abstract:IBM PC DOS (full name: The IBM Personal Computer Disk Operating System) is a DOS system for the IBM Personal Computer and compatibles, manufactured and sold by IBM from the 1980s to the 2000s. From its inception until 1993, PC DOS was a rebranded version of Microsoft MS-DOS.
Those companies were able to clone the IBMPC because IBM made the mistake of allowing its partner, Microsoft, to license a virtually identical version of its PC-DOS operating system to any takers.