This makes no sense. If your program isn't aware of your current state (previous state when you want to change to a new set of states), then setting the new state is just a statement like:

Code:

state = state1;
    or
state = state3 | state4 | state7;

If you can't restrain yourself from writing code like:

Code:

state = state1 | state2;

and you aren't going to set up a function to perform verification of state changes, I have no idea what you are trying to do. And, doing this, there are never any unknown (or unchanged states); you replace (rather than update) states every time to assign a new value to state. So you won't have xxxx x100, you'll have 0000 0001, 0100 1100, or (the undesired) 0000 0011, respectively, for the three samples above; but never any xs.

I must be missing something in your description of what you're trying to do.