Source : Free On-Line Dictionary of Computing

Extended Memory Specification
     
         (XMS) The specification describing the use of {IBM
        PC} {extended memory} in {real mode} for storing data (but not
        executable code).  Memory is made available by {extended
        memory manager} (XMM) software.  The XMM functions are
        accessible through {interrupt} 2FH.
     
        (1996-01-10)