16-bit Windows (Windows 3.x) programs: what to know before the first run

What to know

A Windows 3.x game is an NE executable with 16-bit code in segments. 64-bit Windows cannot run it. Read it with GameFrame's NE tools and Ghidra's New Executable loader. Run it in Wine, in otvdm (winevdm) on 64-bit Windows, or in Windows 3.1 inside DOSBox-X. Emulate single routines with dos_emu in protected mode.

Use 86Box when the result depends on a specific PC model, BIOS, expansion bus or sound card. DOSBox-X remains useful for Windows 3.1 runs where its debugger helps trace behavior. Record the machine and card settings with every capture (86Box guide).

• Recognising it. dosinfo GAME.EXE says NE. A Windows NE program imports from KERNEL, USER and GDI, by ordinal more often than by name. A DOS program in the same format imports from a DPMI runtime (RTM.EXE, DPMI16BI.OVL) instead.
• Addresses. Ghidra numbers the segments as selectors 1000, 1008 and on. Keep that numbering in every document. The system that runs the program chooses a live selector (docs/DOS.md).
• Reading code. ne.py lists the segments, entries and relocations. nedis.py disassembles a segment. readseg.py reads bytes and constants by seg:off. Far calls between segments go through relocations. The relocation table holds a call's target. Do not look for the target in the bytes of the call.
• Running it. Wine runs many Win16 programs directly. On 64-bit Windows, otvdm (winevdm) runs them. Windows 3.1 inside DOSBox-X gives a convenient system with DOSBox-X's debugger; 86Box gives a configurable period PC when machine or card details matter.
• Drawing. Win16 games drew through GDI, or later through WinG and DIB sections. Palette messages (WM_PALETTECHANGED, WM_QUERYNEWPALETTE) matter on an 8-bit desktop. Modern systems emulate the 8-bit desktop.