New lower bounds for asymmetric and unidirectional codes

New lower bounds on the sizes of asymmetric codes and unidirectional codes are presented. Various methods are used, three of them of special interest. The first is a partitioning method that is a modification of a method used to construct constant weight codes. The second is a combining codes method that is used to obtain a new code from a few others. The third method is shortening by weights that is applied on symmetric codes or on codes generated by the combining codes method. Tables for the sizes of codes of length n>