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     This function may be called after any other Int 21h function call
     that returned an error status, in order to obtain more detailed
     information about the error type and the recommended action. If
     the previous Int 21h function call had no error, 0000h is returned
     in register AX. This function may also be called during the
     execution of a critical-error (Int 24h) handler.
 
     The contents of registers CL, DX, SI, DI, BP, DS, and ES are
     destroyed by this function.
 
     Note that extended error codes 13h-1Fh (19-31) and 22h (34)
     correspond exactly to the error codes 0-0Ch (0-12) and 0Fh (15)
     returned by Int 24h.
 
     You should not code your programs to recognize only specific error
     numbers if you want to ensure upward compatibility, because new
     error codes are added in each new version of MS-DOS.
 
     Under DOS 3.1, an application can use function 59h to preserve
     current extended error information and to later restore the
     information to DOS with function 5D0Ah. After calling function
     59h, the application copies registers AX, BX, CX, DX, SI, DI, DX,
     and ES in the order given to an 11-word data structure. The last
     three words of the structure should each be set to zero.
 
     The following defines the extended error structure:
 
       EXTEND_ERR   STRUCT
         rAx        WORD    ?               ; AX
         rBx        WORD    ?               ; BX
         rCx        WORD    ?               ; CX
         rDx        WORD    ?               ; DX
         rSi        WORD    ?               ; SI
         rDi        WORD    ?               ; DI
         rDs        WORD    ?               ; DS
         rEs        WORD    ?               ; ES
         Pad        WORD    3 DUP(0)
       EXTEND_ERR   ENDS
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