The term Windows collectively describes any or all of several generations of Microsoft operating system products. These products are generally categorized as follows:
Early versions
The history of Windows dates back to September 1981, when Chase Bishop, a computer scientist, designed the first model of an electronic device and project "Interface Manager" was started. It was announced in November 1983 (after the Apple Lisa, but before the Macintosh) under the name "Windows", but Windows 1.0 was not released until November 1985. The shell of Windows 1.0 was a program known as the MS-DOS Executive. Other supplied programs were Calculator, Calendar, Cardfile, Clipboard viewer, Clock, Control Panel, Notepad, Paint, Reversi, Terminal, and Write. Windows 1.0 did not allow overlapping windows. Instead all windows were tiled. Only dialog boxes could appear over other windows.
Windows 2.0 was released in October 1987 and featured several improvements to the user interface and memory management. Windows 2.0 allowed application windows to overlap each other and also introduced more sophisticated keyboard shortcuts. It could also make use of expanded memory.
Windows 2.1 was released in two different versions: Windows/386 employed the 386 virtual 8086 mode to multitask several DOS programs, and the paged memory model to emulate expanded memory using available extended memory. Windows/286 (which, despite its name, would run on the 8086) still ran in real mode, but could make use of the high memory area.
The early versions of Windows were often thought of as simply graphical user interfaces, mostly because they ran on top of MS-DOS and used it for file system services. 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. 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.
Windows 3.0 and 3.1
Windows 3.0 (1990) and Windows 3.1 (1992) improved the design, mostly because of virtual memory and loadable virtual device drivers (VxDs) that allowed them to share arbitrary devices between multitasked DOS windows. 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.
Windows 95, 98, and Me
Windows 95 was released in August 1995, featuring a new user interface, support for long file names of up to 255 characters, and the ability to automatically detect and configure installed hardware (plug and play). It could natively run 32-bit applications, and featured several technological improvements that increased its stability over Windows 3.1. There were several OEM Service Releases (OSR) of Windows 95, each of which was roughly equivalent to a service pack.
Microsoft's next release was Windows 98 in June 1998. Microsoft released a second version of Windows 98 in May 1999, named Windows 98 Second Edition (often shortened to Windows 98 SE).
In February 2000, Windows 2000 (in the NT family) was released, followed by Windows Me in September 2000 (Me standing for Millennium Edition). Windows Me updated the core from Windows 98, but adopted some aspects of Windows 2000 and removed the "boot in DOS mode" option. It also added a new feature called System Restore, allowing the user to set the computer's settings back to an earlier date.
The NT family of Windows systems was fashioned and marketed for higher reliability business use. The first release was NT 3.1 (1993), numbered "3.1" to match the consumer Windows version, which was followed by NT 3.5 (1994), NT 3.51 (1995), NT 4.0 (1996), and Windows 2000, which is the last NT-based Windows release that does not include Microsoft Product Activation. Windows 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 with Windows XP that was released on October 25, 2001. It came both in home and professional versions (and later niche market versions for tablet PCs and media centers); they also diverged release schedules for server operating systems. Windows Server 2003, released a year and a half after Windows XP, brought Windows Server up to date with Windows XP. After a lengthy development process, Windows Vista was released on November 30, 2006 for volume licensing and January 30, 2007 for consumers. And its server counterpart, Windows Server 2008 was released in early 2008. On July 22, 2009, Windows 7 and Windows Server 2008 R2 were released as RTM (release to manufacturing) while the former was released to the public 3 months later on October 22, 2009.
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 variously supported PowerPC, DEC Alpha and MIPS R4000, some of which were 64-bit processors, although the operating system treated them as 32-bit processors.
With the introduction of the Intel Itanium architecture (also known as IA-64), Microsoft released new versions of Windows 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 Windows Server 2003 x64 Editions to support the x86-64 (or x64 in Microsoft terminology) architecture. Microsoft dropped support for the Itanium version of Windows XP in 2005. Windows Vista was the first end-user version of Windows that Microsoft released simultaneously in x86 and x64 editions. Windows Vista does not support the Itanium architecture. The modern 64-bit Windows family comprises AMD64/Intel64 versions of Windows 7 and Windows Server 2008, in both Itanium and x64 editions. Windows Server 2008 R2 drops the 32-bit version, although Windows 7 does not.
Windows CE
Windows CE (officially known as Windows Embedded Compact), is an edition of Windows that runs on minimalistic computers, like satellite navigation systems and some mobile phones. Windows Embedded Compact is based on its own dedicated kernel, dubbed Windows CE kernel. Microsoft licenses Windows CE to OEMs and device makers. The OEMs and device makers can modify and create their own user interfaces and experiences, while Windows CE provides the technical foundation to do so.
Windows Embedded Compact is not to be confused with Windows XP Embedded or Windows NT 4.0 Embedded, modular editions of Windows based on Windows NT kernel.
Future of Windows
Windows 8, the successor to Windows 7, is currently in development. Microsoft posted a blog entry in Dutch on October 22, 2010 hinting that Windows 8 would be released in roughly 1 year. Also, during the pre-Consumer Electronics Show keynote, Microsoft's CEO announced that Windows 8 will also run on ARM CPUs. This Windows version will also be more suitable for tablets and netbooks, featuring a more touch-friendly interface. Several new features will also be introduced, such as support for USB 3.0 and the ability to run Windows from USB devices (like USB Hard Disks or USB Flash drives) with Windows To Go.
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