Comma-free error-correcting codes

A method is shown by which it is possible to establish the existence (or nonexistence) of the comma-free properties of any group code from a simple observation of its null-space. Using this technique it is then demonstrated that all (n, k) {em cyclic} group error-correcting code dictionaries can be made comma-free (without adding further redundancy or altering their error-correcting properties) if, and only if, k \leq (n - 1)/2 . If k is larger than (n - 1)/2 it is still possible to detect bit gains or losses of up to n-k-1 code bits.