Although Windows XP could emulate DOS, it could not run many of its applications, as those applications ran only in real mode to directly access the computer's hardware, and Windows XP's protected mode prevented such direct access for security reasons. A member of the series is Windows XP, which debuted on October 25, 2001, to become the first consumer-oriented version of Windows to not use DOS. Conversely, the Windows NT operating systems were not based on DOS. These versions of Windows could run DOS applications. Windows 3.0 and its updates were operating environments that ran on top of MS-DOS, and the Windows 9x series consisted of operating systems that were still based on MS-DOS. Before Windows NT 3.0, consumer-oriented versions of Windows were based on MS-DOS.
