OS/2 Version 2.0 provides the capability for Microsoft Windows applications to run under OS/2 Version 2.0. This support allows applications written for Windows 3.0 and previous versions of Windows (except V1.x) to coexist with OS/2 and DOS applications under OS/2 Version 2.0.
Each Windows application executes in a virtual DOS machine, and is thus a protected mode process. As such, Windows applications are subject to the same application protection facilities provided to other protected mode processes under OS/2 Version 2.0. Windows applications are protected from other Windows applications and from DOS and OS/2 applications executing in the system. This is in contrast to the native Windows 3.0 environment, where limited protection is provided for Windows 3.0 applications, and none at all for DOS applications unless Windows is running in enhanced mode.
The execution of Windows applications as protected mode tasks also allows these applications to take full advantage of the pre-emptive multitasking capabilities of OS/2 Version 2.0, with full pre-emptive multitasking between Windows applications, OS/2 applications, and DOS applications. This is again in contrast to the native Windows 3.0 environment, where pre-emptive multitasking is available only when Windows 3.0 is running in enhanced mode, thereby impacting performance and preventing many applications written for previous versions of Windows from executing. OS/2 Version 2.0 has no such restriction.
Windows applications running under OS/2 Version 2.0 will run in a mode equivalent to the real or standard modes of Windows 3.0; the enhanced mode of Windows 3.0 is not required since the OS/2 Version 2.0 operating system itself provides equivalent function.
Support for Microsoft Windows applications under OS/2 Version 2.0 is discussed in more depth in Windows Applications.