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 that Sierra and IBM wished to market in order to attract consumers to IBM's lower-cost home computer, the IBM 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, the Sierra Creative Interpreter.
History
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. A team of six designers and developers, led by designer Roberta Williams, worked on the game that was eventually titled King's Quest. The Game Adaptation Language was a high-level programming language that resembled C.