Editing Expanded memory (section)

{{Short description|System of bank switching in DOS memory management}}
{{Use dmy dates|date=May 2019|cs1-dates=y}}
[[File:Expanded memory.svg|thumb|Several expanded-memory [[page (computer memory)|pages]] are bank-switched in the [[page frame]], part of the [[upper memory area]].]]
In [[DOS memory management]], '''expanded memory''' is a system of [[bank switching]] that provided additional memory to [[DOS]] programs beyond the limit of [[conventional memory]] (640&nbsp;KiB).

''Expanded memory'' is an umbrella term for several incompatible technology variants. The most widely used variant was the '''Expanded Memory Specification''' ('''EMS'''), which was developed jointly by [[Lotus Software]], [[Intel]], and [[Microsoft]], so that this specification was sometimes referred to as "'''LIM EMS'''". LIM EMS had three versions: 3.0, 3.2, and 4.0. The first widely implemented version was EMS 3.2, which supported up to 8&nbsp;MiB of expanded memory and uses parts of the address space normally dedicated to communication with peripherals ([[upper memory]]) to map portions of the expanded memory. '''EEMS''', an expanded-memory management standard competing with LIM EMS 3.x, was developed by [[AST Research]], [[Quadram]] and [[Ashton-Tate]] ("AQA"); it could map any area of the lower 1&nbsp;MiB. EEMS ultimately was incorporated in LIM EMS 4.0, which supported up to 32&nbsp;MiB of expanded memory and provided some support for DOS multitasking as well. IBM, however, created its own expanded-memory standard called '''XMA'''.

The use of expanded memory became common with games and business programs such as [[Lotus 1-2-3]] in the late 1980s through the mid-1990s, but its use declined as users switched from DOS to [[protected-mode]] operating systems such as [[Linux]], [[IBM OS/2]], and [[Microsoft Windows]].