INT 21 - DOS 3.x Internal - GET ADDRESS OF CRITICAL ERROR FLAG

Input

 DOS1 N DOS2 N

DOS3

 Y DOS5 Y

Output

AX

 5Dh  06h     AX

BX

         BX

CX

     ??? CX

DX

     ??? DX

ES:DI

   Pointer to Critical Error Flag DS:SI 
Notes:  *  This call also does a lot of other work in addition to
           returning the pointer

        *  Setting CritErr flag allows use of functions 50h/51h from
           INT 28h under DOS 2.x by forcing use of correct stack


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