Three of the original Zork programmers joined with others to found Infocom in 1979. That company adapted the PDP-10 Zork into Zork I-III, a trilogy of games for most popular small computers of the era, including the Apple II, the Commodore 64, the Atari 8-bit family, the TRS-80, CP/M systems and the IBM PC. Zork I was published on 5¼" and 8" floppy disks. Joel Berez and Marc Blank developed a specialized virtual machine to run Zork I, called the Z-machine. The first "Z-machine Interpreter Program" ZIP for a small computer was written by Scott Cutler for the TRS-80. The trilogy was written in ZIL, which stands for "Zork Implementation Language", a language similar to LISP. Personal Software published what would become the first part of the trilogy under the name Zork when it was first released in 1980, but Infocom later handled the distribution of that game and their subsequent games. Part of the reason for splitting Zork into three different games was that, unlike the PDP systems the original ran on, micros did not have enough memory and disk storage to handle the entirety of the original game. In the process, more content was added to Zork to make each game stand on its own.
Zork is set in a sprawling underground labyrinth which occupies a portion of the "Great Underground Empire". The player is a nameless adventurer whose goal is to find the treasures hidden in the caves and return alive with them. The dungeons are stocked with many novel creatures, objects and locations, among them grues, zorkmids, and Flood Control Dam #3 -- all of which are referenced by subsequent Infocom text adventures.
Zork and its relatives are works of interactive fiction. 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 grue"), but some prepositions and conjunctions ("hit the grue with the Elvish sword").
After a six 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.
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. This led many to believe that the games had been released as freeware, even though the included license explicitly prohibited redistribution. Activision's legal department has recently stated that the promotion relating to those games has ended and that it is not legal to distribute the games or make them available for download.
Of six novels published as "Infocom Books" by Avon Books between 1989-1991, two were directly based on Zork: The Zork Chronicles by George Alec Effinger (1990) and The Lost City of Zork by Robin W. Bailey (1991). Two further novels in the same series are based on the same universe: Wishbringer by Craig Shaw Gardner and Enchanter, also by Bailey.
In 2006, an over-the-phone version of Zork entitled Zasterisk entered beta testing. Programmed by Simon Ditner using Asterisk and the Festival Speech Synthesis System, players can call in and play Zork over the phone by speaking voice commands. The results are read back by the automated text-to-voice synthesis system. It is now known as Zoip, a reference to VoIP.
In all of the Zork text adventures, the following commands apply:
> n, s, e, w
The Fortran version of Dungeon was widely available on DEC VAXes, being one of the most popular items distributed by DECUS. It went through multiple modifications both to incorporate more features from the original and to track changes in the MDL version. In the late 1980s, the Fortran version was extensively rewritten for VAX Fortran and became fully compatible with the last MDL release. It had one extra joke: an apparent entrance to the Mill (a reference to DEC's headquarters) that was, in fact, impassable.
It also had a gdt command (game debugging technique, a reference to the DDT debugger) which enabled the player to move any object (including the player) to any room. Use of gdt required 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.