The Free On-line Dictionary of Computing (30 December 2018):

Expanded Memory Specification
EMS
LIM EMS

    (EMS) An IBM PC memory paging scheme enabling
   access to memory other than conventional memory in real
   mode.

   Expanded memory is provided through a page frame of at
   least 64 kilobytes in the reserved memory address region.
   Access to this memory is provided by an expanded memory
   manager (EMM) software.  The EMM functions are accessible
   through interrupt 67H.

   In 8086 or 8088 based systems this is the only way to use
   memory beyond conventional memory.  In systems based on
   80286 or later, XMS and HMA provide alternative methods.

   EMS was developed jointly by Lotus, Intel, and Microsoft
   prior to 1988.  Accordingly, this specification is sometimes
   referred to as LIM EMS.

   A complete discussion of EMS and programming examples can be
   found in ["PC System Programming for developers", 1989, ISBN
   1-55755-035-2 (Book only) and ISBN 1-55755-036-0 (Book and
   diskette)].

   EEMS, a competing expanded memory management standard, was
   developed by AST Research, Quadram and Ashton-Tate.

   See also upper memory block.

   (1996-01-10)