The NULL function returns a disassociated pointer.
Syntax
NULL ( [mold] )
mold is an INTENT(IN) variable of any type, and must have the pointer attribute.
mold must be present when a reference to NULL() appears as an actual argument in a reference to a generic procedure if the type, type parameters, or rank is required to resolve the generic reference.
A disassociated pointer of the same type, type parameters, and rank as the pointer that becomes associated with the result.
Example
real,pointer,dimension(:) :: a => null() ! a is disassociated