# Environmental subsystem

> Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Environmental_subsystem
> Markdown URL: https://mediated.wiki/source/Environmental_subsystem.md
> Source: https://en.wikipedia.org/wiki/Environmental_subsystem
> Source revision: 1317432079
> License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/)

{{Multiple issues|
{{refimprove|date=December 2015}}
{{Third-party|date=June 2024}}
}}
'''Environmental subsystems''' are central components of the [Windows NT](/source/Windows_NT) [operating system](/source/operating_system). They allow the operating system to run software developed for the platform in question. For example, [Windows NT 4.0](/source/Windows_NT_4.0) has four environmental subsystems: Win32, DOS or Win16, [OS/2](/source/OS%2F2), and [POSIX](/source/POSIX), the latter of which is a [Unix](/source/Unix) standard.<ref>{{Cite book|title = Inside Windows NT|last = Various|publisher = New Riders press|year = 1993|isbn = |location = |pages = |bibcode = 1993iwn..book.....C}}</ref> The latter resides primarily in the Dynamic Link Library ''posix.dll''.  

The environmental subsystems are one part of the strategy [Microsoft](/source/Microsoft) developed for making the Windows NT stream of operating systems a hub for multi-platform computing.<ref>{{Cite book|title = Windows NT 4.0 Workstation Resource Kit|last = |first = |publisher = Microsoft Press|year = 1996|isbn = |location = |pages = }}</ref> Others include four [Hardware Abstraction](/source/Hardware_abstraction) layers, one for Intel processors, three for [RISC](/source/RISC) processors (DEC Alpha, PowerPC, Mips), and a driver for the [HPFS](/source/High_Performance_File_System), the standard for OS/2. Since Windows 2000, the [FAT32](/source/FAT32) file system first introduced with Windows 95 has also been present, with HPFS deprecated then being omitted in later systems.<ref>{{Cite book|title = Windows NT 4.0 Server Resource Kit|last = |first = |publisher = Microsoft Press|year = 1998|isbn = |location = |pages = }}</ref> A third-party driver for FAT32 can be used on the earlier NT operating systems.{{fact|date=December 2015}} Therefore, Windows NT as of version 4.0  had a default of four file systems ([NTFS](/source/NTFS), HPFS, [FAT12](/source/FAT12), and [FAT16](/source/FAT16)), and installations of the system with a driver allowing access to a fifth (FAT32) are very common, and tools allowing access to Unix file systems are also in existence.{{fact|date=December 2015}} Interoperability with [Novell Netware](/source/NetWare) is generally implemented at the applications and systems programming level rather than at the kernel and data link layer and therefore further from the physical hardware.{{fact|date=December 2015}}

==References==
{{Reflist}}

Category:Windows NT architecture

{{operating-system-stub}}

---
Adapted from the Wikipedia article [Environmental subsystem](https://en.wikipedia.org/wiki/Environmental_subsystem) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Environmental_subsystem?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.