The previous sections have dealt with the subroutine options and variables one at a time. This is certainly important, but for a full use of the capabilities of the program, it is also necessary to understand how to make different pieces work together. This is something that cannot be explained fully in a manual, but must also be learnt by trial and error. This section contains some examples of relationships between subroutines, common blocks and parameters. It also contains comments on issues that did not fit in naturally anywhere else, but still might be useful to have on record.