Windows on Windows

This article is about the 16-bit subsystem in the 32-bit editions of Windows NT. For the 32-bit compatibility layer in the 64-bit editions, see WoW64.
Windows on Windows
Other namesWOW
Developer(s)Microsoft
Initial releaseJuly 27, 1993; 31 years ago (1993-07-27)
Operating systemMicrosoft Windows
PlatformIA-32
TypeCompatibility layer
LicenseProprietary commercial software

In computing, Windows on Windows (commonly referred to as WOW)[1][2][3] is a discontinued compatibility layer of 32-bit versions of the Windows NT family of operating systems since 1993 with the release of Windows NT 3.1, which extends NTVDM to provide limited support for running legacy 16-bit programs written for Windows 3.x or earlier. There is a similar subsystem, known as WoW64, on 64-bit Windows versions that runs 32-bit programs.

This subsystem has since been discontinued as of 2021. The last version of Windows to include this subsystem is Windows 10, as Windows 11 (and Windows Server 2008 R2 and later) dropped support for 32-bit processors and therefore cannot run 16-bit software without third-party emulation software (e.g. DOSBox).

  1. ^ "WOW Environment Remains in Memory After Quitting 16-Bit Program". Support. Microsoft. February 22, 2007. Archived from the original on October 23, 2007. Retrieved February 7, 2017.
  2. ^ "Starting 16-Bit WOW Subsystem on Windows NT Server". Support. Microsoft. November 1, 2016. Archived from the original on May 9, 2007. Retrieved February 7, 2017.
  3. ^ "Disabling the MSDOS and WOWEXEC Subsystems on Terminal Server". Support. Microsoft. November 1, 2006. Archived from the original on January 13, 2008. Retrieved February 7, 2017.