extended memoryMemory above and beyond the standard 1MB (megabyte) of main memory that DOS supports. Extended memory is only available in PCs with an Intel 80286 or later microprocessor.
Two types of memory can be added to a PC to increase memory beyond 1MB: expanded memory and extended memory. Expanded memory conforms to a published standard called EMS that enables DOS programs to take advantage of it. Extended memory, on the other hand, is not configured in any special manner and is therefore unavailable to most DOS programs. However, MS-Windows and OS/2 can use extended memory.