The most basic duality that exists with variables is how the programmer sees them in a totally different way than the computer does. When you're typing away in Project Builder, your variables are normal words smashed together, like software titles from the 80s. You deal with them on this level, moving them around and passing them back and forth.

Note the new asterisks whenever we reference favoriteNumber, except for that new line right before the return.

For this program, it was a bit of overkill. It's a lot of overkill, actually. There's usually no need to store integers in the Heap, unless you're making a whole lot of them. But even in this simpler form, it gives us a little bit more flexibility than we had before, in that we can create and destroy variables as we need, without having to worry about the Stack. It also demonstrates a new variable type, the pointer, which you will use extensively throughout your programming. And it is a pattern that is ubiquitous in Cocoa, so it is a pattern you will need to understand, even though Cocoa makes it much more transparent than it is here.

When Batman went home at the end of a night spent fighting crime, he put on a suit and tie and became Bruce Wayne. When Clark Kent saw a news story getting too hot, a phone booth hid his change into Superman. When you're programming, all the variables you juggle around are doing similar tricks as they present one face to you and a totally different one to the machine.

We can see an example of this in our code we've written so far. In each function's block, we declare variables that hold our data. When each function ends, the variables within are disposed of, and the space they were using is given back to the computer to use. The variables live in the blocks of conditionals and loops we write, but they don't cascade into functions we call, because those aren't sub-blocks, but different sections of code entirely. Every variable we've written has a well-defined lifetime of one function.