Using Free42

Free42 is a free, open source emulator of the HP 42s calculator that can be downloaded and used on an iPhone, Android, and Windows, Mac, or Linux computer. It is WONDERFUL! Once you get used to RPN notation it becomes an extension to your brain! This video is an introduction to the calculator for my physics and math courses for homeschoolers (available for digital download at http://mathwithoutborders.com).

BTW, you don't need to be a homeschooler to teach yourself the parts of high school math (Algebra through Calculus) and physics you missed out on because you were a distracted teenager at the time! ... https://www.youtube.com/watch?v=UKvhBSJPw0o