Microsoft POSIX subsystem – a compatibility layer subsystem for Windows NT which implements the POSIX.1 standard.
The Portable Operating System for UNIX (POSIX) subsystem is not included with Windows XP or with Windows Server 2003. The POSIX subsystem has been replaced with a more UNIX-like environment that is named Windows Services for UNIX. Windows Services for UNIX is a superset of the original POSIX subsystem and provides greater functionality for UNIX programs. Windows Services for UNIX requires Windows XP Professional Service Pack 1 (SP1) or later.
The OS/2 subsystem is not included with Windows XP or with Windows Server 2003. An alternative solution for OS/2 programs is Microsoft Virtual PC 2004. Virtual PC 2004 supports most OS/2 programs including OS/2 programs that have a graphical user interface (GUI).
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