Should you keep a copy of all the code you write?

"The code that you write on the computer should only stay on the compter that you wrote it on and nowhere else."

That is what I was taught. What it means is that if you write some code on your work computer, it stays on your work computer. If you write it on your home computer, it stays on your home computer. Nowhere else.

(obviously there are exceptions, but the basic rule is a good thing to remember)