1   Virtual Memory Manager (VMM)
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     Virtual memory is a generic term for hardware or software
     techniques that allow a limited amount of real memory to emulate a
     much larger virtual memory.

     The Clipper 5.0 Virtual Memory Manager (VMM) is implemented in the
     software.  The system runs in real mode on any 8086-compatible
     processor; it does not directly use the protected mode virtual memory
     capabilities of the Intel 286 and 386 processors.

     The VMM is a segmented memory manager.  Virtual memory is allocated
     in segments, each of which may contain from 1K to 64K of data.
     Initially, the VMM works somewhat like a normal memory allocator
     (although it has an extra advantage: most VM segments are movable; the
     VMM can reorganize them to get maximum utilization of real memory).
     Unlike a normal memory allocator, however, the VMM does not run out
     when the available real memory can no longer contain all of the
     allocated segments.  Instead, one or more of the least recently used
     (LRU) segments are swapped out into secondary storage (or otherwise
     removed from real memory, see below) to make room for new segments.
     Later, if data in a swapped segment must be accessed, it is swapped
     back in, displacing segments which are not currently needed.

     The maximum virtual address space of the Clipper 5.0 VMM is 64MB.