The term Windows collectively describes any or all of several generations of Microsoft (MS) operating system (OS) products. These products are generally categorized as follows:
16-bit operating environments
The early versions of Windows were often thought of as just graphical user interfaces, mostly because they ran on top of MS-DOS and used it for file system services.[3] However, even the earliest 16-bit Windows versions already assumed many typical operating system functions, notably, having their own executable file format and providing their own device drivers (timer, graphics, printer, mouse, keyboard and sound) for applications. Unlike MS-DOS, Windows allowed users to execute multiple graphical applications at the same time, through cooperative multitasking. Finally, Windows implemented an elaborate, segment-based, software virtual memory scheme, which allowed it to run applications larger than available memory: code segments and resources were swapped in and thrown away when memory became scarce, and data segments moved in memory when a given application had relinquished processor control, typically waiting for user input.[citation needed] 16-bit Windows versions include Windows 1.0 (1985), Windows 2.0 (1987) and its close relative, Windows/286.
| Windows OS market share | ||||
| Source | Hitslink[4] | Awio[5] | XiTi[6] | OneStat[7] |
| Date | May 2008 | May 2008 | Apr 2008 | Mar 2008 |
| All versions | 91.13%[8] | - | 94.45% | 95.94% |
| Windows XP | 72.12% | 78.24% | 75.16% | 78.93% |
| Windows | 15.26% | 7.69% | 15.81% | 13.24% |
| Windows 2000 | 2.25% | 3.07% | 1.76% | 2.82% |
| Windows 98 | 0.48% | 0.96% | 0.48% | 0.58% |
| Windows 2003 | - | 0.74% | 0.49% | - |
| Windows NT | 0.68% | 0.05% | 0.05% | - |
| Windows ME | 0.27% | 0.36% | 0.20% | 0.31% |
| Windows CE | 0.06% | - | 0.02% | - |
| Windows 95 | 0.01% | - | 0.01% | - |
| Windows other | - | - | 0.47% | - |
Hybrid 16/32-bit operating environments
Windows/386 introduced a 32-bit protected mode kernel and virtual machine monitor. For the duration of a Windows session, it created one or more virtual 8086 environments and provided device virtualization for the video card, keyboard, mouse, timer and interrupt controller inside each of them. The user-visible consequence was that it became possible to preemptively multitask multiple MS-DOS environments in separate windows, although graphical MS-DOS applications required full screen mode. Also, Windows applications were multi-tasked cooperatively inside one such virtual 8086 environment.
Windows 3.0 (1990) and Windows 3.1 (1992) improved the design, mostly because of virtual memory and loadable virtual device drivers (VxDs) which allowed them to share arbitrary devices between multitasked DOS windows.[citation needed] Also, Windows applications could now run in protected mode (when Windows was running in Standard or 386 Enhanced Mode), which gave them access to several megabytes of memory and removed the obligation to participate in the software virtual memory scheme. They still ran inside the same address space, where the segmented memory provided a degree of protection, and multi-tasked cooperatively. For Windows 3.0, Microsoft also rewrote critical operations from C into assembly, making this release faster and less memory-hungry than its predecessors.[citation needed]
Hybrid 16/32-bit operating systems
With the introduction of the 32-bit Windows for Workgroups 3.11, Windows was able to stop relying on DOS for file management.[citation needed] Levering this, Windows 95 introduced Long File Names, reducing the 8.3 filename DOS environment to the role of a boot loader. MS-DOS was now bundled with Windows; this notably made it (partially) aware of long file names when its utilities were run from within Windows. The most important novelty was the possibility of running 32-bit multi-threaded preemptively multitasked graphical programs. However, the necessity of keeping compatibility with 16-bit programs meant the GUI components were still 16-bit only and not fully reentrant, which resulted in reduced performance and stability.
There were three releases of Windows 95 (the first in 1995, then subsequent bug-fix versions in 1996 and 1997, only released to OEMs, which added extra features such as FAT32 and primitive USB support). Microsoft's next OS was Windows 98; there were two versions of this (the first in 1998 and the second, named "Windows 98 Second Edition", in 1999). In 2000, Microsoft released Windows Me (Me standing for Millennium Edition), which used the same core as Windows 98 but adopted some aspects of Windows 2000 and removed the option boot into DOS mode. It also added a new feature called System Restore, allowing the user to set the computer's settings back to an earlier date.
32-bit operating systems
The NT family of Windows systems was fashioned and marketed for higher reliability business use, and was unencumbered by any Microsoft DOS patrimony.[citation needed] The first release was Windows NT 3.1 (1993, numbered "3.1" to match the Windows version and to one-up OS/2 2.1,[citation needed] IBM's flagship OS co-developed by Microsoft and was Windows NT's main competitor at the time), which was followed by NT 3.5 (1994), NT 3.51 (1995), and NT 4.0 (1996); NT 4.0 was the first in this line to implement the "Windows 95" user interface (and the first to include Windows 95's built-in 32-bit runtimes). Microsoft then moved to combine their consumer and business operating systems. Their first attempt, Neptune was cancelled and replaced with a new project, Whistler, which later became Windows XP, coming in both home and professional versions (and later niche market versions for tablet PCs and media centers) improved stability, user experience and backwards compatibility. Then, Windows Server 2003 brought Windows Server up to date with Windows XP. Since then, a new version, Windows Vista was released and Windows Server 2008, released on February 27, 2008, brings Windows Server up to date with Windows Vista.
Windows CE, Microsoft's offering in the mobile and embedded markets, is also a true 32-bit operating system that offers various services for all sub-operating workstations.
64-bit operating systems
Windows NT included support for several different platforms before the x86-based personal computer became dominant in the professional world. Versions of NT from 3.1 to 4.0 supported DEC Alpha and MIPS R4000, which were 64-bit processors, although the operating system treated them as 32-bit processors.
With the introduction of the Intel Itanium architecture, which is referred to as IA-64, Microsoft released new versions of Windows 2000 to support it. Itanium versions of Windows XP and Windows Server 2003 were released at the same time as their mainstream x86 (32-bit) counterparts. On April 25, 2005, Microsoft released Windows XP Professional x64 Edition and x64 versions of Windows Server 2003 to support the AMD64/Intel64 (or x64 in Microsoft terminology) architecture. Microsoft dropped support for the Itanium version of Windows XP in 2005. Windows Vista is the first end-user version of Windows that Microsoft has released simultaneously in 32-bit and x64 editions. Windows Vista does not support the Itanium architecture. The modern 64-bit Windows family comprises AMD64/Intel64 versions of Windows Vista, and Windows Server 2003, in both Itanium and x64 editions.
