AGI Engine
Sierra's Adventure Game Interpreter
Sierra's Adventure Game Interpreter ran the 3-D Animated Adventures from King's Quest (IBM PCjr, 1984) to Manhunter: San Francisco, at 160×200 with a typed verb-noun parser, until SCI replaced it from King's Quest IV.
The Adventure Game Interpreter (AGI) was the system Sierra On-Line built its “3-D Animated Adventures” on from King’s Quest (1984) until Manhunter: San Francisco (1989). A game was a set of rooms, animated characters and scripts run by a common interpreter, so the same title could be built for the IBM PC, Apple II and IIGS, Atari ST, Amiga and others. Sierra’s own newsletter, looking back from 1989, called it “an older version of the interpreter … used to create King’s Quests I, II, and III and the 256K version of King’s Quest IV”.
Fast facts
- Developer: Sierra On-Line.
- First game: King’s Quest (1984), published by IBM for the 128K PCjr at $50; “designed specifically for the PCjr” and usable on a PC with a colour graphics adapter.
- Resolution: 160×200 — Sierra’s own hardware column told readers its adventures “all run in 160 x 200 (AGI) or 320 x 200 (SCI)”.
- Input: typed verb-noun commands plus joystick or arrow-key movement, with single keys for common actions.
- Last games: the Manhunter pair; Ken Williams said in 1989 that Manhunter: San Francisco “was built using the AGI development language” and could be Sierra’s last adventure for the IIGS, because SCI was “just too big and too complex” for it.
- Replaced by: SCI, from King’s Quest IV (1988).
King’s Quest on the PCjr
Home Computer Magazine reviewed King’s Quest in 1984 as an IBM product for the PCjr: 128K, a colour display or television, joysticks optional. What struck the reviewer was that the hero walked rather than floated, and that he could go behind things: “Oops! Bumped into a tree. That’s okay, just walk behind it. What? Sir Grahame disappears behind the tree!” The magazine also noticed the split between moving and commanding — “one person could control the joystick, while another enters commands at the keyboard” — and the single-key shortcuts for actions such as jumping, ducking and swimming, plus an ECHO key that recalled the last typed command.
Bill Kunkel, reviewing the sequel in ST-Log in 1987, summed up the format: an “early release for the 128K PCjr” in which Roberta Williams “made brilliant use of the extra memory to design a new type of joystick-driven adventure”, combining “the traditional text adventure (verb-noun commands) with sound and graphics more typical of an arcade game”.
The 3-D Animated Adventure
Sierra marketed the interpreter under the label “3-D Animated Adventure” rather than by its initials. Its Fall/Winter 1988 newsletter claimed “over 3 million dollars in underlying technology” for the “3-D Animated Adventure game system” and “over $400,000 in technological improvements” for King’s Quest IV, which would offer “double the graphics resolution of our current adventure game line” — the current line being AGI, as a screenshot captioned “King’s Quest 1 (AGI)” made clear. Magazines used the label too: Antic’s Amiga Plus introduced Manhunter: New York in 1989 as “this Sierra 3-D Animated Adventure”. A 1992 Amiga Format company profile still described it as “its adventure design system, the 3D Adventure Game Interpreter … a main character that could manoeuvre freely through the graphics in 3D perspective”.
The Black Cauldron
Sierra’s Disney licence The Black Cauldron dropped typing for a younger audience. INFO reviewed the Amiga version in November 1988 as “a ‘no-keyboard-required’ game” suitable for “youngsters who have long attention spans, but find text games difficult”, with “delightfully realistic animation in all 73, three dimensional screens” — and slow loading, with Taran frequently seeming to stick.
Superseded by SCI
Ken Williams’ 1990 company history in the newsletter records the changeover: “King’s Quest IV was Sierra’s first SCI release, and it was a beauty. The graphics were breathtaking, the animation was far superior to the AGI games, and SCI would allow us to include a fully orchestrated film-score quality soundtrack.” King’s Quest IV shipped in both forms — the newsletter’s own version table lists a “Kings Quest IV AGI” and a “Kings Quest IV SCI” — and by 1990 Sierra was selling the original King’s Quest and Mixed-Up Mother Goose “rewritten for SCI” with higher-resolution graphics and sound-card support, offering owners of the AGI versions a $20 upgrade.