ a b "Zork: A Computerized Fantasy Simulation Game", IEEE Computer, 12 (4): 51–59, April 1979, doi:10.1109/mc.1979.1658697, S2CID 7845131
  13. ^ Briceno, Hector; Wesley Chao; Andrew Glenn; Stanley Hu; Ashwin Krishnamurthy; Bruce Tsuchida (2000-12-15). "Down From the Top of Its Game: The Story of Infocom, Inc". Retrieved 2007-06-07.
  14. ^ a b Michael Feir (2007). "Zork Turns 30". Archived from the original on 2011-07-19. In the brief time that Zork was known as Dungeon, the Fortran version of Dungeon was widely circulated which caused the name Dungeon to stick in some circles and sectors to this day.
  15. ^ "Oral History of Robert Supnik, part 2" (PDF). Computer History Museum. Interviewed by Gardner Hendrie. 9 May 2017. p. 76.
  16. ^ Roger Firth (2002). "InfLight – Inform debugging". The result, around 1978, was Dungeon, (from which Bob Supnik at DEC created a Fortran version); the MDL original, however, was soon renamed Zork.
  17. ^ Peter Scheyen (1996). "Dungeon". Archived from the original on 2006-06-17. Version FORTRAN IV Zork (Dungeon) Release Date January 1978 Authors A somewhat paranoid DEC engineer
  18. ^ Stanton, Jeffrey; Wells, Robert P.; Rochowansky, Sandra; Mellid, Michael, eds. (1984). The Addison-Wesley Book of Atari Software. Addison-Wesley. pp. 30–31. ISBN 0-201-16454-X.
  19. ^ a b c d Carless, Simon (2008-09-20). "Great Scott: Infocom's All-Time Sales Numbers Revealed". GameSetWatch. Think Services. Archived from the original on 2008-09-24. Retrieved 2008-09-23.
  20. ^ "Activision: Return to Zork". GamePro. No. 49. August 1993. p. 16.
  21. ^ "Top 100 Games of All Time". Next Generation. No. 21. Imagine Media. September 1996. p. 56.
  22. ^ "Top 50 Games of All Time". Next Generation. No. 50. Imagine Media. February 1999. p. 73.
  23. ^ a b Maher, Jimmy (2013-10-23). "Masters of the Game". The Digital Antiquarian. Retrieved 9 January 2015.
  24. ^ "Inside the Industry". Computer Gaming World. Vol. 2, no. 5. September–October 1982. p. 2. Retrieved 2016-03-28.
  25. ^ Sipe, Russell (November 1992). "3900 Games Later..." Computer Gaming World. No. 100. p. 8. Retrieved 4 July 2014.
  26. ^ Maher, Jimmy (2013-03-20). "The Top of its Game". The Digital Antiquarian. Retrieved 21 December 2014.
  27. ^ "The Legend of Zorba". YouTube. Archived from the original on 2021-12-11.
  28. ^ "Tidbits...". Electronic Gaming Monthly. No. 82. Ziff Davis. May 1996. p. 18.
  29. ^ "Celebrity Sightings". GamePro. No. 92. IDG. May 1996. p. 21.
  30. ^ "PORK I: The Great Underground Sewer System (1991)". 1991.
  31. ^ "PORK 2: The Gizzard of Showbiz (1989)". 1989.
  32. ^ MITDDC/zork: Source code for a 1977 version of Zork, 2020-05-05

Further reading[edit]

External links[edit]