You may also download the JRE 1.1.x if you do not need to program in Java. To start the interactive interpreter, run the class yoyo. On Macs, there will be a YoYo CommandCenter application. This will bring up a text window with the interpreter in it. Once YoYo has started, you may type a command in the text box and press return to run it.
Print is a command that takes one input and prints the value in the interpreter window.
Just move the cursor to anywhere on that line and press return. YoYo will run that line again. Intro to Math YoYo supports lots of different math functions with order of operations. That dot tells you that YoYo is computing something. It goes away when you're allowed to type again.