Windows 11 comes with only 64-bit and cannot support 16-bit. The only versions that support 16-bit are some Windows 32-bit versions.

Assuming the software is designed correctly, porting form 32-bit to 64-bit should be simple. Simple like you don't have to change anything. 32-bit programs would just ignore half of each register ...

CPUs that process 64 bits as a single unit, compared to 8, 16 or 32. Today's desktop and laptop computers are mostly 64-bit machines; however, there are countless 32-bit, 16-bit and 8-bit ...