Here is the work for Exercise 19.
1. Go back through the script and type a comment above each line explaining in English what it does.
2. Start at the bottom and read each line backward, saying all the important characters.
3. Write at least one more function of your own design, and run it 10 different ways.
I wrote a function that prints two lines, each line asks whether the number is even and answers true or false. I call the function 10 different ways: using math calculations (addition, modulus, exponents, division) and also call the function with numbers from user input.
This exercise is building upon the introduction to functions in the last exercise. Functions can take any number of arguments (but the practical limit is about 5). Variables inside a function are not connected to variables outside of the function. When outside variables are passed into a function as arguments, temporary versions of these variables are made for use within the function. When the function ends, these temporary variables are gone.