BX 0000H (need for 3.x and 4.x)
Returns: AX extended error code (0 if no error has occurred)
CH location (where the error occurred)
Info: Use this function to figure out what to do after a DOS function
failed because of an error. You can use this:
Inside an INT 24H Critical Error handler
After any INT 21H DOS function which signals an error with CF
After FCB-style functions which return AL=ffH means an error
classes, suggested actions, and loci that may be returned by this
Notes: After an error, you get only on chance to call this fn. After
one call, the error condition is unflagged and subsequent calls
won't return meaningful data.
You can use fn 5D0aH to simulate an error or set your own
Versions: This function is not available before 3.00.
With 2.x, when CF returns indicating an error, use your own
program logic to decide what action to take.
With 3.0+, when a function returns CF=1, Microsoft advises to
ignore the error code returned in AX, call this function, and
take the action suggested in BL.
See Also: Fn 5d0aH (set extended error)