An occurrence is any instance of an entity in your program. An
    entity can be any language construct, such as a variable, a
    routine, or a constant. To further clarify this, consider the
    following code fragment (not written in a particular language):

      1   MODULE myprog;
      2
      3   VAR i,j;
      4
      5   ROUTINE foo()
      6   BEGIN
      7       i = 5;
      8       j = i;
      9   END;
      10  END;

    The code contains four entities: myprog, foo, i, j. There is one
    occurrence each of the module myprog, and the routine foo. The
    variable i, however, has three occurrences, and the variable j has
    two.