Every statement in a session begins with an asterisk, *.  Lines without asterisks are treated as comments.

In the statement *Font("Helvetica", 1, 1, 12), Font is the keyword and the arguments ("Helvetica", 0, 1, 12) specify that the font is  Helvetica bold italic size 12.  If a statement is left out of asession, the program uses the default setting specified in the preferences file.  For settings not specified in the preferences file, the program uses built-in defaults.  If a statement is repeated within a block, the last occurrence of the statement is used unless specified in the statement description, in which case, multiple occurrences are used.