Colossal Cave Adventure

YOU ARE STANDING AT THE END OF A ROAD BEFORE A SMALL BRICK
BUILDING. AROUND YOU IS A FOREST. A SMALL
STREAM FLOWS OUT OF THE BUILDING AND DOWN A GULLY.

Those are the first lines of the first text adventure, exactly as Will Crowther typed them into his data file. Crowther was a programmer at Bolt, Beranek and Newman (BBN), the Massachusetts firm whose team built the ARPANET, the network that grew into the internet. He was also a caver, and the cave under that brick building was modelled on one he had helped to survey in Kentucky. He wrote the game in FORTRAN on a DEC PDP-10 during 1975 and 1976, left a copy on BBN’s computer and went on holiday for a month. When he came back, in his own account, the game was being played all over the network.

In 1977 Don Woods, a student at Stanford, took Crowther’s game and made it bigger, harder and funnier. His version is the one that went round the world’s mainframes, and the one that the authors of Zork, Scott Adams and Roberta Williams all played before they wrote games of their own.

Fast facts

• Author: Will Crowther, at BBN, 1975–76.
• Expanded by: Don Woods, at the Stanford Artificial Intelligence Laboratory, 1977.
• Language and machine: FORTRAN on the DEC PDP-10; Woods’s version needed about 300K of memory.
• Commands: one or two words, such as GET LAMP or NE.
• Scoring: none in Crowther’s version; 350 points in Woods’s.
• Home versions: Microsoft Adventure (1980–81), Jim Butterfield’s abridged PET version, Level 9’s Colossal Adventure (1982) and many more.
• Source code: Crowther’s March 1977 files, recovered in 2005; the 1995 Adventure 2.5 by Crowther and Woods, free software under a BSD licence since 2017.

A real cave

Crowther’s caving came through the Cave Research Foundation, which surveyed the cave passages of Kentucky. In 1975 he drew a map of the Bedquilt region of Colossal Cave, a section of the huge Mammoth Cave system. “Bedquilt” is a room in the game, and the game’s cave follows that stretch of the real one. When the scholar Dennis Jerz went into Colossal Cave in 2005 to compare the two, he found that “real locations in the cave and several artifacts (such as an iron rod and an axe head) correspond to their representation in Crowther’s version”.

The game was also meant to be played by someone. Crowther’s daughter Sandy has said he wrote it after his divorce as something he could share with his children, and colleagues remember him showing it to his Dungeons & Dragons friends. Crowther himself was modest about it. “In those days, the thing I cared most about was rock climbing,” he said, and his daughter recalled him remarking that of all the things he had done, “it’s funny that the one thing I’m remembered for is ‘Adventure.’”

What Crowther wrote

Crowther’s version was small by later standards: its data file describes fewer than 80 locations. Most of the famous parts are already there. The player carries a lamp into the dark, frees the way past a “HUGE GREEN FIERCE SNAKE” with a bird caught in a cage, waves a rod to make a crystal bridge appear across a fissure, and gets lost in rooms that all read “YOU ARE IN A MAZE OF TWISTY LITTLE PASSAGES, ALL ALIKE.” Dwarves lurk below, and one of them “THREW A LITTLE AXE AT YOU WHICH MISSED, CURSED, AND RAN AWAY.” In the building’s debris room “A NOTE ON THE WALL SAYS ‘MAGIC WORD XYZZY’”, and elsewhere “A HOLLOW VOICE SAYS ‘PLUGH’”: both words move the player instantly from one place to another.

What it did not have was a way to keep score. “Crowther’s original version contains no vocabulary words to represent commands for saving a game, reporting the score, or taking inventory of possessions,” Jerz found; “all these elements were added by Woods.”

Woods’s expansion

Woods heard about the game in a Stanford computer science class in 1977, and he and a classmate, John Gilbert, “stayed up all night at the AI lab playing the game and mapping the cave”. Woods then contacted Crowther for the source code and, in Jerz’s words, “greatly increased the game’s size, complexity, and polish”. He added the score, saving and the inventory, more treasures and more of the cave, and fantasy creatures that are not in Crowther’s files: a dragon, a troll guarding a bridge, and a pirate who steals your treasure. A full score was 350 points, and the best players earned the title of Grand Master.

The period press often merged the two men. Books of the early 1980s put both of them at Stanford in 1976, and Usborne’s 1983 Write Your Own Adventure Programs described the game as “written in 1976 on a mainframe computer at Stanford University… by William Crowther and Don Woods”. Other writers had it right: Tim Hartnell’s 1984 Giant Book of Computer Games noted that “the program was actually written by Crowther, and elaborated by Woods”.

Across the mainframes

The FORTRAN program travelled with the machines. Hartnell reported that when it was added to the free program library of DECUS, the Digital Equipment Computer Users’ Society, “it soon became the most-used program in the library”. Crowther put it more simply: he came back from holiday to find the game everywhere.

It needed about 300K of memory, far more than any home computer, and that turned it into a challenge. Microsoft sold Microsoft Adventure on disk for the TRS-80 and Apple II at $29.95. Reviewing it in BYTE in December 1980, Bob Liddil wrote that “none stirs the imagination quite like Adventure”, and the magazine’s editor, who had played the original on a DEC PDP-11/70, found the two “virtually identical in content, program logic, and wording”. Microsoft Adventure was also on sale for the IBM PC when that machine was launched in 1981. Jim Butterfield wrote an abridged version for the Commodore PET, which warned that it read only “the first five letters of each word”, so northeast had to be typed as NE. In 1982 Jeff Jacobsen offered his assembly-language Apple II version free to anyone who sent a blank disk; he had squeezed “the entire game into 48K RAM”, with “over 130 rooms, 15 treasures”. By 1984 Hartnell counted “at least five companies” selling versions for the Apple alone.

In Britain, Level 9 began its adventure business with Colossal Adventure in 1982, a full version of the mainframe game with 70 extra rooms. Later players kept extending it too: Amiga public-domain collections of the early 1990s carried a 550-point version.

The games it started

Adventure set the form that followed: a room described in prose, a two-word command, a world that changes as the player acts, and treasures to collect. Many of the people who defined the genre began as its players.

• At MIT, players of the Dynamic Modelling Group had solved it by late May 1977 and set out to write something better. That became Zork, and then Infocom.
• Scott Adams, a systems programmer at Stromberg-Carlson, played “the classic Adventure game written by Crowther and Woods”. “It took almost ten days of early-morning and late-evening sessions before I achieved the coveted score of 350 and the title of Grand Master,” he wrote in BYTE. It seemed unfair that “such a fascinating game was restricted to such an expensive machine”, so he set out to fit an adventure into a 16K TRS-80, “especially when the FORTRAN version I played took about 300 K bytes”. His solution was an interpreter, his first game was Adventureland, and his company became Adventure International.
• Roberta Williams played Adventure on a teletype at home before she designed Mystery House, the first game of what became Sierra.

Peter Gerrard’s 1983 guide to adventures on the Commodore 64 put the debt plainly: Crowther and Woods’s program was “the origin of every other adventure game”, and without it “people like Scott Adams… would probably have never written their own series”.

The source code

Crowther’s own version was thought lost for decades. In 2005 his files, dated March 1977, were recovered from a backup of Don Woods’s student account at the Stanford Artificial Intelligence Laboratory, found through Dennis Jerz’s research. Three versions of the FORTRAN source and two of the data file are now published on the web and in the Interactive Fiction Archive; no licence is stated for them.

According to Raymond’s history of the game, Crowther and Woods went on working on it on and off for years, and in 1995 released Adventure 2.5, a 430-point version. In May 2017 Woods gave Eric S. Raymond permission to release it under the two-clause BSD licence, and Raymond maintains it as Open Adventure, a modern port that still plays the 1995 game.

Colossal Cave in 2023

Ken and Roberta Williams, the founders of Sierra, came back to the game more than forty years after Roberta first played it. Their company, Cygnus Entertainment, released Colossal Cave, a 3D and virtual-reality version, on 19 January 2023. Ken talked to Don Woods early in the project, and Roberta said the aim was to bring the cave to modern players “in the world that Will Crowther and Patricia Crowther and Don Woods had in their minds”.

Explore the game

Spend time with the cave in our Adventure game study: how its commands, objects, routes and puzzles work together.

See also

• Will Crowther
• Zork
• Infocom
• Level 9
• Sierra
• Microsoft
• Jim Butterfield
• Text adventure