Forming Active-Passive Verbs in Spanish

I currently dug up an old notebook from College (1996) and found this entry on converting singular active verb to past, future, passive by adding suffixes/prefixes.

E.g.

es comprado  --             present
fue comprado --            past
era comprado --            present perfect
sera comprado --          future
ha sido comprado --     have been
habia sido comprado-- had been
habra sido comprado--will have been