It wasn't the first modular computer. The big thing with the IBM PC is that IBM didn't manage to have a single significant component that they licensed exclusiv

It wasn't the first modular computer. The big thing with the IBM PC is that IBM didn't manage to have a single significant component that they licensed exclusively; the most obvious culprit for this was DOS, which they licensed from Microsoft. Other companies at the time had OSes they controlled the distribution of. But Microsoft was able and very willing to sell any company the rights to distribute DOS.