DOS Fn 59H: Get Extended Error Info

                                                         Compatibility: 3.0+ 
 Expects: AH    59H
          BX    0000H (need for 3.x and 4.x)
 Returns: AX    extended error code (0 if no error has occurred)
          BH    error class
          BL    suggested action
          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

          See DOS Error Codes for a full listing of possible error codes,
          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
            internal error codes.

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)
          System Information Functions
          DOS Error Codes
          DOS Functions