Adventure Game Interpreter

The Adventure Game Interpreter (AGI) is a game engine developed by Sierra On-Line. The company originally developed the engine for King's Quest (1984), an adventure game which Sierra and IBM wished to market in order to attract consumers to IBM's lower-cost home computer, the PCjr.

AGI was capable of running animated, color adventure games with music and sound effects. The player controls the game with a keyboard and, optionally, a joystick.

After the launch of King's Quest, Sierra continued to develop and improve the Adventure Game Interpreter. They employed it in 14 of their games between 1984 and 1989, before replacing it with a more sophisticated engine, Sierra's Creative Interpreter.

In late 1982, IBM began work on the PCjr, a lower-priced variant of the IBM Personal Computer with improved graphics and sound. The PCjr's Video Gate Array video adapter could display up to 16 colors at a time—a major improvement over the Color Graphics Adapter's four-color limit. The new sound chip, too, could output a wider range of tones than the PC speaker.

IBM commissioned Sierra to produce a game that could showcase these new capabilities. They discussed some requirements for the game, and IBM supplied Sierra with a PCjr prototype. They both agreed that the game should be animated—a first for Sierra. A team of six designers and developers, led by designer Roberta Williams, worked on the game that was eventually titled King's Quest. Among the developers were Chuck Tingley and Ken MacNeill (later releases also credit Chris Iden).