SubOS

In computing, a SubOS may mean several related concepts: It can also make processes easier and add details to the main operating system.
 * A process-specific protection mechanism allowing potentially dangerous applications to run in a restricted environment. It worked by setting a sub-user id which was user id of the owner of the file rather than the person running the file.
 * A substitute-operating system, which simulated a full operating system. These were mainly developed by the GameMaker community.
 * An interface (graphical or terminal based) that provides additional functions or command for a specific audience target.