Microsoft POSIX subsystem

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Microsoft POSIX subsystem is one of four subsystems of several operating systems from the Windows NT family (together with OS/2, Win32 and Windows Subsystem for Linux[1]).

Microsoft Windows implements only the first version of the POSIX standards, namely POSIX.1. The official code of POSIX.1 is ISO/IEC 9945-1:1990 or IEEE standard 1003.1-1990. The subsystem was included because of 1980s US federal government's requirements listed in Federal Information Processing Standard (FIPS) 151-2.[2] Versions Windows NT 3.5, Windows NT 3.51 and Windows NT 4 were certified as compliant with the FIPS 151-2.

The runtime environment of the subsystem is provided by two files: psxss.exe and psxdll.dll. A POSIX application uses psxdll.dll to communicate with the subsystem while communicating with posix.exe to provide display capabilities on the Windows desktop.

The POSIX subsystem was removed with Windows XP / Windows Server 2003. It was replaced by "Windows Services for UNIX",[3] which uses the Interix subsystem.

Windows 10 anniversary update features a new Windows Subsystem for Linux

See also


  1. ^ Hammons, Jack (22 April 2016). "Windows Subsystem for Linux Overview". Microsoft Developer. Microsoft. Retrieved 21 December 2016. )
  2. ^ "Federal Information Processing Standards Publication 151-2". 
  3. ^ "POSIX and OS/2 are not supported in Windows XP or in Windows Server 2003". 


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