What is Windows on Windows?
{{About|the 16-bit subsystem in the 32-bit editions of Windows NT|the 32-bit compatibility layer in the 64-bit editions|WoW64}} With [[Computing|computers]], '''Windows on Windows''' (often shortened to '''WOW''',<ref>{{cite web|url=http://support.microsoft.com/kb/181333|title=WOW Environment Remains in Memory After Quitting 16-Bit Program|date=February 22, 2007|website=Support|publisher=[[Microsoft]]|access-date=February 7, 2017|url-status=dead|archive-url=https://web.archive.org/web/20071023060218/http://support.microsoft.com/kb/181333|archive-date=October 23, 2007}}</ref><ref>{{cite web|url=http://support.microsoft.com/kb/153544|title=Starting 16-Bit WOW Subsystem on Windows NT Server|date=November 1, 2016|website=Support|publisher=[[Microsoft]]|access-date=February 7, 2017|url-status=dead|archive-url=https://web.archive.org/web/20070509051612/http://support.microsoft.com/kb/153544|archive-date=May 9, 2007}}</ref><ref>{{cite web|date=November 1, 2006|title=Disabling the MSDOS and WOWEXEC Subsystems on Terminal Server|url=https://support.microsoft.com/kb/220159|url-status=live|archive-url=https://web.archive.org/web/20080113000651/http://support.microsoft.com/kb/220159|archive-date=January 13, 2008|access-date=February 7, 2017|website=Support|publisher=[[Microsoft]]}}</ref>) is a [[compatibility layer]] of [[x86]] versions of the Microsoft [[Windows NT]] family of [[operating system]]s that allows many [[Legacy code|legacy]] [[16-bit]] programs run that were made for [[Windows 3.x]] or before to run. == Background == WOW allows many 16-bit Windows programs to run without changes on newer [[32-bit]] versions of Windows. This was made to give [[software developer]]s time to make their software 32-bit while people moved from [[Windows 3.1x]] to [[Windows 95]], so the [[Operating system|OS]] can be upgraded to a newer version while running most, or all of, a customer's 16-bit programs. [[Windows 9x]] operating systems, which were made on top of [[DOS]], had both 16 and 32-bit systems, so if it kept those 16-bit p