The Scratch Team have suggested that there should be a separate version of Scratch for college computer science students. We disagree. By following the principle of first class data, we can have a powerful Scratch with very few visible additions to the interface. These ideas are implemented in BYOB 3, with first class lists and first class procedures. It is available at http://byob.berkeley.edu This project is a severely abbreviated version of the full 20-minute propaganda film we prepared for the Scratch Team, which is called scratch4cs.
