Fano's method divides the source symbols into two sets $("0"$ and $"1")$ with probabilities as close to $1/2$ as possible. Then those sets are themselves divided in two, and so on$,$ until each set contains only one symbol. The codeword for that symbol is the string of $"0"$s and $"1"$s that records which half of the divides it fell on$.$ This method was proposed in a later $($in print$)$ technical report by Fano $(1949).$