Inventory DOS-specific behavior

Preserve data files and code pages, printer control sequences, serial settings and timing, direct hardware access, database runtimes, network redirectors/shares and startup scripts. Capture representative outputs before changing platform.

Choose the smallest safe change

Emulation/virtualization	Continuity when interfaces and timing can be reproduced.
Wrapper/gateway	Modern file, network or device integration around retained logic.
Partial replacement	Move one database, report or protocol boundary.
Full replacement	Requires recovered behavior and reconciled data.

Use DOS engineering, DOS database recovery, 16-bit replacement and control-PC replacement.