Ownership means the implied permission and ability to change the data.
Any variables which are only used within a subroutine are not passed outside the subroutine unless an overriding reason exists. Data for reference only Reference data are entered into a subroutine by way of the common blocks. This is to emphasize their peripheral role. Thus the number of orbitals, while essential to ITER, is not central to the task it has to perform, and is passed through a common block. The data which the subroutine is going to work on Data the subroutine is going to work on are passed via the argument list.