Which also reminds me of the problem of programs assuming that HWNDs are even, including the first version of Project using the low bit to do windowless control

Which also reminds me of the problem of programs assuming that HWNDs are even, including the first version of Project using the low bit to do windowless controls in the days just before Windows 3.0 was released. PowerPoint decided to require protected-mode Windows 3.0 from the beginning instead, as you can see in the book. In retrospect, Windows 3.0 should have been delayed anyway because of DOS 5.0.