Glulx

Glulx is a 32-bit portable virtual machine intended for writing and playing interactive fiction. It was designed by Andrew Plotkin to relieve some of the restrictions in the venerable Z-machine format. For example, because the Z-machine uses 16-bit integers its RAM is limited to 64KB, while Glulx natively supports 32-bit integers and has a 32-bit address space, allowing gigabytes of memory. Glulx programs typically use the Glk API for input and output. In recent years Glulx has overtaken the Z-machine in terms of published works in each format.