The statement "NT is based on OS/2 3.x" is misleading. NT isn't based on OS/2 3.x, it was originally meant to be OS/2 3.x, until the IBM-Microsoft divorce. But, despite being originally intended to be OS/2 3.x, there was not much OS/2 1.x/2.x code in it. The main areas of inherited code were HPFS and the OS/2 compatibility subsystem, neither of which ended up being core features, and were dropped in newer releases. Outside of those, there was very minimal code inherited from 1.x/2.x. "NT is based on OS/2 3.x" makes it sound like NT inherited more of the design or implementation of OS/2 1.x/2.x than it actually did.