where the formula_78 are "don't care" bit values, and the formula_79 are a finite number of explicitly specific bit-values scattered in the infinite don't-care bit-string. These are the open sets of the topology. The canonical measure measure on this space is the Bernoulli measure for the fair coin-toss. If there is just one bit specified in the string of don't-care positions, the measure is 1/2. If there are two bits specified, the measure is 1/4, and so on. One can get fancier: given a real number formula_80