Zork was one of the earliest interactive fiction computer games, with roots drawn from the original genre game, Colossal Cave Adventure. The first version of Zork was written in 1977–1979 using the MDL programming language on a DEC PDP-10 computer. The authors—Tim Anderson, Marc Blank, Bruce Daniels, and Dave Lebling—were members of the MIT Dynamic Modelling Group.
"Zork" was originally MIT hacker slang for an unfinished program. The implementors briefly named the completed game Dungeon, but changed it back to Zork after receiving a trademark violation notice from the publisher of Dungeons & Dragons. Zork has been adapted to a book series.
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 Commodore Plus/4, 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 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").