Microsoft recognized a shift in the market following the success of the Apple Macintosh, which popularized the GUI. To compete and to make computers more accessible to the general public, Microsoft began developing a graphical shell known initially as "Interface Manager." This was later renamed "Windows" to better describe the computing "windows" on the screen.
The "1st Windows OS," officially known as , was released on November 20, 1985 . It was not a standalone operating system but rather a graphical "operating environment" that ran on top of MS-DOS .
1985 Microsoft Boxed Software - Windows Operating System 1.0 Collector Archive Services