the modern unicode set from codice_1 to codice_6. excluding the thirteen "protected" code points encoded as single octets bocu-1 can use formula_1 octets in multi-byte encodings. bocu-1 needs at most four bytes consisting of a lead byte and one to three trail bytes. the trail bytes encode a remaining "modulo 243" (base 243) difference, the lead byte determines the number of trail bytes and an initial difference.