Unix emulators

Cygwin ( ) is a free and open-source Unix-like environment and command-line interface (CLI) for Microsoft Windows. The project also provides a software repository containing open-source packages. Cygwin allows source code for Unix-like operating systems to be compiled and run on Windows. Cygwin provides native integration of Windows-based applications.

Interix was an optional, POSIX-conformant Unix subsystem for Windows NT operating systems. Interix was a component of Windows Services for UNIX, and a superset of the Microsoft POSIX subsystem. Like the POSIX subsystem, Interix was an environment subsystem for the NT kernel. It included numerous open source utility software programs and libraries. Interix was originally developed and sold as OpenNT until purchased by Microsoft in 1999.

UWIN is a computer software package created by David Korn which allows programs written for the operating system Unix to be built and run on Microsoft Windows with few, if any, changes. Some of the software development was subcontracted to Wipro, India. References, correct or not, to the software as U/Win and AT&T Unix for Windows can be found in some cases, especially from the early days of its existence.