Thank you for your answer. This is a rental house. I want to accomplish changing 2 prong (ungrounded) to 3 prong w/grnd to the exterior wall outlets without having to run new wireing on all outlets through attic. I would leave 2 prong outlets on interior walls as is. Bathrooms & kitchen outlets are grounded.

You will need to use 3 conductors for outside recepticles. Hot, Neutral, and Ground.
You could use 1 GFI Breaker, or receptacle to protect all.
Kitchen and Bath should also be GFI protected, Not Refrigerator.