(1) The uppermost end of memory.
(2) In a PC, high memory may refer to any of three areas: (1) the upper memory area (UMA) between 640K and 1M, (2) the 64K High Memory Area (HMA) between 1024K and 1088K or (3) extended memory above 1M. What seems like ridiculously small amounts of memory today were very precious in the early days of DOS and MS-DOS PCs. See
PC memory,
UMA,
HMA and
extended memory.