2. Syntax

integer = DEFI_FICHIER (
    ◇ ACTION =/"ASSOCIER" (by default),
               /"LIBERER ",
               /"RESERVER ",
    # If: equal_to (" ACTION ", 'ASSOCIER')
        ◆ | UNIT = unit,
          | FILE = text,
        ◇ TYPE =/"ASCII" (by default),
                 /"BINARY ",
                 /"LIBRE ",
        # If: equal_to (" TYPE ", 'ASCII')
            ◇ ACCES =/"NEW" (by default),
                      /"APPEND ",
                      /"OLD ",
        # If: not equal_to (" TYPE ", 'ASCII')
            ◇ ACCES =/"NEW" (by default),
                      /"OLD ",
    # If: equal_to (" ACTION ", 'RESERVER')
        ◆ | UNIT = unit,
          | FILE = text,
        ◇ TYPE = "ASCII ",
        ◇ ACCES = "APPEND ",
    # If: equal_to (" ACTION ", 'LIBERER')
        ◆/UNITE = unit,
          /FICHIER = text,
    ◇ INFO =/1,
             /2,
)

◆: mandatory
◇: optional
: present by default
&: together
/: only one among
|: several possible choices