In this final step no matrix operations are involved. Instead the program works with bit strings representing the incidences and dotted-lines. Submodules are calculated generation by generation, the first generation consisting of all submodules generated by one local submodule. In the n th generation all submodules generated by a submodule of generation n plus one local submodule are calculated. If no more submodules appear, the algorithm terminates.
Output is written to three text files and one binary file.
The second output file is Name .lat . It contains the lattice as a list in GAP format. The third output file, Name .gra , contains a description of the submodule lattice together with some additional information. A further output file, Name .sub contains the submodule lattice is binary format. By definition, a block is a set of one or more composition factors which is closed under incidences of local submodules.