macOS, which stands for Macintosh Operating System, is Apple Inc.'s operating system for Apple Macintosh computers, and is closely related to iOS, Apple's operating system for other Apple products such as the iPod Touch, iPhone, and iPad. Mac OS was the first commercially successful operating system to use a purely graphical user interface. The original Macintosh team included Bill Atkinson, Jef Raskin and Andy Hertzfeld.