Microsoft Corporation purchased the rights to QDOS and developed it further, calling it MS (for Microsoft)/DOS. When IBM decided to develop a line of personal computers based on the Intel 8086, they considered both CP/M 86 and MS-DOS, but ultimately decided to use the latter - calling it PC/DOS on their systems.
MS-DOS has gone through a series of versions. Version 1 resembled CP/M very closely. Beginning with Version 2, Microsoft began incorporating ideas from Unix as well, and Version 3 began including support for networking. One consequence of this history is that there are often several ways of accomplishing the same function, since older mechanisms have been left in place for compatibility with older programs.