Portfolio's folios, each a collection of function calls dealing with a
different aspect of 3DO operation, come in two types:
Permanent, where the folio is constantly in RAM and ready to
handle function calls.
Demand-loaded, where the folio is stored on disk and must be
loaded first before tasks can make function calls to the folio.
The Kernel folio is a permanent folio by necessity; it includes the
function calls that open other folios. Other permanent folios are the
Graphics, Audio, Math, and File folios. Examples of demand-loaded folios
include the International and Compression folios.
Demand-loaded folios are automatically fetched from disk when they are
needed by a task. When a task tries to open the folio, the kernel first
looks in memory for the folio. If the folio isn't found in memory, the
kernel then tries to load it from disk. Once the folio has been loaded
from disk, it can be used by other tasks in the system without having to
reload it.
When demand-loaded folios are no longer in use by any task, the kernel can
remove them from memory to make the memory available to other uses in the
system.