Microsoft tried valiantly to make Win16 code portable to Win32, and Win32 to Win64. But it failed miserably, apparently because the programmers had never ported 16 bit C to 32 bit C, etc., and picked all the wrong abstractions.

> Even more fun is pointers, especially when windows / macos were switching from 32-bits to 64-bits (in different ways).

And yet even more of a fun time with porting pointer code was going from the various x86 memory models[0] to 32-bit. Depending on the program, the pain was either near, far, or huge... :-D

0 - https://en.wikipedia.org/wiki/X86_memory_models