Disables the implicit declaration of data types in the program
  unit.  When it is used, you must declare the data types of all
  symbols explicitly.  You must not include any other IMPLICIT
  statements in the program unit containing an IMPLICIT NONE
  statement.  Statement format:

     IMPLICIT NONE

                                 NOTE

          To receive diagnostic messages when  variables  are
          used   but   not  declared,  you  can  specify  the
          /WARNINGS=DECLARATIONS compiler option  instead  of
          IMPLICIT NONE.