Windows NT is a family of Operating Systems created by Microsoft as a part of the Microsoft Windows line of operating systems. Windows NT was the first version of Windows to not need MS-DOS.
Windows NT 3.1 was the first version of Windows NT. The version number took after Windows 3.1's name. NT 3.1's apperance was very similar to Windows 3.1. Because of the high system requirements, not many people were able to find PCs powerful enough for the operating system. NT 3.1 also had the capability of running 32-bit applications.
Windows NT 4.0 was the last version of NT to have NT in the name. The GUI of NT 4.0 took after Windows 96. This version was more wide spread than NT 3.1.
After 4.0, Windows NT went on to appear as Windows NT 5.0, Windows XP, etc. The latest appearence of Windows NT is Windows 10.