For most users, the key measure of interoperability is the ability to run the same applications on multiple platforms. Three key factors are furthering this type of interoperability between UNIX and Windows NT computers.
One factor is the relative ease with which many UNIX independent software vendors (ISVs) are able to port their high-end business and technical applications to the Win32 API of Windows NT. Aiding this process is the fact that most UNIX applications are written in standard C and so are readily adapted to other operating systems (such as Windows NT) for which standard C libraries have been developed. A wide variety of third-party porting aids (including items as diverse asXlibs, GNU tools, and X Client libraries) are available through commercial sources and from Internet. Because application developers are finding it so easy to port their traditionally UNIX-based applications to Windows NT, increasing numbers of such applications will be available for both UNIX platforms and for computers running Windows NT.
Another factor is that Windows NT fully supports programs that conform to the IEEE 1003.1-1990 standard commonly known as POSIX.1 (derived from Portable Operating System Interface). This standard defines a basic set of operating-system services available to character-based applications. Programs that adhere to the POSIX standard can be easily ported from one operating system to another. See Chapter 17, "POSIX Compatibility," of the Windows NT Resource Guide for more information.
Another factor is that third-party products from vendors such as Bristol Technologies are available that enable UNIX to run Windows-based applications. Additionally, there are third-party products, such as Consensys Portage, that enable Windows NT to run UNIX-based applications.