A long time ago, in a galaxy far away, there was the Control Program for Microcomputers, or CP/M. Then came the Digital Research Disk Operating System, or DRDOS, but after this came the mighty Bill 'Pearly' Gates, and the omnipresent Microsoft Disk Operating System, MSDOS, ruled the world of computing, in several iterations up to DOS6.22. The first Windows systems were merely overlays on MSDOS, but by the time of Windows 95, it was fair to say that it was an operating system in its own right.