How does Windows continue supporting programs written decades ago?

Question

How does Windows maintain compatibility with programs written decades ago? I want to understand the technical mechanisms that allow old software to run on modern Windows systems.

hobgood · Answer

Microsoft maintains a system-wide database (sysmain.sdb) containing entries for thousands of applications.

wokhiosk · Answer

Small pieces of code that act as a "buffer" between an old program and Windows.

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How does Windows continue supporting programs written decades ago?

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