The equivalent of a computer created in software rather than in hardware. Java programs, for example, run in a Java virtual machine. Virtual machines such as the Z-machine, Glulx, and the T3 VM make writing interactive fiction easier. Rather than compiling games for each of the new operating systems, authors compile the game only once for the virtual machine. The game can then be run under any operating system for which a version of the virtual machine exists.
(Definition by SG)