Int 21 Fn 69FF  U - Cubit V4.00 - Get Cubit Int 21 Handler                 [d]

   AX = 69FFh
   DX = 0000h
   BX = CB00h (magic value)

Return: ES:BX -> CUBITR.EXE handler for INT 21

Note:  the installation check consists of testing that the first eight bytes
     at the returned interrupt handler are EBh 07h "CUBITR" (a short
     jump around the signature followed by the signature); the byte
     following the signature (i.e. ES:[BX+8]) indicates whether CUBITR
     is active (01h) or disabled (00h)

See Also: AX=69FFh/DX=CFBFh
Index: installation check;CUBIT