Explore the behavior and the blocks. For what reason would you use a variable as an aggregator in your own program? What do the blocks related to the aggregator do, and when do they do it?
Project Lead The Way is a non-profit organization offering curriculum and professional development to U.S. schools. CSE is our new computer science course for high schools. CSE students create projects in many languages, including Scratch, MIT App Inventor, and Python. See http://www.pltw.org/our-programs/computer-science for details.
