(Windows Operating System) A redundant term because Windows "is" an operating system. However, the term may be used to contrast the Windows desktop OS with the Windows Phone smartphone OS. See Windows and Windows Phone.
"Windows OS." YourDictionary, n.d. Web. 16 August 2018. <http://www.yourdictionary.com/windows-os>.
Windows OS. (n.d.). Retrieved August 16th, 2018, from http://www.yourdictionary.com/windows-os