Windows OS is a graphical user interface (GUI) operating system developed by Microsoft. It was first released in 1985 as an add-on for MS-DOS, which was the most popular version of MS-DOS at that time. In its early days, Windows OS was known as “Microsoft DOS” or “MS-DOS” and later on it became known as Windows 1.0 in 1987. The name changed to Windows NT when it was released in 1993 and then again