This paper is the first step in thesolution of the problem of finite completion of comma-free codes.We show that every finite comma-free code is included in afinite comma-free code of particular kind, which we called, for lack of a better term, canonical comma-free code. Certainly, finite maximal comma-free codesare always canonical. The final step of the solution which consistsin proving further that every canonical comma-free code is completedto a finite maximal comma-free code, is intended to be published in a forthcomingpaper.
