Neo:
Are there other programs like you?
The Oracle:
Oh, well, not like me. But… Look, see those birds? At some point a program was written to govern them. A program was written to watch over the trees, and the wind, the sunrise, and sunset. There are programs running all over the place. The ones doing their job, doing what they were meant to do, are invisible. You’d never even know they were here. But the other ones, well, we hear about them all the time.
Neo:
I’ve never heard of them.
The Oracle:
Of course you have. Every time you’ve heard someone say they saw a ghost, or an angel. Every story you’ve ever heard about vampires, werewolves, or aliens is the system assimilating some program that’s doing something they’re not supposed to be doing.
Neo:
Programs hacking programs. Why?
The Oracle:
They have their reasons, but usually a program chooses exile when it faces deletion.
Neo:
And why would a program be deleted?
The Oracle:
Maybe it breaks down. Maybe a better program is created to replace it – happens all the time, and when it does, a program can either choose to hide here, or return to The Source.
From the Matrix Reloaded (2)