While action games were all the rage in the latter part of the ’70s with arcade games and home video consoles being accessible and widely popular, the advent of a unique game would herald a new genre that essentially would leave behind the fast-paced action and quick reflexes for a more slow-paced experience with a focus on exploration and story. In 1976, Will Crowther, a programmer and avid cave explorer would put his finishing touches on his pioneering game Colossal Cave Adventure, programmed in Fortran on Bolt Beranek & Newman’s PDP-10 timesharing mainframe in Boston. Crowther’s game would become one of the very first computer games that could be categorized as an adventure game and is now, 45 years later, considered one of the single most important titles in gaming history. The game was greatly expanded upon in 1977 by Standford graduate student and programmer Don Woods, with double as many rooms and added fantasy-related elements. Crowther and Woods’ Colossal Cave became a huge inspiration and greatly influenced the early computer game industry, not only in the realm of mainframes but also later when the time came for the personal computer to conquer people’s homes and imagination.

In 1977 a small group of students from Massachusetts Institute of Technology, MIT, consisting of Tim Anderson, Marc Blank, Bruce Daniels, and Dave Lebling, started work on their own and far more ambitious variation of Colossal Cave. The game would be called Zork and was developed on MIT’s PDP-10 mainframe using the MDL programming language. MDL provided more powerful string manipulation than other programming languages, consequently, ZORK featured not only more intricate puzzles but also a more complex text parser. The word Zork, one of many nonsense words used by MIT hackers, was the alias for an unfinished program and fitted perfectly since the game was developed in multiple stages over the course of a 3-year period, with the last addition of rooms, puzzles, and other enhancements made in 1979. As the game evolved it became a huge success on MIT’s PDP-10 where it was available to any user with an account. Soon people were logging into the system from every part of the world.
The name Zork was changed to Dungeon for a period of time but to steer free of a lawsuit from TSR, publisher and copyright owner of Dungeons & Dragons, Zork was used when finally made commercially available.

In the summer of 1979, three of the original creators of Zork, and 7 other MIT alumni and professors established Infocom. With no business plan or commercial product to kick off the company, Lebling and Anderson decided to use Zork as the company’s first product.
At the time personal computers were rapidly starting to appear in people’s homes, but with the complete mainframe game taking up a full megabyte of data it was impossible to fit on any cassette or floppy. Also, a typical home computer at the time only came equipped with 32kb of memory, roughly 20 times less than that of the PDP-10. With home computers being miles from the capabilities of minicomputers and mainframes, Zork needed to be revamped and split into multiple parts.
Joel Berez, president of Infocom, and Blank started considering how to not only fit the massive game into the limited home computers but also how to make it available for the numerous different platforms available at the time. Berez came up with the idea for compiling to platform-independent byte-codes which then were interpreted by a virtual machine, called the Z-Machine. The MDL programming language was reconstructed into the Zork Implementation Language, ZIL, which the compiler converted to Z-machine byte-codes.
By loading only certain sections into memory when needed and keeping the bulk of data on the floppy and by only including the first half of the original map and about 100 rooms, Berez and Blank made it possible to run the first part of Zork from floppy on a 32kb system.

The first Z-Machine interpreter for home computers was completed by Scott Cutler, one of the original ten founders of Infocom. Cutler’s TRS-80 interpreter made perfect sense from a marketing perspective, the TRS-80 was the best-selling microcomputer of the time, outselling both the Commodore PET and the Apple II. The TRS-80 version of Zork was demonstrated to one of the earliest software companies, Personal Software in the spring of 1980. Personal Software agreed to distribute the first part of Zork and published it in December of 1980 for the TRS-80. Around 1,500 copies were sold.
A month earlier in November of 1980, a version on an 8-inch floppy disk alongside a photo-copied manual was released for the DEC PDP-11 minicomputer. Since Personal Software had no interest or experience outside the home computer market, this release was distributed by Infocom, as its first-ever self-published title.

After the initial TRS-80 version of Zork, Bruce Daniels, one of the four original developers of the mainframe version, now working at Apple Computer in California, ported it to the Apple II.
Personal Software released it in February of 1981. The Apple II version quickly became popular and soon outsold the TRS-80 version by a factor of four.
Both the TRS-80 and the Apple II version became known as Barbarian Zork, because of the cover art, which didn’t capture the essence of the game.

Shortly after the TRS-80 version, Personal Software published the Apple II version.
The Apple II version is believed to have sold around 6.000 copies

In 1979 Personal Software had published Software Arts’ VisiCalc, the first electronic spreadsheet for the personal computer. The spreadsheet software became hugely successful and Personal Software started tinkering with the idea of its own graphical spreadsheet called VisiOn. With the spreadsheet business taking much of the company’s time and energy, the focus on Zork and other products was diminishing. Infocom had rewritten the remaining half of the original Zork and split it into two parts. The first part, Zork II: The Wizard of Frobozz was also supposed to be published by Personal Software but as the company had shifted focus to its business software, Zork never received the support it deserved and required to become a commercial success. Infocom reacquired the rights to both titles in the autumn of 1981 just as Personal Software chose to exclusively focus on their spreadsheet adventures.

To prevent Personal Software from dumping Zork on the market at bargain prices and lowering the public’s image of Zork with the Barbarian cover, Infocom bought out the remaining Apple II Zork inventory from Personal Software, ditched the cover art but kept the floppies now used with the self-published rerelease of Zork I and the first release of Zork II in November of 1981, both with the now-iconic bricks and trapdoor logo.

Personal Software kept the rights to the TRS-80 version of Zork (the first part) and during the spring and summer of 1982, the first part of Zork was rereleased for the TRS-80 Model I and Modell III.

While the TRS-80 Model III was introduced in mid-1980 and led to the discontinuation of the Model I shortly hereafter, Personal Software released the first part of Zork, separately, for both models during the Spring and summer of 1982.

Zork I: The Great Underground Empire and Zork II: The Wizard of Frobozz was released in blister packs in late 1981, as the first two self-published personal computer games from Infocom

Personal Software’s commitment to its Visi products became apparent when the company changed its name to VisiCorp in 1982.

Zork became the best-selling game of 1982 and before the end of the year, Infocom had released all three parts of Zork, all of which would over the course of the next many years, now in the famous Infocom grey box, see releases for every thinkable platform on the market and sell a million copies.

All three parts of Zork were published for every thinkable platform, now in the famous Infocom grey box. Combined they would go on to sell over a million copies

Sources: Down From the Top of Its Game The Story of Infocom, Inc., Softalk Magazine, InfoWorld, Wikipedia, yois.if-legends.org, Peter Jennings at Benlo Park, Medium…