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.