Glulx

Glulx is a 32-bit virtual machine and bytecode format designed for running interactive fiction. Created by Andrew Plotkin in the early 2000s, it was intended to overcome many of the limitations of the Z-machine, notably larger memory space, Unicode support, and opportunities for multimedia integration. Glulx games are packaged as .ulx files that contain compiled code, data, and metadata describing the program and its resources. The VM provides a substantial, addressable memory space and an API for input, output, and interaction with the host environment through the interpreter.

Inform 7, a popular language for writing interactive fiction, can compile to Glulx bytecode, though other compilers exist as well. The Glulx ecosystem includes multiple interpreters; the reference implementation glulxe executes Glulx games, and frontends such as Gargoyle and other GUI bridges provide cross-platform support. Glulx is valued for its Unicode handling, the ability to support larger game worlds, and a design geared toward portability across operating systems. While not as universally deployed as the Z-machine for older titles, Glulx remains a widely used target for newer Inform 7 projects and other IF authoring tools seeking a modern, flexible VM for interactive fiction.