d (Delete):delete file or directory.
                Read-only cannot be deleted.(Use "/" for that case)
                Deleted file or directory may be Undo-able
                if Undelete option is properly set by OPT UNDelete cmd.
                Default is Undeletable for only file/directory deleted
                in the same session.
                To be undeletable,deleted file/directory is saved to
                certain directories,disk space is not freed at delete.
                Use "z" command if you do not want to be undeletable.
                Especially under DOS,Movement of directory cost some times
                because it involves copy operation.
                Root dir is not deleted.