Bitvectors

Bitvectors (and how to use them).

Before we had OLC, we had to deal with this kind of tables all
the time:

1 a DIRTY  The room is dirty.
2 b STINKY The room stinks.
4 c MUSHY  The floor of the room feels mushy.
8 d SWAMPY The room resembles a swamp. 

The trick was to either add the first coloumn (ie. 2 + 4 = 6 =>
Stinky+Mushy) or write the letters making up the bitvector in a
row (ie. 2 + 4 = 6 = bc => Stinky+Mushy ).

Fortunately we can now peruse them like this instead :P

1) DIRTY     The room is dirty.
2) STINKY    The room stinks.
3) MUSHY     The floor of the room feels mushy.
4) SWAMPY    The room resembles a swamp.

and OLC presents it to us as a small menu:

Enter Choice:
1) DIRTY      3) MUSHY
2) STINKY     4) SWAMPY
Current bits: NOBITS
Enter flags (0 to return):

It is possible to select all the possibilities at once, I.e.

Current bits: DIRTY STINKY MUSHY SWAMPY

Select them again to turn them off, 0 to exit the menu.

Never set UNUSED, DO NOT USE or UNDEFINED
bits, if you find them anywhere.