The Z-machine is a virtual machine

Virtual machine

A virtual machine is a "completely isolated guest operating system installation within a normal host operating system". Modern virtual machines are implemented with either software emulation or hardware virtualization or both together.-VM Definitions:A virtual machine is a software...

 that was developed by Joel Berez and Marc Blank

Marc Blank

Marc Blank is an American game developer and software engineer. He is best known as part of the team that created one of the first hit text adventure computer games, Zork....

 in 1979 and used by Infocom

Infocom

Infocom was a software company, based in Cambridge, Massachusetts, that produced numerous works of interactive fiction. They also produced one notable business application, a relational database called Cornerstone....

 for its text adventure games

Interactive fiction

Interactive fiction, often abbreviated IF, describes software simulating environments in which players use text commands to control characters and influence the environment. Works in this form can be understood as literary narratives and as video games. In common usage, the term refers to text...

. Infocom compiled game code to files containing Z-machine instructions (called story files, or Z-code files), and could therefore port all its text adventures to a new platform simply by writing a Z-machine implementation for that platform. With the large number of incompatible home computer systems in use at the time, this was an important advantage over using native code or developing a compiler for each system.

The "Z" of Z-machine stands for Zork

Zork

Zork was one of the first interactive fiction computer games and an early descendant of Colossal Cave Adventure. The first version of Zork was written in 1977–1979 on a DEC PDP-10 computer by Tim Anderson, Marc Blank, Bruce Daniels, and Dave Lebling, and implemented in the MDL programming language...

, Infocom's first adventure game.