It is only an accident of 1980's technological development that you can run the Microsoft operating systems on hardware other than an official IBM-branded PC.
IBM didn't rush out and license or publish instructions to enable Compaq and Gateway and Dell and Toshiba and Hewlett-Packard and the rest of them to create clones of the PC, clones that would run the very same operating system.
I repeat, they DID NOT DO THAT.
What they
did do was:
• create the original PC with a high percentage of standard off-the-shelf components, mostly cutting corners there to make it easier to develop a personal computer in a hurry and get it out the door; and
• farm out the development of the OS software to a 3rd party (Microsoft), again cutting corners because they didn't take personal computers (microcomputers) seriously enough to put a lot of their own resources into it.
Then, when the architecture was cloned, and folks could buy PCs that weren't from IBM, thereby cutting into IBM revenue, IBM
TRIED BUT FAILED TO:
• develop a new architecture that would be closed, full of proprietary components not so easily cloned. It was called the PS/2, if I recall correctly (not the PlayStation known by the same term, obviously). Google "Micro-channel architecture". They succeeded in developing it, but not in pushing the mainstream conventional clone-PC off the market. MCA died out in fairly short order; and
• develop, in conjunction with Microsoft, a new OS that would supplant DOS. As the OS developer, they could more easily swing a combination hardware/software shift that would leave the clones behind. This was OS/2. Microsoft undercut them with Windows and they parted company and the rest, as they say, is history.
Apple came out with the Mac when Compaq and HP boxes were still called "clones" and "IBM-compatibles"; and had been
developing the Mac when the PC was very new and the best-selling computer out there was the Commodore 64.
Until earlier this very year, Macs used a totally different processor than the PC. And the entire internal chipset was originally quite different, not just the CPU — and prior to the era of hardware abstraction, that mattered. Apple was not, therefore, intentionally
preventing the Mac OS from running on non-Mac hardware, it simply wasn't devoting the development effort into compiling a totally different version of it that
would do so. (And they did
experiment with the possibility.").
All these years later, Apple is still making Macs and OS X is a respected OS that only officially & easily runs on Apple Macintosh hardware. IBM is
not still making PCs, though. Microsoft, which makes no computers, cranks out the Windows operating system to run on the "PC platform" that arose from the IBM-PC and its clones. Microsoft is ubiquitous and is a wealthy and powerful company, but Windows is moribund and losing respect.
Conclude from that what you will.