SwNtfy Fn 0001H: Can Switcher Suspend Your Session?

  Expect: AX    0001H
          BX    ID of the session that is about to be suspended
          ES:DI addr of switcher's service-entry address
  Return: AX    0000H if OK to suspend, as far as you're concerned
                0001H if you object to the switch
    Info: Task switchers call this fn when they are about to perform a
          session switch.  Your application can prevent the switch or
          perform any special cleanup needed, then allow the switch to take
          place.  When called, interrupts are enabled and all DOS fns can
          be used.

       BX will contain the session ID of the session that is about to be
          switched out.  Global TSRs may wish to take special actions for
          each session.

    ES:SI will contain the task switcher's service entry address.  Use this
          address if you need to call service fns such as SwSrvcFn 0001H
          (test memory region) to determine how you feel about being
          switched out.

  Return: AX=0000H if you have no objection to being switched out. If any
          task returns a non-zero value, the session will not be switched
          out and all tasks may receive SwNtfyFn 0004H (session is active).

See Also: Switcher Services and Notifications
          INT 2fH 4bxxH (switcher functions)