OS/2 Version 2.0 provides the capability for Windows applications to run under OS/2 Version 2.0 using its WIN-OS/2* component. This support allows applications written for Windows 3.0 and previous versions of Windows to coexist and execute in the same machine.
Each Windows application executes as a protected mode process. Windows applications are, therefore, subject to the full application protection facilities provided to protected mode applications under OS/2 Version 2.0, and are protected from one another and from DOS or OS/2 applications executing in the system. This protection is in contrast to the native Windows 3.0 environment, where protection is limited to Windows 3.0 applications only, provided these applications use Windows' memory management services. Protection for DOS applications is provided only when Windows is running in 386 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, DOS applications, and OS/2 applications. This protection 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 386 enhanced mode, and only for DOS applications, thereby impacting performance and preventing many applications written for previous versions of Windows from executing. OS/2 Version 2.0 has no such restriction.
Support for Windows applications under OS/2 Version 2.0 is discussed in more detail in OS/2 Version 2.0 - Volume 2: DOS and Windows Environment.