Sierra On-Line · 1984 · 1980s–1990s · Assembly / C
Sierra's Adventure Game Interpreter and Script Creation Interpreter powered a decade of parser-driven adventure games — from King's Quest to Gabriel Knight — establishing the illustrated narrative adventure as a genre.
Sierra On-Line developed two successive engine families for their adventure games. The Adventure Game Interpreter (AGI), introduced with King's Quest in 1984, rendered 160×168 pixel vector-drawn scenes and processed typed English commands, running on the IBM PCjr, Apple II, and Atari ST from a common code base. The Script Creation Interpreter (SCI), introduced in 1988 with King's Quest IV, brought a high-level object-oriented scripting language, significantly improved graphics (up to 320×200 with 256 colours in later versions), and mouse-driven icon interfaces with SCI1 from 1990. Both engines used a virtual machine that insulated game scripts from platform-specific code — an architectural decision that allowed Sierra to maintain compatibility across a wide hardware matrix throughout the 1980s. The SCI engine family remained in use into the mid-1990s, with titles such as King's Quest VII and Phantasmagoria among its last.