Which Microsoft operating system first launched in 1985?

Windows first launched in 1985 as Microsoft Windows 1.0.

Microsoft released Windows 1.0 on November 20, 1985. It provided a graphical environment that ran on top of MS-DOS and included early versions of applications such as Calculator, Paint, Notepad, and a clock.

Windows 1.0 was not a complete replacement for MS-DOS. Instead, it extended Microsoft’s command-line operating system with windows, menus, icons, and support for a mouse. The first release required a computer with at least 256 kilobytes of memory and graphics hardware compatible with the system.

Later Windows versions became far more influential, especially Windows 3.0, Windows 95, and Windows XP. A common mix-up is calling Windows 1.0 the first Microsoft operating system; MS-DOS preceded it, while Windows began as a graphical layer over DOS.