Suppose the alphabet is $[$A$,$B$,$C$,$D$],$ and the known probability distribution is PA$=0\mathrm{.}5,$ PB$=0\mathrm{.}4,$ Pc$=0\mathrm{.}1.$ for simplicity lets assume that both encoder and decoder know that the length of the message is always $3,$ so there is no need for terminator.