This section is concerned with examining the problem of checking inside a routine, what exactly was present of the command line typed by the user, as this often determines the behavior of the routine. You will have to do that for instance to implement an on-line help when no parameter is given (with the n_params() function).
More generally, the presence of parameters and keywords as well as their content will often drive the behavior of your routines and functions. The number of parameters present on the command line is easily checked with:
number_of_par = n_params() This however, says nothing about keywords which are of a different nature (and are named, i.e. appear on the command line as key1=variable). One must distinguish three types of keyword: input keywords that provide a variable to the routine, boolean (i.e. yes/no, true/false) keywords, and output keywords that will be used to retrieve results from the routine.