Master Chief and Cortana (brief history)

So yeah you know about Cortana's job is to protect Master Chief but do you know why she does it in the first place? well it is because she knows that he is humanities last hope so she wants to keep him safe from all threats that might be a danger to him. Cortana was basically born from Dr. Catherine Elizabeth Halsey's mind and is an "Smart AI" so she can think out of the box of her programming. SO yeah I don't want to ruin the ending of Halo 4 so I won't tell you anymore okay thanks.