base memory

from The Free On-line Dictionary of Computing (8 July 2008)

base memory

   <hardware, jargon> The lowest 640 {kilobytes} of memory in an
   {IBM PC}-compatible computer running {MS-DOS}.  Other PC
   {operating systems} can usually compensate and "ignore" the
   fact that there is a 640K limit to base memory.  This was put
   in place because the original {CPU} - the {Intel 8088} - could
   only access one {megabyte} of memory, and {IBM} wanted to
   reserve the upper 384KB for {device drivers}.  The {high
   memory area} (HMA) lies above 640KB and can be accessed on
   MS-DOS computers that have an {A20 handler}.

   (1997-05-30)