Environmental subsystems are central components of
operating system
An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs.
Time-sharing operating systems scheduler (computing), schedule tasks for ...
s of the
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 ...
type. They allow the operating system to run software developed for the platform in question. For example, Windows NT 4.0 has four environmental subsystems, for example Win32, DOS or Win16,
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
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 ...
, the latter of which is a Unix standard. The latter resides primarily in the Dynamic Link Library ''posix.dll''.
The environmental subsystems are one part of the strategy Microsoft developed for making the Windows NT stream of operating systems a hub for multi-platform computing Others include four
Hardware Abstraction
Hardware abstractions are sets of routines in software that provide programs with access to hardware resources through programming interfaces. The programming interface allows all devices in a particular class ''C'' of hardware devices to be acc ...
layers, one for Intel processors, three for
RISC
In electronics and computer science, a reduced instruction set computer (RISC) is a computer architecture designed to simplify the individual instructions given to the computer to accomplish tasks. Compared to the instructions given to a comp ...
processors (DEC Alpha, PowerPC, Mips), and a driver for the
HPFS, the standard for OS/2. Since Windows 2000, the
FAT32
File Allocation Table (FAT) is a file system developed for personal computers and was the default file system for the MS-DOS and Windows 9x operating systems. Originally developed in 1977 for use on floppy disks, it was adapted for use on ...
file system first introduced with Windows 95 has also been present, with HPFS deprecated then being omitted in later systems.
A third-party driver for FAT32 can be used on the earlier NT operating systems. Therefore, Windows NT as of version 4.0 had a default of four file systems (
NTFS
NT File System (NTFS) (commonly called ''New Technology File System'') is a proprietary journaling file system developed by Microsoft in the 1990s.
It was developed to overcome scalability, security and other limitations with File Allocation Tabl ...
, HPFS,
FAT12
File Allocation Table (FAT) is a file system developed for personal computers and was the default file system for the MS-DOS and Windows 9x operating systems. Originally developed in 1977 for use on floppy disks, it was adapted for use on ...
, and
FAT16
File Allocation Table (FAT) is a file system developed for personal computers and was the default file system for the MS-DOS and Windows 9x operating systems. Originally developed in 1977 for use on floppy disks, it was adapted for use on Ha ...
), 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. Interoperability with Novell 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.
References
Windows NT architecture
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