The Visi-On API provides a handle-based memory manager. Handles are a kind of managed pointer that allow memory blocks to be moved around even though the hardware does not have virtual memory. So long as the program always follows the rules on acquiring and releasing the handle before using the underlying pointer, it enables a kind of poor man's virtual memory. The first version of Mac OS and Windows 3.x worked in a similar way. I'm guessing that the designers of Visi-On thought of this, and the other abstractions the API provides, as a kind of virtualization.