By testing concepts on paper I came up with a 'noun' stack (operators like numbers and variable names) and 'verb' stack (every other element in the syntax chart).

FORBES: Steve Wozniak: His Career Challenges, Steve Jobs, Tech Trends and Advice

Many, many experiments up and down the stack are quite exciting when we are able to remove the variable of gravity.

WHITEHOUSE: President Obama's call to the International Space Station