INT 21 - DOS 4+ - GET BOOT DRIVE

Input

 DOS1 N DOS3 N

DOS4

 Y DOS5 Y

Output

AX

 33h 05h   FFh = Error AX

BX

         BX

CX

         CX

DX

       Boot Drive DX

ES:DI

     CF 
Boot Drive:     1 = A:
                2 = B:


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