The first few releases of Microsoft Windows in the early 1980s were little more than clunky graphical application launchers that ran on top of the Disk Operating System (DOS) (see Chapter 14 for details). Version 3.x, released in the late 1980s, gained popularity due to its improved interface (awful by today's standards) and capability to access all of a computer's memory. Being based on DOS, however, it was not terribly stable, crashed frequently, and had very limited support for networking and no support for multiple user accounts.
Soon thereafter, Windows NT 3.1 ("NT" for New Technology) was released. Although it shared the same interface as Windows 3.1, it was based on a more robust and more secure kernel, the underlying code on which the interface and all of the applications run. Among other things, it didn't rely on DOS and was capable of running 32-bit applications (Windows 3.1 could run only more feeble 16-bit applications).[*] Unfortunately, it was a white elephant of sorts, enjoying limited commercial appeal due to its stiff hardware requirements and scant industry support.
In 1995, Microsoft released Windows 95. Although based on DOS, like Windows 3.x (it was known internally as Windows 4.0), it was a 32-bit operating system with a new interface. It was the first step toward bringing the enhanced capability of the Windows NT architecture to the more commercially accepted, albeit less capable, DOS-based Windows line. Soon thereafter, Windows NT 4.0 was released, which brought the new Windows 95-style interface to the NT line. Both of these grand gestures were engineered to further blur the line between these two different Microsoft platforms. Although both operating systems sported the same interface, Windows NT still never garnered the consumer support and commercial success of Windows 95, but it did become popular for use with servers.
As time progressed, the lineage of Microsoft Windows became even less linear. Despite its name, Windows 2000 was not the successor to Windows 98 and Windows 95; Windows Me, released at the same time, had that distinction. Instead, Windows 2000 was the next installment of the NT line; it was actually known internally as Windows NT 5.0. Windows 2000 was particularly notable for being the first version of Windows NT to support Plug and Play, which was yet another move to combine the two platforms.
Then came Windows XP, known internally as Windows NT 5.1. Although it was technically merely an incremental upgrade to Windows 2000, it was positioned as the direct replacement to Windows Me, officially marking the end of the DOS-based Windows 9x/Me line. Windows XP unified both lines of Windows, bringing the stability of NT to home and small-business users and the industry support of Windows 9x/Me to corporate and power users.
Now Windows Vista has entered the picture, and it makes significant improvements to the user experience, the stability of the operating system, and security. It is the first revision to the unified Windows code, and it overhauls the interface itself as well as the internal workings of the operating system, most notably related to security. It was also developed with mobility and networking in mind, and it makes significant advances in how people can collaborate across networks. In addition, it adds more multimedia capabilities to Windows.