d (Delete):delete file or directory.
                Read-only cannot be deleted.(Use "/" for that case)
                Deleted file or directory may be Undoable
                if Undelete option is properly set by OPT UNDelete cmd.
                Default is Undeleteable 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.
                Especialy under DOS,Movement of directory cost some times
                becuse it involves copy operation.
                Root dir is not deleted.