Windows on Windows (WOW) — is a system component, which enables running apps that using legacy 16-bit version of Windows API (Win 16) in 32-bit versions Windows NT.
WOW is implemented with the help of NTVDM and win16api stubs. NTVDM is used for running 16-bit code, and win16api stubs thunk legacy 16-bit APIs to their newer 32-bit equivalents.
Usually, WOW is needed for old 16-bit installers.
29-03-2018 Aleksandar Andrejevic (NTVDM developer) announced that he plans to work on WOW.
Why 16-bit apps work in the Wine?
In the Wine, running of 16-bit apps depends on kernel module ldt16, whereby emulate 16-bit code.
According to the official website:
Win3mu is a Windows 3.0 emulator. It includes an 8086 CPU emulation that loads 16-bit Windows executables and maps API calls onto the modern 32 or 64-bit Windows API. Win3mu currently won't run most Windows 3 programs however it does run quite a few games. Win3mu was started as a hobby project - mainly as a curiousity to see if it could be done. Unfortunately, once that challenge was met my interest in the project waned and due to other commitments (ie: paying projects) and other interests I no longer have much time to spend on it. So I'm planning to hand it over to the open source community in the hope someone might take an interest in it and continue to develop it. Stay tuned...