expanded memory specification (EMS)
Expanded Memory Specification (EMS) is an add-on system for DOS operating systems that can be used to manage main memory with storage capacities of 1 megabyte( MB) and more.
EMS works with a memory address area reserved under the DOS operating system, which is divided into 16 KB sections, so-called pages. At least 4 consecutive pages, corresponding to 64 kilobytes (KB), of DOS memory between 640 KB and 1 MB are used for the EMS. Typically, the address range is between 768 KB and 896 KB. This 64 KB range can be mapped and is known as the Expanded Memory Page Frame. This area can be managed by means of a management program. The EMS range is only supported by programs that take this range into account, for example Lotus 123 and WordPerfect 5.x.