NULL ([mold])

  Class:  Transformational function - Generic

  Initializes a pointer as disassociated when it is declared.

  Argument "mold" is optional and must be a pointer; it can be of any
  type.

  The status of the pointer can be associated, disassociated, or
  undefined.  If the pointer's status is associated, the target does
  not have to be defined with a value.

  The result type is the same as "mold", if present.  Otherwise, the
  type (and rank) is determined by the pointer that becomes
  associated with the result:

  If NULL () Appears...         Type is Determined From...
  ------------------------      -----------------------------------
  Right side of pointer         The pointer on the left side
    assignment

  Initialization for an         The object
    object in a declaration

  Default initialization        The component
    for a component

  In a structure constructor    The corresponding component

  As an actual argument         The corresponding dummy argument

  In a DATA statement           The corresponding pointer object

  It returns a disassociated pointer.

  Example:

    INTEGER, POINTER :: POINT1 => NULL()

  This statement defines the initial association status of POINT1 to
  be disassociated.