This paper describes parallel grammatical evolution (PGE) that can evolve complete programs using a variable length linear genome to govern the mapping of a Backus Naur form grammar definition. To increase the efficiency of grammatical evolution (GE) the influence of backward processing was tested. The significance of backward coding (BC) and the comparison with standard coding of GEs is presented. BC can speed up grammatical evolution with high quality features. The adaptive significance of parallel grammatical evolution with "male" and "female" populations has been studied