SquareGame Confusion with while loop

[textbook91]

In this sample code from the SquareGame class, the variable 'key' is declared, but not assigned to any value. Later on, a while loop uses the 'key' variable in its expression(key=0). How does the while statement tell what value 'key' is, if 'key' has not been assigned to anything.  
 
   method void run() {
        var char key;
        var boolean exit;

        let exit = false;

        while (~exit) {
            // waits for a key to be pressed.
            while (key = 0) {
                let key = Keyboard.keyPressed();
                do moveSquare();
            }

[cadet1620]

The Jack language specification says that "var" variables are initialized to 0.
Note, however, that Memory.alloc() does not initialize the memory it returns.

(If you already wrote your VM translator you did this by initializing functions' local segments to 0.)

--Mark

[textbook91]

thanks for clearing that up!