Like in every computer language, comments are very important for the clarity of a code. The user can make his/her own comments by simply preceding them by the # symbol. So, for example, the following rows of an ASCII file processed by GNU Archimedes will be interpreted as comments
# this is comment # MATERIAL SILICON # even if the precedent row contains a command # this will never processed and it will be consider # simply a comment
Pay attention to the fact that everything after the # symbol is a comment even if this could be a sintaxicaly correct line of an input file.