Microsoft POSIX subsystem is one of four subsystems shipped with the first versions of

Windows NT Windows NT is a Proprietary software, proprietary Graphical user interface, graphical operating system produced by Microsoft as part of its Windows product line, the first version of which, Windows NT 3.1, was released on July 27, 1993. Original ...

, the other three being the

Win32 The Windows API, informally WinAPI, is the foundational application programming interface (API) that allows a computer program to access the features of the Microsoft Windows operating system in which the program is running. Programs can acces ...

subsystem which provided the primary

API An application programming interface (API) is a connection between computers or between computer programs. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how to build ...

for Windows NT, plus the

OS/2 OS/2 is a Proprietary software, proprietary computer operating system for x86 and PowerPC based personal computers. It was created and initially developed jointly by IBM and Microsoft, under the leadership of IBM software designer Ed Iacobucci, ...

and

security Security is protection from, or resilience against, potential harm (or other unwanted coercion). Beneficiaries (technically referents) of security may be persons and social groups, objects and institutions, ecosystems, or any other entity or ...

subsystems.

Features

The subsystem only implements the

POSIX The Portable Operating System Interface (POSIX; ) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines application programming interfaces (APIs), along with comm ...

standard Standard may refer to: Symbols * Colours, standards and guidons, kinds of military signs * Standard (emblem), a type of a large symbol or emblem used for identification Norms, conventions or requirements * Standard (metrology), an object ...

also known as

IEEE The Institute of Electrical and Electronics Engineers (IEEE) is an American 501(c)(3) organization, 501(c)(3) public charity professional organization for electrical engineering, electronics engineering, and other related disciplines. The IEEE ...

Std 1003.1-1990 or

ISO/IEC ISO/IEC JTC 1, entitled "Information technology", is a joint technical committee (JTC) of the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC). Its purpose is to develop, maintain and ...

9945-1:1990 primarily covering the kernel and C library programming interfaces which allowed a program written for other POSIX.1-compliant operating systems to be compiled and run under Windows NT. The Windows NT POSIX subsystem did not provide the interactive user environment parts of POSIX, originally standardized as POSIX.2. That is, Windows NT did not provide a POSIX shell nor any Unix commands out of the box, except for pax. The NT POSIX subsystem also did not provide any of the POSIX extensions that postdated the creation of Windows NT 3.1, such as those for

POSIX Threads In computing, POSIX Threads, commonly known as pthreads, is an execution model that exists independently from a programming language, as well as a parallel execution model. It allows a program to control multiple different flows of work that ov ...

or POSIX

IPC IPC may refer to: Businesses and organizations Arts and media * Intellectual Property Committee, a coalition of US corporations with intellectual property interests * International Panorama Council, an international network of specialists in ...

Background

The NT POSIX subsystem was included with the first versions of Windows NT because of 1980s

US federal government The Federal Government of the United States of America (U.S. federal government or U.S. government) is the national government of the United States. The U.S. federal government is composed of three distinct branches: legislative, execut ...

requirements listed in

Federal Information Processing Standard The Federal Information Processing Standards (FIPS) of the United States are a set of publicly announced standards that the National Institute of Standards and Technology (NIST) has developed for use in computer systems of non-military United Stat ...

(FIPS) 151-2. This standard required that certain types of government purchases be POSIX-compliant, so that if Windows NT had not included this subsystem, computing systems based on it would not have been eligible for some government contracts. Windows NT versions 3.5, 3.51 and 4.0 were certified as compliant with FIPS 151-2. The

runtime environment In computer programming, a runtime system or runtime environment is a sub-system that exists in the computer where a program is created, as well as in the computers where the program is intended to be run. The name comes from the compile time ...

of the subsystem is provided by two files: and . A POSIX application uses to communicate with the subsystem while communicating with to provide display capabilities on the Windows desktop.

Update

The POSIX subsystem was replaced in

Windows XP Windows XP is a major release of Microsoft's Windows NT operating system. It was released to manufacturing on August 24, 2001, and later to retail on October 25, 2001. It is a direct successor to Windows 2000 for high-end and business users a ...

and

Windows Server 2003 Windows Server 2003, codenamed "Whistler Server", is the sixth major version of the Windows NT operating system produced by Microsoft and the first server version to be released under the Windows Server brand name. It is part of the Windows NT ...

by " Windows Services for UNIX", (SFU) which is based in part on

OpenBSD OpenBSD is a security-focused operating system, security-focused, free software, Unix-like operating system based on the Berkeley Software Distribution (BSD). Theo de Raadt created OpenBSD in 1995 by fork (software development), forking NetBSD ...

code and other technology developed by

Interix 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 environme ...

, a company later purchased by Microsoft. SFU was removed from later versions of Windows 8 and Windows Server 2012. SFU is logically, though not formally, replaced by the

Windows Subsystem for Linux Windows Subsystem for Linux (WSL) is a component of Microsoft Windows that allows the use of a GNU/Linux environment from within Windows, foregoing the overhead of a virtual machine and being an alternative to dual booting. The WSL command-lin ...

(WSL) in the

Windows 10 Anniversary Update Windows 10 Anniversary Update (also known as version 1607 and codenamed "Redstone 1") is the second major update to Windows 10 Windows 10 is a major release of Microsoft's Windows NT operating system. The successor to Windows 8.1, it wa ...

and Windows Server 2016 Version 1709 respectively.

Features

Background

Update

See also

References

Further reading