 In the 1990s, the product line evolved from an operating environment into a fully complete, modern operating system over two lines of development, each with their own separate codebase.The first versions of Windows (1.0 through to 3.11) were graphical shells that ran from MS-DOS.Later on, Windows 95, though still being based on MS-DOS, was its own operating system, using a 16-bit DOS-based kernel and a 32-bit user space.