With source code directives you can vary the contents of the listing file for different sections of the source file, whereas (in the absence of source code directives) the PWB or command-line options affect the entire listing.
The /Fl command-line option enables a listing. Without /Fl, no listing is produced. The /S options are legal without /Fl, but they have no effect.
A file generated with /Fl shows all assembled source lines and provides a header at the beginning of the listing. It also adds a header before the symbol table and each section of the symbol table but does not add any page breaks between sections.