Microsoft named their project to develop a new operating system as “Interface Manager”. They followed a marketing strategy of using basic, descriptive, and one-word names. At the time of the original release of OS in late 1985, most of the operating systems were single-tasking, text-only, and ran from a command line like DOS. And Mac was the only GUI system enjoying commercial success at that time. The word “Windows” describes the differences between a GUI and a command-line interface. But, the name was never officially Windows but it is Microsoft Windows.