Get and Enable Virtual Interrupt State


                 This function  will enable  the virtual  interrupt flag
                 and return  the previous state of the virtual interrupt
                 flag.

            To Call

                 AX = 0901h

            Returns

                 Carry flag clear (this function always succeeds)
                 Virtual interrupts are enabled
                 AL = 0 if virtual interrupts were previously disabled
                 AL = 1 if virtual interrupts were previously enabled

            Programmer's Notes

                 o    AH  will   not  be   changed  by  this  procedure.
                      Therefore, to  restore the  previous state, simply
                      execute an Int 31h.