Compatibility: Win 3.x
Expect: AX    1606H
DX    flags: bit 0=1 if standard mode
bit 0=0 if enhanced 368 mode
Return: none
Info: TSRs and DOS-level device drivers may intercept this function as
a way to be notified when Windows is about to terminate.

Your handler will later receive an INT 2fH 1609H notification to
indicate that windows is actually terminating.

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INT 2fH 1606H: Windows Is About to Terminate